DE9012791U1 - Device for positioning workpieces during machining - Google Patents

Description

' DIPL-ING. PETER OTTE PATEWrTANWfT; _: ". _: " _: D-7250Leonberg

Representative at the European Patent Office / European'Patent Attorney ' .'!· \." Tiroler Straße

2368/ot/mu
20.8.1990

Da tron-Electronic GmbH, In den Gänsäckern 1 0 _? 6'ICS Mühltal-Traisa

Device &tgr; : &pgr;&igr; Positioning of pieces of mark during machining

State of the art

The invention is based on a device for positioning workpieces during ^machining according to the preamble of claim 1 and is specifically directed to such machining processes in which, unlike in heavy machine construction, smaller flat, possibly flexible workpieces must be engraved or provided with recesses, openings, holes, etc. in a predetermined pattern.

For a better understanding, in this context, reference is made to the processing of front panels, for example

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of devices, although the invention is, as is to be understood, not limited to such a measure. Device front panels require a large number of cutouts in order to accommodate switches, lighting, display devices and the like; engraving, grinding and the like may also be necessary, whereby the machining or other processing of such a front panel normally presents problems because clamping such a flat plate-like workpiece, for example, only leads to bulging on opposite sides and, in particular, uncontrolled vibration behavior can occur during processing, for example when a high-speed milling cutter produces certain cutouts. The solution that may be offered here of underlaying the clamped workpiece with an additional clamping device in the middle turns out to be difficult, if not impossible, for other reasons, because a clamping device in the middle can only be used if machining has already been carried out at this point, i.e. if a hole has been made, for example, while underlaying causes problems if, when making a cutout with a milling cutter, the cut-out waste piece cannot fall down due to its own weight at the last moment of the machining process, but remains on the base. In this case, it is not uncommon, at least far too common for continuous machining processes, for the milled waste piece to pull itself up on the milling cutter's spiral, which leads to immediate destruction.

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This can lead to a malfunction of the tool and, under certain circumstances, also to major damage to the workpiece and the processing machine. The underlay alone is not suitable for the proper clamping of a flat, plate-like workpiece, as this can still bulge due to the lateral clamping effect and at least start to vibrate during the processing process.

When machining larger workpieces, it is well known to use negative pressure to hold and position the clamping devices that clamp these workpieces, for example by holding base clamping plates on the work table of a milling machine using negative pressure and clamping the workpieces in a different way.

for example, by securing them with hold-down devices, lateral clamping claws or similar, which are screwed onto the base plate of the clamping device at certain intervals or by storing and moving such tools in T-slots of the clamping systems.

The invention is based on the task of enabling the problem-free, quick and, if desired, reproducible mounting of flat workpieces during any machining process, in particular during machining, without the need for mechanical influences such as screwing etc., and at the same time ensuring that the workpiece clamped in vibration-free is securely supported and immovably secured against the machining.

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machining process, but there is still sufficient space for the machining tool itself, including for milling or drilling through the workpiece.

Advantages of the invention

The invention solves this problem with the characterizing features of claim 1

and has the advantage that even flat, plate-like workpieces can be stored and clamped in the area of a machine table without any problem for any machining operations, in particular for machining, without any major effort and without the need for screwing, whereby the holding forces exerted can be considerable to extreme depending on the number of holding suction blocks used.

Furthermore, it is possible to hold the workpiece to be machined securely and vibration-free over its entire surface, even if it is very thin, deformations caused by clamping are excluded and the clamping process itself, since the holding suction blocks used can be arranged in any pattern, leaves the surface areas of the workpiece to be machined free from below, where, for example, a machining deformation such as the creation of openings, holes, etc. is to be carried out.

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Another advantage is that it is possible in this way to machine workpieces, for example device front panels, housing panels or other flat pieces of material in a reproducible manner using the latest fastening techniques, for example a computer-controlled milling control, since the holding suction blocks can be arranged on the base plate, for example the machining table of the cutting deformation or a separate plate placed on it, in such a way that, in accordance with the desired pattern and taking into account the programming of the milling control, the blocks only provide workpiece support and a clamping effect at those points where, according to the program, no machining processes are taking place.

