Device for measuring the maximum pressure in the internal combustion engine cylinders

Claim 1

Apparatus for measuring pressure in an engine cylinder, said apparatus comprising a housing, coupling means on said housing for connecting said housing to said engine cylinder, a first valve member shiftably supported in said housing and communicating through said coupling means with said engine cylinder for controlling outflow of pressurized fluid from said cylinder, a second valve member shiftably supported in said housing, means for supplying a controlled pressurized fluid at a determined pressure to said second valve member, means communicating said first valve member with said second valve member for channeling the flow of said controlled pressurized fluid from the second to the first valve member, said second valve member having a first position in which said controlled pressurized fluid can pass to the first valve member and a second position in which flow of said controlled pressurized fluid Is blocked and prevented from reaching said first valve member, said first valve member having a closed position, means for urging said first valve member to said closed position for blocking the outflow of pressurized fluid from said engine cylinder to thereby protect said second valve member from adverse environmental conditions in said engine cylinder when the apparatus is unemployed for measuring pressure in the cylinder, said first valve member having an open position for passing the outflow of pressurized fluid from the engine cylinder to the second valve member in opposition to the controlled pressurized fluid, said first valve member being movable to said open position in response to the pressure of said controlled pressurized fluid when the apparatus is employed for measuring pressure in the cylinder, said second valve member being shiftable between said first and second positions thereof in response to the outflow of pressurized fluid from said engine cylinder and the controlled pressurized fluid supplied thereto, said second valve member having a position of equilibrium between said first and second positions thereof, said second valve member being movable into said position of equilibrium when the pressure of the outflow of pressurized fluid from said engine cylinder is substantially equal to that of the controlled pressurized fluid.