US2734387A

US2734387A - Jansen

Info

Publication number: US2734387A
Authority: US
Priority date: 1951-03-22
Publication date: 1956-02-14
Anticipated expiration: 1973-02-14
Also published as: CH296808A; BE501371A; GB705845A; FR1034833A

Description

Feb. 14, 1956 JANSEN SPRING ACTION DRIVING SEAR WITH VARIABLE TORQUE FOR LOAQ CHANGEOVER SWITCHES OF REGULATING TRANSFORMERS Filed March 7, 1951 W W a 0 flaw mkw wFWJW H WM 6 M 1 5 W 3 M M 2 m F United States Patent SPRING ACTION DRIVINGGEAR WITH VARIABLE TORQUE FOR LOAD CHANGEOVER SWITCHES OE REGULATING TRANSFORMERS BernhardJansen, Regensburg, Germany Application March 7, 195.1,.SerialN0. 214,281

2 Claims. (Cl. 74'--99) Load changeover switches of regulating transformers, which switch over the load fromone transformer tap to the other with the use of ohmic changeover resistors which can carry the current only transiently, must accomplish the whole load switching movement from the initial movement tothe final position within a period of'about second. For this purpose, there is-generally'employed a spring: action. driving gear which is charged during the preselecting movement and released after the completion oft this movement in order to eifect the proper load changeover switching operation momentarilyand irrevocably. Several types of spring action drives have found their way' to practical application: latchless tilting action spring drives as well as latched. torsional or rotary action spring drives. Both kinds of spring drives, however, show a power or torque versus travel diagram in which the movable parts of the load changeover switch obtain their greatest velocity only after completing half or more ofi their total travel; The current interruptingprocess on the maincontacts of the load changeover-switch which is especially. important at great current intensity; must be mastered. however in the first quarter of the total movement. The safe arc breaking eifect' ishowever dependent on. the opening velocity of the interrupting eontactswhich in turn depends on the velocity which the spring drive has imparted to the movable load changeover switclrpa'tts up to the-interrupting moment.

Latchless. tilting action: spring drives are especially unfavorable in this respect, because their power or torque attains: its maximum only after completing half, of the switching travel onaccountof the lever am only slowly increasing after the moment of tilting. Somewhatmore appropriate is the latched torsional or rotary spring drive which with appropriate choice of the spring characteristics has a power or torque above. the average value at the beginning of the movement, decreasing. steadily to. about half its value at the end of the movement. The. former spring drive releases only about 15% andjthe latter spring drive only about 30% of its total working power up to. the deciding moment of arc extinguishing on the main contact. Both drives must, therefore, be considerably overdirnensioned in order to have discharged to themovable load changeover switch part at this deciding moment as much accelerating power, as is required for safe arc extinguishing. This entails considerable stresses of' the mechanical construction elements of the. load changeover switch, if the remaining 85% or 70% respectively of'the spring drive working power are discharged and must be annihilated. by braking,

According to the present invention, this disadvantage is removed by discharging the spring action driving gear F to the driving shaft M of the load changeover switch through a lever gear which from the initial position to the final position, produces a continually variable torque ratio, either by means of variable lever arm lengths or by means of variable effective angles of the driving lever in relation to the driven one. It is with good result that these two effects (variable lever arm and variable eflective 2. angle) can be used at the same time. The variationof the leverlengths and-the effective angles can be influenced by the design in such a way that with a given spring power curve (e. g. continually decreasing from 100% force in. the initial position to 50% force in the final position) a very great torque may be produced onthe load changeover switch drive in the be 'nning which, rapidly decreasing, passes in the secondhalf of the travel of the movement its minimum which is just suificientjto maintain the velocity at a given amount of braking, and which increases againnear the end of the travel,-in order to ensure safe contact making on the main contact against the elastic force of the contact springs.

In the accompanying drawing,

Fig. 1 is a part elevational andpart diagrammatic view of spring actiondriving gear. with variable torque en1bodying the invention.

