US3702212A

US3702212A - Method and device for the manufacture of electron tubes

Info

Publication number: US3702212A
Application number: US841751A
Authority: US
Inventors: Jean-Charles Viers; Robert Pierre Jaure
Original assignee: US Philips Corp
Current assignee: US Philips Corp
Priority date: 1968-07-16
Filing date: 1969-07-15
Publication date: 1972-11-07
Anticipated expiration: 1989-11-07
Also published as: DE1935300A1; FR1581684A; GB1265888A

Abstract

A METHOD AND APPARATUS FOR MANUFACTURING, WITHIN AN EVACUATED HOUSING, RADIATION SENSITIVE ELECTRON TUBES COMPRISING VAPOR-DEPOSITING A PLURALITY OF WINDOW SECTIONS OF THE ENVELOPE OF THE ELECTRON TUBE IN SEQUENCE, CHECKING FOR DEFECTS AFTER A LAYER IS FORMED ON EACH WINDOW SECTION UNTIL A WINDOW WITHOUT DEFECTS IS FOUND, AND THEN SEALING THIS WINDOW TO THE GLASS ENVELOPE COMPRISING THE ELEMENTS OF THE ELECTRON TUBE.

Description

N 7, 1972 JEANCHARLES VIEIRS E 3,703,212

METHOD AND DEVICE FOR- THE MANUFACTURE OF ELECTRON TUBES Filed July 15, 1969 .2 Sheets-Sheet l mm 'r 1 i 6 E 15 I F E 1 E Z i 5 j 1 I 1 C I v 1 w/ i g l 14 i P 8 n g 3 i i i l III II I I l I 9 I k g l Fug] INVENTORfi JEAN C. VIERS BY ROBERT P. JAURE 9 1972 JEAN-CHARLES VIERS ETAL ,702,

METHOD AND DEVICE FOR THE MANUFACTURE OF ELECTRON TUBES Filed July 15. 1969 .2 Sheets-Sham 2 INVENTORJ JEAN c. VIERS By ROBERT P. JAURE United States Patent 3,702,212 METHOD AND DEVICE FOR THE MANUFACTURE OF ELECTRON TUBES Jean-Charles Viers, Brive-la-Gaillarde, and Robert Pierre Jaure, Rolland-Brive-la-Gaillarde, France, assignors to US. Philips Corporation, New York, N.Y.

Filed July 15, 1969, Ser. No. 841,751 Claims priority, application grance, July 16, 1968,

Int. Cl. H015 9/38, 17/36 U.S. Cl. 316-3 7 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a method and device for the manufacture of electron tubes, particularly tubes comprising elements having a sensitive layer.

It is known to assemble and treat components of an electron tube in a vacuum space and to seal it in the same space by using pressure and/ or heat. In this manner tubes Without exhaust tube are obtained, which have comparatively constant characteristics owing to their construction and seal in the same atmosphere.

The method disclosed in British patent specification No. 871,206 of Mar, 25, 1959 permits activating photocathodes of a cascade-type image intensifier, mounting the photo-cathodes in the glass envelope and sealing the latter in the same space. The photo-cathodes fixed to the internal surface of a large-diameter conical support are introduced by rotation of the cone about its tip into an activating furnace and then brought in front of the opening of the glass envelope, where a simple device permits introducing and disposing them in place.

The part of the glass envelope intended to receive the treated elements is placed in a mount integral with the movable part of a screw press, whereas the part intended to seal the tube is placed on the stationary part of the press. The two metal rings forming the edges of the two parts of the envelope are cold-weldedto each other under a predetermined pressure.

This manufacturing method permits eliminating given causes of pollution involved in carrying out the activation and the assembling in separate spaces. The simplicity of the activating operation consisting in a single heating operation permits using the device described. However, the required dimensions of the support assembly are fairly large and partly necessitated by the conical support and its way of operating. Therefore, the volume of the vacuum bell in which the various operations are carried out, is large, which involves a comparatively long time for exhausting and degassing, so that the efliciency is limited.

