DE1026003B - Process for the production of airtight vessels for electron tubes or the like. - Google Patents

Description

The invention relates to the production of airtight vessels from parts to be connected to one another as used for example for electron tubes.

The airtight vessels are produced in a manner known per se by placing the edge of one of the Parts to be connected to one another or both parts before joining an order of vitreous Email receives and the connection point of the pressed parts is locally heated so high that it, without melting, softens.

In the known methods for producing airtight vessels, two are always different from one another perform thermal operations, namely the connection of the parts forming the vessel and the degassing of the vessel. In the known methods, the degassing and the pumping out take place after the individual parts of the vessel are finally connected to one another. Some of the known methods have the deficiency that When connecting the vessel parts, the electrodes are in an oxygen-containing medium and therefore often worsened by oxidation. This process can also be under the influence of temperature result in a local weakening of the parts forming the vessel. That has a considerable amount of waste result.

In another method, which is intended in particular for the production of miniature tubes, the Above mentioned connection with the help of enamel at low temperature the mentioned local weakening of the tube parts avoid. In this process, too, the connection of the tube parts is only made by a single thermal Operation causes, and the degassing and pumping out of the pipes only takes place after the pipe parts are finally connected to each other. Such a process determines the shape of the tube and its wall thickness not changed. However, the connection of the tube parts takes a relatively long time, and the aforementioned Deterioration of the electrodes is not eliminated.

Finally, it is already known to effect the connection of the vessel parts after the electrodes in a non-oxidizing atmosphere. Such a procedure is cumbersome and it increases the Manufacturing costs.

The invention has the task of remedying the deficiencies outlined. This is done in a process for the production of airtight vessels for electron tubes or the like from parts to be connected to one another, in which the edge of one of these or both parts is coated with vitreous enamel before being joined and the connection point of the pressed parts is locally heated to such an extent that that it softens without melting, achieved according to the invention in that the connection point of the vessel parts first by a short process to produce airtight
Vessels for electron tubes or the like.

Applicant:

Compagnie Generale de Telegraphie
sans FiI, Paris

Representative: Dipl.-Ing. E. Prinz, patent attorney,
Munich-Pasing, Bodenseestr. 3 a

Claimed priority:
France 30 August 1952

Raymond Chaffotte and Pierre Nancbino, Paris,
have been named as inventors

time W ^T is heated ärmestoß until it undergoes a temporary seal that is sufficient for an adjoining Auspumpung and degassing the vessel, during which it is then kept the temperature at a level at which the final connection of the vessel parts is carried out by molecular surface diffusion. The final connection and sealing of the vessel is made with the help of enamel at a low temperature while the vessel is on the pump. The brief thermal shock is intended to locally heat the zone in which the connection of the assembled vessel parts comes to a temperature which is below that which is normally used in the known connections working with enamel. On the other hand, however, this temperature should be sufficient to allow the enamel to become plastic. The pressure that is simultaneously exerted on the parts to be connected is intended to produce a hermetic seal through close contact between these parts.

This preliminary sealing is carried out in a relatively cold state, so that the electrodes are deteriorated avoided and the subsequent pumping out of the vessel can be made possible.

In the further course of the process, the vessel is pumped out to the desired vacuum, the temperature lowered to a certain point and at

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this temperature position causes the degassing. These three pressures are held on the edge of the piston B. Process steps can take place more or less simultaneously. A cylindrical jacket P _{1 is} carried out on the wires f _z and f _i. The final connection and sealing of the glass fabric is fastened in such a way that it encircles the vessel parts at the same time through the molecular upper side wall of the piston B. This jacket P ₁ has area diffusion instead. 5 the task of the electrodes E against heating by

In order to protect the electrodes very effectively against direct irradiation, if the resistor R to the heat occurring during the connection process and thus _{to ensure the ring body F 1} at a high temperature, it is advisable to bring the parts of the vessel with.

Protective means to surround the supply of heat. Assume that the foot .4 and the piston B

Butt to the points of contact of the edges, which are too much made of ordinary glass, the expansion-binding parts of which, with simultaneous damping, have a coefficient of about 95 · 10- '. For the enamel forming the layers on the remaining sections of the tube, a., And δ ₂ are possible as main components. Lead oxide, boric acid, a small amount of silicon dioxide

The thermal shock and the degassing can be assumed with the help of soda and a coefficient of expansion of about a heating device or with the help of two separate 15 100 · 10 ^ ^7. It is known that such facilities are effected. Email through appropriate dosage of its constituents

The drawing illustrates, for example, execution share a coefficient of expansion between 80 and embodiments of the invention, namely 110 x 10 ~ ⁷ may have. With such an email type

1 shows a section through an assembled tube, the lower deformation limit at about 370X and on which a device is placed which causes a preliminary melting temperature of about 600 ^: C. the

