U.S. patent number 3,788,586 [Application Number 04/884,413] was granted by the patent office on 1974-01-29 for torsion rod chair iron.
This patent grant is currently assigned to Steelcase Inc.. Invention is credited to Donald E. McNally.
United States Patent |
3,788,586 |
McNally |
January 29, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
TORSION ROD CHAIR IRON
Abstract
A torsion bar chair iron in which a tubular housing member of
rectangular cross section is secured to the spindle of a chair
base. The spindle passes laterally through the tubular housing and
is secured at the top and bottom thereof. A torsion bar passes
longitudinally through the housing member, passing adjacent the
spindle. It is fixed in one end of the housing but is rotatable in
the other end thereof. At the rotatable end, outside of the
housing, a lever is fixedly secured to the torsion bar. Chair
support members are rotatably secured to the ends of the torsion
bar and a chair is secured to the chair support members.
Inventors: |
McNally; Donald E. (Grand
Rapids, MI) |
Assignee: |
Steelcase Inc. (Grand Rapids,
MI)
|
Family
ID: |
25384573 |
Appl.
No.: |
04/884,413 |
Filed: |
December 12, 1969 |
Current U.S.
Class: |
248/575;
297/302.3; 297/303.3; 297/302.5; 248/608; 248/596 |
Current CPC
Class: |
A47C
7/445 (20130101); A47C 7/441 (20130101); A47C
3/026 (20130101); A47C 7/4454 (20180801) |
Current International
Class: |
A47C
3/02 (20060101); A47C 3/026 (20060101); A47c
003/023 () |
Field of
Search: |
;248/373,374,378,389
;297/303,304,306,333 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Parsons, Jr.; Marion
Attorney, Agent or Firm: Price, Heneveld, Huizenga &
Cooper
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows.
1. In a chair having a spindle, a torsion bar chair iron
comprising: an elongated rigid housing member secured to said chair
spindle, said housing member comprising a bottom, a first end and a
second end; said spindle being mounted directly to said bottom of
said housing member; a torsion bar being mounted in said housing
member, offset from the axis of said spindle; said housing member
and said torsion bar being of comparable length; said torsion bar
passing through said first end of said housing member and being
fixed thereto; said torsion bar passing through said second end of
said housing member and being rotatable with respect thereto; lever
means being operatively connected to said torsion bar and being
fixed thereto; chair support means being operably connected to said
housing member and being rotatable with respect thereto; said chair
support means operably engaging said lever means when said chair is
tilted.
2. In a chair having a spindle, a torsion bar chair iron
comprising: an elongated rigid housing member secured to said chair
spindle, said housing member comprising a top, a bottom, a first
end and a second end; said top and bottom having longitudinal side
edges; means rigidly interconnecting said side edges; said spindle
passing through said housing and being rigidly secured to said top
and said bottom; a torsion bar having a first end and a second end
being mounted in said housing, and being offset from said spindle
passing through said housing; said torsion bar and said housing
being of comparable length; said first end of said torsion bar
being operably connected to said first end of said housing member
and being in fixed rotational relationship thereto; said second end
of said torsion bar being operably connected to said second end of
said housing member and being rotatable with respect thereto; lever
means being operably connected to said torsion bar and being in
fixed rotational relationship thereto; chair support means being
operably connected to said housing member and being rotatable with
respect thereto; said chair support means operably engaging said
lever means when said chair is tilted.
3. The chair iron of claim 3 which also comprises said lever being
secured to said second end of said torsion bar to the outside of
said second end of said housing member.
4. The chair iron of claim 2 wherein said top, bottom and means
interconnecting said side edges thereof define a solid wall tubular
member, of rectilinear lateral cross section.
5. The chair iron of claim 4 which also comprises: said chair
support means being rotatably mounted on said torsion bar.
6. A chair control adapted to be carried by a post for use with an
office-type chair utilizing spider arms for carrying a seat and
back, the improvement comprising a support body having top and
bottom walls integrally interconnected with each other, and end
plate fixed to each end of said top and bottom walls, a torsion bar
intermediate said top and bottom walls, means for securing said
torsion bar adjacent one end in nonrotatable relationship to one of
said end plates, means adjacent the other end plate for securing
one of said spiders in nonrotatable relationship to said torsion
bar adjacent the end of said torsion bar opposite said one end, and
a post support member engaging both said top and bottom walls for
securing said post along an axis displaced from the axis of said
torsion bar to enable said support body to resist stress at two
spaced positions adjacent said bar axis.
