U.S. patent number 3,774,873 [Application Number 05/201,711] was granted by the patent office on 1973-11-27 for equipoised arm assembly.
This patent grant is currently assigned to JAC. Jacobsen A/S. Invention is credited to Jens Krogsrud.
United States Patent |
3,774,873 |
Krogsrud |
November 27, 1973 |
EQUIPOISED ARM ASSEMBLY
Abstract
An equipoised mechanism for supporting an object has a first set
of parallel arms pivotally mounted on a supporting bracket, a first
supported bracket pivotally connected to the first set of arms at
the ends thereof opposite the supporting bracket, a second set of
parallel arms pivotally mounted on the first supported bracket, and
a second supported bracket pivotally mounted at the ends of the
second set of parallel arms, opposite the first supported bracket,
to which a mounting assembly and supported object are attached. The
arms and brackets define two parallelograms by which the first and
second supported brackets are maintained in a predetermined
orientation with respect to the supporting bracket; balance and
equalization forces on the mechanism are provided by a pair of
springs operably connecting the first set of parallel arms and two
sets of parallel springs operably connecting the second set of
parallel arms.
Inventors: |
Krogsrud; Jens (Oslo,
NO) |
Assignee: |
JAC. Jacobsen A/S (Oslo,
NO)
|
Family
ID: |
22746976 |
Appl.
No.: |
05/201,711 |
Filed: |
November 24, 1971 |
Current U.S.
Class: |
248/586; 248/578;
248/324 |
Current CPC
Class: |
F16M
11/2014 (20130101); F16M 11/08 (20130101); A47G
29/00 (20130101); F16M 11/2092 (20130101); F21V
21/26 (20130101); F16M 13/02 (20130101); F16M
11/24 (20130101); F16M 2200/063 (20130101); F16M
2200/04 (20130101) |
Current International
Class: |
A47G
29/00 (20060101); F16M 11/02 (20060101); F16M
13/02 (20060101); F16M 11/04 (20060101); F21V
21/14 (20060101); F21V 21/26 (20060101); A47f
005/00 (); A47g 029/02 () |
Field of
Search: |
;248/123,280,160,292,324
;240/73BJ |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Foss; J. Franklin
Claims
1. In an equipoise mechanism of the character described, the
combination of, a first pair of parallel arms of substantially the
same length and comprising a first arm and a second arm, an
arm-supporting bracket assembly comprising an elongated pivot and
an arm-supporting bracket, first pivot means pivoting said first
and second arms of said arm-supporting bracket respectively upon a
first pair of parallel axes which are spaced from each other at a
predetermined distance axially with respect to said elongated
pivot, a first supported bracket which is positioned at the ends of
said first and second arms opposite said arm-supporting bracket,
second pivot means pivoting said first supported bracket
respectively upon a second pair of parallel axes which are spaced
from each other similarly to said first pair of parallel axes, a
second pair of parallel arms of substantially the same length and
comprising a third arm and a fourth arm, third pivot means pivoting
said third and fourth arms on said first supported bracket
respectively upon a third pair of parallel axes, a second supported
bracket which is positioned at the ends of said third and fourth
arms opposite said first supported bracket, fourth pivot means
pivoting said third and fourth arms on said second supported
bracket respectively upon a fourth pair of parallel axes spaced
similarly to said third pair of parallel axes, and a mounting
assembly attached to said second supported bracket for holding an
object, said arms and said brackets defining a linkage assembly
forming two variable parallelograms by which said first and second
supported brackets and said mounting assembly are maintained in a
predetermined relationship with respect to said elongated pivot
axis when said arms are moved; a spring connecting rod of shorter
length than said second arm located between said first and second
arms and pivotally mounted at one end about one axis associated
with said second pivot means, an adjustable spring operably
connected at one end to said first arm adjacent said arm-supporting
bracket and at its other end to said spring connecting rod at the
end of said rod opposite said second pivot means, a second spring
attached at one end to said first arm at a point between the ends
of said first arm and at its other end to a said spring connecting
rod at the end of said rod adjacent said second pivot means, a
first pair of coil springs positioned in parallel relationship upon
the upposite sides of said third and fourth arms with one end of
each of the first pair of parallel springs being attached to said
first supported bracket along an axis remote from said second and
third pairs of parallel axes and with the other end of each said
first pair of parallel springs attached to said fourth arm, a
second pair of springs positioned respectively upon the opposite
sides of said third and fourth arms and substantially parallel to
each other with one end of each of the second pair of parallel
springs being attached to said second supported bracket along an
axis remote from said fourth pair of parallel axes and with the
other end of each said second pair of parallel springs attached to
said third arm, said springs cooperating to provide balanced and
equalized forces at the pivots to counterbalance the weight of a
supported object.
