US2786113A

US2786113A - Calibration of circuit breaker mechanism within casing

Info

Publication number: US2786113A
Application number: US369366A
Authority: US
Inventors: Alexander R Norden
Original assignee: Federal Electric Products Co
Current assignee: Federal Electric Products Co
Priority date: 1953-07-21
Filing date: 1953-07-21
Publication date: 1957-03-19
Anticipated expiration: 1974-03-19

Description

March 19, 1957 A. R. NORDEN CALIBRATION OF CIRCUIT BREAKER MECHANISM WITHIN CASING s Sheets-Sheet 1 Filed July 21, 1953 INVENTOR 41x44me E. #020541 ATTORNEYS March 19, 1957 A. R. NORDEN CALIBRATION 0F CIRCUIT BREAKER MECHANISM WITHIN CASING Filed July 21, 1953 3 Sheets-Sheet 3 niunum I L l II I 4% w 5 [F INVENTOR 41:0/4252 1Q. A/zQDE/l/ ATTORNEYS FIG. 7.

United States atent CALIBRATION OF CIRCUIT BREAKER MECHANISM WITHIN CASING Application July 21, 1953, Serial No. 369,366 9 Claims. 01. 200-116) The present invention relates to automatic circuit breakers of the general type disclosed in United States Patent No. 2,209,319, and in the United States patent applications of Thomas M. Cole Serial No. 127,433, filed November 15, 194-9, now Patent No. 2,647,186, dated Jul" 28, 1953, and Serial No. 213,591, filed March 2, 1951, now Patent No. 2,647,187, dated July 28, 1953, and in the U. S. patent application of Thomas M. Cole and Paul M. Christensen, Serial No. 217,162, filed March 23, 1951, now Patent No. 2,642,509, dated June 16, 1953, all assigned to the assignee hereof and in particular, to calibrating provision therefor. I

in circuit breakers of the general type to which the present invention relates, provision is made for a movable contact or switch member which bodily mounts currentresponsive latching means, including a fiexible latching element, and which pivotally carries an actuating element, the latter being operatively connected to the movable contact member through a releasable engagement with the latching element, for manually operating the circuit breaker to open and closed positions thereof. The current-time rating for the circuit breaker is dependent upon the degree or extent of overlap of the actuator and the latching element at said releasable connection thereof. In order to calibrate the circuit breaker for a predetermined current-time rating, the releasable connection of the actuator and the latching element is adjusted by varying the degree or extent of overlap thereof. In the previously mentioned patent and applications, provision is made for adjusting said releasable connection in a single sense or direction.

The primary object of the present invention is the provision, in an automatic circuit breaker, of means for varying the calibration of the circuit breaker in opposite senses or directions, whereby to increase or to decrease the current rating of the circuit breaker, as required.

Another object is the provision in an automatic circuit breaker of means for calibrating the latter, said calibrating means having provision to compensate for or to neutralize overcalibration.

in accordance with the foregoing objects, it is a more specific object of the present invention to effect the calibration of the circuit breaker in opposite senses without the necessity of removing the circuit breaker mechanism from its casing, or without the necessity of opening'the casing thereof. 7

Another object is the provision, in an automatic circuit breaker, of generally simplifiedmeans for adjusting in opposite directions or senses the relative disposition of the actuating means and the thermally responsive element or latch thereof, for calibration purposes, to increase or to decrease the current rating of the circuit breaker for a predetermined element as required or to compensate for overcalibration of .the circuit breaker.

