U.S. patent application number 09/992455 was filed with the patent office on 2002-03-21 for hospital bed caster and braking system.
Invention is credited to Cunningham, James D., Larisey, William S. JR., Meyer, Bruce A., Mobley, Donald L., Saar, James J., Tuttle, John.
Application Number | 20020033307 09/992455 |
Document ID | / |
Family ID | 23000130 |
Filed Date | 2002-03-21 |
United States Patent
Application |
20020033307 |
Kind Code |
A1 |
Mobley, Donald L. ; et
al. |
March 21, 2002 |
Hospital bed caster and braking system
Abstract
A patient support apparatus comprises a base frame, a patient
support coupled to the base frame, a plurality of casters each
having a sleeve, and a plurality of caster mounting tubes having an
interior configured to receive the sleeve of a caster. The caster
mounting tubes have a plurality of external side walls, a first
generally planar side wall abutting the base frame. Each of the
plurality of caster mounting tubes are connected to the base frame
by welds located adjacent the first side wall.
Inventors: |
Mobley, Donald L.;
(Batesville, IN) ; Larisey, William S. JR.;
(Summerville, SC) ; Tuttle, John; (Batesville,
IN) ; Saar, James J.; (Guilford, IN) ;
Cunningham, James D.; (Batesville, IN) ; Meyer, Bruce
A.; (Greensburg, IN) |
Correspondence
Address: |
Timothy E. Niednagel
Bose McKinney & Evans LLP
135 N. Pennsylvania Street, Suite 2700
Indianapolis
IN
46204
US
|
Family ID: |
23000130 |
Appl. No.: |
09/992455 |
Filed: |
November 26, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09992455 |
Nov 26, 2001 |
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09263039 |
Mar 5, 1999 |
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6321878 |
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Current U.S.
Class: |
188/1.12 |
Current CPC
Class: |
B60B 33/0049 20130101;
A61G 7/00 20130101; A61G 1/0243 20130101; B60B 33/0021 20130101;
B60B 33/0039 20130101; B60B 33/025 20130101; B60B 33/021 20130101;
B60B 33/026 20130101; B60B 33/0028 20130101; B60B 33/0081 20130101;
A61G 7/0528 20161101; B60B 33/0092 20130101; B60B 33/023 20130101;
B60B 33/0057 20130101; B60B 33/0073 20130101; B60B 33/0068
20130101 |
Class at
Publication: |
188/1.12 |
International
Class: |
B60B 033/00 |
Claims
1. A patient support apparatus comprising: a base frame, a patient
support coupled to the base frame, a plurality of casters each
having a sleeve, and a plurality of caster mounting tubes, each
mounting tube having an interior configured to receive the sleeve
of a caster, a plurality of external side walls including a
generally planar first external side wall abutting the base frame,
the mounting tube being connected to the base frame by welds
located adjacent the first external side wall.
2. The apparatus of claim 1, wherein each of the plurality of
caster mounting tubes has a rectangular outer cross-sectional shape
defined by four external side walls.
3. The apparatus of claim 1, wherein each mounting tube is coupled
to the base frame by first and second welds located at opposite
ends of the first external side wall.
4. The apparatus of claim 3, wherein the first external side wall
abutting the base frame is formed to include a hole, the base frame
is formed to include a hole, the hole in the base frame is aligned
with the hole in the first external side wall, and both holes are
located between the first and second welds.
5. The apparatus of claim 1, wherein the sleeve of each caster has
a cylindrical shape and the plurality of caster mounting tubes each
include interior partially cylindrical concave wall sections
configured to receive one of the cylindrical sleeves.
6. The apparatus of claim 5, wherein the each of the mounting tubes
also includes a corner notch located between the concave wall
sections.
7. The apparatus of claim 1, wherein the plurality of casters each
include a set screw to orient the caster and the caster mounting
tubes are each formed to include a notch configured to receive one
of the set screws.
8. The apparatus of claim 1, wherein each of the caster mounting
tubes has a square cross-sectional shape.
9. The apparatus of claim 1, wherein the sleeve of each caster has
a cylindrical shape.
10. The apparatus of claim 1, wherein the sleeve of each caster has
a rectangular cross-sectional shape.
11. A method for attaching a caster having a cylindrical sleeve to
a base frame of a bed, the method comprising the steps of:
providing a mounting tube having four side walls configured to
provide a substantially rectangular cross-sectional shape; forming
an interior opening through the mounting tube having a generally
round cross-sectional shape to receive the cylindrical sleeve of
the caster therein; placing a first side wall of the mounting tube
against the base frame; welding the mounting tube to the base frame
with the first and second welds located at opposite ends of the
first side wall; and installing the sleeve of the caster into the
interior opening of the mounting tube.
12. The method of claim 11, wherein the caster includes a set screw
to orient the caster, the method further comprising the step of
forming a notch in the mounting tube to receive the set screw of
the caster.
13. The method of claim 11, wherein the four side walls of the
mounting tube are configured to define an interior opening through
the tube having a generally square cross-sectional shape prior to
the forming step.
14. The method of claim 11, wherein each of the caster mounting
tubes has a square cross-sectional shape.
15. The method of claim 11, wherein the welding step is performed
by a two axis welding machine.
16. A method for attaching a caster to a base frame of a bed, the
method comprising the steps of: providing a mounting tube having
four side walls configured to provide a substantially rectangular
cross-sectional shape; providing a caster having a sleeve including
a portion having a substantially rectangular cross-sectional shape,
a lumen having a substantially rectangular cross-sectional shape,
and a spindle having a portion which has a substantially
rectangular cross-sectional shape received in the lumen; placing a
first side wall of the mounting tube against the base frame;
welding the mounting tube to the base frame with the first and
second welds located at opposite ends of the first side wall; and
installing the sleeve of the caster into the interior opening of
the mounting tube.
17. The method of claim 16, wherein the provided caster includes a
brake attached to the spindle.
18. The method of claim 16, wherein the provided caster includes a
locking mechanism attached to the spindle.
19. The method of claim 16, wherein each of the caster mounting
tubes has a square cross-sectional shape.
20. The method of claim 19, wherein each of the caster sleeves has
a square cross-sectional shape, the lumen has a square
cross-sectional shape, and the portion of the spindle has a square
cross-sectional shape.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 09/263,039, filed Mar. 5, 1999, now U.S. Pat. No.
6,321,878, the disclosure of which is incorporated herein by
reference.
BACKGROUND AND SUMMARY OF THE INVENTION
[0002] This invention relates to hospital and long term care beds
and more particularly to hospital beds having four wheels or
casters attached to the base frame for rolling the bed from
location to location and a braking mechanism for maintaining the
bed in a desired location.
