US1976384A - Multivibrator control - Google Patents

Description

Ce 9,' V VT BRAMAN 1,976,384

' MULTIVIBRATOR CONTROL Filed .April 26. 1929 INVENTOR V vem 'r. mmm

ATTORNE'Y FFECE Niwii- TATES- MULTIVIBRATR CONTROL Verne T. Braman, Long Island City, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application Aprill26,, 1929, Serial No. 358,287 2 claims. (oi. 250-436) The' present invention relates to synchronizing be made therein in so far as such modifications systems, and is particularly directed to a synfall Within the spiritand scope of theipresent chronizing arrangement suitable for use in condisclosure as defined by the hereinafter appendedir nection with facsim'le and television systems,` claims. I

5l although it is to be recognizedthat theuse there- Now referring more particularly to the draw- 60 of is not restricted to such systems but that the ing, I have llustrated a tuning fork 1 as being invention'm'ay be used for the purpose of synkof a substantially constant frequency and conchronizing two or more moving or vlbrating bodies trolled as to its frequency by means of a thermolocated at either adjacent or separated points. stat control,` or other suitable control (not Further, the invention relates to a method and shown), whereby the variations in temperature 65 `o means bywhich it is possible to apply a series of tending to change the frequency of the fork` arerelatively low frequency synchronizing pulses for avoided, or the fork may be compensated as to the purpose of synchronizing moving or vibratchanges in its frequency by, .for example, forming v ing bodies located at different points. a portion of the fork of two distinct metals which Therefore, as an object of my present invenhave different coeficients of expansion so that 70 tion, I have sought to provide a method and thefork itself as it expandsor contracts due to means by which moving or vibrating bodies lo-" temperature changes may be made to change theA cated at different points may be synchronized, :frequency of the impressed impulses for driving or by which synchronizing impulscs of a constant the same in any preferred and desired manner.

Vfrequency may be applied for synchronizing mov- As a driving means for' the tuning fork 1, I -75 ing or vibrating bodies, such as synchronous mohave shown an electromagnetic driving system 3, tors, driving impulse Wheels or La Cour wheels, which is driven by means of a vacuum tubeosor driving tuning forks of low vibrational fre- Gilla'bor upOh Which the fork freClU-BHCY impulse-S' quencies, or applied to any other well known and are initially impressed through an electromagsuited Seg o netic pickup 7 associated with the fork 1. VIm- 80 As a further' objectof my invention, I have pulses picked up by the pickup coil 'Z are .transsought to provide a method and means by which ferred throughv the Primary Winding 11 Of the sub-harmonic frequencies may be produced from transformer 9 to the secondary winding 13 thereconstant frequencies. of, where they are impressed upon the grid mem- As a further object of my invention, I have ber 17 of the oscillator 5, and across the circuit 85' sought to provide a multi-vibrator which may be including vthe grid member 17, the biasing battery used as a means for splitting frequencies, and 21 therefor, and the filament member 19. AS thus producing 'fractional parts of the impressed shown, a source of potential 23 serves to provide frequencies, or, what has become known in the heating Current for the filament member, and

'art as the sub-harmonics of a basic impressed the biasing battery 21 with its negative terminal 90 frequency, connected towards the grid member 17 provides a Still other objects of my invention are to proproper b'asng POtenal for the grid. Theoutduce,v in' a method to be hereinafter set forth, an put Circuit Of the OSGllatOr 5 includes the plate arrangement suitable for applying synchronizing member 15 and the drive coil 3, a source of plate 40 pulses to bodies which are to be synchronized, potential B+, WhiChintUrhS COImeGiBl thrugh 95 which is simple in its construction and arrangethe negative Source Of plate ptenfial B- tO the ment of parts, a system Which is cheap and confilament member 19. If desired, a meter for. venient to install; a system which is eicient in measuring the plate output current necessary 150 its use, and a system which can be readily set drive the fOrk may be nserted in the plate Cirup and conveniently operated. cuit of the tube, as shown.

still other and further objects of my invention It is thus seen that when once the fork 1 has will at once suggest themselves and become apbeen set into vibration impulses produced thereby parent to those skilled in the art to which the are transferred to the grid circuit of the oscillator invention relates by a reading of' the ,following 5,.and by amplification are then transferred to specification taken in connection with the acthe drive means 3 for the purpose of keeping the. companying drawing, wherein, the single figure fork in vibration, and the generated impulses from thereof shows a preferred form which my mventhe fork are in turn again picked up by the picktion may assume, although itis to be understood up coil '7 so as to continuously provide a drive that the invention is not limited to the' construcmeans for the fork. For the purpose of keeping 55 tion illustrated, since various modifications may high frequency currents from the source of plate l teries 69 and 71.

element 73 which is connected .potential balance of the 'of each of the tubes 53 and potential B+, I have provided a choke coil 27, and shunting the source of plate potential B+ and B I have provided a by-pass condenser 25 for the purpose of passing the higher frequency currents from the output circuit of the oscillator 5 back to the grid or input circuit.