With regard to the structure of the processing machine, there is the further advantage that it is not necessary to provide the machine table with the usual grooves or holes; it is sufficient if the machine table or the base plate formed by it forms a flat, smooth surface, since with the help of the clamping system according to the invention, any workpiece shape can be clamped and held easily, safely and inexpensively.

The measures listed in the subclaims make advantageous further developments and improvements of the clamping system according to the invention possible. The separate application of negative pressure to the holding suction blocks downwards, i.e. towards the machine table or the base plate or towards

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above, i.e. for fastening the workpiece to be clamped, so that on the one hand it is possible to leave the holding suction blocks constructed in the desired pattern in place even when the workpiece itself is being clamped, so that the same machining pattern can be repeated. In this case it is only necessary to remove the negative pressure effect between the holding suction blocks and the workpiece, but to maintain it in relation to the base plate.

A further advantageous design is that even very thin and flexible workpieces can be held securely and without deformation by the holding suction blocks, since these are provided with support ribs at the top, in contrast to an otherwise possible suction cup-like design, which ensure that the workpiece placed on top is not pulled in centrally in the suction area of the holding block shape, i.e. is not arched downwards, even if the block surface is larger, which of course also results in a greater holding force.

A further embodiment of the present invention consists in that, in addition to the vertical downward pressing effect of the workpiece on the holding suction blocks caused by the negative pressure effects, oblique or horizontal forces, for example shear forces resulting from the processing, can also be absorbed by an additional movable clamping element, which is itself fixed to the base plate by the negative pressure effect, which

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The respective workpiece is pressed against a stationary base plate side jaw in the manner of a vice,

However, a negative pressure effect can also be used here for the primary power generation, since corresponding negative pressure supply sources with associated supply lines are already provided.

The negative pressure can be generated either by conventional vacuum pumps - however, the present invention advantageously uses means that are able to achieve a corresponding negative pressure effect from the pressure sources that are usually available in workshops or laboratories, preferably by means of conventional Venturi nozzles that develop a certain negative pressure effect from an air flow through bypass openings, which leads to a negative pressure of, for example, 0.9 atm. Such a negative pressure is completely sufficient to be able to generate a total pressure of up to 25 kg and more for such a single holding suction block with the usual dimensions of a diameter of, for example, 60 mm, to name a few numerical values for better orientation, to which the present invention is, however, not limited.

A particularly advantageous design of the laterally acting clamping element is that it can exert very strong lateral pressures on the thin workpiece via a single-acting force amplification via a lever.

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kaKL whereby the lateral tension itself is only supported by the base plate by suppression.

drawing

Embodiments of the invention are shown in the drawing and are explained in more detail in the following description. They show: Fig. 1 shows a highly schematic side view of a possible embodiment of a clamping and holding system according to the invention for workpieces in the area of processing machines of any type, while

Figures 2, 3, 4 and 5 show a possible embodiment of a holding suction block in a side view, top view, bottom view and in a sectional view, in that order.

Description of the embodiments

The basic idea of the present invention is to position the workpiece during workpiece machining by means of holding suction blocks that exert a negative pressure effect on both sides, whereby the holding suction blocks are placed on a smooth base and have suitable sealing means on both sides to prevent a loss of negative pressure.

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In Fig. 1, the base plate for a workpiece machining device is designated iO; the milling spindle of a machine tool carrying out a cutting deformation is indicated schematically above the base plate at 11.

The base plate 10 can be part of the machine tool table or can be placed on it and fastened; it preferably has a base plate 11 with a smooth, uninterrupted surface 11a, which makes the usual fastening elements such as T-slots, fixing holes and the like superfluous, and a stationary side surface 12 extending upwards at a right angle, which carries a clamping jaw 12a - this will be discussed further below.

