US1568398A - Power controller for pneumatic-dispatch systems - Google Patents

Description

Jan. 5 .1926.

J. T. COWLEY rowan CONTROLLER FOR PNEUMATIC nisrucu SYSTEMS Filed Apr il 8 1925 3 Sheets-Sheet 1 J! 5 1926u J T COWLEY POWER GONTROLLER FOR PNEUIATIC DISPATCH SYSTEMS Filed April. 8 1925 s Sheets-Sheet 2 Ire/06174907". I (fa/77ml" CowZey Zy E E L Jan. 5 1926.

J- T. COWLEY rowan CONTROLLER FOR PNEUMATIC DISPATCH SYSTEMS 3 Sheets-Sheet 5 Filed April 8 192 5 [77/v67v07": Janwsf GazuZey 0% Patented Jan. 5, 1926.

UNITED STATES PATENT twirli JAMES T. COWLEY, SYRACUSE, NEXV YORK, ASSIGNOR TO THE] LAMSON COMPANY, OF SYRACUSE, NEVJ YOBIK. A CORPORATION OF MASSACHUSETTS.

POWER CONTROLLER FOR PNEUMATIC-DISPATCH SYSTEMS.

Application filed April 8, 1925. Serial No. 21,720.

To all whom it may concern I Be it known that I, JAMES T COWLEY a citizen of the United States of America,v

and residentof Syracuse, in the county of Onondaga and State of New York, have invented new and useful Improvements in Power Controllers for Pneumatic-Dispatch Systems, of which the following is a specifica-tion.

type of which the patentto Libby 968,578.

August 30, 1910 furnishes an early example.

Controllers of this type comprise essentially a valve, hereinafter referred to as the main valve located between the transmissiontube \"rlOlllllll (il'lllll,

and an air exhauster or and which normally cuts oil:

carrier propellingair flow throughthe tube when the tube is idle although a relatively small volume of air insufiicient to propel a carrier, and known as the minimum flow is at all times permitted to flow through the transmission tube, and a pneumatic, for ex ample a piston or diaphragm, which re spends either directly or indirectly to changes in pressure in the tube due to the momentary cutting oil or checking of the minimum flow of air incident to the insertion of a carrier in the tube and which by such response to permit a opens wide the main valve carrier propelling air flow through the transmission tube.

In the form of apparatus described in the Libby patent the period during which the valve remains open is determined solely by the operation of. a timing device.

The

present invention is intended to improve the operation of devices of this general type if. eliminating the timing devlce and in place thereof 1 )roviding means which is respousivc directly to the changein. pressure in, the transmission tube incident to discharge of the last carrier therefrom for initiat ng closure of the main controlling valve.

d r a w in gs Fig. l is a diagranunatic clevat-ionto small scale. partly in SGCtlOH, showing the improved rm Herinstalled bet een one transmission tube of a pneumatic system and the exhaust header thereof;

Fig. 2 is a plan view of the controller to larger scale;

Fig. 3 is a fragmentary vertical section substantially on the line 33 of Fig. 2

showing the parts in normal position with a the main valve closed the transmission line being idle and no carrier being present in the transmission tube;

Fig. 4C is a section similar to Fig. 3 but showing the parts in the position which they occupy during the flight of a carrier through the tube; and

Fig. 5 is a fragmentary section showing the primary and secondary auxiliary valves and their motors as they are posi-- tionedevhen the last carrier has emerged from the transmission line and before the main valve has closed.

. 'Referring to Fig. 1, the numeral 1 indicates a'portiou of a central station desk provided with the open dispatch terminal .2 forming a part of the sending transmis sion tube 3 leading to an outlying station. The corresponding return transmission tube 4: is provided with the usual normally closed delivery terminal 5 and with the extension tube 6 which passes .down through the top of the desk 1 and is connected with the power control apparatus indicated generally by the numeral 7. A suction tube 8 leads from the powercontrol apparatus to the usual suction drum or header 9 in whicha vacuum or sub-atmospheric pressure 1S maintained by means of a suitable eXhauster not shown. A continuous air passage or conduit is thus provided extending from the terminal. 2 to the exhausteigthat portion of the conduit provided by the tubes 3 constituting the transmission line.

