US3562682A

US3562682A - Vacuum switching apparatus

Info

Publication number: US3562682A
Application number: US831951A
Authority: US
Inventors: Katsuo Ohwada; Noriyuki Ichihara
Original assignee: Tokyo Shibaura Electric Co Ltd
Current assignee: Toshiba Corp
Priority date: 1968-06-10
Filing date: 1969-06-10
Publication date: 1971-02-09
Anticipated expiration: 1988-02-09
Also published as: GB1263375A

Abstract

A VACUUM SWITCHING APPARATUS HAVING A STATIONARY CONTACT MEMBER AND MOVABLE CONTACT MEMBER DISPOSED IN A VACUUM VESSEL WHICH IS SO DESIGNED AS TO USE A PRESSURE EQUAL TO A DIFFERENCE BETWEEN THE INTERIOR PRESSURE OF THE VESSEL AND THE ATMOSPHERIC PRESSURE IN URGING THE MOVABLE CONTACT MEMBER INTO THE VESSEL FOR CONTACT WITH THE STATIONARY CONTACT MEMBER, CHARACTERIZED IN THAT THE FORCE OF CLOSING THE MOVABLE CONTACT MEMBER, THE FORCE OF A RESET SPRING MEANS FOR RELEASING THE MOVABLE CONTACT MEMBER BY MEANS OF AN OPERATING LEVER ENGAGING SAID MEMBER, THE INITIAL ATTACTING FORCE OF AN ELECTROMAGNETIC DEVICE FOR DISENGAGING SAID MEMBER AND THE ATTRACTING FORCE WITH WHICH THE CONTACT ELEMENT OF SAID ELECTROMAGNETIC DEVICE IS ATTACHED TO SAID MEMBER ARE ALL KEPT IN A PRESCRIBED RELATIONSHIP IN ORDER TO PREVENT THE RELEASE OF THE MOVABLE CONTACT MEMBER WHICH MIGHT OCCUR DUE TO THE BROKEN VACUUM OF THE VESSEL AT THE TIME THE MOVABLE CONTACT MEMBER IS CLOSED FOR CONTACT WITH THE STATIONARY MEMBER AND ALSO PREVENT THE SUCKING OF THE MOVABLE CONTACT MEMBER WHICH MIGHT BE CAUSED BY SAID BROKEN VACUUM WHEN BOTH CONTACT MEMBERS ARE DISENGAGED FROM EACH OTHER.

Description

Feb. 9, 1971 KATSUO OHWADA ETAL 3,562,682

VACUUM SWITCHING APPARATUS Filed June 10, 1969 "FIG.

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United States Patent 3,562,682 VACUUM SWITCHING APPARATUS Katsuo Ohwada and Noriyuki Ichihara, Tokyo, Japan,

assignors to Tokyo Shibaura Electric Co., Ltd., Kawasaki-shi, Japan, a corporation of Japan Filed June 10, 1969, Ser. No. 831,951 Claims priority, application Japan, June 10, 1968, 43/39,550; Sept. 10, 1968, 43/ 64,798 Int. Cl. H01h 9/30 U.S. Cl. 335-201 7 Claims ABSTRACT OF THE DISCLOSURE A vacuum switching apparatus having a stationary contact member and movable contact member disposed in a vacuum vessel which is so designed as to use a pressure equal to a difference between the interior pressure of the vessel and the atmospheric pressure in urging the movable contact member into the vessel for contact with the stationary contact member, characterised in that the force of closing the movable contact member, the force of a reset spring means for releasing the movable contact member by means of an operating lever engaging said member, the initial attracting force of an electromagnetic device for disengaging said member and the attracting force with which the contact element of said electromagnetic device is attached to said member are all kept in a prescribed relationship in order to prevent the release of the movable contact member which might occur due to the broken vacuum of the vessel at the time the movable contact member is closed for contact with the stationary member and also prevent the sucking of the movable contact member which might be caused by said broken vacuum when both contact members are disengaged from each other.

