WO1983003992A1

WO1983003992A1 - Improvements in and relating to assembling precision rings on workpieces

Info

Publication number: WO1983003992A1
Application number: PCT/GB1983/000132
Authority: WO
Inventors: Arthur Pearson
Original assignee: George Salter & Co. Limited
Priority date: 1982-05-06
Filing date: 1983-05-06
Publication date: 1983-11-24
Also published as: AU1519383A; EP0108087A1

Abstract

Workpieces (W1, W2) are advanced on a conveyor belt in a synchronised manner relative to circlip dispensing means (10) consisting of two overlapping plates (10a and 10b). The upper plate (10a) is reciprocatable radially relative to an indexed magazine (4) having tubular columns (9) containing stacks of circlips. This upper plate (10a) picks up a circlip (C1) from the bottom of a stack in a hole (H) and carries it to a hole of identical dimensions in the lower plate (10b) where it falls onto a tapered mandrel (M1, M2) beneath. A pneumatic push-on locating tool (12) is moved downwardly in the direction of the arrow (F) to move the circlip (C1) over the mandrel (M1, M2) into a locating groove (11, 13) on the workpiece (W1, W2). The invention provides for the automatic assembly of both "external" and "internal" circlips onto workpieces and provides means for assembling circlips onto a workpiece arranged at a given angle, for example horizontally rather than vertically as shown. The push-on locating tool (12) may be operated by variable stroke pressure sensitive actuating means (23).

Description

IMPROVEMENTS IN AND RELATING TO ASSEMBLING PRECISION RINGS ON WORKPIECES

Technical Field

This Invention relates to assembling precision rings, for example circlips, on workpieces and more particularly to apparatus and method for automatically dispensing and locating precision rings on workpieces.

The term "precision rings" is used herein to embrace retaining rings and circlips such as are commonly used as retaining elements arranged to be located, usually in grooves, on shafts or in cylindrical bores.

Background Art

In the past precision rings such as circlips have been located almost entirely manually on workpieces. Thus, in a production run where successive workpieces, for example car shaft components, are conveyed past an operator, precision rings such as circlips have generally been assembled by the operator picking up each ring with his hands and locating It onto the workpiece, perhaps with the aid of a tool such as a pair of pliers. Such a method has obvious disadvantages both in the manufacturing cost and time required to assemble rings onto workpieces in this way.

Disclosure of Invention

It is an object of the present invention to provide a method and apparatus for automatically assembling precision rings on workpieces thereby to alleviate the aforementioned disadvantages.

According to the present invention there is provided apparatus for automatically assembling precision rings onto workpieces, comprising a holder capable of holding at least one stack of said rings, dispensing means capable of dispensing said rings Individually from said at least one stack adjacent a respective workpiece at an assembly station, advancing means capable of advancing workpieces successively, relative to the dispensing means, to the assembly station, and push-on locating means capable of locating a respective ring on a respective workpiece when said workpiece is at said assembly station.

Further according to the present invention there is provided a method of automatically assembling precision rings onto workpieces, said method comprising : (a) bringing a stack of precision rings and individual workpieces into mutually adjacent relationship; (b) dispensing rings individually from said stack to respective workpieces by way of dispensing means; (c) advancing workpieces successively relative to the dispensing means; (d) locating respective ones of said rings on said workpieces by way of push-on locating means.

Preferably, the dispensing means, advancing means and push-on locating means are all operable in time-synchronised manner, so that rings may be assembled on respective workpieces in a fully automated production run.

Preferably, a holder is provided which is capable of holding several stacks of rings and, preferably, sensing means is provided to sense when there is a pre-set number of rings, for example zero, left in the or each stack. This may be done directly, for example by sensing the absence of any rings, or indirectly, either by sensing (counting) for example how many rings have been dispensed from a stack or by any other convenient means, for example by sensing the number of assembled workpieces moving past a point.

Sensing a pre-set number of rings in a stack in this way indicates that another stack of rings is needed and where the holder carries several stacks of rings another stack of rings may be automatically Indexed by the sensing means relative to the dispensing means.

Sensing means may also be provided to ensure that rings are being correctly assembled on workpieces and the apparatus may be automatically shut down if this is not the case.

Preferably, the above-mentioned holder carries at least one magazine having tubular columns for individual stacks of rings, and preferably, the magazine is axially rotatable on the holder to index columns relative to the dispensing means.

