US2620417A - Circuit breaker contact - Google Patents

Description

Dec. 2, 1952 CIRCUIT Filed OCT.. 17, 1947 M. J. LEWS BREAKER CONTACT CVD 6 Sheets-Sheet l M. J. LEWS CIRCUIT Dec. 2, '1952 l BREAKER CONTACT ets-Sheet 2 Filed OCT.. 17, 1947 lNvEN'roR Dec. 2, 1952 M. J. 'Laws 2,620,417

CIRCUIT BREAKER CONTACT l N V EN TOR.

ATTORNEYS Dec. 2, 1952 M. .1. LEWIS CIRCUIT BREAKER CONTACT 6 Sheets-Sheet 4 Filed OCT.. 17, 1947 Dec. 2, 1952 M. J. LEWIS 2,620,417

CIRCUIT BREAKER CONTACT Filed Oct. 17, 1947 6 Sheets-Sheet 5 l INVENTORn /Q/fqwv Mezza mib@ - ATTORNEYS Dec. 2, 1952 M. .1. LEWIS 2,520,417

CIRCUIT BREAKER CONTACT Filed Oct. 17, 1947 6 Sheets-Sheet 6 ATTORNEYS Patented Dec. 2, 1952 UNITED STATES PATENT OFFICE CIRCUIT BREAKER CGNTACT Morgan J. Lewis, Philadelphia, Pa.

- Application October 17, 1947, Serial No. 780,553

5 Claims. 1

My invention relates to electric contact Inaking and breaking devices, particularly of the character which provide automatic quick release in case of overload or short circuit, and are commonly known as circuit breakers.

A purpose of my invention is to concentrate the arcing at the contacts of a switch at one of a plurality of switch pads, following up the contact made at that pad by successive contacts at other pads which make contact later and break contact earlier than the first pad, thereby maintaining clean unpitted contact surfaces for the succeeding pads.

A further purpose is t provide movable contacts which comprise multiple metallic overlapping spring leaves or pads, the longest of which is first brought into contact with a relatively fixed contact, and the others of which successively make such contact.

A further purpose is to incline the fixed contact laterally away from the line joining it with the switch pivot so that the movable contact will first engage the switch contact at an outstanding projection, preferably the most remote point from the switch pivot, and will successively engage at points closer to the base of the fixed contact and preferably closer to the switch pivot.

A further purpose is to provide arcing shoes preferably in spaced relation on either side of the fixed contact and on either side of the movable contact when closing' against the fixed contact, preferably diverging the arcing shoes toward their outer ends and inclining the outer ends of the arcing shoes in general conformity with the inclination of the fixed contact, and preferably also connecting the Varcing shoes with the fixed contact.

A further purpose is to provide a construction which will more amply protect the thermostatic metal and the electromagnetic coils against burning out on a short circuit or the like.

A further purpose is to provide contacts which during the fraction of a second of opening of the circuit breaker will cut down the current to a safe level and prevent damage to the circuit breaker.

A further purpose is to avoid or suppress alternating current hum in the armature of an electromagnetic release for a circuit breaker by radially slotting the armature, preferably of disc type.

Further purposes appear in the specificationy only of the numerous embodiments in which my invention may appear, choosing the forms shown from the standpoints of convenience in illustration, satisfactory operation and clear demonstration of the principles involved.

Figure 1 is a fragmentary top plan view of my improved circuit breaker, eliminating the housing.

Figure 2 is a section of of Figure l on the line 2 2, breaking away one end of the outer housing.

Figure 3 is a section corresponding to Figure 2 showing only the switch in the position at which release begins.

Figure Il is a view corresponding to Figure 3 showing the switch fully open.

Figure 5 is an exploded fragmentary perspective showing the toggle and contacts.

Figure 6 is an enlarged detail longitudinal section through the movable contacts.

Figures 7, 3 and 9 are diagrammatic enlarged side elevations showing the steps in closing the contacts.

Figure 10 is a sectional perspective of the release mechanism.

