WO2017192614A1

WO2017192614A1 - Single pass rotor finishing

Info

Publication number: WO2017192614A1
Application number: PCT/US2017/030679
Authority: WO
Inventors: Maurice P JOLLY
Original assignee: Eaton Corporation
Priority date: 2016-05-02
Filing date: 2017-05-02
Publication date: 2017-11-09

Abstract

A method of forming a finished rotor with a desired lobe shape comprises removing a quantity of coating from a coated form of a rotor by passing a line of points circumscribing a center hole of a form tool with respect to the coated form of the rotor. The line of points imparts a finished edge on the rotor in a single pass. The form tool comprises a first line of points and a second line of points that circumscribe the center hole. A center line of points forms a cutting edge in the center hole. A first cutting surface extends between the first line of points and the center line of points. A second cutting surface extends between the second line of points and the center line of points. The first cutting surface and the second cutting surface are angled such that they are not parallel to the axis.

Description

SINGLE PASS ROTOR FINISHING

Field

[001 ] This application relates to methods and devices for forming a lobed rotor final shape.

Background

[002] Superchargers have two rotors that rotate in opposite directions to pump a fluid. Helically twisted rotors can comprise helix and hi-helix rotor designs, among others. It is difficult to impart a precision edge to the rotor lobes. Many manufacturing techniques require that multiple tools be passed over the rotor as the lobes are shaped, and this amounts to more than one pass to impart the complex shape of the rotor lobes.

SUMMARY

[003] The methods and devices disclosed herein overcome the above disadvantages and improves the art by way of tooling for permitting true shape, on- size rotor lobes in a single pass.

[004] A method of forming a finished rotor with a desired lobe shape comprises removing a quantity of coating from a coated form of a rotor by passing a line of points circumscribing a center hole of a form tool with respect to the coated form of the rotor. The line of points imparts a finished edge on the rotor in a single pass.

[005] The form tool can comprise an axis in a center of a center hole, a first plane in a first side, the first plane comprising a first line of points that circumscribe the center hole. A second plane in a second side comprises a second line of points that circumscribe the center hole. A center plane is in-between and parallel to the first plane and the second plane, the center plane comprises a center line of points forming a cutting edge in the center hole. The center line of points is closer to the axis than either of the first line of points or the second line of points. A first cutting surface is bounded between the first plane and the center plane, the first cutting surface extends between the first line of points and the center line of points. The first cutting surface is angled such that it is not parallel to the axis. A second cutting surface is bounded between the second plane and the center plane. The second cutting surface extends between the second line of points and the center line of points. The second cutting surface is angled such that it is not parallel to the axis.

[006] Additional objects and advantages will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the disclosure. The objects and advantages will also be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

[007] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[008] Figure 1 is a view of a base rotor for a supercharger.

[009] Figure 2 is a view of a coated rotor.

[010] Figure 3 is a view of a rotor finishing assembly kit.

[01 1 ] Figure 4 is a perspective view of an assembled rotor finishing assembly.

[012] Figure 5 is a cross-section view of a rotor passing through a rotor finishing assembly.

[013] Figures 6A-6C include front, cross-section, and detailed views of a form tool.

[014] Figure 7 is a flow diagram for forming a finished rotor in a single pass.

DETAILED DESCRIPTION

[015] Reference will now be made in detail to the examples which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Directional references such as "left" and "right" are for ease of reference to the figures.

[016] Figure 1 shows a rotor form 10. A finished rotor can be used in a positive displacement pump, such as a supercharger. The form 10 is assembled by joining a series of stamped stacked plates 14. Each plate 14 can approximate the desired final shape of the finished rotor. But, as described herein, the rotor form 10 is processed to result in the finished rotor. [017] The plates 14 can comprise one or both of a central locating hole 12 and locating holes 13 in the lobes to align the plates 14. The central locating holes of the plates 14 can be aligned on a central spool or on a rotor shaft 17. As the plates 14 stack on the spool or rotor shaft 17, the rotor form stacks along an axis X. The central locating holes 12 can further comprise locating notches 18. The spool or rotor shaft 17 can include corresponding guides for further alignment of the plates 14, as by imparting alignment of the plates 14 relative to one another. The plates 14 stack to form lobes that can be parallel along the axis X or that can be twisted to form helical or hi-helical lobes, for example. The locating holes 13 can also be used to align the plates 14 to form an outer shape. For example, an alignment

mechanism such as a wire or shaft can be aligned in each locating hole 13 to guide the alignment of the plates 14 along the axis X-X. A locating hole 13 is shown in each lobe, and locating notches 18 are shown corresponding to each lobe.

