US2028507A - Pyrometric device - Google Patents

Description

3 t H. B. HENDERSON Er AL 5 PYROMETRI'C DEVICE Filed April 30, 1935 Zinnentors B .gergieffion.

an e %A attorney Patented Jan. 21, 1936 UNITED STATES PYROMETRIO DEVICE Herbert B. Henderson and Edward 0. Henderson, New Brighton, Pa.

Application April 30, 1935, Serial No. 19,123

Claims.

This invention relates-to an improved pyrometric device and seeks among other objects, to provide a reliable indicator of heat work. Heretofore, pyrometric cones, so called, have been ,5 designed primarily as heat indicators so that by observing the cone during the'course of firing, the temperature of the kiln could be reasonably gauged. Such cones have proven unsatisfactory, however, for many reasons chief among which is the fact that due to the thickness or mass of said cones they are not uniformly affected by kiln gases with the result that a refractory skin is sometimes formed on the exterior of the cone while the interior thereof develops a cellular structure. The cone thus assumes a bi-refractory characteristic and such cones do not behave uniformly under actual firing conditions, with consequent inaccuracy. It may also be mentioned that the usual solid cones have a tendency to bloat and due to their bi-refractory characteristics tend to melt and bend at widely different kiln temperatures and are accordingly inaccurate. Instead of the inaccurate method of gauging the extent of heat work in the kiln by providing 25 a cone intended to function as a heat indicator, the present invention is predicated upon a direct approach to the object of measuring the actual work done by the kiln temperature and seeks in this way, to provide a dependable guide to the firing of ceramic ware. I

A further object of the invention is toprovide a device which, for given size and thickness consistent with stability, will have a maximum of surface exposed for contact by kiln gases, so as 35 to take advantage of the various chemical changes and compounds produced by contact with these gases whereby reaction, which proceeds'from the surface toward the interior, can

4 be completed in time proportional to the surface area.

A further salient object of the invention, there-f fore, is to provide a device wherein its entire inner surface, practically speaking, as well as its entire outer surface will be exposed to the'free 45 circulation of kiln gases, wherein the walls of the device will be thin so that the reaction of the kiln gases may proceed inward from both'surfaces of said walls to penetrate the entire mass so 65 ject, to provide a device of a shape adapted, to ace curate as well as easy manufacture, which can stand handling and such that the device will be capable of standing upright in practical use, and wherein the chemical reactions resulting in softening and fusion may proceed without disrupting 5 the mass of the body of the device to thus provide a reliable guide for the control of the heat treatment of ceramic ware.

Other and incidental objects of the invention will appear during the course of the following 10 description and in the drawing forming part of this application;

Figure 1 is a perspective view of my improved device.

Figure 2 is a side elevation of the device. 15

Figure 3 is a transverse section. v

Figure 4 is a longitudinal section taken medial- 1y through oneof the wings of the device.

Figure 5 is a perspective view showing a variation in the shape of the device. 20

In carrying the invention into effect, our improved pyrometric device may be formed in any one of a number of different shapes meeting the requirements of the invention and in Figures 1 to 5 inclusive of the drawing, we have shown a device the body of which is V-shaped in cross section. The body' of the device thus comprises diverging wings l0 integrally connected at their meeting longitudinal edges. As particularly brought out in Figure 2, each of the wings I0 is tapered in width towards its upper end so that in side elevation, the body of the device is of frhstr'o-pyrarhidal shape. This longitudinal tapering of the body of the device is adopted because of the gravitational action in bending under the influence of kiln temperatures, as to accomplish bending at thermal uniformity, the mass of the tip of the body must be a minimum and the mass of the body must gradually increase towards the base of the body which base serves, in the practical use of the device, as a fulcrum. The cross sectional V-shape of the body in conjunction with the gradual widening of the wings I!) toward the base also imparts stability to the device and resistance to fracture, particularly near the base of the body where it might snap off.

The base of the body is, of course, the surface or surfaces thereof upon which the body rests when arranged in operative upright position upon r the usual holding plaque within a kiln and in this connection, it should be noted that it is imperative the base be of such contour as to firmly support the device in such upright position. Thus, in the instance of the cross-sectional V-shaped device, the long bottom edges ll of the wings l provide the base of the body and, due to the divergence of said edges these edges will, as will be appreciated, rigidly support the body upright. It should be noted, however, that the bottom edges of the side wings H} are tilted or inclined so that the body of the device thus normally sets at a slight angle, possibly 8 more or less from the vertical, this being done to enhance the thermally accurate bending of the device in practical use.

The device may be formed of any suitable plastic or stifi mud and any approved process may be followed in producing the device. It should be noted, however, that a V-shaped body, as shown, is eminently suitable for manufacture by machinery through the use of suitable dies, as by pressing or extrusion methods, in that the device does not possess any pockets or obstructing walls.

Attention is now particularly directed to the fact that the wings in are thin and that each of these wings is of uniform thickness and density throughout the length thereof. These characteristics in a pyrometric body in conjunction with stability and the provision of wholly exposed inner and outer surfaces of a body adapted to stand upright constitutes perhaps the most salient feature of the present invention and in using the term thin herein as applied to the wings or walls of the body, a thickness not exceeding a maximum of 5 is contemplated. Uniformity of thickness and density may readily be obtained by pressing the body in a mold adapted to exert a uniform pressure on the body so that the device may thus be manufactured with accuracy.

