control valve the valving elements of these respective valves 71 73 are biased to certain conditions by springs 76 78 the limit valve 71 is responsive to the vertical position of the can support platform 61 while the limit valve 72 is responsive to the angular position of a latch knob 81 on the door 13 a vertical rod 84 fig1 within the housing 10 converts the pivotal latched and unlatched positions of the knob 81 respectively to high or low positions of the rod which in turn are sensed by the limit valve 72 the latch knob 81 serves to hold the door 13 closed when it is in a latching position and unless the door 13 is closed the vertical rod 84 cannot signal that the door is latched closed the circuit 66 as will be explained will cause the piston 33 of the pneumatic actuator 31 to force the dispensing piston 44 into the filling head bore 19 when the platform 61 is raised by operation of the lever 62 and the door 13 is latched by the knob 81 if either of these conditions namely an elevated platform 61 or a latched knob 81 does not exist the circuit 66 will maintain the pneumatic piston 33 in its upward retracted position or will initiate movement to this position in greater detail when the can platform 61 is raised the spring 76 shifts the poppet of its valve 71 leftward.