Bevel gear cutting tool with four-sided non-rectangular cutter head slot and cutting blade

Abstract

The cutter head (50) has a plurality of cutting blade receiving slots (51), at least one of which has a four-sided non-rectangular cross-section, and the cutting blade (52) has a four-sided non-rectangular cross-section, the cross-sectional shape of the cutting blade being complementary to the cross-sectional shape of the four-sided non-rectangular cutting blade receiving slot (51), so that the cutting blade can be positioned and clamped within the cutting blade receiving slot.

Description

[Technical Field]

[0001] The present invention relates to the manufacture of gears, and in particular to cutting tools for manufacturing gears such as bevel gears and hypoid gears. [Background technology]

[0002] Bevel and hypoid gears can be cut by generating or non-generating methods, using a single or intermittent indexing process (face milling) or a continuous indexing process (face hobbing). The basic cutting setup on the generating or cradle plane involves positioning the center of the cutter head an amount known as the radial distance from the center of the generating gear (cradle axis). The overall profile of the cutter blade represents one tooth of the generating gear as the cutter rotates. A typical face mill for cutting bevel gears has several blade groups, each containing one to four cutting blades, commonly referred to as "stick" or "bar" blades. The most common is the alternating (full) cutter, which has one outer cutting blade and one inner cutting blade. To equalize the chip loads of all inner and outer blades during the cutting process, the goal is for the cutting edges of all outer and inner blades to track each other at the same radial position.

[0003] In the most common stick blade cutter, the cutterhead 10 (FIG. 1) is a disk with a slot and a clamping device for the blade stick. The cutterhead blade-receiving slots can have different cross sections, such as square, rectangular, pentagonal, or circular, as is known in the art. The blade sticks for the different slot designs typically have complementary cross sections to the respective blade-receiving slots. The dimensions of the stick blade are defined by an amount slightly smaller than the cutterhead receiving slot, allowing the blade to be inserted into and positioned within the slot.

[0004] A typical rectangular blade system uses friction to hold the blade in place against cutting forces. Blades with a pentagonal cross section use a push-in seat to hold the blade in place against cutting forces. With a circular blade cross section, the blade can be held in place by friction or a push-in seat depending on the clamping method. Summary of the Invention

[0005] The present invention relates to a cutterhead having a plurality of cutting blade receiving slots, at least one of which has a four-sided non-rectangular cross-section.

[0006] Another embodiment of the present invention includes a cutting blade having a four-sided non-rectangular cross-section, the cross-sectional shape of the cutting blade being complementary to the cross-sectional shape of the four-sided non-rectangular cutting blade receiving slot, so that the cutting blade can be positioned and clamped within the cutting blade receiving slot.

[0007] In a preferred embodiment, the cutterhead includes a plurality of cutting blade receiving slots, and with respect to the direction of rotation of the cutterhead about its axis of rotation during a cutting process, at least one blade receiving slot includes a leading side surface having a slot depth W2 and a trailing side surface that is a seating surface having a slot depth W1, where W2 is less than (<) W1. The blade receiving slot further includes an outer side surface and an inner angled side surface that is also a seating surface extending between the leading and trailing side surfaces. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 shows a three-dimensional view of a face milling cutter head with a rectangular blade slot. [Figure 2] A cutterhead cross section is shown with a rectangular slot cross section and a rectangular blade cross section. A frictional clamping force holds the blade in place against the cutting force FC. [Figure 3]Shown is a cutterhead cross section 30 having a five-sided slot cross section and a five-sided blade cross section. A clamping force presses the blade via contact surface 37 into the polygonal seating formed by contact surfaces 35 and 36, which provides a forced (form) seating. [Figure 4] 4 shows a cutterhead cross section having a circular slot cross section and a blade with a circular cross section interrupted by a flat. The diameter of the slot is larger than the diameter of the blade. The arrangement of FIG. 4 provides friction seating. [Figure 5] 1 shows a cutterhead cross section having a four-sided non-rectangular slot cross section. [Figure 6] 1 shows a cutterhead cross section having a four-sided non-rectangular slot cross section, including machined grooves or checks. [Figure 7] 1 shows a cutterhead cross section having a four-sided non-rectangular slot cross section and a four-sided non-rectangular cutting blade cross section. [Figure 8] 1 shows a cutterhead cross section having a four-sided non-rectangular slot cross section and a four-sided non-rectangular cutting blade cross section with radial spacer blocks. [Figure 9] FIG. 1 is an isometric view of a four-sided non-rectangular cutting blade showing the trailing contact side and the inner angled contact side. [Figure 10] 10 is an opposite side view of the cutting blade of FIG. 9 showing the leading and outer sides, as well as the cutting edge, clearance edge, and front face. [Figure 11] FIG. 1 shows a partial view of a cutterhead having cutting blades positioned in each of two blade receiving slots. [Figure 12] 1 shows a cutterhead cross section having a four-sided non-rectangular slot cross section and a five-sided cutting blade cross section with radial spacer blocks. DETAILED DESCRIPTION OF THE INVENTION

