U.S. patent number 3,733,623 [Application Number 05/199,411] was granted by the patent office on 1973-05-22 for hospital beds.
Invention is credited to John Mervyn Croxton.
United States Patent |
3,733,623 |
Croxton |
May 22, 1973 |
HOSPITAL BEDS
Abstract
A hospital bed having a mattress supporting element which can be
elevated or lowered relative to the bed chassis through the agency
of a mechanical jack is additionally provided with a hydraulic
damper for controlling descent of the supporting element.
Inventors: |
Croxton; John Mervyn
(Birmingham, EN) |
Family
ID: |
27431493 |
Appl.
No.: |
05/199,411 |
Filed: |
November 17, 1971 |
Foreign Application Priority Data
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Nov 24, 1970 [GB] |
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55,709/70 |
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Current U.S.
Class: |
5/611; 5/614 |
Current CPC
Class: |
A61G
7/012 (20130101) |
Current International
Class: |
A61G
7/012 (20060101); A61G 7/002 (20060101); A61g
007/00 (); A61g 007/10 () |
Field of
Search: |
;5/63-69
;297/429,433 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nunberg; Casmir A.
Claims
I claim:
1. A hospital bed of the kind referred to, provided with a canting
plate mechanical jack for raising the top and for permitting
descent, including a pair of canting plates which respectively act
on a ram of the jack to lift the ram in one direction and brake the
ram against descent in the opposite direction, the lifting plate
being operable in response to pivoting of a lever in a first sense,
wherein the improvement comprises a hydraulic damper strut located
to control descent.
2. A hospital bed as claimed in claim 1 in which means are provided
for disengaging the braking plate to permit lowering of the top
under control of the damper strut, said means being operatively
connectible with said lever so as to disengage the braking plate in
response to pivoting of the lever in said first sense.
3. A hospital bed as claimed in claim 1 which includes means for
holding the braking plate in a disengaged condition during pivoting
of said lever.
4. A hospital bed as claimed in claim 1 which includes means for
rendering the lever operable to simultaneously disengage the
braking plate and operate the ram lifting plate.
5. A hospital bed of the kind referred to, provided with a canting
plate mechanical jack for raising the top and for permitting
descent, including a pair of canting plates which respectively act
on a ram of the jack to lift the ram in one direction and brake the
ram against descent in the opposite direction, the lifting plate
being operable in response to pivoting of a lever in a first sense,
wherein the improvement comprises a hydraulic damper strut located
to control descent, and means for rendering the lever operable to
simultaneously disengage the braking plate and operate the ram
lifting plate, including a sleeve slidable on the lever and movable
to a position in which a cam carried thereby cams with a cam
follower associated with the braking plate to disable the latter.
Description
BACKGROUND OF THE INVENTION
This invention relates to hospital beds of the kind in which the
top or mattress support element can be raised and lowered relative
to the chassis of the bed so as to reduce effort involved in
nursing, and facilitate the patient entering and leaving the bed,
since for nursing a high bed is convenient and avoids stooping on
the part of the nurses, and for ingress and egress a low bed is
more suitable for an invalid.
Usually such beds comprise an X-frame and a jack for swinging the
limbs of the X. Hydraulic jacks have been used, but problems are
encountered due to leakage of fluid which cause the bed to slowly
sink. Mechanical jacks avoid such difficulty, but are either of the
continuous screw type in which event lowering is or may be as
laborious as raising, or if a canting plate type is used the
descent tends to be jerky and is not finely controlled. The objects
of this invention are to provide improved means avoiding these
problems.
SUMMARY OF THE INVENTION
In accordance with the invention a hospital bed of the kind
referred to is provided with a canting plate mechanical jack for
raising the top and for permitting descent, and with a hydraulic
strut located to control descent.
The canting plate mechanical jack preferably includes a pair of
canting plates which respectively act on a ram of the jack to lift
the ram in one direction and brake the ram against descent in the
opposite direction, the ram lifting plate being operable in
response to pivoting of a lever in a first sense.
Conveniently means are provided for disengaging the braking plate
to enable lowering of the top to be effected and said means is
preferably operatively connectible with said lever so as to
disengage the braking plate in response to pivoting of the lever in
said first sense.
Preferably means are provided for holding the braking plate plate
in a disengaged condition during pivoting of the lever.
By pivoting the lever in said one sense to operate the lifting
plate when said holding means is operative and then gradually
pivoting the lever in the opposite sense, the load presented by the
platform and a patient can be transferred smoothly from the control
of the mechanical jack to the control of the hydraulic strut so
that the top can descend smoothly without any jerks. This facility
is particularly useful where the mechanical jack is used in
conjunction with a hydraulic strut which is designed to offer
little initial damping resistance to descent and subsequently
increasing damping resistance.
