EP4401886A1 - Multipart material needle for a paint pistol, front needle of a material needle, paint pistol, and method for exchanging a front needle - Google Patents

Abstract

The invention relates to a material needle (3), which extends along a longitudinal axis (X), for a paint pistol, comprising a material nozzle (2). The material needle (3) can be joined into a guiding channel of the paint pistol and can be moved along a longitudinal axis (X) in order to open and close a nozzle opening (2') of the material nozzle (2) by means of a defined needle stroke movement, wherein the material needle (3) comprises a front needle (4), which is at the front in the axial direction, and a rear needle (5), which is at the rear in the axial direction, and the front needle (4) and the rear needle (5) are releasably connected together in order to guide axial forces via an axial form-fitting connection. The axial form-fitting connection is formed by front form-fitting elements, which are arranged on the front needle (4), and rear form-fitting elements, which are arranged on the rear needle (5), and the front and/or the rear form-fitting elements can be elastically deflected in a direction (R) which is perpendicular to the longitudinal axis (X) in order to release the axial form-fitting connection. The axial form-fitting connection is secured against being released by a securing means (7) which prevents a deflection of the front and/or rear form-fitting elements perpendicularly to the longitudinal axis (X), and the securing means (7) comprises an outer sliding bearing surface of the front needle (4) and/or the rear needle (5) in order to interact with a corresponding sliding surface of the paint pistol in a form-fitting manner.

Description

Multi-part material needle for a paint gun, front needle of a material needle and paint gun and method for replacing a front needle

The invention relates to a material needle for a paint gun according to the preamble of claim 1, a front needle according to claim 24, a paint gun according to claim 25 and a method for replacing a front needle according to claims 27 and 29.

Material needles in spray guns are used to open and close nozzle openings and thus control the delivery of sprayable material, such as paints, primers and paints from a nozzle. In order to prevent irreversible contamination with an associated negative influence on the spray pattern of the spray gun, the material needle must be cleaned regularly. Furthermore, the material needle is subject to increased wear when processing abrasive materials, which also has a negative effect on the spray pattern from a certain point. In order to prevent a negative influence on the spray pattern, the material needle must therefore be removed regularly. For this it is usually sufficient to replace the part of the material needle that engages in the nozzle opening, for example a needle head. Interchangeable needle heads are known, for example, from US3463363 A or DE69110099T2.

US3463363A discloses an interchangeable needle head which is detachably connected to a needle shaft via a screw connection.

DE69110099T2 teaches a material needle with an exchangeable needle head (valve tip) which is detachably connected to the needle head via a clamping sleeve screwed onto a needle shaft. The needle head engages with a ball head at the end in an elastically deformable receptacle of the clamping sleeve. The needle head is thus mounted like a ball joint.

Such solutions meet the requirement of a quick replacement of the needle tip, but are difficult to manufacture in terms of manufacturing technology and require either the use of to ensure sufficient positioning accuracy of the needle head technically complex fine threads or do not ensure a sufficiently clear axial alignment of the needle head.

Proceeding from this state of the art, the invention has set itself the task of further developing paint spray guns or their material needles in such a way that a simple and quick replacement of a needle tip is possible with high manufacturing tolerances at the same time. Furthermore, the object of the invention is to provide an exchangeable needle tip of a material needle, in which an unintentional detachment of the needle tip from the rest of the material needle can be reliably prevented and in which a radial centering of the material needle, in particular in the area of a needle tip, is ensured independently of the axial position of the material needle can be.

The object is achieved by a material needle for a paint gun according to claim 1, a pre-needle according to claim 24, a paint gun according to claim 25 and a method for replacing a pre-needle according to claims 27 and 29.

Spray guns according to the invention are preferably designed as high-pressure spray guns or as low-pressure spray guns. The high-pressure paint gun according to the invention atomizes material under high pressure. The material pressure is usually between 50 and 400 bar. The high-pressure paint gun can be embodied as a conventional high-pressure paint gun that does not use compressed air and as an air-assisted high-pressure paint gun that also uses air to assist atomization. The latter requires less material pressure than the high-pressure spray gun without air support. The high-pressure paint spray gun has, for example, a slit-shaped nozzle that generates a flat spray jet without further shaping, with a material valve being provided that serves to control the material delivery.

As a low-pressure spray gun, the spray gun is operated with a low material pressure and is supplied with material either by gravity, vacuum or a low-pressure material feed (less than 40 bar material pressure). The low-pressure spray gun can be designed as a so-called cup gun, in which the material is supplied via a cup attached to the spray gun. It can also be provided a material container from which the material z. B. under a material pressure between 1 and 20 bar is pumped to the spray gun. That as low pressure Spray gun embodiment of a spray gun atomizes the material by means of a gas or gas mixture, preferably compressed air, which emerges from an air gap surrounding the material nozzle, as a result of which the material is entrained from the material nozzle and atomized.

In the case of a particularly preferred exemplary embodiment, the paint spray gun according to the invention is designed as an automatic paint spray gun or as a hand-held paint spray gun. The automatic spray gun is controlled via an external signal source and is not operated directly by a user. The hand-held paint spray gun is held in the hand and actuated by a user.

Furthermore, the spray gun according to the invention can preferably be designed as a uniaxial and dual-axis spray gun. In the variant of the invention designed as a single-axis spray gun, the air valve for controlling the air delivery and the material valve for controlling the material delivery share a common axis. In the case of the variant of the invention designed as a two-axis spray gun, the axes for controlling the air delivery and the material valve for controlling the material delivery are not arranged coaxially. The variant as an automatic or hand-held spray gun can be designed both as a single-axis and as a two-axis paint gun.

According to the invention, a material needle extending along a longitudinal axis for a paint spray gun with a material nozzle is proposed, the material needle being insertable in a guide channel of the paint spray gun and displaceable along a longitudinal axis to open and close a nozzle opening of the material nozzle with a defined needle stroke. The material needle comprises an axially front front needle and an axially rear rear needle, which are detachably connected to one another along a connecting section between the front needle and the rear needle via an axial form fit for conducting axial forces. The axial form-fitting is formed by front form-fitting elements arranged on the front needle and rear form-fitting elements arranged on the rear needle, with the form-fitting being able to be canceled by radial deflection of the front and/or rear form-fitting elements.

In order to prevent an unintentional loosening of the form-fitting, the axial form-fitting is secured by means of a securing device which causes a radial deflection of the front and/or rear Positive locking elements prevented, the securing means containing a radially outer plain bearing surface of the front needle and / or the rear needle for positive interaction with a corresponding plain bearing surface of the spray gun.

As a result, high axial forces can be transmitted between the front and rear needles, and at the same time the detachability of the connection can be ensured with little effort. Furthermore, an unintentional loosening of the axial positive locking in an operating state of the spray gun can be reliably prevented. The securing means or means can be formed, for example, by wings extending radially away from the material needle or by the outer circumference of the material needle itself.

Form locking (positive locking) means a direct or indirect form-fitting connection between at least two connection partners, here the front needle and rear needle, which interlock in such a way that the connection can be made even if there is no normal force (perpendicular to the surfaces of the connection partners or to the direction of the impeded movement ) in the direction of obstructed movement does not disengage.

A frictional connection (frictional connection) is a direct or indirect non-positive connection between at least two connection partners, here the front needle and rear needle, which is to be understood by means of a frictional connection between the contact surfaces caused by a normal force (perpendicular to the surfaces of the connection partners or to the direction of the impeded movement). the connection partner is caused.

The connection between the front needle and the rear needle can be either a form fit or a force fit or a combination of both connection techniques.

