U.S. patent number RE34,433 [Application Number 07/700,244] was granted by the patent office on 1993-11-09 for caster locking mechanism and carriage.
This patent grant is currently assigned to Snap-on Tools Corporation. Invention is credited to Charles H. Heiligenthal, Jack A. Parise, George R. Slivon.
United States Patent |
RE34,433 |
Heiligenthal , et
al. |
November 9, 1993 |
**Please see images for:
( Certificate of Correction ) ** |
Caster locking mechanism and carriage
Abstract
A wheeled carriage has a chassis with a plurality of swivel
casters, and a locking assembly actuated by a foot pedal located
along the front of the carriage. Pushing down on the foot pedal
rotates a cam that engages a cam follower on a "T" bar frame
supporting two locking rings which respectively overlie two of the
caster wheels to move the rings into a locking position in
engagement with the wheels to lock the wheels and the casters in
any position. The cam follower surface includes a ramp portion
engageable by the cam for driving the rings to their locking
position and a horizontal latch portion engageable by the cam in
its "overcenter" position for holding the rings in their locking
position. A lifter bar is engageable by the user's foot to rotate
the cam back off the follower and permit the rings to resiliently
return to their release position. The cam and follower surfaces are
so arranged that a limited rotation of the cam through less than
about 25 degrees is sufficient to move the assembly between its
release and locking configurations so that the locking assembly can
be used where only a few inches of clearance beneath the chassis is
available.
Inventors: |
Heiligenthal; Charles H. (Oak
Creek, WI), Slivon; George R. (Kenosha, WI), Parise; Jack
A. (Kenosha, WI) |
Assignee: |
Snap-on Tools Corporation
(Kenosha, WI)
|
Family
ID: |
26993054 |
Appl.
No.: |
07/700,244 |
Filed: |
May 15, 1991 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
342523 |
Apr 24, 1989 |
04922574 |
May 8, 1990 |
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Current U.S.
Class: |
16/35R; 188/1.12;
280/79.11; 296/20 |
Current CPC
Class: |
B60B
33/021 (20130101); B60B 33/0086 (20130101); B60B
33/0092 (20130101); B60B 33/025 (20130101); B60B
33/026 (20130101); B60B 33/0039 (20130101); B60B
33/0049 (20130101); B60B 33/0057 (20130101); B60B
33/0068 (20130101); Y10T 16/195 (20150115); B60B
2200/43 (20130101); B60B 33/0073 (20130101) |
Current International
Class: |
B60B
33/00 (20060101); B60B 33/02 (20060101); B60B
033/00 () |
Field of
Search: |
;16/35D,35R ;188/1.12,29
;296/20 ;280/79.11 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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568165 |
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Oct 1975 |
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CH |
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2179848 |
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Mar 1987 |
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GB |
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Primary Examiner: Sipos; John
Assistant Examiner: Cuda; Carmine
Attorney, Agent or Firm: Emrich & Dithmar
Claims
.[.We claim.]. .Iadd.What is claimed is.Iaddend. :
1. In a caster locking assembly including mounting means adapted to
be coupled to an associated load, a caster wheel rotatably carried
by the mounting means for rolling engagement with an underlying
support surface, .Iadd.the caster having a swivel yoke supporting
the caster wheel and carried by the mounting means for rotation
about a swivel axis, .Iaddend.and a locking ring resiliently
carried by the mounting means .Iadd.substantially coaxially with
the swivel axis .Iaddend.and overlying the wheel, the locking ring
lying in a plane and .Iadd.having a central axis substantially
perpendicular to said plane and .Iaddend.being movable between a
release position out of engagement with the wheel and a locking
position firmly frictionally engaging the wheel for locking
thereof, the locking ring being resiliently biased toward its
release position, the improvement comprising: a cam follower
coupled to the locking ring and having a follower surface including
.[.an inclined.]. .Iadd.a planar .Iaddend.ramp portion
.Iadd.inclined with respect to said plane,.Iaddend.a locking cam
carried by the mounting means for rotation about a pivot axis
inclined with respect to the direction of movement of the locking
ring and having a cam surface disposed for camming engagement with
said follower surface, and actuator means coupled to said cam for
effecting rotation thereof between release and locking conditions,
.[.said cam surface being out of engagement with said follower
surface when said cam is disposed in its release condition for
permitting the locking ring to move to its release position,.].
movement of said cam from its release condition to its locking
condition moving said cam surface .[.into.]. .Iadd.in
.Iaddend.camming engagement with said ramp portion of said follower
surface for driving the locking ring to its locking positioni ,
whereby the locking ring in its locking position effectively
prevents swiveling of the caster. .[.
