JP2002285777A - Rotary casing drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply pull up a drill after excavation by making a gap between the wall of a drilled hole and the outer face of a rotary casing. SOLUTION: A projection bar 9 is spirally provided on the outer peripheral face of the rotary casing 3. The projection bar 9 spirally winds a circular cross section steel rod around the outer face of a rotor casing 3 to be welded. A support cylinder 10 has a large diameter than the rotary casing 3, and is about 34 mm larger when compared in the diameter. Thus, the projection bar (diameter is 32 mm) is housed in the diameter of the support cylinder 10. Cutting bits 6 are attached to a socket 11 being on the lower part of the support cylinder 10 by bolts 12. The cutting bits alternately arrange outer blades and inner blades, the inner blade is vertical, and the outer blade is attached slantly, and the lower end of the bit is protruded to the outside from the outer wall of the support cylinder. A protrusion amount p is approximately 8 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary casing drill used for drilling rock.

[0002]

2. Description of the Related Art A rotary casing drill has conventionally been used for drilling a hole for a foundation pile or the like in hard rock. Referring to FIG. 1, reference numeral 1 denotes a rotary casing drill, and reference numeral 2 denotes a leader machine 2. The rotary casing 3 is rotated at a slow speed of several revolutions per minute by the drive unit 5, and digs down while cutting the rock with the drill bit 6 fixed to the lower end thereof.

An auger shaft 7 passes through the inside of the rotary casing 3, and the auger shaft is driven in a direction opposite to the casing 3 by a drive unit 5, and has a tip bit (retracted into the rotary casing 3). Drills and transports cuttings to the ground.

[0004] This type of drill has many advantages such as low vibration, good vertical accuracy, and the ability to drill even on solid rock.
There is a disadvantage that the wall surface of the hole and the outer surface of the rotary casing come into close contact with each other, and after drilling, the drill device cannot be lifted smoothly.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a space between a wall of a drilled hole and an outer surface of a rotary casing so that the drill can be easily lifted to the ground after excavation. Make it an issue.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a rotary casing drill in which a support cylinder is extended at the lower end of a rotary casing driven to rotate and a cutting bit is fixed to the lower end of the support cylinder. A spiral ridge is provided. The diameter of the support cylinder is at least larger than that of the rotary casing, and is formed to be substantially the same as the diameter of the rotary casing including the ridge (claim 1).

[0007] In the rotary casing drill configured as described above, since a hole larger than the rotary casing is formed at the time of drilling, a gap is formed between the rotary casing and the hole, and the drill is easily pulled out. Further, even when the gap is filled with collapsed earth and sand, the ridge that rotates together with the rotary casing acts like an auger and scrapes out the earth and sand, so that there is no hindrance to pulling out of the drill. In addition, since the outer diameter of the support cylinder is formed to be substantially the same size as the outer diameter of the rotary casing including the ridge, the ridge is not damaged by excessive force during excavation.
The cross section of the ridge can take various shapes such as a rectangle, a rectangle, a circle, and a semicircle.

[0008] It is preferable that the cutting bit is attached so as to protrude slightly outside the outer surface of the support cylinder (claim 2). By doing so, the diameter of the hole drilled by the cutting bit will be larger than the outer diameter of the support cylinder, so when lifting the drill,
The entire support cylinder is smoothly lifted without being caught.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS This rotary casing drill has the same basic structure as that of a conventional drill, but has a spiral ridge 9 provided on the outer peripheral surface of a rotary casing 3 as shown in FIG. The ridge 9 is formed by spirally winding a steel rod having a circular cross section around the rotary casing 3 and welding it. The rotary casing 3 has a diameter of 650 mm, whereas the diameter of the steel rod is, for example, 32 mm. Spiral pitch is about 80
0 mm. Since the rotation direction of the rotary casing 3 is counterclockwise as viewed from above, the ridge 9 is wound in the same direction as the left-hand thread.

The support cylinder 10 has a larger diameter than the rotary casing 3 and is made larger by about 34 mm in radius. Therefore, the ridge (diameter 32 mm) is contained within the diameter of the support cylinder 10.

A cutting bit 6 is attached to a socket 11 at a lower portion of the support cylinder 10 with a bolt 12. The cutting bit 6 has outer blades and inner blades arranged alternately. The inner blades are vertical as shown in FIG. 3A, whereas the outer blades are inclined as shown in FIG. 3B. The lower end of the bit projects out of the outer wall of the support cylinder. Projection amount p is 8mm
It is about.

With this configuration, when the rotary casing 3 is rotated by the driving device 5 (counterclockwise as viewed from above), the rock is cut by the excavation bit 6 at the lower end of the casing, and the casing 1 is gradually removed. Dig down below. Further, the auger 7 rotates in the opposite direction inside the rotary casing 3, breaks the rock with the cutting bit 7a at the tip thereof, and carries out the cutting waste to the ground.

As described above, since the cutting bit (outer blade) 6 slightly projects outside the support cylinder 10, the hole formed by the bit is larger than the outer diameter of the support cylinder 10.
Further, the diameter is larger than the diameter of the rotary casing 3 including the ridges 9. Therefore, wear of the support cylinder 10 is small. Further, a gap 13 is formed between the rotary casing and the hole, and the ridge is accommodated in the gap, so that no excessive force is applied to the ridge.

As described above, since the outer surface of the rotary casing and the wall of the hole do not adhere to each other and a gap 13 is formed therebetween, the rotary casing can be easily pulled up after excavation. Further, even when the gap is filled with collapsed earth and sand, the ridge that rotates together with the rotary casing functions like an auger, and the earth and sand can be removed by sending them upward.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a conventional casing drill device.

FIG. 2 is an elevational view of a main part of the casing drill device of the present invention.

FIG. 3 is a sectional view of a cutting bit attached.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing drill 2 Leader machine 3 Rotary casing 5 Drive part 6 Cutting bit 7 Auger 9 Ridge 10 Support cylinder 13 Gap p Projection amount

Claims (2)

[Claims] An outer peripheral surface of a rotary casing is provided with a ridge in a spiral shape, and is fixed to a lower end of the rotary casing. A rotary casing drill, which is large and has a size substantially equal to an outer diameter of the rotary casing including the ridge. 2. The rotary casing drill according to claim 1, wherein the cutting bit is attached so as to project slightly outside the outer peripheral surface of the support cylinder.