Grinding tool for grinding drilling bits of rock drilling crowns, a cup-shaped grinding wheel and a grinding spindle

Abstract

The invention relates to a grinding tool (1) for grinding bits (5) of a rock drilling crown, comprising a spindle (2) with a rear shank (3) for rotatable reception in a grinding machine and a front shaft end (6), a cup-shaped grinding wheel (8) which is concentrically mounted on the front shaft end (6) via a hollow hub portion (9), a shoulder (13) extending radially from the spindle, an attachment means (12) with which the grinding wheel (8) is held axially against the shoulder (13) for entrainment. For effective fastening, the attachment means (12) is configured as a screw-nut connection, where the front shaft end (6) of the spindle has a first pin section (6a) located closest to the stop shoulder (13) and having an external thread (15), a longitudinally located second pin section (6b) with a circular cylindrical outer jacket surface, the hub portion (9) internally comprises two hole sections where a first hole section (8a) has an internal thread (16), a second hole section (8b) has a circular cylindrical inner cavity whose jacket wall with a sliding fit surrounds the second pin section (6b) of the spindle (2) when the grinding wheel (8) is screwed onto the front shaft end (6) of the spindle (2).

Description

[0001] Grinding tool for grinding drilling bits of rock drilling crowns, a cup-shaped grinding wheel and a grinding spindle

[0002] TECHNICAL AREA

[0003] The present invention relates to a grinding tool for grinding drilling bits of rock drilling crowns according to claim 1 , a cup-shaped grinding wheel according to claim 13, and a spindle according to claim 14.

[0004] BACKGROUND

[0005] When grinding carbide drill bits (pins) or the like in a rock drilling crown, a grinding tool is used that comprises a cup-shaped rotationally symmetrical grinding wheel which is concentrically attached to the free shaft end of a spindle whose rear shaft is intended to be received in a rotatable mount in a grinding machine.

[0006] In known grinding tools, said grinding wheel is intended to be mounted on a support shaft portion of a pin formed at the free end of the spindle, the shaft pin of known grinding tools having a smaller diameter than the remaining spindle diameter. On the support shaft portion, the grinding wheel is retained by means of the clamping force of a separate mounting part which usually consists of a large-headed screw which is screwed into a threaded bore in the free end of the shaft pin and which keeps the grinding wheel pressed against a shoulder serving as a seat at the transition of the pin to the larger diameter of the support shaft portion of the spindle. In this type of fastening means for entraining grinding wheels on the shaft pin, the grinding wheel is pressed to be entrained on the spindle between its flat radially extending flange portions at the respective shaft end of the grinding wheel. In the grinding tool in question, it is thus necessary to have a separate mounting part in the form of the screw provided with a large head and a mounting tool belonging to this separate mounting part.

[0007] A first object of the present invention is to provide a grinding tool of the type described above in which mounting and dismounting of a grinding wheel on the spindle can be quickly and efficiently carried out manually (by hand) by an operator of a grinding machine, essentially without the need for either mounting tools or separate mounting parts. A second object of the invention is to provide a new type of cup-shaped grinding wheel intended for use in a grinding tool according to the invention. A third object of the invention is to provide a new type of spindle intended for use in a grinding tool according to the invention.

[0008] SUMMARY OF THE INVENTION These objects of the invention are achieved by a grinding tool having the features set forth in claim 1 , a cup-shaped grinding wheel having the features and characteristics set forth in claim 13 and a spindle having the features and characteristics set forth in claim 14.

[0009] FIGURE DESCRIPTION

[0010] In the following, the invention is described in more detail with reference to an exemplary embodiment shown in the accompanying drawings; in which;

[0011] Fig. 1 shows a side view, partly in the longitudinal section, of a grinding tool according to the invention mounted in a grinding machine for grinding bits in a bit-type rock drilling crown.

[0012] Fig. 1A shows a detailed enlargement of a portion of the grinding tool delimited by line II in Fig. 1.

[0013] Fig. 2 shows the grinding tool in a state with parts pulled apart, partly in longitudinal section.

