WO2012055407A1

WO2012055407A1 - Drive system for hospital bed, and hospital bed

Info

Publication number: WO2012055407A1
Application number: PCT/DK2011/000119
Authority: WO
Inventors: Asger Gramkow; Steffen Sundbaek
Original assignee: Hecare Systems Aps
Priority date: 2010-10-27
Filing date: 2011-10-26
Publication date: 2012-05-03

Abstract

The present invention concerns a drive system (2) for a hospital bed (4); which drive system, in the intended orientation in use, comprises a frame (6); which frame comprises at least four wheels (8); where four of the at least four wheels are placed on the frame in an arrangement that defines a geometric quadrangle; where at least two of these four wheels are active wheels (8a) that comprise the means of propulsion (10) that are designed to be able to transfer, independently, energy from an energy source (12) to a rotating movement of the wheel; where each of the active wheels (8a) is fitted with a rotation arrangement (14) to set the angle of rotation of the wheel; characterised in that two of the at least two active wheels are placed diagonally in the geometric quadrangle. The drive system in accordance with the present invention provides improved manoeuvring properties for a bed such as a hospital bed.

Description

Drive system for hospital bed, and hospital bed Technical field The present invention concerns a drive system for a bed, and a bed comprising such a drive system.

Background to the invention In hospitals there is a daily need to move bedbound patients between the various wards and departments. Porters are used for this purpose. Their task is to move these bedbound patients.

Daily shifts involving moving such bedbound patients places great burdens on porters' physical health. This burden is not reduced by the fact that patients are, on average, becoming heavier and heavier. At the same time, more and more equipment and electronics are being fitted to hospital beds, which contributes to a total overall increase in the weight of the bed. The actual manoeuvring of the bed in the room in order to place the bed in the desired position after transport also contributes to the extent of the burden on the porter, because the static friction and rolling resistance of the wheels is greater than the dynamic resistance. This means that the porter has to use relatively high levels of exertion when moving a hospital bed from a stationary position.

To relieve the physical load on the porter, motorised beds have been introduced in some locations. An electric motor permits them to be moved around with a significant reduction in the load on the porter.

Such motorised beds comprise the usual 4 wheels, located at the corners of the bed, plus a fifth, motorised wheel which is installed centrally beneath the bed. Examples of these motorised beds include the brands HillRom, Intellidrive Power Transport - Stryker, Retractable Fifth Wheel.

The fifth, motorised wheel in this type of bed can be rotated to the desired direction of travel and the four other wheels, which are passive wheels, set themselves, via a rotating bearing, to the direction of travel dictated by the fifth wheel.

In general, this type of motorised bed thus solves the problem of the physical burden on the porter fairly satisfactorily manner, as no great physical effort is needed to move the bed.

However, there are certain problems with this type of motorised bed.

Firstly, in hospitals it is common to use patient lifts when a patient needs to be moved. Such lifts frequently comprise a support structure and a vertically oriented arm which extends from the support structure to an upper part, where a lift mechanism is arranged. The support structure is pushed in under the bed in which the patient who is to be lifted is lying. The patient is then attached to the lift mechanism and can be moved.

The installation of a fifth, drive wheel beneath the hospital bed may make it difficult to position the support structure of the lift under the bed in the desired, optimum position as this fifth wheel has a not insubstantial physical extent. This may make it difficult to lift the patient.

Secondly, transporting such a motorised bed over a ramp will entail problems involving interruption of the contact between the fifth wheel and the floor, for example when the bed's two passive, front wheels are lifted a little as they move up onto the first part of the ramp, as this lifting of the bed's front wheels entails a corresponding, although less extensive, lifting of the fifth, motorised wheel, as a result of which the fifth wheel loses contact with the floor. Propulsion is then lost for a while.

Although this type of motorised bed solves certain health-related problems for the care staff, there still remains, therefore, a need for an improved motorised hospital bed.

