US3130250A

US3130250A - Heat treating furnace

Info

Publication number: US3130250A
Application number: US43414A
Authority: US
Inventors: Harold E Mescher
Original assignee: Pacific Scientific Co
Current assignee: Pacific Scientific Co
Priority date: 1960-07-18
Filing date: 1960-07-18
Publication date: 1964-04-21
Anticipated expiration: 1981-04-21
Also published as: GB917537A

Description

April 21, 1964 H. E. MESCHER HEAT TREATING FURNACE Filed July 18. 1960 2 Sheets-Sheet l xm. m4

FWN

April 21, 1964 H. E. MESCHER HEAT TREATING FURNACE 2 Sheets-Sheet 2 Filed July 18. 1960 /Ez Z United States Patent Office 3,130,259 Patented Apr. 21, 1964 This invention relates, generally, to heat treating furnaces, and the invention has reference more particularly to a novel self-contained furnace especially suited for brazing, sintering, and annealing, materials such as stainless steel and metallic coating of ceramics, etc.

Great diriculty has been experienced heretofore in the use of furnaces for treating stainless steel, metallic coating of ceramics and the like, because `such substances tend to oxidize rapidly at higher temperatures in the presence of even minute quantities of air, the oxidation of these materials causing them to lose their bright, clean appearing surfaces and turning them dull and unattractive as a result of the use of ordinary heat treating furnaces.

It is therefore the principal object of the present invention to provide a novel heat treating furnace that is especially adapted to heat treat materids sensitive to oxidization at higher temperatures, such as stainless steel, etc., the said novel furnace employing hydrogen locks or depending loading and unloading compartments or sections constantly supplied with hydrogen to prevent the ingress of air into the furnace, said compartments being sealed olf from outside air during heat treating operations hy use of closure plates.

A feature of the present invention is to provide a novel furnace of the above character employing, in addition to loading and unloading compartments, a tunnel structure comprising a purge chamber, a chamber in which the material is heat treated, and a cooling chamber that preferably is water jacketed for receiving the material after eat treating.

Another feature of the present invention is to provide a novel furnace of the above character having loading and unloading elevators in its loading and unloading sections, said elevators serving to open the closure plates of these sections during the loading and unloading operations only, during which operations the escape of hydrogen aad/or other inert gases through such openings prevent the ingress of oxidizing atmosphere.

These and other features and advantages of the present invention will become more apparent from a perusal of the following specification taken in connection with the accompanying drawings wherein:

FlG. l is a vertical part-sectional View of the novel furnace of this invention;

FIG. 2 is an enlarged sectional view of the loading elevator section of the novel furnace shown in FIG. 1; and

FIG. 3 is a fragmentary sectional view taken along line 3 3 of FIG. 2.

Similar characters of reference are used in the above gures to designate corresponding parts.

Referring now to the drawings, the reference numeral 31 designates the novel heat treating furnace of this invention as a whole, the said furnace comprising a depending leg providing a loading or entrance section 1 which leg depends from one end portion of a tunnel structure or section 2 that extends transversely through a inutile or retort 3 and outwardly thereof and to depending unloading leg or exit section d that is similar in construction to the loading section 1. Thus it will be seen that the novel furnace of this invention is a substantially inverted U-shaped structure with the entrance and exit sections thereof depending from the main transverse tunnel section 2. This structure thus provides hydrogen locks as will further appear to prevent the ingress of air into the furnace inutile.

As particularly shown in FIG. 2, the loading or entrance section 1 is of hollow tubular construction and has movable therewithin an elevator or carriage 5 that is supported on tubular guide shoes 6 fixed on a cross frame 7 that in turn is rigidly attached to and carried by a piston rod S. The piston rod extends upwardly into an operating cylinder 9 positioned above the tunnel structure 2 and has a piston 1d on its upper end movable Within this cylinder under the action of compressed gas supplied through pipes 11 and 11. Although the piston rod 8 is surrounded by an efticient seal such as neoprene O-rings at the base of cylinder 9 to prevent the ingress of air into die system, the cylinder 9 may be supplied with compressed inert gas, such as argon, for operation of the piston rod 8.

