US873737A - Automatic cut-out for electric controllers. - Google Patents

Description

No. 873,737. PATENTED DEC. 17, 1907. A. .C. EASTWOOD. AUTOMATIC GUT-OUT FOR ELECTRIC CONTROLLERS.

APPLICATION FILED JAN.15. 1907.

WITNIIII:

l v 1 m Q $133313,

I I 17 r z ATTORNKY UNITED STATES PATENT OFFICE.

ARTHUR c. EASTWOOD, or OLEVEL ANfi), omo.

I Aurom'rrc CUT-OUT Fon ELECTRIC CONTROLLERS.

v I Specification of Letters Patent. Application and January 15.1907. Serial m. 352.408.

Patented Dec.'1 7, 1907,

To all whom it may concern: I Be it known that I; ARTHUR C. EASTWOOD,

a citizen of the United States re'sidingat Cleveland, in the countyof Cuyahoga and State of Ohio, have invented or discovered new and usefullmprovements in Automatic Cut-Outs for Electric Controllers, of which the following is a specification.

My invention relates to new and improved 1 means for automatically cutting off the supply of current to an electric motor and stopping it in such a manner that, after the motor-has beenautomatically stopped by the action of the automatic means, t e operator may again start the motor in either-direction by theoperation of themaster controller in the ordinary Way, without being required to 0 en or close additionalswitches to secure t 's result.

The drawing is a diagram of electrical con nections of an electric controller equipped with my invention for controlling a com-.

pound wound electric motor.

In the drawing, S, is a knif'e swrtchconnected to the source of current supply,

A, is the armature of the motor having a series field winding F and a shunt field wind.-

is the winding of the magnetizing coil of an-electric [brake p the construction of the brake being suchthat when current flows through the winding P, the'brake is held released by the magnet-and when current ceases .,to, flow through the winding P, the brake is 85 applied by a spring or weight, as is well known I I DQD, U, U? are magnetically o 'erated reversing switches which serve to 'e ect the necessary'connections for causing the'arma-g 40 ture of the motor to rotate in one direction or the other in the well known Way. These switches are operated by electro-magnets having windings d, d, uB-ufi, respectively.

Mechanical interlocking bars F, F are 45. placed between adjacent. switches in such a manner that when switches D .and D" are closed, switches Uf and U can not close, and r vice versa.'

R and R are. sections of resistance'for 5i) limiting the flow of current through the m0- tor during the period of acceleration. The

. circuit through this resistanceis completed at the switch K, which has an operating coil .k,"the'ifesistance being cut out or short cir- {the actuating nd m cuited bythe switches L and M, which-have gized from the supply mains. seen that the overload switch and the shunt R is a bank of resistance which is con 7 nected across the armature of the'motor by the switch NZ, having theactuating' coil n. The operation of this switch will be laterde scribed.

Y'is a master controller havingan operating lever y, whichis shown in the drawing as being in the 0s position; The lever y carries a contact brush g cooperating with con-' tact y in theofi osition in such a manner as to connect it-wit the contact g The brush 31* connects contact y to contact y when moved to the right and connects contact y" to contact 3] when moved to the left from the ofl osition.

C is a circuit breaker which will automatically open upon the flow of a predetermined'current through the motor, upon the failure of the supply of current, upon opening the circuit of t, e shunt field winding f and may also be opened by the operation of the automatic cut-out T. The circuit breaker G is made up of a magnetically operated switch 'havingan actuating coil 0 Current is led to the switch through a helical winding 0 which constitutes the operating coil .of the overload switch; Within the winding 0 is a shunt field winding of the motor, so that as long as current is flowing through the shunt field windin ,the switch member f 2 i'sheld in contact wit the stationary contact members fand f*. If, however, through any reason such as the breakin of a connection, current should cease toow through the shunt field, the winding f will no lon er be energized and the switch member 2 will drop from content with the terminals f and f thus interrupting the. circuit of the coil 0 and causing thecircuit breaker to open. If foran reason the supply of current should fail, t e circuit brea er 0 will, of course,

open, since it is held closed by the electro-- magnet having thewinding c which is ener- It will be field switch act upon the connection of the 'coil to the positive supply main. The

the contact arm t arran ed to be driven from a rotating part of the motor or machine to be controlled. The switch T is shown in the drawing as adapted to automatically stop the motor in two difierent positions, these positions being 180 degrees apart and corresponding to the lower and upper vertical positions of the rotating contact arm t.

