Abstract:
Disclosed is a circuit breaker having a cam rotation delaying function employed to block current, the circuit breaker performing a charging operation and a charting operation, the circuit breaker including a closing spring having one end portion rotatably coupled to each of plates, a driving lever rotatably installed at each of the plates and connected to another end portion of the closing spring so as to be rotated responsive to compression and extension of the closing spring, a cam rotatably installed at each of the plates and configured to press the driving lever for rotation, a link mechanism having a plurality of links rotatably installed at each of the plates and connected to the driving lever for operation, a movable contact rotatably installed at a side of each of the plates and contactable with a terminal by an operation of the link mechanism, and a cam delaying mechanism installed at each of the plates and configured to attenuate a rotational force of the cam due to a restoring force of the closing spring, whereby an excessive rotation of the cam can be prevented by the cam delaying mechanism so as to allow stable and complete toggling operation of the link mechanism and a smooth restoring operation of the closing spring, thereby providing more stable operation of the circuit breaker.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2008-0138522, filed on Dec. 31, 2008, the contents of which is incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a circuit breaker having a cam rotation delaying function, and particularly, to a circuit breaker having a cam rotation delaying function capable of avoiding incomplete closing operation due to a rotation of a cam in a state of mechanically performing an ON/OFF operation for a load side by virtue of the rotatable cam. 
     2. Background of the Invention 
     In general, a circuit breaker is an apparatus for blocking a circuit upon occurrence of overload, short-circuit, electric leakage and electric shock by selectively switching on or off a circuit between a power source side and a load side. A construction of a circuit breaker is disclosed in the Korean Registered utility model application No. 20-0442291. 
     As disclosed in Korean Registered utility model application No. 20-0442291, a circuit breaker executes a charging operation for accumulating elastic energy in a closing spring, a closing operation for connecting a movable contact to a terminal by an elastic restoring force of the closing spring, and an opening operation for separating the movable contact from the terminal. 
     Here, the charging operation is executed as follows. That is, in a blocked state where the movable contact is separated from the terminal, a cam is rotated responsive to rotation of rotational shaft which is rotated manually or rotates automatically, and a driving lever contacted by the cam is rotated in cooperation with the rotation of the cam. Accordingly, the closing spring is compressed by the rotation of the driving lever. 
     The closing operation is executed as follows. Elastic energy of the closing spring is transferred to a link member of a switching mechanism such that a switching shaft connected to a third link is rotated. A leg rotated in cooperation with the rotation of the switching shaft makes the movable contact moved toward the terminal so as to come in contact with the terminal, thereby enabling current flow. During the closing operation, a connection shaft of an opening spring installed at a lower portion of the leg is moved toward the terminal, accordingly the opening spring is extended. 
     Here, the opening operation is executed as follows. The leg is reversely rotated by an elastic restoring force of the opening spring which has been extended during the closing operation and the movable contact is spaced from the terminal to be returned to its original location. 
     Here, the link member is a toggle member including a first link, a second link and a third link, and performs a toggling operation capable of enduring a repulsive load which is generated upon the closing operation of the movable contact with respect to the terminal. The first and second links are rotatably connected to each other by a first rotation pin, and the second and third links are rotatably connected to each other by a second rotation pin. 
     Regarding the charging operation of the thusly configured circuit breaker, when the closing spring is compressed during a closing operation, a restoring force of the closing spring is applied to a cam via a bearing pin, which is disposed at the driving lever so as to be contactable with the driving lever and the cam. 
     Regarding the closing operation, a restoring force of the closing spring rotates the cam in a clockwise direction based upon a cam shaft when a closing latch of a driving mechanism is rotated and accordingly the closing spring in a compressed state is extended. 
     Here, if a force of the closing spring is set greater than a force required for returning the cam to its original location, a force applied to the cam during the closing operation becomes greater accordingly and a rotational force of the cam in the clockwise direction becomes excessive. As a result, upon rotating back to its original location, the cam is rotated over the original location in the clockwise direction, thereby being rotated up to a location interfering with a returning rotation of the driving lever. 
