Abstract:
The present invention relates generally to a mechanism of a contact system for circuit breakers. More particularly, the invention encompasses a mechanism for a rotary double-break contact system, which enables a direct transfer of torque from stored energy components, such as, springs, to the contact arm in the ON-position (contacts closed) without using intermediate cam surface. The mechanism described in the invention also ensures reliable locking of the contact arm in the blow-off position using stationary means that are integral with or fixed to a crossbar module. This invention enables to achieve significant reduction or even to eliminate friction at certain critical interfaces between the contact mechanism components, thus, reducing or potentially eliminating hysteresis, and improving performance consistency, and also eliminating mechanism performance dependency on wear level and condition of an intermediate cam surface. An additional feature of this invention is a reduction of a loss of contact torque/force during over-travel in the ON position when the fixed and/or moveable contacts erode. Configurations described in this invention may also feature physical protection for the moving components of the contact mechanism assembly from flying particles resulting from short circuit shots.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The instant patent application is related to U.S. Provisional Patent Application Ser. No. 60/971,332, filed on Sep. 11, 2007, titled “Double-Break Disconnect/Contact System,” U.S. Provisional Patent Application Ser. No. 60/971,340, filed on Sep. 11, 2007, titled “Rotary Double-Break Contact System Mechanism Directly Creating Contact Torque in the ON position and Locking Contact Arm in the Blow-Off Position,” U.S. Provisional Patent Application Ser. No. 60/971,345, filed on Sep. 11, 2007, titled “Double-Break Contact System,” and, U.S. Provisional Patent Application Ser. No. 60/971,350, filed on Sep. 11, 2007, titled “Double-Break Circuit Breaker Mechanism,” the disclosures of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a mechanism of a contact system for circuit breakers. More particularly, the invention encompasses a mechanism for a rotary double-break contact system, which enables a direct transfer of torque from stored energy components, such as, springs, to the contact arm in the ON-position (contacts closed) without using intermediate cam surface. The mechanism described in the invention also ensures reliable locking of the contact arm in the blow-off position using stationary means that are integral with or fixed to a crossbar module. This invention enables to achieve significant reduction or even to eliminate friction at certain critical interfaces between the contact mechanism components, thus, reducing or potentially eliminating hysteresis, and improving performance consistency, and also eliminating mechanism performance dependency on wear level and condition of an intermediate cam surface. An additional feature of this invention is a reduction of a loss of contact torque/force during over-travel in the ON position when the fixed and/or moveable contacts erode. Configurations described in this invention may also feature physical protection for the moving components of the contact mechanism assembly from flying particles resulting from short circuit shots. 
     BACKGROUND INFORMATION 
     Conventional contact mechanism assemblies for a circuit breaker use intermediate cam surfaces for transferring the contact torque/force from the stored energy components, such as, springs, to the contact arm in the ON position (contacts closed) and during the contact arm dynamical motion when acted upon by repulsion forces prior to getting locked in the blow-off position. Functional performance of such conventional mechanisms is typically affected by the friction between a rolling or a sliding component, which moves with the contact arm, and the intermediate cam surfaces along the entire trajectory. This results in a significant hysteresis, which is undesirable for the contact system as it brings inconsistency and can cause the contact force between the fixed and moveable contacts in the ON position to be compromised. As an important side effect, the mechanism performance becomes dependent on the wear condition of the cam surface. Furthermore, using the intermediate cam to achieve required torque at the contact arm in the ON position has a negative effect on the mechanism&#39;s over-travel performance and it results in substantial loss of a contact force/torque with erosion of the contacts. 
     Another observed issue with the existing prior art configurations is that in some of them the contact spring-cam mechanism is not physically protected and is substantially exposed. Therefore, it can be contaminated by flying particles (beads) during the short circuit shots. 
     Other conventional contact systems utilize locking cam surfaces arranged integrally with contact arm for latching it open in the blow-off position thus preventing from undesirable re-closing when the cam surfaces engage locking pins that are loosely attached to the crossbar. These types of configurations have demonstrated unreliability during latching of the contact arm at the end of its trajectory in the blow-open position. 
     U.S. Pat. No. 4,649,247 (Bernhard Preuss, et al.), the disclosure of which is incorporated herein by reference, discloses a contact mechanism assembly provided for current-limiting low-voltage circuit breakers. The contact mechanism assembly has a two-armed contact lever swivel-mounted on a central bearing pin whose lever arms are equipped at their ends with contact pieces. The contact lever is equipped with a slot for mounting on the bearing pin whose longitudinal axis extends approximately at a right angle to the longitudinal axis of contact lever. The contact lever has a stop extending at approximately a right angle to its longitudinal axis for a catch swivel-mounted on the bearing pin. The contact forces on both lever arms cannot be influenced by the swivel mount or by the drive mechanism of the contact lever, but are determined exclusively by the biasing springs. 
     U.S. Pat. No. 5,310,971 (Denis Vial, et al.), the disclosure of which is incorporated herein by reference, discloses a contact bridge of a molded case circuit breaker which is rotatably mounted in a bar by two springs arranged symmetrically from the rotation axis. Each spring is, on the one hand, anchored to the contact bridge, and, on the other hand, anchored to a rod housed in a notch of the bar. The same springs provide contact pressure and slowing-down of opening of the contact bridge at the end of repulsion travel by electrodynamic effect. The contact bridge bears on its edge cam surfaces which, at the end of opening travel, engage the anchoring rods to move them in the notches in the elongation direction of the tension springs. The energy of the contact bridge is thus taken up and stored in the springs causing slowing-down of the contact bridge. The profile of the cams can be chosen to enable reclosing of the contact bridge, this reclosing naturally being delayed by the slowing-down effect at the end of travel. The cam profile can also ensure latching of the contact bridge in the open position. 
     U.S. Pat. No. 7,005,594 (Yong-Gi Kim), the disclosure of which is incorporated herein by reference, discloses a movable contactor assembly of a circuit breaker capable of enhancing a current limiting function by maintaining a contact state between a movable contactor and fixed contactors in a closed circuit state, by preventing the separated movable contactor from returning towards the fixed contactors at the time of a current limiting operation, by accelerating a separation operation of the movable contactor from the fixed contactors at the time of a current limiting operation, and by continuously maintaining a separated state of the movable contactor from the fixed contactors until a trip operation is performed by a trip mechanism. 
     U.S. Pat. No. 7,145,419 (Yong-Gi Kim), the disclosure of which is incorporated herein by reference, discloses a contactor assembly for a circuit breaker comprises a first spring supporting pin, a cam plate, a second spring supporting plate, a link, and a spring. When a movable contactor is rotated without a rotation axis, a fluctuation of a rotation center of the movable contactor is not generated and a current limiting function is fast performed. Also, after contacts are separated from each other, the movable contactor is prevented from returning towards fixed contactors and the separated position is maintained for a predetermined time. An assembly process of the contactor assembly is simplified. 
     Thus, a need exists for an improved contact mechanism assembly for a circuit breaker. 
     This invention overcomes the problems of the prior art and provides an improved contact mechanism assembly for a circuit breaker. 
     PURPOSES AND SUMMARY OF THE INVENTION 
     The invention is a novel contact mechanism assembly for a contact system of a circuit breaker. 
     Therefore, one purpose of this invention is to provide a novel contact mechanism assembly for a circuit breaker. 
     Still yet another purpose of this invention is to provide a crossbar module (or rotating shaft module) having an integrated locking block(s)/protrusion or surfaces. 
     Another purpose of this invention is to provide the Crossbar module, which also comprises two symmetrically oriented locking blocks/protrusions/surfaces that are arranged integrally either on the inner sides or on the outer circumference surfaces of the crossbar module or on the separate locking plate, which is fixed to the crossbar module, for guiding the sliding pins only as they approach the very end of their respective trajectories but, more importantly, for locking the sliding pins at the very end of their respective trajectories during a blow-off motion of the Contact Arm. 
     Yet another purpose of this invention is to provide a direct transfer of torque from a single pair or two pairs of contact springs to a contact arm in the ON position and through much of the contact arm&#39;s trajectory during the blow-off motion without using an intermediate cam surface. 
     Still yet another purpose of this invention is to provide a reliable locking of a contact arm in a blow-off position by using surfaces of either locking blocks/protrusions or a locking plate that are integral with or fastened to a crossbar module. 
     And yet another purpose of this invention is to reduce or even eliminate friction between the contact mechanism components, such as sliding pins and the Crossbar Module during the short circuit blow-off motion of the Contact Arm until it approaches the end of its trajectory thus minimizing or eliminating hysteresis and mechanism performance dependency on wear level and condition of an intermediate cam surface. 
     A resulting characteristics of this invention is reducing loss of contact torque/force during over-travel in the ON position when the fixed and/or moveable contacts erode. 
     Still yet another purpose of this invention is to provide an enclosure for the physical protection of the contact mechanism moving components. 
     Therefore, in one aspect this invention comprises a mechanism for rotary double-break contact system for a circuit breaker, comprising: 
     (a) a crossbar module, wherein said crossbar module has a first anchor area and a second anchor area, a first limiting surface and a second limiting surface, a first sliding pin travel surface and a second sliding pin travel surface, a first sliding pin stop area and a second sliding pin stop area, a first contact arm resting surface and a second contact arm resting surface;
 
