WO2023156769A1

WO2023156769A1 - Brake mechanism

Info

Publication number: WO2023156769A1
Application number: PCT/GB2023/050340
Authority: WO
Inventors: Andrew ELLIOTT
Original assignee: Accora Limited
Priority date: 2022-02-15
Filing date: 2023-02-15
Publication date: 2023-08-24
Also published as: GB2615603A; GB202202004D0

Abstract

A brake mechanism for a wheel assembly comprises a first lever rotatable about a first pivot axis; a pressure element moveable between a first position in which the pressure element does not apply a force to a surface and a second position in which the pressure element applies a force to said surface; a linkage mechanism arranged to transmit a force from the first lever to the pressure element; and a second lever rotatable about a second pivot axis. The first lever is arranged to move from a deactivated position to an activated position to apply a force to the linkage mechanism to move the pressure element into the second position, and the second lever is arranged to move from an engaged position to a disengaged position to apply a force to the first lever to move the first lever to the deactivated position and thereby cause the pressure element to move to the first position.

Description

Brake Mechanism

FIELD OF THE INVENTION

The present invention relates to the field of brake mechanisms for wheel assemblies, such as casters. The brake mechanisms include a lever designed to be operated by a person’s foot. The wheel assemblies, and therefore the brake mechanisms, may be associated with or connected to items of furniture, such as chairs or beds, or to small non-motorised vehicles, such as a pushchairs, prams and the like.

BACKGROUND TO THE INVENTION

It is known to provide lifting mechanisms in beds used in hospitals and other healthcare facilities. The lifting mechanisms are used to raise and lower the height of the bed, i.e. to increase or decrease a distance between the mattress and the floor.

This has the advantage of allowing the bed to be raised to a height at which a healthcare worker, such as a doctor or nurse, has easy access to the patient without bending. In some situations the lifting mechanisms may also allow the bed to be lowered such that the mattress is close to the floor on which the bed is standing. This has the advantage that, if a patient rolls out of the bed, they will not fall a large distance to the floor. There is, therefore, a lower risk of injury to the patient than if the bed was at a greater height.

Many beds such as these also include wheel assemblies attached to the legs of the bed to allow the bed to be moved. The bed may be moved both when empty, i.e. with nobody lying on the bed, or when it is in use, with a person lying on the bed. This is common in hospitals and other care settings when a bed may be moved from one room to another. It will be appreciated that when a bed is not being moved for a particular purpose it is desirable to apply a brake mechanism connected to the wheels to prevent accidental movement of the bed. It will further be appreciated that it is desirable if this brake mechanism can be operated quickly and easily, especially in the event of an emergency.

In some situations it may be necessary to apply and release a brake mechanism when a bed is in a lowered position, as described above. In this position, the bed frame, and in particular the mattress frame which supports the mattress, may restrict access to the brake mechanism. Furthermore, in some bed designs the lifting mechanism is configured such that the mattress frame may be positioned very close to the floor. In these designs the space available for a brake mechanism is severely limited.

Against this background it is desirable to provide an improved brake mechanism that is quick and easy to operate, and which may be accessed and operated in a restricted space.

SUMMARY OF THE INVENTION

A first aspect of the invention provides a brake mechanism for a wheel assembly, comprising: a first lever rotatable about a first pivot axis; a pressure element moveable between a first position in which the pressure element does not apply a force to a surface and a second position in which the pressure element applies a force to said surface; a linkage mechanism arranged to transmit a force from the first lever to the pressure element; and a second lever rotatable about a second pivot axis, wherein, the first lever is arranged to move from a deactivated position to an activated position to apply a force to the linkage mechanism to move the pressure element into the second position, and the second lever is arranged to move from an engaged position to a disengaged position to apply a force to the first lever to move the first lever to the deactivated position and thereby cause the pressure element to move to the first position.

Preferably movement of the first lever from the deactivated position to the activated position moves the second lever from the disengaged position to the engaged position.

The first lever preferably contacts a part of the second lever when the first lever is in the activated position.

