Abstract:
A riveting apparatus having a support die with a support surface. The support surface supports a rivet that extends through a circuit board and an electrical connector. The support surface has a first inclined surface, a second inclined surface, and a depression positioned therebetween. The depression receives a head of the rivet and positionally aligns the rivet with an upper tool unit as the rivet is guided across the first inclined surface toward the second inclined surface. The upper tool unit fastens the rivet to the circuit board.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a rivet fastening device and, more particularly, to a rivet fastening device that positionally aligns rivots that are fastened to secure an electrical connector to a printed circuit board.  
         DESCRIPTION OF THE PRIOR ART  
         [0002]    Japanese Unexamined Patent Publication No. 2000-334539 teaches a riveting apparatus for securing a plurality of electrical connectors to a printed circuit board. The riveting apparatus has an anvil or support die on a lower side and an upper tool unit or pressing die equipped with a crimper for spreading a rivet facing the anvil. A connector holder is positioned between the anvil and the upper tool unit. The connector holder holds the printed circuit board with the electrical connector temporarily fixed thereto. A linking mechanism slightly raises the anvil when the pressing die is lowered to fasten the rivet and secure the electrical connector to the printed circuit board.  
           [0003]    The connector holder and the printed circuit board are discoid in shape. The electrical connectors are temporarily fixed on the printed circuit board in a radial pattern by the rivets extending therethrough. The electrical connectors are secured to the printed circuit board by fastening the rivets at predetermined positions while the printed circuit board is rotated. To prevent deformation of the printed circuit board or damage to the riveting apparatus during fastening of the rivets, the rivets of the electrical connectors are positionally aligned with the anvil and the upper tool unit. The electrical connectors are positionally aligned by an extension plate attached to the link mechanism that is received in grooves formed on a periphery of the connector holder. The entrance of the extension plate within the grooves causes the connector holder to stop at predetermined positions in the circumferential direction thereof to positionally align the circuit board, the electrical connector, and the rivets.  
           [0004]    Because the connector holder and the link mechanism are both required for positional alignment, the above-described riveting apparatus is a complex structure that requires a high number of parts. As a result, the cost of the riveting apparatus is high. It is therefore desirable to develop an inexpensive riveting apparatus that has a simple positional alignment structure and requires a small number of parts.  
         SUMMARY OF THE INVENTION  
         [0005]    The invention relates to a riveting apparatus having a support die with a support surface for supporting a rivet that extends through a circuit board and an electrical connector. The support surface has a depression that receives a head of the rivet as the rivet slides across the support surface. The depression positionally aligns the rivet with an upper tool unit that fastens the rivet to the circuit board. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is a perspective view of a riveting apparatus.  
         [0007]    [0007]FIG. 2 is a perspective view of a support die of the riveting apparatus.  
         [0008]    [0008]FIG. 3 is a sectional view of the support die and a circuit board assembly showing rivets of an electrical connector temporarily fixed to the circuit board. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0009]    [0009]FIG. 1 shows a riveting apparatus  1 . The apparatus  1  has a substantially rectangular base  2 . A support column  4  protrudes from a rearward edge of the base  2 . A ram support portion  6  is integrally formed with the support column  4  and extends forward therefrom. (The forward direction is indicated by arrow F in the Figures and is the forward direction with respect to an operator of the apparatus  1 . The direction reverse to the arrow F indicates the rearward direction.) The ram support portion  6  has an aperture (not shown) that extends in a vertical direction. A columnar ram  10  is slidably held within the aperture (not shown). The ram  10  has a rack (not shown). The rack (not shown) engages with pinion gears (not shown) driven by a handle  12  pivotally supported on the ram support portion  6 . The ram  10  is structured to move vertically within the ram support portion  6  by rotation of the handle  12 .  