2. The caster locking assembly of claim 1, wherein the caster
includes a swivel yoke supporting the caster wheel and carried by
the mounting means for rotation about a swivel axis, the locking
ring being disposed substantially coaxially with the swivel axis
and, in its locking position, effectively preventing swiveling of
the caster..].
3. The caster locking assembly of claim 1, wherein said cam
follower includes a latch portion intersecting said ramp portion at
the upper end thereof and engageable by said cam surface for
holding the locking ring in its locking position.
4. The caster locking assembly of claim 3, wherein said follower
surface further includes a stop portion intersecting said latch
portion and engageable with said cam surface for limiting the
rotational movement of said cam.
5. The caster locking assembly of claim 1, wherein said cam has a
part-circularly cylindrical portion coaxial with said pivot axis
and a generally triangular prismatic tip portion projecting from
said body portion for engagement with said cam follower.
6. The caster locking assembly of claim 3, wherein said actuator
means includes a locking shaft carried by the mounting means for
rotation about the pivot axis, said cam being carried by said shaft
for rotation therewith.
7. The caster locking assembly of claim 6, wherein said actuator
means further includes foot pedal means projecting from said
locking shaft substantially normal to the pivot axis for access by
the foot of a user, said foot pedal means being depressible by the
user's foot to rotate said locking cam from its release condition
to its locking condition.
8. The caster locking assembly of claim 7, wherein said actuator
means further includes a lifter bar projecting laterally from said
foot pedal means and elevated a predetermined distance thereabove
sufficient so that when said locking cam is disposed in its locking
condition there is sufficient clearance beneath said lifter bar for
insertion of a user's foot for lifting of said actuator means to
rotate said locking cam from its locking condition back to its
release condition.
9. In a caster locking assembly including mounting means adapted to
be coupled to an associated load, a pair of caster wheels
respectively rotatably carried by the mounting means for rolling
engagement with an underlying support surface, a locking frame
resiliently supported by the mounting means, and a pair of locking
rings carried by the locking frame .Iadd.and lying in a plane
.Iaddend.and respectively overlying the wheels .Iadd.and having
substantially parallel central axes substantially perpendicular to
said plane.Iaddend., the locking frame being movable between a
release position wherein the locking rings are out of engagement
with the wheels and a locking position wherein the locking rings
respectively firmly frictionally engage the wheels for locking
thereof, the locking frame being resiliently biased toward its
release position, the improvement comprising: a cam follower
carried by the locking frame and having a follower surface
including .[.an inclined.]. .Iadd.a planar .Iaddend.ramp portion
.Iadd.inclined with respect to said plane.Iaddend., a locking cam
carried by the mounting means for rotation about a pivot axis
inclined with respect to the direction of movement of the locking
rings and having a cam surface disposed for camming engagement with
said follower surface, and actuator means coupled to said cam for
effecting rotation thereof between release and locking conditions,
.[.said cam surface being out of engagement with said follower
surface when said cam is disposed in its release condition for
permitting the locking frame to move to its release position,.].
movement of said cam from its release condition to its locking
condition moving said cam surface .[.into.]. .Iadd.in
.Iaddend.camming engagement with said ramp portion of said follower
surface for driving the locking frame to its locking position.
10. The caster locking assembly of claim 9, wherein the caster
includes a swivel yoke supporting the caster wheel and carried by
the mounting means for rotation about a swivel axis, the locking
ring being disposed substantially coaxially with the swivel axis
and, in its locking position, effectively preventing swiveling of
the caster.
11. The caster locking assembly of claim 9, wherein said pivot axis
substantially bisects a line which interconnects the swivel axes
and is substantially perpendicular thereto.
