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Patent Searching and Data


Title:
DUAL-FUNCTION DAMPER
Document Type and Number:
WIPO Patent Application WO/1998/034047
Kind Code:
A1
Abstract:
A damper, (also called a shock absorber) is provided with the additional function of wheel bouncing so that the vehicle can be moved sideways, whilst airborne, against very little resistance. To achieve this, the damper is provided with an internal central post, (2) fixed to its base which acts as a plunger in the damper's piston rod (4) which is hollow. A high pressure hydraulic bounce fluid supply (14) is attached to the top of the bore of the piston rod which forms a bounce chamber (12). The post is hollow and has an annular space (22) around it which, together, allow damper fluid to pass between the upper (8) and lower (6) damper chambers with little restriction. A pressure sensitive valve (10) in the top of the post prevents flow through the post when the bounce chamber is not pressurised. A variable-speed bounce control valve connects the bounce chamber sequentially to an hydraulic pump and to an hydraulic reservoir to energise and exhaust the bounce chamber in order to create a repetitive wheel bounce of variable height and variable cycle time.

Inventors:
Statham, John Arnold (4 Kennet Park, Bathampton, Bath BA2 6SS, GB)
Application Number:
PCT/GB1998/000213
Publication Date:
August 06, 1998
Filing Date:
January 22, 1998
Export Citation:
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Assignee:
Statham, John Arnold (4 Kennet Park, Bathampton, Bath BA2 6SS, GB)
International Classes:
B60G17/005; B60G17/033; B60G17/04; B60S9/205; F16F9/56; (IPC1-7): F16F9/56; B60G17/033; B60G17/04; B60S9/205
Foreign References:
DE1780323A1
US4850461A
GB533048A
US4936424A
DE19629501A1
CH369668A
US2862567A
GB9524091A1995-11-24
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Claims:
CLAIMS
1. Apparatus to enable a damper with a primary shockabsorbing function, having a piston sliding within a piston cylinder contained within a body, to have the extra function of creating a repetitive bounce motion comprising : * a post within the damper attached to the body of the damper. * a hollow piston rod attached to the piston. * fluid pressure and exhaust means communicating with the bore of the hollow piston rod. * fluid communication means between the two sides of the piston through the post. * means to prevent the fluid communication means through the post when the damper is required to perform its primary shockabsorbing function. * means to control the fluid pressure and exhaust means to create the repetitive bounce motion.
2. Apparatus as claimed in claim 1 in which the post acts as a piston within the hollow piston rod, and the post and rod are adapted to cooperate to act jointly as a hydraulic ram.
3. Apparatus as claimed in claim 1 wherein the fluid communication means between the two sides of the piston is one or more longitudinal ducts within the post, radial holes in the post and in the piston rod and an annular space around the post.
4. Apparatus as claimed in claim 1, or claim 3, wherein the means to prevent the fluid communication means through the post is a pressure sensitive valve means operated by the fluid pressure in the bore of the hollow piston rod.
5. Apparatus as claimed in claim 1 in which the pressure fluid supply and exhaust means is a hydraulic hose connecting the top of the hollow piston rod with a hydraulic pressure pump.
6. Apparatus as claimed in claim 1 or claim 5 in which the means to control the pressure supply and exhaust means is a variable speed bounce control switch valve which connects the bore of the hollow piston rod alternatively and sequentially to a hydraulic pump and to a hydraulic reservoir to energise and exhaust the bore of the piston rod cyclically at variable cycle times.
7. Apparatus as claimed in claim 3 or claim 4 in which the pressure sensitive valve means is a plunger operating against a spring which is compressed by the pressure fluid to allow fluid communication between the longitudinal post ducts and the annular space around the post.
8. Apparatus as claimed in claim 1 or claim 3 in which the post is composed of a solid bar with longitudinal grooves surrounded by a pipe sleeve, the bar and sleeve being made integral and the grooves conveying the pressure fluid longitudinally.
9. Apparatus as claimed in clam 5, or claim 6, in which the flow of fluid exhausting from the bore of the hollow piston rod is restricted.
10. Apparatus as claimed in claim 9 in which the fluid is diverted by a switch valve through a flow restrictor.
11. Apparatus as claimed in claim 1 which has damper fluid operating the shock absorbing function and bounce fluid operating the bounce function and which has no fluid communication between the damper fluid and the bounce fluid.
12. Apparatus as claimed in claim 1 or claim 5 which has only one hydraulic feed pipe which is used to pressurise and to exhaust the damper bounce chamber.
13. Apparatus as claimed in claim 1 or claim 9 which includes a hydropneumatic accumulator into and out of which the damper fluid is directed during the bounce function.
14. Apparatus substantially as described in any preceeding claim or claims in which the post and the hollow piston rod cooperate to form an hydraulic ram which is use to create a repetitive bounce motion.
15. Apparatus substantially as described herein with reference to Figures 1 to 10 of the accompanying drawings.
Description:
DUAL-FUNCTION DAMPER Field of invention This invention relates to a new type of dual-function damper; more specifically it relates to improvements in the present design of a dual-function shock-absorber (also called a damper). Dual-function dampers are used to bounce vehicles so that they can be pushed sideways with very little effort.

