GB2368572A

GB2368572A - Tail lift positioning device

Info

Publication number: GB2368572A
Application number: GB0121441A
Authority: GB
Inventors: Keith Dempsie
Original assignee: Ross and Bonnyman Engineering Ltd
Current assignee: Ross and Bonnyman Engineering Ltd
Priority date: 2000-09-06
Filing date: 2001-09-05
Publication date: 2002-05-08
Also published as: GB0121441D0; GB0021813D0

Abstract

A vehicle tail lift 52 has a sensor assembly comprising a sensor 70 fixed to the vehicle frame 62 and a sensor actuator 72 fixed to the lifting arm 60. The sensor 70 operates through the tail lift control system (Fig 5) to arrest movement of the lifting arm 60 when the sensor 70 aligns with the actuator 72. The sensor 70 may comprise a magnetic proximity sensor and the actuator 72 may comprise a magnet. Alternative sensors may be used such as inductive proximity detectors, switches or microswitches.

Description

"Lifting Apparatus"

This invention relates to lifting apparatus, and particularly, but not exclusively, to tail lifts mounted on vehicles. Tail lifts are typically mounted at the rear of a vehicle to enable the effective transfer of heavy objects from a floor of a vehicle to the ground and vice versa. Although such apparatus is conventionally called a tail lift, the apparatus can be located at the front or side of the vehicle instead of the rear, but it is conventional for tail lifts to be located at the rear of the vehicle.

Although the tail lift allows loading from ground level when a platform of the tail lift is in the lowered horizontal position against the ground, vehicles provided with tail lifts are often loaded or unloaded at raised loading bays, where the vehicle is reversed against a wall below the loading bay. Referring to Fig. 1, there is shown a vehicle 10 (typically a heavy goods vehicle (HGV) ) that is provided with a tail lift, generally designated 12.

Vehicle 10 has been reversed or otherwise positioned in close proximity to a raised loading bay 14. When the vehicle 10 is in use, a platform 16 of the tail lift 12 is generally in a substantially vertical orientation parallel to a rear face (e. g. the door) of the vehicle 10 and occludes an opening 18 to an internal storage space 20.

It is conventional to slide the platform 16 of the tail lift 12 to a lowered vertical position flat against the end of the vehicle 10 (as shown in Fig.

1) before the vehicle 10 approaches the loading bay 14, as the platform 16 obstructs the opening 18 at the rear of vehicle 10 that allows access to the internal storage space 20 within the vehicle 10.

In the Fig. 1 position, the platform 16 of the tail lift 12 no longer interferes with access to the internal storage space 20, and preferably remains some distance above ground level to avoid damage to the tail lift 12 or the vehicle 10 itself, as the vehicle 10 is reversing.

A board 22 or the like (shown in phantom in Fig. 1) is used to bridge a gap between a floor 24 of the vehicle 10 and a floor 14s of the loading bay 14.

The board 22 facilitates movement of heavy objects between the loading bay 14 and the floor 24 of the vehicle 10.

Referring now to Fig. 2, it is conventional in the art to provide a locating means, generally designated 30, to arrest the movement of the platform 16 at the correct lowered vertical position in Fig. 1 to allow access to the internal storage space 20. The locating means 30 typically comprises a fixed plate 32 that extends backwards from a column 34 of the tail lift 12 (it is typically welded to the column 34) into the path of a pin 36 on the downwardly moving platform 16. The pin 36 engages with a locating notch 38 on the fixed plate 32, and the downward movement of the platform 16 is arrested at the appropriate height above ground level so that the platform 16 does not obstruct access to the internal storage space 20, and does not come into contact with the ground.

The conventional locating means 30 has a number of disadvantages. As the fixed plate 32 protrudes some distance (e. g. around 250mm) from the rear of the vehicle 10, it can become damaged when the vehicle 10 is reversed into contact with the loading bay 14, which is commonplace. Some loading bays 14 are provided with rubber or other resilient buffers that engage the plate 32, but damage can often still result.

