GB1582707A - Electron beam heating apparatus - Google Patents
Electron beam heating apparatus Download PDFInfo
- Publication number
- GB1582707A GB1582707A GB1611877A GB1611877A GB1582707A GB 1582707 A GB1582707 A GB 1582707A GB 1611877 A GB1611877 A GB 1611877A GB 1611877 A GB1611877 A GB 1611877A GB 1582707 A GB1582707 A GB 1582707A
- Authority
- GB
- United Kingdom
- Prior art keywords
- aperture
- electron beam
- tubes
- workpiece
- welded
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000010894 electron beam technology Methods 0.000 title claims description 47
- 238000010438 heat treatment Methods 0.000 title claims description 20
- 239000002184 metal Substances 0.000 claims description 15
- 230000004044 response Effects 0.000 claims description 12
- 230000015556 catabolic process Effects 0.000 claims description 9
- 238000003466 welding Methods 0.000 claims description 9
- 230000005684 electric field Effects 0.000 claims description 6
- 239000011810 insulating material Substances 0.000 claims description 6
- 238000002844 melting Methods 0.000 claims description 6
- 230000008018 melting Effects 0.000 claims description 6
- 238000010276 construction Methods 0.000 claims description 4
- 230000000694 effects Effects 0.000 claims description 4
- 239000007789 gas Substances 0.000 claims description 4
- 230000007246 mechanism Effects 0.000 claims description 4
- 230000004075 alteration Effects 0.000 claims description 3
- 230000005484 gravity Effects 0.000 claims description 3
- 239000001307 helium Substances 0.000 claims description 3
- 229910052734 helium Inorganic materials 0.000 claims description 3
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 3
- 150000002500 ions Chemical class 0.000 claims description 3
- 230000009471 action Effects 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 230000003287 optical effect Effects 0.000 claims description 2
- 238000005086 pumping Methods 0.000 claims description 2
- 230000000284 resting effect Effects 0.000 claims description 2
- 230000003340 mental effect Effects 0.000 claims 1
- YUBJPYNSGLJZPQ-UHFFFAOYSA-N Dithiopyr Chemical compound CSC(=O)C1=C(C(F)F)N=C(C(F)(F)F)C(C(=O)SC)=C1CC(C)C YUBJPYNSGLJZPQ-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000010849 ion bombardment Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
- H01J37/302—Controlling tubes by external information, e.g. programme control
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/02—Details
- H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
- H01J37/09—Diaphragms; Shields associated with electron or ion-optical arrangements; Compensation of disturbing fields
Landscapes
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Electron Sources, Ion Sources (AREA)
Description
(54) IMPROVEMENTS IN OR RELATING TO ELECTRON
BEAM HEATING APPARATUS (71) We, THE GENERAL ELECTRIC
COMPANY LIMITED, of 1 Stanhope Gate,
London W1A 1EH, a British Company,
do hereby declare the invention, for which we pray that a patent may be granted to
us, and the method by which it is to be
performed, to be particularly described in
and by the following statement: This invention relates to electron beam
heating apparatus.
One problem which arises in operation
of such apparatus is that, particularly when
a high power electron beam is being used,
it is difficult to alter the heating effect of
the electron beam on the workpiece pre
cisely at a desired moment by control of the electric power supply. A further aspect
of this problem is that in some applications
it is difficult to determine the best moment
to alter the heating effect, with regard to
the operation being performed. For
example, in welding operations, it is desir
able to switch off the electron beam at a
moment just before the parts being welded
become sufficiently molten to run under
gravity, but it is difficult to ascertain when
this moment occurs.
It is an object of the present invention
to provide an electron beam heating
apparatus wherein this problem is alleviated.
According to the present invention, in
an apparatus for heating a workpiece an
electron beam is directed in operation onto
the workpiece via an aperture and means
is provided for altering a dimension of said aperture in response to heating of the work
piece, thereby to alter the heating effect of
the electron beam on said workpiece.
In a preferred apparatus in accordance
with the invention for use in welding a
workpiece, said means for altering a dimen
sion of the aperture is arranged to operate
in response to melting of the workpiece,
thereby substantially to cut-off the electron .beam.
