GB2469633A

GB2469633A - Lifting System

Info

Publication number: GB2469633A
Application number: GB0906766A
Authority: GB
Inventors: Mark Richard Bell
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-04-20
Filing date: 2009-04-20
Publication date: 2010-10-27
Anticipated expiration: 2029-04-20
Also published as: GB0906766D0; GB2469633B

Abstract

The invention relates to a lifting system 2 for lifting a temporary work platform 12 to an elevated position on a structure i.e. high voltage pylons, for maintenance or construction purposes. The lifting system comprises an access platform 4, a lifting arm (6 figure 1) attached to the access platform 4 for lifting the access platform 4 and a releasable securing mechanism attached to the access platform 4. The releasable securing mechanism is engageable with the work platform 12 to secure the work platform 12 to the access platform 4 and allow the work platform 12 to be lifted with the access platform 4 by the lifting arm (6 figure 1). The lifting arm (6 figure 1) may be attached to a vehicle (3 figure 1).

Description

LInING SYSTEM The present invention relates to a lifting system and a method of lifting a work platform.

There are a number of situations in which it is useful to install a temporary work platform in an elevated position on a structure for maintenance or construction purposes.

For example, high voltage transmission towers (also known as pylons) are used to transmit electricity from power generating stations to various locations in a network known in the UK as the National Grid. Maintenance of pylons is essential and can present challenges due to the height of the pylons and their location which can be exposed to strong weather conditions. Safety is an important aspect of all maintenance on pylons.

Standard maintenance practice uses work platforms for maintenance personnel to stand on while working on pylons. These work platforms are moveable and are positioned at the part of the pylon which requires the maintenance. This can be high above the ground.

Moving work platforms in to position presently involves using ground based winches and is labour intensive. Furthermore, there are safety issues because often a worker needs to climb the pylon in order to attach the winch cable to a pulley to enable the work platform to be raised. * . **S.

The present invention improves the efficiency and safety of installing work platforms in **.

: high places.

S

*25 Thus viewed from one aspect the present invention provides a lifting system for lifting a *. I�.* an access platform; a lifting arm attached to the access platform for lifting the access platform; and a releasable securing mechanism attached to the access platform; wherein the releasable securing mechanism is engageable with a work platform to secure the work platform to the access platform and allow the work platform to be lifted with the access platform by the lifting arm.

By securing a work platform to an access platform, the lifting system can be used to lift the work platform instead of a ground based winch. This may reduce the time required to lift a work platform in to position on a structure and may reduce the risk to the operators during the process.

The work platform may be lifted to a position on a structure. The structure may be a free standing structure. The structure may be a building. The structure may be a tower. The structure may be a pylon. The structure may be a transmission tower. The structure may be a high voltage transmission tower.

The work platform may be a transmission tower work platform. The work platform may be elongate. The work platform may have a first side and a second side. The first and second sides may be the longer sides of the elongate work platform. The work platform may comprise a base and a cage attached to the base. The cage may comprise a central segment. The work platform may include a central suspension point. The central : .o suspension point may be positioned so that the work platform can be lifted in equilibrium from the central suspension point. The central suspension point may be positioned in the **..

centre of the first or second sides. **..

The lifting arm may be attached to a vehicle. The lifting arm may be extendable. The lifting arm may be a hydraulic arm.

*. **.. * * S.

* .: The access platform may be a mobile elevated work platform or MEWP. The access platform may a mobile platform known colloquially as a cherry picker'.

The access platform may be elongate. The access platform may have a first side and a second side. The first and second sides may be the longer sides of the elongate access platform. The first side may be adjacent to the releasable securing mechanism. The second side may be opposite the first side. The access platform may comprise a base and a cage attached to the base. The cage may comprises a first side adjacent to the releasable securing mechanism and a second side opposite the first side. The cage may comprise a door. The door may be positioned on the first side of the cage. The positioning of the door on the first side of the cage may allow maintenance personnel easy access to both the work platform and the structure. This may improve safety when working at height.

The releasable securing mechanism may comprise a support member which extends from the access platform. The support member may be elongate. The support member may be attached to the base of the access platform. The support member may be attached to the cage of the access platform. The support member may extend from the first side of the access platform. The support member may extend from the first side of the cage.

The lifting system may further comprise a hoist lifting arm attached to the access platform.

The lifting system may further comprise an upright housing. The upright housing may be mounted on the access platform. The hoist lifting arm may be engageable with the upright housing. The hoist lifting arm may slidingly engage with the upright housing. A hoist may be attached to the hoist lifting arm by a lifting eye.

The hoist lifting arm may be releasably removable from the access platform. The hoist s... lifting arm may be releasably removable from the upright housing. Releasably removable 5**s means that the hoist lifting arm is intended to be removed from the upright housing without 55** excessive force when the hoist lifting arm is not locked to the upright housing. 5S.

The hoist lifting arm may be used in conjunction with the hoist to lift and lower the work i...

platform or a press head. The press head may be used when pressing pylon high voltage lines.

The hoist lifting arm may be used in a first position facing outside the access platform cage when lifting or lowering the work platform. The hoist lifting arm may be used in a second position facing inside the access platform cage when lifting or lowering the press head.

The hoist lifting arm may be moved from the first position to the second position by changing its orientation within the upright housing.

