U.S. patent application number 10/121196 was filed with the patent office on 2003-10-16 for prosthetic locking device.
Invention is credited to Coop, Brian T..
Application Number | 20030195636 10/121196 |
Document ID | / |
Family ID | 28790266 |
Filed Date | 2003-10-16 |
United States Patent
Application |
20030195636 |
Kind Code |
A1 |
Coop, Brian T. |
October 16, 2003 |
Prosthetic locking device
Abstract
A device is provided to lock the residual limb of an amputee
into a prosthesis. The device is comprised of rolling elements
within a tapered housing which accepts a smooth plunger, such as a
wire, cable, or rod connected to a suspension sleeve, with minimal
resistance while opposing removal of the plunger from the locking
device until the rolling elements have been retracted with a
release mechanism. The nature of this device allows it to
compensate for irregularities or wear in the plunger while
continuing to securely lock the prosthesis to the sleeve. This
locking device will function properly with a certain amount of
misalignment between the lock and the plunger.
Inventors: |
Coop, Brian T.; (Soddy
Daisy, TN) |
Correspondence
Address: |
DOUGLAS T. JOHNSON
MILLER & MARTIN
1000 VOLUNTEER BUILDING
832 GEORGIA AVENUE
CHATTANOOGA
TN
37402-2289
US
|
Family ID: |
28790266 |
Appl. No.: |
10/121196 |
Filed: |
April 12, 2002 |
Current U.S.
Class: |
623/36 ;
623/33 |
Current CPC
Class: |
A61F 2002/305 20130101;
A61F 2002/30331 20130101; A61F 2220/0025 20130101; A61F 2002/5073
20130101; A61F 2002/5067 20130101; A61F 2/78 20130101; A61F
2002/7875 20130101; A61F 2/80 20130101; A61F 2220/0033
20130101 |
Class at
Publication: |
623/36 ;
623/33 |
International
Class: |
A61F 002/80 |
Claims
What is claimed is:
1. A prosthetic locking device in a prosthetic socket for receiving
a substantially smooth plunger attached to a prosthetic sleeve
comprising: (a) a lock housing having a proximal opening for
introduction of a plunger, and having a tapered interior expanding
distally from the opening; (b) a rolling element housed within the
tapered interior; (c) a lift to bias the rolling element toward the
proximal opening; (e) a release mechanism which moves the rolling
element distally from the proximal opening when activated.
2. The prosthetic locking device of claim 1 having a plurality of
rolling elements housed within the tapered interior.
3. The prosthetic locking device of claim 2, where the rolling
elements are of a form selected from the group consisting of
spherical, cylindrical, ellipsoidal and columnar.
4. The prosthetic locking device of claim 1, where the rolling
element is made from material selected from the group consisting of
austenitic stainless steel, titanium, and brass.
5. The prosthetic locking device of claim 1, where the release
mechanism is selected from the group consisting of a linearly
actuated cam, radially actuated cam, pin-hinged linkage,
gear-to-gear system, and gear-to-rack system.
6. The prosthetic locking device of claim 1, further comprising an
actuation button connected to said release mechanism and extending
from the lock housing.
7. The prosthetic locking device of claim 6, wherein the actuation
button comprises a draw member connected to the release mechanism
that can be pulled to actuate the release mechanism.
8. A prosthetic locking device in a prosthetic socket for receiving
a plunger mounted on a prosthetic sleeve comprising: (a) a lock
housing having an exterior, a tapered interior, with a top interior
portion, and an opening passing through the top interior portion to
the exterior; (b) a substantially smooth rolling element housed
within said tapered interior; (c) a spring biasing said rolling
element towards the top portion of the tapered interior; (d) a
release mechanism which moves the rolling element away from the top
portion of the tapered interior when activated.
9. The prosthetic locking device of claim 8 having a plurality of
rolling elements housed within the tapered interior.
10. The prosthetic locking device of claim 9, where the rolling
elements are of a form selected from the group consisting of
spherical, cylindrical, ellipsoidal and columnar.
11. The prosthetic locking device of claim 8, where the rolling
element is made of materials selected from the group consisting of
austenitic stainless steel, titanium, and brass.
12. The prosthetic locking device of claim 8, where the release
mechanism is selected from the group consisting of a linearly
actuated cam, radially actuated cam, pin-hinged linkage,
gear-to-gear system, and gear-to-rack system.