In one particular form of said preferred apparatus, a part to be welded is urged into abutment with another such part during a welding operation, and said means for altering a dimension of the aperture is arranged to operate in response to movement of said one part consequent upon melting of abutting portions of the parts being welded.
The aperture is suitably an aperture in an a.node incorporated in an electron gun producing the electron beam. However, in an apparatus in accordance with the invention the aperture may be defined by metal parts which serve to shape the electric field in the region of the electron beam but are electrically isolated from the power supply for the electron gun in operation.
The invention finds. especial application in electron beam heating apparatus of the kind wherein the electron beam is produced by an electron gun comprising an anode and a cathode arranged so that when a suitable voltage is applied between the anode and cathode with the anode and cathode maintained in an atmosphere of gas at a suitable low pressure, a selfsustaining glow discharge is formed due to long-path breakdown, thereby producing ions which liberate electrons from the cathode due to ion bombardment of the cathode, which electrons form an electron beam which may be directed onto a workpiece.
Such an electron gun is hereinafter referred to .as a glow discharge electron gun.
In an apparatus according to the invention the alteration of a dimension of said aperture may change the focus of the electron beam and/or the amount by which the aperture physically impedes the passage of the electron beam.
In apparatus in accordance with the invention wherein the electron beam is produced by a glow discharge electron gun, in addition to or instead of changing the focus of the electron beam and/or the amount by which the aperture physically impedes the passage of the electron beam to the workpiece, the alteration of a dimension of the aperture may be arranged to affect longpath breakdown in the electron gun and thereby affect actual production of the electron beam.
One apparatus in accordance with the invention will now be described, by way of example, with reference to the accompanying drawing which is a sectional elevation of the apparatus.
Referring to the drawing, the apparatus is designed for butt-welding together two metal tubes 1 and 2. Welding is effected by heating the tubes 1 and 2 where they abut by means of an electron beam projected radially inwards to impinge all around the external surface of the tubes where they adjoin, the weld thus being achieved in a single shot.
The electron beam is produced by a glow discharge electron gun comprising an annular metal cathode 3 which surrounds the tubes 1 and 2 where they abut, the cathode being sandwiched between a pair of annular plates 4 and 5 of insulating material and being hermetically sealed tb the plates 4 and 5 by 'O' rings (not shown) housed in annular grooves 6 in the plane faces of the cathode.
Between the tubes 1 and 2 and the internal curved surface of the cathode 3, which acts as the active surface of the cathode, there is disposed an anode structure which comprises two similar parts 7 and 8.
Each part 7 and 8 is of generally tubular form with an outwardly extending flange at one end whose outer face slopes backwardly toward its outer edge. The two anode parts 7 and 8 are disposed coaxially around the tubes 1 and 2 respectively with their sloped faces spaced apart and facing one another, adjacent where the tubes 1 and 2 abut. The parts 7 and 8 thus define an annular aperture 9 between the cathode active surface and the line of abutment of the tubes 1 and 2, the aperture decreasing in width in a direction towards the tubes 1 and 2.
The flange of the anode part 7 is bolted to the outer surface of a flange formed at one end of a metal tubular member 10 which coaxially surrounds the tube 1, the remainder of the part 7 fitting within the member 10. The member 10 is externally threaded and the assembly comprising the member 10 and the anode part 7 is clamped to the plate 4 by means of a nut 11 which co-operates with the thread on the member 10, the nut 11 bearing against a metal plate 12 which fits against the plate 4 and is hermetically sealed thereto by an '0' ring (not shown) housed in an annular groove 13 in the face of the metal plate 12 adjacent the plate 4. The anode part 7 is thus held fixed with respect to the cathode 3.
The tube 1 is located coaxially with respect to the anode part 7 by means of a sleeve 14 of insulating material which fits between the tube 1 and the member 10.
The end of the tube 1 remote from the tube 2 abuts the base of a cap 15 which screws onto the end of the member 10, thereby axially locating the tube 1.
The flange of the anode part 8 is bolted to the outer surface of a flange 16 formed at one end of a metal tubular member 17 which coaxially surrounds the tube 2, the remainder of the part 8 fitting within the member 17.
