US1568806A - Power-control apparatus - Google Patents

Description

Jan. 5,1926. 1,568,806

J. T. cowLEY POWER CONTROL APPARATUS J. T. cowLEY I POWER CONTROL APPARATUS Jan. 5 1926.

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Jan. 5 1926; 1,568,806

J. T. cowLEY f POWER CONTROL APPARATUS I Filed April 8, 1925 5 Sheets-Sheet 5 72 Fay. 9 7,0 7M W 1M 776' .f7 :S ma

Jan. 5 1926.

' J. T. cowLl-:Yy

POWER CONTROL APPARATUS Filed April a, 1925 k5 Sheets-Sheet v4 590i@ @mw A V y #wiwi Jan. 5 1926. 1,568,806-

J. 'r. cQwLEY-l POWER CONTROL APPARATUS V Filed April 8, 1925 5 Sheets-Shea?l 5 vPatented Jan. 5, 1926.

y UNITED STATES PATENT OFFICE.

JAMES T. COWLEY, O SYRACUSE, NEV YORK, ASSIGNOR TO THE LAMSON COVPANY, OF SYRACUSIE,` NET/V YORK A CORPORATION OF MASSACHUSETTS.

POWER-CONTROL APPARATUS.

y Application fiIed April S, 1925. Serial No. 21,721.

fo di whom t may concern? y Be it known that T, Janus T. Cownnr; a citizen of the United States of America,` and resident of Syracuse, in the countyot' Onondaga land State of New York, have invented new and useful Improvements in Power-Control Apparatus, of which the following is a speciiication.

VThis invention pertains to power controllers iorpneumat-ic despatch systems and relates 4more particularly to automatic controllers of the so-called minimum flow type of which the patent to Libby 968,576, August 20, 1910, turnishes an early example Controls of this ty e comprise essentially a valve, hereafter re erred to as the main valve located between the transmission tube and an air exhaustcr or vacuum drum and which normally cuts oit carrier propelling air lowvthrough the -tube when the tube is idle, although a relatively small 'volume of air, ii'isufiicient to propel a carrier, and known as the minimum ilow is at all times 'permitted to flow through the transmission tube,-a"nd a pneumatic, for enampie a piston or dia hragm7 which responds either directly or indirectly to changes in pressure in the transmission tube due to the momentary cutting off or checking' of the minimum flow incident to the insertion of -a carrier in the tube and which, by such response, 'opens wide the main valve to permit carrier propelling air ilow through the transmission tube.

2?5 `in the torni or 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 oi this general type by eliminating the timing device and in place 'thereof providing means which is responsive directly to the change in pressure in the transmission tube incident to discharge oi' the last carrier therefrom, thereby to initiate closure of the main controlling valve ln the accompanyiui;- drawings a preterred embodiment of the'invention is illustrated. by way example and in such drawings: l; l

Fig. l is diagi'annnatic elevation to small scale partly in sectionE showing the improved controller installed between one transmission tube oi a pneumatic system andthe exhauster header thereof;

Fig'. 9L is a plan view or the controlling device to large scale;

Fig. 3 is a fragmentary vertical section, substantially on the line Sw of Fig. 2; showing` the parts in normal position with the main valveclosed, the transmission line being` idle and no carrier being present in the tube; i

l is a tragn'ientary section to smaller scale showing the interior construction ot the lower Dart of the controlling apparatus; Fig. 5 is a view similar to Fig. 3, but showing the parts in the positions which they occupy at the instant of full opening` of the main valve;

Fig. 6 is a fragmentary section showing;` the relative positions of the primary and` secondary auxiliary valves during the flight o'f the carrier through the tube; p

Fig. 7 is a view similar to Fig. 6 showing the primary and secondary auxiliary valves at the instant after the last carrierA has emerged from the transmission tube and be- Afore the main valve has closed;

Fig. 8 is a vertical section substantially on the line 8-8 of Fig. 2;

Fig. 9 is a vertical section substantially on the line 9--9` of Fig. 2; and

Fig'. 10 is an elevation. partly in vertical section on the line 10-10 of Fig. 2.

