US1676876A

US1676876A - Constant-temperature oven

Info

Publication number: US1676876A
Application number: US72208A
Authority: US
Inventors: Winfield H Stannard
Original assignee: Central Scientific Co
Current assignee: Central Scientific Co
Priority date: 1925-11-30
Filing date: 1925-11-30
Publication date: 1928-07-10
Anticipated expiration: 1945-07-10

Description

July 10, 92s. 1,676,876

W. H. STANNARD CONSTANT TEMPERATURE OVEN Filed Nov. 30, 1925 2 Sheets-Shet 1 MLLnesscs 50 15 53 1) hwafl Z! 2/1 [aid Siam/(MY! I M July 10, 1928.

W. H. STAN NARD CONSTANT TEMPERATURE OVEN 2 Sheets-Sheet Inventor mafia 53 M 'ulv'dinesses Hu s Patented July 10, 1928.

UNITED. STATES 6,81 PATENT OFFICE,

-WINFIELD H. STANNARD, OF MATTESON, ILLINOIS, ASSIGNOR TO CENTRAL SCIENTIFIC ,COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS. v

CON STAN IE-TEMPERATURE OVEN.

This invention relates to ovens for at ministering treatment at constant temperatures and has for its principal objects to provide a greater uniformity of temperature throughout the difierent parts of the oven and a greater time-constancy of temperature of the oven as a whole. More specific ob jects will appear and be best understood as the disclosure proceeds and the description is read in connection with the accompanying drawings illustrating the preferred embodiment of the invention, in which Fig. 1 is a vertical section through the oven; Fig. 2 is a transverse section thereof;

Fig. 3 is a perspective view of a unit including the preferred electrical equipment for the oven;

Fig. 4 is a plan view of the panel arrangement, and i I Fig. 5 is a wiring diagram illustrating the most advantageous connection of the apparatus.

The most satisfactory oven enclosure for general application includes a bottom 10 and a top 11 connected by

sides

12 and 13, a back 14 and a front 15. Each of these is so fab ricated of suitable materials as to be as nearly non-conducting as practicable. For example, each part of the enclosure may consist of an outer sheet of asbestos board 16, spaced from an inner sheet of like board 17, by a filling of asbestos fiber, mineral wool, or the like 18. I 5 The front 15 is shown as a door, hinged at 19, and having beveled edges 20m make a close joint with correspondin edges21 on the facings 22 attached to the

sides

12 and 13. For the best results the electric heating 5 element should consist of a pluralit of units presenting uniform wattage throng out their en'gth; For example, the units may be coils 23 extending around the lower portion of the container and supported in notched blocks 5 of asbestos board 24, secured to a base 25 of asbestos board, or other material, that will not reflect or radiate heat to a great extent.

Extending upwardly from the heating element is a flue, or flues, 26, in open communi- 3 cation with the enclosure at both ends." In

the simple construction shown, a wall 27 extends across the enclosure spaced a short distance from the back 14 and terminating just above "the blocks 24 at the bottom 10, and

5 about the same distance 'fromtheto'p'11.

adjustments in opening and closing the inner Secured to this wall and extending parallel to the sides of the corresponding facings, are

walls

28 and 29, which terminate short of the door 15 and are supported by brackets 30.

A wall 31, of glass, normally rests against the front edges of the

walls

28 and 29 and is supported by springs 32 on a door r'ame 33, which is fitted with a second glass wall 34 in spaced relation to the wall 31. The door frame 33 is hinged to one facing 34 and closes against an opposed facing 35 secured. respectively to the

sides

12 and 13. The springs 32 serve to hold the glass wall 31 in proper relation and permit it to make slight door. The

walls

28 and 29 are equipped with supports for shelves 36.

The side 13 is cut away adjacent to the bottom to form an elongated opening 37 through which the base 25 with the heating element thereon, may he [slid in inserting that element into or withdrawing it from the container. Attachedto the base'25 is a block 38 of insulating material,. s uch as transite, and to this, in turn, is attached a panel 39, adapted to carry various instruments and the wiring. The outer casing of the wall 13 is madein two pieces overlapped, as indicated at 40 to provide space 41 inwardly with respect to the panel, for the connections to the various instruments. This wall is also perforated at 42 to admit the thermoregulator 43, which is preferably of the t e set forth in the patent to de Khotinsky, 0. 1,375,780 of April 26, 1921.

In addition to the thermoregulator, the panel carries a connecting plug 44, a switch 45. a pilot lamp 46 and condensers 47.

Referring to the wiring diagram in Fig. 5, it will be seen that the coils 23 are ar ranged as separate units connected in parallel across the line 48. a

The best results are obtained when these units are all'the same wattage and two of the units are controlled by the thermoregulator through

separate contacts

49 and 50. "The bottom 10 is provided'with inlet passages 51 and the top with a vent 52.

Operation: When current is supplied to the heating element, air directly in contact withthe coilsbecomes heated and rises. 'In its upward movement it entrains, or otherwise carries along other air. Thus convection currents are establishedwhich pass upwardly through the fiues then inwardly and no downwardly through the enclosure between the flue walls, and outwardly through and around the coils and upwardly again through the flues. During the upward movement the highly heated air and the air carried with it become mixed until the product at the top of the flues is practically uniform in temperature. This flows inwardly and downwardly over the material to be treated and thus establishes throughout the space between the flue walls a zone of practically uniform temperature.

