Flexible Guards For Undercarriage

Technical Field

This invention relates generally to guards for preventing the intrusion of foreign matter into a confined space and more specifically to flexible guards for preventing the intrusion of foreign matter into the undercarriage of a track-type vehicle.

Background Art

Some of the most significant difficulties faced in the design, operation and maintenance of track-type undercarriages result from the poor ground conditions these undercarriages encounter. It is very common for vehicles utilizing these undercarriages to operate in mud, gravel, sand, snow, clay, rock, and"the like. These materials and other types of foreign matter can present major mechanical and operational problems upon intrusion into an undercarriage.

Typically, metallic track-type undercarriages incorporate a drive sprocket, at least one idler, and a number of rollers, all of which support a track chain. For the proper operation of the undercarriage, it is necessary that the length of the track chain be only slightly greater than the path defined for it by the supporting elements.

Operation of the undercarriage in loose ground material, such as gravel and mud, will result in a certain amount of this material entering the undercarriage. Even with relatively solid ground conditions, turning and side bank dozing will dislodge material and force it toward the interior of the undercarriage. Once this material has entered the undercarriage, it will tend to be compacted between the

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track chain and the sprocket, idler, and rollers. That material which does remain loose is often recirculated as the track chain inverts along the top of the undercarriage and is subsequently compacted into the track chain or other components of the undercarriage.

This compaction of material in the track chain brings about a decrease in available slack resulting in increased track tension and a resulting accelerated wear to the components of the undercarriage. In many modern undercarriages this problem is somewhat mitigated through the use of an expensive recoil system designed to permit the front -idler to move in a stress relieving manner, should track tension reach a preselected, undesirably high value. Elimination of the need for such a recoil system, and elimination of the high undercarriage wear rate would prove highly advantageous.

Entry of material into the undercarriage is further disadvantageous in that the presence of many types of material, e.g. sand and rock dust, can cause wear and surface deterioration by their mere presence intermediate surfaces on the undercarriage which bear one against the other. The mechanism for this wear, often termed "inculcation", is the forcing of small particles of debris into the surface of a metallic element. This establishes an irregularity in the surface which results in localized, rapid wear. Improved guarding can mitigate this problem.

Many track-type undercarriages, such as that proposed by F. L. Lawson in U.S. Patent 2,780,500 issued February 5, 1957, have included guards for decreasing the volume of debris entering the undercarriage. Typically, these guards are rigid metal plates fixedly mounted to the frame of the undercarriage. Lawson*s design, somewhat more advanced, provides for a rigid guard blocking access to

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the interior of the undercarriage, the guard being pivotably mounted to the frame.

Debris guards of this type suffer numerous disadvantages. The outboard face of track-type undercarriages can be expected to come into forceable contact with trees, boulders and other massive objects. As a consequence, debris guards must be designed so as to resist significant permanent deformation as a result of repeated, sustained, high loadings. This requires that metal guards be quite thick. The thickness required of metal guards results in a significant increase in weight and expense of the vehicle incorporating these guards. Such guards are further disadvantageous in that they require that the roller frame be significantly strengthened at the point at which the guard is supported.

The use of conventional debris guards on soft bottom or resilient undercarriages is in many instances impracticable. This is a result of the fact that the guard, if it is to be effective, must be in close proximity to the lower run of the track. Metal guards, if used on such an undercarriage, would obviously have to be mounted with a significant, and highly undesirable, gap intermediate the guard and the lower run of the track to provide the clearance necessary for the vertical resiliency of the track with respect to the roller frame.

U.S. Patent 1,992,702 issued to Koop on February 26, 1935, discloses a flexible ^" strap of a few centimeters in heighth attached to the bottom of a metallic undercarriage debris guard. This strap runs the entire length of the undercarriage and forms a debris seal between the metallic guard and the lower run of the guard. The resulting guard differs only marginally from an entirely metallic guard. This guard, like those discussed previously must be made

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quite thick to avoid permanent deformation. The flexible strap provides relief for the very limited upward track movement of a hard bottom undercarriage. Such a configuration would seem disadvantageous for a soft-bottom undercarriage due to the need for a massive metallic main guard, inadequate lateral support of the flexible strap, and inadequate clearance for vertical track movement.

The present invention is directed to overcoming one of more of the disadvantages as set forth above.

