Patent Publication Number: US-3874215-A

Title: Method of making miniature lamp base shells

Description:
United States Patent 1191 Gruenberg Apr. 1,1975  
 [ METHOD OF MAKING MINIATURE LAMP BASE SHELLS [21] Appl. No.1 415,604  
 [52] US. Cl 72/337, 29/630 R, 72/347, 72/349 [51] Int. Cl. B2ld 28/00 [58] Field of Search 72/332, 335, 337, 324, 72/339, 347. 348, 349; 113/119; 29/630 R, 630 A [56] References Cited UNITED STATES PATENTS 1,838,749 12/1931 Destcr 72/339 2,358,745 9/1944 Stieglitz 29/630 B West 113/119 Locke 113/119 Primary Examiner-C. W. Lanham Assistant Examiner-James R. Duzan Attorney, Agent, or Firm-B. R. Studebaker [57] ABSTRACT A method of manufacturing a metallic base for a miniature-type incandescent lamp, which base has the general configuration of a hollow cylindrical body terminating in a flange portion extending radially from the body portion and including a V-shaped cut out portion in the flange which communicates with a narrow slot in the upper portion of the cylindrical body. A centrally apertured truncated circular disc is stamped from a strip of sheet metal and progressively passed through a series of forming dies causing the two truncated edges of the disc to close toward each other to form both the V-shaped cut out in the flange and the narrow slot in the body portion,  
 3 Claims, 4 Drawing Figures METHOD OF MAKING MINIATURE LAMP BASE SHELLS BACKGROUND OF THE INVENTION The manufacture of miniature incandescent lamps is a highly automated and extremely competitive business. Lamp manufacturers are continuously striving to reduce material costs and manufacturing operations in an effort to maintain a competitive position in the miniature lamp business. One of the more expensive elements in an incandescent lamp, whether manufactured from brass, aluminum or some other metal, is the lamp base.  
  The prior art method of manufacturing miniature incandescent lamp bases involved the stamping of a circular disc from a metal sheet and, forming, through a series of progressive forming dies, a cup-shaped member having a lateral flange at the top. Through a machining process a V-shaped cut is then formed in the flange and a vertical slot is formed in the upper portion of the side wall of the cup-shaped member communicating with the interior apex of the V-shaped cut out. The V-shaped cut out portion in the flange and the vertical slot in the side wall of the base are necessary for attaching the side wall lead-in conductor to the lamp base. As in most incandescent lamps, a side wall contact and a center contact at the bottom of the base are required.  
  As will be apparent, any reduction in the amount of scrap generated in the stamping process and any elimination of machining steps in the manufacture of a metallic miniature lamp base will substantially reduce the cost of a miniature-type lamp.  
 SUMMARY OF THE INVENTION This invention relates to an improved method for forming metallic bases for miniature-type incandescent lamps and it represents an improvement over the prior art practices by significantly reducing the scrap produced and by eliminating the necessity for subsequent machining process steps in producing a finished lamp base.  
  The method of this invention forms a cup-shaped, flanged metal shell base having a V-shaped cut out in the flange communicating with a vertical slot in the upper portion of the base side wall through the steps of: stamping from an elongated metal strip a truncated, generally circular disc, which disc is truncated substantially along a chord perpendicular to a radius of a circular disc. Thereafter, progressively die forming the truncated circular disc into a cup-shaped metal shell base with one-half of the edge of the disc defined by the chord closing toward the other half of the edge of the disc defined by the chord to form the V-shaped cutout in the flange and the vertical slot in the upper portion of the side wall.  
