Apparatus for the exact position feedback of a double-acting power piston in a hydraulic power cylinder

Claim 1

An apparatus for the exact position feedback of a double-acting power piston in a hydraulic power cylinder subject to extreme environmental conditions especially high temperatures comprising: a double-acting detecting follower cylinder having a displacement volume equivalent to that of said power cylinder; a detecting piston in said detecting cylinder; an electrical detection means for detecting and indicating the position of said detecting piston; a first fluid conduit connecting the working space on one side of said power piston to said detecting cylinder on one side of said detecting piston; a second conduit connected to the spaces in said cylinder on the other sides of said pistons; a fluid pump; a fluid reservoir; a control valve operatively connected in said second conduit to selectively connect said spaces on the other sides of said pistons to said pump, and to said reservoir; a first and second pressure limiting switch operatively connected in said first and second conduits, respectively, to prevent transfer of pressure through said conduits which exceeds a predetermined value; a fluid passage through each piston interconnecting the spaces in each respective cylinder on opposite sides of the piston; valve means in each passage to control the flow of fluid therethrough; a pressure measuring device operatively connected to each pressure limiting switch to indicate the pressure in said conduits; a signal converter operatively connected to each of said pressure measuring devices to convert the pressure values to corresponding electrical signals; and a function computer operatively connected to said signal converters for controlling the position of said power piston in accordance with a pre-set value.

Claim 2

An apparatus for the exact position feedback of a double-acting power piston in a hydraulic power cylinder subject to extreme environmental conditions especially high temperatures comprising: a double-acting detecting follower cylinder having a displacement volume equivalent to that of said power cylinder; a detecting piston in said detecting cylinder; an electrical detection means for detecting and indicating the position of said detecting piston; a first fluid conduit connecting the working space on one side of said power piston to said detecting cylinder on one side of said detecting piston; a second conduit connected to the spaces in said cylinder on the other sides of said pistons; a fluid pump; a fluid reservoir; a control valve operatively connected in said second conduit to selectively connect said spaces on the other sides of said pistons to said pump, and to said reservoir; a first and second pressure limiting switch operatively connected in said first and second conduits, respectively, to prevent transfer of pressure through said conduits which exceeds a predetermined value; a fluid passage through each piston interconnecting the spaces in each respective cylinder on opposite sides of the piston; valve means in each passage to control the flow of fluid therethrough; a pressure measuring device operatively connected to each pressure limiting switch to indicate the pressure in said conduits; a signal converter operatively connected to each of said pressure measuring devices to convert the pressure values to corresponding electrical signals; and a function computer operatively connected to said signal converters for controlling the position of said power piston in accordance with a pre-set value.