US3496067A

US3496067A - Horizontal coke oven having plural types of brick linings for heating walls

Info

Publication number: US3496067A
Application number: US612183A
Authority: US
Inventors: Michael Perch
Original assignee: Koppers Co Inc
Current assignee: Raymond Kaiser Engineers Inc
Priority date: 1967-01-27
Filing date: 1967-01-27
Publication date: 1970-02-17
Anticipated expiration: 1987-02-17
Also published as: FR1551842A; DE1671331A1; DE1671331B2; JPS506841B1; GB1193374A; DE1671331C3

Description

Feb. 17, 1970 M. PERCH 3,496,067

HORIZONTAL COKE OVEN HAVING PLURAL TYPES OF BRICK LININGS FOR HEATING WALLS Filed Jan. 27, 1967 3 Sheets-Sheet 1 mesa/ks INVENTOR. MICHAEL "PERCH BY ge M. PERCH HORIZONTAL COKE OVEN HAVING PLURAL TYPES Feb. 17, 1970 OF BRICK LININGS FOR HEATING WALLS 3 Sheets-Sheet 2 Filed Jan. 27, 1967 PRIOR ART F/fi 4 .INVENTOR.

MICHAEL PERcH Feb. 17, 1970 M. PERCH 3,496,067

HORIZONTAL COKE OVEN HAVING PLURAL TYPES v OF BRICK LININGS FOR HEATING WALLS Filed Jan. 27, 1967 3 Sheets-Sheet 5 PUSHER SIDE I INVENTOR. MICHAEL PEPCH PUSHER SIDE COKE SID FIG. I!-

United States Patent 3,496,067 HORIZONTAL COKE OVEN HAVING PLURAL TYPES OF BRICK LININGS FOR HEATING WALLS Michael Perch, Pittsburgh, Pa., assignor to Koppers Company, Inc., a corporation of Delaware Filed Jan. 27, 1967, Ser. No. 612,183 Int. Cl. Cltlb /02 US. Cl. 202-139 9 Claims ABSTRACT OF THE DISCLOSURE A coke oven having heating liner walls constructed of both high density and low density bricks arranged in various patterns whereby the heat transfer profile is nonplanar, and the carbonization pressure on the heating liner walls is significantly reduced. The end portion of the liner walls on the coke side and the top portion of each liner wall throughout its length may be entirely of high density bricks.

BACKGROUND OF THE INVENTION This invention relates to coke ovens and, more particularly, to an improved heating wall liner of horizontal coke oven batteries in which heating walls are arranged side by side in a row, in alteration, with intervening coking chambers. Each heating wall includes a pair of spaced apart heating wall liners extending crosswise of the battery with the walls connecting together the heating wall liners to form thereby a plurality of heating flues in each heating wall. As is customary, a regenerator chamber is provided below each heating wall running parallel to it, and being separated from the heating wall and coking chambers by a horizontally extending partition or floor.

The continual search for ways to increase the throughput of a horizontal coke oven battery has produced many improvements. Among such improvements is a high density silica brick (about 120 pounds per cubic foot) that may be used in place of conventional low density bricks (about 100 pounds per cubic foot). However, certain obvious disadvantages are apparent to the use of an all high density brick liner wall. In the first place, the cost of such a high density brick liner wall would be significantly greater than a liner wall constructed of conventional low density brick. In the second place, the maximum wall pressure generated by coal coking in a battery lined with high density bricks, would be significantly greater than the pressure developed by coal coking in a battery lined with ordinary (low density) brick. Moreover, the increase in coking pressure would necessitate thicker liner walls and these would increase the cost of a coke oven battery materially.

The recent trend to make oven chambers higher (by as much as 50%) also increases the cost thereof, not only because more bricks are used, but also because the increased wall pressure (where all high density bricks are used) and because thicker, higher walls would be required for structural reasons.

Heretofore, coke ovens have been constructed with all high density silica brick liner walls, and the through-put capacity of such coke oven batteries has been significantly increased, but at considerable additional cost. On the other hand, the present invention provides a solution to the problem of providing a significantly greater through-put capacity, but at only a slight additional cost.

SUMMARY OF THE INVENTION The invention comprises heating wall liners for coke oven chambers comprised of bricks having at least two diiferent densities arranged in patterns whereby the carbonization pressure on the heating wall liners due to carbonization of the coal is significantly reduced.