Fig. 2 is the thermal diagram of the method and resistor R (Fig. 1) placed a strong heating current, so

3 shows a schematic sectional illustration of an additional enamel powder layers very quickly, for example assembled tube below a drying oven. after a heat surge of 1 to 3 minutes, to one

The edges of the temperature to be connected, consisting of glass, which the lower limit of the tube parts A and B are designed so that they far exceed the deformation temperature of the enamel, have mutually complementary conical surfaces. In other words, the temperature at the enamel edges, an enamel layer a « or b _{2 is} applied. of the above composition 370 "C. For this purpose, the edges of the to be joined are exceeded in order to soften it. Immediately after parts are immersed in a paste, which is essentially made up of enamel powder in suspension in this thermal shock Stand R switched off to lower the temperature to below After the application has dried, baking takes place to drop 370 ° C. For this purpose, the parts are put into a special oven, in moderate, part F from to produce a substance which has the enamel powder layers in the layers a " and low thermal inertia. The course of this heat oil ₂ can be converted from vitreous enamel, which is _{fixed at the 35 treatment process by the curve ^ 1} in the edges of parts A and JS These layers bounded by the points t = 0 and t = P can then be subjected to fire polishing order. This curve shows that the surfaces of layers ₂ and ₂ are very smooth, but the temperature of the enamel in 1.5 minutes of 25 shows slight undulations. In any case, the 550 ^: C increases and lie between t = 1.5 minutes and layers of vitrified enamel, which fall ^{to 370 1} C at 4 ° t = 3 minutes (t = P). The enamel is covered with the swept surfaces of the two edges and therefore not melted when cold, but only imperfectly attached to one another in the state, so that they have been softened to a degree that is sufficient to generally not seal the two points of contact. The enamel layers a "and b" under the effect of the weight thickness of the enamel layers may be between 0.1 and 0.5 mm of the mass m (Fig. 1) are plastic and are flatten, depending on the enamelled area, the profile 45 to let them penetrate intimately into one another. In that of part A or B and depending on the practice used, the heat treatment described above becomes material. experimentally adjusted so that the interpenetration

Parts A and B are simply put together. Those of the surfaces of the enamel layers held to an extent-current feedthroughs C ₁ and C ₂ are located with the foot A sufficient to connect the tube to a pressure of by glass beads ^ ₁ and g ₂ , and they carry the 50 10 ~ ⁵ to be able to pump out up to 10 ^ ^{7 mm Hg.} In the case of these electrodes, which are represented in their entirety by the rectangle E setting is the resistance of the glass to the. The part B is extended in particular by a pump approach q Influence of rapid temperature changes. to be taken into account during the temperature drop. At the

The assembled tube is arranged vertically. At the end of this treatment process, the condition of the and the pump attachment q is checked with an electrode (not shown). Taking into account all the Förde vacuum pump connected. struggles and conditions, namely the resistance of the

On the assembled tube a device parts against rapid changes in temperature, the duration, which has an annular part F , the amplitude of which and the amplitude of the thermal shock and the upright inner edge is supported on the edges of the foot A. Keeping the electrodes in good condition, they can also have an annular part F ₁ , in which an electrical heating resistor R is arranged in which the expedient implementation of the method is determined. This den. By means of the protective jacket P ₁ (FIG. 1) or a similar resistor, an advantageous compromise between the power source S supplied electrical current to mutually contradicting requirements is facilitated by a controllable device. Whether desired temperature be brought. The ring - although the protective jacket is very useful, it is nevertheless a shaped part F ₁ has a circular slot f ₁ , 65 not always essential.

which is the direct irradiation of the contact zone of the At the end of the heat treatment described is the

Enamel layers a ₂ and δ ₂ with the state of the edges of the parts by the resistance R such that the enamel allows heat generated. On this device layers a " and &" are slightly deformed, so that their an annular mass m of wires f _s and f _{4 are} flattened surface corrugations and the two hangs, so that the edge of part A is somewhat 70 layers hug each other closely. The one so achieved

Contact is not yet the final connection between parts A and S because it does not have sufficient mechanical strength. In this state, the two parts A and B of the cooled tube can easily be separated from one another by turning the foot A relative to the piston B. If the duration and the amplitude of the thermal shock have been selected too high, it can always be determined whether a treatment according to the invention has been carried out if the tube is broken at the point of contact between the edges of the parts. It then follows that the break occurs preferentially in this contact zone and not at any other point without giving preference to this zone, as is always the case with a tube manufactured according to the previously known joining process. J-5

When the contact of the parts of the vessel is in the described state, which corresponds to the point P of the curve - _x of FIG. 2, the vessel is pumped out. From this point on there is no longer the slightest risk that the electrodes will oxidize. In addition, the temperature of the enamel is below its softening temperature, so that there is no need to fear that the contact will be damaged by the outside air pressure and by the release of bubbles in the enamel layers. From point P '(Fig. 2), which is adjacent to point P, from which the tube is evacuated, the tube is placed in a degassing furnace, the temperature of which is kept below the deformation temperature of the enamel but above the temperature which corresponds to the transformation point of the material. When using the enamel described above, the furnace is kept at a temperature of about 350 ° C. After 8 or 10 minutes of degassing (step PD in FIG. 2) and after cooling the tube to about 250 ° C., the tube is removed from the furnace.

