Abstract:
A hot-line plug terminal ( 5 ) comprises a steady-state contact section ( 7 B) and an initial arc contact section ( 7 A) provided at a position which offset to a side of the steady-state contact section.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to hot-line plug terminals and electrical connector having such a terminal. 
     2. Related Art 
     A terminal of this type is disclosed by, for example, Japanese UM patent application Kokai No.  62-70371.    
     As shown in FIG. 8, this terminal is made by bending a metal strip. The terminal  50  comprises a pair of contact pieces  51  making a substantially U-shaped form and a connection piece  52  extending downwardly from the contact pieces  51 . The contact pieces  51  are curved so as to provide throat portions  51 A and  51 B at two different positions in the plugging direction of a mating pin  53 . 
     Where the terminal  50  is used in a hot-line plug electrical connector, the first throat portion  51 A makes an initial arc contact portion while the second throat portion  51 B makes a steady state contact portion. In the hot-line plug electrical connector, the terminal is usually used as a power terminal. When a mating pin  53  is brought to the initial arc contact portion  51 A, it makes an arc and then contact with the steady-state contact portion  51 B. The arc carbonizes carbon containing matter in the atmosphere, and the carbonized matter adheres to the initial arc contact section  51 A and the pin  53 . The carbonized matter is brought to the steady-state contact section  51 B by the plugged pin  53 , making a poor contact. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the invention to provide a hot-line plug terminal capable of preventing adverse effects of the arc upon the steady-state contact section and an electrical connector having such a terminal. 
     According to the invention there is provided a hot-line plug terminal comprising a steady-state contact section having a first front edge portion; and an initial arc contact section having a second front edge portion which extends forwardly more than the first front edge portion. The initial arc contact section is provided at a position offset to a side of the steady-state contact section. 
     When the terminal of a mating connector is brought to the initial arc contact terminal, an arc is produced between them. Then, the terminal makes stable contact with the steady-state contact section. The carbonized matter produced by the arc adheres to the mating terminal. However, according to the invention, the initial arc and steady-state contact sections are offset laterally so that the carbonized matter is not brought to the steady-state contact section by the initial arc contact section. 
     According to an embodiment of the invention, the first and second front edges form a step-like shape. The first and second front edges are tapered toward tips so as to facilitate plugging with the mating terminal. The initial arc contact section is provided on each side of the steady-state contact section so that if the mating terminal is inserted at an angle with respect to the longitudinal direction of the terminal, the production of an arc at the initial arc contact section is ensured. The steady-state contact section is provided with a protruded portion so that even if carbonized matter flies around the protruded portion, the stable contact with the steady-state contact section is maintained. It is preferred that the protruded portion is elongated in the longitudinal direction of the terminal. 
     According to another aspect of the invention there is provided a hot-line plug electrical connector comprising such a terminal as described above. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a top plan view, partially section, of an electrical connector according to an embodiment of the invention; 
     FIG. 1B is a front elevational view of the electrical connector; 
     FIG. 2 is a sectional view of the electrical connector and a mating connector; 
     FIG. 3A is a top plan view of a power terminal for the electrical connector; 
     FIG. 3B is a sectional view taken along line IIIB—IIIB of FIG. 3A; 
     FIG. 4A is a sectional view wherein the mating connector is being plugged into the electrical connector; 
     FIG. 4B is a sectional view wherein the mating connector has been plugged in the electrical connector; 
     FIG. 5A is a top plan view of a terminal according to another embodiment of the invention; 
     FIG. 5B is a sectional view taken along line VB—VB of FIG. 5A; 
     FIG. 6A is a top plan view of a terminal according to still another embodiment of the invention; 
     FIG. 6B is a sectional view taken along line VIB—VIB of FIG. 6A; 
     FIG. 7A is a perspective view of a terminal prior to molding according to yet another embodiment of the invention; 
     FIG. 7B is a sectional view of the terminal of FIG. 7A after molding; and 
     FIG. 8 is a perspective view of a conventional terminal. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the invention will now be described with reference to FIGS. 1-7. 
