US1451815A

US1451815A - Rapid decorating firing furnace or kiln

Info

Publication number: US1451815A
Application number: US433328A
Authority: US
Inventors: Ransom W Davenport
Original assignee: JEFFERY DEWITT Co
Current assignee: JEFFERY DEWITT Co; JEFFERY-DEWITT Co
Priority date: 1920-12-27
Filing date: 1920-12-27
Publication date: 1923-04-17
Anticipated expiration: 1940-04-17

Description

Apr. 17, 1923.

Filed Dec. 27, 1920 5 Shets-Sheet l r/PMM Apr.17,1923. 1,451,815

R. W. DAVENPORT RAPID DECORATING FIRING FURNACE ORIKILN Filed Dec. 27,1920 5 sheets-sheet `2 INV ENTER Apr. 17, 1923. 1,451,815

R. w. DAVENPORT RAPID DECORATING FIRING FURNACE `QR KILN Apr. 17, 1923. 1,451,815

R. w. DAVENPORT RAPID DECORATING FIRING FURNACE OR KILN Filed DeC 27, 1920 5 Sheets-Sheet 4 Apr... 17, 19213,

R Ah-DAVENPORT RAPID DECORATING FLRING FUBNACE 0R KILN Filed DQS.-

`15320 5 Sheets-Sheet 5 Patented Apr. 17, 1923.

' UNITED STATES PATENT OFFICE.l

RANS'OM W. DAVENPORT, OF DETROIT, MICHIGAN, ASSIGNOR TO JEFFERY-DEWITT COMPANY, OF DETROIT, MICHIGAN, yA CORPORATION F MICHIGAN.`

RAPID nEcoRATrNG FIRING rtrniaon on Kinn.

Aptnction inea'nember 27, 1920. serial No. 433,325.

To all wh om 'it man] con cern Be it known that Ransom 1V. DAVEN- PORT, afcihtize'n of the United States, and a resident of Detroit, count-yet' lVayne.k and 5 Stateof il/Ii'chigan`r have made an` .invention`l 'appe lining to Rapid Decorating Firing Furnaces or Kilns; aiidI do hereby declare the following lto be a full, clear,l and exact description of the invention, suchas ywill l0 yenable others skilled in the art to 4which it v'appertaiiisk to make and use the same, reference beinghad to'thc accompanying' drawand tio the ,characters of reference marked thereon, which form a, part of this specification.

My invention has for itsobject to proif'i'de a furnace or kiln for heat treating materials such as vceramic lWare yand metallic an tic-les, ,whereby ithe,temperature of the ar- "ticles and the Increment of reactive gases or vapors may tbe controlled to obtain maximum thermal economy and` chemical erli- Icie'ncy, and high speed of production.

It particularly has for its` object. to pro- Vide in Aa furnace or kiln, a mea-ns `Whereby the ceramic yWare may be continu`ouslY operated step by step to gradually increase the temperature ofthe ceramic 'Ware and to gradually cool the vceramic Ware While being subjected to an atmosphere that will cause or permit certain modificar tions to take place in the Ware lor at the surface of the Ware. It also has for its object to subject the ceramic ware to a regulatixetemperature in close confining chambers 'While the yceramic Ware is subjected to a moving vapor or gas that -eoacts with the heating means of the kiln to form the decorations in the glaze of the ceramic irare`r ,such as for example. 4directirig air in close 'proximity and in Contact. With the 'ceramic Ware While vbeing heated. Wherebj1 the teinperature of the lkiln is not only regulated ont also the'oxygen of the airis distributed uniformly so as to cause or permit reaction at tl1e\-prope.r' tin'ies in the `ten'iperature changes to which thecer'aniic ware is subjected. l H u K l The inyentiona'lsolias 'for i'ts'object other advantages and features which will appear from the following'description and upon examination of the drawings. The ini'e'ntion be contained and performed in furnaces l and kilns .of vdiiferent -l l il iffiitfpuips To illus trate a practical application of the invention. Ihave selected a kiln as an example of such structures and shall describe it hereinafter. The kiln selected for purposes of illustration is shown in the accompanying drawings.