13. The prosthetic locking device of claim 8, further comprising an
actuation button connected to said release mechanism and accessible
from the lock housing.
14. A method of attaching a prosthetic sleeve having a plunger to a
prosthetic socket fitted with the prosthetic locking device of
claim 1 comprising the steps of: (a) guiding the plunger into the
proximal opening of the lock housing; (b) pushing the plunger into
the tapered interior and contacting the rolling element therein;
(c) applying sufficient force on the plunger to urge the rolling
element distally from the opening and the tapered interior wall
such that the rolling element is moved distally from the opening
sufficiently that the width of the tapered interior increases
sufficiently to permit the plunger to pass by the rolling element;
(d) continuing to urge the plunger through the prosthetic locking
device to the desired depth; (e) biasing the rolling element toward
the proximal opening thereby biasing the rolling element against
both the tapered interior and the plunger.
15. The method of claim 15, wherein the rolling elements are of a
form selected from the group consisting of spherical, cylindrical,
ellipsoidal and columnar.
16. The method of claim 15, wherein the plunger is in a form
selected from the group consisting of solid wire, rod, tube, and
stranded flexible wire.
17. A method of detaching a prosthetic sleeve having a
longitudinally smooth plunger passing through the opening to the
top interior portion of the lock housing and engaged in the locking
device of claim 8, comprising the steps of: (a) activating the
release mechanism to move the rolling element retainer away from
the top opening; (b) continuing the distal movement of the rolling
element retainer until the width of the tapered interior is
sufficient that the rolling element does not simultaneously contact
both the tapered interior and the longitudinally smooth plunger;
(c) withdrawing the plunger out through the top opening.
18. The method of claim 18, wherein the release mechanism is
actuated by pulling a draw member connected to the release
mechanism.
19. The method of claim 18, wherein the plunger is in a form
selected from the group consisting of solid wire, rod, and stranded
flexible wire.
20. A prosthetic locking device in a prosthetic socket for
receiving a substantially smooth plunger attached to a prosthetic
sleeve comprising: (a) a lock housing having a top proximal opening
for introduction of a substantially smooth plunger, and having an
interior with a top portion, a conically tapered intermediate
portion expanding distally away from the top portion, and a bottom
portion (b) a rolling element retainer having a base with a central
opening, positioned within the interior of the clutch lock housing
and also having a cam element; (c) at least three spherical rolling
elements positioned upon the base of the rolling element retainer
outward of the central opening; (d) a compressible spring biasing
the rolling element retainer toward the proximal opening; (e) a
release mechanism which engages the cam element and moves the
rolling element retainer distally from the proximal opening when
activated.
Description
FIELD OF THE INVENTION
[0001] The present invention is an improved locking device for
attaching a prosthesis to a suspension sleeve on a residual
limb.
BACKGROUND OF THE INVENTION
[0002] Various methods of attaching a prosthesis to an amputee's
residual limb have been utilized over the years. Despite advances
in materials and design many of the older methods are still being
used. The earliest methods were strap and belt type suspension
systems. In this design, the amputee inserted the residual limb
into the prosthesis and tightened a belt, typically made from
leather, to hold the prosthesis to the limb. This design was
fraught with practical difficulties, but for many years was the
only design available. A second-generation design improvement uses
flexible inner integral suction suspension sockets. These designs
are especially useful for above-knee prostheses. The amputee simply
pulls the prosthesis over the residual limb, while the flexible
interior of the socket adheres to the limb creating a vacuum that
suctions the prosthetic in place. A valve is installed within the
socket to break the suction.
[0003] More recent designs have employed mechanical connectors,
combined with a removable roll-on suction suspension sleeve. These
mechanical connectors consist of: 1) lanyard systems utilizing a
braided or twisted polymeric cord attached to the end of the
suction suspension sleeve which passes through the socket where it
can be secured external to the prosthesis; 2) shuttle lock systems,
having a ring attached to the suspension sleeve to receive a pin
inserted through the socket; 3) a ratchet type shuttle lock system,
using a barbed plunger extending from the end of the suction
suspension sleeve and engaging a ratchet mechanism on the
prosthesis; and 4) gear driven clutch lock systems using a plunger
with teeth to engage a gear mounted to a shaft turning on a one-way
bearing where the plunger once engaged with the gear is restricted
from upward vertical movement.
