Patent Publication Number: US-2010129139-A1

Title: Joining Member and Joining Structure

Description:
TECHNICAL FIELD 
     The present invention relates to a joining member which joins plural wooden pieces, and a joining structure which is formed by such a joining member. 
     This application is based upon and claims the benefit of priority from Japanese Patent Applications No. 2005-229842, filed Aug. 8, 2005; and No. 2005-261212, filed Sep. 8, 2005, the entire contents of which are incorporated herein by reference. 
     BACKGROUND ART 
     Casings that cover electronic equipments such as cameras and portable telephones are mostly made of synthetic resin or metal. Such casings are formed from plural parts which are joined with each other by screws, caulking, or the like. 
     Meanwhile, wood comes to attract attention as a material for jackets of electronic equipments. With a wide variety of grain patterns of wooden materials as being natural materials, wood products made of wood exhibit individual features depending on positions of the raw wood from which the particular wood products are cut out. Such individual features of each wood product give it a unique quality. In addition, surface flaws and discolorations caused by a long-term use create unique textures which tend to evoke warm and familiar feeling in the user. Thus, the wooden material attracts attention as a material for products of uniqueness and taste which cannot be found in products made of synthetic resin or light metals. Techniques for processing wooden materials are also developing dramatically. 
     According to one conventionally known technique for processing wooden materials: a wooden board is softened with water absorption and compressed; the compressed wooden board is cut along a direction substantially parallel with a direction in which the compressive force is applied, whereby a primary fixed product with a board-like shape is obtained; and the primary fixed product is deformed into a desired three-dimensional shape under heat and moisture (for example, see Japanese Patent No. 3078452. Publication). Further, according to another conventional technique, a softened wooden sheet is compressed and temporarily secured in a prepared mold and left in the mold until the wooden board recovers. Thus a wooden product with a desired shape can be obtained (see, for example, Japanese Patent Application Laid-Open No. H11-77619 Publication). 
     DISCLOSURE OF INVENTION 
     When a joining member is to be fixed to a wooden piece, which is formed through compression as described above, by screwing or caulking, the wooden piece is required to have bosses, ribs, or the like so that screws or caulking members can engage therewith. It is, however, technically difficult to form the bosses or ribs which protrude from the surface of the wooden piece and to compress the formed bosses or ribs into desired shapes similarly to other portions. 
     In some cases, the thickness of the wooden piece to be attached and fastened with the shape retaining member has to be smaller than that of other parts. The deference in thickness, which means the difference in compression ratios, results in a deference in color tone depending on thickness. In other words, the compressed wooden piece does not have a uniform color tone, which is not preferable in terms of appearance. 
     In view of the foregoing, an object of the present invention is to provide a joining member and a joining structure by which a wooden piece can be readily attached and detached without deterioration in appearance of the wooden piece. 
     To solve the problems as described above and to achieve an object, a joining member according to one aspect of the present invention is placed between plural wooden pieces to join the plural wooden pieces, and includes a frame that abuts an end face of each of the plural wooden pieces to fix the plural wooden pieces, and a connector that is detachably attached to the frame to connect at least two wooden pieces among the plural wooden pieces. 
     In the joining member according to the present invention, the frame may include a main frame portion that has a contact face which abuts the end face of each of the plural wooden pieces, and a guide portion that extends in a direction substantially perpendicular to the contact face of the main frame portion to guide a moving direction of each of the plural wooden pieces when the end face of each of the plural wooden pieces is made to abut the contact face. 
     In the joining member according to the present invention, the connector may include a flat main plate portion, and at least two pressing protruding portions each projected in a tapered shape from one surface of the main plate portion in a direction substantially orthogonal to the one surface of the main plate portion, and the pressing protruding portions be pressed into respective surfaces of different wooden pieces among the plural wooden pieces. 
     In the joining member according to the present invention, the connector may be fixed to the frame by a screw. 
     In the joining member according to the present invention, the connector may include a screw which has a plate head and is fitted into the main frame portion, and the plural wooden pieces may be sandwiched between the guide portion and the head. 
     In the joining member according to the present invention, a maximum diameter of a surface of the head may be larger than a width of a portion of the main frame portion placed between different wooden pieces. 
     In the joining member according to the present invention, the surface of the head may be substantially perpendicular to the contact face when the screw is fitted into the main frame portion. 
     In the joining member according to the present invention, the guide portion may have grooves that are oriented toward a direction intersecting with a direction in which the guide portion extends from the contact face of the main frame portion on a surface which abuts one of the plural wooden pieces near a position where the screw is fitted into the main frame portion. 
     In the joining member according to the present invention, the guide portion may be tapered so that a thickness thereof increases as a position on the guide portion is far from the contact face of the main frame portion. 
     In the joining member according to the present invention, the head may have a disk shape, and may be provided with a ring flange which forms a closed ring uniform protrusion projected from an outer rim of the one surface, the one surface facing the guide portion. 
     In the joining member according to the present invention, a surface of the head that does not face with the guide portion and a surface of at least one of the wooden pieces sandwiched between the head and the guide portion may together form an identical plane, or a smooth curved surface. 
     In the joining member according to the present invention, the frame may include a protruding strip that protrudes from an edge of an inner periphery of the main frame portion in a direction substantially perpendicular to the contact face, a first protruding portion that protrudes in a tapered shape from a tip end portion of the protruding strip towards an outer periphery of the main frame portion, and a pair of second protruding portions each protruding in a tapered shape from the contact face near a proximal end of the protruding strip in a direction substantially perpendicular to the contact face and in a direction of protrusion of the protruding strip as well, and may be arranged symmetrical about a plane perpendicular to the contact face and passing through the tip end portion of the protruding strip and the apex of the first protruding portion. 
     In the joining member according to the present invention, the frame may include plural wooden piece anchors each of which is a combination of the protruding strip, the first protruding portion, and the pair of the second protruding portions, and the frame may be symmetrical about a plane passing through the main frame portion. 
     In the joining member according to the present invention, in the wooden piece anchor, an apex of the first protruding portion may be arranged at a same distance from apexes of the second protruding portions. 
     In the joining member according to the present invention, the main frame portion may have a closed shape. 
     In the joining member according to the present invention, the connector may have an attachment unit for attachment of a separate member. 
     In the joining member according to the present invention, the attachment unit may have a threaded hole where a screw of a tripod is fitted. 
     A joining structure according to another aspect of the present invention includes the plural wooden pieces and the joining member, which are of the present invention. 
     In the joining structure according to the present invention, the plural wooden pieces may be formed through compression. 
     In the joining structure according to the present invention, the plural wooden pieces each may have a closed loop end face. 
     In the joining structure according to the present invention, the joining member may be formed from a material with a higher strength than a material for the plural wooden pieces. 
     In the joining structure according to the present invention, the plural wooden pieces and the joining member may form a jacket for an electronic equipment. 
