Patent GB-868700-A (GB)
Title: Apparatus for blasting down material such as coal in a mine and valve for use in such apparatus
Inventor: HESSON JAMES CHALMER
IPC: F42D1/06
Filed: 1958-11-06
Abstract: 868,700. Valves. MARMON-HERRING- TON CO. Inc. Nov. 6, 1958, No. 35676/58. Class 135. [Also in Group XXI] , Fluid-pressure blasting apparatus comprises a flow-control device V 1  whereby two cartridges adapted to vent compressed gas, as in Specification 727,128, when a predetermined pressure is reached, are connected to a single gas source. The device, Fig. 3, has a single inlet port 77 and two outlet ports 57, 61 for connection to the source and the cartridges, respectively, a valve member 54 within the device being moved by the pressure of the incoming gas to close first the outlet 61 and allow the gas pressure to build up in the cartridge C 1  connected to outlet 57. Then, when cartridge C 1  is vented, due to the sudden drop in pressure at outlet 57, the valve member 54 moves to its second position in which outlet 57 is closed and outlet 61 communicates directly with the inlet 77. The device V 1  in Fig. 1 is connected to the gas source by a supply line 12 in which is a manually-controlled valve 13 and a bleed-off line 14 controlled by a valve 15. The second outlet of device V 1  is connected to the inlet of a similar device V 2  which has one outlet connected to a cartridge C 2  and the other outlet connected to the inlet of a device V 3 , which is connected to cartridges C 3 , C 4 . The device V 1  comprises a housing 44 having a cylindrical bore 45 housing a piston 72 mounted on a stem 68 which extends through a baffle-plate 52, the plate 52 and piston 72 dividing the bore 45 into three chambers D, E, F. A spacer ring 53 holds the plate 52 against a shoulder 51 in the bore 45 and compressed air entering the chamber F from the inlet 77 by way of a channel 79 and ports 67 leaks through a narrow passage 75 in the plate 52 to chamber E. The effective cross-section of passage 75 is reduced by a wire 76 threaded therethrough. At the same time compressed air enters chamber D through a channel 78 and forces the valve member 54 to close the outlet 61 by reason of the greater thrust on the piston 72 in chamber D. Thus the channel 78 communicates directly through outlet 57 with the cartridge C 1 . After some time the pressures on both sides of the piston become equal. When the cartridge is vented, there is a sudden drop in pressure in chamber D and, in consequence of the higher pressure in chamber E, the member 54 closes the outlet 57 and opens the outlet 61. Devices V 2  and |V 3  then operate in succession in the same way. The space 53 may be replaced by a snap-ring seated in a groove in the periphery of the bore 45. The plugs 46, 47, furnished with outlets 57, 61, respectively, may house annular seatings for the bevelled ends of the valve stem 68. These seatings may be of different materials from the plugs. Instead of the passage 75, a passage 158, Fig. 7, in a plug 159 may be used to leak gas into the middle chamber K, this passage being restricted by a wire 161. In another modification, gas is leaked to the middle chamber through a small clearance between the baffle-plate and the piston stem. A spring may be used to bias the piston towards the baffle-plate. In Fig. 9, the baffle-plate is omitted and a spring 211 thrusts the valve member 205 to close the outlet 203. Compressed air enters the chamber P from an inlet 204 and passes thence through outlet 199. A slight clearance around the piston 209 leaks air to chamber Q until the pressures in chamber P and Q are equal. Whereupon a sudden drop in pressure in chamber P causes the member 205 to close outlet 199 and open outlet 203. Specification 727,128 is referred to.