Abstract:
An electromagnetic relay having superior visibility and a light-emitting device easy to mount. A coil block and a contact opening and closing mechanism are disposed on a base plate and covered with a case, and the electromagnetic relay magnetizes and demagnetizes the coil block via coil terminals to turn a movable core and moves a movable contact part to open and close a contact. Electrical connection portions of the coil terminals are projected upwardly through the top side of the case. A light-emitting device which emits light by the energization of the coil terminals and a holder which holds the light-emitting device are disposed on the top side of the case on the side opposite to a position where the electrical connection portions of the coil terminals of the case are projected. Lead wires connected to the light-emitting device are electrically connected to the electrical connection portions of the coil terminals.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an electromagnetic relay.  
           [0003]    2. Description of the Related Art  
           [0004]    There is a related art electromagnetic relay in which an operation display device (light-emitting device) made of a luminescent resin is integrally provided in a casing (refer to, for example, Patent Document 1).  
           [0005]    There is another related art electromagnetic relay in which an operation display LED (light-emitting device) is previously disposed at a terminal and is formed into a coil block integrally with predetermined members to facilitate the positioning and fixation of the LED (refer to, for example, Patent Document 2).  
           [0006]    Patent Document 1 is JP-A-10-125195.  
           [0007]    Patent Document 2 is JP-A-10-208600.  
         SUMMARY OF THE INVENTION  
         [0008]    However, in the construction of either of the above-mentioned electromagnetic relays, the light-emitting device is disposed in an internal space covered with the case. For this reason, the case is formed of a material having optical transmission characteristics, but has a problem in terms of visibility from the outside. There is also the problem that the light-emitting device needs to be fixed in a limited space within the internal space and the fixed state of the light-emitting device lacks stability. Furthermore, in the case where the light-emitting device is mounted on a printed circuit board, glass dust produced from the printed circuit board may also become a cause which brings about contact failure of contacts and the like.  
           [0009]    The invention provides, therefore, an electromagnetic relay which is superior in visibility and is provided with a light-emitting device easy to mount.  
           [0010]    To solve the above-mentioned problem, the invention provides an electromagnetic relay provided with a coil block and a contact opening and closing mechanism which are disposed on a base plate and covered with a case, and operative to magnetize and demagnetize the coil block to turn a movable core and move a movable contact part to open and close a contact. The electromagnetic relay includes a light-emitting device which emits light during magnetization of the coil block, and a holder which holds the light-emitting device, the light-emitting device and the holder being disposed on a top side of the case.  
           [0011]    According to this construction, it is possible to mount the light-emitting device after the fitting of the case, whereby it is possible to easily perform the work of mounting the light-emitting device. It is also possible to improve the visibility of the light-emitting device by exposing the same.  
           [0012]    The case preferably includes an engagement part which is elastically deformed while the holder is being mounted, and is restored to its original shape after the holder has been mounted, and the engagement part preferably has a top end portion where an engagement claw to engage with a top edge portion of the holder is formed, whereby the work of mounting the holder can be easily performed.  
           [0013]    The case is preferably molded from a resin and has engagement holes with which engagement projections provided on the base plate are respectively brought into engagement, and the engagement claw of the engagement part is preferably able to be formed with a slide mold which forms the engagement holes, whereby the electromagnetic relay can be inexpensively fabricated.  
           [0014]    The holder preferably includes a holder body which holds the light-emitting device, an operating portion which moves the movable core by directly pressing the movable core through a depressing operation of the operating portion, and elastic arm portions which connect the holder body and the operating portion and are elastically deformed by the depressing operation of the operating portion, because the electromagnetic relay can be provided with not only the function of holding the light-emitting device but also a movement confirming function, whereby the electromagnetic relay can be simplified in construction and can be improved in assembling work.  
