WO2018236268A1

WO2018236268A1 - Grinding machine with hydraulic motors.

Info

Publication number: WO2018236268A1
Application number: PCT/SE2018/050605
Authority: WO
Inventors: Frederick WINROTH; Kaj Johansson
Original assignee: Winroth Industri Ab; Torstorps Mekaniska
Priority date: 2017-06-21
Filing date: 2018-06-11
Publication date: 2018-12-27
Also published as: EP3641984A1; EP3641984A4; CA3065227A1; SE542627C2; SE1750796A1

Abstract

The present disclosure relates to a grinding machine (9) for grinding rock drill bit buttons, the machine comprising a grinding arrangement with rotatable grinding spindle (25), a free end of which is configured to drive and to replaceably carry a grinding cup (5). The grinding spindle (25) is configured to rotate about a spindle axis (A) by a spindle motor (23), the grinding spindle further being configured to be rotated about a gyration axis (B) by a gyration motor (29), the gyration axis being inclined relative to the spindle axis. The spindle motor (23) and the gyration motor (23) may be hydraulic motors, which allows both those functions to be driven by for instance a main hydraulic circuit of a drilling rig.

Description

GRINDING MACHINE

Field of the invention

The present disclosure relates to a grinding machine for grinding rock drill bit buttons, the machine comprising a rotatable grinding spindle, a free end of which is configured to drive and to replaceably carry a grinding cup. The grinding spindle is driven by a spindle motor and rotates about a first axis, and the grinding spindle is further configured to gyrate around a second axis, being at an angle with the first axis, driven by a gyration motor. Technical background

Such a grinding machine is disclosed for instance in WO-2016/074067-A1 and is used to maintain the efficiency of a drill bit by frequently sharpening its drill bit buttons. A general problem with grinding machines of this type is how to provide efficient and reliable operation at low cost. Summary of the invention

One object of the present disclosure is therefore to provide a more reliable grinding machine. This object is achieved by a grinding machine as defined in claim 1 . More specifically, in a grinding machine of the initially mentioned kind, the spindle motor as well as the gyration motor are hydraulic motors. This means that both the spindle rotation and the gyrating motion can be obtained with hydraulic power obtained from e.g. a drilling rig. Such a solution is very reliable even under difficult working conditions such as cold and humid conditions where for instance an electric motor with associated control electronics can be unreliable.

A gearbox may be used to connect the gyration motor to an angle displacement bracket carrying the grinding spindle. This means that a hydraulic motor with relatively high speed can be used without providing an unnecessary fast gyrating motion.

The spindle motor and the gyration motor may be connected to a common hydraulic circuit, thereby facilitating connecting the grinding machine e.g. to a drilling rig hydraulic circuit. The common hydraulic circuit may therefore comprise a drilling rig connector. The grinding machine may have a grinding arrangement that is linearly displaceable by means of a hydraulic cylinder. This makes it possible to provide also a linear movement of a grinding cup with hydraulic pressure obtained e.g. from a drilling rig.

A grinding machine may comprise a hydraulic connection configured to connect at least one of the spindle motor and the gyration motor to a drilling rig hydraulic circuit, wherein the hydraulic connection comprises a constriction lowering the hydraulic pressure to below 50 bar. This eliminates the risk that a hydraulic motor in the grinding machine is driven at an excessive speed due to operator error, even if the hydraulic pressure of the drilling rig is very high. The spindle may be connected to the gyration motor via a spindle bracket, wherein the grinding spindle is configured to be slideably connected to the spindle bracket. This allows the grinding machine to operate with grinding cups of different sizes. Typically, the spindle bracket may be L-shaped, the spindle being connected to a first leg thereof, and a second leg thereof being connected to an angle displacement bracket

There may be provided a guide, which is slidably connected to the spindle bracket and is extendible to an extended position in a direction parallel with the spindle axis. This simplifies adjusting the attaching of a new grinding cup to the grinding machine, the guide indicating in the extended position where on the spindle bracket the spindle is to be located in order to position the grinding cup to provide the correct movement.

