AU620612B2

AU620612B2 - Vehicle seat suspension unit

Info

Publication number: AU620612B2
Application number: AU34675/89A
Authority: AU
Inventors: Elliot N. Davis
Original assignee: Rosdon Engineering and Manufacturing Pty Ltd
Current assignee: Rosdon Engineering and Manufacturing Pty Ltd
Priority date: 1989-04-13
Filing date: 1989-05-11
Publication date: 1992-02-20
Anticipated expiration: 2009-05-11
Also published as: WO1990011841A1; EP0600855A4; AU3467589A; EP0600855A1

Description

COMMONWEALTH OF AUSTRALIA a 0 0 1 o 0 m 4t~ 04 4o o, 0f 4. 0 40 0 4 9 0 nn I4

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620612 This document contains the amendments allowed under Section 83 by the Supervising Examiner on and is correct for printing COMMONWEALTH OF AUSTRALIA Patents Act 1952 Name of Applicant ROSDON ENGINEERING MANUFACTURING PTY LTD

AND

Goo 0 00 0 0000 0 0 0 00 0000 004 0000 o 60 00 0 0 0o Address of Applicant Actual Inventor(s) Address for Service COMPLETE SPECIFICATION Maroochydore Road, Buderim, Queensland, 4556, Australia.

ELLIOT NEIL DAVIS GRANT ADAMS COMPANY, Patent Trade Mark Attorneys, 333 Adelaide Street, BRISBANE. QUEENSLAND. 4000

AUSTRALIA.

FOR THE INVENTION ENTITLED: VEHICLE SEAT SUSPENSION UNIT g 00 00O 0 000044 0 0 0 0 The following statement is a full description of the invention including the best method of performing it known to the applicant.

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THIS INVENTION relates to a vehicle seat suspension unit. The term "vehicle" shall be used to include automobiles, four-wheel-drives (4WD), trucks, prime movers, earthmoving machines (eg. bulldozers), aircraft and watercraft.

A vehicle operator's comfort and efficiency is dependent on providing a suitable suspension unit for his seat to eliminate, or at least reduce, the shocks and vibration transmitted from the vehicle to the operator via his seat.

Many suspension units have been proposed to reduce the shocks and vibration. Generally, most rely on a spring-loaded seat support frame which is damped by a hydraulic or pneumatic damper unit. An example is disclosed in AU-B-66509/86 (582031) Culley et al).

The major problem with these units is that the damping can effectively be so slow that the suspension unit goes out of phase with the vehicle suspenison and the damping can apply an additive shock to the operator's seat. In 20 many cases, operators remove the damping effect as it is preferable to have a "floating" undamped suspension unit than a damped one.

One of the reasons for the failure of the existing suspension units has been a basic misunderstanding of seat suspension unit design. The design objective is to provide a unit where the operator's seat follows an almost undisturbed path as the vehicle passes over bumps or depressions. In the past, the designers have worked on the principle of the seat moving relative to the vehicle, whereas they should have been designing for movement of the vehicle relative to the seat. In addition, they have applied damping to the suspension unit which is not required.

It is an object of the present invention to provide a seat suspension unit which provides improved insulation from shock and vibration compared to existing units.

It is a preferred object to provide a unit where damping per se is not required.

It is a further preferred object to provide a unit which has a rising suspension rate from its normal preload position.

It is a still further preferred object to provide a unit which has a very low profile and which incorporates the seat runners within its base frame.

Other preferred objects of the present invention will become apparent from the following description.

In a broad aspect the present invention etc 15 resides in a vehicle seat suspension unit including: 4, ~a base frame mountable on a vehicle; a seat support frame to mount a vehicle operator's seat; a scissor arms assembly interconnecting the frames to enable the frames to move relative to each other in parallelism; a pair of cam track means on the scissor 0 arms assembly engageable by respective cam follower means mounted on a follower support means; 25 spring means interconnecting the follower 4o support means and the scissor arms assembly or one of the frames; and a travel control unit including a bellows assembly interconnecting the two frames, the bellows providing a travel control as the base frame returns to an initial pre-load position after being displaced therefrom, so arranged that as the frames move relatively towards each other, the cam follower means travel along the cam track means to extend the spring means, the extension of the spring means opposing the 3 i r I movement of the frames from the initial pre-load position.

Preferably, the frames are substantially rectangular in plan view. Preferably, the base frame incorporates the runners for longitudinal adjustment of the seat in the vehicle.

The seat support frame may have the seat bolted to it or the frame may be moulded into the base of the seat.

Preferably, the scissor arms assembly includes a pair of primary scissor arms and a pair of secondary scissor arms pivotally connected to the frames and to S0o each other. Preferably, reinforcing plates connect the oo arms in each pair.

o °0 15 Preferably, the cam tracks are provided on the oo rear of the scissor arms and overlap at their forward ,oo ends, the cam tracks moving towards each other as the 0o0 frames move together. Preferably, the cam tracks are offset so that each is engaged by a respective roller (as the cam follower means). Preferably the shape of the cam tracks prevents the "bottoming out" of the frame. 0o°0. Preferably, the rollers are rotatably mounted on the ends of a transverse yoke and a pair of tension 25 springs connect the yoke to the base frame.

