US1944363A

US1944363A - Control device for pneumatic dispatch tube apparatus

Info

Publication number: US1944363A
Application number: US414279A
Authority: US
Inventors: Olson Samuel
Original assignee: G & G Atlas Systems Inc
Current assignee: G & G Atlas Systems Inc
Priority date: 1929-12-16
Filing date: 1929-12-16
Publication date: 1934-01-23
Anticipated expiration: 1951-01-23

Description

Jan. 23, 1934. s OLSON 1,944,363

CONTROL DEVICE FOR PNEUMATIC DISPATCH TUBE APPARATUS 3 Sheets-Sheet 1 Filed Dec. 16, 1929 /l/l/ l 4] 5a zze/0 010.

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8 //I/// III Ill/l Jan. 23, 1934. s. OLSON 1,944,363

CONTROL DEVICE FOR PNEUMATIC DISPATCH TUBE APPARATUS Filed Dec. 16, 1929 3 Sheets-Sheet 2 .4 Is -2% J6 f 4 I 6 2 5 S j 4 l 61 H i K52 5 Jan. 23, 1934. OLSON 1,944,363

CONTROL DEVICE FOR PNEUMATIC DISPATCH TUBE APPARATUS Filed'Dec. 16. 1929 3 Sheets-Sheet 3 a4 l 1; :::'J 173 1 6E, 116 113 D 116 61 66 5 106 9 110 86 r 117 //J J09 J08 l 86 104.

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Patented Jan. 23, 1934 UNITED STATES CONTROL DEVICE FOR PNEUMATIC DISPATCH TUBE APPARATUS Samuel Olson, Oak Park, Ill., assignor, by mesne assignments, to G & G Atlas Systems, Inc., New York, N. Y., a corporation of New York Application December 16, 1929 Serial No. 414,279

26 Claims.

This invention pertains to control devices for pneumatic dispatch tube apparatus for regulating the air fiow through the system, and more particularly to automatically actuated devices adapted for use in connection with systems of the minimum flow or partial flow type, in which a reduced flow of air is normally permitted through the tubes when no carriers are in transit,

which automatically increases to full carrier-impelling air flow upon the introduction of a carrier in the tube, and then automatically reduces to minimum flow after the last carrier therein has been discharged.

The control devices now in general use consurne a certain amount of time in opening and closing; the closing of the device usually being effected by a timing mechanism, thus requiring the device to be kept open to full flow for a predetermined period after discharge of the carrier from the tube, resulting in waste of power.

One of the objects of this invention is to produce an improved controlling device of simplified and relatively compact construction, which will conserve and effect a substantial saving of power. Another object is to produce a device of the character mentioned in which the valve proper is relatively sensitive, so as to be opened and permit full carrier impelling air flow in the transmission tube almost instantaneously upon the insertion of a carrier in said tube, and likewise being instantaneously responsive for closing and shutting off the full carrier-impelling air flow in the transmission tube upon the discharge of the carrier from said tube.

A further object is to provide an improved control device in which the valve proper is arranged for opening by the direct action of the increased suction thereon, resulting from the introduction of a carrier in the transmission tube. A still further object is to provide an improved control device in which the valve proper is arranged for response to the direct action thereon of pressure variations in the transmission tube for causing opening and closing thereof. And still another object of this invention resides in the provision of an improved control device operative when there is no suction in the tubes for insuring positive closure of the valve at such times. The invention consists in certain elements and features of construction in combination, as herein shown and described as indicated by the claims.

In the drawings:

Figure l is a view illustrating somewhat diagrammatically a pneumatic dispatch system employing a control device embodying the present invention.

Figure 2 is a sectional view of a relatively simple of .the operating elements in a position assumed when there is only a minimum flow of air through the tubes. Figure 5 is a sectional view through another modified form of control device.

Figure 6 is a sectional View of still another modified construction, taken substantially at a medial plane.

Figure 7 is a sectional view of a still further modified construction, taken substantially at a medial plane; and

Figure 8 is a fragmentary sectional view taken as indicated at line 8-8 on Figure '7.

