JPS60227934A - Method of molding thin-wall and semicircular shell - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention Industrial Application Field The forming method of the present invention relates to a sheet metal forming method in which a workpiece is formed by inserting the workpiece between concave and convex surfaces of opposing dies at regular intervals. In particular, the method of the present invention is a method for forming a thin-walled seven-semi-annular shell from a flat sheet material.

The flat sheet material is first formed into a cylindrical band and welded.

It is then curled inward and compressed on the gou surface, thereby eliminating tensile fractures in the weld and accurately aligning the workpiece to the gou surface.

PRIOR ART The method of the present invention employs thin walls, an annular groove, a generally U-shaped cross section (
It is suitable for molding an annular shell (doughnut-shaped hollow body) (or divided into two in the horizontal direction). These shells are currently used in liquid couplings or liquid transmissions in which radially extending vanes (or fins) are fixed in grooves on the outer surface of the shell to form a rotor. Two rotors are used in automotive torque converters that form an annular hollow body with blades in open, facing relationship. Therefore,
The outer surface shape of the semi-annular shell is important to the proper operation of the torque converter. For example, the outer tolerance of semi-annular shells used in automotive torque converters must be maintained at 15% of the material thickness. Therefore, the tolerance of the annular shell of thickness 0,1 O16z (0,0 uOin) must be maintained to ±0,051 crn (0,002 in).

Annular shells are currently formed industrially by cutting or punching washer-like blanks from whole sheet stock, which creates significant material waste and increases the cost of the shell. The blank is then formed into a semi-annular shell using conventional die stamping techniques.

PROBLEM SOLVED BY THE INVENTION The method of the present invention substantially eliminates scrap, thus reducing the cost of the shell. U.S. Pat. No. 3,851,517, assigned to General Motors Corporation, discloses a method for forming semicircular shells from flat strip stock that eliminates scrap, but has not been commercially successful. There wasn't. The method disclosed in this patent utilizes rectangular sheet metal stock, which is rolled into a cylinder and welded. One cylinder end is then forced into a first preforming die set to bend the top edge of the cylinder outward first. The outwardly bent end (flare part) of the cylinder is first pushed into a second curling die set having concave surfaces at regular intervals and convex surfaces curved outwardly to match the concave surfaces, and the cylinder is pressed under tension. It is curled outward to form a semi-annular shell, and finally the shell is formed into its final shape in a fifth restriking die set.

The weldment had to be precisely adjusted, leveled, and smoothed before forming, as the weld was placed under extreme tensile stress during curl forming.

Nevertheless, the method disclosed in the aforementioned U.S. Pat. No. 3,851,517 was not commercially successful because the weld repeatedly broke under the tensile stress caused by curling the cylinder outward. Ta.

The method was eventually abandoned. moreover.

The workpiece tends to pull away from the die concavity under the tensile forces created by the curling process, making it difficult to control the subcritical tolerances of the shell.

The method of the present invention involves curling a cylindrical band inward and 5
By placing the weldment in compression, the problems inherent in that patent are eliminated. In fact, semi-annular shells can be formed by the method of the invention without welding (or joining) the abutting portions of the bands by other means, and the method is also suitable for other applications. Furthermore, because the shell can be formed in one press stroke, there is no need for preforming of the cylindrical flare required in the aforementioned patent.

Construction of the Invention The method of forming a thin-walled, semi-annular shell of the present invention involves forming a rectangular flat sheet into a cylindrical band, and preferably, particularly for said semi-annular shell, the abutting free end of the cylindrical band. Including joining parts.

One end of the cylindrical band is then forced into a die set having a cylindrical opening that blends smoothly into an inward curling semi-annular space defined by opposing regularly spaced concave and convex die surfaces.

The diameter of the cylindrical band is equal to the nominal diameter of the opening in the die set located at the radial extension of the gou surface.

As the cylindrical band is forced into the annular space between the concave and convex die surfaces, the band gradually curls inward under compression to meet the semi-annular space. The cylinder is thus placed under compressive force and the annular outer surface of the workpiece coincides exactly with the gouly concave surface.

