Grinding machine

Abstract

A grinding machine (3) for grinding drill bits (6), having a grinding unit (9) which includes a motor unit (10) and a spindle (11) which is driven by the motor and which carries a grinding wheel (12) for rotation by the spindle (11) and for grinding a button bit (8) in the drill bit (6), wherein the grinding unit (9) together with the grinding wheel (12) is adapted to swing forwards and backwards about a vertical shaft which coincides generally with the geometric axis of the button bit (8).

Description

The present invention relates to a grinding machine, and more specifically to a back-carried grinding machine for grinding or honing drill bits.

Drill bits are subjected to a great deal of wear and must be well-honed in order to drill rock effectively. Bits that are poorly sharpened do not only impair the efficacy of rock drilling, but also cause the drill string and the drilling rig to be subjected to a great deal of stress and strain and also wear.

Consequently, there is a great need for grinding, honing, drill bits at regular intervals. There exist to this end special semi-automatic grinding machines for grinding the button bits and also for grinding down the steel included in the drill bit, at the same time. Transportable grinding machines that enable the button bit to be ground at the site where drilling takes place are also available commercially. These machines may be semi-automatic machines or manually operated machines and are exclusively of the type that use grinding cups.

Accordingly, an object of the present invention is to provide a grinding machine of the aforesaid kind which can function at least semi-automatically and which can be used to recreate both a spherical and ballistic button bit and which can be mounted on a drilling rig or on a separate readily transportable arrangement.

This object is achieved with a button bit grinding machine comprising a grinding unit that includes a motor unit which drives a spindle to which a grinding wheel is fitted for rotation by said spindle and therewith sharpen or hone a button bit in the drill bit crown. According to the invention, the grinding unit together with the grinding wheel are adapted to be swung forwards and backwards about a vertical shaft that coincides generally with the geometric axis of the button bit.

The invention will now be described in more detail with reference to a non-limiting exemplifying embodiment thereof and also with reference to the accompanying drawings, in which

FIG. 1 is a side view showing the grinding machine in an adjusted setting in which the grinding wheel is centred around a button bit on a drill bit crown;

FIG. 2 illustrates a grinding unit in a grinding intermediate position, although said unit is shown distanced from the drill bit crown for the sake of clarity;

FIG. 3 illustrates the grinding unit in a first turning position, although corresponding to the view of FIG. 2 in other respects; and

FIG. 4 illustrates the grinding unit in a second turning position.

The grinding machine illustrated in the accompanying drawings is intended to be mounted on a drilling rig and includes a carrier frame 1 intended for fastening to a drilling rig, not shown. The frame 1 has an upper, outwardly projecting carrier arm 2 which carries the grinding arrangement 3 of said grinding machine via a bracket structure 4 that can be displaced in the horizontal plane. The grinding arrangement 3 can be raised and lowered in the bracket structure 4, i.e. can be displaced in the vertical plane. The frame 1 also includes a holder arm 5 which is located beneath the grinding arrangement and adapted to hold firmly a drill bit crown 6. The drill bit crown 6 can be readily fitted to and locked in the holder arm 5, with the aid of a locking lever 7. The crown 6 includes a number of button bits 8. The number of button bits 8 included, and their size and placement on the crown 6, may vary. The crown may also be locked obliquely in the holder arm 5, to enable correct grinding of the peripheral button bits 8a in the drill bit crown 6.

The grinding arrangement 3 includes a grinding unit 9 which, in turn, includes a motor 10, a spindle 11 and a grinding wheel 12 carried on the end of the spindle 11. The grinding unit 9 is fitted so that the spindle will slope slightly in relation to the horizontal plane, wherein the grinding wheel 12 rotates about said spindle. The grinding wheel 12 is of a known type and is provided with a diamond coating and may be designed for grinding spherical or ballistic button bits. The grinding unit 9 is carried by an arm 13 on the grinding arrangement and can be swung about a generally vertical shaft 14 with the aid of a pivot cylinder 15 which is adapted to swing the grinding unit 9 forwards and backwards between the positions shown in FIGS. 3 and 4, i.e. with a pendulum movement of about 180°, preferably slightly greater than 180°. The shaft 14 is arranged so that an extension of the shaft will pass through the centre of the grinding wheel 12 and so that as the grinding unit 9 swings forwards and backwards, the grinding wheel will move about a point which corresponds to the top of one of the button bits 8 when the grinding arrangement 3 is correctly adjusted. The geometric axis about which the grinding unit 9 moves forwards and backwards is a generally vertical axis which coincides with the geometric centre axis of the button bit 8 when the grinding arrangement 3 has been correctly adjusted in relation to the button bit 8. The grinding unit 9 thus moves forwards and backwards in a pendulum movement in the horizontal plane, so as to be able to grind or hone a button bit 8 that extends generally vertically on the grinding occasion concerned.

