The conventional construction of a flashlight-type cell involves a zinc anode can with a depolarizer mix filling most of the can and having a carbon rod in the center as a current collector for the depolarizer mix. The cell is sealed by a soft asphaltic pitch and a metal cap which fits over the carbon rod and serves as the positive terminal. An airspace is provided above the depolarizer mix and below the pitch to permit the collection of gases and cell exudate. The gases are formed during discharge of the cell and means have to be provided for venting the gases before too large a pressure develops within the cell. If the cell is rechargeable, more gases may be evolved during charging and it becomes more important that the gases be vented properly.
There are disadvantages in the conventional cell construction. In particular, several assembly stations are required for placing a seal washer down into the cell, pouring the asphaltic pitch onto the seal washer, placing a vent washer on top of the pitch and finally placing the terminal cap on top of the cell and locking it in place. The vent washer on top of the pitch is used to prevent the cap from becoming embedded in the pitch to form a gastight seal which could prevent venting.
The use of the asphaltic pitch makes the sealing operation dirty and somewhat expensive due to the several steps required in the operation. In addition, the soft pitch does at times squeeze up around the top washer and cause a gastight seal around the terminal cap edge. Another disadvantage is that high temperatures may soften the pitch and cause it to leak from the cell container.
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