Note: Descriptions are shown in the official language in which they were submitted.
CA 02230402 1998-OS-OS
OVERHEAD ARTICULATED SUPPORT FOR THE HUMAN ARM
BACKGROUND OF THE INVEDdTION
1
The ~>resent invention relates to ergonomic apparatus for
supporting the human arm during manual operations so to
counterbalance its weight and reduce the strain on
supporting muscles and tendons. More specifically, the
invention is particularly intended for ultrasonic
diagnostic operations and aims at providing a simple,
esthetical and practical solution to the increasing problem
of fatigue and pain caused to operators by the repetitive
manipulation of the ultrasonic probe in a position where
the operator's arm is usually extended far from his body,
thus causing a high solicitation at the biceps and shoulder
level. Effectively, many current medical applications of
ultrasonic diagnostic,, such as in obstetrics, require
intensive manipulation of the probe around the patient's
tissues and obstacles to obtain images as good as possible
or track moving targets. Therefor, operators arms are much
solicited causing pain, disease, low productivity,
absenteeism, that induce both human and economic costs.
Although the invention will be described in detail with
respect to the latter field of application, it shall be
understood that it might be used in many other fields such
as assembly, physiotherapy and assistance to persons
affected a restriction of arm mobility.
Few solutions to the problem of holding an ultrasonic probe
have been proposed in the past but they all suffer from
major drawbacks. Namely, all of them are designed to hold
the probe itself and ~>rovide no assistance to the operator
for supporting the weight of his own arm acting in
cantilever and causing an important torque to be
CA 02230402 1998-OS-OS
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counterbalanced by the effort of the arm and shoulder
muscles and tendons . Such a mechanism is disclosed in U. S .
patent 5,348,014 which describes an overhead arm mechanism
provided with a constant force spring counterbalanced wire
to which the probe is suspended. Considering that most
contemporary probes are much lighter than the operator's
arm, supporting the probe alone provides very limited
relief of the physical stress to be supported by the
operator. Even if the winding force of the wire was
increased to account for the arm weight, the point of
application of the compensating force would not be adequate
and added stress in the wrist and no significant comfort
improvement if any would yield. Moreover, that support is
limited in mobility and positioning flexibility since it is
fixed to the ultrasonic apparatus body and does not provide
operator adjustable counterbalancing force.
Us patent 5,279,486 discloses a medical support using an
horizontal arm to support a wire through two pulleys. One
end of the wire supports a medical apparatus while a
counterweight is attached to the other end of the wire and
counterbalances the weight of the apparatus. That concept
with limited number of degrees of freedom is only
appropriate for static support of an apparatus and do not
feature practical counterweight adjustment as required for
supporting the arm and providing optimal comfort to
different operators.
US patents 4,548,374 and 4,241,891 provide even worst
solutions for supporting the probe, since the weight of the
most part of the articulated supporting arm is balanced by
a counterweight located near the base. These concepts
result in sturdy and heavy structures which present a high
level of friction and inertia that would prevent
utilisation as a human arm support since freedom of
movement would be too much affected.
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Many arm supports are referenced in the prior art, but they
are all intended to relief stress and pain experienced by
keyboard operators. 'These systems such as US patent
5,074,,501, support the operator's arm from underneath and
provide no supported or balanced mobility over a vertical
stroke, and therefor would not comply with an application
requiring such a level of freedom as for ultrasonic
diagnostic apparatus operators, assembly tasks, restrained
mobility persons or like applications.
SUMMARY OF THE INVENTION
The present invention provides an overhead articulated
support for the human arm which overcomes the limitations
and drawbacks of the above mentioned solutions of the
prior art, and more specifically:
it is a first object of the instant invention to provide
an arm support that counterbalances at least a part of the
weight of the arm of a person and follows its movement
rather than guiding it within a 3-dimensional working
envelope, thus causing a minimal restriction to the
movements, preserving the full mobility of the hand and
wrist of the user and giving a general impression of
flotation;
it is a further object of the present invention to provide
a discrete and safe support for the human arm in which the
arm is supported from overhead to avoid the presence of
obstacles within the working envelope or the line of sight
of the user and eventual patient, collaborator or other
persons, and to prevent people from running into a part of
the support and get injured;
CA 02230402 1998-OS-OS
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it is another object of the present invention to provide
a support which features fast and simple user settable
adjustments over a wide range of values for the
counterbalancing force and the position of the arm rest
to match the personal physical characteristics of any
user;
it is a still further object of the present invention to
provide an arm support in which the counterbalancing force
is substantially linear over the entire vertical stroke;
it is a further object of the present invention to provide
an arm support that :is mobile, compact, collapsible and
requires very low space for storage when not in use;
it is another object of the present invention to provide an
arm support featuring an adjustable friction coupling to
lock the position of the vertical axis or reduce the effect
of the relief force in one or both directions;
it is a further object of the instant invention to provide
an arm support incorporating a fixed supporting ring to
hold the probe cable from a vertical point and thus relief
the ~>tress its weight normally causes on the operator's
wrist;
it is a still further object of the present invention to
provide an arm support: that comprises a minimum number of
parts, requires almost no maintenance, is esthetical and is
economical to produce.
