WO2009113009A1

WO2009113009A1 - Assistive drive system

Info

Publication number: WO2009113009A1
Application number: PCT/IB2009/050972
Authority: WO
Inventors: Henrik Nøhr KOFOED; Mogens Ilsted Bech; Niels Tvergaard Haagh
Original assignee: Borringia Industrie Ag
Priority date: 2008-03-10
Filing date: 2009-03-09
Publication date: 2009-09-17

Abstract

A wheeled object or a vehicle, such as a hospital bed, stretcher or a similar vehicle operated by a walking person includes a vehicle frame supported by caster wheels or ball rollers. The vehicle further includes a drive wheel system mounted on the vehicle frame. The drive wheel system comprises a wheel frame (11) adapted to be mounted on or form part of the vehicle frame, a drive roller or wheel (15) rotate able about a substantially vertical axis, a driving motor (33) for drivingly rotating the drive wheel via power transmission means (17, 26), and steering means (27, 32) for rotating the drive wheel (15) about said vertical axis. In order to avoid up- and downward movements of heavy components, such as the driving motor (33), when the drive wheel passes thresholds and irregularities in the floor surface, the driving motor (33) is fixedly mounted in relation to the wheel frame (11), and to allow that the power transmission means (17, 26) and the drive wheel (15) are adapted to telescope along said vertical axis.

Description

ASSISTIVE DRIVE SYSTEM

Background of the Invention A large number of wheeled structures or "vehicles" are used to transport a variety of different items both inside and outside of houses. They vary from simple transport trolleys e.g. in production facilities over logistics equipment to hospital beds. A person, who takes on the function as a human engine, manually pushes by far the larger proportion of these vehicles.

When transporting heavy objects on a vehicle, the person pushing is exposed to severe physical strain both to initiate movement, to control the movement and in order to brake the vehicle as and when desired. For this reason a number of "assistive drive technologies" have been developed. Typically, such technologies help the person pushing the vehicle by supplying the force needed to propel the vehicle either forwards or backwards. The person normally supplies the steering force, by pushing directly onto the vehicle or onto a steering handle supplied.

Most of the vehicles have four wheels placed in a rectangular formation in order to give the vehicle stability. If traction is supplied by motorizing, e.g. the two rear wheels of the vehicle - as known from many assistive drive systems - the vehicle will have a pattern of movement similar to that of a car, which means that the vehicle needs a lot of space to manoeuvre, turn around corners etc. More importantly, moving such a vehicle sideways will involve "kerb side parking". Therefore, a number of assistive drive technologies have been developed, which supply force and traction to the drive surface via a fifth - often centre placed - wheel. These drive wheels, which are normally equipped with a reversible electric drive motor, are oriented in such a way that when the motor is activated they will supply the power needed in order to move the vehicle either forwards or backwards as desired. An advantage of such centre placed drive wheels is that the centre of the vehicle becomes the turning point of the vehicle, which again means that the vehicle requires less space to e.g. turn around a 90° corner. Examples of beds having such a fifth centre placed drive wheel are disclosed in for example US patents Nos. 6,877,572, 6,752,224, and 6,902,019. See also German patent 0 630 637 Al.

However, the known centre placed assistive drive systems show a number of disadvantages, including:

• As drive force is supplied only "along ships", the known systems do not help move the vehicles sideways. Actually, they may in some instances work against such movements.

• As the weight of the vehicle - for stability reasons - predominantly is carried by the 4 wheels in rectangular formation, it often becomes difficult for the drive wheel to obtain sufficient traction to move the vehicle when heavily loaded and/or when moving on an uneven drive surface.

An invention described in the patent application WO2006/059200 offers an assistive drive wheel system, which allows for movement forwards and backwards as well as sideways. However, this invention requires that a complete subassembly including drive motor, pressure regulation system, turning motor, and control electronics are turned, whenever a change of drive direction is desired. This has several disadvantages:

• In order to turn the subassembly significant consumption of power is required. • Having to turn all components leads to an unnecessarily complex and costly mechanical construction.

• Power and signal conductors have to be moveably arranged between the fixed and moving parts. Such moving power and signal conductors are prone to break and fail.