For a further understanding of the invention and for advantages and features thereof, reference may be made to the following description in conjunction with the drawings which show for the purpose of exemplification several embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a schematic perspective view of a portion of a heating liner wall in accordance with one aspect of the invention;

FIG. 2 is a schematic perspective view of a portion of a heating liner wall in accordance with another aspect of the invention;

FIG. 3 is a schematic arrangement of various patterns of bricks in liner walls constructed in accordance with the present invention;

FIG. 4 is a schematic cross-sectional view of a coking chamber in accordance with the prior art;

FIG. 5 is a schematic cross-sectional view of a coking chamber in accordance with one aspect of the present invention;

FIG. 6 is a graph that schematically compares the carbonization pressure build-up in prior art ovens with that in ovens of the present invention;

FIG. 7 schematically shows the heat distribution during carbonization in a chamber constructed in accordance with the invention;

FIG. 8 is a schematic perspective view of a portion of the end of a heating liner wall adjacent the end fiues;

FIG. 9 is a schematic representation of a coke oven battery along a longitudinal plane, having heating liner walls constructed in accordance with the invention;

FIG. 10 is a schematic plan view of a coke chamber and heating walls in accordance with one aspect of the invention; and

FIG. 11 is a schematic elevational view of a heating wall liner in accordance with another embodiment of the invention.

DETAILED DESCRIPTION Referring to the drawings, FIG. 1 illustrates schematically a portion of a heating wall 11 of a horizontal coke oven battery, comprised of a heating wall liner 13 and the usual tie walls 15, 17 forming therebetween heating flues 19.

The heating wall liner 13 is made up of horizontal courses of refractory brick of different density. In the lowermost course 21 shown in FIG. 1, alternate stretcher bricks are of high and low density; the higher density bricks 210 are shown as stippled and the lower density bricks 21b are shown without stippling. Such bricks are of the type disclosed in Patent 1,782,638 to Totzek. For purposes of reference herein, a high density brick weighs approximately 120 pounds per cubic foot, and a loW density brick weighs about -110 pounds per cubic foot. It is to be understood that these densities are merely representative and do not limit the invention in any way whatsoever.

It will be noted from FIG. 1 that all of the bricks in horizontal course 23, next above the course 21, are of uniformly low density. Immediately above the low density brick course 23 is another course of bricks comprised of alternate high 25a and low 25b density bricks, which are arranged in a manner similar to the

bricks

21a and 21b in the first course 21. Similarly, above the course of bricks 25 is another course 27 wherein all of the bricks are of uniformly low density, and immediately above this course 27 is another course wherein the bricks are alternately of high 29a and low 29b density.

FIG. 2 illustrates schematically a portion of another heating wall liner 31 formed of bricks of the Totzek type laid up in horizontal courses wherein the lowermost course 33 is comprised entirely of high density bricks; a course 35 next above is comprised entirely of bricks of uniform low density; and the course of

bricks

37, 39, 41 successively laid horizontally above course 35 are comprised of alternate high and low density, as shown by the different surface markings used herein for purposes of identification only.

FIG. 3 shows front elevational views of several liner walls wherein various arrangements A-E of high and low density bricks obtain. The arrangement A corresponds to the liner wall described herein and shown in FIG. 2; and the arrangement B corresponds to the liner wall described herein and shown in FIG. 1. Those skilled in the art will, of course, understand that liner walls similar to those of FIGS. 1 and 2 may be constructed following the other arrangement of bricks C, D, and E of FIG. 3. Further, the present invention is not limited to only the arrangements shown in FIG. 3, inasmuch as those skilled in the art will be able readily to make other arrangements of bricks for particular installations.

FIG. 4 schematically illustrates a vertical cross-section through a typical coking chamber 43 of the prior art wherein all of the

bricks

45, 47 of the liner walls 46 are of uniform low density. Since

such bricks

45, 47 are of uniform low density, the heat transfer through these liner 'walls to the coke is also uniform, and

plastic seams

49, 51, that travel normally from the heating liner surface toward a center vertical plane, are, in the prior art, substantially vertical planar plastic seam zones. In FIG. 4, the material between the

plastic seams

49, 51 is understood to be coal that has not been heated sufficiently to become plastic. The material between the

plastic seams

49, 51 and the respective

heating wall liners

45, 47 is understood to be coke. When the

plastic seams

49, 51 meet, at or near the center vertical plane of the coking chamber 43, pressure waves are set up that act substantially uniformly over the entire vertical plane of contact, and these pressure waves, acting through the formed coke, exert a substantial pressure on the respective

heating wall liners

45, 47.