Figure 1 of the'drawings isa longitudinalsectional vienv of apart ofthe kiln selected. Fig. 2 is a.v sectionalview taken on the line 2 -2 indicated in Fig. 1. Fig'. 3 is afsectional vien" of the feeding mechanism. F ig.' 4 is atop Viewkof the' feeding mechanism, the table top shown in Fig. Shaving been removed. Fig'. 5 is one side View of the feeding mechanism and Fig. 6 is another side rien* of the feeding mechanisInfv Fig.'7 illustrates a broken View of the feeding block shown in 3 and Fig. 8 is a. broken View of; the positioning block, also shownin Fig. 3f Fig. 9'is an end View of the positioning block shown in FigB. Fig. 10 illustrates somewhat diagiamniaticallylthe relation of the positioning block to the chambers of the kiln. Fig. 11 is a side View offthe means for pneumaticall;7 controllingv the feeding mechanism; Fig. 12 isa longitudmal sectional vien' of the pneumatic controller illustrated in Fig. 11. Fig. 13 isan end View ofthe control'er illnstratedin Fig. 11. Fig. 14 is an vend 'View of therotary valve that pneumati'calljf controls the feeding mechanism. Fig. 15 is a sectional View taken on the line 15-15 indicat'edin Fig. 11. Fi'gyl is a] diagrammatical' View of the circuit of the heatingl element.

1. in Fig. 1, indicates a supporting frame or standard. which may be yof anxY form, for 'supporting the kiln and the feeding mecha.- nism and: parte associated therewith. 2 is a. box preferabl)T formed of sheet metal for enclosing the kiln'. A plurality of long tubular members 3 li ring a diameter slighly larger 'than the transverse dimension of the articles to be operated upon. are loca-ted in the box orcontainer 2 andare surrounded by heat insulating Ymaterial 1,'such-as infusorial earth. Within the heat insulating ymaterial 'and in close proximityto the banky of tubular members 'isv located an oblong frame 5 'that surrounds the `central portions of the bank of tubular meinliiers il. sbestos sheeti'n'g surrounds the frame 5 and as to enclose the spaceuihin the fraine 5.. A pluraL it;Y of resistors 7 are located Within the frame 5 'and are supported in any suitable manner by th frame '5, While the Seme time Y1si-lit able insulators are located intermediate the resistors 7 and the frame 5 `to prevent conduction oit the electric current that passes through the resistors.

The resistors are located in parallel relation with the tubular members and are so placed in the frame 5 that each tubular member is located between a pair of resistors. Resistors are also located in proximity to the outer sides o1c the outer tubular members 3. By this arrangement a regulative heat of high temperature is produced within the contines ot the asbestos sheeting G and within the oblong frame 5 and at the central portionv of the bank of tubes 3, the

heat beingv confined by the heat insulation 4. The heat insulating materiale surrounding the tubes and Vparticularly surrounding the .grid formed bythe resistors,'is of considerable thickness which prevents practically the loss of' any heat 'from the kiln by conduction. Moreover. the' tubular members 3 are con siderably longer than the grid.

.The resistors are connected in series with each other and to the main line as indicated in Fig. 16.

The trame 5, containing and supporting .the resistors, 1s connected to a plurality of rods Sth'atare suspended from angle irons Slthat extend across the kiln. The ends of the angle irons 9 are supported at the sides ol' the kiln, as upon the angle irons 10 that extend along 'the sides of the kiln.

A lfuse wire or member 1l may be located above the asbestos sheeting 6 or in any other position in proximity to the resistors "i". whereby the circuit of the resistors may be broken if the temperature increases above 4a rcertain limit. This operates to protect the grid from an over supply of current that may be conductedtothe grid.

rlhe tubular members 3 extend through the box or container 2 and the ends thereof tit closely the ends of the container 2. Y Ceramic bodies 73 may thus be passed through the tubular members 8 and consequently passed between the resistors 7 located in the central portion ot the container 2 and finally delivered from the ends of the tubular members.

suitable'trough 12 may be provided for directing` the ceramic bodies into a receptacle such as the receptacle 13.

