A carriage

Abstract

 A carriage has a plurality of ground engageable wheels (206) mounted on a body (200), and a pair of driving wheels (233, 234) independently drivable by drive motors (226, 227). The driving wheels (233, 234) are movably mounted on a chassis (214) so that they can occupy a first position clear of the ground to enable the carriage to be driven over the ground. The carriage may include a seat (210) which can be elevated and tipped forwardly by motor driven actuators (273), (266) to enable the height of the seat (210) to be adjusted and to assist a user to move from the seat (210) into a standing position.

Description

[0001] The invention relates to a carriage and is particularly, but not exclusively, concerned with a powered chair, for example, for use by a disabled person.

[0002] Powered wheel-chairs have been proposed hitherto for use by disabled persons and have generally proved successful. However, whilst such vehicles are usually manoeuvrable when being driven they can be difficult to move around otherwise an object of the present invention is to provide a carriage such as a chair which reduces that disadvantage.

[0003] According to one aspect of the invention there is provided comprising a plurality of ground engageable wheels mounted on a body at least one drivable wheel and drive means for said drivable wheel characterised in that the or each drivable wheel is so mounted that it can occupy a first position clear of the ground and a second position in engagement with the ground whereby the carriage can be driven over the ground by the drivable wheel.

[0004] According to a second aspect of the invention there is provided a carriage comprising a plurality of ground-engageable wheels mounted on a body, at least one drivable wheel carried by a section movable relative to the body, the drivable wheel being drivable by drive means, the drivable wheel being so mounted on the body that the drivable wheel can occupy a first position clear of the ground and a second position in engagement with the ground whereby the carriage can be driven over the ground by the drivable wheel.

[0005] With that arrangement the positioning of the drivable wheel clear of the ground enables the carriage to be pushed along the ground freely and easily.

[0006] According to a third aspect of the invention there is provided a plurality of ground engageable wheels mounted on a body, at least two driving wheels being spaced apart and drivable independently by drive means, the drivable wheels being carried on the body or on a section movable relative to the body so that they can occupy a first position clear of the ground and a second position in engagement with the ground whereby the carriage can be driven over the ground by the drivable wheels.

[0007] With the latter arrangement the carriage can be arranged for steering by the independently drivable wheels whilst retaining the feature of positioning the drivable wheels clear of the ground for free movement of the carriage along the ground.

[0008] The or each drivable wheel is preferably mounted on the aforesaid section such as a chassis on the body movable relative to the body. The said section may be mounted on resilient means. When a downward load is applied to said section on which the or each drivable wheel is mounted the downward load is preferably arranged to overcome the bias of the resilient means to urge the or each drivable wheel into engagement with the ground. If the carriage is in the form of a chair, the downward load applied to said section may be that applied to a seat of the chair by the user.

[0009] Alternatively, the or each drivable wheel may be normally held clear of the ground by means of bias means arranged between the body and at least one of the remaining wheels on the body. Such bias means may be a spring which applies a downward load to one or more of said remaining wheels.

[0010] With either arrangement as set out above, the drivable wheels will engage the ground only when the carriage is carrying a load. When the load is removed, the drivable wheels will disengage the ground and leave the carriage supported by the remaining wheels.

[0011] Preferably, the remaining or non-drivable wheels are freely rotatable and may be in the form of castors to enable the carriage to be moved easily over the ground.

[0012] The body may carry two spaced apart castor wheels at one end, a single central castor wheel at the other end and two drivable wheels between the ends.

[0013] The or each drivable wheel may be barrel or part-­barrel shaped or tapered to provide traction on soft and hard surfaces.

[0014] The or each drivable wheel may be driven through a transmission which will, for example, enable drive to be transmitted in a non-reversing sense. That is, drive may be transmitted from the drive means to the drivable wheel but drive may not be transmitted from the drivable wheel to the drive means. Such a drive transmission may be achieved by using a worm and wheel type of gearing. A motor for transmitting drive to one said drivable wheel may be mounted on the body and drive may be transmitted to the drivable wheel through a flexible drive. Alternatively and where said section is provided, the motor may be mounted on said section and for driving the wheel without the use of a flexible cable.

[0015] Where two drivable wheels are provided, two driving motors may be provided. Preferably, the motors are operable independently to enable one drivable wheel to be rotated relative e.g. opposite to the other drivable wheel. In that way, the drivable wheels may be used to manoeuvre the carriage, for example, in forward, or reverse directions, rotationally about its axis or any combination thereof. If desired each motors may be mounted on said section and may have an output for rotating one of two coaxial drive shafts drivably connected to the drivable wheels.

[0016] The section preferably includes arm means whereby up and down pivotal movement of the drivable wheels causes the arm means to pivot. The arm means may comprise two spaced apart arms which are rigidly connected to parts of said section to provide a rigid mounting chassis for the or each drivable wheel. The arms may be arranged to lie alongside side members of the body and guide means may be provided on the section for inhibiting relative movement between the arms and side members in a direction parallel with the axis of pivoting of the arms. The guide means may comprise spacer elements arranged between surfaces on the section and surface associated with the body. The surfaces associated with the body may comprise opposite surfaces of an upstanding part of a column on which the load carrying portion is mounted.

[0017] The axis of pivoting of the arm means may be spaced from the axis of rotation of the or each drivable wheel.

[0018] Where the aforesaid resilient means is provided, it may be arranged between said section and the body at a position spaced from the axis of pivoting of the arm means.

[0019] The carriage may include a load carrying portion which can be moved up or down relative to the body. In one embodiment, means may be provided for permitting a degree of free relative rotational movement in a substantially horizontal plane between the load carrying portion and the body. Where the carriage is in the form of a chair, the load carrying portion will normally carry a seat and such free rotational movement will enable the user of a chair to effect an angular horizontal movement of the seat which may be useful in certain circumstances.

