US1724956A - Muffle, muffle furnace, and the like - Google Patents

Description

Aug. 20, 1929.

P. H. P. MONCKTON MUFFLE MUFFLE FURNACE, AND THE LIKE Filed Nov. 23, 1927 8 23 U h K a 242 V 8 Mil/3 226 V 7 1o 27 4 [z 45 30 20 n n 55 34- z I o g gO fzN OflMM g i 52 I 516 as 5 QM 8 7 Patented Aug. 20, 1929.

UNITED STATES PATENT OFFICE.

PHILIP HENRY PARR MONCKTON, OF JOHANNESBURG, TRANSVAAL, SOUTH AFRICA, ASSIGNOR TO WILLIAM HENRY CROSS, OF JOHANNESBURG, UNION OF SOUTH AFRICA.

MUFFLE, MUFFLE FURNACE, AND THE LIKE.

Application filed November 23, 1927, Serial No. 235,230, and in the Union of South Africa September 16, 1927.

This invention relates to muflles, mufile furnaces and the like, which are heated electrically.

Electrically heated muffles generally have not proved satisfactory invuse as, owing to the fact that the elements have had to be renewed frequently owing to their having been quickly burnt out or destroyed, such mufl'les have not been economical in use.

Now one object of the invention is to design and construct an electrically heated muffle or the like in such a way that the heating elements will not be subject to such premature destruction. Further ob ects of the invention are to ensure better control of the heat, by varying or regulating the electric current, and better control of the supply of air, by means of induced draught.

Amongst the advantages obtained in a muffie constructed according to the invention, as compared with existing mufiles, are, that it is more efiicient in use, that it occupies less space, that it is more, quickly heated and the heat more effectively distributed in the muflie or heating chamber and, furthermore, that the atmosphere in the vicinity of the muflle is cooler, as the loss of heat by radiation is comparatively small.

In the accompanying sheet of drawings I illustrate a practical embodiment of my invention, wherein Fig. 1 shows a half-sectional elevat1on of the complete muflle.

Fig. 2 is a central sectional side elevat1on of the complete muffle.

Fig. 3 is a plan view of the electrical heating element or resistance, removed from the heating chamber, and

Fig. 4 is a sectional elevat1on lllustratlng a modified form of the mufile chamber.

In the embodiment of the invention illustrated in the annexed drawings, the muflie or furnace includes an inner part or box 1, the interior of which constitutes the heating chamber of the muffle,-on the floor of which the cupels are placed, and an outer casing or enclosing structure. The part or box 1 is open at the front, as seen in Fig. 2, and partially closed at the back or rear end. It may be constructed of fireclay or other suitable refractory material and is shown provided with a false bottom 2 in the form of a slab, which may be made of asbestos cement or other suitable material. The mufile chamber is shown provided along both sides with a row of holes 3 which allow of the passage into the heating chamber 4 of preheated air.

The outer casing or enclosing structure may, as shown, include an external metal casing 5 which is open at the backsee Fig. 2-and formed at the top, bottom and sides of the front with a flange 6. Inside the easing 5, at the sides, top and bottom, are arranged slabs 7 of asbestos cement. Inside the slabs 7 is arranged a box, lining or part 8, constructed of fireclay or other suitable refractory material. This box or part 8, like the box or part 1, is open at the front and partially closed at the back. The box or lining 8 of the outer casing is somewhat larger internally than the external dimensions of the part or box 1 providing the heating chamber, so that a space 9 is left or provided between the fireclay lining or box 8 and said box or part 1 at the top and at both sides. The part or box 1 is arranged inside the lining 8 of the outer casing on the bottom thereof and is placed against the back of said lining 8.

The outer casing at the front has secured to it a plate 10, in which is formed an opening 10 and which may be made of cement asbestos and is shown fixed by screws 11 to the flanges 6.