In a preferred embodiment, the holder comprises radial arms extending from a central member, arranged vertically in use, and each arm is capable of carrying a magazine. Preferably, the arms are rotatable about the axis of the central member to present magazines successively to the dispensing means. Conveniently, three radial arms are provided.

Means may be provided for automatically picking-up full magazines and/or rejecting empty ones.

The or each magazine may be generally cylindrical and the columns may, conveniently, be equiangularly spaced about the axis of the respective magazine. Each column is, preferably, provided with a respective slide cover closing off the bottom of said column. In this arrangement a stack of rings is capable of being supported on each respective slide cover. In one embodiment, the slide covers are arranged to slide radially inwards towards the axis of the respective magazine, preferably, against biassing means so that the bottom of a respective stack of rings drops onto the dispensing means.

In an alternative embodiment, the or each stack may be spring loaded upwardly in use in a respective column and with slide covers provided closing off the tops of the columns. A respective cover may be slid back so that the top of a respective stack may be urged onto the dispensing means. Any alternative slide cover arrangement may be provided to close-off the top or bottom of the columns as appropriate, for example, an indexing plate cover. The slide cover may in some embodiments be part of the dispensing means.

Preferably, the or each magazine is respectively co-operable with the dispensing means so that rings may be dispensed from one end, either the top or the bottom, of said at least one stack and preferably, where slide covers are provided as aforesaid, the dispensing means is advanceable relative to a respective magazine to move a respective slide cover to uncover the top or bottom of a stack. In one embodiment the or each magazine is reciprocatable against biassing means along a respective arm of the holder.

Preferably, the dispensing means comprises first and second coextensive plates, and each plate is provided with an open-ended hole of diameter at least equal to the outside diameter of a ring of the stack, the arrangement being such that, in use, a ring of the stack is capable of being located in a hole in the first plate whilst being in contact with the second plate, and on relative sliding movement of the plates said ring is moved with the first plate, in said hole in the first plate, relative to the second plate until the holes are coaxially arranged and said ring drops through the holes towards a workpiece therebelow.

Where such dispensing means is provided and radially sliding covers are provided on the or each magazine as aforesaid the plates may be moved relative to a respective magazine when a respective radial cover is radially aligned with the plates, so that on said relative movement said respective radial cover is engaged in endwise manner by the plate to uncover one of the top and bottom of a respective stack.

The push-on locating means may comprise a pneumatically operated tube advanceable in use towards a workpiece to push a ring of the stack onto the workpiece in its correct assembled position. The tube may be arranged, in use, to pass through said holes or not depending on the arrangement of the apparatus. The tube may be reciprocatable in use, either vertically or, in alternative embodiments horizontally or at any other convenient angle for assembling a ring of the stack onto a workpiece.

The apparatus may further include one or more ring transfer guide members in the form of tapered mandrels, each positionable over or into a respective workpiece onto which a respective ring of the stack can drop before operation of the push-on locating means. In this way a respective ring is held ready on the mandrel and may be pushed over the mandrel into correct position on a respective workpiece by the push-on locating means.

The apparatus may include means to cycle the or each mandrel onto a production run of workpieces. This cycling means may be synchronized to place a mandrel on a workpiece ready for a ring to drop onto, and then remove the mandrel from the workpiece once the push-on locating means has correctly located a ring onto the workpiece, and then re-position the mandrel onto another workpiece being advanced relative to the dispensing means to bring it into the respective assembly station. Where only one mandrel is provided this is, preferably, the next successive workpiece.

The or each mandrel may be arranged to pivot in a chosen plane, for example a vertical plane, to adjust the orientation of a ring individually dispensed from the stack before being located in a new orientation on a workpiece.

The advancing means is conveniently a conveyor belt.

Brief Description of Drawings

Embodiments of apparatus and method in accordance with the present invention will now be described, by way of example only, with reference to the accompanying simplified schematic drawings in which:- FIGURE 1 shows a plan view of apparatus for automatically assembling precision rings onto workpieces in accordance with the present invention;

FIGURE 2 shows a perspective view of a stage in the method, showing a detail of dispensing means;

FIGURE 3 shows a side view detail of modified apparatus which is partly in section;

FIGURE 4 shows a cut-away perspective view of a further modification to the apparatus; FIGURE 5 shows a pneumatic circuit for the modification of FIGURE 4;

FIGURE 6 shows a further modification for the application of a circlip into an internal groove on a workpiece.

