GB2593976A - Improvements in and relating to pin joints - Google Patents

Abstract

A pin joint with an expander bushing is provided. A pin 3 has at each end a tapering outer surface 9 that engages tapering inner surfaces of segments 111 of a bush 11. A stud 180 has an enlarged circular head 181 at one end of the pin 3 and a shank 182 that extends all of the way through a central bore of the pin 3 to engage within a boss 136 formed on a circular thrust plate 135 at the other end of the pin 3. Set screws 131 engage respective threaded holes formed in the thrust plate 135 and engage respective detents 138 formed in end faces of the bush segments 111. Tightening of the set screws 131 pushes the respective bush segments 111 along the tapered surfaces 9 of the pin 3, thereby expanding the bush segments 111 radially to secure the bush 11 firmly within the respective bore in which the pin 3 is mounted. This embodiment may be fitted from just one end of a pin joint. Other embodiments may have thrust plates 135 or similar at both ends.

Description

IMPROVEMENTS IN AND RELATING TO PIN JOINTS

The present invention relates to pin joints. The invention may find particular advantage in use with earth moving equipment. however, it is not limited to such use and has wider application.

Earth moving equipment is designed and manufactured in many different fm-ms However, there are certain fundamental features that are common to the majority of designs. One such feature is the pin joint, which provides a. single degree of freedom to allow an attached linkage to rotate.

In the context of this specification, a pin joint comprises a pin that is 1 0 anchored in at least one bore to allow a part to rotate about the pin. Typically, a respective bore is provided at each end of the pin. 't he pin and bore are typically circular. As the pin joint is used, the bore becomes worn and the pin progressively becomes loose within the bore, allowing random mutual movement and thus free play between pin and bore. Such movement will become disconcerting to a machine operator, as it means the operator must attempt to allow for the free pla.y when making precise movements.

This fault is usually repaired by taking the pin joint apart, welding up the bore, re-machining the bore back to original specifications and anchoring die pin again in the re-machined bore. However, this is a. time-consuming task and, if 2 0 the machine shop is a long way from the workplace, then the machine can be inoperative for a considerable time.

Another known solution is to insert an expandable circular bush between the pin and bore and force the bush outwardly to grip the bore by means of a circular tapered shaft engaging in a circular tapered hole in the bush. -2 -

Whilst this can work quite satisfactorily where the worn bore is still substantially circular and not too badly worn, it can never work well for bores that have become badly worn to become non-circular.

Prior proposals to repair worn pm joints without having to resort to welding and machining include documents 1:S8221021; US8037783; F,P2340375; and CN20678581415.

A solution that is currently popular is shown in Figure 4 as referenced below and manufactured in one form or another by, at least: Nord-Lock Group (Sweden); Bolt Norge AS (Norway); and Ilarris Paters (Latvia).

Preferred embodiments of die present invention aim to provide improved methods and apparatus for repairing or refurbishing pin joints, and components to facilitate the same. Embodiments of the invention may also be suitable as original pin joints.

According to one aspect of the present invention there is provide a pin 15 joint comprising: a pin that is anchored at each of its ends in a respective bore to allow a part to rotate about the pin, each of the ends of the pin having a tapering outer surface; at each end of the pin, a respective bush that is radially expandable to 20 anchor the pin within the respective bore, each bush having a tapering inner surface that engages a. respective one of said tapering outer surfaces of the pin; and a plurality of screwthreaded members that act upon one of the bushes and are selectively rotatable to move at least one of the bushes along the pin 25 thereby to expand the respective bush. -3 -

Each bush may be a component of circular cross-section, formed with an axial split to allow the bush to expand.

Each bush may comprise a plurality of segments that allow at least a degree of independent movement of each segment with respect to the other 5 segment(s) Said segments may be bonded together by elastomeric material.

At least one of the bushes may have at least one axial slot that terminates in an enlarged portion adjacent an end face of the bush, thereby to afford a portion of reduced thickness of said end face to allow a degree of 1 0 independent movement of one part of die bush with respect to another part of the bush.

A first plurality of said screwthreaded members may engage one of the bushes and a second plurality of said screwthreaded members may engage the other of the bushes.

Said plurality of screwthreaded members may engage only one of the bushes and selective rotation of die screwthreaded members may cause movement of both of the bushes along the pin thereby to expand the bushes.

Said screw-threaded members maybe mounted in at least one washer or thrust plate at a respective end of the pin.

2 0 In one embodiment, said screwthreaded members are mounted on a washer or thrust plate at one end of the pin; a stud has a shank that passes through the pin and a head that engages the respective bush at the other end of the pin; and said washer or thrust plate is mounted on said shank. -4 -

A pin joint according to any of the preceding aspects of the invention may have, at at least one end of the pin, interengaging parts that inhibit mutual rotation between die pin and at least one other component of the pin joint.

Said interengaging parts may comprise a peg and a. slot, provided on the 5 pin and at least one of the stud and the washer or thrust plate.

At least some of said screwthreaded members may engage a respective part-threaded hole formed in the pin and/or respective bush.

Each part-threaded hole may comprise a plain part-hole iii the am or bush and an adjacent threaded part-hole in the bush or pin.

1 0 Preferably, die taper angle of said tapering surfaces is about 7 degrees or less.

Preferably, the taper angle is about 4 degrees.

Each of said screwthreaded members may be a grub screw or set screw.

Preferably, a pin joint according to any of the preceding aspects of the 15 invention has at least one removable cap for a respective end of die pin joint.

Each bush may comprise a. plurality of segments, the segments having different radial extents.

In a further aspect of the present invention, there is provided a pin joint that comprises a. pin that is anchored in a bore to allow a. part to rotate about the 2 0 pin, wherein the pin is of circular cross-section and the bore has become non-circular with wear; the pin has a tapering outer surface at one end; an expandable bush is engaged on said outer surface, the bush having at least one longitudinal -s -slot and a tapering inner surface that engages said outer pin surface; die pin and bush are inserted inside the worn bore; the bush is tightened onto the pin to expand the bush by interengagement of said tapering inner and outer surfaces; the bush has an inner aperture of circular cross-section that receives the pin; and the bush has a non circular outer cross section to provide a close fit between an outer surface of the bush and inner surface of the worn bore.