12. The caster locking assembly of claim 9, wherein said follower
surface includes a latch portion intersecting said ramp portion at
the upper end thereof and engageable by said cam surface for
holding the locking frame in its locking position.
13. The caster locking assembly of claim 9, wherein the locking
frame is in the form of an elongated resilient metal bar
.[.couple.]. .Iadd.coupled .Iaddend.at one end thereof to the
mounting means in cantilever fashion and carrying the locking rings
and said cam follower adjacent to the other end thereof, said bar
being normally disposed in the release position of the locking
frame and being resiliently deflectable from that position.
14. In a wheeled carriage including a chassis, a plurality of
swivel yokes carried by the chassis for rotation respectively about
substantially parallel swivel axes, a plurality of wheels
respectively carried by the yokes for rotation about axes disposed
substantially perpendicular respectively to the swivel axes, a
locking frame resiliently supported by the chassis, and at least
two locking rings carried by the locking frame and respectively
overlying at least two of the wheels substantially coaxially with
the corresponding swivel axes, the locking frame being movable
between a release position wherein the locking rings are out of
engagement with the associated wheels and a locking position
wherein the locking rings firmly frictionally engage the associated
wheels for locking thereof, the locking frame being resiliently
biased toward its release position, the improvement comprising: a
cam follower carried by the locking frame and having a follower
surface including .[.an inclined.]. .Iadd.a planar .Iaddend.ramp
portion .Iadd.inclined with respect to a plane which is
substantially perpendicular to the swivel axes.Iaddend., a locking
cam carried by the chassis for rotation about a pivot axis inclined
with respect to the direction of movement of the locking rings and
having a cam surface disposed for camming engagement with said
follower surface, and actuator means coupled to said cam for
effecting rotation thereof between release and locking conditions,
.[.said cam surface being out of engagement with said follower
surface when said cam is disposed in its release condition for
permitting the locking frame to move to its release position,.].
movement of said cam from its release condition to its locking
condition moving said cam surface .[.into.]. .Iadd.in
.Iaddend.camming engagement with said ramp portion of said follower
surface for driving the locking frame to its locking position.
15. The carriage of claim 14, wherein the chassis .[.i.]. .Iadd.is
.Iaddend.generally rectangular in shape, the at least two wheels
being disposed at one end of the chassis.
16. The carriage of claim 14, wherein said actuator means includes
a locking shaft carried by the chassis for rotation about said
pivot axis, said cam being carried by said shaft for rotation
therewith, foot pedal means projecting from said locking shaft
substantially perpendicular to said pivot axis toward the front of
the chassis for engagement and depression by the foot of a user to
rotate said cam from its release condition to its locking
condition.
17. The carriage of claim 16, wherein said actuator means further
includes a lifter bar projecting laterally from said foot pedal
means and elevated a predetermined distance thereabove sufficient
to permit insertion of a user's foot beneath said lifter bar when
said cam is disposed in its locking condition for lifting of said
actuator means to rotate said cam from its locking condition to its
release condition.
18. The carriage of claim 16, wherein the locking frame includes
means rotatably supporting said shaft adjacent to one end thereof,
and further comprising auxiliary support means carried by the
chassis for rotatably supporting said shaft adjacent to the other
end thereof.
19. The carriage of claim 18, and further comprising guide means
carried by the locking frame and cooperating with said shaft to
inhibit lateral movement of the locking frame during operation of
said actuator means.
20. The carriage of claim 14, wherein the locking frame is in the
form of an elongated resilient metal bar coupled at one end thereof
to the chassis in cantilever fashion and carrying the locking rings
and said cam follower adjacent to the other end thereof, said bar
being normally disposed in the release position of the locking
frame and being resiliently deflectable from that position.
21. The carriage of claim 14, wherein said cam rotates through an
angle of less than 25 degrees between the release and locking
conditions thereof.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to wheeled carriages of the type
wherein the wheels are in the form of casters. The invention
relates in particular to means for locking the casters so as to
prevent rotation of the caster wheels and to prevent swiveling
motion in the case of swivel casters.
