Abstract:
An electrical connector has first and second matable connector housings with circular cross-sections, and has a fixing ring which is rotatably mounted at an outer circumference of the first connector housing. In use, the fixing ring is engaged with the second connector housing to form a screw-action cam mechanism. This draws the connector housings into mating engagement when the fixing ring is rotated in a first rotational direction relative to the connector housings. The connector also has (i) a detent for detaining the fixing ring at a predetermined position corresponding to full mating engagement of the connector housings, and (ii) a return spring which applies a return bias to the fixing ring in the opposing rotational direction as the fixing ring is rotated in the first rotational direction.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electrical connector in which a pair of connector housings containing electrical terminals are fitted to each other, typically with a relatively low force. Such a connector is used for example to connect wire bundles in a motor vehicle. 
     2. Description of the Related Art 
     An example of a connector of this type is disclosed in JP-A-4-132178. The connector has a pair of female and male circular cross-section connector housings to be fitted to each other. A fixing ring is installed on a peripheral surface of the female housing such that the fixing ring is freely rotatable. A follower pin projects inwardly from the fixing ring. A cam groove is formed on a peripheral surface of the male housing. The housings are temporarily fitted to each other by engaging the follower pin to the cam groove. Then, the fixing ring is rotated, and as a result the housings arrive at the fully fitted state by the camming action of the follower pin in the cam groove. 
     In the above-described connector, the fixing ring is rotated to a predetermined position and locked, and an operator then determines if the housings are fully fitted. However, when the fixing ring is rotated to a position close to the predetermined position, fitting resistance may be generated (although the degree of the resistance is generally low). Thus, there is a possibility that the operator stops rotating the fixing ring before the housings are fully fitted. That is, the housings may be held in an incompletely fitted state. It may be very difficult for the operator to detect this. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a connector which allows an operator to detect whether the connector housings have been fully fitted to each other. 
     The present invention provides a connector having first and second matable connector housings with circular cross-sections, and a fixing ring which is rotatably mounted at an outer circumference of the first connector housing. In use, the fixing ring is engaged with the second connector housing to form a screw-action cam mechanism which draws the connector housings into mating engagement when the fixing ring is rotated in a first rotational direction relative to the connector housings. The connector further has a detent for detaining the fixing ring at a predetermined position corresponding to full mating engagement of the connector housings. The connector also has at least one return spring which applies a return bias to the fixing ring in a second rotational direction opposite to said first rotational direction as the fixing ring is rotated in the first rotational direction. 
     Preferably, the return spring is a coil spring which is accommodated in a circumferential groove formed in the first connector housing inwardly of the fixing ring, and a loading member is operably connectable to the fixing ring and projects into the circumferential groove. Therefore, when the fixing ring is rotated in the first rotational direction, the loading member travels around the circumferential groove to load the coil spring and generate the return bias. 
     Preferably, the loading member projects inwardly from a loading ring which is rotatably mounted between the fixing ring and the circumferential groove. The fixing ring has a resiliently deformable latching arm which is engageable with a corresponding portion of the loading ring to operably connect the loading member to the fixing ring. The detent is preferably provided by the latching arm and a locking projection formed on the first connector housing. When the fixing ring reaches the predetermined position of full engagement, to detain the fixing ring the latching arm engages the locking projection with a latching action which involves a deformation of the latching arm. This deformation also disengages the latching arm from the corresponding portion of the loading ring to release the coil spring and at least partially remove the return bias. 
     Preferably, the latching arm and locking projection are adapted so that when at least a predetermined force is applied to the fixing ring to rotate the fixing ring in the opposite rotational direction, the latching arm disengages from the locking projection. 
     As described above, according to the present invention, by rotating the fixing ring, the connector housings are fitted to each other. However, if rotation of the fixing ring is stopped before the fixing ring is locked by the detent, the fixing ring when released rotates in the opposite direction by the elastic restoring force of the return spring so that the connector housings separate from each other. Thereby, it is possible to detect whether the housings are fully engaged. 
     When a coil spring is used for the return spring, it is possible to provide a compact connector. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments 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 longitudinal cross-sectional view of a connector embodying the invention showing housings before they are fitted to each other. 
     FIG. 2 is a longitudinal cross-sectional view showing the housings of FIG. 1 immediately before being fitted to each other. 
     FIG. 3 is a view of a circumferential surface of one of the housings projected onto the plane of the page and showing a cam groove. 
