DE102011079982B4 - Spray head for reactive plastics - Google Patents

Abstract

A spray head (1) for mixing and spraying reactive plastics, comprising: a main body (2) having a bore which extends in the axial direction; a mixing chamber (4) which is formed in the axial direction of the bore at the end portion thereof and in which components for the plastic are mixed; at least two flow channels (5a, 5b) for the components of the plastic, which open into the mixing chamber (4); an actuating piston (3) which is arranged in the bore of the main body (2) and which is between an operating position , in which the flow channels (5a, 5b) are connected to the mixing chamber (4) and can be switched to a rest position in which the connection between the flow channels (5a, 5b) and the mixing chamber (4) is interrupted by the actuating piston (3) is; anda spray device (7) in which a spray channel (8) is formed, through which the mixed components are supplied to the outlet opening (14); wherein the spray head (1) comprises a first inlet bore (9) and a second inlet bore (10), and the actuating piston has a supply channel (16), the supply channel (16) being in connection with the first inlet bore (9) in the operating position of the actuating piston (3), and the second inlet bore (10) in communication with the actuating piston (3) in the rest position the supply channel (16) is in connection, whereby the supply channel (16) opens into the mixing chamber (4) when the actuating piston (3) is in the operating position, so that a gas jet is introduced into the supply channel (16) via the first inlet bore (9) is, can be introduced into the mixing chamber (4) from the feed channel (16) simultaneously with the components of the plastic, and in the rest position of the actuating piston (3) a cleaning agent via the second inlet bore (10) via the Feed channel (16) can be introduced into the spray channel (8).

Description

Field of the invention

The invention relates to a spray head for mixing and spraying reactive plastics (which are used, for example, to produce polyurethane skin components by spraying workpieces) according to the preamble of claim 1.

State of the art

Usually, devices for spraying plastics such as polyurethane use two or more components which are mixed with one another in a mixing chamber. For this purpose, these components are introduced from two channels into the mixing chamber, where they mix when they meet and are then brought from there in the mixed state via a channel to a spray device with which the mixed plastic is sprayed.

Such mixing devices are for example in the WO 2008/122400 A1 or the DE 11 2005 000 794 T5 described. The problem with the spray pattern is overspray, the distribution and variance of the discharge capacity, the discharge capacity per wetted area, as well as increasing contamination in the spray unit.

Furthermore, the U.S. 4,053,283 A known relating to a mixing device for mixing a plurality of plastic materials.

In the DE 87 00 489 U1 describes a two-component mixing gun which has a housing in which a pneumatic adjusting cylinder is arranged.

The DE 10 2007 023 238 A1 describes a spray head for the production of polyurethane films, comprising a mixing block and a spray tube, with a mixing chamber contained in the mixing block, at least two injection nozzles opening into the mixing chamber for at least one polyol and one di-isocyanate and an actuating piston which can be displaced in the mixing chamber a short-circuit position in which its front end covers the mouths of the injection nozzles and the substances exiting therefrom can be guided back into a storage tank via two grooves and short-circuit lines engaging in the outer circumference of the actuating piston and can be retracted into an injection position in which the mouths of the injection nozzles are released to introduce the emerging substances into the mixing chamber, to mix them with one another, to cause them to react, to transfer them into the spray tube and to expel them therefrom.

Presentation of the invention

The object of the present invention is to provide a spray head of the type mentioned at the beginning which reduces the disadvantages presented above.

This object is achieved by a spray head according to claim 1. Particularly preferred developments of the invention are specified in the dependent claims.

The spray head according to the invention comprises the feature that the actuating piston has a feed channel which opens into the mixing chamber in the operating position of the actuating piston, so that a gas jet, which is introduced via a first inlet bore, can be introduced from the feed channel simultaneously with the components of the plastic into the mixing chamber is, and in the rest position of the actuating piston, a cleaning agent can be introduced into the spray channel via a second inlet bore via the supply channel.

This additional gas jet ensures, on the one hand, additional turbulence of the raw materials to be mixed in the mixing chamber and thus intensifies the mixing; on the other hand, the additional gas jet leads to the raw material mixture being torn up into fine droplets. This allows the droplet size and speed to be influenced by varying the gas volume and / or the component mixture volume and / or the ratio of gas volume and component mixture volume and thus the spray pattern of the component mixture can be optimally adjusted. In particular, for example, “overspray” can be reduced and the distribution and variance of the discharge capacity improved. Furthermore, the coaxial introduction of the gas jet makes it possible to avoid or reduce an increasingly build-up of contamination in the spray unit. Furthermore, the spray head can be easily maintained due to the possibility of an integrated supply of a cleaning agent.