The hoist lifting arm may comprises an upright section and a horizontal section. The upright section and the horizontal section may be welded together. The horizontal section may be reinforced by a strengthening beam. The strengthening beam may be welded at an angle between the upright section and the horizontal section. Preferably, the strengthening beam is welded at an angle of approximately 45 degrees to the horizontal section. This 45 degree angle provides increased strength.

The upright section of the hoist lifting arm may comprise a pin hole. The upright section of the hoist lifting arm may comprise an upper pin hole. The upright section of the hoist lifting arm may comprise a lower pin hole. The upright housing may receives the upright section of the hoist lifting arm. The upright housing may comprise an upright housing hole.

The upper pin hole may be used with a pin to lock the hoist lifting arm inside the upright housing in the first position facing away from the access platform. The pin may be placed through the upper pin hole and the upright housing hole to lock the hoist lifting arm in the *:::0 first position. * S

The lower pin hole may be used with a pin to lock the hoist lifting arm inside the upright *SS.

: housing in the second position facing towards the access platform. The pin may be placed through the lower pin hole and the upright housing hole to lock the hoist lifting arm in the second position.

S. S... * . 5

* .: A lifting eye may be used to attach a hoist to the hoist lifting arm. The lifting eye may comprise a circular section attached to a threaded bar. The lifting eye may be secured in place by a locking nut. The lifting eye may be connected to the hoist lifting arm through a lifting eye hole. The lifting eye hole may be located in the horizontal section of the hoist lifting arm.

Strengthening plates may be used to increase the strength of the lower and upper faces of the horizontal section of the hoist lifting arm around the lifting eye hole.

The lifting system may further comprise a hoist attached to the hoist lifting arm and a work platform lifting arm attached to the hoist. The work platform lifting arm may be used to raise from ground level and lower back to ground level the work platform when securing and disconnecting the work platform to and from the access platform. The work platform lifting arm may centralise with respect to the work platform from a central lifting point so the work platform can be lifted by the hoist in equilibrium. The work platform lifting arm may be adapted to lift the work platform at a central point of the work platform.

The work platform lifting arm may comprise a central section. The central section may be elongate. The central section may have a square cross section. The work platform lifting arm may comprise guide plates. The guide plates may be welded to the ends of the central section on the bottom face of the central section. The guide plates may centralise the work platform lifting arm when connecting to the underside of a top bar of the work platform.

This centralisation process may allows the work platform to be lifted in equilibrium.

When the work platform is lifted the guide plates may also provide side to side movement stabilisation. * * *

The work platform lifting arm may comprise end support plates. The end support plates may be welded to the ends of the central section on the side faces of the central section. *. f.

The end support plates may secure the work platform to the work platform lifting arm during lifting of the work platform. The end support plates may provide front to rear *25 stabilisation to avoid the work platform becoming unseated when lifted on the work ** *.*.

platform lifting arm.

A lifting eye may be used to attach a hoist to the work platform lifting arm. The lifting eye may be connected to the work platform lifting arm through a lifting eye hole in the central section. Strengthening plates may be used to increase the strength of the lower and upper faces of the central section around the lifting eye hole.

The support member may comprise a leg support.

The lifting system may further comprise a leg housing attached to the access platform. The leg support may be engageable with the leg housing.

The leg support may be insertable within the leg housing.

The leg support may be moveable between a first position and a second position. The leg support in the second position may be engaged with the leg housing and engageable with the work platform to secure the work platform to the access platform.

The lifting system may comprise at least two leg supports. The leg supports may be spaced equidistantly. The lifting system may comprise at least three leg supports.

Preferably the lifting system comprises at least four leg supports. Four leg supports provide a greater degree of stability for the work platform.

The lifting system may comprises a leg housing for each leg support. The lifting system may comprise at least two leg housings. The lifting system may comprise at least three leg housings. Preferably the lifting system comprises at least four leg housings. * * .

::.. The leg support may be releasably removable from the access platform. The leg support may be releasably removable from the leg housing. In the first position the leg support may be removed from the leg housing. Alternatively in the first position the leg support may be engaged with the leg housing. In the second position the leg support may be engaged with the leg housing. The leg support may be insertable within the leg housing.

*IS...

The leg support maybe lockable in the second position. The leg support maybe held in the second position by a fastener. The fastener may be a pin.

The leg support may provide stability for the work platform in the second position. The leg support may be mounted within the leg housing in the second position. The leg support may be locked in place by a leg support pin in the second position. The leg support pin may be spring loaded. The leg supports may be moveable to the second position without the need for an operator to go underneath the work platform. This may improve the safety of the operation.

The leg support may comprise a central section which is elongate. The central section may have a square cross section. An end support plate may be welded to one end of the central section. The end support plate may be larger than the cross section of the central section.

The end support plate may provide a shoulder which stops the work platform being able to move off the front end of the leg support when the work platform is resting on the leg support in the second position. The end support plate may position the work platform the correct distance away from the access platform to enable the attachment of a work platform clamp.

A leg support hole may be located on the upper face of the central section. A leg support hole may be located on the lower face of the central section. The leg support hole may enable the leg support to be locked in the second position within the leg housings by a leg support pin.

