US2493246A - Furnace - Google Patents

Description

Jan. 3, 1950 F. w. HAYWOOD ETAL FURNACE ZShets-Sheet 1 Filed March 4. 1946 M0064 5. Zcfz cdZef Jan. 3, 1950 F. w. HAYWOOD ET AL 2,493,246

FURNACE Filed March 4, 1946 2 Sheets-Sheet 2 Patented Jan. 3, 1950 UNITED STATES PATENT OFFICE FURNACE. Frederick Wardle, Haywood and Douglas Stuart Laidler, W,atfo rd; England, assignors of. o nehalf to Wild-Barfield Electric- Furnaces Limited, Watford, England Application March 4, 1946, Serial N 0. 651,953 In Great. Britain February 1945 6 Claims. 1'.

In heat treatment furnaces (used in a wide sense to include chambers in which metallurgical and like, industrial heat treatments are carried out at controlled temperatures). it has been increasingl common practice to use fans for moving or circulating the atmosphere in the chamber, whether it be air or a protective or reactive as. g In British Patent No. 552,748 there is described the use, in the heat treatment of powder or small articles, of a number of jets of gaseous atmosphere directed over the surfaces between a series of trays supporting the powder or articles.

The present invention is directed further to the use of numbers of jets of atmosphere directed into the furnace chamber. From one aspect, forming an important part of the invention, it is proposed to carry out gaseous surface treatment especially of relatively large articles (not readily carried in trays) at determined temperatures by any conventional means for spacing them with their surfaces exposed in a retort or furnace chamber and directing fresh treating gas over the surfaces successively throughout the height (or length) of the work space from all directions. If necessary the gas can also be exhausted at successive levels, but in many cases (e. g. carburising) a common outlet at the top or one end or at some other appropriate position will sufiice. In order to equalise the treatment over the surfaces, it is found that a general turbulence or whirling movement of the whole atmosphere is desirable or possibly essential. But in many cases the atmosphere is under conditions as to temperature and density that make the use of a fan inefiicient or impracticable. The desired effect can be obtained by suitably directing jets of incoming atmosphere: in a typical vertical furnace, of the kind already referred to, jets may be directed tangentially from a number of radial pipes disposed under a grid beneath the work, as well as from (preferably radially directed) apertures at successive levels. The bottom jets then tend to have upon the whole furnace atmosphere a similar effect to that which has been found to be so advantageous when a fan is used. From another aspect, this use of multiple small jets of incoming atmosphere directed to give such beneficial turbulence or whirling within the chamber of afurnace (of either batch or continuous type) for metallurgical or like industrial heat treatments is itself an important part of the invention.

Other parts of the invention are embodied in a typical gas carburising furnace having a vertical cylindrical chamber which will now be described by wayof; example with. reference. to the accompanying drawings. r

In the drawings:

Fig. .l is a sectional plan view and Fig. 2. a perspective side elevational view of the retort-or; chamber, partly cut away to show the gas delivery arrangements.

The chamber or retort l is. suitably heated, possibly by electrical elements 2 or other heating means suitably disposed in relation to the surrounding wall 3 of a heating furnace containing the retort. The incoming carburising gas is carried down by gas inlet pipe 4 through the hot zone outside the chamber 1 to an inlet 5 at the centre of the bottom of the chamber. A mani- -fold, including a number of radial branches 6 (preferably four or more) leading to a ring I, is disposed at the bottom of the retort, in some cases beneath a grid or the like according to the method of support and proximit of the work. Further pipes 8 or equivalent gas distributing means lead upwardly from the ring 1 and surround the work space. Apertures in the radial branches 6 are directed more or less horizontally and tangentially in the same sense to give a rotary and outward tendency to the flow and apertures may also be provided in the ring portion I all as indicated by arrows 6 and l. The main flow against the surfaces of the work is provided by apertures, possibly staggered in alternate vertical pipes 8, directed inwardly and preferably substantially radially as indicated by arrows 8, though some additional turbulence jets 8" may be directed from the verticals if found desirable. An outlet 9 leads the gas from the top of the chamber.

We claim:

1. A furnace for heat and gas treatment of the surfaces of articles comprising a treating chamber having side walls and ends, a gas inlet manlfold in one end of the chamber, and a plurality of gas pipes extending radially from the manifold to the side walls and thence in spaced relationship along the side walls, the gas pipes being provided with jet openings directing gas toward the center of the chamber.

2. A furnace as claimed in claim 1 in which the gas pipes are also provided with jet openings directing gas tangentially in the chamber to cause a whirling motion of the gas therein.

3. A furnace for heat and gas treatment of the surfaces of articles comprising a treating chamber having side walls and ends, a gas inlet manifold in one end of the chamber, a plurality of gas pipes extending radially from the manifold to the side walls, the gas pipes being provided with jet openings directing gas tangentially in the chamber, and an opening at the other end of the chamber, whereby the gas moves through the chamber from the gas inlet end to the outlet end with a helical motion.

4. A furnace for heat and gas treatment of the surfaces of articles comprising a treating chamber having side walls and ends, a gas inlet manifold and a ring pipe in one end of the chamber,

the ring pipe being adjacent to the side walls,

a plurality of branch pipes extending radially between the manifold and the ring pipe, and a plurality of pipes in spaced relationship extending from the ring pipe along the side walls, said plurality of pipes being provided with jet openings directing the gas toward the center of the chamber.

5. A furnace as claimed in claim 4 in which said plurality of pipes also have jet openings directing the gas tangentially to impart a whirling motion to the gas in the chamber.

6. A furnace as claimed in claim 4 in which the branch pipes are provided with jet openings directing the gas tangentially to impart a whirling motion to the gas in the chamber.

FREDERICK WARDLE HAYWOOD. DOUGLAS STUART LAIDLER.

REFERENCES CITED The following references are of record in the file of this patent:

, UNITED STATES PATENTS Number Name Date 633,221 Sorlle et a1 Sept. 19, 1899 884,181 Machlet Apr. 7, 1908 I 1,119,941 Elliott Dec. 8, 1914 1,322,428 Gloess Nov. 18, 1919 1,440,540 Harris, Jr Jan. 2, 1923 1,545,155 Mehner July 7, 1925 1,725,129 Carpenter et al Aug. 20, 1929 1,981,436 Shodron Nov. 20, 1934 2,040,679 wean May 12, 1936 2,044,370 Shodron June 16, 1936 2,299,299 Bills Oct. 20, 1942 2,311,344 Machlet Feb. 16, 1943 2,343,004 Elder et al Feb. 29, 1944 FOREIGN PATENTS Number Country Date 552,748 Great Britain Apr. 22, 1943

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