[0003] Hospital beds are typically designed to be moved from
location to location and, therefore, have wheels or casters which
permit the hospital bed to be rolled and steered between locations.
During movement it is desirable to have free rolling wheels but
upon reaching the desired location, brakes are usually applied to
the wheels to maintain the bed at the desired location.
[0004] It is well known to provide hospital beds with brake/steer
casters which include mechanisms for blocking the rotation of the
caster wheel or wheels, i.e. braking mechanisms, and mechanisms for
blocking swiveling movement of the caster wheel fork, i.e.
anti-swivel or directional lock mechanisms. Some beds with four
castered wheels include pedals located on opposite sides of the bed
which control the braking and anti-swivel mechanisms in each
caster. An example of such a bed is shown in Rudolf et al., U.S.
Pat. No. 5,377,372. The pedals in Rudolf et al. may not be readily
accessible by a caregiver who is currently pushing the bed.
[0005] Other hospital beds equipped with such brake/steer casters
include four separate brake and/or steer pedals each associated
with only one of the four casters with each brake pedal only
engaging the brake on the caster with which it is associated and
each steer pedal only actuating the anti-swivel mechanism on the
caster with which it is associated. On such hospital beds having
four casters with four unconnected brake mechanisms, prior to
movement of the bed the caregiver must disengage all four brakes by
operating all four pedals and after movement of the bed engage all
four brakes by again operating all four pedals.
[0006] Caregivers would appreciate being able to engage the brakes
on all four castered wheels by operating any one of four pedals
associated with the wheels. Caregivers would also appreciate being
able to engage all of the anti-swivel mechanisms on the casters
having such mechanisms by operating a steer pedal on any one of the
four casters regardless of whether the chosen caster includes an
anti-swivel mechanism.
[0007] According to the present invention, a braking system for a
hospital bed having a base frame includes a plurality of caster
devices rotatably coupled to the base frame. Each caster device has
a caster frame, a wheel rotatably attached to the caster frame, a
brake attached for movement with respect to the caster frame
between a first position in which the brake inhibits rotation of
the wheel and a second position in which the brake permits the
wheel to rotate freely, and an actuator. A plurality of pedals are
provided with each pedal being adjacent to a different one of the
plurality of caster devices and coupled to the actuator of the
caster device for movement of the brake between the first position
and second position in response to movement of the pedal. A linkage
is coupled to all of the actuators of the plurality of caster
devices so that movement of any one of the plurality of pedals
causes movement of all of the actuators. The actuator includes a
cam attached to a rotatable shaft and a follower coupled to the
brake. Each caster devices has a sleeve, the cam and follower are
disposed within the sleeve, and the shaft extends through the
sleeve. The linkages are coupled to the shafts of the
actuators.
[0008] The base frame has a first side frame member and a spaced
apart second side frame member and at least two of the plurality of
caster devices are attached to the first side frame member and at
least one of the plurality of caster devices is attached to the
second side frame member. The linkage includes a first side link
attached for movement relative to the first side frame member of
base frame and coupling the shafts of the actuators of the caster
devices attached to the first side frame member and a cross shaft
coupling the first side link to the shaft of the at least one of
the caster devices attached to the second side frame member of the
base frame. Rotation of the shaft induces rotation of the cross
shaft.
[0009] At least one of the plurality of caster devices may include
a steer lock attached to the follower for movement relative to the
caster frame. The steer lock may assume a first state in which the
caster device swivels and a second state in which the caster device
does not swivel. Both the steer lock and brake are coupled to the
actuator so that rotation of the rotatable shaft in a first
direction places the brake in the first position and rotation of
the rotatable shaft in a second direction places the steer lock in
the first state.
[0010] A patient support apparatus in accordance with the present
invention includes a base frame, a patient support coupled to the
base frame, a plurality of casters having sleeves, and a plurality
of caster mounting tubes. The caster mounting tubes have an
interior configured to receive a cylindrical sleeve of a caster and
a rectangular outer cross-section defined by four external side
walls. One of the external side walls abuts the base frame and the
plurality of caster mounting tubes are welded to the base frame.
The plurality of caster mounting tubes may each include interior
partially cylindrical concave wall sections configured to receive
the cylindrical sleeves of the casters. Each caster includes a set
screw for orienting the caster and the caster mounting tubes are
formed to include notches for receiving the set screws. The side
wall abutting the base frame is formed to include a hole as is the
base frame, the hole in the base frame is aligned with the hole in
the side wall and both holes are located between the welds.
[0011] A braking system for a hospital bed having a base frame
including a first side frame member and a spaced apart second side
frame member in accordance with the present invention includes a
plurality of casters each having a wheel, a brake, and an actuator.
A first and second of the plurality of casters are attached to one
of the first and second side frame members of the bed and a third
caster is attached to the other of the first and second side frame
members of the bed. A link extends between, and is coupled to, the
actuators of the first and second casters while a cross shaft
extends between the first side frame member and second side frame
member of the bed. The cross shaft has a first end coupled to the
link and a second end coupled to the actuator of the third caster.
The link and cross shaft are arranged so that actuation of one of
the actuators of the first, second, or third casters induces
actuation of the others of the actuators of the first, second, or
third casters. The actuator includes a shaft, a cam mounted on the
shaft, and a follower engaging the surface of the cam at a first
end and coupled to a brake at a second end. The actuator is
arranged such that rotational motion of the shaft induces movement
of the brake. The shaft has an axis of rotation fixed relative to
the base frame. The link is pivotally coupled to the shaft by a
first pivot bracket fixed to the shaft and riding on a first pivot
pin having a pivot axis extending through the link. The cross shaft
is mounted to the frame for rotation about an axis of rotation
fixed relative to the frame and is pivotally coupled to the link by
a second bracket fixed to the cross shaft and riding on a second
pivot pin having a pivot axis extending through the link. The
displacement between the axis of rotation of the shaft and the
first pivot axis is substantially equal to the displacement between
the axis of rotation of the cross shaft and the second pivot axis.
The link may include a vertical offset bracket through which one of
the first and second pivot pins passes so that the axis of rotation
of the shaft and the axis of rotation of the cross shaft are in
different vertical planes. The cross shaft is rotatably mounted to
a cross member extending between the first and second side frame
members so that the axis of rotation of the cross shaft is fixed
relative to axis of rotation of the shaft. Usually a fourth caster
is mounted to the second side of the frame and a second link
extends between, and is coupled to, the actuators of the third and
fourth casters. The cross shaft is coupled at the second end to the
second link so that actuation of one of the actuators of the first,
second, third or fourth casters induces actuation of the others of
the actuators of the first, second, third or fourth casters.
