US1124086A - Controlling means for electric motors. - Google Patents

Description

G. H. WHITTINGHAM 6L W. T. HOLMES.

CONTROLLING MEANS FOR ELECTRIC MOTORS.

APPLICATION FILED MAR. 27, 1911. 1,124,086, Patented Jan.5,1915.

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G. H. WHITTINGHAM & W. T. HOLMES.

CON'LHOLLING MEANS FOR ELECTRIC MOTORS.

APPLICATION TILED MAILZT, 1911.

1, 1 24,086, Patented Jan. 5, 1915.

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[1 -2? F (:5 W W W; awvc-nto'cs G. H. WHITTINGHAM & W. T. HOLMES.

CONTROLLING MEANS FOR ELECTRIC MOTORS.

APPLICATION FILED MAR,27.1911.

1, 1 24,086. I Patented Jan. 5, 1915.

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M aamws G. H. WHITTINGHAM & W. T. HOLMES.

CONTROLLING MEANS FOR ELECTRIC MOTORS.

APPLIUATION FILED MAR. 27, 1911.

1 1 24,086. Patented Jan. 5, 1915.

4 SHBETS SHEET 4.

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GEORGE H. WHI'I'TINGHAM, OF PIKESVILLE, AND \VILLIAM T. HOLMES, OF BALTIMORE, MARYLAND, ASSIGNORS TO MONITOR MANUFACTURING COMPANY, 0Z5 BALTIMORE, MARYLAND, A CORPORATION OF MARYLAND.

CONTROLLING MEANS FOR. ELECTRIC MOTORS.

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Specification of Letters Yatent.

Patented Jan. 5, i915.

Application filed March 27, 1911. Serial No. 617,148.

To all 'w/wm 1' t m (13/ concern Be it known that we, GEORGE H. \Vi-irr- 'IINGIIAM and \ViLmAii T. Homins, citizens of the United States, residing at Pikesville, county of Baltimore, State of Maryland, and Baltimore, State of Maryland, respectively, have invented certain new and useful Improvements in Controlling Means for lilectrio Motors, of which the following is a specification.

This invention relates to a system of control for electric motors, and more especially for such motors as, from the nature of the work which they are called upon to perform, are required .to be frequently and rapidly reversed.

The invention has particular utility when applied to motors used for driving the reciprocating beds or other parts of machines, such as planers, printing presses, and the like. In carrying out our invention we propose to reverse the motor at every stroke of such reciprocating part, and to this end, arrange a tappet lever to be operated thereby. In work of this character, the reversal of the motor must take place quickly, and at the same time the danger of excessive current upon reversal must be guarded against. It is also desirable, if not indeed necessary, that, while responding regularly to move ment of the tappet lever, the machine must also be under perfect and absolute control of the attendant, so that it may be promptly stopped while running in either direction. To this end we propose to arrange a manual lever operating in conjunction with the tappet lever to control the motor.

In order to avoid the loss of time, and other complications. incident to the use of braking devices upon every reversal of the motor, we provide a pair of automatic rheostats or starters, and arrange means for throwing first one and then the other of these starters alternately into the armature circuit at each reversal. These devices produce a quick starting of the motor, and at the same time, serve to limit the current to a safe value.

In order that the invention may be fully understood, reference is had to the accompanying drawings, forming a part of this specification, and in which,

Figure 1 is a diagram illustrating our improved system of motor control and showing the parts in one running position; Fig. 2 is a similar view showing the parts in braking or stop position; Fig. 3 is a similar view showing the parts in the second running position; Fig. 4 is a similar view showing the parts in the second braking or stop positron; Figs. 1 2, 3 and 4: are elementary diagrams showing the connections of the four controlling magnets hereinafter described, as they appear'in Figs. 1, 2, 3 and 4, respectively, and, Fig. 5 is a'fragmentary diagram illustrating the method of using a plurality of controlling levers.

Referring to the drawings in detail, and particularly to Fig. 1, the motor is desig nated by the reference character M. The motor circuit is controlled primarily by means of two main pivoted switch arms A and B operating in connection with two automatic rheostats or starters, designated in their entirety by the characters C and D. These starters are shown as being of the current controlled type, but any other suitable or desired form of starters may be employed. The switch arms A and B are operated by means of four magnets E, F. G and 1-1, the circuits of which will be here inafter described.

