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Publication numberUS474297 A
Publication typeGrant
Publication dateMay 3, 1892
Filing dateNov 26, 1891
Publication numberUS 474297 A, US 474297A, US-A-474297, US474297 A, US474297A
InventorsCarl Hoffmann
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Carl hoffmann
US 474297 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

(No Mod-e1.)


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SPECIFICATION forming part of Letters Patent No. 474,297, dated May 3, 1892.

Application fiied'novemterzt, 1891. serai No. 413,119- (No modem T0 LZ-Z whom, t may concern:

Be it known that I, CARL HOFFMANN, a subject of the King of Irussia, residing at Charlottenburg, Prussia, have invented certain new and useful Improvements in Rock-Drills; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to rock-drills; and it consiste of certain novel features hereinafter described and claimed.

In the accompanying drawings, in which similar letters refer to similar parts throughout the views, Figure l represents a vertical section of one form of drill-head constructed according to my invention, and Fig. lfL represents a view of the lower end of the same looking upward. Figs. 2, 3, 4, and 5 represent modiiications of the device shown in Fig. l; and Figs. 2f, 3, 4E, and 5a represent views of the bottom of the said modifications, respectively, looking upward.

In Figs. l to 5 illustrations are given of various methods of manufacturing drill-heads to carry out the process above described.

In the device shown in Fig. l, R represents any long iron or steel tube, which at its upper end is attached to a drilling machine or mandrel. The steel piece St, Fig, l, attached to the bottom part of the tube R, is provided at the bottom with a semicircular groove intended for the reception of one or more chilledsteel, cast-iron, or other solidmetal balls, preferably magnetic, which, when the borerod is turned, are rolled under pressure over the bottom of the bore-hole. At the center of the steel piece St there is a hole 7i, through which water iiows between the boring-balls. In order to prevent the boring-balls'from falling down from the bore-rod when the borer is Withdrawn or when the same shouldhappen to meet cavities in the rock, both parts are kept together in a permanent connection by magnetic attraction. Thisis shown in Figs. l to 4f.

In Fig. l, Strepresent apermanent magnet.

In Fig. 2 the bottom surface of the borerod consists of the two concentric poles N and S of apot-shaped electro-magnet. The annuter of the bore-hole leaves a core standing.

Fig. 5 shows an enlarging-drill as used, for instance, in bore-holes which, owing to the unevenness of the rock, were not run straight.

The boring itself is done in the following manner: The bore-rod is firmly pressed upon the globes or balls and made to turn. The balls, rolling around in the groove, follow the rotary motion of the axis, and, as they always touch the rock at but few points, upon such points a strong pressure is exerted and the rock at such points is crushed without the occurrence of a sliding friction between it and the balls, which might subject the balls to considerable wear and tear. The iinely-pulverized rock is removed by the jet of water introduced through the hole 71,. The rock at the center of the bore-hole not directly struck by the balls cornes oft in small pieces, owing to the lateral pressure exerted'by the balls, which particles fall below the balls and are here likewise crushed by them. It is, however, not necessary to make the boring-balls and the boring-heads of magnetic or, as the case may be, of magnetizable material. One may just as well make use of bronze or any other alloys or metals sufliciently capable of resistance and of any special stopping or catching apparatus which would prevent the balls from falling out of the end of the drillhead when the latter is withdrawn from the bore-hole or the pressure on the balls is removed.

In the inode of arrangement, as illustrated by Fig. 5, for instance, the middle shoulder enlarged toward the bottom of thebore-head fully suffices to hold the balls and to draw them out by means of the boring-rod without additionally using the magnetic attractive force. In a similar manner one could proceed in case of the remaining forms of construction.


Having thus described my invention, what I claim, and desire to secure by Letters Patent of the United States, is-

l. In a rook-drill, the combination, With a rotary drill-head having an annular groove in the front end thereof, of a plurality of hardmetal balls suitably held in but protruding from and free to roll in said annular groove, substantially as described. i

2. In a rook-drill, the combination, With a rotating drill-head having a conduit for Water therein and having an annular groove in the front end thereof, of a plurality of hard-metal balls free to roll in said groove, but suitably held therein and protruding therefrom, substantially as described.

3. In a roek-drill, the combination, with a magnetized rotating drill-head having an annular groove in the front end thereof, of a plu- CARL HOFFMANN.

Vitnesses: n


Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2626128 *Sep 24, 1951Jan 20, 1953Reed Roller Bit CoDrill bit
US2687875 *Nov 20, 1951Aug 31, 1954Hughes Tool CoWell drill
US2721726 *Aug 10, 1949Oct 25, 1955Johnson Howard LDrill head
US2982367 *Jul 30, 1956May 2, 1961Reed Roller Bit CoDetritus trap for well drill
US3078934 *May 13, 1959Feb 26, 1963Jersey Prod Res CoDrilling of earth formations by extrusion
US3130801 *Feb 9, 1961Apr 28, 1964Reed Roller Bit CoDrill bit having inserts forming a reamer
US3186500 *Feb 9, 1961Jun 1, 1965Reed Roller Bit CoGage maintaining arrangement for drill bit cutters
US4125167 *Jun 6, 1977Nov 14, 1978Smith International, Inc.Big hole bit
US4226285 *Feb 12, 1979Oct 7, 1980Moseley Jr Meekie DMagnetic junk retriever
Cooperative ClassificationE21B31/06