US2294344A - Electric control system - Google Patents

Description

Aug. 25, 1 942. E. D. N UNN ELECTRIC CONTROL SYSTEM Ewin D. N unn ATTORNEY.

Filed July 11, 1940 Patented Aug. 25, 1942 UNITED STATES PATENT OFFICE Claims.

This invention relates to mp ovements in electric control systems.

One of the objects is to provide a system adapted to automatically deliver wattage of a pre-selected value for pre-selected periods at pre-selected intervals.

Another object is to provide an improved control system which will start its recurrent automatic operation without the aid of the breaker contacts thereafter used to cause the continuance of such recurrent operation.

Another object is to provide an improved control system which eliminates the necessity for current passing through the pigtail spring for biasing the momentum timing device.

Another object of the invention is to provide a system wherein the component parts are so arranged and structurally related as to reduce the cost of construction and to form a compact and easily handled unit.

The foregoing objects are accomplished by combining in a system a source of electrical power, a transformer, a momentum controlled timing switch, and a commutator type on and off switch, arranging the circuit so that the source is directly connected to the transformer by the commutator switch only, as that switch is moved from off to on or on to off positions. With this circuit the system is given an initial impulse even though the breaker contact points are electrically insulated from each other by the products of corrosion. By providing the momentum controlled timing device with a floating bridge contactor carried by the flywheel or other momentum establishing weight nection with the accompanying drawing, in P which:

Figure l is a view in elevation of a unit having the parts comprising the system embodying the invention structurally arranged and related;

Figure 2 is an enlarged fragmentary view showing the floating bridge contactor and the relatively fixed, insulated contacts; and

Figure 3 is a wiring diagram of the electrical system embodying the invention.

Referring in greater detail to the drawing, the unit disclosed is particularly adapted for use as a fence charger. To this end the chassis of the unit comprises an elongated base B upon which is secured a frame F of substantially inverted U shape when viewed from the end thereof. The frame is secured to the chassis by means of four pedestal-like feet at the lower corners. Its lefthand portion is cut away, as at [0, to receive a combined step-up transformer and relay coil H. The transformer H is provided with an iron core. The iron core is secured between upright portions formed on the top of the frame F to secure the transformer in position on the frame. The right-hand top portion of the frame F has a rectangularly shaped opening therein to receive a fly-wheel l2. The fiy-wheel i2 is dish-shaped in form and has at one portion of its periphery a pressed out tab l3 to which is floatably connected a bridge contactor M. The contactor I4 is provided with two tungsten breaker points positioned on opposite sides of the floating suspension point. An axle and bearing 15, having the outer ends thereof secured to the sides of the opening in the top of the frame F, rotatably suspends the fly-wheel l2 within the opening. Surrounding the axle in a spirally wound manner is a pigtail spring l5 which is biased to urge the fly-wheel [2 to move in counter-clockwise rotation. Suspended beneath the transformer H is an armature li. One end of the armature is flexibly secured by a spring it to the frame F by means of a bracket IS. The free end of the armature is formed upwardly and then outwardly to provide a relay carrying portion 20. The portion 20 is positioned near the end of the iron core of the transformer H and is operated by magnetic field of the primary of the transformer. To the portion 28 are secured, insulated from each other and from the armature 2, contact arms 2| and 22, each bearing tungsten breaker points on the upper surface of their end portions. Beneath the transformer H and above the armature I "I the sides of the frame F are provided with slots 23 which are adapted to receive and hold a spring member 24. The member 24 extends from side to side of the frame F and is held within the slots by the provision of notches cut from the corners thereof, as indicated at 25 (Figure 2). The under side of the spring 24 is en g d by an upwardly projecting finger 23 formed from the armature I1. Thus the tension in spring 24 is communicated to the armature I'I urging it to non-energized position. The sides of the frame F are likewise provided with oppositely located rectangular slots 27 between which is suspended a beam member 28. In the center of the beam member 28 is provided an adjusting nut and screw 29. The beam member 28 is held in the openings 23 by having its corners notched in the same manner as the spring 24. In order to facilitate the assembly of the beam member 23, one of the rectangular slots 2! is provided at its upper end with notched-out portions 33 sufficiently increasing the width of the slot to permit the beam member to slide therethrough when it is raised upwardly. The slots 21 are so positioned that the adjusting screw 29 bears against the underside of the armature I! to determine its non-energized position. On the top of the frame F adjacent the outer end of the transformer II' is positioned a condenser 3| of approximately .4 mid. capacity of direct current working voltage of approximately 200 volts.

