US3264499A

US3264499A - Relay flip-flop

Info

Publication number: US3264499A
Application number: US311173A
Authority: US
Inventors: Joseph R Moser; Hubert R Schatteiner
Original assignee: Allen Bradley Co LLC
Current assignee: Allen Bradley Co LLC
Priority date: 1963-09-24
Filing date: 1963-09-24
Publication date: 1966-08-02
Anticipated expiration: 1983-08-02

Description

Aug. 2, 1966 R. MOSER ETAL RELAY FLI P -FLOP Filed Sept.

2 Sheets-Sheet 1 Manama .35

INVENTORS JOSEPH R. MOSER HUBERT R. SCHATTEINER BY WA; 6%

AT TOR N EY g- 2, 1965 J. R. MOSER ET AL 3,264,499

RELAY FLI P FLOP Filed Sept 24 1965 2 Sheets-$heet 2 [2% 2 INVENTORS JOSEPH R. MOSER HUBERT R. SCHATTEINER BYVZQW ATTORNEY United States Patent 3,264,499 RELAY FLllP-FLGP Joseph R. Moser, Brookfield, and Hubert R. Schatteiner, Milwaukee, Wis, assignors to Allen-BradieyCompany, Milwaukee, Wis., a corporation of Wisconsin Filed Sept. 24, 1963, Ser. No. 311,173 8 Claims. (Cl. 361-132) The present invention relates to a relay flip-flop comprised of a bistable relay that has a single pole double throw type of contact arrangement controlled by a pair of operating coils, each of said coils being connected between said contacts and an energy storing capacitor, so that each of said coils, when energized, will activate said contacts to interrupt its own energizing circuit and complete a circuit for energizing the other operating coil. The present invention also resides in a signal dividing network utilizing said flip-flop.

The present invention belongs in a class of devices which might be called electrically powered, relay operated flip-flops. The term flip-flop, taken in its broadest sense, could include any bistable device, although it is most commonly used in connection with electrical devices. Flipfiops are probably most frequently used in electronic equipment of various sorts, and for such uses the flip-flops may be made up of electronic, semi-conductor or magnetic core components. The present invention is intended primarily for use with numerical control systems that are equipped, in the main, with mechanical contact control components. In order to achieve optimum operation of such systems, it is desirable to avoid using, for example, an electronic flip-flop, and to employ instead a relay operated flip-flop which, in operating characteristics, will complement the rest of the control components. In addition, relay flip-flops have other advantages, such as current handling capabilities, and asynchronous operation that are usually not found in electronic and other types of flip-flops.

Generally, relay operated flip-flops are slow operating devices, and frequently they require two or more relays for practical operation. The present invention, on the other hand, provides high speed operation, and requires only one relay. Moreover, since the flip-flop of the present invention employs a capacitor and a relay coil in series, it also functions as a tuned circuit, and hence, by changing the values of the components, the operating characteristics of the flip-flop may be varied over a wide range, to provide a highly versatile flip-flop.

Accordingly, it is a primary object of the present invention to provide a high speed relay operated flip-flop.

It is another object of the present invention to provide a relay operated flip-flop requiring only one relay.

It is another object of the present invention to provide a highly versatile relay operated flip-flop.

It is another object of the present invention to provide a relay operated fiip-flop which can be made to operate over a broad range of operating characteristics.

'It is another object of the present invention to provide a highly reliable and stable relay operated flip-flop.

The foregoing and other objects and advantages will appear from the description to follow. In the description, reference is made to the accompanying drawings which form a part hereof and in which there is shown by way of illustration two specific embodiments in which this invention may be practiced. These embodiments will be described in sufiicient detail to enable those skilled in the art to practice this invention, but it is to be understood that other embodiments of the invention may be used and that structural changes may be made in the embodiments described without departing from the scope of the invention. Consequently, the following detailed description is not to be taken in a limiting sense; instead, the scope of the present invention is best defined by the appended claims.

in the drawings:

FIG. 1 is a schematic diagram of an embodiment of the present invention utilized as a signal dividing network,

FIG. 2 is a second embodiment of the flip-flop of the present invention.

FIG. 1 of the drawings, aside from illustrating a specific embodiment of a flip-flop of the present invention, also illustrates a novel modification of the flip-flop in a signal dividing network. The flip-flop thus employed is utilized to direct information from a decoder into successive rows of a cross point switch. Each unit of information fed sequentially from the decoder is to be stored in one row of the cross point switch (not shown), and the flip-flop is connected to separate the sequential units of information so that they may be fed in parallel into the appropriate row of the cross point switch (not shown).