Figs. 2 and 3 are views of charts showing various torque conditions present during the operationv of the driving gear.

Fig. 1 shows the lever mechanism of such a. spring action driving gear. The driven organ A of the lever transmission .gear, connected with the shaft of the movable load changeover switch. part, revolves around the axis M of the load changeover switch; in theillustrated example from the initial position to the final position by an angle of Thesaid organconsistsof a lever with an oblong hole guiding L, in which a roller R is gliding which in turn is mounted on the driving. lever B rotatable around. the auxiliary axis m. In the position represented in Fig. l, the driving lever B is fixed on one side by the spring butter Em, and on the other side by the latch Kli.

The force of the spring action driving gear F is acting in the direction of the arrow Pf on the driving lever B, but can only become eifective if the latch K11 is disengaged. This is done, as customary on other spring drives too, by the organ C effecting the charging motion of the gear spring F, after the full' spring tension is attained, After the latch is disengaged, the spring force Pf turns the driving lever B from left to. right until resting on the right, bufier Epa. In this position, B is locked by the right latch Klz. During this movement, the roller R has proceeded on a circular path. to the right position. During this action, the lever arm m-R of the driving lever B remained unchanged. The lever arm M-R, however, of the driven organ A was shortened, at first quicker, then slower, by gliding of the roller R in the oblong hole L to the middle position, and prolonged again, first slower, thenquicker, by gliding from there to the final'position. The hereby eflfected torque transmission ratio Uh varies as shown, the conditions being as drafted in Fig. 2, between. in the initial and final positions and 50% in the middle position. Parallel with the variation of the lever arm MR, a variation of the effective angle has taken place, the roller R acting upon the radial flank of the. oblong hole L.

Thereby a second variable torque transmission ratio arises which varies, under the conditions shown in Fig:- 2, in the sameway between 100% and 50%. The two variable transmission ratios and Uw compose in the total transmission ratio AwM Ami representing. a portion, varying from one position to the other, of the angle of the driving lever B, and Aw representing the respective portion of the angle of the driven lever A. The torque ratio U, which is shown in Fig. 3 by a dotted line, varies from the initial position through the middle position to the final position in the proportion 100%:25%:100%. After multiplication of ii with the spring force curve Pf, shown in Fig. 3 in a 3 dot-and-dash line and decreasing from 100% to 50%, the solidly drawn actual torque curve Dm=Pf U results, which decreases from 100% to 17% and increases again to 50%. From its tendency it can be seen, that the intended object, e. g. a very great torque in the initial position, a small torque in and after the medium position and a torque moderately increased again in the final position, is actually fulfilled. In this way it is furthermore attained, that up to the decisive moment of interrupting the are on the main contacts half the total working power of the spring action driving gear is discharged to the movable load changeover switch parts, accelerating them already after a small angle of motion to the desired high switching velocity. For realizing the same switching velocity at the main contacts, a more than 70% decrease of total stored energy of the spring action driving gear is hereby obtained as compared with the latchless tilting action spring drive, and more than 40% as compared with the latched torsional or rotary action spring drive. The consequence is a reduction in the dimensions and a lower mechanical stress on the load changeover switch.

The operation of the mechanism is as follows: The crank 1 rotates in a clockwise direction, as indicated by the arrow. It is driven by hand or motor. To the free end of the crank 1 the arm C is pivoted. This arm is in pivoted engagement with one end of a lever 2 which is rotatably supported at its other end at m. The drive lever arm B is also rotatably supported at 111. These two arms 2 and B are loaded by a substantially V-shaped spring P which presses against pins B and 2 respectively, and strives to push these two arms 2 and B together, i. e. to cause them to coincide. On the free end of drive arm B there is provided a projection 3 which serves to work alternately with the pawls Klr and Klz. These two pawls turn around a common fulcrum 4. In the position shown, the arm B is locked by the pawl Kli and the stationary end stop Epr.

The driven lever arm A is pivoted to the drive lever arm B by a pin R and a longitudinal slot L in the arm A. This lever arm A acts directly on the load switch, not shown, the shaft of which is designated M and is perpendicular to the plane of the sheet of drawing.

