U.S. patent application number 10/669751 was filed with the patent office on 2004-04-08 for load-assist actuator.
Invention is credited to Dickie, Paul C., Trippensee, Darin J..
Application Number | 20040066072 10/669751 |
Document ID | / |
Family ID | 32045311 |
Filed Date | 2004-04-08 |
United States Patent
Application |
20040066072 |
Kind Code |
A1 |
Trippensee, Darin J. ; et
al. |
April 8, 2004 |
Load-assist actuator
Abstract
An actuator comprises an actuator member and an assist
mechanism. The assist mechanism comprises an assist element that is
adapted to store energy to assist in moving the actuator member.
The assist element is carried between two members. The members act
upon the assist element to cause the assist element to store energy
when the actuator member is moved in an extended direction and
release the energy when the actuator member is moved in a retracted
direction, whereby the retracted direction is opposite to the
extended direction. The actuator is for use in moving the seat
relative to the frame.
Inventors: |
Trippensee, Darin J.;
(Fresno, CA) ; Dickie, Paul C.; (Clovis,
CA) |
Correspondence
Address: |
MACMILLAN SOBANSKI & TODD, LLC
ONE MARITIME PLAZA FOURTH FLOOR
720 WATER STREET
TOLEDO
OH
43604-1619
US
|
Family ID: |
32045311 |
Appl. No.: |
10/669751 |
Filed: |
September 24, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60415278 |
Oct 1, 2002 |
|
|
|
Current U.S.
Class: |
297/330 ;
297/327 |
Current CPC
Class: |
A61G 5/1075 20130101;
B66F 7/0633 20130101; A61G 5/104 20130101 |
Class at
Publication: |
297/330 ;
297/327 |
International
Class: |
A47C 001/032 |
Claims
What is claimed is:
1. In combination comprising: an actuator member; and an assist
mechanism comprising an assist element that is adapted to store
energy to assist in moving the actuator member, the assist element
is carried between two members that act upon the assist element to
cause the assist element to store energy when the actuator member
is moved in an extended direction and releases the energy when the
actuator member is moved in a retracted direction opposite to the
extended direction.
2. The combination according to claim 1, further including an outer
tube from which the actuator member extends, the assist element
being carried by the outer tube.
3. The combination according to claim 2, wherein the members acting
upon the assist element are abutment members.
4. The combination according to claim 3, wherein one of the
abutment members is maintained in a fixed position and the other
abutment member is adapted to move responsive to movement of the
actuator member.
5. The combination according to claim 4, wherein the fixed abutment
member is fixed relative to the outer tube and the movable abutment
member is movable relative to the outer tube.
6. The combination according to claim 5, wherein the assist element
is a spring, whereby upon extending the actuator member, the
movable abutment member is moved to cause the spring to be
compressed to store energy and upon retracting the actuator member,
the movable abutment member is free to move to permit the spring to
release the energy.
7. The combination according to claim 2, wherein the members acting
upon the assist element are abutment members including a clamp
fixed relative to the outer tube and a collar guide movable
relative to the outer tube, the assist element being a helical
compression spring located between the clamp and the collar
guide.
8. The combination according to claim 1, wherein the members acting
upon the assist element include a movable abutment member that is
adapted for movement by forming a connection between the actuator
member and the movable abutment member.
9. The combination according to claim 8, wherein the connection
between the actuator member and the movable abutment member
includes one or more connection members that extend between the
actuator member and the movable abutment member.
10. The combination according to claim 9, wherein the one or more
connection members are cable assemblies comprising a cable having
opposite ends including a fixed end and a movable end, the fixed
end being fixed relative to the actuator member and the movable end
being adapted to move and engage the movable abutment member.
11. The combination according to claim 10, wherein a clevis is
fixed to the actuator member, the fixed end being attached to the
clevis so that the cable extends from the clevis beyond the
abutment member.
12. The combination according to claim 10, wherein the members
acting upon the assist element include a fixed abutment member and
a movable abutment member, each of the abutment members being
provided with one or more guides through which the cables pass.
13. The combination according to claim 10, wherein the cables, upon
retracting the actuator member beyond a certain distance, extend
beyond the movable abutment member.
