Abstract:
The present invention relates generally to a plastic cradle. More particularly, the invention encompasses a plastic cradle utilized inside a molded circuit breaker (MCB). The present invention is also directed to a novel nonconductive nonmagnetic cradle that engages a contact arm between a first terminal conductor and a second terminal conductor inside a molded circuit breaker (MCB) in an ON state, and disengages same in an OFF or Neutral state.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The instant patent application claims priority to and the benefit of pending U.S. Provisional Patent Application Ser. No. 61/305,993, filed on Feb. 19, 2010, titled “Plastic Cradle,” the entire disclosure of which provisional application is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a plastic cradle. More particularly, the invention encompasses a plastic cradle utilized inside a molded circuit breaker (MCB). The present invention is also directed to a novel nonconductive nonmagnetic cradle that engages a contact arm between a first terminal conductor and a second terminal conductor inside a molded circuit breaker (MCB) in an ON state, and disengages same in an OFF or Neutral state. 
     BACKGROUND INFORMATION 
     Circuit breakers typically have an operating mechanism, and a tripping mechanism, such as, a thermal trip assembly and/or a magnetic trip assembly, which are automatically releasable to effect the tripping operation, and then are manually resettable following the tripping operation. 
     Such circuit breakers, have commonly been referred to as “miniature” circuit breakers, and have been in use for many years. Their design has been improved upon so as to provide an effective, reliable circuit breaker, which can be easily and economically manufactured on a large scale. In addition, circuit breakers of this type may be utilized in conjunction with are fault and/or ground fault trip mechanisms as well. 
     Circuit breakers of this type include at least one set of separable contacts disposed within a non-conductive housing. Typically, there is a fixed contact attached to the housing and a movable contact coupled to the operating mechanism. The operating mechanism includes a movable operating handle that extends outside of the housing. The operating mechanism further includes an operating arm, upon which the movable contact is disposed, the trip mechanism, and a cradle. The cradle is coupled to a spring and is pivotally disposed between the trip mechanism and the operating arm. One portion of the cradle pivots with respect to the housing while another portion of the cradle has a latch ledge, which is latched by the trip mechanism. 
     The operating member or handle has essentially two or three stable positions: (1) ON and OFF; or (2) ON, OFF and TRIPPED. In the latter case, the three positions tell the operator what condition the circuit breaker is operating in when viewed. In normal operation, the handle is maintained in the ON position. Then, once the trip mechanism is automatically released, in order to protect electrical circuitry from damage due to an overcurrent condition, such as, an overload or relatively high level short circuit, the handle automatically moves to the TRIPPED position. The circuit breaker must then be reset, as is well known in the art, by moving the handle beyond the OFF position to a RESET position from which the handle returns to the OFF position when released. The circuit breaker may then be manually operated from the OFF to the ON position, in order to allow the circuit breaker to resume normal operation. In addition, the handle is manually maneuverable from the ON to the OFF position if it is desired to open the protected circuit. A typical circuit breaker is calibrated, for example, to maintain a current flow of 100% of its rated current and to trip within predetermined times at 135% or 200% of such rated current. 
     The following patents are indicative of the state of the art for miniature circuit breakers: U.S. Pat. No. 6,005,207 (Bernard DiMarco, et al.), U.S. Pat. No. 6,172,586 (James F. Ferree, et al.), U.S. Pat. No. 6,392,512 (James Edward Ferree, et al.), U.S. Pat. No. 6,850,134 (Edward E. Lias, et al.), U.S. Pat. No. 6,894,594 (Joseph P. Fello, et al,), and U.S. Pat. No. 7,800,007 (Narayansamy Soundararajan, et al.). 
     However, there is room for improvement in circuit breaker operating mechanisms to prevent arcing, magnetic flux physically displacing component, heat degenerating components. 
     This invention improves on the deficiencies of the prior art, and provides an inventive molded circuit breaker (MCB). 
     PURPOSES AND SUMMARY OF THE INVENTION 
     The invention is a novel molded circuit breaker (MCB). 
     Therefore, one purpose of this invention is to provide a molded circuit breaker (MCB). 
     Another purpose of this invention is to provide a non-electrically conductive cradle in a molded circuit breaker (MCB). 
