US2170694A - Electromagnetic switch and system therefor - Google Patents

Description

Aug. 22, 1939. v c. L. PERRY 2,170,694

ELECTROIAGNETIG SWITCH AND SYSTEM THEREFOR Fi1ed Oct. 1, 1937 HATER/AL Inventor.

IBWIANENTLY HAGNETIZABLE Charles L. P rry.

b if? y Hi Attorhey.

' a portion hereinafter called 5g rial of high magnetic Patented Aug. 22, 1939 UNITED STATES PATENT orrica 7 2,170,667: I I nnacmomcnm'rc 'swrron AND srs'ram mam--03 GharlesL. Perry, Schenectady, N.

General Electric New York Y., asngnor to Company, a corporation of 7Claims.

My invention relates to electromagnetically operated switches and has for its object a simple and reliable electromagnetic switch and system therefor which is held of permanently magnetizable material, and which may be opened and closed by operating coils or opened an overload by. a currentresponsive coil.

In one form of my invention I provide an electromagnet for closing the switch, this magnet-being provided with an armature connected to the switch and a magnet frame member provided with the holding magnet. made of a material having a highcoercive force which holds residual flux when magnetized so as to hold the switch closed. provided for. attracting the armature to close the switch. A second operating coil connected to oppose the holding magnet is provided for releasing the armature to allow the switch to open, and if-desired, one or more additional coils also opposing or neutralizing the holding magnet may be provided and energized in response to the current in the switch so as to open the switch on overload.

For a more complete understanding of my invention, reference should be had to the accompanying drawing, Fig. 1 of which is a side elevation view of a switch embodying my invention; while Fig. 2 is a diagram .ofa control system for an electric motor utilizing this switch.

Referring to the drawing, in carrying out my invention, I provide a pivoted armature l0 mounted rigidly on a pivot shaft I I together with a magnet frame member l2 .of soft magnet core iron and a plurality of operating coils l3, l4, l5 and I6 provided with an axially extending core II. This core I] which forms a field structure with the member l2 has a relatively short circular or disk-shaped portion [8, forming a holding magnet, made of a suitable material having a high coercive force, and a relatively long portion made of soft magnet core iron constructed in two parts, I! and 20. Although the two parts, I! and 20, could be made as one, the provision of the relatively short section 20 makes its possible to leave out this section in the event that the portion I9 is long enough to form,.with the portion II a core of the desired length. The armature II is providedavith a member 20a made of magnet core iron extending across the ends of the core I! and the frame member 2! when the armature is in attracted position as shown in Fig. 1 to complete a magnetic flux path between them.

The portion I8 is preferably made of a mate'- closedby a magnet made An, operating coil is,

coercive force consisting 20% nickel, and 5% cobalt, the balance being iron.

As shown, the core portion 1 8 forming the holding magnet has a length in the direction of the '7 lines of magnetic force, i. e. axially of the coils H to IE, which is only a fraction of its diameter as shown in Fig. 1. I have found that this construction provides for much greater magnetic pull on thu armature per unit weight of holding magnet material than a construction of smaller diameter and greater axial length. For example, a core of this material, four and one-quarter inches (4%") long by two inches (2") in diameter, in one device gave less pull on the armature than a. core one inch (1") long with a diameter of two and one-quarter inches (2%") the remainder of the core in each case being of soft steel. Another advantage of the axially short holding magnet isthat fewer turns in the operating coil are required to pick up the armature.

. It will be understood that the movably mounted contacts of the switch are mechanically connected to the armature I0. As shown in Fig. 2, the three pivotally mounted contact arms 2| are secured to an extension 22 of the pivot shaft II to which the armature I0 is secured. These movable contacts arms, which form with their stationary contacts a three pole switch, are biased to their open circuit positions as by a suitable spring as shown or by the weight of the armature, the armature when released coming to rest against a stop 23 provided for it.

In Fig. 2, I have shown a control system in which the switch of Fig. 1 is embodied, the switch being connected to control the supply of current from suitable three phase mains 24 to a three phase motor 25. In this system the coil It serves as an operating coil to pick up the armature and move it to its attracted position.

The coil I5 serves as an opening coil. This coil when energized produces a flux inopposition to the flux of the holding magnet thus neutralizing the magnet and releasing the armature which thereupon drops to move the contact arms 2| to their open circuit positions, as shown in Fig. 2.

