US2513597A

US2513597A - Radiant tube type annealing oven

Info

Publication number: US2513597A
Application number: US767459A
Authority: US
Inventors: Clarence R Taylor
Original assignee: Whiting Corp
Current assignee: Whiting Corp
Priority date: 1947-08-08
Filing date: 1947-08-08
Publication date: 1950-07-04
Anticipated expiration: 1967-07-04

Description

July 4, 1950 C. R. TAYLOR RADIANT TUBE TYPE ANNEALING OVEN Filed Aug. 8, 1947 5 Sheets-Sheet 1 July 4, 1950 c. R. TAYLOR 2,513,597

RADIANT TUBE TYPE ANNEALING OVEN Filed Aug. 8, 1947 5 Sheets-Sheet 2 July 4, 1950 c. R. TAYLOR 2,513,597

RADIANT TUBE TYPE ANNEALING ovEN Filed Aug. a, 1947 5 sheets-sheet s E il Fl WIE July 4, 1950 c. R. TAYLOR 2,513,597

I RADIANT TUBE TYPE ANNEALING OVEN Filed Aug. -8, 1947 5 Sheets-Sheet 4 SN. kfw

m w w. No M@ Zane/zee July 4, 1950 c. R. TAYLOR 2,513,597

RADIANT TUBE TYPE ANNEALING OVEN Filed Aug. 8. 1947 5 Sheets-Sheet 5 Patented July 4, 1950 RADIANT TUBE TYPE ANNEALING OVEN Clarence B.. Taylor, Chicago, Ill., assirnor to Whiting Corporation, Harvey, Ill., a corporation o! Illinois Application August 8, 1947, Serial No. 767,459

The present invention relates generally to annealing ovens. More particularly the invention relates to that type of annealing oven which is adapted by the application of high temperature heat to effect annealing of a charge of castings, embodies a bottom, a roof, and side and end walls which together define an annealing chamber, and

also embodies side by side radiant tubes which extend transversely through the annealing chamber, have certain ends thereof connected to receive the products of combustion from a fuel burner and their other ends connected to an exhaust conduit, and serve or function in connection with the passage or flow of the products of combustion therethrough to produce within the annealing chamber such radiant heat as to effect the desired annealing of the charge.

It has heretofore been proposed in connection with an annealing oven of the aforementioned type to utilize straight radiant tubes and to dispose or position the tubes so that they extend truly horizontally through the annealing chamber. In practice it has been found that an annealing oven wherein the side by side radiant tubes extend horizontally is subject to certain objections or disadvantages. In the first place, downward deflection or bending of the unsupported portions of the tubes within the annealing chamber occurs because due to elevated or high temperatures the material of which the tubes is made is weakened to the point where the weight of the tubes themselves is an excessive load for the unsupported portions of the tubes to bear or carry and further because at high temperatures the creep of the material is so pronounced that the tubes will become progressively deflected to such an extent that they are unable to return to their original straight form. Secondly, as the result of the tubes extending horizontally such convection heat currents are induced around the outside of the tubes that there is unequal temperature distribution on the surfaces of the tubes thereby resulting in undesirable distortion and reduced efliciency of heat transfer.

With the view of avoiding or eliminating the disadvantages and defects that are incident to the use of horizontally extending radiant tubes it has heretofore been proposed to arrange the tubes at the sides of the annealing chamber and so that they extend truly vertically. In connection with an annealing oven wherein the radiant tubes extend vertically it is customary to introduce the products of combustion from the burner into the upper ends of the tubes and to provide the lower or discharge ends of the tubes with right angle bends leading outwards through the lower portions of the side walls of the oven. In practice it has been found that the use of vertical radiant tubes, although eliminating distor tion in the form of bending or sagging, is ob- 1 1 Claims. (Cl. 263-42) jectionable for the reason that the tubes burn out more rapidly than straight tubes by reason of the fact that there is unequal velocity of the products of combustion at the right angle bends.