(b) a contact arm, wherein said contact arm has a first movable contact and a second movable contact, a first structural stop and a second structural stop, a first outer traveling edge and a second outer traveling edge, and a contact arm slotted opening;
 
(c) an axle, wherein said axle passes through said contact arm slotted opening and said axle is secured to said crossbar, and said axle allows the pivoting of said contact arm about said axle;
 
(d) a first spring, wherein one end of said first spring is secured to a first fixed pin and the other end of said first spring is secured to a first sliding pin, and wherein said first pin is secured to said first anchor area on said crossbar module and said first sliding pin is held in place by said first structural stop in said contact arm;
 
(e) a second spring, wherein one end of said second spring is secured to a second fixed pin and the other end of said second spring is secured to a second sliding pin, and wherein said second pin is secured to said second anchor area on said crossbar module and said second sliding pin is held in place by said second structural stop in said contact arm; and
 
(f) wherein in an ON position said contact arm rests at said first contact arm resting area and said second contact arm resting area, and wherein in a blow-off position said first sliding pin and said second sliding pin engages said first structural stop and said second structural stop of said contact arm and moves said contact arm towards said first limiting surface and said second limiting surface, and thereby forms said mechanism for rotary double-break contact system for a circuit breaker.
 
     In another aspect this invention comprises a mechanism for rotary double-break contact system for a circuit breaker, comprising: 
     (a) a crossbar module; 
     (b) a locking plate, wherein said locking plate has a first anchor area and a second anchor area, a first limiting surface and a second limiting surface, a first sliding pin travel surface and a second sliding pin travel surface, a first sliding pin stop area and a second sliding pin stop area, a first contact arm resting surface and a second contact arm resting surface;
 
(c) a contact arm, wherein said contact arm has a first movable contact and a second movable contact, a first structural stop and a second structural stop, a first outer traveling edge and a second outer traveling edge, a contact arm slotted opening, and wherein said contact arm further comprises a first arm and a second arm, and wherein said first arm and said second arm are connected to each other adjacent said first movable contact and said second movable contact and forming an opening;
 
(d) an axle, wherein said axle passes through said contact arm slotted opening and said locking plate and said axle is secured to said crossbar, and said axle allows the pivoting of said contact arm about said axle;
 
(e) a first spring, wherein one end of said first spring is secured to a first fixed pin and the other end of said first spring is secured to a first sliding pin, and wherein said first pin is secured to said first anchor area on said locking plate and said first sliding pin is held in place by said first structural stop in said contact arm;
 
(f) a second spring, wherein one end of said second spring is secured to a second fixed pin and the other end of said second spring is secured to a second sliding pin, and wherein said second pin is secured to said second anchor area on said locking plate and said second sliding pin is held in place by said second structural stop in said contact arm; and
 
(g) wherein in an ON position said contact arm rests at said first contact arm resting area and said second contact arm resting area, and wherein in a blow-off position said first sliding pin and said second sliding pin engages said first structural stop and said second structural stop of said contact arm and moves said contact arm towards said first limiting surface and said second limiting surface, and thereby forms said mechanism for rotary double-break contact system for a circuit breaker.
 
