WO2015024569A1

WO2015024569A1 - Patient lifter

Info

Publication number: WO2015024569A1
Application number: PCT/DK2014/000042
Authority: WO
Inventors: Troels Staugàrd JACOBSEN
Original assignee: Linak A/S
Priority date: 2013-08-22
Filing date: 2014-08-22
Publication date: 2015-02-26

Abstract

The present invention relates to a patient lifter with an electrically driven lifting unit, a lifting hook connected to the electrically driven lifting unit, a controller, a power supply and an operation device. The electrically driven lifting unit, the power supply and the operation device are connected to the controller. The electrically driven lifting unit can be activated by means of the operation device by which the lifting hook can be raised or lowered. The patient lifter comprises a load sensor for determining the size of the load attached to the lifting hook. The load sensor is connected to the controller, which contains a threshold value for the maximum allowed size of the load attached to the lifting hook. Furthermore, the controller is configured to prevent the electrically driven lifting unit from raising the lifting hook, if the size of the load attached to the lifting hook exceeds the threshold value for the maximum allowed size of the load attached to the patient lifter via the lifting hook.

Description

Patient lifter

The present invention relates to a patient lifter comprising an electrically driven lifting unit, a lifting hook connected to the electrically driven lifting unit, a controller, a power supply and an operation device. The electrically driven lifting unit, the power supply and the operation device are connected to the controller and the electrically driven lifting unit can be activated by means of the operation device by which the lifting hook can be raised or lowered. Patient lifters of the crane type and ceiling hoist systems are extensively used within the hospital and care sector, where they contribute to a patient handling, which is gentle to the patient and provides good working conditions for the nursing staff. Generally seen a patient lifter of the crane type consists of a frame equipped with drive wheels and a cantilever secured to one end of the frame, said cantilever can be turned about a horizontal axis. To the other end of the cantilever a lifting hook is secured. The cantilever can be raised and lowered by means of a linear actuator of which one end is secured to the frame and the other end is secured to the cantilever. The linear actuator is connected to a controller, an operation device and a battery. Thus, the linear actuator can be activated by means of the operation device.

The linear actuators, which are used for patient lifters of the crane type comprises a piston rod as described in e.g. WO 02/29284 A1 to Linak A/S. This type of linear actuator comprises a spindle with a spindle nut. The spindle is driven by a reversible electric motor through a transmission. When the spindle is driven the spindle nut is moved in an inwards or outwards direction depending on the direction of rotation of the electric motor. The linear actuator is a separate product, where the spindle, transmission and electric motor are incased in a housing. The housing typically consists of a motor housing and an outer tube. An inner tube is secured to the spindle nut. The inner tube is displaced in and out of the outer tube concurrently with the spindle nut being moved inwards and outwards on the spindle. In the opposite end of the spindle nut the inner tube is equipped with a front mounting. On the external side the motor housing comprises a rear mounting. The front mounting and rear mounting are used for securing the linear actuator to the structure or the product which should be adjusted. Generally seen, a patient lifter in the shape of a ceiling hoist system consists of a ceiling mounted rail system with a trolley, which enables horizontal displacement and an electrically driven lifting unit secured under the trolley or constructed as an integrated part of the trolley. Internally the lifting unit is equipped with an electrically driven winch for rolling a lifting strap up and down. A lifting harness, which is typically connected to the lifting strap via a lifting bracket, is placed around the person who should be lifted. The horizontal movement of the lifting unit in the rail system can be carried out by one or more motors or alternatively simply in that a nursing assistant pushes or pulls the lifting unit or the person, which/who should be moved. Ceiling hoist systems of this type are e.g. described in EP 1 385 462 B1 to V. Guldmann and WO 2005/074853 A1 to Invacare EC-Hong.

Due to the safety of the patient and the continuous reliability of the patient lifter and thus the safety of the patient it is important that the patient lifter does not lift a patient weighing more than what the patient lifter is dimensioned for. For that purpose there is a clear indication on the patient lifter of the maximum allowed load. In practice this load is a safety factor under the dimensioned load. The nursing staff is, however, not always aware of the weight of the patient. In that case the nursing staff will have to estimate whether or not the weight of the patient at hand exceeds the maximum allowed load. It is likewise plausible that the nursing staff is inattentive to the weight of the patient. In both cases it could have fatal consequences if the patient is lifted by the patient lifter. It is thus likely that the patient lifter will be damaged due to the heavy load. Should this happen in a patient lifter of the crane type the cantilever may be deformed, drive wheels may get stuck and the linear actuator be overloaded. The damage is not only due to the static forces on the patient lifter but just as much due to the dynamic overloads as a result of the cantilever being raised and lowered as well as moving the patient lifter. Similar damages could be present in a patient lifter in the shape of a ceiling hoist system, as the wheel of the trolley can get stuck and the electrically driven winch can be overloaded. The person weighing too much compared to the maximum allowed load or the dimensioned load can thus be put at risk in the patient lifter. Moreover, all future lifts conducted by the patient lifter will be subject to a risk of personal injury.