[0009] The terms "invention," "the invention," and "the present invention" as used herein are intended to broadly refer to all of the subject matter of this specification and any claims that follow. Statements containing these terms should not be understood to limit the subject matter described herein or to limit the meaning or scope of any claims that follow. Furthermore, this specification does not seek to describe or limit the subject matter covered by any claim in any particular part, paragraph, statement, or drawing of this application. The subject matter should be understood by reference to this entire specification, all drawings, and any claims that follow. The invention is capable of other configurations and of being practiced or carried out in various ways. It is also understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting.

[0010] The use of "comprises," "having," and "having" and variations thereof herein is meant to encompass the subsequently listed items and equivalents thereof, as well as additional items. The use of letters to identify elements of a method or process is for identification purposes only and does not imply that the elements should be performed in a particular order. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0011] Hereinafter, when describing the drawings, reference may be made to directions such as top, bottom, upward, downward, rearward, bottom, top, front, and rear, and these are referred to relative to the drawings (as they would normally be viewed) for convenience. These directions are not intended to be interpreted literally or to limit the invention in any way. Additionally, terms such as "first," "second," and "third" are used herein for descriptive purposes and are not intended to denote or imply any importance or significance unless expressly stated.

[0012] The details of the invention will now be discussed, by way of example only, with reference to the accompanying drawings which illustrate the invention, in which like features or components are referred to by like reference numerals, and in which the size and relative sizes of certain aspects or elements may be exaggerated for clarity or illustrative purposes.

[0013] In the context of the present invention, the term "bevel" gear is understood to be broad enough to include bevel gears, the type of gear known as "hypoid" gears, as well as gears known as "crown" or "face" gears.

[0014] 1 shows a three-dimensional view of a known face milling cutter head 10 having a rectangular outer blade slot 15 and a rectangular inner blade slot 16. Slots 15, 16 represent one blade group 11. Cutter head 10 rotates in direction 14 during the cutting process.

[0015] 2 shows a known cutterhead cross section 20 having a rectangular slot 21 and a rectangular blade 22. A clamping screw 23 is in contact with a clamping block 24, which in turn applies a cutting force F C The friction force F is the same magnitude as but in the opposite direction. F1 and F F2 (F C =-F F1 -F F2 ).

[0016] 3 shows a cutterhead cross section 30 having a five-sided (pentagonal) slot 31 and a five-sided blade 32 (see, for example, U.S. Pat. No. 6,120,217). A clamping screw 33 contacts a clamping block 34 and presses the blade 32 through a surface 37 into two prismatic seating surfaces 35 and 36. The cutting force F C When a force F is applied, a reaction force F perpendicular to the surfaces 37 and 35 is generated. R1 and F R2 is the cutting force F C The reaction force acts to counterbalance the force (equilibrium). Because the reaction force does not depend on surface friction at all, the reaction force can (theoretically) be adjusted to any magnitude of cutting force by pressing the blade firmly into the seat.

[0017] FIG. 4 shows a known cutter head cross section 40 having a circular slot 41 and a circular blade 42 with a flat portion 47. The diameter of the blade 42 must be smaller than the diameter of the cutter slot 41 to provide clearance between the slot and the blade so that the blade can be inserted without excessive force. A clamping screw 43 is in contact with the blade surface 47 and presses the blade 42 against a point 45. Depending on the difference in curvature, the point 45 expands to provide a contact surface area. The cutting force F C If there is a reaction force F F1 (friction force on surface 47) and F F2 The friction force F (at point 45) acts against the cutting force in the same magnitude and opposite direction. In the case of large cutting forces, the friction force F F1 +F F2 is the cutting force F C 4, which would result in blade slippage. A further drawback of the arrangement of Figure 4 is that the clamping screw 43 contacting the blade flat 47 is the only geometric feature that provides a defined rotational seating direction 56, which is insufficient for a cutting blade.