     In FIGS. 1A and B, an electrical connector C 1  comprises a housing  1  which is made of a dielectric material so as to have an elongated substantially rectangular shape and a guiding tube  2  which covers the housing  1 . The housing  1  comprises a body section  1 A, a support plate section  1 B extending forwardly from the body section  1 A, and a fixing section  1 C extending laterally from the body section  1 A. A fixing hole  1 D for a screw, etc. is provided in the fixing section  1 C to fix the housing  1  to, for example, a circuit board P. The support plate section  1 B is situated at a middle of the height of the housing  1  and provided with a plurality of grooves  3  on the upper and lower sides. 
     The electrical connector C 1  comprises two types of terminals: signal terminals  11  and power terminals  5  which wider than the signal terminals so that the grooves  3  are provided in the corresponding two types  3 A and  3 B. The width of the grooves  3 A for power terminals is approximately twice that of the signal terminal grooves  3 B. The power terminal grooves  3 A are provided at predetermined intervals in the longitudinal direction on a half of the upper surface of the support plate section  1 B while the signal terminal grooves  3 B are provided at predetermined intervals in the other half of the upper surface and the lower surface of the support plate section  1 B. 
     In FIG. 2, a receiving space  4  is formed between the support plate section  1 B and the guiding tube  2  to receive a mating connector C 2 . The mating connector C 2  comprises power terminals  21  and signal terminals  22  corresponding to the connector C 1 . 
     In FIG. 3A, the power terminal  5  is formed of a metal strip so as to provide at one end a flat contact section  7  and at the other end a pair of connection legs  10 . The contact section  7  is divided into two portions  7 A and  7 B wherein the contact portion  7 A extends forwardly more than the contact portion  7 B. Each of the contact portions  7 A and  7 B has a tapered front edge  7 A 1  or  7 B 1 . The contact portion  7 A makes an arc prior to contact with the power terminal of a mating connector, forming an initial arc contact portion. The contact portion  7 B forms a steady-state contact portion. A pair of barbs  8 A are provided on an intermediate section  8  to engage the housing  1  for attachment. As shown in  3 B, the connection legs  9  are curved to provide connection portions  10  at the ends. The connection portions  10  are situated substantially at a half of the thickness of the support plate section  1 B. 
     As shown in FIG. 2, the signal terminal  11  is made of a metal strip so as to provide a flat contact section  12  at one end and connection legs  15  at the other end. The intermediate sections  8  and  13  of the power and signal terminals  5  and  11  are supported by the body section  1 A such that the contact sections  7  and  12  are placed in the terminal grooves  3 A and  3 B, respectively, while the connection legs  9  and  14  project rearwardly from the body section  1 A such that the connection portions  10  and  15  are placed on the same circuit board. 
     As shown in FIGS. 4A and 4B, the mating connector C 2  is plugged into the connector C 1  such that the respective power and signal terminals are electrically connected. The power terminal  21  of the mating connector C 2  is brought to the initial arc contact portion  7 A of a power terminal  5  and makes an arc therewith and then makes a steady-state contact with the steady-state contact portion  7 B. Since the arc is already produced between the power terminal  21  and the initial arc contact portion  7 A, the subsequent contact with the steady-state contact portion  7 B makes no arc. Since the initial arc contact portion  7 A is offset laterally from the steady-state contact portion, the carbonized matter does not reach the steady-state contact portion  7 B when the mating terminal  21  makes a complete contact with the power terminal  5 . 
     In FIG. 5, a pair of initial arc contact sections  7 A extend forwardly from opposite sides of the steady-state contact section  7 B so as to assure that at least one of the initial arc contact sections  7 A makes an arc with the mating terminal even if the mating terminal is shifted or tilted laterally. 
     In FIG. 6, a steady-state contact section  7 B is formed as a protruded portion so that the matter produced by the initial arc hardly reaches the top of the steady-state contact section  7 B. 
     In FIG.  7 (A), a step-down portion  7 C having a width substantially equal to the width of the steady-state contact section  7 B is provided on the terminal  5 . Then, the terminal  5  is molded up to the phantom line to cover the step-down portion  7 C, forming the initial arc and steady-state contact portions  7 A and  7 B, respectively, as shown in FIG.  7 (B). 
     Since the initial arc contact section is shifted laterally from the steady-state contact section, the carbonized matter produced by the arc does not reach the steady-state contact section, thus making a stable contact at the steady-state contact section.