The purpose of the invention is thus to provide a patient lifter, which does not expose a patient to risks (of injury) while being lifted in the patient lifter.

This is achieved according to the invention in that the patient lifter comprises a load sensor for determining the size of the load attached to the lifting hook, where the load sensor is connected to the controller. This controller contains a threshold value for the maximum allowed size of the load attached to the lifting hook. The controller is configured to prevent the electrically driven lifting unit from raising the lifting hook, if the size of the load attached to the lifting hook exceeds the threshold value. Thus is ensured that the patient being lifted by the patient lifter can be lowered again, thus eliminating the risk of personal injury. Further, the patient lifter is not overloaded, thus ensuring the continuous functionality and reliability of the patient lifter.

In an embodiment of the patient lifter the controller will set off an alarm if the size of the load attached to the lifting hook exceeds the threshold value. Thus, the nursing staff is alerted that they are about to perform a lift with a risk of personal injury and overload of the patient lifter.

In another embodiment of the patient lifter the load sensor is secured to the lifting hook. Thus, a precise determination of the load secured to the lifting hook is achieved as the line of force will be approximately vertical. Further, it is easy to replace the load sensor. In an embodiment the load sensor is wireless connected to the controller, thus avoiding cabling. In addition the risk of damaging the cable is eliminated. The load sensor may be furnished with various sensors for determining the load attached to the lifting hook. Thus, the load sensor may comprise a force sensor, a strain gauge or a piezo element. All these types can very precisely determine the size of a load, e.g. as precisely as a tenth of a kilogram. Together with the position of the load sensor this contributes to a very precise determination of the size of the load attached to the lifting hook. Thus, the patient lifter can be used to its full potential i.e. completely up to the threshold value (the maximum allowed load) without compromising the risk for personal injury or overload of the patient lifter. In an embodiment the patient lifter is of the crane type where the electrically driven lifting unit comprises a frame with drive wheels and a cantilever of which one end is secured to the frame while the other end comprises the lifting hook. Moreover, the electrically driven lifting unit comprises a linear actuator of which one end is secured to the frame while the other end is secured to the cantilever. The linear actuator is connected to the controller and can be activated by means of the operation device, by which the cantilever can be raised or lowered. This embodiment of a patient lifter is particularly suitable for moving or transporting patients from one room to another.

The drive wheels on the patient lifter of the crane type can be equipped with an electrical brake connected to the controller. In another embodiment the controller is configured to activate the electrical brake on the drive wheels such that the drive wheels are braked if the size of the load attached to the lifting hook exceeds the threshold value. Thus, the staff operating the patient lifter will not be able to move the patient but be forced to immediately lower the patient. In yet another embodiment the electrically driven lifting unit is designed as a ceiling hoist system comprising a rail system and a trolley with wheels running on the rail system. The trolley comprises an electrically driven winch connected to the lifting hook. The electrically driven winch can move the lifting hook vertically in an upwards or downwards direction. Since ceiling hoist systems are integrated in a room at e.g. a hospital or nursing home and thus are cost-intensive in terms of investment, installation and repairs, it is especially important that this system is not overloaded.

Further characteristics of the invention will appear from the following embodiment of the invention, which in the following will be described more fully under reference to the accompanying drawing, in which:

Fig. 1 shows a patient lifter of the crane type,

Fig. 2 shows a linear actuator,

Fig. 3 shows the linear actuator from fig. 2, where one of the halves of the housing has been removed,

Fig. 4 shows a schematic view of the linear actuator, control box, operation device and load sensor,

Fig. 5 shows the schematic view from Fig. 4, where the operation device and the load sensor are wireless connected to the controller, and

Fig. 6 shows a schematic view of a patient lifter in the shape of a ceiling hoist system.

Fig. 1 shows a patient lifter of the crane type 1 comprising a frame 2 equipped with drive wheels 3. A cantilever 4 is secured to one end of the frame 2 and can be turned about a horizontal axis. A lifting hook 5 for lifting the patient is secured to the other end of the cantilever 4. The cantilever 4 may be raised and lowered by means of a linear actuator 6, of which one end is secured to the frame 2 and the other end is secured to the cantilever 4. The patient lifter 1 comprises a control box 7 secured to the frame. The control box 7 comprises a controller 8 and a power supply 9 in the shape of a battery. The patient lifter 1 further comprises an operation device 10 connected to the control box 7. The linear actuator 6 can by means of the operation device 10 be activated to raise or lower the cantilever 4. For lifting the patient a lifting yoke 11 is typically inserted in the lifting hook 5. Between the lifting hook 5 and the lifting yoke 11 on the patient lifter a load sensor 12 is inserted for determining the size of the load attached to the lifting hook 5 of the patient lifter. The load sensor 12, which is connected to the controller 8, is equipped with a force transducer 22 (see fig. 4) in the shape of a force sensor, a strain gauge or a piezo element. The load sensor 12 converts the size of the load on the lifting hook 5 into an electrical signal.