The arm carries a brush t adapted to electrically connect the contact ring t alternately with rings t and it The rings t and t are connected together to the negative supply main, the rings being separated at both their upper and lower extremities by a ga which cannot be spanned by the brush t As previously noted, one end of the coil 0 of the circuitbreaker is connected to an auxiliary contact 0 A second auxiliary contact c is connected to the negative main when the brush t connects the ring i with either of the contacts i or I As previously noted the coil 0, which causes the circuit breaker to close, receives its negative connection through the short contact 1; of the master controller when the controller is in the off position. When the circuit breaker is closed, the contacts 0 and c are bridged by a contact member carried by the circuit breaker whichserves to give the coil 0 its negative connection through the contacts of the cut-out, T, provided the arm 11 is not in either of its vertical positions.

The auxiliary contact c is further connected to the negative main through the contacts of acounterE.M. F.'switch V. This switch has a winding c which is connected across the terminals of the armature of the motor so that, when the. armature is revolving, the coil 12 will be excited by the electro motive forcegenerated in the armature and will raise the switch member '0 from contact with the stationary members i)" and '0. \Vhen the armature is at rest, the coil 11 will, of course, not be excited and the switch will be closed, the contact member 12 spanning the contacts '0 and '0. This condition exists at the time of starting from rest, so that, even though the cut-out be in the position shown with its brush t out of contact with either the rings t or t, the coil 0 of the circuit breaker, after the circuit breaker is closed, will receive its negative connection through its auxiliary contacts a and c and counterE. M. F. switch V. The brush y then comes into contact with the segment y. The ath of the control circuit will then be as fol-. ows: from the ositive main through the circuit breaker, tiience to the coils (l and d in parallel, through the wire 90 and the contact y of the master controller, the brush y and the contact y to the negative main. This completes the circuit through the coils d and d and causes the switches D and D to close.

The switch D carries auxiliary contacts d, d,

which are bridged when the switch is closed, one of these contacts (1 being connected to the left terminal of the switch D which is connected to the positive main when the switch is closed. The other auxiliary contact d is connected to one end of the coil is of the switch K. The other end of the winding coil 1c is connected directly to the negative main. Therefore, as soon as switch D is closed, switch K immediately closes and com letes the main circuit through the motor as follows:

from the positive terminal of the switch S to the overload coil 0 and the contacts of the circuit breaker C to the switch D, the coil of the solenoid brake P, the armature A, the switch D the series field F, the resistance R and R and the switch K, to the negative main. The motor should then start. As the motor speeds u the switches L and M will automatically clbse in a manner fully described in U. S. Patent 772,277, issued to me October 11, 1904.

As the armature rotates, the arm t of the cut out switch is rotated, we will assume toward the left or in a clockwise direction,

bringing the brush into contact with the ring 25 As soon as the armature has reached a speed at which it generates suliicient electro motive force, the counter E. M. F. switch V raises its contact member 22 out of engagement with the contacts 22 and v The coil 0 of the circuit breaker then depends for its negat've connection entirely u on the contacts of the automatic cut out When the contact brush f of the cut out passes from the upper segment 15*, its negative connection is interru ted. The coil 0 is thereby denergized an the circuit breaker opens, thus cutting off the sup 1y of current to the motor. The circuit breaker in opening opens the ositive connections of switches D and D ii, L and M, thereby causing these switches to open.

The switch N, which we will call the dy I namic braking switch, has an actuating coil I n, the terminals of which'are connected to stantlv to close while the armature is running.