           [0015]    The electromagnetic relay preferably further includes an indicator to be driven with a turning movement of the movable core, and a display guide portion which provides a space in which the indicator can move is preferably disposed to project from a central portion of the top side of the case, the holder body of the holder being positioned between the engagement part and the display guide portion, whereby the electromagnetic relay can be designed to have a compact construction from which an unnecessary space is excluded. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The invention will become more readily appreciated and understood from the following detailed description of preferred embodiments of the invention when taken in conjunction with the accompanying drawings, in which:  
         [0017]    [0017]FIG. 1 is a perspective view of an electromagnetic relay according to a preferred embodiment of the invention;  
         [0018]    [0018]FIG. 2 is a perspective view of a state in which the cover shown in FIG. 1 is removed;  
         [0019]    [0019]FIG. 3 is a perspective view showing a state in which a case is removed from the state shown in FIG. 2;  
         [0020]    [0020]FIG. 4 is a cross-sectional view of FIG. 1;  
         [0021]    [0021]FIG. 5 is an exploded perspective view of a base plate and a contact opening and closing mechanism;  
         [0022]    [0022]FIG. 6 is a perspective view of an indicator;  
         [0023]    [0023]FIG. 7 is a perspective view of a card;  
         [0024]    [0024]FIG. 8 is a perspective view of a coil block and a movable core;  
         [0025]    [0025]FIG. 9A is a perspective view of an LED holder;  
         [0026]    [0026]FIG. 9B is a perspective view of an LED;  
         [0027]    [0027]FIG. 10A is a bottom view of the LED holder;  
         [0028]    [0028]FIG. 10B is a cross-sectional view taken along line A-A of FIG. 10A;  
         [0029]    [0029]FIG. 10C is a cross-sectional view taken along line B-B of FIG. 10C;  
         [0030]    [0030]FIG. 11 is an exploded perspective view of a cover.  
         [0031]    [0031]FIG. 12A is a top plan view of the cover;  
         [0032]    [0032]FIG. 12B is a bottom plan view of the cover;  
         [0033]    [0033]FIG. 12C is a partial front elevational view showing an internal mechanism;  
         [0034]    [0034]FIGS. 13A to  13 C are views showing the state in which an operating lever is moved to a first opening position;  
         [0035]    [0035]FIGS. 14A to  14 C are views showing the state in which the operating lever is moved to a second opening position;  
         [0036]    [0036]FIG. 15A is a top plan view showing an operating lever according to another preferred embodiment of the invention;  
         [0037]    [0037]FIG. 15B is a front elevational view of the operating lever shown in FIG. 15A;  
         [0038]    [0038]FIG. 16 is an exploded perspective view showing a base block and a contact opening and closing mechanism according to another preferred embodiment of the invention;  
         [0039]    [0039]FIGS. 17A and 17B are perspective views of different cards according to another preferred embodiment of the invention; and  
         [0040]    [0040]FIG. 18 is a perspective view of a cover according to another preferred embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0041]    Preferred embodiments of the invention will be described below in detail with reference to the accompanying drawings.  
         [0042]    FIGS.  1  to  4  show an electromagnetic relay. This electromagnetic relay is generally constructed in such a manner that a coil block  2  and a contact opening and closing mechanism  3  are provided on a base plate  1  and covered with a case  4  and a display block  5  is disposed on the top side of the case  4 .  
         [0043]    As shown in FIGS. 3 and 5, the base plate  1  is sectioned by a first insulating wall  6  into a first area in which the coil block  2  is disposed and a second area in which the contact opening and closing mechanism  3  is disposed. An engagement projection  7  is formed on a side portion of the first insulating wall  6 , and is brought into engagement with an engagement hole  36  (which will be described later) of the case  4  to secure the case  4  to the base plate  1 . The second area is sectioned by a second insulating wall  8  and a third insulating wall  9  into an area in which a first stationary contact part  25  is fixed, an area in which a movable contact part  24  is fixed, and an area in which a second stationary contact part  26  is fixed. A bearing hole  10  is formed in a side portion of the second insulating wall  8 , and an indicator  31  which will be described later is turnably supported by the bearing holes  10 .  
         [0044]    As shown in FIGS. 4 and 8, the coil block  2  has a construction in which a coil  13  is wound around a spool  12  fitted on a core  11 . A horizontal plane portion  14   a  of a yoke  14  which is bent in an approximately L-like shape is fixed to the bottom end portion of the core  11  by caulking. A vertical plane portion  14   b  of the yoke  14  extends upwardly along the wound coil  13 , and a hinge spring  15  is fixed to one side surface of the yoke  14 . A movable core  16  is swingably supported on the top end portion of the vertical plane portion  14   b  of the yoke  14 .  
