Abstract:
A receptacle content comprises a pair of opposed leaf spring members having first spring arms provided with outer contact members and second spring arms extending along the first spring arms provided with inner contact members. 
     An electrical connector includes a dielectric housing in which electrical receptacle contacts are arranged in rows with contact members of the contacts in the rows being staggered so that upon matable connection with a complmentary electrical connector the electrical connection between the respective electrical contacts of the matable connectors is sequentially completed.

Description:
FIELD OF THE INVENTION 
     This invention relates to an electrical receptacle contact which is small in size and thus can be used for higher density applications. In particular, the receptacle contact is provided with a cleaning function by which foreign matter on the tab contact is removed at the time of electrical connection therewith. 
     BACKGROUND OF THE INVENTION 
     Computers and telephone switchboards such as PBX&#39;s and other data processing equipment have been made smaller as well as increasing the speed at which the signal information is processed. This has required miniaturizing the components and increasing the density thereof including the electrical contacts for making the electrical connections therefor. Contacts that have been used for the electrical connections as shown in FIG. 6 are in the form of a receptacle contact in which four resilient cantilever contact members 1a,1b and 2a,2b extend forwardly from a base 3 for electrical connection with a tab contact inserted from the front. The tab contact is electrically engaged by the four leaves 1a,1b and 2a,2b from four directions. In this prior art contact, the four leaves are arranged as opposing pairs, and each pair is arranged orthogonally as shown in FIG. 6. 
     In the above-mentioned receptacle contact, electrical engagement is made with the tab contact at four points, thus, the reliability of the receptacle contact is improved in comparison with a contact having only two contact points. However, a problem arises in that a possibility of an incomplete electrical engagement caused by foreign matter on the surface of the tab contact can take place. Furthermore, one of the pair of contact members 1a,1b or 2a,2b may engage the edge surfaces of the tab contact, therefore these contact members will not provide a reliable electrical connection. The edge surfaces of the tab contact are the surfaces of edges formed when the tab contact is made by stamping a sheet of conductive material. These surfaces are rough in comparison with the planar rolled or formed surface of the sheet, they have a lower contact reliability, and a greater insertion force is required at the time of insertion. Further, in the case of the receptacle contact shown in FIG. 6, the contact members electrically engage the post terminal at spaced opposed locations which makes it difficult to increase the mounting density because the size of the contact is large. This requires that the spacing between contacts must be made larger when a plurality of contacts are mounted in a housing or on a printed circuit boad. 
     SUMMARY OF THE INVENTION 
     The object of this invention is to provide a receptacle contact which is smaller in size to obtain higher density spacing, and it has a higher contact reliability. The receptacle contact of this invention comprises a pair of opposed leaf spring members having first spring arms provided with outer contact members and second spring arms extending along the first spring arms which are provided with inner contact members. The receptacle contact can take the form of a unitary leaf spring member having a long spring arm with an outer contact member and a short spring arm extending along the long spring arm which has an inner contact member in alignment with the outer contact member. 
     When a tab contact is inserted in the four leaf receptacle contact, it is first engaged by the outer contacts which wipe and therefore remove any foreign matter on the tab contact by the outer contacts. Then, further insertion of the tab contact into the receptacle contact connects the inner contact members with the tab contact. Therefore, a reliable connection is established between the second contact members and the tab contact which is not affected by any foreign matter. The outer contact members and the inner contact members engage respective surfaces of the tab contact so that they are both in redundant electrical engagement with such surfaces. The outer contact members are about twice the width of the inner contact members thereby assuring cleaning of the tab contact surfaces during engagement therebetween. Further, since each spring arm is arranged in the same direction, the width of both spring arms on each leaf spring member can be made smaller than in the prior art contact shown in FIG. 6, thus a better contact density can be realized. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a receptacle contact according to this invention. 
     FIGS. 2A to 2C are a top view, a side view, and a lateral cross-sectional view along the line II--II, of FIG. 2B respectively, of the receptacle contact. 
     FIG. 3 is a top view showing a blank of the receptacle contact in a stamped configuration prior to being formed. 
     FIGS. 4A to 4C are side views showing the action of the receptacle contact and the tab contact when the tab contact is inserted in the receptacle contact. 