A frictional connection can be achieved in particular by an oversize fit in a connecting area of the connection between the front and rear needles, so that a connecting area of the front needle is elastically compressed and a connecting area of the rear needle is elastically widened, or vice versa. The connecting section is to be understood as meaning that section of the material needle in which parts of the front needle and the rear needle overlap axially. In addition to the axial form fit, further functions or functional components such as, for example, guide surfaces, tilting bearings and other functional surfaces or components can also be integrated in the connecting section.

In the context of this document, form-locking elements are to be understood as meaning those form-locking elements which contribute to the axial form-locking between the front and rear needles.

The front end of the front needle and/or the rear needle is to be understood as meaning the end that is located downstream in the direction of material delivery essentially along the longitudinal axis of the material needle opposite the rear end of the same part, whereas the rear end is located upstream of the front end in the direction of material delivery. This also applies analogously to the designation front and rear, which also refer to the material delivery direction. In the context of the invention, axial refers to the axis of the material needle, which coincides with the axis of the material nozzle and the front needle axis and the rear needle axis.

Exchanging not only means exchanging a front needle for another front needle, but also removing the front needle and then inserting the same front needle, as is done, for example, when cleaning the front needle and/or the material-carrying areas of the spray gun.

Further configurations and features of the invention result from the dependent claims and the following description.

In an advantageous embodiment, the front needle or the rear needle has a multiplicity of form-fitting elements, which are preferably distributed axially symmetrically and/or radially symmetrically over the circumference of the front needle or rear needle. This means, for example, that two form-fitting elements of the front needle face each other, with a different circumferential distribution of, for example, three or more form-fitting elements being possible, which makes it possible to ensure the coaxial alignment of the front needle and rear needle with one another. The form fit can advantageously act axially on both sides. This means that each form-fitting element has both axially front and axially rear contact surfaces, which interact with corresponding contact surfaces of the corresponding front needle or rear needle. This allows a play-free connection to be implemented. This can be achieved, for example, in that form-fitting elements of the front needle and/or the back needle have concave contact surfaces and the corresponding form-fitting elements of the back needle or the front needle have convex contact surfaces corresponding thereto. Other corresponding shapes of the contact surfaces such as teeth or corrugations are possible.

The plain bearing surface of the securing means is advantageously coated with a friction-reducing material. As a result, frictional forces can be reduced and the ease of movement of the material needle in the spray gun can be ensured. For this purpose, the plain bearing surface can also be provided with a lubricant to reduce friction.

In an advantageous embodiment, the plain bearing surface of the securing means is rounded in the longitudinal direction (in a longitudinal section), for example (circular) arc-shaped or involute-like. By rounding, the contact surface in the plain bearing can advantageously be reduced to a line contact extending in the circumferential direction. Furthermore, the risk of jamming and the occurrence of stick-slip (slip-and-stick effects) are reduced.

In particular, the plain bearing surface can be rounded in the circumferential direction. The rounding can, for example, be adapted to a radius of curvature of the wall of the guide channel or selected to be smaller than the radius of curvature of the wall. As a result, among other things, the elasticity of the securing means can be increased, but above all a cross-sectional shape that is advantageous in terms of flow technology can be achieved. If the rounding of the sliding bearing surface is designed to be larger than the radius of curvature of the wall of the guide channel or if there is no rounding, contact can be achieved at two locations spaced apart from one another. In an advantageous embodiment, it is provided that the maximum static friction force between the plain bearing surface of the securing means and the sliding surface of the paint spray gun is smaller than the force that a counteracting element, for example a spring, exerts on the material needle in the direction of the longitudinal axis in the material dispensing direction and counteracts the needle stroke .

The slide bearing surface of the securing means is advantageously closed continuously in a circumferential direction of the slide bearing. In the case of a cylindrical guide channel, the securing means is designed with the slide bearing surface, for example as a circular disk or as a circular cylinder or as a sleeve, with the casing of the circular disk or circular cylinder forming the slide bearing surface. A closed sliding bearing surface allows the front needle to be centered precisely in the guide channel. Through openings for the passage of material in the longitudinal direction of the guide channel can be provided in the securing means.

As an alternative to this, the plain bearing surface can also be formed with interruptions in a circumferential direction of the plain bearing. In particular, the plain bearing surface can be composed of a large number of non-contiguous partial plain bearing surfaces which are connected to a needle shaft of the front needle and/or the rear needle, for example via radially projecting webs or wings. As a result, static overdeterminations, in particular as a result of manufacturing errors, can be avoided.

In an expedient development of the invention, the sliding bearing surface can be designed to be continuously closed in the axial direction. However, the sliding bearing surface can also be designed with one or more interruptions in the axial direction. An axially continuous plain bearing surface is easy to produce in terms of manufacturing technology. Interruptions in the plain bearing surface are more complex in terms of production technology, but can improve the sliding properties of the plain bearing, for example by a lubricating film of the material to be atomized forming in the interruptions. The interruptions can be formed, for example, as a large number of grooves or grooves in the plain bearing surface.

In order to produce a high degree of angular positional accuracy of the front needle and the rear needle in the sense of coaxiality or concentricity, the material needle advantageously has two axially spaced rocker bearings, each rocker bearing having an outer peripheral bearing surface extending in the axial direction on the front needle or the rear needle and an inner peripheral bearing surface on the rear needle or the front needle, which is associated with the outer peripheral bearing surface and extends in the axial direction, so that the inner peripheral Bearing surface encloses the outer peripheral bearing surface of each tilting bearing, in each case at least partially touching. The two tilting bearings form contact points or surfaces that prevent the front needle from tilting in relation to the rear needle. Due to the tilt bearing, the front needle is statically clearly and tilt-proof compared to the rear needle.

The tilting bearings can expediently be designed as cylinders and a cylinder receptacle assigned to the cylinder, such that the inner peripheral bearing surface forms a cylinder receptacle and the outer peripheral bearing surface essentially forms a cylinder. The cylinder receptacle can be made, for example, as a bore in the front needle or the rear needle. In another embodiment, the cylinder receptacle can also be formed by contact surfaces that bear against the outer peripheral bearing surface in a punctiform or linear manner.

For example, a pin-like projection of the rear needle or the front needle, delimited by a corrugated shoulder, can be used as the cylinder. The cylinder and cylinder seat can be manufactured with a slight interference fit. As a result, there is an interference fit between the front needle and the rear needle, so that the front needle and the rear needle are firmly but releasably connected to one another even when they have been removed from the spray gun. However, this connection can also be realized by an undercut in the front needle or the rear needle, into which a counter-element of the front needle or the rear needle engages.

It is advantageous if one of the tilting bearings is arranged at the axially rear end of the front needle, or if the bearing surfaces of the front or rear needle that form the tilting bearing begin at the height of the axially rear end of the front needle and extend axially over a limited section in the material dispensing direction.

In order to achieve the shortest possible material needle, it is also advantageous if the inner peripheral or the outer peripheral bearing surface of a tilting bearing are also designed as form-fitting elements of the axial form-fitting between the front needle and the rear needle, so the form-fitting elements take on both the function of a tilting bearing and the function of a positive-locking connection. Such positive-locking elements make it possible to secure the connection against unintentional loosening, even when increased forces act on the connection. Such a safety device is important, for example, for use in high-pressure paint spray guns, in which a material is sprayed under pressures of 40 bar to 400 bar, which can result in the high material pressure counteracting the opening of the material valve. In the case of low-pressure spray guns, such a securing of the connection is advantageous, for example, when the front needle becomes wedged or, for other reasons, an increased expenditure of force has to be applied to pull back the front needle.

For a further improvement in the positional accuracy between the front and rear needles, the front needle and/or the rear needle can expediently form at least two form-fitting elements that are axially spaced apart from one another for the axial form-fitting connection between the front needle and the rear needle. In addition, the forces that can be transmitted via the form fit can be increased. High transmission forces also serve to improve the security of the connection between the front and rear needles.