         [0045]    As shown in FIG. 8, the movable core  16  has a pressure receiving portion  18  which is decreased in width and is extended via a bent portion from an attracted portion  17  to be attracted by an attraction surface  11   a  of the core  11 . A connection portion  19  to be connected to a card  27  which will be described later is formed at one end of the pressure receiving portion  18 . The movable core  16  is pressed at the pressure receiving portion  18  by a pressing part  15   a  of the hinge spring  15 , while when the coil block  2  is in a demagnetized state, the movable core  16  turns so that the attracted portion  17  moves away from the attraction surface  11   a  of the core  11 .  
         [0046]    As shown in FIG. 8, the spool  12  has a top end flange portion  12   a  to which first coil terminals  20  are fixed, and a bottom end flange portion  12   b  to which second coil terminals  21  are fixed. The first coil terminals  20  have bottom end leg portions  22  around which the opposite ends of the coil  13  are to be wound, respectively, while lead wires  54  extending from an LED  50  which will be described later are respectively connected to electrical connection portions  23  on the top end surface of the spool  12 . Each of the electrical connection portions  23  has ridges  23   a  formed to extend vertically in its central portion, so that it is possible to positively establish electrical connection between the respective electrical connection portions  23  and the lead wires  54 .  
         [0047]    As shown in FIG. 4, the coil  13  includes a first coil  13   a  which is wound around the trunk portion of the spool  12  and is connected at opposite ends to the first coil terminals  20 , respectively, and a second coil  13   b  which is wound in the outer circumferential portion of the wound coil  13  and is connected at opposite ends to the second coil terminals  21 , respectively. Accordingly, when a voltage is applied across the second coil terminals  21  to energize the second coil  13   b  wound on the outer circumferential side of the coil  13 , induced electromotive force is generated in the first coil  13   a  on the inner circumferential side of the coil  13  by an electromagnetic induction action, whereby a potential difference can occur between the first coil terminals  20 .  
         [0048]    As shown in FIG. 5, the contact opening and closing mechanism  3  includes the movable contact part  24 , the first stationary contact part  25  and the second stationary contact part  26  which are respectively disposed on the opposite sides of the movable contact part  24 . The movable contact part  24  has a plate-like shape, and a movable contact  24   a  which is exposed on the opposite sides of the top end portion of the movable contact part  24  is integrated with the top end portion, while a terminal portion  25   b  is disposed at the bottom end portion of the movable contact part  24 . A through-hole  24   c  is formed in the movable contact part  24  in the vicinity of the bottom portion of the movable contact  24   a . The first stationary contact part  25  and the second stationary contact part  26  have plate-like shapes, and a first stationary contact  25   a  and a second stationary contact  26   a  with either of which the movable contact  24   a  selectively comes into contact are respectively integrated with the top end portions of the first and second stationary contact parts  25  and  26 . The bottom sides of both stationary contact parts  25  and  26  are respectively bent in crank-like shapes to constitute terminal portions  25   b  and  26   b  which project from the bottom side of the base plate  1 . The top end side of the first stationary contact part  25  has a slit  25   c  formed to extend vertically downwardly from a location near the bottom portion of the first stationary contact  25   a.    
         [0049]    The movable contact part  24  is moved by the card  27  which is engaged with one end portion of the movable core  16 . As shown in FIG. 7, the card  27  has a press-inserting projecting portion  28  in the central portion of its plate-like body, and a projection  28   a  provided at the projecting end of the press-inserting projecting portion  28  is inserted through the through-hole  24   c  of the movable contact part  24 . A rectangular hole  29  is formed in the vicinity of the top side of the press-inserting projecting portion  28 , and the connection portion  19  of the movable core  16  is connected to the rectangular hole  29 . Approximately U-shaped guide receiving portions  30  are respectively formed in the opposite side portions of the card  27 .  