In preferred embodiments the linkage mechanism comprises an input link and an output link, a first end of the output link being connected to the pressure element and the input link being connected between the first lever and the output link. The output link may comprise a third lever rotatable about a third pivot axis.

In some embodiments the linkage mechanism further comprises a drive link connecting the first lever to the input link. The drive link, input link and a part of the output link preferably form part of a four-bar linkage. The linkage mechanism may be an over-centre linkage mechanism having a first latch position, or first toggle position, in which the pressure element is in the first position and a second latch position, or second toggle position, in which the pressure element is in the second position. Advantageously, as the first lever moves into the activated position and the pressure element moves into the second position, the drive link preferably moves through a position in which the drive link is colinear with the input link into an overcentre position such that the linkage mechanism is held in the second toggle position.

The pressure element may comprise a foot arranged to contact a floor. In preferred embodiments the brake mechanism further comprises a guide sleeve within which at least a part of the foot is slidably mounted. The first lever preferably comprises a press plate, the press plate overlying a part of the second lever when the first lever is in the activated position.

The second lever preferably comprises a first lever arm on a first side of the second pivot axis and a second lever arm on a second side of the second pivot axis, a part of the second lever arm being in contact with the first lever when the second lever is in the engaged position.

In some embodiments the brake mechanism further comprises a lever stop element, the second lever contacting the lever stop element when the second lever is in the disengaged position.

In some embodiments the brake mechanism further comprises a link stop element, a part of the linkage mechanism contacting the link stop element when the first lever is in the activated position.

A second aspect of the invention provides a wheel assembly comprising: a pair of wheels pivotally attached to a support trolley, the support trolley comprising a support plate; and a brake mechanism according to the first aspect of the invention supported by the support plate.

In preferred embodiments the first lever is pivotally mounted to the support plate by a first pivot rod and the second lever is pivotally mounted to the support plate by a second pivot rod.

A third aspect of the invention provides a bed including a wheel assembly and a brake mechanism according to the first aspect of the invention, the wheel assembly being connected to a lower end of a leg of the bed, an upper end of the leg being connected to a mattress support, and the mattress support being moveable between a raised position in which the mattress support is first distance from a floor and a lowered position in which the mattress support is a second distance from the floor, the second distance being smaller than the first distance.

A fourth aspect of the invention provides a bed including a wheel assembly according to the second aspect of the invention.

A fifth aspect of the invention provides a bed including a pair of wheel assemblies, each wheel assembly being according to the second aspect of the invention in which the first lever is pivotally mounted to the support plate by a first pivot rod and the second lever is pivotally mounted to the support plate by a second pivot rod, the wheel assemblies being connected by a shaft, and wherein the first pivot rod extends through a bore of the shaft and the first lever of a first one of the pair of wheel assemblies is connected to a first end of the pivot rod and the first lever of a second one of the pair of wheel assemblies is connected to a second end of the pivot rod.

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 shows a bed in a first, raised position;

Figure 2 shows the bed of Figure 1 in a second, lowered position;

Figure 3 shows a pair of wheel assemblies according to an embodiment of the invention, each wheel assembly including a brake mechanism, and the brake mechanisms each being in a disengaged configuration;

Figure 4 shows the wheel assemblies of Figure 3, with the brake mechanisms being in an engaged configuration;

Figure 5 shows one of the wheel assemblies of Figure 3, the brake mechanism being in a disengaged configuration, and with a side plate of a support trolley omitted so that the brake mechanism is visible;

Figure 6 is a sectional view of the brake mechanism of Figure 5;

Figure 7 is a perspective view of the brake mechanism of Figure 5, with the support trolley omitted;

Figure 8 is a perspective view of the brake mechanism of Figure 5 in isolation (with no support trolley or wheels);

Figure 9 is a further perspective view of the brake mechanism of Figure 7, with the support trolley omitted and showing the position of the brake mechanism relative to the wheels of the wheel assembly;

Figure 10 is a sectional view of the brake mechanism of Figure 8 in isolation;

