Abstract:
Obtained is a fire alarm system transmitter having an improved insulating property without increasing an entire size of a casing. The fire alarm system transmitter includes: a printed circuit board with a substantially rectangular shape, on which a terminal block including a plurality of terminals aligned along one side of the printed circuit board is disposed; a casing with a substantially rectangular parallelepiped shape, in which the printed circuit board is mounted; and an electric-wire insertion portion provided on a side wall of the casing facing the one side, and extended from the side wall by a predetermined distance toward an outside of the casing, the side wall allowing a plurality of electric wires connected to the plurality of terminals to be inserted through the side wall.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a fire alarm system transmitter for use in a fire alarm system. 
         [0003]    2. Description of the Related Art 
         [0004]    In a transmitter for use in a fire alarm system, a printed circuit board on which a terminal block is fixed is housed inside the transmitter. In an operation of mounting the transmitter to a mounting box, an electric wire extended to an inside of the mounting box is connected to the terminal block, and then, the transmitter is arranged in the mounting box. Finally, a front opening of the mounting box is covered with a plate serving as a decorated frame. Thus, the operation is completed. 
         [0005]    Here, in the printed circuit board, in order that a circuit component is not limited in terms of mounting and a mounting area is maximized, the terminal block is disposed along one side of the printed circuit board. At this time, in consideration of an insulating property for the purpose of preventing contact between the circuit component and the electric wire, an insertion hole is formed in a side wall at one side of a casing, and the electric wire is pulled out through the insertion hole (see JP 2002-170168 A, for example). 
         [0006]    However, a creepage distance (clearance) from the terminal block to the insertion hole as an outside of the casing is set to be short, and hence the insulating property may be adversely affected. At this time, in order to separate the entire side wall on the terminal block side of the casing from the terminal block, it is necessary to increase an entire size of the casing. As a result, there arises a problem in that a resin (material) amount of the casing is increased and an operation of arrangement into the mounting box is difficult. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention has been made to solve the above-mentioned problem, and it is an object of the present invention to obtain a fire alarm system transmitter having an improved insulating property without increasing an entire size of a casing. 
         [0008]    According to the present invention, a fire alarm system transmitter includes: a printed circuit board with a substantially rectangular shape, on which a terminal block including a plurality of terminals aligned along one side of the printed circuit board is disposed; a casing with a substantially rectangular parallelepiped shape, in which the printed circuit board is mounted; and an electric-wire insertion portion provided on a side wall of the casing facing the one side, and extended from the side wall by a predetermined distance toward an outside of the casing, the side wall allowing a plurality of electric wires connected to the plurality of terminals to be inserted through the side wall. 
         [0009]    The fire alarm system transmitter according to the present invention includes the electric-wire insertion portion extended toward the outside of the casing from the side wall of the casing facing the one side at which the terminal block of the printed circuit board is mounted, and hence a distance from the terminal block to the end of the casing is elongated by a length of the electric-wire insertion portion. As a result, it is possible to obtain an effect of securing a sufficient external creepage distance. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    In the accompanying drawings: 
           [0011]      FIG. 1  is a perspective view of a fire alarm system transmitter according to an embodiment of the present invention; 
           [0012]      FIG. 2  is an exploded perspective view of the fire alarm system transmitter according to the embodiment of the present invention; 
           [0013]      FIGS. 3A to 3C  are respectively a front view, a plan view, and a side view of the fire alarm system transmitter according to the embodiment of the present invention; 
           [0014]      FIG. 4  is a sectional view of the fire alarm system transmitter according to the embodiment of the present invention; 
           [0015]      FIG. 5  is a view illustrating a state in which electric wires are connected to the fire alarm system transmitter; 
           [0016]      FIG. 6  is an explanatory diagram illustrating a state in which an external creepage distance is elongated; and 
           [0017]      FIG. 7  is an explanatory diagram illustrating a state in which the fire alarm system transmitter is mounted in a mounting box. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    Hereinafter, a preferred embodiment of a fire alarm system transmitter according to the present invention is described with reference to the drawings. 
         [0019]      FIG. 1  is a perspective view of the fire alarm system transmitter according to the embodiment of the present invention.  FIG. 2  is an exploded perspective view of the fire alarm system transmitter according to the embodiment of the present invention.  FIGS. 3A to 3C  are respectively a front view, a plan view, and a side view of the fire alarm system transmitter according to the embodiment of the present invention.  FIG. 4  is a sectional view of the fire alarm system transmitter taken along the line A-A of  FIG. 3A . 
         [0020]    A fire alarm system transmitter  1  according to the embodiment of the present invention (hereinafter, abbreviated to transmitter  1 ) relays a signal between a receiver and a detector, for example. The transmitter  1  includes a printed circuit board  2  with a substantially rectangular shape, on which a terminal block  4  including a plurality of terminals  3  aligned along one side  2   a  is disposed, and includes a casing  5  with a substantially rectangular parallelepiped shape, in which the printed circuit board  2  is mounted. 