In order to support, hold and clamp a workpiece 13 on the base plate 10, holding suction blocks 14a, 14b, 14c of basically any shape are provided, which are arranged in the manner of spacers between the upper surface 11a of the base plate 10 and the lower surface of the workpiece 13.

In this case, both the height of these holding suction blocks and their shape are basically arbitrary; the only important thing is that the holding suction blocks develop a negative pressure effect on both sides, so that on the one hand they sit firmly with their lower surface on the facing surface 11a of the base plate 10 and also adhere to it by means of the corresponding vacuum-induced suction forces and at the same time are able to

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also vacuum-related, upward-acting suction forces to fix the workpiece 13 in the desired position for the relevant, preferably also computer-controlled, machining process and to hold it immovably.

Before we discuss the lateral clamping option offered by an embodiment of the invention, which is also shown in Fig. 1, we will first look in more detail at a possible embodiment of such holding suction blocks, as shown in Figs. 2, 3, 4 and 5 and provided with the reference number 14.

It has already been mentioned that the holding suction blocks can basically have any shape, height and dimensions, in particular it is possible for these blocks to have different surface dimensions at the top and bottom. In particular, the holding suction blocks do not need to be rotationally symmetrical, but can, for example starting from the lower base, take on an elongated oval shape upwards or even be shaped in such a way that certain fixing patterns for the workpiece are created, which literally bypass the processing surfaces in the workpiece.

In Figures 2 to 5, therefore, a particularly simple embodiment of a holding suction block in the form of a uniform cylinder is shown, which rests with its lower surface 15 on the base plate 10 and on whose surface 16 the workpiece rests and is sucked.

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In order to prevent a constant loss of negative pressure, the lower and upper sides each have a closed ring groove 17, 17' on the edge, into which a closed O-ring or another suitable seal is inserted. The negative pressure then passes from suitable cross holes 18, 18' provided with connection nipples (not shown) to upward and downward directed pressure outlets 19, 19' (see Figure 5) and is then distributed over the upper and lower surfaces to the upper and lower seals 20, 2:0' inserted into the ring grooves 17, 17' on the edge.

In this case, the procedure can be such that the respective, preferably centrally arranged vacuum outlet opening 21 (Fig. 4 in the view of the cylindrical holding suction block from below) opens into a very shallow trough-shaped depression 22, which is worked peripherally outwards up to the ring seal 20, 20' or is limited by an annular wall 23 located between them, so that the vacuum is given the opportunity to spread over the entire upper and lower surface of the holding suction block, with a corresponding, resulting strong suction effect.

It is advantageous if the seal inserted into the ring grooves 17, preferably O-ring 20, 20' in the initial state, i.e. when the holding suction block is not under negative pressure, slightly protrudes over the ring groove, so that the seal is then compressed when negative pressure is applied and in addition to the

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Sealing effect between the respective block and the facing surface due to the seal leads to a metallic contact between the mutually facing surfaces of the holding suction block on the one hand and surface 11a of the base plate 10 or the lower surface of the workpiece 13 on the other hand. This also results in a considerable lateral holding force, which is greatly increased by the vertically acting suction force and is attributable to frictional influences between the metallic surfaces, so that for various applications it is completely sufficient if a workpiece is stored on the base plate 10 solely with the help of holding suction blocks distributed according to the required processing processes and the desired holding force.

From the illustration in Fig. 3, it can be seen that in addition to the peripheral outer ring groove 17 for receiving the seal, further ring grooves 26 are provided, offset inwards, with the inner material rings 25 otherwise lying at the same height as the outer edge 24. This is a practical embodiment of inner support means for the workpiece placed on top, with the inner ring grooves 26 all being connected to one another and, of course, to the upper vacuum outlet opening 21, for example by one or more transverse channels 27 up to the outer seal.

The reason for this is that with very thin workpieces, the strong negative pressure effect in the area of the respective upper surface 16 of each holding

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suction block 14 could cause the workpiece to buckle downwards - as one can imagine, an area of only 30 cm ² already leads to a pressure on the workpiece from above of almost 25 to 28 kg and the remaining inner rings then prevent the aforementioned buckle.