One of the principal objects of this invention is to provide a radiant tube typevannealing oven which eliminates the defects and disadvantages of, and has greater structural and thermal eiiic'iency and longer life than, annealing ovens wherein the tubes extend truly horizontally or extend vertically and have right angle bends at their lower or discharge ends. In general, the improved oven is characterized by the fact that there is a longitudinal series of laterally spaced radiant straight tubes at each side of the annealing chamber and the tubes are inclined upwards and inwards at such a comparatively small angle with respect to the vertical as substantially to preserve the structural and thermal advantages that pertain to the use of truly vertical tubes. By having the two series of radiant tubes upwardly and inwardly inclined manifold advantages are obtained. In the first place, the tubes may be made straight throughout their entire length while at the same time having their lower or discharge ends extending through the lower portions of the side walls of the oven. Secondly, the tubes, as the result of the fact that they are closer together near the top than at the bottom, define between and under them a clear space of such shape as efficiently to envelop a charge (a pile of castings) of the most natural configuration. Thirdly, the tubes, due to their upward and inward inclination, form, in eiect, a radiating arch over the charge of castings and hence tend to focus or direct the ,heat toward the center of the charge. Fourthly, the external surface parts of the tubes that face away from the charge are so spaced from the upper portions of the side walls of the oven and the side portions of the oven roof that the heat that is radiated by such external surface parts is effectively reflected by said portions of the side walls and roof back towards the charge in the annealing chamber.

Another object of the invention is to provide an annealing oven of the last mentioned character in which the upper ends of the upwardly and inwardly inclined radiant tubes extend completely through the roof and the upper portions of the side and end walls are provided with upwardly extending or vertical extensions which support a second roof in vertically spaced relation with the main roof and together with the two roofs define a combustion chamber of such comparatively large size that it may be utilized advantageously and efficiently for the burning of a fuel mixture requiring large cubical space for the combustion reaction, such, for example, as a mixture of pulverized coal and air under pressure.

Another object of the invention is to provide asians? an annealing oven of the type and character under consideration in which the upper ends of the radiant tubes extend slidably through the main roof and the lower ends of the tubes extend slidably through the lower portions of the side walls of the oven to the end that the tu, in response to temperature variations, are free to expand or contract without binding.

Another object of the invention is to provide a radiant tube type annealing oven'in which the lower or discharge ends of the tubes are provided with valves for controlling the ilow of the products of combustion and are connected to a pair of horizontally disposed exhaust manifolds which are located adjacent and extend in parallel relation with the lower portions of the side walls of the oven and have certain ends thereof connected to a common exhaust conduit.

A further object of the invention is the provision in an annealing oven of the type and character under consideration of simple and novel means for effecting a continuous circulation of the heated atmosphere within the annealing chamber in order to promote exceptionally high thermal eiiiciency so far as annealing of the charge is concerned.

A still further object of the invention is to provide a radiant tube annealing oven which is generally of new and improved construction and is characterized by high eiilciency. and also simplicity of design and low cost of operation.

Other objects of the invention and the various advantages and characteristics of the present annealing oven will be apparent from a consideration of the following detailed description.

The invention consists in the several novel features which are hereinafter set forth and are more particularly defined by claims at the conclusion hereof.

In the drawings which accompany and form a part of this specification or disclosure and in which like numerals of reference denote correspending parts throughout the several views:

Figure 1 is a side elevation of a radiant tube type annealing oven embodying the invention;

Figure 2 is an end elevation illustrating in detail the manner in which the oven is supported Ain an elevated position with respect to the'subjacent iioor;

Figure 3 is a side view of the oven proper t0- gether with the pulverized fuel equipment for supplying into the combustion chamber a combustibleV mixture in the form of pulverized coal and air under pressure;

Figure 4 is a plan view illustrating in detail the arrangement and location of the exhaust manifolds to which the lower or discharge ends of the radiant tubes are connected;

Figure 5 is a vertical longitudinal section on the line 5-5 of Figure 4;

Figure 6 is a view of the oven proper partly in end elevation and partly in section and disclosing the arrangement and manner of mounting the radiant tubes; and

Figure 7 is a` detailed section of one of the butterily valves at the lower ends of the tubes.