Preferably, the bellows only provides effective control at the end of its opening stroke to c C prevent "topping-out" of the frames.

To enable the invention to be fully understood, a preferred embodiment will now be described with reference to the accompanying drawings, in which: FIG 1 is a side view of the unit, parts being shown in section for clarity; FIG 2 is a top plan view of the unit; FIG 3 is a sectioned side view taken on line 3-3 on Fig 2; and S- 4 FIG 4 is a sectioned end view of the bellows taken on line 4-4 on Fig 3.

Referring to Figs 1 to 3, the seat suspension 000 0 0 000 o0000 00 0 00 00 00 04! 0 00000 00 00 000 4 C

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C C cV cC unit 10 has a substantially U-shaped base frame 11, the side rails 12 which are of RHS steel, and the rear rail 13 of which is of angle-sectioned steel. The ends of the bottom walls of the side rails 12 are slotted to receive the studs 14 of the seat runners 15 slidably received in the side rails 12. Each runner 15 is releasably locked by a transverse pin 16 which has a finger 17 received in a cam slot 18 in a boss 19. An operating handle 20 extends across the front of the base frame 11 and is connected to the fingers 17 by rods 21.

By rotation of the handle, the pins 16 are rotated and moved to a retracted position by the fingers 17 moving in their cam slots 18. The pins are urged into their locked positions by springs 22 via rods 23.

A substantially rectangular seat support frame 24 has side rails 25 and a rear rail 26 of RHS steel and a front rail 27 of flat steel.

are The base frame 11 and seat support frame 24 are connected one above the other in parallel by a pair C e 20 of primary scissor arms 28 and a pair of secondary scissor arms 29, the middle part of each secondary S't scissor arm 29 being pivoted to the middle part of a at primary scissor arm 28 by a pivot pin 30. Tranverse plates 31, 32 reinforce (and interconnect) the respective scissor arm pairs 28, 29.

The top or front ends of the two primary scissor arms 28 are pivoted about a transverse axis (defined by a transverse shaft) -within the front end of the seat support frame 24. The bottom or front ends of C C 30 the secondary scissor arms 29 are pivoted about a transverse axis (defined by a transverse shaft 33) within the front end of this seat support frame 11. The €t bottom or rear ends of the two primary scissor arms 28 S have pivot pins 34 slidably received in slots 35 in blocks 36 at the inner sides of the rear ends of the U Sec. S77 0 o-" side rails 12 of the base frame 11, and the upper and rear ends of the two secondary scissor arms 29 have similar pivot pins 37 slidably received in slots 38 in blocks 39 on the inner side of the rear ends of the sid rails 26 of the seat support frame 24.

Respective cam tracks 40, 41 are provided on the rear ends of the primary and secondary scissor arms 28, 29. The forward ends of the cam tracks overlap and the cam tracks are transversely offset in front view.

A pair of rollers 42 (spaced by a washer) are rotatably mounted on axles 43 at each end of a substantially U-shaped transverse yoke 44. i A pair of tension springs 45 are anchored at one end to the yoke 44 and at the other end to a balance bar 46 which has a central screw-threaded rod 47 which receives a nut 48. The nut 48 bears on a bracket 49 on the reinforcing plate 32 interconnecting the forward ends of the secondary scissor arms 29.

A bellows assembly 50 has a flexible rubber 20 bladder 51 supported by an internal coil spring 52, the base of the bladder 51 being secured to a rear rail 13 <of the base frame 11. A bracket 54 connects the top of the bladder 51 to the rear rail 26 of the seat support frame 24, the bracket being secured by a nut 55 on a threaded tube 56 open to the interior of the bladder.

A rubber valve member 57 is normally urged 'c into engagement with the end of the tube 56 by a lightweight compression spring 58 and is unseated to allow the rapid egress of air when the bellow assembly 30 50 is collapsed by the frames 11, 24 moving towards each other. A relatively large diameter hole 59 in the valve member 57 allows relatively unrestricted egress of the air into the bellows assembly 50 when the frames 11, 24 are moved apart.

The operation of the suspension unit 10 will S77! 7 >1 1 1 now be described. NB. It will be assumed that the seat support frame remains relatively stationary and that the base frame moves vertically relative to it, the path of the operator's seat is relatively undisturbed as the vehicle moves over bumps and holes (or waves and troughs for watercraft).

