WO2002000466A1

WO2002000466A1 - Load handling

Info

Publication number: WO2002000466A1
Application number: PCT/GB2001/002894
Authority: WO
Inventors: Kevin Moger
Original assignee: Glide-Rite Products Limited
Priority date: 2000-06-29
Filing date: 2001-06-28
Publication date: 2002-01-03
Also published as: AU2001267696A1; GB2366782A; GB0115851D0; GB0016029D0

Abstract

There is described a load handling device for moving a load across a floor of a vehicle loadbed. The apparatus comprises a track extending across the floor, and a follower movable by a drive means along the track. The follower includes means for releasably attaching the load thereto. The apparatus is particularly suited to the loading and unloading of wheeled stretchers into and out of ambulances.

Description

Load Handling

The present invention relates to load handling apparatus, and is particularly concerned with load handling apparatus for use in vehicles, for moving a load onto and off a load bed of the vehicle. Most particularly, the invention is concerned with bringing a wheeled load onto a vehicle load bed by means of a ramp. The apparatus may also be used in buildings for moving a load along a floor, or up a ramp.

A particular application of the invention is in ambulances, in which patients on wheeled stretchers or wheelchair , or infants in incubators , are required to ,be brought into the ambulance for transportation to a treatment centre, and must be taken out of the ambulance on arrival. Since the floor inside the ambulance is spaced at a height above the ground surface, the patient and stretcher or incubator must generally be lifted into the vehicle.

Hitherto, a principal method of loading and unloading a wheeled stretcher or wheelchair into and from an ambulance has been by means of a "tail-lift" platform, which provides a horizontal platform attached to the rear of the ambulance, movable between a lowered position in which the platform is substantially flush with the ground surface, and a raised position in which the platform is level with the interior floor of the ambulance. By lowering the platform the stretcher may be wheeled onto it from the ground, whereupon the platform is lifted to its raised position and the stretcher may then the wheeled into the vehicle. While lifting of the platform is performed under power from the vehicle, attendants are still required to manhandle the stretcher firstly onto the platform and subsequently into the vehicle. The stretcher must thereafter be secured to the floor of the vehicle so that it does not move during transit. Unloading of the stretcher is performed by reversing the above steps, with attendants again wheeling the stretcher out of the vehicle and onto the platform, and thereafter off the platform and onto the ground. The provision of a "tail-lift" platform adds a significant weight penalty at the rear of the vehicle, and may impair the road holding ability of the vehicle.

An alternative prior art loading method is available when the height of the stretcher exceeds the floor height within the ambulance. In such a situation, a stretcher with a folding undercarriage may be used wherein the stretcher is wheeled up to the open doors of the ambulance, one end of the stretcher bed is placed on the ambulance floor while the other end is supported by an attendant, and the undercarriage is then retracted to enable the attendant to slide the stretcher into the ambulance while supporting the other end. This not only involves a complicated and expensive folding structure for the stretcher, but also involves the attendant in a dangerous manual task of simultaneously supporting and moving the stretcher and patient. Any slip by the attendant can result in a fall which may not only injure the patient, but can also injure the attendant.

The present invention seeks to overcome the disadvantages of the prior art, by providing a load handling system for moving a load across a surface by an actuator mounted in the surface.

A further objective is to provide a load handling system for a vehicle and a vehicle wherein a load is moved onto a horizontal load bed of the vehicle by means of a ramp surface, an actuator being movable along the load bed and optionally also the ramp surface to urge the load into or out of the vehicle.

According to a first aspect of the present invention, a load handling device for moving a load across a surface comprises an elongate recess formed in the surface, a movable follower received in the recess for movement therealong, a tension element attached at its ends to the follower and passing round guides positioned at respective ends of the recess, and drive means in engagement with the tension element to move the tension element and the follower along the recess. The follower has a load-engaging element cooperable with a complementary element associated with the load permitting attachment of the load to the follower, so that movement of the follower causes movement of the load.

The surface may be a generally horizontal surface such as a floor in a building or a loadbed of a vehicle. It is further foreseen that the surface may be an inclinad surface such as a ramp, or may be a combination of horizontal and inclined surfaces.

The recess may be rectilinear in plan view, or may be curved along its length to move and guide the load in a curved path across the surface.

