Bed assembly

Abstract

Bed having a base frame supporting a mattress support frame 12 having back 14, seat 16 and leg 18 portions overlaid by an attached mattress, and a mechanism to move mattress support between flat, seat

Description

FIELD OF THE INVENTION The present invention relates to the field of beds that are able to be moved into a seated configuration to enable a person to get into and out of the bed more easily. These beds may be referred to as sit-to-stand beds. These beds are primarily used in hospitals, health care facilities, social care facilities and other similar environments in which people may have limited mobility. BACKGROUND TO THE INVENTION People with limited mobility may have difficulty getting into and out of a bed. In many cases, when mobility is severely restricted a caregiver or medical support worker may need to assist the person to get into and out of bed. There are known bed designs that are moveable from a lying position to a seated position to assist a person to get into and out of the bed. These bed designs can provide increased independence for a person with limited mobility. There are, however, a number of limitations in current bed designs. One such known bed design includes a mechanism which may be operated to move a backrest of a frame to move a person from a lying to a sitting position with their legs out in front of them along the length of the bed. The mechanism may then be operated to rotate the frame so that the person’s legs can be positioned over the side of the bed. This enables the person to then stand up at the side of the bed. There are a number of disadvantages with this design. Firstly, it may be uncomfortable for the person to be rotated around in the sitting position. Secondly, the mechanism is quite complex, having lots of moving parts. This may result in errors in function of the bed, and also results in this bed being expensive. Thirdly, a lot of space is required around the bed, especially along the sides of the bed. Such a rotating bed is sold under the name RotoBed®. Another known bed design includes a mechanism which may be operated to initially move a backrest of a frame to move a person from a lying to a sitting position with their legs out in front of them along the length of the bed. The mechanism may then be operated to slide the frame along the length of the bed until a lower leg portion of the frame overhangs the end of the bed. This part of the frame may then be folded downwardly to allow a person to stand up at the end of the bed. Again, there are a number of disadvantages with this design. Firstly, it may be uncomfortable for the person to be moved along the length of the bed in the sitting position. Secondly, the mechanism is quite complex, having lots of moving parts. This may result in errors in function of the bed, and also results in this bed being expensive. Thirdly, a lot of space is required around the bed, especially at the end of the bed. An example of this type of bed is sold under the name Integrity®. It is an aim of the present invention to provide an improved mechanism for a bed that provides sit-to-stand functionality that is easy to use and offers superior comfort for the user compared to prior art beds. SUMMARY OF THE INVENTION A first aspect of the invention provides a bed assembly comprising: a base frame; a mattress support frame comprising a seat portion, a back portion extending from a rear edge of the seat portion, and a leg portion extending from a front edge of the seat portion, the mattress support frame being supported on the base frame; a mattress secured to the mattress support frame, the mattress including a back region overlying the back portion, a seat region overlying the seat portion, and a leg region overlying the leg portion; and a mechanism configured to move the mattress support frame between a flat configuration, a seated configuration and a rise configuration, the mechanism comprising at least one actuator and a linkage arrangement between the at least one actuator and the leg portion of the mattress support frame, wherein, in the flat configuration, the mattress support frame defines a prone plane, a longitudinal direction of the bed is defined between an end edge of the back portion and a distal end edge of the leg portion, and a perimeter of the mattress support frame defines a footprint of the bed assembly, the end edge of the back portion defining a first end edge of the footprint and the distal end edge of the leg portion defining a second end edge of the footprint, wherein, in the seated configuration, a distal region of the leg portion of the mattress support frame is disposed longitudinally between the front and rear edges of the seat portion, and the at least one actuator and the linkage arrangement is arranged to move the mattress support frame between the flat configuration and the seated configuration with no or negligible longitudinal movement of the rear edge of the seat portion, and wherein, the at least one actuator is arranged to move the mattress support frame between the seated configuration and the rise configuration by moving the rear edge of the seat portion in a direction transverse to the prone plane and away from the base frame, such that, in use, when the mattress support frame is in the seated or rise configuration, the leg portion of the mattress support frame is spaced from the second end edge of the footprint thereby creating a standing space within the footprint of the bed assembly, and wherein, the mattress includes a lower face facing towards said support frame and the lower face is continuous and planar along a full length of the mattress and across a full width of the mattress. The bed assembly of the present invention may, therefore, be used to create a sit-to-stand bed in which a person is able to stand up within the original footprint of the bed, such that the bed can be used in smaller spaces compared to prior designs of sit-to-stand beds. Furthermore, the transition of the bed assembly between the flat configuration, the seated configuration and the rise configuration allows a person to be moved from a lying position to a standing position in a more natural and a more comfortable way than with prior designs of sit-to-stand beds. In preferred embodiments the leg portion is pivotally connected to the seat portion. In particularly preferred embodiments the leg portion comprises a proximal leg portion and a distal leg portion, the proximal leg portion extending between the seat portion and the distal leg portion, and the distal leg portion extending from the proximal leg portion to the distal end edge of the leg portion. The proximal leg portion is preferably pivotally connected to the seat portion and the distal leg portion is preferably pivotally connected to the proximal leg portion. Each of the leg portion, seat portion and back portion preferably includes at least one cross member extending transverse to the longitudinal direction. The cross members support a mattress in use. A lower surface of a mattress may lie in direct contact with an upper surface of each of the cross members. Each of the leg portion, seat portion and back portion therefore may include a plurality of cross members to spread the weight of the mattress and any person lying or seated on the mattress. The bed assembly preferably includes a leg rest actuator and a seat actuator. In these embodiments the leg rest actuator is connected to the leg portion and is arranged to move the mattress support frame between the flat configuration and the seated configuration. The seat actuator is preferably connected to the seat portion and is arranged to move the mattress support frame between the seated configuration and the rise configuration. By providing a separate leg rest actuator and seat actuator movement of the mattress support frame between the flat configuration and the seated configuration may be controlled independently of the movement of the mattress support frame between the seated configuration and the rise configuration. The seat actuator may be connected to a rear member of the seat portion. In preferred embodiments the leg portion comprises a proximal leg portion and a distal leg portion. The proximal leg portion extends between the seat portion and the distal leg portion. The distal leg portion extends from the proximal leg portion to the distal end edge of the leg portion. Preferably each of the proximal and distal leg portions, seat portion and back portion include at least one cross member extending transverse to the longitudinal direction. In these embodiments the at least one actuator may include a leg rest actuator connected to the at least one cross member of the proximal leg portion. The leg rest actuator is preferably a linear actuator. The leg rest actuator may be connected to the at least one cross member of the proximal leg portion by a drive input member. An end of the leg rest actuator may be pivotally connected to the drive input member. In preferred embodiments the linkage arrangement comprises a four-bar linkage connected to the distal leg portion. The linkage arrangement preferably further comprises a coupler arranged to transmit movement of the proximal leg portion to the four-bar linkage. The seat portion preferably comprises a first cross member proximate a front edge of the seat portion and a second cross member proximate a rear edge of the seat portion. In these embodiments, in the flat configuration a distance between the first cross member and a support member of the base frame is preferably substantially equal to a distance between the second cross member and said base support member. In the seated configuration the distance between the first cross member and the support member is preferably greater than the distance between the