Electron gun having cathode with cylindrical extension and control grid with conical section

Claim 1

A device comprising a cathode-ray tube, which cathode-ray tube has a rotationally-symmetric electron gun, in which electron gun are present successively a cathode provided with a plane electron-emitting surface extending substantially at right angles to the axis of the electron gun, a disk-shaped control grid provided with a central control grid aperture, and a disk-shaped anode-grid provided with a central circular-cylindrical anode grid aperture, the control grid being at a negative potential relative to the cathode and the anode being at a higher positive potential relative to the cathode, the space on the side of the anode grid remote from the control grid being substantially field-free, characterized in that the cathode comprises a first conductive circular cylinder from the base of which a second conductive circular cylinder projects the base of which forms the emitting surface and the control grid aperture, on the side of the anode grid, having a circular-cylindrical part and, on the side of the cathode, having a conical part which narrows towards the circular-cylindrical part, of which conical part the wall encloses substantially an angle of 45* with the axis of the electron gun, the diameter of the said first conductive circular cylinder and the diameter of the said circular-cylindrical part being substantially six times as large, the diameter of the anode grid aperture being substantially four times as large, the length of the said second conductive cylinder being substantially twice as large, the distance between the emitting surface and the said circular-cylindrical part and the axial length of the said circular-cylindrical part being substantially equally large, the axial length of the said conical part being at least substantially equally large and the distance between the control grid and the anode grid being substantially one and a half times as large as the diameter of the emitting surface, the anode potential being substantially 4 1/2 times as large as the control grid potential.

Claim 2

A device comprising a cathode-ray tube, which cathode-ray tube has a rotationally-symmetric electron gun, in which electron gun are present successively a cathode provided with a plane electron-emitting surface extending substantially at right angles to the axis of the electron gun, a disk-shaped control grid provided with a central control grid aperture, and a disk-shaped anode-grid provided with a central circular-cylindrical anode grid aperture, the control grid being at a negative potential relative to the cathode and the anode being at a higher positive potential relative to the cathode, the space on the side of the anode grid remote from the control grid being substantially field-free, characterized in that the cathode comprises a first conductive circular cylinder from the base of which a second conductive circular cylinder projects the base of which forms the emitting surface and the control grid aperture, on the side of the anode grid, having a circular-cylindrical part and, on the side of the cathode, having a conical part which narrows towards the circular-cylindrical part, of which conical part the wall encloses substantially an angle of 45* with the axis of the electron gun, the diameter of the said first conductive circular cylinder and the diameter of the said circular-cylindrical part being substantially six times as large, the diameter of the anode grid aperture being substantially four times as large, the length of the said second conductive cylinder being substantially twice as large, the distance between the emitting surface and the said circular-cylindrical part and the axial length of the said circular-cylindrical part being substantially equally large, the axial length of the said conical part being at least substantially equally large and the distance between the control grid and the anode grid being substantially one and a half times as large as the diameter of the emitting surface, the anode potential being substantially 4 1/2 times as large as the control grid potential.