US1731165A - Method of and apparatus for the distillation of carbonaceous material - Google Patents

Description

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Q 1 L', aff Z O. H. HERTEL METHOD 01"'v AND APPARATUS FOR THE DISTILLATION OF CARBONACEOUS MATERIAL Filed March 15, 1924 Paieted oct. 8, 1929 OTTO H. HERTEL, OF CHICAGO, ILLD'OIS` METHOD OF AND APPARATUS FOR THE DISTILLATION OF CARBONAOEOUS MATERIAL Application filed Maren 15, 1924.'4 s'eriai No. 699,402.

The invention relates generally to a method of and apparatus for driving oit' the volatile matteil in coal and ot-her carbonaceous material. The object of the invention, generally stated, is Vto deliver to the charge a relatively large amount of heat in va relatively short period of time without raising the charge or the evolved gases to a high temperature.

l The quality and character of the gases evolved in the coking of coal depend considerably upon the temperature at which the operation is conducted and the duration ot' the heating. To obtain the most desirable coke and gas, continued overheating or local superheating ot' the charge must be avoided, since it results in execs "ve, decomposition and in the formation ot' undesirable compounds as well as giving al variable composition tothe gases, b'uperheating of gases in vertical retorts is generally less than in other types of retorts or ovens because the gases pass up centrall v.through the charge and areh therefore partially protected from the heated external W walls ot' the retort, S'uperheating, however, i is not entirely obvia'ted, since there is considerable. impedance to the upflow `of the gases due to their slow and tortuous passage through the mass of heated coke. or coal.

Au important object of the invention therefore is to provide a vertical retort in which the gas-'es may be quickly removed therefrom and in which the gases near the outer heated walls may be quickly drawn away toward the center ot'fthe retort and thence removed directlyl into the gas main.

lleretot'ore it has been proposed to withdraw the gases through a central passageway or conduit built into the retort. The means t'or doing this have been variously applied 1n ditl'erent forms ot' hollow members forming the cond uit into which the gases were receive through suitable openings. Such a conduit, however` is subject to fouling b v the accumulat ion of tar and carbon within the tube itself and within the openings thereof.

A further object of this invention isto form or create a gas passage of which the charge itselt' constitutes the walls, the interstices of the charge heilig the openings through which 5D the gases enter the passageway. By such a method, fouling is prevented, and the walls are being constantly renewed with each new charge. of coal into the retort.

A further lobject is to provide a vertical retort comprising mechanical means for creyating and maintaining the gas passage through the charge.

In using such a mechanical means located within the charge, the same would ordinarily be subject to fouling in muchthe same manner as the walls of the perforated tube of prior devices. It is therefore a further object of my invention to provide means for heating said mechanical passage-forming means to destroy the fouling matter thereon.

It is a further and very important object of the invention to utilize the heated mechanical means as an internal source of heat to supplenient the external heating of the charge whereby the time of heating a given charge is materially shortened.

A still further object is to apply the heat internally of the charge by means of a heated surface moving in contact with the material, whereby a relatively great. amount of heat is delivered to the charge withoutraising the temperature above the desired point.

A further object ofthe invention is to subject the charge to vertical and lateral pressure during the distillation process to improve the, quality of the coke thus produced.

Still another object is to provide coactng means at each end of the retort for effecting a discharge of coke therefrom.

An apparatus embodying my invention is shown in the accompanylng drawings in -which- Figure 1 is a longitudinal vertical section ot' the retort.

' Fig. A2 is a cross section along theline 2-2 of Fig. 1 showing the arrangement of the parts within the retort proper.

Fig. 3 is a fragmentary longitudinal s ection of the, retort taken along line 3--3 of Fig. 2.

Fig. 4 is a detail view of a heated tubular member which produces the passageway through the retort, showing also one type of heating means therefor.

Fi s. 5, 6 and 7 show modified or alternative orms of the passage-forming means.

Fig. 8 is a cross-section of a retort having a single,` passage forming element.

Fig. 9 is a detail cross-section along line 9-9 of Fig. 1.

The vertical retort 10 is relatively narrow in one direction, say, twelve to eighteen inches in vwidth and of a height suitable for the character of the coke desired. It may be indefinitely extended horizontally by increasing the size of the retort and adding more passage-forming elements. However, it is to be understood that a plurality of passageforming elements of the type to be hereinafter described is not essential to the invention, and

that a single one as shown in Fig. 8 may bey employed which would preferably be used in a retort substantially circular in cross-section.