     In yet another aspect this invention comprises a mechanism for rotary double-break contact system for a circuit breaker, comprising: 
     (a) a crossbar module; 
     (b) a locking plate, wherein said locking plate is integrated with crossbar module, and wherein said locking plate has a first anchor area and a second anchor area, a first limiting surface and a second limiting surface, a first sliding pin travel surface and a second sliding pin travel surface, a first sliding pin stop area and a second sliding pin stop area, a first contact arm resting surface and a second contact arm resting surface;
 
(c) a contact arm, wherein said contact arm has a first movable contact and a second movable contact, a first structural stop and a second structural stop, a first outer traveling edge and a second outer traveling edge, a contact arm slotted opening, and wherein said contact arm further comprises a first arm and a second arm, and wherein said first arm and said second arm are connected to each other adjacent said first movable contact and said second movable contact and forming an opening;
 
(d) an axle, wherein said axle passes through said contact arm slotted opening and said axle is secured to said crossbar, and said axle allows the pivoting of said contact arm about said axle;
 
(e) a first spring, wherein said first spring is inside said opening in said contact arm, and wherein one end of said first spring is secured to a first fixed pin and the other end of said first spring is secured to a first sliding pin, and wherein said first pin is secured to said first anchor area on said locking plate and said first sliding pin is held in place by said first structural stop in said contact arm;
 
(f) a second spring, wherein said second spring is inside said opening in said contact arm, and wherein one end of said second spring is secured to a second fixed pin and the other end of said second spring is secured to a second sliding pin, and wherein said second pin is secured to said second anchor area on said locking plate and said second sliding pin is held in place by said second structural stop in said contact arm; and
 
(g) wherein in an ON position said contact arm rests at said first contact arm resting area and said second contact arm resting area, and wherein in a blow-off position said first sliding pin and said second sliding pin engages said first structural stop and said second structural stop of said contact arm and moves said contact arm towards said first limiting surface and said second limiting surface, and thereby forms said mechanism for rotary double-break contact system for a circuit breaker.
 