In another aspect, the invention provides a pin joint comprising a pin that is anchored in a bore to allow a part to rotate about the pin; an expandable bush that engages the pin and the bore to anchor the pin within die bore; a tightening member tha.t engages the pin and is operative to tighten the bush and expand the bush between the pin and bore; and a washer that transmits force from said tightening member to an end face of the bush; said end face and washer having at least one interengaging projection and detent to inhibit rotation of the washer with respect to the bush.

Preferably, said interengaging projection and detent comprise a path screw that engages a screwthreaded hole in the washer and an end of a slot in the bush.

In a further aspect, the invention provides a. pin joint comprising a. pin tha.t is anchored in a bore to allow a part to rotate about the pin; an expandable bush that engages the pin and the bore to anchor the pin within the bore; a tightening member that engages the pin and is operative to tighten the bush and expand the bush between the pin and bore; a washer that transmits force from said tightening member to an end face of the bush; and a plurality of screwthreaded members that engage respective threaded apertures in die washer and bear against said end face.

Preferably, said screwthreaded members comprise grub screws. -6 -

Preferably, said screwthreaded members engage respective detents in said end face.

In another aspect, die invention provides a pin joint comprising a pin that is anchored in a bore to allow a part to rotate about the pin; an expandable bush that engages the pin and the bore to anchor the pin within the bore; a tightening member tha.t engages the pin and is operative to tighten the bush and expand the bush between the pin and bore; and at least one removable cap to cover a respective end of the bush and pin.

In a further aspect, the invention provides a pin joint comprising a pin that is anchored in a bore to allow a part to rotate about the pin; an expandable bush that engages die pin and the bore to anchor die pin within the bore; and a tightening member tha.t engages the pin and is operative to tighten the bush and expand the bush between the pin and bore; wherein the bush has at least one axial slot that terminates in an enlarged portion adjacent an end face of the bush, thereby to afford a portion of reduced thickness of said end face to allow a degree of independent movement of one part of the bush with respect to another part of the bush.

Preferably, said enlarged portion is of triangular shape.

in another aspect, the invention provides a. pin joint comprising a pin that is anchored in a bore to allow a part to rotate about die pin; an expandable bush that engages the pin and the bore to anchor the pin within the bore; and a. tightening member that engages the pin and is operative to tighten the bush and expand the bush between the pin and bore; wherein the bush comprises a plurality of segments that are bonded together whilst allowing a degree of independent movement of each segment with respect to the other segment(s).

Preferably, said segments are bonded together by elastomenc material. -7 -

In a further aspect, the invention provides a pin joint comprising a pin that is anchored in a bore to allow a part to rotate about the pin; an expandable bush that engages the pin and the bore to anchor die pin within the bore; and a tightening member that engages the pin and is operative to tighten the bush and expand the bush between the pin and bore; wherein the bush comprises a plurality of segments that are independent of one another to allow a degree of independent movement of each segment with respect to die other segment(s).

Preferably, each of said segments has a curved outer surface and a flat under surface.

Preferably, each of said segments has an upstanding end face on which said curved outer surface is provided.

in another aspect, the invention provides a. pin joint comprising a pin that is anchored in a bore to allow a part to rotate about the pin; an expandable bush that engages the pin and the bore to anchor die pin within the bore; and a plurality of screwthreaded members, each of which engages a. respective part-threaded hole formed in the pin and the bush such that rotation of each screwthreaded member causes the bush to tighten on the pin, to expand the bush between the pin and bore.

Preferably, each of said screwthreaded members is a grub screw.

A pin joint as above may further comprise at least one further part-threaded hole formed in the pin and the bush such that rotation of a respective screwthreaded member in the part-threaded hole causes the bush to slacken on the pin. -8 -

Preferably, die bush comprises a plurality of segments, each of which ha.s at one end two smaller part-threaded holes and one larger part-threaded hole between the smaller part-threaded holes.

Preferably, each part-threaded hole comprises a. plain part-hole in the 5 pin or bush and an adjacent threaded part-hole in the bush or pin.

Preferably, each plain part-hole is a blind hole and the adjacent threaded part-hole extends further than the plain part-hole.

Preferably, each part-hole is a half-hole.

Preferably, in pin joints as above, the pin and bush have mterengaging 1 0 tapered surfaces.

Preferably, the taper angle is about 7 degrees or less. Preferably, the taper angle is about 4 degrees.

Preferably, in a pin joint as above, the expandable bush comprises a plurality of segments and one or more shim is fitted between at least one of the 15 segments and die pin, to adjust the radial extent of die segment.

Tn a pin joint according to any of the preceding aspects of the invention, the pin may be anchored in a respective bore at each end of the pin.

A pin joint according to any of the preceding aspects of the invention may be in an earth moving apparatus.

2 0 The earth moving apparatus may be an excavator. -9 -

The invention extends to a pin joint according to any two or more of the preceding aspects of the invention.

The invention extends to a pin assembly for use in a pin joint according to any of the preceding aspects of the invention, comprising said pin and bush or 5 bushes.