The retort 10 'has a slight taper inwardly toward` the top to facilitate the dischar e of coke downwardly. It comprises at the ower end, a discharging mechanism; at the upper retort. It will be understood that the present invention is independent of the particular kind of fuel employed, and that coal, breeze, oil or any other fuel may be used, as desired.

In the embodiment illustrated in the draw-- ings, a heating chamber 12 surrounds the retort in the heated zone, suitable brickwork 13 being provided for the purpose. Heat is supplied to the retort by the introduction of fuel in the form of gas through admission ports such as 14, 15, 16 and 17 suitably disposed in the brickwork laterally and vertically to secure the best distribution of heat to the retort. Chimneyoutlets such as 18 are provided in the walls. near the top of the oven to conduct away Vthe vgaseous combustion products.

In starting the heating means, explosions frequently result due to the sudden ignition of residual gases remaining in the heated chamber .f from the previous operation. To release the excessive pressure due to these explosions venting tubes 19 which are closed at their outer ends by safety valves or covers 5 20 extend through the walls 13. In the present instance I have shown two such passages in different positions, the upper one being inclined outwardly and upwardly.

The brickwork 13 is herein shown as supported on I-beams 21 running lengthwise under the retort. The retort 10 at the bottom has a horizontal flange 22 resting on the lconstitutes one side of a discharge chtite 26 the end of which is closed by a tightly fitting trap door 27. The under sides 28 of each chute are integrally associated with a bottomless box-like structure having vertical sides 29, which structure constitutes part of a water seal for the retort more particularly described hereinafter.

The feeding device for the retort may be of any suitable form properly provided with sealing means. Herein I employ a feeding hopper 30 at the top of the retort 10 above the flange 23,f the hopper extending laterally away from the retort on one side thereof. A trap door 31, suitably sealed in the closed position, is shown through which the charge is introduced by suitable means (not shown). An u w'ardly tapering weight or bell 32 is movable up and down within the retort, the bell being shown in charging position in full lines in Fig. 1. The granular or powdered coal being charged into the retort is compelled to pass down through the relatively narrow space between the bell and the retort walls in the form of a thin stream or layer which in falling exposes the grains and small lumps of coal to the hot air within the retort, thus causing a rapid and uniform heating of the coal before the same is deposited at rest, which substantially reduces the time consumed in distilling the charge. When the retort is fully charged, the bell is lowered onto or pressed against the material by suitable means. Herein I have provided connecting rods 34 from the bell 32 extending through the end of the retort to a controlling device. A hydraulic cylinder 35 `is used to control the motion of the bell through suitable valves (not shown), the rods 34 being combined to work in unison with the .piston rod 36 of the hydraulic piston and cylinder unit. By this means the bell can be raised or lowered as well as adjusted .to resist yieldingly the pressure of the swelling charge. A further use of this device is made at the end of the operation when the bottom is opened to start the charge downwardly out of the retort. The two discharge chutes above described necessitate a division of, the charge into two portions. Because of the gas passageways which have been produced in the charge by means yet to be described, vthe charge is not solid along the required division line ut` is connected by the material between adjacent gas passages and at the side ends of the retort.

In order to facilitate discharge by aiding in the division of the two sections, separating form bars 37, each of which is suspended from pension may l tends vfrom just a cross piece 38 at the u per end of the retort.

' The bla'des ofthe cruel orm bars 37 constitute -knife edges to divide the charge. The adherence of the coke to the blades is broken by the pressure exerted by the bell 32 to effect the discharge thereof. Suitable holes are provided in the bell 32 to permit the motion of the same longitudinally of the bars. The susj 39 of the bars froml the cross iece and the guiding action of the bell 32, eep the bars vertically disposed within the retort.

Suitable means are provided for the conduction of the gases away from the retort and for the sealing of the retort against leakage of the gas. The gas liberated bythe process is led from the retort by a pipe 40 into a hydraulic gasy main 41. A valved vent pipe 42 leads to the atmosphere from the pipe 40. The

upper part of the retort 10 is closed by the top 43 through which extends the mechanical passage-forming means. I

The mechanical means to create the gas passage in the charge may assume a variety of forms, but herein I have chosen to illustrate a rotatable member of non-circular crossseetion hereinafter referred to asl a rotor.

