Metal deforming – Process – Deforming sheet metal
Patent
1993-12-16
1995-11-21
Rada, Rinaldi I.
Metal deforming
Process
Deforming sheet metal
29882, 83 50, 83861, H01R 4316
Patent
active
054676320
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a contact assembly for a magnetic switch comprising a pair of fixed contact members and a plate-shaped moveable contact member adapted to be selectively connected across the fixed contact members, and a method for fabricating the same. The present invention particularly relates to a contact assembly for a magnetic switch suitable for use in a starter motor, and a method for fabricating the same.
2. Background Art
In the magnetic switch of an automotive starter motor, an plunger is driven by selectively supplying electric current to an energization coil, and the resulting movement of the plunger shifts a pinion gear into mesh with a ring gear. A plate-shaped moveable contact member is integrally secured to a rod which is moved by the movement of the plunger, and the motor is electrically connected to a battery by selectively contacting this contact member across a pair of fixed contact members.
In such a magnetic switch, when the switch is closed, a relatively large current flows through the switch, and the temperature of the contact surface tends to rise as a result of this electric current, thereby increasing the contact resistance and impairing the efficiency of the switch. Japanese utility model laid open publication No. 53-155060 discloses a contact assembly in which the contact surface is provided with a surface irregularity, and the state of contact is made stable by preventing slippage at the time of contact. By thus providing a surface irregularity in the contact surface, the effective surface area for heat dissipation is increased, and the heat is more efficiently removed from the contact surface.
To optimize the efficiency of heat dissipation, each projection in the irregular contact surface is required to be separated from other projections. However, forming such surface irregularities will require punches having highly complex configurations, and it will increase the fabrication cost.
DISCLOSURE OF THE INVENTION
In view of such problems of the prior art, a primary object of the present invention is to provide a contact assembly for a magnetic switch suitable for use in a starter motor which can improve the efficiency of heat dissipation from the contact surface without increasing the fabrication cost.
According to the present invention, such an object can be accomplished by providing a contact assembly for a magnetic switch comprising a pair of fixed contact members and a plate-shaped moveable contact member adapted to be selectively connected across the fixed contact members, characterized by that: a contact surface of at least one of the fixed contact members and the moveable contact member is provided with a certain irregularity in a checker board pattern.
According to a broad concept of the present invention, there is provided a contact assembly for a magnetic switch comprising a pair of fixed contact members and a plate-shaped moveable contact member adapted to be selectively connected across the fixed contact members, characterized by that: a contact surface of at least one of the fixed contact members and the moveable contact member is provided with a plurality of projections which are separated from each other or connected by narrowed parts.
By thus providing a surface irregularity in a checker board pattern or a plurality of projections separated from each other in at least one of the fixed and moveable contact members, each projection in the surface irregularity can be separated from other projections.
Thus, the interval between adjacent projections can be relatively large, and the necessary die or the punch can be easily fabricated. Furthermore, the pressing force required for the punching process can be made relatively small, and the fabrication cost can be reduced. In particular, when these projections are provided with polygonal forms, they can be easily fabricated by machining.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partly broken away sectional side view of an essential part of an automotive starter mot
REFERENCES:
patent: 3033959 (1962-05-01), Flanagan
patent: 3509620 (1970-05-01), Phillips
patent: 3670129 (1972-06-01), Cherry et al.
patent: 3950846 (1976-04-01), Johnson
patent: 4376559 (1983-03-01), Instone, Jr.
Enkaku Shigeyuki
Kimura Minoru
Kogure Mitsuhiro
Nagashima Shinichi
Shimayama Hitoshi
Mitsuba Electric Mfg. Co. Ltd.
Rada Rinaldi I.
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