WO2010130011A1

WO2010130011A1 - Lifting mechanism for turntable of pallet wrapping machine

Info

Publication number: WO2010130011A1
Application number: PCT/AU2010/000572
Authority: WO
Inventors: Nicholas Hanlin; Mark Ireland
Original assignee: Stack & Wrap Pty Ltd
Current assignee: Stack & Wrap Pty Ltd
Priority date: 2009-05-15
Filing date: 2010-05-17
Publication date: 2010-11-18
Anticipated expiration: 2011-11-15

Abstract

Disclosed herein is a pallet wrapping machine (10). The pallet wrapping machine includes a lift table (12) comprising a platform (14) having a first major side (16) and a second major side (18). A turntable (20) is rotatably mounted on the first major side (16) of the platform (14) for supporting a pallet. A pair of spaced apart height adjustable legs (22) is connected to the platform (14) and extend from the second major side (16) thereof for supporting the platform above a floor (23). A selectively controllable hydraulic actuator (24) is operable on each of the legs (22) to permit selective adjustment of the height of the platform (14) above the floor (23).

Description

LIFTING MECHANISM FOR TURNTABLE OF PALLET WRAPPING MACHINE

Cross-Reference to Related Applications

This application claims is related to Australian Provisional Patent Application No. 2009902222, filed 15 May 2009, the entire disclosure of which is incorporated herein by way of reference.

Field of the Invention

The present disclosure relates generally to improvements in pallet wrapping and more particularly to a lift table for a pallet wrapping machine and to a pallet wrapping machine including a lift table.

The lift table and pallet wrapping machine have been developed tor use in facilitating the stacking and wrapping of articles on pallets for warehousing and transport and will be described hereinafter with reference to this application. However, it will be appreciated that the invention may also find application in other fields.

Background of the Invention

Known pallet wrapping machine lift tables are typically spring mounted, such that the table lowers under the influence of gravity as articles are stacked on a pallet mounted on the lift table.

A disadvantage of known lift tables is that they have a predetermined initial height, which can only be adjusted by changing the springs supporting the lift table, or by adding or removing weight. Accordingly, it is difficult to adapt such known lift tables for use by operators of different heights. As a result, rather than change the springs or add or remove weight, operators often repetitively over-reach or bend down when adding articles to the lift table, which can result in operator injury. A further disadvantage of known lift tables is their minimum height, which is typically approximately 300mm from the floor. Accordingly, given this substantial height from the floor, a fork lift is required to place pallets on and remove pallets from the lift table.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application. Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Summary of the Invention In a first aspect, there is provided a lift table for a pallet wrapping machine, the lift table comprising: a platform having a first major side and a second major side; a turntable rotatably mounted on the first major side of the platform for supporting a pallet; a lifting mechanism associated with the platform for supporting the platform above a floor; a selectively controllable actuator operable on the lifting mechanism to permit selective adjustment of the height of the platform above the floor.

The lifting mechanism may comprise one or more height adjustable legs connected to the platform and extending from the second major side thereof for supporting the platform above a floor.

The actuator may be a hydraulic actuator. In other embodiments, however, the actuator is a pneumatic actuator.

The height adjustable legs may be able to move into a collapsed position, wherein a height of the turntable is less than 300mm above the floor. In the collapsed position, the height of the turntable may be less than 150mm above the floor, and in some embodiments is approximately 110mm above the floor. The maximum height of the turntable above the floor may be between 500mm and 2000mm, in some embodiments between 700mm and 1100mm, and in yet other embodiments approximately 960mm.

The legs may be mounted to a base defining the floor. The legs may at least partially recess into the base when in the collapsed position. The base may include channels into which the legs are at least partially recessed when in the collapsed position. In the collapsed position, the second major side of the platform may be in register with the base.

Two spaced apart sets of the legs may be provided. Each set of the legs may include a first member hingedly connected to a second member in a scissors arrangement. The actuator may extend between the first and second member of at least one of the sets of legs. In some embodiments, a said actuator extends between the first and second member of each of the sets of legs.