Referring to the drawings and particularly to Fig. l, the numeral l indica-tes a portion of a central station desk or other suitable support provided with the open despatch terminal 2 forming a part of the sending' transmission tube 3 leading to an outlying station. The correspending' return transmission tube Il; is provided with the usual normally closed delivery terminal 5 and with the extension tube 6 which passes down through the top lof the desir l and is connected with the power control apparatus designated generally by the nume-ral A suction tube ti leads 'from the power control apparatus to the usual suction drum oi vheader 9 in which a vacuum or subatinospheric presslu'e is maintained by nie-ans ott a suitableenhauster not shown. A contini-pus air passage or conJ 't is thus provided extending trom the terminal 2 of the transmission tubeto the .exhausten that portion ot the conduit provided by the tubes il and lconstituting the transmission line.

Referring more particularly to F 3 and l the. improved power controller T which Jforms the immediate subject matter ot the present invention comprises an elongate hollow fasing 10 having an opening in its side wall defined by a flange 11 4tor the reception ot the end ot the tube extension (3. 'lhe lower end ot this casing is also turnished with an opening for the reception ot the end ot the suction tube S.

The interior ot the casing l() (Fig. l) is divided into an inlet chamber 1S communieating at all times with the transmission tube end an outlet chamber lt communicating :freely with the suction tube. S b v means ot' a partition or septum Preferably this partition is U-shaped. comprising the substantially parallel walls 17 and 18. These walls are furnished respectively with coaxial valve orifices providing communication between trie chambers 1'3 and ll. Normally these orifices are closed by the heads 1f) and Q0 respectivelyv ot a valve 21 ot bal` anced type. lVhile this form oli' valve is preterred the invention is not concerned particular-lj.'v with the character ot the Valve eu'iployed.

As herein shown the tubes 6 and 9 are connected by means of a small pipe 6 (Fig. ll) 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 :21 is closed. ll'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 110 of the casing 10 (Fig. 3) preferably comprises a removable section tor convenience in assembling the parts. This removable section or cover is vturnished with a. central boss having a guide passage for the stem 24e ot the main valve :21. The upper wall 10"L of the casing is also extended laterally and upwardly to provide the saucer shaped lower member 10b ot the main motor casing. This bottom member 10b terminates in a radial flange Q5 forming a seat for the edge of: a flexible diaphragm 26. The edge ot this diaphragm is clamped between the flange Q5 and a flange 2T at the `margin of an upwardly c oncave cover member 28. The cover member 28 maybe connected to 'the bottom member 10" by means ot bolts 28 or other suitable fasteners.

The vmain -motor casing comprising the members 28 and I10b is divided bythe diaphragm '25 into upper yand lower chambers 29 and 30 respectively. The chamber Il() is always in tree communicalion with the outer atmosphere through the port or ports ill. The central part ot' the diaphragm 2G is preferably clamped bctwccn stiffencr plates 32 and 33. These plates and the diaphragm are provided with aligned apertures for the passage ot the scre,Y threaded upper end ot the stem 2l. A nut 34 clamps the diaphragm and the plates 82 and 233 together and securely connects them to the stem.

An vinternally screw threaded sleeve or nut 35 engages the upper end ol the stem QLlabove the nut l-l and constitutes a socket 'tor the lower end of a rod 53T forming an extension ol the stem 2l and whose upper part passes through a guide opening in the upper end o l a hollow gland 23S having .screw threaded engagement with an opening in a boss 39 projecting l'rom the top of the cover A coiled spring l0 encircles the rod 37, its upper end being seated in the gland 38 and its lower end bearing against the sleeve rfhis spring tends to `depress the diaphragm 2G and thus lo close the main valve and retain the latter in its normal position. The tension ot' this spring may be varied by turning the gland 38. I

small bleeder opening l2 preferably controlled by an adjustable needle valve 'lil permits atmospheric air slowly to leal; into the chamber 29 ot the main motor casing. The wall ot' the chamber 29 may. it desired, be provided with a second .small opening S3 leading from the chamber 29 to the passage hereinafter described and this opening 853 may also it desired be controlled by an adjustable needle valve Sl.

The cover 28 ot the main motor casing is provided with a boss Ll5 which furnishes a support tor the base member 4G ot' the primary auxiliarv pneumatic motor, The base ..f ot this riu-ziliary motor is provided with a radial flange 5T torming a scat tor the edge of a flexible diaphragm 5R. The edge ot' this diaphragm is clamped between the flange 5T and a flange 5f) forming the edge ot a downwardly concave cover member (lo. The diaphragm 58 dividesl the auxiliary motor casing into upper and lower chambers (il and (32 respectively.

