Cable drive mechanical seat suspension

A vehicle seat suspension system is provided which includes, in a seat support comprising an upper housing and a lower housing and a scissors linkage support apparatus, a spring fixed to the upper housing and a cable attached to the spring and wrapping around a pulley attached to the upper housing and downwardly to an arcuate or eccentric pulley attached at the scissors linkage axis pivot and an actuator knob which allows a seat occupant to tighten or loosen the cable and raise or lower the seat to provide a vehicle seat suspension system. The present invention provides a suspension system which can be discreetly and infinitely adjustable and which allows a user to adjust the suspension curve characteristics of the seat by utilizing a non-circular drive pulley which is movably adjustable.

BACKGROUND OF THE INVENTION 
The present invention relates generally to a mechanical, adjustable seat 
suspension device and, more specifically, to a cable drive mechanical seat 
suspension device which uses springs and a cable to allow a seat occupant 
to conveniently adjust the vertical position of a seat and which allows 
for a substantially linear force-versus-deflection curve, and which allows 
height adjustment to a plurality of vertical positions. 
There is a continuing need for suspension mechanisms that are simply 
constructed and inexpensive while still meeting vehicle manufacturers' 
ever increasing demands for compactness and comfort. An additional need 
exists for such a device whose suspension and ride characteristics can be 
easily modified. Other difficulties have been encountered in the height 
adjustment mechanisms of seat suspensions. Frequently, such mechanisms are 
difficult to reach, require levers or triggers that can pinch an operator, 
and generally are complicated and expensive. 
Most known seat suspensions transmit the load from the seat to the 
suspension springs through steel bars comprising scissor arms or 
parallelogram linkages. Typical of these prior art devices include the 
following: U.S. Pat. No. 3,339,906 to Persson; U.S. Pat. No. 3,826,457 to 
Huot de Longcham; and U.S. Pat. No. 4,125,242 to Meiller et al. In such 
systems, the forces exerted on the suspension system by the seat occupant 
may be carried by a cam and a roller bearing. An example of such a system 
is described in U.S. Pat. No. 5,125,631 to Brodersen et al. and U.S. Pat. 
No. 4,448,386 to Moorhouse et al. Such systems are efficient and 
advantageous in that they allow substantial vertical seat adjustment and 
suspension. A disadvantage with such systems is that a substantial force 
is exerted on an arcuate cam and a roller bearing and often in a 
single-point contact relationship. This force requires hardened metal 
surfaces and durable components which can be expensive. Point-to-point 
surface contact also increases the difficulty of achieving a dependable, 
consistent linear relationship between suspension force and vertical 
deflection due to "noise" between contacting surfaces. It would thus be 
highly desirable for a seat suspension to provide maximum height 
adjustment and compactness while also being economical and providing a 
desired force-deflection linear relationship. It would be similarly 
desirable to provide such a seat suspension which provides height 
adjustment capabilities to discreet positions while allowing suspension 
and ride zone adjustment at each position. 
SUMMARY OF THE INVENTION 
The present invention provides an economical, compact and conveniently 
actuated seat suspension and height adjustment mechanism having many of 
the functional characteristics required for use in a heavy duty vehicle. 
It uses springs, a cable drive system, a idler pulley, and a drive pulley 
in conjunction with a scissors linkage seat suspension. The preferred 
embodiment of the present invention also utilizes an adjustable operating 
knob and adjustably eccentric drive pulley to offer various adjustment 
mechanisms to vary the suspension characteristics of the seat. 
The present invention thus provides economical, dependable and convenient 
mechanical seat adjustment and support while also providing a damping 
means and can exhibit a linear relationship between the vertical movement 
of the seat and the force exerted on the suspension system. A linear 
force/deflection relationship is important in a seat suspension to ensure 
that, throughout the distance traveled by the seat, a linearly related 
suspension force is exerted by the suspension system. This linear 
relationship provides the same level of comfort and shock absorption, or 
"feel", to the seat occupant as the seat travels vertically. 
The present invention provides a suspension assembly in conjunction with a 
scissors linkage system using a cable and spring and pulley which allow 
convenient and reliable seat adjustment and suspension in an economical 
apparatus. 
Another object of the present invention is to provide a mechanical, 
adjustable seat suspension system which provides full vertical 
adjustability, is economical to manufacture, and which also provides a 
linear relationship between vertical suspension deflection and force 
exerted on the suspension system. 