The actuator may be responsive to a first controller. In a first mode of operation, the first controller may be configured to control the actuator to maintain the operative height of the turntable, being the height of a pallet on the turntable when unloaded or the height of the topmost layer of articles on the pallet when loaded or partially loaded, at a desired height selected by an operator. Accordingly, as the operator adds articles to the pallet, the first controller may control the actuator to automatically lower the legs until the topmost layer of articles is at the desired height selected by the operator. Likewise, as the operator removes articles from the pallet, the first controller may control the actuator to automatically extend the lifting mechanism to maintain the topmost layer of articles on the pallet at the desired height selected by the operator.

A first sensor may be associated with the turntable for sensing the operative height of the turntable. The first controller may be responsive to the first sensor for controlling the actuator to maintain the operative height of the turntable at the desired height selected by the operator. The first sensor may be an optical sensor.

A selectively operable drive system may be connected to the turntable for rotating the turntable relative to the platform. The drive system may include a chain and sprocket drive. The drive system may provide for turntable rotational speeds of up to 25 rpm, and in some embodiments up to 15 rpm.

In a second aspect, there is provided a pallet wrapping machine comprising: a lift table as described in the first aspect above, or in any one of the abovementioned embodiments of the first aspect; and a pallet wrapping unit associated with the lift table for wrapping a loaded or partially loaded pallet on the turntable.

The pallet wrapping unit may be movable relative to the turntable in a direction substantially parallel to a rotational axis of the turntable. Movement of the pallet wrapping unit may be controlled by a second controller. In a second mode of operation, the second controller may be responsive to changes in the spacing between the pallet wrapping unit and the turntable resulting from movement of the turntable along its rotational axis, so as to control a spacing between the pallet wrapping unit and the turntable, measured along the rotational axis. The second controller may control the spacing between the pallet wrapping unit and the turntable by actuating a motor associated with the pallet wrapping unit to move the pallet wrapping unit along a line parallel to the rotational axis of the turntable. The second controller may be responsive to a sensor for sensing the height of articles stacked on the turntable. In the second mode of operation, when the pallet wrapping unit is activated to initiate wrapping of a partially or fully loaded pallet on the turntable, the controller may control movement of the pallet wrapping unit to height corresponding to a base of the pallet. When the pallet wrapping unit is actuated to wrap the articles, the second controller may control synchronised rotation of the turntable and elevation of the pallet wrapping unit relative to the turntable. When the sensor senses that the pallet wrapping unit has reached the top of the articles on the pallet, the second controller may deactivate the turntable and stop elevation of the pallet wrapping unit. In some embodiments, rotation of the turntable and elevation of the pallet wrapping unit can be manually overridden to halt pallet wrapping at any point. Before recommencement of pallet wrapping, the second controller may adjust for any relative movement between the pallet wrapping unit and the turntable since pallet wrapping was halted based on feedback from a sensor for sensing the height of the turntable. In alternative embodiments, the second controller can be configured for top to bottom wrapping of a loaded pallet on the turntable. In such embodiments, the controller controls movement of the pallet wrapping unit to height corresponding to a top of the articles stacked on the pallet. When the pallet wrapping unit is actuated to wrap the articles, the second controller may control synchronised rotation of the turntable and lowering of the pallet wrapping unit relative to the turntable. When the sensor senses that the pallet wrapping unit has reached the pallet, the second controller may deactivate the turntable and stop lowering of the pallet wrapping unit.

The first and second controllers may take the form of a single controller. In a further aspect, there is provided a lift table for a pallet wrapping machine, the lift table comprising: a lifting mechanism adapted for controlled movement along an axis; a platform extending generally orthogonally from the axis, the platform having a first major side and a second major side; a turntable rotatably mounted on the first major side of the platform for supporting a pallet; wherein the lifting mechanism is adapted to support the platform above a floor and to raise and lower the platform under the control of a first controller.

