Rotary grinding

Abstract

The present disclosure relates to a rotary abrasive machining tool comprising a hub having a plurality of radial slots extending axially around its periphery, and a plurality of abrasive segments (typically polycrystalline diamond) disposed within the radial slots.

Description

Technical Field

[0001] The present disclosure relates to an apparatus for rotary grinding. More particularly, it relates to a rotary dressing tool.

Background Art

[0002] EP 3 415 275 discloses a rotary grinding tool 101 comprising a hub 103 having a plurality of axially oriented radial slots on its outer periphery. A plurality of grinding segments 201, 202 are disposed in the radial slots 701, 702 and together form a grinding surface 102. Each grinding segment comprises grinding edges 402, 403 defining a plurality of grinding segments 405 and further comprises a tab 401 for placement in one of the slots of the hub. In one embodiment, the tab is wider at its base than at its top. A pair of flanges 104, 105 are screwed to the hub 103, whereby rims 504, 505 cooperate with the wider base of the tab 401 to fix the grinding segment in place (see FIGS. 5 and 6). In another embodiment, a ring 1103 is used to fix the grinding segment in place (see FIGS. 11 and 12).

[0003] The problem with these configurations is that it is difficult to individually replace a damaged or worn grinding segment.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Accordingly, an object of the present invention is to provide an alternative method of attaching a grinding segment to a hub that solves the above problems.

Means for Solving the Problems

[0006] According to the present invention, there is provided a rotary grinding tool, the rotary grinding tool comprising a hub having a plurality of radially extending slots extending axially on the outer periphery, and a plurality of grinding segments disposed within the radially extending slots, each grinding segment having a tab for attaching the grinding segment to the hub and further comprising a grinding edge, and each grinding segment being individually fixed to the hub using a pin element that extends at least partially through the grinding segment and / or extends at least partially through the hub adjacent to the grinding segment.

[0007] This configuration is advantageous as it allows individual segments to be replaced without interfering with the remaining segments in their positions. Further, it allows for further use of the rotary grinding tool with one or more individual grinding segments missing. Further, readjustment of the grinding segments after replacement of an individual grinding segment is easier as it only requires contouring of the individual grinding segment with respect to the remaining segments, as opposed to prior art solutions where all the grinding segments need to be contoured. In particular, the greatest advantage of this configuration is that the grinding segments can be manufactured with a very small amount of material, which leads to significant cost savings both in terms of raw materials and the manufacturing process.

[0008] Optional and / or preferred features of the present invention are described in the dependent claims. Next, the present invention will be described more specifically, merely by way of example, with reference to the accompanying drawings.

Brief Description of the Drawings

[0009]

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DETAILED DESCRIPTION OF THE INVENTION

[0010] Referring to FIGS. 1 to 9, a first embodiment of a rotary grinding tool is generally designated 100. The rotary grinding tool 100 includes a hub 102 having a plurality of radially extending slots 104 extending axially on its outer periphery, and a plurality of grinding segments 106 disposed within the radially extending slots. Each grinding segment has a body 108 for attaching the grinding segment to the hub, and further includes a grinding edge 110. Each grinding segment is individually fixed to the hub using pin elements 112 that extend at least partially through the grinding segment and / or at least partially through the hub adjacent to the grinding segment.

[0011] In this first embodiment, as will be described in detail below, the pin elements extend axially, with a portion extending through the grinding segment and a portion extending through the hub adjacent to the grinding segment.

[0012] The hub is annular and has a central opening 114 for attachment to the rotational axis of a rotary dressing machine (not shown). The overall shape of the hub resembles a pipe flange and has a ring portion 116 and a raised surface 118 on one side of the hub, as best shown in FIG. 8. The hub includes opposing first and second major spindle faces 120, 122 (see FIGS. 10 and 11). The outer peripheral surface 124 connecting the first and second major spindle faces is generally tapered radially inwardly from one side to the other.

