WO2012153087A1

WO2012153087A1 - Lifting machine

Info

Publication number: WO2012153087A1
Application number: PCT/GB2012/000419
Authority: WO
Inventors: Roger Bowden
Original assignee: Niftylift Limited
Priority date: 2011-05-12
Filing date: 2012-05-09
Publication date: 2012-11-15
Also published as: GB2493487A; GB201107999D0

Abstract

A lifting machine, for example an elevating work platform comprises a base (4), an operator platform (6) and a lift mechanism (8) for adjusting the height of the operator platform relative to the base. The lift mechanism (8) includes a motor (26) and a screw element (30) that is arranged to be driven by the motor. Rotation of the screw element (30) adjusts the height of the operator platform (6) relative to the base (4). The lift mechanism (8) preferably also includes telescoping tower sections (16,18) and flexible elongate drive elements (42,46) for transferring drive to the operator platform (6).

Description

Lifting machine

The present invention relates to a lifting machine, for example an elevating work platform or a load handling machine, and to a lift mechanism for a lifting machine. In particular, but not exclusively, the invention relates to a low level elevating work platform. An elevating work platform (or "personnel lift") typically comprises a base, an operator platform and a lift mechanism for adjusting the height of the operator platform relative to the base. The operator platform may be raised allowing an operator to work safely at height without requiring scaffolding, ladders or free-standing steps.

Most elevating work platforms use either a boom lift mechanism or a scissor lift mechanism. These lift mechanisms are particularly suitable for medium or high level elevating work platforms that provide a working height of about 8m up to 20m or more. For low level work platforms providing a working height of up to about 5m, a lift mechanism that is lighter, simpler and easier to maintain may be more suitable.

Many existing elevating work platforms use hydraulic systems to operate the lift mechanism. Although this may be acceptable in some situations, it is undesirable in certain environments. For example, hydraulic systems are generally unsuitable for use in locations where food is stored or prepared, owing to the possibility of contamination by leaking hydraulic fluid. The exhaust gases emitted by internal combustion engines commonly used to drive the hydraulic system may also be hazardous and unacceptable in certain situations.

Similar problems are encountered with hydraulically-operated load handling machines such as fork lift trucks.

S-P552548 1 10512 08/05/2012 It is an object of the present invention to provide a lifting machine and/or a lift mechanism for a lifting machine, which each mitigate one or more of the aforesaid disadvantages.

According to one aspect of the present invention there is provided a lifting machine comprising a base, a lifting structure and a lift mechanism for adjusting the height of the lifting structure relative to the base, said lift mechanism including a drive device and a screw element arranged to be driven by the drive device, wherein rotation of the screw element is configured to adjust the height of the lifting structure relative to the base.

Using a screw element to adjust the height of the lifting structure avoids the risks associated with hydraulic systems, such as leakage of hydraulic fluid, allowing the lifting machine to be used in situations where a hydraulically-operated system would be unacceptable. The drive mechanism is also simple, inexpensive and easy to maintain, and can be packaged within a small enclosure. The drive mechanism is also light in weight making it particularly suitable for low level lifting machines.

Advantageously, the lift mechanism is constructed and arranged such that in use the screw element carries a tensile load. This avoids a problem associated with using a screw element that carries a compressive load, which can buckle if subjected to an excessive load. The screw element and its mountings may therefore be lighter and less expensive. However, the screw element may alternatively be constructed and arranged to carry a compressive load. Advantageously, the lift mechanism includes a screw follower that is arranged to travel along the screw element in response to rotation thereof, said screw follower being connected to the lifting structure to adjust the height thereof.

The screw follower is preferably connected to the lifting structure by at least one flexible elongate drive element, for example a chain, rope or belt. The flexible elongate drive element may include a first part attached to the screw follower, a second part connected directly or indirectly to the lifting structure, and an intermediate part that passes around a guide element. The guide element may for example consist of a sprocket, a pulley or a wheel. The guide element is preferably mounted towards an upper end of a tower structure.

S-P552548 110512 08/05/2012 According to a preferred embodiment of the invention there is provided a lifting machine comprising a base, a lifting structure and a lift mechanism for adjusting the height of the lifting structure relative to the base, said lift mechanism including a drive device, a screw element arranged to be driven by the drive device, a screw follower configured to travel along the screw element in response to rotation thereof, and at least one flexible elongate drive element having a first part attached to the screw follower, a second part connected directly or indirectly to the lifting structure, and an intermediate part that passes around a guide element, said guide element being mounted towards an upper end of a tower structure, the lift mechanism being configured such that rotation of the screw element adjusts the height of the lifting structure relative to the base.