In the treatment process described, in addition to degassing, a final connection is also achieved. At the temperature of the furnace there is a gradual transition of the intimate contact of the surfaces a _% , 5 _{2 of} the enamel layers into a connection, so that a single homogeneous enamel layer is obtained after completion of the degassing process. This process can be explained by the molecular diffusion or connection in the solid state of the two surfaces that are in close contact. -

Of course, the specified temperature values can vary depending on the type of enamel used and can be varied according to the heating conditions and the pressure applied in the contact zone. Above all can by increasing the pressure with which the parts are pressed together, the temperature peak of the Thermal shock can be reduced accordingly.

The temperature at which the parts are pressed into one another must be chosen so that they are between the baking temperature of the enamel and the temperature of the Littleton point (softening point) lies. The baking temperature is the one at which the enamel flows due to its own weight and wets the surface of its base. At this temperature its surface tension becomes greater than its viscosity. Under these conditions, the two enamel layers can completely merge into one another secure without excessive flattening of the latter.

The connection temperature (stage PD in FIG. 2) must be kept between the temperature at which air bubbles form in the enamel mass under the effect of the vacuum and the annealing temperature, which generally corresponds to the transformation point of the enamel.

This condition is very important and decisive with regard to the quality of the connection. As already mentioned, there is one in enamel as in every glass-like substance including large quantities of gases which tend to escape under the vacuum and ideinste Air bubbles form on the surface of the enamel, which make the connection spongy and its strength and affect their ability to seal airtight. To avoid the aforementioned disadvantages, once the vacuum is established in the vessel, the temperature of the junction zone must be lowered rapidly be, at least to a value that gives a sufficiently high degree of viscosity, which the counteracts the aforementioned phenomenon. However, the temperature must be increased to a value at which the enamel mass becomes sufficiently compact and dense so that it prevents the trapped gases from escaping.

The lower limit of this temperature range is given by the glow point of the enamel, below which this ceases to diffuse between the surfaces in intimate contact at normal pressures.

When the above conditions are taken into account, one will be obtained by pushing the parts together intimate contact, without the liquid state of the enamel being reached, which is under the action of the exerted pressure flattens out slightly without it being completely flattened and leaking. On the other hand, lets achieve a connection without the formation of air bubbles, so that the enamel mass in a homogeneous Condition remains, and in addition, there are no excessive deformations.

When using types of enamel, the qualitative composition of which was similar to that described above, but which had lower expansion coefficients and contained slightly less lead oxide (Pb O ₂ ) and slightly more silicon dioxide (SiO ₂ ), the difference being about 5%, the following values were determined :

The temperature at which the parts are pressed into one another (T ₂ in FIG. 2) was chosen between 585 and 435 ° C. The outside of the joint was suddenly brought to the mentioned temperature by a thermal shock for a very short period of time.

The bonding temperature was chosen between 450 and 35O ⁰ C.

With the Auspunpem was started after the temperature below 450 ⁰ C, below which no blistering was more done dropped.

The enamel used had a coefficient of expansion of 95.10 ^-6 . Its viscosity was 10 ¹³ poise for the glow point. For the Littleton point (softening point) it fell to 10 ^{7> G5} poise, which represents a lower limit below which the parts can no longer be pressed into one another. ^{It decreased to 10 6} poise for the limit at which blistering occurred under vacuum.

The enamel layer was applied on the edge of a glass bulb of calcium soda glass with a annealing point between 510 and 52o ⁰ C and an expansion coefficient of about 92 · 10. ⁶ Only the flask was enamelled, which was placed on the base of the tube made of the same glass, which was not coated with enamel. The aforementioned enamel completely diffused into this glass and bonded to it directly through molecular surface cohesion.

