GB2215431A - Hydraulic shock absorber - Google Patents

Abstract

A hydraulic shock absorber has an inner cylinder (1), an outer cylinder and a bidirectional valve (4) located at the lower end of the inner cylinder (1) to permit fluid to flow from the inner cylinder to the outer cylinder. A piston having circumferentially spaced apertures therethrough is provided in the inner cylinder and a valve is located over the top of the apertures. At a speed up to 10 cycles per minute of the piston, oil below the piston passes through slots (102) of the valve (4) into the space between the inner and outer cylinders. At speeds above 10 cycles per minute, oil is forced through a hole (96) against a disc (101) of the valve (4) to cause a pin (95) to move against the bias of a spring (100) so that a hole (97) is exposed below the bottom of a support member (89) so that fluid passes through the holes (96, 97) into a recess (87) and thence into the space between the inner and outer cylinders. A manually adjustable valve (60, Fig 1) is provided to control the firmness of the shock absorber on bump and rebound movements of the piston, the manually adjustable valve controlling oil flow between the space between the inner and outer cylinders and the space above the piston. <IMAGE>

Description

HYDRAULIC SHOCK ABSORBER This invention relates to a hydraulic shock absorber particularly, although not exclusively, for use on a motor vehicle.

It is known to provide a hydraulic shock absorber on a motor vehicle to damp movement between the sprung and un-sprung parts of the vehicle.

In a known shock absorber, such as the Armstrong Patents Company Ltd. type 22 Telescopic Adjustable Shock Absorber there is provided an inner cylinder within which a piston reciprocates and an outer, radially spaced cylinder so that a reservoir of hydraulic fluid is provided between the inner and outer cylinders. A valve is provided in the bottom of the inner cylinder to provide a passage to the lower part of the outer cylinder, the opposite end Df the inner cylinder being closed by a gland having an axial passage along which a rod carrying the piston reciprocates, and three passageways inconnect the inner cylinder with respective anti-foam tubes.The piston has apertures therethrough for permitting fluid to pass through the piston and a valve is provided on the piston to close the apertures on the upward or rebound stroke of the piston but to open the apertures on the downward or bump stroke of the piston. One of the anti-foam tubes is provided with a pressure valv6 > and another of the anti-foam tubes is provided with a valve which is manually operable to vary the flow of fluid through the anti-foam tube into the reservoir. Such a manually operable valve is able to control the bump and rebound settings of the shock absorber.

The forementioned, known shock absorber requires at least two anti-foam tubes and has a complex construction which is expensive to produce.

It is an object of this invention to provide a hydraulic shock absorber of simple construction which may be more economically produced.

According to this invention there is provided a hydraulic shock absorber including an inner cylinder and an outer cylinder radially spaced therefrom so as to provide a reservoir radially between the cylinders, said outer cylinder being closed at one end thereof, an axially movable piston means slidable within said inner cylinder, said piston means being connected to a rod extending through a closure means positioned at a further end opposite to said one end for sealing said cylinders, and a bidirectional valve means located in said inner cylinder at said one end arranged to permit working fluid, which in operation is displaced by said piston means, to pass from said inner cylinder to said reservoir upon movement of said piston means toward said one end and to pass from said reservoir to said inner cylinder below said piston means upon movement of said piston away from said one end.

Preferably said bidirectional valve means comprises a body supporting a first valve which is biased toward a first valve seat by a spring and a radially outer second valve which is biased toward a second valve by another spring whereby movement of said piston means toward said one end above a predetermined rate causes working fluid pressure to force said first valve from said first valve sea to permit fluid to pass from said inner cylinder to said reservoir, said second valve remaining seated, and movement of said piston means away from said one end causes fluid pressure to force said second valve from said second valve seat to permit fluid to pass from said reservoir to said inner cylinder, said first valve remaining seated.

Advantageously said body comprises a circularly cross-sectional member having an axial recess therein so as to provide side walls, said side walls having apertures therein for permitting working fluid to pass from said recess to the outside of said member and vice versa, said member having an internally disposed member with a passage therethrough ocmunicating with said recess, said first valve being located in said passage for predeterminedly permitting working fluid to pass from the inner cylinder to said recess, and at least one aperture extending from said recess to a position which is radially outward from said internally disposed member, said second valve being located for closing said at least one aperture.Preferably at least one opening for working fluid is provided between said second valve and its valve seat for permitting working fluid to bypass said second valve when said piston is moved toward said one end at speeds below said predetermined rate.