Hence the advantages of both mechanical and hydraulic systems are
retained, but the disadvantages (notably the difficulties of
sealing the fluid and the jerky descent) are avoided since sealing
of a strut is simpler than of a jack, and the strut avoids
jerkiness in descent.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a fragmentary perspective elevation of a bed;
FIG. 2 is an enlarged scale elevation of part of the same;
FIG. 3 is an elevation in the direction 3 of FIG. 2;
FIG. 4 is an enlarged scale perspective view of a foot-operated
mechanism of the bed; and
FIGS. 5 and 6 are elevational views of the mechanism shown in FIG.
4 illustrating the mode of operation of the mechanism.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The bed generally comprises a wheeled chassis 10, possibly provided
with brakes or floor engaging chocks (not shown) to immobilize the
bed, and a mattress support platform 12 supported for movement
towards and from the chassis 10 by an X-frame. The X-frame has two
limbs 16 and 18 at each side which are pivoted to the chassis 10
and support platform 12 the upper ends 20 of the limbs 16 and 18
being connected to the platform 12 by links 22. The two limbs 16
and 18 are pivoted together on a sliding fulcrum (not shown);
alternative arrangements for raising and lowering the platform 12
relative to the chassis 10 are possible using the invention.
A mechanical jack 13 acts between a strut 30 of the X-frame and the
chassis, the jack comprising an enclosure 15 which is pivotally
mounted on the chassis and a ram 28 which is pivoted to the strut
30 so that in jack extension and retraction the platform 12 can be
respectively raised and lowered.
The enclosure 15 may conveniently be a metal casing of rectangular
cross-section receiving at its lower end two rotatable shafts 32,
34 extending laterally of the chassis 10. The shafts 32 and 34 are
respectively operable by pedals 36 and 38.
The shaft 32 is connected to a pair of cranks 40 within the
enclosure 15 which cranks 40 are pivoted to a push rod 42 which
extends through transverse partitions 44 and 44a in the enclosure
15. The upper end of rod 42 is domed and bears against a first
canting plate 46 (FIG. 2), while the lower end 48 of rod 42 is of
reduced diameter and threadedly engages in a pivot block between
the cranks 40. The lower end 48 of the rod 42 is provided with a
screw slot whereby the length of the rod 42 can be adjusted, access
to the slot being gained from beneath the chassis.
A compression spring 50 is located between the plate 46 and the top
54 of the enclosure 15 and tends to urge the plate 46 into facial
contact with the partition 44. The ram 28 is a tube or rod which
extends upwardly along the enclosure 15 and through the top 54
thereof, and passes through apertures in the plate 46, the
partition 44 and a second or lower canting plate 56 located below
the partition 44. The rod 42 also passes with clearance through the
lower plate 56, and the partitions 44 and 44a.
The second plate 56 is fulcrummed in a slot 58 in the enclosure 15
and is coupled by a rod 60 to a crank 62 fast with shaft 34. A
spring 64 is located between the partition 44 and lower plate 56
and tends to urge the plate 56 to a downwardly canted position
about its fulcrum, as seen in FIG. 2. The crank 62 is straddled by
the limbs 100 and 101 of a U-shaped member 102 secured to one of
the side walls of the enclosure 15 which serve to limit pivoting of
the crank 62 and hence the shaft 34, the limb 100 being arranged so
that when the crank 62 abuts the limb 100 the pivotal connection
between the rod 60 and the crank 62 is just past its top
dead-center position and can be maintained in this position by the
biassing action of the spring 64.
The raise and lower pedals 36 and 38 are rigidly interconnected and
have a first common pivotal connection 65 with a lever 66 fast with
the shaft 32 (FIGS. 4 to 6), the lever 66 being received in a
sleeve 68 which can slide relative thereto towards and from the
pivotal connection 65. The sleeve 68 is provided with an arm 70
which extends towards the pedals 36 and 38, and is connected
thereto by a second pivotal connection 71 so that pivoting of the
pedals 36 and 38 about the pivotal connection 65 serves to
reciprocate the sleeve 68 along the lever 66.
The sleeve 68 carries a cam member 72 of U-shape having limbs 84
and 104 which are operable with a cam follower 74 in the form of a
crank fast with shaft 34. The lever 66 can be pivoted between an
upper position, seen in full outline in FIG. 5, and a lower
position, seen in broken outline in FIG. 5, pivoting beyond these
positions being prevented by engagement of the free ends of the
cranks 40 with upper and lower ends of slots 76 in the casing 15 in
which said free ends are received. A compression spring 80 acting
between the pivot block and the partition 44a biases the lever 66
into its upper position. With lever 66 in its upper position and
sleeve 68 remote from the pivotal connection 65, the rod 42 permits
the plate 46 to lie in a slightly canted position, seen in FIG. 2,
in which it offers little, if any, resistance to movement of the
ram 28 through the corresponding aperture in the plate 46. At the
same time, the lower plate 56 is canted and wedges on the ram 28.