The invention extends to a method of repairing a pin joint that comprises a pin that is anchored in a bore to allow a part to rotate about the pin, wherein the pin is of circular cross-section and the bore has become non-circular with wear, the method comprising the steps of inserting a pin assembly as above into the bore.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which: Figure 1 is a side view of an item of earth moving equipment in the form of an excavator with various parts connected by various pin joints; Figure 2 shows one example of a typical pin joint of the excavator of Figure 1, in cross-section; Figure 3 shows in cross-section a pin within a worn bore; 2 0 Figure 4 is an exploded view of a known device that is intended to compensate for worn bores as shown in Figure 3; Figure 5 is a partial sectional view of part of the device of Figure 4; -10 -Figure 6 is a sectional view of the device of Figure 4 in use; Figure 7 is a more realistic cross-sectional view of a pin within a worn bore; Figure 8 is a cross-sectional view of a bush as one example of die 5 present invention; Figure 9 is a view similar to Figure 6 but showing a bush similar to that of Figure 8, within a non-uniformly worn bore; Figure 10 is a perspective view of the bush shown in Figure 9; Figure 11 is an exploded view of a bush, washer and grub screw; Figure 12 is a part sectional view of the bush, washer and grub screw of Figure 11 in position on a pin, with a shakeproof washer; Figure 13 is a view similar to Figure 12, but without the sha.keproof washer; Figure 14 is an exploded view of a bush, special headed bolt and grub screw; Figure 15 is perspective view of a pin assembly with end caps; Figure 16 is a part sectional view of the pin assembly of Figure 15; Figure 17 is a perspective view of a bush with segments joined by narrow strips; Figure 18 is perspective view of one end of a pin assembly with a special bush; Figure 19 is a perspective view of a pin assembly with discrete segments at each end; Figure 20 is an end view of the pin assembly of Figure 19, showing shims; Figure 21 is a perspective view from one end of another pin assembly; Figure 22 is a perspective view from the opposite end of the pin assembly of Figure 21; 1 0 Figure 23 is an exploded view of the pin assembly of Figures 21 and 22; Figure 24 is a cross-sectional part view of a grub screw engaging a bush and pin to move the bush along the pin in one direction; Figure 25 is a view similar to that of Figure 24, showing the grub screw engaging the bush and pin to move the bush along the pin in an opposite 15 direction; Figure 26 is one end view of the pin assembly of Figures 21 to 25, with a modification; Figure 27 is a view similar to that of Figure 26, for use in a variation of the arrangement of Figure 19; and Figure 28 is a perspective view from one end of a pin assembly for use in a blind bore or with access from one end only of a bore.

-12 -In the figures, like references denote like or corresponding Rifts.

Tt is to be understood that the various features that are described in the following and/or illustrated in the drawings are preferred but not essential. Combinations of features described and/or illustrated are not considered to be the only possible combinations. Unless stated to the contrary, individual features ma.y be omitted, varied or combined in different combinations, where practical.

The excavator (or digger) of Figure 1 has a pin joint 1 that connects a.

piston rod 4 of a hydraulic cylinder to a linkage 2 to afford mutual rotation 1 0 between them. As seen in Figure 2, the piston rod 4 fits snugly between opposing side cheeks of linkage 2, and also is a close running fit on pin 3, with a bearing 20 between piston rod 4 and pin 3. Retaining collars 6 are secured by respective tapered pins 5 that pass through collar 6 and pin 3. In Figure 2, the pin joint 1 is shown in new condition and the pin 3 can rotate with respect to both piston rod 4 and linkage 2 Since the hydraulic cylinder provides a unidirectional force on pin 3, wear on linkage 2 also tends to be mostly unidirectional in the line of greatest load. Referring to Figure 3, such wear may be identified with the bore 8 of linkage 2 no longer being of a circular shape, but instead being more of a shape 2 0 between oval and egg-shaped. 't his means that the pin 3, when acted upon by the end of hydraulic cylinder rod 4 may now move in space 7, without moving the linkage 2, causing a time lag until the space 7 has been traversed. 't his movement may be disconcerting to the machine operator, as it means the operator has to allow for this free play when making precise movements.

An example of the above-mentioned known proposal to repair worn pin joints without having to resort to welding and machining is shown in Figure 4.

-13 -In Figure 4, pin 3 is provided at each of its opposite longitudinal ends with a. respective threaded hole 10, within which a tightening member in the form of a threaded bolt 14 engages. Pin 3 is also provided at both of its longitudinal ends with a respective tapered outer surface 9, which engages with a respective bush 11 that is formed with slots 19 that extend longitudinally of the pin 3 (and bore 8) and is provided with a tapered inner surface 12 that has a similar taper angle to that of the tapered outer surface 9 of the pin 3, with which it engages. The slots 19 extend only partially along the bush 11, except for slot 19A, which is the full length of die bush 11 to allow the bush 11 to expand radially. Plain washer 13, of significant thickness in order to transmit significant forces, has a face 15 abutting a face 16 of bush 11. The inward face 17 of bolt 14 abuts face 18 of washer 13.

Tn use, with the parts assembled as indicated in the exploded view of 1;igure 4 and as shown in the partial sectional view of Figure 5, torque is applied to each of the bolts 14 in order to tighten the respective bush 11, via the respective washer 13, which acts a.s a. thrust plate, onto the respective end of the pin 3. As a result of the tapered surfaces 9, 12 with taper angle a cooperating with one another, the bush 11 progressively expands as it moves longitudinally along the pin 3, the longitudinal slots 19 in the bush 11 permitting such expansion.

It will be appreciated that the torque to be applied by the bolts 14 will typically be very considerable, in order to provide the force necessary to expand the bushes 11. The torque required will depend upon the thread size of the bolts 14. With a large machine, the pin joints will be of a large diameter and will necessarily have large thread sizes. Also, with a large machine, many pin joints may be high off the ground. Considerable care has to be exercised by maintenance workers to ensure their safety when tightening such bolts at -14 -heights. In many cases, die only safe solution is to erect scaffolding to work from.

It has been found dial die torque has to be regularly checked, as die pin joint assembly may work or vibrate loose.

Figure 6 shows pin 3 with bush 11 fitted to it and engaged within worn bore 8 of linkage 2. As can be seen, the bush 11 grips the bore 8 at only two regions 8a and 8b of the bore. As bush 11 is tightened, more and more energy is required to deform the metal of the bush, which progressively gets flattened more against the bore 8. 't his is very wasteful of energy and it is difficult to deform the bush 11 fully. As the pin joint is working, the metal bush 11 flexes resiliently and progressively may lose its resilience, allowing the joint to work loose.

Figure 7 shows a more realistic cross-sectional view of a pin 3 within a worn bore 8. As may be seen, the wear of the bore 8 is far from uniform This 15 further exacerbates the problem of a bush 11, as in the Figure 4 device, being able to afford useful contact with the worn bore 8.