The member 17 fits slidingly within a central aperture formed in a metal plate
18. The plate 18 is secured within a central aperture formed in a plate 19 of insulating material which is bolted to the plate 5, and hermetically sealed thereto by an 'O' ring (not shown) housed in an annular groove 20 in the plate 19.
The tube 2 is located coaxially with respect to the anode part 8 by means of a sleeve 21 of insulating material which fits between the tube 2 and the member 17.
The end of the tube 2 remote from the tube 1 abuts the base of a cap 22 which screws onto the end of the member 17, thereby locating the tube 2 axially with respect to the member 17, the sleeve 20 and the anode part 8.
In the surface of the plate 18 which faces the flange 16 on the member 17 there are formed three holes fonly one visible in the drawing) each of which houses a compression spring 23, the springs 23 bearing on the flange 16. The assembly comprising the member 17, anode part 8, sleeve 21, tube 2 and cap 22 is thus urged away from the plate 18 by the springs 23 towards the tube 1, movement of this assembly being prevented only by the abutment of the tubes 1 and 2.
To complete an evacuable enclosure as is required for operation of the electron gun, a cup-shaped casing 24 is sealed to the exposed face of the metal plate 18.
In operation, the enclosure thus completed is evacuated to a low pressure via an aperture 25 in the base of the cap 15.
Gas within the enclosure passes from the region where the tubes 1 and 2 abut, around the outer edge of the flange 16 of tubular member 17, through apertures 26 formed through the plate 18, through the space between casing 24 and cap 22, through an aperture 27 in the base of cap 22 and via the insides of tubes 1 and 2 to the aperture 25 in the cap 15. Whilst the enclosure is thus evacuated helium is ad mitted to the interior of the enclosure via bleed valve (not shown) to establish an atmosphere of helium at approximately 200 millitorr in the enclosure.
A negative voltage, typically of the order of 14 KV is applied to the cathode 3 while the other metal parts of the apparatus and the tubes 1 and 2 are connected to the positive of the power supply.
The spacing between the cathode 3 and the anode structure 7, 8 and the gas pressure are such that long-path breakdown does not occur between the nearer parts of the cathode and anode structure, but longpath breakdown occurs via the aperture 9 in the anode structure producing a selfsustaining glow discharge. A plasma forms adjacent the tubes 1 and 2, and electrons are emitted from the cathode active surface due to bombardment by ions from the discharge. The electrons thus produced are formed into a beam by the electric field between the cathode active surface and the plasma, which beam is directed onto the line of abutment of the tubes 1 and 2 via the aperture 9.
The electron beam heats the abutting ends of the tubes 1 and 2 causing them to melt. As a result the assembly comprising anode part 8, tube 2 and members 17, 21 and 22 moves towards the tube 1 under the action of the springs 23. The width of the aperture 9 is consequently reduced causing the electron beam to be cut-off from the tubes 1 and 2 before the ends of the tubes melt so much that molten metal runs away under gravity from the region of the weld.
The electron beam is cut off when the aperture 9 reduces in width partly by virtue of the anode part 8 physically impeding the electron beam, and partly by virtue of changes in the electric field configuration as the width of the aperture becomes smaller.
With some constructions of glow discharge electron gun, the possibility of longpath breakdown may be reduced as the aperture becomes smaller to such an extent that an effective electron beam is no longer produced. However, with the particular construction shown in the drawing, this is unlikely to occur due to the relatively long tapered form of the anode aperture 9.
In a typical practical embodiment of the apparatus shown in the drawing the aperture 9 reduces in width by 1.0 to 1.5 millimetres from an initial width of 2.5 millimetres at its narrower end.
In an alternative mode of operation of the apparatus the anode structure may be electrically isolated from the power supply instead of being connected to its positive terminal. The tubes 1 and 2 then effectively serve as the anode of the electron gun, the parts 7 and 8 assisting as fieldshaping electrodes. With this mode of operation a more finely focussed electron beam is produced until the width of aperture 9 is reduced to cut-off the electron beam.
