Explosive charging apparatus for charging explosive pellets to a bore in a rock

Claim 1

An explosive charging apparatus comprising charging pipe means adapted to be inserted into a bore drilled in a rock, body means connected to one end of said charging pipe means and having explosive guiding bore means extending axially in the body means so as to communicate at one end with said charging pipe means, said body means being formed with radially outwardly opening explosive supplying port means leading to an intermediate portion of said guiding bore means, cylinder means provided adjacent to the other end of said guiding bore means and having piston disposed in the cylinder means for reciprocating movement therein to and away from said guiding bore means, biasing means for urging said piston means away from the guiding bore means, rod means having one end connected with said piston means and the other end inserted into the guiding bore means so that said other end of the rod means is movable in response to a movement of said piston means between a retracted position wherein it is between the supplying port means and said other end of the guiding bore means and an advanced position wherein said other end of the rod means is advanced in the guiding bore means beyond said supplying port means whereby said supplying port means is opened to said guiding bore means when the rod means is in the retracted position to make it possible to supply an explosive to said guiding bore means but closed by said rod means when the rod means is in the advanced position, compressed air supply passage means formed in said body means and communicating with compressed air source means, air passage means formed in said rod means for connecting said compressed air supply passage means to said guiding bore means when said rod means is in the advanced position, valve means having a first position wherein said cylinder means is connected with the compressed air source means to move said piston means against said biasing means and a second position wherein said cylinder means is opened to atmosphere whereby the piston means is moved under said biasing means, said valve means being associated with first pilot means which is adapted to be connected with said compressed air supply passage means when said rod means is in the retracted position so as to shift said valve means from said second position to said first position and second pilot means which is adapted to be connected with said cylinder means to receive compressed air therefrom when said rod means is in the advanced position to shift the valve means from said first position to said second position.