A further object is to provide a simplified and .yet micromatically accuratemethod for varying the current time rating of an automatic circuit breaker in opposite senses.

ice

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

In the drawings: I

Fig. 1 is a side view of a circuit breaker pursuant to the present invention and illustrates the best mode presentiy contemplated of carrying out the invention, one part of the casing being removed and the breaker being illustrated in the circuit closed condition thereof; v

Fig. 2 is a view similar to Fig. 1 with the breaker illustrated in the circuit interrupting or open condition thereof;

Fig. 3 is an end view of the circuitbreaker; L g

Fig. 4 is a view of the inner surface or face of the body part of the circuit breaker casing;

Fig. 5 is a view of the inner surface or face cover part of the circuit breaker casing;

Fig. 6 is a fragmentary sectional view taken line 6-6 of Fig. 1;

Pig. 7 is a fragmentary sectional view taken line '7-7 ofFig. 1; I

Fig. 8 is a fragmentary sectional view taken line 8-8 of Fig. 1;

Fig. 9 is a fragmentary sectional view taken line 99 of Fig. 2; v

Fig. 10 is a perspective view of a circuit breaker pursuant to another embodiment of the invention, onepart of the casing being removed and the breaker being illustrated in the circuit closed condition thereof;

Fig. 11 is a sectional view taken on the line 11-11 ofFig. 10;

Fig. 12 is a fragmentary view of the movable switch member of Fig. 10, with parts omitted; v

Fig. 13 is a fragmentary view similar to Fig. 1 and illustrates a modification thereof; and r l 1 Fig. 14 is a fragmentary sectional view taken on the line 14-ld of Fig. 13.

In general, the circuit breaker illustrated herein, and in the above mentioned patent and 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 contactmember is provided with an actuator which is releasably latched to said movable contact memher by means of a current responsive or other overload device. Said device is carried by the movable contact member and releasably engages said actuator under normalload 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. Upon release of said actuator by said device, there results 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 to facilitate 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 actuator and the current responsive device. 'Said means includes provision to effect the displacement of said first mentioned part in opposite directions, as may be required, so as to increase or to decrease, as the case may be, the extent or degree of overlap of the releasably engaged portions for increasing or decreasing, respectively, the current rating or current-time relation of the circuit breaker, as may be required. In accordance withthe presently preferred mode of practicing the present invention, a pair of openings or notches are providedat opposite edge portions of the movable contact member and a tapering element or tool is pressed into said openings of the on the on the on the on the for accomplishing the displacement of the first mentioned part of the movable contact member. In addition to the openings provided in the movable contact member, an opening is provided in the casing of the circuit breaker so that the calibration thereof may be accomplished after the circuit breaker mechanism has been assembled within the casing and without the necessity of removing the circuit breaker mechanism from the casing.

Referring now to Figs. 1-9 of the drawings in detail, there is shown an automatic circuit breaker it) provided with a casing 12 constituted by the insulated body part 14 and the complementary insulated cover part 16, which parts are suitably secured together in housing defining relation, as illustrated in Fig. 3, by means of suitable securing elements provided in aligned openings 18 in said casing parts. The circuit breaker mechanism, generally indicated by the reference numeral 29, and provided in the body part 14, as best shown in Figs. 1 and 2, comprises the pivotally mounted movable contact or switch member 22 provided with a movable contact 24, at one end thereof, for engagement with and disengagement from a companion stationary contact 26 provided on a solderless terminal connector 28. At its other end, the movable contact member 22 is provided with a pivotally mounted actuator 30 which is in operative engagement with the handle or manual operating member 32 by means of a link 34. The movable contact member 22 is also provided with a current-responsive latching means 34 which, as here shown, is constituted by a flexible bimetallic element 36 and an electro-magnetic member 38, which are carried by the movable contact member 22. As here shown, the free end 56 of the latch 36 is in latched engagement with the latching tip 40 of the actuator 39. The latch 36 is connected to a stab or prong element 42, which constitutes the other terminal of the circuit breaker, by means of a flexible conductor 44. A spring 46 is interposed between the handle 32 and the movable contact arm 22, as illustrated. As here shown, the movable contact arm 22 is provided with a resilient mounting constituted by the spring pivot 46 which mounts the movable contact member 22, the opposite ends of the spring pivot being supported in bearing recesses 50 defined in the companion casing parts, as best illustrated in Fig. 6. It will be noted that the bearing recesses 50 are provided with the downwardly inclined surfaces 52 and also with the inclined surfaces 54, as best illustrated in Figs. 4 and 5. The inclined surfaces 52 facilitate the flexing of the resilient pivot 46 in a direction to provide for limited bodily movement of the movable contact member 22 to provide for the required contact pressure, in the engaged condition of the

