CA1069562A - Telescoping energy absorber with pressure relief valve capsule - Google Patents

Abstract

TELESCOPING ENERGY ABSORBER WITH
PRESSURE RELIEF VALVE CAPSULE

Abstract of the Disclosure An energy absorber unit having inner and outer teles-coping cylinders with a pressure relief valve capsule retained in a centralized opening in or forming an integral part of the cylinder cap to control the flow of fluid between contractible and expandable fluid chambers in the unit. The valve capsule being load-sensitive maintains a substantially constant pressure in the unit so that unit stroke is proportional to impact velo-city. With this construction, the corners of vehicle bumpers experience a reduced swing arc as compared to velocity sensitive units so that clearance between bumper corners and vehicle body work can be reduced. On rebound return spring means forces the fluid through the valve capsule which, controlling the return fluid flow, reduces the rate of unit recovery.

Description

This invention relates to energy absorber units for vehicle bumpers having telescoping inner and outer cylinders ~-movable between expanded and contracted positions which may be effectively employed to mount a bumper assembly to a vehicle.
More particularly this invention relates to such an energy absorber unit having new and improved pressure relief valve ¦ capsule means operatively mounted between expandable and con-¦ tractible chambers of the unit to control the flow of fluid between the chambers for energy absorbing purposes and for ~ controlling the speed of rebound.
Prior energy absorber units have utilized metering ~I pins or similar devices to effectively control the pressures within the units so that there is effective energy management of low speed impacts of the bumper assembly. While these units have proven to be quite beneficial, they are velocity sensitive , .- i ,.
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and stroke through a fixed distance for varying impact loads and thus demand considerable clearance between the bumper corners and vehicle body work in order to avoid damage when the bumper is subjected to corner impacts. While some of the bet-ter units have full recovery after low speed impacts, rebound control delaying the recovery time is through auxiliary con-struction.
With this invention a new and improved energy absorber unit is provided with an advanced valving capsule that enhances assembly of the unit while providing an important reduction in weight over many of the prior art devices. More specifically the energy absorber unit of this invention incorporates a new and improved valve capsule for telescoping energy absorber units. The valve capsule is a pressure relief device mounted between expandable and contractible chambers of the unit to control the flow of fluid between the chambers to maintain a constant pressure in the unit so that unit stroke varies with a wide range of speeds and loads. With this invention there is reduced stroke on corner impacts as compared to velocity sensitive devices. The coil or helical spring used in this unit provides better control of production tolerances. In view of the fact that metering pins are eliminated a shorter unit is provided. With this invention there is a built-in rebound con-trol to complement the action of auxiliary rebound control devices.
The valve capsule in some embodiments is a separate valve unit which comprises a cylindrical housing having a head portion with a centralized opening or orifice therethrough. A
coil spring biases a valve element into blocking position against the opening to provide a pressure relief device hydrau-lically separating expandable and contractible chambers from each other. The valve capsule may be readily assembled in a ~ ~;35~d subassembly prior to its insertion and retention into the cap member of the unit. On impact of the bumper the load sensitive valve elemen~ moves away from this opening in accordance with the loads applied thereto so that there is a constant pressure maintenance in the contracting chamber as the cylinders stroke.
With constant pressure maintained in the contracting chamber, energy absorption is substantially uniform throughout the entire stroke of the unit. This provides for reduced strokes on lower speed corner impact and improved energy absorption on higher speed straight-ahead impacts as compared to many prior art devices. The valve capsule may be press fitted or staked in position in the cap member. In another embodiment of the inven-tion, the cap and valve capsule are unitized to further facili-tate assembly of the valving in the energy absorber unit and to insure the integrity of these components under extreme impact load conditions.
These and other features, objects and advantages of this invention will become more apparent from the following detailed description and drawing in which:
FIGURE 1 is a perspective view of a vehicle chassis frame and energy absorber units mounting a bumper assembly to the frame;
FIGURE 2 is an enlarged cross-sectional view of one ;
of the energy absorber units of FIGURE 1 taken generally along the plane indicated by lines 2-2 of FIGURE 1 showing the energy absorber unit in its normally extended position;
FIGU'RE 3 is an enlarged sectional view of the improved pressure relief valve illustrated in FIGURE 2;
FIGURE 4 is a view similar to FIG. 3 showing a modi-fication of the invention;

FIGURE 5 is a view similar to FIG. 3 showing another modification of the invention.

