Pneumatic balancing hoist

Claim 2

A hoist suitable for hoisting a series of loads of different weights, said hoist comprising: a pneumatically-operated device having a fluid power chamber; a piston disposed in the power chamber for movement according to fluid power chamber pressure; a hoisting member having means at one end for connection to a load, and the other end connected to hoist the load according to piston movement; a source of air under pressure; an elongated fluid conduit having one end connected to the source of air pressure; 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 pneumatically operated 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, said pilot chamber having a passage to the atmosphere; a wall disposed between said control chamber and said pilot chamber, said wall having an opening which connects said control chamber to said pilot chamber; a hollow pressure-sensitive device housed in said control chamber, the interior of said hollow pressure-sensitive device being operatively connected to said elongated fluid conduit between its ends so that the interior of said hollow pressuresensitive device is subjected to said air pressure from said source, and the outer surface of said hollow pressure-sensitive device being exposed to the outlet pressure in said control chamber, so that said pressure-sensitive device 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 pressure-sensitive device; said inlet of said pilot operated valve being operatively connected to said elongated fluid conduit between said end of said elongated fluid conduit connected to the source of air pressure and said operative connection of said hollow pressuresensitive device to said elongated fluid conduit; a valve operatively connected to the outer surface of said pressure-sensitive device, said valve being disposed in said opening 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 pressure-sensitive device expands due to a differential higher internal pressure, and to open said opening when said pressure-sensitive device contracts due to a differentially higher 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 said outlet 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 the 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 pressure-sensitive device 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 pressure-sensitive device causing said pressure-sensitive device to contract closing said valve in said opening in said wall between said control chamber and said pilot chamber; and a control member mounted on the opposite end of the fluid conduit adjacent said load connecting means of said housing member for venting air pressure from said elongated fluid conduit to thereby control the pressure of air admitted to said pressure-sensitive device thereby controlling the pressure of the air admitted to the power chamber from the outlet of the pilot-operated valve, the control member consisting of a single needle valve cooperating with a port so that said control member is infinitely variable between fully opened and fully closed positions of said needle valve, a knob carried by said needle valve and a handle disposed beneath said knob whereby said handle can be manipulated by the thumb of the user to rotate said needle valve to permit selective variation of pilot fluid pressure according to the weight of a load being hoisted by the hoisting member.

Claim 3

A hoist as defined in claim 1, in which the pilot-operated valve is responsive to a differential between power chamber pressure and pilot fluid pressure.

Claim 4

A hoist as defined in claim 1, including a relief valve means mounted on said pneumatically-operated device so as to be responsive to power chamber pressure being greater than pilot fluid pressure.

Claim 5

A hoist as defined in claim 1, including a handle structure connected to the hoisting member so as to be movable with the hoisting member, and in which the control member is mounted on the handle structure.