second cross member and said base support member. In the rise configuration the distance between the first cross member and the support member is preferably less than the distance between the second cross member and said base support member. In preferred embodiments a height of the mattress support frame relative to the base frame is smaller when the mattress support frame is in the flat configuration than when the mattress support frame is in the seated configuration. In this way, a bed including the bed assembly can have a low height, relatively close to the ground, to minimise the risk of injury to a person in the bed. When the bed assembly moves the mattress support frame into the seated configuration, however, the mattress in the seated configuration is preferably such that the person can sit comfortably with their feet on the floor. In these embodiments, to accommodate the tucking of the leg portion under the seat portion, it is necessary to raise at least a front edge region of the seat portion. So that the person using the bed assembly may remain in a comfortable position during this movement, it is preferable if an angle between the seat portion and the back portion does not change. Accordingly, it is desirable for the mattress support frame to tilt-in-space when moving from the flat configuration to the seated configuration so that the pelvis of the person is tilted rather than the angle between the seat portion and the back portion changing. In preferred embodiments, therefore, the bed assembly comprises a tilt-in-space mechanism. In preferred embodiments this mechanism comprises a wheel, a drive link connecting the wheel to the linkage arrangement and an axle support member connecting the wheel to the seat portion. The wheel is preferably in contact with or seated on a part of the base frame. The tilt-in-space mechanism is preferably arranged such that movement of the linkage arrangement causes the drive link to apply a force to the wheel to move the wheel along the part of the base frame. Movement of the wheel in turn applies a force via the axle support member to the seat portion to move at least a part of the seat portion in a direction away from the base frame. Preferably the movement applied by the tilt-in-space mechanism causes a front edge region of the seat portion to move upwards away from the base frame, while there is little or no translational movement of the rear edge of the seat portion with respect to the base frame. In embodiments in which the leg portion comprises a proximal leg portion and a distal leg portion, and the linkage arrangement comprises a four-bar linkage connected to the distal leg portion, the drive link may connect the wheel to the four-bar linkage. When the mattress support frame is in the flat configuration and the seated configuration the seat portion is preferably directly supported by the base frame, i.e. a part of the seat portion is in direct contact with the base frame. In other embodiments the tilt-in-space mechanism may be disposed between the seat portion and the base frame. However, as the mattress support frame moves from the seated configuration to the rise configuration the seat portion moves in an upwards direction away from the base frame. Accordingly, the seat portion is no longer supported by the base frame either directly or via the tilt-in-space mechanism. The bed assembly therefore preferably further comprises a lift sub-assembly including a lift strut extending between the seat portion and the base frame. The lift subassembly supports at least some of the weight of the mattress support frame when it is in the rise configuration. The lift strut is preferably elongate and is preferably pivotally attached at a first end to the seat portion and pivotally attached at a second end to the base frame. In preferred embodiments the bed assembly further comprises a back rest actuator connected between the seat portion and the back portion. The back rest actuator is arranged to change an angle between a plane of the seat portion and a plane of the back portion. By providing a separate back rest actuator, an angle between a plane of the seat portion and a plane of the back portion may be changed independently of a position or configuration of the seat portion or the leg portion relative to the base frame. In some embodiments the mattress includes an upper face opposite to the lower face, and the upper face is continuous and planar across the full width of the mattress in at least the back region and the seat region of the mattress. The upper face of the mattress may be tapered or sloped in the leg region of the mattress, such that a thickness of the mattress at a foot end of the mattress adjacent the leg region is smaller than a thickness of the mattress at a head end of the mattress adjacent the back region. In some embodiments the bed assembly may further include a stabilising member connected to and extending from the leg portion of the mattress support frame in a direction towards a surface on which the bed assembly stands. The stabilising member is preferably arranged such that, when the bed assembly is in the seated configuration, an end of the stabilising member is disposed under the seat portion and a gap is defined between the end of the stabilising member and the surface on which the bed assembly stands. Preferably, when the bed assembly is in the flat configuration, the stabilising member is disposed under the leg portion of the mattress support frame. In use, when sufficient force is applied to the leg portion of the mattress support frame in a direction towards the surface on which the bed assembly stands, the end of the stabilising member preferably moves into contact with the surface such that the stabilising member assists in supporting the leg portion of the mattress support frame. It will be appreciated that the mattress should be secured to the mattress support frame so that, as the mattress support frame is moved between the flat configuration, the seated configuration and the rise configuration, the mattress does not move significantly with respect to the mattress support frame. Preferred and / or optional features of each aspect and embodiment described above may also be used, alone or in appropriate combination, in the other aspects and embodiments also. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be further described by way of example only and with reference to the accompanying drawings, in which like reference signs are used for like features, and in which: Figure 1 is a perspective view of a bed assembly according to a first preferred embodiment of the invention which may be moved between a flat configuration, a seated configuration and a rise configuration, shown in the flat configuration; Figure 2 is a perspective view of the bed assembly of Figure 1, shown in an intermediate position between the flat configuration and the seated configuration; Figure 3 is a perspective view of the bed assembly of Figure 1, shown in the seated configuration; Figure 4 is a perspective view of the bed assembly of Figure 1, shown in the rise configuration; Figure 5 is a view from a side of the bed assembly of Figure 1 in the flat configuration, with a side panel removed to show a mechanism of the bed assembly; Figure 6 is a view from a side of the bed assembly of Figure 2 in the intermediate configuration, with the side panel removed to show the mechanism of the bed assembly; Figure 7 is a view from a side of the bed assembly of Figure 3 in the seated configuration, with the side panel removed to show the mechanism of the bed assembly; Figure 8 is a view from a side of the bed assembly of Figure 4 in the rise configuration, with the side panel removed to show the mechanism of the bed assembly; Figure 9 is a perspective view of the mechanism of the bed assembly of Figure 5 with the mechanism in an extended configuration corresponding to the bed assembly being in the flat configuration; Figure 10 is a plan view from above of the mechanism of Figure 9 in the extended configuration; Figure 11 is a cross-sectional view of the mechanism in the extended configuration along the line XI-XI of Figure 10; Figure 12 is a perspective view of the mechanism of the bed assembly of Figure 7 with the mechanism in a tucked configuration corresponding to the bed assembly being in the seated configuration; Figure 13 is a plan view from above of the mechanism of Figure 12 in the tucked configuration; Figure 14 is a cross-sectional view of the mechanism in the tucked configuration along the line XlV-XIVof Figure 13; Figure 15 is a perspective view of the mechanism of the bed assembly of Figure 8 with the mechanism in a tilted configuration corresponding to the bed assembly being in the rise configuration; Figure 16 is a plan view from above of the mechanism of Figure 15 in the tilted configuration; Figure 17 is a cross-sectional view of the mechanism in the tilted configuration along the line XVII-XVII of Figure 16; Figure 18 is a plan view from above of the bed assembly of Figure 1 in the flat configuration showing a footprint of the bed assembly; Figure 19 is a plan view from above of the bed assembly of Figure 3 in the seated configuration, showing the bed assembly relative to the footprint of the bed assembly and showing a standing space created within the footprint when the bed assembly is in the seated configuration; Figure 20 is a perspective view of a part of a bed assembly according to a second preferred embodiment of the invention which may be moved between a flat configuration, a seated configuration and a rise configuration, shown in the flat configuration; Figure 21 is a plan view from a side of a part of the bed assembly of Figure 20; and Figure 22 is a perspective view of a part of the bed assembly of Figure 20, shown in the seated configuration. