Abstract:
An electrical connector has housings that have male and female fitting parts containing electrical terminals. The fitting parts have respective locking elements which interengage to restrain disconnection. The female fitting part has a front portion which is elastically expanded on engagement with the relatively rigid male fitting part, and a second portion rearwardly of the portion which is less elastic than the front portion. The electrical connector may, for example, be used with solar panels.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates to an electrical connector. 
     2. Description of Related Art 
     A solar panel for use in a solar-energy power generation system is constructed of a plurality of modules connected one with another in series. A specific connector is used for an electric connection of the modules. 
     A known connector of this kind and its defects will now be described. As shown in FIG. 7, a single pole connector of this kind is constructed of a plug-side connector member C 1  having a cylindrical housing  1  accommodating a plug terminal  2  which is a male terminal, and a socket-side connector member C 2  having a cylindrical housing  3  accommodating a socket terminal  4  which is a female terminal. 
     A female fitting part  5  is provided at the front side of the housing  1  of the connector member C 1 , and a hollow sleeve-shaped male fitting part  6  is provided at the front side of the housing  3  of the connector member C 2 . As shown in FIG. 8, the plug terminal  2  and the socket terminal  4  are electrically connected with each other by fitting the male fitting part  6  into the female fitting part  5 . Reference symbols W 1  and W 2  denote electric wires connected to the terminals and extending from the connector members C 1  and C 2 , respectively. 
     An outer peripheral surface  6   a  of the male fitting part  6  is tapered towards its front end to facilitate insertion into the female fitting part  5 . 
     In this known connector, the entire housing  1  of the plug-side connector member C 1  including the female fitting part  5  and the entire housing  3  of the socket-side connector member C 2  including the male fitting part  6  are formed of the same plastic material, such as PVC. PVC is comparatively hard and has a low degree of elasticity. Thus, the fitting parts  5  and  6  are hard, and have mechanical properties such that they are difficult to elastically deform. 
     Thus, it is difficult to obtain a mechanical effect such that the fitting resistance of the fitting parts  5  and  6  is low when they are being fitted together, while their removal or disconnection resistance is high after they are fitted together. That is to say, when a construction in which the male fitting part  6  is tight in the female fitting part  5  is adopted in consideration of stability of the connection it is hard to disconnect the male fitting part  6  from the female fitting part  5  and hard to fit the male fitting part  6  into the female fitting part  5 . That is, the operability in connecting the connector members C 1  and C 2  is poor. When a construction in which the male fitting part  6  fits loosely in the female fitting part  5  is adopted in consideration of operability, it is easy to fit the parts together but also easy to disconnect them. That is, the plug terminal  2  and the socket terminal  4  are not stably connected with each other. 
     In this known connector, to prevent the fitting parts  5  and  6  from being disconnected, a locking rib  7  is formed on the outer peripheral surface of the male fitting part  6  and a locking groove  8  is formed on the inner peripheral surface of the female fitting part  5 . The rib  7  and the groove  8  are engaged when the male fitting part  6  is fitted into the female fitting part  5 . 
     The connector alternatively has a plurality of the locking ribs  7  and a plurality of the locking grooves  8  formed axially continuously in the shape of wave in section on the fitting parts  5  and  6 . 
     The rib  7  and the groove  8  allow the male fitting part  6  to be loosely fitted into the female fitting part  5 , but the locking rib  7  gives rise to a large fitting resistance. Thus, the fitting operation in this construction is not substantially different from the operation of press fitting the male fitting part  6  into the female fitting part  5  in a construction having neither locking rib  7  nor locking groove  8   
     SUMMARY OF THE INVENTION 
     This invention avoids or reduces the above-described problems. Therefore, this invention provides an electrical connector in which a male fitting part can be fitted easily into a female fitting part while they are prevented from being easily disconnected from each other. This allows a connection operation to be performed with high efficiency, and allows the terminals to be connected stably with each other. 
     According to the invention there is provided an electrical connector including a first connector member having a first housing and a first terminal accommodated in the first housing, and a second connector member having a second housing and a second terminal accommodated in the second housing. 
     The first housing has a female fitting part having an interior fitting surface and an open front end and the second housing has a male fitting part having an exterior fitting surface and a front end. The male fitting part is adapted to fit into the female fitting part, with the exterior fitting surface of the male fitting part contacting the interior fitting surface of the female fitting part when the first and second connector members are brought together into a connected state of the connector in which the first terminal and the second terminal are engaged to effect electrical connection. 
     The male fitting part has on its exterior fitting surface a first locking element and the female fitting part has on its interior fitting surface a second locking element. The first and second locking elements are adapted to engage when the connector is in the connected state so as to restrain the male and female fitting parts from disconnection. 
