Pivotal adjustment mechanism

A pivotal adjustment mechanism is disclosed for connection to two mutually movable members. More particularly, an adjustment mechanism is disclosed providing torsionally restricted motion in all axes. The composite structure includes a plurality of tubes and torsion bar components interconnected to transmit forces between the movable members. The torsional forces are transmitted through a circuitous path for maximizing restraint in a device of compact size.

BACKGROUND OF THE INVENTION 
The subject invention relates to a new and improved pivotal adjustment 
mechanism for the connection between two mutually movable members. More 
particularly, a pivotal adjustment mechanism is disclosed, particularly 
adapted to interconnect the seat and base portion of a chair. 
In the prior art, a variety of adjustment mechanisms have been developed 
for use with chairs. Initially, adjustment mechanism for office type 
chairs were limited to tilt back devices which restrain the pivoting 
movement of the seat in the rearward direction in response to a user 
leaning backwards. More recently, there have been developed more 
sophisticated mechanisms which permit the user to lean in any axis, 
thereby providing greater support and comfort. These mechanisms also 
provide torsional restraint in all axes of movement. Such prior art 
devices are typically used in office type chairs. However, other 
applications are possible, such as in a boat, enabling a user to sit 
relatively quietly in place, during a swell, in a desired horizontal 
position, while the base of the chair shifts in heavy seas. Similarly, 
advantages are obtained in road vehicles when driving on uneven ground. 
One example of a pivotal adjustment mechanism known in the prior art can be 
found in U.S. Pat. No. 4,185,803, issued Jan. 29, 1980, to Kalvatn. The 
mechanism in Kalvatn includes a pair of concentric rings which are 
interconnected, and having a pair of torsion bars individually connected 
to each ring. The device in Kalvatn is effective to torsionally restrain 
the movement of a chair in all axes of motion. However, the Kalvatn device 
requires relatively large diameter rings to achieve a high level of 
torsional restraint. Accordingly it would be desirable to provide a new 
and improved pivotal adjustment mechanism providing torsional restraint in 
all axes while being compact and having a low profile. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the subject invention to provide a new and 
improved pivotal adjustment mechanism for connection between two mutually 
movable members. 
It is another object of the subject invention to provide a new and improved 
pivotal adjustment mechanism which achieves torsional restraint in all 
axes of motion. 
It is a further object of the subject invention to provide a new and 
improved pivotal adjustment mechanism which achieves high torsional 
restraint in a compact package having a low profile. 
In accordance with these and many other objects, the subject invention 
provides a new and improved pivotal adjustment mechanism particularly 
adapted to interconnect the seat of a chair with a pedestal or base. More 
particularly, an adjustment mechanism is disclosed which includes a 
support means connected to the pedestal and having a pair of spaced apart 
aligned upstanding braces, each brace having an aperature formed therein. 
The adjustment mechanism further includes a tubular structure defined by 
first and second hollow tubes. The tubes are disposed at right angles, to 
define a cross-shaped configuration in plan, and are fixably secured at 
their intersection. The tubular structure is mounted on the support means 
with the intersection thereof being disposed between the upstanding braces 
in a manner such that the opposed ends of the first tube are rotatably 
received through the aligned aperatures of the braces. 
A first tube segment is provided which extends outwardly away from one of 
the two braces in longitudinal alignment with the first tube. The first 
tube segment is fixably secured to the brace. In addition, the first tube 
segment is rotatably mounted with respect to the first tube. A first 
torsion bar is provided which extends longitudinally within the first 
tubes, with one end thereof being affixed to the free distal end of the 
first tube segment. The other end of the torsion bar is affixed to the 
remaining opposed end of the first tube. 
A second tube segment is rotatably mounted to one end of the second tube, 
in longitudinal alignment therewith. A second torsion bar is provided 
which longitudinally extends within the second tubes. One end of the 
torsion bar is affixed to the free end of the second tube segment and the 
other end thereof is affixed to the remaining free end of the second tube. 
The subject mechanism further includes a first bracket member fixably 
connected to the second tube segment and extending perpendicularly 
thereto. A second bracket member is rotatably mounted to the second tube 
adjacent the free end thereof, and parallel to the first bracket member. 
