HK1082932B - Clamping apparatus with a chunk and a pallet releasably attachable thereto - Google Patents

Description

Clamping device with a chuck and a carrier plate releasably connected to the chuck

Technical Field

The present invention relates to a clamping device comprising a chuck member and a pallet adapted to be releasably secured to the chuck member. The chuck member has at least three centering grooves, and the pallet has a corresponding number of centering pins arranged and shaped to correspond to the centering grooves. The chuck member further comprises clamping means for clamping the pallet to the chuck member.

Background

Clamping devices of the type described are primarily used to fix workpieces in a well-defined positioning in the machining area of a machine tool. Thus, the workpiece is first secured to the pallet and the pallet is releasably attached to the chuck member. In most cases the chuck member itself is fixedly attached to the machine tool.

In known devices of this type, the chuck member is typically provided with four centering pins, each having two opposing, tapered side surfaces. The supporting plate is provided with four grooves, and the positions and the shapes of the grooves correspond to those of the centering pins. The pallet comprises a centrally located clamping bar by which the pallet can be clampingly fixed to the chuck member. When the pallet is clampingly secured to the chuck member, the centering pins enter the centering grooves and align the pallet relative to the chuck member in the x and y directions and relative to its angular position.

Document EP0255042 discloses a clamping device of the type described which is suitable for fixing a workpiece to a machine tool. The clamping device basically comprises a chuck member, an electrode holder and a clamping strip fixed to the latter. The top surface of the electrode holder is provided with four grooves, which are mutually offset by 90 ° around the central z-axis. Each side of each groove has a cut-out so that the flange structure is resilient in the z-direction.

Four ridges project from the surface of the chuck member facing the electrode holder. The shape and location of these ridges generally correspond to the shape and location of the four grooves provided in the electrode holder. The corners of the chuck member are provided with four posts that serve as z-direction references. Upon clamping the electrode holder to the chuck member, the ridges of the chuck member engage the resilient flanges of the electrode holder and axially deform the latter in the z-direction until said z-reference post rests on a bearing surface provided on the electrode holder; thus, the z-position of the electrode holder relative to the chuck member is determined. By the ridges in combination with the resilient flanges, the electrode holder is positioned in the x and y directions, as well as its angular position about the z axis relative to the chuck member.

In order to detach the electrode holder from the chuck member, the electrode holder must be moved axially (i.e. in the z-axis direction) along a path corresponding at least to the length of the central clamping bar above the electrode holder. In other words, this means that a free space, which extends in the z direction and is positioned above the electrode holder clamped on the chuck member, must be provided, which at least corresponds to the length of the clamping strip in order to lift the electrode holder off the chuck member and to perform the dismounting.

Disclosure of Invention

It is an object of the invention to provide a clamping device of the kind described which in the assembled state has a low overall height and requires only a relatively small free space in the z-direction for the pallet to be removed from the chuck member.

To meet these and other objects, the present invention provides a clamping apparatus comprising a chuck member and a pallet adapted to be releasably secured to the chuck member. The chuck member has at least three centering grooves, and each centering groove has a first centering groove side and a second centering groove side.

The pallet has at least three centering pins arranged and shaped to correspond to the three centering grooves, and the chuck member comprises clamping means for clamping the pallet to the chuck member.

Each of said first centering groove sides of the chuck member is adapted to determine the position of an associated centering pin of the pallet, and each of said second centering grooves is provided with a clamping member adapted to engage with a notch of the associated centering pin when clamping the pallet on the chuck member, such that each centering pin is pulled into the associated centering groove in the z-direction and simultaneously pressed against said first centering groove side of the associated centering groove.

