US2038702A - Alternating current electric switch - Google Patents

Description

2g, fi fi. I J ANDER5 N ALTERNATING CURRENT ELECTRIC SWITCH Filed Oct. 28, 1955 T 5 Sheets-Sheet l A waa 2& ma. l ANDERSON w smz ALTERNATING CURRENT ELECTRIC SWITCH Filed Oct. 28, 1953 3 Sheets-Sheet 2 April] 2, 19360 J ANDERSQN 2,@38 7@2 ALTERNATING CURRENT ELECTRIC SWITCH Filed Oct. 28, 1933 3 Sheets-Sheet 5 By WWW Patented Apr. 28, 1936 UNITED STATES PATENT OFFICE ALTERNATING CURRENT ELECTRIC SWITCH In Great Britain 7 Claims.

This invention relates to alternating current electric switches, and has for its object to provide improved switches whereby interruption of the circuit can be effected at the zero value of the current.

The invention comprises the combination of a series synchronous motor, a switch tripping or opening device adapted to be actuated by the motor, and means for bringing the said device 7 10 into its operative position for effecting the opening of the switch by the motor at a predetermined instant in the revolution of the motor armature.

In the three accompanying sheets of explanatory drawings:

Figure 1 is a side elevation, and Figure 2 an end elevation showing diagrammatically a switch constructed in accordance with this invention.

Figure 3 is an end view of the spring coupling between the two motors which actuate the switch mechanism.

Figures 4 and 5 are respectively side and end elevation showing diagrammatically a modified form of switch embodying my invention. In carrying the invention into effect in the manner shown in Figures 1-3 of the drawings, I employ any convenient form of synchronous motor. Preferably a pair of interconnected motors w, b, are employed. The main one a is excited by a series winding and is the one on which the apparatus normally depends for its action. The other I) is a supplementary motor and is excited by a shunt winding. This motor serves mainly to start the apparatus and keep it going when a relatively weak current is passing through the series winding. The motors are interconnected by a spring coupling 0 and are such that even when a large phase difference exists between their actuating currents the series motor will not be appreciably out of phase with the current to be controlled. In a modification the shunt and series windings may be arranged on different parts of a single motor provided that the magnetic system is suitably designed so that there is no serious interference between them.

At one end of the rotor spindle d, or of one of the rotor spindles, is arranged on a crank e a projection j which can strike an arm g pivoted on the switch lever h for the purpose of opening the switch. The switch comprises contacts 11 on the lever h and fixed contacts 7' on the base of the apparatus. The contacts are brought together by a closing movement of the lever h which is effected by hand or in any other convenient manner, and separation of the contacts is ef- November 11, 1932 fected by an opening movement of the lever 11. which can be effected automatically in the manner herein described. In Figures 1 and 2 the switch is shown closed. The switch is held either closed or open by a spring acting on atogglelink l which is pivotally connected at one end to the lever h and at the other end to a bracket m on the base.

The crank e and projection f are adjustable angularly in relation to the rotor so that it can open the switch at the instant when the current is at or about zero value. The adjustment can be effected by any convenient means (not shown). The arm 9 is pivoted so that as shown in Figure 1 it can swing in the plane of the paper. Normally it lies out of the path of the projection f on the rotor spindle. For bringing the arm into action I employ a bell crank lever having arms n, 0. One part 0 of this lever is adapted to be. brought into the path of the rotor projection f, and the other part n is adapted to move the switch arm 9 into the active position.

The lever n, 0-, may be actuated by hand or automatically. In the example illustrated the lever is actuated by an electromagnet p through the medium of an armature q which (when the magnet is not in action) is held up by a spring 1'. The armature is connected by a link 3, bell crank lever t, and link 11. to another lever 12 which carries the pivot w of the lever 71, o. The extent to which the lever 1) can move when the armature q is raised by the spring 1' is limited by an extension m which serves as a stop by abutting against an adjacent fixed part associated with the mechanism. The rocking of the lever n, 0, about its pivot to is controlled by a spring g which engages an abutment on the link u.