The direction of the gas jet into the mixing chamber is preferably aligned with the spray channel, preferably in a coaxial configuration of the gas jet and spray channel. This prevents unwanted eddies or dead spaces in the spray channel, reduces the contamination of the spray channel and achieves a symmetrical spray pattern. Furthermore, the spray channel includes a point with an inlet channel at which the mixed components can be supplied with atomizing gas before exiting the spray channel. With this additional gas supply option, the spray cone angle and the atomization of the component mixture / the mixture droplets can be omitted upon exit In addition, at the outlet of the spray channel, at least one gas outlet opening is provided around the outlet, by means of which a gas can be ejected to influence the spray pattern or the spray geometry.

By individually varying the pressure and quantity of the emitted gas of each of the gas feeds shown above, or by varying the quantity or switching off the mixed plastic components during a spraying process, a wide variety of surfaces can be sprayed in a targeted manner and limits can be better adhered to without adjoining surfaces can also be sprayed.

This gas outlet opening can be arranged as a bore or slot partially or completely around the outlet of the spray channel, whereby the spray radius can be influenced locally. A plurality of gas outlet openings can also be provided, which also influences the spray radius, but at the same time also enables influences only in individual directions by only ejecting the gas from individual openings.

Figure list

• 1 shows a spray head according to the invention, in which the actuating piston is in the rest position;
• 2 shows a spray head according to the invention, in which the actuating piston is in the operating position;
• 3a to 3c show various embodiments of the limiting opening in an enlarged view.

Description of preferred embodiments

In the 1 and 2 is a spray head 1 according to the present invention each shown as a schematic diagram.

The spray head 1 consists essentially of a main body 2 with a hole going through the main body 2 extends. There is an actuating piston in this bore 3 arranged, which in the bore between a rest position ( 1 ) and an operating position ( 2 ) can be moved axially. In the main body 2 is a mixing chamber 4th formed, which is in the operating position of the actuating piston 3 from now not through the actuating piston 3 closed bore portion at an end portion of the bore in the main body 2 results.

The transition from the mixing chamber 4th into the spray channel 8th occurs "softly" as a conical narrowing or widening.

The adjusting piston 3 does not have to include the entire mixing chamber in its rest position 4th in the main body 2 take (as in 1 shown). The main body and other components of the spray head are preferably made of metal

Also in the main body 2 Flow channels 5a , 5b formed into the mixing chamber 4th flow out. Components such as polyol and isocyanate are fed through these flow channels into the mixing chamber and mixed there.

The one in the bore of the main body 2 arranged adjusting piston 3 blocks the flow channels in the rest position 5a , 5b for the mixing components (or their mouths) while in the operating position of the piston 3 the mouths of the flow channels 5a , 5b are released and so the flow of the mixing components into the mixing chamber 4th enable.

In the in 1 The embodiment shown has the mixing chamber 4th at the point where the prelims 5a , 5b into the mixing chamber 4th open, the same diameter as the hole in which the actuating piston 3 is arranged, whereby the blockage by the actuating piston 3 is made possible.

As already described, the actuating piston moves axially forwards and backwards in the bore. In the present embodiment, the operating position of the piston is in a retracted position and the rest position is in an advanced position.

The movement of the piston is preferably generated (electro) pneumatically, but (electro) magnetic or (electro) hydraulic or also mechanical embodiments of the piston movement are also conceivable.

In the main body 2 are also return channels 6a and 6b designed for the components through which the components flow back into a corresponding container (eg a collecting tank) when the piston is in a rest position. In 1 this is shown on the basis of a preferred embodiment, so that from the preliminary 5a , 5b the components via grooves 15th extending in the axial direction of the piston into the return lines 6a , 6b flow. This means that the components can always be kept moving and circulated so that the components do not harden in the channels.

The spray head 1 also has a spray device 7th with a spray channel 8th on, through which the mixed components from the mixing chamber 4th from the mixing device 1 be expelled. The spray device 7th can be integral with the main body 2 be formed, but is preferably an independent element, for example. By gluing, screwing or with a form fit (press fit, clip connection with hook-shaped projections) on the main body 2 is attached. The spray device 7th is described in more detail below.

In the mixing chamber 4th also opens a feed channel 16 through which a gas enters the mixing chamber at the same time as the components 4th can be initiated. The feed channel 16 opens at least in the operating position of the actuating piston 3 into the mixing chamber 4th . The gas introduced ensures, through turbulence, that the mixing of the components and thus the spray pattern is improved.

In a preferred embodiment, the feed channel is 16 aligned so that it faces the spray channel 8th in the spray head 7th is directed. In particular, the feed channel 16 in the area of its mouth (into the mixing chamber 4th ) and the inlet opening into the spray channel 8th (from the mixing chamber 4th out) designed coaxially.

In the preferred embodiment, the feed channel is 16 through the setting piston 3 formed therethrough and is in the operating position of the actuating piston with a first inlet bore 9 in connection, through which a gas jet enters the supply channel 16 can be initiated.

There is also a second inlet bore 10 provided that in the rest position of the actuating piston 3 with the feed channel 16 is in connection and via which a cleaning agent (e.g. gas) via the supply channel 16 into the spray channel 8th can be initiated.