14. The combination according to claim 13, further including a stop
member to limit travel of the movable abutment member when the
actuator member is retracted so that the cables extend beyond the
movable abutment member.
15. The combination according to claim 14, further including an
outer tube from which the actuator member extends, the stop member
being an O-ring on the outer tube.
16. In combination: a frame; a seat; and an actuator for use in
moving the seat relative to the frame, the actuator comprising: an
actuator member; and an assist mechanism comprising an assist
element that is adapted to store energy to assist in moving the
actuator member, the assist element is carried between two members
that act upon the assist element to cause the assist element to
store energy when the actuator member is moved in an extended
direction and release the energy when the actuator member is moved
in a retracted direction opposite to the extended direction.
17. The combination according to claim 16, wherein the actuator
further includes an outer tube from which the actuator member
extends, the assist element being carried by the outer tube.
18. The combination according to claim 17, wherein the members
acting upon the assist element are abutment members, one of the
abutment members being in a fixed position relative to the outer
tube and the other abutment member being adapted to move relative
to the outer tube responsive to movement of the actuator
member.
19. The combination according to claim 17, wherein the assist
element is a spring, whereby upon extending the actuator member,
the movable abutment member is moved to cause the spring to be
compressed to store energy and upon retracting the actuator member,
the movable abutment member is free to move to permit the spring to
release the energy.
20. The combination according to claim 17, wherein one or more
cables each has a fixed end that is fixed relative to the actuator
member and a movable end that is adapted to move and engage the
movable abutment member.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates in general to machine elements or
mechanisms and, more particularly, to reciprocating or oscillating
mechanisms. Most particularly, the invention relates to a
load-assist mechanism for actuators. The invention also relates to
a load-assist actuator for use in tilt and recline wheelchairs.
[0002] Tilt and recline wheelchairs are well known. Such
wheelchairs have a reclining seat supported by a frame. An actuator
pulls the seat forward on a movable pivot axis as the seat is
tilted rearward. Load on the actuator is greatest during the first
10-15 degrees of tilting motion. During this range of motion, the
actuator is susceptible to overload. Overloading the actuator may
result in the actuator's inability to tilt the seat or shorten the
life expectancy of the actuator.
[0003] What is needed is an assist mechanism that reduces the load
on the actuator and thus increases its life expectancy.
SUMMARY OF THE INVENTION
[0004] The present invention is directed toward an assist mechanism
that reduces the load on the actuator and increases its life
expectancy. The assist mechanism comprises an assist element that
is adapted to store energy to assist in moving an actuator member.
The assist element is carried between two members. The members act
upon the assist element to cause the assist element to store energy
when the actuator memberis moved in an extended direction and
release the energy when the actuator memberis moved in a retracted
direction, whereby the retracted direction is opposite to the
extended direction.
[0005] Another embodiment of the invention comprises a frame, a
seat, and an actuator for use in moving the seat relative to the
frame. The actuator comprises an actuator memberand an assist
mechanism. The assist mechanism comprises an assist element that is
adapted to store energy to assist in moving the actuator member.
The assist element is carried between two members. The members act
upon the assist element to cause the assist element to store energy
when the actuator memberis moved in an extended direction and
release the energy when the extension tube is moved in a retracted
direction opposite the extended direction.
[0006] Various objects and advantages of this invention will become
apparent to those skilled in the art from the following detailed
description of the preferred embodiment, when read in light of the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a perspective view of an actuator according to a
preferred embodiment of the invention wherein the extension tube of
the actuator is shown fully extended.
[0008] FIG. 2 is a perspective view of the actuator shown in FIG. 1
wherein the extension tube is shown partially retracted in phantom
line and fully retracted in full.
[0009] FIG. 3 is an environmental perspective view of the actuator
shown in FIGS. 1 and 2 wherein the actuator is connected between a
wheelchair seat and frame for tilting the seat.
[0010] FIG. 4 is a diagrammatic representation in elevation of the
actuator and wheelchair seat and frame shown in FIG. 3 wherein the
seat is in an upright position.