     In still another aspect this invention comprises a crossbar module for a circuit breaker, comprising, a first anchor area and a second anchor area, a first limiting surface and a second limiting surface, a first sliding pin travel surface and a second sliding pin travel surface, a first sliding pin stop area and a second sliding pin stop area, a first contact arm resting surface and a second contact arm resting surface, and thereby forming said crossbar module for a circuit breaker. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the invention that are novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The drawings are for illustration purposes only and are not drawn to scale. Furthermore, like numbers represent like features in the drawings. The invention itself, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which: 
         FIG. 1A  is a perspective view of the inventive contact mechanism assembly for a circuit breaker illustrating a first embodiment of the present invention showing the contact mechanism inside the cassette housing and the contact arm in the ON position and in the blow-off position. 
         FIG. 1B  is a perspective view of the inventive contact mechanism assembly for a circuit breaker illustrating a first embodiment of the present invention showing the contact mechanism and the contact arm in the ON position. 
         FIG. 2A  is a perspective detailed view of one half of the crossbar module of the inventive contact mechanism assembly for a circuit breaker illustrated in  FIG. 1 . 
         FIG. 2B  is a perspective detailed view of both halves of the crossbar module of the inventive contact mechanism assembly for a circuit breaker illustrated in  FIG. 1 . 
         FIG. 2C  is a perspective detailed view of one half of the crossbar module with a protective web, which is integral with the crossbar, of the inventive contact mechanism assembly for a circuit breaker illustrated in  FIG. 1 . 
         FIG. 2D  is a perspective view of the inventive crossbar module assembly, which a crossbar module along with the contact arm, with the sliding pin and with the anchor pin, of the contact mechanism assembly for a circuit breaker illustrated in  FIG. 1 . 
         FIG. 3A  is a detailed perspective view of the inventive contact mechanism assembly for a circuit breaker illustrated in  FIG. 1 , with contact arm in the blown-off position. 
         FIG. 3B  is a closer perspective view of the inventive contact mechanism assembly for a circuit breaker illustrated in  FIG. 3A , with contact arm in the blown-off position. 
         FIG. 4A  is a simplified side view sketch of the inventive contact mechanism assembly for a circuit breaker illustrated in  FIG. 1 , showing the contact arm in an ON-position and then in a blow-off position along with simplified schematically shown one or more structural stop. 
         FIG. 4B  is a top view of the inventive contact mechanism assembly for a circuit breaker illustrated in  FIG. 1 . 
         FIG. 5A  is an enlarged detailed view showing a first embodiment of a contact arm that can be used with this invention. 
         FIG. 5B  is an enlarged detailed view showing a second embodiment of a contact arm that can be used with this invention. 
         FIG. 6  is a side view of the inventive contact mechanism assembly for a circuit breaker illustrating a second embodiment of the present invention showing the contact arm in an ON-position and then in a blow-off position. 
         FIG. 7  is a top view of the inventive contact mechanism assembly for a circuit breaker illustrated in  FIG. 6 . 
         FIG. 8  is a side view of the inventive contact mechanism assembly for a circuit breaker illustrating a third embodiment of the present invention showing the contact arm in an ON-position and then in a blow-off position. 
         FIG. 9  is a top view of the inventive contact mechanism assembly for a circuit breaker illustrated in  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     This invention addresses and overcomes typical problems of the prior art, such as, for example, friction between the contact mechanism components, which results in inconsistent mechanism performance and high hysteresis, mechanism performance dependency on wear level and condition of an intermediate cam surface, substantial loss of contact torque/force during over-travel when the fixed and/or moveable contacts erodes, and unreliable locking of the contact arm in the blow-off position, to name a few. 
       FIG. 1A  is a perspective view of the inventive contact mechanism assembly for a circuit breaker  23 , illustrating a first embodiment of the present invention showing the contact mechanism inside a cassette housing  100 , with a contact arm  50 , in an ON position  50 , and then in a blow-off position  50 ′. 
       FIG. 1B  is a perspective view of the inventive contact mechanism assembly for a circuit breaker  23 , illustrating a first embodiment of the present invention showing the contact mechanism and the contact arm  50 , in the ON position  50 . 
       FIG. 2A  is a perspective detailed view of one half of the crossbar module  80 , of the inventive contact mechanism assembly for a circuit breaker  23 , illustrated in  FIG. 1 . 
       FIG. 2B  is a perspective detailed view of both halves of the crossbar module  80  or of a crossbar module  80  made of one piece, of the inventive contact mechanism assembly for a circuit breaker  23 , illustrated in  FIG. 1 . 
       FIG. 2C  is a perspective detailed view of one half of the crossbar module  80 , with a protective web  34 , which is integral with the crossbar of the inventive contact mechanism assembly for a circuit breaker  23 , illustrated in  FIG. 1 . 
       FIG. 2D  is a perspective view of the inventive crossbar module assembly, with a crossbar module along with the contact arm, with the sliding pin and with the anchor pin, of the contact mechanism assembly for a circuit breaker illustrated in  FIG. 1 . 
       FIG. 3A  is a detailed perspective view of the inventive contact mechanism assembly for a circuit breaker  23 , illustrated in  FIG. 1 , with contact arm  50 , in the blown-off position  50 ′. 
       FIG. 3B  is a closer perspective view of the inventive contact mechanism assembly for a circuit breaker  23 , illustrated in  FIG. 3A , with contact arm  50 , in the blown-off position  50 ′. 
       FIG. 4A  is a simplified side view sketch of the inventive contact mechanism assembly for a circuit breaker  23 , illustrated in  FIG. 1 , showing the contact arm  50 , in an ON-position  50 , and then in a blow-off position  50 ′, along with simplified schematically shown structural one or more stop  21 . 
       FIG. 4B  is a top view of the inventive contact mechanism assembly for a circuit breaker  23 , illustrated in  FIG. 1 . 
       FIG. 5A  is an enlarged detailed view showing a first embodiment of a contact arm  50 , that can be used with this invention. 
       FIG. 5B  is an enlarged detailed view showing a second embodiment of a contact arm  150 , that can be used with this invention. 
     Now referring to  FIGS. 1A through 5B , the inventive contact mechanism assembly for a circuit breaker  23 , comprises an arc extinguishing mechanism  10 , a pair of fixed contact assemblies  12 , each having a fixed contact pad  14 . A contact arm assembly  50 , having a movable contact  51 , a contact arm body  58 , contact arm edge-surfaces  59 , a bump or notch or hook or structural stop  56 , and a slotted hole or opening  60 , which encompasses a central pivot axle  32 , which is fixed/secured to the crossbar module  80 . The contact arm assembly  50  is flexibly connected to the crossbar module  80  using either one or two pairs of springs, namely, a first spring  45 , and a second spring  55 , such that one end of the first spring  45 , is secured to a fixed pin or anchor  42 , which is secured to the crossbar module  80 , and the other end of the first spring  45 , is secured to a sliding pin  54 , which is securely held in place by the bump or notch or structural stop  56 , in the contact arm  50 . Similarly, one end of the second spring  55 , is secured to a fixed pin or anchor  44 , that is secured to the crossbar module  80 , and the other end of the second spring  55 , is secured to a sliding pin  52 , which is securely held in place by the bump or notch or structural stop  56 , in the contact arm  50 . The contact arm  50 , pivots about a shaft  32 , wherein the axle  32 , passes through opening  60 , and wherein the axle  32 , is securely held in place by the crossbar module  80 . Preferably, the crossbar module  80 , has a round peripheral edge or surface  22 . 
