US2735027A

US2735027A - Annealing furnace motor

Info

Publication number: US2735027A
Authority: US
Publication date: 1956-02-14
Anticipated expiration: 1973-02-14

Description

W. H. FORMHALS ET AL Filed March 26, 1951 -,|NVENTOR Walhom H. Form uls,

Theodore C. Fockler 8 James H. Penney.

United States Patent ANNEALING FURNACE MOTOR William H. Formhals, Theodore C. Fockler, and James H. Penney, Buffalo, N. Y., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 26, 1951, Serial No. 217,612

3 Claims. (Cl. 310-58) The present invention relates to the construction of dynamo-electric machines and, more particularly, to an electric motor which is especially adapted for driving a fan or blower in an annealing furnace.

In the usual bell-type annealing furnace, the protective atmosphere in the furnace is circulated by means of a large blower within the furnace, which is driven by a motor mounted outside the furnace with its shaft extending through the furnace wall. The blower and the end of the shaft within the furnace are, of course, at the furnace temperature, which may be as high as 1300 F. to 1600 F., for example, and a relatively large amount of heat is, therefore, conducted along the shaft and tends to overheat the motor and especially the bearing at the end of the motor adjacent the furnace. Effective cooling of the motor is, therefore, required, and it is especially necessary to effectively cool the bearing since the temperature of the bearing must be prevented from exceeding about 125 C., to obtain reasonable bearing life, unless very special lubrication means are provided, which is undesirable because of the high cost.

It is also necessary to prevent leakage of the atmosphere gas from the furnace, or leakage of air into the furnace, along the shaft, since the atmosphere gas may have a high content of carbon monoxide, or other dangerous undesirable gases, and in many cases even a slight leakage of air into the furnace will spoil a bright anneal. Various types of water, oil and air cooling have been used for these furnace blower motors, with varying degrees of success, and various types of shaft seals have been used to prevent air or gas leakage into or out of the furnace, but all of these expedients which have been utilized heretofore for cooling and shaft sealing have been relatively expensive, and have involved a considerable amount of maintenance in service, thus undesirably increasing the cost of operation of the motor.

The principal object of the present invention is to provide an electric motor which is adapted to be mounted on a wall of a furnace for driving a blower within the furnace, in which the motor and the bearing adjacent the furnace are effectively cooled without requiring special or expensive arrangements, and in which gase leakage into or out of the furnace .is positively prevented without requiring the use of a shaft seal.

Another object of the invention is to :provide an electric motor adapted to be mounted on a wall of a furnace for driving a blower within the furnace, the motor having heat-exchange means on the shaft outside the bearing adjacent the furnace to transfer heat from the shaft to the motor housing, and means for effectively cooling the motor housing by a stream of air, so that the motor and bearing are effectively cooled and excessive temperature of the bearing is prevented.

A further object of the invention is to provide a motor adapted to be mounted on a furnace wall to drive a blower within the furnace, the motor having a gas-tight housing completely enclosing the motorand adapted to be mounted on the furnace wall with a gas-tight seal, so that leakage of gas from the furnace or leakage of air into the furnace are effectively prevented without requiring a rotating shaft seal.

Other objects and advantages of the invention will be apparent from the following detailed description, taken in connection with the accompanying drawing, the single figure of which is a vertical sectional view of a motor embodying the invention.

The invention is shown in the drawing embodied in a vertical motor adapted to be mounted on a wall 1 of a furnace for driving a blower 2 within the furnace to circulate a protective atmosphere in the furnace. The furnace may be of any desired construction and the motor may be mounted on a mounting plate 3 cemented in the furnace wall, as indicated at 4, or any other suitable means may be provided for mounting the motor on the furnace. It will be understood that, although a vertical motor has been shown for the purpose of illustration, this invention is equally applicable to horizontal motors.

The motor has a housing 5 which completely encloses the motor and which is closed at the lower end but open at the upper end where it is mounted on the furnace. The housing 5 may be cast in one piece as shown, or it may be fabricated by means of welding, or otherwise, to make a substantially gas-tight enclosure for the motor. The upper end of the housing 5 is provided with a flange 6 for securing the motor to the mounting plate 3 by means of bolts 7, or other suitable means, a gasket 8 preferably being utilized to make a gas-tight seal between the motor housing and the furnace wall.

A laminated stator core 9 is supported in the housing 5, and primary windings 10 are placed in slots in the stator core 9. The motor leads 11 are brought out of the housing through a pipe 12 and sealed in the pipe in any suitable manner, as by means of cement 13, to effect a gas-tight seal. A ball bearing 14 is mounted in the closed lower end of the housing, and a ball bearing 15 is mounted in a supporting structure 16 of any suitable construction which is secured in the upper part of the housing 5 by screws 17. It will be apparent that any other suitable type of bearings might be used in place of the ball bearings shown. A laminated rotor core 18 carrying a squirrel-cage winding 19 is secured on the shaft 20, which is supported in the

bearings

14 and 15 and extends upward through an aperture 21 in the furnace wall to drive the blower 2.

