US2642509A - Automatic circuit breaker with calibration provision - Google Patents

Description

June 16, 1953 T. M. COLE ETAL.

AUTOMATIC CIRCUIT BREAKER WITH CALIBRATION PROVISION Filed March 23, 1951 aea ' INVENTORS 77/044491". c045 9404 M. CIMIJrE/VJEAI Jrraeuavfs Patented June 16, 1953 AUTOMATIC CIRCUIT BREAKER WITH' CALIBRATION PROVISION Thomas M. Cole, New York, N. Y., and Paul M. Christensen, West Orange, N. J., assignors to Federal Electric Products Company, Newark, N. J., a corporation of Delaware Application March 23, 1951, Serial No. 217,162

24. Claims.

This invention relates to automatic circuit breakers of the general type disclosed in United States Patents Nos. 2,174,669, 2,209,319, 2,209,352, 2,209,353 and 2,459,427, and in particular to calibrating devices therefor.

One object of the present invention is the provision of an automatic circuit breaker having a generally improved and simplified calibrating means.

Another object is the simplification of the overall circuit breaker construction by eliminating the need for a separate pivot means for the movable contact arm thereof, the pivot function being incorporated in a calibration means.

Another object is to provide for calibrating the circuit breaker after the mechanism is all assembled in the casing.

The above and other objects, features and advantages of the present invention will be more fully understood from the following descript on considered in connection with the accompanying drawings.

In the drawings:

Fig. 1 is a perspective view of an automatic circuit breaker pursuant to the present invention, the cover or one side of the casing being removed and the breaker being closed;

Fig. 2 is a sectional view, on an enlarged scale, taken along the line 2-2 of Fig. 1, the uncallbrated condition of the breaker being shown in full line and a calibrated condition thereof being illustrated in broken line;

Fig. 3 is a sectional view taken along the line 3--3 of Fig. 2;

Fig. 4 is a detail view showing a port1on of the movable contact arm and current responsive or overload device of the breaker, a calibrated condition being illustrated in full line and an uncalibrated condition being illustrated in broken line;

Fig. 5 is a view similar to Fig. 2 illustrat ng the calibrating means in a calibrated condition thereof;

.Fig. 6 is a view similar to Fig. 2 illustrating another embodiment of the invention; and

Fig. 7 is an end view of the circuit breaker.

In general, the circuit breaker illustrated herein, and in my above mentioned prior applications, comprises a movable contact member which carries the movable contact for engagement with and disengagement from the stationary contact of the circuit breaker. Said movable contact member is provided with an actuator which is releasably latched to said movable contact member by means of a current retuator and the current responsive device.

sponsive, or other overload device, which is carried by the movable contact member and releasably engages said actuator under normal load conditions so as to enable the movable contact member to be held in circuit closed position, or to be manually moved to and from said position, and which, upon release of said actuator, results in the movement of said movable contact member automatically to its open circuit position.

Briefly described, the provision for calibrating the circuit breaker, pursuant to the present invention, comprises means associated with the pivot means of the movable contact member to facilitate the displacement of a part of the movable contact member of the circuit breaker in relation to another part thereof in such manner as to move the actuator in relation to the current responsive, or overload device, so as to adjust the releasably engaged portions of the ac- Pursuant to the present invention, the usual pivot opening is provided in the movable contact member and said opening is extended to the lower marginal edge of said member. A pin is inserted into said opening to serve as a pivot for the movable contact member, said pin being adjustably positioned transversely of the movable contact member and being provided with a tapered portion for accomplishing the displacement of said part of the movable contact member.