[0004] Most recently, smooth pin lock systems have been devised in
an attempt to overcome the drawbacks of the earlier mechanical lock
systems such as Gramnas U.S. Pat. No. 5,298,290 ('290). Gramnas
uses a washer to lock the plunger. The washer is housed such that
when the plunger pierces the interior of the washer the washer
becomes biased against the plunger by springs, which flank the
washer. The springs are actuated by a single bearing. The bearing
serves to compress one spring while leaving the other to bias the
washer against the interior of the housing. Thus the washer becomes
angled and the plunger is prevented from exiting the lock. Because
the Gramnas design does not rely on gears or ratchets to secure the
sleeve to the socket less play is introduced into the lock. Despite
the improvements that the smooth pin lock system offers, it has not
been a complete solution and has introduced its own
disadvantages.
[0005] All of the automatic locking mechanical connectors
(ratcheting shuttle, gear driven clutch, and smooth pin) have the
drawback of requiring the plunger and the lock to be aligned on the
same axis. The nature of the design of the ratcheting shuttle and
gear driven clutch type locks permits a certain amount of play or
backlash that allows the residual limb to piston within the socket.
The lanyard and shuttle lock systems do not automatically lock and
cannot accommodate volume changes in the residual limb without
manual adjustments. Volume changes occur as the amputee bears
weight on the residual limb causing swelling or shrinkage in the
fleshy portion of the residual limb. Limb shrinkage loosens the fit
in the socket and causes the residual limb to slip deeper into the
prosthesis. The practical result is that additional play is
introduced requiring the amputee to make frequent adjustments to
maintain a snug fitting. The ratcheting shuttle lock also suffers
from this drawback because the discrete locking steps are spaced
too widely to make fine adjustments.
[0006] Smooth pin systems must conform to tight tolerances in order
to work properly. As components wear, the retention of the
prosthesis becomes less secure. This is particularly true in smooth
pin systems such as the Gramnas invention, where the smooth pin is
restricted from moving out of the lock by a washer that contacts
the plunger with a narrow and limited surface area. Over time, the
limited surface area of the washer becomes worn, introducing
unwanted play or backlash into the locking mechanism. An additional
drawback to the washer design is that it is incapable of accepting
flexible plungers because the angle generated by the washer is
insufficient to prevent a flexible plunger from snaking out of the
lock housing. The design therefore requires the plunger and the
lock to be aligned on the same axis. When the lock is manufactured
with less than perfect alignment in the socket the washer is
subject to extraordinary wear causing the locking mechanism to fail
prematurely.
[0007] A further drawback common to all the mechanical connectors
is that they are necessarily manufactured with materials that can
withstand the rigors of the locking mechanism. Commonly, the moving
and contacting parts are fabricated from high carbon bearing grade
steel and hardening the various parts, such as by heat treatment.
Such steel bearing grade parts, however, are highly subject to
corrosion, particularly when the prosthesis is used in environments
offering exposure to liquids or other contaminants. Internal
corrosion of the locking device can lead to seizure and failure of
the moveable components.
[0008] Efforts to overcome the corrosion problem by forming the
moving components of a corrosion resistant metal alloy, such as
austenitic stainless steel (type 300 series) typically are not
practical since such corrosion resistant steel cannot be hardened
to the extent necessary for satisfactory life of the moving
components. Alternately, forming the moving components of
martensitic stainless steels, such as 440C, may provide a bearing
grade steel which is hardenable. However, the corrosion resistance
is less than that of the 300 series stainless steels. The result is
that neither grade of stainless is suitable for the current lock
designs. Therefore, amputees that live active lifestyles, who are
prone to get their prosthesis wet are forced to live with locking
mechanisms that corrode or fail to operate with peak
efficiency.
[0009] The present invention addresses these potentially
troublesome issues while combining the ease of use of an automatic
lock with the stepless adjustability of the clutch and smooth pin
lock.
BRIEF SUMMARY OF THE INVENTION
[0010] This invention is designed to securely lock a sleeve fitted
to the amputee's residual limb to a corresponding prosthesis
without discrete steps and with little to no backlash during
engagement. The invention utilizes a plunger on the sleeve, which
is engaged in the prosthesis then detaches when a release mechanism
is operated. Rolling elements in the prosthesis portion lock onto
the plunger without the need to hold it in perfect alignment,
allowing a certain amount of angular misalignment when mounting the
lock in the prosthesis. Because the lock is permanently molded or
laminated into the socket of the prosthesis during fabrication, a
design that can function with imperfect alignment offers advantages
to the manufacturer or technician by reducing the likelihood that
the prosthesis would need to be re-fabricated. Such a design, also
offers advantages to the amputee by reducing the difficulty of
adapting to a poorly aligned socket.
