US2173186A

US2173186A - Method of producing electrical resistance units

Info

Publication number: US2173186A
Application number: US742118A
Authority: US
Inventors: Torrence A Swartz; Wilmer P Uhler
Original assignee: SS White Dental Manufacturing Co
Current assignee: SS White Dental Manufacturing Co
Priority date: 1929-08-26
Filing date: 1934-08-30
Publication date: 1939-09-19
Anticipated expiration: 1956-09-19

Description

Sept. 19, 1939. w 11 sw R-rz ET AL 2,173,186

METHOD OF PRODUCING ELECTRICAL RESISTANCE UNITS I I II n c I iiiffliiwiii iili'iiil ii fi 5 7 35 39 .465 .50 5 t 77 v b'u '41 1:

Patented Sept. 19, 1939 UNITED s'mrss PATENT oFFicE METHOD OF PRODUCING ELECTRICAL RESKSTANCE UNITS Original application August 26, 1929, Serial No.

388,359. Divided and this application August 30, 1934, Serial No. 742,118 r V 3 Claims.

This invention relates particularly to the formation of electrical resistance units that are capable of replacement and is especially directed to the method of manufacture of said units, and is a division of our prior application Serial No. 388,359, filed August 26, 1929 now U. S. Patent No. 1,972,411.

This invention comprehends the method by which resistance units may be manufactured in gangs and includes novel means for embedding the terminals therein.

Specifically stated, the form of my invention as hereinafter set forth comprises resistance units which are produced in strip or gang formation and readily separated from such strip by bending back and forth along a restricted groove or furrow. The metallic terminals, being in suitably perforated sheet strip form, are placed in a mold and plastic resistance material subjected to pressur in said mold is caused to be embedded in the perforations provided therefor, said strip being perforated in the line of separation of the individual units so as to facilitate the breaking part of said units from the gang thus formed.

This invention also includes all of the various novel features of construction and arrangement as hereinafter more definitely specified.

In the accompanying drawing, Fig. 1 is a plan View illustrating a sheet metal strip of connected contact members adapted to be molded into the gang resistance elements; Fig. 2 is a fragmentary plan View of the base flask or lower section and coping of the mold showing the resistance units molded in gang formation; Fig. 3 is a fragmentary transverse vertical sectional view of the assembled mold taken transversely through said units on the line 33 in Fig. 2; Fig. 4 is a fragmentary transverse vertical sectional view of the assembled mold taken longitudinally of the units therein on their line of separation as indicated by the line i4 in Fig. 2; and Fig. 5 is a perspective view of a fragment of the lower former bar of the mold.

The new resistance unit has made possible a unique and economical method of manufacture. Under this method the lugs are punched from sheet metal, preferably copper tinned on both sides, the punching being done in such manner that the lugs remain connected together in strip form as shown in Fig. 1; in other words, the lugs are produced in a series, the strip which units the lugs being punched out to afford the apertures 3 and 5, so that the individual adjacent lugs are connected only by narrow webs 32 and 33 of metal left between them, whereby the units may be readily separated by bending and causing fracture of said webs. The strip may be of any desired length and therefore may contain as many lugs as there are units to be molded. Applicant has found that thirty units can be conveniently handled at a single operation.

The portion of the strip of lugs above the dotand-dash line in Fig. 1 is held in that part of the mold which may be termed the insert or lug v holder, while that portion of the'strip below line,

extends into the hollow portion of the mold in which the resistance material is molded. This material is thus molded into intimate contact with all that portion of the strip below said dotand-dash line and not only embraces the inner margin of said strip but is forced through the perforations 3 and '5 so that the materialon one side of the strip is united to that on the other side, thus securely locking the strip in the molded material to form an integral structure.

The mold, as illustrated in Figs. 2, 3, 4 and 5, is preferably made of hardened steel and comprises the bottom plate 35, the side and

end pieces

36 and 3? respectively, which may be best attached to the bottom plate 35, the filler or holding blocks 33 and 39 between which the lug portion of the lug strips, as shown in Figs. 2 and 3, may be inserted, the position of said lug strips being determined by the

stop pins

40 and 4|.

Said mold is so constructed as to produce a multiple im pression, being provided with the forming blocks t2 and 43 respectively having wedge-shaped dividing ridges 45 and 46 which register in opposed relation so that when the two halves of the mold are brought together under pressure the moldable material is formed into individual units which may either be taken from the mold with the lugs of the units still connected by a. thin web, which may be readily broken, or the mold may be so constructed as to sever the said webs and deliver the units already separated. It has been found in practice that best results are obtained by forcing the forming blocks together in the press to partially cut through the webs 32 and 33, thereby facilitating the separation of the units.

The form of electrical resistance unit chosen for illustration in the mold as shown in Fig. 2, has the margin of the sheet metal strip of lugs i5 being embedded in the upper ends of the elements I and the margin of the sheet metal strip of lugs I6 being embedded in the lower ends of said elements.

This invention is advantageous in that] by means of the method of production and distribution as above described substantial economies are effected as compared with the methods heretofore employed, wherein each individual lug or insert had to be picked up and loaded into the mold.

It is desired that this invention be not limited to the precise details of construction and arrangement as herein set forth, as it is obvious that various modifications may be made therein without departing from the essential features of this invention as defined in the appended claims.

Having thus described our invention, we claim:

1. The method of producing resistance units comprising a plastic body connecting relatively spaced terminal members having relatively separable regions affording oppositely directed alined terminal contacts, which consists in forming metallic strips with an indented edge, weakening the strips along the lines of indentation, mounting said strips with the terminal contacts of the respective strips joined in unitary relation in a common plane in relatively spaced relation in a mold having movable members each provided with opposed antagonized edged ridges, introducing a plastic molding material into the mold cavity in contact with the opposing margins of said strips to form a connecting body for said strips, and forcing together the relatively movable mold members with sufiicient force to form a plurality of parallel grooves upon the opposite faces of said body and strips in alinement with the indentations in the edges of said strips.

2. The method of producing resistance units comprising a plastic body connecting relatively spaced terminal members each having relatively separable regions aifording oppositely directed alined terminal contacts, which consists in forming metallic strips with an indented edge, perforating said strips at the regions of indentation, mounting said strips with the terminal contacts of the respective strips joined in unitary relation in a common plane in relatively spaced relation in a mold having relatively movable members each provided with opposed antagonized ridges, introducing a plastic molding material into the mold cavity in contact with the opposing margins of said strips to form a connecting body for said strips and forcing together the relatively movable mold members with sufficient force to form a plurality of parallel grooves upon the opposite faces of said body and said strips in alinement with the indentations in the edges of said strips and across the perforated regions.

3. The method of producing resistance units comprising a plastic body connecting relatively spaced terminal members each having relatively separable regions affording opposed oppositely directed alined terminal contacts, which consists in forming metallic strips having relatively separable regions, mounting said strips with the terminal contacts of the respective strips joined in unitary relation in a common plane in relatively spaced relation in a mold having relatively movable members each provided with antagonized regions, introducing plastic molding material into the mold cavity in contact with the opposing margins of said strips to form a connecting body for said strips and forcing together the relatively movable mold members with sufiicient force to form a plurality of parallel grooves upon the opposite faces of said body and strips between the relatively separable regions of said strips.

TORRENCE A. SWARTZ. WILMER P. UHLER.