GB2041490A - Cushioning support for vehicle seat - Google Patents

Abstract

A vehicle seat suspension device comprises a cylinder body (10) (10 min ) connected with the vehicle chassis and a piston (11), (11 min ) slidable up and down in the cylinder body and connected with the seat. An accumulator port (28) is communicated, through a manually adjustable throttling valve (29), with an accumulator (30) that tends to maintain pressure fluid in the body (10) (10 min ) by which the piston (11) (11 min ) is biased upwardly. The piston (11) (11 min ) tends to maintain an equilibrium position intermediate the ends of its stroke, in which a valving portion of the piston (11) (11 min ) blocks a pressure fluid port (26) and a vent port (27) in the body (10) (10 min ). With the piston above its normal position, the vent port (27) is uncovered and fluid escapes from the body (10) (10 min ) through it, to reduce upward force on the piston (11) (11 min ). With the piston (11) (11 min ) below its normal position, pressure fluid, as from a pump (31), enters the body (10) (10 min ), through the port (26) and passes down through a passage in the piston to increase the upward force on the piston. <IMAGE>

Description

SPECIFICATION Cushioning support for vehicle seat This invention relates to a cushioning suspension device for the seat of an off-highway vehicle such as a tractor or a bulldozer, and the invention is more particularly concerned with a shock absorbing device by which such a seat is resiliently supported and in which pressure fluid exerts forces that cushion abrupt relative motions between the vehicle and the seat.

A tractor, bulldozer or similar off-highway vehicle has an unsprung chassis, and therefore the operator of such a vehicle would be subjected to severe jolting and shaking if the vehicle seat were not supported on the chassis by means of a resilient shock absorbing suspension. Among the cushioning devices heretofore proposed for resilient seat support are those comprising metal springs, such as disclosed in U.S.A. Patents Nos. 2,840,140 and 3,787,025, and those comprising air springs, such as disclosed in U.S.A. Patents Nos.

3,913,975 and 3,994,469.

Since a resilient seat suspension must permit the seat to have a certain amount of and down motion with respect to the vehicle chassis in order to afford the necessary cushioning action, it has heretofore been a problem to make provision for heightwise adjustability of seat irrespective of the weight of its occupant.

A heavy occupant tends to depress a resiliently supported seat and maintain it at a height lower than average, whereas a heavy occupant may be a short person who needs to have the seat at a higher than average height.

Air springs tend to accomodate this paradoxical situation better than metal springs, because an air spring can be inflated or deflated until the seat occupant, whatever his weight, finds himself at a comfortable seating height.

However, because there is no fixed relationship between the heights and the weights of different seat occupants, different adjustments tend to provide different springing rates for the seat, that is, the natural frequency of the seat suspension will be different for different seat occupants. Since a resilient seat suspension should be able to accommodate the typical 1.5 to 2.5 Hz bouncing or pitching motion to which off-highway vehicles are subjected, regardless of the size and weight of the seat occupant, it has heretofore been difficult to design a heightwise adjustable resilient suspension that was completely satisfactory for seat occupants of all sizes and weights.

A merely resilient seat suspension would tend to afford a bouncy ride, and therefore a seat suspension usually also includes shock absorber means for damping or retarding the up and down motion of the seat and for preventing the seat from bottoming in response to very large forces. It is desirable that there be provision for adjustment of the amount of damping to which the resilient suspension is subjected by the shock absorber, to permit the occupant to select harder or softer riding characteristics. Heretofore, as may be seen from the above identified patents, the shock absorber, if there was one, comprised a separate unit from the metal spring or air spring, and its adjusting mechanism tended to be rather complicated.

By contrast with the problems and complexities presented by prior cushioning suspensions for off-highway vehicle seats, the general object of the present invention is to provide a simple and very compact shock absorbing support for such a seat, comprising one unit which serves both as a resilient suspension and as a shock absorber and which enables the heightwise position of the seat to be adjusted by simple means external to the shock absorbing support unit-because the unit always tend to maintain the seat in any heightwise position to which it may be adjusted, regardless of the weight of the occupant.

Another object of this invention is to provide a shock absorbing and cushioning seat suspension unit that comprises a piston slidable in a cylinder body, wherein the piston is at all times urged upwardly under yielding bias, to resiliently support the load of a seat and its occupant, and wherein the biasing force imposed upon the piston is automatically so varied in response to variations in downward load force that the piston tends to remain in a position intermediate the ends of its stroke.

A further object of the invention is to provide a resilient vehicle seat supporting device which is cooperable with generally conventional parallelogram linkage arrangements by which the seat is guided in its yielding up and down motion relative to the vehicle that carries it, and which is likewise cooperable with simple means for effecting heightwise adjustment of the seat and with other very simple means for adjusting firmness of the riding qualities of the seat.