With reference to the diagrammatic illustration of the pneumatic dispatch system shown in Figure 1, the apparatus includes a suction or vacuum drum, 1, connected by an exhaust tube, 2, to the casing of the control device indicated generally at 3, and connected to the opposite side of the control device is a pipe, 4, which is connected directly to the transmission tube, 5. may be understood that, for convenience, any subsequent reference (in the description or claims) to the transmission tube, also includes the extension pipe, 4. The end of the transmission tube, 5, at the remote station is provided with a flap closure, 6, through which car- I riers may be inserted for transit and discharge at the opposite end through the spring actuated closure flap, '7, at the central station which is usually located adjacent the source of suction. To complete the system a second transmission tube, 9, is shown extending parallel to the transmission tube, 5, and provided with a bell-shaped mouth, 10, for entry of carriers, adjacent the discharge end of the transmission tube, 5, at the central station, and it is provided at its opposite end at the remote station with a springactuated closure flap, 11, through which the carriers are discharged. The ends of the transmission tubes, 5 and 9, at the remote station, are connected'together by a coupling indicated at 12, thus forming in effect, a continuous single tube for the purpose of maintaining continuous suction in both tubes for the movement of carriers in either direction. The continuous suction in the tube circuit may be broken by opening of the closure flap, 6, for introduction of a. carrier, or by the opening of either of the closure flaps, '7 or 11, upon discharge of carriers from the transmission tubes, 5 or 9, respectively.

In systems of this kind it may be understood that the suction drum, 1, is connected to a suitable compressor or pump for maintaining the drum under a predetermined, reduced pressure or vacuum. In all of the forms of control device herein illustrated, the main feature, common to all the constructions, resides in the provision of a valve member which is directly acted upon for opening by the reduced pressure in the transmission tube caused by the insertion of a carrier in said tube. Another feature common to all constructions illustrated, is the utilization of the follow-up blast or gust of air in the transmission tube, resulting from the discharge of the carrier from the tube for directly acting upon the valve for closing it. A still further feature common to all these constructions resides in the particular arrangement of the vital elements which permits dispensing with all forms of timing mechanisms which have been an inherent part of practically all controlling devices heretofore.

Referring now particularly to the construction illustrated in Figure 2 of the drawings, the control device includes a casing, 15, formed with a valve port, 16, substantially the same size and in approximate registration with the tube, 4, connected to the transmission tube, 5. Co-operating with the valve port is a disk type valve member, 1'7, disposed perpendicularly to the path of air iiow and rigidly secured to a reciprocating valve stem, 18, which is guided at its lower end in a hollow boss formation, 19, and at its upper end in a bearing, 20, formed in the spider, 21, carried by the coverplate, 22, of the casing, 15.

Circumscribing the lower portion of the valve stem, 18, is a compression spring, 23, reacting between the stop disk, 18 on the stern and the boss formation, 19. It is to be understood that this spring is relatively light and exerts a substantially uniform pressure, and by virtue of its location, normally tends to move the valve member in an upward direction for opening. The casing, 15, is provided with the usual partial flow vent consisting of an aperture, 24, opening into the lower part of the casing, and provided with an adjusting screw, 25, for varying the effective area of said opening. This opening, 24, is connected by a passageway, 26, to the transmission tube, thus by-passing the valve proper.

To assist in relieving the impact of the valve member as it engages its seat, it is preferable to provide a yielding member to act as a buffer. For this purpose I form a flange, 28, on the lower end of the valve stem which reacts against a spherical form of resilient body, 29, such as rubber which is housed in the hollow boss formation, 19, and seated in a bracket, 30. An adjusting screw, 31, is provided in the bracket, so,

andengages a disk, 32, which is in contact with the resilient body, 29, by means of which said body may be moved relatively to the end of the valve stem, 18, for obtaining accurate cushioning effect and seating of the valve member.

The operation of this control device is as follows:

When there is no carrier in the transmission tubes, a minimum flow of air is permitted through the tubes by reason of the bleed aperture, 24, connecting the exhaust tube with the transmission tube, and the effect of the suction on the under side of the valve member, 17, is sufficient to maintain said valve member on its '1 seat against the reaction of the coil spring, 23,

When a carrier is inserted in the transmission tube, the pressure therein is reduced by reason of the minimum air flow until the suction on t -e upper side of the valve member partially offsets the eifect of the reduced pressure acting on the under side of the valve member, and by the spring, 23, the

valve member is caused to move upwardly to the open position indicated in dotted lines, thus admitting full suction and producing the carrierimpelling air flow in the transmission tube, for swiftly moving the carrier therein to its destination.

Imm diately upon discharge of the carrier from the transmission tube, the sudden venting of the transmission tube to atmospheric pressure causes a relatively heavy gust or blast of air which.

impinges directly against the valve member, 17, and forces it to its seat, and once this valve member is in contact with its seat and overcomes the reaction of the spring, 23, it is held in closed position by the suction to which the under side of the valve member is subjected by the exhaust tube. To obtain maximum benefit of the force exerted by this heavy air blast or gust of air following discharge of the carrier in the transmission tube, I preferably employ a valve member of valve member, will tend to assist in moving it to its full open position.

