AU7735101A - Cutting tool for producing toothed articles - Google Patents

Description

AUSTRALIA

PATENTS ACT 1990 DIVISIONAL APPLICATION NAME OF APPLICANT: The Gleason Works DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street SMelbourne, 3000.

0 ADDRINVENTION TITLE: 0 performing it known to us: performing it known to us: P:\OPER\Arl%2462225Div.doc0 1/10/01 -1A- CUTTING TOOL FOR PRODUCING TOOTHED ARTICLES 0 0

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S0The present invention is generally directed to cutting tools for toothed 10 articles such as gears and the like. Particularly, the present invention is directed to a cutting blade for a cutting blade for improving the machining accuracy of the cutting tool.

15 It is known in the art to produce toothed articles, such as bevel and hypoid gears, with cutting tools comprising a head portion in which a plurality of cutting blades are positioned, for example, stick-type cutting blades manufactured from bar stock such as shown in U.S. Patent No. 4,575,285 to Blakesley.

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In the type of cutting tool mentioned above, it is customary to provide a circular cutter body having a plurality of slots extending inwardly a predetermined distance from the periphery of the cutter body for receiving and positioning cutting blades in the cutter body. In many instances, extending about the periphery of the cutter body is a clamping ring (or locking ring) which is secured to the cutter body and in which is mounted means to clamp one or more cutting blades in each of the positioning slots. Cutting tools including a clamping ring and blade clamping means can be seen, for example, in U.S. Patents Nos. 4,621,954 to Kitchen et al.; 3,760,476 to '.010 Kotthaus; 4,093,391 to Bachmann et al.; or 4,197,038 to Hipp et al.

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S.o Traditionally, the positioning slots in a cutter head have been in a 0 "generally rectangular form of opposing side walls and an inner end wall which is perpendicular to the side walls. In machining these slots into the cutter head, it is understood that some clearance must be included in the slot dimensions in order for a cutting blade to be positioned in the slot. As such, Soeven with the most accurate machining methods, there is always some amount of clearance between a cutting blade and a side wall surface when a 00 cutting blade is clamped in position in a receiving slot.

9@00 0 0 With the square-cornered form of the prior art receiving slots and the 0 o e" clearance which exists between the cutting blade and a side wall surface of the slots, cutting blades have shown a tendency to twist in the receiving slots when subjected to the forces of some cutting operations thereby resulting in the formation of undesirable tooth geometries.

One arrangement for alleviating the problem of blade twist is addressed in international publication no. WO 97/39851 to Clark et al. The blade receiving slots comprise opposing side surfaces and an end portion comprising blade mounting surfaces which are angled toward one another with each mounting surface preferably extending at an angle of about degrees with respect to its associated side surface.. With this arrangement, a P:\OPER\ArlI2462225Div.do-0 1/1010/1 -3cutting blade with complementary shaped sides can positively seat against these angled mounting surfaces when clamped thus eliminating unwanted blade clearances as well as twisting of the blades during cutting.

The above-mentioned WO 97/39851 also proposes a cutter head comprising a plurality of double-dovetail shaped projections located on the outer portion of the cutter head body member. The double-dovetail projections are positioned in a complementary-shaped channel of a two-part cutter ring. The 0e parts of the cutter ring are positioned above and below the projection and then S 10 drawn together by several screws thus securing the clamping ring to the cutter o head body. By attaching the clamping ring in this manner, no heating of the cutter head is necessary and thus any heat-related distortions attributable to welding and/or heat shrinking are eliminated.

15 However, while avoiding heat-related distortions, formation of the doubledovetail projection requires significant machining accuracy which is quite time consuming. Tightening of the screws which join the two parts of the cutter ring •900: -may cause unwanted tension in the dovetail portion resulting in the formation of cracks between the projections of the cutter head during cutting operations or the dovetail portion may break off from the cutter head body member. Subsequent g tightening blade clamping bolts adds more tension to the dovetail portion thereby further enhancing the possibilities of cracking and/or breakage.

