Patent Description:
Patient lifts, also referred to as patient hoists, are commonly used to raise, lower and transfer patients who are disabled or who otherwise have mobility problems. Two common types of patient lifts are stanchion-mounted lifts, also known as floor lifts. and ceiling lifts. Floor lifts often have a hoist assembly which may be disposed at the upper end of a stanchion. The stanchion has a wheeled base, which allows for the lift to be moved along the ground to different locations.

A lifting member which may be in the form of a spreader bar, such as a two-point attachment spreader bar, a three-point attachment spreader bar, a four-point attachment spreader bar, a five-point attachment spreader bar or a powered spreader bar for adjusting the angle of the spreader bar, for supporting a patient harness or sling descends from the hoist assembly on a strap or a cable. The strap or cable is wound around a motorized drum for raising and lowering the patient harness or sling.

For example, the lift might be wheeled to position the hoist assembly and lifting member over or adjacent to a patient. The lifting member may then be lowered to receive the patient and subsequently raise the lifting member and patient so that they may be wheeled elsewhere to be lowered and placed. A ceiling lift may be utilized in a similar manner, however the hoist assembly is movably engaged to ceiling-mounted tracks such that the hoist assembly can be moved about the track from location to location.

A ceiling lift may be described as a motor unit movable along a rail, a flexible member is attached to a spreader bar. The motor unit commonly comprises a transmission, batteries and a control module.

The transmission is subjected to a number of challenges. For example, the transmission needs to be able to lift a patient, maintain the patient at a prescribed height for a certain period of time and lower the patient. Further, the transmission needs to be able to lift and support a weight of around <NUM>.

Manufacturers often use smaller motors able to deliver a high RPM. In order for the smaller motors to be able to support and lift higher loads, the RPM is often reduced and torque increased by means of different types of transmissions.

Transmissions are in most cases in the form of parallel transmissions in the form of standard gears and strap, pulley and planetary gears or worm gear stages. The toughest challenge for such transmissions is to allow for a locking functionality. The locking allows for the transmission to maintain a load at a fixed position even when the lift is in a powerless state. Parallel transmissions are in themselves not locking but allows for high efficiency. Thus, a mechanical brake is required to allow for the locking functionality. The mechanical brake may be applied directly on the motor shaft to reduce the required braking torque to a minimum. Such a mechanical brake may comprise a solenoid and a braking pad. The solenoid is often expensive and requires a lot of power to operate.

Worm gear transmissions are often less efficient but allows for locking up to a certain load, often around <NUM> to <NUM>. Past said load, the motor has to be provided with power to give a small amount of torque to maintain the load suspended in the lift at the same height. In an emergency situation where the power is down and the patient weighs more than the certain load described above, the patient will slowly move downwards. To counteract such downward movement an electrical brake may be utilized. However, these electrical brakes are expensive and difficult to disengage in case of an emergency.

In the light of the above, there is a need for a locking or braking arrangement which is associated with a low cost and high efficiency.

A known braking arrangement is disclosed in <CIT>.

According to one aspect a locking arrangement for a patient lift is provided. The locking arrangement is configured to selectively lock the vertical movement of a patient support mounting device connected to a lifting device of the patient lift via a load bearing member.

The locking arrangement comprises a shape memory alloy element and a locking device. The shape memory alloy element is connected to the locking device and arranged to selectively actuate said locking device to control a locking force on an engagement member mechanically connected to a motor and the load bearing member of the patient lift. The motor is arranged to raise and lower the patient support mounting device.

The locking arrangement is configured to operate in an engaged mode and a disengaged mode.

In the engaged mode the shape memory alloy element is in a first configuration and the locking device is in an engaged position in relation to the engagement member for exerting a locking force on the engagement member thereby preventing vertical movement of the patient support mounting device.

In the disengaged mode the shape memory alloy element is in a second configuration actuating the locking device to a disengaged position in relation to the engagement member thereby enabling vertical movement of the patient support mounting device.

According to an aspect a patient lift is provided. The patient lift comprises a lifting device, a patient support mounting device and a load bearing member. The patient support mounting device is connected to the lifting device via the load bearing member. Further, the patient lift comprises a locking arrangement according to the above.

Further objects and features of the present invention will appear from the following detailed description of embodiments of the invention.

The invention will be described with reference to the accompanying drawings, in which:.

<FIG> show a non-limiting example of elements of a patient handling system with a patient lift. The patient lift may be in the form of a patient ceiling lift. A patient support mounting device <NUM> is connected via a load bearing member <NUM> to a lifting device <NUM> in <FIG>. The lifting device <NUM> may be arranged to be moveable along a track <NUM>. The lifting device <NUM> may thus be in engagement with the track <NUM>, e.g. movably connected to the track <NUM>. The lifting device <NUM> may move along the track <NUM>, preferably in both directions.

The lifting device <NUM> may be in the form of a trolley movable along said track <NUM>.

The lifting device may comprise a drum for winding of the load bearing member <NUM> and motor and transmission for driving said drum. The load bearing member <NUM> may be wrapped around said drum for lowering and raising the patient support mounting device <NUM>.

In one embodiment, the lifting device <NUM> comprises wheels for interfacing with the track <NUM>. In one embodiment, the lifting device <NUM> is slidably connected to the track <NUM>.

The patient support mounting device <NUM> may be a spreader bar or hanger bar. The load bearing member <NUM> may be a flexible member such as a strap. The patient support <NUM> may, as shown in <FIG>, be a sling.

The patient support mounting device <NUM> may comprise attachment elements <NUM> for attaching the patient support <NUM> to the patient support mounting device <NUM>. The attachment elements may comprise hooks with latches.

The lifting device <NUM> is configured to move the patient support mounting device <NUM> between a raised position situated closer to said lifting device <NUM> and a lowered position located more distantly from said lifting device <NUM>. The lifting device <NUM> may thus be configured to move the patient support mounting device <NUM> vertically between said raised and lowered position.

