US2445390A - Vibrator circuit with primary current division - Google Patents

Description

July 20, 1948. R. M. ELLIS 2,445,390

VIBRATOR CIRCUIT WITH PRIMARY CURRENT DIVISION Filed Jan. 4, 1944 INVENTOR.

Pmied July 2c, 1948 'VIBRATOR CIRCUIT WITH PRI MARY CURRENT DIVISION Robert M. Ellis, Indianapolis, Ind., assignor to P. R. Mallory & 00., 1110., Indianapolis, Ind., a corporation of Delaware Application January 4, 1944, Serial No. 516,985

6 Claims. (01. 175-365) This invention relates to vibrators and has for its object to provide a simple and efficient electrical system employing a vibrator for converting direct current into alternating current. This alternating current can be converted to any desired voltage by the use of an appropriate transformer, and the resultant output voltage or voltages may be utilized directly, or may be recon- I verted to direct current by suitable rectification.

Another object of the invention is to provide a new and improved system for adapting a shunt driver type vibrator to a primary current division circuit in a manner to insure positive starting of the vibrator, increased load carrying capac= ity, and longer life by reason of uniform distribution of wear on the vibrator contacts.

Another object of the invention is to provide a vibrator system of the above type having novel and improved details of construction and features of operation.

Various other objects and advantages will be apparent as the nature of the invention is more fully disclosed.

There are certain definite limits to the amount of .power which can be handled by any given vibrator mechanism such as is employed in converter systems of the type referred to above. Therefore, if the load current exceeds the carrying capacity of a 4-contact vibrator, it is customary to employ an 8-contact vibrator which may have two paralleled pairs of contacts on each side of the vibrator reed for the purpose of increasing the load carrying capacity of the unit.

Such paralleled contacts will increase the life of the vibrator in situations where the circuit is loaded to the point where contact wears occurs at a rapid rate. -Since two sets of contacts will provide twice as great a volume of tungsten or other contact metal as a single set, the life of the vibrator is theoretically doubled. However, it is impossible to adjust paralleled contacts so that each pair of contacts will make at precisely the same instant, and it is equally impossible to insure that two'paralleled contacts will break at exactly the same instant. The contacts with the closest spacing will make first and break last, and thus will assume all the load. This condition will continue until the tungsten or other contact metal has been eroded on the active contacts to a point where their spacing is greater than that of the other pair of contacts, at which instant the circuit load will be transferred to the other pair of contacts. From then on, operation will be alternately with one pair of contacts active, and then with the other pair active.

Because contact wear increases rapidly and non-linearly with increasing current density, it will be seen that if the primary load current could be divided evenly between two paralleled contacts, the life of the vibrator would be greatly increased; or conversely the vibrator could handle more power for a given life.

One method heretofore proposed for achieving the division of the current load 'between two sets of contacts is to operate each pair of contacts through a current limiting resistor, but this method is open to the objection that there is always some resistance in the main load circuit which results in lowered efllciency.

Another method proposed for achieving the desired efiect is to use consecutively closing contacts, wherein the first .pair of contacts are closed through a resistor which limits the flow oi current to a safe value for the contacts, this resistor being shorted out of the circuit by a second pair of contacts which close later in the cycle. The practical objection to this method is the dimculty of adjusting two sets of contact points for diiierent time sequences or spacings, and the further difficulty of balancing the electric circuit so that relative spacings will be maintained during the life of the vibrator as the contacts wear.

A third method proposed for dividing the primary current is to use two separate transformers, with each transformer carrying half the load,

or alternately a single transformer with two pri-- mary windings. With these arrangements the primary load is divided evenly between each pair of contacts, since the pairs of contacts connect to separate primary windings. Such an arrangement is eiiicient from electrical standpoint because no resistance is connected in the main load circuit, and also because all contacts can be adjusted to the same spacing. Furthermore, the tendency is for the contacts to wear uniformly and maintain constant relative spacing since the load current is the same for both sets of contacts.

This thirdmentioned method of primary current division in the past has been used exclusively with separate driver type vibrators. In this form of construction, the action of making and breaking the electrical circuit actuating the electromagnet is obtained by means of a separate pair of contacts which are divorced from the load circuit. In actual practice the result is a complex vibrator mechanism having five .pairs, or a total of ten contacts.