Figure 11 shows one of the wheel assemblies of Figure 4, the brake mechanism being in an engaged configuration, and with a side plate of a support trolley removed so that the brake mechanism is fully visible;

Figure 12 is a sectional view of the brake mechanism of Figure 11 ;

Figure 13 is a perspective view of the brake mechanism of Figure 11 , with the support trolley omitted; Figure 14 is a perspective view of the brake mechanism of Figure 11 in isolation (with no support trolley or wheels);

Figure 15 is a further perspective view of the brake mechanism of Figure 13, with the support trolley omitted and showing the position of the brake mechanism relative to the wheels of the wheel assembly; and

Figure 16 is a sectional view of the brake mechanism of Figure 14 in isolation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figures 1 and 2 show a bed 10 comprising a support frame 12 for supporting a mattress. The support frame 12 defines a support plane of the bed 10. A mattress (not shown) may be supported directly on the support frame 12, or may be supported on an additional mattress frame (not shown) that is connected to or supported by the support frame 12.

The bed 10 comprises four feet 14. Each foot 14 is in the form of a wheel assembly 16 and includes a trolley 18 to which two wheels or casters 20 are attached. A first pair of wheel assemblies 16 is disposed proximate a first end of the frame 12 and a second pair of wheel assemblies 16 is disposed proximate a second end of the frame 12. In this example the two wheel assemblies 16 of the first pair are connected by an elongate shaft 22. Similarly, the two wheel assemblies 16 of the second pair are connected by an elongate shaft 22.

The wheels 20 are provided to allow the bed 10 to be moved over a surface such as a floor on which the bed 10 is standing. The wheels 20 may allow the bed to be moved from one room to another room within a hospital or other care setting, for example.

Each of the wheel assemblies 16 is connected to the support frame 12 by a leg 24. The legs 24 are configured to allow the support frame 12 to move with respect to the wheel assemblies 16 between a raised position, illustrated in Figure 1 , and a lowered position, illustrated in Figure 2. Preferably, each leg 24 is both pivotally connected to the support frame 12 and pivotally connected to the respective wheel assembly 16.

In this example the connection between each leg 24 and the support frame 12 permits movement of the leg 24 with respect to the support frame 12 such that the support frame 12 can be moved between the raised and lowered positions without a distance between the first and second pairs of wheel assemblies 16 changing. In other words, the bed 10 may be raised and lowered without the wheel assemblies 16 moving. In other examples one or more of the wheel assemblies may move as the bed is raised and lowered. Preferably movement of the wheel assemblies is limited so as not to destabilise the bed.

Figures 3 and 4 show a pair of wheel assemblies 16’ according to an embodiment of the present invention. The wheel assemblies 16’ are connected by an elongate shaft 22’.

In this example, each wheel assembly 16’ includes a trolley 18’ to which two wheels or casters 20’ are pivotally connected, such that each of the wheels 20’ is able to rotate about a respective vertical pivot axis 26. Each trolley 18’ comprises an upper plate 28, to which the two casters 20’ are pivotally attached, and a pair of support plates 30 which extends from the upper plate 28 between the two casters 20’. The support plates 30 extend from side edges of the upper plate 28, and a plane of each of the support plates 30 is substantially perpendicular to a plane of the upper plate 28. An end of the shaft 22’ is connected to one of the support plates 30. In this example, a longitudinal axis of the shaft 22’ lies in substantially the same plane as the rotational axes of the axles of the casters 20’. This has the advantage that the bed 10 may be lowered very close to the floor.

Each wheel assembly 16’ further comprises a brake mechanism 40. In this example, each brake mechanism 40 is connected to and supported by the trolley 18’, and in particular is supported between the support plates 30 of the trolley 18’.

Each brake mechanism 40 comprises a first lever 42, a second lever 44 and a pressure element 46. In this example the pressure element 46 is in the form of a foot 46. The first and second levers 42, 44 are arranged to be operated to move the brake mechanism 40 between a disengaged configuration, shown in Figure 3, and an engaged configuration, shown in Figure 4. In the disengaged configuration the foot 46 is raised such that the foot 46 does not contact the floor, and the wheel assembly 16’ may be freely moved around on the floor by rotation of the wheels 20’. In the engaged configuration the foot 46 is lowered such that the foot 46 contacts the floor. This resists or prevents movement of the wheels 20’ over the floor.