Referring now to Figs. 1 through 5 of the drawings in detail, there is shown in Fig. 1 an automatic circuit breaker l0 provided with the body part 12 of a two-part insulated casing or housing, the cover therefore being indicated at It in Fig. 2. The circuit breaker mechanism l6 provided in said body part, as here shown, comprises the contact arm l8, mounted for pivotal movement, as hereinafter described in detail. Said contact arm is provided with the movable contact 20, at one end thereof, for engagement with and disengagement from a companion stationary contact 22 provided on a solderless terminal connector 24. At its other end, the movable arm I8 is provided with a pivotally mounted actuator 25 which is in operative engagement with the handle or manual operating member 28 by means of a resilient link 30. The movable contact arm [8 is also provided with a current responsive oroverload device, here shown as a bi-metallic element or latch 32, the free end of which is in latched engagement with the actuator 26 in the circuit making or closed condition of the mechanism. As here shown, the latch is connected to a stab element 34, which constitutes the other terminal of the circuit breaker, by means of a flexible conductor 36. Also, as here shown, the circuit breaker mechanism i6 is provided with electro-magnetic means for effecting the disengagement thereof, said means comprising a magnetic member 38 carried by the latch 32, and the rigid armature 40 which is secured at one end thereof to the latch and to the movable contact member. A spring 42 is interposed between the handle 28 and the movable member l8, as illustrated in Fig. l.

The operation of the circuit breaker is described in detail in the above mentioned patents. However, it will be understood that the bimetallic element 32 operates to latch the manually operable member 28 and to unlatch said actuator from the movable contact member, the unlatching taking place upon deflection of the bi-metallic element 32 causing the disengagement of the free end it thereof from the bottom part 5.6 of the actuator 26 upon the occurrence of an overload, or under other abnormal predetermined current conditions in the circuit controlled by the circuit breaker. When the bimetallic element 32 is deflected from engagement with the actuator 2%, spring %2 is effective to move the contact member E8 to its open position wherein the contact 20 is disengaged from the companion stationary contact 22.

Pursuant to the present invention, the movable contact member i8 is provided with a generally circular opening 48 at the axis about which it pivotally moves. An opening formed in the lower marginal edge of the contact member l8 constitutes an interruption in the periphery thereof and extends to the circular aperture 48 with which it is in communication, as illustrated in Fig. 3. It will be noted that the opening 50 is formed in the narrower portion 52 of the movable contact member, on the free end of which portion the actuator 26 is pivotally mounted. The body portion M of the movable contact member forms the wider and generally larger portion thereof and extends to the left (viewing Fig. 1) of the circular aperture 48 through which the pivot axis of the movable contact member extends.

In order to provide for both the pivotal mounting and the calibration of the movable contact member i8, there is provided a calibrating element or pin member 56. Pin 55 is provided at one end thereof with a portion having a screw driver slot 58, an adjacent bearing'portion 60, an intermediate tapering portion 6-2, and a threaded portion 64 which extends from said tapering portion to the other end of the pin. It will be noted that the portion 62 has its maximum diameter adjacent the bearing portion 6!] and its minimum diameter adjacent the threaded portion 64 The pin 58 is threadedly engaged in a nut 66. More particularly, said nut is provided at one end thereof with an interiorly threaded collar 68 of reduced diameter and at its other end with a lateral generally circular flange Hi. The collar 68 is disposed within a bearing aperture .72 provided in the body part l2 of the circuit breaker casing. In order to prevent relative movement between the nut 65 and the movable contact member 18, the latter is provided with a preferably pressed-out part '14 adjacent the aperture 48 therein, and the flange 70 is provided with a cut-out portion 16 into which said part 14 engages. Therefore, it will be apparent that as a result of the engagement of part M in the cut-out it, the nut 66 is retained 4 against rotation relative to the outer surface 78 of the movable contact member. It will be noted that the cover [4 of the casing is provided With an aperture 80 which extends completely therethrough and which is in registry with the bearing aperture 72 formed in the casing part [2. It willbe understood that the pivot axis for the movable member i8 extends through said casing apertures and through the aperture G8 in said member. Therefore, it will be apparent that when the pin member 56 is disposed in the aperture 80 so that the bearing portion Ell thereof has bearing engagement in said aperture, and with the threaded part 6-4 engaged in the collar 68 which has bearing engagement in the bearing apertur 12, said pin will serve as the pivot for the movable. contact member is in view of the fact that the nut 66 does not rotate relative to said movable member, as previously described. In calibrating the circuit breaker mechanism 16, the pin 56 is threaded into the collar 68 sufficiently to obtain the desired degree of overlap of the actuator end 46 and the free end 34 of the bi-metallic element 32. More specifically, as pin 56 is threaded into the collar 53, the tapering portion 60 is progressively moved into the aperture 48, as the entire pin member 56 moves transversely of the plane of the movable contact member I8. As the tapering portion advances into and moves through the aperture 43 the latter is distended and the narrower portion 52,

of the movable contact member is displaced in the plane thereof from the wider body part 54. This action is due to the fact that the distention of aperture 58 causes the distention of the aperture to which extends through the movable contact member from the aperture 38 therein to the marginal edge thereof.

