US2229700A - Selective space discharge device - Google Patents

Description

Jan. 28, 1941. H E HOLLMANN i 27,229,700

SELECTIVE SPACE DISCHARGE DEVICE Original Filed June 9, 1937 INVENTOR.

,fs rich 'Hollmann BY M i@ ATTORNEY.

Patented Jan. 28, 1941 l UNITED STATES PATENT OFFICE SELECTIVE SPACE DISCHARGE DEVICE Hans Erich Hollmann,

Berlin-Lichterfelde, Germany, assignor to Radio Patents Corporation, New York, N. Y., a corporation of New York Claims.

In the parent application there is described a' composite structure comprising an electro-mechanical vibrating device such as a piezo-crystal and a ca-thode ray oscillograph wherein the vibrating iield of the crystal or equivalent device is directly exercised. upon 'the cathode ray -to cause its deflection without requiring the establishment of a current ilow or expenditure of energy in an associate electric circuit. There are speciiically described in said parent application arrangements of the above type for visually indicating or recording the oscillations of a piezocrystal or the like for frequency measurement or similar purposes.

An object of the present invent-ion is to translate the oscillations of the crystal or equivalent device into corresponding current variations in a local electric circuit to serve as an amplifier, rectifier or oscillator or for any other desired purpose.

A further object is the provision of a crystal controlled oscillogr-aph of the above character in an oscillator cir-cuit for producing sustained oscillations controlled and stabilized by the crystal or equivalent device.

Another object is the provision .of a -crystal controlled oscillator functioning substantially free from the effect of interelectrode capacity and enabling the production of oscillations of extremely high frequency.

35 Another object is to Iprovide a regenerative oscillator operating With constant phase and independently of exterior influences such as load variations or changes of other operating conditions.

These and further objects and aspects of the invention will become more apparent from the following detailed description taken with reference to .the accompanying drawing forming part of this spe'ciiication and wherein:

Figure 1 represents .an 4oscillating system embodying a composite piezo-crystal and cathode ray -device constructed according to the invention,

Figure 2 is a modification of Figure 1 illus- 50 trating the invention as applied to Ia push-pull oscillator.

Similar reference numerals identify simi-lar parts in both views of the drawing.

Referring to Figure 1, there is shown a cath- 55 ode ray tube comprising an evacuated envelope III having mounted therein a cathode II of suitable construction cooperating with a pair of accelerating or focussing electrodes in the form of positively biased .apertured discs I2 and I3 .to produce a concentrated electron beam indicated at a in a manner Well understood by those skilled in the art. It is understood that the ray generating or electron gun system indicated in the drawing is by way of example only and that numerous arrangements known per se may be employed to genera-te a concentrated electron beam or pencil.

The electron beam in the example shown is deected in .a direction parallel to the plane dened by the drawing by -the aid of a -pair of electrostatic deecting plates I6 and I'I disposed at opposite sides of the beam and a piezo-electric crystal I5 mounted adjacent to the plate I6 as described in greater detail in the parent application. Thus, by exciting the crystal in any suitable manner by an alternating potential impressed upon the plates II6 and II and having a frequency equal to or close to the natural oscillating frequency of ythe crystal, the cathode beam a will be deflected in opposite directions from its zero or rest position a. in synchronism with the exciting frequency of the crystal (opposite positions a and a) Instead of impinging the beam a upon a uorescent screen to produce a luminous indication or record as described in the parent application, the beam according .to .the present embodiment is iin-pinged upon a target or output electrode I8 so as to vary the beam current collected by this electrode as the beam is deected in accordance with the piezo electric potential or field .produced by the crystal. In the example illustrated the electrode I8 is arranged symmetrically to the zero or normal position a of the electron beam and is connected through an outside terminal to a source of high potential 2I in series with a load impedance 2U which latter may be an ohmic resistance, choke coil, tuned circuit, or the like.