Preferably, the load is provided with wheels or runners such as skids or "Caterpillar" tracks to facilitate its movement and to reduce the power requirement for the actuator. Alternatively, the load bed and/or ramp surface may be provided with rails, rollers or other friction-reducing structures, to facilitate movement of the load over the ramp surface and/or load bed.

Preferably, the ramp surface is pivotally mounted to the vehicle adjacent an end of the load bed, and is movable between a stowed position wherein the ramp surface is substantially perpendicular to the load bed, and a deployed position wherein the ramp surface extends from the load bed of the vehicle to the ground.

Most preferably, the ramp surface comprises a first ramp portion pivotally mounted to the load bed and a second ramp portion pivotally mounted to the first ramp portion, the arrangement being such that in the stowed position the first and second ramp portions are substantially perpendicular to the load bed, and in the deployed position the first ramp surface extends substantially parallel to the load bed beyond said end, and the second ramp portion extends from the first ramp portion to the ground.

In an alternative embodiment, the ramp may comprise a fixed inclined surface extending downwardly from the loadbed, and a ramp component of substantially triangular section pivotally attached to the lower end of the fixed inclined surface, the ramp component having a stowed position in which it overlies the fixed inclined surface and a deployed position in which it extends from the fixed inclined surface to the ground. Preferably the ramp component is so arranged that in its stowed position it provides a horizontal continuation of the loadbed above the fixed inclined surface.

The actuator of the load handling system preferably comprises a first elongated track portion extending substantially in the plane of the load bed, and a second track portion extending across the ramp surface in alignment with the first track portion. A follower is mounted to the track so as to be movable from a position within the load bed to a position adjacent the end of the ramp surface remote from the load bed. The follower is provided with an engagement means cooperable with the load, for releaseably securing the load to the follower.

The present invention thus provides a means for moving a wheeled load into and out of the vehicle without the need for an attendant to manhandle or support the load at any time during the transfer operation. While the invention will be described principally in relation to patient handling apparatus for use in ambulances, it is to be understood that the system is applicable to the handling of other loads, and may be used in other types of vehicle such as trains, aircraft, ships and boats, or hovercraft.

An embodiment of the present invention will now be described in detail with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of a vehicle load bed and a ramp surface, in side view with the ramp surface in the stowed position;

Figure 2 is a view similar to figure 1, showing the ramp surface in a first partially-deployed position;

Figure 3 is a view similar to figures 1 and 2 , showing the ramp surface in a second partially-deployed position;

Figure 4 is a view similar to figures 1 to 3 , showing the ramp surface in the deployed position;

Figure 5 is a schematic side view of a driving section of the actuator;

Figure 6 is a plan view of the driving section of the actuator seen in figure 5;

Figure 7 is a sectional view of the track and follower, taken in the plane VII-VII of figure 3, to an enlarged scale;

Figure 8 is a side view of the track and follower, to an enlarged scale;

Figure 9 is a partial sectional side view of the ramp surface in the deployed position;

Figure 10 is a side view of the distal end of the ramp surface in the deployed position;

Figure 11 is a plan view of the distal end of the track;

Figure 12 is a schematic side view of a second embodiment of the invention, in which the tension element is in two separate parts;

Figure 13 is a schematic perspective view of a first drive arrangement for the second embodiment;

Figure 14 is a schematic perspective view of a second drive arrangement for the second embodiment; and

Figure 15 is a schematic side view showing a third embodiment of the invention. Referring now to figures 1 to 4, there is seen in side view a vehicle chassis 1 supported by wheels 2 are. The chassis supports a load bed 3, into which is set a track 4 extending longitudinally of the vehicle to the rear end of the load bed. At the rear end of the load bed 3, a first ramp portion 5 is pivotally mounted to the load bed by means of a pivot 6. The first ramp portion 5 is pivotally movable between a stowed position seen in figure 1 in which the first ramp portion 5 is substantially vertical, and a deployed position seen in figures 3 and 4 in which the first ramp portion 5 is substantially horizontal and extends from the end of load bed 3 beyond the rear end of the vehicle chassis 1. The upper surface of the first ramp portion 5 is ^• a substantially coplanar with the upper surface of the load bed 3 in this latter position. The first ramp portion 5 may be a simple metal plate divided into left and right halves by a slot 14 and having a channel section attached to the undersides of the left and right halves to form an extension of the track 4. Alternatively, the first ramp portion 5 may be a box section, and the track may be built into the box section. The edges of the ramp portions may be provided with low sidewalls upstanding from the upper surface of the ramp.

