MID 068 P2 -1~
MOTORI Z~ED STRETCHER
Backqround of the Invention It i~ common practice in hospitals to transport patients within the hospital on wheeled stretchers, and minimum requirement for such a stretcher i~ that it he sufficiently large and sufficiently strong to support a supine patient weighing in excess of 200 lbs. Necessarily, therefore even the simplest such stretcher must be in excess of 6 feet in length and at least 2 feet in width, and one model currently marketed by applicant's assignee has overall dimension of 84 inches and 29 inches.
Further, many such ~tretchers currently in use are con~tructed to provide many options in addition to simply transporting a patient, including relea~able side rails, height adjustment, and provisions for altering the position of the patient. For example, some such stretchers include provisions for tilting the bed portion to aid in transporting the patient to a bed or operating table, or for changing the physical orientation of the patient ~uch as from a horizontal position to a Trendelenburg position wherein the body of the patient is tilted to rai~e the feet above the head, or to a reverse Trendelenburg position wherein it is the head which is higher than the feet.
Rai~ing the bed part of the ~tretcher, requires power, which is usually hydraulic but may be electric, and all such special equipment adds to the total weight of the stretcher. For example, the above stretcher currently marketed by the assignee of this application has a base weight of 270 pounds, which may of course be doubled or more by the weight of a patient.
Currently, at least the great majority of stretchers of thi type include a cha~sis having casters mounted at it~ four corner~ on which it can be rolled along a hospital floor. Because of the dimension and weight factors discu~sed above, a minimum of two attendants will be needed to propel and guide such a stretcher, and additional attendants may al~o be needed in situations where the patient i~ being treated during transport, such or example as in emergency or delivery situations.
There is therefore a considerable practical need for a self-propelled stretcher that requires only guidance by a single attendant during all transport operations of a supine patient, which will not only reduce the physical labor of transport as well as injuries to nur~es, but will also reduce the number of attendants needed for each transport, with resultant reduction of hospital labor costs.
Summary of the Invention It i~ the primary object of the present invention to provide a self-propelled stretcher which incorporates a self-contained drive for propelling the stretcher along the floor of a hospital or other place of use under the guidance of a single attendant who can selectively control both the direction and speed of travel of the stretcher, and who is therefore not required to exert any more force than i~ needed to steer the stretcher in the proper direction.
Thi~ objective is achieved in accordance with the invention by equipping the stretcher chas~is with a drive unit comprising a driving wheel and a motor for driving the wheel, with all of the drive components being mounted as a sub-assembly in a single support which is in turn so mounted on the stretcher chassis that the wheel can be readily moved into and o~t of driving engagement with the floor~ In addition, the drive motor is provided with a manual control which is mounted on the ~tretch~r, and which enables a single operator to select both whether the stretcher i~ to move forward or back, and also the speed of such movement.
Another feature of the invention is that the support for the drive assembly is pivotally mounted on the stretcher cha~sis, and simple means are provided for moving this pivotally mounted support between lowered and raised positions with respect to the floor. Further, the invention provide~ a latching assembly which releasably secures the drive assembly in its rai~ed position in re~ponRe to movement of the drive assembly to that position. This latching assembly also includes provision for preventing relea~e of the drive to its lowered, operative position except in responRe to positive action by the operator to effect release of the latching aRsembly.
Other ob jects and advantages of the invention, and the structure by which they are achieved, will be apparent from or pointed out in connection with the description of the preferred embodiment which follows.
Brief Description of the Drawin~s Fig. l is a perspective view showing a stretcher incorporating a self-contained drive in accordance with the invention for propelling the stretcher along a floor;
Fig, 2 is a view taken generally on the line 2--2 in Fig. 4 with some part~ removed;
Fig. 3 is a fragmentary elevational view looking from left to right in Fig. 2;
Fig. 4 i~ a fragmentary plan view illustrating the meehanism for latching the drive support in it~ unlatehed position;
Fig. 5 is a view similar to Fig. 4 showing the latch meehanism in latehed position;
Fig. 6 is an enlarged fragmentary section on the line 6--6 in Fig. S; and Fig. 7 is a schematic wiring diagram.
Deseription of the Preferred Embodiment The ba~ic structure of the streteher shown in Fig. 1 is essentially as shown and de~cribed in the commonly owned Kuck U.S. Patent No. 4,691,393. It inelude~ a rectangular bed 10 on which the patient is placed, and this bed is mounted, as deseribed in the above patent, on a chassis indieated generally at 11 which is in turn ~upported on four ea~ters 12 for movement along the hospital floor.
