GB2201915A

GB2201915A - Press forming an article

Info

Publication number: GB2201915A
Application number: GB08802617A
Authority: GB
Inventors: Akira Taniguchi; Yoshitaka Kawamura; Sadao Horii
Original assignee: Asahi Seiki Manufacturing Co Ltd
Current assignee: Asahi Seiki Manufacturing Co Ltd
Priority date: 1987-02-07
Filing date: 1988-02-05
Publication date: 1988-09-14
Also published as: KR880009782A; DE3801249A1; GB8802617D0; JPS63194824A

Description

2 2- 0 19 1 J ARTICLE AND METHOD OF FORMING THE SAME This invention

relates to an article formed from sheet material by drawing and also to a method of forming this type of article.

A tape guide cylinder, for example, which is used in a device such as tape cassette. must be formed from a hard, non-magnetic material because of conditions under which the guide cylinder is used. Conventionally, it was common practice to form such a member by cutting a pipe made of stainless steel or by working a plate made of stainless steel. Methods for performing this process are disclosed in Japanese Patent Examined Publication No. 60-38778 and Japanese Patent Unexamined Publication No. 61-88926. Although-press working for producing various press-formed articles is usually conducted on single-component metallic sheets, it may be worth considering producing articles by press working from composite materials such as, for example, stainless steel-aluminium clad sheets, aluminium-duralumin clad sheets and other bimetallic sheets which are now commercially available. Unfortunately, however, it is rather difficult to obtain blanks of composite strip materials which have desired combination of metals and sizei so that it is very rare that articles are pressformed from composite metallic sheets. Proposals have also been made in Japanese Unexamined Publications Nos. 53-108064 and 57- 39041 for the simultaneous pressworking of two sheets. Special measures, for example, 1 1 i the preforming of recesses, are however required to ensure tight contact between the two sheets.

Stainless steels are often used as the materials for special articles such as, for example, tape guide cylinders which are required to meet both demands for high hardness and excellent non-magnetic characteristics, and, in order to mass-produce such parts from stainless steels in large quantities, it has been a conventional measure to employ press working. In general, however, stainless steels are rather difficult to work so that difficulties are encountered in producing articles by press working from stainless steels with high degree of precision. More specifically, when a hard stainless steel sheet is subjected to press working involving multi-stage drawing, the bending effect produced by the curvature of the shoulder of a punch used in a preceding drawing step, i.e., a first drawing step, has an adverse affect in the subsequent drawing step, e.g., a second drawing step, such that rounded recesses are formed in the lower end portion of the side wall of the half-finished blank adjacent to the bottom thereof. As the successive drawing steps are executed gradually to reduce the diameter of the blank, the rounded recesses formed in the successive drawing steps are inconveniently accumulated so as to form an undulation a in the region of the inner surface of the blank adjacent to the bottom 1 i 1 thereof, as illustrated in Fig. 5. Such undulation seriously impairs the commercial value of the products, particularly when the products are required to have high degrees of precision not only at the exterior diameter but also at the inner diameter thereof.

Another problem encountered by press working with stainless steels is that the price of the products are inevitably raised because the stainless steels are generally expensive. This is quite inconvenient from the view point of mass-production at reduced costs.

Though composite materials such as bimetallic niaterials and clad materials are available commercially as explained before, the combinations of the materials and the thicknesses are rather limited so that they often find it difficult to obtain composite materials which well meet the requirements for the materials of the articles to be press-formed. Problems are also encountered even when a composite sheet material which well meets the requirements could be found. Namely, composite materials such as clad material, which has been formed by simultaneously rolling two metallic strips, cannot be annealed in such a way as to provide a suitable level of workability over the entire portion of the clad material because different metals have different annealing temperatures for attaining a desired level of workability. In addition, clad materials are usually manufactures with a comparatively large tolerance of dimensions, so that they are not suitable as materials i of parts such as tape guide cylinders which are required to have specifically high degree of precision.

It is also to be pointed out that, since two metallic materials of a clad strip are bonded together through rolling, it is difficult to separate these metals from each other. This undesirably limits the use of wasted material such as the material left after punching.

The invention makes it possible to provide an improved method of press-forming cylindrical parts, as compared with previously proposed methods of pressforming these parts from example, a single-component metallic strip such as a stainless steel strip or from a composite material such as a bimetallic strip or a clad strip, without suffering from the above-described problems encountered by the prior art.

To this end, according to the invention, there is provided a method of press-forming a cylindrical article comprising the steps of: preparing a strip of a stainless steel and a strip of a metal which is easy to process by plastic working; subjecting said strips to rolling and annealing independently so as to optimize said strips for press working; placing said strips one on the other without allowing any oily content to exist therebetween; blanking said strips to form laminated sheets; and simultaneously subjecting said sheets to press working so as to cold-draw said sheets simultaneously; ^c z 1 whereby the cylindrical article is obtained with an outer part constituted by said stainless steel and an inner part constituted by said material easy to process by plastic working, with the latter plastically deformed to fill recesses in an undulation formed on the inner surface of said outer part of said stainless steel so as to attain a close and tight contact between said stainless steel and said material easy to process by plastic working.