contacts

24 and 26, and the inclined surfaces 54 provide for limited bodily movement of the movable contact member 22 in an additional direction to effect a wiping action of the contacts, all as fully described and claimed in the copending applications of Thomas M. Cole and Paul M. Christensen Serial No. 285,418 filed May 1, 1952, and Serial No. 367,324 filed July 10, 1953, both of which are assigned to the assignee of the present invention. However, it will be understood that it is not essential to the practice of the present invention to provide for the limited bodily movement of the movable contact member 22 but, on the contrary,

the contact member may be otherwise mounted, for example and not by way of limitation, as in the previously identified Patent No. 2,209,319 wherein the movable contact member is mounted on a rigid pivot and provision is made for a resilient link between the handle and the actuator to provide for the required contact pressure.

The operation of the circuit breaker is described in detail in the above mentioned patent and applications. However, it will be understood that the flexible bimetallic element 36 operates to latch the manually operable actuator 30 to the movable contact member 22 and to unlatch said actuator from the movable contact member, the unlatching taking place upon deflection of the bimetallic element 36, causing the disengagement of the free end 56 thereof from the tip 40 of the actuator 39 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 36 is deflected from engagement with the actuator 30, the spring 46 is effective to move the contact member 22 to its open position, as illustrated in Fig. 2, wherein the contact 24 is disengaged from the companion stationary contact 26, the spring also returning the handle 32 to the off position thereof illustrated in Fig. 2. As described in the Patent No. Re. 23,188, upon the occurrence of an overload in excess of that for which the circuit breaker is designed to open under the control of the thermal element 36 by fiexing of the latter in re sponse to the heating thereof, the electro-magnetic device 33 is operable instantaneously to efiect disengagement of the companion contact members. It will be understood that the electro-magnetic member 38 is rigid and, since the bimetallic element 36 is flexible, upon the occurrence of such excess overload the magnetic attraction between the

members

36 and 38 results in the deflection of the thermal strip 36 for disengaging the latter from the actuating lever 30, member 36 moving by magnetic attraction to the member 33, thus deflecting or unlatching the thermal member 36 from the actuator 3t Pursuant to the present invention, and in order to provide for fine or micromatic adjustments of he actuator for calibration purposes, said adjustments being in opposite senses or directions to either increase or decrease the degree or extent of overlap of the latching tip 4% of the actuator 30, relative to the free end 56 of the bimetal 36, as may be required, the movable contact member 22 is provided, adjacent the end thereof which carries the contact 24, or at the side of the pivot 46 opposite the side thereof which mounts the actuator 30, at the op posite marginal edge portions thereof with the generally circular, peripherally interrupted apertures or

notches

58 and 60.