     That is, upon the closing operation, the cam may interfere with the rotation of the driving lever and a toggle pin of the link member is located above the first link to thereby suppress a complete toggle operation. Further, the returning rotation of the driving lever is suspended by the cam, and accordingly a stopping pin of the driving lever cannot be moved up to a second support shaft, which is disposed at a lower side of the driving lever for supporting the stopping pin, resulting in disabling the closing spring to be extended to its original state. 
     Consequently, the related art circuit breaker has a problem in that the cam may be rotated up to an excessive location by a preset tensile force of the closing spring, thereby having the chance of being operated in an unstable state. 
     SUMMARY OF THE INVENTION 
     Therefore, to obviate the problems of the related art, an object of the present invention is to provide a circuit breaker having a cam rotation delaying function capable of ensuring more stable operation in terms of allowing a toggling operation of a link mechanism to be stably completely performed and ensuring smooth returning of a closing spring by preventing an excessive rotation of a cam. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a circuit breaker having a cam rotation delaying function, the circuit breaker performing a closing operation and a charging operation, the circuit is breaker including, a plurality of plates spaced apart from each other, a closing spring having one end portion rotatably coupled to each of the plates, a driving lever rotatably installed at each of the plates and connected to another end portion of the closing spring so as to be rotated responsive to compression and extension of the closing spring, a cam rotatably installed at each of the plates and configured to press the driving lever for rotation, a link mechanism having a plurality of links rotatably installed at each of the plates and connected to the driving lever for operation, a movable contact rotatably installed at a side of each of the plates and contactable with a terminal by an operation of the link mechanism, and a cam delaying mechanism installed at each of the plates and configured to attenuate a rotational force of the cam due to a restoring force of the closing spring. 
     Here, the cam delaying mechanism may include a delay link elastically rotatably installed at each of the plates and configured to delay the rotation of the cam. 
     The cam delaying mechanism may include a delay link rotatably installed at each of the plates and contactable with the supplementary cam, a rotation pin inserted into the delay link to be coupled to the plate so as to transfer a rotation of the delay link, and a delay spring installed between the delay link and each plate and configured to elastically support the rotation of the delay link. 
     The delay link may include a supporting portion protrudingly formed and slidably inserted into an outer circumferential portion of the supplementary cam. 
     A contact portion of the delay link with the supplementary cam may be formed to be round. 
     The delay link may include an accommodation groove, wherein the delay spring comprises a first stopper locked at the accommodation groove and a is second stopper locked at the plate. 
     The supplementary cam may include a contact groove in which the delay link is detachably inserted. 
     The supplementary cam may be installed at both sides of the rotational shaft, and provided with coupling holes formed along a central portion of the cam, the cam being coupled to the coupling holes. 
     In another aspect of the present invention, there is provided a circuit breaker having a cam rotation delaying function, in a circuit breaker performing a closing operation and a charging operation, the circuit breaker including, a plurality of plates spaced apart from each other, a closing spring having one end portion rotatably coupled to each of the plates, a damper installed within the closing spring and contracted and extended in cooperation with the closing spring to attenuate a restoring force of the closing spring, a driving lever rotatably installed at each of the plates and connected to another end portion of the closing spring so as to be rotated responsive to compression and extension of the closing spring, a cam rotatably installed at each of the plates and configured to press the driving lever for rotation, a supplementary cam installed at the same rotational shaft as that of the cam so as to be cooperatively rotated with the cam and having a rotational radius greater than that of the cam, a link mechanism having a plurality of links rotatably installed between the plates by virtue of toggle pins and connected to the driving lever so as to be toggled, and a movable contact rotatably installed at a side of each of the plates and contactable with a terminal by an operation of the link mechanism. 
     The damper may be configured as dual pipes slidably coupled to each other so as to be contracted and extended. 
