Patent GB-268347-A (GB)
Title: Improvements in and relating to power controlling apparatus for pneumatic despatch systems
IPC: B65G51/16
Filed: 1927-03-22
Abstract: 268,347. Lamson Pneumatic Tube Co., Ltd., (Assignees of Maclaren, J. G.). March 26, 1926, [Covention date]. Pneumatic dis- Patch apparatus. - Power control apparatus for a pneumatic dispatch system comprises means actuable automatically on the insertion of a carrier in the dispatch terminal of the system to initiate flow of the propelling air current, and means operating automatically when the last carrier leaves the delivery terminal to cut off the air current. The dispatch tube 2 of a, pneumatic system is provided with a continuation 4 connecting with the casing 8 of a power control device 5, which communicates through a suction tube 7 with a. vacuum drum 9. A partition 10, formed with an aperture 13, divides the casing 8 into chambers 11, 12 communicating respectively with the tubes 4, 7. A flexible diaphragm 17, stretched across the chamber 12, is clamped against a seat 16 by the flange of a dished cover 18, the space 15 between the partition 10 and the diaphragm communioating with the inlet chamber 11 through an orifice 21, and the space 22 between the diaphragm 17 and the cover 18 communicating with the atmosphere through a, port 23. A bleed hole 27 allow restricted communication between the chambers 15, 22. A valve actuating rod 31 sliding in bosses 29, 30 in the casing and clamped to the diaphragm, is normally held by a spring 33 in the position shown in Fig. 2, a stop collar 39 limiting the movement of the rod. The port 23 is adapted to be closed by a valve 26 carried by a pivoted arm 25 and attached to an arm 36 mounted on the rod 31. The inner rod 40 of the rod 31 abuts a pivoted valve 41 which governs the flow of air through the aperture 13 and is carried on a shaft 42 encircled by an adjustable coil spring. When the valve 41 is closed, a toe 50 on the valve, engages the end of a screw 51 which is adjusted to allow a slight flow of air through the aperture 13. A contact portion 52 of the toe 50 bears against a latch spring 53. In a, modified construction, the valve is formed with a latch finger which is adapted to engage the toe of a counterbalanced latch lever. In operation, when a carrier is inserted in the tube 2, the flow through the aperture 13 past the closed valve 41 is reduced and the pressure in the chamber 11 falls, moving the diaphragm to the position shown in Fig. 3. The outer side, of the diaphragm is open to atmospheric pressure, but, as the diaphragm moves, the rod 31 opens the valve 41 and closes the valve 26. The air is then sucked from the chamber 22 through the bleed hole 27 until the pressures on the opposite sides of the diaphragm balance, the spring 33 then returning the diaphragm to its normal position, leaving the valve 41 held open by the coil spring. When the carrier leaves the tube 2, the sudden rush of air swings the valve 41 to the closed position against the action of the spring. When the diaphragm returns to its normal position. the valve 26 is held closed against its seat by the suction in the chamber 22. a spring 38 between the valve 26 and the arm 36 being adapted to stretch. When the valve 41 is closed. the pressure in the chambers 15. 22 rises until the pressures on opposite sides of the valve 26 are sufficiently nearly equal to allow the spring 38 to reset the valve 26 in the open position.