Patent Publication Number: US-6707368-B2

Title: Manually trippable circuit breaker

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Serial. No. 60/306,258 filed Jul. 18, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to circuit breakers and, more particularly, to thermal circuit breakers. 
     Circuit breakers are electrical circuit protective devices that interrupt a flow of current when the current exceeds a specified value, sometimes referred to as an overcurrent value. In an overcurrent condition, the circuit breaker rapidly separates a pair of contacts that normally conduct the current. Circuit wiring and associated circuit components may therefore be isolated from potentially damaging and undesirable exposure to excess currents. Conventionally, circuit breakers are either thermally or magnetically actuated. 
     One type of known thermal circuit breaker includes a nonconductive housing with conductive line and load contact terminals therein for electrical connection to a circuit to be protected. A temperature responsive element, sometimes referred to as thermal trigger element, is extended across the line and load contacts, and when the breaker is connected to an energized circuit, current flows between the breaker contacts through the trigger element in normal operation. Current flow through the trigger element heats the trigger element, and when current flow exceeds a predetermined level, the trigger element trips, deflects, or deforms to an activated position separated from each of the breaker contacts, thereby breaking the current through the breaker and protecting load side electrical devices. 
     Additionally, some thermal circuit breakers include manual reset and manual trip features to interrupt the breaker circuit independently of thermal conditions. Implementing such features can lead to relatively complicated constructions that increase manufacturing and assembly costs of the breaker. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, a circuit breaker is provided comprising a nonconductive housing, a first breaker contact within said housing, and a trigger element comprising a second breaker contact located within said housing. The trigger element is thermally activated to separate said second breaker contact from said first breaker contact in an overcurrent condition. A nonconductive reset mechanism is located in said housing and configured for sliding actuation to prevent electrical connection between said first breaker contact and said second breaker contact after said trigger element has activated. 
     In another aspect, a circuit breaker is provided. The circuit breaker comprises a nonconductive housing, a first breaker contact within said housing, and a trigger element comprising a second breaker contact located within said housing. The trigger element is thermally activated to separate said second breaker contact from said first breaker contact in an overcurrent condition. A nonconductive reset element is located in said housing and configured for sliding actuation to prevent electrical connection between said first breaker contact and said second breaker contact after said trigger element has activated, and a manual trip element comprises opposite legs pivotally mounted to said housing. The opposite legs of the manual trip element contact said trigger element and separate said first and second breaker contact when said trip element is pivoted. 
     In another aspect, a circuit breaker comprises a nonconductive housing and first and second terminal blades extending from said housing. A first breaker contact is located within said housing and is in electrical contact with said first blade terminal. A trigger element comprises a second breaker contact located within said housing, and the second breaker contact is in electrical contact with said second blade terminal. The trigger element is thermally activated to separate said second breaker contact from said first breaker contact in an overcurrent condition. A reset element comprises opposite legs in sliding engagement with said first and second blade terminals and a nonconductive portion extending between said opposite legs. The nonconductive portion is positionable between said first breaker contact and said second breaker contact to prevent electrical connection therebetween after said trigger element has activated. A manual trip element comprises opposite legs and a cross member therebetween, and the legs are pivotally mounted to said housing. The trip element legs contact the trigger element and separate the first and second breaker contacts when said manual trip element is pivoted. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a circuit breaker according to the present invention. 
     FIG. 2 is an end elevational view of a portion of the circuit breaker shown in FIG.  1 . 
     FIG. 3 illustrates a portion of the circuit breaker shown in FIG. 1 in a reset position. 
     FIG. 4 illustrates a portion of the circuit breaker shown in FIG. 1 in a tripped position. 
     FIG. 5 is a perspective view of the circuit breaker shown in FIG. 1 with parts removed. 
     FIG. 6 is a cross-sectional view of the circuit breaker shown in FIG.  1 . 
     FIG. 7 is a magnified view of a portion of FIG.  6 . 