A second pivot 7 connects the first ramp portion 5 to a second ramp portion 8. The second ramp portion 8 is pivotable relative to the first ramp portion 5 between a stowed position wherein the first and second ramp portions 5 and 8 are in substantially parallel planes, to a deployed position wherein the first and second ramp portions subtend an obtuse angle. The second ramp portion 8 may be formed from a metal plate divided into left and right halves by a slot 14 and having a channel section 8a attached to the undersides of the left and right halves to form an extension of the track 4. Alternative materials for the ramp may include glass- reinforced plastics, composite materials, wood, etc.

Extending along the load bed 3 in the longitudinal direction of the vehicle, and preferably on the vehicle centerline, is a track 4 comprising a channel situated below the load bed 3, with an open side of the channel accessible via a slot in the load bed 3. A cross- sectional view of the channel is seen in figure 7, and a sectional side view is seen in figure 8. The loadbed may be provided with a number of tracks extending toward and away from a loading station such as a door in the vehicle, or extending from one part of the loadbed to another .

Referring now to figure 7, there is seen the load bed 3 in which an elongated slot is formed. A channel section comprising sidewalls 10 and 11, and a bottom wall 12 is received in the slot in the load bed 3, supported by a pair of plates 13a and 13b attached to the edges of the slot. The adjacent edges of plates 13a and 13b are spaced apart to define a narrow slot 14 which extends longitudinally of the load bed 3 and of the ramp surface. The sidewalls 10, 11 and the bottom wall 12 may be fixed to the plates 13a and 13b by any suitable means, such as threaded fasteners or by bonding or welding.

A follower 20 has a body portion 21 situated within the channel section between the sidewalls 10 and 11, and a load-engaging portion 22 positioned above the plates* 13a and 13b. The load-engaging portion 22 is joined to the body portion 21 by a web 23 extending through the narrow slot 14.

The body portion 21 of the follower 20 is provided with stub axles 24 on which rollers 25 are journalled. The diameter of the rollers 25 is slightly less than the height of the sidewalls 10, 11 so that when the rollers bear on the upper surface of the bottom wall 12 there is a slight clearance between the rollers and the undersides of the plates 13a and 13b. As it can be seen from figures 7 and 8, the follower 20 has two pairs of rollers situated at respective ends of the body portion 21. The body portion 21 and rollers 25 are a close fit within the channel section, and thus maintain the follower 20 in longitudinal alignment with the channel section.

Situated centrally in the channel are a number of chain guides 26 spaced longitudinally of the channel, and supported on the bottom wall 12. These chain guides 26 are arranged as portals each extending transversely of the channel section, and serve to support the upper run 27a of a chain 27 attached to the ends of the body portion 21 of the follower 20. The chain guides 26 are so dimensioned and configured that the follower 20 can move along the channel section without contacting the chain guides 26.

At the forward end of the track 4 is a driving section 30, illustrated schematically in figures 1 to 4 and shown in more detail in figures 5 and 6. The driving section comprises a motor 31 and a gearbox 32 transmitting the drive from the motor to a driving sprocket 33 which engages the chain 27. An idler roller 34 guides the chain 27 from the driving sprocket 33 into the track 4 adjacent the bottom wall 12 to form a lower chain run 27b, while a tensioning roller 35 guides the chain 27 from the driving sprocket 33 into the track 4 adjacent the plates 13a and 13b to form and upper chain run 27a. The tensioning roller 35 is mounted for horizontal movement controlled by a threaded rod 36 and lock nuts 37, to enable the tension in the chain 27 to be adjusted.

The driving section may be positioned at any location along the length of the track, and may even by housed in a casing which extends above the loadbed at the forward end of the track. The motor gearbox may be positioned at a distance laterally of the track, driving the sprocket by an elongated shaft. In an advantageous embodiment, the track may dip below the loadbed at its forward end so that the follower may be moved to a stowed position where it does not protrude above the loadbed.

