GB1587637A

GB1587637A - Suspension mechanism for a vehicle seat

Info

Publication number: GB1587637A
Application number: GB2045077A
Authority: GB
Original assignee: Deere and Co
Current assignee: Deere and Co
Priority date: 1976-05-24
Filing date: 1977-05-16
Publication date: 1981-04-08
Also published as: CA1068207A; DE2721926B2; AU498376B2; FR2352686B1; DE2721926C3; IT1084068B; FR2352686A1; DE2721926A1; ES459042A1; AU1964276A

Description

(54) SUSPENSION MECHANISM FOR A VEHICLE SEAT (71) We, DEERE & COMPANY, a corporation organised and existing under the laws of the State of Delaware, United States of America, of Moline, Illinois 61265, United States of America do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a suspension mechanism for a vehicle seat.

Vehicle seat suspensions rely generally on springs to absorb and isolate the operator from vehicle shocks and vibration above the vehicle's natural frequency. For shocks and vibrations at or below the natural frequency, the suspensions are locked out and prevented from operating so that the seats are rigidly locked to the vehicle.

Springs are energy accumulating devices rather than energy damping devices, and as such require relatively long travel distance and times to dissipate vibration and shocks imposed on the operator by the vehicle.

Furthermore, where the springs are unrestrained as to the working length, there is a tendency to oscillate which imposes further vibrations on an operator than would be the case in a dampened system. Likewise, the springs which define an elastic support system are of limited use where the shocks and vibrations are near the natural frequency of the system because resonance will occur and the vibration and shocks will be re-inforced rather than dissipated.

According to the present invention a suspension mechanism for a vehicle seat comprises an upper assembly for attachment to the seat and a lower assembly connected to the upper assembly for fore-and-aft movement of the upper assembly with respect to the lower assembly, one assembly having a pair of springs mounted thereon and the other assembly being connected between the springs with the arrangement such that the upper assembly is urged to a datum position under the influence of a spring of the pair in either the fore or the aft direction away from the datum position and of the other spring of the pair in the other direction away from the datum position, the springs pre-loading the upper assembly against movement away from the datum position, and a shock absorber being connected between the said one assembly and the connection between the springs.

The suspension includes a shock absorber which dampens shocks and vibrations to cause a periodic motion of the seat regardless of frequency. This reduces the forces normally imposed on the operator when driving the vehicle on rough terrain slopes, reduces the discomfort of operating the vehicle and improves the stability of the horizontal suspension. The centring springs have a small initial tension which must be overcome before the seat can move. This prevents excessive motion when operating on smooth surfaces.

An embodiment of the invention will now be described with reference to the accompanying diagrammatic drawings in which: Figure 1 shows a vehicle seat; Figure 2 is a plan view of an upper assembly of a horizontal suspension of the seat; Figure 3 is a plan view of a lower assembly of the horizontal suspension; Figure 4 is a sectional view taken along line 4-4 of Figure 2; Figure 5 is a sectional view taken along line 5-5 of Figure 3; Figure 6 is a front view of Figure 2; and Figure 7 is a front view of Figure 3.

Referring now to Figure 1, there is shown a seat 10 having a cushioned seat portion 12, a vertical seat suspension 14, and a horizontal seat suspension 16. The horizontal seat suspension 16 consists of two basic assemblies.

Referring to Figure 2, a seat assembly 18 is shown which is the upper assembly of the horizontal seat suspension 16 and, referring to Figure 3, there is shown a base assembly 20 which is the lower assembly of the horizontal seat suspension 16.

The seat assembly 18 includes a pair of seat support brackets 22 and 24 having downturned flanges 26 and 28, respectively, which may better be seen by reference to Figures 4 and 6. Inserted in the downturned flanges 26 and 28 is a pair of linear bearing shafts 30 and 32 which are spaced parallel to one another and parallel to the direction in which the vibration and shock is to be dampened.

The seat assembly 18 further includes a conventional variable rate shock absorber 34. The rod of the shock absorber 34 is secured to the seat support bracket 24 by means of a bracket 36. The shock absorber 34 contains internal porting to make the dampening effect equal for both directions of travel. The porting further ensures greater dampening at the ends of the stroke than at the middle. It may be noted that in some aPPlications where unequal dampening effect in each direction is desired, the change can be accomplished by modification to the shock absorber 34. Integral with, and medially positioned on, a cylinder hod 37 of the shock absorber 34 is an ear 3 for receiving a double-ended centring stud 40, the purpose of which will be explained later.

Secured to the cylinder body 37 opposite the ear 38 is a notched plate 42 having therein first, second, and third notches 44, 46, and 48, respectively. Engageable with the notches is a lock-out pin 50 which is inserted in a shock absorber lock-out lever 52. The lever 52 is pivotally secured to the seat support bracket 22 and protrudes through a conventional leaf spring detent mechanism 54 in the turndowned flange 26.