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Figures 1 to 4, a bed assembly 10 according to the present invention comprises a mattress support frame 12 that may be moved between a flat or prone configuration, a seated configuration and a rise configuration. The bed assembly 10 is generally designed to move from the flat configuration to the seated configuration and then from the seated configuration to the rise configuration. Likewise, the bed assembly 10 is generally designed to move from the rise configuration to the seated configuration and then from the seated configuration to the flat configuration. The mattress support frame 12 is configured to support a mattress (not shown), which may be a mattress typically used on a care bed or a hospital bed or the like. The mattress support frame 12 comprises a back portion 14, a seat portion 16 and a leg portion 18. It will be understood that the back portion 14 of the mattress support frame 12 is generally disposed under a region of the mattress upon which a person’s back and head will be supported, the seat portion 16 of the mattress support frame 12 is generally disposed under a region of the mattress upon which a person’s hips and upper legs will be supported, and the leg portion 18 of the mattress support frame 12 is generally disposed under a region of the mattress upon which at least a person’s lower legs will be supported. In the flat configuration the mattress support frame 12 defines a footprint 20 of the bed assembly 12, as illustrated in Figure 18. In particular, a perimeter of the mattress support frame 12 defines the footprint 20, with an end edge 22 of the back portion 14 defining a first, rear end edge 24 of the footprint 20 and a distal end edge 26 of the leg portion 18 defining a second, front end edge 28 of the footprint 20. When the mattress support frame 12 is in the seated configuration and in the rise configuration, the distal end edge of the leg portion 18 is spaced from the second end edge 28 of the footprint 20 such that a standing space 30 is defined within the footprint 20 between the mattress support frame 12 and the second end edge 28 of the footprint 20, as illustrated in Figure 19. In this way, a person may lie flat on the mattress on the mattress support frame 12 with the bed assembly 10 in the flat configuration. When the person wishes to sit, the person may move the bed assembly 10 into the seated configuration. In the seated configuration the leg portion 18 of the mattress support frame 12 is disposed generally under the seat portion 16 so that the person can place their feet on the floor within the standing space 30. If the person needs additional help to stand, the person may move the bed assembly into the rise configuration. In the rise configuration the seat portion 16 of the mattress support frame 12 is raised and tilted thereby guiding the person into a standing position. Importantly, the person is guided to stand in the standing space 30 that is within the original footprint 20 of the bed assembly 10. Accordingly, minimal additional space is required around the bed assembly 10, which may be beneficial in environments in which there is limited space around the bed assembly 10. In the following description, references to a forward direction or forwardly refer to directions generally towards the second, front edge 28 of the footprint 20 and references to a rearward direction or rearwardly refer to directions generally towards the first, rear edge 24 of the footprint 20. Referring now additionally to Figures 5 to 8, the bed assembly 10 comprises a base frame 32 on which the mattress support frame 12 is supported. In this embodiment the base frame 32 comprises a base support member 33 that has two side regions and a rear region. The base support member 33 lies in a generally horizontal plane in use. Legs 34 on which the base frame 32 stands extend downwardly from the base support member 33. In this embodiment the legs 34 terminate in feet arranged to stand on a surface. In other embodiments the legs may terminate in castors, or the legs may terminate in an attachment device for attaching the base frame 32 to a further base structure of a bed. The base frame 32 comprises a rear support sub-frame 36 that extends downwardly from the base support member 33. In this embodiment two adjustable feet are provided on a lower member of the rear support sub-frame 36. Two actuators 38, 40 are connected to the rear support sub-frame 36. A first, leg rest actuator 38 is connected between the base frame 32 and the leg portion 18 of the mattress support frame 12. A second, seat actuator 40 is connected between the base frame 32 and the seat portion 16 of the mattress support frame 12. In this embodiment each of the leg rest actuator 38 and the seat actuator 40 are linear actuators. The leg rest actuator 38 extends between a first end connected to the rear support sub-frame 36 and a second end connected to a drive input member 42 that is, in turn, attached to the leg portion 18 of the mattress support frame 12. The seat actuator 40 extends between a first end connected to the rear support sub-frame 36 and a second end connected to a rear member 44 of the seat portion 16 of the mattress support frame 12. In this embodiment the bed assembly 10 further comprises a third, back rest actuator 46. The back rest actuator 46 extends between the seat portion 16 and the back portion 14 of the mattress support frame 12. The back rest actuator 46 is preferably a linear actuator. The back rest actuator 46 extends between a first end connected to a mounting plate 82 of the seat portion 16 and a second end connected to a bracket 84 of the back portion 14. The leg rest actuator 38 and the back rest actuator 46 are arranged to cause the mattress support frame 12 to move between the flat configuration and the seated configuration. The seat actuator 40 is arranged to cause the mattress support frame 12 to move between the seated configuration and the rise configuration. In other embodiments the bed assembly 10 may comprise only two actuators or a single actuator. As will be appreciated from the following description, in embodiments in which the bed assembly only includes one or two actuators, additional linkage mechanisms may be provided to translate or transfer movement of the actuator or actuators into the required movement of the mattress support frame 12 between the flat, seated and rise configurations. Each of the leg portion 18, seat portion 16 and back portion 14 of the mattress support frame 12 comprise a plurality of support cross members 48. When the mattress support frame 12 is in the flat configuration an upper surface of each of the support cross members 48 lies in and defines a mattress support plane or prone plane. A longitudinal direction of the bed assembly 10 is defined between the end edge 22 of the back portion 14 and the distal end edge 26 of the leg portion 18. Each of the cross members 48 extends in a transverse direction, substantially perpendicular to the longitudinal direction. In this embodiment the leg portion 18 includes a proximal leg portion 18A and a distal leg portion 18B. The proximal leg portion 18A extends between the seat portion 16 and the distal leg portion 18B, and the distal leg portion 18B extends from the proximal leg portion 18A to the distal end edge 26. The distal leg portion 18B includes first and second leg support cross members 48A, 48B and the proximal leg portion 18A includes third and fourth leg support cross members 48C, 48D. In use a foot end of a mattress is supported by the four leg support cross members 48A, 48B, 48C, 48D. In this embodiment the seat portion 16 of the mattress support frame 12 includes two support cross members 48E, 48F, on which a central section of a mattress is supported in use. The drive input member 42 forms part of a linkage mechanism 50 that is connected between the leg rest actuator 38 and the leg portion 18 of the mattress support frame 12. In this embodiment the drive input member 42 is pivotally connected at a first end to the second end of the leg rest actuator 38 and is attached at a second end to the third leg support cross member 48C. The connection between the drive input member 42 and the third leg support cross member 48C is fixed. The linkage mechanism 50 is connected to both the proximal and distal leg portions 18A, 18B such that operation or movement of the leg rest actuator 38 results in movement of the proximal and distal leg portions 18A, 18B with respect to each other and with respect to the seat portion 16. As the mattress support frame 12 moves from the flat to the seated configuration the linkage mechanism 50 moves from an extended configuration to a tucked configuration thereby causing the proximal and distal leg portions 18A, 18B to fold under the seat portion 16 of the mattress support frame 12. The distal leg portion 18B is connected to the proximal leg portion 18A at a pair of front pivot plates 52. The front pivot plates 52 are attached to a first, front one of the seat cross members 48E, with a first one of the front pivot plates 52 attached to a first end of the front seat cross member 48E and a second one of the front pivot plates 52 attached to an opposite second end of the front seat cross member 48E. In this way, a front pivot plate 52 is provided at either side of the mattress support frame 12. The first and second front pivot plates 52 are identical in their configuration and operation and in the following description connections between components of the bed assembly 10 and only one of the front pivot plates 52 will be described. Further, it will be understood that a first part of the mechanism 50 is connected to the first front pivot plate 52 and an identical second part of the mechanism 50 is