My UK Patent application 9524 091-7 filed 24 November 1995 described a system for moving vehicles sideways (that is laterally) by a bouncing process which was achieved by adapting the vehicles dampers (otherwise called shock absorbers) to perform a second (dual) function.

The dual-function damper previously mentioned was complex, could not be tuned, and failed to block one fluid escape route in the travel mode of operation. Furthermore, it has become apparent that the low pressure, high flow, hydraulic fluid required in the parking mode of operation would be difficult to obtain without special equipment.

The present invention solves these problems neatly by providing a dual-function damper with a central hollow post which acts as a plunger in a simple hollow piston rod composed of a single pipe instead ofthe two coaxial pipes previously used. Furthermore, the new damper uses high pressure, low flow, hydraulics which enables the overall diameter of the dual-function damper to be very little greater than the single-function damper which it replaces on a particular model of vehicle. A further advantage is that the basic design of the piston for a particular make of damper remains basically unchanged, - so that manufacture of the dual-function damper is very easily adapted from the single function damper presently being manufactured. Further advantages are that there is no fluid communication between the damper fluid operating the first function in the travel mode and the bounce fluid operating the second function in the parking mode; and that the hydraulic flow to the bounce chamber of the dual-function damper has only one feed hose which is used for both pressurising and exhausting the bounce chamber.

The diameter of the hollow piston will not be much greater than the solid piston rod (which it replaces) because the structural strength of a slender rod resides mostly in its outer fibres. Furthermore the addition of the post to the lower chamber helps to balance the discrepancy between the areas of the upper and lower chambers and reduces the size of the outer reservoir surrounding both chambers, - thus helping to contain the overall diameter of the damper.

Summary of the invention According to the present invention a damper (which has a primary shock-absorbing function, and has a piston sliding within a piston cylinder and a body) is provided with a central post which is attached to the body and which acts as a piston within the damper piston rod which is hollow. The empty length of the bore of the hollow piston rod acts as a bounce chamber by being alternatively pressurised and exhausted by a high pressure hydraulic bounce

fluid supply, creating a hydaulic ram action. The post is also hollow and allows fluid communication between the two sides of the piston with little restriction, the fluid flow being controlled by a pressure sensitive valve in the post which prevents the flow when the bounce chamber is not being pressurised. The hydraulic bounce fluid supply is controlled by a variable speed bounce control switch valve which creates a bounce of variable bounce height and variable bounce cycle time. The two sides of the piston are termed the upper and lower chambers.

As in the above mentioned patent application the dual function dampers have two modes of operation corresponding to their two functions. The vehicle travels along the road in the travel mode and, once stationary, can be changed to its parking mode so that it can be bounced laterally into a convenient parking space.

In the travel mode each damper has two strokes, - the bump stroke when the wheel is forced upwards by striking a bump in the road surface, the damper being compressed; and the rebound stroke when the damper is extended by the suspension coil spring.

In the parking mode each damper also has two strokes, - the bounce stroke as the (second function) hydraulic ram action propels the vehicle vertically upwards, and the recovery stroke as the vehicle falls back to the ground.

In the recovery stroke of the parking mode the exhausting bounce fluid is switched so that it passes through a flow restrictor which creates sufficient back pressure to operate the pressure sensitive valve and allow the damper fluid to pass from the lower damper chamber through the hollow post to the upper damper chamber; in the travel mode the bounce fluid is diverted through a stop valve to a hydro-pneumatic accumulator to absorb the pressures and to provide a spring return for the bounce fluid in the rebound stroke.

Brief description of the drawings Fig. 1 is a vertical cross-section through a dual-function damper showing the fundamental parts and the working principles.

Fig. 2 is a horizontal cross-section through the post and piston rod at AA on Fig 1.

Fig. 3 is a vertical cross-section through the top of the post showing details of the pressure sensitive valve.

Fig. 4 shows a horizontal cross-section through a post with an alternative design to the post shown in Fig. 2.

Fig, 5 shows a vertical cross-section through a post of the alternative design shown in Fig. 4.

Fig. 6 shows a hydraulic circuit necessary for energising a vehicle bounce system having dual-function dampers of the type described in this invention.

Fig. 7 shows the hydraulic flow during the bump stroke of the travel mode.

Fig. 8 shows the hydraulic flow during the rebound stroke of the travel mode.

Fig. 9 shows the hydraulic flow during the bounce stroke of the parking mode.

Fig. 10 shows the hydraulic flow during the recovery stroke of the parking mode.

The drawings are diagrammatical and are meant to show the idea schematically. The proportions ofthe different elements in the drawings are chosen for drawing clarity rather than for engineering practicality.

