GB2120350A - Stop system of rotary shaft for driving pivotable gripper mechanisms - Google Patents

Abstract

A system whereby a rotary shaft 1 is stopped in predetermined positions comprises a clutch part 11 which is axially movable but rotationally fixed on the shaft. The part 11 is moved axially (by release of the pressure acting in a chamber 6) into engagement with a second clutch part 12 when a certain rotary position of the shaft is reached (as detected by a switch 15 actuated by cams 15.1 on the shaft). Part 12 carries stops engageable with respective fixed abutments limiting travel in each direction of rotation, so that after such limited further rotation the shaft reaches the predetermined position at which it stops. A clutch 4 through which the shaft is driven by a motor 5 and belt 3 then slips. For return rotation, the polarity of motor 5 is reversed and chamber 6 is repressurised to disengage the clutch. The clutch drive elements are pins 11.1 projecting from part 11 into respective part-circumferentially extending slots 12.1 in part 12. <IMAGE>

Description

SPECIFICATION Stop system for pivotable gripper mechanisms The present invention relates to a stop system which may be used for the controlled pivoting of a pivot shaft, in particular in the case of gripper mechanisms.

West German Patent Specification O/S 2111 495 discloses a device for the damping and halting of the rotary movement of a shaft which supports the gripper of a robot. A locking component rotates with the shaft, which component is provided with a first member for contacting damping elements and a second member for contacting fixed stops. The damping elements and the fixed stops are fastened adjustably to the housing which receives the shaft.

The locking component in the first instance contacts a damping element as a result of which the rotary movement of the shaft is delayed, the movement of the shaft being halted as soon as a fixed stop prevents any further rotation of the locking component and the shaft. The fixed stops limit the angle of rotation of the shaft and therefore the pivot region of the gripper mechanism. In order to provide a further pivot region varying from that enabled by the position of the fixed stops the apparatus must be manually adjusted.

As described in West German Patent Specification O/S 29 03 1 85 the shaft which supports the gripper mechanism of a robot has its rearward end in a housing which is provided at the end of a horizontal gripper arm. A two-armed stop lever is disposed on the shaft end in a rotationally fixed manner in this housing. Both a damping device and stops are also fastened to the housing.

The stop lever is pivoted between these elements by the driven shaft such that one lever end comes into contact towards the end of its pivot region with the damping device as a result of which the remaining pivot movement is braked and is halted when the other lever end reaches a stop. The assembly is ensured via a constantly effective drive moment. The pivot region of the shaft and therefore of the gripper mechanism is in this respect determined by the position of the stops in combination with the configuration of the stop lever which is only designed for one pivot region.

Differently formed stop levers enable the use of different pivot regions although this also necessitates manual adjustment. In the case of both these prior devices there are therefore relatively long down times for the robot as well as for the associated machine. In addition the two end positions of these devices may not be used for a double gripper mechanism as these must be provided in each case with two pivot positions with respect to the magazine and the chuck, i.e.

four pivot positions in total.

The chief defects of these prior devices may be traced to the following causes: the fastening of the stop faces to the ends of a pivot area, which may only be manually modified.

The object of the invention is to provide more than two pivot positions of the gripper mechanism without conversion times.

According to the invention there is provided a stop system for a pivotable gripper mechanism having a housing which receives a driven pivot shaft and two stops rotatable with the pivot shaft and limiting its opposing pivot movements by each of the stops contacting a respective abutment fastened to the housing wherein both stops are fastened to a stop ring which is disposed in a freely rotatable manner on the pivot shaft and is formed as part of a shift clutch, whose other part is formed by a clutch ring which is disposed in a rotationally fixed manner adjacent to the stop ring on the pivot shaft and is axially displaceable by a linear drive.

