US3534192A

US3534192A - Vacuum switch structure

Info

Publication number: US3534192A
Application number: US725645A
Authority: US
Inventors: Floyd Delbert Miles
Original assignee: Deutsche ITT Industries GmbH
Current assignee: Thomas and Betts Holdings Inc
Priority date: 1968-05-01
Filing date: 1968-05-01
Publication date: 1970-10-13
Anticipated expiration: 1987-10-13
Also published as: FR2007594A1; GB1256385A; DE1920463A1; ES366642A1; DE1920463B2; DE1920463C3; JPS4812349B1; IE33085B1; IE33085L

Description

Oct. 13, 1970 D. MILES 3,534,192

VACUUM SWITCH STRUCTURE Filed May 1, 1968 Fm. J.-

INVENTOR. F D. M7455 A rmeA/a United States Patent 3,534,192 VACUUM SWITCH STRUCTURE Floyd Delbert Miles, Santa Clara, Calif., assignor to International Telephone and Telegraph Corporation, New York, N.Y., a corporation of Delaware Filed May 1, 1968, Ser. No. 725,645 Int. Cl. H01h 33/66 US. Cl. 200-144 7 Claims ABSTRACT OF THE DISCLOSURE A single pole-double throw hermetically sealed switch having two axially aligned ceramic envelope sections closed at each opposite end by metallic end caps, one of which constitutes a diaphragm and the other includes a fixed electrode. A second fixed electrode is mounted intermediate the end cap assemblies. Either one of two selected circuits through the switch is made or broken by an axially extending contact rod pivotally supported on the diaphragm. The electrodes embody novel fixed contact portions which function as shields to intercept and condense vaporized metal. An improved diaphragm mounting struc' ture is also disclosed. I I

BACKGROUND OF THE INVENTION This invention relates to electrical switches and, more particularly, to a vacuum switch susceptible of miniaturization.

Miniaturized vacuum relays are known in the art in which a single pole, double throw vacuum switch is actuated by an electromagnetic actuator assembly which constitutes a separate assembly outside of the switch envelope. In this type of relay, normally the switch envelope comprises a pair of axially aligned tubular sections formed of insulator material, such as ceramic. These sections are closed at their remote ends by metallic end cap assemblies. One of the end cap assemblies includes an annular electrode while a second electrode is positioned intermediate the end cap assemblies, with the inner periphery of each annular electrode terminating inside of the envelope. The other end cap assembly comprises a diaphragm upon which an axially extending actuator rod is pivotally mounted. One end of therod extends into the envelope to provide a mobile contact for making or breaking a circuit through either of the electrodes and the actuator rod. The other end of the actuator rod extends into the electromagnetic actuator which determines the position of the rod.

In one form of the aforementioned vacuum switch the annular electrodes are flat so as to provide only a narrow inner circular edge which is engageable by the actuator rod. As a consequence, any vaporized metal which results from the contact between the actuator rod and the electrode deposits upon the insulator sections of the envelope, thereby limiting the life of the switch. In addition, since the electrodes are spaced axially apart in the ceramic envelope, axially spaced portions of the actuator rod engage the respective electrodes when the rod is pivoted by the electromagnetic actuator. Thus, the distances between such contact portions of the actuator rod and the pivot point of the rod are unequal with the result that the distance of movement required for the actuator rod to shift from its axial position to engage the fixed electrodes differs depending upon which electrode is being contacted. Thus, the electrical characteristics of the switch varies slightly depending upon which electrode is being contacted by the actuator rod. In addition, because of the axial spacing between the electrodes, there is required a greater amount of electromagnetic energy to effect operation of the switch than would be required if the electrodes had ice fixed contact surfaces which were not axially spaced. Finally, since the surfaces of the electrodes which are contacted by the actuator rod are curved, if there is any deviation from the normal path of movement of the pivoted actuator rod, the distance of movement required for the rod to contact the fixed contact surfaces will vary, thus altering the electrical characteristics of the switch.

