US4317983A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Setting the electron gun cathode heating current of an electron beam machine
Assignee: Messer Griesheim GmbH
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Filing: 1979-10-10
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Granted: 1982-03-02
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Expires: 1999-10-10
Abstract
Abstract In an electron beam machine for e.g. beam welding, the beam current I em is stabilized by negative feedback applied to the grid of the electron gun. The optimum cathode heating current is ascertained by causing the cathode heating current I H to decrease steadily from a maximum value. The beam current is kept constant by the feedback, which adjusts the grid voltage U W to offset the decrease in cathode temperature caused by the decreasing heating current; the rate of change of the grid voltage U W is monitored, and when this rate of change exceeds a threshold, the decrease in heating current is arrested, and the heating current is maintained at the thus established optimal value or preferably set at a slightly higher value, which secures an extended length of life of the cathode. This setting of the cathode heating current is repeated after a predetermined interval of time to establish a new value in response to a change of the condition of the cathode.
Inventors
- 👤 Wilhelm Scheffels
- 👤 Ruprecht Hoffmann
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 14:09
CPC Classifications
H; H01; H01J; H01J37/00; H01J37/02; H01J37/24; H01J37/242
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
65 words
In an electron beam machine with an electron gun including a cathode, a Wehnelt electrode, and a beam current, a method for setting a cathode heating current comprising the steps of: stabilizing the beam current by Wehnelt voltage control; and setting the cathode heating current on the basis of the dependence of the Wehnelt voltage to the heating current while the beam current is stabilized.
Claim 2
Dependent Claim
65 words
In an electron beam machine with an electron gun including a cathode, a Wehnelt electrode, and a beam current, a method for setting a cathode heating current comprising the steps of: stabilizing the beam current by Wehnelt voltage control; and setting the cathode heating current on the basis of the dependence of the Wehnelt voltage to the heating current while the beam current is stabilized.
Claim 3
Dependent Claim
51 words
The method according to claim 1 and further comprising the steps of: generating a heating current/Wehnelt voltage characteristic curve; determining a region in the characteristic curve where the curve has a bend; and setting said cathode heating current at a value in the region of the bend in the characteristic curve.
Claim 4
Dependent Claim
28 words
The method according to claim 2 and further comprising the step of setting the cathode heating current at a value somewhat above the bend in the characteristic curve.
Claim 5
Dependent Claim
30 words
The method according to claim 2 or 3 and further comprising the steps of determining the characteristic curve and setting the cathode heating current during normal operation of the machine.
Claim 6
Dependent Claim
21 words
The method according to claim 1 and further comprising the step of repeating the cathode heating current setting step at intervals.
Claim 7
Dependent Claim
138 words
An electron beam machine with a beam current and an electron gun containing a heated cathode, a Wehnelt electrode responsive to a Wehnelt voltage to control the beam current and at least one anode, and a beam regulator acting on the Wehnelt voltage, comprising: (a) first means (32, 40) to vary a cathode heating current (I H ) supplied to said heated cathode; (b) a second means (44) to determine changes of the Wehnelt voltage (U W ) which are necessary in order to keep the beam current constant; and (c) third means (70, 76) which responds to a rate comprising the change of the Wehnelt voltage to the variation of cathode heating current to terminate the variation of the heating current at a predetermined value of said ratio and maintain said heating current at a constant level.
Claim 8
Dependent Claim
138 words
An electron beam machine with a beam current and an electron gun containing a heated cathode, a Wehnelt electrode responsive to a Wehnelt voltage to control the beam current and at least one anode, and a beam regulator acting on the Wehnelt voltage, comprising: (a) first means (32, 40) to vary a cathode heating current (I H ) supplied to said heated cathode; (b) a second means (44) to determine changes of the Wehnelt voltage (U W ) which are necessary in order to keep the beam current constant; and (c) third means (70, 76) which responds to a rate comprising the change of the Wehnelt voltage to the variation of cathode heating current to terminate the variation of the heating current at a predetermined value of said ratio and maintain said heating current at a constant level.
Claim 9
Dependent Claim
38 words
An electron beam machine according to claim 6 wherein said first means contains a saw-tooth generator (40) and further comprising means (32) controlled by said saw-tooth generator (40) to alter the heating power supplied to the cathode (10).
Claim 10
Dependent Claim
34 words
An electron beam machine according to claim 6 and further comprising: a beam current regulator (28); and means for supplying an A.C. output signal from the beam current regulator (28) to said second means.
Claim 11
Dependent Claim
51 words
An electron beam machine as in claim 6 and further comprising means for establishing a heating current value at a bend of the heating current/Wehnelt voltage characteristic curve and means to set and maintain the heating current at a second value which is a predetermined amount greater than said first value.
Claim 12
Dependent Claim
22 words
An electron beam machine according to claim 6 wherein said third means contain a differentiator circuit (70) and a threshold circuit (76).
Claim 13
Dependent Claim
58 words
An electron beam machine according to claim 10 wherein said differentiator circuit establishes the magnitude of the change of the Wehnelt voltage for a given amount of change of the heating current and said threshold circuit is responsive to a predetermined value of said amount of change of Wehnelt voltage per given amount of variation of heating current.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-03-01 | 1985-08-31 | 1986-03-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-03-01 | 1989-08-31 | 1990-03-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-03-01 | 1993-08-31 | 1994-03-02 | $7700.00 | Window Closed / Lapsed |