GB2118075A - Apparatus for the automatic clamping and unclamping of a workpiece support to a machine table - Google Patents

Abstract

A clamping element (11) housed in the table (1) is formed as a rocker arm which is pivoted about a guide pin (10) in a bearing (12). The short lever arm of the rocker arm is engaged by the drive head (6) of an actuating member (5), whilst the hook-shaped long lever arm projects over the surface between the table (1) and the workpiece support (21). The rocker arm is displaceable in its bearing (12) in the direction of the clamping force against the action of a spring (9). In operation when the member (5) is moved downwards, the arm first pivots about the pin (10) such that the hook (15) engages fully with the L-slot (22) in the work support (21) (see Fig. 2). Further movement of the member (5) then causes the arm to move linearly in the direction of the clamping force to effect the clamping via the abutment face (24) (see Fig 3). The arrangement is particularly useful in the automatic clamping of workpieces in a production process. <IMAGE>

Description

SPECIFICATION Apparatus for the automatic clamping and unclamping of workpiece supports The invention relates to an apparatus for the automatic clamping and unclamping of workpiece supports on the machine table of a machine tool, in particular but not exclusively for use in the automatic exchanging of workpieces during a production process.

It is known to clamp a workpiece support with the help of T-slots present in a machine table by means of T-slot blocks. The introduction of the slot blocks into the T-slots during automatic operation requires an accurate horizontal feed of the workpiece support in a relatively horizontal manner over the machine table.

This is problematic in particular with large workpiece supports and requires additional auxiliary devices if damage to the slot blocks or to the workpiece support or to the machine table is to be avoided.

The Democratic German Republic Patent Specification No. 122 337 has already disclosed a clamping device for the automatic clamping and unclamping of workpiece supports, by means of which it is also possible to feed the workpiece support vertically with respect to the machine table. This is possible as the T-slot blocks are rotated through 900 before commencement of the clamping phase via a gear which is in operational connection with a connecting rod and the T-slot blocks are thereby positively connected in the clamped position with the T-slots of the machine table. An additional movement is however required for the production of positive locking, this movement being complex in terms of gearing which occupies a large amount of space.

The object of the invention is to provide an improved apparatus for clamping workpiece supports.

The apparatus according to the invention comprises at least one clamping device arranged in the machine table and engaged in or disengaged from a complementary profile of the workpiece support, the or each clamping device having a profiled clamping element actuated by a connecting rod, wherein the profiled clamping element is formed as a rocker arm which is pivoted in a bearing by means of a guide pin, a short lever arm of this rocker arm being positively guided by a drive head of the connecting rod, whilst a long lever arm is hook-shaped to project over the surface of the machine table and the workpiece support; and the rocker arm in the bearing is displaceable in the direction of the clamping force against the action of a spring so that in the clamping position a clamping surface of the long lever arm contacts a clamping surface of the complementary profile.

The workpiece support may be fed horizontally whilst spaced from the machine table, with the clamping elements extending into the L-slots.

Then it is fed in the vertical direction after the required position has been reached so that the workpiece support is positioned on the table. The rocker arm only moves as a result of movement of the connecting rod so that positive connection with an L-slot in the workpiece support is produced in a first stage and clamping takes place in a second stage.

In an advantageous embodiment of the invention, the rocker arm has as a bearing a longitudinal slot which, under the action of the spring acting on a suitable location on the short lever arm, is pivoted on a lower abutment seat about a guide pin fastened to the machine table.

Alternatively in another embodiment, the guide pin is fastened to the rocker arm; the pin is guided in a groove associated with the machine table and extending in the direction of the clamping force; and the pin is pivotably mounted on an upper abutment surface of the groove under the action of the spring acting on a suitable location of the short lever arm.

Thus, with a very low degree of technical complexity, the rocker arm is pivoted in the first instance when the clamping action is initiated and the spring force acting on the short lever arm is only then overcome and the rocker arm displaced in the direction of the clamping force so that clamping takes place.

In an advantageous embodiment of the invention the rocker arm is formed as a profiled clamping bar. In this way the clamping force is distributed over a large surface area so that high clamping forces may be transmitted. In a further embodiment of the invention the profiled clamping bars of several clamping devices are connected together so that a synchronised path of movement is achieved in a simple manner.

To help understanding of the invention, it will now be described in more detail with reference to two embodiments illustrated in the accompanying drawings, in which: Figure 1 is a part-sectional side view of a clamping device of the first embodiment after positioning of a workpiece support on a machine tool, Figure 2 in a similar view shows the clamping device after partial downward movement of a connecting rod, Figure 3 similarly shows the clamping device in its clamping position, Figure 4 similarly shows the clamping device of the second embodiment after positioning of a workpiece support on a machine tool, Figure 5 similarly shows the clamping device of the second embodiment after partial downward movement of its connecting rod, and Figure 6 similarly shows the clamping device of the second embodiment in its clamping position.