[0011] This device is also designed to compensate for dimensional
variances in the plunger that may occur between plungers of
different construction, for example, solid wire or flexible
stranded cable, as well as variances that may occur throughout the
life of the plunger due to wear.
[0012] Another significant advantage of the invention, not
addressed by the prior art, is that the moving components, which
include the plunger and rolling elements, can be made of softer
materials, which are more resistant to oxidation in wet or humid
environments. Examples of suitable materials include but are not
limited to austenitic stainless steel, titanium, and brass. This
feature will allow the amputee to use the locking device in aquatic
sports with less concern of the lock rusting or corroding.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a partial sectional view of a prosthetic socket
containing a prosthetic lock according to the invention.
[0014] FIG. 2a is a cross-sectional front plan view of a prosthetic
lock according to the invention with a plunger in an unlocked
position just before making initial contact with a rolling
element.
[0015] FIG. 2b is a complementary side plan view of the locking
device as illustrated in FIG. 2a showing the cam follower at the
top of the cam track.
[0016] FIG. 3a is a cross-sectional front plan view of a prosthetic
lock according to the invention with a plunger contacting a rolling
element with sufficient force to compress the lock spring.
[0017] FIG. 3b is a complementary side plan view of the locking
device as illustrated in FIG. 3a showing the cam followers
descending the cam track in response to the initial compression of
the lock spring.
[0018] FIG. 4a is a cross-sectional front plan view of a prosthetic
lock according to the invention with the plunger in a locked
position.
[0019] FIG. 4b is a complementary side plan view of the locking
device as illustrated in FIG. 4a showing the cam follower
descending the cam track in response to the plunger compressing the
lock spring to a locking depth.
[0020] FIG. 5a is a cross-sectional front plan view of the
prosthetic lock according to the invention with the plunger
released from the locked position by the release mechanism.
[0021] FIG. 5b is a complementary side plan view of the locking
device as illustrated in FIG. 5a showing the cam follower fully
descended along the cam track to an unlocking position.
[0022] FIG. 6 is a partial section front plan view of a prosthetic
lock according to the invention with a flexible plunger with an
off-axis translation
[0023] FIG. 7 is a partial section view of a prosthetic release
mechanism according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] Referring now to the drawings and in particular to FIG. 1, a
cross-sectional view of a prosthetic socket 15 with a smooth
plunger 30 engaged in a locking device 10 is shown. The plunger 30
is attached to the distal end of a sleeve 6 adapted to fit over the
residual limb of an amputee. Typical sleeve materials are
urethanes, thermoplastic elastomers, or silicone based polymers.
The socket 15 and locking device 10 are secured to the proximal end
of a prosthesis, typically a prosthetic limb. The plunger 30 is
shown fully engaged within the locking device 10. The distal end 31
of the plunger has passed through the locking device 10 and
occupies the prosthetic socket plunger cavity 16. The plunger 30
may be tubular or rigid as depicted in FIG. 2a, or flexible such as
the braided or twisted cable depicted in FIG. 6.
[0025] In a preferred embodiment the plunger 30 should be
substantially smooth along its length, however, as in the case of
braided cable, ridges in and around the circumference of the
plunger 30 are not objectionable. In addition, the plunger 30
should not be limited to a cylindrical form and may also be a
multifaceted prismatic member (triangular, rectangular, hexagonal,
etc.). Typically, the locking device 10 contains a release
mechanism 19 that detaches the plunger 30 by depressing a release
button 22, shown in FIG. 1. Also shown is button shield 23 to
prevent accidental release of the locking device 10. The release
mechanism 19 is not essential to the success of the invention and
may be any one of a variety of means to disengage the plunger 30
from the locking device 10. For instance, cam mechanisms that are
linearly or radially actuated, a pin hinged linkage, or
gear-to-gear or gear-to-rack mechanisms that may be actuated by a
pushing member or a drawing member may be used. An exemplerary
release mechanism is disclosed in more detail in FIG. 7.
[0026] FIGS. 2a-b, 3a-b, 4a-b, and 5a-b depict the plunger 30, at
various stages of engagement with the locking device 10. For
convenience of illustration plunger 30 is shown in isolation from
sleeve 6 (shown in FIG. 1) in which it is secured during use.
