Patent GB-323978-A (GB)
Title: Improvements in power control apparatus for pneumatic despatch systems
IPC: B65G51/16
Filed: 1929-03-22
Abstract: 323,978. Lamson Co., and Cowley, J. T. March 22, 1929. Pneumatic dispatch apparatus.-Power control apparatus for pneumatic dispatch systems of the minimum flow type, is disposed in a pipe leading to an exhauster and so constructed that the main controlling valve is partly opened automatically by a main actuating member when a carrier is inserted in the tube, the opening being completed by the action of the air current on the valve; further, the valve remains fully open until the actuating member has nearly completed its return movement, and is then closed suddenly. One form is shown in Fig. 2 with the parts in the positions assumed when no carrier is in the tube, and the minimum flow taking place through an adjustable bye-pass 17 round the closed butterfly valve 15. The insertion of a carrier diminishes the pressure in a chamber C' on one side of a diaphragm 23, so that the atmosphere acting through a port P moves the diaphragm and its stem 24 to the left against the action of a spring 31, thus causing a shoulder 38 on the stem to move the valve past its vertical position. The upper half of the valve is larger than the lower half, so that the air current moves the valve further to a position in which a lever 16 on its spindle contacts with a stop 17<a>. As the valve 15 approaches its open position, a shoulder 54 on the stem 24 unseats a valve 50, which is then moved outwards by a spring 51 until it engages a stop 52 linked to the lever 16. The unseating of the valve 50 allows air slowly to enter a chamber 44 through a passage 47 at a rate limited by the setting of a screw 48, so that a spring S is ultimately able to move a diaphragm 43 to the left against atmospheric pressure, and through an abutment 56 and stem 40 close a valve 39 to prevent communication between the tube and chamber C<1>. The stem 40 through an abutment 61 simultaneously moves a vane member 60 against spring action into a position where it is more sensitive to the air current. During the movement of the carrier in the tube, air leaks into the chamber C<1> through an opening 63, so that the spring 31 is able to return the diaphragm 23 to its initial position. When the carrier emerges from the tube, the resulting rush of air swings the vane member 60 to the left until it engages the opposite wall, where it acts as a deflector to cause the air current to engage the right-hand face of the valve and swing the latter into its closed position, the lever 16 acting through the link 53 to close the valve 50. The air is then slowly sucked out of the chamber 44 to allow the diaphragm 43 to be moved to the right by atmospheric pressure to cause the opening of the valve 39 and to allow the vane member 60 to return to its non-sensitive position. In another form, the vane member 60 is replaced by a fixed deflector 65, Fig. 8, so proportioned and arranged that when the air current is flowing at carrier impelling velocity, the air is not defleeted to a sufficient extent to close the valve 15. In a third form, no deflector is provided, and the initial part of the closing movement of the valve 15 is effected by an adjustable abutment 38<a>, Fig. 13, on the stem 24.