[0018] FIG. 5 shows a cross-section of a cutterhead 50 of the present invention, which includes a four-sided non-rectangular (i.e., not rectangular) cutting blade receiving slot 51a (as viewed in an axial cross-section defined by a plane perpendicular to the axis of rotation of the cutterhead 50) having sides 55, 56, 57, and 58. For purposes of explanation and illustration, the cutting blade receiving slot 51 (in all figures) extends parallel to the axis of rotation of the cutterhead 50 between the cutterhead's top surface (106 in FIG. 11) and bottom surface (not shown). Sides 55 and 56 are mounting or seating surfaces that contact and seat a cutting blade when positioned and clamped within slot 51. Side 55 is the trailing or rear seating surface with respect to the cutterhead's direction of rotation "R" during machining, and is preferably parallel to leading side 57. The distance between sides 55 and 57 is referred to as the width of the tooth slot. Side 56 is an angled seating surface that extends between and intersects leading or front side 57 (defined relative to direction R) and trailing side 55 .

[0019] The intersection angle α1 between sides 57 and 56 is greater than 90 degrees (i.e., >90°), and the intersection angle α2 between sides 55 and 56 is less than 90 degrees (i.e., <90°). Side 58 is the outer side of slot 51 and includes at least one opening, preferably a threaded opening, through which a clamping screw (e.g., 53 in FIG. 7) or other clamping mechanism may extend. Outer side 58 is preferably perpendicular to sides 55 and 57. Because angled side 56 is closer (radially) to the axis of rotation than side 58, angled side 56 can be considered the "inner" side relative to the axis of rotation of cutterhead 50 (see FIG. 11). Side 58 is therefore the "outer" side of slot 51 relative to the same axis of rotation. Side 55 has a slot depth W1, and side 57 has a slot depth W2 that is less than W1 (i.e., W2 <W1)。

[0020] FIG. 6 is the same as FIG. 5 except that it includes a groove 59 known as a "check," which serves to provide machining clearance when finishing the clamping surface 55 and the seating surface 56, since many tools cannot adequately and repeatedly machine sharp corners, and sharp corners can also cause stress concentrations.

[0021] FIG. 7 illustrates the inventive cutterhead 50 of FIG. 5 including a stick- or bar-type cutting blade 52 (shown in cross section defined by a plane perpendicular to the axis of rotation of the cutterhead 50) mounted within the slot 51, the cutting blade 52 including four non-rectangular (i.e., non-rectangular) sides defined by an outer side 60, a leading or front side 61, a trailing or rear contact side 62, and an inner angled contact side 64. The distance between sides 61 and 62 is referred to as the width of the cutting blade, and the distance between side 60 and contact side 64 is referred to as the thickness of the cutting blade. The terms "leading" and "trailing" are defined according to the operational orientation of the cutting blade 52 mounted within the slot 51 during machining. A cutting edge (not shown) is located on the leading side 61 of the blade 52, at the end of the portion of the blade that protrudes from the front face of the cutterhead 50. For purposes of explanation and illustration, the cutting blade 52 extends parallel to the axis of rotation of the cutterhead 50.

[0022] Clamping force F from the clamp screw 53 and the clamp block 54 Clamp is transferred to the blade 52 through contact with the surface of the blade's outer side 60. To achieve equilibrium between the clamping force and the surfaces of the blade's contacting sides 62 and 64, the clamping force F Clamp is the normal force F N1 and F N2 The normal force F N1 presses the blade against the slot seating surface 55, applying a normal force F N2 presses the blade against the slot seating surface 56. R1 is F N1 is the reaction force of F R2 is F N2The clamping force holds the blade firmly and tightly in the correct position. The cutting force F C is the reaction force F on surface 55 R3 The surface 55 has only the average cutting force F C This creates a reaction force F that is equal in magnitude to the cutting force but in the opposite direction. R3 This condition is optimal for accurate and firm blade seating in the cutterhead. As a result of the clamping and cutting forces, a small gap 70 exists between the leading side 61 of the cutting blade 52 and the leading side 57 of the slot 51. If desired, the blade corner formed by the intersection of sides 55 and 56 may be slightly radiused to eliminate sharp corners.

