US2506796A - Nonfree-tripping overload circuit breaker - Google Patents

Description

y 1950 A. w. KRIEGER 2,506,796

NONFREE-TRIPPING OVERLOAD CIRCUIT BREAKER Original Filed May 10, 1944 Sheets-Sheet 1 69 78 70 50 73 56 7a 3 76 m5 I35 y 1950 A. w. KRIEGER 2,506,796

NONFREE-TRIPPING OVERLOAD CIRCUIT BREAKER Original Filed May 10, 1944 3 Sheets-Sheet 2 y 1950 A. w. KRIEGER 2,506,796

NONF'REE-TRIPPING OVERLOAD CIRCUIT BREAKER Original Filed May 10, 1944 3 Sheets-Sheet 3 a I4 I29 H7 2.! 22. 1/7 129 \flk. g

1a 64 65a 9 as 55 Patented May 9, 1950 2,506,796

NONFREE-TRIPPING OVERLOAD CIRCUIT BREAKER Alvin W. Krieger, Milwaukee, Wis., aasignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Original application May 10, 1944, Serial No.

534,907, now Patent No. 2,453,235, dated November 9, 1948. Divided and this March 27, 1948, Serial No. 17,542

3 Claims. 1 This invention relates to improvements in noni'ree-tripping overload circuit breakers.

A primary object of the invention is to improve the details of construction and the operation of circuit breakers of the aforementioned character.

Another object is to provide improved and simpliil d means for varying the normal degree of sens.tivity of the bimetallic thermal element to given overload current conditions, whereby the normal current controlling capacity of the circuit breaker may be reduced to a relatively low value if desired.

Another object is to provide means for facilitating assembly and support of the bimetallic thermalelement with respect to other elements of the device.

Another object is to minimize the number of elements required to secure all parts of the device in assembled relation.

application and claimed in my prior Patent No. 2,342,945, granted February 29, 1944, for Circuit breaker. In the devices of Patent No. 2,342,945, however, it was found that upon manual retention of the controlled circuit closed under certain overload conditions of relatively high value, there was danger of the bimetallic thermal element burning out or fusing, with resultant creation of an unnecessary fire hazard. This is especially true in respect of relatively low capacity circuit breakers wherein bimetallic thermal elements of small caliber are employed; and the use of an automatically operable switch adapted to periodically shunt the thermal element as shown in Figs. 1 to 6, hereof, provides for overcoming this difficulty.

Also in accordance with the disclosure of said Patent No. 2,342,945 four rivets were employed to secure the upper and lower insulating bases to Another object is to provide improved means 2 each other, and fouradditional rivets were for eflecting attachment of the complete device molded or embedded in the upper base to provide toapanel or other suitable support. for rigid attachment of the metal support or Another object is to insure a large degree of cover plate thereto. In accordance with the presseparation of exposed conductin parts of opent invention only four rivets are required to seposite polarity. cure said bases and the cover plate in assembled Other objects and advantages of the invention relationship to each other. will hereinafter appear. Referring first to the-circuit breaker shown This application is a division of my copending in Figs. 1 to 6, the numerals l0, H, and i2 reapplication which has resulted in Patent No. spectively designate the metal support or cover 2,453,235, granted November 9, 1948. plate and the upper and lowermolded insulating The accompanying drawings illustrate certain bases. Plate 10 is punched and stamped to the embodiments of the-invention which will now be described; it being understood that the embodiments illustrated are susceptible of modification within the scope of the appended claims.

In drawings:

Figure 1 is an enlarged vertical sectional view of a circuit breaker constructed in accordance with my invention.

Fig. 2 is a fragmentary sectional view, on the form thereof illustrated in Figs. 1, 3, 4, and 6; the same having a relatively large centrally located circular opening 13 which is adapted to pro-- vide clearance for the intermediate enlargements I4 and i5 upon an operating lever it which is essentially like that shown in Patent No. 2,342,945. Thus the enlargement l5 consists of a separately formed metal ring having integral diametrically opposed cylindrical lugs Hi and H, which line 2-2 ofFig. l. jointly serve as a pivot for said lever. Lugs it Fig. 3 is a top plan view of the circuit breaker and I! are adapted to seat within open pivotal illustrated in Fig. 1. bearings l8 and it formed in the upper surface Fig. 4 is a sectional view, on the line 4-4 of of base H (see Figs. 4 and 7); said lugs project- Fig. 3. ing slightly'above said surface, and plate l0 being Fig. 5 is a sectional view, on theline 5-5 of offset upwardly at 20 and 2! to provide parts'of Fl 6 is a sectional view, on the. line 6-6 of Fig. 3.

