US1794961A - Control system - Google Patents

Description

H. D. JAMES CONTROL SYSTEM March 3, 1931.

Filed Jan. 3, 1927 3 Sheets-Sheet l INVENTOR AfToRNEY Hell/y 0. James March 3, 1931. H. D. JAMES 1,794,961

CONTROL SYS TEM Filed Jan. 5, 1927 3 Sheets-Sheet 2 /5 a I a Filed Jan. 3, 1927 5 Sheets-Sheet 3 Spee a /0 1'2 4 /a 20 Toryua WHySSES: INVENTOR Ag 61/ W hkw y 0. James Patented Mar. 3, 1931 UNITED STATES PATENT OFFICE HENRY 1). JAMES, OF EDGEWOOD, PENNSYLVANIA, ASSIGNOB T0 WESTINGHOUSE ELEC- TBIC & MANUFACTURING COMPANY, A CORPORATION 01 PENNSYLVANIA CONTROL SYSTEM Application filed January 3, 1927. Serial No. 158,536.

My invention relates to control systems for motor-actuated machines and it has special relation to the electrical control of motordriven washing machine equipments.

In providing and using electric motor driven washing machine equipments of laundry size, considerable trouble has been encountered in providing means for reversing and braking the driving motor and the washing machine. The strain placed upon the washer at the period of reversal, and the cumbersome control provided, have been the most objectionable features. These features were more pronounced because of the especially high-plugging-torque values generally present in the motors when reversal was taking place. To overcome these objections, the present system was devised.

One of the objects of my invention is to provide a system for operating electric washing machines or reversin machines of similar characteristics, whereln a motor especially designed to withstand frequent reversals is re uired.

second object of my invention is to provide a system of the above-described character embodying a motor having a low plugging torque, thereby permitting it to come to rest and reverse gradually, thus imparting a gentle mechanical action, as compared with the abrupt reversal of the high-pluggingtorque motors previously used.

A third object of my invention is to provide a system embodying a driving motor and switching means for governing the direction of operation and also the time that the motor will be operating in either direction.

Another object of my invention is to provide a system of the character set forth wherein the control equipment is small, compact and readily mounted upon the machine.

A still further object of my invention is to provide a system, as described above, which shall be easy to manufacture and install and reliable in operation.

Other objects of my invention will become evidentffrom the following detailed description taken in conjunction with the accompanying drawings, wherein Fig. 1 is a view, in elevation, of a washing machine that is equipped with an electrical driving system in accordance with my present invention;

Fig. 2 is a diagrammatic view of the main circults embodied in the preferred form of my invention;

Fig. 3 is a view, in elevation, of a travellingnut-actuated reversing switch; and

Fig. 4 is a chart graphically illustrating the operating characteristics of the specially designed induction motor with respect to the torque-and-speed conditions present in the motor.

Referring to Fig. 1 of the drawing, the washing machine here shown comprises a cylinder 1, Within which is enclosed the washing-machine equipment proper and which is supported substantially as shown. An induction motor 2 is mounted upon the frame of the washing machine, being firmly secured to a platform 3 and being geared mechanically, by means of a pinion 4 and a gear-wheel 5, to the operating mechanism of the washing machine. The operating mechanism of the washing machine being no part of this invention and within the common knowledge of the art, it is deemed unnecessary to further illus trate or describe it.

A conduit 6 is utilized to carry the power conductors for the motor. The control of the motor is accomplished by means of a reversing switch contained within the housing 8 and actuated by means of a travellin -nut device. This device is contained in the ousing 9, the operation of which is fully described below. A panelboard 7 supports the necessary controlling mechanism, other than the reversing switch.

Referring to Fig. 2, the system shown comprises the induction motor 2, having a stator winding 12 and a rotor winding 13, which is utilized for driving the washing machine.

A reversing switch 14, a main line contactor 15, a start push-button 16 and a stop push-button 17 constitute the controlling mechanism which regulates the flow of current from the main- line conductors 18, 19 and 20 to the motor 2.

This motor is of the induction type and is specially designed to incorporate characteristics that are set forth below. The reversing switch 14 is also fully described hereinafter.

The operation of this system is very simple. The stop button 17, which is normally maintained closed, permits a circuit to be established through the actuating coil 15a of the main-line contactor 15 when the start button 16 is pressed. Completion of the circuit, however, is dependent upon the position of a contact-making member 24 on the reversing switch 14. The circuit comprises conductors 18 and 25, actuating coil 15a, stop switch 17, starting switch 16, contact member 24 on the reversing switch 14, and conductor 26 to the main-line conductor 19. Inasmuch as the reversing switch 14 is normally in either the one or the other of its closed positions corresponding to the operation of the motor in the one of the other direction, contact member 24 is usually closed.

However, as described below, should the reversing switch 14 stop in a neutral position, means are provided for mechanically throwing the reversing switch to either of the desired positions. Upon the energization of the actuating coil 15a, the main-line contactor 15 will close to impress the main-line voltage upon the stator winding 12 of the motor, through the reversing switch 14, and start the motor in operation.

