US2724749A - Adjustable contact rectifier mechanism - Google Patents

Description

Unite 2,724,749 Patented Nov. 22, 1955 ADJUSTABLE CONTACT RECTIFIER MECHANISM Harold N. Schneider, Springfield, and John A. Oppel, Aldan, Pa;, assignors to General Electric Company, a corporation of New York Application May 14, 1953, Serial No. 355,044

Claims. (Cl. 200-31 Thus, if the mechanical rectifier is operating normally to supply a certain load current, any substantial increase injthe load current may require an increase in the dwell or closed time of all the contacts of the rectifier. Also, it is essential that the dwell or closed time of all the contacts be substantially uniform. Since manufacture of parts to a uniform degree of accuracy is difficult and difierences of wear during operation would, in any case,

destroy such initial accuracy, it is desirable to afford compensation by providing some means for accurately adjusting individually the dwell time of each contact.

Furthermore, means for collective adjustment of the contacts with the cyclic cam-operating mechanism running are desirable for, when starting a. mechanical rectifier, it is advantageous to utilize the contacts of the rectifier for connecting the energized A.-C. supply circuit to the respective D.-C. buses prior to closing the D.-C. switch which connects these buses to the D.-C. load. Thus, the contact dwell of all the contacts would initially be adjusted to zero so that, though reciprocating, they -will remain open. From this zero condition the contactdwell period, relative to the open time, is gradually increased until the correct overlap period has been established among the associated contacts of the rectifier mechanism preparatory to the ensuing connection of the buses to the associated load circuits.

With some forms of mechanical contact rectifiers, it is always necessary to shut down the cyclic cam operating mechanism of the contact rectifier in order to make any adjustment of the dwell time of the contacts.

One object of this invention is to provide an improved mechanism having adjustable fulcrum levers for regulating the dwell time of the contacts of a mechanical rectifier whereby any desired adjustment can be made by adjusting the fulcrum while the cyclic cam mechanism of the rectifier is in operation.

Another object of this invention is to provide an improved mechanical rectifier sequential contact dwell adjusting mechanism which is characterized by a high degree of individual and joint adjustment adaptability so as to accommodate a wide variety of service conditions.

Another object is to provide a compact mechanical rectifier sequential contact dwell mechanism having separate and joint adjustment for the contacts and where it is not possible or convenient to arrange the opposing reciprocating contacts in alignment with the actuating cam shaft as in the aforesaid application Serial No. 286,907.

In carrying out the invention a rotatable cam member is spaced from each switch contact operating member of the rectifier and cooperates with an adjustably fulcrumed lever interposed between the cam member and the switch contact operating member. The fulcrum of this lever is made adjustable in order to provide for varying the position of the switch contact operating member relative to the actuating cam member. In this way, by separately adjusting the fulcrum of each lever, the dwell time of the corresponding switch contact member can be regulated during rotation of the cams that produce the opening and closing operation of all the switch contact members. Also, by jointly adjusting the fulcrums of all the levers, the dwell or closing time of all the rectifier contact members can be varied uniformly under operating conditions.

For a better understanding of the invention, reference may be had to the following description taken in conjunction with the accompanying drawings in which Fig. 1 is a schematic representation of a mechanical rectifier system embodying the improved adjustable fulcrum lever mechanism of the present invention;

Fig. 2 is a partial sectional view of a mechanical rectifier contact adjusting mechanism embodying the principles of the invention;

Fig. 3 is a cross-sectional view of a modified form of adjustable fulcrum lever contact dwell control mechanism. p