[0014] Fig. 3 shows a perspective view of a grinding tool according to the invention, in an alternative embodiment,

[0015] Fig. 4A, 4B, 4C show side views of grinding wheels included in the grinding tool, in three different embodiments,

[0016] Fig. 5 shows a longitudinal side view, partly in the longitudinal section, of the spindle shown in Fig. 3 in an alternative embodiment.

[0017] DETAILED DESCRIPTION

[0018] In the drawing figures in Figs. 1 and 2, 1 denotes a grinding tool which comprises a spindle 2 which at its rear end comprises a shank 3 for rotatable reception in a grinding machine (not shown) for grinding bits 5 in a rock drilling crown. The free front shaft end 6 or shaft journal of the spindle 2 carries on the one hand a cup-shaped grinding wheel 8 which, via a continuous hollow hub portion 9, concentrically surrounds the shaft end 6 of the spindle 6 like a cylinder bore, and on the other hand an annular wheel support 10 which also concentrically surrounds the shaft end 6 of the spindle 2 via its continuous hole 11 and which precedes the grinding wheel 8 when a combination of said parts, by means of an engagement means generally designated by 12, are mounted and axially engaged against a shoulder 13 (stop shoulder) arranged on the spindle 2, the annular plane of which runs perpendicular to the central axis 7 of the spindle 2. The shoulder 13 is formed as part of a thickened flange portion 14 extending radially from the spindle 2 and formed in one piece with the spindle 2, which is suitably made of case-hardened steel. In accordance with the invention, the attachment means 12 is designed as a screw and nut member in which the free shaft end 6 of the spindle 2 comprises an external thread 15 which, extending along the shaft end 6, in the direction towards the shoulder 13, transitions and terminates in a thread clearance groove 15A. The hollow hub portion 9 of the grinding wheel 8 comprises a corresponding internal thread 16 in its inner hollow wall. The axial position of the grinding wheel 8 on the spindle 2 during movement along the shaft end 6 and thus along the spindle's central axis 7 for contact with the shoulder 13 is determined by the axial length Lx of the wheel support 10 provided with internal thread 17 which, with respect to the shoulder 13, precedes the grinding wheel 8 when a combination of said parts is screwed onto the shaft end 6 of the spindle 2. The internal thread 17 of the wheel support 10 extends along the hole wall of the axial length of the through hole 11 in order tojn a portion of the hole wall facing the shoulder 13 of the wheel support, it ends with a thread clearance groove 17A.

[0019] In one embodiment of the invention, the wheel support 10 can be fixed to the free shaft end 6 of the spindle by gluing or similar connecting means that allow permanent fixation.

[0020] As mentioned above, the grinding wheel 8 is intended for grinding bits 5 (cutting pins) of hard metal or the like of a pin-type drill bit (not shown). Such a bit 5 in a drill bit crown is shown schematically in Fig. 1 with dash-dotted contour lines. The drill bit whose bit 5 is to be ground is held firmly in a holder rotatable about a vertical axis 18 mounted in a grinding machine. Such grinding machines have been known for a long time and will therefore not be described in more detail.

[0021] The grinding wheel 8 comprises a cup-shaped rotationally symmetrical body with a defined central axis 7. The cup-shaped body is manufactured as a solid steel part with end portions in the form of circular radially extending flange parts 20 and 21 , each with a rounded end profile 24 in cross-section and which flange parts delimit the grinding wheel 8 in its axial direction. The function of the flange parts 20, 21 is to remove material around the drill bit 5. A profiled groove 22 is designed as a groove or waist between said flange parts 20, 21. A first hole section 8a of the grinding wheel 8 with the internal diameter D1 and provided with said internal thread 16, adjoins and is surrounded by the circular flange part 21 of the grinding wheel 8 with the largest diameter, while a second section 8b of the grinding wheel 8 with the internal diameter D2 and having a circular cylindrical inner jacket wall adjoins and is surrounded by the circular flange part 20 of the grinding wheel 8 having the smaller diameter.

[0022] The expression bowl-shaped or bowl-shaped refers in the following to a hollow rotationally symmetrical body which is delimited in its axial direction by radially extending flange parts 20, 21 and whose central centre, between the flange parts, has a defined waist (the profile groove 22). The grinding wheel 8 is provided along its circumference with a coating of some suitable hard synthetic material for grinding carbide bits. A suitable synthetic crystalline material may consist of diamond grains bonded by a suitable material, for example nickel. Cubic boron nitride is also present.