At any convenient place on the frame F there is positioned an upright bracket 32, which holds a socket and incandescent bulb 33 and a small fixed resistor 34. The base is provided with a porcelain, insulated connecting terminal 35, to which the fence wire is normally secured, and a terminal 33 grounded to the chassis. Positioned beneath the transformer II is a rotary commutator switch 3? of the type customarily used for switching circuits in radio-receiving sets. This switch has an index mechanism which locates it in either the on or off position. However, in passing from the "off to on position, a supplementary circuit is established, as will be later described.

The above parts, comprising the unit charger, are electrically connected, as illustrated in Figure 3, in the following manner:

To a source 45 of D. C. voltage present in the customary storage battery is electrically connected the primary winding P of the step-up transformer Ii. A relay switch I4, 2i and 22 and commutator switch 31 are interposed between the source 45 and the primary winding P. The commutator terminal 33 is directly connected with one side of the primary P and the commutator terminals 43 and 44 and line termi nal 40 are directly connected with the source 45. The on terminal 33 is connected to the relay breaker terminal 22. The other relay breaker terminal 2| is directly connected with primary P. Thus, when the rotors 4| and 42 are simultaneously moved in counter-clockwise direction, the source 45 is directly connected to the primary P of the transformer through the terminals 43, 44, and 38. The line between the terminal 38 and the primary P may be of fine wire covered with asbestos to permit it to act as a fuse and burn out if the switch 31 should accidentally lodge between the indexing of off and on for too long a period. As the rotors 42 and 4| are further moved in counterclockwise rotation, the terminals 39 and 43 become connected through the rotor 4|, and the terminals 43 and 44 become disconnected from the rotor 42 and the commutator terminal 38. When the switch 31 is in fully on position, it is only necessary to close the relay switch I4, 2| and 22 in order to electrically connect the primary P to the source 45. A condenser 3| is electrically connected in parallel across the relay switch I4, 2|, and 22 to smooth its action. The secondary winding S of the transformer I has connected serially across its terminals a fixed resistance 34 and the incandescent lamp 33. The secondary transformer S is also connected to the insulated terminal 35 and the ground 35.

The system has a cyclic operation as follows:

(1) The primary P of the transformer II is energized from the source 45 when the commutator switch 3'! moves from index position off to index position on. This energization of the primary P causes the armature I! to be suddenly and swiftly drawn upwardly toward the iron core. The upward movement of armature I! gives a kick to the tab I3 of the fly-wheel I2, causing the latter to rotate in a clockwise direction against the tension in the pigtail spring I5.

(2) Upon continued rotation of the commutator switch 31 the source 45 is disconnected from the primary P and it is deenergized. The armature I1 is then urged downwardly by the tension of the spring member 24 to assume its non-energized position against the adjustable screw 29.

(3) Further rotation of the commutator switch 31 to its indexed on position connects the source 45 to the primary P through the relay switch I4, 2| and 22. When the tension in the pigtail spring 16 overcomes the momentum imparted to the fiy-wheel 52, the fiy-wheel I2 ceases clockwise rotation and moves in counter-clockwise rotation until the bridge contactor I4 engages with the contact arms 2| and 22. When this occurs the primary P of the transformer II is again energized. The armature I! is again attracted upwardly and momentum is imparted to the fly-wheel I2 in clockwise rotation. In order to establish a good electrical connection at the relay I4, 2| and 22, the bridge contactor I4 is loosely mounted on the tab I3 so that there is always even pressure between the tungsten breaker points on the bridge contactor I4 and the contact arms 2| and 22.