The leg support may be tapered at one end. The leg support may be tapered at one end to cam against the fastener when the leg support is inserted in the leg housing. *

The leg support may comprise a tapered section at the opposite end of the leg support from *SS the end support plate. The tapered section may be present on the upper or lower face of the central section. Tapered sections may be present on more than one face of the central section. The tapered section may enable the leg support to slide in to the leg housing without the operator needing to pull up on the leg support pin which will lock the leg ** *s. * *

* support in the second position. The tapered section may provide a cam surface for the leg support pin to move over and push up the leg support pin. This allows the leg support to be inserted without the operator needing to climb underneath the work platform when it is suspended in the air by the hoist. This may reduce any risk associated with the operation of the lifting system.

The lifting system may further comprise a work platform clamp attached to the access platform for securing the work platform to the access platform. The work platform clamp may further secure the work platform to the access platform. The work platform clamp may provide a rigid fixing between the access platform and the work platform to allow the work platform to be lifted safely. The work platform clamp may not project above than the work platform when in position on the work platform. This may enable the work platform to be lifted through transmission tower jumpers on the end of transmission tower arms due to the compact height of the work platform clamp.

The work platform clamp may be moveable between a first position and a second position.

In the second position the work platform clamp may be mounted in the upright housing and may be engaged with the work platform. In the first position the work platform clamp may be removed from the upright housing. The work platform clamp may be releasably removable from the access platform. The work platform clamp may be releasably removable from the upright housing.

The work platform clamp may comprises a horizontal section which is elongate. An upright section may be connected to the horizontal section. The upright section may be mountable within the upright housing. The work platform clamp may be releasably removable from the upright housing. When mounted in the upright housing, the work platform clamp may face away from the access platform. The work platform clamp may be lockable to the upright housing in the second position. The upright section may comprise a clamp pin hole. An upright housing pin may pass through the clamp pin hole and the upright housing hole to lock the work platform clamp to the upright housing. *... * S * ** 25 S...

" The work platform clamp may further comprise a lanyard attachment point. The lanyard : attachment point may be attached to the upright section. The lanyard attachment point S...

:. may be a rectangular metal plate with a hole drilled through the centre. The hole may have a diameter large enough to enable a lanyard karabiner to fit through. The lanyard * 10 attachment point may allow a lanyard to be used to attach the work platform clamp to the * :1 * access platform. With the use of a lanyard, should the work platform clamp be dropped in error when the work platform is being released in position on a structure, it would not fall to the ground. Instead, the work platform clamp would remain securely attached to the access platform via the lanyard.

The work platform clamp may further comprise a shoulder stabiliser. Preferably the work platform clamp comprises two shoulder stabilisers. The shoulder stabilizer may restrict sideways movement of the work platform when the work platform clamp is in the second position. The shoulder stabiliser may be mounted on the horizontal section of the work platform clamp. The shoulder stabiliser may comprise an L-shaped section. When in the second position the shoulder stabilizer may be located at the side of the central suspense point of the work platform. This means that the central suspense point is not restricted in any way by the shoulder stabiliser. This means the central suspense point can still be used when landing the work platform on a transmission tower arm before the work platform clamp is released from the work platform. If the work platform clamp comprises two shoulder stabilisers, the stabilisers may be positionable on either side of the central suspense point of the work platform when the work platform clamp is in the second position.

The work platform clamp may further comprise a vertical stabiliser. The work platform clamp may comprise two vertical stabilisers. The vertical stabiliser may restrict the work platform from any vertical movement when the work platform clamp is in the second position. The vertical stabiliser may be positioned at the end of the horizontal section of the work platform clamp. The vertical stabiliser may comprise a u-shaped section. The vertical stabiliser may hook over the top bar of the work platform which is nearest to the *:. access platform. This may create a firm vertical holding for the work platform between the vertical stabiliser and the leg support. ***.

** The lifting system may further comprise a press head lifting arm. The press head lifting * . arm may lift a press head by being attached to a hoist which is attached to a hoist lifting arm. The press head lifting arm may be adapted to lift the press head by the press head :. 0 handles. The press head lifting arm may lift different sizes of press head. The press head * lifting arm may comprises a horizontal section. The horizontal section may comprise an elongate metal plate. The press head lifting arm may further comprise an upright section at each end of the horizontal section. Press head handle hooks may be cut out of the upright sections. The horizontal section may have a centralised lifting eye hole to receive a lifting eye. The lifting eye hole may be centralised on the press head lifting arm to enable the press head to be lifted in equilibrium. The press head handle hooks may be oriented at a 50 to 60 degree angle approximately relative to the longitudinal direction of the upright sections to facilitate lifting of the press head handles. Preferably the press head handle hooks are at a 57 degree angle to the longitudinal direction of the upright sections.

The lifting system may further comprise a press head support. The press head support for receiving a press head may be attached to the access platform. The press head support may hold the press head in the access platform whilst the access platform is at height during the process of pressing the high voltage power lines on the transmission tower. The press head support may comprise an elongate arm. The arm may have a claw mounted at one end.

Preferably the arm has a claw mounted at each end. The claw may be a U-shaped section.

The claw may be an L-shaped section. The press head support may further comprise a pan mounted on the arm. The pan may be cylindrical. The pan may be free to rotate around a rotation shaft mounted on the arm. The pan may be lockable to the arm to prevent rotation.