However, more or less locating mechanisms can be used in practice.

[018] With the rotor form 10 assembled to approximate the desired final shape of the finished rotor, the rotor form 10 can be processed, as by welding to adhere the plates 14 together. Machining can be performed to remove burrs or other artifacts of the stamping and assembly process. Or, as described herein, when the rotor form 10 comprises the appropriate material, a form tool 503 can be applied to the rotor form 10 to impart a desired final shape to the outer perimeter of the rotor form. So, a rotor form 10 can be a work piece for single-pass processing.

[019] As shown in Figure 2, however, the rotor form 10 is transformed in to a coated form 1 1 . A coating 15 can be applied. The coating 15 can perform a variety of functions. For example, in lieu of welding to adhere the plates together, the coating 15 can adhere the plates together. The coating 15 can fill in gaps between the plates, or provide a particular chemical resistance, for additional examples. Whether applied by spraying, laminating, dipping, molding or other techniques, the coating 15 can require further processing to impart the desired final shape of the finished rotor.

[020] As an alternative, rotor form 10 can comprise a 3-D printed rotor form or a molded, extruded, or cast rotor form, or the like. The rotor form 10 can be 3-D printed of "maraging steel" or carbide or other suitable machining materials for removing a layer of material from the work piece. A coating 15 can be applied thereon to form coated form 1 1 . Or, the entire coated form 1 1 can be formed of a printed, dipped, molded or cast material that is as malleable as a coating 15. So, when discussing the coated form 1 1 below, or the coating 15, unless otherwise restricted, it is not required that the rotor be a multi-layer structure. Coated form 1 1 can be molded, cast, sprayed, dipped, printed, among others, so that it comprises a material that can be removed by the form tool 503. The coated form 1 1 is a work piece that can be processed using the disclosed form tool 503.

[021 ] A tool assembly 300 is shown in Figures 3-5. The tool assembly permits alignment of the coated form 1 1 with a form tool 503 so that the coated form 1 1 can be processed in a single pass to result in the desired final shape of the finished rotor.

[022] Prior techniques require multiple passes of the rotor form 10 or the coated form 1 1 . In these prior art techniques, tooling is repeatedly applied to shape the forms, or some other back and forth motion is necessary to impart the final shape to the rotor lobes. The devices and techniques disclosed herein eliminate these multiple passes and back and forth motions.

[023] Form tool 503 is designed to remove a portion of the coating 15 to impart the precise desired final shape of the finished rotor 19. Form tool 503 can be used to remove the coating 15 to impart a final, finished edge. This is unlike broaching, which is a multiple-pass process. The form tool 503 disclosed herein permits single-pass finishing techniques.

[024] Form tool 503 comprises a center hole 505 comprising an inverse of the desired final shape of the finished rotor 19. The center hole 505 surrounds the entire perimeter of the rotor assembly, shown in Figure 5, as it passes through the form tool 503. This is unlike other processing tooling that contacts single surfaces or planes and that must be repositioned for each lobe, cusp, root, etc. A complex shape can be imparted to the form tool 503, and the complex shape can be uniformly applied to the whole axial length to form finished rotor 19. A three-lobe rotor is detailed in the figures, but the invention is not so limited. One or more of many alternatives can be accounted for, such as having any number of lobes, for example 2, 4, 5, 6, etc.; the lobes can comprise involute, hypoid, cycloid, or complex spline curves; or, the lobes can be parallel or twisted along the length of axis X-X. [025] The coated form 1 1 transforms to the final rotor 19 as the form tool 1 1 processes in a single pass with respect to the rotor assembly. Figure 6A illustrates the form tool 503 from a top view. Figure 6B illustrates a section view of the form tool 503. First plane 510 extends on a first side of form tool 503. A second plane 512 extends on a second side of form tool 503. A middle, cutting plane 520 is between the first plane 510 and the second plane 512. The form tool 503 permits true shape, on-size rotor lobes in a single pass. The cutting plane 520 comprises a line of points M to permit the form to have the true shape of the finished rotor 19. Having a line of points M instead of a plane of points permits the form to have a true shape, instead of an undercut shape. The true-shape in the cutting plane 520 lends ease of use to selecting the appropriate form for a project. The true-shape of the finished rotor is selected instead of a tool suitable for multiple pass machining, which requires calculating an undercut for the shape imparted.