(4) With the commutator switch 31 in the on position, the transformer II will be intermittently energized at periods pre-selected by the adjustment of the screw 29 and by the tensioning in the pigtail spring I6. These periods are of such duration that the time of energization of the primary P is exceedingly short in comparison with the time in which it is nonenergized. Each time the primary P is energized, a stepped-up voltage is induced in the secondary winding of the transformer II, which voltage is used for such purposes as charging electric fences or the like.

The use of the bridge contactor I4 carried by the momentum device eliminates the necessity of carrying electric current through the pigtail spring I6. This increases the life of the spring and does away with the ill effects resulting from change in the tension of the spring caused by the carrying of current. In addition, the system has an increased efficiency because there will be no voltage drop through the pigtail spring.

When the device is in use as an electric fence charger, the presence of sulphur and ammonia. fumes materially increases the corrosion of the surfaces of the tungsten breaker points. Corrosion causes the formation of a very fine film of tungsten oxide, an insulating material which destroys the electrical contact between the breaker points. This film is not strongly bonded to the points and can be flaked off by the opening and closing of the points. The commutator switch, being designed to directly energize the primary P when the switch is moved from off to on position, automatically causes an opening and closing of the breaker points, thereby flaking off any tungsten oxide and preparing them for intermittent operation in the customary manner.

Although there are shown and described specific embodiments of the invention, many modifications thereof are possible. The invention is not to be restricted except in so far as it is necessitated by the prior art and by the spirit of the appended claims.

I claim:

1. In combination, a source of electric power, a transformer, an armature operated by the field of said transformer, breaker points carried in an insulated manner by said armature, a springbiased momentum wheel having a floating bridge contactor adapted to electrically connect said breaker points upon contact therewith whereby said source is electrically connected with said transformer, said armature when energized transmitting motion to said momentum wheel causing it to move said contactor out of engagement with said breaker points.

2'. In combination, a source of electrical power, a combined transformer and relay, said relay being operable to intermittently connect said source to said transformer, one element of said relay comprising a bridging contact member, and a momentum device adapted to be intermittently motivated by the action of said relay, said contact member being floatatably carried by said momentum device.

3. In combination, a source of electrical power, a combined transformer and relay, said relay being operable to intermittently connect said source to said transformer, one element of said relay comprising a bridging contact member carried by a momentum device intermittently energized by the action of said relay, and a switch having one pair of contacts for connecting and disconnecting said source and one contact of said relay and another pair of contacts for momentarily connecting said source and said transformer when said switch is operated from off" to on positions.

4. In combination, a source of electrical power, a transformer, an armature influenced by the primary of said transformer, a pair of contacts carried by said armature and insulated from each other, and a spring biased momentum wheel having a bridging contactor carried on its periphery, said bridging contact adapted to close the electrical circuit between said pair of contacts whereby the source is caused to energize the transformer and the armature is motivated to cause the momentum wheel to rotate and carry the bridging contactor out of contact with said pair of contacts.

5. In combination, a source of electric power, a transformer, an armature influenced by the primary of said transformer, a pair of contacts carried by said armature and insulated from each other, a spring biased momentum wheel having a bridging contactor adapted to electrically connect said pair of contacts, and a manually operable on and off switch having an auxiliary terminal, one of said pair of contacts being electrically connected with said primary, the other of said pair of contacts being connected through said on and off switch to said source whereby when said on and off switch is in on position said primary is connected and disconnected to said source by the connection of said pair of contacts by said bridging contactor, said auxiliary terminal being adapted to momentarily connect said source directly to said primary as said switch is moved from off to on position.

EWING D. NUNN.

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