[0020] Preferably, the load carrying portion is connected to the said section of the body so that a load applied to the load carrying portion will urge the section downwardly to move the drivable wheel or wheels into engagement with the ground. The said section may support a lower end of part of a vertical column on the upper end of which the load carrying portion is mounted.

[0021] According to a further aspect of the invention there is provided a carriage comprising a plurality of ground engaging wheels, a load carrying portion, a body on which said ground engaging wheels and load carrying portion are mounted, and elevating means for moving the load carrying portion up or down relative to the body.

[0022] Where the aforesaid column is provided, the column may comprise an outer member fixed to the body and an inner member movable relative to the outer member. The outer section preferably provides a guide for the inner section as it is elevated.

[0023] The elevating means may comprise an actuator such as a screw jack and, e.g., a driving motor therefor. The screw jack may have a lower end pivotally connected to said section whereby the jack reacts against said section when elevating the load carrying portion.

[0024] Where the load carrying portion is connected to the section of the body carrying the or each drivable wheel, the screw threaded member of the screw jack may be rotated by means of a motor and gearbox at the upper end of the column. In that way, the motor can easily be houses immediately beneath or on the load carrying portion. Alternatively, the screw threaded member may be rotated by means on said section carrying the driving wheels.

[0025] Sensing means may be provided for sensing an elevated position of the load carrying portion. The sensing means may comprise one or more microswitches arranged in a control circuit for the elevating motor.

[0026] Tipping means may be provided for tipping a part on the load carrying portion. In one embodiment, tipping may occur as a result of the elevating means moving the load carrying portion towards its highest position. In another embodiment tipping may be effected by the user on operation of independent tipping means as desired.

[0027] According to another aspect of the invention there is provided a carriage comprising a plurality of ground engaging wheels, a load carrying portion mounted on a body, a tipping part pivotally connected to the load carrying portion, elevating means for moving the load carrying portion up or down relative to the body and tipping means for tipping the said tipping part relative to the load carrying portion.

[0028] In one embodiment, the tipping means is a connection such as a cable between the tipping part and the body. As elevation of the load carrying portion proceeds, the connecting means preferably causes the tipping part to tip about its pivot. Preferably, the connection is arranged to effect tipping of the tipping part of the load carrying portion only after it has been elevated beyond a certain position.

[0029] Stop means may be provided for limiting the pivotal movement of the tipping part of the load carrying portion.

[0030] In another embodiment, the tipping part of the load carrying portion may be tipped by means of an actuator which may take the form of a screw jack driven by a motor. The tipping of the tipping part may take place after the load carrying portion has been elevated to a given height. At that point sensing means for sensing the elevated position is preferably arranged to switch off the elevating motor and switch on the motor for tipping the tipping part. Therefore on actuating switch means for elevating the seat to an upper limit, continued actuation of the switch means may be arranged to effect the tipping of the tipping part.

[0031] Preferably the tipping part is a seat and in such a case, a leg rest may be provided which may itself be pivotable into a desired position by means of an actuator which may take the form of a screw jack driven by a motor. The movement of the leg rest may be prevented during tipping of the seat by means of a switch which isolates the driving motor for the leg rest actuator. Preferably the tipping of the seat is permitted only after the leg rest has been adjusted so as to occupy a position in which it will not impede movement of the user from the seat into the standing position, e.g., its lowest position.

[0032] Where the aforesaid actuators are used, one or more of them may be driven by a motor or motors each of which incorporates a temperature sensor for sensing a rise in temperature of the motor armature or other motor part. Such a rise in temperature will typically occur when the rotating armature is braked or brought to a stop while electric current is still being supplied thereto. In the present case, such a situation could arise if an operating switch for a motor is held in an ON position after the actuator concerned has reached a limit of travel and no travel limit switch is provided. Preferably the actuator includes means which will gradually inhibit rotation of a screwed member of the actuator as the actuator approaches its travel limit so as to avoid high inertia loads on the armature due to sudden stopping of the screwed member. The temperature sensor will be arranged to switch off the motor after a given rise in temperature occurs. The means for gradually inhibiting the rotation of the screwed member may comprise resiliently compressible means which begins to compress and slow down the motor towards a travel limit. In certain cases, e.g., in the case of the leg rest actuator, such means may be provided towards both limits of travel. In the case of the seat tipping actuator, such means may be arranged to operate towards the tipping limit and in the case of the elevating actuator such means may be arranged to operate towards the lowest travel limit. The resiliently compressible means may be one or more Belleville washers.

[0033] If desired, the carriage may be connected to a load-­carrying basket. Where the carriage is a chair, the basket may be positioned adjacent a seat of the chair to enable a user to sit close to the basket. In such a case, the user may conveniently place purchased articles in the basket where, say, the carriage is used for shopping. The basket may be of substantially inverted L-shaped form for optimum capacity.

[0034] Whilst specific reference has been made to the use of the carriage as a chair, the aforesaid load carrying portion could simply be a load carrying platform or skip. If desired, the load carrying platform could be so arranged that the user could stand on it for transport purposes. Preferably, the carriage would include some form of handrail or other support which the user could grasp during transport.

[0035] Preferably, a control such as electrical switch means may be provided at a convenient location e.g., on one or more arm rests to enable one or more of the driving motors to be operated. Where two independently drivable wheels are provided, it may be convenient to locate two switches for independently operating the driving motors for those drivable wheels so that the switches lie side by side. In such a case, the switches may be operated by levers which could be interconnected at their upper ends by a bridging piece. By moving the bridging piece forwards or backwards, the driving motors could be arranged to drive the carriage forwards or backwards. If desired, the bridging piece could be arranged so that twisting movement thereof would move one lever forwards and the other backwards to steer the carriage or, if desired, turn the carriage on its own axis. Alternatively, a single joystick control may be provided for controlling the driving motors.

