Abstract:
A bedframe for medical beds has a height-adjustable frame member and an obstruction detector on the height-adjustable frame member. The obstruction detector has a contact member which is displaceable, for obstruction detection, both upwardly and downwardly relative to the frame member. A sensor detects such displacement to stop movement of the frame member. The frame member may be a height adjustable lower frame member of a bedframe having also a height adjustable upper frame member. The bedframe also has a manually removable panel of its headboard and footboard, to allow access to a patient between columns carrying the height-adjustable upper frame member.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to height-adjustable bedframes, in particular for height-adjustable beds for medical use. 
       BACKGROUND OF THE INVENTION 
       [0002]    Height-adjustable beds are known in the art, and are commonly used in hospitals and other medical institutions. A frame member of the bed, that supports e.g. a mattress for a patient to lie on, is adjustable in an upward and downward direction. The frame member may be adjustable independently at its head and foot end, in order that the angle of incline of the mattress can be adjusted. 
         [0003]    Height-adjustable beds have numerous advantages. For example, the mattress of a height-adjustable bed can be lowered to a position close to the ground. A low mattress position is particularly advantageous for elderly or mentally disabled patients, who are prone to falling out of the bed accidentally or intentionally. The lower the position of the mattress, the less likely it is that a falling patient will be hurt. Furthermore, it is harder for a patient to alight from a mattress positioned close to the ground. However, it is advantageous that the mattress can be raised so that a patient lying on the mattress is at a suitable height for care workers to attend to. 
         [0004]    It is desirable that patient care access is provided at the head and/or foot ends of the bed when the mattress is adjusted to any height. 
         [0005]    In known height-adjustable beds, the height-adjustable frame member is held at the head and foot end of the bed by respective supports. These supports are often cumbersome, or insufficiently strong to provide a stable platform that will meet the European regulations for hospital bed frames, and comprise powered drive means for raising and lowering the respective ends of the height-adjustable frame member. The supports limit or prevent patient care access from the head and foot ends of the bed. This is a particular problem when certain medical procedures must be carried out on a patient, such as cardiopulmonary resuscitation (CPR). CPR is usually carried out from the head end of a bed, since access to the patient&#39;s head is required. 
         [0006]    Known height-adjustable beds generally comprise a height-adjustable upper frame member and a fixed lower frame member, the upper frame member being for supporting the mattress and the lower frame member providing rigidity to the bed when the upper frame member is at a raised position. WO01/45626 shows a height-adjustable bed without a lower frame member. 
         [0007]    WO03/070145 discloses a height-adjustable bed having both a height adjustable upper frame member and a height-adjustable lower frame member. 
         [0008]    However, safety problems arise with beds having height-adjustable frame members. Most notably, it is possible for a person to trap a limb between the height-adjustable parts, e.g. between the upper frame member and the fixed lower frame member during lowering of the upper frame member. WO03/088885 describes obstacle detection devices in such a bed in the form of a wireless curtain, e.g. formed by light beams, or a force-sensing switch. 
       SUMMARY OF THE INVENTION 
       [0009]    One object of the invention is to provide a bedframe having an improved safety against trapping of objects, such as a person&#39;s limb, by a height-adjustable member. 
         [0010]    Another object of the invention is to provide a bedframe having improved access to the patient on the bed at one or both ends of the bed. 
         [0011]    The present invention according to a first aspect provides: 
         [0012]    a bedframe having a height-adjustable upper frame member for supporting a patient, the upper frame member being height-adjustable at a foot end and a head end by respective support means; 
         [0013]    a first said support means comprising two vertically elongate columns, the columns being spaced from one another in a horizontal direction; wherein 
         [0014]    over at least part of the height travel of the upper frame member, patient care access is provided through a gap between the columns. 
         [0015]    Preferably, the bedframe comprises a manually removable structure, wherein the gap between the columns for patient care access is provided by removal of the manually removable structure. 