         [0021]    On a side wall  5   a  of the casing  5 , there is provided an electric-wire insertion portion  5   b  through which electric wires connected to the terminals  3  are guided. 
         [0022]    The casing  5  includes a lower case  6  having an opened upper surface and an upper case  7  having an opened lower surface. 
         [0023]    A plurality of substantially semi-circular cutouts  6   b  are provided in a top of a side wall  6   a  of the lower case  6  facing the one side  2   a  of the printed circuit board  2 . The cutouts  6   b  are provided so as to correspond to the number of the terminals  3  of the terminal block  4 . A lower guide  9  is extended substantially upright from an outer edge of the side wall  6   a  situated around the cutouts  6   b . The lower guide  9  has a substantially comb-like cross-section. In the cross-section of the lower guide  9 , a plurality of substantially semi-circular portions corresponding to the plurality of cutouts  6   b  are cut out along one side of a rectangle. In other words, the lower guide  9  includes a bottom wall  9   a  provided upright from the side wall  6   a  over a lateral direction of the side wall  6   a , and a plurality of division walls  9   b  provided upright from the bottom wall  9   a  toward the top of the side wall  6   a , to thereby form the cutouts  6   b  corresponding to the terminals  3 . 
         [0024]    Further, at the residual top (on the side wall  6   a  side of the division walls  9   b ) of the side wall  6   a  after forming the cutouts  6   b , at tops of two side walls  6   c  and  6   d  provided continuously with the side wall  6   a , and at a top of a side wall  6   e  opposing the side wall  6   a , a recessed stepped portion is formed inwardly in a wall thickness direction of the side walls  6   a ,  6   c ,  6   d , and  6   e.    
         [0025]    Further, two engagement tongue pieces  12  are provided on the one side  2   a  (lower guide  9 ) side of the side walls  6   c  and  6   d , and one engagement tongue piece  12  is provided at substantially the center of the side wall  6   e . Each of the engagement tongue pieces  12  is protruded toward an upper portion of the casing  5  from an inner wall of each of the side walls  6   c ,  6   d , and  6   e , and includes an engagement hole  11  formed therein. 
         [0026]    Further, L-shaped board seats  13  and a mounting seat  14  are provided. The board seats  13  are extended inwardly from the side walls  6   a ,  6   c ,  6   d , and  6   e . The mounting seat  14  is protruded toward the upper portion of the casing  5  from a position of a bottom wall  6   f  corresponding to a screw hole  2   b  formed at the center of the printed circuit board  2 , and includes a screw hole  14   a  formed therein. 
         [0027]    A plurality of substantially semi-circular cutouts  7   b  are provided in a top of a side wall  7   a  of the upper case  7  facing the one side  2   a  of the printed circuit board  2 . The cutouts  7   b  are provided so as to correspond to the number of the terminals  3  of the terminal block  4 . An upper guide  16  is extended substantially upright from an outer edge of the side wall  7   a  situated around the cutouts  7   b . The upper guide  16  has a substantially comb-like cross-section. In the cross-section of the upper guide  16 , a plurality of substantially semi-circular portions corresponding to the plurality of cutouts  7   b  are cut out along one side of a rectangle. In other words, the upper guide  16  includes a bottom wall  16   a  provided upright from the side wall  7   a  over a lateral direction of the side wall  7   a , and a plurality of division walls  16   b  provided upright from the bottom wall  16   a  toward the top of the side wall  7   a , to thereby form the cutouts  7   b  corresponding to the terminals  3 . 
         [0028]    Further, at the residual top (on the side wall  7   a  side of the division walls  16   b ) of the side wall  7   a  after forming the cutouts  7   b , at tops of two side walls  7   c  and  7   d  provided continuously with the side wall  7   a , and at a top of a side wall  7   e  opposing the side wall  7   a , a recessed stepped portion is formed outwardly in the wall thickness direction of the side walls  7   a ,  7   c ,  7   d , and  7   e.    
         [0029]    Further, two engagement protrusions  15  are provided on the one side  2   a  (upper guide  16 ) side of the side walls  7   c  and  7   d , and one engagement protrusion  15  is provided at substantially the center of the side wall  7   e . The engagement protrusions  15  are provided on the inner wall side of the side walls  7   c ,  7   d , and  7   e , and are engaged with the engagement tongue pieces  12  provided on the side walls  6   c ,  6   d , and  6   e  when the upper case  7  is fitted to the lower case  6 . 
         [0030]    Further, L-shaped seats  17  extended inwardly from the side walls  7   a ,  7   c ,  7   d , and  7   e  are provided. 