Fig. 7 is a view, partly in side elevation and partly in vertical section, of a slightly modified form of the device shown in Figs. 1 to 6, and

Fig. 8 is a fragmentary sectional view, on the line 8-8 of Fig. 7. I

The non-free-trippin circuit breakers herein disclosed are in general of the character described the bearings therefor.

In practice plate In is provided with a rectangular upwardly oifs'et portion 22 the fiat upper surface of which is coplanar with the upper extremities of oifset portions 20 and 2| (as best illustrated in Fig. 7).' Such offsets, 2| and :22 thus provide a relatively large flat or coplanar area to seat against the lower surface of a panel or the like (not shown) to which the complete unit may be attached in the manner hereinafter 3 set forth. As best illustrated in Fig. 1, the lower surface of offset portion 22 is so positioned as to provide clearance for element 23 carried by lever ll upon movement of the latter to its opposite extreme positions.

Element 23 is of substantially inverted U- shape, as best illustrated in Fig. 4; the perforated connecting portion thereof fitting onto a reduced portion of lever l6, which reduced portion is peripherally upset over the inner surface of said connecting portion, as indicated at 24 in Figs. 1 and 4. to rigidly and non-rotatably secure element 23 and ring l to lever l6. As shown in Fig. 4 the arms 25 and 26 of element 23 are positioned closely adjacent, but are freely movable with respect to, the opposite side walls of the switch recess 21 which opens to the upper surface of base H. As shown in Fig. 1, the lower end portion of arms 25 and 26 are of inverted triangle form, the opposite side edges of said triangles being respectively engageable with the walls of the opening 28 between switch recess 21 and the lower recess 29 in which the molded insulating plunger 30 is slidable. Plunger 30 is provided with an enlarged head portion 3| (Fig. 4) which is slidable between and guided by the opposed side walls of recess 29, the relatively narrower lefthand end portion of plunger 30 (Fig. 1) being also slidable between and guided by vertical shoulders (not shown) formed upon the walls of recess 29. Plunger 30 is provided at the head end 3| there of'with a cylindrical recess 32 (Fig. l) which is adapted to accommodate a coiled compression spring 33 the free outer end of which is adapted to surround a boss or abutment 34 formed upon the vertical arm 35 of an inverted L-shaped metal member, the horizontal arm 36 of said member having a contact tip 31 of fine silver or the like spot-welded or otherwise rigidly attached to the upper surface thereof, said arm 36 being positioned within a groove 38 in the upper end wall of recess 29 and rigidly attached to base Ii, as by means of a rivet 39.

The lower end portions of arms'25 and 26 of element 23'are bent inwardly toward each other, as shown at 40 and-4| in Fig.4 to insure proper engagement thereof with the shoulders formed between the head 3| and the relatively narrower portion of plunger 30.

Also seated in a groove in the upper end wall of recess 29 is the horizontal portion 42 of a punched and formed sheet metal member, said portion being secured to base ll as by means of a rivet 43. Portion 42 extends toward the right into alinement with opening 28, and has a forked end thespaced portions 44 and 45 of which are bent upwardly at substantially right angles to provide a fulcrum for an oscillatable contactor 46 to the lower surface of the right-hand end of which a tip 41 of fine silver or the like is rigidly attached. Contactor 46 is substantially like that shown in Patent No. 2,342,945, the same having a fiat portion 48 angled upwardly from the main body portion thereof at one side of the fulcrum or pivot point thereof.

Lever I6 is recessed asshown in Fig. 1 to accommodate an insulating plunger 49 which is biased outwardly from the recess by a coiled compression spring 50. with lever I6 manually moved to the full line position thereof shown in Fig. 1 contactor 46 will be correspondingly moved to and normally held in its circuit completing position as illustrated. Also upon manual or automatic movement of lever 16 to its dotted line position plunger 49 will engage the portion 43 of the contactor to move the same with a quick action to its circuit-interrupting or oil' position shown in dotted lines.