[0013] The slots extend axially between the first and second spindle faces. Also, the slots extend radially into the hub, thereby defining a series of support portions 126 between the slots. For each slot, there are adjacent support portions. Each support portion is generally L-shaped and includes a first support leg 128 that extends radially and a second support leg 130 that extends axially. The first support leg is shorter than the second support leg. The first support leg is disposed adjacent to the first spindle face, and the second support leg terminates at the second spindle face.

[0014] A first pin recess 132 for partially receiving a pin element extends along the longitudinal extent of each support portion. The first pin recess has a semi-circular transverse cross-section and is intended to become complete, i.e., completely circular, when aligned with another pin recess having a semi-circular transverse cross-section. This will be explained in more detail below.

[0015] In the first embodiment, each polishing segment is also generally L-shaped and is best shown in FIG. 12. For this reason, the polishing segment includes a first segment leg 134 that extends from a second segment leg 136. The first segment leg is shorter than the second segment leg. The first segment leg extends at an angle X with respect to the second segment leg, and the angle X ranges from 75 degrees to 100 degrees. As shown in FIG. 13, the angle X is measured between the respective outer faces of the first segment leg and the second segment leg. Preferably, the angle X is about 80 degrees.

[0016] Due to the L-shaped configuration, the resulting rotary abrasive machining tool is particularly suitable for machining the contoured shape of a conical frustum. The L-shape helps to minimize the amount of material of the polishing segments required for the machining operation. This is particularly important when expensive superhard materials such as PCD or polycrystalline cubic boron nitride (PCBN) are required to have maximum wear resistance and long life.

[0017] Each abrasive segment is inserted into a slot between two support portions. When the final position is reached, the first segment leg aligns with the first support leg of the hub, and the second segment leg aligns with the second support leg. The L-shaped configuration of the support portions helps to minimize the mass of the hub and supports only the necessary parts.

[0018] As shown in FIGS. 12 and 13, the abrasive segment further includes a nested surface 138 that is intermediate the outer surfaces of the first and second segment legs. The nested surface is important for maximizing the number of abrasive segments that can be extracted from a blank 140 during manufacturing (see FIG. 14). Typically, the blank is a disk of abrasive material such as PCD backed with a carbide layer. By incorporating the nested surface, when determining the appropriate nesting configuration, the number of abrasive segments that can be stacked on the blank increases compared to stacking abrasive segments without a nested surface. As shown in FIG. 13, the nested surface extends at an angle Y in the range of 30 to 50 degrees from the outer surface of the second segment leg. Preferably, the angle Y is about 45 degrees.

[0019] In the hubs of FIGS. 1 to 9, the number of slots and the corresponding number of abrasive segments is 80. This number is determined considering factors such as the target number, rotational speed, feed rate, etc. of the wheel machined by the tool. There are also geometric constraints to consider, such as the minimum distance between abrasive segments (e.g., 15 mm) and / or the radial thickness of the support portion (e.g., 0.75 mm).

[0020] The number of abrasive segments required is related to the total thickness l of each abrasive segment and the diameter D of the hub. From experiments, the relationship between the number of abrasive segments, the thickness of the abrasive segments, and the diameter of the hub has been experimentally obtained and can be defined by the following two equations. Max = Int(πD / (l + 0.75)) Min = Int(πD / (l + 15)) In practice, when the hub is tapered (as in the first embodiment), the diameter used is actually the diameter measured up to the minimum height of the contoured grinding edge. In the case of a non-tapered hub, it is very easy to specify the diameter dimension.

[0021] For example, in the graph of Figure 15, when l = 1 mm and D = 150 mm, the number of grinding segments required for the hub is between the maximum value indicated by line L max and the minimum value indicated by line L min It is also possible to use a number of grinding segments outside these two lines L min and L max but at some point, it will result in a service life and the number of wheels that can be machined by the tool.