     In the joining member and the joining structure according to the present invention, the joining member is placed between the plural wooden pieces, and the joining member includes a frame that abuts an end face of each of the plural wooden pieces to fix the plural wooden pieces, and a connector that is detachably attached to the frame to connect at least two wooden pieces among the plural wooden pieces. Therefore, the wooden pieces can be readily attached to and detached from the joining member without deterioration in the appearance of the wooden pieces. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a configuration of a digital camera to which a joining member according to a first embodiment of the present invention is applied; 
         FIG. 2  is a bottom view of the digital camera shown in  FIG. 1  viewed in the direction of arrow A of  FIG. 1 ; 
         FIG. 3  is a sectional view of the digital camera taken along line B-B of  FIG. 1 ; 
         FIG. 4  is a perspective view of a configuration of a front cover member of the digital camera; 
         FIG. 5  is a perspective view of a configuration of a rear cover member of the digital camera; 
         FIG. 6  is an exploded perspective view of a configuration of the joining member according to the first embodiment of the present invention; 
         FIG. 7  schematically shows how the cover members are joined together by the joining member according to the first embodiment of the present invention; 
         FIG. 8  schematically shows a process of compression of a wooden piece; 
         FIG. 9  is a vertical sectional view of a wooden piece during application of compressive force (where deformation of the wooden piece has nearly completed); 
         FIG. 10  is a partially enlarged sectional view showing the stage that a second protruding portion is being pressed into an end face of a cover member in an attachment process of a joining member to the cover member; 
         FIG. 11  is a partially enlarged sectional view showing the stage that a first protruding portion had been buried into an internal surface of a cover member in an attachment process of a joining member to the cover member; 
         FIG. 12  shows a configuration of relevant parts of a modification of the joining member according to the first embodiment of the present invention; 
         FIG. 13  schematically shows how the cover members are joined by the modification of the joining member according to the first embodiment of the present invention; 
         FIG. 14  is a perspective view of a configuration of a digital camera to which a joining member according to a second embodiment of the present invention is applied; 
         FIG. 15  is a bottom view of the digital camera shown in  FIG. 14 , viewed in the direction of arrow F of  FIG. 14 ; 
         FIG. 16  is an exploded perspective view of a configuration of the joining member according to the second embodiment of the present invention; 
         FIG. 17  schematically shows a joining structure which joins cover members by the joining member according to the second embodiment of the present invention; 
         FIG. 18  is a partially enlarged view of a portion near a bottom face of the joining structure shown in  FIG. 17 ; 
         FIG. 19  shows a configuration of grooves formed in a guide; 
         FIG. 20  schematically shows a joining structure which joins cover members by a first modification of the joining member according to the second embodiment of the present invention; 
         FIG. 21  schematically shows a joining structure which joins cover members by a second modification of the joining member according to the second embodiment of the present invention; 
         FIG. 22  schematically shows a joining structure which joins cover members by a third modification of the joining member according to the second embodiment of the present invention; 
         FIG. 23  is a perspective view of a configuration of a screw which is a part of the third modification of the joining member according to the second embodiment of the present invention; 
         FIG. 24  is an exploded perspective view of a configuration of a joining member according to a third embodiment of the present invention; 
         FIG. 25  schematically shows a joining structure which joins cover members by the joining member according to the third embodiment of the present invention; and 
         FIG. 26  shows a configuration of relevant parts of a modification of the joining member according to the third embodiment of the present invention. 
     
    
    
     BEST MODE(S) FOR CARRYING OUT THE INVENTION 
     Exemplary embodiments (hereinafter simply referred to as embodiments) of the present invention will be described in detail below with reference to the accompanying drawings. 
       FIG. 1  shows an example of application of a joining member according to a first embodiment of the present invention. More specifically,  FIG. 1  is a perspective view of a configuration of a digital camera  1  whose jacket is formed from two wooden pieces joined together by the joining member according to the first embodiment.  FIG. 2  is a view (bottom view) of the digital camera viewed in the direction of arrow A of  FIG. 1 .  FIG. 3  is a sectional view taken along line B-B of  FIG. 1  and shows an internal configuration of the digital camera  1 . The digital camera  1  shown in  FIGS. 1 to 3  includes two cover members  2  and  3  that are substantially of the same shape, and a joining member  4  which joins two cover members  2  and  3 . 
       FIG. 4  is a perspective view of a configuration of the cover member  2  which covers a front portion of the digital camera  1 . The cover member  2  shown in  FIG. 4  includes a substantially rectangular main plate portion  2   a , two side plate portions  2   b  that extend from two sides substantially parallel to a lengthwise direction of the main plate portion  2   a  making a predetermined angle to the main plate portion  2   a , respectively, two side plate portions  2   c  that extend from another two sides substantially parallel to a breadthwise direction of the main plate portion  2   a , respectively, and a closed loop end face  2   d . The main plate portion  2   a  has a cylindrical opening  21  which exposes an image pick-up unit  5  having an imaging lens, and a cuboid opening  22  which exposes a photoflash  6 . Further, a semi-cylindrical cut-out portion  23  is formed in the side plate portion  2   b.    
       FIG. 5  is a perspective view of a configuration of the cover member  3  which covers a rear portion of the digital camera  1 . The cover member  3  shown in  FIG. 5  includes a substantially rectangular main plate portion  3   a , two side plate portions  3   b  that extend from two sides substantially parallel to a lengthwise direction of the main plate portion  3   a  making a predetermined angle to the main plate portion  3   a , respectively, two side plate portions  3   c  that extend from another two sides substantially parallel to a breadthwise direction of the main plate portion  3   a  making a predetermined angle to the main plate portion  3   a , respectively, and a closed loop end face  3   d . The cover member  3  is substantially of the same shape as the cover member  2 . 
     The main plate portion  3   a  has a cuboid opening  31  to expose a display unit  7 , which is realized by a liquid crystal display, plasma display, organic electroluminescence (EL) display, or the like, to display image information and/or text information. The side plate portion  3   b  has a semi-cylindrical cut-out portion  32 . When the cover members  2  and  3  are joined, the cut-out portion  32  is placed opposite to the cut-out portion  23  of the cover member  2  to form an opening for exposing a shutter button  8 . 
     Each of the cover members  2  and  3  is formed by compressing a wooden piece taken out from the uncompressed raw wood. The raw wood may be selected from various types of wood including Japanese cypress, hiba cedar, paulownia, Japanese cedar, pine, cherry, zelkova, ebony wood, bamboo, teak, mahogany, and rosewood, for example. In the drawings such as  FIG. 1 , the grain patterns of the cover members  2  and  3  are not shown, since the joining structure of the first embodiment can be realized irrespective of the grain patterns of the cover members  2  and  3 . The manner of shaping the wooden piece, which is a raw material for the cover member  2  or  3 , from the raw wood is determined depending on the conditions, such as strength and appearance required for the cover members  2  and  3 . Thus the shaped wooden piece may have a straight-grain pattern, a flat-grain pattern, an intermediate grain pattern between the straight grain and the flat grain, an end-grain pattern, for example, as appropriate. 
     Inside the digital camera  1 , various components are housed, such as the display unit  7 , an imaging element  9  such as a Charge Coupled Device (CCD) or a Complementary Metal Oxide Semiconductor (CMOS), a circuit having a Central Processing Unit (CPU) to perform drive control related to the imaging process or the like and various operations, a driving circuit that drives respective functional units under the control of the control circuit, and the like.  FIG. 3  schematically shows various functional units having electronic or optical functions as described above in region D (surrounded by a broken line) inside the digital camera  1 . 
       FIG. 6  shows a detailed configuration of the joining member  4 . The joining member  4  of  FIG. 6  is placed between the cover members  2  and  3  to join the cover members  2  and  3 . Specifically, the joining member  4  includes a frame  4   a  and a connector  4   b . The frame  4   a  abuts each of the end face  2   d  of the cover member  2  and the end face  3   d  of the cover member  3  to fix the cover members  2  and  3 . The connector  4   b  is arranged at bottom faces of the cover members  2  and  3  and fixed to the frame  4   a , thereby connecting the side plate portion  2   b  of the cover member  2  and the side plate portion  3   b  of the cover member  3 . 