         [0016]    In this specification the term ‘manually’ is used to describe removable structures that can be removed by a person without the use of an external tool. The removable structures may be held in guides, e.g. grooves, and may be removed by sliding or lifting in an upward direction. 
         [0017]    Preferably the manually removable structure is not part of the structure supporting the upper frame. 
         [0018]    Preferably a mattress is provided on the upper frame member. Preferably the bedframe has a generally rectangular shape, appropriate to receiving a standard mattress. 
         [0019]    The elongation direction of the bedframe is defined herein as a substantially horizontal direction substantially parallel with the longest side edge of the bedframe. The head and foot ends of the bedframe, and its component parts, are defined herein respectively as the ends adjacent the head and feet of a patient lying on the bed during normal use. 
         [0020]    In this specification the term ‘patient care access’ is used to describe entry for a care worker (e.g. a doctor, nurse, etc.) to a region above the upper frame member, in particular to a region above the mattress, from a region peripheral to the bedframe, the entry being such as to allow normal care procedures to be carried out on the patient by the care worker, most preferably CPR procedures. Preferably the care worker can lean through the space between the two columns of the support, in order to e.g. lean over a patient. Preferably the clear, i.e. unobstructed, space between the two columns for patient care access is between 30 and 200 cm long, more preferably between 40 and 60 cm long, in the horizontal direction, i.e. in the width direction of the bed. 
         [0021]    Preferably, the first support means is located at the head end of the bedframe. Preferably, the manually removable structure is a headboard. Preferably, the headboard moves upwards and/or downwards in accordance with height-adjustment of the upper frame member. Preferably, the headboard is manually removably mounted to the support means and/or the upper frame. More preferably, the manually removable structure is a panel which is part of a headboard, the headboard being mounted on the support means and/or the upper frame. Preferably, when the panel is fitted with the remainder of the headboard fixed to the support means and/or the upper frame (i.e. the height-adjustable fixed portion of the headboard), the panel spans the horizontal distance between the two columns. Preferably, the height-adjustable fixed portion of the headboard extends in the region between the columns to a point no higher than the height of a standard mattress located on the upper frame member. Preferably, the panel is slidably fitted to the fixed portion of the headboard. 
         [0022]    Removing only a portion, e.g. a panel, of the headboard is easier than removing the entire headboard, as it is lighter. Furthermore, the fixed portion may serve as a mounting point for medical equipment, electrical connection points, or side rails etc. 
         [0023]    Alternatively, the bedframe may comprise no headboard. 
         [0024]    The bedframe may comprise a second support means configured similarly to the first support means but located at the opposite end of the bed. The second support frame means, if located at the foot end of the bed, may include a footboard similar to the headboard described above, with a similar manually removable panel, for example. 
         [0025]    Preferably each column projects upwardly from a base of the support means, and preferably each column comprises a movable portion, the movable portion being height-adjustable, the upper frame being height-adjustable in accordance with height-adjustment of the movable portion. 
         [0026]    Preferably, each column has a respective powered drive means for respectively moving each movable portion. Having separate drive means for each column makes it simpler to provide minimal structure between the columns than if a single drive means were used for both columns. Nevertheless, it is understood that a single drive means could be adapted to move each movable portion, the drive means being configured such that patient care access is available in accordance with present invention. Preferably, each drive means comprises an electric motor. 
         [0027]    It is preferable that the drive means of the same support means are synchronised with one another in order that heights of the respective movable portions can be adjusted at the same rate, e.g. with a single actuation step. This prevents the upper frame member tipping to one side during height adjustment, which could cause a patient to fall off a mattress in use. 
         [0028]    Preferably, the bedframe comprises a lower frame member, the lower frame member being height-adjustable at a foot end and a head end by the respective support means, the lower frame being located underneath or on the same horizontal plane as the upper frame member. Preferably, upon upward movement of the movable portion of each column, the lower frame member moves upwards at half the speed of the upper frame member, and upon downward movement of the movable portion of each column, the lower frame member moves downwards at half the speed of the upper frame member. It is desirable that the lower frame can be raised from the ground. Preferably, the lower frame can be raised to a position halfway between the upper frame and the ground, in order to maximise bed rigidity. Furthermore, raising the lower frame provides space underneath the bedframe, e.g. for cleaning, and/or for locating X-ray machines, frame members of hoists etc., or even a care worker&#39;s feet, whilst the care worker cares for a patient. 
