GB2297962A - Lifting Devices - Google Patents

Abstract

A pneumatic lifting device 1 comprises a trolley 6 adapted to engage an overhead gantry 7 and to be movable therealong, and a piston and cylinder unit 2 which is extendible and retractable by air pressure and which is suspended at its upper end 3 from the trolley 6 so as to be movable with the trolley transversely of the length of the piston and cylinder unit. A load support member such as gripper 8 is connected to the other end 9 of the piston and cylinder unit 2 and is adapted to support a load to be lifted by the device. Furthermore a manually operable control unit 12 is mounted on the lower end 9 of the piston and cylinder unit 2 by a flexible arm 14 and is operable to control the air pressure applied to the piston and cylinder unit 2 to lift the load by retraction of the piston and cylinder unit and subsequently, after conveyance of the load by movement of the trolley 6 along the gantry 7 with the load suspended therefrom, to lower the load by extension of the piston and cylinder unit. Since, unlike a vacuum lifting device, such a lifting device does not need to be engaged with an impermeable substantially flat surface, a variety of heavy loads may be lifted by the device including permeable loads and unevenly shaped loads. Various types of gripper or forks are dislodged (Figs 2 and 4-6).

Description

"Lifting Devices" This invention relates to lifting devices for the lifting of heavy loads, for example to enable heavy objects to be conveyed between two locations on a factory floor.

A known lifting device for factory use is in the form of a telescopic vacuum tube suspended at one end from a trolley on an overhead gantry, a foot member provided at the other end of the vacuum tube for engaging a load to be lifted by the device, and a manually operable control unit mounted on the foot member and adapted to control a vacuum supply so as to cause the foot member to engage a suitable surface of the load under vacuum pressure and so as to subsequently retract the tube under vacuum pressure in order to lift the load. Once the load has been lifted by manual operation of the control unit, it can be moved to the required location simply by manipulating the load in order to cause the trolley to move along the gantry with the load suspended therefrom by the retracted vacuum tube.Such a vacuum operated lifting device is widely used in applications in which lifting of heavy loads on a repetitive basis is required, since it prevents injury to personnel by repetitive manual lifting of such loads.

Whilst such a lifting device may be used in association with various forms of load support member to enable various shapes and forms of load to be lifted, it will always require an impermeable, substantially flat surface to be engaged by the foot member under vacuum pressure, and this means that there are certain loads, such as fluid permeable loads or unevenly shaped loads, which are not suitable to be lifted by such a lifting device. Also the need to provide an appropriate vacuum source for operation of the lifting device can rule out the use of such a lifting device in certain circumstances.

It is an object of the invention to provide a lifting device which may be used to lift heavy loads which are not suitable to be lifted by such vacuum operated lifting devices.

According to the present invention there is provided a lifting device comprising a trolley adapted to engage an overhead gantry and to be movable therealong, a piston and cylinder unit which is extendible and retractable by fluid pressure and which is suspended at one end from the trolley so as to be movable with the trolley transversely of the length of the piston and cylinder unit, a load support member connected to the other end of the piston and cylinder unit and adapted to support a load to be lifted by the device, and a manually operable control unit mounted on the piston and cylinder unit in the vicinity of said other end and adapted to control the fluid pressure applied to the piston and cylinder unit to lift the load by retraction of the piston and cylinder unit and subsequently, after conveyance of the load by movement of the trolley along the gantry with the load suspended therefrom, to lower the load by extension of the piston and cylinder unit.

Since such a lifting device does not need to be engaged with an impermeable, substantially flat surface, a variety of loads may be lifted by including permeable loads and unevenly shaped loads, provided that the load support member is suitably adapted to engage the load. Furthermore such a lifting device may be installed at relatively low cost, particularly in applications in which a source of fluid under pressure, such as a pneumatic source, is already provided for other purposes.

In a preferred embodiment of the invention said one end of the piston and cylinder unit is pivotally connected to the trolley so as to permit limited swinging movement of the piston and cylinder unit and the load suspended therefrom relative to the trolley. Alternatively or additionally said one end of the piston and cylinder unit may be connected to the trolley by a swivel joint so as to permit swivelling of the suspended piston and cylinder unit about a vertical axis relative to the trolley.

Furthermore the load support member may be connected to said other end of the piston and cylinder unit by a swivel joint so as to permit swivelling of the suspended load relative to the piston and cylinder unit, and/or by a pivot joint so as to permit pivoting of the suspended load.

Conveniently the piston and cylinder unit comprises a cylinder having an upper end and a lower end to which the load support member is connected, a piston within the cylinder, and a piston rod connected at one end to the piston, projecting from the upper end of the cylinder and connected at the other end to the trolley.

Alternatively the cylinder may be connected at its upper end to the trolley in which case the piston rod projects from the lower end of the cylinder and is connected to the load support member.

The control unit may be mounted on the piston and cylinder unit by an arm which extends transversely of the length of the piston and cylinder unit. The arm may be flexible so as to permit limited movement of the control unit relative to the piston and cylinder unit.