Brief description of the invention These problems are solved in accordance with a first and a second aspect of the present invention. The first aspect of the present invention concerns a drive system for a hospital bed; which drive system, in the intended orientation in use, comprises a frame; which frame comprises at least four wheels; where four of the at least four wheels are placed on the frame in an arrangement that defines a geometric quadrangle; wherein at least two of said four wheels are active wheels that comprise the means of propulsion that are designed to be able to transfer, independently, energy from an energy source to a rotating movement of the wheel; wherein each of the active wheels is fitted with a rotation arrangement to set the angle of rotation of the wheel, and wherein two of the at least two active wheels are placed diagonally in the geometric quadrangle. A second aspect of the present invention concerns a hospital bed comprising a system in accordance with the first aspect of the present invention.

Using the drive system and hospital bed according to the present invention, it is possible to achieve improved transport and manoeuvring of hospital beds with a significant reduction in the load on the care staff as a consequence.

These improvements consist e.g. in that, as the drive system comprises at least four wheels, two of which are located in the corners and are active wheels that comprise the means of propulsion to enable them to rotate and which can also be set in an angle of rotation, the drive system can move in different directions preferably all directions. Independently of this, the drive system can be rotated about a vertical axis of rotation. As the active wheels are not placed beneath the centre of the drive system and thus beneath the centre of the bed, the known problems associated with the use of patient lifts are avoided. At the same time, the problems incurred by other systems' drive wheel's lack of contact with the floor when the drive system moves over a ramp are avoided, as the active, driving wheels in the drive system according to the present invention are placed diagonally at the corners of a quadrangle. Manoeuvring the drive system in accordance with the first aspect of the present invention is made possible e.g. by i) being able to set one or more of the active wheels to a specific angle of rotation, independently of each other; ii) being able to set the direction of rotation of one or more of the active wheels, independently of each other; iii) being able to set the speed of rotation of one or more of the active wheels, independently of each other.

These settings, and combinations of these settings, make it possible to provide transversal and rotating movements of the drive system in accordance with the first aspect of the present invention. Figures

Fig. 1 shows a preferred embodiment of a drive system for a hospital bed according to the present invention.

Fig. 2 shows a diagram that illustrates the control principle of a drive system for an embodiment according to the present invention in which the drive system has two active wheels. Fig. 3 shows a diagram that illustrates the control principle of a drive system for an alternative embodiment according to the present invention, in which the drive system has two active wheels.

Fig. 4 shows a diagram that illustrates the control principle of a drive system for an embodiment according to the present invention in which the drive system has four active wheels.

Figs. 5a -5i illustrate different combinations of the drive system's active wheels' angle of rotation, direction of rotation and speed of rotation, and the consequence of this is expressed in the consequent direction and/or direction of rotation of the drive system.

Detailed description of the invention As indicated above, the present invention concerns, in its first aspect, a drive system 2 for a hospital bed; which drive system, in the intended orientation in use, comprises a frame 6; which frame comprises at least four wheels 8; wherein four of the at least four wheels are located on the frame in an arrangement that defines a geometric quadrangle; wherein at least two of these four wheels are active wheels 8a that comprise means of propulsion 10 that are designed to be able to transfer, independently, energy from an energy source 12 to a rotating movement of the wheel; wherein each of the active wheels 8a is fitted with a rotation arrangement 14 to set the angle of rotation of the wheel, and wherein the two of the at least two active wheels are placed diagonally in the geometric quadrangle.

The drive system in accordance with the first aspect of the present invention is designed for use with a bed, such as a hospital bed, where there is a need for superior manoeuvring abilities.

The feature that the drive system comprises at least four wheels 8, where four of the at least four wheels 8 are placed on the frame in an arrangement that defines a geometric quadrangle and where at least two of the wheels are active wheels 8a that comprise the means of propulsion 10 that are designed to be able to transfer, independently, energy from an energy source 12 to a rotating movement of the wheel, brings about such superior manoeuvring abilities.

Detailed description of preferred embodiments

The drive system preferably comprises a frame 6. The frame 6 comprises at least four wheels 8, and four of these at least four wheels are arranged in a geometric quadrangle. In a preferred embodiment of the first aspect of the present invention, one or more of the active wheels' means of propulsion comprises one or more electric motors 16, and the drive system also comprises an energy source 18 in the form of a battery or an accumulator for supplying electric power to the system.