         [0050]    The movement of the movable contact part  24  by the card  27  can be easily confirmed by means of an indicator  31 . As shown in FIG. 6, the indicator  31  has an approximately frame-like shape, and has a display part  32  formed in the center of the top-end joining portion of the indicator  31 . The extending end of the display part  32  is bent approximately at right angles and constitutes a visible portion  33 . Support pins  34  which project in mutually opposite directions are respectively formed at the bottom ends of the opposite side portions of the indicator  31 , and the respective support pins  34  are brought into engagement with the bearing holes  10  of the base plate  1 , whereby the indicator  31  is turnably secured to the bearing holes  10 . Guide projections  35  which project in mutually opposite directions are respectively formed in the centers of the opposite side portions of the indicator  31 , and the respective guide projections  35  are guided by the guide receiving portions  30  of the card  27  so that both the indicator  31  and the card  27  can move integrally. The turning center (the support pins  34 ) of the indicator  31  is positioned on the opposite side to the display part  32  with respect to the pressing position of the card  27 . Accordingly, the amount of movement of the display part  32  can be amplified with respect to the amount of movement of the card  27 .  
         [0051]    As shown in FIG. 2, the case  4  has a box-like shape opened at the bottom, and is obtained by molding a resin material having optical transmission characteristics. Engagement holes  36  with which the engagement projections  7  of the base plate  1  disengageably engage are respectively formed in the centers of the bottom portions of opposite sides of the case  4 . Claw portions  37  on which a user is to hook his/her fingers to remove the electromagnetic relay from a panel (not shown) disposed in a vertical plane after the electromagnetic relay has been fitted to the panel are formed on one end side of the case  4 . A display guide portion  38  is disposed to project from the central portion of the top side of the case  4 , an engagement part  39  and a reinforcing portion  40  are projectingly disposed on one end side of the same top side, and first guide parts  41  and second guide parts  42  are projectingly disposed on the other end side of the same top side and slits  4   a  are also formed on the other end side. The display guide portion  38  has a box-like shape and provides a space in which the display part  32  of the indicator  31  can move. The engagement part  39  guides an LED holder  43  between itself and the display guide portion  38 , and prevents the LED holder  43  from coming off the case  4 , by means of engagement claws  39   a  provided at the top end of the engagement part  39 . The reinforcing portion  40  reinforces the engagement part  39 , and is provided with engagement claws  40   a  with which second engagement claws  69  of a cover  46  (to be described later) disengageably engage. Each of the first guide parts  41  has an engagement groove  41   a  which is formed on its one side in the central portion thereof and with which the corresponding one of first engagement claws  62   a  (refer to FIG. 11) of the cover  46  is to engage, and is tapered toward its top end so that the cover  46  can be easily fitted. Each of the second guide parts  42  is made of a pair of juxtaposed projecting plates and guides the corresponding one of the lead wires  54  extending from the LED  50 . The electrical connection portions  23  of the first coil terminals  20  are respectively inserted through the slits  4   a.    
         [0052]    The display block  5  has a construction in which, as shown in FIG. 2, the LED holder  43  is disposed on the top side of the case  4  and is covered with the cover  46  provided with an operating lever  44  and a display panel  45 .  
         [0053]    As shown in FIG. 9A, the LED holder  43  has a construction in which elastic arm portions  48  are extended from a holder body  47  and an operating portion  49  is formed at the extending end of the elastic arm portions  48 .  
         [0054]    The holder body  47  has a guide hole  51  for guiding the LED  50  and an escape hole  53  for preventing interference of the holder body  47  with a resistor  52  connected to the LED  50 . The lead wires  54  extending from the LED  50  are led out via cutouts  55  formed at corners of the bottom side of the holder body  47 .  
         [0055]    The elastic arm portions  48  are formed to be respectively extended toward one side from opposite side edges of the holder body  47 , extended obliquely upwardly, bent toward each other, and joined to the operating portion  49 . Accordingly, the deformation of the elastic arm portions  48  is facilitated and the interference of the elastic arm portions  48  with projecting portions of the case  4  can be avoided.  