Referring additionally to Figures 5, 6, 11 and 12, the first lever 42 is moveable between a deactivated position (Figures 3, 5 and 6) and an activated position (Figures 4, 11 and 12). In this embodiment the first lever 42 comprises a lever arm 48 that extends between a first end 50 and a second end 52. The lever arm 48 includes a first portion 54 extending from the first end 50 and a second portion 56 extending from the second end 52 (shown most clearly in Figure 10). The first portion 54 joins the second portion 56 at a bend in the first lever arm 48 between the first and second ends 50, 52.

The first end 50 of the first lever 42 is pivotally mounted to the trolley 18’. In this example, a first pivot rod 58 extends through the two support plates 30 of the trolley 18’. The first pivot rod 58 defines a first pivot axis 60 about which the first lever 42 rotates. The first pivot rod 58 extends through apertures in the support plates 30, such that a first end of the pivot rod 58 is disposed on an external side of a first one of the support plates 30a and a second end of the pivot rod 58 is disposed on an external side of a second one of the support plates 30b. In this example, the first support plate 30a is an outer support plate 30a, and the shaft 22’ is connected to the second support plate 30b, which is an inner support plate 30b. The first lever 42 is connected to the first end of the pivot rod 58 such that the first lever 42 is disposed on the external side of the first, outer support plate 30a. In this example, the first lever 42 is rigidly connected to the pivot rod 58, and the pivot rod 58 rotates about its axis 60 with respect to the support plates 30. The pivot rod 58 preferably extends through a bush mounted in each of the apertures in the support plates 30. The pivot rod 58 may have a hexagonal cross-section, as illustrated.

A press plate 62 extends from the second portion 56 of the first lever 42. The press plate 62 extends in a direction away from the support plate 30a. The press plate 62 provides a press surface 64 which may be contacted by a user’s foot to operate or move the first lever 42. The bend in the lever arm 48 is preferably such that the press surface 64 is generally horizontal when the first lever 42 is in the deactivated position.

The second lever 44 is moveable between a disengaged position (Figures 3, 5 and 6) and an engaged position (Figures 4, 11 and 12). The second lever 44 is pivotally mounted to the trolley 18’. In this example, a second pivot rod 66 extends through the two support plates 30 of the trolley 18’. The second pivot rod 66 defines a second pivot axis 68 about which the second lever 44 rotates. The second pivot rod 66 extends through apertures in the support plates 30, such that a first end of the pivot rod 66 is disposed on the external side of the first, outer support plate 30a and a second end of the pivot rod 66 is disposed on the external side of the second, inner support plate 30b. The second lever 44 is connected to the first end of the pivot rod 66 such that the second lever 44 is disposed on the external side of the first, outer support plate 30a. The second pivot axis 68 is preferably offset from the first pivot axis 60.

The second lever 44 is pivotally mounted to the trolley 18’ in a central region of the second lever 44. The second lever 44 comprises a first lever arm 74 that extends in a first direction away from the central region on a first side of the pivot rod 66 and a second lever arm 76 that extends in a second direction away from the central region on a second side of the pivot rod 66.

The second lever 44 includes a press plate 78 and a contact plate 80. The press plate 78 extends from the first lever arm 74. The contact plate 80 extends from second lever arm 76. The contact plate 80 preferably extends from the second lever arm 76 on the same side as the press plate 78 extends from the first lever arm 74. Both the press plate 78 and the contact plate 80 preferably extend in a direction away from the support plate 30a. In this example the press plate 78 and contact plate 80 are joined at the central region of the second lever 44. The press plate 78 provides a press surface 82 which may be contacted by a user’s foot to operate or move the second lever 44.