In order to vary the anode current in the output circuit including the impedance 20 in accordance with .the deflection of the electron beam impinged upon the target I8, there is provided an auxiliary anode I 9 directly connected tothe high potential source 2l and arranged laterally of and partly overlapping .the electrode I8. Thus, in the position a of the elect-ron beam, the entire beam current is impinged upon lthe electrode I9 and the output current through 20 reduced to zero or a minimum. In the position a of the electron beam, the entire beam current is collectedV by the anode I8 whereby the output current through the load impedance 20 is Iat a maximum. The potential developed at the anode side of the impedance 20 by the current variations is impressed or fed back to the input plate I'l thereby in turn exciting the crystal I5. In this manner a regenerative excitation of the crystal is obtained in its natural oscillating frequency until the oscillations assume a stationary const-ant amplitude determined by the output capacity of the tube. By suitably shaping the electrode I9, it is possible to adjust the phase of the feedback potential in such a. manner that the operation takes place either -along the inductive or t-he capacitative branch of the resonance curve of the crystal.

A regenerative piezo-electric loscillator of the aforedes-cribed ty-pe is substantially free from reaction between Ithe output circuit and the lcrystal whereby the generator oscillates with a substantially constant phase and independently of exterior influences such as load variations or changes of other oper-ating conditions. Instead of producing anode current by directly collecting the electron beam current by a target electrode, a capacitative or inductive coupling of the output electrode with :the electron beam may be employed for the purpose of the invention.

In Figure 2, there is shown a modified arrangement of a piezo-electric oscillator of the type according to the invention and differing from Figure 1 by the employment of a push-pull oscillating circuit. According to this embodiment, the electron beam is impinged upon a pair of similar target anodes 25 and 2S, respectively, arranged symmetrically to the beam in its normal position in such a manner that the beam current is collected in variable amounts by the one or other anode depending upon the defiection from its central or zero position. Thus, if the current collected by one electrode increases, the current collected by the other electrode will be decreased, while the sum of the current remains substantially constant as in the case of similar push-pull circuits known in the art. In order to prevent secondary electrons produced by impact of the electron beam upon the targets from affecting the focus or sharpness of the beam, a suppressor grid 29 of known construction may be provided in front of the targets 25 and 26. The grid 29'is preferably negatively biased relative to the targets in any suitable manner such as by the provision of a separate biasing potential source or by directly connecting the screen 29 to the high potential source indicated by the -lsymbol through a suitable bleeder or drop resistor in a manner Well understood by those skilled in the art. In this manner, the grid 29 serves as a suppressor by preventing secondary electrons from being emitted from the anode and affecting the focus or sharpness of the electron beam. In addition, by negatively biasing the grid 29, an accelerating electric field is set up in the space between the grid and the anodes 25 and 2S resulting in a refocussing and increased sharpness and definition of the beam and in turn in increased control sensitivity of the device.

The anode or targets 25 and 26 are connected to the high tension source in series With output or coupling impedances 2I and 28 on the one hand and to the input electrodes I6 and II, respectively, on the other hand in such a manner that the high frequency potentials developed at the anode side of the impedances 2'I and 28 are fed back upon the crystal in proper phase relation to maintain the system in continuous oscillating condition. As is understood many variations may be made in the specific circuit arrangements shown such as by the employment of inductive or capacitative feedback in place of the direct feedback and other modifications obvious to those familiar with electron tube oscillators of similar character.

A regenerative oscillator of the type described may be easily and eifectively modulated in ac` cordance with a low frequency or modulating potential by applying the latter'to a suitable means adapted to control the intensity of the electron beam such as to a grid electrode or any other control element.

In, Figure 1 there is further shown means such as a biasing battery 24 connected between the lower plate I6 and ground or any other zero reference point of the system to counteract the anode potential impressed upon the plate I'I through the feedback circuit and/or to bias the electron beam in the normal position to be impinged upon the electrode I8 as shown at a.

