AU629545B2 - Crawler track assemblies - Google Patents

Description

ii OPI DATE 05/10/89 v AOJP DATE 02/11/89 APPLN. ID 33530 89 PCT NUMBER PCT/AU89/00106 INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (51) International Patent Classification 4 (11) International Publication Number: WO 89/ 08577 B62D 55/21 Al (43) International Publication Date: 21 September 1989 (21.09.89) (21) International Application Number: PCT/AU89/00106 Published With international search report.

(22) International Filing Date: 17 March 1989 (17.03.89) (31) Priority Application Number: PI 7317 (32) Priority Date: 18 March 1988 (18.03.88) (33) Priority Country: AU (71X72) Applicant and Inventor: TURNER, Robert, John [AU/AU]; 13 Cullen Street, Warwick, QLD 4370

(AU).

(74) Agent: FISHER, Peter; G.R. Cullen Co., 79 Eagle Street, Brisbane, QLD 4000 (AU).

(81) Designated States: AU, BR, DE, JP, KR, US.

OCT PATEN!T O CE (54) Title: CRAWLER TRACK ASSEMBLIES liv (57) Abstract A crawler track mechanism comprises a plurality of track plates each mounted on track chain links, the chain links being interconnected by bushes having an outer sleeve rotatably journalled on an inner sleeve which in turn is rotatably journalled on a central cylindrical pin A drive sprocket (60) (and if required, an idler sprocket) comprises recesses (62) having a semi-circular cross section to receivably locate the bushes. The bushes, by virtue of the relative rotation between the pin the inner sleeve and the outer sleeve reduce friction and wear between the drive sprocket and the chain bushes.

WO 89/08577 1 PCT/AU89/00106 CRAWLER TRACK ASSEMBLIES THIS INVENTION is concerned with improvements in or relating to crawler track assemblies.

More particularly the invention is concerned with an improved bush for connection of crawler track chain links and a crawler track system employing such links.

The most commonly used bush for joining crawler track links comprises a cylindrical pin with an annular sleeve rotatably mounted thereon in a plain bearing relationship. In assembling a crawler track chain, the sleeve is press fitted into aligned apertures in opposing sides of one end of a chain link. An adjacent link is then connected by passing the central pin through the sleeve and press fitting the pin in aligned apertures in the spaced jaws of the adjacent link.

Accordingly while the pin and sleeve are relatively rotatable to some degree as adjoining links are flexed, the pin and sleeve are not rotatable relative to respective links in which they are press fitted.

Such prior art chain bushes are particularly susceptible to wear. As a crawler tractor moves across a ground surface the tension in the track is borne by the pin and sleeve. Constant tension combined with relative rotation as the links flex while moving around the drive sprocket and idler gives rise to substantial wear on the outer surface of the pin and the inner surface of the sleeve.

In addition, the outer surface of the sleeve is SSUBSTITUTE SHEET WO 89/08577 PCT/AU89/00106 2 subjected to substantial wear from the drive sprocket teeth due to the combined effects of tension and the fact that the surface of the sleeve grinds against the sprocket teeth as the chain links flex around the sprocket. Generally speaking it is preferred that the bushes wear preferentially over the sprocket as it is less expensive to replace chain bushes than drive sprockets.

Rebushing of crawler track chains is a function often carried out in the field and this task is extremely expensive and time consuming. Apart from the actual cost to an operator of the re-bushing of a crawler track chain system, a loss in earning capacity results from having the crawler tracked vehicle out of operation for two or three days while the track maintenance procedure is being carried out.

In ordei to alleviate the problems of crawler track maintenance due to worn chain bushes, it has been proposed to use a bush comprising a central pin and a sleeve rotatably journalled on the pin by a roller bearing assembly. Although such bushes show a reduction in internal wear between the pin and sleeve, there still exists the problem of wear between the bushes and the drive sprocket.

It is an aim of the present invention to overcome or alleviate the problems associated with prior art crawler track chain bushes and to provide an improved crawler track assembly.

~x~ According to the invention there is provided a crawler track mechanism for tracked vehicles including a plurality of track links pivotally connected at respective ends to form a continuous track, each said track link comprising a generally U-shaped channel member having a transverse base portion and spaced side walls, said side walls including at opposed ends thereof, aligned apertures to receivably locate a bush assembly comprising a cylindrical pin having rotatably journalled thereon a first sleeve member and a second sleeve member rotatably journalled on said first sleeve member, each said track link being pivotally connected to an adjacent track link by a respective said bush assembly; said crawler track mechanism characterised in that the circumferential surface and peripheral edge portions of said second sleeve members are adapted to engage in a channel shaped lower track guide associated with said vehicle, said lower track guide comprising an inverted channel shape.