Figure 11 is a perspective of the main supporting bracket.

Figure 12 is a detail perspective of the thermostatic elements and magnetic armature.

Describing in illustration but not in limitation and referring to the drawings:

Subject matter divided from the present application and relating to the housing and covers appears in my copending application Serial No. 255,000 filed November 6, 1951 for Circuit Breaker.

The present subject matter is a further development of my U. S. Patent No. 1,888,559, dated November 22, 1932, for Electric Switch, Insofar as the construction and operation of the present device is the same as that of my prior patent. I will describe it generally and refer to those interested to my patent for further details.

In the prior art, on a dead short circuit or other similar condition circuit breakers for eX- ample of the type of my Patent No. 1,888,559 have in some cases suffered serious damage, due to the fact that the current was not reduced rapidly enough during the first part of the opening movement of the contacts, so that damage was in some cases done to the circuit breaker itself. This condition was in part due to the character of contacts used in the prior art device, and the fact that during the opening of the breaker the current was not cut down suiiiciently rapidly when the contacts were just beginning to open, partly open or just completely open.

The damage caused to the breaker in some cases took the form of burning out the thermostatic elements or alternatively of burning out the electromagnetic coils or both. While these injuries to the breaker could of course be repaired they did place the equipment out of service until a repair was completed and were very annoying.

The present invention represents an improvement over the prior art in avoiding this 'diinculty by assuring that even on a dead short-circuit the reduction in current through the breaker will be so rapid that not only will the breaker protect the load and the generation system, but it will of course adequately protect itself. The present invention, therefore, is especially well suited to provide protection of electromagnetic and thermostatic elements of a breaker during the opening of the breaker.

The switch of the present invention comprises an 4outer Ymetallic `housing `2l) of general box formation, `which islclosedlat-the top Vby an outer cover 12| ,suitably fastened thereto, as Lby screws and seals ordinarily used in electrical work (not shown), and outwardly deformed at 22 .to permit motion vof the switch. Within the housing 2liY and suitably bolted at 23 to the rear or bottom thereof, I provide an insulating base 24, preferably `of electrical porcelain or thelike. At one end the base is formed to provide a terminal block 25 withsuitable separating ribs 2.5 spacing terminals 21 connectedto the line, and terminals 28 Yconnected to the load. VThe ribs 26 terminate short of ribs 3i) for mounting the switch, leaving a space 3| extending across vthe base and engaging and locking the lower end .of an insulating end wall 32 (Figure 2) of an inner cover v33 which encloses the switch proper while permitting access to the terminal block. The upper andsuitably 4metallic portion 34 of `the'inner cover Yis joined to the insulating .end wall 32 as by rivets 321, shrouded by washers 322 of rubber or `the like. The inner cover is deformed at-341'to fit within deformed portion 22 on the outer cover.

It will thus ,be evident that the inner-cover 33 is suitably secured (as by screws and seals not shown) and prevents unauthorized access tothe switch while nevertheless permitting access to the .terminal block for connection or disconnection.

The switch proper is mounted on a channelshaped bracket 34 suitably fastened to the insulating base at 35 and insulated from the electrical parts (the bracket is seen more in detail in Rgure ll). .The bracket has a suitable base 35, side walls 31 anda cover 38having projections 49 for protecting thebiasing spring later to be described, and guiding the upper ends of the releasing plates. At the end Aremote from .the switch there is also a tongue 4l for protecting another biasing spring.

From the bracket, Yoperating vmechanism manipulates switch blades 42 and 43 pivoted at 44 on conducting standards 45. 'The standards are suitably mounted on the insulating base and interconnected to the load through thermostat supports 4S mounted on the base, metallic thermostatic strips 41 vertically supported thereon near the bottoms of the strips, then through downwardly extending metallic thermostatic strips 48 joined at the top to strips 41, through support 50 on which the strip 48 is .mounted through magnet coil l and then through terminal strip 28.

