WO1996004198A1

WO1996004198A1 - Beam sling

Info

Publication number: WO1996004198A1
Application number: PCT/GB1995/001826
Authority: WO
Inventors: Robin Dawson
Original assignee: Dawson Construction Plant Limited
Priority date: 1994-08-05
Filing date: 1995-08-02
Publication date: 1996-02-15
Also published as: GB9415856D0; AU3182995A; EP0728118A1

Abstract

The application describes a beam sling for lifting structural members such as beams, the sling comprising a lifting strap (1) and a main body (2) through which the lifting strap can pass in order to form a loop, with one end of the strap locating in a slot (5) in the body member. The said one end of the strap (1) has an aperture (6) and the main body (2) includes a pin (7) which can move between a first position bridging the slot (5) and a second position free of the slot, whereby the apertured end of the strap can be held in the slot (5) by the pin (7). The pin (7) can be moved from the first to the second position by means of a rotational movement and an elongate member (9, 10) is provided to generate the rotational movement from a remote position.

Description

BEAM SLING

The present invention relates to a beam sling for lifting beams and other structural members used in the construction industry.

The erection of steel framed buildings has traditionally been a hazardous operation. This arises from the need to lift beams about their point of balance so that they can be lifted to a considerable height, tilted to pass between column flanges, then installed in the required permanent horizontal position, and finally released from the crane hook. This final operation of releasing a secure fixing conventionally requires a person progressing along the beam, often tens of metres above the ground level, sometimes hundreds of metres, to disconnect the fixing and then return along the beam to a safe position. During this operation there is generally no safety net, no safety fixing and no guard rails.

The purpose of this invention is to provide a reliable lifting device which can be attached to a beam or similar component but which can be disconnected safely.

Accordingly, the invention provides a beam sling for lifting structural members such as beams, the sling comprising a lifting strap and a body member through which the lifting strap can pass in order to form a loop, with one end of the strap locating in a slot in the body member, wherein the said one end of the strap has an aperture and wherein the body member includes a pin which can move between a first position bridging the slot and a second position free of the slot, whereby the apertured end of the strap can be held in the slot by the pin, and wherein the pin can be moved from the first to the second position by means of a rotational movement and wherein an elongate member is provided to generate the rotational movement from a remote position.

The advantage of the invention is that, using the elongate member, the loop of the sling can be broken and the beam released from a remote, safe location.

There will generally be a threaded connection between the pin and the body member so that relative rotation between the part of the body member and the pin will move the pin along its axis. Preferably, the rotational movement is provided through a ratchet wheel which can be rotated by the elongate member in several individual stages to move the pin to its second position.

Advantageously, the main body comprises a roller inside of which the strap passes and the roller includes a locking mechanism, so that the strap can pass through the main body to tighten the loop as more weight is carried but the roller is locked to prevent opposite movement of the strap (which would loosen the loop) . Thus, slipping of the beam during any tilting operations is prevented.

The beams or components to be lifted may be of a variety of shapes and sizes, e.g. H, I, square, rectangular or round cross-sections. The beam sling may use a chain or strap of steel or polymer fibres, or a combination of these materials, as in normal lifting operations.

The present invention also provides a protective member for the lifting member, the protective member comprising an elongate band of flexible (e.g. elastomeric) material, the band having on one surface (that surface which in use contacts the strutural member to be lifted) a series of spaced ribs which extend across a substantial portion of the width of the band.

The invention further provides a lifting strap for structural members, the strap having on its inside face a protective member as just described.

The advantage of the protective member is that the ribs will tend to close together at the edges of the structural member being lifted and thus provided the maximum protection at the point where the lifting member is most likely to be damaged.

Preferably, the ribs have a rounded outer end and preferably the gap between adjacent ribs is substantially equal to or less than their height.

A preferred embodiment of the invention is described in more detail below, by example only, with reference to the accompanying drawings, wherein:

Fig. 1 is a perspective view of a beam sling in accordance with the invention;

Fig. 2 is an elevational view of the beam sling of Fig. 1, looking along the beam;

Fig. 3a is a plan view of an apertured plate to be fitted at the end of the lifting strap and Fig. 3b is a side view thereof; and

Fig. 4 is a side view of a part of the main body of the beam sling.

The beam sling shown in Figs. 1 and 2 comprises a lifting strap 1 and a main body 2 through which the strap 1 can pass to form a loop 3, one end 4 of the strap 1 locating in a slot 5 of the main body 2. The end 4 of the strap has an aperture 6 (see Fig. 3a) and the main body includes a pin 7 which is moveable between a first position bridging the slot 5 and a second position free of the slot.