     FIGS. 4A and 4B are transverse cross-sectional views at positions I—I and II—II respectively of FIG. 1 showing the female housing prior to engagement with the male housing. 
     FIGS. 5A and 5B are transverse cross-sectional views similar to FIGS. 4A and 4B, but with the fixing ring rotated about half a turn. 
     FIGS. 6A and 6B are transverse cross-sectional views similar to FIGS. 5A and 5B, but with the fixing ring rotated a further amount and engaging the coil spring. 
     FIGS. 7A and 7B are transverse cross-sectional views similar to FIGS. 6A and 6B, but with the fixing ring rotated a still further amount and the coil spring in a relaxed state. 
     FIGS. 8A and 8B are transverse cross-sectional views similar to FIGS. 7A and 7B, but with the housings fully engaged with each other. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIG. 1, the connector has a male connector housing  10  (hereinafter referred to as male housing  10 ) and a female connector housing  20  (hereinafter referred to as female housing  20 ) to be fitted in the male housing  10 . 
     In the description below, the side of each of the male and female housings  10  and  20  which is fitted to the other housing is called the front side. 
     The male housing  10  is formed by combining two pieces made of synthetic resin with each other. More specifically, the male housing  10  has a body part  11  of circular cross-section and a cylindrical hood part  12  projecting forward from the body part  11 . The male housing  10  is shown installed in an installing hole  17  of a panel  16  of, for example, a motor vehicle (not shown) in preparation for engagement with the female housing  20 . 
     A plurality of cavities  13  is formed in the body part  11 . Male terminal metal fittings (not shown) are inserted into respective cavities  13  from the rear end thereof and are held therein, and have tabs which project into the hood part  12 . The male terminal metal fittings are locked by retainers  14  to prevent removal of the fittings from the cavities  13 . 
     The female housing  20  is also made of synthetic resin and is of general circular cross-section. The front side of the female housing  20  can be fitted in the hood part  12  of the male housing  10 . 
     A plurality of cavities  21  is formed in the female housing  20  such that the cavities  21  confront the cavities  13  of the male housing  10 . Female terminal metal fittings (not shown) are inserted into respective cavities  21  from the rear end thereof and are held therein. The female terminal metal fittings are locked by retainers  22  to prevent removal of the fittings from the cavities  21 . 
     An outer circumferential seal ring  24  is installed midway along the female housing  20 . The seal ring  24  is elastically sandwiched between the outer surface of the female housing  20  and the front side of the hood part  12  when the male housing  10  and the female housing are engaged with each other (see FIG.  2 ). 
     A fixing ring  30  is also made of synthetic resin and is cylindrical. The fixing ring  30  can be fitted on the periphery of the female housing  20 , with a predetermined clearance provided between the fixing ring  30  and the periphery of the female housing  20 . A plurality of circumferentially-spaced, inwardly-projecting locking hooks  31  are formed at the rear side of the fixing ring  30 . The locking hooks  31  are fitted in a circumferential groove  26  formed at the rear side of the peripheral surface of the female housing  20 , and in this way the fixing ring  30  is supported on the peripheral surface of the female housing  20  such that the fixing ring  30  can rotate freely. 
     A shoulder  35  is formed at the root (front) side of the peripheral surface of the hood part  12  of the male housing  10 . As shown in FIG. 3, a cam groove  36  is formed in the shoulder  35 . The start portion  36 A of the cam groove  36  opens to the front edge of the shoulder  35 . An inclined portion  36 C of the groove extends between a first linear portion  36 B and a second short linear portion  36 D. The end of the second linear portion  36 D forms a termination portion  36 E. The start portion  36 A and the termination portion  36 E circumferentially overlap each other. 
     A follower pin  38  that can be received in the cam groove  36  projects from the front end of the inner surface of the fixing ring  30 . 
     Although a detailed description is not provided here, the fixing ring  30  can be temporarily held, by an operator&#39;s fingers, for example, on the female housing  20  in a predetermined rotational position, and by aligning marks formed on the fixing ring  30  and on the hood part  12  of the male housing  10 , the cavities  13  of the male housing  10  and the cavities  21  of the female housing  20  can be put into alignment. 
     Next, the male housing  10  and the female housing  20  are fitted to each other. As a result, the follower pin  38  of the fixing ring  30  enters the start portion  36 A of the cam groove  36 . 