It can also advantageously be provided that the form-fitting elements are arranged in an axially front half of the front needle and—analogously—the rear form-fitting elements are arranged at the level of the front half of the front needle, i.e. essentially at the axial end of the rear needle, in particular at the axially front end the rear needle, are arranged.

It is particularly expedient if the securing means, and in particular the plain bearing surface of the securing means, is formed axially at the level of the front positive-locking elements. The sliding bearing surface is preferably arranged axially between two axially spaced form-fitting elements of the front and rear needles. Positioning the securing means or its plain bearing surface in this way relative to the form-locking elements can produce a force that is essentially vertical (i.e. acting in the radial direction to the axis of the material needle) to secure the axial form-lock between the front and rear needles, and also a uniform force Distribution of this force can be realized on two or more axially spaced-apart form-fitting elements of the pre-needle.

The axial form fit or the connecting section can be arranged at different positions within a spray gun. In one embodiment, the axial form fit or the connecting section can be arranged at the front, viewed relatively, so that they are located within a material-carrying guide channel (paint channel). The entire front needle is preferably located in the guide channel, as a result of which the plain bearing between the sliding surface of the wall of the guide channel and the plain bearing surface of the securing means is partially lubricated by the material itself.

In an alternative embodiment, the axial form fit or the connecting section can be located outside of the material-carrying channel, preferably in a guide channel that is sealed off from the material-carrying channel and is arranged axially behind it. This guide channel, which does not carry material, is also referred to below as a guide bush. The slide bearing formed in the guide bush can then be lubricated, for example, by means of a separate lubricant. This solution has the advantage that the entire section of the material needle located in the material-carrying channel is formed by the front needle, and therefore no flow resistance of the detachable connection, such as that represented by the securing means, impede a material flow. Furthermore, the entire part of the material needle that comes into contact with the material can be cleaned by simply removing it.

In an expedient embodiment, the front needle has guide surfaces for forming a second plain bearing with the wall of the guide channel. The second plain bearing is located at a different axial position than the first plain bearing formed by the plain bearing surface and the sliding surface. This ensures the coaxial alignment of the front needle and/or the rear needle and reduces the tendency of the material needle to vibrate.

The guide surface of the second plain bearing is advantageously twisted radially relative to the plain bearing surface of the first plain bearing, ie it assumes a radial position (angular position) that differs from the radial position (angular position) of the plain bearing surface. It is advantageous if the form-fitting elements of at least the front needle and/or the rear needle are arranged on radially deflectable spring tongues, in particular in such a way that the spring tongues of the front needle do not touch the rear needle in certain areas or over the entire axial length when connected, or that in the case of The spring tongues arranged on the rear needle do not touch the front needle, preferably only the positive-locking elements arranged at the ends of the spring tongues and the opposite area of the front needle or rear needle touch. A radial elasticity of the front needle or the rear needle can be increased in some areas via the spring tongues and, for example, a release of the axial form fit can be facilitated. The spring tongues can be produced, for example, by making longitudinal slots or recesses in a closed circular cylindrical lateral surface of the front needle and/or the rear needle.

It is possible that the axial form fit between the front needle and the rear needle is prestressed in the radial direction, in particular by forming a pairing of the front form-fitting elements with the rear form-fitting elements as an interference fit. As a result, there is a release safeguard between the front needle and the rear needle, which prevents the front needle from detaching or falling off the rear needle when the safety device is lifted, for example in a maintenance state for replacing the front needle. Otherwise it is also possible to ensure this by means of a corresponding rigidity of the spring tongues, without the need for an interference fit. In addition, the positive-locking elements can be designed in such a way that a tactile and/or acoustic feedback is produced when the front needle is connected to the rear needle.

The axial form fit between the front and rear needles can be designed to be self-locking or non-self-locking with respect to an axial tensile force in a release direction. The axial form fit is expediently not designed to be self-locking, so that the form fit can be released simply by applying an axial tensile force. In contrast to, for example, self-locking clip connections, cumbersome loosening operations, in which a form fit has to be levered out with a tool, can be avoided.

A form fit that is not self-locking can be implemented in particular via a force converter acting between the front and rear needles. Under one suggested here A force translator is a mechanical effective surface pair, in which an introduced axial tensile force is at least partially converted into a radially acting force, which causes the form-fitting connected form-fitting elements of the axial form-fitting between the front and rear needle to be lifted from each other. The force translator can be implemented, for example, in the form of an inclined surface that deflects the adjacent area of the front or rear needle in a radial direction during a movement in the axial direction and thus serves to translate an axial force component into a radial force component. As a result, the smooth running of a release process can be advantageously influenced.

In one embodiment it can be provided that the securing means is radially elastically deformable, in particular through a recess located in the securing means and/or an opening located there. As a result, the first plain bearing can be slightly radially braced between the plain bearing surface and the sliding surface of the guide channel. This allows improved centering with only a slight increase in the frictional forces in the plain bearing.

Another aspect of the invention relates to a front needle for the material needle described above, the front needle having a needle tip forming a valve seat and a connecting section with front positive-locking elements for detachable connection to a rear needle. The front needle is characterized in that the front needle comprises, at the level of the connecting section, a radially projecting securing means having a sliding bearing surface for introducing radially acting forces onto the connecting section.

The features described in connection with the material needle can be transferred to the front needle.

The invention also relates to a rear needle of the material needle described above with the features mentioned in relation to the rear needle.

In particular, the above statements should not be understood to mean that the invention should be limited to a material needle that includes a front needle and a rear needle. Both the front needle and the rear needle can form independent objects of the invention. Furthermore, the material needle can also be made up of more than two parts, which in particular can be separated from one another. According to yet another aspect of the invention, a paint spray gun with a material needle mounted in the paint spray gun, as described above, is proposed. The paint spray gun includes a material nozzle (nozzle) with a nozzle orifice defining an axis. The material needle extends along a longitudinal axis. The longitudinal axis of the material needle and the axis of the nozzle opening coincide. The spray gun comprises a guide channel which extends in the direction of the axis of the nozzle opening and in which the material needle runs at least in sections. The material needle can be moved axially along the longitudinal axis to open or close the nozzle opening within a defined needle stroke in the guide channel. The guide channel has a sliding surface facing the axis of the nozzle opening and forms an axial sliding bearing with the sliding bearing surface of the securing means of the material needle to ensure the axial form fit between the front needle and the rear needle.

It can be advantageous to form the sliding surface of the guide channel from a first material and the sliding bearing surface of the securing means from a second material that is different from the first material. In particular, the guiding channel can be formed from a metal or a metal alloy, while the sliding surface is formed from an engineering plastic. As a result, abrasion effects can essentially be limited to the front needle, which serves as a wearing part. On the other hand, a part forming the sliding surface or the entire front needle can consist of a particularly abrasion-resistant material such as a metal alloy suitable for this purpose or a technical ceramic. On the other hand, only the tip of the needle or the front part of the front needle can consist of such a material.

The invention also relates to a first method for exchanging a front needle of a material needle mounted in a spray gun with a longitudinal axis, this longitudinal axis coinciding with an axis of the nozzle opening defined by a nozzle opening of a material nozzle. The longitudinal axis defines a radial direction which extends circumferentially perpendicular to the longitudinal axis. The material needle comprises an axially front front needle and an axially rear rear needle, which are detachably connected to one another via an axially extending connecting section in order to transmit axial forces. The spray gun has a extending in the direction of the axis defined by the nozzle opening guide channel in which the material needle axially to the longitudinal axis for release or for Closure of the nozzle opening is displaceable in an operating mode for spraying paint or another liquid within a defined Nadelhubes and wherein the guide channel clearly defines a radial position of the connecting portion. The axially extending connecting section of the material needle is located at least in sections in the guide channel when the material needle is within the defined needle stroke. The material needle can be moved beyond the defined needle stroke in a maintenance mode (maintenance state) to replace the front needle, so that the connecting section is outside of the guide channel, with the front needle and the rear needle being able to be separated from one another only and precisely when the connecting section is outside of the guide channel. The following steps must be carried out to replace the front needle: a) axial displacement of the material needle beyond the defined needle stroke up to a point at which the connecting section lies outside the guide channel, b) loosening the front needle from the rear needle by applying an axial tensile force to the front needle , c) connecting the same or another front needle to the rear needle at the connecting section by pushing the same or another front needle onto the rear needle and d) axially pushing in the material needle up to a point at which the connecting section lies within the guide channel.

