US 3733623 A
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.
Description (OCR text may contain errors)
nited States Patent [1 1 Qroxton  References Cited  HOSPITAL BEDS Inventor: John Mervyn Croxton, Sirmingham, V
UNITED STATES PATENTS England Mommsen............ .....297/433 X Kotter  Assignee: J. Nesbit-Evans Primary Examiner-Casmir A. Nunberg Attorney-Marsha11 & Yeasting  Filed:
 Appl. No.: 199,411
ABSTRACT  Foreign Application Priority Data Nov. 24, 1970 Great A hospital bed having a mattress supporting element 557o9/70 which can be elevated or lowered relative to the bed mm 30 o Mr. ch .m l a .wmm S e m adm u wh n .ws e e F u mag g In m 0.1 fyfl W oho m y D. M w D m 6, aw s n .m .me h Mm C m: 5 r m m u Sa mnm mm h C m" 20 3 9 NH 57. m q ,2 .M 5A "7 9", no 2 mm" "7m m 1 m W mmm L l WM te I ll UMF 1.1] 218 555 [.131
PATENIH] M22 1915 SHEET 1 [1F 3 PATENTED HAYZZIQTS SHEET 2 [1F 3 PATENTED M22193 SHEET 3 [1F 3 HOSPITAL BEDS 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 THEYINVENTION 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 bydraulic 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 footoperated 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 I3 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 partition44 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 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 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 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 thiscase, 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.
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.