Both the bracket members may be fixably secured to the seat portion of the 
chair. 
Any relative motion between the seat portion and the base is transmitted 
through the mechanism and restrained by the torsion bars. For example, 
motion having a force component causing a rotational torque to be placed 
on the first bracket member is transmitted along a path defined by the 
connection between the second tube segment, along the second torsion bar 
and through the second tube to the intersection of the tubular structure. 
Similarly, side to side swaying motions generate a force component which 
is transmitted through the intersection of the support members into the 
first tube, along the first torsion bar, through the first tube segment 
and to the support means. As can be appreciated, the long circuitous paths 
of force transmission enhances the torsional restraining capabilities of 
the subject mechanism and permits construction of an operable device in a 
package of reduced dimensions. 
Further objects and advantages of the subject invention will become 
apparent from the following detailed description, taken in conjunction 
with the drawings in which:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1 through 3, there is illustrated the new and improved 
pivotal adjustment mechanism 10 of the subject invention. The adjustment 
mechanism 10 is intended to be connected between two members to permit 
movement therebetween in all directional axes. The subject mechanism is 
also tensioned to torsionally restrain extreme movements. The subject 
mechanism is particularly adapted for use with chairs. As illustrated in 
FIGS. 1 and 3, the mechanism 10 can be connected between a chair base 12 
and a seat 14 (shown in phantom). 
Mechanism 10 includes a support means defined by plate 20, which is 
connectable to the pedestal or base 12 of the chair. The connection can be 
made, for example, by using a tapered bushing 22 which is welded to the 
lower surface of support means 20. The bushing 22 is receivable over a 
conical tip 24 of the pedestal 12. Plate 20 is provided with a pair of 
spaced apart, aligned, upstanding braces 26 and 28. Each brace 26, 28 is 
provided with an aperature 30 and 32, respectively which are disposed in 
longitudinal alignment. 
The subject mechanism further includes a tubular structure, shown generally 
at 40, which is defined by first and second hollow tubes 42 and 44, 
respectively. Tubes 42 and 44 are disposed at right angles to define a 
cross-shaped configuration in plan, as illustrated in FIG. 2. Tubes 42 and 
44 are fixably connected at their intersection via clamp 46. Clamp 46 acts 
as a guide for supporting the members during assembly. Tubes 42, 44 are 
welded to clamp 46 along weld joints 50, as illustrated in FIG. 2. 
In the preferred embodiment of the subject invention, tubes 42 and 44 are 
provided with complimentary, eliptical cutouts 52 and 54. In the assembled 
condition, cutouts 52 and 54 enable the tubes to be interlocked. The 
interlocking of the tubes reduces the profile height of the tube structure 
40, as illustrated in FIG. 3, such that the mechanism 10 may be more 
readily mounted to the chair. 
Tubular structure 40 is mounted to the support plate 20 with the center 
clamp 46 being disposed between the upstanding braces 26 and 28. In 
addition, and as illustrated in FIGS. 2 and 3, the opposed ends of the 
first tube are rotatably received in the aligned aperatures 30 and 32 of 
the braces. The rotatable mounting can be enhanced by utilizing a pair of 
bushings 56 and 58. 
The subject mechanism 10 is further provided with a first tube segment 60 
which extends outwardly from one brace 26, in longitudinal alignment with 
first tube 42. First tube segment 60 is fixably secured to brace 26 by 
weld joint 62. In the illustrated embodiment, the diameter of tube segment 
60 is equal to the diameter of first tube 42. Accordingly, first tube 42 
must terminate at rotatable bushing 56. In an alternative embodiment of 
the subject mechanism (not shown), first tube 42 is rotatably and 
telescopingly received within first tube segment 60. In the latter 
embodiment, the first tube segment is formed with a larger diameter than 
the first tube. In this configuration, the first tube will extend beyond 
brace 26, and be received within the first tube segment. While the latter 
construction enhances the torsional capabilities of the mechanism, 
fabrication of the device is facilitated by configuring the tubes with 
equal diameters, as in the illustrated embodiment. 