[026] The first plane 510 comprises a first line of points F, F1 , F2, etc. that circumscribe the center hole 505. Likewise, the second plane comprises a second line of points S, S1 , S2, etc. that circumscribe the center hole 505. The first line of points F, F1 , F2 can be in-line with the second line of points S, S1 , S2 along the axis X-X so that a line between points S & F is parallel to the axis X-X, or the lines of points can be offset so that a line between points S & F is skewed with respect to axis X-X. In the illustration, points S & F align to be parallel with the axis X-X.

[027] The middle cutting plane 520 comprises a center line of points M, M1 , M2, etc. The center line of points is closer to the axis X-X than either the first or second line of points. The center line of points form a cutting edge that is applied to remove a layer of coating 15 to impart the final shape of the finished rotor 19. A first cutting surface 51 1 between the first line of points F, F1 , F2 and the center line of points M, M1 , M2 is slanted at an angle Lambda with respect to the middle cutting plane 520 and first plane 510. As one example, the first cutting surface 51 1 can be at a 45 Degree angle relative to the center plane 520. This is shown in Figure 6B by extending the line for the first cutting surface 51 1 beyond the first plane 510 (planes 510 and 520 are parallel). Other values for angle Lambda are contemplated, as the angle Lambda adjusts based on material hardness of the coating 15 and based on the material hardness of the form tool 503. However, the center line of points should not align with the first line of points such that a line parallel to the axis X-X is formed. This would create a planar surface in the form tool 503. This would not permit single-pass processing. If a planar surface were formed, the rotor assembly must be flipped with respect to the form tool (or vice versa), and a second pass of the form tool with respect to the rotor assembly must be done.

[028] So, similar constraints apply to the non-alignment of the center line of points M, M1 , M2 with second line of points S, S1 , S2. With second plane 512 parallel to center plane 520, a second cutting surface 513 bounded there between is slanted with respect to the axis X-X.

[029] Imagine extending each cutting surface 51 1 and 513 to intersect the cutting plane 520. The intersection can be a point. Or, a small radius can be formed to join first cutting surface 51 1 to second cutting surface 513. The radius can be, for example, from 0.1 to 0.13 millimeters for a form tool that is 2.2 mm thick. A maximum radius can be set, based on material, for example, a radius of 0.127 mm for the 2.2 mm thick form tool. Such a feature can be scaled for other size applications.

[030] Tool alignment holes 507 align the form tool 503 with a first support platform 403 and with a base 303 when aligners 305 are inserted in corresponding platform alignment holes 407 and base alignment holes 307.

[031 ] Base 303 can be a variety of shapes, such as triangular, rectangular, or as shown, cylindrical. The base 303 can cooperate directly or indirectly with an alignment machine. Base 303 can comprise base alignment holes 307 on both first base end 310 and second base end 312. First base end 310 can align with first support platform 403 and second base end 312 can align with second support platform 603 by aligning platform alignment holes 407, 607 with respective base alignment holes 307 and securing an aligner 305 there through.

[032] Alternatively, the base 303 can be integrally formed with the first support platform 403 or the second support platform 603, with accommodations to service the form tool 503. Alternatively, second support platform 603 can be omitted altogether.

[033] First support platform 403 can be omitted in some alternatives, while in other alternatives, the first support platform 403 enhances the stiffness of the form tool 503, as by providing support to the form tool 503. The form tool 503 comprises the proper cutting surfaces and edge to machine the coated form 1 1 , while the first support platform 403 comprises one or more of guidance and structural integrity that enhances single-pass processing.

[034] First support platform 403 comprises platform alignment holes 407. Aligners 305, such as screws, bolts, pins, or the like can be inserted to align first support platform 403 with base 303. In some cases, the tool assembly 300 can be an independent capsule or pod inserted in processing machine for manipulation of the tool assembly 300. For example, a bracket, grip, or other holder can receive the tool assembly and move it with respect to coated form 1 1 . Or, processing machine can comprise extensions that couple to aligners 305 or are integrally formed with aligners 305; so, in this example, the tool assembly is assembled onto the

processing machine. Platform alignment holes 407 can comprise other shapes and can accommodate other coupling techniques, such as keyed couplings, threaded couplings, anti-jiggle couplings, among others. Aligners 305 can be integrally formed with one or more of the base 303 and first and second support platforms 403, 603 so that alignment is achieved by tab and slot, finger in recess, or like techniques. Likewise, second support platform 603 can comprise platform alignment holes 607 or the like for aligning with base alignment holes 307 or the like on second base end 312.