     A locking (detent) mechanism and a system for detecting incomplete engagement are provided by the female housing  20  and the fixing ring  30 . The function of the locking mechanism is to lock the housings  10  and  20  to each other in a fully engaged state. The function of the system for detecting incomplete engagement is to provide an indication whether the housings  10  and  20  have been locked to each other in the fully engaged state. The locking mechanism and the system for detecting incomplete engagement are described below. 
     Two circumferential spring accommodation grooves  41 , spaced from each other with a partitioning wall  40 , are formed on an outer surface of the female housing  20 . The spring accommodation grooves  41  are located rearwardly from the seal ring  24 . As shown in FIG. 4A, each spring accommodation groove  41  accommodates a spring seat  42 . 
     A loading ring  44  is rotatably mounted on the periphery of each spring accommodation groove  41 . A loading member  45  having a relief groove  46  to accommodate the partitioning wall  40  is formed at a predetermined position of the inner surface of the loading ring  44 , such that the loading member  45  projects into the spring accommodation groove  41 . A connection portion  48  to be connected with the fixing ring  30  projects outwardly from the loading member  45 . An engagement concavity  49  is formed inwardly in the connection portion  48  at its rearward end. 
     Each spring accommodation groove  41  accommodates a coil spring  50 , with one end of the coil spring  50  in contact with one surface of the spring seat  42  and the other end thereof in contact with the loading member  45 . Thus, each coil spring  50  is accommodated in the respective spring accommodation groove  41 , with the loading member  45  being pressed against an opposing surface of the spring seat  42 . 
     A locking projection  52  is formed on the peripheral surface of the female housing  20  rearwardly from the spring accommodation grooves  41  and circumferentially opposing the spring seat  42  as shown in FIG.  4 B. The side surfaces  52 A of the locking projection  52  converge toward each other. Thus, the locking projection  52  is tapered. 
     A locking arm  54  forms a portion of the fixing ring  30 . As shown in FIG. 1, front and rear slits are formed in the fixing ring  30  to define the locking arm  54 . The locking arm  54  radially overlaps the rearward spring accommodation groove  41  and (when aligned) the locking projection  52 . As shown in FIG. 4B, the locking arm  54  extends clockwise and is cantilevered so that the front (free) end is displaceable radially outwardly when the locking arm  54  is elastically deformed. 
     A tapered projection  55  with converging side surfaces is formed at the front end of the inner surface of the locking arm  54  and extends across the whole width of the locking arm  54 . In FIG. 4B, the rearward (relative to the front and rear ends of the housing  20 ) half of the projection  55  abuts the front side (relative to a clockwise rotational direction) of the locking projection  52 . When the fixing ring  30  is temporarily held on the female housing  20  as described above, they assume this relative positioned relationship. 
     The forward half of the projection  55  in its widthwise direction fits in the engagement cavity  49  formed on a connection portion  48  of the fixing ring  30 . 
     The operation of the connector of the first embodiment having the above-described construction is described below. 
     The male terminal metal fittings (not shown) are accommodated in the male housing  10  and are locked by the retainers  14 . The male housing  10  is installed on an installing hole  17  of a panel  16  in preparation for engagement with the female housing  20 . 
     The female terminal metal fittings (not shown) are accommodated in the female housing  20  and locked by the retainers  22 . The fixing ring  30  is installed on the female housing  20  and is temporarily held at the predetermined position thereof, as described above. 
     A mark (not shown) on the fixing ring  30  and a mark (not shown) on the male housing  10  are then aligned with each other. Next, as indicated by the arrow of FIG. 1, the female housing  20  is pressed into the male housing  10 . The female housing  20  is fitted in the hood part  12 , with the cavities  21  thereof aligned with the cavities  13  of the male housing  10 . As a result, the follower pin  38  of the fixing ring  30  penetrates into the start portion  36 A of the cam groove  36 . Then, the fixing ring  30  is rotated clockwise (as indicated by the arrows in FIGS.  4 A and  4 B). As a result, the follower pin  38  proceeds from the first linear portion  36 B of the cam groove  36  to the inclined portion  36 C thereof. Owing to the camming action of the follower pin  38  in the inclined portion  36 C, the housings  10  and  20  are drawn toward each other. 
     When the fixing ring  30  rotates about  180  degrees, the locking arm  54  elastically deforms as it rides over the connection portion  48  of the loading ring  44 . Then, as shown in FIG. 5A, the locking arm  54  relaxes to fit projection  55  in the engagement concavity  49 . In this way, the fixing ring  30  and the loading ring  44  are connected to each other so that they rotate together. 
