A three-pole plug

Abstract: The present invention relates to a three-pole plug of which the junction sleeve and the terminal holder are not individually and separately injection molded but are integrally formed into one piece at the very beginning. The sleeve has three bottom holes formed on its bottom surface, and the terminal holder has three slide grooves formed on its one side, communicable with the sleeve via the three bottom holes on bottom surface of the sleeve. Each of the three slide grooves has a vertically projected flange and a terminal passage located in front of the flange and leading to one corresponding bottom hole on bottom surface of the sleeve. The terminals according to the present invention each is provided with a notch near its rear end and two side lugs in front of the notch. The positions of the notch and the lugs of the terminals correspond to the flange and the vertically cut end surface of the terminal passage, respectively, so that the terminal shall be fixed in place through the engagement of the flange with the notch on the terminal and the bearing of the lugs on the terminal against the end surface of the terminal passage when the terminal is inserted into the slide groove and is pushed toward and finally extends into the sleeve via the terminal passage and the bottom hole of the sleeve. A recess is provided on the other side of the terminal holder, allowing the material used for the second time injection molding to firmly wrap the sleeve and terminal holder with inserted terminals together to form a finished product of plug which shall have better conduction effect and requires fewer numbers of injection molding.

Description: BACKGROUND OF THE INVENTION It is known that three-pole plugs and associated sockets are safe in use and therefore, they are now widely used in the connection of computer, fax machine, etc. One of such plugs A is shown in Fig. 8 which is characterized by that the terminals A' thereof which are otherwise exposed to outside are now hidden in a front sleeve B which constitutes a junction portion. A specially formed front part of the socket C is adapted to insertion into the sleeve B so that the plug is electrically connected. A conventional three-pole plug, as shown in Fig. 9, usually includes two parts, namely, the sleeve 1 and the terminal base 2. The sleeve 1 has a housing which consists of a circle of side wall and a bottom wall. There are three terminal holes 11 formed on the bottom wall of the sleeve 1 and a plurality of tongue pieces 12 projected backward from the bottom wall. The terminal base 2 is provided with three terminals 21 corresponding to the terminal holes 11 and a plurality of cotters 22 suitable for engaging with the tongue pieces 12. To assemble the sleeve 1 and the terminal base 2, first insert the three terminals 21 on the terminal base 2 into and through the terminal holes 11 on the sleeve 1, then fix the terminal base 2 onto the sleeve 1 by separately engaging the upper and the lower cotters 22 of the terminal base 2 with the tongue pieces 12 of the sleeve 1. The joined sleeve 1 and terminal base 2 are then integrally injection molded to form a plug A as shown in Fig. 8. Such a plug has, however, following disadvantages: <1>. the terminals 21 for connecting a power line must be manually inserted into the mould for terminal base 2 before the terminal base 2 as shown in Fig. 9 is formed through injection molding. However, since the mould for the terminal base 2 is not designed with any means to adequately fix the terminals 21, the manually inserted terminals 21 tend to deviate from correct position. Such deviation of terminals from their position may very possibly have reverse effect on quality of the plug A formed through integrally injection molding the joined sleeve 1 and terminal base 2 because the injection molded plug with deviated terminals may have poor contact with the socket when it is plugged into the latter. <2>. There are at least three times of injection molding required to complete the manufacture of a plug, i.e., the injection molding of the sleeve 1, of the terminal base 2, and of the integral plug. The time and cost for such injection moldings is high. As a result, there was attempt made to improve the position deviation of manually inserted terminals 21. A bridge 3 as illustrated in Fig. 10 is provided. The bridge 3 has three grooves 31 for the disposition of terminals 21. Lugs 32 are provided at proper positions near the front of the grooves 31 such that the lugs 32 are frictionally engaged with recesses 23 formed on the terminals 21 and thereby fix the terminals 21 in place without unwanted shifting. The bridge 3 with positioned terminals 21 and the sleeve 1 are then together injection molded to form an integral plug. It is to be noted the above described bridge 3 is designed mainly to solve the problem of poor contact of the terminals with the socket caused by the position deviation of the terminals 21 in the conventional terminal base 2. The sleeve 1 and the bridge 3 still have to be individually and separately injection molded