A first torsion bar 64 is provided and extends longitudinally within the 
first tube 42 and first tube segment 60. One end of first torsion bar 64 
is affixed to the free end 66 of the first tube segment 60. The opposed 
end of torsion bar 60 is affixed to the free end 68 of the first tube 42. 
To facilitate the interconnection of the torsion bar, a pair of plugs 72 
and 74 can be welded into the ends of the first tube and first tube 
segment, respectively. When the torsion bar 64 is constructed with a 
square cross-sectional configuration, each plug 72, 74 is provided with a 
square aperature for fixably receiving the ends of the torsion bar. 
The interconnections described above define a circuitous path for the 
transmission of forces generated by movement in one direction, between 
members 12 and 14. For example, and as described more fully hereinbelow, 
side to side shifting of the pedestal 12 is transmitted to the plate 20 
and to the first tube segment 60 through the fixed connection between the 
segment and brace 26. Torsional forces generated by the shifting are 
transmitted outwardly along first tube segment 60 and transferred to the 
end of first torsion bar 64. The force is then transmitted along first 
torsion bar 64 and transferred to the opposed end 68 of first tube 42. 
Finally, the force is transmitted back along the first tube 42 to the 
center clamp 46. The shifting movement is torsionally restrained by all 
the elements along the path. 
In accordance with the subject invention, a second tube segment 80 is 
rotatably mounted to one end of the second tube 44, in longitudinal 
alignment therewith. In the illustrated embodiment, the rotational 
connection is established utilizing a support bearing 82, as illustrated 
in FIG. 2. The support bearing 82 is utilized when the diameters of the 
second tube 44 and the second tube segment 80 are equal. In an alternative 
embodiment (not shown), the diameter of second tube segment 80 is enlarged 
such that the end of second tube 44 can be telescopingly and rotatably 
received therein. However, as discussed above, by providing tubes with 
equal diameters, fabrication of the device is facilitated. 
A second torsion bar 86 is provided and longitudinally extends within 
second tube 44 and second tube segment 80. One end of torsion bar 86 is 
fixably connected to the free end 88 of the second tube 44. The opposed 
end of the torsion bar is fixably connected to the distal end 90 of the 
second tube segment. Similar to the interconnection of the first torsion 
bar, a pair of plugs 92 and 94 may be welded within the respective tubes 
to facilitate the fixed connection. 
A first bracket member 96 is fixably connected to the second tube segment 
80 and extends perpendicularly thereto. Bracket 96 may be formed 
integrally with the second tube segment or welded thereto as illustrated 
at 98 in FIG. 2. A second bracket 100 is rotatably mounted around second 
tube 44, in parallel relationship to the first bracket 96. Bracket 100 is 
provided with an aperature 102 for receiving a bearing 104 to facilitate 
rotation. Brackets 96 and 100 are intended to be fixably secured to the 
second movable member 14. 
The latter described construction defines a second circuitous force path 
for transmitting forces generated by movement between the members 12, 14 
in a second direction. As described more fully below, front to back 
shifting of bracket 96 is transmitted to second tube segment 90 and along 
torsion bar 96. These forces are then transmitted to second tube 44 and 
into clamp 46. Similar to the first path, the shifting movement is 
torsionally restrained by all the elements in the path. 
As discussed above, the subject mechanism 10 is particularly adapted for 
use with a chair in environments where tilting will occur between the seat 
14 and the base 12. For example, in an office situation, a user will lean 
in various directions in the chair, causing the seat to tilt relative to 
the base. As can be appreciated, relative movement about a pivotal joint 
can be broken down into a composite of two directional vector components, 
extending perpendicularly to one another, as indicated by the Arrows A and 
B in FIGS. 2 and 3. Accordingly, the torsional restraining features of the 
subject mechanism 10 can be explained with reference to these two 
perpendicular axes. It is to be understood however, that any tilting force 
at an angle not aligned with the perpendicular force arrows is merely a 
composite of the two motions. 
