Rubber Case Batteries. Another development of recent years consists of the replacing of the wood case and rubber jars by a one-piece container of hard rubber with compartments for the elements The Philadelphia Storage Battery Co. has developed the Diamond Rubber case, which combines strength and lightness with an attractive appearance. See Fig. 260. One of the troubles experienced with the earlier designs of the rubber case was the bulging of the end, due to the pull of the battery hold down rod on a small handle attached to the center of the end. In the Philadelphia battery this has been overcome by the use of a wide handle which snaps into openings in the end of the case in such a way that the pull on the handle is transferred to the sides. Another feature of this type handle is that it is a separate piece snapped into the case without the use of any metal insert in the rubber case, and if the handle should break, it can be replaced at small expense without the use of any tools.
The Philadelphia vent plug is of the bayonet type, and is tightened by a quarter turn. The plug simply has a small vent hole in the top, and may either be taken out or left on while battery is charging.
The Philadelphia Separator
The Philadelphia separator is made of quarter sawed hardwood. It has a hard resinous wood in which the hard and soft portions occur in regular alternating vertical layers. The soft layers are porous, and permit the diffusion of the acid from plate to plate. The hard layers give the separator stiffness and long life. The alternating hard and soft layers are at right angles to the surface of the separator, so that the electrolyte has a direct path between plates.
The methods of repairing Philadelphia Diamond Grid batteries are no different from those already given, on pages 328 to 374.
When the elements of the old type batteries have been assembled and returned to the jars, put the covers in place, and pour the compound around the edges of the cover, and in the post wells. The old compound must be removed from the petticoats on the posts before new compound is poured in. The compound must be warm and thin enough to flow around and fill up the petticoat spaces on the posts in order to get a good seal. When the post wells are full of compound, and while compound is still warm, put on the square sealing washers and press them down so that the holes in the washers fit closely around the octagonal part of the posts.