US2134407A - Electron discharge device - Google Patents

Description

act. 25, 1938. J L. JONKER 2,134,407

ELECTRON DISCHARGE DEVICE Filed Feb. 9, 1933 INVENTOR. JOHAN L.H. JONKER ATTORNEY.

Patented Oct. 25, 1938 PAT ELECTRON DISCHARGE DEVICE,

Johan Lodewijk Hen drik J onker, Eindhoven,

Netherlands, assignor to N. V. Philips Gloeilampenfabrieken, Eindhoven, Netherlands Application February 9, 1938, Serial No. 189,507

In the Netherlands February 12,1937

6 Claims.

My invention relates to an electron discharge device of the so-called converter type and sometimes referred to as a pentagrid or octode, such devices being particularly useful in superhetero- 5 dyne circuits for mixing the received signal im pulses and locally generated oscillator impulses to provide an alternating voltage of an intermediate frequency.

The principal object of my invention is to provide an improved electron discharge device of the converter type. The pentagrid usually comprises a cathode, an anode and five or six other electrodes of which usually two electrodes located in the neighborhood of the cathode are utilized as oscillator electrodes and are located on the oathode side of a screening electrode on the other side of which are arranged an input control grid, a screen grid and an anode. In an octode between the two last-mentioned electrodes a grid, pref erably at cathode potential, may be arranged.

The invention concerns means for giving the local oscillator an anode-current grid-voltage characteristic having a very steep slope by utilizing the phenomenon of secondary emission. With a device according to the invention, the electrons proceeding from the cathode of the electron discharge tube are caused to travel over curved paths to electrodes which are coated with a material that readily emits secondary electrons and which are arranged in close proximity to the anode of the local oscillator in such manner that material which vaporizes from the cathode cannot reach the secondary emission electrodes. As the applicant has found, there is thus obtained an appreciable increase of the slope of the oscillator with respect to the slope which may be attained with the conventional pentagrid and octode construction while owing to the arrangement of the secondary emission electrodes material vaporized from the cathode is prevented from precipitating on these electrodes so that the latter lose their activity.

The curved paths desired may be obtained by controlling the electrons by electrostatic or electromagnetic means. A very satisfactory arrangement is obtained if the secondary emission electrodes are arranged in the shadow of the supporting members or side rods of the control grid 50 of the oscillator, viewed from the cathode. The secondary emission electrodes may be connected to the first screening electrode which is formed as a grid completely surrounding the cathode, the control grid of the oscillator, the secondary emission electrodes and the anode of the oscillator, which ano rods or plates.

According to another embodiment of the present invention, an indirectly heated cathode of a pentagrid or octode is surrounded by a control grid which is partly surrounded in its turn by a screening electrode part of which, that is to say that part which is coated'with a material that readily emits secondary electrons, is arranged in the shadow of the supporting members of the control grid, viewed from the cathode. If this screening electrode is partly made of sheet material and'only leaves a few apertures for the passage .of electrons towards the amplifier portion of the tube and if the oscillator anode, which may be formed, for example, by a few rods, is arranged inside the full portion of the screening electrode, a steep-slope characteristic of the local oscillator will be obtained and at the same time no electrons returning from the virtual cathode which is formed; in front of the input signal or control grid can reach the anode of the oscillator.

The novel features which I believe to be characteri'stic of my invention are set forth with particularity. in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 is a transverse section of an electron discharge device embodying 'my invention and Figure 2 is a transverse section of a modification of an electron discharge device embodying my invention.

In Figure 1 of the drawing a straight indirectly heated cathode I consisting of a cylindrical cathode body inside of which a heating element (not shown) is arranged is surrounded by a control grid 2 which is secured to supporting members or side rods 3 and which is surrounded in its turn by a screening electrode 4 formed as a grid and which carries two longitudinally extending rectangular shaped plates 5 which are coated with a material that readily emits secondary electrons. The tube comprises, in addition a control grid 9, a screen grid I0, an anode I I, a suppressor grid I2 arranged between the anode and the screen grid I0. Oscillator anode rods I3 are positioned inside the screen and adjacent the secondary electron emitting members 5., In operation the voltage on the oscillator rods I3 assisting some of the electrons from cathode I travel over curved paths to anodes I3 and elements '5, striking the elements 5 with sufiicient force to knock out secondaries which go to the oscillator anode rods I3. This results in a large increase demay consist of a number of OFFICE of current to the oscillator anode rods over that which would normally flow to the rods without the elements 5. Additional means could be used to increase the primary electrons or electrons from the cathode to the elements 5. All of the electrodesare enclosed by envelope [4.

In a tube according to Figure 2 the screening electrode comprises the U-shaped members 4' of solid sheet material and at the surfaces indicated ,by 6 on the inside of the rectangular, sheet metal members, forming the legs, it is coated with a material that readily emitssecondary electrons. The legs are radially positioned and lie in planespassing through the parallel grid side rods and the cathode. The channel members 6 of U-shape, adjacent the coated surfaces of which anode rods I3 are positioned, may be used to support along their outer edges the grid wires 41 of the screen grid. 7

While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only two specific appli cations for which my invention may be employed, it'will be apparent that my invention, is by no means limitedto the :exact forms illustrated or the use indicated; but that many variations may be made in the particularstructureused and the purpose for which it is employed without departing from the scope of. my. invention'as set forth in the appended claims.

What I claim as new is:

1. An electron discharge device having a cathode for emitting electrons and an anode for receiving said electrons, a control grid surrounding said cathode and a screen grid surrounding said control grid, and a second control grid between said screen grid and. said anode, an auxiliary anode positioned between said first control grid and screen grid and means for emitting secondary electrons positioned inside said screen grid and adjacent said auxiliary-anode.

2. An electron discharge device comprising a cathode surrounded by a control grid, and a screen grid, an anode, and a control electrode between said screen grid and anode, members positioned between said control grid and said screen grid and coated with material for emitting secondary. electrons, and auxiliary anodes positioned between the control grid and screen grid and adjacent said members.

3. An electron discharge device having a straight thermionic cathode surrounded by a control grid having a pair of oppositely disposed side rods parallel to said cathode, and a screen grid and a control electrode and anode outside of said screen grid, sheet metal members positioned between the screen grid and control grid and in the electron shadow of said side rods and coated with a material for emitting secondary electrons, and oscillator anode rods positioned adjacent the coated surfaces of said sheet metal members.

each of the side rods of the control grid and the screen grid and lying in the electron shadow cast by said side rods, and oscillator anode rods positioned adjacent the coated surfaces of said sheet metal members.

- 5. An electron discharge device comprising a straight thermionic cathode surrounded byoa control grid provided with side rods parallel to saidcathode and ascreen grid, a control electrode and an anode outside said screen grid, a radially positioned sheet. metal member coated with material for emitting secondary electrons positioned between each of the side rods of said control grid and said screen grid and lying in a plane passing through said cathode and control grid side rods,

andoscillator anode rods positioned on opposite sides of each of said sheet metal members and adjacent the coated surfaces thereof.

.6. An electron discharge device having a straight thermionic cathode, a first control grid surrounding said cathode and having a plurality of parallel longitudinally extending side rods, oppositely disposed sheet metal U-shaped members having rectangularly shaped legs radially positioned with respect, to said cathode and lying in planes passing through the cathode and the side rods of said control grid, said legs being coated on the inside with material for emitting secondary electrons, and an oscillator anode rod positioned adjacent each coated surface of the legs of said U-shaped member, and a second control grid and anode surrounding said cathode, first control grid and U-shaped members.

JOHAN LODEW'IJK HENDRIK JONKER.

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