Patent Publication Number: US-9887054-B2

Title: Electromagnetic contactor having snap-fit section coupling frames

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application filed under 35 U.S.C. § 111(a), of International Application PCT/JP2015/001949, filed Apr. 7, 2015, and claims foreign priority benefit to Japanese Patent Application No. 2014-104751, filed May 20, 2014, the contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an electromagnetic contactor in which a first frame in which an operation electromagnet is mounted and a second frame in which a contact mechanism is mounted are coupled to each other. 
     BACKGROUND ART 
     As an electromagnetic contactor of such a type, electromagnetic contactors disclosed in PTLs 1 and 2 have been proposed. An electromagnetic contactor disclosed in PTL 1 is configured to couple, by a bolt, a first frame serving as a lower frame into which a fixed core, an operation coil, and so on, of an operation electromagnet are incorporated to a second frame serving as an upper frame into which a contact mechanism, a contact support, a movable core of the operation electromagnet, and so on, are incorporated. 
     An electromagnetic contactor disclosed in PTL 2 is configured to provide a joining section between a first frame serving as a lower frame that contains a fixed core and a second frame serving as an upper frame that contains a movable core, fixed contacts, and movable contacts with a clamp wire spring to couple the first frame to the second frame, and to couple the first frame to the second frame by the clamp wire spring. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: JP 2006-216437 A 
         PTL 2: JP 2009-009813 A 
       
    
     SUMMARY 
     Technical Problem 
     However, in the electromagnetic contactors disclosed in the above-described PTLs 1 and 2, the first frame serving as a lower frame and the second frame serving as an upper frame are coupled by bolting or by using a clamp wire spring. 
     Therefore, although the first frame and the second frame can be fixed to each other firmly by a bolt or a clamp wire spring, use of a bolt or a clamp wire spring is required for the coupling of the first frame and the second frame, which causes an unsolved problem of an increase in the number of components. 
     Recently, first frames and second frames of electromagnetic contactors have been formed by injection-molding fiber-reinforced thermoplastic resin, which is reinforced by glass fiber or the like, and coupling a first frame to a second frame in a snap-fit manner has been conceived. 
     However, it is difficult to secure toughness of fiber-reinforced thermoplastic resin, and wear of a snap-fit section progresses due to vibration produced in changing an operation electromagnet into a released state by switching the operation electromagnet from an excited state to a non-excited state to separate movable contacts from fixed contacts of the electromagnetic contactor itself and, thus, looseness is produced to the snap-fit section, which causes another unsolved problem of being unable to secure durability. 
     Accordingly, the present invention is made by focusing on the above-described unsolved problems in the conventional examples, and an object of the present invention is to provide an electromagnetic contactor that is capable of suppressing looseness due to wear of a snap-fit section coupling a first frame to a second frame from being produced. 
     Solution to Problem 
     In order to achieve the object mentioned above, according to an aspect of the present invention, there is provided an electromagnetic contactor, including: a first frame in which an operation electromagnet is mounted; a second frame in which a contact mechanism is mounted; and a snap-fit section that is made up of a fitting protruding section and a hook section formed to one and the other of the first frame and the second frame, respectively, the hook section fitting to the fitting protruding section. The hook section has a flexible projecting plate section formed in a projecting manner to an open end of either the first frame or the second frame and a fitting section formed at a tip of the flexible projecting plate section, the fitting section fitting to the fitting protruding section. The flexible projecting plate section is provided with elasticity that fits the fitting section further to a base side of the fitting protruding section in accordance with progress of wear between the fitting section and the fitting protruding section. 