 BRIEF DESCRIPTION OF THE DRAWING Many of the attendant advantages of the present invention will be more readily apparent and better understood as the following detailed description is considered in the connection with the accompanying drawings, in which:  
  FIG. 1 is an isometric view of a typical finished metallic base for a miniature-type incandescent lamp;  
  FIG. 2 is a schematic view of the stamping step of the method of this invention illustrating the material savmgs;  
  FIG. 3 is a top-plan view of the stamped metal blank of this invention; and  
  FIG. 4 is a schematic view illustrating the successive die forming operations of this invention which transforms the metal blank of FIG. 3 into the finished miniature-type lamp base of FIG. 1.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in detail to the drawings wherein like reference characters represent like parts throughout the several views, there is illustrated in FIG. 1, an isometric view of a metallic base for a miniature-type incandescent lamp. The miniature-type incandescent lamp base generally designated 10 takes a generally cup or thimble shape and includes a cylindrical or tubular portion 12 terminating at its upper end in a radially directed annular flange 14. The bottom end of the cylindrical side wall portion 12 terminates in an annular ring which forms the bottom 16 (FIG. 4) of the base shell. The annular ring 16 surrounds a circular aperture 18 which will later contain the bottom eyelet for connection to the bottom lead of the lamp. The annular radially extending flange 14 includes a V or pie-shaped cut out portion 20 which connects at its apex to a vertical slot 22 in the upper portion of the side wall or cylindrical portion 12.  
  As previously described, the miniature-type incandescent lamp base illustrated in FIG. 1 was die-formed from a circular disc and in subsequent machine operations the V or pie-shaped cut out 20 and the vertical slot 22 were cut in the base and the cuts subsequently deburred.  
  In accordance with the present invention, a truncated circular disc (FIG. 2) is cut from a narrower metal strip than the prior art full circular disc had to be cut from. The truncated circular disc generally designated 10a has a central aperture ll8a punched out which later forms the circular hole 18 and is truncated substantially along a chord perpendicular to a radius of the disc. As best illustrated in FIG. 3, the cut is not necessarily along a true chord but preferably along lines which extend on each side of the point where the radius of the disc bisects the chord at angles of 5 with that chord forming a obtuse angle at the point of intersection. These angular edges 24 of the truncated disc-shaped blank 10a may be separated at there intersection by a small semi-circular cut out 26 which will eventually form the bottom of the slot 22.  
  As illustrated in FIG. 4 the truncated, generally circular disc 10a is then drawn between a series of male and female dies to progressively form a finished cupshaped, flanged metal shell base for a miniature-type incandescent lamp having a V or pie-shaped cut out 20 in the flange communicating at its apex with a vertical slot 22 in the upper portion of the base side wall 12 without the need for subsequent cutting and deburring operations having to be performed on the base prior to its use in the assembly of a miniature-type incandescent lamp. Additionally, as illustrated in phantom in FIG. 2, a substantially, about 20 percent, narrower metal strip can be utilized in stamping the blanks and hence a substantial material savings realized.  
 What is claimed is:  
  l. The method of forming a cup-shaped, flanged, metal shell base for a miniature incandescent lamp having a V-shaped cut out in the flange communicating with a vertical slot in the upper portion of base side wall comprising the steps of:  
 stamping from an elongated metal strip; a truncated generally circular disc, said disc being truncated substantially along a chord perpendicular to a radius of said circular disc; and  
 progressively die forming said truncated circular disc into a cup-shaped metal shell base with one-half of the edge of said disc defined by said chord closing toward the other half of the edge of said disc defined by said chord to form said V-shaped cut out in said flange and the vertical slot in the upper portion of said side wall.  
  2. The method of claim 1 wherein said truncated generally circular disc being truncated substantially along a chord perpendicular to a radius of said circular disc is truncated along lines which extend from the point at which said radius bisects said chord at an angle of 5 with said chord in each direction from the point of said bisection.  
  3. The method of forming a metallic base for a miniature-type lamp, which base has a general configuration ofa hollow cylindrical body terminating in a flange portion, with a generally V-shaped opening in the flange and a thin slot portion extending from the V-shaped opening into the hollow cylindrical body thereof to facilitate receiving a lead-in wire for the lamp, which method comprises:  
 forming a generally circular and a generally planar blank which has cut therefrom one generally chordal segment perpendicular to a radius of said circular blank, said cut defining an edge;  
 progressively passing said blank through a series of forming dies to form said flanged cylindrical body portion from said blank and in the course of forming said body portion, causing opposite sides of said edge to close toward each other to form the thin slot in said body and the V-shaped slot in said flange.