US 3924087 A
An interruptor having a cylindrical metallic envelope and two cylindrical insulators secured to the envelope on both ends thereof in a vacuum tight fashion. The free ends of the cylindrical insulators support contact rods in a vacuum tight fashion. Contact members are then respectively secured to the contact rods, which members are arranged within the envelope. The contact rod of the movable contact member is secured to the associated insulator by means of a bellows. Both of the insulators have their ends secured to the envelope and are directed towards one another and disposed within the metallic envelope.
Claims available in
Description (OCR text may contain errors)
[ 1 Dec. 2, 1975 3,705,281 12/1972 Luehring..........i.............. 200/144 B l ge 0 Primary Examiner-Robert S. Macon Attorney, Agent, or Firm-Watson. Cole. Grindle & Watson  ABSTRACT An interruptor having a cylindrical metallic envelope and two cylindrical insulators secured to the envelope on both ends thereof in a vacuum tight fashion. The 72/3302 free ends of the cylindrical insulators support contact rods in a vacuum tight fashion. Contact members are ZOO/144 B then respectively secured to the contact rods. which H01 33/66 members are arranged within the envelope. The 200/144 B contact rod of the movable contact member is secured to the associated insulator by means of a bellows. Both References Cited of the insulators have their ends secured to the enve- UNITED STATES PATENTS lope and are directed towards one another and disposed within the metallic envelope. 3,590,185 6/1971 200/144 B 3,674,958 Attia et a1. 200/144 B 2 ai 1 Drawlng Figure Jan Christiaan Clason, Hen Netherlands Hazemeijer B.V., Netherlands Oct. 1, 1973 VACUUM CIRCUIT INTERRUPTOR Inventor:
Appl. No.: 402,129
Foreign Application Priority Data Oct. 2, 1972 Field of Search United States Patent Clason 2 EZWHU9W475W3BM 2 ll rill Illa Illlli IIII lll l l v I I I I VACUUM CIRCUIT INTERRUPTOR BACKGROUND OF THE INVENTION The invention relates to a vacuum circuit interruptor. Such an interruptor includes a cylindrical metallic envelope and two cylindrical insulators secured to the envelope on both ends thereof in a vacuum tight fashion. The free ends of the cylindrical insulators support the contact rods in a vacuum tight fashion, to which contact rods the two contact members are secured, which are arranged in said envqgpe. The contact rod of the movable contact member is secured to the associated insulator by means of a bellows. Such apparatus is disclosed in the US. Pat. No. 3,280,286.
The known vacuum circuit interruptor comprises a stainless steel envelope to which the insulators are secured in such a way that with respect to the envelope they are directed outwardly and point away from one another. One of the insulators at its free end is closed by a metal ring, to which the contact rod of the stationary contact member is secured in a vacuum tight fashion. The other insulator at its free end is secured vacuum tight to a bellows, which for the greater part is disposed in the insulator, the free end of the bellows being coupled to the contact rod of the movable contact member. In the space enclosed by the metal envelope and the two insulators high vacuum is present, in which an AC-current discharge develops if the contact members are separated, which discharge disappears at the next zero-crossing of the AC-current. The AC-current has then been switched off.
The volume of the vacuum space of the known circuit interruptor is relatively small so that the vapour pressure in the interruptor during the interrupting process will increase rapidly and may exceed a dangerous value of between to 10* mm mercury at which pressure the mean free path of the electrons becomes smaller than the maximum contact member spacing, so that a self maintained plasma discharge is formed, which will not extinguish by itself. Accordingly the circuit interruptor cannot interrupt the current flow anymore.
Moreover the contact rods of the known vacuum interruptor are relatively long and since the material thereof is usually soft copper, the rods can easily be deformed.
SUMMARY OF THE INVENTION The invention has for its object to eliminate the above defects and provides a vacuum circuit interruptor of the type specified above, which is characterized in that the two insulators from their ends which are secured to the envelope are directed towards one another and are disposed within said envelope.
I-Ierewith the advantage is obtained that with similar external dimensions of the vacuum interruptor, the vacuum space is increasedso that pressure rises during the interrupting process can be accomodated more easily. Thus in the circuit interruptor according to the invention the occurence of self maintained plasma discharges has been prevented. Also with the structure in which the insulators are directed inwardly the length. of the contact rods is much smaller so that deformations cannot occur anymore.
According to a preferred arrangement of the apparatus according to the invention the inner cylindrical surface of each insulator is provided with a sleeve of elastic insulating material and a stub of non-elastic insulating material, such as moulding resin, pressed into the sleeve, in such a way that no voids are present in the interface between the insulator and the sleeve nor in the interface between the sleeve and the insulating stub, each stub having an axial passage, in which the connecting rod of the associated contact member is disposed. In this arrangement the flash over voltage between the contact members of the interruptor around the exterior of the vacuum space is remarkably increased. In this case the insulators may be arranged shorter.