Referring more particularly to Figs. 23 and l. the improved power controller '7 which forms the inunediate subject matter of the present invention comprises an elongate hollow casing 10 having an opening in its side wall defined by a flange 1i forthe reception of the end of the tube extension (5. The lower end of this casing is also furnished with an opening for the reception. of the end of the suction tube 8.

The interior of the casing 10 is divided into an inlet chamber 13, communicating at all times with the transmission tube and an outlet chamber 14, communicating freely and 4 with the partition partition suction tube 8, by means of a or septum 15. Preferably this is U-shape, comprising the substantially parallel walls 17 and 18. These walls are furnished respectively with coaxial valve orifices providing communication between the chambers 13 and 14. Normally these orifices are closed by the heads 19 and 20 respectively of a valve 21 of balanced type. \Vhile a valve of this type is preferred, the particular type of valve employed does not constitute an essential feature of the present invention.

As herein shown the tubes 6 and 9 are connected by means of a small pipe 6*, Fig. 1, which permits a constant flow of air of small volume known as the minimum flow to be drawn through the transmission tube even when the main valve is closed. Vhile it is preferred to employ this small pipe outside of the casing 10, it is contemplated that similar results may be obtained by providing a small passage through the septum 15 or alternatively by permitting leakage past the valve heads.

The upper wall 10 of the casing 10 is preferably provided with a removable section 22 for convenience in assemblage of the parts. This removable section or cover is furnished with a central boss 23 having a guide passage for the stem 24 of the main valve 21. The upper wall 10 of the casing is also extended laterally and upwardly to provide the saucer shaped lower member 10 of the main motor casing. This bottom member 1O terminates in a radial flange 25 forming a seat for the edges of a flexible diaphragm 26. The edge of this diaphragm is clamped between the flange 25 and a flange 27 forming the edge of a downwardly concave cover member 28. The cover member 28 and the bottom member 10 may be connected by bolts 28 or in any other suitable manner.

The main motor casing comprising the members 10 and 28 is divided by the diaphragm 26 into upper and lower chambers 29 and 30 respectively. The chamber 30 is always in free communication with the outer atmosphere through a port or ports 31. The central part of the diaphragm 26 is preferably clamped between stiffener plates 32 and 33. These plates and the diaphragm are provided with aligned apertures for the passage of the screw-threaded upper end of the valve stem 24. A nut 34 engaging this screw-threaded end of the stem clamps the diaphragm and the plates 32 and 33 together and securely connects them to the stem.

An internally screw-threaded sleeve or nut 35 engages the upper end of the stem 24 above the nut 3a and constitutes a socket f r t e, le e end 0 a 3 13 f rm ng n extension of the stem 24:, and whose upper part is guided by passing through an opening in the upper end of a hollow gland 38 having screw-threaded engagement with an opening in a boss 89 projecting from the top of the cover 28. A coiled spring 10 surrounds the rod 37, its upper end being seated in the gland 8S and its lower end bearing against the sleeve 35. This spring tends to depress the diaphragm 26 and thus to close the main valve and retain the latter in its normal position. The tension of this spring may be varied by turning the gland 38.

A small bleeder opening 42 preferably controlled by an adjustable needle valve 4L3 normally permits atmospheric air slowly to leak into the chamber 29 of the main motor casing.

The wall of the chamber 29 may if desired be provided with a second small opening 83, leading from the chamber 29 to the passage 76 hereafter described, and this opening 83 may also if desired be controlled by an adjustable needle valve 84:.