[0012] A method for attaching a caster having a cylindrical sleeve
to a base frame of a bed in accordance with the present invention
includes the steps of providing a mounting tube having four side
walls configured to provide a substantially square cross sectional
shape, forming an interior opening through the mounting tube having
a generally round cross sectional shape to receive the cylindrical
sleeve of the caster therein, placing a first side wall of the
mounting tube against the base frame, welding the mounting tube to
the base frame with the first and second welds located at opposite
ends of the first side wall, and installing the sleeve of the
caster into the interior opening of the mounting tube. The caster
includes a set screw for orienting the caster and a notch is formed
in the mounting tube to receive the set screw of the caster.
[0013] A patient support apparatus in accordance with the invention
includes a base frame, a hex shaft, and a caster mounting tube
attached to the base frame. The caster mounting tube is formed to
include a shaft hole through which the hex shaft extends. The
patient support also includes a caster having a wheel rotatably
mounted to a caster fork, a hollow sleeve having a top surface and
a bottom surface and being swivelably connected to the caster fork
at the bottom surface, a cam disposed within the interior of the
hollow sleeve, a follower engaging the cam at a first end and
extending through the caster fork at a second end, and a hex
shaft-receiving hole formed in the hollow sleeve adjacent the cam.
The hex shaft-receiving hole is closer to the bottom surface than
to the top surface. Attached to the second end of the follower is a
brake pad. The hex shaft extends through the hex shaft-receiving
hole in the hollow sleeve, the cam is received on the hex shaft,
and rotation of hex shaft induces rotation of cam which displaces
follower until brake pad engages wheel thereby inhibiting rotation
of wheel with respect to caster fork. The patient support apparatus
may also include a second wheel and an axle, wherein the axle is
attached to the caster fork and the first and second wheel are
spaced apart and rotatably mounted on the axle so that rotation of
the hex shaft induces brake pad to engage both wheels inhibiting
rotation of the wheels and swiveling of the sleeve relative to the
caster fork. The patient support apparatus also includes a set
screw-receiving hole formed between the shaft-receiving hole and
the top surface of the sleeve, a set screw hole formed above the
shaft hole in the mounting tube, and a set screw extending through
the set screw hole and being received in the set screw-receiving
hole.
[0014] A method for attaching a caster to a base frame of a bed in
accordance with the present invention includes the steps of
providing a mounting tube having four side walls configured to
provide a substantially square cross sectional shape, providing a
caster having a sleeve including a portion having a substantially a
square cross sectional shape, placing a first side wall of the
mounting tube against the base frame, welding the mounting tube to
the base frame with the first and second welds located at opposite
ends of the first side wall, and installing the sleeve of the
caster into the interior opening of the mounting tube.
[0015] Additional features and advantages of the invention will
become apparent to those skilled in the art upon consideration of
the following detailed description of an illustrated embodiment
exemplifying the best mode of carrying out the invention as
presently perceived.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a perspective view of a hospital bed with four
casters (one is obscured) each having a brake/steer actuator having
a break pedal to the left, i.e. toward the head end of the bed, and
a steer pedal to the right, i.e. toward the foot end of the bed (as
seen in the drawing), each caster is received in a square mounting
tube attached to a base frame within which a brake/steer device of
the present invention is incorporated;
[0017] FIG. 2 is an exploded view of the hospital bed frame of FIG.
1 rotated approximately 150 degrees so that the head end is to the
right showing an articulating deck located above an intermediate
frame which is located above a weigh frame which is located above
the base frame within which large components of the brake/steer
device are shown in phantom lines;
[0018] FIG. 3 is a partially exploded perspective view of the base
frame of FIG. 1 rotated approximately sixty degrees so the head end
remains on the left showing a side frame member broken away to
reveal a brake/steer link of the brake/steer device;
[0019] FIG. 4 is a partial cross-section of the side frame member
and brake/steer link taken along line 4-4 of FIG. 7 showing a cross
shaft received in the interior of a cross member of the base frame,
linkage between the cross shaft and the brake/steer link, links
between the brake/steer link and a hex shaft for activating brake
mechanisms and anti-swivel mechanisms (shown in phantom lines)
incorporated in the caster received in the square mounting
tube;
[0020] FIG. 5 is a top view of the square mounting tube welded in
only two locations to the side frame member of the base frame
showing the interior surface of the walls of the mounting tube
formed to include partial cylindrical concave sections for receipt
of the caster;
[0021] FIG. 6 is a bottom view of the square mounting tube of FIG.
5 showing a notch formed in the mounting tube for receiving a set
screw of a caster;
[0022] FIG. 7. is a partially broken away side view of the base
frame of FIG. 2 showing hex rods from two different castors
received in brake/steer brackets pivotally mounted near both ends
of the brake/steer link, and two cross shafts each of which are
pivotally coupled by a cross shaft link to an arm bracket attached
to the brake/steer link;
[0023] FIG. 8 is a view similar to FIG. 7 showing the effect of
rotation of either one of the hex shafts by approximately thirty
degrees in the clockwise direction and also showing the effect of
rotation of either one of the hex shafts by approximately thirty
degrees in the counter-clockwise direction in phantom lines;
[0024] FIG. 9 is a side elevation view of the cross shaft of the
present invention showing attachment holes near both ends of the
cross shaft and medial holes (in phantom lines) extending through
the cross shaft orthogonal to the attachment holes;
[0025] FIG. 10 is the cross shaft of FIG. 9 rotated ninety degrees
about its longitudinal axis;
[0026] FIG. 11 is front plan view of the cross shaft link of FIG.
7;
[0027] FIG. 12 is side view of the cross shaft link of FIG. 11;
[0028] FIG. 13 is a front plan view of the arm bracket of FIG.
7;
[0029] FIG. 14 is a side view of the arm bracket of FIG. 13;
[0030] FIG. 15 is a front plan view of the brake/steer bracket of
FIG. 7;
[0031] FIG. 16 is a side view of the brake/steer bracket of FIG.
15;
[0032] FIG. 17 is an exploded view of a low profile caster, a side
frame member of a base frame, and a square mounting tube for use
with the braking system of the present invention;
[0033] FIG. 18 is a partial cross sectional view of the assembled
caster, side frame member, and square mounting tube of FIG. 17;
[0034] FIG. 19 is a view taken along line 19-19 of FIG. 18;
and,
[0035] FIG. 20 is a perspective view of an alternative caster
mounting tube and caster for use with the braking system of the
bed, showing a brake/steer caster formed with a sleeve having a
square cross-section portion and a square lumen and a spindle
having a square cross section for receipt in the square lumen, and
a mounting tube formed from square tube stock.