In another form of a vacuum switch, the electrodes embody axially aligned cylindrical parts which extend toward each other and form the fixed contacts of the switch. This arrangement has the advantage over the lastmentioned switch arrangement in that the cylindrical fixed contact portions of the electrodes provide shields for intercepting vaporized metal which results when the actuator rod engages the contact surfaces. However, the contact surfaces are still circular and are axially spaced apart and thus do not avoid the problems mentioned above in connection with the vacuum switch which embodies flat annular electrodes.

Thus, what is desired and constitutes one object of the present invention is to provide an improved vacuum switch configuration which eliminates the axial spacing between the fixed contacts of the switch and also embodies shielding characteristics so that vaporized metal will not become deposited upon the inner surface of the ceramic envelope of the switch. Another object of the invention is to provide an improved diaphragm-actuator rod mounting arrangement for a switch of the class described.

SUMMARY OF THE INVENTION According to the principal aspect of the present invention, there is provided a vacuum switch generally of the type discussed above in which the axially spaced electrodes in the insulator envelope are provided with parts which extend axially toward each other, with the end of one extending beyond the end of the other in spaced relationship, to provide laterally spaced opposed fixed contact surfaces. Since these contact surfaces are spaced laterally apart, rather than axially as in the conventional switches discussed previously, the distance of movement of the actuator rod required to engage either of the surfaces is equal and a minimum and equal amount of electromagnetic energy is required to make or break a circuit through either of the electrodes embodying these fixed contact surfaces. In addition, since the axially extending parts of these electrodes extend beyond each other in spaced overlapping relationship, the overlapping portions of these electrode parts function as shields to intercept and condense vaporized metal which may be produced when the actuator rod engages either of the fixed contacts. In addition, it is preferable that the axially extending parts of the electrodes include generally parallel flat opposed walls so as to provide uniform spacing between the contact surfaces which are engaged by the actuator rod. This arrangement insures that the electrical characteristics of the switch will not vary even though the actuator rod deviates from its normal path of pivotable movement.

According to another aspect of the invention, I have "found that the electrical characteristics of a vacuum switch embodying an actuator rod which is pivotally mounted on a diaphragm are affected by the area of the diaphragm which is exposed to the interior of the envelope. More precisely, the pivotable movement of the actuator rod is affected by such exposed area of the diaphragm which in turn is determined by the dimensions of the inner diameter of the ceramic envelope. The ceramic tubular envelope sections are conventionally formed by molding techniques which do not permit high tolerances to be maintained. As a result, the inner diameters of ceramic sections formed by molding varies among different ceramic sections so that when switches are assembled utilizing sections of different dimensions, the exposed areas of the diaphragms bonded thereto varies and, hence, so does the electrical characteristics of these switches. In accordance with the present invention, I have eliminated this problem by bonding to the diaphragm a rigid metallic ring which is coaxial with the tubular envelope of the switch. This ring is formed so as to have an inner diameter less than that of the ceramic envelope so that the effective area of the diaphragm is determined by the dimensions of the ring rather than by the inner diameter of the ceramic envelope. Since a metal part may be formed to high tolerances by stamping or punching operations, a large number of rings may be inexpensively formed with uniform inner diameters so that when such rings are utilized in the assembling of a plurality of switches in the manner discussed above, the switches will have uniform electrical characteristcis insofar as such characteristics are determined by the diaphragm mounting of the actuator rod.

Other objects, aspects, and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG, 1 is a partial longitudinal cross-sectional view through a relay embodying the features of the present invention; and

FIG. 2 is a top plan view of the relay illustrated in FIG. 1, with the upper cap thereof removed.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing in detail, there is illustrated a relay, generally designated 10, which includes a Single pole-double throw vacuum switch 12 and an actuating assembly 14 for the switch. The actuating assembly includes a mounting flange 15. The switch includes an envelope composed of two axially aligned elongated tubular insulator envelope sections 16 and 18, preferably formed of ceramic. A third ceramic tubular section 20 is provided for assemblying the switch envelope to the actuating assembly 14.

The tubular envelope sections 16 and 18 are closed by upper and lower

end cap assemblies

22 and 24, respectively. The end cap assembly 22 includes a circular metallic terminal electrode 26 which is hermetically brazed at its outer peripheral portion to an upper metallized edge of the ceramic section 16. The electrode 26 includes a radially extending apertured lug portion 28 to which may be connected a conductor leading to a source of electric current. The end cap assembly 22 also includes a domeshaped cap 30 which is hermetically brazed to the terminal electrode 26.