These objects and other objects and features of the present
invention will become apparent through the following
description that will be carried out by reference to the
appended drawings.
CA 02230402 1998-OS-OS
BRIEF DESCRIPTION OF THE DRAWINGS
5
FIG. 1 is an isometric view of the overhead articulated arm
support of the present invention, with an ultrasonic probe
and cable.
FIG. 2 is a longitudinal cut-away isometric view of the
sliding arm members of the support of FIG. 1.
FIG.3 is an enlarged isometric view of the fore-end of the
support of FIG.1, showing the operator's arm, the probe and
its cable in a typical position.
FIG. 4 is an enlarged assembly drawing of the friction
coupling assembly of FIG.3.
FIG. 5 a) and b) show alternate embodiments of the arm rest
assembly.
DETAILED DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the safety apparatus of the
present invention will now be described in detail referring
to the appended drawings.
Referring to FIG.1, there is provided an overhead
articulated support for the human arm comprising a base
assembly 1 provided with locking rollers 2 and a height
adjustment knob 3. A graduated post 4 with reference
numerals is inserted in base 1 and locked at the desired
height using knob 3. A main arm member 6 has one end
pivotally mounted on a rotary joint 5 assembled to the
top of post 4. In the operating position, the main arm
member 6 is moving on an horizontal plane over 360
%, ~.
CA 02230402 1998-OS-OS
6
degrees, and it can be unfolded 90 degrees upright to
take less space for storage. During storage, the post 4
can also be lowered to hide almost completely in the base
assembly 1. A sliding arm assembly 7 slides in a self
lubricated bushing inside a generally horizontal bore
provided in a ~~T" connector 8 which is rotatably mounted
on the other end of main arm member 6, permitting
rotation of the sliding arm assembly over 360 degrees in
an horizontal plane. The sliding arm assembly 7 is also
free to rotate in the bore around its longitudinal axis.
A vertical arm assembly 9 is rotatably suspended to one
end of the sliding arm assembly 7, said vertical arm
comprising a tube 10 in which a rod 11 is sliding, said
rod being provided at its lower end with a universal
joint 12 holding an arm rest 13. The upper end of said
rod is attached to a wire 14 guided by a pulley 15 to a
counterbalancing unit incorporated in the sliding arm
assembly 7, as shown in detail in FIG. 2. A stop member
24 on the rod 11 limits the penetration of the rod within
the tube 10.
A friction coupling assembly 29 is assembled between the
tube 10 and the rod 11 to adjust the friction force
acting against rod movement, between a free sliding
position and a locked position. This feature allows the
user to reduce or eliminate the counterbalancing force to
maintain a fixed position for a certain time or apply
downward pressure as a function of the operations to be
carried out.
Referring to FIG. 2, the counterbalancing unit located in
the tube 16 of the sliding arm assembly 7 comprises a
force adjustment device 17, a coil spring 18 and two
pulley assemblies 19, 20, the pulley assembly 20 being
CA 02230402 1998-OS-OS
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rotatably mounted on an axle assembled across one end of
the tube 16 near the pulley 15. The wire 14 guided by the
pulley 15 successively passes through each pulley of
assemblies 19 and 20 and is finally connects to one end
of th.e coil spring 18. Since the pulley assembly 19 is
free to move along the longitudinal axis of the tube 16.
the pulleys act as a stroke divider. The stroke of the
rod is transmitted to one end of the wire 14 and the
pulled length splits equally in each loop between the two
pulley assemblies. Hence, the spring 18 is only extended
by a length equal to the stroke of the rod divided by the
number of loops between the pulley assemblies 19. 20. For
example, if the initial counterbalancing force is
determined by an initial elongation of the spring that is
in the range of 15 cm, a stroke of 15 cm of the rod 11
and 5 pulleys per assembly would yield an additional
spring elongation of 3 cm representing a difference of
20% in the counterbalancing force between the two extreme
positions of the rod. A force adjustment device 17
comprising a lever 21 and a pulley 22 is connected to the
second end of the coil spring 18 through a wire 23.
Moving the lever winds or unwinds the wire on the pulley
and extends the spring by a maximum additional length of
about 6 cm, providing an adjustment up to about +40o with
respect to the initial counterbalancing force. The force
adjustment device 17 is so assembled to the tube 16 to
have a high level o.f static friction to maintain the
lever at the set position despite the reaction force
exerted by the spring through the wire 23.
In operation, the user first adjusts the height of the
graduated post 4 so that his arm lying on the rest member
13 is floating at the desired average working height.
Moving the arm up or down within a range of 15 cm will
only change the counterbalancing force by ~l0o according
CA 02230402 1998-OS-OS
8
to the previous example. Fine adjustment of the neutral
position is accomplished by moving the lever 21 up or
down.
The above described counterbalancing mechanism represents
a simple, compact, reliable and low cost solution to
produce a relatively constant counterbalancing force.