Preferably, an intermediate step is performed between releasing and connecting the same or another front needle to the rear needle. This can involve cleaning the front needle and/or choosing a different front needle, preferably an unused one.

If necessary, components of the spray gun closing the guide channel axially and/or axial stop surfaces impeding the axial movement of the material needle, such as an air cap, must be removed from the spray gun in order to carry out the method.

The spray gun can advantageously be designed in such a way that the material needle is axially displaced backwards beyond the defined needle stroke up to a point at which the connecting section lies outside of the guide channel. This is achieved, for example, in that the guide channel is open to the rear is carried out and / or one or more components are provided which impede a backward movement of the material needle and are detachably attached to the spray gun and preferably provide an end stop for the rear end of the rear needle s.

In another, second method for replacing a front needle of a material needle mounted in a paint spray gun with essentially the same structure as described in connection with the first method, - instead of removing the connecting section of the material needle from the guide channel by axially displacing the material needle from the guide channel move - be provided to remove the guide channel from the spray gun and thereby cancel the slide bearing between the slide bearing surface of the securing means and the sliding surface of the guide channel, so that the securing of the axial form fit is canceled.

To do this, the following steps in particular must be carried out: a) Axial removal of the guide channel to release the slide bearing surface of the front needle, b) Removal of the front needle from the rear needle by applying an axial tensile force to the front needle, c) Attaching the same or another front needle to the rear needle, and c ) Reattachment of the same or a different guide channel.

Analogously to the first method, an intermediate step is carried out between releasing and connecting the same or another front needle to the rear needle. This can involve cleaning the front needle and/or choosing a different front needle, preferably an unused front needle.

The invention is described below by way of example using the enclosed set of figures, with the explanations being to be understood equally in relation to a front needle according to the invention, a material needle according to the invention and a paint spray gun according to the invention as well as the method according to the invention. show it

1 shows a perspective view of a first spray gun according to the invention in an operating state A,

FIG. 2A shows the spray gun from FIG. 1 in a longitudinal section,

FIG. 2B shows a detailed view of a front section of the spray gun from FIG. 2A,

3 shows a front section of a material needle according to the invention of the spray gun from FIG. 1 in a perspective view,

4 shows a front section of a rear needle of the paint spray gun from FIG. 1 in a perspective view,

5A shows a longitudinal section through a guide channel of the spray gun from FIG. 1 in operating state A,

5B shows a longitudinal section rotated by 45° about the longitudinal axis in relation to FIG. 5A,

6 shows a section of the longitudinal section according to FIG. 2 without the air cap and duct component in a maintenance state B of the spray gun,

7 shows an illustration analogous to FIG. 6 with a front needle and an air cap and channel component to be attached,

8 shows a second spray gun according to the invention in a perspective view in an operating state A,

9 shows a perspective view of a paint channel of the spray gun according to FIG. 8 and a material needle inserted therein,

10 shows a front needle according to the invention of the paint spray gun from FIG. 8 in a perspective view,

11 shows a longitudinal section of the color channel from FIG. 9,

Fig. 12 shows a cross section through the color channel according to section A-A from Fig. 11,

FIG. 13 shows a rear needle for the spray gun from FIG. 8 in a perspective view

Opinion,

14 shows an alternative front needle for the spray gun from FIG. 8 in a perspective view,

15 shows a third spray gun according to the invention in a sectional view in an operating state A,

16 is a perspective view of a connecting portion between a front needle and a rear needle connected to the front needle for the paint spray gun of FIG. 15;

FIG. 17 shows a detail of the longitudinal section from FIG. 15, 18 shows the longitudinal section according to FIG. 17 in a maintenance state B, in which an air cap, a duct component and a rear part have been removed,

19 shows a section of the longitudinal section from FIG. 17 with a material needle in an operating state A, in which the connecting section is located inside the guide channel, and FIG

20 shows a section of the longitudinal section from FIG. 18 with a material needle in a maintenance state B, in which the connecting section is located outside the guide channel.

Figures 1 to 7 show a first embodiment of the invention. Shown is a spray gun 1 designed as an air-assisted high-pressure spray gun with a compressed air connection L and a material connection S. Paint under pressure of, for example, 100 bar is fed into a paint channel F′ via the material connection S and is discharged via a nozzle 2 or a nozzle opening 2′. of the spray gun 1 delivered. Due to the pressure, the paint is atomized immediately upon exiting the nozzle opening 2'. The shape of the emitted paint jet can be adjusted via air outlet openings 18' of an air cap 18. Horns 25 can be provided on the air cap for this purpose. These can protrude from the air cap in the material discharge direction M, as can be seen from FIG. 8, for example. Air outlet openings 18' can be provided on the horns, which are directed from the outside in the radial direction inwards towards the extended axis X' of the nozzle opening. The air released at these air outlet openings 18 ′ is sometimes also referred to as horn air and can be regulated via the adjusting screw 21 and/or the lateral adjusting screw 23 . Furthermore, air outlet openings 18′ can be provided directly on the air cap, which are diametrically opposite with respect to the axis X′ of the nozzle opening and are used to transport the atomized material in the material discharge direction M and, if necessary, to shape the jet. In addition, an annular gap 26 shown in FIG. 8 can also be provided, which surrounds the material nozzle and from which compressed air exits, which is used for atomization or to support atomization.

A material needle 3 is mounted so that it can be displaced axially along the longitudinal axis X of the material needle 3 in the paint channel F′, which is designed as a circular cylinder and as a hollow cylinder, of the paint spray gun. The longitudinal axis X coincides with the axis X' of the color channel F'. The longitudinal axis X defines a radial direction R perpendicular to the longitudinal axis. In the normal state, the material needle 3 is preloaded by a counteracting element 11 designed here as a spring, as can be seen from Fig. 2 A, among other things, with an axial pretensioning force acting in a material dispensing direction M and closes the nozzle opening 2' or an upstream one with a needle tip 16 valve seat.

To dispense paint from the nozzle opening 2', a trigger element 20 of the paint spray gun 1 is actuated manually, via which the material needle 3 is displaced axially backwards over a defined needle stroke to release the nozzle opening 2'.

The material needle 3 is essentially in two parts, with an axially front front needle 4 and a rear needle 5 connected to the front needle 4 along a connecting section V. The front needle 4 and rear needle 5 are connected to one another via an axial form fit.

The form fit is formed by interlocking form fit elements 6a and 6b attached to the front needle 4 and the rear needle 5, respectively. The form-fitting elements 6b of the rear needle 5 in the exemplary embodiment shown here are two form-fitting elements 6b that are spaced apart axially and are designed as circumferential annular grooves on a front end of the rear needle 5' and have a concave cross-section, as can be seen from the illustration of a front section of the rear needle 4 can be seen from FIG. Form-fitting elements 6a of the front needle 4, which are arranged diametrically opposite one another and are convex in cross section but do not extend over the entire circumference of the front needle 4, engage in these annular grooves, as can be seen from FIG. 3, among other things. The positive locking elements 6a are attached to a radially deflectable spring tongue 14 of the front needle 4 so that the positive locking can be canceled by the positive locking elements 6b of the rear needle 5 by applying an axial tensile force to the front needle 4 .

