US2176473A - System for heat treatment - Google Patents

Description

Oct. 17, 1939- c. z. RosEcRANs SYSTEM FOR HEAT TREATMENT Filed July 22, 1936 4 Shee ts-Sheet l Mn v Oct. 17, 1939. c. z. RosEcRANs SYSTEM FOR HEAT TREATMENT Filed July 22, 1956 4 Sheets-Sheet 2 fr, w

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JNVENTOR: CrarzcaZZZPOJec/Jw {11d-L4 24. Giu/- ATTORNEY,

Oct. 17, 193.9. C, z RQSECRANS 2,176,473l

SYSTEM FUR HEAT TREATMENT Filed July 22, 1936 4 Shec-ts-Shee'.` 3

, E' .5. u l? 77 l nvt/Emma;r l CrandaZLROsecr-ansj BY l 1 se@ .4..L..vs.%m.

` ATTURNEY.

Oct. 17, 1939. c. z. RosEcRANs SYSTEM FOR HEAT TREATMENT Filed July 22, 1956 4 Sheets-Sheet 4 A TTORNEY.

Patented oet. 17, 193494v UNITED STATES to Leeds 8s Northrop Philadelphia' Pa., a corporation of Pennsylvania' Application July 22, 1938. Serial No. 91,855 's canna (01. zee-s) My invention relates to systems for treatment of metal objects in furnace atmospheres, and more particularly to the treatment of metal objects in chemically active, gpccincaliy carbonaceous atmospheres, to form a diiusion alloy case or toprevent loss oi carbon during hardening.

In accordance with my invention. a treating or processing id of deilnite chemical composition is positively fed at metered rate to the furnace atmosphere and is therein dissociated to maintain or form a processing or treating atmosphere of definite reproducible composition: more particularly. the metered agent is intermittently or continuously injected into the furnace atmosphere at high velocity to preclude pyrolytic breakdown or dissociation of the agent at or adjacent the point or points of injection, to avoid clogging of the one or more injection nozzles or oriiices; the forcible injection of the agent also acts to effect turbulence of the furnace atmosphere to enhance uniformity of reaction temperature and uniformity in characteristics imparted to the objects treated.

In certain forms `of my invention, the fluid l agent is fed to the injection nozzle by a positive displacement pump: the rate of iced oi the agent ,i

may be varied, as by adjustment of the pumpe speed, or the timing of a valve in the pump. to

obtain the desired reactive state of furnace at mosphere.

My invention further resides in the apparatus having the features of novelty hereinafter de` scribed and claimed;

Application .Serial No. 696,020, as originally led October 3l, 1933, (now Patent No. 2,056,175,

Oct. 6, 1936), by applicant `and another, disclosed and described subject matter herein specifically claimed as applicants sole invention.

For an understanding of my invention. referenh is made to the accompanyingdrawings in w A Fig. 1. with parts in section, illustrates a furnace and a system for injecting a treating agent;

Fig. 2, on enlarged scale, 'is a sectional view of the injection nozzle of Fig. 1;

Fig. 3,1 on further enlarged scale, is a detail view in section of the tip of the nozzle of Fig'. 2;

Fig. 4 is a cross-section on enlarged scale of the feed-pump shown in Fig. 1;

Fig. 5. on further enlarged scale, is a sectional view oi the plunger mechanism of Fig. 4;

Fig. 5a is a detail view showing the plunger o Fig. 5 in another operating position;

Fig, 6 illustrates diagrammatically a modiiied 55 feed system:

Fig. 'l is a sectional view on enlarged scale of the nozzle of Fig. 6:

Fis. 8, with parts in section, illustrates another furnace and feed system therefor: Fig. 9 is a detail view on enlarged scale of the 5 injection nozzle of Fig. 8; r

Fig. 10 illustrates, in section. the feed pump oi Fig. 8;

Fig. 1i illustrates another form of furnace mode of injecting a treating agent: lo

Fig. 12, on enlarged scale, is a sectional view of the injection nozzle of Fig. 11.

