US3524033A - Bypass switch and vacuum interrupter - Google Patents

Description

8- 11970 c. w. SCHOENDUBE 3,524,033

BY PASS SWITCH AND VACUUM INTERRUPTER Filed April 5, 1968 3 Sheets-Sheet l 7""? r" g; 16 l2; l I. .4 non [2' i E l i 15 E 19 20 f 2 i i E 14'. i 6 a i E v 1' E 22 l i 3 '--z4 I i l Aug. 11, 1970 v -c. w. SCHOENDUBE BYPASS SWITCH AND VACUUM IN'IERRUPTER 3 Sheets-Sheet. 2

Filed April 3, 1968 Aug. 11, 1970 c. w. SCHQENDUBE 3 BYPASS SWITCH AND VACUUM INTERRUPTER 3 Sheets-Sheet 3 Filed April 5, 1968 (Zar/es W 52606120256 United States Patent 3,524,033 BYPASS SWITCH AND VACUUM INTERRUPTER Charles W. Sclroendube, Lee, Mass., assignor to General Electric Company, a corporation of New York Filed Apr. 3, 1968, Ser. No. 718,597 Int. Cl. H01h 33/66, 3/42 US. Cl. 200-144 8 Claims ABSTRACT OF THE DISCLOSURE The application discloses a combined bypass switch and vacuum interrupter to be used in connection with a tap-changing mechanism for a transformer or regulator. A rotatable bypass switching cam disc alternately makes and breaks a pair of contacts which are connected to both the vacuum interrupter and the tap-changing contacts. The bypass switching cam disc is also electrically connected to the load. Two concentric cylindrical cams are mounted with the cam disc on a hollow shaft. A yoke is provided and is imparted with a reciprocating motion by two cam followers which are connected to the yoke and operated by the cylindrical cams. The yoke is adapted to transmit the reciprocating motion to a push-pull shaft which is positioned concentrically within the hollow shaft and is connected to a butt contact within the vacuum interrupter. All the cams are adapted and arranged to synchronize the bypass switching with the vacuum interrupter switch so as to provide a proper sequence of operation for safely changing tap connections on a transformer.

BACKGROUND OF THE INVENTION The invention relates to switching mechanisms and, more specifically, to a mechanism which properly synchronizes the operation of two bypass switches with a vacuum interrupter switch shunted across them, which These costly mechanisms have proved impractical as they include large, motor-driven, bypass and oil-break interrupter switches switches which are linked to a tap changer mechanism by a dispersed configuration of members which are complexly arranged over a large insulating board. Furthermore, with each operation of each oilbreak interrupter switch, carbon particles are formed in the oil surrounding the switch mechanism. This results in the degradation of the dielectric strength of the oil which, in turn, requires that greater strike and creep insulation distances, and also interrupter movement, be provided between the live parts of the mechanism to insure safe operation. For these reasons the existing mechanisms have had to be unduly large, unnecessarily complicated and undesirably ineflicient.

If a smaller vacuum type interrupter switch were to be used in place of the oil-break interrupter, however, the carbon-forming arc would be isolated from the oil and a more compact and simplified unit would be possible. Likewise, a more efiicient mechanism could be provided as the improved interrupting features of a vacuum switch would provide a greater number of interruptions than presently obtainable with existing oil-break interrupters from the same volume of contact material. Further, less contact gap opening is required with vacuum switches which reduces the power drive requirement of the mechanism.

Accordingly, it is one object of this invention to provide a combined bypass and interrupter switch mechanism which will not cause a reduction in the dielectric strength of a surrounding oil.

It is another object of this invention to provide a combined bypass and interrupter switch mechanism which is compact and simple.

It is a further object of this invention to provide a combined bypass and interrupter switch mechanism which is inexpensive and adaptable for use with existing transformer tap selector mechanisms.

A. still further object of this invention is to provide a combined bypass and interrupter using a vacuum switch to increase the efiiciency and reduce power drive requirements.