The metallic material having high plastic workability used in the present invention is preferably aluminum or a copper alloy.

The press working method of the present invention suitably be used in the production of tape guide cylinders which are used in devices such as tape cassettes.

The above and other objects, features and advantages of the present invention will become clear from the following description of the preferred embodi- ment when the same is read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is an illustration of a blank of a tape guide cylinder in successive steps Of a transfer press working conducted in accordance with the method of the present invention; Fig. 2 is an illustration of successive steps 1 1 9 1 of the press working conducted on the blank shown in Fig. 1; Fig. 3 is a longitudinal sectional view of a tape guide cylinder produced by the method of the present invention; Fig. 4 is a longitudinal sectional view of another example of the tape guide cylinder; Fig. 5 is an enlarged longitudinal sectional view of a cylindrical part which is formed by a multi- stage drawing process from a stainless steel sheet, showing particularly an undulation formed on the portion of the inner peripheral surface adjacent to the bottom of the cylindrical part; and Fig. 6 is an enlarged sectional view of a portion of a cylindrical part which is press-formed in accordance with the method of the present invention from a stainless steel strip and a bronze strip superposed thereon, the bronze constituting an inner layer having been plastically deformed to partially flow into recesses of undulation formed in the surface of an outer layer constituted by the stainless steel.

DESCRIPTION OF PREFERRED EMBODIMENTS

A press working method disclosed in Japanese Patent Unexamined Publication No. 61-88926 can be applied to the working process of forming a cylindrical article in accordance with the present invention.

That is, a process of forming by press working i 1 a tape guide cylinder 1 having a thin outer layer 2 made of stainless steel and a thick inner layer 3 made of brass, as shown in Fig. 3, will be described below. A brass plate is superposed on a thin stainless steel plate, and these metallic plates are successively worked by deep drawing using punches and dies from a shape of a large diameter and a small depth to a shape of a small diameter and a large depth, thereby forming a cylindrical blank having a bottom. This blank is further worked by being pressed at its bottom and then at its flange, is thereafter pierced at its bottom and is cut to produce predetermined dimensions, and opposite ends of this blank are struck, thereby forming the tape guide cylinder 1 of desired dimensions. In this example, the forming work is performed by using a transfer-working machine which has fourteen work stages and one discharging stage combined, as shown in Fig. 2.

A stainless steel strip 10 and brass strip 12 are supplied from corresponding reel stands (not shown) in such a manner that the brass strip 12 is superposed on the stainless steel strip 10. These strips are made to stick fast to each other without applying oil or the like to their contact surfaces, and they are transported to the first stage of the press machine after press-working oil has been applied to the upper surface of the brass strip and the lower surface of the stainless steel strip.

In the first work stage, a blank Bl is formed i k 1 by a blanking punch and drawing die in such a manner that a blank BO is punched out from the superposed strips while it is worked large-diameter drawing to a small depth by using a first working die Al which is constituted by a punch P1 consisting of a blanking punch P1A and drawing punch P1B disposed coaxially with each other, and a die D1 consisting of a blanking die D1A and a drawing die D1B disposed coaxially with each other and with the punch Pl.

In the second to seventh work stages, the shallow and large-diameter blank B1 is worked by drawing to successively form deeper and smaller diameter blanks B2 to B7 by using second to seventh working dies A2 to A7 which are constituted by drawing punches P2 to P7 having drawing diameters successively reduced and drawing dies D2 to D7 disposed coaxially with each other. The working dies A2 to A7 are designed to leave a flange forming portion at the head of the blank.

In the eighth work stage, a blank B8 having a pressed bottom portion Bb is formed by a eighth working die A8 which is constituted by a bottom-pressing punch P8, a knockout N8, liner L8, and a guide G8 disposed coaxiallY with each other.

In the ninth and tenth work stages, flange formation is performed by flange pressing work using ninth and tenth working dies A9 and A10 which are constituted by a flange-pressing punches P9 and P10, and guides G9 and G10 disposed coaxially with each other, A 1 1 thereby successively forming blanks B9 and B10 so that a flange Ba becomes perpendicular to the cylindrical body.

In the eleventh working stage, the bottom portion Bb of the blank B10 which has been finished by drawing in the preceding steps to have a desired shape is pierced by an eleventh working die All which is constituted by a piercing punch P11 and a piercing die Dll disposed coaxially with each other, thereby forming a blank B11.