2. A mechanism as described in claim 1, wherein said first arm has
a longitudinally extending recess therein and said second arm is
narrower than said first arm and fits within said recess to prevent
any external gap between said first and second arms at any position
of said linkage assembly.
3. A mechanism as described in claim 2, wherein said first and
second arms are generally U-shaped in cross-section and open
towards each other, and wherein the open side of said first arm
defines said recess receiving said second arm.
4. A mechanism as described in claim 1, wherein the axis at which
said first pair of springs are connected to said first supported
bracket and the axis at which said second pair of coil springs are
connected to said second supported bracket are located to provide a
point of maximum spring extension during rotation of said third and
fourth arms about their respective pivot axes on each side of which
the torque applied by the two pairs of springs is in opposite
directions.
5. A mechanism as described in claim 1, wherein the second and
third pivot means are positioned to permit folding of the linkage
assembly to a position wherein said fourth arm is adjacent to said
second arm.
6. In an equipoised object-supporting mechanism, the combination
of, a first pair of adjacent parallel arms of substantially equal
length and comprising a first arm and a second arm, an
arm-supporting bracket, first pivot means pivoting said first and
second arm at one end on said arm supporting bracket respectively
upon first and second parallel axes which are spaced a first
predetermined distance from each other, a first supported bracket
which is positioned at the end of said first and second arms
opposite said arm-supporting bracket, second pivot means pivoting
said first supporting bracket respectively upon third and fourth
parallel axes which are spaced said first predetermined distance
from each other, a second pair of adjacent parallel arms of
substantially equal length and comprising a third arm and a fourth
arm, third pivot means pivoting said third and fourth arms at one
end on said first supported bracket respectively upon fifth and
sixth parallel axes spaced a second predetermined distance from
each other, a second supported bracket which is positioned at the
end of said third and fourth arms opposite said first supported
bracket, fourth pivot means pivoting said third and fourth arms on
said second supported bracket respectively upon seventh and eighth
axes which are spaced said second predetermined distance from each
other, a mounting assembly attached to said second supported
bracket for holding an object, said arms and said brackets defining
a linkage assembly forming two variable parallelograms by which
said first and second supported brackets and said mounting assembly
are maintained within a predetermined range of relative
relationships with respect to said arm-supporting bracket when said
object is moved, an elongated connecting member positioned between
said first and second arms and extending along said second arm with
one end pivoted to said second arm at said fourth axis and with a
free end connecting portion positioned substantially intermediate
said first and fourth axes, a first counterbalance spring connected
at one end to said free-end connecting portion and at its other end
at said first axis, a second counterbalance spring connected at one
end to said first arm substantially intermediate said first and
third axes and connected at its other end to said connecting member
at a zone which is spaced radially from said fourth axis toward
said second arm, whereby said second spring tends to swing said
connecting member about said fourth axis toward the adjacent
portion of said second arm, said springs cooperating to urge said
arms toward each other and to provide counterbalancing forces, and
a plurality of springs each of which is connected at one end to one
of said supported brackets and at its other end to one of said
third and fourth arms, all of said springs cooperating to provide
counterbalancing forces for the support of said object.
7. The mechanism as described in claim 6 wherein said first and
second axes are positioned to swing said first and second arms
between first rest position wherein they extend substatially
vertically upwardly from said axes and are adjacent each other and
a second rest position wherein they extend substantially
horizontally and are separated from each other the maximum
distance, and wherein said springs and said arms cooperate to exert
forces which cooperate with the weight of said object to tend to
hold said arms in each of said rest positions.
