US2668884A

US2668884A - Electrical switch apparatus

Info

Publication number: US2668884A
Application number: US257519A
Authority: US
Inventors: James W Jacobs
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1951-11-21
Filing date: 1951-11-21
Publication date: 1954-02-09
Anticipated expiration: 1971-02-09

Description

Fb. 9, 1954 w, JACOBS 2,668,884

ELECTRICAL SWITCH APPARATUS Filed NOV. 21, 1951 o 5 IO I5 20 I4!) CURRENT F 2 l W W INVENTOR.

Patented Feb. 9, 1954 UNITED STATES iATENT OFFICE ELECTRICAL :S'WITGH APPARATUS James W. Jacobs, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware 4 Claims. 1 This invention relates to electrical apparatus and more particularly to electric switches and relays.

It is an object of my invention to provide a simple, reliable, low cost switch using a minimum of strategic materials.

It is another object of my invention to provide switch in which there are no parts to wear and in which there is an absence of contact difficulties.

It is another object of my invention to provide a relay which is simple, reliable and low in cost.

It is another object of my invention to provide a relay in which there are no contact difficulties and no parts to wear.

To attain these objects .I provide a sealed enclosure containing a suitable non-conducting gas such as hydrogen. Separated electrical terminals are exposed within the interior of the enclosure. In one form of the invention an electromagnet, when energized, provides an electromagnetic field between the poles causing particles within the enclosure to bridge the gap between the terminals to allow current to flow. In a modified form, the particles may be permanently magnetized and .have a low Curie point for use as a thermal current overload.

Further objects and advantages of the present invention will be apparent from the following description, reference being bad to the accompanying drawings, wherein .a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a view partly in section of a relay switch embodying one .form of my invention connected to a wiring diagram for a split phase motor;

Fig. 2 is a sectional view of another form of my improved relay switch which includes both a starting relay switch and a thermal overload switch connected to a wiring diagram of a split phase motor circuit;

Fig. 3 is a sectional view of a third form of my invention likewise connected to a split phase motor circuit; and

Fig. 4 is a main winding current speed diagram of an electric motor.

In the drawings, the switch is shown used as the starting relay for a split phase motor. Starting relays are used in great quantity and have been of many different designs. They are ordinarily controlled either by motor speed or by the motor current. All types seem to be subject to some difficulties. To overcome difiicultiee found in such starting relays, I provide a sealed enclosure 20 preferably of some suitably insulating material such as a thermo-plastic, for example, phenol formaldehyde resin. This sealed enclosure is provided with an upper electrical terminal 22 and a lower electrical terminal '24. These terminals should be larger in size than conventional contact terminals. Preferably they are of a paramagnetic or ferromagnetic material, for example, very soft iron which may be silver plated. The sealed enclosure is also provided with a multitude of ferromagnetic particles such as soft iron. These particles may be copper or silver plated to increase their electrical conductivity. The area of the terminals and the quantity of the particles should be in proportion to the amount of current it is desired to carry with the maximum allowable contact resistance. The sealed enclosure 20 is preferably completely evacuated and charged with a suitable gas such as hydrogen under pressure.

To cause the particles 2% to bridge the gap between the

terminals

22 and 22 there is provided a U-shaped electromagnet 28 provided with pole pieces 30 and 52 directly adjacent the nearest terminals 22 and 2-4. The U-shaped magnet 2'8 is provided with an energizing winding tit connested in the supply circuit of the main winding 35 and the starting winding 44 of the electric motor 38. The supply circuit includes a control switch it and a thermal overload control 42 in series with the motor winding circuits. The motor 33 is also provided with a starting winding" M which has one terminal connected to the adjacent terminal of the main winding 3% and to the supply conductor 46. The other terminal of the starting winding Ml is connected to the upper contact terminal 22 while the lower contact terminal M is connected by the conductor 48 to the main winding circuit.

When the switch so is closed, the current first flows from the supply conductor it through the main winding 36 and the electromagnet coil 34. the overload protector switch 42, and the switch it to the supply conductor 53. In a typical motor this current may be as high as 20 amperes as shown in Fig. 4. This current flowing through the eiectromagnet coil as is sufficient to set up a magnetic field between the pole pieces of the electromagnet 28 which will cause the magnetic particles 2'8 to arrange themselves in this magnetic field between the terminals 22 and This bridges the contacts and 1M causes the current to flow through the conductor is to the lower contact M, the magnetic particles 26, to the contact 22 and thence through the starting winding 44 to the supply conductor 46. This causes the motor 38 to start. As the motor picks up in speed according to Fig. 4, the main winding current falls and when the current is reduced to about 15 amperes, the electromagnetic field is insuflicient to hold the particles 26 as a bridge between the

terminals

22 and 24 so that they fall with the bottom of the sealed enclosure 20, thereby breaking the bridge and stopping the current flow between the

terminals

22 and 24. The current falls to 15 amperes at about 15 to 1600 R. P. M. which is a desirable switching speed.