The grinding machine may comprise a base plate formed as a box which provides a space on the rear side where parts of the hydraulic layout can be located and wherein the grinding arrangement is located on a front side.

There is also considered a grinding machine for grinding rock drill bit buttons, and comprising a grinding arrangement with rotatable grinding spindle, a free end of which is configured to drive and to replaceably carry a grinding cup. Such a machine may comprise a cooling liquid feeding arrangement, adapted to controllably feed cooling liquid through a conduit to the grinding cup, A grinding screen may be provided, and an actuator cylinder may have a movable end which is connected to the grinding screen. The actuator cylinder may be connected to the conduit, such that it is activated to make the grinding screen cover an end of the grinding cup when liquid is fed through the conduit, while a return arrangement lifts the grinding screen to expose the end of the grinding cup when the liquid flow through the conduit is reduced. This provides an efficient splash protection arrangement covering the end of the grinding cup when grinding takes place.

Brief description of the drawings

Fig 1 shows a perspective view of a drill bit comprising buttons.

Fig 2 illustrates the movement pattern of a grinding cup.

Fig 3 shows a front view of a grinding machine.

Fig 4 illustrates a drill rig. Fig 5 shows a side view of a spindle attached to a gyrating device.

Fig 6 shows a perspective view of a spindle adjustably attached to a bracket of a gyrating device.

Fig 7 shows the spindle of fig 6 as seen from the base plate. Fig 8 shows a side view of a spindle arrangement with an extended guide. Fig 9 shows a perspective view of a linear actuator arrangement. Fig 10 schematically illustrates a hydraulic circuit layout. Fig 1 1 A and 1 1 B shows the use of a grinding screen.

Detailed description

The present disclosure relates to improvements in a grinding machine, which is used for grinding buttons 3 of rock drill bits 1 , as illustrated with an example in fig 1 . The buttons 3 are hard metal inserts in the crown of a drill bit 1 , the buttons typically comprising cubic form boron nitride or similar, and protruding from the drill bit, which is otherwise made for instance of steel. During drilling, the buttons 3 become worn, typically becoming flatter. Regular maintenance of drill bits 1 by grinding and thereby sharpening the buttons 3 substantially improves drilling efficiency.

Different grinding machines are available both for workshop use and for use in the field. The grinding machine of the present disclosure is particularly suitable for field use, for instance in connection with a drilling rig, although the grinding machine of the present disclosure may also be used in other applications.

In the grinding machine, the buttons are ground, one at a time, using a grinding cup 5 which is caused to carry out a rotating and gyrating movement as schematically illustrated in fig 2. The grinding cup 5 thus rotates at a high rpm about a first axis A, a spindle axis, while the axis A carries out a gyrating motion, rotating about a second axis B, a gyration axis, and forming with this rotation/gyration an envelope surface of a cone with the end of the grinding cup 5 at the tip of the cone. This motion serves to grind the entire visible surface of a button 3. The grinding cup typically has a cylindrical body with a cup-shaped bottom working surface 7. The working surface 7 may comprise a diamond/metal matrix with a central recess providing a cup-shape having a suitable profile for a button to be ground. The rim surrounding this recess may be shaped, for example, to remove steel from the face of the drill bit that surrounds the button. Grinding cups may be provided in different sizes and profiles to match the sizes and profiles of different drill bit buttons.

The present disclosure relates to an improved grinding machine 9, a front view of which is illustrated in fig 3. The grinding machine 9 comprises a grinding arrangement 1 1 comprising a grinding cup 5, and may comprise an adjustable vice 13 in which a drill bit 1 can be attached in various positions to allow grinding of different buttons 3 thereon. The grinding arrangement 1 1 as well as such a vice 13 may be attached to a base plate 15, which as will be shown may be formed as a box and may comprise a thick sheet metal plate. During use, the grinding arrangement may be covered by an outer cover 17 through which the grinding cup extends such that the risk of a user being injured by moving parts of the grinding arrangement can be reduced.