Reierring Fig. 1, the lower edge ofthe retort 4I rests `thin a peripheral groove, deiined by the flanges 2, i of plate l. which is lled with 15 a suitable sealing material, such as oil or an oxide, such as hematite. The groove also serves and to center the retort with respect to the base member 5 of suitable heat-insulating material. Up

wardly from the upper face of the base member 5 20* relation aroundretort l by the housing member 30 i2 having an inner shell i3 and an outer shell il. the space between which is iilled with material of suitably high heat-resisting insulating properties as Sil-oce1.

Other methods. such as gas-firing, may be used, 35 instead oi heaters Il. but the electrical method is preferred because affording better temperature control.

The weight of the housing assembly is carried by the structure i5 which. in turn, is mounted o upon the main frame It of the furnace. The housing or-heatlng bell I i is removable from the position shown by lifting it upwardly and to vthat end, one or more eyes il or the like, are provided to facilitate attachment of suitable 45 liftin chains.

Assguming that the parts are in the position shown and that heaters Il are energized; the fan 2i, which `may be of the propeller type. or of the blower type. or oi the propeller type with high blade angie to obtain centrifugal or blower action, is rotated at suitably high speed. ior exampie, i800 revolutions per minute, by motor i8 SUPDOrbed by bracket I8 from plate 4;. The gas within the retort, which initially may be air. is

circulated in the closed path through the work basket 3 and the space between the retort I and the work basket, (in the sequence named when fan 23 is of the centrifugal type. and in either sequence when fan 23 is of the propeller type) uniformly to heat the articles or objects, such as gears, shafts, roller-bearing races, or the like, within the basket.

When the fan is of the centrifugal blower type,

-the air or gas always ows downwardly through the work basket irrespective of the direction of rotation of the fan: when the ian is of the propeller type, the direction 4,of circulation may be reversed by reversing the direction of rotation of the fan.

To use the furnace for carburizing, a carburizing agent, preferably iuseloil, carbitol, or other compound of the character specied in the aforesaid Patent No. 2,056,175, is discharged from the atomlzer 2li in the form of'a jet of line mist or spray into the space between the basket 9 and retort I where it is quickly vaporized by contact with the circulating gas and/or the -wall structure of retort I or the external wall structure of basket 9. The vaporized agent shortly thereafter contacts the articles within basket 3. The carburizing liquid is preferably not injected until after the preliminary heating period during which air, or a substantially inert gas. as nitrogen. has been circulated to raise the work to carburizing temperature. The atmosphere within the retort, within a. short time after injection has begun. consists substantially solely of the products of the pyrolytic breakdown of the carburizing agent, principally carbon monoxide,

methane and hydrogen, the air or the gas previously in the retort having been forced out through the bleeder 2I which discharges to atmosphere. in the particular arrangement of Fig, 1, through the liquid seal 22.

The reaction between the articles and the treatlng atmosphere forms at and near the surface of the articles a diffusion alloy case. specically a carburized case.

Preferably for carburizing the agent is of the character claimed in the aforesaid Patent No. 2,056,175, for example, fuse! oil, dlethyleneglycol, o'r diethyleneglycolmonoethylether, since for these compounds the time of pyrolytic breakdown is suitably short so that the gas or vapor is in suitably active state or some of its components, as carbon, are nascent by the time it reaches the work; It is also characteristic of use of such compounds that there is substantial freedom from hard or tarry .deposits on thel work l and furnace parts within the retort.

from the position shown and may be lowered in e position to' heat a similar set-up which, in the meantime, has been loaded; i. e., the installation may include a set-up similar to that shown in Fig. 1, except for heating bell i2 which may be used alternately to heat the retorts and work therein.

After removal of heating bell I2, a forcible circulation by fan 23 or equivalent may be continued more quickly to bring the temperature ot the work to a desired lower magnitude, whereupon the retort I may be liftedoii', allowing the basket 3 and its contents to be lifted from the furnace.

