IL34932A - Vehicle seat incorporating a gas spring - Google Patents

Description

Vehicle seat incorporating a gas spring This invention relates to seats for vehicles, in particular for tractors, and mor© particularly to. a vehicl.-? seat in which a seat part ia mounted for upward and downward movement relative to a base part, a gas spring being interposed between the seat part and the base part to oppc.33 resiliently the downward movement. Usually, the gas sprir.g takes the form of an air spring.

In a vehicle seat incorporating a gas springj the static position to which the seat part is depressed by thv-weight of the seat occupant will depend both on the occupant' n weight and the mass of gas within the gas spring. Since however it is desirable that the static-loaded position 01 the seat should be approximately equidistant from the up and down stop position of the seat (this being referred to hereinafter as the "ride" position) it is important that the mass of &aa within the gas spring should be variable to match the weight of the seat occupant and that this variation should be effected in a simple and efficient manner.

According to the present invention, there is provided a vehicle seat comprising a seat part mounted on a gas spring for upward and downward movement relative to a base part, a pump forming part of the seat and fixed to said bi.se part, said pump being permanently connected to the said spring and operable to introduce gas into said spring in order to rais the level of the seat part to the ride position, and a valve operable to release gas from said spring in order to low ■·< it.r. level of the seat part to the ride position, and wherein ir.e pump comprises an assembly of a piston, a piston rod and a cylinder, the assembly being mounted for pivotal movement &bc/u.-, an axis perpendicular to the axis of the cylinder, a linkage' ar Figure 1 is a diagrammatic view of the base part and the air spring with' its operating pump .and control mechanism; Figure, 2. is a side elevation of a seat, part in section, showing the air spring connected between the base part and seat part; Figure 3 is a side elevation, on the side opposite to that of Figure 2, showing a hand-operable pump in section; Figure 4 is a perspective view of the seat after removal of the seat pan; Figure 5 is a diagrammatic view of a modified embodiment incorporating an inertia pump.

The seat part 10 of the vehicle seat comprises a substantially L-shaped sheet-metal pan 11 for supporting a seat squab and back squab, the seat pan being mounted on a spring suspension for upward and downward movement relative to a base part 12. The base part comprises a column "13 extending upwardly at the rear of the seat part from a base plate .14 designed to be fixed to the floor of a vehicle.' The column is of generally rectangular section having a relatively wide opening 15 extending upwardly throughout the "forward facing side of the column..

- The suspension comprises a carriage 16 disposed partially within the column and having rollers 17 which roll in guides 18 on opposite sides of the column, the seat part having a rearward extending U section hook member 20 which hooks over outwardly projecting lugs 21 on the carriage. The suspension further comprises a U shaped suspension arm 22 which is pivoted at one end to the underside of the seat part and at its opposite end to the "base part, a gas spring 23 connected between the carriage and the "base part and a shock absorber 24 also connected between the carriage and the base part.

The air spring comprises a constant volume chamber 25 defined within' the carriage , and a flexible chamber 26 whose peripheral vrall is" formed by a bellows 27. which is fixed on the one hand' to the underside of the lower wall 28 of the carriage and on the other hand to a hub 30. This hub. is supported above the base part of the seat by an upright cylindrical spigot 31» the interior of the bellows communicating with the interior of the constant volume chamber 25. The flexible chamber defined by the bellows, which conveniently is of a rolling lobe type-, has a relative narrow outlet 26a clamped to the inlet of the constant volume chamber by a pair of opposite apertured clamping plates 32, 33.» the apertures of which can be dimensioned to control the speed of air flow from one chamber to the other.. The inlet 26b of the flexible chamber is secured by a clamp 3^ to the outlet end of a 237 pipe 35 which extends from a pump or other source of gas under pressure.

The pump, in the illustrated embodimen , is a hand-operable air pump, comprising a cylinder 37 containing a piston 38» and having an outlet fitted with a check valve 39· The cylinder is connected by a pivot 40 at one end to a support '41 on the column for rotation about a first horizontal axis remote from the piston and the piston rod 42 secured thereto, and a linkage arm 43 being connected by a pivot 44 at one end to ■ the column on a second horizontal axis spaced from that of the cylinder, the opposite end of the linkage arm being connected by a pivot 45 on a third horizontal axis to the outer end of the piston rod. The arrangement is such that movement of the linkage arm 43 about its pivotal axis in the column causes the piston to move, the pumping strokes occurring as the linkage arm moves towards the dead-centre position in which the third pivot axis is coplanar with- the first and second pivot axes. The exhaust stroke occurs as the third axis moves away from the. plane of the first and second axes. In the illustrated embodiment, the movement of the linkage arm is effected by a handle 46 secured thereto adjacent the second axis.