To permit this mode of operation, the bases of the caps 15 and 22 are constructed with inserts 28 and 29 of insulating material, thereby to insulate the metal parts 7, 8, 10, 11, 12, 15, 17, 18, 22 and 24 from the tubes 1 and 2. However, even when these parts are connected to the positive terminal of the power supply in operation, the inserts 28 and 29 may usefully be included since they allow the fraction of electron beam current delivered to the tubes 1 and 2 to be monitored.
The apparatus shown in the drawing is designed for operation with the axis of the tubes 1 and 2 vertical, with tube 2 above tube 1, the apparatus being bolted to a pumping port indicated by chain dotted line 30 in the drawing. The parts of the apparatus not bolted together, but merely resting on one another, are held together firmly in operation of the apparatus by atmospheric pressure when the interior of the apparatus is evacuated.
It will be appreciated that the apparatus may easily be adapted for use with the axis of the tubes 1 and 2 not vertical.
It is further pointed out that in alternative forms of apparatus in accordance with the invention a dimension of the aperture need not be altered directly in response to movement of a part being welded consequent upon melting of abutting portions of the parts being welded. For example, some form of gearing may be provided between a part defining the aperture and the part being welded, so that the aperture dimension changes by a greater or smaller amounb than the part being welded moves.
Alternatively, the part defining the aperture may not be mechanically coupled with a part being welded, but may be moved by a quite separate mechanism. Such mechanism may be operated in response to movement of the workpiece, but alternatively may be operated in response to a predetermined condition of the workpiece, for example, a predetermined temperature which might for example be detected by an optical pyrometer.
Some such arrangement will of course necessarily be used where the invention is applied to electron beam heating apparatus other than welding apparatus where no movement of the workpiece occurs as a result of heating.
WHAT WE CLAIM IS:
1. An apparatus for heating a. workpiece wherein an electron beam is directed in operation onto the workpiece via an
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (9)
1. An apparatus for heating a. workpiece wherein an electron beam is directed in operation onto the workpiece via an
aperture and means is provided for altering a dimension of said aperture in response to heating of the workpiece, thereby to alter the heating effect of the electron beam on said workpiece.
2. An apparatus according to Claim 1 for use in welding a workpiece, said means for altering a dimension of the aperture is arranged to operate in response to melting of the workpiece, thereby substantially to cut-off the electron beam.
3. An apparatus according to Claim 2 wherein a part to be welded is urged into abutment with another such part during a welding operation, and said means for altering a dimension of the aperture is arranged to operate in response to movement of said one part consequent upon melting of abutting portions of the parts being welded.
4. An apparatus according to Claim 3 wherein said aperture is partly defined by a member which is coupled to said one part to be welded for movement therewith.
5. An apparatus according to any one of the preceding claims wherein said aperture is an aperture in an anode incorporated in an electron gun producing the electron beaim
6. An apparatus according to any one of Acclaims 1 to 4 wherein said aperture is defined by mental parts which serve to shape the electric field in the region of the electron beam but are electrically isolated from the power supply for the electron gun in operation.
7. An apparatus according to any one of the preceding claims wherein the electron beam is produced by a glow discharge electron gun.
8. An apparatus according to Claim 7 wherein the alteration of a dimension of the aperture is arranged to affect longpath breakdown in the electron gun and thereby affect actual production of the electron beam.
9. An electron beam heating apparatus substantially as hereinbefore described with reference to the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1611877A GB1582707A (en) | 1978-04-18 | 1978-04-18 | Electron beam heating apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1611877A GB1582707A (en) | 1978-04-18 | 1978-04-18 | Electron beam heating apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1582707A true GB1582707A (en) | 1981-01-14 |
Family
ID=10071507
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB1611877A Expired GB1582707A (en) | 1978-04-18 | 1978-04-18 | Electron beam heating apparatus |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB1582707A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2140199A (en) * | 1983-04-19 | 1984-11-21 | Balzers Hochvakuum | A method of heating products |
-
1978
- 1978-04-18 GB GB1611877A patent/GB1582707A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2140199A (en) * | 1983-04-19 | 1984-11-21 | Balzers Hochvakuum | A method of heating products |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed | ||
| PCNP | Patent ceased through non-payment of renewal fee |