Referring now to Fig.2, the full line position of the pin 56 shows the tapering portion 62 as it enters the aperture 43, thus indicating a minimum calibration adjustment or maximum overlap of the actuator end 46 relative to the free end 44 of the bi-metal. This maximum overlap condition is illustrated in broken line in Fig. 4, Fig.-

3 also illustrating this condition and showing the undistended relationship of the opposing sides of the edge aperture 50. As the pin 56 is threaded further into the aperture 58, the latter is distended and the-sides of the aperture 50 are forced apart, the relative displacement of said opposing sides resulting from full entry of the tapering portion 62 into the aperture 48 being illustrated in full line in Fig. 4-. It will be apparent that as a result of said distention or displacement of the opposing sides of aperture 50, the entire narrower portion 52 of the movable contact member i8-is moved in the plane thereof from the broken line position thereof, in Fig. l, to the full line position thereof, thereby moving the actuator 26 relative to the bi-metal' 32 to reduce the degree of overlap, as illustrated in said figure. The position of the pin 56 at the maximum penetration of the tapering portion 62 into the aperture 48 is illustrated in Fig. 5, it being noted that the said portion projects outwardly from the collar 68; As illustrated in Fig. 2, the bearing apertur 72 in the casing part i2 is deep enough to accommodate the extended portion of the pin 56.

The adjustment of the pin 56 may be conveniently made with the cover M of the casing in position thereon. This may be accomplished by inserting a screw driver into the open-ended aperture 80 in the cover, which'rem'ains open' until the 5. ciwuit breaker is calibrated ll-fter- -the-circiiit breaker is calibrated, and in order to prevent the misadlius'tment thereof, washer 82, preferably formed offiber glass or other suitable material, is inserted in the casing cover I l to close the aperture 8U,- as illustrated in Fig, 2. Thereafter; anysuitable sealing compound Blm'ay be inserted into the opening in the cover 1 '4- to seal the washer in position.

Figure 6' illustrates another embodimentoi the invention. Pursuant thereto, the 'pivot meinber 56A is provided with a screw driver slotted end portion 58A, an intermediate threaded taperin portion 62A,- and an unthreaded bear-mg end en tio'n MA at the other end thereof. The Contact member MA is provided with a threaded pivot aperture 48A which extends to or communicates with the previously mentioned marginal ed'ge opening 50. The tapering portion 62A is in threaded engagement in the 'pivot'opening can and the bearing portion A is directly engaged in'the bearing aperture 72A provided in the casing body 1 2 it being noted that the portion 5 8A extends into the aperture 80A provided in the casing cover [4. Therefore, it will be apparent that as the tapering portion 52A is screwed further into the pivot opening 48A, the marginal opening 50 W111 be distended in the same manner, as previoust-y described, to effect the displacement of the part 52 of the contact member I8A in the plane thereof for adjusting the amount of overlap of the end portion 46 of the actuator 2%. This ad justment may take place by inserting a screw driver into the casing opening 80A, prior to clos i-n g'the latter, for turning portion 58A of the pivot member 58. After the circuit breaker is calibrated, to the desired degree, the opening 89A may be closed by means of the washer 82 and the sealing compound 841, as previously described.

It will be noted that in both of the described embodiments of the present invention, the movable contact member is retained against lateral displacement. In the embodimer-it illustrated in Fig. 2, the nut 65 and the inwardly extending portion of casing part I 4 which defines the aperture 80 therein serve to revent lateral displacement of the movable contact member T8. In the embodiment illustrated in Fig. 6, the movable contact member I8A is retained against lateral displacement by the inwardl extending casing portions which define the bearing apertures 12A and 80A, respectively.

