FR2613970A1 - DEVICE FOR ATTACHING PALLETS TO A SUPPORT TABLE - Google Patents

Abstract

THE INVENTION CONCERNS A DEVICE INCLUDING, ON THE HOLDING TABLE 2, INDEXING PINS 5 WHICH ENGAGE IN CONICAL BORES 4 HOUSES IN EACH PALLET 1. THE DEVICE IS DESIGNED TO ALLOW AN EXACT POSITIONING OF THE PALLETS DESPITE EXPANSIONS THERMAL. THE BORES 4 ARE HOUSED IN AT LEAST ONE INTERCALAR ELEMENT 4 FIXED TO THE PALLET 1. NEAR THE BORES, THIS ELEMENT 6 IS ELASTICALLY DEFORMABLE PERPENDICULARLY TO THE DIRECTION OF INSERTION OF THE ANKLES 5, IN PARTICULAR THANKS TO THE CONCENTRIC ANNULAR GROOVES 8, 9 AT L'ALEAGE. THE ANCHORS 5 HAVE OVER THE ENTIRE SURROUND THEIR A SHAPE COMPLEMENTARY TO THAT OF THE BORES 4, WHICH ALLOWS THE CORRECT POSITIONING OF THE PALLET TO BE CONTROLLED BY INJECTION OF COMPRESSED AIR INTO THE BALEAGE. SUCH A DEVICE CAN BE USED FOR FIXING PALLETS SUPPORTING WORKPIECES, IN PARTICULAR IN A SERIES MANUFACTURING LINE.

Description

DEVICE FOR ATTACHING PALLETS TO A SUPPORT TABLE

  The present invention relates to a device for fixing pallets on a holding table, this table comprising several indexing pins having at least partially a frustoconical shape and arranged to fit in bores of the pallet to be fixed, or-d ' a piece integral with the pallet, when the pallet is pulled towards the support table. Pallets are used to reduce the ancillary technological time in the manufacture of machined parts, because each change of parts in a treatment station represents a dead time and must be done as quickly as possible. The holding table is then used to hold the pallet in a station where the part undergoes machining. Its function is to precisely position and block the pallet during machining. This holding table can be fixed on a fixed table of a machine, or can be rotated

  on a circular table or on a lathe.

  However, for the machining of parts fixed on a pallet, it is essential that a precise position is always preserved. The room must be maintained

  in position with extreme precision and with high reproducibility.

  This means high demands on a precise connection between the pallet and the support table. For example, if the pallet is clamped to the support table, it must not result in

  deformations. In addition, the pallet must be kept safe.

  For this purpose, it is known to pull the pallet from above against the holding table by means of a hydraulic device. Positioning without play is done by means of indexing pins provided on the holding table and engaging in bores of the pallet to fix. However, there is a problem that the expansions of the materials due to changes in temperature must be considered. This is why the pegs, which are generally three in a row, are not frustoconical shape all around their edges, but are chamfered each in a manner offset by 900 between them. This creates free surfaces

  which provide compensation zones for expansion of the materials.

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  2- However, this has the disadvantage of the need for special organs for the indispensable control of the exact positioning, in which it is necessary to establish whether the pallet has its correct position on the holding table. Such control bodies are complex and therefore expensive. In addition, the manufacture of indexing pins in the known form is relatively expensive. The object of the present invention is therefore to provide a pallet fixing device of the type indicated above, with which it is possible to obtain, by means of

  simple means, exact positioning despite thermal expansion.

  According to the invention, this object is achieved by a device characterized in that the bores in which the indexing pins are inserted are formed in at least one intermediate element dimensioned so as to be elastically deformable perpendicularly to the direction of insertion. , close to the bores, and in that the indexing pins have on

  all around them a shape corresponding to that of the bores.

  Thus, because the bores are formed in a separate spacer element whose elastic deformability allows expansion, for example due to temperature variations, the peripheral surfaces of the indexing pins can fit exactly in the bores. This means that the indexing dowels can be made in a way

  simple and do not need to undergo an additional shaping step.

  In addition, there can be a circular and closed contact surface between the indexing pins and the corresponding bores. As a result, it is possible to control, with substantially simpler means, the accuracy of the positioning and the fixing of the pallets on the holding table. This can be done by suitable means such as for example contact sensors, a control air circuit, etc. The elastic deformability of the intermediate element perpendicular to the direction of insertion and pulling of the pallet can be obtained in different ways. One simple way is to give the spacer element the shape of a plate which has grooves extending in the direction of insertion from at least one face of the element. Thanks to

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  These grooves, made by any appropriate means such as rol ge,

  milling, turning etc., we obtain a weakening of the material and onla.

  desired deformability, which is usually only in nmcrorettres.

  Said grooves may consist simply of annular ribbings concentric to the bore, and they may extend from both sides of the element. In order to obtain the desired deformability, it can be provided that the annular grooves each have a depth greater than half the thickness of the plate and are in zones of different respective diameters. In this way, we obtain a sinuous profile

  or accordion, with high elasticity.