         [0056]    The operating portion  49  is made of a pressing portion  56  which projects downwardly from the central portion of the bottom side of a support plate  49   a  formed continuously with the elastic arm portions  48 , a first pressure receiving portion  57  which projects upwardly from the central portion of the top side of the support plate  49   a , and second pressure receiving portions  58  which respectively project upwardly from opposite side portions of the top side of the support plate  49   a . The pressing portion  56  can press one end portion of the movable core  16  to move the movable contact part  24  via the card  27 . The first pressure receiving portion  57  is made of a central cylindrical portion  59  and extending portions  60  which are respectively formed to extend along the cylindrical portion  59  on opposite sides thereof. A depressed portion  59   a  is provided in the center of the cylindrical portion  59 , and groove portions  59   b  are formed continuously with the extending portions  60  and the cylindrical portion  59 . The depressed portion  59   a  prevents a positional deviation of pointed matter such as a pen when the first pressure receiving portion  57  is being pressed by the pointed matter, while the groove portions  59   b  prevent a positional deviation of plate-shaped matter such as a screwdriver when the first pressure receiving portion  57  is being pressed by the plate-shaped matter. Each of the second pressure receiving portions  58  has an inclined surface  58   a  formed by cutting a top corner closer to the holder body  47 . When the inclined surfaces  58   a  are pressed by pressing projections  74  of the operating lever  44 , the attracted portion  17  of the movable core  16  can be pressed by the pressing portion  56 .  
         [0057]    Accordingly, the above-described LED holder  43  has a construction capable of not only holding the LED  50  but also causing the movable core  16  to move by means of the operating portion  49 . Therefore, the LED holder  43  can be reduced in the number of component parts and can be fabricated inexpensively. In addition, the LED holder  43  is superior in workability because the LED holder  43  can be assembled merely by being placed on the top side of the case  4 .  
         [0058]    As shown in FIGS.  11  to  12 C, the cover  46  has a box-like shape opened at the bottom, and a window portion  61  is formed in the central portion of the top wall of the cover  46 . The window portion  61  enables the user to view the display part  32  when the indicator  31  moves. An opening  62  into which the operating lever  44  is to be fitted and a depressed portion  63  which is formed continuously with the opening  62  and is made narrower than the opening  62  are formed in one end portion of the cover  46 . The opening  62  is opened in the top side and one end side of the cover  46 . The depressed portion  63  is positioned on the top side of the cover  46 , and an inserting hole  64  which is positioned so that the first pressure receiving portion  57  of the LED holder  43  can be press-inserted into the inserting hole  64  is formed in the central portion of the depressed portion  63 . First, second and third engagement receiving portions  65   a ,  65   b  and  65   c , which are respectively made of three pairs of receding portions respectively arranged on the opposite sides of the opening  62  in a continuous wave-like form, are formed on the bottom side of the top wall (ceiling surface) of the cover  46 . The first, second and third engagement receiving portions  65   a ,  65   b  and  65   c  stop the operating lever  44  (to be described later) at a closing position, a first opening position and a second opening position, respectively. First engagement claws  62   a  are respectively formed on inside surfaces of the opening  62  so that the respective engagement grooves  41   a  of the first guide parts  41  projecting from the top side of the case  4  engage with and disengage from the first engagement claws  62   a . A panel-fitting depressed portion  66  into which the display panel  45  is to be fitted is formed in the other end portion of the cover  46 . Rectangular communication holes  67  are formed in the panel-fitting depressed portion  66  on the opposite sides thereof, and mounting portions  68  project from the respective communication holes  67 . Each of the mounting portions  68  has a rod-like shape in top plan view, and has a cross-sectional shape in which a trapezoidal portion which becomes gradually wider downwardly is extended from a circular portion. The mounting portions  68  extend in the width direction of the cover  46  on the reverse side of the depressed portion  66 , and one end of each of the mounting portions  68  is formed as a free end within the respective one of the communication holes  67 . The display panel  45  is not only secured to the mounting portions  68 , but the mounting portions  68  also serve to reinforce a portion which is thin-walled owing to the formation of the depressed portion  63 , and further serve to improve resin flows during a molding process. The second engagement claws  69  which extend vertically in the vicinity of the respective communication holes  67  are formed in inside surfaces of the cover  46 , and disengageably engage with the respective engagement claws  40   a  formed on the reinforcing portion  40  of the case  4 . Owing to the presence of the communication holes  67 , the cover  46  can be molded without the need for a slide mold in spite of its construction in which the second engagement claws  69  are formed on the inside surfaces. A through-hole  46   a  in order to expose the LED  50  is formed in the vicinity of the window portion  61 .  