connected to the second front pivot plate 52. This spreads the loads and forces equally between the two sides of the bed assembly. In the following description, in general, only one part of the mechanism 50 is described. In this example the front pivot plate 52 is generally triangular having a base edge generally level with the mattress support plane. The front pivot plate 52 is attached to the front seat cross member 48E at a first lower corner. A first one of the leg cross members 48A is connected to the front pivot plate 52 by a pair of arms 54, 56. A proximal arm 54 is pivotally attached at its first end to the front pivot plate 52 at a lower pivot point in a second lower corner of the front pivot plate 52. A second end of the proximal arm 54 is pivotally connected to a first end of a distal arm 56. A second end of the distal arm is connected to the first leg cross member 48A. The second lower corner of the front pivot plate 52 is disposed towards the distal end edge 26 of the leg portion 18 from the first lower corner of the front pivot plate 52. A second one of the leg cross members 48B is connected to the front pivot plate 52 by a primary lever 58. The primary lever 58 is pivotally attached at its first end to the front pivot plate 52 at an upper pivot point in a third corner of the front pivot plate 52 above the mattress support plane. In this embodiment the primary lever 58 is generally L-shaped. A first lever portion 58A extends between the first end and a lever bend 59 and a second lever portion 58B extends between the second end and the lever bend 59. An angle between an axis of the first lever portion 58A and an axis of the second lever portion 58B is preferably between 70° and 110°, and more preferably between about 90° and 100°. In this embodiment the first lever portion 58A is longer than the second lever portion 58B. A pivot connection 57 between the primary lever 58 and the distal arm 56 is provided at the lever bend 59. In particular, the pivot connection 57 connects the primary lever 58 to a pivot point between the first and second ends of the distal arm 56. In this embodiment the pivot point is closer to the first end of the distal arm 56 than to the second end of the distal arm 56. A first section of the distal arm 56 is therefore defined between the pivot point and the first end, and a second section of the distal arm 56 is defined between the pivot point and the second end. In this embodiment the primary lever 58 further includes a recess 63 in an edge of the first lever portion 58A. The pivotal connection between the proximal arm 54 and the distal arm 56 is seated or disposed in the recess 63 when the mattress support frame 12 is in the flat configuration and the mechanism 50 is in the extended configuration, as illustrated in Figures 9 to 11. In this way, a first four-bar linkage is formed by the first lever portion 58A of the primary lever 58, the first section of the distal arm 56, the proximal arm 54, and a part of the front pivot plate 52 between the lower and upper pivot points. The proximal arm 54 crosses over the first lever portion 58A of the primary lever 58. Third and fourth leg cross members 48C, 48D are connected to the front pivot plate 52 by a primary drive link 60. The primary drive link 60 is attached at a first end to the front pivot plate 52 at a mid pivot point between the lower and upper pivot points. In this embodiment the primary drive link 60 is V-shaped. A first drive link arm 60A of the primary drive link 60 extends between the first end and an apex 62, and a second drive link arm 60B of the primary drive link 60 extends between the apex 62 and a second end. The third and fourth leg cross members 48C, 48D are connected to the second drive link arm 60B. The third leg cross member 48C is connected proximate the apex 62. The fourth leg cross member 48D is connected at or proximate the second end. A seat rail 64 is attached to the front seat cross member 48E and extends in the longitudinal direction. A second one of the seat cross members (mid seat cross member) 48F is connected to and extends from the seat rail 64. In preferred embodiments the bed assembly 10 comprises two seat rails 64 disposed at ends of the seat cross members 48E, 48F such that the seat cross members 48E, 48F extend between the two seat rails 64 and the seat rails 64 define sides of the seat portion 16 of the mattress support frame 12. A rear end of the seat rail 64 is pivotally connected to a rear pivot plate 65. The rear pivot plate 65 is fixed to the rear member 44 of the seat portion 16. In this way, the seat rail 64, front seat cross member 48E and mid seat cross member 48F may rotate about this pivotal connection with respect to the rear member 44. Furthermore, this pivotal connection is preferably disposed above the rear member 44. A mid pivot plate 66 is also attached to the seat rail 64. The mid pivot plate 66 is disposed between the front pivot plate 52 and the rear pivot plate 65. In this embodiment the mid pivot plate 66 is disposed between the front and mid seat cross members 48E, 48F. The mid pivot plate 66 preferably extends from the seat rail 64 so that an upper edge of the mid pivot plate 66 is disposed above the seat rail 64. An axle support member 68 is pivotally connected at a first end to the mid pivot plate 66. The axle support member 68 is preferably pivotally connected to the mid pivot plate 66 proximate the upper edge of the mid pivot plate 66 such that the first end of the axle support member 68 is disposed above the seat rail 64. A second end of the axle support member 68 is connected to an axle of a wheel 70. When the mattress support frame 12 is in the flat configuration the wheel 70 is seated on a surface of the base support member 33. In this embodiment the wheel 70 is seated on one of the side regions of the base support member 33 proximate a front edge of the base frame 32 nearest the distal end edge 26 of the leg portion 18. A secondary drive link 72 extends between the wheel 70 and the primary lever 58. A first end of the secondary drive link 72 is connected to the axle of the wheel 70 and a second end of the secondary drive link 72 is pivotally attached to the primary lever 58. In this embodiment the second end of the secondary drive link 72 is connected to the first lever portion 58A of the primary lever 58. In particular, the second end of the secondary drive link 72 is connected to the first lever portion 58A approximately midway between the between the first end of the primary lever 58 and the lever bend 59. The second end of the secondary drive link 72 is preferably connected between the first end of the primary lever 58 and the recess 63. In this embodiment a second axle support member 74 extends between the axle of the wheel 70 and a mounting bracket attached to the seat rail 64. A first end of the second axle support member 74 is pivotally connected to the mounting bracket and a second end of the second axle support member 74 is attached to the axle of the wheel 70. A rotational axis of the pivotal connection of the first end of the second axle support member 74 is coaxial with a rotational axis of the pivotal connection of the first end of the first axle support member 68. The first and second axle support members 68, 74 extend either side of the seat rail 64 such that the wheel 70 is disposed between the second ends of the first and second axle support members 68. 74 and the wheel 70 is disposed under the seat rail 64. Preferably, when the mattress support frame 12 is in the flat configuration the seat rail 64 is seated on or is in contact with the wheel 70. The proximal arm 54 comprises a spur 76 projecting transversely from the primary axis of the proximal arm 54 between the first and second ends of the proximal arm 54. An end of the spur 76 is pivotally connected to the secondary drive link 72 between the first and second ends of the secondary drive link 72. A second four-bar linkage is therefore formed with the four pivots of the linkage provided by (i) the connection between the proximal and distal arms 54, 56, (ii) the connection between the primary lever 58 and the distal arm 56, (iii) the connection between the primary lever 58 and the secondary drive link 72, and (iv) the connection between the proximal arm 54 (spur 76) and the secondary drive link 72. With this arrangement, the section of the proximal arm 54 between the spur 76 and the second end crosses over the primary lever 58. The provision of a spur 76 allows the pivotal connection between the proximal arm 54 and the secondary drive link 72 to be formed such that the second four-bar linkage has the required geometry. A coupler 78 extends between the proximal arm 54 and the primary drive link 60. In this embodiment a first end of the coupler 78 is pivotally attached to the primary drive link 60 at its apex and a second end of the coupler 78 is pivotally attached to the spur 76 of the proximal arm 54. The pivotal connection between the coupler 78 and the spur 76 is preferably coaxial with the pivotal connection between the secondary drive link 72 and the spur 76. The back portion 14 of the mattress support frame 12 includes a base cross member 48H, a head cross member 48J, and two side members 80 extending longitudinally between the base cross member 48H and the head cross member 48J. The head cross member 48J provides the end edge 22 of the back portion 14. A plurality of intermediate back rest cross members 48K are disposed between the base cross member 48H and the head cross member 48J. The mounting plate 82 is attached to the rear member 44 of the seat portion 16 and the first end of the back rest actuator 46 is pivotally connected to the mounting plate 82 at a distance from the rear member 44. The bracket 84 is attached to one of the back rest cross members 