The piston J8 of the pump is formed with an annular recess >Qa. in its outer wall for the reception of a seal, th< base wall of the recess being tapered such that the depth of the recess increases in a direction towards the forward face 38b of the piston. A circular-section O-ring seal 30 is located in the recess and so. dimensioned in relation to the recess that as the piston moves forwards, the seal rolls relative to the piston in a rearward direction and is compressed between the ihner wall of the cylinder and the base and rear walls of the recess. On the other hand, as the piston is .withdrawn, the ring seal rolls forwards relative to the piston into the deeper part of the .recess, i.e. on to a portion of the piston of reduced diameter, thus relaxing the ring seal and reducing friction between it and the cylinder, wall. An air-leak passage 51 is formed through the piston from the face of the piston to the recess to avoic the formation of a substantial pressure difference across the seal during the recovery stroke of the piston which v/oulc" increase friction between the seal and the cylinder wall during the recovery stroke.

When the pump is of. a manually-operable type, as illustrated, the air sprin is fitted with an air pressure gauge 52 calibrated to indicate the air pressure v/ithin the air spring in terms of the load on the seat, and v/ith a combined air pressure relief valve 53 which also serves as an unload control. This valve is manually operable to release air and so lower the seat height. .&' t a predetermined air pressure in the spring it will open automatically to prevent overloading the air spring or pump. < and the barrel 8 is connected via a stem 85 to the base part. The interior of the valve is connected to the pump and to the air spring via pipes 78 and 35» and the barrel has a vent 86 to atmosphere. When the spool is at a level corresponding to the ride position of the seat, it seals off the inlet pipe 35 of the air spring from both the pump and the vent 86. When the seat part is raised above the ride position,, the interior of the barrel connects the inlet pipe 35 with the vent 86 and allows excess air from the air spring to exhaust to atmosphere. Conversely, when the seat part is depressed below the ride position, the interior of the barrel connects the inlet pipe 35 with the outlet pipe 78 from the pump and allows the pump to force air into the spring until the seat part regains the ride position.

A delay mechanism 87, for example a spring, is fitted between the levelling valve and the seat or base part to reduce the response of the valve to transient movement of the seat part relative to the base part v/hen the vehicle is moving over rough terrain.

Claims (6)

34932/2 r WHAT WE CLAIM IS: ■ f

1. A vehicle seat comprising a seat part mounted on a gas spring for upward and downward movement relative to a base part, a pump forming part of the seat and fixed to said base part, said pump being permanently connected to the said spring and operable-to introduce gas into said , spring in order to raise the level of the seat part to the ride position, and a valve operable to release gas from said spring in order to lower the level of the seat- part to the ride position, and wherein the pump- comprises an assembly of a piston-, a piston rod and a cylinder, the assembly being mounted for pivotal movement about an axis perpendicular to the axis of the cylinder, a linkage arm^pivoted at one end to one end of the assembly and the outer ends of the linkage arm and assembly being pivoted to two relatively-fixed points, the cylinder and linkage being movable during a pumping stroke towards and away from a position in which they are r co-linear thereby to move the piston relative to the cylinder, and.means for moving said linkage arm.

2. A vehicle seat according to claim 1 wherein the pump is a manually-operable pump, and said valve is operable manually by the occupant of the seat.

3. A vehicle seat according to claim 1 wherein said pump is an inertia-operable pump operable in response to upward and downward movement of the base part of the seat. ·':...■: ■· .' '. ■.·' · \ ■·:'■' ''·' ."· '34932/4 ■ !..' ·': ■ ' ::'■_ ■ ■ ' ■ ■ ' ' ■ ·. \, , ·,' ■ V . ¾ Γ^ ^

4. A vehicle seat according to claim 3 wherein said' valve is a levelling valve operable to connect the spring to atmosphere when the seat part remains above the ride position, and to connect th@ spring to the pump when the seat part remains below the ride position.

5.· A vehicle seat according to claim 1 or claim 2 wherein said gas spring comprises two adjacent chambers opening into one another at their adjacent ends and connected respectively to the seat part and the base part at their cmter ends, one of said chambers being flexible to accommodate ' relative movement between the seat and base parts.

6. A vehicle seat according to claim 1 or claim 2, wherein the base part comprises a column extending upwardly at the rear of the seat part from a base plate fixable to the floor of the vehicle, and the suspension comprising a carriage mounted in guides on the column for movement up and down the column, the seat part having a connection to the carriage,^ a suspension arm being pivoted at one end to the base part and at its opposite end to the seat part, the gas spring opposing ; the downward movement of the carriage, and a shock absorber connected between the carriage and the base part, said spring comprising a first gas chamber mounted on the base part and in communication with a second gas chamber mounted on the carriage one of the chambers being of constant volume and the other being flexible to permit expansion and contraction of the space within the flexible chamber in response to upward and downward movement of the seat part.