K and L designate the tappet and manual controlling levers respectively. These levers are provided with off-center springs K and L, respectively, so arranged as to hold the levers in one of two positions and to prevent such levers from remaining in any other position. The lever K engages a contact when in each position, while the lever L serves, in each position, to bridge two contacts as will hereinafter more fully appear.

S designates a supply switch which connects with any suitable source of direct current. From this switch extends a main lead 1 which, for the sake of convenience, will be assumed to be the positive side of the circuit. In our preferred arrangement, we provide the motor with two separate and independent series field windings, one of which is permanently connected to the positive side of the line and the other of which is poi-manentlyconnected to the negative side of the line. In the drawings these two series field windings are designated by 2 and 2 respectively. The motor also has the usual shunt winding 30.

The starters or automatic rheostats C and D are similar, and a single description will sutIice for both. The starter D, for instance, comprises a pivoted arm to operatively connected to the core of a solenoid 42 and serving to cimtrol sections of resistance 11, The starter is also provided with a resetting solenoid l having a core which rests loosely upon the end of the arm 45 at the opposite side of its pivot from the solenoid -12. When the core of the solenoid i is lifted it leaves the arm 15 free to move downward by gravity, provided the current through solenoid 42 is not suliicient to maintain the arm 45 in its raised position. If, however, the current through the solenoid L2 is excessive, the arm will remain in its raised position, thus maintaining the resistance H in the circuit until such time as the current has fallen to a safe value. When the circuit through the starter is interrupted, the weight of the core of solo- 'noid -1 serves to restore the arm 45 to its normal position by over-balancing the core of solenoid 42.

lhe controlling magnets E, F, G and H are all connected in a series circuit across the line. This circuit may be traced as follows: Beginning with the positive lead 1, the circuit extends through wire 31, magnet G, wire 34, magnet F, wire 18, magnet E, wire 19, magnet I-I, wire :20, and back to the negative lead 11. Owing to the controlling levers, however, current does not normally flow through the complete circuit just traced. With these preliminary remarks it is thought that a better understanding of the invention may be had by a discussion of the running and braking circuits as disclosed in Figs. 1 to 1, successively. Fig. 1 shows the apparatus in the first running position. In this position, only'magnets E and H are energized, magnets F and G being short circuited as indicated in Fig. 1 by the line to. This connection 10 is in reality formed as. follows: wire 12, contact 13, lever K, wire 11, contacts 15 and 1G, bridged by lever L, and wire 17. It will be seen that the circuit just traced forms a connection from one side of the line to a point between magnets E and F, the same as indicated in Fig. 1. The current therefore flows from the point where the wire 17 joins the wire 18, through wire 18, magnet E, wire 19, magnet H to wire 20, thus energizing magnets E and H and causing them to move the arms A and B to the position shown in Fig. 1. In this position, current from the line flows through'switch S, conductor 1. series field 2, conductor 3, setting solenoid 4.- of starter D, conductor 5 to contact 6, thence through arm B, wire 7,

armature 8, wire 9, arm A, contact 10, back to the negative side of the line 11. Current also flows from wire 1, through the starting resistance 41, wire 43, solenoid 4'2, resistance 41, and wire 39. The motor immediately starts, and as soon as the current has fallen to a predetermined amount, the solenoid -12 permits the arm if) to move downward by gravity as indicated in Fig. 1, and when it has reached the lower limit of its travel it rests upon contact 40, thus cutting out the solenoid 1-2, and the resistances 41 and M, and completing the running circuit oi the motor through wire 46, direct to arm l5, thence through wire and on. It will be particularly noted also that the series field 2 is connected in parallel with the starting resistances ii and 44, and that-when the arm -15 engages the contact 10, the field 2 is short (-ircuited as well as the starting resistance, and that the entire operating current passes direct from wire 1., through wire 4:6, to wire In other words, the series field is in circuit only at starting and serves to give a strong starting torque, and that as soon as the current in the motor circuit falls to normal, the series field is cut out and the motor depends for its operation upon the shunt field, it being understood, of course, that the series and shunt fields produce magnetism in the same direction.

