[Fig. 74] shows the lifter ready to be pulled forward by the next notch.
Note that the circuit is closed only during the brief instant of the spark. No current can flow at any other time, not even if the switch is left on when the motor is not running. No matter how slow or how fast the notched shaft is turning, the lifter spring will always pull the lifter back at exactly the same speed, so that the operation of the contact, and therefore the spark, will always be the same no matter how fast or how slow the engine is running. The brief instant that the contact points touch, results in very little current consumption. The high tension current from the coil is conveyed to the rotating distributor block, which seats on the end of the unisparker shaft to each of the spark plug terminals in the order of firing.
Fig. 75. Atwater Kent Distributor and Contactless Block
The important advantage which the distributor possesses is the fact that there are no sliding contacts or carbon brushes. The distributor blade is so arranged that it passes close to the spark plug terminals without quite touching (as shown in [Fig. 75]), thus permitting the spark to jump the slight gap without any loss of current pressure. This also eliminates all wear and trouble caused by sliding or rubbing contacts.
[Fig. 76] shows the wire connections and direction of current flowage. The distributor blade is about to make contact with the terminal leading to the spark plug in No. 2 cylinder. At the instant that contact is made the breaker points in the contact maker shown in the lower part of the diagram close, thus allowing a primary or low tension current to flow between the contact maker, coil, and battery. The sudden breaking of this current occurs when the points open again, thereby creating a current of high tension voltage in the secondary coil which is conducted to the center terminal of the distributor where it is distributed to the spark plug terminals through the rotation of the distributor blade. The high tension cables leading from the distributor are heavily insulated, thus the current in seeking ground return chooses the easiest path, by jumping the slight gap at the spark plugs.
DISTRIBUTOR
GROUND
COIL