Adjustment to the setting of the grinding arrangement 3 is achieved with the aid of a centring body 16 which can be placed and centred over a button bit 8, as shown in FIG. 1. In this position, the centring body is located in the extension of the shaft 14 and on the geometric axis about which the grinding unit 9 is intended to swing. When the grinding arrangement 3 has been centred over a button bit in this way, the arrangement 3 is locked against movement in the horizontal plane and can then be solely raised and lowered. Subsequent to being centred, the grinding arrangement 3 must first be raised so that the centring body 16 can be swung to one side, to the position shown in FIGS. 2-4, and so that the grinding disc can be lowered down onto the drill bit crown 6 and against the button bit 8 for grinding said bit. Locking of the grinding arrangement in the horizontal plane is the subject of a separate patent application filed at the same time as the instant application.

The grinding arrangement 3 includes an operating lever 17 with which said arrangement can be moved to the correct position in the horizontal plane for adjusting the setting of the arrangement with the aid of the centring cup 16. The arrangement 3 may also include in connection with the lever 17 a control device 18 with which movement of said arrangement 3 in the horizontal plane can be locked/released. The lever is also used for raising and lowering the grinding arrangement. There may also be provided in connection with the lever 17 activating means with which the grinding arrangement 3 can be activated, i.e. with which the motor 10 can be activated for rotation of the grinding wheel 12, and also activation of the pivot cylinder 15 for causing pendulum movement of the grinding unit 9. This activation may also take place automatically when the arrangement 3 has been brought to its correct position.

The grinding unit 9 is thus able to achieve automatic grinding of the button bits 8 in a drill bit crown 6, subsequent to the grinding unit 9 having been adjusted manually by the operator in relation to the bit to be ground. The cylinder 15 is adapted to pivot the grinding unit 9 forwards and backwards about the centre of the button bit 8 concerned, for instance for a pre-set period of the time normally taken to grind or hone a button bit. The pendulum movement of the grinding unit will preferably cover at least 180°, preferably slightly more than 180°, in order for the bit to be ground correctly.

The grinding wheels 12 used in the grinding machine according to the invention are of the same type as those used in the grinding machines mentioned in the introduction for workshop use, and comprise diamond-coated grinding wheels that are available in both spherical and ballistic designs, said grinding wheels being chosen in accordance with the type of button bit to be ground. These wheels have the form of a pulley or roller that includes two ends which have a larger diameter than the intermediate part and which have a spherical or ballistic recess to give the button bit to be ground the desired shape.

The inventive grinding machine is, as before mentioned, suitably mounted on a drilling rig and is suitably supplied with power, electrical, pneumatic or hydraulic power, and water from the drilling rig. Alternatively, the grinding machine may, of course, be mounted on an own transportable device, for instance a wagon or carriage, although this will then require an additional electrical, pneumatic or hydraulic supply means for driving the grinding machine. The inventive grinding machine may also, of course, be used conveniently in a permanent structure in a workshop environment.

Claims

1-9. (canceled)

10. A grinding machine (3) for grinding drill bits (6), comprising a grinding unit (9) which includes a motor unit (10) and a spindle (11) which is driven by said motor and which carries a grinding wheel (12) for rotation by the spindle (11) and for grinding a button bit (8) in the drill bit (6), characterised in that the grinding unit (9) together with the grinding wheel (12) is adapted to swing forwards and backwards covering an angle of about 180° about a vertical shaft which coincides generally with the geometric axis of the button bit (8).

11. A grinding machine according to claim 10, characterised in that that the grinding unit (9) is adapted to swing forwards and backwards in a plane close to the horizontal plane.

12. A grinding machine according to claim 10, characterised in that the grinding unit (9) can be moved in the horizontal plane so as to enable said unit to be centred over a button bit (8) in a drill bit (6).

13. A grinding machine according to claim 12, characterised in that the grinding machine includes a centring cup (16) for centring the grinding unit (9) over the button bit (8) in said drill bit.

14. A grinding machine according to claim 13, characterised in that subsequent to centring of the grinding unit (9), said unit can be locked in the horizontal plane so as to be moveable solely in the vertical plane.

15. A grinding machine according to claim 10, characterized in that the grinding machine is mounted on a drilling rig.

16. A grinding machine according to claim 10, characterised in that the grinding machine is mounted for transportation on a wagon or carriage.

17. A grinding machine according to claim 10, characterised in that the grinding machine is fixedly mounted in a workshop environment.

18. A grinding machine according to claim 11, characterised in the grinding unit (9) can be moved in the horizontal plane so as to enable said unit to be centred over a button bit (8) in a drill bit (6).