The platform may be removably connected to the lifting mechanism. The lifting mechanism may include a plurality of tines for engaging the platform. The platform may include a plurality of openings for receiving the tines. The lifting mechanism may include a hydraulic cylinder extending along the axis. However, in other embodiments, the lifting mechanism may include a drive chain and sprocket arrangement or pneumatic actuator to provide for the movement along the axis. The lifting mechanism may be able to move the platform into a lowered position wherein a height of the turntable is less than 300mm above the floor. In some embodiments, in the lowered position, the height of the turntable may be less than 150mm above the floor, and in yet further embodiments may be approximately 110mm above the floor. The maximum height of the turntable above the floor may be between 500mm and 2000mm, in some embodiments between 700mm and 1100mm, and in yet further embodiments approximately 960mm.

In a first mode of operation, the first controller may be configured to control the lifting mechanism to maintain the operative height of the turntable, being the height of a pallet on the turntable when unloaded or the height of the topmost layer of articles on the pallet when loaded or partially loaded, at a desired height selected by an operator. Accordingly, as the operator adds articles to the pallet, the first controller may control the lifting mechanism to automatically lower the platform until the topmost layer of articles is at the desired height selected by the operator. Likewise, as the operator removes articles from the pallet, the first controller may control the lifting mechanism to automatically raise the platform to maintain the topmost layer of articles on the pallet at the desired height selected by the operator.

A first sensor may be associated with the turntable for sensing the operative height of the turntable. The first controller may be responsive to the first sensor for controlling the lifting mechanism to maintain the operative height of the turntable at the desired height selected by the operator. The first sensor may be an optical sensor.

A selectively operable drive system may be connected to the turntable for rotating the turntable relative to the platform. The drive system may include a chain and sprocket drive. The drive system may provides for turntable rotational speeds of up to 25 rpm, and in some embodiments up to 15 rpm. A pallet wrapping unit may be associated with the lift table for wrapping a loaded or partially loaded pallet on the turntable.

The pallet wrapping unit may be movable relative to the turntable in a direction substantially parallel to a rotational axis of the turntable. Movement of the pallet wrapping unit may be controlled by a second controller. In a second mode of operation, the second controller may be responsive to changes in the spacing between the pallet wrapping unit and the turntable resulting from movement of the turntable along its rotational axis, so as to control a spacing between the pallet wrapping unit and the turntable, measured along the rotational axis. The second controller may control the spacing between the pallet wrapping unit and the turntable by actuating a motor associated with the pallet wrapping unit to move the pallet wrapping unit along the rotational axis of the turntable.

The second controller may be responsive to a sensor for sensing the height of articles stacked on the turntable. In the second mode of operation, when the pallet wrapping unit is activated to initiate wrapping of a partially or fully loaded pallet on the turntable, the controller may control movement of the pallet wrapping unit to height corresponding to a base of the pallet. When the pallet wrapping unit is actuated to wrap the articles, the second controller may control synchronised rotation of the turntable and elevation of the pallet wrapping unit relative to the turntable. When the sensor senses that the pallet wrapping unit has reached the top of the articles on the pallet, the second controller may deactivate the turntable and stops elevation of the pallet wrapping unit. In some embodiments, rotation of the turntable and elevation of the pallet wrapping unit can be manually overridden to halt pallet wrapping at any point. Before recommencement of pallet wrapping, the second controller may adjust for any relative movement between the pallet wrapping unit and the turntable since pallet wrapping was halted based on feedback from a sensor for sensing the height of the turntable. In alternative embodiments, the second controller can be configured for top to bottom wrapping of a loaded pallet on the turntable. In such embodiments, the controller may control movement of the pallet wrapping unit to height corresponding to a top of the articles stacked on the pallet. When the pallet wrapping unit is actuated to wrap the articles, the second controller may control synchronised rotation of the turntable and lowering of the pallet wrapping unit relative to the turntable. When the sensor senses that the pallet wrapping unit has reached the pallet, the second controller may deactivate the turntable and stops lowering of the pallet wrapping unit.

The first and second controllers may take the form of a single controller.