The present invention provides a cutting blade insertable into a cutter body member having a generally circular shape, a front surface, a back surface and an axis of rotation, said cutter body member having a plurality of individual projections arranged spaced from one another about said cutter body, the space between successive projections defining receiving slots for the cutting blades, said cutting blade comprising: a tip, a first side surface and a second side surface, P:\OPER\Arl\2462225Div.doc-O/IO/Ol -4an outer end surface extending between said first and second side surfaces, an inner end surface comprising first and second angled portions, said first angled portion extending from said first side surface and said second angled portion extending from said second side surface, said angled portions extending toward one another, said first angled portion being arranged at an angle of one of 55o 60 degrees or 30 degrees with respect to said second side surface and said second angled portion being arranged at an angle of the other of 60 degrees or S" degrees with respect to said second side surface, 10 a cutting profile surface located on one of said inner or outer end surfaces at an end of said length, back second side surface, a first cutting edge being defined at the intersection of said cutting profile surface and said first side surface, a clearance profile surface located on the other of said inner or outer end surfaces at said end of said length, said clearance profile surface extending from said first side surface to said second side surface, a clearance edge being defined at the intersection of said clearance profile surface and said first side surface.

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A preferred embodiment will now be described, by way of example only, with reference to the drawings, in which: Figure 1 shows a front perspective view of the cutter body member of a cutting tool; Figure 2 shows a rear perspective view of the cutter body member of the cutting tool of Figure 1; Figure 3 illustrates a top view of the cutter body member of the cutting tool of Figure 1; Figure 4 illustrates a cross-sectional view of the cutter body member of Figure 1; P:\OPER\Arl,2462225Div.do.0 I/I /oI e

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Figure 5 is an enlarged view of a section of the cutter body member of Figure 1 showing successive cutting blade receiving slots; Figure 6 is an enlarged view of a section of the cutter body member of Figure 1 showing successive cutting blades receiving slots having cutting blades positioned therein; Figure 7 illustrates a rear perspective view of a clamping ring; Figure 8 illustrates a sectional view of the inside of the clamping ring of Figure 7; Figure 9 illustrates a front perspective view of an assembled cutting tool; Figure 10 illustrates a rear perspective view of the assembled cutting tool of Figure 9; *000SO 0 6

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Figure 11 shows a cross-sectional side view of a clamping block; Figure 12 shows a front view of the clamping block of Figure 11; Figure 13 illustrates a top view of the clamping block of Figure 11; Figure 14 shows a cross-sectional view of a clamping arrangement positioned in a clamping ring; Figure 15 illustrates a top sectional view of the assembled cutting tool of Figure 9 having cutting blades according to a preferred embodiment of the present invention; P:\OPER UA \246222Div.doc.28a/09 1 -6- Figure 16 shows a cutting blade blank from which a cutting blade according to the preferred embodiment is formed for the cutting tool; Figure 17 is a cross-sectional view of the cutting blade blank of Figure 16; Figures 18 and 19 are cross-sectional views of the cutting blades shown in Figure 15; and 0O S 10 Figure 20 illustrates a cutting blade formed from the cutting blade blank of Figure 16.

A cutting tool is illustrated in Figure 9 and comprises a cutter body member 2, and a clamping ring 40 which together comprise a cutter head. In addition to the cutter head, the cutting tool further includes cutting blades 80, 82 and clamping means 60 to secure the cutting blades 80, 82 in position in the cutter

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0 The cutter body member 2, as shown in Figures 1-4, is rotatable about an axis T and comprises a front surface 4 and back surface 6 which may include a keyway 8 into which a key on a machine tool spindle is inserted when the cutting tool is mounted on the machine tool. The outer portion of the cutter body member 2 includes a plurality of individual projections 10 between which is defined cutting blade receiving slots 12 which are oriented at a desired hook angle. Each of the projections 10 has an outer surface 14 and least one, and preferably all, of the projections outer surfaces 14 includes a protrusion 16 of a form, usually rectangular, which generally corresponds to respective receiving slots in the clamping ring as will be described in detail below.

The front surface 4 of the cutter head may further include an annular depression 18 located concentric about the axis T. In some cutting processes, P:\OPER\Arl2462225Div.doc-28/09/01 -7such as cutting of pinions, interference can occur between the workpiece and the face of the cutting tool. By including the annular depression 18, sufficient clearance is created to allow the tool and workpiece to be properly positioned for cutting without interference.

Figure 5 is an enlarged view of two successive blade receiving slots 12, however, the following description applies to all slots in the cutter head.

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*o S6 .e* The slots each comprise opposing first and second side surfaces 20, 22.

Each slot also includes an inner end portion comprising first mounting surface 24 and second mounting surface 26. First and second mounting surfaces 24, 26 extend toward one another with first mounting surface 24 extending at an angle A of less than 90 degrees with respect to first side surface 20 and second mounting surface 26 extending at an angle B of less than 90 degrees with respect to second side surface 22. First and second mounting surfaces 24, 26 extend toward one another and terminate short of their intersection at 000 an innermost groove 28 known as a "check" which serves to provide .0 10 machining clearance when finishing the mounting surfaces because a tool *eScannot adequately and repeatedly machine a sharp corner and besides, a sharp corner causes stress concentration.