     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
       In the drawings: 
         FIG. 1  is an internal front view of a circuit breaker having a cam rotation delaying function in accordance with one embodiment of the present invention; 
         FIG. 2  is a perspective view showing a contact state of a supplementary cam by virtue of a cam delaying mechanism of  FIG. 1 ; 
         FIG. 3  is a view showing a delayed state of the cam due to the cam delaying mechanism of  FIG. 2 ; 
         FIG. 4  is a disassembled perspective view of the cam delaying mechanism of  FIG. 2 ; 
         FIG. 5  is a view showing a completely closed state from the state of  FIG. 1 ; 
         FIG. 6  is an internal front view of a circuit breaker having a cam rotation delaying function in accordance with another embodiment of the present invention; and 
         FIG. 7  is a sectional view of a damper of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Description will now be given in detail of a circuit breaker having a cam rotation delaying function in accordance with the preferred embodiments of the present invention, with reference to the accompanying drawings. 
     As shown in  FIGS. 1 and 2 , a circuit breaker having a cam rotation delaying function in accordance with one embodiment of the present invention may include a plate  100 , a closing spring  105 , a driving lever  110 , a cam  115 , a supplementary cam  120 , a link mechanism  130 , a terminal  140 , a movable contact  135  and a cam delaying mechanism  150 . 
     Here, the plate  100  may be provided in pair to be spaced apart from each other.  FIGS. 1 and 2  show one plate  100  in a separated state. Here, the closing spring  105  may be disposed, having one end portion rotatably coupled to a lower portion of the plate  100 . A rotatable circular plate  102  rotatably coupled to the plate  100  may be coupled to a left end of the closing spring  105 , and the cam  103  rotatably coupled to the driving lever  110  may be disposed at a right end of the closing spring  105 . 
     Referring to  FIG. 1 , the driving lever  110  may have an upper portion rotatably installed at the plate  100  and be connected to a right end portion of the closing spring  105 . The driving lever  110  may be configured to be rotated in a clockwise direction in a state of the closing spring  105  being compressed and rotated in a counterclockwise direction in a state of the same being extended. 
     Also, the cam  115  which presses the driving lever  110  for rotation may be rotatably installed at the plate  110 . The cam  115  may be rotated in a clockwise is direction by an external force so as to press a bearing  112  installed at a left upper portion of the driving lever  110 . As a rotational radius of the cam  115  contacted by the bearing  112  is increased, the bearing  112  is pushed up such that the driving lever  110  can be rotated in the clockwise direction. 
     Referring to  FIG. 2 , the supplementary cam  120  may be connected to the cam  115 . The supplementary cam  120  may be installed at the same rotational shaft as that of the cam  115  so as to be cooperatively rotated with the cam  115  and formed to have a rotational radius greater than that of the cam  115 . The supplementary cam  120  may physically cooperate with a display on which a compressed state and an extended state of the closing spring  105  are visibly displayed. 
     Referring to  FIGS. 1 and 5 , the link mechanism may be provided with a plurality of links rotatably installed at the plate  100  by toggle pins  131  and toggled in a connected state with the driving lever  110 . The link mechanism  130  may include three links  130   a ,  130   b  and  130   c  cooperative with the driving lever  110 . During a charging operation, the driving lever  110  is rotated clockwise and accordingly the closing spring  104  is compressed, thereby securing one link  130   a . The other two links  130   b  and  130   c  may be rotated toward the secured one link  130   a  when the driving lever  110  is rotated counterclockwise by extension of the compressed closing spring  105  upon a closing operation. Accordingly, a leg  132  connected to the movable contact  135  is allowed to be rotated in a clockwise direction. The link mechanism  130  is a known component of an air circuit breaker, so its detailed configuration and operation will not be explained. 
