GB2033531A

GB2033531A - Vehicle seat suspension

Info

Publication number: GB2033531A
Application number: GB7901789A
Authority: GB
Original assignee: UOP LLC
Current assignee: Honeywell UOP LLC
Priority date: 1978-11-09
Filing date: 1979-01-18
Publication date: 1980-05-21
Also published as: GB2033531B

Abstract

In a vehicle seat suspension arrangement in which rotation of a manually operable knob 12 can vary the preload torque in a seat-supporting torsion spring 11, the spring has a radial arm 19 carrying a first rotor 18 which bears against the surface of a cam 14 fixed to a shaft which is rotatable by the knob via a gearbox. The opposite side of the cam bears against a reaction rotor 17. Thus rotation of the knob 12 causes rotation of the cam 14 to vary the distance between the rotors 17, 18 and hence vary the preload in the spring 11. <IMAGE>

Description

SPECIFICATION Improvements in and relating to force-transmission mechanisms providing a mechanical advantage and to vehicle seats incorporating such mechanisms This invention relates to force-transmission mechanisms which provide a mechanical advantage, in particular without the use of conventional gearing at the point at which heavy loads are carried. More particularly the invention relates to a vehicle seat having a mechanism for converting the rotation of a knob or handle into a much smaller angular movement of a member driven thereby, to vary the preload in the spring by means ofwhich a seat part of the seat is biassed upwardly relative to a base part of the seat.

The invention is particularly applicable in a vehicle seat such as those described in our British Patent Specifications Nos. 957 332 and 1 070 381 in which a seat part is mounted on a base part by a spring suspension which includes a torsion bar spring. The torsion bar spring biasses the seat part upwardly with respect to the base part to balance the weight of the seat part and its occupant, and the preload in the spring is manually adjustable to match the weight of the occupant. The mechanism described in these Patent Specifications for adjusting the preload of the spring involves a screw which carries a very heavy load and is subject to heavy wear.

According to the present invention there is provided a vehicle seat having a seat part mounted via a suspension on a base part, the suspension including a spring for biassing the seat part in an upward direction relative to the base part, and a mechanism for varying the preload in the spring, said mechanism comprising a first rotor mounted on the seat for movement along a predetermined path under the force of said spring, and a body mounted on the seat for rotation about an axis parallel to that of the first rotor, the surface of the body making contact with the surface of the first rotor and transmitting the load of the first rotor to the part of the seat on which said body is mounted, the body being such that the distance between its axis of rotation and the position of contact between the first rotor and the body varies as the body rotates about its axis, and means for rotating the body to vary said distance.

More particularly the present invention provides a vehicle seat having a seat part mounted via a suspension on a base part, the suspension including a spring for biassing the seat part in an upward direction relative to the base part and a mechanism for varying the preload in the spring, said mechanism comprising a first rotor mounted on the seat for movement along a predetermined path under the force of the spring, a second rotor mounted on a part of the seat which is stationary relative to said path of movement of the first rotor, and a body mounted for rotation about an axis parallel to the axis of rotation of said rotors and maintained in peripheral contact with said rotors at positions on the body which are substantially opposite each other, the body being such that as it rotates about its axis, the distance between said positions increase in one direction of rotation and decreases in the opposite direction of rqtation, means supporting the body for movement towards and away from the second rotor as the distance between said positions decreases and increases and means for rotating the body to vary said distance.

The invention will now be particularly described by way of example with reference to the accompanying drawings in which: Figure lisa section through part of a vehicle seat in which a manually-rotatable knob is connected through a force-transmission mechanism to a torsion bar spring which biasses a seat part of the seat away from a base part of the seat; Figure 2 is a section through the forcetransmission mechanism of Figure 1 on a larger scale, and Figure 3 is a section on the line Ill-Ill of Figure 2.

As shown in the drawings the vehicle seat comprises a seat part 7 supported on a base part 8 by an X type suspension comprising two laterally spaced pairs of scissor-acting suspension arms 9, 10 (only one of each being visible in Figure 1). These arms 9, 10 are biassed upwardly by a torsion bar spring 11 to counterbalance the weight of the seat occupant, as described in detail in British Patent No. 957,332.

The torsion spring 11, which extends across the back of the seat part 7 is contained within a tube 11' which is fixed to the upper rearward ends of suspension arms 10, the tube 11' being journalled at its opposite ends in the seat frame 7', (see Figure 3).

