| 摘要 |
An air hoist having a reversely rotatable drum adapted to have an elongated flexible load-carrying element, such as a cable, wound onto or off of the drum to permit lifting or lowering of a load. The drum also serves as a reciprocating cylinder and is axially slidably disposed in sealed engagement with an internal piston which, while it rotates with the drum, is axially restrained. A fluid pressure chamber is formed between the end wall of the drum and the piston so that the pressure fluid which is supplied to or discharged from this chamber controls the axial displacement of the drum. A ball-screw arrangement coacts between the drum and a stationary support so as to cause rotation of the drum in response to axial movement thereof, whereby the drum undergoes a helical-type motion during winding or unwinding of the load-carrying element. A control device is associated with the hoist for controlling the flow of pressure fluid to or from the pressure chamber. |
