GB2079649A

GB2079649A - Workpiece transfer mechanism

Info

Publication number: GB2079649A
Application number: GB8122159A
Authority: GB
Original assignee: TORRINGTON MACHINE TOOL CO Ltd
Current assignee: TORRINGTON MACHINE TOOL CO Ltd
Priority date: 1980-07-18
Filing date: 1981-07-17
Publication date: 1982-01-27
Also published as: GB2079649B

Abstract

Workpiece transfer mechanism primarily for a centreless grinding machine is provided in which a transfer member (10) carrying a gripping head (15) is operable for back and forth axial movement along a path aligned with the working station of the machine and with the axis of a workpiece (7) on a support such as a conveyor (6) at a loading location. Operation of the transfer member (10) is controlled and effected by means such as a ram (14) and gear and opposed rack mechanism (12, 10A and 11) where by a workpiece to be machined can be gripped and transferred from the conveyor (6) to the working station and released thereat and, after machining, gripped again and returned to the conveyor (6). The gripping head (15) may consist of jaws (24) operated by gear and rack mechanism (21, 22, 23) in turn driven by a shaft (16) carried by the transfer member (10). The conveyor (6) is operated for unidirectional indexing movement such as by a ram (29), with provision (39, 45, 46A) for compensating adjustment. <IMAGE>

Description

SPECIFICATION Workpiece transfer mechanism This invention relates to a workpiece transfer mechanism for use with or forming part of a machine tool and is primarily for use in loading cylindrical workpieces to be machined especially hollow cylindrical workpieces such as cylinder liners into a working station of a centreless grinding machine and removing the machined workpieces therefrom.

Various means have been employed over many years for the loading and unloading of workpieces in relation to a centreless grinding machine. These have included chutes arranged to deliver workpieces to the working station from locations above and laterally of the grinding and control wheels, and other mechanisms arranged to lower the workpieces into position from above the wheels. None of these arrangements has provided wholly satisfactory location of the workpieces at the working station and it is quite common to load the workpieces manually which, although often more accurate, is relatively slow and leads to a risk of injury to operatives.

The object of the present invention is to provide a workpiece transfer mechanism for use with or forming part of a machine tool which is able to transfer cylindrical workpieces to and from a working station of a centreless grinding machine in an accurate, reliable and relatively rapid manner, as compared with some conventional arrangements.

According to the invention, a workpiece transfer mechanism for use with or forming part of a machine tool, such as a centreless grinding machine, comprises means for supporting a cylindrical workpiece at a loading location and in alignment with a working station of the machine tool; a transfer member carrying gripping means for engaging a said workpiece and movable along a path generally aligned with the working station and the axis of the workpiece at said location support, and means for effecting and controlling movement of the transfer member along said path in timed relationship with operation of the gripping means and of the machine tool whereby a workpiece to be machined can be transferred from the support means at said loading location to the working station of the machine tool and, after machining, is returned to the support means at said location.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a general perspective diagrammatic view of a centreless grinding machine workpiece transfer mechanism in accordance with the invention, Figure2 is a view taken generally along the line Il-Il of Figure 1, partly in transverse cross-section, further illustrating the workpiece transfer mechanism, Figure 3 is a plan view of part of the loading mechanism of Figure 2, Figure 4 is a cross-section along the line IV-IV of Figure 3, ,-,t,r r ~ ^ e rç elevation of a compensating device associated with the transfer mechanism, and Figure 6 is an enlarged scale cross-section along the line VI-VI of Figure 2.

Referring to Figure 1 of the drawings, this illustrates a centreless grinding machine incorporating in conventional manner a grinding wheel 1 and a control wheel 2 arranged in opposed relationship to either side of a work support blade 3. The control wheel 2 is mounted on an upper slide 4 (Figure 2) for reciprocal movement towards and away from the work support blade 3, the latter being itself mounted on a lower slide 5 (Figure 2). The slides 4 and 5 are normally locked together so as to move as a unit towards and away from the grinding wheel 1, but they can be released to permit relative adjustment between the work support blade 3 and control wheel 2 when, for example, a change in diameter of workpiece is to be accomodated.

