METHOD AND TOOL FOR MANUFACTURING SPIRAL TOOTH FACE COUPLINGS

Abstract

A method and cutting tool for producing spiral toothed face couplings whereby a two-part cutter and a two-part machine tool spindle are not needed. The process includes a set-over between the cutting of convex (41) and concave (43) tooth surfaces and the tool (59) comprises inside and outside cutting blades positioned in a single cutter head blade slot (57) and separated from one another by a blade spacing angle (51).

Claims

1. A method of manufacturing spiral tooth face couplings having a plurality of teeth with each of said teeth having concave and convex tooth flanks, said method comprising: providing a face hobbing cutter rotatable about a cutter axis and having a plurality of cutting blade slots arranged spaced about a face of the cutter with at least a first cutting blade and a second cutting blade positioned in each of said slots, wherein said first and second cutting blades in each of said slots being spaced from one another by a spacing angle, rotating said face hobbing cutter and rotating a face coupling workpiece, engaging said face hobbing cutter with said face coupling workpiece in a continuous indexing manner at a first machining position, wherein one of said first cutting blade and said second cutting blade produces one of a finished concave or a finished convex tooth flank surface on each of said teeth of said face coupling workpiece, repositioning said face hobbing cutter and said face coupling workpiece at a second machining position based on said spacing angle, and engaging said face hobbing cutter with said face coupling workpiece in a continuous indexing manner at said second machining position, wherein the other of said first cutting blade and said second cutting blade produces the other of a finished concave or a finished convex tooth flank surface on each of said teeth of said face coupling workpiece.

2. The method of claim 1 wherein at said first machining position, said face hobbing cutter is fed into said face coupling workpiece to a full depth position followed by said repositioning while said face hobbing cutter remains at said full depth position.

3. The method of claim 1 wherein at said first machining position, said face hobbing cutter is fed into said face coupling workpiece to a full depth position, said cutter is then withdrawn from the face coupling workpiece followed by said repositioning to said second machining position and then feeding said cutter said face coupling workpiece to said full depth position.

4. A cutting tool for manufacturing spiral tooth face couplings having a plurality of teeth with each of said teeth having concave and convex tooth flanks, said tool comprising: an axis of rotation, a plurality of cutting blade slots arranged spaced about a face of the cutter with at least a first cutting blade and a second cutting blade positioned in each of said slots, wherein the first and second cutting blades in each of said slots being spaced from one another by a spacing angle.

5. The cutting tool of claim 4 wherein both first and second cutting blades include positive side rake angles.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 shows a cross sectional view of a face coupling with the top of a tooth in a cutting zone and the top of a tooth in the opposite section of the face coupling.

[0016] FIG. 2 illustrates a conventional face hobbing cutter with equally spaced outside cutting blade slots and inside cutting blade slots.

[0017] FIG. 3 shows a top view of a generating gear, with only two teeth with one slot represented, illustrating a conventional set-up for producing a face coupling.

[0018] FIG. 4 shows a bevel gear cutting machine with a double spindle arrangement and an interlocking cutter head where one part of the cutter head carries inside cutting blades and the other part of the cutter head caries outside cutting blades.

[0019] FIG. 5 illustrates a front view of the imbedded double spindle arrangement of the cutting machine of FIG. 4.

[0020] FIG. 6(a) shows a top view of a generating gear, with only two teeth with one slot represented, illustrating an inventive set-up for producing a the convex tooth flank of a face coupling.

[0021] FIG. 6(b) shows a top view of a generating gear, with only two teeth with one slot represented, illustrating an inventive set-up for producing a the concave tooth flank of a face coupling.

[0022] FIG. 7 illustrates a face hobbing cutter according to the invention having a small blade spacing angle and a blade mounting double slot.

[0023] FIG. 8 shows a face hobbing cutter head comprising double slots.

[0024] FIG. 9 shows a spiral toothed face coupling produced by a cutter utilizing the cutter head of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0025] The terms invention, the invention, and the present invention used in this specification are intended to refer broadly to all of the subject matter of this specification and any patent claims below. Statements containing these terms should not be understood to limit the subject matter described herein or to limit the meaning or scope of any patent claims below. Furthermore, this specification does not seek to describe or limit the subject matter covered by any claims in any particular part, paragraph, statement or drawing of the application. The subject matter should be understood by reference to the entire specification, all drawings and any claim below. The invention is capable of other constructions and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purposes of description and should not be regarded as limiting.