Pursuant to the presently preferred practice of the present invention, the circuit breaker mechanism 25} is calibrated after it is assembled within the casing 12. To allow for said calibration after assembly of the mechanism in the casing, the casing cover is provided with an opening 62 and the casing body part 14 is provided with a recess 64 defined therein in alignment with said opening. In order to effect the calibration, current is applied to the circuit breaker, the handle 32 being in the circuit closed disposition thereof, as illustrated in Fig. 1. Referring now to Figs. 1 and 8, it will be noted that in the closed condition of the circuit breaker, the aperture 60 in the movable contact member 22 is aligned with the opening 62 in the casing cover 16 and with the recess 64 in the casing body 14 it being also noted that the aperture 58 is not accessible through the casing cover opening. A tapered element or tool 66 is then inserted through the casing opening 62 into the aperture 60 of the movable contact member and urged therein transversely of the movable contact member, in any suitable manner. This will result in the displacement of the movable contact member 22 in its own plane. More specifically, the portion of the movable contact member 22 to the right of the notch 60, viewing Fig. 1, will bend upwardly, as indicated by arrow 68, in the plane of the movable contact member 22, relative to the portion to the left of the notch 60. It will be apparent that said upward movement in the direction of the arrow 68, is due to the fact that the notch 60 is in the lower marginal edge of the movable contact member, viewing Fig. l. Said movement or bending of the movable contact memher will carry the actuator 30 upwardly relative to the latch element 36 to decrease the extent by which the end part 40 of the actuator 30 overlaps the marginal edge portion 56 of the latch element 36. As previously indicated, with the current applied to the circuit breaker for the calibration operation, the tool 66 is urged in its transverse movement until the circuit breaker trips. Therefore, it will be apparent that with the current set at a predetermined value and with a bimetallic element of predetermined dimensions there is a predetermined current-time rating established for the circuit breaker when it trips as a result of the tapered tool being pressed into the movable contact member. Thereafter, the calibration is rechecked and if it is found that the degree or extent of overlap has been made too small, provision is made, pursuant to the present invention to compensate for or to neutralize the overcalibration by the. provision to calibrate the breaker in the opposite sense or direction whereby to increase the degree or extent of overlap to achieve the predetermined current-time relation. This is accomplished by having the circuit breaker in the open or ofl condition thereof and it Will be noted from Figs. 2 and 9 that in said condition of the circuit breaker, the notch 60 is no longer aligned with the casing opening 62 and the casing recess 64, but the companion notch .58 is now in registry therewith. The tapered tool 66 .is now to be inserted into the notch 58 and urged therein transversely of the movable contact member. This will result in the displacement or bending of the movable contact member 2?; in its own plane in a direction opposite the arrow 68, as indicated by the arrow 79 in Fig. 2. More specifically, it will be noted that the notch 58 being in the upper edge of the movable contact member, viewing Figs. 1 and 2, the portion of the movable contact member to the right of said notch will move downwardly so as to increase the degree or extent of overlap of the actuator tip it? relative to the free marginal edge 56 of the latching element 36. in this manner, the circuit breaker may be calibrated in opposite senses or directions to compensate for overcalibration in either direction, as may be required. After each calibration adjustment, the tool or spindle 66 is Withdrawn from the circuit breaker.

From the foregoing it will be apparent that the provision of the notch 58 in the upper edge of the movable contact member, viewing Figs. 1 and 2, permits for a compensating or neutralizing adjustment in the event of overcalibration resulting from the use of the notch 60 in the lower marginal edge. Similarly, the notch 60 may be used to compensate for overcalibration resulting from the use of the notch 58. In addition to the feature of a compensated calibration operation, the

notches

58 and 60 provide means to increase or decrease the current rating of a circuit breaker, as desired. this connection, it will be understood that the physical dimensions of the current-responsive element 36 determines the basic current rating of the circuit breaker. However,

through the use of the notch 6d, the degree of overlap of the latching tip it) relative to the end 56 of the element 36 may be decreased, whereby to require alesser current magnitude to trip the reaker, and, consequently, to reduce the current-rating of the breaker without the necessity of providing a control element of different dimensions. Through the use of the notch 58, the degree of overlap may increased, whereby to require a greater current magnitude to trio the breaker, and, consequently to increase the current rating of the breaker again Without the necessity of providing a control element of different dimensions.

It will be noted from the foregoing that in each poactuator .50 which is moved relative to the latch 36since I .65 sition of the circuit breaker, only one of the notches is the actuator is carried by the POItion of the movable contact member which is displaced during calibration in either direction.

While the calibration operation has been illustrated and described in connection with the use of a tapered tool to eiiect the bending of the movable contact member, which tool is withdrawn from each notch upon completion of each calibration adjustment, it is Within the scope of the present invention to utilize tapered elements which are not Withdrawn from the respective notches. More specifically, the notches may each be threaded and tapered screw, as at 144 in Fig. 11, may be engaged in each notch. However, the notches need not be threaded, and in lieu of a tapered screw, a tapered pin may be forced into each notch, as illustrated at 118 in the previously identified application Serial No. 127,433. In either case, whether a tapered screw or a tapered pin is used, the particular element would ordinarily not be Withdrawn from the companion notch but would remain therein after the completion of the calibration adjustment.

