US2800317A

US2800317A - Heat treating furnace

Info

Publication number: US2800317A
Application number: US386834A
Authority: US
Inventors: Harold N Ipsen
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-10-19
Filing date: 1953-10-19
Publication date: 1957-07-23
Anticipated expiration: 1974-07-23

Description

y 1957 H. N. IPSEN 2,800,317

HEAT TREATING FURNACE Filed Oct. 19,1955

T0 may United States Patent ()fiice Pa n ed July .3,, 957

HEAT TREATING FURNACE Harold N. Ipsen, Rockford, Ill.

Application October 19, 1953, Serial No. 386,834

1 Claim. (Cl. 263-2) This invention relates to heat treating furnaces and has particular reference to a furnace in which the atmosphere within the furnace chamber is circulated by a fan mounted on the inner end of a shaft projecting through one wall of the furnace. In furnaces of this type, the shaft, which is driven by a motor disposed outside the furnace, is journaled exteriorly of the furnace wall and is cooled by a water jacket to prevent overheating of the bearings.

One object of the invention is to provide a furnace of the above character with a new and improved water jacket which insures that the fan shaft is uniformly cooled, which prevents the shaft from becoming distorted both when the shaft is idle and when it is turning, and which maintains the shaft concentric with the bore of the water jacket without the necessity of a special and complicated construction.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawing, in which the single figure is a transverse sectional view of a furnace with a water jacket embodying the novel features of the present invention.

As shown in the drawing for the purpose of illustration, the invention is embodied in a heat treating furnaoe whose top, bottom and

side walls

11, 12 and 13 define a chamber 14 in which workpieces (not shown) are placed for treatment. In furnaces of this type, the workpieces are disposed within a box-like baffle 15 which rests on blocks 16 on the bottom wall 12 of the furnace and is spaced from the furnace walls. To heat the chamber 14, heating elements such as vertical gas burner tubes 17 are disposed between the side walls of the baffle 15 and the furnace side walls 13 and extend between the top and bottom walls 11 and 12 of the furnace, the tubes being secured to these walls.

In order that the workpieces within the baffie 15 are heated uniformly, the atmosphere in the chamber 14 is circulated about the workpieces by a fan 18 which directs the atmosphere laterally over the top of the baffie, then down between the side walls 13 and the sides of the bafile across the heating tubes 17, up into the inside of the baffle through holes 19 in the baffle hearth 20, and finally back to the fan through a central hole 21 in the arch 22 of the baffle. The fan 18 is mounted on the lower end of a vertical shaft 23 projecting down through a hole 24 in the top wall 11 of the furnace and connected to the shaft 25 of a motor 26 which is secured to the top of the furnace.

Herein, the motor shaft 25 is hollow and its bore 27 is flared at the lower end to receive the tapered upper end portion 28 of the fan shaft 23. The latter is held rigidly on the motor shaft by a draw bolt 29 projecting down through the motor shaft and threaded into the fan shaft. Thus, by tightening the bolt, the fan shaft is drawn into the flared portion of the motor shaft so that, in effect, the fan shaft becomes a rigid extension of the motor shaft. Within the casing of the motor, the hollow shaft 25 is journaled in spaced

bearings

30 and 31 dis posed at opposite ends of the motor and mounted in the motor casing. In order that the fan and motor shafts 23 and 25 as well as the

bearings

30 and 31 do not become overheated, a water jacket 32 seated in the top wall 11 of the furnace encircles and cools the fan shaft.

In accordance with the present invention, the water jacket 32 is constructed in a novel manner to insure effective and uniform cooling of the fan shaft 23 while holding the shaft out of running contact with the jacket.

For this purpose, the shaft 23 is journaled on the water' jacket so that it is maintained in true coaxial relationship with the jacket. In this way, only a small clearance between the shaft and the water jacket is required permitting the latter to dissipate the heat from the shaft quickly and effectively while, at the same time, the spacing between the shaft and the jacket is maintained precisely the same around the entire periphery of the shaft which thus is uniformly cooled and prevented from becoming distorted.

In the present instance, the water jacket 32 is in the form of a tubular member which is flanged at its upper end as indicated at 33 to seat in the outer side of the top wall 11 of the furnace coaxially with the hole 24 and extend in along the fan shaft 23. The shaft projects down through the cylindrical bore 34 of the jacket which is hollow and thus provides an annular cavity 35 encircling the fan shaft. Coolant, such as water, is admitted to the cavity through an inlet pipe 36 threaded into the tubular jacket and flows around the shaft 23 and out through a second pipe 37. The coolant carries away the heat from the surface of the jacket bore 34 and thus cools the shaft 23.

To maintain the fan shaft 23 concentric with the bore 34 of the water jacket 32, the shaft is journaled directly on the water jacket. To this end the casing of the motor 26 is rigid with and may, as shown in the drawing, be cast integrally with the jacket. Thus, the

bearings

30 and 31, which in effect are mounted on the water jacket, are fixed relative to the bore 34. Since the bearings and the bore bear a constant relationship, the fan shaft 23 is held exactly concentric with the bore.

By journaling the fan shaft 23 directly on the water jacket 32, only a very small spacing between the shaft and the wall of the bore 34 is required. This spacing may be on the order of .005 of an inch while maintaining the shaft concentric with the bore so that the shaft is out of running contact with the water jacket at all times. Such close spacing allows the water to cool the fan shaft effectively since little of the cooling effect is lost between the shaft and the wall of the bore 34. At the same time, there is no danger of the shaft binding in the bore. Because the shaft is precisely concentric with the bore wall, the spacing between the two is, for all practical purposes, exactly the same all around the shaft. As a result, the cooling effect of the water jacket is the same at all points around the shaft. Hence, no part of the shaft is cooler than another even when the shaft is not turning and, therefore, the likelihood of warping or distortion of the shaft due to uneven heating is substantially eliminated.

I claim as my invention:

A furnace having, in combination, a walled enclosure defining a heated chamber, one of the walls of said enclosure having a hole therethrough and opening into said chamber, a tubular member seated in said Wall on the out er side of said enclosure and having a bore coaxial with said hole, said member having an annular cavity encircling said bore, a motor disposed exteriorly of said enclosure and having the stationary parts thereof rigidly and solely mounted on said member, an annular bearing supported on said member coaxially with said bore, a

shaft driven by said motor and journaled on said bearing to project through said bore with the surface of said shaft close to but out of running contact with the surface of the bore, and means for circulating a coolant through said cavity to cool the surface of said bore and hence uniformly cool said shaft.

References Cited in the file of this patent UNITED STATES PATENTS 1,727,192 Baily Sept. 3, 1929 4 Roth et al. Dec. 3, 1935 Harsch Aug. 1, 1939 Rosecrans Oct. 17, 1939 Mumford Mar. 3, 1953 FOREIGN PATENTS France Apr. 25, 1938 Great Britain July 5, 1938