[0022] For perfection, in the first embodiment, the total thickness of the grinding segments is about 3 mm and the diameter of the hub is about 140 mm. Thereby, the number of available grinding segments ranges from 24 to 117, and 80 are selected. Preferably, the thickness of the grinding segments ranges from 1 to 4 mm.

[0023] The second pin recess 142 having a semi-circular transverse cross-section extends along the longitudinal extent of the grinding segment and is best shown in Figure 16. At the above-mentioned final position, the second pin recess of the grinding segment aligns with the first pin recess of the adjacent support portion and together forms a hole 144 having a circular transverse cross-section (see Figure 17). When a pin element is inserted into this hole, the grinding element is fixed within the slot (see Figure 18). The grinding element can be removed from the hub simply by pulling out the pin element.

[0024] The pin element can be a spring pin 146 (also known as a slotted spring tension pin) or a screw member such as a grub screw 148. In a first embodiment of the tool, the pin element is a spring pin, made, for example, of zinc-plated spring steel. The spring pin is elongated and consists of a single coil 150 with a gap 152 open in its uncompressed state. When compressed, as occurs when the spring pin is driven into a hole formed by aligned first and second pin recesses, the spring pin reduces in diameter and, due to its inherent spring biasing, attempts to return to its uncompressed state. This behavior causes the spring pin to function as a fastener between the abrasive segment and the hub. In the compressed state, the gap of the spring pin aligns with the respective surfaces of the abrasive segment and the support (see FIG. 19).

[0025] In second and third embodiments of the tool, described below, the pin element is a grub screw or other similar type of screw member.

[0026] Referring briefly again to FIG. 13, the abrasive edge forms part of the second segment leg. In its final position, the abrasive edge projects radially beyond the second support leg in order to function as intended. The abrasive edge has a profile formed, for example, by laser machining in the second segment leg. This profiling is preferably carried out after the abrasive segments have been positioned in situ within their respective slots, as described in UK Patent No. 2574492, with typical outer profiles of the abrasive segments before and after profiling being shown as P and Q respectively. Profile P is essentially artificial and phantom, depicting the outer profile at a particular point in time. Ultimately, profile Q is, for example, the desired profile (one) imparted to the wheel. In practice, since the initial profile can, for example, be repeated at a shallower depth during re-profiling, the desired profile can be finished on the abrasive edge at some depth between line P and line Q. Thus, the depth of the abrasive material between line P and line Q can also be considered as the regrind cost.

[0027] The flange 154, also known as the backing plate, is coaxially attached to the hub with respect to the first principal axis plane (see FIGS. 1 and 4). The flange is fixed in place using a plurality of screws 156 and screw holes 158 (FIG. 8) provided in the hub at a distance from the polishing segments. The flange serves to prevent axial movement of the polishing segments under severe operating conditions. Optionally, the flange is an annular plate having a patterned surface (not shown). The patterned surface on or within the flange engages in a mating configuration with a corresponding pattern on the hub. The cooperating patterns minimize relative rotation between the hub and the flange. Typically, the pattern is a series of recesses and / or protrusions. An example is shown in FIG. 11, where the pattern includes a pair of inscribed arcuate recesses 160.

[0028] Referring now to FIGS. 20 through 26, a second embodiment of the rotary polishing tool is generally designated 200. The rotary polishing tool includes a hub 202 having a plurality of radially extending slots 204 that extend axially along its outer periphery, and a plurality of polishing segments 206 disposed within the radially extending slots. Each polishing segment has a body 208 for attaching the polishing segment to the hub and further includes a polishing edge 210. Each polishing segment is individually fixed to the hub using pin elements 148 that extend at least partially through the polishing segment and / or at least partially through the hub adjacent to the polishing segment. In this second embodiment, the pin elements extend adjacent to the polishing segments and partially through the hub.