In Fig. 2 there is shown another form of the invention in which there is provided a sealed container I2Ii of a suitable thermo-plastic material such as phenol formaldehyde resin. Molded into this sealed container I23 is a dividing plate I2I which divides the interior of the container I20 into an upper compartment I23 and a lower compartment I25. The conductor plate I2I is provided with a dual contact terminal I24 in its center portion which projects upwardly and downwardly into the spaces I23 and I25. Coaxial with the container I23 and the terminal I24 is an upper terminal I22 mounted in the center of the top wall of the sealed container I23. The space I23 is filled with a sufiicient quantity of soft iron particles I23 to bridge the gap between the terminals I22 and I24 in suificient quantity to carry the starting winding current.

To cause these particles I25 to bridge the gap between the terminals I22 and I24, there is embedded in the walls of the chamber portion I23 an electromagnet coil I3 3 which is connected between the control switch I II] and a lower terminal I33 provided coaxially with the terminals I22 and I24 in the bottom wall of the sealed container I20. This sealed chamber I25 contains particles I2! having a low Curie point. These particles I21 as well as the particles I25 and the terminals limited that upon excessive current flow the parjticles I2! will be heated above their Curie point,

thereby losing their magnetic properties so that they fall to the bottom of the chamber 225 to break the bridge across the terminals I24 and I 33.

The alloy may be varied to change the Curie point. For example, if it is desired to use particles having a Curie point of about 300 F. a 31% nickel, 69% iron alloy may be used. Also nickel silicon, nickel molybdenum, and nickel zinc, and nickel copper alloys may be used for example. To

obtain a Curie temperature of about 300 a 2 silicon, 97 70 nickel alloy may be used. A 300 Curie temperature may also be obtained by a 6% molybdenum, 94% nickel alloy or a 12 zinc, 87 70 nickel alloy, or a 19% copper, 81% nickel alloy.

To cause these particles I27 to bridge the gap between the terminals I33 and I24 there is embedded in the wall of the chamber I 25 an electromagnet coil I29 which has one terminal connected to the supply conductor I4I under the control of the control switch I lIi while the other terminal of .the coil I23 is connected to the supply conductor I46. This arrangement acts as a low voltage protector, since whenever the supply voltage is too low for proper operation, the magnetic field provided by the energization of the coil I29 will not be strong enough to cause the particles I27 to arrange themselves across the gap between the terminals I33 and I24 or to hold them in bridging arrangement. When the supply voltage is adequate, the magnetic field between the terminals I33 and I24 will be strong enough to cause the particles to arrange themselves across the gap and bridge the terminals I33 and I24. The central electrical divider plate I2I is connected to the main winding I36 oi the electrical motor I38. The starting winding I44 of the motor I38 has one end connected to a common connection with the supply conductor I45 while the other end is connected to the upper terminal I22.

When the switch MI] is closed, current will first flow through the supply conductor I43 and the electromagnet coil I29 to the supply conductor I4I. This will set up a magnetic held between the terminals I23 and I33 causing the particles I21 to bridge the gap between these terminals I24 and I33. When this bridge is established current will flow from the main winding I36 through the plate i2I to the terminal I24 and across the bridge of the particles I2! to the terminal I33 and thence through the starting electromagnet coil I34 to the supply conductor I 4 I. The energirzation of the coil I34 will provide an electromagnetic field between the terminals I22 and I24 thereby causing the particles I26 to bridge the gap between these terminals and close the starting winding circuit. Both windings of the motor I33 are thereby energized. In accordance with the current diagram in Fig. i, the main winding current will reduce as the motor speed increases and at a desirable switching speed this current will be reduced suificiently that the elec tromagnetic coil I34 will not provide a field which is strong enough to hold the particles I25 across the terminals I22 and IE4 so that they will fall to the bottom of the chamber I23. This will deenergize the starting winding I44.

The quantity of the particles I2? and the area of the terminals I24 and I33 are limited to the extent that upon excessive current flow to the motor I38, the particles I21 will be heated above their Curie point, thereby losin their magnetic properties so that they fall to the bottom of the chamber I25 to break the bridge across the terminals I33 and I24 which conducted the motor current. As soon as the particles I2! are cooled below their Curie range, they will gradually recover their magnetic properties. The coil I29 remains energized. Therefore when th particles I21 have sufficiently recovered their magnetic properties, they will again return to the magnetic field and bridge the gap between the terminal I33 and I 24 to reclose the motor circuit. Thus automatic reclosing thermal overload and low voltage protection are provided.