A twelve inch retort would have a rotorv of approximately four and one-half inches as its transverse dimension. In the case of an eighteen-inch retort, the rotor would be about eight inches in its transverse dimension. The rotor may extend through the retort from end to end, being supported' externally of the retort in the present instance. In Fig. designatedby the numeral 44, each having a cross-section which may be described as produced by the Hattening of a tubular member. The attening of the tubular member illustrated is` confined the rotors length which exabove the bottom of the retort to a point opposite the feeding hopper 30. If desired, the rotor may be ofthe cross? sectional'form shown in Figs. 5 and 6 or it may be of any other suitable form. The portion of the rotor which is within the retort, proper, be cylindrical (as shown in Fig. 7) and may be mounted for rotation' upon an eccentric axis a.

to a portion of In the hollow member 44 of Fig. 1 there is comprising an arrangeshown heating means In Fig. 4 these are desment ot' gas burners.

ignated by the ynuimerals'45, 46 and 47 each burner having its own supply pipe 48 with an iudepenldentvalve contr-0149. The burners are preferably constructed in a spiral form like a triple threaded screen. as illustrated. The use of gas burners within the hollow rotor may make it desirable to provide the rotor with a corrosion or oxidation (see Fig. 4).

stitues the bottom of the retort..

i cape of lining 50 of metal adapted to ,resist The construction herein employed for each rotor necessitatesv a guide bearing at the bot- ,nular base 51 through which enter the fuel pipes 48. An antifriction' thrust bearing support of suitable form is provided asillustrated bv t-he numeral'52. Each rotor extends upwardly through the space between the vertical sides 29 of the bottomless box structure hereinbefore described. Between the sides 29 is verticallyslidable a structure having an upper side 53 of inverted V-shape which con- In'the discharging position of the retort bottom, the sloping sides 53 are alined with the plates 28, and serve to'divide the charge into two portions. The retort bottom comprises vertical sides 54 which are vertically slidable between ythe sides 29. Along the ridge of the retort bottom are openings .for the rotors 44. Said openlngs have tubular extensions lor sleeves 55 surrounding the rotors and extending downwardly toward the base 51, where they terminate by junction with the bottom 56 of a box trough 157, thev sides ofwhich extend upwardly outside of the'box sides 29. The retort bottom and the trough-thus become a unitary structure which is arranged to be slidable longitudinally of the rotors. Suitable means are provided to control the movements ofthis unit, said means being herein shown as comprising control, rods `58 secured to the yoke 59 which is operated by-a hydraulic cylinder (not shown).

In the drawings the retort bottom is shown in full lines in its lowermost position-and in vopera-tive relation to the discharge chutes 26.

In the dotted-line position it is indicated in its uppermost position to close the lower end of the retort. The joint at the point 60 need not be particularly tight, since the lower structure already described constitues a water seal against leakage of gas from the bottom. The trough 57 is. adapted to contain waterl which in the upper position .of the retort bottom acts as a seal to prevent the escape of gases between the plates-29 and" 54. Theosgases through the sleeve 55 about each rotor is prevented bythe rovision of a suitable stutling box 61. v-The rotor at its upper Y end has a suitable gas tight bearing in the top 43 at they point 62. v v

' A gear. 63 rigid with the rotor has a thrust bearing support on a fixed member 64. Suit-I fable power means for driving each rotor may be supplied in any well known manner, as for example. by means lof a drive shaft 65, and bevel gea'r 66. v A fixed elbow 67 leading to a. stack by pipe 68 has a relatively gas-tight bearing about the end of the rotor to conduct away the combustion gases from the burners within the rotor. Y

In the type of retort herein described the 'coal is admitted at the top to charge the retort completely, after which the retortis sealedv the distillation process carried out. As thecoal becomes heated and the gases begin t`o evolve, lthe mass swells which results in expansion upwardly toward the top of the retort. The4 weight 32 is operable to resist yieldingly the upward expansion to any deportion in a yielding manner, I impose upon y the upper portion the conditions which ordinarily obtain at the bottom and therefore produce a morej nearly uniform product in a 'single charge.

'As the gases are evolved and the mass bel/- comes plastic through heating, it ordinarily becomes 'more diliicult for the gas to escape I l from within the mass to the receiving chamber provided therefor, but in a retort 'embodying the present invention the rotors 44 produce vertical passageways throughout the charge.