         [0010]    An upper tool unit  14  is mounted on a lower portion of the ram  10 . The upper tool unit  14  has an upper plate  14   a  and a lower plate  14   b . The upper plate  14   a  is mounted on the lower portion of the ram  10 . The lower plate  14   b  moves about the upper plate  14   a  in a reciprocal motion by a bolt  14   d  that extends through a compression spring  14   c  positioned between the upper plate  14   a  and the lower plate  14   b . The bolt  14   d  extends through the upper plate  14   a  and is secured to the lower plate  14   b . A crimper (not shown) for spreading a tip  112  of a rivet  110 , shown in FIG. 3, is mounted on the lower portion of the ram  10 . A crimper cover  14   e  is positioned on the lower plate  14   b  to guide the crimper (not shown).  
         [0011]    A horizontally extending plate  20  is provided at an upper edge of the ram support portion  6 . A bottom dead point adjustment dial  22  is mounted at an outer edge of the plate  20 . A bottom dead point determining member  24  for determining the bottom dead point of the ram  10 , that is, the lowermost fastening position of the ram  10 , is provided at an upper portion of the ram  10 . The bottom dead point determining member  24  co-operates with the bottom dead point adjustment dial  22 . Because the bottom dead point adjustment dial  22  and bottom dead point determining member  24  have similar features and similar functions to those disclosed in the prior art, detailed descriptions thereof have been omitted.  
         [0012]    A circuit board support portion  16  is positioned toward a front of the apparatus  1  and above the base  2 . The circuit board support portion  16  has a base body  18 . A rearward edge of the base body  18  is mounted on the base  2 . A first support rod  26  extends forward from the base body  18 . A second support rod  28  extends horizontally outward from the base body  18  and perpendicular to the support rod  26 .  
         [0013]    Support blocks  33  for receiving an annular plate  30  are mounted on the first and second support rods  26 ,  28 . Grooves  38  are formed in each of the support blocks  33  for receiving the annular plate  30 . Support protrusions  34  that support the circuit board  150  are formed on interior sides of each of the support blocks  33 . Positioning blocks  32  with positioning protrusions  36  for positioning the circuit board  150  are mounted on the support rods  28  adjacent to the support blocks  33  on the exterior sides thereof. Positioning surfaces  36   a  are formed on the upper edges of the positioning protrusions  36 . The positioning surfaces  36  face toward the support protrusions  34 . The circuit board  150  is supported by the support protrusions  34  while being positioned by the positioning surfaces  36   a  so that the positioning surfaces  36  and a front edge  56   a  of a block  56  restricts a positional shift in the radial direction of the circuit board  150 . The support blocks  33  and the positioning blocks  32  may be separate members formed from a resin or integrally formed from metal.  
         [0014]    The annular plate  30  is positioned on a top surface of the first and second support rods  26 ,  28 . The annular plate  30  is formed from a metal such as aluminium, and is generally formed in a ring-like shape. The annular plate  30  has a space  40  for receiving a lower tool unit  8  and a pair of flanges  42  that rest on blocks  43  provided on the base body  18 . Pins  46  for preventing rearward movement of the flanges  42  are mounted adjacent to rear edges  42   a  of the flanges  42 . Cut-outs (not shown) for receiving butterfly screws are formed in the rear edges  42   a  to secure the flanges  42  to the blocks  43 .  
         [0015]    The lower tool unit  8  is mounted on the rearward edge of the base body  18  at a position corresponding to the upper tool unit  14 . The lower tool unit  8  has an anvil or a support die  50  placed in the space  40  of the annular plate  30 . The support die  50  is fixed to the base body  18  by screws  52 . A bracket  54  supports a connector mounting surface  103 , shown in FIG. 3, of the circuit board  150  and is fixed to the base body  8  by screws  52 . A block  56  prevents the circuit board  150  from moving rearward with a front edge  56   a  and is fixed to the base body  8  by screws  52 .  
         [0016]    As shown in FIG. 2, the support die  50  comprises a main block  58  and a sub-block  60 . The main block  58  has a rectangular base  62  and a protrusion  64  integrally formed with the base  62  at a position shifted from the center thereof, extending from the front to the rear. Screw receiving apertures  63  are provided at corners of the base  62 . Upwardly extending first guide portions  66  are formed at the front and rear edges of the protrusion  64 . First tapered portions  68  that open toward exterior sides of the first guide portions  66  are formed on each of the first guide portions  66 . An upper portion of the protrusion  64  is formed as a first inclined surface  64   a  that inclines downward toward the exterior side. A first narrow flat surface  64   b  extends in a front to rear direction along an edge of the sub-block  60 .  
