DE29904297U1 - Punching device - Google Patents

Description

The present invention relates to a punching device with a needle holder and a guide head for a needle and optionally with a piston, wherein the needle holder is connected to the piston.

Such a punching device is known in particular from the further processing of plastic parts. There it is often necessary that carrier parts, which have been produced by injection molding or pressing, for example, are gas-permeable for further processing. This is the case, for example, when the carrier parts are to be laminated with films using a vacuum, whereby the film is placed over the carrier part and the vacuum is created by sucking the air through the carrier part. Gas-permeability of the carrier part is also advantageous in press lamination if this can prevent air bubbles trapped between the carrier part and the only partially laminated film.

by venting them through the carrier part. In addition, methods are known which apply liquid adhesives, foam starting materials or the like from the back of the carrier part due to the porosity of the carrier part.

If the carrier material itself does not have any gas permeability or porosity due to its specific characteristics, it is necessary to make (small) holes in the carrier parts for the passage of the above-mentioned media. When holes are made subsequently, holes with a diameter of 1.5 to 3 mm are usually made at specified positions by hand or machine using twist drills. However, this is very time-consuming and costly.

Punching units with fine needles with a diameter of 1 to 3 mm that work against a precisely fitting hole matrix are also known. However, they are very sensitive to needle breakage and therefore do not provide sufficient process reliability.

Furthermore, punching units are known that create the desired holes in the carrier part using a pulse-like process - also known as "pitching". As a rule, a flywheel, at the front end of which a punching needle is arranged, is accelerated by a (standard) pneumatic cylinder. The needles have a useful path of 2 to 5 mm after emerging from their longitudinal guide. Due to the combination of pneumatic element, flywheel piston and needle guide, these assemblies have a large overall length, a large volume, a large weight and a considerable number of components. Since the needles are classified as wearing parts, the punching unit must meet high standards in terms of function monitoring and easy maintenance. However, known devices do not have an automatic needle breakage control or a possibility for quick, tool-free needle replacement. In order to replace the needle, such devices require the entire unit to be removed and disassembled on the workbench.

The invention is based on the object of developing a perforation unit of the type mentioned above, particularly with regard to construction volume, weight and

to simplify the number of individual parts, reduce their energy consumption, enable rapid needle replacement with as few tools as possible and ensure complete monitoring of needle breakage.

This object is achieved by the features specified in the independent claims 1, 2 and 5.

According to claim 1, the punching device contains a piston, a needle holder connected to the piston, and a guide head for the needle in a known manner. The punching device is characterized in that the piston is dimensioned as a flywheel. This measure according to the invention achieves a considerable simplification of the design of the punching device, which simultaneously leads to weight, volume, component and cost savings and helps to minimize friction losses. In fact, a piston and a separate flywheel of a suitable size are not provided - as is generally the case in the prior art - but both components are combined in one element by enlarging the piston accordingly and dimensioning it as a flywheel. The expert can determine the exact size of the piston (flywheel) mass using simple theoretical considerations or a few tests, whereby the mass of the conventional separate flywheel can serve as a first and often already satisfactory indication. The invention thus achieves a considerable improvement in the punching device through a surprising simplification of the design.

Claim 2 relates to a punching device which also contains a piston, a needle holder connected to the piston, and a guide head for a needle in a known manner. This punching device is characterized in that the needle holder is a quick-change device. A quick-change device enables needles to be exchanged easily, quickly and without the need for tools. Since the needles are wearing parts, they must be replaced relatively frequently due to normal wear and tear or if the needle breaks. The use of a quick-change device according to the invention allows such changes to be made with considerable savings in working time and thus also in labor costs. The specific design of the quick-change device is available to the

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The expert has various options to choose from, a preferred one of which is described below. The use of a quick-change device also simplifies the design of the punching device and thus achieves the desired weight reduction.

Of course, it is possible and also preferred to combine the inventive measures according to claims 1 and 2.

The special design of the quick-change device according to claim 3 is based on a punching device with a piston rod that is connected to the piston. According to the invention, the quick-change device is arranged on the piston rod so that it can be moved against a counterforce, whereby the holder releases the needle when the quick-change device is moved against the counterforce. The needle is preferably fixed in the rest position of the quick-change device with a force and/or a form fit. For example, the needle can have a bead, a collar, a groove or the like on the needle base, which interact with a clamping device or a lock to fix the needle. Similar devices are known, for example, from screwdrivers with interchangeable inserts. A needle can then be changed in an extremely simple manner by pushing the quick-change device back against the counterforce on the piston rod. The use of tools is no longer absolutely necessary for this.