As the mass becomes plastic and pliable it tends to flow into the passageway to close it up. The rotation of the rotor is sufficiently ast to prevent this, and in thus preventing the'inward flow of the material the rotor exerts a pressure thereon laterally with respect to the retort which gives a desirable density and hardness to the coke. The heat which is applied to the rotor is suflicientl great to destroy any tarry products whic may collect thereon during the distillation process, such destruction possibly leaving thereona coating of coke or carbon. This coa-tin ,'however, is not accumulative, because 1n the charging of the apparatus the granular material will lie closely a ainst this member and the mechanical scraplng which results at'the beginning of the process will efectively remove such carbon layer.

The rotor 'serves to distribute heat to the charge, thus shortening the coking operation without danger of local or excessive overheating.

When the distillation process has been completed as far as desired, which may be determined by suitably testing by the'character of the gases collected at the valved outlet 42, the-'retort is opened by lowering the bottom 53 to the position shown in full lines in Fig.

1. Simultaneously or thereafter the bell`32"- ,reduced vand the heating surface is increased. f

Being quickly conducted away from the h'ot zones, the gases are not subjected to detrimental heating, the quality of the coke is improved, and the rate at which coking proceeds is' increased. l

Asthe eccentric or non-circular. tube revolves the coal will follow the travel of the eccentric portion or portions of the tube, that is to say, the coal will move to fill the con- Stantly shifting gas passage, until the stage where the coal becomes plastic is reached. Such movement'of the coal is desirable, as it diffuses the heat through the mass. TheA friction-amon 'thesolid particles likewise conduces to tie heating of the charge. Moreover, the rubbing action of the tube accelerates the delivery of the heat into the mass.

When the mass begins to set, there is less and less tendency to close in around the rotor,and thus the delivery 4of`heat to the mass from the rotor is self-regulating, the amount of heat supplied to the mass from the rotor being automatically reduced as the need for the application-of heat diminishes.

In the coking of coal exothermic reactions set in at about 350 C. I deem it desirable,

as regards economy of operation, character of by-products and quality of coke, to make use of the exothermic reactions to the greatest practicable extent in the distillation of the coal. In other words, I aim to avoid the creation of conditions under which endothermic reactions occur. lFor this reason I prefer to maintain outside the retort and within the lrotor a temperature of approximately 500 C.-at least until the exothermic reactions have commenced.

The apparatus and certain features of the process herein disclosed are highly advantageous in the distillation of carbonaceous material, whether the product chieiy sought be-coke, gas-or oils.

I believe myself to be the first to provide practicalmeans for agitating a charge of coal undergoing distillation. By reason of the agitation to which the coal is subjected in an apparatus embodying my invention, heat is rapidly and uniformly disseminated throughout the charge, and the entire mass quickly raised to the desired temperature.

I also believe that I am the first to distill a batch or unit mass of carbonaceous maand aim to claim such an apparatus -broadly in certain of the following claims.

I claim as my invention:

1. An apparatus for the distillation of carbonaceous material comprising, in combination, a vertical retort adapted to contain a charge of such material, means for heating the retort, a plurality of means for creating a vplurality of vertical gas passages in the retort, separating blades vertically Adisposed between adjacent passage-creating means, av

bottom for the retort movable away thererom,means to push the finished charge downwardly in the vretort iwhereby` the adherence of the charge to the retort walls andthe blades may be broken, and dischargechutes below the retort and extending from opposite sides thereof, said blades and passage-creating means being arranged substantially to divide the charge into half portions, one for each discharge chute.

2. An apparatus for the distillation of carbonaceousmaterial comprising, in combination, a vertical retortadapted to contain a charge of such material, means for heating the retort, means for creating a plurality of vertical gas passages in the retort, a bottom :tor the retort, said bottom being of inverted Vform to divide the material when said bottom is lowered for removal of said material, means to move said bottom vertically, and means to push the finished charge downwardly onto the lowered bottom to split the charge into two portions along the line of the vertical passages therein.

3.` An apparatus for the distillation of carbonaceous materlal comprising, in combination, a vertical retort adapted to contain a charge of suchmaterial, heating means for said retort, means for creating a plurality of laterally alined vertical gas passages through the charge, and means movable vertically in said retort a't the lower portion thereof, and adapted for separating the charge into two portions along the line of said valined passages.

