Abstract:
An invalid lifting device includes a mobile chassis, a lifting mechanism and a sling connectible to the arm supports to assist in raising a seated person to a standing or substantially standing position. The lifting mechanism includes a lifting arm and an actuator device operative to raise and lower the lifting arm. The lifting arm is pivotable about first and second horizontal axes, the first horizontal axis being fixed and being further from the arm supports than the second horizontal axis. The lifting mechanism also includes guiding elements defining a guide path along which the second horizontal axis is caused to move as the actuating device raises and lowers the lifting arm.

Description:
INTRODUCTION 
     This invention relates to an invalid lifting device and more particularly to such a device for lifting an invalid from a seated to a substantially standing position, especially but not exclusively as part of a toileting procedure. 
     Lifting devices for lifting an invalid (which term includes infirm, disabled and elderly persons) from a seated to a standing position nowadays generally make use of a sling which is passed around the back and below the armpits of the invalid. The sling is attached to two laterally spaced sling attachment points on a lifting arm which is pivoted, typically by a motor driven linear actuator, relative to a mast upstanding from a mobile chassis to raise the shoulders of the invalid along a generally arcuate path. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided an invalid lifting device comprising a mobile chassis, a lifting mechanism and a sling connectible to the lifting mechanism to at least assist in raising a seated person to a standing or substantially standing position, wherein the lifting mechanism comprises a lifting arm, an actuating device operative to raise and lower the lifting arm, the lifting arm being pivotable about first and second horizontal axes, the first horizontal axis being substantially fixed and being further from a projecting end of the lifting arm than the second horizontal axis, and means defining a guide path along which the second horizontal axis is caused to move as the actuating device raises and lowers the lifting arm. 
     Preferably, the guide path is generally upwardly inclined in an in use direction away from the person being lifted. In one embodiment, the guide path may be a rectilinear guide path. This has the effect of flattening out the arc through which the end of the lifting arm distal from the horizontal axes would otherwise pivot to thereby mimic the way in which a person stands when lifting himself from a seated position using downward pressure of his hands on the armrests of a chair. Alternatively, the guide path could be a curved guide path and, in this case, it could be an S-shaped or substantially S-shaped guide path so that the person being lifted can be initially moved generally forwards and then moved generally upwards. 
     Preferably, the lifting device further comprises arm supporting means for supporting the arms of a person to be lifted, the arm supporting means including at least one hand grip. In this case, preferably, the lifting mechanism comprises two arms which are pivotably connected to the arm supporting means. These two arms could form a parallelogram linkage, but are preferably arranged so as to move the arm supporting means from a position in which it is upwardly inclined in an in use direction away from a person to be lifted to, or towards, a position in which it is substantially horizontal as the arm supporting means is raised by the lifting mechanism. This has the advantage that the lifting mechanism can raise and lower a taller person to a standing or substantially standing position than would otherwise be the case with lifting arms of the same length. 
     Preferably, the invalid lifting device further comprises at least one footrest and knee abutment means above the at least one footrest to support the knees of a person being lifted. The knee abutment means may be mounted for pivotable movement from a vertical or substantially vertical position to an upwardly inclined position in an in use direction away from the person to be lifted against the urging force of spring means. This allows the knees of the patient to move slightly forwards as the patient is lifted, the spring means urging the knee abutment means and the knees of the person being lifted rearwards as the person reaches a standing or substantially standing position. 
     The knee abutment means and the at least one footrest may be removably supported by the chassis. With the footrest or footrests removed, the lifting device can be used as a rehabilitation aid. 
     Preferably, the arm supporting means comprises two arm supports. These may be mounted on an inverted U-shaped bracket which is supported by the lifting mechanism. An adjustable strap may be provided between the free ends of the arms of the inverted bracket to prevent a person falling into the bracket. Each arm support is preferably generally L-shaped to support the forearms and at least part of the upper arms of a person to be lifted. In this case, the position of the hand grips may be adjustable so that the elbow of the person to be lifted can rest in contact with the junction between the two limbs of the generally L-shaped arm supports. The arm supports may be provided with releasable straps for holding a person&#39;s arms firmly in place in the arm supports. The arm supports may be shaped to cradle the person&#39;s arms. 
