Push rod for a brake booster

A brake booster having a valve body for retaining a plunger of a control valve, said plunger being connected by an input push rod to a brake pedal, said brake pedal responding to an input force by an operator by moving the plunger to control communication of a source of pressure between a first chamber and a second chamber and create a pressure differential across a wall for developing an output force to effect a brake application, the input push rod being characterized by a cylindrical tube having a first end and a second end with an external annular rib located between the first end and the second end and an internal annular groove located between said annular rib and said first end, said cylindrical tube having a substantially rectangular shape with a hole therein perpendicular to the cylindrical body adjacent said second end, said cylindrical body being connected to said brake pedal by a pin located in said hole and first end of said cylindrical tube receiving a semi-spherical ball that engages said internal annular groove and said first end being crimped around said semi-spherical ball to define a mechanical connection such that an input force applied from the brake pedal through the pin is linearly transmitted directly through the cylindrical tube to move the plunger.

A method of fabricating an input push rod that links a brake pedal with a plunger in a control valve assembly of a brake booster comprising the steps of:

• cutting a cylindrical tube to a desired length corresponding to a distance between the brake pedal and the plunger in the control valve assembly;
• transmitting said cylindrical tube to a first station and holding the cylindrical tube stationary while applying a first axial force to a first end and a second axial force to a second end causing a portion of said cylindrical tube to up set into a die to form an external annular rib between said first end and said second end;
• holding said cylindrical tube stationary while rolling a first internal annular groove between said external annular rib and said first end and a second internal groove between said first internal groove and said first end to define a socket adjacent said first end, said depth of said second internal groove being less than said first internal groove such that a semi-spherical ball that extends from the plunger may be pushed into said socket to secure said cylindrical tube to the plunger.