Pin Bearings

Abstract

A pin bearing lubrication system is described which comprises a pin bearing having a bush recessed each end thereof; a sealing ring disposed in each recess in the bush; a bearing pin passing through the bush and forming seals with the sealing rings; a reservoir for lubricant formed in the bearing pin; a duct formed the bearing pin connecting the reservoir with bearing surfaces formed between the bush and the bearing pin; and a diaphragm movable in and relative to the reservoir, the arrangement being such that the diaphragm is acted upon by the pressure prevailing outside the bearing pin and by a biasing spring so as to urge the diaphragm in a direction tending to reduce the volume of the reservoir. Such a pin bearing lubrication system may be incorporated in, for example, a chain of dredge buckets which are hinged together by pin bearings. 1. Field of the Invention This invention relates to pin bearings and, more particularly, is concerned with pin bearing lubrication systems for use, inter alia, in dredge buckets. 2. Description of the Prior Art Dredge buckets such as that shown in FIG. 1 of the accompanying drawings are used for removing material from, for example, sea beds or river beds. The material removed can vary from soft silt to hard rock which is broken up and removed by the action of the dredge buckets. Generally, a number of dredge buckets are hinged together by means of pins passing through holes formed in each pair of buckets to form a bucket chain. Dredging operations unavoidably result in a certain amount of disturbed material, e.g. sand or particles of other solid matter, around the dredge buckets which disturbed material may get between the pins and the holes thus resulting in wear of the pins and the holes. It is known to provide rubber sealing rings in pin bearings for use inter alia with dredge buckets (see for example, British Patent Specification No. 655,179). The sealing rings are for retaining lubricant in the pin bearings between the pin and the bush and thus serve to reduce wear of the bearing surfaces. However, such sealing rings are often used under arduous conditions and it is very difficult to prevent leakage of lubricant or ingress of water or particles of solid matter, each of which can result in increased wear of the bearing surfaces. It is an object of the present invention to provide a pin bearing in which the rate of wear of the bearing surfaces is reduced. According to the present invention, therefore, there is provided a pin bearing lubrication system which comprises a pin bearing having a bush recessed each end thereof, a sealing ring disposed in each recess in the bush, a bearing pin passing through the bush and forming seals with the sealing rings, a reservoir for lubricant formed in the bearing pin, a duct formed in the bearing pin connecting the reservoir with bearing surfaces formed between the bush and the bearing pin, and a diaphragm movable in and relative to the reservoir, the arrangement being such that the diaphragm is acted upon by the pressure prevailing outside the bearing pin and by biasing means acting between the diaphragm and the bearing pin so as to urge the diaphragm in a direction tending to reduce the volume of the reservoir. In one form of the invention the bush comprises two parts; an outer bush to which the retaining plate is fixed and an inner bush forming that part of the bearing in contact with the bearing pin. Advantageously, the sealing rings are made of an elastomeric material, e.g. a natural or synthetic rubber; they can, however, be made of any suitable material. Each sealing ring is provided with a garter spring, which garter spring increases the pressure exerted by the sealing rings on the surface of the bearing pin and thereby improves the effectiveness of the seals. The sealing rings may also be provided with a cylindrical surface resting on the surface of the bearing pin, thereby providing additional protection against the ingress of particles. In one embodiment of the invention each sealing ring is retained in a recessed bush and urged against the end of the bush by an annular plate fixed to the bush. The sealing ring may also be provided with an annular ring projecting from the surface of the sealing ring, which annular ring is urged against the surface of the annular plate, creating a seal at the area of contact and substantially eliminating any loss of lubricant around the sealing ring. Advantageously that part of the sealing ring which is urged against the bush is provided with notches to allow lubricant to flow to the seal between the annular plate and the annular ring projecting from the surface of the sealing ring. The diaphragm may comprise a flexible sleeve fastened around a rigid portion. Advantageously, the rigid portion is a spring-retaining cup which houses the biasing means, which biasing means is in the form of a coil spring acting between the diaphragm and an annular plate fixed to the bearing pin. In one embodiment of the invention the system includes a pressure release valve which prevents overfilling of the system with lubricant. Advantageously the pressure release valve is disposed within a coil spring which forms the biasing means and which is housed in a spring-retaining cup forming part of the diaphragm. A pin bearing lubrication system according to the present invention may be used for the lubrication of, for example, underwater bearings or the pin bearings of dredge buckets. For a better understanding of the invention and to show more clearly how the same may be carried into effect reference will now be made, by way of example, to the accompanying drawings.

Patent Drawings (4 sheets)

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