In the copending Serial No. 181,224 filed August 24, 1 950, by myself and Paul M. Christensen, as joint inventors, and assigned to the assignee hereof, there is disclosed a multi-pole circuit breaker, wherein the circuit breaker mechanism at each pole is substantially of the type illustrated and described herein. In said application, the actuators of the separate poles are interconnected by a universal joint so that the tripping action at one pole of said multi-pole circuit breaker operates through the universal joint to ,efiect the tripping of the other pole of the circuit breaker. In such a multi-pole circuit breaker the calibration of one pole of the circuit breaker affects the calibration of the companion pole of the circuit breaker due to the fact that the bending of the movable contact member in the circuit breaker pole which is being calibrated transmits a force through the universal joint to affect the calibration of the companion pole. in such an arrangement, the companion calibrat ing notches 58 and 64) of the present invention are especially advantageous at each pole of the multi-pole breaker. More specifically if the calibration operation at one pole of the multi-polc circuit breaker results in over or under calibration of the companion pole of the .multipole circuit breaker, the latter may then be recalibrated in either direction, as may be required, all without the necessity of removing the multipole circuit breaker mechanism from its casing.

Referring now to Figs. 10-12 of the drawings in detail there is illustrated a circuit breaker 80 which is substantially similar to the previously described automatic circuit breaker. More specifically, the circuit breaker 80 is also provided with a casing 82 constituted by the insulated body part 34 and the complementary insulated cover part 86 which parts are suitably secured in housing defining relation, as previously described. The circuit breaker mechanism, generally indicated by the reference numeral 88 and provided in the body part 84, is essentially the same as the previously described circuit breaker mechanism 20, comprising the pivotally mounted switch member 96 provided with a movable contact 92, at one end thereof, for engagement with and disengagement from a companion stationary contact 94 provided on a solderless terminal connector 96. At its other end, the movable contact member 9% is provided with a pivotally mounted actuator 98 which isin operative engagement with the handle 1% by means of a resilient link 102. The movable contact member is also provided with a current responsive latching means 104, which, as here shown, is constituted by the flexible bimetallic element 106, the electromagnetic armature res, both of which are carried by the movable contact member 90, and by .the.companion electromagnetic member provided on the latch element 166. ,As previously described, the free .e'ndfllz of the'element l0;6is inlatched engagement with the latch tip 114 of theactuator. A spring 116 is interposed between the handle and the movable contact mem ber as illustrated.

The operation of the circuit breaker 80 is similar to that previously described in connection with the circuit breaker 20, the occurrence of an overload or other abnormal predetermined current conditions in the circuit controlled by the circuit breaker resulting in the deflection of the control element 106 to release the actuator 98 whereupon the spring 116 is operable to move the movable switch member 90, substantially to the position of the movable switch member in Fig. 2 for opening the circuit breaker.

Pursuant to the present embodiment, the circuit breaker 80 is also provided with means to effect the calibration thereof in opposite senses or opposite directions, whereby to compensate or neutralize for overcalibration in either direction or to increase or decrease the current rating of the breaker for a control element 106, of predetermined physical dimensions. More specifically, the movable contact member 90 is provided with a generally circular opening 118 at the axis about which it pivotally moves. An opening 120 formed in the lower marginal edge of the contact member 90 constitutes an interruption in the periphery thereof and extends to the circular aperture 118 with which it is in communication, as illustrated in Fig. 12. It will be noted that the opening 120 is formed in the narrower portion of the movable contact member on the free end of which the actuator 98 is pivotally mounted. The body portion of the movable contact member forms the wider and generally larger portion thereof and extends to the left (viewing Fig. of the circular aperture 118 through which the pivot axis of the movable contact member extends. As fully illustrated and described in the previously identified application Serial No. 217,162, and as here shown, in order to provide for both the pivotal mounting of the movable contact member and for calibration in a direction to decrease the extent of overlap of the actuator 93 relative to the control element 106, there is provided a calibrating element or pin member 122. Pin 122 is provided, at one end thereof, with a portion having a screwdriver slot 124, and with an adjacent bearing portion 126, an intermediate tapering portion 128 and a threaded portion 130 which extends from said tapering portion to the other end of the pin. The pin is threadedly engaged in a nut 132 which is mounted in a bearing aperture 134 of the casing part 84, interengaging means indicated at 136 and 138 preventing relative movement of the nut and the movable switch member, as described in said application. The cover 86 is provided with an aperture 140 which extends completely therethrough, and which provides access to the pin 122, said aperture being in registry with the bearing aperture 134 in the casing part 34. It will be understood that the pivot axis for the movable member 90 extends though said casing apertures and through the aperture 118 in said member.