     The frame  4   a  has a main frame portion  41  and a guide portion  42 . The main frame portion  41  has a contact face  411  that abuts the end face  2   d  of the cover member  2  and the end face  3   d  of the cover member  3  and has a closed shape. The guide portion  42  extends from an inner peripheral edge of the main frame portion  41  in a direction substantially perpendicular to the contact face  411  of the main frame portion  41 , and serves to guide the cover members  2  and  3  along the frame  4   a  at the attachment thereto. Further, the frame  4   a  has a protruding strip  43  that protrudes from an edge of the guide portion  42  in a direction perpendicular to the contact face  411  of the main frame portion  41 , a trigonal pyramidal protruding portion  44  (first protruding portion) that protrudes from a tip end portion of the protruding strip  43  towards an outer periphery of the main frame portion  41 , and two circular conic protruding portions  45  (second protruding portions) each of which is provided near a proximal end of the protruding strip  43 , and protrudes from the contact face  411  in the direction of protrusion of the guide portion  42 . Two protruding portions  45  are arranged symmetrical about a plane perpendicular to the contact face  411  and passing through the tip end portion of the protruding strip  43  and the apex of the protruding portion  44 . Two protruding portions  45  are arranged as a pair. 
     The protruding strip  43 , the protruding portion  44 , and a pair of protruding portions  45  each having an above configuration constitute a wooden piece anchor  400  in combination. The wooden piece anchors  400  are plurally provided on each contact face  411  of the frame  4   a . As shown in  FIG. 6 , the main frame portion  41  is of a substantially rectangular shape, and has two long sides and two short sides. Each contact face  411  of the main frame portion  41  includes two sets of wooden piece anchors  400  on the upper long side (a side on which the shutter button  8  is exposed), and one wooden piece anchor  400  on each opposite position of two short sides. In brief, each contact face  411  has four wooden piece anchors  400 . Since the main frame portion  41  has two contact faces  411 , one facing the front side and another facing the rear side, the frame  4   a  includes eight wooden piece anchors  400  in total. 
     On an upper side of the main frame portion  41 , a cylindrical hollow opening  413  is formed at a position corresponding to the cut-out portions of the respective cover members so as to expose the shutter button  8 . On a lower side of the main frame portion  41 , holes  412  are formed so that the connector  4   b  can be fixed to the frame  4   a  by fitting screws through the holes  412 . An inner wall of the hole  412  is threaded so that a screw  200  can be fitted thereto. 
     The frame  4   a  with above-described configuration is symmetrical about a plane which passes through axis lines of all holes  412  among the planes passing through the closed outer rim of the main frame portion  41 . Hence, when the cover members  2  and  3  that are substantially of the same shape are joined by the frame  4   a , the cover members  2  and  3  are arranged symmetrically about the frame  4   a.    
     A configuration of the connector  4   b  will be described. The connector  4   b  includes a main plate portion  46  and two pressing protruding portions  47 . The main plate portion  46  is a flat plate with an octagonal surface. The two pressing protruding portions  47  are provided near respective opposing sides of the octagonal surface of the main plate portion  46 , and are projected orthogonal from the surface of the main plate portion  46 . The pressing protruding portion  47  has a trigonal pyramidal shape. The two pressing protruding portions  47  are pressed into different cover members. The main plate portion  46  has three holes  48  arranged at equal intervals. The connector  4   b  can be fixed to the frame  4   a  by fastening the screws through the holes  48 . The holes  48  are arranged in a direction perpendicular to the direction of arrangement of two pressing protruding portions  47  on the surface of the main plate portions  46 . 
       FIG. 7  shows a configuration of a jacket of the digital camera  1 .  FIG. 7  is a vertical sectional view of the jacket when viewed along a line corresponding to line C-C of  FIG. 6 . As can be seen from  FIG. 7 , the protruding portions  44  are buried into the cover members  2  and  3 , respectively, from internal surfaces of the side plate portions  2   b  and  3   b . The protruding portions  44  have a function of preventing the cover members  2  and  3  from being detached from the main plate portion  41  (anchoring function). 
     In  FIG. 7 , the pair of protruding portions  45  belonging to the same wooden piece anchor  400  as that which the protruding portion  44  pressed into the side plate portion  2   b  belongs to is pressed into the end face  2   d  of the cover member  2 , symmetrically arranged about the section shown in  FIG. 7 . The pair of protruding portions  45  has a function of suppressing an excessive deformation of the side plate portion  2   b  toward an external surface of the side plate portion  2   b  when the side plate portion  2   b  is subjected to a force which acts in an outward thickness direction of the side plate portion  2   b  (upward direction in  FIG. 7 ). On the other hand, in  FIG. 7 , the pair of protruding portions  45  belonging to the same wooden anchor  400  as that which the protruding portion  44  that is pressed into the side plate portion  3   b  belongs to is pressed into the end face  3   d  of the cover member  3 , symmetrically arranged about the section shown in  FIG. 7 . The pair of protruding portions  45  facing the cover member  3  similarly has the function of suppressing the excessive deformation of the cover member  3  by an external force. 
     The wooden piece anchors  400  that are provided on the short side portions of the main frame portion  41  are attached respectively to the side plate portions  2   c  and  3   c  which correspond to side faces of the digital camera  1  in a similar fashion as described above, though not specifically shown. Thus, when all the wooden piece anchors  400  are attached to the cover members  2  or  3 , the cover, members  2  and  3  are completely fixed to the frame  4   a.    
     The connector  4   b  is fixed to the frame  4   a  by screws  200 , and at the same time the pressing protruding portions  47  are pressed into respective external surfaces of the cover members  2  and  3 . The pressing protruding portions  47 , thus has a function of securely fixing the connector  4   b  to the cover members  2  and  3  and preventing separation of the end faces  2   d  and  3   d  from the contact faces  411  of the frame  4   a.    
     When such connector  4   b  is provided, the joining member  4  can be detached from the cover members  2  and  3  simply by unfastening the screw  200  and removing the connector  4   b  from the frame  4   a . Hence, the repair and maintenance check of the inside of the digital camera  1  can be readily performed. In addition, since the main plate portion  46  is a flat plate, the digital camera  1  does not wobble when placed on a table, and is suitable for self-timer shooting, for example. 
     The joining member  4  with above-described configuration is formed from a material which has a significantly higher strength and endurance for bending and tension than a material for the cover members  2  and  3 . For example, the joining member  4  is formed from metal, or super engineering plastic represented by polyimide. 
     The protruding portion  44  may have a tapered shape other than the trigonal pyramid (for example, the shape of the protruding portion  44  may be a circular cone, or any polygonal pyramid). Similarly, the protruding portion  45  and the pressing protruding portion  47  may have a tapered shape other than the circular cone (for example, polygonal pyramid). In addition, the surface of the main plate portion  46  does not need to be octagonal. The numbers of the pressing protruding portions  47  and the holes  48  are also not limited to the numbers in the above described embodiment. In addition, as far as there is one connector  4   b , the number of the connectors  4   b  can be changed as appropriate depending on conditions such as the size of the digital camera  1 . 