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Referring now in particular to FIG. 1 of the drawing, there is a vehicle chassis frame 10 comprising a pair of later-ally spaced side rails 12 having forwardly extending horn por-tiOllS 14 interconnected by a front cross beam 16. Bolted to each horn portion 14 are front and rear L-shaped brackets 18 and 20 which are longitudinally spaced from each other that connect identical left and right energy absorber units 22 to the chassis frame 10. Each energy absorber unit 22 extends through a circular opening in its associated front or outermost bracket 18 and has an outer cylinder 24 welded at 26 to a col-lar 28. The collar 28 is in turn bolted or otherwise rigidly secured to the front bracket 18. The outer cylinder 24 is closed by a circular end cap 30 which is secured thereto by annular weld 31. Annular flash ~hield 32 secured in the end of cylinder 24 makes peripheral contact with the inner wall of this cylinder to bar the entry of weld flash into the energy absorber unit~ The end cap 30 has an axially extending threaded stud 33 rigidly fixed thereto which projects outwardly :~
through an opening 34 in bracket 20. ~ut 36 threaded onto stud 33 rigidly secures the end cap and thus the outer cylinder to bracket 20.
In addition to the outer cylinder 24, each energy absorber unit 22 comprises an inner cylinder 38 that is mounted for limited telescoping movement within cylinder 24 and that projects forwardly therefrom. The forward end of the inner cylinder 38 is closed by a base plate 40 welded thereto which is adapted to be secured to a bumper assembly 41 by suitable connector or pivot means 42. An annular flash shield 43 seated on a central internal shoulder of the base plate 40 contacts the inner wall of cylinder 38 to keep weld flash from entering the unit 22. Secured to the inner or rearward end of the inner cylinder 38 is a cap 44 that separates the interior of ~V~95~i~

the cylinders into intermediate and rear fluid chambers 46 and 48, each of which is filled with a suitable hydraulic fluid such as oil. A cylindrical cap sleeve 50 of suitable material such as glass-filled Nylon is mounted over the cylinder cap 44 to slidably fit the inner diameter of the outer cylinder 24.
There is , however, sufficient clearance between the cap sleeve 50 and the inner wall of the cylinder 24 so that chamber 48 is in direct hydraulic communication with the inner annular space 51 formed between the outer and inner cylinders. The forward end of this inner space is sealed by O-ring 52 disposed between cylinders 24 and 38.
Mounted within the inner cylinder 38 is a floating sheet metal piston 54 fitted with an O-ring 56 that separates chamber 46 from a front chamber 58 formed between floating piston 54 and base plate 40. A quantity of gas is compressed in chamber 58 being injected through an orifice 60 formed in the base plate which is subsequently sealed by a ball 62 welded therein. The force of gas compressed within chamber 58 acts on the oil in chambers 46 and 48 and urges the cylinders 38 and 24 to the normally extended position shown in FIGS. 1 and 2. Stop sleeve 63 rigidly secured to cylinder 38 contacts the inwardly crimped end 65 of cylinder 24 to limit the outward movement of cylinder 38 relative to cylinder 24. The sleeve 67 mounted on cylinder 38 between stop sleeve 63 and O-ring 52 contacts the inner wall of the outer cylinder on return stroke to add a friction drag load to reduce the recovery rate.
The cap sleeve 50 is generally cylindrical in shape and has an outer peripheral portion hooked around the circum-ferential outer edge of cap 44 and has an inner peripheral por-tion extending radially inwardly to partially cover the frontface of the cap 44.
As shown in FIGS. 2 and 3 the end cap is formed , 1(~69S~i2 with a centralized opening into which a unitary valve capsule 70 is secured. The valve capsule 70 comprises a generally cylindrical body 72 having an enlarged head portion 74 that is seated against the outer face of the end cap 44. The valve capsule is inserted within the centralized opening of the end cap and is press fitted or otherwise secured to this member in ;
a suitable manner. The head portion 74 of the valve has a central passage 78 which is normally closed by a cup-shaped valve element 80 which completely spans passage 78. As illus-trated this valve element is biased linearly into the closed spanning position shown in FIG. 2 by coil spring 82 trapped `
within the capsule. The coil spring is seated on a base plate 84 thatis secured within the end of the capsule housing. The capsule has side passages 86 and 88 formed therein and the base plate has a shouldered central opening 90 to provide for the flow of fluid therethrough under operating conditions which will be hereinafter described. Flow past the valve element 80 is through peripheral openings 94 formed therein.
The energy absorber construction described above is a constant force unit as opposed to the velocity sensitive unit found in many of the prior art devices. In this invention the retarding force in chamber 48 remains constant for all impact loads, while the stroke changes with impact velocity of the vehicle. For example, a five mph impact may stroke the unit