Plunger 30 is substantially like that shown in said Patent No. 2,342,945, the same being recessed as shown in Fig. 1 to accommodate a vertically positioned coiled compression spring 5| which biases plunger 30 toward the upper end wall of recess 29, and the lower end of said spring surrounds a boss 52 formed upon a relatively thin sheet metal plate 53 to bias the latter downwardly. Plate 53 is provided with notches at the respective ends thereof for engagement with integral upwardly bent relatively narrow lugs 54 and 55 formed at opposite ends of a relatively thicker sheet metal plate 56. Lug 54 projects upwardly at substantially a right angle to plate 56, and lug 55 extends upwardly and inwardly as shown for cooperation with an angular cam-like wall 51 of the recess aforementioned. Plate 56 is sheared on opposite sides of a lug 58 which is bent downwardly at a predetermined angle as 11- lustrated; and the or! metal edge 59 of lug 58 is located in a substantially vertical plane.

A fiat punched insulating plate 60 is interposed between the insulating bases ii and I2; plate 56 being slidably movable over plate 60, and the latter having a relatively narrow slot Si formed therein to provide just sufiicient clearance for lug 58, the width of which is shown in dotted lines in Fig. 4. Slot Si is made relatively wider at a predetermined point in the length thereof, as indicated at 62 in Figs. 1 and 4, to accommodate the substantially vertical upstanding latch lug 63 which extends upwardly into said enlargement of the slot under normal conditions. By this means the cooperating lug 58 may be made substantially shorter, and therefore stronger, than the corresponding lug in Patent No. 2,342,945, and the overall depth of the complete device is thereby reduced to a corresponding degree.

Latch lug 53 is formed integrally with a horizontal portion 54 of corresponding width; and portion 54 is spot-welded or otherwise rigidly secured to a rectangular enlargement of corresponding size at a predetermined point in the length of a bimetallic electro-thermally responsive element 65, as indicated at 6B in Figs. 1 and 4.

As shown, the bimetallic element 65 is supported within the upwardly opening recess 6! in base 12. The left-hand end 68 of element 65 is enlarged and notched as indicated at 68 and 69 in Figs. 1 and 5. Notch 69 is adapted to fit around the reduced or neck portion 10 of a machined metal member whose head H is thus adapted to overlie said enlarged end 68. Said metal member is provided with an externally screw-threaded portion 12 which is adjustable within a threaded passage or opening '83 in the bottom wall of recess 61. The lower end of portion 12 is provided with a kerf T4 to provide for adjustment thereof as by means of a screw-driver. Interposed between the bottom wall of recess 61 and the lower surface of enlarged end 68 is a coiled compression spring 15, which biases said end against the lower surface of head H. A countersink or recess 16 surrounds the kerfed end 14 of portion 12 to receive a quantity of cement or the like 11 to maintain head ll in the position to which it has been adjusted at the factory.

The right-hand end of bimetallic element 65 is of enlarged rectangular contour, as indicated at 18, and is interposed between the horizontal portion l9 of an inverted substantially L-shaped sheet metal bus member (preferably a copper asoavoo strip), the substantially vertical portion of which is designated by numeral 88, and the rectangular portion of a punched and stamped sheet metal contactor the arm of which is designated by numeral 82. .Loosely interposed between said portion II and the lower surface of plate 80 is the intermediate portion of a pin 83. The parts I8. I8. and II are rigidly connected or united, as by subiecting the same jointly to aspot welding operation; the pin 88 serving to space said parts a predetermined distance below the upper surface of base I2.

As shown in Figs. 1, 2, and 5 the opposite ends of pin 88 are adapted to fit rather snugly within a pair of opposed vertical grooves 84 and 85 extending downwardly to a plane slightly above the bottom wall of main recess 51 in base I2 (see Fig. 2). Interposed between the bottom wall of main recess 81 and the lower surface portion 8I of the switch contactor is a coiled compression spring 86, whose lower end surrounds a boss 81 formed integrally with said bottom wall. As best illustrated in Fig. 2, portion 8| of said contactor is provided with downwardly oil'set lugs 88 and 88, which are also positioned within grooves 84 and 85 respectively; lugs 88 and 89 being of slightly less width than said grooves,.to act as a pivot and to permit tilting of contactor 82 in the manner hereinafter described. The insulating plate 80 overlies the pin 83 (Figs. 1 and 2) to limit the upward displacement of the aforementioned parts under the bias of spring 85.