As. schematically shown in Fig. l, a polyphase alternating current circuit comprising conductors 1, 2, and 3, supplies energy which is converted to direct current energy by the cyclic closing of the rectifier contacts and supplied to the direct current load conductors 4 and 5. The alternating current circuit comprising conductors 1, 2, and 3, is connected to the primary 6 of a three phase transformer. having Y-connected secondary windings 7. The three phase secondary windings 7 are respectively connected to the saturable commutation control reactors 8, 9, and 10. These saturable reactors are constructed with amain and one or more control windings wound on a metallic core. Thus, the reactors 8, 9, and 10, change their impedance as a function of control excitation together with the magnitude and polarity of the transformer secondary potential so that, following commutation of current from the outgoing to the incoming phase circuit, the current in the outgoing phase circuit is reduced to substantially zero and held there for a brief interval during which the corresponding outgoing rectifier contact may be successfully opened without deleterious arcing or sparking. The function of reactors such as 8, 9, and 10, as a part of a rectifier system is more fully described in application Serial No. 172,134, filed July 5, 1950, by August Schmidt, Charles H. Titus, and Clodius H. Willis, and assigned to the assignee of this invention. The reactors 8, 9, and 10, are excited by the control windings l1, l2, and 13, which are energized from a source of electric energy having a controlled wave shape and polarity. The adjustable resistor 14 is used to efi'ect variations in the magnitude of current flowing through the control windings 11, 12, and 13. A reactor 15 may be connected in series with the windings ll, 12, and 13, so as to smooth the fiow of current through these control windings. Each of the reactors is provided with a main winding and such windings are designated by the numerals 16, 17, and 18.

Winding 16 is connected to fixed contacts 19 and 20, winding 17 is connected to the fixed contacts 21 and 22, and winding 18 is connected to fixed contacts 23 and 24. Negative direct current conductor 4 is connected to fixed contacts 25. 26. and 27, while positive direct current conductor 5 is connected with fixed contacts 28, 29 and 30.

As is indicated in Fig. 1, the above-mentioned fixed contacts may be bridged by the bridging contacts 31-36 each of which is respectively biased to the closed position by its own closing spring 3742. Each pair of contact sets such as 19, 25, 31 and 20, 28, 32, is controlled as indicated in Fig. 1 by its own contact operating mechanism generally designated by the numerals 43, 44, and 45. Means not shown in the drawing such as a synchronous motor is used to rotate the shaft member 47 and thereby produce synchronous operation of the contact operating mechanisms 43, 44, and 45. Since these contact operating mechanisms are identical, the following description will be by reference to the operating mechanism 43.

Contact operating mechanism 43 utilizes a rotatable cam member generally designated by the numeral 46 as is shown in both Figs. 1 and 2. The cam member 46 is driven by the rotatable central shaft member 47 to which is secured one of the three eccentric cam elements 48. Disposed about the eccentric cam 48 is an internal ball bearing race 49 upon which a plurality of balls 50 ride, while the operating surface of the cam member 46 is constituted by the outer race 51 of the ball bearing. lf preferred, the race 51 may be anchored for eccentric motion only by a radially extending arm 52 on which is mounted a roller 53 movable vertically in a guide slot formed in the fixed support structure. The synchronous rotation of the shaft member 47 and of the eccentric member 48 which is integrally movable therewith imparts a cyclic camming action to the ball bearing components 49, 5t), 5t, and causes the outer race 51 to exert periodic side thrusts which are applied to a pair of spaced apart adjustably fulcrumed levers 54 and 55, so as to exert opposite cyclic thrusts to the left and to the right. Outer race member 51 does not rotate due to the restraining action of the radially extending element 52 and the roller 53 mounted thereon. If desired, the elements S2 and 53 may be omitted, for the above-described camming action is not affected one way or the other.

Disposed for respective engagement with the levers 54, 55 intermediate the ends thereof are the reciprocating contact operating pins 56 and 57. The pin 56 slides in bearing 58 and is biased by spring 59 into engagement with the lever 54 to be reciprocated upon oscillation of lever 54 due to rotation of shaft 47. The opposite pin 57 is slidably mounted and operated by its lever 55 half a rotation later in exactly the same way. Thus the reciprocating contact operating pins 56 and 57 periodical ly impart a thrust respectively to the contact members 31 and 32 so as to move those contact members toward the open circuit position against the bias of their respective biasing springs 37 and 38. The distance that the contact end 560 of the reciprocating pin 56 can move away from contact 31 after closure thereof during each revolution of cam shaft 47 will determine the dwell or closed time of this contact. Thus by shifting the reciprocating range of pin 56 to the left or to the right relative to the cam shaft the dwell time of contact 31 may be varied from zero to any desired value.