[0036] Preferably, key-operated means may be provided for switching on and off a main source of electrical power which may, for convenience, be a heavy duty rechargeable battery.

[0037] The carriage may include and a battery charger. The battery charger may be connectable to an electrical supply cable by means which causes all connections between the battery and operation circuits of the carriage to be disconnected during battery charging

[0038] Carriages in accordance with the invention will now be described by way of example only with reference to the accompanying drawings in which:-

Fig.1 is a schematic elevation of one form of carriage in accordance with the invention in the form of a chair and shown partly in vertical cross-­section,

Fig.2 is a view of part of the chair shown in Fig.1 looking in the direction of arrow II in Fig.1,

Fig.3 is a schematic diagram of electrical connection, and control panels,

Fig.3a is a view of a control panel arrangement for single hand operation,

Fig.4 is a schematic elevation of the chair of Fig.1 having a basket attached thereto,

Fig.5 is an elevation of a further form of carriage in accordance with the invention in the form of a chair,

Fig.6 is a plan view of the part of the chair shown in Fig.5, and

Fig.7 is a cross-section through part of the chair shown in Fig.6 on the line VII-VII in Fig.6.

Fig.8 is a cross section through a screw jack for operating a leg rest,

Fig.9 is a diagrammatic end view of the chair of Fig.5 looking in the direction of arrow IX in Fig.7,

Fig.10 is a diagrammatic plan view of a control panel for use with the chair of Fig.5,

Fig.11 is a diagram of circuitry used in controlling the operation of screw jacks of the chair of Fig.5, and

Fig.12 is a diagram showing circuitry used to control motors for driving the chair.

[0039] A chair base 10 (constituting the aforesaid "body") comprises a plurality of legs 12 which extend radially from the hub 13. Any convenient number of legs may be provided but a minimum of four is envisaged. The chair base may be a simple alloy casting similar to the type commonly used on office chairs. The radially outer ends of the legs 12 are provided with ground engageable castor wheels 14. The hub 13 supports a column 11 which includes a vertical tube 15 projecting beneath the hub 13 by a short distance and extending above the chair base to form an outer guide member for an inner circular cross-section tube 16 The tube 16 is welded to a load carrying portion in the form of a seat plate 17 at its upper end. The vertical outer tube 15 is welded at its lower end to an annular plate 18 which is also welded to a square cross-section vertical tube 19. The tube 19 extends co-axially of the tubes 15, 16 towards the seat plate 17. The seat plate 17 is welded to a downwardly projecting cross-section tube 20 which fits with substantial clearance within the tube 19. A scrap transverse cross-section is indicated at A in Fig.1 which shows the relative cross-sectional sizes of the tubes 19, 20 quite clearly. The lower end of the tube 20 is rotatably and axially fast with a screw threaded sleeve 22. The lower end of the outer tube 15 is welded to a bush 23 on which is journalled a vertical sleeve 24 rotatably and axially fast with a chassis 25 (constituting the aforesaid "section") for independently drivable wheels 39, 40. The chassis constitutes the aforesaid section of the body.

[0040] The chassis 25 is movable up and down along the bush 23 relative to the chair base 10 and is guided in its upward movement by means of guide bars 28 on the chassis which pass slidably through bores 29 in selected legs 12. The upper ends of the guide bars 28 are screw threaded and carry nuts 30 which act as stops for limiting downward travel of the chassis 25. A plurality of tension springs 31 extend between selected legs 12 and the chassis 25 so as normally to bias the chassis upwardly towards the legs.

[0041] The chassis 25 carries two co-axial and horizontal tubes 32, 33 which rotatably support in bearings 34 therein two shafts 35, 36 respectively. Each shaft has a screw-threaded end section 37 on which a hexagon nut 38 is drivably fast. The shafts 35, 36 are also rotatably fast with the ground wheels 39, 40 adjacent the nuts 38. The ground wheels lie between adjacent legs 12. The nut 38 on the shaft 35 is positioned within a complementary female hub section (not shown) of an output gear wheel (also not shown) of a worm and wheel gear box 42. The casing of the gear box 42 is held against rotation relative to the tube 32 by means not shown. Drive is transmitted to the worm gear of the gear box 42 through a flexible drive 43 leading from a motor 44 carried by the chair base 10. The shaft 36 also has its nut 38 arranged within a gear box 45 identical to the gear box 42 and drive is transmitted to the gear box 45 by means of a flexible drive 46 from a motor 47 identical to the motor 44 and mounted on the chair base 10.

[0042] The under surface of the chassis 25 carries a gear box 48 (Fig.1) substantially identical to the gear boxes 42, 45 which has an output gear wheel drivably connected to a hexagon nut 49 drivably fast with a screw threaded bar 50 which screws into the screw threaded sleeve 22. The screw threaded bar also carries a flanged member 52 by which thrust is transmitted from the bar 50 to the chassis 25 through a thrust bearing 53. The screw threaded bar 50 extends substantially throughout the full length of the downwardly projecting square cross-section tube 20. Drive to the gear box 48 is transmitted through a flexible drive 54 from a motor 55 conveniently placed on the chair base.