Best Mode(s) for Carrying Out the Invention

Referring to the drawings, Figure 1 shows apparatus for assembling precision rings onto workpieces including a holder 1, suitable for precision rings such as circlips, located to one side of workpieces 2 on advancing means in the form of conveyor belt 3.

The holder 1 comprises a fixed central member 1a and three radial arms 1b, 1c, 1d (shown equiangularly spaced about member 1a in Figure 1) which are rotatable about member la as represented by arrow A in Figure 1. The arms 1b, 1c, 1d may be individually rotatable or if preferred rotatable in unison about member la and may be rotatable in a clockwise and/or an anti-clockwise direction. Alternatively, arms 1b, 1c, 1d may be fixed relative to member 1a and member 1a is arranged to be rotatable on its axis X. The arms are robotically operated.

Respective ring magazines 4, 5, 6 are pivotally located at the ends of respective arms 1b, 1c, 1d. Each magazine 4, 5, 6 may hold

1200 circlips and is rotatable on Its axis Y (see arrow B, for example in respect of magazine 4) and carries facility for six vertical stacks of rings equiangularly spaced about axis Y. Each magazine could be adapted to carry more or less stacks as desired. Each magazine is generally of cylindrical shape (see Figure 2) and comprises upper and lower plates 7, 8 supporting columns 9 dimensioned to receive individual stacks of precision rings, in this case circlips. The columns 9 are open-topped and the bottom plates 8 are equipped with spring-loaded radial slide covers (not shown) which can be reciprocated radially inwardly at C on Figure 1 against spring biasing to open and close the bottom of a respective one of the columns 9.

Dispensing means 10, shown in more detail in Figure 2, extends radially from the bottom of magazine 4, in a direction across the conveyor belt 3 towards an assembly station at the centre of the row of workpieces 2 illustrated In Figure 1.. The dispensing means 10 consists of two plates 10a, 10b, and plate 10a overlies and is coextensive with plate 10b. Plate 10a is reciprocatable radially relative to magazine 4 and is provided with an open-ended hole H matching the outside diameter of the circlip. The plate 10a is slidable in direction of arrow D from a first position relative to the lower plate 10b in which the hole H is located immediately under the bottom of one of the columns 9, specifically column 9a in the FIGURES, to a second position (shown schematically in FIGURE 2) in which hole H is co-axial with a hole of identical dimensions at one end of lower plate 10b.

FIGURE 2 shows a particular workpiece W having an upper end into which a tapered mandrel M has been located. This workpiece W₁ is at the assembly station and a circlip C Is shown on the mandrel which is to be located in groove 11 on workpiece W₁ by push-on locating means in the form of pneumatically-operated reciprocatable cylinder 12. The relative directions of advancement of the workpiece production line (workpieces W₁ and W₂ in FIGURE 2) and the push-on locating means are represented by arrows E and F in FIGURE 2. Workpiece W₂ is about to receive a tapered mandrel M₂ prior to having a circlip located in its groove 13. FIGURE 1 shows schematically means for introducing mandrel M₂ onto a workpiece W₂ just prior to advancement to the assembly station and dispensing means 10. It also shows means for removing the mandrel M₂ from the workpiece W₂ just after a circlip has been located in its groove 13, and means for introducing mandrel M₂ onto another workpiece. In this manner a cycle of locating the same mandrel or mandrels on and off successive workpieces may be established.

The operation of the apparatus will now be described. Initially, the columns 9 of magazines 4, 5, 6 are loaded with circlip stacks. The arms 1b, 1c, 1d may be arranged to automatically pick up fullyloaded magazines individually and/or automatically reject empty magazines. The arms 1b, 1c, 1d may be rotated as necessary through arrow A, until one of the magazines 4, 5, 6, more specifically magazine 4 as shown in FIGURE 1, Is arranged adjacent dispensing means 10. This magazine can be rotated as necessary in the direction of arrow B until one of the filled columns 9, more specifically column 9a, is positioned correctly as shown in FIGURE 1 relative to the dispensing means 10. Both plates 10a, 10b of the dispensing means may, in this case, be radially advanced towards axis Y to move the radial slide cover in endwise manner (not shown), located directly under column 9, so that the stack of circlips rests on the lower plate 10b and the lowermost circlip of the stack is located in hole H of plate 10a.