The method of connecting the shunt field in the circuit also forms an important feature of our invention. The novelty of this method consists in providing two separate field resistances 23 and 33, which are normally connected in series from the wire 20, through wire 21, rheostat arm 22, resistance 23, wire 24, rheostat arm resistance 33, wire 29, and field 30-to wire 1. The arms .22 and 32 may of course be adjusted so as to cut in or out more or less of the respective resistances and 33, the position of the arms in the drawing being such that all of resistance 23 is in circuit, while resistance 33 is entirely out out.

The arm B is arranged 1 to control the resistance 23 and 3 in such a I way as to short circuit one or the other of these resistances according to its position. In the position of the parts shown in Fig. 1, the rheostat 33 is cut out, by means of a contact carried by the arm B bridging contacts .26 and 27 connected by wires 25 and 28 to opposite sides of the rheostat, so that, regardless oi the position of the arm 32, the field current actually flows, in Fig. 1, through wire 21, rheostat 23, wire 2-1, wire 25, contacts 28 and 27, and wires 28, 29, thrmigh the field 30. In the other position of the arm 13,-the rheostat is short circuited in a manner hereinafter described, thus leaving the field to be controlled by rheostat 33. Itwill thus be seen that while two rheostats are provided, only one of them is in circuit at any one time.

\Ye will now suppose that with the parts in the position shown in Fig. 1, the operator desires to stop the machine. This is done by throwing the lever L from the running position, shown .in Fig. 1, over to the stop position, shown in Fi". 2. In this position, curmaaoee rent flows from the line 1, through wire 31, magnet G, wire 3%, magnet F, wire 18, magnet E, wire 19, and then, instead of flowing through iagnet H and wire 20, it takes the 5 short circuits-d path through Wire 47 contacts &3 and 49, bridged by lever L, wire 50, wire 51, contacts '52 and 53, back to the negative side of the line, it being observed that the arm A, in this position bridgesihe contacts 52 and 53, and thus completes the circuit. This circuit, as traced from character 47 to 53, inclusive, corresponds to the connection indicated at a: in Fig. 2?. Therefore, although magnet G is energized, magnet E still holds the arm A in its original position,

and this arm does not move. Owing to the short circuiting of magnet H, however, and the energization of magnet F, the arm B is thrown into the position shown in Fig. 2. This breaks the supply circuit the contact 6 and closes a circuit at 6, the corresponding contact, such circuit serving to connect the armature upon itself so as to constitute a dynamic brake. This circuit may be traced as follows; from one side of the armature 8, through Wire 7, arm B, contact 6', Wire 5', solenoid a, wire 3, series field 2', wire 1, wire 11, contact 10, arm A, wire 9, back to the other side of the motor. From the solenoid 4:. in the circuit above traced, the current divides and part of it also passes through wire 39, solenoid 42 and resistance 44 of starter C, the resistance of this starter and the series field 2 being connected in parallel in this braking circuit, in the same manner that series field 2 and starter D were connected in parallel in the operating circuit, shown in Fig. 1. This braking circuit afiords a path of low resistance so that a powerful braking effect is produced, and the moving part of the machine is quickly brought to a stop without jar or concussion. It will be also noted that the'rheostat 23, is short circuited by the arm B through wires 0 and 38 and contacts 36 and 37, thus leaving the rheostat 33 in circuit.