Although the patient lift in <FIG> is depicted as a ceiling patient lift, the patient lift may also be floor lift with a base comprising a set of wheels for moving the lift across a floor.

<FIG> discloses aspects of embodiments of locking arrangements for implementation in the patient lift depicted in <FIG>.

The locking arrangement for the patient lift is configured to selectively lock the vertical movement of the patient support mounting device <NUM>. The patient support mounting device <NUM> is connected to a lifting device <NUM> of the patient lift via the load bearing member <NUM>.

The locking arrangement comprises a shape memory alloy element <NUM>, <NUM> and a locking device <NUM>, <NUM>. The shape memory alloy element is connected to said locking device <NUM>, <NUM> and arranged to selectively actuate said locking device <NUM>, <NUM> to control a locking force on an engagement member <NUM>, <NUM>. The engagement member <NUM>, <NUM> is mechanically connected to a motor <NUM>, <NUM> and the load bearing member <NUM> of the patient lift, i.e. the motor <NUM>, <NUM> of the patient lift and the load bearing member <NUM> of the patient lift. Said motor <NUM>, <NUM> is arranged to raise and lower the patient support mounting device <NUM>.

The locking arrangement is configured to operate in an engaged mode and a disengaged mode. In the engaged mode, the shape memory alloy element <NUM>, <NUM> is in a first configuration and the locking device <NUM>, <NUM> is in an engaged position for exerting a locking force on the engagement member <NUM>, <NUM> thereby preventing vertical movement of the patient support mounting device <NUM>.

In the disengaged mode, the shape memory alloy element <NUM>, <NUM> is in a second configuration actuating the locking device <NUM>, <NUM> to a disengaged position in relation to the engagement member <NUM>, <NUM> thereby enabling vertical movement of the patient support mounting device <NUM>.

Compared to known patient lifts implementing locking worm gear transmissions this allows for locking without creeping even when a large load is suspended by means of the patient support mounting device <NUM>. Furthermore, the shape memory alloy allows for a more cost-efficient and less power consuming solution compared to a solenoid activated mechanical brake.

A shape-memory alloy is as is known in the prior art an alloy which can be deformed in a cold state but returns to a pre-deformed shape when heated. Shape-memory alloys are also known in the prior art as memory metals, memory alloys, smart metals, smart alloys or muscle wires.

The shape memory alloy element <NUM>, <NUM> may be in one of: Ag-Cd, Au-Cd, Co-Ni-Al, Co-Ni-Ga, Cu-Al-Ni, Cu-Al-Ni, Cu-Al-Ni-Hf, Cu-Sn, Cu-Zn, Cu-Zn-Si, Cu-Zn-Al, Cu-Zn-Sn, Fe-Mn-Si, Fe-Pt, Mn-Cu, Ni-Fe-Ga, Ni-Ti, Ni-Ti-Hf, Ni-Ti-Pd, Ni-Mn-Ga, Ti-Nb alloy.

The shape memory alloy element <NUM>, <NUM> may be a two-way memory effect element. In the first configuration, the shape memory element <NUM>, <NUM> forms a shape which allows the locking device <NUM>, <NUM> to in the engaged position in relation to the engagement member <NUM>, <NUM>. In the second configuration <NUM>, <NUM> forms a shape which is arranged to force the locking device to the disengaged position in relation to the engagement member <NUM>, <NUM>.

The locking device <NUM>, <NUM> may thus be a movable by means of the shape memory alloy element <NUM>, <NUM>. Accordingly, the shape memory alloy element <NUM>, <NUM> may be arranged to move the locking device <NUM>, <NUM> between the engaged position and disengaged position. The shape memory alloy element <NUM>, <NUM> may be directly attached to the locking device <NUM>, <NUM>.

To allow for the locking device <NUM>, <NUM> to provide the locking force, the locking device <NUM>, <NUM> may be biased. Accordingly, the locking device <NUM>, <NUM> may be biased to exert the locking force onto the engagement member <NUM>, <NUM> and actuating the locking device <NUM>, <NUM> to the engaged position when the locking arrangement operates in the engaged mode and shape memory alloy element <NUM>, <NUM> is in the first configuration.

Further, the shape memory alloy element <NUM>, <NUM> is arranged to actuate the locking device <NUM>, <NUM> to the disengaged position in relation the engagement member <NUM>, <NUM> by being in the second configuration when the locking arrangement operates in the disengaged mode. The shape memory alloy element <NUM>, <NUM> thus actuates the locking device <NUM>, <NUM> away from the engaged position against the locking force exerted by the biasing of the locking device <NUM>, <NUM>.

This is associated with the advantage of the shape memory alloy element only having to provide a disengaging force, which reduces the wear of the locking arrangement. Furthermore, biased locking device provides for a more reliant and robust locking functionality.

In an alternative embodiment however, the shape memory alloy element may be arranged to actuate the locking device <NUM>, <NUM> to exert the locking force. Accordingly, in the first configuration, the shape memory element <NUM>, <NUM> forms a shape which forces the locking device <NUM>, <NUM> into in the engaged position in relation to the engagement member <NUM>, <NUM>. In the second configuration <NUM>, <NUM> forms a shape which is arranged to force the locking device to the disengaged position in relation to the engagement member <NUM>, <NUM>.

In one embodiment, the shape memory alloy element <NUM>, <NUM> is a muscle wire.

The shape memory alloy element <NUM>, <NUM> may be arranged to be electrically connected to at least one power source for selectively transitioning between the first and second configuration.

The locking arrangement <NUM>, <NUM> is further arranged to switch from the engaged mode to the disengaged mode by means of the shape memory alloy element <NUM>, <NUM> transitioning from the first configuration to the second configuration in response to receiving a current provided by said power source exceeding a first configuration threshold current. In one embodiment, the current is provided by a single power source. In one embodiment, the current is provided by a plurality of power sources.

Each of the first and second configuration may be associated with a temperature interval. The first configuration is associated with a first temperature interval, the second configuration is associated with a second temperature interval.