During this time-synchronized operation the workpieces 2 are advanced in time-synchronized manner from left to right of FIGURE 1 by the conveyor belt 3, and workpiece W₁ equipped with tapered mandrel M₁ is located at the assembly station beneath the hole in the lower plate 10b. The top plate 10a moves slidably with the lowermost circlip in the direction of arrow D until the holes in the upper and lower plates are co-axially aligned so that the circlip drops through the holes onto the tapered mandrel M₁. Again in time synchronized manner, the cylinder 12 is pneumatically advanced through the holes over the mandrel M₁ into engagement with the circlip (shown as C₁ in FIGURE 2) which is forced over the mandrel M₁ and correctly positioned into the groove 11.

The cylinder 12 is then retracted, the next workpiece W₂ is advanced towards dispensing means 10 and workpiece W₁ is advanced away from the dispensing means. Mandrel M₁ is removed from workpiece W₁ just as workpiece W₂ is advanced into position beneath the aligned holes in plates 10a, 10b. During the intervals of time between successive introductions of workpieces under the dispensing means 10 circlips are collected individually from the bottom of the stack In column 9a by the reciprocating plate 10a, and are dropped onto respective mandrels.

Once all the circlips in one stack have been dispensed magazine 4 may be indexed automatically so that the next column 9b is located in a ring-dispensing position. This indexing may be arranged to occur automatically by sensing means (not shown) which, for example, senses when a particular column is empty or when a particular number of rings have been dispensed from a column, and then automatically indexes the magazine. Similarly, once an entire magazine is empty, this may be sensed and an arm or arms automatically rotated to present another magazine, magazine 5 as shown, to the dispensing means.

The apparatus may be modified so that only one magazine is provided, and/or so that as a magazine is rotated the bottom or top of a column is automatically uncovered with a stack engaging one of the plates 10a, 10b (i.e. the slide covers need not be radial slide covers). Additionally, where radial covers are provided each magazine may, in some embodiments, conveniently be reciprocatable against spring biassing along the arms towards axis X.

The apparatus as described so far allows for the transfer of horizontally orientated rings onto respective workpieces whilst they are still horizontally orientated, but the apparatus of the present invention may be modified as shown in FIGURE 3 where it is desired to change the orientation of a circlip through an angle, in this case 90° in a vertical plane. FIGURE 3 shows a section through one of the columns 9 and six Individual circlip rings R stacked at the bottom of the column. Individual circlip rings such as the particular circlip indicated at C₁ can drop onto the mandrel M as previously explained but now the mandrel is arranged to pivot in time-synchronized manner about axis Z of pivot pin P to the position shown partly in dashed lines. The mandrel M fits over the workpiece, which is in the form of a horizontal shaft S, in this position and push-on locating means 12 which is now horizontally orientated can be advanced to push circlip C₁ into groove S₁ on the shaft. Locating means 12 is then retracted and the mandrel M is pivoted to its inclined position to receive another circlip.

FIGURE 4 shows a part cut-away perspective view of a modification to the mandrel arrangement shown in FIGURES 1 and 2 and also to the push-on locating means. In this modification only one mandrel M₃ is used for the application of circlips onto a workpiece (not shown).

The mandrel M₃ is joined to a mandrel carrier M_c which is vertically reciprocatable with the mandrel M₃ and movable downwardly against spring Massing means in the form of helical coil compression spring 14. The mandrel carrier M_c is reciprocatable along two vertical guide rods 15 which are spaced from one another and the rods

15 pass through the carrier M_c. The coil spring 14 is wound around one of the rods and acts against the underside of the carrier M_c and on a base 16 of the apparatus and effectively spring loads the mandrel carrier M_c into contact with the underside of a horizontal floor 17 of the apparatus. Since a circlip is introduced onto a workpiece by being passed completely over the top of the mandrel M₃ and along the entire length of the mandrel, the mandrel is joined to the carrier M_c by a thin vertical web portion P which is of a thickness less than the gap between the ends of the circlip so that the motion of the circlip along the mandrel is unhindered as the circlip Is passed along the mandrel, the web portion P being positioned in said gap.

A three-legged spider 18 (only legs shown) is located above the floor 17 and is part of circlip push-on locating means. The legs of the spider 18 replace the push-on locating tube shown in FIGURE 2 and are perhaps more convenient since they are capable of flexing to a limited extent whilst being used to push a circlip over the tapered mandrel M₃. The spider 18 is vertically reciprocatable and the legs of the spider are equiangularly spaced and can be advanced downwardly through a hole 19, which hole Is vertically above the mandrel M₃ and in floor 17. Hole 19 is provided with guide portions 19a conforming to the contour of the legs in order to provide some measure of guidance or alignment of the legs on passage of the legs through the hole whilst pushing a circlip over the mandrel M₃.