Heating wall liners constructed in accordance with the invention, however, transmit heat non-uniformly and so non-uniform plastic seams and pressure waves are thereby produced. FIG. is a vertical schematic view of a coking chamber 53 between

heating wall liners

55, 57 in accordance with one aspect of the invention. The bricks comprising the

heating Wall liners

55, 57 are arranged generally in the pattern A of FIG. 3; that is, alternate horizontal courses of bricks are comprised entirely of high 59 and of low 61 density. For purposes of illustration in FIG. 5, the high density bricks 59 (having a density of about 120 pounds per cubic foot) are shown as stippled, whereas the low density bricks (having a density of 100-1 pounds per cubic foot) do not have any stippling.

Since the high density bricks 59 have a higher heat transmission rate than the low density bricks 61, the hea p etrat on nto the coa and the CQking rate opposite the high density bricks 59, is significantly greater than the heat penetration and coking rate opposite the low density bricks 61. Consequently, in the coking chamber 53, the plastic coal seams 63, 65 have a wavy, wafilelike, sinusoidal appearance. In FIG. 2, such a wavy, wafile-like, or sinusoidal plastic seam 65 is shown perspectively in relation to the heating wall liner 31.

Referring again to FIG. 5, it is apparent that when the plastic seams 63, 65 meet, they will meet at respective nodal points 67. Practically, the meeting of the plastic seams 63, 65 at the nodal points 67 establishes horizontal lines of contact lengthwise of the coking chamber 53, and, as the plastic seams 63, 65 continue to progress toward the center of the coking chamber 53, only horizontal lines of contact exist, or, at most, parallel, horizontal, narrow bands of contact are established. The area of contact provided by such narrow horizontal bands in such a wall is to be contrasted with the maximum planar area of contact established in the wall (FIG. 4) of the prior art. Accordingly, in the heating wall liner of FIG. 5, only horizontal narrow bands of pressure are transmitted through the coke to the

liner walls

55, 57, and these bands vary vertically in position as the sinusoidal plastic seams 63, 65 progress toward each other.

FIG. 6 illustrates graphically and comparatively the carbonization pressure 69 obtained when the flat planar

plastic seams

49, 51 of FIG. 4 meet, and the carbonization pressure 71 attained when the nodal points 67 of the sinusoidal plastic seams 63, 65 meet. It will be recognized that there is a considerable difference in carbonizetion pressure between

peak

69 and 71; consequently, less stress is placed on the

heating wall liners

55, 57 of the invention than on the

heating Wall liners

45, 47 of the prior art.

FIG. 7 illustrates schematically a portion of the heating wall liner 57 (FIG. 5), the plastic seam 65, and an isothermal curve 73 associated with the plastic seam 65. It will be noted that the isothermal curve 73 is generally similar in shape to the plastic seam 65, but that a thermal nodal point 75 of the isotherm 65 is slightly sharper than the nodal point 67 of the plastic seam 65. Further, it will be noted that the direction in which heat vectors 76 are believed to travel outwardly from the plastic seam are not parallel. Generally, the effective area for heat transfer to the coal is greater in a heating wall liner in accordance with the invention, because of the sinusoidal of wave-like effect of the plastic seam 65 and isothermal line 73, than in the heating liner of the prior art (FIG. 4).

Generally, the total heat passing through the plastic seam 65 into the coal, yet uncoked, is proportional to the area of the plastic seam in contact with the uncoked coal. From FIG. 7, it will be observed that the area of plastic seam 65 per unit of length in contact 'with uncoked coal in oven chamber 53 is greater than the area of the plastic seam 49 (FIG. 4) per unit of length in contact with uncoked coal in the oven chamber 43. This is because the sinusoidal plastic seam 65 is longer than the vertical straight plastic seam 49.