Disclosure Of The Invention

An undercarriage adapted for use on a track-type vehicle has a front and a rear wheel, a frame, a roller assembly, an endless track trained about the front and rear wheels and the roller assembly, and a guard. The guard has a first and a second portion and is connected at the first portion to at least one of the roller assembly and the frame. The guard extends generally downwardly to a position adjacent one of the track inboard and outboard edges, and contacts at least one of said roller frame and said roller assembly in response to forces on said flexible guards in a direction toward said respective frame and roller assembly.

A serious problem in the operation of track type vehicles is the accumulation of debris such as rocks, clay, mud and the like in the undercarriage. This debris accelerates the rate of wear of undercarriage components, robs the vehicle of power and, in some cases, can result in the overstressing of critical undercarriage elements.

This problem has been dealt with in the past through the use of metal guards intended to limit the intrusion of foreign matter. Guards of this type add undue weight and expense to the vehicle incorporating them. Furthermore, rigid guards are of limited practicability on soft-bottom undercarriages since they must provide clearance for allowed vertical displacement of the track. This clearance necessitates a gap establishing an unprotected pathway to the interior of the undercarriage.

The present invention avoids this difficulty through the use of flexible guards. These flexible guards are preferably attached directly to the roller frame and extend downwardly to the top of the bottom run of the track. An inwardly directed force on these guards urges them against the roller assemblies and other components of the undercarriage directly inboard of the guard. This cooperation of the guard with the underlying undercarriage components establishes a laterally supported, resilient membrane serving to prevent the intrusion of debris. Upward movement of the track serves merely to elastically deform the guard which, once the track returns to the normal position, will again assume its natural position.

Brief Description Of The Drawings

For a better understanding of the present invention, reference may be had to the accompanying drawings in which Fig. 1 shows a partial diagrammatic side view of track-type tractor incorporating an embodiment of the present invention;

Fig. 2 shows a more detailed diagrammatic view of a portion of an undercarriage incorporating an embodiment of the present invention, showing the behavior of the embodiment of the present invention as the undercarriage passes over a bump;

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Fig. 3 shows a diagrammatic sectional view taken through line III-III of Fig. 2;

Fig. 4 shows an additional embodiment of the elastomeric portion of a guard adapted for use in one embodiment of the present invention;

Fig. 5 shows a diagrammatic view of yet another embodiment of the present invention;

Fig. 6 shows an alternative embodiment of the present invention; Fig. 7 shows the behavior of the embodiment of

Fig. 6 in response to an object pushing against it; Fig. 8 shows Section VIII-VIII of Fig. 6; Fig. 9 shows an alternative manner of connecting the flexible guard to the undercarriage. This view is taken along the longitudinal axis of the guard.

It is to be understood that the drawings are not intended as a definition of the invention, but are provided for the purpose of illustration only.

Best Mode For Carrying Out The Invention

Referring to the drawings, a track-type tractor embodying certain of the principles of the present development is generally indicated by the reference numeral 10. It should be understood that the following detailed description of flexible guards for an undercarriage relates to the best presently known embodiment of this advance. The flexible guards for an undercarriage can assume numerous other "embodiments, as will become apparent to these skilled in-the art, without departing from the appended claims.

The track-type tractor 10 preferably incorporates an undercarriage 12 of the soft-bottom or resilient type. This undercarriage 12 has an elevated sprocket 14, a support frame 16, a front idler 18 attached to a front portion 20 of the support frame 16

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and a rear idler 21 attached to a rear portion 22 of the support frame 16. Each of the front idler 18, the rear idler 21, and the sprocket 14, can generally be referred to as "wheels". In certain alternate undercarriages, not shown, the sprocket 14 replaces the rear idler 21. In the preferred embodiment, the support frame 16, and hence the undercarriage 12, is recoilable. That is, the front idler 18 can move fore and aft with respect to the rear idler 21 and sprocket 14. As will be recognized by those skilled in the art, these flexible guards are also suitable for use with non-recoilable undercarriages.

As best shown in Fig. 2, a plurality of rollers 24 are mounted in pairs to the support frame 16 through major and minor bogies 26,28. Each pair of rollers 24 mounted on a minor bogie 28 defines a roller assembly 29, said roller assembly 29 including the corresponding minor bogie 28. The major bogies 26 are each attached to the support frame 16 through support frame pin connections 27. Upward rotation of the major bogies 26 is resisted by resilient pads 30, as best shown in Fig. 2. The forwardmost and rearmost major bogies 26 extend past their respective support frame pin connections 27 to an idler connection point (not shown) to which, respectively, the front and rear idlers 18,21 are rotatively connected. Each of the rollers 24 and the front and rear idlers 18,21 are movable with respect to the support frame 16 due to the resiliently restrained pivotability of the major bogies 26 to which they are attached.