The shift clutch is preferably formed as a positive drive coupling with several cam pairs, wherein there is provided in each case between a pairing of the cam of the stop ring and the cam of the clutch ring a play along the periphery on which all the cams are disposed. The cams of the clutch ring may be formed as axially parallel projecting pins and the cams of the stop ring as slots, the slots and pins being distributed about the periphery in equal numbers. The linear drive may be formed as a piston spring drive.The piston is preferably a plunger piston which is fastened to a cap which is rigidly connected with the coupling ring and houses a disc and compression springs in an annular chamber, which springs are supported on one hand on the clutch ring and, on the other hand, on the disc which is fastened in a rotationally fixed manner to the pivot shaft in whose end facing away from the gripper mechanism there is centrally disposed a cylinder chamber which houses the plunger piston.

Whilst the stop system therefore comprises as before a constant pivot angle, the pivot shaft may be released from the stop system and carry out controlled part steps which are determined by the number of pairs of coupling elements. These coupling elements operate in the manner of a dividing mechanism. As the stop system ceases to be effective as a result of uncoupling, the pivot shaft may carry out the required part steps after which the stop system comes into operation by means of engagement of the coupling elements and terminates the pivot movement. The control of the coupling process between the stop system and the pivot shaft takes place for example in a known manner by control cams on the pivot shaft.

As a result of this separation of the stop system and the pivot shaft the pivot angle may be automatically modified to predetermined sizes as a result of which there are no longer down times for manual conversion.

To help understanding of the invention, a specific embodiment thereof will now be described in more detail with reference to the accompanying drawings, in which: Figure 1 is a partially-sectioned view showing a pivot shaft with a drive and stop system in longitudinal section, and Figure 2 is a partially-sectioned view on the line Il-Il of Figure 1.

Referring to Figure 1 a pivot shaft 1 is rotatabiy mounted in a housing 2. A gripper mechanism, not shown, is fastened to the end of the shaft which projects to the right. In order to pivot this gripper mechanism the pivot shaft 1 is connected via a toothed belt 3 and a slipping clutch 4 with a drive unit 5 which is fastened to the housing 2 and is provided with a servo brake 5.1. Facing away from the gripper mechanism a cylinder chamber 6 in the form of a blind bore is arranged axially in the pivot shaft.This houses a plunger piston 7 which is fastened inside an axially displaceable cap 8 which covers a free annular chamber 8.1 surrounding the pivot shaft 1, which chamber houses a disc 9 and compression springs 1 0. The disc 9 is fastened coaxially to the outermost end of the pivot shaft 1 and supports the compression springs 10 on its annular surface facing away from the cap 8, the other ends of these springs contacting a clutch ring 11 which is disposed coaxially on the pivot shaft 1, is connected to the cap 8 and is axially displaceabie in the same way as the latter. The clutch ring 11 is provided with axially-projecting pins 11.1 facing away from the compression springs 10, which pins are arranged peripherally in a uniform distribution.Adjacent to the clutch ring 11 there is also axially disposed on the pivot shaft 1 a stop ring 1 2. This is mounted to be freely rotatable but axially fixed and has slots 12.1 on its annular face facing the pins 1 1.1 which slots are disposed around its entire periphery in the same way as the pins 1 These are the same number of slots as pins and they are at the same pitch. Figure 2 shows that the stop ring 12 supports two stops 13 each having its own stop face 13.1, 13.2 one of these facing in each case in one of the two pivot directions. In the pivot path of each of these stop faces 13.1, 13.2 there is arranged its own shock absorber 14, both of which are fastened to the housing 2.In addition a switch 1 5 is also arranged on the housing 2, cams 1 5.1 located on the pivot shaft 1 being associated with this switch, only one of these cams being shown in Figure 1. Figure 1 also shows that pressure medium may be supplied to the cylinder chamber 6 via the stop ring 12 by means of a supply line 1 6.

The stop system of the invention operates as follows: Figure 2 shows one end position of the stop system. In this position the stop having the face 1 3.1 has displaced its shock absorber 14 into its end position. This position is achieved by a driving moment whose value is limited by the slipping clutch 4 and maintained by switching on of the servo brake 5.1. From this point the power flow via the slipping clutch 4, the geared belt 3 and the pivot shaft 1 is supplied to the clutch ring 11 which in this respect assumes the axial position shown in Figure 1. This means that the plunger piston 7 is unloaded so that the compression springs 10 press this piston together with the cap 8 and the clutch ring 11 against the stop ring 12 as a result of which the pins 11.1 engage the stop ring 12.