It Will be noted that the guides 6 ride upon guide rods 12 which are attached at their lower ends to a spring loaded sealing closure plate 13. This plate 13 is shown urged upwardly by coil springs 14 connected at their lower ends to screws 15 threaded through plate 13 and at their upper ends to lugs 15 extending from the loading section 1. The closure plate 13 is provided with a sealin'I ring 17, as of reclay or sand, which positively contacts the periphery of the lower open end of loading section 1 when the piston 10 is raised in cylinder 9, as shown in FlG. l, the sealing ring 17 serving to seal the joint between closure plate 13 and loading section 1, preventing the ingress of air while in such position. With the elevator 5 in its lowermost position, in which position the gas pressure within the cylinder 9 serves to hold down piston 1li thereby distending springs 14, as shown in FIG. 2, a load such as 13 can be placed upon the carriage 5. For example, this load can be pushed upon the carriage as from a suitable conveyor 19. With the load upon the elevator or carriage 5, piston 1@ is energized to raise piston rod 8 and carriage 5 within loading section 1 until the carriage reaches its uppermost position shown in FIG. l. During the upward movement of the carriage, the springs 14 contract automatically to raise closure plate 13 until the sealing ring 17 carried by this plate contacts the lower end of section 1, closing this section against atmospheric air.

During the entire operation of the furnace, dry hydrogen is supplied through pipe 29 into a purge chamber section 21 of tunnel structure 2, from whence this gas flows through the purge chamber and downwardly through loading section 1, escaping at the bottom end of section 1 when the elevator is in its loading position (shown in FIG. 2), and, since the speciiic gravity of hydrogen is .096, this gas serves to prevent the entrance of atmospheric air into the chamber 1. As soon as the springloaded closure plate 13 closes, any air that did manage to get into the chamber 1 is immediately flushed out by the hydrogen which continuously enters pipe 20, owing downwardly through section 1, and out through a bleedout pipe 22.

With the load 1S in its upper position in loading section 1, as shown in FIG. 1, it can be pushed into the purge chamber 21 through use of a piston rod 23 having a push plate 24 on the inner end thereof, the said piston rod being actuated as by a piston contained within the cylinder 28, which piston can also be actuated by an inert gas, such as argon, just as in the case of the piston within cylinder 9, so that any leakage around the rod 23 and into the loading section 1 will not cause oxidization of the work. The piston rod 23, as well as the piston rod 8, may be water cooled, if desired, to prevent their overheating in use. After the Work has been pushed from elevator into the purge chamber 21, it is allowed to remain for a few minutes to permit lany air that has been entrained in the work (such as in hollow parts of the material or load to be treated) to exhaust through the tunnel structure 2, through loading section 1, and out through bleed-out pipe 22, along with hydrogen entering tunnel 2 through pipe 2t). After the purge cycle, the timing of which depends upon the nature of the work, the load is moved by the push plate 24 along tunnel structure 2 into the high heat section 2 of the mue 3. Preferably, this mutle is heated on all four walls to obtain uniform heating as by use of iron-aluminum-chromium elements 25, ereby providing the ultimate in temperature uniformity and heat transfer. Temperatures of 2200" F. are readily obtained in this structure by the use of Inconel for tunnel structure 2 which tunnel structure extends directly through the interior of the muflle 3.

Within the high heat section 2 of the tunnel structure 2, the work can be either annealed, brazed, or heat treated, in accordance with the wishes of the operator, and, after sufficient time has elapsed to perform the desired operation, the load is further moved by push plate 24 into a water jacketed cooling section 2 of the tunnel structure 2 for a cooling cycle determined in time only by the size of the load and the weight of the parts. After the load has cooled sufciently, it is moved to the unloading carriage or elevator 5 which, at this time, is in its upper position and thereafter is moved downwardly into the position shown in FIG. 1, whereupon the treated material 18 can be removed from the furnace.