7. The improvement claimed in claim 6 in which said means securing
said torsion bar to said one plate includes a boss on said plate
extending along the axis of said bar and defining a passageway
having a cross section and dimension corresponding to said bar to
prevent rotation of said bar in said passageway.
Description
BACKGROUND OF THE INVENTION
This invention relates to a torsion bar chair iron.
There are basically two types of chair irons, coil spring and
torsion bar. From an economic standpoint, torsion bar chair irons
are somewhat more desirable since they can be more simply
constructed.
One of the most economical and popular torsion bar chair iron
constructions is that comprising a longitudinal housing for the
torsion bar with the chair spindle being secured to the bottom
thereof. The housing is generally a flat dish-like construction in
which the torsion bar is fixed at one end but freely rotatable at
the other. A fairly long torsion bar must be used in order to
obtain the requisit amount of flexibility. Thus, the housing in
such a construction must correspondingly be quite long. When the
chair mounted on such an iron is tilted backwards, considerable
force is put on the housing member about the mounting between the
stationary spindle and the housing with the result that
considerable distortion or warpage takes place in the housing. This
distortion is a detriment both to the durability and to the safety
of the chair iron.
As an example, I have discovered one chair mounted on one such
chair iron will tilt through 18.degree. to its stops when a minimum
of tilting force is applied. If a person sits in the chair and
tilts it backwards, it will tilt through 22.degree. to its stops
simply because of the distortion that takes place in the chair
iron. Eventually, this distortion will become permanent and the
chair will begin to tip even farther backwards. It is even possible
that warpage in the chair iron housing will allow sufficient
tilting that the torsion bar will snap and the person sitting in
the chair will go over backwards.
In order to aid large scale purchasers in avoiding such undesirable
torsion bar chair irons, Buyers Laboratories, Inc. has devised
tests which are standard in the office furniture industry. They
apply 300 pounds of pull at the top of the back of a chair and if
the chair "sets" one-quarter of an inch or more, it fails the test.
The torsion bar chair iron discussed above fails this test and,
hence, is generally undesirable to the consumers and manufacturers
of office furniture.
One obvious way to avoid warpage in the long torsion bar housing
member is to secure the spindle of the chair base to a separate
member or housing rather than to the same member in which the
torsion bar is housed. However, this eliminates the simplicity and
economy and, hence, the general desirability of a torsion bar chair
iron and does not provide an acceptable solution to the
problem.
This invention is a torsion bar chair iron for a chair having a
spindle type base. It comprises a rigid housing member secured to
the chair spindle, with the housing member comprising a top, a
bottom, a first end and a second end. The spindle extends through
and is rigidly secured to the bottom and the top of the housing
member. A torsion bar is mounted in the housing member such that
its longitudinal axis does not intersect the vertical axis of the
spindle. It passes through the first end of the housing member and
is in fixed rotational relationship thereto. It also passes through
the second end of the housing member but is rotatable with respect
thereto. A lever means is operably connected to the torsion bar and
is in fixed rotational relationship to it. Finally, chair support
means are operably connected to the housing member and are freely
rotatable with respect thereto, such that the chair support means
operably engage the lever means when the chair is tilted.
This chair iron provides a simple and economical construction
wherein no special spindle housing or fixture is necessary as an
addition to that member which houses the torsion bar. At the same
time, the unique arrangement of the spindle and the torsion bar in
the unique housing structure provides a chair iron which is
sufficiently strong and which uniquely distributes the loads
applied to the housing and tilting that this chair iron will pass
the BLI torsion bar chair iron tests. Distortion and warpage of the
chair iron housing are substantially eliminated. The danger of
snapping a torsion bar because of distortion in the housing is
substantially eliminated. Even if a bar should snap, the tubular
shaped housing constitutes an important safety feature by
containing any flying bar fragments which might otherwise prove
injurious. Finally, these ends are achieved by using a single
housing structure to which and in which both the chair spindle and
the torsion bar are mounted.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and advantages of the invention can be seen
by reference to the preferred embodiment and appended drawings
wherein:
FIG. 1 is a perspective view of the chair iron mounted on a chair
spindle with a portion of the housing member being broken away;
FIG. 2 is a bottom plan view of the chair iron;
FIG. 3 is a cross section taken along III--III of FIG. 1;
FIG. 4 is a cross section taken along IV--IV of FIG. 1.