In order to start the machine it is only necessary to throw the manual lever back to the running position shown in Fig. 1. We

will assume that this has been done, and that the bed of the machine has made a complete stroke and has engaged the tappet lever K and thrown it to its other position, as shown in Fig' 3. lhe effect of this-is to short circuit magnets H and E and leave magnets F and G magnetized, as indicated by the connection i in Fig. 3% This connection, in fact, is constituted by the wire 17, contacts 15, 16, wire 14. contact 54 and wire 55. over which thecurrent flows from wire 18, instead of going through magnets E and H to Wire 20, as will be evident. Immediately therefore upon the deenergization of'niagne't E, the arm it moves to the. position shown in Fig. 3, the. arm B remaining stationary. An

operating circuit in Fig. 3 can therefore be traced as follows: from wire 1, contact 10', arm A, wire 9, motor armature 8, wire 7, arm B, contact (5, wire 5, solenoid 4, from whence it divides, part passing through the 79 resistance of starter C, and part passing through the series field 2 back to the negative side of the line 11. After the motor has gotten under way and the current has fallen to normal, the solenoid 42 drops its core and '25 permits the arm 45 to descend, and finally, when it engages contact d0, to short circuit both the starter and the series field, the running circuit being completed direct through the wire 1L6, as above described in connection :30 with starter D of Fig. 1. Meanwhile it will be observed that the core of solenoid l of starter D has dropped and restored this starter to normal position, read y for the next reversal of the motor.

It will be observed that in the position shown in Fig. 3, which we shall call the second running position, the rheostat 23 is short circuited, and since the rheostat 33 is practically cut out by its own adjustable .910 arm, the shunt field gets the full effect of the line voltage, and is therefore stronger than in Fig. l, where rheostat 23 is in the circuit.

It therefore follows that the speed of rotation of the armature in one direction is greater than in the other. This higher speed resulting from the position of the parts in Fig.1 may be advantageously utilized during the back or return stroke of the planer bed or similar part, while the higher torque of Fig. 3 is best adapted for the forward or working stroke of the planer. By varying the relative adjustment of resistances 23 and 33. any desired relation between the speeds on the forward and back ard stroke of the machinemay be obtained.

It will, of course, be understood that during normal operation. the circuits are shifted from the running position, shown in Fig. 1, to the running position, shown in Fig. 3, and back again. continuously. in other words the motor is reversed while running at full speed. Reversal takes'place the instant the tappet lever K is thrown in either direction. At the moment of reversal. therefore, the motor armature is subjected to the combined effect of the impressed line voltage and the existing counter-electro1notive force. This, in well designed motors, amounts to nearly double the normal voltage. In order to prevent excessive current at the moment of reversal, therefore, it is necessary that the rheostats or starters G, D, each have a resistance value much greater than would be required to"limit to a safe figure the starting current under normal conditions. As soon. however, as the motor comes to rest, after having its connections reversed, the effective voltage is reduced by the dying out of the counter-electromotive i electromotivc force, which, after reversal of the motor connections, acts, of eourse, in

the same direction as the impressed voltage. As the motor starts up in the reverse direction, the arm 45 continues to move down, cutting out the rest of resistance as in starting from rest under normal conditions.

Should it he desired to stop the machine, while running in the direction indicated in Fig. 3, the manual controlled lever L is again thrown to the right as shown in Fig. .lz, and this has the effect of short circuiting magnets E and)? as indicated by the con-- nection 2 in Fig. a, while leaving magnets H and Ur energized. In this position of the parts, current flows from wire 1, through wire/ 31, magnet G,,wire 56, contacts 57 and '58, wire 59, contacts 49 and i8. wire -17, wire 19, magnet ll and wire :20 backto negative side of the line, thus cutting out magnets E and F,- it being observed. that in the running position. shown in Fig. 3, the arm A serves to bridge contacts 51' and 58. This energization of magnet H and corre' sponding dei nergization of magnet F serves to throw the arm I) to the position shown in Fig. 4, into engagement with contact 6 again, while arm A remains 1111-- changed. This has the eti'ectof interrupting the operating circuit thr ugh contact 6', traced in connection with Fig. 2. and establishing abral-Iing circuit through the armature of the motor and contacts 6 and 10', such circuit including the series field 2 and the starter l) in the manner described in connection with series field 2 and starterC in Fig; 2. It is important to note the direction of this braking current through the-se ries lield. and its relation to the operating current. in Fig. 1, which is the first run- 'n-ing. position. current flows through the sejries' 'field :2 from left to right and through the armature S from right to left as indicated by. the arrows. The dynamic current in Fig. '2 flows. of course, through, the armature in a direction opposite to this,

