Abstract:
A jack having enhanced reliability and strength against torsional forces is provided. The jack including a plug inlet for receiving a plug having at least one electrode formed thereon for electrical signals, comprises an elongated spring having a free end part with a pressing portion capable of pressing a side surface of the inserted plug, and a proximal end part fixed to the jack. The jack further comprises a retaining portion capable of contacting a first contact portion and a second contact portion arranged at opposite sides thereof along a direction of inserting the plug when the plug is inserted into the jack.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a jack comprising a spring provided along a plug inlet formed in a jack body. 
         [0003]    2. Description of the Related Art 
         [0004]    One example of conventional jacks used in audio devices or the like comprises a plug inlet formed in a jack body for receiving a plug, and a plurality of electrodes formed of a conductor and arranged inside the plug inlet. Such a jack allows a plurality of conductive surfaces (connecting terminals) formed on the plug and acting as the connecting terminals for the plug to contact the electrodes provided inside the plug inlet when the plug is inserted into the plug inlet. Each of the electrodes provided inside the plug inlet has a spring-shape so as to contact a conductive surface of the plug by its own action when the plug is inserted, and is formed by press working. 
         [0005]    Such a jack having the above-noted construction is used as a connecting element for connecting headphones or earphones to a mobile audio device or mobile phone. When the mobile audio device is operated, the user not only holds the mobile audio device with one hand while controlling a play button or the like provided on the mobile audio device with the other hand, but also holds the mobile audio device and controls the buttons with one hand. Such operations sometimes place the relative posture between the plug and jack in an unstable condition, as a result of which the plug is likely to be removed from the jack. Otherwise such an unstable posture produces a torsional force exerted on the jack. Repeatedly producing the torsional force often leads to poor contact between the connecting terminals formed on the plug and the electrodes provided in the jack. 
         [0006]    As a countermeasure against such a torsional force, Japanese Unexamined Patent Publication No. 2000-340311 discloses a connector comprising an electrode with a bent portion for allowing a distal end of the electrode or a back contact to contact a plug thereby preventing the distal end of the electrode or the back contact from being excessively displaced by the torsional force (see paragraph 0021, 0029, 0033, 0037 and so on). Also, Japanese Utility Model Application Laid-Open Publication No. 56-62680 discloses a jack comprising a projection such as a boss formed on a body for contacting an electrode thereby preventing excessive displacement (see page 2, FIGS. 4 to 6). However, the above-noted conventional connector or jack has not the least possibility of a contact failure caused by deterioration of the bent electrode or damage of the boss per se resulting from a repetition of torsional forces. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention has been made having regard to the above-noted problems, and its object is to provide a jack having enhanced reliability and strength against torsional forces. 
         [0008]    In order to achieve the above-noted object, a jack in accordance with the present invention comprises a plug inlet for receiving a plug having at least one electrode formed therein for electrical signals, and an elongated spring. The elongated spring has a pressing portion formed in a free end part thereof for pressing a side surface of the plug, and a proximal end part fixed to the jack. The jack also comprises a retaining portion capable of contacting a first contact portion and a second contact portion provided at opposite sides of the pressing portion of the free end part along a direction of inserting the plug when the plug is inserted into the jack. 
         [0009]    With this arrangement, in addition to the pressing portion provided in the spring pressing the side surface of the plug inserted into the jack, the retaining portion can support the first contact portion and second contact portion of the spring. This can increase a pressing force of the spring. As a result, a retaining force for the jack to support the plug can be enhanced thereby preventing the plug coming off inadvertently to the user. 
         [0010]    It is also preferable that the jack further comprises a guide mechanism for preventing out-of-plane displacement of the pressing portion from a predetermined rocking plane defined by the spring rockable about the proximal end part when the plug is inserted into the jack. With this guide mechanism provided for the spring and jack, the pressing portion is prevented from displacing from the side surface of the plug to be pressed even if a torsional force is exerted on the jack or the plug. Thus, the plug can be reliably pressed. 
         [0011]    It is also preferable that the guide mechanism includes a projection provided in the jack and extending through an opening formed in the spring. This arrangement can improve the effect produced by the guide mechanism. 
         [0012]    Further, the projection may be formed along an extending direction of the plug inlet, and the retaining portion may be formed on an outer surface of the projection. This arrangement makes it possible to simply form the guide mechanism and a retainer mechanism having the retaining portion. Thus, the jack can be efficiently manufactured. 