PREFERRED EMBODIMENT OF THE INVENTION
The torsion bar chair iron 1 is designed for mounting atop a
spindle 2 and comprises the following basic members: housing member
10, torsion bar or rod 30 and chair support members 40a and 40b
(FIG. 1).
Housing 10 comprises a tubular member of rectangular cross section
defining top 11, bottom 12 and sides 13 (FIGS. 3 and 4), which is
sealed off by first end 14 and second end 15 being welded to the
ends of tubular housing member 10 (FIG. 2). It is preferably made
of cold roll steel about 0.180 inches thick.
Approximately equidistant between first end 14 and second end 15,
but offset from the lateral center of tubular housing 10, are
parallel apertures 16 and 17 in the bottom 12 and top 11 of housing
10, respectively (FIG. 1). Spindle 2 is of a narrower diameter at
its top 3 such that the latter passes through apertures 16 and 17
while the rest of spindle 2 does not (FIGS. 1, 3 and 4). It is
securely fastened in place in these apertures.
In first end 14, there is a square aperture 18 which bevels
inwardly (FIGS. 2 and 3). Second end 15 has a round aperture 19
(FIGS. 2 and 4) which is opposite square aperture 18.
First end 14 is slightly longer than second end 15 and extends
rearwardly of housing 10 to form chair stop 20 (FIG. 3) which
limits the extent to which a chair can be tilted backwardly with
this chair iron 1. Both first and second ends 14 and 15 define
forward stops 21 (FIGS. 3 and 4) which limit the extent to which
the chair can be tilted forward.
Torsion rod 30 is generally of a square cross section (FIGS. 3 and
4) and extends through and snugly fits in square aperture 18 in
first end (FIGS. 2 and 3). Hence, torsion rod 30 is maintained in
fixed rotational relationship with respect to first end 14. Torsion
rod 30 also passes through aperture 19 in second end 15 and is
rotatably mounted in that aperture by means of nylon bushing 31
which is slipped over the end of torsion rod 30 and which has a
flange such that it will not pass completely through aperture 19
(FIG. 2).
Lever 32 is operably connected to torsion rod 30 adjacent second
end 15 (FIG. 2). It has a square aperture corresponding roughly to
the square cross section of rod 30 and is passed over the end of
rod 30, thereby being maintained in fixed rotational relationship
with respect thereto (FIG. 2). Located in the end of lever 32 is an
adjusting screw 34 (FIGS. 1 and 4).
A chair support member 40a is a rotatably mounted on one end of
torsion rod 30 while a comparable support member 40b is designed
for rotatable mounting on the other end thereof. Each has a side 41
and a flat top 42 (FIG. 1). Each side 41 has a round aperture
defined by a metal bushing 44 which is rigidly secured to side 41
(FIG. 2). A nylon bushing 45 (only partially visible) having a
square aperture and being comparable to nylon bushing 31 is fitted
over each end of torsion rod 30 with its flange portion to the
inside and the metal bushing 44 of a chair support member 40a or
40b is slipped over nylon bushing 45 and rotates thereon. Nylon
washers 46 are then slipped over the end of torsion rod 30 and the
entire assembly is then locked in place by lock washers 48 which
are slipped over the ends of torsion rod 30 and snapped in place in
grooves in the ends of rod 30.
Finally, the tops 42 have holes thereon to which a seat can be
mounted (FIGS. 1 and 2).
OPERATION
As a chair which is mounted on members 40a and 40b is tilted
backwards, support members 40a and 40b rotate on the nylon bushings
at the ends of torsion rod 30. Support member 40b engages the end
of lever 32 or screw 34 and as it tilts backwardly, a force is
applied to the end of lever 32. In turn, a rotational force is
applied to torsion rod 30 since it and lever 32 are in fixed
rotational relativity. One end of torsion rod 30 is free to rotate
since it is rotatably mounted in second end 15 of housing 10. The
other end, however, is in fixed rotational relationship to first
end 14 of housing 10 which in turn is rigidly secured to spindle 2
which will not rotate about a horizontal axis. Thus, torsion rod 30
begins to twist. It is sufficiently flexible that it allows a chair
to be tilted backwardly when the person occupying the chair so
desires, but it is sufficiently stiff that it resists the tendency
of the chair to tilt backwardly on its own or when such tilting is
not desired.