In the modified construction shown in Figures 3 and 4, the control device includes a cylindrical casing, 35, formed with a port, 36, in registration with the tube, 4, and with an inclined seat, g

37, surrounding said port. is a disk type valve member, 38, disposed perpendicularly to the path of air flow in the tube, 4. Connected to the valve member is a reciprocating stem, 39, journaled adjacent its center in Controlling the port a spider, 40, formed integral with the casing, 35,

and guided at its lower end in a spider, 41, which is secured to the lower end of the casing, 35, in the assembly of the device.

Secured to the casing, 35, below the spider, 41, and substantially concentric with the valve stem is a pneumatic, 42, having secured on the inner side adjacent its center an annular cup-shaped bearing, 43, whose outer periphery is formed to seat a cylindrical thimble, 44, which is provided with slots, 45, for straddling the arm, 41 of the spider, 41, to accommodate movement of said thimble by the pneumatic as it is buckled in opposite directions. The inner side of the pneumatic is subject to the reduced pressure in the exhaust tube, 2, and at its other side to atmospheric pressure; a cap plate, 35 being provided merely as protection of the pneumatic against injury.

Encompassing the upper portion of the valve stem, 39, and reacting against the upper side of the spider, 40, and the under side of the valve member, 38, is a compression spring, 46, of relatively light material and of just sufiicient strength to offset the weight of the valve and its associated parts for cracking the same off its seat to open it, when there are no counteracting forces. Encompassing the lower end of the valve stem is another compression spring, 47, which is seated on the thimble, 44, at its lower end and acts at its upper end against the spider, 40. This spring, 47, is slightly heavier than the spring, 46, and is adapted to offset the effect of the spring, 46, when there is no suction in the tubes.

The lower end of the valve stem is provided with stop nuts, 48, disposed within the thimble, 44, which act as a shoulder against which said thimble engages for positively moving the valve to its closed position when all suction is shut off in the system. Another stop shoulder in the form of a nut, 49, is disposed on the valve stem slightly below the spider, 40, and is adapted to engage the under side of said spider for limiting the valve in its opening movement. The casing, 35, is provided with apertures, and 51, and an adjusting screw, 52, for varying the effective size of the opening of the aperture, 50, by means of which a minimum flow of air is permitted through the transmission tubes and exhaust tube.

The operation of the device illustrated in Figures 3 and 4 is substantially as follows:

When there is minimum flow of air through the tubes, the pneumatic, 42, is buckled inwardly to the position indicated in Figure 4, compressing the coil spring, 47, by moving the thimble upwardly away from the stop nuts, 48, on the valve stem, thus allowing substantial clearance for movement of the valve stem without obstruction by the thimble, 44. In this position the spring, 47-,

' exerts no force whatever on the valve stem and the diiferential pressure on the valve member, i. e., the suction on the under side and approximately atmospheric pressure on the upperside, is sufiicient to hold the valve seated against the reaction of the spring, 46.

When a carrier is inserted in the line, it causes a reduction in pressure in the transmission tube, which pressure acting directly on the upper surface of the valve member, together with the pressure exerted by the spring, 46, offsets the suction on the under side of the valve member and causes said valve member to be forced off its seat and moved to full open position, permitting full suction to the transmission tube for impelling the carrier to its destination. In substantially the same manner as the construction shown in Figure 2, the inclined seat, 37, assists in moving the valve member, 38, to open position; and said valve member being of relatively large area, is caused to be moved to its seat by the heavy air blast in the transmission tube resulting from the discharge of the carrier, this blast by impinging directly on the upper surface of said valve member, causing it to close against the reaction of the spring, 46. After the valve member has been seated, the suction acting upon the under side thereof will tend to hold it to its seat. It is apparent that by reason of the pneumatic, 42, the spring, 47, rendered ineffective during the entire period that there is any suction whatsoever in the tubes of the system. However, when suction is compl tely shut off, the pressure in the interior of the casing, 35, increases, approximating atmospheric pressure. This increased pressure upon the inner surface of the pneumatic, acting with the spring, 47, is sufficient to overcome the atmospheric pressure on the outer side of the pneumatic, and the pneumatic buckles outwardly, causing the thimble, 44, to engage the stop nuts, 48, on the valve stem and positively hold or move the valve member to its seat. This feature of construction is considered relatively important because it has been found practical that the exhaust apparatus employed in systems consisting of a large number of transmission tubes-need only be capable of producing full carrier-impelling suction for approximately 46% to of the total requirement for all the tubes if they were functioning simultaneously. Hence it is necessary that the valves of the control devices be positively closed after the source of suction is shut down so that upon starting up the motive power for creating the necessary suction again the suctiomproducing apparatus will not be overloaded. It is apparent that if the majority of the valve members were permitted to stand open upon shutting off of all suction in the system, it would be necessary in starting up, to create a suction. considerably in excess of the capacity of the source of suction normally employed to operate the system.

