AU2003250612B2 - An improved lifting frame - Google Patents

Description

WO 2004/018800 PCTIAU2003001065 AN IMPROVED LIFTING FRAME This invention relates to an improved lifting frame, and in particular to ensure the lifting means of the frame are maintained principally in tension.

BACKGROUND OF THE INVENTION An earlier patent application by the applicant (PCT/AU02/00506), describes a lifting frame used with a moving screen. The preferred application for the moving screen comprises a safety screen used during construction of multi-storey buildings. The description and disclosure of that earlier patent application is hereby incorporated within this specification.

One of the methods described in the earlier patent application for lifting the screen comprises a pair of lead screws or spindles which are operated between two beams, one being a motor beam and the other being a support beam. As the screen is lifted, the two beams come together. The support beam is then secured to the building and the motor beam is released. The motor is operated so that the lead screws push the motor beam upwardly.

It would be preferable that, in addition to the motor beam being lifted, the screen may also be lifted in combination with the motor beam. In other words, the motor beam is secured to the screen so that both raise up in relation to the support beam.

However, one problem with this arrangement is that the spindles would be placed into compression. This is likely to result in bending of the spindles and resultant failure of the lifting mechanism. The spindles may also bend when just lifting the motor beam.

00 2 C Accordingly, it is an object of this invention to overcome the abovementioned e, problem and to provide a lifting frame where only tensile forces are applied to the spindles.

SUMMARY OF THE INVENTION ID In one aspect, the invention is a lifting frame and includes: t a first frame; 3 a second frame slidable with respect to said first frame; a hoist means extending vertically and held with respect to said first frame; 0 and a hoist actuator mounted on said second frame that operatively engages said hoist means between its ends to cause movement of said first frame with respect to said second frame where, in use, fixing of said second frame to a fixed support results in said first frame being lifted or lowered with respect to said second frame so that the portion of said hoist means below said hoist actuator is maintained in tension wherein said hoist means comprises a threaded spindle.

In accordance with the invention, the portion of the hoist means that is below the hoist actuator is maintained in tension during the lifting of the first frame. However, the invention also includes the first frame being held with respect to a fixed support.

In this case the portion of the hoist means above the hoist actuator is maintained in tension.

A number of different hoist means may be used. For example, the hoist means may comprise one or more elongate threaded spindles that are secured at either end to the first frame. In the case of a threaded spindle, the hoist actuator may comprise a threaded collar which is rotated by an electric motor via associated gearing. The threaded collar is fixed with respect to the second frame and therefore rotation of the threaded collar causes the first frame to move with respect to the second frame.

WO 2004/018800 PCT/AU20031001065 3 Alternatively, the hoist means may comprise an elongate tooth rack that is fixed to the first frame with the hoist actuator comprising a driven gear wheel which is fixed to the second frame. Again, the portion of the rack below the gear wheel will be in tension as the first frame is being lifted with respect to the second frame.

Other combinations of hoist means and hoist actuator may be used which will provide the essential requirement of the invention which is the portion of the hoist means below the hoist actuator being maintained in tension during the lifting of the first frame.

In operation, once the first frame is lifted to the extent where the hoist actuator reaches the lower end of the hoist means, the first frame is preferably supported from the upper end of the hoist means so that the second frame can be released to allow it to travel upwardly along the hoist means. Once the hoist means reaches the upper end of the hoist actuator, the second frame can then be re-supported at a higher level to again cause raising of the first frame. Again, in this mode of operation, the hoist means are maintained in tension as the second frame is lifted. Accordingly, the invention provides a means of always maintaining the hoisting means in tension as both the first and second frames are lifted vertically.

One application for this invention will be the raising of safety screens the subject of the earlier PCT application (PCT/AU02/00506). However, this invention is not to be limited to this particular application. Other applications for the invention will be readily apparent to a skilled addressee.

In order for the invention to be fully understood, a preferred embodiment will now be described. However, it should be realised that the invention is not to be confined or restricted to the elements of this particular embodiment.

WO 2004/018800 PCTAU2003/001065 4 BRIEF DESCRIPTION OF THE DRAWINGS The embodiment is illustrative in the accompanying drawings in which: Figures 1 to 3 show three stages of movement of a lifting frame in accordance with the invention, and Figure 4 shows a plan view of the lifting means shown in Figures 1 to 3.

