SE445621B - PROCEDURE FOR THE PREPARATION OF A SODIUM FILLED VALVE - Google Patents

Description

8006097-3 By evacuating the cavity, all oxidation of the sodium and thus aging of the device is avoided. In addition, no foaming occurs, so a very constant heat transfer can be obtained.

In a first embodiment of the method, the channel with a small cross-section must lie in the valve disc. In this way it is achieved that both during the production of the duct with a small cross-section and thereafter during the closing, no thermal or mechanical loads affect the already closed filling hole.

In another embodiment, the channel with a small cross-section must be arranged as an axial bore in the filling plug.

Finally, the channel with a small cross-section can also consist of a hole sloping towards the longitudinal axis of the valve stem through the wall of the valve stem.

In a preferred embodiment of the method, the channel is closed with a small cross-section by means of electron beam welding. The use of electron beam welding to close the cavity is a very simple and successful solution, since by means of electron beam welding a channel with a small cross section of the kind, which is only necessary for the evacuation, can be closed quickly and without problems and because at the same time the evacuation of the cavity within the framework of this electron beam welding automatically takes place in the vacuum chamber of the electron beam welding apparatus.

In a preferred embodiment of the method, the electron beam in the electron beam welding is guided circularly around the hole. In this way, it is achieved that the hole with a small diameter melts, without the electron beam through the hole possibly encountering the sodium present in the interior of the cavity. Namely, if the electron beam were to strike the sodium, this would entail a risk that the sodium would evaporate and thus during the melting of the small diameter hole in the cavity vapor pressure would form, which could push out the existing material melt. Furthermore, it is advantageous if, when drilling and / or closing the channel with a small cross-section, the valve is brought into such a position that the sodium is far from the channel. Also in this way a heating of the sodium should be avoided if possible.

Finally, it has been found that the channel with a small cross-section should preferably have a cross-section of about 1 mm 2, in order for the procedure to be carried out with the best results.

Finally, the method according to the invention can also be carried out in such a way that the cavity is evacuated via a duct with a small cross-section and closed in a vacuum-tight manner, by applying an extension to the valve stem by means of friction welding, the friction welding taking place under vacuum bell.

This embodiment is important insofar as it is often necessary to attach hollow valves to hollow valves, which have retaining grooves for fastening the valve springs. Such solid spindle end pieces are then usually attached by friction welding or burn welding to the end of the hollow valve spindle, whereby it may be advantageous to carry out this welding procedure in vacuum and thereby at the same time evacuate the cavity of the valve spindle.

The accompanying drawing serves to illustrate the method according to the invention.

In this case, Fig. 1 shows a sodium-filled disc valve in longitudinal section. Pig. Fig. 2 shows a filling plug for a poppet valve according to Fig. 1 and Fig. 3 shows a partial longitudinal section of the valve spindle of a poppet valve according to Fig. 1 in a special embodiment.

In Fig. 1, the valve spindle is denoted by 1. This valve spindle 1 is drilled hollow and to a large extent filled with sodium. A filling hole 7 is located on the rear spindle end and is closed with a plug 3, which is preferably welded together with the valve spindle 1 in place H. The cavity of the valve spindle 1 began to be drilled with a small diameter hole located in the middle of the valve plate 5. This channel 6 with 8006097-3 small cross section (dashed inriïad) is closed again by means of electron beam welding.

The filling plug 3 shown in oblique view in Fig. 2 shows a second possibility of arranging an evacuation channel.

In the second embodiment, the channel with a small cross-section is shown as a centered hole 33 through the filling plug 3.

The cut-out of a valve spindle 1 shown in Fig. 3 shows a further alternative of arranging an evacuation channel. The evacuation channel is then designed as a hole Sa sloping with the longitudinal axis of the valve stem 1 through the wall of the valve stem.

Claims (4)

s 8006097-3 P A T E N T K R A V A process for producing a sodium-filled valve with a cavity arranged in the hollow valve stem (1) of the valve, which is provided with a filling opening (2) of relatively large diameter through which sodium is introduced into the cavity, which is evacuated and sealed in a vacuum-tight manner. by means of a plug (3) arranged in the filling opening and / or welding and soldering, characterized in that the filling opening (2) in a first working operation is closed in a vacuum-tight manner by means of said plug (3) and / or welding or soldering and that in a second, subsequent work operation evacuation of the cavity takes place through a channel (6, 33) with a small cross-sectional area, which channel is separate from the filling opening or forms an axial central bore in the plug (3), after which the channel is finally vacuum-tight to - closed in a vacuum by welding or soldering. Method according to claim 1, characterized in that the channel (6) is located in the valve plate (5) of the valve. 3. A method according to claim 1, characterized in that a heel (island) inclined relative to the axis of the valve stem (1) is received in the wall of the valve stem (1) and forms said channel. 4. A method according to any one of claims 1-3, characterized in that the outer opening of the channel (6; 33) is closed by means of electron beam welding and that the electron beam is passed circularly around the opening.