     FIG. 8 is a top plan view of the circuit breaker shown in FIG.  1 . 
     FIG. 9 is a perspective view of an upper portion of the circuit breaker shown in FIG.  1 . 
     FIG. 10 is a side elevational assembled view of the circuit breaker shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is an exploded view of a circuit breaker  10  according to the present invention. It is recognized, however, that circuit breaker  10  is but one embodiment of circuit breakers in which the benefits of the invention may be appreciated. Thus the description set forth below is for illustrative purposes only, and it is contemplated that the benefits of the invention accrue to various sizes and types of circuit breakers. Therefore, there is no intention to limit practice of the inventive concepts herein solely to the illustrative embodiment described, that is circuit breaker  10 . 
     Circuit breaker  10  includes a housing  12  and a thermal trigger element therein. In an exemplary embodiment, the trigger element is a thermal material  14  fabricated from a metallic alloy, and a rivet  16  serves to attach thermal material  14  to housing  12 . To attach thermal material  14  to housing  12 , rivet  16  is inserted through a mounting aperture  18  in thermal material  14  and through a cylindrical receptacle  20 , which is electrically conductive and molded into housing  12 . Installation of rivet  16  to thermal material  14  and housing  12  establishes an electrical connection between thermal material  14  and cylindrical receptacle  20 . Cylindrical receptacle  20  is also electrically connected to a first blade contact  22 . In the embodiment shown, thermal material  14  further includes a number of indentations or dimples  23 , further described below, which serve to accentuate a reaction of thermal material  14  to heat as current passes through material  14 . 
     In operation, when breaker  10  is coupled to an energized circuit (not shown), current flows through first blade contact  22  to cylindrical receptacle  20  where it enters and continues to pass through thermal material  14 . On an underside  24  of thermal material  14  there is an electrically and physically attached breaker contact  26 . Attachment of thermal material  14  to housing  12  causes breaker contact  26  to physically touch a second breaker contact  28 . The current passes from breaker contact  26  to second breaker contact  28 , which is electrically connected to a circuit path  30  molded into housing  12 . Current continues through circuit path  30  and exits through a second blade contact  32 , which is electrically connected to circuit path  30 . Current passes through contacts  26  and  28 , as stated above, when breaker  10  is subjected to normal operating conditions. The direction of current described herein is by way of example only. Circuit breaker  10  is also operable when current enters at second blade contact  32  and exits at first blade contact  22 . 
     The flow of current through thermal material  14  causes a heating of material  14 . Circuit breaker  10 , like conventional circuit breakers, is rated to withstand a predetermined current flow. If breaker  10  is subjected to a current flow which is in excess of the predetermined rated current, based upon selected dimensions and properties of thermal material  14 , thermal material  14  is heated to an activation point where it will change its shape. The change in shape of material  14  causes breaker contacts  26  and  28  to separate, breaking the current flow through circuit breaker  10  and opening the associated electrical circuit to prevent damage to components and equipment coupled thereto. Current ratings for circuit breakers such as breaker  10  may be varied by adjustments to thermal material  14 , for example, alloy composition and thickness of the material. 
     Circuit breaker  10  further includes a trip indicator/reset mechanism  34 . Mechanism  34  is a molded plastic device which includes two legs  36 . Legs  36  include an upper portion  38 , which is molded to form a right angle with a side portion  40 . Mechanism  34  is configured for reciprocating motion within housing  12  and rests within housing  12  with side portions  40  against a side  42  of guide  44  and a side  46  of circuit path  30 , respectively. Upper portions  38  of legs  36  rest against an upper portion  48  of guide  44  and an upper portion  50  of circuit path  30 . Once in place, legs  36  of mechanism  34  are configured to slide back and forth in a substantially linear movement along circuit path  30  and guide  44 . A bias spring  52  is mounted between a protrusion  54  on mechanism  34  and a protrusion  56  on housing  12 , and an indicating end  58  of mechanism  34  extends through an opening  60  in housing  12  when breaker contacts  26  and  28  are separated. A fiberglass insert  62  mounted in mechanism  34  serves to electrically isolate breaker contacts  26  and  28  when contacts  26  and  28  separate (based on a reaction of thermal material  14 ). To reset breaker  10 , after thermal material  14  has cooled, indicating end  58  of mechanism  34  is pushed partially back into opening  60 , against the bias of spring  52  and once fiberglass insert  62  has cleared breaker contacts  26  and  28 , contacts  26  and  28  contact one another and lock fiberglass insert  62  beneath them. As a result spring  52  is compressed, ready to push mechanism  34  through opening  60 , should contacts  26  and  28  again separate when thermal material  14  reaches the activation point. 
