Method of forming a tubular ring

Abstract

A method of forming a tubular ring comprising spinning a flat blank having a bore, expanding the bore using a tubular shaft shaped spinning roller by initially engaging the tubular shaft shaped spinning roller with the flat blank bore at an angle (α) to the spinning axis, forming the flat blank into a tubular ring by rotating the tubular shaft shaped spinning roller about a center of rotation (B) such that the tubular shaft shaped spinning roller becomes substantially parallel to the spinning axis, and forming a contour on an outer surface of the tubular ring.

Description

FIELD OF THE INVENTION

The invention relates to a method of forming a tubular ring comprising expanding the bore of a flat blank using a tubular shaft shaped line contact spinning roller.

BACKGROUND OF THE INVENTION

Spinning is a manufacturing process where a part is formed by being subjected to forming stresses applied by a roller (or rollers) many times over very small areas. Each element of metal is brought into the plastic region for a very short period of time during which it is formed. The process repeats as many times as required.

Known processes for manufacturing tubular rings include making a tube and cutting it into rings, deep drawing a cup and removing the face of the cup, expanding a blank in ring rolling, forging, casting, or welding a strip to make a ring. All of these processes are feasible, but variable cost and quality can present problems. Welded hoops can have problems in the weld area when the ring is flow formed further to make certain products such as gears, pulleys, splined rings and so on. Cut seamless tubes are expensive and making a cup in a press and removing the face creates excessive waste.

Representative of the art is U.S. Pat. No. 6,298,702 which discloses a method for forming seamless tubular workpieces, such as vehicular wheel rim components. In the method, a flat circular blank having a central aperture is expanded into the interior of a hollow mandrel using a mushroom-shaped spinning roller. In this expansion operation, the blank is caused to take on a tubular shape having an exterior contour which conforms to the interior contour of the hollow mandrel.

What is needed is a method of forming a tubular ring comprising expanding the bore of a flat blank using a tubular shaft shaped line contact spinning roller. The present invention meets this need.

SUMMARY OF THE INVENTION

The primary aspect of the invention is to provide a method of forming a tubular ring comprising expanding the bore of a flat blank using a tubular shaft shaped line contact spinning roller.

Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.

The invention comprises a method of forming a tubular ring comprising spinning a flat blank having a bore, expanding the bore using a tubular shaft shaped spinning roller by initially engaging the tubular shaft shaped spinning roller with the flat blank bore at an angle (α) to the spinning axis, forming the flat blank into a tubular ring by rotating the tubular shaft shaped spinning roller about a center of rotation (B) such that the tubular shaft shaped spinning roller becomes substantially parallel to the spinning axis, and forming a contour on an outer surface of the tubular ring.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part of the specification, illustrate preferred embodiments of the present invention, and together with a description, serve to explain the principles of the invention.

FIG. 1 is a typical stress-strain curve for metal.

FIG. 2 is a cross-section of the tool and mandrel.

FIGS. 3(a) and 3(b) are a cross-section of an alternate tool and mandrel.

FIGS. 4(a) through FIG. 4(d) are side views of alternate tools.

FIG. 5 is a cross-section view of an alternate tool and mandrel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a typical stress-strain curve for metal. In the case of spinning metal, each element the plastic region as shown in FIG. 1. Each element is in the plastic region for a very short period of time wherein the metal is formed with or without application of heat. The process repeats as many times as required until the part is formed into the desired shape.

This invention comprises a method of flow forming a flat blank by spinning into a ring. The ring can be used in making gears, pulleys, sprockets, bearing races, one-way clutch races and similar products.

FIG. 2 is a cross-section of the tool and mandrel. A circular flat blank 100 having a central opening 101 is mounted in shoulder 12 of tooling 10. Shoulder 12 can be as small as one or two millimeters and as large as desired to create an inverted “L” shaped cross section for the ring. Shoulder 12 has a diameter that is larger than a diameter of tooling bore 11. Blank 100 rests upon and is fully supported about its entire perimeter by shoulder 12.

The loaded blank in the beginning of the process does not need any clamping, as the first contact of the roller with the blank forces the outer edge of the blank to the tooling and locks it in place. However, for very thin materials, or under any other requirements, a segmented upper ring (not shown) could be made to engage the top of tooling 10 that moves radially inwards with segments after loading the blank 100, thereby locking the edge 103 of the blank between the shoulder 12 and the segmented ring. At the end of the cycle, the segmented ring will open, allowing the ejection of the part.

Tooling 10 is mounted to a rotating mandrel 13. Tooling 10 and blank 100 rotate during the forming process. An inner surface 14 of tooling 10 defines a surface profile. For example, the surface profile may comprise splines, ribs, grooves, flat or any other shape that is desired. The inner surface 14 need not be configured to accommodate a spinning process since the metal can be flow formed into any desired surface profile. The surface profile defines the outer surface of the tubular ring formed using the disclosed method. In case of having any shape other than flat, a second roller (not shown) with a point contact may be used (round in X-Z plane, as well as round in X-Y plane). The second roller moves from one end of the inside of the ring back and forth to the other end while turning, thereby forcing the metal into the cavities in the surface 14 of the tooling 10. The second roller may also be used on the flat OD rings to make the outside diameter net-shaped and very accurate.

Roller 200 comprises an elongate tubular shaft member having a substantially constant diameter along its metal contacting length L. Roller 200 may or may not have one or two shoulders 12 to contain the blank 100, if needed. Roller 200 can be point contact type or line contact type and may also have differing diameters, see FIG. 5. The line contact type will have some limitations on the length of the contact depending on the material type (composition) and thickness and also the equipment capacity (tonnage). Roller 200 is rotatingly connected to roller holder 201.