[0043] As shown clearly in FIg.2 the seat plate 17 is of inverted channel shape cross-section. Sides 56 of the seat plate extend forwardly and rearwardly of the centre column 11 of the chair base 10 and support between them at their forward ends a pivot tube 57 for a seat cushion 58 of a seat indicated generally at 51. The seat cushion is mounted on spaced apart angle plates 59 to which the underside of the cushion is fastened to enable the seat cushion to pivot from the full line position to the broken line position in Fig.1. The angle plates 59 are formed with co-axial side apertures 60 which locate reduced diameter screw threaded ends of a pivot bar 62. The bar 62 extends co-axially through the pivot tube 57 and is journalled on bearings 63 (one only of which is shown) at the ends of the pivot tube 57. The angle plates 59 are held in place on the pivot bar 62 by means of locking nuts 64. One of the angle plates 59 has its side flange extended to form a lever 65 which at its radially outer end is provided with an inwardly directed stud 66 projecting through a quadrant-like slot 67 in a stop plate 68. The slot 67 controls the forward tipping position of the seat cushion at its broken line position shown in Fig.1. The full line position of the seat cushion is fixed by a transverse stop tube 69 which extends between the angle plates 59 to the rear of the column 11. The tube 69 engages a strip of cushioning material 70 on a stop plate 72 extending between support sections 73 of the sides 56 of the seat plate 17. One of the angle plates 59 is provided with a bracket 74 which can be connected to a bracket 75 on the chassis 25 by means of a flexible steel cable 76. Conveniently, the cable may be fastened to the brackets by means of releasable snap-fasteners of the dog-clip type.

[0044] The angle plates 59 extend forwardly and upwardly to form two spaced apart vertical support arms 77 at the front of the seat. The spacing between the support arms is such that a user may sit between them comfortably. The upper ends of the support arms 77 are pivotally connected to respective side members 78 of a leg-rest 79. The side members 78 have downwardly extending arms 80 thereon one of which is pivotally connected to a thrust tube 82 of a screw jack arrangement 83. The arrangement 83 includes a screw threaded bar 84 which engages a screw-threaded member (not shown) within the thrust tube 82 and has a hexagon nut 85 drivably fast therewith at its rear end. The bar 84 is drivably by a worm and wheel gear box 86 similar to the gear boxes 42, 45 and 48. Thrust from the bar 84 reacts against a bracket 87 on the support sections 73 of the seat plate through a thrust bearing 88. Rotation of the screw-threaded bar 84 will cause the thrust tube to pivot the leg-­rest 79 between the full and broken line positions shown in Fig.1. Drive to the gear box 86 is transmitted by means of a flexible drive 89 from a motor (not shown) mounted e.g., on one of the angle plates 59.

[0045] The seat plate 17 and the angle plates 59 together constitute the aforesaid load carrying portion and in particular comprise the aforesaid first and second pivotally interconnected parts.

[0046] The motors 44, 47, 55 and 90 are controlled from two panels 92, 93 arranged adjacent respective arm rests 94 (one only of which is shown in Fig.1) of the chair. The arm rests 94 and a backrest 91 are suitably supported from the angle plates 59. The panel 92 has a switch 95 operated by a lever 96 and a rocker switch 97 thereon. The lever operated switch 96 is arranged to connect a battery 98 (suitably mounted on the chair base 10) to the motor 40 to provide a forward or reverse drive to the wheel 39 depending on whether the lever 96 is pushed forwardly or rearwardly by the user. The rocker switch 97 is arranged to connect the battery 98 to the motor 55 so that drive will be transmitted to the screw threaded bar 50 to raise or lower the downwardly projecting square cross-tube and the inner tube 16 within the vertical tube 15 depending on which way the rocker switch is rocked. The control panel 93 has a switch 99 operated by a lever 100 and a rocker switch 102 thereon. The switches 99 and 102 are identical to the respective switches 95 and 97. Appropriate operation of the switch 100 will connect the battery 98 to the motor 47 to effect forward or reverse drive of wheel 40 and operation of the rocker switch 102 will connect the motor 90 to the battery 98 so as to cause the screw jack arrangement 83 to raise or lower the leg-rest 79 depending upon which way the switch 102 is rocked.

[0047] It is envisaged that the electrical circuitry may incorporate electronic control devices whereby operation of the switches will permit voltage to be applied to the motors gradually to avoid sudden or jerky transmission of drive.

[0048] The circuitry also includes limit switches to limit the upward movement of the seat cushion through operation of the screw-threaded bar 50 and to limit the pivotal movement of the leg rest 79. Operation of the limit switches is described below with respect to the general operation of the invention.

[0049] In use, with the chair unoccupied, the castor wheels 14 engage the ground and the springs 30 lift the chassis 25 upwardly so that the driving wheels 39, 40 are clear of the ground. In that way, the chair may be freely moved over the floor from one place to another when unoccupied. When the user sits on the seat cushion 58, the weight of the user forces the seat plate 17 and tubes 16 and 19 secured thereto to move axially downwardly within the vertical tube 15 taking the cassis 25 with it. Such movement of the chassis 25 causes the ground wheels 39, 40 to move into engagement with the ground and the weight of the user is thereby transmitted directly to the ground through the wheels 39, 40. The non-reversibility of the gear boxes 42, 48 i.e., drive cannot be transmitted from the wheels 39, 40 to the motors 44, 47 through the flexible drives 43, 44, means that the chair will effectively be braked against rolling once the user occupies the seat. The wheels 39, 40 face the fore-and-aft direction although, as described above, the seat itself may pivot horizontally from side to side by the amount permitted by the tubes 19, 20 in practice through around 12 degrees. The user may operate the levers 96, 100 so as to drive the wheels 39, 40 to manoeuvre the chair as required. For example, movement of both levers 96, 102 forwardly together will drive the seat forwardly, movement of both levers rearwardly will cause the seat to be driven in reverse and movement of one lever forwardly and the other rearwardly will cause the chair to turn on its own axis. Any combination of movements may, therefor, be used to manoeuvre the seat as desired.

