US1490990A - Resistance thermometer - Google Patents

Description

April 22, 1924. 1,490,990

G. F. TAYLOR RESISTANCE THERMOMETER med Dec. 1s, 192s l Patented Apr. 22, 1924.

UNITED 's'rATEsrATENT carica.

anonce r. rama, or wasnnite'ron,

DISTRICT Ol' COLUMBIA, DEDICATED, BY' MEBNE ASSIGNMENTS, T THE CITIZENS 0F THE UNITED STATE 0F AMERICA.

RFSISTAN THERMOMETER.

' appuomonmea December 1a, 192s. semi nu. 330,472.

(FILED UNDER TBE ACT 0F MARCH 3, 1883, 22 STAT. 1.

To all whom it may concern.'

Be it known that I, Gaonea F. Tanon, a citizen of the United States of America, and -an employee of the United States Del partment of Agriculture, residin in the city of Washington District of lumbia whose post-ofiice address is Dpa griculture, Washington, D. have `1invented a certain new and useful Resistance le Thermometer.

This application is made under the act of March 3, 1883, chapter 143 (22 Stat. 625) and the invention erein described and -claimed may be used by the Government of ll the United States or any -of its oicers or employees inthe prosecution of work for the Government, or by any citizen of the United States without payment to 'me of royalty thereon.

an le The object of my invention is to provide a resistance thermometer which is small, of low heat capacity, and short lag, an thoroughly protected from moisture and corrosive gases without the use 0f a desiccating il agent, or chemicals inside the bulb.

The invention will be fully described in connection with the accompanying drawing in which Fig. 1 represents a vertical sectional view of the entire thermometer; Fig. a0 2 is a top plan view thereof; Fig. 3 is a horizontal sectional view taken on ine 3-3 of Fig. 1; Fig. 4 is a' horizontal sectional view taken on line 4 4 of Fig. 1, and Fig. 5 is an elevation view of my improved theran mometer, actual size. H is a hard rubber or bakelite head. The upper end of the head is hollowed out, with only a thin fiange P left around the edge. This depression, as well as the entire tubeV en A is filled with a wax, which serves to stiifen the tube A, holds the lead wires B and C rigidly in place, and prevents electrical leakage between the studs S due to the formation of moisture films which would form on hard rubber or bakelite. Into the head H fits a-glass or metal tube A containing and protecting all the working parts. The metal studs S fit into the upper end of the head H, and to them the ead wires (not shown) from a Wheatstone bridge (not shown) are attached to the up r end ofthe studs, S, and the leads from e rtment of d of the' tube O.

element are soldered to the lower end of the studs S.

A represents the walls of the protecting tube. is a mass of metal into which the resistance element K andthe ends of the lead wires B and C are embedded.` K is the resistance element, which consists of a fine thread of metal drawn in glass. This thread K at its lower end makes electrical .contact with the metal in which it is embedded. The filament K at its upper end expands into a slightl larger portion N at which point it is sol ered to the enlarged end of the lead B. Thus the circuit is completed from the lead C through the mass of metal I, through the filament K, to the second lead B. This leadv B is enclosed in a small, thick-walled glass tube O with a slight flare at its lower end to hold it firmly in the embedding metal. The lead B has a spherical enlar ement just below the end he junction of the lead and filament is covered with a coating of porlain cement J, which extends some distance into the tube O. The pur ose of this arrangement is to'insulate t ese parts from the surrounding metal, holdthem firmly in lace, and prevent any metal from flowing into the tube O inthe process of molding.

I claim:

1. A resistance thermometer, comprisin a casing, a head affixed to one end of sai casing, a metal body in said casing, a resistance element embedded in said metal body, two lead wires one of which is secured to said resistance element vand the other embedded in said metal body, means for preventing contact between-the resistance element,its lead wires and saidl metal body except at the end of the resistance element farthest from the lead wire to which it is secured.

2. A resistance thermometer, comprising a casing, a head, a resistance element embedded in said me body, two lead Wires one of which is secured to said resistance element and the other embedded in said metal body, said head consisting of a cylindrical mass of hard rubber having a hole through its axis adapted to receive and support said and said lead wires, the upper end of sai a metal body in said casing head havin being cireum erence oeption of aI wax filler said lead wire casing, a meta tance element providedwith a glass eovenng aixed thereto two posts and rovided with a flange around the thereof to ermit of the readapted to insulate s and said posts.

sa l body in said casing, a resistembedded-in said metal body, for said resistance element an opening at its upper end to permit the resistance element 'to be aix'ed to its lead wire end to permit 15 contact with t and an opening at its lower thev resistance element to form he metal body, two lead wires one of which is embedded in said metal body and the other of which hasan enlargement at Aits lower end and at which lower end is aiiixed the said resistance element, a glass tube surrounding said lead wire having an enlargement, extendin from the enlar ment to the vend of t e casing inside e said head, said enlargement on the aforesaid lead wire being provided with a. coating of porcelain cement, exten ing from the lower end of said glass tube surrounding the lead wire to the upperv end of the glass covering of the resistance element.

' i GEORGE` i?. TAYLOR.

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