Socket for circuit element

Abstract: A circuit element comprising a plurality of contacts having elasticity which are arranged in such a manner as to be able to contact a plurality of leads of the element, and an operating member adapted to shift the contacts to location away from the leads against elasticity of the contacts, the circuit element further comprising a first cam portion formed in such a manner as to be able to bring contacting portions of the contacts away upwardly from the leads resisting the elasticity of the contacts, and a second cam portion formed in such a manner as to be able to bring the contacting portions away backwardly from the leads, the first cam portion acting on the contacts prior to the second cam portion, the second cam portion being allowed to act on the contacts under the action of the first cam portion.

Description: BACKGROUND OF THE INVENTION [Field of the Invention] This invention relates to a socket in which contacts are shifted backwardly by an operating member so that the contacts are brought away from a circuit element. The terms "circuit element" used herein refers to an element which forms a circuit. [Brief Description of the Prior Art] According to the invention discussed in Japanese Patent Early Laid-Open Publication No. Hei 4-154065, contacts arranged in rows are engaged with a swing lever, so that when the swing lever is swung, the contacts can be shifted, as a group, backwardly away from leads of an electric part in order to facilitate zero-insertion of the electric part. However this prior art has the problems that when the contacts are shifted backwardly upon operation of the swing lever, or when the contacts are shifted forwardly by elasticity of the contacts, a vertical contact pressure is difficult to obtain efficiently because a contacting portion of each contact is brought into contact with or away from an upper surface of each lead at a comparatively small angle of inclination. As a result, reliability in contact is lowered, Recently, there is a tendency that miniaturization of the contacts is further progressed and elasticity is lowered, a proper contact pressure is increasingly difficult to obtain. And the solution of the problem is demanded. Furthermore, since the contacting portion of each contact is brought closer to the upper surface of each lead from a location away from the lead at a low altitude, there is the risk that the contacting portion collides with the leading end of each lead owing to a manufacturing error, turning-up or warping of the leading end of each lead, etc. EP-A-0,481,727 discloses a socket having the features of the preamble of Claim 1. SUMMARY OF THE INVENTION It is therefore a general object of the present invention to provide a socket for a circuit element which is capable of solving the above-mentioned problem. A specific object of the present invention is to provide a socket for a circuit element, in which a contacting portion of each contact is brought into contact with an upper surface of each lead under a comparatively strong pressure, so that the contacting portion will not be damaged due to its collision with the leading end of each lead when the contacting portion is brought into contact with the upper surface of each lead. The invention provides a socket according to Claim 1. As mentioned above, the first cam portion acts as means for bringing the contacting portions of the contacts away generally upwardly from the leads, while the second cam portion acts as means for bringing the contacting portions of the contacts away generally backwardly from the leads. Since the first and second cam portions have their own functions, there can be easily obtained a favourable design with a simple construction, in which the contacting portions of the contacts can not only be brought away from the leads but also brought into contact with the leads in an inclination angle generally equal to or larger than the right angles (perpendicular) with respect to upper surfaces of the leads respectively. Similarly, the contacting portions of the contacts can be brought backwardly efficiently by the second cam portion. By virtue of the above-mentioned arrangement, a vertical contact pressure of the contacting portion of each contact with respect to the upper surface of each lead can be obtained efficiently. As a result, each contacting portion can be highly reliably brought into contact with each lead with a high contact pressure. This contact pressure can be properly obtained particularly for minute contacts. Furthermore, since the contacting portions are brought into contact with the leads in an inclination angle generally equal to or larger than the right angles (perpendicular) with respect to upper surfaces of the leads respectively, possible collision between the leading ends of the leads and the contacting portions of the contacts, and possible damages resulting therefrom can be prevented effectively. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a socket according to one embodiment of the present invention; Fig. 2 is a perspective view of the above socket but a pressure cover is already removed therefrom; Figs. 3 to 7 inclusive are sectional views of an important portion of the socket, schematically showing the actions of the contacts and the operating member in sequential steps; and Fig. 8 is a side view of a lead and a contacting portion, showing how the contacting portion moves with respect to the lead. DETAILED DESCRIPTION OF THE EMBODIMENT One embodiment of the present invention will now be described in detail with reference to the drawings 1 through 8 inclusive. A base member 1 formed of an insulating material has a central opening 2 which is opened up at upper and lower surfaces 2, an accommodation space 3 being formed on an upper surface side of the central opening 2, a plurality of contacts 4 being arranged in array at least at opposing two sides of the accommodation space 3. The contacts 4 are implanted in the base member 1. Each contact 4 has a male terminal 5 extending downward from the lower surface of the base member 1, a plain portion 6 connected to a basal portion of the male terminal 5 and vertically raised from an upper surface of an implanting wall of the contact 4, and a spring portion 7 connected to an inner edge of an upper end of the plain portion 6. The spring portion 7 is curved such that it is extended first downward from an area of connection (basal portion 8) with respect to the plain portion 6 and then turned upwardly and backwardly to the vicinity of the area of connection 8. In other words, an angle of curvature is set such that the spring portion 7 exhibits a curved-shape facing downward, and a short distance 10 is formed between the basal portion 8 and an upper end 9 thereof extending from the basal portion 8, so that the curved-shape of the spring portion 7 is opened at upper location. This angle of curvature is 180° or more, and preferably 250° or more. An contacting arm 11 extends from the upper end 9 of the curved spring portion 7 in such a manner as to incline forwardly, and a contacting portion 12 is formed on an upper end of the contacting arm 11 in such a manner as to project forwardly and then downwardly. As shown in Fig. 3, the spring portion 7 urges the contacting arm 11 and the contacting portion 12 inwardly so that the contacting portion 12 is brought into contact with a corresponding lead 25 of the circuit element 23. Furthermore, a hook portion 13 extends from the upper end of the spring portion 7 through a connection arm 13' which extends upwardly at angle from the area of connection between the arm portion 11 and the connecting portion 12, and an acting portion 15 of the operating member 14 is brought into engagement with a free end of the hook portion 13. The hook portion 13 and the contacting portion 12 are disposed at the free end of the contact and extending in the opposite direction with each other. A first cam portion 15a and a second cam portion 15b as will be described are formed on the acting portion 15, i.e., the surface of the engaging portion. As shown in Fig. 2, the operating member 14 is formed of an elongated pivotal member disposed in parallel relation with the rows of the contacts 4. The operating member 14 has an operating portion 16 extending outwardly from one end thereof and an acting portion 15 formed on the other end thereof so as to be engaged with the hook portion 13. The operating member 14, the operating portion 16, and the acting portion 15 are disposed at the outside of the contacting arm 11 in such a manner as to be in parallel relation with the rows of the contacts 4, and are pivotable upwardly and downwardly about an axis P parallel to the rows of the contacts 4. The operating member 14 is provided at both ends thereof with a shaft portion 17 projecting onto the axis P. The shaft portion 17 is slide fitted into a bearing portion 18 formed on the base member 1 in order to facilitate the pivotable movement of the operating member 14. The bearing portion 18 has a cut-out portion 19 which is opened upwardly, and the shaft portion 17 is slip fitted into the cut-out portion 19 so that the operating member 14 can be removed upwardly from the cut-out portion 19, and engaged into the cut-out portion 19 from the above. The operating member 14 is further provided with an engaging holes 20 adjacent to the operating portion 15 and opened upwardly. The engaging holes 20 are arranged in array in the axial direction through partition walls 20', respectively. By loosely inserting a bending portion 13c at a foremost end of the hook portion 13 of each contact 4 into each engaging hole 20, the hook portion 13 is engaged with the acting portion 15. The operating member is integrally formed of an insulating material, and is provided with the above-mentioned various elements 15, 16, 17, and 20. In the illustrated example, the operating member 14 is supported such that it can be pivoted about the fixed axis P. In the operating member 14, the operating portion 16, as shown in Fig. 2, can be pushed down directly by a robot or a manual