[0050] To elevate the seat cushion 58, the rocker switch 97 is used to operate the motor 55. Initially, current to the motor passes through a diode (not shown) which by-passes a first microswitch 103 on the vertical tube 15, which, in the lowest position of the seat cushion, is actuated by a finger 104 (on the seat plate 17) to cut the supply of current to the motor 55. Once current flows through the diode to the motor the seat begins to elevate and the finger releases the microswitch 103 so that current can continue to flow to the motor through the switch rather than the diode. If the rocker switch 97 is held in a depressed condition, the seat cushion will continue to elevate until slack in the cable 76 is taken up. Continued elevation will then cause the cable to tip the seat cushion about the axis of pivot tube 57 until the stud 66 moves to the position shown in the slot 67. At that point a second microswitch 105 co-operates with a groove 106 in the inner tube 16 to cut the electrical supply to the motor. The tipping of the seat into the broken line position helps a disabled user to move from the seat into a standing position. Preferably, the leg-rest 79 will then be in the lowest position shown in broken lines so as not to interfere with movement of the user into a standing position. To lower the chair, current by-­passes the switch 105 through a diode to drive the motor 55 in an opposite sense. Once the microswitch clears the groove 106, current then flows through the microswitch 105 to the motor. When the lowest position of the seat is reached, the microswitch 103 operates to cut supply of current to the motor 55. In case of failure of the microswitch 105 to sense the upper travel limit, a suitable mechanical stop may be provided which will prevent the inner tube 16 being lifted clear of the tube 15. In such a case, the mechanical stop will simply cause the motor 55 to stall. A similar arrangement may be provided for the screw jack arrangement 83. For clarity in Fig.1, the tipped position of the seat cushion 58 is shown in the non-elevated position of the seat cushion. As the seat lowers, the weight of the user causes the seat cushion 58 to pivot back into the full line position as shown in Fig.1.

[0051] Operation of the switch 102 will enable the user to move the leg rest 79 up or down to achieve the most comfortable position. The travel limit of the screw jack 83 is controlled by a microswitch 107.

[0052] If the user does not require the seat pivoting feature to assist standing, the cable 76 can be unclipped from the bracket 75 and passed through aligned apertures (not shown) in two adjacent plates (not shown) one of which extends between the sides 56 of the seat plate 17 and the other of which extends between the angle plates 59. When the seat cushion occupies the full line position shown in Fig.1, apertures formed in the adjacent plates are coaxially aligned to enable the steel cable 76 and/or clip thereon to be passed through them. The clip may then be clipped through the apertures or be secured to a further bracket (not shown) on one of the angle plates 59 or on one of the adjacent plates. In that way, the seat will be prevented from tipping by virtue of the clip or cable passing through the aligned apertures.

[0053] Instead of using a cable 76 to effect tipping movement of the seat cushion 58, the tipping movement may be effected by a screw jack. In such a case, a stirrup 108 has its upper ends bolted to the support sections 73 of the seat plate 17. A screw threaded bar 109 of a screw jack 110 passes through the lower end of the stirrup 108 and a hexagon nut 111 drivably fast with the bar 109 is drivably connected to the output of a gear box 112 which is substantially the same as the gear boxes 42, 45, 48 and 86. Drive is transmitted to the gear box through a flexible drive (not shown) from a motor (also not shown). The screw threaded bar 109 engages a threaded element within a thrust tube 113 which is pivotally connected at its upper end to a cross pin 114 extending between brackets 115 on the tube 69. Thrust reaction from the screw-threaded bar 109 is transmitted to the stirrup through a thrust bearing 116. Two microswitches 117, 118 are carried by the stirrup 108. The microswitch 117 co-operates with a finger 119 at the lower end of the thrust tube 113 and the microswitch 118 co-operates with a finger 120 at the upper end of the thrust tube 113. The microswitches 117, 118 are arranged in an electrical control circuit for the unshown motor to act as limit switches for tipping of the seat. As will be apparent operation of the motor to rotate the screw threaded bar 109 and extend the screw jack 110 will cause the seat cushion to tip about the pivot bar 62 towards the broken line position. The micro switches 117, 118 act in the same way as micro switches 103, 105 and can be by-passed by diodes as described above to operate the screw jack.

[0054] As shown in Fig.4, one of the angle plates 59 may be bolted to a basket 122 which is substantially of inverted L-shape when viewed from the side to enable the basket to extend over the lap of a user. The basket may have one or more ground engageable castor wheels 123 thereon. The basket may be used for shopping making the invention particularly useful as a means of transport for a disabled person in a supermarket. One of the arm rests 80 may be pivoted upwardly as shown in broken lines in Fig.4 to enable the user to slide sideways onto the chair between the seat cushion, leg-rest and the basket. The arm rest can then be pivoted downwardly into its normal position and the seat controlled as required. If the user wishes to elevate the seat cushion the ground engaging wheel 123 on the basket will be lifted clear of the ground. However, the basket may be so bolted to the angle plate 59 that it will be supported entirely by the angle plate in such circumstances.

[0055] Instead of the chassis 25 and drivable wheels 39, 40 being biased upwardly by springs 31, the chassis may be rigid with the seat base 10 and the castor wheels resiliently biased downwardly. In that way the resilient bias will lift the seat base 10 upwardly to raise the wheels 39, 40 from the ground. Once the seat is occupied, the weight of the user will be sufficient to overcome the resilient bias and move the chair base 10 downwards until the wheels 39, 40 engage the ground.