The first configuration temperature interval defines a temperature interval substantially lower than the second configuration temperature interval. The first configuration threshold current is thus associated with a temperature of the shape memory alloy element <NUM>, <NUM> within the second configuration temperature interval, causing the transition from the first configuration to the second configuration.

Hence, when a current is induced through the shape memory alloy element <NUM>, <NUM> the temperature of the shape memory alloy element will increase causing the temperature of said shape memory alloy element <NUM>, <NUM> to exceed the first configuration temperature interval and enter the second configuration temperature interval which will cause the switch from the first configuration to the second configuration. When the current is not provided the temperature of the shape memory alloy element will decrease, causing the temperature to subceed the second configuration temperature interval and enter the first configuration temperature interval which will cause the switch from the second configuration to the first configuration.

As will be described in more detail with reference to <FIG>, the current received by the shape metal alloy element may be considered a control current Ic. The control current Ic is of a hold-level amplitude provided by the power source PS1, PS2. Hence, the shape memory alloy element <NUM>, <NUM> is configured to transition from the first configuration to the second configuration in response to a hold-level amplitude I<NUM> exceeds the first configuration threshold current.

For example, the shape memory alloy element <NUM>, <NUM> may be a muscle wire. As is known to the skilled person a muscle wire is a wire comprising a shape memory alloy which is adapted to contract in response to receiving a current. Hence the muscle wire may be adapted to contract to the second configuration, i.e. shape in response to the current exceeding the first configuration threshold current.

The locking arrangement may be arranged to switch from the disengaged mode to the engaged mode by means of the shape memory alloy element <NUM>, transitioning from the second configuration to the first configuration in response to receiving a current provided by the power source subceeding, i.e. being smaller than, a second configuration threshold current. This includes the shape memory alloy element <NUM>, <NUM> being configured to transition from the first configuration to the second configuration in response to not receiving any current from said power source. In one embodiment, the current is provided by a single power source. In one embodiment, the current is provided by a plurality of power sources.

The second threshold current is thus associated with the first configuration temperature interval. Accordingly, the second threshold currents result in the temperature of the smart metal alloy element <NUM>, <NUM> cooling down, allowing for the transition from the second configuration to the first configuration.

As will be described in more detail with reference to <FIG>, considering the current received by the shape metal alloy element being the control current Ic. Hence, the shape memory alloy element <NUM>, <NUM> is configured to transition from the second configuration to the first configuration in response to control current Ic subceeding the second threshold current.

For example, if the shape memory alloy element <NUM>, <NUM> is a muscle wire the muscle wire may be further adapted to expand to the first configuration, i.e. shape in response to the current subceeding the second configuration threshold current.

The power source may be electrically connected to the motor <NUM>, <NUM> for driving said motor <NUM>, <NUM>. In one embodiment, the first configuration threshold current may be associated with an operating current range of the motor <NUM>, <NUM>. In one embodiment, a plurality of power sources may be electrically connected to the motor for driving said motor.

Thus, the locking arrangement is arranged to switch from the disengaged mode to the engaged mode in response to no power being provided to the motor <NUM>, <NUM>. The locking arrangement may thus function as an emergency brake which is actuated in response to the patient lift not being supplied with power. As soon as power is supplied to the motor <NUM>, <NUM> the locking arrangement switches from the engaged mode to the disengaged mode, which allows for normal operation of the patient lift.

The power source PS1, PS2 is further arranged to provide the control current Ic at a rush-level amplitude I<NUM> for a rush current period before providing the control current Ic at the hold-level amplitude I<NUM>. A magnitude of the rush-level amplitude I<NUM> being larger than a magnitude of the hold-level amplitude I<NUM>. One or more power source PS1, PS2 may be utilized. The power source may be any type of power source known to the skilled person.

The electrical connection will be further described with reference to <FIG>.

Referencing <FIG>, the locking device <NUM>, <NUM> may be a braking member arranged to selectively provide a braking torque to an output shaft <NUM>, <NUM> of the patient lift via the engagement member <NUM>, <NUM>. The output shaft <NUM>, <NUM> is connected to the motor <NUM>, <NUM>. The engagement member <NUM>, <NUM> may be a friction disc or friction wheel fixed to the output shaft <NUM>, <NUM>.

<FIG> depicts aspects of a locking arrangement according to an embodiment.

<FIG> depicts the locking arrangement mounted in the patient lifting device <NUM>. The motor <NUM> of the patient lift is connected to the load bearing member <NUM> via the transmission <NUM>. The lifting device <NUM> is mountable to the rail <NUM> by means of set wheels <NUM>.

<FIG> depicts a cross-section view of the self-locking arrangement. The locking arrangement comprises a casing <NUM>. The casing <NUM> is arranged to receive the engagement member <NUM>. In one embodiment, the engagement member <NUM> is a friction disc fixated to the output shaft <NUM>.

The shape memory alloy element <NUM> may be configured to contract in response to a current passing through it. The contracting of the shape memory alloy element <NUM> pulls the locking device <NUM> away from engagement with the engagement member <NUM>. Hence, the locking device <NUM> is arranged to disengage from the engagement member <NUM> by means of contraction of the shape memory alloy element <NUM> in response to a current exceeding the first configuration threshold current.

The casing <NUM> may be arranged to surround the output shaft <NUM>. The casing <NUM> may be arranged to be substantially coaxial to the output shaft <NUM>. The casing may be substantially cylindrical.

The locking device <NUM> may be arranged to be in braking contact with the engagement member <NUM> while the locking arrangement <NUM> operates in the engaged mode. The locking device <NUM> in the engaged position may form a tangent to said engagement member <NUM> and in the disengaged position is arranged to be in an offset angle to said engagement member <NUM>.

the shape metal alloy element <NUM> is arranged to allow for the locking device <NUM> to be in its engaged position, wherein the locking device <NUM> comes into braking contact with the engagement member <NUM> when the locking arrangement operates in the engaged mode. The shape metal alloy element <NUM> may thus be arranged to expand to allow for the locking device <NUM> to come into braking contact with the engagement member <NUM> in response to receiving a current subceeding the second threshold current.