2~ inches while a 3 mph impact velocity may produce a 1~ inch stroke. This is of prime importance to vehicle designers work-ing with vehicle bumpers who must allow sufficient space between the bumper and body work to permit the energy absorber to func-tion in a manner to prevent substantial low impact speed damage.
With this invention the bumper can be designed to curl back around the corners of the vehicle to give better protection for the corners and still provide protection when the bumper is

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stroked on corner impact. Assuming a 3 mph corner impact on the bumper assembly at point I, the bumper would swing about axis A
toward the vehicle body work W as indicated by the arrow in FIG.
1. Since the movement of the impacted corner is multiplied, dam;~ge to the body work W would occur without suitable control ~uch a~ provided by this invention. However, the stroke of the unit is effectively reduced 90 the cramping action of the rear-wardly curled corner of the bumper is reduced to a point where there is no contact between the corner and body work.
As the bumper is impacted on a corner, for example, the cylinders will telescope and the fluid in chamber 48 will move the valve element 80 linearly from passage 78 and will be ~ -forced through the valve capsule into the chamb0r 46 as it expands to compress the gas spring. With this construction the pressure in chaT~iber 48 remains substantially constant for all impact velocities so that the stroke varies with impact load.
On removal of the impact load, spring 82 moves the valve element 80 to the restricted position of FIG. 2. The gas 20 spring, responding to this, forces the fluid from chamber 46 through passages 90, 86, 88 past the seated flange 97 of the valve element 80, through the central orifice 78 and back into chamber 48. The restriction of this return path results in the slow recovery of the unit to its normalized position augmented by drag ring 67.
The unitary capsule can be preassembled as a unit and press fitted into the centralized orifice of the cap 44 to pro-vide for improved assen~bly and rebuild if merited.
FIGURE 4 illustrates another embodiment of the inven-30 tion which is basically the same in construction and operationas the embodiment of FIGURE 3. In the FIG. 4 embodiment the valve capsule 70' is secured in the central opening of the ,v ~o~

piston cap 44' by sta~ing material M of the capsule body 72' against the inner wall of the piston cap. With this staking, the piston cap is trapped between the staked material M and the head portion 74' of the capsule so that the strength of the valve - piston cap connection is improved. After staking the piston cap is fitted on and welded to the end of the inner cylinder 38'.
FIGURE 5 illustrates still another embodiment of the invention to provide for maximum service life under heavy duty conditions. As shown in FIG. 5 the cylinder cap 44'' and the valve capsule 70'' are of a unitary construction. This one-piece construction is secured to the end of the inner cylinder 38'' by welding or other suitable means so that the pressure relief valve is in place and ready for operation. The operating components of the valve element of the FIG. 5 construction have been described in connection with FIGS. 1 through 3 so that further detailed description is not needed.
While preferred embodiments of this invention have been shown and described to illustrate the invention, other embodiments will become apparent to those skilled in the art.
Accordingly, the limits of this invention are defined in the following claims.