A still further object of the present invention is to provide a mechanical 
seat suspension system which can be adjusted to vary the suspension curve 
characteristics of the system easily by an operator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
One preferred embodiment of the present invention, as shown in FIGS. 1 and 
2 and designated generally 15, utilizes a scissors linkage support 
assembly well known in the art. In conjunction with the support assembly, 
the suspension system utilizes actuator knob 25 rotatably mounted on front 
95 of upper housing member 90, front spring bar 27 operatively attached to 
coil springs 28, 29, rear spring bar 32, cable holder 40, cable 45, guide 
31, idler pulley wheel 41, drive pulley 37, pivot axle 61, and shock 
absorber 50. 
As best seen in FIGS. 3 and 4, a preferred embodiment of the present 
invention also includes a rack 112 with teeth 109 for adjustably receiving 
knob bar 105 to adjust the spring tension height of the seat. A preferred 
embodiment also includes an eccentric drive pulley 37 and drive pulley 
adjustment device 140, as best seen in FIG. 4. 
As is well known in the art, scissors linkage support assemblies work to 
provide seat height adjustment in the following general manner. An upper 
housing 90 and a lower housing 80 each includes flanges 100 around the 
perimeter thereof. Toward the rear of each is an axle 81, 91. Attached to 
lower housing axle 81 and extending outwardly therefrom are parallel 
linkage arms 72, 73. Linkage arms 72, 73 extend upward and terminate at 
upper guide bar 94. Upper guide bar 94 extends across upper housing 90. At 
either end of upper guide bar 94 are rotatably attached rollers 99. 
Rollers 99 of upper guide bar 94 are slidably disposed within upper 
linkage tracks 92, 93 formed with flanges 100 of upper housing 90. 
Attached to upper housing axle 91 are parallel linkage arms 75, 76. Linkage 
arms 75, 76 extend downwardly from axle 91 and terminate at lower guide 
bar 85. Lower guide bar 85 extends across lower housing 80. At either end 
of lower guide bar 85 are rotatably attached rollers 99. Rollers 99 of 
lower guide bar 85 are slidably disposed within lower linkage tracks 82, 
83 formed within flanges 100 of lower housing 80. 
Linkage arms 72, 73 cross inside of and adjacent linkage arms 75, 76 to 
form a cross pivot axis 60. Linkage arms 75, 76 and 72, 73 are axially 
connected through cross pivot axis 60 with linkage axle 61. Integrally and 
coaxially connecting linkage arms 72, 73 is linkage axle housing 62. 
Pivotally attached to lower guide bar 85 is the stationary portion of shock 
absorber 50. Extending upward from lower guide bar 85, piston 51 of shock 
absorber 50 is pivotally connected to linkage arm 72 or 73 above axis 60. 
As will be apparent to those of ordinary skill in the art, this scissors 
linkage assembly works to provide mechanical connection for vertical 
movement of upper housing 90 relative to lower housing 80. When upper 
housing 90 is in its lowest position, angle .THETA. is minimized. As 
linkage arms 72, 73 and 75, 76 work to provide a mechanical linkage as 
upper housing 90 is raised relative to lower housing 80, angle .THETA. 
increases. As is well known to those of ordinary skill in the art, 
scissors linkage assemblies vary significantly and are not limited herein 
to the specific embodiment just described. Any scissors linkage assembly 
will suffice for the purposes of the present invention. 
The present invention utilizes a cable suspension assembly in conjunction 
with a scissors linkage support assembly to provide seat vertical 
adjustability and suspension. The present invention employs, between the 
upper and lower housings, to vary the spacial relationship therebetween, 
at least one spring, a drive pulley mounted to the suspension linkage, and 
a cable operatively connecting the spring and drive pulley such that 
vertical movement of the upper housing is translated to rotational 
movement of the drive pulley and wherein the drive pulley and spring 
cooperate to provide seat suspension to a seat occupant. 