         [0059]    The operating lever  44  has an operating portion  70 , a closing portion  71  and engagement portions  72 , as shown in FIG. 11. The operating portion  70  closes the opening  62  of the cover  46  on its top side and its end side. A groove portion  70   a  which extends in the width direction of the operating portion  70  is formed in the top side of the operating portion  70 . The groove portion  70   a  is used by the user when the user is to slide the operating lever  44  with respect to the cover  46  by means of the nail of any of his/her fingers hooked on the groove portion  70   a . The closing portion  71  extends from the operating portion  70  in the horizontal direction and is positioned in the depressed portion  63 , thereby covering the first pressure receiving portion  57  positioned in the inserting hole  64 . The engagement portions  72  extend from the operating portion  70  and are positioned under the opposite sides of the closing portion  71 . Hill-shaped elastic swollen portions  73  are respectively provided on side portions of the extending ends of the engagement portions  72 , and the pressing projections  74  are respectively provided on the bottom sides of the extending ends of the engagement portions  72 . The elastic swollen portions  73  disengageably engage with any of the first to third engagement receiving portions  65   a  to  65   c  formed on the ceiling surface of the cover  46 , and stop the operating lever  44  at any of the closing position (refer to FIG. 12), the first opening position (refer to FIG. 13) and the second opening position (refer to FIG. 14). The respective pressing projections  74  press the second pressure receiving portions  58  of the LED holder  43  when the operating lever  44  is slid. Securing projections  75  for preventing the operating lever  44  from coming off the cover  46  by coming into abutment with the guide projections  35  projecting from the top side of the case  4  are formed on the bottom sides of the respective engagement portions  72 .  
         [0060]    Incidentally, the operating lever  44  may have, instead of the above-mentioned construction, a construction in which, as shown in FIGS. 15A and 15B, the extending end of each of the engagement portions  72  is divided into a first elastic part  76  on which the elastic swollen portion  73  is formed and a second elastic part  77  on which the pressing projection  74  is formed. According to this construction, it is possible to independently carry out engagement and disengagement between the engagement receiving portion  65  of the cover  46  and the elastic swollen portions  73  of the first elastic parts  76  and application of pressures to the second pressure receiving portions  58  of the LED holder  43  by the respective pressing projections  74  of the second elastic parts  77 . Accordingly, variations in the movement of the movable core  16 , that is to say, variations in the amount of depression of the movable core  16  by the LED holder  43 , can be absorbed by the elastic force of the second elastic parts  77 .  
         [0061]    As shown in FIG. 11, the display panel  45  has a predetermined visual display applied to its plate-like surface by printing or label sticking, and engagement claws  78  each having an approximately C-like cross section are respectively formed on the opposite end sides of the reverse surface of the display panel  45 . The respective engagement claws  78  are brought into engagement with the mounting portions  68  which project into the respective communication holes  67  of the cover  46 , thereby fixing the display panel  45  to the panel-fitting depressed portion  66 . Since the engagement claws  78  are respectively provided at two locations on the opposite ends of the display panel  45 , there is no risk of causing a warp or the like in the display panel  45 , whereby it is possible to stabilize the mounted state of the display panel  45 .  
         [0062]    A method of assembling the above-mentioned electromagnetic relay will be described below.  
         [0063]    In an advance step, the coil  13  is wound around the spool  12  fitted on the core  11  and the yoke  14  is fixed to the core  11  by caulking, thereby forming the coil block  2 . The ends of each of the coils  13   a  and    13   b which are wound around the trunk portion of the spool  12  in the respective inner and outer circumferential portions are wound around the corresponding ones of the coil terminals  20  and  21  which are insert-molded on the flange portion  12   a  and the flange portion  12   b  of the spool  12 .  
