Balancing apparatus with servo relief valve

Claim 2

In a pneumatic hoist for raising and lowering a load including a pneumatic device having a fluid power chamber and a piston movably disposed within the power chamber, a hoisting cable connected to the piston to be raised and lowered according to movement of said piston, a source of air under pressure and regulator means for connecting the source to the power chamber to urge movement of the piston in a direction shortening the cable, valve means carried by the cable so as to be raised and lowered with it, said valve means having a fluid port connected to the regulator means and being operable to open said port to change fluid pressure in the power chamber as the valve means is moved from a closed position toward an open position, means connecting the load to the valve means to move said valve means from said closed position toward said open position as the load is manually lowered from a hoisted position, said valve means comprising an elongated housing member, said port formed in said housing member and connected with the outlet of said regulator means, a passage connected with said port and extending through said housing member to one end thereof, said passage being parallel to and spaced from the axis of said elongated housing member, said passage connecting said port to an annular recess formed in the end of said housing member, a valve closure member mounted to said housing member and including a seal member fixed to said valve closure member, said valve closure member and said seal member adapted for relative movement toward and away from said annular recess, whereby said seal member is moved into and out of said annular recess upon separation of said valve closure member and said housing member to thereby open and close said port for the passage of air from said regulator means through said valve means to atmosphere and a spring carried by said housing member and urging said housing member and said valve closure member toward a position closing said annular recess.

Claim 3

A hoist as defined in claim 1 and in which the pneumatic device comprises an elongated cylindrical housing, said piston being slidably disposed in said elongated cylindrical housing, and including a sheave mounted in said last mentioned housing so as to be rotated by the cable as the piston is being moved.

Claim 4

A hoist as defined in claim 1 and in which the regulator means is a pilot operated valve comprising: means defining an inlet for receiving air from said source of air under pressure, means defining an outlet communicating through said pilot operated valve with said inlet, said outlet operatively communicating with the fluid power chamber of the pneumatic device to provide pressurized air thereto, means defining a control chamber, means defining a passage connecting said control chamber to said outlet so that outlet pressure is communicated to said control chamber, means defining a pilot chamber having a passage to the atmosphere, a wall disposed between said control chamber and said pilot chamber having an opening which connects said control chamber to said pilot chamber, a hollow pressure-sensitive aneroid housed in said control chamber having its hollow interior operatively connected to said source of air under pressure between said source of air and said power chamber so that the interior of said aneroid is subjected to said air pressure from said source and the outer surface of said aneroid is exposed to the outlet pressure in said control chamber so that said aneroid expands and contracts in response to a differential pressure between the outlet pressure in said control chamber and the air pressure in the interior of said aneroid, said inlet of said pilot operated regulator valve being operatively connected to the source of air under pressure, a valve operatively connected to the outer surface of said aneroid, said valve being disposed in said wall between said control chamber and said pilot chamber to control the communication between said control chamber and said pilot chamber to close said opening in said wall when said aneroid expands due to a relative increase in internal pressure, and to open said opening when said aneroid contracts due to a relative increase in pressure on its outer surface, a spacer forming a movable wall between said outlet and said wall, said pilot chamber being defined by said spacer and said wall, said spacer having a relief passage connected to the atmosphere, a valve disposed in said relief passage to control the opening and closing of said relief passage, a valve disposed between said inlet and said outlet to close and open communication therebetween so that when the outlet pressure is less than either the pilot pressure or the inlet pressure the air pressure in said control chamber is equal to the outlet pressure causing said aneroid to open said valve disposed in said opening in said wall between said control chamber and said pilot chamber, and as the outlet pressure increases the pressure in said control chamber increases to a value greater than the air pressure interior to said aneroid causing said aneroid to contract closing said valve in said opening in said wall between said control chamber and said pilot chamber, said fluid port of said valve means being connected to the hollow interior of said aneroid.