Figure 5 illustrates another modified construction which consists of a casing, 60, formed with a port, 61, registering with the tube, 4, connecting to the. transmission tube, 5; the seat surrounding the port is inclined, as seen at 62, and is furnished with a disk type valve member, 63, which has an area considerably greater than that of the port, 61. Secured to the valve member is a reciprocating valve stem, 64, which extends through and is guided in a casing cap plate, 69, and also (at its outer end) in a tie bar, 65, connected by tie bolts, 66, to the cap plate. Disposed in the lower portion of the casing is a pneumatic, 67, which is directly connected to the valve stem and exposed at one side to the suction in the exhaust tube, 2, and at its other side to the atmospheric pressure through the apertures, 68, formed in the cap plate, 69. Exterior of the casing and encompassing the valve stem are two coil springs, and 71, respectively, the former reacting between the casing cap and a stop, 72, on the valve stem and the latter reacting between the clamp plate, 65, and the stop, 73, on the valve stem. The spring, 70, reacts in a direction for maintaining the valve member against its seat and is adapted to exert suflicient force for substantially counteracting the effect of the pneumatic, 67, on the valve stem while the coil spring, 71, is relatively light and is adapted for exerting pressure for moving the valve member to its open position. The casing is also provided with apertures, and 76, and an adjusting screw, 77, for controlling the effective size of aperture, 75, by

means of which a minimum flow of air is permitted through the transmission tubes.

The operation of this construction is substantially as follows:

It is to be understood that the valve proper,

and its seat formation, function in substantially the same manner for opening and closing of the valve as in the constructions disclosed in Figures 2 to 4 inclusive. And the purpose of the pneumatic, 67, is substantially the same as the pneumatic, 42, in the constructions shown in Figures 3 and 4; that is, it permits the use of the spring, 70, for positively closing the valve member when till all suction in the system is shut off.

When there is a minimum flow of air through the tubes, the reduced pressure in the casing, 60, acting on the pneumatic, 67, exerts a force in direct opposition to that of the spring, 76. Said spring tends to hold the valve, 63, in closed position, but the effect of suction in the casing,

60, is to negative the retaining force of the 71, exerted against the valve, 63, through its 5 However, the same suction acts upon stem, 64. After a carrier is inserted in the transmission tube, the pressure therein is rapidly diminished by exhaustion of air through the minimum iiow port, until the pressure acting on the upper sunrface of the valve, 63, is reduced to such an extent as to offset the suction on the under cf the valve, so that the pressure of the spring, 71, is able to move the valve to its open position and hold it there, permitting a full flow of air through the transmission tube for impelling the carrier therein. I

When the carrier is discharged from the tube, the resultant gust or blast of air which follows up the tube impinges against the upper surface of the valve, 63, forces the valve to its seat in opposition to the relatively light resistance of the spring, '71; and once seated, the valve is held in this position by the suction within the casing, 69, as before. In the event of shutting down the entire suction apparatus of the system, the pressure in the casing, 60, becomes atmospheric pressure, thus equalizing with the pressure on the outer side of the diaphragm, 67, and permitting the spring, 70, to come into action to positively hold the valve in closed position.

Figure 6 illustrates a further refinement of the primary features of my invention. In this construction, the casing, 80, is provided with a port, 81, approximate registration with the transmission tube, 4, and also formed with an inclined seat, 82, surrounding the port, for the purpose previously men ioned. Co-operating with the port is a multiple valve consisting of a main valve member, 83, and a pilot valve member, 84. The main valve member is just slightly larger in area than the port, 81, and is provided with radially spaced downwardly projecting ribs, 85, which merge into a threaded boss, 86, in which is supported a guide sleeve, 86 The main valve member is also provided with a centrally located reduced port, 87, which is only a fraction of the area of the main port, 81, and is provided with a seat, 88, with which co-operates the auxiliary or pilot valve, 84. i

The pilot valve, 84, which is also of disk type, is or" a relatively large area substantially greater than the port, 81, which permits the final blast of air to move valve members to their seats in substantially the same manner as in the constructions above described. This pilot orauxiliary valve member is connected to a stem, 89,, slidably journaled in the sleeve, 86*, and extendthrough the cover plate, 90, of the casing; said stem is guided at its outer end in a plate, 91, which. is rigidly supported by tie rods, 92, connecting the plate to the cover plate, 90.

