Method and apparatus for fabricating battery plate envelopes

An apparatus for fabricating battery plate envelopes from a folded sheet of microporous plastic material having facing folds and having a width which is greater than that of the battery plate to be enveloped, said apparatus comprising:

• a pair of opposing rotatably mounted pressure rollers having parallel axes, each of said rollers including two sealing wheels which are axially spaced on each of said rollers by a distance greater than the width of the battery plate but less than the width of the folded sheet, each of said sealing wheels being radially aligned with one of the sealing wheels mounted on the other of said pressure rollers, said aligned rollers being arranged such that the clearance therebetween remains constant throughout the entire rotational travel of said rollers thereby defining a constant sealing wheel interface, said sealing wheels being adapted to receive the side edges of the folded sheet at their interface;
• and
• means for rotating said rollers so that the edges of the sheet are compressed into each other by said sealing wheels, thereby continuously sealing the edges to form an envelope.

A method for sealing facing surfaces of a microporous battery plate insulation material comprising:

• feeding the facing surfaces edgewise toward a pair of sealing surfaces, at least one of which includes a rotatably mounted sealing wheels, the other sealing surface acting as an anvil against which the sealing wheel is adapted to be pressed;
• and
• sealing at least two edges of the facing surfaces by continuously compressing the edges into one another between said pair of sealing surfaces, the compressive force being applied uniformly along the entire extent of said overlapping edges.

The method of claim 22 wherein the second sealing surface comprises a pair of axially spaced, rotatably mounted, second sealing wheels and wherein the step of forming mating indentations comprises forming a multiplicity of aligned, evenly spaced, mating indentations and projections in the facing edges of the sheet through the use of evenly spaced gear teeth on the peripheral faces of the sealing wheels, the gear teeth shaped and spaced so that the clearance between opposing sealing wheels remain constant during wheel rotation.