AU603455B2

AU603455B2 - Flexible load cell

Info

Publication number: AU603455B2
Application number: AU18144/88A
Authority: AU
Inventors: Keith Charles Wooldridge
Original assignee: POLYFORM Pty Ltd
Current assignee: POLYFORM Pty Ltd
Priority date: 1987-06-23
Filing date: 1988-06-20
Publication date: 1990-11-15
Anticipated expiration: 2008-06-20
Also published as: AU1814488A

Description

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AUSTRALIA

PATENTS ACT 1952

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31f COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority: Related Art: T &j~C 1 2LIir it CO I~fJ tc, L. iorJ TO BE COMPLETED BY APPLICANT O."I"Name of Applicant: Address of ApplicantL: ,Actual Inventor: Address for Service: POLYFORM PTY. LIMITED 37 Justin Street SMITHFIELD N.S.W. 2164 KEITH CHARLES WOOLDRIDGE ARTHUR S. CAVE CO.

Patent Trade Mark Attorneys Level Barrack Street SYDNEY N.S.W. 2000 AUSTRAL IA *~Complete Specification for the invention entitled: FLEXIBLE LOAD CELL.

The following statement is a full description of this invention including the best method of performing it known to me:- 1- ASC 4 9 r 1 ~99~.

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FLEXIBLE LOAD CELL The present invention relates to a load-cell particularly for use as a prop head in the construction industry.

Whilst the present inv-..'ion has a wide range of uses, it will be particularly now described with reference to its use as a prop head in the construction industry.

In the construction of multi-storied buildings the concrete to floor slab on an upper deck is poured before the floor slabs on lower decks are fully cured, thus the live deck load is superimposed on the three floors below.

The live deck is supported on false work or shoring, which is removed once the floor slab is poured and partially cured and is then used in the construction of the next upper deck. As the false work is removed props are placed, usually in a diamond pattern to replace the support previously provided by the false work.

There are presently two types of prop namely a heavy duty prop and a standard adjustable prop. The heavy duty prop has a threaded jack at its base and is adjustable in height whereas the standard adjustable prop is adjustable at its top. Either prop may be placed between the floor slab and the soffit and adjusted in height to rigidly abut the floor slab at its base, and the soffit, at its top.

As the concrete dries in the floor slab the floor slab relaxes and the once rigid props, if not manually adjusted, are liable to fall causing serious accidents to any person in the vicinity. As a safety measure it is normal that one man as part of his duties on a building site manually checks all the o o a o os o so *s 0 0010 o a iii 2 0372E 1 0382v/MS 2 props and adjusts them during the 28 days that it takes for a floor slab to fully cure and be relieved of the superimposed load from live deck.

The present invention seeks to substantially overcome this problem and its inherent danger to life by providing a biased load-cell which wil.l automatically takes up the slack as the floor slab relaxes.

In one broad form the present invention is a load cell for use as a prop head to support a moveable load, said a,, age,* load-cell having a top plate and a bottom plate adapted to interconnect in spigot fashion and having, a spring loaded o biasing means therebetween, said bottom plate connected to an adjustable prop wherein in use said prop is placed under said load and adjusted such that said load is supported by said top plate of said load-cell, said spring loaded biasing means adapted to move as said load moves thereby maintaining support of said load by said prop.

~.'The present invention will be more fully described with reference to the attached drawings in which FIG 1. is a side view of a preferred top plate, FIG 2. is plan view of the top plate of Fig. 1., FIG 3. is a side view of the bottom plate, FIG 4. is paln view of the bottom plate of Fig 3., FIG 5. is a view, partly in section, of a preferred load-cell.

FIG 6. is a schematic of the arrangement used to test the apparatus according to the invention.

In Fig 1. the top plate 1 comprises a planar upper surface 2, an upper surface 3 and a hollow shaft 4 projecting from lower surface 3. A bolt o ii affixed at its head to lower ~cVR.4 ~3 ic Ianan 4

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*t I iC C C an upper surface 8 and a hollow shaft 9 projecting therefrom.

The flat surface 7 as shown in Fig 4 is provided with two holes 10, through which bolts are placed (not shown) to secure the load-cell 11 to the top of prop (not shown) there is also provided a central hole 12 adapted to receive the projecting end of bolt In Fig 5. is shown a load cell 11. The shaft 4 of top plate 1 is shown spigotly connected to shaft 9 of bottom plate 6, A nut 13 and washer 14 are placed over projecting end of bolt 5. A biasing means, namely a heavy duty spring 15, is held captive within the hollow shafts 4 and 9 and is biased to maintain top plate 1 apart from bottom plate 6.

In use the spring 15 is placed over bolt 5 and shaft 4 is spigotly connected to shaft 9. A washer 14 and nut 13 are put onto the bolt 5 and the nut i is welded to bolt 5. Through holes 10 the bottom plate 6 is affixed by bolting to the top of a heavy duty prop (not shown). The prop is then placed in position between a floor slab and adjusted to rigidly abut the soffit of the upper deck. As the floor slab relaxes the biasing means 15 maintains upper surface 2 of top plate 1 in rigid abutment with the soffit.

A test of the invention was carried out to simulate the condition where the load on a prop used to back-prop a floor slab was relaxed due to upward movement of the floor. The testing arrangement is shown in Figure 6. This was done by lowering the screw jack at the base of the heavy duty prop by and 10mm. At each of these two positions, and in the no movement case, a lateral load was applied progessively at the 4 0372E i p 1- I t prop head until the prop fell, simulating pedestrian impact on a relaxed prop, The results in Table 1 below show the loads required to dislodge the prop, and these have been converted to an equivalent lateral load at shoulder height (assumed to be m).

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4 41 *i 4 TABLE 1 RELEASE OF PROP NO. 25kg WTS. MASS EQUIV. LOAD AT (TO FALL) SHOULDER HEIGHT 6 150kg 2.83 kN 8 200ka 3.76 kN OMM >16* >400kg* >7.53 kN* *TESTING DISCONTINUED AT 16 WEIGHTS PROP DID NOT FALL The results show that even with a simulated up movement of the lateral force required to dislodge the prop would be 2.83kN. The results show that the present invention is capable of resisting any lateral load likely to be applied by pedestrian impact.

It is to be understood that modifications both in design and materials used can be made to the present invention, for example, pneumatic or hydraulic biasing means can be used in the place of a spring, without departing from the spirit and scope of the present invention.

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Claims

1. A load cell for use as a prop head to support a moveable load, said load-cell having a top plate and a bottom plate adapted to interconnect in spigot fashion and having, a spring loaded biasing means therebetween, said bottom plate connected to an adjustable prop wherein in use said prop is placed under said load and adjusted such that said load is supported by said top plate of said load-cell, said spring loaded biasing means adapted to move as said load moves thereby maintaining support of said load by said prop.

2. A load-cell according to claim 1 wherein a central shaft is attached at one end to said top plate and slidably passes through said bottom plate and having a stop means thereby providing said top plate with a detent.

3. A load-cell susbtantially as herein described and with reference to the accompanying drawings. DATED this 16th day of August, 1990. 0 v I i POLYFORM PTY LTD By Its Patent Attorneys ARTHUR S. CAVE CO. 6 O ^LSS^