Enoompassing the valve stem, 89, outside the casing are coil springs, 93 and 94, the former reacting between the casin plate, 90, and the s stop, 95, on the valve stem, and the latter reacting between the tie plate, 91, and the stop, 96, on said vaive stem. The spring, 93, reacts in a direction to hold the valve members on their respective seats while the spring, 94, works in opposition to the spring, 93, and exerts a force in a direction tending to move the pilot or auxiliary valve off its seat. It may be understood that the springs, 93 and 94, are substantially balanced.

against each other when the valve members are in open position; consequently, if. there were no other influencing forces, and the suction in the system completely shut off, these springs would normally tend to approach their balanced position-holding the main valve member open.

Thus when the valve members are caused to be seated by forces hereinafter described, the tension in the spring, 93, is. relieved, rendering it practically ineffective; while the spring, 94, is compressed, building up its pressure.

To insure against imperfect operation of the mechanism by leakage around the valve stem through the cover plate, 90, I employ a casing, 97, completely housing the projecting valve stem and the springs, 93 and 94. Provided at the outer end of the casing, 9'7, is a bracket, 98, in which is seated a spherical resilient element, 99, such as rubber, adapted to be engaged by the flange, 100, carried on the end of the valve stem as the valves approach seating position. The bracket member is also provided with an adjusting screw, 101, co-operating with the plate, 102, which is in contact with the opposite side of the resilient sphere, 99, for adjusting the same relatively to the flange on the valve stem for insuring correct cushioning action;

The valve casing is also provided with apertures, 104 and 105, respectively, and an adjusting screw, 106, for varying the effective size of the apertures, 104, by means of which a minimum flow of air is permitted through the system for the purpose indicated.

Fulcrumed at 108 on the inside of said casing, 80, is a lever, 109, which is provided with a forked end engaging a stop shoulder, 110, on the valve stem, 89, while the opposite end of said lever operates between the stop shoulders, 111, on the lower end of a reciprocating stem, 112, which is directly connected to a pneumatic, 113, mounted laterally with respect to the valve members. The pneumatic, 113, is exposed on one side to the pressure in the exhaust tube, 2, and at its other side to atmospheric pressure through openings, 114, in the plate, 115. A coil spring, 116, encompasses the stem, 112, and reacts against a shelf member, 117, of the casing and against a stop, 118, on the stem, 112, and normally tending to move the stem upwardly and urge the pilot or auxiliary valve in a direction for closing.

The operation of the construction disclosed in Figure 6 is as follows:

When the suction producing apparatus is operating the pneumatic, 113, is caused to buckle inwardly, thereby swinging the lever, 109, about its fulcrum, 108, swinging the inner end of the arm of said lever away from the stop shoulder, 110, on the valve stem, and said lever is caused to remain in such inoperative position so long as the suction is maintained. When there is a minimum flow of air through the tubes, the valve members are held to their seats by the diiierential pressures thereon, that is, a relatively high pressure acting on the upper surfaces of the valve members, and low pressure or high suction acting on the under surfaces of the valve members; the resultant pressure being sufficient to ofiset the spring, 94, and hold the valve members to their seats. After a carrier is inserted in the transmission tube, the reduced pressure in the transmission tube will act directly upon theupper surface of the pilot valve, 84, and by reason of the fact that there is such a relatively small part of its area (defined by the port, 8'7) exposed to the suction in the exhaust tube, the pilot valve by the assistance of the spring, 94, will be quickly cracked off its seat.

This now allows partial equalization of pressure on opposite sides of the main valve, 83, so that the suction on its under side is no longer effective to hold it seated, and the spring, 94, acting through the valve stem, 89, and its crosspin, 119, lifts the valve, 83, 01f its seat. In fact, the action may occur so rapidly that the opening movement of pilot valve, 184, operates through the stem and cross-pin, 119, to practically jerk the valve, 83, off its seat. The heavy air blast resulting from the discharge of the carrier from the transmission tube will be caused to impinge against the relatively large area of the pilot or auxiliary valve, 84, and force it in a downward direction, and in doing so by reason of the engagement of said pilot valve with the seat, 88, on the main valve, said main valve is simultaneously forced to its seat; the valve members being held seated by the suction on the under side thereof, and the device is in condition for repeating the cycle.