8. In an equipoised object-supporting mechanism, the combination
of, a first pair of adjacent parallel arms of substantially equal
length and comprising a first arm and a second arm, an
arm-supporting bracket, first pivot means pivoting said first and
second arm at one end on said arm supporting bracket respectively
upon first and second parallel axes which are spaced a first
predetermined distance from each other, a first supported bracket
which is positioned at the end of said first and second arms
opposite said arm-supporting bracket, second pivot means pivoting
said first supporting bracket respectively upon third and fourth
parallel axes which are spaced said first predetermined distance
from each other, an elongated connecting member positioned between
said first and second arms and extending along said second arm with
one end pivoted to said second arm at said fourth axis and with a
free end connecting portion positioned substantially intermediate
said first and fourth axes, a first counterbalance spring connected
at one end to said free-end connecting portion and at its other end
at said first axis, and second counterbalance spring connected at
one end to said first arm substantially intermediate said first and
third axes and connected at its other end to said connecting member
at a zone which is spaced radially from said fourth axis toward
said second arm, whereby said second spring tends to swing said
connecting member about said fourth axis toward the adjacent
portion of said second arm, said springs cooperating to urge said
arms toward each other and to provide counterbalancing forces.
9. In an equipoised object-supporting mechanism, the combination of
an arm supporting bracket, a first pair of adjacent parallel arms
of substantially equal length and comprising a first and a second
arm, first pivot means pivoting said first and second arm at one
end on said arm supporting bracket respectively upon first and
second parallel axes, a first supported bracket positioned at the
ends of said first and second arms opposite said arm supporting
bracket, said second pivot means pivoting said first supporting
bracket respectively upon third and fourth parallel axes, a second
pair of adjacent parallel arms of substantially equal length and
comprising a third and a fourth arm, third pivot means pivoting
said third and fourth arms at one end on said first supported
bracket respectively upon fifth and sixth parallel axes, a second
supported bracket positioned at the end of said third and fourth
arms opposite said first supported bracket, fourth pivot means
pivoting said third and fourth arms on said second supported
bracket respectively upon seventh and eighth axes, said arms and
brackets defining a linkage assembly forming two variable
parallelograms, a first set of springs operatively connected
between said first and second arms in a generally parallel and
longitudinal spaced relationship with respect to each other, and at
least a second pair of spring operatively connected to said third
and fourth arms in parallel spaced relation with respect to each
other, one of said springs in said second pair being connected at
one end to said fourth arm and at its opposite end to said first
supported bracket at a point remote from said fifth and sixth axes
located to position said one spring from one side to the other of
said first axis as said third and fourth arms move through a
position wherein said fifth axis, said point remote from said fifth
axis, and the point of connection of said one spring to said fourth
arm all lie on a common straight line whereby said one spring acts
with an "overcenter effect" to reverse the restoring torque applied
to said third and fourth arms.
10. A mechanism as defined in claim 9 wherein the other of said
springs in said second pair is connected at one end to said third
arm and at its opposite end to said second supported bracket at a
point remote from said seventh and eighth axes located to position
said other spring from one side to the other of said eighth axes as
said third and fourth arms move through a position wherein said
eighth axis, said point remote from said seventh and eighth axes
and the point of connection between said other spring and said
third arm all lie in a common straight line whereby said other
spring also acts with an "overcenter effect" to reverse the
restoring torque applied to said third and fourth arms.
Description
This invention relates to equipoise support mechanisms, and more
particularly to an equipoise mechanism utilizing two sets of
parallel arms forming a linkage assembly having counterbalance
springs which provide an equilibrium or balance condition
throughout a range of movement of the arms for supporting unitary
objects such as lamps and small television sets.
An object of this invention is to provide improved counterbalance
and equipoising support mechanisms. A further object of the
invention is to support relatively heavy objects throughout a wide
range of movement with minimum variations in the balancing forces.