While we have shown and described the preferred embodiment of our invention, it will be understood that various changes may be made in the present invention without departing from the underlying idea or principles of the invention within the scope of the appended claims.

Having thus described our invention, what we claim and desire to secure by Letters Patent is:

1. An automatic circuit breaker, comprising a casing having laterally spaced walls provided with aligned bearing portions, a movable contact member, pivot means on which said movable contact member is mounted for pivotal movement between said walls, said pivot means being supported for pivotal movement by said bearing portions of the casing, an actuating member carried by said movable contact member anda current responsive device for operatively connecting said actuating member releasably to said movable contact member for operating the latter except when'said cure rent responsive device is disconnected from sald actuating member upon overload, and means 111- cluding interengaging relatively adjustable parts of said pivot means and said movable contact 6 member, respectively, for z'aidiusti 'g the releasable connection between said actuating member and said current responsive device whereby to calibrate the circuit breaker for automatic opening thereof upo'n overload.

2. Anautomatic circuit breaker, comprising -a casing haying laterally spaced walls provided with alignedbearing portions, a movable contact membei pivot means on h said movable contact member is mounted to pivotal movement between saidwans, said pivot means being supported for pivotalmovement by said bearing portions-or the cast. an actuating member "carried by said movable contact member and a current responsive device for opera'tively connecting said actuating member releasably tosaid movable cont-act membe! for operating the latter exceptwhen said current responsive device is disconnected from said actuating member upon overload, and means including inter'engaging relatively adjustable parts or said pivot means and said movable contact member, respectively, for adjusting the releasable connection between said actuating member and said current responsive device whereby t'o ca1i brate -the circuit breaker for automatic opening thereof uponoverlo'ad, one of said walls having an opening at said bearing portion thereof for access tosaid part of the pivotmeans for moving the latter axially of the pivotfor eiieting said adjustment of the parts.

3. An automatic circuit breaker, comprising a casing having laterally spaced Walls provided'with aligned bearing portions, a movable contact member, pivot means on which said "movable contact member is mounted for pivotal movement between said walls, said pivot means being supported for pivotal movement by said bearing portions of the casing, an actuating member carried by said movable contact member and a current responsive device for operatively connecting said actuating member releasably to said movable contact member for operating the latter except when said current responsive device is disconhosted from said actuating member upon overload, said pivot meansincluding a member which is internally screw threaded and which has a cylindrical portion turnably sup orted by one of said'bearing portions, a spindle on which said movable contact member is mounted, one end portion of said spindle being in screw threaded engagement with said internally screw threaded member and the opposite end of said spindle being' supported by the other of said bearing portions, said movable contact member having an opening therethrough, said opening extending to an edge of the contact member, and said spindle having an axially tapering part passing through said opening in engagement with the wall of said opening, whereby turning of said spindle about its axis relatively to said movable contact member is efiective to displace a part of the latter for adjusting the releasable connection between said actuating member and said current responsive device whereby to calibrate the circuit breaker for automatic opening thereof upon'ov'erload, and interengaging means on said internally screw threaded member and said movable contact member for retaining said members against relative rotation.

4. An automatic circuit breaker, comprising a casing having laterally spaced Walls provided with aligned bearing portions, a movable contact member,pivot means on which said movable c'ontact member is mounted for pivotal movement between said walls, said pivot means being supported for pivotal movement by saidbearing portions of the casing, an actuating member carried by said movable contact member and a current responsive device for operatively connecting said actuating member releasably to said movable contact member for operating the latter except when said current responsive device is disconnected from said actuating member upon overload, said pivot means being a spindle extending between said bearing portions and supported thereby, said movable contact member having an opening therethrough, said opening extending to an edge of the contact member, and said spindle having an axially tapering threaded part passing through said opening in threaded engagement with the wall of said opening whereby turning of said spindle about its axis relatively to said movable contact member is effective to displace a part of the latter for adjusting the releasable connection between said actuating member and said current responsive device whereby to calibrate the circuit breaker for automatic opening thereof upon overload.