     The female fitting part has a front portion which includes the open front end and the second locking element and is formed of elastic material so as to be resiliently expansible. The male fitting part is made of material of lower elasticity than the front portion of the female fitting part, whereby the male fitting part is less deformed than the female fitting part when they are fitted together. 
     The female fitting part has a second portion located rearwardly with respect to the front portion and providing part of the interior surface of the female fitting part. The second portion has a lower elasticity than the front portion. 
     In one exemplary construction of the invention, when the male fitting part fits into the female fitting part, the front portion of the female fitting part expands elastically, thus relieving the fitting resistance of the locking elements and allowing easy receipt of the male fitting part. Accordingly, the construction allows the fitting resistance to be small. 
     After the male fitting part is fully received, the female fitting part returns to its original shape, or near to its original shape, due to its elasticity. Thus, the fitting state can be reliably maintained by the locking operation of the locking elements. The disconnection force required can be greater than the connection force, due to the shape of the locking elements. 
     Owing to the action of the construction, it is possible to satisfy the apparently opposite demands of ease of fitting the male fitting part into the female fitting part and difficulty in disconnecting them from each other. 
     The first locking element may be a locking projection on the exterior surface of the male fitting part and the second locking element may be a locking recess in the interior surface of the female fitting part, and the female fitting part may have at its front end a contact surface located so as to be engaged by the locking projection when the male fitting part is inserted into the female fitting part so as to provide resistance to the insertion. 
     In this case, in the fitting operation: 
     (1) The locking projection portion collides with the front end of the female fitting part. As a result, an initial fitting resistance is generated. 
     (2) When the locking projection portion is forced forward against the initial resistance, the front portion of the female fitting part expands outward elastically, with a small resistance being applied thereto. 
     (3) When the locking projection portion is locked into the locking recess, the front portion of the female fitting part contracts, and returns to its original shape, or near to its original shape. 
     In a series of the above operations (1) to (3), an operator presses one connector member with a comparatively large force to advance the locking projection toward the locking recess after the locking projection first contacts the front end of the female fitting part. As a result, the locking projection advances to the locking recess portion with an inertial effect and is locked into the locking recess portion. At this time, the construction may be such that operator senses the completion of fitting, e.g. as a “click”. The operator thus knows that the fitting operation is complete. The inertial effect minimizes the risk of an imperfect connection. 
     As described above, the front portion of the female fitting part expands elastically, and the second portion rearward of the front portion is undeformable or relatively hard to deform. Thus, when an external force (in particular, a bending load) is applied to the female fitting part after the connection between the connector members is completed, the second portion protects the terminal connection. Thus, there is no possibility that the terminal connection is placed out of position, deformed or connected defectively due to an external force. 
     These and other features and advantages of this invention are described in or are apparent from the following description of various exemplary embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the invention will now be described by way of non-limitative example with reference to the accompanying drawings, in which: 
     FIG. 1 is a front view, half in section, of a connector embodying this invention in a state before a plug-side connector member and a socket-side connector member are connected with each other; 
     FIG. 2 is a front view, half in section, of the connector members shown in FIG. 1 just before they are fully connected with each other; 
     FIG. 3 is a front view, half in section, of the connector members shown in FIG. 1 connected with each other; 
     FIG. 4 is an enlarged partial view of a state of the connector members immediately before the state shown in FIG. 2; 
     FIG. 5 is an enlarged partial view of the state shown in FIG. 2; 
     FIG. 6 is an enlarged partial view of the state shown in FIG. 3; 
     FIG. 7 is a front view, half in section, of a known connector described above in a state before a plug-side connector member and a socket-side connector member are connected with each other; 
     FIG. 8 is a front view, half in section, of the connector members shown in FIG. 7 connected with each other; 
     FIG. 9 is a diagrammatic view of a building having an array of solar panels with which the connector of this invention may be employed; and 
     FIG. 10 is a view of a solar panel including connector members of this invention. 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Various exemplary embodiments of this invention will be described below with reference to FIGS. 1 to  6 . 
     In FIG. 1, an electrical connector includes a plug-side connector member C 3  having a housing  11  accommodating a male terminal  13 , and a socket-side connector member C 4  having a housing  12  accommodating a female terminal  14 . 
     The housing  11  of the plug-side connector member C 3  and the housing  12  of the socket-side connector member C 4  may be cylindrical, or any other desired or practical shape, such as square, rectangular, triangular, hexagonal, octagonal or the like in section, or any combination thereof. The housing  11  of the plug-side connector member C 3  includes a first molded part  15 , a second molded part  16 , and a third molded part  17 , which are formed separately and joined together. The first part  15  is at a rear side of the housing  11  where an electric wire W 1  projects, the third part  17  is at a front side of the housing  11 , and the second part  16  is between the first part  15  and the third part  17 . The first part  15  and the second part  16  are fitted together and non-removably connected with each other and the second part  16  and the third part  17  are fitted together and non-removably connected with each other to form the housing  11  of the plug-side connector member C 3 . 