Operatively, rotatably attached to the front 95 of upper housing 90 is knob 
25 and threaded member 24 forming knob axis 26. Member 24 is rotatably 
disposed in placement rod 105. Rod 105 securely resides in a pair of 
notches 108 between teeth 109 of rack 112. As can be seen from FIG. 4, rod 
105 can be moved into various pairs of notches 108 of rack 112 to vary the 
height of upper plate 90 while maintaining the same spring tension, and 
suspension curve characteristics, of the seat suspension system. This is 
accomplished by lifting rod 105 out of the notches 108 in which it is then 
placed, and placing it into another set of notches 108. Attached to member 
24 rearwardly from rod 105 is laterally extending front spring bar 27. 
Rearward of front spring bar 27, upper housing 90 includes a slot 30 which 
houses guide 31. Depending from guide 31 is rear spring bar 32. Extending 
between rear spring bar 32 and front spring bar 27 along either side of 
knob axis 26 are springs 28 and 29. Cable 45 extends rearward from rear 
spring bar 32 to pulley wheel 41 which is secured to upper housing 90. 
(See FIG. 2). 
Cable 45 extends around and down from wheel 41 to drive pulley 37 and is 
fixedly secured thereto. Drive pulley 37 is an integral part of axle 
housing 62 between linkage arms 72, 73 and has around its arcuate 
perimeter an annular cable-receiving recess 42. Drive pulley 37 can be 
substantially semi-circular (as shown in the FIG. 1) with its flat edge 
substantially along the line defined by linkage arms 72, 73 and its 
arcuate periphery extending upwardly therefrom (Of course, drive pulley 37 
may also form a circular pulley or other shapes as described below). Thus, 
as is shown in FIG. 2, cable 45 travels the path between points A and J. 
As illustrated in FIG. 3, suspension assembly 15 works to provide seat 
suspension and vertical adjustability in the following manner. When upper 
housing 90 is in its lowermost position, linkage arms 72, 73 and 75, 76 
are substantially horizontal, angle 8 being minimized. (FIG. 3A) As such, 
the path defined by the length of springs 28, 29 and cable 45 in the path 
extending over pulley wheel 41 to and substantially around drive pulley 37 
is maximized. This position results when knob 25 is rotated to place front 
spring bar 27 in its most rearward position thus allowing cable 45 to 
extend fully through the path from point A to point J. As knob 25 is 
rotated, causing front spring bar 27 to be moved forward, springs 28, 29 
are pulled forward causing rear spring bar 32 to be pulled forward. (FIG. 
3B) Causing rear spring bar 32 to be pulled forward pulls cable 45 
forward. Pulling cable 45 forward creates an upward rotational force on 
drive pulley 37 which causes linkage arms 72, 73 to rise. Raising linkage 
arms 72, 73 operates to actuate the scissors linkage support assembly to 
raise upper housing 90. Continuing to similarly operate knob 25 continues 
to cause upper housing 90 to be raised. (FIGS. 3B, 3C) Operating knob 25 
in the opposite direction causes front spring bar 27 to move toward rear 
spring bar 32 which allows upper housing 90 to descend. (FIGS. 3C, 3D) 
It will, thus, be appreciated that, as knob 25 is actuated to pull cable 45 
forward, angle .THETA. will increase. As this occurs, drive pulley 37 
rotates in a clockwise direction as depicted in FIG. 3. As drive pulley 37 
rotates with linkage arms 72, 73, displacement of cable 45 between pulley 
wheel 41 and drive pulley 37 varies. Operating knob 25 thus works to 
rotate point J of drive pulley 37 upward and toward pulley wheel 41 which 
causes linkage axle housing 62 and linkage members 72, 73 and 75, 76 to be 
raised. 
Springs 28, 29 in conjunction with cable 45, pulley wheel 41, and drive 
pulley 37 provide suspension for the seat occupant as the seat is adjusted 
vertically. Springs 28, 29 provide equal and adequate tension to cable 45 
to provide a range of comfortable suspension for a seat occupant. Springs 
28, 29 offer the most adequate suspension support when the vertical 
deflection distance is linearly related to the force exerted on the 
suspension, as shown in curve A in FIG. 4. As will be appreciated by those 
of ordinary skill in the art, springs 28, 29 may be varied to provide 
differing tension strengths and length to provide a suspension assembly 
for varying seat heights and weights. Similarly, the radius and location 
of pulley wheel 41 and drive pulley 37 can be varied to provide suspension 
systems of variable height and weight adjustment parameters. Additionally, 
it is highly preferable to achieving the force/deflection linear 
relationship to use springs 28, 29 which have a 3:1 spring stretch to 
suspension travel ratio. 