     The crossbar module  80 , or the rotation shaft module  80 , is fabricated either as one piece or made as a two-half assembly out of a non-electrically conductive material, preferably having an opening or hole  37 , for fixing/securing a central pivot axle  32  for independent floating and rotation of the contact arm  50 . The crossbar module  80 , also comprises two symmetrically oriented locking blocks/protrusions  20 , that are arranged integrally either on the inner sides or on the outer circumference surfaces of the crossbar module  80 . 
     In certain cases, assuming a sufficient space within the dimensional ‘envelope’, the crossbar module  80 , configuration can also include a circumferential web  34  protruding out of the inner sides of the crossbar module  80  as clearly shown in the  FIG. 2C , so as to provide a physical protection to the contact mechanism components against contamination, such as, by the flying particles, which result from short circuit condition. 
     It should be appreciated that the central pivot axle  32 , is preferably positioned in the geometrical center or pivot point  30 , of the crossbar module  80 , and is oriented perpendicular to its sides. The central pivot axle  32 , can be either integral with or fixed-mounted to the crossbar module  80 , or just go through it. 
     Side walls of the crossbar module  80 , have a varying thickness. The locking block/protrusion  20  of the crossbar module  80 , preferably has an upper anchor area or surface  24 , and a similar lower anchor area or surface  24 . On the upper anchor area or surface  24 , the fixed pin or anchor  44 , having the one end of the spring  55 , is secured. On the lower anchor area or surface  24 , the fixed pin or anchor  42 , having the one end of the spring  45 , is secured. The locking/block surface  20 , also has an upper pin stop area or locking surface  26 , and a similar lower pin stop area or locking surface  26 . The locking block/protrusion  20  is integral with side surface  28  of the crossbar module  80 . The locking block/protrusion  20  is terminated by a surface  38 , by a sequence of locking surfaces  26 , limiting surfaces  33 , and by connecting protrusions  35 . The sequence of locking surfaces  26  comprises surfaces  27 ,  29  and  31  that are arranged on the locking block/protrusion  20  of the crossbar module  80 . Basically, the sequence of the locking surface  26 , comprises a first surface  27 , a second surface  29 , and a locking surface  31 . The connecting protrusions  35 , of the crossbar module  80 , have structural surfaces  36 . 
     As shown in the  FIGS. 1A and 1B , the sliding pins  52  and  54 , are resting on the outer edges  59  of the contact arm body  58 , and are being supported by standouts  56  or by bumps  56  or by cavities/slots  56  or structural stops  56 . During blow-off, the sliding pins/rollers  52  and  54 , move together with the contact arm  50  toward the sequence of the locking surfaces  26  while not engaging the surfaces  38  of the locking block/protrusion  20 . At the very end of their respective trajectories, the sliding pins/rollers  52  and  54  engage the first surface  27  and then the second surface  29  of the sequence of the locking surfaces  26  of the locking blocks/protrusions  20  of the crossbar module  80 . The sliding pins/rollers get locked upon reaching locking surfaces  31  of the sequence of the locking surfaces  26  of the locking blocks/protrusions  20  of the crossbar module  80  as clearly shown in the  FIGS. 3A and 3B . 
     The contact arm  50 , or contact bridge  50 , floats inside the crossbar module  80 , and is biased by the two pairs of the contact tension springs, namely springs  45  and  55 , that are located inside the crossbar module  80 , and are on both sides of the contact arm  50 , as shown in  FIG. 4B . The contact arm  50 , has a central slotted opening or hole  60 , which is oriented preferably perpendicularly to the longitudinal plane of the contact arm  50 , but, which can also be oriented at a different angle, and surrounds the central pivot axle  32  thus allowing translational motion of the contact arm  50 , in the direction of longitudinal axis of the slotted opening  60 , but within limits defined by the slot geometry and size. The contact arm  50 , also has two or more pin-retaining features  56 , such as hooks  56 , standouts  56 , bumps  56 , slots  56 , to name a few, that are arranged integrally on the opposite edges of the contact arm  50 . Current paths  70  are integral with fixed contact assemblies  12 . 
     The two contact pads  51 , also called the moveable contacts  51 , are attached symmetrically to the opposite ends of the contact arm  50 . In the ON position, the moveable contacts  51 , are intended to be pressed against the fixed contact pads  14  that are attached to the fixed contact assembly  12  and that are symmetrical with respect to the geometrical center or pivot point  30  of the crossbar module  80 . 
     As stated earlier that the two sliding pins or rollers  52 ,  54 , are pressed against the anchor-shapes pin-retaining features  56  or  156 , but on the opposite edge surfaces  59  or  159  of the contact arm  50  or  150 , and serve as moveable supports for the tension springs  45 ,  55 . It is important to point out that in case of the contact arm configuration, which is shown in the  FIG. 5B , the sliding pins or rollers  52 ,  54  are placed in the spaces  154  between the standouts or bumps  156 , and the standout or bumps  157 . The two anchor pins  42 ,  44 , are mounted symmetrically to the crossbar module  80 , but perpendicular to its side surfaces  28 , and these anchor pins serve as fixed supports for the tension springs  45 ,  55 . 
     The two structural stops  21 , that are reinforced structural components of the circuit breaker housing or of the circuit breaker contact system housing  100 . They are positioned symmetrically at the desired opening angle of the contact arm  50 . 
       FIG. 5A  is an enlarged detailed view showing a first embodiment of a contact arm  50 , that can be used with this invention. 
       FIG. 5B  is an enlarged detailed view showing a second embodiment of a contact arm  150 , that can be used with this invention. It is important to point out that in case of this contact arm configuration, the sliding pins or rollers  52 ,  54  are placed into the spaces  154  between the standouts or bumps  156  and  157 . One purpose of the small bumps  157 , is to limit, if needed, inertia-driven linear motion of the sliding pins  52 ,  54  during the initial moments of the rotation of the contact arm  50 , caused by the blow-off forces. It should be appreciated that the sliding pins or rollers  52 ,  54 , are contained between the standouts  156  and  157 , and rotate or slide along the edge  159 , at spaces  154 . 
       FIG. 6  is a side view of the inventive contact mechanism assembly for a circuit breaker  223 , illustrating a second embodiment of the present invention showing the contact arm  250 , in an ON-position and then in a blow-off position. 
       FIG. 7  is a top view of the inventive contact mechanism assembly for a circuit breaker  223 , illustrated in  FIG. 6 . 
     Now referring to  FIG. 6  and  FIG. 7 , the crossbar module  280 , or the rotation shaft  280 , is basically similar to the crossbar module  80 , but only without the two symmetrically oriented locking blocks/protrusions  20 , on the inner sides of the crossbar module  80 . 