The annealing oven which is shown in the drawings constitutes the preferred embodiment of the invention. It is adapted in connection with operation to anneal or heat treat a charge of casings (see dotted lines in Figure 5). As its principal components the annealing oven comprises a supporting structure 8. an oven proper 9 and pulverized coal equipment I0 for firin the oven proper. A

pit It which underlies and este tranversely of,

theoven proper. The supporting structure s comprises four I-beam variety uprights it and a f1-:ru: frame i@ at the upper ends of thc uprigh The uprights are located at the sides of the pit it -and have the lower ends thereof fixedly connected to bases i5 on the foundry floor li. 4'.li'he frame It consists of a pair of horizontally and longitudinally extending I-beams I6, a pair of horizontally and transversely extending I-beams Ii and a rectangular plate it. The longitudinally exten we. ie are arranged in parallel and spaced apart relation and have the ends thereof welded or otherwise iixedly secured to the ends of the transversely extending I-beams Il. The extend transversely o the pit I2 and have ,the ends thereof suitably mounted on. and fixed to.the upper ends of the uprights I3. The rectangular plate le rests on. and is fixed to, the upper iianges of the beams it and I1 and is so proportioned that the inner mar gin thereof projects inwards of the inner edges of the top flanges of the beams it and il and its outer margin projects beyond or outwards of the outer edges of the top anges of said beams.

The oven proper 9 comprises a bottom le, a pair of side walls 20, a pair of end walls 2i and 22, a first roof 23 and a second roof 26. The bottom I9 is normally supported by raising and lowering mechanism 25 and when in its up position nts within the rectangular frame It ot the supporting structure 9. It is adapted to support the charge of castings to be annealed and embodies a bottom plate 26, a rectangular frame 2. a re brick iioor 28 and a charge supporting pan 29. The bottom plate 26 overlies and is iixedly secured to the upper flanges of a series of spaced apart, horizontally Iand transv jects upwards from, the edge portions of the.

bottom plate 26 and has at the upper portion thereof an outwardly disposed, rectangular, channel forming flange structure 32. The channel that is formed by this flange structure is position to receive a rectangula downwardly extending flange 93 on the inner edge or marginal portion of the rectangular plate i9 constituting a part of the rectangular frame I4 of the supporting structure 9. When the bottom I9 is shifed upwards into its up or operative position as hereinafter described, the flange 33 embeds itself in the sand in the channel that is formed by the flange structure 32 and forms therewith a seal around said bottom I9. The fire brick floor 28 of the bottom I9 rests on the bottom plate 26 and is disposed and conned within the rectangular frame 21. The pan 29 overlies the fire brick door 28 and is supported in spaced relation with the latter by way of elongated, longitudinally extending flre brick blocks 34. 'I'he latter are spaced laterally apart and deine under the pan 29 longitudinally extending, open ended ducts'E. The pan 29 is adapted to have the charge of castings piled onto it and amasar has perforations 36 throughout its area in order to permit the heated atmosphere to flow upwards through it from the longitudinally extending ducts 35. The side walls 20 of the oven proper 9 are formed of fire brick and rest on. and project upwards from, the side parts of the rectangular plate I8. They are arranged in parallel and laterally spaced relation and are reenforced against outward deflection by way of exteriorly disposed vertically extending I-beams 31. The lower ends of the I-beams 31 are suitably secured to the outer margins of the side parts of the plate I8 and the upper ends are cross connected by transversely extending tie rods 38. The end walls 2I and 22 of the oven proper are formed of re brick and rest on, and extend upwards from, the end parts of the plate I8. They extend between, and are joined to the ends of the side walls 20 and are reenforced against outward defiection by way of vertically extending I-beams 39. The lower ends of the I-beams 39 are flxedly connected to the outer margins of the end parts of the plate I8 and have the upper ends thereof cross connected by way of longitudinally extending tie rods 40. The first roof 23 is formed of re brick and is joined to, and extends across, the central portions of the side and end walls. It is preferably upwardly arched and defines with the bottom I9 andthe lower portions of the side and end walls an annealing chamber 4I. The second roof 24 is formed of fire brick, 'is upwardly arched the same as the first roof 23, and rests on the top surfaces of the side and end walls of the oven proper. It defines with the first roof 23 and the upper portions of the side and end walls a combustion chamber 42. As shown in the drawings the tie rods 38 between the upper ends of the I-beams 31 and the tie rods 40 between the upper ends of the I-beams 33, overlie and serve to protect the second roof 24.