DETAILED DESCRIPTION OF THE DRAWINGS
[0036] Referring to FIGS. 1-3, hospital beds 20 for use in
healthcare facilities typically include a mattress 22 located on an
articulating deck 24 pivotally mounted to an intermediate frame 26
which is vertically adjustable relative to a weigh frame 27
connected to a base frame 28. Base frame 28 includes two
spaced-apart longitudinally extending side frame members 32
connected by laterally extending cross members 68, 70. At head end
34 and foot end 36 of each side frame member 32, a caster mounting
tube 38 is typically welded to side frame member 32 as shown by
weld beads 40, in FIGS. 5-6. A sleeve 42 of a caster device 44 is
received in each of the caster mounting tubes 38.
[0037] Two types of caster devices 44 are utilized in conjunction
with bed 20 in the presently preferred illustrated embodiment. The
first type of caster device 44, commonly called a brake/steer
caster 46, includes a mechanism therein to inhibit the rotation of
the wheels of the caster (i.e. brake mechanisms 48) and a mechanism
to prevent swiveling of the caster forks (i.e. anti-swivel or
directional lock mechanisms 50), as shown, for example,
diagrammatically in phantom lines in FIG. 4. The second type of
caster device 44, commonly called a brake caster 52, includes only
a brake mechanism 48. The anti-swivel mechanism 50 and brake
mechanism 48 are actuated through rotation of a hex shaft 54. Hex
shaft 54 acts as a fulcrum of cantilevered brake/steer actuator
128. Disposed on opposite sides of hex shaft 54 are brake pedal 56
and steer pedal 58, both of which are operable by the foot of the
caregiver. Each caster device 44 preferably includes its own hex
shaft 54, brake pedal 56, and steer pedal 58 regardless of whether
the specific caster device 44 is a brake/steer caster 46 or a brake
caster 52, as shown, for example, in FIGS. 2-3.
[0038] In the illustrated embodiment, base frame 28 includes a pair
of spaced-apart side frame members 32 extending longitudinally
along each side of bed 20 and a pair of cross members 68, 70
extending laterally between, and connecting, the side frame members
32. Illustratively, side frame members 32 are rectangular tubes
having a top surface 60, a bottom surface 62, an inside surface 64,
an outside surface 66, head end 34, and foot end 36. Welded near
head end 34 and foot end 36 to outside surface 66 of side frame
member 32 are square caster mounting tubes 38 for receipt of
sleeves 42 of caster devices 44.
[0039] Welded to the bottom surface 62 and extending between side
frame members 32 are head end cross member 68 and foot end cross
member 70. Illustratively, head end cross member 68 and foot end
cross member 70 are formed from a metal plate which is bent to form
two spaced-apart sidewalls 72 extending downwardly from a top wall
74. Thus cross members 68, 70 include a first end 76, a second end
78, top wall 74, and two spaced-apart downwardly extending
sidewalls 72. Top wall 74 at first end 76 of cross members 68, 70
is welded to the bottom surface 62 of side frame member 32 and top
wall 74 of second end 78 of cross members 68, 70 is welded to
bottom surface 62 of second side frame member 32.
[0040] Square cross section caster mounting tubes 38 include an
outside wall 80, an inside wall 82, a front wall 84, a rear wall
86, an upper edge 88, a lower edge 90, an interior, and an
exterior. As shown, for example, in FIGS. 5 and 6, inside wall 82
of caster mounting tube 38 contiguously engages outside surface 66
of side frame member 32. Mounting tube 38 is welded to side frame
member 32 at the comer 92 formed by front wall 84 and inside wall
82 and at the comer 94 formed by rear wall 86 and inside wall 82 to
outside surface 66 of side frame member 32. Vertical axis of
mounting tube 38 extends substantially perpendicular to
longitudinal axis of side frame member 32. Since caster sleeves 42
typically have a circular cross section, the interior surface of
each of inside wall 82, outside wall 80, front wall 84, and rear
wall 86 are drilled, machined, bored, or otherwise formed to
include partial cylindrical concave sections 93, as shown for
example in FIGS. 5-6, for receiving the sleeve 42 of the caster. In
the illustrated caster mounting tubes 38, comer notches are
residual portions of the internal square tube left after hollow
square tube has been drilled out to form partial cylindrical
concave sections 93.
[0041] Square cross section mounting tubes 38 may be attached to
base frame 28 using fewer parts and fewer operations than are
required for attachment of standard tubes. Standard tubes have
circular cross-sections and cannot securely be welded directly to
side frame members 32. Thus, an intermediate bracket is typically
welded in two locations to the standard tube and then the bracket
is welded in two locations to side frame member 32. Providing bed
20 with square mounting tubes 38 eliminate eight welds and four
parts from the assembly of a bed having four casters.
[0042] While illustrated square cross section caster mounting tubes
38 are connected to the rectangular side frame member of bed 20, it
is within the teachings of the invention to mount caster mounting
tubes 38 to any rectangular frame member of a patient support
apparatus such as a bed, stretcher, chair, or the like. Attachment
of caster mounting tubes 38 to a rectangular frame member can be
accomplished with a two axis welding machine which is substantially
cheaper than the four axis welding machine required to weld a
standard tube and intermediate bracket to a frame member.
[0043] The braking system 30 of the present invention allows a
caregiver to actuate the brake pedal 56 or steer pedal 58 of any of
the caster devices 44 and thereby engage the brake mechanisms 48 or
anti-swivel mechanisms 50 respectively of all of the caster devices
44 simultaneously. Thus while called a "braking system", it is to
be understood that braking system 30 provides both brake control
and steer control. Illustrated braking system 30 accomplishes
simultaneous engagement of all braking mechanisms 48 or steering
mechanisms 50 by mechanically linking the brake/steer actuators 128
of all of the caster devices 44. Since the illustrated caster
devices 44 include brake mechanisms 48 and steer mechanisms 50
which are actuated by rotation of a hex shaft 54, the illustrated
braking system 30 mechanically links the hex shafts 54 of each
caster device 44 so that rotation of one hex shaft 54 induces
rotation of all of the hex shafts 54.