The thermostatic 4strips 41 and 48 are positioned so as to move toward the magnet coils with increased temperatures as later explained.

The switch blades 42 and 43 are interconnected by an insulating bar 52 extending from side to side toward the outer ends and suitably fastened to the switch blades as at 53 (Figure 5).

The cooperating xed contacts comprise elongated strips 54 of copper or the like suitably mounted on the base and interconnected with the .line by bush/ars 55, preferably carried in recesses beneath the base. Each of the fixed contacts is generally bent away from the base at v56 and above this point is inclined with respect tothe Vbase and with respect to an imaginary lineb'etwe'en the switch pivot 44 and any point on the'jxed contact. Thus there is in the form shown an outer, less steeply inclined portion 51 near the end of the Vfixed contact remote from theupivot of the switch blade, and an intermediate more steeply inclined portion 58 as best seen in Figures F1, 8 and 9.

On the outerend of each 'switch'blade is a movable contact ,5.0 -electrically connected "to the blade asby anelectrically conducting Spacer '6l screwed to the blade at B2 andiriveted to the contact at 63 (Figure 6). Rotation" is prevented by notch 621 engaging the blade.

The movable contact is specially-constructed so as to prevent fouling. 'With this object it is constructed of a number of 'separate contact pads .preferably in the form of Yresilient strips f spring material such as spring bronze, spring brass or beryllium copper, with or without contact blocks. The pads are preferably "arranged as overlapping Vleaves so that they'will contact the fixed contact at a `plurality of points and preferably successively. The forwardmost (pad as shown is-made up of vtwo Yleaves V(i4 andl mounting a metallic contact block 66 at the outer ends, and-in closing the switch making contact with the outer extremity .ofthe fixed-contact "54 before any other contact pad has made contact. Thus if any arcing is .likely -to take place, on the making or on the breaking, `it will take place in the .region V61 of Figure Y"i, since in this position no other portion Yof the contact pads will be closely adjacent to thexed contact. Thus .arcing and pitting over the portion 58 of the fixed contact is prevented.

The successive contact kin closing and the successive breaking in opening will be accomplished by other contact pads, suitably Ythe lpad 68 which is next to .make contact in closing as shown by Figure-8, backed up by the padabove at 10. lAn instant after contact is made-by the paci 68, contact is made by the next padY 1| which is somewhat shorter, and finally contact is made by the last pad 12. The pads B8, 1D and 1l vsuitably have reverse bends on their outer ends -to'rin'- crease the current carrying capacity slightly. Of course any suitable number of contact pads arranged in echelon maybe used.

It will be evident, therefore, thatin closing the contacts of each switch blade, contact will first be made by the outermost pad and then successively by the pads whose outer ends are nearer to the pivot, whereas in opening the reverse will take place, and the pads whose outer ends are nearer to the `pivot will break contact while cur rent is still flowing through the outermost pad and therefore while there is little or no tendency to arc and spool the contact surface-at 58.

Whereas in the present Yinvention any suitable number of switch poles may be used, I have illustrated in this case a two -pole switch, but it will lbe lunderstood that the invention is in no way restricted to a switch of this type.

`Eachof the fixed contacts is 'surrounded on both 'sidesby an'arcing shoe 13, suitably of steel, which is preferablya Ueshaped member having a base 14, upstanding sides `15, flaring outer ends 15 and inclined outer edges 11 which conform generally to the slope of the fixed contact at 51 and 58. vIt will thus be evident that as the movable contacts separate lthey 'are laterally within arcing distanceof the arcing shoes at each side, whereas the xed contact is likewise at each side within arcin'g'distance of the arcing shoes. The alrcing shoes are, however, preferably electrically connected to the fixed contacts,"and therefore it will 'be evident that vthe'arcirig will primarily be between the movable contact and the arcing shoes, and will be ilnally broken by the outwardly flaring edges of the shoes. AIt is important to note, however, that the inclined character of the outer edges of the shoes tends "to space the contact pads substantially widely from the arcing shoes as the movable contact moves outwardly, but the contact block 66 is made slightly-` wider as shown-in Figures l and 5, so that most Vof the arcing willtake place on the contact block, protecting the'sides of the contact-pads. Y

