US3640556A

US3640556A - Tab welded joint and method of making

Info

Publication number: US3640556A
Application number: US868259A
Authority: US
Inventors: Moreland P Bennett
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-08-22
Filing date: 1969-08-22
Publication date: 1972-02-08
Anticipated expiration: 1989-02-08

Abstract

A welded joint comprising overlapped strips of metal with tabs formed by piercing or lancing through the overlapped portion. The formed tabs are flattened against the metal and resistance spot welded to such metal. The resistance welding forms a metallurgical bond between the metal members.

Description

I Umted States Patent 1151 3,640,556 Bennett Feb. 8, 1972 [54] TAB WELDED JOINT AND METHOD OF 3,247,316 4/1966 Weimer ..174/94 MAKING 3,278,880 10/1966 Lewis et al.... ..336/192 3,281,923 11/1966 Best et al. ..29/470.5 X 1 lnvemofl Mordqnd Bennett, 45 Concord Park- 2,149,844 3/1939 George ..287/l 89.36 8 Mass- 01201 2,814,810 12/1957 Kelly ..287/l89.36 B x [22] Filed: Aug. 22, 1969 Primary ExaminerDavid J. Wilhamowsky [21] Appl' 868,259 Assistant Examinerwayne L. Shedd Attorney-Gilbert P. Tarleton, Francis X. Doyle, Melvin A. Rem! Amman Dam Goldenberg, Frank L. Neuhauser and Oscar B. Waddell [62] Division of Ser. No. 616,945, Feb. 17, 1967.

[57] ABSTRACT [52] US. CL ..287/ 189.3613, 29/432, 29/4705,

29/509 29/513, 219/91 219/92 A welded 1011112 comprising overlapped stnps of metal w1th tabs 51 1 m1. (:1 ..F16b 5/07, F16b 5/08 frmed by Piercing aiming through mflapped [58] Field of Search ..287/189, 36 B; 219/91, 92, The formed tabs are flattened against the metal and resistance 219/93; 24/4705 509 5 3 spot welded to such metal. The resistance welding forms a metallurgical bond between the metal members.

[56] References Cited 6 Cl 5 Dn Figures UNITED STATES PATENTS 2,190,621 2/1940 Baer ..219/91 TAB WELDED JOINT AND METHOD OF MAKING This is a division of application Ser. No. 616,945, filed Feb. 17, 1967, which is assigned to the same assignee as this present application.

BACKGROUND OF THE INVENTION This invention relates to metal joints and more particularly to a welded joint and the method of making such joint. The joints of this invention find special utility in the electrical industry.

As is well known to those skilled in the metal joining art, it is often necessary to joint metal members to provide not only a secure mechanical joint, but one which will provide a sound electrical connection. These types of joints are usually required in the electrical industry for securing electrical conductive members to each other. One well-known connection which must be both mechanically secure and electrically sound is the connection made between the lead or tap strap and an electrical coil. In many modern day coils a very thin foil is used for the coil winding with somewhat thicker strip material used for leads or tap straps. In many coils, the winding is made of one metallic material such as aluminum while the leads or tap straps are made of another metallic material such as copper. Much difficulty has been experienced in providing adequate mechanical and electrical connections between the foil wound coils and the leads or tap straps.

Mechanical connections are usually formed by riveting or crimping and are generally undesirable because they depend solely on the contact between adjacent surfaces for transmission of electrical current. As these joints age, the connections tend to relax and oxides may form on the adjacent surfaces, providing very poor electrical connections. Solder connections are not useful for high current uses since the solder has a very low melting temperature. Further, there is no metallurgical bond between the solder and the joint surfaces, which often leads to a poor electrical connection. Brazing and welding of joints require an expensive cleaning process and also are very difficult to make without damage to the thin foils. It has recently been discovered that thin foils and strips of similar and dissimilar metals may be joined in a strong mechanical and electrical connection by piercing tabs in the metal and spot welding the formed tabs.

SUMMARY OF INVENTION It is therefore one object of this invention to provide a welded joint for joining thin foil and strips of metal.

A further object of this invention is to provide a method of making a mechanical weld joint between thin metal members.