boss (lo projects upwardly from the central part ol the .base mei'nber ol' the auxiliary motor Casing and provided with a guide passage 'tor a sliding stem (3G. The central part of the diaphragm 5S is clamped between stifieiiing plates G9 which have central openings v'for the reception of the screw threaded upper end of the stem 6G, and a clamping nut 71 holds the several parts in assembled relation. A 'rod T2, 'forming an extension of the stem 66, is connected at its lower end to the nut T1 and its upper part passes ,through 'a guide opening in the top ol a gland T3 -havnig screw threaded engagement with the opening in a boss '74 projecting up from the top of the cover 60. A coiled spring surrounds the rod 72 bearing at one end' against the inner surface of the gland 7 3 and at its other end against the top of the nut 71. The

tendency yof this spring is to'depress the' diaphragm 58 and the tension of the spring may be varied by turning the gland 73. y

r. valve disk`79 is secured tothe lower end of the stem 66. This valve disk cooperates with an annular seat 7 8 defining a valve orilice 77 connecting the chamber38 of the main motor casing with a eha1nloer76a 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 thevalve disk 79 is spaced from its seat 78 as shown in Fig. 3 so as yto provide free communication between the chamber 29 and the transmission tube. The ldiaphragm 58 is `furnished with a small vent opening 80-per mitting .the slow passage of air from one side' to the other thereof. v

The numeral 81v indicates generally a secondary auxiliary motor which is mounted upon a bracket 82 which may be integral with the base 46 of the primary motor or which may be supported in any other desired manner. This. secondary motor comprises the bottom rmember 85 and the cover member 86 furnished with flanges 87 and 88 respectively at their edges between which Vthe edge ot a flexible diaphragm 89 is clamped. This diaphragm separates the interior of the secondary `auxiliary motor casing into an upper chamber' 90 and a lower chamber 91.r The latter communicates at all timeswiththe outer atmosphere by means of a port or ports 92.

The base member 85 or' the secondary auxiliary motor casing is furnished with a central boss 93 having a guide passage for a sliding stem 94. The upper end of this stem is redufed in diameter and screw threaded and passes up through central openings in stilfener plates 95 disposedupon opposite sides of the diaphragm 'and which are clamped to the stem 94 by 'means of a nut 96. A rod 97'forming an'extension of the stem 94 is connected'at its lower end to the upper end of the stem 94 and its upper part passes through a guide opening in the top of a hollow gland 98 having screw threaded engagement with an opening in a boss 99 at the central part of a cover 86.' A. coiled spring 100 encircles the. rod 97, bearing at its upper end against the gland 98 and at Yits lowerend against the nut 96. Thetension of this spring is varied by turning the 4land 98 and the tendency of the spring is c I to' depress the diaphragm 89. K

AThe lower part or base member'85 ot' the 4secondary motor casingis furnished with an annular sleeve-like boss 101 concentric with the `ste-111 94, The chamber 102 within this boss 101 is normally open at the orice 103 to the outer atmosphere. A pilot valve 104 is secured to the lower end of the stem 94 and when the diaphragm 89 is raised, this valve seats against the lower edge 101a of vvthe boss 101, thus closing the orifice 103. A

into a boss (Fig. 9) upon the base 46 of the primary auxiliary motor casing. The

Vpassage 109 is connected (see Fig. 8) with a radial passage 111 extending inwardly through the base member 46 of the primary motor casing and opening into the chamber 76 at the point 112.. Since the chamber 76 is always iu con'imunication with the transmission tube th-e pressure in the upper cha-mber 90 of the secondary auxiliary motor casing is always substantially'that of the transmission tube. f l

Referring to Figs. 9 and 10 a passage 113 extends upwardly from the passage 109 into a boss 114 projecting from the cover 60 of the primary auxiliary motor. This passage 113 communicates by means ot' a downwardly inclined passage 115 with the upper chamber 61 of the primary auxiliary motor. An adjustable needle valve 116 is provided for regulating the effective size of the passage 113. i

The operation of the device is substantially as follows, it being assumed that when the transmission line is idle the parts of the control device occupy the positions shown in Fig. 3, the main valve being closed and the auxiliary valves 79 and 104 being open. It is also assumed that the spring 100 is stiffer than the spring 75 so that a greater degree ot' vacuum is necessary to close the valve 104 than is necessary to close the valve 79.