     Yet another purpose of this invention is to provide molded non-electrically conductive cradle for use in a molded circuit breaker (MCB). 
     Therefore, in one aspect this invention comprises a molded circuit breaker for an electrical circuit, comprising: 
     (a) a first terminal conductor having at least one connector means; 
     (b) a second terminal conductor having at least one stationary contact; 
     (c) a magnet, a bimetallic strip, and an armature in electrical contact with at least a portion of said first terminal conductor, said armature having an armature pivot arm, and an armature opening; 
     (d) a nonconductive nonmagnetic cradle having an operating spring opening, a first cradle extension and a second cradle extension, said first cradle extension has a cradle kick, a cradle pivot and a circuit breaker reset arm, said second cradle extension has a latch kick; and 
     (e) a contact arm having a spring hook, and a movable contact, such that a first end of an operating spring is in engageable contact with said operating spring opening and a second end of said operating spring is in engageable contact with said spring hook, and wherein in an ON position said movable contact is in electrical contact with said stationary contact, and in an OFF position said movable contact is disengaged from said stationary contact. 
     In another aspect this invention comprises a molded circuit breaker for an electrical circuit, comprising:
         (a) a first terminal conductor having at least one connector means;   (b) a second terminal conductor having at least one stationary contact;   (c) a magnet, a bimetallic strip, and an armature in electrical contact with at least a portion of said first terminal conductor, said armature having an armature pivot arm, and an armature opening;   (d) a nonconductive nonmagnetic cradle having a first cradle extension and a second cradle extension, said first cradle extension has a first body portion, wherein said first body portion has an operating spring opening at an upper end, a pivot extension at a lower end, and between said upper end and said lower end of said first body portion having a circuit breaker reset arm on a first side and a cradle kick on a second side, said pivot extension has a cradle pivot, said second cradle extension has a second body portion, wherein said second body portion has a latch extension having a latch kick; and   (e) a contact arm having a spring hook, and a movable contact, such that a first end of an operating spring is in engageable contact with said operating spring opening and a second end of said operating spring is in engageable contact with said spring hook, and wherein in an ON position said movable contact is in electrical contact with said stationary contact, and in an OFF position said movable contact is disengaged from said stationary contact.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Although the scope of the present invention is much broader than any particular embodiment, a detailed description of the preferred embodiment follows together with drawings. These drawings are for illustration purposes only and are not drawn to scale. Like numbers represent like features and components in the drawings. The invention may best be understood by reference to the ensuing detailed description in conjunction with the drawings in which: 
         FIG. 1  illustrates a front perspective view of an inventive circuit breaker in accordance with one aspect of the present invention. 
         FIG. 2  is a detailed perspective view showing the inventive molded plastic cradle in according to one aspect of this invention. 
         FIG. 3  illustrates internal assembly parts of the inventive circuit breaker in accordance with the present invention, but without the base and the cover. 
         FIG. 4  is a detailed front view showing the latch or ON state of the inventive circuit breaker. 
         FIG. 5  is a detailed front view of the inventive circuit breaker in accordance with the present invention in a de-latched or Neutral or Tripped or OFF state. 
     
    
    
     DETAILED DESCRIPTION 
     The inventive cradle is one part of the circuit breaker which is used to operate the molded circuit breaker (MCB). It should be appreciated that in the prior art the cradle is a ferrous material, such as, steel or stainless steel materials, which are also electrically conductive materials. The ferrous material is always attracting the arc during fault current, creating a secondary current path. The ferrous material of the cradle of the prior art generates a magnetic field when current flows through the cradle thus causing magnetic attractive forces on the adjacent metal parts thus causing displacement of the adjacent part. However, with a nonconductive and nonmagnetic cradle of this invention, the tracking or attracting of the arc during fault current is prevented. Since, the non-electrically conductive and non-magnetic cradle of this invention cannot conduct an electrical current, no magnetic field is generated, eliminating the magnetic forces on the adjacent components to cause displacement. The nonconductive and nonmagnetic cradle of this invention is composed of a nonconductive, nonferrous material such as a plastic. 
     As stated earlier the low voltage circuit breaker is designed to protect an electric circuit and its components due to overload and short circuit. Its basic function is to detect a fault condition, by interrupting continuity, to immediately discontinue electrical flow. 