     A method of processing the cover members  2  and  3  will be described. In the following, the method of processing the cover member  2  will be described by way of example, and the cover member  3  is processed in the same manner. First, a wooden piece is taken out from uncompressed raw wood by cutting or the like so that the wooden piece has a predetermined three-dimensional shape. The wooden piece thus taken out is larger in volume than a finished wooden piece by an amount to be decreased during a compression process described later. Hereinbelow, thus shaped wooden piece is referred to as wooden piece  51 . A portion that is processed into either the main plate portion  2   a  of the cover member  2  or the main plate portion  3   a  of the cover member  3  is referred to as main plate portion  51   a . A portion that is processed into either the side plate portion  2   b  (and  2   c ) of the cover member  2  or the side plate portion  3   b  (and  3   c ) of the cover member  3  is referred to as side plate portion  51   b  (and  51   c ). 
     Thereafter, the wooden piece  51  taken out is compressed (compression process). Before the compression process, the wooden piece  51  is left in a water vapor atmosphere of high temperature and high pressure for a predetermined time period, so that the wooden piece  51  excessively absorbs moisture to be softened. Here, the high temperature means 100 to 230° C. and more preferably approximately 180 to 200° C., and the high pressure means 0.1 to 3 MPa (MegaPascal) and more preferably approximately 0.45 to 2.5 MPa. Alternatively, the wooden piece may be heated and softened by application of high-frequency electromagnetic wave such as microwave rather than by being left in the waver vapor atmosphere as described above. 
     Subsequently, the softened wooden piece  51  is compressed in the same water vapor atmosphere.  FIG. 8  schematically shows an outline of the compression process. In  FIG. 8 , the wooden piece  51 , which is taken out from the raw wood as described above, is sandwiched between a pair of metal molds  11  and  12  and compressed. The metal mold  11  which is employed for applying compressive force to the wooden piece  51  from above at the time of compression has a protrusion  111  shaped to fit with the internal surface of the wooden piece  51 . When the radius of curvature of an internal surface of a curved portion  51   ab  extending from the main plate portion  51   a  to the side plate portion  51   b  of the wooden piece  51  is represented as RI, and the radius of curvature of a curved surface, which abuts the curved portion  51   ab  during compression, on the protrusion  111  is represented as RA, relation represented as RI&gt;RA is satisfied. 
     On the other hand, the metal mold  12  which is employed for applying compressive force to the wooden piece  51  from below has a depression  121  that fits an external surface of the wooden piece  51 . When the radius of curvature of an external surface of the curved portion  51   ab  extending from the main plate portion  51   a  to the side plate portion  51   b  of the wooden piece  51  is represented as RO, and the radius of curvature of a curved surface, which abuts the external surface of the curved portion  51   ab  during compression, on the depression  121  is represented as RB, relation represented as RO&gt;RB is satisfied. 
     When the metal molds  11  and  12  and the wooden piece  51  are viewed along a section passing through the main plate portion  51   a  and the side plate portion  51   c , the shape of the metal molds  11  and  12  and positional relation among the metal molds  11  and  12  and the wooden piece  51  are similar to those shown in  FIG. 8  other than dimension. In addition, the radius of curvature of an internal surface of a curved portion extending from the main plate portion  51   a  to the side plate portion  51   c  is larger than the radius of curvature of a curved face of the metal mold  11  that abuts the internal surface. The radius of curvature of an external surface of the curved portion that extends from the main plate portion  51   a  to the side plate portion  51   c  is larger than the radius of curvature of a curved surface of the metal mold  12  that abuts the external surface. 
     In the first embodiment, the metal molds  11  and  12  are formed so that compression rate in the thickness direction is substantially uniform at respective portions of the wooden piece  51  (here, the compression rate means a ratio of decrease in the thickness of the wooden piece by the compression to the thickness of the wooden piece before the compression). Thus, the color tone of the cover member  2  obtained after the compression can be made uniform. 
       FIG. 9  is a diagram showing that the softened wooden piece  51  placed at a predetermined position is sandwiched and compressed by the metal molds  11  and  12 . In  FIG. 9 , the deformation of the wooden piece  51  into a three-dimensional shape corresponding to a gap between the metal molds  11  and  12  has been nearly completed. After the wooden piece  51  is left in a state shown in  FIG. 9  for a predetermined time period, the wooden piece  51  is released from compression as the metal molds  11  and  12  are separated from each other. Then, the water vapor atmosphere of high temperature and high pressure as described above is removed and the wooden piece  51  is dried. Thereafter, the openings  21  and  22 , and the cut-out portion  23  are formed by cutting or the like, whereby the cover member  2  shown in  FIG. 4  is completed. 
     As a result of the compression process as described above, the cover member  2  or  3  comes to have a substantially uniform thickness, which is approximately 30 to 50% of the thickness of the wooden piece  51  before the compression process (here, the compression rate is approximately 0.5 to 0.7). Generally, the wooden piece  51  can be compressed to approximately 20% the thickness before the compression (in this case compression rate is approximately 0.8). In the present embodiment, however, the compression of the wooden piece  51  is not performed to such a limit. Hence, the cover member  2  or  3  still contains some space inside. The existence of such space prevents changes in the appearance of the cover member  2  or  3  by the intrusion of the protruding portion  44  or the press fit of the protruding portion  45 . 
     An outline of an attachment process in which the cover members  2  and  3  are attached to the joining member  4  will be described.  FIGS. 10 and 11  schematically show how the protruding portion  44  is intruded and the protruding portion  45  is pressed into the cover member  2 .  FIGS. 10 and 11  show a section along line D-D of  FIG. 6 . First, the protruding portion  45  is pressed into the end face  2   d . In  FIG. 10 , the apex of the triangular pyramid of the protruding portion  44  has not yet been buried into the side plate portion  2   b , and the protruding strip  43  is bending so that the tip end thereof stays away from the side plate portion  2   b . In the state shown in  FIG. 10 , a proximal end portion of the protruding portion  45  has not been completely pressed into the end face  2   d , and some portions of the contact face  411  has not yet come into contact with the end face  2   d.    
     Thereafter, the main frame portion  41  is further pressed against the end face  2   d  and the protruding portion  45  is further pressed into the side plate portion  2   b . On the other hand, a portion around the bottom face of the protruding portion  44  is pressed against the side plate portion  2   b , and the protruding portion  44  is buried into the internal surface of the side plate portion  2   b . Thus, the attachment of the wooden piece anchor  400  to the cover member  2  is completed. Here, the protruding portion  44  and the pair of the protruding portions  45  belonging to the specific wooden piece anchor  400  are focused, and the attachment of these portions to the side plate portion  2   b  is described. With regard to the joining member  4  having a shape as shown in  FIG. 6 , for example, a swift attachment of the joining member  4  to the cover member  2  can be realized when the wooden piece anchors  400  are attached to the main frame portion  41  by the side of the rectangle formed by the main frame portion  41 . 
     When the joining member  4  is formed from a hard metal, the protruding strip  43  bends only slightly, and it may not be easy to attach all the wooden piece anchors  400  to the cover member  2  by the same process. In this case, after the wooden piece anchor  400  on one side of the rectangle of the main frame portion  41  is attached to the cover member  2 , the wooden piece anchor  400  on the opposing side of the main frame portion  41  may be attached to the cover member  2  while being properly positioned with the use of a suitable jig. 
     The cover member  3  may be attached to the frame  4   a  in a similar manner to the attachment process of the cover member  2  described above. As a result, two cover members  2  and  3  come to be joined via the frame  4   a  at the upper side portion. Needless to say, the joining member  4  can be attached first to the cover member  2  and then to the cover member  3 , or vice versa. 
     After the frame  4   a  is attached to the two cover members  2  and  3 , the connector  4   b  is fixed to the frame  4   a . For the fixation of the connector  4   b , the holes  412  of the frame  4   a  and the corresponding holes  48  of the connector  4   b  are aligned with each other, and the connector  4   b  is fixed to the frame  4   a  by the screws  200 . Thus, the digital camera  1  is completed. 