The basic idea of the invention can thus be seen in the fact that it is not necessary to provide separate clamping bolts or rods for fixing the pallet to the chuck member. Instead, the centering pins provided on the pallet may be used to center the pallet relative to the chuck member and simultaneously to secure the pallet to the chuck member. To this end, in each centering groove of the chuck member, one groove flank is adapted to center and position the centering pin in engagement therewith, while the opposite groove flank is constituted by a clamping member adapted to engage with a recess and/or projection provided on the associated centering pin. Thereby, the clamping member not only pulls the centering pin into the centering groove in the z-direction, but at the same time pushes it against the opposite groove flank serving for centering purposes.

Drawings

FIG. 1 shows a perspective view of a chuck and pallet;

FIG. 2 shows a top view of the chuck;

FIG. 3 shows a cross-sectional view of the pallet and chuck, with the two elements separated from each other;

FIG. 4 shows a cross-sectional view of the pallet and chuck in an assembled state, but not yet clamped to each other; and

fig. 5 shows a cross-sectional view of the pallet and chuck assembled and clamped to each other.

Detailed Description

Fig. 1 shows a pallet 2 and a chuck 1 in a perspective view, including some details described below. The chuck has a substantially cylindrical shape and comprises a substantially circular base plate 3 to which a ring element 4 is fixed by means of a plurality of screws 5; the ring element 4 thus surrounds the actual chuck member 1. The chuck member 1 is provided with a central continuous opening 6 adapted to receive a sleeve member 7.

Annular sealing members 8 and 9 are inserted into the annular element 4 and the sleeve 7, respectively, from the top. The chuck member 1 is further provided with four centering grooves 10a, 10b, 10c and 10d which are mutually offset by 90 ° and coaxially arranged about the central z-axis 26. On the other hand, the pallet 2 is provided with four centering pins 20a, 20b, 20c and 20d arranged in correspondence with the centering grooves 10a, 10b, 10c and 10d of the chuck member 1 and adapted to cooperate therewith when assembling the two elements 1 and 2.

In the case of the centering grooves 10a, 10b, 10c and 10d each being provided in the chuck member 1, one side or flank of the groove is adapted to serve as a centering pin for centering the pallet 2 cooperating therewith, while the other groove side or flank is formed by a clamping element in the form of a pivotally supported lock bolt 11a, 11b, 11c and 11 d. A total of four latches 11a, 11b, 11c and 11d are used to clamp the pallet 2 to the chuck member 1, as will be described in more detail hereinafter. The particular latches 11a, 11b, 11c and 11d move laterally into recesses provided in the chuck member. In the assembled state of the clamping device, the associated locking bolt 11a, 11b, 11c and 11d is fixed axially on its inside by the sleeve 7 and on its outside by the ring element 4.

Fig. 2 shows a top view of the chuck member 1. In addition to the four centering grooves 10a, 10b, 10c and 10d and the four latches 11a, 11b, 11c and 11d, the figures also show four groove sides or flanks 14a, 14b, 14c and 14 d. Considering that the two centering grooves 10c and 10a are opposite when viewed in the vertical direction of the drawing, it should be noted that the right-hand groove flanks 14a, 14c constitute references for determining the position of the pallet 2 relative to the chuck 1 in the x-direction. Considering now that the other two centering grooves 10d and 10b are opposite when viewed in the horizontal direction of the drawing, it should be noted that the lower groove sides 14a, 14c each constitute a reference for determining the position of the pallet 2 in the y-direction relative to the chuck 1. The other surfaces 15a, 15b, 15c and 15d, each located between a groove 10a/10b, 10b/10c, 10c/10d, 10d/10a of an adjacent pair, form resting surfaces determining the position of the pallet 2 in the z-direction with respect to the chuck 1.

