WO2005080182A2

WO2005080182A2 - Load guidance system

Info

Publication number: WO2005080182A2
Application number: PCT/GB2005/000595
Authority: WO
Inventors: Mike Catling
Original assignee: Coldra Engineering Company Limited
Priority date: 2004-02-20
Filing date: 2005-02-17
Publication date: 2005-09-01
Also published as: GB2411159A; GB2411159B; GB0403890D0; WO2005080182A3

Abstract

A load guidance system, usable with a load-carrying device (1) which has a support (3) for a load mounted on moveable members, such as wheels (6, 7). A connecting member (10) extends between a leader and the device (1) and a control arrangement can monitor the connecting member and can act to modify the action of a drive arrangement for a steering mechanism of the device (1) to cause the device to follow the leader.

Description

Load Guidance System

This invention relates to a load guidance system. In particular, but not exclusively, the invention relates to a load guidance system, which is usable with a load-carrying device where the position of a device or person (acting for example, as a leader) that is manoeuvring the load-carrying device influences the load guidance system. With load-carrying devices such as golf trolleys, it is desirable that the trolley can follow the person leading it at a constant distance. In the case of a golf trolley in particular, the trolley needs to follow the person irrespective of varying influences such as the terrain or incline to be covered. It is clear that varying ground surfaces, such as whether the trolley is travelling over a road surface or wet grass, can severely alter the ability to control movement of the trolley. Control systems have been proposed that provide a way of controlling movement of a load-carrying device, such as a golf trolley. Such devices involve using an electronic control arrangement, where a transmitter is mounted on the load-carrying device. The transmitter sends signals, such as infra-red signals, to a target carried by a person leading the golf trolley. These types of devices have the disadvantage that as control is achieved by way of indirect contact between the transmitter and the target, there is a need for alignment of the two devices so that the target is capable of reflecting the signals that are sent to it by the transmitter. Further, the degree of reliability of transmission of the signals can be severely compromised by factors such as weather conditions, because such external influences can affect whether a signal is successfully received or not . Other types of signal transmitting devices, such as radio transmitters, have been suggested as a means of controlling the positioning of a load-carrying device. In such arrangements a person leading a load-carrying device would carry a transmitter that is incorporated in a key-fob and then the transmitter would be operable in order to send signals to the load-carrying device, which itself is equipped with one or more antennae for receiving the signals. The antennae receive the radio signals from the key-fob and these are transmitted to software, again incorporated in the load-carrying device. The software can then control the movement of the load-carrying device. However, such an arrangement has the disadvantage that signals may not be transmitted accurately to the antennae due to reflection of radio waves from surrounding objects. This would result in a decrease in the level of control of the movement of the load-carrying device and in some circumstances, where the is a high level of deflection of radio waves, there may be no transmission of signals at all, resulting in the load-carrying device not being able to move. Further, because there is no direct control between the load positioning control system and the load- carrying device it would not be possible to control the position of a load-carrying device accurately so leading to the device moving in a "stop-start" fashion as it follows the person leading it . Another suggested system for allowing control of the position of a load-carrying device involved the use of a Global Positioning (GPS) System with satellite navigation. However, such systems are expensive to produce and again, rely on the transmission of signals from one device to another, which can lead to a reduced level of control in the movement of a load-carrying device. None of the known arrangements provide a system whereby a load-carrying device can be caused to move so that it matches the travel characteristics of an individual or device that is moving the load. Further, known devices do not have the facility whereby compensation can be made so that the load-carrying device can continue to move at a constant rate irrespective of the terrain to be covered and the varying ground conditions that the load-carrying device is to travel over. In addition, known devices have the added disadvantage in that, as they rely on the transmission of signals between remote devices. Signal transmission can be influenced by external factors such as fluctuations in weather conditions e.g. bright sunlight or torrential rain. This can again affect the ability to control the movement of a load-carrying device. An aim of the current invention is to provide a load guidance system, which allows for accurate directional control of a load-carrying device, and also, the speed of the device, while providing a system that is simple and efficient to operate. Accordingly to the invention there is provided a load guidance system, usable with a load-carrying device having a load support mounted on movable members to allow the support to be moved from one position to another, wherein the load guidance system includes : (a) a connecting member to extend between a leader and the load-carrying device; (b) a control arrangement to monitor one or more parameters relating to the condition of the connecting member and produce an output to modify operation of a drive arrangement connected to a steering mechanism of the load-carrying device to cause said device to follow the leader.

