AU2013100816B4

AU2013100816B4 - Improvements relating to the lifting of gridmesh

Info

Publication number: AU2013100816B4
Application number: AU2013100816A
Authority: AU
Inventors: Paul Hibbert
Original assignee: MESHLIFT Pty Ltd
Current assignee: MESHLIFT Pty Ltd
Priority date: 2013-04-23
Filing date: 2013-06-11
Publication date: 2014-04-17
Anticipated expiration: 2021-06-11
Also published as: AU2013100816A4; WO2014174377A2; AU2013101149A4; AU2013101149B4; WO2014174377A3; AU2014256843A1

Abstract

In one preferred form there is provided a lifting device 600. The lifting device 600 comprises an upper portion 602 including a shank 610 and a lower portion 604 comprising a number or foot portions 606, 608 providing a foot member 612. The two foot portions 606, 60-8 extend in opposite direction transversely from the shank 610 to provide the foot member 612. The foot member 612 is able to be inserted through a grid opening 614 of a sheet of gridmesh 605 between the bars of the gridmesh 605, when the foot member is rotated to a first orientation. The foot member 612 is able to be rotated to a second orientation in which the foot member 6.12 is unable to be withdrawn from the grid opening 614 through which the foot member 612 was inserted due to the or each foot portion 606, 608 bearing against the gridmesh 605.

Description

1 IMPROVEMENTS RELATING TO THE LIFTING OF GRIDMESH FIELD OF THE INVENTION In embodiments, the invention concerns the lifting of grid mesh panels at a building or industrial site. BACKGROUND To THE INVENTION Gridmesh panels often need to be lifted into position by a crane on a building or industrial site such as an offshore platform for example. Gridmesh is the type of rigid open grid panels commonly used for the flooring work platforms and walkways in exposed areas of industrial sites. There are a variety of configurations. Most gridmesh is of mild steel construction hot dip galvanized to protect it from corrosion, but other materials such as stainless steel, in food handling operations, and plastics are also used. In some configurations each panel is made of steel bars and consists of a perimeter frame surrounding a first array of flat bars parallel to and spaced from each other with a gap of about 2cm to 3cm between adjacent bars, plus a second array of bars aligned transversely to the first array and welded to those first bars. The bars in the second array may be round or flat. The second array is commonly welded directly on the top surface of the first array, but some versions have the second array recessed wholly or partly into the first array. Usually the spacing between the bars in the second array is substantially greater than the spacing between the bars in the second array so the apertures through the panels take the form of elongated slots. Other configurations of gridmesh are panels of integrally moulded plastics material. These are sometimes used in offshore marine situations and other corrosive environments. In these configurations the first and second arrays are of the same size and spacing so the apertures through the panels are square. Further configurations of gridmesh are formed as expanded metal mesh where sheet metal is first slit discontinuously and then stretched to open the slits out into apertures. Again the apertures are not very large.

2 The lifting of such panels by crane is often awkward because the bars in the grid are spaced too close together for a conventional crane hook to slide between them. Timesaving but unsafe practices are sometimes adopted which can allow the panels to sometimes accidentally slide out from a sling. Usually however a shackle and/or sling arrangement needs to be threaded through the apertures and the crane hook engaged with the shackle or sling. This can be awkward to engage and disengage. It would be preferred for gridmesh panels to be lifted with their major plane in a generally horizontal alignment so the panel did not tilt or swing during the lifting operation and to facilitate easy stacking/positioning of the panels when they are being unloaded from the crane. But when gridmesh panels are lifted by the methods described above, it is difficult to get them to lift in a neat horizontal manner. An aim of the present invention is to provide a method and apparatus which overcome or at least alleviate these difficulties, or at least provide the public with a useful choice. SUMMARY OF THE INVENTION According to a first aspect of preferred embodiments herein described there is provided a method of lifting a panel of a walkway gridmesh on a building site, said gridmesh comprising a plurality of interlinked bars with apertures between the bars, and said method comprising: inserting a foot of a lifting device downwards between a pair of adjacent said bars, with the lifting device in a first orientation; rotating the lifting device to a second orientation and engaging said foot with a lower edge of at least one of said pair of bars; and lifting the panel by means of the lifting device so engaged; wherein: said lifting device comprises an upper portion comprising a shank; and said foot of the lifting device comprises two foot portions extending in opposite directions from the shank and separated from each other and which engage the panel beneath the bars. Preferably said gridmesh comprises metal bars welded together to form a rectilinear grid having: a first array of said bars parallel to and spaced from each other, and a second array of said bars parallel to and spaced from each other, and aligned transversely to the bars in said first array.