An endless track 31 is trained about the sprocket 14, the idlers 18,21 and the rollers 24. This endless track 31 has an inner face 36, an outer ground contacting face 38, and first and second edges 40,42 joining the inner and outer faces 36,38. The first and second edges 40,42 each define a plane, these planes

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being parallel one to the other. The longitudinal axis of the undercarriage 12 is intermediate, inboard of, and parallel to these two planes. Henceforth, the term "inboard" shall refer to the undercarriage 12, and shall be defined to mean "that which is relatively toward the central, longitudinal axis of the undercarriage 12."

Elastomeric guards 32 having a flexible element 33, for example, reinforced sheet rubber, are connected to metallic mounting brackets 34 located on the support frame 16, as best shown in Fig. 3. These elastomeric guards 32 are disposed substantially vertically in a plane substantially parallel to the planes of the first and second edges 40,42. The elastomeric guards 32 are preferably shaped to cover the greatest possible area intermediate the major bogies 26 while not being so large as to come into substantial contact with the major bogies 26 during normal bogie movement. Consequently, as best shown in Fig. 1, the guards 32 overlie portions of the corresponding minor bogies 28 and rollers 24. The flexible guards 32 have an upper first portion 44 by which they are attached to the undercarriage 12, and a lower second portion 45. The elastomeric guards 32 extend downwardly to a location which is preferably immediately adjacent the inner face 36 of the bottom run of the track 31. The flexible guards 32 are positioned inboard of the corresponding track edge plane, preferably being substantially coplanar with the major bogies 26. Consequently, as best indicated in Fig. 3, when the guards 32 are in a relaxed condition they are somewhat inboardly recessed of the support frame 16 and are also inboard of projecting attachments to the major bogies 26. This serves to protect the edges of the flexible guard 32, especially the leading and trailing edges, from catching on obstructions such as protruding rocks, brush and the like.

The flexible guards 32 are connected by their first portions 44 to the corresponding one of the mounting brackets 34. A clamp plate 46 is positioned such that the first portion 44 of the guard 32 is intermediate the clamp plate 46 and the mounting bracket 34. Mounting bolts 48 pass through apertures 50 in the clamp plate 46, mounting bracket 34 and guard 32. Steel spacers 52, best seen in Fig. 4*, are provided in the guard apertures 50 to permit the mounting bolts 48 to be adequately torqued without damage to the guard 32. The spacers 52 are of somewhat smaller length than the uncompressed thickness of the guard 32.

Alternatively, the attachment of the elastomeric guards 32 to the support frame 16 can be effected by the arrangement shown in Fig. 9. A retaining member 64 is affixed to the support frame 16 by welding, bolts or the like. The retaining member 64, as shown in Fig. 9, defines a recess 66 which, in cross section, is preferably C-shaped with the open portion of the recess 66 facing downwardly. In this embodiment each elastomeric guard 32 has a longitudinally extending thickened upper portion 68 which can be slidingly received within the recess 66. Means (not shown) is provided for preventing substantial longitudinal movement of the guard 32 relative to the retaining member 64. This means can be a retaining screw, a plate blocking the fore and aft openings of the recess 66, or the like. In this embodiment, the narrowed portion of the retaining member 64 acts in conjunction with the thickened, longitudinally extending upper portion 68 to prevent the guard 32 from being forced in a downward direction out of the retaining member 64.

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Preferably, as shown in Fig. 4, the elastomeric guards 32 are ^" reinforced with a reinforcing ply 54 such as is used in tire technology. In certain applications it is preferable to incorporate a reinforcing ply 54 having reinforcing elements 56 all parallel one to the others. This yields a guard 32 with flexibility which is greater in one direction that it is in another. The reinforcing elements can be metallic or made of nylon, fiberglass, Kevlar or other materials as would be recognized by those skilled in the art. For example, in the embodiment shown in Fig. 4, the metallic reinforcing elements 5.4 are all oriented so as to be parallel to the longitudinal axis of the undercarriage 12, resulting in a guard 32 which is more easily deformed vertically than longitudinally. This is especially advantageous where it is necessary to extend the guard 32 very close to the inner face 36 of the lower run of the endless track 31. A plurality of reinforcing plies, biased one with the respect to the others, can also be used.

Additionally, the guards 32 can include grooves 57 formed in the elastomeric element 33 of each guard 32. These grooves 57 provide the guards 32 with increased flexibility in response to forces acting perpendicularly to the direction of the grooves 57. Preferably, as shown in Fig. 4, these grooves 57 run parallel to the longitudinal axis of the undercarriage 12.