[0023] The coating is indicated in Fig. 1 by a chain line 23 and has in cross-section an extension indicated by said chain line, i.e. the coating extends radially inward to some extent along the outer surfaces of said respective flange parts 20 and 21 .

[0024] As can be seen from Fig. 2, the shaft end 6 has over its axial length a pin with two sections 6a, 6b with different diameters, where a first pin section 6a with diameter d1 is located closest to the shoulder 13 and is provided with the said external thread 15. The second pin section 6b with diameter d2 located further out on the shaft end 6 is designed with a circular cylindrical outer surface. The first pin section 6a and the second pin section 6b each have an axial length L1 , L2 from the shoulder 13.

[0025] In a manner corresponding to the shaft end 6, the hollow hub portion 9 of the grinding wheel 8 has two hole sections 8a, 8b internally along its axial length, where a first hole section 8a with diameter D1 is located closest to the shoulder 13 and is provided with said internal threading 16. The second hole section 8b with diameter D2 located in the hub portion 9 at a greater distance from the shoulder 13 has a circular cylindrical inner surface.

[0026] It should thus be understood that the second pin section 6b located further out on the shaft end 6 with the circular cylindrical outer jacket surface is configured to be received with a sliding fit against the hole wall of the hollow hub portion 9 of the grinding wheel 8 when the grinding wheel 8 is screwed onto the shaft end 6 of the spindle 2 during axial movement.

[0027] In accordance with the invention, one or a plurality of support sections can be arranged between the shoulder 13 and the parts screwed onto the shaft end 6 of the spindle 2 by threading, in the form of the wheel support 10 and the grinding wheel 8.

[0028] The wheel support 10 has a cylindrical outer surface and is defined at its ends by flat and axially spaced end surfaces 10a, 10b. The connection between one end surface 10a of the wheel support 10 and the shoulder 13 forms a first bearing surface defined by the shoulder 13, which extends at right angles to the axis of rotation of the spindle 2 and against which the wheel support 10 is held axially firmly pressed when screwed onto the shaft end 6 of the spindle 2. The connection forms a first support section 25.

[0029] A second support section 26 is operative between the second end surface 10b of the wheel support 10 and the radially extending flange portion 21 with a larger diameter of the grinding wheel 8.

[0030] As shown in the detailed enlargement in Fig. 1A, the second support section 26 may be designed as a mating male and female part where the second end surface 10b of the wheel support 10 forms a hub part that axially projects into an annular inner shoulder 9a in the radial flange part 21 of the grinding wheel 8 with a larger diameter and is supportively surrounded by a circumferential edge 9b that radially outwardly delimits the inner shoulder 9a. A third support section 27 is formed between the grinding wheel 2 and the shaft end 6 of the spindle 1 and which third support section comprises an axially extending non-threaded portion of an inner wall of the hub portion 9 of the grinding wheel 8 which, like a circular cylindrical housing, rotatably surrounds the circular cylindrical shell portion defined by the pin portion 6b on the shaft end 6 of the spindle 2 and as described above allows the grinding wheel 8 to be screwed onto the shaft end 6 of the spindle 2 during axial movement.

[0031] Said third support section 27 thus comprises a sliding fit occurring between the circular cylindrical outer second pin section 6b located longitudinally on the pin with diameter d2 and the corresponding circular cylindrical inner jacket surface in the hollow hub portion 9 of the grinding wheel 8 which is adjacent to the smaller diameter of the circular flange portion 20 of the grinding wheel 8.

[0032] In one embodiment of the invention, the threading can be chosen so that a right-hand rotation results in a movement of the wheel support 10 and the grinding wheel 8 in a direction axially rearward, towards the shoulder 13 on the shaft end of the spindle 2. In an alternative embodiment of the invention, a left-hand threaded connection can be used. Advantageously, a thread direction for screwing on that is opposite to the normal direction of rotation of the spindle 2 in the grinding machine can be chosen in order to thus counteract the connection becoming loose. In one embodiment of the invention, the threading can be of the type M12x1.5 mm with double thread entries (double start threading) or more to achieve fast and effective locking, which also means that each of the spindle 2, the wheel support 10 and the grinding wheel 8 for interaction therewith has corresponding threads.

