429,807. Compressed air blasting-. cartridges. SAFETY MINING CO., 307, North Michigan Avenue, Chicago, U.S.A. May 7, 1934, Nos. 13709 and 13710. Convention dates, May 29, 1933 and March 30, 1934. [Class 9 (i)] Relates to blasting-cartridges containing compressed air or other gas, for example of the kind described in Specification 406,523, and consists mainly in the provision of a valve mechanism adapted to be closed by the pressure of the compressed air and to be opened to discharge the cartridge by a reduction of the pressure. As shown in Fig. 1, the cartridge 1 has an outlet nozzle 3 normally closed by a valve 5, the stem 8 of which extends through the chamber 12 of the cartridge to a pocket 10, where it is loosely surrounded by a sleeve 11. The pocket 10 is connected to an outlet passage sealed by a disc 14 and is also connected to an inlet valve 2a. Compressed air is supplied through this valve and drives the valve 5 against its seat and gradually passes between the stem 8 and the sleeve 11 into the main chamber 12. The valve 2<a> is then screwed down, the cartridge inserted in the bore-hole, and the seal 14 broken. The sudden release of pressure from the pocket 10 allows the pressure within the main chamber 12 to thrust the sleeve 11 to the left into sealing contact with the head 9 of the stem 8 and thus to force the valve 5 open. In another form shown in Fig. 4, the control pocket 61 is vented by a valve 72 when this is opened by a plunger 76, 77 operated by compressed air supplied by a connection 81. In this figure the stem 60 of the outlet valve 59 has a plunger 62 with ports 63 controlled by a disc 64 subject to a spring 65, which is supported by a fixed abutment 66 and allows the air to flow only one way through the ports 63. In a modification, the control pocket is vented by a seal ruptured by a small detonator. In the form shown in Fig. 8, the control pocket 26 is connected to the main chamber 27 through a non-return ball valve 36 in the plunger head 95 of the stem 24 of the outlet valve 20, and is charged and vented off by a pipe 90. In another form shown in Fig. 2, the control pocket 26 and the main cartridge chamber 40 are supplied with compressed air from a pipe 42, and when this pipe is vented to the atmosphere by a suitable valve, the differential air pressure on a plunger system 28, 29 opens the outlet valve 20 and also uncovers ports 41 for quickly venting the space 34. In a modification of this, a coiled spring is added to hold the valve in the open position ; and in another modification the coiled spring is replaced by an air pocket in which pressure is built up when the cartridge is charged. To ensure a quick venting of the control pocket when the supply pipe is connected to the atmosphere from a distance especially when the cartridge is as in Fig. 8, a relay venting valve device B, Fig. 7, may be inserted in the supply pipe close to the cartridge A in the bore-hole. In one form, Fig. 9, the relay valve B comprises a plunger system 99, 100 forming a valve at 102, which is closed and kept closed by air pressure admitted by pipe 92 to a space 107, from which the air also passes through a non- return ball valve 106 to the pipe 90, which supplies the cartridge. When the pipe 92 is vented off at a distance, a spring 108 opens the valve 102 and the pipe 90 is vented by ports 109 close to the cartridge ensuring a quick release of the pressure of the control pocket of the cartridge. In a modification, Fig. 10, the relay valve 113, which takes its seat at 132, contains non-return ball valves 129, 126 and compressed air is admitted by pipe 92 to a space 125 and thence to spaces 122, 131 and to the pipe 90 leading to the cartridge, the space 118 at the left end of the valve being exposed to the atmosphere. When the pipe 92 is vented off at a distance, pressure in the space 125 falls and differential air pressure opens the valve and vents the cartridge quickly through ports 134. When the cartridge is vented by the breaking of a sealing disc, a pneumatic device is provided to shear this disc. This device, as shown in Fig. 12, contains a plunger 144 provided with a wedge-shaped punch 145 and held cocked by a trigger 146. To operate this device compressed air is admitted behind the plunger by a pipe 154; the pressure leaks through holes 143 and expands a sleeve 141 tightly against the bore-hole ; and when a certain pressure is reached, it deflects a diaphragm 147 and a finger 150 thereon pulls the trigger, and the released plunger is thrust forward to pierce the sealing disc 137 of the cartridge as shown in dotted lines. The outlet ports of the nozzle of the cartridge may be directed in a forwardly inclined direction to produce a reaction tending to hold the cartridge in the bore-hole. This is specially desirable when the air pressure used is comparatively low and the action of the cartridge consequently slow.