While the switch is closed and the motors a, b, are in action both parts 9, o, are clear of the rotary projection f. To open the switch, the lever n, o, is advanced. This, in the example illustrated, is efiected by exciting the magnet p. The part 0 then lies in the path of the projection f, and the part 11. lies beneath the arm 9 on the switch lever. As soon as the projection ,f reaches the part 0 it rocks it about its pivot w causing the part n to lift the arm g into the path of the projection f. In the next revolution of the rotor, the projection f strikes the switch arm 9 and opens the switch. The opening of the the lever n, 0, is returned to the position shown by the spring 1. Reclosing of the switch lever h when it is required to re-establish the circuit controlled by the switch is effected by hand.

By arranging the pivoted switch arm 9 to be brought into action as above described I am able to reduce to the minimum the time occupied in effecting the opening of the switch and also to ensure that the switch shall be actuated at exactly the right instant.

The mechanism above described is applicable to a switch of light construction in which the inertia forces to be overcome are relatively small, but when a heavier construction is necessary and the inertia forces are correspondingly large, the mechanism shown in Figures 4 and 5 is preferred. Referring now to these figures, a crank disc 2 driven by a motor or motors as above described is provided with a projection 3 which may be adjustable in any convenient manner. The pivoted switch lever 4 which co-operates with a fixed contact 9 is connected by a link 5 with a lever B pivoted at 1. To the link 5 is also attached a locking lever 8 adapted to engage a fixed abutment 32 for holding the switch open. The lever 6 has pivoted to it one end of a bar I!) which at its lower end is pivotally attached at H to a striking lever l2, the latter being pivoted on a pin l3 which lies in a gap or slot l4 in this lever. The striking lever I2 is arranged for engagement by the crank projection 3, and the bar In is formed with a gap I5 which can also be engaged by the projection 3.

In association with the mechanism above described is arranged an electromagnet l6 which can act on a lever l1 controlled by a spring l8. This lever I1 is connected by a link 19 to a lever 20 pivoted at 2|, and to the lower end of this lever is pivoted a lever 22 formed with a striking piece 23 which can be moved into the path of the projection 3. The part 24 of the lever 22 serves for engagement by a resetting rod 25 carried on the lever 20 and controlled by a spring 26. The lever'22 is held in either of two positions by a spring 21 acting through a link 28. The lever 22 is also connected by a slotted link 29 to a bell crank lever 30- adapted to act on the striking lever l2, the lever 30 being pivoted at 3|.

When the switch 4 is closed and the motor is rotating the parts of the mechanism above described occupy the position shown in Figure 4. To open the switch 4 the magnet I6 is brought into action (by actuating any conveniently arranged hand switch) and the lever I1 is thereby moved against its spring l8. This has the eifect of moving the lever 20 in the direction for bringing the part 23 of the lever 22 into the path of the rotating crank projection 3. When the part 23 is struck by the projection 3 it causes the link 29 to move downwards and through the medium of the bell crank lever 3|] to rock the striking lever l2 into such a position that its upper end lies in the path of the projection 3.

During the next revolution of the crank disc the projection 3 rocks the striking lever 12 about its pivot and this has the effect of bringing the gap l5 of the bar l0 into the bath of the projection 3, so that immediately after the projection 3 has cleared the striking lever I2 it passes into the gap I5. With the continued movement of the projection 3 the bar i0 is lifted by the projection causing it to move the lever B and so open the switch 4 through the medium of the link 5. This movement of the bar ID has the effect of rocking the lever i2 completely about its pivot l3 into the position shown in Figure 5, so

that at the instant immediately after the switch has been opened all the parts of the mechanism occupy the position shown in Figure 5. The switch is held open by the engagement of the catch lever B with the abutment 32.

The parts are so adjusted in relation to the phase of the current which actuates the motor that this opening movement of the switch occurs at the instant of zero current.

As the motor may continue to rotate, the later engagement of the projection 3 with the inverted end of the lever l2 merely has the effect of knocking the lever l2 and bar H) aside without further action on the mechanism. On releasing the magnet E6, the lever 11, link [9 and lever 20, together with the lever 22, link 29 and lever 30 resume the position shown in Figure 4 under the action of the spring 13, but the remainder of the mechanism remains in the position shown in Figure 5.

