Miniaturized, round, electric plug contacts with round plug sleeves and round plug prongs
FIELD OF THE INVENTION 
     The invention pertains to round, electric plug contacts with a miniaturized, round plug sleeve which has an override spring, and a miniaturized, round plug prong. 
     BACKGROUND OF THE INVENTION 
     Known from German Pat. No. 2,731,001 is a round plug sleeve with an override spring, which has two contact-spring arms, against which two override-spring arms press from the outside. The contact-spring arms and the override-spring arms are not symmetrically spaced around the periphery, so that, effectively, only a one-sided contact can be established. This round plug sleeve is not amenable to miniaturization, since the asymmetrical spring action will not guarantee a secure contact. In the case of this known round plug sleeve, the override spring has locking-spring arms which snap behind a locking edge in a plug housing. These locking-spring tongues represent obstacles when used in a locking plug housing, since, at a minimum, they make it difficult to remove the round plug sleeve from the housing after unlocking and, in addition, would tend to destroy, during their withdrawal, a rubber seal placed, e.g., in the insertion aperture of a compartment of the plug housing. Furthermore, it is practically impossible to equip miniaturized round plug sleeves with catch-spring tongues. 
     Additionally, round plug prongs are known with longitudinally sequential sections consisting of a crimp section at the rear end, then a connection section followed by a support section, and a hollow, cylindrical section with a rounded point at the front end. For a miniaturized configuration and for use in a lockable plug housing, the known round plug prongs are not suitable, since the transition zones from the crimp section to the support section and from the support section to the round point section are not sufficiently stable to resist moments of flexion. 
     Also known is a lockable plug housing with two side walls, two end walls, and housing compartments separated by partitions. At least one compartment partition paralleling the side walls, which has matching holes in the longitudinal direction for the insertion of a locking slide, extends from one end wall to the other. The bar-like locking slide can be advanced into a matching hole in the end wall of the housing. It has laterally projecting cams, which, in the inserted state, protrude into the inner space of a compartment and snap behind an edge or the like of a plug sleeve or a plug prong, so that the plug contact is seated in the compartment of the housing and secured against withdrawal. 
     The installation and/or replacement of plug contacts already crimped to electric conductors requires careful attention and painstaking effort. The plug contacts are loose inside a compartment and have therein no restraints to prevent their removal or falling out; only the cams of the subsequently inserted locking slide provide such restraint. The known plug contacts insertable in the housing compartment have, for the most part, a sharp cornered cutting edge behind which a cam of the locking slide engages. When the plug contact is withdrawn, this sharp edge can destroy the rubber seal. In addition thereto, the known plug contacts have still other sharp projections, which can also damage the rubber seal even during the insertion of the plug element into the compartment of the housing. 
     SUMMARY OF THE INVENTION 
     The objective of the invention is the creation of round plug contacts in miniaturized form, which ensure a very good electrical contact, are very stably constructed, and, preferably, make it possible to achieve a snug fit in a housing compartment and to achieve, during their installation in a housing compartment prior to insertion of the locking slide, a prelocking capability. Furthermore, the plug contacts should have no lateral, sharp cornered projections. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     With references to the appended drawings, the invention is explained in detail below by way of examples. The drawings depict: 
     FIG. 1, a perspective view of a plug prong in keeping with the invention. 
     FIG. 2, a front view of the plug prong in FIG. 1. 
     FIG. 3, a side view of the plug prong in FIG. 1. 
     FIG. 4, a longitudinal cross section through the front contact section and the base section of the plug prong along line IV--IV in FIG. 3, with the viewing direction indicated by the arrow. 
     FIG. 5, a side view of a plug housing for the plug prong in FIGS. 1-4. 
     FIG. 6, a bottom view of the plug housing in FIG. 5. 
     FIG. 7, a front view of the plug housing in FIG. 5. 
     FIG. 8, a side view of the locking slide for the plug housing in FIGS. 5-7. 
     FIG. 9, a top view of the locking slide in FIG. 8. 
     FIG. 10, a front view of the locking slide in FIG. 8. 
     FIG. 11, a cross section through the plug housing in FIGS. 5-10 with inserted plug prongs. 