The patient lifter of the crane type 1 is dimensioned for a given load. Due to the safety of the patient and the continuous functionality as well as compliance with the norms applying, the allowed maximum load is a safety factor under the dimensioned load. The allowed maximum load can e.g. be two thirds of the dimensioned load, by which a dimensioned load of 300 kilograms equals an allowed maximum load of 200 kilograms.

The ratio between the dimensioned load and the allowed maximum load is utilized in the controller 8. I.e. the controller 8 comprises a threshold value for the size of the load attached to the patient lifter 1. This threshold value is an expression of the maximum load, which the patient lifter is allowed to lift. This is utilized in the controller 8 for comparing the signal from the load sensor 12 to the threshold value. Depending on the signal type of the load sensor 12 the controller 8 can compare the signal from the load sensor 12 directly to the threshold value or calculate a value which also is an expression of the load on the patient lifter 1 and thereafter compare this to the threshold value. Thus, the controller 8 comprises a processor, which can execute a computer code stored in the memory of the controller. The threshold value for the allowed maximum load is also stored in the memory. When the computer code in the memory is executed the processor compares the signal from the load sensor to the threshold value. If the signal from the load sensor 12 does not exceed the threshold value the controller will allow for normal operation of the patient lifter. If the signal from the load sensor on the other hand exceeds the threshold value the controller 8 will via the computer code executed in the processor generate one of the following actions:

- Set off an alarm, which may be auditory, visual and/or tactile,

- block an activation of the linear actuator 6 such that the cantilever 4 cannot be raised, only lowered.

- Activate an electrical braking of one or more of the drive wheels 3 of the patient lifter 1.

Fig. 2 shows a linear actuator 6 of the crane type comprising a piston rod as stated in the preamble. The piston rod is also known as an inner tube 13. The linear actuator 6 comprises an outer tube 14 and a housing 15. The latter is constituted by two halves (not referenced), having a joining surface coinciding with the longitudinal axis of the linear actuator. The linear actuator 6 further comprises a front mounting 16 at the outer end of the inner tube 13 and a rear mounting 17 secured to the housing 15.

Fig. 3 shows the linear actuator 6 of which one of the halves of the housing has been removed. The main components of the linear actuator 6 consists of a spindle unit consisting of a spindle 18 on which a spindle nut (not shown) is arranged. The spindle nut can be secured against rotation. The inner tube 13 is secured to the spindle nut and can thus be moved in and out of the outer tube 14 depending on the direction of rotation of the spindle 18. The spindle 18 is through a transmission driven by a reversible electric motor 19. Here, the transmission comprises a worm (not shown) arranged in continuation of the drive shaft of the electric motor and a worm wheel 20 secured to the spindle 18. A bearing 21 is moreover secured to the spindle. The bearing 21 can e.g. be a ball bearing or a roller bearing. The spindle 18 is self-locking, i.e. the pitch of the spindle 18 threads is of such a nature that the spindle 18 cannot be set into rotation by the load on the spindle nut. Fig. 4 shows a schematic view of the linear actuator 6, the control box 7, the operation device 10 and the load sensor 12. It can be seen that the control box 7 comprises the controller 8 and the power supply 9. The linear actuator 6, the operation device 10 and the load sensor 12 are connected to the controller 8. The load sensor 12 comprises a force transducer 22 for determining the size of the load attached to the lifting hook 5 of the patient lifter 1.

Fig. 5 shows a schematic view of the linear actuator 6, the control box 7, the operation device 10 and the load sensor 12 of Fig. 4, where the operation device 10 and the load sensor 12 are wireless connected to the controller 8.

Fig. 6 shows a schematic view of a section of a patient lifter in the shape of a ceiling hoist system 23, which generally seen consists of a rail system 24 and a trolley 25 with an electrically driven winch 26. The electrically driven winch 26 comprises a lifting strap 27 to which a lifting hook 28 is connected. A load sensor 29 is moreover secured between the lifting strap 27 and the lifting hook 28.