The cover 28 is provided with a boss 15 which supports the base member #26 of a primary auxiliary pneumatic motor. The base as of this auxiliary motor is provided with a radial flange 57 forming a seat for" the edge of a flexible diaphragm 53. The edge of this diaphragm is clamped between the flange 57 and a flange 59 forming the edge of a downwardly concave cover member 60. The diaphragm 5S divides the auxiliary motor casing into upper and lower chambers 61 and (32 respectively, the latter communicating freely with the atmosphere by means of an opening port 63.

A boss 65 projects up from the central part of the base member 46 of the auxiliary motor casing and is provided with a guide passage for a sliding stem 66. The central part of the diaphragm 58 is clamped between stiffening plates 69 which have central openings for the reception of the screwthreaded upper end 70 of the stem 66 and a clamping nut 71 holds the several parts in assembled relation. A rod '72 forming an extension of the stem 66 is connected at its lower end to the nut '71 and its upper part is guided by passing through an opening; in the top of a gland 73 having screw-threaded engagement with an opening in a boss 74: projecting up from the top of the cover 60.

A coil spring 75 surrounds the rod 72, bearing at one end against the inner surface of the gland 73 and at its other end against the top of the nut 71. The tendency of this spring is to depress the diaphragm 58 and the tension of the spring may be varied by turning the gland 73.

A valve disk 79 is secured to the lower end of the stem 66. This valve disk cooperates with an annular seat 78 defining a valve orifice 77 connecting the cham er 29 with '10lfthus to hold the valve a chamber in the boss 45 and which in turn opens into a passage 76 which leads to the chamber 13 and thus to the transmission tube. Normally the valve disk 79 is spaced from its seat 78 as shown in Fig. 3 so as to provide free communication between the chamber 29 and the transmission tube.

The stem 66 is furnished with an axial passage 80 of small" capacity opening through the side of the stem at the point 81 above the disk 79 and communicating at its upper end with a portion 82 in the nut 71, thus providing a conduit leading from the chamber 7 6 to the uper chamber 61 of the primary auxiliary motor.

As herein illustrated a bracket 85 is clamped to a vertical portion of the tube extension 6, but while this is a convenient arrangement, it is contemplated that the bracket 85 or the parts carried thereby may be supported in any other suitable manner, for example by being mounted upon the cover 28 of the main motor.

The bracket 85 supports a hollow casing providing a chamber 86 which communicates by means of an open port 87 with the interior of the tube 6 so that transmission tube ressure is always maintained in the chamher 86. The lower wall of the chamber 86 is provided with an opening 86 providing free communication with the interior of a valve housing 88 preferably'segarate from the bracket 85 and secured thereto in any desired manner. This valve housing 88 is furnished with an annular valve seat 89 surrounding a chamber 90 which communicates by means of a pipe 91 with the chamber 29 of the main motor casing, opening into the latter at the point 92. A pilot valve disk 93 cooperates with the seat 89, and normally shuts ofli' the chamber 86 from the chamber 90.

The valve disk 93 is secured to the lower end of the stem 94 of a secondary pneumatic auxiliary motor comprising a casing having a bottom member 97 and a cover member 98. The bottom and cover members are provided .respectively with radial flanges 99 and 100 between which the edge of a flexible diaphragm 101 is clamped. The central part of this diaphragm is preferably stiliened by means of plates 102 and the diaphragm and plates are secured to the stem 94 by means of a clamping nut 103.

A rod 104 forming an extension 01'' the stem 94 is secured at its lower end to the nut 103 and is guided at its upper end by passing through an opening in the top of a gland 105 having screw-threaded engagement with a boss 106 projecting up from the cover 98. A coil spring 107 encircles the rod 104. hearing at its upper end. against the gland 105 and at its lower end against the nut 103. This spring tends to depress the diaphragm 93 against its seat 89. The tension of the spring may be variedby turning the gland 105.

i The operation of the device is substantially as follows, it being assumed that when the line is idle the parts occupy the position shown in Fig. 3. At this time the main valve 21 is closed and a small volume of air" is passing through the transmission tube and the pipe 6 toward the exhauster.