     In the above described method of forming the joining structure, the cover members  2  and  3  are attached to the joining member  4 . As a matter of course, before the attachment process, various functioning units are already housed inside the digital camera  1 . That is to say, the internal components of the digital camera  1  are arranged at predetermined positions of the cover members  2  and  3  at an appropriate timing at least before the cover members  2  and  3  are completely fixed to the joining member  4 . 
     In the joining member and the joining structure according to the first embodiment of the present invention as described above, a frame and a connector are provided. The frame abuts respective closed loop end faces of two cover members, and fixes the cover members. The connector can be detachably attached to the frame, and connects the side faces of the cover members with each other. Thus, the joining member can be attached to and detached from the wooden pieces without deterioration of the appearance of the wooden piece. 
     Further, according to the first embodiment, the compression rate of the wooden piece is controlled so as not to reach the limit value. Hence, even when the wooden piece is thin, the protruding portions that constitute the wooden piece anchor and that are pressed into the wooden piece do not affect the appearance of the side surface of the wooden piece. 
       FIG. 12  schematically shows a modification of the joining member of the first embodiment. A joining member  61  of  FIG. 12 , similarly to the joining member  4  described above, includes a frame  61   a  and a connector  61   b  connected to the frame  61   a  by screws. The connector  61   b  includes a main plate portion  62 , two pressing protruding portions  63 , and a threaded cylinder  64  for a tripod. The main plate portion  62  is a flat plate with an octagonal surface. The two pressing protruding portions  63  are provided near respective opposing sides of the octagonal surface of the main plate portion  62 , and are projected orthogonal from the surface of the main plate portion  62 . The pressing protruding portion  63  has a trigonal pyramidal shape. Two pressing protruding portions  63  are pressed into different cover members. The threaded cylinder  64  is a cylindrical portion which includes a threaded hole running inside. The threaded cylinder  64  is projected cylindrically in a direction perpendicular to the surface of the main plate portion  62  and longer than the pressing protruding portion  63 . A screw of the tripod is screwed into the threaded cylinder  64  from the bottom face side, i.e., lower side of  FIG. 12 . The main plate portion  62  also includes two holes  65  so that the connector  61   b  can be fixed to the frame  61   a  by screws. Two holes  65  are arranged at both sides of the threaded cylinder  64 . The holes  65  are arranged in a direction perpendicular to the direction in which the pressing protruding portions  63  are arranged on the surface of the main plate portion  62 . 
     The frame  61   a  which corresponds to the connector  61   b  having the above-described configuration includes a main frame portion  66  and a guide portion  67  that have similar functions as the main frame portion  41  and the guide portion  42  described above, respectively. Further, the frame  61   a  includes an opening  68  and holes  69  on a side of the bottom faces of the main frame portion  66  and the guide portion  67 . The opening  68  can receive the threaded cylinder  64 , and the hole  69  is arranged at a position corresponding to the hole  65  and allows to be screwed. Inner walls of the respective holes  69  are threaded so that the screws  200  can be fixed therethrough. Only one threaded cylinder  64  for a tripod is sufficient for the digital camera. Hence, when two connectors are attached to the frame  61   a  similarly to the configuration of the joining member  4  described above, one connector may be formed as the connector  61   b , and another connector may be formed as the connector  4   b . Then, the bottom side of the frame  61   a  may be configured to have a portion having the configuration of  FIG. 12  to which the connector  61   b  is attached and a portion having the configuration of  FIG. 6  in which three holes  412  are formed to which the connector  4   b  is attached. 
       FIG. 13  shows a configuration around a portion where the connector  61   b  is fixed to the frame  61   a  in the joining structure realized by the joining member  61 .  FIG. 13  is a partial vertical sectional view of the joining structure that joins the cover members along a line corresponding to line E-E of  FIG. 12 . In  FIG. 13 , a cut-out portion that has a corresponding shape to the outer periphery of the opening  68  of the frame  61   a  is formed in each of a side plate portion  71   b  located at a bottom face of a front cover member  71  and a side plate portion  72   b  located at a bottom face of a rear cover member  72 . In other points, the configuration of each of the cover members  71  and  72  is similar to the configuration of each of the cover members  2  and  3 , respectively. 
     The conventional digital camera is provided with a threaded hole so that a tripod can be attached by a screw. Such a hole is fabricated so as to be broken when an excessive external force is applied via the screw in order to prevent damages to a main body of the digital camera. When the threaded hole is integrated with the cover member, replacement of the threaded hole inevitably accompanies replacement of the whole cover member with a new one. In the modification of the first embodiment, the threaded hole for a tripod is integrated with the connector of the joining member. Hence, even when the threaded hole is broken, only the connector in which the threaded hole is formed can be replaced, with the cover member left as it is. As a result, there is no need of replacement of the cover member to which unique texture is added by use. 
     In the above, a threaded hole is provided in the joining member to allow attachment of a separate member. Alternatively, a strap holder may be provided for an attachment of a strap. When the strap holder is to be formed in the connector, it may be preferable that the connector be arranged at a side face or an upper face of the jacket rather than the bottom face thereof, depending on types of electronic equipment to which the joining member is applied. 
       FIG. 14  shows an example of application of a joining member according to a second embodiment of the present invention. Specifically,  FIG. 14  is a perspective view of a configuration of a digital camera whose jacket is formed from two wooden pieces joined by the joining member according to the second embodiment.  FIG. 15  is a bottom view of the digital camera of  FIG. 14  viewed in, the direction of arrow F of  FIG. 14 . A digital camera  101  shown in  FIGS. 14 and 15  includes two cover members  2  and  3  that are substantially of the same shape and a joining member  100  that joins two cover members  2  and  3 . 
     The configuration of each of the cover members  2  and  3  (see  FIGS. 4 and 5 ) and a method of processing the cover member  2  or  3  (see  FIGS. 8 and 9 ) are the same as those of the first embodiment described above. The digital camera  101 , similarly to the digital camera  1  described above, includes the image pick-up unit  5 , the photoflash  6 , and the shutter button  8  (see  FIG. 1 ). Further, the inner configuration of the digital camera  101  (including the display unit  7 , the imaging element  9 , or the like) is the same as the inner configuration of the digital camera  1  (see  FIG. 3 ). 
       FIG. 16  shows a detailed configuration of the joining member  100 . The joining member  100  shown in  FIG. 16  is placed between the cover members  2  and  3  to join the cover members  2  and  3 . The joining member  100  includes a frame  104  and screws  105 . The frame  104  abuts each of the end face  2   d  of the cover member  2  and the end face  3   d  of the cover member  3  to fix the cover members  2  and  3 . The screw  105  is turned into the frame  104  and has a function of a connector that connects the side plate portion  2   b  of the cover member  2  and the side plate portion  3   b  of the cover member  3 . 