Another object of the invention is to support an object with great
precision and yet permit the object to be moved with relatively no
resistance forces. A still further object of the invention is to
support an object by an assembly which folds into a relatively
small space when not in use. A still further object is to provide
an equipoise support mechanism which is sturdy in construction,
dependable and safe in use, and which will perform satisfactorily
even after long periods of use. These and other objects will be in
part obvious and in part pointed out below.
According to an aspect of the invention, an object supporting
mechanism is provided in which two independent linkage assemblies,
each consisting of a set of parallel arms, maintain a supported
object in a fixed orientation as it is moved to various positions.
Springs associated with each set of arms are positioned so as to
develop forces drawing the two arms in each set together thereby
countering the force created by the weight of the supported object.
In one set of arms, the spring force exactly balances the torque
created by the weight of the supported object. The spring force in
the other set, however, balances the torque created by the combined
weights of the other set of parallel arms and the supported object.
As the arms are rotated about their respective pivots to a
horizontal position, the torque created by the supported object
increases. However, the restoring force created by the springs also
increases since the springs are stretched during arm rotation. This
increase in spring tension exactly balances the increase in torque
created by relocation of the supported object so that the net
torque about the arm pivots is maintained at zero. In order to
ensure proper folding of the mechanism into a small space when not
in use, separate pairs of pivot axes between the two sets of arms
are provided which are spaced so as to permit folding of the two
sets of arms to where they are adjacent. The connection points of
the springs are so located as to not only provide maximum
supporting torque when the mechanism is not in use, but also
provide a reversed torque for holding one set of arms in a folded
position when not in use.
Utilization of such an arrangement permits a wide area of possible
object location. One example of such use is for supporting
television sets in hospital rooms. Since each patient may be
required to lie in a different position than others, it is
important that the television set be locatable in many positions in
order to ensure proper viewing.
Since in the preferred embodiment of this invention relatively
strong springs may be used, it is important to provide some
additional safety feature. Safety is increased by utilizing an arm
construction which eliminates gaps between the two arms of one set.
Such construction also permits concealment of two of the springs
associated with this set.
In the drawings:
FIG. 1 is a side view of one embodiment of the invention;
FIG. 2 is a side view of a portion of the embodiment of FIG. 1,
moved to a second position;
FIG. 3 is a top plan view of the portion of the invention shown in
FIG. 2;
FIGS. 4 and 5 are sectional views respectively taken along lines
4--4 and 5--5 of FIG. 1; and
FIGS. 6, 7 and 8 are enlarged sectional views of the
interconnecting pivot structures for the arm assembly shown in FIG.
1.
Referring to FIG. 1 of the drawings, an equipoise support mechanism
10, includes a first pair of channel arms 12 and 14, an
arm-supporting bracket 20, a first supported bracket 22, a second
pair of parallel arms 16 and 18 and a second supported bracket 24.
Arm-supporting bracket 20 is formed by two similarly shaped flat
parallel plates 19 which are attached to the opposite sides of a
pivot block 21 (see FIG. 7), the lower portion of which is an
integral elongated pivot pin 30. The entire mechanism 10 can
therefore be pivoted about the vertical axis of pin 30 when the
pivot is inserted in a complementary bracket or base (shown in
dotted lines in FIG. 1).
Arms 12 and 14 are pivoted at their lower ends upon arm-supporting
bracket 20 respectively at pivots 32 and 34. The ends of arms 12
and 14 opposite bracket 20 are connected to first supported bracket
22 through pivots 36 and 38, respectively. The distance between
pivots 36 and 38 is equal to the distance between pivots 32 and 34
and the distance from pivot 32 to pivot 36 is equal to the distance
between pivot 34 and pivot 38. Thus, these four pivots form a
parallelogram having sides of predetermined constant length, but
the parallelogram is adapted to be varied in shape as arms 12 and
14 are turned about their respective pivots.
