US2448470A - Latch-trip type circuit breaker - Google Patents

Description

Aug. 1948. A. B. RYPlNSKl LATCH-TRIP TYPE CIRCUIT BREAKER Filed Sept. 25, 1941 Patented Aug. 31, 1948 LATCH-TRIP TYPE CIRCUIT BREAKER Albert B. Rypinski, Laurelton, N. Y., assignor to Metropolitan Device Corporation, N. Y., a corporation of New York Brooklyn,

Application. September 25, 1941, Serial No. 412.210

1 Claim. (01 175-294) The invention herein disclosed relates to a relay or circuit breaker of the kind which while under normal conditions maybe operated manually in the manner of an ordinary switch, operates automatically to open the circuit upon the existence of a short circuit or a continued overload. More particularly, the invention relates to a relay or circuit breaker of the kind disclosed in the co-pending applications for patents, Serial Nos. 309,521 and 321,022, filed December 16, 1939, and February 27, 1940, respectively, now Patent Nos. 2,260,583 and 2,336,036, granted October 28, 1941, and December 7, 1943, respectively.

I In the aforesaid applications for patents there is disclosed a circuit breaker that primarily includes a case and two movable elements within the case, preferably rotatably mounted about a common axis and resiliently urged toward off position. The two elements comprise the primary operating parts and consist of a manually operative element or handle, and a switch element or rotor. Normally, when the handle is moved to the on position, it is releasably latched to the case in this position. The switch element normally moves to, and is positioned in, the on position with the handle, as it is latched thereto through current releasable latching means. On the existence of abnormal current conditions, the switch element is released from the handle and moves to 011" position and in so doing releases the handle which .follows the switch element to off" position.

In another co-pending application Serial No. 335,488, filed May 16, 1940, now Patent No. 2,389,- 999, granted November 27, 1945, there are disclosed circuit' breakers of the kind mentioned above in which a coil is utilized as a part of the current releasable means that are mounted on the switch element and in which there is included means for obtaining a time delay in the operation of the circuit breaker on the existence of slight overloads.

The invention herein disclosed has for an object to provide a circuit breaker of this kind in which the force tending to effect the release of the rotor or switch element is materially increased with increases in current so that on slight overloads there is a delayed action and on short circuits a rapid action.

A circuit breaker embodying the invention and which is in part disclosed in the aforesaid application for patent Serial No. 335,488, is illustrated in the accompanying drawings in which:

Fig. 1 is a plan of a circuit breaker embodying the invention;

Fig. 2 is a transverse section of the same taken on the line 2-2 of Fig. 1

Fig. 3 is a sectional side elevation taken on the line 3-3 of Fig. 1;

Fig. 4 is a sectional side elevation taken on the line 44 of Fig. 1; and

Fig. 5 is a diagrammatic illustration of the electrical arrangement of the circuit breaker iilustrated in Figs. 1 to 4.

The circuit breaker illustrated in Figs. 1 to 4 of the drawings essentially includes a case and operating parts that are housed within the case. The case is the same for the modified form of the circuit breaker that is illustrated in Figs. 6 and '1 of the drawings, and, fundamentally, the operating parts are the same, the differences residing primarily in the mechanical and electrical arrangement constituting the current releasable means for effecting a release of the cir-. cuit-controlling or switch element of the circuit breaker. The case A for the circuit breaker is open at the bottom and has an opening I through the top for a finger piece 2 by means of which the circuit breaker may be manually actuated, A base B serves as afclosure for the bot-- tom of the case and as a, support for stationary contacts 3 and 4, associated with connecting pieces 5 and 6 and terminals 1' and 8. The case and base together form a complete enclosure for the circuit breaker. except for vents 9 and I0 extending vertically through the case to permit the free pass-age of gases generated by arcs formed within the case.

The operating mechanism in general includes two movable elements, a manually operative element or handle C from which the finger piece 2 extends, and a switch element or rotor D. The handle consists of a disc-like wall II from which a, shaft I2 formed integral therewith extends. An axial flange I3 is formed at one portion of the handle, the outer portion in the assembled circuit breaker, and extends from the wall H. The finger piece 2 extends radially from this flange through the opening in the case. The rotor is partially encased within the handle. It is rotatably mounted upon the shaft I2 which in turn isrotatably mounted in a slide ll, re-

. ceived in a complementary groove in one side wall of the case, and in the arcuate end of a slot H5 in the opposite side wall.

A spring element acts upon the handle and rotor to effect independent movement thereof towards 011" or open-circuit position. This spring element consists of two torsional spring sections l6 and 11, one on each side of a central loop l8 extending substantially tangentially of the spring. The end of the spring section I6 is received in a groove or keyway in the shaft l2 and the end of the section I1 is received in a. groove in the rotor.

