Patent ID: 6694732
Filing Date: 2004-02-24
Classification: B60T

Abstract:
A brake master cylinder comprising:a cylinder body having a cylinder bore including a closed end and an open end; a plug shaped member positioned in the open end of the cylinder bore and secured to the cylinder body; a slidable first piston extending through the plug shaped member; a second piston positioned in the cylinder bore; a first sealing member engaged with an outer periphery of the first piston and an inner periphery of the cylinder body; a second sealing member engaged with an outer periphery of the second piston and the inner periphery of the cylinder body; a third sealing member positioned between the second sealing member and the closed end of the cylinder bore, the third sealing member being engaged with the outer peripheral surface of the second piston and the inner peripheral surface of the cylinder body; a first pressure chamber, one end of which is defined by the second piston and the second sealing member, and the other end of which is defined by the first piston and the first sealing member; a second pressure chamber, one end of which is defined by the cylinder body and the other end of which is defined by the second piston and the third sealing member; a piston return mechanism for returning the first piston and the second piston to respective return positions; a first radial bore formed on the first piston and movable from one side of the first sealing member to an opposite side of the first sealing member upon sliding movement of the first piston from the return position toward the closed end of the cylinder bore, the first radial bore establishing communication between the first pressure chamber and a reservoir when the first piston is positioned at the return position; a second radial bore formed on the second piston and movable from one side of the third sealing member to an opposite side of the third sealing member upon sliding movement of the second piston from the return position toward the closed end of the cylinder bore, the second radial bore establishing communication between the second pressure chamber and the reservoir when the second piston is positioned at the return position; and an annular member supported by the cylinder body and positioned between the second sealing member and the third sealing member for supporting the second and third sealing members with respect to the cylinder body.