In the event that the entire suction is shut on by reason of the minimum flow, the pres: sure in the chamber, 80, will gradually approximate atmospheric pressure, and the eifect of this pressure on the inner side of the pneumatic, 113, together with the coil spring, 116, will force the pneumatic, 113, to buckle outwardly as illustrated in Figure 6 of the drawings, swinging the lever, 103, about its fulcrum, 108, for positively moving the valve members to their seats and holding them in such position until suctionis again restored to the system. r

In the modified construction illustrated in Figures 7 and 8, the casing, 125 is formed in the usual manner for connection to the exhaust tube, 2, and transmission tube. The casing is provided with a valve port, 126, disposedin substantial registration with the transmission tube, and

is provided with a disk valve member, 127, for

controlling said port. Connected to the valve member is a stem, 128 reduced at its upper end and'slidably guided in an adjustable spider, 129, carried by adjusting screws, 130, suspended from the casing cap, 131. The lower end of thestem has a telescopic connection with a rod, 133, of

a pneumatic, 134, disposed in the casing opposite the valve, 127; said connection including a central bore, 135, in the end of the stem, in which is slidable the reduced end, 1333, of the rod, 133, for insuring guidance for the respective ends of said stem and rod of the pneumatic, The rod, 133, extends beyond said pneumatic and is guided in two spaced bearings, 136 and 137, formed in the protector plate, 138,. of the casing and serves to house the pneumatic. Said pneumatic is sub-v jected on one side to atmospheric pressure by the openings, 139, in the plate, 138, and at the other side to the exhaust tube pressure.

Reacting between the pneumatic, 134, and a stop nut, 141, on the lower end of the stem, is a coil spring, 142, tending to separate the stem and rod, 133, and unseat the, valve member, 127; the nut, 141, being threaded on the stem permits 5 i its being adjusted for varying the tension spring,

' the force exerted by the spring, 143.

142. Encompassing the upper end of the valve stem is a coil spring, 143, acting between the valve member and the spider, 129. This spider is adjustable relative to the valve memberfor varying This adjustment is effected by thescrews, l30,'which are threaded through the arms, 129, of the spider, and have their heads engage against the under side of lugs, 145, of a ring, 146, interposed between the casing and cap, 131. For facilitating the adjustment, the upper ends of the screws areprovided with slots, 130 for engagement by a screw driver or other tool. It will be understood that .any other suitable form of adjustment may be substituted if desired. I

The valve casing is provided with apertures, 147 and 148, respectively, and an adjusting screw, 149, for varying the eifectivesize of the aperture, 147, by means of which apertures a .minimum flow of air is permitted through the tubes, for the purpose of initiating opening of the valve as will presently be seen.

The operation of the device shown in Figures 7 and 8 is substantially as follows:

In the drawings, the parts are shown in the position assumed when there is no suction at all in the system. It will be manifest that under a condition the side of the pneumatic normally subjected to the pressure in the exhaust tube aproximates atmospheric pressure and the spring, 142, is permitted to extend and cause the pneumatic to buckle outwardly. The spring, 142, then has practically'no eiiect on the valve stem, 128, and the spring, 143, positively holds the valve member, 127, to its seat. When there is aminimum or restricted flow of air through the system,

the pneumatic, 134, is drawn inwardly, compress: ing spring, 142, which in turn imparts this increased tension to the valve stem in the direction for opening the valve member. It is to be understood that when spring, 142, is so compressed the force exerted on the stem in valve opening direction is just slightly more than the counter force of the spring, 143. However, since there is a differential pressure acting on the valve,.(that is i substantially atmospheric on upper side, and exhaust tube pressure on the other), the valve member is held seated. When a carrier is introduced in the transmission tube, the pressure on the upper side of the valve member is reduced, so that when this pressure decreases to a'point at which it, together with the resultant spring pressure, overcomes the suction on the under side of the valve member and causes it .to move to open position ;--to permit full carrier-impelling air flow in the transmission tube. The valve member, 127, as in the construction previously'described, is of an area considerably greater than its port, 126, so that it will receive substantially full impact of the sudden rush of air following up the transmission tube incident to the discharge of the last carrier therefrom, for forcing the valve member to its seat, and when once seated, the suction action on the under side of the valve member holdsit seated.

It will be understood that the resilient element disclosed in connection with the constructions shown in Figures 2 and 6 may be readily adapted to the other constructions illustrated, but for the purpose of simplicity it is shown only in certain of said constructions.

I claim:-

1. In a pneumatic dispatch system of the minimum flow type, a transmission tube, an exhaust tube connected to a source of suction, and a normally closed control valve interposed between the tubes for regulating the flow of air therethrough, a minimum flow of air being permitted when the valve is closed, said valve being arranged for opening by the direct action of the change in suction resulting from the introduction or" a carrier in the transmission tube, spring means normally tending to open the valve and adapted for holding it open during the transit of a carrier in the tube, and means for adjusting the spring for varying the force exerted thereby.

2. In a pneumatic dispatch system of the minimum flow-type, a transmission tube, an exhaust tube connected to a source of suction, and a normally closed control device connecting the tubes 1 50 for regulating the air flow therethrough, a minimum flow of air being permitted through the tubes when the control device is closed, said control device including a valve member and a seat therefor, means normally tending to move the valve member to open position, and yielding means arranged to act as a bufier for cushioning the impact of the valve member as it approaches its seat, said valve member being adapted for movement in closing direction by the direct impingement of the increased air pressure thereon caused by the discharge of a carrier from the transmission tube.

