US2937252A

US2937252A - Circuit breaker

Info

Publication number: US2937252A
Application number: US690393A
Authority: US
Inventors: Russell C Strother; Borough Rochester; Robert H Flick
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1957-10-15
Filing date: 1957-10-15
Publication date: 1960-05-17
Anticipated expiration: 1977-05-17

Description

y 1960 R. c. STROTHER ETAL 2,937,252

CIRCUIT BREAKER 2 Sheets-Sheet 1 Filed Oct. 15, 1957,

m: 0 5 T-1 8 [NH m: on m9 7c .5. 52 0 l NVENTORS Russell C. Strothers 8 Robert H. Flick A'TTORNEY United States Patent C) CIRCUIT BREAKER Russell C. Strother, Rochester Borough, and Robert H. mFlick, Brighton Township, Beaver County, Pa., as- .signors .to Westinghouse Electric Corporation, East Pittsburgh, Pa.,= a corporation of Pennsylvania "a lication bctober 15, 1951, Serial No. 690,393

' 6 Claims; or. 200-109 Another object of the invention is to provide a circhit-breaker embodying an electromagnetic tripping means, having a fixed magnet yoke and a movable annature with improved means for adjusting one element of said electromagnetic tripping means to vary the minimum overload. current required to instantaneously trip the breaker. v

' Another objectof the invention-is to provide a circuit breaker embodying a tripping electromagnet having a fixed 'magnet yokeand a movable armature with improved adjusting means using only a' very narrow space-for adjusting the position of the armature relative to the magnet yoke to vary the tripping characteristic of the tripping electromagnet.

Another object of the invention is to provide an adjusting device according to the preceding paragraphsthat is not affected by sudden jars or shocks.

A further object of one form of the invention is to make possible the use of a large diameter adjusting wheel, which may be readily turned by hand without use of a tool such as a screw driver, which is accessible from, andprojects only from, the front surface of the trip unit, and which occupies a minimum of space at the front surface of the trip unit and also within the trip unit. This is accomplished by using a calibration adjusting wheel carrying cam surfaces and which is rotatable about an axis parallel to the base of the circuit breaker with one edge of the wheel projecting into a narrow slot in the front face of the cover of the trip unit.

The invention both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of several embodiments thereof when read in conjunction with the accompanying drawings.

In said drawings:

Figure 1 is a vertical sectional view of a circuit breaker embodying the principles of the invention;

'Fig. 2 is a sectional view on an enlarged scale of the trip device; V

Fig. '3 is a sectional view taken on line III III of Fig. 2 showin'g the adjusting device for one of the poles of tripping electromagnet;

"-Figl'4 is an enlarged elevational view of the adjusting device shown in Figs. 1 and 2; l

Fig. 5 is 'an enlarged side elevational view partly in section of a modification of the adjusting device; and

the. breaker being omitted to more clearly illustrate the 2,937,252 Patented May 17, 1960 ice - Fig. 6 is an enlarged front elevational view of the adjus'ting device shown in Fig. 5.

Referring to Fig. 1 of the drawings, the circuit breaker comprises a base 11 and a cover 13 both of molded insulating material. The circuit breaker is of the threepole type, each pole having a line terminal 15 and a load terminal 17 at opposite ends of the base 11.

The circuit breaker includes a stationary contact 21, a movable contact 23 and an arc extinguisher 25 for each pole of the breaker. A common operating mechanism indicated generally at 27 is provided for simultaneously actuating the three movable contacts to open and closed positions, and a trip device indicated generally at 29 serves to effect automatic opening of the breaker contacts in response to predetermined overload conditions in the circuit through any pole of the breaker.

The line terminal 15. forms the outer end of a conducting strip 31 which extends into the housing and rigidly supports the stationary contact 21. The movable contact 23 for each pole is rigidly mounted on a contact arm 33 supported on a switch arm 35 secured on a tie bar 37 which extends across all of the poles of the breaker and supports the switch arms for the several poles for unitary movement to open and closed positions.