Preferably the condition of the connecting member is selected from one or more of, the extension of the member, tension on the member, rotational orientation position from a datum. It is envisaged that the control arrangement includes a reactive member which is used to detect the condition of the connecting member relative to a predetermined parameter of the connecting member, said reactive member activating one or more signals that cause one or more of the moveable members to move such that the load-carrying device follows the orientation of the leader such as a person or device leading the load-carrying device. Preferably the reactive member of the load guidance system is a spring-loaded rotating member that is caused to rotate as a result of pull on the connecting member. Typically, the connecting member is a cord of approximately 400 mm in length, though longer or shorter lengths may be used depending on the type of load to be moved. It is envisaged that the connecting member that is attached to the spring-loaded device passes through a tube connected to a pivot, such that the tube can move through an angle about a pivot point . Preferable, the angle of movement about the pivot point is substantially 90 degrees, which provides a deviation of 45 degrees either side of a central position that determines the predetermined value . The angle of deviation from the predetermined central position is proportional to the signal level sent to the steering mechanism to control movement of the moveable members . In an alternative arrangement, the reactive member includes one or more beam transducers . It is envisaged that the reactive member comprises at least two beam transducers each being mounted in a respective support, the transducers being connected by a cross-member that is reactive to forces placed on it, these forces being measured by the beam transducers to produce signals that can be used to control movement of the moveable members . Preferably, the cross member is an elastic cord having an attachment member, for releasably securing to the connecting member. It is envisaged that when there is an equal force on each of the transducers, the sum of the forces is measured and sent to a control device that controls the speed of the moveable members. If there is an unequal force on the transducers, the difference in the forces is measured and signals are sent to a control device that can alter the direction of movement of the moveable members . It is envisaged that the reactive member converts mechanical forces into an electrical output to dedicated software used used to control the movement of the moveable members . Preferably, the control device is in communication with a slave device that monitors the position of a controller for one or more of the moveable members. It is envisaged that the controller is a geared motor and preferably there is a geared motor associated with each moveable member so providing independent drive to each moveable member. It is envisaged that each moveable member comprises a wheel having a recess for housing the, or each motor. It is also envisaged that pairs of wheels may be coupled by a steering linkage to assist directional control of the load-carrying device. A typical steering linkage would be similar to an automotive linkage. According to a further aspect of the invention, there is provided a support for a power pack for a load-carrying device, the support provided as a plug mounted on a frame forming part of the load carrying device, the plug projecting at an upwards angle, wherein the power pack is provided with a socket on an upper part of the power pack, such that when the socket is attached to the plug, the socket is directed downwards onto the plug, with the weight of the power pack depending from the socket such that the force provided by the weight holds the socket on the plug, which supports the weight of the power pack. Preferably, pins for the plug project upwards at a degree of substantially 35 degrees from the horizontal. It is envisaged that the support for the power pack can be used with known load carrying-devices such as golf trolleys, or with the arrangement as described above. According to yet a further aspect of the invention, there is provided a golf trolley having a load guidance system, the golf trolley including load support mounted on movable members to allow the load support to be moved from one position to another, wherein the load guidance system includes : a) a connecting member, a first end of which is attached to a reactive member of the load guidance system and a second end which is releasably attachable to a person or device that is to move the golf trolley; b) a sensor to detect the position of, or force on, the connecting member relative to a predetermined parameter, so providing an indication of the position of the person or device relative to the golf trolley; c) a powered steering mechanism, which in response to one or more signals from the control system, which cause one or more of the movable members to move such that the golf trolley is caused to follow the orientation of the person or device . Although the invention has been defined above, it is to