4. An apparatus for the distillation of carbonaceous material comprising, in combination, avertical retort adapted to contain a charge of such material, heating means for said retort, revolving means extending vertically through said retort for creating a plurality of laterally alined gas passages through the charge, and means movable vertically in said retort at, the lower portion thereof, and adapted for dividing the charge along the line of said passages.

5. An apparatus for the distillation of solid carbonaceous material and production of coke having, in combination, a vertical retort adapted to contain a charge of such material, means for heating the outer surface l' of said retort,`a non-conveying member extending vertically through said retort, heating means associated with said member for heating the interior of said retort, means for moving said member in a fixed path within said retort from one position to another to create a relatively straight longitudinally gas passage through the charge and means for permitting the removal of the resulting batch of coke from said retort,

6. An apparatus for the distillation of carbonaceous material comprising, in comb1na" tion, a vertical retort adapted to contain a7 charge ofsuch material, a revolvable member extending longitudinally through said retort and adapted to be revolved on a longitudinal axis and upon being revolved to create a'gas passage vertically through the charge, means for closing the lower end of said retort, means for heating said retort, an annular weight fitting around said member and disposed in the upper end of said retort, said weight being adapted to rest upon the charge to more nearly equalize the pressure throughout said charge, and being adapted to be lowered to remove said charge,and means for actuating said weight,

7. An appara/tus for the distillation of carbonaceous material comprising, in combination, a vertical retort having a feeding hopper at its upper end and being vadapted to contain a charge of such material, means for closing the lower end of said retort, means for heating said retort, an upwardly tapering weight member centrally disposed in the upper end of said retort-below said feeding hopper, said weight member being slightly less in dimension than said retort to define therewith a narrow peripheral passage through which a charge may be passed into said retort, and means for supporting said weight member.

8. An apparatus for the distillation of` carbonaceous material comprising, in combination, a vertical `retort adapted to contain a charge of such material, a plurality of consecutively arranged laterally spaced members adapted upon lrotation to create a plurality of vertical gas passages through the charge, means for rotating said lmembers on a vertical axis, a plurality of laterally spaced auxiliary membersbetween said rotary memmembers extending central through said retort, means for closing the ower end of said retort to retain the charge therein, a weight member having a plurality of openings fitting respectively over said members and being adapted to rest upon said charge to equalize the pressure thereof and to resist expansion thereof, and means for lowering said weight to remove said charge when said retort is open.

10. An apparatus for the distillation of carbonaceous material comprising, in combination, a vertical retort adapted to contain a charge of such material, the lower end of said retort being formed with divergent discharge chutes, a closure having an inverted V-shaped upper end in the lower end of said] retort movable verticallyto open orclose said discharge chutes, the inclined sides of said inverted V-shaped end having the same slope as the walls of said discharge chutes, and means extending vertically through said retort adapted to divide the charge in line with the apex of said closure.

11. An apparatus for the distillationof solid carbonaceous material to form coke, comprising, in combination, a vertical retort adapted to contain a charge of such material, a vertical member extending longitudinally through said retort and rotatable on a vertical axis and beingadapted upon rotation to 4create a passage through the charge, means for heating the exterior of said retort, and

heating means within said member adapted to heat the latter to heat the interior of the material.

12. An apparatus for the distillation of carbonaceous materialcomprising, in combination, a vertical'retort adapted to contain l al charge of such material, a pluralityA of laterally spaced members extending longitudinally through said retort and substantially dividing the interior of said retort into two parts, a closure movable in the lower end of said retort, the inner end of which is inverted- V-shaped with the apex in line with said members, and means for heating said retort.

A13. An apparatus for the distillation of carbonaceous material comprising, in combination, a vertical retort adapted to contain a charge of such material, the lower end of said retort being formed with two diametrically opposed discharge chutes, saidl discharge chutes having a central downwardly extending sleeve at their junction, a rotatable member extending through said sleeve and vertically through said retort, said member being shaped to create upon rotation a path centrally through the charge in said retort, a

lclosure movable in said sleeve and adapted closure for the bottom of said retort for conlining said batch 7in said retort, a non-convey# ing member extending vertically through said retort, saidmember being mounted for lateral recurrent movement and adaptedupon such movement to form a vertical gas passage through said batch, means for actuating said member, means for heating said retort, and means for opening said closure to remove coke from said retort. v y

15. An apparatus' for the distillation of solid carbonaceous material and production of coke comprising, in combination, a vertical retort, means for admitting a batch of such material to the top of said retort, a re-4 movable closure for the bottom of said retort for confining said batch in said retort, a hollow non-conveying member extending vertically through said retort and mounted for lateral recurrent movement about a vertical axis, said member d having a substantially straight longitudinal and laterally ofset portion adapted upon said movement to exert a wiping action on the interior of said batch and thereby to form a relatively straight vertical gas passage through said batch, means for actuating said member, means for heatin said retort, means for heating the interior o said member, and means for opening said closure to remove coke from said retort.