In a typical installation, it is estimated that a sinusoidal plastic seam, such as 65, transmits at least 8 percent more heat per unit of time than a flat vertical plastic seam such as 49. This means, then, that the wall liner 31, constructed of bricks having alternate high and low density, may be nearly as effective as a wall liner constructed entirely of high density bricks; however, such a wall liner 31 is only about one-half as expensive to make as the wall liner made entirely of high density brick. In most instances, the percentage increase in heat transmission alone is of such significance that it outweighs any disadvantages because of the additional cost of the high density brick used in such a wall.

Those skilled in the art will recognize that the arrangement of bricks in the wall liner 13 of FIG. 1 produces an isothermal front 77 that has mountain-like peaks 78 pp t each h gh densi y isk. 21a, 25 etc. a d. such peaks meet similar peaks in an isothermal front (not shown) advancing toward it from an opposite similar heating wall liner. When the respective peaks of the isothermal fronts 77 meet, they meet in distinct, short zones of contact, in contrast to continuous horizontal lines of contact established when the isothermal fronts 73 mentioned hereinbefore meet, and in contrast to the vertical continuous fiat plane of contact when the fronts of the oven 43 (FIG. 4) meet. Because the isothermal fronts 77 meet in separate small zones of contact, such a heating wall liner would be subjected to much less pressure even than the wall 31 wherein the lines of contact are horizontal continuous lines.

FIG. 3 illustrates a few of the many other arrangements of bricks that may be used effectively in heating liner walls to achieve particular purposes. Those skilled in the art will appreciate that for each arrangement of bricks shown, there is a particular plastic seam configuration and isothermal front. While FIG. 3 illustrates only a few of the arrangements that may be made, those skilled in the art will undoubtedly be able to construct other suitable arrangements to suit particular conditions.

In some applications, heating wall liners may be constructed using bricks of more than two densities; with or without matching patterns in opposite wall liners, as the occasion requires. Further, heating wall liners constructed in accordance with the teaching of Tucker Patent 3,102,846 would include low density bricks for the intermediate courses (the thicker bricks shown in the Tucker Patent) and high density bricks for the alternate courses (the thinner bricks shown in the Tucker Patent). This, then, would effectively even out the heat transmitted through such a heating wall liner, and such an arrange ment might be used when carbonization pressures are not a severe problem.

In some other instances, opposite heating wall liners may be constructed by using high density bricks (or low density brick) for one entire heating wall liner, and both high and low density bricks may be arranged, in any of the other manners suggested herein, in the opposite heat ing wall liner. Such an arrangement of bricks in the opposite walls of the coking chamber may be used throughout the entire coke oven battery.

FIG. 8 illustrates a portion of an end of heating wall liner 79 wherein the bricks forming the end fiues 81, 81a are of high density. It will be noticed that bricks 83 disposed between the end fiue 81 and the usual buckstay 85 are of low density which is to reduce the amount of heat transmitted to the steel structure (buckstays) of the coke oven battery. Rather, in accordance with the invention, it is desirable to increase the amount of heat transmitted from the end flues 81, 81a only to the coal that is to be coked.

The bricks that form the remainder of the heating wall liner 79, may be arranged in any of the Ways suggested in FIG. 3, or in any other manner preferred by those skilled in the art. An advantage derived from using high density bricks to form the end fiues 81, 81a is found in the fact that more heat is transmitted through the high density bricks to the coal adjacent the end flue; whereas, under the usual conditions, poor coking adjacent the end flues is generally experienced where bricks of uniform low density are employed.

FIG. 9 illustrates a portion of the structure of a horizontal coke oven battery heating wall liner 87, wherein the up er half portion 89, above the line AA, is constructed entirely of high density brick and the lower portion 91 is constructed of mixed density bricks or in some cases of uniform low density bricks. A feature and advantage of making the upper half portion 89 of heating wall liner 87 entirely of high density bricks is that a faster coking rate is achieved in a zone of the coking chamber where slower coking normally occurs. Usually, less heat reaches the upper regions of the coking chamber than is available in the bottom or lower zone of the chamber. For this reason, it requires a longer time to coke the coal in the upper portion of the coking chamber. Likewise, coking occurs at a faster rate in the lower portion of the chamber because more heat is available. Therefore, in accordance with the invention, a faster coking rate is achieved by making the courses of brick in the upper half portion of the heating wall liners entirely of high density brick.