It will be noted that, upon the closing of the main-line contactor, an interlock 27 thereon is provided to establish a holding circuit for the actuating coil 15a, when the start push-button 16 is released.

The reversing switch 14 is connected in such a manner that the voltage impressed on conductors 28 and 29 leading to stator winding 12 is reversed when the switch is thrown from one position to the other, whereby the direction of rotation of the motor is reversed.

, Contact member 23 on the reversing switch is adapted to maintain the same voltage phase upon conductor 30 leading to the stator winding 12, when the switch 14 is thrown to either position, and the interlocking member 24 of the reversing switch is a protective means placed in the circuit of the actuating coil 15a of the main-line contactor 15, the purpose of which is to prevent the possibility of energizing the actuating coil 15a and thereby connecting switch 15 to the line without starting the motor. The structure of the reversing switch 14 is illustrated in detail in Fig. 3.

The contact-making members 21, 22, 23 and 24 are suitably mounted upon a shaft 31 in a well-known manner, so that they are readily actuated to make contact with their respective stationary contact elements; and a travellingnut device 32, for regulating the operation of the reversing switch 14, as desired, is geared to some suitable part of the washing machine or motor by means of a sprocket 33 and chain (not shown).

The travelling-nut device 32 comprises a threaded shaft 34, a travellin -nut 35 and movable stops 36 and 37, which may be adjusted as desired to regulate the distance of travel of the nut 35 and thereby predetermine the number of revolutions of said machine in either direction.

Two V-shaped elements 28 are also mounted upon the shaft 34-,near the respective ends thereof. To these elements are fastened a pair of guides 38 and 39, which extend substantially parallel to shaft 34 and cooperate with the nut 35 to actuate the reversing switch. The sprocket 33 is loosely mounted upon the shaft 34 and is rotated by means of a chain (not shown) which is geared in some suitable manner to the washing machine.

A friction-slip-clutch disc 41imparts a rotating motion to sprocket 33, friction between sprocket 33 and clutch disc 41 being obtained by means of a spring 42 associated therewith, which may be adjusted by a nut 43. A handle 44 is also provided for manually throwing the reversing switch in either desired direction, in case the travelling-nut device should fail, or the motor should stop while the reversing switch is in its neutral position. A coupling device 45 is also provided for connecting the reversing-switch elements proper to the travelling-nut device.

The operation of the switch, as a whole, is substantially as follows: The sprocket 33 is driven by means of a chain (not shown) connected to some part of the machine. With the motor operating in a certain direction, the nut 35 travels along the threaded shaft 34 until it hits one of the stops 36 or 37, when it carries the reversing switch to the opposite position through the action of the travellingnut 35 upon one or the other of the shafts 38 and 39, which are coupled to the V-shaped elements 28, and which, in turn, are coupled to the reversing switch by the coupling device 45. This action forces the reversing switch to the opposite position, thus reversing the voltage impressed upon conductors 28 and 29, as described above, thereby plugging the motor, causing it to stopand then start in the reverse direction.

In all cases, the over-travel of the motor caused by the rotation of the cylinder 1, from the time the reversing switch operates until the motor actually stops, is absorbed partially by the slip-clutch 41 on the sprocket of the reversing mechanism and partially by the motor while it is being driven in a direction opposite to that in which the motor would normally operate with the power supply to the motor reversed.

Referring to Fig. 4, a curve is set forth showing the speed-torque characteristics of the specially designed motor 2. The upper portion of this diagram indicates the speedtorque characteristics of this motor between the points of zero and maximum speed. The

lower portion indicates the torque of the motor when the same is plugged or when two of the phase conductors leading to the stator winding are interchanged directly across the line. The negative speed, as plotted on the drawing, represents the negative slip with respect to the reversal of the voltage on the motor.

The speed-torque characteristics of motors of the general type employed previouslyto this invention were such that, if the motor ,was plugged directly across the line, a torque of several times the normal running torque would result, thus causing a very heavy strain on the actuating parts of the machinery, and, in order to avoid this, it was necessary-to insert' a large resistancein the motor circuit, which required additional control apparatus. To avoid the undesirable features of high plugging torque and unnecessary resistance and controlling mechanism, a motor having the above-described speed-torque characteristics was designed by developing a' stator which produced the desired results.

The motor is especially built to Withstand frequent reversals, the reversing being accomplished by simply changing two of the phase conductors, or in other words, plugging the motor. Its low plugging torque permits the actuating the switch through its limiting positions.

In testimony whereof, I have hereunto subscribed my name this 29th day of December,

HENRY D. JAMES.

motor and cylinder 1 to come to rest and I limitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

1. The combination with a machine and a reversible induction motor having a substantially low starting torque and a plugging torque substantially equal to the full load torque coupled thereto, of a reversing switch for reversing the flow of current to said motor, and a travelling-nut device coupled to said machine, said switch being actuated by said device, and means associated with said travelling-nut device for permitting the driving means of said travelling-nut device to over-travel between the time the reversing switch operates and the time said motor actually stops or reverses, without disconnecting the motor from the machine.

2. In combination, an induction motor having a low plugging torque, a machine driven thereby, a source of alternating-current pow-

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