CA1090138A

CA1090138A - Grinding fixture

Info

Publication number: CA1090138A
Application number: CA296,551A
Authority: CA
Inventors: Osten Karlsson
Original assignee: Fagersta AB
Current assignee: Fagersta AB
Priority date: 1977-02-11
Filing date: 1978-02-09
Publication date: 1980-11-25
Also published as: ZA78762B; SE416115B; FR2380104A1; AU515994B2; DE2804003A1; IE46404B1; AT357059B; ATA73778A; GB1591435A; SE7701534L; IE780301L; BR7800820A; JPS53104493A; AU3292478A; JPS6117619B2; FR2380104B3

Abstract

ABSTRACT OF THE DISCLOSURE

A grinding fixture for grinding the buttons in rock drilling button bits comprising a means in which the bit is intended to be anchored during grinding, a horizontally arranged disk rotatably driven about a vertical axis through the center of the disk on which the means rests, and an arm extending over the disk for centering a button which is to be ground so that the button will be concentric with the rotational axis of the disk, the arm being arranged displaceable along, and swingable about a vertical column, and a cup-shaped recess at the end of the arm, the shape of the recess substantially corre-sponding to the shape of the button.

Description

109013~

The present invention relates to a grinding fixture ~or grinding the cutting buttons in rock drilling button bits.
In rock drilling technology rock drilling button bits are taking up an ever-increasing place, due to their greater drilling capacity between grindings in comparison with bits having chisel-edge type cutting teeth.
Not in the least with drifting and tunnelling has this meant a very large advance. In drilling holes of smaller diameter, the use of button bits is increasing as well. Outton bits functioned as disposable products to begin with, and after its becoming worn the bit was thrown away. Today however, attempts are being made to get greater drill sinking distances from button bits by grinding or dressing the buttons after they have become worn, so that they regain their hemi-spherical form~ which is their ideal shape. - -Up to now however~ grinding the buttons i9 still a very primitive craft where the button bit is kept stationary and a small high-speed grinding ~heel works with point contact on the buttons. Such a procedure can never give the button its exact hemi-spherical shape. Since the buttons in a drill bit sit very close together, it is also very difficult to get at the right places with the grinding wheel. The work takes a long time and the result will be far from a spherical surface. Only grinding wheels with very s~all diameters can be used~ which means that ~he wheels are -;~
rapidly worn down. The whole procedure is a very expensive work process.
The object of the invention is to provide an apparatus~ by the aid of which an increase in the life of rock drilling button bits is enabled ~;~
by repeated grindings without deterioration of the drilling function. ~t ;-the same time, the work of grinding can be made very efficient. The funda-mental idea i9 that grinding is best carried out if the button ratates while movement of the grinding machine is kept to a minimum. For thi~ to be possiblie it must also be possible to center the button in question on a rotating grinding fixture in a simple way.

The advantages mentioned are achieved by the grinding Fixture being given the cheracterizing features recited in the following claims.

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: . :

109t~3~
In on~ aspect of the present invention, there is provided a grinding fixture for grinding the buttons in rock drilling button bits, characterized by a container filled with sandy material, in which the bit is intended to be embedded and anchored during grinding, by a horizontally arranged disk rotatably driven about a vertical axis through the center of the disk, on which the container with the sandy material rests:
and by an arm extending over the disk, for centering a button which is to be ground, so that the button will be concentric with the rotational axis of the disk.
In a further aspect of the present invention, there is provided a grinding fixture for grinding the buttons in rock drilling button bits comprising a means in which the bit is intended to be anchored during grinding, a horizontally arranged disk rotatably driven about a vertical axis through the center of the disk on which said means rests, and an arm extending over the disk for centering a button which is to be ground so that the button will be concentric with the rotational axis of the disk, said arm being arranged displaceable along, and swingable about a vertical column, and a cup-shaped recess at the end of the arm, the shape of the recess substantially corresponding to the shape of the button.

C -la-: , :

109~13t~

A pref~rred embodiment of the invention will now be described while referring to the attached drawings, where Fig 1 sho~s a per~pective view of the construction of the fixture, an~ Fig Z sho~s a grinding wheel and a rock drilling button bit during grinding.
As shown in Fig 1, a disk 1 is mounted for rotation on a base frame Z, and can be driven at an infinitely variable speed by the motor arrange-ment 3 via a belt 10. Attached to, and upstanding from, the frame there is a column 5, on which there is glidably mounted a centering arm 6. At the same distance from the chief axis of the column as this axis i9 from the center of the disk, a locating cup 7 has its center, the cup being attached to the centering arm.
On the disk there i9 placed a container 4, filled with a suitable sandy material, e.g. steel shot or grit, such as particles of white cast iron~ granulated heat-treated malleable castings, granulated steel or cut steel wire. The bit is pressed into the shot 90 that the button 12 to be dressed i8 approximately over the center of the disk, and with the principal axis of the button substantially perpendicular to the surface of the disk. The cup is then moved down over the button and the button centered under it, which is facilited by moving the container. The position of the button i8 thu9 fixed, and the centering arm can be moved out of the way. The disk can now be brought intd ibtation by means of the foot pedal 9~ whereat the button also rotates concentrically with the disk,-and grinding can be carried out.
A cup-shaped grinding wheel 11 with a relative large diameter is used for ginding, as is apparent from Fig 2. The button 12 will be easily accessible to such a wheel, and since its circumference i8 relatively large, each grinding wheel will suffice for many drill bits of the kind in question.
The work of qrinding i9 easy to do, since the grinding machine only needs to be moved slightly for each button.
Although only one embodiment has been described and illustrated by way of an example, the invention is naturally not limited to this embodiment, _ z _ - , , 109~13~

but can be modified within the purview af the inventive concept. For example, mechanical adjusting means can be utilized for positioning the cup and button. It is also possible to arrange for the grinding machine to have its motion mechanically controlled.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A grinding fixture for grinding the buttons in rock drilling button bits comprising a means in which the bit is intended to be anchored during grinding, a horizontally arranged disk rotatably driven about a vertical axis through the center of the disk on which said means rests, and an arm extending over the disk for centering a button which is to be ground so that the button will be concentric with the rotational axis of the disk, said arm being arranged displaceable along, and swingable about a vertical column, and a cup-shaped recess at the end of the arm, the shape of the recess substantially corresponding to the shape of the button.

2. A grinding fixture as claimed in claim 1 wherein said anchoring means comprises a container filled with sandy material the uppermost surface of the rotatable disk has large frictional resistance.

3. A grinding fixture as claimed in claims 1 or 2 wherein the rotatable disk is coupled to a driving unit, the speed of which is infinitely variable.