The present invention relates to a vacuum switching apparatus so designed as to use a pressure equal to a difference between the interior pressure of a vacuum vessel and the atmospheric pressure in urging a movable contact member into said vessel and more particularly to a vacuum switching device which is capable of preventing the release or closing of the movable member which might result when the vacuum of the vessel is broken.

A vacuum switching apparatus is generally so arranged that if the vacuum of a vessel is broken when a movable contact member comes in, it is detached from a stationary contact member. Accordingly, if said broken vacuum should happen from an external impact or other causes after the closing of the movable contact member, namely during the operation of a vacuum switching apparatus, then current will be cut off in the air to cause both contact members to be melted together due to the occurrence of arcs therebetween, perchance leading to a severe accident. Accordingly, the conventional vacuum switching apparatus has the drawback that if the movable contact member is closed into the vessel unawares of the fact that there occurs a broken vacuum therein, then the switching apparatus may become defective and unable to be opened when it is so desired, thus leading to absence of phases, failure to cut off power and obstructed operation.

It is accordingly the object of the present invention to provide a vacuum switching apparatus in which the force of closing the movablecontact member, the force of a reset spring for releasing the movable contact member, the initial attracting force of an electromagnetic device for disengaging said member and the attracting force with which the contact element of said electromagnetic device is attached to the movable contact member are all maintained in a prescribed relationship in order to prevent the danger of the aforementioned difiiculties happening in said vacuum switching apparatus.

The present invention can be more fully understood from the following detailed description when taken in connection with reference to the accompanying drawing, in which:

FIG. l represents the arrangement of a vacuum switching apparatus according to an embodiment of the present invention; and

FIG. 2 shows an arrangement illustrating the operation of said embodiment.

There will now be described an embodiment of the present invention by reference to the appended drawing. Referring to FIG. 1, there is securely suspended a switching apparatus 3 by a support member 2 in the upper half of a support frame 1 thereof. In the lower half of said frame 1 is positioned a mechanism 4 for operating the switching apparatus 3. The switching apparatus 3 comprises a vacuum vessel 5, a stationary contact member 6 fixed to the support member 2 and penetrating through the vacuum vessel 5 in airtight relationship so as to hold the switching apparatus in position, and a movable contact member 7 penetrating the vacuum vessel 5 through bellows 8 in airtight relationship and vertically moving to contact or be detached from the stationary contact member 6. There is further provided an operating rod 10* detachably coupled with the movable contact member 7 and extending downward. At an intermediate point of said rod 10 there is fitted a flange 9' made of electrically insulating material so as to electrically shield the operating mechanism 4 below.

The stationary contact member 6 is connected to one terminal 11 of a power source and the movable contact member to the other terminal 13 through a lead line 12. The operating mechanism 4 comprises an engagement strip 14 fixed to the bottom end of the operating rod 10, an operating lever 15 freely engaging said rod 10 and regulating the closing of the movable contact member 7 by registering with said engagement strip 14, a contact spring 23 interposed between the operating lever 15 and the insulating flange 9 to apply a supplementary contact pressure to the movable contact member 6, an armature 18 connected ot the operating rod 10 through the operating lever 15 and a rotatable shaft 17, a reset spring 19 constantly applying a repulsive force to said armature 18 in the direction of the arrow A, and an electromagnet 22 which generates an attractive force in the direction of the arrow B in opposition to said repulsive force. Numeral 24 of FIG. 1 is an insulating barrier.

There will now be described the operation of the vacuum switching apparatus of the present invention arranged as described above. Normally when there is not applied a signal to close the movable contact member 7, there is applied a force in the direction of the arrow A by the repulsive force of the reset spring 19' to cause the operating lever 15 to press the engagement strip 14 downward in a manner to release the movable contact member 7 from the stationary contact member 6. At this time, the force of keeping both contact members 6 and 7 detached from each other, namely, the repulsive force applied by the reset spring 19 in the direction of the arrow A, has a larger value than the force of closing the movable contact member 7, that is, a pressure equal to a difference between the interior pressure of the vacuum vessel 5 and the atmospheric pressure.