In the front end of the box or part 8, at the back of the plate 10, is tightly fitted a slab or piece 12 which contacts with the front end of the box or part 1 and so closes the space 9 at the front of the furnace. The slab 12 is provided with an opening 13 which opens into the heating chamber 4: and is closed by the door 14. The false bottom 2 is shown slightly longer than the bottom of the box or part 1, so that the slab 12 fits under the forwardly projecting portion of the false bottom 2 beyond the front end of the part or box 1. Through the slab 12 holes 15 are formed which allow heated air to pass from the front end of the space 9 to the open front end of the heating chamber 1. The front plate 10 is shown provided with guides 16 for the door 14, and the door 14 is shown consisting of a metal casing 17 lined with a block of refractory material 18. In the door let an inspection hole or opening 19 is provided which is adapted to be closed by a hinged door or cover 20. The door 14 is counterbalanced by a weight 21 which is at tached to the door by a cord or flexible connection 22, which passes over the guide pulleys 23 carried by brackets 24 fixed to the top of the casing 5 at the front, 14- being a stop for limiting the upward movement of the door let.

At the front of the opening in the front plate 10, which opening 10 is closed by the sliding door 14, a rest or plate 25 is provided, carried by a bracket 26, for use in putting the cuples into and taking them out of the heating chamber.

A hole or opening 27 is provided, which passes through the outer metallic casing 5, the slab 7, and the top of the box or lining 8, and leads into the space 9, which allows of the passage of induced air to said space 9. Such induced air is heated in its passage through the space 9 from'the inlet 27 'to the rows of holes 3 in the sides of'the box or part 1 and to the holes 15 provided in the slab or piece 12 at the front of the heating chamber 4.

An opening 28 is provided through the back of the box or part 1, the back of the box or lining 8 and through a slab or sheet 28 which is fitted into the back of the outer casing against the back of the box or lining 8. This opening 28 forms the outlet for thefumes and gases from the heating chamber 4. Inthe opening 28 in the back of the box or lining 8 and in the slab or sheet 28 is fitted and cemented a tubular fireclay piece or socket 29 which communic ates with a vertical pipe or flue 30 through a coupling piece or nipple 31 and a T piece 32. In the pipe or flue 30 means are provided for introducing a jet of compressed air r thelike for inducing the passage of air through the muffle. The'means for effecting this are shown consisting of the upwardly directed nozzle 33 attached to an air supply pipe 34 in which is provideda valve 35. In the bottom of the T piece a screw plug or cover 36 is provided for removing any accumulated litharge or other deposit from the T piece 32 or flue 30. The jet of compressed air ensures the passage of the induced air current through the furnace and may also be used for blowing out of the flue or pipe 30 any accumulated fumes. The T piece 32 is shown carried or supported by 'legs or supports 37.

v The electrical heating means for the muflle includes an element or resistance which is arranged in the upper portion of the heating chamber 4 so as to be in a suitable position above the tops and out of the way of the cupels, which are not shown in the .drawing. This heating element 38 may be made of any suitable material and is shown constructed of zig-Zag shape with a centre space or gap This form of resistance or element is best adapted to effect a practically uniform distribution of the heat throughout the heating'chamber 4:,and the gap or space 39 prevents excessive heating of the element whichwould otherwise obtain at this point. The element 38 is supported at suitable points by hook bolts 40, of refractory material, from the top or roof of the box or part 1. The leads 41 for the element 38 pass through holes or openings 42 in the back of the boxes or parts 1 and 8 and slab 28 to the exterior of the muffle, and are suitably connected to the electrical wires or conductors 43 by'suitable terminals. The leads or portions 41 which pass through the openings 42 and connect the element 38 with the electrical wires I3 are of considerably greater cross-sectional area than the element 38, so" that little or no heat is generated in said leads 41.

In the modification illustrated in Fig. 4, the roof or upper portion of the box or part 1, which provides the heating chamber at, is arched or curved, andthe roof or upper portion of the box orpart 8 is similarly arched or curved. In this way the upper portion of the space or chamber 9 is of arch shape. In this modification the heating element 38 will also be arched or curved. In other respects the muffle or muffle furnace may be similar to that described, andshown in Figs. 1 to'3.

What I claim as my invention and desire to protect by Letters Patent is 1- 1. A muffle, muffle furnace or the like, comprising an inner part which provides the heating chamber, an outer casing enclosing said inner part and forming 'a'space between it and said inner part, said outer casing being provided with an inlet for air leading into said space, and the inner part being constructedwith a row of holes along each side near the floor which allow air which is preheated in its passage through the inlet and space to pass directly into the heating chamber, electrical heating means in said heating chamber, and an outlet leading from the heating chamber to the open, as set forth.

