AU5189600A - Auger - Google Patents

Description

Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

Name of Applicant: Actual Inventor(s): Address for Service: Invention Title: Vibro-pile (Aust.) Pty. Ltd.

of No. 1 Steele Court, Mentone, Victoria 3194, Australia DAVIES COLLISON CAVE, Patent Attorneys, 1 Little Collins Street, Melbourne 3000, Victoria, Australia Auger Details of Associated Provisional Application No: PQ2317 filed 19 August 1999 The following statement is a full description of this invention, including the best method of performing it known to us: -1- Q:\OPER\DH\AUG '00\PQ2317 CAP 0808.DOC 8/8/00 P:\OPERMDH\pq2317 cap 0808,doc-08/08M -2-

AUGER

Field of the Invention The present invention relates to the field of augers, particularly soil displacement augers used for pile construction.

Background of the Invention A known form of auger is provided with a ground engaging thread defined by a flange, which is wound helically around a central stem of the auger. An enlarged displacement body is provided on the stem for the purpose of displacing soil radially outwardly for compaction against sides of a hole formed by the auger, as the auger is driven into a oooo ground surface. The soil displacement increases the density of the soil adjacent the hole o* S. "and improves the load bearing capacity of the soil for when a pile is subsequently formed therein.

S"In International Patent Application No. PCT/BE94/00078, a displacement body is formed by increasing the diameter of the stem from a tip of the auger up to a maximum diameter, axially spaced from the tip. The pitch of the thread is also shown as increasing from the tip of the auger, consistent with the increase in the stem diameter, so that substantially the same volume of soil is transported along at least a portion of the screw thread during each revolution of the auger, despite the increase in diameter of the displacement body.

Summary of the Invention P:\OPERDHpq2317 cap 0808.doc-&MiO -3- In accordance with the invention, there is provided an auger with a central stem and a thread defined by a flange, which is helically wound about the stem, the auger further including a displacement body with an increased diameter relative to the stem, for outwardly displacing soil transported along the thread as the auger is driven into a ground surface, wherein the pitch of the thread increases over a first portion, between a tip of the auger and the displacement body, to provide for an associated increase in volume defined between adjacent flights of the thread and the stem of the auger, in a direction away from the tip.

The increase in volume reduces frictional forces acting on the auger during initial installation to thereby minimise torque requirements during installation, as compared to a conventional auger.

Preferably, the stem is of substantially constant diameter over the extent of the first portion.

Preferably, the pitch of the thread continues to increase axially from the first portion, 15 over the displacement body toward a maximum diameter of the displacement body.

More preferably, the auger includes a second portion with a second thread, provided on *a side of the body opposite that of the first thread, the second thread having an opposite handedness relative to the first thread.

Preferably, the displacement body increases in diameter between the first portion and the maximum diameter, in a continuous manner.

P:\OPER\DHpq2317 ap O08.doc-)8/OMM -4- Brief Description of the Drawings Figure 1 is a side view of an auger in accordance with the invention; and Figure 2 is a cross-sectional view of the auger, taken along the line A-A, shown in Figure 1.

Detailed Description of a Preferred Embodiment The auger 1 shown in Figures 1 and 2 includes a central stem 2 and a thread 3 defined by a flange 4 which is helically wound about the stem. The auger 1 also includes a displacement body 5 with an increased diameter, relative to the stem, for outwardly displacing soil transported along the thread 3, as the auger is driven into a ground surface.

The thread 3 is provided in combination with a flight 6, so as to form a double start thread adjacent a tip 7 of the auger 1. The pitch of the thread increases over a first portion 10, in a direction away from the tip 7, while the outer diameter of the stem 2 remains constant. The pitch of the thread continues to increase over the displacement 15 body 5 toward a region 11 whereat the displacement body is at a maximum diameter, corresponding to the external diameter of the thread 3. The increase in diameter of the displacement body is continuous. For that purpose the body 5 is preferably constructed from a metal sheet 20 which is wrapped about the stem 2 and welded in place to present a smooth continuous surface 21 of progressively increasing diameter. A second surface 22 of progressively decreasing diameter is similarly formed on an opposite side of the region 11.

P:\OPERDH\pq2317 cap O08.doc-O8//M The reduced diameter surface 22 forms part of a second portion 12 which is provided with a second thread 13 on a side of the displacement body 5 opposite that of the first thread. The second thread 13 has a constant pitch above the displacement body and an opposite handedness as compared to the first thread 3.

The flange of each of the threads 3,12 may be of uniform thickness however it may be advantageous for at least the thickness of the flange 4 of the first thread 3 to vary, such as being of greater thickness at locations near the stem.

The stem 2 itself is hollow so as to permit flowable, settable material such as concrete to be passed therethrough to emerge from an opening 14 at the tip which is selectively 10 covered with a cap member 15 during a drilling operation.