The weight of the mattress frame and the patient urges the ram 28
downwardly and increases the wedging action exerted by the plate
56.
If the raise pedal 36 is depressed to pivot the lever 66 towards it
lower position the plate 46 is lifted away from the partition 44 by
the link rod 42 and cants further (against the spring 50 which
holds the one end down) so as to wedge on the ram 28. Lifting of
the plate 46 lifts the ram 28 and hence raises the platform 12. The
lifting action pulls the ram 28 through the lower plate 56, the
wedging action exerted by the latter being disabled by upward
travel of the ram but becoming effective upon termination of said
upward travel to act as a brake and prevent descent when the raise
pedal completes its travel.
As the raise pedal stroke is completed and the lever 66 returns to
its upper position under the action of springs 80, the plate 46 is
returned by the spring 50 towards the partition 44. Hence by
effecting an appropriate number of strokes of the lever 66, the
mattress platform 12 may be elevated to a desired position.
The plates 46 and 56 are designed to exert a wedging action on the
ram 28 at the appropriate points during operation of the lever 66,
the size of the apertures in the plates 46 and 56 relative to the
ram diameter, and the degree of canting allowable in any particular
construction being chief design considerations.
Adjacent the jack 13, and generally parallel to the ram 28 thereof,
is a closed hydraulic damper strut 82 acting between the strut 30
and chassis 10. The damper strut 82 comprises a telescopic body and
ram and a piston provided with, e.g., restricted apertures so that
in extension and contraction, oil flows from one side of the piston
to the other. Alternatively the arrangement may include one-way
acting restriction valves so that flow on extension is unimpeded
but is restricted on contraction.
In lowering the mattress, the pedal 38 is depressed to draw the
sleeve 68 towards the pivotal connection 65 so that camming action
can take place between the cam follower 74 and the limb 84 of the
cam member 72. As the lever 66 pivots downwardly, the limb 84
engages the followers 74 and turns the latter in a clockwise sense
as viewed in FIGS. 4 to 6. This turning serves to rotate the shaft
34 in a clockwise sense, in FIG. 2, to push the lower plate 56
upwardly through the agency of crank 62 and link 60 so as to
disengage the wedging action exerted thereby on the ram 28. The
lower plate is maintained in this position as the spring 64 holds
the crank 62 in its over top dead center position.
At the same time, the rod 42 is operated to move the plate 46 into
wedging engagement with the ram 28 and lift the same slightly. By
allowing the lever 66 to pivot slightly away from its lower
position the wedging action on the ram 28 can be released
sufficiently to allow the operator to control transfer of the load
of the platform 12 and patient to the hydraulic damper 82 smoothly
without permitting the plate 56 to exert a wedging action on the
ram 28 which would otherwise prevent lowering of the platform
12.
The platform 12 then begins its descent, and the damper 82 checks
this so that it is controlled and smooth. For example, the
restriction may be such that the mattress frame takes of the order
of ten seconds to descend through a distance of twenty inches.
While the pedal 38 is depressed the wedging action exerted by the
lower plate 56 is disabled. To arrest descent of the platform 12
the pedal 36 is depressed to return the sleeve 68 towards the shaft
34 so that the limb 104 of the member 72 engages the follower 74
and turns the same counterclockwise. This results in the crank 62
and the rod 60 being returned towards the position shown in FIG. 2,
wherein the braking action of the lower plate 56 is effective.
The smooth transfer of the load from the mechanical jack 13 to the
damper 82 is particularly important where the design of the damper
is such that on the start of descent of the platform 12 the initial
descent rate is rapid until the damper is operating fully. This is
because such rapid initial descent may give rise to a jerk.
The invention has been described above in relation to an embodiment
in which the braking plate, constituted by the plate 56, and the
lifting plate 46 are operatively connected with a common lever 66.
However, it is within the ambit of the invention to provide
separate levers one for each canting plate 46, 56. In this case,
the shaft 34 could be connected directly to a second lever
extending in a direction generally opposite to the lever 66 so that
downward pivoting of the second lever rotates the shaft 34 in the
clockwise sense required to disable the wedging action of plate 56
with the ram 28. In such an embodiment although it would be
possible to effect a smooth transfer of load from the mechanical
jack 13 to the hydraulic strut 82, it would be necessary to operate
both levers simultaneously.
* * * * *