     The first part  15  located at the rear side of the housing  11  seals the housing  11  to the electric wire WI and is made of an elastic material such as rubber. The first part  15  is in close contact with the peripheral surface of the electric wire W 1  to make the member C 3  water-proof. 
     The third part  17  is also made of a resiliently deformable material such as rubber, preferably a rubber, such as silicone rubber, which does not suffer “creep” when subjected to stress. 
     The second part  16  is formed of a relatively rigid synthetic plastic material, such as modified PPE (polyphenylene ether), modified PPO (polyphenylene oxide), PPS (polyphenylene sulfide), UP (unsaturated polyester) or the like, which can be suitably used in a connector to constitute a part of a solar-energy power generation system. These plastic materials are weather resistant, hydrolysis resistant, fire-retardant, comparatively hard, and have a low degree of elasticity. In normal use, the third part  17  is not deformed, or is deformed very little. 
     A female fitting part  18  of the connector member C 3  is formed of the third part  17  and a front portion of the second part  16  that overlaps the third part  17 . Thus the female fitting part  18  has an elastically expandable/contractible portion  18   a  formed of elastic material and located at its front side, and a less deformable or undeformable portion  18   b  formed of a material which is harder than the expandable/contractible portion  18   a  and difficult to elastically deform located at its rear side. A male terminal  13  is located in this female fitting part  18 . 
     To simplify the drawings, the reference numerals  15 ,  16  and  17  of the first, second and third parts are not shown in FIGS. 2 to  6 . 
     A locking groove  19  is formed around part or all of the inner peripheral surface of an intermediate portion of the expandable/contractible portion  18   a . As shown enlarged in FIGS. 4 to  6 , the groove  19  may be approximately V-shaped in section, and its surface at its front side is formed perpendicularly, or at an angle close to perpendicular, to the central axis of the connector. 
     A resistance locking surface  20  (see FIGS. 4 to  6 ) perpendicular, or at an angle close to perpendicular, to the central axis is formed on the inner peripheral surface of the front end of the expandable/contractible portion  18   a . A guide surface  21  tapering outward towards the front end is formed at an outer peripheral edge of the resistance locking surface  20 . 
     The housing  12  of the socket-side connector member C 4  is formed of a first part  22 , which seals the housing  12  to an electric wire W 2 , located at a rear side of the housing  12  from which the electric wire W 2  projects, and a second part  23  located at a front side of the housing  12 . The first part  22  and the second part  23  are fitted together and non-separably connected with each other to form the housing  12 . A male fitting part  24  is formed at a front portion of the second part  23 , and houses a female terminal  14 . 
     The first part  22  is made of an elastic material such as rubber or the like to cause the housing  12  to be waterproof. To allow the male fitting part  24  to be sufficiently rigid as to be smoothly inserted into the female fitting part  18  of the connector member C 3 , the second part  23 , similarly to the second part  16  of the plug-side connector member C 3 , is formed of a synthetic plastic material such as PVC or modified PPE. PVC or modified PPE allows the connector to constitute a part of a solar-energy power generation system, is comparatively hard, and has a low degree of elasticity. In normal use of the connector, the part  24  is substantially not deformed. 
     To simplify the drawings, the reference numerals  22  and  23  of the first and second parts are not shown in FIGS. 2 to  6 . 
     A locking rib  25  that engages in the locking groove  19  of the female fitting part  18  is formed on the outer peripheral surface of the male fitting part  24  close to a rear end of the male fitting part  24 . 
     In correspondence to the shape of the groove  19 , the rib  25  is, for example, V-shaped in section, and a surface at the rear side of the rib  25  is formed perpendicularly, or at an angle close to perpendicular, to the central axis, while a forward-facing surface of the rib  25  slopes more gently. 
     A maximum outer diameter of the rib  25  is equal to or a little larger than a maximum outer diameter of the groove  19 . 
     A forward-facing stepped annular surface  26  (see FIGS. 4 to  6 ) is formed at the rear end of the male fitting part  24  of the housing  12 . When the male fitting part  24  of the housing  12  is inserted fully into the female fitting part  18  of the housing  11 , the resistance locking surface  20  and the guide surface  21  of the female fitting part  18  contact the stepped surface  26 . 
     An external peripheral surface  24   a  of the male fitting part  24  is formed tapering towards its front end so that the male fitting part  24  can easily fit into the female fitting part  18 . The outer diameter of the male fitting part  24  at its front end is set a little smaller than the inner diameter of the female fitting part  18 . 
     To allow the female fitting part  18  and the male fitting part  24  to contact closely when fitted, the diameter of the male fitting part  24  at its rear end is set equal to or a little larger than the inner diameter of the female fitting part  18 . This achieves a seal. 