The pan may have a channel in its side. The channel may allow the press head hydraulic hoses free movement to the outside of the pan. The press head support may accommodate all sizes of press head. The arm may be attached to the access platform by the claw. The claw may attach to the access platform cage. The press head support may be releasably removable from the access platform.

Viewed from a further aspect, the present invention provides a vehicle comprising a lifting system as hereinbefore defined. The lifting arm may be attached to a platform on the *S..

vehicle.

*. Viewed from a yet further aspect, the present invention provides a method of lifting a work platform to a position on a structure using a lifting system comprising an access platform * 0 and a lifting arm which comprises the following steps: a) releasably securing the work platform to the access platform; and -Il-b) lifting the access platform and work platform with the lifting arm to the position on the structure.

The structure may be a free standing structure. The structure may be a building. The structure may be a tower. The structure may be a pylon. The structure may be a transmission tower. The structure may be a high voltage transmission tower.

The method may further comprise the step of attaching the work platform to the structure.

The method may further comprise the step of releasing the work platform from the access platform.

The method may further comprise the step of lowering the access platform while leaving the work platform at the position on the structure.

The method may further comprises the step of lifting the access platform to the work platform which is attached to the structure at the position on the structure.

The method may further comprises the step of releasably securing the work platform to the access platform.

The method may further comprises the step of detaching the work platform from the structure. * * I

::. .25 The method may further comprises the step of lowering the access platform and work I...

platform with the lifting arm. **.

I

The lifting system of the method may be a lifting system as hereinbefore defined.

I..... * S S. I * I I

S IS

An embodiment of the invention will now be described in detail, and by way of example only, with reference to the accompanying drawings in which: Figure 1 is a front view of an embodiment of the lifting system of the present invention with a work platform secured to the lifting system; Figure 2 is a side view of the lifting system shown in Figure 1; Figure 3 shows the lifting system further comprising a hoist lifting arm; Figure 4 shows the hoist lifting arm; Figure 5 shows the work platform lifted by a work platform lifting arm; Figure 6 shows the work platform lifting arm; Figure 7 shows the leg supports of the lifting system in position under the work platform; Figure 8 shows a leg support; Figure 9 shows the work platform secured to the access platform by a work platform iS clamp; Figure 10 shows the work platform clamp; Figure 11 shows a press head suspended from a hoist via a press head lifting arm; Figure 12 shows the press head lifting arm; Figure 13 shows a press head support attached to the access platform; Figure 14 shows the press head support; and Figure 15 shows the access platform cage.

Referring to the drawings, Figures 1 and 2 show a lifting system 2 which comprises an r. access platform 4 and a lifting arm 6. The lifting arm 6 is attached to a vehicle 3. The :. access platform comprises a base 22 and a cage 24.

** A work platform 12 is secured to the access platform 4 via leg supports 10. The work * . platform 12 is further secured to the access platform 4 via a work platform clamp 20.

*.*...

3J Figure 3 shows the lifting system 2 of Figure 1 with the work platform clamp 20 replaced * by a hoist lifting arm 14. The work platform 12 is not secured to the lifting system 2 in this Figure. The hoist lifting arm 14 is engaged with an upright housing 26 on the access platform 4. The upright housing 26 is a hollow metal tube with a square cross section.

The hoist lifting arm 14 is releasably removable from the access platform 4 by removing the hoist lifting arm 14 from the upright housing 26. A hoist 16 is attached to the hoist lifting arm 14 by a lifting eye 28.

Figure 4 shows the hoist lifting arm 14 in more detail. The hoist lifting arm 14 is used in conjunction with the hoist 16 to lift and lower the work platform 12 and a press head 27 (see Figure 11 and description below for more details). The press head 27 is used when pressing the transmission tower high voltage lines.

The hoist lifting arm 14 is used facing outside the access platform cage 24 when lifting or lowering the work platform 12. The hoist lifting arm 14 is used facing inside the access platform cage 24 when lifting or lowering the press head 27.

The hoist lifting arm 14 comprises an upright section 38 welded to a horizontal section 40.

The horizontal section 40 is reinforced by a strengthening beam 34 welded at a 45 degree angle between the upright section 38 and the horizontal section 40. The strengthening beam 34 is used to increase the lifting capacity of the hoist lifting arm 14. The strengthening beam 34 is placed between the upright section 38 and the horizontal section 40 at a 45 degrees angle for maximum strength.

The upright section 38 of the hoist lifting arm 14 comprises an upper pin hole 30 and a lower pin hole 32. p... * * *

*..25 The upper pin hole 30 is used when the hoist lifting arm 14 is used to lift or lower the work * p..

platform 12 in to position to enable the securing of the work platform 12 to the access *I*.

platform 4. This upper pin hole 30 is used to secure the hoist lifting arm 14 when it is * placed inside the upright housing 26 in a first position facing away from the access * platform 4 (see Figure 3). A pin (not shown) is placed through the upper pin hole 30 and the upright housing hole 42 to fix the hoist lifting arm 14 in the first position to enable the * lifting or lowering of the work platform 12.