Connected with the output circuit of tube 5 through a capacity coupling 29, I have provided a further amplifying tube 31 whose grid member 33 is connected with one side of the capacity coupling 29. The usual type of grid leak 41 connecting the grid 33, through a suitable source of biasing potential for the grid, and the filament member 37 at the tube 31 has been provided for permitting electrons to leak off the grid and thus prevent blocking of the tube 31; Output energy from the tube 31 flowing from the plate member 35, which is provided with asource of plate potential from a source B+ connected through the choke coil 43 to keep high'frequency potentials from the source of plate potential, is then passed through a capacity coupling 45 and a resistance 47 to a multi-vibrator unit, including apair of vacuum tube oscillators 53 and 55. In this connection, I have provided the resstor element 47, which may be variable where desired, for the purpose of adjusting the amplitude of the impulses supplied from the amplifier 31 to the vibrator unit.

The impulses transferred to the multi-vibrator unit including oscillators 53 and 55 are superimposed upon the output of these tubes through resistances 49 and 51 respectively, and energy flowing from the plate members 57 and 59 of the tubes 53 and 55 will then be subjected to a series of superimposed impulses from the tuning fork 1. Each of the vacuum tubes 53 and 55, respectively, are provided with the usual grid members 61 and 63 and filament members 65 and 67, which are heated, respectively, by the usual heating bat- For the purpose of connecting the tubes 53 and 55 of the multi-vibrator system together, so that one tube reacts upon the other, I have connected in the plate circuit, including the plate member 57, of the tube 53, a capacity with'V the grid member 63 of the tube 55, and, similarly, to connect the plate 59 of the tube 55 with the grid member 61 of the tube 53, I have provided a Similar capacity element 75.

It will thus be seen when frequencies proportional to the frequency of the tuning fork 1 are impressed upon the multi-vibrator system, including the oscillators 53 and 55, that these ir'- pressed frequencies from the fork change the vibrator system by changing the potential on both the plate and grid members of each of the tubes 53 and 55, and thus, as will be seen from a consideration of the' drawing, since the vibrator system including the tubes 53 and 55 is in a most unstable condition, the superimposed impulses originating from the fork 1 will tend to stabilize the vibrator system and cause it to vibrate at its own natural period. The natural period of the vibrator system is a function of and is determined by the valves, of the resstor members 49 and 51, the capacity elements 73 and 75, and the resistors 77 and 83 respectively, connected through a second set of variable resistors 79 and 81 in the input circuit 55 respectively by a;V connection with the filament members 65 and 67 thereof, as well as the tubes 53 and 55 which may be provided.

Suppose, for example, and for the purpose of as-i suming valves by which a concrete illustration of operation may be given, that the vibrator system, including the oscillators 53 and 55, should have a natural period of vibration of 100 cycles per second, then, due to the inherent unstable character of the vibrator, it will be readily seen that this frequency might change and vary between a pair of limiting values of say, for example, 95 to 105 cycles per second. Now, if we assume for the purpose of further illustration that the fork 1 has a natural period of vibration of 400 cycles per secondl, then, if the frequency corresponding to the fork frequency is impressed upon the multi-vibrator system from the amplifier 31 through the capacity couplin'g and the resstor 47, to control the energy supplied-to the vibrator from the fork, it: will be seen that this impressed energy of the fork 1 tends to stabilize the vibrator system and cause it to vibrate continuously at its natural period. The natural period of vibration of the vibrator system may correspond to either the fork frequency, a harmonic thereof, ora subh'armonic thereof. In'the present case illustrated, it will be recognized, with the natural frequency of the vibrator system including. tubes 53'and 55 assumed to be 100 cycles, and the fork frequency assumed to be 400 cycles; that the vibrator system will maintain a steady vibration at 100 cycles per second during periods when the fork frequency is superimposed there'on. This frequency, according to the example illustrated; is the fourth sub-harmonic or the quarter harmonic, of the natural fork frequency. Thus, a means for splitting frequeneies and/or determining' sub-harmonics thereof which are constant has been provided.