[0056] As shown in Fig.3a the switches 95, 97, 99 and 102 could be arranged on one side of the chair for use by a person having use in one hand only. In such a case, the levers 96, 100 could be ganged together by a bridging piece 124 so that movement of the latter fore-and-aft will move the levers 96, 100 fore-and-­aft simultaneously. Clockwise or anticlockwise twisting of the bridge piece would cause one of the levers to move back and the other to move forward to turn the chair.

[0057] A key-operated main switch 125 can be arranged on the or one of the control panels to switch on and off the supply from the battery 98 to the panel or panels.

[0058] Referring to Figs.5 to 11 an alternative form of chair is shown. The actual seat section 210 of the chair can be of very similar construction to that shown in Figs.1 - 4 but the base 200 is different as will be described below.

[0059] The chair base 200 (constituting the aforesaid "body") comprises parallel side members 202 welded to a front cross member 203 and a rear cross member 204. The front cross member 203 is welded to a mid member 205. The members of the base may conveniently be formed from hollow steel tubing. The rear cross member 204 supports two castor wheels 206 and a mid member supports a further castor wheel 206. The front cross member 203 is welded to a guide tube 208 of a column 209 for a frame 251 for supporting the seat 210. The column includes a centre tube 212 which fits within the tube 208 with sliding clearance. As shown in Fig.7, the tube 212 houses a screw jack 273 comprising an outer tube 274 which is pivotally connected at its lower end to a chassis (constituting the aforesaid "section") indicated generally 214. The jack also includes a screw threaded bar 242 which runs in a nut 211 fast in the upper end of tube 274.

[0060] The chassis 214 includes a main cross member 215 having forwardly facing ends 216, two side plates 217 (constituting the aforesaid "arm means") welded to the main cross member and an angle section 218 welded to the front lower ends of the side plates 217. Each side plate is pivotally at 213 connected to the adjacent side member 202 so as to lie alongside the adjacent side member. Each side plate 217 is formed with a slot 211 which is arcuate about the axis of bolt 213 and which receives a stop bolt 219 mounted on the adjacent side member 202 to limit the amount of pivotal movement of the side plate 217. The main cross member 215 has two forwardly projecting strips 220 which are connected to respective strips 222 on the front cross member 203 by means of tension springs 223. A channel 224 is welded between the main cross member 215 and an angle section 218 which interconnects plates 217. Two locating pads 225 (co constituting the aforesaid guide means) are attached to the inner faces of the channel 224 and slidably engage opposed outer surfaces of the guide tube 208 on the front cross member 203. The pads help to locate positively, the sub frame relative to the base 200 in the side to side direction.

[0061] The chassis 214 carries two independently operable motors 226 227 which incorporate a worm gearbox providing drives to respective shafts 228 229 which pass through bearings 230, 232 on the ends 216 and are drivably connected to driving wheels 233, 234.

[0062] As shown in Fig.6a, the driving wheels are semi-­barrel shaped providing a tapering ground engaging surface 235. At its widest diameter, the wheel provides a narrow contact 236 for riding along a hard surface 237. However, where the chair is being driven over a soft surface, such as a pile carpet or soft ground 238, the ground engaging surface 235 will provide a relatively large area of contact improving traction over soft surfaces.

[0063] The seat 210 is supported on the frame 251 (constituting the aforesaid load carrying portion) attached to the upper end of the centre tube 212 and can be height adjusted relative to the base 200 by means of the screw jack 273 the screw threaded bar 242 of which is driven by a motor and gearbox 239 mounted on the frame. The motor 239 is preferably identical to the motors 226, 227. Rotation of the screw threaded bar 242 causes the bar 242 to move upwardly or downwardly in nut 211 relative to the tube 274 which reacts through a pivot pin 275 against the chassis 214.

[0064] The seat 210 includes spaced apart angle mounting members 243 which are connected to the frame 251 by pivot bolts 241. The members 243 support two spaced apart L-shaped members 244 at their front ends. The members 244 pivotally support a leg-rest 245 similar to the leg-rest 79 shown in Fig.1. The frame 251 includes two spaced apart outer side plates 251a. The leg rest 245 pivotally supports a motor and gearbox 246 which drives a screw jack 247 shown in detail in Fig.8.

[0065] The screw jack 247 comprises an outer tube 248 having a screw threaded nut 250 fast with its left hand end and a screw threaded bar 252 in the nut. The bar 252 has a reduced diameter portion 253 at its inner end to define a shoulder 254 which forms a stop for a washer 255. Two Belleville washers 256 are positioned back-to-back on the portion 253 and are held lightly in compression by means of a washer 257 and a bolt 258 screwed into the bar 252. The bar 252 is drivably connected to a drive member 259 and two further Belleville washers 260 are arranged between the drive member and a washer 262 on the bar. The washer 262 abuts a shoulder 263 on the bar 252. The drive member 259 receives drive from an output member 261 of the motor and gearbox 246. The motor 246 has an in-built temperature sensor 246a which, on detecting a certain increase in temperature due to stalling or heavy loading at the output will interrupt flow of current to the motor to prevent further transmission of drive to the output. Such motors are commonly used to operate electric windows in motor vehicles. The outer tube 247 is pivotally mounted on a pin 264 (Fig.9) at one side on one side plate 251a and on its other side on a rigid tension strip 265 connected to the frame 251 towards the front of the seat. Such an arrangement provides support for the outer tube 247 on both sides. The screw jack is pivotally connected to the leg-rest 245 to enable the leg rest to be raised and lowered about an axis 248.