     Advantageous Effects of Invention 
     According to the present invention, even when wear progresses between a fitting section of a hook section and a fitting protrusion, which forms a snap-fit section that couples a first frame in which an operation electromagnet is mounted to a second frame in which a contact mechanism is mounted, it is possible to maintain a fitting state between the fitting section of the hook section and the fitting protruding section, and to improve durability in the case of coupling the first frame to the second frame in a snap-fit manner. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an external perspective view illustrating an electromagnetic contactor according to the present invention; 
         FIG. 2  is a front view of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along the line III-III in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view taken along the line IV-IV in  FIG. 2 ; 
         FIG. 5  is an exploded perspective view illustrating a state in which a first frame and a second frame are separated from each other; 
         FIGS. 6A, 6B, and 6C  are a front view, a side view, and a plan view of the first frame, respectively; 
         FIGS. 7A, 7B, and 7C  are a plan view, a side view, and a rear view of the second frame, respectively; and 
         FIGS. 8A to 8D  are enlarged cross-sectional views illustrating a snap-fit section. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 
     As illustrated in  FIG. 1 , an electromagnetic contactor  10  according to the present invention is made up of a first frame  11 A and a second frame  11 B coupled to each other, both of which are formed by, for example, injection-molding fiber-reinforced thermoplastic resin, with which glass fibers or the like are mixed. 
     In the first frame  11 A, an operation electromagnet  12  that is made up of, for example, an AC electromagnet is mounted, as illustrated in  FIGS. 3 and 4 . In the second frame  11 B, a contact mechanism  13  that is on/off-driven by the operation electromagnet  12  is mounted, as illustrated in  FIGS. 3 and 4 . 
     The first frame  11 A has a bottomed angular cylindrical section  21  that houses the operation electromagnet  12 . As illustrated in  FIG. 6A  when viewed from the front, the bottomed angular cylindrical section  21  is made up of a wide width section  21   a  in the middle and narrow width sections  21   b  and  21   c  that are formed to one pair of opposing side walls, for example, the upper and lower side walls, of the wide width section  21   a  in a line-symmetric manner with respect to the vertical center line of the wide width section  21   a  so as to be continuous with the wide width section  21   a . On the bottom between the narrow width section  21   b  and the narrow width section  21   c  that sandwich the wide width section  21   a , an E-shaped fixed core  22  is mounted with protruding sections  22   a  to  22   c  facing the front and a coupling section  22   d  contacting the bottom. 
     To the middle protruding section  22   b  of the fixed core  22 , a spool  23  around which an excitation coil  23   a  is wound is mounted, as illustrated in  FIGS. 4 and 6A to 6C . To the spool  23 , coil terminals  25 , which are fixed to a terminal block  24  that protrudes outward from one narrow width section  21   b  of the first frame  11 A, are formed in one body. 
     To both end sections on the narrow width sections  21   b  and  21   c  sides of the front ends of the other pair of opposing side walls, for example, the right and left side walls, of the wide width sections  21   a  of the first frame  11 A, for example, four hook sections  26  that extend to the front are formed, as illustrated in  FIGS. 3 and 4 . 
     Each hook section  26  is made up of a flexible projecting plate section  26   a  that extends from the front end of the wide width section  21   a  to the front, has flexibility, and has a relatively wide width and a fitting section  26   b  formed to the inner side of the tip portion of the flexible projecting plate section  26   a , as illustrated in an enlarged manner in  FIG. 8A . 
     Each fitting section  26   b  is formed into a cross-sectional trapezoidal shape with an inclined surface  26   c  that increases in thickness along the direction from the front end of the flexible projecting plate section  26   a  toward the rear side, that is, the base side of the flexible projecting plate section  26   a , a level surface  26   d  that extends rearward slightly from the rear end of the inclined surface  26   c , a fitting surface  26   e  that extends from the rear end of the level surface  26   d  toward the flexible projecting plate section  26   a  in the direction orthogonal to the flexible projecting plate section  26   a  to approximately half the thickness of the fitting section  26   b , and a circular arc surface  26   f  that is made up of a round chamfer continuously connected to the outer side of the fitting surface  26   e.    
     Each hook section  26  is formed integrally with the open end face of the first frame  11 A in injection-molding fiber-reinforced thermoplastic resin, and the thickness of the flexible projecting plate section  26   a  being thin causes the flexible projecting plate section  26   a  to extend in an inwardly inclined manner due to residual stress after injection molding. 