SUMMARY OF INVENTION In carrying out the invention in the preferred form, a combined bypass and vacuum interrupter switch mechanism is provided having a switching cam disc for operating two bypass switches. Two concentric cylindrical cams are provided for operating the vacuum interrupter in proper synchronization with the bypass switches. The switching cam disc and the concentric cylindrical cams are mounted on a hollow shaft which has a push-pull shaft positioned concentrically therein. As the hollow shaft is rotated, the disc operates the bypass switches and the two cylindrical cams operate the vacuum interrupter through a yoke member which transmits a reciprocating motion to the push-pull shaft which, in turn, operates the vacuum interrupter.

BRIEF DESCRIPTION OF DRAWINGS The specification concludes with claims which partic ularly point out and distinctly claim the invention which issought to be protected and a preferred embodiment is disclosed in the following detailed description in connection with the accompanying drawings in which:

FIG. 1 is a schematic diagram of a tap changing circuit to which the switching function of the invention is to be applied;

FIG. 2 is a perspective view of a vacuum interrupter and bypass switch according to the preferred embodiment of this invention; 1

FIG. 3 is a plan view of the driving gear and cam portion of the preferred embodiment of the invention;

FIG. 4 is a front view of the preferred form of bypass switching cam of the invention;

FIG. 5 is a side view of one of the bypass switch contacts;

FIG. 6 is a partial sectional view showing the relation of one cylindrical cam and the roller cam follower according to the preferred embodiment; and

FIG. 7 is a partial sectional view showing the relation of the other cylindrical cam and the roller cam follower according to the preferred embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawings in which like numerals are used to indicate like parts throughout the various views thereof, a schematic diagram of the circuitry to which the preferred embodiment of this invention is to be applied is shown in FIG. 1 as two tap selector contacts 12 and 14 which are connected through reactor coils 16 and bypass switch contacts 12' and 14 to a load contact 18. A vacuum interrupter switch 20- is shunted across the parallel circuit formed by the aforementioned connections and it is to the proper synchronizing of the operation of the vacuum interrupter 20 with the opening and closing of the bypass switch contacts 12' and 14 that the function of the invention is specifically directed. The portion of the circuit which is to be directely affected by the subject matter of this invention is shown diagrammatically as block 22.

When a transformer or regulator tap changer mechanism, shown as block 24, causes contact 12 to move from stationary contact 26 toward stationary contact 28, it is necessary to open contacts 12 whereby, one-half the load current is shunted through vacuum interrupter 20. Interrupter 20 must then be opened to cause zero current through contact 12 and full load current through the connection between contact 14, contacts 14 and load contact 18. As contact 12 physically reaches stationary contact 28, it is necessary to reclose vacuum interrupter 20 so as to divide the load current through tap selector contacts 12 and 14 which are now both on stationary contact 28. Bypass contacts 12 must now be closed to relieve vacuum switch 20 of continuous current carrying duty.

Referring now to FIG. 2, the preferred embodiment of the bypass and vacuum interrupter of this invention is shown as including the bypass switch contacts 12 and 14 and vacuum interrupter switch 20. A switching disc 30' is mounted on a hollow shaft 32 and, when rotated, disc 30 properly opens contacts 12' or 14', depending on the direction of traverse applied to tap selector contacts 12 and 14. The preferred shape of disc 30 is clearly shown in FIG. 4. As shown in FIG. 4 disc 30 has a hub 30- rmounted on and secured to hollow shaft 32. Switching disc 30 rotates 180 per tap change sequence, opening contacts 12 and 14 alternately. A smaller concentric shaft 34 is positioned within hollow shaft 32 and is directly connected to a butt contact 36, which is housed within the overall vacuum interrupter 20 along with a mating butt contact 38. By a driving means described later in the disclosure, a reciprocating motion is transmitted to shaft 34 in such a manner that butt contact 36 is separated from butt contact 38 immediately after either contacts 12' or 14' are opened. The load current contact 18 also engages switching disc 30 and is so adapted as to provide proper and continuous electrical contact regardless of the angular position of disc 30. As shown in FIG. 2, the parallel circuit of FIG. 1 is structurally provided by connecting tap selector contacts 12 and 14 through mutually coupled induction coils 16 and contacts 12' and 14 to load contact 18 by means of disc 30. Vacuum switch 20 is shunted across the circuit by connecting contacts 14' to the butt contact 38 and contacts 12 to the butt contact 36, which is mounted on one end of the rod 34.

