Patent Publication Number: US-6210239-B1

Title: Contact element with a screw-type terminal

Description:
THE FIELD OF THE INVENTION 
     The invention relates to a contact element with a screw-type terminal for electric conductors, wherein the contact element comprises a conductor connection part provided with a bore, into which the conductor is insertable and clampable by means of a screw insertable at right angles to the bore and/or conductor into a threaded bore in the conductor connection part, and wherein between the end of the screw directed towards the conductor and the conductor a wire protection plate is provided in the bore. 
     With such screw-type terminals, it is necessary to provide a wire protection element so that the conductor to be connected is not damaged by the terminal screw when the latter is tightened. 
     From DE-GM 19 65 790 it is known, with such contact elements, to snap a substantially U-shaped wire protection plate onto the barrel of the terminal screw, one end of the wire protection plate being disposed between the screw and the conductor to be connected. In said case, upon tightening of the screw, the wire protection plate is displaced axially with said screw. Given said construction, however, it is necessary for the screw and the wire protection plate to be prefabricated into a subassembly, which is then inserted into a support body of a plug-in connector and has to be locked in said support body by means of an additional contact retention plate. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to design a contact element of the type described initially, i.e. the screw-type terminal thereof, in such a way that it is insertable into a support body and retained therein without additional retaining means being required. 
     Said object is achieved in that the wire protection plate is substantially L-shaped and comprises an angled foot, that the wire protection plate is inserted into the bore in such a way that the foot is situated at the base of the bore, and that the foot is provided with lateral, barb-like mouldings which, upon insertion of the wire protection plate, dig into the wall of the bore. 
     Advantageous refinements of the invention are indicated in claims  2  to  4 . 
     The advantages achieved by the invention are, in particular, that a contact element which is simple and inexpensive to manufacture has been created by virtue of designing the wire protection plate and its retention device in accordance with the invention. Said contact element is insertable without difficulty into a location chamber of the support body and no separate contact retention plate is required for its retention. 
     A further advantage is provided, given a wire protection plate having a reinforced limb and a rounded transition between the foot and the limb, in that the reinforced region is not deformed during tightening of the terminal screw and the resilient properties of the rounded transition remain unaffected. As a result, the wire protection plate presents optimum elastic and elastic recovery properties. 
     A further advantage is provided, given the fashioning of the conductor insertion bore with a tulip-shaped insertion region and a correspondingly adapted limb of the wire protection plate and the use of a terminal screw with a spherical tip, in that the distance between the point of introduction of force and the point of support of the wire protection plate against the conductor/stranded conductor is considerably reduced compared to conventional constructions. The resultant effect is that, given an identical tightening torque of the screw, the flexural stress of the component is virtually halved, with the result that the return deformation is increased and the service life prolonged. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the invention is illustrated in the drawings and described in detail below. The drawings show: 
     FIG. 1 a sectional view of a support body with inserted contact elements, 
     FIG. 2 a sectional view of a conductor connection part of the contact element, 
     FIG. 3 the sectional view of the conductor connection part according to FIG. 2 with an inserted conductor, 
     FIG. 4 a perspective view of the wire protection plate, 
     FIG. 5 a plan view of the screw-type terminal of a contact element, and 
     FIG. 6 a perspective sectional view of the contact element. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a sectional view of a support body  1  made of insulating material for an electrical plug-in connector. The support body is provided with chambers  2 , into which electrical contact elements  3  are inserted. In said case, the contact elements are retained with positive engagement in the chambers. 
     The contact elements are provided with a screw-type terminal  4  for connecting and fastening electric conductors  5 . 
     In FIGS. 2 and 3, the screw-type terminal  4  of a contact element is shown in a cutout and enlarged manner. 
     In the present case, the contact element for forming the screw-type terminal is provided with an axial bore  6  in the form of a blind hole. There is further provided, extending at right angles to said bore, a threaded bore  7  into which a terminal screw  8  is inserted. 
     Inserted into the bore  6  is a substantially L-shaped wire protection plate  9 , the limb  10  of which is situated, after the insertion of a conductor  5  into the bore, between the front end of the screw  8  and the conductor  5 . 
     The wire protection plate  9 , a perspective enlarged view of which is shown in FIG. 4, comprises an angled foot  11  and the limb  10  already mentioned. Formed on the foot are lateral mouldings  12 . The outside distance A of said mouldings is slightly greater than the diameter of the bore  6  of the screw-type terminal. The effect thereby achieved is that, when the wire protection plate is pressed into the bore  6 , the mouldings dig into the wall of the bore and the wire protection plate is held captive therein (see FIGS.  5  and  6 ). 
     Said securing of the wire protection plate by means of the mouldings moreover acts in the manner of a pivot bearing and the wire protection plate may swivel to a slight extent about the axis X. 
     The transition  13  from the foot  11  to the limb  10  of the wire protection plate is preferably rounded in order to achieve a resilience of the wire protection plate in said region. The limb  10  of the wire protection plate is moreover provided with an embossed portion  14  having an outward curvature which, after mounting of the wire protection plate, is situated in the region of the screw  8 . By virtue of said embossed portion, the limb as such is stiff and inflexible and the resilience and deflexion of the wire protection plate upon clamping of a conductor occurs in the transition  13 . 
     The upper end  15  of the limb  10  is moreover bent outwards to a slight extent and the tip  16  of the screw  8  is hemispherical. Viewed as a whole, the limb is therefore slightly S-shaped. The insertion region  17  of the bore  6  is in said case preferably flared in a tulip-like manner. The effect achieved by said measures is that the pressure point D 1  of the screw  8  upon the limb  10  and the pressure point D 2  of the limb upon the conductor are always a distance apart in every tightening position of the screw, i.e. the pressure point D 2  lies in the front region of the bore  6 . The result is a high clamping force upon the conductor and a reduction in the flexural stress of the wire protection plate. With regard to the retention of the contact elements in the support body, it is additionally mentioned that the contact elements are inserted with positive engagement into the chambers of the support body and prevented from sliding out of the contact chambers by means of the screws of the screw-type terminals extending through lateral openings of the support body.