While the ceramic bodies are being moved through the tubular members 3 and being subjected to the temperature changes, a vapor or* gas is also directed through the tubular members 3 to raise and lower the temperature of the ceramic'bodies and also thatV in' which the ceramic bodies move as they progress through the tubular members tained in each 3. They will then be successively raised in temperature, maintained for a short period at the desired temperature and subsequently cooled by the moving gas or vapor while at thesame time the active elements of the gas or vapor are brought into intimate relation with the ceramic bodies to cause or permit the necessary chemical reaction of the decorative material as it is being formed in or at the surface of the ceramic bodies. lt oxygen is the desired reagent for forming the decorative material at the surface of the ceramic bodies, air may be directed through the ends of the tubular members and caused to flow in a direction reverse to that in which the ceramic bodies progress through the kiln and the flow thereof may be regulated so as to permit the ceramic bodies to rise and fall in temperature at the desired rates and be maintained at a desired temperature while at the same time the arrangement of the parts of the kiln is such that an intimate contact is brought about between the decorative material and the gaseous reagent. The air may be torced through the tubular Vmembers 3 or it may be drawn through the tubular members. lllhere air is used in the operation of the liln. l iindit preferable to draw atmospheric air through the tubes and l provide means tor enclosing the ceramic body receiving ends of the tubular members. llhere some other gaseous material is used to treat the decorative material. I find it preferable to torce the through thetubes and direct it into the tubes at the delivering ends ot the tubes. These ends of the tubes may also be enclosed so as to permit delivery ofthe articles treated and yet direct gaseous materials int-o the tubular members. LIn `the ltorni of construction shown in the drawings. air is drawn through the tubular members 9. the receiving ends of the tubular members being enclosed. together with mechanism for delivering the ceramic bodies to the receiving ends of the tubes. in a shell or casing that is connected with a suitable suction means.

14. in Fig. 3. is a pipe that is connected with a suction means. siich as a centrifugal exhauster. The pipe 14 communicates` with a chambei l5 located in casing` which isconfnected with the tubular members. or covers the endsof the tubular members whereby the air is drawn through the bank of tubular members. l The tubular members. being slightly-.greater than the cross dimensioniof the beramic bodies with which they are i'lled. comosman tively a very small. area of air 'stream through the tubular members is produced which brings the air into intimate Vand close Contact with each of the ceramic bodies cono't the tubular members. Also` to the airl iow is great. while exhaustion. or vacuous condi the resistance the degree of tion ofthe chamber 15 lis relatively high. In other `words5 the-quantity ofair'moving through the tubular members is small but the vclocityis high. rlhe movement of the ceramic bodies through the tubular members 3 'is step bystep and intervals of. time are permitted to lapsebetwee'n each step by step movement. The ceramic bodies are `thus raised in.v temperature yat a uniform rate and yet, comparatively, 'rapidly raised to the desired high 'temperature and maintained at that temperature during a number of such intervals' and then gradually cooled by the air'e'ntering thev delivering ends of the tubular `members. The movement of the air throu'gh'the tubularimembers does not cause a loss of the heat produced 'by the heating element, but' operates, in a more or less degree, to move the zoneot high temperature gforward, that is, toward the *receiving ends Vof the tubular mem-bers.; The air entering, gradually cools the'ceramic bodies.l as they are carried'. from thezone. of highv tempera- Ature 'and is itself-'raised vin temperature to [that-produced by the grid of-resistors and on -further 'movement this high temperature is conveyed to the ceramic bodies as they approach. the yzone of high".y temperature .while it 'itselfis being'cooled, until it finds its exit into the chamber 15. Duringthis movement ofl the air' relative `to the ceramic bodies, the chemical reaction-of the oxygen `ot the air on the decorative materials gradually takes place. l v

`Where air isused, thereaction may beto roxidize certain ingredient-sof the decorative vcoating; suchas the oil used as a vehicle for 'the-pigment;` and in this case itis importa-nt 'to oxidi'z'e and remove, by wayothe air current, all carbonaceous matter and the prodvucts of vits combustion before the ware 'reaches temperature sufiicient to iuXvthe decoration into the surface of the ware, else bl'ackening of the decoration may result.