Brief Description of the Drawings

A preferred embodiment will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. l is a schematic perspective view of a first embodiment of a pallet wrapping machine according to the present disclosure, with its lift table shown in a partially elevated position; Fig. 2 is a schematic perspective view of the pallet wrapping machine of Fig. 1, with its lift table shown in a collapsed position; and

Fig. 3 is a schematic side elevational view of a second embodiment of a pallet wrapping machine according to the present disclosure, with its elongate support structure shown partly cut-away and with its lift table shown in a partially elevated position.

Preferred Embodiment of the Invention

Referring firstly to Figs. 1 and 2 of the drawings, tlieτe is shown a pallet wrapping machine 10. The pallet wrapping machine includes a lift table 12 comprising a platform 14 having a first major side 16 and a second major side 18. A turntable 20 is rotatably mounted on the first major side 16 of the platform 14 for supporting a pallet. A lifting mechanism, comprising a pair of spaced apart height adjustable legs 22, is connected to the platform 14 and extend from the second major side 16 thereof for supporting the platform above a floor 23. A selectively controllable hydraulic actuator 24 is operable on each of the legs 22 to permit selective adjustment of the height of the platform 14 above the floor 23.

Each of the legs 22 includes a first member 26 hingedly connected to a second member 28 in a scissors arrangement. Each actuator 24 extends between the first 26 and second 28 member of each set of legs. A floor engaging end of the first member 26 of each set of legs is adapted to be translationally fixed relative to the floor 23. A floor engaging end of each of the second members 28 is adapted to be slidable relative to the floor 23 to facilitate scissoring of the legs 22. The floor engaging end of each of the second members 28 is engaged in a channel 30 in the floor 23 and traverses this channel during scissoring of the legs 22.

The legs 22 are mounted to a base 32, which defines the floor 23. The legs 22 recess into the channels 30 when in a collapsed position, as shown in Fig. 2, to provide the lift table 12 with a low profile, in which the second major side 18 of the platform 14 is in register with the base 32 and the turntable 20 is approximately 110mm above the floor 23. With the legs 22 fully extended, the maximum height of the turntable 20 above the floor 23 is approximately 960mm. The actuators 24 are responsive to a controller 34. In a first mode of operation, the controller 34 is configured to control the actuator to maintain the operative height of the turntable 20, being the height of a pallet on the turntable when unloaded or the height of the topmost layer of articles on the pallet when loaded or partially loaded, at a desired height selected by an operator. Accordingly, as the operator adds articles to the pallet, the controller 34 controls the actuators 24 to automatically lower the legs 22 until the topmost layer of articles is at the desired height selected by the operator. Likewise, as the operator removes articles from the pallet, the controller 34 controls the actuators 24 to automatically extend the legs 22 to maintain the topmost layer of articles on the pallet at the desired height selected by the operator.

A first optical sensor 36 is associated with the turntable 20 for sensing its operative height. The first sensor 36 is axially movably mounted on a vertical structure 38 adjacent the lift table 12 and directed toward the lift table 12. When the operator selects a desired operative height of the turntable 20, the controller 34 controls actuation of a motor (not shown) connected to the first sensor 36 to automatically move the first sensor to that desired height. The controller 34 is responsive to the first sensor 36 for controlling the actuators 24 to maintain the operative height of the turntable 20 at the desired height selected by the operator.

A selectively operable chain and sprocket drive system 40 is connected to the turntable 20 for rotating the turntable 20 relative to the platform 14. The drive system 40 provides for turntable 20 rotational speeds of up to approximately 15 rpm.

Associated with the lift table 12 is a pallet wrapping unit 42, which is axially movably mounted on the vertical structure 38, in a direction substantially parallel to a rotational axis 44 of the turntable 20, for wrapping a loaded or partially loaded pallet on the turntable 20. Movement of the pallet wrapping unit 42 is controlled by the controller 34 actuating a motor (not shown) connected to the pallet wrapping unit 42.