Since the form-fitting elements 6a and 6b are concave-convex, the form-fitting elements 6a and 6b form a force converter which causes tensile forces applied in the axial direction into radial deflection forces to lift the form-fitting elements 6a from the form-fitting elements 6b. In other words, the form fit designed in this way not designed to be self-locking and not designed to be detachable without a deflection of the spring tongue 14 in the radial direction R.

The form fit can be produced by sliding the front needle 4 axially onto the rear needle 5 or by axially pulling the front needle 4 off the rear needle 5 .

In order to prevent the axial form fit from being canceled in an operating state A of the paint spray gun, the front needle 4 has a wing-like securing means 7 which protrudes radially from the spring tongue 14 . The securing means 7 has radially on the outside a slide bearing surface 8 which is arcuate in the axial direction and shown in FIG. In the operating state A, the plain bearing surface 8 and the sliding surface 9' form an axial plain bearing 10 for axial-radial guidance of the front needle 4, ie for defining a radial position of the front needle 4 relative to the guide channel F'. The securing means 7 thus serves on the one hand to secure the axial form fit and on the other hand the positional orientation of the front needle, ie the concentric alignment of the front needle 4 in the guide channel F'.

The slide bearing 10 formed in this way prevents the spring tongue 14 from deflecting radially and thus prevents the form-fitting elements 6a from lifting off from the form-fitting elements 6b. The corresponding contact of the sliding bearing surface 8 against a section of the wall 9 of the guide channel F', the sliding surface 9', can be seen, for example, in FIG. 5A.

Such an improved positional accuracy of the front needle 4 allows the needle tip 16 to be positioned more precisely in relation to the nozzle opening 2' or the valve seat. This leads to less and in particular more even wear and thus a longer service life of the front needle 4 and a more even spray pattern of the spray gun 1.

In addition, in the exemplary embodiment shown here, the securing element 7 is designed to be “soft” in a radially elastic manner, namely web-like and with an opening O located in the securing element 7 or at least one recess, see for example Figure 5B. Preferably, the securing element 7 becomes radial when it is inserted into the guide channel F slightly prestressed and initiates corresponding radially acting forces in the axial form fit. On the other hand, a small amount of play can also be provided between the securing element 7 and the channel wall 9, with the forces acting radially on the channel wall 9 only beginning to act when the spring tongues 14 are released by slightly opening the connection between the front needle 4 and the rear needle 5 via the interaction of the form-fitting elements 6a and 6b, are deflected in the radial direction R. In this way, improved protection of the form-fit against radial deflection and, in particular, an additional, friction-locked connection in the pairing of the form-fitting elements 6a and 6b can be implemented.

Operating state A is understood to be a state of the paint spray gun 1 in which the paint spray gun 1 is ready for dispensing paint or another liquid from the nozzle opening 2' and in which in particular the slide bearing surface 8 and the slide surface 9' are in contact .

For a coaxiality of the front needle 4 in relation to the rear needle 5 that is as consistent as possible, which can be described via the front needle axis Xv and the rear needle axis XH, the material needle 3 has two tilting bearings, namely an axially front tilting bearing 12a and an axially rear tilting bearing 12b, which prevent tilting of the front needle 4 (Front needle axis Xv) against the rear needle 5 (rear needle axis XH).

The rear rocker bearing 12b is formed by an outer peripheral bearing surface 12b" of the lateral surface of a front end of the rear needle 5, which is formed by an inner peripheral bearing surface 12b', an inner surface of an end sleeve section at the rear end of the front needle 4. The front rocker bearing 12a is formed by the form-fitting elements 6a and 6b.

The tilting bearings 12a, 12b, which are axially spaced apart from one another, thus form, via their bearing surfaces, support points which prevent the front needle axis Xv from tilting relative to the rear needle axis XH.

The overlapping portion of the front needle 4 and the rear needle 5 between the axially front end of the rear needle 5' and the axially rear end of the front needle 4' forms the connecting portion V. In addition, on the connecting section V of the fore-needle 4, here a guide sleeve of the fore-needle 4 designed as a hollow cylinder and forming the bearing surface 12b', another guide surface 13 is formed on a protruding wing, projecting radially, which in combination with the channel wall 9 of the guide channel F' second slide bearing 10 'forms. The guide surface 13 is arranged at a different angular position in the circumferential direction U relative to the plain bearing surface 8 of the securing means 7 . This angular position is rotated by approximately 45° relative to a radial position (circumferential direction) of the plain bearing surface 8 . The plain bearing surface 8 thus defines a first radial position of the front needle 4 , while the guide surface 13 defines a second radial position of the front needle 4 . As a result, the front needle 4 is supported in the guide channel F' in a statically unambiguously determined manner. A corresponding contact of the guide surface 13 with the wall 9 of the guide channel F' can be seen from FIG. 5B, which shows a longitudinal section rotated by 45° compared to that in FIG. 5A. As an alternative to the second plain bearing 10', an extended first plain bearing 10 can also be provided in order to ensure security against tipping. Such a sliding bearing is shown, for example, in FIGS. In this case, the first slide bearing 10 is preferably longer in the longitudinal axis than the diameter of the material needle 3 at the slide bearing point, preferably twice or three times the length of the diameter.

In summary, the front needle 4 can be subdivided accordingly into three functional sections, namely the guide sleeve at the axially rear end of the front needle 4 to form a tilting bearing 12b, spring tongues 14 adjoining axially in the material dispensing direction M, and on the radially inner side the form-fit elements 6a for forming an axial form-fit with the rear needle 5 and at the same time the bearing surface 12a' of the first tilting bearing 12a as well as a securing means 7 with a plain bearing surface 8 for forming the plain bearing 10 are arranged on the outside, and finally a front needle head adjoining the spring tongues 14 in the direction of material delivery, on which a valve (needle valve ) serving needle tip 16 for opening and releasing the nozzle 2 is formed.

In summary, the rear needle 5 has two at the axially front end of the rear needle 5'

Annular grooves (positive locking elements 6b) to form the axial positive locking and the Bearing surface 12a", following in the opposite direction to the material dispensing direction, the rear needle 5 has a bearing surface 12b' for forming the tilting bearing 12b.

In order to increase the service life, the needle tip in this exemplary embodiment is designed in several parts, here with a ball made of a hard metal or a technical ceramic that is introduced into the needle tip as a separate component. The rest of the front needle 4 is made here from a fiber-reinforced engineering plastic, a ceramic or a metal alloy. The rear needle 5 is made of a metal, a metal alloy or a ceramic. As a result, signs of wear are essentially limited to the replaceable front needle 4, so that regular replacement of the rear needle 5 can be avoided.

In order to replace the front needle 4, the spray gun can be put into a maintenance state B shown, for example, in FIG. The maintenance state B can be defined as that state of the spray gun 1 in which the contact between the plain bearing surface 8 and the sliding surface 9' is eliminated.

In the embodiment shown here, maintenance condition B is established by removing an air cap 18 and a channel component 17 forming the guide channel F' Rear needle 5 is no longer secured, so that the front needle 4 can be pulled off the rear needle 5 by axial pulling forward (to the left in the plane of the drawing) with radial elastic deflection of the tongue 14 . The removed front needle 4 can be exchanged for a new front needle and pushed onto the rear needle 5 until an axial form fit of the form-fitting elements 6a, 6b is restored. Subsequently, first the duct component 17 and then the air cap 18 are mounted again on the spray gun or the base body 30 of the spray gun 1 .

