Patent Publication Number: US-4836807-A

Title: Screw-plug-terminal

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a screw-plug terminal having a housing into which electrical leads can be inserted and fixed in a desired position by spring tension. 
     With a two-pole screw-plug terminal it is common practice to attach one leg of a substantially V-shaped leaf spring to an inner wall of a housing, while the other leg of the leaf spring provides clamping engagement with a maximum of two leads. Several of these well-known and technically quite cumbersome arrangements must be used if more than two principal connecting leads are to be connected. 
     OBJECT OF THE INVENTION 
     The object of the invention is to provide a screw-plug terminal capable of accomodating at least four leads of equal or unequal capacity, leaf springs being integrated into the housing of the terminal to clamp the leads. 
     SUMMARY OF THE INVENTION 
     The above object is achieved in accordance with the invention by providing four holes in one end of a substantially rectangular housing for receiving four principal connecting leads. The housing end has two end pieces, the end pieces having sections angled toward one another in a V-shape. On an inner surface of each section is mounted a leaf spring, partially slit in its longitudinal direction. Between a free end of each leaf spring and an inner wall of the housing is inserted a principal lead, which is thus detachably fixed by clamping engagement of the leaf spring. 
     The main advantage of this arrangement is the provision of spaces for the insertion of principal leads by the angling of the sections, and the integration of the leaf springs into the housing interior. These springs work independently of one another, so the inserted leads each are effectively held in position inside the screw-plug terminal. 
     Each leaf spring has a long base leg having a rectangular opening. A butt strap is provided integral with the inner surface of each section to project through the rectangular opening, and is bent against the base leg of each leaf spring. This provides a safe and simple method of fixing the spring within the housing. 
     Each leaf spring has a free end projecting into the housing which is bent away from the base leg toward an inside wall of the housing. This provides more clamping force for each leaf spring, and allows the leaf spring to take up less space in the housing. 
     The butt strap is stamped out of the corresponding spring mounting section, and extends inwardly. The butt strap can be formed on the section before the housing, which consists of a metal band, is bent into its final shape. 
     Openings are provided in the housing wall for access to the inserted leads. The leads held in the housing can then be removed by relieving the clamping effect of the leaf springs. For example, a screw driver can be inserted into a hole to push the leaf spring off of the lead. 
     The invention will be discussed in detail hereinbelow with reference to the preferred embodiment and in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevational view of a screw-plug terminal according to the present invention. 
     FIG. 2 is a side view of the screw-plug terminal of FIG. 1 partially in section. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The screw-plug terminal includes a substantially rectangular housing 1, formed from a stamped-out band or strip of conductive material that has been bent through several right angles. In a longitudinal wall 19 of the housing 1, an opening is provided for a threaded pin (not shown). The pin can be screwed into an internally threaded spacer 11. The threaded pin allows a connector to be firmly clamped in the housing. 
     The end of the housing, shown on the right in FIG. 2, includes end pieces 2, 3, in which are provided holes 4, 5, 6, and 7 (see FIG. 1) for a corresponding number of principal connecting leads (not shown). The leads are inserted (i.e. plugged) into the housing from the right as viewed in FIG. 2. In order to provide space in the housing for the inserted leads, sections 8, 9 of the end pieces 2, 3 are bent so as to be oriented towards each other in a V-shaped form. 
     A pair of leaf springs 13, 14 are located inside the housing 1, and extend from the interior of sections 8, 9, respectively, to the interior of the housing adjacent housing walls 19, 20, respectively. The leaf springs each have a long base leg, 13b and 14b respectively, which are each provided with a rectangular opening, 17 and 18, respectively. Butt straps 15, 16 are stamped out of sections 8, 9, respectively, and extend through respective rectangular openings 17, 18. The butt straps 15, 16 are bent in order to fix the leaf spring base legs 13b, 14b to the sections 8, 9 in the position shown in FIG. 2. Attached to the long base legs 13b, 14b are angled end sections 13a, 14a, respectively, extending into the housing 1. Each section 13a, 14a extends at an approximate angle of 45° with housing walls 19, 20. Each leaf spring 13, 14 is partially slit in its longitudinal direction. The end sections 13a, 14a of the leaf springs will then clamp the leads inserted through the holes 4, 5, 6, and 7, each lead being held independently of the others. The leads can be easily detached from the housing 1 via openings 12 provided in the housing walls 19, 20 (only one such opening 12 shown in FIG. 2). A screw driver, for example, is inserted in an opening 12 to push a leaf spring end section away from its position clamping a lead, and the lead can then be removed. 
     A four-pole screw-plug terminal has been described above. However, it should be understood that the angled spring mounting sections and leaf springs shown on the right hand side of FIG. 2 could also be provided to the left hand side of the housing, so as to form an eight-pole screw-plug terminal, thus enabling eight leads to be detachably mounted. 
     While a specific embodiment of the invention has been shown and described in detail to illustrate the principles of the invention, it will be understood that the invention may take on other forms and embodiments without departing from such principles.