Preferably, when first side surface 20 precedes second side surface 22 in the cutting direction as is shown by cutter rotational direction arrow R, angle A will be equal to about 60 degrees and angle B will be equal to about degrees. Of course, if the direction of rotation is opposite that shown, the angular orientations of the mounting surfaces will be reversed. In all see* e -oinstances, it is desirable to have the steeper mounting surface (26 in Figure be positioned to absorb a greater amount of the cutting forces than the other mounting surface. The steeper surface directs more of the cutting forces .i inward toward the center of the cutter head thus reducing the tendency for cracks to develop between the projections 10 because there are less tangential forces exerted on the projections. As such, the back surface of a cutting blade should be positioned against the steeper mounting surface.

To examine cutter head strength, the following cutter heads were evaluated: a cutter head having a generally rectangular-shaped slot, the cutter head of previously-discussed WO 97/39851 having inner end blade mounting surfaces each oriented at 45 degrees with respect to their adjoining side surfaces, and, P:\OPER\ArlU2462225Di.doc-28/09101 -9the cutter head, as discussed above, having inner end blade mounting surfaces oriented at 60 degrees (angle A) and 30 degrees (angle B) with respect to their adjoining side surfaces.

The test was conducted by mounting a cutting blade in a slot of each of the above cutter heads and exerting a force in the appropriate direction on the cutting edge of the cutting blade so as to emulate actual cutting. The force was increased So on each cutter head until cracks appeared in the cutter head. The conventional *0 .0 cutter head exhibited cracks at a force of 4,800 pounds while the cutter head 10 with 45 degree mounting surfaces cracked at 6,100 pounds. The cutter head cracked at 9,200 pounds, thus clearly showing a significant increase in strength over the other two cutter heads.

Each blade receiving slot 12 preferably further includes a first shoulder 0 15 and a second shoulder 32 at the intersection of the respective side surface with its mounting surface. The purpose of these shoulders is to provide a small amount of •0*0 clearance C about 0.005 inch (0.127 mm)) between a cutting blade 34 and 0.:00 the first and second sides of the receiving slot 12. See Figure 6. With this 0 arrangement, all contact between the cutting blade 34 and the receiving slot 12 occurs at the seating surfaces 24, 26 thus creating a positive seating of the cutting blade against these mounting surfaces.

Positioned around the cutter body member 2 is a clamping ring 40 as seen in Figure 7 which illustrates a bottom view thereof. The clamping ring 40 is heated to about 400°F (2040C) to expand the ring diameter sufficiently to allow the heated ring to be placed over the cutter body member 2 (Figure Upon cooling, the ring diameter shrinks thus adhering the clamping ring 40 to the cutter body member 2.

The clamping ring 40 is placed about the cutter body member such that the protrusions 16 on the outer surface 14 of the projections 10 are inserted into respective slots 42 located in the inside of the clamping ring 40 (Figure 10). Once the protrusions 16 are inserted into the receiving slots 42, the protrusion 16 and the receiving slot 42 may be spot welded together, as shown by 52 in Figure 10, to further ensure the adherence of the clamping ring 40 to the cutter body member 2 and prevent any relative rotation between the two components during cutting operations.

For illustrative purposes, two cutting blade blanks 34 are shown positioned in receiving slots in Figures 9 and Also included in the clamping ring 40 is an inner channel 44 as shown in Figure 8. Blade clamping means, discussed below, are positioned via 10 screws extending through threaded holes 46. With this arrangement, the clamping means can be retained in the channel when the screws are withdrawn thus allowing cutting blades to be inserted into and removed from the receiving slot 12 without the clamping means failing from the receiving slot. Also seen in Figure 8 are the receiving slots 42 into which the protrusions 16 are inserted when the clamping ring 40 is placed about the •cutter body member 2. The clamping ring further includes a top surface 48 as "ee. well as a tapered bottom surface 50 which not only reduces the weight of the "•cutter head, but also forms a convenient handle to grasp for moving the cutter es 0 head.