It goes without saying that a completely different approach can be taken here, for example by leaving individual tenons in a general recess or trough shape 22, as is provided for the underside of the block. Such internal supports are not required on the underside, since the block is sufficiently solid and rests securely and deform-free on the base plate 10 with its peripheral edge.

From the illustration in Fig. 5 it can be seen best that separate supply lines are provided to achieve the upper and lower negative pressure effects, which can also be conveniently closed or opened via separately switchable valve controls or manual slides.

This provides the advantage that it is possible to leave the negative pressure on some or all of the holding suction blocks on the lower surface 15 so that they remain firmly anchored to the base plate 10, while removing the negative pressure on the surfaces 16 means that a machined workpiece can be easily exchanged for a blank or alignment work can be carried out without great effort.

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Another measure is advantageous here, which consists in the fact that the negative pressure can be generated as usual by means of suitable pumps etc., but preferably small venturi nozzles are used in a separate housing, which are subjected to the overpressure that is present everywhere in workshops or laboratories, for example 6 atm, and which thereby generate a suction effect on a parallel bore due to the amount of air flowing past, as is known for such devices, which is in the order of magnitude of a negative pressure of up to 0.9 atm. Since a loss of negative pressure is not to be feared or only to a very small extent due to the seals, such venturi nozzles can be used preferentially for generating negative pressure, which has the further advantage that the entire effect can be reversed by simply temporarily closing the overpressure outlet opening of the venturi nozzle; because in this case the connection opening, where the negative pressure normally builds up, is now also put under positive pressure, so that the pressure effect is reversed. This can be an advantage, for example, if you want to move the blocks on the base plate; you then only close the outlet opening for a very short time; the block lifts itself almost by itself and floats above the surface 11a of the base plate 10, so that it can be moved easily and positioned very precisely; if you then release the outlet opening again, the block sucks itself in and can then no longer be moved.

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A further very advantageous embodiment of the pneumatic clamping system according to the invention is that, if there is an occasional need for a strong lateral securing of the workpiece 13 on the base surface 10, a device can be used which is mechanically clamped in a certain area and which is referred to below as a lateral clamping element 28 and is shown in Fig. 1.

Such a lateral clamping element 28 consists of a part which is also held on the base plate 10 by the effect of a vacuum, which is brought laterally to the stop on the workpiece 13 and clamps/supplements the workpiece horizontally by means of a mechanically reinforced lever effect, which is ultimately also due to the effect of a vacuum, in the transverse direction, i.e. in addition to the strong holding suction effect exerted from top to bottom by the holding suction blocks 14, 14a, 14b, 14c, which is of course also used to fix and position it against being pushed away sideways due to the friction caused by this.

In the embodiment shown, the lateral clamping element 28 consists of a lower bearing part 29 and an upper pressure part 30, which is moved pneumatically and, in the embodiment shown, generates strong lateral forces through a mechanical lever effect.

The lower bearing part 29 as well as the upper pressure

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part 30 are both L-shaped and placed together so that a rectangular cross-sectional shape is obtained, as shown in Fig. 1, whereby a hinge effect is formed at 31 between these two parts, for example by a resilient metal band or a spring ring 32 being fixed in a stationary manner to both parts. As a result, the upper pressure part 30 is able to move up and down with its rear end area at 30a relative to the bearing part 29 in accordance with the double arrow A, due to the hinge effect at 31, which results in a pressure effect acting in the direction of arrow B on the front edge of the pressure part 30 facing the workpiece 13 at 30b, which pressure effect is mechanically significantly increased in accordance with the L-shape of the lever thus formed, which acts on the facing lateral edge of the workpiece 13 via an intermediate clamping jaw 31.

On the other hand, as already mentioned above, the workpiece can also be held and clamped by the stationary clamping jaw 12a of the lateral, upwardly projecting flank 12 of the base plate 10.