be understood that it includes any inventive combination of the features set out above or in the following specific description. The invention may be performed in various ways but specific embodiments of the invention will now be described by way of example only, with reference to the accompanying figures in which: Figure 1 : shows a side view of an embodiment of the invention, where the load-carrying device is specifically designed as a golf trolley; Figure 2 : shows a view from above of a part of the load guidance system, which is attached to the main frame of the golf trolley as shown in Figure 1; Figure 3 : shows a side view of the arrangement of Figure 2 in which first and second potentiometers are shown as means for detecting the angle of deviation of the connecting member from a predetermined position; and the extension of the connecting member from the fully re-wound zero position Figure 4A: shows a front perspective view of a pair of wheels acting as the moveable members to supporting a load- carrying device shown in the previous Figures; Figure 4B: shows a view from above of the wheels shown in Figure 4A; Figure 5A: shows a further embodiment of the invention where the load guidance system uses cantilever beam transducers ; Figure 5B : shows a front view of load guidance system as shown in Figure 5A; Figure 5C: shows a side view of a transducer as shown in Figure 5B; Figure 6A: shows a power pack and support device as shown in Figure 1; Figure 6B : shows the power pack of Figure 6A when connected to the support device; and Figure 6C: shows a connection member used to connect the power pack and support device as shown in Figure 6B. Figure 1 illustrates a load-carrying device, generally shown as 1, which in this case is a golf trolley. However, it is envisaged that the invention can be used with other types of load carrying devices. The golf trolley has a main frame 2. A load support 3 is attached to the main frame 2, and as can be seen the load support is in the form of a bag, which can receive one or more golf clubs 4. The load support 3 is attached to the frame 2 by attachment means 5, which may be bolts, pins or even a quick release mechanism so that the bag can be detached from the main frame 2, if needs be . The golf trolley has a pair of front wheels 6 on a front frame support 7. Also there is a pair of rear wheels 8 towards the base of the load support . At the opposite end of the main frame 2 to which the rear wheels 8 are attached is a guidance device 9. The guidance device 9 houses the load guidance system, which is shown in more detail in Figure 2. The guidance device 9 houses a support for a connecting member 10. The connecting member 10 can be extended from the guidance device by a separate external tether connected to ring 13 and retracted back into the guidance device 9 by part of the load guidance system. Also attached to the frame is a bracket 11, which supports a power pack 12, such as a battery, which is used to provide power to the load- carrying device 1. It is envisaged that the connecting member is a cord or tether of approximately 400mm in length, although this length can vary. Figure 2 shows a cut away view from above of a housing part of a load guidance system which can be used to control the speed and/or the direction of the device. The connecting member, which in this case is shown as a cord, is attached at one end to a spring-loaded winding drum 17, positioned within guidance device 9. The other end of the connecting member, which extends out from the device 9 has an attachment member 13, with this attachment member being positioned outside the device 9. The attachment member 13 is shown as an O-ring, which can be secured to a device having a hook or clasp, or indeed grasped by an individual so that they can lead the trolley. Alternatively, the attachment 13 may be provided as a hook or locking device which can be latched onto a towing device such as a tether. It is envisaged that the tether could be hooked to the waist belt of an individual so that the load-carrying device follows the individual as they are walking. When controlling the speed of the load-carrying device, typically, the device will be kept at a substantially constant distance of approximately one metre from the individual. When a golf shot is to be played, the attachment member 13 can be unhooked from the individual and the trolley would be "parked" during play. The attachment member is of a greater dimension than the aperture in the guidance device 9, from which it extends and therefore the attachment member acts as a stop to prevent the connecting member being totally withdrawn into the guidance device 9. The end of the connecting member 10, closest to the pivot 15 passes through a tube 14, which is secured to the pivot member 15. The connecting member 10 passes between guide rollers 16a, 16b and then around a winding drum 17, which is spring loaded. The winding drum retains a degree of tension on the connecting member, as a result of the spring biasing the drum. Consequently, the drum is always trying the rewind the connecting member 10 back into the guidance device 9, and this tension allows for controlled extension