The grinding machine 9 may be arranged in a workshop, but is also adapted to be mounted on a drilling rig, such as a surface drilling rig 19 as shown in fig 4. Such an arrangement allows grinding of drill bits on the site where they are used which significantly simplifies logistics. The grinding machine 9 of the present disclosure is well adapted to be mounted on such a drilling rig 19, and may use hydraulic and electric arrangements of such a drilling rig for driving and controlling the grinding machine 9.

Fig 5 shows a side view of the grinding arrangement 1 1 of fig 3, where the cover 17 has been removed to reveal inner features of the arrangement. The grinding arrangement may comprise a spindle arrangement 21 , a gyration arrangement 27, and a linear movement arrangement 37, as will be described. In the present disclosure, it is possible to drive all those arrangement with hydraulic power fed from a main hydraulic circuit of a drilling rig, as the one shown in fig 4.

The spindle arrangement 21 has an interchangeable grinding cup 5 attached at its distal end and comprises a spindle 25, enclosed in a spindle box 26, to which the grinding cup 5 is attached. The spindle 25 is driven by a spindle motor 23, which may be driven by a main hydraulic circuit of a drilling rig as will be shown. The spindle 5 provides the grinding cup's 5 rotation about the axis A as illustrated in fig 5 and fig 2. The rotation speed may for instance be around 2000 rpm. As is known per se, the spindle box 26 may comprise cooling fluid connections which feeds a cooling fluid such as water mixed with an anti-freezing agent to the working surface 7 of the grinding cup 5.

The gyration arrangement 27 provides the motion where the spindles axis A in turn carries out a gyrating motion about an axis B. This motion is produced by a gyration motor 29, which as well may be driven by the main hydraulic circuit of a drilling rig. The gyration motor 29 may be connected to a gear box 31 which lowers the rotation rpm produced to e.g. 30-60 rpm. Thanks to the use of a gear box 31 , the gyration motor 29 and the spindle motor 23 may be connected to a common hydraulic circuit. The arrangement allows the gyration motor 29 to operate at a speed significantly higher than the gyration speed, and to be adjusted without changing the spindle rotation speed too much.

The gear box 31 in turn is connected to an angle displacement bracket 33, which reaches out laterally from rotation axis B of the gear box 31 while being curved, such that an axis A projecting perpendicularly from the angle displacement bracket 33 will intersect the rotation axis of the gear box 31 . A gyrating slider 39 is attached to the angle displacement bracket 33 in a slidable adjustable manner as will be shown later, such that different gyrating movements may be produced by adjusting the location of the gyrating slider 39.

The gyrating slider 39 is connected to an L-shaped spindle bracket 41 via a bushing 35 or bearing, which connection allows the spindle bracket 41 to carry out the gyrating movement without rotating with the angle displacement bracket 33 and slider 39. As will be shown, the spindle motor's 23 hydraulic connections 24 (cf. fig 5) to the base plate 15 may be sufficient to prevent the spindle arrangement 21 from rotating with the angle displacement bracket 33, although other means for preventing this motion, such that a spring connected to the base plate 15 may be provided. As will be shown, the spindle 25 and spindle motor 23 may be slideably connected to the spindle bracket, to adjust the spindle arrangement for use with grinding cups 5 of different types with different lengths.

