wiper motors since each cam 170 cannot pivot as the wiper arm moves in the first direction and up the ramp portion 170 a from position a to position b in fig8 a because of interference by the boss 176 the pivotable arm portion 108 d of the wiper arm pivots see arrows p u2032 and the wiper blade becomes spaced from the glass surface until a maximum height ramp location is attained at position b and the wiper blade is maximally spaced from the glass surface as shown at fig9 b with further movement in the first direction of the reciprocation of the wiper arm by the wiper motor the wiper arm encounters the drop portion 170 b whereupon the biasing spring 116 causes the wiper blade to drop shakingly strikingly upon the glass surface to shake off i e knock loose or break up any debris stuck to the wiper blade or stuck to the glass surface as indicated at fig7 a whereby any trapped debris is dislodged from the wiper blade in the return second direction of the reciprocation of the wiper arms in which the wiper arms move opposite to the first direction the wiper arms encounter the drop portion of each respective cam 170 but the cam is able to pivot see arrows p u2033 due to a force from this direction overcoming the biasing of the cam spring 174 such that the cam will now pivot to allow the wiper arm to pass thereover without interference as shown at fig8 b fig1 a depicts an example of an algorithm for implementing the first aspect of the second embodiment of the present invention.