In Fig. 3 the portion above the dividing plate 22I is similar to that shown in Fig. 2 and includes a terminal 224 projecting into the upper chamber 223 and the lower chamber 225 within the sealed enclosure 223. The upper contact 222 is com nected to the starting winding 244 while the dividing plate 222 is connected to the main winding 236 of the motor 238. As in Fig. 2 the sealed enclosure 220 may contain an atmosphere of a ber 223 is surrounded by an electromagnet .coil

234 embedded in the wall of the sealed enclosure 220. One terminal of this coil 234 is connected to the control switch 240 while the other terminal is connected to the terminal 233 provided in the bottom of the sealed enclosure 234 ccaxially with the enclosure and the

contacts

222 and 224. This circuit differs from Fig. 2 in that there is no electromagnetic winding for surrounding the bottom chamber 225 but one or both the

terminals

233 and 224 are permanently magnetized. The chamber 225 also contains an adequate quantity of permanently magnetized particles 22'! having a relatively low Curie point such as between 130 and 300 F. The metallurgic composition of the particles 22'! may be the same as the particles I21 of Fig. 2.

With this arrangement, as long as the particles 22'! are below their Curie point they will bridge the gap between the terminals 223 and When the switch 240 is closed the current will flow from the supply conductor 248 through the main winding 236 to the plate 21%| and the terminal 22 3. The magnetic particles 22? will carry the current to the bottom terminal 233 from which point the current will now through the winding 234 and the switch 240 to the other supply conductor 250. The flow of current through the winding 234 will cause the particles 226 to form a bridge between the

contacts

222 and 224 thereby permitting current to flow from the terminal 224 through the bridge of particles 226 to the terminal 222 and thence through the starting winding 244.

The motor will have a current characteristic like that shown in Fig. 4 and when the current drops by reason of the acceleration of the motor from a standing start below 15 amperes, the magnetic force provided by coil 234 will be insufficient to maintain the particles 228 in a bridge across the

terminals

222 and 224. This will permit the particles to fall to the bottom of the chamber 223 thereby breaking the circuit of the starting winding 244. The motor 238 will then continue to operate until either the switch 258 is opened or the particles 221 are heated above their Curie point by reason of either excessive current flow or high environment temperature. When so heated, the particles 22'! will fall to the bottom of the chamber 225 and break the motor circuit. The motor circuit will remain broken until the particles are cooled below their Curie point. After the particles 221 are so cooled, they will recover their magnetic properties and again arrange themselves as a bridge across the

terminals

224 and 233 to reclose the circuit of the motor 238. In all modifications, the contact terminals should be adequate in area and the particles sufiicient in quantity to provide the necessary current carrying capacity. Both terminals and particles may be plated with silver, copper or other good electrical conductor to improve the electrical conductivity.

While I have shown the switch as used for a starting relay and current overload protector for a split phase motor, there is evidence that this is merely one of many practical applications of the invention and the invention may be used wherever it is desired to start and stop the energization of any electric circuit.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. A switch including a sealed enclosure provided with two spaced electrical terminals, at least one of said terminals being of a permanent magnetic material and being located above the other, said sealed enclosure containing a sufficient quantity of magnetized particles having a low Curie point to bridge the gap between the terminals when the particles are below the Curie point temperature, said terminals having a sufficiently limited exposed area and being spaced sufficiently far apart and said quantity of particles being so limited that an excessive current flow through the particles across the gap will heat the particles above their Curie point to demagnetize the particles to break the bridge.

2. A Switch including a sealed enclosure provided with two spaced electrical terminals, at least one of said terminals being of a permanent magnetic material and being located above the other, said sealed enclosure containing a sufficient quantity of magnetized particles having a low Curie point to bridge the gap between the terminals when the particles are below the Curie point temperature, the quantity of particles and the rate of heat dissipation being proportioned to provide resistance heating of the particles under an excessive current flow sufficient to raise the temperature of the particles above the Curie point to break the circuit between the terminals.

3. A switch including a sealed enclosure provided with two spaced electrical terminals and means for creating a magnetic field between the terminals, said sealed enclosure containing a sufficient quantity of magnetized particles having a low Curie point to bridge the gap between the terminals when the particles are below the Curie point temperature, the quantity of particles and the rate of heat dissipation being proportioned to provide resistance heating of the particles under an excessive current flow suflicient to raise the temperature of the particles above the Curie point to break the circuit between the terminals.

4. A switch including a sealed enclosure enclosing a chamber, an electromagnet winding encircling said chamber, a wall extending across said chamber dividing said chamber into two sub-chambers, said wall being provided with an electrical terminal extending into each of said sub-chambers, each of said sub-chambers being provided with a second electrical terminal separated from said first mentioned terminal, each of said sub-chambers being provided with paramagnetic particles, the particles in one of said sub-chambers having a sufficiently low Curie point that an excessive current flow between the terminals through the particles will cause the particles to be heated above their Curie point to disperse the particles and break the current flow.

JAMES W. JACOBS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 721,387 Potter Feb. 24, 1903 781,993 Bell Feb. 7, 1905 1,185,240 Petersen May 30, 1916 1,380,752 Toomey June 7, 1921 1,655,852 Adams Jan. 10, 1928 1,675,680 White July 3, 1928 1,764,375 White June 17, 1930 1,868,559 Bascom July 26, 1932 2,015,156 Richmond Sept. 24, 1935