Grease Injector for Bicycle Crank Bearings

The invention relates to a device by which bearing lubrication can be replaced in a bicycle crank bearing without need for dissassembly by injecting grease into a fitting under pressure and directing it to the bearings. The invention relates to bicycle crank bearings with ball bearing races, henceforth referred to as bearing cups, located into a cylindrical housing referred to as the bottom bracket shell.

The invention may be more readily described by reference to the accompanying drawings.

FIG. 1 shows an isometric view of a bicycle crank bearing housing with a cut away section revealing a sectional view of the bearing mechanism with the invention in place.

FIG. 2 shows a half section of the isometric view shown in FIG. 1.

FIG. 3 shows an alternate method of producing the invention in a half section view.

FIG. 4 and 5 show alternate methods of sealing the sleeve of the invention to the bearing cups showing a detail section view of the sleeve sealing against the bearing cup.

The crank housing 1 consists of a metal tube with internal threads in each end. The crank housing is attached to the tubes to produce the frame of the bicycle. The crank housing generally has radially drilled holes in its periphery on the centerlines of the frame tubes. The bearing cups 2 and 3 are threaded on their outer circumference and thread into the crank housing. Bearing cup 2 is threaded until the shoulder of which meets the end of the crank housing. Bearing cup 3 is retained by means of an internally threaded lockring 4. The spindle 5 turns on ball bearings 6 within the bearing cups. The invention is composed of a tubular sleeve 7 coaxially located over the crank spindle and between the bearing cups with the entire assembly inside of the crank housing. The sleeve is composed of a polymer plastic material with elastic properties. This sleeve is produced such that the ends are perpendicular to the axis of the bearing assembly and provided with sealing surfaces where it contacts the bearing cups. The length is such that when the crank bearings are properly adjusted, the corrugations in the sleeve permit it to compress and seal against the face, outer tapered surface and the inner edge of the bearing cups. This seal can be any combination of surfaces described. FIG. 2 shows the outer tapered surface of the bearing cup sealing against a mating tapered surface of the invention. The sleeve is produced from a material such that after it as been installed into the bicycle crank housing with a properly sized hole in its surface, it can be drilled and have a grease fitting 8 threaded into the hole producing its own threads. The grease to lubricate the bearings is then introduced through the grease fitting under pressure and travels between the sleeve and the crank spindle into the bearings forcing out the contaminated grease between the spindle and the bearing cups. The sleeve is produced from this material also to provide enough resilience to form a seal where it contacts the bearing cup. The seals provide that the grease injected into the invention will only be forced out between the spindle 5 and the bearing cups 2 and 3 and will not leak out into the frame through the radially drilled holes in the crank housing on the centerlines of the frame tubes.

FIG. 3 shows an alternate method of producing the invention using a ring of an elastomer material 9 to make the overall length of the sleeve adjustable and to provide the necessary pressure of the sealing surface against the bearing cups. This has the same effect as the corrugated section shown in the second of FIG. 2. The main body of the invention is composed of two lengths of tubular section material 10 and 11 one end of which is provided with a sealing surface to seal against the bearing cup. FIG. 3 shows an externally tapered sealing surface of the invention which fits inside the inner diameter of the bearing cup and provides a seal as it is forced into the cup by the elastomer ring. The inner end of the lengths of tubing are provided with a reduced outside diameter with an undercut in the surface between the reduced diameter and the outer diameter of the sleeve. The two of these lengths of tubing are connected by a ring of elastomer material, the inside diameter of which slips over the reduced outside diameter of the lengths of tubing. As the sleeves are compressed, the elastomer material is squeezed down into the undercut between the outside diameter and the reduced diameter of the sleeve to provide the pressure necessary to seal against the bearing cups.

FIGS. 4 and 5 show alternate methods of sealing the sleeve comprising the body of the invention to the bearing cup. FIG. 4 shows a rubber o-ring compressed in an axial direction between the body and the bearing cup. FIG. 5 shows a rubber o-ring located co-axially to the assembly with radial contact between the body and the bearing cup.