[0044] Shaft access holes 96 are drilled or otherwise formed
through outside wall 80 and inside wall 82 of mounting tube and
outside surface 66 and inside surface 64 of side frame member 32 so
that hex shaft 54 used to actuate the anti-swivel mechanism 50
and/or the brake mechanism 48 of caster device 44 may extend from
the exterior of the mounting tube 38 through the interior of the
side frame member 32. A cap bushing 111 is welded to the inside
surface 64 of side frame member 32 at each caster 44 location. Hex
shaft 54 extends into cap bushing 111. by receiving hex shaft 54,
cap bushing 111 acts to stabilize hex shaft 54 to minimize play in
the brake/steer system 30. A brake/steer link 98 is disposed and
extends longitudinally within the interior of side frame member 32
as shown, for example, in FIGS. 3, 4, 7, 8 and by phantom lines in
FIGS. 2-3 Illustratively, brake/steer link 98 is formed from square
metallic tubular material having a head end 100, a foot end 102, a
top wall 104, an outside side wall 106, an inside side wall 108,
and a bottom wall 110. Brake/steer brackets 112 are pivotally
mounted to brake/steer link 98 about pivot axis 114 near head end
100 and foot end 102 of brake/steer link 98. As shown, for example,
in FIGS. 7, 8, brake/steer link 98 is formed to include a slot 115
through bottom wall 110 extending longitudinally from head end 100
and foot end 102 for a distance 117 sufficient to accommodate
rotation of the brake/steer bracket 112. Illustratively, distance
117 is approximately 1.5".
[0045] Rivet holes 116 are formed in inside wall 108 and outside
wall 106 of brake/steer link 98 adjacent the head end 100 and foot
end 102 for receipt of a rivet 118 that acts as a pivot pin for
brake/steer bracket 112. Illustratively, brake/steer bracket 112 is
U-shaped having bottom member 120 extending between two
spaced-apart arms 122 in which are formed pivot holes 124 through
which rivet 118 extends and hexagonally-shaped shaft-receiving
holes 126 through which the hex shaft 54 of the brake/steer
actuator 128 is received.
[0046] Brake/steer link 98 is disposed within and free to move
longitudinally and horizontally relative to side frame member 32.
The location of rotational axis 130 of hex shaft 54 is fixed by
shaft access holes 96 through which it extends. Therefore, rotation
of hex shaft 54 causes brake/steer bracket 112 to rotate on rivet
118 causing brake/steer link 98 to move downward in an arc in the
direction of rotation of the hex shaft 54 as shown by curved arrows
132 in FIG. 8. Since hex shaft 54 of the brake-steer actuators 128
at the head end 34 and foot end 36 of each side frame member 32 are
received in brake/steer brackets 112 pivotally connected to the
same brake/steer link 98, rotation of one hex shaft 54 will induce
rotation of the other hex shaft 54 on the same side of bed 20.
Thus, when the caregiver steps on the brake pedal 56 (typically
color coded orange) at the head end of bed 20 to induce
counterclockwise rotation of the hex shaft 54 at the head end of
bed 20, the hex shaft 54 at the foot end 36 of bed 20 will also
rotate in a counterclockwise direction as shown by phantom lines in
FIG. 8. The same applies to clockwise rotation which is induced by
stepping on the steer pedal 58 (typically color coded green) at the
head end of bed 20 which is shown in solid lines in FIG. 8. It
should be understood that clockwise or counterclockwise rotation of
the hex shaft 54 at the foot end 36 of bed 20 will induce clockwise
or counterclockwise rotation respectively of the hex shaft 54 at
the head end of bed 20. Thus, by manipulating either of the
brake/steer actuators 128 at the head end 34 or foot end 36 of one
side of bed 20, the brake mechanisms 48 and anti-swivel mechanisms
50 of the caster devices 44 at both ends of bed 20 will be
actuated.
[0047] In order to allow manipulation of any one of the brake/steer
actuators 128 to actuate all of the brake mechanisms 48 or
anti-swivel mechanisms 50 of the caster devices 44, cross shafts
134 extend between each of the brake/steer links 98. Welded, or
otherwise appropriately connected, to the bottom of brake/steer
link 98 are U-shaped downwardly opening arm brackets 136 having a
top plate 138 extending between spaced-apart inside arm 140 and
outside arm 142. Inside arm 140 and outside arm 142 are formed to
include rivet holes 144 for receipt of a rivet 146. Each arm
bracket 136 is displaced from the rivet holes 116 in the end of
brake/steer link 98 by a distance 148 equal to the distance 150
between hex shaft access hole 96 in side frame member 32 and the
center of cross member 68, 70 as shown, for example, in FIG. 7.
[0048] A cross shaft link 152 having a cylindrical housing 154 and
a pivot flange 156 extending upwardly therefrom is pivotally
mounted to arm bracket 136 about pivot axis 158. Pivot flange 156
is formed to include a pivot hole 160 centered about pivot axis
158. Rivet 146 extends through rivet hole 144 and pivot hole 160
coupling cross shaft link 152 to arm bracket 136 in a manner
allowing pivoting of cross shaft link 152 relative to arm bracket
136. Illustratively, rivet 144 is inserted through outside arm 138
of arm bracket 136, a first cylindrical spacer 162, pivot hole 160
of pivot flange 156, a second cylindrical spacer 164, and rivet
hole 144 in inside arm 140 of arm bracket 136 so that cross shaft
link 152 pivots relative to arm bracket 136.
[0049] Cylindrical housing 154 has an inside diameter 166 sized to
receive the outside diameter 168 of cross shaft 134 as shown, for
example, in FIG. 4. Diametrically opposed pin holes 170 are formed
in housing 154 of cross shaft link 152 to receive a rotation pin
172. The axis of rotation 174 of cross shaft 134 passes through the
center of cylindrical housing 154 which is displaced from the pivot
axis 158 of rivet 146 which passes through the center of pivot hole
160 by a displacement 176. Displacement 176 is equal to the
displacement 178 between the pivot axis 114 of rivet 118 which
passes through the center of pivot hole 124 and the rotational axis
130 of hex shaft 54 which passes through the center of hex shaft
receiving hole 126 in brake/steer bracket 112. Since rotation axis
130 of hex shaft 54 and axis of rotation 174 of cross shaft 134 are
fixed in space relative to each other, rotation of hex shaft 54 by
a specified number of degrees will induce rotation of cross shaft
by the same number of degrees as indicated by slash marks 177 and
179 through curved arrows 132 and curved arrows 181 in FIG. 8.
[0050] Cross shaft 134 extends between cross shaft link 152 on one
side of bed 20 and the associated cross shaft link 152 on the other
side of bed 20. Cross shaft 134 is received in the interior 180 of
cross member 68, 70 which is formed to include gussets 182 formed
to include cylindrical holes 184 having an inside diameter 186
sized to receive the outside diameter 168 of the cross shaft 134.