  It has proven generally sufficient to provide that each pallet is provided with two of said bores spaced apart from each other to cooperate with two corresponding indexing pins. We obtain

safe centering.

  In a very advantageous and particularly original embodiment of the invention, the holding table is provided with air control ducts, connected to air ducts which pass through the indexing pins so as to open into the front face. ankles inserted into the bores. Since a sealed seal is obtained by pressing all the periphery of the indexing pins in the bores, an injection of compressed air therein makes it possible to check in a simple manner whether the pallet is fixed correctly and without any play on the holding table. If any foreign bodies have entered the bores and prevent the pallet from being properly fastened, this will result in air leakage

  tablet that can be detected by simple control means.

  According to another original improvement of the invention, the intermediate element or the indexing pin is mounted respectively in a recess of the pallet or in a recess of the holding table, with a game on the back of the element or of the peg in the draw direction of the pallet, so as to have an elastic flexibility in its central part. This elastic flexibility makes it possible to compensate in a simple manner inaccuracies which are in the field of tolerances and which can thus be absorbed by the aforementioned game. The inaccuracies of this kind can come in particular from normal wear. In such cases, the arrangements according to the invention make it possible to obtain all the same a

exact positioning of the pallet.

  The necessary clearance can be created by the conformation or by the mode of support of the intermediate element or the indexing peg. For example, the intermediate element may be supported on a support washer in its

  peripheral part, while its central part is spaced from the pallet.

  On the contrary, it can be provided that one or each indexing peg comprises a flange which is only supported on the holding table in its peripheral part. In this case, it is sufficient to size or arrange the flange so as to give it even minimal flexibility. For example, it can be provided that the flange and / or indexing pin has (nt) in their central portion of the recesses giving them elasticity in the direction of pulling the pallet. In particular, the indexing pin may be connected to the peripheral portion supported by the flange by a thinned annular zone. In addition, an intermediate washer can be placed with play in the elastic bending zone respectively under or behind the intermediate element or the indexing pin, to serve as a

  abutment and organ limiting flexion.

  Schematic examples of embodiment of the invention will be described below, with reference to the drawings, in which FIG. I is a partial longitudinal sectional view through a pallet and a table holding the pallet, in the area of an indexing pin, and FIG. 2 is a view similar to FIG. I and represents another form of

  realization of the indexing peg.

  The drawings show a pallet I of the usual type, removably attached to a holding table 2. The pallet 1 and the holding table 2 are known in principle and will not be described in detail in the following. It is the same for the organs used to pull the pallet I against the support table to fix it. For this purpose, the pallet 1 comprises

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  1t 3 9 7 - in general two longitudinal grooves T-profile as the rairure 3 shown on the upper face of the pallet and for fixatior, parts. Each of said T-slots, not shown, receives a T-shaped bar which is pulled downwards by a hydraulic cylinder provided on the holding table, so that the pallet is pulled in the direction of the holding table 2. The exact positioning and blocking of the pallet are made by means of tapered bores 4 of the pallet 1, in which are inserted indexing pins 5 arranged on the table 2 and having the same taper. Thus, the two corresponding conical surfaces are applied exactly against one another in a sealed manner. In general, it is sufficient to have for each pallet two of these bores 4, arranged to

  distance from each other opposite the corresponding indexing dowels.

  The depth of each bore is such that the corresponding peg does not

  do not go all the way to it.

  As shown in the figures, the bore 4 is not formed directly in the pallet 1, but in a special intermediate element 6 which itself is attached to the pallet, for example by screws 7. The intermediate element 6 may have the shape of a plate, especially a disc. From the two opposite faces of the element 6, respective annular grooves S and 9 extend into the interior of the disk, the diameters of the two grooves S and 9 being different. In this way, the depths of the grooves can be chosen so that each one is greater than half the thickness of the disc. As can be seen in the drawings, the result is a sinuous or accordion profile in which the choice of an appropriate spacing between the grooves 8 and 9 determines the desired reduction in the rigidity of the disc. For this purpose, for example, the distance between the two grooves 8 and 9 can be fixed at a value which does not exceed or slightly exceeds the width of the grooves. If it is necessary, it can obviously provide more annular grooves. It depends on the particular conditions and the amplitude of the dilations

thermals to take into account.

  To accept and possibly compensate for unevenness, it is possible to provide a respective bearing washer 11, 12 under the intermediate element 6 and / or under a flange 10 secured to the indexing peg 5. By replacing the washer 6, support 1l or 12 by a washer of different thickness, we can

  make necessary adaptations.

  The holding table 2 is equipped with an air control duct 13 which communicates via a branch 14 with each centering device and

  positioning device consisting of a bore 4 and an indexing pin 5.