The relative ease of difficulty with which a chair can be tilted,
i.e., the load or force necessary to cause it to tilt, can be
varied by turning adjustment screw 34. By turning the latter
upwardly, lever 32 is forced away from support member 40b and an
initial torque is applied to torsion rod 30. The farther adjustment
screw 34 is turned upwardly, the greater the initial torque implied
to torsion rod 30 and the greater the initial force required to
tilt a chair rearwardly. The adjustment of screw 34 downwardly
results in less initial tension in torsion rod 30.
The rearward tilting of a chair is stopped when support member 40a
contacts first end chair stop 20 and when support member 40b
contacts the edge housing 10. Second end 15 preferably does not
extend rearwardly of housing member 10 lest it interfere with the
action of lever 32. The extent of forward movement of the chair is
limited by forward stops 21 which are defined by both first end 14
and second end 15. Support member 40b does not sit squarely over
second end 15 as does support member 40a over first end 14 because
lever 32 and an additional nylon bushing 31 must be placed on that
end of torsion rod 30 which is operably connected to second end
15.
The tendency of housing member 10 to distort or warp is effectively
eliminated by a unique distribution of stresses. The rigid securing
of spindle 2 to top 11 and bottom 12, these being spaced apart from
each other and being rigid with respect to each other, effectively
distributes the stress between the two separated members.
Furthermore, the stress on each top and bottom member 11 and 12 has
been found to be less where those members are spaced farther apart.
Of course, there are practical design limitations on the extent to
which these two members can be separated. An inch to an inch and a
half has been found to be sufficient.
The distribution of stresses is further achieved by rigidly
interconnecting top and bottom members 11 and 12 along their
longitudinal side edges as well as at their ends. In the preferred
embodiment, this is achieved by using a tubular housing member 10,
in this case, of rectangular cross section. The side walls 13 of
the tubular member 10 act to give rigidity to housing 10 and
thereby resist the tendency of housing 10 to distort and warp.
The unique location of torsion rod 30 within housing 10 further
acts to distribute stresses therein. In the old torsion bar chair
ions of the unitary housing type, the torsion bar is located
directly over the mounting of the spindle in the housing such that
it intersects the vertical axis of the spindle. By arranging
torsion bar 30 such that it does not intersect the vertical axis of
spindle 2, less stress is placed on housing 10 in the area where
spindle 2 is secured to housing 10. These stresses can be further
decreased by further increasing the distance between torsion bar 30
and spindle 10. In the preferred embodiment, torsion rod 30 is
indeed set apart from spindle 2 rather than being set such that it
abuts spindle 2. As with varying the distances between top and
bottom members 11 and 12, there are practical design limitations on
the spacing between torsion rod 30 and spindle 2. It has been found
that even a spacing of 3/8 inches on the perpendicular between
torsion rod 30 and spindle 2 reduces the tendency of housing 10 to
"oil can," i.e. warp and distort.
The result of this invention is a simple but efficient torsion bar
chair iron. It can be easily and economically constructed.
Furthermore, it can be of a clean-cut and slim, trim design such
that it does not detract from the beauty of the chair on which it
is mounted. No bushing or other special structure is required to
operably secure the spindle to the torsion bar housing. The offset
arrangement of the spindle and torsion bar also facilitates the
removal of the spindle for field service purposes since it is more
readily accessible than are spindles which are mounted directly
below the torsion bar. On the other hand, because of the strength
achieved by its design and because of the distribution of stresses
achieved through its unique design, the housing of this torsion bar
chair iron will not warp and distort in operation or under the
conditions imposed by the Buyers Laboratories, Inc. tests for
torsion bar chair irons.
It is understood that the above is merely a preferred embodiment of
this invention and that a number of changes and alterations can be
made thereof without departing from the broader aspects and spirit
of the invention.
* * * * *