which send it through the held :2 from right to left, When. therefore, we come to-the second running position, namely, that shown in Fig. 3,- we find that the operating current runs through the series field 2 in the same direction as this braking current, namely, from right to left. as shown by the arrows. Also in Fig. l, the b 'aking current, since it flows through the armature in a. di rection the reverse of that in Fig. 3, flows "through the field 2 from left to right, that is, in the-same direction as the operating current in Fig. 1. In other words, it will be observed that in all cases whether in the braking or operating circuit, the current through each series field winding is always in a direction to assist the magnetism of the shunt field, thereby securing the maximum braking effect as well as the maximum starting torque.

Front the foregoing it will be observed that we have provided a pair of automatic rheostats or starters which are alternately thrown into the armature circuit as the motor reverses. one serving to start the motor in one direction and the other serving to start it in the other direction. and that while one starter is working, the other one is automatically reset to normal position. It will also be noted that either starter-can be thrown into a braking circuit through the armature, depending upon the position of the reversing lever. The movements of the main switches are produced by selectively short circuiting oneor more of the controlling magnets, all of which are connected in series across the line.

In considering the foregoing operations it will be noted that when the switch arm B is in either position it short circuits one or the other of the rheostats 2 or When, however, it is in an intermediate position, such as it occupies at the moment of changing from contact 6 to.6, or vice versa, the rheostats Q3 and 33 are both in circuit. This results in the fact that, at the moment when the switch arm B is shifting, that is to say, at the moment when there is no current in the armature one way or the other, the shunt field is at its weakest, and that, upon the switch arm 13 arriving at either limit of its stroke, one of the rheostats is short circuited and the shunt field thereby strengthened. In other words the field is strengthened at each stroke of the reverser.

In many classes of work, particularly where the machines being driven are large or complex, it is desirable to be able to stop and start the motor from any one of a number of points about the machine. To meet the requirements of this class of service we arrange a plurality of manual controlling levers at any desired points of the machine. These levers are connected in the manner shown in Fig. 5, in which L, L and L represent three such levers. By reference to this figure it will be seen that all ofthe contacts such as 15and 16, which are bridged by' the levers when in running position, are connected in series with each other and with the reversing or 'tappet lever K, while the pairs of stop contacts, such as 18 and 49, are connected in multiple across the wires 47 and 59. The result of this arrangement is that all of the levers must be in running position before the machine can start and that the machine can be stopped by throwing any one of such levers over to the stop position, as indicated at L in Fig. 5. Thus throwing over any lever results in opening" the series circuit through the running contacts, and closing the stop circuit through a pair of the other contacts.

ll'hile we have shown, and in most cases prefer to use a motor having two independent series field windings, still it is possible to dispense with one of these windings and still. retain the main principle or" the invention. It it is not necessary or desirable to cut out the series field by means of the starters, as described, a single field can be equally well employed, or, even. with a single field, the starters may be arranged to cut it out at the proper time by means of an extra magnetic switch or relay operated by both starters.

o make no claim herein to the use of two separate series field windings, as above described, one for each direction of rotation, or to the arrangement of these field wind- 7 ings in such manner that one may be connected in an operating circuit and the other in a braking" circuit, as these features form no part of our invention.

While in the specification and claims we have used the terms reversing lever and manual lever, it will, of course, be understood that theword lever is to be construed as meaning any pivoted or shift-able element, capable of being moved from one position to another to control a circuit. It will thus be seen that we have Provided a very efficient and simple system of motor control which, while adaptable to many uses, is particularly applicable to machine having a reciprocating part which serves to reverse the motor at each stroke thereof, and it is thought that the many advantages of our invention will be readily appreciated by those skilled in the art.

"What we claim is V l. The combination with a motor, of a pair of separate automatic starting rheostats of the current-controlled type associated therewith, and means for connecting the controlling coils of said rheostats alternatelyin the armature circuit of the motor.

2. The combination with a motor, of a pair of electromagnetically controlled automatic rheostats associated therewith, and automatic means for connecting the controllin coils of said rheostats alternately in the armature circuit for predetermined intervals.