         [0017]    The sub-block  60  is positioned adjacent to the protrusion  64  and on a surface  70  of the base  62 . Second guide portions  72  having a similar height as the first guide portions  66  are positionally aligned with the first guide portions  66 . Each of the second guide portions  72  have second tapered portions  73  opening toward an exterior side for guiding an electrical connector  100 . A peak  74  is formed between the second guide portions  72 . The peak  74  is a narrow second flat surface  76  of substantially the same height as the first flat surface  64   b . A second inclined surface  74   a  inclines downward from the second flat surface  76  toward an upstream side of a conveyance motion of the circuit board  150  (the right side of FIG. 2). The second inclined surface  74   a  and the first inclined surface  64   a  have lengths equal to a length of the electrical connector  100  with respect to a conveyance direction. The main block  58  and the sub-block  60  co-operate to construct a groove  78  for guiding the electrical connector  100 . The groove  78  is formed by the first and second inclined surface  64   a ,  74   a , the first and second flat surfaces  64   b ,  76 , and the first and second guide portions  66 ,  72 . The second flat surface  76  and the second inclined surface  74   a  are collectively referred to as a support surface, because a head  116  of the rivet  110  moves over the second inclined surface  74   a  and the second flat surface  76  while in contact therewith.  
         [0018]    Cut-outs  82 , corresponding to the rivets  110  of the electrical connector  100 , are formed in the second flat surface  76  of the sub-block  60  and extend to the lower edge thereof. The cut-outs  82  co-operate with a side surface  65  of the main block  58  to form substantially rectangular holes. As best shown in FIG. 3, rectangular columns  86  that have substantially U-shaped recesses  84  are received in the rectangular holes. Bevels  86   a  are formed from upper surfaces  86   b  to lower surfaces  86   c  of the rectangular columns  86  at corners thereof to facilitate insertion into the rectangular holes. The lower surfaces  86   c  of the rectangular columns are supported by the surface  70  of the main block  58 . Horizontally extending bolt apertures  80  that communicate with each other are formed through the main block  58  and the sub-block  60 . A bolt  87  is inserted through the bolt aperture  80  to secure the main block  58  and the sub-block  60  to each other.  
         [0019]    The electrical connector  100  discussed herein is similar to the electrical connector described in Japanese Unexamined Patent Publication 2000-334539. As shown in FIG. 3, the electrical connector  100  has a wide base  102  and an engagement portion  104 . A plurality of terminals  106  having tines  108  are arranged on the electrical connector  100  and extend from the base  102  to the engagement portion  104 . The tines  108  protrude from a surface of the base  102 .  
         [0020]    The electrical connector  100  is surface mounted to an underside of the circuit board  150  to form a circuit board assembly  101 . The electrical connector  100  is secured to the circuit board  150  by rivets  110 , which penetrate through the electrical connector  100  and into the circuit board  150 . The rivets  110  penetrate from the engagement portion  104  of the electrical connector  100 , perpendicularly through a bottom surface  102   a  of the base  102 , and further through a mounting aperture  152  of the circuit board  150 . The electrical connector  100  having the rivet  110  penetrating therethrough is temporarily fixed by the circuit board  150  so that it does not fall therefrom. The mounting aperture  152  is of a diameter such that the rivet  110  is press-fit therein.  
         [0021]    The positional alignment of the rivets  110  for fastening the electrical connector  100  to the circuit board  150  will now be described in greater detail with reference to FIGS.  1 - 3 . An operator holds the circuit board  150  by hand and rotates the circuit board  150  until the connector mounting surface  103  of the circuit board  150  is supported by the support blocks  33  and the bracket  54  shown in FIG. 1. As shown in FIG. 3, the circuit board assembly  101  is conveyed in the direction of arrow A from an upstream side so that the electrical connector assembly  101  is conveyed between the upper and lower tool units  14 ,  8 . As the electrical connector  100  moves toward the second flat surface  76 , heads  116  of the rivets  110  move in a sliding manner on the second inclined surface  74   a  in a state in which the heads  116  bear the weight of the circuit board  150  under manual power. At this time, the circuit board  150  moves upward along the second inclined surface  74   a  so it floats slightly above the bracket  54 . The heights of the support protrusions  34  are set to enable movement in this manner.  