[0027] FIG. 2a shows the locking device 10 in an unlocked position
with no plunger 30 engaged in the lock. The plunger 30 is shown
entering the proximal end of the lock housing 20 just before making
initial contact with rolling elements 35. Once separated by the
plunger 30, the rolling elements 35 remain in contact with the
tapered interior 32 of the clutch lock body 29 due to force applied
by a lift such as, lock spring 37, which biases the rolling element
retainer 36 to the top most portion 33 of the tapered interior 32.
The shape of the rolling elements 35 may be cylindrical, spherical,
elliptical or any other shape that allows rolling elements 35 to
contact the tapered lock-housing interior 32 when force is applied
by the plunger 30. The number of rolling elements 35 may also be
variable. The embodiment shown in FIG. 2a has three rolling
elements 35 within the rolling element retainer 36, but it is
possible to have a larger plurality or only one rolling element 35
in a properly configured retainer 36. For instance, single rolling
element 35 requires that at least one interior surface not be
tapered. With a single cylindrical rolling element 35, only one
wall of the retainer 36 would need to be tapered.
[0028] As illustrated in FIG. 2a the rolling elements 35 have not
yet begun begun to be forced outward. Before the plunger comes into
contact with the rolling elements 35 the lock spring 37 has not yet
been compressed. Cam followers 27 are shown attached by the cam
spacers 28 to the rolling element retainer 36. The cam follower 27
are shown between upper cam track wall 34a and lower cam track wall
34b.
[0029] FIG. 2b shows the exterior of the locking device 10 and the
position of cam follower 27 when plunger 30 is in the uncompressed
position depicted in FIG. 2a. The cam follower 27 is at the top of
radial cam track 18.
[0030] FIG. 3a shows the plunger 30 beginning to penetrate the
interior of the clutch lock body 29. The downward force placed on
the rolling elements 35 begins to compress the lock spring 37. The
rolling elements 35 begin to spin or roll along the walls of
tapered interior 32 as the plunger 30 is inserted deeper into the
clutch lock body 29. The rolling element retainer 36 and rolling
elements 35 descend within the tapered interior 32 of the clutch
lock body 29. As illustrated, a small clearance space has developed
between the retainer 36 and the top most portion 33 of the tapered
interior 32.
[0031] FIG. 3b shows the exterior of the locking device 10 and the
position of cam follower 27 when the plunger 30 is in the position
depicted in FIG. 3a. The cam follower 27 has descended down the cam
track 18 a distance, which corresponds to the partial compression
of the lock spring 37.
[0032] FIG. 4a shows the plunger 30 after fully penetrating the
clutch lock body 29. In addition the plunger distal end 31 has
passed through the lock spring 37 and out of the locking device 10.
Once the distal end 31 has passed the rolling elements 35, and the
full diameter of plunger 30 is disposed between those elements 35,
the plunger 30 resists removal. Notably, in this locked position
the plunger 30 may still pass freely downward through the rolling
elements 35 of the locking device 10 until the plunger face 17
strikes the plunger guide 21.
[0033] In the locked position shown in FIG. 4a the plunger 30 has
moved the rolling elements 35 down the tapered interior 32 to a
position where the width of the interior 32 is just adequate to
accommodate the plunger 30 and the rolling elements 35. This
position generally results after the full diameter of plunger 30
has passed the equator of the rolling elements 35. At this point
the plunger 30 cannot be retrieved from the locking device 10
without activating the release mechanism.
[0034] After the plunger 30 has passed the equator of the rolling
elements 35 it cannot be removed from the locking device 10 because
the rolling elements 35 are biased upwards by lock spring 37 and
inwards against plunger 30 by the tapered interior 32. Pulling the
plunger 30 upward in the direction that would remove it from the
lock 10 causes the plunger 30 to frictionally interface with
rolling elements 35, which are thereby encouraged to roll up the
tapered interior 32 of the clutch lock body 29. This action causes
the rolling elements 35 to be even more tightly compressed against
the plunger 30. Because rolling elements 35, plunger 30 and the
tapered interior 32 are not made of compressible material, the
plunger 30 and rolling elements 35 in rolling element retainer 36
effectively form a wedge, which cannot be moved upwards within the
lock 10. While the rolling elements 35, plunger 30 and tapered
interior 32 are not made of compressible material, they are
preferably made of softer more corrosion resistant materials than
prior art prosthetic locking devices. Examples include corrosion
resistant grades of stainless steel, titanium, and other corrosion
resistant alloys. This is possible because the invention, unlike
prior locks, displaces wear over a larger surface area and requires
less force to initially secure and hold the prosthesis in place.