When a carrier is placed in the transmi sion tube either at the terminal 2 or at the outlying station, this small flow of air is cut oil or substantially diminished with the result that the suction in the transmission tube is increased and acting through the passage 7 6 and the opening valve orifice 77 causes increased suction in the chamber 29 with consequent lifting of the diaphragm 26. As soon as the diaphragm lifts, even slightly, the vacuum in the transmission tube and in the chamber 29 is greatly increased due to the opening of the main valve 21 so that the diaphragm 26 continues to rise rapidly until the main valve is fully open".

The suction is also transmitted through the passage 80 in the stem 66 of the primary auxiliary motor to the chamber 61 ot the latter but as the passage 80 is of small capacity the diaphragm 58 does not rise and close the valve 79 until the main valve has been fully opened.

The spring 107 of the secondary auxiliary motor is substantially stitier than the spring 7 5 off the primary auxiliary motor so that while the diaphragm 58 tends to rise even before the main valve has fully opened, the diaphragm 101, which is directly connected with the transmission tube, does not rise until the main valve is substantially wide open and the maximum vacuum has been established in the transmission tube. As

, soon as the diaphragm 101 rises it opens the pilot valve 93 thus reestablishing communication betwen the transmission tube and the chamber 29.

The parts now remain in this position as indicated in Fig. 4 during the cut flight of the carrier and so long as any carrier remains in the transmission line. hen the last carrier emerges from the transmission line the pressure in the line rises slightly and this slight rise in pressure is suiiicient to permit the spring 107 to close the pilot valve 93, thus cutting off communication between the transmission line and. the chamber 29, the valve 79 remaining closed. Air at atmospheric pressure now bleeds in slowly through the orifice 42 and tends to reestablish. equality of pressure upon opp 'to sides of the diaphragm 26. The restoraion of atmospheric pressure in chamber 29 may be controlled with great nicety by adjustment of the needle valve 43 and also by adjustment of the valve 84 it such beelnployed.

hen the pressure upon opposite sides of the diaphragm 26 has been partially equalized the spring so closes the main valve 21, thus cutting off the suction tube 8 from the chamber 13 and permitting the pressure in the latter to rise. Pressure now gradually builds up in the chamber 61 of the primary auxiliary motor and eventually the spring is able to depress the diaphragm 58 and to open the valve 79, thus restoring the parts to their initial position.

The device thus operates without reference to any timing mechanism and directly in accordance with pressure changes in the transmission line due to introduction and discharge of carriers.

While the device as illustrated is of preferred construction, I contemplate that various changes in shape, proportion and arrangen'ient of parts may be made without departing from the spirit of the invention.

I claim:

1. Pneumatic dispatch apparatus having a transmission tube, an eithauster connected therewith and a main valve for controlling the flow 01 air through the transmission tube, a minimum flow of air through the tube being permitted when the valve is in closed position, and apneumatic motor for operating the main valve, said motor responding directly to slight drop in pressure in the transmission tube incident to insertion of a carrier in the tube to open the main valve, an auxiliary pneumatic responsive to pressure change in the transmission tube, means actuable by the auxiliary pneumatic for cutting oit communication between the main motor and the transmission tube when the main valve opens, and independent means operative immediately to recstablish communication between the main motor and the transmission tube.

2. Pneumatic dispatch apparatus having a transmission tube, an exhauster connected therewith and a main valve for controlling the flow of air through the transmission tube, a minimum flow of air through the tube eing permitted when the main valve is in closed position, and a pneumatic motor for operating the main valve, said motor responding directly to slight drop in pressure in the transmission tube incident to insertion of a carrier in the tube to open the main valve, an auxiliary pneumatic responsive to pres ure change in the transmission lube. means actuable by the auxiliary pneumatic for cutting ott communication between the main motor and the transmission tube when the main valve opens and indepenoent means including a secondary auxiliary pneumatic operative to reestablish (Ollinunication between the main motor and the transmission tube.