         [0031]    The side wall  5   a  of the casing  5  is constituted by the side wall  6   a  of the lower case  6  and the side wall  7   a  of the upper case  7 . Further, a plurality of insertion holes are formed in the side wall  5   a  of the casing  5  so as to correspond to the terminals  3 , respectively. Each of the insertion holes is constituted by one of the cutouts  6   b  of the lower case  6  and corresponding one of the cutouts  7   b  of the upper case  7 . Further, the electric-wire insertion portion  5   b  extended from the side wall  5   a  of the casing  5  is formed into a substantially multi-channel shape in cross-section. The lower guide  9  of the lower case  6  and the upper guide  16  of the upper case  7  are fitted to each other so that the substantially semi-circular cutout portions of the lower guide  9  of the lower case  6  and the substantially semi-circular cutout portions of the upper guide  16  of the upper case  7  are fitted to each other to form substantially circular cutout portions. That is, in the electric-wire insertion portion  5   b , an insertion hole is partitioned from another insertion hole by a partition wall  23  formed through fitting the division wall  9   b  and the division wall  16   b  to each other and by another partition wall  23  adjacent to the former partition wall  23 . The partition walls  23  can prevent an electric wire  21  (see  FIG. 5 ) connected to one of the terminals  3  from being held in contact with another adjacent electric wire  21 . Therefore, it is possible to achieve protection against an adverse effect such as noises and the like generated due to interference. 
         [0032]    Next, the procedure for mounting the transmitter  1  according to this embodiment of the present invention to a mounting box  20  is described.  FIG. 5  is a view illustrating a state in which the electric wires  21  are connected to the transmitter  1 .  FIG. 6  is an explanatory diagram illustrating a state in which an external creepage distance is elongated.  FIG. 7  is an explanatory diagram illustrating a state in which the transmitter  1  is mounted in the mounting box  20 . 
         [0033]    The terminal block  4  is mounted on the printed circuit board  2  through soldering the terminals  3  onto the printed circuit board  2 . 
         [0034]    Next, the printed circuit board  2  is arranged on the board seats  13 , and is fixed with a screw  18  after the screw hole  2   b  of the printed circuit board  2  is aligned with the screw hole  14   a  of the mounting seat  14  of the lower case  6 . At this time, the printed circuit board  2  is almost held in contact with the lower case  6  and is mounted in the lower case  6 . 
         [0035]    Next, insulating films are peeled off from end portions of the electric wires  21  extended to an inside of the mounting box  20 , and wires are connected to the terminals  3 . 
         [0036]    Next, the upper case  7  is placed to cover the lower case  6 , to thereby form the casing  5 . Then, the engagement protrusions  15  are engaged with the engagement holes  11  of the engagement tongue pieces  12  so that the upper case  7  and the lower case  6  are fixed to each other. 
         [0037]    Finally, the transmitter  1  is housed together with the electric wires  21  in the mounting box  20  of a type embedded in a wall surface, and a decorated plate  22  is fixed with a screw so as to cover a front opening of the mounting box  20 . 
         [0038]    The transmitter  1  according to this embodiment of the present invention includes the electric-wire insertion portion  5   b  which is extended outwardly from the side wall of the casing  5  facing the one side  2   a  mounted with the terminal block  4  of the printed circuit board  2 , and hence a distance from the terminal block  4  to the end of the casing  5  is elongated by a length of the electric-wire insertion portion  5   b . As a result, it is possible to secure a sufficient external creepage distance. 
         [0039]    Further, the lower case  6  and the upper case  7  are stopped from moving in a horizontal direction owing to the stepped portions provided at the top of the lower case  6  and the top of the upper case  7 . Thus, even in a case where the electric-wire insertion portion  5   b  is provided, the lower case  6  and the upper case  7  are prevented from being separated from each other in the horizontal direction even when an external impact or the like is applied to the lower case  6  and the upper case  7 . 
         [0040]    Further, the engagement protrusions  15  of the upper case  7  are engaged with the engagement holes  11  of the engagement tongue pieces  12  of the lower case  6 , and hence the lower case  6  and the upper case  7  are prevented from being separated from each other in an up-down direction even when the external impact or the like is applied to the lower case  6  and the upper case  7 . 
         [0041]    Further, the stepped portion provided at upper end portions of the side walls  6   a ,  6   c ,  6   d , and  6   e  of the lower case  6  is recessed on an inner side of the stepped portion. Thus, an entire length of each of the engagement tongue pieces  12  can be elongated, and the engagement tongue pieces  12  can be easily deformed and engaged with the upper case  7 . Note that, the stepped portion recessed on the inner side thereof may be provided in the upper case  7 , and the stepped portion recessed on an outer side thereof may be provided in the lower case  6 . 
         [0042]    Note that, grooves provided in the lower guide  9  and the upper guide  16  constituting the electric-wire insertion portion  5   b  have the substantially semi-circular cross-sections. However, as long as the grooves have shapes capable of guiding the electric wires, shapes of the grooves are not limited thereto. Further, the insertion holes are formed so as to correspond to the terminals  3 , respectively. However, one insertion hole corresponding to all of the terminals  3  may be formed. 
         [0043]    Further, though the number of the engagement tongue pieces  12  is three, the number of the engagement tongue pieces  12  is not limited thereto.