[0029] Specifically, the pin elements are inserted radially into the outer peripheral surface 212 of the hub between adjacent abrasive segments. In cooperation with a series of radially extending slits 214, the pin elements are used to help clamp the abrasive segments in a predetermined position within the slots. The slits extend into the hub parallel to the slots on both sides. At the base of each slit, there is an axially extending opening 216 having a circular cross-section to reduce the risk of crack generation. The hub also includes a plurality of radially extending holes 218 adjacent to the slits. Optionally, each slit includes one (Figs. 20 and 30) or two (Fig. 37) holes. When all the abrasive segments are inserted into their respective slots, the pin elements are inserted into each of the radially extending holes, thereby closing the slits and clamping the abrasive segments in a predetermined position. For balanced load transfer and thus to achieve maximum effect, it is important that the slits close one by one (always with adjacent slits) around the hub.

[0030] In this embodiment, each of the abrasive segments is individually attached to the slot via an intermediate abrasive segment holder 220. In this way, the pressure required to hold the abrasive segments in a predetermined position is achieved without filling the entire slot with a highly wear-resistant material. The intermediate holder essentially functions as a substitute for the more expensive PCD material. This is possible because the lower part of the abrasive segment is only required to attach the abrasive segment to the holder and does not contact the grinding wheel, so in practice it does not particularly need to be wear-resistant.

[0031] Examples of suitable abrasive segment holders are shown in FIGS. 27, 28, and 29. Usually, the abrasive segment holder is made of steel. In FIG. 27, the abrasive segment holder 220a includes a seat portion 222 and a back portion 224 perpendicular to the seat portion. In FIG. 28, the abrasive segment holder 220b includes a seat portion 226 and a back portion 228 inclined with respect to the seat portion. In use, the abrasive segment holders of FIGS. 27 and 28 face their back portions rearward of the abrasive segments defined with respect to the forward rotation direction of the hub. In FIG. 29, the abrasive segment holder 220c includes a seat portion 230 and two spaced-apart back portions 232, 234 perpendicular to the seat portion. The back portions have a triangular longitudinal cross-section. Two back portions define a slot 236 where the abrasive segment is received.

[0032] During the test, it was found that the abrasive segment tool holders of the first and second embodiments had more problems than expected. When supporting the abrasive segment, misalignment frequently occurred at the tip surface between the abrasive segment and the abrasive segment holder. Due to tolerance problems, the abrasive segment protruded beyond the tip surface of the abrasive segment holder, or the abrasive segment holder protruded beyond the abrasive segment. In either case, the load applied to the tip surface was not distributed to both the abrasive segment and the holder. Therefore, a third embodiment was then developed. In this embodiment, since the abrasive segment is located in the slot between the two back portions, the load is evenly transmitted from the holder to the abrasive segment. A modification of this third embodiment is shown in FIG. 37.

[0033] In the second embodiment of this tool, the hub is not tapered radially inwardly from the first spindle surface toward the second spindle surface. Instead, the outer peripheral surface is generally perpendicular to the first and second spindle surfaces (see FIG. 23). As a result, the tool remains suitable for many types of rotary grinding applications, but is not suitable for grinding complex contours such as the contour of a coniferous tree.

[0034] Also, in this embodiment, the number of polishing segments and slots is significantly reduced. This rotary polishing tool is suitable for machining operations that require a smaller diameter. Also, since it is less costly compared to the first embodiment, it is also ideal as a test fixture used for optimizing operating parameters. Finally, the flange 238 is attached to the hub in the same manner as in the prior art.

[0035] Next, referring to FIGS. 30 to 36, a third embodiment of the rotary polishing tool is shown generally at 300. The rotary polishing tool includes a hub 302 having a plurality of radially extending axial slots 304 on its outer periphery, and a plurality of polishing segments 306 disposed within the radial slots via an intermediate holder. Each polishing segment has a body 308 for attaching the polishing segment to the hub, and further includes a polishing edge 310. Each polishing segment is individually fixed to the hub using pin elements 312 that extend at least partially through the polishing segment and / or at least partially through the hub adjacent to the polishing segment. Similar to the second embodiment, in the third embodiment, the pin elements extend partially through the hub adjacent to the polishing segment.