. The contact arm 33 is connected by means of a flexible conductor 39 to a terminal 41 (Fig. 2) secured to the base 11 of the breaker by a screw 42 which also serves to secure one end or leg of a heater element 43 to the base.; A bimetal element 45 forming .a part of the trip device 29 is mounted on the other leg of the heater elemeat 43 which is electrically integral with an. energizing one turnwinding 44.

The operating mechanism 27 (Fig. 1') is disposed lating shield 67 for substantially closing an opening 69 in the cover 13 is mounted on the end of the operating lever 55 and has an integral handle 71 extending out through the opening 69 to permit manual operation of the breaker mechanism The toggle links are pivotally connected together by a knee pivot pin 73. The toggle link 57 is pivotally connected by a pivot pin 75 to the cradle 63 and the toggle link 59'is pivotally connected to the switch arm 35 for the centerpole by a pin 77. The overcenter spring 61 is connected under tension between the knee pivot pin 73 of the toggle 5759 and the outer end of the operating lever 55.

The circuit breaker is operated to open position by movement of the handle 71 (Fig. 1) in a clockwise direction to the off position actuating the overcenter spring 61 to cause collapse of the toggle 5759 and opening movement of the switch arms 35 for all of the poles of the breaker in a well known manner.

The breaker is manually closed by reverse movement of the handle 71 from the off to the on position which. causes the spring 61 to move overcenter and straighten the toggle thereby moving the switch arm 35 v for all of the poles to the closed position.

,In addition to the bimetal element 45, the trip device includes a series overload tripping magnet 79 (Fig. 2)

for each pole and a trip bar 81 common to all of the poles and biased to latching position by a spring 82. The trip bar. 81 is made of insulating material and is pivotally supported by means of pins 83 (Fig. 3) supported in a bracket 85 secured to the base 11 by the screws 42. The

bracket 85 also supports an insulating base 87 for the trip device. A cover 89 of insulating material is provided to enclose the trip device and is sealed to the base 87 for the trip device. A latch 91 on the trip bar 81 normally eng ges a latch me hanism 93 which, in. turn, engages and releasably restrains the cradle 63 to releasably restrain the operating mechanism in closed position.

The tripping electromagnet 79 comprises a U-shaped magnet yoke 95 supported by means of; rivets 96 on a. bracket 97 which is rigidly supported on the base 87 for the trip device. A movable armature 99 is slidably supported in an extension 101 of the bracket 97 and has secured thereto a rod 103 which, at its other end, has a head 105 for engaging and operating the trip bar upon energization of the magnet. A compression spring 107 coiled about the rod 103 biases the rod and the armature 99 to the unattracted position. The tripping magnet is energized by the energizing one turn winding 44 which extends between the legs of the U-shaped magnet yoke 95.

When a low overload current occurs, the bimetal element 45 is heated by the heater element 43. and when heated a predetermined amount bends toward the right (Fig. 2) to engage an adjusting screw 109 on the trip bar 81 and actuates the latter to effect release of the cradle 63 and opening of the breaker contacts after a time delay in a manner well known in the art.

The circuit breaker is tripped open instantaneously by operation of the tripping magnet 79. When the magnet .is energized by overload currents of, for instance, 1000% or more of normal rated current, or by a short-circuitcurrent, the armature 99 is attracted causing the head 105 to engage and actuate the trip bar 81 thereby effecting instantaneous release of the cradle 63. This elfects automatic opening of the contacts for all of the poles of the breaker- It is necessary to reset and relatch the breaker mechanism before the contacts can be. closed following an automatic opening; operation. Resetting and relatching is effected. by moving the handle clockwise as faras it will go During this movement a, projection 111 on the oper-. ating lever 55 engages a shoulder on the cradle 63 and moves the latter in a clockwise direction. Near the end of. this movement the. free end of the cradle 63 is reengagccl with the latch mechanism 93in a well known manner. The breaker. contacts are then closed. in the Previously described. manner y movement of the. handle to the on position.