3. Pneumatic dispatch apparatus having lesion tube, an exhauster connected therewith and a main valve for controlling the How of air through the transmission tube, a minimum flow of air through the tube being permitted when the main valve is in closed position, and a pneumatic motor for operating the main valve, said motor responding directly to slight drop in pressure in the transmission tube incident to insertion of a carrier in the tube whereby to open the main valve, a primary auxiliary pneumatic responsive to pressure change in the transmission tube, means actuable by the primary pneumatic for cutting olf communication between the main motor and the transmission tube when the main valve opens, a secondary auxiliary motor responsive to pressure change in the transmission tube, and a normally closed valve which is opened by said latter motor to reestablish comnnmieation between. the main motor and the tube.

4. Pneumatic dispatch apparatus having a transmission tube, an exhauster connected therewith and a main valve for controlling the flow of air through the transmission tube, a minimum flow of air through the tube being permitted when the valve is in closed position, and a pneumatic motor for operating .tne main valve, said motor responding directly to slight drop in pressure in the transmission tube incident to insertion of a carrier in the tube to open the main valve, an auxiliary pneumatic responsive to pressure change in the transmission tube, means actuable by the auxiliary pneumatic for cutting off communication between the main motor and the transmission tube when the main valve opens, a secondary auxiliary pneumatic responsive to pressure change in the transmission tube, said latter pneumatic being less sensitive to variation from normal pressure in the tube than the first auxiliary pneumatic, and means controlled by said secondary pneumatic for roestablishing communication between the main valve and the tube.

5. Power control apparatus for a pneumatic dispatch system having a transmission tube and a main valve for controlling the carrier propelling air flow therethrough comprising a pneumatic motor for operating the main valve, an auxiliary pneun'iatic responsive to pressure change in the transmission tube means actuable by the auxiliary pneumatic for cutting of? communication between the main motor and the trans mission tube when the main valve opens, and independent means for reestablishing coup muni'cation. between the main motor and the tube and for maintaining such connnnniczn tion during the flight ot the carrier.

6. Pnucmatic dispatch apparatus having a transmission tube, an exhauster connect crl therewith and a main valve for conrolling the flow ofair through the trans mission tube, a minimum flow of air through the tube being permitted When the valve is in closed position, and a pneumatic motor for operating the main valve, said motor responding directly to slight drop in pressure in the. transmisison tube incident to insertion of a carrier in the tube to open the main valve, an auxiliary pneumatic responsive to pressure change in the transmission tube, means actuable by the auxiliary pneumatic for cutting off communication between the main motor and the transmission tube when the main valve opens, and a secondary auxiliary pneumatic responsive to high vacuum in the tube due to opening of the main valve to reestablish communication between the main motor and the tube, said secondary pneumatic responding to the slight increase in pressure in the tube incident to delivery of the last carrier from the latter again to cut off communication between the main motor and tube.

7 Pneumatic dispatch apparatus having a transmisison tube, an exhauster connected therewith and a main valve for controlling the flow of air through the transmission tube, a minimum flow of air through the tube being permitted when the valve is in closed position, and a pneumatic motor for operating the main valve, said motor responding directly, to slight drop in pressure in the transmission tube incident to insertion of a carrier in the tube to open the main valve, an auxiliary pneumatic responsive to pressure change in the transmission tube, means actuable by the auxiliary pneumatic for cutting off communication between the main motor and the transmission tube when the main valve opens, a normally closed pilot valve controlling a passage from the main motor to the transmission tube, and means responsive to the high vacuum in the tube occasioned by the opening of the main valve to open said pilot valve, said means responding to the change in pressure in the tube incident to delivery of the last carrier therefrom again'to close said valve.

8. Pneumatic dispatch apparatus having a transmission illlb8,xfll1 exhauster connected therewith, and a main valve for controlling the flow of air through the transmission tube, a minimum flow of air through the tube being permitted When the valve is in closed position, a main pneumatic motor responsive to introduction of a carrier into the transmission tube to open the main valve, said motor having a chamber normally communicating with the transmission tube by means of an open passage, an auxiliary valve for closing said passage, means for closing said auxiliary valve when the main valve opens, and independent means operating when the main valve opens to reestablish communication between the main motor chamber and the'tube.

