Claims
- 1. An air balancing hoist comprising:
- a housing having an interior bore therein;
- a ball screw mounted in said housing to extend axially through said interior bore;
- a ball nut received over said ball screw;
- a drum reel fixed to one of said ball nut and said ball screw to move therewith, the other of said one of said ball screw and said ball nut fixed to said housing;
- a cable attached to said drum reel so as to be wound thereon and unwound therefrom upon rotation of said drum reel in either direction;
- a movable element axially movable in said housing interior bore and sealed therein to define a pressure chamber on one side thereof, the other side drivingly engaging one end of said drum reel to create an axial force thereon when said chamber is pressurized;
- a source of regulated air pressure in communication with said chamber applying a pressure level sufficient to at least substantially balance an axial force exerted by said cable supporting a load acting through said ball screw and nut to generate an axial force on said drum reel acting oppositely to said axial force generated by said regulated air pressure acting in said chamber;
- a centrifugal brake mounted to one end of said drum reel having an element moved radially outward upon rotation of said drum reel at a predetermined rate corresponding to loss of said load on said cable;
- a cylindrical fixed surface surrounding said drum reel and centrifugal brake to be engaged by said element by said radially outward movement;
- said centrifugal brake element comprising an elongated arm, a pivotal support adjacent one end thereof, said arm having a radially outwardly projecting rounded end surface at said pivoted end, said arm further having a tail portion extending circumferentially away from said pivoted end, said pivot being eccentrically located with respect to said rounded surface so as to bring successive sections thereof radially outward as said tail portion moves radially outward, and wherein an inner surface of said fixed surface is formed with a series of recesses configured to be adapted to receive and interfit with said end surface upon activation of said brake by movement of said tail portion outwardly and initial frictional engagement of said rounded surface until one of said recesses becomes aligned with said rounded end surface;
- whereby said centrifugal brake allows substantially unimpeded rotation of said drum reel during normal winding and unwinding of said cable thereon but substantially locks said drum reel against rotation thereof under a condition wherein said load is suddenly lost.
CROSS REFERENCE TO RELATED PATENT APPLICATIONS
This is a continuation-in-part of U.S. Ser. No. 08/030,768 filed on Mar. 12, 1993, now U.S. Pat. No. 5,370,367, for a "Safety Device for an Air Balancing Hoist", and a continuation-in-part of U.S. Ser. No. 08/260,194 filed on Jun. 15, 1994.
US Referenced Citations (11)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
30768 |
Mar 1993 |
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