Air hoist and its control device

In combination with an air hoist, a working fluid control device for controlling the flow of pressurized air to and from the hoist, comprising:

• means defining a pressurized fluid chamber to which pressurized fluid from a fluid source is introduced through a supply passage, a working fluid chamber communicating with the pressurized fluid chamber through a valve port, and a diaphragm chamber adjoining the working fluid chamber and separated therefrom by a movable diaphragm;
• a movable hollow valve rod having a valve to open and close the valve port in response to the motion of the diaphragm, and a fluid discharge passage passing through the valve rod and valve and whose one end opens into the working fluid chamber and is opened and closed by the action of the diaphragm, and whose other end opens to the atomosphere;
• a guide rod fixed to the diaphragm, the guide rod having the same cross-sectional area as the hollow valve rod and projecting toward the diaphragm chamber so that the diaphragm receives pressure on substantially the same areas on its working fluid chamber and diaphragm chamber sides when said one opening of the hollow valve rod is closed by the diaphragm;
• conduit means connected between the pressurized fluid chamber, the working fluid chamber and the atmosphere;
• shiftable valve means associated with said conduit means for selectively connecting and disconnecting the diaphragm chamber to or from the pressurized fluid chamber, the working fluid chamber and the atmosphere by operating said shiftable valve means;
• said shiftable valve means including a lifting change-over valve for controlling the lifting of a load by the hoist, a lowering change-over valve for controlling the lowering of a load by the hoist, and a balancing change-over valve for maintaining the fluid pressure in the working fluid and diaphragm chambers balanced when a load is suspended from the hoist;
• said conduit means including a first circuit providing fluid communication between the diaphragm chamber and said shiftable valve means, a second circuit providing fluid communication between the working chamber and said shiftable valve means, and a third circuit providing fluid communication between said pressurized fluid chamber and said shiftable valve means;
• said lifting changeover valve when activated causing said first and third circuits to be in open communication with one another so that fluid is supplied from said pressurized fluid chamber through said first and third circuits into said diaphragm chamber to thereby displace same, which in turn axially displaces said hollow valve rod so that the valve associated therewith is moved into position so as to open said valve port, whereby the pressure fluid flows directly from said pressurized fluid chamber through said valve port into said working chamber and thence into the hoist;
• said lowering change-over valve when activated causing said first circuit to be connected to a low-pressure reservoir or the atmosphere so that the pressure in the diaphragm chamber is reduced, whereby the diaphragm is moved away from the hollow valve rod so that the pressure fluid in the working chamber is vented to the atmosphere through the hollow valve rod, whereby the fluid in the air hoist likewise communicates with the atmosphere through the working chamber, thereby permitting lowering of a load;
• and
• said balancing change-over valve when activated causing said first and second circuits to be in fluid communication with one another so that pressure fluid is supplied from said diaphragm chamber through said first and second circuits to said working chamber, and vise versa, to maintain a pressure balance on opposite sides of the diaphragm.

In a hoist actuated by a compressible pressurized fluid, comprising:

• a support frame having a screw-threaded nut fixedly associated therewith, said nut defining a substantially horizontally extending rotational axis;
• a screw-threaded shaft extending through and being in rotatable screw-threaded engagement with said nut, whereby rotation of said screw-threaded shaft in one direction causes one end thereof to axially move outwardly away from said nut, rotation of said shaft in the opposite direction causing said one end to axially move inwardly toward said nut;
• a substantially cylindrical drum disposed concentric with and positioned in surrounding relationship to said screw-threaded shaft, said cylindrical drum being fixedly interconnected to said shaft so as to rotatably and axially move synchronously therewith;
• piston means disposed within said cylindrical drum, said piston means having first seal means associated with the outer periphery thereof for creating a linearly slidable sealed engagement between said piston and said cylindrical drum;
• means coacting between said piston means and said support frame for rotatably supporting said piston means on said support means while preventing said piston means from linearly or reciprocably moving relative to said frame in the axial direction of said drum;
• second seal means coacting between said piston means and said support frame for creating a relatively rotatable fluid-type seal therebetween;
• said cylindrical drum having a pressure wall which extends radially inwardly from the cylindrical peripheral wall of said drum and is axially spaced from said piston means for defining a pressure chamber therebetween;
• and
• passage means communicating with said pressure chamber for supplying a pressure fluid thereto so that said pressure fluid reacts with said piston means and said pressure wall for moving said pressure wall axially away from said piston means so that said drum, due to the rotative support by said shaft within said nut, is simultaneously rotated and axially displaced so that a selected point on the periphery of said drum moves along a helical path.