         [0013]    Further, it is preferable that the spring is an electrode electrically connectable to the plug. Where the spring acts as an electrode of the jack for connection with the electrodes formed on the plug, the spring can have a function as the electrode and a pressing function. As a result, the jack has a compact construction which is less subject to influences of a torsional force, and also improves reliability of electrical connection. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0014]      FIG. 1  is a perspective view of a plug and a jack for connecting a mobile audio device to earphones; 
           [0015]      FIG. 2  is a perspective view of the plug and the jack; 
           [0016]      FIG. 3  is an exploded view showing terminal electrodes forming the jack; 
           [0017]      FIG. 4  is a perspective view showing a relationship between the jack and an earth spring; 
           [0018]      FIG. 5  is a view showing how the earth spring is retained; 
           [0019]      FIG. 6  is a circuit diagram showing connections among the terminal electrodes of the jack; 
           [0020]      FIG. 7  is a bottom view of the jack; 
           [0021]      FIG. 8  is a sectional view of the jack taken along line VIII-VIII of  FIG. 7 ; 
           [0022]      FIG. 9  is a sectional view of the jack taken along line IX-IX of  FIG. 7 ; 
           [0023]      FIG. 10  is a perspective view of an earth spring in accordance with an alternative embodiment of the present invention; and 
           [0024]      FIG. 11  is a view showing how the earth spring is retained in accordance with the alternative embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]    Embodiments of a jack in accordance with the present invention will be described hereinafter with reference to the accompanying drawings. 
         [0026]    A jack  11  is provided in a mobile audio device  12  as shown in  FIG. 1 , and includes a plug inlet  17  for receiving a plug  15  connected to a pair of stereo-type earphones  14  or headphones (not shown) through a cable  13 . Such a mobile audio device  12  includes a plurality of control switches  12 A operable to play and stop audio data stored in the device  12  and further to control the volume of sound. In the present embodiment, the jack  11  will be described as provided in the mobile audio device  12 . However, the scope of the present invention is not limited to such an application. The jack  11  in accordance with the present invention may be used in mobile phones or mounted on other electric appliances. 
         [0027]      FIG. 2  shows the plug  15  insertable into the jack  11  of the present invention. The plug  15  includes a tip  21  provided at a distal end thereof to act as an electrode for stereo audio signals outputted to the left earphone. The plug  15  further includes a ring  22  acting as an electrode for stereo audio signals outputted to the right earphone, and a sleeve  23 , the ring  22  and the sleeve  23  being arranged in the mentioned order from adjacent the distal end of the plug. Insulating rings  24  are mounted between the tip  21  and the ring  22  for insulating one from the other. A further insulating ring  24  is provided between the ring  22  and the sleeve  23  as well. The sleeve  23  is connected to a shield layer used for protecting the right and left stereo audio signals from outside noise in the cable  13 . Thus, the tip  21  and ring  22  are connected to the jack for transmitting audio signals from the mobile audio device  12  to the earphones  14  through the cable  13 . The sleeve  23  is connected to have the same potential as the ground of the mobile audio device  12 . 
         [0028]    The plug inlet  17  is provided in a body  16  of the jack  11  for receiving the plug  15 . Outside of the body  16  (the side facing away from the plug inlet  17  in  FIG. 2 ) are provided a plurality of terminal electrodes  1  to  7  connected to a plurality of electrodes provided inside the body, respectively. These terminal electrodes  1  to  7  are insulated from one another by a separator  8  formed of an insulating material for preventing short-circuits of those electrodes. Further, each of the terminal electrodes  1  to  7  includes a soldered portion (not shown) formed thereon to facilitate wiring with the exterior. 
         [0029]      FIG. 3  is an exploded view of the jack  11  showing the terminal electrodes and the like. The jack  11  includes a spring  1 , a tip spring  2 , a ring spring  3 , a first B-armature  4 , a first T-armature  5 , a second B-armature  6  and a second T-armature  7 , all of which act as the electrodes. Since the sleeve  23  is connected to have the same potential as the ground as noted above, the spring  1  for contacting the sleeve  23  will be referred to as the earth spring  1  and described in detail hereinafter. 