of the connecting member from the guidance device 9 and also, on release of the connecting member it can automatically rewind back into the guidance device 9. As shown in Figure 3 , the winding drum 17 is pivotally supported on a shaft 18, which also secures spring 19 in position. The spring 19, provides the automatic winding facility for the drum 17. The connecting member is attached to the drum 17 at a first end and extends from the guidance device 9, through aperture 20. The lower end of the support shaft 18 is attached to a potentiometer 21. Preferably, the potentiometer is a three-turn servo potentiometer, which measures the revolution of the drum 17 to provide a measurement of the difference between the extended and the fully rewound state of the connecting member 10. This difference indicates how far an individual is from the load-carrying device/trolley. The potentiometer 21 transits a signal to a controller on the trolley and this regulates the speed of motors attached to wheels (shown in Figures 4A and 4B) , which form the moveable members. The control of the wheels as a result of a signal from the potentiometers 21, 22 allow the movement of the load-carrying device to be controlled by the load guidance system. Speed control is controlled by the spring loaded winding drum 17. If an individual, such as a golfer who is connected to the connecting member by way of a tether hooked onto the attachment member 13, moves away from the load-carrying device, the connecting member pulls on the winding drum 17, causing it to rotate. The trolley accelerates from a speed "zero" to a speed where the load- carrying device starts to gain on the golfer. At this point, because there is less tension in the connecting member, the distance between the trolley and the golfer then begins to decrease and the connecting member, due to the spring loading on the winding drum is caused to automatically rewind onto the drum 17 until a point is reached where the speed of the trolley substantially matches the speed of the golfer. A typical walking pace is about 1.5 metres per second. When the golfer meets a gradient, due to the weight of the load-carrying device, this device will tend to slow down more than the golfer, which results in the connecting member 10 being unwound from the drum 17 causing the connecting member 10 to be released from the housing 9. As a consequence, the speed of the load-carrying device increases until the speed substantially matches that of the person leading the device. When the person reaches a downhill gradient, the tension on the connecting member 10 is reduced and due to the spring loading on the drum 17, it is rewound back into the guidance device 9. This results in the load-carrying device tracking the golfer at a slightly closer distance than when he or she moved uphill, thereby exerting control on the speed of the load-carrying device relative to the person leading it . If the golfer stops abruptly, due to the spring loading of the winding drum 17, the connecting member 10 is caused to retract fully into the guidance device 9, bringing the load-carrying device to a rapid stop but in a controlled manner. The controlled stopping of the device is achieved by the natural Direct Current braking in the four wheel motors, or by the employment of motors configured with automatic brakes, and may be assisted by inherent inertia in the control system of a driven device. It is envisaged that the connecting member may be caused to stop so that a length of connecting member still remains outside the guidance device 9 when fully rewound and this could be said to be a "dead length" of connecting member which provides for a degree of slack so that the trolley will be caused to stop at a minimum distance, of approximately half a metre for example, away from the golfer, rather than coming into contact with the golfer when the golfer stops abruptly. The dead length provides a degree of "slack" between the person/device and the load- carrying device so the two do not come into contact . The "slack" can be provided by a length of connecting member 10 per se, which does not become re-wound into the handle. Alternatively, the "slack" may be provided by a hook-on attachment, which a person can attach to the connecting member so that there is always a length of material between the individual and the load-carrying device. As well as controlling the speed of the load-carrying device, there is directional control that is provided by tracking the movement of tube 14 away from a predetermined position, the predetermined position, being shown as a position when the tube 14 is pointing straight ahead (shown as 23) . The dimensions of the aperture through which the connecting member passes are such that typically the movement of the tube 14 is constrained so that it can move plus or minus 45 degrees from the straight ahead position shown as 23. The degree of movement of the tube 14 can be translated to limit the movement of the movable members so allowing for guidance of the load-carrying device. A potentiometer 22 is responsive to the movement of the tube 14 that is attached at one end to pivot point 15. The directional movement of an