The chain 27 extends from the driving section 13 along the track 4 in the load bed 3 of the vehicle, and through a track extending across the ramp surface to a point adjacent the distal end of the ramp. Figure 9 shows the arrangement of a pair of idler sprockets 40 and 41 at the pivoting joint between the first and second ramp portions to guide the chain 27 during relative pivotal movement of the first and second ramp portions 5 and 8. Idler sprocket 41 is concentric with the pivot axis between the two ramp portions, while idler sprocket 40 is mounted to the first ramp portion 5 and is spaced from idler sprocket 41 so as to allow the lower chain run 27a to pass over idler sprocket 40 and under idler sprocket 41. The upper chain run 27a is supported on chain guides 26 in the track 4, to pass over and clear of idler sprocket 40. Since idler sprocket 41 is concentric with the pivot axis 7 , relative pivoting of the second ramp portion 8 simply increases the arc of contact of the upper chain run 27a with the idler sprocket 41, and does not allow the upper chain run 27a to come into contact with the lower chain run 27b passing over idler sprocket 40.

Figures 10 and 11 are detailed views showing the arrangement of a tensioning sprocket 50 in the track extending across the second ramp portion 8. The tensioning sprocket 50 is supported on a shaft 50a received in a pair of aligned slots in the sidewalls of the channel section 8a. Pivotally mounted at the end of the channel section 8a is a swinging arm 51, and the distal end of which is a pair of ground-engaging rollers 52. The ends of the shaft 50a supporting the tensioning roller 15 are linked to the swinging arm 51 by a pair of yokes 53 a which lie against the outer surfaces of the sidewalls of the channel section 8a.

The swinging arm 51 is movable between two positions, as shown in figure 10. When the second ramp portion 8 is raised so that its distal end leaves the ground, the rollers 52 remain in contact with the ground until the swinging arm 51 has swung away from the second ramp portion to the position shown in dashed lines in Figure 10. In this position, the yokes 53 move the tensioning roller 50 along the slots away from the distal end of the second ramp portion 8 , to allow slack in the upper and lower chain runs 27a and 27b, for purposes to be described later. Conversely, as the second ramp portion 8 is lowered from its stowed position to its deployed position the rollers 52 will contact the ground before the distal end of the ramp, and further lowering of the ramp will cause the swinging arm 51 to be moved to its position adjacent to the second ramp portion 8, as seen in solid lines in figure 10. An adjustable abutment 54 may be provided to limit the movement of the swinging arm 51 towards the ramp surface. Preferably, when the tensioning sprocket 50 is at the left-hand end of its slot, the lengths of the yokes 53 and the swinging arm 51 are such that when the rollers 52 contact the ground, a moment is exerted on the swinging arm 51 urging it to rotate towards the distal end of the second ramp portion 8.

As will be understood from figure 9, the pivot axis 6 between the vehicle chassis and the first ramp portion 5 is positioned above the upper surface of the load bed 3. As the first ramp portion is raised, a gap is formed between the rear end of the track in the load bed and the proximal end of the track in the first ramp portion 5, and this gap must be traversed by both of the upper and lower chain runs 27a and 27b. Thus, as the first ramp portion is raised from its deployed position, slack must be given to the chain to enable the chain runs to pass across the gap and round the pivot axis 6. It is for this reason that the tensioning roller 50 is provided at the distal end of the second ramp portion, since raising the second ramp portion clear of the ground causes the tensioning roller 50 to move towards the pivot axis 7 and provide slack to the chain runs, which then enables first ramp portion 5 to be lifted from its deployed position without overstressing the chain.

In operation, the load or a patient handling device of the present invention starts from its stowed position within the vehicle or ambulance, with both the first and second ramp portions substantially vertical and the swinging arm 51 extending away from the second ramp portion 8 and towards the rear of the vehicle.

The rear doors (if any) of the vehicle are opened, and the ramp portions are lowered so as to pivot about pivot axis 6 until the first ramp portion 5 contacts the vehicle chassis. During this movement, the gap between the rear edge of the load bed 3 and the proximal edge of the first ramp portion 5 is closed, and the chain 27 becomes slack.

Further lowering of the second ramp portion causes it to pivot downwards below the horizontal, until the rollers 52 at the end of swinging arm 51 engage the ground. This pivoting movement opens a slight gap between the first and second ramp portions, taking up some of the slackness in the chain.