     In connecting the connector members C 3  and C 4  with each other, the following actions occur: 
     (1) As shown in FIG. 4, the locking rib  25  engages the resistance locking surface  20 . As a result, a resistance to fitting is generated. 
     (2) When the rib  25  is pressed toward the female fitting part  18  against this fitting resistance, the expandable/contractible portion  18   a  of the female fitting part  18  expands outward elastically, thus receiving the rib  25 . As a result, the rib  25  advances, with a small resistance being applied thereto. 
     (3) When the rib  25  is locked into the groove  19 , the expandable/contractible portion  18   a  returns to its original shape, or nearly so. 
     In the operation of connecting the connector members C 3  and C 4  with each other, the operator presses the members together with a comparatively large force when the locking rib  25  collides with the resistance locking surface  20 . As a result, the expandable/contractible portion  18   a  expands outward. At this time, the male fitting part  24  becomes fully fitted in the female fitting part  18  owing to the inertia generated in overcoming the resistance between the locking rib  25  and the resistance locking surface  20 . Consequently, the advance of the locking projection portion  25  is stopped at the correct position, which is the fully engaged position, rather than being stopped at a partially engaged position. 
     That is, after the locking rib  25  passes the resistance locking surface  20 , the male fitting part  24  is capable of fitting into the female fitting part  18  securely by applying a small force to the locking rib  25 . There is very low possibility that the male fitting part  24  will not be fitted correctly into the female fitting part  18 . 
     In an exemplary connection operation, the advance of the locking rib  25  is stopped, and then the locking rib  25  again advances and is locked into the locking groove  19 , thus generating a “click”. At this time, the advance of the rib  25  stops again and the operator senses the “click”, which allows the operator to know that the connection between the plug-side connector member C 3  and the socket-side connector member C 4  has been completed. 
     Referring to FIG. 6, when the male fitting part  24  fits into the female fitting part  18 , the resistance locking surface  20  and the fitting guide surface  21  contact the stepped surface  26 , and the external peripheral surface of the male fitting part  24  and the internal surface of the female fitting part  18  become flush and in continuous contact with each other. This state allows the operator to recognize the completion of the connection between the plug-side connector member C 3  and the socket side connector member C 4 . 
     The guide surface  21  guides the locking rib  25  toward the inside of the female fitting part  18  during the fitting operation. 
     The female fitting part  18  is not deformed entirely; only the front portion, which is the expandable/contractible portion  18   a  including the groove  19 , is elastically deformed. The rear portion, which is the less deformable or undeformable portion  18   b , is undeformed, or deformed only slightly compared to the expandable/contractible portion  18   a . Thus, when an external force is applied to the female fitting part  18  after the connection between the connector members C 3  and C 4  is completed, the less deformable or undeformable portion  18   b  protects the terminal connection region. Thus, there is low risk that the terminal connection region is placed out of position, deformed or connected defectively by an external force. 
     In the above-described embodiment, the locking recess  19  is formed in the female fitting part  18  as a locking portion, and the locking projection  25  is formed on the male fitting part  24  as a locking portion. However, the locking projection portion  25  may be formed on the inner peripheral surface of the female fitting part  18 , and the locking recess  19  may be formed on the peripheral surface of the male fitting part  24 . 
     Further, a plurality of locking projections  25  and locking recesses  19  may be formed at a plurality of positions spaced at appropriate axial intervals, or formed continuously in the shape of a wave. 
     Furthermore, in the above-described embodiment, only the expandable/contractible portion  18   a  of the female fitting part  18  is constructed as an elastically deformable part. However, the entire female fitting part  18  may be formed as an elastically deformable part. 
     The electrical connector of this invention can be used, for example, for electric connection between modules of a solar battery panel and between solar battery panels. The electrical connector of this invention can also be used widely for connections of other electric components. Furthermore, the illustrated connector is single-pole, but the invention is also applicable to multi-pole connectors. 
     FIG. 9 shows a building  30  having a roof  31  whose exterior face is partly composed of an array of solar panels  32 . The solar panels  32  are electrically interconnected, e.g. in series, by connectors of the invention such as shown in FIGS. 1 to  6 . FIG. 10 shows one solar panel  32  having electrical wires  33  connected into connector members  34 . These connector members  34  may both be plug-side members C 3  of FIGS. 1 to  6 , or both socket-side members C 4 , or one may be a plug-side member C 3  and the other a socket-side member C 4 . Such connectors may also be used for connecting solar panels to exterior circuits. The connector is compact, strong and easy to connect correctly in the confined spaces present in, for example, a roof. 
     While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent alterations, modifications and variations will become apparent to those skilled in the art once given this disclosure. Accordingly, the exemplary embodiments of the invention as set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.