The lower pin hole 32 is used when the hoist lifting arm 14 is used in a second position when lifting or lowering the press head 27 within the access platform cage 24 (see Figure 11). This lower pin hole 32 is used to secure the hoist lifting arm 14 when it is placed inside the upright housing 26 facing towards the inside of the cage 24 in the second position. A pin (not shown) is placed through the lower pin hole 32 of the hoist lifting arm 14 and a hole 42 in the upright housing 26 to lock the hoist lifting arm 14 in the second position to enable the lifting or lowering of the press head lifting arm 80 by the hoist 16.

The lifting eye 28 is used to attach the hoist 16 to the hoist lifting arm 14. The lifting eye 28 comprises a circular section attached to a threaded bar and is secured in place by a locking nut. The lifting eye 28 is connected to the hoist lifting arm 14 through a lifting eye hole 36 drilled vertically through the horizontal section 40 of the hoist lifting arm 14.

Strengthening plates 37 are used to increase the strength of the lower and upper faces of the horizontal section 40 of the hoist lifting arm around the lifting eye hole 36.

Figures 5 and 6 show a work platform lifting arm 18 which is used to raise from ground level and lower back to ground level the work platform 12 when securing and disconnecting the work platform 12 to and from the access platform 4. When lifting the work platform 12, the work platform lifting arm 18 is located in the work platform cage in a central segment. The work platform lifting arm will then centralise the work platform 12 and lift the work platform 12 from a central lifting point on the cage so the work platform 12 will lift in equilibrium.

*: :: : Figure 6 shows that the work platform lifting arm 18 comprises a central section 44 which is elongate and has a square cross section. Guide plates 46 are welded to the ends of the central section 44 on the bottom face of the central section 44. These guide plates 46 *.

centralise the work platform lifting arm 18 when connecting to the underside of a top bar * of the work platform 12 (see Figure 5). This centralisation process allows the work * platform 12 to be lifted in equilibrium. When the work platform 12 is lifted the guide 0 plates 46 also provide side to side movement stabilisation.

End support plates 48 are welded to the ends of the central section 44 on the side faces of the central section 44. These end support plates 48 are designed to secure the work platform 12 to the work platform lifting arm 18 during lift. The end support plates provide constant front to back stabilisation to avoid the work platform 12 becoming unseated when lifted on the work platform lifting arm 18 (see Figure 5).

A lifting eye 28 is used to attach the hoist 16 to the work platform lifting arm 18. The lifting eye 28 comprises a circular section attached to a threaded bar and is secured in place by a locking nut. The lifting eye 28 is connected to the work platform lifting arm 18 through a lifting eye hole 52 drilled vertically through the central section 44.

Strengthening plates 50 are used to increase the strength of the lower and upper faces of the central section 44 around the lifting eye hole 52.

Figures 7 and 8 show the leg supports 10 which are load bearing for the weight of the work platform 12. The leg supports 10 can be moved from a first position where they are detached from the access platform 4 to a second position where the leg supports 10 are attached to the access platform 4 via the leg housings 8. Figure 7 shows the leg supports in their second position, ready to secure the work platform 12 to the access platform 4. In Figure 7, the work platform 12 is suspended from the hoist lifting arm 14 via the hoist 16 and work platform lifting arm 18 (as shown in Figure 5).

The leg supports 10 provide both side to side and front to back stability for the work platform 12. The leg supports 10 are mounted within the leg housings 8 and are each **:.. locked in place by a spring loaded leg support pin 61. The design of the leg supports 10 enables the operator to fix each leg support 10 in position in the corresponding leg housing * **.

8 without the need to go underneath the work platform 12. This is achieved by a tapered *.** section 60 of the leg support 10 camming against the leg support pin 61 (as shown in Figure 8).

**.a** * 0 Referring to Figure 8, each leg support 10 comprises a central section 54 which is elongate * and has a square cross section. An end support plate 56 is welded to one end of the central section 54. The end support plate is larger than the cross section of the central section 54 and therefore provides a shoulder 57 which stops the work platform being able to move off the front ends of the leg supports 10 when lowered on to the leg supports 10 by the hoist 16. The end support plate 56 positions the work platform 12 a predetermined distance away from the access platform 4 to enable the attachment of a work platform clamp 20 once the hoist lifting arm 14 is removed from the upright housing 26.

Leg support holes 58 are located on the upper and lower faces of the central section 54 to enable the leg support 10 to be locked in the second position within the leg housings 8.

The leg support 10 is locked in position by leg support pins 61 (see Figure 7). Each leg support 10 can slide into a leg housing 8 and the leg support pins 61 mounted in leg housing holes 59 on the upper and lower side of the leg housing 10 lock in to the leg support holes 58 on the leg support 10.

Tapered sections 60 are present at the opposite end of the leg support 10 from the end support plate 56. The tapered sections are present on the upper and lower faces of the central section 54. The tapered sections 60 are angled by 15 degrees to enable the leg section 10 to slide in to the leg housing 8 without the operator needing to pull up on the spring loaded leg support pins 61 which lock the leg support 10 in the second position.

The tapered sections 60 provide a cam surface for the leg support pins 61 and are effectively able to push up leg support pins 61 from inside as opposed to the operator having to do this manually from the outside. This allows the leg support 10 to be inserted without the operator needing to climb underneath the work platform 12 when it is suspended in the air by the hoist 16. This helps to reduce any risk associated with the operation of the lifting system. * S *S.S

Figures 9 and 10 show the work platform clamp 20 which further secures the work * * Sa platform 12 to the access platform 4. The work platform clamp 20 is designed to provide a * rigid secure fixing between the access platform 4 and the work platform 12 to allow the work platform 12 to be lifted safely. The design of the work platform clamp 20 also enables the work platform to be lifted through transmission tower jumpers on the end of transmission tower arms due to the compact height of the work platform clamp 20.