The primary movement of the lateral clamping element 28 can then be derived from a pneumatic piston-cylinder unit 32, which works with overpressure or, since this is available everywhere, with negative pressure and has a small piston 32a, which, when negative pressure is applied to the space of the cylinder accommodating the piston rod, causes an upward displacement

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experiences when the lower working chamber is ventilated. As the clamping effect achieved in this way is enormous, the piston-cylinder unit 32 does not need to have any large dimensions in order to exert a force of 50 kg or more on the singly clamped workpiece 13, for example from the side. This also results in an extremely firm fixation of the workpiece 13 in the lateral direction, whereby with thinner workpieces the suction effect of the four holding suction blocks naturally ensures that the workpiece remains flat, even if the pressure exerted here by the lateral clamping element is considerable.

The reaction force on the lateral clamping element caused by this pressure effect is compensated by fixing the bearing part 29 over a large area to the surface 11a of the base plate 10, in that the lower surface 29a of the bearing part 29 is fixed to the surface 11a of the base plate 10 in the same way, but if desired with a larger area and therefore also with a correspondingly greater pressure, also against lateral slipping, as already explained above with regard to the holding suction blocks.

However, in this embodiment it can be advantageous if the dimensions of the peripheral seal or the peripheral O-ring are designed in such a way that even with the strongest negative pressure, the O-ring is not completely compressed, i.e. there is no metallic contact between the lower surface of the bearing part 29 and the surface 11a of the base plate 10. In fact,

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then the rubber-like material of the seal has such a strong adhesive and EL·,' .axl effect, reinforced by the full acting suction pressure of, for example, 50 or 60 or even more kg, that a lateral

Slipping is no longer possible - any elastic yielding that may occur here is easily compensated for by a correspondingly stronger pressure in the area of the pressure part 30. It can be seen that here a balancing of the horizontal forces exerted or absorbed by the lateral clamping element occurs.

In order to ensure that the workpiece 13 does not accidentally slip upwards, slightly inclined incisions 33 can be provided on the facing lateral clamping jaws 12a and 31, so that the workpiece is securely and immovably positioned and fixed in all directions.

To clamp with the lateral clamping element, the procedure is therefore that the clamping element 28 is first pushed sideways against the workpiece 13 until it stops, then the vacuum effect is switched on to fix the bearing part 29 and then pneumatic positive or negative pressure is applied to the piston-cylinder unit 32 so that the pressure part 30 tilts around its hinge bearing 31, presses sideways with great force against the workpiece 13 and holds it immovably.

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Finally, it is pointed out that the claims and in particular the main claim are attempts to formulate the invention without comprehensive knowledge of the
State of the art and therefore without restrictive jurisdiction. Therefore, all features shown in the description, claims and drawings are reserved, both individually and
in any combination with one another as essential to the invention and to be set out in the claims and to reduce the feature content of the main claim.

Claims (1)