         [0029]    Preferably, the lower frame member is fixed in position with respect to the movable portions. More preferably, the lower frame member is fixed to the movable portions. 
         [0030]    In order to facilitate the relative movement of the upper and lower frame members as discussed above, i.e. the 2:1 ratio in speeds of the upper and lower frame members respectively, preferably each column comprises a pulley system, the pulley system comprising a cable or chain fixed at one end to the base of the support means and fixed at the other end to the upper frame member. Preferably the cable or chain extends between the base and the upper frame member via a pulley block, the pulley block being mounted on the movable portion. 
         [0031]    In this specification the terms “cable” and “chain” are used for simplicity. The terms are intended to cover other flexible, elongate articles, suitable for transferring load, such as ribbons, tapes, ropes, and wires etc. 
         [0032]    Preferably, the movable portion of each column is a sleeve such as an outer tube, the outer tube being slidable over an inner tube, the inner tube being fixed with respect to the base of the support means. Preferably the base is a rigid support bar extending between, and preferably beyond, the bottom ends of each column. Preferably a wheel is provided at each end of the support bar, so as to provide means for transporting the bedframe. 
         [0033]    Preferably, the upper frame member, lower frame member and support means are configured such that lower frame member rests at the same height as the upper frame member, when the upper and lower frame members are at a minimum height. Preferably, when at a minimum height, the bottom faces of the upper and lower frame members are lower than the top of the wheels. 
         [0034]    The present invention according to a second aspect provides: 
         [0035]    a bedframe having a height-adjustable member and an obstruction detector for the height-adjustable member, wherein the obstruction detector comprises a contact member displaceably mounted on the height-adjustable member so as to be displaced relative thereto when encountering an obstruction during upward and/or downward movement of the height-adjustable member, and a sensor arranged to detect such displacement of the contact member; 
         [0036]    wherein the contact member has upper and lower portions lying respectively above and below the height-adjustable member and is displaceable, for obstruction detection, both upwardly and downwardly relative to the height-adjustable member. 
         [0037]    The bedframe of the second aspect of the present invention may have any or all of the features of the bedframe of the first aspect of the present invention set out above, and vice versa. 
         [0038]    Preferably, there is a control system arranged so that, when the obstruction detector detects displacement of the contact member, the height-adjustable member is stopped from moving upwards and/or downwards. This provides a safety feature to the bedframe, reducing the risk that a moving portion of the bedframe can trap an obstacle, e.g. the limb of a person. Alternatively, the height-adjustable member may be prevented from moving downwards but not from moving upwards, as this may allow an object trapped by the height-adjustable member to be released. 
         [0039]    Preferably the height-adjustable frame member is supported at its foot end and a head end by respective support means. 
         [0040]    Preferably the bedframe according to the second aspect comprises a powered drive means for moving the height-adjustable member up and/or down, and preferably the control system is arranged to stop the drive means when the obstruction detector detects an obstruction. 
         [0041]    Preferably the height-adjustable member is a lower frame member of the bedframe, the bedframe also comprising an upper frame member. Preferably two or more contact members are provided which, in combination, extend at least the full width and/or length of the lower frame member. Using e.g. two contact members makes transportation of the contact members easier, since they are each smaller than a single contact member that can extend across the same space. 
         [0042]    Preferably, both the lower frame member and the upper frame member are height-adjustable, e.g. in the same or a similar manner to the upper frame member and the lower frame member discussed with respect to the first aspect of the present invention. For example, preferably the lower frame member moves upwards and downwards at half the speed of the upper frame member. Preferably, the support means are the same or similar to the support means described with respect to the first aspect of the invention. Nevertheless, known support means, which e.g. provide no such patient care access, may be used. 