If the gripper mechanism, i.e. the pivot shaft 1 is to be moved from this end position into an opposite position, the drive unit 5 has its polarity reversed and the servo brake 5.1 is released. The stop face 13.1 therefore leaves its shock absorber 14. The plunger piston 7 is simultaneously loaded so that the clutch ring 11 moves spirally against the force of the compression springs 10 during its rotary drive by the pivot shaft 1 with its pins 1 1.1 leaving the slots 12.1. The pivot shaft 1 is therefore released from the stop system and can be rotated about one or several pitch angles. This pitch angle is determined by the spacing between the ends of two slots 12.1 and is in particular dependent on the number of these slots 12.1 which have been provided peripherally.The required part steps are predetermined by cams 15.1 and when a specific cam is activated the switch 1 5 is switched over as a result of which the plunger piston is again unloaded. The clutch ring 11 1 and its pins 11.1 then move back into the slots 12.1 until each of the pins 11.1 comes into contact at the end of a slot 12.1 and the rotary drive is transmitted to the stop ring 12. The latter moves over a uniform residual path, which provides a brake path, until the stop having the face 13.2 has pressed its shock absorber 14 into its end position as a result of which the pivot shaft halts and remains in this position as described above.

it is also possible to pivot the pivot shaft 1 further from a stop position, for exampie from the position of Figure 2, in the stop direction. For this purpose the servo brake 5.1 is firstly released and therefore unloads the stop system. The plunger piston 7 is then loaded and removes the clutch ring 11 from the stop ring 12 as a result of which the associated shock absorber 14 is also unloaded. If the stop system is uncoupied, the drive 5 is released in the required direction of rotation and rotates the pivot shaft 1 about the necessary part steps. A predetermined cam 1 5.1 is actuated and on reaching the position opposite to the switch 1 5 the plunger piston 7 is unloaded as a result of which the pins 1 1.1 project into the slots 12.1 once more and the stop ring 12 halts the pivot movement over the remaining path.

Claims (7)

1. A stop system for a pivotable gripper mechanism having a housing which receives a driven pivot shaft and two stops rotatable with the pivot shaft and limiting its opposing pivot movements by each of the stops contacting a respective abutment fastened to the housing wherein both stops are fastened to a stop ring which is disposed in a freely rotatable manner on the pivot shaft and is formed as part of a shift clutch, whose other part is formed by a clutch ring which is disposed in a rotationally fixed manner adjacent to the stop ring on the pivot shaft and is axially displaceable by a linear drive.

2. A stop system as claimed in claim 1 , wherein the shift clutch is formed as a positive drive coupling with several drive pairs, a play along a periphery being provided in each case between a pairing of a drive element of the stop ring and a drive element of the clutch ring, on which periphery all the drive elements are arranged.

3. A stop system as claimed in claim 1 or claim 2, wherein the drive elements of the clutch ring are formed as axially parallel projecting pins and the drive elements of the stop ring are formed as slots, the slots and the pins being distributed over the periphery in equal numbers.

4. A stop system as claimed in any preceding claim, wherein linear drive is formed as a piston spring drive.

5. A stop system as claimed in claim 4, wherein the piston is a plunger piston which is fastened to a cap which is rigidly connected to the clutch ring and receives a disc and compression springs in an annular chamber, which springs are supported at one end on the clutch ring and at the other end on the disc which is fastened in a rotationally fixed manner to the pivot shaft in which a cylinder chamber is centrally disposed in the end facing away from the gripper mechanism, which chamber receives the plunger piston.

6. A stop system as claimed in any preceding claim wherein the abutments are dampers.

7. A stop system substantially as hereinbefore described with reference to the accompanying drawings.