Plug-jack connecting structure

Abstract: A jack (1) carries at its forward end a sleeve (7) of a noncircular outside shape and having grooves (12) cut in its outer periphery. A plug (20) has a ring (30) rotatably mounted thereon at one end thereof for receiving the sleeve (7), and a sleeve receiving hole (31) of the ring (30) has a shape complementary to the outside shape of the sleeve (7). By turning the ring (30) through 90° (B into engagement with the grooves (12), the jack (1) and the plug (20) are connected in a state in which they are prevented from disengagement.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a structure for interconnecting a plug and jack by inserting the former into the latter and, more particularly, to a plug-jack connecting structure which would not unexpectedly come off of the plug even when vibrated or shocked. Description of the Prior Art A car phone or TV is put into its operative state when its plug is inserted into a jack mounted on the front panel of the car. The connection between the plug and the jack is usually made by elastic contact between terminals disposed along a plug receiving hole of the jack and the periphery of the plug. That is, there are mounted inside the jack a plurality of terminals serving as a grounding terminal and positive and negative electrode terminals; these terminals are partly bent or punched to form elastic contact portions. When inserting a multi-polar plug into the jack of such a construction, the respective terminals elastically contact the corresponding electrodes of the plug, establishing electric connections therewith and firmly holding the plug in the jack. Only with the forces exerted on the periphery of the plug by such elastic contact therewith of the terminals, however, the plug is very likely to come off the jack due to vibrations and shocks created during travelling, often resulting in telephone communication or TV reception being broken off. To overcome such a disadvantage, the plug is conventionally screwed into the jack. This traditional plug-jack connecting structure has a male screw thread cut on the outer surface of a sleeve that guides the plug into the jack, a ring mounted on the plug at one end thereof and a female screw thread cut on the inner surface of the ring. With such a structure, the ring carried by the plug is butted against the sleeve of the jack and then rotated into threaded engagement with the sleeve, by which the plug and the sleeve can be firmly coupled with each other. This structure provides the coupling between them by screwing, and hence it precludes the possibility of the plug accidentally becoming detached from the jack due to vibrations and shocks. With the screwing structure, however, the ring mounted on the plug needs to be frequently rotated into threaded engagement with the sleeve, making the connecting operation cumbersome. In the case of connecting the plug to the sleeve during driving, in particular, the driver's attention is divided, posing the danger of a traffic accident. Another problem of the conventional structure is the need for forming screw threads on both of the sleeve and the ring. The use of metal for the sleeve and the ring for cutting thereon the screw threads would inevitably increase the manufacturing cost of the plug-jack connecting structure. On the other hand, the formation of screw threads during the formation of dies by molding of a resin material would require highly developed molding techniques and complicated molding machine which involve a screw-wise transfer of one of the dies during molding--this would also raise the manufacturing cost of the connecting structure. EP-A-0660452 discloses a structure according to the preamble of claim 1. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a simple-structured, easy-to-fabricate plug-jack connecting structure which permits connection between the plug and the jack through a simple manipulation even if the jack is made by molding. According to the present invention, there is provided a plug-jack connecting structure for making connections between a plurality of terminals secured to a jack and a plurality of corresponding electrodes of a plug by inserting the plug into the jack, which is characterized by : a sleeve of a noncircular outside shape and formed as a unitary structure with the jack at one end thereof; a ring having a sleeve receiving hole of a shape complementary to that of the sleeve and rotatably mounted on the plug at one end thereof opposite the jack; and grooves cut in the outer periphery of the sleeve along the direction of rotation of the ring so that when the ring is rotated, the inner periphery of the sleeve receiving hole comes into engagement with the grooves to prevent disengagement of the ring and the sleeve from each other. With this structure, the grooves cut in the outer peripheral surface of the sleeve and the inner peripheral surface of the sleeve receiving hole of the ring are brought into engagement by the rotation of the ring to establish a connection between the plug and jack. In this state the engagement of the