         [0043]    Preferably the lower frame member comprises two or more beams extending in a direction substantially parallel to the elongation direction of the bedframe, the beams spaced apart in a horizontal direction. Preferably the upper frame member comprises two or more beams extending in a direction substantially parallel to the elongation direction of the bedframe, the beams spaced apart in a horizontal direction. Preferably the beams of the upper frame member support a substantially rectangular mattress support. Preferably, when the upper frame member is in a minimum height position, the beams of the upper frame member lie to one side of the beams of the lower frame member, in a horizontal direction. Such an arrangement means that the minimum height of the upper frame member can be lower than if the upper frame member remained above the lower frame member at all times. 
         [0044]    Preferably, the contact member comprises a flange portion that extends to a region directly underneath a beam of the upper frame member, when the upper frame member is in a minimum height position. This enhances safety, as the obstruction detector may detect obstruction directly between a beam of the upper frame member and the floor even if this obstruction is not directly between the lower frame member and the floor. 
         [0045]    Preferably the contact member has substantially tubular portions, the tubular portions each comprising first and second side portions, the first and second side portions, in combination with respective upper and lower portions, substantially surrounding the periphery of at least a portion of the beams of the lower frame member. This enhances safety, as it allows the detector to detect obstructions directly between the beams of the lower frame member and the floor, and between the lower frame member and the upper frame member. The tubular portions may have a cross-section that is rectangular, circular or otherwise. The tubular portions need not completely enclose the beams; they may have windows and/or gaps etc. 
         [0046]    Preferably, the contact member comprises one or more plate portions that extends between the tubular portions. This enhances safety, as it allows the detector to detect obstruction directly between e.g. the mattress support of the upper frame member and the floor, even if this obstruction is not directly between the beams of the lower frame member and the floor, or the beams of the upper frame member and the floor. 
         [0047]    Preferably the sensor is an optical detector. Preferably the optical detector is provided on the inside of a tubular portion. In this position, since the tubular portions may provide a shield, operation of the optical detector is less likely to be affected by external light sources, and the optical detector is less prone to physical damage or accidental operation. 
         [0048]    Preferably the optical detector comprises a light transmitter and a receiver. Preferably the transmitter transmits light which is reflected and received by the receiver, when the contact member is not displaced by an obstruction, and which is not reflected and not received by the receiver, when the contact member is displaced by an obstruction. Preferably, when the light is not received, the upper and/or lower frame member is prevented from moving, e.g. by halting power supply to the drive means. 
         [0049]    Preferably, an optical detector is provided adjacent each end of each tubular portion. 
     
    
     
       INTRODUCTION OF THE DRAWINGS 
         [0050]    Embodiments of the present invention will be described by way of non-limitative example, referring to the drawings. In the drawings:— 
           [0051]      FIGS. 1   a ,  1   b ,  1   c  and  1   d  show an oblique view, foot end view, side view and bottom view respectively of a bedframe according to the present invention with upper frame member in an elevated position; 
           [0052]      FIGS. 2   a ,  2   b ,  2   c ,  2   d  and  2   e  show an oblique view, foot end view, side view, top view and head end view respectively of the bedframe of  FIGS. 1   a - 1   d  with upper frame member in a minimum height position; 
           [0053]      FIGS. 3   a  and  3   b  show a side view and an oblique view respectively of the bedframe of  FIGS. 1   a - 1   d  in a Trendelenburg position; and  FIGS. 3   c  and  3   d  show a side view and an oblique view respectively of the bedframe of  FIGS. 1   a - 1   d  in a reverse Trendelenburg position; 
           [0054]      FIGS. 4   a  and  4   b  show oblique views of the bedframe of  FIGS. 1   a - 1   d  with the upper frame in a minimum position and in an elevated position respectively and with panels of the headboard and footboard absent; 
           [0055]      FIG. 5  shows an enlarged sectional view of a column, of the bedframe of  FIGS. 1   a - 1   d;    
           [0056]      FIGS. 6   a  and  6   b  show slide carriages of the pulley system of the bedframe of  FIGS. 1   a - 1   d ; and  FIG. 6   c  shows the adjustor plate assembly of the pulley system of the bedframe of  FIGS. 1   a - 1   d;    
           [0057]      FIGS. 7   a  and  7   b  show, respectively, oblique top and oblique bottom views of the contact member of the bedframe of  FIGS. 1   a - 1   d.    