In that regard, drilling is effected by either allowing the auger to penetrate a ground surface under its own weight or by assisting penetration by downwards winching or jacking the auger into the soil. The auger design is such that ground or soil will be displaced to the full diameter of a pile to be formed whereby the soil will be densified to 15 provide load carrying capacity for the pile, similar to, or greater than, a driven precast concrete pile of the same proportions or displacement. During initial penetration of the .soil, the increasing pitch of thread 3 and constant stem diameter throughout portion allows soil to relax on and around the flange 4 thus reducing installation torque and facilitating auger installation before the soil is displaced laterally by the displacement body 5. More particularly, the increase in pitch of thread 3 and constant diameter of the stem 2 throughout portion 10 allows for an increase in volume of soil to be stored on the P:\OPERI)H\pq2317 cap 0808.doc-8OM)00 -6flange 4, between, for example, adjacent flights 16,17 of the thread. This increasing volume allows the soil to temporarily loosen over the portion 10 which leads to a reduction in total frictional forces acting on this portion of the auger. Reducing the friction between the auger and the soil provides an advantage that the torque required to install the auger is reduced to thereby increase efficiency of drilling.

Further efficiency may be realised in that a drilling rig (not shown) used for rotating the auger need not be reversed for extraction of the auger after drilling, as is the case with a number of conventional augers. During extraction, the auger 1 may be simply driven in the same rotational direction as for installation since the second thread 13 will move any soil which may have collapsed onto the auger downwardly onto the displacement body 11 for compaction against the sides of the hole formed during drilling.

It has been found that the most optimal results are achieved with an auger having the following dimensions: SOverall length of portion 10 (constant stem, increasing pitch screw section) o should be approximately 45 of the total length of the auger and could vary between 35% and 65% of the total length of the auger. Actual dimension, 1070mm for a 2300mm long auger (400mm diameter).

S Overall length of the expanding displacement body (portion 5) should be approximately 115% of the diameter of the auger and could vary between 100% and 150% of the diameter of the auger. Actual dimension, 450mmfor a 400mm diameter auger.

S Overall length of the reducing diameter portion above the displacement body P:\OPER\DH\pq2317 cap 0808.doc-08/08/00 -7- (portion 12) should be approximately 65% of the diameter of the auger and could vary between 50% and 75 of the diameter of the auger. Actual dimension, 270mm for a 400mm diameter auger.

Overall length of portion 12 should be approximately 20% of the total length of the auger and could vary between 15% and 30% of the total length of the auger.

Actual dimension, 500mm for a 2300mm long auger (400mm diameter).

The pitch of the first flight should be approximately 65 of the diameter of the displacement body (region 11) and vary between 50% and 75% of the diameter of region 11. Actual dimension, 350mm for a 400mm diameter auger.

S 10 The pitch of the second flight should be approximately 85% of the diameter of region 11 and vary between 75 and 95% of the diameter of region 11. Actual dimension, 450mm for a 400mm diameter auger.

The pitch of the third flight should be approximately 112 of the diameter of region 11 and vary between 100% and 140% of the diameter of region 11.

15 Actual dimension, 450mm for a 400mm diameter auger.

The diameter of the constant diameter, hollow central stem (portion 2) should be minimised. However, the diameter of this section will be governed by the structural capacity of the auger (plate or tube thickness) and the minimum diameter of hollow stem required to allow concrete to flow through the orifice. At this stage the stem diameter is approximately 220mm.

The auger has been described by way of example only and many modifications or variations may be made thereto without departing from the spirit and scope of the invention described.

Claims (6)

1. An auger with a central stem and a thread defined by a flange, which is helically wound about the stem, the auger further including a displacement body with an increased diameter relative to the stem, for outwardly displacing soil transported along the thread as the auger is driven into a ground surface, wherein the pitch of the thread increases over a first portion, between a tip of the auger and the displacement body, to provide for an associated increase in volume defined between adjacent flights of the thread and the stem of the auger, in a direction away from the tip.

2. An auger as claimed in claim 1, wherein the stem is of substantially constant diameter over the extent of the first portion.

3. An auger as claimed in claim 1 or 2, wherein the pitch of the thread continues to increase axially from the first portion, over the displacement body toward a e maximum diameter of the displacement body.

4. An auger as claimed in any one of the preceding claims, wherein the auger includes a 15 second portion with a second thread, provided on a side of the body opposite that of the first thread, the second thread having an opposite handedness relative to the first thread. An auger as claimed in any one of the preceding claims, wherein the displacement body increases in diameter between the first portion and the maximum diameter, in a continuous manner.

P:\OPER\flH~pq23l7 cap 08O8.dmo-O&jMM -9-

6. An auger, substantially as hereinbefore described with reference to the drawings. DATED this 8th day of August, 2000 Vibro-pile (Aust.) Pty. Ltd. By DAVIES COLLISON CAVE Patent Attorneys for the applicant