Referring now specifically to the drawing, in the center of FIG. 1 there is a bistable relay 1, which in the embodiments shown is of the mercury wetted contact variety having type C, or break-before-make contacts. The bistable relay 1 has a pair of

operating coils

2 and 3, each with a polarity dot 4 adjacent one end. For the sake of convenience of expression, the

operating coils

2 and 3 shall be referred to as polarized

operating coils

2 and 3 since a signal entering either of the polarized

operating coils

2 and 3 from the end adjacent the polarity dot 4 will have the effect of actuating the relay contacts in a predetermined manner, and current entering from the ends of either of the coils opposite to the end adjacent the polarity dot would have the opposite effect. The bistable relay 1 has a set of single pole double throw type contacts consisting of a pair of stationary contacts 5 and 6 and a common contact 7 capable of alternately engaging either of the two stationary contacts 5 or 6. The relay 1 is rendered bistable by a pair of latching magnets 8 and 9, which serve to hold the common contact 7 against the respective adjacent stationary contact 5 or 6. Connecting each of the fixed contacts 5 and 6 with the common contact 7 is an arc suppressing network consisting of an arc suppressing capacitor 10 in series with a current limiting resistor 11. The arc suppressing network is a requirement peculiar to the mercury wetted contact type of relay used in this embodiment and not necessarily a part of the invention.

In the drawing, the uppermost operating coil 2 has its end adjacent the polarity dot 4, hereinafter referred to as the polarity dot end, connected through a blocking diode 12 to the lowermost stationary contact 6. The other end of the uppermost operating coil 2, which is remote from the polarity dot is connected through a reset switch 13 and a current limiting resistor 14 to a positive potential conductor 15 which is-adapted for connection to the positive pole of a 24 volt unidirectional source (not shown). The same end of the upper operating coil 2, that is, the end remote from the polarity dot 4-, is also connected through a second blocking diode 16 to a stationary contact 17 of a single side stable relay 18, which will be referred to as the input relay 18. Also connected to the stationary contact 17 through a blocking diode 19 is the polarity dot end of the lower operating coil 3, the anodes of the blocking diodes l6 and 19 meeting at a common point. The other end of the lower operating coil 3, remote from the polarity dot 4, is connected through a blocking diode 20 to the upper stationary contact 5 of the bistable relay 1. The common contact 7 of the bistable relay 1 is connected to a ground conductor 21.

The contacts of the input relay 18, which serve as a current gate between the alternative charge and discharge paths for the capacitor 24, are of the single pole double throw, mercury wetted type, including a common contact 22 which is connected to what will be termed a charge side 23 of an energy storing capacitor 24. The other side of the energy storing capacitor 24, which will be termed the fixed potential side 25., is connected to the positive potential conductor 15. The contacts of the input relay 18 are completed by an upper stationary contact 26 which is connected through a discharge conductor 27 and a contact protecting resistor 28 to the positive potential conductor 15, to form a discharge path for the energy storing capacitor 24. The contact set of the input relay 18 is provided with a single stable condition by means of a latching magnet 29, and it is activated by a single coil 30. One end of the coil 30 is connected to the ground conductor 21 and the other is connected through a loading resistor 31 to the output 32 of a decoder 33. The potential level of the output signal from the decoder 33 is established by a power supply (not shown) connected to the decoder through a supply conductor 34. The output 32 of the decoder is also connected to a common contact 35 of an output relay 36.

The output relay 36 is also a single side stable relay of the mercury wetted contact variety and it is activated by a single coil 37. One end of the output relay coil 37 is connected to the positive potential conductor 15, and the other end of the coil 37 is connected through a resistor 38 to the lower stationary contact 6 of the bistable relay 1. The output relay also has a pair of

fixed contacts

39 and 40 and is made stable in one position by means of a latching magnet 41. The

fixed contacts

39 and 40 are connected respectively to a pair of output terminals 42 and 43. It is important to note at this point that although only one output relay 36 is illustrated, it is intended that another output relay (not shown) also be connected to the upper stationary contact 5, but to preserve clarity in the drawings, the second output relay was omitted, the teaching with respect to the output relay 36 being sumcient to show one skilled in the art how to add another output relay (not shown) to the upper stationary contact 5.