The operation of the circlip assembly apparatus shown in FIGURE 4 will now be described. The movable components of the apparatus described are arranged to co-operate in a synchronised manner under the control of a pneumatic feedback circuit (see FIGURE 5). A circlip is picked up from a magazine stack (not shown) in a magazine holder

(not shown) by a slide dispensing means (not shown) all of which may be of the same general form as shown in FIGURES 1 and 2, and the circlip is advanced in direction of arrow 20 and through the hole 19 in the direction of arrow 20' onto the mandrel M₃ held in its uppermost position. In synchronised manner, the spider 18 is advanced downwardly and the legs pass through hole 19 and engage the flat upper edge of the circlip. The mandrel M₃ and the carrier M_c are thereby moved downwardly against the blassing provided by spring 14 until the bottom of the mandrel engages a workpiece (not shown) located directly underneath the mandrel at the assembly station. Preferably, the workpiece will have been advanced to Its location by suitable advancing means such as a conveyor belt moving in the direction of arrow E in time-synchronised manner. However, it is possible in a cheaper version of the apparatus for the advancing and positioning of the workpieces relative to the mandrel M₃ to be done manually rather than by a conveyor belt, merely by selecting a workpiece and placing it on a support underneath the mandrel M₃. Once the circlip has been assembled on the workpiece the workpiece could be removed manually or by automatic means. Once the bottom of the mandrel M₃ engages the workpiece the legs of spider 18 continue to be moved downwardly thereby pushing the circlip over the tapered end of the mandrel (while temporarily expanding the circlip) onto the workpiece and into an external groove on the workpiece (see FIGURE 2). The correct location of the circlip is sensed by appropriate sensing means (not shown), preferably pressure sensitive means controlling the stroke of an actuator which operates the spider, and the spider 18 is returned automatically to its former position above floor 17 for assembly of the next circlip on another workpiece. As the spider 18 is returned to this position the mandrel M₃ is also moved back to its uppermost position under the action of compression spring 15 on mandrel carrier M_c.

FIGURE 5 shows a suitable pneumatic feedback circuit 21 for use with the apparatus shown in FIGURE 4. A similar circuit may be envisaged for use with the apparatus shown in FIGURES 1 and 2.

The pneumatic circuit 21 shows a schematic arrangement for the co-operative control of two double-acting pressure cylinders 22 and 23. Cylinder 22 is arranged horizontal and may be arranged in endwise manner (for example under floor 17 in FIGURE 4) with slide dispensing means to control the horizontal reciprocation of said dispensing means by reciprocating movement of its piston 22a to feed circlips one by one onto the mandrel M₃.

Cylinder 23 is vertically-arranged and its piston 23a may be arranged to actuate vertical reciprocation of the spider 18 in a readily envisaged manner.

With reference to FIGURE 4, on a first stroke of cylinder 22 a circlip is picked up from the bottom of a magazine stack and advanced to hole 19. On the return stroke of cylinder 22 the slide dispensing means is moved back to pick up another circlip and cylinder 23 is then pressurized to move the legs of spider 18 downwardly with the circlip and mandrel. Cylinder 23 is pressure sensitive so that its piston 23a has a variable stroke and once the circlip is located in a groove in a workpiece, bearing against a side wall of the groove which forms an abutment surface, a predetermined pressure is built up which returns the piston 23a and spider 18 to its previous position above floor 17. The cycle may then be repeated to locate further circlips on further workpieces and this operation may be synchronised with the movement of the workpiece advancing means (for example, conveyor belt).

The arrangement and operation of two position flow-port valves V and restrictor valves RV connected between the cylinders 22 and 23 which provide the synchronised operation of the cylinders should be self explanatory from FIGURE 5.

The present invention has so far been described in relation to apparatus for assembling a circlip into an external groove on a workpiece by means of a tapered mandrel. Circlips of this type are known as 'external' circlips but the present invention is equally applicable to the assembling of 'internal' circlips (circlips for internal grooves in workpieces) onto a workpiece using, for example, a tapered sleeve as a ring transfer guide member. FIGURE 6 shows how this is done. A tapered sleeve S_T replaces the mandrels previously described and is positioned on the workpiece W_T; a tool T_T is advanced axially to push the circlip C_T down the internal taper of sleeve S_T thereby contracting the circlip until it expands into its location groove S_T on workpiece W_T.