[0036] The second and third embodiments are very similar, so only the important differences are emphasized here. In the third embodiment, the hub does not have a raised surface, and both the hub and the flange 314 are annular and lie coaxially side by side with each other. In contrast, in the second embodiment, the flange is attached to the raised surface of the hub.

[0037] Next, referring to FIGS. 37 and 38, a fourth embodiment of the rotary lapping tool is generally indicated at 400. The rotary lapping tool includes a hub 402 having a plurality of radially extending slots 404 that extend axially along its outer periphery, and a plurality of lapping segments 406 disposed within the radially extending slots. Each lapping segment has a body 408 for attaching the lapping segment to the hub and further includes a lapping edge 410. Each lapping segment is individually fixed to the hub using a pin element (not shown) that extends at least partially through the lapping segment and / or at least partially through the hub adjacent to the lapping segment. Similar to the second embodiment, in the fourth embodiment, the pin element extends at least partially through the hub adjacent to the lapping segment.

[0038] The second and fourth embodiments are very similar, so only the important differences are emphasized here. In the fourth embodiment, as described above, the type of lapping segment holder 220 is different. The lapping segment holder 220d includes a seat 412 and two spaced-apart backs 414, 416 that are perpendicular to the seat. The backs have a rectangular longitudinal cross-section. The lapping segments are clamped in a predetermined position of the holder 220d. Similarly, the holder is clamped in a predetermined position of the hub.

[0039] Furthermore, as described above, there is only one pin element used as part of the clamping mechanism. Two smaller pin elements would allow for better load transfer to the lapping segments, but one larger pin element also functions effectively.

[0040] For each of the various tool embodiments described above, each polishing segment preferably comprises PCD. Preferably, the PCD is provided as a layer 500 having a thickness in the range of 1 to 2 mm. Although it is also possible to use PCBN, PCD is excellent in terms of wear resistance due to its extremely high hardness. The drawback is that PCD is more expensive than PCBN, and there is a trade-off between performance and cost. Using FIG. 39, it is shown that the volume of PCD used in the polishing segments of the second, third, and fourth embodiments of the tool is significantly reduced compared to the polishing segments of the prior art. The same finding is widely applicable to the L-shaped polishing segments of the first embodiment.

[0041] Optionally, the polishing segment also includes a carbide substrate 502 adjacent to the PCD at the interface surface 504 (see FIG. 40). The position of this interface surface relative to the hub center line 506 is of utmost importance. As in the example of FIG. 41a, it is important that the interface surface is offset from the center with respect to the hub center line. In other words, as in the example of FIG. 41b, the interface surface should not coincide with the center line. Ideally, as in the example of FIG. 41c, the center line coincides with the PCD layer of the polishing segment.

[0042] In FIG. 41a, the geometry of the cutting edge 508 will be lost earlier due to wear, which is bad, but the PCD will wear, which is good. Tests have shown that when the interface surface coincides with the center line as in FIG. 41b, cracks are likely to occur at the interface surface and the polishing segment is likely to break early. In FIG. 41c, the geometry of the cutting edge is maintained and wear has started in the PCD layer, both of which are good.

[0043] In practice, the position of the interface surface relative to the hub center line is achieved by varying the ratio of the PCD layer to the carbide layer. Preferably, the total thickness of the polishing segment (i.e., PCD and, if present, the carbide layer) is less than 5 mm, more preferably less than 4 mm. Preferably, the ratio of the carbide layer to the PCD layer is 1 to 3.

[0044] The rotary grinding tool can be configured as a grinding wheel, a rotary dressing tool, or some other similar form of machining tool. As described above, the rotary grinding tool is particularly useful for dressing a grinding wheel having a contour of a complex shape such as a coniferous tree-like contour.

