Sealed pivot joint

Details Sealed pivot joint Sealed pivot joint

1985-09-18

1987-05-26

Shoap, Allan N.

Wheel substitutes for land vehicles

Combined or convertible

198851, 277 12, 305 58R, 403223, 403226, 474207, B62D 55088, B62D 5520

Patent

active

046680250

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to sealed pivot joints of the type in which a pin pivots within a bearing. It is particularly, but not exclusively, applicable to hinge joints suitable for joining the adjacent links of endless belts such as used for the tracks of tracked vehicles and conveyor belts.


BACKGROUND ART

Sealed pivot joints are known in which the interface between the pin and the bearing is protected against the ingress of abrasive material, or the loss of lubricant, by one or more sleeves the axial extremities of each being sealed to the pin and bearing respectively, either directly or by way of intermediate sealing members. In applications where the angular displacement of the pin relative to the bearing is limited the interface between the sleeve and the member to which it is sealed may be made as a stationary seal to reduce wear.
In known sealed pivot joints utilising such stationary seals the angular displacement of the ends of the sleeve that results when the pin and bearing oscillate relative to one another is accomodated by providing the sleeve with folds or corrugations that are free to flex and distort. However, when such sleeves are used to seal pivot joints that are used in abrasive environments it has been found that the outer surfaces of the sleeves wear preferentially in the vicinity of the corrugations. This limits the useful life of the sleeve resulting in the need more frequent maintenance of the pivot joints.
It is an object of the invention to provide a sealed pivot joint which is less susceptible to such preferential wear.


DISCLOSURE OF THE INVENTION

According to the invention there is provided a sealed pivot joint having a pin rotatable in a bearing characterised in that there is included an elstic sleeve disposed about the pin, the sleeve having a first and second axial extremity in sealed relationship with the bearing and the pin, respectively, and an intermediate portion maintained in circumferential tension by one or more tensioning members disposed within the sleeve.
The circumferential tensioning of the sleeve acts to prevent the sleeve wrinkling when the pin and bearing oscillate relative to one another.
The tensioning members may comprise a suitably configured portion of the pin, of the bearing end portion, a cylinder rotatably disposed on the pin between the pin and the elastic sleeve, or a combination of these.
The elastic sleeve is preferably of chloroprene polymer. The seals may be maintained by wire or garter springs at each extremity, but the preferred arrangemment is to use two pairs of circlips, one pair being located at each of the extremities of the sleeve by a pair of spaced circumferential ribs formed on the outer surface of the sleeve during its manufacture. Sealing by adhesives has been found to be unsatisfactory with a chloroprene polymer sleeve because the sleeve develops cuts on its inner surface along the edge of the adhesive area next to the intermediate portion of the sleeve, although it may be satisfactory with a sleeve of a different material.


DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings of which--
FIG. 1 is an axial section of a sealed pivot joint showing one of the elastic sleeves sealing the joint;
FIG. 2 is an axial section of a pivot cartridge having three bearing surfaces, each being sealed by sleeves in the manner shown in FIG. 1; and
FIG. 3 is a part cut-away view of the pivot cartridge of FIG. 2 applied between the adjoining track links of an endless track of a tracked vehicle .
Referring to FIG. 1 there is shown a pivot joint 2 which provides articulation between a pin collar 4 and a bearing collar 6 so as to permit relative angular rotation about an axis A. The joint 2 includes a pin 8 which is a running fit in an annular bearing 10 at a bearing surface 12, the bearing 10 being fixed within the bearing collar 6. The bearing 10 extends axially beyond the bearing collar 6 in a direction towards the pin collar 4 to provide

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