Under normal conditions, the handle, when moved to the on" position, is restrained against the action of the spring section l6, which acts to urge the handle toward "011 position, by a 3 latching lever l9 that enters in a recess 20 in the flange on the handle and engages the end wall of the recess. This lever is resiliently urged into latching relation with the end of the slot or recess 20 by the spring loop l8 which engages the latching end of the lever. The lever is pivoted between its ends upon a pivot pin 2! that extends from the slide I4 in which the shaft i2 is .iournaled. A cam surface 22 on the rotor is arranged to engage the end 28 of the lever when the rotor moves to oil position. Upon engagement of the end of the lever by the cam surface 22, the lever is withdrawn from the recess in the handle and the handle is thus released to move to off position, under the action of the spring section l6.

The latch-engaging end wall of the recess 20, and the latching end of the lever l9 are designed and shaped to retain the handle in "on" position against the action of the spring section l8. These surfaces have, however, a relation such that upon additional pressure being exerted on the handle in a direction to move it toward "off" position, such for example as a force exerted manually on the finger piece 2, the lever is moved about its pivot and is released from the recess 20. In this manner the handle may be actuated manually.

The rotor normally is latched, in a manner hereinafter described, to the handle so that when the handle is moved to "on circuit position, the rotor moves with the handle. Likewise, the latching arrangement is such that if the handle be moved to off circuit position, the rotor under the action of the spring section I! will follow the handle to the oil position. The rotor carries contacts 24 and 25 which engage respectively, in the on" position, with the stationary contacts 3 and 4. When the rotor moves to the ofl" circuit position, the contacts 24 and 25 move away from the stationary contacts. Normally, the section I! of the spring and the stationary contacts exert a force tending to rotate the rotor to the "off" position. The stationary contacts are mounted and arranged so as to have a certain amount of resiliency and are positioned with respect to the contacts on the rotor so that they are under tension in the "on" circuit position of the rotor.

The rotor is provided with current-releasable means for effecting the release of the rotor from the handle upon continued overloads or short circuit. It is with this current releasable means, as arranged in a circuit breaker of this kind, that the invention of this application is primarily concerned.

In the circuit breaker illustrated in Figs. 1 to 4, there is provided an electro-magnetic arrange-' ment for releasing the rotor from the handle upon the existence of abnormal current conditions. The latching arrangement by which the rotor is normally secured to the handle includes a detent which consists of a dog-pointed, hardened set screw 26 that is threaded in an opening in the flange l3 and extends axially of the circuit breaker. The end 21 of the set screw acts as a detent and is engaged, under normal conditions, by the shaped end 28 of a lever or keeper 29. The lever 29 is pivotally mounted upon a pin 30 extending between brackets 3i, secured to the face of the rotor, and through brackets 32 formed on the lever. Embedded within the rotor there is a coil 33. One end of thiscoil is connected to the contact 24 and the other end is connected to the contact 25.

A spring 84 coiled around the pin- 30 acts upon the lever and normally biases it to a position in which the detent engaging end is held against the face of the rotor, in which position the end 28 engages the detent 21. By turning the set screw in the threaded opening in the handle, the extent of engagement between the lever and detent may be varied. and in consequence, the point at which the circuit breaker opens or the capacity of the circuit breaker may be varied or adjusted. Once set, the screw is preferably sealed against rotation. The engaging section or edge of the latch may be rounded to make a point contact with the detent and so minimize the drag on the lever when urged to the release position. The opposite edge 35 of the lever is preferably bent outwardly to form a lead-in.

It will be apparent that when the circuit breaker is closed the current passing through the circuit passes through the coil 33. This coil is calibrated so that upon the passage of a particular current through it, the keeper :9 is actuated or drawn to the coil causing the engaging end 28 to be released from the detent 21. When this occurs, whether by virtue of a short circuit or a continued overload, the rotor is moved to the oil" position by the action of the spring section II. Upon arriving at the "011 circuit position, the rotor, as previously described, trips the latching lever l9 and the handle follows the rotor to the of! position. The lead-in on the latching lever permits the detent to pass the lever and since the circuit through the coil is broken, the lever will assume a position under the action of spring 34 in which it again engages the detent when the handle is moved to the on position.

For the purpose of effecting a time delay in the operation of the circuit breaker for slight overloads and a more rapid operation in the case of and in accordance with heavier overloads and short circuits, a resistor connected across the rotor contacts and shunting the coil is provided. This resistor is preferably one in which the resistance increases rapidly on heating. A resistor made of nickel has been found satisfactory for this purpose. In the construction illustrated in Figs. 1 to 4, a resistor 36 of this kind is connected across the contacts 24 and 25. This resistor is mounted in a groove 31 in the face of the rotor. It is secured to the rotor and electrically connected to the contacts by rivets 38 and 39 which are formed on the contacts 24 and 25 respectively.