To reclose the switch 4, the lever B is raised, and this lever can be used for moving the lever 4 into the closed position. Or an extra hand lever (not shown) may be provided for closing the switch after release of the lever B. For some purposes an extra isolating switch may be employed, and this is interlocked with the switch 4 in such a manner that the switch 4 cannot be closed until the isolating switch is opened, the latter being closed independently after the main switch 4 has been closed. The act of reclosing the switch 4 brings the striking lever l2 and bar l0 back to the position shown in Figure 4. The resetting of the lever 22 is effected by pressing the rod 25 into en gagement with the part 24.

The invention is not limited to the examples above described as subordinate mechanical or constructional details can be varied to meet different requirements.

Having thus described my invention what I claim as new and desire to secure by letters Patent is:

1. In alternating current electric switches, the

combination of a series synchronous mot0r,,

switch actuating means driven by the motor, a movable switch contact, and a setting device for enabling movement to be transmitted from the said actuating means to the movable contact at a predetermined instant in the revolution of the motor armature, which setting device comprises relatively movable members, normally lying out of the path of the said actuating means but adapted to be moved successively into such path, whereby the transmission of motion from the actuating means to the contact is made dependent upon successive actuations of the said device by the said means, substantially as described.

2. In alternating current electric switches, the combination of a pair of synchronous motors, one of which is provided with a series winding and the other with a shunt winding, a resilient coupling interconnecting the motors, switch actuating means driven by the motor with the series winding, a movable switch contact, and a setting device for enabling movement to be transmitted from the said actuating means to the movable contact at a predetermined instant in the revolution of the motor armature, which setting device comprises relatively movable members, normally lying out of the path of the said actuating means but adapted to be moved successively into such path, whereby the transmission of motion from the actuating means to the contact is made dependent upon successive actuations of the said device by the said means, substantially as described.

3. In alternating current electric switches, the combination of a synchronous motor provided with series and shunt windings, switch actuating means driven by the motor, a movable switch contact, and a setting device for enabling movement to be transmitted from the said actuating means to the movable contact at a predetermined instant in the revolution of the motor armature, which setting device comprises relatively movable members, normally lying out of the path of the said actuating means but adapted to be moved successively into such path, whereby the transmission of motion from the actuating means to the contact is made dependent upon successive actuations of the said device by the said means, substantially as described.

4. In alternating current electric switches, the combination of a series synchronous motor, a crank device driven by the motor, a movable switch opening member connected with the switch and normally lying out of the path of the crank device, a pivoted lever adapted to move the switch opening member into the path of the crank de vice, a movable support carrying the pivoted lever, and means for actuating the support for moving the lever into and out of the path of the crank device, substantially as described.

5. In alternating current electric switches, the combination of a series synchronous motor, a crank device driven by the motor, a movable switch opening member connected with the switch and normally lying out of the path of the crank device, a pivoted lever adapted to move the switch opening member into the path of the crank de vice, a lever mechanism for carrying and moving the said pivoted lever into and out of the path of the crank device, and electromagnetic means for actuating the said lever mechanism, substantially as described.

6. In an alternating current electric switch, the combination of a series synchronous motor, a crank device driven by the motor, a striking lever movable into the path of the crank device, a gapped bar for opening the switch and connected to the striking lever, this bar being movable into the path of the crank device by the striking lever, another striking lever mounted on a movable support and adapted to be moved into the path of the crank device, the movement of the first named striking lever into the path of the crank device being effected by the second named striking lever, and means for actuating the movable support of the second named striking lever, substantially as described.

'7. In alternating current electric switches, the combination of a series synchronous motor, a crank device driven by the motor, a striking lever movable into the path of the crank device, a gapped bar for opening the switch and connected to the striking lever, this bar being movable into the path of the crank device by the striking lever, another striking lever adapted to be moved into the path of the crank device, the movement of the first named striking lever being efiected by the second named striking lever, lever mechanism for carrying the second striking lever and moving it into its active position, and electromagnetic means for actuating the said lever mechanism, substantially as described.

JAMES ANDERSON.

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