         [0022]    The heads  116  of the rivets  110  are received in the depressions  84  of the rectangular columns  86  formed in the second flat surface  76 . The heads  116  of the rivets  110  are at a position slightly above the surface  30   a  of the annular plate  30  and lower than the flat surface  76  of the sub-block  60 . When the heads  116  become seated within the depressions  84 , a clear sensation of positioning is transmitted to the hand of the operator through a click.  
         [0023]    The fastening position is set to a desired height by rotating the bottom dead point adjustment dial  22 . The upper tool unit  14  descends to fasten the rivets  110 , by operation of the handle  12 . During the fastening operation, the crimper cover  14   e  abuts the circuit board  150  in the vicinity of the rivet  110 . The crimper then descends to spread the tip  112  of the rivet  110  to secure the electrical connector  100  to the circuit board  150 . As shown in FIG. 3, a metal plate  114  having apertures  114   a  that receive the rivets  110  may also be provided on the circuit board  150 . The metal plate  114  protects the circuit board  150  and during the fastening operation the tips  112  of the rivets  110  may be crushed on the metal plate  114 . When the rivets  110  are fastened, the tines  108  of the terminals  106  are pressed against conductive traces (not shown) on the circuit board  150  to establish electrical connections between the terminals  106  and the circuit board  150 . During fastening of the rivets  110 , the circuit board  150  moves slightly downward due to deformation of the heads  116  of the rivets  110  and the elasticity of the tines  108  of the terminals  106 . The circuit board  150  absorbs this movement, because the circuit board  150  floats slightly above the bracket  54 . Accordingly, deformation of the circuit board  150  is prevented.  
         [0024]    After the fastening operation, the circuit board  150  is conveyed further in the direction of arrow A, and another electrical connector (not shown) is received between the upper and lower tool units  14 ,  8  for fastening rivets  110  thereto. A single electrical connector may be fastened to the circuit board  150 , or a plurality of electrical connectors may be fastened thereto. When a plurality of electrical connectors  100  are to be fastened to the circuit board  150 , if the rivets  110  of an electrical connector  100  not yet secured to the circuit board  150  shift due to mechanical shock of the fastening operation, the heads  116  of the unfastened rivets  110  abut the annular plate  30  and are supported thereby so that the rivets  110  and the electrical connector  100  are prevented from disengaging from the circuit board  150 .  
         [0025]    Positive positional alignment of the rivet is enabled by the co-operative relationship between the anvil  50  and the rivet  110 , without employing a complex mechanism. As a result, the apparatus  1  has a small number of parts, is of a simple structure, and is inexpensive. In addition, the rivets  110  are directly positioned in the depressions  84  of the anvil  50  for high positional accuracy. Therefore, in the case that the support surface comprises an incline plane that inclines upward from the upstream side of the direction of travel of the circuit board assembly  101  to the downstream side thereof, even if there are minor fluctuations in the vertical position of the circuit board  150  to which the electrical connector  100  is mounted, positive positional alignment is enabled. The apparatus  1  may also be used for correcting the positioning of an electrical connector  100  already mounted on the circuit board  150 .  
         [0026]    The foregoing illustrates some of the possibilities for practicing the invention. Many other embodiments are possible within the scope and spirit of the invention. It is, therefore, intended that the foregoing description be regarded as illustrative rather than limiting, and that the scope of the invention is given by the appended claims together with their full range of equivalents. For example, the upper portions of the main block  58  and the sub-block  60  need not be inclined surfaces, but may be flat surfaces. In this case, to perform positive positioning, it is necessary that the heads  116  of the rivets  110  slide along the flat surface in a state in which the heads  116  are urged downward by the weight of the circuit board assembly  101 . By this downward urging, the heads  116  of the rivets  110  will be seated within the depressions  84  with a click sensation.