Detailed description of the preferred embodiments A dual-function damper, according to the invention, differs from the single-function damper which it replaces by having a central post, 2, and a hollow piston rod, 4, such that the post acts as a piston within the hollow piston rod. Fluid communication between the lower chamber, 6, and the upper chamber, 8, ofthe damper is provided through and around the post so that, in the parking mode, the damper fluid passes freely upwards and downwards between the upper and lower chambers. A pressure sensitive valve, 10, Figs. 1 and 3, prevents fluid flow through the post when the bounce chamber, 12, is not being pressurised by a hydraulic fluid supply hose, 14. In the parking mode of operation (during the bounce stroke) the damper fluid flows from the top chamber, through radial holes, 24, at the bottom of the hollow piston rod, up the annular space, 22, between the post and the piston rod, through radial holes, 20, in the top of the post, through the pressure sensitive valve (which will have been opened by the pressure of the fluid in the bouncer chamber), down the central hole, 18, through radial holes, 16, in the bottom of the post, and out into the bottom chamber. The damper fluid returns by the same route during the recovery stroke.

In the travel mode of operation the bounce chamber is not being pressurised and the small plunger, 26, in the pressure sensitive valve, is pressed upwards by its spring, 28, in which position it stops damper fluid passing between the post and the annular space; whereas, in the parking mode, the bounce chamber is pressurised by the bounce fluid and the plunger is pressed down to overcome the spring force and allow damper fluid to pass from the post to the annulus and vice versa.

There are many methods of making a post convey fluid by being hollow. One alternative method is to have a post composed of a solid bar, 30, Figs. 4 & 5, surrounded by a pipe sleeve, 32. The bar has longitudinal grooves, 34, which allow fluid to flow longitudinally.

Whatever design of hollow post is chosen the post is fixed to the damper body, 36, and has a piston rod/damper chamber seal, 38, an upper post/piston rod seal, 40, and a lower post/piston seal, 42, to contain the fluid between the moving parts.

There is also a seal, 41, between the plunger and the post wall, and a circlip, 43, which contains the vertical movement ofthe plunger. In the alternative design, Figs 4 and 5, the bar and sleeve are fixed together after assembly, and the top cap, 45, is integral with the post

sleeve and provides a seal housing and a plunger stop. In both designs the post is fixed into the base of the body. Flow routes are indicated by arrows.

It will be usual for the dual-function dampers to be energised by the vehicle's hydraulic pump, 44, Fig. 6, which energises the power steering motor, 55, assisted by a hydro- pneumatic accumulator, 46. The bounce fluid will flow through a pressure relief valve, 48, and a mode switch valve, 50, to a variable speed bounce control valve 52, and out to the bounce chambers ofthe four dampers to create the bounce stoke of the parking mode. As the vehicle falls back to the ground in the recovery stroke the dampers are contracted by the weight ofthe vehicle and the bounce fluid is exhausted from the bounce chambers and returns, through the bounce control switch valve, to the reservoir, 54. In the travel mode the bounce fluid must be free to travel backwards and forwards between the dampers and the hydro- pneumatic accumulator, 62. The probable power steering element, 56, of the hydraulic layout comprises a large part ofthe total hydraulic requirement.

The variable speed bounce control valve has to connect all the bounce chambers of the numerous dampers alternately to the pump, then to the reservoir and then back to the pump, to energise and exhaust the bounce chambers sequentially, repetitively, and cyclically. The cycle time has to be variable to control the bounce rate and bounce height.

In order to make the damper work efficienly in the parking mode it is necessary to pass the bounce fluid through a flow restrictor, 58, on the recovery stroke in order to create a back pressure to open the pressure sensitive valve and allow the damper fluid to circulate..

In the travel mode, Figs 7 and 8, the four dampers (a, b, c, and d) will be working independently as the wheels to which they are each attached strike different road surface conditions. They are all connected, though a stop valve, 60, to a hydro-pneumatic accumulator, 62, which absorbs the fluid pressures. When damper, d, is in the bump stroke, Fig 7, the fluid flows into the accumulator and back to the damper, d, Fig 8, in the rebound stroke. A second stop valve, 64, is required to stop the fluid going elsewhere. The conditions of the dampers a, b, and, c, at any particular time depend on the road surface conditions. Each one could be either in the bump or the rebound stroke.

In the parking mode, Figs 9 and 10, the pressure fluid is directed through the variable- speed bounce control switch valve, 52, to pressurise all the damper bounce chambers in the bounce stroke, Fig 9, and create the ram action which lifts the vehicle; whereas in the recovery stroke, Fig 10, the fluid is fed back to the reservoir through the flow restrictor, 58, to create the back pressure necessary to keep open the pressure sensitive valves in the dampers.

The stop valves are synchronised to work with the variable speed bounce control switch valve to create the bounce cycle. They can be either electrically controlled or built into the bounce control switch valve.

In a typical example ofthe use ofthe invention the maximum sustained wheel load for a fully loaded 2 litre car might be 0.45 tonnes and the required acceleration 4.9 metres per second squared so that the required vertical ram force would be 0.34 tonnes. Then with a fluid pressure of 250 bars in the bounce chamber the internal diameter of the bounce chamber should be 1.5cm.

There are many other embodiments of the apparatus described which could be used in the manner described to achieve the same results. The post and hollow piston rod could be incorporated into almost any of the many different designs of single-function dampers, the hydraulic layout could have many variations, and generally many details could be changed without departing from the spirit and scope of my claims.