With the construction shown in Fis. l. there is no need to disconnect any of the pipes communicating with the interior of the retort to allow removal of either the retort I or the heating bell i2.

The atomizer nozzle structure 20 may be similar to that used for iuel injection in Diesel engines, Figs. 2 and 3. I'he plunger 24 is forced by spring 25 to seat its valve surface 26 against the face 27 of the body member 28 of the nozzle. When the pressure of the liquid carburizing agent within the chamber 28, which is supplied through pipe 30 from pump 3|, attains a pressure high enough to overcome spring 25, the liquid is forced through the nozzle into the passage 32 in the base 5; the valve surfaces 26, 21 remain slightly separated until the liquid pressure, in the cycle of operation of pump 3i, falls below the value for which spring 25 is set or adjusted. The pipe 33 drains oli any of the liquid which may pass between the plunger 24 and the side walls of the guide chamber 34 therefor.

The positive feed pump 3i as appears from Figs. 4 and 5 comprises a piston 31 which is pericdically lifted by cams 33 on the motor-driven pump shaft 33 against the action of the return spring 4D. When the top of the piston is below the two inlet ports 4I, 42, interconnected by an annular channel in the pump body, Fig. 4, the carburizing liquid flows from the container |43 through ports 4|,.42 into the cylinder space above the piston. As the piston continues to rise, the

pressure attains a value sufiicient to overcome the bias of spring '25 in the nozzle, whereupon the fluid is ejected from the nozzle into the furnace at high velocity until the piston reaches such position that the helical edge 43 is above port 42 (Fig. 5a) allowing iiuid above the piston to iiow down through slot 31a in the piston and thence out of port 42, and whereupon the pressure on the iluid abruptly falls and the nozzle valve 24 is seated by its spring 25. 1

To vary the amount of carburlzing agent injected for each cycle, the piston 31 is rotatable inits barrel or cylinder 44 by movement of the control rod 45 which is provided with a rack 48 engaging the toothed quadrant 41 oi the control sleeve 48 which, at its lower end, is provided with a guide slot 43 which receives the cross piece 50 secured to and extending from the piston 31. Adjustment of piston 31 in the direction of the ari-bw, Fig. 5a, reduces the output because the helical edge 43 passes port 42 earlier in the cycle; conversely, adjustment of piston 31 in reverse direction increases the amount of carburizing agent fed by the nozzle for each cycle of the pump.

The rate of feed of the carburizing agent may also be adjusted by changing the speed of the pump. ,for example, by changing the setting of the rheostat'l in circuit with the pump motor 36.

The pump 4i is a positive displacement pump, consequently the amount of carburizlng liquid fed within any given time is deiinltely fixed by either of the adjustments above described.

'I'he carburizlng atmosphere within thelretort is of deilnite reproducible composition because the rate of feed of the agent is denitely metered, because the proportions of carbon monoxide,

methane and hydrogen are deanicely nxed by the stoichiometric composition of the agent, cracked or dissociated, and because tbe temperature is denitely known and controllable.

arrearsl The-pressure at which the liquid is ejected is suitably high, for example. of the order of 2500 pounds per square inch. The agent therefor, asA

it issues from the nozzle into the furnace atmosphere, is in the form of a ietof fine mist or spray moving at very high velocity. The temperature within the retort is so high. of the order of 1700 F.. that vaporization of the Jet is practically instantaneous upon contact with the furnace. atmos-phare and, in addition, the iet velocity is so high there is no tendency for liquid to ow back and clog the passage 32 or the nomic oriiice. Moreover, the velocity is so high there is no opportunity lfor the agent to crack while in the passage 32 and cause deposits therein.

Preferably. as shown 'in Fig. i, the atomizing nozzle may be provided with a jacket Si through which water or other suitable cooling fluid is circulated to maintain it at a temperature low enough to insure proper working of the nozzle mechanism and suitably below the cracking temperature of the carburizing agent. In actual practice, the nozzle temperature has been maintained below about 550 F. l

The bushing i3 for the fan shaft il may be provided with a cooling Jacket 58 and. if desited. the seal for the retort l may be provided with a cooling coil 66.