The rear needle 5 can remain in the spray gun 1 for replacement and does not have to be loosened, loosened or removed from the spray gun 1 in any other way. A corresponding configuration of the paint spray gun 1 enables quick, simple and above all tool-free cleaning or such an advantageous exchange of a front needle 4 .

The rear needle 5 is mounted circumferentially over the entire circumference of the needle shaft of the rear needle 5 via a guide bushing F" located axially behind the color channel F'. The guide bushing F" is sealed off from the color channel F' by sealing elements D. The radial position of the rear needle 5 is clearly defined via the guide bushing F".

8 to 12 a second embodiment of the invention is shown.

Insofar as the same or similar components are provided with the same or similar reference symbols for the second and subsequent embodiment variants of the invention, reference is made to the previous statements and only the essential differences are emphasized and explained.

The paint spray gun 1 shown in the second exemplary embodiment is a low-pressure paint spray gun 1 in a paint-flow cup variant, in which paint can be introduced into the paint channel F' by gravity via a paint-flow cup that can be attached to the material connection S and via the material nozzle 2 or its nozzle opening 2 ' is sprayable. In contrast to the high-pressure paint spray gun of the first embodiment, the paint is not fed under high pressure into the paint-carrying guide channel F' and atomized under pressure, but is entrained and thereby atomized by a separate air stream, which exits as atomizing air at the annular gap 26 near the nozzle opening .

The second exemplary embodiment differs in addition to the different design of the dye feed S, the nozzle 2 and the compressed air distribution via differently arranged and designed air outlet openings 18' with regard to the valve seat and the needle tip 16 forming the valve head, which is needle-shaped here, i.e. conically pointed tapering end, cf. in particular Fig. 10.

A further difference relates to the design of the second section of the front needle 4, which is arranged between the needle tip 16 and the second tilting bearing 12b in the first embodiment, it is not open at the side and has a spring tongue 14 - but is closed around the circumference, so that the fore-needle 4 has essentially a continuous sleeve-like shape from the axially rear end of the fore-needle 4' to the needle tip 16, with the front half of the Fore needle 4 analogous to the first exemplary embodiment, a sliding bearing surface 8 is formed on the radially projecting and wing-like securing means 7 . On the inside, as in the first exemplary embodiment, positive-locking elements 6a, which can only be seen in the figures with longitudinal sections, are formed pointing radially inwards.

The rear needle 5 shown in FIG. 13 is designed in the same way as the first exemplary embodiment, i.e. analogously to FIG. 4.

Due to the sleeve-like design of the front needle 4, the elasticity in the radial direction R or the deflectability of the form-fit elements 6a is reduced compared to the first exemplary embodiment and made stiffer, so that slightly higher axial forces are required to release the axial form-fit. As a mixed form of both configurations, the lateral recesses of the first configuration, which are provided for easier deflection of the spring tongues in the radial direction R and run in the direction of the longitudinal axis X, can also have a different shape, different length and/or width or different depth and, for example, not be designed to penetrate be.

However, the function of securing the axial form fit in the operating state (FIG. 11) via the slide bearing 10 between the wall 9 of the guide channel F' and the slide bearing surfaces 8 of the securing means 7 are comparable. Here, too, the front needle 4 can be exchanged by removing the channel nozzle component 17 in the axial direction, exchanging the front needle and then reapplying the guide channel 17 .

In the cross-sectional representation of FIG. 12 according to section AA from FIG. 11, the cross-sectional design of the securing means 7 and the associated plain bearing surface 8 can be seen. In particular, it can be seen that the securing part 7 does not extend over the entire circumference of the guide channel F′ but only in sections, here for example over an angular range of a few degrees, on the wall 9 of the guide channel F′. As a result, paint can flow axially past the securing means 7 laterally, approximately unhindered, via interruptions 8 ′ in the securing means 7 . Furthermore, the reference numerals 7', 8" and 10" indicate that, in addition to the securing means 7 with the slide bearing surface 8, the forehand needle comprises a diametrically opposite second securing means 7' with an associated slide bearing surface 8, which has a second opposite slide bearing 10" with the wall 9 of the guide channel F' forms.

However, instead of a front needle 4 with two securing means 7, 7', any other preferably radially symmetrical arrangement of a plurality and in particular exactly three securing means 7 with corresponding three plain bearing surfaces 8 is also conceivable.

13 and 14 show a variant of the second embodiment of FIG of the guide sleeve forming the tilting bearing 12b and the needle tip 16 is open at the side. The use of a spring tongue 14 can be made dependent on whether or which pretensioning forces are to be implemented in the form fit between the form fit elements 6a, 6b and how high the release forces are to be designed to cancel the axial form fit, i.e. the pulling of the front needle 4 from the rear needle 5 . Otherwise, reference is made to the statements relating to the previous configurations, which can be applied analogously to this configuration.

15 to 20 show a third exemplary embodiment of a spray gun according to the invention with a material needle 3 according to the invention, which is designed as a high-pressure spray gun analogously to the spray gun 1 of the first exemplary embodiment. In this regard, reference is made to the statements on the first exemplary embodiment, which can be applied analogously to this embodiment.

The third exemplary embodiment differs from the first exemplary embodiment essentially in the arrangement and design of the connecting section V. In the third exemplary embodiment, the front needle 4 is also connected to the rear needle via an axial form fit, which is formed by form-fitting elements 6a, 6b of the front needle 4 and the rear needle 5, respectively. The positive-locking elements 6b are, however, designed as latching projections on a fork-shaped front end with two spring tongues 14 End 'of the rear needle 5' is formed, which engage in a circumferential annular groove at the axially rear end of the front needle 4', the annular groove representing the positive-locking elements 6a.

Unlike in the first exemplary embodiment, the front, essentially cylindrical end of the rear needle 5' forms the securing means 7, with a lateral surface of the cylindrical end of the rear needle 5' forming the slide bearing surface 8. The lateral surface is mounted in a guide channel F, which is designed as a guide bushing F" for the cylindrical front end of the rear needle 5'. The inner lateral surface of the guide bushing F" forms the counter-bearing surface required for the plain bearing 10 in the form of the sliding surface 9'. Here, too, the axial form fit is secured against cancellation via the sliding bearing 10 as long as the connecting section V between the front and rear needles 4, 5 is within the guide channel F".

The safety device is unlocked by moving the connecting section V of the material needle along the longitudinal axis of the material needle X, counter to the material dispensing direction M. The material needle is pushed in this direction until a point is reached at which the connecting section V is outside the guide channel F ", which removes the security. This state indicates a maintenance state B.

Depending on the design of the spray gun 1, it may be necessary - as indicated here in FIGS. 17 and 18 - to remove a rear part 22 of the spray gun 1 in order to release the material needle 3 in the opposite direction to the material M, i.e. axially to the rear. to be able to move until the point where the safety is released is reached. Only in this state is the securing of the axial form fit, ie the plain bearing 10, canceled and the front needle 4 can be removed from the rear needle 5 by applying an axial tensile force axially forward and replaced with a new front needle. In order to facilitate this process, the front needle 4 can have a shoulder 24 in the area which is in the operating state A in the material-carrying guide channel F', on which the circumference of the front needle 3 widens from the back to the front. The shoulder 24 can be designed in such a way that after the safety device has been released and the material needle 3 has been pulled back further, it abuts against a wall in the material-guiding channel F′, the connection between the front needle 4 and the rear needle 5 being released as the needle is pulled back further. Also In the third exemplary embodiment, it is necessary to remove an air cap 18 and a channel component 17 forming the color channel F' before the front needle 4 is removed.