The movable member 90 is also provided with the peripherally interrupted aperture 142 in the marginal edge thereof opposite the marginal edge in which the peripheral interruption 120 is defined. A tapered adjusting screw 144 is threadedly engaged in the notch 142, and the casing part 86 is provided with an opening 146 which is in registry with the adjusting screw. As described in said last mentioned application, the combined pivot and adjusting member 122 operates to effect a decrease in the degree or extent of overlap of the latching tip 114 of the actuator 98 relative to the free end 112 of the bimetal 106. More specifically, referring now to Fig. 11, the full line position of the member 122 shows the tapering portion 128 as it enters the aperture 118, indicating a minimum calibration adjustment or maximum overlap of the actuator and the bimetal, for example as illustrated in broken line Fig. 12. As the member 122 is threaded into the nut 132, the tapered portion 128 advances into the opening 118, the latter is distended and the sides of the aperture are forced apart whereby to bend the portion of the movable contact member to the right of the member 122, viewing Figs. 10 and 12, in the plane of said movable contact member, upwardly as from the broken line to the full line position thereof in Fig. 12, to decrease the degree of overlap. This adjustment may be readily made through the opening in the casing 86 by inserting a screwdriver therein, it being understood that after the complete calibration of the circut breaker has been accomplished, the opening 140 may be sealed as by the insulated washer 150 and the sealing compound 152.

The screw 144 may be conveniently operated, by means of a screwdriver inserted in the casing opening 146, to bend the portion of the movable contact member to the right of the pivot member 122 in the opposite direction, and in the plane of the movable contact member, for increasing the degree of overlap, for example by moving the actuator 98 from its full line position in Fig. 12 toward the broken line position thereof. Consequently, it will be apparent that overcalibration resulting from operation of one of the adjusting

members

122 or 144 may be compensated or neutralized by calibration in an opposite direction by the other of the adjusting members in the same manner as previously described in connection with the circuit breaker 10 of Figs. 1-9. Similarly, the adjusting

elements

122 and 144 may be utilized to vary or change the current rating for the circuit breaker from that which is predetermined by the physical dimensions of the control element 106 thereof.

While the adjusting member 144 is illustrated and described herein as a tapered screw, it will be understood that said member need not be screw threaded but may be constituted by a tapered pin, for example as illustrated and described in the previously mentioned application Serial No. 127,433. it will be understood that when the screw 144, or an equivalent tapered element, is used as the adjusting member in the notch 142, said member is not withdrawn from the movable switch member but remains therein. However, it will be understood that it is Within the scope of the present invention, to use a tapered tool, in lieu of the adjusting element 144, as illustrated and described in the previously identified application Serial No. 213,591, which can be withdrawn from the notch 142 upon completion of the calibrating operation. It will be understood also that, if desired, the opening 146 may be sealed in the same manner as the opening 140 in the casing.

Referring now to Figs. 13 and 14 in detail, there is illustrated a modification of the circuit breaker illustrated in Figs. 1 and 2. Pursuant to said modification, in lieu of the generally circular peripherally interrupted apertures or

notches

58 and 60 the movable contact member 22A is provided with the substantially rectangular peripherally interrupted apertures, notches or