Claims

1. Apparatus for assembling precision rings onto workpieces, characterized by a holder capable of holding at least one stack of said rings, dispensing means capable of dispensing said rings individually from said at least one stack adjacent a respective workpiece, and push-on locating means capable of locating a respective ring on a respective workpiece.

2. Apparatus as claimed in Claim 1 comprising advancing means capable of advancing workpieces successively relative to the dispensing means and in which the dispensing means, advancing means and push-on locating means, preferably all operate in time-sychronised manner.

3. Apparatus as claimed in any one of the preceding claims in which sensing means is provided to sense when there is a pre-set number of rings left in the or each stack and, preferably, in which there are several stacks of rings and the stacks of rings are automatically Indexable by the sensing means relative to the dispensing means, and preferably in which sensing means, for example variable stroke pressure sensitive actuating means of the push-on location means, is arranged to sense when each respective ring is correctly located on a workpiece.

4. Apparatus as claimed in any one of the preceding claims in which the holder carries at least one magazine having tubular columns for individual stacks of rings and preferably in which the holder comprises radial arms extending from a central member, arranged vertically in use, and each arm carries a magazine, and preferably, in which the arms are rotatable about the axis of the central member to present magazines successively to the dispensing means, and preferably, in which means is provided for automatically picking-up full magazines and/or rejecting empty ones, and preferably in which the or each magazine is generally cylindrical and the columns are equiangularly spaced about the axis of the respective magazine, and preferably in which each column is provided with a respective slide cover closing off the bottom of said column, and preferably in which the slide covers are arranged to slide radially Inwards towards the axis of the respective magazine so that the bottom of a respective stack of rings drops onto the dispensing means, and preferably in which the slide covers move against biassing means.

5. Apparatus as claimed in any one of the preceding claims in which the dispensing means comprises first and second co-extensive plates, and each plate is provided with an open-ended hole of diameter at least equal to the outside diameter of a ring of the stack, the arrangement being such that, in use, a ring of the stack is capable of being located in a hole in the first plate whilst being in contact with the second plate, and on relative sliding movement of the plates said ring is moved with the first plate, in said hole in the first plate, relative to the second plate until the holes are co-axially arranged and said ring drops through the holes towards a workpiece therebelow.

6. Apparatus as claimed in any one of the preceding claims in which the push-on locating means comprises a pneumatically operated tube in the form of a tube or multi-legged spider advanceable in use towards a workpiece to push a ring of the stack onto the workpiece in its correct assembled position.

7. Apparatus as claimed in any one of the preceding claims comprising one or more ring transfer guide members in the form of tapered mandrels and/or tapered sleeves, and preferably comprising means to cycle the or each transfer guide member onto a production run of workpieces, and preferably in which the cycling means is synchronized to place a respective transfer guide member on a workpiece ready for a ring to drop onto, and then to remove the transfer guide member from the workpiece once the push-on locating means has correctly located a ring onto the workpiece, and then to re-position the transfer guide member onto another workpiece being advanced relative to the dispensing means.

8. Apparatus as claimed in Claim 7 in which the or each transfer guide member is arranged to pivot in a chosen plane, for example a vertical plane.

9. Apparatus as claimed in Claim 7 or 8 comprising one transfer guide member which is joined to a transfer guide member carrier and the carrier and transfer guide member are biassed to an uppermost position, the transfer guide member and carrier being displaceable against said last mentioned biassing by the push-on locating means.

10. A method of automatically assembling precision rings onto workpieces, said method comprising:-

(a) bringing a stack of precision rings adjacent a workpiece;

(b) dispensing rings individually from said stack to respective workpieces by way of dispensing means;

(c) positioning workpieces successively relative to the dispensing means;

(d) locating respective ones of said rings on said workpieces by way of push-on locating means.

11. A method as claimed in Claim 10 further comprising advancing workpieces successively relative to the dispensing means, preferably in time-synchronised manner.

12. A method as claimed in Claim 10 or Claim 11 in which step (a) comprises bringing a magazine having a plurality of columns in which precision rings are stacked adjacent a production run of workpieces.

13. A method as claimed in Claim 12 comprising indexing columns of the magazine in time-synchronised manner.

14. A method as claimed in any one of Claims 10 to 13 comprising cycling a tapered mandrel or tapered sleeve onto workpieces.

15. A method as claimed in Claim 14 in which the mandrel or sleeve is spring-loaded.

16. A method as claimed in any one of Claims 10 to 15 in which the push-on locating means is pneumatic and co-operable in synchronised manner with pneumatically operated precision ring slide dispensing means.