A second circular terminal electrode 32 is interposed between the ceramic sections 16 and 18 and hermetically brazed at its outer peripheral portion to metallized adjacent ends of the tubular sections. The terminal electrode 32 also includes an aperture lug portion 34.

The lower end cap assembly 24 includes a relatively thin metallic diaphragm 36 which is hermetically brazed to the upper metallized edge of the ceramic section 20. A third terminal electrode 38 in the form of a rigid metallic ring coaxial with the ceramic envelope is interposed between the diaphragm 36 and the lower metallized end of ceramic section 18 and hermetically bonded to both, This electrode includes an apertured lug portion 39 which provides a terminal for the actuator rod 40 of the switch.

The diaphragm 36 is sufliciently flexible to permit transverse pivotal movement of the longitudinally extending actuator rod 40. The rod is provided with a lower ceramic contact end 42 extending into the actuating assembly 14, while the upper end of the rod extends through an aperture formed in the flexible diaphragm 36 and is hermetically brazed thereto.

The upper end of the actuator rod 40 extends through an opening 44 in the terminal electroe 32 and terminates in a pair of

contact buttons

46 and 48 which serve as the mobile contact of the switch which is adapted to engage fixed contacts 50 and 52 when the actuotor rod 40 is pivoted in the direction of the arrows in FIG. 1 by the electromagnetic assembly (not shown) in the actuator 14.

The

terminal electrodes

26, 32, and 38 are preferably formed of copper to provide a high current carrying capacity while the actuator rod 40' is preferably formed of molybdenum coated with a thin coat of copper. The

contact buttons

46 and 48 are formed of tungsten and are brazed to the rod 40. The molybdenum rod provides the recquisite rigidity to avoid the problems which exist when a malleable rod is utilized, such as a copper rod, while the copper coating on the rod provides the rod with high current carrying characteristics.

In accordance with an important feature of the invention, the fixed contacts 50 and 52 are fixedly mounted to the

terminal electrodes

26 and 32, respectively, and extend axially toward each other in spaced relationship with the end of each contact extending beyond the end of the other contact so that there is an overlapping relationship between the contacts. As best seen in FIG. 2, the contacts 50 and 52 have a U-shaped cross-section. Each contact includes a generally vertical flat wall 54 parallel to the corresponding wall of the other contact and generally

parallel side flanges

56 and 58 which extend toward the other contact. The opening 44 in the terminal electrode 32 has a generally rectangular configuration with its center offset from the longitudinal axis of the tubular ceramic envelope of the switch. A similarly shaped opening 60 is formed in the terminal electrode 26 with its center olfset from the axis of the envelope in the direction opposite to that of the center of opening 34. The configuration of the fixed contacts 50 and 52 is complementary to the

openings

60 and 44, respectively, so that the remote ends of the contacts may be positioned in tight fitting engagement within the respective openings and attached to the respective terminal electrodes as by welding or brazing, Since the

openings

44 and 60 and, hence, the contacts 52 and 50 are offset from the axis of the tubular switch envelope in opposite directions, the side flanges 56 of the two contacts are positioned outside of the flanges 58 as best seen in FIG. 2. These side flanges extend in the lateral direction a sufiicient distance so as to be in overlapping relationship. Hence, the portions of the U-shaped contacts which overlap each other in both the axial and lateral directions provide a shield surrounding the

mobile contacts

46 and 48 which will intercept and condense metal vapor that might occur during the operation of the switch.

It can be appreciated that the flat parallel walls 54 of the fixed contacts 50 and 52 provide uniformity spaced contact surfaces so that if there is any deviation in the normal path of movement of the actuator rod 40, the distance of movement required for the rod to contact these surfaces will not vary, thus insuring that the electrical characteristics of the switch will remain constant even if the path of movement of the rod alters. Also, the distance of movement required for the rod to make contact with either of the walls 54 of the two fixed contacts from the normal axial position of the rod is equal, thus insuring uniform electrical characteristics regardless of which

terminal electrode

26 or 32 is electrically connected by the rod. Moreover, since the walls 54 are laterally opposed rather than axially spaced as in the prior art switches, only one axial portion of the actuator rod engages both of the fixed contacts, thus further lending to uniformity and reliability of the operation of the switch and minimizing the electromagnetic energy requirements for pivoting the actuator rod.

