Rock drill

Abstract

A rock drill (1) with a helical thread (2) and a hard material insert (3, 9) in the drilling head, form a radically outer guiding surface (6), with the guiding edge (6) forming an acute angle (&agr;) with the direction of the tool axis (A).

Description

FIELD OF INVENTION

[0001] The invention relates to a rock drill for abrasively working rock or a similar hard material by a movement, which is at least a partially rotating and striking movement with respect to the axis of the drill, with a helical thread and a hard material insert in the drill head.

BACKGROUND INFORMATION AND PRIOR ART

[0002] Conventional rock drills have a hard material insert, formed as a hard material plate or as a solid hard material drilling head, which is fastened to the tool head, from which a shaft with a helical thread extends, and finally ends in a plug-in or chuck region for accommodation in a tool device.

[0003] For guiding the drill radially in the borehole, for decreasing the vibrations and for producing an approximately circular borehole, rock drills with diameters of about 5 mm have main cutting edges as well as subsidiary cutting edges, set at an angle to the main cutting edges. Generally, the main cutting edges as well as the subsidiary cutting edges have blunt guiding surfaces, which are disposed at the radial periphery and guide the tool head axially, in that they slide past the inner surface of the borehole. Such guiding surfaces, which cause friction, are dimensioned as small as possible.

[0004] According to the U.S. Pat. No. 5,553,682, a rock drill has a solid hard material head with two main cutting edges and two subsidiary cutting edges, the peripheral blunt guiding surfaces of which, extending in each case parallel to the axis of the drill, change over into quadruple helical threads. The guiding sector region in the cross sectional plane, which is only small and is guided with the guiding surface of each cutting edge, is a disadvantage.

[0005] According to the DE 602663, a twist drill, for working materials by cutting, has a tool head with two hard material plates, which form the main cutting edges, and the peripheral, blunt guiding surfaces of which change over into the quadruple helical threads. Moreover, the individual hard material plates, and the guiding surfaces of which continue the helical threads smoothly, are disposed at an angle to the drill axis and are fastened to the tool head by, in each case, one of the side surfaces, and facing the drilling direction. As a result, the side surface is integrated in the end region of the helical grooves, which is highly stressed by the cutting operation. An axially striking stress exerted on such a hard material insert would stress the attachment of this insert to the tool head, resulting in failure after a short time.

SUMMARY OF THE INVENTION

[0006] It is an object of the invention to provide a rock drill with a large guiding sector region in the cross sectional plane.

[0007] Essentially, in the case of a rock drill with a helical thread and a hard material insert, the fastening of which to the rest of the tool is designed for an at least partially rotating and striking stress, at least one guiding surface of a hard material insert is disposed at an acute angle to the direction of the tool axis.

[0008] By these means, the guiding sector region in the cross sectional plane is enlarged approximately in proportion to the sine of the angle without increasing the friction-producing region of the guiding surface.

[0009] The hard material insert is fastened only over the surfaces of the insert, which face opposite to the drilling direction or at right angles thereto. With that, the fastening is exclusively for compression and shear stresses and will not fail due to impact stresses.

[0010] Advantageously, the guiding surface smoothly continues the helical threads, as a result of which the resistance to conveying the excavated material in the helical groove is reduced.

[0011] In a first advantageous embodiment, the rock drill has a solid hard material head, which is fastened at its surface facing opposite to the drilling direction or oriented perpendicularly thereto. The guiding surface edge of at least one hard material insert forms an acute angle with the direction of the tool axis.

[0012] In a second advantageous embodiment, the rock drill has a hard material plate, which is fastened with its surfaces, which face opposite the drilling direction or oriented perpendicularly thereto. The guiding surface of at least one hard material insert forms an acute angle with the direction of the tool axis.

[0013] Advantageously, a hard material plate is fastened only along a surface, facing opposite to the drilling direction, to the remainder of the tool. Furthermore, preferably, a free surface facing in the drilling direction is integrated smoothly into the highly abrasively stressed end region of the helical grooves.

[0014] With the inventive solution, a large, hard material-faced, wear-resistant guiding sector can be realized in the cross sectional plane with a small volume of hard material.

[0015] Due to the inclined guiding surface, the solid material head no longer is completely prismatic. Advantageously, it is produced by injection molding.

BRIEF DESCRIPTION ON THE DRAWINGS

[0016] The invention is explained in greater detail with respect to an advantageous example in:

[0017] FIG. 1 is a axially extending side view of a drilling head end of a first rock drill; and

[0018] FIG. 2 is a axially extending side view of a drilling head end of a second rock drill.

DETAIL DESCRIPTION OF THE INVENTION

[0019] According to FIG. 1, a rock drill 1, with a quadruple helical thread 2, has a solid hard material head which has main cutting edges 4 and is mounted on the drilling head end of an axially extending shaft on which the helical threads 2 are formed. The peripherally extending guiding surface 6 of a main cutting edge 4 forms an acute angle &agr;, with the direction of the shaft A, as a result of which, with respect to a parallel orientation, an enlargement of a guiding sector region 7 is achieved in the cross sectional plane. The solid hard material head 3 is fastened with its rear end surface 8, facing opposite to the drilling direction, to the remainder of the tool. The guiding surface 6 smoothly continues the helical thread 2.

[0020] In FIG. 2, a double helical thread 2 has two hard material plates 9, which form main cutting edges 4 of the drilling head and are disposed radially about a central cutting member 10. The radially outer peripheral guiding surface 6 of a main cutting edge 4 forms an acute angle &agr; with the direction of the tool axis A and smoothly continues the helical thread 2. With its end surface 8, facing opposite to the drilling direction, the hard plate 9 is fastened to the drilling head end of the tool. As a result, the free cutting surfaces 11 leading in the drilling direction are integrated smoothly into the highly abrasively stressed drilling end region of the helical grooves.

Claims

1. A rock drill having a shaft with an axis (A), said shaft having a drilling head end with at least one helical thread (2) extending from said drilling head end, at least one hard material insert (3, 9) mounted on said drilling head end and designed for rotating and axially striking stresses, said insert (3, 9) having at least one guiding surface (6) at a radially outer peripheral surface of said drilling head end and said guiding surface (6) forms an acute angle with said shaft axis.

2. A rock drill, as set forth in claim 1, wherein said hard material insert (3, 9) is fastened only on a surface (8) facing one of opposite to a drilling direction of said rock drill and opposite to and extending perpendicularly to the drilling direction.

3. A rock drill, a set forth in claim 2, wherein said guiding surface (6) smoothly continues said helical thread (2).

4. A rock drill, as set forth in claim 3, wherein said hard material insert (3, 9) is formed as a hard material head (3) with a drilling end facing in the drilling direction and a trailing end secured to said shaft.

5. A rock drill, as set forth in claim 3, wherein said hard material insert is formed as a hard material plate (9).

6. A rock drill, as set forth in claim 5, wherein said hard material plate (9) is fastening only to said drilling head end on a surface (8) facing opposite to the drilling direction.

7. A rock drill, as set forth in claim 6, wherein said hard material plate (9) has a cutting surface (11) facing in the drilling direction and forming a smooth transition with an end surface of said helical thread at said drilling head end and facing in the drilling direction.