In the disclosed example, a grinding machine thus comprises a grinding spindle 25, a free end of which is configured to drive and to replaceably carry a grinding cup 5. The spindle 25 is driven by a spindle motor 23 and rotates about a first axis A. The grinding spindle is further configured to gyrate around a second axis B, being at an angle with the first axis, driven by a gyration motor 29. The spindle motor and the gyration motor may both be hydraulic motors. With such an arrangement, no electric motor need be provided to drive the spindle as is commonly used in known grinding machines. Instead, the spindle rotation as well as the spindle gyration may for instance be driven by a main hydraulic circuit of a drilling rig at which the grinding machine is mounted. This provides a reliable grinding machine which may be provided at low cost. It may be sufficient to connect the grinding machine to such a main hydraulic circuit and to e.g. a 24 V connection of a drilling rig, the latter connection to provide power for control circuits, for instance.

A common connection to the main hydraulic circuit may be provided, which drives both the gyration and the spindle rotation.

Thanks to the use of a gearbox 31 connecting the gyration motor 29 and the angle displacement bracket 33, the gyration speed can be kept down e.g. to 30 rpm while the spindle 25 as well as the gyration motor 29 may operate at 2000 rpm. As will be shown a, constriction may be provided to the connection to the drilling rig's main hydraulic circuit, such that it can be avoided that the hydraulic motors are inadvertently driven at a too high speed.

Fig 6 shows a perspective view of a spindle box 26 adjustably attached to a spindle bracket 41 connected to a gyrating arrangement. The slider 39 runs on rails 47 on the angle displacement bracket 33, and the rails 47 extend in a curved shape, such that different inclinations between the rotation axes A and B can be obtained, i.e. the axis A can be made to carry out different motions around the axis B. By tightening bolts (not shown) in threaded holes on the rails and through elongated openings 49 in the slider 39, the slider can be fixed at a desired location along the rail 47.

Thanks to the bushing 35 connecting the slider 39 with one leg of the L-shaped spindle bracket 41 , the spindle arrangement need not follow the rotation of the angle displacement bracket 33 around the axis B, but still follows the path forming the envelope surface of a cone as described in fig 2. Flexible tubes (24, see fig 5) connect the hydraulic connections 43 of the spindle motor 23 to the hydraulic system mounted on the base plate, and may be sufficient to avoid rotating the spindle bracket 41 .

The spindle box 26 has a slidable connection to the spindle bracket 41 . This connection is achieved by providing an elongated slot 45 in the spindle bracket 41 and attaching bolts to threaded holes in the spindle box 26 through this slot 45. This means that before tightening the bolts, the spindle 25 can be slid in the direction of the spindle axis A to a desired position. Thereby, it can be made sure that the working surface of the grinding cup 5 is located where the axes A and B intersect, cf. fig 2. A slidable guide 51 may be provided to facilitate this adjustment as will be described.

Fig 7 shows the spindle of fig 6 as seen from the base plate. In this drawing, the threaded holes 53 are visible, which are used to attach the spindle 25 at a desired location to the spindle bracket 41 by using bolts extending through the latter's elongated slot 45. Typically, a hydraulic motor will have three connections 43, and inlet and an outlet, illustrated to the left and right in the drawing, and a drain connection in the middle. As shown, the tube of the drain connection may pass through an elongated opening 55 in the spindle bracket 41 to facilitate adjusting the spindle.

Fig 8 shows a side view of the spindle arrangement 21 with the sliding guide 51 fully extended. The guide 51 is attached to the spindle bracket 41 . During normal use of the grinding machine, the guide 51 is slid up to a retracted position. When a new grinding cup 5 is attached to the spindle 25, the guide 51 is pulled down to a fully extended position, where the guide cannot be extended further. In this position, the guide 51 indicates a suitable position for the grinding cup 5 end, and the spindle 25 may thus be adjusted to a suitable location on the spindle bracket 41 to locate the end of the grinding cup 5 correctly at the tip of the cone formed by the spindle axis' movement.

