SE542627C2

SE542627C2 - Grinding machine

Info

Publication number: SE542627C2
Application number: SE1750796A
Authority: SE
Inventors: Frederick Winroth; Kaj Johansson
Original assignee: Torstorps Mek; Winroth Ind Ab
Priority date: 2017-06-21
Filing date: 2017-06-21
Publication date: 2020-06-23
Also published as: CA3065227A1; SE1750796A1; EP3641984A1; WO2018236268A1; EP3641984A4

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

HYDRAULIC GRINDING MACHINE FOR GRINDING ROCK DRILL BIT BUTTONS 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 configur-ed to drive and to replaceably carry a grinding cup. The grinding spindle is driven bya spindle motor and rotates about a first axis, and the grinding spindle is further con-figured to gyrate around a second axis, being at an angle with the first axis, driven by a gyration motor.

Technical backgroundSuch a grinding machine is disc|osed for instance in WO-2016/074067-A1 and is used to maintain the efficiency of a drill bit by frequently sharpening its drill bitbuttons. 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 grindingmachine. This object is achieved by a grinding machine as defined in claim 1. l\/lorespecifically, in a grinding machine of the initially mentioned kind, the spindle motor aswell as the gyration motor are hydraulic motors. This means that both the spindlerotation and the gyrating motion can be obtained with hydraulic power obtained frome.g. a drilling rig. Such a solution is very reliable even under difficult working condi-tions 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 displacementbracket carrying the grinding spindle. This means that a hydraulic motor withrelatively 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 hydrauliccircuit, thereby facilitating connecting the grinding machine e.g. to a drilling righydraulic circuit. The common hydraulic circuit may therefore comprise a drilling rig COnneCtOf.

The grinding machine may have a grinding arrangement that is linearly displaceableby means of a hydraulic cylinder. This makes it possible to provide also a linearmovement 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 atleast one of the spindle motor and the gyration motor to a drilling rig hydraulic circuit,wherein the hydraulic connection comprises a constriction lowering the hydraulicpressure to below 50 bar. This eliminates the risk that a hydraulic motor in thegrinding 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, whereinthe 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 firstleg thereof, and a second leg thereof being connected to an angle displacementbracket There may be provided a guide, which is slidably connected to the spindle bracketand 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 spindleis 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 aspace on the rear side where parts of the hydraulic layout can be located andwherein the grinding arrangement is located on a front side.

Brief description of the drawinqs 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.

Detailed descriptionThe present disclosure re|ates 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. Thebuttons 3 are hard metal inserts in the crown of a drill bit 1, the buttons typicallycomprising cubic form boron nitride or similar, and protruding from the drill bit, whichis otherwise made for instance of steel.

During drilling, the buttons 3 become worn, typically becoming flatter. Regular main-tenance of drill bits 1 by grinding and thereby sharpening the buttons 3 substantiallyimproves drilling efficiency.

Different grinding machines are available both for workshop use and for use in thefield. The grinding machine of the present disclosure is particularly suitable for fielduse, for instance in connection with a drilling rig, although the grinding machine of thepresent disclosure may also be used in other applications. ln the grinding machine, the buttons are ground, one at a time, using a grinding cup 5which is caused to carry out a rotating and gyrating movement as schematicallyillustrated in fig 2. The grinding cup 5 thus rotates at a high rpm about an axis A,while the axis A carries out a gyrating motion, rotating about an axis B and formingwith this rotation/gyration an envelope surface of a cone with the end of the grindingcup 5 at the tip of the cone. This motion serves to grind the entire visible surface of abutton 3.

The grinding cup typically has a cylindrical body with a cup-shaped bottom workingsurface 7. The working surface 7 may comprise a diamond/metal matrix with acentral recess providing a cup-shape having a suitable profile for a button to beground. The rim surrounding this recess may be shaped, for example, to remove 3 steel from the face of the drill bit that surrounds the button. Grinding cups may beprovided in different sizes and profiles to match the sizes and profiles of different drillbit buttons.

The present disclosure relates to an improved grinding machine 9, a front view ofwhich is illustrated in fig 3. The grinding machine 9 comprises a grinding arrange-ment 11 comprising a grinding cup 5, and may comprise an adjustable vice 13 inwhich a drill bit 1 can be attached in various positions to allow grinding of differentbuttons 3 thereon. The grinding arrangement 11 as well as such a vice 13 may beattached to a base plate 15, which as will be shown may be formed as a box andmay comprise a thick sheet metal plate. During use, the grinding arrangement maybe covered by an outer cover 17 through which the grinding cup extends such thatthe 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 bemounted on a drilling rig, such as a surface drilling rig 19 as shown in fig 4. Such anarrangement allows grinding of drill bits on the site where they are used whichsignificantly simplifies logistics. The grinding machine 9 of the present disclosure iswell adapted to be mounted on such a drilling rig 19, and may use hydraulic andelectric arrangements of such a drilling rig for driving and controlling the grindingmachine 9.