It will be appreciated that changes in the spacing between the pallet wrapping unit 42 and the turntable 20 result from the turntable moving along its longitudinal axis 44, under the control of the controller 34, as described above, to maintain the desired operative turntable height selected by the operator. In a second ("pallet wrapping") mode of operation, the controller 34 is responsive to changes in this spacing between the pallet wrapping unit 42 and the turntable 20 so as to control the spacing between the pallet wrapping unit 42 and the turntable 20, measured along the rotational axis 44. The controller 34 controls this spacing by actuating the motor (not shown) associated with the pallet wrapping unit 42 to move the pallet wrapping unit along the vertical structure 38 parallel to the rotational axis 44of the turntable 20.

A second sensor 46, to which the controller 34 is responsive, is provided for

^• sensing the height of articles stacked on the turntable 20. The second sensor 46 is also an optical sensor, is mounted to the pallet wrapping unit 42 and is directed toward the rotational axis 44 of the turntable 20. In the second ("pallet wrapping") mode of operation, when the pallet wrapping unit 42 is activated to initiate wrapping of a partially or fully loaded pallet on the turntable 20, the controller 34 controls movement of the pallet wrapping unit 42 to height corresponding to a base of the pallet, as sensed by the second sensor 46. When the pallet wrapping unit 42 is actuated to wrap the articles on the turntable 20, the controller 34 controls synchronised rotation of the turntable 20 and actuation of the motor (not shown) associated with the pallet wrapping unit 42 to elevate the pallet wrapping unit 42 relative to the turntable 20. When the sensor 46 senses that the pallet wrapping unit 42 has reached the top of the articles on the pallet, the controller 34 deactivates the turntable 20 and stops elevation of the pallet wrapping unit 42. Rotation of the turntable 20 and elevation of the pallet wrapping unit 42 can also be manually overridden to halt pallet wrapping at any point. Before recommencement of pallet wrapping, after stacking of further articles on the pallet, the controller 34 adjusts for any relative movement between the pallet wrapping unit 42 and the turntable 20 since pallet wrapping was halted based on feedback from the sensor 36, which senses the operative height of the turntable 20.

In a third ("pallet wrapping") mode of operation, the controller 34 is configured for top to bottom wrapping of a loaded pallet on the turntable 20. In this mode of operation, the controller 34 controls movement of the pallet wrapping unit 42 to height corresponding to a top of the articles stacked on the pallet, as sensed by the second sensor 46. When the pallet wrapping unit 42 is actuated to wrap the articles, the controller 34 controls synchronised rotation of the turntable 20 and lowering of the pallet wrapping unit 42 relative to the turntable 20. When the second sensor 46 senses that the pallet wrapping unit 42 has reached the pallet, the controller 34 deactivates the turntable 20 and stops lowering of the pallet wrapping unit 42.

In use, an operator sets their desired operative turntable height and activates the first mode of operation using an input terminal 48 connected to the controller 34. In response, the controller 34 actuates the actuators 24 to adjust the turntable operative height based on feedback from the first sensor 36. As the operator adds articles to a pallet on the turntable 20, the controller 34 automatically actuates the actuators 24 to lower the turntable 20 and maintain the topmost layer of the articles, which define the operative height, at the user's desired operative height. When the operator wishes to wrap articles stacked on the turntable 20, they activate the second operative mode (bottom to top wrapping) or the third operative mode (top to bottom wrapping) using the input terminal 48. In response, if the second operative mode is selected, the controller 34 moves the pallet wrapping unit 42 to a level corresponding to a base of the pallet, as sensed by the second sensor 46. The operator then draws pallet wrap from the pallet wrapping unit 42 and attaches the pallet wrap to the pallet. The operator then initiates pallet wrapping using the input terminal 48, which signals the controller to initiate synchronised rotation of the turntable 20 and actuation of the motor (not shown) 5 associated with the pallet wrapping unit 42 to elevate the pallet wrapping unit 42 relative to the turntable 20. When the sensor 46 senses that the pallet wrapping unit 42 has reached the top of the articles on the pallet, the controller 34 deactivates the turntable 20 and stops elevation of the pallet wrapping unit 42. When pallet wrapping is stopped, either due to the pallet wrapping unit reaching the top layer of articles or

10 due to manual override, the operator may add further articles to the pallet. Before recommencement of pallet wrapping, after stacking of further articles on the pallet, the controller 34 adjusts for any relative movement between the pallet wrapping unit 42 and the turntable 20, since pallet wrapping was halted, based on feedback from the sensor 36, which senses the operative height of the turntable 20. This ensures that no

15 gaps in the wrapping are created due to the turntable 20 automatically lowering when further articles are added.

