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.BACKGROUND OF THE INVENTION1.