     Therefore, to fit a hook section  26  to a fitting protruding section  36  as described later, the hook section  26  is fitted to the fitting protruding section  36  with the flexible projecting plate section  26   a  thereof being bent outward. Thus, elasticity that biases the fitting section  26   b  to the base side of the fitting protruding section  36  is provided to the flexible projecting plate section  26   a.    
     To the four corners of the bottom of the bottomed angular cylindrical section  21  of the first frame  11 A, mounting plate sections  27  each of which has a mounting hole are formed. 
     The second frame  11 B includes an angular cylinder section  30  the shape of which on the coupling section side at which the second frame  11 B is coupled to the first frame  11 A is identical to the shape of the bottomed angular cylindrical section  21  of the first frame  11 A, as illustrated in  FIGS. 7A to 7C . The angular cylinder section  30  has, as with the bottomed angular cylindrical section  21 , a wide width section  31   a  and narrow width sections  31   b  and  31   c  that are continuous with the wide width section  31   a.    
     The angular cylinder section  30  also has opposing side face plate sections  30   a  and  30   b  with which the narrow width sections  31   b  and  31   c  are not continuous and that extend to the opposite side to the coupling section side, as illustrated in  FIG. 5 . Middle sections of the extension end sections of the opposing side face plate sections  30   a  and  30   b  are bridged by coupling plate sections  30   c . On the upper side of the coupling plate sections  30   c , a plurality of, for example, three partition walls  31  that partition the interspace between the opposing side faceplate sections  30   a  and  30   b  into parallel subspaces are formed, and main circuit power supply side terminal sections  32   a  and an auxiliary terminal section  33   a  are mounted in the subspaces. 
     On the upper side of the coupling plate sections  30   c,  a plurality of, for example, three partition walls  34  that partition the interspace between the opposing side faceplate sections  30   a  and  30   b  into parallel subspaces are formed, and main circuit load side terminal sections  32   b  and an auxiliary terminal section  33   b  are mounted in the subspaces. 
     Further, to the opposing side face plate sections  30   a  and  30   b , recessed sections  35  that open the side faces from the lower end side are formed at four locations opposed to the hook sections  26  of the first frame  11 A, and, on the lower end side of the base of each recessed section  35 , a fitting protruding section  36  to which the fitting section  26   b  of a corresponding hook section  26  formed to the first frame  11 A is fitted from the outer side is formed. 
     Each recessed section  35  has a tool insertion space section  35   a  formed on the front end side thereof when the fitting section  26   b  of a hook section  26  is locked to a fitting protruding section  36 , as illustrated in  FIGS. 8A to 8D . By using a flat-blade screwdriver inserted into the tool insertion space section  35   a , the locking state between the fitting section  26   b  of the hook section  26  and the fitting protruding section  36  can be released. 
     Each fitting protruding section  36  includes a rear end surface  36   a  that is flush with the rear end surface of a recessed section  35 , an inclined surface  36   b  that is formed in such a way as to gradually increase in thickness outward along the direction from the outer end of the rear end surface  36   a  toward the front, a level surface  36   c  that extends from the outer side end section of the inclined surface  36   b  to the front, and a fitting surface  36   d  that extends from the front end of the level surface  36   c  toward the base side of the recessed section  35 , as illustrated in an enlarged manner in  FIG. 8A . 
     A snap-fit section  37  is made up of a hook section  26  formed to the first frame  11 A and a fitting protruding section  36  formed to the second frame  11 B. 
     An arc-extinguishing chamber  38  is formed behind the coupling plate sections  30   c , and, inside the arc-extinguishing chamber  38 , a contact support  39  that holds movable contacts  39   a  is held slidably in the front and rear direction. To the rear face side of the contact support  39 , a movable core  40  that is opposed to the fixed core  22  is coupled by a coupling spring  40   a , as illustrated in  FIG. 3 , and, between the movable core  40  and the spool  23  of the first frame  11 A, a not-illustrated return spring is arranged. 
