Abstract:
An electric connector assembly includes an intermediate connector for connecting the first attaching connector to the second attaching connector. The intermediate connector includes a power source terminal. The first attaching connector includes a first receiving terminal for contacting with the power source terminal, and the second attaching connector includes a second receiving terminal for contacting with the power source terminal. One of the first receiving terminal and the power source terminal and one of the second receiving terminal and the power source terminal include a metal cylindrical member capable of elastically deforming in a radial direction. Therefore, the power source terminal can incline and move in the radial direction at an arbitrary angle along a circumferential direction around an axial line of the power source terminal. The elastic cylindrical member includes a circumference elastically contacting with the power source terminal, the first receiving terminal, and the second receiving terminal.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
     The present invention relates to an electrical connector assembly. More specifically, the present invention relates to an electrical connector assembly including a power supply terminal. 
     Patent Reference 1 has disclosed a conventional electrical connector assembly. The conventional electrical connector assembly disclosed in Patent Reference 1 includes a mating connector attached to a circuit board and an intermediate connector for connecting the mating connector to another mating connector attached to another circuit board. 
     In the conventional electrical connector assembly, each of the mating connectors includes a fixed contact (a terminal) having a pin shape and extending in a connecting direction of the mating connectors. A plurality of the fixed contacts is planted in multiple places forming rows and columns on a plane perpendicular to the connecting direction. The intermediate connector includes a movable contact formed by bending a metal strip in a thickness direction thereof. The movable contact is capable of elastically displacing in the thickness direction. 
     In the conventional electrical connector assembly, the movable contact includes a pair of elastic pieces provided so as to face each other in the thickness direction in order to sandwich and hold the fixed contact. A connecting portion connects the elastic pieces in the pair as one component, so that the elastic pieces of the pair have a certain amount of space with each other. The pair of the elastic pieces of the movable contact has a cantilever shape with the connecting portion as a base portion thereof. Further, the elastic piece includes contact portions on both of distal ends thereof for contacting both of the mating connectors. The contact portion is formed by partially narrowing the space of the pair of the elastic pieces. In addition, the pair of the elastic pieces further includes a pair of contact pieces facing each other. The pair of the contact pieces is displaced by bending elastically in order to receive and sandwich the fixed contact of the mating connector. 
     In the conventional electrical connector assembly described in Patent Reference 1, when the mating connectors are connected to the intermediate connector, the two mating connectors are allowed to move relatively against the intermediate connector in directions different from each other, within a plane perpendicular to the connecting direction in a permissible range, respectively. 
     Particularly further, one of the directions, in which the mating connectors move relatively, is the thickness direction of the elastic piece of the movable contact of the intermediate connector. More specifically, when the fixed contact presses the movable contact, the movable contact is elastically displaced in the thickness direction, so that the mating connector is allowed to move in the thickness direction of the elastic piece. As the other one of the directions, the mating connectors move relatively in a direction of a plate surface of the metal strip. More specifically, when the fixed contact is moved slidingly along the plate surface of the elastic piece of the movable connector, the mating connector is allowed to move in the direction of the plate surface of the elastic piece. 
     As described above, in the conventional electrical connector assembly described in Patent Reference 1, the mating connectors are capable of compensating a shift in positions of each other in the two directions within the plane perpendicular to the connecting direction. In other words, the mating connectors are capable of floating in the two directions. 
     Patent Reference 1: Japanese Patent Publication No. 2011-060732 
     In the conventional electrical connector assembly disclosed in Patent Reference 1, the movable contact of the intermediate connector is formed by bending the metal strip in the thickness direction. Further, the intermediate connector includes the pair of the elastic pieces facing each other in the thickness direction. The elastic pieces in the pair are connected to each other through the connecting portion. With a configuration described above, the conventional electrical connector assembly includes some problems as described below. 
     First, in the conventional electrical connector assembly, the contact portion is bent only in the thickness direction. As a result, the floating in the two directions described above is composed of the elastic displacement in the thickness direction and a sliding movement being accompanied with a friction force in the direction of the plate surface. Consequently, when the mating connector moves in the two directions, two forces in different types, in other words, the elastic force in one direction and the friction force in another direction, are applied between the fixed contact and the movable contact. 
     As a result, in the conventional electrical connector assembly, an amount of the shift and the contact pressure are varied according to the direction of the shift. Accordingly, when the mating connectors move in the direction along the same straight line, capability of compensating the shift in positions thereof is varied according to the direction of the shift. For example, the contact pressure is proportional to the amount of the displacement in the direction of the elastic displacement. Therefore, the contact pressure may be increased or decreased according to the amount of the displacement. On the other hand, regardless the amount of the sliding movement, the contact pressure in the direction of the sliding movement is equal to an initial elasticity the contact portion receives in the first place. 