When a carrier is introduced into the transmission line either at the terminal 2 or at the outlying station the minimum flow of air normally entering the terminal 2 is out off or substantially diminished with the result that the suction in the transmission tube and the chambers connected therewith is increased.` The spring 37 of the main motor is so adjusted that when the carrier is introduced into the transmission tube and the suction thus increases the main dlaphragm 26 will rise thereby opening the main valve 21. The diaphragme 58 and 89 of the auxiliary motors do not respond to -to the `chamber thisfinitial `increase in suction, but when the now 'respond to this suction to close their re- Sinee the passage leading (i1 of the primary auxiliary motor `is restricted by a .proper setting of the needle valve 116, this motor is prevented from closing-its valve prior to the tull opening ot' the main valve or prior to theclosure of the valve 10%, As soon as the valve 79 closes, air which constantly ileaks inithrough the passage l2 begins gradually to build -up pressure upon the upper side ot' the diaphragm 2G and thus eventually would allow the main valve to close. Before such action can take place the valve 10ft is closed, as already pointed out, `thus cutting oil.E the chamber G2 of t-he primary auxiliary motor from the atmosphere. As Vthe upperchamberl ot' this motor communicates w-ith the transmission tube, and as the lower chamber communicates with the upper chamber by means of the passage the pressures upon the opposite side ot the diaphragm 58 tend to equalize and the spring 'T5 again opens the valve 79. This act-ion takes place very rapidly so that the chamber 290i the main motor is again placed in full communication with the transmission tube before the main valve can close.

The parts now remain in this position until the last carrier emerges from the transmission tube. lVhen this occurs a. slight decrease in suction in the transmission tube is produced since the rictional drag -and inertia of the carrier are removed. The spring 100 is so -adjustedthat Vthis slight change in pressure in the transmission tube is suiiieient to allow the diaphragm 89 to drop, thus opening the valve 104. iVhen the valve 104- opens as indicated in Fig. 7, communication is established between the lower chamber G2 of the primary auxiliary motorand the outer atmosphere, and the diaphragm 58 being undei' suction immediately rises and again closes the valve 79 as indica-ted in Fig. 7. Since the chamber 29 of the main motor is now cut ott from the transmission tube the pressure slowly builds up in the chamber 29 through the port until the spring` si() is able to vdepi'ess the diaphragm 26 and thus to close the main valve. The iate ot .pressure equalization in the chamber Q9 may be very nicely adjusted by the two needle valves i3 and 8l so that the inter fal between the delivery ot' the carrier from the tube and the closure of the mai-n valve may be deterspective valves.

-mined with 4great accuracy.

l Then the mainvalve closes, the suction in the transmission tube immediately returns substantially to normal. the original pressure in the chamber 61 of the primary auxiliary motor is gradually restored, and the SPlllg 75 again opens the valve T9. The. parts are all thus returned 'to their initial position ready vfor a repetition otthe operation.

Vhile l have shown a Ipreferred arrangement of parts I contemplate that various changes and modifications may be made 'both Vtube con'iprising a main valve Yfor controlling carrier propelling air flow through the tube, a. main pneumatic motor for yoperating the main valve, said motor having a pressure actuated element normally exposed to the pressure obtaining in the transmission tube, controlling means responsive to a predeter mined pressure in the transmission tube for cutting off communication between the main motor and the transmission tube, and means to terminate response of said controlling means to said predetermined pressure.

2. Pneumatic 'despatch apparatus having a transmission tube, an exhanster connected therewith, and a nia-in valve for controlling the iiow 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 having a `pressure sensitive element normally exposed -to the pressure obtaining in ther transmission tube, an auxiliary pneumatic motor having a pressure sensitive element nioi'iircy from normal position upon the occurrence of a predetermined pressure in the transmission tube `thereby to cut oit communication between the tube and main motor, and means to terminate response of the auxiliary motor to such predetermined pressure whereby to permit its pressure sensitive element to return to noi'inal position.

3. Power control apparatus 'tor a pneumatic despatch system having a transmission tube comprising a main valve for controlling carrier propelling air tlow through the tube, a main pneumatic. motor tor operating lthe main valve, said motor having a pressure actuated element responsive to pres sure change in the transmission tube` an auxiliary motor having a pressure sensitive element 4exposed on one side to transmission `tube pressure and normally exposed upon its other side to atmospheric pressure, said element respond-ing to a predetermined pres sure in the transmission tube to cut oV` coinmunication between the main motor and the transmission tube, and means lfor cutting oit` the auxiliary motor from atmospheric pressure.

