| 429 / | HD | CHEMISTRY: ELECTRICAL CURRENT PRODUCING APPARATUS, PRODUCT, AND PROCESS |
| 72 | DF | HAVING SPECIFIED VENTING, FEEDING OR CIRCULATION STRUCTURE (OTHER THAN FEEDING OR FILLING FOR ACTIVATING DEFERRED ACTION-TYPE BATTERY) {5} |
| 74 | DF | .~ Having means to control electrolyte level when liquid is added, other than a visual reference point {3} |
| 77 | | .~.~ By establishing an air lock {2} |
| 78 | DF | .~.~.~> Liquid seal only |
| 79 | DF | .~.~.~> Movable valve structure supported within the filler opening |