     The split version of the contact arm  250 , which consists of two symmetrical formed halves, that are secured together, such as, by brazing or welding or by other methods, to form a contact arm assembly  250 , with a space  290 , in the middle. The contact arm  250 , comprises a first arm  257 , and a second arm  259 , that are joined together at locations  297 , and  299 , and then extend as a single unit or extension  258 , as clearly seen in  FIG. 7 . Current paths  270  are integral with the fixed contact assemblies  12 . 
     This contact arm  250 , has two sets of pin-retaining shapes  256 , hooks  256 , standouts  256 , bumps  256 , that are arranged integrally on the opposite edges of the contact arm halves. 
     Each half of the contact arm assembly  250 , has a central slotted opening or hole  260 , which is oriented preferably perpendicularly to the longitudinal plane of the contact arm  250 , but, which can also be oriented at a different angle, and surrounds a central pivot axle  232 , thus allowing translational motion of the contact arm  250 , in the direction of longitudinal axis of the slotted opening  260 , within limits defined by the slot geometry and size. 
     In this case the two symmetrically oriented sequences of locking surfaces  226 , comprise a first surface  227 , a second surface  229 , and a locking surface  231 , instead of being integral with sides of the crossbar module  280 , are arranged on the outer edges of a separate locking plate  220 , fabricated out of a, preferably, an electrically non-conductive or a low-conductive material. This locking plate  220 , is located inside the space  290 , in the middle of the contact arm  250 . The locking plate  220 , will be fixed to the crossbar module  280 , by mechanical fastening means. 
     The central pivot axle  232 , which is fixed or secured to the crossbar module  280  or to the locking plate  220  or to the both, moveable contacts  251 , and fixed contact pads  14 , that are attached to the fixed contact assembly  12 , two pairs of contact tensions springs, namely, a first spring  245 , and a second spring  255 , two sliding pins or roller  252 ,  254 , two anchor pins  242 ,  244 , and two structural stops  256 , are correspondingly identical to those described for the embodiment illustrated with reference to  FIGS. 1A through 5B . 
     The contact arm  250 , pivots about a central pivot axle  232 , wherein the axle  232 , passes through opening  260 , and wherein the axle  232 , is securely held in place by the crossbar module  280  or by the locking plate  220  or by the both. The crossbar module  280 , has a structural surface  236 , which is similar to the structural surface  36 , a limiting surface  233 , which is similar to the limiting surface  33 , a surface  238 , which is similar to the surface  38 . 
       FIG. 8  is a side view of the inventive contact mechanism assembly for a circuit breaker  323 , illustrating a third embodiment of the present invention showing the contact arm  350 , in an ON-position  350 , and then in a blow-off position  350 ′. 
       FIG. 9  is a top view of the inventive contact mechanism assembly for a circuit breaker  323 , illustrated in  FIG. 8 . 
     Now referring to  FIG. 8 , and  FIG. 9 , the crossbar module  380 , central pivot axle  332 , moveable contacts  351 , and fixed contact assemblies  12 , two sliding pins or rollers  352 ,  354 , and two anchor pins  342 ,  344 , are correspondingly identical to those described for the preferred embodiment of  FIGS. 1A through 5B . 
     A split contact arm assembly  350 , identical to the one described for the second embodiment described in  FIGS. 6 and 7 . 
     The split version of the contact arm  350 , which consists of two symmetrical formed halves, that are secured together, such as, by brazing or welding or by other methods, to form a contact arm assembly  350 , with a space  390 , in the middle. The contact arm  350 , comprises of a first arm  357 , and a second arm  359 , that are joined together at locations  397 , and  399 , and then extend as a single unit or extension  358 , as clearly seen in  FIG. 9 . Current paths  370  are integral with the fixed contact assemblies  12 . 
     One pair of larger contact springs, namely, a first contact spring  345 , and a second contact spring  355 , in comparison to those described for the preferred embodiment. This one pair of larger contact springs  345 ,  355 , is located inside the space  390 , between the halves of the contact arm assembly  350 . 
     Each half of the contact arm assembly  350 , has a central slotted opening or hole  360 , which is oriented preferably perpendicularly to the longitudinal plane of the contact arm  350 , but, which can also be oriented at a different angle, and surrounds a central pivot axle  332 , which is fixed or secured to the crossbar module  380 , thus allowing translational motion of the contact arm  350 , in the direction of longitudinal axis of the slotted opening  360 , within limits defined by the slot geometry and size. 
     In this case the two symmetrically oriented locking surfaces  326 , comprise a first surface  327 , a second surface  329 , and a locking surface  331 , instead of being integral with sides of the crossbar module  380 , are arranged on the outer edge surfaces of crossbar module  380 . 
     The central pivot axle  332 , moveable contacts  351 , and fixed contact pads  14 , that are attached to the fixed contact assembly  12 , two pairs of contact tensions springs, namely, a first spring  345 , and a second spring  355 , two sliding pins or roller  352 ,  354 , two anchor pins  342 ,  344 , and two standouts or bumps or structural stops  356 , are correspondingly identical to those described for the embodiment illustrated with reference to  FIGS. 1A through 5B . 
     The contact arm  350 , pivots or floats about a central axle  332 , wherein the axle  332 , passes through opening  360 , and wherein the axle  332 , is securely held in place by the crossbar module  380 . The crossbar module  380 , has a structural surface  336 , which is similar to the structural surface  36 , a limiting surface  333 , which is similar to the limiting surface  33 , a surface  338 , which is similar to the surface  38 , and a side surface  328 , which is similar to the side surface  28 . 
     In order to further illustrate the operations of this invention we use  FIG. 1A  through  FIG. 5B  as an example, however, the operation mechanism would be the same for the other embodiments. In the ON position  50 , the contact springs  45 ,  55 , supported by the sliding pins  52 ,  54 , are pressed against the anchor-shapes pin-retaining features  56 , of the contact arm  50 , and by the anchor pins  42 ,  44 , that are fixed to the crossbar module  80 , to create a force-couple, which generates a required contact torque at the contact arm  50 , with respect to the central pivot  32 ,  60 . This contact torque in turn creates a pair of equally balanced pressing forces between the moveable contacts  51 , and the fixed contacts  14  that are attached to the fixed contact assembly  12 . It is important to point out that the sliding pins or rollers  52 ,  54 , do not engage the aforesaid surfaces of the locking blocks/protrusions  20 , in the ON position. 
     During blow-off, the electro-magnetic repulsion forces cause a highly accelerated disengagement of the moveable contacts  51 , from the fixed contact pads  14  of the fixed contact assemblies  12 , thus causing the contact arm  50 , along with the sliding pins or rollers  52 ,  54 , to rotate in a clockwise direction towards the full-open position, as indicated by arrow  63 . This motion of the contact arm  50 , stretches the contact springs  45 ,  55 , thus increasing the spring force applied to the contact arm  50 . However, at the same time with rotation of the contact arm  50 , the springs  45 ,  55 , within each pair move closer to each other and closer to the central pivot axle  32 , thus reducing the moment arm with respect to the center of rotation or pivot point  30 ,  230 ,  330 . This ensures relatively equalized torque at the contact arm  50 , which resists the rotational opening motion of the contact arm  50 . At the end of the trajectory of the contact arm  50 , the sliding pins or rollers  52 ,  54 , engage the sequence of the locking surfaces  26  that comprises locking surfaces  27 ,  29  and  31 , of the locking blocks/protrusions  20 , of the crossbar module  80 . The torque at the contact arm  50 , created by the resultant forces, will decrease while the sliding pins or rollers  52 ,  54 , engage the locking surfaces  27 , and then  29 , until it becomes negative when the sliding pins or rollers  52 ,  54 , reach the locking surfaces  31 , of the locking blocks/protrusions  20 , thus resisting the reverse rotation of the contact arm back to the closed contacts position and effectively locking the contact arm  50 , in the blow-off position. 