Accordingly, if the user in the seat leans in either a forward or backward 
direction, rotatable second bracket 100 will move freely with respect to 
the mechanism 10, in a direction indicated by arrows A.sub.1 in FIG. 3. In 
contrast, the tilting motion in this direction will be imparted as a 
rotational torque to the second tube segment 80 through fixably connected 
first bracket 96. As described above, the rotational torque will be 
transmitted from the end 90 of second tube segment 80 into the torsion bar 
86. The forces are then transferred from torsion bar 86 to second tube 44 
and into the center clamp 146. Because the tubular structure 40 is mounted 
in the braces 26 and 28 of plate 20, forces initially imparted to bracket 
96, in the direction of Arrows A.sub.1, are then transmitted to base 12. 
Accordingly, any movement in the direction of Arrows A.sub.1 is 
torsionally restrained by the combination of torsion bar 86, second tube 
44 and second tube segment 80. The amount of torsional restraint can of 
course be regulated by adjusting the length and stiffness of the 
components. 
Movement of seat 14 in a side to side direction, relative to base 12, will 
cause the ends C of second tube and second tube segment to move either up 
or down as indicated by Arrows B.sub.1 in FIG. 3. Since the tubes 42, 44 
are fixedly connected to each other and first tube 42 is rotatably mounted 
in braces 26 and 28 of plate 20, movement in this direction will result in 
the rotation of first tube 42, in the direction of Arrows B.sub.2, in FIG. 
3. This rotational movement is transmitted to the end 68 of first tube 42 
and transferred to torsion bar 64. Torsion bar 64 transmits the force to 
the first tube segment 60 where the force is transferred to brace 26 via 
the fixed connection between the latter elements. Rotational forces on 
brace 26 are imparted to plate 20 and into pedestal 12 of the chair. Thus, 
movement in the side to side direction is torsionally restrained by a 
combination of the first tube 42, torsion bar 64 and first tube segment 
60. As stated above, any tilting in a intermediate direction will be 
torsionally restricted in both axes in accordance with the distribution of 
the component force vectors. As can be appreciated, when the subject 
mechanism 10 is used in a situation such as a boat, where the base shifts, 
the forces are transmitted through identical paths in the reverse order. 
In summary, there is provided a new and improved pivotal adjustment 
mechanism 10 for use with movable members. More particularly, an 
adjustment mechanism is disclosed having a support means 20 fixably 
connected to one of the two mutually movable members. Support means 20 
includes a pair of spaced apart, aligned, upstanding braces 26 and 28, 
each brace having an aperature therein. The adjustment mechanism further 
includes a tubular structure 40 defined by first and second hollow tubes 
42 and 44, respectively. The hollow tubes are disposed at right angles to 
define a cross-shaped configuration in plan and are fixably secured at 
their intersection. Tubular structure 40 is mounted on support means 20, 
with the intersection thereof being disposed between the upstanding braces 
and with the opposed ends of the first tube 42 being rotatably received 
through the aligned aperatures in the braces. A first tube segment 60 
extends outwardly away from one brace 26, in longitudinal alignment with 
the first tube and is fixably secured to the brace. The first tube is 
rotatably mounted with respect to the first tube segment. A first torsion 
bar 64 extends longitudinally within the first tube and first tube segment 
with one end thereof being affixed to the free end of the first tube 
segment and with the other end being affixed to the remaining opposed end 
of the first tube. A second tube segment 80 is rotatably mounted to one 
end of the second tube 44, in longitudinal alignment therewith. A second 
torsion bar 86 longitudinally extends within the second tube and second 
tube segment. One end of torsion bar 86 is affixed to the remaining free 
end of the second tube while the opposed end of the torsion bar 86 is 
connected to the distal end of the second tube segment. A first bracket 
member 96 is fixably connected to the second tube segment 80 and extends 
perpendicularly thereto. A second bracket member 100 is rotatably mounted 
to the second tube, adjacent the free end thereof, in parallel relation to 
the first bracket member. The first and second bracket members are fixably 
connected to the remaining movable member. By this arrangement, relative 
motion between the movable members is transmitted through the mechanism 
and is torsionally restrained by the component parts. 
While the subject invention has been described with reference to a 
preferred embodiment, it is to be understood that various modifications 
and changes could be made therein, by one skilled in the art, without 
varying from the scope and spirit of the subject invention as defined by 
the appended claims. For example, and as discussed above, first and second 
tubes 42 and 44 may be configured to be telescopingly and rotatably 
received within the associated tube segments.