As previously indicated, the blower 2 and the upper end of the shaft 20 within the furnace are at the high furnace temperature and a considerable amount of heat is, therefore, conducted along the shaft towards the motor, so that if no special precautions were taken, the upper bearing 15 would be heated to an excessive temperanrre and would have a very short life, unless very special and expensive lubricating means were utilized. In accordance with the present invention, the temperature of the bearing 15 is limited to a safe range by providing heat-exchange means on the shaft 20 outside the bearing 15 to remove a substantial part of the heat from the shaft before it reaches the bearing.

in the illustrated embodiment of the invention, the heat-exchange means includes a blower 22 pressed, or otherwise mounted, on the shaft 20 so as to be in good thermally conductive relation to the shaft. As shown, the blower 22 has a hub portion 23, which directly engages the shaft Zti, and a series of radial blades 24. The blower 22 is made of a material having high thermal conductivity and the hub and blades are designed to have high thermal capacity and to effectively transfer a substantial amount of heat from the shaft to the surrounding gas. The upper portion of the housing 5 has longitudinal ribs 25 on its inside surface closely adjacent the blower 22 for picking up the heat from the air or gas flowing over the ribs and transferring it to the housing 5. Thus, heat flowing from the furnace through the shaft 2t) is effectively removed from the shaft and transferred to the housing 5.

The motor is totally enclosed by the housing 5 and the internal air or other gas within the motor is circulated in the usual manner by blower blades 26 formed on the rotor winding, and also to some extent by the blower 22. The heat from the shaft and the heat generated in the motor windings are thus transferred to the housing 5 and dissipated by directing a stream of cooling air over the outside of the housing. In order to facilitate cooling, because of the relatively large amount of heat to be dissipated, longitudinal ribs 27 are provided on the outside of the housing 5 extending from end to end of the housing. A stream of cooling air is provided by means of a blower 30 outside the housing driven by a small auxiliary motor 31 of any suitable type. The motor 31is shown as being mounted directly on the lower end of the housing 5, although it will be apparent that the motor 31 might be separately mounted if desired. A duct 32 is preferably provided to direct the stream of air from the blower 38* directly over the housing 5 in the spaces between the ribs 27.

It will be seen that since the motor housing 5 is completely gas-tight and is secured to the furnace wall with a gas-tight seal, atmosphere gas escaping from the furnace through the aperture 21 cannot escape into the surrounding air but is retained within the motor housing, which is not objectionable since the gases usually used are not corrosive or harmful to the materials used in the motor. Entrance of air into the furnace is also positively prevented by the gas-tight enclosure. Gas leakage into or out of the furnace is therefore positively and substantially completely prevented without requiring the use of a shaft seal, or any type of rotating seal. Thus, the difficulties of providing a satisfactory shaft seal which have previously been encountered are eliminated, and the expense of continued maintenance, which is unavoidable with any type of rotating seal is eliminated. The heat flowing from the furnace along the shaft is conducted away from the shaft by the blower 22 and transferred to the surrounding air or gas from which it is picked up by the ribs 25 on the inside of the housing, so that a large proportion of the heat flowing from the furnace is transferred from the shaft to the housing 5 before it reaches the bearing 15, and the bearing temperature is thus kept within reasonable limits so that ordinary lubricants can be used and normal hearing life is obtained. The motor is effectively cooled by the stream of air from the blower 3t) directed over the outside of the housing 5, which removes the heat transferred to the housing from the shaft as well as the heat generated in the motor itself.

It should now be apparent that a motor has been provided for driving a blower in an annealing furnace which substantially eliminates the difficult problems encountered in previous designs of motors for this purpose, since excessive heating of the bearing adjacent the furnace is prevented and the necessity of sealing the opening in the furnace wall through which the shaft passes is avoided. These problems have been solved in an effective and inexpensive way which avoids the necessity of expensive special arrangements and of excessive maintenance after the motor is in service.

A particular embodiment of the invention has been shown and described for the purpose of illustration but it will be apparent that various other embodiments and modifications may be made within the scope of the invention. Thus, the invention may be applied to horizontal motors as well as vertical, and other means may be utilized for providing the stream of cooling air. It is to be understood, therefore, that the invention is not limited to the particular arrangement or the specific details of construction shown and described, but in its broadest aspects it includes all equivalent embodiments and modifications which come within the scope of the appended claims.

We claim as our invention:

1. An electric motor adapted to be mounted on a wall of a furnace and having a shaft adapted to extend into the furnace, said motor having a unitary housing adapted to be secured at one end to the furnace with a substantially gas-tight seal, the other end of the housing being completely closed to form a solid, gas-tight enclosure for the motor and shaft, bearings for the shaft supported within the housing adjacent the ends thereof, heat transfer means on the shaft on the furnace side of the bearing nearest the furnace, and means on the housing cooperating with said heat transfer means to transfer heat from the shaft to the housing.

2. An electric motor adapted to be mounted on a wall of a furnace and having a shaft adapted to extend into the furnace, said motor having a unitary housing adapted to be secured at one end to the furnace wall with a substantially gas-tight seal, the other end of the housing being completely closed to form a solid, gas-tight enclosure for the motor and shaft, bearings for the shaft supported within the housing adjacent the ends thereof, blower means on the shaft on the furnace side of the bearing nearest the furnace, and a plurality of ribs on the interior of the housing closely adjacent said blower means, the blower means and ribs cooperating to transfer heat from the shaft to the housing.

3. An electric motor adapted to be mounted on a wall of a furnace and having a shaft adapted to extend into the furnace, said motor having a unitary housing adapted to be secured at one end to the furnace wall with a substantially gas-tight seal, the other end of the housing being completely closed to form a solid, gas-tight enclosure for the motor and shaft, bearings for the shaft supported within the housing adjacent the ends thereof, blower means on the shaft on the furnace side of the bearing nearest the furnace, a plurality of ribs on the interior of the housing closely adjacent said blower means, the blower means and ribs cooperating to transfer heat from the shaft to the housing, and means for directing a stream of air over the outside of the housing to dissipate said heat from the housing.

References Cited in the file of this patent UNITED STATES PATENTS