     The contact arm  50 , will be in the reverse rotation and movable contacts  51 , will re-close automatically with the fixed contact pads  14  of the fixed contact assembly  12 , if the blow-off force disappears before the sliding pins or rollers  52 ,  54  reach the locking surface  31  of the sequence of locking surfaces  26  of the locking blocks/protrusions  20 , as illustrated by arrows  61 . Otherwise, the contact arm  50 , will be locked in the blow-open position at the required angle at the locking surface  31  of the sequence  26 . 
     The tripping motion of the crossbar module  80 , takes place after the repulsion opening of the movable contacts  51 , from the fixed contacts  12 , and the blow-off rotation of the contact arm  50  in the direction  63 . The breaker operating mechanism, which is not described in this invention, rotates the crossbar module  80 , in a clockwise direction  63 , to catch up with the contact arm  50 , and to indicate the breaker ‘Trip’ state. In the beginning of this clockwise rotation  63 , of the crossbar module  80 , the sliding pins/rollers  52 ,  54  are pressed against the locking surface  31  of the sequence of the locking surfaces  26  of the locking blocks/protrusions  20  of the crossbar module  80  and against the structural stops  56  or against edge surfaces  59  of the contact arm  50 . As the crossbar module  80  keeps rotating in the direction  63 , the sliding pins/rollers  52 ,  54  remaining pressed against the structural stops  56  or against edges  59  of the contact arm  50  but they disengage from the locking surface  31  and engage the locking surface  29 , then disengage it as well and engage the locking surface  27  of the sequence of the locking surfaces  26  of the locking block/protrusion  20 . Immediately after that the sliding pins/rollers  52 ,  54  completely disengage from the locking block/protrusion  20  or from the locking plate  220  in case of the second embodiment. 
     As the disengagement happens, the contact arm  50 , rotates in a counter-clockwise direction  61 , biased by the contact springs  45 ,  55 , toward the ON position, but then, at a certain pre-determined angle it engages structural surfaces  36 , of the crossbar module  80 , which is being rotated in the clockwise direction  63  by the operating mechanism of the circuit breaker  23 . The contact arm  50  then rotates together with the crossbar module  80  (clockwise) in the direction  63  back to the blow-off position, which indicates a ‘Trip’ state of the breaker. 
     During normal opening operation of the circuit breaker  23 , operating mechanism rotates the crossbar module  80 , in a clockwise direction  63 , from the ON position toward the OPEN or a TRIP positions. The structural surfaces  36  of the crossbar module  80 , engage the contact arm  50 , and force it to separate the moveable contacts  51 , from the fixed contact pads  14  of the fixed contact assembly  12 , and to rotate in a clockwise direction  63 , together with the crossbar module  80 , toward the OPEN or a TRIP positions. 
     For closing the contacts of the circuit breaker  23 , operating mechanism rotates the crossbar module  80 , in a counter-clockwise direction  61 , from the OPEN or TRIP position towards the ON position. This rotation of the crossbar module  80 , removes the force applied by the crossbar&#39;s structural surface  36 , as an active body, towards the contact arm  50 . This removal of the active force allows the contact arm  50 , which is biased by the contact springs  45 ,  55 , to rotate in a counter-clockwise direction  61 , towards the ON position thus closing the moveable contacts  51 , and the fixed contact pads  14  of the fixed contact assembly  12 . When the crossbar module  80 , along with the anchor pins  42 ,  44 , approaches its ON position, the contact springs  45 ,  55 , are being oriented and stretched to the length required to produce sufficient force-couple, which results in the required torque level at the contact arm  50 , which in turn creates a specified pressure forces between the moveable contacts  51 , and the contact pads  14  of the fixed contact assembly  12 . 
     With this invention a loss of the contact force/torque due to the over-travel of the contact arm  50  pass its initial ON position is substantially reduced in comparison to the conventional art systems that use intermediate cam surface for generating contact pressure. Over-travel condition, which can happen in a number of ways as a result of reduced thickness of either fixed contact pads  14  of the fixed contact assembly  12 , or the moveable contact pads  51 , or both because of loss of the contact pad material due to erosion, causes the contact arm  50  to rotate past its initial ON position. This reduces the stretching of the contact springs  45 ,  55 , thus resulting in decrease of the spring forces applied to the contact arm  50 . At the same time, however, with rotation of the contact arm  50 , past the initial ON position the springs  45 ,  55 , within each pair move away from each other and also farther away from the central pivot point or axle  32 , thus increasing the moment arm with respect to the center of rotation or pivot point  30 ,  230 ,  330 . Once again, this ensures relatively equalized torque at the contact arm  50 , when the moveable contact  51 , and the fixed contact pads  14  of the fixed contact assembly  12 , are closed or made to contact each other in an over-travel ON position. 
     In case of unequal line and load side contact erosion, the slotted profile of the central opening  60 , in the contact arm  50 , enables shifting of the true center of rotation along the longitudinal axis of the slotted opening  60 . In this case, difference between the moment arm lengths will balance a difference between spring forces on a line and load sides, thus, once again, relatively equalizing torque at the contact arm  50 , and uniformly distributing contact pressure forces when the moveable contacts  51 , and the fixed contact pads  14  of the fixed contact assembly  12 , are closed or made to contact each other in an over-travel ON position. 
     As stated earlier that this invention allows the direct transfer of the torque from stored energy components, such as the springs  45 ,  55 , to the contact arm  50 , in the ON position (contacts closed) without using any intermediate cam surface. 
     With this invention one also gets the reliable locking of the contact arm  50 , in the blow-off position using stationary means that are integral with or fastened to the crossbar module, such as the locking blocks/protrusions  20 , that are made either integral with the crossbar module, as in the preferred embodiment  23 , and in the third embodiment  323 , or such as locking plate  220 , which is mechanically fastened to the crossbar module  280 , as in the second embodiment  223 . 
     The locking blocks/protrusions  20 , of the crossbar module  80 , in the preferred embodiment  23 , and in the third embodiment  323 , or of the locking plate  220 , in the second embodiment  223  comprise a sequence of pin-engaging or locking surfaces  26 , which consists of three major consecutive surfaces, namely, first surface  27  and second surface  29 , and locking surface  31 . 