As aforementioned the locking device <NUM> maybe biased. For example, by means of being spring-loaded. In one embodiment, the locking device <NUM> is in a resilient material. Said resilient material is biased to exert the locking force onto the engagement member <NUM> and actuating the locking device <NUM> to the engaged position when the locking arrangement operates in the engaged mode and the shape memory alloy element <NUM> is in the first configuration.

The resilient material thus causes the locking device <NUM> to come into braking contact with the engagement member <NUM> while the shape memory alloy element <NUM> is in the first configuration. Thus, the resilient material causes the locking device <NUM> to come into braking contact with the engagement member <NUM> when the shape memory alloy element <NUM> transitions from the second to the first configuration, i.e. expands.

When the shape memory alloy element <NUM> transitions from the first to the second configuration, the contraction of said shape memory alloy element <NUM> causes the locking device <NUM> to be moved out of braking contact with the engagement member <NUM>. Thereby said transition counteracts the biasing force provided by resilient material of the locking device <NUM>.

In one embodiment, the locking device <NUM> may comprise a friction pad arranged to come into braking contact with the engagement member <NUM>.

Further referencing <FIG>, a first end portion <NUM> of the locking device <NUM> is attached to an inner surface of the casing <NUM>. A second end portion, i.e. an opposite end portion, of the locking device <NUM> is attached to the shape memory alloy element <NUM>.

The locking device <NUM> is arranged to move between the engaged position and the disengaged position in an angle relative a tangent of the engagement member <NUM>. In the engaged position the locking device <NUM> is arranged to form a tangent to the engagement member coming into braking contact with said engagement member <NUM>. Accordingly, the angle in relation to said tangent may be zero. In the disengaged position, the locking device <NUM> is inclined relative said tangent to the engagement member <NUM> to not be in braking contact with said engagement member <NUM>.

In one embodiment, the first end portion <NUM> may be attached to the inner surface of the casing <NUM> by means of fastening element(s) <NUM>.

As further depicted in <FIG>, the shape memory alloy element <NUM> is arranged in a suspension arrangement <NUM>. The suspension arrangement <NUM> is mounted to the casing <NUM>. The shape memory alloy element has a first end <NUM> and a second, i.e. opposite, end <NUM>. Each of the first and second ends are mounted to the suspension arrangement <NUM> such that the shape memory alloy element <NUM> is arranged to at least partially surround the engagement member <NUM>. The shape memory alloy element <NUM> has an intermediate portion <NUM> arranged to extend inwards towards the engagement member <NUM>. The intermediate portion <NUM> is connected to the locking device <NUM>. Said intermediate portion <NUM> may thus be arranged to cause the movement of the locking device <NUM> between the engaged position and the disengaged position.

The intermediate portion <NUM> may be a bent portion of the shape memory alloy element <NUM> for example in the form a loop-shaped portion. The bent portion is arranged to extend inwardly towards the engagement member <NUM>. The inward end of the bent portion <NUM> may be attached to the locking device <NUM>. The end portion may be attached to the second end portion <NUM>.

The suspension arrangement <NUM> may comprise a first and second port <NUM> for electrically connecting the shape memory alloy element <NUM> to the power source. The ports may be connected to the power source via a first and second cable <NUM>, <NUM>. Referencing <FIG> and <FIG>, the casing <NUM> may be arranged to receive the motor <NUM> therein. Hence, the motor <NUM> of the patient lift may be mounted inside the casing of the self-locking arrangement. The motor <NUM> and the locking arrangement may thus constitute a single motor unit which includes the locking functionality. This enables a more efficient and less complex retro-fitting of the locking arrangement to existing patient lifts.

The engagement member <NUM> may be directly mounted to the output shaft <NUM>. The engagement member <NUM> may be in the form of a friction wheel or disc. The friction wheel may be fixed to the output shaft <NUM>. The friction disc may be coaxial with the output shaft <NUM>.

Referencing <FIG>, the suspension arrangement may comprise a guiding channel <NUM> for receiving the intermediate portion <NUM>. The guiding channel may extend along the suspension arrangement <NUM>. A portion of said guiding channel <NUM> extends inwardly towards the locking device <NUM>. The shape metal alloy element <NUM> extends along the walls of the guiding channel <NUM> inwards through the inwardly extending portion through an aperture allowing passage for said shape metal alloy element <NUM> towards the locking device <NUM>. The intermediate portion <NUM> of the shape metal alloy element <NUM> extends along opposite guiding surfaces of said guiding channel <NUM>, the intermediate portion being in contact with said guiding surfaces.

In one embodiment wherein the suspension arrangement <NUM> is mounted to the outside of the casing <NUM>, the casing may comprise a through-hole for allowing passage of the intermediate portion <NUM>.

The suspension arrangement <NUM> may arc shaped and arranged to be mounted to the outer cylindrical surface of the casing <NUM>.

<FIG> depicts aspects of another embodiment of the locking arrangement. The locking arrangement <NUM> is arranged to mechanically connect the motor <NUM> and a transmission unit <NUM> of the patient lift <NUM>. Thus, the locking arrangement may be arranged to transfer torque between the motor <NUM> and the transmission unit <NUM>. The transmission unit <NUM> is arranged to transfer torque from the motor <NUM> to the load bearing member of the patient lift.

More specifically, the locking arrangement <NUM> is arranged to selectively transfer torque between said motor <NUM> and transmission unit <NUM>. In the engaged mode, the locking arrangement is arranged to disable torque transfer between the motor <NUM> and the transmission unit <NUM>. In the disengaged mode, the locking arrangement is arranged to enable torque transfer between the motor <NUM> and the transmission unit <NUM>.

The patient lift may thus comprise the motor <NUM> and transmission unit <NUM>. Said motor and transmission unit may be comprised in the lifting device.