operation. Furthermore, as shown in Figs. 1 and 3, a presser cover 21 is disposed at an upper portion of the base member 1, with a center window 22 of the cover 21 facing with the accommodation space 3, so that the circuit element 23 can be inserted into and removed from the accommodation space 3 through the center window 22. The circuit element 23 is, for example, an integrated circuit element, a printed wiring board, a liquid crystal panel, or the like. The circuit element 23 has a plurality of leads 25 arranged in array along the side portions of a main body 24. As shown in Fig. 3, the first cam portion 15a is formed by an angular portion which is formed by a top surface of the acting portion 15 and one side surface of the acting portion 15. Similarly, the second cam portion 15b is formed by an angular portion which is formed by the top surface and the other side surface of the acting portion 15. A first pressure bearing portion 13a is formed by a basal portion of the hook portion 13, and a second pressure bearing portion 13b is formed by the bending portion 13c at the foremost end of the hook portion 13. The acting portion 15 is brought into engagement with the bending portion 13c at the foremost end of the hook portion 13 and an inner side of the basal portion, i.e., inner sides of the first and second pressure bearing portions 13a, 13b, and the first cam portion 15a is brought into abutment with an inner surface of the first pressure bearing portion 13a. A predetermined loose space 30 is formed between a side surface (engaging surface) of the acting portion 15 and an inner surface of the bending portion 13c (second pressure bearing portion 13b) at the foremost end of the hook portion 13, and the first and second cam portions 15a and 15b are arranged in the space 30 such that the first and second cam portions 15a and 15b act on the first and second pressure bearing portions 13a and 13b, respectively, with a time difference. The arrangement being such that when the second cam portion 15b is exerting a backward pressure to the second pressure bearing portion 13b, the first cam portion 15a pushes up the first pressure bearing portion 13a. The inner surface of the first pressure bearing portion 13a is disposed in a lateral direction, while the inner surface of the second pressure bearing portion 13b is disposed in a vertical direction. The first and second cam portions 15a, 15b act on the respective inner surfaces with a time difference. More specifically, after the first cam portion 15a begins to exert a pushing-up pressure to the first pressure bearing portion 13a, the second cam portion 15b acts on the second pressure bearing portion 13b with a delaying time difference in order to exert a backward pressure thereto. As shown in Figs. 3 to 8 inclusive, by pushing down the operating portion 16, the operating member 14 is pivoted downwardly about the shaft portion 17. As a result, the first cam portion 15a is pivoted while pushing up the first pressure bearing portion 13a. By this pushing-up operation, the contacting portion 12 is brought away upwardly from a lead supporting surface 28 and an upper surface of the lead 25. In other words, the contacting portion 12 is shifted from a point indicated by P1 or P2 to a point indicated by P3 in Fig. 8. An angle α formed between this shifting orbit and the lead is an angle of inclination which is generally equal to or larger than the right angles (perpendicular). Next, while the first cam portion 15a is pushing up the contacting portion 12, the second cam portion exerts a backward pressure to the second pressure bearing portion 13b. As a result, the contacting portion 12 is shifted backwardly at angles from the point indicated by P3 toward a point indicated by P4 against the elasticity of the spring portion 7, and brought to a location where the contacting portion 12 does not interfere the lead 25 of the circuit element 23 accommodated in the accommodation space 3. Accordingly, the circuit element 23 can be inserted into the accommodation space 3 with no load, and removed therefrom with no load. When the push-down pressure to the operating portion 16 is removed, the operating member 14 is pivoted upwardly by the elasticity of the spring portion 7 exerted to the acting portion 15 so as to be ready to be pushed down. At the same time, the contacting arm 11 and contacting portion 12 of the contact 4 is shifted inwardly by the spring portion 7 so as to be pressure contacted with the upper surface of the lead 25 of the circuit element 23. More specifically, when the contacting portion 12 is brought to the upper surface of the lead 25, it is also brought from the point indicated by P4 to the point indicated by P2 via the point indicated by P2. In other words, owing to the action of the first cam portion 15a, the contacting portion 12 is moved downward from the point P3 to the point P2 at the inclination angle α generally equal to or larger than the right angles (perpendicular) so as to be pressure contacted with the upper surface of the lead 25. Accordingly, the