2. Description of the Prior Art
In caster-wheeled carriages, it is frequently desirable to lock the
caster wheels against rotation for holding the carriage in a
predetermined location and preventing any accidental movement
thereof. It is well known to provide a separate caster brake or
lock for each caster wheel. Such brake or lock assemblies are
disclosed, for example in U.S. Pat. No. 3,942,608. It is also known
to provide locking mechanisms which simultaneously lock more than
one caster.
This latter type of caster locking mechanism is disclosed, for
example, in U.S. Pat. Nos. 3,304,116 and 4,164,355. This type of
assembly provides a locking ring overlying each of several swivel
caster wheels substantially coaxially with the caster swivel axis.
The locking rings are all interconnected by a locking frame which
is moved by means of a cam mechanism between an upper release
position wherein the rings are out of contact with the caster
wheels to permit free movement thereof and a lowered locking
position wherein the rings firmly engage the caster wheels to
prevent rotation thereof and also to prevent swiveling thereof. In
that prior art device the locking assembly is actuated by a handle
member which rotates an eccentric cam through an angle of about
90.degree. between the release and locking configurations. That
arrangement is satisfactory where there is a large amount of
under-chassis clearance, such as hospital beds or the like, to
accommodate the wide-angle rotation, or where the handle assembly
can extend beyond the ends of the chassis.
But that prior arrangement is not suitable for use where there is
very limited clearance which will not permit a full 90.degree.
rotation of the cam member. For example, in carriages with
low-slung chassis, such as garage mechanic tool chests, there are
only a few inches of clearance between the chassis and the floor.
This would make it effectively impossible for a user to exert
sufficient leverage to rotate a cam mechanism through a 90.degree.
angle. It would be possible to extend a cam shaft beyond an end of
the carriage, but this increases the effective floor space occupied
by the carriage and also necessitates that the carriage always be
utilized in an orientation which maintains access to the end from
which the actuator shaft projects.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide an
improved caster locking assembly which avoids the disadvantages of
prior locking assemblies while affording additional structural and
operating advantages.
An important feature of the present invention is to provide a
caster locking assembly which can be disposed beneath the chassis
of a wheeled carriage and requires only a few inches of floor
clearance for operation thereof.
Still another feature of the invention is to provide a locking
assembly of the type set forth which includes a rotatable cam which
requires rotation through a range of less than 25.degree. to effect
operation thereof between release and locking configurations.
Still another feature of the invention is the provision of a
locking assembly of the type set forth, which simultaneously locks
plural caster wheels against both wheel rotation and caster
swiveling.
Another feature of the invention is the provision of a wheeled
carriage having plural swivel casters which are lockable by a
locking assembly of the type set forth.
These and other features of the invention are attained by
providing, in a caster locking assembly including mounting means
adapted to be coupled to an associated load, a caster wheel
rotatably carried by the mounting means for rolling engagement with
an underlying support surface, and a locking ring resiliently
carried by the mounting means and overlying the wheel, the locking
ring being movable between a release position out of engagement
with the wheel and a locking position firmly frictionally engaging
the wheel for locking thereof, the locking ring being resiliently
biased toward its release position, the improvement comprising: a
cam follower coupled to the locking ring and having a follower
surface including an inclined ramp portion, a locking cam carried
by the mounting means for rotation about a pivot axis and having a
cam surface disposed for camming engagement with the follower
surface, and actuator means coupled to the cam for effecting
rotation thereof between release and locking conditions, the cam
surface being out of engagement with the follower surface when the
cam is disposed in its release condition for permitting the locking
ring to move to its release position, movement of the cam from its
release condition to its locking condition moving the cam surface
into camming engagement with the ramp portion of the follower
surface for driving the locking ring to its locking position.
The invention consists of certain novel features and a combination
of parts hereinafter fully described, illustrated in the
accompanying drawings, and particularly pointed out in the appended
claims, it being understood that various changes in the details may
be made without departing from the spirit, or sacrificing any of
the advantages of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
For the purpose of facilitating an understanding of the invention,
there is illustrated in the accompanying drawings a preferred
embodiment thereof, from an inspection of which, when considered in
connection with the following description, the invention, its
construction and operation, and many of its advantages should be
readily understood and appreciated.