In the twelfth stage, inner chamferring is performed by using a twelfth working die A12 constituted by a chamferring punch P12 having a stepped portion, a knockout N12 having a chamferring projection N12A extending upward from its top end,-and a liner L12 disposed coaxially with each other, in such a manner that the flange Ba of the blank B11 is pressed by the stepped portion P12A of the punch P12 while the end of the blank B11 is chamferred by the knockout N12, thereby forming a blank B12.

In the thirteenth stage, trimming is performed at the position of the flange Ba of the blank B12 by using a thirteenth working die A13 which is constituted by a trimming punch P13, a trimming die D13, a liner L13, and a knockout N13 disposed coaxially with each other, and thereby forming a blank B13 having predetermined dimensions. Remaining scrap S attached to the punch 13 is removed from the punch by a stripping device (not i 1 shown) and is discharged by air pressure in the direction perpendicular to the transfer work line.

In the fourteenth stage, dimension-producing forming exerted on opposite ends of the blank B13 is performed by using a fourteenth working die A14 constituted by a striking punch P14, a die D14, knockout N14, and a liner L14 disposed coaxially with each other, in such a manner that the opposite ends of the blank B13 are struck in the vertical direction by the stepped portion of the striking punch P14 and the top end of the knockout N14 while the inside and outside diameters of the blank B13 are being restrained by a small-diameter portion of the striking punch P14 and the die D14, thereby completing the tape guide cylinder 1 of desired dimensions as shown in Fig. 3.

It is therefore possible to make the entire length of the blank B13 uniform and reduce deviations of the opposite end surfaces of the blank relative to the axis thereof by striking the opposite ends of the blank 13 while restraining the inside and outside diameters thereof so as to eliminate the possibility of buckling.

In the fifteenth working state, a completed blank B14 is discharged without being worked.

The illustrated transfer-working process may be altered as desired in accordance with the dimensions of the tape guide cylinder 1, and idle stages may be added for the purpose of, for example, reducing deformation of the blank and improving the balance of pressing i 1 loads. In the illustrated example, the present invention is applied to transfer working, but it can, of course, be applied to progressive working. Also, in the process of transfer woking or progressive working in accordance with this embodiment, the blank may be formed, depending upon a specific shape desired, by secondary working which is performed instead of striking working in the fourteenth stage by increasing the drawing dimensions and using an automatic lathe or the 10 like to produce predetermined dimensions, as shown in Fig. 4.

About a hundred tape guide cylinders having an outside diameter of about 6 mm, an inside diameter of about 4.8 mm, and a length of about 16 mm were formed in accordance with the embodiment and were tested with respect to the force needed for pulling out the brass inner tube from the outer stainless steel tube. It was confirmed that this force ranged from 95 to 110 kgf and these test pieces were suitable for ordinary use of 20 tape guide cylinders.

As has been described, the present invention proposes to form an article such as a tape guide cylinder by simultaneously press working stacked sheets of different metallic materials, thus offering the following advantages.

First of all, it is to be understood that the method of the present invention makes it possible to produce a cylindrical product such that an expensive i - 12 material is used only on the outer part of the product so as to provide required properties, while an inexpensive material is used on the inner part which is required merely to provide reinforcement, thereby making it possible to reduce the production costs. The strips used in the method of the present invention can be independently rolled so that they have high degrees of precision in thickness, thus offering a high accuracy of the total thickness of the stack of the strips, which in turn ensures a high accuracy of the press-formed cylindrical part. It is also to be noted that the functional part of the product, e.g., the stainless steel part 2 of the tape guide cylinder 1 can be formed to have any desired thickness from an available blank sheet of any appropriate thickness. Furthermore, since two materials can be annealed independently before they are stacked, it is possible to adopt suitable annealing temperatures for the respective strips so as to maximize the press workability of these materials, thus facilitating the press working. An undulation formed on the inner surface of the part formed by the material having inferior press workability is conveniently filled by the other material which has higher press workability, since a part of the other material is plastically deformed to flow into the recesses of the undulation as shown in Fig. 6, whereby a high bonding effect is developed between both materials. The use of the material having high press workability as the material 1 of the inner part of the cylindrical product ensures that the inside diameter of the cylindrical product is maintained constant over the entire axial length of the product, thus eliminating local change in the diameter 5 such as that shown in Fig. 5.

The remainder parts of the blank sheets are easily separable because these blank sheets are merely laid one on the other, so that the respective materials can be forwarded as they are for various other uses.

Thus, the present invention also offers a high utility of the waste materials. It is also possible to make an effective use of any difference in the springing back characteristics produced between two materials during press working, such as to enable the product to easily maintain its shape.

It will be clear to those skilled in the art that, though a specific product made from specific materials has been described, the present invention can be applied to the production of various parts such as casing of a button cell, battery case and so forth, as well as the described tape guide cylinder, and the materials of the outer and inner parts are selectable from various available materials in accordance with the required properties such as non-magnetic characteristic, wear resistance, corrosion resistance and so forth.