'l'he following is given as an example, illustrative of the practice of the invention.

The furnace, similar to Fig. l. was provided with a` cylindrical work basket t. fourteen inches in diameter, containing 150 pounds of cylindrical specimens of S. A. E. 1020 steel, 75 inch in diameter and six inches long, positioned haphazard with respect to the basket and each other. filling the basket toabout three-fourths of its capacity. Fan 23 was of the propeller type.diameter 131k inches, four blades. pitch 21, rotated by motor i8 at a speed of 1800 revolutions per minute. The carburizing agent was fusel oil and was fed at the rate of 450 cubic centimeters per hour throughout the run which was of two hours' duration. after raising the temperature of .the furnace. during circulation of nitrogen therein. for` a preliminary period of about fifty minutes. The temperature as measured by the thermocouple pyrometer P was maintained at 1700 F. throughout the run. 'I'he results were as follows:

Dems in inches Hyper c oiz Eutcctol 0.009 Hypoeu n 0.009

The magnitudes in the above table are in een This furnace may also be used practice the method of hardening described and claimed in HalSh Plent N0. 2,103,848, 0f which it is (Bharacteristic that the furnace atmosphere. during i heating of the work. such as dies, of his!! wbon or other tool steels, to quenching temperature, is maintained in a slightly carburlzing state to preclude loss of carbon from the steel.

When the source of the carburizing component of the agent introduced into the furnace atmosphereffor example kerosene, is deiicient in oxygen. and so requires admixture of its dissociation products with air. or other source of oxygen, the arrangement diagrammatically shown in Fig. 6 and using the nozzle shown in detail in Fig. 'l may be used to obtain a carburlzing atmosphere of definite reproducible composition.

The spindle 51, Fig. 7. of the nozzle is provided with its' tapered end it biased against the lower end of the seat 69 in the casing G0 by the spring 6l. Immediately surrounding the spindle il is the sleeve 62 which rests on the cone 66 engaging the upper part of seat 59 and fluted to permit passage of air and carburizing liquid.. Above the cone 63 area plurality ofsmall perforated -discs 6l through which the air and carburizing liquid is forced. as hereinafter described.

The carburizing liquid is fed to the space above the discs 64 through pipe 85 in communication therewith by the pump 66 whose inlet is connectedto a suitable reservoir 61 of carburizing liquid. An air compressor 88, driven by motor 69,

or equivalent. is connected by pipe 10 to the space above the discs 64; a reservoir or air-storage tank may be connected to the line from the compressor to the nozzle. Alternatively. Pipe 10 may connect the nozzle to any suitable source of air. or oxygen. under high, constant pressure.

The cam H driven by motor 69 at suitable speed, for example, 250 revolutions. per minute, periodically lifts the spindle l against spring 6i. as viewed in Fig. '7. whereupon the compressed air, which is at high pressure, for example, of the order of 2000 pounds per squareinch, ows through the nozzle orice I2 at high velocity carrying with it the charge of carburizlng fluid above the discs. The movement of the air and liquid at high velocity through the small perforations of the disc causes the liquid and air to be mixed and issue from the nozzle as a ne spray or iet travelling at high speed into the furnace atmosphere.

The amount oi air entering the furnace through the nozzle for each injection may be varied by changing the length of the portion of each cycle during which the spindle valve is' away from its seat 5B: for example, as appears from Fig. 6, the proportion of the cycle during which cam 'Il is effective to hold the valve fromvits seat may be varied by adjustment of the screw I3 supported by the rocker arm 1I.

The amount of carburizing liquid entering the furnace for each injection may be predetermined. for example, by varying the time of cut-off, as described in connection with the pump of Figs.

burizing liquid may be controlled by varying the speed of the pump motor 15. In either event, change in the rate cfafeed of carburizing liquid varies the amount of liquid in the 4nozzle above the discs B4 for each cycle of the valve spindle 51.