DETAILED DESCRIPTION The figures show the lifting frame for a movable screen. For purposes of clarity, the screen elements that are attached to the assembly are not shown in dashed outline.

In this embodiment, a first frame comprises vertical frame members 11 and horizontal frame members 12. A pair of vertical spindles 13 are secured at each end of the spindle 13 to the vertical frame member 11.

Referring to Figure 4, I-beams are secured at either end of the beams 15. The I-beams in turn locate within channels which are secured to the vertical frame members 11.

In this way, the vertical frame members 11 and the horizontal frame members 12 are held together but are able to slide in relation to one another.

The lower horizontal beam 15 carries a motor 17 that drives a gear box 18 that in turn drives a pair of threaded collars 19. The threaded collars 19 engage respective spindles 13 and rotation of the threaded collars 19 via the motor 17 cause the second frame to move with respect to the first as the threaded collars 19 turn with respect to the spindles 13.

In this embodiment, the first frame carries screen elements that are to be raised as part of a building construction. In this example, the second frame is secured to a building in a manner similar to that described in the earlier patent application (PCT/AU02/00506). The second frame is initially located towards the upper end of each spindle 13. In order to raise the first frame and attached screen, the motor 17 is WO 2004/018800 PCT/AU2003/001065 operated so that the threaded collars 19 rotate with respect to each spindle 13. This in turn moves the spindles 13 upwardly through the collars 19 so that the first frame and screen elements are raised.

Once the threaded collars 19 reaches the lower end of each of the spindles 13, then the first frame can be supported at a different level of the building, preferably by the spindles 13, so that the second frame can be released from the building. The motor 17 is then again operated, but in an opposite direction so that the threaded collars 19 advance upwardly with respect to the spindles 13. This moves the second frame upwardly with respect to the first frame. Once the second frame reaches the upper end of the spindles 13, it can again be supported with respect to the building so that the first frame can again be raised with respect to the second frame.

As can be seen from the above description, the invention results in the spindles 13 always having a tensile load applied. That is, the first frame, when supported by the second frame, results in those portions of the spindles 13 below the threaded collars 19 being placed in tension. When the second frame is being lifted, the first frame is supported by the spindles 13 and again a tensile load is applied as a result of the second frame being supported by the spindles 13. This allows any compressive loads to be avoided.

This embodiment is described in relation to the raising of safety screens in accordance with the prior mentioned patent application. However, the invention will have numerous other applications where the first frame can provide a lifting force with respect to the second frame while at the same time providing a means of advancing both the second and first frame upwardly with respect to a supporting structure.

Claims (9)

1. A lifting frame including: a first frame; a second frame slidable with respect to said first frame; Sa hoist means extending vertically and held with respect to said first frame; S and Sa hoist actuator mounted on said second frame that operatively engages said hoist means between its ends to cause movement of said first frame with respect to 0 said second frame where, in use, fixing of said second frame to a fixed support results in said first frame being lifted or lowered with respect to said second frame so that the portion of said hoist means below said hoist actuator is maintained in tension wherein said hoist means comprises a threaded spindle.

2. A lifting frame according to Claim I wherein said hoist actuator comprises a collar threadably engaging said spindle and a means for driving said collar.

3. A lifting frame according to Claim 1 or Claim 2 comprising a pair of hoist means.

4. A lifting frame according to Claim 3 wherein said pair of hoist means are spaced apart and located on the left and right hand sides respectively of said first frame.

5. A lifting frame including: a first frame; a second frame slidable with respect to said first frame; a hoist means extending vertically and held with respect to said first frame; and 00 7 c a hoist actuator mounted on said second frame that operatively engages said hoist means between its ends to cause movement of said second frame with respect to said first frame where, in use, fixing of said first frame to a fixed support results in said second frame being lifted or lowered with respect to said first frame so that the N 5 portion of said hoist means above said hoist actuator is maintained in tension ID wherein said hoist means comprises a threaded spindle. S

6. A lifting frame according to Claim 5 wherein said hoist actuator comprises a N collar threadably engaging said spindle and a means for driving said collar. 0

7. A lifting frame according to any one of Claims 5 or 6 further comprising a pair of hoist means.

8. A lifting frame according to Claim 7 wherein said pair of hoist means are spaced apart and located on the left and right hand sides respectively of said first frame.

9. A lifting frame according to any one of the preceding claims used to lift or lower safety screens on a multi-storey building. A lifting frame substantially as herein described with reference to the accompanying drawings.