FIG. 10 is a schematic transverse sectional view of a typical coking chamber 93 which tapers in the normal manner from the pusher side toward the coke side. The heating liner walls on the coke side are frequentl thinner than the walls on the pusher side so that more heat is transmitted to the greater volume of coal on the coke side and a more nearly uniform balance in the coking rate between the pusher side and the coke side is achieved. But, thin heating wall liners have structural disadvantages. In accordance with the invention, however, the portion of

heating wall liners

95, 95a on the coke side of chamber 93, from a section line B-B in FIG. 10 to the exit on the coke side, are composed entirel of high densit brick. But, in some applications, the

wall liners

95, 95a on the coke side may be of mixed density bricks and the liners on the pusher side may be of uniform low density bricks. Wherefore, even though the

heating Wall liners

95, 95a are of uniform thickness, more heat is transmitted to a greater volume of coal near the coke side of the chamber 93 and a more uniform wall liner temperature and a balanced coking rate throughout the coking chamber 93 is achieved. As shown in FIG. 10, the thickness of the

heating wall liners

95, 95a on the coke side is not reduced, as is customary in some ovens, which means that the strength of the heating wall liners is not impaired as it frequently is when the coke side portion of the heating wall liners has a reduced thickness.

Several features and advantages of the heating Wall liners, constructed in accordance with the invention, are apparent from the foregoing.

Heating wall liners are normally priced according to the weight of brick used rather than according to the number or volume or bricks used. Hence, a heating wall liner constructed entirely of high density brick would be a much faster heating wall liner, but, would, on the other hand, be substantially more costly than a heating wall liner constructed of conventional, low-density brick. A heating wall liner constructed in accordance with the mixed-density feature of the invention, would provide a significantly faster coking rate than an all low density liner, but it would not be significantly more expensive than the conventional low density liner. Furthermore, the mixed density brick wall liner of the invention provides a coking rate that is significantly greater than the coking rate with a conventional low-density wall construction, and that approximates closely the coking rate of high density brick wall liners.

A feature of the invention is that the heat penetration profile for a heating wall liner of mixed density bricks is non-uniform in the sense that the heat penetration profile of heating wall liners comprised entirely of low density brick is planar and uniform (FIG. 4). The profile of the mixed density brick liner of the invention, on the other hand, has a waffie-like, sinusoidal appearance and, in some instances, the profile may even be discontinuous. In coke ovens having such heating wall liners, the maximum will pressure 71 (FIG. 6) due to carbonization of the coal is significantly reduced and, in some instances, the maximum pressure peak may entirely disappear. The waffle-like, or discontinuous, heat profile effect not only reduces significantly the maximum wall pressure, but also admits of the use of coals that have a greater free swelling index without fear of structural damage to the heating wall liner.

While in a heating wall liner of conventional low density brick the heat transfer is believed to be linearly parallel toward the center line vertical plane of the oven, in an oven having heating wall liners of mixed density bricks in accordance with the invention, the heat transfer is believed to be linearly nonparallel (as suggested by the isotherm line 73 in FIG. 7). Accordingly, the eifective area for heat transfer to the coal in an oven constructed in accordance with the invention is greater since the length and surface area of the sinusoidal or wafiie-like front is greater than the length and surface area of the fiat front, as exemplified by a conventional heating wall liner. That is to say, the coking time in an oven constructed in accordance with the invention, is significantly reduced with only a practically insignificant increase in cost of construction of a heating Wall liner due to the use of mixed density bricks.

Although the invention has been described herein with a certain degree of particularity, it is understood that the present disclosure has been made only as an example and that various modifications and changes may be made within the scope of the invention as defined by the appended claims.

What is claimed is:

1. A horizontal coking retort oven having heater walls between adjacent chambers for coking coal, including spaced apart heating wall liners with spaced apart tie walls tying said wall liners together and defining within each heating wall separate vertical combustion fines wherein heat is generated that is transmitted through said wall liners to carbonize the coal in said coking chambers, the improved construction comprising:

(a) a heating wall liner of bricks arranged in horizontal courses; with (i) all of the bricks in alternate, vertically spaced apart, first horizontal single courses having a high rate of heat transmission; and with (ii) all of the bricks in alternate second horizontal single courses disposed intermediate said first single courses having a lower rate of heat transmission than the bricks in said first single courses.