16. An apparatus for the distillation of solid carbonaceous material and production of coke comprising, in combination,.a vertical retort, means for admitting a -batch of such material to the top of said retort, a removable closure for the bottom of said retort for confining said batch in said retort, a non-conveyingmember extending vertically through said retort, said member being mounted for lateral recurrent movement and adapted upon such movement to form a vertical gas passage through said batch, means for actuating said member, a pressure member adjustably and yieldingly mounted in the upper end of said retort for resisting swelling of said batch, means for heating said retort, and

means to open said closure from said retort.

17. For use in a vertical retort having an inwardly spaced longitudinal core, the batch to remove coke process of distilling and coking of granular,

carbonaceous material' which will become plastic upon being heated to a predetermined temperature, comprising feeding a batch of said material into the top of said retort and confininoi said batch in a hollow vertical column deiined by said retort and said core, creating a vertical gas passage through said batch along the exterior of said core, applying heat to said batch Afrom within said passage, agitating said batch whilev in granular form, applying mechanical pressure to said batch from within said passage while said batch is plastic, and removing the coked batch from the bottom of saidretort.

18. For use in a vertical retort having an inwardly spaced longitudinal core, the batch process of distilling and cokinggranular carbonaceous material which' will become plastic upon being heated to a predetermined temperature, comprising feeding a batch of said material into the top of said retort and confining said batch ina `hollow vertical column defined by said retort and said core, creating a relatively straight vertical gas passage through said rior of said core, heating said batch, applying mechanical pressure laterally to said "batch from within said passage and vertically to the top of said batch while said batch is plastic, and removing the coked batch from the bottom of said retort. l

19. For use in a vertical retort having an inwardly spaced longitudinal core, the batch process of distilling and coking granular carbonaceous material which will become plastic upon being material into the top of said retort arid con# fining said batch in a hollow vertical column defined by said retort and said core, creating an interior vertical gas passage through said batch along the exterior of said core, heating the outside of said column, applying heat to said batch from within said passage, applying a yielding pressure vertically to the top of said batch while said batch is plasticwhereby swelling of said batch is resisted, and removing the coked batch from the bottom of said retort.

20. For use in a vertical retort having an inwardly spaced longitudinal core, the batch process o f distilling and coking granular car bonaceous material which will become plastic upon being heated to a predetermined temperature, comprising feeding a batch of said material into the top of said retort andconning said batch in a hollow vertical column defined by said retort and said core, creating an interior Vertical gas passage through said batch alongthe exterior of said core, heat-ing the outside of said column, applying heat to said batch from within said passage, agitating said batch while in granular form, causing said batch to be substantially quiescent and applying mechanical pressure laterally 111g pressure 'thereto from within said passage when said batch is plastic, applying a yiel vertically to the top of said batch while said batch is plastic whereby swelling of said batch is resisted, and removing the coked batch from the bottom of said retort..

21. For use in a vertical retort having an inwardly spaced longitudinal core, the batch process of distilling and coking granular carbatchfalong the eXteheated to a predetermined tem-1 perature, comprising feeding a batch of said fixed my signature.

' i V O'lITO H. HERTEL.

bonaceous material which will becomefplastic upon being heated to a predetermined temperature, comprising heating the exterior of said retort, feeding a batch of said material in a thin stream about said core into the top CERTIFICATE or CORRECTION.

Patent No. 1,731,165. Granted October 8, 1,929, to

l oT'ro H. HERTEL.

It is hereby certified that error appears in the printed specification of the aboYe numbered patent requiring correction as follows: Page 3, line 61, for the word "screen" read "screw"; page 5, line 69, claim 5, strike out the Word "longitudinally" and insert the same after the word "passage" in line 70, same claim; page 7, line 52, vclaim 20, for the word "when" read "while"; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 26th day of November, A. D. 1929.

M. J. Moore,

(S081) Acting Commissioner of Patents.

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