As the second ramp portion is lowered yet further, the swinging arm 51 is moved towards the distal end of the second ramp portion, and tensioning sprocket 15 is moved along its slot thus bringing the chain to the correct tension for use.

The drive motor 31 is then operated to rotate driving sprocket 33 clockwise as shown in figure 5, thus placing the lower chain run 27b in higher tension than the upper chain run 27a. The follower 20 is moved along the track 4 to the distal end of the second ramp portion, positioning the load-engaging portion 22 ready for engagement with a stretcher or other load to be drawn into the vehicle.

The stretcher or load is attached to the load-engaging portion 22, by complementary engagement means formed on the stretcher and on the load-engaging portion 22. Preferably the engaging means comprise a socket with a snap-action detent on the load, positioned so that as the load is moved towards the load-engaging portion 22, the portion 22 enters the socket and is retained therein by the action of the detent. In a further advantageous embodiment, the detent may be releaseable by engagement with an abutment surface at the distal end of the track, so that the load is automatically released when it reaches the unloading/loading position. Magnetic elements may be used in securing the load to the follower 20, preferably not to transmit holding force, but to hold force-transmitting parts in engagement positions.

Drive motor 31 is then operated again, this time to rotate the drive sprocket 33 anti-clockwise as seen in Figure 5. This rotation places the upper chain run 27a in higher tension than the lower chain run 27b, and the follower is moved along the track 4 towards the driving section 30. The engagement between the portion 22 and the stretcher or load causes the stretcher or load to be drawn up the second ramp portion, across the first ramp portion, and across the load bed into the vehicle.

Once the load is clear of the first ramp portion, the drive motor can be stopped. The reduction gearbox 32 may include means for selectively locking the rotation of drive sprocket 33 in order to fix the position of the follower 20 in the track 4. Alternatively, the gearbox 32 may include a worm drive or other high-reduction gear mechanism which prevents rotation of the drive sprocket 33 due to the resistance of the transmission and motor 31.

With the load clear of the first ramp portion, the first and second ramp portions may be raised to return them' to their stowed position and the rear doors or the vehicle (if any) may be closed for transit. Lifting and lowering of the ramp portions may be achieved by means of cables attached to the distal end of the second ramp portion and to winches in the vehicle body, in the manner of a drawbridge. However, alternative means of raising and lowering the ramp may be provided, such as hydraulic or pneumatic actuators positioned between the rear of the vehicle chassis and the undersides of the ramp portions. Counterbalancing weights or springs may be provided to reduce the power requirement of these actuators. In the embodiment described, the ramp surface comprises first and second ramp portions which are substantially coplanar when stowed, and subtend an obtuse angle when deployed. In alternative arrangements, not illustrated, the first and second ramp portions may be substantially equal in size, and in the stowed position the first ramp portion may extend substantially vertically upwards from the rear of the load bed, while the second ramp portion extends substantially vertically downwards from the upper edge of the first ramp portion, with the distal end of the second ramp portion adjacent the plane of the load bed. To deploy the ramp from the stowed position, the second ramp portion is pivoted away from the first ramp portion, and then the first ramp portion is pivoted downwards to a position substantially coplanar with and adjacent to the load bed. The first ramp portion will then extend from the distal end of the second ramp portion to the ground. During the deploying operation, the first and second ramp portions will rotate about respective horizontal axes in opposite senses.

In the embodiments described above, the first ramp portion functions as an extension of the load bed, and is supported when deployed in a substantially horizontal position adjacent the load bed. It is foreseen that the pivotal connection between the load bed and the ramp surface may be at the extreme end of the vehicle, so that both the first and second ramp portions are inclined to the horizontal when deployed. In such an arrangement, the pivoting joint between the first and second ramp portions must be provided with rotation limiting means of sufficient strength to prevent collapse of the ramp surface when loaded. It is further foreseen that the ramp surface may be a single pivoting element attached at the extreme rear of the vehicle for pivoting movement between a deployed position in which the ramp surface extends from the vehicle load bed to the ground, and a stowed position in which the ramp surface extends upwardly from the vehicle load bed, or overlies a part of the loadbed.

In a yet further alternative embodiment, the track may extend only part-way across the ramp surface, and the load attachment device may extend from the follower in the direction of the track such that when the follower is at the end of the track, a load adjacent the end of the ramp may be connected thereto.