A still further object of this invention is to provide a mechanical weld joint for metal members.

In carrying out this invention in one form, metal members to be joined are placed in overlapping relation. Tabs are formed through the overlapped portions of the metal members, the formed tabs are flattened and then spot welded to one of the metal members. The spot welding forms a metallurgical bond between the tab and the various metal members.

The invention sought to be protected will be particularly pointed out and distinctly claimed in the claims appended hereto. However, it is believed that this invention and the manner in which its various objects and advantages are obtained as well as other objects and advantages thereof, may be better understood from the following detailed description of a preferred embodiment especially when considered in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF DRAWING FIG. 1 is a perspective view of a preferred joint made according to this invention;

FIG. 2 is a top view of the joint shown in FIG. 1;

FIG. 3 is an enlarged sectional view of metal members to be joined showing the preferred method of this invention;

FIG. 4 is an enlarged sectional view of a completed joint made a ccording to this invention; and

FIG. 5 is an enlarged sectional view of a completed joint made according to another embodiment of this invention.

DESCRIPTION OF PREFERRED EMBODIMENTS As above noted, it has been discovered that thin foils and strips of metal may be joined by using tabs formed in overlapped portions of the metal members and then spot welding the tabs to one of the metal members. The metals to be joined are placed in overlapped relation and a plurality of tabs are formed through the overlapped portions. A resistance spot welder is then applied to opposite sides of the joint flattening the tabs and welding them to the metal. The welding step metallurgically bonds the metals together providing a good electrical connection strengthened by the formed and welded tabs. In a preferred form of joint, a pair of relatively thicker strips are placed on each side of a foil member providing a joint which is mechanically stronger than can be obtained by a single strip and foil member.

Where copper and aluminum are to be joined by a method of this invention, it is found desirable to first tin-plate the copper and then to provide copper on each side of the aluminum. Of course, the copper could be silver-plated, if desired. However, from the cost view, tin-plating is preferred. This will provide a better metallurgical bond between the copper and the aluminum. Referring now to the drawings, in which like numerals are used to indicate like parts throughout the various views, FIG. 1 shows a perspective view of a preferred joint made according to this invention. As shown in FIG. 1, a joint is formed between a metal foil member 10 and a pair of

thin metal strips

12 and 14. The

metal strips

12 and 14 are placed on opposite sides of the foil 10. The three metal members have overlapped portions as shown. As can be seen, a plurality of tabs 16 are formed through the overlapped portions of the metal members l0, l2 and 14. As is shown, particularly in FIG,. 2, the tabs 16 are preferably of substantially triangular shape, leaving the triangular holes 18 through the overlapped metal portions. The tabs are flattened against the top metal strip 12 and welded thereto as will be more fully discussed with reference to FIG. 3.

FIG. 3 shows the preferred method of making the joint of this invention. FIG. 3 is an enlarged sectional view showing a tab 16 pierced or lanced from the three overlapped portions of the foil 10 and the

metal strips

12 and 14. As is apparent from FIG. 3, tab 16 is formed from parts of each metal member and has been folded over the top of the strip 12. A resistance spot welder indicated by

electrodes

20 and 22, is then brought in contact with opposite sides of the overlapped metal members l0, l2 and 14 at the tab 16 as indicated. The welder is energized by a source of electrical energy indicated at 24, such that when

electrodes

20 and 22 contact the overlapped metal members, current will flow through the metal members to weld the members together. Sufficient pressure is applied by

electrodes

20 and 22 as indicated by the arrows to flatten tab 16 against the metal strip 12. It is preferred to use refractory or other high-resistance electrodes so that the electrodes provide the major heating for welding the joint.

A portion of a completed joint is shown in enlarged sectional view in FIG. 4. As can be seen in FIG. 4, the heat and pressure from the

welding electrodes

20 and 22 has forced the tab 16 into the surface of the strip 12, welding the metal parts of tab 16 to each other and to the strip 12. The welding heat has also substantially welded the metal members l0, l2 and 14 to each other in the area of tab 16 as is shown by the drawing in FIG. 4. Of course, it will be apparent that each tab in the joined surfaces will be similarly welded and that as many tabs as desired may be provided.