When a signal is applied to the electromagnet 22 so as to urge the movable contact member 7 toward fixed contact 6, said magnet 22 attracts the armature 18 in the direction of the arrow B in opposition to the repulsive force of the reset spring 19 acting in the direction of the arrow A. Then the rotation of the shaft 17 lifts up the operating lever to relieve it of registration with the engagement .strip 14 and releases the movable contact member 7 from the operating rod 10. Accordingly, the movable contact member 7 is urged into the vessel by a pressure corresponding to a difference between the interior pressure and the atmospheric pressure for contact with the stationary contact member 6 so as to close a circuit. At this time, the requisite condition for closing the movable contact member7 is that the initial attractive force of the electromagnet 22 be larger than the value arrived at by substracting the closing force or the aforesaid differential pressure from the force of disengaging both contact members. The closing operation is carried out pursuant to the action of the operating lever 15, and to allow for the required action of the operating lever 15, there is provided a clearance G between the insulation flange 9 and operating lever 15. The contact spring 23 disposed in the clearance G supports the weight of the movable contact member 7 and applies a contact pressure.

The pressure exerted by the contact spring 23 is of such order as to be just sufficient to keep the movable contact member 7 pressed to the stationary contact member 6 when the vacuum of the vessel is broken. Accordingly, said pressure does not obstruct the release of an electrode by the reset spring 19, but is set at a value equal to a fraction of the force of closing the movable contact member 7 applied by a pressure corresponding to a difference between the interior pressure of the vacuum vessel and atmospheric pressure.

The interior of the vessel of a vacuum switching apparatus is kept in vacuum and said vacuum is sometimes disturbed by external shocks. As described above, therefore, if there is applied a signal to urge the movable contact member 7 toward the fixed contact 6 unawares of said broken vacuum, it has previously led to the occurence of ditficulties. Now, in the vacuum switching apparatus according to the present invention, the closing of the movable contact member 7 is carried out under the condition that the initial attractive force of the electromagnetic 22 is made larger than the value arrived at by substracting the closing force from the releasing force. Accordingly, when the vacuum of the vessel is broken, the closing force will be reduced to zero and the releasing force will become stronger than the initial attractive force of the electromagnet 22. Consequently the operation of the movable contact member 7 cannot be effected, even though the electromagnet may be excited, thus preventing the occurrence of accidents.

There will now be described by reference to FIG. 2 the functional effect of the present invention when the broken vacuum of the vessel is caused by external impacts or for other reasons after the movable contact meniber is closed into said vessel, namely, during the operation of a switching apparatus. The same parts of FIG. 2 as those of FIG. 1 are denoted by the same numerals and description thereof is omitted. The attractive force of the electromagnet 22 when the armature 18 is attracted thereto to close the movable contact member 7 is previously so set as to have a larger value than the aforementioned releasing force. As shown in FIG. 2 therefore, the electromagnet 22 is energised by a closing signal to attract the armature 18 in the direction of the arrow B in opposition to the repulsive force of the reset spring 19 acting in the direction of the arrow A, thereby urging the movable contact member 7 due to release of its registration with the engagement strip 14 by means of the operating lever 15. If, under such condition, there should occur the broken vacuum of the vessel, the closing force will be reduced to zero. As described above, however, the releasing force is smaller than the attractive force of the electromagnet 22 when it attracts the armature 18, so that unless the electromagnet 22 is demagnetised it will not happen that both contact members are disengaged from each other to open the circuit. Accordingly, these contact members are kept in a state as indicated in FIG. 2.

At this time, the contact spring 23 applies a contact pressure to the movable contact member 7 to maintain its engagement with the stationary contact member 6.