     Second, in the conventional electrical connector assembly, the elastic piece is bent only in the thickness direction. Therefore, a contact region of the elastic piece contacting to the fixed contact has a shape of a straight line. That is, a length of one side of a rectangular sectional shape of the fixed contact corresponds to the longest contact region. Accordingly, the length of the contact region tends to be insufficient. When the fixed contact has the circular sectional shape, the contact region has the shape of a dot. 
     Third, in the conventional electrical connector assembly, as described above, the elastic pieces on an upper side and a lower side are formed as the one component. Therefore, because of the difference between the floatings in the two directions described above, when the mating connectors move in the different directions from each other, not along the same straight line, the electrical connector assembly has a different capability for compensating the shift for each of the mating connectors. 
     Fourth, in the conventional electrical connector assembly, the elastic pieces on the upper side and on the lower side are formed as the one component. Therefore, the elastic piece has relatively high rigidity since the elastic pieces on the upper side and on the lower side restrain each other. As a result, when the elastic piece shifts in the direction of the elastic displacement, the amount of the elastic displacement thereof is relatively low while the contact pressure thereof is relatively high. In addition, it is difficult that the elastic pieces on the upper side and on the lower side are displaced elastically as being independent of each other. 
     In view of the problems described above, an object of the present invention is to provide an electrical connector assembly which solves the problems of the conventional electrical connector assembly. In the electrical connector assembly of the present invention, mating connectors include a receptacle terminal being independent of each other mating connector. Further, the receptacle terminal contacts a power supply terminal of an intermediate connector with both ends thereof. Accordingly, the mating connector is capable of floating in two directions at any angle in a circumferential direction thereof. 
     SUMMARY OF THE INVENTION 
     In order to attain the objects described above, according to a first aspect of the present invention, an electrical connector assembly includes a first mating connector attached to a first circuit member, a second mating connector attached to a second circuit member and an intermediate connector being arranged between the first mating connector and the second mating connector for connecting the first mating connector and the second mating connector. The intermediate connector includes a power supply terminal having a straight shape. Further, the first mating connector and the second mating connector include a first receptacle terminal and a second receptacle terminal, respectively. The first receptacle terminal and the second receptacle terminal receive a corresponding end portion of the power supply terminal and contact a circumferential surface of the corresponding end portion, respectively. 
     According to the first aspect of the present invention, in the electrical connector assembly, either the first receptacle terminal or the power supply terminal includes, further, either the second receptacle terminal or the power supply terminal includes an elastic tubular member made of metal and capable of elastic displacement in a direction of a radius thereof. Accordingly, the power supply terminal is able to tilt toward any angle in a circumferential direction around an axis thereof or able to move in the direction of the radius. Further, when the elastic tubular member is elastically displaced, the power supply terminal contacts the first receptacle terminal or the second receptacle terminal through a circumferential surface of the elastic tubular member. 
     According to the first aspect of the present invention, in the electrical connector assembly, the power supply terminal of the intermediate connector contacts the first receptacle terminal of the first mating connector and the second receptacle terminal of the through the circumferential surface of the elastic tubular member. The elastic tubular member is independently provided so as to correspond to the both ends of the power supply terminal which has the straight shape and rigidity. As described above, the elastic tubular member situated between one end of the power supply terminal of the intermediate connector and the receptacle terminal of the first mating connector is provided independently of the elastic tubular member situated between another end of the power supply terminal of the intermediate connector and the receptacle terminal of the second mating connector, and vice versa. Accordingly, the first mating connector and the second mating connector are capable of floating without influence from each other. Further, the elastic tubular member has a tubular shape having a constant elasticity in the direction of the radius at any angle in the circumferential direction thereof. Therefore, the elastic tubular member is displaced equally regardless of the angle in the circumferential direction. As a result, the floating is caused by a single mechanism. 
     According to a second aspect of the present invention, the elastic tubular member is formed by rolling a metal plate into a tubular shape. The elastic tubular member may include a slit in multiple positions in the circumferential direction thereof. The slit may be formed between the both end portions so as to extend in the direction of an axis of the elastic tubular member. Further, an annular narrow portion may be formed in a middle portion in the direction of the axis of the elastic tubular member. The annular narrow portion has a radius narrower than the radius of both end portions in the direction of the axis of the elastic tubular member, enabling the elastic tubular member to be retained in the first receptacle terminal and the second receptacle terminal. 
     According to the second aspect of the present invention, side edge portions of the elastic tubular member in the circumferential direction formed upon being rolled into the tubular shape may be arranged to have a space so as to be apart from each other, allowed to abut against each other. Or the side edge portions may be connected to each other by welding and the like. Moreover, the side edge portions may be arranged so as to have a gap therebetween or so as to overlap with each other. The elastic tubular member is most displaced elastically at the annular narrow portion thereof. 
     According to a third aspect of the present invention, the first receptacle terminal and the second receptacle terminal may include receptacle holes for receiving the elastic tubular member, respectively. It is preferable that the receptacle hole includes a controlling portion in an inner circumferential portion thereof. The controlling portion prevents the radius of the annular narrow portion of the elastic tubular member from being enlarged excessively. With the controlling portion, it is possible to prevent the elastic tubular member retained in the receptacle hole from being elastically displaced excessively. 