As will, now'be perceived, the body of the device provides a structure wherein, for given size, a maximum area is exposed to direct circulation of and contact with kiln gases whereby reaction can be completed in time proportional to the surface area of a Wall thickness of uniform thinness and density. Advantage is thus taken of the various chemical changes and compounds produced by contact of those kiln gases which in the use of conventional pyrometric cones are frequently injurious. the device provides a structure wherein the kiln gases will not be entrapped by the device. In other words, the kiln gases may freely circulate about the wings ll of the body at both sides of said wings and throughout the length thereof to directly act upon the entire vertical surfaces of the wings.

At this point, it should be noted that in the i use of conventional thick pyrometric cones, kiln gases penetrate the exposed surface thereof to a shallow depth only and change the character of the surface material to produce a refractory shell. Thus, in the kiln, the ordinary thick pyrometric device possessing no uniformity of mass in any dimension, assumes, contrary to the results desired, a makeup of an outer refractory shell and an inner cellular mass. Such a bi-refractory device does not behave dependably under practical firing conditions nor is it a reliable guide in kiln firing. Furthermore, certain gases under some kilnconditions react with the surface material of a conventional pyrometric device to cause such a change in the material that the device will melt or fall at erratic and entirely different temperatures than when said gases are absent.

In this connection, it is also to be noted that all so-called pyrometric cones contain an organic binder to, impart the necessary working quality to the material in molding and to give the finished device suflicientstrength when dryv to withstand As will also be perceived, the body of.

shipping and handling. This organic material is sometimes entrapped in the heavy thick part of the cone and as the temperature in the kiln rises and gases are developed, swelling and bloating of the cone occurs in the thicker portion thereof. Also, the usual cone bodies conta n mineral carbonates which give off gas on heating as do oxides of minerals when combining to form other minerals during fusion. Fusion like oxidation proceeds from the outside of the cone body toward the center and as the fusion progresses, the body shrinks and becomes denser, sealing the interior to produce the well known effect of an outer refractory shell and an inner cellular core.

In contrast, thin walls of uniform density and thickness exposed to the free circulation of kiln gases, as in the present invention, offer a maximum of uniformly exposed surfaces to in turn assure a maximum change in the material of the body by absorption and reaction of the surrounding atmosphere. Due to the thinness of said walls, fusion or oxidation can proceed from both sides thereof to penetrate the entire thickness of said walls while the decomposition products have a chance to escape so that there is no swelling or bloating. Fusion may accordingly proceed without disrupting the body of the device and as the kiln gases will completely penetrate the thickness of the walls thereof, the entire thickness of said walls will become uniform in composition and no cellular core will develop. The device of the present invention is thus monorefractory and advantage is thus taken of the action of the kiln gases to provide a dependable guide to the firing of ceramic ware in instances where conventional pyrometric cones will not function in a dependable manner.

Exhaustive tests have demonstrated that a pyrometric body having a thin wall of uniform thickness and density, wherein the body is scientifically constructed to stand upright andattain proper bending upon fusion, and wherein the kiln gases may have a free circulation about a maximum surface of the walls of said body at both sides of said walls, provides a pyrometric device capable of complete thickness penetration by the kiln gases to convert the body into a monorefractory substance, the thin walls being uniformly afiected under substantially all kiln conditions. When the fusion temperature of the refractory material of the body is attained, the body will bend normally. This will occur at a higher temperature than the normal bending of conventional pyrometric devices but this feature is of no importance as it is only necessary to designate a higher index for the thin walled device of the present invention or the user of the device may select by trial, the proper device for this kiln.

In Figure of the drawing, we have shown a variation in the shape of the device wherein the body l2 thereof is semi-circular in cross section. As will be observed, when the device is arranged in upright position upon the usual holding plaque, kiln gases may freely circulate about the walls of the device at both sides thereof. Except as to shape, the device of Figure 5 of the drawing possesses all of the characteristics described in connection with the device of Figures 1 to 4 inclusive and further amplification would accordingly appear unnecessary.

Having thus described the invention, we claim:

1. A pyrometric device including a body having thin wall portions lying in more than one plane and providing a base adapted to support the body in upright position, one of said wall portions having its opposite major surfaces exposed to the free circulation of kiln gases thereabout when the body is disposed upright.

2. A pyrometric device including a body having angularly disposed wall portions providing a base adapted to support the body in upright position, one of said wall portions being thin and having its opposite major surfaces exposed to the free circulation of kiln gases thereabout when the body is' disposed upright.

3. A pyrometric device including a body having angularly disposed wall portions providing a base adapted to support the body in upright position, one of said wall portions being thin and of uniform thickness and having its opposite major surfaces exposed to the free circulation of kiln gases thereabout when the body is disposed upright.

4. A pyrometric device including a body having angularly disposed wall portions providing a base adapted to support the body in upright posi- 7 tion, one of said wall portions being thin and of uniform thickness and density throughout at least one dimension thereof and having its opposite major surfaces exposed to the free circulation of kiln gases thereabout when the body is disposed upright.

5. A pyrometric device including a body having angularly disposed wall portions providing a base adapted to support the body in upright position, the mass of the body gradually increasing towards the base thereof, one of said wall portions being thin and of uniform thickness and density throughout at least one dimension thereof and having its opposite major surfaces exposed to the free circulation of kiln gases thereabout when the body is disposed upright.

HERBERT B. HENDERSON. EDWARD O. HENDERSON.

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