5. An automatic circuit breaker, comprising a casing having laterally spaced walls provided with aligned bearing portions, a movable contact member, pivot means on which said movable contact member is mounted for pivotal movement between said walls, said pivot means being supported for pivotal movement by said bearing portions of the casing, an actuating member carried by said movable contact member and a current responsive device for operatively connecting said actuating member releasably to said movable contact member for operating the latter except when said current responsive device is disconnected from said actuating member upon overload, said pivot means including a member which is internally screw threaded and which has'a cylindrical portion turnably supported by one of said bearing portions, a spindle on which said movable contact member is. mounted, one end portion of said s'p-indle'being in screw threaded engagement with said internally screw threaded member and the'opposite end ofsaidspindle being supported by the other of said bearing portions, said movable contact member having-an opening therethrough, said opening extendingto an edge of the contact member, and said spindle having an axially tapering part passing through said opening in engagement with the wall of said opening whereby turning of said spindle about its axis relatively to said movable contact member is effective to displace a part of the latter for adjusting the releasable connection between said actuating member and said current responsive device whereby to calibrate the circuit breaker for automatic opening thereof upon overload, and means for retaining said internally screw threaded member and said movable contact member against relative rotation.

6. An automatic circuit breaker, comprisinga casing, a movable contact member in said casing, pivot means for mounting said contact member in the casing for pivotal movement therein, an actuating member, means including a currentresponsive device for operatively connecting said actuating member releasably to said contact member for actuating the latter, and means including interengaging relatively adjustable parts of said pivot means and said movable contact member, respectively, for adjusting the releasable connection between said actuating member and said current responsive device whereby to calibrate the circuit breaker for automatic opening thereof upon overload. l

7. An automatic circuit breaker, comprising a casing, a movable contact member in said casin pivot means for mounting said contact member in the casing for pivotal movement therein, an actuating member, means including a current responsive device for operatively connecting said actuating member releasably to said contact member for actuating the latter, and means including interengaging relatively adjustable parts of said pivot means and said movable contact member, respectively, for adjusting the releasable connec tion between said actuating member and said current responsive device whereby to calibrate the'circuit breaker for automatic opening thereof upon overload, said interengaging parts comprising an apertured edge portion of the movable contact member and a tapering portion of said part of the pivot means whereby axial movement of said tapering portion in said apertured portion displaces a part of said movable contact member in relation to said actuating member for the adjustment of said releasable connection.

8. An automatic circuit breaker, comprising a casing, a movable contact member in said casing, pivot means for mounting said contact member in the casing for pivotal movement therein, an actuating member, means including a current responsive device for operatively connecting said actuating member releasably to said contact member for actuating the latter, and means including interengaging relatively adjustable parts of said pivot means and said movable contact member, respectively, for adjusting the releasable connection between said actuating member and said current responsive device whereby to calibrate the circuit breaker for automatic opening thereof upon overload, said interengaging parts comprising a recessed edge portion'of the movable contact member provided with a threaded aperture and a tapering threaded portion of said part of the pivot means in threaded engagement in said aperture, whereby turning movement of said tapering portion in said apertured portion results in axial movement of said tapering portion in said apertured portion to displace a part of said movable contact member in relation to said actuating member for the adjustment of said releasable connection.

9. An automatic circuit breaker, comprising a casing having laterally spaced walls provided with aligned bearing portions, a movable contact member, pivot means on which said movable contact member is mounted for pivotal movement between said walls, said pivot means being supported for pivotal movement by said bearing por tions of the casing, an actuating member carried by said movable contact member and a current responsive device for operatively connecting said actuating member releasably to said movable contact member for operating the latter except when said current responsive device is disconnected from said actuating member upon overload, said pivot means including a member which is internally screw threaded and which has a cylindrical portion turnably supported by one of said bearing portions, means for retaining said internally screw threaded member and said movable contact member against relative rotation, a spindle on which said movable contact member s mounted, one end portion of said spindle being in screw threaded engagement with said internally screw threaded member and the opposite end of said spindle being supported by the other of;

Said. bearing portions, said movable contact member having an opening therethrough, said opening extending to an edge of the contact, member, said spindle having an axially tapering part passing through said opening in engagement, with the wall of said opening, and means for retaining said movable contact member against lateral displacement, whereby turning of said spindle about itsv axis causes axial movement of said tapering part relatively to said movable contact member todisplace a part of the latter for adjusting the releasable connection between said actuating member and said current responsive device whereby to calibrate the circuit breaker for automatic opening thereof upon overload.

