ZA200608287B - Rock drill and steel connection - Google Patents

Description

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ROCK DRILL BIT AND STEEL CONNECTION

FIELD OF THE INVENTION

The invention relates to the connection of aa bit to the end of a drill steel for drilling holes in rock.

BACKGROUND TO THE INVENTION

The steels referred to are normally used with percussion roc k drills in underground mining operations. They are hexagonal in cross-section and include an axial flushing bore. A drill engages the rear end of a steesl to impart impact and rotation. The forward, working emd receives a bit to peretrate the rock.

Conventionally, the forward end of such a dril I steel has a frusto-con&cal shape.

The shaped end engages into a correspondin gly tapered socket in th e rear of a bit. The steel is driven or forced into the bit. This provides a frictional engagement between the components which is not always satisfa ctory. The engagement is also around the circumference of the steel end and can, on the other hand, make removal of worn bits very difficult.

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OBJECT OF THE INVENTION

It is an object of the current invention to provide a n<ovel and effective connection between a bit and a drill steel.

SUMMARY OF THE INVENTION

In accordance with one aspect this invention there is provided a rock drill bit comprising a forward cutting end and a rear end having a drill steel socket with a spline provided therein.

The invention further provides for the spline to be a weedge with a pair of opposite inwardly tapered longitudinal flats; and for the sockzet to have inwardly tapered walls facing the flats. The socket walls facing the flats are also provided as flat surfaces.

Further features of the invention provide for the spline to b e located axially in the socket; and to extend across the socket.

In accordance with another aspect of this invention there is provided a drill steel with a forward end having an axial slot to engage a spline in =a drill bit as defined above.

The invention further provides for the steel to have a hexagonal cross-section and the slot to extend parallel to a pa ir of opposite sides.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will become more apparent frorm the following description, by way of example only, of the accompanying drawin gs in which

Figure 1 shows a schematic side cross-sectional view of a drill bit and steel; and

Figure 2 shows the rear end view of the bit and forward end view of the steel.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, a drill bit (1) and a drill steel (2) in accordance with this invention are shown. The bit (1) has a forward cutting end (3). A socket (4) is formed longitudinally in the rear end (5). The bit (1) is to be connected to the forward end (6) of the steel (2). Both components (1) and (2) have an axial flushing passage (7). When connected, during use, the pressurized wowking fluid (air or water) that drives a drill to which the steel (2) is fitted will taravel through the passage (7) to the bottom of the drill hole.

A spline (8) is formed axially within and across the width of the socket (4). The spline is provided as a wedge (8) with a pair of opposite inwardly tapered flats (9). The socket (4) has inwardly tapered opposite walls (10) facing the flats (9).

The tapered portions of the walls provide flat surfaces (10) as shown.

An axial slot (11) is provided in the forward end (6) of the steel (2). The slot (11) bisects the portion of the steel (2) adjacent the forward end (6) to co-operate with the spline (8). More specifically the space across the slot (11), betwee=n its two flat sides (13), is a close fit over the thick outer edge of the wedge (8).

In this embodiment, the steel (2) has the often conventional hexagonal cr-oss- section. The slot (11) extends parallel to a pair of opposite sides (12). The

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AID T028Y socket (4) is also provided with a hexagonal shape to receive the forward end (6) of the steel (2). It can be= seen that the flat surfaces (10) correspond in their position to opposite sides (122) of the steel (2).

The bit (1) will be pressed omto the end (6) of the steel (2) with the slot (11) and the wedge (8) aligned. The relative movement of the components (1) and (2) into overlapping engagemerst is accompanied by a closi ng of the slot (11) from its open end onto the wedge (8). This is due to the inward biasing effect of the surfaces (10) on the steel sicles (12) respectively. The sides (13) of the slot (11) are pressed against the flats (9) of the wedge (8).

The connection provides a positive drive for rotation of the bit (1) through the overlapping engagement between the slot (11) and wedge (8). The positive drive is also supported through the angular socket (4) on the steel (2). The frictional engagement is corcentrated on the four pairs of longitudinal planar surfaces (10), (12), (13) and (9), rather than around t he circumference of a tapered steel end.

Machining the end (6) of a steel (2) with a slot (11) rather than a taper is easier and cheaper. The socket (4) can be formed with a pair of opposite longitudinal grooves (not shown) and the wedge (8) as an insert. The wedge (8) can then be pressed into position with its hin sides secured in the gro oves.

A suitably skilled person willl appreciate that a number of variations can be made to the described embodiments without departing from the scope of the present invention.

Claims (10)

1. A rock drill bit comprising a forward cuttirmg end and a rear end having a drill steel socket with a spline provided thezrein.

2. A bit as claimed in claim 1 in which the spline is a wedge with a pair of opposite inwardly tapered longitudinal flats.

3. A bit as claimed in claim 2 in which the somcket has inwardly tapere=d walls facing the flats.

4. A bit as claimed in claim 3 in which the ssocket walls facing the fl ats are provided as flat surfaces.

5. A bit as claimed in any of claims 1 to 4 in which the spline is located axially in the socket.

6. A bit as claimed in claim 5 in which the sgoline extends across the socket.

7. A drill steel with a forward end having are axial slot to engage a spline in a drill bit as claimed in any of claims 1 to 6.

8. A steel as claimed in claim 7 having a heexagonal cross-section and the slot extending parallel to a pair of opposite sides.

9. A rock drill bit substantially as herein described with reference to the drawings.

10. A drill steel substantially as herein described with reference to the drawings.

CL 7 EATS Et ¥- I DATED THIS 3%° DAY OF OCTOBER 2006 (hy DE BEER FOR THE APPLICANT