Another object of the invention is to provide a seat suspension device for off-highway vehicles and the like that has an automatically variable springing rate which so adjusts itself to the severity of seat displacing forces and to seat occupant weight as to afford the most comfortable ride attainable under prevailing conditions.

It is also an important object of this invention to provide a seat supporting shock absorbing and cushioning device that comprises a piston which is slidable in a cylinder body between defined upper and lower limits, wherein the piston is urged upwardly with a force that is rapidly increased as the piston nears the lower limit of its stroke, to thus prevent an abrupt jolting deceleration of the seat due to the piston "bottoming" at either limit of its stroke.

Another and more specific object of the invention, particularly achieved in a preferred embodiment of it, is to provide a resilient, shock absorbing seat suspension device of the character described that is cooperable with a hydraulic accumulator which provides the resiliency for the seat suspension and which can be very compact and relatively inexpensive.

In general, the objects of the invention are achieved with a device for connection between a vehicle chassis member and a seating member to provide for support of the seating member in a manner to cushion relative motion between said members in upward and downward directions, said device being of the type comprising a cylinder body for connection to one of said members and a piston for connection to the other of said members, said piston being coaxially slidable in the cylinder body in said directions, said device being characterized by: said cylinder body having an open top which is closed by the piston and having a bottom wall, an annular side wall which projects up from said bottom wall, and an accumulator port opening to its interior in a lower portion thereof for connection with a fluid accumulator which tends to maintain pressure fluid in the interior of the cylinder body whereby a yielding upward force is imposed upon the piston; said cylinder body further having a cylindrical surface in its interior in which there are a pressure fluid port for connection with a source of fluid under substantially constant pressure, which pressure fluid port is spaced below an upper end of the cylinder body, and a vent port through which fluid can be vented out of the cylinder body and which is spaced below said pressure fluid port but above said bottom wall; said piston having on a lower portion thereof a cylindrical valving surface which closely opposes said cylindrical surface in the cylinder body and cooperates therewith to cover and block said pressure fluid port and said vent port, said valving surface being of such axial extent that both of those ports are blocked by it only when the piston is in a normal position intermediate its stroke limits; said piston cooperating with the cylinder body in defining a lower chamber which is in substantial part below the piston, to which said accmulator port at all times opens and which is communicated with said vent port when the piston is above its normal position so that fluid can then escape from the cylinder body to reduce the upward force upon the piston and thereby cause it to return to its normal position, said piston also cooperating with the cylinder body in defining an upper chamber which is above said valving surface and which is communicated with said pressure fluid port when the piston is below its normal position; and said piston further having a passageway therethrough by which said upper and lower chambers are substantially unrestrictedly commuicated with one another so that pressure fluid entering the cylinder body through said pressure fluid port when the piston is below its normal position can increase the upward force upon the piston and thus return it to its normal position.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a view in side elevation, with portions shown broken away, of a seat installation comprising the resilient supporting the shock absorbing device of this invention; Figure 2 is a fragmentary rear view of a lower portion of the installation shown in Fig.

1; Figure 3 is a view in vertical section of a preferred embodiment of the cushioning device of this invention with the piston thereof in its normal position; Figure 4 is an exploded perspective view of the device; Figure 5 is a diagram of an equivalent hydraulic circuit for the device of this invention; Figure 6 is a view generally similar to Fig. 3 but on a smaller scale, showing the piston of the device in its lower range of positions; Figure 7 is a more or less diagrammatic side view of the seat installation under conditions corresponding to those illustrated in Fig.

6; Figure 8 is a view generally similar to Fig. 6 but showing the piston at a level just below its normal position; Figure 9 is a view generally like Fig. 7 but showing conditions corresponding to those of Fig. 8; Figure 10 is a view generally like Fig. 6 but showing the piston at the upper limit of its motion; Figure ii is a view like Fig. 7 but showing conditions corresponding to those of Fig. 10; and Figure 12 is a view in vertical section of a modified embodiment of the device of the invention.

Referring now to the accompanying drawings, the numeral 5 designates a seat to be occupied by the operator of an off-highway vehicle, having a generally horizontal seating member 6 and a more or less upright back rest 7. Interposed between.the seating member 6 and a seat mounting member 8 of a vehicle upon which the seat is carried is the resilient seat supporting and shock absorbing device of this invention, which is designated generally by 9 and which comprises a cylinder body 10 and a piston 11 that is slidable in the cylinder body. As shown, the cylinder body 10 is secured to the seat mounting member 8 while the seating member 6 is secured to the piston 11. This relationship could obviously be reversed but is preferred for convenience in making fluid connections to the device.