     In addition, an arc-extinguishing cover  41  is arranged so as to cover the upper face, the front face, and the lower face of the coupling plate section  30   c.    
     The first frame  11 A and the second frame  11 B are coupled into one body with the hook sections  26  of the first frame  11 A being fitted to the fitting protruding sections  36  of the second frame  11 B, as illustrated in  FIG. 8C . 
     When the first frame  11 A is coupled to the second frame  11 B, the hook sections  26  formed to the first frame  11 A are made to face the fitting protruding sections  36  formed to the second frame  11 B in such a way that the coil terminal  25  protruding from the first frame  11 A faces the main circuit power supply side terminal sections  32   a  and the auxiliary terminal section  33   a  of the second frame  11 B. 
     When each hook section  26  is in a free state in which the hook section  26  is not fitted to a corresponding fitting protruding sections  36  of the second frame  11 B, the flexible projecting plate section  26   a  thereof extends in an inwardly inclined manner at a predetermined angle due to residual stress in injection molding, as illustrated in  FIG. 8A . When in this state, the inclined surface  26   c  of each fitting section  26   b  faces the ridgeline between the rear end surface  36   a  and the inclined surface  36   b  of a corresponding fitting protruding section  36  of the second frame  11 B. 
     It is now assumed temporarily that, when the first frame  11 A and the second frame  11 B are coupled to each other by the hook sections  26  being fitted to the fitting protruding sections  36 , there is no interference between the fitting sections  26   b  of the hook sections  26  and the fitting protruding sections  36 . In this case, it is set so that, to cause the flexible projecting plate section  26   a  of each hook section  26  to be flush with side faces of the first frame  11 A and the second frame  11 B, the ridgeline between level surface  36   c  and the fitting surface  36   d  of the fitting protruding section  36  is located at a position inside the fitting section  26   b  anterior to the circular arc surface  26   f  continuously connected to the fitting surface  26   e  of each hook section  26 , as illustrated in  FIG. 8B . 
     Moving the second frame  11 B toward the first frame  11 A side with each hook section  26  facing a corresponding fitting protruding section  36  causes the inclined surface  26   c  of each hook section  26  to contact the ridgeline between the rear end surface  36   a  and the inclined surface  36   b  of a corresponding fitting protruding section  36 . Further moving the second frame  11 B toward the first frame  11 A side causes the ridgeline between the inclined surface  26   c  and the level surface  26   d  of each hook section  26  to contact the inclined surface  36   b  of a corresponding fitting protruding section  36  to cause the flexible projecting plate section  26   a  of the hook section  26  to be bent outward. 
     Thereafter, the level surface  26   d  of each hook section  26  is engaged with the level surface  36   c  of a corresponding fitting protruding section  36 , and the fitting surface  26   e  of the hook section  26  is locked to the fitting surface  36   d  of the fitting protruding section  36 . At this time, when in a state in which no wear has occurred to the fitting surface  36   d  of each fitting protruding section  36 , the first frame  11 A and the second frame  11 B are coupled to each other with the boundary position between the fitting surface  26   e  and the circular arc surface  26   f  of each hook section  26  contacting the ridgeline between the level surface  36   c  and the fitting surface  36   d  of a corresponding fitting protruding section  36  and the flexible projecting plate section  26   a , for example, being bent outward, as illustrated in  FIG. 8C . 
     However, when the electromagnetic contactor  10  is operated while the hook sections  26  are in a state of being fitted to the fitting protruding sections  36  as illustrated in  FIG. 8C , in the case in which the excitation coil  23   a  of the operation electromagnet  12  is in a non-conducting state and thus the operation electromagnet  12  is in a non-excited state, the movable core  40  is biased to the front by the not-illustrated return spring. When in this state, the electromagnetic contactor  10  is in a released state, that is, a state in which the movable contacts  39   a  supported by the contact support  39  are separated from fixed contacts. 