The invention described in WO2006/059200 uses a pressure regulation system whereby the pressure of the drive wheel against the floor can be adjusted to match the total weight of the vehicle. This mechanism is by definition mechanically complex and costly to produce. Summary of the Invention

The present invention provides wheeled object or a vehicle including a drive wheel system and a vehicle frame, which frame is supported on a supporting surface or floor surface by supporting rollers or wheels, said drive wheel system comprising a wheel frame adapted to be mounted on or form part of the vehicle frame, a drive roller or wheel rotatable about a substantially vertical axis, a driving motor for drivingly rotating the drive wheel via power transmission means, and steering means for rotating the drive wheel about said vertical axis, and the vehicle according to the invention is characterized in that the driving motor is fixedly mounted in relation to the wheel frame and that the power transmission means and the drive wheel are adapted to telescope along said vertical axis.

Because the driving motor is fixedly mounted in relation to the vehicle, while the drive wheel may telescope vertically the steering means need not rotate the driving motor. The drive wheel may be rotated by the steering means in order to change the angular position of the drive wheel in relation to the chassis or frame and consequently the driving direction of the drive wheel and the driven vehicle. Therefore, a wheeled object according to the invention, such as a hospital bed, can be moved much more easily than most conventional beds. The supporting wheels or rollers may be of the swivelling caster wheel type or of the ball roller type movable in any direction.

The power transmission means may be of any type allowing a vertical reciprocating movement of the drive wheel. In the presently preferred embodiment, however, the power transmission means may comprise a driving shaft having a longitudinal axis substantially coinciding with said substantially vertical axis, said driving shaft having a pinion or worm gear at its lower end engaging with a ring gear connected to the drive wheel. The said driving shaft may then for example have a splined upper end portion engaging with a surrounding sleeve having a splined inner surface. As an example, the output shaft of the driving motor may be offset from and arranged substantially parallel with the splined upper end portion, said output shaft being drivingly interconnected with said sleeve. Thereby simple and reliable transmission means are provided.

In order to allow a proper contact between the drive wheel and the floor surface, means may be provided to secure a proper contact pressure between the drive wheel and the floor surface. Such means may be manually or automatically adjustable so as to secure a substantially uniform contacting load sufficient to transfer the necessary driving force without lifting the supporting wheels out of engagement with the floor surface. These contact means may, for example, comprise spring means for biasing with or without adjustable spring force for biasing the drive wheel into contact with the floor surface. In many cases a constant contact pressure between drive wheel and floor surface in accordance with customer's specific requests would suffice, whereby a very simple embodiment is obtained.

When the driving direction of the wheeled object has to be changed, the angular position of the drive wheel may be changed by manual force. However, the wheeled object preferably further comprises power operated steering means to rotate the drive wheel about said substantially vertical axis between predetermined angular positions. The angular position of the drive wheel may then be changed, for example by actuating a man/machine interface of any suitable type, such as a joystick, or a pressure sensitive switch.

In principle, any angular position may be chosen. However, for the sake of simplicity the said predetermined angular positions may comprise only a position corresponding to the usual driving direction and a position perpendicular thereto.

In the present invention the drive wheel may be a standard wheel with driving force being transmitted to the drive wheel using conventional mechanical means such as e.g. a chain, belt or similar. In a presently preferred embodiment the drive wheel is of the type described in European Patent 0991529. The key advantage of applying this drive wheel is that a change of drive direction can be obtained without any significant friction against the drive surface, even when said drive wheel is pressed with significant force against the drive surface.

In the presently preferred embodiment the steering means comprise a steering motor having an output shaft, which is connected to the drive wheel via a steering mechanism so as to turn the drive wheel backwards and forwards through an angle not exceeding 360° when the output shaft of the steering motor is rotated. The said steering mechanism may, for example, comprise a crank mechanism including a connecting rod, so as to turn the drive wheel when the output shaft of the steering motor is rotated.

The upper part of the drive wheel is preferably surrounded by a housing having an outer cylindrical surface, which is displace ably and rotate ably received in a bore defined by the wheel frame and having a longitudinal axis substantially coinciding with said vertical axis. This means that axial and rotational movements of the housing and the drive wheel mounted therein may be guided by the outer cylindrical surface of the housing and the co-operating inner cylindrical surface of the bore defined by the wheel frame. In this case one end of the connecting rod of the steering mechanism may be pivotally connected to an upper surface of said wheel housing, the other end of said connecting rod being displace ably and pivotally connected to a vertically extending crank pin. Preferably, the crank mechanism is adapted to turn the drive wheel backwards and forwards through an angle not exceeding 180°, preferably 90°, for each revolution of the crank of the crank mechanism.