48K and the second end of the back rest actuator 46 is pivotally connected to the bracket 84. The bracket 84 may be attached to a back rest cross member 48K approximately midway between the base cross member 48H and the head cross member 48J. A pivot assembly 86 is connected between the rear member 44 and the base cross member 48H. The pivot assembly 86 permits the back portion 14 of the mattress support frame 12 to rotate about the pivot assembly 86 relative to the seat portion 16 of the mattress support frame 12. In this embodiment the pivot assembly comprises the rear pivot plate 65 attached to the rear member 44 and a back rest pivot plate 90 attached to the base cross member 48H. The rear pivot plate 65 and back rest pivot plate 90 are joined at a back rest pivot 92 about which the back portion 14 rotates. The bed assembly 10 further comprises a lift sub-assembly 94. The lift sub-assembly 94 comprises a base support plate 96 attached to the base frame 32 and a seat support plate 98 attached to the seat portion 16 of the mattress support frame 12. In this embodiment the lift sub-assembly 94 comprises a pair of base support plates 96 attached to the rear region of the base support member 33 and a pair of seat support plates 98 attached to the rear member 44. The lift sub-assembly further comprises first and second lift struts 100, 102 extending between the base support plates 96 and the seat support plates 98. A first end of the first lift strut 100 is pivotally connected to the base support plate 96 at a first support pivot point 104 and a second end of the first lift strut 100 is pivotally connected to the seat support plate 98 at a second support pivot point 106. Similarly, a first end of the second lift strut 102 is pivotally connected to the base support plate 96 at a third support pivot point 108 and a second end of the second lift strut 102 is pivotally connected to the seat support plate 98 at a fourth support pivot point 110. In this embodiment the first ends of the first and second lift struts 100, 102 are disposed between the pair of base support plates 96 and the second ends of the first and second lift struts 100, 102 are disposed between the pair of seat support plates 98. The first support pivot point 104 is spaced apart from the third support pivot point 108, and the second support pivot point 106 is spaced apart from the fourth support pivot point 110. In this way the lift sub-assembly 94 is in the form of a four-bar linkage including the first lift strut 100, the second lift strut 102, a section of the base support plate 96 between the first and third pivot points 104, 108, and a section of the seat support plate 98 between the second and fourth pivot points 106, 110. When the mattress support frame 12 is in the flat configuration the lift sub-assembly 94 is preferably arranged so that the first and second lift struts 100, 102 extend parallel to each other and there is a first distance between the first and second lift struts 100, 102. When the mattress support frame 12 is in the rise configuration the lift sub-assembly 94 is preferably arranged so that there is a second distance between the first and second lift struts 100, 102, the second distance being greater than the first distance. Furthermore, in the rise configuration the first and second lift struts 100, 102 may no longer extend parallel to each other. In preferred embodiments the bed assembly 10 comprises two lift sub-assemblies 94. A first lift sub-assembly 94 preferably includes a base support plate 96 proximate one of the side regions of the base support member 33 and a seat support plate 98 proximate one of the seat rails 64. A second lift sub-assembly 94 preferably includes a base support plate 96 proximate the other one of the side regions of the base support member 33 and a seat support plate 98 proximate the other one of the seat rails 64. Operation of the bed assembly 10 to move the mattress support frame 12 from the flat configuration to the seated configuration and then from the seated configuration to the rise configuration will now be described. It will be appreciated that to move the mattress support frame 12 from the rise configuration to the seated configuration and then from the seated configuration to the flat configuration uses the same mechanisms described below, but with the components and elements moving in the opposite directions. Starting from the flat configuration (Figure 1) a user may initially raise the back rest to bring the bed assembly 10 into an intermediate rise position as illustrated in Figure 2. To achieve this, the user operates the back rest actuator 46 in a first mode to lengthen the linear actuator 46. This lengthening of the back rest actuator 46 causes the back portion 14 of the mattress support frame 12 to rotate about the back rest pivot 92. An angle between a plane of the seat portion 16 defined by the seat cross members 48E, 48F and a plane of the back portion 14 defined by the back rest cross members 48K increases until the angle is preferably between 20° and 90°. The user may then move the bed assembly 10 from this intermediate rise position to the seated configuration. In the seated configuration the proximal and distal leg portions 18A, 18B are moved so that they tuck under the seat portion 16 of the mattress support frame 12. In a simplest embodiment of the bed assembly 10, the proximal and distal leg portions 18A, 18B move with no movement of the seat portion 16. In this embodiment the user operates the leg rest actuator 38 in a first mode to shorten the length of the linear actuator. The shortening of the leg rest actuator 38 applies a force to the drive input member 42 which in turn applies a force to the third leg support cross member 48C. The third leg support cross member 48C applies a force to the primary drive link 60 causing the primary drive link 60 to rotate about the mid pivot point at the first end of the primary drive link 60. As the third and fourth leg cross members 48C, 48D are both connected to the second drive link arm 60B, rotation of the primary drive link 60 about its first end, causes the third and fourth leg cross members 48C, 48D to move from a position in which they lie in a plane generally parallel to an axis of the seat rail 64 to a position in which they lie in a plane generally and substantially perpendicular to the axis of the seat rail 64. This rotation of the primary drive link 60 therefore has the effect of moving the proximal leg portion 18A of the mattress support frame 12 into a position that is generally perpendicular or transverse to the seat portion 16 of the mattress support frame 12. The drive input member 42 and the primary drive link 60 therefore form a first linkage subassembly of the linkage mechanism 50 configured to move the proximal leg portion 18A with respect to the seat portion 16. Rotation of the primary drive link 60 further causes rotation of the proximal arm 54 about its first end due to the connection between the primary drive link 60 and the proximal arm 54 provided by the coupler 78. As described above, the proximal arm 54 forms part of a four-bar linkage. The four-bar linkage is a second linkage sub-assembly of the linkage mechanism 50 configured to move the distal leg portion 18B with respect to the proximal leg portion 18A and the seat portion 16. In particular, the four-bar linkage is arranged to rotate the distal leg portion 18B through an angle of about 180°. When the bed assembly 10 is in the flat configuration the distal leg portion 18B is spaced from the seat portion 16 in the longitudinal direction by the proximal leg portion 18A. Furthermore, the first leg support cross member 48A is further from the seat portion 16 than the second leg support cross member 48B. When the bed assembly 10 is in the seated configuration the first and second leg support cross members 48A, 48B are not spaced from the seat portion 16 in the longitudinal direction but are, instead, disposed below the seat portion 16. A plane defined by the first and second leg support cross members 48A, 48B is spaced apart from a plane defined by the seat cross members 48E, 48F in a direction transverse to the longitudinal direction. Furthermore, the first leg support cross member 48A is disposed closer to the rear member 44 than the second leg support cross member 48B. As the proximal arm 54 rotates due to the force applied by the coupler 78, the second end of the proximal arm 54 initially moves in a downward direction, towards a floor or surface on which the base frame 32 is standing. The second end of the proximal arm 54 is connected to the first end of the distal arm 56, and the pivotal connection between the proximal arm 54 and the distal arm 56 is seated in the recess 63 of the primary lever 58. Accordingly, as the second end of the proximal arm 54 moves downwardly, the pivotal connection between the proximal arm 54 and the distal arm 56 presses on the primary lever 58 at the recess 63. This, in turn, causes the primary lever 58 to rotate about its first end. The arrangement of the four-bar linkage means that, as the second ends of both the proximal arm 54 and the primary lever 58 move downwardly, the distal arm 56 rotates about the pivot connection 57 between the primary lever 58 and the distal arm 56. An angle between the second section of the distal arm 56 and the second lever portion 58B changes, and the second end of the distal arm 56 and the first leg support cross member 48A pass under the second leg support cross member 48B. In a preferred embodiment, when the bed assembly 10 is in the flat configuration each of the primary lever 58, proximal arm 54 and primary drive link 60 extend in a generally forwards direction from the front pivot plate 52. When the bed assembly 10 is in the seated configuration each of