It will also be appreciated from the foregoing description and FIGURES that 
pulley wheel 41 may be manufactured of inexpensive materials such as 
plastic. This is so because cable 45 is generally contacting approximately 
180.degree. or more of pulley wheel 41. (FIG. 3) As such, the loads 
associated with the suspension are well-dispersed along a substantial 
length of the circumferential surface of pulley wheel 41. This allows 
wheel 41 to be constructed of material less expensive than the hardened 
metal surfaces of prior art suspension devices. 
In another preferred embodiment, as best seen in FIG. 4, upper housing 90 
is vertically adjustable relative to lower housing 80 independently of 
spring adjustment. The height of upper housing 90 is adjustable to various 
discreet positions via knob bar 105 as described above. In this 
embodiment, the height of upper housing 90 can be adjusted to multiple 
positions, and ride characteristics can be adjusted via knob 25 and 
springs 28, 29 as described above. 
In another preferred embodiment, as best seen in FIGS. 3A-3D, a device is 
provided which allows suspension adjustment positions within a given range 
of seat height. In this embodiment, drive pulley 37 is rotatably affixed 
to linkage axle housing 62. A threaded pin 130 is rotatably disposed in 
pulley 37 extending transversely therefrom. Pin 130 has a threaded 
aperture in which is disposed a bolt 133 extending parallel to linkage 
arms 72, 73 to knob 135. Knob is rotatably secured to arm 72, 73 by 
bracket 140. Bracket 140 is secured to arm 72, 73. Rotating knob 135 
rotates pulley 37 which draws or releases cable 45, thereby raising or 
lowering upper housing 90. Thus, within the given range of movement knob 
135 and bolt 133 can impart to drive pulley 37, the height of upper 
housing 90 is infinitely adjustable. 
In another preferred embodiment, as best seen in FIG. 4, a vehicle seat 
suspension is provided which provides adjustable, non-liner 
force/deflection curve characteristics, as best seen in FIG. 5, which 
provides a representation of desirable force/deflection curve 
characteristics. In this embodiment, drive pulley 37 is radially movable 
relative to linkage axle 61 substantially only along a line defined by 
linkage arms 72, 73 because drive pulley 37 has an elongated slot therein 
in which axle 61 resides. Axle 61 preferably, where it passes through the 
slot, is flat-sided so that drive pulley 37 is slidable along axle 61 but 
is not rotatable about axle 61. Drive pulley 37 is slidable along the slot 
such that the center of pulley 37 can be eccentric to axle 61. An 
adjustment mechanism 140 as seen in FIG. 4, and similar to that described 
above, is provided to slidably adjust drive pulley 37. As seen, mechanism 
140 includes bracket 141 secured to link arms 72, 73, knob 145 and pulley 
arms 143, 144 connected to drive pulley 37. Arms 143, 144 are 
substantially parallel to the slot in drive pulley 37 and linkage arms 72, 
73, so that when knob 145 is rotated, pulley 37 slides along a line 
parallel to linkage arms 72, 73. In an eccentric position as best seen in 
FIG. 4, it will be appreciated that as upper housing descends, 
increasingly more cable 45 is drawn by the surface of drive pulley 37, 
thus increasing suspension force provided by springs 28, 29 as upper 
housing 90 reaches lower levels. This is shown graphically in FIG. 5 by 
curves B, C and D. This becomes important when upper housing 90 reaches 
its lowermost position because it tends to prevent upper housing 90 from 
contacting lower housing 80 which would eliminate all suspension 
capabilities of the seat. 
A similar force/deflection curve may be obtainable by using a drive pulley 
37 which is spiral shaped. It will therefore be appreciated that the drive 
pulley 31 can take on any of the very many non-circular shapes available 
to achieve a consistent, predetermined suspension curve. In this 
embodiment, the drive pulley 37 can also be radially slidably, mounted to 
axle 61 to provide a variable, non-linear suspension curve or can be 
fixed. 
Of course, it should be understood that various changes and modifications 
to the preferred embodiments described herein will be apparent to those 
skilled in the art. Other changes and modifications, such as those 
expressed here or others left unexpressed but apparent to those of 
ordinary skill in the art, can be made without departing from the spirit 
and scope of the present invention and without diminishing its attendant 
advantages. It is, therefore, intended that such changes and modifications 
be covered by the following claims.