Patent GB-593954-A (GB)
Title: Improvements in or relating to hydraulic shock absorbers
IPC: F16F9/516
Filed: 1943-11-03
Abstract: 593,954. Hydraulic shock-absorbers. FOCHT, N. S. Nov. 3, 1943, No. 18216. Convention date, Oct. 30, 1942. [Class 108 (iii)] In a hydraulic shock-absorber having a cylinder 10 and piston 11 connected between the axle and chassis of a motor vehicle a spring loaded disc valve 48 controlling a passage through the piston and which opens an amount depending on the severity of the shock co-operates with a metering pin 65 controlling a port 82 in the disc valve through which fluid flows in the return direction driving the rebound following the shock, the metering pin being arranged to move with the disc valve when it is opened 'and to return gradually following the closing of the disc valve, so that the throttling effect of the metering pin during the rebound is dependent upon the severity of the shock. The piston is hollow and has a seat 47 against which the disc valve 48 is pressed by a spring 49 and the metering pin 65 has a flared portion 81 extending through the post 82 in the disc, valve, and has a valve 71 controlling a post 66 in a sleeve 55 slidable in a chamber 52 in the piston rod 44 and pressed downwardly against the disc valve by a spring 63. A pin and slot connection 73 allows limited movement between the metering pin and the sleeve 55 for opening and closing the valve 71. Clearance at 85 allows liquid to flow slowly from the chamber 52 to the interior of the piston 11. When the vehicle wheels encounter an obstruction and the vehicle springs are compressed, the liquid pressure at b below the piston increases, the disc valve 48 is raised and the pressure is relieved by flow of liquid to the chamber a above the piston. The opening of the disc valve 48 raises the sleeve 55 which can only move slowly due to the clearance 85. The seat of the valve 48 is flared at 51 to increase the orifice area as the valve opens, and the position taken up by the sleeve 55 and the metering pin is dependent upon the severity of the shock. On rebound the disc valve 48 closes, but the sleeve 55 returns slowly due to the clearance 85. Liquid flows downwardly through openings 87 in the piston, beneath the lower end of the sleeve 55 and through the port 82 in the disc valve, the speed of rebound being thus controlled by the position in which the flared portion 81 of the metering pin was set by the immediately previous compression stroke of-the shock absorber. Communication between the cylinder and a reservoir 12 surrounding it is controlled by a valve on a metering pin 25 and by a disc valve 27. Bottoming of the vehicle springs is prevented by a closure of the valve on the pin 25 on increase of pressure in the space b. If the pressure rises above the maximum pressure which the shock absorber is designed to withstand ball valves 41 in the base of the cylinder are opened. To adjust the metering pin 65 the upper end 74 of the pin is slidably and non-rotatably connected to a rod 58 passing upwardly through the piston, rod 44. By rotating the rod 58 the metering pin 65 and its guide member 64 screwed into the non-rotatable sleeve 55 may be vertically adjusted relatively to the sleeve 55 to dispose any portion of the flared portion 81 of the metering pin in the port 82. If the vehicle wheel enounters a depression in the roadway the pressure in the space b decreases, retaining the disc valve 48 on its seat, the pressure in the space a increases and the liquid acts through holes 70, 68 to open the valve 71 on the metering pin 65 against the action of a spring 80. The liquid then flows through the port 82 in the disc valve to the space b. The strength of the spring 80 is adjusted when the rod 58 is turned, by a nut 77 engaging slots 79 in the sleeve 55 and threaded on the metering pin 65, this thread being of lesser pitch than the thread between the guide 64 and the sleeve 55. An inclined port 86 in the valve 71 allows transfer of liquid without opening of the valves 48, 71 to provide for pitching of the vehicle and for low frequency movement. A hood 114 fixed to the piston rod 44 encloses the top of the cylinder. Specifications 594,006 and 594,007 are referred to.