     The frame  104  has a main frame portion  141  and a guide portion  142 . The main frame portion  141  has a contact face  1411  that abuts the end face  2   d  of the cover member  2  and the end face  3   d  of the cover member  3 . The guide portion  142  extends from an inner rim of the main frame portion  141  in a direction substantially perpendicular to the contact face  1411  of the main frame portion  141 . The guide portion  142  has a function of guiding a movement of each of the cover members  2  and  3  when the cover members  2  and  3  are attached to the frame  104 . The frame  104  has a protruding strip  143 , a trigonal pyramidal protruding portion  144  (first protruding portion), and two circular conic protruding portions  145  (second protruding portions). The protruding strip  143  protrudes from an edge of the guide portion  142  in a direction perpendicular to the contact face  1411  of the main frame portion  141 . The protruding portion  144  protrudes from a tip end portion of the protruding strip  143  towards an outer periphery of the main frame portion  141 . Each of the two protruding portions  145  is provided near a proximal end of the protruding strip  143  and protrudes from the contact face  1411  in the direction of protrusion of the guide portion  142 . Two protruding portions  145  are arranged symmetrical about a plane perpendicular to the contact face  1411  and passing through the tip end portion of the protruding strip  143  and the apex of the protruding portion  144 . Two protruding portions  145  are arranged as a pair. 
     The protruding strip  143 , the protruding portion  144 , and a pair of protruding portions  145  each having an above configuration constitute a wooden piece anchor  1400  in combination. The wooden piece anchors  1400  are plurally provided on each contact face  1411  of the frame  104 . As shown in  FIG. 16 , the main frame portion  141  is of a substantially rectangular shape, and has two long sides and two short sides. Each contact face  1411  of the main frame portion  141  includes two sets of wooden piece anchors  1400  on the upper long side (a side on which the shutter button  8  is exposed), and one wooden piece anchor  1400  on each opposite position of two short sides. In brief, each contact face  1411  has four wooden piece anchors  1400 . Since the main frame portion  141  has two contact faces  1411 , one facing the front side and another facing the rear side, the frame  104  includes eight wooden piece anchors  400  in total. 
     On the upper side of the main frame portion  141 , a cylindrical hollow opening  1413  is formed at a position corresponding to the cut-out portions of the respective cover members so as to expose the shutter button  8 . On the lower side of the main frame portion  141 , holes  1412  are formed so that the screw  105  can be fixed therethrough. An inner wall of the hole  1412  is threaded so that the screw  105  can be fitted thereto. 
       FIG. 17  schematically shows a joining structure including the joining member  100 , and is a vertical sectional view taken along a line corresponding to line G-G of  FIG. 16 . As shown in  FIG. 17 , the protruding portion  144  is pressed into the internal surfaces of the side plate portions  2   b  and  3   b . The protruding portion  144  has a function of preventing the cover members  2  and  3  from being detached from the main frame portion  141 , i.e., anchoring function. 
     In  FIG. 17 , a pair of protruding portions  145  belonging to the same wooden piece anchor  1400  as that which the protruding portion  144  pressed into the side plate portion  2   b  belongs to is pressed into the end face  2   d  of the cover member  2  symmetrically arranged about the section shown in  FIG. 17 . The pair of protruding portions  145  has a function of suppressing an excessive deformation of the side plate portion  2   b  toward external surface when the side plate portion  2   b  is subjected to a force which acts in an outward thickness direction of the side plate portion  2   b  (upward direction in  FIG. 17 ). On the other hand, in  FIG. 17 , the pair of protruding portions  145  belonging to the same wooden piece anchor  1400  as that which the protruding portion  144  that is pressed into the side plate portion  3   b  belongs to is pressed into the end face  3   d  of the cover member  3 , symmetrically arranged about the section shown in  FIG. 17 . The pair of protruding portions  145  similarly has the function of suppressing an excessive deformation of the cover member  3  caused by an external force. 
     The wooden piece anchors  1400  that are provided on short side portions of the main frame portion  141  are attached respectively to the side plate portions  2   c  and  3   c  that correspond to the side faces of the digital camera  101  in a similar fashion as described above, though not specifically shown. Thus, when all the wooden piece anchors  1400  are attached to the cover members  2  or  3 , the cover members  2  and  3  are completely fixed to the frame  104 . 
       FIG. 18  is a partially enlarged sectional view showing a detailed configuration of a portion near the bottom face shown in  FIG. 17 . As shown in  FIG. 18 , the screw  105  which constitutes the joining member  100  together with the frame  104 , includes a disk head  151  and a threaded portion  152 . The threaded portion  152  extends from a central portion of the head  151  in a direction perpendicular to a surface of the head  151 . The threaded portion  152  fits into the hole  1412 . The surface from which the threaded portion  152  is projected among the surfaces of the head  151  is partly in contact with the cover members  2  and  3  and perpendicular to the contact face  1411 . As is clear from  FIGS. 18 and 15 , a diameter of the circular head  151  is larger than a gap between the cover members  2  and  3  in (the main frame portion  141  of) the frame  104 . Therefore, the cover members  2  and  3  can be securely sandwiched and held in the thickness direction by the head  151  and the guide  142  at a portion near the end faces thereof. Thus, the side plate portion  2   b  of the cover member  2  can be connected to the side plate portion  3   b  of the cover member  3 , whereby the cover members can be joined. 
       FIG. 19  shows a configuration of the bottom face side of the frame  104 .  FIG. 19  shows a portion near the hole  1412  viewed in the direction of arrow H of  FIG. 16 . As shown in  FIG. 19 , the guide portion  142  has grooves  1421  formed in a direction substantially parallel to a longitudinal direction of the main frame portion  141  on the bottom face (surface that abuts one of the cover members  2  and  3 ) near the hole  1412  through which the screw  105  is fitted. The grooves  1421  have a function of preventing the end faces  2   d  and  3   d  of the cover members  2  and  3  from being separated from the contact face  1411  and preventing the cover members  2  and  3  from falling out from the joining member  100 , i.e., anchoring function. The grooves  1421  are formed by straight knurling, for example. The grooves  1421  may be formed like diamond-shaped patterns. The direction of the diamond-shaped patterns may be set so as to intersect with a direction in which the guide  142  extends from the contact face  1411 . The grooves  1421  can be formed by criss-cross knurling. 
     The joining member  100  with the above-described configuration is symmetrical about a plane which passes axis lines of all the holes  1412  among the planes passing through the closed outer rim of the main frame portion  141 . Hence, the cover members  2  and  3  that are substantially of the same shape are joined together so as to be located symmetrically about the joining member  100 . 
     When the joining member  100  is to be detached from the cover members  2  and  3 , first, the screw  105  is removed, and then the side plate portions  2   b  and  3   b  are removed from the frame  104 . Thus, the repair and maintenance check of the inside of the digital camera  101  can be readily performed. In addition, since the head  151  is of a disk shape, the digital camera  101  does not wobble when placed on a table, and is suitable for self-timer shooting. 
     The joining member  100  with the above-described configuration is formed from a material having a significantly higher strength and endurance for bending and tension than a material for the cover members  2  and  3 . For example, the joining member  100  is formed from metal or super engineering plastic represented by polyimide. 
     The protruding portion  144  may be of a tapered shape other than trigonal pyramid (e.g., circular cone, polygonal pyramid, or the like). The protruding portion  145  may similarly be of a tapered shape other than circular cone (e.g., polygonal pyramid, or the like). In addition, the cover members  2  and  3  may be fixed by the screws  105  to the frame  104  at any numbers of positions on the bottom face of the digital camera  101  depending on conditions such as the size of the digital camera  101 . 
     When the cover members  2  and  3  are attached to the joining member  100 , the cover members  2  and  3  are first attached to the frame  104  in a similar manner to in the first embodiment (see  FIGS. 10 and 11 ). Needless to say, either of the two cover members  2  and  3  can be attached to the frame  104  first. 
     After two cover members  2  and  3  are attached to the frame  104 , the cover members  2  and  3  are fixed to the frame  104  from the bottom face of the cover members  2  and  3  by the screws  105 . Thus, the digital camera  101  is completed. 