     According to a fourth aspect of the present invention, the elastic tubular member is formed by rolling the metal plate into the tubular shape. And the elastic tubular member may include the slit in multiple positions in the circumferential direction thereof. Further, the slit may be formed between the both end portions so as to extend in the direction of the axis of the elastic tubular member. Furthermore, the elastic tubular member may include an annular expanding portion in the middle portion in the direction of the axis thereof. The annular expanding portion has a radius larger than the radius of both end portions in the direction of the axis of the elastic tubular member. Accordingly, the elastic tubular member is allowed to be fitted to outer circumferential surfaces of the both end portions of the power supply terminal. In this case, it is preferable that the power supply terminal includes a fitting outer circumferential surface to which the elastic tubular member is fitted. In addition, it is preferable that the fitting outer circumferential surface includes a regulating portion for preventing a radius of an inner circumferential surface of the annular expanding portion of the elastic tubular member from shrinking. 
     According to a fifth aspect of the present invention, the regulating portion may abut against the annular expanding portion in order to prevent the elastic tubular member from being elastically displaced excessively. 
     As described above, according to the present invention, the receptacle terminals of the mating connectors to be connected respectively to the both end portions of the power supply terminal are provided so as to be independent of each other. Further, either the receptacle terminal or the end portion of the power supply terminal includes the elastic tubular member. Accordingly, it is possible to obtain the floating by the same amount at any angle in the circumferential direction. As a result, it is possible to contact at any angle between the mating connector and the intermediate connector, as well as enabling the floating sufficiently and obtaining the contact pressure sufficiently. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1(A) and 1(B)  are perspective view showing an electrical connector assembly according to a first embodiment of the present invention, wherein  FIG. 1(A)  shows an intermediate connector, a first mating connector and a second mating connector of the electrical connector assembly in a state before being connected to each other, and  FIG. 1(B)  shows the intermediate connector, the first mating connector and the second mating connector of the electrical connector assembly in a state after being connected to each other; 
         FIG. 2  is a longitudinal sectional view showing the electrical connector assembly taken along a direction perpendicular to a direction in which power supply terminals are arranged according to the first embodiment of the present invention; 
         FIG. 3  is a longitudinal sectional view showing the electrical connector assembly taken along the direction in which the power supply terminals are arranged according to the first embodiment of the present invention; 
         FIG. 4(A)  is an enlarged sectional view showing a first receptacle terminal of the electrical connector assembly according to the first embodiment of the present invention; 
         FIG. 4(B)  is a perspective view showing an elastic tubular member to be retained in the first receptacle terminal of the electrical connector assembly according to the first embodiment of the present invention; 
         FIGS. 5(A) and 5(B)  are longitudinal sectional views showing the electrical connector assembly in a state that the intermediate connector, the first mating connector and the second mating connector are connected to each other according to the first embodiment of the present invention, wherein  FIG. 5(A)  is a longitudinal sectional view of the electrical connector assembly taken along the direction perpendicular to the direction in which the power supply terminal are arranged, and  FIG. 5(B)  is a longitudinal sectional view of the electrical connector assembly taken along the direction in which the power supply terminals are arranged; 
         FIG. 6  is a longitudinal sectional view showing the electrical connector assembly in a state that the power supply terminals are tilted as the first mating connector and the second mating connector are shifted from each other according to the first embodiment of the present invention; 
         FIG. 7  is a longitudinal sectional view showing an intermediate connector, a first mating connector and the second mating connector of an electrical connector assembly in a state before being connected to each other according to a second embodiment of the present invention; and 
         FIG. 8  is a front view showing a power supply terminal and an elastic tubular member of the electrical connector assembly according to the second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereunder, embodiments of the present invention will be explained with reference to the accompanying drawings. 
     First Embodiment 
     A first embodiment of the present invention will be explained.  FIGS. 1(A) and 1(B)  are perspective views showing an electrical connector assembly according to the first embodiment of the present invention.  FIG. 1(A)  shows an intermediate connector  10 , a first mating connector  30  and a second mating connector  50  of the electrical connector assembly in a state of before being connected to each other.  FIG. 1(B)  shows the intermediate connector  10 , the first mating connector  30  and the second mating connector  50  of the electrical connector assembly in a state of after being connected to each other. 
       FIG. 2  is a longitudinal sectional view showing the electrical connector assembly taken along a direction perpendicular to a direction in which power supply terminals are arranged, according to the first embodiment of the present invention.  FIG. 3  is a longitudinal sectional view showing the electrical connector assembly taken along the direction the power supply terminals are arranged, according to the first embodiment of the present invention.  FIGS. 5(A) and 5(B)  are longitudinal sectional views showing the electrical connector assembly in a state that the intermediate connector  10 , the first mating connector  30  and the second mating connector  50  are connected to each other according to the first embodiment of the present invention.  FIG. 5(A)  is a longitudinal sectional view of the electrical connector assembly taken along the direction perpendicular to the direction the power supply terminals are arranged, and  FIG. 5(B)  is a longitudinal sectional view of the electrical connector assembly taken along the direction the power supply terminals are arranged. 
