IL33755A - Suspensions for vehicle seats - Google Patents

Description

3 IMPROVEMENTS IN AND SUSPENSIONS FOR VEHICLE SEATS This invention relates to a a resilient in particular to tractor or other vehicle designed for use over rough I important of such a seat suspension it should the resiliently for upward and downward movement to reduce the transmission of vibrations the wheels of the vehicle to the occupant of the the of the seat being opposed by a particularly the spring force should be variable to suit the weight of the seat occupant so that under static load the seat located at a ride position is substantially midway between and positions of the It is also a desirable characteristic of such a seat suspension that the height of the seat relative to the steering wheel or other part of the vehicle should be variable to suit the height of the seat without varying the ride position the position of the seat under static load conditions with respect to the and positions of the According to the invention there is provided a seat comprising a seat part mounted on a pivotal suspension arm for resilient upward and downwards movement between and positions the influence of a means operable to vary the bias exerted by the and means operable to raise or lower seat part without varying the bias exerted by the spring to respectively raise or lower the and Further according to the invention there is provided a seat comprising a base a seat part on a pivotal suspension member for resilient upwards and downwards movement between and a device operable to vary the bias exerted by the a device operable to pivot the suspension member so as to or lower the seat part without varying the bias exerted by the and an arm pivotal with the suspension the spring being interposed between one of said members and the and the varying device being interposed between the other of said members and the arm and being effective to respectively raise or lower the and positions when raising or lowering the seat An embodiment of the present invention will now be by way of example with reference to the accompanying in Figure 1 is a partially in section of a vehicle seat Figure 2 is a side elevation of the suspension of Figure Figure is a section line of Figure a section taken on lino of and Figure 5 is fragmentary section taken line of Figure As in the a seat suspension for a tractor comprises a base plate assembly 2 for attachment to the floor of the this assembly having an outer of parallel spaced upright walls 2a extending in a spring in the form of fore and aft direction and forming bearings for bar which provides the spring bias of the seat and an inner pair parallel spaced upright walls 2 These pairs of walls form part of a assembly and assembly The torsion bar assembly comprises a pivot tube divided into two parts each which is in a respective one of the outer walls of the base plate a d a pair of outer tubes 6 which are fitted like sleeves on to the portions of the pivot tube 4 extending outwardly of the outer these two outer tubes 6 being cast integrally with a central or suspension which thus rotates about the axis of the pivot tube At its radially outer end the seat part in form oft lever pivotally supports an mounting TO together with a parallelogram linkage for maintaing the plate will be further described The torsion bar assembly further includes a laminated steel torsion 12 which extends axially through the pivot tube and is secured at its outer operative ends in the outer ends of the two outer tubes Torque is applied to the torsion bar 12 by means of a assembly operable to vary the bar and comprising a lever 18 which is formed as a casting to fit around the pivot tube 4 and an intermediate frame comprising a mounting 20 which is with the pivot tube 4 passing through opposed openings in the side walls 20a of the mountin and uster lever 18 lying arm side walls each constitute an arm pivotal with the suspensi between these side walls integral extension of the lever 18 extends the two parts of the pivot tube 4 and is provided with central rectangular opening matching the shape of the torsion and through which the central part of the torsion bar Thus the lever is rigidly connected to the centre of the torsion the inner operative end of torsion The assembly further comprises slide rails 22 formed by elongated slots in of the frame side walls of the mountin 20 and so arranged they extend parallel to one the rails 22 forming a slide for the cylindrical portions of a nut 2 which mates with a screw 26 journalled in the end of the mounting The nut 2 is of generally cylindrical form about an axis perpendicular to the axis of the screw The lever which is forked at its outer end to straddle the screw bears against the cylindrical surface o the nut so that movement of the nut along the rails 22 by rotation of the screw 26 effects angular movement of lever frameJ relative the mounting 20 and about the axis of the torsion bar and thus effects angular movement of the pivot tube relative to the central seat supporting lever Rotation of the screw is effected by a handle and it will be apparent that as the load applied to the torsion bar 12 rotation of the handle and movement of the nut along the slide rails 22 so the distance between the axis of the torsion bar assembly and line of engagement betwee the nut 24 and the lever 18 increases so that the effective length of the lever 18 is increased and the angle between the lever 18 and the slide rails 22 is Consequently the mechanical advantage of the mechanism increases with increasing load on the torsion bar 12 and enables the force required to rotate the handle 28 to be maintained constant or to rise at a relatively low rate with increasing torsion bar In to adjust the seat to the weight of the the screw 26 is rotated to increase or decrease the twist in the torsion bar 12 in accordance with the weight to be supported and locate lever 8 at a mid position its path This mid position corresponds to the ride position of the An for limiting upward movement of mounting 10 shown in dashed lines in Figure to 20 provided a vibration dampe preferably of the pot connected between the o the side walls of the mounting plate and central lever A for limiting downward movement of the ba assembly without varying the torque in the torsion bar and is screwed in a selected angular position relative to the base plate This is effected by screw 3 extending parallel to the screw 26 and likewise in the fron wall of mounting frame A nut which mates with the screw 32 is generally oyllndrioal about an perpendicular to the of the screw 32 and has outer end portions o reduced diameter which slide steeply Inclined slots 36 the inner upright walls 2c of the base plate assembl Thus by rotating the screw reaction between the nut 3k and the inclined slots 3 will cause the mounting frame 20 to rotate about the axis of the torsion bar assembl Since the up and down stops are provided between the lever 8 the 20 on which this lever is of the Will the up and down stops by an equal amount and thus position is automatically maintained for the seat occupant weight despite change of static The seat screw 32 can be rotated by a separate handle coaxial with the handle 28 and on the uster screw the said separate handle having external gear teeth meshing with a pinion wheel 37 secured to the uster screw as the 28 serves to selectively rotate either the screw 26 or the screw 32 and is made movable along the axis of the scre 26 to disengage the screw and lock the handle to the uster screw 26 for example by engagement a roll pin through the screw with slots in the of the In to maintain the plate 10 horizontal or at a constant angle to the base plate assembl as shown in dashed lines in Figure the mounting plate is formed with vertically downward extending side and stabiliser arms 38 on opposite sides of the are journalled at their lower end to the base plate assembly In particular the stabiliser arms are provided at their lower ends transverse sleeves 40 which are journalled on between the outer 2a of the base plate assembly and flanges 2d on the outer edges of the base plate The upper ends the arms 38 are journalled in the side walls of the mounting plate 10 below the pivot axis between the mounting plate 10 and the central lever is clearly show the linkage extends from the forward end position of the base assembly and the plate extends forwardly from the rear end Of the A hot secured to the pivot tube moves over a between and markings on the to the amount of twist in torsion ba and therefore the weight of seat occupant fo the seat s Although as particularly described a torsion bar is operable to bias the seat a torsion springs for example of the in a torque is developed by rubbe or the like placed in compression or can be used insufficientOCRQuality

