Piston with improved displacement properties

Abstract

A brake pad actuating device comprising: a piston including: a first pocket; an opposing second pocket; and an internal wall located in the piston separating the first pocket and the second pocket, wherein the volume of the first pocket to the volume of the second pocket form a ratio of less than about 20:1; and wherein the piston is adapted to be used as a brake piston.

What is claimed is: 
     
         1 ) A brake pad actuating device comprising:
 a) a piston including:
 i) a first pocket; 
 ii) an opposing second pocket; and 
 iii) an internal wall located in the piston separating the first pocket and the second packet, 
 wherein the internal wall is located between the first pocket and the second pocket so that a depth of the first pocket to a depth of the second pocket has a ratio of about 2:1 or less and a wall thickness of the internal wall of the piston is between about 0.5 mm and about 15 mm; 
 wherein the piston is made of a moldable plastic and is adapted to be used as a brake piston. 
   
     
     
         2 ) (canceled) 
     
     
         3 ) The brake pad actuating device of  claim 1 , wherein a volume of the first pocket to a volume of the second pocket form a ratio of between about 5:1 to about 1:1. 
     
     
         4 ) The brake pad actuating device of  claim 1 , wherein a volume of the first pocket to a volume of the second pocket form a ratio of between about 2:1 to about 1:2. 
     
     
         5 ) The brake pad actuating device of  claim 1 , wherein the moldable plastic material does not dissolve in brake fluid. 
     
     
         6 ) The brake pad actuating device of  claim 1 , wherein the piston is sufficiently rigid to withstand fluid pressure that pushes the piston into contact with an inboard brake pad. 
     
     
         8 ) The brake pad actuating device of  claim 1 , wherein substantially equal amounts of force, in a radial direction, are exerted on the inside of the second pocket wall and the outside of the second pocket wall. 
     
     
         9 ) The brake pad actuating device of  claim 1 , wherein pressure is exerted on the piston, and substantially all of the pressure is exerted axially on the internal wall. 
     
     
         10 ) The brake pad actuating device of  claim 1 , wherein the internal wall of the piston is located proximate to a seal groove when brake pads are fully worn, and the piston is in a fully extended position. 
     
     
         11 ) The brake pad actuating device of  claim 1 , wherein the internal wall does not travel past a seal groove when pressure is applied to the piston. 
     
     
         12 ) The brake pad actuating device of  claim 1 , wherein a wall thickness of the second pocket of the piston is between about 5 mm and about 8 mm. 
     
     
         13 ) The brake pad actuating device of  claim 1 , wherein a wall thickness of the internal wall of the piston is between about 5 mm and 14 mm. 
     
     
         14 ) (canceled) 
     
     
         15 ) The brake pad actuating device of  claim 1 , wherein a wall thickness of the first pocket is greater than a wall thickness of the second pocket. 
     
     
         16 ) The brake pad actuating device of  claim 1 , wherein a draft angle of the second pocket and the first pocket are reduced. 
     
     
         17 ) The brake pad actuating device of  claim 1 , wherein the piston is made of a phenolic resin or Acrylonitrile butadiene styrene (ABS). 
     
     
         18 ) The brake pad actuating device of  claim 1 , wherein the internal wall is located between the first pocket and the second pocket so that the depth of both the first pocket and the second pocket are substantially the same. 
     
     
         19 ) The brake pad actuating device of  claim 1 , wherein the piston is free of a closed end. 
     
     
         20 ) A brake pad actuating device comprising:
 a) a cylindrical piston adapted for use as a brake piston including:
 i) a first pocket; 
 ii) an opposing second pocket; 
 iii) an internal wall located in the piston separating the first pocket and the second pocket; and 
 iv) an annular boot groove located in the cylindrical piston adjacent to the first pocket; 
   b) a piston bore that houses the piston, the piston bore including a seal groove;
 wherein the volume of the first pocket to the volume of the second pocket form a ratio of about 2:1 or less; 
 wherein the internal wall is located between the first pocket and the second pocket so that a depth of the first pocket to a depth of the second pocket forms a ratio of 1.5:1 or less; 
 wherein the cylindrical piston is made of a moldable plastic material that does not dissolve in brake fluid, and the cylindrical piston is sufficiently rigid to withstand fluid pressure that pushes the cylindrical piston into contact with an inboard brake pad; 
 wherein brake fluid fills the second pocket and surrounds the second pocket of the cylindrical piston so that equal amounts of force, in a radial direction, are exerted on an inside of the second pocket of the cylindrical piston and an outside of the second pocket of the cylindrical piston. 
   
     
     
         21 . The brake pad actuating device of  claim 17 , wherein the piston has a length of about 25 mm or longer. 
     
     
         22 . The brake pad actuating device of  claim 20 , wherein a thickness of a wall adjacent to the first side pocket are greater than a thickness of a wall adjacent to second side pocket.