           [0058]      FIG. 8   a  shows an end view of a contact member of the bedframe of  FIGS. 1   a - 1   d ; and  FIG. 8   b  shows an end view of a tubular portion of the contact member with optical sensor attached thereto. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0059]    An embodiment of the present invention is shown in  FIGS. 1   a - 1   d . A bedframe  1  is provided, having an upper frame member  2  and a lower frame member  3 . The upper and lower frame members  2 ,  3  are supported at the head end of the bedframe (generally indicated by reference numeral  11 ) and the foot end of the bedframe (generally indicated by reference numeral  12 ) by respective head and foot support means  4  ( 4   a ,  4   b ). 
         [0060]    In this specification, terms such as “upper”, “lower”, “top”, “bottom”, “side”, “inner”, “outer”, “above”, “below”, “vertically” and “horizontally” etc. are used for simplicity, in order to describe features of the bedframe  1  as oriented normally during use. In this specification, the term “height” is used to describe the distance, in a vertical direction, of components of the bedframe from the ground during normal use. 
         [0061]    The support means  4  ( 4   a ,  4   b ) each comprise two columns  5 , each column  5  extending vertically from respective head and foot base portions  6  mounted on wheels  61 . Each column  5  comprises an outer tubular portion  51 , which is slidable with respect to an inner tubular portion  52 , the inner tubular portion fixed with respect to the base portion  6 . 
         [0062]    A respective drive means  7  is connected to the outer tubular portion  51  of each column, in order to raise and lower the outer tubular portions. The drive means may be a standard drive means configured for raising and lower bedframe components. In the present embodiment, each drive means  7  comprises an electric motor disposed in a lower housing  71  for driving a telescopic portion  72  of the drive means  7  upwards and downwards. The end  73  of the telescopic portion  72  is fixed to the outer tubular portion  51 . 
         [0063]    A control means for controlling the drive means  7  is provided (not shown). The drive means  7  of each column are synchronised with one another such that the outer tubular portions  51  of the same support means  4  can be raised and lowered synchronously, e.g. so as to prevent rotation (tipping) of the upper frame member  2  about an axis parallel with the elongation direction of the bedframe  1 . 
         [0064]    The upper and lower frames  2 ,  3  are movable from an elevated position, as shown in  FIGS. 1   a - 1   d , to a minimum height position, as shown in  FIGS. 2   a - 2   e . In  FIGS. 1   a - 1   d , the upper frame member  2  is approximately twice the height of the lower frame member  3 . Having the lower frame member  3  halfway between the upper frame member  2  and the ground in this manner optimises stability of the bedframe  1 . In  FIGS. 2   a - 2   e  the upper frame member  2  and the lower frame member  3  are both adjacent the ground. The upper frame member  2  may be raised or lowered as desired to positions in between the positions shown in  FIGS. 1   a - 1   d  and  2   a - 2   e , with the lower frame member  3  moving accordingly. 
         [0065]    The upper frame member  2  comprises two beams  21  extending between the head and foot support means  4   a ,  4   b . The upper frame member  2  further comprises an articulated mattress support  22 . A mattress (not shown) is placed on the mattress support  22  to provide a comfortable surface for a patient to lie upon. The mattress support  22  is articulated such that its joints are positioned adjacent a patient&#39;s hips and knees, in use. Accordingly, the mattress support  22  can be configured to well known patient support positions e.g. the ‘Gatch’ position, as shown in  FIGS. 1   a - 1   d , where, in use, a patient is positioned in a sitting state and is so maintained by elevating his knees to prevent his sliding toward the footboard. The mattress support  22  may also be configured to lie flat, for example, as shown in  FIGS. 2   a - 2   e . Articulated mattress supports are known in the art and do not need to be discussed here in any further detail. 