at first and then to be integrally injection molded again. The time and cost needed to make plug so structured is not improved anyway. GB 2 144 929 discloses a three pin electrical connector having a unitary body with electrical terminals extending within a housing, the terminals being secured in a passage extending through the body and the passage including resilient stop means to engage a shoulder portion of the terminal to retain it within the housing portion. SUMMARY OF THE INVENTION The invention provides a three-pole plug in accordance with claim 1 of the appended claims. The plug according to the present invention is developed to improve the structure of the conventional sleeve, terminal base, and bridge and is characterized by a holder laterally and backward extending from outer side of the bottom wall of the sleeve. On one side of the holder, there are provided with three slide guides and three corresponding terminal passages. The slide guides each has a vertically projected flange, and the terminal passages each has a vertically cut end surface. By this way, a terminal having a notch and two side lugs, when being inserted through one of the slide guides and into one of the terminal passages, may be stopped from moving any further when the notch of the terminal contacts the flange of the slide guide and the side lugs contact the vertically cut end surface of the terminal passage. On the other side of the holder, a recess is formed so that a second material used in injection molding to wrap the holder, the sleeve and terminals to form a plug may have stronger grip force and accordingly stronger joining force over the components. In the manufacture of the plug according to the present invention, better conduction effect than conventional three-pole plugs can be achieved and the numbers of injection molding required are reduced to two that economically enhances the productivity thereof. BRIEF DESCRIPTION OF THE DRAWINGS The structure of the present invention and the technical means used to achieve the objects thereof can be best understood through referring to the following detailed description of preferred embodiments and the accompanying drawings wherein Fig. 1 is a three-dimensional perspective showing the appearance of the joined sleeve and terminal holder according to the present invention; Fig. 2 is a side sectional view of the joined sleeve and terminal holder shown in Fig. 1; Fig. 3 illustrates the way the terminals are inserted into the slide guides of the terminal holder; Fig. 4 is a vertical sectional view of the joined sleeve and terminal holder with three terminals inserted into the terminal holder; Fig. 5 is a cross sectional view of the joined sleeve and terminal holder in which one terminal inserted into the terminal holder can be seen; Fig. 6 is a three-dimensional perspective showing a finally injection molded plug according to the present invention; Fig. 7 is a three-dimensional perspective of the joined sleeve and terminal holder of the present invention, viewing from the other side of the terminal holder; Fig. 8 illustrates the manner in which a three-pole plug connects to an associated socket; Fig. 9 is an analytical perspective showing a conventional three-pole plug; and Fig. 10 is also an analytical perspective showing another type of conventional three-pole plug. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Please refer to Figs. 1, 2, the present invention mainly consists of an integral three-pole plug having a front junction sleeve portion 4 and a terminal holder portion 5. The junction sleeve portion 4 is mainly a housing 41 which is suitable for engaging with the front junction portion of a three-pole socket C. There are three bottom holes 42 formed at bottom wall of the housing part 41 and disposed at positions suitable for three corresponding terminals 61 to pass through. The terminal holder portion 5 has a substantially arcuate profile and laterally and backward projects from outer side of the bottom wall of the housing part 41. On one side of the terminal holder portion 5, there are three slide grooves 51 for separately guiding the terminals 61 to slide into corresponding terminal passages 512 provided at front part of the terminal holder portion 5. Each of the slide grooves 51 is provided with a vertically projected flange 511 at adequate position. The terminal passages 512 are separately disposed in front of the flanges 511 and are communicable with the junction sleeve portion 4 via the bottom holes 42 so that each terminal 61 may pass through one of the terminal passages 512 and corresponding bottom hole 42 and extends into the junction sleeve portion 4. To ensure the firmly positioning of the terminal 61, the terminal passages 512 each has a vertically cut end surface 513 facing the flange 511. The terminals according to the present invention each has a notch 612 formed at rear end and two lugs 611 provided at two sides terminal 61 just in front of the notch 612. The positions of the lugs 611 and the notch 612 shall permit the terminal 61, when being inserted into the terminal