[035] Additional alignment holes can be included to align the tool assembly 300 with respect to the coated form 1 1 . Likewise, the coated form 1 1 or the rotor shaft 17 can comprise one or more alignment features, such as holes, tabs, grooves, threads, etc. Rotor shaft 17 can comprise a stop, bearing, bushing or other feature 16.

[036] First support platform 403 comprises rotor guide-hole 405, and second support platform 603 comprises rotor guide-hole 605. The guide-holes 405 & 605 can differ in size so that the coated form 1 1 is supported by and passes through rotor guide-hole 605, and so that the tooled rotor having the desired final shape is supported by and passes through rotor guide-hole 405. To achieve the supporting function, and to avoid interference with the shape of the coated form 1 1 and final tooled rotor, the guide-holes 405 & 605 can comprise an outer profile corresponding the coated form 1 1 and final tooled rotor. So, the guide-holes 405 & 605 can comprise sidewalls 415, 615 that are parallel and complementary to the parallel- lobed rotor. But for a helix or hi-helix rotor, the sidewalls 415, 615 of the guide-holes 405, 605 can comprise a complementary twist.

[037] Computer control can rotate the rotor assembly or the base 303 so that a helically twisted rotor 19 can maintain a perpendicular line of points with respect to the form tool 503. As one example, centering holes are included on both the rotor shaft and the base 303 to permit tracking of relative positions. The tool assembly 300 can be held stationary, or it can be moved relative to the coated form 1 1 , or vice versa, or both the tool assembly 300 and the coated form 1 1 can move relative to each other. The coated form 1 1 is guided through the guide-hole 605, then the coating 15 impinges on the form tool 503 as the coated form 1 1 is pressed against it. Perpendicularly applying the center line of points M, M1 , M2, etc. to the coated form 1 1 imparts the finished edge on finished rotor 19 in a single pass. The coated form 1 1 is pressed only once against the form tool 503 to impart the desired final shape of the finished rotor. The finished rotor 19 is guided through the guide- hole 405.

[038] In other words, the cutting edge 525 conforms to the coated form 1 1 such that the coated form is cut in a work piece plane WP perpendicular to the center of the work piece along all points in contact with the cutting edge 525. Since it is advantageous to finish all surfaces of the coated form 1 1 in the single pass, it is possible to remove so much of the coating 15 that the cutting edge 525 conforms to the coated form 1 1 such that, as the coated form is processed using the form tool 503, the entire perimeter of the coated form 1 1 along a work piece plane WP co- located with the center plane 520 is in contact with the form tool 503.

[039] Turning to Figure 6, a method of forming a finished rotor can comprise securing a form tool 503 to a base 303 in step S713. A base rotor 10 can be formed in step S701 . Forming the base rotor can comprise the techniques outlined above, such that forming the base rotor in step S701 is an integral part of coating a base rotor in step S703, as when the forming of the base rotor results in a machinable exterior essentially forming coating 15. Next, in step S705, the coated form 1 1 is passed through the guide-hole 605 of second support platform 603. With the form tool 503 secured to the base in step S713, as above, the coated form 1 1 can be rotated with respect to the base 303 in step S706 or the base 303 can be rotated with respect to the coated form 1 1 in step S708, or both steps S706 and step S708 are performed together. The coated form 1 1 is passed through the form tool 503 to remove a portion of coating 15 in step S709. Then, the finished rotor can be passed through the first support platform 403 in step S71 1 .

[040] Because several physical parts and pre-processing steps are optional, the method of forming a finished rotor can consist essentially of steps S713, one or both of steps S706 and S708, and S709.

[041 ] Other implementations will be apparent to those skilled in the art from consideration of the specification and practice of the examples disclosed herein.

Claims

WHAT IS CLAIMED IS:

1 . Tooling, comprising:

a form tool comprising a center hole for passing over a work piece, the form tool comprising:

an axis in the center of the center hole and extending along a length of the center hole;

a first plane in a first side, the first plane comprising a first line of points that circumscribe the center hole;

a second plane in a second side, the second plane comprising a second line of points that circumscribe the center hole;

a center plane in-between and parallel to the first plane and the second plane, the center plane comprising a center line of points forming a cutting edge in the center hole, the center line of points being closer to the axis than either of the first line of points or the second line of points;

a first cutting surface bounded between the first plane and the center plane, the first cutting surface extending between the first line of points and the center line of points, the first cutting surface being angled such that it is not parallel to the axis; and

a second cutting surface bounded between the second plane and the center plane, the second cutting surface extending between the second line of points and the center line of points, the second cutting surface being angled such that it is not parallel to the axis.