Similarly, the guards 32 can include relatively a thin portion 70 to promote controlled and localized deformation. As best shown in Figs. 6-8, where a guard 32 can contact another portion of the undercarriage, it is desirable to provide a relatively thin portion 70 adjacent this point of expected contact to allow controlled deformation of the guard 32 in response to this contact, thereby mitigating

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undesirable stresses and avoiding damage. Fig. 6 shows an embodiment in which a guard 32 is a spaced longitudinal distance from a moveable undercarriage element 72, which can be a roller. In response to the element 72 coming into contact with the guard 32 the relatively thin portion 70 deforms, allowing deflection of the guard 32 sufficient to accommodate the movement of the element 72. This is shown in Fig. 7.

The flexible guards for an undercarriage can assume numerous other embodiments. For example, a single large guard rather than a plurality of individual guards 32 can be used. Such guard 32 extends from the front to the rear of the undercarriage 12 and is positioned sufficiently far outboard to overlie all of the major bogies 26 rather than be positioned intermediate the major bogies 26. Such an arrangement is most feasible on an undercarriage 12 having bogies 26,28 recessed significantly inboard of the track edges 40,42. Alternatively, as shown in Fig. 5, the guards

32 can include rigid fore and aft members 58,60 connected to the major bogies 26. Extending from the fore to the aft member 58,60 is a shield 62 formed of interlocking chain.- This shield 62 forms a flexible barrier preventing the intrusion of debris into the undercarriage 12. One such guard 32 could be attached to cover each individual gap intermediate adjacent bogies 26^ Such a flexible guard 32 can, of course, assume other embodiments. For example, ^" they can utilize interlocking spring rather than interlocking chain.

Industrial Applicability

The flexible guards 32 for an undercarriage described above are attached at first portions 44 thereof to the support frame 16. They extend downward

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to a position adjacent the lower run of the endless track 31 so as to provide ^' a covering for each of the gaps intermediate adjacent major bogies 26.

In the operation of this embodiment, a force applied in an inboard direction to each guard 32 serves to force the guard 32 against those portions of the rollers 24 and minor bogies 28 which are immediately inboard of the guard 32. With the guard 32 so supported, the intrusion of debris is resisted. The guards 32 act as membranes which, in conjunction with the adjacent undercarriage elements which serve as supports, form a barrier to the intrusion of debris into the undercarriage 12. This barrier extends from the lower run of the track 31 upwardly to the support frame 14. An undercarriage 12 incorporating such a debris guard need not incorporate any additional metallic elements for the purpose of shielding the undercarriage 12.

Due to their flexibility, the guards 32 cannot apply a significant force to the support frame 14 through the mounting bracket 34 in response to a side loading situation. Metal guards rigidly attached to the support frame 14 transmit very significant and disadvantagerous loads to the support frame 34 under side loading. As a consequence, undercarriages 12 incorporating these flexible guards 32 avoid the application to the support frame 14 of certain forces which would be applied by rigidly mounted metallic guards. The flexible guards for an undercarriage are further advantageous in that they permit soft bottom undercarriages to resist the intrusion of debris to an extent unobtainable with rigid metallic guards. These flexible guards are further advantageous in that their constant flexure tends to prevent the accumulation of caked mud, ice and other debris on the outboard face of the guard.

Though the flexible debris guards can be utilized on either hard bottom (unsuspended) or soft bottom (suspended) undercarriages, it must be emphasized that there are three differences between hard bottom and soft undercarriages which make the use of flexible guards especially advantageous on the latter. First, the soft bottom roller frame is weak at the point of the debris guard connection relative to the hard bottom roller frame. Thus, the use of flexible guards does not require a soft bottom roller frame to be structurally strengthened at this connection point. Second, the vertical distance from the bottom of the roller frame to the top of the track shoes is significantly greater for the soft bottom than for the hard bottom undercarriage. Consequently, were rigid guards utilized on soft bottom undercarriage they would have to be of increased size and thickness. Lastly, the vertical roller travel inherent to soft bottom undercarriages could allow the track shoe to touch the guard - were metallic guards utilized, damage would result. The flexible design eliminates the need for structural strength for reacting forces from rocks and from interferences during backbending. The flexible guard becomes a movable membrane that deflects until it is backed up by a bogie member and imposes no significant loadings on the roller frame or track shoes. Other aspects, objects, advantages and uses of this invention can be obtained from a study of the drawings, the disclosure, and the appended claims.

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