Claims (5)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An impact energy absorbing unit mounting a bumper assembly to a support on an automotive vehicle comprising: first and second cylinders, support means mounting said first cylinder for telescopic movement with respect to said second cylinder between an extended position and a retracted position, said first and second cylinders having cooperating stop means to establish the extended position of said cylinders, said first cylinder having piston cap means fixed at one end thereof and slidably disposed in said second cylinder to provide variable volume first and second fluid chambers in said unit, said cap means having inner and outer sides and having a centralized opening there-through, a hydraulic fluid in said first and second chambers, pressure relief valve means interposed between said chambers, said pressure relief valve means comprising a discreet valve capsule secured directly to said cap means and operatively secured in said centralized opening in said cap means and extending into said second chamber, said capsule having an enlarged head portion seated against the outer side of said cap means and having an elongated body integral with and extending from said head portion through said centralized opening of said cap means into said second chamber, said body having a peripheral wall forming an inner chamber between said first and second chambers, said wall having a fluid passage therein connecting said inner chamber and said second chamber, said head portion having a fluid flow orifice therethrough leading from said inner chamber to said first chamber, a valve element internal of said capsule and positioned on the inner side of said head portion completely spanning said orifice, spring means preloaded within said capsule for biasing said valve element into blocking position with respect to said orifice to restrict the flow of fluid between said chambers and yieldable in response to the application of an impact load of at least a predetermined magnitude to said bumper assembly so that said cylinders tele-scope toward a retracted position as said valve element moves linearly from said orifice and fluid is fed from said first chamber through said orifice and into said second chamber through said inner chamber to maintain a pressure level in said first chamber, and additional spring means to restore said first and second cylinders to the extended position after removal of said impact load.

2. An impact energy absorbing unit mounting a bumper assembly to a support on an automotive vehicle comprising: first and second cylinders, support means mounting said first cylinder for telescopic movement with respect to said second cylinder between an extended position and a retracted position, said first and second cylinders having cooperating stop means to establish the extended position of said cylinders, said first cylinder having piston cap means fixed at one end thereof and slidably disposed in said second cylinder to provide variable volume first and second fluid chambers in said unit, said cap means having inner and outer sides, a hydraulic fluid in said first and second chambers, and pressure relief valve means interposed between said chambers, said pressure relief valve means comprising a discreet cylindrical valve capsule secured directly to said cap means, said capsule having a hollow body portion hydraulically communicating with said second chamber and extending completely through said cap means, said capsule having a head portion with a fluid flow passage therethrough hydraulically communicating with said first chamber, said head portion being seated against the outer side of said cap means, a valve element internal of said body portion completely spanning said orifice, coil spring means preloaded within said body portion for urging said valve element linearly into engagement with said head portion and into blocking position with respect to said passage to restrict the flow of fluid between said chambers and yieldable in response to the application of an impact load of at least a predetermined magnitude to said bumper assembly so that said cylinders tele-scope toward a retracted position as said valve element moves linearly away from said passage and fluid is fed through said passage to maintain a pressure level in said first chamber, and additional spring means in said second cylinder to restore said first and second cylinders to the extended position after removal of said impact load.