The press plate 62 of the first lever 42 is disposed above the contact plate 80 of the second lever 44. When the first lever 42 is in the deactivated position there is a first distance between the press plate 62 of the first lever 42 and the contact plate 80 of the second lever 44. When the first lever 42 is in the activated position there is a second distance between the press plate 62 of the first lever 42 and the contact plate 80 of the second lever 44, the second distance being smaller than the first distance. In preferred embodiments the press plate 62 of the first lever 42 is in contact with the contact plate 80 of the second lever 44 when the first lever 42 is in the activated position.

When the first lever 42 is in the activated position, at least a part of the press surface 82 of the press plate 78 of the second lever 44 remains exposed. Preferably, no part of the first lever 42 extends over or covers a part of the press surface 82 when the first lever 42 is in the activated position. A user is therefore able to access the press surface 82, and in particular apply a force to the press surface 82 when the first lever 42 is in the activated position.

Referring now to Figures 5 to 16, the brake mechanism 40 further comprises a linkage mechanism 84. The linkage mechanism 84 is arranged to transmit a force from the first lever 42 to the pressure element 46 to move the pressure element 46. In this example the pressure element 46 moves between a first position, in which the pressure element 46 in the form of a foot 46 is raised and does not contact the floor, and a second position, in which the pressure element 46 in the form of a foot 46 is lowered and contacts the floor.

In its simplest form the linkage mechanism 84 comprises an input link 86 and an output link 88. A first end 90 of the output link 88 is connected to the pressure element 46. The input link 86 is connected between the first lever 42 and the output link 88. Rotation of the first lever 42 about the first pivot axis 60 causes movement of the input link 86 which in turn applies a force to the output link 88. The output link 88 is moved by this force which causes subsequent movement of the pressure element 46.

In the illustrated embodiment, to allow the linkage mechanism 84 to be spaced from the first lever 42 and, in particular, to allow the linkage mechanism 84 to be housed between the support plates 30 while the first lever 42 is disposed on the external side of the first, outer support plate 30a, the linkage mechanism 84 further comprises a drive link 92. The drive link 92 is connected at a first end 94 to the first pivot rod 58. The drive link 92 is rigidly connected to the pivot rod 58 such that, when the first lever 42 is moved so as to rotate the pivot rod 58, the drive link 92 also rotates. Movement or rotation of the drive link 92 therefore corresponds to movement or rotation of the first lever 42. The drive link 92 is, however, spaced from the first lever 42 along the length of the pivot rod 58 such that the first lever 42 is disposed on the external side of the first, outer support plate 30a and the drive link 92 is disposed between the support plates 30.

A second end 96 of the drive link 92 is pivotally or rotatably connected to a first end 98 of the input link 86. A second end 100 of the input link 86 is rotatably connected to the output link 88.

In this example the output link 88 is in the form of a dog-leg link or L-shaped link. The second end 100 of the input link 86 is rotatably connected to the output link 88 at the bend in the output link 88. The input link 86 is therefore connected to the output link 88 between the ends of the output link 88. A second end 102 of the output link 88 is pivotally or rotatably mounted to the trolley 18’. In this example, the second end 102 of the output link 88 is pivotally or rotatably mounted to a third pivot rod 104 that extends between the two support plates 30 of the trolley 18’. The third pivot rod 104 defines a third pivot axis 106 about which the output link 88 rotates.

A first arm or first section 108 of the output link 88 extends between the connection to the second end 100 of the input link 86 and the first end 90 of the output link 88 connected to the pressure element 46. A second arm or second section 110 of the output link 88 extends between the pivotally mounted second end 102 of the output link 88 and the connection to the second end 100 of the input link 86.

The drive link 92, input link 86 and second arm 110 of the output link 88 form three moving links of a four bar linkage. The fourth static link is provided by a part of the support plate 30 extending between the first pivot rod 58 and the third pivot rod 104. It will be appreciated that the first pivot rod 58 and the third pivot rod 104 provide two fixed pivots, while the connection between the drive link 92 and the input link 86 and the connection between the input link 86 and the output link 88 provide two moving pivots.