     Three basic operating conditions must be presented on each circuit breaker, which are close electric circuit, open the electric circuit, and reset if the circuit breaker is tripped by overload and/or short circuit. The cradle is one of the components to accomplish these operations. 
     As stated earlier, there are several major problems presented by the cradles of the prior art. For example, the steel cradles attract the arc when the contacts open, which results in the arc sugaring and eroding of the operating parts unexpectedly. 
     Additionally, the electrical conductivity creates a second undesirable current path which is parallel to the main current path. During the current fault the second current path could pass enough current sharing with the main current path, which will heat each part of the second path and anneal some of them. Consequently some of the operating parts are disabled. 
     Furthermore, an electric sparking and arcing could happen due the difference of the electric potentials between the main and the second current path. In this case the parts could be damaged or even welded to each other and may not be able to function. 
     Moreover, due to the use of ferrous material the magnetic flux is created during the arc fault which also causes the magnetic field, which in turn also causes the physical displacement of some of the metal parts, such as, for example, the braid, and particularly those parts that are formed of a ferrous material. It has now been discovered that the physical displacement of the metal parts also causes failure in the whole mechanical system. Additionally, the conventional metal cradle is difficult to manufacture in terms of dimensional control under the manufacturing process. 
     The molded circuit breaker for an electrical circuit of this invention has a line terminal having a stationary contact, an operating mechanism for separating contacts by handle, plastic cradle, a contact arm having a movable contact, and an operating spring, a trip unit for actuating or operating mechanism to latch or de-latch when a fault and or over load current are detected in electrical circuit, which include armature, armature spring, bimetal, load terminal, and a wire connector. 
     The plastic cradle is a nonconductive, nonmagnetic material, which eliminates the secondary electric path, even though the plastic cradle is physically close to or adjacent the electric circuit or electrically conductive materials, such as, the armature, operating spring, contact arm, movable contact, stationary contact, load terminal, line terminal, etc. 
     The nonconductive, nonmagnetic cradle of the molded circuit breaker of this invention eliminates the magnetic field generated by the current when overload and/or fault current as in the cradle of the prior art, thus eliminating any physical forces on adjacent parts or parts in close proximity and not causing damage to the adjacent parts. 
     With the plastic cradle in the place, the elimination of the secondary current path prevents arcing and/or sparking between the cradle of this invention and the braid since no electric potential can exist. 
     The metallic cradle of the prior art is a stamped part to meet the requirements of the strength and the dimensionality. When the arc occurs during the arc fault, it will erode and heat some parts near the metallic cradle, which further disables the operating system. This also creates the secondary current path white the contacts are closed. 
     The arc erosion damages the contact arm, operating spring, and the metallic cradle itself thus causing the circuit breaker to potentially malfunction. The failure of the metallic cradle of the prior art within the circuit breaker causes failure of required standard tests. 
     The secondary current path permits current flow when the contacts are not closed. This in turn heats the parts of the path, such as the operating spring. The overheating of the operating spring anneals and disables the operating spring and ultimately causes failure. 
     The tolerances of the dimensions during the process in the stamping and the plating of the metallic part are difficult to control in the manufacture of the ferrous metal cradle of the prior art. In the manufacture of the molded non-metallic, nonconductive, nonmagnetic cradle of this invention, the tolerance is easy to control. The nonmetallic nonconductive, nonmagnetic cradle of this invention will not be plated as the ferrous metal cradle of the prior art, thus the nonconductive, nonmagnetic cradle of this invention will be a more environment friendly product and will also result in the cost reduction of the part. 
     The low voltage molded circuit breaker is packed by several major units which includes the operation mechanism, thermal and magnetic trip unit, terminals and lugs, arc quenching assembly, and a molded plastic case. In the operation mechanism unit it includes four parts which are a handle, an operating spring, a cradle, and a movable contact arm. In this invention a molded plastic cradle is introduced to replace a metallic cradle. 
     In the switch operation or close and open the electric circuit, the plastic cradle does not rotate. It supports the operating spring while the handle swings between “ON’ and “OFF” positions. When an over load and a fault current are detected in the electric circuit the circuit breaker is de-latched immediately. The plastic cradle is forced to rotate direction rapidly. In this situation the arc is drowned by the movable contact, directed towards the arc chutes, and is not attracted by the plastic cradle. This invention also eliminates the second electric path, prevents annealing of the parts, does not generate sparks, and limits the braids movement to disable the operating system. 