In the position shown, the crank 1 has already turned so far in clockwise direction that the lever arm 2 has passed against the action of spring F out of the position in which it coincides with the lever arm B into the position shown in the drawing. Upon further rotation of the crank 1, a projection 5 on the free end of the lever arm C comes against a trip-lever 7 rotatably supported at 6, in such a manner that this lever 7 is swung in clockwise direction and its stop 8 comes against a stop 9 on the pawl Kli, during which operation the latter rotates in counter-clockwise direction and releases the projection 3 of the drive lever arm B. The result of this is that am B, under the action of the spring F, now snaps in counterclockwise direction, toward the lever arm 2 until it coincides with same. The driven lever arm A is carried along in clockwise direction by the pin R and the longitudinal slot L and moved out of the solid-line position shown in the drawing into the dotted line position A about 90 away, but it may be moved up to 120 away.

By means of the shaft M which is coupled with lever arm A, the load switch is also moved about 90 or more from one operating position into the next operating position. In the new position A, the drive lever arm B is now held fast by the pawl K12 and the stationary end stop Epz. Upon continuation of the rotation of crank 1, the same operation now takes place in reverse in such manner that a projection on lever C releases the pawl Klz in the same manner as the projection 5 previously released pawl K11. During this operation, the stop 8 on the trip-lever 7 acts in an analogous manner by means of a counterstop 11 on pawl Klz.

I claim:

1. Spring-pressed driving mechanism with variable torque for load changeover switches including, in combination, a crank, a fixed shaft member, a lever arm having one end pivotally mounted on said shaft member, another lever arm having one end pivotally mounted on shaft member and spaced from said first-named lever arm, a spring member supported on the shaft member and operatively connected to said lever arms for continually pressing said lever arms into alignment with each other, another lever arm flexibly connected to one end of the first-named lever arm and to a changeover switch, an actuating arm connected at one end to said crank and at its other end to one end of said second-named lever arm, latching devices for holding said first-named lever arm in moved position when moved by said spring, and tripping means operatively connected to said actuating arm and means for releasing the latter.

2. Spring-pressed driving mechanism with variable torque for load changeover switches including, in combination, a fixed shaft member, a driving lever arm having one end pivotally mounted on said shaft member, a pin carried adjacent the free end of said arm, a projection on the free end of said arm, another lever arm having one end pivotally mounted on said shaft member and spaced from said driving lever arm, a spring member supported on the shaft member and operatively connected to the lever arms for continually pressing said lever arms into alignment with each other, a driven lever arm having a slotted portion at one end flexibly connected to the pin on said driving lever arm, the other end of said driven lever arm being operatively connected to a rotatable shaft of a load changeover switch, an elongated actuating arm pivotally connected at one end to said crank and pivotally connected at its other end to the other end of said second-named lever arm, spaced projections on one edge of said actuating arm, spaced stop members at the ends of the path of movement of said driving lever arm, pivotal pawl members interposed between said top members and adapted to engage the projection on said driving lever arm for holding said driving lever arm in spring-moved positions against said stop members, and a trip lever operatively connected to said pawl members and disposed in the path of movement of the projections on said actuating arm whereby the holding action of the pawl members is released.

References Cited in the file of this patent UNITED STATES PATENTS Re. 18,933 Tarbox Sept. 5, 1933 164,212 Prouty June 8, 1875 795,235 Richards et al July 18, 1905 876,355 Hovey Jan. 14, 1908 1,540,247 Bowman June 2, 1925 2,009,383 Blume July 30, 1935 2,177,109 Hill Oct. 24, 1939 2,231,696 Wolfe Feb. 11, 1941 2,427,621 Peterson Sept. 16, 1947 2,453,560 Westberg Nov. 9, 1948 2,513,677 Rigert July 4, 1950 FOREIGN PATENTS 414,119 Italy June 27, 1946 621,078 Great Britain Apr. 4, 1949