       FIGS. 1(A) ,  2  and  3  show the electrical connector assembly in a state of before the intermediate connector  10  thereof is connected to mating connectors, that is, the first mating connector  30  and the second mating connector  50  thereof.  FIGS. 1(B) ,  5 (A) and  5 (B) show the electrical connector assembly in the state that the intermediate connector  10  thereof is connected to the mating connectors, that is, the first mating connector  30  and the second mating connector  50  thereof. 
     As shown in  FIGS. 1(A) and 1(B) , the intermediate connector  10  includes a housing  11  and two power supply terminals  21 . The housing  11  is made of an electrical insulating material and has a substantial rectangular tubular shape with a space penetrating in a vertical direction. The power supply terminal  21  is supported by the housing  11  and extending in the vertical direction within the space of the housing  11  penetrating vertically. The power supply terminal  21  is made from a metal and has a shape of a straight pin. In the embodiment, the intermediate connector  10  includes two power supply terminals, but number of the power supply terminals is not limited two. The number of the power supply terminals may be one or three and more. Further, the power supply terminals may be arranged in a single row or in multiple rows. 
     In the first embodiment of the present invention, the power supply terminal  21  is made as a rigid body and includes a main body portion  22  and a flange portion  23 . The main body portion  22  has a shape of a pin with a circular sectional shape. The flange portion  23  is provided in a lower portion of the power supply terminal  21 . The flange portion  23  has a shape of a ring projecting outward in a direction of a radius of the main body portion  22 . An upper end and a lower end of the main body portion  22  are formed to be rounded, so that the first mating connector  30  and the second mating connector  50  as the mating connectors are able to be connected thereto ideally, as described later. Further, the flange portion  23  includes a circumferential surface  23 A having a conic shape expanding in a lower direction. 
     In the first embodiment of the present invention, the power supply terminal  21  is longer than a size of the housing in the vertical direction. Therefore, upon being supported by the housing  11 , the power supply terminal  21  protrudes from an upper end and a lower end of the housing  11 . In the embodiment, the power supply terminal  21  protrudes from the upper end and the lower end of the housing  11 . The power supply terminal  21  may be depressed from the housing  11 . In this case, terminals of the mating connectors, that is, terminals of the first mating connector  30  and the second mating connector  50  enter the housing  11 . 
     In the first embodiment of the present invention, the housing  11  for supporting the power supply terminal  21  having the rectangular tubular shape has a rectangular sectional shape which is elongated in a direction the power supply terminals  21  are arranged. The housing  11  includes receptacle portions  12  and  13  in an upper and lower edge portions thereof, respectively. The receptacle portions  12  and  13  receive the first mating connector  30  and the second mating connector  50  having rectangular tubular shapes as described later, respectively. A terminal penetrating portion  14  is formed between the receptacle portions  12  and  13  in the vertical direction. 
     As shown in  FIG. 3 , the terminal penetrating portion  14  has a hole formed on a central wall portion  15  as being viewed in the direction the power supply terminals  21  are arranged. A space is formed between an inner surface of the terminal penetrating portion  14  and the power supply terminal  21 . 
     Further, as shown in  FIG. 2 , the terminal penetrating portion  14  has a hole formed between thin walls  16  as being viewed in the direction perpendicular to a direction the power supply terminals  21  are arranged. A space is formed between an inner surface of the thin wall  16  and the power supply terminal  21 . In addition, the thin wall  16  forms a space  16 A between a rear side thereof and a sidewall  17 . 
     In the first embodiment, the terminal penetrating portion  14  includes a concaved portion  14 A as shown in  FIG. 3  in a lower portion thereof. As shown in  FIG. 3 , an upper surface of the flange portion  23  is to abut against a bottom portion of the concaved portion  14 A situated in a lower side. 
     As shown in  FIG. 2 , the terminal penetrating portion  14  further includes an elastic arm portion  18  in the lower portion thereof. The elastic arm portion  18  extends from a middle portion of the sidewall  17  of the housing  11 , at a position situated on an upper side relative to the flange portion  23 . The elastic arm portion  18  extends in the lower direction. The elastic arm portion  18  engages a lower surface of the flange portion  23  with a hook portion  18 A provided in a lower end thereof. 
     Accordingly, the upper surface of the flange portion  23  is held by the bottom portion of the concaved portion  14 A and an edge portion of the thin wall  16  in one of the direction of the radius, as well as the lower surface of the flange portion  23  is held by the hook portion  18 A of the elastic arm portion  18  in a direction perpendicular to the direction supra. Thereby, the power supply terminal  21  is positioned vertically. 