3. In a pneumatic dispatch system of the minimum flow type, a transmission tube, an exhaust tube connected to a source of suction, and a normally closed control device interposed between the tubesfor regulating the flow of air therethrough, a minimum flow of air being permitted through the tubes when the control device is closed, said device including a reciprocating valve member movable substantially parallel with the direction of flow of air in the transmission tube and normally held to its seat by the suction acting directly on the under side thereof, said valve being arranged for movement in opening direction by the direct action of the increased suction acting on the upper side of said valve member resulting from the introduction of a carrier in said tube.

4. In a pneumatic dispatch system of the minimum flow type, a transmission tube, an exhaust tube connected to a source of suction, and a normally closed control device for governing the carrier-impelling flow of air through the tubes, a minimum flow of air being permitted through the tubes when the control device is closed, said control device including a valve member, a seat therefor, and a spring normally tending to move the valve member off its seat, said valve member comprising a disk disposed substantially centrally of and in a plane perpendicular to the path of air flowing in the transmission tube and having an area substantially greater than that of the port over which it seats, said valve member being arranged for movement in opening direction by the direct action of the increased suction thereon caused by the introduction of a carrier in the transmission tube, and adapted to be closed against the reaction of said spring, by the direct impingement of the air current thereon resulting from the discharge of the carrier from the tube.

5. In a pneumatic dispatch system of the minimum flow type, a transmission tube, an exhaust tube connected to a source of suction, and a normally closed control device for governingv the carrier-impelling flow of air through the tubes, a minimum flow of air being permitted through the tubes when the control device is closed, said control device including a reciprocatory valve member and a seat therefor, a stem associated with said member, a spring encompassing said stem and normally tending to move the valve member to open position, a resilient member engageable with a stop surface on the stem for cushioning the impact of the valve member as it approaches its seat, the valve member being directly responsive to pressure variations in the transmission tube for eiiecting the opening and closing of said valve member.

6. In a pneumatic dispatch system of the minimum flow type, a transmission tube, an exhaust tube connected to a source of suction, and a normally closed control device interposed between the tubes for regulating the flow of air therethrough, a minimum flow of air being permitted through the tubes when the device is closed, said device including a reciprocatory valve member and a seat therefor, a stem connected at one end to said valve member, a spring normally tending to move the valve member to open position, said valve member being adapted for movement in opening direction by the direct action of the increased suction in the transmission tube resulting from the introduction of a carrier therein, and a resilient body adapted to be engaged by the other end of the stem for cushioning the impact of the valve member as it approaches its seat.

7. In a pneumatic dispatch system, a transmission tube, an exhaust tube connected to a source of suction, and a normally closed valve for regulating the flow of air through said transmission tube, a minimum flow of air being permitted through the tubes when the valve is closed, a spring, eiiective for maintaining said valve closed only when there is nosuction in the tubes, and a pneumatic adapted for rendering said spring substantially inefiective during said minimum flow of air through the tubes.

8. In a pneumatic dispatch system, a transmission tube, an exhaust tube connected to a source of suction, and a normally closed valve for regulating the flow of air through said transmission tube, a minimum flow of air being permitted through the tubes when the valve is closed, a spring normally tending to open the valve and adapted for holding it open during transit of a carrier in the tube, said valve being arranged for opening in direct response to increased suction in the transmission tube resulting from the introduction of a carrier therein, and means adapted to positively cause closure of the valve when there is no suction in the tubes.

9. In a pneumatic dispatch system, a transmission tube, and exhaust tube connected to a source of suction, and a normally closed valve for regulating the flow or" air through said transmission tube, a minimum flow of air being permitted through the tubes when the valve is closed, a spring normally tending to open the valve and adapted for holding it open during transit of a carrier in the tube, said valve being arranged for opening in direct response to increased suction in the transmission tube resulting from the introduction of a carrier therein, a spring effective onlywhen there is no suction in the line for maintaining the valve closed, and a pneumatic responsive to suction in the tubes for counteracting the pressure exerted by said last mentioned spring to permit said valve to be opened.

10. In a pneumatic dispatch system, a transmission tube, an exhaust tube connected to a source of suction, and a normally closed valve for regulating the flow of air through the tubes, a

minimum flow of air being permitted through the tubes when the valve is closed, a spring normally tending to move the valve to open position, a pneumatic exposed to atmosphere at one side and to the pressure in the exhaust tube at the other, and means controlled by said pneumatic for causing closing of the valve against the reaction of the spring when there is no suction in the exhaust tube.