         [0030]    The earth spring  1  according to the present invention is movable under its spring action and includes an earth spring fixing portion  1 A provided in a proximal part  100  thereof for fixing the earth spring  1  to the body  16  of the jack  11 . At a free end part  101  of the earth spring is provided a pressing portion  1 B which is bent for pressing a side surface of the plug  15  when the earth spring  1  contacts the sleeve  23  of the plug  15  inserted into the jack  11 . Also, as shown in  FIG. 3 , the earth spring  1  includes a first contact portion  1 C at a distal end thereof extending from the pressing portion  1 B and bent at a substantially central portion thereof. Further, the free end part  101  has a slot  1 D formed therein with an opening edge acting as a second contact portion  1 E. As shown in  FIG. 3 , a boundary portion defined between the proximal part  100  and the free end part  101  is also bent. Thus, the first contact portion  1 C and the second contact portion  1 E are arranged along the plug inlet  17  at opposite sides of the pressing portion  1 B. 
         [0031]      FIG. 4  is a prospective view of the jack  11  and the earth spring  1  showing the relationship therebetween. The body  16  includes a first opening  31  and a second opening  32  formed parallel to each other adjacent the inlet opening of the plug inlet  17  for receiving the plug  15 . A bar  30  is formed between the first opening  31  and the second opening  32 , to have a projection  33  formed at a distal end thereof to extend through the slot  1 D of the earth spring  1 . The bar  30  and the projection  33  act together as a guide mechanism for preventing out-of-plane displacement of the pressing portion  1 B from a predetermined position where the earth spring  1  is movable with reference to the proximal part  100  when the plug  15  is inserted and the pressing portion  1 B presses the side surface of the plug  15 . 
         [0032]      FIG. 5(   a ) is a side view of the earth spring  1  and the body  16  showing how these elements are held with each other, while  FIG. 5(   b ) is a bottom view thereof. It should be noted that the bar  30  and the projection  33  are made of a reinforced resin. Thus, even when a torsional force occurs as the plug  15  is inserted to apply a twisting force to the earth spring  1 , the projection  33  made of the reinforced resin extends through the slot  1 D of the earth spring  1 , which allows outer surfaces of the bar  30  and the projection  33  to act as a retaining portion  102 . Not only is the plug  15  is pressed by the pressing portion  1 B, both the first contact portion  1 C and the second contact portion  1 E contact the bar  30 , thereby preventing poor contact resulting from out-of-plane displacement between the pressing portion  1 B and the sleeve  23  which should properly contact each other. 
         [0033]      FIG. 6  is a circuit diagram showing connection among the terminal electrodes of the jack  11 . As noted above, the jack  11  includes the earth spring  1 , tip spring  2 , ring spring  3 , first B-armature  4 , first T-armature  5 , second B-armature  6  and second T-armature  7 . When the plug  15  is not inserted into the plug inlet  17 , the first B-armature  4  and first T-armature  5  are electrically connected to each other, and the second B-armature  6  and second T-armature  7  are also electrically connected to each other as shown in  FIG. 6(   a ). On the other hand, when the plug  15  is inserted into the plug inlet  17 , the first B-armature  4  and first T-armature  5  are disconnected from each other, and the second B-armature  6  and second T-armature  7  are also disconnected from each other as shown in  FIG. 6(   b ). The details will be described later. 
         [0034]      FIG. 7  shows the jack  11  viewed from the side where the terminal electrodes formed outside the jack  11  are provided (from the side facing away from the plug inlet  17  in  FIG. 2 ).  FIG. 8(   a ) shows the jack  11  taken along the line VIII-VIII of  FIG. 7  without the plug being inserted. Inside the jack  11  are the tip spring  2  to be connected, along with the earth spring  1 , to the tip  21  of the plug  15 , and the ring spring  3  to be connected to the ring  22  of the plug  15 . The earth spring  1  is fixed to the body  16  by the earth spring fixing portion  1 A. Similarly, the tip spring  2  and ring spring  3  are fixed to the body  16  by a tip spring fixing portion  2 A and a ring spring fixing portion  3 A, respectively. 