         [0066]    The upper frame member  2  may be positioned in an inclined state, as shown in  FIGS. 3   a  and  3   b . This is possible since the head and foot ends of the upper frame member  2  can be raised and lowered by the respective support means  4   a ,  4   b  independently. 
         [0067]      FIGS. 3   a  and  3   b  show the bedframe  1  with the upper frame member  2  in the known “Trendelenburg” position, where the head end of the upper frame member  2  is lower than the foot end. Accordingly, in use, the patient&#39;s head is low and the patient&#39;s body and legs are on an elevated and inclined plane. The lower frame member  3  is inclined in accordance with the upper frame member  2 . 
         [0068]      FIGS. 3   c  and  3   d  show the bedframe with the upper frame member  2  in the known “reverse Trendelenburg” position, where the head end of the upper frame member  2  is higher than the foot end of the upper frame member  2 . Accordingly, in use, the patient&#39;s head is high and the patient&#39;s body and legs are on a lowered and downwardly directed plane. The lower frame member  3  is downwardly directed in accordance with the upper frame member  2 . 
         [0069]    A headboard  8   a  and a footboard  8   b  are fitted to the bedframe  1  at the head and foot ends  11 ,  12  respectively. The headboard  8   a  and footboard  8   b  are both aligned in standard positions, i.e. in vertical planes perpendicular to the elongation direction of the bedframe. The headboard and footboard are fixed in position with respect to the height-adjustable upper frame member  2 . 
         [0070]    As shown in e.g.  FIG. 1   a , the headboard  8   a  and the footboard  8   b  have a manually removable portion (panel  81 ). Each panel  81  is slidably fitted to a respective fixed portion  82  of the headboard  8   a  or footboard  8   b . The fixed portion  82  is generally u-shaped. The panel  81  is aligned between the axes of elongation of the two columns  5  of the respective support means  4   a ,  4   b . The panel  81  is rectangular and spans the horizontal distance between the two axes of elongation of the columns  5 . As shown in  FIGS. 4   a  and  4   b , both panels  81  can be removed entirely from the bedframe  1 . This is accomplished by sliding the panels  81  upwards with respect to the respective fixed portions  82 . The panels  81  slide in grooves provided by brackets  83   a ,  83   b.    
         [0071]    When the panels  81  are removed, patient care access between the columns  5  is possible between the columns  5  of the head and foot support means  4 . For example, CPR may be carried out by a care worker since the care worker can lean through the space between the columns  5  at the head end  11  of the bedframe  1 . 
         [0072]    Between the columns  5  of each support means  4  a bottom portion  821  of the fixed portions  82  is present, however the bottom portion  821  extends no higher than a standard mattress placed on the mattress support  22 . Accordingly, this bottom portion  821  does not significantly reduce the amount of patient care access available. 
         [0073]    It is desirable, as is the case in this embodiment, that no cross-member is fixed to, and extends between, the outer tubular portions  51  of the columns  5 , of a support means  4 , at a height above the lower frame member  3 . Although such a cross-member could help to increase the rigidity of the support means  4 , it would restrict the amount of patient care access available. However, it is understood that a cross-member could be fixed between the outer tubular portions  51  up to positions halfway up the outer tubular portions  51 , with some patient care access still being available. 
         [0074]    As shown in  FIG. 4   b , similar patient care access is provided when the upper frame member  2  is in an elevated position. 
         [0075]    Side portions  822  of the fixed portions  82  provide useful mounting points for e.g. side rails and electrical connection sockets etc. (not shown). 
         [0076]    The headboard  8   a  and footboard  8   b  are both provided with a respective handle  84 , to facilitate manual transport of the bedframe, e.g. by rolling the bedframe  1  on the wheels  61 , and to assist with manual removal of the panels  81  during e.g. CPR or other care procedures. The footboard  8   b  is provided with a linen tray  85 , for holding clean bedclothes. 