10. An automatic circuit breaker, comprising a casing, a movable contact member in said casing, pivot means for mountin said contact member in the casing for pivotal movement therein, an actuating member, means including a current responsive device for operatively connecting said actuating member releasably to said contact member for actuating the latter, and means including interengaging relatively adjustable parts of said pivot means and said movable contact member, respectively, for adjusting the releasable connection between said actuating member and said current responsive device whereby to calibrate the circuit breaker for automatic opening thereof upon overload, said interengaging parts comprising an apertured edge portion of the movable contact member and a tapering portion of said part of the pivot means, and means for retaining said movable contact member against lateral displacement, whereby turning of said part of the pivot means about its axis causes axial movement of said tapering portion relatively to said movable contact member to displace a part of the latter for adjusting the releasable connection between said actuating member and said current responsive device whereby to calibrate the circuit breaker for automatic opening thereof upon overload.

11. In a movable contact member for a circuit breaker, said movable contact member having an actuator movably mounted on a part thereof and having a current responsive device releasably engageable with said actuator for releasably latching said actuator to said member for movement of said member by said actuator; pivot means for said contact member, said pivot means and said contact member being provided with interengaging relatively movable portions for displacing said part in said member and thereby moving said actuator in relation to said current responsive device for adjusting the releasably engaged portions of said actuator and said current responsive device.

12. In a movable contact member for a circuit breaker, said movable contact member having an actuator movably mounted on a part thereof and having a current responsive device releasably engageable with said actuator for releasably latching said actuator to said member for movement of said member by said actuator; pivot means for said contact member, said pivot means being provided with means for displacing said part in said member and thereby moving said actuator in relation to said current responsive device for adjusting the releasably engaged portions of said actuator and said current responsive device, said member having provision therein operable in response to said displacing means for facilitating the displacement of said part by said pivot means.

13; In a movable contact member for a circuit breaker, said movable contact member having an member having an opening defined therein at,

the pivotal axis thereof, said displacing means being disposed in said opening and being adjustably positionable along said pivotal axis to effect said displacement.

14,. In a movable contact member for a circuit breaker, said movable contact member having an actuator movably mounted on a part thereof and having a. current responsive device releasably engageable with said actuator for releasably latch ing said actuator to said member for movement of said member by said actuator; pivot means carried by said contact member for pivotal movement thereof, said pivot means being provided with means for displacing said part of said member, said member having an opening therein at the pivotal axis thereof, said displacing means being disposed in said opening and being adjustably positionable along said pivotal axis, and said member havin an interrupted peripheral edge portion extending to said opening, said interrupted portion being distended in response to said adjustment of said displacing means, whereby to effect displacement of said part of the member and thereby move said actuator in relation to said current responsive device for adjusting the releasably engaged portions of said actuator and said current responsive device.

15. An automatic, circuit breaker comprising a casin a movable contact member for said circuit breaker contained therein, said movable contact member having an actuator movably mounted on a part thereof and having a current responsive device releasably engageable with said actuator for releasably latching said actuator to said member for movement of said member by said actuator, said part, having a distensible portion, and pivot means for said contact member having bearing engagement in said casing, said pivot means being adjustably positionable axially iereof and transversely of said casing and having a portion engaged in said distensible portion for displacing said part in said member in response to said adjustment thereof, whereby to adjust the releasably engaged portions of said actuator and said current responsive device for calibrating the circuit breaker.