     In the first embodiment, when the power supply terminal  21  is inserted into the terminal penetrating portion  14  from the lower direction, the circumferential surface  23 A having the conic shape of the flange portion  23  thereof abuts against the hook portion  18 A. Then the power supply terminal  21  is inserted further as the elastic arm portion  18  is pushed outward to be displaced elastically. When the upper surface of the flange portion  23  abuts against the bottom portion of the concaved portion  14 A, the elastic arm portion  18  stops being displaced or recovers from the elastic displacement thereof as the hook portion  18 A leaves the flange portion  23 . Therefore, the hook portion  18 A engages the lower surface of the flange portion  23 . Thereby, the flange portion  23  is held as the upper and lower surfaces thereof are sandwiched. 
     The housing  11  includes a window portion  17 A (refer to  FIGS. 1(A) and 1(B) ). The window portion  17 A is provided on the sidewall  17  and communicates with the space  16 A formed between the thin wall  16  and the sidewall  17  shown in  FIG. 2 . The housing  11  further includes a window portion  17 B on the sidewall  17 . The window portion  17 B is provided on a side position relative to the elastic arm portion  18 . The window portions  17 A and  17 B ventilate the housing  11  to radiate heat generated by the power supply terminal  21 . 
     In the first embodiment, as shown in  FIGS. 1(A) and 1(B) , the housing  11  further includes a groove portion  19  in an outer surface of the sidewall  17  thereof having the window portions  17 A and  17 B. The groove portion  19  extends in the vertical direction. A locking arm  19 A extending in the lower direction and capable of elastic displacement is provided in a lower portion of the groove portion  19 . Further, a button portion  19 B is provided in a lower edge of the locking arm  19 A. Therefore, by being operated externally, a hook portion  19 B- 1  provided in the button portion  19 B is allowed to lock and unlock a lower surface of a corresponding engaging portion  44 A of the first mating connector  30  from inside. 
     In the first embodiment, the first mating connector  30  and the second mating connector  50  as the mating connectors are assigned different numbers for being situated in different positions in the vertical direction. The first mating connector  30  and the second mating connector  50  have the same configuration. Therefore, hereunder, the first mating connector  30  situated in a lower position will be explained. As for the second mating connector  50  situated in an upper position, components thereof will be numbered adding twenty to numbers of corresponding components of the first mating connector  30  and explanation thereof will be omitted. 
     In the first embodiment, the first mating connector  30  and the second mating connector  50  are attached to a first circuit board P 1  and a second circuit board P 2  as circuit members, respectively. The first circuit board P 1  and the second circuit board P 2  have similar configurations. 
     As shown in  FIGS. 2 and 3 , the first mating connector  30  includes a first receptacle terminal  31 , a housing  41  for holding the first receptacle terminal  31  and an elastic tubular member  35 . The first receptacle connector  31  is made of metal and has a cylindrical shape with a bottom surface. The housing  41  is made of an electrical insulating material. The elastic tubular member  35  is made of metal and retained in the first receptacle terminal  31 . 
       FIG. 4(A)  is an enlarged sectional view showing the first receptacle terminal  31  of the electrical connector assembly, according to the first embodiment of the present invention. When the first mating connector  30  in  FIG. 4(A)  is flipped over in the vertical direction, the second mating connector  50  in  FIGS. 1 to 3  is shown in a similar way in the vertical direction with the first mating connector  30  in  FIG. 4(A) . 
     In the first embodiment, a receptacle hole  32  is formed in the first receptacle terminal  31  as shown in  FIG. 4(A) . An inner surface of the receptacle hole  32  has a cylindrical shape opening in an upper direction. The first receptacle terminal  31  has a cylindrical outer circumferential surface in both of an opening side and a bottom side. That is, an opening side cylindrical outer circumferential surface  31 A and a bottom side cylindrical outer circumferential surface  31 B. The opening side cylindrical outer circumferential surface  31 A has an outer radius smaller than the bottom side cylindrical outer circumferential surface  31 B. The first receptacle terminal  31  includes an annular protrusion  31 C on a boundary region between the opening side cylindrical outer circumferential surface  31 A and the bottom side cylindrical outer circumferential surface  31 B. The annular protrusion  31 C has a larger radius than either the opening side cylindrical outer circumferential surface  31 A or the bottom side cylindrical outer circumferential surface  31 B. 
     In the first embodiment, the opening side cylindrical outer circumferential surface  31 A includes an engaging protrusion  31 A- 1 . Further, an annular abutting portion  32 B having a step-like shape is formed in a bottom side of the inner surface of the receptacle hole  32 . The inner surface of the receptacle hole  32  is tapered so as to slightly decrease an inner radius thereof toward a middle portion in a direction of an axis of the cylinder. The inner surface of the receptacle hole  32  has a controlling portion  32 A in the middle portion thereof. The radius of the inner surface of the receptacle hole  32  becomes the smallest where the controlling portion  32 A is situated. The controlling portion  32 A and neighborhood thereof prevent a radius of the elastic tubular member  35  from being excessively enlarged elastically. 