Figure 8 is a cross-sectional view of a bush 11 as one example of the present invention, around a pin 3. A respective bush 11 of Figure 8 replaces each corresponding bush 11 of Figure 4 and is expanded by tightening bolts 14, 20 generally as explained above with reference to Figure 4.

In the example of Figure 8, the bush 11 is itself of non-uniform shape, its height Y (as seen) being greater than its width X. Thus, the overall shape of the bush 11 corresponds more closely to the non-unifortnly worn bore 8 as illustrated in Figure 7. In particular, as seen, the bush 11 has four radiused portions at top, bottom, left and right, joined by relatively straight portions. Each of the four radiused portions has a radius R corresponding to the outer -15 -radius R of the pin 3. Even though die bore 8 may be worn, die wear at top and bottom (a.s seen) will be caused largely by impact of the pin 3, the impact increasing as the wear increases. As die pin 3 is of radius R, the wear at top and bottom of the bore 8 will tend to be of a. similar radius. There is a. similar consideration for the left and right worn portions of die bore 8.

By adopting the radius R ((Jr thereabouts) for the four ra.diused portions of the bush 11, and adopting a dimension Y that is greater than the dimension X, with both Y and X matching the corresponding dimensions of the bore 8, the bush 11 may achieve a much better fit within a non-uniformly worn bore 8.

Whilst principal dimensions X and Y are shown as orthogonal, they may not be so in practice, since a worn bore such as 8 is likely to wear asymmetrically.

Figure 9 shows a bush 11 as illustrated in Figure 8, engaged within a non-uniform bore 8 of linkage 2. As may readily be seen, the bush 11 may achieve a much better fit within die bore 8, than previously proposed devices.

Tn particular, the bush 11 engages the worn bore 8 at four regions (top, bottom, left and right as seen), at each of which the respective radii of the bush 11 and bore 8 are similar, to provide a useful area of contact. This provides an interference fit between the bush 11 and the bore 8, with the bush 11 largely secured against rotation within the bore 8 when the bush 11 is expanded by tightening respective bolt 14.

Pin 3 and bush 11 have respective tapered surfaces 9,12 and, in a. similar way to that described above with reference to Figure 4, as a result of the tapered surfaces 9, 12 cooperating with one another, the bush 11 progressively expands as it moves longitudinally along the pin 3, the longitudinal slots 19 in die bush 11 permitting such expansion.

-16 -Figure 10 shows one example of the bush 11 of Figure 9, in perspective. In this example, there are 4 longitudinal slots 19, including full-length slot 19A. However, there may be any other number of slots 19 (for example, 6 or 8 or any number from 1 upwards).

A bush 11 as shown in Figure 10 may be manufactured in various ways.

For example, using traditional machine tools where the bush is first turned and then the profile is milled around the outside; or using a CNC lathe where the bush is both turned and then milled in consecutive operations.

It may be appreciated from the foregoing that embodiments of the invention may provide significant advantages over previous proposals. By forming bush 11 of a shape to reflect that of the worn bore 8, with maximum dimensions that match those of non-uniform bore 8 and with regions of a radius that matches that of pin 3, a good interference fit is achieved between bush 11 and bore 8, with bush 11 largely secured against rotation within bore 8. With this enhanced fit, there is less likelihood of the pin joint working loose and the requirement (if any) for re-tightening bolts 14 is much reduced.

It may be noted that piston rod 4 and pin 3 both also wear due to interengagement and rotttion. Bearing 20 is typically provided between piston rod 4 and pin 3 and may be periodically replaced -as may piston rod 4. By applying a hard chrome finish to the pin 3, wear may be significantly reduced. For cost, the hard chrome finish may be applied only to a central section of the pin 3 that faces bearing 20 or rod 4.

Embodiments of the invention may find application with pins 3 having a diameter in the range 20 to 200 mm, although other diameters are possible.

Further embodiments of the invention are shown in Figures 11 to 27.

-17 -in Figure 11, a screwthreaded member in the form of a headless grub screw 131 screwthreadedly engages a tapped hole 132 in washer 13. A leading end of the grub screw 131 el-lig-ages in an open end of slot 19A and thereby prevents rotition of washer 13 with respect to bush 11.

As seen in Figure 12, a shakeproof washer 145 is interposed between the head of bolt 14 and washer 13. As the washer 13 is secured against rotation, when the bolt 14 is tightened, the shakeproof washer 145 inhibits unwanted rotation of the bolt 14 with respect to the washer 13 and therefore the bush 11.

in the variation of Figure 13, the shakeproof washer 145 is omitted.

However, the washer 13 and bolt 14 may be formed or joined as a unitary item -that is, the bolt 14 cannot then rotate with respect to the washer 13. Pf hus, with the grub screw 131 engaged in the end of the slot 19A, the bolt 14 cannot rotate at all, with respect to the bush 11. Whilst securing the bolt 14 against rotation is very useful, it can be secured in only one angular position, with a single grub screw 131, a single tapped hole 132 and a single slot 19A to engage the grub screw 131. However, if a plurality of tapped holes 132 are provided around the washer 13 and/or a plurality of indents are provided in an end face of the bush 11 (for example, as in Figure 14), then there is a plurality of angular positions in which the bolt 14 with washer 13 may be locked against rotation by the grub screw 131 -or by a plurality of grub screws 131.

t hus, the examples shown in Figures 11 to 13 can be effective in preventing or reducing the likelihood of bolt 14 and bush 11 working loose in use.

in Figure 14, a bush 11 has an end face 16 formed with eight uniformly 25 spaced indents 161. A bolt 14 ha.s an enlarged hea.d 143 that replaces the washer 13 of previous embodiments. The head 143 is formed with eight uniformly -18 -spaced threaded holes 142, which correspond in spacing and position with the indents 161. A respective grub screw 141 is provided for each of the threaded holes 142, with which it screwthreadedly engages.