     Advantageously, the lifting sling has a cord at each end and the inverted U-shaped bracket is provided with two jamb cleats for receiving the two cords, respectively. This allows the effective length of the sling to be adjusted. 
     Preferably, the lifting device further comprises a support structure upstanding from the chassis, the means defining the guide path being supported between the chassis and the support structure. In this case the support structure may also support means defining said first horizontal axis. The support structure may also support a handle by which an attendant can wheel the lifting device along the floor. 
     The invention will now be more particularly described, by way of example, with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a  is a side view of a first embodiment of an invalid lifting device, in a first position, according to the present invention, 
     FIG. 1 b  is a side view of the first embodiment, in a second position, and 
     FIG. 2 is a side view of another embodiment of an invalid lifting device according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring firstly to FIG. 1 of the drawings, the invalid lifting device shown therein comprises a mobile chassis  10 , a footrest  11 , a support structure  12  upstanding from the chassis  10 , two arm supports  13  mounted on an inverted U-shaped bracket  14  and a lifting mechanism  15  for raising and lowering the arm supports  13 . 
     The chassis  10  comprises two legs  16  and a cross member  17 . The legs  16  are provided with castors  18  at opposite ends and are pivotable relative to the cross member  17  from a position as shown and in which they are in parallel spaced relationship to a position in which they diverge towards their free ends. 
     Two knee abutments  19  are supported by arms  20  which are detachably connected to a bracket  21  mounted on the chassis  10 . The knee abutments  19  are pivotably connected to the arms  20  about a horizontal axis  22  and are urged into a vertical or substantially vertical position (as shown in FIG. 1) by compression springs  23 . The footrest  11  is detachably connected to the arms  20 . The footrest  11  can be removed on its own or the footrest  11  and the knee abutments  19  can be removed so that the lifting device can be used as a rehabilitation aid. 
     The lifting mechanism  15  comprises two lifting arms  25  and  26 , a power driven linear actuator  27 , typically a motor driven hydraulic actuator of the type made and sold by Smiths Industries Limited as a Single Acting Electrohydraulic Actuator 102740, and two spaced apart guide plates  28 . 
     The guide plates  28  are secured between the chassis  10  and an upper end of the support structure  12 . Each guide plate  28  has an elongate guide slot  29 . In the embodiment shown, these are rectilinear slots, but they could be curved or S-shaped slots. The slots  29  are upwardly inclined in a direction away from a person to be lifted. 
     The actuator  27  is pivotably connected at its lower end about a horizontal axis  30  between the two guide plates  28 . 
     The lower lifting arm  26  is bifurcated at its projecting end where it is pivotably connected to the bracket  14  and is pivotably connected at horizontal axis  31   a  at its other end about a pivot pin  31  supported by the upstanding support structure  12 . The lower lifting arm  26  is also pivotably connected at horizontal axis  31   b  to the extendible part of the actuator  27  and has two rollers  32  which are located in the two guide slots  29 , respectively. The upper lifting arm  25  is pivotably connected at its projecting end to the bracket  14  and at its other end to the extendible part of the actuator  27 . 
     It will be appreciated that as the lower lifting arm  26  is pivotably connected about both the pin  31  and to the extendible part of the actuator  27 , there has to be some provision for limited movement of this lifting arm  26  relative to one of these two pivots. This limited movement is provided relative to the pivot pin  31  by an elongate slot  39  in the lower lifting arm  26  for receiving the pivot pin  31 . 
     Pivoting the lower lifting arm  26  about the extendible part of the actuator  27  as well as about the pivot pin  31  and guiding the rollers  32  along the guide slots  29  has the effect of flattening out the arc through which the outer end of the lifting arm  26  would otherwise pivot if it was pivoted only about the pivot pin  31 . The bracket  14  is thus raised along what approximates to a rectilinear path to thereby closely mimic the way in which a person stands when lifting himself from a seated position using downward pressure of his hands on the armrest of a chair. This is in contrast to the hitherto known practice of lifting a person along an arcuate path and is considered to provide a more comfortable lift. 