Because the rolling elements 35 roll and spin during the locking
process no single portion of the rolling elements 35 consistently
contacts the plunger 30. The plunger 30 also being cylindrical
offers more surface area to contact the rolling elements. The use
of a plurality of spherical rolling elements acts to both
distribute the contacting portions of rolling elements 35 over the
entire surface of those elements, and to maximize the number of
contacts between plunger 30 and rolling elements 35.
[0035] FIG. 4b shows the exterior of the locking device 10 and the
position of cam follower 27 when plunger 30 and retainer 36 are
positioned as depicted in FIG. 4a. The cam follower 27 has
descended down the cam track 18 a distance, which corresponds to
the partial compression of the lock spring 37. The lock spring 37
does not need to compress further to accommodate any length of
plunger 30, because the width of the tapered interior 32 is
adequate at this point to accommodate the plunger 30 and the
rolling elements 35. Thus even as the plunger 30 is inserted
further until the plunger face 17 interfaces with guide 21, there
is no additional downward pressure to further compress the lock
spring 37.
[0036] FIG. 5a shows the plunger 30 in an unlocked position as the
release mechanism has compressed the lock spring 37 to the extent
that the rolling elements 35 are no longer in intimate contact with
both the plunger 30 and the tapered interior 32. So long as the
release mechanism holds the lock spring 37 in this compressed
position the plunger 30 can be pulled back through the top 11 of
the locking device 10, because the rolling elements 35 will not
simultaneously engage both plunger 30 and tapered interior 32 and
roll upward as the plunger 30 is removed.
[0037] FIG. 5b shows the exterior of the locking device 10 and the
position of cam follower 27 when the retainer 36 is in the position
depicted in FIG. 5a. The cam follower 27 has descended to the
bottom of the cam track 18, a distance, which corresponds to the
nearly total compression of the lock spring 37. The cam follower 27
is typically placed in this position by a radially actuated release
mechanism. A linearly actuated release mechanism is disclosed in
greater detail below in connection with FIG. 7.
[0038] FIG. 6 illustrates a unique feature of the present
invention, which allows flexible plungers 30 to enter the locking
device 10 at irregular angles while maintaining reliable locking
function. This is particularly beneficial when the locking
mechanism has been cast into the prosthetic socket or limb at an
imperfect angle. As shown in FIG. 6 the plunger 30 has entered the
locking device 10 at a slight angle from the right side of the
plunger guide 21. The rolling elements 35 accommodate the angled
entry directing the plunger 30 through the rolling element retainer
36 and the locking device 10 while establishing a reliable lock. As
previously described once the full diameter of plunger 30 has
passed the equator of the rolling elements 35 it cannot be removed
through the locking device top 11. Other locking devices that allow
angular plunger 30 entry usually impart some amount of play in the
locking hold. The present invention provides a consistent lock
while minimizing any play or looseness due to an angled entry.
[0039] FIG. 7 illustrates one embodiment of the release mechanism
19 that can be used with the invention. The plunger 30 is shown
fully engaged within the locking device 10. The plunger 30 is
released by pressing the release button 22 that communicates via
release pin 25 to release cam 26. The release cam 26 has a
downwardly slanted face 26a, which pushes the cam follower 27
downward in the linear cam track 18 in the clutch lock body 29. Cam
follower 27 is connected to the rolling element retainer 36. As the
downward slanted face 26a passes over cam followers 27, both cam
followers 27 and attached rolling element 36 move downward
compressing the lock spring 37 to the extent shown in FIG. 5. The
rolling element retainer 36 also moves the rolling elements 35
downward within the tapered interior 32 to a wider portion. The
width of the tapered interior 32 at this point is such that rolling
elements 35 do not simultaneously contact both the plunger 30 and
the tapered interior 32 of the clutch lock body 29, thereby
effecting the release of the plunger 30 from the locking device 10.
Release button 22 is normally held in the locked position by the
release spring 24 and may be protected from accidental actuation by
a button shield 23 as shown in FIG. 1.
[0040] While a preferred embodiment has been shown and described,
it will be understood that it is not intended to limit the
disclosure, but rather it is intended to cover all modifications
and alternate methods falling within the spirit and the scope of
the invention as defined in the appended claims.
* * * * *