The embodiment of Figure 14 operates in a. similar manner to those 5 described above. That is, the bolt 14 is screwed into one end of a pin 3, to which end the head 143 is formed with two further holes 144 with which a. spanner may engage to turn the bolt 14. When the bolt 14 is tightened against the pin 3, with bush 11 interposed, and the holes 142 are brought into register with the indents 161, the grub screws 141 are individually tightened to bear against the end face 16 of the bush 11 and thereby push the bush 11 along the pin, so that mating tapered surfaces of the pin 3 and bush 11 serve to push die bush 11 radially outwardly to engage within a respective bore 8.

A significant advantage of the arrangement of Figure 14 is that, whereas in previous devices, a very substantial force has to be applied to bolt 14 by a single tool such as a very long spanner, that substantial force is now shared between the eight grub screws 141. Thus, for each grub screw 141, a relatively smaller force (torque) needs to be applied, to push the bush 11 along the pin 3. Such a smaller force can be applied more readily and more safely.

Tt may be noted that, in previous devices, when a large bolt ((Jr nut) has to be tightened, a minimum of 3 operators may be required to tighten a bolt such as 14 (or nut). One person to hold a spanner at the opposite end to the bolt 14; and two persons to hang onto the spanner to tighten the bolt and expand the bush. Tn contrast, with an arrangement as shown in Figure 14, one person can readily effect an initial tightening of the bolt 14 and die same person can then tighten each of the grub screws 141 individually by the required amount.

-19 -Figure 13 shows a pin assembly that utilises components as shown in Figure 14, and is provided with end caps 30. One of the end caps 30 is shown in die part sectional view of Figure 16. Figure 16 shows the grub screws 141 engaging the bolt head 143 and the end face of the bush 11, which engages the tapered surface 9 of pin 3.

Each end cap 30 snap engages the periphery of the respective bolt head 143 and protects the components within from both dirt and corrosion. 't his is important because, when a pin joint requires servicing, it is necessary to remove components from it. if they have been subjected to dirt and/or corrosion, this can prove very difficult. The outer faces of the caps 30 provide an area that ma.y carry information or advertising. As seen in Figure 15, die pin 3 is provided with an oil groove 32 that is fed from an oil passage 33, in order to provide lubrication of the pin 3.

In Figure 17, slots 19 of a bush 11 have triangular enlargements 191 adjacent an end face 16 of the bush 11. The enlargements 191 leave a relatively thin portion of material 163 in the adjacent part of the end face 16. This allows a degree of independent movement of the segments 111 of die bush 11 that arc separated by the slots 19. Each segment 111 can be pushed along the pin 3 (for example by one or more respective grub screw) by a different amount to the other segments and therefore be pushed outwardly by a different amount. Thus, the bush 11 may conform better to an irregular shape of a worn bore. 't he enlargements 191 could be of different shapes as the objective is to provide a thin, flexible portion 163 of the bush 11 to allow independent movement of the segments 111. However, a triangular shape is both convenient and effective.

An alternative is for every slot 19 to be a slot 19A. That is, there are then four (or other number) of segments 111 that are independent of one another and are fitted around the pin 3. Where bush segments are independent -20 -of one another, they may be held together temporarily by adhesive tape, elastic bands, etc. until the moment they are introduced into a bore 8. Then the tape etc. is removed and grub crews tightened.

Figure 17 shows an indent 162 to receive a. locating screw or other 5 projection -for example a. grub screw 131 or 141.

Whilst the bush 11 is shown in Figure 17 as non-circular, suitable to fit a well-worn and therefore non-uniform bore 8, it could alternatively be circular.

Tn Figure 18, a bush 11 comprises eight segments 111 that are linked together by an elastomer 114 (or other suitable material) so that they are capable of a degree of movement independently of one another. Each segment 111 cooperates with its own corresponding grub screw 131 that screw-threadedly engages a respective aperture 132 in washer 13. Each segment 111 has a radially extending end face 112 formed with a radially extending detent or groove 113. Each grub screw 131 engages a respective one of die detents 113. Thus, by tightening the grub screws 131 individually, each segment 111 ca.n be moved a different amount along the tapered surface 9 of the pin 3 and thereby be pushed radially outwardly by a different amount until a peripheral curved surface of each end face 112 engages a bore 8 in which the pin 3 is engaged. An alternative to using elastomer 114 is to assemble the segments 111 by means of one or more wire ring that fits into a respective circumferential groove on the outer surface of the segments 111 -again, permitting a degree of movement of the segments 111 independently of one another.

In the embodiment of Figure 19, eight individua.l bush segments 111 are provided at each end of pin 3 (not all segments are shown in die figure). In this 25 example, the tapered surface 9 at each end of the pin 3 is formed with eight adjacent tapered flats 91, rather than being formed as a frustoconical surface as -21 -in previous examples. To illustrate options, a different configuration of flats 91 is shown at each respective end of the pin 3. Each segment 111 has a radially extending end face 112 formed with a radially extending detent or groove 113 and a peripheral curved surface 115 to engage a bore 8 in which the pin 3 is engaged. In this example, the under face of each bush segment 111 is flat, with a taper angle that matches that of the flats 91.

It will be appreciated that, in Figure 19, each bush segment 111 can be moved along the respective tapered surface 9 independently of the other bush segments 111 and therefore be pushed radially outwardly by a different amount until the respective peripheral surface 115 engages the bore 8 in which the pin 3 is engaged. The bush segments 111 may be pushed along die pin 3 by respective grub screws such as those (131, 141) illustrated by way of example in Figures 14 and 18, or in other configurations.

The taper angle of the flats 91 and corresponding under surfaces of the bush segments 111 is about 7° or less. An advantage of this is that, with this relatively low taper angle, the bush segments 111 and tapered surfaces 9 of pin 3 become self-locking. Thus, there is little or no tendency for the bush segments 111 to work loose, even under hard conditions.

An effect of the relatively low tiller angle is that the amount of radial movement of a bush segment 111 for a given axial movement along the pin 3 is also relatively low. Thus, the range of radial adjustment of each bush segment 111 may be less than other configurations. To compensate for this, simple, flat shims 120 may be inserted between the bush segments 111 and flats 91, as shown in Figure 20. One or more slum 120 may be used with any given bush segment 111. The shims may be of a common thickness, or a set of shims of differing thicknesses may be provided. In this way, the bush segments 111 may be used to good effect in bores 8 of various degrees of non-uniform wear.