It is, however, prevented from closing while the switch K is closed l through the action'of' the interlocking lever F. As soon, however, as switch K opens, switch N will instantly close since, although the main circuit is opened the armature will still continue to generate electro motive force due to its rota-' tion under its own momentum and that of the driven parts in the magnetic field set up by the shunt field winding f.

It will be noted that one terminal of the switch N is connected through the winding of the magnetic brake to the terminal of the armature while the other terminal of the switch is connected through the braking resistance R to the other termin'al of the armature. When the switch N closes, the armature, therefore, generates current through this circuit, theamount of the current being regulated by the resistance R. --This, of course,

' imposes a load on the motor and the armature is speedily brought to're st through this generation of current, the ener due to the motion of the moving parts eing (trans formed into electric current and dissipated as heat in the braking resistance R. t will be noted that the coil of the magnetic brake 1 is in series with this circuit so that this brake will not be applied until the armature has practically ceased to generate current, or, in other words, until the armature has substantially come to rest. By this arrangement the larger part of the energy due to the motion of'the parts is dissipated as heat in the resistance R withoutwear of the braking surfaces of the magnetic brake, the magnetic brake becoming practlcallv a holding brake capableofuholding theload after it has i been brought to rest through the dynamic.

braking action. As the armature comes to rest the coil n of the switch N is no longer excited and this switch opens.

When the; circuit breaker has opened through the action of the automatic cut-out T, it will not again close until the lever 3 of the master controller is again brought to 3 of the master controller to the negative main. This completes the circuit through the coil 0 and causes the circuit breaker C to close. When the armature of the motor is at rest, the counter 'E. M. F. switch V is closed so that the motor may be again started by operating the master controller in either direction from the off position. I

When the lever y of the master controller is moved to the left, the brush 'y makes; contact with the segment yi, which connects through the wireas with the coils 'u and a of the reversing switches U and U This completes the circuit through these coils, the other end of each of them being connected to the positive main near the lower terminal of the circuit breaker 0. Closure of switches U and U serve to make the necessary connections for causing the armature to rotate in'a direction the reverse of that above described. The succeeding action of the other will of the operator in eit er direction.

While in the drawings I have indicated only two points on the switch T, at which the motor may be automatically stopped, it will be understood that the motor may be auto maticall stopped at any number of desired points dctermined simply by the arrangement of the contacts of the cut-out switch T.

I claim:

1. In a controller for electric motors, the

combination of. an electro-magnet, a circuit switch adapte reaker normally held closed by the electro magnet, an o crating switch, a cut-out to open the circuit of the winding of the electro-magnet of said circuit breaker when said cut-out switch has been ahtuated in a predetermined manner, a master'eontroller, and contacts adapted to cause said circuit breaker to close when said master switch has been returned to the oil-position. 2. In a controller for electric motors, the combination of an electro-magnet, a circuit breaker normally held closed by the electromagnet, a cut-out switch, adapted to open the circuit of the electromagnet of said circuitbreakerwhen a predetermined limit of travel has been reached, and an electromotive force switch, adapted to close the circuit opened by said cut-out switch when the motor'has come to rest..

3.- In an electric controller, a motor switch, a cut-out switch for opening the motor switch when a predetermined limit of travel has been reached, and a switch controlled by the armature of the motor and causing the closure of the circuits opened. by the cut-out switch when the motor has eome-substantially to rest.

4. In an electric controller, a motor switch, a cut-out switch for opening the motor switch when a predetermined limit of travel has been reached, and automatic means for closing the circuits opened by the cut-out switch when the motor has come substantially to rest.

5. In an electric controller, a motor switch, a cut-out switch for opening the motor switch when a limit of travel has been reached, and a magnetically operated switch having its terminals connected to short circuit the contacts of the cut-out switch. and having its operating Winding connected in shunt to the armature of the motor.

ARTHUR (l. EASTWOOD.

Witnesses:

J. E. WELLMAN, M. N. REED.

Images