[0066] To tip the seat in this embodiment I propose to use a seat screw jack 266 including a motor and gearbox 267 similar to the motor 246. The motor 267 is pivotally connected between two brackets 243a on a cross member 243b which interconnects members 243. A screw threaded bar 268 is drivable by the motor 267 through a drive output member and drive member arrangement similar to that shown in Fig.8. The screw threaded bar 268 has a Belleville washer arrangement 268a at its inner end identical to that on bar 252 in Fig.8.

[0067] As in Fig.8, the jack 266 has an outer tube 269. The outer tube 269 is pivotally connected by a pin 270 on one side to the adjacent side plate 251a and on its other side to the lower end of a tension strip 272 connected at its upper end to the frame 215. In that way, the outer tube 269 is supported on both sides.

[0068] With reference to Figs.10 to 12, on arrangement of four microswitches is provided to control elevation and tipping of the seat 210 and movement of the leg rest 245. The circuit includes a printed circuit board 304 and receives power from a battery 258 via a fuse 305, a charging inhibitor switch 306 and a switch 295 described below.

[0069] A first microswitch 280 is mounted on the guide tube 208 and has an operating member 282 which co-operates with an aperture (not shown) in or lower edge of the centre tube 212. Second and third microswitches 284 and 281 are carried by a mounting plate 285 on the frame 251 and have respective operating members 286, 291 which co-operate with the underside of one of the seat mounting members 243. A fourth microswitch 287 is mounted on the frame 251 and has an operating member 288 which co-operates with the outer tube 248 of screw jack 247.

[0070] In use, with the chair unoccupied, the castor wheels 206 engage the ground and the springs 223 lift the chassis 214 and driving wheels 233, 234 clear of the ground as shown in Fig.7. In that way, the chair may be freely moved over the floor from one place to another when unoccupied. When the user sits on the a cushion 290 of the seat 210, the weight of the user forces the centre tube 212 downwards thereby causing the side plates 217 of the chassis 214 to pivot downwardly about the bolts 213 and causing the wheels 233, 234 to move from the full line position in Fig.5 to the broken line position into engagement with the ground. In that way, the weight of the user is transmitted directly to the ground through the chassis 214 and wheels 233, 234. The use of the side plates 217 connected rigidly by the main cross-member 215 provides a positive resistance to roll if the user tends to tip the chair.

[0071] The motors 226, 227 can be independently controlled in the same way as motors 44, 47 in Fig.1 but this time by means of a joystick 292 on the conveniently mounted control panel 293 (Fig.10) on one or each arm 294 of the chair. The motors can then be operated via the printed circuit board 304 to move the chair forward, backward or to turn the chair in the manner similar to that described with respect to Figs.1 - 4. The switch 295 is a main ON/OFF switch of a key operated or rocker switch type. A lamp 296 is provided to indicate an ON condition.

[0072] To elevate the seat 201 from its lowest position (shown in broken lines in Fig.5) to its upper, full line position, the motor 239 is operated by using a rocker switch 297 causing current to flow to the microswitch 280. To lower the seat 210, the switch 297 is operated again but in reverse and current flows in a reverse sense to drive the motor 239 in reverse to begin lowering the seat. The outer end of the screw threaded bar 242 has a Belleville washer arrangement 300 identical to that of bar 252 in Fig.8 and the motor 239 is identical to motor 246. As the bar 242 approaches its lowest position, the Belleville washers begin to compress if the user holds down the switch 297 and the motor 239 gradually comes to a stop. The loading and stopping of the motor 239 causes heating of the armature and the temperature sensor eventually cuts off supply of current to the motor.

[0073] Where it is desired to tip the seat 210 about bolts 241, the seat must first be fully elevated by motor 239. Also the leg rest 245 must occupy, e.g., its lowest position shown in full lines in Fig.5 in which position the outer tube 248 of screw jack 247 engages the operating member 288 of microswitch 287. While the microswitch 287 is in that condition, the motor 267 can be operated as described below. However, if the leg rest occupies a raised position such as that indicated at 245a in Fig.5, the microswitch 287 will operate to isolate the motor 267 to prevent tipping of the seat. Assuming that the leg rest is fully lowered, the switch 297 is operated to elevate the seat 210 as described above. When the centre tube 212 reaches its maximum height, the operating member 282 of microswitch 280 senses the aperture in or the lower edge of the centre tube 212. A switching arm 298 in the microswitch 280 then moves from the broken line position to the full line position to switch off the motor 239. Such switch over of the arm 298 causes current to flow through microswitch 287 and initially through a diode 299 across two of the terminals of microswitch 284 and to the motor 267 which begins tipping the seat. As soon as tipping begins a switching arm 307 in microswitch 284 switches from its broken line position to the full line position as mounting member 243 adjacent microswitch 284 disengages the operating member 286 and current then by-passes diode 299. Also as soon as tipping begins, the mounting member 243 adjacent the microswitch 281 disengages the operating member 291 thereby causing the microswitch 281 to isolate the leg rest motor 246. In that way the leg rest 245 cannot be moved while the seat is being tipped. The tipping continues as long as the user continues to depress the switch 297 until the Fig.5 broken line limit of tipping T is reached. Continued operation of the switch will cause the Belleville washers of screw jack 266 to compress and gradually bring the motor 267 to a stop. The motor 267 is identical to motors 239 and 246 and the sensed increase in temperature eventually switches off the motor 267.

[0074] To move the seat back to its un-tipped position, the switch 297 is operated in reverse and current flows to the motor 267 through microswitches 280, 284 and 287 until the seat resumes its un-tipped position. Once the switching arm 307 of microswitch 284 from its full line to its broken line position, current flow to motor 267 ceases and current will flow momentarily through a diode 308 to motor 239 to begin lowering the seat. As soon as the seat begins to lower, the centre tube 212 depresses operating member 298 of microswitch 280 so as to move the switching arm 298 into its broken line position. Current then flows directly to the motor 239 so as to by-pass diode 308.