slots

58A and 60A. It will be noted that the

slots

58A and 60A are defined in opposing marginal edges, respectively, of the movable contact member 22A between the pivot thereof, which may be of the type illustrated in Figs. 1 and 2, and the movable contact 24. A fiat rectangular shaped tool 160, is used to calibrate the circuit breaker, as illustrated in Fig. 14. More specifically, in the closed condition of the circuit breaker, the slot 60A will be accessible through the opening 62 in casing 16, as in Fig. 14, the fiat tool is inserted through the casing and into the slot 60A. By rotating the tool 160 counter-clockwise, viewing Fig. 13, the actuator 30 may be moved relative to the control element 36, to decrease the degree or extent of overlap, as previously explained. In the open condition of the circuit breaker, it will be apparent that the slot 53A will be accessible through the casing opening 62, in the same manner as illustrated in Fig. 9, in connection with the aperture 58. By inserting the tool 160 into slot 58A and rotating the tool in a clockwise direction, viewing Fig. 13, the degree or extent of over- 9 lap of the actuator 30 relative to the element 36 may be increased, as previously described in connection with Fig. 9.

While the tool 160 has been described as a fiat rectang'ular element, said tool, if desired, may have a wedgeshaped or flat tapered tip, for example, like the operating end of a screwdriver. In the latter case, the calibration would be effected by pressing said wedge shaped tip into the

rectangular slot

58A or 60A, transversely of the plane of the movable member 22A, instead of rotating the tool in the slot.

While I have shown and described the presently preferred embodiments of my invention, it will be understood that various changes may be made in the idea or principles of the invention within the scope of the appended claims.

Having thus described my I invention, what I claim and desire to secure by Letters Patent, is':

1. In an automatic circuit breaker having a movable contact member, an actuating member carried by said movable contact member, and a control device for operatively connecting said actuating member releasably'to said movable contact member for operating the latter except when said control device is disconnected from said actuating member upon overload, said control device being fixed in relation to said movable contact member, and said contact member having dual means separately adjustable in opposite senses in relation to said control device to calibrate the circuit breaker for automatic opening thereof upon overload.

2. In an automatic circuit breaker having a movable contact member, an actuating member carried by said movable contact member, and a control device for operatively connecting said actuating member releasably to said movable contact member for operating the latter except when said control device is disconnected from said actuating member upon overload, said control device being fixed in relation to said movable contact member, and said actuating member being adjustable in opposite senses in relation to said control device to calibrate the circuit breaker for automatic opening thereof upon overload, said movable contact member having a relatively nonresilient part which is bendable in opposite directions and said actuating member being secured to said bendable part, said bendable part having apertures defined in opposite edge portions, respectively, thereof, for receiving a tool in said edge portions thereof, whereby to bend said bendable part in a first direction upon the application of the tool in one of said apertures and to bend said bendable part in an opposite direction upon the application of the tool in the other of said apertures.

3. In an automatic circuit breaker having a movable contact member, an actuating member carried by said movable contact member, and a control device for opera tively connecting said actuating member releasably to said movable contact member for operating the latter except when said control device is disconnected from said actuating member upon overload, said control device being fixed in relation to said movable contact member, and said actuating member being adjustable in opposite senses in relation to said control device to calibrate the circuit breaker for automatic opening thereof upon overload, said movable contact member having a part which is bendable in opposite directions and said actuating member being secured to said bendable part, said bendable part having apertures defined in opposite edge portions, respectively, thereof, for receiving a tapered tool in said edge portions thereof, whereby to bend said bendable part in a first direction upon the pressing of the tool into one of said apertures and to bend said bendable part in an opposite direction upon the pressing of the tool into the other of said apertures, and a casing in which said movable contact member, said actuating member and said control device are disposed, said casing having provision for access to said apertures to insert the tool therein,

10 whereby the circuit breaker can be calibrated within; the casing.