3 Preferably: said lifting device comprises a shank extending between said ring and said foot and extending between said pair of bars, said foot portions extend in opposite directions from said shank, and said lifting device is rotated after insertion between said pair of bars, such that said shank extends between said pair of bars, and said engagement of the foot portions with the panel is such that each said foot portion engages a different one of said pair of bars. Preferably a flange extends from said shank immediately below said eye. Alternatively: said lifting device comprises a pair of spaced apart legs which extend down between said pair of bars; each said leg has a respective foot portion extending laterally therefrom; and each said foot portion engages beneath the same one of said pair of bars. Preferably said lifting device has a bifurcated member which engages the panel astride one of the bars in said second array. Preferably said foot portions include recesses on their upper edges into which said lower edge of said at least one bar is located. According to another aspect of preferred embodiments herein described there is provided a lifting device for lifting gridmesh having a number of interlinked bars, the device comprising an upper portion and a lower portion; the upper portion including a shank; the lower portion comprising two foot portions providing a foot member; the two foot portions extending in opposite directions transversely from the shank to provide the foot member; the foot member being able to be inserted through a grid opening of a sheet of gridmesh between the bars of the gridmesh, when the foot member is rotated to a first orientation, and then be rotated to a second orientation in which the foot member is unable to be withdrawn from the grid opening through which the foot member was inserted due to the two foot portions bearing against the gridmesh. Preferably a ring structure is provided at a first end of the shank, the ring structure able to be lifted by a crane; the foot portions being provided at an opposite end of the shank to the ring structure for engaging two adjacent bars of the gridmesh. Preferably the foot portions include elements adapted to engage further grid openings of the gridmesh when in the second orientation, the further grid openings engaged by the 4 elements being located in the vicinity of the grid opening through which the foot member is able to be inserted. Preferably the elements are provided by a regular spacing of recesses in the upper edges of the foot member. Preferably the lifting device includes a safety arrangement for securing the elements in position and preventing them from being removed from the further openings. Preferably the lifting device includes a safety arrangement provided in the form of a retraining pin able to secure the elements in position and prevent them from being removed from the further openings According to another aspect of preferred embodiments herein described there is provided a lifting device comprising a shank member having a lifting portion and an anchor portion, the anchor portion being able to be inserted through a first grid opening of a sheet of gridmesh, when in a first orientation; the anchor portion comprising at least two elements able engage further grid openings spaced apart from the first grid opening when the anchor portion is rotated to a second orientation, once inserted through the first opening, the engagement provide by the at least two elements with the further openings able to prevent rotation of the anchor portion to the first orientation during lifting. Preferably the two elements comprise two support members that extend transversely, in opposite directions, from the lifting portion, the support members having a number of recesses between upper areas, the upper areas being shaped to be received in the further openings. Preferably each support member includes the recesses as a pair of notches, each pair of notches for engaging two bars of a gridmesh panel when the anchor portion is positioned for lifting is in the second orientation underneath the gridmesh panel. Preferably rotating the anchor portion from the first position by 90 degrees in the general plane of the gridmesh disposes the anchor portion in the second position. Preferably the lifting device includes a safety arrangement for securing the at least two elements in position and preventing them from being removed from the further openings 5 Preferably the lifting device includes a safety arrangement provided in the form of a retraining pin able to secure the at least two elements in position and prevent them from being removed from the further openings. BRIEF DESCRIPTION OF DRAWINGS In order that the invention may be more fully understood there will now be described, by way of example only, preferred embodiments and other elements of the invention with reference to the accompanying drawings where: Figure 1 shows a lifting device according to a first embodiment of the invention; Figure 2 shows part of the lifting device illustrated in Figure 1 when being used to lift a panel of a first configuration of gridmesh, with part of the gridmesh shown in phantom; Figure 3 is a downwards view showing the way in which the lifting device in Figure 1 is hooked onto a second configuration of gridmesh panel; Figure 4 is a view of a lifting device according to a second embodiment of the invention; Figure 5 is a central cross section view along the length of a lifting device according to a third embodiment of the invention; Figure 6 is a side view of a lifting device according to a fourth embodiment of the invention; Figure 7 is a front view of the lifting device in Figure 6 shown when lifting a third configuration of gridmesh panel; Figure 8 is a side view of a lifting device according to a fifth embodiment of the invention when lifting a gridmesh panel of the first configuration; Figure 9 is a front view of the device in Figure 8; and Figure 10 is a side view of a lifting device according to a sixth embodiment of the invention when lifting a gridmesh panel of the first configuration; Figure 11 is a front view of the device in Figure 10; and 6 Figures 12a and 12b shows a lifting device according to another embodiment of the invention. DETAILED DESCRIPTION OF THE EMBODIMENTS It is to be appreciated that each of the embodiments is specifically described and that the present invention is not to be construed as being limited to any specific feature