-22 -Shims may also be used where die tapered surfaces 9 of a pin 3 are frustoconical and the under surfaces of bush segments 111 a.re correspondingly curved. In such a case, die shims are correspondingly curved.

Tt may be noted that, in Figure 19, the pin 3 cannot rotate about its axis 5 when the bush segments 111 are fully engaged within the respective bore (8), due to the engagement of the mating flat, tapered surfaces afforded by the flats 91 and the under surfaces of the bush segments 111. 't he flat under surfaces of the bush segments 111 afford full engagement with the flats 91 on the pin 3 and the curved outer surfaces 115 engage the respective bore (8) at at least one point, 10 which is sufficient to lock the pin 3 and bush segments 111 in place. With all eight segments 111 engaging the bore (8), a very solid assembly may be achieved.

Use of flat shims 120 is very simple and effective to provide a large range of adjustment.

Whilst the curved outer surfaces 115 are shown in Figures 18, 19 and 20 15 as part circular, they could be non-circular, particularly where they are to fit a well-worn and therefore non-uniform bore 8.

As an alternative (or addition) to the use of shims 20, the bush segments 111 may be of differing radial extents -that is, of differing overall radial thicknesses. For example, the radial end faces 112 may be of differing dimensions. A selection of bush segments 111 of differing radial extents may be provided, so that a given bush segment 111 of most appropriate radial extent may be selected for a given position, having regard to the profile of bore 8 within which the pin joint fits. The use of bush segments 111 of differing radial extents may be adopted in various embodiments of the invention.

Figures 21 to 25 show a pin assembly in which a pin 3 has a circumferential oil groove 32 at its centre and a cross-drilled hole 33 from the oil -23 -groove 32 to die centreline of the pin 3. At the right-hand side of die pin 3 (as seen in Figure 21) another hole 34 communicates with the cross-drilled hole 33. Oil is introduced under pressure into the end hole 34 and therefore exudes under pressure into the oil groove 32, thereby to lubricate the pin 3.

The pin 3 has tapered end surfaces 9 as previously described. In this example, the tapered end surfaces 9 are frustoconical, as previously shown. However, in this case, the taper angle is around 4°. This low taper angle provides a high degree of self-locking of bushes 11 on the pin 3. The bush 11 at the right-hand side of Figure 21 has triangular cutouts 191 as described above, to provide four (in this example) bush segments 111 that have a degree of independent movement. The bush 11 at die left-hand side of Figure 21 has four (in this example) separate bush segments 111 that afford independent movement. Independent bush segments 111 can require a little more time to assemble and fit into a bore 8. However, once in place, they can be more efficient in gripping.

Each bush segment 111 is formed with two half holes 116, 117 on its inner surface, to afford a total of eight half holes around the inner circumference of the bush 11. The half holes are formed parallel to the axis of the pin 3 and are alternately plain (116) and threaded (117). Corresponding half holes 316, 317 are formed in the respective end of the pin 3, again parallel to the axis of die pin 3, and also on the same pitch circle as die half holes 116, 117 in the bush 11. The pin half holes are also alternately plain (316) and threaded (317), each plain half hole 316 in the pin 3 matching up with a threaded half hole 117 in the bush 11. Every plain hole 116, 316 is blind. Every threaded hole 117, 317 is longer than the corresponding plain hole 116, 316.

Figure 23 shows various components of Figures 21 and 22 as an exploded view, along with grub screws 151.

-24 -Referring now to Figure 24, a grub screw 151 is shown engaged in a hole made up of a threaded half hole 317 in the pin 3 and a plain half hole 116 in die bush segment 111. As shown, the grub screw 151 has been turned clockwise and, due to its engagement with the threaded half hole 317, ha.s travelled to the right (as seen) until it has engaged the blind end of the plain half hole 116 and therefore cannot move axially with respect to the bush segment 111 any further. As the grub screw 151 continues to be turned clockwise, it continues to travel to the right (a.s seen) due to engagement with the threaded half hole 317, taking the bush segment 111 with it. This travel continues until die bush segment 111 has 1 0 travelled as far to the right as is desired, or until it meets the end of the threaded half hole 317. As described above, as the bush segment 111 is moved along the pin 3, it is moved radially outward.

This procedure is repeated for each of the four grub screws 151 that is engaged in a respective hole made up of a. threaded half bole 317 in the pm 3 and a plain half hole 116 in the bush segment 111, until each grub screw 151 and its associated bush segment 111 is in the desired axial position along the pin 3.

Whilst this provides a very useful arrangement for positioning and expanding outwardly the bush segments 111, there will come a time when it is desired to extract die bush segments 111 -typically for maintenance or repair.

Since pin joints are often used in hostile environments, there may be the effects of dirt and corrosion to overcome, in order to extract the bush segments 111.

In this example, the four grub screws 151 are extracted by turning them anticlockwise, whereupon they are extracted from the holes made up of the plain half holes 116 and die threaded half holes 317.

The grub screws 151 are then inserted into the holes that have not been used so far, comprising the plain half holes 316 in die pin 3 and threaded half -25 -holes 117 in the bush segments 111. This is as shown in Figure 25. In that figure, the grub screw 151 has been screwed into its respective hole until it Ins met die blind end of plain half hole 316. Upon continuing to rotate the screw clockwise, its threaded engagement with the threaded half hole 117 causes the respective bush segment 111 to be moved to the left, until it is extracted from the pin 3.

t hus, there is provided a very convenient and effective arrangement for both inserting bush segments 111 into a bore, around pin 3, and subsequently extracting those bush segments 111.