Additionally, as the vehicle 10 is unloaded, the height of the floor 24 rises because the suspension raises the vehicle as the weight in the vehicle is reduced. Thus, as the vehicle 10 rises due to the reduction in weight, the platform 16 is forced

against the loading bay buffers which causes damage to the plate 32 and/or the buffers and/or the platform 16.

Furthermore, the locating means 30 is typically provided on only one side of the platform 16, which can be lowered too far if a user of the tail lift 12 is not paying attention. Continual lowering of the platform 16 when the pin 36 has engaged the plate 32 can cause damage to the platform 12, the plate 32 and/or the pin 36 as the platform 16 can be twisted or pivoted around the plate 32.

According to the present invention, there is provided a movable lifting arm for a vehicle having a sensor assembly capable of generating signals to control movement of the arm, the sensor assembly comprising a first part provided on the moving arm and a second part provided on the vehicle, wherein convergence of the first and second parts generates a signal that arrests movement of the lifting arm.

The invention also provides lifting apparatus comprising two spaced-apart movable lifting arms with a platform mounted between the arms, wherein at least one of the arms and/or the platform is provided with a sensor assembly that is capable of generating signals to control movement of the arm, the sensor assembly comprising a first part provided on the moving arm and a second part provided on the vehicle, wherein convergence of the first and second

parts generates a signal that arrests movement of the lifting arm.

The signal is typically generated when the two parts are substantially aligned, although the signal can be generated when the two parts converge to within a predetermined distance.

The sensor assembly preferably comprises a contactless assembly, so that there is no mechanical contact between the first and second parts, but this is not essential. However, it is preferred that any mechanical contact is minimal.

The first part typically comprises a proximity sensor, and the second part typically comprises a magnet. Alternatively, the first part may comprise an inductive sensor, and the second part may comprise a corresponding metal. However, the sensor assembly may comprise an electrical switch with conventional contacts. Optical switches may also be used, or any combination of these. As an example, the first part may comprise a light emitting diode and light sensor, and the second part a pin or the like that interrupts the beam of light.

In an alternative embodiment, the first part comprises a micro-switch and the second part comprises a shoulder capable of engaging the first part.

The lifting arm typically forms part of a tail lift, the tail lift including a platform. Two spaced apart lifting arms are typically provided where the platform extends between the two arms. Optionally, both arms of the tail lift are provided with the sensor assembly.

Where the lifting arm forms part of a tail lift, the first part is typically located on a column of the tail lift, and the second part typically moves with the platform. For example, the second part may be located on a runner of the tail lift, where the platform is attached to the runner. The runner is typically slidably engaged in the column. However, the second part may be provided on the platform itself.

The first part is typically located on the column at a predetermined position at which the platform is in a lowered vertical position where it is clear of the access opening of the vehicle, but above ground level.

In an exemplary embodiment, the first part may be located on the vehicle at a predetermined position that is below the level of a floor of the vehicle.

In this embodiment, the second part is located on an uppermost part of the platform when it is in a lowered vertical position. Thus, the platform will be clear of the vehicle opening when lowered.

The first part is typically a normally-open switch. Actuation of the sensor assembly deactivates a relay (forming part of the lifting apparatus) that controls downward movement of the platform. Thus, when the first and second parts are substantially aligned, the switch is actuated so that the relay is deactivated causing the movement of the platform to stop. Thus, even if an operator of the lifting apparatus is not paying attention whilst the platform is being lowered, the platform will be located at the correct position due to the actuation of the sensor assembly.

The lowering of the platform is typically actuated using a switch.

Embodiments of the present invention shall now be described, by way of example only, with reference to. the accompanying drawings, in which: Fig. 1 is a schematic drawing showing the position of a tail lift attached to a vehicle, the vehicle being in close proximity to a loading bay; Fig. 2 is a side elevation of a prior art locating means for correctly locating a platform of the tail lift apparatus of Fig. 1 for loading and unloading the vehicle; Fig. 3 is a side elevation of an embodiment of lifting apparatus; Fig. 4 is a plan view of part of the lifting apparatus of Fig. 3; and

Fig. 5 is a schematic circuit diagram of a control mechanism for the apparatus of Figs 3 and 4.