In order that the invention may be more clearly understood, a preferred embodiment will now be described with reference to the accompanying drawings in which:- Fig 1 illustrates a sectioned track chain bush Ii assembly; Fig 2 illustrates a side elevation of a track chain link fitted with bushes according to the invention; Fig 3 shows an alternative embodiment of the chain link of Fig 2; Fig 4 shows schematically a crawler track mechanism according to the invention;

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I I 4 Fig 4 shows schematically a crawler track mechanism according to the invention; Fig 5 shows a cross sectional view of a track guidance and support member in association with a track chain

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H f* N li WOs8Ibj77 PCT/A189/00106 link and bush assembly; Fig 6 shows a drive or idler sprocket; In Fig 1 the bush comprises a solid central pin 1 on which a first sleeve 2 is rotatably journalled by a needle roller race 3. A second sleeve 4 is rotatably journalled on first sleeve 2 by a further needle roller race Needle roller races 3 and 5 comprise conventional grease filled caged races with outer seals to prevent ingress of foreign matter and egress of the grease packing.

For the sake of clarity the race cages and seals are omitted.

Fig 2 shows a chain link 10 which comprises a pair of spaced side members 11 joined along their lower edges by a transverse base 12 to which track plates (not shown) are releasably mounted by bolts passing through apertures 13.

One end 14 of the chain link 10 includes aligned bores 15 into which central pin 1 of the bush assembly of Fig 1 is frictionally engaged by press fitting or the like.

At the opposite end 16 of chain link 10 aligned bores 17 of a somewhat larger diameter are adapted to frictionally engage the inner sleeve 2 of the bush assembly.

Outer sleeve 4 is thus able to rotate on inner sleeve 2 between the opposed side members 11 of chain link 10. The width of the chain link 10 in the region 11a of side members 11 is narrower than that of region lib such that the corresponding region 11b of an adjacent chain link 10a lies outside region lla when the axes of respective bores 1E,17 WO 89/08577 PCT/AU89/00106 6 are aligned to receive pin 1 and inner sleeve 2 respectively.

Such an arrangement is illustrated in Fig 4.

Fig 3 shows an alternative embodiment of the of the chain link 10 of Fig 2.

In Fig 3 there is shown an alternative embodiment of the chain link illustrated in Fig 2.

The chain link 50 as illustrated comprises a body 51 formed from cast or forged metal and is formed as two mating portions 51a, 51b which are clamped together by bolts (not shown) which pass through track plates (not shown) via apertures 52 in body portion 51a to threaded apertures 53 in body portion 51b. The clamping bolts serve to mount the track plates to the chain links and at the same time to clamp the body portions 51a, 51b together.

When body portions 51a, 51b are separated, bush assemblies 54 of the type shown in Fig 1 may be mounted in body 1 by locating the free ends of central pins 1 respectively within the laterally opposed partially circular jaws 55 in body portion 51h. When the track plate and body portions 51a, 51b are clamped together the free ends of the central pins 1 of the bush assemblies 54 are firmly clamped into the chain link 51.

To alleviate the risk of longitudinal spreading of jaws 55 one or more tapered pins 56 may extend from body portion 51a into tapered recessas 57 in body portion 51b or vice versa. Alternatively a key may be located in

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WO 89/08577 PCT/AU89/00106 7 transversely extending keyway recessed into body portions 51a, 51b or body portions 51a, 51b may be provided respectively with complementary shouldered abutments.

To facilitate separation of body portions 51a, 51b after prolonged periods of use a hex headed grub screw 58 or the like may be located in a threaded aperture 58a and by use of an Allen key or the like, a separating force may be applied between body portions 51a, 51b. If required, shouldered abutments 59 may be provided on body portions 51b to assist separation by tapping these abutments 59 with a hammer whilst tensioning grub screw 58. A plastic dust cap is employed to seal aperture 58a against ingress of dirt or moisture.

Fig 4 shows a partial schematic view of a crawler track mechanism according to the invention.

The crawler track mechanism comprises an idler and a drive sprocket 21.

The drive sprocket 21 may comprise a plurality of generally radially directed teeth 22 having therebetween recesses 23 of semi-circular cross sectional shape, the recesses being of dimensions to receivably locate the chain bushes 24. The idler 20 comprises a sprocket member similar to the drive sprocket except that the teeth 25 are separated by shallower recesses 26 having a part-circular cross section to receivably locate the chain bushes 24.

Preferably both the idler 20 and the drive sprocket r WO 89/08577 PCT/AU89/00106 8 21 include side walls on recesses 23,26 (as generally shown at 27 on idler 20) to assist in guidance of the track chain around ths idler and drive sprocket.

The crawler track comprises a plurality of track plates 30 each attached to a chain link 31 to form an endless chain when links 31 are pivotally connected by bushes 24.