or element of any one of the embodiments. Neither is the present invention to be construed as being limited to any feature of a number of the embodiments or variations described in relation to the embodiments. The lifting device 10, according to a first preferred embodiment is shown in Figure 1, and partly in Figure 2, is made entirely of steel. It comprises an upper portion 12 including a circular eye or ring 14, a lower portion 16 including a foot 18, and an intermediate portion 19 including a circular shaft 20 carrying a thread 22 on its lower portion 21 but having a smooth surfaced, unthreaded upper portion 28. The shaft 20 has captive upon it a disc shaped locking member 24 having a threaded central bore 26 (not visible in Figure 1) through which the shaft 20 passes and a knurled rim 25. The disc 24 is free to slide up and down on the unthreaded upper portion 28 but its threaded bore 26 mates with the thread 22. The diameter of the unthreaded upper portion 28 of the shaft 20 is a little less than the root diameter of the thread 22 so the disc 24 is free to spin on the unthreaded upper portion 28 of the shaft. The foot 18 is formed from flat metal plate aligned vertically and is securely fastened to the lower portion 21 of the shaft. The ring 14 is securely fastened to the upper portion 28 of the shaft 20, so the disc 24 is held captive on the shaft. In one method of making the device 10, the eye 14, shaft 20 and foot 18 are manufactured separately and then welded together while incorporating the disc 24 captive on the shaft. Alternatively the shaft and eye can be formed integrally as a single forging. Two notches 30 and 32 are recessed into the top edge 34 of the foot 18. The width and spacing of the notches 30 and 32 are such that the main bars 36 of the grid 38 are aligned 7 generally centrally through the notches when in engaged with the lifting device 10 as indicated in Figure 2. Only a small section of the gridmesh panel 38 is shown in Figure 2. The panel 38 comprises a rectilinear grid formed by a first array of main bars 36 laid parallel to each other and a second array of secondary bars 37 welded to the top edges 44 of the main bars and at right angles to the main bars. The secondary bars 37 stand proud of the top edges 44 and provide skid resistance to foot traffic as well as lateral support to the main bars 36. The panel 38 also has a peripheral rectangular frame 39 (shown in Figure 3) of bars the same as the main bars 36. The device 10 is considered to provide a lifting device 10 comprising an upper portion 12 able to be lifted by a crane and a lower portion 16 comprising a number or foot portions providing a foot member 18. The foot member 18 is able be inserted through a grid opening of a sheet of gridmesh between the bars of the gridmesh with the foot member being in a first orientation. The foot member 18 is then rotated to a second orientation as described in which the foot member 18 is unable to be withdrawn from the grid opening through which the foot member was inserted due to the foot member 18 bearing against the gridmesh. Figure 3 illustrates a pair of lifting devices 10a and l0b the same as device 10 being installed ready to lift the gridmesh panel 40. For clarity the devices 10a and l0b have been sectioned below the disc 24. Whereas the gridmesh panel 38 shown in Figure 2 has the bars in the secondary array 10 formed from round section steel and welded across the top edges of the main bars, the secondary bars 42 in Figure 3 have the same cross section as that of the main bars 36 and are welded between the main bars 36. To install the lifting device 10 ready for lifting the gridmesh panel 40, the foot 18 is slipped between a central pair of main bars 36 to be in the position shown for the device 10a in Figure 3. The disc 24 is at this stage on the unthreaded upper portion 28 of the shaft. The lifting device is then twisted through 900 as indicated by the arrows marked A and lifted to engage the two adjacent bars 36 with the notches 30 and 32. The disc 24 is then spun by hand to engage with the thread 22 such that the disc runs down the shaft 20 until it bears 8 lightly upon the top edges 44 of the bars 36 and thus acts as a locking member to prevent the bars 36 from coming out of the notches 30 and 32. The lifting device 10b is shown in that position in Figure 3. The knurled rim 25 on the disc provides secure finger grip when wet. The diameter of the disc 24 is sufficient for the disc to extend beyond the closest bar 36 on each side. The eye/ring 14 is engaged with a shackle, or directly with a crane hook, to lift the panel. A pair of lifting devices 10 are preferably used in conjunction, joined by a chain with a central ring. Four devices 10 may alternatively be linked by four respective chains to a central ring for a more stable quad lift. In a variation of the device shown in Figure 1, the ring 14 is turned at 900 to the foot 18. The lifting device 110 shown in Figure 4 has many similarities with device 10 in Figure 1. It has a ring 114 in its upper portion 112 and a transversely extending foot 118 in its lower portion 116. However the foot 118 in device 110 has a pair of notches 130, 131 and 132, 133 let into the top edge 134 of the foot on either side of the central portion 120 so that when lifting a panel of gridmesh, the foot engages four main bars of the gridmesh panel. The device 110 has no thread on its shaft 120, and no disc-shaped locking member, but does have a pair of latching arms 127 that each 10 pivot about a pin 128. The arms 127 tilt upwards individually to allow the device to move into position but the arms 127 then drop down into a latched position to prevent the main bars of the panel from coming out of the notches 130-133. The lifting device 210 illustrated in Figure 5 in cross section has a ring 214 and flange 223 in its upper portion although the flange is significantly smaller in diameter than that of the embodiment in Figure 4. The lower portion of the shaft 220 is bent by about 30' transverse to the plane of the foot 218. This variation allows the transversely extending foot 218 of the device 210 to be aligned generally vertically so that the notches therein better engage the bars of the gridmesh panel even though the upper portion of the shaft 220 is aligned at 300 to the vertical because both devices 210 used for lifting the panel are suspended by chains from a single crane hook with the two arms of the chain subtending an angle of about 600.