Fig. 3 shows a cross-sectional view of the pallet 2 and the chuck member 1 taken along a plane extending through the centering grooves 10a and the associated centering pins 20a of the pallet 2, wherein the circular base plate is shown on a reduced scale. The bottom of the associated lock bolt 11a includes a cylindrical portion 12a which is received in a corresponding recess in the chuck member 1. At the same time, the cylindrical portion 12 constitutes a support for pivoting the latch 11 a. For operating the blocking bolt 11a, a clamping piston 16 is provided, which is biased in the direction towards the blocking bolt 11 by a spring 19 resting on the bottom 3. The clamping piston 16 comprises an annular shoulder 17 and a cylindrical projection 18 with a conical front, by means of which the locking bolt 11a is supported for radial movement and pivoting, respectively. Preferably, the protrusion 18 is slightly flattened on the side facing the latch 11a in order to increase the contact surface between the protrusion 18 and the latch 11a, thereby reducing the specific load pressure applied to the top 13a of the latch 11 a.

To move the clamping piston 16 to its initial rest position against the force of the spring 19, as shown in fig. 3, pressurized air is supplied into the chamber above the shoulder 17. The supply of air under pressure into the chamber is achieved by means of the annular groove 21 and the channel 22. In the assembled state of the clamping device shown in fig. 3 and 4, the groove 21 cooperates with the annular circular element 4 (see fig. 1) to constitute an annular channel sealed by a sealing element, not shown.

The particular centering pin 20a is provided with notches 23a, 24a on opposite sides thereof. As shown in fig. 3, the right-hand groove flank 14a provided for centering the relevant centering pin 20a is designed as a projection which is adapted to rest on one of the right-hand recesses 23a of the centering pin 20a when clamping the pallet 2 to the chuck 1, as shown in fig. 3. For the locking bolt 11a, a projection 13a is also provided which is adapted to rest against the other left-hand recess 24a of the centering pin 20a when clamping the pallet 2 to the chuck 1, as shown in fig. 3.

Fig. 4 shows a cross-sectional view of the assembled but unclamped state of the pallet 2 and the chuck member 1. In order to ensure that a particular centering pin 20a of the pallet 2 is inserted into a corresponding centering groove of the chuck member 1, the piston 16 must be pneumatically moved downward in its rest or initial position, as shown in fig. 4. Thereby, the latch 11a is located at the initial position in which it is pivoted to the left as shown in fig. 4. To further ensure that the locking bolt 11a is in its said initial left position, once the clamping piston 16 is in its lower rest position, a spring element (not shown) may be provided if desired. On the other hand, the locking bolt 11a is designed such that it can be moved into its desired left-hand rest position, and also into its right-hand position, by the centering pin 20a being inserted into the centering groove 10 a.

Once the pallet 2 rests against the z-direction reference surface of the chuck member 1 and the centering pins are received in the associated centering grooves, the pneumatic force acting on the clamping piston 16 is reduced, with the result that the latter moves under the influence of the associated springs 19 into the operating position of fig. 5. In the upward movement of the clamping piston 16, the slightly conical projection 18 presses against and moves the locking bolt 11a in the direction of the groove side or flank 14a, the centering pin 20a being drawn into the relevant groove, with the result that centering is effected in the z direction on the one hand. On the other hand, at substantially the same time, a centering of the pallet 2 in the x and y directions and with respect to the angular position around the z-axis is achieved. By moving the clamping piston 16 upwards, the latch 11a is pivoted towards the right along a path between some tens of millimetres and some millimetres, according to its actual configuration, to its operative position in which the pallet 2 is clamped to the chuck member 1. It thus rests on the z-reference surfaces 15a, 15b, 15c and 15d (see fig. 2), with the result that, in addition to being accurately positioned in the z-direction, it is not only accurately positioned in the x-and y-directions, but also its angular position relative to the axis about z is ensured. It should be noted that the centering pin 20a is dimensioned so that it does not rest against the bottom of the centering groove once the clamping operation is completed.

It is understood that all the above description given for the operation of the centering pin 20a and the centering groove 10a applies equally to the three other centering pins 20b, 20c and 20d and to the three other centering grooves 10b, 10c and 10d, including all the corresponding elements.