[0045] In summary, the inventors have devised an alternative method for attaching a grinding segment to a hub for rotary grinding applications. This new method can reduce the amount of wear-resistant material required for the grinding segment, making it cost-effective from a structural perspective. Furthermore, since individual segments can be replaced and reformed, it is highly flexible from a maintenance perspective.

[0046] Although the present invention has been shown and described with particular reference to embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as defined by the claims.

Explanation of Reference Numerals

[0047] 100 Rotary grinding tool 126 Support portion 128 First support leg 130 Second support leg 132 First pin recess

Claims

1. A rotary grinding tool, comprising: a hub having a plurality of radially extending slots extending axially on the outer periphery; a plurality of grinding segments disposed within the radially extending slots; Each of the grinding segments has a body for attaching the grinding segment within the hub and further comprises a grinding edge. Each of the grinding segments is individually fixed to the hub using pin elements that extend at least partially through the grinding segment and / or at least partially through the hub adjacent to the grinding segment. The grinding segment comprises a first partial opening for partially receiving the pin element, the hub comprises a second partial opening for partially receiving the pin element, and when the grinding segment is within the slot and the first and second partial openings are aligned, the first and second partial openings together form a complete opening. A rotary grinding tool characterized by this.

2. The rotary grinding tool according to claim 1, wherein the grinding segment is L-shaped and comprises a second leg received within the radially extending slot of the hub and a first leg extending from the second leg.

3. The second leg extends at an angle X with respect to the first leg, the angle X is measured between the outer surfaces of the L-shape formed by the first and second legs, and the angle X ranges from 75 degrees to 100 degrees. The rotary grinding tool according to claim 2.

4. The rotary grinding tool according to claim 2 or 3, wherein the grinding segment further comprises a nested surface intermediate the outer surfaces of the first and second legs.

5. The rotary grinding tool according to claim 4, wherein the nested surface extends at an angle in the range of 30 degrees to 50 degrees with respect to the outer surface of the second leg.

6. The rotary grinding tool according to claim 1, wherein the hub is tapered axially from one side towards the other side.

7. The rotary grinding tool according to claim 1, wherein the hub comprises an L-shaped support portion.

8. The rotary grinding tool according to claim 1, wherein the hub comprises a patterned shaft end face coupled to a flange, and the flange comprises a corresponding patterned shaft face that matches the patterned shaft end face.

9. The rotary grinding tool according to claim 1, further comprising a flange coupled to the hub.

10. ​ The flange has a patterned axial surface that is coupled to the hub, and the hub has a corresponding patterned axial end surface that matches the patterned axial surface, the rotary abrasive machining tool according to claim 9.

11. The hub has a plurality of radially extending slits that terminate at the outer peripheral surface of the hub, the rotary abrasive machining tool according to claim 1.

12. The slit extends parallel to the radial slot, the rotary abrasive machining tool according to claim 11.

13. The slit further comprises one or more radially extending closed holes for receiving grub screws, the rotary abrasive machining tool according to claim 12.

14. The rotary abrasive machining tool according to claim 11 further comprises an abrasive segment holder intermediate the hub and the abrasive segment.

15. The abrasive segment includes polycrystalline diamond (PCD), the rotary abrasive machining tool according to claim 1.

16. The rotary abrasive machining tool according to claim 15 further comprises a carbide substrate adjacent to the PCD at the interface.

17. The interface is located at a position offset from the center with respect to the center line of the hub, the rotary abrasive machining tool according to claim 16.

18. The PCD is provided as a layer having a thickness in the range of 1 to 2 mm, the rotary abrasive machining tool according to claim 15.

19. The total thickness of the abrasive segment is less than 5 mm, preferably less than 4 mm, the rotary abrasive machining tool according to claim 15.

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