[0023] The four-sided non-rectangular blade slot 51 and cutting blade design allows one seating surface 55 of the slot 51 to apply an average cutting force F C The second seating surface 56 is oriented at an angle (FIG. 5) and therefore the clamping force F Clamp 7 achieves sliding of the cutting blade 52 against the seating surface 55 during blade clamping by the force F. Compared to the prior art, the inventive configuration arrangement between the cutting blade and the cutter head mounting slot allows the clamping force to firmly press the blade against the seating surface while one of the seating surfaces is perpendicular to the average cutting force. The arrangement shown in FIG. 7 presents a significant static and dynamic increase in seating stiffness and seating accuracy during the cutting process compared to state-of-the-art solutions. Cutting force F C As increases, the contact pressure on the seating surface 55 also increases by the same factor.

[0024] FIG. 8 shows a cross-section of a cutterhead 50 having a four-sided non-rectangular slot cross-section 51 and a four-sided non-rectangular cutting blade 52 shown in cross-section as in FIG. 7. To achieve a different radial position of the blade (relative to the axis of rotation of the cutterhead 50), a radial shimming spacer block 67 is used to increase the radial blade position (i.e., the distance of the blade 52 from the axis of rotation of the cutterhead 50) by an amount 63. The spacer block 67 is shaped to firmly contact not only the slot seating surfaces 55 and 56 at their respective contact surfaces 65 and 66, but also the blade contact surface 64 via a spacer block seating surface 69. A connecting screw 68 connects the spacer block 67 to the body of the cutterhead 50.

[0025] Radial blade shimming using spacer blocks 67 allows a wider range of different gear shapes to be cut with the same cutterhead. This flexibility is highly desirable for reducing cutterhead inventory, which was previously only possible by accepting reduced stiffness and precision when conventional parallel spacers were placed between the slot surface 25 and the cutting blade 22 (see FIG. 2) in a friction blade clamp. The spacer blocks 67 of the present invention are shaped to accommodate and maintain secure blade seating of the blade 52 with their surfaces facing the slot seating surfaces 55 and 56 of the cutterhead body 50 and their surfaces facing the blade surface 64. The spacer blocks 67 increase the radial position of the blade 52 by an amount 63. The amount 63 may vary among the various available spacer blocks to provide greater flexibility for the use of different blade sizes and cover a wider range of gear shapes.

[0026] The cutting blade 52 shown in cross section in FIGS. 7 and 8 is shown in isometric views in FIGS. 9 and 10. FIG. 9 illustrates a cutting blade 52 with a four-sided, non-rectangular cross section, having a total length between the tip and bottom ends of the cutting blade, as would normally be seen in FIG. 9, including a lower shank portion and an upper cutting end portion. The cutting blade 52 includes an outer side 60, a leading or front side 61, a trailing or rear contact side 62, and an inner, angled contact side 64. The terms "leading" and "trailing" are defined according to the operational orientation of the cutting blade 52 during machining when mounted in the blade mounting slot (e.g., 51 in FIG. 7). The thickness of the cutting blade 52 is greater at the trailing contact side 62 than at the leading side 61. A cutting edge 90 is located on the leading side 61 of the blade 52, at the end of the portion of the blade that protrudes from the front face of the cutterhead (e.g., 50 in FIG. 11) (i.e., the cutting end). The cutting blade 52 also includes a shoulder 91, a cutting side profile surface 92, and a tip flank 98. A rectangular reference cross section is shown at 100.

[0027] Figure 10 shows an opposite view of the cutting blade of Figure 9, revealing the front face 94, clearance edge 95, clearance side profile relief surface 96, and shoulder 93. The front face 94 is shown oriented with a rake angle K which, although shown to indicate a positive value for the rake angle, may also be zero or a negative value.

[0028] 11 shows a partial view of a cutterhead 50 that is rotatable in a clockwise direction R about a tool axis T. The cutterhead 50 includes a plurality of cutting blade receiving slots 51. An inner cutting blade 102 and an outer cutting blade 104 are positioned within the respective receiving slots of the cutterhead and are shown protruding from a face 106 of the cutterhead 50.