In order to vary the range of reciprocation of pins 56 and 57 and thereby control the contact dwell time of contacts BI and 32 in accordance with this invention, the levers 54 and 55 are pivoted respectively at 62 and 63 to the horizontally movable pivot bearing or adjustable fulcrum members 64 and 65 which constitute the heads of the individual screws 64a and 65:: respectively which will be described in more detail later. These individual screws and their adjusting sleeves 66 d 67 are carried for collective adjustme t by the rgnnecal crossheads 68 and 69 which may entry are oted heel: of the three litCChtiI1i IHs 45, 44, and 45 and which in 'turn are adjustable laterally on the right and left-hand threaded rod 70 that is rotatably mounted in the split bearings 71.

The hand operating wheel or star member 72 is afiixed at the midpoint of the threaded rod 70 so that, like a turnbuckle, rotation thereof will impart opposite horizontal displacement to the crossheads 68 and 69 as will be obvious from Fig. 2. Suitable guide means (not shown) are provided to insure only such horizontal positioning of these blocks. Thus, it will be seen that manual rotation of the threaded rod 70 effectively imparts opposite lateral adjusting or positioning motion in the same direction as the reciprocation of the contacts to the pivotal bearing members 64 and 65 and thereby jointly varies the range of reciprocation of pins 56 and 57 to regulate the instant at which the contact members 31 and 32 are respectively opened or closed so as to regulate the dwell or closed time during each cycle of opening and closing of these contacts. It will be understood that in order to obtain accurate operation the contact operating pins 56 and 57 preferably are biased as described by the springs 59 into engagement with the levers 54 and 55 respectively so that there will be no lost motion in any of the parts of the individual and joint fulcrum adiusting mechanism.

From Fig. 2 it will be understood that the cam member and associated structure already described in connection with Figs. 1 and 2 is mounted on a metallic support plate member which is supported on the frame member 86 in any suitable manner. The biasing force exerted by spring 37 is adjustable by means of the ad justing bolt 92 and lock nut 93 and parts associated therewith which structures are respectively mounted in the insulating block 94 which is secured to the frame 86 by the bolts 96, 97. These bolts are respectively insulated from the current carrying elements by means of insulating tubes -102.

The alternating current bus 16a which leads from reactor 8 to the fixed contact 19 and the opposite fixed contact 25 with thedirect current bus 4 and parts associated therewith are insulated from the frame members 86 by insulating means 104. The pivotal bearing or fulcrum members 64 and 65 are individually adjustable during operation of the rectifier by means of the adjusting sleeves 66 and 67 which are held in position respectively by their locking nuts 108 and 109. The fulcrum screws 64a and 65a do not turn because their heads 64 and 65 bear against the stepped portion of the crosshcads 68 and 69. However, because the internal and external threads of the adjusting sleeves 66 and 67 are of different pitch, a micrometer adjustment is provided thereby whenever these sleeves are individually slacked and turned in their threaded sockets. The fulcrum or pivot members 62 and 63 are jointly adjustable during operation of the rectifier simply by rotating the tumbuckle screw 70. Rotation of the screw 70 may be accomplished by suitable manual means such as a wheel or start as is indicated in Fig. 2 by the numeral 72, and the split bearings 71 may constitute locking means if the clamping bolts 110 as shown in Fig. 2 are made for tightening after adjustment. However, the manual screw operating member 72 may be replaced by a pinion so as to enable a suitable rack to effect joint adjustment of the oppositely screw threaded rods 70 of all the contact mechanisms 43, 44, and 45, if desired. It will also be understood that suitable automatic means such as an electric motor, could be used to rotate the shaft 70 or move the rack and that such a motor could be made responsive to the magnitude of current being delivered by the rectifier or supplied thereto. In such a construction it will be appreciated that the rectifier would be fully automatic and would respond to the magnitude of load current in such a way as to adjust the dwell time of the contacts to accommodate changes in the magnitude of the load.