Such a type of means of propulsion and energy supply is a simple, convenient way to bring about propulsion. This type of drive is also low-noise and does not emit polluting emissions during operation.

The means of propulsion 10 may thus be considered as constituting drive means for driving the drive system over a surface such as a floor.

In an embodiment of the first aspect of the present invention, the drive system comprises a steering unit 20, a control unit 22, means of communication 24 for transferring signals from the steering unit to the control unit and means of communication 26 for transferring impulses from the control unit 22 to the rotation arrangement 14 belonging to two or more of the at least two active wheels 8a;

where the steering unit 20 is designed to be able to receive input from an operator; where the steering unit is designed to convert the input received into electrical signals; where the control unit 22 is designed to be able to receive the electrical signals from the steering unit; where the control unit 22 is designed to be able to convert the electrical signals received from the steering unit 20 into impulses to control the rotation arrangement belonging to two or more of the two or more active wheels 8a; where the steering unit 20 is designed to receive inputs which, via the control unit 22, cause the active wheels 8a to rotate in one of two opposite directions of rotation; and where the steering unit 20 is designed to receive input which, via the control unit 22, cause the active wheels 8a to be set to a specific angle of rotation. Providing the drive system with such a steering unit and control unit and means of communication makes it possible for an operator of the drive system, such as a porter in a hospital, to supply the steering unit with input, where this input represents a desired motion characteristic for the drive system. By means of the steering system, this information, which represents the desired immediate motion characteristic, is communicated via the means of communication 24 to the control unit, which then converts these steering signals into impulses that are supplied to the rotation arrangement belonging to one or more of the two or more active wheels and/or to one or more of the active wheels' means of propulsion. The result is intuitive steering of the drive system as the steering unit can convert input that represents a desired immediate motion characteristic for the drive system into the signals that are to be supplied to the rotation arrangement and/or the means of propulsion for one or more of the active wheels so that this desired motion characteristic is achieved. It is preferable for the drive system in accordance with the first aspect of the present invention to also comprise a system which, via the control unit, allows the angle of rotation to be set and/or locked for one or more of the active wheels in one or more predefined directions. For example chosen from the following: 0° in relation to a longitudinal axis of the frame; 30 - 60°, such as roughly 45° for one side in relation to a longitudinal axis of the frame; 30 - 60°, such as roughly 45° for another side in relation to a longitudinal axis of the frame; 75 - 105°, such as roughly 90° for the one side in relation to a longitudinal axis of the frame; 75 - 105°, such as roughly 90° for another side in relation to a longitudinal axis of the frame, where this setting and/or locking of the angle of rotation for one or more of the active wheels takes place mutually independently or mutually dependently.

This embodiment may e.g. have the advantage that, when a hospital bed is moved into the room in which the bed is to be placed at a few metres' distance from the desired final location, an operator can activate a mechanism that offers this feature, whereby the wheels are set and/or locked to a specific angle of rotation in relation to a longitudinal axis of the frame 6. The operator can then activate the means of propulsion for the active wheels, whereby the drive system and thus the hospital bed can be parked via oblique motion, for example sideways motion in the case in which all active wheels are set to an angle of rotation of 90° in relation to a longitudinal axis of the frame of the drive system.