The pulverized coal equipment I for firing the oven is located outwards and alongside of the end wall 22 of the oven proper and is supported by any suitable platform 43. It comprises a pulverizer 44 and a burner 45. The pulverizer is supplied with coal by way of a hopper 46- and operates in connection with drive thereof to pulverize the coal. The pulverized coal is fed by a screw conveyor (not shown) into a pipe system 41, the inlet end of which is connected to receive air under pressure from a centrifugal air compressor (also not shown). The burner 45 is in the form of an elongated elbow type tube and has one end thereof connected to the discharge end of the pipe system 41. The other end of the burner extends horizontally and fits within an opening in the upper central portion of the end wall 22 of the oven proper. 'Ihe burner is ignited' by any suitable pilot light (not shown). When the oven is in operation the mixture of pulverized coal and air under pressure burns within the combustion chamber 42. As a result oi the particular disposition or arrangement of the burner 45 of the pulverized coal equipment I0 the products of combustion flow lengthwise of the combustion chamber 42. Access to the combustion chamber is provided by way of an opening 48 in the upper portion of the end wall 2l. This opening is normally 'closed by way of a door 49 which is hinged at one side thereof in order that it may be swung back and forth between open and closed positions.

In addition to the parts heretofore referred to the oven comprises two opposed, longitudinally disposed series of radiant tubes l, a pair of exhaust manifolds 5I and an exhaust conduit 52. 'I'he radianttubes 50 are disposed for the most part within the side portions of the annealing chamber 4I and each is straight throughout its entire length. The tubes of each series are spaced equidistantly apart-and are in transverse alignment with the tubes of the other series. As Ibest shown in Figure 6 .the tubes are upwardly and inwardly inclined vat approximately an angle of 221/2o with respect to the vertical. The upper ends of the tubes extend loosely through upwardly and inwardly inined, substantially cylindrical openings 53 inthe `iirst roof 23 and are in communication with the combustion chamber 42. Tubular packings 54 of mineral wool or like insulating material surround the upper ends of the radiant Atubes 50 and fit tightly within the openings 53. The lower ends of the tube extend loosely through upwardly and inwardly inclined, substantially cylindrical openings 55 in the lower portions of the side walls 20 oi the oven proper and terminate adjacent the longitudinally extending I- beams I6 of the rectangular frame I4. Tubular packings 56 surround the lower ends of the tubes 50 and fit snugly within the openings 55. The tubes are slidable with respect to the packings 54 and 56 and hence in response to variations in temperature are free to expand or con` tact without binding. Wheu the annealing oven is in operation the products of combustion flow from the combustion chamber 42 downwards and outwards through the tubes 50 and result in the latter producing the desired radiant heat for effecting annealing of the charge within the annealing chamber 4I. By reason of the fact'that the tubes are disposed at but a comparatively small angle with respect to the vertical the strains or stresses incident to high temperature do not result in temporary or permanent lateral distortion of the tubes and the tubes maintain at all times their straight form. Also by reason of the fact that the tubes are disposed at but a small angle with respect to the vertical any iiy ash in the products of combustion passes downwards through the tubes instead of lodging on the tube interiors. Due to upward and inward inclination the radiant tubes 50 form, in effect a radiating arch over the charge of castings in the annealing chamber 4I and hence tend to focus or direct the heat toward the center of the charge. Also due to the particular inclination of the tubes the external surface parts of the tubes that face away from the charge are so spaced from the adjacent portions of the side walls of the oven and the side portions of the rst roof 23 that the heat that is radiated by such external surface parts is effectively reflected by said portions of the side walls and first roof back towards the charge. Another feature or advantage of having the tubes inclined upwards and inwards is that the space between and under th tubes is of such shape as efficiently to envelop a charge in the form of an upwardly tapered pile of castings. The lower ends of the radiant tubes 50 have extension nipples 51 and these are provided with butterfly valves 58 for controlling the downflow of the products of combustion through the tubes. The Valves are mounted on horizontally extending rock shafts 59 which extend transversely through the extension nipples 51 and have handles 60 whereby the shafts together with the butteriiy valves may be turned for valve adjusting purposes. By