To confine the seating member 6 to up and down substantially translatory motion, and also to prevent it from rotating about the axis of the device 9, there is a generally conventional parallelogram linkage between the seating member and the mounting member 8, comprising substantially identical linkage assemblies 1 2 at the left and right sides of the seat.Each linkage assembly comprises a lower bracket 14 that is fixed to the mounting member 8 and projects upwardly from it, an upper bracket 1 5 that is fixed to the seating member 6 and projects downward from it, and upper and lower link arms 1 7 and 18, each having at one end a pivotal connection 20 to the lower bracket 14 and at its other end a pivotal connection 21 to the upper bracket 15, the axes of said pivotal connections being parallel to one another and being so located that the link arms always remain parallel to one another as they swing about the pivotal connections with up and down motion of the seating member.

As here shown, the device 9 has its axis substantially vertical, but it still will be understood that it could be so connected with the seating member 6 and with the seat mounting member 8 that its axis extends obliquely upwardly. In any event, upward swinging motion of the link arms 1 7 and 1 8 about their connections 20 to the relatively fixed lower bracket 1 4 imparts to the seating member 6 a small componnt of rearward motion, as can be visualized from Fig. 1; hence, the device 9 must be so mounted as to be swingable sufficiently to accommodate the fore-and-aft component of seating member motion.The cylinder body 10 of the device is therefore formed with a bearing boss 23 at its underside in which there is a laterally extending swivel pin 24 that comprises a hinge connection with seat mounting member 8; and the upper end portion of the piston 11, which projects a substantial distance above the cylinder body 10, has an upwardly opening socket in which is received the spherical head of a swivel link 25 by which the piston is connected with the seating member 6.

The piston 11 serves to transmits forces between the seating member 6 and pressurized hydraulic fluid in the interior of the cylinder body 10. The piston is at all times urged upwardly by such fluid. However, in addition to this conventional piston function, the piston 11 also serves as a valve that controls flow of fluid into and out of the cylinder body 10 through a pressure fluid inlet port 26 and a ventport 27, both of which are in the interior of the cylinder body.

Fluid can also flow into and out of the cylinder body through an accumulator port 28 in its interior which is not controlled by the piston 11 and which is therefore open at all times. By way of passages in the cylinder body 10 that are described hereinafter, the several ports 26, 27 and 28 in the interior of the cylinder body are communicated with re respective fittings 126, 1 27 and 128 on the exterior of the cylinder body. The accumulator port 28 is communicated, by means of the fitting 1 28 and by way of a manually adjustable throttling valve 29, with a hydraulic accumulator 30.The pressure fluid port 26 is connected by way of the fitting 1 26 with a source of fluid at substantially constant pressure, illustrated as a pump 31 that can energize hydraulic equipment of the vehicle by which the seat is carried. The vent port 27 is connected by means of the fitting 1 27 with a tank or reservoir 32 for unpressurized fluid.

By reasons of its valving action, which is illustrated symbolically in Fig. 5, the piston 11 so controls flow of fluid into and out of the cylinder body 10 through the ports 26 and 27 that fluid pressure on the piston always tends to maintain it in a normal position in which it is illustrated in Fig. 3 and in which it is intermediate the ends of its stroke. When the piston is in that normal position, fluid in the cylinder body 10 is under pressure developed only by the accumulator 30, because the piston blocks the ports 26 and 27 and thus prevents other flow of fluid into and out of the body. Since fluid under accumulator pressure exerts a yielding upward force upon the piston, the piston can be resiliently displaced both upward and downward from its normal position.If the piston is displaced downward from that position, it uncovers the pressure fluid port 26 to allow pressure fluid from the pump 31 to enter the cylinder body, and the consequently increased upward force upon the piston urges it back up to its normal position. Conversely, if the piston rises above its normal position, it uncovers the vent port 27, allowing fluid to escape from the cylinder body to the tank 32, and the consequent decrease in upward force upon the piston allows it to move back down to its normal position.

Because the piston 11 always tends to return to its normal position, regardless of the load upon the seating member 6, the means for effecting heightwise adjustment of the seat must be external to the device 9, that is, the connection between the seating member 6 and the piston 11 can be arranged for adjustment of the vertical distance between those components, or else the mounting member 8 can be heightwise adjustable relative to tt.

vehicle that carries it. Since, for example, a suitable arrangement of the mounting member as a heightwise adjustable platform would be obvious, details of the height adjustment mechanism are not shown.