In a preferred method of forming annular shells suitable for couplings or converters such as automotive torque converters, the free ends of the bands are preferably welded. Wipe that weld.

As the band is gradually curled inward, it is compressed into the annular, concave surface of the die, causing the welded surface to conform precisely to the concave surface of the die.

Thus, the weldment does not undergo tensile failure as in the prior art methods described above. As will be appreciated, the weld is not as pure as the base metal and will fail in short applications when expanded by about 20%. There is no known limit to compressive force. moreover.

Since the semi-annular shell can be formed by the method of the present invention in one press stroke, there is no need to pre-form the flared end of one cylinder (of course, the semi-annular shell can be pressed again with a re-strike die, resulting in an even more complex process). shape). Finally, the non-critical surface of the annular shell is easily kept within precise tolerances, as it precisely coincides with the Gouy concavity during the compression curling process.

Other advantages and features of the method of the invention will be more fully understood from the following detailed description of the method of the invention.

FIG. 1 shows a thin-walled, annular channel or semi-annular shell 2o formed by the method of the invention. shell 20
consists of a cylindrical outer lip 22, a U-shaped intermediate portion 211 and an inner lip 26. The shell 2° is formed from a cylindrical band 3o as shown in FIG. The cylindrical band 30 is formed from a rolled flat straight strip and welded to the semi-annular shell shown in FIG. 1 at points 2g to form a weld.

The formation of the cylindrical band 3o as shown in FIG.
No. 517 provides further details.

The semi-annular shell 2o of FIG. 1 is formed by a die set assembly 31i shown in FIGS. 5 and 4. Thailand·
The set assembly 311 is connected to the cylindrical hole II of the riser 58.
It includes an annular cylindrical ram 56 that enters O.

Riser 38 includes a conical counterbore 142 that receives cylindrical band 3o when ram 36 is raised above the position shown in FIG. Ram 56 includes an annular lip 11 and an end 116 that engages cylindrical hand 50 .

The cylindrical band 50 first enters a curling die 5o having an annular cylindrical surface 52 receiving the cylindrical band and an annular concave surface 511 terminating in a cylindrical hole 56. An annular forming post 6o that enters the curl die 50 is attached to the cylindrical surface 5 of the curl die.
2 and an annular convex surface 6 facing the concave surface 5+1 of the curl die. The forming post 60 and curling die 50 thus form a U-shaped annular space that receives the cylindrical band 30 as described below.

Die set assembly IJ 511 includes static 1 cylindrical center post 66, spring pad 68, and molded post 6
It also includes a plurality of coil springs 70 that are evenly distributed into the cylindrical insert 58 within the cylindrical insert 58 . Center guide post 72 with cylindrical outer surface
receives the ram 56 in telescopic relationship, and the ram has a conical flange 7u that receives the die pin 76.
Including tr. The die pin 76 is attached to the upper die platen (not shown).
bolted or otherwise secured to the In the disclosed embodiment, there are 11 die pins 76 and 1+:+
There is a spring 70. It will be appreciated by those skilled in the art that only half of the die assembly is shown to illustrate the present method, and that the die assembly typically includes a lower die platen (not shown) that supports the curl die 50 of a conventional bolster assembly. There will be. Reference is also made to the aforementioned US patents.

The method of the present invention includes the steps of forming the cylindrical band 30 of FIG. 2 from a flat IJ tube stock and welding the free end of the strip, indicated at 2g. As previously mentioned, the free ends of the bands can also be joined by other means, including TIG welding. In fact, the method of the present invention compresses the band during molding, so that the band does not join its abutting free ends.

Molded into a U-shaped annular channel.

One end of the cylindrical band 30 is then forced into the semi-annular space defined by the curling die 50 and the forming post 60. The opening to the semi-annular space in the preferred embodiment is cylindrical as defined by opposing cylindrical surfaces 52,62. As shown, the cylindrical opening blends smoothly into the semi-annular space defined by the annular quadrature 511 and the annular convex surface 611. The nominal diameter of the cylindrical band 50 is
Equal to the nominal diameter of the cylindrical opening between curling die 50 and forming post 60. Opposite ends of the one-tube band are engaged by the annular lip III of the ram 36. Thus, the lowering of the ram 56 pushes the cylindrical band downward in FIG. 5, gradually curling the band radially inward between the curling die 50 and the forming post 60, and forming the cylindrical band and the welded portion 2g as shown in FIG. compress. Thus, the semicircular shell 20
Since it is formed in one press stroke, there is no need for a preforming step as described in the cited patent.