[0033] More specifically, the threading on the shaft end 6 of the spindle 2, the internal threading 17 of the wheel support 10 and the internal threading in the hub portion 9 of the grinding wheel 8 each comprise a corresponding number of thread entries in which the corresponding number of thread entries comprise at least two thread entries.

[0034] In one embodiment of the invention, the flange portion 14 includes on its outer surface a socket 19 for a tool wrench (not shown). The tool wrench can, for example, be of the block type with a defined wrench width. The tool wrench is then intended to serve as a counterweight to facilitate the mounting or unscrewing of said wheel support 10 and / or said grinding wheel 8 on the free shaft end 6 of the spindle 2.

[0035] Fig. 2 shows, in a top-down view, how the various parts of the grinding tool 1 are assembled together. The support hub 10 is first screwed onto the shaft end 6 of the spindle 2 by hand so that the first support section 25 between the first support surface 10a of the wheel support 10 and the facing surface of the shoulder 13 comes into contact. The wheel support 10 is suitably permanently fixed in place by gluing. The grinding wheel 8 is then screwed onto the shaft end 6 so that the second support section 26 in the form of the said hub portion 9 and the annular inner shoulder 10a, 10b between the second support surface 10b of the support hub 10 and the facing bearing surface of the grinding wheel 8 come into contact with each other. The third support section 27 occurs as the circular cylindrical shell portion of the pin section 6b on the shaft end 6 of the spindle 2 is enclosed with a sliding fit by the complementary hub portion 9 of the grinding wheel 8. In Fig. 3 and Fig. 5 a grinding tool 1 according to the invention is shown in an alternative one-piece embodiment lacking the above-described wheel support 10. In this alternative embodiment, the thickened flange portion 14 extending radially from the spindle 2 has been extended a length in the axial direction forward towards the free shaft end 6 of the spindle corresponding to the axial length Lx of the wheel support 10 so that the shoulder 13 obtains the desired positioning axial position for the grinding wheel 8 on the spindle 2.

[0036] In Figs. 4A, 4B, 4C, the above-described grinding wheels are shown in a number of different embodiments, whereby embodiment 4B corresponds to that described in more detail above.

Claims

CLAIMS1 . Grinding tool (1) for grinding bits (5) of a rock drilling crown, comprising on the one hand a spindle (2) with a rear shank (3) for rotatable reception in a grinding machine and a front shaft end (6), on the other hand a cup-shaped grinding wheel (8) which is concentrically mounted on the front shaft end (6) via a hollow hub portion (9), a shoulder (13) extending radially from the spindle (2), an engagement means (12) with which the grinding wheel (8) is held axially engaged against the shoulder (13) for entrainment, characterised in that the engagement means (12) is configured as a screw-nut connection in which the front shaft end (6) of the spindle comprises a pin with two axially defined pin sections, where a first pin section (6a) located closest to the stop shoulder (13) has an external thread (15) and a second pin section located furthest out on the pin (6b) has a circular cylindrical outer surface, wherein the hub portion (9) internally along its axial length comprises two hole sections where a first hole section (8a) has an internal thread (16) in its inner hole wall and a second hole section (8b) has a circular cylindrical inner cavity whose outer wall surrounds the second pin section (6b) of the spindle (2) with a sliding fit when the grinding wheel (8) is screwed onto the front shaft end (6) of the spindle (2).

2. Grinding tool according to claim 1 , wherein the cup-shaped grinding wheel (8) is formed with two circular flange parts (20, 21), each with a rounded end profile (24) in cross-section, one of which has a larger diameter than the other flange part (20), and a profile groove (22) located between the flange parts (20, 21) and corresponding to the intended end profile of the rock drill bit (5), and that the first hole section (8a) of the hub portion (9) with the internal thread (16) adjoins the circular flange part (21) with the larger diameter and the second hole section (8b) with the circular cylindrical cavity adjoins the circular flange part (20) with the smaller diameter.