1k The present invention also provides a method of press-forming an article comprising simultaneously subjecting to press-working sheet material of a first substance and sheet material of a second substance, so as to cold- draw the substances simultaneously, the second substance being easier to process by plastic working than the first substance and in the press- formed article giving a layer further from the outer surface of the article than a layer of the first substance, the pressworking operation producing one or more irregularities in the inner surface of the layer of the first substance and the second substance being plastically deformed during press-working at least partially to conform to the irregularities. Preferably, the layer of the first substance forms the outer surface of the press-formed article and the layer of the second substance forms the inner surface of the article.

Preferably the first substance and/or the second substance is metallic.

The first substance may be stainless steel, but if desired other substances that are relatively difficult to work may be used as the first substance. The second substance may comprise, for example, copper or aluminium.

Advantageously, the press-working operation includes the steps of forming from the sheet material of the first substance and the sheet material of the second l 4 11 i k - is - substance a cylindrical blank having a flat bottom and subsequently subjecting the blank to further pressworking at least once so as to cold- draw the blank to a cylindrical article having a diameter smaller than that of the blank.

The press-formed article formed by the method of the invention is advantageously generally cylindrical, and may have the form of a rightcircular cylinder, although cylindrical articles with cross-sections other than circular, for example, elliptical, rectangular or triangular crosssections, may be obtained. A generally cylindrical article may include, for example, one or more protuberances, for example flanges.

The invention also provides an article, particularly a tape guide cylinder,, made by the method of the invention.

a -1

Claims

1. A method of press-forming an article comprising simultaneously subjecting to press-working sheet material of a first substance and sheet material of a second substance, so as to cold-draw the substances simultaneouslyr the second substance being easier to process by plastic working than the first substance and in the press-formed article giving a layer further from the outer surface of the article than a layer of the first substance, the press-working operation producing one or more irregularities in the inner surface of the layer of the first substance and the second substance being plastically deformed during press-working at least partially to conform to the irregularities.

2. A method as claimed in claim 1, wherein the layer of the first substance forms the outer surface of the press-formed article and the layer of the second substance forms the inner surface of the article.

3. A method as claimed in claim 1 or claim 2. wherein the first substance is a metal.

4. A method as claimed in any one of claims 1 to 3, wherein the second substance is a metal.

1 i 17 -

5. A method as claimed in any one of claims 1 to 4, wherein the first substance is stainless steel.

6. A method as claimed in any one of claims 1 to 5, wherein the second substance is aluminium.

7. A method as claimed in any one of claims 1 to 5, wherein the second substance comprises copper.

8. A method as claimed in any one of claims 1 to 7, wherein the pressworking operation includes the steps of forming from the sheet material of the first substance and the sheet material of the second substance a cylindrical blank having a flat bottom and subsequently subjecting the blank to further press-working at least once so as to cold-draw the blank to a cylindrical article having a diameter smaller than 15 that of the blank.

9. A method as claimed in any one of claims 1 to 7, wherein the pressformed article is cylindrical.

10. A method as claimed in any one of claims 1 to 9, wherein the pressformed article has the form of a right-circular cylinder.

z 1 k

11. A method as claimed In any one of claims 1 to 10, wherein each of the first and second substances is metallic and before press-working the sheet material of the first metal is rolled and annealed and, independently, the sheet material of the second metal is also rolled and annealed.

12. A method of press-forming a cylindrical article comprising the steps of: preparing a strip of a stainless steel and a strip of a metal which is easy to process by plastic working; subjecting said strips to rolling and annealing independently so as to optimize said strips for press working; placing said strips one on the other without allowing any oily content to exist therebetween; blanking said strips to form laminated sheets; andsimultaneously subjecting said sheets to press working so as to cold-draw said sheets simultaneously; whereby the cylindrical article is obtained with an outer part consistuted by said stainless steel and an inner part constituted by said material easy to process by plastic working, with the latter plastically deformed to fill recesses in an undulation formed on the inner surface of said outer part of said stainless steel so as to attain a close and tight contact between said f 1 stainless steel and said material easy to process by plastic working.

13. A method as claimed in claim 12, wherein said material easy to process by plastic working is aluminium.

14. A method as claimed in claim 12, wherein said material easy to process by plastic working is a copper alloy.

15. A method as claimed in claim 1 carried out substantially as described herein with reference to the accompanying drawings.

16. A press-formed article produced by a method as claimed in any one of claims 1 to 15.

17. A tape guide cylinder produced by a method as claimed in any one of claims 1 to 15.

18. Any novel feature described herein or any nove combination of hereindescribed features.

Published 1988 at The Patent Office, State House, 65171 High Holborn, London WOIR 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Mary Oray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Oray, Kent. Oon. 1/87.