The drive wheel and its housing may be suspended by a lever, which is pivotally connected to the wheel frame. In such case said spring means are preferably interposed between said lever and said wheel housing.

When the drive wheel is not in use, it may be desirable to lift it out of engagement with the floor surface. Therefore, the wheeled object according to the invention may further comprise means for moving the drive wheel along a substantially vertical axis into and out of engagement with the floor surface. Such moving means may, for example, comprise said crank including a threaded shaft end, which engages with a nut member connected to said lever.

According to a further aspect the present invention provides a drive wheel system for use in a wheeled object or a vehicle as described above.

Brief Description of the Drawings The invention will now be further described with reference to the drawings, which show a presently preferred embodiment of the drive wheel system according to the invention, and wherein

Figs. 1 and 2 are top and bottom perspective views, respectively, of the drive wheel system,

Figs. 3 and 4 are top and bottom perspective views, respectively, of the drive wheel system, where en outer cover or shield has been removed,

Fig. 5 is an end view of the system, where en upper mounting plate has been removed,

Figs. 6 and 7 are top and bottom perspective views, respectively of the system in Fig. 5,

Fig. 8 is a top plan view of the system in Fig. 5,

Figs. 9 is a sectional view along a vertical longitudinal plane extending through the drive wheel, and

Fig. 10 is a cross-sectional view along a vertical plane extending at right angles to the longitudinal plane.

Fig. 11 shows the invention mounted on a stylized bed. Detailed Description of the Preferred Embodiment

The drive wheel system shown in the drawings may be mounted on a hospital bed, a stretcher or any other wheeled object or vehicle (See Fig 11) by means of a mounting plate 10 forming part of the base frame 11 of the drive wheel system. The complete fixed base frame 11 of the system further comprises two side plates 12 and a lower base plate 13 (Figs. 3 and 4). An outer cover or shield 14 is mounted on the fixed base frame 11 to protect the system against mechanical damage and dirt.

As best shown in Figs. 9 and 10 a drive wheel 15 has a vertical tubular axle 16 for rotation of the complete wheel unit. A wheel drive shaft 17 having a pinion 18 at its lower end is arranged inside this tubular axle 16. The pinion 18 engages with a helical ring gear 19 that drives the wheel 15. The wheel shaft 20 is tilted to offset the wheel foot point 21. By offsetting the wheel foot point it is possible to have the wheel rolling in a small circle when the wheel unit is rotated around the vertical axle. This effectively eliminates any surface friction and wear on floor materials. (Such drive wheel is described in European Patent 0991529)

The drive wheel unit is mounted fixedly inside a cylindrical, upwardly closed wheel cup 22 that secures no penetration of dust, dirt or fluids into the inner of the drive wheel system. The wheel cup 22 is mounted in a set of bearings allowing the cup and the wheel to be rotated around a vertical axis and slide up and down along the same axis. The lower wheel cup bearing 23 is a special ball bearing where the wheel cup makes up the inner ring of the bearing. There is no ball groove in the wheel cup allowing for the cup to move freely up and down as well as to rotate. An outer cylindrical part 24 of the lower wheel cup bearing 23 is rigidly fixed to the lower base plate 13. An upper wheel cup bearing 25 is integrated with the drive transmission. The wheel drive shaft 17 has a splined shape at its upper end. This splined end is inserted into a complementary shaped sleeve 26 that is rotationally mounted in a ball bearing, also being the upper wheel cup bearing 25. The ball bearing 25 is fixedly mounted within a tubular housing 25' depending from the mounting plate 10. This arrangement allows the drive wheel unit to move freely up and down and to rotate around a vertical axis. Integrating the wheel cup 22 in the complete drive wheel system design offers several big advantages. The cup design allows for the lower bearing 23 to be positioned very close to the floor surface. The horizontal forces from the drive wheel are therefore supported in an optimal way introducing very low torque. Placing the vertical axis bearings 23 down on the sides of the wheel 15 minimizes the total height of the drive wheel system substantially as only one bearing 25 needs to be placed above the wheel.