     In the above described method of forming the joining structure, the cover members  2  and  3  are attached to the joining member  100 . Needless to say, various functioning units are arranged inside the digital camera  101  at an appropriate stage before the attachment process. That is to say, the internal components of the digital camera  101  are arranged at predetermined positions of the cover members  2  and  3  at an appropriate timing at least before the cover members  2  and  3  are completely fixed to the joining member  100 . 
     In the joining member and the joining structure according to the second embodiment of the present invention as described above, the joining member includes a main frame portion, a guide portion, and a screw. The main frame portion has a contact face which abuts each end face of two cover members (wooden pieces). The guide portion is projected in a direction substantially perpendicular to the contact face of the main frame portion, and guides the movement of the two cover members when the end faces of the cover members are made to abut the contact face. The screw has a flat head and fixed to the main frame portion. The joining member holds the two cover members by sandwiching the cover members between the guide portion and the head, whereby the joining member can be attached to and detached from the wooden piece without deterioration of the appearance of the wooden pieces. 
     Further, according to the second embodiment, the compression rate of the wooden piece is adjusted so as not to reach the limit value. Therefore, even when thin wooden pieces are to be joined, the appearance of the side surfaces of the wooden pieces is not affected by the protruding portions that constitute the wooden piece anchor and that are pressed into the side surfaces of the wooden piece. 
       FIG. 20  schematically shows a first modification of the joining structure having the joining member according to the second embodiment.  FIG. 20  is a sectional view of a detailed configuration of a portion near a bottom face of a digital camera which has the similar configuration to that of the digital camera  101  (corresponding to  FIG. 18 ). A joining member  110  shown in  FIG. 20  includes a frame  106  and a screw  105  which is fitted into the frame  106 . The frame  106  is provided with a main frame portion  161  and a guide portion  162 . The guide portion  162  extends from the main frame portion  161  in a direction substantially perpendicular to the contact face  1611 . Thickness of the guide portion  162  gradually increases outwards from a side of the contact face  1611 . Thus the guide portion  162  has a tapered shape. When the screw  105  is fitted into the main frame portion  161 , the tapered guide portion  162  gradually bites into the side plate portion  2   b  of the cover member  2  and the side plate portion  3   b  of the cover member  3 . Thus, the cover members  2  and  3  are fixed to the frame  106 . The tapered shape of the guide portion  162  serves to prevent the cover members  2  and  3  from falling out from the frame  106  similarly to the grooves  1421  of the joining member  100 . The configuration of the frame  106  is the same as the configuration of the frame  104  if not specified otherwise above. 
       FIG. 21  schematically shows a second modification of the joining structure having the joining member according to the second embodiment.  FIG. 21  is a sectional view of a detailed configuration of a portion near a bottom face of a digital camera which has a similar configuration to that of the digital camera  101  (corresponding to  FIG. 18 ). A joining member  120  shown in  FIG. 21  includes a frame  107  and a screw  153 . The frame  107  has a main frame portion  171  whose contact face  1711  is depressed inwardly by the amount corresponding to the thickness of a disk-like portion of a head  154  at least at a position where a hole is formed for the attachment of the screw  153 . Therefore, when the screw  153  is fitted into the frame  107 , the screw  153  is buried into the hole until the bottom surface of the head  154  becomes coplanar with the bottom surfaces of the cover members  2  and  3 . The screw  153  is buried into the cover members  2  and  3  in the thickness direction until the upper face of the head  154  abuts an edge of the main frame portion  171 . The configuration of the frame  107  is the same as that of the frame  104  if not specified otherwise above. Also in the frame  107 , similarly to the frame  104 , grooves  1721  that are similar to the grooves  1421  are formed on a face of a guide portion  172  which abuts the cover members  2  and  3 . 
     In the second modification, if the cover members  2  and  3  are formed from a relatively hard wooden piece, edge portions of the cover members  2  and  3  may be cut out in positions that abut the periphery of the head  154 , so that the screw  153  can be fitted without depressing the edges of the cover members  2  and  3  by the head  154 . In the above described configuration, the head  154  is coplanar with the bottom faces of the cover members  2  and  3 . Alternatively, however, the bottom face of the head  154  may smoothly lead to the faces of the cover members while forming a smoothly curved surface, depending on the shape of the cover members. 
       FIG. 22  schematically shows a third modification of the joining structure having the joining member according to the second embodiment.  FIG. 22  is a sectional view of a detailed configuration of a portion near a bottom face of a digital camera which has a similar configuration to that of the digital camera  101  (corresponding to  FIG. 18 ). Further,  FIG. 23  is a perspective view of a configuration of a screw which is employed in the joining member according to the third modification. A joining member  130  shown in  FIGS. 22 and 23  includes a frame  108  and a screw  156  fitted into the frame  108 . The screw  156  is provided with a ring flange  159  which forms a closed ring uniform protrusion projected from an outer rim of the surface of the head  157  from which a threaded portion  158  is projected. When the screw  156  is fitted into a main frame portion  181  of the frame  108 , the ring flange  159  is pressed into the side plate portions  2   b  and  3   b  so that the ring flange  159  serves as an anchor that prevents the cover members  2  and  3  from falling out from the frame  108 . Here, a lower end face of the main frame portion  181  is not brought into contact with the head  157  of the screw  156 . Such arrangement intends to prevent the ring flange  159  from being caught by the main, frame portion  181  at the fitting of the screw  156  into the main frame portion  181 , in order to facilitate the press fitting of the ring flange  159  into the cover members  2  and  3 . 
     A guide portion  182  of the frame  108  extends from a bottom face of the main frame portion  181  in a direction perpendicular to the main frame portion  181 , and is not provided with an additional structural element such as the groove  1421  of the frame  104 . The configuration of the frame  108  is the same as that of the frame  104  if not specified otherwise. 
     According to the first to the third modifications of the second embodiment of the present invention, the joining member can be readily attached to and detached from the wooden piece without deteriorating the appearance of the wooden piece similarly to the second embodiment. The above-described second embodiment and its modifications can be appropriately combined in order to realize various modifications of joining member and joining structure of the second embodiment. 
       FIG. 24  schematically shows a detailed configuration of a joining member according to a third embodiment of the present invention.  FIG. 25  schematically shows a joined state of the cover member and the joining member of the third embodiment at a portion near a bottom face of the cover member.  FIG. 25  is a partial vertical sectional view taken along a line corresponding to line I-I of  FIG. 24 . A joining member  210  shown in  FIGS. 24 and 25  is placed between two cover members  1041  and  1042  that cover a digital camera which has the same configuration as that of the digital camera  101  of the second embodiment. The joining member  210  includes a frame  109   a , a connector  109   b , and a screw  105 . The frame  109   a  abuts an end face of each of the cover members  1041  and  1042 . The connector  109   b  is detachably attached to the frame  109   a , and connects a side plate portion  1041   b  of the cover member  1041  and a side plate portion  1042   b  of the cover member  1042 . The screw  105  has a function as a connector that connects the side plate portion  1041   b  of the cover member  1041  and the side plate portion  1042   b  of the cover member  1042  similarly to the connector  109   b , though different in shape from the connector  109   b . The screw  105  is fitted into the frame  109   a.    