     The two arms  25  and  26  could form a parallelogram linkage between the actuator  27  and the bracket  14 , but are preferably arranged to move the bracket  14  and thereby the arm supports  13  from a position in which they are upwardly inclined in an in use direction away from a person to be lifted to, or towards, a position in which they are substantially horizontal as the brackets  14  and arm supports  13  are raised by the lifting mechanism  15 . This is achieved by spacing the pivotable connections between the two arms  25  and  26  and the bracket  14  closer together than the pivotable connections between the two arms  25  and  26  and the actuator  27  and has the advantage that the lifting device can raise and lower a taller person to a standing or substantially standing position than would otherwise be the case with lifting arms of the same length. 
     The arm supports  13  are generally L-shaped to support the forearms and at least part of the upper arms of a person to be lifted. Each arm support is provided with a hand grip  33  and a position of each hand grip  33  may be adjustable so that the elbow of the person to be lifted can rest in contact with the junction between the two limbs of the generally L-shaped arm supports  13 . The arm supports  13  are shaped to cradle the persons arms and are padded to give added comfort. 
     Releasable straps (not shown), typically having hook and loop fastening means, may be provided on the arm supports  13  to hold the arms of the person firmly in place. 
     A sling  34  is also provided. The sling  34  is made of a woven fabric material and a central part of the sling  34  may be padded for comfort. The sling  34  has a cord  35  at each end and the bracket  14  is provided with two jamb cleats  36  (shown in FIG. 2) for receiving the two cords  35 , respectively. This allows an effective length of the sling  34  to be adjusted. 
     An adjustable strap (not shown) is provided between the free ends of the arms of the bracket  14  to prevent a person to be lifted falling into the bracket  14 . 
     A handle  38  is provided at the upper end of the support structure  12  to allow an attendant to wheel the lifting device over a floor. 
     In use, the lifting device is presented to a seated person with the legs  16  of the chassis  10  straddling a chair on which a person to be lifted is seated. The person places his/her feet on the footrest  11  with his/her knees against the knee abutments  19 . The person then places his/her arms in the arm supports  13  and takes hold of the hand grips  33 . The releasable straps (if provided) can then be secured in place around the arms by a nurse or other attendant. The sling  34  is then placed around the lower back of the seated person and connected to the jamb cleats  36 . The arm supports  13  are then raised. As the person is raised, the knee abutments  19  pivot against the urging force of the springs  23  so that the knees of the patient move slightly forwards. As the person reaches a standing or substantially standing position, the springs  23  urge the knee abutments  19  and the knees of the person being lifted rearwards. 
     The arm supports  13  provide control of the upper body for the person and prevent the person swaying from side to side. 
     If the lifting device is to be used as a rehabilitation aid to help a person practice walking, the footrest  11  is removed before the patient is lifted. When the person has been lifted to a standing position, the knee abutments  19  are also removed to create clearance for the patient to walk. 
     Referring now to FIG. 2 of the drawings, the lifting device shown therein differs from the device shown in FIG. 1 in that the arm supports  13  and bracket  14  have been replaced by a sling support  40  which is pivotably connected to both the upper and lower arms  25  and  26 . The sling support  40  has two laterally spaced apart sling attachment points  41  for supporting the sling  34  passing around the back and below the armpits of the person to be lifted. In this case, the person is supported solely by the sling  34 . 
     The above embodiments are given by way of example only and various modifications will be apparent to a person skilled in the art without departing from the scope of the invention. For example, as stated previously, the guide slots  29  need not be rectilinear, but could be curvilinear and, indeed, S-shaped. In this case, the slots  29  could be so arranged that the person being lifted is initially moved in a generally forwards direction and then in a generally upwards direction.