According to another feature of the invention, the ring 38 which is interposed between the diaphragm 36 and the lower end of tubular section 18 has an inner diameter less than that of the tubular ceramic envelope. The opening in this ring is preferably formed by a stamping or punching operation which permits very high tolerances to be maintained in the dimensions of the opening. Since this ring is hermetically bonded in contiguous relation to the diaphragm 36, the exposed or effective area of the diaphragm is determined by the dimensions of the opening in the ring 38 rather than by the internal diameter of the ceramic section 18, which may vary appreciably between different ceramic sections as explained previously due to the fact that these sections are formed by molding processes rather than by matching. Thus, by this arrangement the exposed or effective areas of the diaphragms of vacuum switches made on a mass-production basis may be maintained within very close tolerances so that the operating characteristics of the switches as affected by the pivotal movement of the rods 40 will be uniform.

Although the invention has been herein shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent structures and devices.

What is claimed is:

1. A switch structure which includes a sealed tubular insulator envelope assembly, at least two generally circular metallic terminal members hermetically and concentrically attached between axially adjacent sections of said envelope, and an elongated conductive actuator rod extending between said terminal members, said actuator rod being pivotally mounted for actuation from a point outside the space between said terminal members and passing through a clearance aperture in one of said terminal members to form a mobile contact, comprising the combination of:

a pair of electrode members comprising parts extending axially oppositely with the end of one extending beyond the end of the other, in spaced relationship to provide a pair of laterally spaced opposed contact surfaces, one from each of said terminal members, for alternative electrical engagement by said mobile contact;

and means comprising at least on side flange on each of said axially extending electrode members, said side flanges each extending generally toward the opposite electrode member, thereby to provide shielding of the electrical contacts among said mobile contact and said electrode members.

2. Apparatus according to claim 1 in which said axially extending electrode and flange members are of generally U-shaped cross-section open toward each other in a plane normal to the axis of said envelope, thereby to provide generally parallel intermediate walls defining said fixed contact surfaces and generally parallel side flanges, said side flanges extending oppositely toward each other in spaced overlapping relationship.

3. The invention set forth in claim 2 in which said side flanges are defined as being laterally located with respect to the direction of motion of said mobile contact.

4. Apparatus according to claim 1 in which said contact surfaces are substantially flat and parallel.

5. The invention set forth in claim 2 in which said U- shaped electrode members are staggered in the direction normal to the motion of said mobile contact and said side flanges extend at least half of the distance between said contact surfaces, thereby to provide overlapping shielding of said switch.

6. In a switch enclosed within a generally tubular assembly including first and second substantially circular metallic terminal members, each with an external lug, and each joined to an annular end of a tubular insulator, the combination comprising:

first and second axially and oppositely extending, substantially flat and parallel conductive contact members attached to said first and second terminal members respectively, Within said tubular insulator, whereby electrical continuity between each of said contacts and a corresponding one of said lugs is extant;

a pair of side flanges at the sides of each of said contact members, said flanges each lying in a plane parallel to the axis of said tubular assembly, each making a substantial angle with its respective contact member, and each extending generally toward the opposite one of said contact members, thereby forming said first and second contact members with integral shielding to intercept vaporized contact metal from arcing at said contact members;

and a generally central aperture in one of said terminal members, whereby an elongated conductive actuator rod may be axially mounted through said aperture to engage said contact members alternately as said rod is moved laterally.

7. Apparatus according to claim 6 in which said substantial angle between said flanges and corresponding contact members is substantially a right angle, and said contact members and flanges are constructed such that flanges of opposite contact members tend to be interleaved but not in electrical contact.

References Cited UNITED STATES PATENTS 2,285,467 6/ 1942 Schwartz et al. 335196 3,260,828 7/1966 Cartier. 3,406,268 10/ 1968 Hansen.

ROBERT S. MACON, Primary Examiner US. Cl. X.R.