It is the receipt of cross shaft 134 in these gussets 182 which
fixes the axis of rotation 174 of the cross shaft 134 relative to
the cross member 68, 70 and base frame 28.
[0051] Near first end 188 and second end 190 of cross shaft 134,
attachment holes 192 are drilled or otherwise formed to extend
diametrically through cross shaft 134. Cross shaft 134 is formed to
include two medial holes 194 extending diametrically through cross
shaft 134 orthogonal to the attachment holes 192 on the ends of
cross shaft. Each medial hole 194 is displaced from its adjacent
attachment hole 192 by a displacement 196 so that orientation of
cross shaft 134 is not critical during assembly. Medial holes 194
are designed to receive lever arms (not shown) which can actuate
switches or sensors 198 (FIGS. 2, 3) connected to an indicator
system (not shown) which indicates when the brake mechanisms 48 are
engaged.
[0052] In order for cross shaft link 152 to extend between arm
brackets 136 located in the interior of side frame member 32 and
cross shaft 134, access aperture 191 is formed in bottom surface 62
of side frame member 32. Likewise access aperture 193 is formed in
top wall 74 of cross member 68, 70. Access apertures 191, 193 have
a length 195 sufficient to allow uninhibited rotation of hex shaft
54 through ninety degrees and the associated movement of arm
bracket 136 and cross shaft link 152 as shown, for example, in FIG.
8.
[0053] First end 188 of cross shaft 134 is received in the housing
154 of cross shaft link 152 so that pin receiving holes 170 in
cross shaft link 134 and attachment holes 192 in cross shaft 134
are aligned and rotation pin 172 extends therethrough to fix cross
shaft 134 to cross shaft housing 154 so that rotation of cross
shaft housing 154 will induce rotation of the cross shaft 134.
Second end 190 of cross shaft 134 is received in the cross shaft
housing 154 associated with the brake/steer link 98 on the other
side of bed 20 so that attachment hole 192 in cross shaft 134 and
pin receiving pin hole 170 in cross shaft housing 154 are aligned
and rotation pin 172 extends therethrough to fix cross shaft 134
relative to the housing 154 so that rotation of the shaft 134 will
induce rotation of the housing 154. Thus, when a caregiver steps on
any one of the brake pedals 56 to actuate the braking mechanism 48
of a single caster device 44, the various links of the braking
system 30 induce the braking mechanisms 48 to be actuated in all of
the other caster devices 44. Likewise, if a caregiver steps on the
steer pedal 58 associated with a single caster device 44 to actuate
the anti-swivel mechanism 50, the links of braking system 30 induce
actuation of the anti-swivel mechanisms 50 in all of the other
caster devices 44 equipped with such mechanisms. By this
arrangement, a caregiver can actuate all of the brake mechanisms 48
or all of the anti-swivel mechanisms 50 on all of the caster
devices 44 through manipulation of any one of brake/steer actuators
associated with any one of the caster devices 44.
[0054] Brake mechanisms 48 and anti-swivel mechanisms 50 of caster
devices 44 on opposite sides of the same end of a bed may be
connected by a single hex shaft (not shown) extending from the
caster device 44 on one side of the bed to the caster device 44 on
the opposite side of the bed. Rotation of extended hex shaft will
simultaneously rotate cams 53 in both caster devices 44 so that
rotation of the extended hex shaft is directly translated to the
caster 44 on the opposite side of the bed eliminating the need for
the cross shaft 134. Because the extended hex shaft must extend
through the caster stem 42 it is typically located above the bottom
surface 62 of side frame member 32. In certain beds, the extended
hex shaft can interfere with the hi/lo operation of the bed. In the
illustrated device, cross shaft 134 is received in the interior of
cross member 68, 70 and therefore is not as likely to interfere
with the hi/lo functions as an extended hex shaft because cross
shaft 134 is located below the bottom surface 62 of side frame
member 32.
[0055] Illustratively, caster devices 44 at head end of bed 20 are
brake/steer casters 46. An example of a commonly available
brake/steer caster 46 is the caster from Tente-Rollen GmbH and
Company, Part No. 2044UAP125R36-32S30. As mentioned above, brake
mechanism 48 and anti-swivel mechanism 50 are represented
diagrammatically in phantom lines in FIG. 4. This diagrammatic
representation is not intended to precisely depict the internal
components of brake/steer casters as such components are known.
[0056] Brake/steer casters 46 include brake mechanisms 48 which are
activated through counterclockwise rotation of a hex shaft 54 and
anti-swivel mechanisms 50 which are activated by clockwise rotation
of the hex shaft 54. Throughout this application the terms
counter-clockwise and clockwise are used to describe the rotation
of hex shafts 54, it should be understood that the terms are
defined with reference to a caregiver on the near side (as shown in
FIG. 1) of bed 20 facing toward the near side of bed 20. It should
also be understood that what appears to be clockwise rotation to a
caregiver on the near side of bed 20 facing near side of bed 20
would appear to be counter-clockwise rotation to a caregiver on the
far side of bed 20 facing the far side of bed 20.
[0057] Rotation of the hex shaft 54 induces displacement of a
spindle 49 which is disposed concentric to the swivel axis 47 of
the caster wheel fork 51. Internally, a cam 53 is attached to the
hex shaft 54. Cam 53 has a lobe (not shown) and an indentation (not
shown) formed therein which induce displacement of spindle 49,
which acts as a follower, upon rotation of the hex shaft 54. In the
illustrated embodiment, cam 53 is in neutral position, in which the
wheels are free to turn and the caster is free to swivel, when the
arms 129, 131 of brake/steer actuator 128 are parallel to the floor
as in FIGS. 1-4 and the brake/steer link 98 and brake/steer bracket
112 are in the position shown in FIG. 7. Rotation of the hex shaft
54 counterclockwise induces cam 53 to rotate so that lobe displaces
spindle 49 downward to engage braking mechanism 48 against the
wheel 55 of the brake/steer caster 46. Rotation of the hex shaft 54
clockwise causes rotation of the cam so that spindle 49 falls into
indentation so that anti-swivel mechanism 50 is engaged.
[0058] Illustratively, caster devices 44 at foot end 36 of bed 20
are brake casters 52. An example of a commonly available brake
caster 52 is the caster from Tente-Rollen GmbH and Company, Part
No. 2046UAP125R36-32S30. Brake casters 52 while not illustrated are
similar to brake/steer casters 46 shown in FIG. 4 except that brake
casters 52 do not include anti-swivel mechanisms 50. Like reference
numerals will be used in the description of brake caster 52. Brake
casters 52 are used in conjunction with brake/steer casters 46 to
facilitate steering of bed 20 during transportation of bed 20. If
brake casters 52 were used for all four caster devices 44, steering
of bed 20 would be very difficult. Combining brake/steer casters 46
with brake casters 52 allows the anti-swivel mechanisms 50 to be
activated on the brake/steer casters 46 so that bed 20 can then be
steered in the same fashion as the familiar shopping cart.