[0026] The details of the invention will now be discussed with reference to the accompanying drawings which illustrate the invention by way of example only. In the drawings, similar features or components will be referred to by like reference numbers.

[0027] The use of including, having and comprising and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of letters to identify elements of a method or process is simply for identification and is not meant to indicate that the elements should be performed in a particular order.

[0028] Although references may be made below to directions such as upper, lower, upward, downward, rearward, bottom, top, front, rear, etc., in describing the drawings, there references are made relative to the drawings (as normally viewed) for convenience. These directions are not intended to be taken literally or limit the present invention in any form. In addition, terms such as first, second, third, etc., are used to herein for purposes of description and are not intended to indicate or imply importance or significance.

[0029] The inventive process utilizes one right hand cutter head with inside and outside blades for the manufacture of the right hand coupling member and one left hand cutter with inside and outside blades for the manufacture of the left hand coupling member. The process is not a completing method. Only a single tool spindle is required on a cutting machine for the cutting process. Machines suitable for cutting spiral tooth couplings, such as the machine of commonly-assigned U.S. Pat. No. 6,712,566, are readily known to the skilled artisan and are commercially available.

[0030] FIG. 6(a) shows a top view of a generating gear 46 for a face coupling (the generating gear being identical to the face coupling as stated above) with only two teeth and one tooth slot between them being represented for ease of explanation and illustration. The rotational position of generating gear 46 about its axis 49 is adjusted with respect to angle 44 such that the center point of the convex flank 41 (convex-shaped in lengthwise direction) is contacting the horizontal axis 48 of the coordinate system. The direction and length of vector RW.sub.IB defines the length and direction of the vector EX.sub.IB (42) which establishes the appropriate machine settings required for the positioning of the cutter head. In the position of generating gear 46, the convex flank 41 is cut and the concave side 43 (concave-shaped in lengthwise direction) is merely pre-cut with a desired finishing stock. The angle 51 is the reduced blade spacing angle of the inventive method.

[0031] FIG. 6(b) is a top view of a generating gear 46 for a face coupling (the generating gear being identical to the face coupling as stated above) with only two teeth and the tooth slot between them being represented for ease explanation and illustration. The rotational position of generating gear 46 is adjusted with respect to angle 45 such that the center point of the concave flank 43 is contacting the horizontal axis 48 of the coordinate system. The direction and length of vector RW.sub.OB defines the length and direction of the vector EX.sub.OB (40) which establishes the appropriate machine settings required for the positioning of the cutter head. In the position of generating gear 46, the concave flank 43 is cut and the convex side 41 is not contacted by the inside blades represented by RW.sub.IB.

[0032] As shown in FIG. 6(a), an initial plunging is performed with a first set of machine settings represented by 42 (EX.sub.IB) which makes the inside blades form the convex flanks 41. After reaching the full depth position, a transition to a second set of machine settings 40 (EX.sub.OB) occurs (which includes a generating gear axis set-over rotation) as shown by FIG. 6(b). At the end of this set-over, the outside blades will cut the concave flanks 43. The cutter withdraws away from the slots and both convex and concave flanks (41 and 43) as well as the bottoms of the tooth slots are finished. While it is preferred the cutter remain at the full-depth position during the set-over, the cutter may be withdrawn after the initial flanks (i.e. convex or concave) are cut, followed by the set-over and then plunging again to cut the remaining flanks (i.e. concave or convex).

[0033] The set-over between convex and concave flank cutting is required because of the different machine settings needed for convex and concave cutting. The particular machine settings are dependent on individual machine kinematics as will be understood by the skilled artisan but must be set in accordance with FIGS. 6(a) and 6(b). While changing the machine settings, a certain stock allowance for a sufficient cleanup of the second cut concave flanks is additionally required. If the blade spacing angle 51 was zero, then the generating gear axis set-over rotation would be equal to the angle 44 (shown before the rotation) or 45 (shown after the rotation). The correct generating gear set-over rotation angle DW12Z is calculated with equation (8) below by employing the blade spacing angle WAME.

[0034] The equally spaced conventional face hobbing cutter (FIG. 2) would create tooth thicknesses and slot widths which are equal. However, due to the spiral angle error caused by the dedendum angle 15 (FIG. 1), the flank surfaces would be incorrect. A set-over due to different machine settings would not be possible, because it would increase the slot width and deliver incorrect parts.