WOther reactions may also be effected, or 'inhibitedby the-v use'ofother reactive or inert gases which may be'broughtinto intimate contact'with allparts of theware-at any desired temperature within the range of activity ofthe ingredients of'the decorative coating.

By this'arrang'ementevery particle of the "air lcomes f into Contact with the ceramic bodies.v wherebyv heat is transmitted one to thefother without lloss'or` thermal efficiency fand falso within theirange of receptivity of `.the ingredientfmoditiedqby the `gaseous or I vaporous atmosphere contact with; the ceramic body so" that as fthe decorative -maated ini the' ceramic`Y bodies at; their.' surfaces.

.fl-@aeimmane@tf-:aambeienmaar@3 tari-als orthe .ingredients A"thereof are modirelation to the tubular members 3. Between lthe ends of the plungers 19 and the ends of `the tubular'members 3, is located a positioning block v20 which is pivotally supported, in its relation to the enclosing walls of the chamber 15, by means of the centering pin 21 and the shaft 22. The shaft 22 is secured in the boss '23, formed on the end of the .positioning lock 20, by means of thepin 24. The shaft 22 is pivoted in one of the wallsV of the chamber 15 and is connected to thea-rm 2,5.to produce oscillatory move- "ments of the block 20. The axis of the pin 21, and the shaft 22 is located in proximity Ato the lower forward corner of the delivery block 2() and consequently the block 20 is vtiltedupwards soasto bring the lower` side of the block 20 in line with the end of the tubular members 3 and of the feeding tubes 7 26. The forward side of the block 20 is beveled sol as to permit the oscillatory move- -ment of the block so as to bring the bottom ot the block in line with the bottom of the ltubular members 3 when in one position and the feeding tubes 26 when in the other position. v

`The 'feeding tubes 26 are also located in the chamber 15 and are located in an inclined position so as to cause the ceramic bodies which are inserted/therein to slide onto-the block 20 from whence they are pushed by the plungers 19 into the tubular members 3 when the block. 20 is lowered so asto be placed 1n line with the plungers 19. andthe tubular members 3. Y `The position of the block 20 when in, its lowered position may be regulated by means of the screws `74 on which the block rests when in its lowermost position.

The chamber 15 is., in the form oit the intion of the chamber 15 with the outsidev atmosphere would short circuit any moving V"air 'through the tubular members to the chamber 15. F or this reason one vor the otherend `of each of the inclinedgfeeding tubes 26 is kept closed b v a suitable door. E1n the-form of the invention shown I have provided a door f27`that ycovers the lower e'ndsbt' the -inclinedt'eeding tubes 26. rhe

-doorf27-is connected to the shaft 28 whereby bodies that have been placed in the tubes 26 to fall into the block 20. The vblock 2O is provided with a plurality oftroughsv29 whichare adapted to register withthe in clined" feeding tubes 26 andthe tubular members 3. llhenthe door v27 is opened the block 2O is also raised and as the ceramic bodies pass fromA the endsofthe inclined feeding tubes they enter 'the troughs 29 and then immediately by vtheir momentum and by the inclined position ofthe trough of the block 2O enter the ends of the tubular members 3. The block is lowered and the plungers 19'are thenA moved forward so as to move all of the ceramicbodleswithin the tubular members 3 the length of each of the ceramic. bodies. The shaft 28 is pivotally supported on the walls of the chamber 15 and is provided with an arm 30 which is Vconnected by means of a llink 31 to a-plunger bar 32 that is operated by a piston and vcylinder 33, whereby the plunger bar 32 is moved rearward which pulls the link 31 rearward and the arm 30 downward and forward thereby causing rotation of ythe shaft 28. .The shaft 28 is also-provided with an arm 34 which is connected by mean's'of a link 35 to the arm 25 located .on the shaft 22. Simultaneously with the movement of the arm 30, the shaft 22 isv rotated, which causes the block 20 to rise and receive the ceramic bodies that are admitted upon openin'gfof the door 27 and deliver them to the ends of the tubes 3. Y

The bar 32 is provided with a means for preventing rotation vof the bar during its operation upon the link 31. of construction shown the bar 32 has a square cross-section along a part thereof,

that lis located in the pillow y36 having the vsame cross section.