In further embodiments, the system according to the invention may be able to adjust the active wheels between a plurality of positions substantially step-less dependent on the input from e.g. the steering unit. In a preferred embodiment of the drive system in accordance with the first aspect of the present invention, the steering unit 20 comprises a joystick and/or handlebars or a handle 30; where the joystick or handlebars or handle 30, with the steering unit 20, is/are designed, by pushing or pulling, via the control unit 22, to enable rotation of one or more of the active wheels 8a in one of two directions of rotation; and/or where the joystick or handlebars or handle 30, with the steering unit 20, is/are designed, via the control unit 22, to set the speed of rotation of one or more of the active wheels 8a; and/or where the joystick or handlebars or handle 30, with the steering unit 20, is/are designed, by pushing or pulling, via the control unit 22, to make it possible to set the angle of rotation of one or more of the active wheels 8a; where the rotation of one or more of the active wheels 8a in one of two directions of rotation and/or where the setting of the speed of rotation of one or more of the active wheels 8a; and/or where the setting of the angle of rotation of one or more of the active wheels 8a take(s) place mutually independently or mutually dependency. In an additional preferred version of this embodiment, the steering unit 20 comprises handlebars or a handle 30, where the handlebars or handle, with the steering unit 20, are designed, by the application of a larger or smaller push/pull to one side 30a of the handlebars/handle in relation to the other side 30b of the handlebars/handle, via the control unit 22, to make possible a different speed of rotation and/or direction of rotation of one or more of the two or more active wheels 8a and/or make it possible to set the angle of rotation of one or more of the active wheels 8a, whereby, with different pushes or pulls on either side 30a, 30b of the handlebars or handle, it is possible to determine the character of the motion of the drive system.

Providing the steering unit with a joystick and/or handlebars or a handle 30 of the above types makes it possible, in a particularly favourable manner, to achieve intuitive steering of the drive system in accordance with the first aspect of the present invention and thus of the hospital bed in accordance with the second aspect of the present invention.

Such intuitive steering is desirable as this type of steering guarantees safe, proper manoeuvring of the drive system and thus the bed.

In a preferred embodiment of the drive system in accordance with the first aspect of the present invention, the steering unit is fitted on the end of the frame 6, which corresponds to the location of the head or foot of the hospital bed.

It has proved practical to fit the steering unit, or at least that part of the steering unit that comprises the means with which the operator supplies input for the desired motion characteristic, on the end of the frame 6, which corresponds to the location of the head or foot of the hospital bed, as it is usual during transport for the drive system to be made to move in a longitudinal direction of the drive system and thus the bed.

In an embodiment of the drive system in accordance with the first aspect of the present invention, each of the wheels 8 that are not active wheels 8a are passive wheels 8b, each of which is suspended in a mainly vertically oriented rotating bearing 32, whereby each of the passive wheels 8b can rotate freely about a mainly vertical axis 34 and thus adapt to the direction of travel defined by the active wheels 8a. Within the sense of the present invention, the expression 'passive wheels' should be understood to mean wheels that do not comprise, or are not connected to, active means of propulsion to drive them and do not comprise, or are not connected to, a rotation arrangement to set an angle of rotation of the wheel.

The result is that the passive wheels just adapt to the direction of travel defined by the active wheels. The passive wheels have the character of support wheels here. They serve solely to contribute to maintaining the stability of the drive system. It may be advantageous for the passive wheels to be suspended on the frame 6 via a hoist system that makes it possible to raise and lower the passive wheels in relation to the frame 6.

It may also be advantageous for the passive wheels to be suspended on the frame 6 via a spring-mounted system to ensure that the passive wheels always support the bed.

In a preferred version of this embodiment, the drive system 2 comprises active wheels 8a and two passive wheels 8b.

Using only two active wheels offers price advantages as this embodiment is the embodiment that permits improved manoeuvrability of the drive system in accordance with the present invention with the least possible number of active wheels.

In another preferred embodiment, the drive system comprises four active wheels 8a.

This embodiment offers the advantage that there are more active wheels that can share the load to which the active wheels are subjected. Thus each active wheel will have less load, which will ultimately entail a longer service life for each active wheel, including its means of propulsion. Moreover, in this embodiment, the drive system will not necessarily become unable to function if one wheel or its means of propulsion cease to be active on account of a defect, as the other three wheels can function satisfactorily without an active fourth wheel. In a second aspect, the present invention concerns a hospital bed 4 comprising a drive system 2 in accordance with any of claims 1-9.

The hospital bed in accordance with the second aspect of the invention comprises, at minimum, a drive system according to the first aspect of the invention. Moreover, the hospital bed will typically also comprise a bed frame, various fittings for attachment of the necessary hospital equipment and a mattress.

Preferred embodiments of the present invention will now be described in further detail with reference to the figures.