Claim 6

In combination, a pneumatically operated hoist having a hoist housing, a piston assembly movable in said housing, a first set of pulleys fixed within said housing, a second set of pulleys within the housing supported by said assembly for movement therewith towards and away from said first set of pulleys, a cable wound around said first and said second set of pulleys having one end anchored in said housing, the other end of said cable extending out from said housing for attachment to and support of a load therein, a fluid pressure chamber defiNed between the front end of said piston assembly and one end of said housing, means supplying said fluid pressure chamber with fluid under pressure to move said piston assembly and said second set of pulleys towards or away from said first set of pulleys, said means comprising a a pilot operated valve including: means defining an inlet connected with a source of fluid pressure; means defining an outlet communicating through said pilot operated valve with said inlet, said outlet operatively communicating with the fluid pressure chamber of the said hoist 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, said pilot chamber having a passage to the atmosphere; a wall disposed between said control chamber and and said pilot chamber, said wall having an opening which connects said control chamber to said pilot chamber; a hollow capsule housed in said control chamber, the interior of said hollow capsule being operatively connected to said elongated fluid conduit between its ends so that the interior of said hollow capsule is subjected to said air pressure from said source and the outer surface of said hollow capsule being exposed to the outlet pressure in said control chamber, so that said hollow capsule 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 hollow capsule; a valve operatively connected to the outer surface of said hollow capsule, said valve being disposed in said opening 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 hollow capsule expands due to a differential higher internal pressure, and to open said opening when said hollow capsule contracts due to a differentially higher 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 connecting said outlet 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 the 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 hollow capsule 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 pressure-sensitive device causing said hollow capsule to close said valve in said opening in said wall between said control chamber and said pilot chamber; the improvement comprising an elongated fluid conduit having one end connected to a source of fluid pressure, the interior of said capsule being connected to the elongated fluid conduit between its ends, said inlet of said pilot operated valve being connected to said elongated fluid conduit between said end of said elongated fluid conduit connected to the source of fluid pressure and said connection of said capsule to said elongated fluid conduit, and a control member mounted on the opposite end of the fluid conduit adjacent th free end of said cable for venting fluid pressure from said capsule to thereby control the pressure of air admitted to the fluid pressure chamber, the control member comprising a needle valve cooperating with a port connected with said fluid conduit so that said control member is infinitely variable between fully opened and fully closed positions, sAid needle valve including a knob and said control member including a handle portion disposed below said knob whereby said knob can be rotated by the thumb of user while its handle portion is grasped to rotate said needle valve to permit selective variation of pilot fluid pressure according to the weight of a load being hoisted by the hoisting member.

Claim 7

In combination, a pneumatically operated hoist having a hoist housing, a piston assembly movable in said housing, a first set of pulleys fixed within said housing, a second set of pulleys within the housing supported by said assembly for movement therewith towards and away from said first set of pulleys, a cable wound around said first and said second set of pulleys having one end anchored in said housing, the other end of said cable extending out from said housing for attachment to and support of a load therein, a fluid pressure chamber defiNed between the front end of said piston assembly and one end of said housing, means supplying said fluid pressure chamber with fluid under pressure to move said piston assembly and said second set of pulleys towards or away from said first set of pulleys, said means comprising a a pilot operated valve including: means defining an inlet connected with a source of fluid pressure; means defining an outlet communicating through said pilot operated valve with said inlet, said outlet operatively communicating with the fluid pressure chamber of the said hoist 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, said pilot chamber having a passage to the atmosphere; a wall disposed between said control chamber and and said pilot chamber, said wall having an opening which connects said control chamber to said pilot chamber; a hollow capsule housed in said control chamber, the interior of said hollow capsule being operatively connected to said elongated fluid conduit between its ends so that the interior of said hollow capsule is subjected to said air pressure from said source and the outer surface of said hollow capsule being exposed to the outlet pressure in said control chamber, so that said hollow capsule 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 hollow capsule; a valve operatively connected to the outer surface of said hollow capsule, said valve being disposed in said opening 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 hollow capsule expands due to a differential higher internal pressure, and to open said opening when said hollow capsule contracts due to a differentially higher 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 connecting said outlet 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 the 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 hollow capsule 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 pressure-sensitive device causing said hollow capsule to close said valve in said opening in said wall between said control chamber and said pilot chamber; the improvement comprising an elongated fluid conduit having one end connected to a source of fluid pressure, the interior of said capsule being connected to the elongated fluid conduit between its ends, said inlet of said pilot operated valve being connected to said elongated fluid conduit between said end of said elongated fluid conduit connected to the source of fluid pressure and said connection of said capsule to said elongated fluid conduit, and a control member mounted on the opposite end of the fluid conduit adjacent th free end of said cable for venting fluid pressure from said capsule to thereby control the pressure of air admitted to the fluid pressure chamber, the control member comprising a needle valve cooperating with a port connected with said fluid conduit so that said control member is infinitely variable between fully opened and fully closed positions, sAid needle valve including a knob and said control member including a handle portion disposed below said knob whereby said knob can be rotated by the thumb of user while its handle portion is grasped to rotate said needle valve to permit selective variation of pilot fluid pressure according to the weight of a load being hoisted by the hoisting member.