For a more complete explanation of how the piston functions as an automatic valve, the device 9 will now be described in detail with reference to the particular embodiment of it that is illustrated in Fig. 1 2. As there shown, the cylinder bpdy 10' is generally cup-shaped, with an open top that is closed by the piston 11'. The cylinder body can be made as two parts which can have a threaded connection with one another, as at 134, and which respectively comprise an annular side wall 34 and a bottom wall 35. The upper portion 36 of side wall 34 has a smaller inside diameter than its lower portion 37, to have a close slidable fit around a rod portion 38 of the piston 11'. The piston body proper, designated 111', has a close sliding fit in the lower portion 37 of the cylinder body side wall.The length of the piston stroke is determined by the height of the lower side wall portion 37, inasmuch as the upper limit of the piston stroke is defined by the arrangement of the piston body 111' against a downwardly facing circumferential shoulder 39 in the cylinder body, at the junction of its upper and lower portions 36 and 37, while the lower limit of piston motion is of course defined by the bottom wall 35 of the cylinder body.

The pressure fluid port 26 is in the inner surface of the lower portion 37 of the cylinder body side wall and is communicated with the pressure fluid fitting 1 26 by means of a bore 226 that extends radially through the side wall 34 and has its outer end portion threaded to accommodate that fitting. The vent port 27 is likewise at the interior of the lower portion of the side wall 34 and is communicated with its fitting 1 27 by means of a radial bore 227 through that side wall.

Attention is directed to the fact that the pres sure fluid port 26 is spaced below the circumferential shoulder 39, while the vent port 27 is spaced a distance below the pressure fluid port but is spaced above the bottom wall 35 of the cylinder body. The accumulator port 28, which is communicated with the accumu lator 30 through the manually adjustable throttling valve 29, is so located (in the bottom wall 35 of the cylinder body, as shown) that it is never blocked by the piston 11'.

The piston body 111', which comprises the lower portion of the piston 11', cooperates with the cylinder body 10' to define a lower chamber 40 and an upper chamber 41. The accumulator port 28 opens to the lower cham ber 40, and since the piston never blocks that port, the lower chamber 40 is alsways in communication with the accumulator 30, re gardless of the position of the piston.

However, the cylindrical surface on the pis ton portion 1111 closely opposes the inner cylindrical surface of the cylinder body in which the pressure fluid port 26 and the vent port 27 are located; hence, those ports can be blocked or covered by the piston portion 111', which thus constitutes a valving portion of the piston. Furthermore, the axial extension (i.e., the height) of the valving portion 111' is such that both the pressure fluid port 26 and the vent port 27 are covered by it when the piston is in its normal position, but one or the other of those ports is uncovered as soon as the piston moves out of its normal position. It will be seen that the normal position of the piston is determined by the spacing of the pair of ports 26 and 27 from the annular shoulder 39 and from the bottom wall 35.

One or more passages 42 extend axially through the body portion 111' of the piston so that the upper chamber 41 is substantially unrestrictedly communicated with the lower cylinder body chamber 40 and hence with the accumulator port 28. Because of these passages 42 through the piston, fluid pressure is substantially equal in the chambers 40 and 41; but because the rod portion 38 of the piston 11' projects up out of the cylinder body 10', the piston body 111' has unequal horizontal surface areas exposed to fluid in the respective chambers 40 and 41, and the net force upon the piston is an upward one.

The resilient pressure loading that the accu mulator 30 imposes upon fluid in the cylinder body 10' allows the piston 11' to rise above its normal position or to be forced down from it.

The piston may be forced down by an upward acceleration of the carrying vehicle when it passes over a bump (the situation diagrammatically respresented in Fig. 7) or by an increased load on the seating member 6, as when an operator sits down in it. Upon such downward movement of the piston 11', its valving portion 111' uncovers the pressure fluid port 26 to permit pressure fluid from the pump 31 to enter the lower chamber 40 in the cylinder body, by way of the upper cham ber 41 and the passage or passages 42 through the piston body. Since pressure due to the pump 31 will normally be substantially higher than the accumulator pressure, such entry of pressure fluid into the cylinder body 10' increases the upward force upon the piston 11' to return it to its normal position.

The piston can move up from its normal position as the result of a decreased load on the seat, as when an occupant leaves it, or (as represented in Fig. 9) by downward accelera tion of the carrying vehicle as when it drops into a hole. Upon such upward movement, the valving portion 111' of the piston unco vers the vent port 27 to permit escape of fluid from the cylinder body. Fluid in the lower cylinder body chamber 40 flows directly out of the vent port 27, while fluid from the upper chamber 41 flows to the vent port through the passage or passages 42 in the piston.

The communication between the vent port 27 and the tank 32 is through a fixed throttle 44 that restricts the outflow of vented fluid and consequently damps the rate of down ward movement of the piston in response to fluid escape.