     FIG. 12a, a perspective view of the plug sleeve in keeping with the invention. 
     FIG. 12b, a perspective view of the plug sleeve of the invention without its override spring. 
     FIG. 13, a top view of the plug sleeve in FIG. 1. 
     FIG. 14, a side view of the plug sleeve in FIG. 1. 
     FIG. 15, a longitudinal cross section through the front contact section and the base section of the plug sleeve along line XV--XV in FIG. 14, with the viewing direction indicated by the arrow. 
     FIG. 16, a side view of a plug housing for the plug sleeve in FIGS. 12a-15. 
     FIG. 17, a bottom view of the plug housing in FIG. 16. 
     FIG. 18, a front view of the plug housing in FIG. 16. 
     FIG. 19, a cross section through the plug housing with inserted plug sleeves as depicted in FIGS. 12a -15. 
     FIG. 20, a top view of a portion of the plug housing in FIGS. 16-19 with the locking slide in a prelocking position. 
     FIG. 21, a top view of a portion of the plug housing with the prelocking slide in its locked position. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     The plug prong (1), which is rolled from a stamped piece of sheet metal and is especially well suited for the miniature design, is, e.g., 16 mm long and has a crimp section (2), a hollow, cylindrical base section (3), and a round, pin-like, hollow, cylindrical plug or contact section (4) with a rounded, conically tapered tip (5). The outside diameter of the contact section (4) in the miniature configuration is, e.g., 1 mm, as can be seen in FIG. 2. Stability vis-a-vis moments of flexion is ensured in a practical fashion by a short cylindrical transition section (6) between the crimp section (2) and the base section (3) and a shoulder (7) between the base section (3) and the plug section (4), the edges (8) and corners (9) of which are rounded off, while the outside diameter of the base section (3) is greater than the outside diameters of the contact section (4) and the transition section (6) and the outside diameter of the transition section (6) is greater than the outside diameter of the contact section (4). This design or stepping of the sections (4, 3, 6) provides a high degree of resistance to moments of flexion. 
     In a special embodiment form of the invention, the part of the base section (3) bordering on the transition section (6) is designed as a bulged bead (10), which is semicircular in cross section, so that a relatively large undercut or a relatively deep step with pronounced transition is formed for the transition from the bead (10) to the transition section (6), which greatly simplifies the shaping and provides a relatively large annular locking surface (11), while also making possible a cylindrical and pronounced design of the transition section (6) with a relatively great outside diameter. 
     Several plug prongs (1) can be inserted into the cross sectionally rectangular plug housing (12) of an electric plug connector, which connector basically consists of a plug housing and a sleeve housing (63). The plug housing (12) consists of a prong trough (13) and a compartmentalized housing (14) ordered one over the other. The prong trough (13) has a base plate (15), two parallel side walls (16, 17) and two end walls (18, 19). The base plate (15) has holes (20) oriented perpendicularly to the plane (20a) of the base, each of which facilitates the positioning of the contact section (4) of a plug prong (1). The compartment housing (14) situated beneath the prong trough (13) has side walls (21, 22) paralleling and inwardly slightly offset from the side walls (16, 17) of the prong trough (13), so that in each case a stepped rim (23) is formed. The side walls (21, 22) are frontally delimited by the end walls (24, 24a). Parallel to the side walls (21, 22) there is a medial, longitudinal partition (25) with several transverse partitions (26) arranged at right angles thereto, so that essentially square compartments (27) for prong contacts are formed. In the area of each compartment (27), a prelocking stay (29), which can swing elastically outward, fits into U-shaped holes (28) in the side walls (21, 22), while the base stay uniting the two arms of the U is situated slightly above or at the level of the base plane (15b) which is provided with a base-side, rounded, protruding engagement shoulder (30) with a guide incline (31) oriented toward the interior of the compartment. 
     The holes (20) widen in stages toward the compartments (27) and the holes (20a) in such a way that the holes (20) can snugly receive the contact sections (4) and the holes (20a) can receive the base sections (3) of the plug prongs (1). 