These rivets extend through the rotor and openings provided therefor in the resistor. They are headed over and so mechanically secure the resistor to the rotor and electrically connect the resistor to the contacts.

Various metals which have a positive temperature coefllcient of resistance may be used for the resistor, pure metal and certain alloys. In general, the solid elementary metals have a positive temperature coeilicient of resistance, that-is their resistance increases with an increase in temperature. On pages 323-324-325 of the Smithsonian Physical Tables for 1939, the following temperature coefiicients of resistance are given:

These are considered to be, insofar as the presanauo eat application is concerned,

The electrical arrangement is illustrated in Fig.-

5. The current comes in at the point marked "Line." It passes from line wire it through the circuit breaker indicated at E, in which the rotor is indicated at F; thence through the "Load and back to the supply at 52. The numerals 58 and I3 indicate diagrammatically the switch breaks between the rotor and the stationary contacts. From this diagram it will be seen that the coil 33 is shunted by the resistor 36. When current is at full load value it divides between the coil and resistor in such proportion that the coil will not pull in the keeper 2! and the resistor is relatively cool. As the current rises above the full load, the resistor heats. increases in resistance, and the coil carries a proportionately larger percentage of the total current. At a predetermined critical value the keeper is attracted and the breaker trips. If the overload is of brief duration the resistor does not have time to heat and a large percentage of the total current passes through the resistor. The coil only gets a sufllcient percentage to permit it to trip when the overload continues long enough to heat the resistor to a critical value.

Connected as indicated in the diagram, assuming a direct current supply, the current in the circuit will split in the inverse ratio of the resistance of the coil 33 and the resistor 38. With an alternating current supply, the current split will be affected quantitatively by the inductance of the coil, but the net result will be the same as described below. Normally, the resistor may have a higher resistance than the coil so that the greater portion of the current passes through the coil. Under normal conditions, there will be little heating of the resistor. However, upon an increase of current passing through the circuit, heating oi the resistor will occur depending upon the additional amount of current passing through the circuit. For example, if an overload occurs in which the amount of current passing through the circuit is double the rated capacity of the breaker, the greater portion of the current will pass through the coil. However, additional current will pass through the resistor, in fact twice the normal current will ass through the resistor. This additional current will effect the heating of the resistor. As the resistor heats, its resistance becomes greater, thus cutting down the amount of the current that passes through it. The relation of the resistor and coil may be such that upon a condition 01' this kind, 1. e., a current of double the rated capacity. the b'reaker will trip after a period of two minutes. On the other hand, it a very heavy overload or a small short circuit occurs, causing a current over five or six times the rated capacity of the breaker, the

amount of current that will pass through the coil will immediately cause the coil to trip the breaker and the heavier the current, the more rapid the tripping of the breaker will be.

From the foregoing description of the construction illustrated in the drawings, it will be apparent that by this invention there is provided a circuit breaker that is comparativelysimple in construction, inexpensive to manufacture, that may be of such size as to be housed in the ordinary wall switch box and in which a delayed action is obtained for light overloads with rapid action on heavy overloads and short circuits.

It will be obvious that various changes may be made by those skilled in the art in the details of the embodiments of the invention illustrated in the drawings and described in detail above within the principle and scope of the invention as expressed in the appended claim.

I claim:

In a circuit controlling device of the kind described, the combination comprising a switch element movable between on and of! positions and biased toward ofl position, current releasable latching means for releasably latching the switch element in on" position including a coil carried by the switch element. and a shunt carried by the switch element and arranged to by-pass a portion of the current around said coil, said shunt having a positive temperature coeiilcient of resistance.

ALBERT B. RYPINSKI.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 603,594 Cutler May 3, 1898 923,839 Henry June 8, 1909 1,531,722 Adams Mar. 31, 1925 1,728,038 Burstyn Sept. 10, 1929 1,728,551 Jennings Sept. 17, 1929 1,763,197 Speiser June 10, 1930 1,812,843 Sachs June 30, 1931 1,812,845 Sachs June 30, 1931 1,872,122 Cook Aug. 16. 1932 1,909,057 Hines May 16, 1933 1,968,051 Sperry July 10, 1934 2,134,593 Wulsten Oct. 25, 1938 2,170,412 Jennings Aug. 22, 1939 2,260,583 Rypinski Oct. 28, 1941 2,281,950 Rypinski May 5, 1942 FOREIGN PATENTS Number Country Date 652,228 France Oct. 22, 1928 695,442 France Sept. 30, 1930

Images