Me ns is provided to. selectively determine the. minimum overload current required to instantaneously trip the breaker. This, is accomplished by adjusting the position ofv the armature. Secured to the U-shaped magnet yoke 95 by the screws or rivets 96, is a bracket 113 hav-v ing projections 115 extending adjacent the ends of the armature 99. The projections, 115 have ears 117 bent inwardly toward each, other to form auxiliary pole pieces which, when the magnet is energized, exert a back pull on the armature 99. The purpose of the projection 115 and the auxiliary pole pieces 11'] is to provide limited paths for at least a portion of the magnetic fiux to thereby provide a difierential pull on the armature, which may be varied according to the adjustment of, the armature relative to the yoke member 95 andv the auxiliary pole pieces 117.

The armature 99 is adjusted by means of an adjusting slide 119 (Figs. 3' and 4;), which engages the, back face of the armature 99. The slide 119 is formed from aflat sheet and is sli'dabl'y supported by means of pins 121 and slots 123 on an L-shaped bracket, 125 formed from a fiat sheet and rigidly secured by" means of screws 121' to cars 129 formed on the auxiliary pole pieces 117'. Pivotally mounted by means: of a pivot pin 131 on, the outer end of the L-shaped bracket 125 is an adjusting wheel 133' which extends out through a narrowslot- 135 in the top. of the trip device cover 89; Integral with the wheel 133 is a stepped cam 137 which engages an, angular camsurface 4 139 on the outer end of the adjusting slide 119. The pivot axis 131 of the adjusting wheel 133 and cam 137 is parallel to the base of the circuit breaker and extends in the same direction as the length of the breaker so that the projecting upper rim of the adjusting wheel extends in the direction of the width of the breaker and does not increase its length. The adjusting slide 119 is biased outwardly into engagement with the stepped cam 137 by means of a spring 141 compressed between one of the auxiliary pole pieces 11.7 and a portion 143 struck out from the adjusting slide 119. The flat surfaces or the slide 119 and bracket 125 fit close together and take very little space in the direction of the length of the breaker.

As seen in Fig. 3,, the trip magnet 79 is adjusted to trip the breaker in response to overload currents of high value. In this adjusted position, the armature 99 is biased by its spring 107 against the inner end of the adjusting slide 119 and the slide is biased by the spring 141 against the stepped cam 137. In this position the armaturn 99 is in its position of greatest retraction permitted by the adjusting cam 137. This position of the armaturev 99 provides the greatest air gap between the armature and. the magnet yoke and the smallest, air gaps between the back of. the armature and the auxiliary pole pieces 117. This increases the magnitude of overload current required to operate the magnet and t the breaker. CountcrclockwiSe rotation of the whee 133 and of the. integral cam 13.7 to the next notch or step hmsts the slide 119 downwardly and moves the. armaone 99 a predetermined. distance. toward the magn t yoke 95. This has the. etiect of increasing the forward pull of the magnet on the armature and decreasing the back pull opposing movement of the armature in tripping direction. When. the device is adjusted to a position below the highest position to which it is capable of adjustment, the tripping magnet will be actuated by overload currents of lesser magnitude to trip the breaker.

As an example, assuming that the breaker is rated to carry a normal load indefinitely without actuating the trip device, the bimetal 45' may be calibrated to trip the breaker with an inverse time delay in response to overload currents of, for instance, between and 300% of the normal rated current. The tripping electromagnet may be calibrated and, adjusted to instantaneously trip the breaker in response to overload currents of, for instance, between 300% and 1100% of rated current depending on the adjustment of the armature 99. With the trip device calibrated to the above arbitrarily selected values, and with the cam 137 adjusted so that its highest notch engages the slide 119, the armature 99 will be correspondingly moved closer to the magnet yoke 95 and the magnet will function to trip the breaker in response to overload currents of 300% or more of rated current. It the cam; 137 is rotated to bring the lowest notch into engagement with the adjusting slide 119, the armature 99 will be moved away from the yoke 95, and the armature will not be attracted until the occurrence of an overload current of 110070 of rated current.

