US2090754A - Electric circuit interrupter - Google Patents

Description

1937- w H. c. GRAVES, JR 2,090,754

I ELECTRIC CIRCUIT INTERRUPTER Filed Jan. 21, 1936 3 Sheets-Sheet l amm? A TTORNE Y.

,1937. H. c. GRAVES, JR 2,090,754

ELECTRIC CIRCUIT INTERRUPTER Filed Jan. 21, 1936 3 Sheets-Sheet 2 IN VEN TOR.

WWW @owmaczm A TTORNE Y.

Aug. 24, 1937. H, c, GRAVES, JR 2,090,754

ELECTRIC CIRCUIT INTERRUPTFJR Filed Jan. 21, 1936 s Sheets-Sheet s Q If g W- f,57c A f a:

INVENTOR F BY i 7 M24615 ATTORNEY.

Patented Aug. 24, 1937 ELECTRIC CIRCUIT INTEBRUPTEB.

East Bradford Township, Chester County, Pa., assignor to I-T-E Circuit Herbert C. Graves, Jr.,

' Breaker Company;

ration of New Jersey Philadelphia, Pa.,

Application January 21, 1936, Serial No. 60,017

18 Claims.

My invention relates to electric circuit interrupters or automatic circuit breakers, more par ticularly to new and improved separable contacts therefor, and has for an object the provision of simple, rugged and inexpensive contact structures of high current-carrying capacity.

In my Patent-2,028,204, issued January 21, 1936, for Electric circuit interrupters, a circuit breaker and contact structure of which the preslo ent application is an improvement is disclosed.

While circuit breakers of the type shown in my aforesaid patent have been entirely satisfactory for their intendedpurposes, something was yet 15 to be desired in simplification of the structure to provide ready removal of the bridging elements as well as to prevent movement of the bridging elements by the magnetic forces produced upon flow of abnormally high currents or currents of short-circuit magnitude.

In carrying out myv invention, in one form thereof, I provide a plurality of ridges along the faceof one of the contact structures. which ridges cooperate respectively with the ends of a u plurality of bridging elements to prevent movement thereof and insure the maintenance of substantial contact pressures between'the elements and their associated contact structures. The ridges are also utilized to support corresponding 30 ends of leaf springs interposed between adjacent bridging elements. The opposite ends of the by cross bars extendingsprings are supported as between the walls of a frame or housing or by separate mounting means having projections cog operating'with notches formed in the walls of the associated housing. In either case, the springs and bridging elements are removable from the housing without disturbing other parts of the interrupter.

The leaf springs are, according to a further aspect of my invention, preferably dimensioned so that when compressed upon closureof the circuit interrupter the springs are uniformly loaded throughout their length; that is to say, 45 every portion of each spring is stressed or loaded to the same extent as every other portion. Overstressing of the springs at any one particular point is thereby eliminated although the springs are suihciently flexible to permit wiping and/or rolling contact engagement between the respective ends of each bridging element and their associated stationary and movable contact structures. For a more complete understanding of my invention, reference should be had to the accompanying drawings wherein Figure l is a vertical elevation, partly in section, of a circuit interrupter embodying my invention;

Fig. 2 is a front elevation of the stationary contact structure and bridging elements of Fig. 1

with the movable contact blade or structure omitted Fig. 3 is a perspective view of the supporting frame of Figs. structure and 1 and 2 with the stationary contact other parts removed;

Fig. 4 is a perspective view of one of the duplicate bridging elements of Figs. land 2;

Fig. 5 is a perspective view of one form of leaf spring and its associated supporting member;

Fig. 6 is a fractional side elevation of a circuit interrupter embodying my invention in modified form;

Fig. '7 is a plan view, partly injection, of Fig. 6 with a bridging element omitted to illustrate the manner in which the leaf springs are supported;

Fig. 8 is a perspective frame of Figs.

Fig. 9 is a perspective view of springs of Figs. 6 and 7.

view of the supporting 6 and '7;

one of the leaf Referring to the drawings, I have shown my invention in one form as applied to a circuit interrupter comprising a base or panel member bly l2.

ill from which is supported a terminal stud or post Ii connected to a stationary contact assem- A second terminal stud or post l3, also supported from the panel It, has secured to its inner end; as by cap screw H, one end of a flexible conductor l5,

connected to the opposite end of which is a movable contact structure or bridging arm I6 as by cap screws I1 and a clamping plate It. Preferably insulation, as indicated at is interposed between the arm I6 and an operating member or shaft 20. The movable contact structure or arm I6 is operable between the closedcircuit the full lines of Fig. 1 and tion indicated by the broken position illustrated by an open circuit posilines of Fig. 1 by any ing elements 21 for cooperation with each of the arms it. To simplify the description and operation, only one arm l6 and its associated stationary contact assembly will be described, it being understood that the operation of additional due plicate parts is the same as that described.