When the piston returns to its normal position after an upward or downward displacement out of that position, the charge on the accumulator 30 will differ from what it was before the excursion, owing to the venting or infeed of fluid that took place during the excursion. As a result, the return movement of the piston may carry it slightly beyond its normal position, to bring about an offsetting change in accumulator pressure. However, the piston has little tendency to hunt about its normal position because flow of fluid both to and from the accumulator 30 is throttled by the manually adjustable throttling valve 29 that is connected between the accumulator and the cylinder body interior, and also because escape of fluid from the cylinder body is throttled by the flow restrictor 44.Because of the throttling of these fluid flows, the resilient movements of the seating member 6 are damped and the device is able to perform its shock absorbing function.

The seat occupant can adjust the riding characteristics of the seat to his preference by adjustment of the throttling valve 29. Closure of that valve 29 makes for a harder ride, while opening it makes for a softer but more bouncy ride.

It will be observed that there is no throttling of flow of pressure fluid into the cylinder body through the port 26. This is because full pump pressure is needed to augment or, if necessary, to supercede the pressure due to the accumulator charge. However, it will be apparent that there is some metering restriction of fluid pressure inflow when the piston body 111' is near its normal position and only partially uncovers the port 26; and there is a similar metering of vented fluid outflow when the port 27 is only partially uncovered.

The embodiment of the invention illustrated in Fig. 12, although suitable for some installations and relatively easy to manufacture, has the disadvantage that its piston body 111 has substantial upwardly facing surface areas upon which fluid exerts a downward force that opposes the seat-supporting upward force exerted upon its underside. The net upward force upon the piston 11' is substantially equal to prevailing fluid pressure multiplied by the cross-section area of its rod portion 38.

Hence relatively large flows of fluid into and out of the cylinder body 10' are needed to effect a given change in the upward force exerted upon the piston 11'. One practical result of this disadvantage is that a relatively large accumulator 30 is required for cooperation with the Fig. 1 2 embodiment of the device.

The preferred embodiment of the device 9 that is illustrated in Figs. 1 to 11 can cooperate with a substantially more compact accumulator, because its piston 11 has relatively little upwardly facing surface area upon which fluid can exert downward force.

The cylinder body 10 of the preferred embodiment is like that of Fig. 1 2 in having a bottom wall 35 and an annular side wall 34 that has a reduced inside diameter in its upper portion 36. The cylinder body 10 differs principally in having a concentric postlike portion 46 that projects up from its bottom wall 35 to about the level of the annular downwardly facing shoulder 39 at the junction of the upper and lower portions 35 and 37 of the side wall; and this postlike portion 46, which is of uniform diameter along its length, is embraced by the valving portion 111 of the piston. Thus the piston 11 is in this case hollow, having a downwardly opening concentric wall that defines an annular side wall 45; and the lower portion of that side wall comprises its valving portion 111.In this case, therefore, the pressure fluid port 26 and the vent port 27 are located in the post-like portion 46 and open to its cylindrical side surface, while the valving portion 111 of the piston has a radially inwardly facing cylindrical surface which fits closely slidably around the post portion for covering the ports 26 and 27.

Since the outside diameter of the piston 11 is uniform all along its length and is substantially equal to the inside diameter of the upper portion 36 of the cylinder body side wall, the lower portion 37 of that side wall, owing to its larger inside diameter, is radially spaced from the piston. The accumulator port 28 is located in that lower side wall portion and can be communicated with the accumulator fitting 1 28 by a short radial bore 228 through that side wall. Thus, as veith the Fig. 1 2 embodiment, the accumulator 30 is at all time communicated with the interior of the cylinder body.

The piston 11 and the cylinder body 10 again cooperate to define a lower chamber 40 which is below the piston and to which the accumulator port 28 opens as well as an upper chamber 41 which is above the valving portion 111 of the piston. To define the upper chamber 41, which is above the post-like portion 46 of the cylinder body the upper portion of the annular side wall 45 of the piston 11 has a somewhat larger inside diameter than its valving portion. The closed upper end of the piston defines a downwardly facing surface 141 of the upper chamber upon which pressure fluid can exert an upward force. One or more passage 42 extend axially through the valving portion 111 of the piston to substantially freely communicate the upper chamber 41 with the lower chamber 40.As with the Fig. 1 2 embodiment, the passage or passages 42 through the piston 11 provide for communication between the pressure fluid port 26 and the accumulator port 28 when the piston is below its normal position, and provide for communication of the upper chamber 41 with the vent port 27 when the piston is above its normal position.

If its piston 11 were made in one piece, the preferred embodiment of the device 9 might present manufacturing problems with respect to maintenance of precise concentricity between the post-like portion 46 of the cylinder body and its annular side wall 34 and between the innter and outer surfaces of the annular piston wall 45. The piston 11 is therefore formed in two parts, one of which is a substantially cup-shaped main piston member 48 and the other of which is a generally tubular insert 49 that is confined in the lower portion of the main piston member and serves as the valving portion 111 of the piston. The annular wall of the main piston member has a larger inside diameter in its lower portion that in its upper portion, to define a downwardly opening counterbore in which the insert 49 is received with substantial radial clearance that accommodates any lack of concentricity.The outer surface of the insert 49, as best seen in Fig. 4, has longitudinally extending grooves 142 which define the passages 42 through the piston, hence loose fit of the insert 49 in the main piston member 48 merely enlarges these passages.