2. A muille, muiile furnace or the like comprising an inner part which provides the heating chamber, an outer casing enclosing said inner part and forming aspace between it and said inner part, said outer casing being provided with an inlet for air leading into said space, and the inner part being'constructed with a row of holes along each side near the floor, a slab arranged at the front end of the inner part, which closes the space between said inner part and the outer casing at the front and is provided with a plurality of holes which lead from'the space to the front of the heatingchamber, said holes in the inner part and slab allow-ing'air which is preheated in its passage through the inlet and spaceto pass into the heating chamber,

electrical heating means in said heating chamber, and an outlet leading from the heating chamber to the open, as set forth.

3. A mufiie, muffle furnace or the like, comprising an inner part which provides the heating chamber, an outer casing enclosing said inner part and forming a space between it and said inner part, said outer casing being provided with an inlet for air leading into said space, and the inne part being constructed with a row of holes along each side near the floor which allow air which is preheated in its passage through the inlet and space to pass directly into the heating chamber, electrical heating means, in the form of an element or resistance of zig-zag shape constructed to forma gap at the center thereof, in said heating chamber, and an outlet leading from the heating chamber to the open, as set forth.

4. A muffle, muffle furnace or the like, comprising an inner part which provides the heating chamber, an outer casing enclosing said inner part and forming a space between it and said inner part, said outer casing being provided with an inlet for air leading into said space, and the inner part being constructed with a row of holes along each side near the floor which allow air which is preheated in its passage through the inlet and space to pass into the heating chamber, electrical heating means, in the form of an element or resistance of zig-zag shape constructed to form a gap at the centre thereof, in said heating chamber, means for suspending the element from the top of the heating chamber comprising hook-shaped members of refractory material, and an outlet leading from the heating chamber to the open, as set forth.

5. A muffle, muffle furnace or the like, comprising an inner part which provides the heating chamber, an outer casing enclosing said inner part and forming a space between it and said inner part, said outer casing being provided with an inlet for air leading into said space, and the inner part being constructed with openings which allow air which is preheated in its passage through the inlet and space to pass into the heating chamber, electrical heating means in said heating chamber, an outlet leading from the heating chamber to the open, and means co-operating with said outlet for inducing a current of air through the muffle furnace, as set forth.

6. A muffle, muffle furnace or the like, comprising an inner part which provides the heating chamber, an outer casing enclosing said inner part and forming a space between it and said inner part, said outer casing being provided with an inlet for air leading into said space, and the inner part being constructed with openings which allow air which is preheated in its passage through the inlet and space to pass into the heating chamber, electrical heating means in said heating chamber, an outlet leading from the heating chamber to the open, and means cooperating with said outlet for inducing a current of air through the muffle furnace, said latter means consisting of a nozzle for directing a jet of compressed air, as set forth.

7. A muffle, muflie furnace or the like, comprising an inner part which provides the heating chamber, an outer casing enclosing said inner part and forming a space between it and said inner part, said outer casing being provided with an inlet for air leading into said space, and the inner part being constructed with openings which allow air which is preheated in its passage through the inlet and space to pass into the heating chamber, electrical heating means in said heating chamber, an outlet leading from the heating chamber to the open, a flue communicating with the outlet, and a nozzle directing a jet of compressed air through the flue for inducing a current of air through the muffle or furnace, as set forth.

8. A muffle, mufile furnace or the like, comprising an inner part, of arch shape in its upper portion, which part provides the heating chamber, an outer casing of arch shape in its upper portion, which casing encloses said inner part and forms a. space between it and said inner part, said outer casing being provided with an inlet for air leading into said space, and the inner part being constructed with a row of holes along each side near the floor which allow air which is preheated in its passage through the inlet and space to pass directly into the heating chamber, electrical heating means of arch shape in said heating chamber, and an outlet leading from the heating chamber to the open, as set forth.

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

PHILIP HENRY PARR MONCKTON.

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