Now, in order to further amplify the subharmonic frequency corresponding to the natural period ofv vibration of the muti-vibrator system, I have provided amplifying tubes 95' and 97, whose filament members 99 and 101 ar'e connected inparallel with the'filament member's and 67 of the vibrator tubes 55 and 53. Each of tubes 95 and 97 have' their filament members 99 and 101 heated from the sources of filament potentials 69 and 71I respectively. The grid member 91 of the amplifier 95 is connected with the grid member 61 of the tube 53, and also with theplate member 59 of the vibrator tube 55'by Way of the capacity element 75, and similarly, the grid member 93 of the amplifying tube 97 is connected with the grid member 63 of the vibrator tube 55, and also through capacity element '73 with the'plate' member 57 of the'vibratortube 53'. It will thus be seenl that energy from the'vibrator may readily be transferred'y to the; amplifying system, including, the tubes 95 and'97, and therein amplified, so that amplified energy fiowing from the plate members 103 and 105 of the afmplifiers 95 and 97 respectively may be directed through the c'oils 109 and' 1111 of thek relay member 107. ThroughA a common connectiony to a source of plate potential B+, potentials are suppliedl to platevmembers 1'03 and 105 of the tubes 95 and 97. Thus, it will be seen that since the tubes 95 and 97 are' connected in push-pull fashion with the vibrators 53 and 55, the armature 113 of the relay 107v will be caused to vibrate alternately between contacts 115 and 117 respectively in accordance with whether or not energy is being fed from the plate' member of the tube 95 or 97.

As has been shown by the: drawing, the armature 113 of the relay 107 is connected through a contact point 1 19 to a point of zero potential, the contact 115 is connected through a second contact member' 121 toia point of negative pote'n- 150 tial, and, in a similar manner, the contact 117V is connected through a contact point 123 with a source of positive potential. Thus, as the armature 113 vibrates between the contacts 115 and 1 1'7 at a frequency corresponding to the frequency of the vibrator system, current will alternatelyflow in the circuit including the circuit connecting points 119 and 121, or the circuit including the contacts 119 and 123. In either or both of these orcuits I have provided a second synchronizing member, which, for example, may be a 100 cycle tuning fork, or any of the other forms of constant speed or period systems above mentioned.

Referring to' the above illustrated example for illustrating the principle of my invention, it will be readily seen that it is possible to accurately drive from the output of either the circuit including the contact 119 and 121, or the circuit including the contact 119 and 123, a fork of a frequency of 100 cycles in an accurate manner. It has long been recognized in the prior art that it is most difiicult to accurately drive low frequency forks for the reason that the frequency thereof is rather unstable and due to the fact that it is practically impossible to provide a constant source of the desired frequency for applying driving impulses to a fork of low frequency in a manner similar `to that shown in connection with the drive of the fork l. A means has herein been provided whereby a relatively high frequency fork which can be conveniently controlled as to its frequency may be used to drive a second fork of a lower frequency, or instead of a fork, an impulse or La Cour wheel, or a low frequency synchronous motor of any desired type or style.

As a means for keeping high frequency currents generated in the vibrator system including the tubes 53 and 55 from the source of plate potential therefor, I have provided a choke coil 125 in series with the source of plate potential B+ for the oscillators 53 and 55 in a manner similar to that shown in connection with the oscillator 5.

While the accompanying diagram shows the i supplying the desired plate potential to any of the vacuum tubes included in the system.

Other modifications of my invention than those herein disclosed will at once suggest themselves and become apparent to those skilled in the art to which the invention relates by a reading of the hereinafter appended claims.

Having now described my invention, what I claim and desire to secure by Letters Patent is the following:

1. An energy transfer system comprising a source of .high frequency energy, a thermionic device serving as a low frequency unstable oscillator, a coupling tube connected between said high frequency source and said low frequency oscillator for transferring energy from said high frequency source to said low frequency oscillator and for preventing reaction upon said high frequency source from said low frequency oscillator, a therm'onic amplifying system having its input circuit connected in parallel with the grid circuit of the low frequency oscillator, and a load circuit connected with the output of said amplifier.

2. A multi-vibrator unit comprising a pair of thermionic tubes having interconnected plate electrodes, a capacity connection between a grid electrode of each tube and the plate electrode of the other tube, meansifor supplying energy of predetermined frequency to the circuit including the plate electrodes of each of the said pair of thermionic tubes, a pair of push-pull amplifying tubes having the input electrodes thereof connected to the grid electrodes of the said first mentioned pair of tubes, and a load circuit oonnected with the output of said push-pull tubes.

VERNE T. BRAMAN.

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