It is further foreseen that the ramp surface may be mounted to the vehicle for horizontal sliding movement to and from a stowed position beneath the vehicle load bed.

In such an embodiment, the distal end of the ramp surface will move horizontally out of the vehicle during deployment, and will subsequently pivot so that the distal end of the ramp can contact the ground. The proximal end of the ramp moves from a position below the load bed to a position adjacent the rear end of the load bed during this deployment operation.

It will be understood that the load handling device may be mounted in a vehicle loadbed only, without the track extending across a loading ramp associated with the loadbed. Such a device may be used when the vehicle is loaded and unloaded at a loading dock whose height is similar to that of the loadbed, or in a vehicle capable of lowering its loadbed to or near ground level Cor loading.

Further, the described embodiment uses sprockets and chain for transmitting the drive from the motor 31 to the follower 20. It is envisaged that a toothed belt, similar to the timing belt of a car engine, may be used instead of the chain 27. Clearly, in such an instance, the sprockets will be replaced by pulleys appropriate to the face of the belt which they will engage. For example, at the joint between the first and second ramp portions, the pulley replacing idler sprocket 41 will be a toothed pulley to engage the toothed side of the belt, while the pulley replacing idler sprocket 40 may be a smooth pulley since its will engage a smooth surface of the belt. In a further alternative, a webbing strap or belt similar to the material used in car seat belts may serve as the tension element, in place of a chain.

As a further alternative tension element, the chain 27 may be replaced by a wire rope. To ensure the transmission of sufficient force to the wire rope, the drive sprocket 33 may be replaced by a capstan-type pulley round which the rope passes a number of times.

In a yet further alternative, to reduce weight, a chain- type tension element may be used, with the drive transmitted to the tension element by means of a driving sprocket 33, but part of the chain run extending from the rear end of the follower 20 may be replaced by wire rope. The length of the wire rope run is such that, when the follower 20 is at the rearmost position, the wire rope run does not reach the drive sprocket. The idler sprockets 40 and 41, and the tensioning sprocket 50 may be replaced by pulleys if the extent of the wire rope run is such that it will pass over these elements during movement of the follower.

Referring now to figure 12, an alternative arrangement for the load handling apparatus is shown. The apparatus comprises a track 4, preferably formed by a channel section set into the load bed 3 of the vehicle as before. A follower 20 is mounted for movement along the length of the track, and is moved by a tension element as before.

In this arrangement, however, the tension element is not a chain, but is a length of webbing or strap material, such as is used in seat belts for vehicles. Furthermore, the tension element is provided in two distinct parts, each part being attached to the follower at one end, and to a winch drum at the other end. In the Figure, the follower 20 is seen at a position towards the rearward end of the track, with a first part 60 of the tension element extending forwardly from the follower 20 to a guide pulley 61 at the forward end of the track 4. After passing around the guide pulley 61, the tension element is then attached to a winch drum 62.

A second part 63 of the tension element extends rearwardly from the follower 20 and passes around a rear guide pulley 64 at the rear end of the track 4. The second part 63 of the tension element then extends along the track to a further guide pulley 65, and thence to a second winch drum 66. In the position shown in figure 12, the follower 20 is near to the rear end of the track 4. Thus, most of the first part 60 of the tension element has been drawn off the winch drum 62, while the winch drum 66 has wound around it a considerable length of the second part 63 of the tension element. By adjusting the lengths of the first and second portions of the tension element 60 and 63, the follower 20 can be made to stop adjacent respective ends of the track 4 when the entire length of the tension element has been paid out from the respective winch drum 62 or 66.

The winch drums 62 and 66 are preferably driven from a common drive source such as an electric motor. Figures 13 and 14 show schematically two different drive arrangements for the winch drums.

