Abstract:
A trolley is provided and includes at least one driven wheel and non-driven wheels. The at least one drive wheel may be moved to a position clear of the ground or to a position in which it contacts the ground with the adjacent non-driven wheels being raised off the ground. Movement between these two positions is effected by pivoting a sub-frame to which the driven wheel and the non-driven wheels are connected. During this movement, the region of the trolley above the driven wheel is first lowered and then raised slightly such that the end elevation of the support for a patient remains the same.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a stretcher and a method of operating a stretcher. Herein any reference to a stretcher includes a stretcher trolley. 
       BACKGROUND OF THE INVENTION 
       [0002]    Stretchers are presently maneuvered manually by an operator who exerts the forces required to direct and move the stretcher about hospital ward, between wards, between ambulances and between ambulances and incidents. During the course of maneuvering the stretcher the operator has to exert a considerable force in order to control the stretcher. The effect can be bad for the back of the operator. The force is increased when maneuvering the stretcher up steep inclines or ramps, such as an ambulance ramp or hospital ramp. Furthermore, the wheels of the stretcher are mounted on swivels, which, particularly if the ramp tilts to one side (such as may occur when the vehicle is not parked on level ground), as the operator pushes the stretcher up it can run off the stretcher. In addition the stretcher can run off course when going up or down hill or on a slope. Alternatively, the stretcher can run away down hill if on a steep hill or if the operator slips and loses grip. All of these problems are accentuated when the patient on the stretcher is particular heavy. 
       SUMMARY OF THE INVENTION 
       [0003]    It is a feature of the present invention to attempt to overcome at least some of the above or other disadvantages. 
         [0004]    According to one aspect of the present invention a stretcher trolley arrangement includes at least three non-driven wheels and at least one driven wheel, the driven wheel being moveable relative to at least one of the non-driven wheels between a driving position in which the driven wheel is in contact with the ground and a non-driving position in which the driven wheel is spaced from the ground. 
         [0005]    At least one of the driven wheels or a non-driven wheel may be moveable mounted on the stretcher in order to effect the movement between the two positions. 
         [0006]    In the travelling position at least one of the non-driven wheels may be spaced on the ground. The driven wheel may be pivotally mounted on the stretcher about an axis offset from that wheels rotational axis to effect the movement between the driven and non-driven positions. 
         [0007]    The movement in at least one direction between the positions may be effected by a drive mechanism. 
         [0008]    The drive mechanism may be arranged to hold the stretcher in at least one of the positions with the hold being exerted in at least one of the positions being releasable. 
         [0009]    The movement from at least one position to another may be effected by manual movement of a telescopic arm. 
         [0010]    The movement in at least one direction between the positions may be effected by a drive mechanism which may include an extendable and contractible member pivotably connected to the stretcher and a link at a location spaced from the pivotal mounting of the link to the stretcher. 
         [0011]    The movement from the driving position to the non-driving position may be at least initially pivotal movement about the point of contact of the driven wheel with the ground. 
         [0012]    The driven wheel may be larger than the non-driven wheel such as being more than twice the diameter of the non-driven wheel. 
         [0013]    When the wheel is in the driving position the drive may be arranged to be able to act as a brake should the stretcher be going down an incline. 
         [0014]    The arrangement may include a battery arranged to power the drive wheel. A battery may be arranged to drive the movement between at least one of the positions. 
         [0015]    The angle of the axis of the driven wheel may be fixed with respect to the longitudinal extend of the stretcher. 
         [0016]    The axis of at least one non-driven wheel may be able to move about an upwardly extending axis and may be selectively lockable in at least one position of the upwardly extending axis. 
         [0017]    The driven wheel may be located between non-driven wheels in the direction of longitudinal extend of the stretcher. 
         [0018]    The non-driven wheel may be located towards one end of the stretcher in the region of a support extending up from a lower region of the trolley to a support for a body. The driven wheel may be pivotally connected to the support. The driven wheel and the non-driven wheel may be located in the region of the support with each being either side of the support in the longitudinal extent of the trolley. 
         [0019]    According to a further aspect of the present invention a method of operating a stretcher arrangement that includes at least three non-driven wheels and at least one driven wheel comprises moving at least one of the wheels between a driving position in which the driven wheel is in contact with the ground and a non-driving position in which the driven wheel is spaced from the ground. 