     The connector  109   b  includes a main plate portion  193 , two pressing protruding portions  194 , and a threaded cylinder  195  for a tripod. The main plate portion  193  is a flat plate with an octagonal surface. The two pressing protruding portions  194  are provided near respective opposing sides of the octagonal surface of the main plate portion  193  and are projected orthogonal from the surface of the main plate portion  193 . The pressing protruding portion  194  has a trigonal pyramidal shape. The two pressing protruding portions  194  are pressed into different cover members. The threaded cylinder  195  is a cylindrical portion which includes a threaded hole running inside. The threaded cylinder  195  is projected cylindrically in a direction perpendicular to the surface of the main plate portion  193  and longer than the pressing protruding portion  194 . A screw of the tripod is screwed into the threaded cylinder  195  from the bottom face side, i.e., lower side of  FIG. 24 . The main plate portion  193  also includes two holes  196  so that the connector  109   b  can be fixed to the frame  109   a  by screws. Two holes  196  are arranged at both sides of the threaded cylinder  195 . The holes  196  are arranged in a direction perpendicular to the direction in which the pressing protruding portions  194  are arranged on the surface of the main plate portion  193 . 
     The frame  109   a  which corresponds to the connector  109   b  having the above-described configuration includes a main frame portion  191  and a guide portion  192  that have similar functions as the main frame portion  141  and the guide portion  142  described above, respectively. Further, the frame  109   a  includes an opening  1914  and holes  1915  on a side of the bottom faces of the main frame portion  191  and the guide portion  192 . The opening  1914  can receive the threaded cylinder  195 , and the hole  1915  is arranged at a position corresponding to the hole  196  and allows to be screwed. Inner walls of the respective holes  1915  are threaded so that screws  1500  can be fixed therethrough. Here, only one threaded cylinder  195  is sufficient for a digital camera. Hence, on the bottom face of the guide portion  192 , a hole  1912  which is similar to the hole  1412  formed on the guide portion  142  of the second embodiment is provided. The screw  105  is fitted into the hole  1912 . Here, if the thicknesses of the main plate portion  193  of the connector  109   b  and the thickness of the head  151  of the screw  105  are made equal, the bottom face of the digital camera becomes more flat and the digital camera can be more stably placed on a table, for example. 
     Further, the frame  109   a  has a protruding strip  197  that protrudes from an edge of the guide portion  192  in a direction perpendicular to the contact face  1911  of the main frame portion  191 , a trigonal pyramidal protruding portion  198  (first protruding portion) that protrudes from a tip end portion of the protruding strip  197  towards an outer periphery of the main frame portion  191 , and two circular conic protruding portions  199  (second protruding portions) each of which is provided near a proximal end of the protruding strip  197 , and protrudes from the contact face  1911  in the direction of protrusion of the guide portion  192 . Two protruding portions  199  are arranged symmetrical about a plane perpendicular to the contact face  1911  and passing through the tip end portion of the protruding strip  197  and the apex of the protruding portion  198 . Two protruding portions  199  are arranged as a pair. The protruding strip  197 , the protruding portion  198 , and the pair of the protruding portions  199  constitute a wooden piece anchor  1900  similarly to the first and the second embodiments (in  FIG. 24 , eight wooden piece anchors  1900  are formed in total). 
     As shown in  FIG. 25 , the side plate portion  1041   b  of the front cover member  1041  and the side plate portion  1042   b  of the rear cover member  1042   a  are partially cut out at the bottom face so that an outer periphery of a portion surrounding the opening  1914  of the frame  109   a  can be made to fit therewith. In other points, the configuration of the cover members  1041  and  1042  is the same as that of the cover members  2  and  3 . 
     Thus, similarly to the first and the second embodiment, according to the third embodiment of the present invention as described above there is provided a joining member and a joining structure which a wooden piece can be readily attached to and detached from without deterioration in the appearance of the wooden piece. 
     Further, according to the third embodiment, the threaded hole for a tripod is integrated with the connector of the joining member. Hence, even when the threaded hole is broken, only the connector in which the threaded hole is formed can be replaced, with the cover member left as it is. As a result, there is no need of replacement of the cover member to which unique texture is added by use. 
     Similarly to the second modification of the second embodiment, the bottom face of the main plate portion  193  of the connector  109   b  may be formed to be coplanar with the bottom face of the cover member  1041  or the bottom face of the cover member  1042 . 
     Still further, in the above, a threaded hole is provided in the joining member to allow attachment of a separate member. Alternatively, a strap holder may be provided for an attachment of a strap. When the strap holder is to be formed in the connector, it may be preferable that the connector be arranged at a side face or an upper face of the jacket rather than the bottom face thereof, depending on types of electronic equipment to which the joining member is applied. 
       FIG. 26  shows a configuration of relevant parts in a modification of the joining member according to the third embodiment. A joining member  220  shown in  FIG. 26  includes a frame  291   a , a connector  291   b  that is detachably attached to the frame  291   a  to connect two cover members (not shown), and screws  1500  that are fitted to the frame  291   a . The connector  291   b  includes a main plate portion  297  and two pressing protruding portions  298 . The main plate portion  297  is a flat plate with an octagonal surface. Two pressing protruding portions  298  are provided near respective opposing sides of the octagonal surface of the main plate portion  297  and are projected orthogonal from the surface of the main plate portion  297  in a trigonal pyramidal shape. The pressing protruding portion  298  are pressed into different cover members. The main plate portion  297  has three holes  299  arranged at equal intervals. The connector  291   b  can be fixed to the frame  291   a  by fastening the screws  1500  through the holes  299 . The holes  299  are aligned in a direction perpendicular to the direction of arrangement of the pressing protruding portions  298 . 
     A main frame portion  1901  of the frame  291   a , to which the connector  291   b  with the above-described configuration is fixed, has three holes  1916  at a bottom face thereof arranged at equal intervals. The connector  291   b  can be fixed to the frame  291   a  by inserting the screws  1500  into the holes  1916 . Inner walls of the holes  1916  are threaded so as to fit with the screws  1500 . In other points than those described above, the frame  291   a  has the same configuration as that of the frame  109   a.    
     In the third embodiment described above, the connector has the threaded cylinder for a tripod. In general, however, the connector may not always have the threaded cylinder for a tripod. The joining member  220  according to the modification of the third embodiment is suitable for the configuration of a jacket of an electronic equipment which does not need the threaded cylinder for a tripod. 
     In the third embodiment, the surfaces of the main plate portion  193  of the connector  109   b  and the main plate portion  297  of the connector  291   b  are octagonal. The octagonal shape in the third embodiment, however, is merely described by way of example. Needless to say, the shape of the connector can be changed depending on the shape of the cover member or the like. 
     In the above, the exemplary embodiments of the present invention are described in detail as the first to the third embodiments. It should be noted, however, that the present invention is not limited to the three embodiments described above. For example, the number of wooden pieces to be joined by the joining member can be three or more. 
     Further, though the wooden piece anchor is provided on the upper face and the side face of the main plate portion to secure the cover members in the above embodiments, the cover members may be fixed on the upper face and the side face of the main plate portion similarly to the bottom face of the main plate portion. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. 
     INDUSTRIAL APPLICABILITY 
     The present invention is suitable for a jacket for small portable electronic equipments such as digital camera, portable telephone, portable communication terminal such as Personal Handyphone System (PHS) and Personal Digital Assistant (PDA), portable audio device to which audio recording medium such as MiniDisc® (MD), Compact Disc (CD), Digital Versatile Disk (DVD); or cartridge tape is attached for sound output, IC recorder, portable television set, portable radio set, remote control for various home appliances, and digital video player/recorder. Further, the present invention can be applied to a compressed wood product other than the jacket for electronic equipments.