Placing the

walls

27, 28, 29 and 31, inwardly with respect .to the coils, not only 5 insures that the heated air will immediately pass into the fines, but results in shielding the test material near the top of the oven from heat radiated directly from the coils while allowing such radiated heat to reach the test material near the bottom; thus the radiated heat reaches only that material that, were it heated by convection currents only,

' would be cooler than material near the top.

Thus, the two sources of heat are so balanced that material near the top of the oven is at heating element substantially equal to two of the unregulated units the danger from changes in room temperature is practically eliminated. Suppose the room temperature to be 71 F. atthe beginning of the treatment, the desired temperature in the oven 100 F., the wattage in the two units 23 suflicient to raise the temperature 20. If only a single unit 23 was under the control of the thermoregulator and the room temperature dropped 3 there would be a failure of regulation. However, by having the regulated portions of the heating element of substantially the same watt-age as two units 23 it is always possible to prevent either a drop or an increase in room temperature from taking the desired temperature out of the range of control of the regulator.

By breaking the regulated portion into a plurality of units the damage to the contacts is greatly reduced.

The pilot lamp 46 connected as shown in Flg. 5, will be lighted when the re lated units are in operation and'will be dar when the regulated units are cut out. To reduce the current through the lamp it may be connected across a suitable shunt 53.

I claim as my invention:

1. In a device of the class'described, the combination of an oven enclosure, including abottom, a top and walls, a heating element extending about the enclosure and located adjacent to the bottom, and the walls, and a flue communicating at its bottom with the heating element and extending upwardly along the walls and delivering adjacent to t e to 2. Iii a device of the class described, the combination of an oven enclosure including a bottom, a top and walls connecting the bottom and top, inner walls spaced inwardly from the walls of the enclosure and forming with the first wall a flue surrounding the oven space, said inner walls being cut away adjacent to the bottom and top, and a heating element adjacent to the bottom of the space between the outer and inner walls, said flue communicating at its bottom with the heating element, and at its top with the oven space.

3. In a device of the class described, the combination of an oven enclosure including a bottom and a top connected by side walls, an electric heating element of uniform wattage arranged around the oven adjacent to the bottom and the walls, and flue walls extending upwardly inside of the heating element and defining with the side walls upright flues havin open bottoms in communication with the eating elements.

4. In a device of the class described,"'the combination of an oven enclosure includinga bottom and. top connected by walls having a door, flue walls spaced inwardly from the walls of the enclosure and including a transparent door opposite to the first door.

5. Ina device of the class described, the combination of an oven enclosure including a bottom and a top connected by front, back and side walls, one of said walls having a door permitting access to the enclosure, a flue within the enclosure including a transparent door opposite to the door in the .wall of the enclosure.

6. In a device of the class described, the combination of an oven enclosure includin a bottom and atop connected by front, bac and side walls one of said walls including a door and a flue connectin the lower and upper portions of the enc osure adjacent to each of said walls.

7. In a device of the class described, the combination of an oven enclosure including a bottom and a top connected by front, back and side walls, one of said walls having a 1 door, a flue within the enclosure including a plurality of transparent walls movable to and from a position behind said door.

8. In a device of the class described, the combination of an oven enclosure including a bottom and a top connected by walls, one of which has an opening adjacent to the bottom, a base movable through said opening into and out of the enclosure and an electrical resistance element carried by the base and movable therewith through the opening. 9. In a device of the class described, the combination of'an oven enclosure including a bottom and a top connected by walls, one of whiclr-has an opening adjacent to the bottom-fan electrical resistance element, a base'lior said element movable through said opening into and out of the enclosure, and an instrument panel attached to the base and adapted to close said opening when the base is within the enclosure.

10. In a device of the class described, an electrical heating element including several units, a plurality of which are of substantially equal wattage and a thermo-regulator controlling a portion only of said units sub- 7 stantiallyequal in wattage to two of the units of equal wattage, the remaining heating units being permanently in circuit.

11. In a device of the class described, an electrical heating element, including a pinrality of units of substantially equal wattage, and thermo-regulating means controlling two of said units only, the 'remaining heating units being permanently in circuit.

12. In a device of the class described, the combination of an oven enclosure including a bottom, a top and Walls connecting the bottom and top, inner walls spaced inwardly from the walls of the enclosure and cut away adjacent to the bottom and top, and a .heating element looped about the bottom of the enclosure between the inner and outer walls.

13. In a device of the class described, the combination of an oven enclosure including abottom,-a top and walls connecting the bottom and top, inner walls spaced inwardly from the walls of the enclosure ,and cut away adjacent to the bottom, the inner and enclosure walls defining fines having open bottoms, one of the enclosure walls. having an opening adjacent to the bottom, and an electrical resistance element extending about the bottom of the oven adjacent to the bottom of the inner walls and being removable through said opening, said resistance being in communication with the open bottoms of the fines.

In testimony whereof I aflix my signature.

WINFIELD H. STANNARD.