Disposed adjacent to the wheels 1 and 2 is an indexible conveyor 6 operable in conjunction with the workpiece transfer mechanism 8 to move successive hollow cylindrical workpieces 7 to be machined to a loading location for transfer onto the work support blade 3 and to move successive workpieces received from the work support blade 3 to a disposal location as will be described hereafter.

As will be seen more clearly from Figure 2, the workpiece transfer mechanism 8 comprises an outer member 9 rigidly secured to the upper slide 4 and extending in a direction parallel to the rotational axes of the wheels 1 and 2. The member 9 has an inner transfer member or arm 10 slidably mounted therein and carrying a rack 10A extending along the underside of the member 10. A fixed rack 11 mounted on the slide 4 is arranged with its teeth in opposition to those of the rack 1 OA and the spacing between the sets of teeth is such as to enable a drive gear wheel 12 to engage with both of the racks. The gearwheel 12 is rotatably mounted on a carrier 13 which is connected to a driving ram 14 which has a stroke such that extension of the ram 14 can move the gear wheel 12 from its rear. position to a forward position shown at 12'.Since free rotation of the gear wheel 12 is prevented by its engagement with the fixed rack 11, the aforesaid movement of the gear wheel 12 has the effect of moving the inner transfer member 10 from its rear position to an extended position indicated in broken lines at 10', i.e. telescopically from the member 9. A protective spring guard is provided at 100.

The inner member 10 carries, at its forward end nearest to the wheels 1 and 2, an expanding caliper or gripping head 15 for the purpose to be described.

A drive shaft 16 to the head 15 extends through the inner member 10 and is connected at one end to a drive gear 17 meshing with a drive rack 18 actuated by a fluid pressure drive ram 18A (Figure 1). The shaft 16 extends rearwardly beyond the drive gear 17 and carries an arrangement of cams 19 which are arranged to actuate micro-switches 19A at the limits of rotation of the shaft 16 in either direction for the purpose to be described.

The forward end of the shaft 16 is formed as an nionoate drive near 20 which, as will be seen more clearly from Figure 6 extends through a central hub 21 of the head 15 and meshes with pairs of opposed racks 22, 23, each rack carrying a respective clamping jaw 24 for contact with the internal cylindrical wall of a workpiece 7. It will be seen that rotation of the gear 20 by actuation of the rack 18 will cause the jaws 24 to expand outwardly into gripping engagemenu with the internal wall of the workpiece, or to be withdrawn inwardly therefrom, according to the direction of rotation of the gear 20.

The indexible conveyor 6 is illustrated in more detail in Figures 3 and 4. The conveyor includes a frame 25 carrying rotatably mounted pairs of sprockets 26 respectively engaged with a pair of endless carrier chains 27 which are straddled by pairs of spaced oppositely inclined workpiece support blocks or slats 28 connected to the chains to be driven thereby in the direction indicated by the arrow A in Figure 4. The conveyor is driven intermittently through fixed increments of movement by means of a constant stroke ram 29 connected by its piston rod 30 to a slide 31 mounted for sliding movement on guide rails 32 and carrying a pair of driving latches 33 which are spring loaded into raised positions as shown in Figure 4 whereby they can engage behind one of the blocks 28 to enable the ram 29 to impart drive to that particular block and thereby to the entire chain and block assembly.Each pair of blocks is spaced from the pair at either side thereof by a distance equal to one aforesaid increment of conveyor chain movement so that each such movement brings each pair into the position previously occupied by the next preceding pair. The ram 29 is carried by a support 34 also mounted on the rails 32, the support 34 being secured to a non-rotatable screw 35 engaged by a nut 36, to which is secured a bevel gear 37 engaged with a further bevel gear 38 rotatable manually by means of a handwheel 39 via a shaft 39A. The latches 33 can thus be accurately adjusted or set by rotation of the handwheel 39 in the appropriate direction for obtaining their constant stroke operation by the ram 29 at the required location for the incremental movement of the conveyor chains 27 and blocks 28 and thus of the workpieces 7 thereon in relation to the transfer mechanism.