In addition to four different clamping pistons for operating the four latches, a common ring piston may be provided, which has four cylindrical projections for operating the four latches. Alternatively, instead of or in addition to the described recesses, special centering pins can be provided, the projections of which cooperate with correspondingly configured clamping means.

The advantages of the clamping device of the invention and of the possible embodiments are summarized below:

the structure is very compact, in particular with a very low height, since the central clamping bar, which is usually very long, provided in most prior art devices can be eliminated;

for the removal of the pallet, a free space in the region of 10 mm above the clamping chuck is sufficient;

very accurate centering for absolute and repeatability;

the chuck member may be provided with a continuous central opening, since the central clamping member does not have the shape of a long pin member;

due to the provision of the two annular sealing members, it is possible to effectively protect the elements for centering and positioning between the two sealing members;

a clamping piston arranged to operate the bolt pneumatically sealing the environment;

no air jets are necessary to pneumatically clean the neutralizing and/or static surfaces; and

there is no need to apply a high clamping force in the z-direction, so that the pallet can be designed very shallow.

Claims (11)

1. Clamping device comprising a chuck member and a pallet adapted to be releasably secured to the chuck member, the chuck member having at least three centering grooves and each centering groove having a first centering groove side and a second centering groove side, the pallet having at least three centering pins arranged and shaped to correspond to the at least three centering grooves, and the chuck member further comprising clamping means for clamping the pallet to the chuck member, characterized in that each centering pin has a lateral recess and/or projection and each first centering groove side of the chuck member is adapted to determine the position of the associated centering pin of the pallet and each second centering groove side is provided with a pivoting latch member adapted to pivot towards the first centering groove side, the pivoting latch member is adapted to engage with the recesses and/or projections of the associated centering pin when clamping the pallet against the chuck member, such that each of the centering pins is drawn into the associated centering groove in the direction of the central axis (26) of the chuck member and simultaneously pressed against the first centering groove side of the associated centering groove.

2. A clamping arrangement according to claim 1, characterised in that each of said centering pins is provided with recesses and/or projections on both sides thereof, and that the side of said first centering groove adapted to determine the position of the associated centering pin has a shape corresponding to the shape of the centering pin engaging therewith, so as to draw said centering pin into the centering groove in the direction of the central axis (26) of the chuck member under the influence of said pivoting latch member.

3. Clamping device according to claim 1 or 2, wherein the chuck member is provided with four centering grooves, which are mutually offset by 90 ° around the central axis direction (26) of the chuck member, whereby the pallet is provided with four correspondingly positioned centering pins, and whereby two diametrically opposite centering grooves are each adapted to determine the position of the pallet in the x-direction, while two other diametrically opposite centering grooves are adapted to determine the position of the pallet in the y-direction.

4. The clamping apparatus as claimed in claim 1 wherein said pivoting latch member is adapted to be pivoted towards the sides of the first pair of central recesses by a clamping piston moving in the direction of the central axis of the chuck member.

5. A clamping arrangement according to claim 4, characterised in that the centre of rotation of the pivoting latch member is located below the associated centring recess.

6. A clamping arrangement according to claim 4 or 5, wherein the clamping piston is provided with a cylindrical projection adapted to pivot the pivoting latch member from an initial or rest position to an operating or clamping position.

7. The clamping apparatus as recited in claim 6, wherein said cylindrical protrusion has a tapered front portion.

8. The clamping device of claim 4, wherein said clamping piston is biased in a direction toward said pivoting latch member by a spring member.

9. The clamping apparatus as claimed in claim 1, wherein said chuck member is provided with a central continuous opening.

10. Clamping apparatus according to claim 1 wherein the chuck member is provided with a plurality of rest surfaces which act as references to the central axis direction (26) of the chuck member and each surface is located between adjacent pairs of recesses.

11. The clamping device as recited in claim 10, wherein said resting surfaces are distributed to form an annular structure interrupted by said centering grooves.