US1526139A - Electrical resistance unit - Google Patents

Description

Feb. 10, 1925. I 1,526,139

| o. GRONDAHL ELECTRICAL RESISTANCE UNIT Filed Dec. 4, 1922 INVENTOR 7 BYQJZ: z

IY ATTORNEY Patented Feb; 10, 1925.

UNITED. STATES PATENT OFFICE.

LABS O. GRONDAHL, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO THE UNION SWITCH & SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION or PENNSYLVANIA.

ELECTRICAL RESISTANCE: UNIT.

Application filed December 4, 1922. Serial No. 604,673.

To all whom it may concern:

Be it known that I, LARS O. GRoNDAHL, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented cer-' tain new and useful Improvements in Electrical Resistance Units, of which the following is a specification.

My invention relates to' electrical resistance units, and particularly to units having the characteristic of varying in resistance in response to changes in temperature.

I will describe several forms of resistance units embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 is a view showing in cross-section one formof resistance unit embodying my invention. Fig. 2 is a similar view showing a modified form of resistance unit embodying my invention, andFig. 3 is an end view of the unit shown in Fig. 2. Fig. 4: is an end view showing a modification of the unit shown in Figs. 2 and 3. Fig. 5 is a view showing one manner of mounting" the units in the preceding views.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Fig. 1, the unit comprises two electricalconductors 10 and 11, portions of which are enveloped in a bead T of thermo-sensitive substance, that is, a substance having the characteristic of varying in electrical resistance in response to changes in temperature. This substance preferably has a'negative temperature coeflicient and may for example be cupric oxide, cuprous oxide, a mixture of different oxides. or a mixture of one or more oxides with other substances such as some silicates.

The unit shownin Fig. 1 may be conveniently manufactured by clampin the two conductors 10 and 11 in space relation, applying heat to restricted portions thereof, dipping the heated portions into a powdered thermo-sensitive substance, so that a smallportion of the substance adheres to the conductors, and repeating the process until av suflicient quantity of the substance has adhered to the conductors to form a bead,

in which they are embedded. As a modification of this process the two conductors may be clamped in spaced relation and then thermo-sensitive' substance T will increase the temperature of this substance so that its resistance will decrease, thereby permitting a still greater amount of current to flow in the circuit. This decrease of resistance will not occur immediately, however, but, on the other hand, a certain time interval will exist between the initial increase of current in the circuit and the ultimate greater increase of current due to the reduction in the resistance of the therm0-sensitive substance T. One characteristic of the unit, therefore, is that it is slow-acting in operation.

Referring now to Figs. 2 and 3, one of the conductors, which is here designated 10*,

is cylindrical or tube-like in formation, and

is filled with thermo-sensitive substance T. The other conductor 11 passes through this substance at substantially the center of the tube 10 The unit shown in Figs. 2 and 3 can be constructed in substantially the same manner as the unit shown in Fig. 1.

Referring to Fig, 4;, the structure herein illustrated is similar to that shown in Figs. 2 and 3, except that the outer conductor, which is here designated 10", is trough-like .in formation and is filled with the thermosensitive substance T through which passes the other conductor 11.

Each of the units shown in Figs. 1, 2 and 4, as well as all suitable modifications thereof, may be mounted in the manner shown in Fig. 5, wherein the reference character 7 designates a glass tube, one endbf which is closed and the other end of which is provided with a lamp base 8 comprising a shell 12 and a button 9 insulated from the shell. The conductors 10 and 11 are located within the tube 7 and are connected respectively with the shell 12 and the button 9. ,The lamp base 8 is threaded to fit the ordinary standard lamp socket, thereby facilitating the application ofthe resistance unit to an electric circuit. Obviously, the threaded base8 may be replaced by a base of any Resistance units embodying my invention may be used in place of slow-acting relays in electrical apparatus of any kind, but are particularly well suited for use in connection with railway signaling apparatus.

Although I have herein shown and described only a few forms of resistance units embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims Without departing from the spirit and scope of my invention.

' Having thus described my invention, what I claim is: i i

1. A resistance unit comprising a head of a substance the electrical resistance of which decreases with increase in temperature, and two electrical conductors in contact with said bead.

2. A resistance unit comprising a bead of copper oxide, and two electrical conductors embedded therein.

3. A resistance unit comprising a bead of thermo-sensitive substance, and two conductors embedded therein.

4. A resistance unit comprising a tube like conductor, a bead of thermo-sensltive 1,52e,1se

substance in said conductor, and a second conductor embedded in said bead.

5. A resistance unit comprising a troughlike conductor, a bead of thermo-sensitive substance in said conductor, and a second conductor embedded in said bead.

6. The method of making a thermo-sensitive unit which consists in clamping two electrodes in spaced relation, applying heat to a restricted portion of said electrodes, dipping them into a powdered thermo-sensitive substance so that a small portion of the substance adheres to the electrodes, heating said adhering substance until it is :said electrodes into molten thermo-sensitive substance to form a bead in which said electrodes are embedded.

In testimony whereof I affix my signature.

LABS o. GRONDAHL.

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