The free end of contactor 82 preferably has attached thereto a tip 90 of fine silver or the like, as by spot welding. Tip 90 is adapted for cooperation with a stationary contact tip 9| of like or similar material; tip 9| being carried at the upper end of a screw or stud 92 which is initially adjustable within the screw-threaded opening through a rivet 93 the rectangular head 94 of which is fitted snugly between the opposed side walls of an auxiliary recess 95 formed in the bottom wall of main recess 61, whereby rotation of said rivet head is positively prevented. Also positioned within auxiliary recess 95 (beneath rivet head 94) is a punched and stamped sheet metal terminal member, the horizontal portion of which is designated by numeral 96, and the initially vertical portion of which is designated by numeral 91. After downward insertion of portion 9} through a suitable opening 98 in the bottom wall of base I2 and securing of portions E such as the metal alloy known as Nichrome., Wire I02 is spirally wound in situ around therelatively narrow portion of element 65 between enlargements 68 and 68 in coils of gradually increasing size; as by temporarily positioning the two halves of a split conical mandrel (not shown) on opposite surfaces of said element 65 so that the smaller coils will rather closely surround the left-hand end of said narrow portion and the largest coil will be located adjacent the latch lu 88, a straight or vertical portion I03 being adapted to fit into an opening of suitable size formed in portion 88 of the aforementioned terminal member, as shown in Fig. l. Portion I88 is spot-welded, brazed, or otherwise mechanically and electrically connected with portion 98, as indicated at I04. By this means any current passing through element 85 is also required to traverse the heater coil I02, whereby element 88 is subjected to the heat of coil I02 to increase the degree of downward bending or deformation of said element under given overload conditions. By employment of the conical coil I02 the degree of radiation of heat therefrom to strip II is accentuated and is substantially constant (for given current conditions) in all positions assumed by said strip when in use. son also the strip 65 may be of substantially heavier caliber than would otherwise be possible, while retaining the desired high degree of sensitivity thereof to given values of overload current.

As shown in Fig. 1 the aforementioned sheet metal member which provides the fulcrum or pivotal support for contactor 48 has formed integrally with the horizontal portion 42 thereof a vertical portion I 05; insulating plate 80 having a correspondingly shaped rectangular opening (not shown) to provide for downward insertion of portion I05, and the bottom wall of recess 01 in base I2 having a similar opening I06 (see Fig. 5) through which said portion is adapted to extend. Portion I05 is provided at its lower end with an angular edge I01. A punched and stamped sheet metal terminal member has a vertical portion I08 (Figs. 1 and 7) which is positioned exteriorly of the lower end of portion I05, the latter end portion I08 having alined openings (not' shown) to accommodate the hollow shank of a headed rivet, the end of which shank is upset as shown at I09 to secure said parts to each other. After said riveting operation a small amount of molten solder (not shown) is applied at the area designated at III! in Figs. 1 and 7 to insure a rigid mechanical and good electrical connection between said parts. Formed integrally with vertical portion I08 and bent forwardly in a plane parallel to the lower edge I01 of portion I05 is a portion I I I which is provided with a tapped opening to accommodate the shank of a second terminal screw I00; whereby the axes of both screws are at approximately 45 'degrees from the vertical, to facilitate attachment of the circuit wires.

The aforementioned metal cover and support plate I0 is provided adjacent opposite nds thereof with circular openings H2 and H3 to accommodate the reduced hollow neck portions Ill of a pair of like machined resilient locking nuts the intermediate portions I I 5 of which are preferably of square contour. Extruded or pressed downwardly from plate I0 are a pair of straight elongated bosses H6 against the outer side edges of which one side of each of the portions H5 are respectively adapted to fit to positively restrain said nuts against rotation. The upper ends-of neck portions III are spun or upset over the upper surface of plate I0, as indicated III, to rigidly secure said nuts in position. Each nut "is initially provided at its lower end with a reduced cylindrical porton which I have designated by the numeral II8; each nut in its initial form being also rovided with a screw-threaded through passage H9 (Fig. 1) of usual form. After the threading operation said portion I I8 of the nuts are each provided with a diametrical kerf or saw-cut I20 which extends throughout For this reasubstantially the entire length thereof. Thereupon the parts of each portion H8 separated by kerf I20 are pressed or bent toward each other to provide substantially an inverted frusto-conieal contour thereof, thus reducing the diameter of the lower portion of screw-thread I I9 to effect resilient gripping and holding or locking of the threaded shank of a. screw or bolt which fits the upper portion of screw-thread H3 in the usual manner. The upper surface of base II is provided at opposite-ends thereof intermediate its width with upwardly and endwise opening recesses I2I and I22 (Fig. l) to accommodate the lock-nuts, and to afford access to the heads of rivets 39 and 43. The longitudinal sides of base II remain substantially unbroken and smooth, as best illustrated in Fig. 7.