contacting portion 12 is contacted with the upper surface of the lead 25 with a comparatively large perpendicular pressure. A positioning ridge 26 projecting upward is formed on a wall 27 defining the accommodation space 3. The side surface of the circuit element 24 is supported by the positioning ridge 26, and the lower surface of the lead 25 is supported on a lead supporting surface 28 formed on the upper surface of the partition wall 27 at the outer side of the positioning ridge 26. The contacting portion 12 is pressure contacted with the upper surface of the contact 25 thus supported, with a downward pressure. When the circuit element 23 is already removed as shown in Fig. 3, the contacting portion 12 is brought into abutment with the supporting surface 28 so that the contact 4 is not excessively shifted inwardly. More specifically, the supporting surface 28 forms a stopper for limiting the inwardly shifting amount of the contact 4. As a result, the operating portion 16 of the swing lever 14 is normally swung upwardly to a fixed position by the elasticity of the contact so as to be ready to be pushed down. As described in the foregoing, the first cam portion is functioned as means for bringing the contacting portion of the contact generally upwardly away from the lead, and the second cam portion is functioned as means for bringing the contacting portion of the contact generally backwardly away from the lead. Since the first and second cam portions have their own functions, there can be easily obtained a favorable design with a simple construction, in which the contacting portions of the contacts can not only be brought away from the leads but also brought into contact with the leads in an inclination angle generally equal to or larger than the right angles (perpendicular) with respect to upper surfaces of the leads respectively. Similarly, the contacting portions of the contacts can be brought backwardly efficiently by the second cam portion. By virtue of the above-mentioned arrangement, a vertical contact pressure of the contacting portion of each contact with respect to the upper surface of each lead can be obtained efficiently. As a result, each contacting portion can be highly reliably brought into contact with each lead with a high contact pressure. This contact pressure can be properly obtained particularly for minute contacts. Furthermore, since the contacting portions are brought into contact with the leads in an inclination angle generally equal to or larger than the right angles (perpendicular) with respect to upper surfaces of the leads respectively, possible collision between the leading ends of the leads and the contacting portions of the contacts, and possible damages resulting therefrom can be prevented effectively.

Claims: A socket for a circuit element comprising a plurality of contacts (4) having elasticity which are arranged in such a manner as to be able to contact a plurality of leads (25) of said element (23), and an operating member (14) adapted to shift said contacts (4) to location away from said leads (25) against elasticity of said contacts, said operating member further comprising a first cam portion (15a) formed and engaged with said contacts to bring contacting portions (12) of said contacts (4) upwardly away from said leads (23) resisting the elasticity of said contacts on actuation of said operating member, and a second cam portion (15b) formed and engageable with said contacts to bring said contacting portions (12) backwardly away from said leads during actuation of said operating member, characterized in that said first cam portion (15a) engages said contacts at an initial stage of actuation of said operating member (14) when said second cam portion (15b) is out of engagement with said contacts, after which initial stage both said first cam portion (15a) and said second cam portion (15b) are engaged with said contacts. A socket as claimed in Claim 1, wherein said operating member (14) is in the form of a pivotal member adapted to engage with a hook portion (13) formed on each of said contacts (4), said first cam portion (15a) and said second cam portion (15b) being formed on said operating member (14) at an engaging portion thereof with said hook portion (13), said first cam portion (15a) exerting an upward pressure to a first pressure bearing portion (13a) formed on a basal portion of said hook portion (13), said second cam portion (15b) exerting a backward pressure to a second pressure bearing portion (13b) formed on a bending portion (13c) at a foremost end of said hook portion (13). A socket as claimed in Claim 2, wherein a loose space (30) is formed between said second pressure bearing portion (13b) of said hook portion (13) and said second cam portion (15b) formed at said engaging portion of the operating member in order to form a standby state.

Inventors: MATSUOKA NORIYUKI, MATSUOKA, NORIYUKI
Applicants: YAMAICHI ELECTRONICS CO LTD, YAMAICHI ELECTRONICS CO., LTD.
Application year: 1993
Main classification: H05K7
IPC codes: H01R33, H05K7, H01R24