The decorative materials may be placed lon the ceramic bodies in' any way desired.

I have shown somewhat conventionally a printing machine 37 that is located yon the top of the table. rIhe ceramic lbodies are taken from the printing machine 37 and placed in a feeding block- 38 which is' disposed at a convenient position relative to the printingv machine and below the table top. The block 33 is provided with a plurality of troughs 39 into which the ceramic bodies may be placed by hand or by any other suitable means. The troughs 39 are located substantially in alignment with the ends'of the inclinedfeeding tubes 26. A. plurality of plungers 40 are located in line with 'the troughs 39 and when the plungers are moved forward the ceramic bodies placed within the troughs 39 are pushed into the upper ends of the inclined feeding tubes 26. They then slide down the inclinedfeeding tubes'26 until ,they slide into the ends of the tubular members 3 since the 'n door is opened f substantially at the Ysame vIn the vform i time or shortly after the beginningof the forwardmovement of the plungers 40.

'l .The plungers 40 are connected to `a crossbar 41 loca-ted on ways 42 on which the ends` ofthe bar 41 slide.v IThe cross-bar 41visconnected with links 43 to arms `44 keyed to the shaft1 45. One of the links 43 and one of the arms Ll4-are connected by means of afspring 46with a link 48 through a'slotted plate47 and the screw 49. The spring tension as between the shaft and the link 47 may be adjusted by Vthe slotted plate 47 andthe screw 49, whereby the .plungers 40 are yieldingly moved against theceramicwbodies located on the block 38. This is a protecting means for preventing the injury ofc-perators when placing ceramic bodies in the troughs'39. The link 47 is connected tol an arm 5() located on thenon-rotative plunger bar 32. The operation of the piston 71 and cylinder 33 causes the operation of the plungers 40 and the block V20 and, aty a very short interval thereafter, the opening of the door 27. The link 31 is located at right angles to the arm 30 whenthe door 27 is closed and thus locks the door 27 in its closed position and prevents the reduced pressure in thechamber 15 .fromwopening the ,door -hy the difference in pressures on the door.

Under certain conditions the feeding block 38 may be eliminated Aand the ceramic ybodies placed in the block 20 directly, but

for convenience of Vmanipulation I have provided a means whereby the tubular, members 3 may-be located well below` they vtop 72 of the table to provide space for the heat vinsulating bed in which the tubular members 3 are locatedl and` give room Afor inspection ofthe porcelain bodies or for other purposes on the table top. This is obtained'4 by keeping the table top at the proper working height. Byl providing the means for feeding the ceramic'bodiesto the positioning block, T have provided a Ameans `whereby' the ceramic bodiesfmay be placed in recesses located in proximity .to the table top and also' in proximity to the delivering end of the printing machine, whereby the 'operative expense' of feeding the porcelain 'bodies to the kiln is materially reduced.y

The plungers 19, the plungers ,40, the block 2O and the door 27 are operated at proper intervals of time to move or per-` mit the movement of the ceramic bodies into the tubular members 3. The alternatel operation-of

the'plungers

19 and 40 isobtained Vby means of the rotary valve' 51 which is loc-ated onthe. shaft 52 and is rotated by any suitable means, such as by the gear wheels 53 that are connected with' any source *ofy power, such. as to van electric motor. The -valve memberl is keyed to the shaft 52 which extends throughv a housing`73.. The shaft 52 has a reducedportion 54 leaving a space between the shaft llO 52 and. the housing 73, While thevalvel.

the housing 73. The valve housingv 73 is closed by al lenticular plate 59that is connected by means of a pipe 60,with a source of compressed air. Air entering through the pipe 60 passes through the opening 55 and alternately enters the passageways 56l and 57.y The passageway 56 is connected through the pipe 61 to the cylinder 17 for the-.operationofthe piston16 and the pas,- sageway 57 is connected through thel pipe 62 with the cylinder 33, whereby the pressure is. communicated through the valve membernl to the pistons contained in the cylinders and they plungers 4Oand19k are operated alternately.