These disadvantages are partly eliminated by the device disclosed in French patent specification 1,434,291 of Feb. 23, 1965. The method also disclosed in said patent specification permits manufacturing photo-multipliers. These tubes comprise a sensitive layer deposited on the input face for the radiation.

The glass envelope comprising the mechanical elements of the tube is inserted into a device for pressurized closure similar to that described above, arranged in an exhaustable space, while the envelope portion forming the 3,702,212 Patented Nov. 7, 1972 window is disposed opposite the envelope against the stationary part of the press. After a satisfactory vacuum is attained the sensitive layer is formed in situ by bringing one or more Vaporizers above the window. The evaporation times are adjusted so that a layer of desired characteristics is obtained.

Before the tube is closed, the layer is checked. If the measures do not yield results corresponding to the desired characteristics, the operation is stopped. It is then neces sary to allow air to enter in order to be able to withdraw the bell and to replace the defiective window. Then the sequence of operation is repeated.

When it is necessary to change the Window in this way, the loss of time is very considerable, Moreover, the comparatively great displacement of the Vaporizers is critical on account of the electric connections.

The method and the device in accordance with the invention are related to the methods and devices of the type described above and eliminate the disadvantages involved in an accidental formation of a defective sensitive layer, since the formation of a new layer has only little influence on the rhythm of the production.

The method according to the invention for the manufacture of electron tubes in which a sensitive layer is formed in the same space where the tube is exhausted and sealed, is mainly characterized in that the formation of the sensitive layer is carried out after a support is arranged above one or more stationary Vaporizers, said support provided with the sensitive layer being located in front of a checking device permitting defining the characteristics of the layer prior to its incorporation in the structure of the tube, while a further sensitive layer is formed on a further support also located in the space only when the first layer is found to be defective.

According to the invention the device for the manufacture of electron tubes comprising a housing containing a vacuum, a device for holding and sealing by pressure an electron tube, a vaporizer to form the sensitive layer on a support, is mainly characterized in that the vacuum comprises at least two supports to form the sensitive layer, which supports are independent of each other.

The invention will be better understood with reference to the accompanying drawing, which is given by way of non-limiting example.

FIG. 1 is a general view of the device in accordance with the invention illustrating the positions of the vaporizers and a target support.

FIG. 2 is a plan view of the device.

' FIG. 1 shows the whole system for treating and sealing. Beneath the vacuum bell 10 is arranged an auxiliary member 11 comprising the electric through-connections for feeding the vacuum pump, the vaporizers and the checking devices for the sensitive layer; at 12 is arranged the jack-screw integral with the movable portion 14 of the press for welding together the parts of the tube in the cold state and at 9 is arranged the vacuum channel between the space and the secondary pump.

The press for sealing the tube comprises (see FIG. 1) two columns 1 firmly secured to the base plate of the housing containing a vacuum, while the piston of the screw 12 passes through the plate via vacuum-tight bellows 3 and bears on a transverse member 14 adapted to slide along the two columns 1; a support 2, secured to the transverse member 14, receives the glass envelope of the electron tube comprising already the mechanical components. At the ends of the two columns 1 a transverse member 15 serves as a stop and withholds the front part 5 of the tube, so that the two tube portions can be sealed together by pressure.

This front part of the tube 5, forming the window, is fixed prior to its disposition on the transverse member 15,

to a support adapted to move around a shaft 6, whose rotation is controlled at 7 from without the vacuum space with the aid of a mechanical device 8 or the like (FIGS. 1 and 2), which is vacuum-tight.

The vaporizer 4 is secured to the support 2 of the electron tube, whereas the support of the window 5 is moved to a position above the vaporizer. The distance between the window and the vaporizer may be varied by actuating the screw and since the vacuum space comprises at least two window supports, the axes of the window supports are located each on one side of the vaporizer so that the distances 'between the axes of the supports and the centre of the vaporizer and the centre of the stop of the press are equal.