As best shown in Figs. 6 and 8, the wheel direction is controlled by a crank mechanism 27 comprising a circular disc 28 and a crank arm 29. One end of the crank arm 29 is connected to the wheel cup 22 through a pivot joint 30, and the other end of the crank arm is connected to the circular disc 28 through a pivot joint pin 31. The disc 28 may be rotated by a steering motor 32, whereby the crank arm 29 is actuated. The geometry of the crank mechanism 27 is designed to rotate the wheel cup 22 through 90° when the steering motor 32 rotates 180°. This has the advantage that the crank mechanism is self blocking when the wheel 15 is in one of the two main drive directions. It also allows the steering motor to run a complete 360°.

While the steering motor 32 and the disc 28 are mounted on the base frame 11, the crank arm 29 has one end connected to the vertically moveable wheel cup 22 and the other end to the disc. To allow the crank arm to follow the movements of the wheel cup 22 the crank arm 29 is adapted to slide up and down along the pivot joint pin 31.

A drive motor 33 for driving the wheel 15 and thereby the vehicle on which the drive wheel system is arranged, is mounted on the fixed lower base plate 13. A sprocket 34 on the output shaft of the drive motor 33 drives another sprocket 35 via a roller chain (not shown). The sprocket 35 is fixed to the internally splined sleeve 26 on which the ball bearing 25 is mounted via a roller chain (not shown). The splined transmission between the sleeve 26 and the drive shaft 17 allows the drive wheel 15 to move vertically while the drive motor 33 is fixed. This means that the weight moving up and down when the drive wheel system is driven on uneven ground (across thresholds, drops, etc.) is limited, which improves dynamic response of the system substantially. The drive motor 33 may be controlled by an electric control system 36.

The wheel cup 22 with the wheel 15 is biased towards the floor by a pair of gas springs 37. The lower ends of the gas springs 37 push on the wheel cup 22 via a yoke 42, and the yoke is connected to the wheel cup through a bearing 43 allowing the wheel 15 to be turned while the gas springs 37 remain in the same position. The gas springs maintain a constant wheel pressure against the floor surface to give the necessary wheel/floor friction to propel the system and allows at the same time the wheel 15 to move up and down when crossing e.g. thresholds and/or drops in the floor. The size of the wheel pressure against the floor is a result of the gas springs' specifications. The use of the wheel cup/yoke design allows for the gas springs to be mounted down the sides of the wheel minimising the overall height of the drive wheel system. At the same time it is possible to mount the gas springs in a stationary position only having the wheel cup 22 rotating. By limiting the number of moving parts a simplified, more stable and cost efficient system is achieved.

The top end of each gas spring is pivotally connected to the middle of either one of a pair of parallel levers 38. One end of each lever 38 is mounted on a horizontal pivot pin 39 allowing the lever to pivot in a vertical direction. The other end of each lever is controlled by a common horizontal rod 40 extending into a slot in each lever 38. The vertical position of the rod 40 is controlled by a nut/spindle system 41. The spindle is driven by the steering motor 32. Running the steering motor 32 in one direction will rotate the spindle of the system 41 and thereby lift or lower the rod 40 that will force the levers 38 and the gas springs 37 in the same direction. When the levers 38 has been moved to their uppermost position the gas springs 37 will expand to their maximum length and then pull the wheel 15 off the floor to allow the wheeled object to be pushed freely. When the levers are moved to their lower position the gas springs are compressed and bias the wheel 15 against the floor.

The special design of the wheel steering crank mechanism 27 is important as it allows the steering motor 32 to rotate through several 360°. When the steering motor rotates through 180°, the wheel 15 is turned through 90°. If the motor 32 is left to rotate through several 360° the wheel 15 will - depending on the direction of rotation - be either lifted out of or lowered into contact with the floor. Consequently, the same motor 32 can be used to drive both the nut/spindle system 41 for engaging and disengaging the drive wheel 15 and to control the drive direction. This solution simplifies the complete drive wheel system and is cost efficient.

The drive wheel system may be controlled through a Man Machine Interface (MMI) (not shown). The MMI may contain one button that engages/disengages the drive wheel 15. When the system is engaging the wheel is lowered and biased towards the floor and the motor amplifier is activated. When the system is disengaging the wheel is lifted off the floor and the system is powered off.

When the system is engaged it may be possible to select drive speed by pushing a speed button. Pushing the button more times, may step the system through different drive speeds. The selected speed may be displayed by LEDs. Pushing one of the four drive buttons may command the system to position the wheel 15 in the selected direction and start the drive motor 33 with the selected speed in the corresponding direction. The system may slow down and stop as soon as no input is received from the MMI. If the system is driving in one direction and the push button indicates that the opposite direction is pushed, the system may actively brake the vehicle to a complete stop.