Thistype nozzle is not, without modification, suited for a bottom-inlection furnace such as shown in Fig. 1; it is used with a top-injection furnace such as shown in Fig. Bshaving the nozzle in the position shown in Figs. 6 and 'l with its orice at the lower end of the nozzle structure.

'4 and 5. If desired, the rate of feed of the car- 'I'he type nozzle shown in Fig. 2 may be used with The modification shown in Fig. 8, is characterized by absence of a retort such as retort I of Fig. 1. The work basket 9 rests upon the upper ends of the vertical supports E, the inner wall of the basket defining what may be considered a work chamber. The space between the outer wall of the basket and the inside face of the shell |3a is the chamber in which the carburizing gas-or furnace atmosphere is heated by transfer of heat from the'heater units 1S.

Since it would not be practical or desirable toy expose the heating resistors to direct contact withthe carburizing gas, the heating resistance is divided into a plurality of encased units 'IB circumferentially spaced within the shell i3d.. Each unit may comprise resistance wire helically wound and supported in U-form by a refractory cement. The assembly is encased by' the housing of the unit which is nichrome, or other metal substantially unaffected by the high temperature and the carburizing atmosphere. The space within the unit housing is lled with material, for example, Austrian furnace magnesite, having high electrical resistance and high thermal-conductivity.

l As in the modification of Fig. l, the carburizing gas is forcibly circulated by a fan 23 through the work and heating chambers` When the carburizing agent is injected into the furnace atmosphere by a nozzle structure. such as shown in Fig. 2 or "I, the tip of the nozzle preferably does not extend into the furnace chamber, but is in communication with a passage in the cover 'I1 corresponding to passage 32 of Fig. 1. As in the modification of Fig. l, the carburizing agent, in metered quantity, is forcibly injected into the furnace as a fine spray which is immediately vaporized, the high velocity of the jet precluding clogging of the jet orifice and premature crackling of the carburizing agent which would tend to cause deposits fouling the orice and the .iet passage. In lieu of the valved nozzles of Figs. 2 and 7, there may be used a simple nozzle, such as an open ended tube 18, Fig. 9. having one or more small openings 18a at its lower end. The discharge end of the nozzle enters the pipe 'i9 which is directed or extends into the heating chamber of the furnace and which serves the same general purpose as passage 32 of Fig. 1. Pipe 19 may be omitted and the nozzle I8 fitted into'the passage through the cover 11.

The pump l is a positive displacement pump; it may be of the type shown in Figs. 4 and 5 having a variable cut-oil' for adjustment of the rate of feed of the carburizing agent to nozzle 18 from the reservoir H3, or it may be a gear pump 80. as shown in Fig. 10. In either case, the speed of the pump may be controllable, as by rheostat in circuit with the pump motor 82 to permit variation in the rate of feed of the carburizing liquid.

The carburizing agent issues from the nozzle in jet form, the iet travelling at high velocity through pipe 'iii into the furnacewhere it is substantially immediately vaporized. Clozgine of the nozzle cannot arise because of the capability of the pump to develop, in event of stoppage. high pressure which blows out or away any obstruction tending to close the orifice. Moreover, the time required for the agent to traverse tube 'I9 is so'short that premature cracking therein does not occur thus avoiding deposits within the tube.

The cover 'I1 is provided with a deep flange 83 received by channel 8| containing suitable sealing liquid or material.

The operating procedure is readily understandarrears able from the previous description of Fig. l. The metering of the carburizing agent and the control of the furnace temperature provide for definite, controllable and reproducible composition of the furnace atmosphere insuring consistently good and uniform results for different runs. The forcible circulation or stirring of the carburizing atmosphere by fan 23 insures uniformity of the reaction temperature and of the composition of the furnace atmosphere throughout the furnace load, with resultant uniformity of characteristics v In the modification of my invention shown in l Figs. 11 and l2, a carburizing liquid, as carbitol, is fed at metered rate,'as by a positive displacement pump, to pipe |04 which terminates in a nozzle I IIS in a vaporizing chamber IDG suitably heated to a temperature high enough to vaporize the liquid but well below the cracking temperature of the liquid; for example, the temperature to which the chamber is heated as by heater coil IIII may be of the order of 350 F.