of the products of combustion t ough lthe tubes may be s o controlled as to e ect-uniform or equal heating of the tubes. The exhaust manifolds 3| arelocated directly outwards of. and in parallel relation with, the longitudinally extending I-beams I6 of the frame I4 and are connected to said I-beams by way of brackets 8l. They are provided with upwardly and inwardly extending nipples 62 and these are connected to the lower ends of the extension nipples 51 and together with the last mentioned nipples establish communication between the lower ends of the radiant tubes 50 and the interiors of the exhaust manifolds I. The ends of the 'exhaust manifolds that are adJacentthe end wall 2| of .the oven proper are closed. The other ends of the exahust manifolds 5I. i. e., the ends that lare adjacent the end wall 22 of the oven proper,

are cross connected by a horizontally extending duct 63, the central portion of which is provided with an outwardly and horizontally extending outlet branch 64. The exhaust conduit 52 extendsvertically and has the lower end thereof connected to the outlet branch 64 by a horizontally extending duct structure 65. The products of combustion which flow downwards from the radiant tubes 50 into the exhaust manifolds 5I pass rst into the horizontally extending'duct 63, then through the outlet branch 64, then through the duct structure 65 and finally up-l wards through the exhaust conduit 52. Nozzles $6 are located in the lower portions of theinteriors of the exhaust manifolds 5I and serve to jet streams of air under pressure through the manifolds in the direction of the duct 63. Suchr streams serve to rid the exhaust manifolds of y ash and any other deposit. The nozzles are connected to any suitable source of air under pressure by way of horizontally extending pipes 51 which extend alongside of the exhaust manifolds.

The high temperature atmosphere within the annealing chamber 4I is circulated by way of a blade. type fan wheel 68. The latter is located in the upper portion of the end of the annealing chamberthat is defined by the end wall 22 and is keyed or otherwise fixedly secured to the inner end of a drive shaft 69 which extends horizontally through a hole in the end wall 22. 'I'he outer end of the shaft is connected to the armature of an electric motor 1I. A bearing 12 for rotatably supporting the shaft 69 is mounted in the hole 10 and serves to seal the hole against out-ow of the high temperature atmosphere therethrough.

When the fan wheel 68 is driven by the motor it causes the high temperature atmosphere in the annealing chamber 4I to ow continuously rst lengthwise through the upper portion of the annealing chamber in the direction of the end wall 2 I, then downwards in to the adjacent ends of the ducts 35 between the fire brick blocks 34, then longitudinally through the ducts. and then upwards to the fan wheel. A portion of the high temperature atmosphere that flows into the ducts 35 flows upwards through the perforations 36in the pan 29. By employing thefan wheel 68 there iscontinuous circulation of thevhigh temperature atmosphere in the annealing chamber and hence uniform annealing of the charge, that is, the pile of castings on the pan 28, is obtained.

As shown in Figures 1 and 2 of the drawings the pit I2 from which the anealing oven proper is supported is provided with a longitudinallyextending track in the form of a pair of laterally spaced raus 1a. e rt as @templates that the here; indescribed annealing oven will be usedwith other ovens and lthat all of the ovens will be arranged in side by said relation and so that the ovens proper `overlie and extend transversely or cross- Wise ofthe pit I2.

The raising and loweringmechanism for the bottom I9 is in the form of a transfer and elevator car comprising a rectangular, horizontally l0 form 15. thereof wheels I6 and these engage and are capable of travelling along the rails 13 and permit the truck to be wheeled along the track that .is .formed by said rails 13. An electric motor 11 is connected to certain of the wheels 16 by'way of 'speed reducing gearing 18 and operates when driven to propel the truck 14 along the pitv I2.