According to claim 4, the quick-change device of the type described is mounted in a connecting tube in a displaceable manner, the connecting tube having an opening through which the quick-change device is accessible from the outside. This special construction means that the quick-change device is guided through the connecting tube and protected from the outside so that it cannot be opened accidentally with the corresponding dangerous consequences of releasing the needle. On the other hand, the connecting tube has an opening so that deliberate manipulation is possible, i.e. moving the quick-change device to replace the inserted needle. The opening means that merely accidental actuation of the quick-change device is practically impossible. Depending on the size of the opening, it may be helpful or necessary to use a non-specific, pointed tool, such as a screwdriver or a mandrel. This

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However, it is still a radical simplification compared to the state of the art, which requires the use of very special tools.

Furthermore, the invention according to claim 5 comprises a punching device with a needle holder for a needle, the punching device containing a sensor for detecting a needle break. According to the prior art, there are no devices for automatically detecting errors such as a needle break. Such an error must therefore be detected or checked by hand using tactile force, and the suspicion of such an error usually only arises long after it has occurred. In this time period, a considerable amount of rejects have already been produced. The sensor according to the invention for detecting a needle break, which is preferably arranged on the guide head of the needle, enables immediate automatic detection of the error. Little or no rejects are produced. Furthermore, there is no risk of injury to the staff, who no longer have to feel for a broken needle with sharp fragments by hand.

Various options are available to the expert for the specific design of the sensor. In one of these, according to claim 6, the sensor contains a light guide that is connected to a light evaluation unit, preferably a photocell. The light guide absorbs light in the punching device, the amount of which is influenced by the needle. For example, the light can be completely shielded by the (intact) needle (the light guide then absorbs no light in the normal state), whereby a needle breakage removes the shielding and the entry of light into the light guide thus signals the error. The light guide can also absorb light reflected by the (intact) needle, so that the absence of this light indicates that the needle has broken. It is also conceivable that the amount of light absorbed by the light guide during a working stroke varies in a certain way, which could be achieved, for example, in the reflection arrangement described above by a corresponding surface design (blackening) of the needle. Then it would be possible, by observing the variation in the amount of light transmitted from the light guide to the light evaluation unit and comparing

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With a target curve, it is also possible to detect more complex errors that are not limited to a needle breakage.

According to claim 7, the sensor contains a light source, which is preferably formed by a light guide connected to an artificial light source. The use of such a light source has the advantage that a known and constant amount of light is available, which is generally not the case when using natural light from the environment of the punching device. In the latter case, there is therefore a risk of misinterpretation (e.g. shading of the punching device is interpreted as a needle breakage) if corrective measures are not taken (e.g. reference measurement of the ambient light).

Since the light guides are sensitive elements, they are preferably connected to the housing of the punching device, which is stationary when the needle is changed, according to claim 8. This means that the light guides do not have to be moved or detached from the punching device when the needle is changed. In one of the above-mentioned embodiments of the invention, the light guides are preferably attached to the connecting tube in which the quick-change device is mounted so that it can move.

According to claim 9, the counter support for the needle can be firmly connected to the guide head. This is possible in particular when machining the edges of workpieces and has the advantage that the exact position of the counter support relative to the needle guide is fixed by solid structural connections. This eliminates the need for complex, precise positioning of the counter support and needle guide.

Of course, it is possible within the scope of the invention to implement the special embodiments described both independently of one another and together.

An embodiment of the invention is explained in more detail below with reference to the drawings.

Figure 1 shows the device according to the invention in cross section.

Figure 2 shows a special counter bearing in detail.

The perforation unit 100 according to the invention is shown in Figure 1. It is based on standard elements from the field of pneumatic cylinders, which reduces costs. The cylinder tube 18, the cylinder base 21 with the air supply connection 20 and the cylinder head with the exhaust air or return stroke connection 15 are parts from a large series. In order to minimize the number of components, the length of the unit and the number of energy-consuming sliding guides, the swing piston 17 with a suitably selected mass simultaneously takes over the function of the pneumatic piston; it is equipped with special, low-friction guide bands and a labyrinth seal. The piston rod 16 is firmly connected to the piston 17. A quick-change device 12 is provided at the front end of the piston rod. The pitch needle 10 has a raised collar at the lower end and is held in the piston rod head by a clamping device 12. The needle 10 is guided and protected by the guide head 23.