Referring first to Figures 1, 2 and 3 showing the first embodiment it should be noted that the reference numerals are shown in Figure 1 alone. In the machine tool table 1 there is disposed in the longitudinal direction an L-shaped groove 2 which intersects at one point with a bore 3 extending at right angles thereto. The bore 3 opens into a central counter-bore 4 on the machine table surface. A connecting rod 5 is guided in the bore 3, the drive head 6 of this rod being received by the counter-bore 4. A blind bore 7, in which a piston 8 and a spring 9 are disposed, extends from the groove 2 parallel to the bore 3.

A guide pin 10 is fastened in the groove 2 in the area of the counter-bore 4. On this pin a bracket-shaped rocker arm 11 is rotatably and displaceably mounted via a longitudinal slot 12 with an abutment seat 13. The rocker arm 11 has on its long lever arm an abutment surface 14 and at right-angles thereto a clamping surface 15. The drive head 6 has on the lower surfaces of its jawopening an abutment edge 16 for contacting the short lever arm of the rocker arm 11. The short lever arm is acted on by the piston 8.

A workpiece support 21 has in its under-side an L-shaped groove 22 which is disposed in mirror symmetry with respect to the groove 2 of the machine table 1. This groove 22 has an abutment surface 23, complementary to the abutment surface 14, and at right angles thereto a clamping surface 24. The rocker arm 11 may have the width of a profiled clamping bar (not shown).

The operation of this first embodiment of the invention is as follows: when the workpiece support 21 is positioned on the machine table 1, as in Figure 1, by being fed both in the horizontal direction along the groove 2 and vertically in the direction of a clamping force to be applied, the connecting rod 5 with its drive head 6 is in its upper end position. As a result of the frictional guiding of the short lever arm in connection with the force of the spring 9 on the piston 8, the rocker arm 11 is urged upwardly so that the guide pin 10 is adjacent to the lower abutment seat 13 of the longitudinal slot 12 of the rocker arm 11.

The rocker arm 11 thus assumes the tilted position shown in Figure 1.

On initiation of the process for locking the workpiece support 21, i.e. the downward movement of the connecting rod 5, the rocker arm 11 rotates about the guide pin 10 until the abutment surface 14 of the rocker arm 11 comes to rest on the abutment surface 23 of the groove 22 of the workpiece support 21. Under the action of the spring 9, the piston 8 ensures that the rocker arm 11 is held up with abutment being maintained between the guide pin 10 and the lower seat 13 of the longitudinal slot 12, see Figure 2.

When the downward movement of the rod 5 is continued the force of the spring 9 is overcome and the rocker arm 11 undergoes a downward longitudinal movement until the clamping surface 15 of the rocker arm 11 comes into contact with the clamping surface 24 of the workpiece support 21, see Figure 3. From this point the clamping force of the connecting rod 5 is transmitted to the workpiece support 21. During this longitudinal movement of the rocker arm 11 the longitudinal slot 12 in connection with the guide pin 10 acts as a longitudinal guide.

Since the full clamping force contacts the connecting rod 5, there is a torque-free transmission of this force to the workpiece support 21.

After the workpiece has been machined the workpiece support 21 is released in the reverse sequence. In the first instance the clamping force is relaxed by raising of the connecting rod 5 and is then discontinued. After this the rocker arm 11 is raised via the piston 8 as a result of the pressure of the spring 9 until the condition of Figure 2 is reached, i.e. the guide pin 10 has come to rest on the lower abutment seat 1 3 of the longitudinal slot 12. This is followed by further raising of the connecting rod 5 and therefore by the introduction of the pressure of the edge 1 6 resulting in the tilting of the rocker arm 11 about the guide pin 10 and therefore the opening of the rocker arm 11, so that the workpiece support 21 may again be shifted.

The clamping device of the second embodiment is substantially identical with respect to its layout to the first embodiment, with the exception that certain elements and functions are somewhat modified.

The L-shaped slot 2 is disposed in the machine table 1, see Figure 4, in the longitudinal direction and intersects at one point with the bore 3 extending perpendicular thereto and opening into a central counter-bore 4 in the machine table surface. The connecting rod 5 is guided in the bore 3, the drive head 6 of this rod being received by the counter-bore 4. The drive head 6 is provided on the lower surface of its jaw-opening with a bevel sufficient to ensure that the edge produced no longer has any function. A blind bore 17 is provided in the groove 2 of the machine table 1 in front of and behind the connecting rod in each case, in which bores respective springs 19 are disposed between pairs of balls 18.