     The movable contact  135  which is rotated toward the terminal  140  by the leg  132  cooperative with the link mechanism  130  may be rotatably disposed at a side of the plate  100 . When the movable contact  135  is rotated counterclockwise responsive to extension of the closing spring  105  which was in the compressed (charged) state, the movable contact  135  cooperates with the link mechanism  130  to be in contact with the terminal  140 . Also, the leg  132  is rotated in the counterclockwise direction by the tensile force of the opening spring  133  such that the movable contact  135  is separated from the terminal  140 . The separation of the movable contact  135  from the terminal  140  may allow cut-off of power applied to a load side. 
     When the closing spring  105  is extended from the compressed state, the cam  115  is rotated in the clockwise direction by the bearing  112  of the driving lever  110  so as to be returned to a state just before the charging operation. Here, the cam  115  should be rotated until before it passes over the closing spring  105  by pressurization of the bearing  112  due to the extension of the closing spring  105 . If the closing spring  105  applies an excessive elastic force, the cam  115  is rotated over 180°. Accordingly, the cam may be rotated until supporting the bearing  112  of the driving lever  110  by the portion having the shortest rotational radius. In a state where the bearing  112  of the driving leer  110  is interfered with the clockwise rotation of the cam  115 , the driving lever  110  cannot be rotated in the counterclockwise direction any more, and thereby cannot be returned to its original location. 
     Hence, a configuration of delaying a rotating speed of the cam  115  when the cam  115  is rotated responsive to the extension of the closing spring  105  is needed. Here, it may also be possible to directly control the rotating speed of the cam  115 . The rotating speed of the cam  115  can be controlled to be delayed by reducing the rotating speed of the supplementary cam  120  coupled to the cam  115 . That is, the cam delaying mechanism  150  may be installed at an upper side of the supplementary cam  120 . The cam delaying mechanism  150  may contact the supplementary cam  120  so as to delay the rotating speed of the supplementary cam  120  at a rotation interval in which the cam  115  is returned. 
     Here, referring to  FIGS. 2 to 4 , the cam delaying mechanism  150  may be rotatably installed at the plate  100 , and include a delay link  151  contacted by the supplementary cam  120 , a rotation pin  153  inserted into the delay link  151  to be coupled to the plate  100  and allowing the rotation of the delay link  151 , and a delay spring  154  installed between the delay link  151  and the plate  100  for elastically supporting the rotation of the delay link  151 . The rotation pin  153  may be inserted into a right side of the delay link  151  to be coupled to the plate  100 , and the delay link  151  may be rotatable in the coupled state with the rotation pin  151 . Here, the delay link  151  may include an accommodation groove  151   a , and the delay spring  154  may include a first stopper  154   a  locked at the accommodation groove  151   a  and a second stopper  154   b  locked at the plate  100 . 
     Still referring to  FIGS. 2 and 4 , the clockwise rotation of the delay link  151  may be supported by the delay spring  154 . The delay link  151  may include a supporting portion  152  protruded to be inserted into an outer circumferential portion of the supplementary cam  120 . An end portion of the supporting portion  152  may be formed to be round, which facilitates a slidable movement at the inserted portion of the supplementary cam  120 . 
     Still referring to  FIGS. 2 and 3 , the supplementary cam  120  may include a contact groove  121  in which the supporting portion  152  of the delay link  151  is detachably inserted and formed to be supported by the supporting portion  152 . When the supplementary cam  120  is rotated, because the supporting potion  152  of the delay link  151  is in an inserted state in the contact groove  121 , the rotation of the supplementary cam  120  may be suspended by the delay link  151 . The rotating speed of the supplementary cam  120  is reduced until the supporting portion  152  is slid out of the contact groove  121  up to an outer circumferential portion of the contact groove  121 . 
     That is, the rotation of the supplementary can  120  is delayed within an interval from the supporting portion  152  being moved along an internal surface of the contact groove  121  up to reaching an outer circumferential surface of the contact groove  121 . The delay link  151  may function to obstruct the rotation of the cam  115  so as to prevent an excessive rotation of the cam  115  when the driving lever  110  is rotated by an initial tensile force of the closing spring  105 . Also, tilt surfaces configuring the contact groove  121  may be formed such that a tilt surface at the side of a guide surface  122  of the contact groove  121  is more sharply inclined. Here, the guide surface  122  formed at an upper portion of the contact groove  121  may ensure a smooth movement of the supporting portion  152  to the outer circumferential portion of the cam  115 . 