Figure 26 is an end view on the right hand side of the pin assembly of Figures 21 to 23, with a modification. In Figure 26, each bush segment 111 has three half holes comprising a single, centrally located, larger threaded half hole 117 and, to either side of it, symmetrically, two threaded, smaller plain half holes 116. An advantage of this configuration is that grub screws 151 in the two smaller half holes 116 can together apply a force to the respective bush segment 111 in a balanced manner whereas, in the illustrative view of Figures 21 to 23, the force applied by each single grub screw 151 is applied to one side of the respective bush segment 111. The two grub screws 151 in the pair of half holes 116 can be adjusted individually to provide differential movement of the respective sides of die bush segment 111 until each side touches bore S. As may be seen in Figures 24 and 25, pin 3 and bush 11 may project little or no distance beyond linkage 2 This may be compared with a typical, known arrangement as illustrated in Figure 2, where various components are located or project outside the linkage 2 and are therefore susceptible to damage in hostile environments.

-26 -in Figure 26, the grub screw to engage each hole 117, 316 is necessarily larger than the grub screw to engage each hole 116, 317. The force that can be transmitted by a larger grub screw in hole 117, 316 may be at least twice that transmittable by a smaller grub screw in hole 116, 317.

Figure 27 illustrates how a configuration as shown in Figure 26 may be applied to a pin assembly as shown in Figure 19, where radial position of bush segments 111 is adjusted by grub screws such as 131 in holes such as 116, 317 and 117, 316, rather than using shims such as 120.

t he pin assembly of Figure 28 is suitable for use with a blind bore or 1 0 where access is possible from only one end of a pin joint. The pin assembly of Figure 28 has various features in common with pin assemblies as previously shown and/or described, with which the reader will now be familiar. Therefore, the following description will concentrate mainly on particular features of the Figure 28 embodiment.

As before, a pin 3 has at each end a tapering outer surface 9 that engages tapering inner surfaces of segments 111 of a. bush 11. To assist clarity, only one bush 11 is shown at the near end of the pin 3 (the left-hand side as seen). However, in use, a corresponding bush 11 is provided at the far end of the pin 3 (the right-hand side a.s seen).

A stud 180 has an enlarged circular head 181 at the far end of the pin 3 and a shank 182 that extends all of the way through a central bore of the pin 3 to engage within a boss 136 formed on a circular thrust plate 135 at the near end of the pin 3. The thrust plate 135 is similar to washers such as 13 as previously described. I lowever, it is referred to as a thrust plate here because its function is rather different to the usual function of a. washer.

-27 -t he stud 180 does not screwthreadedly engage the central bore of the pin 3 but is axially slidable with respect to the pin 3. The head 181 bears against die end face of die respective bush 11 when in position on the pin 3. The near end of the shank 182 is secured to the thrust plate 135 by means of a grub screw or set screw 137 that screwthreadedly engages the boss 136 and engages a detent (e.g. a dimple) in the shank 182, formed to receive the grub screw 137.

Grub screws or set screws 131 engage respective threaded holes formed in the thrust plate 135 and engage respective detents 138 formed in end faces of the bush segments 111. "11 hus, in a manner similar to that described previously for other embodiments, tightening of the set screws 131 pushes the respective bush segments 111 along die tapered surfaces 9 of the pin 3, thereby expanding the bush segments 111 radially to secure the bush 11 firmly within the respective bore in which the pin 3 is mounted.

It is to be noted, however, that thrust plate 135 and respective set screws 131 are provided at only one end of the pin 3 -the left-hand end as seen.

Four pegs 170 are mounted in the head 181 of stud 180. Each peg 170 engages a respective tapered slot 171 formed in the tapered outer surface 9 at the respective end of the pin 3. The purpose of the pegs 170 is to prevent rotation of the stud 180 with respect to the pin 3.

Similarly, pegs 170 are mounted in die thrust plate 135 at die near end of the pin 3 and engage corresponding tapered slots 171 in the outer surface 9 of the pin 3, to prevent rotation of the thrust plate 135 with respect to the pin 3.

Any other number of pins 170 and slots 171 ma.y be employed, but here four pegs 170 may help to position the four bush segments 111.

-28 -in use of the pin assembly of Figure 28, the illustrated components are assembled as shown, with bush segments 111 at the far end of the pin 3, as well as at the near end. The thrust plate 135 and shank 182 are secured together by tightening the grub screw 137. Tn this condition, the stud head 181 and the thrust plate 135 bear gently against the respective end faces of the bush segments 111. Tt is not necessary to apply a significant force to the end faces of the bush segments 111 at this stage.

The pin assembly is then introduced into the bores of a pin joint, each of the bushes 11 being positioned within a respective one of the bores. When the pin assembly is correctly positioned, the set screws 131 are progressively tightened. This causes compression of the bushes 11 between the stud head 181 and thrust plate 135. As the set screws 131 are tightened, the force applied to the end faces of the bushes 11 is increased, thereby causing the bushes 11 to move along the pin 3 and increase the radial expansion of the bush segments 111 to secure the pin 3 firmly within the respective bores of the pin joint.

Tt will thus be appreciated that the pin assembly of Figure 28 can be fitted into a pin joint from one end only, as the bush expansion is effected by tightening the set screws 131 at one end only. This is particularly advantageous where one end of the pin joint is not readily accessible -or not accessible at all.

To remove the pin assembly from a pin joint, the set screws 131 are slackened to reduce the radial gripping force of the bushes 11. The pin assembly can then be removed by applying a force to the thrust plate 135 or anything secured to it. If desired, the outer surface of the boss 136 may be screw-threaded, such that an extraction tool (e.g. a slide hammer) may be engaged with it. To similar effect, the boss 136 may be extended and formed with an internal screw thread. The near end of the shank 182 may be forined with an internal -29 -screw thread; or the shank 182 may be extended and formed with an external screw thread.

Typically, ends of set screws 131 bear directly against end faces of bush segments 111. However, a material may be interposed between the end of a. set screw 131 and the end face of a. bush segment 111, to transmit force between set screw 131 and bush sejgment 111. For example, such a material may be a flexible washer or part-washer that is common to two or more set screws 131, to allow for differential movement of bush segments 111. Such arrangements may be adopted in various embodiments of the invention.