The cha~si~ 11 includes a main frame plate 13 having one of a pair of cross tubes 14 and lS welded thereto at the head and foot ends of the ehas~i~ respectively. Each of the~e tubes has a easter 12 mounted at eaeh end thereof in a conventional ~wiveling mounting in a tubular hou~ing 16, and provided with a foot-operated brake 17 of well-~nown eonventional eonstruetion. The frame plate 13 also supports a hollow eolumn 18 within which i~ mounted the powered system for tilting the bed 10, whieh may be hydraulie, as described in the above patent, or eleetrieal.
The power unit for propelling this ~treteher is identified generally as 20 and i~ mounted in a frame eompri~ing a pair of side plate~ 21 and 22 welded to the oppo~ite edges of a eroQs member 23. The side plate~ 21-22 2~ 4 3 are pivotally mou~ted on the chas~is 11 by a cro~s shaft 25 mounted at it~ opposite ends in the lower ends of a pair of tubes 26 which extend vertically through and are welded to the foot end chassis tube 15.
The power unit 20 includes a rubber tired driving wheel 30 freely rotatable on a shaft 31, each end of which is supported in a spacer 33 of square section that is in turn mounted for sliding movement in a slot 34 in an adjustment mechanism 35 welded to the outside of the plate 21 or 22 respectively. Screws 36 and 37 threaded through opposite ends of the adjustment mechanism 35 adjust the position of the associated spacer 33 in the ~lot 34 to tension the drive belt for wheel 30 as now described.
The drive train to the wheel 30 includes a gear motor 40 bolted or otherwise mounted on the frame side plate 21. Satisfactory results for the purpo~es of the invention have been obtained utili~ing a 12-volt, one-half horsepower permanent magnet motor 40 having a gear box reducer 41 which provides a 10:1 reduction by use of helical gears to a drive pulley 42 having a driving connection through belt 44 to a pulley 45 secured to one side of driving wheel 30. As noted in the preceding paragraph, the tension of belt 44 may be changed by adjusting the position of the wheel shaft 31 in the adjustment mechanism 35.
Mean~ are provided for continuou~ly applying a downward bia~ing force on the drive unit frame 21~23 and thus on the wheel 30 to maintain it in driving engagement with the floor. More specifically, an elongated bolt or threaded rod 50 is welded to the frame cross member 23 and projects upwardly through a slot 51 in the chassis frame plate 13. A
MID 068 P2 ~6 large washer 52 is ~upported on the base of the rod SO and in turn supports a tubular guide member 54 o~ low friction plastic material which is sized to pas~ freely through the slot 51.
A compression spring 55 fits loosely over the guide 54 and is supported at its lower end by the washer 52. A
second large washer 56 i~ too large to pass through the slot 51 and has a central opening sized to rece.ive the spring guide 54, but not the spring 55, freely therethrough. The spring 55 is thus confined between the wa~hers 51 and 56 so that it exert~ a con~tant biasing force between the frame plate 13 and the power unit 20 which urges the latter in clockwise direction on pivot shaft 25 a~ viewed in E'ig. 2.
It i~ normal practice in the use of a wheeled stretcher to move it with its foot end leading, 80 that in the event of a collision, the head of the patient will be as remote as possible from the point of impact. The head end of the stretcher is therefore provided with guide means, comprising a pair of handles 60 mounted on conveniently located components of the structure supporting the bed 10.
The handles 60 are connected by a cross bar 62 on which in turn are mounted an On-Off key switch 65 for the powe.r to drive motor 40, and a joy stick 66 for controlling the speed and direction of motor 40, as described hereinafter.
Since the axis of driving wheel i8 nor~al to the length of the ~tretcher, its driving force is lengthwi~e of the ~tretcher, but the ~tretcher can be steered, by means of handles 60, by swinging the head end of the stretcher to one ~ide or the other about a vertical axi~ centered on the wheel 3Q 30 so that the caster3 12 at the head end of the stretcher can turn on the vertical axes of their connections to the frame bar 16. There are times, however, when it i8 nece~sary to move the ~tretcher at right angles to its length, such as when moving it înto sidewise relation with a bed. Such sidewise movement would be difficult so long as the driving wheel 30 is in contact with the floox, and means are therefore provided for lifting power unit 20 to a position wherein the wheel 30 is free of the floor, and for releasingly latching it in that raised, inoperative position.
Referring to Fig. 2, a lift lever arm 70 is mounted on a pivot shaft 71 having its opposite ends mounted near the upper ends of the same pair of tubes 26 on which the power unit i~ pivotally mounted. A lift bar 72 extends freely through a ~lot 73 in the frame plate 13 and is pivotally connected at 74 to the inner end of lever arm 70 and at 75 to a clevis 76 welded on the top of the frame cross member 23. A keeper or pawl member 77, consisting of a rectangular piece of flat bar stock, i~ welded to one side of the lift bar 72.