the primary lever 58, proximal arm 54 and primary drive link 60 extend in a generally rearwards direction relative to their respective first ends connected to the front pivot plate 52. With the bed assembly 10 in the seated configuration, the bed assembly 10 folds a mattress attached to the mattress support frame 12 into a chair-like shape. It is therefore desirable for a person to be able to sit on the mattress in this configuration with their feet on the floor in a comfortable sitting position. It is also, however, desirable for a height of the mattress, when the bed assembly 10 is in the flat configuration, to be relatively low so that the risk of injury from the person falling out of bed is reduced. The desired height of the mattress in the flat configuration is generally lower then the desired height of a seat portion of the mattress in the seated configuration. It will be appreciated, however, that to enable the distal leg portion 18B to fold under the seat portion 16 there must be sufficient clearance below at least a front region of the seat portion 16 during this folding operation. In a preferred embodiment the bed assembly 10 is arranged such that the mattress support plane when the bed assembly 10 is in the flat configuration is lower that the plane defined by the seat support cross members 48E, 48F when the bed assembly 10 is in the seated configuration. In preferred embodiments, therefore, to allow the distal leg portion 18B to fold under the seat portion 16, the seat portion 16 tilts so that a front or forward region of the seat portion 16 is raised. So that the person remains in a comfortable seated position, it is preferable if the angle between the plane of the seat portion 16 defined by the seat cross members 48E, 48F and the plane of the back portion 14 defined by the back rest cross members 48K does not change as the seat portion 16 tilts. Accordingly, in preferred embodiments the bed assembly 10 comprises a tilt-in-space mechanism which operates to tilt the plane of the seat portion 16 while the angle between the plane of the seat portion 16 and the plane of the back portion remains constant. In the illustrated embodiment the tilt-in-space mechanism comprises the axle support members 68, 74, the wheel 70, and the secondary drive link 72. The tilt-in-space mechanism is driven by the second linkage sub-assembly of the linkage mechanism 50 such that the seat portion 16 tilts as the distal leg portion 18B is tucked under the seat portion 16. In particular, as the primary lever 58 rotates, the second end of the secondary drive link 72 is moved in a downward and rearward arc. The secondary drive link 72 applies a force to the wheel 70 to move the wheel 70 rearwardly along the base support member 33. The axle support members 68, 74 connect the wheel 70 to the seat rail 64. As the wheel 70 moves rearwardly, in contact with the surface of the base support member 33, the resultant movement of the axle support members 68, 74 causes the seat rail 64 to move upwardly in a direction away from the base frame 32. When the bed assembly 10 is in the flat configuration the wheel 70 is in a forward position and the second ends of the axle support members 68, 74 are forwards of the pivotal connections at the first ends of the axle support members 68, 74. As the wheel 70 is pushed rearward, the axle support members 68, 74 restrain the wheel 70 along an arcuate path relative to the axis of the pivotal connections at the first ends of the axle support members 68, 74. However, because the wheel 70 in in contact with the base support member 33, the axle support members 68, 74 apply an upward force to the seat rail 64. The upward force applied to the seat rail 64 by the axle support members 68, 74 causes the seat rail 64 to rotate about the pivotal connection between its rear end and the rear pivot plate 65. This tilts the plane of the seat portion 16, lifting the front region of the seat portion 16 relative to the rear member 44, as illustrated in Figures 12 to 14. Once the bed assembly 10 is in the seated configuration and the mechanism 50 is in the tucked configuration, a user may then raise the rear member 44, to raise a rear region of the seat portion 16, by operating the seat actuator 40 to increase a length of the seat actuator 40. As the length of the seat actuator 40 increases the wheel 70 is lifted away from the base support member 33. Accordingly, the seat portion 16 is no longer supported by the wheel 70. However, as the rear member 44 is raised, the second ends of the first and second lift struts 100, 102 are lifted as these are connected to the rear member 44. The weight of the mattress support frame 12 is then transmitted to the base frame 32 through the leg rest actuator 38, the seat actuator 40, and the first and second lift struts 100, 102. A user may operate the seat actuator 40 to raise the rear member 44 a small distance to reduce the tilt of the seat portion 16. A person may then remain seated on the mattress. If a user wishes to stand, a user may continue to operate the seat actuator 40 to further lengthen the seat actuator 40. As the seat actuator 40 is lengthened, the rear member 44 is raised further away from the base frame 32. A position of the leg support cross members 48A, 48B, 48C, 48D relative to each other and relative to the seat support cross members 48E, 48F remains fixed as the mechanism 50 moves from the tucked configuration to a tilted configuration and the bed assembly moves from the seated configuration to the rise configuration. Accordingly, as the rear member 44 is raised by the seat actuator 40, movement of the third leg support cross member 48C is constrained by the leg rest actuator 38 and the drive input member 42. Lengthening of the seat actuator 40 results in an upward and rearward movement of the rear member 44 and an upward movement of the third leg support cross member 48C. The upward movement of the rear member 44 is greater that the upward movement of the third leg support cross member 48C so the plane of the seat portion 16 tilts as the seat actuator 40 is lengthened. When the bed assembly 10 is in the rise configuration, as illustrated in Figures 15 to 17, the front region of the seat portion 16 (including the third leg support cross member 48C) is lower than the rear region of the seat portion (including the rear member 44). As the seat actuator 40 is lengthened, the leg rest actuator 38 pivots about its first end, and the drive input member 42 pivots with respect to the leg rest actuator 38. This, in turn, results in a tilting of the third leg support cross member 48C due to the fixed connection between the drive input member 42 and the third leg support cross member 48C. As the bed assembly 10 moves into the rise configuration the angle between a plane of the seat portion 16 and a plane of the base support member 33 changes such that the first and second lift struts 100, 102 rotate about their respective support pivot points 104, 106, 108, 110 and the distance between the first and second lift struts 100, 102 increases. The lift sub-assemblies 94 therefore help to support the weight of the mattress support frame 12 and mechanism 50, and transfer forces to the base frame 32. When the bed assembly 10 is in the seated configuration, a distance between the rear member 44 and the base support member 33 is smaller than a distance between the third leg support cross member 48C and the base support member 33. When the bed assembly 10 is in the rise configuration, a distance between the rear member 44 and the base support member 33 is greater than a distance between the third leg support cross member 48C and the base support member 33. The bed assembly 10 of the present invention therefore allows a mattress support frame 12 to be moved from a prone configuration which is relatively low to the ground, to a seated configuration at a correct height for a person to sit in and place their feet comfortably on the floor, and to a rise configuration in which the mattress support frame 12 is raised and tilted to aid a person to stand. As described above, with the mechanism in the tucked configuration the distal leg portion 18B is held under the seat portion 16, and the seat portion 16 is not moved in a longitudinal direction with respect to the base frame 32. A person’s legs are, therefore, able to be placed on the floor within the original footprint of the mattress support frame 12 in its flat configuration. This has the benefit that less space is required around the bed assembly 10, allowing the bed assembly to be used in smaller spaces than were possible with prior art sit-to-stand beds. Furthermore, in the bed assembly 10 described above, the functions of (i) tilting the back portion 14 with respect to the seat portion 16 with the back rest actuator 46, (ii) tucking the leg portion 18 under the seat portion 16 with the leg rest actuator 38, and (iii) tilting the seat portion 16 with the seat actuator 40, are provided as independent functions. This allows a person to raise or recline the back portion 14 of the mattress support frame 12 independent of whether the leg portion 18 is extended with the mechanism 50 in its extended configuration or tucked with the mechanism 50 in its tucked configuration. In the above embodiment the mechanism 50 comprised a first linkage sub-assembly including the drive input member 42 and the primary drive link 60, and a second linkage sub-assembly comprising the four-bar linkage including sections of the primary lever 58, the distal arm 56, the proximal arm 54, and the front pivot plate 52. This mechanism enabled the proximal and distal leg portions 18A, 18B to move with respect to each other and with respect to the seat portion 16 to tuck the distal leg portion 18B under the seat portion 16. In other embodiments this