The ceiling hoist system 23 comprises a controller 30 and a power supply provided in the rail system 24. The ceiling hoist system 23 further comprises an operation device 31 connected to the controller. Via the operation device 31 the electrically driven winch 26 can be activated to move the lifting hook 28 vertically in an upwards or downwards direction. For lifting the patient a lifting yoke 32 is typically inserted in the lifting hook 28. The load sensor 29 connected to the controller 30 has a force transducer 33 in the shape of a force sensor, a strain gauge or a piezo element. The load sensor 29 converts the size of the load on the lifting hook 28 into an electrical signal. The ceiling hoist system 23 is dimensioned for a given load. Due to the safety of the patient and the continuous functionality of the ceiling hoist system as well as compliance with the norms applying, the allowed maximum load is a safety factor under the dimensioned load. The allowed maximum load can e.g. be two thirds of the dimensioned load, by which a dimensioned load of 300 kilograms equals an allowed maximum load of 200 kilograms.

The ratio between the dimensioned load and the allowed maximum load is utilized in the controller 30. I.e. the controller 30 comprises a threshold value for the size of the load attached to the lifting hook 28. This threshold value is an expression for the maximum load, which the ceiling hoist system is allowed to lift. This is utilized in the controller 30 for comparing the electrical signal from the load sensor 29 to the threshold value. Depending on the type of signal from the load sensor 29 the controller 30 can directly compare the signal from the load sensor to the threshold value or calculate a different value which is also an expression for the size of the load on the ceiling hoist system 23 and thereafter compare this to the threshold value. If the signal from the load sensor 29 exceeds the threshold value, the controller 30 can generate one or more of the following actions:

- Set off an alarm, which may be auditory, visual and/or tactile,

- Prevent the electrically driven winch from mowing the lifting hook in the upwards direction, but allow for the lifting hook to be moved in a downwards direction,

- Activate an electrical braking of one or more of the wheels of the trolley.

Claims

Patent claims:

1. A patient lifter comprising:

an electrically driven lifting unit (1,23),

a lifting hook (5,28) connected to the electrically driven lifting unit (1 ,23), a controller (8,30),

a power supply (9),

an operation device (10,31),

where the electrically driven lifting unit (1,23), the power supply (9) and the operation device (10,31) are connected to the controller (8,30) and where the electrically driven lifting unit (1,23) can be activated by means of the operation device (10,31) by which the lifting hook (5,28) can be raised or lowered,

characterized in

that the patient lifter comprises a load sensor (12,29) for determining the size of the load attached to the lifting hook (5,28) and where the load sensor (12,29) is connected to the controller (8,30) and where the controller (8,30) contains a threshold value for the maximum allowed size of the load attached to the patient lifter via the lifting hook (5,28) and where the controller (8,30) is configured to prevent the electrically driven lifting unit (1,23) from raising the lifting hook (5,28), if the size of the load attached to the lifting hook (5,28) exceeds the threshold value for the maximum allowed size of the load attached to the patient lifter via the lifting hook (5,28).

2. A patient lifter according to claim ^ c h a ra c te r i z e d in that the controller (8,30) is configured to set off an alarm if the size of the load attached to the lifting hook (5,28) is greater than the threshold value.

3. A patient lifter according to one or more of the claims 1-2, character! zed in that the load sensor (12,29) is secured to the lifting hook (5,28).

4. A patient lifter according to one or more of the claims 1-3, character! z e d in that the load sensor (12,29) is wireless connected to the controller (8,30).

5. A patient lifter according to one or more of the claims 1-4, c h a r a c t e r i z e d in that the operation device (10,31) is wireless connected to the controller (8,30).

6. A patient lifter according to one or more of the claims 1-5, c h a r a c t e r i z e d in that the load sensor (12,29) comprises a force sensor.

7. A patient lifter according to one or more of the claims 1-5, character! z e d in that the load sensor (12,29) comprises a strain gauge.

8. A patient lifter according to one or more of the claims 1-5, character! z e d in that the load sensor (12,29) comprises a piezo element.

9. A patient lifter according to one or more of the claims 1-8, where the electrically driven lifting unit (1) comprises:

a frame (2) equipped with drive wheels (3),

a cantilever (4), where one end is secured to the frame (2) and the other end comprises the lifting hook (5),

a linear actuator (6), where one end is secured to the frame (2) and the other end is secured to the cantilever (4),

where the linear actuator (6) is connected to the controller (8) and where the linear actuator (6) can be activated by means of the operation device

(10), by which the cantilever (4) can be raised or lowered. 0. A patient lifter according to claim 9characterizedin that the drive wheels (3) comprise an electrical brake connected to the controller (8) and where the controller (8) is configured to activate the electrical brake on the drive wheels (3) for braking the drive wheels (3) if the size of the load attached to the lifting hook (5) exceeds the threshold value.

11. A patient lifter according to one or more of the claims 1-8, where the electrically driven lifting unit (23) comprises:

a rail system (24),

a wheeled trolley (25), which can run on the rail system,

where the trolley (25) comprises an electrically driven winch (26) connected to the lifting hook (28) and where the electrically driven winch (26) can move the lifting hook (28) vertically in an upwards or downwards direction.