       FIG. 4(B)  is a perspective view showing the elastic tubular member  35  of the electrical connector assembly according to the first embodiment of the present invention. The elastic tubular member  35  is retained in the first receptacle terminal  31 . As shown in  FIG. 4(B) , the elastic tubular member  35  to be retained in the receptacle hole  32  of the first receptacle terminal  31  is made by rolling a metal plate into a tubular shape after forming a slit  36  on the metal plate. The slits  36  extend in the direction of the axis being situated in multiple positions in a circumferential direction of the elastic tubular member  35 . Further, the slit  36  is formed between both end portions in the direction of the axis of the elastic tubular member  35 . Accordingly, the elastic tubular member  35  has a ring shape at the both end portions in the direction of the axis thereof, since the slit  36  is not provided in the both end portions thereof. 
     In the first embodiment, the elastic tubular member  35  is formed so as to shrink a radius thereof in a middle portion in the direction of the axis. Therefore, the elastic tubular member  35  includes an annular narrow portion  35 A in the middle portion thereof. When the elastic tubular member  35  is rolled into the tubular shape with the annular narrow portion  35 A after forming the slit  36  on the metal plate, abutting portions thereof to be faced each other in the circumferential direction may be connected or may be left so as to be apart from each other. The elastic tubular member  35  is retained in the receptacle hole  32  as the radius thereof is elastically crimped temporarily. After being retained in the receptacle hole  32  of the first receptacle terminal  31 , the elastic tubular member  35  is positioned as the radius thereof is recovered then elastically abuts against the inner surface of the receptacle hole  32 . Further, the elastic tubular member  35  is positioned in the direction of the axis as a circumferential edge of one end portion thereof abuts against the annular abutting portion  32 B situated in the bottom side of the receptacle hole  32 . 
     As shown in  FIG. 3 , the housing  41  for supporting the first receptacle terminal  31  includes two supporting holes  42  for holding the first receptacle terminals  31 , respectively. A region of the bottom side cylindrical outer circumferential surface  31 B of the first receptacle terminal  31  is retained to be held in the supporting hole  42 . 
     As shown in  FIGS. 2 and 3 , the housing  41  includes an inner annular protruding portion  43  protruding inwardly in a direction of the radius. The inner annular protruding portion  43  is provided on a circumferential edge of the opening side of the supporting hole  42 . Further, the housing  41  includes an outer annular protruding portion  44  provided in the bottom side of the supporting hole  42 . The outer annular protruding portion  44  protrudes outwardly in the direction of the radius from an outer circumferential surface of the housing  41 . An inner circumferential edge of the inner annular protruding portion  43  has an inner radius capable of receiving the power supply terminal  21 . 
     In the first embodiment, the outer annular protruding portion  44  includes the corresponding engaging portion  44 A at a position corresponding to the button portion  19 B in the circumferential direction (refer to  FIG. 1(A) ). The corresponding engaging portion  44 A is formed by raising the outer annular protruding portion  44  into a shape of a gate. The button portion  19 B is provided in the housing  11  of the intermediate connector  10  and capable of elastic deformation. The hook portion  19 B- 1  of the button portion  19 B engages the lower surface of the corresponding engaging portion  44 A from an inner direction. The opening side cylindrical outer circumferential surface  31 A of the first receptacle terminal  31  is forcibly inserted into the supporting hole  42  of the housing  41 . Then the engaging protrusion  31 A- 1  formed on the opening side cylindrical outer circumferential surface  31 A bites into an inner surface of the supporting hole  42 . Thereby, it is possible to prevent the first receptacle terminal  31  from coming off. Accordingly, the bottom side cylindrical outer circumferential surface  31 B of the first receptacle terminal  31  held by the housing  41  protrudes from the supporting hole  42  of the housing  41 . Further, the bottom side cylindrical outer circumferential surface  31 B protrudes from an attachment surface of the housing  41  for attaching to the first circuit board P 1  as well. Thereby, the first mating connector  30  is configured completely. 
     In the first embodiment, the first mating connector  30  is attached to the first circuit board P 1 . The first circuit board P 1  includes a through hole P 1 - 1  thereon. The bottom side cylindrical outer circumferential surface  31 B of the first receptacle terminal  31  enters into the through hole P 1 - 1  without penetrating. An inner surface of the through hole P 1 - 1  conducts electrically with a circuit layer P 1 - 2  formed on both surfaces and inside of the first circuit board P 1 . Therefore, the first receptacle terminal  31  conducts to the circuit layer P 1 - 2  electrically by soldering a space formed between the bottom side cylindrical outer circumferential surface  31 B thereof and an inner circumferential surface of the through hole P 1 - 1 . Thereby, the first mating connector  30  is attached to the first circuit board P 1 . 
     In the first embodiment, the second mating connector  50  has the same configuration with the first mating connector  30  and is attached and connected to the second circuit board P 2  in a similar way. 
