METHOD AND APPARATUS FOR COLLECTING ATMOSPHERIC SAMPLES IN ATMOSPHERIC GEOCHEMICAL PROSPECTING

摘要

1480419 Analyzing airborne samples BARRINGER RESEARCH Ltd 13 Nov 1975 [23 Nov 1974] 50849/74 Heading G1B [Also in Division E1] In an apparatus for atmospheric geochemical prospecting for deposits of minerals and hydrocarbons, atmospheric air e.g. containing particulates is drawn through a pipe 10 and is fed to a concentrator 11, e.g. a cyclone separator, and the concentrated particles passed to a pipe 13 with air being discharged from the cyclone separator via an axial pipe 12. Air containing the particles is led via a pipe 13 which branches into two pipes 13a and 13b which terminate in a housing 14 having chambers 15 and 16 which communicate with the pipes 13a and 13b. The chambers 15 and 16 communicate with pipes 17 and 18 which lead to the respective inputs of a two-way solenoid valve 19. The downstream end of the solenoid valve 19 is connected via a pipe 20 to a pump 21 which provides suction to either of the pipes 17, 18 and their associated chambers 15 or 16 depending upon the condition of the valve 19. The outlet end of the pump 21 is connected to the atmosphere via a pipe 22. The lower ends of each of the chambers 15 and 16 taper inwardly and are open ended. The lower surface of the housing 14 is contiguous with a tape 23 supported on a plate 27 and may be disposed on feed and take-up reels and moved stepwise or continuously past the housing 14. The direction of motion of the tape 23 is at right angles to the plane of the paper. The tape 23 preferably is made of a thin strong non-contaminating synthetic resin which preferably is coated with an adhesive material to facilitate capture on the tape 23 of particles, to be subsequently analyzed, discharged from the chambers 15 and 16 respectively. The lower ends of the pipes 13a and 13b are open and are positioned near to the open ends of the chambers 15 and 16, and since the tape 23 is supported in close proximity with the lower end of the housing 14, the air emerging from the lower ends of the pipes 13a and 13b respectively is required to change direction through a comparatively sharp angle. As a result of the momentum of the particles in the air-stream flowing through pipes 13a and 13b, the particles tend to travel in a straight line and hence pass through the open ends of the chambers 15 and 16 and are deposited on the adhesive side of the tape 23. After a suitable collection interval e.g. five seconds, the tape 23 is transported a short distance and a fresh surface of the tape 23 is exposed to the particles respectively emerging from the chambers 15 and 16. The valve 19 is controllable by an electrical control signal from an electronic control circuit 25 which in turn is operated by an updraft sensor 26. When an updraft is being sensed, a control signal or voltage from the sensor 26 is fed to the control circuit 25 which causes the valve 19 to operate whereby suction from the pump 21 is applied via pipe 18 to the chamber 16. When the control signal ceases, the valve 19 is returned to its other condition whereby suction from the pump 21 is applied to the chamber 15 via the pipe 17. The apparatus can be used also in collecting gases or vapours during atmospheric prospecting.