Turning now to the second embodiment of the present invention as shown in FIG. 2, once again the primary component is a bistable relay 44 having a pair of

operating coils

45 and 46 which, like the

corresponding coils

2 and 3 in FIG. 1, will be termed polarized operating coils 4-5 and 46 because they are arranged so that an input signal entering either of the coils from an end adjacent a polarity dot 47 will energize the

coil

45 or 46 to activate the relays 44 contacts in a predetermined manner. The bistable relay 44 also has a single throw double pole contact arrangement containing a pair of

stationary contacts

48 and 49 and a common contact 50 which is adapted to engage alternately either of the

stationary contacts

48 or 49. The relay 44 is rendered bistable by means of two

latching magnets

51 and 52. Although arc suppressing circuits like those in the first embodiment about the

contacts

48, 49 and 50 of the bistable relay 44 are not shown, the omission is made for the sake of simplicity in the diagram, as the relay used in the second embodiment is of the same, mercury wetted, break-before-make contact relay described in connection with the embodiment shown in FIG. 1.

The uppermost operating coil 45 of the bistable relay 44- has its polarity dot end connected through a blocking diode 53 to an output terminal 54,, and to the upper stationary contact 48. The opposite end of the uppermost operating coil 45, the end remote from the polarity dot 47, is connected, first, to a charge side 55 of an energy storing capacitor 56, and, second, through a charge path blocking diode 57 to a ground terminal 70. The energy storing capacitor 56 has a side opposite the charge side 55 which is termed here the grounded side 59 since it is connected to the common ground conductor 58. A second energy storing capacitor 60 is also shown with its grounded side 61 connected to the ground conductor 58 and its charge side 62 connected to the polarity dot end of the lowermost operating coil 56. The other end of the lowermost operating coil 46 is connected both through a blocking diode 63 to an output terminal 64 and to the lower stationary contact 49.

The common contact 50 of the bistable relay 44 is adapted for connection to a pulse input signal source which may be a decoder output as in the previous embodiment. A capacitor discharge path is provided in this embodiment, from the ground conductor 58 through a blocking diode 65 and a loading resistor 66 to the common contact 50 of the bistable relay 44. In the common ground conductor 58, between the grounded sides 59 and 61 of the

energy storing capacitors

56 and 60 respectively and the ground terminal a discharge path blocking diode 67 is provided to prevent the

energy storing capacitors

56 and 60 from discharging through ground. A reset circuit is provided for the second embodiment in a reset switch 68, which is adapted to be connected on one side to a source of negative potential (not shown) and is connected on the other side through a current limiting resistor 69 to the polarity dot end of the operating coil 45 which appears as the upper operating coil 45 in the drawing.

Turning now to the operation of the embodiments of the present invention described above, in the first embodiment shown in FIG. 1, the flip-flop operates during the charging of the energy storing capacitor 24. Beginning in the position shown, a signal from the decoder 33 passes throuh the coil 30, connecting the charge side 23 of the energy storage capacitor 24 to the discharge conductor 27, and the energy storing capacitor 24 discharges through the resistor 28 to the positive potential conductor 15. Since the common contact 35 in the output relay 36 is against the upper stationary contact 39, the first input signal Will appear at the upper output terminal 42. On the trailing edge of the first input signal from the decoder 33, the input relay 18 is deenergized, forcing the common terminal 22 to close with the lower stationary contact 17, completing a charge circuit for the energy storing capacitor 24 through one of the bistable relay coils 2 or 3. Since the common contact 7 of the bistable relay is at the upper stationary contact 5, capacitor charging current will pass from the charge side 23 of the energy storing capacitor 24 through the common contact 22 of the input relay to the stationary contact 17, and from there through the blocking diode 19, the lower operating coil 3, the blocking diode 28, the upper stationary contact 5, the contact 7, to the ground conductor 21. This current, entering the operating coil 3 from its polarity dot end will have the effect of activating the common terminal 7 to move away from the stationary terminal 5 and into contact with the lower stationary terminal 6, breaking the energizing circuit for the operating coil 3 and completing a circuit for energizing the upper operating coil 2.

At this point there is no signal being emitted from the output 32 of the decoder 33, so there is no output. However, as soon as the common contact 7 of the bistable relay contacts the lower stationary contact 6, current will flow from the positive potential conductor 15 through the coil 37 of the output relay 36, the resistor 38, and the bistable relay 1 contacts 6 and 7 to ground 21. This current energizes the output relay 36, moving the common contact 35 into contact with the lower stationary contact 40. Hence, the next output from the network wil1 appear at the lower terminal 43.