The insert 49 is restrained against axial motion relative to the main piston member 48 by reason of its being confined between a downwardly facing circumferential shoulder 50 in the main piston member, defined by the change in inside diameter of its annular wall 45, and a spring clip ring 51 seated in an inwardly opening circumferential groove near the bottom of the main piston member.

Another spring clip ring 52, received in an outwardly opening circumferental groove near the bottom of the piston, provides a radially projecting circumferential abutment that is engageable against the downwardly facing annular shoulder 39 in the cylinder body to define the upper limit of the piston stroke. A resilient annular bumper 53 overlies the bottom wall 35 of the cylinder body, around the post-like portion 46, to define the lower limit of the piston stroke.

As best seen in Fig. 3, the passages in the cylinder body 10 that communicate the pressure fluid port 26 and the vent port 27 with the pressure fluid fitting 1 26 and the outlet tank fitting 127, respectively, are defined by bores 326 and 327 which are drilled up from the bottom of the cylinder body and axially through the post-like portion to the respective ports, and communicating bores 426 and 427, respectively, which are drilled radially into the bottom wall 35 of the cylinder body.

The lower ends of the vertical bores 326 and 327, below their junctions with the respective radial bores 426 and 427, are suitably plugged as at 54. The radial bore 427 has a reduced diameter portion that provides the fixed throttling restriction 44.

In the upper portion of the cylinder body there are axially spaced resilient annular seals 57 and 58, seated in inwardly opening circumferential grooves, which closely surround the piston to wipe dirt off it as it descends and wipe hydraulic fluid off it as it rises.

Between the seals the cylinder body has a radially inwardly opening groove 59 for collection of hydraulic fluid that passes the inner annular seal 57, and that groove 59 is communicated with the tank 32 through a bore 1 59 in the cylinder body and an external fitting 259, to permit return to the hydraulic system of leakage fluid collected in the groove.

It is not necessary that there be fluid in the cylinder body of the device 9 nor in the accumulator 30 when those units are installed and connected. When installation is completed and all fluid connections are made, it is merely necessary to supply fluid at suitable pressure to the pressure fluid port 26, and this will automatically effect charging of the accumulator, filling of the interior of the cylinder body with fluid, and movement of the piston to its normal position.

From the foregoing description and the accompanying drawings it will be seen that the present invention provides a simple, compact, and inexpensive device that provides both for resilient support of a vehicle seat and for damping of its up and down motion; and it will also be apparent that in the device of this invention the piston always tends to maintain a predetermined position relative to the cylinder body, regardless of changes in load on the seat, so that heightwise adjustment of the seat can be effected with simple means external to the device.

Claims (11)

1. A device for connection between a vehicle chassis member and a seating member to provide for support of the seating member in a manner to cushion relative motion-between said members in upward and downward directions, said device being of the type comprising a cylinder body for connection to one of said said members and a piston for connection to the other of said members, said piston being coaxially slidable in the cylinder body in said directions between defined stroke limits, said device being characterized by:: A. said cylinder body having an open top which is closed by the piston and having (1) a bottom wall, (2) an annular side wall which projects upon from said bottom wall, and (3) an accumulator port opening tp its interior in a lower portion thereof, for connection with a fluid accumulator which tends to maintain pressure fluid in the interior of the cylinder body whereby a yielding upard force is imposed upon the piston; B. said cylinder body further having a cylinder surface in its interior in which there are (1) a pressure fluid port for connection with a source of the fluid under substantially constant pressure, said pressure fluid port being spaced below an upper end of the cylinder body, and (2) a vent port through which fluid can be vented out of the cylinder body and which is spaced below said pressure fluid port but above said bottom wall;; C. said piston having on a lower portion thereof a cylindrical valving surface which closely opposes said cylindrical surface in the cylinder body and cooperates therewith for covering and blocking said pressure fluid port and said vent port, said valving surface being of such axial extent that both of those ports are blocked by it only when the piston is in a normal position intermediate its stroke limits;; D. said piston being arranged to cooperate with the cylinder body in defining (1) a lower chamber (a) which is in substantial part below the piston, (b) to which said accumulator port at all times opens and (c) which is communicated with said vent port when the piston is above its normal position so that fluid can then escape from the cylinder body to reduce the upward force upon the piston and thereby cause it to return to its normal position, and (2) an upper chassis which is above said valving surface and which is communicated with said pressure fluid port when the piston is below its normal position; and E. said piston further having a pasage therethrough by which said upper and lower chambers are substantially unrestrictedly communicated with one another so that pressure fluid entering the cylinder body through said pressure fluid port when the piston is below its normal position can increase the upward force upon the piston and thus return it to its normal position.