Nevertheless, other types of known adjustable
counterbalancing mechanisms such as spiral springs could
be used to generate a relatively constant
counterbalancing force over the stroke of the rod 11
without departing from the spirit of the present
invention.
In FIG.3 an operator's arm is shown in a working
position, holding an ultrasonic probe 26 having a cable
27 supported by a cable supporting ring 28 to
counterbalance its weight. The arm is directly supported
on a rest member 13 usually under the forearm between the
wrist and the elbow for maximum comfort and mobility. The
rest assembly is removably connected to the lower part of
the rod 11 by a quick connect fastener 25. A "C" shaped
open type rest is represented in that figure. However,
alternate embodiments of the rest of the closed type and
having one or more point of support as respectively shown
in FIG. 5 and FIG. 6, r_an be used according to the
preference of the user.
FIG. 4 shows the details of the friction coupling 29. A
threaded connector 30 is fixed to the lower end of the
tube 10, a frustoconical friction ring 31 made of a
resilient material is sled on the rod 11 and is more or
less compressed by screwing the torque knob 32 on the
threaded part of the connector 30. It is also
contemplated that asymmetrical friction devices providing
/J ~-
CA 02230402 1998-OS-OS
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rotatably mounted on an axle assembled across one end of
the tube 16 near the pulley 15. The wire 14 guided by the
pulley 15 successively passes through each pulley of
assemblies 19 and 20 and is finally connects to one end
of the coil spring 18. Since the pulley assembly 19 is
free to move along the longitudinal axis of the tube 16,
the pulleys act as a stroke divider. The stroke of the
rod is transmitted to one end of the wire 14 and the
pulled length splits equally in each loop between the two
pulley assemblies. Hence, the spring 18 is only extended
by a length equal to the stroke of the rod divided by the
number of loops between the pulley assemblies 19, 20. For
example, if the initial counterbalancing force is
determined by an initial elongation of the spring that is
in the range of 15 cm, a stroke of 15 cm of the rod 11
and 5 pulleys per assembly would yield an additional
spring elongation of 3 cm representing a difference of
20o in the counterbalancing force between the two extreme
positions of the rod. A. force adjustment device 17
comprising a lever 21 and a pulley 22 is connected to the
second end of the coil spring 18 through a wire 23.
Moving the lever winds or unwinds the wire on the pulley
and extends the spring by a maximum additional length of
about 6 cm, providing an adjustment up to about +40o with
respect to the initial counterbalancing force. The force
adjustment device 17 is so assembled to the tube 16 to
have a high level of static friction to maintain the
lever at the set position despite the reaction force
exerted by the spring through the wire 23.
In operation, the user first adjusts the lateral position
and the height of the graduated post 4 so that his arm
lying on the rest member 13 is floating at the desired
average working height within the work envelope. Moving
f
CA 02230402 1998-OS-OS
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the arm up or down within a range of 15 cm will only
change the counterbalancing force by ~l0o according to
the previous example. Fine adjustment of the neutral
vertical position is accomplished by moving the lever 21
up or down. The nominal horizontal distance between the
base 1 and the centre of the work envelope is adjusted by
manually sliding the sliding member 7 in or out.
The above described counterbalancing mechanism represents
a simple, compact, reliable and low cost solution to
produce a relatively constant counterbalancing force.
Nevertheless, other types of known adjustable
counterbalancing mechanisms such as spiral springs could
be used to generate a relatively constant
counterbalancing force over the stroke of the rod 11
without departing from the spirit of the present
invention.
In FIG.3 an operator's arm is shown in a working
position, holding an ultrasonic probe 26 having a cable
27 supported by a cable supporting ring 28 to
counterbalance its weight. The arm is directly supported
on a rest member 13 usually under the forearm between the
wrist and the elbow for maximum comfort and mobility. The
rest assembly is removably connected to the lower part of
the rod 11 by a quick connect fastener 25. A "C" shaped
open type rest is represented in that figure. However,
alternate embodiments of the rest of the closed type and
having one or more point of support as respectively shown
in FIG. 5 and FIG. 6, can be used according to the
preference of the user.
FIG. 4 shows the details of the friction coupling 29. A
threaded connector 30 is fixed to the lower end of the
CA 02230402 1998-OS-OS
9
tube 10. a frustoconical friction ring 31 made of a
resilient material is sled on the rod 11 and is more or
less compressed by screwing the torque knob 32 on the
threaded part of the connector 30. It is also
contemplated that asymmetrical friction devices providing
resistance to the movement in only one direction could
also be used, depending on the requirements of the
envisaged application of the arm support.
Although the present invention has been described by means
of preferred embodiments thereof, it is contemplated that
various modifications may be made thereto without departing
from the spirit and scope of the present invention.
Accordingly, it is intended that the embodiments described
be considered only as illustrative of the present invention
and that the scope thereof should not be limited thereto
but be determined by reference to the claims hereinafter
provided and their equivalents.
For instance, it is contemplated that a version of the
support without the base could be mounted on a workbench or
wheelchair to accommodate usage for assembly operations or
by a person with restrained mobility.