Furthermore the piston and cylinder unit is advantageously provided with brake means which is adapted to prevent extension or retraction of the piston and cylinder unit in the absence of applied fluid pressure. Such brake means renders the device failsafe in the event of failure of the fluid supply.

The device may include a main control valve for supplying fluid from a fluid source to the two ends of the piston and cylinder unit, and a pilot control valve operable in response to manual operation of the control unit to control the main control valve in order to effect flow and return of the fluid under pressure to and from the piston and cylinder unit to cause extension or retraction of the piston and cylinder unit.

The piston and cylinder unit is preferably operable by air pressure applied to the piston and cylinder unit in response to manual operation of the control unit in order to extend or retract the piston and cylinder unit in dependence on the applied air pressure.

The load support member may comprise a gripper unit incorporating at least two clamping arms which are movable to grip the load under fluid pressure.

Alternatively the load support member may take a variety of other forms depending on the nature of the load to be lifted, and may for example consist of one or more hook members if the load has one or more suitable fixing points to which the hook members may be attached.

In order that the invention may be more fully understood, a pneumatic lifting device in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of the lifting device; Figure 2 shows a modification of the lower part of the lifting device; Figure 3 is a flow diagram of the pneumatic circuit of the lifting device; Figure 4 is a side view of a load support member which may be used with the lifting device; and Figures 5 and 6 are two side views of an alternative form of load support member which may be used with the lifting device.

Referring to Figure 1 the pneumatic lifting device 1 comprises a piston and cylinder unit 2 which is connected at its upper end 3 by a swivel joint 4 and a pivot joint 5 to a trolley 6 which is movable along an overhead gantry 7. The overhead gantry 7 may be of the jib, monorail or bridge beam type. A load support member 8 is connected to the other end 9 of the piston and cylinder unit 2 by a swivel joint 10 and a pivot joint 11. A manually operable control unit 12 is mounted on the lower end 9 of the piston and cylinder unit 2 by a flexible arm 14 and incorporates a springbiased lever 15 for controlling extension and retraction of the piston and cylinder unit 2 during lifting and lowering of the load.The piston and cylinder unit 2 consists of a cylinder 2A and a piston rod 2B connected at its lower end to a piston (not visible in Figure 1) within the cylinder 2A and projecting from the upper end of the cylinder 2A for connection to the trolley 6. Flow/return lines 13 are provided for the flow and return of air to opposite sides of the piston within the cylinder 2A.

The lifting device 1 is shown in Figure 1 with a load support member 8 provided at its lower end which is specifically adapted to lift a load in the form of a pallet. To this end the load support member 8 comprises an upper clamping plate 17 and a lower clamping plate 18 which is movable upwardly and downwardly relative to the upper clamping plate 17 in response to manual operation of a rotary actuator 19.As may be seen in Figure 1, the lower clamping plate is adapted to engage below an upper portion of the pallet 20 (and is provided with projections 21 to assist gripping), whereas the upper clamping plate 17 is provided to engage the upper surface of the pallet portion, so that the pallet portion can be securely held between the upper and lower clamping plates 17, 18 after suitable adjustment of the rotary actuator 19 to move the lower clamping plate 18 upwardly to effect the required clamping.

Figure 2 shows a simplified form of load support member 24 which may be used for supporting a pallet 20. In this case the load support member 24 incorporates an upper plate 25 intended to engage the upper surface of the pallet portion, and a fixed lifting plate 26 intended to be introduced into the space below the pallet portion from one side in order to engage the lower surface of the pallet portion when the pallet 20 is lifted. In this case the control unit 12 is mounted on the load support member 24, rather than being provided on a separate flexible arm 14 as in Figure 1. Furthermore an extension 27 of the load support member 24 provides a handle for manipulating the load support member 24 and for moving the lifted load.

The operation of the lifting device 1 will now be described with reference to the flow diagram of Figure 3 which illustrates the control of air pressure applied to the two sides of the piston 30 of the piston and cylinder unit 2 by way of the flow/return lines 13 by a main spool valve 31 which is actuated by pilot fluid flows in pilot flow lines 32 controlled by a pilot spool valve 33. The pilot spool valve 33 is operated by operator actuation of the lever 15 of the control unit 12.In the absence of actuation of the lever 15, the lever 15 is spring biased into its neutral position and the pilot spool valve 33 is maintained in its central position shown in Figure 3, and this in return results in the main spool valve 31 being in its central position in which the air pressures acting on the opposite sides of the piston 30 are equalised so that the piston 30 is retained in its set position within the cylinder 2A.

A spring-biased brake unit 35 acting between the cylinder 2A and the piston rod 2B serves to prevent extension or retraction of the piston and cylinder unit 2 even if the air pressure fails.

In order to lift the load, the lever 15 of the control unit 12 is moved in one direction in order to displace the spool of the pilot spool valve 33 in such a direction as to control the main spool valve 31 so as to apply air pressure to the upper side of the piston 30, and so as to vent air pressure from the lower side of the piston 30 in order to retract the piston and cylinder unit 2. On release of the lever 15, the lever is automatically returned to its neutral position and the retraction of the piston and cylinder unit 2 will cease, and the spool valves 33 and 31 will again be placed in their central positions to retain the set position of the piston and cylinder unit 2.Actuation of the lever 15 of the control unit 12 in the opposite direction causes the spool of the pilot spool valve 33 to be displaced in such a direction so as to apply air pressure to the lower side of the piston 30, and so as to vent air pressure from the upper side of the piston 30, in order to effect subsequent extension of the piston and cylinder unit 2 to lower the load. A valve 36 is provided for supplying air pressure to the brake unit 35 to release the brake pressure applied to the piston rod 2B during extension and retraction of the piston and cylinder unit 2.