     The first surface  27  and the second surface  29  are located, oriented and sized in a pre-determined manner, either as option A or option B or option C. 
     In option A, the first surface  27  can have its center of curvature located outside the material block, and the second surface  29 , can have its center of curvature located inside the material block. This kind of surface transition, being properly designed, sized and oriented, will allow for a smooth engagement between the sliding pins or rollers  52 ,  54 , and the locking block/protrusion  20  of crossbar module  80  for the preferred embodiment  23 , or locking plate  220  for the second embodiment  223 , thus reducing an impact force on the crossbar module  80 , during the blow-off rotational motion of the contact arm  50 . 
     In option B, the first surface  27 , can be a straight surface and the second surface  29 , can have its center of curvature located inside the material block. This kind of surface transition, being properly designed, sized and oriented, will allow for a smooth engagement between the sliding pin or roller  52 ,  54 , and the locking block/protrusion  20  of crossbar module  80 , or locking plate  220  for the second embodiment  223 , thus reducing an impact force on the crossbar module  80 , during the blow-off rotational motion of the contact arm  50 . 
     In option C, the first surface  27 , can have its center of curvature located inside the material block, and the second surface  29 , can have its center of curvature located also inside the material block. This kind of surface transition being properly designed, sized and oriented will allow for a smooth engagement between the sliding pins or rollers  52 ,  54 , and the locking block/protrusion  20  of crossbar module  80  for the preferred embodiment  23 , or locking plate  220  for the second embodiment  223 , thus reducing an impact force on the crossbar module  80 , during the blow-off rotational motion of the contact arm  50 . 
     The locking surface  31 , preferably, is a straight surface, which is located and oriented in a pre-determined manner at a certain pre-determined angle to ensure retaining the sliding pin or roller  52 ,  54 , at the end of the blow-off trajectory thus locking the contact arm  50 , in the blow-off position and preventing it from a nuisance rotation toward the ON position. 
     As shown in  FIGS. 5A and 5B , the contact arm  50 ,  150 , features two or more pin-retaining shapes or structural stops  56 , such as, hooks  56 , standouts  56 , bumps  56 , cavities/slots  56 , to name a few, that are arranged integrally on the opposite outer edges of the contact arm  50 , and that serve as means to limit motion of the sliding pins or rollers  52 ,  54 , with respect to the contact arm  50 , thus still allowing the sliding pins or rollers  52 ,  54 , to slightly move along the edges  49  of the contact arm  50 , while enabling a direct transfer of torque from the springs  45 ,  55 , to the contact arm  50 . 
     Both the second embodiment  223 , and the third embodiment  323 , feature a ‘split’ version of the contact arm  250 ,  350 , which consists of two symmetrical formed halves, that are brazed or welded together to form a contact arm  250 ,  350 , assembly with a space  290 ,  390 , respectively, in the middle. 
     For the second embodiment  223 , the available space  290 , in the middle between the symmetrical halves  257 ,  259 , of the contact arm  250 , enables placing a single locking plate  220 , right in the center of the mechanism. At the same time, the sliding pin or roller  252 ,  254 , are supported by and can slide along the two edges of the symmetrical halves  257 ,  259 , of the contact arm  250 . These both features are beneficial from the standpoint of stability and equilibrium of the motion when the contact arm  250 , is in rotation and when it gets locked. Furthermore, from the stand point of structural rigidity, if the locking plate  220 , is made out of a preferably low electrically conductive metal it enables a rigid metal-on-metal contact between the sliding pins or rollers  252 ,  254 , and the locking plate  220 . 
     For the third embodiment  323 , the available space  390 , in the middle between the symmetrical halves  357 ,  359 , of the contact arm  350 , enables placing a single pair of contact springs  345 ,  355 , right in the center of the mechanism. At the same time, the sliding pins or rollers  352 ,  354 , are supported by and can slide along the two edges of the symmetrical halves  357 ,  359 , of the contact arm  350 . These both features are beneficial from the standpoint of stability and equilibrium of the motion during the rotation and locking of the contact arm  350 . Furthermore, it enables reducing quantity of the contact springs  345 ,  355 , from four to two that is one pair instead of two pairs. 
     A crossbar module  80 , configuration described in this invention, may also feature, assuming sufficient space within a dimensional ‘envelope’, an integral circumferential web  34  protruding out of the inner sides of the crossbar module  80  as shown in the  FIG. 2C , to provide a physical protection to the contact mechanism components against contamination by flying particles resulting from short circuit condition. 
     As one can appreciate that with this invention the contact torque or force in the ON position and during much of the contact arm&#39;s trajectory is generated through direct transfer of spring force from the contact springs to the contact arm without using the cam surface. This invention also provides a reliable locking of the contact arm at the end of its trajectory during short circuit when it is acted upon by the sufficient electro-magnetic repulsion forces. It is worth of pointing out a resulting characteristics of this invention, which is minimization of the reduction of the contact torque or force that occurs during over-travel due to contact erosion. This invention has also minimized or eliminated effect of friction on the mechanism performance, such that the hysteresis are either very small or non-existent. Additionally, the inventive crossbar provides enclosure and physical protection to the contact mechanism. 
     The contact arm  50 ,  250 ,  350 , is preferably made of a metallic material, wherein the metallic material is selected from a group comprising, aluminum, steel, copper, composite material, and combination thereof, to name a few. 
     The cross-bar module  80 ,  280 ,  380 , is preferably made of a plastic material, and preferably featuring thermal stability capabilities. 
     The locking block/protrusions  20  and  320 , is preferably made of a plastic material, and preferably featuring thermal stability capabilities. 
     The locking plate  220  is preferably made of a plastic material, and preferably featuring thermal stability capabilities. In certain designs, the locking plate  220  can be made out of a preferably electrically non-conductive or very low electrically conductive metallic material. 
     The slotted opening  60 , is preferably selected from a group comprising, an oval shaped slot, a circular shaped slot, a trapezoidal shaped slot, a square shaped slot, a rectangular shaped slot, an elliptical shaped slot, a triangular shaped slot, and combination thereof, to name a few. 
     The material for the various components of this invention could be selected from a group comprising, a plastic material, a thermally stable plastic material, an electrically non-conductive material, a very low electrically conductive metallic material, and combination thereof, to name a few. 
     As stated earlier that adjacent the limiting surface  33 , is a pin stop area  26 , wherein the pin stop area  26 , preferably comprises a first portion  27 , a second portion  29 , and a third portion  31 , wherein during a blow-off of the contact arm, the first portion  27 , is an engaging surface  27 , for the sliding pin  52 ,  54 , the second portion  29 , is a ratchet surface  29 , and the third portion  31 , is a locking surface  31 , for the sliding pin  52 ,  54 . 
     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.