The coils l3 and N are connected respectively in two of the alternating current supply lines running to the electric motor 25. These coils are energized in response to the current passing through the switch,i. e. the current in the motor 25, and upon the occurrence of a predetermined switch arms 2i.

- released and its upper pair of contacts being"- closed, the relay coil 28 is again energized as pre-'" 70' current in these coils, neutralize the permanent magnet and allow the armature to drop and open the switch.

I have provided direct current supply mains 25 and 21 for energizing the coils i5 and I5, and also for energizing the coil 28 of a relay provided with bridging switch contacts 29 and 30. This relay is biased to its open position, as shown by gravity, and when the switch arms 2| are in their open circuit positions, as shown, the coil 28 is normally energized. Its circuit leads from main 26 through a normally closed two-way push-button 3|, condoctor 32, coil 28, and conductor 33 to the main 21.

- Two interlock switches 34 and 35 are mounted on the frame member l2 with their operating rod 36 in position to be engaged by an extension ill on the end of the armature 3 when the armature reaches its attracted position. The switch 35 is normally closed whereas the switch 3:3 isnormally opened as indicated in Fig. 2, and the armature when picked up, closes the switch 34 and opens the switch 35, the switches being biased by a spring 31.

When it is desired to start the motor, the push? button 3| is pressed to its lowermost position. This first opens the circuit through the uppermost contact of. the push-button 3| whereby the circuit for the coil 28 is transferred through the switches 29' and 35. This circuit leads from the main 26 through the conductor 38, the switch 29, conductor 39, switch 35, coil 23, and the conductor 33 to the supply main 27. When a circuit through the lower contact of the push-button 3i is completed, a circuit is established for the coil it which picks up the armature H3, closing the This circuit leads from the supply main 26 through conductor 38, switch 29, conductor 39, the lower pair of contacts of the push-button 3|, through the switch 30, conductor 40, and the. coil Hi to the supply main 2?. When the armature opens the switch 35, the circuit of the coil 28 through this switch is opened whereupon the switches 29 and 38 drop open, thereby opening the circuit for the coil it. The switch is now closed and the motor 25 energized, the armature l being held in its closed position by the holding magnet IB.

Should it now be desired to open the switch arms 2|, the push-button ll is depressed whereby the coil i is energized. This circuit leads from the main 26 through the button M, the switch 36' which is then closed, the conductor 42, and the coil Hi to the main 2?.

In the event of an excessive load on the motor, the coils l3 and i4 produce jointly a magnetic flux suflicient to neutralize the holding magnet whereupon the armature Ill drops to open the switch arms 2|. fective to open the switch despite the fact that they are energized with alternating current, for the reason that the alternating flux of these coils neutralizes the residual magnetism of the holding magnet.

When the armature is released, the switch 34 opens and switch 35 closes in accordance with their biases and the push-button 3| having been viously described. The push-button 3| must now lie-depressed again'to energize the coil IS in order that the switch arms 2| may again be moved to' their closed positions. This interlocking arrangement prevents repeated opening and closing of the switch-in the event that an overload oc- The coils l3 and M are ef-- cars at the instant the switch closes and before the push-button 3| is released. Even though .theif.

interlock switch 35 is closed'when the armature l0 isreleased, the armature cannot be picked up again because the relay switches 29 and 3B are both open thus maintaining open circuits for the coils i6 and 28. As previously indicated, to reclose the switch the button 3| must be released to close the relay switches 29 and 30, and then pressed.

The energization of the coils l3, It and id to open the switch demagnetizes the holding magnet |8 to a very great extent so that it cannot at tract the armature with suficient force to hold the switch closed. When the pick-up coil it is energized, however, the holding magnet is again magnetized and holds the switch closed. A property of this material is that-after once being magnetized, it is very readily re-magnetized. The pick-up coil it must be energized with direct current in order that the holding magnet may be re-magnetized, while the opening coils l3, M and I5 may be energized with either alternating current or direct current. As shown, the coil i5 is energized with direct current and in that case it must be energized in such direction that its magnetic field opposes the field of the holding magnet.