In another configuration of the MMI the drive speed may be directly controlled by sensors integrated in the direction push buttons.

The drive system according to the invention may be used on any kind of normally manually pushed wheeled objects or vehicles supported by wheels or rollers of the caster or ball roller type, such as hospital beds, stretchers, load carrying trolleys, etc.

Claims

1. A wheeled object or a vehicle including a drive wheel system and a vehicle frame, which frame is supported on a supporting surface or floor surface by supporting rollers or wheels, said drive wheel system comprising a wheel frame (11) adapted to be mounted on or form part of the vehicle frame, a drive roller or wheel (15) rotatable about a substantially vertical axis, a driving motor (33) for drivingly rotating the drive wheel via power transmission means (17, 26), and steering means (27) for rotating the drive wheel (15) about said vertical axis, characterized in that the driving motor (33) is fixedly mounted in relation to the wheel frame (11) and that the power transmission means (17, 26) and the drive wheel (15) are adapted to telescope along said vertical axis.

2. A wheeled object or vehicle according to claim 1, wherein the power transmission means comprise a driving shaft (17) having a longitudinal axis substantially coinciding with said vertical axis, said driving shaft having a pinion (18) or worm gear at its lower end engaging with a ring gear (19) connected to the drive wheel (15).

3. A wheeled object according to claim 2, wherein said driving shaft (17) has a splined upper end portion engaging with a surrounding sleeve (26) having a splined inner surface.

4. A wheeled object according to claim 3, wherein the output shaft of the driving motor (33) is offset from and arranged substantially parallel with the splined upper end portion, said output shaft being drivingly interconnected with said sleeve (26).

5. A wheeled object according to any of the claims 1 - 4, further comprising spring means (37) for biasing the drive wheel (15) into contact with the floor surface.

6. A wheeled object according to any of the claims 1 - 5, wherein said steering means comprise a steering motor (32) having an output shaft, which is connected to the drive wheel via a steering mechanism (27) so as to turn the drive wheel (15) backwards and forwards through an angle not exceeding 360° when the output shaft of the steering motor is rotated.

7. A wheeled object according to claim 6, wherein said steering mechanism comprises a crank mechanism (27) including a connecting rod (29), so as to turn the drive wheel when the output shaft of the steering motor is rotated.

8. A wheeled object according to any of the claims 1 - 7, wherein the upper part of the drive wheel is surrounded by a housing (22) having an outer cylindrical surface, which is displace ably and rotate ably received in a bore (24) defined by the wheel frame and having a longitudinal axis substantially coinciding with said vertical axis.

9. A wheeled object according to claims 7 and 8, wherein one end of said connecting rod (29) is pivotally connected to an upper surface of said wheel housing (22), the other end of said connecting rod being displace ably and pivotally connected to a vertically extending crank pin (31).

10. A wheeled object according to any of the claims 7 - 9, wherein the crank mechanism (27) is adapted to turn the drive wheel (15) backwards and forwards through an angle not exceeding 180°, preferably 90°, for each revolution of the crank mechanism.

11. A wheeled object according to any of the claims 8 - 10, wherein the drive wheel (15) and its housing (22) is suspended by a lever (38), which is pivotally connected to the wheel frame (11).

12. A wheeled object according to claim 5 and 11, wherein said spring means (37) are interposed between said lever and said wheel housing (22).

13. A wheeled object according to any of the claims 1 - 12, further comprising means (41) for moving the drive wheel along a substantially vertical axis into and out of engagement with the floor surface.

14. A wheeled object according to claims 11 and 13, wherein said moving means comprise said crank mechanism including a threaded shaft end, which engages with a nut member connected to said lever (38).

15. A drive wheel system for use in a wheeled object or a vehicle according to any of the claims 1 - 14, said drive wheel system comprising a wheel frame (11) adapted to be mounted on or form part of the vehicle frame, a drive roller or wheel (15) rotatable about a substantially vertical axis, a driving motor (33) for drivingly rotating the drive wheel via power transmission means (17, 26), and steering means (27, 32) for rotating the drive wheel (15) about said vertical axis, characterized in that the driving motor (33) is fixedly mounted in relation to the wheel frame (11) and that the power transmission means (17, 26) and the drive wheel (15) are adapted to telescope along said vertical axis.