inner peripheral surface of the sleeve receiving hole with the grooves on the sleeve surface serves to provide firm coupling of the plug to the jack. Moreover, since the sleeve of the jack has a noncircular outside shape and since the sleeve receiving hole of the ring has a shape complementary to the outside shape of the sleeve, it is easy to position the ring and the sleeve relative to each other. According to an optional other aspect of the present invention, the width of each groove and the thickness of the inner periphery of the sleeve receiving hole are substantially equal to each other. With this structure, the inner side walls of each groove and the outer surface of the ring make close contact with each other, providing the coupling between the jack and the plug with no play. According to still another optional aspect of the present invention, recesses are formed in the inner side walls of the grooves and protrusions are protrusively provided on the ring for engagement with the recesses at a rotational angular position where the sleeve receiving hole and the grooves engage each other. With this structure, the engagement of the protrusions of the ring with the recesses in the grooves arrests rotational motion of the ring, ensuring holding of the plug in the jack. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an exploded perspective view of a jack according to an embodiment of the present invention; Fig. 2 is a side view of the jack; Fig. 3 is a sectional view taken on the line A-A in Fig. 2; Fig. 4 is a front view of a sleeve; Fig. 5 is a bottom view of the jack; Fig. 6 is a side view, partially broken away, of a plug; Fig. 7 is a front view of a ring; Fig. 8 is a sectional view of the ring; Fig. 9 is a side view of the ring; and Fig. 10 is a sectional view showing the connection between the jack and the plug. DESCRIPTION OF THE PREFERRED EMBODIMENT The accompanying drawings illustrate an embodiment of the present invention, Figs. 1 through 5 showing a jack 1, Figs. 6 through 9 a plug 20 and Fig. 10 the state in which the plug 20 is inserted in the jack 1. The jack 1 is mounted, for example, on the front panel of a car and, as shown in Fig. 1, the jack 1 has sleeve, chip and ring terminals 3, 4 and 5 made of a conductive material and secured to a jack housing 2 to make electric connections with corresponding electrodes of the plug 20, respectively. The jack housing 2 is substantially a box-shaped molding of an insulating synthetic resin and, as shown in Fig. 10, it has a plug receiving hole 6 extending therethrough in its axial or lengthwise direction. The jack housing 2 carries at its forward end a tubular sleeve 7 formed integrally therewith and having a plug guide hole 8 that communicates with the plug receiving hole 6. The end portion of the sleeve 7 contiguous to the jack housing 2 forms a base portion 9 of a circular outside shape, which has at its forward end a mounting portion 10 formed as a unitary structure therewith. The mounting portion 10 is composed of circular-arc portions 13 concentric with the base portion 9 and flat portions 11 formed by cutting the circle of the base portion 9 to provide the same chords at right and left sides of the circular-arc portions 13; outwardly, the mounting portion 10 is oval-shaped as a whole. The mounting portion 10 of the sleeve 7 has, as shown in Figs. 2 to 5, a pair of grooves 12 cut in its upper and lower peripheral surfaces along a circular arc that crosses the axial direction of the sleeve 7 at right angles. Thus, the grooves 12 extend in the direction of rotation of a ring 30 of the plug 20 that will be described later on. The grooves 12 each have a sloped portion 12a extending from an intermediate portion of one of the flat portions 11 and concentric with the base portion 9 and a flat engaging portion 12b contiguous to the sloped portion 12a at one end thereof. Thus, each flat engaging portion 12b lies inside one of the circular-arc portions 13. Each groove 12 has a recess 14 cut in the flat engaging portion 12b by forming a stepped portion in the side wall of the base portion 9 facing the engaging portion 12b. The plug 20 is connected to a connecting cord terminal of equipment such as a car phone or the like. As depicted in Fig. 6, the plug 20 has a cover 21 made of insulating rubber or similar material and a rod-shaped plug body 22 extending in the axial direction of the cover 21 and having its forward end portion extending out therefrom. The plug body 22 extending out of the cover 21 forms a chip electrode 24, a ring electrode 25 and a sleeve electrode 23, which are separated by insulators 26. Inside the cover 21 the plug body 22 is connected to a connection cord 27 from the equipment. In the outer surface of the forward end portion of the cover 21 there is cut a ring receiving groove 28 extending circumferentially thereof. The ring 28 receives a stopper portion 38 extending inwardly from a ring 30 at the rear end thereof so that the ring 30 is mounted on the plug 20 at the forward end thereof in a manner to be rotatable and movable back and forth. The ring 30 is a