The spray device 7th as noted, is integral with the main body 2 or designed as an attachable attachment. The spray channel of the spray device 7th is with the mixing chamber 4th In the present case it is directly connected, but can also be connected to it via further intermediate elements. In the preferred embodiment, the spray head is 7th Rod-shaped and in particular has a deflection section 11 in which the channel experiences a curvature so that the component mixture is deflected.

The curvature has an angle of curvature of inlet 11a and outlet 11b from 45 ° to 135 °, more preferably 80 ° to 100 ° or essentially 90 °. Such a deflection creates a better geometry for the surfaces to be sprayed, since it is easier to get to hidden and angled surfaces. So that the energy of the component mixture lost by the deflection can be compensated for and, above all, an improved discharge of the component mixture can be achieved, the deflection section can be used 11 an atomizer duct 12th be provided. Through the atomizer channel 12th a gas such as air is preferably introduced into the spray channel, so that the introduced gas moves the component mixture in the direction of the outlet 14th the spray device 7th accelerated (the atomizer channel is preferably on the outlet 11b of the deflection section 11 aligned).

For example, the atomizer channel can open into the spray channel in such a way that the two axes of the channels (atomizer and spray channel) form an acute angle α (see Fig. 1 ). In the present embodiment, however, it is preferred that the atomizer channel is coaxial with the outlet 11b of the deflection section 11 is arranged.

As in the 3a to 3c can be seen at the exit 14th the spray device 7th one or more openings 13th be arranged, preferably around the outlet 14th are arranged around. Through these openings 13th a gas can be emitted with which the spray pattern of the spray jet of the spray head can be influenced. It is also possible for only a small punctiform opening to be provided on any side of the spray device. However, it is preferred that the opening is arranged in the form of a slot around the outlet (for example (semicircular) circular) or several point or slot-shaped openings which are preferably arranged uniformly around the outlet at four, eight or sixteen locations. An air duct leads to these openings 15th (or multiple channels 15th ) connected to a gas supply.

All gas channels of this invention are preferably supplied with (compressed) air, but various other gases can also be used.

Claims (8)

A spray head (1) for mixing and spraying reactive plastics, comprising: a main body (2) having a bore extending in the axial direction; a mixing chamber (4) which is formed in the axial direction of the bore at the end portion thereof and in which components for the plastic are mixed; at least two flow channels (5a, 5b) for the components of the plastic, which open into the mixing chamber (4); an actuating piston (3) which is arranged in the bore of the main body (2) and which is between an operating position in which the flow channels (5a, 5b) with the Mixing chamber (4) are connected, and a rest position can be switched over, in which the connection between the flow channels (5a, 5b) and the mixing chamber (4) is interrupted by the actuating piston (3); and a spray device (7) in which a spray channel (8) is formed, through which the mixed components are fed to the outlet opening (14); wherein the spray head (1) comprises a first inlet bore (9) and a second inlet bore (10) and the actuating piston has a feed channel (16), the feed channel (16) having the first inlet bore (9) in the operating position of the actuating piston (3) ) is in communication, and the second inlet bore (10) in the rest position of the adjusting piston (3) is in communication with the supply channel (16), whereby the supply channel (16) opens into the mixing chamber (4) in the operating position of the adjusting piston (3) so that a gas jet, which is introduced into the supply channel (16) via the first inlet bore (9), can be introduced from the supply channel (16) simultaneously with the components of the plastic into the mixing chamber (4), and in the rest position of the actuating piston ( 3) a cleaning agent can be introduced into the spray channel (8) via the second inlet bore (10) via the feed channel (16). Spray head (1) Claim 1 , in which the feed channel (16) is aligned with the spray channel (8), preferably in a coaxial configuration of the feed channel (9) and spray channel (8). Spray head (1) Claim 1 or 2 , in which the main body (2) comprises two return ducts (6a, 6b) which, when the piston is in the rest position, are connected to the flow ducts (5a, 5b) via a groove (15). Spray head (1) according to one of the preceding claims, in which atomizer gas can be supplied to the mixed components at a point (11) in the spray channel (8) via an inlet channel (12). Spray head (1) Claim 4 , in which the inlet channel (12) is aligned with the outlet channel (14), preferably in a coaxial configuration of inlet channel (12) and outlet channel (14). Spray head (1) according to one of the preceding claims, in which at least one opening (13) is provided at the outlet (14) of the spray channel (8) around the outlet (14), by means of which a gas can be ejected to further influence the spray pattern . Spray head (1) according to one of the preceding claims, in which the transition from the mixing chamber (4) into the spray channel (8) tapers to the cross section of the spray channel. Spray device for mixing and spraying reactive plastics, comprising: a spray head (1) according to one of Claims 1 - 7th a metering unit with at least two containers for the components of the plastic, which are connected to the flow channels and preferably also to the return channels; a device for supplying the gas channels with a gas; and a control unit for the actuating piston (3).

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