     When the electromagnetic contactor  10  is in the released state, supplying AC power to the excitation coil  23   a  of the operation electromagnet  12  to change the operation electromagnet  12  into an excited state causes the movable core  40  to be attracted to the fixed core  22  against the return spring. Thus, the movable contacts  39   a  supported by the contact support  39 , which is connected to the movable core  40  by the coupling spring  40   a , contact the fixed contacts to electrically connect the main circuit power supply side terminal sections  32   a  and the auxiliary terminal section  33   a  to the main circuit load side terminal sections  32   b  and the auxiliary terminal section  33   b , respectively, causing the electromagnetic contactor  10  to be brought to a conducting state. 
     When in the conducting state, breaking the AC power supply to the excitation coil  23   a  of the operation electromagnet  12  causes attractive force by the fixed core  22  to disappear to cause the movable core  40  to be returned to a released position in front by the return spring. On this occasion, vibration is generated due to the movable core  40  being returned to the released position by the return spring, and the vibration being transmitted to the first frame  11 A and the second frame  11 B causes wear to be produced to a contact section at which the fitting surface  26   e  and circular arc surface  26   f  of each hook section  26  contact the fitting surface  36   d  of a corresponding fitting protruding section  36 , which is a coupling section of the first frame  11 A and the second frame  11 B. 
     The conducting state and the released state being repeated causes wear between the fitting surface  26   e  and circular arc surface  26   f  of each hook section  26  and the fitting surface  36   d  of a corresponding fitting protruding section  36  to progress. 
     The wear is produced to a ridgeline section between the level surface  36   c  and the fitting surface  36   d  of each fitting protruding section  36  substantially, and the ridgeline section becomes a circular arc surface that gradually increases in radius due to wear. In this case, since the flexible projecting plate section  26   a  of each hook section  26  originally extends in an inwardly inclined manner and is caused to be bent, as illustrated in  FIG. 8A , the flexible projecting plate section  26   a  of each hook section  26  becomes bent inward by elastic force of the flexible projecting plate section  26   a  as wear progresses, causing the outer side surface of the flexible projecting plate section  26   a  to become flush with side faces of the first frame  11 A and the second frame  11 B, as illustrated in  FIG. 8B . 
     As wear between each hook section  26  and a corresponding fitting protruding section  36  further progresses, the flexible projecting plate section  26   a  of the hook section  26  is brought to a state of being inclined, as illustrated in  FIG. 8D . When in this state, a ridgeline section between the inclined surface  26   c  and level surface  26   d  of each fitting section  26   b  is brought to a state of contacting the bottom of a corresponding recessed section  35 , causing a further inclination of the flexible projecting plate section  26   a  to be restricted. 
     As described above, even when wear between each hook section  26  and a corresponding fitting protruding section  36  progresses, the flexible projecting plate section  26   a  becomes inclined in accordance with the wear by elastic force caused by bending of the flexible projecting plate section  26   a  of the hook section  26 , causing the fitting section  26   b  of the hook section  26  to contact a position further on the base side of the fitting protruding section  36 . Therefore, it is possible to suppress a gap from being produced between the fitting surface  26   e  and circular arc surface  26   f  of each hook section  26  and the ridgeline section between the level surface  36   c  and the fitting surface  36   d  of a corresponding fitting protruding section  36 . 
     Therefore, even when a snap-fit connection is applied to the coupling of the first frame  11 A to the second frame  11 B, it is possible to surely suppress a coupling state between the first frame  11 A and the second frame  11 B from changing due to long-time use. Thus, it is possible to suppress occurrences of vibration sound that is produced between the first frame  11 A and the second frame  11 B when the electromagnetic contactor  10  is switched to the released state. 