In a test of this invention, a pair of joints were made, each joint was formed of two strips of 0.010 inch thick copper 0.75 inch wide with a l0 inch portion of 0.006 inch aluminum foil secured between the copper strips. The copper for both joints were tin plated. One joint was made with seven tabs, while the 1 other joint was made with 13 tabs. The joints were welded with the current of approximately 4,000 amperes and a pressure of approximately 75 pounds. Both joints were subjected to pull tests and to heat and short circuit tests. Both joints exhibited satisfactory strength, sustaining a tensile pull of approximately 90 pounds. The joints also passed 18 times normal current for 3.5 seconds. In the heat test the seven-tab joint ran approximately C. hotter than the l3-tab joint. However, both joints were considered adequate for use in connecting lead wires to coils.

FIG. 5 shows a completed joint made between a single strip of metal and a piece of foil, according to another embodiment of this invention. This form of the invention is especially useful when the foil member has been coated with insulation. As is shown in FIG. 5, a foil member 30, provided with insulation 32 is joined to a metal strip 34. A tab 36 has been struck from the overlapped metals, leaving an opening 38. Tab 36 is then flattened against the insulation 32 on foil 30. Then a resistance spot welder, such as is indicated in FIG,. 3, is applied to opposite sides of the

metal members

30, 34 at tab 36. The heat and pressure provided by the resistance spot welder burns off the insulation 32 beneath tab 36 and welds foil 30 and strip 34 together, as shown. This method provides very good electrical joints between a lead and a foil winding without the necessity of removing the insulation prior to making the joint.

While there has been shown and described the present preferred embodiments of this invention, it will be clear that .various changes may be made by those skilled in this art. For

example, it will be apparent that sections of foil may be connected to each other by a metal strip by use of this invention. Other changes or uses may also be made by those skilled in this art without departing from the spirit and scope of the invention, particularly as defined in the appended claims.

What is claimed as new and which it is desired to be secured by Letters Patent of the United States is:

17 A welded metal joint between a metal foil member and at least one metal strip member, said metal members having portions in overlapped spatial contacting relation comprising; a plurality of tabs, each of said plurality of tabs having superposed material of said metal members and being bent together over the uppermost metal member, said plurality of tabs being welded to said uppermost metal member.

2. A welded metal joint as claimed in claim 1 which said foil is coated with insulation, said insulation burned off below said plurality of welded tabs.

3. A welded metal joint as claimed in claim 1 in which a pair of metal strips are provided, one metal strip on each side of said metal foil.

4. A welded metal joint as claimed in claim 1 in which said metal foil is aluminum and said metal strip is copper.

5. A welded metal joint as claimed in claim 3 in which said metal foil is aluminum and said pair of metal strips are copper.

6. A welded joint as claimed in claim 5 in which said copper is tin plated.

Patent 3,640,556 v v Dated February 8, 1972 r Moreland P Bennett inver; tor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as. shown-below:

' On the cover sheet, insert [73 Assignee: General Electric Company, a corporation of New York Signed and sealed this 14th dayof November 1972.

(SEAL) Attest:

EDWARD MTLETCHERJR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-IOSO (10-69) uscoMM-oc 60376-P69 fi US. GOVERNMENT PRINTING OFFICE: I989 0-366-334;

Patent 3,640,556 Dated February 8, 1972 Moreland P Bennett inver.tor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shownbelow:

On the cover sheet, insert [73 Assignee: General Electric Company, a corporation of New York a Signed and sealed this 14th day of November 1972.

(SEAL) Attest:

EDWARD I -I.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM o-1050 (10-69) uscoMM-oc scam-ps9 fi U.S GOVERNMENT PRINTING OFFICE I965 D-356-334

Claims

1. A welded metal joint between a metal foil member and at least one metal strip member, said metal members having portions in overlapped spatial contacting relation comprising; a plurality of tabs, each of said plurality of tabs having superposed material of said metal members and being bent together over the uppermost metal member, said plurality of tabs being welded to said uppermost metal member.

6. A welded joint as claimed in claim 5 in which said copper is tin plated.