United States Patent Office
Harris I. Sianback and Ralph H. Kingflon, Birmingham,
Mieis., assignors to Square D Company, Detroit, Mich.,
a corporation of Michigan
Filed Suns 9, 1955, Ser. No. 514,222
24 Claims. (CI 200—88)
This invention relates to apparatus for making and breaking electrical circuits, particularly circuit breakers automatically operable in response to current overloads, and more particularly to the current responsive trip devices incorporated within the circuit breaker.
An object of the present invention is to provide an improved current responsive trip unit for an automatic electric circuit breaker of simple and economical construction.
A further object of the present invention is to provide an improved ambient temperature compensation arrangement within the current responsive trip section of an automatic electric circuit breaker.
A further object of the present invention is to provide an improved magnetic trip mechanism for an automatic electric circuit breaker.
A further object of the present invention is to provide a trip mechanism for an automatic electric circuit breaker wherein parts of the trip mechanism constitute a latching surface for the circuit breaker mechanism so as to present a smooth durable latching surface for the mechanism without additional machining operations.
A further object of the present invention is to provide an ambient temperature compensation limiting device for an automatic electric circuit breaker whereby the circuit breaker will be compensated for ambient temperature in its normal range of operation, but wherein the compensation mechanism will be restricted from operation when the surrounding atmosphere has caused the circuit breaker to attain a predetermined temperature.
Further objects and features of the invention will be readily apparent to those skilled in the art from the following specifications and appended drawings illustrating a certain preferred embodiment of the invention in which:
FIGURE 1 is a side view of the circuit breaker with the side cover removed and showing the operating mechanism in the ON position.
FIGURE 2 is a vertical sectional view of the circuit breaker taken along the lines II—II of FIGURE 1.
FIGURE 3 is a vertical sectional view of the trip mechanism of the circuit breaker taken along the lines III—III of FIGURE 2.
FIGURE 4 is a sectional view through the trip mechanism of the circuit breaker taken along the lines IV—IV of FIGURE 3.
FIGURE 5 is a sectional view through the trip mechanism of the circuit breaker showing the latch window insert modification of the present invention.
The circuit breaker, as shown, comprises an open sided casing 1 of molded insulating material having molded recesses and ribs for the support of the circuit breaker mechanism and contacts therein. A cover 2 of molded insulating material, providing complementary recesses and barriers, closes the open side of the casing 1 and is mounted thereon by means of a plurality of rivets 3. Both the base and side cover are provided with top and bottom openings through which extend the operating and con
necting members of the circuit breaker mechanisms now to be described.
In one end of the insulating base 1, and supported on barriers established by portions of the base, is a conducting
g terminal strap 4 provided at its outside end with a terminal screw 5 and having secured thereto, at its inside end, the current responsive trip mechanism 6 of the circuit breaker. An adjustment screw 7 extends through a slot in the base 1 and threadedly engages the conducting strap
1q 4 in the interior of the base 1 with the head thereof operating against the slotted portion of the base 1 to provide an adjustment for the calibration of the automatic circuit breaker. The adjustment screw, in cooperation with the engagement of the strap 4 with the barriers of the base 1,
15 also serves the additional purpose of maintaining the strap within the base, thereby eliminating the need for a separate supporting stud or screw.
The conducting strap 4 bears at one end against a nib 8 in the insulating base 1 and substantially at its mid point
20 against a shoulder 9 on a portion of the insulating base so that rotation of the adjustment screw 7 operates to determine the angular position of the trip mechanism 6 within the interior of the base 1. The terminal end of the conducting strap 4 is suitably supported between support
25 ribs molded into the base and cover as generally shown in FIGURE 1.
The current responsive trip mechanism 6 supported on the interior end of the conducting strap 4 constitutes a bimetallic member 11 attached by suitable means, such as
30 welding, to the strap 4 at one end and has fixed thereto at its other end, by a means such as welding, a magnetic yoke member 12 of a generally U shape. The magnetic yoke member is provided with a pair of vertically disposed nibs 13 at which the weld to the bimetallic mem
35 ber is made and between which there is welded to the bimetallic member 11 and yoke 12, at the same time, a braided conductor or pigtail 14. The magnetic yoke member is provided with an offset lower extension 15 centrally thereof and, at the uppermost ends thereof, the arms of
40 the U are formed into supported pivot arms 16 disposed on the opposite side of the bimetal member 11 from that side on which the yoke member and bimetal 'are welded together. A movable magnetic armature member 17 having a central cutout 18 is pivotally supported on the
45 pivot arms 16 of the magnetic yoke 12 by outwardly extending shoulders 19 with the armature body formed so as to extend toward the lower end of the circuit breaker. The armature is formed to provide an arm 21 extending beyond the bimetallic member 11 toward the upper end
50 of the circuit breaker at ian offset angle away from the bimetallic member 11 and a helical coil spring 22 engages the magnetic armature member 17 at the shoulders 19 and about the arm 21 at one end and, at the other end, operates against the insulating base member 1 in a suitable
55 recess provided therein. To the lower end of the armature member 17 there is secured a U-shaped ambient temperature responsive bimetal 23 having the upper portion of one end 24 thereof extending along the inner side of the magnetic armature member 17 and bent over at its
60 extreme end at 25 to extend along the lower surface of the cutout 18 in the armature. The other leg 26 of the U-shaped bimetal 23 extends into cooperating relationship with the offset extension 15 at the lower end of the magnetic yoke member 12. An ambient temperature com
65 pensator limiter is provided in the trip mechanism 6 and