Patent GB-1431126-A (GB)
Title: Load lowering and control system for cranes shovels hoists and the like
IPC: B66C23/00
Filed: 1974-07-30
Abstract: 1431126 Reversing gear; clutch combinations TWIN DISC Inc 30 July 1974 [4 Sept 1973] 33534/74 Headings F2C and F2D Power is transmitted to load raising and lowering machinery, e.g. in cranes, digging shovels, hoists &c. by means providing for positive lowering of the load and comprising a modulatable friction-type input clutch controlled by a centrifugal valve and connecting a power source with a torque converter, a modulatable friction-type "up" clutch connecting the torque converter with a hoist driving shaft, a modulatable friction-type "down" clutch connecting the hoist driving shaft with the power source, a centrifugal valve selectively controlling the up and down clutches, and means for regulating both of the centrifugal valves. In one embodiment an engine E drives the impeller I of the torque converter through the input clutch 4, with a centrifugal valve 10, and the converter turbine T drives the outer member 20 of the up clutch 21 of which the inner member forms part of the hoist driving shaft 25. The shaft 25 also forms the inner member of the down clutch 41 whose outer member 51 is connected to the engine by reversing gearing 43, 44 ... 49, 50. A centrifugal valve 60 controls the clutches 21, 41. Selection of upward drive of the hoist by a control lever 16 results in pressure fluid being directed by a valve 15 through passages 17, 12 and the centrifugal valve 10 to a chamber 13 to engage the clutch 4 so that the shaft 25 is driven through the torque converter and the clutch 21, which is normally engaged by a spring 35. Balance between the centrifugal force on the valve 10 and the pressure supplied through the passages 17, 12 determines the pressure in the chamber 13, which is continuously bled at 19, and thus the output speed. Controlled lowering of the hoist is accomplished by movement of the lever 16 to terminate flow of pressure fluid to the clutch 4 and operate a valve 63 to pressurize passages 64, 65 to load the outermost end of the centrifugal valve 60 and thereby increase the pressure in a chamber 34, which is continuously fed with pressure fluid through a restriction 82, so that an annular piston 32 is moved to the right to reduce the spring pressure on the clutch 21 and thus lessen the braking action of the turbine T on the shaft 25. The speed of descent is then controlled by the balance between the centrifugal force on the valve 60 and the fluid pressure applied to it, and if the speed is insufficient, due, e.g., to light load on the hoist, the valve 60 will remain closed until pressure in the chamber 34 has engaged the clutch 41 to provide a positive downward drive through the gearing 43, 44... 49, 50. Modifications are described in which the down clutch is arranged concentrically within the up clutch and its inner, input member has a direct connection by a central shaft with the power source. In one such modification the gearing for reversal is provided between the torque converter turbine and the outer, input member of the up clutch, and in another it is situated between the power source and the input member of the input clutch 4.