[0059] Brake casters 52 include brake mechanisms 48 which are
activated through counterclockwise rotation of a hex shaft 54 but,
because they do not include anti-swivel mechanisms 50, the caster
wheel 55 is always free to swivel. Rotation of the hex shaft 54
induces displacement of a spindle 49 which is disposed concentric
to the swivel axis 47 of the caster wheel fork 51. Internally, cam
153 is attached to the hex shaft 54. Cam 153 has a lobe (not shown)
formed therein which induces displacement of spindle 49, which acts
as a follower, upon rotation of the hex shaft 54. In the
illustrated embodiment, cam 153 is in neutral position, in which
the wheel 55 is free to turn and the caster is free to swivel, when
the arms 129, 131 of brake/steer actuator 128 are parallel to the
floor as in FIGS. 1-4 and the brake/steer link 98 and brake/steer
bracket 112 are in the position shown in FIG. 7. Rotation of the
hex shaft 54 counterclockwise induces cam 153 to rotate so that
lobe displaces spindle 49 downward to engage braking mechanism 48
against the wheel 55 of the caster. Rotation of the hex shaft 54
clockwise causes rotation of cam 153 so that spindle 49 rides off
the lobe and brake mechanism 48 is disengaged.
[0060] To prevent rotation of sleeve 42 within mounting tube 38,
brake/steer caster 46 and brake caster 52 are provided with a set
screw 57 near the point of connection between sleeve 42 and caster
fork 51. Set screw 57 is displaced 900 from hex shaft 54. Mounting
tube 38 is formed to include a notch 59 formed in lower edge 90 of
rear wall 86. When caster devices 44 are received in mounting tubes
38, set screw 57 is received in notch 59 as shown, for example in
FIG. 4. Set screw 57 and notch 59 prevent rotation of sleeve 42 in
mounting tube 38 which prevents binding of hex shaft 54 in shaft
access holes 96.
[0061] While the presently preferred embodiment of braking system
30 is described as using brake/steer casters 46 at the head end of
bed 20 and brake casters 52 at the foot end 36 of bed 20, it is to
be understood that all caster devices 44 could be brake/steer
casters 46 or brake casters 52 within the scope of the invention.
Likewise any combination and configuration of brake casters 52 and
brake/steer casters 46 mounted to a bed 20 employing braking system
30 is within the teaching of the invention.
[0062] Intermediate frame 26 is designed to be raised or lowered
with respect to weigh frame 27 and base frame 28 using what is
commonly called the hi/lo function of the bed 20. If a caregiver
desires to improve the lower limit of the hi/lo operation of bed
20, the low profile casters 200 shown in FIGS. 17-19 may be
incorporated with braking system 30 instead of the caster devices
44 described above. Commonly available caster devices 44 including
braking mechanisms 48 typically have hex shaft 54 extending through
sleeve 42 above the location of set screw as shown, for example, in
FIG. 4. This typical arrangement places hex shaft 54 substantially
above the surface of the floor on which wheel 55 rests. Often hex
shaft 54 and pedals 56, 58 actuating hex shaft 54 can interfere
with the operation of the hi/lo mechanism which raises and lowers
intermediate frame 26 with respect to the base frame 28.
Interference with the hi/lo function occurs only at the lower limit
of the height adjustment, if at all. In order to allow the hospital
bed 20 to be adjustable to a lower level, it is desirable to
include a caster 200 which is designed so that hex shaft 54 extends
through the caster sleeve 242 closer to the bottom 202 of the
caster sleeve 242 than in commonly available casters.
[0063] Low profile caster 200 is designed for use with braking
system 30. Low profile caster 200 may also be used in an
alternative embodiment of braking system (not shown) wherein the
cross shafts 134 are eliminated and extended hex shafts extend
between casters at the same end but on opposite sides of bed
20.
[0064] Referring to FIG. 17, there is shown an exploded view of a
low profile caster 200 in accordance with the present invention.
Low profile caster 200 includes a sleeve 242 formed from two half
shells 242a, 242b attached to swivel with respect to a caster fork
251 to which two counter-rotatable wheels 255a, 255b are rotatably
mounted. Half shells 242a, 242b are joined together with a first
washer 204 having the inside diameter 205 substantially equal to
the outside diameter 207 of the outside wall 206 at base 201 of the
sleeve 242 and a second washer 208 having an inside diameter 209
substantially equal to the outside diameter 211 of the wall 210 of
a recessed step 212 formed at the top edge 203 of the sleeve
242.
[0065] Half shells 242a, 242b are formed so that when joined they
create a sleeve 242 having an interior, an exterior, and a height
297. Height 297 of sleeve is related to the stability of the sleeve
in the caster mounting tube 38 and to maximum stresses which sleeve
can endure when received in mounting tube 38. Up to a point, the
taller the sleeve 242 the more stable the sleeve 242 is when
received in caster mounting tube 38. Also taller sleeves can endure
the more stress. However, stability and stress tolerance are not
improved when sleeve height 297 exceeds caster mounting tube
height.
[0066] Interior of sleeve 42 is formed to have a cavity 213 for
receipt of a cam 253, a screw 214, a spring 215, and a pivot
housing 216. Sleeve 242 is formed to include shaft holes 217
extending therethrough for receipt of the hex shaft 54 of a
brake/steer actuator 128. Cam 253 includes a substantially
cylindrical outer surface 218 which is deformed to include a lobe
219 and a longitudinal hexagonal opening 221 through which hex
shaft 54 extends so that rotation of hex shaft 54 will induce
rotation of cam 253.
[0067] Downwardly extended arms 223 of caster fork 253 are formed
to include axle holes 225. Twin wheels 255a, 255b separated by a
spacer (not shown) are mounted for rotation relative to caster fork
253 by an axle 227 extending through both axle holes 225, each
wheel 255a, 255b, and the spacer separating the wheels 255a, 255b.
Twin wheels 255a, 255b and spacer are arranged so that the inner
side 229 of each wheel is displaced from the inner side 229 of the
other wheel 255b, 255a by a displacement 231.