The locking device <NUM> may be arranged to move between the engaged position and the disengaged position in a direction substantially parallel to the output shaft <NUM>. Accordingly, the shape memory alloy element <NUM> is arranged to move the locking device <NUM> between the engaged position and the disengaged position in said direction substantially parallel to the output shaft <NUM>. In response to receiving a current exceeding the first threshold current, the shape memory alloy element <NUM> is arranged to contract to the second configuration causing the locking device <NUM> to move to the disengaged position in the direction substantially parallel to the output shaft <NUM>. In response to receiving a current subceeding the second threshold current, the shape memory alloy element <NUM> is arranged to expand to the first configuration causing the locking device to move to the engaged position in the direction the direction substantially parallel to the output shaft <NUM>.

The shape memory alloy element <NUM> may thus be arranged parallel to the output shaft <NUM>. In other words, the shape memory alloy element <NUM> may be arranged in a direction parallel to the output shaft <NUM>. Hence, the shape memory alloy element <NUM> may be further arranged to contact in a direction parallel to the output shaft <NUM>.

As depicted in <FIG>, the transmission unit <NUM> may be a worm gear transmission. The output shaft <NUM> may be connected to a worm gear shaft <NUM>. The output shaft may be interfacing with a worm gear wheel <NUM>. The worm gear wheel may be connected to a drum or winch for raising and lowering the patient support mounting device. The load bearing member, which may be a flexible member, may be wrapped around said drum or winch.

Referencing <FIG>, multiple views of the locking arrangement <NUM> are presented.

As most clearly depicted in <FIG>, a first portion <NUM> of the shape memory alloy element <NUM> may be attached to the locking device <NUM>. A second portion <NUM> of the shape memory alloy element <NUM> is fixed. In further detail, said first portion <NUM> may be attached to an actuated part <NUM> of the locking device <NUM> for moving said locking device <NUM>. Preferably said second portion <NUM> may be arranged to be fixated to the motor <NUM>, i.e. an encasing of the motor <NUM>.

In one embodiment, the locking arrangement may comprise a plurality of shape memory alloy elements <NUM>. The shape memory alloy elements <NUM> may extend parallel to each other and to the output shaft. Each shape memory alloy element may be arranged to be electrically connected to the power source.

In one embodiment, the shape memory alloy element <NUM> is in the form of a muscle wire. The first portion <NUM> of the muscle wire may be connected to the locking device <NUM>, i.e. the actuated part <NUM> of the locking device <NUM>, by means of being at least partially wrapped around one or more protrusions <NUM> of the locking device <NUM>, i.e. the actuated part <NUM>. The wrapping of the shape memory alloy element <NUM> may allow for a more robust connection between the shape metal alloy element and the locking device, capable of carrying a higher load. Thus, a safer and more reliable locking arrangement may be achieved.

According to above described embodiment, a first and second end of the shape memory alloy element <NUM> may be fixed, i.e. comprised in the second portion of the shape memory alloy element <NUM>. The first and second end may be arranged to be electrically connected to the power source. The first and second end are fix, preferably said first and second end are arranged to be fixated to the motor <NUM>, i.e. the encasing of the motor.

The locking arrangement may comprise a suspension console <NUM>. The second portion <NUM> of the shape memory alloy element <NUM> is attached to the suspension console. The suspension console may comprise one or more passages arranged to receive the shape memory alloy element <NUM>. Said passages are arranged to extend substantially parallel to the output shaft <NUM>. Preferably the suspension console <NUM> may comprise ports for receiving the first and second end of the shape memory alloy element <NUM> and electrically connect the first and second end of the shape memory alloy element <NUM> to the power source. The suspension console may be mounted to the motor <NUM>.

Further referencing <FIG>, the locking arrangement <NUM> may further comprise a housing <NUM> for receiving the output shaft <NUM> and the engagement member <NUM>. The locking arrangement <NUM> may further comprise at least one friction member <NUM>. The at least one friction member <NUM> may be arranged in said housing <NUM>. Said friction member <NUM> may be arranged to be in the proximity of the engagement member <NUM>. Accordingly, the locking device <NUM> in the engaged position may be arranged to cause the at least one friction member <NUM> and the engagement member <NUM> to come into contact thereby providing a braking torque to the output shaft <NUM>.

The locking device <NUM> may thus be arranged to in the engaged position push the engagement member <NUM> towards the friction member <NUM> and thereby provide the braking torque to the output shaft <NUM>. In one embodiment, the locking device <NUM> may be provided with a friction material and arranged to directly coming into contact with the engagement member <NUM> in the engaged position and thereby provide braking torque to the output shaft. The friction member <NUM> may be movably arranged in the casing.

The friction member <NUM> may be arranged in a recess of the housing, said recess enabling movement of the friction member <NUM> substantially parallel to the direction of the output shaft <NUM>.

In one embodiment, which is depicted in <FIG>, the locking device may be biased by means of further comprising a biasing part <NUM>. The biasing part <NUM> is spring loaded for exerting a locking force onto the engagement member <NUM>. The biasing part <NUM> is arranged to engage the actuated part <NUM> for actuating the locking device <NUM> to the engaged position when the locking arrangement operates in the engaged mode.

Further, the biasing part <NUM> may be arranged to engage the actuated part <NUM> upon the locking device moving from the engaged position towards the disengaged position.

The biasing part <NUM> may comprise at least one abutment heel <NUM> arranged to latch onto the actuated part <NUM>. The abutment heel <NUM> may provide a latching surface abutting to the actuated part <NUM>. Upon the locking device <NUM> moving from the engaged position towards the disengaged position, the biasing part <NUM> is arranged to be pushed away from the engagement member <NUM> by the actuated part <NUM>. Hence the shape metal alloy element <NUM> is arranged to push the biasing part <NUM> against the spring force exerted by said biasing part <NUM> upon said shape metal alloy element <NUM> transitioning from the first configuration to the second configuration.

Accordingly, the output shaft <NUM> may extend distally, whereby the first end of the shape metal alloy <NUM> may be a distal end of said shape metal alloy element <NUM>. The latching surface of the abutment heel <NUM> may be a distal surface of the biasing part <NUM>. Said latching surface is in abutment with a proximal surface of the actuated part <NUM>, whereby the actuated part is arranged to push the biasing part away, i.e. in a proximal direction, from the engagement member by the proximal surface of the actuated part255 pushing the distal surface <NUM> of the biasing part <NUM>.