The linkage mechanism 84 may be an over-centre linkage mechanism having a first latch position, or first toggle position, in which the pressure element 46 is in the first raised position and a second latch position, or second toggle position, in which the pressure element 46 is in the second lowered position.

The arrangement of the linkage mechanism 84 is preferably such as the first lever moves into the activated position and the pressure element moves into the second position, the drive link preferably moves through a position in which the drive link is colinear with the input link into an over-centre position such that the linkage mechanism is held in the second toggle position. This arrangement of the drive link 92 and the input link 86 creates an over-centre position of the linkage mechanism 84 such that the linkage mechanism 84 is held in a resting position. To prevent the linkage mechanism 84 moving past the toggle position, thereby limiting rotation of the input link 86 and drive link 92 and defining the activated position of the first lever 42, the linkage mechanism 84 includes a stop 112. When the first lever 42 is in the activated position the input link 86 contacts the stop 112 preventing further rotation of the input link 86. In this example the stop 112 comprises a rod 112 extending between the two support plates 30.

In this example the first end 90 of the output link 88 is connected to the pressure element or foot 46 by a foot coupler 114. A first end 116 of the foot coupler 114 is rotatably connected to the first end 90 of the output link 88 and a second end 118 of the foot coupler 114 is rotatably connected to a top of the foot 46. In this embodiment the inclusion of a foot coupler 114 allows an arcuate movement of the first end of the output link 88 to be transferred to linear movement of the foot 46. However, it will be appreciated that in other embodiments, especially ones in which the pressure element 46 has a different form, the first end 90 of the output link 88 may be directly connected to the pressure element 46.

Referring to Figures 10 and 16, the foot 46 includes an upper portion 120 and a lower portion 122. A spring or other resilient member 124 connects the upper portion 120 to the lower portion 122 so that the lower portion 122 is moveable with respect to the upper portion 120. In particular, a gap 126 between the upper portion 120 and the lower portion 122 may be varied to accommodate differences in a distance between the linkage mechanism and a surface, such as a floor, that the foot 46 contacts during use.

The upper and lower portions 120, 122 of the foot 46 are at least partially housed within a guide tube 128. The guide tube 128 is fixed to the trolley 18’ and constrains movement of the foot 46 along an axis 130 of the guide tube 128. In this example the guide tube 128 is mounted such that the axis 130 is vertical. In this way, the foot 46 is constrained to move vertically. The foot coupler 114 is connected to the upper portion 120 of the foot 46. A lower surface 132 of the lower portion 122 of the foot 46 contacts the floor, or other similar surface, when the foot 46 is in its second lowered position. In this example the lower surface 132 is provided on a flange 134 of the lower portion 122 of the foot 46. When the foot 46 is in its first raised position the flange 134 contacts a lower end of the guide tube 128 and limits further upwards movement of the foot 46. A foot pad 136 may be attached to the lower surface 132 of the foot 46. The foot pad 136 may provide a gripping surface or compliant surface. The foot pad 136 may, for example, be made of rubber or a rubber-like material.

Starting with the brake mechanism 40 in a disengaged position, to apply the brake (i.e. lower the foot 46) a user pushes on the press plate 62 to move the first lever 42 from the deactivated position to the activated position. The user preferably presses their foot on the press surface 64 to move the press plate 62 in a downwards direction. During this movement the press plate 62 contacts the contact plate 80 of the second lever 44 which causes the second lever 44 to be moved from its disengaged position to its engaged position. Movement of the first lever 42, as described above, also results in movement of the linkage mechanism 84. In particular, rotation of the drive link 92 causes movement of the input link 86 until the input link 86 contacts the stop 112. Movement of the input link 86 causes the output link 88 to rotate about the third pivot axis 106, which in turn causes movement of the foot coupler 114. The foot coupler 114 transfers the force to the foot 46 which moves downwards through the guide tube 128 to its lowered position in which the foot pad 136 is in contact with the floor.

