US1584882A - Thermoelectric pyrometer - Google Patents

Description

May 18 1926.

H. S. MARSH ET AL THERMOELECTRIC PYROMETER Filed Sept. 24 1925 Patented May is, 192e.

HENRY S. MARSH AND RAL'F S. COCHRAN, 0F YOUNGSTOWN, OHIO.

THERMOELECTRIC P YROMETER.

Application filed September 24, 1925. Serial No. 58,384.

Our invention relates to the structure of thermo-electric pyrometer's, and consists in features of structures which render such instruments more durable under service conditions.

kA theremo-electric pyrometer of our invention is shown somewhat diagrammatically and in longitudinal'section in Fig. I of the accompanying drawings. Fig. ll is a view in vertical section and Fig. III in horizontal section through an annealing furnace for steel sheets and they show the pyrometer of our invention in one typical application. Figs. 1I and III are drawn to much smaller scale than Fig. l.

The pyrometer of our invention involves the use of a thermo-couple, that is to say, two lengths of dissimilar metals united at one end and otherwise insulated one from the other. A circuit including afgalvanometer or other measuring instrument is completed between the otherwise free ends of the two lengths of metal, and the united ends are subjected to the temperature condition, whose value is to be determined.

The Leeds and Northrup potentiometer system includes a thern'io-couple Whose component-s are vformed of base metals. Two wires are employed, one of iron, the other of constantan. Constantan is an alloy of copper and nickel. lVe preferably employ like materials, and our invention lies in structure.

For the particular use to be indicated below we take an eighth-inch constantan wire eighteen feet long, indicated at 1, Fig. I. Upon this wire we string a succession of clay beads 2, to serve as insulators. These beads are of suitable diameter to slip Within a three-eighths inch pipe, and may be an inch long. "Instead of an iron wire (the Leeds and-Northrup system employs iron).We provide a steel pipe 3 of three-eighths inch diameter and seventeen feet long. Into it we draw the beaded constantan wire. The end of the -wire projects somewhat beyond the final bead. The end ofthe pipe is hammered 'lat upon the end of the end of the included constantan wire, and the two metal bodies are welded at this point 4, to

form the hot end of the thermo-couple.` Brass electrical couplings 5 and 6 are at tached, one to the free end of the constantan wire 1, the other to the free end of the steel pipe 3. Leads of constantan and of iron Wire may manifestly be secured to these couplings, to complete a circuit through a galvanometer or other measuring instrument.

Turning to Figs. II and HI, 10 indicates thewall and 1l a ydoor of an annealing furnace. 12 is an annealing box Within the furnace, and 18 a pile of sheets Within the annealing box. At about one third of the distance from the base a layer 14 of one-inch bars is introduced in the pile, and between the bars of this layer the hot end of the pyrometer is introduced. The pyrometer is proportioned and shaped to occupy the position clearly illustrated in Figs. II and Ill. From the hot end which, as has been said, extends into the interior of the pile 13, the pyronieter extends externally of the pile to the base of the box; thence beneath the rim and through the luting Which seals the box upon its base; thence across the furnace space, and out beneath the furnace door, and through the luting, if any, found at that point. The free ends of the couple, externally of the furnace, are connected as has been said.

It is that portion of the couple particularly which extends from beneath the annealing box, across the furnace chamber to exit beneath the furnace door which particularly is subject to destruction. The hot furnace gases which at this point sweep over the introduced instrument tend to destroy it rapidly.

By forming our couple as a wire within a tube, we protect one element of the couple by the other, and, as we have explained, We make the more costly and more perishable member the inner member. We also have a construction in which one envelope of insulation suffices; otherwise, two are necessary, one surrounding each element of the couple.

Additionally, we provide an extra heavy, three-quarter inch steel sleeve 7 and surround With it so much of the couple as in service extends through the furnace space. When the couple has been formed and the sleeve 7 has been brought to place, the assembly is bent hot to the shape required for service. The assembly of the one-eighth inch constantan Wire within the three-eighths inch steel ipe, may be bent by hand; accordingly eyond the sleeve 7 and toward its inner or hot end, the couple is easily shaped, to itboxes of different sizes.

But for our invention, such a. pyrometer made of wires and wrapped for protection .with asbestos, is :de endable forl accuracy for only one heat; uilt according to our invention, thev pyrometer lasts perfectly fromv twenty to forty heats. We have found that so far as temperature detection is con- We have Aillustrated and particularly described one application of the pyrometer of our invention; manifestly it is applicable generally, and particularly Where the temperature of an object is to be measured,

which is situated within a box or under a cover, and to 'which there is no approach but yacross a zone of oxidizing flame; to`carbon- 1z1ng boxes, for example.

Wewclaim as our invention:`

1. thermo-couple in which beads of insulation are strung upon one member While the other member in tubular form envelops the assembly.

- 2. A thermo-couple of which one member in the form of a steel tube encircles the otherl member in the form of -a Wire of dissimilar metal, a succession of clay beads being threaded on the wire Within the tube.,

In testimony' whereof we have hereunto set our hands. v

HENRY s. MARSH. HALF s. COCHRAN.

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