The method in accordance with the invention comprises the following steps: the vacuum bell is lifted from the base plate and a window is placed on each of the supports (adapted to move about the shafts 6 and 16) (FIG. 2). The vaporizer 4 is filled with the substance intended to form the sensitive layer and after the tube portion to be sealed is placed on the support 2, the bell is put on the base plate and exhausted through the channel 9. The diameter of this channel is very large as compared with the dimension of the base plate; since, in addition, the secondary pump directly communicates with this channel, the efiiciency is at a maximum so that the exhaust time is comparatively short. During the exhaust operation the windows are in extreme positions 17 and 17'.

When the desired vacuum is attained, one of the windows is moved into the position 18 directly above the vaporizer 4, after which the sensitive layer is formed by the evaporation of the various substances contained in the vaporizer. For the duration of this operation up to the end the formation of this layer is checked so that in the event of defects the process can be stopped and the window can be replaced by a second window for a new formation without the need for opening the vacuum space.

The disposition of the mechanical elements, i.e. the eccentric position of the jack-screw, leaves an important part of the base plate unoccupied so that direct pumping can be carried out with a minimum loss in each stroke.

Moreover, the disposition of the pumping gear permits of minimizing the height of the part 11 (FIG. 1), which now serves only for the various electric through-connections. a

The disposition of at least two independent window supports provides considerable advantages:

the volume of the vacuum space is smaller than in the case of a common support, sparing of at least one window ready for use in the event of a defect of the first window avoids the quite considerable loss of time involved in the necessity of breaking the vacuum in the space for exchanging the window and for reobtaining the operative conditions;

the time of pumping and degassing is fairly long and it is often only possible to manufacture one tube a day, when the operation is successful from the start.

What is claimed is:

1. A method of manufacturing radiation sensitive tubes from envelopes having base and window portions comprising positioning said window portion at a first position within an evacuated housing, forming a first sensitive layer upon said window portion, checking for defects in the first sensitive layer while said window portion is in said first position, moving said window portion to a second position within said evacuated housing, sealing said window portion to said base portion if said sensitive layer is free of defects without interrupting the vacuum in said housing, and forming a further sensitive layer on another window portion at said first position only when said first sensitive layer is found to be defective.

2. Apparatus for manufacturing radiation sensitive electron tubes from envelopes having a base portion and a window portion with a sensitive layer comprising an evacuated housing, supports for positioning said window portions in first and second operating positions within said housing, at least one vaporizer within said housing to form the sensitive layer on said window portion while said window portion is in said first position, means within said housing for checking for defects in said sensitive layer while at said first position, and a device within said housing for holding said base portion in said second position and sealing said window portion to said base portion if said sensitive layer is free of defects, said vaporizer forming a further sensitive layer on another window portion at said first position only when said first sensitive layer is found to be defective.

3. Apparatus for manufacturing radiation sensitive electron tubes as claimed in claim 2 wherein said holding and sealing device comprises movable and stationary sections of a press, said stationary part having rotatable members supporting said window portions on each side of said vaporizer to make the distances from the rotatable members to the centers of said vaporizer and the center of said press equal.

4. Apparatus for manufacturing radiation sensitive electron tubes as claimed in claim 3 wherein the center of said window portion coincides with the center of said vaporizer when said vaporizer is depositing said sensitive layer and with the center of said press when sealing said support to the glass envelope comprising the elements 0 said electron tube.

5. Apparatus for manufacturing radiation sensitive electron t-ubes as claimed in claim 2 further comprising means outside said housing for independently positioning said window portions and operating said holding and sealing device.

6. Apparatus for manufacturing radiation sensitive electron tubes as claimed in claim 2 further comprising external means for evacuating said housing.

7. Apparatus for manufacturing radiation sensitive electron tubes as claimed in claim 6 wherein said evacuated housing provides for direct pumping with a minimum loss by said external means for evacuating said housing.

References Cited UNITED STATES PATENTS 5/1967 Keller et a1 3163 2/ 1968 Yoshida et a1. 3163 US. Cl. X.R. 3163l