[0029] FIG. 12 shows a portion of a cutterhead 50 having a four-sided non-rectangular slot cross-section 51 and a five-sided blade 72 shown in cross-section. A cutting edge (not shown) is located on the leading side of blade 72 (i.e., the side adjacent gap 70) at the end of the portion of the blade that protrudes from the front face of cutterhead 50. To achieve a different radial position of the blade (relative to the axis of rotation of cutterhead 50), a radial shimming spacer block 77 is used to increase the radial blade position (i.e., the distance of blade 72 from the axis of rotation of cutterhead 50) by an amount 73. Spacer block 77 is shaped to firmly contact slot seating surfaces 55 and 56 via respective contact surfaces 81 and 82, as well as contact surfaces 74 and 79 of cutting blade 72 via respective spacer block seating surfaces 83 and 84. A connecting screw 78 connects spacer block 77 to the body of cutterhead 50. As a result of the clamping and cutting forces, small gaps 70, 71 exist between the leading side of the cutting blade 52 and the leading side 57 of the slot 51, and between the trailing side of the cutting blade 52 and the trailing side 55 of the slot 51.

[0030] Spacer block 77 is shaped to seat against slot surfaces 55 and 56 of cutterhead body 50 and against cutting blade 72 having contact surfaces 74 and 79. Spacer block 77 increases the radial position of blade 52 by an amount 73. Amount 73 can be varied among the various available spacer blocks to provide greater flexibility for use of different blade sizes and to cover a wider range of gear shapes.

[0031] While the present invention has been described with reference to preferred embodiments, it should be understood that the invention is not limited to these particular embodiments. The present invention is intended to include modifications that would be apparent to those skilled in the art to which the present subject matter pertains without departing from the spirit and scope of the appended claims.

Claims

1. 1. A gear cutting tool having an axis of rotation and including a cutterhead, the cutterhead including a plurality of cutting blade receiving slots, at least one of the receiving slots being four-sided non-rectangular in axial cross section with respect to a direction of rotation of the cutterhead about the axis of rotation during a gear cutting process, and having a slot depth W ２ a leading side surface having a slot depth W １ and W ２ W １ a trailing side seating surface that is less than 1 / 2 of the leading side surface; an outer side surface; and an inner angled side seating surface extending between the leading side surface and the trailing side surface.

2. The leading side is parallel to the trailing side, and the inner angled side intersects with the leading side at an intersection angle α that is greater than 90 degrees. １ wherein the inner angled side intersects with the trailing side at an intersection angle α of less than 90 degrees. ２ The gear cutting tool of claim 1 , defining

3. The gear cutting tool of claim 1 , wherein the outer side surface is perpendicular to the leading side and the trailing side.

4. The gear cutting tool of claim 1 , further comprising a cutting blade positioned in said at least one of said four-sided non-rectangular blade receiving slots.

5. 5. The gear cutting tool of claim 4, wherein the cutting blade has a cross-sectional shape complementary to the cross-sectional shape of the at least one of the four-sided non-rectangular blade-receiving slots.

6. 10. The gear cutting tool of claim 1, wherein the cutterhead further includes a radial shimming spacer block that increases the radial blade position distance of the cutting blades from the axis of rotation.

7. 8. The gear cutting tool of claim 7, wherein the radial shimming spacer block is configured to accommodate a five-sided cutting blade mounted therein.

8. 1. A cutterhead for a gear cutting tool, the cutterhead having an axis of rotation and including a plurality of cutting blade receiving slots, at least one of the receiving slots being four-sided non-rectangular in axial cross section with respect to a direction of rotation of the cutterhead about the axis of rotation during a gear cutting process, and having a slot depth W ２ a leading side surface having a slot depth W １ and W ２ W １ a trailing side seating surface that is less than 1 / 2 of the leading side surface; an outer side surface; and an inner angled side seating surface that extends between the leading side surface and the trailing side surface.

9. 9. The cutterhead of claim 8, further comprising a radial shimming spacer block for increasing the radial blade position distance of the cutting blade from the axis of rotation.

10. 8. The cutterhead of claim 7, wherein the radial shimming spacer block is configured to accommodate a five-sided cutting blade mounted therein.

11. 1. A cutting blade for a gear cutting tool, the cutting blade having a four-sided non-rectangular cross-section and including, with respect to the orientation of the cutting blade when positioned within a cutterhead during a gear cutting process, an outer side, a leading side, a trailing contact side, and an inner angled contact side.

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