Blower speed control resistors for automotive or other service

Abstract

A layered electrical resistor having flat components stacked as follows: a first metal outer plate, a first thin outer electrical insulator, a first thin sheet metal resistor element, a first thin inner insulator, a metal midplate, a second thin inner insulator, a second thin sheet metal resistor element, a second thin outer insulator and a second metal outer plate. The stacked components are compressed together by rivets or otherwise. Each sheet metal resistor element is stamped, punched or otherwise cut with at least first and second terminals and interconnected ribbons forming a resistive path therebetween. A thermal fuse or other circuit breaker is thermally engaged with a seat on the midplate and is connected in a series circuit with the resistor elements to open the circuit to prevent overheating thereof. Structural tie bars are formed integrally with ribbons and terminals of the resistor elements and are severable therefrom before assembly of the components. Bypass bars are integrally formed between ribbons of the resistor elements and are selectively serverable for adjusting their resistance. Each terminal is initially flat but is folded twice upon itself to form a layered wire-like prong. The midplate comprises sheared loops for receiving a prong after which the loops are clenched. The outer insulators are thinner than the inner insulators to conduct more heat to the midplate than to the outer plates whereby the thermal fuse opens the circuit before the outer plates become excessively heated.