     In the first embodiment, the first mating connector  30 , the second mating connector  50  and the intermediate connector  10  thus configured are utilized as follows. 
     As shown in  FIGS. 2 and 3 , the first mating connector  30  attached to the first circuit board P 1  is placed so as to face upward. Next, the intermediate connector  10  placed above the first mating connector  30  so that the button portion  19 B of the locking arm  19 A thereof is situated in a lower side. Then the intermediate connector  10  thus placed is moved in the lower direction. 
     Next, the power supply terminal  21  of the intermediate connector  10  is inserted into the tubular cylindrical member  35  in the first receptacle terminal  31  of the first mating connector from the lower end thereof. When the power supply terminal  21  is inserted further, a lower end of the power supply terminal  21  reaches a predetermined position, elastically enlarging the radius of the annular narrow portion  35 A of the tubular cylindrical member  35 . The tubular cylindrical member  35  thus enlarged the radius thereof elastically abuts against an outer circumferential surface of the lower end of the power supply terminal  21  as well as increasing an elastic contact pressure thereof against the inner surface of the receptacle hole  32  of the first receptacle terminal  31 . 
     When the lower end of the power supply terminal  21  is inserted to the predetermined position, the hook portion  19 B- 1  of the button portion  19 B of the locking arm  19 A of the intermediate connector  10  engages the lower surface of the corresponding engaging portion  44 A formed in the outer annular protruding portion  44  of the first mating connector  30  from the inner direction. Therefore, it is possible to prevent the intermediate connector  10  from coming off from the first mating connector  30 . When the intermediate connector  10  is extracted, the intermediate connector  10  is lifted as unlocking the hook portion  19 B- 1  thereof by pushing the button portion  19 B thereof. 
     Next, the second mating connector  50  attached to the second circuit board P 2  is placed so as to face downward. Then the second mating connector  50  is moved downward to the intermediate connector  10  connected to the first mating connector  30 . Accordingly, an upper end of the power supply terminal  21  of the intermediate connector  10  is inserted into the elastic tubular member  55  in the second receptacle terminal  51  of the second mating connector  50 . As a result, the intermediate connector  10  is connected to the second mating connector  50  in a similar way to be connected the first mating connector  30 . 
     The intermediate connector  10  does not include a button portion for engaging an outer annular protruding portion  64  of the second mating connector  50 . Therefore, the second mating connector  50  is extracted from the intermediate connector  10  by only being lifted. As described above, the first mating connector  30  and the second mating connector  50  are connected to each other through the intermediate connector  10  (refer to  FIGS. 5(A) and 5(B) ). 
     As described above, in the first embodiment, when a force in a horizontal direction is applied to the first circuit board P 1  and the second circuit board P 2 , the first mating connector  30  and second mating connector  50  connected to each other through the intermediate connector  10  move with the first circuit board P 1  and the second circuit board P 2 , respectively. 
       FIG. 6  is a longitudinal sectional view showing the electrical connector assembly according to the first embodiment of the present invention, in a state that the power supply terminal  21  is tilted since the first mating connector  30  and the second mating connector  50  are shifted from each other. 
     As shown in  FIG. 6 , the power supply terminal  21  situated in a regular position before being tilted has an axis line X. In the case mentioned above, the axis line X is tilted to the axis line X- 1  as the power supply terminal  21  is tilted. The elastic tubular member  35  of the first mating connector  30  and the elastic tubular member  55  of the second mating connector  50  enable the axis line to tilt in such a way by elastic displacement in the direction of the radius thereof. 
     In the first embodiment, the elastic tubular members  35  and  55  are capable of the elastic displacement at any angle within a circumference direction of the power supply terminal  21 . Further, the elastic tubular members  35  and  55  are displaced elastically by the same amount at any angle when the force being applied has the same strength. Furthermore, the elastic tubular members  35  and  55  are displaced elastically as being independent of each other. 
     In the first embodiment, the elastic tubular members  35  and  55  are most displaced elastically toward the angle to be shifted in the circumferential direction. The elastic tubular members  35  and  55  are most displaced elastically at the annular narrow portions  35 A and  55 A thereof in the direction of the axis. The annular narrow portions  35 A and  55 A contact the power supply terminal  21  along a circular line before the power supply terminal  21  is tilted, while the annular narrow portions  35 A and  55 A contact the power supply terminal  21  along an oval line as the power supply terminal  21  is tilted. 
     As shown in  FIG. 4(B) , the elastic tubular members  35  and  55  include the plurality of the slits  36  and  56  arranged in the circumferential direction thereof, respectively. Accordingly, fine strip portions  35 B and  55 B situated between the slits  36  and  56  are displaced elastically in the direction of the radius as a thickness direction thereof, respectively. Therefore, an elastic force (pressure) applied to the power supply terminal  21  as a reaction force is applied in the direction of the radius toward the axis line X- 1  at each of the fine strip portions  35 B and  55 B. 
