AU4542097A - Three prong borer - Google Patents

Description

Regula6tiont 3.2 Patents Act 1990 COMPLETE

SPECIFICATION

FOR A STANDARD

PATENT

(ORIGINAL)

Name of Applicant: Actual Inventor(s): Address for Service: UNIROC AB Robert Herman Gerrit Landsmfanl SAIIDERCOCK

&COWIE

69 Robinson Street, DANDENONG VIC 3175

S

THREE PRONG BORER Invention Title: Details of South African Patent Application No. ZA97/7 286 filed on 14th August, 1997-from which Convention Priority is claimed.

The followinlg statement -is full description of this invention, jncludiflgthe best method of performing it known 9aWU 2 s~S1tUWOCdzJ j

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I I This invention relates to rock drill bits.

The invention is concerned with a rock drill bit which is particularly intended for drilling anchor holes in sandstone in coal mines. Known rock drill bits for use in such purpose each comprise a body incorporating a shank whereby it may be connected to a drill steel end and a pair of lugs supporting respectively a pair of drill inserts.

In one of these known rock drill bits, the inserts can be embodied in a single hard metal (normally tungsten carbide part arranged to extend diametrally across the body part with opposite sides supported by the lugs. The TC part has an inverted .VI-shaped cutting edge with the apex on the axis of the-bit so that there is a straight cutting edge on each side of the insert. In another known rock drill bit there are two separate inserts supported respectively by the lugs and are of varying rake angles and may be for example slightly negatively raked. Each 20 insert has an arcuate rock cutting edge (which is known to those in the art in the Republic of South Africa as a ,thumbnail" edge). A flushing opening, connectable tothe flushing conduit, is provided centrally of the body for flushing water to flush the drilled hole. Such known rock drills, which are two samples of many variant, jare reasonably satisfactory and are in ide use.

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According to one aspect of the invention there is I provided a rock drill bit comprising a body incorporating a shank, whereby it may be connected to a drill steel end, and at least three lugs extending axially of the body, which lugs are shaped to receive respectively at least three hard metal inserts, there being a groove between each pair .of adjacent lugs into which opens a flushing opening. Hard metal inserts are i preferably received by the lugs, conveniently in pockets formed in the lugs, and are attached thereto, preferably by brazing. The inserts are preferably backwardly raked by a small angle of conveniently The cutting edge of each insert conveniently has a main part which is preferably straight and which extends 15 radially away from the body. The cutting edge preferably further comprises an end part which is preferably S :I straight and which extends from the end of the main part towards the body.

.1 An embodiment of the invention will now be described by way of example with reference to the accompanying drawings.

In the drawings: Figure 1 is a side view ofa drill bit of the invention, i 25 Figure 2 is a plan of the drill bit in the direction of an arrow 2 of Figure 1, 225 <:page 3 Figure 3 is an underplan of the drill bit in the direction of an arrow 3 of Figure 1, and Figure 4 is a perspective view of the drill bit. Referring now to the drawings, there is shown a rock drill bit 10 of the invention. The bit comprises a short cylindrical body 12. The body 12 incorporates at one end (hereinafter called for convenience "the lower end") a hollow concentric shank 14 which is threaded to be received in the drill steel end i 10 (not shown).

Three equispaced grooves 16 extend generally I ."axially of the body 12. The grooves 16 increase in I depth and width away from the lower end of the body..

The rear side 18 of each groove 16 that surface that trails the groove in the direction of rotation

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of the bit 10) lies on a plane radial of the body 12 (as is best shown in Figure The forward side of Sthe groove 16 is inclined to the rear side 18 to leave a lug 20 between it and the next groove 16. This lug 20 is similar in appearance to (although much S: smaller than) a cutting tooth on a rotary drum cutter.

Each lug 20 has a pocket 22 formed therein.

A TC insert 24 is received in the pocket 22 and is 'attached, e.g. by brazing, in position. The insert 24 is mouted so that its front face 26 is slightly backw" ardly raked by a small angle of 6. The upper or cuti 1 e tU9Itjjj .\MUROC%, Dril %722 Page 4' Vf f!; ting edge of the insert 24 is of inverted "V-shape in front view It comprises a main edge part 28 which is front view. w straight and which extends upwardly radially away from the body 12). The cutting edge further comprises an end part 30 which extends from the end of the main part 28 downwardly towards the body 12). The cutting edge is relieved by having the upper surface 32 of the insert 26 inclined to the front face 26 by an angle of about 700. The inside surfaces 34 of the S insets ae spaced apat by 6,5 mm (or put another inserts 24 are way are tangential to a circle centred on the axis of the bit 10 of 6,5 mm diameter)- The drill bit 10 is used with flushing water.

Accordingly it has a conduit 36 through the shank 14 15 which extends upwardly to three upwardly and radially inclined passages (not shown) that lead respectively to flushing openings 38 through the bases of the S. grooves 16.

We have found that the drill bit 10 is especially useful for drilling anchor holes in sandstone in the :rooves of drives of coal mines. The drill bit 10 is able, we have found, to drill a greater number of metres through the sandstone than has been found possible with known drill bits, especially those known .drill bits mentioned above.

Page asanasdso I-tnf AUS1 The invention is not limited to the precise constructional details hereinbefore described and illustrated in the drawings. For example there may be four or more lugs to hold respectively four or more cutting inserts. Naturally the number of lugs depends upon the diameter of the body. The various angles and dimensions mentioned above may vary as described.

Other hard metal inserts may be used. The rock drill may be used for drilling in other rock and for other purposes to those described above. The attachment for connection to the drill steel end may comprise internal threading, external or internal taper connections or any other convenient connection

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Claims (8)

1. 2. A rock drill bit as claimed in claim 1 whefein hard metal inserts are received by the lugs and are 10 attached thereto. 3 A rock drill bit as claimed in claim 2 wherein the hard metal inserts are attached to the lugs by brazing.
2. 4. A rock drill bit as claimed in claim 2 or 3 Swherein the lugs are provided with pockets into which 15 the hard metal inserts are respectively received and i. .attached.- A rock drill bit as claimed in claim 2, 3 or 4 S: wherein the inserts are backwardly raked by a small angle. A rock drill bit as, claimed in laim 5 wheren the s mall angle s AnatalingglRO m Dnl 1,- A I 2. t
3. 7. A rock drill bit as claimed in any one of claims 2 to 6 wherein the cutting edge of each insert has a main part which extends radially away from the body.
4. 8. A rock drill bit as claimed in claim 7 wherein the main part of the cutting edge is straight.
5. 9. A rock drill bit as claimed in claim 7 or 8 wherein the cutting edge further comprises an end part which extends from the end of the main part towards the body.
6. 10. A rock drill bit as claimed in claim 9 wherein the end part of the cutting edge is straight. 1ii. A rock drill bit substantially as hereinbefore I described with reference to and as illustrated in the accompanying drawings. ,-Ti a iia\ TRGCS 5' nan11'an* Page J d t -9-
7. 12. The steps, features, compositions and compounds referred to or indicated in the spacificatiOn and/or claims of this application, individually or collectively, and any and all combinations or any two or more of said steps or features. Dated this 26th day of November,
8. 1997. SANDERCOCK COWIE pIATENT ATTORNEYS FOR UNIROC AB I j Q 671i~'