In Figure 13, the winch drums 62 and 66 are mounted to respective drive shafts 62a and 66a. Also mounted to the drive shafts 62a and 66a are drive gears 62b and 66b, respectively. A motor 67 is connected to a driving pinion 68, which meshes with both drive gears 62b and 66b, so that rotation of the driving pinion 68 rotates the drive gears 62b and 66b in the same direction as each other and at the same speed. The first and second parts 60 and 63 of the tension element are wound on their respective drums in opposite senses, so that when the drums 62 and 66 rotate in the same direction, one of the drums pays out its tension element while the other drum draws in its tension element. As can be seen from the arrangement of Figure 13, when the motor 67 rotates the driving pinion 68 anticlockwise, as indicated by the arrow in the Figure, the first part 60 of the tension element is drawn in while the second part 63 of the tension element is paid out. This results in the follower 20 moving forward along the track 4 shown in figure 12. Clearly, rotation of the motor 67 and driving pinion 68 in a clockwise direction as seen in figure 13 will result in the first part 60 of the tension element being paid out while the second part 63 of the tensipn element is drawn in, moving the follower 20 toward the rear of the track 4.

In the arrangement shown in figure 14, the winch drums 62 and 66 are again provided with drive shafts 62a and 66a, on which are mounted drive gears 62b and 66b respectively. However, in the arrangement of figure 14, the drive gears 62b and 66b mesh with each other, causing the winch drums 62 and 66 to rotate in opposite senses at the same speed. A motor 67 is directly linked to one of the drive gears 66b. In this arrangement, the tension elements are wrapped around their respective winch drums in the same sense so that when the winch drums rotate together in opposite directions, one winch drum draws in its tension element while the other winch drum pays out. When the motor and drive gear 66b are rotated anticlockwise, as indicated by the arrow in figure 14, winch drum 66 draws in the second part 63 of the tension element while winch drum 62 pays out the first part 60 of the tension element.

In a further alternative arrangement of the winch drums, the drums may be arranged coaxially on the same shaft to be simultaneously drive by a motor. Guide means, preferably in the form of a pair of parallel pulleys oblique to the axis of the winch drums, will be needed, to align the belts from the "side by side" alignment of the winch drums into the "over and under" alignment necessary for them to enter the track.

In the above-described arrangements, the winch drums rotate at equal angular speeds. As the tension element is wound onto the winch drum, the winding radius will increase and thus for the same angular rotation a longer length of tension element will be wound on to the winch drum. When the follower 20 is at one end of the track, and is to be moved toward the other end, one of the winch drums will be substantially empty while the other will be substantially full. The amount of tension element drawn onto the empty drum for a given angular rotation will be less than the amount paid out from the full drum, resulting in a reduction in tension in the tension element .

As the follower reaches the midpoint of the track, both winch drums will have a similar amount of tension element wound round them and thus the winding radius of the winch drums will be the same. This will result in substantially equal amounts of tension element being paid out and drawn in.

As the follower 20 moves past this point towards the other end of the track, the fuller of the two winch drums will draw in more tension element than the emptier drum pays out and thus the tension in the tension element will again be increased.

In order to provide a substantially constant tension in the tension element, a tensioning device is preferably placed in the run of the tension element at a suitable point. The tensioning device may comprise a pair of fixed rollers and a resiliently-biased movable roller round which the tension element passes in serpentine fashion. Alternatively, the rear guide roller 64 shown in figure 12 may be mounted for movement along the length of the track, and may be biased towards the rear end of the track in order to maintain a predetermined tension level in the first and second parts 60 and 63 of the tension element.

Figure 15 shows a further alternative arrangement of the load handling device. In this arrangement, a track 4 extends along the load bed 3 of the vehicle and has a guide roller 70 at its forward end and a guide roller 71 at its rear end. A first winch drum 72 driven by a first motor (not shown) is provided at the forward end of the track 4, and a second winch drum 73 driven by a second motor (not shown) is provided at the rearward end of the track 4. A first tension element 74 extends from the first winch drum 72, over the guide roller 70 and along the track 4 to the follower 20. A second tension element 75 extends from the winch drum 73, over the guide pulley 72, and along the track 4 to the follower 20. The first and second motors are controlled so that as one of the motors drives its winch drum to wind in its respective tension element, the other motor allows its winch drum to rotate to pay out its tension element. If the resistance in the transmissions between the motors and their respective winch drums is too great to allow the winch drum to rotate the motor in its paying-out sense, the motors may be controlled so that they are driven both in the winding-in and in the paying-out directions . In an advantageous embodiment, the transmission between the motor and the winch drum has such a large resistance to back-driving that the follower 20 can only be moved along the track 4 by the simultaneous driving of the both of the motors. This ensures that the follower 20 is held in position along the track 4 when no power is supplied to the motors.