The device may be associated with a suitable panel (not shown) preferably having a circular opening of slightly larger diameter than opening I3 in plate I0, and a pair of circular openings alined with the threaded passages I IS in the locking nuts to provide clearance for the shanks of headed clamping bolts or screws (not shown) which are threaded into said passages; such shanks, of course, being of suificient length to extend downwardly at least a substantial distance into the kerfed and deformed portions I I8 of said nuts.

Assuming that the circuit breaker is connected in series in a circuit to be controlled, by attachment of the wires by means of the pair of screws I00, the same will function normally in substantially the same manner and for the same purposes as set forth in said Patent No. 2,342,945. That is to say, with lever IS in the dottedv line position thereof shown in Fig. 1, with consequent disengagement of contact tip 41 from tip 31, and with plunger 30 in its extreme left-hand position, manual movement of handle I 6 to the full line position thereof illustrated will effect closure or completion of the circuit to be controlled. At the same time the aforementioned arms 25 and 20 will drive plunger 30 toward the right, so that lug 58 will be carried to the right beyond latch lug 63, and upon manual release of lever I6 the edge 59 of lug 58 will engage latch lug 63 (if the bimetallic strip is sufficiently cool to provide for latching positioning of the last mentioned lug), thus restraining plunger 30 against movement toward the left under the bias of spring 33. Under these conditions the contact tip 41 will be permitted to remain in engagement with tip 31 under the bias of switch spring 50. Moreover, under normal conditions the lever I6 of the switch may be manually moved to its opposite extreme positions respectively, to sequentially complete or interrupt the controlled circuit, without requiring unlatching of the plunger 30.

Closure of switch contacts 41, 31 eflects completion of a circuit, which may be traced from the left-hand terminal member III in Fig. 1, through vertical portion I and horizontal portion 42 of the aforementioned metal member, through contactor 40 (and tips 41, 31) to and through horizontal portion 30 and vertical portion 35 of the other metal member, by strip 80 through bimetallic element 65, and through heater coil I02 to portions 96 and 31 of the righthand terminal member.

Under given overload conditions bimetallic element 65 will bow downwardly (say to the dotted line position thereof shown in Fig. 1) under the heating effect of the excess current flowing therethrough and through the coil I02; and the coil I02, with resultant continued downward bending or bowing of element 65. The switch.

contactor 02, which is attached to the lower face of the right-hand end of element 65 will continue to move downwardly beyond the dotted line position thereof shown in Fig. 1 (which corresponds to the aforementioned latch=tripping position of element 65) until the tip 30 engages stationary contact tip 9|. When this occurs both element 05 and coil I02 will be short-circuited, while the controlled circuit is maintained, thus insuring against overheating or fusion of element 65 and/or coil I02, whereby the fire hazard incident to burning out or destruction of such parts (which would be likely to follow in the absence of shorting switch 82, 92) is obviated. As will be understood, when element 65 and coil I02 are thus short-circuited, the former upon cooling will automatically return toward its dotted line position (Fig. l) with consequent disengagement of contact tip 90 from tip 3|, so that element 65 and coil I02 will again be subjected to the overload current, and after a given length of time (depending upon the degree or value of the overload) tip 90 will again be engaged with tip 9|, with the result aforedescribed. If the overload disappears or is removed the parts will again assume the normal positions shown in full lines in Fig. 1, so that the controlled circuit will be maintained closed, if desired, without requiring manual retention of lever It in its circuit completing position.

