Electric lamp and discharge devices – Cathode ray tube – Ray generating or control
Reexamination Certificate
1999-08-06
2004-08-24
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Ray generating or control
C313S542000, C219S121120
Reexamination Certificate
active
06781300
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an electron gun employing an indirectly heated cathode, gate electrode and anode.
Electron guns constructed for and used for processing workpieces have been generally known and there exist many publications relating to such electron guns.
A majority of conventional electron guns are based on directly heated cathodes. These cathodes are heated separately by a heating voltage, and an high voltage for electron escape from the cathode surface and for electron acceleration is applied to cathode independent of a heating means for the cathode. This separation of heating voltage and electron acceleration voltage is necessary in connection with the required overlay of the two electrical voltage variables. The electrons emitted from the cathode can only be controlled with some effort due to the high voltage involved. Furthermore, the only cathode type that can be used with direct heating is a band cathode. Such constructions have been described, for example, in U.S. Pat. No. 386,222, U.S. Pat. No. 3,433,922, and U.S. Pat. No. 4,317,983.
A combined laser and plasma arc welding torch is taught in U.S. Pat. No. 5,700,989 and 5,700,785 to Dykhno et al. In each case the laser beam passes through a hole in a cathode. U.S. Pat. No. 3,621,324 to Fink teaches a high power cathode. The bolt electrode is heated by electron bombardment.
Indirectly heated cathodes are associated with the advantage of in general allowing a longer service life also allowing more independence for geometrical shaping of the electron gun configurations. Known constructions employ electric heating systems and in particular resistance heating as an energy source for indirect heating. Such configurations are presented in the printed patent documents European Patent Document EP 0,416,535, European Patent Document EP 0,505,211 and German patent Document DE 44,43,830.
High electric currents in the electric heater are required to achieve a sufficient temperature that will cause emission of electrons from the cathode. Moreover, the resistive sources of heat are non-focussed such that a major part of the thermal energy generated by the heater does not reach an appropriate cathode surface for electron emission and a large part of the heat generated in the heater is dissipated into the space of the electron gun and to the casing of the electron gun. The uncontrolled dissipation of thermal energy by the electric heater results in an increase of the electric energy required to achieve the required cathode temperature. This is why indirectly heated electron guns can only be used efficiently in lower-power electron guns. Indirectly heated electron guns are less suited for high-power electron guns. There is only limited control of the generation process of electron emission due to the non-directional thermal radiation in case of an indirect source of heat.
Band cathodes are conventionally heated directly by means of an electric resistor heating element with electrical consumptions of for example 8 volts and 10 amps. Such electric resistors encountered difficulties with the connections to the power source, because the connection resistance would frequently be higher than the resistance of the heating element.
SUMMARY OF THE INVENTION
Purposes of the Invention
It is an object of the present invention to furnish an electron gun which is convenient to control in its output characteristics.
It is another object of the present invention to eliminate problems in electron guns associated with high heating currents for the cathode.
It is yet another purpose of the present invention to eliminate problems in electron guns associated with heating of the junctions to the cathode heater.
It is a still further purpose of the present invention to avoid a magnetic field generated by a heating current for the cathode heater from interfering with the direction and/or bundling of the emitted electron beam.
These and other objects and advantages of the present invention will become evident from the description which follows.
BRIEF DESCRIPTION OF THE INVENTION
The present invention provides an electron gun comprising an indirectly heated cathode, a gate electrode and an anode, for generating electron beams of various shapes and power that are preferably used for processing workpieces.
The electron gun comprises a housing, a cathode having an emission surface on a first side and an irradiation surface on a second side of the cathode disposed opposite to the first side and said cathode being mounted in the housing, a gate electrode disposed adjacent to the cathode for controlling the beam of electrons emitted by the cathode and mounted in the housing, an anode mounted in the housing and disposed at an appropriate distance from the cathode for building up a voltage between cathode and anode and for accelerating electrons emitted by the cathode, a source of a laser beam for directing a laser beam to the irradiation surface of the cathode.
The source of the laser beam is a member selected from the group consisting of solid-state laser, an optical facility to decouple laser beams and combinations thereof. The source of the laser beam is placed opposite to a surface other than the emission surface of the cathode. The side disposed opposite to the emission surface of the cathode is located in the laser beam path.
A member selected from the group consisting of a photodetector, a solid-state image sensor, an optical fiber waveguide connected to a photo detector, an optical fiber waveguide connected to a solid-state image sensor and combinations thereof is placed opposite to a surface of the anode and in the path of the light of the laser beam. The source of the laser beam and the member selected from the group consisting of a photodetector, a solid-state image sensor, an optical fiber waveguide connected to a photo detector, an optical fiber waveguide connected to a solid-state image sensor and combinations thereof and the member selected from the group consisting of a control unit, a closed-loop control system and combinations thereof are interconnected.
The source of the laser beam can be an optical facility to decouple a laser beam together with and optically connected to a laser beam generating facility through at least one optical fiber. The laser beam generating facility for generating a laser beam is disposed outside of the housing.
An optical fiber can be located in the waveguide. A hole of the cathode anchor forms a direct electroconductive connection to the waveguide.
A high voltage plug is connected to the power supply unit. The waveguide is a component of the high-voltage plug. A first end of said waveguide is placed outside the housing wherein and a second end of said waveguide is disposed at a distance from about 2 to 150 millimeters relative to the cathode or inside the cathode anchor. The waveguide can be furnished with an electroconductive connection to the power supply unit for the cathode.
The facility generating the laser beam can be a solid-state laser.
The facility generating the laser beam can be connected to the optical fiber through a member selected from the group consisting of a spherical lens, a half sphere, a taper, a two-sided beveling of the optical fiber, and combinations thereof.
The optical facility to decouple laser beams can be connected through the fiber laser to a light beam generating facility that functions as a pumping source. The cathode can be located in the laser beam path.
The optical facility to decouple laser beams can be a member selected from the group consisting of the end of at least one optical fiber, a half sphere placed at the end of said optical fiber, a lens placed in the downstream beam path from the end of said optical fiber, and combinations thereof. The half sphere can be melted on and comprises a cast resin.
The facility to decouple laser beams can comprise two lenses placed at a distance of from about 5 to 50 millimeters relative to one another. The cathode can be a member selected from the group consisting of a band cathod
Kasper Horst
Patel Vip
Williams Joseph
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