Figs. 5 and 6 illustrate a modification of the invention in which a bracket 145' is rigidly supported on one of the ears 129 and extends upwardly where it has a portion 147 bent inwardly at right; angles. An adjusting rod 149 has its inner end rotatably mounted in the. adjacent auxiliary pole piece 117 and a head 151 at the outer end of. the rod is rotatably supported in the. portion 147. Secured to. the. r d 149 for rotation, therewith is, a, cam member -1 53 which has a cam surface 155 on the upper face here f eng ging: a fixed p n 157- in the adjacent, ear 129. A spring 159 compressed bet en the. bottom. of. the. cam 15.3.. and. he auxiliary pole piece 1.17. biases he cam W wardly into engagement with the fixed, pin 151.

The. adjusting rod. 149 is turned by inserting; a, screw driver through an opening in the cover 89 into. a suitable lot in. the head. 151. When rotated counterclockwise, due

together with the rod 149 is moved axially down- Y wardly causing the lower end of the rod to move the armature 99 toward the magnet yoke 95. Upon clockwise rotation of the rod 149 the spring 159 moves the rod 149 and the cam outwardly and the armature spring 107' biases the armature 99 against the inner end of the rod 149. In this manner the armature is adjusted and the adjustment is indicated on a scale plate 161 attached to the cover 89 and surrounding the opening through which the rod is accessible.

It will be noted that the form of the invention shown in Figs. 1 through 4 has important advantages in that it permits the use of a relatively large diameter adjusting wheel 133 which may be readily turned by hand and does not require the use of a screwdriver for changing the calibration of the breaker. This is accomplished without taking up a large amount of space in the trip unit by having the adjusting wheel mounted edgewise in the trip unit and rotatable with its cam 137 about an axis parallel with the base of the circuit breaker. Then it is only necessary to have a relatively narrow slot 135 in the top or front face of the cover of the trip unit into which one edge portion of the wheel projects so that it may be rotated by the thumb or finger.

Space is conserved within the trip unit and low cost is obtained because both the bracket 125 and slide 119 are made from stampings from flat sheet material. Little space is required for these members because they are positioned close to each other edgewise with respect to the base of the circuit breaker. The motion of the slide 119 takes a minimum of space since it moves edgewise in the plane of its flat faces.

Both forms of the invention have the advantage that the adjusting means is at the top of the trip mechanism and does not project, nor require access, from the side of the trip unit facing the end of the breaker. This keeps the trip unit small in the direction of the length of the breaker and leaves the space at the end of the breaker clear for the mounting of various terminal structures or for the mounting of current limiting faces.

While the invention has been disclosed in accordance with the provisions of the patent statutes, it is to be understood that various changes in the structural details and arrangement of parts thereof may be made without departing from the spirit of the invention.

We claim as our invention:

1. In a circuit interrupting device, a trip unit comprising an energizing winding, a U-shaped magnet yoke disposed to be energized by said winding, a movable armature movable toward and away from said magnet yoke, an adjusting member having one end disposed to engage said armature and rectilinearly slidable in a plane to vary the position of said armature relative to said magnet yoke, means mounted on said magnet yoke supporting said slidable member, cam means mounted on said support means at a point remote from said magnet yoke near the front of said trip unit cooperating with the other end of said slidable means, manual means for actuating said cam means to cause said slidable member to varythe position of said armature relative to said magnet yoke, and said manual means comprising a rotatable Wheel disposed with its axis normal to said plane.