9 The lifting device 310 shown in Figures 6 and 7 engages the main bars 336 in a different manner to the embodiments described above. The lifting device 310 has a ring 314 in its upper portion 312, an intermediate portion 319 and a lower portion 316. The intermediate portion 319 comprises a laterally extending body portion 315, and a pair of downwardly extending legs 317 each having a transversely protruding foot 318 at its lower end. Each foot 318 has downwardly extending groove 330 and 332 let into its upper face. The device 310 sits astride a secondary bar 337 in the gridmesh panel 338 while each of the legs 317 extends down between a common pair of main bars 336 and the bottom edge of one of the main bars engages into the grooves 330 and 332. A small flat plate 346 is rotationally pivoted from a pin 348 on the main body 315 such that it forms a safety catch. The plate carries a notch 350 in its lower edge and the notch engages with the secondary bar 337 which the device 301 sits astride. The lifting device 301 does not need to be rotated to engage the lower edges of the bars in the gridmesh panel but instead a simple sideways movement is all that is required for the engagement. The lifting device 410 shown in Figures 8 and 9 has an upper portion 412, an intermediate portion 419 and a lower portion 416, and engages the gridmesh in a similar manner to the device 310 shown in Figures 6 and 7. The intermediate portion 419 comprises a laterally extending body portion 415, and a pair of downwardly extending legs 417. The body 415 and legs 417 sit astride a secondary bar 37 in the gridmesh panel 38 while each of the legs 417 extends down between a common pair of main bars. At the lower portion 416, each leg 417 has a transversely protruding foot 418 at its lower end. Each foot 418 has an upwardly extending toe portion 452 which forms a rectangular slot 454 between the leg 417 and toe 452. A main bar 36 of a gridmesh panel fits loosely into the slot 454 whereupon the latch arm 456 of a Townley type spring latch mechanism 457 mounted on respective legs 417 snaps outwards to retain the main bar 36 in the slot 454. A secondary bar 37 of the gridmesh extends through the arch 462 between the legs 417.