The stationary contact assembly it! comprises 5 a stationary contact block or member 2! mounted as by screws 22 and 23 between opposite walls. of a frame or housing 24 fastened to the panel; iii as by screw 25, the stud ii being secured in.

intimate electrical contact with the s'tationary contact member 2i. One face of'the member 2 is provided with reentrant angles Zia formed; bya series of ridges 26 spaced one above the other. Within the angles or recesses: Zia formed there-' between are disposed theinner ends or edges of the series of duplicate bridging elements: 2? each of which is provided withan oifset portion form ing a hook-shaped end 275a. Engaging each. end 27a is an upturned end. or flange 28a of a plurality of fiat or plane supporting members 28 provided for curved leaf sprlngsid. Each supporting member 28 adjacent its end 280. rests upon the upper portion of an associated ridge 26. The opposite end of each supporting member 28 is provided with lateral projections 28b, Fig. 5, arranged. to fitwithin C-shaped slots or recesses 30, Fig. 3, provided in the front of the respective walls of the housing 24.. Preferably the C-shaped recesses 30 are staggered with respect to the reentrant angles so that the bridging elements 27, their springs 29 and supporting members 28, extend diagonally between the opposing contact faces of contact member 2i and of the movable bridging arm iii.

In order to relieve the bridging elements, the

3 primary functions of which are to provide low resistance paths between the movable and stationary contact members, from the duty of making and breaking the circuit, which may extend between posts ii and i2, an auxiliary arcing contact structure is provided and comprises an arcing contact 32 journalled on a pivot pin 33 supported between the side plates of the housing 26. The arcing contact 32 has an associated arm 32a to which is secured a biasing spring 3d efiec- ,5 tive to maintain the lower end of the contact 32 in a position, indicated by broken lines, .first to be engaged by the movable arm i6 during circuit-closing operation, the arm is also interrupting the circuit at the arcing contact after the current has been transferred from the bridging elements 2'! to the arcing contact 32. In order better to withstand the heat of the arc incident to the opening of the circuit, the arcing contact 32 and the associated movable contact or arm I 6 are provided, respectively, with arc-resistant inserts or facings 32b and ifia. A; flexible conductor 35 is electrically connected to the stationary contact member or block 2i and to the arcing contact 32 to insure a low resistance our- 0 rent path therebetween.

Assuming the movable contact arm i6 is in the open circuit position, it will be observed the respective leaf springs 2c support their asso-. ciated bridging elements 2? in elevated positions 5 shown by the broken lines. As the movable contact arm i6 is rotated in a counterclockwise or circuit-closing direction, it first engages the arcing contact 32 to complete an electrical circuit between terminal posts it and it. The arcing 70 contact 32 upon further movement of the arm it rotates in a clockwise direction, and a regular contact surface i6b of arm id is moved into engagement with the corresponding outer and rounded ends of the bridging elements 2?. By 75 a regular contact surface, I mean one which does reason of a camming action between the rounded end of. each element and the angularly disposed contact arm it, is efiective to press the inner rounded ends of the: elements against the stationary contact member. outer ends of the bridging'elements slide and wipe and clean the plane contact surface Nib to insure good electrical contact therebetween, the inner rounded ends; of the bridging elements by virtue of their rolling and sliding engagement" with the walls of the respective recesses, wipeand clean the surface of the stationary contact member. The final closed circuit position, is shown in Fig. 1, the distance between the respective contact surfaces being uniform atv all points.