     In the first embodiment, when the power supply terminal  21  is tilted a size of a space between the terminal penetrating portion  14  and the power supply terminal  21  is varied at positions. Further, the power supply terminal  21  is tilted around a plane formed where the power supply terminal  21  contacts with the annular narrow portion  35 A of the elastic tubular member  35  situated in the lower side. The controlling portion  32 A provided in the receptacle hole  32  of the first receptacle terminal  31  controls the elastic tubular member  35  so that the elastic tubular member  35  is not displaced excessively. It is similar about the elastic tubular member  55 . 
     Second Embodiment 
     Next, a second embodiment of the present invention will be explained. As shown in  FIGS. 1(A) ,  1 (B) and  6 , in the first embodiment, the elastic tubular members  35 ,  55  are respectively provided in the first mating connector  30  and the second mating connector  50 . In the present invention, the elastic tubular member  35  may be provided in the intermediate connector  10 , not limited to the first embodiment. 
       FIG. 7  is a longitudinal sectional view showing an intermediate connector  10 , a first mating connector  30  and the second mating connector  50  of an electrical connector assembly according to the second embodiment of the present invention.  FIG. 8  is a front view showing an elastic tubular member  37  and the power supply terminal  21  of the intermediate connector  10  of the electrical connector assembly according to the second embodiment of the present invention. 
     As shown in  FIG. 7 , the elastic tubular member  37  is attached to the power supply terminal  21  of the intermediate connector  10 . The power supply connector  21  includes a concaved supporting surface  24  at each of both end portions thereof. The concaved supporting surface  24  is formed in a concaved shape to be narrow in order to attach the elastic tubular member  37  thereto. The concaved supporting surface  24  gradually increases a radius thereof toward a central portion in a direction of an axis thereof and provides a regulating portion  24 A at a position having the largest radius thereof. 
     As shown in  FIG. 8 , the elastic tubular member  37  to be attached to the concaved supporting surface  24  is formed by rolling a metal plate including the slit  36  into a tubular shape, similar to the first embodiment shown in  FIGS. 4(A) and 4(B) . On the other hand, unlike the first embodiment shown in  FIGS. 4(A) and 4(B) , the elastic tubular member  37  has a tapered shape with a radius being the largest at a middle portion in the direction of the axis thereof. Therefore, the elastic tubular member  37  includes an annular expanding portion  38  at a position having the largest radius thereof. 
     In the second embodiment, the annular expanding portion  38  elastically expands the radius thereof for being attached to the concaved supporting surface  24 . Then the annular expanding portion  38  is supported by the concaved supporting surface  24  with a contact pressure as an elastic force thereof in a direction of shrinking the radius for recovering. In this state, an outer radius of the annular expanding portion  38  is larger than an outer radius of the main body portion  22  of the power supply terminal  21 . The main body portion  22  is situated between the both of the concaved supporting surfaces  24  in the direction of the axis. 
     In the second embodiment, as described above, the elastic tubular member  37  thus supported by the concaved supporting surface  24  of the power supply terminal  21  is connected to the first mating connector  30  and the second mating connector  50  as the both end portions of the power supply terminal  21  are inserted into the first receptacle terminal  31  of the first mating connector  30  and the second receptacle terminal  51  of the second mating connector  50 , respectively. Further, the power supply terminal  21  is connected electrically with the first receptacle terminal  31  and the second receptacle terminal  51  as an elastic force due to an elastic displacement is generated between the first receptacle terminal  31 , the second receptacle terminal  51  and the power supply terminal  21 , respectively. 
     In the second embodiment, the elastic tubular member  37  is elastically displaced in the direction of shrinking the radius thereof. The regulating portion  24 A provided in the concaved supporting surface  24  regulates the elastic tubular member  37  so that the elastic tubular member  37  is not displaced excessively. As described above, the elastic tubular member  37  is displaced elastically, enabling the power supply terminal  21 , the first mating connector  30  and the second mating connector  50  to relatively move and tilt in the direction of the axis at any angle within the circumference direction around the axis of the power supply terminal  21 , with a similar principle to the first embodiment shown in  FIGS. 1(A) ,  1 (B) and  6 . 
     In the present invention, the elastic tubular member attached to each of the end portions of the power supply terminal may not have the same shape. For example, the elastic tubular member shown in  FIGS. 1(A) ,  1 (B) and  6  may be attached to one end portion of the power supply terminal and the elastic tubular member shown in  FIGS. 7 and 8  may be attached to another end portion of the power supply terminal. 
     In the present invention, in the embodiments described above, the connector includes only the power supply terminal. The connector may include a signal terminal as well as the power supply terminal. Further, other connector including the signal terminal may be used in combination. 
     Furthermore, the elastic tubular member is not limited to be configured as shown in the drawings. The elastic tubular member may be any conductive members having a substantial cylindrical shape capable of elastic displacement by the same amount at any angle within a circumferential direction. 
     The disclosure of Japanese Patent Application No. 2011-232903 filed on Oct. 24, 2011, is incorporated in the application by reference. 
     While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.