10 The square ring 414 in the upper portion 412 is connected to the intermediate portion 419 by a 3600 swivel mechanism 458. In a variation of the above described lifting device 410, a Townley latch is provided on only one of the two legs 417. The lifting device 510 shown in Figures 10 and 11 is similar in most respects to the lifting device 410 shown in Figures 8 and 9. However in device 510, each Townley latch 457 is replaced by a pin 560 which passes through aligned holes 565 and 564 in each leg 517 and toe 552 respectively. The arch 562 formed between the legs 517 is a little lower than that in device 410 and is also more pointed. In a variation of the above described lifting device 510, a retaining pin 560 is 10 provided in only one of the two legs 517. Referring to Figures 12a and 12b there is shown a lifting device 600 according to a further preferred embodiment of the present invention. The lifting device 600 comprises an upper portion 602 able to be lifted by a crane and a lower portion 604 able to support gridmesh 6-05. (see Figure 12b). In operation at least four lifting devices 6-00 are attached to the gridmesh 605 in a four point configuration and are lifted using tethers. Referring to Figure 12a, the lower portion 604 comprises a first foot portion 606 and a second foot portion 608. The first foot portion 606 and the second foot portion 608 extend either side of a shaft 610 and form a foot member 612. The foot member 612 is able to be inserted through a grid opening 614 of the sheet of gridmesh 605. As shown in Figure 12b the openings of the gridmesh 605 are of an elongate substantially rectangular shape and regularly space apart bars 616 of the gridmesh 605. The opening of the gridmesh 605 are provided in grid configuration. In order to insert the foot member 6.12 through the grid opening 614, the foot member 6.12 is rotated to a first orientation aligned with the length 618 of the grid opening 614. Once received through the grid opening 614 the foot member 612 is rotated 90 degrees to a second orientation extending across the grid opening 614. In this position beneath the gridmesh 605, in the second orientation, the foot member 612 is unable to be withdrawn 11 from the grid opening 614 through which the foot member 612 was inserted due to the two foot portions 606, 608 bearing against the gridmesh 605. In the industrial walkway construction, gridmesh such as gridmesh 605 is commonly used to provide walkways. The applicant considers that the lifting device 600 provides an advantageous manner of lifting gridmesh of this type into position. Referring to Figure 12a, the upper portion 602 includes a ring structure 620 at a first end 622 of the shank 610. The ring structure 620 is provided for being lifted by a crane. As shown the foot portions 606. 608 extend in opposite directions transversely from the shank 602 at an opposite end 624. Each of the two foot portions 606, 608 include projecting elements 626 adapted to engage further grid openings 628 of the gridmesh 605 when in the second orientation. The further grid openings 628 engaged by the projecting elements 626 are located in the vicinity of the grid opening 614. More particularly, the further grid openings 628 are transversely positioned either side of the grid opening 614 through which the foot member 612 is inserted. As shown in Figure 12a the projecting elements 626 are provided by a regular spacing of notches 630 in the upper edges 632 of the two foot portions 606, 608. Notably the lifting device 10 includes a safety arrangement 634 for securing the projecting elements 626 in position preventing them from being removed from the further openings 628. The safety arrangement 634 is provided in the form of a retraining pin 636 and a passageway 638. The passageway 638 extends through the projecting elements 626 to allow the retaining pin to be received therethrough with the gridmesh 605. secured in the notches 630 between the elements 626. Advantageously in this embodiment the lifting device 600 is able to be used to lift one or two sheets of gridmesh 605 at a time. For this purpose there are provided a series 640 of passages, the passages comprising passage 638 and a passage 642 there below. The retaining pin 636 is secured in the passage 638 when lifting two sheets of gridmesh and is 12 secured in passage 648 when lifting one sheet of gridmesh. A pin 644 is provided for extending through an end 646 of the pin 644. It would be apparent that the lifting device 600 provides a lower anchor portion that is able to be inserted through the grid opening 614, when in the first orientation (aligned in the elongate direction). The elements 626 of the anchor portion engage further grid openings 628 spaced apart from the first grid opening 614 when the anchor portion is rotated to the second orientation, after being inserted through the opening 614. The engagement with the further openings 628 prevents rotation of the anchor portion to the first orientation during lifting. The elements 626 are provided as part of a foot member 6.12 that extends transversely to the shank 610. The foot member 612 has a number of recesses that define areas shaped to be received in the further openings 628. The areas are sequentially spaced apart by a number of recesses/notches 630. The recesses are provided in the form of pairs of notches for engaging corresponding bars of the gridmesh. Each foot portion 606, 608. provides two notches. After insertion the anchor portion is rotated from the first position by 90 degrees in the general plane of the gridmesh 605 to dispose the anchor portion in the second orientation. Advantageously the projecting elements 626 are able to accommodate multiple mesh panels stacked on top of the other. A series of vertically extending passages is provided as part of a safety mechanism for securing a stack of gridmesh. Whilst the above description includes the preferred embodiments of the invention, it is to be understood that many variations, alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the essential features or the spirit or ambit of the invention. It will be also understood that where the word "comprise", and variations such as "comprises" and "comprising", are used in this specification, unless the context requires 13 otherwise such use is intended to imply the inclusion of a stated feature or features but is not to be taken as excluding the presence of other feature or features. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that such prior art forms part of the common general knowledge. There is no intention to limit the present invention to the specific embodiments shown in the drawings. The present invention is to be construed beneficially to the applicant and the invention given its full scope.

