Pressurized hub cap for vehicle wheel

Claim 2

A vehicle wheel hub cap comprising: a cylindrical cup-shaped member closed at one end and having at least two orifices extending through the wall thereof at different distances from the closed end thereof; a piston slidably mounted in said cylindrical member and adapted to serve as a movable wall for confining viscous lubricant in said cylindrical member; and a compression spring confined in said cylindrical member between the closed end thereof and said piston and adapted to the extent of its self-expansibility from fully compressed condition to maintain the piston in contact with the lubricant in said cylindrical member, one of said orifices being located between the closed end of the cylindrical member and the position of minimum distance of said piston from the closed end as permitted by said spring and the other being located in a position to be at least partially exposed by the piston and in communication with the interior of the cylindrical member between the open end thereof and the piston at least when the pistion is at minimum distance from the closed end of the cylindrical member to provide a passage only directly to the outside of the cylindrical member for lubricant unable to pass from the cylindrical member into the wheel hub.

Claim 3

A hub cap in accordance with claim 1 wherein: said piston is comprised of a flexible self-sustaining disc portion of substantially the same diameter as the internal diameter of the cylindrical member and an integral skirt portion of substantially uniform thickness and flaring conically to a diameter exceeding the internal diameter of the cylindrical member, said skirt portion being deformable upon insertion of the piston into the cylindrical member to effect sealing contact between the skirt portion and the internal surface of the cylindrical member.

Claim 4

A hub cap in accordance with claim 2 wherein the wall of the skirt portion of the piston has a thickness proportioned to accommodate flexure of the skirt as the piston is placed in the cylindrical member while assuring sealing contact of the skirt portion with the internal surface of the cylindrical member and the flexible disc portion has a thickness several times that of the wall of the skirt portion to render it self-sustaining and to reinforce it against wear and puncture by vehicle axle components intruding into the hub cap at its open end.

Claim 5

A vehicle wheel hub cap comprising: a transparent plastic cylindrical cup-shaped member closed at one end and having a least two orifices in the wall thereof at different distances from the closed end thereof: a flexible piston slidably mounted in said cylindrical member and comprised of a self-sustaining body portion and a flared skirt portion facing the open end of the cylindrical member to serve as a movable wall for confining viscous lubricant in said cylindrical member; and a helical compression spring confined in said cylindrical member between the closed end thereof and said piston and adapted to the extent of its self-expansibility from fully compressed condition to maintain the piston in contact with the lubricant in said cylindrical member, one of said orifices being located between the closed end of the cylindrical member and the position of minimum distance of said piston from the closed end as permitted by said spring to vent the portion of the cylindrical member behind the piston to atmospheric pressure and the other being located in a position to be at least partially exposed by the piston and in direct communication with the portion of the cylindrical member between the open end thereof and the piston at least when the piston is at its minimum distance from the closed end of the cylindrical member to enable the escape of viscous lubricant from the interior of the cylindrical member directly to the outer surface thereof upon the occurrence of an over-pressure condition in said viscous lubricant.

Claim 6

A vehicle wheel hub cap comprising: a transparent plastic cylindrical cup-shaped member closed at one end and having a least two orifices in the wall thereof at different distances from the closed end thereof: a flexible piston slidably mounted in said cylindrical member and comprised of a self-sustaining body portion and a flared skirt portion facing the open end of the cylindrical member to serve as a movable wall for confining viscous lubricant in said cylindrical member; and a helical compression spring confined in said cylindrical member between the closed end thereof and said piston and adapted to the extent of its self-expansibility from fully compressed condition to maintain the piston in contact with the lubricant in said cylindrical member, one of said orifices being located between the closed end of the cylindrical member and the position of minimum distance of said piston from the closed end as permitted by said spring to vent the portion of the cylindrical member behind the piston to atmospheric pressure and the other being located in a position to be at least partially exposed by the piston and in direct communication with the portion of the cylindrical member between the open end thereof and the piston at least when the piston is at its minimum distance from the closed end of the cylindrical member to enable the escape of viscous lubricant from the interior of the cylindrical member directly to the outer surface thereof upon the occurrence of an over-pressure condition in said viscous lubricant.