Fig. 1 shows a preferred embodiment of the invention in accordance with the first aspect. Fig. 1 shows a drive system for a hospital bed. The drive system comprises a frame 6, which has two active wheels 8a and two passive wheels 8b fitted to it. The active wheels comprise, integrated in the wheels, a means of propulsion 10 in the form of an electric motor 16. Alternatively, the wheels and the means of propulsion may be non-integrated. The angle of rotation of the active wheels in relation to a longitudinal axis of the drive system can be adjusted by means of rotation

arrangements 14 that are shown in Figure 1 as an electric actuator. The passive wheels are suspended in a freely rotating bearing 32, in which connection the wheels 8b can rotate freely about a mainly vertical axis 34.

Alternatively to a total number of wheels of four, the drive system in accordance with the present invention may comprise six or eight wheels or any other number of wheels greater than four. It is preferable for the wheels to be placed near the outer periphery of the frame. Fig. 1 also shows that the drive system is provided with a battery 18, a control unit 22 and a steering unit 20. The steering unit 20 is designed to be able to receive inputs from an operator. These inputs represent instructions for a desired motion

characteristic. For example, a desired motion characteristic may be parallel displacement of the drive system, for example straight travel in a forward direction, straight travel in a backward direction, sideways travel in one of two directions, or a desired motion characteristic may also be rotation in one of two directions or combined parallel displacement and rotation of the drive system. The desired motion characteristic is achieved with the embodiment in fig. 1 by means of acting on handlebars or a handle 30 with a left side 30a and a right side 30b. By pressing uniformly on the left and right sides of the handlebars or handle 30, forward motion without turning or rotation can be achieved. By pulling uniformly on the left and right sides of the handlebars or handle 30, backward motion without turning or rotation can be achieved. By pressing non-uniformly on the left and right sides of the handlebars or handle 30, forward motion with turning or rotation can be achieved. By pulling non-uniformly on the left and right sides of the handlebars or handle 30, backward motion with turning or rotation can be achieved. Moreover, the steering device may be designed so that the force with which the operator presses or pulls on one or the other side of the handlebars is converted into a correspondingly high or low speed of rotation of the wheel or wheels activated by such a push or pull. These embodiments produce very intuitive steering that contributes to safe, controlled steering of the drive system of the bed during transport and manoeuvring.

Alternatively (or additionally) to handlebars or a handle, the steering unit could be provided with a joystick. The steering unit may also comprise a number of control buttons. These may, for example, be used to set and/or lock a fixed angle of rotation for the active wheels, for example in a 90-degree setting for sideways motion. The steering unit may also comprise a display that gives the operator information about the state of the drive system, for example battery capacity, presence of any defects, the current angle of rotation of the active wheels, etc.

When the steering unit 20 receives inputs from an operator regarding instructions for a desired motion characteristic, the signals are transferred from the steering unit to the control unit 22 via means of communication/communication means 24. In the control unit, the signals received from the steering unit are converted into impulses which are transferred via means of communication/communication means 26 to the active wheels 8 or, more precisely, to their means of propulsion in accordance with a predetermined program in the steering unit and/or the control unit. The control unit and the steering unit may be integrated or also separate from each other as shown in fig. 1. The means of communication 24 and 26 are not shown in fig. 1.

Figures 2, 3 and 4 illustrate the steering diagram for the drive system in accordance with the first aspect of the present invention. Fig. 2 shows as steering diagram for a drive system comprising two active wheels 8a and two passive wheels 8b. Inputs from an operator are received by the steering unit 20. This steering unit generates signals which are transferred via means of communication 24 to the control unit 22. Both the steering unit 20 and the control unit 22 are supplied with voltage from a power supply 18 via supply cables 19. In the control unit 22, impulses are generated which are transferred via means of communication 26 to the active wheels 8a or, more precisely, to the means of propulsion of the active wheels.

In the system in fig. 2, the impulses that are transferred to the means of propulsion of the active wheels comprise impulses that are supplied directly to the means of propulsion and have a voltage that is adapted to the means of propulsion. Fig. 3 shows an alternative embodiment in which the impulses that are transferred to the means of propulsion of the active wheels are pure signal impulses at a much lower voltage. These signal impulses are supplied to a relay that, using a supply voltage supplied by the cables 19, supplies the correct/rated voltage to the means of propulsion of the active wheels.