While the previous embodiments describe the track as being mounted within the loadbed, it is to be understood that the track may be mounted above the level of the loadbed, for example in retro-fit embodiments. The drjye means may also be housed in a position above the level of the loadbed.

Claims

Claims :

1. A load handling apparatus for moving a load across a load-supporting surface, comprising: an elongate guide track extending across the surface; a follower mounted to the guide track for movement along the track; a tension element attached to the follower and extending along the track; a drive means for inducing a tension in the tension element to draw the follower along the track; and load attachment means on the follower for releaseable attachment to the load;

2. A load handling apparatus according to claim 1, wherein the tension element comprises a first tension element extending in a first direction from the follower, and a second tension element extending in a second direction from the follower.

3. A load handling apparatus according to claim 1 or 2, wherein the drive means is a winch drum.

4. A load handling apparatus according to claim 3 , wherein a first winch drum is provided to wind up the first tension element, and a second winch drum is provided to wind up the second tension element.

5. A load handling apparatus according to claim 4, wherein the first and second winch drums are driven by a common drive source.

6. A load handling apparatus according to claim 5, wherein the first and second winch drums rotate in the same direction when driven.

7. A load handling apparatus according to any of claims 4 to 6, wherein the winch drums are coaxial.

8. A load handling apparatus according to claim 4 or claim 5 , wherein the first and second winch drums rotate in opposite directions when driven.

9. A load handling apparatus according to any of claims 4 to 8 , wherein a first winch drum is situated adjacent one end of the track to wind up the first tension element, and a second winch drum is situated adjacent the other end of the track to wind up the second tension element.

10. A load handling apparatus according to any of claims 4 to 9, wherein the first and second winch drums are driven by respective first and second drive means.

11. A load handling apparatus according to claim 10, wherein control means are provided to control the first and second drive means so that as one winch drum is rotated to draw in its tension element, the other winch drum is rotated to unwind its tension element.

12. A load handling apparatus according to claim 10, wherein control means are provided to control the first and second drive means so that as one winch drum is rotated to draw in its tension element, the other winch drum is undriven, and is rotated to unwind its tension element by the tension in that tension element.

13. A load handling apparatus according to any preceding claim, wherein the tension element is a woven belt of synthetic material

14. A load handling apparatus according to claim 1, wherein the tension element is continuous and extends from the follower along the track in a first direction, turns at one end of the track and extends back along the track in a second direction, and turns again at the other end of the track to extend along the track in the first direction to the follower.

15. A load handling apparatus according to claim 14, wherein the tension element is a belt or rope, and the drive means is a capstan.

16. A load handling apparatus according to claim 14, wherein the tension element is a chain and the drive means is a sprocket.

17. A load handling apparatus according to claim 14, wherein a part of the tension element is a chain, and the remainder is a rope or wire, and the drive means engages the chain part of the tension element.

18. A load handling apparatus according to any preceding claim, wherein a tensioning device maintains a minimum tension in the tension element.

19. A load handling apparatus according to any preceding claim, wherein the track extends across a ramp pivotally associated with the load supporting surface.

20. A load handling apparatus according to claim 19, wherein the ramp comprises a number of relatively pivotable sections.

21. A load handling apparatus according to any preceding claim, wherein the load supporting surface is provided with means to reduce friction between the load and the load supporting surface.

22. A load handling apparatus according to any preceding claim wherein the load supporting surface is a loadbed of a vehicle.

23. A load handling apparatus according to any preceding claim, wherein the apparatus comprises means to release the attachment between the follower and the load when the follower reaches an end of the track.

24. A load handling apparatus according to any preceding claim, wherein the load supporting surface is a floor of an ambulance, and the load is a patient-carrying device.

25. A load handling apparatus according to claim 24, wherein the load is a stretcher.

26. A load handling apparatus according to claim 24, wherein the load is an infant incubator.

27. The combination of a load and a load handling apparatus according to any preceding claim, wherein the load is provided with wheels.

28. A method of moving a load across a load-supporting surface provided with a guide track extending across the surface, a follower movable along the guide track, and drive means for moving the follower along the guide track, comprising the steps of: attaching the load to the follower; and operating the drive means to move the follower along the track and to cause the load to be drawn across the surface.