[0075] Provided that the seat is in its untipped condition so that microswitch 281 does not prevent operation of the leg rest motor 246, a switch 302 is operated either one way to raise or an opposite way to lower the leg rest. If the switch is held in a depressed condition at either limit of travel of screw jack 247, the Belleville washers 256, 260 as appropriate will compress and the motor will gradually stop, heat up and then switch off.

[0076] Instead of using Belleville washer arrangements, additional microswitches could be used to limit travel.

[0077] As before, it is envisaged that the electrical circuitry may incorporate electronic control devices whereby operation of the joystick 292 will permit voltage to be applied to the motors 226, 227 gradually to avoid sudden or jerky transmission of drive.

[0078] Conveniently, the base 200 carries a battery 358 on a suitable transverse plates 359 extending between the side members 202. A battery charger (not shown) may be provided in a box 360 on the frame 251 which also houses circuit board 304. The end of a charging lead (not shown) may be connected from the mains to the box 360 for powering the battery charger. The charging inhibitor switch 306 is operated by connecting the end of the charging lead and is arranged to isolate all circuits of the chair from the battery 358 during charging. In that way, the chair cannot be driven while the mains lead is connected to the charger.

[0079] One great advantage of this invention over known types of motorised wheel chairs is that the chair base and castors of the Figs.1 - 4 embodiment may be made in large quantities somewhat like chair bases for existing office chairs. In each embodiment the seat cushion, backrest and armrests can be of a standard office chair or motor vehicle type which are easily available and which may be mounted easily on the seat plate. That is clearly unlike motorised wheel-chair arrangements which require special seats normally manufactured in relatively small quantities. Moreover all the motors used may be of a conventional type. In particular those used in Figs.1 to 12 may be of a type used for electrically operated windows in motor vehicles and which have a built-in worm and wheel reduction drive. Also, whereas wheel-chairs are designed specifically for disabled persons, the chair described above can be used in any office or home even if the user is not disabled as the chair itself will have an appearance acceptable for such purposes. To enhance appearance of the chair in Figs.7 to 12 covers (not shown) may be provided to enclose the outer ends of main cross member 215.

[0080] Whilst specific reference has been made to the use of the invention as a chair, the base 10 or 200 could, in fact, be adapted so that the centre column 11 or 209 carries a platform on which a user can stand. Ideally, the platform would also incorporate some form of handrail or armrest which the user could hold for support and would also incorporate a control panel to enable the user to operate the motors 44, 47; 226, 227 for transport whilst in the standing position. The weight of the user would, again, urge the ground wheels 39, 40 or 233, 234 into engagement with the ground to provide the necessary traction.

Claims

1. A carriage comprising a plurality of ground engageable wheels (14, 206) mounted on a body (10; 200) at least one drivable wheel (39, 40; 233, 239), and drive means (44, 47; 226, 227) for said drivable wheel characterised in that the or each drivable wheel (39, 40; 233, 239) is so mounted (10; 200) that it can occupy a first position clear of the ground and a second position in engagement with the ground whereby the carriage can be driven over the ground by the drivable wheel (39, 40; 233, 239).

2. A carriage according to Claim 1 characterised in that two drivable wheels (39, 40; 233, 239) are drivable independently by said drive means (44, 47; 226, 227).

3. A carriage according to Claim 1 or 2 characterised in that the body (10, 200) carries a load carrying portion (51; 251) and the movement of the or each drivable wheel (39, 40; 226, 227) into engagement with the ground is effected as a result of a load being applied to the load carrying portion.

4. A carriage according to Claim 1, 2 or 3 characterised in that the or each drivable wheel is carried by a section (25, 214) mounted for up and down movement on the body (10; 200).

5. A carriage according to Claim 4 characterised in that resilient means (31, 223) is arranged between said section (25; 214) and the body (10; 200) so that when a downward load is applied to said section to move the or each drivable wheel (39, 40; 233, 239) into engagement with the ground, the load is arranged to overcome the bias of the resilient means.

6. A carriage according to Claim 4 or 5 characterised in that the section (214) is pivotally connected to the body (200) by arm means (217) whereby up and down movement of the drivable wheels (233, 239) pivots said arm means.

7. A carriage according to Claim 6 characterised in that the arm means comprises two spaced apart arms (217) rigidly connected to said section.

8. A carriage according to Claim 6 or 7 characterised in that the section carries two independently operable driving motors (226, 227) for the drivable wheels (233, 234).

9. A carriage according to Claim 6, 7 or 8 characterised in that the section (214) supports the lower end of part of a vertical column (209) on the upper end of which a load carrying portion (210) is mounted.

10. A carriage according to any preceding Claim characterised in that where a load carrying portion (51, 210) is provided motorised elevating means (50; 273) is provided for the load carrying portion.

11. A carriage according to any preceding Claim characterised in that where a load carrying portion is provided, the load carrying portion is in the form of a seat (51, 210) and motorised tipping means (110; 266) is provided for tipping the seat to assist a user in moving from the seat into a standing position.

12. A carriage according to Claim 11 characterised int hat the motorised tipping means (110; 266) is actuated after the load carrying portion has been elevated to its highested elevation position.

13. A carriage according to any preceding Claim characterised in that where a load carrying portion in the form of a seat (51, 210) is provided, the seat includes a leg rest (79; 247) and motorised adjustment means (83; 247) is provided to adjust the position of the leg rest (79; 245) relative to the remainder of the seat.

Drawing