As shown in FIG. 2, the driving portion of the preferred embodiment includes a drive pinion 40 and a large driven gear 42. Pinion 40 is driven from a motor (not shown) through a gear train (not shown) which, as will be understood, also operates the tap changer mechanism. Gear 42 is directly and concentrically secured to a cylindrical cam 44. A hub 46 is formed on cylindrical cam 44, which hub 46 fits within one end of the hollow shaft 32. Cylindrical cam 44 is formed with two gradual rise and dropoff projections 50 with which rollers 52 cooperate as cam followers. The rollers 52 are mounted on a reciprocating yoke 54 and cause the yoke to move to the right as the rollers 52 are forced to ride up the gradual cam projections 50.

FIG. 3 shows the driving portion of the invention as it is properly secured to a panel 56 by means of a large hollow and flanged stud 58 over which the hub 46 is rotatably mounted. As previously explained, hollow shaft 32 is rotatably mounted on hub 46. A hammer member 60 is attached to the inside of the yoke 54 and is adapted to engage an anvil member 62 which is secured to the push-pull shaft 34. A helical spring 64 is disposed between the yoke 54 and the mounting panel 56 so as to exert a force slightly greater than 30 pounds to the yoke 54 in biasing it to the left. Stop means 66 which mount roller cam followers 52 on the yoke 54 on the opposite side of panel 56 from spring 64 limit the stroke travel of yoke 54 as it moves to the left. The limit to the travel of yoke 54 as it is moved to the right is determined by the projections 50 on cam 44. The yoke 54 is slidably mounted in bearings '68 which are formed in the panel 56. As will be apparent, this mounting prevents the rotation of yoke 54 when roller cam followers 52 engage the cam projections 50. The hollow stud 58 provides the supporting means for the hub 46 and hollow shaft 32 as previously described.

As is apparent from FIGS. 2 and 3, when cam 44 is rotated, roller cam followers 52 will engage the leading edge of cam projections 50. Further rotation of cam 44 causes cam followers to ride up the gradual slope of cam projections 50, moving yoke 54 and hammer member 60 to the right, compressing spring 64. This will relieve the spring pressure on shaft 34 permitting the vecuum contacts 36 and 38 to be closed by atmospheric pressure. In the preferred embodiment shown, the spring 64 must apply a bias force to the shaft 34 of a magnitude greater than 30 pounds when hammer 60 engages anvil 62 in order to permit separation of the vacuum enclosed contacts 36 and 38. This requirement is due to atmospheric pressure acting on some two square inches of bellows area 70, which are located within the vacuum switch 20 and within which the contact 36 is mounted.

To obtain proper interrupting action at low erosion rates, it becomes necessary to open the vacuum contacts 36 and 38 rapidly. However, to insure long bellows life and a bounce-free closing action, it is necessary to close these contacts slowly. Since it is desirable to be able to tap select in both directions, it is important that this quick opening and slow closing action be provided regardless of the direction of rotation of cylindrical cam 44. It is for this reason that an inner cylindrical cam 72, which is concentrically attached to cam 44, is provided. The inner cam 72 is provided with a hub 73 which fits over hollow shaft 32 and is secured thereto by a set screw 75. Cam 44 is provided with two pins 74, which couple with two arcuate slots 76 formed in cam 72. The inner cam 72 is also provided with two cam projections 78 which correspond to the projection 50, except that the projections 78 have a sharp drop-off profile and projections 50 have a gradual drop-off. This can be clearly seen in FIGS. 6 and 7.

In operation, if power is applied by the drive pinion 40 so as to rotate the gear 42 in a clockwise direction, a complete operating sequence occurs. The large driven gear 42 rotates until the coupling pins 74 bottom against the leading edges of the slots 76 formed in the inner cylindrical cam 72. As previously mentioned, hollow shaft 32 is rotatably mounted on hub 46 of cam 44 while both cam 72 and switch cam 30 are fixed to hollow shaft 32. The sliding friction provided by the contacts 12, 14' and the contact 18 on switch cam 30 prevents any friction drive between the inner cam 72 and the outer cam 44. As can be seen from FIG. 5, switch contacts 12' are forced against switch cam 30 by spring 13, providing the desired friction. The width of the slot 76 is such as to have the trailing gradual rise portion of the outer cam projection 50 of cam 44 completely overlapped by the trailing portion of the sharp rise projection 78 of cam 72 when the pins 74 bottom. A sharp drop-out point is thus formed for the roller cam followers 52, which sharp drop-out provides the means for satisfying the requirement for quickly opening the vacuum switch contacts 36 and 38.