At the corners of-the truck 14 are uprstanding.

rotatably mounted screw shafts 19. 'Ihese have the lower ends thereof connected by gearing to a reversible electric motor4 80 onthe truck 14. The last mentioned gearing is so designed and arranged that when the motor 80 is driven in one directionvthe screw shafts 13 are conjointly rotated in one direction and whenthe motor SII is reversely driven the screw shafts are conjolntly` driven in the opposite direction. The platform v I5 is rectangular and has at its cornersxedly mounted nuts 8| which are mounted on the screw shafts 19. When the s'crew shafts are conjointly driven' in one direction the platform 15 is lcaused -to be loweredy and when the screw shafts are vconjointly driven inthe opposite direction the platform is caused to be raised. On'the top of the platform 15 are two laterally spaced rails 82. The latter extend transversely of the pit I2 and are adapted when the platform 15 is lowered to its fullest extent to bridge pairs of rails 83 which are mounted on the foundry oor II and lead from the sides of the pit I2. The end portions of the bottom I9 of the oven proper are provided with wheels 84 which when the bottom is supported by the platform 15 rests on the rails 82. As shown in Figures 1 and 2. the wheels 84 are disposed be-A of the I-beams 30. Stub axles 85 serve rotatably` to support the wheels 84 and have the ends there- "5" of journalled in bearings on the ends of the channel bc'ams'3l. When the platform 15 is lowered with the bottom I9 thereon the bottom, after the rails 82 on the platform 15 are brought into bridging relation with the rails 83 on the floor I I may be propelled along either pair of rails, to a casting loading or unloading station. The bottom I8 lof the oven proper is provided with lock bolts 86 for releasably locking it in its up or operative position. These lock bolts are four in number and are mounted between the ends of certain of the I-beams 3.0 so Athat they are slidable outwards into a bottom locking'position and inwards into a bottom releasing position. When the bolts are in their locking position the outer ends thereof rest on the inner portions of the bottom anges of the longitudinally extending I-beams I6 of the frame I4, as shown in Figure 6. When the bottom I9 is locked in its upper or operative position by way of the lock bolts86the transfer and elevator car comprising the truck 14 and the platform 15-may be used to raise or lower the bottom of anotherjannealing oven over the pit I2.

, When it isk desired to use the annealing oven the 15 bottom I! while supported on one of the pairs extending truck 14 and a vertically movableplatf The truck embodies at the corners` 9 of tracks 88 is loaded with the castings to be annealed. In connection with loading the castings are piled on the pan 28 constituting a part ofthe bottom I9. After loading the bottom I9 is propelled onto the'tracks 82 while the latter are Ain bridged relation with the tracks 83 as the result of the platform -15 being disposed in its fully lowered position. As soon as the bottom I9 is supported by the tracks 82 the motor 80 is operated so as to effect raising of the platform I and resultant upward shift of the bottom I9 into its up or operative position. As soon as the bottom I5 is in such position the lock bolts 86 are shifted outwards into their locking position wherein they serve to hold the bottom I9 in place. .As soon as the bottom I9 is locked in place the transfer and elevator car consisting of the truck 14 and the vertically movable platform 15 may be used to effect raising and lowering of the bottom of one of the other ovens, as heretofore described. Annealing of the charge, i. e., the pile of castings on the bottom I9, is effected by firing the oven proper. In connection with operation of the burner 45 the mixture of pulverized coal and air under pressure burns within the combustion chamber 42. The products, of combustion, as heretofore described, flow downwards through the radiant tubes 50 and are exhausted by the exhaust conduit 52 after successively passing through the exhaust manifolds 5|, the duct 63, and the duct structure 65. The radiant heat that is produced as the result of the products of combustion iiowing through the tubes 50' effects the desired annealing of the charge. The high temperature atmosphere within the annealing chamber 4I is constantly circulated by the motor driven fan wheel 68. After the annealing operation the transfer and elevator car is positioned under the oven proper and the platform 15 is elevated until the tracks 82 are in supporting relation with the wheels 84 at the ends of the bottom I9. After raising of the platform the lock bolts 86 are shifted inwards into their inoperative position so as to release the bottom. Upon release of the bottom the latter is lowered and then propelled laterally to the point or station where the castings are to be removed.