Preferably an adjustable valve means is located in said reservoir, said adjustable valve means having a first port and variable means for varying the volume of fluid out of a second port, and a single fluid channel means is provided between said inner cylinder through said closure means to said first port, whereby in dependence upon the volume of fluid permitted to pass through said second port by said variable means so the rate of permissible movement of the piston means is controlled in both directions of movement.

Conveniently said variable means comprises a manually rotatable member mounted externally to said outer cylinder, means for securing said manually rotatable member in each of a plurality of arcuate positions, and a driven valve connected to said manually rotable member for varying the volumetnc size of said second port.

Advantageously said adjustable valve means has a housing, said manually rotatable member is arranged to drive said driven valve along a screw thread inside said housing and said means for securing comprises a boss on said housing extending radially outside said outer cylinder, said boss being located inside said manually rotatable member and having a plurality of circumferential recesses therein each for receiving a bearing means biased thereinto, so as to provide rotating click-stop arrangement for said manually rotatable member at each position of which the volmetric size of said second port is varied by said driven valve.

Preferably the piston means comprises a piston having a circumferential sealing ring thereabout for sealing the piston to the inner periphery of said inner cylinder, a plurality of radially disposed piston apertures extending substantially parallel to the longitudinal axis of said cylinders, and a valve disc biased to close said piston apertures which is movable against said bias to open said piston apertures upon movement of the piston toward said one end, and a piston rebound stop located over said valve disc, said rebound stop having fluid apertures therethrough.

The invention will now be described by way of exanple with reference to the accompanying drawings in which: Figure 1 shows a schematic view of a longitudinal cross-section of a hydraulic shock absorber in accordance with this invention, Figure 2 shows a longitudinal cross-section of a manually adjustable valve for use in the shock absorber shown in Figure 1, and Figure 3 snows a bidirectional valve for use in the shock absorber of Figure 1.

In the Figures like reference numerals denote like parts.

The shock absorber shown in Figure 1 has an inner cylinder, pressure tube 1 spaced from and radially encoupassed by an outer cylindrical tube 2 having an arcuately closed lower end 3 to provide a radially disposed reservoir 40. A bidirectional valve 4 is fixedly secured at the lower end of tube 1 and is arranged to permit the flow of working fluid, such as oil 5, between the inner tube 1 and the outer tube 2. The end of the tubes remote from the end 3 are closed by a piston rod guide 6 having a protruding smaller diameter member 7 which sealingly locates inside the inner tube 1. The top outer surface of the piston guide rod 6 is pyrimidal and a multi-lip annular rubber-type seal 8 is located in a recess in the top of guide rod 6.A gland screw 9 having an external screw thread coqperating with an internal screw thread on the outer tube 2 abuts against an C-ring 10 to hold the piston rod guide 6 in position. A piston 15 is longitudinally slidable along the axis of the tubes 1 and 2. The piston 15 is connected to a rod 16 and the end of the rod 16 remote from piston 15 is connected to a bushing 17 having a rubber insert 18 for connection to a sprung part of a motor vehicle. The lower end 3 of the outer tube 2 is also connected to a bushing 19 having a rubber insert 20 for connection to an unsprung part of the motor vehicle.

The e piston 5 has a piston ring 30 for circumferentially sealing with the inside of rube 1, and three equi-circumferentially spaced apertures 31 are provided through the piston substantially parallel to the longitudinal axis of the cylinders. A steel valve disc 32 is located over the top end of the apertures 31 and held in position by a spring 33.

A piston rebound stop 34 formed by an annular disc with six equicircumferentially spaced holes 35 extending transversely through the stop for preventing cavitation when the stop hits member 7 is secured on top of the spring 33. An overflow passage 36 is provided from the recess for the seal 8 through the piston rod guide 6 into the reservoir 40 so that oil passing up the piston rod 16 is wiped therefrom by the seal 8 and recirculated.

A fluid passage 50 extends through member 7 from the inside of tube 1 and through the piston rod guide 6 to connect with a bleed tube 51 located in the reservoir 40. The lower end of the bleed tube 51 is located in an inlet port of a manually adjustable valve 60.