         [0035]      FIG. 8(   b ) shows the jack  11  taken along the line VIII-VIII of  FIG. 7  with the plug being inserted. The tip  21  contacts tip contact portions  2 B when the plug  15  is inserted. Then, the ring  22  contacts a ring contact portion  3 B while the sleeve  23  contacts the pressing portion  1 B of the earth spring  1 . The earth spring  1  is pressed by the plug  15  by virtue of its spring action, whereby the first contact portion  1 C and the second contact portion  1 E contact the bar  30 . It should be noted that a conventional jack is not provided with the second contact portion  1 E, which brings the pressing portion  1 B into contact the sleeve  23  and allows only the first contact portion  1 C to contact the bar  30 . Thus, the three points provided by the pressing portion  1 B, first contact portion  1 C and earth spring fixing portion  1 A constitute a plate spring. On the other hand, according to the jack  11  of the present invention, the first contact portion  1 C and second contact portion  1 E arranged at opposite sides across the pressing portion  1 B provide two points for contacting the bar  30 , and these three points constitute the plate spring noted above. In comparison between the present invention and the conventional art, a distance between the pressing portion  1 B and first contact portion  1 C is the same while a distance between the pressing portion  1 B and the earth spring fixing portion  1 A in the prior art corresponds to the decreased distance between the pressing portion  1 B and the second contact portion  1 E in the present invention. Since the plate spring shape is formed to have a small distance, the posture of the spring is stabilized thereby to enhance the strength against torsional forces. 
         [0036]      FIG. 9  is a sectional view of the jack  11  taken along the line IX-IX of  FIG. 7  without the plug being inserted. The first B-armature  4  contacts the first T-armature  5  while the second B-armature  6  contacts the second T-armature  7 . The separator  8  is provided in the central portion of the jack assembly. When the plug  15  is inserted, the separator  8  receives a pressing force to expand in the direction of arrows shown in  FIG. 9 . Due to this pressing force, the separator  8  expands the first T-armature  5  and second T-armature  7  outward. As a result, the first T-armature  5  is disengaged from the first B-armature  4  and the second T-armature  7  is also disengaged from the second B-armature  6 . 
         [0037]    According to the above embodiment, the second contact portion is formed in the slot  1 D. However, the scope of the present invention is not limited to this arrangement. Naturally, for instance, cutout portions  35  may be provided as shown in  FIG. 10  instead of the opening such as the slot  1 D. With such an arrangement, as shown in  FIGS. 11(   a ) and  11 ( b ), two bars  30  are provided to extend from the body  16  thereby to hold the earth spring  1  therebetween. This allows the pressing portion  1 B to press the sleeve  23  while the first contact portion  1 C and the second contact portion  1 E contact the bars  30  as in the above-noted embodiment. Thus, naturally, it is possible to secure the functions and effects of the present invention for providing a countermeasure against a torsional force 
         [0038]    In  FIG. 10 , the cutout portions  35  are provided at the opposite sides of the earth spring  1 . However, the scope of the present invention is not limited to this arrangement. For example, it is also possible to provide a single cutout portion  35  at only one side of the earth spring  1  and dispense with the other side cutout portion  35 , thereby allowing the earth spring  1  to be pressed and fixed directly to the body. 
         [0039]    According to the first embodiment, the electrodes provided for the plug  15  include the tip  21 , ring  22  and sleeve  23 . However, the scope of the present invention is not limited to this arrangement. For example, even if only the two electrodes, the tip  21  and sleeve  23 , are provided, it is possible, naturally, to enhance the countermeasure against a torsional force according to the present invention by using the pressing portion  1 B, first contact portion  1 C and second contact portion  1 E. The present invention is also applicable where the number of terminal electrodes is increased as where a remote controller is provided between the earphones  14  and plug  15 . 
         [0040]    In the first embodiment, the earth spring  1  acts as one of the electrodes. However, the scope of the present invention is not limited to this arrangement. For example, the earth spring  1  may be provided to simply act as a reinforcing jig, instead of the electrode, operative against a torsional force. 
         [0041]    According to the first embodiment, the pressing portion  1 B, first contact portion  1 C and second contact portion  1 E contact the sleeve  30  and bar  30 , respectively, to enhance the strength against a torsional force. However, the scope of the present invention is not limited to this arrangement. Naturally, for example, it is possible to allow an edge opposed to the edge of the slot  1 D acting as the second contact portion  1 E to act as a third contact portion and contact the bar  30 , thereby enhancing the strength against a torsional force. 
         [0042]    Further, the projection  33  acting as the guide mechanism is formed along the plug inlet  17  in the first embodiment. However, the scope of the present invention is not limited to this arrangement. For example, it is also possible to provide the projection  33  to extend across the plug inlet in a direction from an outer periphery toward the center of the plug inlet. With this arrangement, the position of the second contact portion  1 E is shifted to the opposite edge of the slot  1 D, which makes it possible to secure the functions and effects of the present invention for counteracting a torsional force by using the second contact portion  1 E as well as the pressing portion  1 B and the first contact portion  1 C.