[0068] Caster fork 251 includes a top surface 233 having a hole 235
therethrough sized to receive shaft of pivot housing 216 which is
swedged between top surface 233 and bottom surface 237 of caster
fork 251. Bottom surface 237 of caster fork 251 is formed to
include a hole 295 through which hex spindle 248 extends. Pivot
housing 216 is formed to include a hexagonally shaped internal
lumen 239 through which hex spindle 249 of an locking mechanism 248
extends. Locking mechanism 248, when engaged simultaneously brakes
the wheels 255a and 255b and inhibits swivelling of caster 200 as
will be described hereafter. Hex spindle 249 has a first end 241
which is tapped to receive screw 214 and a second end 243 to which
a plunger wedge 245 is attached. Plunger wedge 245 is designed to
engage the wheels 255a, 255b of the caster 200 providing braking of
the same. The hexagonal shape of the spindle 249 and internal lumen
239 prevents rotation of hex spindle 249 and plunger wedge 245 to
resist caster swivelling.
[0069] Pivot housing 216 has a body 261 having a flange 263 with a
first diameter 265 and a top surface 267 which acts as a spring
engaging face, a faceted hexagonal section 269, and a lower flange
271. Pivot housing also includes a recessed shaft 237 and a flared
portion 275. Recessed shaft has a second diameter smaller than the
first diameter and is sized to extend through the hole 235 in top
surface 233 of caster fork 251. Recessed shaft 273 is connected at
one end to body 261 and at the other end flared portion 275 of
pivot housing 216.
[0070] Cavity 285 in interior of sleeve 242 is formed to have a
hexagonal cross-section and is sized to receive faceted hexagonal
section 269 of pivot housing 216. Receipt of the hexagonal section
269 in the hexagonal cavity 285 prevents pivot housing 216 from
rotating relative to sleeve 242. Rotation of sleeve 242 within
mounting tube 238 is prevented by set screw 257 which passes
through set screw hole in outside wall 280 of mounting tube 238 and
is received in tapped screw hole 287 in sleeve 242. Tapped screw
hole 287 is located above shaft holes 217 in sleeve 242 and set
screw hole 259 is located above shaft access hole 296 in mounting
tube 38.
[0071] Screw 214 acts as a follower and engages surface of cam 253.
When screw 214 engages neutral surface 218, plunger wedge 245 does
not engage the wheels 255a, 255b of caster 200. Top flange 268 and
bottom flange 271 are received in channels 277 and 279 formed in
interior of sleeve 242 respectively so that rotation of the cam 253
counterclockwise as shown by arrow 281 causes screw 214 to follow
the lobe 219 and compress spring 215 between screw 214 and top
surface 267. Rotation of cam 253 causes spindle 249 to move
longitudinally as shown by arrow 283 within hexagonally shaped
internal lumen 239 in pivot housing 216 until plunger wedge 245 is
wedged between the wheels 255a, 255b of the caster 200 to prevent
rotation of the wheels 255a, 255b and provide braking to the caster
200. Since swiveling is facilitated by wheel 255a rotating in the
opposite direction as wheel 255b, when plunger wedge 245 is lodged
between wheels 255a, 255b as shown in phantom lines in FIG. 18,
swiveling of caster 200 is also inhibited. Clockwise rotation of
hex shaft 54 from the brake position causes screw 214 to follow
lobe 219 back onto the neutral surface 218 as spring 215
decompresses.
[0072] Low profile caster 200 is designed so that the displacement
289 between shaft holes 217, and therefore hex rod 54, and floor
291 upon which the caster wheels rest is less than five inches. As
a result of this positioning, hex rod 254 will not inhibit
adjustment of intermediate frame 26 relative to base frame 228
until intermediate frame 26 is substantially closer to the floor
than the lowest position that it can achieve with a standard caster
44. In order to limit displacement 289 to five inches or less while
providing wheels 255 having sufficient diameters to accommodate
movement of bed 20, shaft holes 217 are displaced from base 201 of
by a displacement 295 which is less than half of height 297 of
sleeve 242.
[0073] An exploded view of additional alternative embodiments a
caster 444 and a square caster mounting tube 438 in accordance with
the present invention is shown in FIG. 20. Caster 444 includes a
wheel 55 (not shown) rotatably mounted to a caster fork 51 (not
shown) a brake pad 445, an anti-swivel or directional locking
mechanism 450, a spindle 449, a sleeve 442 formed to include a hex
shaft-receiving hole 417 and being mounted to swivel with respect
to caster fork 51, a cam 53 (not shown) having a brake surface and
a steer lock surface internally located in sleeve. Caster sleeve
includes a medial portion 541 having a square cross section, an
upper portion 543 having a circular cross section, and a lower
portion 545 having a circular cross section. Spindle 449 includes a
follower end 547, an upper portion 549 having a circular cross
extending between follower end 547 and a medial portion 551 having
a square cross section, a lower portion 553 having a circular cross
section extending between medial portion 551 and a connector end
555. In assembled caster 444, upper portion 549 and medial portion
551 of spindle 449 is received in square lumen 439 of sleeve 442
with follower end 547 engaging cam 53. Lower portion 553 of spindle
449 extends through top surface 433 of caster fork 51. Anti-swivel
mechanism 50 is received on lower portion 553 of spindle 449 and
brake pad 445 is connected to connector end 555.
[0074] Square caster mounting tube 438 is similar to square
mounting tube 38 except that it does not include partial
cylindrical concave sections 93 and thus includes an inner tube 557
having a square cross section for receipt of sleeve 442. Square
caster mounting tube 438 is attached to side frame member 32 with
two welds 40 extending along the corners formed by rear wall 486
and inside wall 482 and front wall 484 and inside wall 482. Square
caster mounting tube 438 is formed to include shaft access holes
496 through outer and inner walls 482,480.
[0075] Sleeve 442 is received in inner tube 557 of square caster
mounting tube 438 so that hex shaft-receiving hole 417 is aligned
with shaft access holes 496 and hex shaft 54 passes through both
holes 417, 496 and engages cam 53 in the interior of sleeve 442.
Operation of the brake and anti-swivel mechanism 448, 450 is
similar to the operation previously disclosed. Because of the
square cross sections of mounting tube 438 and sleeve 442, sleeve
442 self aligns when received in inner tube 557 of mounting tube
438 eliminating the need for a set screw. Square lumen 439 and
square cross section of medial portion 551 of spindle 449 prevent
spindle 449 from spinning within the lumen 439 enhancing both brake
and anti-swivel mechanism 448, 450 operation.
[0076] Although the invention has been described in detail with
reference to certain illustrated embodiments, variations and
modifications exist within the scope and spirit of the invention as
described and as defined in the following claims.
* * * * *