9. Pneumatic dispatch apparatus having a transmission tube, an exhauster connected therewith, and a main valve for controlling the flow of air through the transmission tube, a minimum flow of air through the tube being permitted When the valve is in closed position, a main pneumatic motor responsive to introduction of a carrier into the transmission tube to openthe main valve, said motor having a chamber normally communicating with the transmission tube by means of an open passage, an auxiliary valve for closing said passage, means for closing said auxiliary valve when the main valve opens, and independent pressure-actuated means for reestablishing and maintaining communication between the main motor chamber and the tube during the entire flight of the carrier.

10. Pneumatic dispatch apparatus having a transmission tube, an exhauster connected therewith, and a main valve for controlling the flow of air through the transmission tube, a minimum flow of air through the tube being permitted when the valve is in closed position, a main pneumatic motor responsive to introduction of a carrier into the transmission tube to open the main valve, said motor having a chamber communicating with the transmission tube by means of two passages, a normally open auxiliary valve controlling one of said passages, a normally closed auxiliary valve controlling the other passage, and independent auxiliary pnuematic motors for operating said auxiliary valves.

11. Pneumatic dispatch apparatus having a transmission tube, an exhauster con nected therewith, and a main valve for controlling the fiow of air through the transmission tube, a minimum flow of air through the tube being permitted when the valve is in closed position, a main pneumatic motor responsive to introduction of a carrier into the transmission tube to open the main valve, said motor having a chamber communica ing with the transmission tube by means or" two passages, a normally open auxiliary valve controlling one of said passages, a normally closed auxiliary valve controlling the other passage, and independent auxiliary pneumatic motors for operating said auxiliary valves, each of said motors being responsii e to change in pressure in the transmission tube.

12. Pneumatic dispatch apparatus having a transmission tube, an exhauster connected therewith, and a main valve for controlling the flow of air through the transmission tube, a minimum flow of air through the tube being permitted when the valve is in closed position, a main pneumatic motor responsive to introduction of a carrier into the transmission tube to open the main valve, said motor having a chamber communicating with the transmission tube by means of two passages, a normally open auxiliary valve controlling one of said passages, a normally closed auxiliary valve controlling the other passage, and independent auxiliary pneumatic motors for operating said aux liary valves, each of said auxiliary motors being responsive to drop below normal in pressure in the transmission tube, one of said auxiliary motors responding to a smaller drop in pressure than the other.

13. Pneumatic dispatch apparatus having a transmission tube, an exhauster connected therewith, and a main valve for controlling the flow of air through the transmission tube, a minimum How of air through the tube being permitted when the valve is in closed position. a main pneumatic motor responsive to the introduction of a carrier into the transmission tube to open the main valve, said motor having a chamber com municating with the transmission tube by means or two passages, a normally open auxiliary valve controlling one of said passages, a norn'ially closed auxiliary valve controlling the other passage, and independent auxiliary pneumatic motors for operating said auxiliary valves, said auxiliary motors closing and opening their respective valves substantially simultaneously with the opening of the main valve and maintaining these valves in said respective positions so long as a carrier remains in the tube 14. Pneumatic dispatch apparatus having a transmission tube, an exhauster connected therewith. and a main valve for controlling the flow of air through the transmission tube, a minimum flow of air through the tube being permitted when the valve is in closed position, a main pneumatic motor responsive to introduction 0'1". a carrier into the transmission tube to open the main valve, said motor having a chamber communicating with the transmission tube by means of two passages, a normally open auxiliary valve controlling one or said passages, a normally closed auxiliary valve controlling the other passage, and independent auxiliary pneumatic motors for operating said auxiliary valves, both of the auxiliary motors responding to the drop in pressure in the transmission tube occasioned by opening the main valve to close and open their valves respectively, and the latter'auxiliary motor only responding to subsequent increase in pressure in the tube incident to delivery of the last carrier therefrom again to open its v alve.

