Dc motor switching arrangement

Claim 1

A switching arrangement for controlling the operation of a two-speed PDC motor in a windshield wiper system, comprising: a DC motor having first, second and third brushes, said DC motor providing high-speed operation when said first and said third brushes are energized and low-speed operation when said first and said second brushes are energized, a first electrical relay means having an actuating coil and first and second fixed contacts and a third contact movable between said first and second fixed contacts, means connecting said third motor brush and said second motor brush respectively with said first fixed contact and said second fixed contact of said first electrical relay means, said movable contact of said first electrical relay means being normally in contact with said first fixed contact and being moved into engagement with said second fixed contact when said actuating coil of said first electrical relay means is energized, a second electrical relay means having an actuating coil and first and second fixed contacts and a third contact movable between said first and second fixed contacts, means connecting said movable contact of said first electrical relay means with said movable contact of said second electrical relay means, a parking switch means having first and second fixed contacts and a third contact movable between said first and said second fixed contacts, said movable contact of said parking switch means connected with said first fixed contact of said second electrical relay means, a source of direct voltage having first and second terminals, means connecting said first terminal of said source of direct voltage with said second fixed contact of said second electrical relay means, said movable contact of said second electrical relay means being normally in contact with said first fixed contact and being moved into contact with said second fixed contact when said actuating coil of said second electrical relay means is energized, means connecting said first fixed contact of said parking switch means with said second terminal of said source of direct voltage, said second fixed contact of said parking switch means connected with said first terminal of said source of direct voltage, wiper linkage connected with said DC motor, means connecting said parking switch means with said wiper linkage, said movable contact of said parking switch means being moved into contact with said first fixed contact when the wiper linkage is in the park position, a selector switch having first and second switching sections, said selector switch providing high speed, low speed and off positions, each section of said selector switch having a fixed contact corresponding to at least two positions of the selector switch, each section of said selector switch having a movable contact engageable with respective fixed contacts, said movable contacts being connected for concurrent movement, means connecting each of said two movable contacts of said selector switch with said second terminal of said source of direct voltage, means connecting said off and low-speed contacts of said first section of said selector switch with one end of said actuating coil of said first electrical relay means, means connecting other end of said actuating coil of said first electrical relay means with said movable contact of said first electrical relay means, means connecting said low-speed and high-speed contacts of said second section of said selector switch with one end of said actuating coil of said second electrical relay means, and means connecting the other end of said actuating coil of said second electrical relay means with said first terminal of said source of direct voltage whereby, two-speed operation of said DC motor results from switching said selector switch to determine the energization of said electrical relay means and concurrently said three brushes of said DC motor and a park function including dynamic braking to terminate motor operation is provided when said selector switch is moved to its off position.