Advantageously, the screw element extends substantially vertically within the tower structure. The tower structure preferably includes a first tower section and a telescopically adjustable second tower section that is connected to the first tower section for telescopic extension relative thereto. This increases the operational height range of the lifting structure without increasing the length of the tower structure.

The lift mechanism preferably includes first and second flexible elongate drive elements, wherein the first flexible elongate drive element has a first part connected to the screw follower, a second part connected to the second tower section and an intermediate part that passes around a guide element mounted towards an upper end of the first tower section, and wherein the second flexible elongate drive element has a first part connected to the first tower section, a second part connected directly or indirectly to the lifting structure and an intermediate part that passes around a guide element mounted towards an upper end of the second tower section.

Advantageously, the base is mounted on wheels or tracks for movement across a floor surface. Alternatively, it may be mounted on feet or skids for a static machine.

Advantageously the drive device is an electric motor, for example an AC motor or a brushless DC motor. This avoids the problems associated with exhaust fumes produced by internal combustion engines. The electric motor is preferably powered from leak-proof batteries, for example sealed lead-acid batteries, such as Gel or Absorbed Glass Mat

S-P552548 110512 08/05/2012 batteries, or it may be powered by mains electricity. Alternatively, the drive device could use air power.

The electric motor is preferably a regenerative motor, allowing it to recover and store electrical energy when the operator platform descends from an elevated position. Alternatively, the drive device may be a manual drive device, for example a crank handle or pedals.

Advantageously, the lift mechanism includes a brake that is operative to prevent rotation of the drive device and/or the screw, so as to lock the lifting structure in the chosen operating position. The brake can be disengaged using a manual over-ride, allowing the lift structure to descend under the force of gravity. Alternatively, the lift mechanism could be configured to descend under power.

Advantageously, the lift mechanism comprises an elevating work platform having a base, an operator platform and a lift mechanism for adjusting the height of the operator platform relative to the base. Advantageously, the maximum range of height adjustment is in the range 1m to 8m, preferably 2m to 5m.

According to another aspect of the invention there is provided a lift mechanism for lifting machine comprising a base, a lifting structure and a lift mechanism for adjusting the height of the lifting structure relative to the base, said lift mechanism including a drive device and a screw element arranged to be driven by the drive device, the lift mechanism being configured such that rotation of the screw element adjusts the height of the lifting structure relative to the base.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is an isometric view of a mobile elevating work platform showing the rear and right sides;

Figure 2 is an isometric view of the mobile elevating work platform showing the front and right sides;

S-P552548 110512 08/05/2012 Figure 3 is a top plan view of the mobile elevating work platform; Figure 4 is a right side view of the mobile elevating work platform; Figure 5 is a front view of the mobile elevating work platform;

Figure 6 is an isometric view, showing internal components of a lift mechanism of the mobile elevating work platform;

Figure 7 is a side view of the lift mechanism in a fully lowered position, and

Figure 8 is a side view of the lift mechanism in a partially raised position.

An embodiment of the invention in the form of an elevating work platform 2 is shown in the accompanying figures. The elevating work platform 2 includes a base (or chassis) 4, a lifting structure in the form of an operator cage 6 and a lift mechanism 8 that is operable to adjust the height of the operator platform 6 relative to the base 4.

In this example the base 4 is mounted on two pairs of wheels 10a, 10b, the first pair of wheels 10a being fixed wheels and the second pair of wheels 10b being pivoting casters. Locking brakes 12 may be provided on some or all of the wheels to lock the wheels during lifting operations. In this example, the wheels are not driven as the work platform is light enough to be pushed manually into a desired location. Alternatively, powered wheels or tracks may be provided, or the wheels may be replaced by feet or skids if mobility is not important. In that case, the platform may be moved using for example a pallet truck, trolley jack or a forklift truck. The operator platform 6 includes a floor plate 14 with a peripheral wall 16 and a safety cage 18. A control console (not shown) for controlling operation of the elevating work platform may be mounted on the safety cage 18 and/or elsewhere on the elevating work platform.

The lift mechanism 8, which is shown in detail in Figure 6, includes a tower structure 14 comprising a fixed first tower section 16 and a telescopically adjustable second tower section 18, which is connected to the first tower section 16 for telescopic extension relative thereto. A roller and track mechanism 20, optionally including wear pads, connects the

S-P552548 110512 08/05/2012 first and second tower sections 16, 18 to allow for telescopic adjustment. The first tower section 16 is mounted substantially vertically on the base 4 and is supported by a pair of braces 22. The second tower section can be adjusted substantially vertically relative to the first tower section. A support arm 24 is mounted on the second tower section 18, for example by means of a roller and track mechanism, to allow for vertical adjustment of the arm 24 relative to the second tower section 18. The arm 24 extends beneath and supports the operator platform 6.