The. valvememberl rotates in the direction indicated'I in Fig. 14 and thecham nel.` 58 is locatedl on thefollowing side of the.y open-ing`55. The space between the shaft 5,2 and. thehousing is connected to the outsideatmosphere by thek passageway or opening 63.v Airpressure is thus alternateiyprodueed inthe pipes 61 and 62 and be hind the pistons in the cylinders 17 and 33 and then exhausted, or reducedl by the communication that is establishedthrough the channel 58 registering, with ther openings 56 and 57H and establishing a communicaf tion with the'exterior atmosphere .through theopening` 63, immediately after the plungers havehad opportunity to perform theiry 'forward movements. The pistons are connectedl to rods 64 that extendI through plates 65loca-.ted'on the ends ofthe cylinders. The rodsv 64 are provided with washers 66 that are secured on the rods vby Ierieansy ofthe nuts 67 and springs 6 8 are located intermediatethe washers .66 andthe plates 65 whereby the `springsf68 will be compressed by the forwardmovementfof the pistonsy when subjectedy to the air pressure admitted' througlrthe operation of thel valve 51.2'y When communication is established between the cylinders and theA atmospheric air through the channel 58 located in the valve 51, the springs68 operate to cause the. pistons` and the plungers to return.

This causes the. plungers to reciprocate alternately and moreover causes the plungers l9tom'ove the ceramic bodies contained in the tubular members 3 forward the length of the. ceramic. bodies at intervals measured Aby the` cycle of operations performed by the valve 51.

The valve ,51. is sotimed that the cycles are` performedat" such intervals, that, op.- portunitv if, 'fiven for .filling the feeding block 3.8.v It is alsdso timed relative to,

perature of the ceramic bodies will be raised, maintained and lowered and the temperature of the vaporous or gaseous materialsby heat transmission will be raised, maintained and lowered so as to secure the desired decorative effect as described above.

1. In a furnace for heat treating bodies a tubular member for containing bodies, means for heating the central portioniof the kwall of the tubular member, a plunger for movingthe bodies through the tubular member, and means, for directing a chemical reagent through the tubular member.

2.V In a furnace for, heat treating. bodies, a tubulary member for containing bodies, meansr forheatingthe centralvportion of the wall of the tubular member, a plunger for moving the .bodies through the tubular member, and means` fory directing a chemical reagent through the tubular member ina direction reverse tothat inwhich the bodies are moved. i i

3. Inra lfurnace for heat. treating bodies, an elongated'- tubular member, means. for mov-ing the bodies through the tubular member, means for. heating the central portion of the walls of the tubularl member, and means for directingA a' movinglheat transferring material through the tubular memberk in a direction opposite to that in whi'chthey bodies., are y moved.

4. Inw'a` furnace for. heatr treating bodies, a tubular member, means lfor moving the bodies through lthe tubular. member, a heater for heating a'y portion of the walls vof' the tubular'member, and means fory transferring the heat ofthe bodies leaving the said portion of the tubular member to the bodies entering. the said portion. i,

5. In a. furnace for heat treating bodies. a long tubular member, the interior having a crossI sectional area slightly greater than the. major cross sectional area ofthe bodies, means for, heatin the central portion of the wallsof thetubidar member, a plunger for moving the bodies and the tubular member the. length of the bodies, and means for directing air through the tubular member.

6. Ina furnace lfor heatv treating bodies, a long tubular member, the interior having a cross sectional area slightly greater than the major cross sectional area of the bodies, means fork heatingthe central portion of the walls of the tubularmember, a plunger with the tubular member land with the plunger, a chute for directing the bodies to the positioning block, and means for closing 1 y the lower end of the chute.

7. 'In a furnace for heat treating bodies, along tubular member, the interior having a cross sectional area slightly greater thanI tioning block loca-ted in alignment with the tubular member and With the plunger, a chute for directing the bodies to the positioning block, means for closing the lower end of the chute, a feeding block located in alignment with the upper end of the chute, and a plunger fo-r moving the bodies from the feeding block to the chute.

Y8. In a furnace for heat treating bodies, along tubular member, theinterior having across sectional area slightly greater than theimajor cross` sectional area of the bodies, means for heating the central portion of the Walls of the tubular member, a plunger for moving the bodies in the tubular member the length of the bodies,cmeans for directing air through the tubular member, a positioning block located in alignment with the tubularmember and With the plunger, a chute for directing the bodies tothe positioning block, means for closing the lower end of the chute, a feeding blocl; located in alignment With theupper end of the chute, a plunger' for moving the bodies from the :feeding block to the chute, and means for ,causing the alternate operation of the said plunger.