2. The device of Claim 1, in combination with: (1) an accumulator, and (2) a manually adjustable throttling valve through which said accumulator port and which restricts flow of fluid between the accumulator and the interior of the cylinder body to thus damp motion of the piston in said directions, adjustability of said throttling valve providing for regulation of the damping imposed upon piston motion.

3. The combination of Claim 2, in further combination with: means for throttling flow of fluid issuing from said vent port.

4. The device of Claim 1, further characterised by: (1) said cylinder body further having a postlike portion projecting upward from its said bottom wall and providing said cylindrical surface in the interior of the cylinder body; and (2) the piston having an annular wall portion, the radially inner surface of which comprises said valving surface.

5. The device of Claim 4 wherein the piston comprises: (1) a main piston part that comprises: (a) an upper end portion of the piston and (b) an annular wall portion projecting downwardly therefrom, said annular wall portion having a larger inside diameter in its lower portion than in its upper portion to define a downwardly facing circumferential shoulder in the annular wall portion; (2) a substantially tubular insert part received with radial clearance in said lower portion of said annular wall portion of the main piston part and the bore of which provides said valving surface, said insert part cooperating with its surrounding portion of the main piston part to define said passage through the piston; and (3) securement means near the bottom of said main piston part cooperating with said circumferential shoulder to confine said insert part against axial displacement relative to the main piston part.

6. A device for connection between a vehicle chassis member and a seating member to provide for support of the seating member in a manner to cushion relative motion between said members in upward and downward directions, said device being of the type comprising a cylinder body for connection to one of said members and a piston for connection to the other of said members, said piston being coaxially slideable in the cylinder body in said directions between defined stroke limits, said device being characterized by:: A. said cylinder body having an open top in which an upper portion of the piston is received with a close sliding fit and having (1) a bottom wall and (2) an annular side wall which cooperate with the piston to define a chamber in a lower portion of the cylinder body; B. said cylinder body further having a coaxial cylindrical surface in its interior in which there are (1) a pressure fluid port for connection with a source of fluid at substantially constant pressure, said pressure fluid port being spaced below the top of the cylinder body, and (2) a vent port through which fluid can be vented out of the cylinder body and which is spaced below said pressure fluid port but above said bottom wall;; C. the piston having a cylindrical valving surface which closely opposes said cylindrical surface in the cylindrical body and cooperates therewith for covering and blocking said ports, said valving surface being of such axial extent as to cover both of said ports only when the piston is in a normal position intermediate its stroke limits; D. said cylinder body further having an accumulator port opening to said chamber, said accumulator port being in an interior surface of the cylinder body that is at all times spaced from the piston and providing for communication of said chamber with a fluid accumulator, whereby pressure fluid tends to be maintained in said chamber that imposes upon the piston an upward biasing force which is decreased in consequence of communication of said chamber with the vent port when the piston is above its said normal position; and E. said piston further having a passage therethrough by which said pressure fluid port is communicated with said chamber when the piston is below its normal position, for increasing the upward biasing force imposed upon the piston by fluid in said chamber.

7. A device for connection between a vehicle chassis member and a seating member to provide for support of the seating member in a manner to cushion relative motion between said members in upward and downward directions, said device comprising a cylinder body for connection to one of said members and a piston for connection to the other of said members, said piston being coaxially slideable in the cylinder body in both of said directions from a normal position intermediate defined limits of its stroke, said device being characterized by:: A. said cylinder body comprising (1) a bottom wall, (2) a post-like portion projecting upward from said bottom wall and having a cylindrical surface, and (3) an annular side wall projecting up from said bottom wall, concentrically surrounding said post-like portion in radially spaced relation thereto and in the upper portion of which the piston has a close sliding fit; B. the piston comprising (1) an upper end wall, and (2) an annular side wall which projects down from said upper end wall and surrounds said post-like portion in radially spaced relation thereto;; C. said cylinder body having therein (1) an accumulator port which at all times opens to its interior and is communicable with a fluid accumulator by which fluid under pressure tends to be maintained in the cylinder body, (2) a vent port opening to said cylindrical surface at a level above said bottom wall, through which fluid can flow out of the cylinder body, and (3) a pressure fluid port opening to said cylindrical surface in upwardly spaced relation to said vent port and communicable with a source of fluid at substantially constant pressure; D. tubular valving means closely slideably surrounding said post-like portion and having an axial extent such as to cover both of said ports in said cylindrical surface only when in one position of its sliding motion along said post-like portions; and E. cooperating means on said piston and on said valving means defining a connection between them whereby upward movement of the piston from its normal position raises said valving means above its said position to open the vent port and thereby reduce the pressure of fluid in the cylinder body and downward movement of the piston from its normal position lowers said valving means from its said position to open the pressure fluid port and thereby cause an increase of pressure in the cylinder body.