It will be noted that the holding magnet i8 is located in a position, axially of the coils, which is remote from the armature no. In other words, the magnet core iron portions 99 and 26 are next to the armature. This isolation of the holding magnet from the armature assures that the effect of the residual magnetization of the holding magnet will not be sufficiently strong to hold the armature up in case it is accidentally knocked upward, but without completely seating the switch contacts.

The electromagnet having a magnetic circuit formed at least in part of permanently magnetizable material disclosed in this application is covered by my copending application, Serial No. 218,829, filed'July 12, 1938, for Electromagnet.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and I therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention What I claim as new and desire toobtain by Letters Patent of the United States is:

1. The combination with a switch provided with a circuit controlling member mounted for movement between two positions and biased to one of said positions, of an operating coil for moving said member to the other of said positions, a magnetic flux core extending axially of said coil having a portion formed of magnetic core iron and another portion formed of a material capable of retaining a high residual magnetic fiux for holding said member in said position, and means operated by movement of said member for controlling the circuit of said operating coil.

2. The combination with a switch provided with a circuit controlling member mounted for movement between two positions and biased to "'one of said positions, of an operating coil for moving said member to the other of said positions, a magnetic flux core extending axially of said coil having a portion formed of magnet core open circuit position, an armature connected to said movable contact, a field structure provided with a portion made of permanently magnetizable material having a high coercive force forming a magnet for holding said armature. in a closed circuit position, said portion being remote from said armature, an operating coil on said field structure for moving said armature to the closed circuit position, electrical connections for controlling the energization of said operating coil including a switch connected with the circuit of said operating coil so as to deenergize said coil when said switch is opened, and a mechanical connection between said switch and said armature for opening said switch when said armature is moved to its closed circuit position by said operating coil.

4. The combination with a switch provided with a movably mounted contact biased to its open circuit position, an armature connected to operate said movable contact to its closed circuit position, a field structure provided with a portion of permanently magnetizablematerial forming a magnet for holding said armature in said closed circuit position, an operating coil on said field structure for moving saidarmature to said closed circuit position, a switch operated by said armature to deenergize said operating coil when said armature moves to said closed circuit position,

whereupon said armature is heldby said mag-- net, a second operating coil on said field structure, connections for energizing said second coil to neutralize the eiiect of said permanent mag-.

net-and release said armature whereupon said switch opens in accordance with its bias, a third operating coil on said field structure, and connections for energizing said third coil in response to the current in said switch so as to neutralize said magnet and open said switch upon the occurrence of a predetermined current in said switch.

5. The combination with a switch provided with a movably mounted circuit controlling member biased to one position, an armature connected to said circuit controlling member, a field structure provided with a portion of permanently magnetizable material forming a magnet for holding said armature in an attracted position, an operating coil on said field structure for moving said armature to said attracted position,

a relay switch biased to the open position, a coil for operating said relay switch to the closed position; a switch member biased to one position to close a circuitior said relay coil and thereby normally maintain said-coil energized and said relay switch closed, a connection whereby said relay coil is energized through said relay switch after said relay switch has closed, switching means for said operating coil closed by movement of said switch member to another position, and a switch operated by said armature for opening the circuits of said relay coil and said operating coil.

6. .The. combination with a switch provided with a movably mounted contact biased to its open circuit position, an armature connected to operate saidmovable contact to its closed circuit position, a field'structure provided with a portion of permanently magnetizable material forming a magnet for holding said armature in said closed circuit position, an operating coil on said field structure for moving said armature to said closed circuit position whereupon said oper- '.ating coil may be deenergized and said armature held in said closed circuit position by said magnet, a second coil on said field structure, and

electrical connections for energizing said second coil in accordance with the current in said switch so as to neutralize said magnet and there-- by open said switch upon the occurrence of a predetermined current in said switch.

7. The combination with a switch provided with a movably mounted circuit controlling member biased to one position, an armature connected to said circuit controlling member, a field structure provided with a portion of permanently magnetized material forming a magnet for holding said armature in an attracted position, a pair of relay switches biased to the open position, a coil for operating said relay switches to their closed positions, a switch member biased to one position to close a circuit for said relay coil and thereby maintain said coil energized-and said relay switches closed, electrical connections whereby said relay coil is energized through one of said relay switches after said relay switch is closed, an energizing circuit for said operating coil including the other one of said relay switches and switching means closed by movement of said CHARLES L. PERRY.

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