     With further rotation of the fixing ring  30 , the housings  10  and  20  continue to be drawn together as the follower pin  38  travels along the cam groove  36 . With this rotation of the loading ring  44 , the coil springs  50  are gradually compressed by the loading member  45 , as shown in FIG.  6 A. This applies a return bias to the fixing ring  30 . 
     Due to the camming action of the follower pin  38  in the cam groove  36 , the housings  10  and  20  gradually approach the fully engaged position under a comparatively small applied rotational force. However, when the engagement operation approaches its final stage, the male terminal metal fittings of the male housing  10  and the female terminal metal fittings of the female housing  20  are deeply interconnected which increases resistance to further engagement. Thus, there is a possibility that an operator may stop rotating the fixing ring  30  before the housings  10  and  20  are fully engaged. 
     If this happens, and if the operator releases the fixing ring  30  or relaxes his or her grip on the fixing ring  30 , the loading ring  44  and the fixing ring  30  are rotated together counterclockwise in FIG. 6 by the elastic restoring force of the compressed coil springs  50 , and the housings  10  and  20  separate from each other. Therefore, the operator knows that the housings  10  and  20  were incompletely engaged. 
     When the operator rotates the fixing ring  30  until it has made a  360  degree rotation, the follower pin  38  enters the second linear portion  36 D of the cam groove  36 , and the housings  10  and  20  are fully engaged. At the same time, as shown in FIG. 7B, the projection  55  of the locking arm  54  rides over the locking projection  52  of the female housing  20  and the locking arm  54  deforms outwardly elastically. Therefore, as shown in FIG. 7A, the projection  55  disengages from the engagement concavity  49  of the connection portion  48 . Consequently the loading member  45  is no longer operatively connected to the fixing ring  30 . As a result, as shown in FIG. 8A, the coil springs  50  recover their original elongation and rotate the loading ring  44  counter-clockwise until the loading member  45  strikes the spring seat  42 . 
     With a slight further rotation of the fixing ring  30 , the projection  55  passes the locking projection  52 . As a result, as shown in FIG. 8B, the locking arm  54  recovers its original form and is detained adjacent the locking projection  52 . In this way, both housings  10  and  20  are held together in the fully engaged state. 
     When the fixing ring  30  is rotated counterclockwise from the position of FIGS. 8A and 8B at a force greater than a predetermined force, the inclined surface  52 A allows the projection  55  to ride back across the locking projection  52  in the opposite direction while the locking arm  54  is deformed elastically outwardly. Counterclockwise rotation of the fixing ring  30  continues until the projection  55  rides over the connection portion  48  (with a passing engagement) and disengages. Further counterclockwise rotation is not prevented. Meanwhile, both housings  10  and  20  are gradually separated from each other through the action of the follower pin  38  in the cam groove  36 . 
     When the fixing ring  30  has made one full counterclockwise rotation and returned to the position at which the projection  55  contacts the locking projection  52 , as shown in FIG. 4B, the follower pin  38  returns to the start portion  36 A of the cam groove  36 . This allows complete separation of the housings  10  and  20 . 
     Slightly before the housings  10  and  20  become fully engaged, the coil springs  50  are unloaded and cause the loading ring  44  to rotate in the opposite direction (counterclockwise direction). Therefore, when the housings  10  and  20  are fully engaged, the spring force of the coil springs  50  no longer acts to separate the housings  10  and  20  from each other. However, the coil springs  50  are not disabled and can be reused. 
     Also the locking projection  52  has a semi-locking construction. That is, the locking arm  54  can ride across the locking projection  52  in both directions. Thus, when the fixing ring  30  is rotated in the counterclockwise direction at a force higher than a predetermined force, the fixing ring  30  escapes the detent, and then the fixing ring  30  can continue to be rotated to separate the housings  10  and  20 . 
     The present invention is not limited to the embodiment explained above by way of the above description and drawings. For example, the following embodiments are included in the technical scope of the present invention. 
     (1) The coil spring can be a tension spring rather than a compression spring, allowing elastic restoring force to be stored as the spring is extended. 
     (2) The fixing ring may be mounted on the male housing. In this case, the locking mechanism and the coil spring are mounted between the male housing and the fixing ring. 
     While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention 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.