I6. In amovabl'e contact member for a circuit breaker; said movable contact member having an actuator movably mounted on a part thereof and having a current responsive device releasably engageable with said actuator for releasably latching said actuator to said member for movement of said member by said actuator; pivot means carried by said contact member for pivotal movement thereof, said pivot means being provided with means for displacing said part of said member and thereby moving said actuator in relation to said current responsive device for adjusting the releasably engaged portions of said actuator and said current responsive device, said i i displacing means being a tapering portion of said pivot means.

17. In a movable contact member for a circuit breaker, said movable contact member having an actuator movably mounted on a part thereof and having a current responsive device releasably engageable with said actuator for releasably latching said actuator to said member for movement of said member by said actuator; pivot means carried by said contact member for pivota1 movement thereof, said pivot means being provided with means for displacing said part in said member, said member having a pivot opening therein and an additional opening at an edge portion thereof in communication with said pivot opening, said displacing means being a tapering portion of said pivot means adjustable transverse- 1y of said pivot opening for distending said additional opening, whereby to effect displacement of said part of the member and thereby move said actuator in relation to said current responsive device for adjustingthe releasably engaged portions of said actuator and said current responsive device.

18. In a movable contact member for a circuit breaker, said movable contact member having an actuator movably mounted on a part thereof and having a, current responsive device releasably engageable with said actuator for releasably latching said actuator to said member for movement of said member by said actuator; a pivot member for said contact member, said pivot member having a threaded end portion and a tapering portion, said contact member having a pivot opening therein and an interrupted peripheral edge portion in communication with said opening, a bearing member carried by said contact member and retained against rotation relative thereto, said bearing member having an internally threaded portion in registry with said opening, said tapering portion being disposed in said opening and said threaded end being engaged in said threaded portion, whereby, as said pivot member is threaded into said bearing member, said tapering portion thereof effects displacement of said part of the contact member and thereby moves said actuator in relation to said current responsive device for adjusting the releasably engaged portions of said actuator and said current responsive device.

19. In a movable contact member for a circuit breaker, said movable contact member having an actuator movably mounted on a part thereof and having a current responsive device releasably engageable with said actuator for releasably latching said actuator to said member for movement of said member by said actuator; a pivot member for said contact member, said pivot member having a tapering threaded portion and a. bearing end extending therefrom, said contact member having a threaded pivot opening therein and an interrupted peripheral edge portion in communication with said opening, said tapering portion being threaded into said opening for movement transversely of said contact member whereby to effect displacement of said part of the contact member and thereby to move said actuator in relation to said current responsive device for adjusting said releasably engaged portions of said actuator and said current responsive device.

20. In combination, a movable contact member for a circuit breaker and a pivot member therefor, said contact member having a pivot opening defined therein and a recessed edge portion in communication with said opening, said pivot member having an axially tapering portion engaged in said opening and movable axially of said 'pivot member for enlarging said pivot opening whereby to enlarge said recess for calibrating the circuit breaker.

21. A pivot member for the pivot opening of a movable contact member in a circuit breaker, said pivot member having a tapering portion for engagement in said opening for enlarging the latter, and a bearing portion at each end of said tapering portion, said bearing portions being of constant diameter, respectively.

22. A pivot member for the pivot opening of a'movable contact member in a circuit breaker, said pivot member having a tapering portion for engagement in said opening for enlarging the latter, and a bearing portion of constant diameter extending from said tapering portion.

23. A pivot member for the pivot opening of. a movable contact member in a circuit breaker, said pivot member having a tapering portion for engagement in said opening for enlarging the 1atter, and a bearing portion of constant diameter extending from said tapering portion, said tapering portion being unthreaded and said bearing portion being threaded.

24. A pivot member for the pivot opening of a movable contact member in a circuit breaker, said pivot member having a tapering portion for engagement in said opening for enlarging the latter, and a bearing portion extending from said tapering portion, said tapering portion being threaded and said bearing portion being unthreaded.

' THOMAS M. COLE.

PAUL M. CHRISTENSEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name I Date 232,580 Welch Sept. 21, 1880 2,209,319 Christensen July 30, 1940 2,209,351 Sachs July 30,- 1940 2,209,352 Sachs July 30, 1940 2,362,664 Reed Nov. 14, 1944 2,438,186 Randall Mar. 23, 1948

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