     In the meantime, the supplementary cam  120  may be installed at both sides of the rotational shaft  125 . The supplementary cam  120  may be provided with coupling holes  123  to which the cam  115  is coupled. The coupling holes  123  may be formed along a central portion of the cam  115 . The cam  115  may be provided with insertion protrusions  116  inserted into the coupling holes  123 . The cam  115  and the supplementary cam  120  may be firmly coupled by the insertion protrusions  116  and the coupling holes  123  disposed conformable to the shape of the cam  115 , thus to endure the pressure applied by the bearing  112  of the driving lever  110 . 
     As such, the rotation of the supplementary cam  112  can be delayed by the delay link  151  supported at the contact groove  121  of the supplementary cam  120 , and the rotation of the cam  115  coupled to the supplementary cam  120  can be cooperatively delayed. 
       FIG. 6  is an internal front view of a circuit breaker having a cam rotation delaying function in accordance with another embodiment of the present invention, and  FIG. 7  is a sectional view of a damper of  FIG. 6 . 
     As shown in  FIG. 6 , a circuit breaker having a cam rotation delaying function in accordance with another embodiment of the present invention, which executes a closing operation and a charging operation, may include a plate  100 , a closing spring  105 , a driving lever  110 , a cam  115 , a supplementary cam  120 , a link mechanism  130 , a terminal  140 , a movable contact  135  and a damper  155  for attenuating an excessive extension of the closing spring  105 , which is further provided compared to the previous embodiment. Here, the plate  100 , the closing spring  105 , the driving lever  110 , the cam  115 , the supplementary cam  120 , the link mechanism  130 , the terminal  140 , the movable contact  135  are the same components to those in the previous embodiment, so the detailed description thereof will be omitted. 
     Here, the damper  155  may be configured to provide a weak damping force when the closing spring  105  is compressed and a strong damping force when the closing spring  105  is extended, thus attenuating a drastic extending speed of the closing spring  105 . For example, the damper  155  may be considered to be similar to a door damper which is installed at a door in a link structure so as to allow a rapid opening of the door and slow closing thereof. 
     Referring to  FIG. 7 , the damper  155  may be configured by including dual is pipes  156  disposed within the closing spring  105  and slidably coupled to each other to be contracted and extended, and a damping spring  157  disposed between the dual pipes  156  and compressed responsive to extension of the dual pipes  156 . That is, when the closing spring  105  is extended, the dual pipes  156  are extended and accordingly the damping spring  157  disposed between the dual pipes  156  is compressed. Hence, the extending speed of the closing spring  105  is reduced and the rotating speed of the driving lever  110  in a counterclockwise direction is also reduced. Cooperatively, an excessive rotating speed of the cam  115  due to the rotation of the link member  130  connected to the driving lever  110  can be reduced. Consequently, the rotation of the cam  115  as excessive as interfering with the rotation of the driving lever  110  can be prevented. 
     Also, the damper  155  may be configured as a damper in a cylinder type which is disposed outside or inside the closing spring  105  along the closing spring  105  and contains fluid for damping. 
     In the circuit breaker having the cam rotation delaying function in accordance with the one embodiment of the present invention, the cam delaying mechanism for delaying a returning rotation of the supplementary cam is provided at the circumferential surface of the supplementary cam, which is configured to be rotated with the cam, so as to prevent an excessive rotation of the cam, thereby allowing the stable and complete toggling operation of the link mechanism and the smooth returning of the closing spring, resulting in ensuring more stable operation of the circuit breaker. 
     The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present disclosure. The present teachings can be readily applied to other types of apparatuses. This description is intended is to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments. 
     As the present features may be embodied in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.