2, A circuit interrupting device comprising an energizing winding, a U-shaped magnet yoke structure disposed to be energized by said winding, a movable armature movable toward and away from said magnet yoke structure, a rectilinearly slidable fiat adjusting member having one end disposed in engagement with said armature and movable longitudinally in a plane to vary the position of said armature, a manually operable rotatable cam member engaging the other end of said slidable member for actuating said slidable member, said slidable member and cam member being positioned so that the line of force of said slidable member is through the axis of rotation of said cam member which axis is normal to said plane, and a -fiiicket mounted on said magnet yoke structure slidably supporting said slidable'member and rotatably supporting said cam member.

3. In a circuit interrupting device, a trip unit comprising an energizing winding, a magnet yoke disposed to be energized by said winding, a movable armature movable toward and away from said magnet yoke, a rectilinearly slidable adjusting member having one end disposed in engagement with said armature and movable to vary the position of said armature, a manually operable rotatable cam member engaging the other end of said slidable member for actuating said slidable member, a wheel manually rotatable to rotate said cam member, biasing means biasing said slidable member into engagement with said cam member, a bracket mounted on said magnet yoke slidably supporting said slidable member, said bracket rotatably supporting said cam member near the front of said tn'p unit, and a cover for said trip unit having an opening therein providing access to the outer edge of said wheel whereby said wheel may be manually rotated from the outer side of said trip unit cover.

4. A circuit interrupting device comprising an energizing winding, a U-shaped magnet yoke structure disposed to be energized by said winding, a movable armature slidable toward and away from said magnet yoke structure, a bracket rigidly supported on said magnet yoke structure, a member rectilinearly slidably mounted on said bracket having one end engaging said armature, a rotatable cam member rotatably supported on said bracket and engaging the other end of said slidable member, said slidable member and cam member being positioned so that the line of force of said slidable member is through the axis of rotation of said cam member, manual means for rotating said cam member to move said slidable member longitudinally in a plane and cause said slidable member to vary the position of said armature relative to said magnet yoke structure, and said manual means comprising a rotatable wheel disposed with its axis normal to said plane.

5. In a circuit interrupting device, a trip unit comprising an energizing winding, a U-shaped magnet yoke disposed to be energized by said wind-ing, a movable armature slidable toward and away from said magnet yoke, a flat bracket rigidly'supported on said magnet yoke, a flat member rectilinearly slidably mounted on said bracket having one end engaging said armature, biasing means biasing said armature against said one end of said slidable member, a rotatable cam member rotatably supported on said bracket at a point remote from said armature near the front of said trip unit and engaging the other end of said slidable member, a wheel manually rotatable to actuate said cam member to cause said slidable member to vary the position of said armature relative to said magnet yoke, a cover for said trip unit having an opening therein, and the outer portion of said wheel extending through said opening so that said wheel may be manually rotated from the outer side of said trip unit cover.

6. A circuit interrupting device comprising an energizing winding, a magnet yoke structure disposed to be energized by said winding, a movable armature slidable toward and away from said magnet yoke, a bracket rigidly supported on said magnet yoke structure, a member rectilinearly slidably mounted on said bracket having one end engaging said armature, biasing means biasing said armature into engagement with said one end of said slidable member, a rotatable cam member rotatably supported on said bracket and engaging the other end of said slidable member, said slidable member and cam member being positioned so that the line of force of said slidable member is through the axis of rotation of said cam member, said axis of rotation of said cam member being normal to said line of force of said slidable member, biasing means biasing said other end of said slidable means into engagement with said cam 7 member, and manual means for rotating said cam memher to cause said slidable member to vary the position of said armature relative to said magnet yoke structure.

References Cited in the file of this patent UNITED STATES PATENTS 8 Mayer May 1, 1906 Smythe Mar. 19, 1907 Dyer Dec. 20, 1949 Lindstrom May 16, 1950 Edmunds Nov. 6, 1951 Grissinger Feb. 19, 1952 Kathe Aug. 30, 1955