My invention provides a new and improved vibrator system in which a primary current division circuit, employing either twin transformers or a transformer having twin primaries, can be operated from a vibrator having four .pairs of contacts. My system includes a center-tapped resistor which is connected in series with the driver coil circuit where the current is relatively low, and where the power requirements are relatively small. This center-tapped resistor enables the driver coil to actuate from two sets of contacts, and distributes the driver coil load to two contacts to provide a symmetrical circuit for the driver coil load. My system results in a symmetrical circuit so that the driver coil load is equally distributed on both contacts, thus resulting in uniform contact wear.

Although the novel features which are characteristic of the invention are set forth more in detail in the claims appended hereto, the nature and scope of the invention may be better understood by referring to the following description, taken in connection with the accompanying drawing forming a part thereof, in which certain specific embodiments have been set forth for purposes of illustration.

In the drawing:

Fig. 1 is a schematic diagram of a system embodying the invention and employing a single transformer with twin primary windings; and

Fig. 2 is a similar diagram illustrating a modification of the invention employing a driver magnet with twin windings.

In the following description certain specific terms are used for convenience in referring to the various details of the invention. These terms, however, are to be given an interpretation commensurate with the state of the art.

The system shown in Fig. 1 includes a source of current H), such as a storage battery, which is connected to the mid-points of the twin primary windings II and I2 of a transformer I3 having a secondary winding IA.

The vibrator mechanism comprises a driver coil I5 which is connected by conductor Hi to the source of current I and by return'conductor II to the center-tap of a resistor I8; vibrator reed 20 which is connected to said source of current; and two sets of contacts 2|, 22 and 23, 24, re spectively, which are mounted on opposite sides of the reed 20.

Vibrator contacts 2i and 22 are connected to opposite ends of the resistor I8, and they are likewise connected by conductors 25 and'26, respectively, to the upper ends of the respective primary windings II and I2 of the transformer. The contacts 23 and 24 on the opposite side of vibrator reed 20 are connected by conductors 27 and 28, respectively, to the lower ends of the respective primary windings II and I2 of the transformer.

Assuming that the contacts 2I and 22 at the upper side of reed 20 are open, current will flow through the driver coil I over a circuit extending from one pole of battery I0, through the upper half of primary winding II, the left half of resistor I8, conductor I'I, winding of coil I5, and conductor It to the other pole of battery I0; and the driver coil I5 will also be energized over a parallel circuit extending from the one side of battery III, through the upper half of primary winding I2, the right half of resistor I8, conductor I1, winding of coil I5 and conductor I6 to the other side of battery I0.

The vibrator magnet I5, thus energized over the parallel circuits described above, will attract the reed 20 and cause same to close both of the contacts 2I and 22. 2| and 22 are closed, current will flow momentarily from one side of battery I0, through the upper halves of primary windings I I and I2, contacts 2| and 2.2 respectively, and reed 20 to the other side of battery III. The driver cell will thus be deenergized, releasing the reed 20 and causing same to close the contacts 23 and 24.

Closing of contact 23 causes current to flow momentarily, in a direction opposite to that previously described, from one side of battery II, through the lower half of primary winding II, contact 23, and reed 20 to the other side of battery I0; while closing of con-tact 24 completes a similar circuit extending from one side of battery i0, through the lower half of primary winding I2, contact 24, and reed 20 to the other side of battery III. Thus the alternate interruption and reversal of the current flow through the primary windings II and I2 induces an alternating current of increased voltage in the secondary winding ll of the transformer.

It will be observed that in the system described above the flow of current to the driver coil is shunted by closing either contact, but the driver coil energizing current will not be completely cut off until both of the contacts 2I and 22 are closed. It will be evident from the description and drawing that both vibrator contacts participate equally in the driver coil action.

Fig. 2 shows a modification of the invention employing a driver coil with twin windings ill and 3|. These windings each have one terminal connected to one of the vibrator contacts 2I and 22 by conductors 33 and 34, respectively, while the other terminals are connected to the negative side of battery I0 by conductor 35. In this embodiment the primary transformer windings II and I2 are shown on separate transformer cores, each having its own secondary 36 and 21. However, it is to be understood that twin driver coil arrangement 30, 3| may be used with a single transformer having two primary windings as shown in Fig. 1. This transformer may have one or more secondary windings as required by the circuit application.

Likewise, the system illustrated in Fig. 1, wherein a single driver coil I5 is connected to two contacts 2i and 22 by a center-tapped resistor I8 is equally adapted for use with primary windings on two separate transformers, as shown in Fig 2.

The operation of the system of Fig. 2 is the same as that previously described in connection with Fig. 1. The flow of current to the driver magnet is shunted by either contact 2I or 22, and this magnet will not be deenergized until the current to both of its windings 30 and SI is cut off by the closing of both of the contacts 2| and 22 by the vibrator reed 20.