The manually adjustable valve 60, shown more particularly in Figure 2, has a circularly cross-sectioned housing 61 having a longitudinal axis 62. The tube 51 is inserted into a radial hole in the housing 61 and abuts an C-ring 63, a concentric port 64 communicates with an axial aperture in the housing. The axial aperture has a port orifice 65 comcnicating with an enlarged, internally threaded bore 66 which in turn communicates with an axial hole 67 via a recess 68.Externally, the housing 61 has an enlarged portion 68 and a boss 69 of smaller diameter extending radially externally of the tube 2, the outer surface of the boss 69 being provided with a plurality of recesses, in the present enbodiment preferably 12, so as to present a series of axially parallel and circumferentially disposed castellations 70 into which a ball-bearing 71 biased by a spring 72 is able to locate. The ball-bearing is retained in a kndb 73 having an axial internal recess 74 for accimodating the boss 69. The spring 72 and ball-bearing 71 are retained in a blind hole 75 radially extending from within the recess 74.The portion of the knob surrounding the recess 74 has a smaller diameter than a radially outer, from the tubes 1, 2, portion 77 of the knob 73, the portion 77 having a circumferentially knurled outer surface for providing a good manual grip upon the knob 73.

A rotatable and longitudinally movable needle valve 80 is secured to the knob 73 by a cross-pin 81 and the needle valve 80 has two axially spaced d circumferential seals 82 for ensuring sealing contact between the needle valve 80 and the walls of axial hole 67. The needle valve has a head 83 having an external screw thread 84 for cooperating with the internally threaded bore 66 and the head 83 has a taper corresponding to a taper on the inside of the housing 61 so that the orifice 65 may be closed off.

Thus rotation of the knob 73 moves the ball-bearing 71 around the castellations 70 in a click stop fashion and rotation of the knob causes rotational and longitudinal movement of the needle valve 80 toward or away from the outlet orifice 65 so that fluid flow through tube 51 into reservoir 40 may be controlled. The control by the needle valve 80 is effective on both blimp and rebound movements of the piston 15. The rotational movement of the knob 73 has the same number of discrete settings as there are recesses in the boss 69 so that the firmness of the shock absorber is thereby adjusted.

The bidirectional valve 4 shown in Figure 3 has a circularly cross-sectioned body 86 secured in the bottom of tube 1 but providing access through the body from the interior of the tube 1 to the reservoir 40. Tb provide the aforesaid access the body 1 has an axially disposed internal recess 87 and the lower end of the annular wall thus formed has a series of apertures 88 to form a castellated appearance for permitting oil to pass from the inside to the outside of the valve and vice versa. The body 86 has a head 88 and a concentrically disposed member 89 having an axial bore 90 therethrough is located such that the lower part of the member 89 is in the recess 87 and an annular space 91 is formed between the external diameter of member 89 and the internal diameter of recess 87.The upper part of member 89 has a flange 92 and a valve formed by an annular plate 93 is positioned to peripherally encompass the upper part of member 89 to cover the annular space 91 over the top part of the head 88. The plate 93 is biased by a conical carpression spring 94 located between the plate 93 and the flange 92. A further valve is formed by a tubular pin 95 having an axial hole 96 and a radial hole 97 extends through the side wall of the pin from hole 96 to a location in a lower part of the member 89. The pin 95 protrudes upwardly from the bore 90 inside the member 89 and has a flange 98 forming a stop for an annular washer 99. A compression spring 100 is located between the washer 99 and the top of the flange 92.The remote end of the pin 99 from flange 98 has a concentric disc 101 for abutting an underside of the member 89 so as to form a valve seat therewith.

Radially disposed slots 102 are provided in the top of the head 88 to provide an oil passage of limited volume under plate 93 into recess 87.

In operation, when the piston 15 is driven downwardly by a bump, oil 5 passes through apertures 31 and lifts valve disc 32 against the pressure of spring 33 so that oil moves from below the piston to above the piston (as viewed in Figure 1). At a speed up to 10 cycles per minute of the piston the oil below the piston passes through slots 102 beneath the plate 93 and into the recess 87 whereupon the oil is transferred through apertures 88 into reservoir 40. At speeds above 10 cycles per minute the oil forced through hole 96 against disc 101 causes the pin 95 to move downwardly against the bias of spring 100 so that the hole 97 is exposed below the bottom of the member 89 and fluid passes through the hole 96 and hole 97 into recess 87. Again, the oil passes through apertures 88 into the reservoir 40.

By virtue of the setting of the manually adjustable valve 60 so fluid passes through orifice 65 and up tube 51. The setting of the needle valve 80 thus controls the firmness of the shock absorber on the bump, that is downward motion of the piston.

When the piston moves on the rebound stroke, that is upwardly, the disc 32 will close the apertures 31 in the piston and the oil above the piston is put under pressure and passes through passage 50 into tube 51.