The wall |08 lof the vaporizing chamber and the target 109 may be of nichrome or other suitably resistant material.

The .vaporized carburizing agent enters the throat I Ill of the nozzle II I 'and expands through the throat to the point where it enters the bottom of the furnace H2. Because of the pressure developed in the vaporizing chamber and the expanding passage of the nozzle, the vapor or gas issues from the nozzle at high velocity, for example. of the order of 400 feet per minute. The turbulence created by the high-velocity iet in the work chamber II3 of the furnace, which specifically is a small hardening furnace, procures substantial uniformity of the composition of the of Rezistal or other suitable metal which enf" cases nozzle III. The temperature of the vapor is thus increased during its passage through the nozzle, consequently its rate of expansion is increased materiallyto increase the velocity of the vapor as it emerges from the nozzle. The heater IIE also avoids any great temperature gradients along the nozzle which would tend to cause deposits of carbon. The heaters are preferably so designed that the vapor is almost at furnace temperature by the time it leaves the nozzle. The throat and divergent portion of the nozzle are designed to px'iovide maximum possible velocity of the gases issuing from the nozzle to promote a maximum turbulence in the' work chamber.

Since the jet is substantially at furnace temperature, it causes no localized cold spot in the furnace near its region of entry.

The furnace H2 is provided with resistors, not shown, for maintaining or obtaining the desired andere temperature o! the work and the furnace atmosphere. The temperature may be measured and/or controlled by a pyrometer. not shown.

In all modifications, since the rate at which the carburizing iluid is fed to the furnace is deilnite- 1y controllable, and the composition of the fluid is determined stoichiometricaily, or by chemical law of combination, the composition of the treating atmosphere is deiinite and reproducible, insuring consistent results for different carburizing or hardening runs. Moreover, because the carbur-A izing liquid is fed to the nozzle or pipe by a positive displacement pump capable of producing high pressure, clogging of the nozzle, by products of cracking oi' the carburizing liquid or agent, is precluded and feed of the liquid at predetermined, metered rate is ensured.

While I have illustrated and specifically described preferred iorms of apparatus, it is to be understood my invention is not limited thereto but is coextensive in scope with the appended claims.

What I claim is:

l. A system i'or heat-treatment oi metal objects comprising a` furnace including a chamber for said objects. means providing 'a passage for discharge into said chamber of a treating liquid, unmixed with gas, which by pyrolytic breakdown forms the atmosphere in which said objects are treated. and feeding means for the liquid comprising a positive displacement pump for exerting upon the liquid a pulsating pressure which increases upon increase of resistance to flow ot the liquid through said passage to ensure feed o! a constant metered amount o! said liquid per unit of time irrespective oi' greater or lesser obstruction oir4 saidpassage as by said breakdown products of said liquid.

2. A system ior heat-treatment oiizmetal ohjects comprising a furnace including a chamber for said objects. a nozzle for discharging a treating liquid into said chamber, a high pressure pump having a reciprocating piston for feeding a predetermined amount of said liquid to said nozzle for each reciprocation oi' said piston, valve means in said nozzle for controlling the discharge from said pump, and means for opening and closing said valve means at predetermined times in the cycle ot reciprocation of said piston.

3. A system for heat-treatment of metal objects comprising a furnace including a chamber for said objects, a nozzle for discharging a treating liquid into' said chamber, a high pressure pump having a reciprocating piston for feeding a predetermined amount of said liquid to said nozzle for each reciprocation o! said piston, valve means in said nozzle for controlling the discharge from said pump, and means for opening said valve when the pulsating pressure exerted on said liquid by said piston exceeds a predetermined magnitude and for closing said valve when the pressure is less than a predetermined magnitude.