The cutting blade clamping means is shown in Figures 11-14. The clamping block 60 is shown in Figure 11 wherein the clamping block is shown in an unclamped position. The clamp block includes a front surface 70 which contacts a cutting blade and a back surface 72. The clamping means includes a housing 62 integral with the clamp block 60 for receiving the head portion 64 of a clamping screw 66 as shown in Figure 14. The threaded portion of the clamping screw 66 is connected to the head portion 64 via a neck portion 68. The receiving housing 62 comprises a generally box-like shape with an open bottom and a front portion 74 having a semi-circular opening 76 (Figure 12) formed therein. The semi-circular opening 76 is large enough to fit over the neck portion 68 of the clamping screw 66 but is small enough to prevent passage of the larger-diameter head portion 64 11 therethrough. The top surface 79 of the clamp block may be angled as shown in Figure 12 by an amount to match the hook angle of the receiving slot 12 in the cutter head.

It should be noted that within the receiving housing 62, the back surface 72 of the clamp block 60 should be machined to be essentially parallel with the front surface 70 as is shown by 78 in Figure 13. This will allow the head portion 64 of the clamp screw 66 to evenly seat against the back surface 72 when clamping a cufftting blade into position in the receiving slot 12 as is illustrated in Figure When it is necessary to remove or insert a cutting blade into a receiving slot 12 of the cutter head, clamping screw 66 is rotated to withdraw it from the clamping ring 40. This movement results in the head portion 64 engaging the inside surface 81 of the front portion 74 of the receiving housing S62 thus moving the clamp block 60 toward the inside surface of the clamping C"ring 40. The receiving housings74 is of a size whereby is fits into inner channel 44 of the clamping ring 40 as can be seen in Figure 14. The back surface 72 of the clamp block 60 is an angled surface, as seen in Figure 13, which approximates the curvature of the inner surface of the clamping ring el•• thereby allowing the back surface 72 of the clamp block 60 to be positioned o against the inner surface of the clamping ring 40. With this arrangement, sufficient clearance is provided to insert and/or remove a cutting blade from a receiving slot while maintaining the clamp block 60 in position in the receiving slot 12 of the cutter head.

The form of the front surface 70 of clamping block 60 is similar to that disclosed in previously discussed WO 97/39851 in that the form of the front surface 70 is generally concave-shaped, preferably constructed from throughhardened spring steel. The advantage of this form is that when clamped against a cutting blade, clamping forces are exhibited not only in line with the force of the clamping screw 66, but clamping, forces are also present at the ends of the clamping block 60 due to the form of the clamping block 60 and Sthe increased forces created at the ends of the clamping block 60 when it is elastically distorted from its original concave shape to an essentially flat form against a cutting blade. In addition to clamping forces, frictional forces are also present between the end and clamp screw clamping forces which assist in securing the cutting blade in its position in the cutter head slot. After the concave shape is straightened, an increase in torque occurs on the clamping screw. This can be sensedas a stop signal and therefore, a torque wrench is S* not necessary.

*o SWith the clamping block of Figure 11, it can be seen that the clamp screw and/or attachment means is located asymmetrically along the length of the clamp block thus providing differing clamp pressures at the ends of the clamp block. This arrangement is beneficial when additional clamping pressure is desired near the cutting end of a cutting blade such as in those situations where a significant length of cutting blade extends beyond the face of the cutter head.

SOO The concave clamp block controls the clamp force and pressure 0:0°*o distribution between the clamp block the cutting blade. Primarily, the radius of curvature of the concave clamp block is the control parameter and this permits a "built-in" mechanism to control clamping pressure by varying the radius of curvature of the clamp block. By controlling the clamping force of the clamp block, an allowable maximum clamp force can be designed into the clamp block which, when exceeded, permits movement of the cutting blade in a cutter head slot, such as when cutting forces become greater than the maximum clamping force, thus preventing damage to a cutter.

Figure 15 shows cutting blades 80 and 82 according to a preferred embodiment of the present invention clamped into position in a cutter head.

Clamp screws 66 have been rotated inwardly thus engaging clamp screw head portion 64 with the surface 78 within receiving housing 62 thereby moving the receiving housing 62 in an WO 99/41035 PCT/US99/03021 13 inward direction out of the inner channel 44 while simultaneously moving clamp block 60 inward into contact with a side surface of cutting blades and 82 Cutting blades 80 and 82 are shown in Figure 15 as having respective rake faces 84, 86 inclined in opposite directions whereby it is understood by the artisan that given the direction of cutter rotation, R, as shown, cutting blade 80 is an outside cutting blade and will cut a concave tooth flank of a 0workpiece while cutting blade 82 is an inside cutting blade and will cut a convex tooth flank of the workpiece.

t S ego*A cutting blade blank 88 suitable for positioning if the receiving slots 12 :0.

of the inventive cutting tool is shown in Figure 16. The general form of the cutting blade is that as shown in previously discussed WO 97/39851 except that instead of mounting surfaces 96 and 98 each being oriented at degrees with respect to their respective side surfaces 90 and 92 as is preferred in the above-mentioned publication, the mounting surfaces are oriented at an angle A equal to 60 degrees and an angle B equal to 6600 degrees as can be seen in Figure 17. These angles correspond to angles A *:so*t and B shown with respect to the mounting surfaces 24, 26 of the blade •receiving slots 12 in Figures 5 and 6. Cutting blade blank 88 further includes outer end surface 94 and inner end surface 100.