     As a result, the durability of the electromagnetic contactor  10  can be improved, and, without a clamp wire spring or a bolt to coupling the first frame  11 A to the second frame  11 B being provided as in the afore-described conventional example, it is possible to securely couple the first frame  11 A to the second frame  11 B by the snap-fit sections, making it possible to decrease the number of components and to reduce the production cost of electromagnetic contactors. 
     In addition, since inclination due to residual stress after injection molding of fiber-reinforced thermoplastic resin is used to incline the flexible projecting plate section  26   a  of each hook section  26  inward, no special design is required to incline the flexible projecting plate section  26   a ,  and neither is it required to design a shape that suppresses an inclination of the flexible projecting plate section  26   a  due to residual stress. 
     In the above-described embodiment, a case in which, when in a state in which no wear is produced, the flexible projecting plate section  26   a  is in a state of being bent outward, as illustrated in  FIG. 8C , was described. However, the present invention is not limited to the above-described case, and it may be configured so that, when in a state in which no wear is caused, the outer side surface of each flexible projecting plate section  26   a  is in a state of being flush with side faces of the first frame  11 A and the second frame  11 B, as illustrated in  FIG. 8B , and, alternatively, it may be configured so that the flexible projecting plate section  26   a  is positioned slightly on the inside of side faces of the first frame  11 A and the second frame  11 B. The essential thing is that the flexible projecting plate section  26   a  may be in a state of being bent outward. 
     Although, in the above-described embodiment, a case in which an AC electromagnet is used as the operation electromagnet  12  was described, the present invention is not limited to the case, and a non-polarized DC electromagnet or a polarized DC electromagnet can also be used. In such a case, a plunger may be coupled to the contact support  39  by a coupling spring. 
     In the above-described embodiment, a case in which the hook sections  26  and the fitting protruding sections  36  are formed to the first frame  11 A and the second frame  11 B, respectively, was described. However, the present invention is not limited to the above-described configuration, and the fitting protruding sections  36  and the hook sections  26  may be formed to the first frame  11 A and the second frame  11 B, respectively. 
     The number of arranged pairs of a hook section  26  and a fitting protruding section  36  is not limited to four pairs, and an arbitrary number of pairs, such as three pairs and five or more pairs, may be arranged. 
     Furthermore, although, in the above-described embodiment, a case in which an AC electromagnet is used as the operation electromagnet  12  was described, the present invention is not limited to the case, and a non-polarized DC electromagnet or a polarized DC electromagnet can also be used. In such a case, a plunger may be coupled to the contact support  39  by a coupling spring. 
     In the above-described embodiment, a case in which the hook sections  26  and the fitting protruding sections  36  are formed to the first frame  11 A and the second frame  11 B, respectively, was described. However, the present invention is not limited to the above-described configuration, and the fitting protruding sections  36  and the hook sections  26  may be formed to the first frame  11 A and the second frame  11 B, respectively. 
     The number of arranged pairs of a hook section  26  and a fitting protruding section  36  is not limited to four pairs, and an arbitrary number of pairs, such as three pairs and five or more pairs, may be arranged. 
     REFERENCE SIGNS LIST 
       10  Electromagnetic contactor 
       11 A First frame 
       11 B Second frame 
       12  Operation electromagnet 
       13  Contact mechanism 
       21  Bottomed angular cylindrical section 
       22  Fixed core 
       23  Spool 
       25  Coil terminal 
       26  Hook section 
       26   a  Flexible projecting plate section 
       26   b  Fitting section 
       26   c  Inclined surface 
       26   d  Level surface 
       26   e  Fitting surface 
       26   f  Circular arc surface 
       30  Angular cylinder section 
       32   a  Main circuit power supply side terminal section 
       32   b  Main circuit load side terminal section 
       33   a ,  33   b  Auxiliary terminal section 
       35  Recessed section 
       36  Fitting protruding section 
       36   a  Rear end surface 
       36   b  Inclined surface 
       36   c  Level surface 
       36   d  Fitting surface 
       37  Snap-fit section 
       39  Contact support 
       40  Movable core