The narrow side of the L-shaped groove 2 is formed as an abutment surface 20. A bearing 31 with a groove 32 which is downwardly open is fastened in the groove 2 laterally of the counterbore 4, the groove 32 having an upper abutment surface 33. The short lever arm of a rocker arm 34 projects into the jaw opening of the drive head 6.

This rocker arm 34 has a guide pin 35 which is guided in the groove 32 of the bearing 31. The short lever arm is acted on by upper balls 18.

The rocker arm 34 is provided on its long lever arm with a clamping surface 15 and at right angles thereto an abutment surface 36 which cooperates with the abutment surface 20 of the groove 2. A stop 37 is disposed in the groove 2 opposite the abutment surface 20.

The rocker arm 34 may also be formed as a profiled clamping bar (not shown).

The operation of the second embodiment is as follows: The workpiece support 21 is positioned on the machine table 1 in the same way as in the first embodiment, see Figure 4. In this respect the connecting rod 5 with its drive head 6 is disposed in its upper end position.

This together with the force of the spring 19, which presses the short lever arm of the rocker arm 34 upwardly via the balls 18, to the contacting of the guide pin 35 with the upper abutment surface 33 of the groove 32. In this way the rocker arm 34 assumes the tilted position limited by the stop 37.

During the downward movement of the connecting rod 5 and the simultaneous effect of the force of the spring 1 9, the rocker arm 34 and therefore also the guide pin 35 is rotated in the groove 32. The contact of the guide pin 35 on the upper abutment surface 33 is maintained until the abutment surface 36 of the rocker arm 34 comes to rest on the abutment surface 20 of the groove 2 of the machine table 1, see Figure 5.

On further downward movement of the connecting rod 5 the rocker arm 5 undergoes a longitudinal downward movement until the clamping surface 1 5 of the rocker arm 34 comes to rest on the clamping surface 24 of the workpiece support 21, see Figure 6. During this longitudinal movement the groove 32 serves as a longitudinal guide in cooperation with the guide pin 35. From this point the clamping force of the connecting rod 5 is transmitted to the workpiece support 5 in a torque-free manner.

After the workpiece has been machined, the workpiece support 21 is released in the reverse sequence.

Thus the above embodiments may be seen to provide devices for the automatic clamping and unclamping of workpiece. supports on the machine tables of machine tools, enabling feeding of the workpiece supports in the vertical and the horizontal directions with respect to the machine tables and enabling torque-free clamping with a low degree of technical complexity.

Further an automatic clamping device is provided, which is disposed in the machine table and is engaged in or disengaged from a complementary profile of the workpiece support by means of a profiled clamping element actuated by a connecting rod and enables positive connection and frictional torque-free clamping solely by means of this linear traction movement.

Claims (6)

1. Apparatus for the automatic clamping and unclamping of a workpiece support on the machine table of a machine tool, comprising at least one clamping device arranged in the machine table and engaged in or disengaged from a complementary profile of the workpiece support, the or each clamping device having a profiled clamping element actuated by a connecting rod, wherein the profiled clamping element is formed as a rocker arm which is pivoted in a bearing by means of a guide pin, a short lever arm of this rocker arm being positively guided by a drive head of the connecting rod, whilst a long lever arm is hook-shaped to project over the surface of the machine table and the workpiece support; and the rocker arm in the bearing is displaceable in the direction of the clamping force against the action of a spring so that in the clamping position a clamping surface of the long lever arm contacts a clamping surface of the complementary profile.

2. Apparatus as claimed in claim 1, wherein the rocker arm has as the said bearing a longitudinal slot which, under the action of the spring acting on a suitable point of the short lever arm, is pivotable on a lower abutment about the guide pin, which is fastened to the machine table.

3. Apparatus as claimed in claim 1, wherein the guide pin is fastened to the rocker arm; the pin is guided in a groove associated with the machine table and extending in the direction of the clamping force; and the pin is mounted pivotably on an upper abutment surface of the groove under the action of the spring acting on a suitable point of the short lever arm.

4. Apparatus as claimed in claim 1, claim 2 or claim 3, wherein the rocker arm is formed as a profiled clamping bar.

5. Apparatus as claimed in claim 1, claim 2, claim 3 or claim 4, wherein the profiled clamping bars of several clamping devices are connected together.

6. Apparatus for the automatic clamping and unclamping of a workpiece support on the machine table of a machine tool substantially as hereinbefore described with reference to Figures 1 to 3 or Figures 4 to 6 of the accompanying drawings.