A motor 26, for example an electric motor, is mounted towards the lower end of the first tower section 16 and is connected via a gearbox 28 to an elongate lead screw 30, which extends vertically towards the upper end of the first tower section 16. A screw follower 32 is mounted in engagement with the thread of the lead screw 30 for vertical movement along the screw as it rotates. In this example, the screw follower 32 comprises a nut 34 that is attached to or formed with a plate 36. Alternatively, a ball screw or roller screw mechanism may be used.

The plate 36 extends transversely on either side of the lead screw 30 and is captured between an adjacent face of the first tower section 16 and a housing 38 attached to the first tower section 16 (the housing 38 has been omitted in Figure 6 to reveal the internal components of the tower structure). The housing 38 and the first tower section 16 together prevent rotation of the screw follower 32, thereby ensuring that the rotation of the lead screw 30 drives the screw follower 32 along the lead screw 30.

A brake 40 is attached to the lower end of the motor 26. The brake 40 can be actuated to prevent rotation of the motor 26 and the lead screw 30.

A pair of flexible elongate drive elements 42 are connected to the screw follower 32 and extend upwards towards the upper end of the first tower section 16, where they pass around guide elements 44. In this example the drive elements 42 are chains and the guide elements 44 are sprockets mounted at the upper end of the first tower section 16. Alternatively, the drive elements 42 may be wire ropes or belts and the guide elements 44 may be wheels or pulleys.

S-P552548 1 10512 08/05/2012 After passing around the guide elements 44, the flexible drive elements 42 extend downwards through the first tower section 16 and are attached at their lower ends to the telescopically adjustable second tower section 18. The mechanism is configured so that when the lead screw 30 rotates in a first direction to draw the screw follower 32 downwards, the flexible drive elements 42 draw the second tower section 18 upwards. This is illustrated in Figures 7 and 8, where in Figure 7 the second tower section 18 is shown in a lowered position and in Figure 8 it is shown in a partially raised position. When the lead screw 30 rotates in an opposite second direction, the second tower section 18 is returned to the lowered position shown in Figure 7. A second set of flexible elongate drive elements 46 is provided to drive movement of the support arm 24 relative to the second tower structure 18. The second drive elements 46 are attached at their first ends to a bracket 48 at the upper end of the first tower section 16 and extend upwards towards the upper end of the second tower section 18, where they pass around second guide elements 50. The second drive elements 46 then extend downwards through the second tower section 18 and are attached at their second ends to the support arm 24. As with the first drive elements 42, the second drive elements 46 may consist of chains, ropes or belts and the second guide elements 50 may be sprockets, pulleys or wheels as appropriate.

A third flexible drive element 52 is provided on an external side of the tower structure 14. The third drive element 52 is connected at one end to the first tower section 16 and extends downwards and around a guide element 54 mounted towards the lower end of the second tower section 18. The second end of the third flexible drive element 52 is connected to the support arm 24. Again, the third drive element 30 may be a chain, rope or belt as required. In use, the third drive element ensures that when the second tower section 18 is lowered relative to the first tower section 16, the support arm 24 is simultaneously returned to its lowered position.

Operation of the elevating work platform is as follows. To ascend, the motor brake 40 is disengaged and the motor 26 is actuated. This causes the lead screw 30 to rotate, thus drawing the screw follower 32 downwards. The first and second flexible drive elements 42,46 transfer this motion to the second tower section 18 and to the support arm 24, causing the second tower section 18 to extend telescopically relative to the first tower S-P552548 110512 08/05/2012 section 16 and simultaneously raising the support arm 24 relative to the second tower section. The operator cage 6 is thus lifted to the desired height. The motor brake 40 is then actuated to hold the cage at that height.

To descend, the motor brake 40 is disengaged, allowing the operator cage 6 to descend under the force of gravity. As the cage descends, the lead screw 30 rotates, driven by the screw follower 32. Rotation of the lead screw 30 causes corresponding rotation of the motor 26 and, if desired, the motor can be used to regenerate electric energy, which is stored in storage batteries (not shown). Once the operator cage 6 has descended to the required position, the brake 40 is actuated to hold the cage in that position. The elevating work platform illustrated in the drawings is designed to provide a working height of approximately 5 metres. If a greater working height is required, the height of the tower structure 8 may be increased or one or more additional telescoping tower sections may be provided. If a reduced working height is needed, the telescopically extending second tower section 18 may be omitted. In this case, the first flexible drive elements will be attached at their second ends to the support arm 24.