The operation of the switch is accomplished preferably by a crank handle 10 which is pivotallyinmounted at 80 on the housing and extends outside the housing to provide a suitable handle for operation- The crank 18 is biased toward Athe switch closting position by a torsion spring one end of which engages the housing. Throughout the portion of the crank which contacts the operating parts it is surrounded by insulating sleeve 82. The crank extends through an elongated slotf83 of a-channel-shaped toggle member S4 which makes toggle pivotal connection at 85 -with a channel-'shaped forward toggle member 86 which has pivotal connection at ill with alongitudinal slot 88 of a 'saddle 90 mount ed near the middle 'on the insulating Vcross con'- nection -52 of the switch. The toggle is spring urged toward straightening by a torsion spring 9| suitably surrounding the :pivot Y85.

To sustain the pressure in closing the switch and avoid breaking through the insulation 82, a socket`92 is provided at the end of slot 83 toward the fixed contacts.

The switch blades are biased toward opening by a tension spring 93`conhecting from a spring abutment 94 on thebracket 34 to aspring engaging hook S on the insulating bar 52.

The switch is secured in closed position by a latch 96 (one for each pole) Lpivotally mounted at 91 on the bracket and spring urged toward latching position by a compression spring 98 engaging a lever end |00 near the base of the latch. The latch is limited against moving rearwardly beyond its latching position through engagement of projections |0| with the base 'of the bracket.

The switch may be opened manually by pulling on the handle in such. a way as to operate the crank 80 counterclockwise in Figure 2, pulling on the'toggie and moving the pivot 81 in the slot 88 toward the switch blade pivot so as vto with-y draw the pivot 31 froinengagementbeneath the latch as in 'my patent above referred to.

The switch may likewise be manually closed by moving the handle in the direction to swing the crank clockwise in Figure 2, forcing the Vmovable contacts into clamping engagement with the iixed contacts, forcing the pivot `81 forward in the slot 88 and permitting it to deflect the latch and be held beneath the latch as shown in Fig"- ur'e 2.

Automatic release of the latch is accomplished by a releasing plate |02 as best seen in Figure 10. One releasing plate is provided for each switch blade, and the releasing plate is conveniently pivoted at 91 on the latch pivot, suitably on the inside of the corresponding latch, the releasing plates being separated by a spacer |03 (Figure 10). Each releasing plate has a latch releasing arm |04 extending away from the base and adapted to engage a cross connection |05 between the latches, which, with a top cross connection 0E, assures that the latches move together. The

releasing plate also has a longitudinal extending body |01 (Figure l0) from which projects away from the base a toggle breaking arm |08, adapted to `engage the toggle pivot 85. Also at the rearward end is the automatic releasing arm ||0 which projects outwardly through an opening in the bracket to engage under an automatic releasing dog (best seen in Figure l0) which is mounted on the thermostatic arms 41 and 43 in the position opposite to the coil 5 i The upper joining ends of the thermostatic arms 41 and 48 are `preferably insulated on either side at ||2 and H3 to permit mounting the dog H without connecting it into the electrical circuit.

On the side of the upper ends of the thermostatic arms 41 and 43 toward the coil is mounted an armature I4 of suitable magnetic susceptible material, such as low carbon steel. In the prior art when an unbroken disc armature was employed, considerable diniculty was encountered with alternating current hum when the over loa-d approached a condition close to that for kicking out the circuit breaker. I have discovered that this diiiculty may be overcome by inserting an air gap or slot H5 extending radially through the armature from the outer circumference to a point adjacent to the interior as best seen in Figure 12. It has been found that by employing the slot described it is possible to maintain sharp overload release and nevertheless operate witnout objectionable -noise for long periods at overloads slightly below the release point. The coils 5| are provided with suitable cores and pole pieces IIB to cooperate with the armature.