The cutting blade blank 88 may be made of any suitable tool material such as high speed tool steel M4) or carbide such as Fine Grain or Ultra- Fine Grain K-grade WC-Co or K-P grades WC with one or more of Co, Ti and Ta.

Figures 18 and 19 illustrate, in enlarged fashion, cross-sectional views of cutting blades 80 and 82 having rake faces 84 and 86 (as seen in Figure with the dashed lines indicating the stock material removed from a blade blank, such as the blade blank of Figures 16 and 17, in order to form the rake 14 faces shown. Of course, the end 102 would have cutting and clearance side profile surfaces formed thereon. It can also be recognized that angle A could be measured with respect to side surface 92 if rake faces 84 or 86 are present.

Figure 20 shows such cutting blade 80 whose cross-section is shown in Figure 18. Cutting blade 80 includes a cutting side profile surface 108 which forms a cutting edge 110 at its intersection with front rake face 84. A 0 clearance side profile surface (not shown) is formed on the opposite side of S0 10 cutting blade 80 and its intersection with front rake surface 84 and mounting

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0surface 96 form respective clearance edges 112 and 114. Cutting blade S0" also includes a tip 116 oriented at a relief angle ca. If desired, cutting blade Si 80 may further include a slot extending lengthwise in the front surface of the blade for forming a secondary cutting edge as is known from previously discussed U.S. Patent No. 4,575,285.

i 0 *0000: It is to be understood if the direction of cutter rotation shown in Figure were reversed, the cutting blade blank 88 as shown in Figure 16 could be *0 rotated 180 degrees end-for-end (ends 102 and 104 reversed) and cutting and clearance profile surfaces could then be formed on end 104.

•0 While the invention has been described with reference to preferred embodiments it is to be understood that the invention is not limited to the particulars thereof. The present invention is intended to include modifications which would be apparent to those skilled in the art to which the subject matter pertains without deviating from the spirit and scope of the appended claims.

P:\OPER\l2462225Di .doc-28/09/01 Throughout this specification and claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or of integers or steps.

reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms of the common general knowledge in Australia.

Claims (2)

16- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: S A cutting blade insertable into a cutter body member having a generally circular shape, a front surface, a back surface and an axis of rotation, said cutter body member having a plurality of individual projections arranged spaced from one another about said cutter body, the space between successive projections defining receiving slots for the cutting blades, said cutting blade comprising: a tip, S* a first side surface and a second side surface, 1 an outer end surface extending between said first and second side surfaces, an inner end surface comprising first and second angled portions, said first angled portion extending from said first side surface and said second angled portion extending from said second side surface, said angled portions extending toward one another, said first angled portion being arranged at an angle of one of 60 degrees or 30 degrees with respect to said second side surface and said second angled portion being arranged at an angle of the other of 60 degrees or 30 degrees with respect to said second side surface, a cutting profile surface located on one of said inner or outer end surfaces at an end of said length, back second side surface, a first cutting edge being defined at the intersection of said cutting profile surface and said first side surface, a clearance profile surface located on the other of said inner or outer end surfaces at said end of said length, said clearance profile surface extending from said first side surface to said second side surface, a clearance edge being defined at the intersection of said clearance profile surface and said first side surface. 2. The cutting blade of claim 12 further including an end surface extending between said first and second angled portions. P:\OPER\Arl2462225Div doc-02/10/01

17- 3. The cutting blade of claim 12 further comprising at least a portion of said first side surface being oriented at a predetermined rake angle. 4. A cutting blade insertable into a cutter body member having a generally circular shape, a front surface, a back surface and an axis of rotation, said cutter body member having a plurality of individual projections arranged i* spaced from one another about said cutter body, the space between successive 10 projections defining receiving slots for the cutting blades, substantially as hereinbefore described with reference to the drawings. oo 15 DATED this 2 nd Day of October, 2001 The Gleason Works by its Patent Attorneys DAVIES COLLISON CAVE es