3. The combination with a motor of a pair of automatic current-controlled rheostats or starters associated therewith, and reversing means for said motor, serving, when operated, to connect the controlling coils of said starters alternately in the armature circuit of the motor.

t. The combination with a motor, of a pair of automatic rheostats' or starters associated therewith, a supply circuit, means for connecting the armature to the supply circuit through either one of: said starters, and means operating. when said circuit is opened, to short circuit said armature on itself through. the other of said starters.

5. T he combination with a motor, of two separate series field winiflings therefor, a supply circuit, a shunt field winding connectcd thereto, means for connecting the armature of the motor through one of said series field windings to the supply circuit, and means operating, when said circuit is open, to short circuit said armature upon itself through the other of said series field windings to constitute a braking circuit, the direction of current flowing in said braking circuit being such as to cause said last mentioned series winding to assist the mag netism of the shunt winding.

6. The combination with a motor, of a pair of separate series field windings therefor, means for connecting said field windings alternately in series with the armature of the motor in the operating circuit, and means for connecting either of said field windings in a. braking circuit also including said armature, the arrangement being such that the braking current flows through said field windings in the same direction as the operating current.

7. The combination with a motor, 01"

means for reversing the direction of rota-f tion of the armature thereof, and a. pair of automatic current-contmwlled rheostats associated therewith, said reversing means serving to connect the controlling coil of one of said rheostats in the armature circuit for rotation in one direction, and the other of said rheostats in such circuit for rotation in the other direction.

8. The combination with a motor, of two separate series field windings therefor, and two separate automatic rheostats, each associated with one of said field windings, and means for connecting each rheostat and its corresponding field winding, as a unit, alternately in the armature circuit of the motor.

9. The combination with a motor, of two separate series field winding-s therefor, and two separate automatic rheostats, each associated with one or" said field windings, and reversing means for said motor, serving, when operated, to connect each rheostat and its corresponding field winding, as a. unit, alternately in the armature circuit.

10. The combination with a motor. of two separate series field windings therefor, and two separate automatic rheostats, each associated with one of said field windings, and means for connecting either rheostat and field winding, as a unit, in either an operating or braking circuit, including the armature of the motor.

11. The combination with a motor, of two separate series field windings therefor, and

a two separate automatic rheostats, each as sociated with one of said field windings, and

a series field winding, of an automatic rheo-' stat or starter for said motor, such rheostat comprising resistance coils connected in parallel with the said series field winding and means serving to short-circuit said field winding when the starter is in running position. v

14. The combination with a motor, of means for reversing the same, a'fieldwinding for said motor, a pair of field rheostats connected in series with said winding, and means operated by said reversing means for alternately short circuiting said rheostats, such means being so constructed as to prevent the simultaneous short circuiting of said rheostats.

15. The combination with a motor, of means for reversing the same, a field Winding for-said motor, a pair of rheostats hav- .ing means for adjusting the resistances thereof to difierent values, and means operated by said reversing means for throwing said rheostats alternately into circuit with the field winding, whereby the[ speed of the motor in one direction may be made greater than its speed in theother direction, one or the other of said rheostats being always in circuit.

16. The combination with a motor, of a pair of switch arms controlling the circuit thereof, a pair of magnets for operating each of said switch arms, all four of said magnets being permanently connected in a series circuit across the line, and means for selectively short circuiting said magnets to produce movements of said switch arms...

17. The combination with a motor, of a pair of levers controlling the same, a supply circuit, means operated by one of said levers for reversing the connections of the armature of the motor to the supply circuit and means operated by the other of said levers forinterrupting such circuit, and

connecting the armature of the motor in a closed circuit upon itself, regardless of the direction of rotation thereof.

18. The combination with a motor, of a reversing lever therefor, said lever being capable of occupying either of two extreme positions, means for preventing said lever from remaining in any other vposition, a controlling lever having running and 7 stop positions, and means operated by positions, and means operated by said lever when in stop position for connecting said armature in a closed circuit upon itself, including a resistance.

