Patent GB-581420-A (GB)
Title: A suspension unit, particularly for a motor-vehicle
IPC: B60G17/044
Filed: 1944-04-14
Abstract: 581,420. Vehicle &c. suspension devices. S.S. CARS, Ltd., and HEYNES, W. M. April 14, 1944, No. 6894. [Class 108 (iii)] A telescopic suspension unit, particularly for vehicles, compression of which is resisted by compressed gas in a chamber 21 of variable volume, includes a liquid reservoir 31, a pump actuated by fluctuations in the length of the unit for transferring liquid from the reservoir to the pressure chamber so as to increase the supporting pressure of the gas and thus the length of the unit, a leak path for the liquid from the chamber to the reservoir by which the gas pressure is reduced at a lesser rate than that at which it is increased by the pump, and port means for preventing effective action of the pump when the unit is extended to a predetermined length, the port means enabling the unit to assume a predetermined mean length after the static load is altered. The suspension unit shown comprises a lower portion consisting of three concentric cylinders 16, 13, 32 and an upper inverted cylinder 12 carrying a pump plunger 15 which is slidable in the cylinder 16, constituting the pump chamber. A piston-head 18 at the upper ends of the cylinders 13, 16 slidably engages the cylinder 12 the open end of which is slidable on the cylinder 13. For normal load the unit is approximately halfexpanded and is filled with liquid to the level shown, the remaider of the cylin-. der 12 above the liquid which constitutes the chamber 21, being filled with compressed gas through an opening 23. Bleed passages 25, 27 in the piston-head interconnect the portion of the cylinder 12 above the pistonhead with the chambers 26, 28 respectively and a third bleed passage 30 interconnects the pump chamber 16 with the reservoir 31 which is enclosed by flexible gaiter 33. Normally, a port 29 in the pump chamber 16 is just covered by the plunger 15. In operation, reciprocatory movements of the unit operate the plunger to withdraw liquid from the reservoir 31 through an inlet valve 34 and deliver it along the passage 36, thus extending the unit until the port 29 is uncovered by the plunger when the pump is ineffective. Momentary shock loads are resisted by the gas chamber 21 and damping is provided by liquid being forced through the bleed passages 25, 27. Slight leakage of liquid through the third bleed passage 30 tends to reduce the length of the unit until the port 29 is again covered, when the cycle of operations repeats itself. If the unit is overloaded, its length is reduced, compressing the gas in the chamber 21, but when the vehicle is again put into motion, the pump will be operated as before until the unit is extended to its normal length. The gas may be totally enclosed as described in Specification 581,417. The chamber 28 need not be completely filled with liquid, provision being made for it to communicate with the delivery from the pump, and the chamber 26 may be entirely free of liquid, damping being provided by the passage of gas through the bleed passages 25, 27. Instead of the bleed passage 30, a bleed hole may be provided in the cylinder 13 and controlled by the seal 20 so as to place the chamber 28 in communication with the reservoir 31 only when the strut is sufficiently extended.