Claims

1. A lifting device for lifting gridmesh having a number of interlinked bars, the device comprising an upper portion and a lower portion; the upper portion including a shank; the lower portion comprising two foot portions providing a foot member; the two foot portions extending in opposite directions transversely from the shank to provide the foot member; the foot member being able to be inserted through a grid opening of a sheet of gridmesh between the bars of the gridmesh, when the foot member is rotated to a first orientation, and then be rotated to a second orientation in which the foot member is unable to be withdrawn from the grid opening through which the foot member was inserted due to the two foot portions bearing against the gridmesh.

2. A lifting device as claimed in claim 1 wherein a ring structure is provided at a first end of the shank, the ring structure able to be lifted by a crane; the foot portions being provided at an opposite end of the shank to the ring structure for engaging two adjacent bars of the gridmesh.

3. A lifting device as claimed in claim 1 or 2 wherein the foot portions include elements adapted to engage further grid openings of the gridmesh when in the second orientation, the further grid openings engaged by the elements being located in the vicinity of the grid opening through which the foot member is able to be inserted.

4. A lifting device comprising a shank member having a lifting portion and an anchor portion, the anchor portion being able to be inserted through a first grid opening of a sheet of gridmesh, when in a first orientation; the anchor portion comprising at least two elements able engage further grid openings spaced apart from the first grid opening when the anchor portion is rotated to a second orientation, once inserted through the first opening, the engagement provide by the at least two elements with the further openings 15 able to prevent rotation of the anchor portion to the first orientation during lifting.

5. A method of lifting a panel of a walkway gridmesh on a building site, said gridmesh comprising a plurality of interlinked bars with apertures between the bars, and said method comprising: inserting a foot of a lifting device downwards between a pair of adjacent said bars, with the lifting device in a first orientation; rotating the lifting device to a second orientation and engaging said foot with a lower edge of at least one of said pair of bars; and lifting the panel by means of the lifting device so engaged; wherein: said lifting device comprises an upper portion comprising a shank; and said foot of the lifting device comprises two foot portions extending in opposite directions from the shank and separated from each other and which engage the panel beneath the bars.