As shown in Fig. 1, upon manual adjustment of screw 92 to effect the desired position of tip 9 I a quantity of suitable material (such as molten lead or solder) is deposited in the hollow lower end of member-93 to cover the kerfed lower end of said screw, whereby accidental movement of said screw or further manual adjustment thereof is eifectively prevented.

Also as shown at the lower right-hand end of Fig. 1, when the lower ends of portions 35 and have been spot-welded, brazed, or otherwise rigidly connected to each other, I prefer to cover said exposed ends, as by means of a molded insulating member !23, which is recessed at I20 I23 onto the otherwise exposed ends of the united metal members would be provided.

As shown in Figs. 3, 5 and 6 top plate i0, base II, insulating plate 60 and base I2 are respectively provided adjacent the four corners thereof with alined openings or passages to accommodate, with a, rather close fit, the relatively long shanks I25 (see Fig. 6) of a corresponding number of rivets the heads I26 of which are located Anfour corner-recesses in base I2: two of which recesses are shown at I21 and I28 in Fig. 6. The hollow upper ends of rivets I25 are upset over the upper surface of plate I0, as shown at I20,

-to rigidly and permanently secure the aforementioned parts in assembled relation. In this manner the, required number of fastening elements is only one-half as large as the number required in the devices of said Patent No. 2,342,945; and, moreover, the necessity for molded-in fastening elements or inserts in the upper insulating base is obviated.

- In the modification illustrated in Figs. '7 and 8 the lever I6, top plate I0, upper insulating base ll, and all of the elements directly associated scribed for cooperation with the supporting and adjusting elements 'I I, I5, I2, I4, etc., and a filling of a suitable insulating cement TI is utilized to retain screw I2 in adjusted position. The lower insulating base I30 differs slightly from the base I2 of Figs. 1 to 6, in that the right-hand end of the bottom wall of recess I3I therein is closed, as indicated at I32 in Fig. 7; the centering abutment for the coiled spring 86 of Fig. 1 is omitted from the lower base I30 in Fig. 7; and relatively shallow vertical grooves I33 and I34 are provided in base I30 to accommodate pin 83, as distinguished from the substantially deeper grooves 84 and 85 of base I 2 (see Fig. 2). In the device of Figs. '7 and 8 the pin 83 is spot-welded, brazed or otherwise rigidly attached to the upper surface of the right-hand end portion of element 65 whereby said pin acts as a pair of pivot lugs, and pin 83 is biased into engagement with the bottom end walls of grooves I33 and I34 as by means of the resilient, downwardly angled tongue or extension I35 of an inverted U-shaped sheet metal member, one of whose opposite sides is designated by numeral I36 in Fig. '7, and the connecting portion of which is designated by numeral I3I. Said sides (see I36, Fig. '7) are adapted to fit rather closely but slidably between the opposite side walls of recess I3I in base I30; and the vertical edges of said sides are adapted to fit between pairs of vertical shoulders formed upon the opposed side walls of recess I3I one pair of said shoulders being shown at I38 and I39 in Fig. 7. Insulating plate 60 overlies connecting portion I3'I to retain the same and tongue I35 in proper position.

A multiple-strand copper wire or bus member I40 has one end thereof spot-welded or otherwise rigidly attached to the lower surface of the right-hand end of element 65; the other end of bus member I40 being rigidly attached, as by spot welding, to the lower end portion 35 of a metal member which preferably does not extend downwardly beyond the upper surface of base I30. In other respects portion 35 of the metal member in Fig. 7 corresponds with the aforedescribed portion 35 of the similar metal member in Fig. '1.

In like manner element 65 has spot-welded or otherwise rigidly attached to the upper surface of its left-hand enlarged end portion one end of a multiple-strand copper wire or bus member I4I the other end of bus member I being .10 similarly spot-welded to the upper surface of portion 36 of terminal member 01.

Inasmuch as the ai'oredescribed shorting switch of Figs. 1 to 6 is not required in the device of Figs. 7 and 8, the aforementioned portion 96 is merely perforated to accommodate the shank 33 of a rivet whose square head 94 is adapted to fit non-rotatably between the straight side walls of a recess, one side wall of which is shown at I42 in Fig. 7. The hollow lower end 99' of rivet shank I33 is upset over the lower surface of base I30 to secure terminal member 91 in assembled position; the head 84* and the upper portion of shank 93 of said rivet being preterably of solid or closed form.

