GB2329200A

GB2329200A - Piling auger

Info

Publication number: GB2329200A
Application number: GB9719341A
Authority: GB
Inventors: Donald Timothy Sillis
Original assignee: MAY GURNEY
Current assignee: MAY GURNEY
Priority date: 1997-09-12
Filing date: 1997-09-12
Publication date: 1999-03-17
Also published as: GB9719341D0

Abstract

A ground displacement auger comprises a body 3 which tapers over a lower portion from a tip 2 increasing in diameter toward an upper portion. The body 3 has a twin helical blade 4 which extends over at least the lower portion. The helical blades 4 have a constant pitch and their outer diameter is constant. Although the average diameter of the body 3 taperingly increases away from the tip 2, the actual core diameter of each interblade section 5 of the body 3 decreases in diameter away from the tip. The invention also includes discontinuous flightings 6 which serve to reduce the quantity of soil which reaches the surface.

Description

PILING AUGER This invention relates to the field of augers for use in the formation of displacement piles.

European patent number 0 693 158 (HARENINVEST) discloses a ground displacement auger having a displacement body of increasing core diameter (in a direction away from the auger tip) combined with a screw flange of increasing pitch. These features sought to provide more efficient ground displacement in comparison with the prior art described in EP 0 693 158, in particular by requiring less energy during screwing in than previously-known augers.

However, the auger described in EP 0 693 158 is prone to the disadvantage of localised wear owing to the profile of the displacement body. Although the substantially constant volume between each successive diameter transition slope (17) facilitates the efficient transportation of soil, wear on the auger is particularly localised at the region where the displacement body has the widest core diameter.

As described in EP 0 693158 (p7, line 15 et seq) radial displacement of the ground is mainly achieved in the region of the last transition slope (17), i.e. just before the maximum displacement body core diameter (dry) is reached, and hence this is the region where wear is most significant. A further disadvantage is that penetration in denser strata can be slow.

It is thus an object of the present invention to provide a ground displacement auger which displaces soil and also penetrates denser, harder layers more efficiently but on which wear is minimised, or at least more evenly distributed.

Summary of the Invention According to a first aspect of the present invention, there is provided a ground displacement auger for making piles in the ground comprising a tip, a displacement body having at least over a lower portion an average core diameter increasing in a direction away from said tip and a twin helical flight extending over at least said lower portion of the displacement body wherein the twin screw helical flight is of a substantially constant pitch.

Preferably, the outer diameter of the twin helical flight is substantially constant.

In a preferred form, a twin helical flight can be used in the region of the tip with a single helical flight over the remainder of the lower portion.

Advantageously, the displacement body has an upper portion, distant from the auger tip, comprising a region of discontinuous or reversed flighting which, in use, reduces the quantity of soil which reaches the ground surface.

Ideally, although the average core diameter, (over the entire lower flighted portion of the displacement body) increases in a direction away from the tip, within each section the core diameter decreases away from the auger tip.

The present invention is intended to include within its scope a ground displacement auger substantially as described herein with reference to and as illustrated by the accompanying drawings.

Brief Description of the Drawings Preferred embodiments of the invention will now be more particularly described, by way of example only, with reference to the accompanying drawings wherein: Figure 1 is a side view of the ground displacement auger embodying the invention.

Figure 2 is a view of elevation BB.

Figure 3 is a view of section CC.

Description of the Preferred Embodiments Figure 1 shows a ground displacement auger embodying the present invention.

The auger comprises a displacement body 1 having at one end a tip 2.

The displacement body 1 has a core 3 whose average diameter increases in a direction away from the tip 2. Extending over at least the lower portion of core 3 (the region between section line AA and tip 2 in Figure 1) is a helical flight 4 whose outer diameter do is preferably substantially constant. In the illustrated example, helical flight 4 is twin start helical flight which extends over the lower portion of core 3. In an alternative embodiment, a twin helical flight can be used in the region of tip 2 with a single helical flight extending over the remainder of the lower portion of the displacement body core 3.

Although the average core diameter (over the entire lower flighted portion of the displacement body 1) increases in a direction away from the tip 2, the displacement body core 3 is divided into discrete sections 5. Within each section 5, the actual core diameter decreases away from the auger tip 2, although it is to be noted that the average core diameter increases away from the tip 2. When the auger is rotated, in use, the effect of the decreasing core diameter within each section is to increase the force that makes the auger penetrate the ground and also has the effect of moving the spoil up the auger in a more efficient manner. From the latter, the lateral displacement of the spoil is more evenly distributed over the auger's length, thus reducing wear on the auger generally.

The upper portion of the displacement body 1 (that region extending from section line AA in Figure 1 away from tip 2) is provided with a region of discontinuous or reversed flighting which, in the illustrated example, take the form of cleats 6.

Provision of cleats 6 in use, reduces the quantity of soil which reaches the ground surface and, in an embodiment having discontinuous flighting the lateral movement of soil is achieved without the flighting becoming blocked with soil.

In use, on site the auger 1 is attached to the rotary table of a piling rig.

Prior to drilling, the auger is accurately positioned at the required location and the end closure is effected, using either a metal plug or hinged flap, to prevent the ingress of soil and/or water to the hollow central stem of the auger 1.

Rotation is commenced and the winch and/or rope holding the rotary table is operated to allow the table to be lowered.

The initial penetration of the auger into the ground is achieved owing to the weight of the rotary table and auger combined. The downward force can be supplemented by a device for "crowding" the auger into the ground (generally a winch or hydraulic ram.

During rotation, on the lower part of the auger the helical flight 4 and the decreasing core diameter within each section have the effect of making the auger penetrate. Both the decreasing core diameter within each section and the helical flight 4 have the effect of distributing the soil efficiently up the length of the auger.

In addition, the increasing average core diameter in a direction away from the tip causes the soil to be displaced laterally.

Claims

1. A ground displacement auger for making piles in the ground comprising a tip, a displacement body having at least over a lower portion an average core diameter increasing in a direction away from said tip and a twin helical flight extending over at least said lower portion of the displacement body wherein the twin screw helical flight is of a substantially constant pitch.

2. A ground displacement auger as claimed in Claim 1, characterised in that the outer diameter of the twin helical flight is substantially constant.

3. A ground displacement auger as claimed in Claim 1 or Claim 2 characterised in that a twin helical flight can be used in the region of the tip with a single helical flight over the remainder of the lower portion.

4. A ground displacement auger as claimed in any of the preceding Claims, characterised in that the displacement body has an upper portion, distant from the auger tip, comprising a region of discontinuous or reversed flighting which, in use, reduces the quantity of soil which reaches the ground surface.

5. A ground displacement auger as claimed in any of the preceding Claims, characterised in that although the average core diameter, (over the entire lower flighted portion of the displacement body) increases in a direction away from the tip, within each section the core diameter decreases away from the auger tip.

6. A ground displacement auger substantially as described herein with reference to and as illustrated by the accompanying drawings.