Although, during the aforesaid closing operation, the bridging elements are capable of selfadiustment and have sufficient independent freedom of movement to take care of misalignment and different degrees of wear as between-dinerent elements, it is desirable when the circuit interrupter is in its fully closed position to prevent movement of the elements because of magnetic forces or the like. To this end the ridges 26 form rigid stops for the inner ends or edges of each of the bridging elements and prevent, as viewed in Fig. 1, upward movementthereof. A strong Therefore, while the tendency to move the elements 2? upwardly may be'created by flow of short-circuit current or currents of high or like value because the ma netic forces developed are applied to each bridging element in a direction to lift its inner end as well as its outer end. In accordance with my invention, however, such magnetic forces'as may be produced are effective to increase the contact pressure between each bridging element and its associated overlapping ridge. With respect to the outer ends of the bridging elements, the mag netic forces produced are in a direction tending to lift and hold them against the plane or regular contact surface itb of the contact member or arm is. The upward tendency of the outer ends of the elements, because of the angular relation between each element and surface i512, is prevented. Stated differently, the magnetic forces tend to move the bridging. elements toward the outside of the angles formed between the plane of each member and the face of the movable and stationary contact structures. The respective ridges and surface i611, however, form stops which prevent any movement thereof toward the outside of said angles. The angular relation between each bridging element and the contact surface itb gives rise to a camming action therebetween which actually moves or tends to move the bridging element towards the contact block 2i, thereby increasing the bias of each element within its recess or against the ridge. Because of the aforesaid features increased circuit-closing pres- In addition to the aforesaid structural features of my invention, I have found it advantageous to construct each leaf spring so that the contact stamped from sheet metal, opposite edges or flanges 28a and 28b of which are bent at right angles to the body portion thereof. To provide uniform loading of the spring, the cross-sectional 15 area of the intermediate curved portion 29b diminishes from its central portion towards opposite ends of the spring in accordance with the increase of lever arm; i. e., the smaller the crosssectional area the farther from the point where 20 the load is applied. In consequence, each spring, the body portion of which is diamond-shaped,

has substantially uniform unit stress for any given deflection; there are no over-stressed portions and the life of each spring is corresponding- 25 ly lengthened.

Further in accordance with my invention, the bridging elements may be readily removed from the interrupter without disturbing other parts of the circuit interrupter. As will be clear by refer- 30 ring to Figs. 2 and 3, the respective C-shaped slots 30 are wide enough at their open ends to permit removal of the lateral projections 28b of the supporting member 28, the removal being accomplished by lifting the supporting element 29 until 35 its outer end can be moved outwardly through the recesses '30. The bridging elements and spring assembles are then free for complete removal from the interrupter. To insert new bridging elements, or to return the old ones into- 40 position, the aforesaid steps are repeated in the reverse order. The ready accessibility and removability of the bridging elements is of great practical advantage inasmuch as the bridging elements 21' may be readily removed for inspec- 45 tion or renewal without disturbing other parts of the interrupter.

As shown in Fig. 2, two stacks of bridging elements 21 are arranged side by side, for cooperation with a movable contact structure (not 5 shown). For even greater current-carrying capacities, it may be desirable to provide additional duplicate contact structures. The spring supports 28 in each case may be provided with a plurality of openings in their respective flanges for 55 insertion therein of a number of springs 29 corresponding to the number of stacks of bridging elements, or separate supports may be provided for each corresponding spring of each stack.

While the example of the invention disclosed 60 has four bridging elements assembled in vertical relationship, it is obvious that any convenient number maybe used.

Referring to Figs. 6 to 9, inclusive, I have shown a modified form of my invention wherein 65 each leaf spring performs the dual functions of retaining the bridging elements in position and of biasing them against. their respective contact surfaces under circuit-closing pressure. As illustrated in'Fig. 9, each arcuate leaf spring 31 is 70 relatively wide at its center, gradually decreasingin cross-sectional area towards opposite ends thereof as described in connection with Fig. 5. In this case, however. the leaf spring terminates in a wide, laterally extending edge 31a which is 75 curved-upwardly, pointed projections or nibs 31b at opposite ends of said edge extending into engagement with the hook-like ends 2111 of the respective bridging elements. The wide lateral edge or end 31a, in efiect formed by arms extending at right angles to the longitudinal axis of the spring, increases the stability of the supporting arrangement and is particularly desirable where the bridging elements are relatively great in width. The outer rectangular end 310 of each leaf spring is provided with shoulders 31d which engage the inner wall of its associated cross bar 38 to prevent outward movement of the spring. The outer ends 310 of the springs rest within notches or recesses 38b provided in each cross bar. As shown, each cross bar is formed integrally with the side walls of the housing 36, though it is to be understood the cross bar may be rigidly secured thereto or to other supporting structure as by fastening screws.