movement of the proximal and distal leg portions may be achieved by a different mechanism. For example, the mechanism may comprise a chain linked to part of the proximal leg portion and / or distal leg portion that acts to pull the first leg cross member under the seat portion. In other embodiments the mechanism may include more or fewer levers and arms than has been described above. For example, the leg portion of the mattress support frame may be divided into three sections rather than two sections. In the above embodiment all of the actuators were linear actuators. In other embodiments one or more of the actuators may not be linear actuators. For example, in one embodiment the actuator may form part of a pulley system or retracting system. The pulley system or retracting system may comprise a chain or cable connected to a distal leg portion, and the actuator may be configured to rotate to wind or retract the chain or cable to pull the distal leg portion under the seat portion. The bed assembly may include suitable linkages to enable fewer than three actuators to be used. A second embodiment of a bed assembly 210 is illustrated in Figures 20 to 22. The bed assembly 210 of this embodiment is substantially the same as the bed assembly 10 of the first embodiment and like features have been indicated with reference numerals incremented by 200. The only difference between this second embodiment of the bed assembly 210 and the bed assembly 10 of the first embodiment is the addition of a stabilising member 314. The stabilising member 314 is connected to the leg portion 218 of the mattress support frame 212. The stabilising member 314 extends from the leg portion 218 of the mattress support frame 212 in a direction towards a surface on which the bed assembly 210 stands. As described above in relation to the first embodiment, the bed assembly 210 preferably comprises legs 234 that terminate in feet arranged to stand on a surface, for example a floor or the ground. In other embodiments the legs may terminate in castors, or the legs may terminate in an attachment device for attaching the base frame 232 to a further base structure of a bed. As illustrated in Figure 21, a lower face of each of the feet of the legs 234 define a plane 316 of a surface or other structure on which the bed assembly 210 stands in use. The stabilising member 314 extends from a first end connected to the leg portion 218 of the mattress support frame 212 to a second end in a direction towards the plane 316. In this embodiment a wheel or castor 318 is mounted at the second end of the stabilising member 314. The castor 318 is preferably mounted to the stabilising member 318 by a suitable axle so that the castor 318 is free to rotate about an axis defined by the axle. In this embodiment the stabilising member 314 extends from the linkage mechanism 250 connected between the leg rest actuator 238 and the leg portion 218 of the mattress support frame 212. In particular, the stabilising member 314 extends from the drive input member 242 of the linkage mechanism 250. In this embodiment the stabilising member 314 extends from the first end of the drive input member 242. As in the first embodiment, the first end of the drive input member 242 is pivotally connected to the second end of the leg rest actuator 238 and a second end of the drive input member 242 is connected or attached to the third leg support cross member 248C. Accordingly, in this embodiment the drive input member 242 extends between the second end of the leg rest actuator 238 and the third leg support cross member 248C generally on a first side of the pivotal connection at the second end of the leg rest actuator 238, and the stabilising member 314 extends from the second end of the leg rest actuator 238 generally on a second side of the pivotal connection at the second end of the leg rest actuator 238. It will be appreciated that in preferred embodiments the drive input member 242 and the stabilising member 314 may be parts or sections of a single, continuous element or member. As illustrated in Figure 22, when the bed assembly 210 is in the seated configuration, the second end of the stabilising member 314 is disposed under the seat portion 216. In this embodiment the stabilising member 314 is disposed rearward of the first leg support cross member 248A, i.e. closer to the rear member. The second end of the stabilising member 314, is disposed above the plane 316 by a first distance. In this embodiment the first distance is defined between the axle of the castor 318 and the plane 316. As shown most clearly in Figure 21, when the bed assembly 210 is in the flat configuration the stabilising member 314 is disposed under the leg portion 218 of the mattress support frame 212. When no downward force is applied to the leg portion 218 of the mattress support frame 212, i.e. there is no person sitting or lying on the leg portion 218 of the mattress support frame 212, the second end of the stabilising member 314 is disposed above the plane 316 by a second distance. In this embodiment the second distance is defined between the axle of the castor 318 and the plane 316. The second distance may be less than the first distance. Both of the first distance and the second distance are non-zero. When a downward force is applied to the leg portion 218 of the mattress support frame 212, for example by a person sitting, lying or leaning on the leg portion 218 of the mattress support frame 212, the second end of the stabilising member 314 moves downwardly until the second end of the stabilising member 314, or the wheel or castor 318 disposed at the second end of the stabilising member 314, contacts the surface on which the bed assembly 210 is standing. In other words, when a downward force is applied to the leg portion 218 of the mattress support frame 212 the second end of the stabilising member 314 moves downwardly until there is no gap between the plane 316 and the second end of the stabilising member 314 or the wheel / castor 318 disposed at the second end of the stabilising member 314. In this way, the stabilising member 314 assists in supporting the weight on the leg portion 218 of the mattress support frame 212. As described above, in the above embodiments the mattress support frame 12, 212 is configured to support a mattress (not shown). The mattress support frame 12, 212 comprises a back portion 14 generally disposed under a region of the mattress upon which a person’s back and head will be supported, a seat portion 16 generally disposed under a region of the mattress upon which a person’s hips and upper legs will be supported, and a leg portion 18 generally disposed under a region of the mattress upon which at least a person’s lower legs will be supported. It is important that the mattress provides the correct level of support and comfort to a person lying or sitting on the mattress. It is therefore desirable if the mattress is of generally uniform thickness along the majority of a length of the mattress. The mattress extends in a length direction from a first, head end to a second, foot end. The mattress extends in a width direction between first and second sides of the mattress. The mattress extends in a thickness direction between a lower face and an upper face. The lower face will generally be in contact with the support frame 12, 212, and the upper face will typically be covered with a sheet or similar and provides a face of the mattress on which a person lies or sits. When the mattress is correctly positioned on and attached to the support frame 12, 212, a back region of the mattress, adjacent the head end, overlies the back portion 14 of the support frame 12, 212, a seat region of the mattress overlies the seat portion 16 of the support frame 12, 212, an upper leg portion of the mattress overlies the proximal leg portion 18A, and a lower leg portion of the mattress overlies the distal leg portion 18B. In preferred embodiments the lower face of the mattress is continuous and planar along the full length of the mattress and across the full width of the mattress. Preferably a thickness of the mattress is constant through the back region and the seat region of the mattress. More preferably the thickness of the mattress is constant through at least the back region, the seat region and the upper leg region of the mattress. Preferably the upper face of the mattress is continuous and planar across the full width of the mattress in at least the back region and the seat region of the mattress. The upper face of the mattress may be tapered or sloped in the lower leg region of the mattress to minimise pressure in the heel area of a patient’s legs. In particular, a thickness of the mattress at the foot end of the mattress may be between 50% and 80% of the thickness of the mattress at the head end of the mattress. The mattress may include an inner core structure, which may comprise a suitable foam material, and an outer cover surrounding the inner core structure. The inner core structure may include one or more pressure features such as protrusions, ridges, grooves, and other 5 contoured shapes in one or both of an upper surface and a lower surface of the inner core structure. In these embodiments the cover preferably extends over any such pressure features and forms a planar upper surface and a planar lower surface of the mattress. Accordingly, references to the mattress having a planar lower face and a planar upper face does not preclude the inclusion of pressure relieving features such as ridges and grooves, 10 but refers to a lower face and an upper face of the complete mattress including any such cover. Other modifications and variations not explicitly disclosed above may also be contemplated without departing from the scope of the invention as defined in the appended claims. 15