The toggle breaking projection |08 of the releasing plate may be conveniently guided by the side of one of the protecting prongs 40 as seen at H1, and the base of the automatic releasing arm H8 is suitably guided by the side of the tongue 4| at ||8 (Figure 10). Each releasing plate is biased toward release position by a tension spring |20 extending from the abutment 9| to a spring anchor |2| on the rearward edge of each releasing plate. y

In operation the switch of the present invention will frequently be used to replace the main fuses on a 1 10 volt alternating or direct current supply to a house, or the like, although of course it may be used in numerous other applications, as for example, to provide a circuit breaker for motors or other load equipment at any suitable voltage.

The device can be opened and closed like an ordinary switch to turn the current of or on manually simply by operating the handle. The toggle will remain stiff and the contacts will be forced closed, -nrst bringing the contact blocks 55 into engagement with the portions 51 of the fixed contacts and then successively bringing the individual lresilient metallic contact pads into engagement with the portions 58. In breaking the circuit the reverse sequence will be followed, the contact at each block B6 being the last broken, and the arcing shoes having diverging edges terminating on an incline similar to that of the fixed contacts and that of the movable contacts at that position, breaking the arc.

When the device is closed, automatic operation will begin, since the current will pass through the thermostatic arms 4l and 48 which are biased toward opening of the automatic release by moving the release dog III away from engagement with `the automatic releasing arm I l (Figure 10), thus protecting against long continued overloads slightly above the proper value, and also because the current is flowing through coil 5I, which by pulling on the amature I I4 is tending to pull the automatic release dog III! out from engagement with the arm IIB. There is enough time lag to prevent release on a momentary somewhat excessive current flow incident to starting a motor or the like.

The thermostatic arms are not used to open the switch but to keep the coils from opening the switch on momentary overloads such as starting motors. The heavier the overload or short, the more the coil is eiective and the less the thermostatice arms are e'ective, so that as the thermostatic arms heat up they move the armature nearer to the coil.

Should an excessive overload or a short circuit occur, the automatic release dog I II will move out from engagement with the automatic releasing arm III) and the corresponding releasing plate IEIZ will swing pivotally under the action of its biasing spring IZB. This will cause the arm |04 to move the latch 96 to unlatching position and will cause the toggle breaking projection IGS to break the toggle as shown in Figure 3, causing the switch to open under the action of the switch biasing spring 93 as shown in Figure 4. As the switch opens, its movable contacts break in the order referred to and the arching shoes break the arc.

The switch is now reset manually, after repairing the difficulty in the circuit, by moving the handle in the direction to pull the crank counterclockwise in Figures 2, 3 and 4, so that the toggle breaking projection Hi8 is engaged at !22 with the anchorage 9U on the insulating cross bar 52. This engagement is shown in Figure 4, although the crank is no longer in the limited counterclockwise position. This restores the releasing plate to its engagement with the automatic release dog as shown in Figure 10, prepared for further automatic release. The switch handle is then moved in the opposite direction to carry the toggle forward and close the switch as in the previously described manual operation, restoring the condition shown in Figure 2. Should the device nevertheless encounter a further short circuit or excessive overload when it is manually closed, it will kick out notwithstanding the pressure on the handle due to the breaking of the toggle and the release of the latch.

An important function of the special contacts and arcing horns in accordance with the invention is that the thermostatic elements and/or electromagnets of the breaker are adequately protected against damage during the opening, due to the fact that the current incident to a short circuit or other greatly abnormal current flow is cut oi too rapidly to do permanent damage.

It Will be evident of course that the present invention finds its best expression' in circuit breakers, but it also may be applied to great advantage in switch mechanism of other types.

In View of my invention and disclosure'variations and modifications to meet individualwhim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benets of my invention without copying the structure shown, and I, therefore, claim all such insofar as they fall within the reasonable spirit and scope of my claims.