         [0020]    The method may comprise causing at least one non-driven wheel to be clear of the ground in the driving position. The method may comprise causing the non-driven wheel to be clear of the ground in the driving position at a location spaced from the longitudinal extent of the remaining wheels in contact with the ground. 
         [0021]    Further features of the present invention are defined in the claims. 
         [0022]    The drive mechanism may include, although by no means be limited to, linear lead-screw actuators, hydraulic actuators, or electro-hydraulic actuators. 
         [0023]    The present invention includes any combination of the herein referred to features or limitations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The present invention can be carried into practice in various ways but several embodiments will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0025]      FIG. 1  is a side perspective view of a stretcher trolley showing the patient support, castor wheels, a driven wheel, and a main frame; 
           [0026]      FIGS. 2 and 3  are a side perspective and rear perspective view of the rear trolley end region showing the rear castor wheels and the driven wheels connected to a sub frame. The sub frame is assembled to the main frame at a fixed pivot point to enable it to rotate about a first axis; 
           [0027]      FIG. 4  is a side view of a first transition position showing the rear castor wheels in contact with the surface and the driven wheels free from the surface such that the stretcher trolley is solely supported by castor wheels; 
           [0028]      FIG. 5  is a side perspective view of a mid transition position showing the driven wheels and all castor wheels in contact with the surface; 
           [0029]      FIG. 6  is a side perspective view of a second transition position showing the driven wheels in contact with the surface with the rear castor wheels clear from the surface such that the trolley is solely supported by the front castor wheels and the driven wheels; and 
           [0030]      FIGS. 7 and 8  show side views in the two transition positions effected by pulling a lever down. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]    As shown  FIGS. 1 and 2 , the patient support  4  is mounted on a first support  32 , which extends upwardly from the front of the main frame  10 , and a second support  34 , which extends upwardly from the rear of the main frame  10  so that the patient support  4  is held mainly flat or horizontal. 
         [0032]    The lower end of the second, rear support  34  is fixed to an upwardly extending arm  10   a  of the main frame  10 . The upper end region of the second, rear support  34  is connected by a first group of co-operating parts  36  to the patient support  4 . 
         [0033]    The lower end region of the first, front support  32  is attached to a piston of a first linear actuator  38  by a second group of co-operating parts  40 . The upper end region of the first support  32  is connected by a third group of co-operating parts  42  to the patient support  4 . The lower end of the actuator  38  is fixed to an upwardly extending arm  10   b  of the main frame  10 . The configuration of the patient support  4 , the first support  32 , the second support  34 , the first linear actuator  38 , and the three groups of co-operating parts  36  and  42  is such that the first linear actuator may be driven to extend or contract a piston  38   a  of the linear actuator in order to incline or decline the angle of the patient support  4 . When inclined, the patient support  4  may, for instance, be raised up to 15° to drain fluid from the legs of a patient on the support  4  with pivot occurring about the parts  36 . 
         [0034]    The first linear actuator  38  may be controlled by an operator controlling a two-position or multi-position switch, such as a rocker switch (not shown), which may be positioned at the rear of the trolley. A battery  56  mounted on the main frame  10  is able to power the actuator  38  in order to extend or contract the piston  38   a  using any well known method. 
         [0035]    The main frame  10  provides the housing for the two front castor wheels  6   a  and  6   b . The castor wheels  6   a  and  6   b  are aligned substantially in the same plane and at the first trolley end region and are spaced apart laterally across the stretcher, generally being positioned on the widest portion of the main frame  10 . The front castor wheels are able to rotate about a horizontal axis and can swivel about a vertical axis on a stub shaft  47 , offset from the horizontal axis. 
         [0036]    The rear castor wheels  6   c  and  6   d  are able to rotate in the same way as the front castor wheels and, in addition. 
         [0037]    As shown in relation to  FIGS. 2 and 3 , a sub frame comprising of two side rails  50  and two cross rails  52  is pivotally mounted at points  20  on the main frame  10  at the rear end such that the sub frame  16  is able to pivot about a horizontal axis. 
         [0038]    A rear castor wheels  6   c  and  6   d  are located on the rearward projecting end region of the sub frame  16 . The castor wheel sub axles  48  of the rear castor wheels pivot with the sub frame about the pivot points  20 . 