The operation of the circuit breaker shown in Figs. 7 and 8 will be apparent to those skilled in the art; but it may be pointed out that upon connection of the circuit breaker into the circuit to be controlled, and with the switch mechanism in circuit completing position (as indicated by the position of lever I6), the lever I6 when manually released will provide for maintenance of the controlled circuit pending a given degree of downward bending or bowing of bimetallic element 65 under overload conditions of predetermined value. Also, as in my Patent No. 2,342,945, the controlled circuit may be interrupted or completed at any time at will, whether or not the circuit is subjected to overload conditions. That is to say, the circuit breaker, is of the non-free-tripping type.

In each form of circuit breaker herein disclosed the means for supporting the bimetallic element (65 or 65) have been improved to provide for easier assembly thereof than in my aforementioned Patent No. 2,342,945, while at the same time effecting a reduction in the degree of variation of the operating characteristics of the breakers resulting from normal manufacturing tolerances.

I claim:

1. In a non-free-tripping overload circuit breaker, in combination, a molded insulating base having an upwardly opening recess formed therein, a bolt having screw threaded adjustable engagement with the bottom wall of said recess adjacent one end of the latter, said bolt having a neck and a head at the upper end portion thereof, a normally fiat bimetallic strip having a notched end fitting onto said neck and underlying said head, a coiled spring interposed under compression between the bottom wall of said recess and the lower surface of said end of the strip, the side walls of said recess having a pair of vertical grooves formed therein respectively adjacent the other end of said strip, a pin and a bus member associated with said last mentioned and of the strip, the ends of said pin being respectively positioned within said grooves, a coiled spring interposed under compression between the bottom wall of said recess and the last mentioned end of said strip, a flat punched insulating plate overlying the upper end of said base and said grooves for engagement by the ends of said pin to positively limit the degree of upward displacement of the last mentioned end of said strip, and a metal member to which said bus member is rigidly and permanently attached.

2. In a non-free-tripping overload circuit breaker, in combination, a molded insulating base having an upwardly opening recess formed therein, a bolthaving screw threaded adjustable engagement with the bottom wall of said recess QJOGIJQQ 31 adjacent one end of the latter, said bolt having a neck and a head at the upper end portion thereof, a normally flat bimetallic strip having a notched end fittin onto said neck and underlying said head, a coiled spring interposed under compression between the bottom wall of said recess and the lower surface oi said end of the strip, the side walls of said recess having a pair of vertical grooves formed therein respectively adjacent the other end of said strip, a pin and a bus member associated with said last mentioned end of the strip, the ends of said pin being respectively positioned within said grooves, a coiled spring interposed under compression between the bottom wall of said recess and the last mentioned end of said strip, a flat punched insulating plate overlylng the timer end of said base and said grooves for engagement by the ends of said pin to positively limit the degree of upward displacement or the last mentioned end of said strip, a metal member to which said bus member is rigidly and permanently. attached, said metal member and said bus member having the connected portions thereof exposed below the lower surface of said base, and a recessed molded insulating member overlying and concealing said portions of said members and held against displacement relatively thereto.

3. In a non-free-tripping overload circuit breaker including a switch manually operable 12 said plunger, a latch member rigidly attached to said strip and adapted to engage said ilrst mentioned latch to hold said plunger in a given position thereof against its bias, said position of said plunger resulting from closed circuit positioning of said switch, the supporting insulating base having an upwardly opening recess, an adjustable screw at one end of said recess, said screw having a head and a neck portion adjacent the upper end thereof, said bimetallic strip having a notch at one end adapted to fit around said neck and underlying said screw head, and a coiled spring interposed under compression between the bottom wall of said recess and said end of the strip, the combination of a pair of pivot lugs and a bus member associated with said strip at the other end of the latter, the side walls of said base recess having a pair of vertical grooves formed therein to accommodate said lugs, and spring means within said base recess and adapted to bias said lugs to a predetermined position within said grooves, said lugs forming a fulcrum to insure a predetermined degree of downward bending of the intermediate portion of said strip, for the purpose set forth, upon occurrence of an overload of given value in the circuit controlled by said switch.

ALVIN W. IEGER.

REFERENCES @H'EED UNITED STATES PATENTS Name Date Krieger Feb. 19, 1944 Number

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