         [0064]    First of all, the contact parts  24   a ,  25   a  and  26   a  are press-fitted into the base plate  1  from above, and the terminal portions  24   b ,  25   b  and  26   b  are projected from the bottom side of the base plate  1 . Then, the indicator  31  is secured so that the support pins  34  are rotatably supported in the bearing holes  10 . Then, the projection  28   a  provided at the extending end of the card  27  is inserted through the through-hole  24   c  of the movable contact part  24 , and the respective guide receiving portions  30  are brought into engagement with the guide projections  35  of the indicator  31  to temporarily fix the card  27 .  
         [0065]    Then, the coil block  2  is placed on he base plate  1 , and the terminal portions of the coil terminals  20  and  21  are projected from the bottom side of the base plate  1 . Then, the movable core  16  is turnably disposed on the top end of the vertical plane portion of the yoke  14  as a fulcrum and is urged by the pressing part  15   a  of the hinge spring  15 , and the connection portion  19  of the movable core  16  is connected to the rectangular hole  29  of the card  27 . In this state, the urging force of the hinge spring  15  acts to move the attracted portion  17  of the movable core  16  away from the attraction surface  11   a  of the core  11 , and the movable contact part  24  brings the movable contact  24   a  into contact with the first stationary contact  25   a.    
         [0066]    After the completion of the mounting of the contact opening and closing mechanism  3  and the coil block  2  on the base plate  1 , the case  4  is placed on the base plate  1 . At this time, the display part  32  of the indicator  31  is positioned in the display guide portion  38  of the case  4 , and the electrical connection portions  23  of the first coil terminals  20  are projected upwardly through the slits  4   a  of the case  4 .  
         [0067]    Then, the LED  50  is incorporated into the LED holder  43 , and the LED holder  43  is placed on the top side of the case  4 . The LED holder  43  is inserted between the display guide portion  38  and the engagement part  39  of the case  4  and is fixed by the engagement claws  39   a . The lead wires  54  extending from the LED  50  are welded to the electrical connection portions  23  of the first coil terminals  20  which project upwardly from the top side of the case  4 . Since the ridges  23   a  are formed on the electrical connection portions  23 , the electrical connection portions  23  can be positively connected to the lead wires  54 .  
         [0068]    Finally, the cover  46  is fitted on the top side of the case  4 . The operating lever  44  and the display panel  45  are secured to the cover  46  in advance. The operating lever  44  is secured by being slid from one end side of the cover  46  into the opening  62 . The display panel  45  is positioned in the depressed portion  63  from above the cover  46 , and is secured by engaging the respective engagement claws  78  with the mounting portions  68 .  
         [0069]    The operation of the electromagnetic relay will be described below. When the coil  13  is in the demagnetized state where it is not energized, the movable contact part  24  is placed in an upright state by its own elastic force to hold the movable contact  24   a  in contact with the first stationary contact  25   a . The movable core  16  is turned to move the attracted portion  17  away from the attraction surface  11   a  of the core  11 , by the elastic force of the movable contact part  24  via the card  27 . Accordingly, the indicator  31  turns about the support pins  34  in the counterclockwise direction as viewed in FIG. 4 together with the card  27 . Accordingly, the user cannot view the display part  32  in the window portion  61  of the cover  46 .  
         [0070]    Then, when the coil  13  is energized and magnetized, the attracted portion  17  of the movable core  16  is attracted to the attraction surface  11   a  of the core  11 , whereby the movable core  16  is turned in the clockwise direction as viewed in FIG. 4. Accordingly, the movable contact part  24  is moved via the card  27  so that the movable contact  24   a  moves away from the first stationary contact  25   a  and comes into contact with the second stationary contact  26   a . In addition, with the movement of the card  27 , the indicator  31  turns about the support pins  34  in the clockwise direction as viewed in FIG. 4. Accordingly, the display part  32  is externally visibly positioned in the window portion  61  of the cover  46 . The user can therefore understand the operating state of the contact opening and closing mechanism  3  at a glance. Also, the LED  50  is lighted by energizing the coil  13 , whereby the magnetized state of the coil block  2  can be understood at a glance.  