3. An impact energy absorbing unit mounting a bumper assembly to a support on an automotive vehicle comprising: first and second cylinders, support means mounting said first cylinder for telescopic movement with respect to said second cylinder between an extended position and a retracted position, said first and second cylinders having cooperating stop means to establish the extended position of said cylinders, said first cylinder having piston cap means fixed at one end thereof and slidably disposed in said second cylinder to provide variable volume first and second fluid chambers in said unit, said cap means having an outer face, a hydraulic fluid in said first and second chambers, and pressure relief valve means operatively connected between said chambers, said pressure relief valve means comprising a discreet valve capsule to control the pressure of fluid in at least one of said chambers when said cylinders are directly telescoped, said valve capsule comprising an elongated body secured to and extending completely through said cap means and having an enlarged head portion seated against the outer face of said cap means, said head portion having a centralized fluid flow passage therethrough leading to said first chamber, an annular valve element internal of said body completely spanning said fluid flow passage, helical spring means preloaded within said capsule for yieldably urging said valve element into engagement with said head portion and into blocking position with respect to said passage to block the flow of fluid between said chambers and yieldable in response to the application of an impact load of at least a predetermined magnitude to said bumper assembly so that said cylinders telescope toward a retracted position and fluid is fed through said passage past said valve element dis-placed from said passage and additional spring means to restore said first and second cylinders to the extended position after removal of said impact load.

4. An impact energy absorbing unit mounting a bumper assembly to a support on an automotive vehicle comprising: first and second cylinders, support means mounting said first cylinder for telescopic movement with respect to said second cylinder between an extended position and a retracted position, said first and second cylinders having cooperating stop means to establish the extended position of said cylinders, a discrete cup shaped piston cap fitted over and secured to one end of said first cylinder and slidably disposed in said second cylinder to provide variable volume first and second fluid chambers in said unit, said cap having inner and outer faces, a hydraulic fluid in said first and second chambers, and a discrete pressure relief valve capsule interposed between said chambers, said capsule comprising a head portion and an integral valve body means extending through said cap into said second chamber, means securing said valve body directly to said cap, said valve body means forming an inter-mediate chamber between said first and second chambers, said head portion being positioned against the outer face of said cap, a centralized fluid flow orifice in said head portion communi-cating with said first chamber, a thin annular valve disc internal of said valve body means spanning said orifice, first spring means preloaded within said valve body means for biasing said valve disc into engagement with said head portion and into blocking position with respect to said orifice to block the flow of fluid between said chambers and yieldable in response to the application of an impact load of at least a predetermined mag-nitude to said bumper assembly so that said cylinders telescope toward a retracted position as said valve disc moves linearly from said orifice and fluid is fed through said valve body means to maintain a pressure level in said first chamber, and second spring means to restore said first and second cylinders to the extended position after removal of said impact load.

5. An impact energy absorbing unit mounting a bumper assembly to a support on an automotive vehicle comprising: first and second cylinders, support means mounting said first cylinder for telescopic movement with respect to said second cylinder between an extended position and a retracted position, said first and second cylinders having cooperating stop means to establish the extended position of said cylinders, said first cylinder having piston cap means fixed at one end thereof and slidably disposed in said second cylinder to provide variable volume first and second fluid chambers in said unit, said cap means having inner and outer faces, a hydraulic fluid in said first and second chambers, and pressure relief valve means interposed between said chambers, said pressure relief valve means com-prising a discrete cylindrical valve capsule, said capsule having a hollow cylindrical body portion extending completely through said cap means into said second chamber and having an integral and annular head portion diametrically larger than said body portion seated against the outer face of said cap means, said head portion having a fluid flow passage therethrough leading to said first chamber, means trapping said capsule in position directly to said cap means, a disk like valve element internal of said body portion spanning said passage, spring means preloaded within said body portion for urging said valve element linearly into engagement with said head portion and into blocking position with respect to said passage to restrict the flow of fluid between said chambers and yieldable in response to the application of an impact load of at least a predetermined magnitude to said bumper assembly so that said cylinders tele-scope toward a retracted position as said valve element moves linearly away from said passage and fluid is fed through said passage to maintain a pressure level in said first chamber, and additional spring means in said second cylinder to restore said first and second cylinders to the extended position after removal of said impact load.