9. In a furnace for heat treating bodies, a plurality of tubular members, an electricl heatingv grid surrounding the tubular members, a heat insulating material surrounding the tubular members and the grid, a plurality of plungers for moving the bodies in the tubular members the length Vof the bodies.

. 10. In a furnace for heat treating bodies, av plurality of tubular members, an electric heating grid surrounding the tubular members,v al heat insulating material surrounding the tubular members and the grid, the cross sectional area of the interior of each of the tubular members being slightly larger than the majorcross sectional area of the bodies, and avplurality of plimgers for moving the bodies the length ofthe bodies at intervals in the tubular members.

l1. In a furnace forheat treating bodies,`

a plurality of tubular members, an electric heating grid surrounding the tubular members, a heat insulating material surrounding the tubular members and the grid, the cross sectional area of the interior of each of the tubular members being slightly larger than the major cross sectional area of the bodies,

a plurality of plungers for moving the bodies the length of the vbodies at intervals in the tubular members, a shell for enclosing the ends of the tubular members, and means lfprv directing air through the tubular mem-v ers.

l2. In a furnace for heat treating bodies,

a plurality of tubular members, an electric heating grid surrounding the tubular members, a heat insulating material surrounding the tubular members and the grid, the cross sectional area of the interior of each of the tubular members being slightly larger vthan the major cross sectional area of the bodies, a plurality of plungers'for moving the bodies the length of the bodies at intervals in the tubular members, a shell for enclosing the ends of the tubular members, means for directing air through the tubular members, a positioning block having a plurality of troughs for placing the bodies in line with the plungers and the ends of the tubular members and located inthe shell.

' 13. In a furnace for heat treating bodies,

tubular members, a shell for enclosing the i,

ends ofthe tubular members, means for directing air through the tubular members, a positioning block having. a v'plurality of troughs for placing ythe bodies inline vWith the plungers and the ends of the tubular members and located in theshell, a plurality of inclined chutes fordirecting the bodies to the positioning block, and a door for closing the ends of the chute and located in the shell.

lll. In a furnace for ,heatl treating bodies,

a plurality of tubularmembers, anelectric heating gridsurrounding the tubular members, aheat insulating material surrounding the tubularmembers and the grid, thecross sectional area of the interior of each of the tubular members being slightly larger than the major cross sectional area of the bodies, a plurality of plungers for moving the vbodies the length of the bodies at intervals in the tubular members, a chamber for enclosing the ends ofthe tubular members, means for directing air through the tubular members, a positioning block ,having a plurality vof troughs for placingctheV bodies in line lwith the plungers and the ends ofthe t tubular members and located in the chamber, a plurality of inclined chutes for directing the bodies to the positioning block, a door` for closing the ends ofthe chute and located in the chamber, a feeding block having a plurality of troughs locatedin line with the feeding chutes, and a plurality of plungers for moving the bodies from the feeding troughs into the chute.

l5. In a furnace for heat treating bodies, a plurality of elongated tubular members, an electric heating grid surrounding the tubular members, a heat insulating material surrounding the tubular members and the grid, the cross sectional area of the interior of each of the tubular members being slightly larger than the major cross-sectional area of the bodies, a plurality of plungers for moving the bodies the length of the bodies at intervals in the tubular members, a chamber for enclosing the ends of the tubular members, means for directing air through the tubular members, a posltioning block having a plurality of troughs for placing the bodies in line with the plungers and the ends of the tubular members and located in the chamber, a plurality of inclined chutes for directing the bodies to the positioning bloc-k, a door for closing the ends of the chute and located in the chamber, a feeding block having a plurality of troughs located in line with the feeding chutes, a plurality of plungers for moving the bodies from the feeding trough into the chute, and means for causing the two sets of plungers to operate alternately.

In testimony whereof I have hereunto signed my name to this specification.

RANSOM W. DAVENPORT.