         [0077]    Although the headboard  8   a  and footboard  8   b  both have manually removable portions (panels  81 ), it is understood that e.g. the headboard  8   a  only could be provided with a manually removable portion, since patient care access at the foot end  12  of the bedframe  1  generally is not as important as at the head end  11  of the bedframe  1 . 
         [0078]    The mechanism provided by the columns  5  of the supports  4   a ,  4   b  is now described in detail, with reference to  FIG. 5  in particular. Each column  5  comprises a pulley system including a pulley wheel  53 , over which passes a cable  54 . The cable  54  is fixed at a first end to the base portion  6  of the support via an anchor assembly  55 . The anchor assembly  55  is shown in detail in  FIG. 6   c ; it comprises a locknut  551 , and an adjuster plate  552 . The cable  54  is fixed to the adjuster plate via a clevis pin  553 . The adjuster plate allows fine-tuning of the position of the anchor assembly  55  from which the cable  54  extends. 
         [0079]    The cable  54  extends upwards from the anchor assembly  55  to the pulley wheel  53  through a passage provided by the (hollow) outer and inner tubular portions  51 ,  52 . The cable  54  runs over the pulley wheel and extends downwards. The pulley wheel is rotatably fixed to the top end of the outer tubular portion  51 . The second end of the cable  54  is fixed to a slide carriage assembly  56 . The end of a beam  21  of the upper frame member  2  is fixed to the slide carriage assembly  56 . The slide carriage assembly  56  is slidable in a channel  561  provided in the outer tubular portion  51 . 
         [0080]    A beam  31  of the lower frame member  3  is fixed to the bottom end of the outer tubular portion  51  via a bracket  57  (see e.g.  FIG. 4   b ). 
         [0081]    Accordingly, in use, when the drive means  7  raises the outer tubular portion  51 , the lower frame member  3  moves upwards at the same rate as the outer tubular portion  51 . At the same time, since the upper frame member  2  is fixed to the end of the cable  54  of the pulley system, the upper frame member moves upwards at twice the rate of the lower frame member. Nevertheless, the upper frame member  2  will move upwards stably, since the slide carriage assembly  56  slides in the channel  561  of the outer tubular portion  51 , as mentioned above. It will be clear that, with this configuration, when the drive means  7  lowers the outer tubular portion  51 , from a high position to a low position, the upper frame member  2  moves downwards at twice the rate of the lower frame member  3 . The slide carriage assembly  56  can be either of ‘fixed’ design, as shown in  FIG. 6   b  or of a ‘movable’ design as shown in  FIG. 6   a . With the ‘movable’ design, the slide carriage assembly  56  is articulated to allow the upper frame member to achieve the Trendelenberg position in a stable manner, as shown in e.g.  FIG. 3   a . The slide carriage assemblies  56  are either right- or left-handed (not shown in the Figures). 
         [0082]    A safety assembly of the bedframe  1  will now be described with reference to  FIGS. 7   a ,  7   b ,  8   a  and  8   b .  FIGS. 7   a  and  7   b  show, respectively, a top view and a bottom view of a contact member  9 . The contact member comprises two parallel, spaced, elongate main tubular portions  91 , each having substantially rectangular cross-sections in a direction perpendicular to their elongation directions. A lateral tubular portion  92  extends between the main tubular portions  91  in a direction perpendicular to the elongation direction of the main tubular portions  91 . The main tubular portions  91  each comprise an upper wall  911 , an outer side wall  912 , an inner side wall  913  and a lower wall  914 . The lateral tubular portion  92  comprises an upper wall  921 , a first side wall  922 , a second side wall  923  and a lower wall  924 . 
         [0083]    Plate portions  93  extend between the bottom end of the inner side wall  913  of one of the main tubular portions  91  to the bottom end of the inner side wall  913  of the other main tubular portion  91 , except where the lateral portion  92  is provided. The plate portions  93  have shallow pyramidal structures formed therein, to increase their strength. 