The work platform clamp 20 comprises a horizontal section 62 which is elongate and to which an upright section 64 is welded in a central position. In use, the upright section 64 is mounted within the upright housing 26 with the work platform clamp 20 facing away from the access platform cage 24. The upright section 64 comprises a clamp pin hole 66 which with the use of an upright housing pin 43 allows the work platform clamp 20 to be quickly locked into or released from the upright housing 26. When the work platform clamp 20 is placed in to the upright housing 26 facing away from the access platform cage 24 and both the shoulder stabilisers 70 and the vertical stabilisers 72 are in position in the work platform 12 (as described below) the clamp pin hole 66 will be in line with the upright housing hole 42. When both these holes 42, 66 are in line the upright housing pin 43 can then be used to secure the work platform clamp 20 to the work platform 12 and the access platform 4.

The work platform clamp 20 further comprises a lanyard attachment point 68 attached to the upright section 64. The lanyard attachment point 68 is a rectangular metal plate with a hole drilled through the centre. The hole should have a diameter large enough to enable a lanyard karabiner (not shown) to comfortably fit through. The lanyard attachment point 68 allows a lanyard (not shown) to be used to attach the work platform clamp 20 to the access platform 4. With the use of a lanyard, should the work platform clamp 20 be dropped in error when the work platform is being released in position on a transmission tower pylon, it would not fall to the ground. Instead, the work platform clamp 20 would remain securely attached to the access platform 4 via the lanyard.

The work platform clamp 20 further comprises shoulder stabilisers 70 which are used to * ** *25 restrict sideways movement of the work platform 12 once it is attached to the access platform using the work platform clamp 20. The shoulder stabilisers 70 are mounted on * . *.

the horizontal section 62 of the work platform clamp 20. When in position on the work platform 12, the shoulder stabilizers 70 are positioned either side of the central suspense point 74 of the work platform 12. This means that the central suspense point 74 is not *:..30 restricted in any way when the shoulder stabilisers 70 are in position. This means the central suspense point 74 can still be used when landing the work platform on a transmission tower arm before work platform clamp 20 is released from the work platform 12.

The work platform clamp 20 further comprises vertical stabilisers 72 which are used to restrict the work platform 12 from any vertical movement when in use and to also firmly hold the work platform 12 down on to the leg supports 10. There are two vertical stabilisers 72, one positioned at each end of the horizontal section 62 of the work platform clamp 20. The vertical stabilisers 72 are U-shaped and hook over the top bar of the work platform 12 which is nearest to the access platform 4 (see figure 9). This creates a firm vertical holding for the work platform 12 between the vertical stabilisers 72 and the leg supports 10.

Figures 11 and 12 show a press head lifting arm 80 which is designed to lift a press head 27 with the aid of a hoist 16. The press head lifting arm 80 attaches to the press head 27 via the press head handles 89 (see Figure 11). The press head lifting arm 80 allows different sizes of press head to be lifted. The press head lifting arm 80 comprises a horizontal section 82 made of an elongate metal plate with an upright section 84 welded at each end of the horizontal section 82. Press head handle hooks 88 are cut out of the upright sections 84 to allow easy attachment to the press head handles 89. The horizontal section has a centralised lifting eye hole 86 to receive a lifting eye 28 (not shown in Figure 12). The lifting eye hole 86 is centralised on the press head lifting arm 80 to enable the press head 27 to be lifted in equilibrium. The press head handle hooks 88 are formed by cuts made in to the upright sections 84. The cuts are made at a 57 degrees angle relative to * the longitudinal direction of the vertical sections and go to just past the centre point of each ::. 2' upright section 84. This allows a central lifting point for the press head handles 89. **.*

** Figures 13 and 14 show a press head support 90 which is designed to hold the press head *. 27 securely in the access platform 4 whilst the access platform is at height during the process of pressing the high voltage power lines. The press head support 90 comprises an 3'O arm 92 which is elongate and has a claw 94 mounted at each end. The press head support * further comprises a circular pan 96 which is mounted on the arm 92 and free to rotate around a rotation shaft 100.

In use, the press head 27 is lowered in to the pan 96 and released to allow it to stand free within the outer walls of the pan 96. The pan 96 rotates 360 degrees to allow the press head 27 to be rotated and align with the high voltage power lines in any situation. The rotation function can be locked in place when the press head 27 and high voltage power lines (not shown) are aligned. The pan 96 has a vertical channel 98 cut into a side wall to allow the press head 27 hydraulic hoses free movement to the outside of the pan 96. The press head support 90 can accommodate all sizes of press head 27. The arm 92 is attached to the cage of the access platform 4 by the claws 94. The press head support 90 can be placed across the access platform cage 24 at any point and is held in place by weight.

Figure 15 shows the access platform cage 24. A door 102 is positioned on a first side of the cage 24. The positioning of the door 102 allows maintenance personnel easy access to both the work platform 12 and the high voltage transmission tower arm. Having the door 102 on the first side of the cage 24 eliminates the need to climb over the top of the cage 24 when needing to access the tower arm or the work platform 12. This helps improve safety The lifting system 2 will now be described in use during the operation of moving a work platform 12 from the ground into position on a transmission tower and installing the work platform 12 on the transmission tower.