8. A device for connection between a vehicle chassis member and a seating member substantially as described and as shown in the accompanying drawings.

CLAIMS (28 May 1980)

7. A device for connection between a vehicle chassis member and a seating member to provide for support of the seating member in a manner to cushion relative motion between said members in upward and downward directions, said device comprising a cylinder body for connection to one of said members and a piston for connection to the other of said members, said piston being coaxially slideable in the cylinder body in both of said directions from a normal position intermediate defined limits of its stroke, said device being characterized by:: A. said cylinder body comprising (1) a bottom wall, (2) a post-like portion projecting upward from said bottom wall and having a cylindrical surface, and (3) an annular side wall projecting up from said bottom wall, concentrically surrounding said post-like portion in radially spaced relation thereto and in the upper portion of which the piston has a close sliding fit; B. the piston comprising (1) an upper end wall, and (2) an annular side wall which projects down from said upper end wall and surrounds said post-like portion in radially spaced relation thereto; ; C. said cylinder body having therein (1) an accumulator port which at all times opens to its interior and is communicable with a fluid accumulator by which fluid under pressure tends to be maintained in the cylinder body, (2) a vent port opening to said cylindrical surface at a level above said bottom wall, through which fluid can flow out of the cylinder body, and (3) a pressure fliud port opening to said cylindrical surface in upwardly spaced relation to said vent port and communicable with a source of fluid at substantially constant pres sure;; D. tubular valving means closely slideably surrounding said post-like portion and having an axial extent such as to cover both of said ports in said cylindrical surface only when said valving means is in one position of its sliding motion along said post-like portion, said valving means having a substantially loose fit within said annular side wall of the piston to be radially displaceable relative to it; and E. cooperating means on said piston and on said valving means defining a connection between them whereby upward movement of the piston from its normal position raises said valving means above its said one position to open the vent port and thereby reduce the pressure of fluid in the cylinder body and downward movement of the piston from its normal position lowers said valving means from its said one position to open the pressure fluid port and thereby cause an increase of pressure in the cylinder body.

8. A device for connection between a vehicle chassis member and a seating member to provide for support of the seating member in a manner to cushion relative motion between said members in upward and downward directions, said device being of the type comprising a cylinder body for connection to one of said members and piston for connection to the other of said members, said piston being coaxially slidable in the cylinder body in both of said directions from a normal position intermediate defined limits of its stroke, and said cylinder body having in its interior a pressure fluid port which is communicable with a source of fluid under substantially constant pressure, a vent port through which fluid can flow out of the cylinder body, and an accumulator port which is communicable with a fluid accumulator that tends to maintain fluid under pressure in the cylinder body, said device being characterized by: A. said cylinder body comprising (1) a bottom wall, (2) a post-like portion projecting upward from said bottom wall and having a cylindrical surface to which said vent port and said pressure fluid port open, and (3) an annular side wall projecting up from said bottom wall and conecentrically surrounding said post-like portion in radially spaced relation thereto; B. tubular valving means surrounding said post-like portion with a substantially close slideable fit and having an axial extent such as to cover both said vent port and said pressure fluid port only when said valving means is in one position of its sliding motion along said post-like portion;; C. said piston (1) having a close sliding fit in the upper portion of said annular side wall of the cylinder body and (2) having an annular wall portion that surrounds said tubular valving means in radially spaced relation thereto; and D. cooperating means on said piston and on said valving means defining a connection between them whereby upward movement of the piston from its normal position raises said valving means above its said one position to open the vent port and downward movement of the piston from its normal position lowers said valving means from its said one position to open the pressure fluid port.

9. The device of claim 8, wherein said cooperating means on said piston and on said valving means comprises: (1) a downwardly facing shoulder in the interior of said annular wall portion of the piston, spaced above the bottom thereof, against which the upper end of said tubular valving means is engaged; and (2) an upwardly facing shoulder in the interior of said annular wall portion of the piston, near the bottom thereof, against which the lower end of said valving means is engaged, said upwardly facing shoulder being defined by a spring ring received in a circumferential groove in the inner surface of said annular wall portion.

1 0. The device of claim 9, wherein said annular wall portion of the piston has a larger inside diameter in its lower portion than in its upper portion, to define said downwardly facing shoulder.

11. The device of claim 8, wherein said tubular valving means has axially extending grooves in its external surface to provide for communication between the portions of the cylinder body interior that are thereabove and therebelow.