FIG. 1 is a fragmentary, side elevational view of a wheeled
carriage incorporating the locking assembly of the present
invention, with a portion of the carriage removed;
FIG. 2 is a fragmentary end elevational view of the carriage of
FIG. 1, as viewed from the right-hand end thereof;
FIG. 3 is an enlarged, perspective, exploded view of the caster
locking assembly of FIG. 1;
FIG. 4 is an enlarged, fragmentary, bottom plan view of the
right-hand end of the carriage of FIG. 1;
FIG. 5 is a top plan view of the assembled caster locking assembly
of FIG. 3, removed from the carriage;
FIG. 6 is an enlarged view, similar to FIG. 2, in partial vertical
section, with the locking assembly illustrated in its release
configuration and with the casters swiveled 90.degree. from their
positions in FIG. 2;
FIG. 7 is a view similar to FIG. 6, illustrating the locking
assembly in its locking configuration;
FIG. 8 is an enlarged, fragmentary view in vertical section taken
generally along the line 8--8 in FIG. 2, and illustrating the
locking assembly in its release configuration; and
FIG. 9 is a further enlarged, fragmentary, perspective view of the
cooperation of the cam and cam follower of the present invention in
the locking configuration of the locking assembly.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGS. 1, 2, 4 and 6-8, there is illustrated a wheeled
carriage, generally designated by the numeral 10, which includes an
elongated, substantially rectangular chassis 11 provided with a
bottom wall 12 having a raised central portion 14 (FIGS. 4 and 8).
The chassis 11 includes a pair of longitudinally extending angles
15 along either side of the raised central portion 14, the angles
15 being connected intermediate the ends thereof by a transverse
channel member 16 which has a pair of parallel vertical side walls
17 interconnected by a bottom wall 18.
Mounted on the chassis 11, respectively adjacent to the four
corners thereof, are four casters, including two swivel casters 20
at one end of the chassis 11 and two fixed casters 20A at the other
end of the chassis 11 (FIG. 1). Each of the casters 20 and 20A
includes a yoke 21 having a bight portion 22 (FIG. 6) which, in the
case of the swivel casters 20, is fixedly secured to a swivel plate
23 mounted on the bottom wall 12 of the chassis 11 for rotation
about a swivel axis 28 (FIG. 6). In the case of the fixed casters
20A, the bight 22 is fixedly secured to the bottom wall 12 of the
chassis 11. The yoke 21 also includes a pair of legs 24 depending,
respectively, from the opposite ends of the bight 22, the legs 24
being substantially vertical in the case of the fixed casters 20A
and being inclined to the vertical in the case of the swivel
casters 20. Disposed between the legs 24 is a wheel 25 rotatable
about a horizontal axle 26, the opposite ends of which are
journaled in the legs 24. If desired, any one or more of the
casters 20 and 20A may be provided with an individual wheel lock 27
(see FIGS. 6-8), but this is optional. In use, it will be
appreciated that the wheels 25 are adapted for rolling engagement
with an underlying support surface, such as a floor 29 (FIGS. 6-8),
for moving the carriage 10, it being appreciated that steering of
the carriage 10 is permitted by the swivel action of the casters
20.
Referring now also to FIGS. 3, 5 and 9, the carriage 10 includes a
caster locking assembly, generally designated by the numeral 30,
constructed in accordance with and embodying the features of the
present invention. The locking assembly 30 includes a frame 31 in
the form of a "T" bar (FIGS. 4 and 5), which includes an elongated
bar 32 extending longitudinally of the chassis 11 and provided at
one end thereof with an upstanding mounting flange 33 which is
fixedly secured to one of the side walls 17 of the channel 16 by
suitable fasteners 34 (FIG. 8). Integral with the bar 32 at the
other end thereof is an upstanding guide flange 33a, having a guide
slot 34a in the upper edge thereof, centrally thereof. The frame 31
also includes a cross bar 35 which extends between the swivel
casters 20 substantially normal to the bar 32, and includes a flat
central portion 36 integral at its opposite ends, respectively,
with a pair of upwardly inclined shoulders 37, which are in turn
integral with raised horizontal end portions 38. The central
portion 36 is fixedly secured to the distal end of the bar 32 by
suitable fasteners 39 (FIG. 4). One or more shims 40 may be
disposed between the cross bar 35 and the bar 32 for proper
adjustment thereof in a manner to be described more fully below,
each of the shims 40 having an elongated longitudinal slot 41
therein to receive the fasteners 39 therethrough. The slots 41
permit the shims 40 to be added or removed by simply loosening the
fasteners 39 without disassembly of the frame 31. The end portions
38 of the cross bar 35 are respectively integral with two locking
rings 43 and 44, which are respectively disposed above the wheels
25 of the swivel casters 20 in encircling relationship with the
yokes 21 and respectively substantially coaxial with the swivel
axes 28.