The next pulse from the decoder 33 again energizes the coil 30 of the input relay 18 to close the common terminal 22 with the upper stationary contact 26 so that the energy storing capacitor 24 may discharge through the discharge path consisting of the resistor 28 and the discharge conductor 27. This signal from the decoder 33 will appear at the lower output terminal 43. The trailing edge of this signal from the decoder 33 will deenergize the input relay 18, once again closing the common a) terminal 22 with the lower stationary contact 17 so that the energy storing capacitor 24 can recharge through the bistable relay 1. Charging current will flow from the charge side 23 of the capacitor 24- through the common contact 22 and the stationary contact 17 of the input relay 18, the blocking diode 16, the operating coil 2, the blocking diode 12, the stationary contact 6 and the common contact 7 of the bistable relay to ground 21. Since this current entered the operating coil 2 from its end remote from the polarity dot 4, the magnetic field generated by the current in the operating coil 2 will have the efiect of activating the common contact 7 to move upward into contact with the stationary contact 5, breaking the energizing circuit for the upper operating coil 2. The opening of the common contact 7 with the lower stationary contact 6 also interrupts the energizing circuit of the output relay 36. When the output relay 36 deenergizes, its common contact 35 is moved back into contact with the upper stationary contact 39 as is shown in the drawing.

The embodiment shown in FIG. 1 has now passed through its complete cycle and is returned to its original condition as shown in the drawing. The third signal will, thus, like the first signal from the decoder 33 appear at the output terminal 42. The third output pulse from the decoder 33 would have the same efiect as did the first output pulse described above so that the fourth output pulse would be directed once again to the lower output erminal 43, and so on, the odd numbered pulses appearing from the output terminal 42 and the even numbered pulses appearing on the output terminal 43.

Turning now to the second embodiment shown in FIG. 2, the first input signal pulse will be fed into the flip-flop through the common contact 56 of the bistable relay 44 and through the stationary contact 49, the blocking diode 63 to the output terminal 64, and also through the lower operating coil 46 to the charge side 62 of the energy storing capacitor 60. Since this current enters the operating coil 46 from its end remote from thepolarity dot 47, no change occurs in the flip-flop, and the energy storing capacitor 60 is permitted to charge, the charge current passing from the grounded side 61 of the capacitor 60 to the common ground conductor 58, through the diode 67 to the ground terminal '70. However, on the trailing edge of the first input pulse, the energy storing capacitor 60 will begin discharging back through the operating coil 46, the stationary contact 49, the common contact 50, the blocking diode 65 and the loading resistor 66 to the common ground conductor 58.

This discharge current from the energy storing capacitor 60, entering the coil 46 from its polarity dot end, will have the effect of activating the common contact 50 upward into contact with the upper stationary contact 48, breaking the discharge circuit for the energy storing capacitor 60, but not before the capacitor 60 has been substantially discharged. The second input pulse will now pass through the common contact 50 and the upper stationary contact 48, through the blocking diode 53 to the output terminal 54 and through the upper operating coil 45 to the charge side 55 of the energy storing capacitor 56. The charging current for the energy storing capacitor 56 enters the upper operating coil 45 from its polarity dot end so that it tends to draw the common terminal 50 upward into tighter contact with the upper stationary contact 48.

Once again, on the trailing edge of the second input pulse, the energy storing capacitor 56 will begin discharging through the upper operating coil 45, the upper stationary contact 48, the common contact 50, the diode 65, and the loading resistor 66 back through the common ground conductor 58 to the grounded side 59 of the capacitor 56. Since this discharge current enters the operating coil 45 from its end remote from the polarity dot, it energizes the coil to drive the common contact 50 downward to close with the lower stationary contact 49,

breaking the discharge path for the energy storing capacitor 56 and completing the charging path for the energy storing capacitor 66 which is associated with the lower operating coil 46. The flip-flop is now returned to its original condition so that the third input pulse would begin the cycle again, and appear at the output terminal 64. In summary then, the output for the odd numbered input pulses will appear at the output terminal 64 and the output signal for the even numbered input pulses will appear at the output terminal 54.