The modification of the invention shown in Fig. 3 is essentially the same structure as previously described in conne3tfc1. .ffh Ff, l and 2 except that the adjusting arrangement of Fig. 3 does not incorporate the oppositely threaded rod 70 shown in the modification of Figs. 1 and 2 and thus only the means for adjusting the fulcrums of levers 54 and 55 is different in the two modifications.

As shown in Fig. 3 the adjustable fulcrum members 64b and 65b may be adjusted individually by means of the adjusting screws 111 and 112 which are threadedly mounted respectively in the adjustable fulcrum members 64b and 65b and locked in position by the lock nuts 113 and 114. The adjustable fulcrum member 64b is slidably mounted in the supporting member 85 and is biased by spring 115 to carry the head 116 of adjusting screw 111 into engagement with the cam 117 carried on the rotatable shaft 118.

The adjustable fulcrum member 651) likewise is slidably mounted on the opposite side of shaft 118 and biased by spring 121 to engage the head 120 of the individiual adjusting screw 112 with the opposite face of the cam 117 which is symmetrical with the face engaged by the head 116.

Thus, by individual adjustment of the screws 111 or 112, either of the fulcrum members 64b or 65b may be individually adjusted in the same direction as the reciprocation of the pin 56 and contact 31 and thereby vary the dwell time of the corresponding contact of the rectifier. By rotating shaft 118, manually or otherwise, the fulcrum members 64b and 65b may be jointly adjusted to correspondingly vary the dwell time of the corresponding contacts, it being understood that for the three-phase rectifier mechanism as seen in Fig. 1, three cams 117 would be mounted on the common shaft for serving the three mechanisms 43, 44, and 45. The shaft 118 is well adapted to be rotated by motor means which in turn could be responsive to the magnitude of direct or alternating current through the mechanical rectifier and in this way the rectifier would be automatically adjustable during operation insofar as the dwell time is concerned in response to variations in the magnitude of the load current.

While particular embodiments of the invention have been shown and described, we do not wish to be limited thereto and intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What we claim as new and desired to secure by Letters Patent of the United States is:

1. In combination, an electric switch having a reciprocating operating member, a rotatable cam having its cam surface spaced from said switch operating member, a lever interposed between said cam and switch operating member, means biasing said switch operating member into engagement with said lever so that rotation of said cam imparts oscillating motion to said lever to reciprocate said switch operating member, said lever having a fulcrum adjustable for shifting the range of reciprocation whereby to vary the effective stroke of said switch operating member.

2. In combination a reciprocating switch member biased to the circuit closing position, means for opening the switch member including a rotatable cam member and a lever operatively related with said cam member so that rotation of said cam member imparts oscillating motion to said lever and causes periodic opening of said switch member, said lever being pivotally mounted and having the mounting pivot thereof adjustable in a direction corresponding to the direction of reciprocation of said switch member for changing the dwell of said switch member in the cir' cuit closing position upon each revolution of the cam member.

3. A mechanism for cyclically operating an electric contact comprising a reciprocating operating pin for engaging the contact, a rotatable cam member, a cam follower assembly including a lever operatively engaging said cam member and said operating pin for cyclically opening and closing said contact, said lever having a fulcrum adjustable during operation of the mechanism to vary the closing time of said contact relative to the opening time.

4. A mechanism for variably closing an electric contact comprising a reciprocating operating pin for engaging the contact, a continuously rotating cam member, a cam follower assembly including a lever operatively related intermediate its ends with said operating pin and having one end engaging said cam member for periodically opening and closing said contact, said lever having a fulcrum at the other end thereof, and means for moving said fulcrum in a direction generally transverse to the length of the lever to vary the closing time of said contact upon each revolution of the cam member.

5. A mechanism for sequentially operating a plurality of electric switch members comprising a plurality of synchronously rotatable cam members each spaced from a corresponding switch member, operating means including a separate lever interposed between each cam and switch member and each lever having a separately adjustable fulcrum, means for jointly adjusting the fulcrums of all the levers and means for separately adjusting the fulcrum of each lever.

References Cited in the file of this patent UNITED STATES PATENTS

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