Claims

1. A bed assembly comprising:a base frame;a mattress support frame comprising a seat portion, a back portion extending from a rear edge of the seat portion, and a leg portion extending from a front edge of the seat portion, the mattress support frame being supported on the base frame;a mattress secured to the mattress support frame, the mattress including a back region overlying the back portion, a seat region overlying the seat portion, and a leg region overlying the leg portion; anda mechanism configured to move the mattress support frame between a flat configuration, a seated configuration and a rise configuration, the mechanism comprising at least one actuator and a linkage arrangement between the at least one actuator and the leg portion of the mattress support frame,wherein, in the flat configuration, the mattress support frame defines a prone plane, a longitudinal direction of the bed is defined between an end edge of the back portion and a distal end edge of the leg portion, and a perimeter of the mattress support frame defines a footprint of the bed assembly, the end edge of the back portion defining a first end edge of the footprint and the distal end edge of the leg portion defining a second end edge of the footprint,wherein, in the seated configuration, a distal region of the leg portion of the mattress support frame is disposed longitudinally between the front and rear edges of the seat portion, and the at least one actuator and the linkage arrangement is arranged to move the mattress support frame between the flat configuration and the seated configuration with no or negligible longitudinal movement of the rear edge of the seat portion,wherein, the at least one actuator is arranged to move the mattress support frame between the seated configuration and the rise configuration by moving the rear edge of the seat portion in a direction transverse to the prone plane and away from the base frame,such that, in use, when the mattress support frame is in the seated or rise configuration, the leg portion of the mattress support frame is spaced from the second end edge of the footprint thereby creating a standing space within the footprint of the bed assembly, andwherein, the mattress includes a lower face facing towards said support frame and the lower face is continuous and planar along a full length of the mattress and across a full width of the mattress.

2. A bed assembly according to Claim 1, in which the leg portion is pivotally connected to the seat portion.

3. A bed assembly according to Claim 1 or Claim 2, in which each of the leg portion, seat portion and back portion include at least one cross member extending transverse to the longitudinal direction.

4. A bed assembly according to any one of Claims 1 to 3, in which the leg portion comprises a proximal leg portion and a distal leg portion, the proximal leg portion extending between the seat portion and the distal leg portion, and the distal leg portion extending from the proximal leg portion to the distal end edge of the leg portion, and wherein the proximal leg portion is pivotally connected to the seat portion and the distal leg portion is pivotally connected to the proximal leg portion.

5. A bed assembly according to any one of Claims 1 to 4, in which the at least one actuator includes a leg rest actuator and a seat actuator, the leg rest actuator being connected to the leg portion and being arranged to move the mattress support frame between the flat configuration and the seated configuration, and the seat actuator being connected to the seat portion and being arranged to move the mattress support frame between the seated configuration and the rise configuration.

6. A bed assembly according to Claim 1 or Claim 2, in which the leg portion comprises a proximal leg portion and a distal leg portion, the proximal leg portion extending between the seat portion and the distal leg portion, and the distal leg portion extending from the proximal leg portion to the distal end edge of the leg portion, and in which each of the proximal and distal leg portions, seat portion and back portion include at least one cross member extending transverse to the longitudinal direction, and in which the at least one actuator includes a leg rest actuator connected to the at least one cross member of the proximal leg portion.

7. A bed assembly according to Claim 6, in which the leg rest actuator is a linear actuator, and the leg rest actuator is connected to the at least one cross member of the proximal leg portion by a drive input member, and wherein an end of the leg rest actuator is pivotally connected to the drive input member.

8. A bed assembly according to Claim 6 or Claim 7, in which the linkage arrangementcomprises a four-bar linkage connected to the distal leg portion, and the linkage arrangement further comprises a coupler arranged to transmit movement of the proximal leg portion to the four-bar linkage.

9. A bed assembly according to Claim 5, in which the seat actuator is connected to a rear member of the seat portion.

10. A bed assembly according to Claim 3, in which the seat portion comprises a first cross member proximate a front edge of the seat portion and a second cross member proximate a rear edge of the seat portion, and in which in the flat configuration a distance between the first cross member and a support member of the base frame is substantially equal to a distance between the second cross member and said base support member, and in which in the seated configuration the distance between the first cross member and the support member is greater than the distance between the second cross member and said base support member, and in which in the rise configuration the distance between the first cross member and the support member is less than the distance between the second cross member and said base support member.

11. A bed assembly according to Claim 1, further comprising a tilt-in-space mechanism comprising a wheel, a drive link connecting the wheel to the linkage arrangement and an axle support member connecting the wheel to the seat portion, the wheel being in contact with a part of the base frame, and the tilt-in-space mechanism being arranged such that movement of the linkage arrangement causes the drive link to apply a force to the wheel to move the wheel along the part of the base frame, and movement of the wheel applies a force through the axle support member to move at least a part of the seat portion in a direction away from the base frame.

12. A bed assembly according to Claim 11, in which the leg portion comprises a proximal leg portion and a distal leg portion, the linkage arrangement comprises a four-bar linkage connected to the distal leg portion, and the drive link connects the wheel to the four-bar linkage.

13. A bed assembly according to any one of Claims 1 to 12, further comprising a lift subassembly including a lift strut pivotally attached at a first end to the seat portion and pivotally attached at a second end to the base frame.

14. A bed assembly according to any one of Claims 1 to 13, further comprising a back rest actuator connected between the seat portion and the back portion and arranged to change an angle between a plane of the seat portion and a plane of the back portion.

15. A bed assembly according to any one of Claims 1 to 14, in which the mattress includes an upper face opposite to the lower face, and the upper face is continuous and planar across the full width of the mattress in at least the back region and the seat region of the mattress.

16. A bed assembly according to Claim 15, in which the upper face of the mattress is tapered or sloped in the leg region of the mattress, such that a thickness of the mattress at a foot end of the mattress adjacent the leg region is smaller than a thickness of the mattress at a head end of the mattress adjacent the back region.

17. A bed assembly according to any one of Claims 1 to 16, further including a stabilising member connected to and extending from the leg portion of the mattress support frame in a direction towards a surface on which the bed assembly stands, the stabilising member being arranged such that, when the bed assembly is in the seated configuration, an end of the stabilising member is disposed under the seat portion and a gap is defined between the end of the stabilising member and the surface on which the bed assembly stands, and when the bed assembly is in the flat configuration the stabilising member is disposed under the leg portion of the mattress support frame, and wherein, in use, when sufficient force is applied to the leg portion of the mattress support frame in a direction towards the surface on which the bed assembly stands, the end of the stabilising member moves into contact with said surface such that the stabilising member assists in supporting the leg portion of the mattress support frame.IntellectualPropertyOfficeApplication GB2508011.0Search report under Section 17 of the Patents Act 1977Date search completed: 20 June 2025Claims searched: 1-17International classificationSubclass and subgroup Valid from A61G1 / 017 01 / 01 / 2006 A61G5 / 10 01 / 01 / 2006 A61G5 / 14 01 / 01 / 2006 A61G7 / 16 01 / 01 / 2006Field of searchWorldwide search of patent documents classified in the following areas of the IPC:A61GDatabases used in the preparation of this search report:SEARCH-PATENTDocuments considered to be relevantPatent literatureCategory Relevant Document of relevanceclaimsX 1-10, 13-16 US 2013 / 0212807 A1 (MANSON et al.), See figures 56-72, especially figures 56-58 A - GB 2617570 A (CAREMED ALRICK UK LTD), See figures; page 8, lines 2832Non-patent literatureCategory Relevant claims Document of relevanceCategoriesLetter or DescriptionsymbolX Document indicating lack of novelty or inventive step.Y Document indicating lack of inventive step, if combined with anotherdocument of the same category.& Member of the same patent family. A Document indicating technological background. P Document published on or after the priority date but before the fling date of the present application. E Earlier application published on or after the filing date of the present application.

Images