     The base side of the bead (10) on the plug prong (1) can rest directly on the surface (15b) of the base or is arranged above the base surface (15b) and is overridden by the engagement shoulder (30) on the transition-section side. 
     From the end wall (24a), a passageway (32) leads through the longitudinal partition (25) and the transverse partitions (26), which passageway is traversed by a bar-like, insertable, and removable locking slide (33). The cross-sectional configuration of the slide (33) is matched to that of the passageway (32), while the slide is designed in a known manner with lateral locking cams (34) on both sides, which protrude into the inner space of the compartment, are so arranged as to face the engagement shoulders (30) when the slide is inserted, and have approximately the same cross-sectional configuration as these engagement shoulders. The locking cams (34) also override the bead (10) on the plug prong (1) (FIG. 11). 
     In keeping with the invention, the plug prongs (1) can be inserted into the compartments (27) whenever the slide (33) is not in the housing or is in a position in which the cams (34) do not protrude into the inner space of the compartments. Since the engagement shoulders (30) of the prelocking stays fit behind the bead (10) on the plug prong (1), a sort of prelocking action takes place, which can, nonetheless, be disengaged when the plug prong (1) is pulled against the spring power of the locking stay (29) with sufficient force. The prelocking stays (29) greatly facilitate the insertion and replacement of plug contacts by securing the inserted contacts. 
     The round plug sleeve (35) has a crimp section (36), a short, cylindrical transition section (37), an ensuing bead (38) with an annular locking edge (39), and a contact section (40) extending forward and terminating in a conical tip. 
     The contact section (40) begins at its point of connection to the bead (38) with a cylindrical, spring-tongued base (41), the diameter of which is greater than the diameter of the transition section (37). The contact section (40) has a longitudinal abutment joint (42). At the front end of the spring-tongued base (41), a circular cutout (43) is formed in the vicinity of the abutment joint (42); a second circular cutout (44) is made in the spring tongued base (41) opposite the first cutout. Extending forward from these circular cutouts (43, 44) are wedge-shaped slits (45), which converge toward the end of the contact section (40) or the circular orifice (46), so that two opposing spring arms (47, 48) are formed. The ends (49) of these spring arms (47, 48) are bent inward toward the plug orifice (46) and are punched in such a way that they form said circular plug orifice (46), the diameter of which corresponds with the outside diameter of the contact section (4) of the round plug prong (1). 
     Opposite the abutment joint (42) and between the cutout (44) and the bead (38), there is a rectangular cutout (50) in the spring-tongue base (41), the purpose of which is explained further below. 
     In the vicinity of the longitudinal middle of each spring arm (47, 48), there is an approximately rectangular cutout (51), which begins at the approximate level of the cutouts (43, 44) and terminates in an edge (52) shortly before the orifice (46). Joining this edge (52) is a short, incised tab (53), the width of which matches that of the cutout (51) and which extends to the spring-tongue base (41); this tab is recurved on itself toward the inner space of the contact section (40) to form a resistance stay (54) (FIG. 15) which is hook-like in cross section and whose function will be explained further below. 
     The spring-tongue stays (55, 56) of each spring arm (47, 48) formed in the punching of the cutout (51) are outwardly offset by a material thickness at the point where they join the spring-tongue base (41), so that an offset rim (57) is formed. 
     The round plug sleeve (35) is equipped with an override spring (58) with a cylindrical base (59), which fits snugly over the spring-tongue base (41), so that the abutment joint of the base (59) of the override spring aligns opposite the abutment joint (42). In the vicinity of this abutment joint (42) of the base (59) of the override spring, there are peripheral, incised tabs (60), which curve into and border the edges of the cutouts (50) to ensure that the override spring (58) makes secure contact with the round plug sleeve (35). 