In the third operative mode, the controller 34 moves the pallet wrapping unit 42 to a level corresponding to a top layer of articles stacked on the pallet, as sensed by the second sensor 46. The operator then draws pallet wrap from the pallet wrapping unit

20 42 and attaches the pallet wrap to the top layer of articles. The operator then initiates pallet wrapping using the input terminal 48, which signals the controller to initiate synchronised rotation of the turntable 20 and actuation of the motor (not shown) associated with the pallet wrapping unit 42 to lower the pallet wrapping unit 42 relative to the turntable 20. When the sensor 46 senses that the pallet wrapping unit 42 has

25 reached the base of the pallet, the controller 34 deactivates the turntable 20 and stops lowering of the pallet wrapping unit 42.

Fig. 3 shows a second preferred embodiment of a pallet wrapping machine 10, where reference numerals corresponding with those of the first embodiment indicate corresponding features with corresponding functions. However, in the second

30 embodiment, the height adjustable legs 22 are replaced with a lifting mechanism 50 adapted for controlled movement along a pair of poles 52 defining an axis 54. The poles 52 extend between top and bottom end plates 56, 57 of an elongate support structure 58. A mounting block 60 is slidably connected to the poles 52. A plurality of tines 64 extend from the mounting block 60 for engaging a plurality of openings 66 in

35 the platform 14. A hydraulic cylinder 68 extends between the bottom plate 57 and the π mounting block, along the axis 62, for facilitating raising and lowering of mounting block 60 and thereby the platform 14.

When connected to the lifting mechanism 50, the platform 14 extends generally orthogonally from the axis 54. The lifting mechanism 50 is adapted to support Hie platform 12 above a floor 23 and to raise and lower the platform 12 under the control of controller 34.

The lift table 12 can be removed from the lifting mechanism 50 by disengaging the platform 14 from the tines 64. The removability of the lift table 12 facilitates repair and maintenance and also allows the lift table 12 / platform 14 to be used as a pallet for transporting stacked articles, if required.

With the hydraulic cylinder 68 in a retracted configuration, the lift table 12 has a low profile, in which the second major side 18 of the platform 14 is in register with the floor 23 and the turntable 20 is approximately 75mm above the floor 23. With the hydraulic cylinder 68 fully extended, the maximum height of the turntable 20 above the floor 23 is , approximately 960mm.

Whilst not shown, the pallet wrapping machine 10 of Fig. 3 also includes a sprocket drive system, a pallet wrapping unit and its associated raising and lowering elements, and various sensors, to which the controller 34 is responsive, substantially the same as those described in the first embodiment above with reference to Figs. 1 and 2. Control of the raising and lowering of the platform to facilitate stacking and wrapping of articles on a pallet is achieved in substantially the same manner as for the first embodiment described with reference to Figs. 1 and 2.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above described embodiments without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. Examples of variations and modifications in some other embodiments include, but are not limited to:

• the actuators 24 being pneumatic actuators; ' • the relative spacing between the turntable 20 and the pallet wrapping unit being controlled by actuating the actuators 24 to adjust the height of the turntable 20, rather than by adjusting the height of the pallet wrapping unit; and/or

• the lifting mechanism 60 can include a drive chain and sprocket arrangement or pneumatic actuator to provide for the movement along the axis.