Finally it is also possible that the sleeves are integral with an insulating sheath, which is arranged across the external surface of the metal envelope. The sheath is not intended to prevent the metal envelope from being touched, since the envelope is normally not live, but to further increase the flash over voltage.
BRIEF DESCRIPTION OF THE DRAWING The invention will now be explained further in reference to an embodiment thereof referring to the drawing which shows a cross-sectional view of the interruptor according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing the vacuum interruptor comprises a cylindrical metallic envelope 1, to which two insulators 2 and 3 respectively, are secured, which are directed inwardly. These three members are disposed on one and the same axis. The connections between the insulators 2 and 3 on the one hand and the envelope 1 on the other hand are vacuum tight. To the insulator 3, which is the lower one in the drawing, a contact rod 5 is secured by means of a profiled ring 10. The contact rod 5 in turn supports the stationary contact member 7. The other insulator 2 is connected to a bellows 9 by means of a profiled ring member 18, and the other end of the bellows 9 supports the contact rod 4 for the movable contact member 6. In order to prevent copper vapour, which is liberated during the interrupting process and originates from the copper contact members 6 and 7, from depositing on the outer surfaces of the insulator 2 and 3, screen members 11, 12, 13 and 14 are arranged in the vacuum space. It is clearly visible that in the circuit interruptor according to the invention the contact rods 4 and 5 are very short, so that deformations thereof cannot occur. It also appears that with a predetermined axial external size the volume of the vacuum space 8 is a maximum.
The inter-cylindrical surface of the insulator 3 is provided with a rubber sleeve 16, an insulating stub 20 being pressed into the sleeve. The pressure between the insulator 3 and the sleeve 16 as well as between the sleeve 16 and the insulating stub 20 is so high that no voids are present in the interfaces between the insulator 3 and the sleeve 16 on the one hand and between the sleeve 16 and the insulating stub 20 on the other hand. A connecting rod 22 is arranged in the insulating stub 20, i.e. the stub 20 is moulded around the connecting rod, and the connecting rod 22 is secured to the contact rod 5 by means of a bolt 24. The upper insulator 2 is in a similar way provided with an elastic insulating sleeve 15, in which is pressed the insulating stub 19. Here also no voids are present in the interfaces be tween insulator 2 and sleeve 15 on the one hand and between sleeve 15 and insulating stub 19 on the other hand. The contact rod 21 is movably arranged in the insulating stub 19 to enable the movable contact member to be operated. The connecting rod 21 is connected to the contact rod 4 through the bolt 23. The circuit interruptor is illustrated in its opened position and it can be closed by operating the contact rod 21 in the direction of the arrow.
In the preferred arrangement according to the drawing the metallic envelope 1 is provided with an insulating elastic sheath 17, which is integral with the two sleeves l and 16. It is observed that the two connecting rods 21 and 22 are disposed outside the vacuum space and hence need not be made of copper but may consist of alloyed copper or hard drawn copper, for example, so that deformations of the connecting rods are not to be feared.
With respect to the absence of voids on both sides of the sleeves l5 and 16, it is observed that such voids between the connecting rod 22 and the insulating stub 20 are completely absent due to the method of making the stub, while the axial passage in the insulating stub 19, in which the movable connecting rod 21 is inserted is metallized, so that the hollow space between the rod 21 and the stub 19 is delimited by two electrodes, being connected to the same potential, so that no discharged can develop in this hollow space.
It is observed that the circuit interruptor according to the invention is well suited to be includedin a com- 4 pletely insulated high voltage apparatus. which is insulated with moulding resin. for example,
What we claim is:
l. A vacuum circuit interruptor comprising: a cylindrical metallic envelope; two cylindrical insulators secured to said envelope on both ends thereof in a vacuum tight fashion, said two insulators from the ends which are secured to said envelope being directed towards one another and disposed within said envelope; contact rods supported by free ends of said cylindrical insulators in a vacuum tight fashion; two contact members secured to said contact rods, said contact members being arranged in said envelope; one of said contact members being movable and the associated said contact rod being secured to the associated said insulator by a bellows; the outer cylindrical surface of each said insulator being provided with a sleeve of elastic insulating material, a stub of non-elastic insulating material, pressed into said sleeve, in such a manner as to be free of voids in the interface between said insulator and the associated said sleeve and in the interface between said sleeve and said insulating stub, and each stub having an axial passage, in which the respective contact rod of the respective contact member is disposed.
2. Apparatus according to claim 1, wherein said sleeves are integral with an insulating sheath, which is arranged across the external surface of said metal envelope.