During the rolling process, roller 200 is brought into contact with an inner edge 102 of blank 100 at an angle (α) to the centerline A-A, approximately 45°. Engaging at an angle to the spinning axis centerline allows control of the flow direction of the blank material as the bore is expanded. The range for angle (α) is in the range of approximately 30° to 60°.

Roller 200 is moveable in direction x, y and z. After entering the bore 101, roller 200 starts rotating from its steep initial angle to smaller angels gradually, namely, by rotating the roller about a center of rotation (B) such that the roller 200 is substantially parallel to the spinning axis A-A as the spinning process is completed. As roller 200 moves radially outward, blank 100 is flow formed radially outward. The radially outward movement of the material of blank 100 is a function of the radial position of roller 200 with respect to spinning axis A-A. Roller 200 moves in the x and y directions simultaneously in order to form a ring 100′ from blank 100. Finished ring 100′ has a tubular form aligned with a major axis A-A.

For thicker and harder material, roller 200 will oscillate back and forth along side its centerline axis to make the forming easier. Once the roller reaches the zero degree angle (parallel to the axis A-A of the ring, see 200′ FIG. 2), the process is finished and the ring 100′ is ejected.

The spinning operation can control the change in the thickness of the blank material throughout the process. The finished ring 100′ can be the same thickness as original blank 100, or be thicker or thinner. Thickening is done by using shoulders on the tooling 10 and/or roller 203 to limit the material flow, while thinning is done by stretching the material.

The spinner for this process does not need a tailstock but will require that the roller holder 201 have an angular movement capability, at least for the first roller holder 201. Other roller holders may or may not have the angular motion capability. The number of roller holders 201 can be as many as desired and the architecture of the equipment can handle. Roller holders can be attached to the spinner table or to an upper moving plate.

FIGS. 3(a) and 3(b) are a cross-section of an alternate tool and mandrel. Roller 203 comprises a protruding rim 202. Protruding rim 202 forms blank 100 into what is a substantially “L” shaped form comprising a radially extending portion 100″. Shoulder 13 of tooling 10 limits the extent to which blank material may flow while being formed by roller 203.

The second step of forming ring 100 is shown in FIG. 3(b). Portion 10″ is formed from the “L” shape in FIG. 3(a) to the final cylindrical shape using a shaping roller 220 in a manner known in the art. Creating the final cylindrical shape in this manner balances the metal flow. In the process shown in FIGS. 3(a) and 3(b) the metal is first flowed outwardly from the bore to create the “L” shape. The “L” shape is then formed inwardly to create the final cylindrical shape shown in FIG. 3(b). Use of this alternate method avoids potential thinning of the metal which may occur if the metal flow is entirely from the bore in a radially outward direction. This alternate method is useful for creating large radial increases from a relatively small diameter bore in a flat blank.

FIG. 4(a) through FIG. 4(d) are side views of alternate rollers. Roller 203 is described in FIG. 3. Roller 200 is described in FIG. 2. Roller 204 comprises a point contact roller having a point contact 207 for engaging a work piece. Roller 205 comprises a protruding rim 206 that extends radially from an end of roller 205.

FIG. 5 is a cross-section view of an alternate roller and mandrel. Yet another aspect of this invention is using a roller 208 that moves in X and Z directions with a rounded stepped tip 209. A plurality of steps 209 on roller 208 may be used to expand bore 101 by progressively moving roller 208 in the “y” direction until the desired bore diameter is achieved. Each step 209 has a progressively larger diameter.

However, a single step can be also used to expand bore 101 and then the same step can be used again to expand the hole further as many times as needed until the ring is made.

During the forming process, both the stepped roller (208) and single roller (200, 203, 204, 205) may oscillate in the x and y directions to make the blank metal material flow more efficiently.

It is also possible using this process to make a ring having an extended length which is then cut into two, three, four, or more rings afterwards to save time and reduce the cost.

The advantages of this invention are a reduction of the steps needed to make a ring, and reduction of the offal of process.

The inventive process can be used for manufacturing metallic automotive and non-automotive products for use in engines, transmissions, bearings, one-way clutches, gears, splines and various other products.

Although a form of the invention has been described herein, it will be obvious to those skilled in the art that variations may be made in the construction and relation of parts without departing from the spirit and scope of the invention described herein.

Claims

1. A method of forming a tubular ring comprising:

spinning a flat blank having a bore;

expanding the bore using a tubular shaft shaped spinning roller by initially engaging the tubular shaft shaped spinning roller with the bore at an angle (α) to the spinning axis;

forming the flat blank into a tubular ring by rotating the tubular shaft shaped spinning roller about a center of rotation (B) such that the tubular shaft shaped spinning roller becomes substantially parallel to the spinning axis; and

forming a contour on an outer surface of the tubular ring.

2. The method as in claim 1, wherein the tubular shaft shaped spinning roller is a line contact tubular shaft shaped spinning roller.

3. The method as in claim 1, wherein the tubular shaft shaped spinning roller is a point contact tubular shaft shaped spinning roller.

4. The method as in claim 1, wherein the tubular shaft shaped spinning roller further comprises a plurality of steps, each step having a different diameter.

5. The method as in claim 1 further comprising expanding the bore using a roller having a protruding rim.

6. The method as in claim 1 further comprising forming a radially extending portion into a tubular shape.