US2484596A

US2484596A - Lamp socket for series lighting circuits

Info

Publication number: US2484596A
Application number: US776607A
Authority: US
Inventors: Maynard C Waltz
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1947-09-27
Filing date: 1947-09-27
Publication date: 1949-10-11
Anticipated expiration: 1966-10-11

Description

Oct. 1l, 1949. M. c. wALTz LAMP SOCKET FOR SERIES LIGHTING CIRCUITS Filed Sept. 27, 1947 /N VEA/TOR M. C .W4 L TZ Patented Oct. 11, Y1949 'ffUNTED,,STATE Maynard o. Wal-tz,

Maplewood, assigner-tto Bell Telephone Laboratories, Incorporated, New

York, N. Y., a corporation of New Yorkv r v Application This inventionv relates to lamp sockets and more particularly to sockets for use in series-lighting circuits.

The object of thisinventionis to automatically shunt an inoperative series-connectedlamp on thefailure of said lamp. ,ff'Heretofore numerous means have been vSuggested and, employed to maintain the operation of a series-lighting circuit, notwithstanding a failure of one or more of the lamps. Broadly classed, these means have included mechanical shunts both automatically and manually operated, and electrical shunts operated by the rupturing of an insulating lm, by placing a high resistance across the lower resistance of the filament, or by connecting a semiconductor having a negative temperature coefficient of resistance across the lamp.

In accordance with this invention an improved structure is provided for shunting a series-connected lamp which has failed by utilizing a material having a negative temperature coefficient oi resistance and associating it with a shell for a socket in a manner such that a very satisfactory lamp socket is realized which is compact, simple and easily manufactured.

More particularly this invention comprises a lamp socket for a series-lighting circuit, for example, a series-lighting circuit for a Christmas tree, having a centrally apertured disc of material having a negative coeiiicient of resistance secured in the bottom of the shell forming a mechanical support for the lamp. The central contact of the lamp passes through a central aperture in the disc thereby permanently shunting the disc across the lamp lament.

The various features of this invention will be better understood from the following detailed description when considered in conjunction with the accompanying drawings in which:

Fig. 1 discloses in the main a sectional view of a socket illustrative of one embodiment of this invention, and

Fig. 2 is a detailed plan View of the socket of Fig. 1.

The drawings show a lamp socket of the conventional typev having an outer casing I of insulating material in which a threaded shell contact I I containing a central contact I2 is suitably secured. Leads I3 and I4 are connected to the shell contact Il and the central contact I2, respectively, to complete the circuit from the source through the leads I3 and I4, the contacts II and I2 and a lamp L mounted in the socket. Secured within the bottom of the shell contact II in a September 27, 1947; Serial No. 775,697 J3 cisnes.- 01; 2er-449i suitable manner, such as by spinning or lcrimpin in its lower edge 'I5 is a centrally apertured disc I6 of a material having a high negative tempera@ ture coefficient of resistance. A suitable material for this disc is that disclosed in Patent 2,258; l(546 to Grisclale of October 14, 1941. This disc .I6 structurally replaces the nber or ceramic insulating-ldisc which is usuallymounted inthe shell contact of an ordinary socket to support the central contact, and simultaneously provides a shunt between the shell contact II and the central contact I2 across the filament of the lamp. In order to insure adequate electrical contacts having constant resistances between the shell contact Il and the disc I6 and between the central contact I2 and the disc I6 the outer and inner peripheries have coverings or electrodes I1 and I8 (shown with an exaggerated thickness for purposes of clarity) deposited thereon, thus providing metal-to-metal contacts between these members.

This socket may be employed in a series circuit. for example, a Christmas tree lighting circuit having a plurality of lamps. W'hen connected in a circuit of this nature with an operative lamp secured in the socket, the resistance of the material of the disc I6 is such that the resistance between the contact II and the contact I2 across the disc is, relative t0 the lamp lament, effectively an open circuit, and the disc performs only the mechanical function of supporting the central contact I2. However on rupture of the circuit through the lamp an increased electromotive force is impressed across the disc causing an increase in the normally minute current flowing therethrough. The increased current flow increases the rate of heat generation within the disc such that it ls greater than the heat dissipated and thus the thermal unbalance causes an increase in the temperature and a corresponding decrease of the resistance of the disc to a point limited by the resistance of the circuit where the resistance of the disc again stabilizes. This second stable resistance value is approximately equal to the resistance of the parallel lamp and disc which it has replaced, thus restoring the normal operation of the remainder of the circuit, the value being determined in the well-known manner by the selection of a material having the desired negative temperature coeflicient of resistance and a structure having the desired thermal, electrical and mechanical characteristics.

As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter herelnbefore set forth, or shown in the accompanying draW- ings, is to be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A lamp socket Comprising an electrically conductive shell having twoy open= ends, the opening in one of said ends being smaller than the opening in the other of said ends, a disc of resistance material having a negative temperature coem cient of resistance inalterablyv secured in the,

smaller opening of said shell, said disc havingan aperture at its center, a contact in said aperture,

and separate metallic coatings on. the-aperture a contact member spaced from said shell, a shunt connected between said shell and said contact, said shunt comprising a disc of material having a high negative temperature coetlicient of resis tance permanently secured in an end of said shell and supporting said contact member in spaced relationship to said shellseparate metallic coatings on said disc engaging saidzcontactand said shell respectively, and a pair of leading-in conductors for supplying energy to said socket, one

conductor being connected to said shell and the other conductor being xedly and directly connected to said contact member.

MAYNARD C. WALTZ.

REFERENCES CITED The following references are of record in the me of'this patent:

UNITED. STATES PATENTS Number Name Dots 1,536,332 Dam May, ma 1,641,564 Zierdt Sept; 6, 1927 1,941,984 Gustin. et al 1. Jan. 2, 1934 1,950,028 Gustin .Mar.,6', 1934 1,954,355 Handy: Apr. 10, 1934 2,258,646 Grisdale. Oct. 14, 1941