The upper end of the centring stud 40 is connected by a first centring extension spring 56 to a bolt 58 in the seat support bracket 22 and is connected by a second centring extension spring 60 to a bolt 62 in the seat support bracket 24. Since the centring springs 6 and 60 are generally selected to be of equal capacity, they act to keep the centring stud 40 substantially centred between the seat support brackets 22 and 24 and thus maintain the shock absorber 34 in a centred position also. The centring springs 56 and 60 have an initial tension wound into them which must be overcome before they will extend from their normally closed coiled positions. This provides a minimum centring force for the seat assembly 18 at all times. Since the centring springs 56 and 60 are used only for centring and not for absorbing shock or vibration loads, they may be relatively low capacity springs.

Referring now to Figure 3, the base assembly 2 includes a pair of base brackets 64 and 66. The base bracket 64 has a pair of integral upright ears 68 and 70 into which a pair of parallel linear bearings 72 and 74, respectively, are inserted and secured. The base bracket 66 likewise has a pair of upright integral ears 76 and 78 holding parallel linear bearings 80 and 82, respectively.

The bearings 72 and 80 are co-linear to encircle and allow reciprocating motion of the linear bearing shaft 30; and linear bearinns 74 and 82 are co-linear to encircle, and allow reciprocating motion of, the linear bearing shaft 32.

The base brackets 64 and 66 are connected by a slider assembly generally designated by the reference numeral 84. The slider assembly 84 includes a lower slide portion 86, best seen by reference to Figure which is secured by bolts (not shown) at one end to the base bracket 64 and at the other end to base bracket 66. The lower slide portion 86 further includes laterally extending teeth 88, the purpose of which will be described later. Anti-friction means in the form of balls 90 roll in the lower slide portion 86 and allow reciprocating motion of the upper slide portion 92. The upper slide portion 92 contains a hole 94 into which the lower end of the centring stud 40 is inserted and fixed.

Attached to the upper portion 92 and extending to one side thereof is a plate 96 to which is secured a pivot pin 98. An adjustment latch 100 is secured to the pivot pin 98 for pivoting thereabout. The adjustment latch 100 contains a downturned finger 102 which engages the teeth 88 when the adjustment latch 100 is in the position shown in Figure 3. When the finger 102 is in engagement with the teeth 88, relative movement between the lower slide portion 86 and the upper slide portion 92 is prevented. By moving the adjustable latch 100 to move the finger 102 out of engagement, the lower slide portion 86 and the upper slide portion 92 are free to reciprocate relative to one another.

In operation, the seat is first adjusted to suit an individual occupant by moving the adjustment latch 100 so as to disengage the finger 102 from the teeth 88. This allows relative movement between the lower slide portion 86 and the upper slide portion 92 of the slider assembly 84 and also the seat assembly 18 relative to the base assembly 20. When the seat reaches the desired position, the adjustment latch 100 is re-engaged to fix the slider assembly 84. Due to the centring forces imposed on the centring stud 40 by the centring springs 56 and 60, the seat assembly 18 will be positioned in a centred operating position which will only slightly be affected by the operation of a vehicle containing the seat 10 on various types of slopes.

For the majority of shock loads which impose high acceleration forces on operators in the fore-and-aft pitch mode, under severe field conditions, the shock will be taken up by the shock absorber 34 which will dampen the energy normally imposed on the operator. The variable rate operation of the shock absorber will cause the dam pening factor to increase as the seat assembly slides in the linear bearings 72, 74, 80, and 82 further and further away from the centred operating position.

In the event that it is desired to lock out the horizontal seat suspension, the shock absorber lock-out lever 52 can be moved in the detent mechanism 54 so as to cause the lock-out pin 50 to engage in a notch in the notch plate 42. The engagement of the lock-out pin 50 in one of the notches 44,46, or 48 operates to secure the seat assembly 18 to the base assembly 20 and prevent relative motion therebetween.

WHAT WE CLAIM IS: 1. A suspension mechanism for a vehicle seat comprising an upper assembly for attachment to the seat and a lower assembly connected to the upper assembly for foreand-aft movement of the upper assembly with respect to the lower assembly, one assembly having a pair of springs mounted thereon and the other assembly being connected between the springs with the arrangement such that the upper assembly is urged to a datum position under the influence of a spring of the pair in either the fore or the aft direction away from the datum position and of the other spring of the pair in the other direction away from the datum position, the springs preloading the upper assembly against movement away from the datum position, and a shock absorber being connected between the said one assembly and the connection between the springs.

2. A suspension mechanism according to Claim 1 in which the pair of springs is mounted on the upper assembly, the shock absorber is connected between the upper assembly and the connection between the springs, and the said connection is anchored to the lower assembly.

3. A suspension mechanism according to claim 1 or 2 in which the springs are in tension at the datum position.

4. A suspension mechanism according to claim 3 in which each spring is connected to the connection between the springs so that movement of the spring relative to the connection can take place once the tension in the spring is exhausted by movement in the relevant direction.

5. A suspension mechanism according to claim 4 in which each spring is connected to the said connection by a hook at the end of the spring.

6. A suspension mechanism according to any preceding claim in which the connection between the springs comprises a stud.

7. A suspension mechanism for a vehicle seat substantially as described herein with reference to, and as illustrated in, the accompanying diagrammatic drawings.

8. A vehicle seat having a suspension mechanism according to any preceding

Claims

claim.