Background Art Crawler-type vehicles typically include a main frame flanked by a pair of track roller frames which are pivotally connected to the main frame by a shaft. In such vehicles, high loads are directed to the shaft from the track frames and in prior art systems where the shaft has been secured to the main frame by caps bolted to the main frame, the high loading has resulted in the fracturing of the bolts over the operational life of the vehicle. To avoid this problem, it has been proposed to provide a vehicle main frame having apertures extending therethrough for receiving the shaft which mounts the track frame such that the shaft is rotatable about and slidable along its longitudinal axis. In such a construction, to prevent scuffing of the shaft, lubrication at various points is provided. And to prevent loss of lubricant as well as the entry of abrasive material into the interface between the shaft and the frame, seals have been provided. Because of the high loading placed on the shaft in such vehicles, it may deflect substantially and thus the seals proposed for the construction have been wholly resilient and elastomeric to, ensure that sealing contact between the seal and the shaft is maintained even for large shaft deflections. Moreover, the resilient elastomeric seals uti¬ lized have been in the form of sealing rings with the consequence that when seal replacement is required, it has been necessary to disassemble the shaft from the main frame and/or track frames to allow a new sealing ring to be disposed on the shaft.

Disclosure of Invention . The present invention is directed to overcoming one or more of the above problems.

According to the present invention, there is provided a sealed joint including a shaft, an element having a bore slidably and rotatably receiving the shaft, and a packing box surrounding the shaft. Packing is dis- posed within the box and a packing gland is located about the ^* shaft and removably secured to the packing box for * compressing the packing into sealing engagement with the shaft and the packing box. A resilient, elastomeric seal interconnects the packing box and the element and sealingl engages the two. The packing will maintain sealing contac with the shaft even through large shaft deflections due to the fact that the packing box may be carried by the shaft through such deflections against the resilience of the elastomeric seal. Other features and advantages will become apparen from the following specification taken in connection with the accompanying drawings.

Brief Description of Drawings Fig. 1 is a perspective view of the main frame of a vehicle which may typically incorporate a sealed joint made according to the invention;

Fig. 2 is a sectional view of a portion of the vehicle main frame, an adjacent track frame, and a sealed joint;

Fig. 3 is an enlarged, fragmentary, sectional vie of the sealed joint; and

Fig. 4 is an exploded view of packing employed in the sealed joint. Description of the Preferred Embodiment

A sealed joint made according to the invention is ideally suited for use in vehicle constructions and, to that end, will be described in connection therewith. How¬ ever, it is to be observed that the sealed joint is not limited to such use, but rather, may be employed with efficacy in other sealed shaft joint constructions, par¬ ticularly where the shaft is subject to forces that produc substantial deflection.

-3- ith reference to Fig. 1, the main frame of a crawler-type vehicle is illustrated and is seen to include side frame members 10 and 12 interconnected at their front . by a cross member 16 and intermediate their ends by a saddle 18 which typically will mount the usual equalizer bar assembly for the vehicle. The rear of the frame members 10 and 12 are interconnected by a drive train housing 20. Just below the drive train housing 20, each of the frame members 10 and 12 has an opening 22 (only one of which is shown) and the two openings 22 are aligned with each other for slidable and rotatable receipt of a shaft 24 shown in dotted lines in Fig. 1.

Fig. 2 illustrates in greater detail the inter¬ relation of the components including- the shaft 24 and the frame member 12. It is to be understood that the inter¬ relationship of the shaft 24 and the frame member 10 is the mirror image of the relationship shown in Fig. 2.

A bushing 26 is press-fit into the opening 22 and the shaft 24 extends through the bushing 26. A small annular gap between the bushing 26 and the shaft 24 is provided, though not illustrated in the drawings, to permit relative rotative and sliding movement of the shaft 24 within the frame member 12 without binding or scuffing. A track roller frame 28 is mounted in adjacency to the side frame 12 and includes a pair of longitudinally extending rails 30 which mount a plurality of track rollers 32 which, in turn, guide a crawler-type track assembly 34. The track frame 28 includes a passage 36 extending from side to side thereof and bushings 38 and 40 are disposed at opposite ends of the passage 36 to receive the end of the shaft 24. Small annular gaps, again, are provided at the interface of the bushings 38 and 40 and the shaft 24.

A retaining cap 42 is secured to the end of the shaft 24 in any suitable fashion and a cover 44 is connected to the track frame 28 by any suitable means to enclose the cap 42. While not shown in the drawings, the elements 42 and 44 are slightly spaced to allow small amounts of relative sliding movement.