In order to load the workpieces 7 successively into a working position on the support blade 3, the following cycle of operations is effected. The first step is to ensure that actuation of the ream 29 brings successive pairs of blocks 28 accurately into a position so as to support a workpiece 7 thereon with its axis in alignment with the support blade 3. The adjustment is made, as necessary, by rotating the handwheel 39 to adjust the position of the ram 29 so that a full extension and retraction of the ram 29 will bring the workpiece 7 into the desire aligned position. With a workpiece 7 supported in this position, the ram 14 is operated to move the transfer member 10 from the rear position to the forward position 10' in which the expansible head 15 will be disposed within a workpiece 7 resting on the conveyor 6.

Because of the co-operation of the gear 12 with the racks 1 OA and 11, it will be seen that the movement of the member 10 is twice that of the stroke of the ram 14 and this enables a relatively compact driving mechanism for the member 10 to be provided. When the member 10 reaches its fully extended position at 10', the carrier 13 actuates a micro-switch Xwhich provides an electrical signal to an electrical control; unit (not shown) to cause the head 15 to be expanded within the workpiece 7 by operation of the ram 18A and rack 18.

As the shaft 16 is rotated by the driving rack 8, its degree of rotation is controlled by dogs (not shown) carried on an end face of the gear 17 and which can be adjusted to enable the jaws 24 of the head 15 to provide just the required grip against the inner surface of the workpiece 7. In fact, the workpiece 7 is supported on the conveyor at a level such that its axis is slightly below the longitudinal axis of the head 15 and since the jaws 24 are expanded uniformly, this produces a centring effect on the workpiece 7 and raises it slightly from the conveyor blocks 28.

End location of the workpiece 7 on the conveyor 6 is provided by a stop 7A fixed to the frame 25 and engaged by one end of the workpiece, and by an abutment 7B carried by the transfer member 10 acting on the opposite end of the workpiece.

When the expansion of the jaws 24 is complete, one of the cams 19 carried by the shaft 16 actuates a micro-switch 19Ato signal completion of the expansion, permitting the control unit to signal retraction of the ram 14 so as to move the workpiece 7 from the conveyor 6 to its operative position over the support blade 3, i.e. at the working station between the wheels 1 and 2. The arrival of the gear wheel 12 at its fully retracted position enables the carrier 13 to actuate a micro-switch Yto provide a signal causing the control unit to actuate the ram 18A and rack 18 and so cause the shaft 16 to rotate in a direction such as to contract the jaws 24 of the head 15.This permits the workpiece 7 to rest on the work support blade 3, the supporting surface of which is inclined downwardly in a direction towards the control wheel 2, thus causing the released workpiece 7 to fall against the peripheral surface of the control wheel 2.

This reverse rotation of the shaft 16 causes the other one of the cams 19to actuate a microswitch at 19A enabling the control unit to move the upper slide 4 so as to move the control wheel 2 towards the rotating grinding wheel 1 and thereby urge the workpiece 7 against the grinding wheel forthe grinding operation.

Once this has been completed, the control wheel 2 moves away from the grinding wheel 1, allowing the machined workpiece 7 to fall back to the position in which it is supported by the blade 3 and control wheel 2. Completion of the machining operation is signalled to the control unit by a micro-switch (not shown) carried by structure associated with the control wheel 2 and this provides a signal initiating expansion of the jaws 24 to engage within the machined workpiece, which is thereby lifted from the support blade 3. One of the cams 19 again actuates its associated micro-switch 19Ato enable the control unit to initiate actuation of the ram 14to extend the transfer member 10 once again to its forward position at 10' above the conveyor 6.A further micro-switch or the micro-switch X is actuated by the carrier 13 this time to initiate contraction of the jaws 24, allowing the workpiece 7 to rest on the blocks 28 from which it was originally removed.

The transfer member 10 then returns to its original position and a further micro-switch (not shown) is actuated to initiate actuation of the ram 29 to bring the next workpiece 7 into the loading position and simultaneously to move the machined workpiece forward so that it eventually rolls onto a fixed lower support 40 from which it can be removed by means of a ram 41 actuating a finger 42 located in a slot of the support 40 to move the workpiece laterally to a position in which a further ram 43 actuating a pusher plate 43A can push the workpiece into a delivery shute 44 for retrieval. The above described cycle is repeated as many times as required to machine the desired number of workpieces 7.

Each cycle of operation can be carried out in a short period of time, e.g. of fifteen seconds or thereabouts and this period can be further reduced by arranging early commencement of return move mentofthe ram 29, i.e. prior to full completion of return operation of a workpiece 7 back onto the conveyor 6 by the transfer member 10 so that further indexing of the conveyor can commence immediately after the workpiece is back on the aligned blocks 28 and after the head 15 has been fully withdrawn from the workpiece.