individual pulling on the connecting member 10 causes the tube to deviate at an angle from the central position 23. It is this degree of deviation which influences the potentiometer 22 so that it gives out a voltage that is proportional to the degree of movement of the tube 14 from right to left about central line 23. As a result, potentiometer 22, which acts as a control potentiometer, sends signals to one or more "slave" potentiometers that cooperate with a steering linkage attached to moveable members such as wheels on the device. As the person pulling the load-carrying device moves either left or right, the tube 14 is caused to point in that direction as a result of the connecting member being moved as a result of movement of the person. As a result of the signal that has been sent from the control potentiometer 22, and then the signal being sent to slave potentiometers (not shown) , the load-carrying device turns and follows the direction of travel of the individual . As the load-carrying device squares up with the connecting member, resulting in the connecting member 10 and the central point 23 aligning, the signal from the potentiometer is returned to a central direction position as the steered wheels of the load-carrying device move straight ahead. This provides an elegant system where the steering control is totally self- regulating as a result of movement of the individual relative to the load-carrying device. Preferably, the potentiometers 21, 22 are of the ultra low friction servo type and this allows for the maximum tension on the connecting member 10, to be kept to a minimum, typically 100-120 grams, when the connecting member is completely extended. By keeping the tension to a minimum, this reduces the drag on a person or device, which is pulling the load-carrying device and provides a much smaller degree of drag than known golf trolleys. Figures 4A and 4B show respectively a perspective and a plan view of movable members i.e. wheels which support the load-carrying device. As can be seen, there are recesses on the internal surfaces of the wheels. This is so that drive motors 25 can be incorporated within the wheels. The motors are supplied with power by cables running in polyurethane tubing -26-which protect against abrasion and the ingress of water, and are manoeuvrable by way of a steering linkage 27. The steering linkage is a scaled down version of the type of linkage that would be found in automobiles. Ideally, the geared motor is protected from the ingress of water, for example, when the load-carrying device travels across grassed surfaces which may be damp or which may have standing water. Ideally, the steering mechanism of the load-carrying device is powered by a 12 volt DC geared motor. The rear end of the armature of this motor carries a third 10-turn electronic potentiometer. This slave potentiometer measures the angular position of the steering mechanism from the central position and transmits a proportional signal back to a main electronic control for the load-carrying device. The electronic control includes a control such as a microchip, which enables the steering mechanism to follow the movement of the tube 14 within the guidance device 9. The load-carrying device ideally has a high level of stability, to provide even weight distribution for the load. This is typically provided by a four wheeled device having two front and two rear wheels. The rear wheels have a narrower spacing or "track" than the front wheels to allow the vehicle to fold up into a minimum space envelope when not in use for portability and transport, and the automotive type steering linkage allows for a turning differential between the outer and inner wheels so that wheels on the inside of a turn bend progressively sharper than those on the outside. Such steering geometry, reduces the risk of skidding of the wheels and so increases traction and stability, whilst keeping the maximum steering displacement to a high degree. This allows for a sharp turning circle for the load-carrying device. Although the moveable members have been described as wheels, it is envisaged that they could be wheeled tracks or there may even be a combination of tracks and wheels forming the moveable members, depending on the terrain to be covered. The electronic control also includes means to scale movement detected for the tube 14 and scale this movement into a signal which controls the greater movement of the steering mechanism so that the load-carrying device can turn to the left or the right in accordance to the movement of the individual pulling the trolley. Figures 5A to 5C show an alternative guidance module for a load guidance system. Instead of having a guidance module in the form of a housing 9 with an aperture 20 through which connecting member 10 extends, the alternative guidance module uses two beam transducers mounted within tubes 30. As shown in Figure 5A, these load cells are attached to the support 2 of the load-carrying device by arm 28. The support is attached to the tubes 30 by a connection member 29, which forms a cross bar between the tubes 30. Inside the tubes are thin film cantilever beam transducers, shown in detail in Figure 5C. The