In many applications of flip-flops, it is desirable to reset the flip-flop at a predetermined position after each use, so that in a subsequent use of the flip-flop it will always begin at the same place. For that reason, reset circuits have been provided in both the first and second embodiments. In the first embodiment shown in FIG. 1, the flip-flop may be reset by closing the reset switch 13 so that current will pass from the positive potential conductor 15 through the resistor 14, the reset switch 13, the upper operating coil 2, the lower stationary contact 6, the common contact 7, to ground 21. This reset current, entering from the end of the operating coil remote from the polarity dot 4 will have the effect of energizing the operating coil 2 to move the common terminal 7 upward to close the circuit with the upper stationary contact 5 and open the circuit through the lower stationary contact 6. In other words, the eitect of the reset current is to return the flip-flop to the condition shown in the drawing. If the flip-flop is already in that condition, closing the reset switch will have no effect upon it. In the second embodiment, reset is accomplished by closing the reset switch 68, but the reset switch 68 is connected to a source of negative potential (not shown) so that the reset signal will pass from the ground terminal 70 through the diode 5'7, the upper operating coil 45, the resistor 6% and the reset switch 68 to the source of negative potential (not shown). The reset signal entering the upper operating coil from its end remote from the polarity dot 47 will have the efiect of returning the common contact to the lower stationary contact 49, as shown in the drawing. Once again, if the relay is already in that predetermined position, closing the reset switch will have no effect on its condition.

The embodiment shown in FIG. 1 provides an isolated output by activating the output relay 36. However, the embodiment shown in FIG. 2 illustrates how an output may be taken directly from the contacts of the flip-flop relay 4'4 and demonstrates that in many applications no auxiliary apparatus is required to produce a directly usable output signal. Similarly, an output signal might be taken directly from the stationary contacts 8 and 9 of the first embodiment. Also, the specific type of relay described as used in the preferred embodiments shown is not a limitation of the invention. Other types of relays may be used; type D, or make-before-break contacts may also be used although the results in some applications may not be as good. While a single

bistable relay

1 or 44 with a pair of operating coils is shown, it would be possible to use two separate relays, each with one coil, although the careful synchronization required limits the commercial feasibility of such an arrangement. Both embodiments described operate on the trailing edge of the input signal since such operation is generally preferable. However, both embodiments will also operate on the leading edge of the input signal, after obvious modifications, although in the second embodiment, the first input would produce a double output pulse which might limit its practical use.

The flip-flop of the present invention thus provides the advantages of a relay flip-flop along with high speed operation. In addition, the flip-flop of the present invention is not a sensitive device, but, rather, is a stable, highly reliable component. Hence, its operating characteristics are broadly variable giving the flip-flop of the present invention great versatility.

We claim:

1. In a relay flip-flop, the combination comprising:

a bistable relay having a pair of operating coils, and

contacts with two stationary contacts and a grounded common contact, one of said stationary contacts being connected to an end of one of said pair of operating coils, and the other of said stationary contacts being connected to an end of the other of said pair of operating coils;

an energy storing capacitor having one side connected to a potential source, and a charge side connected to ends of said pair of operating coils remote from said fixed terminals;

a capacitor discharge path connected between said potential source and said charge side of said capacitor;

and a current gate adapted to alternately connect said charge side of said capacitor to said operating coils and said discharge path.

2. In a relay flip-flop, the combination comprising:

a bistable relay having contacts with a pair of stationary contacts and a common contact connected to a pulse input signal source and through a load to ground, and a pair of operating coils, each of said coils having a polarity dot end for receiving an input signal to activate said common contact to close with a predetermined stationary contact;

a pair of capacitors, each having a grounded side and a charge side;

said operating coils each being connected between one of the stationary contacts of said relay and the charge side of one of said capacitors;

and one of said operating coils having its polarity dot end connected to said capacitor, and the other of said operating coils having its polarity dot end connected to said stationary contact.

3. In a relay flip-flop, the combination comprising:

a bistable relay having contacts and a pair of oppositely oriented polarized operating coils;

said contacts including a common contact connected both to asource of input signals and through a load to ground, and a pair of stationary contacts, one of said stationary contacts being connected to an end of one of said pair of operating coils and the other of said stationary contacts being connected to the other of said pair of operating coils;

and each of said pair of operating coils having its end remote from said stationary contact connected through a capacitor to ground.