The lift mechanism 8 comprising tower structure 14, the support arm, the motor 26, the lead screw 30, the screw follower 32 and the flexible elongate drive elements 42, 46 may also be provided separately for fitting to an alternative fixed or movable base unit.

Various modifications of the lifting machine described above are envisaged, some of which will now be described.

First, the lifting machine may take the form of a load handling machine instead of an elevating work platform. In this case, the lifting structure will consist of a load lifting device, for example a fork lift structure, replacing the operator cage.

The motor may be replaced by a manual drive device, for example a crank handle, a winch or pedals, which may be connected to the screw element via a one-way clutch or ratchet to prevent reverse rotation of the manual drive device as the platform descends. A releasable ratchet may also be provided to prevent unintended descent of the lift mechanism.

S-P552548 110512 08/05/2012 The screw element may alternatively be constructed to operate in compression, so that it pushes the screw follower upwards rather than pulling it downwards. In this case a larger, more rigid screw element may be required to resist buckling forces.

S-P552548 110512 08/05/2012

Claims

1. A lifting machine comprising a base, a lifting structure and a lift mechanism for adjusting the height of the lifting structure relative to the base, said lift mechanism including a drive device and a screw element arranged to be driven by the drive device, wherein rotation of the screw element adjusts the height of the lifting structure relative to the base.

2. A lifting machine according to claim 1, wherein the lift mechanism is constructed and arranged such that in use the screw element carries a tensile load.

3. A lifting machine according to claim 1 or claim 2, wherein the lift mechanism includes a screw follower that is arranged to travel along the screw element in response to rotation thereof, said screw follower being connected to the lifting structure to adjust the height thereof.

4. A lifting machine according to claim 3, in which the screw follower is connected to the lifting structure by at least one flexible elongate drive element.

5. A lifting machine according to claim 4, in which the flexible elongate drive element includes a first part attached to the screw follower, a second part connected directly or indirectly to the lifting structure, and an intermediate part that passes around a guide element.

6. A lifting machine according to claim 5, wherein said guide element is mounted towards an upper end of a tower structure.

7. A lifting machine according to claim 6, in which the screw element extends substantially vertically within the tower structure.

S-P552548 110512 08/05/2012

8. A lifting machine according to claim 6 or claim 7, in which the tower structure includes a first tower section and a telescopically adjustable second tower section that is connected to the first tower section for telescopic extension relative thereto.

9. A lifting machine according to claim 8, in which the lift mechanism includes first and second flexible elongate drive elements, wherein the first flexible elongate drive element has a first part connected to the screw follower, a second part connected to the second tower section and an intermediate part that passes around a guide element mounted towards an upper end of the first tower section, and wherein the second flexible elongate drive element has a first part connected to the first tower section, a second part connected directly or indirectly to the lifting structure and an intermediate part that passes around a guide element mounted towards an upper end of the second tower section.

10. A lifting machine according to any one of the preceding claims, in which the base is mounted on wheels or tracks for movement across a floor surface.

1 1. A lifting machine according to any one of the preceding claims, in which the drive device is an electric motor.

12. A lifting machine according to claim 11, in which the electric motor is a regenerative motor.

13. A lifting machine according to any one of the preceding claims, including a brake that is operative to prevent rotation of the drive device and/or the screw.

14. A lifting machine according to any one of the preceding claims, said lift mechanism comprising an elevating work platform having a base, an operator platform and a lift mechanism for adjusting the height of the operator platform relative to the base.

15. A lifting machine according to any one of the preceding claims, wherein the maximum range of height adjustment is in the range lm to 8m, preferably 2m to 5m.

16. A lift mechanism for a lifting machine comprising a base, a lifting structure and a lift mechanism for adjusting the height of the lifting structure relative to the base, S-P552548 1 10512 08/05/2012 said lift mechanism including a drive device and a screw element arranged to be driven by the drive device, the lift mechanism being configured such that rotation of the screw element adjusts the height of the lifting structure relative to the base.

17. An elevating work platform substantially as described herein with reference to and as illustrated by the accompanying drawings.

18. A method of operating a lifting machine, the method being substantially as described herein with reference to and as illustrated by the accompanying drawings.

S-P552548 1 10512 08/05/2012