tubes 30 guard against extraneous damage that could occur to the load cells and also provide protection against the ingress of water or other external factors so providing a sealed unit which is less likely to be accidentally damaged. Each of the tubes 30 has an aperture 31. There is a cord 32 extending between the two tubes, the ends of the cord being attached to the respective free ends of the beam transducers. The cord is such that under normal conditions the cord is under zero tension. Attached to the cord is an attachment point such as a rubber ring 13 which allows an individual to hook themselves to this connecting member of the load guidance system, with a thin elastic separate tether. When an individual moves away from the load-carrying device, tension is placed on the cord which applies a small but increasing load to both of the transducers . When an individual moves straight ahead, both parts of the cord on either side of the O-ring will be subject to an equal load that will be transmitted to each of the transducers. A processor associated with the load guidance system uses the sum of the output signal from each of the transducers to control the speed of the trolley. When the individual turns to the right or the left the load on the individual transducers will become progressively mismatched as the CD- ring is pulled either to the left or the right. An electronic central control will summate the two outputs to control the forward speed of the load-carrying device. The processor can also use the difference in the two outputs to control the steering. The central control will receive signals from a slave potentiometer or encoder on the steering motor associated with the wheels so that the electronic control centre will provide information at all times about the position of the wheels which are being steered. It is to be understood that rather than using a potentiometer, it is possible to use a rotary encoder which is a non-contract device not subject to wear. Figure 6A shows a further aspect of the invention in which a power pack such as a battery can be secured to a main body 2 of a load-carrying device. The power pack 12 has a support handle 33 at its upper surface, which can be used to carry the power pack. The handle 33 is secured to the main body of the power pack 12 by securing members 37, for example bolts. Secured to the upper part of the handle 33 is a connector 34, which in this case is a female connector in the form of a socket . On the support 2 of the load-carrying device there is a plug 35 which can either be permanently fixed to the body 2 or alternatively it can be releasably secured by, for example, bolts should there be a need for the plug to be removed for maintenance or the replacement of the plug. However, the plug is secured firmly enough for it to support the power pack 12 when the plug 35 is connected with socket 34. The plug projects at an angle upwards and will mate with the socket when pushed down onto it. Figure 6B shows the plug and socket joined. As the plug projects upwards, it support the weight of the power pack 12, as it hangs from the joined plug and socket and the force of this weight keeps the plug and socket joined. If the power pack is to be moved, it is lifted upwards by handle 33, away from the plug, so reducing the force on the plug which allows the plug and socket to be released. It is envisaged that the socket has brass sleeves, which are furnished with a material, such as MC-Multilam (TM) contact rings, so ensuring good electrical contact. Plug pins 36 point at substantially 35 degrees to the horizontal and this arrangement provides the plug and socket with both structural and electrical connections due to the weight of the pack being held by the plug. Figure 6B shows the power pack and plug and socket arrangement in connection. Figure 6C shows a plug 35 having two pins 36 for joining with socket 34. By having a self-supporting plug and socket arrangement, this avoids the need for connecting holders or devices for supporting the power pack/battery. Also cumbersome arrangements such as a folding down battery support tray are not needed. Further there is no need for strapping the battery into position for example a bungy rope or crocodile switch can be cumbersome, especially in wet conditions. Although the Figures show the arrangement when used with a golf trolley, it is to be emphasised that the load guidance system as described can be used with other devices where controlled movement that mirrors the movement of an individual or machine that is connected to the load- carrying device. An example of other types of load- carrying devices that could be used with the invention described are powered wheelchairs for handicapped people so that there is less effort needed for a carer to manoeuvre the individual. Also, there are applications in the health service where nurses can more easily move trolleys. In the retail sector, the control system could be used with for example supermarket trolleys. There are also industrial applications for the movement of vehicles weighing hundreds of tons in order to reduce the loading on other vehicles that are used to manoeuvre such loads .

