Patent GB-710268-A (GB)
Title: Variable pressure-responsive torque controls for hydraulic clutches
Inventor: THOMAS JOHN ROBERT
IPC: F16D31/08
Filed: 1951-04-16
Abstract: 710,268. Hydraulic clutches. THOMAS HYDRAULIC SPEED CONTROLS, Inc. April 16, 1951, No. 8826/51. Class 69 (2). [Also in Group XXX] In a hydraulic rotary power transmission and control system having a casing 30 containing a fluid and a gear type power transmitting pump mechanism 33 provided with inlet and outlet ports 44F, 44G, including a hydraulic clutch mechanism 17 having an inlet port 44D and a valve 47 co-operating with said port, the valve contains two passages 50, 53 spaced a short distance apart so that they may both be in partial registration with the inlet port at the same time, one passage 53 being adapted to admit air and the other, 50, liquid, into the port, the valve being movable from an extreme position in which only the air passage 53 communicates with the port in a direction to bring the liquid passage 50 into communication with the port. A hoist drum 16 which may be held by a brake band 27 is secured to a shaft 23 driven by the pump 33 in the casing 30. The casing is rotated from an electric motor by a belt-driven pulley 37 secured to the closure plate 32 and has chambers 30E, 30F partially filled with oil which, due to centrifugal force, forms an annulus having an inner face O surrounding a core of air. A cylindrical portion 44C of the pump closure plate 44 provides the seat for the valve 47 operating in the chamber 30F. The chamber 30E has a scavenging duct 67 and contains a piston 63 secured on a rod 56 attached to the valve 47. The rod 56 is connected to a non-rotatable head 72 of a shaft 73 which slides in an adjustable sleeve in a post 75 and carries a collar 86. A yoke 88 pivoted to the post 75 at 88G and connected to the collar 86 by links 90 carries a spring 93, the tension of which is adjusted by the movement of a threaded stem 94 in a hand-wheel 97, so that the yoke 88 is urged to take the valve 47 to the right. The yoke has a foot 88C by which it may be locked in its neutral position by a latch 99 having a release rod 99E, and which is connected to a hand lever 100 by a link 100A. With the valve 47 in the neutral position shown in Fig. 3 and the casing 30 rotated by the pulley 37, air only is admitted from the passage 53 to a groove 44H and inlet port 44D, 44F, to the pump, hence no power is transmitted to the shaft 23. Assuming that a known load of 100 lbs. is to be raised by the cable 91, that the brake 27 is engaged, and that the hand-wheel 97 is in the neutral position, the rod 99E is pushed inwards to release the latch 99 so that the yoke 88 is moved by the slightly tensioned spring 93, which tension is increased by rotation of the adjustment handwheel 97. The yoke moves the valve 47 progressively to the right, the passage 50 admitting an increasing volume of oil to the inlet groove 44H into admixture with the air from passage 53, the flow of air being simultaneously decreased until the passage 50 registers with the groove 44H and the passage 53 has passed out of register so that oil only is being supplied to the pump. As the valve 47 moves to the right a slot 58A in the peripheral face thereof comes into register with the pump outlet groove 44J, and the piston 63 blocks the scavenging duct 67. Fluid from the pump flows from the port 44G, 44E to groove 44J, slot 58A, passage 58 in the valve 47, into passage 61 in the rod 56 and out of a port 62 into the chamber 30E wherein it urges the piston 63 to the left against the tension of the spring 93. Fluid also flows along the passage 61 to the head 72 and through a conduit 81 to a pressure gauge 82 calibrated to show the pull of the cable 91. When this registers 100 lb. the brake 27 is released and the load in the cable will balance the transmitted torque. To raise the load the lever 100, and hence the valve 41, is moved to the right so that the clutch will develop a greater torque. To lower the load the lever is moved to the left so that the clutch develops less than the balance torque. The valve 47 comprises parts A and B separated by shims 49, and the piston 63 is positioned relative to the valve by shims 64. The positions at which the oil passage 50 communicates with the inlet 44D and the piston 63 closes the scavenging port 67 may be varied by changing the thickness of the shims 49 and 64 respectively. Specifications 573,669 and 671,351 are referred to.