Fig 5 shows a side view of the grinding arrangement 11 of fig 3, where the cover 17has been removed to reveal inner features of the arrangement. The grindingarrangement may comprise a spindle arrangement 21, a gyration arrangement 27,and a linear movement arrangement 37, as will be described. ln the presentdisclosure, 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 itsdistal end and comprises a spindle 25, enclosed in a spindle box 26, to which thegrinding cup 5 is attached. The spindle 25 is driven by a spindle motor 23, which maybe driven by a main hydraulic circuit of a drilling rig as will be shown. The spindle 5provides 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 whichfeeds a cooling fluid such as water mixed with an anti-freezing agent to the workingsurface 7 of the grinding cup 5.

The gyration arrangement 27 provides the motion where the spindles axis A in turncarries out a gyrating motion about an axis B. This motion is produced by a gyrationmotor 29, which as well may be driven by the main hydrau|ic circuit of a dri||ing rig.The gyration motor 29 may be connected to a gear box 31 which lowers the rotationrpm produced to e.g. 30-60 rpm. Thanks to the use of a gear box 31, the gyrationmotor 29 and the spindle motor 23 may be connected to a common hydrau|ic circuit.The arrangement allows the gyration motor 29 to operate at a speed significantlyhigher 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, whichreaches out laterally from rotation axis B of the gear box 31 while being curved, suchthat an axis A projecting perpendicularly from the angle displacement bracket 33 willintersect the rotation axis of the gear box 31. A gyrating slider 39 is attached to theangle 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 bushing35 or bearing, which connection allows the spindle bracket 41 to carry out thegyrating movement without rotating with the angle displacement bracket 33 and slider39. As will be shown, the spindle motor's 23 hydrau|ic connections 24 (cf. fig 5) to thebase plate 15 may be sufficient to prevent the spindle arrangement 21 from rotatingwith 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 tothe spindle bracket, to adjust the spindle arrangement for use with grinding cups 5 ofdifferent types with different lengths. ln the disclosed example, a grinding machine thus comprises a grinding spindle 25, afree end of which is configured to drive and to replaceably carry a grinding cup 5. Thespindle 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 anangle with the first axis, driven by a gyration motor 29. The spindle motor and thegyration motor may both be hydraulic motors. With such an arrangement, no electricmotor need be provided to drive the spindle as is commonly used in known grindingmachines. lnstead, the spindle rotation as well as the spindle gyration may forinstance be driven by a main hydraulic circuit of a drilling rig at which the grindingmachine is mounted. This provides a reliable grinding machine which may beprovided at low cost. lt may be sufficient to connect the grinding machine to such amain hydraulic circuit and to e.g. a 24 V connection of a drilling rig, the latterconnection 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 angledisplacement 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'smain hydraulic circuit, such that it can be avoided that the hydraulic motors areinadvertently driven at a too high speed.

Fig 6 shows a perspective view of a spindle box 26 adjustably attached to a spindlebracket 41 connected to a gyrating arrangement. The slider 39 runs on rails 47 onthe angle displacement bracket 33, and the rails 47 extend in a curved shape, suchthat different inclinations between the rotation axes A and B can be obtained, i.e. theaxis A can be made to carry out different motions around the axis B. By tighteningbolts (not shown) in threaded holes on the rails and through elongated openings 49in 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-shapedspindle bracket 41, the spindle arrangement need not follow the rotation of the angledisplacement bracket 33 around the axis B, but still follows the path forming theenvelope 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 systemmounted on the base plate, and may be sufficient to avoid rotating the spindlebracket 41.