         [0039]    The driven wheels  8  are mounted on axles  54  that project from a forward region of the sub frame, spaced from the pivot points  20  of the sub frame. The battery  56  powers a drive mechanism such as motor  58  mounted on the axle  54  or the sub frame  16  in order to drive the axle  54  and subsequently the wheels  8  in any well known manner. For instance, the motor may impart a drive via an induction force being applied to a magnet fast with the axles  54 . 
         [0040]    A second actuator  60  controls the movement of the sub frame  16  about the pivot points  20 . The second actuator  60  is rotatably fixed at the upper end to the upwardly extending arm  10   a  just forward of that arm. The lower end of the actuator  60  is pivotally connected to the axle  54  of the sub frame  6  such that when the piston  66  of the second actuator  60  is located on the sub frame  16  moves up or down through a circumferential path by rotating about the pivot points  20 . 
         [0041]    The battery  56  powers the actuator  60  to extend or contract a piston  66  of the actuator. A two-position switch, such as a rocker switch (not shown), which may be positioned at the rear end of the trolley and controlled by an operator, may control the extension or contraction of the actuator  60 . 
         [0042]    It should be clear from  FIGS. 4 ,  5  and  6  that extending the piston  66  of the actuator  60  effects a movement between the first, mid, and second transition positions of the surface  24 . In the second transition position the co-operating parts of the actuator resist any rotational movement of the sub frame  16 . During the transition between the first position  22  and the second position  30  the patient support  4  moves only marginally. It can be seen that as the rear of the trolley is being moved between the position shown in  FIGS. 7 and 8  the castor wheels are moved down, initially, to cause a slight lowering of the pivot points  20  about the contact of the driven wheels with the ground until the castors contact the ground. Then the pivot points  20  are raised slightly about the contact point of the castors with the ground. Accordingly the inclination change of the patient support  4  is minimal and the support is at substantially the same inclination regardless of the positions shown in  FIGS. 7 and 8 . 
         [0043]    It is possible to lock the castors in a fixed rotational position about the stub axles. Thus, if the stub axles are locked in the position shown in  FIG. 8  when, or after the driven wheels only at the rear contact the ground, as in  FIG. 7 , there is significant clearance for the trolley to negotiate small steps or ledges without the rear castor wheels contacting the step or ledge. In the locked position the tangent between the raised castor wheels and the driven wheels and the included angle to the horizontal may be more than 8°, or more than 10°, or in the region of 12°-15°. 
         [0044]    When the second trolley end region  12  is orientated in the second transition position, the stretcher can be moved by an operator at the rear of the trolley using a lever, which initiates and varies the speed of rotation of the drive shaft from the motor and the speed of travel of the trolley. Similarly, the lever can be moved in an opposite direction to initiate and vary the speed of reverse rotation of the axle  54 . The motor may include a positive drive that prevents the axle  66  from being able to rotate faster than that set by the lever to prevent the runaway of the stretcher down inclines. 
         [0045]    Furthermore, it will be appreciated that not all of the power to move the stretcher need be applied by the motor and an operator could assist in providing the necessary power. 
         [0046]    Should the motor fail or should it be desired to maneuver the stretcher in a traditional manner, both sets of castor wheels  26  and  14  or the front castor wheels and the driven wheels may be used. The actuator piston  66  may contract to initiate the transition to the first position  22 . Alternatively the actuator may relax such that all driven and non-driven wheels contact the ground. 
         [0047]    Should the battery fail the transition may be effected manually as depicted by  FIGS. 7 and 8 . A telescopic lever  31  held fast to the sub frame is extended from the sub frame  16  by any well-known mechanism. The actuator piston  66  is unloaded such that the co-operating parts of the actuator  60  do not resist rotational movement of the sub frame  16 . A downwards force exerted on the lever  31  by the hand or foot of an operator acts to rotate the sub frame  16  in to the first transition position. The actuator piston  66  may be re-locked in order to impart the necessary rotational movement of the sub frame  16  or the lever may be moved sideways to engage with a locking part of the main frame. Return movement and locking is a reverse of this operation. 
         [0048]    The pistons may comprise linear actuators whereby a nut is axially fixed but rotated to drive the piston axially with regard to the rotation of the nut. 
         [0049]    All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.