Again the position of needle valve 80 as determined by the rotation of knob 73 will control the volume of oil passing from a port 64 through orifice 65 into reservoir 40 so that the firmness on rebound is predetermined. As the piston travels upwardly in tube 1 so oil is drawn from reservoir 40 through apertures 88 and the annular space 91 to lift plate 93 against the pressure of spring 94 so as to refill the space under the piston, disc 101 being seated against the underside of member 89.

It will therefore be seen that the hydraulic shock absorber of this invention has fewer parts than the prior art shock absorber and is more economically produced, the shock absorber also being capable of being adjustable on both bump and rebound settings.

Claims (9)

1. A hydraulic shock absorber including an inner cylinder and an outer cylinder radially spaced therefrom so as to provide a reservoir radially between the cylinders, said outer cylinder being closed at one end thereof, an axially movable piston means slidable within said inner cylinder, said piston means being connected to a rod extending through a closure means positioned at a further end opposite to said one end for sealing said cylinders, and a bidirectional valve means located in said inner cylinder at said one end arranged to permit working fluid, which in operation is displaced by said piston means, to pass from said inner cylinder to said reservoir upon movement of said piston means toward said one end and to pass from said reservoir to said inner cylinder below said piston means upon movement of said piston away from said one end.

2. A hydraulic shock absorber as claimed in claim 1 wherein said bidirectional valve means comprises a bodysupporting a first valve which is biased toward a first valve seat by a spring and a radially outer second valve which is biased toward a second valve by another spring whereby movement of said piston means toward said one end above a predetermined rate causes working fluid pressure to force said first valve from said first valve sea to permit fluid to pass from said inner cylinder to said reservoir, said second valve remaining seated, and movement of said piston means away from said one end causes fluid pressure to force said second valve from said second valve seat to permit fluid to pass from said reservoir to said inner cylinder, said first valve remaining seated.

3. A hydraulic shock absorber as claimed in claim 2 wherein said body comprises a circularly cross-sectioned member having an axial recess therein so as to provide side walls, said side walls having apertures therein for permitting working fluid to pass from said recess to the outside of said member and vice versa, said member having an internally disposed member with a passage therethrough communicating with said recess, said first valve being located in said passage for predeterminedly permitting working fluid to pass from the inner cylinder to said recess, and at least one aperture extending from said recess to a position which is radially outward from said internally disposed member, said second valve being located for closing said at least one aperture.

4. A hydraulic shock absorber as claimed in claim 3 wherein at least one opening for working fluid is provided between said second valve and its valve seat for permitting working fluid to bypass said second valve when said piston is moved toward said one end at speeds below said predetermined rate.

5. A hydraulic shock absorber as claimed in any preceding claim wherein an adjustable valve means is located in said reservoir,said adjustable valve means having a first port and variable means for varying the volume of fluid out of a second port, and a single fluid channel means is provided between said inner cylinder through said closure means to said first port, whereby in dependence upon the volume of fluid permitted to pass through said second port by said variable means so the rate of permissible movement of the piston means is controlled in both directions of movement.

6. A hydraulic shock absorber as claimed in claim 4 wherein said variable means comprises a manually rotatable member mounted externally to said outer cylinder, means for securing said manually rotatable member in each of a plurality of arcuate positions, and a driven valve connected to said manually rotable member for varying the volumetric size of said second port.

7. A hydraulic shock absorber as claimed in claim 5 wherein said adjustable valve means has a housing, saidmanually rotatable member is arranged to drive said driven valve along a screw thread inside said housing and said means for securing comprises a boss on said housing extending radially outside said outer cylinder, said boss being located inside said manually rotatable member and having a plurality of circumferential recesses therein each for receiving a bearing means biased thereinto, so as to provide rotating click-stop arrangement for said manually rotatable member at each position of which the volmetric size of said second port is varied by said driven valve.

8. A hydraulic shock absorber as claimed in any preceding claim wherein the piston means comprises a piston having a circumferential sealing ring thereabout for sealing the piston to the inner periphery of said inner cylinder, a plurality of radially disposed piston apertures extending substantially parallel to the longitudinal axis of said cylinders, and a valve disc biased to close said piston apertures which is movable against said bias to open said piston apertures upon movement of the piston toward said one end, and a piston rebound stop located over said valve disc, said rebound stop having fluid apertures therethrough.

9. A hydraulic shock absorber substantially as herein described with reference to and as shown in the accompanying drawings.