During the course of grinding a series of workpieces 7, wear of the grinding wheel 1 takes place and the grinding machine includes means which are brought into operation automatically after a predetermined number, e.g. twelve, grinding cycles have occurred to dress the periphery of the grinding wheel. Such dressing ofthe grinding wheel results in a small reduction in the diameter thereof, typically .002" (.050 mm), and the control wheel 2 and work support bade 3 are automatically moved by a corresponding amount towards the grinding wheel 1. This then entails adjustment of the conveyor 6 so that the blocks 28 will continue to be indexed to a position substantially in line with the transfer member 10 and head 15.

Such adjustment is effected by a ram 45 (Figures 1, 3 and 5) fixed to the conveyor frame and cooperating via a linkage indicated generally at 46 with a ratchet wheel 46A fast for rotation with the shaft 39A. The linkage 46 includes a first lever 47 connected directly to the piston rod 48 of the ram 45 and carried on a pivot 49 fixed to the frame. The lever 47 is of angled or bell crank form and a second lever 50 is pivoted thereto at the apex of the angle and fixedly carries a pin 52 movable within a slot 53 in a fixed block 54. A pawl 51 is pivotally mounted on the arm 50 and a spring 55 connected between the pawl 51 and block 54 urges the pawl into engagement with the teeth of the ratchet wheel 46A.It will be seen that when the piston rod 48 is moved to the right, as seen in Figure 5, the arm 47 will move angularly in a clockwise direction about the pivot 49 and the arm 50 will move in a direction such as to bring the pin 52 towards the bottom of the slot 53, thereby moving the pawl 51 clockwise to ride over one or more teeth.

TA ++h ^^ +hn hanl AI4A orp : > rrsnslPrl qn that when the arm 50 moves in the opposite direction, by reverse actuation of the ram 45, the pawl 51 will engage a tooth to rotate the wheel 46A through a distance according to the number of teeth over which the pawl originally moved, thereby producing a corresponding adjustment in the position of the conveyor ram 29.

The teeth may conveniently be spaced to provide .001" (.025 mm) increments of ram adjustment which is transferred to the conveyor blocks 28 when the ram 29 is next actuated. The effective stroke of the ram 45 is governed by abutment of the arm 47 against a stop screw 56, which may be adjusted to enable the ram 45 to provide the desired rotation of the wheel 46A. It is thus possible, by means of the aforesaid adjustment, to ensure that a workpiece 7 arriving at the loading station is always accurately centred in relation to the transfer member 10. Thus dressing of the grinding wheel 1 is effected with corresponding adjustment of the operation of the conveyor 6, e.g. in an automatic compensating manner which can be overridden by the handwheel 39.

It will be understood that the conveyor 6 and its intermittent drive mechanism can be of any convenient type and may be arranged vertically or in another convenient direction. In the construction illustrated, the conveyor 6 can be pivotally connected to the grinding machine at one end and secured to the machine at the other end by a locking mechanism which can be released to permit the conveyor to swing about its pivotal connection away from the machine in order to facilitate access, when necessary, to the grinding and control wheels 1,2.

Alternatively the conveyor could be rigidly fixed to the machine or be incorporated in the machine frame.

In a simplified arrangement the conveyor 6 can be omitted and a support provided, e.g. in the form of a single pair of blocks 28 which support is fixed in use although it has provision for alignment adjustment with the transfer member 10. Each workpiece is manually loaded onto the fixed support for transfer by the member 10 and gripping head 15 to the operative position on the blade 3 between the wheels 1,2 and, after machining, is then returned back onto the support for manual unloading.

Thus the machine operator is only required to load workpieces one at a time onto the support and similarly remove them and is not required to load and unload workpieces to and from the operative position so that risk of possible injury in this respect is virtually avoided. Further in this regard required operation of the transfer mechanism may be effected, for example, by a pair of push button switches spaced a distance apart so as to require two handed operation well clear of the wheels 1,2.