A cam follower 45 is mounted on the upper surface of the bar 32
adjacent to the distal end thereof by means of the fasteners 39.
The cam follower 45 is an elongated, generally oval body having an
inclined ramp surface 46 formed in one side thereof, the upper end
of the ramp surface 46 intersecting a horizontal latch surface 47
which is recessed below the upper surface of the cam follower 45,
being spaced therefrom by a vertical stop surface 48 (see FIGS. 3
and 9).
The locking assembly 30 also includes an elongated cam shaft 50
which extends through a complementary bore 51 in the mounting
flange 33 of the bar 32 and projects forwardly above the bar 32
through a complementary guide slot 52 in the bottom edge of a
mounting block 53, which is fixedly secured to the bottom wall 12
of the chassis 11 by suitable fasteners 54 (FIG. 4), and thence
through the guide slot 34a in the guide flange 33a of the bar 32.
The shaft 50 is freely rotatable about its axis in the bore 51 and
the slots 34a and 52 and has a cam 55 fixedly secured thereto
between the guide flange 33a and the mounting block 53. The cam 55
has a part-cylindrical body 56 which is coaxial with the shaft 50,
and has projecting therefrom a triangular tip 57 which has a pair
of flat side surfaces 58 which converge to a tip surface 59 (FIGS.
3 and 9). The cam 55 is positioned immediately above the cam
follower 45 for engagement of one of the side surfaces 58 and the
tip surface 59 of the cam 55 with the ramp surface 46 and the latch
surface 47 of the cam follower 45, as will be described in greater
detail below.
Rotation of the shaft 50 and the cam 55 is effected by means of a
crank arm 60 which is unitary with the end of the shaft 50
projecting beyond the attachment flange 33 of bar 32. The crank arm
60 extends substantially perpendicular to the longitudinal axis of
the shaft 50 to the front side of the carriage 10, and is provided
at its distal end with a pedal portion 61 which is disposed
substantially normal to the crank arm 60. The crank arm 60 is also
provided with a lifter bar 62 which has an attachment portion 63
fixedly secured to the crank arm 60, as by welding, adjacent to the
pedal portion 61, but extending in the opposite direction
therefrom. The lifter bar 62 is elevated a predetermined distance
over the pedal portion 61.
Preferably, the bar 32 is preloaded, i.e., it is bent so that it is
inclined at an angle of slightly less than 90.degree. with the
attachment flange 33 and at an angle of slightly greater than
90.degree. with the guide flange 33a. Thus, in its mounted
condition, with the flanges 33 and 33A disposed vertically, the bar
32 is normally disposed in a release position (FIGS. 1, 6 and 8)
inclined slightly upwardly. Preferably, the bar 32 is formed of a
resilient material, such as steel, so as to accommodate deflection
downwardly from its normal release position, and to act essentially
as a leaf spring inherently biased back to its normal release
position. In this normal release position, the locking assembly 30
is disposed in a release configuration, wherein the locking rings
43 and 44 are respectively spaced a slight distance above the
caster wheels 25, out of engagement therewith, for accommodating
free rotation thereof and free swiveling movement thereof (FIGS. 6
and 8). Adjustment of this release position to obtain the proper
clearance between the locking rings 43 and 44 and the wheels 25 can
be effected by insertion or removal of shims 40.
