US2052318A

US2052318A - Electric switching device

Info

Publication number: US2052318A
Application number: US19128A
Authority: US
Inventors: Humphreys O Siegmund
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1935-05-01
Filing date: 1935-05-01
Publication date: 1936-08-25
Anticipated expiration: 1953-08-25

Description

Aug. 25, 1936. H. o. SIEGMUND ELECTRIC SWITCHING DEVICE Filed May 1, 1935 APPl/ED VOL TA 65 MUG 3 H 4 mm o 2 r H. M um m E m w T w J M //v VEN TOR H. 0. 5/5 GM UND A TTOP V Patented A6 25,1936

PATENT OFFICE 2,052,318 ELECTRIC SWITCHING DEVICE Hnmphreys O. Siegmund, West Orange, N. 1., assignor to Bell Telephone Laboratories, In-

corporated, New York, N. Y., a corporation of New York Application May 1, 1935, Serial No. 19,128

5 Claims.

tecting the contacts of electric switching devices against erosion such as is caused at the contacts by sparks resulting from-the interruption oftion energy in the form oi. a spark at the in-- terrupting contacts caused by an abnormal increase in voltage due to the opening of the inductive circuit. Such contact sparking causes a rapiddeterioration of the contact metal and renders the switching device less reliable in operation.

Several expedients in the nature of spark suppressors, such as condensers, filters, copper oxide rectifiers, and the like, have been resorted to in an eilort to render the contact elements oi. switching devices immune to the deleterious eftests 01' sparking. .The use of such remedial measures, however, requires a suitable mounting tor the suppressor which, for the best results, should be located close .to the contacts with which it is to function. It also necessitates wiring the suppressor to the contacts or to the springs upon which the contacts are mounted which is usually accomplished after the switching device has been installed. Such requirements are not always easily satisfied and are, therefore, objectionable.

It is the object of this invention to provide protection for the contact elements of a switching device in such a manner that the objectionable features heretofore encountered are overcome.

This object is attained in accordance with a feature of the invention by the use of a Thyrite resistance element as the spark suppressor and by including the suppressor as an integral part of the spring pile-up in which the contact bearing springs are assembled as a unit.

The invention will be readily understood from the following detailed description made with reference to the accompanying drawing, in which:

Fig. 1 is an exploded view of a simple spring pile-up, such as may be employed in a relay, key

or other type of switching device and which illustrates the position of the suppressor element This invention relates to electric contact protection and moreparticularly to means for prowith respect to the contact springs with which it functions;

Fig. 2 is a characteristic curve illustrating the resistance voltage characteristic of Thyrite;

Fig. 3 is a circuit schematic showing the electrical connection of the Thyrite resistance in a contact controlled circuit; and

Figs. 4 and 5 show practical applications of the present invention to an electromagnetic switching device and a manually operated key, respectively.

In accordance with this invention, as illustrated by Fig. 1, the spring pile-up consists primarily of a pair of cooperating contact bearing springs l0 and II between which is interposed a block I2 01' Thyrite of suitable dimensions and drilled as shown, with holes which align themselves with corresponding holes in the springs and II for the reception of screws It. Insulating separators M and I5, also provided with holes through which the screws l3 pass, complete the pile-up illustrated. The pile-up is assembled in the well-known manner, by placing the various elements I, III, I2, H and I5 thereof, one on top of the other, with their respective holes in alignment and passing the screws I! through the aligned holes and screwing them into the mounting bracket |6., The element l2 serves the dual purpose of a spark suppressor and spring separator.-

The substance, Thyrite, has a non-linear resistance characteristic such as illustrated by the curve in Fig. 2. It will be. noted from the curve that the Thyrite has a substantially linear resistance at applied voltages below a certain value V but that when the applied voltage increases to a value of V, the resistance ismaterially diminished. The voltage V may be considered to be the peak voltage of the inductive discharge of the load L shown in Fig. 5 when the contacts I! are opened. The resistance of the element l2 being very low at this voltage, the energy stored in the inductive load L finds a ready path to ground, said path being in shunt with the contact springs IO, N. The stored energy is, accordingly, dissipated without injury to the contacts I? and does not manifest itself in the form of a spark at these contacts.

The contact protector of this invention is simple, inexpensive and practicable and occupies less mounting space than other arrangements heretofore used for the same purpose.

Fig. 4 discloses an electromagnetic switching device, such as a rela and Fig. 5 shows a manually operated key, in t e spring pile-ups or each of which is included a 'i it. te hicch, such as 92, which functions in the nner just described to'protect the contact elements of the springs against the deleterious effects of spar.

What is claimed is:

1. In a switching device, a spring pile-up in= eluding a pair of cooperating contact hearing springs and a separator interposedbetween said springs, said separator comprising an electrical conductor having a negative non-linear resistance-voltage characteristic.

2. In a switching device, a. spring pile-up comprising three contiguous electrical conducting elements, one of said elements having a negative non-linear resistance-voltage characteristic and located intermediate the other two elements. j 3. In a switching device, a spring pile-up comprising a pair of circuit controlling contact accents ing springs, a separator having a. negative non linear resistance-voltage characteristic interposed between said contact springs, and means for securing said springs and separator to said switching device.

5. In a switching device, a pair of contact ring springs. a spark suppressor interposed between said springs, and means for securing said 15 springs and said suppresson'as a unit, to said device.