Patent GB-271047-A (GB)
IPC: B65G51/16
Filed: 1927-03-28
Abstract: 271,047. Lamson Pneumatic Tube Co., Ltd., (Assignees of Maclaren, J. G.). May 12, 1926, [Convention date]. Pneuntatic dispatch apparatus.-Means for automatically controlling the supply of air to the transmission tube of a pneumatic dispatch system comprise automatic pressure actuated means for initiating the flow of carrier impelling air and means for automatically cutting off the air supply on the discharge of the last carrier from the tube, the closure of the main valve of the controlling apparatus depending solely upon the delivery of the carrier from the tube. The power control device comprises a hollow casing 8 divided into a chamber 11 connected to the transmission tube 4, and a chamber 12 connected to a suction tube 7. The U- shaped partition 10 between the chambers 11, 12 is formed with apertures for the heads 17, 18 of a balanced valve. The stem 19 of the valve is guided in a boss 20 in the upper wall 21 of the casing, and in a gland 22 secured to the lower wall of the casing. A coil spring 25 within the gland 22 bears against the head 18 of the valve and holds the valve normally in the closed position, a stop finger 28 and stop 29 limiting the closing movement so as to permit a small flow of air through the valve at all times. A flexible diaphragm 32, stretched across an upper chamber formed on the casing 8, divides it into parts 33, 34, a sleeve 35 telescoping on the valve stem being carried by the diaphragm. A boss 36 on the end of the sleeve 35 is adapted to engage a collar 37 on the valve stem 19, and a coil spring 39 in the chamber 34 bears against the diaphragm and the wall 21. The chamber 34 communicates with the inlet chamber 11 through an open port 40, and with the chamber 33 through a bleed-hole 41. A port 43 in the chamber 33 communicates with the atmosphere, and can be closed by a valve 44. A coil spring 48 is attached to a pin 47 on a bracket 50 secured to the valve stem 19. As the valve stem moves from the, upper to the lower position, the eye 49 passes below the pin 47 so that in the upper position the spring 48 tends to hold the valve open, and in the lower position, to hold the valve closed. A spring-controlled rocking shaft 57, Fig. 6, extending transversely across the inlet passage of the casing, carries a vane 58, the oscillation of which is controlled by stops 60, 61 acting on an extension 62 of the shaft 57, a spring normally holding the vane in the position shown in Fig. 2. Fingers 67 on the vane 58 receive a sliding spring-controlled latch rod 52 between them, and, when the vane 58 is swung downwardly, engage a button 56 on the rod 52 to withdraw it from engagement with a recess 51 in the valve stem 19. The parts are normally positioned as shown in Fig. 2, the port 43 being open and the balanced valve allowing a small air flow in the transmission tube 4. When a carrier is introduced, the flow of air through the tube 4 ceases so that the pressure in the chamber 34 falls, and the diaphragm 32 is depressed to open the balanced valve. The latch 52 snaps into the recess 51 and locks the balanced valve in the full open position, and the valve 44 is closed. The opening of the balanced valve reduces the pressure in the chamber 11, and in the chamber 34 through the port 40. Air is then sucked from the chamber 33 through the bleed-hole 41 until the diaphragm 32 is under balanced pressures. The spring 39 then restores the diaphragm to its normal position. On the delivery of the last carrier from the transmission tube, the sudden rush of air through the tube 4 swings down the vane 58 to retract the rod 52 from the recess 51. The spring 25 then closes the balanced valve, and the spring 48 opens the valve 44, thus restoring the parts to the normal positions.