' CRANDALL Z. ROSECRANS.

l CERTIFICATE or coRREcTroN.

Patent No. 2,176,1i7. october 1?, 1959.

GRANDALL z.' RosEcRANs.

s It 4is hereby certified that error appears in the printed specification of the alcove numbered patent requiring correction as follows: Page 2, first.

column, lines 5, hand 5, strike out "iin the sequence named when fan 25 is of the oentrifugalype, and in eithqr sequence when fan25 is of the propeller type),; and second column, )line 50, after "14.21d strike out the comme; and that the said Letters Patent shouldbe read with this corr-ecltion therein that `the same may conf-om to the record of the case in the Patent Office, e Y

' Signed and sealed this 1st day of October, A, D. l9li0.

Henry van Arsdale,"

(S6111) -Aci-.ing VCommis sioner of 4Patents.y

andere temperature o! the work and the furnace atmosphere. The temperature may be measured and/or controlled by a pyrometer. not shown.

In all modifications, since the rate at which the carburizing iluid is fed to the furnace is deilnite- 1y controllable, and the composition of the fluid is determined stoichiometricaily, or by chemical law of combination, the composition of the treating atmosphere is deiinite and reproducible, insuring consistent results for different carburizing or hardening runs. Moreover, because the carbur-A izing liquid is fed to the nozzle or pipe by a positive displacement pump capable of producing high pressure, clogging of the nozzle, by products of cracking oi' the carburizing liquid or agent, is precluded and feed of the liquid at predetermined, metered rate is ensured.

While I have illustrated and specifically described preferred iorms of apparatus, it is to be understood my invention is not limited thereto but is coextensive in scope with the appended claims.

What I claim is:

l. A system i'or heat-treatment oi metal objects comprising a` furnace including a chamber for said objects. means providing 'a passage for discharge into said chamber of a treating liquid, unmixed with gas, which by pyrolytic breakdown forms the atmosphere in which said objects are treated. and feeding means for the liquid comprising a positive displacement pump for exerting upon the liquid a pulsating pressure which increases upon increase of resistance to flow ot the liquid through said passage to ensure feed o! a constant metered amount o! said liquid per unit of time irrespective oi' greater or lesser obstruction oir4 saidpassage as by said breakdown products of said liquid.

2. A system ior heat-treatment oiizmetal ohjects comprising a furnace including a chamber for said objects. a nozzle for discharging a treating liquid into said chamber, a high pressure pump having a reciprocating piston for feeding a predetermined amount of said liquid to said nozzle for each reciprocation oi' said piston, valve means in said nozzle for controlling the discharge from said pump, and means for opening and closing said valve means at predetermined times in the cycle ot reciprocation of said piston.

3. A system for heat-treatment of metal objects comprising a furnace including a chamber for said objects, a nozzle for discharging a treating liquid into' said chamber, a high pressure pump having a reciprocating piston for feeding a predetermined amount of said liquid to said nozzle for each reciprocation o! said piston, valve means in said nozzle for controlling the discharge from said pump, and means for opening said valve when the pulsating pressure exerted on said liquid by said piston exceeds a predetermined magnitude and for closing said valve when the pressure is less than a predetermined magnitude.

' CRANDALL Z. ROSECRANS.

l CERTIFICATE or coRREcTroN.

Patent No. 2,176,1i7. october 1?, 1959.

GRANDALL z.' RosEcRANs.

s It 4is hereby certified that error appears in the printed specification of the alcove numbered patent requiring correction as follows: Page 2, first.

column, lines 5, hand 5, strike out "iin the sequence named when fan 25 is of the oentrifugalype, and in eithqr sequence when fan25 is of the propeller type),; and second column, )line 50, after "14.21d strike out the comme; and that the said Letters Patent shouldbe read with this corr-ecltion therein that `the same may conf-om to the record of the case in the Patent Office, e Y

' Signed and sealed this 1st day of October, A, D. l9li0.

Henry van Arsdale,"

(S6111) -Aci-.ing VCommis sioner of 4Patents.y

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