With the interrupter in the open-circuit position, the upwardly extending nibs or projections 31b engage their respective elements 21 to hold them in position. Obviously, by raising the outer and lower ends 310 of each of the springs until their shoulders 31d respectively clear the notches 38b, the springs and elements 21 may be removed I for inspection or replacement.

The normal curvature of the diamond-shaped body portion 310 of each spring is sufficient to retain the outer end of its associated bridging element in an elevated position. As the movable contact arm is moved into engagement with the outer ends of the bridging elements, the sliding and rolling engagement of the contact surfaces under circuit-closing pressure cleans them. Each spring is compressed in the fully-closed circuit position to insure substantial contact pressure. In addition to the forces applied along the diagonally disposed bridging elements, a component of the force developed by each spring is applied through nibs 31b to the left-hand end of each bridging element in a direction to increase the contact pressure between each element and the stationary contact member 2 I.

While I have shown particular embodiments of my invention, it will be understood, of course, that I donot wish to be limited thereto since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the. true spirit and scope of my invention.

What I claim is: v

1. In an electrical circuit interrupter, cooperating relatively movable contact structures, one of which is provided with a plurality of contact surfaces disposed respectively within reentrant portions thereof, and the other of which is provided with a regular contact surface, a plurality of rigid bridging elements extending, respectively, diagonally outwardly from within said reentrant portions, and resilient means yielding to permit said elements to tilt slightly, opposite endsof said elements in circuit-closing position of the interrupter engaging respectively said contact surfaces of said structures.

2. In an electrical-circuit interrupter, cooperating relatively movable contact structures, one of said structures including a plurality of parallel rigid conducting elements extending diagonally outwardly therefrom, said one structure having a plurality of ridges respectively forming stops for corresponding ends of said elements, the other of said structures having a regular contact surface, a plurality of springs alternately disposed between and each engagingpne of said rigid con- 10 3. In an electrical circuit interrupter, a contact member the cross-section of which has reentrant angles, bridging elements individual to, and one end of each disposed within, said angles, biasing means individual to said elements for retaining ,15 said elements within said angles and in diagonal outwardly extending positions, a second contact member in circuit-closing position of the interrupter engaging under circuit-closing pressure the ends of said elements remote from said angles,

20 said biasing means yielding to permit said elements to tilt a slight amount and at their opposite ends wipe said contact members under circuit-closing pressure;

4; In an electric circuit interrupt-er,- a contact 25 member provided with a plurality of recesses, a plurality of rigid conducting elements, one end of each .of said elements being operatively associated with one of said recesses, individual means for retaining corresponding ends of said 3!) elements within said respective recesses, individual leaf springs, the respective ends of which are supported by said individual retaining means for exerting a bias against their associated elements, a second contact member for engaging in 35 circuit-closing position of the interrupter the opposite ends of said elements, said springs, upon application of circuit-closing pressure between said contact members, yielding to permit said elements to rotate a slight amount about their re- 40 spective ends within said recesses and thereby provide wiping contact engagement between opposite ends of each of said elements and said contact members.

. 5. In an electrical circuit interrupter, cooperat- 45 ing relatively movable contact structures one of which has a series of recesses disposed between a plurality of ridges, a series of rigid bridging elements extending diagonally between said contact surfaces, one end of each of said elements 50 nesting within one of said recesses, individual resilient means engaging said elements adjacent one end and engaging said elements intermediate the ends, and yielding to permit said elements while substantially parallel to rotate about their 5 respective ends to wipe said structures under circuit-closing pressure.

6. In an electrical circuit interrupter comprising a contact member provided with a plurality of ridges spaced one above the other along one 30 face thereof to form a plurality of recesses therebetween, a plurality of bridging elements, each of the corresponding ends of said elements respectively nesting within one of said recesses, said elements extending diagonally from said recesses, individual supporting means disposed adjacent the ends of said elements remote from said recesses, individual springs for said elements, one end of eachofv said springs being supported from one of said ridges, and the opposite end of each 0 of said springs being supported respectively by said individual supporting means, each of said springs being formed ,to engage its associated bridging element intermediate the ends thereof, a second contact member having a contact, face 75 for simultaneously engaging said remote ends of said elements, and means for producing a circuitclosing pressure between said contact members, said springs yielding to permit wiping engagement of the respective ends of said elements with said contact members.