The arms 16 and 18 are of square tubular construction and are
connected at one end to supported bracket 22 at pivots 40 and 42,
respectively. Bracket 22 is formed by two parallel plates 41 each
having an angular portion between two parallel bends 43 to
accommodate the different width of arms 16 and 18 relative to arm
12. The other ends of arms 61 and 18 are connected to bracket 24 at
their respective pivots 44 and 46. The distance between pivots 44
and 46 is equal to the distance between pivots 40 and 42 and the
distance from pivot 40 to pivot 44 is equal to the distance between
pivot 42 and pivot 46. Thus, a second parallelogram is formed by
these four pivots which, in this case, varies in shape as arms 16
and 18 are turned about their respective pivots, as shown in FIG.
2.
Bracket 24 is formed by two parallel plates 45 each having an
angular portion between two parallel bends 47 to accommodate the
narrower width of an interface bracket 56 therebetween. Bracket 56
is formed from a single plate which is bent to form two parallel
sides 51 and 53 (removed in FIG. 8) and a rounded lower portion 57.
Pins 54 and 55 secure bracket 56 to bracket 24. Rounded lower
portion 57 is maintained by the parallel linkage assemblies in a
constant vertical portion as the two sets of arms are moved. A
pivot bracket 58 of known construction is attached to lower portion
57 and permits rotational movement of a supported object (such as
the television shown in dotted lines in FIG. 1) about an axis
parallel to the axis of elongated pivot 30. Pivot bracket 58 also
provides a transverse pivot 62 for swinging bracket 60 to which the
supported object is attached.
The weight of a supported object is counterbalanced by a series of
springs attached to the linkage assemblies. A first pair of
parallel coil springs 26, located on opposite sides of arms 16 and
18 as shown in FIG. 3, are connected at one end to the ends of a
post 50 mounted on arm 18, and at the other end to the ends of a
post or pivot pin 48 located slightly above and to the left of
pivot 40 on bracket 22 in FIGS. 1 and 6. A second set of parallel
coil springs 28, also located on opposite sides of arms 16 and 18,
are connected to the ends of a post 52 mounted on upper arm 16, and
to the ends of a post or pivot pin 54 located slightly below and to
the right of pivot 46 on bracket 24 in FIGS. 1 and 8. Spring pairs
26 and 28 are selected to as to provide counterbalance forces
within the probable weight range of the supported object.
Referring now to FIG. 4, positioned between arms 12 and 14 is a
spring connecting member or rod 70, of square tubular construction
having two hooks 72 and 74 at its ends formed from its wall 75. Rod
70 is freely pivoted on pivot 38 and is not otherwise physically
attached to arm 14. A coil spring 66 has one end looped onto upper
hook 74 and its other end looped onto a hook 82 which is attached
to arm 12 by screw 80. A second coil spring 64 has one end looped
onto the lower hook 72 and its other end attached to an adjustment
bolt 76. The head of bolt 76 is seated in a flat portion 78 formed
from a wall extension of arm 12 which is looped around pivot 32.
Thus, spring 64 is operatively connected to pivot 32 and
facilitates counterbalancing forces thereat. Spring 64, the only
adjustable spring in the mechanism, can be adjusted to provide the
proper counterbalance for the supported object and to balance the
action of adjacent spring 66.
A cross-section of arms 12 and 14 is shown in FIG. 5. Each of these
arms consists of a single plate which is bent in a generally
rectangular U-shape channel. The external width of arm 14 is
slightly smaller than the internal width of arm 12 thus permitting
arm 14 to nest into arm 12 in an unobstructed manner. As arms 12
and 14 are moved about their respective pivots, as the position of
the supported object is changed, they are displaced relative to
each other. However, at no point does the open section of arm 14
move past the open section of arm 12 and thus no gap ever exists
between arms 12 and 14.
This construction also provides a concealed passageway for an
electrical cord which may be required by the supported object. Such
a cord may pass from the supported object up through the center of
brackets 60 and 58, through brackets 56 and 24, through arm 52 and
bracket 22, down through the center cavity between arms 12 and 14
and out of bracket 20 through a horizontal hole 23 in the upper
square portion of the pivot block 21.