     Referring now to  FIGS. 1-5 , where  FIG. 1  illustrates a front perspective view of an inventive circuit breaker  23 , in accordance with one aspect of the present invention, where the circuit breaker  23 , comprises a non-electrically conductive or plastic or non-metallic housing  10 , having a cavity  11 , to accommodate circuit breaker operating components or assembly  21 . The plastic housing  10 , has a handle member or switch  12 , that typically protrudes out of the plastic housing  10 . A non-metallic non-electrically conductive non-magnetic cradle  30 , a first terminal conductor or toad terminal  14 , and a second terminal conductor or tine terminal  24 , having a stationary contact  44 , are typically contained inside the cavity  11 , and are a part of the circuit breaker operating components or assembly  21 . Some of the other components of the circuit breaker operating components or assembly  21 , include, but are not limited to, a magnet  18 , a bimetal strip  29 , an armature  26 , to name a few. One end of a cradle operating spring  41 , is engaged to the plastic cradle  30 , via an operating spring hole or opening  31 , shown in  FIG. 2 . The load terminal  14 , is in electrical contact with a wire connector  13 . An armature  26 , is engageably in contact with the plastic cradle  30 , and a bimetallic strip  29 . 
       FIG. 2  is a detailed perspective view showing the inventive molded ptas cradle  30 , in according to one aspect of this invention. The plastic cradle  30 , has a first cradle extension  33 , a second cradle extension  35 , and an operating spring hole or opening  31 . The first cradle extension  33  and the second cradle extension  35  are substantially planar. The first cradle extension  33 , has a cradle pivot  34 , a cradle kick or ledge  32 , and a circuit breaker reset arm  38 . The circuit breaker reset arm  38  is substantially perpendicular to at least a portion of said first cradle extension  33 . The second cradle extension  35 , has a latch kick or ledge  36 . The first cradle extension  33 , has a first body portion  63 , having an operating spring opening or hole  31 , at an upper end, and a pivot extension  64 , at a lower end, and wherein between the upper end and the lower end of the first body portion  63 , is the circuit breaker reset arm  38 , and the cradle kick or ledge  32 . The pivot extension  64 , has the cradle pivot  34 . The second cradle extension  35 , has a second body portion  65 , having a latch extension  66 . The latch extension  66 , has the latch kick or ledge  36 . For some embodiments the second body portion  65 , will have an average thickness that is greater than the average thickness of the first body portion  63 . The cradle pivot  34 , is preferably shaped in a circular shape or in a C-shape with an opening so as to pivot around a cradle pivot knob  54 , shown in  FIGS. 4 and 5 . The cradle kick or ledge  32 , preferably has a fiat or planar surface so as to be able to move about a kick feature of a contact arm  40 , shown in  FIGS. 4 and 5 . The cradle ledge  32 , extends substantially inwardly towards the second cradle extension  35 , while the cradle pivot  34 , has a substantial circular shape within an opening facing outwardly towards the second cradle extension  35 . For most applications the latch ledge  36 , protrudes outwardly and away from the operating spring opening  31 . For some applications it is preferred that the average thickness of the second cradle extension  35 , is greater than the average thickness of the first cradle extension  33 . 
       FIG. 3  illustrates internal assembly parts of the inventive circuit breaker assembly  21 , in accordance with the present invention, but without the plastic base  10  of  FIG. 1 , and a cover. The armature  26 , has an armature spring  27 , an armature pivot arm  56 , and an opening  28 , to which in engageable contact is the latch kick or ledge  36 , of the plastic cradle  30 . The circuit breaker assembly  21 , has a magnet  18 , in engageable contact with the load terminal  14 , and the bimetallic strip  29 . One end of the cradle operating spring  41 , is securely engaged to the operating spring hole or opening  31 , of the plastic cradle  30 , while the opposite end is securely engaged with spring hook or tab  51 , of a contact arm  40 , shown in  FIGS. 4 and 5 . A calibration screw  15 , is provided with the circuit breakers  23 , so as to adjust and make desired contact at the location of the load terminal  14 . Secured to the line terminal or second terminal conductor  24 , is at least one stationary contact  44 . 