The vehicle 3 is made stable on the ground and the lifting arm 6 is retracted to provide :. maximum lifting strength. The lifting arm 6 is moved to position the access platform 4 close to the ground in front of the vehicle 3. * .**

The hoist lifting arm 14 is placed into the upright housing 26 leg positioned second in from * * the left hand side of the access platform 4 as you look at the front of the access platform 4.

The front of the access platform 4 is opposite the rear of the access platform 4 and the rear ** p*.* of the access platform is closest to the vehicle 3.

The hoist lifting arm 14 is then secured to the upright housing 26 by the upright housing pin 43 which passes through the upright housing hole 42 and the upper pin hole 30 of the hoist lifting arm 14 (see Figure 3).

With the hoist lifting arm 14 now in place, the hoist 16 can now be attached. The operator stands inside the cage 24 while attaching the hoist 16 to avoid over stretching. The upper end of the hoist 16 is attached to the lifting eye 28 on the hoist lifting arm 14 and the lower end of the hoist 16 is attached to the lifting eye 28 on the work platform lifting arm 18.

The access platform 4 is then positioned next to the work platform 12 on the ground while making the hoist lifting arm 14 central to the centre of the work platform 12.

The work platform lifting arm 18 is then raised by the hoist 16 into place on the underside centre of the top bar of the central segment of the cage of the work platform 12 (see Figure 5). Due to the design of the guide plates 46 on the work platform lifting arm 18, the work platform lifting arm 18 is centralised when lifting the underside centre of the top bar of the cage of the work platform 12 with the hoist 16 (see Figure 5). This centralisation process allows the work platform 12 to be lifted in equilibrium. When the work platform 12 is lifted the guide plates 46 also provide side to side movement stabilisation. At this point it is possible to raise the work platform 12 safely from the ground with the hoist 16.

The work platform 12 is suspended from the hoist 16 via the work platform lifting arm 18 (see Figure 5). The underneath of the work platform 12 should be higher than the leg housings 8 on the access platform 4. The operator then inserts the leg supports 10 into the leg housings 8 (see Figure 7). The operator does not need to go underneath the work platform 12 to complete this process. Each of the four leg supports 10 will simply slide into each of the leg housings 8. Each leg support 10 should be pushed far enough in to each leg housing 8 to allow the tapered sections 60 of each leg support to cam up each leg * support pin 61 and then allow each leg support pin to lock into the respective leg support hole 58.

*. S... :. 30

* Once the operator is satisfied the leg supports 10 are locked in the leg housings 8 by the leg support pins 61 (see Figure 7), the work platform 12 is then lowered by the hoist 16 on to the leg supports 10. Once this is done the work platform lifting arm 18 can be removed from the hoist 16. The hoist 16 can also be removed from the hoist lifting arm 14 and the hoist lifting arm 14 can be removed from the upright housing 26 (see Figure 1).

Now that the work platform 12 is secure on the leg supports 10, the work platform clamp can be placed in position. The work platform clamp 20 is inserted in to the upright housing 26 where it will clamp on to the top centre section of the work platform 12 via the shoulder stabilisers 70 and vertical stabilisers 72 (see Figure 9). Once in position, an upright housing pin 43 is inserted through the upright housing hole 42 and the clamp pin hole 66 to lock the work platform clamp 20 in position. The work platform 12 is now unable to move in any direction. A lanyard (not shown) is attached to the work platform clamp 20 via the lanyard attachment point 68. The lanyard is also attached to the access platform 4. The lanyard prevents the work platform clamp 20 from falling to the ground if it is dropped at height. Instead, the work platform clamp 20 would remain securely attached to the access platform 4 via the lanyard.

With the work platform 12 secure on the access platform 4, the lifting arm 6 can now be extended to lift the work platform 12 and the access platform 4 up into position on the transmission tower.

The work platform 12 should be lifted up to attachment straps attached to the transmission tower (not shown). The work platform 12 should then be accurately positioned to allow the straps to just reach the attachment points on the work platform 12. The operator should r. then attach the straps from the transmission tower to the work platform 12. With the work platform attached to the transmission tower via the straps, the work platform 12 should then be stabilized from ground level using tension wires from each end of the work *. *.

: platform 12 travelling down to concrete blocks on the ground (not shown).

S

The work platform 12 can now be released from the work platform clamp 20. The upright S. .SS * 0 housing pin is removed from the work platform clamp 20 and then the work platform clamp 20 is totally removed from the work platform and placed in the access platform 4.

At this point the work platform 12 is only resting on the leg supports 10 and attached to the transmission tower via the straps.

The operator now lowers the access platform 4 down vertically which transfers the work platform 12 weight from the leg supports 10 to the straps attached to the transmission tower arm. The work platform 12 is now suspended from the transmission tower arm and the access platform 4 is free to move away from the tower. Once the access platform 4 has returned to ground level the leg supports 10 can be easily removed by simply releasing the leg support pins 61 and removing the leg supports 10 one by one. The access platform 4 can then be used to lift both tower maintenance personnel and tools up to the work platform 12 on the transmission tower arm.

