Mechanism for purging a plural component mixing and dispensing gun

In a plural component mixing and dispensing gun comprising a gun body, a head secured to said body, said head having a mixing chamber with a discharge outlet at its forward end, inlet orifices communicating with said chamber, means for intermittently feeding streams of reactant liquids through said orifices into said chamber so that the liquids form a reactive mixture which is discharged through said discharge outlet, said reactive mixture being one which solidifies rapidly after reactive mixtures of said liquids and said head including an opening axially aligned with said chamber disposed rearwardly thereof, the improvement comprising purging means selectively operable to purge said mixing chamber of residual reactant mixture including means to insert a separate scaping member into said opening at an angle to an axis of the opening and a purging rod received in said opening, said scraping member being positioned between the end of said purging rod and said inlet orifices to effectively seal the purging rod from contact with liquid introduced into said mixing chamber, said rod being selectively movable from a first retracted position having an end spaced rearwardly from said scraping member to a second extended position, wherein said purging rod abuts said scraping member to move said scraping member through said opening and said mixing chamber and out said discharge outlet to purge said mixing chamber of residual reactant mixture and any reactant mixture which has solidified as said purging rod moves from said first position to said second position.