tubular molding of a resin which is highly slippery, such as polyacetal or polyimide resin. The ring 30 has its front side bent inwardly as indicated by 38 to form a sleeve receiving hole 31 into which the sleeve 7 of the jack 1 is inserted when the plug 20 is coupled to the jack 1. The inner periphery 34, which defines the sleeve receiving hole 31, has upper and lower circular-arc portions 32 and flat portions 33 forming parallel chords at both sides of the circular arc portions 32, as illustrated in Fig. 7, so that the inner periphery 34 has substantially an oval configuration. Hence, the inner periphery 34 of the sleeve receiving hole 31 has a shape complementary to the outside shape of the sleeve 7 of the jack 1 to permit the insertion thereinto of the sleeve 7. The inner periphery 34 of the sleeve receiving hole 31 engages the grooves 12 of the sleeve 7 to provide the coupling of the plug 20 to the jack. By turning the ring 30 after the insertion of the sleeve 7 along the sleeve receiving hole 31, the sleeve 7 is locked in place. On the front surface of the ring 30 there are protrusively provided protrusions 35 which are disposed on the bent portion 36 of the ring 30 outside the sleeve receiving hole 31. The protrusions 35 provided corresponding to the recesses 14 of the sleeve 7 and are fitted into the latter when the ring 30 and the sleeve 7 are coupled to each other. The thickness T of the inner periphery 34 of the sleeve 31 of the ring 30 (see Fig. 8) and the width W of the groove 12 of the sleeve 7 (see Fig. 2) are chosen about the same. For example, the thickness T is chosen exactly the same as or about 0.1 mm smaller than the width W. By such setting of the thickness T and the width W, the grooves 12 of the sleeve 7 and the inner periphery 34 of the sleeve receiving hole 31 can be held in close contact with each other, ensuring tight coupling between the sleeve 7 and the ring 30. While in this embodiment the outside shape of the ring 30 is substantially oval as is the case with the sleeve 7 of the jack 1, it is not limited specifically to such a shape but may also be arc-shaped. The oval outside shape of the ring 30 allows ease in holding it at flat portions 37 (see Fig. 7) with a hand and facilitates positioning of the plug 20 relative to the sleeve 7, and hence enables the ring 30 to be turned. Turning back to Fig. 1, the terminals secured to the jack 1 and their electric connections will be described. In the rear end portion of the plug receiving hole 6 in the jack housing 2 there are formed contact housing grooves (not shown) for housing the chip and ring terminals 4 and 5. In the top of the jack housing 2 at the rear of the sleeve 7 there is made a window 15 which communicates with the plug receiving hole 6. On either side of the jack housing 2 a little rearward of the window 15 there is formed a concave portion 16 where to position a side panels 3a of the sleeve terminal 3 lengthwise of the jack housing 2. Protrusively provided on the concave portion 16 centrally thereof is a lug 17 for engagement with a hole 3b made in the side panel 3a of the sleeve terminal 3 to prevent it from coming off the jack housing 2. The side panel 3a of the sleeve terminal 3 extends down from either side of a horizontal panel 3f and the side panel 3a has a leg 3d formed integrally therewith and to be soldered to an earth pattern (not shown) of a printed circuit board. The horizontal panel 3f has at its forward end a contact portion 3e bent downward in a U-letter shape, which makes elastic contact with the sleeve electrode 23 of the plug body 22. The chip terminal 4 is an inverted L-shaped member formed by punching and has an upper horizontal mounting portion 4b and a downward leg portion 4c. The mounting portion 4b has its intermediate portion folded back to form a chip contact portion 4a. The chip contact portion 4a makes elastic contact with the chip electrode 24 of the plug body 22 and is electrically connected therethrough to the plug 20. On the other hand, the leg portion 4c is connected to a pattern of the printed circuit board placed under the jack 1. Reference numeral 4d denotes a lug formed on the upper edge of the mounting portion 4b for locking the chip terminal 4 in the contact housing groove after the chip terminal 4 is inserted into the jack housing 2. The ring terminal 5 is also an inverted L-shaped member by punching as is the case with the chip terminal 4 and has a flat base portion 5b and a downward leg portion 5c, which is connected to a pattern of the printed circuit board. The base portion 5b has an acutely bent ring contact portion 5a, which makes elastic contact with the ring electrode 25 of the plug body 22. Reference numeral 5d a lug for engagement with the contact housing groove to lock therein the ring terminal 5. As will be seen from the above, when to establish connection between the jack 1 and the plug 20, the sleeve receiving hole 31 is placed in alignment with the sleeve 7 in accordance with its outside shape, then the sleeve 7 is inserted into the sleeve receiving hole 31, and the inner periphery 34 of the