In order to prevent the ingress of air into the unloading section 4 of the furnace, a hydrogen inlet pipe 20' is provided in the water jacketed cooling section 2" just as in the case of the purge chamber 21. Entrance and exit hinged radiation shield doors 26 and 26' are provided at the entrance and exit of the high heat section 2 to prevent as much heat as possible from entering the purge chamber 21 and the water jacketed cooling section 2" in use. These doors are mounted entirely internally of the tunnel structure and with no rods or protrusions extending outside the same so that no outside atmosphere can enter the tunnel 2 through use of these doors.

If desired, in order to further ensure the prevention of the entrance of any atmosphere into the loading section 1 or unloading section 4 when these sections are opened by the lowering of the carriages 5 or 5 to their lowermost positions, an additional inert gas inlet 27, such as a nitrogen gas inlet, can be provided on these members which supply gas immediately upon the openings of the seals 17, i.e., the downward movement of the springloaded closure plate 13 serves to actuate a relay 28 (see FIG. 2) controlling a motor 30 operating a valve 29 in pipe 27 so that a large ilow of nitrogen gas takes place into the loading or unloading section as the case may be when its lower end has been opened, positively preventing any air from entering such section.

Thus, in using the novel furnace of the present invention, substances that are highly sensitive to oxidation are heat treated, brazed, or otherwise handled, as desired, without any possibility of oxidization taking place, since all oxygen is excluded completely from the system, in all '4 phases of the operation, i.e., the purging, the heat treating, and the cooling, sections, so that the cooled material leaving the unloading section is just as shiny and bright as when it was placed in the furnace.

Since many changes could be made in the above construction of the novel furnace of this invention and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shail be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A heat treating furnace comprising a muflle, a work receiving tunnel structure having a transverse section of gas tight construction extending through said mule for having a portion thereof to be heated thereby, said tunnel structure having gas tight depending entrance and exit sections at the opposite end portions of the transverse section forming an inverted U-shaped hollow tunnel structure, means for supplying purging gas to said transverse and depending sections, one of said depending sections serving as a work loading section and the other of said depending sections serving as a work unloading section, said sections being provided with horizontally extending openings at their lowermost points, vertically movable horizontal closure plates for normally closing said openings in gas tight condition, movable work carrying elevators provided within said depending loading and unloading sections, piston means for raising and lowering said elevators, said piston means being sealed to prevent ingress of air into said furnace, movement of said elevators downwardly and below the lowermost points of said loading and unloading sections serving to depress and open said horizontal closure plates enabling the insertion or removal of work, movement of said elevators upwardly from their lowered positions permitting said closure plates to automatically close and seal off the lower ends of said sections, thereby positively preventing the ingress of outside atmosphere, the horizontal openings in said depending sections preventing the mixing of hydrogen gas With air in said furnace to prevent the formation of explosive mixtures, said tunnel structure transverse section providing a purge chamber for retaining the work for a period before it reaches the heated portion of said tunnel structure, said purge chamber having an inert gas inlet adjacent said heated portion for purging work before it reaches said Alatter portion, such inert gas and purged gases moving outwardly of said purge chamber and said transverse section downwardly through said loading section and outwardly adjacent the lowermost end thereof.

2. A heat treating furnace as delined in clmerein said depending loading section also has an inert gas inlet, and relay control means for opening said latter inlet to admit inert gas to said loading section whenever said loading section horizontal closure plate is depressed from closed and sealing relation to said loading section.

3. A heat treating furnace as deined in claim 1 wherein said tunnel structure transverse section provides a cooling section for the work after it leaves the heated portion of said tunnel structure, said cooling section having an inert gas inlet for purging said cooling section and said connected unloading section with inert gas in use, said gas escaping downwardly through said unloading section and outwardly at the lower end portion thereof.