holder portion 5 via the slide groove 51 and being pushed toward in the direction of the junction sleeve portion 4 as shown in Fig. 3, to be firmly stuck in the slide groove 51 with the flange 511 engaging with the notch 612 and the lugs 611 bearing against the vertically cut end surface 513 of the terminal passage 512 as shown in Fig. 4. Since the flange 511 is provided with some elasticity that facilitates the sliding of terminal 61 toward the junction sleeve portion 4 and the terminal 61 shall be fixed in place and can not be withdrawn when the flange 511 finally engages with the notch 612 formed on the rear end of terminal 61. On the other hand, the two lugs 611 bearing against the end surface 513 of the terminal passage 512 shall prevent the terminal 61 from moving further into the terminal passage 512, and accordingly, the housing 41 of the front junction sleeve portion 4. By this way, the terminal 61 can be well located, as shown in Fig. 4, without any unwanted shifting or deviation from desired position. At this point, a second time injection molding can be performed to integrally wrap the sleeve portion 4, terminal holder portion 5, and the terminals 61 together to form a complete three-pole plug as shown in Fig. 6 which shall provide better conduction effect than the conventional three-pole plug does. The present invention also provides adequate means to enhance the join of material used in the second time injection molding to the integral sleeve portion 4 and terminal holder portion 5 and the terminals 61. As shown in Fig. 7, the terminal holder portion 5 has a recess 50 provided at it another side opposite to the slide groove side. The recess 50 allows a different material used for the second time injection molding to deeply enter into there and firmly grip the integral body of sleeve portion 4 and terminal holder portion 5 as well as the terminals 61 inserted in the terminal holder portion 5. The major advantages of the plug according to the present invention are: <1>. The sleeve and the terminal holder are two portions of an integrally injection molded piece, and no sleeve, bridge, or terminal holder requires individual and separate injection molding. That is, the numbers of injection molding can be reduced by one and the time and cost for such process is largely saved. <2>. The flange of the slide grooves and the vertically cut end surface of the terminal passages on the terminal holder portion may together with the notch and lugs formed on the terminals firmly fix the terminals in place to get excellent conduction effect.

Claims: A three-pole plug comprising a front junction sleeve portion (4) and a rear terminal holder portion (5) which are integrally injection moulded into one piece without the need to individually and separately injection moulding any of said sleeve portion (4) or said terminal holder portion (5); said front junction sleeve portion (4) mainly consisting of a housing (41) which is suitable for adapting to a junction part of a three-pole socket (C) and has three bottom holes (42) formed on its bottom surface generally disposed to correspond to the three terminals (61) of said plug; characterised in that: said terminal holder portion (5) is provided with three slide grooves (51) on its one side and a recess (50) on the other side; each of said slide grooves (51) is provided with a vertically projected flange (511) at adequate position and a terminal passage (512) which is located in front of said flange (511) and is communicable with said bottom holes (42) formed on bottom surface of said sleeve portion (4) and thereby allowing a terminal (61) to pass through there and extend into said sleeve portion (4), and has a vertically cut end surface (513) facing said flange (511); said terminals (61) each having a notch (612) formed near its rear end and two lugs (611) provided at two sides thereof at positions in front of said notch (612) such that when each of said terminals (61) is inserted into one of said slide grooves (51) and is pushed toward said terminal passage (512), said flange (511) in said slide groove (51) engages with said notch (612) on said terminal (61) and said two lugs (611) bear against said vertically cut end surface (513) of said terminal passage (512) to fix said terminal (61) in place with its front end passing through said terminal passage (512) and said bottom holes (42) on bottom surface of said sleeve portion (4) without unwanted deviation from position or shifting and thereby provides better conduction effect. A three pole plug according to claim 1 characterised in that the sleeve portion (4), the terminal holder portion (5) and the terminals (61) where held in the terminal holder portion (5) are further enclosed in a second time injection moulding material. A three pole plug according to claim 1 or claim 2 characterised in that the terminal holder portion (5) has a generally arcuate profile.

Inventors: SU TUN LI, SU,TUN LI
Applicants: GEM MACHINERY IND CO LTD, GEM MACHINERY IND CO. LTD.
Application year: 1992
Main classification: H01R13
IPC codes: H01R13, H01R43