hole 31 is fitted into the grooves 12, after which the ring 30 is turned clockwise. By the clockwise turning of the ring 30, the inner periphery 34 of the sleeve receiving hole 31 slides in the sloped portions 12a of the grooves 12. When the ring 30 is further turned 90 degrees, the inner periphery 34 of the sleeve receiving hole 31 reaches the flat engaging portions 12b of the grooves 12 and the protrusions of the ring 30 fall into the recesses 14 made in the grooves 12, arresting further turning of the ring 30 and establishing a connection between the jack 1 and plug 20. In this state, the terminals 3, 4 and 5 of the jack 1 make contact with the corresponding electrodes 23, 24 and 25 of the plug 20, and the engagement of the inner periphery 34 of the sleeve receiving hole 31 with the grooves 12 prevents accidental disconnection of the terminals and the electrodes due to vibrations or shocks applied thereto and hence ensures reliable connections between them. Thus, the structure of the present invention provides the coupling between the jack 1 and the plug 20 without the need for forming complex screw threads, and hence it is simple in construction and easy to fabricate, besides it allows ease in connecting the jack and the plug without the necessity of turning the ring 30. When the jack 1 and the plug 20 are held together, the protrusions 35 of the ring 30 are engaged with the recesses 14 in the grooves 12, so that the ring 30 would not accidentally turn and hence would not come off the sleeve 7. Additionally, since the grooves 12 and the inner periphery 34 of the sleeve receiving hole 31 make close contact with each other, the jack 1 and the plug 20 can stably be connected. In the present invention, the outside shape of the sleeve 7 and the sleeve receiving hole 31 may be made in an elliptic, oblong, polygonal or similar noncircular form as well as the oval one. The recesses 14 and the protrusions 35 for engagement therewith need not always be provided. The width of the groove 12 and the thickness of the inner periphery 34 of the sleeve receiving hole may also be suitably chosen. EFFECT OF THE INVENTION According to the first aspect of the present invention, since the grooves 12 cut on the outer periphery of the sleeve 7 and the inner periphery 34 of the sleeve receiving hole 31 are brought into engagement by turning the ring 30, the plug 20 and jack 1 can easily be connected and, in addition, the engagement of the inner periphery 34 of the sleeve receiving hole 31 with the grooves 12 permits firm coupling of the plug 20 to the jack 1 and prevents accidental disconnection of the former from the latter. This avoids the necessity of using complicated screwing and provides a connecting structure which would not allow the plug 20 to come off the jack 1. According to the optional second aspect of the present invention, the jack 1 and the plug 20 can be connected without play therebetween since the grooves 12 and the inner periphery 34 of the sleeve receiving hole 31 make close contact with each other. According to the optional third aspect of the present invention, since the engagement of the protrusions 35 of the ring 30 with the recesses 14 in the grooves 12 arrests accidental turning of the ring 30, ensuring the connection between the jack 1 and the plug 20. It will be apparent that many modifications and variations may be effected without departing from the scope of the claims.

Claims: A plug-jack connecting structure for making connections between a plurality of terminals (3, 4, 5) secured to a jack (1) and a plurality of corresponding electrodes (23, 24, 25) of a plug (20) by inserting said plug (20) into said jack (1), comprising: a sleeve (7) formed as a unitary structure with said jack (1) at one end thereof; a ring (30) having a sleeve receiving hole (31) of a shape complementary to that of said sleeve (7) and rotatably mounted on said plug (20) at one end thereof opposite said jack (1); and grooves (12) cut in the outer periphery of said sleeve (7) along the direction of rotation of said ring (30) so that when said ring (30) is rotated, the inner periphery (34) of said sleeve receiving hole (31) comes into engagement with said grooves (12) to prevent disengagement of said ring (30) and said sleeve (7) from each other, characterised in that the outside of said sleeve and said sleeve receiving hole are of a non circular shape. The structure of claim 1, characterized in that the width of each of said grooves (12) and the thickness of said inner periphery (34) of said sleeve receiving hole are substantially equal to each other. The structure of claim 2, characterized by recesses (14) formed in the inner side walls of said grooves (12) and protrusions (35) protrusively provided on said ring (30) for engagement with said recesses (14) at a rotational position where said sleeve receiving hole (31) and said grooves (12) engage each other.

Inventors: SUZUKI YOSHIAKI, SUZUKI, YOSHIAKI, Suzuki, Yoshiaki, c/o Ibaraki Works, SMK Co., Ltd.
Applicants: SMK KK, SMK CO., LTD.
Application year: 1997
Main classification: H01R24
IPC codes: H01R24