Fig. 4 shows an alternative version of the embodiment shown in fig. 2 in which the drive system comprises four active wheels.

The means of communication 24 and 26 are usually just electric cables but other types of means of communication, such as wireless means of communication, may also be relevant. Figs. 5a-5i illustrate various motion characteristics that are possible with the drive system in accordance with the present invention. Figs. 5a-5i indicate the active wheels 8a with a rectangle and the passive wheels 8b are indicated with a circle. Arrows with the same size on the active wheels indicate the same speed of rotation for the wheels. Arrows with different sizes on the active wheels indicate different speeds of rotation for the wheels. Arrows with different directions on the active wheels indicate different directions of rotation for the wheels. In figs. 5a-5i, a straight arrow placed centrally in the frame represents parallel displacement of the drive system in accordance with the present invention, whereas a curved arrow represents rotation of the drive system.

For a drive system with two active wheels and two passive wheels, it can be seen that rotation of two active wheels in an angle of rotation so that each of the wheels defines a plane, where these two planes do not coincide, will result in a situation in which rotation of the drive system can be achieved by having the active wheels rotate at different speeds and/or in different directions of rotation. It can also be seen that if rotation of two active wheels is set at an angle of rotation so that each of the wheels defines a plane, where these two planes coincide, it is not possible in this situation to achieve rotation of the drive system but only parallel displacement of the drive system.

The drive system in accordance with the first aspect of the present invention may suitably be built of components that are, in themselves, of the prior art and are commercially available. Such components include active wheels in the form of HUB motors from the producer Golden Motor Technology Co., LDT, 608 Suncity

Business Center, 367 Tong Jiang Zhong Road, China, actuators, for example model LL 1000 from the producer MBL A/S, Ballevej 1 C, 8600 Silkeborg, Denmark, actuators, for example DB 500 and 303x00 from the producer Linak A/S,

Monstedsvej 9, 8600 Silkeborg, Denmark, and steering systems, for example VR2 and I-drive from the producer PG Drives Technology LTD, 10 Airspeed Road, Christchurch BH23 4HD, United Kingdom.

A specialist in this field will, on the basis of the information provided in this application, be able to assemble and build a drive system in accordance with the first aspect of the invention and he will be able to produce a bed such as a hospital bed in accordance with the second aspect of the invention on the basis of this drive system.

Although the present invention in its first and second aspects is called a drive system for a hospital bed and a hospital bed comprising such a drive system, it should be understood that these aspects also comprise drive systems and beds for any other purpose. The invention is thus not limited to hospital use, although the first and second aspects of the invention may be used for bedbound patients, for example in a hospital. Figure references

2. Drive system

6. Frame

8. Wheels

8a Active wheels

8b. Passive wheels

10. Means of propulsion

12. Energy source

14. Rotation arrangement

16. Electric motor

18. Battery or accumulator

20. Steering unit

22. Control unit

24. First means of communication

26. Second means of communication

30. Handlebars/handle

30a. One side of handlebars/handle

30b. Other side of handlebars/handle 32. Rotating bearing

34. A mainly vertically oriented axis

Claims

1. A drive system (2) for a hospital bed; which drive system, in the intended orientation in use, comprises a frame (6), which frame comprises at least four wheels (8), wherein four of the at least four wheels are placed on the frame in an arrangement that defines a geometric quadrangle, wherein at least two of said four wheels are active wheels (8a) that comprise the means of propulsion (10) that are designed to be able to transfer, independently, energy from an energy source (12) to a rotating movement of the wheel, wherein each of the active wheels (8a) is fitted with a rotation arrangement (14) to set the angle of rotation of the wheel, and wherein two of the at least two active wheels are placed diagonally in the geometric quadrangle.

2. A drive system according to claim 1, wherein said means of propulsion of said active wheels comprise one or more electric motors (16) and where the drive system comprises an energy source (18) in the form of a battery or an accumulator.