The guide head 23 is provided with cross holes into which flexible light guide elements 11 are inserted. One light guide element serves as a light transmitter. It can be omitted if sufficient light entry is ensured by other means. The second light guide element serves as a sensor and is connected to a photoelectric evaluation device. This arrangement ensures complete needle breakage monitoring. This means that a needle breakage is immediately detected and the production of reject parts is therefore minimized. Furthermore, the risk of accidents caused by tactile testing of the parts by hand when touching needle residues that may still be stuck in the parts is reduced.

If the guide head 23 is removed when changing the needle, the light guide elements 11 can remain on the guide or connecting tube 13, to which they are screwed with small threaded nipples. This means that changing the needle is particularly easy and the sensitive fiber optic cables are not moved unnecessarily or even damaged by improper handling.

To replace a broken needle, the guide head 23 can be dismantled without tools by removing a special spring

The bow spring ensures the correct, torsion-proof position of this part during assembly by interacting with grooves in the connecting tube 13 and in the guide head 23.

To replace a needle 10, the grooved ring 12 can be operated from the outside, usually in the installed state, using a screwdriver or a suitable mandrel through an opening in the protective tube 13. For this purpose, the grooved ring can be moved lengthways on the piston rod and is held in its front locking position by a spiral spring. By pushing it back relative to the piston rod, a clamping device in the piston rod head is released, so that the raised needle foot is released and the (used) needle can be removed. To insert a new needle, proceed in the reverse order.

To complete the device, a pneumatic valve is included to control the working movement by pressurizing the supply air connection 20. Immediately before the working stroke, the counter pressure at connection 15 is reduced by a suitable control of the control valve to such an extent that only a residual holding pressure fixes the working piston in the rest position.

The needle diameter is 1.0 to preferably 2.5 mm. The gap to the counter support 22 is 0.1 to 0.5 mm. The cylinder diameter can typically be 16 to 32 mm, the stroke of the cylinder 10 to 40 mm with a useful stroke of 1 to 5 mm.

Figure 3 shows an arrangement which is suitable when holes have to be pitched directly at the edge of articles. In this case, the counter support 24 can be connected laterally to the guide head 23 via a cantilevered support and form a unit with it.

Reference symbols Punching device 100 needle 10 Light guide elements 11 Quick change device 12 Connecting pipe 13 Coupling piece 14 Exhaust or return stroke connection 15 Piston rod 16 Swing piston 17 Cylinder tube 18 Piston chamber 19 Supply air connection 20 Cylinder base 21 Counterposition 22 Guide head 23 Counterposition 24

Claims (9)

1. Punching device, comprising a piston ( 17 ), a needle holder ( 12 ) which is connected to the piston, and a guide head ( 23 ) for a needle ( 10 ), characterized in that the piston is dimensioned as a flywheel. 2. Punching device, preferably according to claim 1, comprising a piston ( 17 ), a needle holder ( 12 ) which is connected to the piston, and a guide head ( 23 ) for a needle ( 10 ), characterized in that the needle holder is a quick-change device ( 12 ). 3. Punching device according to claim 2, characterized in that the quick-change device ( 12 ) is arranged so as to be displaceable against a counterforce on a piston rod ( 16 ) which is connected to the piston, and that the needle ( 10 ) is released by a displacement of the quick-change device against the counterforce. 4. Punching device according to claim 3, characterized in that the quick-change device ( 12 ) is mounted in a connecting tube ( 13 ) so as to be displaceable, and that the connecting tube has an opening through which the quick-change device is accessible from the outside. 5. Punching device, preferably according to one of claims 1 to 4, containing a needle holder ( 12 ) for a needle ( 10 ), characterized in that the punching device contains a sensor ( 11 ) for detecting a needle breakage. 6. Punching device according to claim 5, characterized in that the sensor contains a light guide ( 11 ) which is connected to a light evaluation unit, preferably a photocell. 7. Punching device according to claim 6, characterized in that the sensor contains a light source, which is preferably formed by a light guide connected to an artificial light source. 8. Punching device according to claim 6 or 7, characterized in that the light guide or guides are connected to the housing of the punching device which is stationary during needle change, preferably to the connecting tube ( 13 ) according to claim 4. 9. Punching device according to one of claims 1 to 8, characterized in that the counter-support ( 24 ) for the needle ( 26 ) is firmly connected to the guide head ( 25 ).