Before this drop-out point is reached, however, the switching disc 30 will be rotated the required number of degrees needed to disengage the contacts 12 from the disc 30. Thus, with 12' open, the rollers 52 drop-off sharply from the inner cam projection 78 as shown in FIG. 7 and the yoke 54 moves to the left causing the hammer 60 to strike the anvil 62 which is connected to the vacuum switch push-pull rod 34. The vacuum switch butt contacts 36 and 38 are thereby rapidly opened. The cam yoke 54 continues to move to the left until the stop means 66 contact the mounting panel 56 which relieves the cams of any unnecessary impact forces. The anvil 62 and pull rod 34 continue to move to the left after impact until they are stopped by the atmospheric 30-pound pull force exerted on butt contact 36 by the vacuum bellows 70 of switch 20. The motion of the rod 34 is then reversed by the atmospheric pressure until a cushioned catch is made by the hammer 60 which is biased to the left by the discharge spring 64.

After the vacuum switch 20 is opened, the tap selector contact 12 may be moved to stationary contact 28. A conventional tap selector (not shown) is geared off of the drive pinion 40 in such a manner as to be synchronized with the operation of the present invention. After further rotation of the inner cam 72 and outer cam 44, a gradual rise slope of the outer cam projection 50 is encountered by the rollers 52, as shown in FIG. 6. As the rollers are driven to the closed position shown in FIG. 3, the yoke 54 slowly moves to the right, carrying with it the hammer 60, which in turn permits contacts 36 and 38 to slowly close under the 30-pound atmospheric force. In this manner the second requirement of slowly closing contacts 36 and 38 has been satisfied.

A complete sequence of operation has been described with such a sequence occurring no matter which direction the mechanism is driven. To minimize overshoot of the anvil 62, a dashpot dampening mechanism (not shown and described a particular embodiment of the into the end of the stroke of yoke 54. A set of electrical control contacts (also not shown) which are to be operated off of the tubular shaft 32, may be provided to insure that the drive power is removed and rotation stopped when the rollers 52 rest at approximately the central portion of the inner cam projections 78 after every 180 of rotation of the cylindrical cams 44 and 72 from this position.

It should be understood that, while there has been shown and described a particular embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.

For example, if desired, cam 44 and gear 42 could be a single member, with cam projections 50 and pins 74 directly mounted on gear 42. It will be apparent that these and other modifications may be made within the scope of the invention as defined in the claims appended hereto.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A bypass switch and vacuum interrupter mechanism comprising, in combination:

(a) a pair of bypass switches,

(1) a switching cam disc opening and closing said bypass switches,

(b) a hollow, rotatable shaft,

(1) said cam disc secured to said hollow shaft,

(c) a second shaft,

(1) said second shaft concentrically mounted within said hollow shaft,

(d) a vacuum interrupter electrically connected between said bypass switches,

(1) one contact of said vacuum interrupter connected to one end of said second shaft,

(e) a cylindrical cam,

(1) said cylindrical cam having a pair of cam projections,

(2) means for rotatably mounting said cylindrical cam,

(3) said cylindrical cam including means to rotatably mount said hollow shaft,

(f) a yoke member,

(1) said yoke member slidably mounted with re spect to said cylindrical cam,

(2) a pair of cam followers on said yoke member riding on said cylindrical cam,

(3) means interconnecting said yoke and said second shaft for reciprocal movement of said second shaft,

(g) means for driving said cylindrical cam, and

(h) lost motion means interconnecting said cylindrical cam and said hollow shaft for rotation of said hollow shaft and said switching cam disc.