3. A grinding tool according to any one of claims 1 - 2, further comprising a wheel support (10) provided with an internal thread (17) which precedes the grinding wheel (8) when said parts are screwed onto the front shaft end (6) of the spindle (2), whereby the axial position of the grinding wheel (8) on the front shaft end (6) of the spindle (2), when abutting against the shoulder (13), is determined by the axial length (Lx) of the wheel support (10).

4. Grinding tool according to claim 3, wherein the screwed-on wheel support (10) is fixed to the free shaft end (6) of the spindle (2) by gluing, thread locking fluid or by means of a corresponding connecting means that allows a permanent connection.

5. A grinding tool according to any one of claims 1 - 2, wherein the external thread (15) on the shaft end (6) of the spindle (2), and the internal thread (16) in the hub portion (9) of the grinding wheel (8) each comprises a corresponding number of thread inputs of two or more thread inputs.

6. Grinding tool according to any one of claims 3 - 4, wherein the external thread (15) on the shaft end (6) of the spindle (2), the internal thread (17) in the wheel support (10) and the internal thread (16) in the hub portion (9) of the grinding wheel (8) each comprises a corresponding number of thread inputs of two or more thread inputs.

7. A grinding tool according to any one of claims 1 - 6, wherein the shoulder (13) is formed by a flange portion (14) extending radially from the spindle (2).

8. Grinding tool according to claim 7, wherein the flange portion (14) has a socket (19) for a tool key on its outer surface.

9. Grinding tool according to claim 3, wherein the wheel support (10) comprises a cylindrical outer jacket surface which is delimited at its ends by flat and axially directed end surfaces (10a, 10b), where a connection between one end surface (10a) of the wheel support (10) and the shoulder (13) forms a first support section (25).

10. A grinding tool according to claim 9, comprising a second support section (26) which is operative between the second end surface (10b) of the wheel support (10) and the radially extending flange portion (21) with a larger diameter of the grinding wheel (8).

11. A grinding tool according to claim 10, wherein the second support section (26) is designed as a mating male and female part where the second end surface (10b) of the wheel support (10) forms a hub part which axially projects into an annular inner shoulder (18a) in the radial circular flange part (21) of the grinding wheelwith the larger diameter and is supportively surrounded by a circumferential edge (18b) which radially outwardly delimits said inner shoulder.

12. Grinding tool according to any one of claims 1 - 11 , wherein the sliding fit occurring between the circular cylindrical outer second pin section (6b) located longitudinally on the shaft end (6) and the corresponding circular cylindrical inner jacket surface in the hollow hub portion (9) of the grinding wheel (8) forms a third support section (27) occurring between the grinding wheel (8) and the shaft end (6) of the spindle (2).

13. Cup-shaped grinding wheel (8) for grinding drill bits (5) in a grinding machine, comprising two circular flange parts (20, 21) each with a rounded end profile (24) in cross-section and of which one flange part (21) has a larger diameter than the other flange part (20), and a profile groove (22) located between the flange parts (20, 21) surrounding the end profile of the bit (5) of the rock drilling crown, corresponding to the intended end profile, and a hollow central hub part (9) intended to concentrically surround a spindle (2), characterized in that the hollow central hub part (9), internally along its axial length, comprises two hole sections where a first hole section (8a) has an internal thread (16) in its inner hole wall and adjoins the circular flange part (21) with the larger diameter and the second hole section (8b) has a circular cylindrical cavity with a circular cylindrical inner surface and is adjacent to the circular flange portion (20) of the smaller diameter.

14. Spindle (2) comprising a rear shaft (3) for rotatably receiving in a grinding machine for grinding drill bits, a flange portion (14) extending radially from the central axis of the spindle and defining a shoulder (13) and a front shaft end (6) intended to concentrically support a cup-shaped grinding wheel (8) , characterised in that the front shaft end (6) over its axial length comprises a pin with two sections where a first pin section (6a) located closest to the shoulder (13) has an external thread (15) and a second pin section (6b) located further away from the shoulder (13) has a circular cylindrical outer surface.

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