Resilient leg

The present invention concerns a resilient leg as part of an attachment for the wheel of a vehicle.

The overall design of such a resilient leg is generally known. A piston rod travels into and out of a housing. The inner end of the piston rod is provided with a shock-absorbing piston. The piston itself can be provided with channels and valves to establish a prescribed shock-absorption performance curve.

Resilient legs are attached, preferably at one end, to the vehicle's chassis. They are generally but not necessarily provided with a resilient disk to accommodate the base of a helical spring. The bottom of the leg is provided with a flange. Both the wheel bearing components and the wheel-turning rods are attached to the flange.

Since the wheel is attached remote from the leg's midline, the leg will need to transmit moments that express themselves as radial forces exerted on both the piston and the piston rod's upper guide. Attempts have of course been made to compensate for moments introduced by the wheel by tilting the disk and modifying the spring. This approach, however, is inadequate because the force of the moment varies with the vertical distance of the wheel from the chassis.

One attempt to compensate for these moments and their accompanying horizontal forces is illustrated in Figure 6.43, Reimpell-Stoll, Fahrwerktechnik: Stoss- und Schwingungsdämpfer, 1989. Here, the piston rod is radially supported by two separated bearings. This approach, however, is very complicated and is to some extent applicable only to light-weight legs.

The object of the present invention is accordingly to improve the generic resilient leg to the extent that moments of force will be reliably transmitted from the piston rod to the housing. Such a leg can be light in weight.

A resilient leg in accordance with the present invention has several advantages. First, moments of force exerted on the leg can be transmitted from the piston rod to the housing in accordance with the least possible radial forces. Second, the piston-rod alignment and sealing components will be subject to little friction, facilitating the rod's travel into and out of the housing. Finally, since the piston rod will need to transmit only slight angular moments, it can be thinner and hence lighter in weight.

One embodiment of the present invention will now be specified with reference to the accompanying drawing. The single FIGURE is a section through a schematically depicted resilient leg.

Although the resilient leg specified herein is single-cylinder, the present invention is also applicable to other designs, two cylinder versions for instance.

The leg is provided with a housing 1 , a dashpot cylinder in the present embodiment. Each end of the housing is provided with a piston-rod alignment-and-sealing component 2 and 3 , the details of which—the seal and low-friction bearing—are not illustrated.

A piston rod 4 travels into and out of housing 1 through openings in the center of each alignment-and-sealing component 2 and 3 . A dashpot piston 5 is mounted on piston rod 4 half-way along it. In a known approach, piston 5 is provided with channels 6 that operate in conjunction with stacks 7 and 8 of cup springs to control the flow of fluid and accordingly establish a specified level of shock absorption.

Piston 5 divides the interior of housing 1 into two fluid-charged chambers 9 and 10 . As piston 5 travels down, fluid will flow out of lower chamber 10 and into upper chamber 9 through channels 6 , lifting upper cup-spring stack 7 . As the piston travels up on the other hand, the fluid will flow in the opposite direction, lifting lower cup-spring stack 8 .

Piston rod 4 is appropriately separated in the vicinity of piston 5 into two sections, an upper section 11 and a lower section 12 , each with approximately the same diameter. Since sections 11 and 12 travel in the same direction, lower section 12 emerging from housing 1 as upper section 11 enters it, no fluid will, as at the state of the art, be forced out as the piston enters. It would accordingly seem unnecessary to provide a fluid-charged pressure compensation chamber. Such a compensation chamber 13 , however, demarcated from the leg's fluid-occupied space by a partitioning piston 14 , is in fact necessary to compensate for any thermal expansion on the part of the fluid. This function, however, requires only a little fluid.

Pressure-compensation chamber 13 can accordingly be in the form of a bore extending along the central axis of lower piston-rod section 12 . Piston 14 moves back and forth inside this bore.

Lateral ports 15 allow a fluid-containing section 16 of lower section 12 to communicate with lower chamber 10 . To prevent fluctuations in the pressure exerted by the fluid due to the shock-absorbing action of piston 5 from leading to unnecessary vibrations on the part of partitioning piston 14 , the fluid containing length 16 of lower section 12 accommodates a constriction 17 that suppresses the fluctuations, especially the high-frequency fluctuations.

The bore that extends along the central axis of lower section 12 terminates in a base 18 that is not illustrated in detail. An unillustrated valve can be provided in the vicinity of base 18 to inject a cushion of air into pressure-compensation chamber 13 once the overall resilient leg has been entirely assembled and charged with fluid.

Upper section 11 can also include a central bore 19 to accommodate controls for establishing and regulating the widths of bypasses.

The outer end 20 of upper piston-rod section 11 is provided with means appropriate for attaching the resilient leg to the chassis of a vehicle. It can for instance have outside threads. Housing 1 is also conventionally provided with a flange 21 for attaching the wheel and its associated rods and with a resilient disk 22 to support the bottom of the helical spring.

To prevent overdetermination of the position of piston rod 4 in relation to its travel against the inner surface of housing 1 , piston-rod alignment and sealing components 2 and 3 ′ can pivot with three degrees of freedom around the end of the housing as indicated in the drawing by spherical surfaces 23 and 24 .

A fluid injection valve 25 may be included at the end of the hollow outward-extending section 12 .

List of Parts

1 . housing

2 . piston-rod alignment and sealing component

3 . piston-rod alignment and sealing component

4 . piston rod

5 . piston

6 . channels

7 . upper cup-spring stack

8 . lower cup-spring stack

9 . upper housing chamber

10 . lower housing chamber

11 . upper piston-rod section

12 . lower piston-rod section

13 . pressure-compensation chamber

14 . partitioning piston

15 . port

16 . fluid-containing length

17 . constriction

18 . base

19 . bore

20 . outer end

21 . flange

22 . resilient disk

23 . spherical surface

24 . spherical surface