The herein described annealing oven is highly efficient and has extremely long life due to the arrangement and design of the radiant tubes 50. The expense of operation of the oven is comparatively low, especially when the oven proper is fired by pulverized coal equipment.

The invention is not to be understood as restricted to the details set forth since these may be modified within the scope of the appended claims without departing from the spirit and scope of the invention.

Having thus describedthe invention what I claim as new and desire to secure by Letters Patent is:

1. An annealing oven comprising a wall structure arranged to form an annealing chamber and a separate combustion chamber over the annealing` chamber, a plurality of laterally spaced, straight radiant tubes disposed at the sides of the annealing chamber, inclined upwards and inwards at a comparatively small angle with respect to the vertical and having the upper ends thereof communicating with the combustion chamber, and a burner adapted and arranged to burn fuel in the combustion chamber.

2. An annealing oven comprising a refractory wall structure consisting of a bottom, opposed side walls, opposed end walls and a roof and delining an annealing chamber therein, two opposed series of laterally spaced, truly straight and cylindrical radiant tubes disposed at the sides of the chamber respectively, and for the most part inwards of the side walls, inclined upwards and inwards at a comparatively small angle with respect to the vertical and having the upper ends thereof extending through the roof and their lower ends extending through the lower portions of the side walls of the wall structure, a pair of horizontally extending exhaust manifolds disposed outwards and extending lengthwise of said lower portions of the side walls and connected to the lower ends of the tubes, a fuel burner, and means for causing the products of combustion emanating from the fuel burner to flow downwards through the tubes.

3. An annealing oven comprising a wall structure consisting of a bottom, opposed side walls, opposed end walls and a roof and defininga horizontally elongated annealing oven therein, two opposed series of laterally spaced, straight radiant tubes disposed at the sides .of the chamber respectively and for the most part inwards of the side walls of the wall structure, inclined upwards and inwards at a, comparatively small angle 'with respect to the vertical and having the upper ends thereof extending slidably through the roof and their lower ends extending through the lower portions of said side walls, a pair of horizontally extending exhaust manifolds disposed outwards and extending lengthwise of said lower portions of the side walls and connected to the lower ends of the tubes, a fuel burner, and means for causing the products of combustion emanating from the burner to flow downwards through the tubes.

4. An annealing oven comprising a, refractory wall structure consisting of a bottom, opposed side walls, opposed end walls and a roof and deilning an annealing chamber therein, two opposed series of laterally spaced, straight, cylindrical radiant tubes disposed at the sides of the chamber respectively and for the most part inwards of the side walls, inclined upwards and in'wards at a comparatively small angle with respect to the vertical and having the upper ends thereof extending through the roof and their lower ends extending slidably through the lower portions of the side walls of the wall structure, a pair of horizontally extending exhaust manifolds disposed outwards and extending lengthwise of said lower portions of the side walls and connected to the lower ends of the tubes, a fuel burner, and means for causing the products of combustion emanating from the'burner to iiow downwards through the tubes.

5. An annealing. oven comprising a refractory wall structure consisting of a bottom, opposed side walls, opposed end walls and a roof and dening an annealing chamber therein, two opposed series of laterally spaced, truly straight and cylindrical radiant tubes disposed at the sides of the chamber respectively, and for the most Vpart inwards of the side walls of the wall structure, and having the upper ends thereof extending slidably through packing equipped openings in the roof and their lower ends extending slidably through packing equipped openings in the lower portions of the side walls of the wall structure, a pair of horizontally extending exhaust manifolds disposed outwards and extending lengthwise of said lower portions of the side walls and connected to the lower ends of the tubes, a fuel burner, and means for causing the products of combustion emanating from the burner to iiow downward through the tubes.