If a press head 27 is required during the maintenance work on the transmission tower, the press head 27 can be lifted by the access platform 4 using the press head support 90. The press head 27 is lifted into the pan 96 of the press head support 90 using a hoist 16 on the hoist lifting arm 14 in the second position facing into the access platform 4 (see Figures 11 and 13). The press head lifting arm 80 is attached to the hoist 16 to lift the press head 27 (see Figure 11). Once the press head 27 is located in the pan 96, the access platform 4 can be elevated to locate the press head 27 in the correct position on the transmission tower to press the high voltage power lines (not shown).

Once maintenance on the transmission tower is complete, the work platform 12 can be retrieved from its position on the transmission tower using the lifting system 2. This is essentially the same process as described above for placing the work platform 12 on the ** ,25 transmission tower but each stage is completed generally in reverse order. Note that the leg supports 10 are attached to the access platform 4 before the access platform 4 ascends . up to the transmission tower to retrieve the work platform 12.

S. S.** * . * * S **

Claims

CLAIMS: 1. A lifting system for lifting a work platform comprising: an access platform; a lifting arm attached to the access platform for lifting the access platform; and a releasable securing mechanism attached to the access platform; wherein the releasable securing mechanism is engageable with a work platform to secure the work platform to the access platform and allow the work platform to be lifted with the access platform by the lifting arm.
2. A lifting system as claimed in claim 1 wherein the releasable securing mechanism comprises a support member which extends from the access platform.
3. A lifting system as claimed in claim 1 or 2 which further comprises a hoist lifting arm attachable to the access platform.
4. A lifting system as claimed in claim 3 wherein the hoist lifting arm is releasably removable from the access platform.
5. A lifting system as claimed in claim 3 or 4 which further comprises: a hoist attached to the hoist lifting arm; and a work platform lifting arm attached to the hoist. * I * ** **::::.25
6. A lifting system as claimed in claim 5 wherein the work platform lifting arm is adapted to lift a work platform at a central point of the work platform. * I..

I I...
7. A lifting system as claimed in any of claims Ito 6 which further comprises a * work platform clamp attachable to the access platform for securing the work platform to I.....the access platform.
8. A lifting system as claimed in claim 7 where the work platform clamp is releasably removable from the access platform.
9. A lifting system as claimed in claim 3 or 4 which further comprises: a hoist attached to the hoist lifting arm; and a press head lifting arm attached to the hoist.
10. A lifting system as claimed in claim 9 wherein the press head lifting arm is adapted to lift a press head by the press head handles.
11. A lifting system as claimed in any preceding claim which further comprises a press head support for receiving a press head, the press head support being attachable to the access platform.
12. A lifting system as claimed in claim 11 where the press head support is releasably removable from the access platform.
13. A lifting system as claimed in any of claims 2 to 12 wherein the support member comprises a leg support.
14. A lifting system as claimed in claim 13 wherein the lifting system further comprises a leg housing attached to the access platform and wherein the leg support is engageable with the leg housing. S.. * * S

*::::
15. A lifting system as claimed in claim 14 wherein the leg support is insertable within the leg housing. **SS
16. A lifting system as claimed in claim 14 wherein the leg support is moveable between a first position and a second position and wherein the leg support in the second *.* * 0 position is engaged with the leg housing and engageable with the work platform to secure the work platform to the access platform.
17. A lifting system as claimed in claim 16 wherein the leg support is releasably removable from the leg housing.
18. A lifting system as claimed in claim 16 wherein the first position of the leg support is removed from the leg housing.
19. A lifting system as claimed in claim 16 wherein the leg support is held in the second position by a fastener.
20. A lifting system as claimed in claim 19 wherein the fastener is a pin
21. A lifting system as claimed in claim 19 wherein the leg support is tapered at one end to cam against the fastener when the leg support is inserted in the leg housing.
22. A lifting system as claimed in claim 13 which comprises at least two leg supports.
23. A lifting system as claimed in any preceding claim wherein the access platform further comprises: a base; and a cage attached to the base; wherein the cage has a first side adjacent the releasable securing mechanism and wherein the cage comprises a door in the first side. *.ea * * * ** .*,25
24. A vehicle comprising a lifting system as claimed in any preceding claim. P*1** * **
25. A method of lifting a work platform to a position on a structure using a lifting system comprising an access platform and a lifting arm which comprises the following * steps: **.*** a) releasably securing the work platform to the access platform; and b) lifting the access platform and work platform with the lifting arm to the position on the structure.
26. A method as claimed in claim 25 which further comprises the step of attaching the
27. A method as claimed in claim 26 which further comprises the step of releasing the work platfonn from the access platform.
28. A method as claimed in claims 27 which further comprises the step of lowering the access platform while leaving the work platform at the position on the structure.
29. A method as claimed in claim 28 which further comprises the steps of: a) lifting the access platform to the work platform attached to the structure at the position on the structure; b) releasably securing the work platform to the access platform; c) detaching the work platform from the structure; and d) lowering the access platform and work platform with the lifting arm.
30. A method as claimed in any of claims 25 to 29 wherein the lifting system is a lifting system as claimed in any of claims 1 to 23. I... * * S ** S * *0* * S * .5 *SSSS S...S *5*SS*5S*SS * SS * SS S *-