2. The tooling of claim 1 , wherein the first line of points is in-line with the second line of points along the axis so that a line between the first line of points and the second line of points is parallel to the axis.

3. The tooling of claim 1 , wherein the first line of points is offset from the second line of points along the axis so that a line between the first line of points and the second line of points is skewed with respect to the axis.

4. The tooling of claim 1 , wherein one or both of the first cutting surface and the second cutting surface is at a 45 degree angle with respect to the center plane.

5. The tooling of claim 1 , wherein the cutting edge conforms to the work piece such that the work piece is cut in a plane perpendicular to the center of the work piece along all points in contact with the cutting edge.

6. The tooling of claim 5, wherein the cutting edge conforms to the work piece such that, as the work piece is processed using the form tool, the entire perimeter of the work piece along a workpiece plane co-located with the center plane is in contact with the form tool.

7. The tooling of claim 1 , wherein the cutting edge formed by the center line of points imparts a finished edge on the work piece in a single pass processing step.

8. The tooling of claim 1 , further comprising a base, wherein the form tool is secured to the base.

9. The tooling of claim 8, further comprising a first support platform adjacent the form tool, the first support platform comprising a guide-hole for receiving the work piece after the work piece is processed using the form tool.

10. The tooling of claim 9, wherein the work piece is a supercharger rotor comprising helically twisted lobes, and wherein the guide-hole comprises a shape complementary to the helically twisted lobes of the supercharger rotor.

1 1 . The tooling of claim 9, wherein the work piece is a supercharger rotor comprising cycloid spline-shaped lobes, and wherein the guide-hole comprises a shape complementary to the cycloid spline-shaped lobes of the supercharger rotor.

12. The tooling of claim 1 1 , wherein the cycloid spline-shaped guide-hole twists along a longitudinal axis of the guide-hole.

13. The tooling of claim 9, wherein the first support platform supports the form tool as the work piece is applied to the cutting edge.

14. The tooling of claim 9, further comprising a second support platform attached to the base, the second support platform a second guide-hole comprising a shape complementary to an unprocessed portion of the work piece.

15. A method of forming a rotor with a desired lobe shape, consisting essentially of:

removing a quantity of coating from a coated form of a rotor by passing a line of points circumscribing a center hole of a form tool with respect to the coated form of the rotor, wherein the line of points imparts a finished edge on the rotor in a single pass, wherein the form tool comprises: an axis in the center of the center hole, the axis extending along a length of the center hole;

a center plane in-between and parallel to the first plane and the second plane, the center plane comprising a center line of points forming a cutting edge in the center hole, the center line of points being closer to the axis than either of the first line of point or the second line of points; a first cutting surface bounded between the first plane and the center plane, the first cutting surface extending between the first line of points and the center line of points, the first cutting surface being angled such that it is not parallel to the axis; and

16. The method of claim 15, comprising conforming the cutting edge of the form tool to the coated form of the rotor such that the coated form of the rotor is cut in a plane perpendicular to the center of the coated form of the rotor along all points in contact with the cutting edge.

17. The method of claim 15, comprising conforming the cutting edge of the form tool to the coated form of the rotor such that, as the coated form of the rotor is processed using the form tool, the entire perimeter of the coated form of the rotor along a workpiece plane co-located with the center plane is in contact with the form tool.

18. The method of claim 15, further comprising moving the coated form of the rotor with respect to the form tool to traverse the line of points.

19. The method of claim 15 or 18, further comprising moving the form tool with respect to the coated form of the rotor to traverse the line of points.

20. The method of claim 15, further comprising twisting one of the coated form of the rotor or the form tool while traversing the line of points.

21 . The method of any one of claims 15-20, further comprising:

supporting a first end of the coated form of the rotor with a first support

platform connected to a base; and

supporting a finished end of the rotor comprising the desired lobe shape with a second support platform connected to the base,

wherein the form tool is secured to the base.

22. The method of claim 15, wherein the first support platform comprises a first guide-hole, and the second support platform comprises a second guide-hole, and wherein the first guide-hole comprises a shape that twists along a first longitudinal axis, and wherein the second guide-hole comprises a second shape that twists along the longitudinal axis, and the method further comprises twisting one of the coated form of the rotor or the base while traversing the line of points..