In addition, the rear part 22 can also serve as a material quantity regulator, with which the maximum material quantity dispensed can be set. In this case, the rear part 22 in operating state A forms a stop for the rear end of the rear needle 5", which, when the material needle is maximally deflected counter to the material dispensing direction M, i.e. when the trigger element 20 is fully pulled off, abuts against an inner surface of the rear part 22. If this stop or the The rear part 22 itself is displaced in the opposite direction to the material delivery direction M, the material needle can be further deflected in the opposite direction to the material delivery quantity M, as a result of which the material valve can be opened further and a larger quantity of material can be delivered. If the rear part is shifted in the opposite direction, i.e. in the material direction, the maximum The rear part preferably has an adjustment mechanism that allows a translatory movement relative to the longitudinal axis X of the material needle 3, which preferably takes place via a rotary movement in or against the circumferential direction and preferably in the manner of a helical gear. Such a material quantity regulation is preferably used in air-atomizing low-pressure paint spray guns according to FIGS. 8 to 14. However, these air-atomizing low-pressure paint spray guns can also be designed in a single-axis design according to FIGS. 1 to 7 and , the material valve or the material needle preferably being designed according to FIGS.

As can be seen in particular from FIG. 20, an axially rear tilting bearing 12b in the material needle 3 is formed by a pin-shaped, cylindrical rear end of the front needle 4, with the opposite receiving opening of the rear needle 12b" being received, preferably with a slight oversize fit. A second, The rocker bearing 12a, which is axially further forward in the material discharge direction M, is formed by the form-fitting elements 6b in the form of the locking projections, in interaction with the form-fitting elements 6a, in the form of the circumferential annular groove.The spring tongue 14 of the rear needle 5 touches the rocker bearing 12a between the first and the second or 12b located section of the front needle 4. In this way, a statically unambiguously determined position of the front needle relative to the rear needle can be achieved. In all figures except FIG. 12, only one securing means 7, one spring tongue 14, etc. is shown for reasons of clarity, but this should not be understood to mean that only exactly one securing means 7, one spring tongue, etc. is provided, but rather that at least one securing means 7, a spring tongue 14, etc., but expediently several such functional elements are provided. As can be seen from FIGS. 1 to 7, in the exemplary embodiment illustrated therein, two diametrically opposite spring tongues 14, two diametrically opposite securing means 7 and two diametrically opposite positive-locking elements 6a are provided. A different circumferential distribution of, for example, three or more elements is also possible, insofar as the material flow in the material delivery direction M continues to be guaranteed by the distribution and number of elements.

The invention presented here makes it possible to easily and simply manufacture a front needle that is inexpensive to produce with a rear needle for use in a paint spray gun, which ensures excellent positional accuracy between a guide channel and the front needle and between a front needle and a rear needle.

Preferred exemplary embodiments of the invention are described merely by way of example on the basis of the figures and the above statements. Other designs, materials or types of connection are conceivable and will become apparent to the person skilled in the art when reading the statements and the prior art. All of the individual features of the exemplary embodiments can be combined with one another, even if this is not explicitly mentioned. This also applies to the exemplary embodiments themselves. The person skilled in the art clearly recognizes when a combination is not possible or makes no sense. All of the configurations can be applied to different types of spray guns, even if this is not explicitly described.

The invention described can be applied to all types of spray guns, even if they do not fall within the above categorization. In particular, the uniaxial spray guns shown in the drawings 1 to 7 and 15 to 20 can also be equipped with a material valve according to FIGS. 9 to 11 and 13 and 14, preferably as a low-pressure spray gun. Furthermore, the connection between the front needle and the rear needle of FIGS. 1 to 7 and 9 to 14 can be made with a connection be combined according to Figures 15 to 20. The connection of FIGS. 15 to 20 can also be used in a paint spray gun according to FIGS. 1 to 19.