When the shape memory alloy element <NUM> transitions from the second configuration to the first configuration the biasing part reaches its locking position, i.e. the biasing part locks the engagement member <NUM>. Thus, the expansion of the shape memory alloy element <NUM> causes the biasing part to push the locking device <NUM> to its engaged position, whereby the locking force is provided.

In an alternative embodiment the biasing part <NUM> may be directly connected to the actuated part <NUM>. Thus, the biasing part <NUM> may be attached to the actuated <NUM> for example by means of fastening elements such as screws.

Compared to the fixed attachment, the embodiment implementing the abutment heel allows for the actuated part <NUM> and the biasing part <NUM> to not be completely aligned and still provide the necessary locking force, whereby the locking arrangement is less susceptible to wear and functional issues due to inaccurate tolerances. Thus, a more stable and efficient locking arrangement may be achieved. As depicted in <FIG>, biasing part may comprise a pair of abutment heels. A first abutment heel may extend outwardly in a first direction, whereby a second abutment heel may extend outwardly in a second direction opposite to the first direction.

The housing <NUM> may comprise one or more locking device tracks <NUM> for supporting the locking device <NUM> along its movement between the engaged position and the disengaged position. The guided movement of the locking device provided by the locking device tracks allows for a more exact and reliable locking. Preferably said locking device tracks may be arranged to support the actuated part <NUM> of the locking device <NUM>.

The locking device tracks <NUM> may be arranged to extend substantially parallel to the output shaft <NUM>.

In one embodiment, the actuated part <NUM> is substantially U-shaped, whereby the housing <NUM> may comprise a first and second locking device tracks for receiving a first and second flange of said U-shaped actuated part <NUM>.

In one embodiment, the actuated part <NUM> is provided with one or more wheels <NUM> arranged to run in said one or more locking device tracks.

Further referencing <FIG>, the biasing part <NUM> may be connected to a fix surface by means of springs <NUM>. Said springs may be connected to the motor <NUM>, i.e. the encasing of the motor <NUM>. In one embodiment, the springs may extend substantially parallel to the output shaft <NUM>.

As depicted in <FIG>, the engagement member <NUM> may be as earlier described in the form of a friction disc or wheel fixated to the output shaft <NUM>. The engagement member <NUM> extends substantially orthogonal to the output shaft <NUM>.

The at least one friction member <NUM> may be a friction washer. Said at least one friction washer may be an annular friction washer with an aperture for receiving the output shaft <NUM>. The at least one friction member <NUM> is arranged to be coaxial to the engagement member <NUM> and the output shaft <NUM>. The at least one friction element <NUM> may be coaxial to the biasing part <NUM>. The biasing part may comprise an aperture for receiving the output shaft <NUM>, i.e. allowing passage of the output shaft <NUM>.

Each of the at least one friction member <NUM> may be movably arranged in the housing <NUM>. Each of the at least one friction member <NUM> may be arranged to move along a direction substantially parallel to the output shaft <NUM>. Hence, the biasing part <NUM> is arranged to push the at least one friction member <NUM> onto the engagement member <NUM> thereby locking the output shaft <NUM>.

Said at least one friction member <NUM> may be provided with at least one guide element <NUM>. The housing <NUM> may comprise a corresponding guide element <NUM>. The corresponding guide element <NUM> is arranged to guide the at least one friction member <NUM> in a direction substantially parallel to the output shaft <NUM>. As depicted in <FIG>, the at least one guide element may be a guiding protrusion, whereby the guide element <NUM> may be a guiding channel extending in the housing in a direction substantially parallel to the output shaft <NUM>. Said guiding channel is arranged to receive the guiding protrusion.

In one embodiment, the locking arrangement may comprise two friction members <NUM>. The friction members <NUM> may be arranged in the recess of the housing <NUM> at a distance from each other for receiving the engagement member <NUM> there between.

Further referencing <FIG>, the output shaft <NUM> extends distally, whereby the first friction member is a distal friction member and the second friction member is a proximal friction member. The biasing part <NUM> may be arranged to come into contact with the proximal friction member to push said proximal friction member to a proximal surface of the engagement member <NUM> when the locking device <NUM> is in the engaged position. Thus, the biasing part <NUM> pushes the proximal friction member towards the engagement member and the distal friction member thereby locking the engagement member <NUM>.

According to an aspect a patient lift comprising the locking arrangement according to any of the embodiments described above is provided. Hence, said patient lift comprises the lifting device <NUM>, <NUM>, <NUM> the patient support mounting device <NUM>, the load bearing member <NUM>. The patient support mounting device <NUM> is connected to the lifting device <NUM>, <NUM>, <NUM> via the load bearing member <NUM>. The patient lift further comprises the locking arrangement <NUM>, <NUM> as described with reference to any of the above embodiments.

<FIG> discloses embodiments of the circuitry for controlling the locking arrangement. With reference to <FIG>, the patient lift comprises the power source PS1, PS2. The power source PS1, PS2 is electrically connected to the motor <NUM>, <NUM> for driving said motor <NUM>, <NUM> by providing a drive current Id to the motor <NUM>, <NUM>. The first configuration threshold current may be associated with an operating current range of the motor <NUM>, <NUM>. The power source PS1, PS2 is also electrically connected to the shape memory alloy element <NUM>, <NUM> such that the power source PS1, PS2 controls the configuration of the shape memory alloy element <NUM>, <NUM> by supplying a control current Ic to the shape memory alloy element <NUM>, <NUM>. The power source PS1, PS2 is provided with a power supply <NUM> which is typically connected to mains power but may in all embodiments be arranged to comprise one or more batteries suitable to supply the drive current Id to the motor <NUM>, <NUM> and the control current Ic to the shape memory alloy element <NUM>, <NUM>. Said one or more batteries may be rechargeable batteries and the power source PS1, PS2 may be provided with means for charging the battery when the power source PS1, PS2 is connected to mains power. It should be emphasized that the power source PS1, PS2 is described as providing power to both the motor <NUM>, <NUM> and the shape memory alloy element <NUM>, <NUM> but it can very well be seen as two separate power sources PS1, PS2 that may or may not be in communication with each other.