     In a further embodiment, isolating insert  62  is integrally formed with reset mechanism  34  in a monolithic piece in a known fabrication process, including but not limited to molding processes using nonconductive thermoset materials to fabricate reset mechanism  34 . 
     Breaker  10  also includes a cover  64  which is placed over housing  12  to protect internal components of breaker  10  herein described, and a manual trip mechanism  66 , which, as further described below, allows an external force to be applied to separate breaker contacts  26  and  28 . In a further embodiment, cover  64  is embossed to provide added rigidity and structural strength. 
     FIG. 2 is an end elevational view of an exemplary embodiment of thermal material  14  used in circuit breaker  10  (shown in FIG.  1 ). It is recognized, however, that thermal material  14  is but one embodiment of thermal material used in circuit breakers in which the benefits of the invention may be appreciated. Thermal material  14  has an electrical contact  26  extending therefrom which provides a contact point to breaker contact  28  (shown in FIG. 1) as part of the current path through breaker  10  as above described. A mounting aperture  18  (shown in FIG. 1) allows mounting thermal material  14  to housing  12  of circuit breaker  10 . As described above and shown in FIG. 2, thermal material  14  further includes dimples  23  pressed or formed into thermal material  14  which serve to accentuate reaction of thermal material  14  to heat which is generated as breaker current is conducted by thermal material  14 . Thermal material  14  has a slightly convex shape, as illustrated in FIG.  2 . In one embodiment, thermal material  14  is fabricated from a metal alloy which is configured to react to heat generated by current flow through thermal material  14 . As circuit breaker  10  is exposed to a predetermined overcurrent condition, thermal material  14  is heated to an activation temperature wherein thermal material  14  reacts and assumes a concave shape. The reaction of thermal material  14 , and the assumption of the concave shape causes breaker contact  26  to break electrical (and physical) contact with breaker contact  28  (shown in FIG. 1) located in housing  12  (shown in FIG.  1 ), thereby opening the protected circuit. 
     FIGS. 3 and 4 are cutaway views of breaker contacts  26  and  28  attached to thermal material  14  and circuit path  30  of housing  12  (shown in FIG. 1) respectively. Referring specifically to FIG. 3, breaker contacts  26  and  28  are physically and electrically connected, and thermal material  14  is in a convex reset position. In addition, fiberglass insert  62  of mechanism  34  (shown in FIG. 1) is in a position below breaker contacts  26  and  28 . The convex position of thermal material  14 , the position of fiberglass insert  62 , and the contact of breaker contact  26  to second breaker contact  28  are indicative of normal current flow in a circuit. 
     FIG. 4 illustrates a result of an overcurrent condition to which circuit breaker  10  (shown in FIG. 1) has been exposed. Thermal material  14  has attained a temperature, resulting from excess current, which has caused thermal material  14  to activate and assume a concave trip position. Assumption of the concave position causes breaker contact  26  to separate from second breaker contact  28 . In addition, and as described above, separation of breaker contacts  26  and  28  allow spring  52  (shown in FIG. 1) to uncompress, forcing mechanism  34  (shown in FIG. 1) to extend further into opening  60  of housing  12  (both shown in FIG.  1 ), placing fiberglass insert  62  between breaker contact  26  and  28 , ensuring no current flow through circuit breaker  10  until breaker  10  is reset. Breaker  10  is reset by pushing indicating end  58  of mechanism  34  (both shown in FIG. 1) towards housing until breaker contacts  26  and  28  resume contact, with fiberglass insert  62  below contacts  26  and  28 , as shown in FIG. 3 
     FIG. 5 is a perspective view of an illustrative embodiment of circuit breaker  10  with thermal material  14  (shown in FIGS. 1-4) and cover  64  (shown in FIG. 1) removed, and illustrating a placement of mechanism  34  and spring  52  within housing  12 , and in which the benefits of the invention are demonstrated. 