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

Fig 7 shows the spindle of fig 6 as seen from the base plate. ln this drawing, thethreaded holes 53 are visible, which are used to attach the spindle 25 at a desiredlocation to the spindle bracket 41 by using bolts extending through the latter'selongated 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. Asshown, the tube of the drain connection may pass through an elongated opening 55in 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 fullyextended. The guide 51 is attached to the spindle bracket 41. During normal use ofthe grinding machine, the guide 51 is slid up to a retracted position. When a newgrinding cup 5 is attached to the spindle 25, the guide 51 is pulled down to a fullyextended position, where the guide cannot be extended further. ln this position, theguide 51 indicates a suitable position for the grinding cup 5 end, and the spindle 25may thus be adjusted to a suitable location on the spindle bracket 41 to locate theend 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 infig 5, and mounted on the base plate 15. ln order to make the gyrating arrangementand the spindle arrangement slide down to the location where the grinding cup worksthe surface of a drill bit button, a grinding arrangement carrier 57, indicated in fig 5, ismounted on a linear slider 59 which runs on a rail 61 attached to the base plate 15 asshown in fig 9. This movement is accomplished by means of a hydraulic cylinder 63connecting the base plate 15 to the grinding arrangement carrier 57. lt 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 arrangementcarrier 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 spindlemotors as well as a number of controls 71 that can be used to set gyration andspindle rotation speeds, for instance. As shown, the base plate 15 may be formed asa box which provides a space on the rear side where parts of the hydraulic layout canbe located. With an arrangement where both gyration, spindle rotation and optionallythe linear movement are achieved with hydraulic power provided from a drilling rig, asignificantly more robust and reliable configuration is obtained as compared forinstance where an electronically controlled electric motor is used for the spindle orwhere a pneumatic control system is used. ln those cases, problems caused byextreme and frequently varying temperature and humidity conditions during work inthe field often occur, for instance with regard to inverters used to drive the motor. lnthe present disclosure, only a 12 or 24 V electric connection to supply simple controlcircuits, typically relays, is optionally used in addition to the hydraulic connection.

Fig 10 schematically illustrates a hydraulic circuit layout. A common hydraulic con-nector 75 may be provided to connect the grinding machine to a drilling rig. Apressure reduction valve 73 may be used to provide a suitable working pressure forthe hydraulic motors 23, 29. A further pressure reduction valve may be used toprovide an even lower operating pressure at the hydraulic cylinder 63. As the drillingrig 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 beconnected to the circuit in order to avoid excess motor speeds should the controlshave been incorrectly set. Each motor 23, 29 as well as the hydraulic cylinder 63 mayhave an individual control valve 71. Return flows 77 from each component may be connected to main hydraulic by a common connector as well.

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

CLAIIVIS

1. A grinding machine (9) for grinding rock drill bit buttons, the machinecomprising a grinding arrangement with rotatable grinding spindle (25), a free end ofwhich is configured to drive and to replaceably carry a grinding cup (5), the grindingspindle (25) being configured to rotate about a spindle axis (A) by means of a spindlemotor (23), the grinding spindle further being configured to be orbit about a gyrationaxis (B) by means of a gyration motor (29), the gyration axis being inc|ined relative tothe spindle axis, characterized in that the spindle motor (23) and the gyration motor(23) are hydraulic motors, wherein a gearbox (31) connects the gyration motor (29) toan angle displacement bracket (33) reaching out laterally from the gyration axis (B)and carrying the grinding spindle (25).

2. Grinding machine according to c|aim 1, wherein the spindle motor (23) andthe gyration motor (29) are connected to a common hydraulic circuit.

3. Grinding machine according to c|aim 2, wherein the common hydraulic circuitcomprises a hydraulic dri||ing rig connector (75).

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

5. A grinding machine (9) for grinding rock drill bit buttons, comprising arotatable grinding spindle (25), a free end of which is configured to drive and toreplaceably carry a grinding cup (5), the grinding spindle being driven by a spindlemotor (23) and rotating about a first axis (A), the grinding spindle further beingconfigured 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 machinecomprises a hydraulic connection (75) configured to connect at least one of thespindle motor and the gyration motor to a drill rig hydraulic circuit, wherein thehydraulic connection comprises a constriction (72) lowering the hydraulic pressure tobelow 50 bar.

6. A grinding machine (9) for grinding rock drill bit buttons, comprising arotatable grinding spindle (25), a free end of which is configured to drive and toreplaceably carry a grinding cup (5), the grinding spindle being driven by a spindlemotor 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 gyrationmotor via a spindle bracket (41), wherein the grinding spindle is configured to beslideably connected to the spindle bracket in the direction of the first axis (A).

7. Grinding machine (9) according to c|aim 6, wherein the spindle bracket is L-shaped, the spindle (25) being connected to a first leg thereof, and a second legthereof being connected to an angle displacement bracket (33) reaching out laterallyfrom the second axis (B).

8. Grinding machine according to c|aim 7 or 8, wherein a guide (51) is slidablyconnected to the spindle bracket (41), being extendible to an extended position in adirection parallel with the spindle axis (A).

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