US 3,960,362 A · Hoist control with limit switches

Abstract

A hoist control system having a limit switch assembly is utilized in a pendant controlled pneumatic hoist to limit hoist travel to a predetermined range within preset upper and lower limits. The hoist travel limits and the range are controlled by a pair of limit switches which are actuated by a pair of actuating members which move in response to rotation of the hoist motor. The initial positions of these movable members are independently preset by initially setting them on a threaded shaft which is mounted proximately to the limit switches. The shaft rotates in response to hoist motor rotation causing the constrained movable members to move linearly along the threaded rotating shaft until they actuate one of the limit switches. The actuated limit switch controls a valve assembly to prevent supply air from driving the hoist motor to thereby stop further hoist movement.

Claims7

Dependent claims

A limit switch actuated control valve assembly for supplying power to the air motor of an air motor driven hoist comprising:

a housing forming a main chamber communicating with an exhaust port for venting the main chamber, a supply inlet port for providing supply air to the main chamber, and an outlet port for supplying supply air from the main chamber to the air motor;
piston means slidably mounted within the main chamber to seal the exhaust port and connect the supply inlet port to the outlet port in a first position and to seal the air supply port and connect the outlet port to the exhaust port in a second position;
a biasing pressure chamber formed in said housing on one side of said piston means
limit switch means for moving said piston means between said first and second positions in response to a control signal, said limit switch means including a normally open valve connected to the biasing pressure chamber to supply air to the pressure chamber and maintain said piston means in said first position until said control signal is provided;
and
means for providing a control signal to said limit switch means upon the hoist reaching a predetermined hoisting position.

3 more elements

A hoist control system having limit switches to maintain hoist travel within predetermined limits comprising:

an air motor for driving the hoist in either a load raising or a load lowering direction in response to rotation thereof;
a control valve connected between an air supply and said air motor for selectively activating said air motor in either the load raising or lowering direction;
pendant means for providing said air supply to said control valve in response to actuation thereof by a hoist operator;
limit switch means for deactivating said control valve in response to a predetermined movement of the hoist in either the load raising or lowering direction;
connecting means for coupling said hoist motor to said limit switch means including a threaded shaft rotatably mounted proximately to said hoist motor and being responsive thereto to rotate in response to rotation of said hoist motor;
said limit switch means including a first traveling nut threaded on one end of said shaft, a second traveling nut threaded on the opposite end of said shaft, a first actuator mounted proximate one end of said shaft to be triggerable by said first nut, a second actuator mounted proximate the opposite end of said shaft to be triggerable by said second nut, retaining means for preventing rotation of said first and second nut with rotation of said shaft while allowing said first and second nuts to laterally move along said shaft in response to rotation of said shaft, and signal generating means including a normally open valve connected between said pendant means and said control valve, said normally open valve being closed by one of said actuators when moved to a predetermined spot on said shaft by the rotation thereof to shut off said air supply to said control valve.

3 more elements

Dependencies are inferred from the claim text.

Hoist control with limit switches

Life of this patent

Hoist control with limit switches

Life of this patent

Abstract

Claims7