     As described above, circuit breaker  10  includes housing  12 , which is constructed of an injection molded plastic or other suitable material. Molded into housing  12  are a plurality of keys  80  which configure housing  12  and therefore circuit breaker  10  for insertion into a circuit (not shown). 
     Trip indicator/reset mechanism  34  is mounted within housing  12 , and legs  36  are configured to engage and rest upon circuit path  30  and guide  44 . Mechanism  34  is illustrated in a tripped position, as spring  52  is uncompressed and fiberglass insert  62  is in front of breaker contact  28  (shown in FIG.  1 ). Spring  52  provides a biasing force to slide mechanism  34  along circuit path  30  and guide  44  when breaker contacts  26  and  28  (shown in FIGS. 3 and 4) separate, thereby placing fiberglass insert  62  between breaker contacts  26  and  28 . Indicating end  58  of mechanism  34  also is caused to extend further out of opening  60  molded into housing  12 . To reset a tripped circuit breaker  10 , force is applied to indicating end  58  of mechanism  34 , compressing spring  52  and sliding mechanism  34  along circuit path  30  and guide  44 , until fiberglass insert  62  is located below breaker contacts  26  and  28 , which then again make contact and serve to restrain mechanism  34  and maintain spring  52  in a compressed position. Resetting circuit breaker  10  also causes indicating end  58  of mechanism  34  to partially recede into opening  60 , providing a visual indication that breaker  10  is in a reset (not tripped) state. 
     Circuit breaker  10  further includes a manual tripping device  66 . Manual tripping device  66  serves to manually trip breaker  10  by applying a mechanical force to thermal material  14  (shown in FIGS.  1 - 4 ), thus forcing thermal material  14  from the convex form to the concave form, causing contacts  26  and  28  to separate and allowing mechanism  34  to slide along circuit path  30  and guide  44  until fiberglass insert  62  assumes a position between breaker contacts  26  and  28 . 
     In an exemplary embodiment, manual tripping device  66  is a molded plastic device and includes a pair of parallel leg members  82  which engage thermal material  14  as described above and a cross-member  84  to which is applied a force causing molded protrusions  86  on members  82  to engage thermal material  14 . When the force is applied to cross member  84 , a pivoting action of device  66  causes molded protrusions  86  on device  66  to engage thermal material  14 , thereby causing breaker contacts  26  and  28  (shown in FIG. 1) to separate, and allowing mechanism  34  to move into a tripped position as previously described. 
     FIG. 6 is a cross-sectional view of circuit breaker  10  further illustrating features of both breaker  10  and manual tripping device  66 . Referring to first blade contact  22 , the cross sectional view of circuit breaker  10  indicates the connection, described above in relation to FIG. 1, between contact  22  and cylindrical receptacle  20 . In the embodiment shown, contact  22  and receptacle  20  appear as a single piece assembly. Further, attachment of fiberglass insert  62  to mechanism  34  is shown at connection point  88 . Connection point  88  may be any of a number of known attaching methods, including, but not limited to, a molded post on mechanism  34  onto which a hole in fiberglass insert  62  is engaged, or a rivet inserted through openings in both mechanism  34  and fiberglass insert  62 . 