As noted above, the method of the present invention provides a 50% material cost savings over current methods that involve die forming a semi-annular shell from a washer-shaped blank. The outer surface of the semi-annular shell precisely matches the concave surface 5u of the curling die as it curls inward and compresses the band to match the curling die. More importantly, because the weld 28 is placed under compression, tensile failure of the weld as experienced in the methods described in the cited patents is eliminated. Additionally, the outer surface of the weld 28 is wiped with the concave surface 511 so that the weld precisely matches the concave surface 511. Because the band is placed under compression rather than tension during molding, the band does not tend to pull away from the die outer surface, maintaining the non-critical surface within tolerances.

The semi-annular shell 20 may be formed in more steps depending on the application. For example, a coring impeller for an automotive fluid converter includes an inner cylindrical surface that receives a shaft, as shown at 80 in FIG.

This shape is formed using a restriking die set as shown in FIG. The semi-annular shell 80 shown in FIG.

The cylinder includes an inner lip portion 82 and an outer annular portion gq.

The restriking die assembly includes a female die member 86 that corresponds to the curling die 50 of FIGS. The molded post 911 has an annular convex surface 96 and a cylindrical surface 9F! including. As previously discussed with respect to FIGS. 5 and 4, female die member 86 and forming boss 91+ are spaced apart to define a semi-annular space therebetween. The semi-annular shell 80 is then formed by a die member.

In the disclosed embodiment of the restriking die assembly shown in FIG. 6, the semi-annular shell 80 is retained by an outer retainer ring 100 having an annular lip 102 and an inner retainer ring 1011 that views the annular lip 106. The semi-annular shell 20 shown in FIG. 1 is inserted into the female gouge member 86. and molded post 911 and retainer ring 100
．． 1011 is lowered into the female gouge to form the final shape of the semi-annular shell 80 shown in FIG. Changes in the shape of the shell can be better understood by comparing FIGS. 7 and 8. FIG. 7 shows the cross-sectional shape of the semi-annular shell 20 of FIG. 1, and FIG. The cross-sectional shape of shell 80 is shown. The restriking die assembly expands the shell to form a cylindrical outer lip with a continuous, outer annular portion 8I as shown in FIG.
Reshape into l.

The inner lip 26 is a cylindrical lip 8 as shown in FIG.
Reshape into 2.

Thus, the method of the present invention significantly reduces the cost of forming semi-annular shells by rolling and welding two shells as shown in FIG. 2 from rectangular strips of sheet material. This results in substantial savings in material. Furthermore, the shell is formed in one stroke of the press, as shown in FIGS. The shell can be molded from a variety of materials depending on the application. For example, the coring impeller can be formed from 1010 or 101 g steel plate having a thickness of 1, for example 0.10 cy++ (0, On Oin ). As previously mentioned, the weld 2g is placed under compression during the curling process as shown in FIGS. 5 and 4. The outer lip 22 of the shell is expanded in the restriking die set assembly of FIG. 6, but the expansion is less than 10% to avoid failure of the weld. Thus, the method of the present invention can form a semi-annular shell go of complex shape as shown in FIG. 5, while avoiding tensile forces on the weld that would otherwise destroy the weld during manufacturing.