The seat runners 15 are bolted to the floor of the vehicle cabin (not shown) via the studs 14 and the position of the suspension unit 10 (and the seat) can be adjusted by operating handle 20 to release the pins 16 to allow the seat frame 11 to move along the runners The operator sits in the seat (not shown) bolted to the seat support frame 24 and the distance between the frames is reduced to the initial preload height determined by the tension set on the springs via adjustment of the nut 48. (This allows operators ofi different weights to be easily accommodated). When the vehicle strikes a bump and tends to rise, the base frame :o 11 moves upwardly (in the direction of arrow A) towards 20 the seat support frame (as a datum). The cam tracks o 40, 41 converge due to the closing of the scissor arms o 28, 29 about their pivot pins 30 and the rollers are o0 urged rearwardly in the direction of the arrow B. The o yoke 44 pulls on the springs 45 and the base frame 11 rises until the tension in the springs 45 on the yoke 44 equals the force on the roller 42 from the cam tracks 40, 41 tending to move the rollers in the direction of 44 C arrow B.

c When the vehicle passes over the bump, the rollers 42 are pulled against the cam tracks 40, 41 in the direction opposite to arrow B to restore the distance between the frames 11, 24.

As the displacement of the base frame 11 in the direction of arrow A increases the angular displacement of the scissor arms 28, 29 at an increasing "j "CY Y- I~Y^ qgplUlir* pl: rate, the suspension unit has a rising rate of force opposing further vertical displacement of the base frame 11 from its initial position. This means that the effective springing rate of the unit increases with displacement of the base frame from its initial preload position. The shape of the cain tracks prevents the seat frame from bottoming out.

When the vehicle falls into a hole, the base frame 11 will move in the direction opposite to arrow A and the rollers will move in the direction opposite to arrow B. By selecting the contours of the cam tracks 41, a reduced restoring force is applied on the rollers by the springs and the base frame 11 can then move in the direction of arrow A to its initial preload position.

The bellows assembly 50 does not provide damping but only travel control when the vehicle encounters a hole. Assuming the vehicle has encountered a bump and the base frame 11 is moved in the direction S 20 of arrow A, the bladder 51 begins to collapse, supported oQ o by the internal spring 52 and air is exhausted from the bladder by the unseating of the valve member 57. The 0o, pressure inside the bladder exceeds atmospheric pressure 9 0 towards the end of the stroke. When the base frame begins to fall (ie. move in the direction opposite to arrow the valve member 57 is reseated but the air rapidly enters the bladder via the hole 59. Initially, SooOO the air pressure in the bladder falls to atmospheric and it is only towards the end of the stroke that the a 30 pressure becomes negative (ie. a vacuum) to provide a "damping" effect and indeed, is more accurately termed a travel control. This prevents the frames going past the o 4% pie-load position and "topping-out".

8" L By charging the profile of the cam tracks 41 and the tension on the springs 45, the seat 8 t 77 WT JvTL I. 11 suspension unit 10 can be tailor made for a particular operator, eg. an owner/drive of an interstate semitrailer. However, general cam track profiles can be provided which, with adjustment of the tension of the springs, can enable a wide range of operators to use the unit and receive a very high standard of ride. Because the bellows does not provide damping, but only travel control, the unit does not allow the operators' seat to go out-of-phase with the vehicle suspension and so a high quality ride is ensured.

It will be readily apparent to the skilled addressee that the present invention provides a simple, yet highly efficient seat suspension unit and its comfort nature allows it to have a very low profile with the desired range of travel.

Various changes and modifications may be made to the embodiments described and illustrated without departing from the scope of the present invention as S defined in the appended claims.

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Claims

2. A unit according to Claim 1 wherein: a scissor arms assembly includes a pair of primary scissor arms and a pair of secondary scissor arms pivotally conr.ected to the frames and to aach g 30 other; reinforcing plates being provided to interconnect the scissor arms in each pair.
3. A unit according to Claim 2 wherein: the cam tracks are provided on the scissor arms rearwardly of the pivotal interconnection of the arms, the cam tracks overlapping at their forward ends and being axially offset to be engaged by respective cam followers. N I V I /2
4. A unit according to any one of Claims 1 to 3 wherein: the camn followers are rollers rotatably mounted in spaced pairs at the ends of a transverse yoke provided as the cam follower support means. A unit according to Claim 4 wherein: the springs interconnect the yoke to a reinforcing plate interconnecting one of the pairs of scissor arms; and means are provided to enable adjustment of tension on the springs.
6. A unit as claimed in any one of Claims 1 to I wherein: I the camn tracks are profiled to provide a 9915 rising rate of suspension as the distance between the V frames is reduced due to displacement of the base frame relative to the seat support frame prior an initial pre- load position.
7. A unit as claimed in any one of Claims 1 to 6 wherein: the bellows assembly includes a bladder p rovided with an internal supporting spring; a relatively large air passage to the interior of the bellows; a valve means in the air passage arranged I to be opened to allow the rapid egress of air from the bladder when the bladder is collapsed; and an air bleed hole in the valve means to- allow air to rapidly egress into the bladder when the bladder is restored, a vacuum being generated in the bladder at the end of its return stroke.
8. A vehicle seat suspension unit substantially as hereinbefore described with reference to the accompanying drawings. DATED this twenty-ninth day of November 1991. ROSDON ENGINEERING MANUFACTURING PTY LTD, I by its Patent Attorneys, -1 GRANT ADAMS COMPANY. Jt