Master cylinder compensation ports

In a master cylinder having a housing with a bore therein, first and second pistons located in said bore to define first and second chambers, respectively, said first and second chambers being connected to front and rear brake systems in a vehicle, said housing having first and second compensation ports for connecting said first and second chambers with a reservoir, first and second seals, respectively, retained on said first and second pistons, said first and second pistons responding to an initial input force by moving in said bore to initially move said first seal past said first compensation port and said second seal past said second compensation port to thereafter pressurize fluid in said first and second chambers, said pressurizing fluid being supplied to said first and second brake systems to effect a brake application, return spring means for moving said first and second pistons toward a stop on termination of said input force to allow fluid to be communicated from said reservoir to said first and second chambers through said first and second compensation ports to maintain the fluid level in said front and rear brake systems in a full condition, said first and second compensation ports being characterized by a first plurality of openings having a first center hole with adjacent first and second holes and a second plurality of openings having a second center hole with adjacent first and second holes, said first and second plurality of openings allowing fluid to rapidly flow into said first and second chambers while said center holes and said first and second holes being of a size which precludes extrusion of said first and second seals into said first and second compensation ports by pressurized fluid to thereafter permit a later input force to immediately develop pressurized fluid for effecting a subsequent brake application, said first and second center holes being of the same size while said first and second holes are approximately one half the size of said first and second center hole and offset therefrom, said first and second holes being the last to engage said seal on movement of said piston in response to said initial input force and the first to engage the seal on movement of said piston toward said stop on termination of said initial input force, said force and second holes providing an initial flow path between said bore and reservoir to allow for a rapid replenishment of fluid on termination of said initial input force to maintain the fluid level in said front and rear brake systems in a full condition and thereby at provide a ready condition for a brake application in response to any subsequent input force.