[0035] In order to form flank lead lines with a desired length crowning between the two coupling members the outside blade point radius has to be increased and/or the inside blade point radius has to be reduced. This is not possible with an equally spaced face hobbing cutter head (negative blade distance difference 53 as seen in FIG. 2), because this will additionally increase the slot width.

[0036] In order to change the cutter blade radii to achieve length crowning and to allow for the set-over between the convex and concave flank cutting, a sufficient amount of room between the two flanks 41, 43 has to be available. The inventive process utilizes therefore a modified cutter head 59 design (FIG. 7) with a very small or even zero blade spacing angle 51 between the leading outside blade 71 and the following inside blade 73. Zero blade spacing is possible, if the same blade is used for example with its outside edge as outside blade and with its inside edge as inside blade. Zero blade spacing is also possible if two half blades were mounted next to each other in the same slot. The preferred embodiment however is the design of a double slot 57 which contains both an outside blade 71 and an inside blade 73 with a small spacing angle 51. This case makes it possible to prepare both inside and outside blades with positive side rake angles for an optimal chip removal process. For ease of illustration, only one slot 57 with two cutting blades 71, 73 is shown in FIG. 7 but it should be understood that any number of slots (e.g. nine) with the appropriate number of cutting blades (e.g. two blades per slot) are envisioned.

[0037] In one example of the invention, a face hobbing cutter head 59 as shown in FIG. 8 having a nominal radius of 125 mm and including nine double slots 57 was utilized to produce a spiral toothed face coupling. An inside cutting blade and an outside cutting blade were positioned in each double slot (e.g. cutting blades 73 and 71 of FIG. 7) with the inside cutting blade positioned at a blade spacing angle of 5.6 degrees behind the leading outside cutting blade. The cutter head was utilized in accordance with the inventive set-over method discussed above to cut a spiral toothed face coupling (FIG. 9) having 24 teeth, an outer diameter of 60 mm and a face width of 13 mm.

[0038] The following calculations are required to compute the final blade radii as well as the generating gear axis set-over angle.

[0039] The final slot width angle is:

SLTW=/Z(1)

[0040] The slot width cut by plunging with DRCOW=0 depends only on the blade spacing angle WAME (51), the number of cutter starts Z.sub.C and the number of coupling teeth Z:

SLCT=[(WAME*Z.sub.C)/Z](2)

[0041] The stock allowance angle is chosen between 0 and (SLTWSLCT):

SCST=0.6 mm/RM(3)

[0042] The maximal increase of the outside blade radius and the maximal reduction of the inside blade radius in order to leave the desired stock allowance after plunging is:

DRMAX=[(SLTWSLCTSCST)/2]*RM(4)

[0043] The effective radii increase and reduction has to be equal or smaller than DRMAX:

[0044] DRCOW . . . calculated for desired length crowning

If DRCOW>DRMAX.fwdarw.DRCOW=DRMAX(5)

[0045] The inside blade and outside blade cutter radius calculation at the reference point is calculated as:

RW.sub.IB=RW0DRCOW(6)

RW.sub.OB=RW0+DRCOW(7)

[0046] Although the radius difference has to be considered for leaving the desired stock allowance value when cutting the first tooth flank (convex flank), it has no influence on the generating gear axis set-over rotation DW12Z:

DW12Z=SLTW/Z*[WAME/(/Z.sub.C)](8)

[0047] Where: [0048] SLTW . . . final slot width angle [0049] SLCT . . . slot width produced by unequally spaced blades in cutter [0050] SCST . . . stock allowance angle for set-over from convex flank cutting to concave flank [0051] DRMAX . . . maximal radius difference to allow for set-over stock allowance [0052] DRCOW . . . radius difference in reference point 52 for desired length crowning [0053] RW.sub.IB . . . inside blade reference radius (see FIG. 3) [0054] RW.sub.OB . . . outside blade reference radius (see FIG. 3) [0055] Z.sub.C . . . number of cutter blade starts [0056] Z . . . number of coupling teeth [0057] RM . . . generating gear mean radius [0058] WAME . . . blade spacing angle (51)

[0059] The two sets of machine settings are determined by considering the different radii of RW.sub.IB and RW.sub.OB and by the direction of the radius vectors RW.sub.IB and RW.sub.OB. The radius vector direction is defined by the spiral angle of the coupling (commonly 0) and by the spiral angle correction which becomes necessary if the dedendum angle 15 is not equal to zero. The set-over rotation of the generating gear depends on the blade spacing difference between angles 51 and 50. The set-over rotation does not depend on the blade distance difference.

[0060] 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.