Automatic plastering machine

Claim 1

A PLASTERING MACHINE COMPRISING A HOPPER ADAPTED TO HOLD PLASTER, A PISTON CHAMBER HAVING A PLASTER INLET WHICH COMMUNICATES WITH SAID HOPPER, A PISTON SLIDABLY MOUNTED WITHIN SAID CHAMBER, A PISTON ROD CONNECTED TO SAID PISTON FOR RECIPROCALLY MOVING SAID PISTON WITHIN SAID CHAMBER, OUTLET MEANS AT ONE END OF THE CHAMBER, PASSAGEWAY MEANS INCLUDING A FORWARD AND A REARWARD PASSAGE FORMED AXIALLY THROUGH SAID PISTON, BALL VALVE MEANS POSITIONED WITHIN SAID PASSAGEWAY MEANS, CONSTRICTION MEANS INCLUDING A SMOOTH CONTINUOUS REARWARDLY SLOPING SURFACE PORTION CONTIGUOUS WITH SAID REARWARD PASSAGE AND A SMOOTH CONTINUOUS FORWARDLY SLOPING SURFACE PORTION CONTIGUOUS WITH SAID FORWARD PASSAGE FORMING A SEAT FOR SAID BALL VALVE MEANS, THE CONSTRUCTION AND ARRANGEMENT BEING SUCH THAT THE PASSAGEWAY MEANS IS SUBSTANTIALLY SELF-CLEANING BY REASON OF THE FLOW OF PLASTER THERETHROUGH TO PREVENT SUBSTANTIAL BUILD UP OF PLASTER WITHIN THE PISTON, AND CLEANING MEANS COOPERATING WITH SAID PISTON TO PREVENT BUILD UP OF PLASTER AT THE REARWARD END OF SAID PISTON AND AT THE REARWARD END OF SAID CHAMBER.