The carriage 10 may be any type of carriage, but in the preferred
embodiment it is in the form of a mechanics' tool chest of the type
utilized by automotive mechanics in automotive garages and the
like. In such carriages, there is typically only a four or
five-inch clearance between the chassis 11 and the floor 29. In
use, the crank arm 60 is so positioned that the pedal portion 61 is
disposed adjacent to the front wall of the carriage 10 so that,
when the crank arm 60 is in its normal release condition (FIGS. 1
and 2) the pedal portion 61 is spaced slightly below the chassis 11
a distance sufficient for a user to insert his foot to depress the
pedal portion 61, thereby rotating the shaft 50 about its axis in a
counterclockwise direction, as viewed in FIGS. 6-8. The cam 55 is
fixed so that when the crank arm 60 is disposed in its normal
release condition, the cam 55 is in the position illustrated in
FIGS. 6 and 8, with its inner side surface 58 disposed closely
adjacent to, but not necessarily in contact with the inclined ramp
surface 46 of the cam follower 45.
When the crank arm 60 is depressed by the user's foot, the side
surface 58 of the cam 55 moves into camming engagement with the
inclined ramp surface 46 of the cam follower 45, depressing the cam
follower 45 and, thereby, the locking frame 31. As the rotation of
the cam 55 continues, the tip surface 59 thereof moves into
engagement with the ramp surface 46 and cams upwardly along it and
then rides up onto the horizontal latch surface 47. At this point,
the cam 55 is in an "over-center38 condition, wherein a line
extending through the axis of the shaft 50 and the line of contact
between the tip surface 59 and the latch surface 47 will be
substantially vertical.
In this condition, the locking assembly 30 is in a locking
configuration (FIG. 7), wherein the pedal portion 61 is closely
adjacent to the floor 29, and wherein the locking rings 43 and 44
have been respectively moved down into firm frictional engagement
with the wheels 25 of the swivel casters 20. Further rotation of
the cam 55 beyond this locking configuration is prevented by
engagement of the side surface 58 of the cam 55 with the stop
surface 48 of the cam follower 45 (FIG. 9). It will be appreciated
that during depression of the crank arm 60 by the users foot,
vertical and lateral movements of the shaft 50 are effectively
prevented by the mounting block 53 and the guide flange 33A. It
will further be noted that the locking assembly 30 is effective for
locking the swivel casters 20 in any swivel position thereof and
effectively preventing not only rotation of the wheels 25 about the
axles 26, but also preventing swiveling of the casters 20.
Because of the cooperation of the cam 55 and the cam follower 45,
it is only necessary to rotate the shaft 50 through a limited angle
of substantially less than 45.degree. to effect movement of the
locking assembly 30 from its release configuration to its locking
configuration. In the preferred embodiment of the invention, it has
been found that rotational movement through an angle of about
22.degree. is sufficient. However, even with this limited
rotational movement, substantially all of the available clearance
between the chassis 11 will be used, so that in the locking
configuration of the locking assembly 30, the pedal portion 61 will
be disposed very closley adjacent to the floor 29. However, the
elevated position of the lifter bar 62 relative to the pedal
portion 61 provides sufficient clearance from the floor 29 to
permit the user to insert his foot beneath the lifter bar 62 to
pivot the crank arm 60 back up to its normal release condition to
move the locking assembly 30 back to its release configuration to
unlock the casters 20.
In a constructional model of the present invention, the cam
follower 45 and the mounting block 53 are formed of suitable
low-friction plastic material, such as nylon. The bar 32 and the
cam 55 may be formed of steel. The clearance beneath the chassis 11
is 4 or 5 inches and the locking rings 43 and 44 move about
one-quarter inch between their release and locking positions. The
height of the cam follower 45 is about 0.2 inch and the cam 55
measures about 1.15 inch from its pivot axis to the tip surface
59.
From the foregoing, it can be seen that there has been provided an
improved caster locking assembly which provides efficient
foot-pedal operation between release and locking configurations for
simultaneously locking plural swivel casters by rotation of a cam
through a limited angle, so as to be operable where only limited
floor clearance is available.
* * * * *