As i~ apparent from Fig. 2, counterclockwise movement of the lever arm 70 resulting from downward pre~sure on its outer end will have the effect, through lift bar 72, of lifting the entire drive unit 20 against the force of spring 55, and releasable means are provided for latching the parts in this position. More specifically, a latching member 80 of flat bar stock is mounted for guided sliding movement on top of the frame plate 13 by means of a bolt 81 which extend~ through a slot 82 in plate 13, and another bolt 83 which projects upwardly from the plate 13 through a slot 84 in the member 80.
As shown in Figs. 4 and 5, the plate 13 i~ also provided with a channel-~haped slot 85, and a knob 86 includes a stem which passes fl~eely through the slot 85 for sidewise movement between the two ends of thi~ slot. A coil spring 88 is connected between this stem portion of knob 86 and the bolt 81 on member 80. When the knob 86 is at the end 85a of slot 85, the spring 88 will apply a biasing force to member 80 outwardly of the chassis. As shown in Fig. 4, this i8 the unlatched position, and lift bar 72 is free to move up and down between the limit po~itions established by contact of the drive wheel 30 with the floor and maximum compression of spring 55.
When the knob 86 is moved to the other end 85b of slot 85, the spring 88 will bia~ the member 80 inwardly of the chassis, so that its inner end will abut the side of the pawl 77. However, when the lever arm 72 is depressed to raise the power unit, then as ~oon as the pawl 77 has been raised above the member 80, that member will slip under the pawl 77 to latch the lever arm 72 against movement in the reverse direction, as ~hown in Figs. 5 and 6, and thereby will prevent the power unit from returning to operative position.
When it is desired to resume driving of the stretcher, the knob 86 i8 again moved to the end 85a of slot 85. This will not release the latch mechanism, however, becau~e the weight of the power unit coupled with the force of spring 55 will cause the pawl 77 to hold the member 80 by friction in its latched position. In order to release the latch mechanism, it i8 then neces~ary first to depres~ the lever arm 72 to a sufficient extent to release the member 80 5 ~ ~
for movement to its unlatched position under the biasing force of ~pring 88. When the arm 72 i8 then again released, the power unit will move down to its operative, driving position of engagement of the wheel 30 with the floor. For ease of operation, lift arm 70 is preferably provided with a foot pedal 90 on its outer end.
The drive motor 40 i~ battery-powered, and the related electrical components and circuits are shown diagrammatic~lly in Fig. 7. With the motor 40 of the characteristics already indicated, satisfactory results under test~ have been obtained using, aQ a direct power source, two rechargeable 12-volt batteries 100 of the type sold as Globe Gel/Cell 12-volt batteries. One of these batteries is carried in each of a pair of baskets 101 suspended on the frame tube~ 14 and 15, one of which is shown in Fig. 1.
Since the batterie~ 100 are rechargeable, a recharger 102 i~ also carried by the stretcher, in one of the baskets 101. Test re~ults have ~hown that a satisfactory such charger is marketed a~ Model CCR 12 by Schauer Manufacturing Corp., 45 Alpine Avenue, Cincinnati, Ohio 45242.
The electric control system includes a motor speed and direction controller 105 which is conveniently carried in the basket 101 which does not contain the recharger 102.
Satisfactory test re~ults have been obtained using a motor speed controller Model 1203 marketed by Curti~ PMC, 6591 Sierra Lane, Dublin, California 94568. Manual control over the operation of the controller 105 i~ provided hy the joy stick 66, an example of a suitable commercially available 3n unit for this purpose being the joy stick control unit JS 4 2~5l~
marketed by Flight Link Control in Altow, Hant~, Great Britain.
It ~hould now be apparent that for normal use, a ~ingle person can drive and steer the above-de~cribed stretcher by controlling its speed and direction of driven movement through manual manipulation of the joy stick 66, with the steering being effected by swinging the head end of the stretcher to one side or the other by means of the handle~ 60. Power operation of the stretcher will accordingly be available for all tran~port purpGses except when it i8 necessary to move the stretcher sidewi~e, e.g. to bring it into accurate side-by-side alignment with a bed or operating table. For ~uch purposes, the power unit 20 i~
lifted and latched as described, 80 that the stretcher a~ a whole can then be maneuvered on its casters 12. Since ~uch manual maneuvering of the stretcher normally involves relatively little actual movement, this al~o can be readily done by a single per~on.
While the form of apparatus herein de~cribed constitutes a preferred embodiment of the invention, it is to be understood that the invention i~ not limited to this precise form of apparatus and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.