Although certain specific embodiments of the invention have been shown for purposes of illustration, it is to be understood that the invention is capable of various modifications and adaptations which will be readily apparent to a person skilled in the art. The invention is only to be limited in accordance with the scope of the appended claims. I

What is claimed is:

1. A vibrator system comprising in combination a pair of primary transformer windings, a source of current having one of its terminals connected to the midpoints of said windings, a vibratory reed connected to the other terminal of said source, a pair of contacts on opposite sides When both of the contacts of said reed for each winding connected to the ends of the respective windings and adapted to cooperate with the reed during vibrations thereof to alternately pass current in opposite directions through the respective halves of said windings, a driver coil adapted when energized to displace the reed into a deflected position, a resistor connected between the contacts closed in said deflected position, and leads connecting the ends of said coil between said reed and the midpoint of said resistor whereby the driver coil will be alternately energized in the open contact position and disabled in the said deflected position by the bypassing eiiect of said contacts and will maintain the reed in continuous vibration.

2. In a vibrator system, the combination of a vibratory reed, a pair of primary transformer windings each having two half sections, twin pairs of stationary contacts electrically connected to the ends of said windings wherein said reed cooperates with said pairs of contacts to alternately pass current in opposite directions through respective sections of said windings during vibrations of the reed, a driver coil, and dual resistive path, each including a resistor and a section of one of said primary windings, through which said coil is normally energized to deflect the reed into contact-closing position, the closure of one of said contacts as the reed moves to deflected position being effective to shunt the resistor and the driver coil out of the first of said paths, the closure of another of said contacts as the reed moves to deflected position being efiective to shunt the resistor and the driver coil out of the other of said paths.

3. A vibrator system comprising in combination a pair of primary transformer windings, a source of current having one'of its terminals connected to the midpoints of said windings, a vibratory reed connected to the other terminal of said source, a pair of contacts on opposite sides of said reed for each winding and connected to the ends of the respective winding adapted to cooperate with the reed during vibrations thereof to alternately pass current in opposite directions through the respective halves of said windings, and a pair of driver coils having one of their ends connected to said reed and having their other ends respectively connected to the two contacts crates with said pairs of contacts to alternately pass current in opposite directions through respective halves of the said two primary transformer windings. a pair of driver coils each being serially connected with one-half of one of the respective primary windings and energized to deflect the reed into one of its contact-closing positions, and connections between said coils and the contacts on one side of the reed to shunt and to disable the coils in the said position of the reed thereby maintaining the reed in continuous vibration. I

5. A vibrator system comprising, in combination, a pair of transformer primary windings, a source of current having one of its terminals connected to the midpoints of said windings, a

vibratory reed connected to the other terminal of said source, a driver coil for said reed, a pair of contacts for each winding, said contacts being connected to the respective ends of the associated winding and being adapted to cooperate with the reed during vibration thereof to alternately pass current in opposite directions through the respective sections of said windings, each pair of contacts including one contact on the driver coil side of the reed and a second contact on the other side of the reed, a lead connecting one end of the driver coil to the reed, the other end of said driver coil being connected through individual resistive paths to the respective driver coil side contacts whereby, when one of said driver side contacts is open, current passes through the associated section of said primary winding and one of said resistive paths to the driver coil, the driver coil and the resistive path being shunted from the circuit when said one driver side contact is closed with the result that the coil is energized when either of said driver side contacts is opened and deenergized whenever both of said driver side contacts are closed.

6. A vibrator system comprising, in combination, a pair of centertapped primary windings, a source of current having one terminal thereof connected to both of said center taps, a vibratory reed connected .to the other terminal of said source, a driver coil for said reed, a pair of contacts connected, respectively, to the terminals of the first primary winding, a pair of contacts connected, respectively, to the terminals of the second primary winding, each pair including a contact on the driver coil side of the reed and a contact on the other side of the reed, and a dual branch circuit for energizing said driver coil, one branch of said circuit being connected between the first driver coilside contact and the reed, another branch of said circuit being connected between the second driver coil side contact and the reed, each branch circuit being disabled when the contact associated therewith is engaged by the reed, whereby current flows through the driver coil wheneither of said driver coil side contacts is not engaged by the reed and no current flows through the driver coil when both of said driver coil side contacts are engaged by the reed.

ROBERT M. ELLIS.

nnrmnncns orran The following references are of record in the flle of this patent:

UNITED STATES PATENTS Brown Aug. 24, 19 13

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