Referring to the drawings, Fig. 3 shows an exemplary embodiment of lifting apparatus, generally designated 50, that is attached to a vehicle, generally designated 52. Lifting apparatus 50 is generally referred to as a tail lift. Although called a tail lift, such apparatus 50 can be located at the front or side of the vehicle 52 instead of the rear, but it is conventional for tail lifts to be located at the rear of the vehicle 52.

Lifting apparatus 50 includes a flat platform 54 hingedly attached at a lower end 541 to a bracket 56, typically by a pivot pin 58. The platform 54 can pivot in a cantilever fashion around the pin 58 through an arc between a substantially vertical orientation (as shown in Fig. 3) where the platform 54 rests substantially parallel to a rear face of the vehicle 52, and a substantially horizontal orientation (not shown).

The brackets 56 are attached to a pair of spacedapart slide runners 60 (only one shown in Fig. 3).

The runners 60 are slidably engaged within a pair of spaced-apart columns 62 that are attached to the rear of the vehicle 52 at each side, as can be seen more clearly in Fig. 4. As is conventional in the art, cables (not shown) run from a hydraulic ram (not shown) in a crossbar 64 at the base of the

columns 62 over pulleys (not shown) to the slide runners 60 on the rear face of the columns 62. The cable and pulley arrangement facilitates upward and downward movement of the platform 54, as is known in the art.

The lifting apparatus 50 is provided with a sensor assembly, generally designated 66. The purpose of the sensor assembly 66 is to prevent movement of the platform 54 in a downward direction once the platform 54 has reached a given position.

Vehicle 52 complete with lifting apparatus 50 is often loaded and unloaded at a raised loading bay, as described above with reference to Fig. 1. At least the platform 54 of the lifting apparatus 50 must be lowered sufficiently to allow access to an internal storage area-68 within the vehicle 52, typically via an opening (not shown). It is important that the platform 54 is not lowered sufficiently so that it touches the ground, otherwise the platform 54 and/or the lifting apparatus 50 may become damaged.

Thus, the sensor assembly 66 is used to prevent further downward movement of the platform 54 once it has reached a position where it is clear of the opening of the vehicle 52, but located at some distance above ground level.

In the embodiment shown, sensor assembly 66 comprises a proximity sensor 70 that is attached to

one or both of the columns 62. The sensor assembly 66 includes a magnet 72 that is attached to one or both of the slide runners 60. In the embodiment shown, the magnet 72 is attached at the top of the runner 60. The proximity sensor 70 is located on the column 62 so that when the magnet 72 moves down into alignment with the sensor 70, the sensor 70 is actuated to prevent any further downward movement of the platform 54. Thus, the proximity sensor 70 is located at a height above the ground that stops the movement when the platform 54 is clear of the access opening and also clear of the ground.

It should be noted that the locations of the proximity sensor 70 and the magnet 72 are exemplary only and these can be located at any convenient location. For example, the sensor 70 may be provided on-the slide runner 60, and the magnet 72 provided on the column 62. Additionally, the sensor 70 may be located at a level that is just below a floor 76 of the vehicle 52, with the magnet 72 being disposed on an uppermost part of the platform 54 (when the platform is in the vertical orientation as shown in Fig. 3). In this embodiment, the platform 54 would be lowered until the magnet 70 on the uppermost part of the platform 54 is below the floor 76, and thus the platform 54 will be clear of the opening.

Referring now to Fig. 5, there is shown a schematic circuit diagram of a control mechanism, generally designated 80, for use with the lifting apparatus of

Figs 3 and 4. Mechanism 80 includes an external control box 82 that is provided with an up switch 84, a down switch 86, and a park switch 88. The up and down switches 82,84 are conventional switches that are used to raise and lower the platform 54, the platform 54 typically being in the horizontal configuration. The control box 82 conventionally has a key switch 90 that controls the operation of the switches 84,86, 88.

The park switch 88 is used to lower the platform 54 whilst the platform 54 is in the vertical orientation, so that it can be moved clear of the access door. Thus, when the platform 54 is to be lowered in the vertical orientation, park switch 88 is depressed continuously. This vents hydraulic pressure (typically to a storage tank (not shown)) from the hydraulic ram through a valve 92 that lowers the platform 54. Valve 92 is actuated through a relay 94 that is located in a box 96 that houses an electrical connector block 98 and the relay 94. Box 96 is typically externally mounted to a chassis of the vehicle 52.