The pin 7 in its first position can thus hold the end 4 of the strap in the main body, the pin passing through the aperture 6. The pin is moved to the second position, in which the strap 1 is released, by means of a rotational movement which can be provided through a ratchet mechanism, generally indicated by the reference numeral 8. An elongate member, here in the form of a toothed strap 9 and ropes 10, is provided in order to provide the rotational movement from a distant position. The rotational movement and the operation of the ratchet mechanism and the release of the lifting strap will be described in more detail later.

The lifting strap is formed of steel or polymer fibre (or both) with the desired strength characteristics. As shown in Fig. 2, a rubber toothed drive belt 11 can be fitted on the inside of the strap 1 in order to protect the strap from being abraded by the corners of the beam being lifted. The belt 11 is attached to the strap 1 by means of a sleeve 12 (Fig. 6) ^'which permits differential shortening or lengthening. The toothed belt has proved to be extremely effective in protecting the lifting strap - or any other lifting member - from damage in view of its inherent resilience, the cushioning effect of the teeth and the ability of the teeth to close up on each other when the belt passes around an edge or corner.

The end 4 of the strap passes through the main body 2, between a roller 13 and slotted member 14 including the slot 5. A small loop 15 is formed at the end 4 of the strap, the width of the loop 15 being narrower than the width of the remainder of the strap, and a pin 16 is fitted in the loop. The pin 16 is mounted in apertures 17 in two rear arms 18 of a link plate 19, shown in Fig. 3, which includes the aperture 6; thus, the link plate 19 is fixed to the end of the strap 1 and when the link plate 19 is fitted in the main body 2 a loop is formed for encircling the beam.

The main body 2 includes a pair of side plates 20 between which are clamped, at one end, the slotted member

14 and, at the other end, the roller 13. The roller 13 is rotatably mounted on a shaft 21 fitted in apertures in the side plates 20 and includes a wedge lock 23, mounted between circular plates 24, the purpose of which will be explained later.

The slotted member 14 is shown in greater detail in Fig. 4. In addition to providing the slot 5 of the beam sling, the slotted body also houses the ratchet mechanism 8. Extending across the member 14, above the slot 5, is a second slot 24. Bore 25 extends substantially centrally through the member 14, perpendicular to slots 5 and 24. Bore 25 has a wider section 25a and a narrower section 25b. A second bore 26, of much narrower diameter than bore 25, is provided perpendicularly to bore 25 and between the slots 5 and 24. The bore 26 opens out at the front of the slotted member 14. The ratchet mechanism, in this embodiment, consists of a ratchet wheel 27 fitted in slot 24 of the member 14, pawl 28 (seen most clearly in Fig. 1) and the toothed strap 9.

The pin 7 terminates on the outside of the body inside threaded nut or boss 29. The pin 7 extends through the bore 25 in the body 14 and can be moved by the ratchet wheel from a position bridging the slot 5 to a position in which the slot is open. The ratchet wheel is operated by means of the strap 9 which is threaded through the slot 24 and partly surrounds and engages the wheel. An indicator bar 30 is arranged on the end of the pin 7 remote from the slot 5.

As shown in Fig. 2, the pin 7 comprises a main threaded portion 31, the indicator bar 30 (which is narrower than the main portion) and an inner unthreaded portion 32 which bridges the slot 5. A longitudinal slot 33 is formed along the surface of the main and inner portions. The boss 29 comprises a neck portion 34 and a threaded bore 35 extends through the neck portion and into the boss 29. The boss also has a narrower bore 36 for the indicator bar 30. The ratchet wheel 27 has a central bore of a similar diameter to that of the outside of the neck portion of the boss.

The pin and ratchet mechanism are assembled in the body of the beam sling by placing the ratchet wheel and belt in the slot 24, sliding the pin across the slot 5 and then threading the boss onto the pin from the outside of the body. The neck portion of the nut fits in the bore of the wheel, and in part 25a of bore 25, and is locked with the wheel by means, for example, of screws.

As discussed, rotational movement to withdraw the pin is provided by means of the ratchet wheel 27 and the toothed strap 9 and ropes 10. Pulling on the rope attached to one end of the strap will draw it through the recess in one direction, pulling on the other rope attached to the other end will draw the strap in the other direction. In one direction of strap movement the teeth of the wheel 27 engage the indentations of the strap and the pawl 28 slips over the teeth so the wheel rotates. In the other direction of strap movement the pawl 28 catches in the teeth preventing the wheel 27 from rotating and the strap slips around the wheel. When the wheel 27 rotates so does the boss 29 which is fixed to it. The rotation of the threaded bore of the boss 29 and its neck portion 34 engaging with the correspondingly threaded portion 31 of the pin 7 forces the pin to move out of the body 13 and away from the slot 5. The pin is prevented from rotating by a key extending through the bore 26 and engaging in the slot 33 of the pin.