         [0071]    When the operating lever  44  is slid to the first opening position during the demagnetized state where the coil  13  is not energized, the first pressure receiving portion  57  of the LED holder  43  is exposed as shown in FIG. 13A. Accordingly, it becomes possible to depress the first pressure receiving portion  57 . When the first pressure receiving portion  57  is depressed, the elastic arm portions  48  are elastically deformed and the pressing portion  56  is moved downwardly. Accordingly, the movable core  16  is turned to move the movable contact part  24  via the card  27 . At this time, with the movement of the card  27 , the indicator  31  turns and the display part  32  becomes visible in the window portion  61 . Namely, the user can view the operating state of the movable core  16 .  
         [0072]    When the operating lever  44  is further slid from the first opening position to the second opening position, the pressing projections  74  of the operating lever  44  press the second pressure receiving portions  58  of the LED holder  43  to elastically deform the elastic arm portions  48 , as shown in FIG. 14C. Accordingly, the pressing projections  74  press the operating portion  49  of the LED holder  43  downwardly, whereby the movable core  16  is maintained in a pressed state by the pressing portion  56  and the movable contact  24   a  is brought into contact with the second stationary contact  26   a . At this time, the display part  32  of the indicator  31  becomes visible in the window portion  61  of the cover  46 . Namely, the user can view the operating state of the movable core  16 .  
         [0073]    Incidentally, in the above-mentioned embodiment, the single movable contact  24   a  is brought into and out of contact with the two stationary contacts  25   a  and  26   a , but it is also preferable to adopt a construction in which two movable contacts are brought into and out of contact with two stationary contacts, respectively.  
         [0074]    In this case, as shown in FIG. 16, the base plate  1  is constructed so that two contact opening and closing mechanisms  3 , one of which includes a movable contact part  24 A and a pair of first stationary contact part  25 A and  26 A and the other of which includes a movable contact part  24 B and a pair of first stationary contact part  25 B and  26 B, can be press-fitted into the opposite side portions of the base plate  1 . The second area is divided into two areas in the width direction by a fourth partition wall  79  so that the two contact opening and closing mechanisms  3  can be insulated from each other. The indicator  31  is bifurcated in its lower half, and the support pins  34  which project toward each other are respectively formed at the bottom ends of the bifurcated portions. The respective support pins  34  are rotatably supported in bearing holes (not shown) formed in the fourth partition wall  79 . The card  27  is provided with two press-inserting projecting portions  28  at opposite side locations for pressing the respective movable contact parts  24 . The other constructions are substantially the same as those of the above-described embodiment, and the descriptions of the same constructions are omitted.  
         [0075]    Although in the above-described embodiment the card  27  and the indicator  31  are separately constructed, they may also be integrally constructed.  
         [0076]    In FIG. 17A, the display part  32  is integrally formed on the central portion of the top edge of the card  27 .  
         [0077]    In FIG. 17B, an extended portion  80  is formed on the central portion of the top edge of the card  27 , and the display part  32  is joined to this extended portion  80 . Specifically, the display part  32  is secured to the case  4  for turning movement about support pins  82 , and an engagement part  83  of the display part  32  is rotatably joined to an engagement receiving hole  81  formed in the extended portion  80 . Accordingly, the turning range of the display part  32  can be made wide compared to the case where the display part  32  is extended directly from the card  27 . Accordingly, even in a small-size electromagnetic relay in which the amount of movement of the card  27  is small, since the movement of the display part  32  can be amplified, it is possible to realize a construction which enables the user to positively confirm the movement of the display part  32 . In addition, since the display part  32  is turnably provided in the case  4 , the space occupied by the display part  32  can be reduced, whereby the overall size of the electromagnetic relay can be reduced.  
         [0078]    In this case, the cover  46  can be modified as shown in FIG. 18 by way of example. Specifically, the panel-fitting depressed portion  66  is formed in the central portion of the cover  46 , and the display panel  45  may be secured to this depressed portion  66  formed in the central portion.  
         [0079]    As is apparent from the foregoing description, according to the invention, a light-emitting device can be disposed on a top side of a case by holding the light-emitting device by a holder, whereby it is possible to improve the visibility of the light-emitting device. Also, since the light-emitting device is disposed outside, it is possible to surely prevent dust or the like from entering into an interior of the case.