As mentioned above, the lower spring 64 within arms 12 and 14 is
adjustable, whereas the adjacent spring 66 as well as the two pairs
of parallel springs 26 and 28 are not. Adjustment of springs 64 can
be made to compensate for variations in the weight of the supported
object. The strength of the other springs are selected to provide
counterbalance forces within acceptable ranges determined by
probable usage. Attachment of springs 64 to the spring connection
rod 70 rather than to the adjacent wall of arm 14 ensures that
spring 64 will be stretched to a maximum amount equal to the
increase in distance between pivot 32 and pivot 38 as the two
parallel arms 12 and 14 are moved. Spring 66 is stretched a
proportionally smaller distance because of the closeness between
its points of connection to arm 12 at hook 82 and pivot 38. Springs
64 and 66 exert opposite torques on the spring connection rod about
pivot 38. However, since the points of connection of springs 64 and
66 to rod 70 are selected so that spring 66 has a longer lever arm
about pivot 38 than does spring 64, the torque produced by spring
66 about pivot 38 is greater than that produced by spring 64 so
that rod 70 is held firmly against the inside wall of arm 14 as
shown in FIG. 4.
Arms 12 and 14 have two positions of maximum stability or limits of
movement with respect to each other, both occurring when the arms
are in a closed configuration with respect to each other. One of
these positions is shown in FIGS. 1 and 4, wherein pivot pin 38 is
engaged by the side edges of arm 12, so that no further
counterclockwise movement of the arms can take place. The second
position of maximum stability (not shown) occurs when arms 12 and
14 are lowered below the horizontal (in a clockwise direction as
seen in FIG. 1) so that the parallelogram formed by the arms is
reversed from that shown in FIG. 4 with pivots 32 and 36 positioned
to the left of pivots 34 and 38, respectively, and pivots 34 and 36
respectively engage the edges of arms 12 and 14 and thus further
movement in a clockwise direction is prevented.
Another feature of the invention is that arms 16 and 18 also have
two positions of maximum stability or limits of movement. The first
of these positions is shown in FIG. 1 and occurs when the two arms
are in a generally vertical position touching each other. The
second such position is when the arms are folded down below the
horizontal and again touch each other.
Because of the locations of posts 48 and 54, an overcenter effect
is created so that a counterclockwise restoring force is provided
by springs 26 and 28 as arms 16 and 18 are rotated clockwise
(direction defined in accordance with FIG. 1) until a point is
reached in which posts 48 and 50 and pivot 42, as well as posts 52
and 54 and pivot 44, are in a straight line. This point is a null
position on each side of which there is a reversal in restoring
torque. As arms 16 and 18 are rotated clockwise past this point,
springs 26 and 28 act to rotate arms 16 and 18 toward arms 12 and
14.
By the above described construction it is thus seen that the
equipoise mechanism may be considered to be two independent
parallelogram linkage assemblies; arms 12 and 14 and springs 64 and
66 providing support for bracket 22, the second parallelogram
linkage assembly and the supported object, and the second
parallelogram linkage assembly, consisting of arms 16 and 18 and
springs 26 and 28, providing support for the supported object
relative to bracket 22.
As a result of the configuration of the arms, as described above,
and the location of their respective pivot points and spring
connections, the linkage mechanism is stable at any position in
which the arms are placed, between their respective positions of
maximum stability. Accordingly, the flexibility of the device,
i.e., the number of positions in which it may be placed is
substantial. For example, arms 12 and 14 may be placed in any
position between their two extremes, and arms 16, 18 may then be
varied or moved as desired to any position between their extremes
in order to properly position the television set or other supported
article. Similarly, the relative position of arms 16 and 18 may be
adjusted and then the arms 12, 14 moved as desired. Of course, both
sets of arms may be moved simultaneously until the desired position
of the supported article is attained.
Moreover, at the positions of maximum stability of the lower arms
12, 14, an extremely stable stable condition is provided for the
entire range of movements of the upper arm. Further, heavier
objects may be supported on the arm assembly of the present
invention than have heretofore been able to be supported on
equipoised mechanisms.
As many possible embodiments may be made of the apparatus of the
above invention, all without departing from the scope of the
invention, it is to be understood that all matter hereinabove set
forth, or shown in the accompanying drawings is to be interpreted
as illustrative and not in a limiting sense. What is claimed
is:
* * * * *