[Brief explanation of the drawing]

FIG. 1 is a side view of a semi-annular shell formed by the method of the invention. 2 is a side view of the cylindrical band forming the semi-annular shell of FIG. 1; FIG. FIG. 5 is a side partial cross-sectional view of one embodiment of a die set used in the method of the present invention, showing the ram starting condition for forming the cylindrical band of FIG. 2; 4 is a side cross-sectional view of the guiset shown in FIG. 5, with the ram lowered to form the semi-annular shell shown in FIG. 1; FIG. FIG. 5 shows the semi-annular shell of FIG. 1 after restriking. FIG. 6 is a side cross-sectional view of a portion of an embodiment of the restriking die used to form the semi-annular shell of FIG. 5. FIG. 7 is a side cross-sectional view of the semi-annular shell shown in FIG. 1; FIG. 8 is a side cross-sectional view of the semi-annular shell shown in FIG. 5. FIG. Explanation of symbols in the figure 20. IH) - one semi-annular shell 2F3 - one strip free end (or weld) 50 - cylindrical band 311 - die set assembly 36 - ram 3g - riser

Claims (1)

[Claims] 1. (al) A rectangular flat sheet having a free end and upper and lower edges is formed into a cylindrical band, and the free ends are brought into contact with each other,
a step of forming upper and lower ends of the cylindrical band with the upper and lower edges; (bl a step of joining the mating ends; (cl
One end of the cylindrical band 5 is between a fixed gouing surface of concave and convex surfaces aligned at equal intervals of V and a goui member having an opening having the same diameter as the nominal diameter of the cylindrical band at the radially outer side of the semi-annular space. pushing the cylindrical band between the fixed die surfaces into the defined semi-annular space and engaging the other end of the cylindrical band, gradually radially inwardly between the concave and convex die surfaces in the semi-annular space; forming said cylindrical band into a semi-annular shape by curling and compressing the joint between said cylindrical band and said abutting end; Method for forming annular shells. 2, fa) A step of forming a rectangular flat sheet having a free end and upper and lower edges into a cylindrical band in which the free ends are brought together; (b) A step of welding the joining ends of the cylindrical band; ( c) It has a cylindrical opening on the outside in the radial direction, and adjacent to the opening, the y-cylindrical space smoothly blends into the semi-annular space. providing a die set having a fixed goo surface;
and (di) forcing one end of the cylindrical band into the cylindrical opening by engaging the other end of the band, causing the band to gradually curl under compression into the semi-annular space between the concave and convex fixed die surfaces. , wiping and compressing the weld onto the concave die surface, and forming the cylindrical band into a semi-annular shape having an annular outer surface that exactly matches the concave die surface. A method for forming a thin-walled, semi-annular shell having a letter-shaped cross section. 3. Step of forming a rectangular flat sheet having a free end into a cylindrical band by butting the free ends together; (cl) one end of the cylindrical band is formed at equal intervals to form a cylindrical opening on the radially outer side and a U-shaped space opening that blends smoothly with the cylindrical opening; inserting the cylindrical band into a die set having matching concave and convex fixed die surfaces; and (al) forcing the cylindrical band between the concave and convex die surfaces by mating the other ends of the band;
Curling the cylindrical band inward, aligning the outer surface of the cylindrical band exactly with the outer circumferential surface of the die, and compressing the joint between the mating ends of the band'! 1. A method for forming a thin-walled, channel-like shell with a U-shaped cross section. 14, (al) a step of bending a rectangular flat sheet having free ends by bringing the free ends together; (bl) a step of joining the joined free ends of the cylindrical band; (c) the cylindrical band and a regularly spaced die member having a cylindrical opening having the same diameter as the outer opening and defining a cylindrical space in the outer opening that blends smoothly with the inwardly curved concave and convex surfaces, and defining a U-shaped space communicating with the cylindrical space. (a) inserting one cylindrical end of the cylindrical band into a die set having a
forcing the cylindrical band into the die set space and gradually curling the cylindrical band under arbitrary contraction force to form a semi-annular shell having five cylindrical outer lips and a U-shaped middle portion terminating in a circular inner lip; and tel The semi-annular shell is re-struck between opposing die members, the outer lip is expanded by less than 10% within the allowable stress of the joint between the abutting ends, and the inner lip is attached to the cylindrical inner wall. U having a continuous, U-shaped semicircular outer part with a cylindrical inner lip part, characterized in that it consists of a reshaping process.
A method for forming thin-walled, semi-annular shells with glyph-shaped cross sections.