       FIG. 4  is a detailed front view showing the latch or ON state of the inventive circuit breaker  23 . A braid  48 , is in electrical contact with the armature  26 , and the contact arm  40 , during the latch or ON state. The contact arm  40 , has at least one moveable contact  42 , which is in physical contact with at least one stationary contact  44 , at the location of the line terminal  24 , during the ON state. A spring clip  46 , may be provided to secure the tine terminal  24 , to a line feature (not shown). A detailed view of latch location  39 , is shown in  FIG. 4 , where the latch kick or ledge  36 , of the plastic cradle  30 , is in secure and engageable contact with the opening  28 , of the armature  26 . The cradle pivot  34 , of the plastic cradle  30 , is engaged to a pivot knob  54 , such that the plastic cradle  30 , can pivot around the pivot knob  54 . The armature pivot arm  56 , is engaged with an armature pivot knob  58 , such that the armature  26 , can pivot around the armature pivot knob  58 . In the switch operation or close and open the electric circuit, the plastic cradle  30 , does not rotate. The plastic cradle  30 , supports the cradle operating spring  41 , while the handle or switch  12 , is swung between “ON’ and “OFF” positions. A first end of the cradle operating spring  41 , is engaged to the plastic cradle  30 , via the operating spring hole or opening  31 , while the opposite or second end of the cradle operating spring  41 , is securely engaged to and held by the spring hook or tab  51 , of the contact arm  40 . 
       FIG. 5  is a detailed front view of the inventive circuit breaker  23 , in accordance with the present invention in a de-latched or Neutral or Tripped or OFF state. When an overload and/or a fault current is detected in the electric circuit the circuit breaker  23 , is de-latched immediately. The plastic cradle  30 , is forced to rotate in the clockwise direction rapidly and the circuit breaker  23  goes into a de-latched or Neutral or Tripped or OFF state. View of the de-latched state  49 , shows that the latch kick or ledge  36 , of the plastic cradle  30 , has disengaged from the opening  28 , of the armature  26 , and the plastic cradle  30 , has rotated or pivoted about the cradle pivot knob  54 , such that the movable contact  42 , of the contact arm  40 , has also disengaged from the stationary contact  44 , of the line terminal  24 . Once tripped or de-latched, the circuit breaker  23 , can be reset manually by moving the handle or switch  12 , from the OFF position to the ON position, which allows the circuit breaker reset arm  38 , to engage the contact arm  40 , and move the complete circuit breaker operating assembly  21 , into an ON state. 
     The molded circuit breaker  23 , comprising of a trip unit connected such that the nonconductive nonmagnetic cradle  30 , automatically rotates to disengage the movable contact  42 , from the stationary contact  44 , to actuate the OFF position in response to a predetermined electrical overload and fault current. It should be understood that the non-electrically conductive cradle  30 , is not excited by an electrical current to establish a magnetic field when the trip unit automatically actuates the OFF position in response to a predetermined electrical overload and fault current. Furthermore, the non-electrically conductive cradle  30 , prevents a secondary conducting path, while a primary conductive path is created via the second terminal conductor  24 , magnet  18 , bimetallic strip  29 , armature  26 , contact arm  40 , movable contact  42 , stationary contact  44 , and the first terminal conductor  14 , in an ON position. It should be appreciated that the handle  12 , can be used to move the non-electrically conductive cradle  30 , from an OFF position to an ON position, and vice versa. For most applications at least a portion of the braid  48 , is adjacent the nonconductive, nonmagnetic cradle  30 , and wherein there is no arcing and sparking between the braid  48 , and the non-electrically conductive cradle  30 , when a trip unit automatically actuates the OFF position in response to a predetermined electrical overload and fault current. 
     It is preferred that the non-electrically conductive cradle  30 , is made from a material selected from a group comprising plastic materials, polymer material, polyester material, nonconductive material, non-ferrous material, composite material, to name a few. 
     While the present invention has been particularly described in conjunction with a specific preferred embodiment, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. It is therefore contemplated that the appended claims will embrace any such alternatives, modifications and variations as falling within the true scope and spirit of the present invention.