     FIG. 5 is a cross-sectional view showing an electrical connector having a plurality of receptacle contacts connected to tab contacts of header connector. 
     FIG. 6 is a perspective view of a prior art receptacle contact. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following is a description of the preferred embodiment of this invention by way of example with reference to the accompanying drawings. 
     Receptacle contact 10 according to this invention is stamped and formed from a suitable electrically-conductive metal sheet having the desired spring characteristics. It is comprised of opposed leaf spring members 11a,11b which are two parallel plates that the linked through a U-shaped portion 11c extending between adjacent sides of members 11a,11b. Members 11a,11b include first spring arms 12,13 and second spring arms 14,15 which are formed integrally with leaf spring members 11a,11b. 
     Spring arms 12,13 and spring arms 14,15 are opposed to each other, and outer contact members 12a,13a and inner contact members 14a,14b at the free ends of spring arms 12,13 and 14,15 respectively are also opposed to each other. Further, contact members 14a,15a are located to the rear of contact members 12a,13a. Spring arms 12,13 and 14,15 extend side-by-side from leaf spring members 11a,11b and outer contact members 12a,13a are slightly twice the width of inner contact members 14a,15a. Contact members 12a,13a,14a,15a are arcuate to facilitate insertion of a tab contact therebetween. Note that the direction of arrow A denotes the front of contact 10 in FIGS. 1,2A,2B. 
     Contact leg 16 which projects rearward is integrally formed adjacent the rear of base 11a. Since the receptacle contact 10 formed as explained above is formed with contact members 12a,13a and 14a,15a which are respectively opposed, the width W can be the same as the width of the complementary tab contact, and thus is reduced in comparison with the width of the prior are receptacle contact shown in FIG. 6, thereby resulting in a smaller receptacle contact. 
     Receptacle contact 10 having the above shape is made by stamping and forming from a suitable metal sheet having the desirable conductive and spring characteristics. The stamping process is conducted by shaping the metal sheet as shown in FIG. 3, and then folding the spring arms 12,13 and 14,15 to the shape required while folding portion 11c into a U-shape. Accordingly, spring arms 12,13 and 14,15 are made to oppose each other, and the four leaf contact 10 with the shape shown in FIGS. 1 and 2 is produced. In this process, a plurality of contacts 10 are formed at the same time, and therefore, each contact 10 is joined to another in one row through a portion 17, and portion 17 is cut along a broken line as shown in FIGS. 2A,3 when the contacts are to be used. Portions 17 also have holes 17a therein forming a carrier strip for feeding the row of contacts through application equipment. 
     The following is an explanation of the electrical connection of the receptacle contact 10 made as explained above with tab contact 20, with reference to FIGS. 4A to 4C. Tab contact 20 has tapered surfaces at its front end to facilitate insertion into the arcuate contact members 12a,13a,14a,15a. 
     First, the tip of tab contact 20 is inserted in the space between outer contact members 12a,13a opposed to each other at the front portion of the receptacle contact 10. Upon insertion, upper and lower surfaces 21a,21b of contact 20 are brought into wiping engagement with contact members 12a,13a; accordingly, foreign matter on upper and lower surfaces 21a,21b of contact 20 is removed. When contact 20 is inserted further, upper and lower surfaces 21a,21b which have been cleaned by contact members 12a,13a, are also wipingly engaged by contact members 14a,15a while still being engaged by contact members 14a,15a, as shown in FIG. 4C. Therefore, the surfaces of contact 20 in electrical engagement with contact members 14a,15a are free from any foreign matter because of the cleaning function carried out by contact members 12a,13a. Surfaces 21a,21b of tab contact 20 are assured of being cleaned in the area of electrical engagement by contact members 14a, 15a because contact members 12a,13a are about twice the width of contact members 14a,15a. Thus, a greater electrical connection reliability between contact 20 and inner contact members 14a,15a is realized. At this time, preferably outer contact members 12a,13a and inner contact members 14a,15a are in electrical engagement with upper and lower surfaces 21a,21b, which are the planar surfaces, of contact 20, and not with surfaces 22a,22b, (only 22a being shown) which are the cut edge surfaces of contact 20. This decreases the force needed to insert contact 20 into receptacle contact 10 thereby improving the reliability of the electrical connection therebetween. 