4. In a relay flip-flop, the combination comprising:

a bistable relay having a pair of operating coils connected to a common point through blocking diodes, and contacts including a pair of stationary contacts and a grounded common contact;

ends of said operating coils opposite said diodes, each being connected to one of said stationary contacts;

a capacitor having a fixed potential side adapted to be connected to a potential source and a charge side;

a capacitor discharge path adapted to be connected at one end to said potential source;

a current gate connected to said charge side of said capacitor, another end of said capacitor discharge path, and said common point between said blocking diodes connected to said operating coils, and adapted to alternately electrically connect said charge side of said capacitor to said discharge path and said operating coils;

and a reset switch connected on one side between one of side blocking diodes and the immediately adjacent operating coil and having its other side adapted for connection to said potential source. 5. A signal divider network comprising the combination of:

3 contacts including a common contact connected to said capacitor, a stationary contact connected to said discharge path and a second stationary contact connected to said common point;

and an output relay having a winding with one end connected to a stationary contact of said bistable relay of said flip-flop and another end adapted to be connected to said potential source in said flip-flop, and output contacts connected to provide a divided output signal.

6. In a relay flip-flop, the combination comprising:

a bistable relay including a pair of polarized coils each having a polarity dot end, a pair of stationary contacts and a common contact adapted for connection to a source of pulse input signal;

a pair of capacitors, each having a grounded side and a charge side;

a capacitor discharge path including a load and being connected between said common contact and said grounded sides of said capacitors;

each of said operating coils being connected between one of said stationary contacts and said charge side of one of said capacitors, the polarity dot end of one of said operating coils being connected to its said stationary contact, and the polarity dot end of the other of said operating coils being connected to its said capacitor;

output terminals connected through diodes to said fixed contacts;

and a reset circuit including in series a reset switch,

either one of said operating coils, and a blocking diode, connected at one end to ground and adapted for connection at an opposite end to a reset potential source.

7. In a relay flip-flop, the combination comprising:

a bistable relay having a pair of operating coils and a single pole double throw type of contact arrangement, said contacts being adapted for connection to a pulse signal relay energizing source and being con nected to each of said operating coils so that the energization of each of said coils through said contacts activates said contacts to deenergize said coil;

an energy storing capacitor having a charge side connected to said relay contacts through said operating coils to be charged by pulse signals from said relay energizing source,

and a capacitor discharge path connected to said charge side of said capacitor to discharge said capacitor between pulse signals from said relay energizing source.

8. In a relay flip-flop, the combination comprising:

a bistable relay having a pair of operating coils and a single pole double throw type of contact arrangement, said contacts being connected between a common ground and an end of each of said operating coils so that the energization of each of said operating coils activates said contacts to deenergize said operating coil;

an energy storing capacitor having a charge side adapted for connection through each of said operating coils to said contacts to charge said capacitor;

and a capacitor discharge path adapted for connection to said charge side of said capacitor to permit discharge of said capacitor.

References Cited by the Examiner UNITED STATES PATENTS 2,914,710 11/1959 Bell 3l7-l40 3,174,080 3/1965 ScOtt 3l7155.5 3,189,794 6/1965 Currie 317-l40 3,206,653 9/1965 MacArthur 3l7-l55.5

ORIS L. RADER, Primary Examiner.

W. SHOOP, Examiner.

Claims

4. IN A RELAY FLIP-FLOP, THE COMBINATION COMPRISING: A BISTABLE RELAY HAVING A PAIR OF OPERATING COILS CONNECTED TO A COMMON POINT THROUGH BLOCKING DIODES, AND CONTACTS INCLUDING A PAIR OF STATIONARY CONTACTS AND A GROUNDED COMMON CONTACT; ENDS OF SAID OPERATING COILS OPPOSITE SAID DIODES, EACH BEING CONNECTED TO ONE OF SAID STATIONARY CONTACTS; A CAPACITOR HAVING A FIXED POTENTIAL SIDE ADAPTED TO BE CONNECTED TO A POTENTIAL SOURCE AND A CHARGE SIDE; A CAPACITOR DISCHARGE PATH ADAPTED TO BE CONNECTED AT ONE END TO SAID POTENTIAL SOURCE. A CURRENT GATE CONNECTED TO SAID CHARGE SIDE OF SAID CAPACITOR, ANOTHER END OF SAID CAPACITOR DISCHARGE PATH, AND SAID COMMON POINT BETWEEN SAID BLOCKING DIODES CONNECTED TO SAID OPERATING COILS, AND ADAPTED TO ALTERNATELY ELECTRICALLY CONNECT SAID CHARGE SIDE OF SAID CAPACITOR TO SAID DISCHARGE PATH AND SAID OPERATING COILS;