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

1. In a circuit maker and breaker, a switch blade, pivotal support for the switch blade, a fixed metallic contact remote from the switch blade pivot and inclined with respect to a line between the switch blade pivot and the fixed contact, a movable contact on the switch blade cooperating with the fixed contact and arcing shoes one on either side of the xed contact and the movable contact when closed, in spaced relation to the fixed contact, laterally diverging therefrom and inclined at the outer end in general conformity with the inclination of the ilxed contact.

' 2. In a circuit maker and breaker, a switch blade, pivotal mounting for the switch blade, a metallic xed contact remote from the pivotal support and inclined laterally with respect to a lineV between the nxed contact and the pivotal support, a movable contact on the switch blade cooperating with the xed contact and comprising a plurality of overlapping resilient metallic contact pads which successively make and successively break contact on the inclined portion of the xed contact and arcing shoes laterally spaced from the fixed contact at either side and extending beyond the xed contact in the direction of the movable contact in closed position to surround the movable contact throughout the in closed position, and diverging progressively from the movable Contact in the direction taken' by the movable contact in opening.

3. In a circuit maker and breaker, a switch blade, pivotal mounting for the switch blade, a metallic xed contact remote from the pivotal support and inclined laterally with respect to a line between the fixed contact and the pivotal support, a movable contact on the switch blade cooperating with the fixed contact and comprising a plurality of overlapping resilient metallic contact pads which successively make and successively break contact on the inclined portion of the fixed contact and arcing shoes laterally spaced from the fixed contact at either side and extending beyond the fixed contact to surround the movable contact throughout the length of the contact area of the successive pads in closed position, and diverging progressively from the mov-- able contact, the arcing shoes being electrically connected to the fixed contact.

4. In a circuit maker and breaker, a switch blade, pivotal mounting for the switch blade, a metallic fixed contact remote from the pivotal support and inclined laterally with respect to a line between the xed contact and the pivotal' support, a movable contact on the switch blade cooperating with the fixed contact and comprising a plurality of overlapping resilient metallicv contact pads, and a block on the contact side of .i

the most remote of the pads which extends laterally Wider than the pads, the block and the pads successively making and breaking contact on the inclined portion of the xed Contact, and arcing shoes laterally spaced from the xed contact on either side and extending beyond the fixed Contact to surround the movable contact throughout the length of the contact area of the successive pads and the block in closed position and diverging progressively away from the movable contact from the closed position in the direction of opening, whereby in opening contact between the movable contact and the fixed contact is broken nally at the block, and the greater lateral extent of the block as compared with the pads concentrates the arcing at the edges on the block.

5. In a circuit breaker, a switch blade, pivotal mounting for the switch blade, a metallic nxed contact remote from the pivotal support and inclined laterally with respect to a line between the iixed contact and the pivotal support, a movable contact on the switch blade cooperating with a fixed Contact and comprising a plurality of overlapping resilient metallic contact pads, and a block on the contact side of the most remote of the pads which extends laterally wider than the pads, the block and the pads successively making and breaking contact on the inclined portion of the xed contact, and arcing shoes laterally 10 spaced from the xed contact on either side and extending beyond the fixed contact to surround the movable Contact throughout the length of the contact area of the successive pads and the block in closed position and dverging progressively away from the movable contact from the closed position in the direction of opening.

MORGAN J. LEWIS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,370,914 Rippl Mar. 8, 1921 1,399,491 Krantz Dec. 6, 1921 1,769,279 True July 1, 1930 1,888,559 Lewis Nov. 22, 1932 1,960,402 Wilckens May 29, 1934 1,971,586 Sperry Aug. 28, 1934 1,975,901 Mayer Oct. 9, 1934 1,987,555 Foster Jan. 8, 1935 2,117,892 Koch May 17, 1938 2,158,317 Allen May 16, 1939 2,294,838 Dorfman Sept. 1, 1942 2,414,526 Horn et al Jan. 2l, 1947 2,443,230 De Coursey June 15, 1948 2,454,788 Frese Nov. 30, 1948

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