A sleeve 46 is press-fit into an end of the passage 36 in the track 'frame 28 and has its end remote from the cap 42 engaging a plate-like thrust bearing 48 secrued to the frame member 12. As seal 50 seals the interface of the sleeve 46 and the thrust bearing 48.

The inner side of the frame member 12 mounts a seal which sealingly engages the shaft 24 to maintain lubricant at the interface of the bushing 22 in the shaft 24 and prevent foreign material from entering such interface. With reference to Fig. 3, the seal is shown In fragmentary and ¹ section form. However, it is to be under¬ stood that the seal components are annular in configuration, as depicted in Fig. 2. The seal includes a cup-shaped packing box 60 having a central opening 62 through which the shaft 24 extends. The packing box 60 includes an interior, annular cavity' 64 which opens away from the frame member 12, that' is, towards the center line of the vehicle. Within the cavity 64 are a plurality of chevron packing rings 66 which are stacked. As seen in Fig. 4, the packing rings 66 are split at 68 and it will be observed that the splits 68 are circu ferentially staggered.

The cavity 64 is closed 'by an annular packing gland 70 which has a central opening 72 through which the shaft 24 extends. The packing gland 70 is"removably secured to the packing box 60 by a ^' series of bolts 74 (only one of which is -shown) and when in place serves to compress the packing rings 66 to urge them into sealing engagement with the shaft 24 and the interior of the packing box 60. The degree of compression can be suitably regulated by inter- ^• posing, one or more shims 76 between the paςking gland 70 in the packing box 60. The packing gland 70 is provided with an annular lip 78 which is axially directed to slidably engage the inner surface of the cavity 64.

An annular, elastomeric, resilient sealing ring 80 has its radially inner surface 82 in sealing engagement with the radially outer surface of the packing boxes 60 and may be secured thereto by any suitable adhesive. The radially outer surface of the sealing ring 80 is secured

to a support ring 84 which, in turn, is secured in any suitable fashion to the frame member 12 about the shaft 24 and within a recess 86 in the inner side of the frame member 12. As a consequence of the foregoing construction a lubricant-receiving space 90 adjacent the bushing 26 is provided. The space 90 is sealed by a seal 80, the packing 66 and the backing box 60 to prevent loss of lubricant and the entry of foreign material. Because the shaft 24, when subjected to high loads, may undergo considerable deflection, the sealing ring 80 is made quite thick, as illustrated, and mounts the packing box 60 such that the latter may move through large deflec¬ tions with the shaft. This factor permits a seal to be maintained at the interface of the shaft 24 and the packing 66 notwithstanding the fact that the packing 66 will not respond rapidly to changes in the relative positions of members in the seal joint and may wear ^' rapidly when , subjected to flexure. To ensure that the relative position of the com¬ ponents does not change to the point where the packing 60 cannot respond to relative movement and continue to sealingly engage the shaft 24, the centeral opening 62 of the packing box 60 is made only slightly larger than the diameter of the shaft 24. That is, a small annular gap exists and, in one embodiment, the gap will be on the order of about 0.020 inches. As a consequence, the packing box will not rub against the shaft 24, but at the same time may be engaged by the same when the shaft undergoes large deflections to cause the packing box 60 and the packing 66 contained therein to deflect with the shaft against the resilience of the seal 80. The above-mentioned dimension is chosen for the reason that it is sufficiently small that the packing 66 can respond to deflections on the order of the amount of the gap.

A number of advantages result from the above con¬ struction. The first is that it enables the use of packing as opposed' to resilient, elastomeric seals. Packing

exhibits superior sealing qualities over the typical resilient, elastomeric seal but frequently has not been utilized because of its poor response to relative movement between components to be sealed and excessive wear when flexed. A construction made according to the foregoing takes advantage of the excellent sealing characteristic of packing and yet avoids the known disadvantages thereof by virtue of the structure previously described.

A second advantage is that it enables the seal to be replaced without disassembling the shaft 24 from other vehicle components. More specifically, because packing is utilized, and the same is compressed by the packing gland 70, lubricant travel along the interface of the various rings and through the slits 68 is avoided, particularly when the slits 68 are staggered, as described previously.

Thus, to change the seal engaging the shaft 24, it is only necessary to remove the bolts 74 and slide the packing gland 70 axially on the shaft 24 sufficiently to remove the packing rings 66. New packing rings, in slit form, may then be assembled to the shaft 24 and within the cavity 64 of the packing box 60 and the gland 70 again secured thereto.

Finally, the construction permits the use of the shims 76 whereby sealing pressure can be suitably regulated as desired.