It will be appreciated that such an arrangement permits lifting of heavy loads to any desired height, and that the load can then be held with hands off the control unit, the load being manually movable as required whilst suspended from the overhead gantry prior to subsequent lowering of the load under operator control when it has been moved to the required position. The lifting stroke of the device is determined by the length of the piston rod 2B of the piston and cylinder unit 2 and the suspension height of the unit.

A variety of load support members may be used, including various clamping attachments, hooks and forks, to allow a variety of loads to be lifted, moved and lowered under operator control. Figure 4 shows a load support member 40 which is operable by air pressure to grip a load using two side clamping plates 41 and 42 which are movable together and apart by a pneumatic clamping unit 43 supplied with air pressure by flow/return lines 44 under control of the control unit 12. A push button 45 is provided on the control unit 12 to enable manual operation of the clamping unit 40 to move the clamping plates 41 and 42 apart, the clamping plates 41 and 42 being moved together automatically on release of the push button 45 in order to grip the load.

Figures 5 and 6 show an alternative load support member 50 comprising pivotal clamping arms 51 and 52 pivotally supporting gripping members 53 and 54 for engaging the load 55. A pneumatic ram 56 is operable in similar manner to the clamping unit 40 of Figure 4 in order to effect movement apart and together of the gripping members 53 and 54 in order to grip the load 55. As shown by the broken lines in Figure 6, the retraction of the ram 56 is variable to accommodate loads of different sizes.

Although the above described lifting device makes use of air pressure to effect lifting and lowering of the load, it should be understood that, in other embodiments of the invention, hydraulic pressure is utilised for such lifting and lowering.

Claims (12)

1. A lifting device comprising a trolley adapted to engage an overhead gantry and to be movable therealong, a piston and cylinder unit which is extendible and retractable by fluid pressure and which is suspended at one end from the trolley so as to be movable with the trolley transversely of the length of the piston and cylinder unit, a load support member connected to the other end of the piston and cylinder unit and adapted to support a load to be lifted by the device, and a manually operable control unit mounted on the piston and cylinder unit in the vicinity of said other end and adapted to control the fluid pressure applied to the piston and cylinder unit to lift the load by retraction of the piston and cylinder unit and subsequently, after conveyance of the load by movement of the trolley along the gantry with the load suspended therefrom, to lower the load by extension of the piston and cylinder unit.

2. A lifting device according to claim 1, wherein said one end of the piston and cylinder unit is pivotally connected to the trolley so as to permit limited swinging movement of the piston and cylinder unit and the load suspended therefrom relative to the trolley.

3. A lifting device according to claim 1 or 2, wherein said one end of the piston and cylinder unit is connected to the trolley by a swivel joint so as to permit swivelling of the suspended piston and cylinder unit about a vertical axis relative to the trolley.

4. A lifting device according to claim 1, 2 or 3, wherein the load support member is connected to said other end of the piston and cylinder unit by a swivel joint so as to permit swivelling of the suspended load relative to the piston and cylinder unit, and/or by a pivot joint so as to permit pivoting of the suspended load.

5. A lifting device according to any preceding claim, wherein the piston and cylinder unit comprises a cylinder having an upper end and a lower end to which the load support member is connected, a piston within the cylinder, and a piston rod connected at one end to the piston, projecting from the upper end of the cylinder and connected at the other end to the trolley.

6. A lifting device according to any preceding claim, wherein the control unit is mounted on the piston and cylinder unit by an arm which extends transversely of the length of the piston and cylinder unit.

7. A lifting device according to claim 6, wherein the arm is flexible so as to permit limited movement of the control unit relative to the piston and cylinder unit.

8. A lifting device according to any preceding claim, wherein the piston and cylinder unit is provided with brake means which is adapted to prevent extension or retraction of the piston and cylinder unit in the absence of applied fluid pressure.

9. A lifting device according to any preceding claim, which includes a main control valve for supplying fluid from a fluid source to the two ends of the piston and cylinder unit, and a pilot control valve operable in response to manual operation of the control unit to control the main control valve in order to effect flow and return of the fluid under pressure to and from the piston and cylinder unit to cause extension or retraction of the piston and cylinder unit.

10. A lifting device according to any preceding claim, wherein the piston and cylinder unit is operable by air pressure applied to the piston and cylinder unit in response to manual operation of the control unit in order to extend or retract the piston and cylinder unit in dependence on the applied air pressure.

11. A lifting device according to any preceding claim, wherein the load support member comprises a gripper unit incorporating at least two clamping arms which are movable to grip the load under fluid pressure.

12. A lifting device substantially as hereinbefore described with reference to the accompanying drawings.