As mentioned above, the vacuum switching apparatus of the present invention is so arranged that the pressure of releasing the movable contact member 7 due to the repulsive force of the reset spring 19 acting in the direc' tion of the indicated arrow A is larger than the closing pressure which is equal to a difference between the interior pressure of the vacuum vessel and atmospheric pressure generated when the operating lever 15 is disengaged from the engagement strip 14, the releasing force is stronger than the initial attractive force of the electromagnet, the electromagnet has a greater force than the releasing force when it attracts the armature and there is provided between the insulation flange 9 and the operating lever 15 the contact spring 23 so as to support the weight of the movable contact member 7 and apply a contact pressure to cause the movable contact member 7 to be urged to the stationary contact member 6. Therefore, it does not happen that there is given a signal to close the movable contact member una-wares of the occurrence of a broken vacuum in the vessel or that said broken vacuum during the closing operation will lead to the disengagement of the movable contact member. Accordingly, the vacuum switching apparatus of the present invention is free from the absence of phases in the circuit, failure to cut off current or occurrence of difficulties.

The foregoing embodiment relates to the case where a single vacuum switch was used. However, it will be apparent that a plurality of juxtaposed vacuum switches may also be employed with the aforesaid insulating barrier interposed therebetween.

What we claim is: 1. A vacuum switching apparatus comprising: at least one vacuum switch (3) including a stationary contact member (6) and a movable contact member (7) for selectively closing with the stationary contact member (6) disposed in a vacuum vessel (5);

operating lever means (15) cooperating with the movable contact member (7 reset spring means 19) for providing a releasing force to the operating lever means (15) and tending to engage said operating lever means (15) with the movable contact member (7 such that said movable contact member (7) tends to release from the stationary contact member (6), said releasing force of said reset spring means (19) being greater than a differential pressure closing force corresponding to the difference between the interior pressure of the vacuum vessel (5) and atmospheric pressure;

electromagnetic means (18, 22) coupled to the operating lever means (15 and energised by a closing signal, the initial attractive force of the electromagnetic means (18, 22) being larger than a force having a value corresponding to the difference between the releasing force applied by the reset spring means (19) and the differential pressure closing force, and the steady state attractive force of the electromagnetic means (18, 22) being larger than the releasing force; and

a contact spring (23) coupled to the movable contact member (7 and supporting the weight of the movable contact member (7), the contact spring (23) normally applying a supplementary contact pressure to the movable contact member (7 such that when said electromagnetic means (18, 22) is energised to close said contacts (6, 7) and said differential pressure closing force is lost when said contacts are closed, said contact spring (23) maintains a contact pressure to cause the movable contact member (7 to remain contacted with the stationary contact member (6) as long as the electromagnetic means (18, 22) is energised.

2. Apparatus according to claim 1 wherein the releasing force is greater than the initial attractive force of the electromagnetic means (18, 22) so that when said differential pressure closing force is lost when said contacts (6, 17) are open, said contacts (6, 7) remain open even when the electromagnetic means (18, 22) is energised.

3. Apparatus according to claim 1 wherein the electromagnetic means (18, 22) includes an armature (18) coupled to the operating lever means (15) and a coil means (21) for selectively attracting the armature 18).

4. Apparatus according to claim 3 wherein the reset spring means (19) applies a force to the armature (19) which couples the releasing force to the operating lever means (15).

5. Apparatus according to claim 4 wherein the reset spring means (19) applies a repulsive force to the armature (19) in a direction substantially opposite to the direction of attraction of the armature (18) to the coil means (21).

6. Apparatus according to claim 1 comprising a flange (9) coupled to the movable contact (7) and wherein the contact spring (23) is interposed between the flange (9) and the operating lever means (15 7. Apparatus according to claim 6 wherein the movable contact (7 is rod-shaped and wherein the contact spring (23) is a coil spring mounted on the rod-shaped contact (7 References Cited UNITED STATES PATENTS HAROLD BROOME, Primary Examiner