When the parts were pressed into one another, the pressure exerted on the enamel was between 0.2 and 0.5 kg / cm ² . This pressure can vary depending on the condition of the surfaces to be connected, the shape of the contact and the contact cross-section, and the temperature used

Claims (2)

etc. can be changed. For example, if the peak temperature is reduced and a support is used that counteracts excessive deformation of the enamel layer, the pressure can be increased to 1 kg / cm2. In contrast, for the connection process, the pressure is determined by the total cross section of the tube exposed to the outside air pressure and by the cross section of the connection that absorbs this pressure. The enamel leads the two heat treatment processes with the help of a single heating means, namely through the furnace. In this case, however, one is forced to use separate ovens for each tube or for a group of several tubes on a fixed pump connection bank, which can lead to disadvantages. The method described in connection with FIG. 1 permits the use of a rotatable pump connection disk with a circularly arranged pump. As can be seen from FIG. 3, the two heat treatment processes, namely the supply of the thermal shock and the degassing, can be carried out with the aid of one and the same means. According to FIG. 3, there is one that allows the enamel to diffuse into the glass of the non-enamelled edge, thus ensuring the formation of the final connection. In certain cases, curved, for example spherical, contact surfaces that complement one another are used. In this case it is sometimes advantageous to give the convex surface a smaller radius of curvature than the concave surface, since this allows the penetration process to achieve a degassing tunnel between 2 and 10 kg / cm2. Such a pump connection disk will experience pressure. is known per se, so that its description can be. Pumping down to a pressure of 10 ~ 4 mm Hg, the rest. With the use of such a disk the degassing of the tube is made possible, happens very quickly, with the heating device shown in FIG. H. in a few seconds, exerted by the sudden impulse of heat at the entrance of the furnace tunnel, the tube to the vacuum pump close at time. can be removed from the tunnel again. The latter method is preferable because the ultimate bond can be favored by the application of pressure. Of course, this pressure can be generated with the aid of an adjustable spring or by any other means. In certain cases, as already mentioned, it is possible to enamel only one of the edges. If, for example, it is a part made of glass and a part made of joined tube, which is the enamelled ceramic shown in Fig. 1, then these parts can be used in the same way with the aid of a mass m as they are are, d. H. without a repeated and a part F charged. This tube is under an enamelling. In this case, the penetration of the furnace shown in the upper part of FIG. 3 is arranged. Enamel layer that covers the edge of the ceramic part, the latter has an outer jacket V1 as well as an inner one in the glass part caused by the thermal shock. The antechamber F4, which forms a cylindrical, open at the bottom 30-barrel connection, has the same properties as the cavity and is dimensioned so that it is as described above. If you now warm to the temperature, a small amount of space can be slipped over the tube. An electrical resistor V2 is arranged between the outer jacket and the inner chamber of the furnace and is connected to the power supply terminals X1 and X, which are connected to a controllable power source (not shown). A part F3 connects the furnace to a device, not shown, by means of which it can be raised and lowered. The parts of the furnace must have a suitable thermal inertia that is relieved during the thermal shock, which is set experimentally and on the basis of the following calculation documents. usual tubes for the radio-technical need, After the furnace by a heating current I1 on a triodes, pentodes and cathode ray tubes, manufacture. Temperature T1 has been brought, it is lowered so that the process can also be used for the manufacture of any other vessel that surrounds one of the tubes A and B at the point of contact of the parts A 45. At the same time, the current is regulated to a degassing equivalent heat treatment value i2, which is lower than iv the furnace will. cools down by releasing heat to the edges of parts A and B that are in contact with each other. bonds between parts made of different fabrics. The temperature of these edges rises rapidly, becoming 50 such. B. different types of glass, ceramic materials reach the temperature T2, which is the thermal and metals, applicable. Equilibrium of the aggregate. The temperature of the unit then drops to a point which corresponds to the point in time P 'of curve d & of FIG. As can be seen from this figure, the curve d2 deviates from the curve ax described above only during the temperature drop. This is due to the fact that the thermal inertia of the furnace used for the treatment process just described is always higher than that of the small heating ring shown in FIG. In the present case, the pumping out takes place at point P '. The degassing is then carried out, for which purpose the furnace shown in Fig. 3 is completely lowered so that it completely surrounds the tube. The current u is regulated in such a way that the unit consisting of tube and furnace is kept at the desired heat treatment temperature, which is maintained up to point D '(FIG. 2). This procedure takes a little more time than the one described above, but allows you to run through .T ~ XTAXSPRÜGHE: 1. Process for the production of airtight vessels for electron tubes od. Like. From each other too connecting parts, in which the edge of one of these or both parts before joining a Order of vitreous enamel received and the connection point of the pressed parts locally is heated so high that it softens without melting, characterized in that the connection point initially heated by a brief burst of heat until it forms a temporary seal learns that is sufficient for a subsequent pumping out and degassing of the vessel, during which the temperature is then maintained at a level at which the final connection of the Vessel parts takes place through molecular surface diffusion. 2. The method according to claim 1, characterized in that the enamel layer is a fire polishing is subjected. 10 Documents considered: German Patent No. 709 201; Swiss Patent No. 234 666; German patent application N 1484 VIIIc / 21g; Philips ¹ tech. Rdsch., 8, 1946, pp. 290, 291. 1 sheet of drawings