To release the brake (i.e. raise the foot 46) a user pushes on the press plate 78 of the second lever 44 to move the second lever 44 from its engaged position to its disengaged position. The user preferably presses their foot on the press surface 82 to move the press plate 78 in a downwards direction. Movement of the second lever 44 in this direction is limited by a stop 138. The stop 138 may be arranged to contact the first lever arm 74 of the second lever 44 when the second lever 44 is in the disengaged position. In this example the stop 138 comprises a rod 138 extending between the two support plates 30.

Movement of the second lever 44 from its engaged position to its disengaged position causes the contact plate 80 to push against the press plate 62 of the first lever 42 to return the first lever 42 to its deactivated position. This movement of the first lever 42 results in movement of the linkage mechanism 84 that draws the foot 46 upwards through the guide tube 128 to its raised position.

The brake mechanism 40 may comprise a spring or other biasing element arranged to urge the first lever 42 into the deactivated position. Similarly, the brake mechanism 40 may include a spring or other biasing element arranged to urge the second lever 44 into the disengaged position.

It will be appreciated that the second lever 44 is not directly connected to the linkage mechanism 84. Furthermore, the second lever 44 is not connected to the first lever 42, but contacts a part of the first lever 42 during part of the movement of the second lever 44 from the engaged position to the disengaged position.

The dual lever arrangement of the brake mechanism 40 of the present invention has the benefit that the distance between the second end 52 of the first lever 42 and a free end of the first lever arm 74 of the second lever 44 is less than the length of the equivalent single lever that would be required to provide the same leverage and ease of use. This is because, in a single lever mechanism, the lever would comprise the equivalent of the lever arm 48 of the first lever 42 on a first side of the pivot axis and the equivalent of the first lever arm 74 of the second lever 44 on a second side of the pivot axis. In the present brake mechanism 40, the first pivot axis 60 of the first lever 42 is offset from the second pivot axis 68 of the second lever 44 such that part of the length of the lever arm 48 of the first lever 42 overlaps part of the length of the first lever arm 74 of the second lever 44.

This means that the brake mechanism 40 may be installed in a location with limited access or limited clearance compared to that which is required with a traditional single lever mechanism. The brake mechanism 40 of the present invention finds particular utility when connected to beds having a support frame or mattress support which can be lowered very close to the ground. It will be appreciated that the brake mechanism is preferably connected to one or more of the wheel assemblies of the bed, which are located between the floor and the support frame of the bed. When the bed is in its lowered position the gap between the support frame and the floor, and therefore the gap available for the brake mechanism, can be very small. It may still be necessary, however, to be able to access the brake mechanism when the bed is lowered.

In the above example the pressure element 46 is in the form of a foot 46 that contacted the floor when the brake mechanism 40 was in the engaged configuration. In other embodiments the pressure element 46 may be arranged to contact a part of a wheel or one of the wheels when the brake mechanism 40 is in the engaged configuration. The pressure element may be arranged to contact a part of the wheel such that the pressure element applies a frictional force to the wheel to resist or prevent movement of the wheel. In particular, when the pressure element is in the first position the pressure element may be spaced from the wheel and when the pressure element is in the second position a part of the pressure element may directly contact a part of the wheel.

In embodiments in which there are a pair of wheel assemblies, for example in a bed as described above, it may be desirable to functionally connect the two brake mechanisms of the two wheel assemblies. This may have the advantage that a user can apply or release both brake mechanisms in a single operation. In one example, the pivot rod to which the first lever is connected may extend between and connect the two brake mechanisms. The first lever of a first brake mechanism (of a first wheel assembly) may be connected to a first end of the pivot rod and the first lever of a second brake mechanism (of a second wheel assembly) may be connected to a second end of the pivot rod. As both first levers are rigidly connected to the same pivot rod, when a user presses one of the first levers the other of the first levers will also rotate, thereby operating both brake mechanisms to apply the brakes. When a user presses one of the second levers to release the brake, as described above, the second lever causes the first lever to rotate back to its deactivated position and the connection via the pivot rod causes the other first lever to also rotate to its deactivated position. In the example described above, the pivot rod 58 preferably extends through a bore of the shaft 22’, coaxial with the shaft 22’, to connect the two brake mechanisms 40 of the pair of wheel assemblies 16’.

