US2156826A - Thermometric means - Google Patents

Description

R. ULLMAN THERMOMETRiC MEANS May 2, 1939.

Filed April 28, 1936 INVENTOR ROY ULLMAN ATTORNEY Patented May 2, 1939 UNITED STATES 2,158,828 THERMOMETRIC MEANS Roy Ullman, Roslyn, Pa., assignor to The Brown Instrument Company, Philadelphia, Pa., a corporation of Pennsylvania Application April 28, 1936, Serial No. 76,763

Claims.

The present invention relates'to thermometric means of the type in which a thermo re-. sponsive element, commonly referred to as a bulb, is received in a sheath or protective casing adapted for insertion into a furnace chamber or' other chamber or passage containing hot gases or other fluid to determine the temperature in said chamber or passage. The bulb receiving space in said sheath or casing is sometimes referred to as a thermometer well, and is closed at its inner end and open at its outer end for the necessary connection between the thermo responsive means and the measuring instrument associated therewith. The theme responsive element is may take various forms and in particular may comprise an electrical conductor, the resistance of which varies with its temperature, or the bulb may comprise a chamber including a liquid more or less of which is vaporized in accordance with the temperature to which the bulb is exposed, so that the varying pressure of the vapor formed will furnish a measure of the bulb temperature.

The general object of the present invention is 1 to provide thermometer means of the character as described, with novel means effective to improve the heat transfer relation between the bulb and the wall of the well or casing in which the bulb is received, whereby the latter may respond more quickly and directly to variations in the temso perature to which the casing or well wall is extremely exposed, The means provided'for the attainment of the above mentioned object, also seernve to keep the bulb properly positioned in the 35 In accordance with thepresent invention, I interpose metallic means between the bulb and casing, which preferably acts resiliently, initially at least, between the casing and bulb, and have suitably large surfaces in contact with the casing 40 and with the bulb. Even though the inserts, if initially resilient, lose all, or the major portion of their resiliency in operation, their loss of re-,

siliency will not prevent the continued maintenance of extended contact of the insert with the 45 casing and with the bulb, and'will not result in freedom of the bulb to rattle about in the casing.

As will be apparent, the metallic inserts employed, in accordance with the present invention, may take various forms, some of which are illustrated 50 in the accompanying drawing, of which:

Fig. 1 is a sectional elevation;

Fig. 2 is a section on the line 2- 2 of Fig. 1;

Fig. 3 is a perspective view of the insert employed in Figs. 1 and 2;

Fig. 4 is a section taken similarly to Fig. 2,

of a construction including a modified form of insert;

Fig. 5 is a perspective view of another form of insert;

Fig. 6 is a. perspective view of insert arrange- 5 ment comprising two separable insert parts; and

Fig. '7 is a partial section taken similarly to Fig. lillustrating the use of an insert of still different form.

The construction shown in Figs. 1 and 2, com- 10 prises a thermometer bulb head member A in the form of a tubular plug, which is adapted to be screwed into a threaded aperture formed in the top or side wall of a furnace, and which supports a therrnometric bulb protecting tube or casing B. 16'

The latter, as shown, is formed of suitable refractory metal, and has its open outer end extending into the axial passage of the member A, and welded to the latter. The thermometer bulb member C received in the thermometer well or chamber, 20 within the sheath or casing B, as shown in Fig. 1, is of the resistance thermometer type, C" representing the terminal conductors of the bulb.

As shown, and as is usual, the external diameter of the bulb C is appreciably smaller than the internal diameter of the casing B. The insert D, shown in Figs. 1, 2, and 3, is made of resilient sheet metal and is shaped to have an extended surface area in snug contact with the inner wall of the casing and extended surface areas in snug contact with the outer surface of the bulb at opposite sides of the latter, so as to hold the latter centrally in the casing. To this end, the element D is formed with a body portion and integral edge portions D. The'body portion is in the form of a segment of a hollow cylinder, extending about the cylinder axis for more than 180. Each edge portion D of the insert D is an integral extension of. the corresponding side of the body portion folded back on, and curved to form a seg-' 40 ment of a cylinder substantially coaxial with the body portion cylinder. I

When the outer insert is in place, as shown in Fig. 2, the convex side of the body portion fits snugly about the concave inner wall of the casing 13, and the concave inner sides of the two edge portions D fit snugly against diametrically opposed portions of the outer surface of the bulb C. Advantageously, the radius of curvature of the body portion of the insert in its initial condition 'exceeds the radius of the chamber within the tion with the casing, and of the edge portions D with the bulb.

By reason of the extended contact surface, the joint resistance to heat conduction from the bulb to the insert, and from the insert to the casing is comparatively very small, and the insert thus provides a good heat conducting path between the bulb and the casing. It also serves to maintain the bulb in fixed relation in the casing. The fact that the bulb is not free to move, .or rattle around, in the casing, is practically important in that it reduces the risk of injury to the bulb and its connections when the plug A, casing B, and enclosed bulb are being put in place or removed, or being transported.