4. Pneumatic despatch apparatus having a lofi transmission tube, an exhauster connected therewith, 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, anda pneumatic motor for operating the main valve, said motorhaving a pressure sensitive element responsive to pressure change inthe transmission tube incident to insertion oi' a carrier into they transmission tube thereby to open wide the main valve, a controlling valve, an auxiliary pneumatic responsive to pressure drop in the transmission line incident to introduction of a carrier thereby temporarily to close the controlling valve and cut oliC communication between the main motor and tube, and a second auxiliary pneumatic operative to open `said controlling valve again and to hold it open so long as a carrier remains in the tube. c

5. Power control apparatus for a pneumatic despatch system having a transmission tube comprising a main valve for controlling carrier `propelling air flow through the tube, a main pneumatic motor for operatingthe main valve, said vmotor having a pressure actuated element responsive to pressure change in the transmission tube, an auxiliary motor comprisinga casing having chambers separated by `a flexible diaphragm, one of said chambers communicating by `means `oi a restricted passage with the transmission tube and the other communicating by means of a normally open passage with the outer atmosphere, a valve actuable by said diaphragm`A to2 cut 0E communication between the main motor and the transmission tube, a pilot valve for closing said normally open passage, and `means responsive to delivery of a carrier from thetransmission tube to close said pilot valve.

v6. Pneumatic despatch apparatus having a transmission tube, an exhauster connected therewitlnand a main valve for controlling the flow ot air through the transmission tube, a minimum flowof air through the tube being permitted when .the Yvalve is in closed position, and a pneumatic motor for operating the main valve, said motor having a pressure sensitive element responsive to pressure change in the transmission tube,

' an auxiliary motor comprising a casing having chambers separated by a flexible diaphragm, one of said chambers communicating by means of a passage with the transmission tube, adjustable means for varying the eifectivesize of saidpassage, a normally open passageleading yfrom the other of said chambers to the outer atmosphere, an aux' iliary `valve actuable by the diaphragmto cut off communication between the main motor and the transmission tube, a pilot valve for closing said normally open passage, and

a-pneumatic for operating the pilot valve.

7. Pneumatic despatch 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 oiu air through the tube being permitted when the valve is in closed position, and a pneumatic motor yfor operating the main valve,said moto-r having a pressure sensitive element responsive to pressure change in the transmission tube, an. auxiliary motor comprising a casing having chambers separated by a pressure sensitive element, one chamber communicating with the transmission tube and the other communicating by means ot' a normally open passage with the atmosphere, said sensitive element responding to a predetermined pressure in the tube to cut oiil communication between t-he tube and the main motor, and a valve for closing the passage leading from the auxiliary mot-or to the atmosphere.

8. Power control apparatus for a pneumatic. despatch system having a transmission tube comprising a main valve for controlling carrier propelling vair flow through the tube, a main pneumatic motor for operating the main valve, said motor having a pressure actuated element responsive to pressure change in the transmission tube, an auxiliary motor having a diaphragm posed on one side at all times to transmission/line pressure and exposed on its other side, by means of a normally open passage, to the outer atmosphere, there being an opening of small capacity to permit air to pass slowly from one side of the diaphragm to the other, an auxiliary valve connected to the diaphragm and actuable thereby to close communication between'the main motor and the transmission tube, and a valve torclosing said normally open passage.

9. Pneumatic despatchapparatus having a transmission tube, an exhauster connected therewith, and a main valve `for controlling the flow of air through lthe transmission tube, a minimum flow 01"' air through the tube being permitted when the valve is in closed position, and a pneumatic motor for operating the main valve, said motor having a pressure sensitive element responsive to pressure change in the transmission tube, an auxiliary pneumatic forcontrolling the action of the main motor, and a second auxiliary pneumatic controlling the action of the first auxiliary pneumatic.

10.= Power control apparatus for apneumatic despatch system having a transmission tube comprising a main valve for controlling carrier propelling air flow through the tube, a main pneumatic motor for operating the main valve, said motor having a pressure actuated element responsive to lpressure change in the transmissiontube, controlling valve for the main motor, an auxiliary pneumatic for actuating the convla@ trolling valve, a pilot valve-tor determining operation of the auxiliary pneumatic, andf a pressure actuated pneumatic tor actuating'v the pilot valve. A

ll. .Pneumatic despatch apparatus having a transmission tube, an exhauster connected therewith, and a main valve for controlling the iiow of air through the transmission tube, a minimum flow ot' air through the tube being permitted when the valve is in closed position, and a pneumatic motor tor ope ating the main valve, said motor having a pressure sensitive element responsive to pressure change in the transmission tube, an auxiliary motor having a diaphragm exposed on one side to transmission tube pressure and normally exposed on its other side, through a normally open passage, to atmospheric pressure, an auxiliary valve for controlling the main motor, means connecting the auxiliary valve to the diaphragm, a pilot valve for closing said normally open pas` -sage, and a pneumatic for actuating the pilot valve, said pneumatic being exposed on one side to transmission tube pressure and on its other side to atmospheric pressure.

