US2974946A - Pneumatic spring structures - Google Patents

Description

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United States Patent C) P Ice Patented Mar. 14, 1961 This invention relates to the control of pneumatic spring structures, for example for vehicles, in which the spring force is produced by the elastic compression of a gas cushion yand is variable, the gas pressure being suited to the vehicle load and/ or to the state of the road. Controls areV known in which gas can be discharged from the gas cushion through a valve into the open air, whereby the spring force is reduced, andgas can be yadmitted from a compressor or from a pressure bottle, whereby the kspring `force is increased. These` controlsr have the disadvantage that the discharged gas itself and the energy contained in this gas while still compressed are completely lost. Also a compressor, for example, when air is used for springing,rnustovercome the whole pressure diiierence between the atmospheric pressure and the pressure in the cushion.

The control according to the invention is characterised by the gas cushion being connected through valves or other control members to two gas containers which are connected together through a compressor, of which one, the lower pressure container, is lled with gas at a lower pressure than the operating pressure of the gas cushion and the other, the higher pressure container, with gas at a higher pressure than the operating pressure of the cushion. If the pressure of the gas cushion is to be reduced, gas is discharged into the lower pressure container. Then only the energy corresponding to the pressure drop from the gas cushion to the container is lost. If the pressure of the gas cushion is to be raised, gas is admitted to it from the higher pressure container.

The compressor between the lower pressure and higher pressure containers now only has to overcome the small pressure difference between these two containers. With the existence of the containers, in particular a higher pressure container, the advantage is at the same time -obtained that the admission of gas into the cushion canv take place very rapidly, in any case more rapidly than if the compressor had to supply gas directly to the cushion without the interposition of a gas container.

In pneumatic spring structures in which the gas cus'hi example, for hydraulic damping of Vibrations, it is advantageous to let the lower pressure container and the higher presusre container also co-operate with Volumes of oil and to connect all the oil volumes together through valves, in which case an oil pump may also be arranged between the low pressure container and the high pressure container. In this way, it is possible to reduce the volume of oil which is combined with the gas cushion by discharging oil into the low pressure container or to increase it by admitting oil from the high pressure In this way the Volume of the gas cushion can be varied and a desired alteration in spring characteristic be obtained. Also the volume of oil co-operating with the gas cushion can be rectified if there is a free surface between the oil volume and the gas cushion,

.and upon discharge or admission of gas, oil may be car- .ried with the gas so that the oil volume changes.

The accompanying drawing is a diagrammatic sec-- tional view of an example of a pneumatic spring struc' ture according to the invention which co-operates with a volume of oil. c

A piston 1, having a piston rod 2, slides in a working cylinder 3 which contains a gas cushion 4r and an oil volume 5 separated by a free surface 6. The piston 1 is provided with valves not shown of a known kind which produce damping forces when the piston moves in Vthe working cylinder. The free spring force corre-y sponds to the product of the piston rod area and thel pressure of the gas cushion. The damping and spring forces are transmitted from the end of the piston rod 83 and a base part 9 of the working cylinder 3 to corresponding parts of a vehicle. The piston rodis sealed in relation to the outside air by a packing 7.

The gas cushion 4 is in communication through a nonreturn valve 1li and a regulating valve 11 with a;

lower pressure container V12 and also through a non# with the oil space 18 of the lower pressure container` through a non-return valve 22 and a regulator valve/23 and with the oil space 19 of the higher pressure container through a non-return valve 24 and a regulating valve 25. The function of the non-return valves 10 and 22 is to prevent the outllow of gas or oil from the lower pressure container, if when the regulating valve 11 or 23 is open in consequence of the movements of the piston rod S, the pressure of the gas cushion 4 falls below the pressure within the lower pressure container. Similarly, the non-return valves 13 and 24 prevent the return of gas or oil into the higher pressure container when the valves 14 and 25 are open, if the pressure of the gas cushion should rise above the pressure in the higher pressure container, due to the movements of the piston rod 8.

The lower pressure container and higher pressure container are connected by pipes 26 and 27 in which are incorporated respectively a compressor diagrammatically i indicated at 28 and pump diagrammatically indicated at 29, by which means the desired pressure difference bewith said gas cushion, a lower pressure container having a gas space communicating with said gas cushion, a volume of oil,in said lower pressure container, a higher pressure container having a gas space communicating with said gas cushion, a volume of oil in said higher pressure container, connections between the volume of oil in said containers with the volume of oil co-operating with the gas cushion, means for regulating the flow of gas between said cushion and said containers, means for regulating the flow of oil between the oil co-operating with the gas cushion and that in the containers, a com-V pressor connecting the gas space of said lower pressure container with the gas space of said higher pressure container, and an oil pump connecting the oil in said lower pressure container with the oil in said higher pressure container.

2. A pneumatic spring structure as set forth in claim 1 wherein said gas cushion 'is constituted by a gas filling in a working cylinder which also contains the volume of oil co-operating with the gas cushion, said cylinder having a piston working therein immersed in the oil and having valves in the piston whereby movements of the piston are hydraulically damped, said piston being attached to a rod projecting out of said cylinder and said cylinder and piston rod constituting the -anchorages of the spring structure.

i 3. A pneumatic spring structure as set forth in claim l also comprising non-return valves which prevent backow of gas or oil from said lower pressure container to said gas cushion or the oil volume co-operating therewith and preventing backow of gas or oil from said gas cushion or the volume of oil co-operating therewith to said higher pressure container.

4. A liquid pneumatic suspension systemfor vehicles, of the type which is variable in accordance with vehicle conditions, comprising in combination a cylinder having an oil volume and a gas cushion at elevated pressure above ambient, a piston in said cylinder for connection to a part of the vehicle, a lirst pressure container having an oil volume and a gas volume at elevated pressure 4 umes of the said first and second pressure containers and an oil pump connected between the respective oil volumes of the said first and second pressure containers. 6. A pneumatic spring structure for vehicles comprising in combination, a gas cushion having a volume of oil and a volume of gas and variable pressure to suit external conditions such as loading or road surface conditions, a lower pressure container having a volume of oil and a volume of gas, a higher pressure container having a volume of oil and a volume of gas, control means connecting the volume of gas in each said container with the volume of gas in said gas cushion, a gas compressor connecting the respective volumes of gas in the said containers whereby pressures higher and lower than the operating pressures of the gas cushion are maintained respectively in the higher pressure container and the lower pressure container, and control means connecting the volume of oil in each said container with the volume of oil in said gas cushion.

7. A pneumatic spring structure as set forth in claim 6, including an voil pump connecting the respective volurnes of oil in the said containers.

References Cited in the tile of this patent UNITED STATES PATENTS

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