Claims (8)

V/HAT WE CLAIM IS:

1. A seat comprising a seat part mounted on a pivotal suspensio arm for resilient upward and downwards ' movement between up-stop and down-stop positions under the influence of a spring^, means operable to vary the bias exerted by the spring, and means operable to raise or lower the seat part without varying the bias exerted by the spring and to respectively raise or lower the up-stop and down-stop positions.

2. , A seat comprising a base member, a seat part mounted on a spring-biased pivotal suspension member for resilient upwards and downwards movement between up-stop I- *' and down-stop positions, a bias-varying device operable to J vary the bias exerted by the spring, a height-varying device operable to pivot the suspension member so as to raise or lower the. seat part without' altering the bias exerted by the spring, and an arm pivotal co-axially with the suspension member, the spring being interposed between one of said members and the arm, and the height-varying device being interposed between the other of said members and the arm and being effective to respectively raise or lower the up-stop and down-stop positions when raising or lowering the seat part.

3. A seat according to claim 2 wherein the spring is a torsion spring pivotally mounted in the base member, the suspension member being coupled to one operative end of the spring·„

4. .4·. A seat according to. claim 3 wherein the arm is incorporated in a frame mounted for rotation about the axis of the spring and wherein the height-varying device comprises a device for securing the frame in a selected angular position relative to the base member, the bias-varying device bein carried by the frame and being operable to rotate a lever, coupled to the other operative end of the spring, relative to the frame about the axis of the spring to alter the bias exerted by the spring.

5. · A seat according to claim 4 wherein the bias-varying device .includes' an adjuster nut for' applying a force to the lever about the axis of the spring, and an adjuster screw journalled in the frame and coupled with the nut for moving the point of application of the force progressively away . from the axis of the spring as the bias exerted by the spring is increased.

6." A seat according to any one of claims 2 to 5 in which the seat part is supported from the base member by a parallelogram linkage, the said pivotal suspension member forming one side of said linkage.

7. · A seat according to claim .6 wherein the parallelogram linkage extends rearwardly from the forward end portion of the base member, and the seat part extends forwardly from the rearward end of the linkage, 33755/2

8. A seat substantially as hereinbefore described with reference to the accompanying Attorney or App cants