Although the transfer mechanism has particular practical application in the volume production of externally ground hollow cylindrical workpieces open at at least one end, the gripping head 15 may be adapted to externally grip a cylindrical workpiece of solid form or where internal access for gripping purposes is not feasible. In such a case the gripping head 15 must be retracted fully clear of the wheels 1 and 2 during grinding. Fluid pressure, (e.g. hydraulic) operation of the gripping head 15 may be employed.

Claims

1. Workpiece transfer mechanism for use with or forming part of a machine tool such as a centreless grinding machine comprising means for supporting a cylindrical workpiece at a loading location and in alignment with a working station of the machine tool; a transfer member carrying gripping means for engaging a said workpiece and movable along a path generally aligned with the working station and the axis of the workpiece at said location support, and means for effecting and controlling movement of the transfer member along said path in timed relationship with operation of the gripping means and of the machine tool whereby a workpiece to be machined can be transferred from the support means at said loading location to the working station of the machine tool and, after machining, is returned to the support means at said location.

2. Workpiece transfer mechanism according to claim 1 wherein the gripping means is operable to release a said workpiece at the working station and to re-engage the workpiece after machining and prior to return of the workpiece by the transfer member to the support means.

3. Workpiece transfer mechanism according to claim 1 or 2 wherein the gripping means is adapted to engage within the interior of a hollow cylindrical workpiece for gripping the latter.

4. Workpiece transfer mechanism according to claim 1,2 or 3 wherein the transfer member is operable such as by ram means for back and forth axial movement along the path aligned with the working station of the machine tool and with the axis of a workpiece when on the support means.

5. Workpiece transfer mechanism according to claim 4 wherein the transfer member is operable for back and forth axial movement by ram means through gear and opposed rack mechanism in order to obtain a greater (.e.g double) extent of axial movement of the transfer member than the stroke of the ram means.

6. Workpiece transfer mechanism according to any of the preceding claims wherein the gripping means comprises radially movable gripping elements or jaws operable for gripping contact with an inner or outer peripheral part of a said workpiece.

7. Workpiecetransfer mechanism according to claim 6 wherein the gripping elements or jaws of the gripping means are operable by gear and rack mechanism.

8. Workpiece transfer mechanism according to any of the preceding claims wherein the transfer member carries a shaft drive to the gripping means for operation of the latter.

9. Workpiece transfer mechanism according to any of the preceding claims wherein the support means for supporting a said workpiece at the loading location consists of a conveyor operable for indexing movement in timed relationship with oper ation of the transfer member in order to successively bring workpieces placed thereon to the loading location and after machining and return of each workpiece convey the latter to a position for removal.

10. Workpiece transfer mechanism wherein the conveyor is operable for uni-directional indexing movement by constant stroke operating means such as ram means in order to obtain uniform increments of indexing movement.

11. Workpiece transfer mechanism according to claim 9 or 10 wherein the conveyor is operable for indexing movement by reciprocating or ram means through latch means which is adapted to engage the conveyor for unidirectional indexing movement of the latter but which is further adapted to yield for permitting return operation of the reciprocating or ram means relative to the conveyor.

12. Workpiece transfer mechanism according to claim 9 or 10 wherein the reciprocating means such as ram means is adjustably mounted for required location of indexing movement of the conveyor at the loading location in maintaining alignment of a workpiece at said location with the transfer member, e.g. on change of the specified diameter of workpieces to be machined and/or after dressing the grinding wheel in the case of a grinding machine tool such as a centreless grinding machine.

13. Workpiece transfer mechanism according to claim 12 wherein the mounting of the reciprocating or ram means is adjustable manually and/or by power operated means such as ram means.

14. Workpiece transfer mechanism according to claim 13 wherein power or ram operated adjustment of the mounting of the said reciprocating or ram means is effected incrementally such as through pawl and ratchet mechanism to said mounting.

15. Workpiece transfer mechanism according to claim 13 or 14 wherein the power or ram operated adjustment of the mounting of the said reciprocating or ram means is arranged to be effected in an automatic compensating manner e-.g. in conjunction with dressing of the grinding wheel in the case of a grinding machine tool, such as a centreless grinding machine.

16. Workpiece transfer mechanism when substantially as herein described with reference to the accompanying drawings.

17. Workpiece transfer mechanism according to any of the preceding claims when in combination with or incorporated with a machine tool such as a centreless grinding machine.