  The flange 10 and the ankle 5 enclose an air duct J 5 whose anterior end opens into a free space 16 remaining at the bottom of the bore 4. To check if the situation and the level of the pallet on the table of maintenance are correct, is sent compressed air in the free space 16 through the conduit 13, the branch 14 and the conduit 15. If the bore contains no foreign body that prevents a continuous support of the peripheral surface of the peg 5 in the bore 4, the air pressure is maintained

  and can be used to signal correct positioning.

  The indexing peg 5 and its flange 10, which is generally made of a piece with the peg, are fixed to the table 2 by means of screws 17 and a special intermediate element 18, which is fixedly mounted in

the support table 2.

  In the case of FIG. 1, the ring washer 11, which has an annular shape, supports the disc-shaped spacer element 6 only in the peripheral zone thereof. In the central part, there is a small space or clearance between the back of the intermediate element 6 and the pallet or an intermediate washer 19. This provides a possibility of bending to compensate for

  tolerances when attaching the pallet to the table 2.

  The device represented in FIG. 2 is substantially like that of FIG. 1, so that it bears the same reference numbers. The essential difference is that the kinematics is reversed because the flexibility to absorb the tolerances in the draw direction of the pallet is

  elastic deformability of the ankle 5, and more particularly

  10. As shown in the figure, in this case the intermediate element 6 is supported substantially flat over its entire dorsal surface, thanks to a second annular washer 20 covering the central part of the element 6. Of course , one can provide a single washer support instead of two washers II and 12, and to support

2 6 1 3 9 7 C

  7- directly the back of the intermediate element 6 against a piece irterrm, ed.aire

21 fixed in the pallet 1.

  In order to present the desired elasticity, the indexing pin 5 is partially recessed, for example by means of a relatively large central bore 22. In addition, there is provided an annular groove 23 wider suitable in the flange 10. The width and depth of the groove 23 are chosen so that there remains a relatively thin annular connecting zone 2 between the peg 5 and the part annular outside and supported flange 10. As seen in the figure, a game is provided under the pin 5 between the flange and an annular intermediate washer

  applied against the piece 18, to allow a corresponding bending.

  The intermediate washer 25 shown in FIG. 2 and the intermediate washer 19 shown in FIG. I also serve as stop members limiting the flexion play. The expansions of the materials can be absorbed without problems thanks to the deformability created in the disc 6

by the annular grooves 8 and 9.

  The present invention is not limited to the embodiments described above, but it extends to any obvious modifications or variations.

for a person skilled in the art.

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Claims (9)

1. Device for fixing pallets on a holding table, this table comprising several indexing pins having at least partially a frustoconical shape and arranged to fit into bores of the pallet to be fixed or a part integral with the pallet when the pallet is pulled towards the holding table, characterized in that said bores (4) are formed in at least one intermediate element (6) dimensioned so as to be elastically deformable perpendicularly to the direction of insertion, close to the bores, and in that the indexing pins (5) have all their periphery a shape complementary to that of the bores (4).   2. Device according to claim 1, characterized in that the spacer element is in the form of a plate (6) which has grooves (8, 9) extending in the direction of insertion from at least a face of 1 5 the element.   3. Device according to claim 2, characterized in that said grooves   are annular grooves (8, 9) concentric with the bore (4).   4. Device according to claim 2 or 3, characterized in that said   grooves (8, 9) extend from both sides of the element.   5. Device according to claims 3 and 4, characterized in that the   annular grooves (8, 9) each have a depth greater than half the thickness of the plate (6) and are in zones of diameters respective different.   6. Device according to claim 1, characterized in that each pallet (I) is provided with two of said bores (4), arranged at a distance one of the other.   7. Device according to claim 1, characterized in that the holding table (2) is provided with air control ducts (13), connected to air ducts (15) which pass through the indexing pins (5). ) so that 261397C -9   lead into the front face of the pins inserted into the bores.   S. Device according to claim 1, characterized in that the intermediate die (6) or the indexing pin (5) is mounted respectively on a recess of the pallet (1) or in a recess of the holding table (2), with a game on the back of the element or ankle in the draw direction of the pallet, so as to have an elastic flexibility in its central part.   9. Device according to claim 8, characterized in that the intermediate element (6) is supported on a bearing washer (II) in its part.   peripheral, while its central part is spaced from the pallet (1).   G10. Device according to claim 8, characterized in that each indexing pin (5) comprises a flange (10) which is not supported on the table of   maintaining (2) only in its peripheral part.   He. Device according to claim 10, characterized in that said flange (10) and / or the indexing peg (5) comprises (nt) in their central part recesses (22, 23) giving them an elasticity in said direction of draw.   12. Device according to claim 11, characterized in that the indexing pin (5) is connected to the supported peripheral portion of said flange.   (10) by a thinned annular zone (24).   13. Device according to claim 8, characterized in that an intermediate washer (19, 25) is placed with play in the elastic bending zone respectively under or behind the intermediate element (6) or the   indexing pin (5), to serve as a stop and member limiting flexion.