DE2008783A1 - Method for assembling an X-ray tube - Google Patents

Description

"Procedure for assembling an X-ray tube"

The invention "relates to a method of assembling a X-ray tube, the glass bulb of which is glazed onto a ring made of an alloy, which approximately resemble ά ^ ν V / has a coefficient of thermal expansion like glass, with the Ring with one of the electrodes, preferably the anode, connected is.

X-ray tubes of this type are known, for example AU3 US ή - Patent 2,431 Ζ'Π. The ring generally consists of an iron, nickel, or kofcalt alloy which is known under the Indian names Vacon or Kovar. This ring is hard soldered to the solid copper anode (soft soldering is out of the question because of the high operating temperatures of the anode). During hard soldering, the metal ring can be heated to above the glass rupture point, so that it is necessary to solder the ring to the anode and - after cooling down the tempering between the glass bulb and the ring -

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gain weight. This results in various sewing parts in practice.

Since the final closure of the vacuum vessel takes place in the known method in glass blowing, it leaves do not prevent impurities (dust or the like) from getting into the tube. Also oxidizes in the in most cases the ring when glazing. If, when the X-ray tube is heated, atoms from this oxide layer are released, it comes - especially at high voltages - to disturbances (breakdown) in the X-ray tube .

Another disadvantage of the known method is that the residual stresses that occur after glazing in remain on the glass bulb or in the ring, cannot be completely removed. A "tempering", i.e. a repeated one It is hardly possible to heat the glass-metal connection until the glass becomes soft because the glass bulb is involved must be evacuated so that the external air pressure would compress the glass bulb.

Finally, a major disadvantage of the known method is that the anode and the cathode cannot be precisely aligned with one another. The reason for this lies not only in the generally used pinch foot structure through which the leads to the cathode are passed, but also in the fact that the anode and cathode can never be clamped and glazed at the same time, because the inside of the flask has to be filled with nitrogen during the annealing process tarnishing of the anodes or cathode components is prevented. During the glassing of the cathode, the glass bulb is therefore closed at its anode-side end with a stopper and through a pump nozzle attached to the cathode side

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Nitrogen supplied. Then the stopper is pulled out and the anode is covered with glass, whereby nitrogen is again supplied through the pump nozzle. The alignment of the anode with the cathode depends essentially on the eye of the glass blower. It will be understood that more precise alignment is not possible with this method. This is a serious disadvantage in particular in the case of omnidirectional X-ray tubes with a conical anode, in which the electron beam hits the tip of the anode cone, because then the X-ray yield is not the same in all directions around the cone.

The invention has the object of eliminating the disadvantages mentioned similar to '. In a method of the type mentioned at the outset, this task is achieved according to the invention in that first a ring is glazed on each side of the glass bulb and that then the anode and the cathode are welded to the rings.

The invention is explained below using an exemplary embodiment shown in the drawing, which is a view of an X-ray tube manufactured by the method according to the invention.

The drawing shows an X-ray tube with a metal bulb 1, a cathode 2 and an anode 3. The anode 3 * is welded to a ring 5 which is glazed onto the glass bulb. Likewise, the cathode 2 or the metal disk 7 welded to the cathode cylinder 6 made of metal is welded to a ring 4 which is glazed onto the glass bulb 1.

The assembly of this tube proceeds roughly as follows: The two rings 4 and 5 are clamped into the coaxially running chucks of a suitable device and glazed onto the glass bulb 1. The ones that are created during glass-fitting

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Glass tensions are then eliminated by tempering. Tempering results in temperatures which lead to oxidation or tarnishing of rings 4 and 5. The oxide layers and any other impurities can be chemically or mechanically in a known manner (Sandblast cleaning). The glazing can then be examined for any leaks so that even at this stage any leaky fumigation can be improved.

Then the welding of the anode 3 or the takes place Cathode 2 with rings 5 or 4. Suitable for this purpose \ especially that under the name "Argonarcschwaißverfahren "Known processes. Here the arc or the welding point is flushed with argon. Except Argon, other protective gases can also be used to prevent oxidation. Let go of these procedures almost point-like welds reach, so that the heating of the rings or the anode or the cathode close to the weld is very small. This is essential because otherwise the order of the Steps of the known process - first connect ring and anode, then glaze on - cannot be reversed. the The temperature of these areas can be adjusted if the setting is appropriate Keep the arc current below 100 degrees. One advantage of this process is that it is all in one so-called "white room", i.e. in one provided with airlocks and the like, almost dust-free room. First, the anode is clamped in a lathe chuck, the glass bulb or the one on it Glazed ring 5 is slipped over the anode and placed on a projection 8 on the anode 3, which is attached to one of the Copper anode brazed ring 9, which consists of the same material as the rings 4 and 5, is provided. The ring 9 is necessary for the weld, as the solid copper anode 3 is directly welded to the de; .. 5 ring because of the different melting points and the

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good thermal conductivity of the anode is difficult to achieve. At the same time, the disk 7 welded to the cathode cylinder 6 is inserted into a recess in the ring 4. During the welding of the anode, the inside of the piston is opened via the pump nozzle 10 fastened in the disk 7 purged with nitrogen. This rinsing also takes place during the subsequent welding of the disc 7 to the Ring 4.

The rings 4, 5 and 9 and the disk 7 are preferred Turned parts adapted to each other with tight tolerances

are. This results in a very precise alignment a

the cathode on the anode, so that only minor deviations are possible during production. These Deviations are sufficient in most applications.

In the case of omnidirectional X-ray tubes with a conical anode, however, these are also small deviations (less than 1/10

Millimeter) is still annoying because this means that the intensity of the X-ray radiation is no longer the same in the different directions. In order to achieve an exact adjustment in these cases, the cathode cylinder 6 can opposite the

Washer 7 may be bent.

Claims;

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Claims (4)

PATENT CLAIMS: 2008783 Method for assembling an X-ray tube whose glass piston on a ring made of an alloy with approximately the same coefficient of thermal expansion as glass is glazed, the ring being connected to one of the electrodes, preferably the anode, characterized that initially on both sides of the metal piston (1) each a ring (4, 5) is glazed and that then the cathode (2) and the anode (3) are welded to the rings (4 and 5) will. 2.) Method according to Claim 1, characterized in that the metal pistons are tempered after the chamfering and before the welding. 3.) Method according to one of the preceding claims, characterized in that the X-ray tube is prior to welding is cleaned chemically or mechanically. 4.) Method according to claim 3 »characterized in that before welding the anode (3) to the ring (5) a Ring (9) is soldered to the anode, which is then welded to the ring (5). 109838/0838 originally inspected