DIPL-ING. PETER OTTE PATENT ATTORNEY ....... 0-7250Leonberg Representative at the European Patent Office / European Patent Office Tiroler Straße 2368/ot/mu
20.8.1990 Patron-Elect;onic GmbH, In den Gänsäckern 10, Mühltal-Traisa Protection claims 1. Device for positioning, holding and clamping preferably flat, plate-like workpieces during machining, engraving, grinding, polishing and the like by means of machine tools, milling machines, drilling machines, grinding machines, wherein the workpiece is held by means of negative pressure, characterized in that holding suction blocks (14; 14a, 14b, 14c) which develop a negative pressure effect on both sides are provided between a base plate (10) of the processing machine and the workpiece (13) to be positioned and held. 2. Device according to claim 1, characterized in that the holding suction blocks (14; 14a, 14b, 14c) having any shape (14; 14a, 14b, 14c) with a lower surface (15) and a vacuum supplied separately to this sit in a sealed manner on the facing smooth surface (11a) of the base plate (10) and with a surface (16) in a sealed manner against the lower surface of the workpiece (13), with vacuum supply elements for the workpiece fastening that can also be controlled separately. • I ♦ · a • I · t · 2368/ot/mu " ^l: 20.8.1990 - 2 - 3. Device according to claim 1 or 2, characterized in that the holding suction blocks (14; 14a, 14b, 14c) are arranged in a predetermined pattern, surface-oriented to the mechanical processing operations of the workpiece, below the workpiece (13) and have such an upper shape that when the workpiece is deformed by cutting through the material, free spaces are formed, for example by smaller upper cross-sectional areas. ) given holding suction blocks (14b) relative to their lower re contact area. 4. Device according to one of claims 1 to 3, characterized in that support means for the workpiece (13) are arranged in the suction surface area of the surface (16) of the holding suction blocks (14; 14a, 14b, 14c). 5. Device according to claim 4, characterized in that the support means are concentric annular elevations (25) separated by annular grooves (26) which all extend to the outer peripheral seal with the vacuum inlet (21) opening into the surface (16). 6. Device according to one of claims 1 to 5, characterized in that the vacuum inlet (21') of the lower surface (15) of the holding suction block (14; 14a _f 14b, 14c) opens into an extended trough-shaped depression (22) which is delimited by a peripherally surrounding seal. 7. Device according to one of claims 1 to 6, 2368/ot/mu 20.8.1990 - 3 - characterized in that endless ring seals (20, 20') are inserted into peripheral ring grooves (17, 17') of both the underside and the surface (15, 16) of each holding suction block (14) 14a, 14b, 14c), which protrude beyond the groove receiving them to such an extent that, when negative pressure is applied, they are pressed together, increasing their sealing effect, until the facing surfaces of the holding suction blocks on the one hand and the base plate surface (11a) and the underside of the workpiece (13) on the other hand come into metallic contact. 8. Device according to one of claims 1 to 7, characterized in that separate channels (18, 19; 18'19') leading to external separate connection nipples are provided within the holding suction blocks for the separately controllable negative pressure supply either to the lower surface (115) or the (Si J- J. cn-lic viu; W^=J- ^U JDSiuS 9. Device, in particular according to one of claims 1 to 8, characterized in that a lateral clamping element (28) is provided which exerts a clamping and holding force laterally and thus perpendicular to the suction forces of the holding suction blocks, which ^is also held on the surface (11a) of the base plate (10) by the effect of negative pressure. .0. Device according to claim 9, characterized in that the lateral clamping element consists of a lower bearing part (29) resting on the base plate (10) and an upper pressure part (30) connected to it in an articulated manner - with a merely II • It»
· · · · 2368/ot/mu 20.8.1-990 - 4 Pivoting action between the two enabling hinges (hinge band 32) as well as a pneumatic pressure cylinder (32) on the side facing away from the hinge. 11. Device according to claim 9 or 10, characterized in that the bearing part (23) and the pressure part (30) are each L-shaped and are assigned to one another in such a way that the shorter leg of one part rests on the longer leg of the other in such a way that a lateral pressing force with an increased leverage effect is produced on the outer edge (30b) of the pressure part (30) facing away from the pneumatic pressure cylinder (32) on the workpiece (13) clamped on the other side by means of a stationary base plate jaw (12a). 12. Device according to claim 9, 10 or 11, characterized in that for the secure, frictionally effective anchoring of the bearing part (29) on the base plate surface (11a), its lower peripheral seal extends so far beyond the receiving groove that even in the case of the strongest negative pressure, metallic contact between the facing parts is avoided and the reaction force absorbed by the lateral clamping element (28) is compensated by the elastomeric anchoring effect of the ring seal. 13. Device according to one or more of the claims 1 to 12, characterized in that to generate the negative pressure effect, Venturi nozzles are provided which are pressurized with compressed air and which are connected to the • » ' f · ■ 4 2368/ot/mu 20.8.1990 - 5 - The flow channel and the side channel open create negative pressure in such a way that when the outlet opening is closed, the suction effect is reversed in the area being suctioned .