[0011] FIG. 5 is a diagrammatic representation in elevation of the
actuator and wheelchair seat and frame shown in FIG. 3 wherein the
seat is in a partially tilted position.
[0012] FIG. 6 is a diagrammatic representation in elevation of the
actuator and wheelchair seat and frame shown in FIG. 3 wherein the
seat is in a fully tilted position.
BRIEF DESCRIPTION
[0013] Now, with reference to FIGS. 1 and 2 initially, there is
illustrated an electromechanical linear actuator 10 having a
reversible electric motor 12, gear box 14, and a ball nut and screw
mechanism (not shown) housed within a fixed outer tube 18. Ball nut
and screw mechanisms are well known to those of ordinary skill in
the art, and further details concerning their construction and
operation are disclosed, for example, in U.S. Pat. Nos. 5,485,760
and 6,101,889, the disclosures of which are incorporated herein by
reference.
[0014] Extending longitudinally from the fixed outer tube 18 is an
extension tube 28, which includes an end fitting 29 that, in the
illustrated embodiment, takes the form of a clevis. Other types of
end fittings commonly used in linear actuator applications, such as
externally threaded shanks, may also be employed.
[0015] The electric motor 12 activates the ball nut and screw
mechanism through gearing (not shown) inside the gear box 14,
causing a screw (not shown) to rotate about its axis within the
fixed outer tube 18. A ball nut (also not shown) converts the
rotary motion of the electric motor 12 and screw into linear
motion, enabling the extension tube 28 to telescope relative to the
fixed outer tube 18 between extreme positions, illustrated in the
drawings.
[0016] A fixed stop (not shown), which could be carried on the
fixed outer tube 18 or on the screw, may be provided to confront
the ball nut at the point of full retraction to limit inward
movement of the extension tube 28. The screw likewise may carry a
stop (also not shown) adjacent its outboard end which is confronted
by the ball nut at full extension of the extension tube 28 to limit
outward movement of the extension tube 28.
[0017] The components and operation of the actuator 10 thus far
described are conventional. Thus far, it will be seen that there is
nothing to reduce the load on the actuator 10 or lengthen its life
expectancy. It will be appreciated that, for the actuator load to
be reduced and its life expectancy lengthened, a mechanical assist
30 is provided. The mechanical assist 30 uses an assist element to
reduce a load sustained by the actuator 10 to accommodate heavier
weight limits and extend the life of the actuator 10.
[0018] The assist element 32 is adapter to store energy to assist
in moving the extension tube 28. Upon moving the extension tube 28
in a first direction to extend or retract the extension tube 28,
the assist element 32 stores energy that assists in moving the
extension tube 28 when the extension tube 28 is moved in a second
direction opposite to the first direction.
[0019] The assist element 32 may be in the form of a spring, such
as the helical spring shown. The spring is adapted to be compressed
to store energy when the extension tube 28 is extended. Upon
retracting the extension tube 28, the spring expands and the energy
stored in the spring is released or exerted to assist in retracting
the extension tube 28.
[0020] As shown in the drawings, the assist element 32 may be
carried by the fixed outer 18 between two members that act upon the
assist element 32 to cause the assist element 32 to store energy
when the extension tube 28 is moved. The members acting upon the
assist element 32 may be in the form of abutment members, such as
the abutment members 34, 36 shown. In a preferred embodiment of the
invention, one of the abutment members 34 is maintained in a fixed
position and the other abutment member 36 is adapted to move
responsive to movement of the extension tube 28. The fixed abutment
member 34 is preferably fixed relative to the fixed outer tube 18.
The movable abutment member 36 is movable relative to the fixed
outer tube 18. Upon extending the extension tube 28, the movable
abutment member 36 is moved to cause the assist element 32 to be
compressed to store an assistive energy. Upon retracting the
extension tube 28, the movable abutment member 36 is free to move
to permit the assist element 32 to release the assistive energy,
which assists in retracting the extension tube 28. In the
embodiment shown, the fixed abutment member 34 is in the form of a
clamp, the movable abutment member 36 is in the form of a collar
guide, and the assist element 32 is in the form of a helical
compression spring located between the fixed abutment member 34 and
the movable abutment member 36.