The various options and modifications as illustrated and/or described with reference to the preceding embodiments may be applied to the pin assembly of Figure 28, so far as is practical. For example, instead of bush segments 111, a single split bush may be used, in which case only a single peg 170 and slot 171 is needed at the thrust plate 135 and no peg 170 is needed at the stud head 181.

However, of particular note is the ability to use bush segments 111 of differing thicknesses, particularly where the pin 3 is to be fitted into one or more bore that is worn. For example, if there is insufficient fit between a bush segment 111 and the internal surface of the bore at the far end of the pin 3, the pin assembly may be removed, the bush segment 111 replaced with another, thicker segment and the pin assembly refitted. This process may be repeated iteratively until a good fit is achieved. Alternatively or additionally, precision measuring tools may provide accurate dimensions of pin joint bores, to increase the chances of a good initial fit. Even though an iterative fitting process may take a little time, it will result in an excellent fit, with greatly reduced likelihood of future wear.

-30 -t he use of bush segments 111 enables the complete bush 11 to be of greater diameter than the pin 3, when the bush 11 is expanded.

In the above described examples, a taper angle in the range 4 to 7 degrees provides self-locking of the bush 11 on the pin 3, so that the bush 11 is 5 unlikely to come out, even if the bolt 14 works loose.

In addition to being useful for worn, non-circular bores 8, examples of the invention may also be used as original components in a new pin joint. In such a case, the bore 8 will be largely circular. However, the bush 11 is adjusted to provide a firm fit within the bore 8 to inhibit future wear of the bore.

1 0 In this specification, the verb "comprise" has its normal dictionary meaning, to denote non-exclusive inclusion. That is, use of the word "comprise" (or any of its derivatives) to include one feature or more, does not exclude the possibility of also including further features. The word "preferable" (or any of its derivatives) indicates one feature or more that is preferred but not essential.

All (Jr any of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all or any of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

rad, feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated othenvise, each feature disclosed is one example only of a generic series of equivalent or similar features.

-31 -t he invention is not restricted to the details of die foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of die features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of die steps of any method or process so disclosed

Claims (23)

1. -32 -CLAIMSA pin joint comprising: a pin that is anchored at each of its ends in a respective bore to allow a part to rotate about the pin, each of the ends of the pin having a tapering outer 5 surface; at each end of the pin, a respective bush that is radially expandable to anchor the pin within die respective bore, each bush having a tapering inner surface that engages a respective one of said tapering outer surfaces of the pin; and 1 0 a plurality of screwthreaded members that act upon one of the bushes and are selectively rotatable to move at least one of the bushes along the pin thereby to expand the respective bush.
2. 2. A pin joint according to claim 1" wherein each bush is a component of circular cross-section, formed with an axial split to allow the bush to expand.
3. 3. A pin joint according to claim 1, wherein each bush comprises a plurality of segments that allow at least a degree of independent movement of each segment with respect to the other segment(s).
4. 4. A pin joint according to claim 3, wherein said segments are bonded together by elastomeric material.
5. 5. A pin joint according to any of claims 1 to 4, wherein at least one of the bushes has at least one axial slot that terminates in an enlarged portion adjacent an end face of the bush, thereby to afford a portion of reduced thickness of said end face to allow a degree of independent movement of one part of the bush with respect to another part of the bush.
6. -33 - 6. A pin joint according to any of claims 1 to 3, wherein a first plurality of said screwthreaded members engage one of the bushes and a second plurality of said screwthreaded members engage die other of die bushes.
7. 7. A pin joint according to any of claims 1 to 5, wherein said plurality of 5 screwthrea.ded members engage only one of the bushes and selective rotation of the screwthrea.ded members ca.uses movement of both of the bushes along the pin thereby to expand the bushes.
8. 8. A pin joint according to any of the preceding claims, wherein said screwthreaded members are mounted in at least one washer or thrust plate at a 10 respective end of the pin.
9. 9. A pin joint according to claims 7 and 8, wherein said screwthreaded members a.re mounted on a. washer or thrust plate at one end of the pin; a stud has a shank that passes through the pin and a head that engages the respective bush at the other end of the pin; and said washer or thrust plate is mounted on said shank.
10. 10. A pin joint according to any of the preceding claims, having at at least one end of the pin interengaging parts that inhibit mutual rotation between the pin and at least one other component of the pin joint.
11. 11. A pin joint according to claims 9 and 10, wherein said interengaging 20 parts comprise a peg and a slot, provided on the pin and at least one of the stud and the washer or thrust plate.
12. 12. A pin joint according to any of the preceding claims, wherein at least sonic of said screwthreaded members engage a respective part-threaded hole formed in the pin and/or respective bush.
13. -34 - 13. A pin joint according to claim 12, wherein each part-threaded hole comprises a. plain part-hole in the pin or bush and an adjacent threaded part-hole in the bush or pin.
14. 14. A pin joint according to any of the preceding claims, where the taper 5 angle of said tapering surfaces is about 7 degrees or less.
15. 15. A pill joint according to claim 14, where the taper angle is about 4 degrees.
16. 16. A pin joint according to any of the preceding claims, wherein each of said screwthreaded members is a grub screw or set screw.
17. 17. A pin joint according to any of die preceding claims, having at least one removable cap for a respective end of the pin joint.
18. 18. A pin joint according to any of the preceding claims, wherein each bush comprises a plurality of segments, the segments having different radial extents.
19. 19. A pin joint according to any of the preceding claims, wherein the pin 15 joint is in an earth moving apparatus.
20. 20. A pin joint according to claim 19, wherein the earth moving apparatus is an excavator.
21. 21. A pin assembly for use in a pin joint according to any of the preceding claims, comprising said pin and bushes.
22. 2 0 22. A method of repairing a pin joint that comprises a pin that is anchored in a bore to allow a part to rotate about the pin, wherein the pin is of circular cross-section and the bore has become non-circular with wear, the method -35 -comprising the steps of inserting a pin assembly according to claim 21 into the bore.
23. 23. A pin joint, a pin joint assembly or a method of repairing a pin joint, substantially as hereinbefore described with reference to the accompanying 5 drawings.