One (not shown) of the torsion spring 11 is secured to one end of the tube 1 thereby securing it to the arms 10, and the opposite end (seen in Figure 3) of torsion spring 11 is fixed to a rotor 11" journalled within tube 11'. A radial arm 19 extends from this end of the spring 11 outwardly of the tube for connection to the frame 7' via a force transmission mechanism, in accordance with the present invention, which forms a substitute for the screw-action mechanism described in the above-mentioned patent.

The force transmission mechanism comprises a rotary body 14 having a cam periphery, mounted on a shaft 13 which is journalled in the outer end of an arm 15. The opposite end of arm 15 is pivoted at 16 to the seat frame 7'.

Afirst rotor 18 mounted on a needle bearing 18a at the outer end of the radial arm 19 is maintained in contact with the cam body 14 at a first position 14a thereon located substantially in the plane containing the axis of the cam body and the first rotor. A second and reaction rotor 17 is mounted on a needle bearing 17a carried in a bracket 17b on a part 7" of the frame 7' so that the second rotor contacts the opposite side of the cam body 14 at a position 14b located substantially in the plane containing the axes of the cam body 14 and the second rotor 17. The axis of the shaft 13 is arranged to move so that it lies in or close to the plane A containing the axes of the rotors 17, 18.

The cam is arranged with two substantially S shaped peripheral cam surfaces, each for contact with a separate one of the rotors, each cam surface having a negative acceleration profile, i.e. a profile such that as the contact load between the cam and a said rotor increases, the work done in moving the cam through each equal increment decreases.

The means for rotating the shaft 13 of the cam comprises a knob 12 mounted for rotation in the part 7" of the frame 7' and a planetary gearbox 20 having a high stepdown ratio such as 90:1.

In operation of the mechanism, the preload of the torsion bar spring 11 is transmitted from the first rotor 18 to the cam body 14 and thence to the second or reaction rotor 17. Thus the cam floats between the two rotors and acts in the manner of a wedge therebetween. As the knob 12 is rotated in one direction or the other, the rotary motion is transmitted through the gearbox 20 to the shaft 13 of the cam body 14, and the rotation of the cam body either urges the rotors 17, 18 apartto increase the preload, or permits them to approach one another to decrease the preload.

In a modification of the illustrated embodiment, the cam body could be journalled directly in bearings carried by the frame, but in this event, the movement of the first rotor is halved for each rotation of the knob.

Claims

1. Avehicle seat having a seat part mounted via a suspension on a base part, the suspension including a spring for biassing the seat part in an upward direction relative to the base part, and a mechanism for varying the preload in the spring, said mechanism comprising a first rotor mounted on the seat for movement along a predetermined path under the force of said spring, and a body mounted on the seat for rotation about an axis parallel to that of the first rotor, the surface of the body making contact with the surface of the first rotor and transmitting the load of the first rotor to the part of the seat on which said body is mounted, the body being such that the distance between its axis of erotation and the position of contact between the first rotor and the body varies as the body rotates about its axis, and means for rotating the body to vary said distance.

2. A vehicle seat having a seat part mounted via a suspension on a base part, the suspension includ ing a spring for biassing the seat part in an upward direction relative to the base part and a mechanism for varying the preload in the spring, said mechanism comprising a first rotor mounted on the seat for movement along a predetermined path under the force of the spring, a second rotor mounted on a part of the seat which is stationary relative to said path of movement of the first rotor, and a body mounted for rotation about an axis parallel to the axis of rotation of said rotors and maintained in peripheral contact with said rotors at positions on the body which are substantially opposite each other, the body being such that as it rotates about its axis, the distance between said positions increases in one direction of rotation and decreases in the opposite direction of rotation, means supporting the body for movement towards and away from the second rotor as the distance between said positions decreases and increases and means for rotating the body to vary said distance.

3. A vehicle seat according to claim 2 wherein the means for supporting said body is an arm which is pivoted about an axis parallel to the rotary axis of the body.

4. A vehicle seat according to claim 1 or claim 2 wherein said body is a cam.

5. A vehicle seat according to claim 4 wherein the periphery of the cam has a negative acceleration characteristic.

6. A vehicle seat according to any preceding claim wherein the means for rotating the body comprise a rotatably handle and gearing connecting the handle to the body.