As the tractor or the like moves across a ground surface the exterior surface of a bush 24a engages the side of a tooth 25a and as sprocket 21 continues to rotate in the direction indicated by the arrow, bush 24a rolls into recess 23a with the surfaces of bush 24a and recess 23a in rolling contact. Once located in the recess 23a, the surface of the bush 24a remains stationary relative to the surface of the recess 23a even although adjacent links of the track chain pivot relative to each other as they move around the sprocket 21. As the sprocket passes through 180 of revolution the bush 24a leaves its respective recess 23a with the same rolling motion with which it previously entered the recess.

The initial and final rolling movements of the bushes as they respectively engage and disengage either the idler or drive sprocket, combined with their stationary engagement whilst moving between the engaged and disengaged positions substantially minimises wear on both the outside surface of the bushes as well as the drive sprocket and idler.

WO 89/08577 PCT/AU89/00106 9 The ground enagaging portion of the track may be supported on conventional idler/guide rollers (not shown) or the track may be supported by a support member 32 in the form of an inverted channel.

The width and depth of the channel recess 33 are chosen to accommodate the peripheral portions of the bushes 24 whereby the substantial portion of the weight of the tractor is supported by rolling engagement between bushes 24 and the floor 34 of channel member 32.

The track system according to this aspect of the invention demonstrates a substantially reduced level of energy consuming frictional drag when compared with conventional crawler track systems. Accordingly apart from reduced maintenance costs due to reduced wear, the present invention also offers the advantage of reduced fuel costs in operation of a crawler tracked vehicle.

Fig 5 shows a part cross-sectional view of the channelled support member 32 chain link 10 and bush assembly of Fig 1 illustrating the manner in which the bushes 24 zravel to support the mass of the tracked vehicle.

The various aspects of the invention may be incorporated in a crawler tracked vehicle during construction. Alternatively a vehicle having a conventional crawler track system may be readily retro-fitted with a system according to the invention by replacement of the drive sprocket and idler. Additionally the channelled support

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i WO 89/08577 PCT/AIJ89/00106 member 32 may be adapted to be bolted directly into existing bolt holes for the lower track idler/guide rollers.

Fig 6 shows a drive or idler sprocket 60 which may be utilized with the invention.

The sprocket 60 may be fabricated from a machined or cast central member 61 having a plurality of spaced semicircular apertures 62 about its periphery, the central member 61 being sandwiched between annular cheek plates 63.

Alternatively the sprocket of Fig 6 may be cast as an integral structure.

It will be clear to a skilled addressee that the chain link/bush assemblies of the present invention facilitate simpler and more economic in-field maintenance of crawler track assemblies and substantially minimize operational down time of crawler track vehicles.

It further will be appreciated by a skilled addressee that many variations and modifications may be made to the invention in its various aspects without departing from the spirit and scope thereof.

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Claims (9)

1. A crawler track mechanism for tracked vehicles including a plurality of track links pivotally connected at respective ends to form a continuous track, each said track link comprising a generally U-shaped channel member having a transverse base portion and spaced side walls, said side walls including at opposed ends thereof, aligned apertures to receivably locate a bush assembly comprising a cylindrical pin having rotatably journalled thereon a first sleeve member and a second sleeve member rotatably journalled on said first sleeve member, each said track link being pivotally connected to an adjacent track link by a respective said bush assembly; said crawler track mechanism characterised in that the circumferential surface and peripheral edge portions of j said second sleeve members are adapted to engage in a channel shaped lower track guide associated with said vehicle, said lower track guide comprising an inverted channel shape.

2. A crawler track mechanism as claimed in claim 1 wherein said lower track guide comprises a load bearing member adapted in use to support at least portion of the gravitational mass of said vehicle between respective drive and idler sprockets of said vehicle.

3. A crawler track mechanism as claimed in claim 1 or claim 2 wherein pivotal connection between adjacent track links is effected by frictional engagement between said cylindrical pin and aligned apertures in side walls of a track link and frictional engagement between said first sleeve member and respective aligned apertures in side walls of an (4 adjacent track link.

4. A crawler track mechanism as claimed in any preceding claim wherein a track plate is removably attached to a respective track link by fastening means extending through apertures in said base portion.

A crawler track mechanism as claimed in any one of claims 1 to 4 wherein said track links each comprise a first body member and a second body member removably securable to said first body member by track plate attachment means extending through aligned apertures in said first and second body members.

6. A crawler track mechanism as claimed in claim wherein said first body member and said second body member i, comprise opposed jaw members which cooperate to form aligned i apertures in said side walls of a track link. I

7. A crawler track mechanism as claimed in claim 6 i including locking means to secure adjacent free ends of said I opposed jaw members.

8. A crawler track mechanism as claimed in claim 7 including separating means to enable application of a force to separate said first body member from said second body member.

9. A crawler track mechanism substantially as hereinbefore described with reference to the accompanying drawings. A tracked vehicle incorporating a crawler track mechanism according any one of claims 1 to 9. I