The present invention therefore provides an improved brake mechanism that is quick and easy to operate, and which may be accessed and operated in a restricted space.

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.

Claims

1 . A brake mechanism for a wheel assembly, comprising: a first lever rotatable about a first pivot axis; a pressure element moveable between a first position in which the pressure element does not apply a force to a surface and a second position in which the pressure element applies a force to said surface; a linkage mechanism arranged to transmit a force from the first lever to the pressure element; and a second lever rotatable about a second pivot axis, wherein, the first lever is arranged to move from a deactivated position to an activated position to apply a force to the linkage mechanism to move the pressure element into the second position, and the second lever is arranged to move from an engaged position to a disengaged position to apply a force to the first lever to move the first lever to the deactivated position and thereby cause the pressure element to move to the first position.

2. A brake mechanism according to Claim 1 , in which movement of the first lever from the deactivated position to the activated position moves the second lever from the disengaged position to the engaged position.

3. A brake mechanism according to Claim 1 or Claim 2, in which the first lever contacts a part of the second lever when the first lever is in the activated position.

4. A brake mechanism according to any preceding claim, in which the linkage mechanism comprises an input link and an output link, a first end of the output link being connected to the pressure element and the input link being connected between the first lever and the output link.

5. A brake mechanism according to Claim 4, in which the output link comprises a third lever rotatable about a third pivot axis.

6. A brake mechanism according to Claim 4 or Claim 5, in which the linkage mechanism further comprises a drive link connecting the first lever to the input link, the drive link, input link and a part of the output link forming part of a four-bar linkage.

7. A brake mechanism according to any preceding claim, in which the linkage mechanism is an over-centre linkage mechanism having a first toggle position in which the pressure element is held in the first position and a second toggle position in which the pressure element is held in the second position.

8. A brake mechanism according to any preceding claim, in which the pressure element comprises a foot arranged to contact a floor.

9. A brake mechanism according to Claim 8, further comprising a guide sleeve within which at least a part of the foot is slidably mounted.

10. A brake mechanism according to any preceding claim, in which the first lever comprises a press plate, the press plate overlying a part of the second lever when the first lever is in the activated position.

11. A brake mechanism according to any preceding claim, in which the second lever comprises a first lever arm on a first side of the second pivot axis and a second lever arm on a second side of the second pivot axis, a part of the second lever arm being in contact with the first lever when the second lever is in the engaged position.

12. A brake mechanism according to any preceding claim, further comprising a lever stop element, the second lever contacting the lever stop element when the second lever is in the disengaged position.

13. A brake mechanism according to any preceding claim, further comprising a link stop element, a part of the linkage mechanism contacting the link stop element when the first lever is in the activated position.

14. A wheel assembly comprising: a pair of wheels pivotally attached to a support trolley, the support trolley comprising a support plate; and a brake mechanism according to any preceding claim supported by the support plate.

15. A wheel assembly according to Claim 14, in which the first lever is pivotally mounted to the support plate by a first pivot rod and the second lever is pivotally mounted to the support plate by a second pivot rod.

16. A bed including a wheel assembly and a brake mechanism according to any one of Claims 1 to 13, the wheel assembly being connected to a lower end of a leg of the bed, an upper end of the leg being connected to a mattress support, and the mattress support being moveable between a raised position in which the mattress support is first distance from a floor and a lowered position in which the mattress support is a second distance from the floor, the second distance being smaller than the first distance.

17. A bed including a wheel assembly according to Claim 14 or Claim 15.

18. A bed including a pair of wheel assemblies, each wheel assembly being according to Claim 15, and the wheel assemblies being connected by a shaft, wherein the first pivot rod extends through a bore of the shaft and the first lever of a first one of the pair of wheel assemblies is connected to a first end of the pivot rod and the first lever of a second one of the pair of wheel assemblies is connected to a second end of the pivot rod.