     Also, in receptacle contact 10, the length L1 of spring arms 12,13 which provide the contact force created between contact members 12a,13a and contact 20, is longer than the length L1 of spring arms 14,15, which provide the contact force between contact members 14a,15a and contact 20. Therefore, the insertion force is reduced by reducing the contact force created between contact 20 and contact members 12a,13a, which clean upper and lower surfaces 21a,21b of contact 20 by engagement with contact members 12a,13a, and an excellent electrical engagement is provided between surfaces 21a,21b of contact 20 and contact members 14a,15a by increasing the contact force created between contact members 14a,15a and contact 20. Thus, the initial insertion force of tab contact 20 within contact members 12a,13a is less than the insertion force of contact members 14a,15a. 
     The following is an example of an electrical connector as shown in FIG. 5 in which a plurality of the above-mentioned receptacle contacts 10 are used for electrical connection with a plurality of tab contacts 20. In this case, a header connector 6 having a dielectric housing 6a including a plurality of tab contacts 20a-20d is mounted on a first wiring board 5 with contacts 20a-20d being electrically connected respectively with conductive paths of the first wiring board. Also, a plurality of receptacle contacts 10a-10d, which are shown electrically connected to contacts 20a-20d, are arranged and retained in contact-retaining passages 7b of a dielectric housing 7a of matable electrical connector 7. Further, contact legs 16a-16d at the rear end of each of receptacle contacts 10a-10d are electrically connected to respective conductive paths on second wiring board 8. A dielectric spacer 7c extends between side walls 7d (only one being shown) and it has tapered holes 7e through which legs 16a-16c extend so that the outer ends of legs 16a-6c are in alignment and properly spaced for disposition in respective holes 8a in board 8. Inner sections of legs 16d are disposed in recesses 7f of spacer 7c. Recesses 7f communicate with apertures 7g through which the outer ends of legs 16d extend for alignment and positioning in holes 8a. 
     Connector housing 7a of connector 7 having a plurality of receptacle contacts 10a-10d is inserted in housing 6a of header connector 6, and accordingly, each tab contact 20a-20d is respectively electrically engaged by each receptacle contact 10a-10d, thus both connectors are electrically connected, as shown in FIG. 5. According to connector 7, the positions of outer contact members 12a,13a of receptacle contacts 10a-10d in passages 7b of housing 7a are arranged at different positions therein, as shown by B,C, and D in FIG. 5, so that the contact members of the upper row of contacts 10a is at position B, the next row of contacts 10b have the contact members at position C and the contact members of contacts 10c,10d are at position D. Thus, the insertion of tab contacts 20a-20d into receptacle contacts 10a-10d is sequentially conducted in order to reduce the insertion force required when connector housing 7a of connector 7 is inserted in housing 6a of header connector 6. Moreover, receptacle contact 10a, which makes contact at position B, is used as the receptacle contact for ground, and preferably, the connection of the ground is first carried out to avoid short circuiting at the time of the connection. In addition, the receptacle contact 10b, which makes contact at the position C, is used as the contact for the power source, and the receptacle contacts 10c-10d, which make contact at the position D, are used as the contacts for signal transmission. In this way, the insertion force when the connectors 6 and 7 are connected is reduced and the ground and power connections are made before the signal connections are made. When the connectors are disconnected, the signal connections are disconnected before the power and ground connections. Thus, the signal connections are protected during the connecting and disconnecting of the connectors. 
     As explained above, according to this invention, when a tab contact is inserted in a receptacle contact, any foreign matter is first removed from the surfaces thereof by the wiping action of the outer contact members, and the cleaned surfaces then electrically engage the inner contact members. Thus, the connection of the inner contact members and the tab contact is not affected by foreign matter, therefore, a reliable electrical connection is effected. Further, since both the outer and inner contact members are arranged to be respectively opposed in the same direction, the width in the lateral direction can be reduced, and thus the mounting density can be increased because of the considerable reduction of the size of the receptacle contact.