'7. In an electrical circuit interrupter, a bridging element having an off-set portion adjacent a rounded end thereof, a contact member associated with said rounded end andhaving a ridge overlapping the same, means including a spring engaging said oil-set portion to retain said element beneath said ridge and a support loosely retaining said means in a predetermined position.

8. In an electrical circuit interrupter, a bridging element, an arcuate leaf spring for supporting said element, one end of said spring having a shoulder, means engaging said shoulder to prevent movement of said corresponding end of said spring, and means slidably supporting the opposite end of said spring.

9. In an electrical circuit interrupter, a support, a bridging element, an arcuate leaf spring, the central portion thereof engaging said element, and the width of said spring decreasing from opposite sides of said central portion, one end of said spring having supporting arms extending at right angles to the longitudinal axis of the spring,- and the opposite end of said spring engaging said support.

10. In an electrical circuit interrupter, a bridging element, an arcuate leaf spring for supporting said element, one end of said spring being curled and engaging a corresponding end of said element, the central portion of said spring being of relatively great width and gradually decreasing in width toward opposite ends thereof and means cooperating with the opposite end of said spring Y to hold the same in a fixed position and thereby localize movement of the spring at the opposite end thereof, and means for moving said bridging element against the bias of said spring.

11. In an electrical circuit interrupter, a bridging element, an arcuate leaf spring for supporting said element intermediate the ends thereof, one end of said spring of substantial width being curled, the cross-sectional area of said spring adjacent said end being relatively small and gradually increasing towards its center and thereafter decreasing towards its opposite end, and relatively movable contact structure for moving said bridging element against the bias of said spring.

12. In an electrical circuit interrupter, cooperating relatively movable contact structures one of which has a series of recesses disposed between a plurality of ridges, a series of rigid bridging elements extending diagonally between said contact surfaces, one end of each of said elements nesting withinone of said recesses, individual supporting means associated with the opp'osite ends of said bridging elements, and means including individual springs, corresponding ends of which are supported by said ridges and the opposite corresponding ends of which are supported by said supporting means for opposing movement of said elements under circuit closing pressure.

13. In an electrical circuit interrupter, cooperating relatively movable contact structures one of which has a series of recesses disposed between a plurality of ridges, a series of rigid bridging elements extending diagonally between said contact surfaces, one end of each of, said elements nesting within one of said recesses, individual supporting means associated with the opposite ends of said elements and disposed in staggered relationship with respect to said recesses, individual leaf springs, the respective ends of each spring being supported from one of said ridges and one of said supporting means, for retaining said individual bridging elements beneath said ridges and for opposing movement of said ele- 'elements extending'diagonally between said contact surfaces, one end of each of said elements nesting within one of said recesses, individual pressure.

15. In an electrical circuit interrupter, a contact block, a plurality of bridging elements extending at an angle therefrom, a plurality of ridges individual thereto and forming stops to prevent movement of the inner end of each element under influence of magnetic forces, individual springs, corresponding ends being supported from said ridges, individual means for supporting the opposite ends of said springs, and

a contact member for engaging the outer ends of said elements, said springs yielding to permit said elements to wipe said block and said contact member under circuit closing pressure.

16. In an electrical switch a conducting block having a plurality of parallel slots in one surface thereof, a plurality of rigid conducting elements each having one edge pivotally resting in one of said slots, said elements extending substantially parallel therefrom, means for retaining said elements in said slots and limiting the pivotal movement thereof, a conducting member movable relative to said block and said elements, and means biasing said elements into engagement with said block and said member in one position of said member.

17. In an electrical circuit interrupter, having relatively movable conducting members, rigid elements, the opposite ends of which respectively engage said members for carrying current therebetween, individual spring-supports for said elements comprising a substantially plane member with flanges at opposite edges thereof, each flange having at least one slot, and individual leaf springs each having portions at the respective ends passing through said slots and a central portion engaging an associated one of said elements.

18. In' an electrical circuit interrupter, cooperating relatively movable contact structures, a plurality of rigid conducting elements, opposite edges of which, in the closed-circuit position of the interrupter, respectively engage said structures to form a bridging electrical connection therebetween, the current path in each structure being at a substantial angle to the direction of the current path through said elements, and resilient means biasing said opposite edges of said elements toward the outsides of said respective angles and yielding to permit said edges to wipe said structures under circuit closing pressure, said structures respectively having portions forming stops to prevent movement of said elements toward the outside of said angle. I

HERBERT C. GRAVES, JR.

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