If the system is put in operation such as by exciting the crystal I5 by a suitable alternating potential impressed upon the plates I6 and I'I, sustained oscillations will be maintained after subsequent removal of the exciting potential. It is however also possible to make the tube self-starting such as by closing the anode circuit similar as in the case of the known regenerative oscillators comprising an oscillatory circuit associated with a triode amplifier and including a back coupling arrangement for feeding back output energy upon the input or grid circuit. In the present case if the anode circuit is closed, the electron beam will be slightly deflected from its lower or normal position a due to the switching or transient impulse Whereby a small portion of the beam current is impinged upon the electrode I9 resulting in a slight decrease of the output current through the load impedance 2li and in turn a change of the potential at the anode I8. This potential change is reflected upon the plate I'I thereby changing the excitation of the crystal I5. AS a result, a piezoelectric potential is generated which in turn causes a greater deflection of the electron beam resulting in a further decrease of the output current through the impedance 20 and so on. In this manner a gradual building up of the oscillations will take place until reaching a stage of equilibrium and stable oscillating condition.

As is understood, an arrangement of the type shown is not limited to the use as oscillator but It will be obvious from the foregoing that the invention is not limited to the specific arrangements and details shown herein for illustration,

but that the underlying novel concept and inn ventive principle are susceptible of numerous variations and embodiments coming within the broad scope and spirit of the invention as defined in the appended claims.

1, An electrical translating device comprising an envelope enclosing an evacuated space, means for producing a concentrated electron beam Vwithin said space, further means for developing an electrical field capable of deecting said beam arranged in said space, said further means comprising a piezo-electric element, at least one output electrode arranged Within said space to be variably impinged by said beam when said beam is deflected by said eld, means for applying an electrical potential to said further means for developing said field and causing a piezoelectric efect of said element, and an' electric circuit connected to said output electrode and including said electron beam.

2. A translating device comprising an envelope enclosing an evacuated space, means for producing a concentrated electron beam within said space, further means for developing an electrical field capable of deflecting said beam, said further means comprising a deflecting electrode and a piezo-electric element mounted in said envelope opposite said electrode and having an exposed surface directed towards said beam, at least one output electrode arranged Within said space to be variably impinged by said beam when said beam is deflected by said field, means for applying a high frequency potential to said further means for developing said field and exciting vibrations of said element in its natural oscillation frequency, and an electric circuit connected to said output electrode and including said elecron beam.

3. A translating device comprising an envelop-e enclosing an evacuated space, means for producing a concentrated electron beam within said space, a number, two as a minimum, of electrodes arranged in said space capable of developing an electrostatic field crossing said beam, a piezoelectric element arranged in said field outside said beam, at least one output electrode arranged within said space to be variably impinged by said beam when deected by said electrostatic field, means for applying a varying electric potential to said electrodes for creating said field and thereby causing a piezo-electric effect of said element resulting in an increase of said field, and an electric circuit connected to said output electrode and including said electron beam.

4. An electric circuit comprising a translating device substantially consisting of an envelope enclosing an evacuated space, a cathode therein, means for concentrating the electrons emitted from said cathode into a beam, a number, two as a minimum, of electrodes arranged within said space for developing an electrostatic field capable of defiecting said beam, a piezo-electric element arranged so as to be excited by said electrostatic field, at least one output electrode arranged within said space to be variably impinged by said beam when deflected by said electrostatic field, electric circuit means including a source of current connected With said cathode and output electrode, and feed-back means connected with said circuit means and said first mentioned electrodes for controlling said electrostatic field and exciting vibrations of said element in its natural oscillation frequency.

5. An electrical translating device comprising an envelope enclosing an evacuated space, a cathode, means for concentrating the electrons emitted from said cathode into a beam, further means arranged within said space for developing an electrostatic field crossing said beam, a piezoelectric element arranged Within said field so as to be excited thereby, at least one output electrode arranged Within said space to be variably impinged by said beam When deflected by said field, an output circuit connected to said output electrode and said cathode, and an input circuit connected with said further means forapplying a varying potential to said further means, the natural oscillation frequency of said element being substantially equal to the frequency of said varying potential.

HANS ERICH HOLLMANN.

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