The platform 54 is continually lowered until the proximity sensor 70 is actuated by alignment of the magnet 72 and the sensor 70. As the proximity sensor is typically a normally-open switch, actuation of the sensor 70 closes the switch which deactivates the relay 94 via appropriate connections at the connector block 98, and thus lowering of the platform 54 is stopped.

It will be appreciated that other types of sensor may be used in place of the proximity sensor. For example, an inductive sensor may also be used, with a suitable metal being provided on the platform 54 so that the inductive sensor is actuated.

With the embodiments described above, there is a reduced possibility of damage to the lifting apparatus 50, the platform 54 and the vehicle 52.

This is because there is no mechanical contact between portions of the conventional locating means that engage with one another that can lock-up in use.

It is also possible to use a micro-switch provided on the column in place of the proximity sensor 70.

In this embodiment, a portion of the platform 54 is provided with a shoulder or the like that is capable of engaging the micro-switch. Although there is mechanical contact between the switch and the shoulder, such contact is minimal and there is no mechanical stop or other physical restrictions that could prevent movement of the platform 54 thus causing damage.

Modifications and improvements may be made to the foregoing without departing from the scope of the present invention.

Claims

1. A movable lifting arm for a vehicle having a sensor assembly capable of generating signals to control movement of the arm, the sensor assembly comprising a first part provided on the moving arm and a second part provided on the vehicle, wherein convergence of the first and second parts generates a signal that arrests movement of the lifting arm.

2. A lifting arm according to claim 1, wherein the signal is generated when the parts are substantially aligned.

3. A lifting arm according to claim 1 or claim 2, wherein the sensor assembly can generate the signal without contact between the first and second parts.

4. A lifting arm according to any preceding claim, wherein the first part comprises a proximity sensor, and the second part comprises a magnet.

5. A lifting arm according to any one of claims 1 to 3, wherein the first part comprises an inductive sensor, and the second part comprises a corresponding metal.

6. A lifting arm according to any one of claims 1 to 3, wherein the sensor assembly comprises an electrical switch.

7. A lifting arm according to claim 1 or claim 2, wherein one of the first and second parts comprises a micro-switch and the other comprises a shoulder capable of engaging the first part.

8. A lifting arm according to any preceding claim, wherein the arm forms part of a tail lift, the tail lift including a platform.

9. A lifting arm according to claim 8, wherein two spaced-apart lifting arms are provided with the platform extending between the two arms.

10. A lifting arm according to claim 8 or claim 9, wherein each arm of the tail lift is provided with a sensor assembly.

11. A lifting arm-according to any one of claims 8 to 10, wherein the first part is located on a column of the tail lift, and the second part moves with the platform.

12. A lifting arm according to claim 11, wherein the second part is located on a runner of the tail lift.

13. A lifting arm according to claim 11 or claim 12, wherein the first part is located on the column at a predetermined position at which the platform is in a lowered vertical position clear of an access opening of the vehicle, but above ground level.

14. A lifting arm according to any one of claims 8 to 10, wherein the first part is located on the vehicle at a predetermined position that is below the level of a floor of the vehicle, and the second part is located on an uppermost part of the platform when it is in a lowered vertical position.

15. A lifting arm according to any preceding claim, wherein the first part is a normally-open switch.

16. A lifting arm according to any one of claims 8 to 15, wherein actuation of the sensor assembly deactivates a relay that controls downward movement of the platform.

17. Lifting apparatus comprising two spaced-apart movable lifting arms with a platform mounted between the arms, -provided with a sensor assembly that-is capable of generating signals to control movement of at least one arm, the sensor assembly comprising a first part provided on one of the arms or the platform and a second part provided on the vehicle, wherein convergence of the first and second parts generates a signal that arrests movement of the lifting arm.

18. A lifting arm substantially as hereinbefore described with reference to Figs 3 to 5 of the drawings.

19. Lifting apparatus substantially as hereinbefore described with reference to Figs 3 to 5 of the drawings.