Master cylinder with extended piston

A master cylinder comprising a casing formed of a plastic material in a molding operation and defining a bore, an annular groove surrounding the bore between forward and rearward ends of the bore and defining a forward bore portion forwardly of the annular groove and a rearward bore portion rearwardly of the annular groove, and a port connecting the annular groove with a reservoir for containing hydraulic fluid;

• a seal positioned in the annular groove;
• and a piston mounted in the bore for stroking movement between extended and retracted positions, characterized in that:
• the piston has a forward end positioned forwardly of the annular groove in a rearward section of the forward bore portion with the piston in its retracted position whereby in its retracted position a rear end of the piston is guided in the rearward bore portion and the forward end of the piston is guided in the rearward section of the forward bore portion;
• axial groove means are provided at the interface between the forward end of the piston and the rearward section of the forward bore portion establishing communication, with the piston in its retracted position, between the bore forwardly of the piston and the annular groove;
• and
• port means are provided in the piston communicating at one end thereof with the bore forwardly of the piston and opening at another end thereof exteriorly of the piston at a location, with the piston in its retracted position, rearwardly of the seal.

A master cylinder comprising:

• a casing defining a bore, an annular groove surrounding the bore between the forward and rearward ends of the bore and defining a forward bore portion forwardly of the annular groove and a rearward bore portion rearwardly of the annular groove, and a port connecting the annular groove with a reservoir for containing hydraulic fluid;
• a seal assembly positioned in the annular groove;
• a piston mounted for stroking movement between extended and retracted positions and having a forward end positioned forwardly of the annular groove in a rearward section of the forward bore portion with the piston in its retracted position whereby, in its retracted position, a rear end of the piston is guided in the rearward bore portion and the forward end of the piston is guided in the rearward section of the forward bore portion;
• and
• axial groove means at the interface between the forward end of the piston and the rearward section of the forward bore portion establishing communication, with the piston in its retracted position, between the bore forwardly of the piston and the annular groove;
• the casing defining an annular shoulder defining a forward end of the annular groove and an annular lip projecting rearwardly from the shoulder into the annular groove;
• the seal assembly including an annular seal positioned in the annular groove against the annular lip;
• the annular lip being crenelated and coacting with the seal to define a plurality of circumferentially spaced crenel passages there between providing fluid communication between the reservoir port and the axial groove means;
• the seal including an outer flexible lip moveable in response to variations in fluid pressure between an outwardly flexed position blocking fluid communication between the reservoir port and the crenel passages and an inwardly flexed position allowing fluid communication between the reservoir port and the crenel passages and thereby between the reservoir port and the axial groove means.

A master cylinder comprising a casing formed of a plastic material in a molding operation and defining a bore, an annular groove surrounding the bore between forward and rearward ends of the bore and defining a forward bore portion forwardly of the annular groove and a rearward bore portion rearwardly of the annular groove, and a port connecting the annular groove with a reservoir for containing hydraulic fluid;

• a seal positioned in the annular groove;
• and a piston mounted in the bore for stroking movement between extended and retracted positions, characterized in that;
• the piston has a forward end positioned forwardly of the annular groove and a rearward section of the forward bore portion with the piston in its retracted position whereby in its retracted position a rear end of the piston is guided in the rearward bore portion and the forward end of the piston is guided in the rearward section of the forward bore portion;
• axial groove means are provided at the interface between the forward end of the piston and the rearward section of the forward bore portion establishing communication with the piston in its retracted position, between the bore forwardly and the piston and the annular groove;
• the casing defines an annular shoulder defining a forward end of the annular groove and an annular lip projecting rearwardly from the shoulder into the annular groove;
• the seal assembly includes an annular seal positioned in the annular groove against the annular lip;
• the annular lip is crenelated and coacts with the seal to define a plurality of circumferentially spaced crenel passages therebetween providing fluid communication between the reservoir port and the axial groove means;
• the seal includes an outer flexible lip moveable in response to variations in fluid pressure between an outwardly flexed position blocking fluid communication between the reservoir port and the crenel passages and an inwardly flexed position allowing fluid communication between the reservoir port and the crenel passages and thereby between the reservoir port and the axial groove means.