The insert DA shown in Fig. 4 difiers in form from the insert D in that the body portion of the bulb DA is an appreciably smaller segment of a hollow cylinder than is the body portion of the element D, and in that the edge portions D of the insert DA are so shaped and disposed that they both bear against the bulb wholly or mainly at one side of a diametral plane through the latter, so that the bulb, instead of being held centrally of the casing as in Figs. 1 and 2, has one side pressed into snug engagement with the adjacent portion of the inner wall of the casing. In consequence, the heat conduction between the bulb and the casing through the insert DA, is supplemented by heat conduction between the surfaces of the bulb and casing directly in contact with one another. In Fig. 2 the portions B may be regarded -as segments of a cylinder concentric with the cylinder of which the body portion forms a segment. Mathematically considered, the segments formed by the parts D and by the body portion of the insert DA are not concentric, but for the purposes here involved the last mentioned. cylinders may be regarded as approximately concentric.

The insert DB, shown m Fig. 5, difiers in form from the inserts D and DB, in that the edge portions D of the insert DB are turned outwardly and back to lie alongside adjacent portions of the outer side, instead of the inner side, of the body portion of the insert, and are adapted to bear against the inner wall of the casing, while the body portion of the insert is adapted to partially surround and fit snugly against the outer surface of the bulb.

In the construction shown in Fig. 6, the insert consists of two separate insert parts D0, which may be identical in form, and each of which may be formed by folding a strip of sheet metal along a fold line parallel to, and midway between its side edges, andby transversely curving the two parts of the strip at opposite sides of the fold line, so that they form adjacent segments of approximately concentric cylinders. The outer portion D of each part DC is adapted to bear against the inner wall of the bulb casing while the inner part D bears against the outer surface of the bulb. In use, the two inserts DC may be assembled in the casing, so that their inner portions D occupy the same relative positions as do the parts D of Fig. 2, or the same relative positions as do the parts D of Fig. 4, and so that the outer portions of the inserts DC occupy the same positions as do the sections of the body portion of the insert Dor DA, respectively adjacent the parts D or parts D thereof.

In the modification shown in Fig. 7, the insert is formed by resilient wire wound into a helix surrounding the bulb CA, and having large con= greases volutions W, and small convolutions D distributed along the length of the bulb and easing, the large convolutions D being large enough to fit snugly against the inner wall of the casing 15 when inserted in the latter, while the small 5 convolutions D are small enough to fit snugly about and resiliently grip the bulb which the helical insert surrounds. The particular form of bulb CA shown in Fig. 7, is not a resistance thermometer bulb, but an expansible fluid bulb having a tubular terminal portion 0 through which the bulb vapor pressure may be transmitted to any suitable pressure meter (not shown).

While in accordance with the provisions of the 5 statutes, I have illustrated and described the best forms of embodiment of my invention not known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. A thermometric device comprising a thermometer bulb, a bulb surrounding casing formed with a bulb receiving chamber of an internal cross section appreciably larger than the bulb cross section, and an insert interposed between the bulb and casing consisting of a piece of metal bent to form integrally connected portions in the form of segments of approximately concentric hollow cylinders, the outer portion bearing against the inner wall of the casing and the inner portion bearing against the bulb.

2. A thermometric device comprising a thermometer bulb, a bulb surrounding casing formed with a bulb receiving chamber of an internal cross section appreciably larger than the bulb cross section, and an insert interposed between the bulb and casing consisting of a piece of sheet metal folded on itself and bent to form integrally connected portions in the form of adjacent segments of approximately concentric hollow cylinders, the outerpor'tion bearing against the inner wall of the casing, and the inner portion bearing against the bulb.

3. A thermometric device comprising a thermometer bulb, a bulb surrounding casing formed with a bulb receiving chamber of an internal cross section appreciably larger than the bulb cross section, and a wire helix surrounding the bulb and interposed between the latter and the casing and comprising large convolutions alternating with smaller convolutions, the larger convolutions bearing snugly against the inner wall of the casing and the smaller convolutions fitting snugly about, and bearing against the bulb.

4. A thermometric device comprising a thermometer bulb, a bulb surrounding casing formed with a bulb receiving chamber of an internal cross section appreciably larger than the bulb cross section, and a metal insert interposed between said bulb and casing and. formed of sheet metal shaped to provide a body portion in the form of a segment of a hollow cylinder, and a portion respectively adjacent and integrally connected to said body portion adjacent each side edge of the latter, each of the last mentioned portions being folded back alongside thebody portion and being curved to form a segment of a hollow cylinder approximately concentric with the first mentioned cylinder.

between the bulb and the casiflg, one limb of each 01' said U shaped inserts bearing against the inner wall of said casing, and the other limb of each of said U shaped inserts bearing ainst .7

the said bulb.

ROY Oil-MAN.

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