     The base (59) of the override spring extends from the bead (38) to the offset rim (57). Joined to the base (59) of the override spring are two curved, opposing override-spring arms (61, 62) which extend forward in the cutouts (51) to the juncture edge (52), while their free ends override and press against the matching resistance stays (54). This design of the round plug sleeve (35) makes it possible for the override spring (58) to be kept within the contours of the round plug sleeve. The arms (61, 62) of the override spring essentially fill completely the gaps in the spring arms (47, 48) formed in the punching of the cutouts (51). The depression in the spring-tongue base (41) formed by the offset (57) of the spring arms (47, 48) is filled by the base (59) of the override spring. In this manner, a smooth contact section (40) of the round plug sleeve (35) is formed, which, e.g., can be inserted through matching holes in a rubber seal or removed therefrom without fear that the rubber seal will be destroyed or damaged. The arms (61, 62) of the override spring press against the resistance stays (54) and reinforce the spring action of the spring arms (47, 48). 
     The spring arms (47, 48)--as already noted--taper conically to a point, which results from the conical course of the slits (45). Accordingly, the arms (61, 62) of the override spring also converge, so that the outside diameter of the base (59) of the override spring is greater than the outside diameter of the contact section (46a) of the spring arms (47, 48) (FIGS. 13, 15, and 18). 
     The sleeve housing (63) in keeping with the invention fits in the plug trough (13) of the plug housing (12) to establish the plug contact (FIG. 19). The sleeve housing (63) has longitudinal sidewalls (64, 65), end walls (55, 67), and a base plate (68). A longitudinal compartment partition (69) paralleling the side walls (64, 65) extends medially through the sleeve housing (63) from one end wall (66) to the other end wall (67). Transverse partitions (70) -form, together with the side walls (64, 65) and the longitudinal partition (69), compartments (71) for, e.g., round plug sleeves (35). The height of such a compartment (71) is approximately the same as the length of a round plug sleeve, while the contact section (40) lies in a cylindrical portion (72) of the compartment, so that the spring arms (47, 48) have room (73) to spring outward. 
     In the part of the side walls (64, 65) above the compartment section (72)--as in the case of the plug housing (12)--each compartment (71) has a prelocking stay (29a), which can swing elastically outward and which is inserted through a U-shaped hole (28a), the base stay of which is situated immediately above the compartment section (72), while its engagement shoulder (30a) protruding into the inner space of the compartment is designed with a guide incline (31a). A passageway (32a) leads from the end wall (66), through the longitudinal partition (69) and the transverse partitions (70), and into a depression (32a) in the other end wall (67); a bar-like locking slide (33) can be inserted into and withdrawn from this passageway. The cross-sectional configuration of the slide (33) is matched to that of the depression (32a) and has lateral locking cams (34) of known design on both sides of the part of the slide protruding into the inner space of the compartment, which cams have approximately the same cross-sectional configuration as the engagement shoulder (30a) and align opposite such shoulder when the slide is fully inserted. The locking cams (34) override both the engagement shoulder (30a) and the bead (38) on the round plug housing (35) (FIG. 18). The function of the locking slide (33) and the prelocking stays (29a) is the same as that of the comparable parts in the plug housing (12). 
     FIGS. 20 and 21 depict a different configuration of the locking slide (33). Between the cams (34), this locking slide has curved depressions (34a) whose radius of curvature matches that of the bead (10, 38). When the locking slide (33) is in the position illustrated in FIG. 20, the depressions (34a) are in the area of the compartments (71). Then, only the engagement shoulders (30,30a) extend into the inner space of the chambers. After the insertion of a plug contact (1, 35) into a compartment (71), the engagement shoulder (30, 30a) locks behind the bead (10, 38) of the plug contact, so that it can no longer fall out of the compartment. When the required plug contacts have been inserted into the compartments, the locking slide (33) is seated in the housing, so that the locking cams (34) are properly positioned in the individual compartments. In this manner, the plug contacts are locked in place. This locked position is illustrated in FIG. 21. 
     The described plug contacts in keeping with the invention can also be installed in other housings or used without housings, in which case especially that part of the round plug housing behind the override spring can be designed differently than as described above. Specifically characteristic of the invention is the stepped configuration of the sections (4, 3, 6) of the plug prong. Furthermore, the plug contacts can be combined with other plug contacts, i.e., a plug prong (1) can be assembled with another plug sleeve and a plug sleeve (35) can be assembled with another plug prong. To this extent, both the plug prong (1) and the plug housing (35) exhibit characteristics representing justification for an invention.