4. In an automatic circuit breaker having a movable Contact member, an actuating member carried by said movable contact member, and a control device for operatively connecting said actuating member releasably to said movable contact member for operating the latter except when said control device is disconnected from said actuating member upon overload, said control device being fixed in relation to said movable contact member, and said actuating member being adjustable in opposite senses in relation to said control device to calibrate the circuit breaker for automatic opening thereof upon overload, said movable contact member having a part which is bendable in opposite directions and said actuating member being secured to said bendable part, said bendable part having apertures defined in opposite edge portions, respectively, thereof, for receiving a tapered tool in said edge portions thereof, whereby to bend said bendable part in a first direction upon the pressing of the tool into one of said apertures and to bend said bendable part in an opposite direction upon the pressing of the tool into the other of said apertures, and a casing in which said movable contact member, said actuating member and said control device are disposed, said casing having laterally spaced walls, one of said walls having an opening defined therein to insert the tapered member in said apertures, respectively, whereby to calibrate the circuit breaker within the casing and the other of said walls having a recess defined therein, said recess and said opening being aligned for projection of the tapered member into said recess through said apertures, respectively.

5. In an automatic circuit breaker, a movable contact member, an actuator movably mounted thereon, a thermally-responsive control element carried by said member and having a free end in releasable engagement with said actuator to latch and unlatch said member thereto, said actuator and said element being provided on spaced portions of said member, and means provided in said member to facilitate the relative displacement of said portions in opposite directions for adjusting said actuator in opposite directions relative to said free end whereby to calibrate said circuit breaker, said member being relatively nonresilient and said means comprising opposite marginal edge portions of said member in each of which there is defined a peripheral interruption.

6. In an automatic circuit breaker, a movable contact member, an actuator movably mounted thereon, a thermally-responsive control element carried by said member and having a free end in releasable engagement with said actuator to latch and unlatch said member thereto, said actuator and said element being provided on spaced portions of said member, and means provided in said member to facilitate the relative displacement of said portions in opposite directions for adjusting said actuator in opposite directions relative to said free end whereby to calibrate said circuit breaker, said means comprising opposite marginal edge portions of said member in each of which there is defined a peripheral interruption, and a casing for said circuit breaker having provision for access to one of said interruptions in the circuit making condition of the breaker and for access to the other of said interruptions in the circuit interrupting condition of the breaker.

7. In an automatic circuit breaker, a movable contact member having an actuator movably mounted on a part thereof and having a current-responsive control device releasably engageable with said actuator for releasably latching said actuator to said member for movement of said member by said actuator, means for use in calibrating the circuit breaker comprising provision in said member of dual means separately adjustable to facilitate displacement of said part in opposite directions in said memher and thereby move said actuator in opposite directions in relation to said current-responsive device for adjusting the releasably engaged portions of said actuator and said current-responsive device, means mounting said movable contact member for pivotal movement, said actuator and said control device being secured to said movable member at-opposite sides, respectively, of said pivot, said member being relatively non-resilient and said calibrating provision being openings at opposite edge portions, respectively, of said member, said openings being defined in said member between said pivot and the portion thereof to which said control device is secured.

8. In an automatic circuit breaker, a movable contact member having an actuator movably mounted on a part thereof and having a current-responsive control device releasably engageable with said actuator for releasably latching said actuator to said member for movement of said member by said actuator, means for use in calibrating the circuit breaker comprising provision in said member of means to facilitate displacement said port in opposite directions in said member, 1 other being relatively non-resilient and said means comprising circular openings at opposite edge portions, respectively, of said member to receive a tool for causing said displacement of said part in a first direction when one of said openings receives the tool and for causing said displacement of said part in an opposite direction when the other opening receives the tool, to thereby move said actuator in opposite directions in relation to said current-responsive device for adjusting the releasably engaged portions of said actuator and said current-responsive device.

9. In an automatic circuit breaker, a movable contact member having an actuator movably mounted on a part thereof and having a current-responsive control device releasably engageable with said actuator for releasably latching said actuator to said member for movement of said member by said actuator, means for use in calibrating the circuit breaker comprising provision in said member of means to facilitate displacement of said part in opposite directions in said member, said member being relatively non-resilient and said means comprising rectangular openings at opposite edge portions, respectively, of said member to receive a tool for causing said displacement of said part in a first direction when one of said openings receives the tool and for causing said displacement of said part in an opposite direction when the other opening receives the tool, to thereby move said actuator in opposite directions in relation to said current-responsive device for adjusting the releasably engaged portions of said actuator and said current-responsive device.

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