In one embodiment of the power source PS1, PS2, as seen in <FIG>, the power source PS1, PS2 comprises the power supply <NUM> and a current generator <NUM>. As mentioned earlier, the power supply <NUM> may be a mains connection, battery or any other suitable means for providing power such as a low voltage DC or AC. The skilled person has knowledge of how to adapt different power supplies <NUM> to suit the power source PS1, PS2. The current generator <NUM> may be implemented in numerous different ways. The simplest implementation is by having the current generator connect the power source directly to the shape memory alloy element <NUM>, <NUM>. In such an implementation the control current Ic is only limited by the impedance of the shape memory alloy element <NUM>, <NUM> and the parasitic impedances of the circuitry connecting the powers source <NUM> to the shape memory alloy element <NUM>, <NUM>, this is assuming that the power source <NUM> itself is capable of supplying such currents. Such a current generator <NUM> may be problematic as it will consume a fair amount of power but it will be as quick as can be in transitioning the shape memory alloy element <NUM>, <NUM> from the first configuration, engaged mode of the locking arrangement <NUM>, <NUM>, to the second configuration, disengaged mode of the locking arrangement <NUM>, <NUM>. Another implementation of the current generator may be a series passive component such as a resistor connected in series between the power supply <NUM> and the shape memory alloy element <NUM>, <NUM>. The impedance of the passive component will determine the control current Ic provided to the shape memory alloy element <NUM>, <NUM> in accordance with the well-known Ohms law. Other implementations of the current generator <NUM> are suitable off the shelf components e.g. a transistor that is controlled from the power supply <NUM>, the NCP3066 buck/boost/inverting, Regulator, Switching, Constant Current generator from ON Semiconductor or any other current controlling means.

The shape memory alloy element <NUM>, <NUM> may not be instant in its response to the control current Ic. In fact, the shape memory alloy element <NUM>, <NUM> may be such that the time it takes to transition from the first configuration to the second configuration will depend on the control current Ic. An increased control current Ic will result in a decreased transition time from the first configuration to the second configuration of the shape memory alloy element <NUM>, <NUM>. The shape memory alloy element <NUM>, <NUM> typically changes configuration in response to reaching a certain temperature and the more current that is supplied to the shape memory alloy element <NUM>, <NUM> the faster it will heat. With continued reference to <FIG>, in order to make the transition from the engaged position to the disengaged positon as fast as possible without consuming too much current, a rush current source <NUM> may be comprised in the power source PS1, PS2. The rush current source <NUM> is arranged to provide a comparably high control current Ic for a limited period of time allowing the shape memory alloy element <NUM>, <NUM> to transition from the engaged position to the disengaged positon before the control current Ic is reduced to a comparably low level as provided by the current generator <NUM>. One advantage of such an arrangement is that the current consumption in steady state, disengaged position, can be reduced whilst keeping the time is takes to transition from the engaged position to the disengaged position as short as possible. This is provided for by the dual current sources where the rush current generator <NUM> provides the control current Ic for a comparably short period of time before control current Ic is provided solely by the current generator <NUM>. It should be mentioned that the both the rush current generator <NUM> and the current generator <NUM> can work in parallel during the transition from the engaged position to the disengaged position by the shape memory alloy element <NUM>, <NUM>.

In <FIG>, a graph of the amplitude of the control current Ic is shown as over time t as a dotted line in. Initially, the control current Ic is off and an at off-level amplitude Ioff. At a point in time, the shape memory alloy element <NUM>, <NUM> is to be transitioned from the engaged position to the disengaged positon. At that point the amplitude of the control current Ic is driven to a rush-level amplitude I<NUM> provided by the rush current source <NUM>. After a period of time, the rush current source <NUM> stops providing current and the control current Ic is supplied at a hold-level amplitude I<NUM> supplied by the current source <NUM>.

The rush current source <NUM> may be implemented in many ways. One embodiment of the rush current source <NUM> is shown by the simplified schematic in <FIG>. The control current Ic is in this embodiments enabled by the activation of a rush current transistor Q<NUM>. As power is supplied to the rush current generator by the power source <NUM>, the rush current transistor Q<NUM> will connect the power source <NUM> to the shape memory alloy element <NUM>, <NUM> via an optional rush current limiting element R330_lim. The rush current limiting element R330_lim will set the rush-level amplitude I<NUM> of the control current Ic. The control voltage of the current transistor Q<NUM> will gradually increase to the level of the power supply <NUM> as a rush timing capacitor C330_t is charged via a rush timing resistor R330_t. Once the rush timing capacitor C330_t is charged, the control voltage of the current transistor Q<NUM> will be substantially the same as a voltage provided by the power source <NUM> and the current transistor Q<NUM> will disconnect the power source <NUM> from the shape memory alloy element <NUM>, <NUM>. The duration the control current Ic is supplied at the rush-level amplitude I<NUM> by the rush current source <NUM> is consequently controlled by the dimensioning of the rush timing capacitor C330_t and the rush timing resistor R330_t. The dimensioning of RC-circuitry and calculation of the corresponding time constant is well known to the skilled person.