3. A drive system according to claim 1 or 2, comprising a steering unit (20), a control unit (22), means of communication (24) for transferring signals from the steering unit (20) to the control unit (22), and means of communication (26) for transferring impulses from the control unit (22) to the rotation arrangement (14) of two or more of the at least two active wheels (8a), wherein the steering unit (20) is designed to be able to receive input from an operator; where the steering unit is designed to convert the input received into electrical signals; where the control unit (22) is designed to be able to receive the electrical signals from the steering unit, wherein the control unit (22) is designed to be able to convert the electrical signals received from the steering unit (20) into impulses to control the rotation arrangement belonging to two or more of the two or more active wheels (8a), wherein the steering unit (20) is designed to receive input that, via the control unit (22), causes the active wheels (8a) to rotate in one of two opposite directions of rotation, and wherein the steering unit (20) is designed to receive input that, via the control unit (22), causes the active wheels (8a) to be set to a specific angle of rotation.

4. A drive system according to claim 3 where the steering unit (20) comprises means which, via the control unit, allow the angle of rotation to be set and/or locked for one or more of the active wheels in one or more directions chosen from the following: 0° in relation to a longitudinal axis of the frame; 30 - 60°, such as roughly 45° for one side in relation to a longitudinal axis of the frame; 30 - 60°, such as roughly 45° for another side in relation to a longitudinal axis of the frame; 75 - 105°, such as roughly 90° for the one side in relation to a longitudinal axis of the frame; 75 - 105°, such as roughly 90° for another side in relation to a longitudinal axis of the frame, where this setting and/or locking of the angle of rotation for one or more of the active wheels takes place mutually independently or mutually dependently.

5. A drive system according to claim 3 or 4, where the steering unit (20) comprises a joystick and/or handlebars or a handle (30); wherein the joystick and/or handlebars or handle (30), with the steering unit (20), are designed, by pushing or pulling, via the control unit (22), to make possible rotation of one or more of the active wheels (8a) in one of two directions of rotation, and/or where the joystick and/or handlebars or handle (30), with the steering unit (20), are designed, via the control unit (22), to set the speed of rotation of one or more of the active wheels (8a), and/or where the joystick and/or handlebars or handle (30), with the steering unit (20), are designed, by pushing or pulling, via the control unit 22, to make it possible to set the angle of rotation of one or more of the active wheels (8a), and where the rotation of one or more of the active wheels (8a) in one of two directions of rotation and/or where the setting of the speed of rotation of one or more of the active wheels (8a) and/or where the setting of the angle of rotation of one or more of the active wheels (8a) take(s) place mutually independently or mutually dependently.

6. A drive system according to any of claims 3, 4 or 5, where the steering unit (20) comprises handlebars or a handle (30), and where the handlebars or handle, with the steering unit (20), are designed, by the application of a larger or smaller push/pull to one side (30a) of the handlebars/handle in relation to the other side (30b) of the handlebars/handle, via the control unit (22), to make possible a different speed of rotation and/or direction of rotation of one or more of the two or more active wheels (8a) and/or make it possible to set the angle of rotation of one or more of the active wheels (8a), whereby, with different pushes or pulls on either side (30a, 30b) of the handlebars or handle, it is possible to determine the character of the motion of the drive system.

7. A drive system according to any of the preceding claims, wherein the steering unit is mounted on the end of the frame (6) that corresponds to the location of the head or foot of the hospital bed.

8. A drive system according to any of the preceding claims, wherein each of the wheels (8) that are not active wheels (8a) are passive wheels (8b), each of which is suspended in a mainly vertically oriented rotating bearing (32), whereby each of the passive wheels (8b) can rotate freely about a mainly vertical axis (34) and thus adapt to the direction of travel defined by the active wheels (8a).

9. A drive system according to any of the preceding claims, comprising two active wheels (8a) and two passive wheels (8b).

10. A drive system according to any of the preceding claims comprising four active wheels (8a).

1 1. A hospital bed comprising a drive system (2) according to any of claims 1 - 10.