2. In a horizontal coke oven structure including spaced apart heating wall liners that define coking chambers and that are subdivided by tie walls connecting said wall liners into end and intermediary heating fines wherein heat is generated that is transmitted through the wall liners to carbonize coal in said coking chamber, the improved heating wall liner construction comprising:

(a) first bricks having a high rate of heat transmission arranged in alternate vertically spaced-apart single courses;

(b) second bricks having a low rate of heat transmission arranged in a single courses located intermediate said first courses in said heating wall liners; and with (c) the portions of the heating wall liners that define the side Walls of end heating fiues of such coking chambers being constructed of bricks having a high rate of heat transmission arranged in contiguous courses.

3. In a horizontal coke oven structure including spaced apart heating wall liners that define coking chambers and that are subdivided by tie walls connecting said wall liners into heating fiues wherein heat is generated that is transmitted through the wall liners to carbonize coal in said coking chamber, the improved heating wall liner construction comprising:

(a) an upper horizontal portion of each heating wall being comprised of a plurality of contiguous courses of first bricks having a high rate of heat transmission; and

(b) the remaining lower portion of each heating wall liner being comprised of a plurality of contiguous courses of second bricks having a low rate of heat transmission.

4. The structure of claim 2 wherein:

(a) the end fiues of said heating wall liners are coma high rate of heat transmission;

(b) the upper horizontal portion of each heating wall between said end fiues is comprised of a plurality of contiguous courses of said first bricks; and

(c) the remaining lower portion of each heating wall between said end fiues is comprised of a plurality of courses of second bricks having a low rate of heat transmission, whereby heat is transmitted to said coal at a non-uniform rate to produce an undulating plastic seam in the coal during coking.

S. In a horizontal coke oven structure including spaced apart heating wall liners that define coking chambers having coke discharge end portions and that are subdivided by tie walls connecting said wall liners into heating fiues wherein heat is generated that is transmitted through the wall liners to carbonize coal in said coking chamber, the improvement comprising:

(a) a zone of each heating wall liner adjacent the coke discharge end portion of each coking chamber that is comprised of a plurality of contiguous courses of first bricks having a high rate of heat transmission.

6. In a horizontal coke oven structure including spaced apart wall liners that define coking chambers having pusher side and coke side end portions and that are subdivided by tie walls connecting said wall liners into heating fiues wherein heat is generated that is transmitted through the wall liners to carbonize coal in said coking chamber, the improvement comprising:

(a) a zone of each heating wall adjacent the coke side end portion of each coking chamber that is comprised of a plurality of courses of both first and second bricks, said first bricks having a high rate of heat transmission and said second bricks having a low rate of heat transmission; and

(b) a zone of each heating wall adjacent the pusher side end portion of each coking chamber that is comprised of a plurality of said second bricks disposed in vertically contiguous courses.

7. In a horizontal coking chamber, the improved heating wall liner comprising:

(a) a plurality of bricks arranged in horizontal courses,

with the,

(i) alternate first bricks in each course having a high rate of heat transmission, and with the (ii) intermediary second bricks in each horizontal course having a low rate of heat transmission.

8. In a horizontal coking chamber, the improved heating wall liner comprising:

(a) a plurality of first and second types of bricks arranged in horizontal courses with 50 (i) the first bricks having a high rate of heat transmission and with (ii) the second bricks having a low rate of heat transmission,

(iii) each course of bricks including spaced apart pairs of second bricks with one first brick interposed between said pairs of second bricks, and with (iv) the first brick of alternate courses being contiguous with both second bricks of each pair of second bricks of the intermediary courses. 9. In a horizontal coking chamber, the improved heating wall liner comprising:

(a) a plurality of first and second types of bricks arranged in horizontal courses with (i) the first bricks having a high rate of heat transmission and with (ii) the second bricks having a low rate of heat transmission, (iii) each course of bricks including spaced apart pairs of first bricks with a second brick contiguous with each first brick and with a single brick dispersed between adjacent second bricks, and with (iv) said pair of first bricks being contiguous with the single first brick of each of the contiguous courses of bricks.

References Cited UNITED STATES PATENTS 3,102,846 9/1963 Tucker 202223 3,259,551 7/1966 Thompson 202-267 FOREIGN PATENTS 491,278 8/1938 Great Britain. 5 1,122,492 1/1962 Germany.

WILBUR L. BASCOMB, JR., Primary Examiner US. Cl. X.R.