Fig 9 shows a perspective view of the linear movement arrangement 37, outlined in fig 5, and mounted on the base plate 15. In order to make the gyrating arrangement and the spindle arrangement slide down to the location where the grinding cup works the surface of a drill bit button, a grinding arrangement carrier 57, indicated in fig 5, is mounted on a linear slider 59 which runs on a rail 61 attached to the base plate 15 as shown in fig 9. This movement is accomplished by means of a hydraulic cylinder 63 connecting the base plate 15 to the grinding arrangement carrier 57. It is also possible to manually pull the grinding arrangement down by means of a lever 67, indicated in fig 3, for instance to verify the correct positioning of a drill bit button with respect to the grinding cup 5.

A gas spring cylinder 65, connecting the base plate 15 to the grinding arrangement carrier 57, may be used to push the grinding arrangement back up once the pressure on the hydraulic cylinder 63 is relieved. Fig 9 also shows hydraulic connections 69 for the gyration motor and the spindle motors as well as a number of controls 71 that can be used to set gyration and spindle rotation speeds, for instance. As shown, the base plate 15 may be formed as a box which provides a space on the rear side where parts of the hydraulic layout can be located. With an arrangement where both gyration, spindle rotation and optionally the linear movement are achieved with hydraulic power provided from a drilling rig, a significantly more robust and reliable configuration is obtained as compared for instance where an electronically controlled electric motor is used for the spindle or where a pneumatic control system is used. In those cases, problems caused by extreme and frequently varying temperature and humidity conditions during work in the field often occur, for instance with regard to inverters used to drive the motor. In the present disclosure, only a 12 or 24 V electric connection to supply simple control circuits, typically relays, is optionally used in addition to the hydraulic connection.

Fig 10 schematically illustrates a hydraulic circuit layout. A common hydraulic drilling rig connector 75 may be provided to connect the grinding machine to a drilling rig. A pressure reduction valve 73 may be used to provide a suitable working pressure for the hydraulic motors 23, 29. A further pressure reduction valve may be used to provide an even lower operating pressure at the hydraulic cylinder 63. As the drilling rig operates at a very high operating pressure, typically 250 bar, a constriction 72 (also schematically indicated in fig 9) that lowers the pressure to 40-50 bars may be connected to the circuit in order to avoid excess motor speeds should the controls have been incorrectly set. Each motor 23, 29 as well as the hydraulic cylinder 63 may have an individual control valve 71 . Return flows 77 from each component may be connected to main hydraulic by a common connector as well.

Fig 1 1 A and 1 1 B shows the use of a moveable grinding screen 79. The grinding screen 79 is brought down to cover the end of the grinding cup 5 when grinding takes place. This is done to reduce splashing of cooling liquid by the grinding cup 5 when rotating at a high speed. Such liquid typically includes water mixed with an anti- freezing agent such as an alcohol. The splashed liquid however is also contaminated with grinding debris and may be considered dirty. The grinding screen however to a great extent protects the operator or other bystander from being soiled.

In order to allow accurate setting of the grinding cup 5 it is also preferred that the end of the grinding cup is unobscured when the grinding cup is not running. The grinding screen 79 arrangement shown in figs 1 1 A and 1 1 B provides both functions.

As shown in fig 1 1 A, the grinding screen 79 which may be shaped e.g. as a hollow cone or cylinder, or as illustrated as a combination thereof, may surround the grinding cup, and be made of a plastic material such as polypropylene, for instance. The grinding screen may be shaped differently, for instance as a flat screen only covering one side of the grinding cup 5. A collar 81 is attached to the grinding screen 79 at the top end thereof, and is connected to a moving end of an actuator cylinder 83, which is attached for instance to the spindle box 26. The actuator cylinder 83 may in turn be connected to the inner cooling liquid conduit 85 in the spindle box 26. Therefore, when the conduit 85 is pressurized when grinding takes place and cooling liquid is forced through the conduit 85, the actuator cylinder 83 is activated and pushes down the grinding screen 79 to cover the space where splashing takes place as shown in fig 1 1 B. When grinding stops and pressure falls in the cooling liquid conduit 85, a return spring e.g. included in the actuator cylinder 83 moves the screen back up to the state shown in fig 1 1 A.