20. The combination with a motor, of a supply circuit, a pair of substantially similar resistance device's, means for connecting said supply circuit with the armature to form an operating circuit, including either one of said resistance devices, and means serving, when such circuit is broken, to antomatically connect the armature in a closed circuit on itself, including the other of said resistance devices.

21. The combination with a motor adapted .to be operatively connected with a machine having a reciprocating part to be driven, of a tappet lever arranged to be ()p erated by such reciprocating part at each end of its stroke to reverse the motor, and amanual controlling lever, serving, when in one position, to cooperate with said tappet lever to complete an operating circuit connecting the motor with a source of cur-. rent, and when in another position, to break such operating circuit, and connect the armature of the motor in a closed circuit on itself.

22. The combination with a motor, of a reversing lever and a controlling lever, wholly independent of each other, means governed by said controlling lever, when thrown to one position, for automatically connecting the motor to the sup-- ply circuit, and, when thrown to another position, for automatically connecting the motor armature upon itself, the arrangement being such that said automatic operations take place regardless of the position of the reversing lever.

23. The combination with a motor, of a reversing lever and a controlling lever, wholly independent of each other, means governed jointly by said levers for connecting the motor to the supply circuit through a resistance, and means overned wholly by said controlling lever tor connecting the armature of the motor in a closed circuit on itself.

2a. The combination with a motor, of a reversing lever therefor, capable of occupying either one of two positions, means controlled by said lever, when thrown to either position, for inserting a starting resistance in the armature circuit, a controlling lever having running and stop positions, and means operated by said lever when in stop position for connecting said armature in a closed circuit upon itself, including a resistance, said two levers being wholly independent.

25. The combination'with a motor, of a reversing lever therefor, and a plurality of controlling levers, and connections whereby all of said controlling levers cotiperate with said reversing lever to simultaneously control the operation of the motor.

.26. The combination with a motor, of a reversing lever therefor, and a plurality of controlling levers, each capable ofoccupying either of two positions, and connections whereby all of said levers, when in one position, cohperate with the reversing lever to close the running circuit, and any of said levers serve, when thrown to the other position,'to break such running circuit, and to short circuit the motor on itself.

27. The combination with a motor, of a reversing lever therefor, and a plurality of controlling levers, each being capable of occupying either of two positions. a pair of contacts arranged to be closed by each of said levers when in either position, the contacts on one side of said levers being all connected in series with each other and with the reversing lever, and the pairs of contacts on the other side of said levers being connected in multiple across a controlling cir cuit.

28. The combination with a motor, of a controlling circuit therefor running and stop connections, a plurality of controlling levers, each capable of occupying either of two positions, a pair of contacts arranged to be closed by each of comprising said levers when in either position, the contacts on one side of said levers being all joined in series and serving to establish the running connection for the motor, and the pairs of contacts on the other side of said levers being connected in multiple across said controlling circuit, and any of which, serving, when closed, to establish the stop connection for the motor.

29. The combination with a motor, having a shunt field, of a reversing switch for said motor, and means operated at each movement of said switch for first weakening and then strengthening said shunt field.

30. The combination with a motor, having a shunt held. of a resistance connected in the shunt field circuit. a'reversing switch capalole of movement from one extreme position to another, and means operated by said switch when in either extreme position for short circuiting part of said resistance, the arrangement being such that for any intermediate position of the said switch, all or" said resistance is in circuit.

31. The combination with a motor, having a shunt field. of a resistance connected in the shunt field circuit. such resistance comprising a plurality of sections, a reversing switch operatively connected with the motor, means for moving said switch, and means operated by said switch at each stroke thereof for short circuiting part of said resistance. and thus strengthening the field.

32. The combination with an electric motor comprising field and armature, OflTIGflDS "for reversing the connections of one of said parts, and interposing in the armature circuit a resistance sufficient to limit to a. safe value the current due to the cumulative effect of the impressed voltage, and existing counter-electromotive force, and currentcontrolled means for automatically cutting out part of such resistance as the motor comes to rest.

In testimony whereof we afiix our signatures in presence of two witnesses.

' GEORGE H. W I-HTTINGHAM.

WILLIAM T. HOLMES.

Witnesses:

FRInnA ERNST, BERNIGE WARD.

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