l2. Power control apparatus for a pneumatic despatch system having a transmission tube comprising a main valve for controlling` carrier propelling air flow through the tube, a main pneumatic motor for operating the main valve, said motor having a pressure actuated element responsive to pressure change in the transmission tube, anauxiliary pneumatic for controlling the action of the main motor, and a second auxiliary pneumatic controlling the action of' the first auxiliary pneumatic, each ot said pneumatics being exposed at one side. to transmission tube pressure, one of said' pneumatics responding more. quickly to predetermined pressure change in the transmission tube than the other.

13. Pneumatic despatch apparatus having a transmission tube', an exhauster connectei therewith, and a main valve for controlling the tlow of air through the transmission tube` a minimum flow ot air through thc tube being permitted when thc valve is in closed position, and a pneumatic motor tor operating the main valve, said motor having a pressure sensitive element responsive to pressure change in the transmission tube, a primary auxiliary pneumatic for controlling the action of the main motor. a secondary auxiliary pneumatic controllingl the first auxiliary pneumatic, each of said pneun'iatics being exposed on one side to transmission tube pressure', both ot said pneumatica being responsive to the drop in pressure in the transmission tube incident to opening of the main valve, the secondary pneumatic only being responsive to the slight increase in pressure in the tube incident tfi delivery oi" the last carrier therefrom;

1ste Pneumatic despatch apparatus having a transmission tube, an exhauster connected` therewith, and a main valve for controlling carrier propelling air iiow through the tube, a minimum flow of air through the tube being permittedfwhen the main valve is closed, a main pneumatic motor tor actuating the mainv valve, said motor comprising a casing having chambers separated by a iiexible diaphragm, one ot said chambers always being open to atmospheric pressure and the other communicating by means ot a normally open passage with the transmission tube, a controlling valve for closing said passage, meansl connectingr the diaphragm ot' the main motor toi the main valve, a primary auxiliary pneumatic Tt'or closing thecontrolling valve, and aI secondary auxiliary pneumatic for determining the pressure acting upon one sidefof the primary auxiliary pneumatic.

15. Pneumatic despatch apparatus having a transmission tube, an exhauster connected therewith, and a main valve for cont-rolling carrier propelling air flow through thetube, a minimum How o;t` air through. the tube being permitted when the main valvev is closed, a main pneumatic motor for actuating the main valve, .said motor comprising a casing having chambers separated by ai tlexible diaphragm, one ot said chambersbeing always open to atn'iospheric pressure and the other communicating by means. of a normally open passage with the transmission tube, a controlling valve for closing said passage, means connectingl the diaphragm or' the main motor to: the main valve, means for closing the controlling valve, and an auxiliary pneumatic motor for controlling said valve closing means, said auxiliary motor comprising a casing having chambers separated. by a flexible diaphragm, one of said chambers being always open to the atmosphere and the other communicating with the transmission tube.

1G. Pneumatic despatch apparatus having a transmission tube, an exhauster connected therewith, and a main valve 'for controlling carrier propelling air flow through the tube, aminimum flow it air through the tube being permitted when the main valve is closed, a main pneumatic motor for actuating the main valve, said motor comprising a casing having chambers separated by a flexible diaphragm, one of said chambers being always open to atmospheric pressure and the other conmnicating by means of a normally open passage with the transmission tube. a controlling valve for closing said passage, means connecting the diaphragm ot the main motor to the main valve, a primary auxiliary motor comprising a casing having chambers scparated by a dexible diaphragm, one oi said chambers con'in'iunicating with the transmission tube and the other normally communieating With the outer atmosphere by means of a normally open passage, means connecting the iexible diaphragm of the primary auxiliary motor With the controlling valvel of the main motor, a pilot Valve for closing said last named open passage, and a secondary auxiliary motor for actuating said pilot valve, said secondary motor comprising a casing having chambers separated by a leXible diaphragm, one of said chambers communicating with the transmission tube and the other being open al all times to the outer atmosphere, and means connecting the diaphragm of the secondary motor to the pilot valve.

Signed by me at Syracuse, New York, this twenty-fifth day of March, 1925.

JAMES T. COVLEY.

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