In one embodiment, not shown, of the power supply PS1, PS2, the power supply <NUM>, or a separate controller, provides a PWM signal to the current generator <NUM> and the current generator <NUM> provides a control current Ic that is proportional to a duty cycle of the PWM signal. Such an embodiment is beneficial as it allows the current generator to directly generate a control current Ic of a rush-level amplitude I<NUM> simply by providing it with a PWM signal of a comparably higher duty cycle compared to the duty cycle provided to the current generator when it is to provide a control current Ic of hold-level amplitude I<NUM>. The PWM signal can be controlled by software and the different amplitudes I<NUM>, I<NUM> of the control current Ic can be configurable. The duration the control current Ic is supplied at the rush-level amplitude I<NUM> may in some embodiments be controlled by a control loop where a configuration sensing signal indicates the current configuration of the shape memory alloy element <NUM>, <NUM>. When the shape memory alloy element <NUM>, <NUM> has transitioned to the second configuration, the PWM signal can change duty cycle such that a control current Ic of hold-level amplitude I<NUM> is provided to the shape memory alloy element <NUM>, <NUM>. In some embodiments the duty cycle of the PWM signal is controlled by the configuration sensing signal where the control current is kept as low as possible while keeping the shape memory alloy element <NUM>, <NUM> in the second configuration. This may be achieved by having the configuration sensing signal activate as soon as the shape memory alloy element <NUM>, <NUM> is not in its second configuration and having the active configuration sensing signal activate the current generator <NUM>. As soon as the shape memory alloy element <NUM>, <NUM> has returned to the second configuration the configuration sensing signal is deactivated and so is the current generator <NUM>. This process is repeated and the current configuration sensing signal will act as a PWM signal for the current generator <NUM>. The configuration sensing signal may be implemented in one of several different ways where the simplest example may be an electromechanical switch arranged to sense the configuration of the shape memory alloy element <NUM>, <NUM>. Another example may be to sense a force that the shape memory alloy element <NUM>, <NUM> exerts in a direction and use this to generate the configuration sensing signal. Hence, a force sensor may be operatively connected to the shape memory alloy element.

In one embodiment of the power source PS1, PS2, the duration the control current Ic is supplied at the rush-level amplitude I<NUM> is between <NUM> and <NUM>.

In one embodiment, the hold-level amplitude I<NUM> is at a level of the first configuration threshold.

In <FIG>, one embodiment of the power source PS2 is shown wherein an operation detection module <NUM> is arranged between the power supply <NUM> and the current generator <NUM> and the optional rush current generator <NUM>. This embodiment of the power source PS2 may be combined with any of the other embodiments and examples presented herein. The operation detection module <NUM> is a module arranged to detect if there is manual operation of the patient lift and in turn the locking arrangement <NUM>, <NUM>. This enables the shape memory alloy element <NUM>, <NUM> to maintain the locking device <NUM>, <NUM> in its engaged position even if there is power supplied to the power source PS2 and consequently power can be saved since the control current Ic can be turned off when no manual operation of the patient lift is performed. The operation detection module <NUM> will supply power to the generator(s) <NUM>, <NUM> of the power source PS2 only when it detects operation of the patient lift. The detection of operation may comprise detecting if e.g. switches operating the patient lift are pressed or a power switch is activated. Alternatively, or in addition, sensors arranged to detect motor activation may be utilised for detecting operation of the patient lift. This may be performed by for example detecting changes in any one of torque or RPM provided by the motor or voltage and current supplied to the motor. Once operation is detected, the operation detection module <NUM> supplies power to the generator(s) <NUM>, <NUM> and the control current Ic is provided to the shape memory alloy element <NUM>, <NUM> in any of the ways described earlier.

In one embodiment of the operation detection module, a timer is configured to be activated and reset each time an operation is detected and power is supplied to the generator(s) <NUM>, <NUM> until the timer has reached a predefined or configurable hold off value. Once the hold off value has been reached, the operation detection module <NUM> is configured to stop supplying power to the generator(s) <NUM>, <NUM> and consequently the control current Ic is turned off. Said timer may be operatively connected to the power supply and/or the separate controller. This is beneficial since in many cases more than one operation will be performed within a limited period of time, e.g. the patient is raised from a bed and shortly thereafter lowered into a wheelchair. Such frequent triggers of the shape memory alloy element <NUM>, <NUM> will introduce unwanted wear of the system and reduce the lifetime of the locking arrangement <NUM>, <NUM>.

It should be mentioned that the operation detection module <NUM> may be implemented in hardware, software or in a combination of them both. The operation detection module may also be considered as part of the current generator <NUM>, especially in embodiments where a controller is used in the power supply PS2.

In one embodiment of the operation detection module, the hold off value corresponds to a duration of between <NUM> and <NUM>. This will decrease the stress on the locking arrangement due to limiting rapid switching between the disengaged mode and the engaged mode.

Claim 1:
A locking arrangement (<NUM>, <NUM>) for a patient lift configured to selectively lock the vertical movement of a patient support mounting device (<NUM>) connected to a lifting device (<NUM>, <NUM>, <NUM>) of the patient lift via a load bearing member (<NUM>),
the locking arrangement comprising a shape memory alloy element (<NUM>, <NUM>) and a locking device (<NUM>, <NUM>), the shape memory alloy element (<NUM>, <NUM>) being connected to the locking device (<NUM>, <NUM>) and arranged to selectively actuate said locking device (<NUM>, <NUM>) to control a locking force on an engagement member (<NUM>, <NUM>) mechanically connected to a motor (<NUM>, <NUM>) and the load bearing member (<NUM>) of the patient lift, the motor (<NUM>, <NUM>) being arranged to raise and lower the patient support mounting device (<NUM>),
the locking arrangement being configured to operate in:
an engaged mode wherein the shape memory alloy element (<NUM>, <NUM>) is in a first configuration and the locking device (<NUM>, <NUM>) is in an engaged position in relation to the engagement member (<NUM>, <NUM>) for exerting a locking force on the engagement member (<NUM>, <NUM>) thereby preventing vertical movement of the patient support mounting device (<NUM>);
a disengaged mode wherein the shape memory alloy element (<NUM>, <NUM>) is in a second configuration actuating the locking device (<NUM>, <NUM>) to a disengaged position in relation to the engagement member (<NUM>, <NUM>) thereby enabling vertical movement of the patient support mounting device (<NUM>),
wherein the shape memory alloy element (<NUM>, <NUM>) is arranged to be electrically connected to at least one power source (PS1, PS2) for selectively transitioning between the first and second configuration.