[0021] The movable abutment member 36 may be adapted for movement
by forming a connection between the extension tube 28 and the
movable abutment member 36. This connection may be formed in any
suitable manner. For example, one or more connection members,
generally indicated 38, may extend between the extension tube 28
and the movable abutment member 36. As shown in the drawings, the
connection members 38 may be in the form of cable assemblies. Each
cable assembly may be comprised of a cable 40 having opposite ends,
generally indicated at 42, 44. One end 42 may be fixed relative to
the extension tube 28 and the other end 44 may be adapted to move
relative to, and ultimately engage, the movable abutment member 36.
As shown in the drawings, a clevis 46 may be fixed to the extension
tube 28. The clevis 46 is preferably fixed to the extension tube 28
adjacent the end fitting 29. The fixed end 42 of the cable 40 may
be attached to the clevis 46 so that the cable 40 extends from the
clevis 46 beyond the abutment members 34, 36.
[0022] As shown in the drawings, the fixed abutment member 34 may
be provided with guides 50, through which the cables 40 may pass.
The movable abutment member 36 may likewise be provided with guides
52. The cable 40 may likewise pass through these guides 52. The
movable ends 44 of the cables 40 are adapted to move relative to
the movable abutment member 36 as the extension tube 28 is extended
and retracted, and ultimately engage and displace the movable
abutment member 36 when the extension tube 28 is extended beyond a
certain distance. Displacement of the movable abutment member 36 by
the cables 40 causes the movable abutment members 36 to act upon
the assist element 32 to cause the assist element 32 to store an
assistive energy. An assist element 32 in the form of a spring
would be compressed between the abutment members 34, 36 as the
movable abutment member 36 is displaced upon extending the
extension tube 28, as shown in FIG. 1.
[0023] It should be noted that the cables 40, upon retracting the
extension tube 28 beyond a certain distance, may extend beyond the
movable abutment member 36, as shown in FIG. 2. It may be desirable
to limit travel of the movable abutment member 36 when the cables
40 extend beyond the movable abutment member 36. This may be
accomplished by use of a stop member 54, such as the O-ring shown
on the fixed outer tube 18, to limit travel of the movable abutment
member 36 relative to the fixed outer tube 18 and thus limit travel
of the assist element 32 when the extension tube 28 is retracted so
that the cables 40 extend beyond the movable abutment member
36.
[0024] The actuator 10 is adapted for use in moving a reclining
seat 58 relative to a wheelchair frame 56. More particularly, the
actuator 10 is adapted for use in tilting the reclining seat 58
relative to the wheelchair frame 56. As shown in FIG. 3, the
actuator 10 is adapted to be connected between the wheelchair frame
56 and the reclining seat 58. When the extension tube 28 is fully
extended, as shown in FIG. 4, the reclining seat 58 is in a
non-tilted position. When the reclining seat 58 is in this
position, the assistive energy is at its peak. An assist element 32
in the form of a spring, as shown in the drawings, would be
compressed between the abutment members 34, 36 when the reclining
seat 58 is in the non-tilted position. Retracting the extension
tube 28 tilts the reclining seat 58. The load on the actuator 10 is
greatest when the extension tube 28 begins to retract from the
fully extended position. Assistive energy stored in the assist
element 32 aids in retracting the extension tube 28 and thus, aids
in tilting of the reclining seat 58. Continued retraction of the
extension tube 28 uses all the assistive energy. An assist element
32 in the form of a spring, as shown, would eventually decompress,
as shown in FIGS. 2 and 5, until no assistive energy remains.
Further retraction of the extension tube 28 moves the movable ends
44 of the cable 40 well beyond the movable abutment member 36, as
shown in FIGS. 2 and 6. The stop member 54 limits travel of the
movable abutment member 36. As shown in the drawings, the stop
member 54 keeps the assist element 32 and the movable abutment
member 36 in place until the extension tube 28 is once again
extended.
[0025] The principle and mode of operation of this invention have
been explained and illustrated in its preferred embodiment.
However, it must be understood that this invention may be practiced
otherwise than as specifically explained and illustrated without
departing from its spirit or scope.
* * * * *