         [0084]    Flange portions  915  extend outwardly, in a horizontal direction, from the outer side wall  912  of each of the main tubular portions  91 . Each flange portion  915  has an upwardly projecting lip  916 . 
         [0085]    As can be seen in  FIGS. 8   a  and  8   b , the upper walls  911 ,  921  and side walls  912 ,  913 ,  922 ,  923  of the main tubular portions  91  and the lateral portion  92 , in combination with the flange portions  915  and the plate portions  93 , are one-piece, and are formed e.g. by moulding/pressing a single sheet of metal. The lower wall  914  of each of the main tubular portions  91 , and the lower wall  924  of the lateral tubular portion  92  are discrete portions that are e.g. screw fitted to elements of the single sheet. This allows the lower walls  914 ,  924  to be removed (as shown in  FIG. 7   b ) in order that the contact members  9  can be fitted easily to beams  31  of the lower frame member  3 . 
         [0086]    The bedframe  1  comprises two contact members  9 , which are mounted on the lower frame member  3  (see e.g.  FIG. 1   a ). The lower frame member  3  comprises two parallel, spaced main beams  31  extending between the head and foot support means  4   a ,  4   b . The lower frame member  3  further comprises two lateral beams extending between the main beams  31 , in a direction perpendicular to the elongation direction of the main beams  31 , although these lateral beams can not be seen in the Figures due to the positioning of the contact members  9 . 
         [0087]    In combination, the two contact members  9  surround substantially the entire lengths of the main beams  31  and lateral beams of the lower frame member  3 . In particular, the main tubular portions  91  surround substantially the main beams  31  of the lower frame member  3  and the lateral portions  92  surround substantially the lateral beams of the lower frame member  3 . 
         [0088]    The contact members  9  are displaceably mounted to the lower frame member  3  via a plurality of springs, e.g. conical springs  94  (two of which can be seen in  FIG. 8   a ). The springs are fitted between a top side of the main beams  31  and a bottom face of the upper walls  911  of the main tubular portions  91 . The springs  94  permit the contact members  9  to be displaced upwardly, downwardly and side-to-side, from rest positions. 
         [0089]    In  FIG. 8   a , the upper frame member  2  and the lower frame member  3  are shown in their minimum height position. In this state, the beams  21  of the upper frame member  2  lie to one side of the main beams  31  of the lower frame member  3 , in a horizontal direction and the flange portions  915  of the main tube portions  91  lie directly underneath the beams  21  of the upper frame member  2 . 
         [0090]    A plurality of optical detectors  95  are fixed to the contact members  9  (see  FIGS. 7   b  and  8   b ). The optical detectors  95  each comprise a transmitter and receiver, for transmitting and receiving light respectively. The optical detectors  95  are fixed to the inner sidewall  913  of each main tubular portion  91  and each face a respective reflector label  96  located on the main beams  31  of the lower frame member  3 . 
         [0091]    Each contact member  9  have four optical detectors  95  fixed thereto, one adjacent each end of each main tubular portion  91 . 
         [0092]    In use, when the contact members  9  are in a rest position, each optical detector transmits a signal, which is reflected by the respective reflector label  96  and received by the optical detector  95 . In this state, the drive means  7  may be actuated to raise or lower the upper and lower frame members  2 ,  3 . However, if one or both contact members  9  are displaced substantially, e.g. by an obstruction blocking the path of a the upper and/or lower frame members  2 ,  3 , the transmitted signal from one or more optical detectors  95  will no longer be received by the optical detector  95 , since the signal will no longer reflect off the reflector label  96 . In this state, the drive means  7  are prevented from raising or lowering the upper and lower frame members  2 ,  3 . Alternatively the drive means are prevented from lowering the upper and lower frame members  2 ,  3 , but not from raising the upper and lower frame members  2 ,  3 , as this may allow an object trapped by the frame members to be released. 
         [0093]    While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.