2. A bypass switch and vacuum interrupter mechanism as set forth in claim 1 in which said yoke is provided with a sliding connection to the other end of said second shaft for moving said second shaft to open said vacuum interrupter, spring biasing means to bias said yoke in position to maintain said vacuum interrupter open, and said cam followers cooperating with said cam projections to compress said spring and close said vacuum interrupter.

3. A bypass switch and vacuum interrupter as set forth in claim 1, said driving means include a gear fixed to said cylindrical cam and said lost motion connection includes a second cylindrical cam fixed to said hollow shaft and connected to said cylindrical cam through pins on said cylindrical cam and slots in said second cylindrical cam.

4. The bypass switch and vacuum interrupter mechanism as set forth in claim 1 in which pins project from one face of said cylindrical cam; a second cylindrical cam; arcuate slots formed in said second cylindrical cam; said second cylindrical cam fixed on said hollow shaft with said pins of said first cam extending through said slots of said second cam forming a lost motion connectio, cam projections formed on said second cam; each said second cam projection having a sharp rise and a sharp drop-off; said first and second cam projections being so positioned and said second cam slots being of such a width that, as said second cam is driven by said first cam; said first cam projections and said second cam projections form a single composite cam projection with a gradual rise leading edge and a sharp drop-off trailing edge, regardless of the direction of rotation.

5. A bypass switch and vacuum interrupter mechanism comprising, in combination: two bypass switches; a Switching cam disc for operating said bypass switches; a first shaft for mounting said switching cam disc; a load current switch; said load current switch adapted to engage said switching cam disc regardless of the angular position of said disc; a vacuum switch interrupter connected between said bypass switches; a second shaft; said vacuum interrupter switch connected to a first end of said second shaft; said second shaft adapted for applying a push-pull operating force to said vacuum interrupter; a cylindrical cam mounted rotatably with respect to said first shaft for operating said vacuum switch through a mechanical linkage with said second shaft; a yoke member; said yoke member provided with cam followers for riding on said cylindrical cam; a hammer member mounted on said yoke; an anvil member mounted on a second end of said second shaft; said hammer and said anvil disposed in driving relationship so that a reciprocating motion may be transmitted between said second shaft and said yoke; a panel for mounting said shafts and said yoke; a spring disposed between said panel and said yoke for biasing said vacuum interrupter to the open position through a mechanical linkage between said yoke and said second shaft; means for driving said first shaft; said driving means adapted to synchronize said bypass switches and said vacuum interrupter with a linked electrical contact changer; cam projections formed on said cylindrical cam; said cam projections so formed as to cause the vacuum interrupter to open immediately after one said bypass switch is opened and to close immediately before said bypass switch is closed.

6. A bypass switch and vacuum interrupter as claimed in claim 5 in which said first shaft is hollow and said second shaft is concentrically mounted in said first shaft.

7. A bypass switch and vacuum interrupter as claimed in claim 5 in which a lost motion connection is provided between said cylindrical cam and said bypass switching cam disc, said lost motion connection comprising a second cylindrical cam fixed to said first shaft, said second cylindrical cam having a pair of arcuate slots, pins on said first cylindrical cam and extending through said arcuate slots.

8. A bypass switch and vacuum interrupter as claimed in claim 7 in which said second cam has cam projections provided with sharp rise and drop-off edges, said first cylindrical am having gradual rise and drop-off edges on said cam projections and said arcuate slots so positioned that as said second cylindrical cam is driven by said first cam said first cam projections and said second cam projections form single composite cam projections with a gradual rise and a sharp drop-01f, regardless of direction of rotation.

References Cited UNITED STATES PATENTS 3,206,580 9/1965 McCarty. 3,404,247 10/ 1968 Glassanos. 3,467,800 9/1969 Barr.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,524 ,033 Dated August 11 1970 Charles W. Schoendube Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 71, "directely" should read directly Column 4, line 12, "vecuum" should read vacuum Column 5 line 24, cancel entire line and insert shown) may be provided so as to engage slightly prior Column 6, line 25 "tio" should read tion Column 7, line 6 "am" should read cam Signed and sealed this 24th day of November 1970 (SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents FORM PO-IOSO (10-69) a u s covnuunn rmn'rmc QH'ICE: uu o-su-su

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