     Referring to manual tripping device  66 , device  66  is inserted into housing  12  into a plurality of molded slots  90 , which are molded as part of production of housing  12 . Members  82  of device  66  are inserted into molded slots  90 . Upon insertion of members  82  a pair of angular projections  92  engage indentations  94  molded into housing  12  providing a snap fit mechanism to retain device  66  in place. Device  66 , in one embodiment, is sufficiently flexible so as to allow some compression of members  82 , thereby allowing angular projections  92  of device  66  to pass through non-indented portions  96  of molded slots  90 . Further, device  66  includes molded semi-circular protrusions  98 , which, when device  66  is inserted in place into housing  12  provide an axis of rotation, or pivot point, for device  66 . The axis of rotation is provided as housing  12  includes molded stops  100  on which protrusions  98  rest. Molded slots  90  and indentations  94  are molded into housing  12  so as to allow members  82  of device  66  some freedom of movement about the axis of rotation thereby allowing molded protrusions  86  (shown in FIG. 5) to engage thermal material  14  (shown in FIGS.  1 - 4 ), as described above, when force is placed on cross-member  84 . 
     FIG. 7 is a detailed view of a portion of device  66  engaging a portion of housing  12 . As described above members  82  of device  66  are inserted into molded slots  90 . Upon insertion of members  82  angular projections  92  engage indentations  94  molded into housing  12  providing a retention mechanism which retain device  66  in position with snap-fit engagement. As also noted above, device  66  is flexible allowing angular projections  92  to pass non-indented portions  96  of molded slots  90 . Further, molded semi-circular protrusions  98 , provide an axis of rotation for device  66  when protrusions  98  come to rest on molded stops  100  on which protrusions  98  rest. 
     FIG. 8 is a top view of breaker  10  illustrating cross-member  84  of manual tripping device  66  and molded slots  90  of housing  12 , into which members  82  (shown in FIGS. 6 and 7) are inserted. Protrusions  98  extend from members  82  of device  66  to provide the axis of rotation for device  66 . Further, indicating end  58  of mechanism  34  extends through opening  60  in housing  12 . 
     FIG. 9 is a perspective view of an upper portion of housing  12 , which serves to illustrate insertion of manual tripping device  66  (shown in FIGS. 1,  5 ,  6  and  8 ). As described above, housing  12  includes molded slots  90  into which members  82  (shown in FIGS. 5 and 6) of device  66  are inserted. Also shown are molded stops  100  on which protrusions  98  (shown in FIGS. 6-8) of device  66  rest, to provide the axis of rotation, or pivot point. 
     Manual tripping device  66  provides a benefit over known manual tripping devices in that device  66  is not continuously mechanically or electrically attached to a current path. Further, unlike known circuit breakers employing manual trip devices, circuit breaker  10  configured with manual tripping device  66  simulates circuit breaker tripping action by separating contacts of the circuit breaker. Circuit breaker  10  is configured to separate breaker contacts by placing a force on thermal material  14 , thereby changing its shape. Changing shape of thermal material  14  is a normal operation for circuit breaker  10 . By providing a manual tripping device, such as device  66 , which allows circuit breaker  10  to simulate normal operation, a circuit breaker is provided that eliminates additional latching devices of conventional circuit breakers. 
     FIG. 10 illustrates circuit breaker  10  in an assembled state with blade terminal  22  extending from a lower periphery of housing  12  and manual tripping device  66  extending above an upper periphery of housing  12 . Front and rear covers  64  each include a number of embossments  110  projecting outwardly therefrom. Embossments  12  stiffen covers  64  and provide increased structural strength and rigidity to circuit breaker  10  for demanding operating environments. It is recognized that in alternative embodiments of circuit breaker  10  varying numbers of embossments  110  may be employed in various sizes and shapes without departing from the scope of the instant invention. 
     Still further, while embossments  110  are believed to be advantageous for at least some applications of circuit breaker  10 , it is contemplated that the benefits of the present invention may nonetheless be achieved in other applications without the presence of embossments  110 . In other words, covers  64  may be flat in alternative embodiments while capably meeting circuit protection needs. 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.