The actuator cylinder 83 does not need to handle any stronger forces and may be a simple inexpensive pneumatic return function cylinder, even though operated with a liquid.

The present disclosure is not limited to the examples described above, and may be varied and altered in different ways within the scope of the appended claims.

Claims

1 . A grinding machine (9) for grinding rock drill bit buttons, the machine comprising a grinding arrangement with rotatable grinding spindle (25), a free end of which is configured to drive and to replaceably carry a grinding cup (5), the grinding spindle (25) being configured to rotate about a spindle axis (A) by means of a spindle motor (23), the grinding spindle further being configured to be orbit about a gyration axis (B) by means of a gyration motor (29), the gyration axis being inclined relative to the spindle axis, characterized in that the spindle motor (23) and the gyration motor (23) are hydraulic motors.

2. Grinding machine according to claim 1 , wherein a gearbox (31 ) connects the gyration motor (29) to an angle displacement bracket (33) carrying the grinding spindle.

3. Grinding machine according to claim 1 or 2, wherein the spindle motor (23) and the gyration motor (29) are connected to a common hydraulic circuit.

4. Grinding machine according to claim 3, wherein the common hydraulic circuit comprises a drilling rig connector (75).

5. Grinding machine according to any of the preceding claims, wherein the grinding arrangement is linearly displaceable by means of a hydraulic cylinder (63).

6. A grinding machine (9) for grinding rock drill bit buttons, comprising a rotatable grinding spindle (25), a free end of which is configured to drive and to replaceably carry a grinding cup (5), the grinding spindle being driven by a spindle motor (23) and rotating about a first axis (A), the grinding spindle further being configured to gyrate around a second axis (B), being at an angle with the first axis, driven by a gyration motor (29), characterized in that the grinding machine comprises a hydraulic connection (75) configured to connect at least one of the spindle motor and the gyration motor to a drill rig hydraulic circuit, wherein the hydraulic connection comprises a constriction (72) lowering the hydraulic pressure to below 50 bar.

7. A grinding machine (9) for grinding rock drill bit buttons, comprising a rotatable grinding spindle (25), a free end of which is configured to drive and to replaceably carry a grinding cup (5), the grinding spindle being driven by a spindle motor and rotating about a first axis (A), the grinding spindle further being configured to gyrate around a second axis (B), being at an angle with the first axis, driven by a gyration motor, characterized by the spindle (25) being connected to the gyration motor via a spindle bracket (41 ), wherein the grinding spindle is configured to be slideably connected to the spindle bracket.

8. Grinding machine (9) according to claim 7, wherein the spindle bracket is L- shaped, the spindle (25) being connected to a first leg thereof, and a second leg thereof being connected to an angle displacement bracket (33).

9. Grinding machine according to claim 7 or 8, wherein a guide (51 ) is slidably connected to the spindle bracket (41 ), being extendible to an extended position in a direction parallel with the spindle axis (A).

10. Grinding machine according to any of the preceding claims, comprising a base plate (15) formed as a box which provides a space on a rear side where parts of the hydraulic layout can be located and wherein the grinding arrangement is located on a front side.

1 1 . A grinding machine (9) for grinding rock drill bit buttons, the machine comprising a grinding arrangement with rotatable grinding spindle (25), a free end of which is configured to drive and to replaceably carry a grinding cup (5),

characterized by

- a cooling liquid feeding arrangement, adapted to controllably feed cooling liquid through a conduit (85) to the grinding cup,

-a grinding screen (79),

-an actuator cylinder (83), a movable end of which is connected to the grinding screen (79), wherein

-the actuator cylinder (83) is connected to the conduit (85), such that it is activated to make the grinding screen (79) cover an end of the grinding cup (5) when liquid is fed through the conduit (85), while a return arrangement lifts the grinding screen (79) to expose the end of the grinding cup (5) when the liquid flow through the conduit (83) is reduced.