Claims

Expectations 1. Material needle (3) extending along a longitudinal axis (X) for a spray gun (1) with a material nozzle (2), the material needle (3) being insertable in a guide channel (F) of the spray gun (1) and being insertable along a longitudinal axis ( X) can be displaced with a defined needle stroke to open and close a nozzle opening (2') of the material nozzle (2), the material needle (3) comprising an axially front front needle (4) and an axially rear rear needle (5), and wherein the The front needle (4) and the rear needle (5) are detachably connected to one another via an axial form fit for conducting axial forces, the axial form fit being provided by front form-fitting elements (6a), which are arranged on the front needle (4), and by rear form-fitting elements ( 6b), which are arranged on the rear needle (5), is formed, with the front and/or the rear form-fitting elements (6a, 6b) for canceling the axial form-fitting in a direction perpendicular to the longitudinal axis (X). ung (R) can be elastically deflected, characterized in that the axial positive locking is secured against cancellation by a securing means (7) which prevents the front and/or rear positive locking elements (6a, 6b) from being deflected perpendicularly to the longitudinal axis (X), wherein the securing means (7) comprises an external sliding bearing surface (8) of the front needle (4) and/or the rear needle (5) for positive interaction with a corresponding sliding surface (9') of the spray gun (1). 2. Material needle (3) according to one of the preceding claims, characterized in that the plain bearing surface (8) is rounded in the direction of the longitudinal axis (X). 3. Material needle (3) according to one of the preceding claims, characterized in that the sliding bearing surface (8) is rounded in the circumferential direction (U). 4. Material needle (3) according to one of the preceding claims, characterized in that the maximum static friction force between the plain bearing surface (8) of the front needle (4) and/or the rear needle (5) and the sliding surface (9') of the channel (F) of the spray gun (1) is smaller than the force that a counter-actuating element (11) exerts in the material delivery direction (M) on the material needle (3) in the direction of the longitudinal axis (X) and counteracts the needle stroke. 5. Material needle (3) according to one of the preceding claims, characterized in that the sliding bearing surface (8) is continuously closed in a circumferential direction (U) of the sliding bearing (10) or is formed with interruptions (8'). 6. Material needle (3) according to one of the preceding claims, characterized in that the plain bearing surface (8) along the longitudinal axis (X) is continuously closed or is designed with interruptions (8'). 7. Material needle (3) according to one of the preceding claims, characterized in that the front needle (4) and the rear needle (5) are axially spaced from each other by at least two to ensure coaxial alignment of a front needle axis (Xv) and a rear needle axis (XH). Tilting bearings (12a, 12b) are connected to one another, each tilting bearing (12a, 12b) having an outer peripheral bearing surface (12a", 12b") of the front needle and/or the rear needle (4, 5) extending along the longitudinal axis (X) and an inner peripheral bearing surface (12a ¹ , 12b') of the rear needle and/or the front needle (4, 5) extending along the longitudinal axis (X), wherein the inner peripheral bearing surface (12a ¹ , 12b') surrounds the outer peripheral bearing surface (12a ", 12b") touchingly encloses. 8. Material needle (3) according to one of the preceding claims, characterized in that at least one of the tilting bearings (12a, 12b) is designed as a cylinder-cylinder receptacle, the inner peripheral bearing surface (12a', 12b') being a cylinder receptacle and the outer peripheral bearing surface ( 12a", 12b") forms a cylinder. 9. Material needle (3) according to one of the preceding claims, characterized in that a tilting bearing (12a, 12b) is arranged at the axially rear end (4') of the front needle (4). 10. Material needle (3) according to one of the preceding claims, characterized in that the inner peripheral or the outer peripheral bearing surface (12a ¹ , 12b ', 12a', 12b'') of a tilting bearing (12a, 12b) at the same time as the form-fitting elements (6a, 6b) of the axial form fit between the front needle (4) and the rear needle (5). 11. Material needle (3) according to one of the preceding claims, characterized in that the front needle (4) and the rear needle (5) each have at least two axially spaced form-fitting elements (6a, 6b) for the axial form-fitting between the front needle (4) and the rear needle (5). 12. Material needle (3) according to one of the preceding claims, characterized in that the front form-fitting elements (6a) are arranged in a front half of the front needle (4). 13. Material needle (3) according to one of the preceding claims, characterized in that the plain bearing surface (8) is formed axially at the level of the front form-fitting elements (6a). 14. Material needle (3) according to any one of the preceding claims, characterized in that the slide bearing surface (8) is arranged axially between two axially spaced form-fitting elements (6a). 15. Material needle (3) according to one of the preceding claims, characterized in that the rear form-fitting elements (6b) are arranged at the axially front end (5') of the rear needle (5). 16. Material needle (3) according to one of the preceding claims, characterized in that the guide channel (F) is a material-carrying guide channel (F ¹ ) and the detachable connection between the front and rear needles (4, 5) within the material-carrying guide channel (F ¹ ) is arranged. 17. Material needle (3) according to one of the preceding claims, characterized in that the guide channel (F) is designed as a non-material-carrying guide bushing (F") and is preferably arranged axially behind a material-carrying guide channel (F ¹ ). 18. Material needle (3) according to one of the preceding claims, characterized in that the front needle (4) form guide surfaces (13) for forming a second plain bearing (10') with the channel wall (9) of the guide channel (F). 19. Material needle (3) according to one of the preceding claims, characterized in that the guide surfaces (13) assume a different radial position from the radial position of the sliding bearing surface (8) of the securing means (7). 20. Material needle (3) according to one of the preceding claims, characterized in that the form-fitting elements (6a, 6b) of the front needle (4) and/or the rear needle (5) are arranged on radially deflectable spring tongues (14), in particular in such a way that the spring tongues (14) of the front needle (4) or the rear needle (5) do not touch the rear needle (5) or the front needle (4) when connected. 21. Material needle (3) according to one of the preceding claims, characterized in that the axial form fit between the front needle (4) and the rear needle (5) is prestressed in the radial direction, in particular by forming the pairing of the front form-fitting elements (6a) with the rear form-fitting elements (6b) as an interference fit. 22. Material needle (3) according to one of the preceding claims, characterized in that the axial form fit between the front and rear needles (4, 5) is not self-locking with respect to an axial tensile force in a release direction, and/or that the material needle (3) has a force converter (15) acting between the front and rear needles (4, 5), in particular in the form of a withdrawal bevel, for converting an axial force component into a radial force component, namely in such a way that the force converter (15) at least partially transfers an axial tensile force that has been introduced into a radial force, which causes the form-fitting connected form-fitting elements (6a, 6b) of the axial form-fitting between the front and rear needles (4, 5) to lift off from one another. 23. Material needle (3) according to any one of the preceding claims, characterized in that the securing means (7) is radially elastically deformable. 24. Front needle (4) for a material needle (3), preferably according to one of the preceding claims, wherein the front needle (4) has a needle tip (16) forming a valve seat and a connection area (V) with front form-fitting elements (6a) for detachable connection a rear needle (5), characterized in that the front needle (4) at the level of the connecting area (V) comprises a radially projecting securing means (7) having a sliding bearing surface (8) for introducing radially acting forces onto the connecting section (V). 25. Spray gun (1) with a spray gun (1) mounted material needle (3), preferably according to one of claims 1 to 23, wherein the spray gun (1) has a material nozzle (2) with an axis (X ¹ ) defining a nozzle opening (2') and the longitudinal axis of the material needle (X) coincides with the axis (X ¹ ) of the nozzle opening (2'), the spray gun (1) having a direction of the axis (X ¹ ) of the nozzle opening (2') ) has an extending guide channel (F), the material needle (3) running at least in sections in the guide channel (F), wherein the material needle (3) can be displaced axially of the longitudinal axis (X) to open or close the nozzle opening (2') within a defined needle stroke in the guide channel (F), and the guide channel (F) is one of the axis (X ¹ ) of the Has a sliding surface (9') facing the nozzle opening (2') to form an axial sliding bearing (10) with the sliding bearing surface (8) of the securing means (7) of the material needle (3) for securing the axial form fit between the front needle (4) and the rear needle (5). 26. Paint spray gun (1) according to claim 25, characterized in that the sliding surface (9') of the guide channel (F) is made of a first material and that the slide bearing surface (8) of the securing means (7) is made of a second material different from the first material consists. 27. A method for replacing a pre-needle (4) of a material needle (3) mounted in a spray gun (1), preferably a spray gun (1) according to one of claims 25 or 26, having a longitudinal axis (X), the longitudinal axis (X ) defines a radial direction (R) perpendicular to the longitudinal axis (X), the material needle (3) comprising an axially front front needle (4) and an axially rear rear needle (5) which are used for the transmission of axial forces via an axially extending connecting section ( V) are detachably connected to one another, the paint spray gun (1) having a material nozzle (2) with a nozzle opening (2') defining an axis (X ¹ ), and the longitudinal axis of the material needle (X) having the axis of the nozzle opening (X ¹ ) coincides, the spray gun (1) having a guide channel (F) extending in the direction of the axis (X ¹ ) defined by the nozzle opening (2'), the material needle (3) being axial to the longitudinal axis (X) for release or for Miscellaneous The end of the nozzle opening (2') can be displaced in an operating mode (A) for spraying paint within a defined needle stroke in the guide channel (F), the axially extending connecting section (V) of the material needle (3) being located at least in sections in the guide channel (F) located when the material needle (3) is located within the defined needle stroke, and the guide channel (F) clearly defines a radial position of the connecting section (V) and the material needle (3) can be moved beyond the defined needle stroke in a maintenance mode (B), see above that the connecting section (V) is outside the guide channel (F), and the front needle (4) and the rear needle (5) can only and precisely then be separated from one another when the connecting section (V) is outside the guide channel (F). , comprising the steps: a) axial displacement of the material needle (3) beyond the defined needle stroke up to a point at which the connecting section (V) lies outside of the guide channel (F), b) releasing the front needle (4) from the rear needle (5), c) exchanging the front needle (5) for another front needle (4) or reinserting the same front needle (5) and connecting the front needle (4) to the rear needle (5) at the connecting section (V ), d) axially pushing in the material needle (3) up to a point at which the connecting section (V) lies within the guide channel (F). 28. The method according to claim 27, characterized in that the axial displacement of the material needle (3) beyond the defined needle stroke up to a point at which the connecting section (V) lies outside of the guide channel (F) takes place in the axial direction backwards . 29. A method for replacing a pre-needle (4) of a material needle (3) mounted in a spray gun (1), preferably a spray gun (1) according to one of claims 25 or 26, having a longitudinal axis (X), the longitudinal axis (X ) Defines a radial direction (R) perpendicular to the longitudinal axis (X), the material needle (3) comprising an axially front front needle (4) and an axially rear rear needle (5) which are used to transmit axial forces via an axial extending connecting section (V) are detachably connected to one another, the paint spray gun (1) having a material nozzle (2) with a nozzle opening (2') defining an axis (X ¹ ), and the longitudinal axis (X) of the material needle (3) having the Axis (X ¹ ) of the nozzle opening (2') coincides, the spray gun (1) having a guide channel (F) extending in the direction of the axis (X ¹ ) defined by the nozzle opening (2'), the material needle (3) is displaceable axially of the longitudinal axis (X) for opening and closing the nozzle opening (2') in an operating mode (A) for spraying paint within a defined needle stroke in the guide channel (F), and the front needle has a plain bearing surface (8) which forms an axial plain bearing (10) with a wall (9) of the guide channel (F), wherein the guide channel (F) can be pulled off the material needle (3) axially in a maintenance mode (B), so that contact between a channel wall (9 ) of the guide channel (F) and the slide bearing surface (8), with the following steps: a) axial removal of the guide channel (F) to release the slide bearing surface (8) of the front needle (4), b) replacing the front needle (4) with a different front needle (4) or reinserting the same front needle (5) and c) applying the guide channel (F).