Claims

1. A load guidance system, usable with a load-carrying device having a load support mounted on movable members to allow the support to be moved from one position to another, wherein the load guidance system includes : (a) a connecting member to extend between a leader and the load-carrying device; (b) a control arrangement to monitor one or more parameters relating to the condition of the connecting member and produce an output to modify operation of a drive arrangement connected to a steering mechanism of the load-carrying device to cause said device to follow the leader.

2. A load guidance system according to Claim 1 , wherein the condition of the connecting member is selected from one or more of a force acting on the member, tension on the member, rotational orientation position from a datum.

3. A load guidance system according to Claim 1 or Claim 2 , wherein the control arrangement includes a reactive member which is used to detect the condition of the connecting member relative to a predetermined parameter for the connecting member, said reactive member, activating one or more signals that cause one or more of the moveable members to move such that the load-carrying device is caused to follow the orientation of the leader.

4. A load guidance system according to claim 3 , wherein the reactive member is a spring-loaded rotating member that is caused to rotate as a result of pull on the connecting member .

5. A load guidance system according to claim 4 , wherein the connecting member that is attached to the spring-loaded device passes through a tube connected to a pivot, such that the tube can move through an angle about a pivot point

6. A load guidance system according to claim 5, wherein the angle of movement about the pivot point is substantially 90 degrees, having a deviation of 45 degrees either side of a central position that provides the predetermined value.

7. A load guidance system according to claim 6, wherein the angle of deviation from the predetermined central determines the signal level sent to steering mechanism to control movement of the moveable members.

8. A load guidance system according to claim 3 , wherein the reactive member includes one or more beam transducers.

9. A load guidance system according to claim 8, wherein the reactive member comprises at least two beam transducers each being mounted in a respective support, the transducers being connected by a cross-member that is reactive to forces placed on it, these forces being measured by the beam transducers to produce signals that can be used to control movement of the moveable members .

10. A load guidance system according to claim 9, wherein the cross-member is an elastic cord having an attachment member, for releasably securing to the connecting member.

11. A load guidance system according to any of claims 7 to 10, wherein when there is an equal force on each of the transducers, the sum of the forces is measured and sent to a control device to vary the speed of the moveable members .

12. A load guidance system according to any of claims 7 to 10, wherein if there is an unequal force on the transducers, the difference in the forces is measured and signals are sent to a control device that can regulate the direction of movement of the moveable members.

13. A load guidance system according to any preceeding claims wherein the control arrangement includes a potentiometer or an encoder.

14. A load guidance system according to claim 15, wherein the control arrangement includes a potentiometer it is a low friction servo type potentiometer.

15. A load guidance system according to any preceeding claims, wherein the control arrangement is in communication with a slave device that is associated with a controller for one or more of the moveable members .

16. A load guidance system according to claim 15, wherein the controller is a geared motor.

17. A load guidance system according to claim 16, wherein each moveable member comprises a wheel having a recess for housing the, or each geared motor associated with said wheel .

18. A load guidance system according to claim 17, wherein pairs of wheels may be coupled by a steering linkage to assist directional control of the load-carrying device.

19. A load-carrying device including a load-guidance system according to any preceeding claim.

20. A support for a power pack for a load-carrying device, the support provided as a plug mounted on a frame forming part of the load carrying device, the plug projecting at an upwards angle, wherein the power pack is provided with a socket on an upper part of the power pack, such that when the socket is attached to the plug, the socket is directed downwards onto the plug, with the weight of the power pack depending from the socket such that the force provided by the weight holds the socket on the plug, which supports the weight of the power pack.

21. A support for a power pack according to claim 20, wherein the pins for the plug project upwards at a degree of substantially 35 degrees from the horizontal.

22. A support for a power pack according to claims 20 or 21 in combination with a load-carrying device having a load guidance system according to any of 1 to 18 preceding.

23. A golf trolley in combination with a load guidance system the golf trolley including load support mounted on movable members to allow the load support to be moved from one position to another, wherein the load guidance system includes : a) a connecting member, a first end of which is attached to a reactive member of the load guidance system and a second end of which is releasably attachable to a person or device that is to move the golf trolley; b) a sensor to detect the position of, or force on, the connecting member relative to a predetermined parameter, so providing an indication of the position of the person or device relative to the golf trolley; c) a powered steering mechanism, which in response to one or more signals from the electronic control centre, which cause one or more of the movable members to move such that the golf trolley is caused to follow the orientation of the person or device.

24. A load guidance system as substantially described herein, with reference to and as illustrated in the accompanying Figures .

25. A golf trolley as substantially described herein, with reference to and as illustrated in the accompanying Figures .

26. A power pack support as substantially described herein, with reference to and as illustrated in the accompanying Figures .