4. A furnace of the character described comprising a substantially inverted U-shaped hollow structure having a transverse sealed tunnel section provided with vertically depending entrance and exit leg sections at the ends thereof, said depending leg sections having horizontal openings at their lowest points, spring pressed horizontal closure plates for normally closing and sealing the lower open ends of said leg sections, said structure beaing sealed against outside air excepting when said closure plates are opened, said entrance leg section being adapted to receive work to 'oe heated and the exit leg section being adapted to discharge treated Work, sealed piston means movable Within said leg sections for forcing said horizontal closure plates open when receiving or discharging Work, a muifle surrounding a portion of said transverse tunnel section for heating the same, a purge chamber provided in said transverse tunnel section in advance of said mue, a cooling section provided in said transverse tunnel section immediately following said mue, and radiation shield doors hinged within the heated portion of said transverse tunnel section adjacent the end Walls of said Inutile and sealed from outside atmosphere for preventing the escape of heat into the remainder of said transverse tunnel section, said doors swinging automatically under pressure of the Work to permit the ready movement of Work through said transverse tunnel section heated portion.

References Cited in the le of this patent UNITED STATES PATENTS 1,073,235 Hillebrand Sept. 16, 1913 1,789,177 Ipsen et al. lan. 13, 1931 2,269,838 Wroblewski Jan. 13, 1942 2,290,551 Gier July 21, 1942 2,332,943 Sobers Oct. 26, 1943 2,891,659 Westeren June 23, 1959

Claims

4. A FURNACE OF THE CHARACTER DESCRIBED COMPRISING A SUBSTANTIALLY INVERTED U-SHAPED HOLLOW STRUCTURE HAVING A TRANSVERSE SEALED TUNNEL SECTION PROVIDED WITH VERTICALLY DEPENDING ENTRANCE AND EXIT LEG SECTIONS AT THE ENDS THEREOF, SAID DEPENDING LEG SECTIONS HAVING HORIZONTAL OPENINGS AT THEIR LOWEST POINTS, SPRING PRESSED HORIZONTAL CLOSURE PLATES FOR NORMALLY CLOSING AND SEALING THE LOWER OPEN ENDS OF SAID LEG SECTIONS, SAID STRUCTURE BEING SEALED AGAINST OUTSIDE AIR EXCEPTING WHEN SAID CLOSURE PLATES ARE OPENED, SAID ENTRANCE LEG SECTION BEING ADAPTED TO RECEIVE WORK TO BE TREATED AND THE EXIT LEG SECTION BEING ADAPTED TO DISCHARGE TREATED WORK, SEALED PISTON MEANS MOVABLE WITHIN SAID LEG SECTIONS FOR FORCING SAID HORIZONTAL CLOSURE PLATES OPEN WHEN RECEIVING OR DISCHARGIN WORK, A MUFFLE SUROUNDING A PORTION OF SAID TRANSVERSE TUNNEL SECTION FOR HEATING THE SAME, A PURGE CHAMBER PROVIDED IN SAID TRANSVERSE TUNNEL SECTION IN ADVANCE OF SAID MUFFLE, A COOLING SECTION PROVIDED IN SAID TRANSVERSE TUNNEL SECTION IMMEDIATELY FOLLOWING SAID MUFFLE, AND RADIATION SHIELD DOORS HINGED WITHIN THE HEATED PORTION OF SAID TRANSVERSE TUNNEL SECTION ADJACENT THE END WALLS OF SAID MUFFLE AND SEALED FROM OUTSIDE ATMOSPHERE FOR PREVENTING THE ESCAPE OF HEAT INTO THE REMAINDER OF SAID TRANSVERSE TUNNEL SECTION, SAID DOORS SWINGING AUTOMATICALLY UNDER PRESSURE OF THE WORK TO PERMIT THE READY MOVEMENT OF WORK THROUGH SAID TRANSVERSE TUNNEL SECTION HEATED PORTION.