15. Pneumatic dispatch apparatus having a transmission tube, an exhauster connected therewith, and a main valve for controlling the flow of air through the transmission tube, a minimum flow of air through the tube being permitted when the valve is in closed position, a main pneumatic motor responsive to introduction of a carrier into the transmission tube to open the main valve, said motor having a chamber comnmnicating with the transmission tube by means of primary and secondary passages, a normally open auxiliary valve controlling the primary passage, a normally closed auxiliary valve controlling the secondary passage, primary a'nd secondary pneumatic motors for actuating the respective auxiliary valves, each motor being responsive to pressure change in the transmission tube, both motors responding to drop in pressure in the tube due to opening the main valve and thereby closing the primary auxiliary valve and opening the secondary auxiliary valve, the secondary auxiliary motor only responding to increase in pressure in the tube incident to delivery of the last carrier from the latter to close its valve while the other auxiliary valve remains closed.

16. Pneumatic dispatch apparatus having a transmission tube, an exhauster connected therewith, and a main valve for controlling the How of air through the transmission tube, a minimum flow of air through the tube being permitted when the valve is in closed position, a main pneumatic motor responsive to introduction of a carrier into the transmission tube to open the main valve, said motor having a chamber communicating with the transmission tube by meansof primary and secondary passages, a normally open auxiliary valve controlling the primary passage, a normally closed auxiliary valve controlling the second passage, primary and secondary pneumatic motors for actuating the respective auxiliary valves, each auxiliary motor comprising a flexible diaphragm forming one wall of a chamber communieating with the transmission tube, means connecting each diaphragm to its respective auxiliary valve, and springs opposing movement of the respective dia'phragms, the spring of the secondary motor being stiiier than that of the primary motor.

17. Pneumatic dispatch apparatus having a transmission tube, an exhauster connected therewith, and a main valve for controlling the flow of air through the transmission tube, a minimum flow of air through the tube being permitted when the valve is in closed position, a main pneumatic motor responsive to introduction of a carrier into the transmission tube to open the main valve, said motor having a chamber communicating with the transmission tube by means of primary and secondary passages, a normally open auxiliary valve controlling the primary passage, a normally closed auxiliary valve controlling the secondary passage, primary and secondary pneumatic motors for actuating the respective auxiliary valves, each auxiliary motor comprising a flexible diaphragm forming one wall of a chamber communicating at all times by means of a passage with the transmission tube, the passage leading to the primary motor being of less capacity thanthat leading to the secondary motor, the outer face of each auxiliary motor diaphragm being at all times exposed to atmospheric pressure, means connecting each diaphragm to its respective valve, and a spring opposing movement of each diaphragm responsive to pressure decrease in the transmission tube.

18. Pneumatic dispatch apparatus having a transmission tube, an exhauster connected therewith, and a main valve for controlling the flow of air through the transmission tube, a minimum flow of air through the tube being permitted when the valve is in closed position, a main pneumatic motor responsive to introduction of a carrier into the transmission tube to open the main valve, said motor having a chamber c0mmunicating with the transmission tube by means of primary and secondary passages, a normally open auxiliary valve controlling the primary passage, a normally closed auxiliary valve controlling the secondary passage, primary and secondary pneumatic motors for actuating the respective auxiliary valves, each auxiliary motor comprising a flexible diaphragm forming one Wall of a chamber communicating at all times by means of a passage With the transmission tube, the passage leading to the primary motor being of less capacity than that leading to the secondary motor, the outer face of each auxiliary motor diaphragm being at all times exposed to atmospheric pressure, and a. spring opposing response of each of the auxiliary diaphragm to pressure decrease in the transmission tube, the spring of the vsecondary auxiliary mot-or being stiffer than the spring of the primary auxiliary motor.

Signed by me at Syracuse, New York, this th day of March, 1925.

JAMES T. COWLEY.

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