In use, the beam sling is fitted around a beam by passing the plate 19 at the end of the strap 1 underneath the beam and fitting it into the slot 5 in the body 13. The pawl 28 is then depressed and the pin 7 made to pass through the aperture 6 in the plate 19 by turning the boss 29 by hand. The beam is then lifted by means of a crane, with a crane hook fitting into a ring at the end of the strap 1, and the beam guided into the correct position. As the weight is taken by the strap, it tightens around the beam, with slack passing past the roller. The locking wedge prevents the sling from loosening when the load is relaxed and so slippage of the beam through the sling is effectively prevented.

To release the beam sling, one of the ropes 10 is pulled to draw the full length of the strap 9 across the ratchet wheel 27 to rotate it. This causes the boss 29 to rotate and thus the pin to partially retract. The strap 9 is then pulled by the other rope 10 back across the ratchet wheel 27 but, as explained above, this does not cause the boss to rotate and so the pin is not moved back into the body. The strap is then pulled back across the ratchet wheel with the first rope to further retract the pin. The process is repeated until the pin is clear of the slot 5 so the plate 19 at the end of the strap is released from the slot and the beam sling is thus freed from the beam.

The pin and ratchet mechanism might be designed such that five or six strokes of the strap are necessary to fully move the pin and release the plate 19. As the pin is being retracted, the indicator bar 30 extends from the boss to a greater and greater extent so that is possible to see from the distant position how close to release the beam sling is.

In addition to the advantage of the sling being released from a safe position, the invention also has the advantage that the release procedure for the sling could not be instigated by accident. On the other hand, the force needed to release the end of the strap is not too great.

As an alternative to the ratchet wheel described, the beam sling could incorporate a ratchet jack with a spring- loaded oscillating lever to rotate the boss 29. The lever could again be operated from a remote position by means of a rope. If no ratchet mechanism were used, the neck portion of the boss could be toothed and a longer toothed strap 9 could be pulled continuously in one direction to release the pin.

The toothed belt used to protect the lifting strap may, for example, be a rubber transmission drive belt as provided by Fenner (Hull) . An HTD timing belt 2450 14M 85 may be appropriate, although of course other types of toothed belt can be used. This belt has a width of 85 mm, an overall thickness of 10 mm (tooth height 6 mm) and a tooth spacing of 14 mm (tooth width 8 mm) . The length of the belt is selected acording to the beam to be lifted. Different widths of belt can of course be used and different tooth pitches can be used (e.g. 10 mm or 6 mm); in fact the belt illustrated in Fig. 2 is of a relatively narrow pitch. The belt can be formed of rubber or polymer (e.g. polyurethane) or other flexible material and can be fibre-reinforced.

Claims

1. A beam sling for lifting structural members such as beams, the sling comprising a lifting strap and a body member through which the lifting strap can pass in order to form a loop, with one end of the strap locating in a slot in the body member, wherein the said one end of the strap has an aperture and wherein the body member includes a pin which can move between a first position bridging the slot and a second position free of the slot, whereby the apertured end of the strap can be held in the slot by the pin, and wherein the pin can be moved from the first to the second position by means of a rotational movement and wherein an elongate member is provided to generate the rotational movement from a remote position.

2. A beam sling according to claim 1, wherein a threaded connection is provided between the pin and the body member so that relative rotation between the body member and the pin will move the pin along its axis.

3. A beam sling according to claim 1 or 2, wherein the rotational movement is provided through a ratchet wheel which can be rotated by the elongate member in several individual stages to move the pin to its second position.

4. A beam sling according to claim 3, wherein the body member comprises, in addition to the slot for the end of the strap, a slot for the ratchet wheel.

5. A beam sling according to claim 4, wherein the slots open out substantially perpendicularly to one another.

6. A beam sling according to any preceding claim, wherein the main body comprises a roller inside of which the strap passes and wherein the roller includes a locking mechanism, so that the strap can pass through the main body to tighten the loop as more weight is carried but the roller is locked to prevent opposite movement of the strap (which would loosen the loop) .

7. A protective member for a lifting strap for structural members, the protective member comprising an elongate band of flexible (e.g. elastomeric) material, the band having on one surface - that surface which in use contacts the structural member to be lifted - a series of spaced ribs which extend across a substantial portion of the width of the band.

8. A protective member according to claim 7, wherein the ribs have a rounded outer end.

9. A protective member according to claim 7 or 8, wherein the gap between the adjacent ribs is substantially equal to or less than their height.

10. A lifting strap for structural members, comprising on its inside face a protective member as claimed in any of claims 7 to

9.