Prior to filling this application the most pertinent prior art known to me was:
L. T. McBEE, U.S. Pat. No. 2,474,200;
A. R. MOORE, U.S. Pat. No. 2,801,630;
A. TEUFEL, U.S. Pat. No. 2,807,260;
N. J. HALL, U.S. Pat. No. 2,820,455;
A. CALABRESE, et al, U.S. Pat. No. 3,756,226.