6. An annealing loven comprising a wall strucl ture consistingof a bottom, opposed side walls,

opposed end walls, a .rst roof between the central lportions of the side and end walls and a second roof between the upper portions of said -side and end walls and denin'g a lower annealing chamber and an upper combustion chamber, aplurality of laterallyspaced straight radiant .adapted and arranged to burn fuel in the combustion chamber.

7. An annealing oven comprising a wall structure consisting of a bottom, opposed side walls,

opposed end walls, -a first roof between the central portions of the side and end walls and a second roof between the upper portions of said side and end wallsand deiining a lower annealing chamber and an upper combustion chamber, two opposed series of laterally spaced straight radiant tubes disposed at the sides of the annealing chamber respectively, inclined upwards and inwards at -a comparatively small angle with respect to the vertical, and having the upper ends thereof extending through the first roof ,and communicating 'with the combustion chamber and their lower ends extending throughthe lower portions of the vside walls and terminating exteriorly of the wall structure, a pair of horizontally extending exhaust manifolds disposed `outwards and extending lengthwise of said lower portions of the side walls and connected to the lower ends of the tubes, and a. burnervadapted and, arranged to burn fuel in the combustion ch.

8. An annealing'oven comprising/a ilre brick wall structure consisting of a, bottom, opposed side walls, opposed end walls. a iirst roof between the central portions of the side and end walls and a second roof between the upper portions of said side and end walls and dening a lower horizontally elongated annealing chamber and lan. upper horizontally elongated combustion chamber, two opposed series of laterally spaced straight radiant tubes disposed4 at the sides of vto the lower ends of the tubes, and a burner extending through the upper central portion of one of the end walls and arranged and adapted to supply lengthwise through the combustion chamber a mixture of powdered fuel and air under pressure for burningin said combustion chamber.

9. An annealing oven comprising a iir brick wall structure consisting of a bottom, opposed side walls, opposed end walls, a first roof between the central portions of the side and end walls and a second roof between the upper portions of l said side and end walls and defining a lower horizontally elongated .annealing chamber and an .upper horizontally elongated combustion chamber, two opposed series of laterally spaced straight radiant tubes disposedA at .and extending along the side of the annealing chamber respectively, inclined upwards and inwards at a comparatively small angle with respect to the ver-v tical, having the upper ends thqeof extending through the roof and communicating with the combustion chamber and their lower ends extending through the lower portions of the side walls and .terminating exteriorly of the wall structure and provided with control valves therein, a pair of horizontallyextending exhaust manifolds disposed outwards and extending lengthwise of said lower portions of the side walls and connected to the lower ends of the` tubes, and a burner extending through the upper central portion of one of the end walls and arranged and adapted to supply lengthwise through the combustion chamber a mixture of powdered fuel and air under pressure for burning in said combustion chamber.

10. An annealing oven comprising a wall structure arranged to form an annealing chamber and a. separate combustion chamber over the annealing chamber, a plurality of laterally spaced, radiant tubes disposed at the sides of the annealing chamber, inclined upwards and inwards at a comparatively small angle' with respect to the Vertical and having the upper ends thereof straight and communicating with the r combustion chamber, and a burner adapted and arranged to burn fuel in the combustion chamber.

11. An annealing oven comprising a wall structure consisting of a bottom, opposed side walls, opposed end walls, a first roof between the central portions of the side and end walls and a second roof between the upper portions of said side and end walls and defining a lower annealing chamber and an upper -combustion chamber, two opposed series of laterally spaced radiant tubes disposed at the sides of the annealing chamber respectively, inclined upwards and inwards at a comparatively small angle with respectvto the vertical, and having the upper ends thereof straight, extending through the, first roof and communicating with the combustion chamber and their lower ends terminating exteriorly of the wall structure, a pairof horizontally extending exhaust manifolds. disposed outwards. and

extending lengthwise of the lower portions of the side walls and connected to the lower ends of the tubes, and a burner adapted and arranged to burn fuel in the combustion chamber.

CLARENCE R. TAYLOR.

REFERENCES CITED The following references are of record in` the ille of thispatent:

UNITED sTATEs PATENTS