Claims

CLAIMS:

1. A lift table for a pallet wrapping machine, the lift table comprising: a platform having a first major side and a second major side; a turntable rotatably mounted on the first major side of the platform for supporting a pallet; a lifting mechanism associated with the platform for supporting the platform above a floor; a selectively controllable actuator operable on the lifting mechanism to permit selective adjustment of the height of the platform above the floor.

2. A lift table according to claim 1, wherein the lifting mechanism comprises one or more height adjustable legs, which are able to move into a collapsed position, wherein a height of the turntable is less than 300mm above the floor.

3. A lift table according to claim 2, wherein, in the collapsed position, the height of the turntable is less than 150mm above the floor.

4. A lift table according to claim 2 or claim 3, wherein the one or more legs are mounted to a base defining the floor and the one or more legs at least partially recess into the base when in the collapsed position.

5. A lift table according to any one of claims 2 to 4, wherein two spaced apart sets of the legs are provided, each set of the legs comprising a first member hingedly connected to a second member in a scissors arrangement.

6. A lift table according to claim 1, wherein the lifting mechanism comprises a plurality of tines for engaging a plurality of corresponding openings in the platform.

7. A lift table according to any one of the preceding claims, wherein the platfown is removably connected to the lifting mechanism.

8. A lift table according to any one of the preceding claims, further comprising a first controller to which the actuator is responsive, and wherein, in a first mode of operation, the first controller is configured to control the actuator to maintain the operative height of the turntable, being the height of a pallet on the turntable when unloaded or the height of the topmost layer of articles on the pallet when loaded or partially loaded, at a desired height selected by an operator.

9. A lift table according to claim 8, further comprising a first sensor associated with the turntable for sensing the operative height of the turntable, the first controller being responsive to the first sensor for controlling the actuator to maintain the operative height of the turntable at the desired height selected by the operator.

10. A pallet wrapping machine comprising: a lift table according to any one of the preceding claims; and a pallet wrapping unit associated with the lift table for wrapping a loaded or partially loaded pallet on the turntable.

11. A pallet wrapping machine according to claim 10, wherein the pallet wrapping unit is movable relative to the turntable in a direction substantially parallel to a rotational axis of the turntable, wherein movement of the pallet wrapping unit is controlled by a second controller.

12. A pallet wrapping machine according to claim 11, wherein, in a second mode of operation, the second controller is responsive to changes in the spacing between the pallet wrapping unit and the turntable resulting from movement of the turntable along its rotational axis, so as to control a spacing between the pallet wrapping unit and the turntable, measured along the rotational axis.

13. A pallet wrapping machine according to claim 12, wherein: the second controller is responsive to a sensor for sensing the height of articles stacked on the turntable; in the second mode of operation, when the pallet wrapping unit is activated to initiate wrapping of a partially or fully loaded pallet on the turntable, the controller controls movement of the pallet wrapping unit to height corresponding to a base of the pallet; when the pallet wrapping unit is actuated to wrap the articles, the second controller controls synchronised rotation of the turntable and elevation of the pallet wrapping unit relative to the turntable; and when the sensor senses that the pallet wrapping unit has reached the top of the articles on the pallet, the second controller deactivates the turntable and stops elevation of the pallet wrapping unit.

14. A pallet wrapping machine according to any one of claims 11 to 13, wherein rotation of the turntable and movement of the pallet wrapping unit parallel to the rotational axis of the turntable can be manually overridden to halt pallet wrapping at any point, and wherein, before recommencement of pallet wrapping, the second controller adjusts for any relative movement between the pallet wrapping unit and the turntable since pallet wrapping was halted based on feedback from a sensor for sensing the height of the turntable.

15. A pallet wrapping machine according to claim 12, wherein: the second controller controls movement of the pallet wrapping unit to height corresponding to a top of the articles stacked on the pallet; when the pallet wrapping unit is actuated to wrap the articles, the second controller controls synchronised rotation of the turntable and lowering of the pallet wrapping unit relative to the turntable; and when the sensor senses that the pallet wrapping unit has reached the pallet, the second controller deactivates the turntable and stops lowering of the pallet wrapping unit.