11. In a pneumatic dispatch system, a transmission tube, an exhaust tube connected to a source of suction, and a normally closed control device connecting said tubes and adapted for governing the flow of air through the system, a minimum flow of air being permitted through the tubes when the control device is closed, said device including a reciprocatory valve member and a seat therefor, a guided stem associated with the valve, a spring normally tending to move the valve member oil its seat, a pneumatic connected to the stem and exposed at one side to atmosphere and at the other side to the exhaust tube pressure, and means controlled by the pneumatic for moving the valve to its seat when there is no suction in the tubes.

12. In a pneumatic dispatch system, a transmission tube, an exhaust tube connected to a source of suction, a normally closed control device connecting said tubes and adapted for regulating the flow of air therein, a minimum flow of air being permitted through the tubes when the control device is closed, said control device including a valve member, spring means normally tending to move the valve member to open position, said valve member being held to its seat against the reaction of said spring means by the suction in the exhaust tube acting on the under side of said valve member, and arranged for opening in response to the direct action on the upper side thereof by the increased suction in the transmission tube, resulting from the insertion of a carrier therein, and means arranged to positively close said valve member when there is no suction in the tubes.

13. In a pneumatic dispatch system of the minimum flow type, a transmission tube, an exhaust tube connected to a source of suction, and a normally closed control valve interposed between the tubes ior regulating the flow of air therethrough, a minimum ilow of air being permitted when the valve is closed, said valve being directly responsive to pressure variations in the transmission tube for causing opening and closing thereof, and means arranged for positively closing said valve when there is no suction in the tubes.

14. In a pneumatic dispatch tube system, a transmission tube, an exhaust tube connected to a source of suction, a normally closed control device connecting said tubes and adapted for governing the air flow therein, a minimum flow of air being permitted when the control device is closed, said device including a reciprocatory valve member of the disk type disposed perpendicularly to and in registration with the transmission tube, a valve stem connected to the valve member, a spring normally tending to move the valve member to open position, means acting to hold the valve member seated against the reaction of the spring, said means including a spring member, and a pneumatic associated therewith, said pneumatic being exposed on one side to atmospheric pressure and on the other side to the pressure in the exhaust tube, and adapted to render the second mentioned spring member ineffective when there is suction in the tubes, whereby the increased suction in the transmission tube resulting from the in'lroduction of a carrier which acts directly upon said valve member causes it tornove to open position, and the increased pressure in the transmission tube resulting from the dis- :harge of the carrier therefrom impinges against said valve member and forces it to its seat.

15. In a pneumatic dispatch tube system, a transmission tube, an exhaust tube connected to a source of suction, a normally closed control device connecting said tubes and adapted for governing the air flow therein, a minimum flow of air being permitted when the control device is closed, said device including a reciprocatory valve member of the disk type disposed perpendicularly to and in registration with the transmission tube, a valve stem connected to the valve member, a spring arranged for acting on the stem, tending to hold the valve member seated, and a pneumatic mounted independently or" the stem and arranged for reacting on the spring to relieve the stem of all pressure exerted thereby when there is suction in the tubes.

16. In a pneumatic dispatch tube system, a transmission tube, an exhaust lube connected to a source of suction, a normally closed control device connecting said tubes and adapted for governing the air flow therein, a minimum flow of air being permitted when the control device is closed, said device including a reciprocatory valve member of the disk type disposed perpendicularly to and in registration with the transmission tube, a valve stem connected to thevalve member, a spring encompassing the stem and adapted to engage a stop shoulder thereon for moving the valve member to its seat, and a pneumatic mounted independenlly of and concentric with the stem, provided with a seat for the end of the spring adjacent the stop, said pneumatic being adapted when there is suction in the tubes to move said spring out of engagement with the stop on the stem, permitting the valve member to be opened, and adapted when there is no suetion in the tubes to permit the spring to engage the stop for moving the valve member to its seat.

17. In a pneumatic dispatch tube system, a transmission tube, an exhaust tube connected to a source of suction, a normally closed control device connecting said tubes and adapted for governing the air flow therein, a minimum flow of air being permitted when the control device is closed, said device including a reciprocatory valve member of the disk type disposed perpendicularly to and in registration with the transmission tube, a valve stem connected to the valve member, a spring engaging a slop on the stem, normally tending to move the valve member to open position, a second spring acting against a stop on the stem tending to close the valve member, and a pneumatic connected to the valve stem, adapted when there is suction in the tubes to counteract the last mentioned spring, for permitting the first mentioned spring to move the valve member to open position when the suction in the transmission tube is increased by the introduction of a carrier therein.

18. Ina pneumatic dispatch system, a transmission tube, an exhaust tube connected to a source of suction, a normally closed control de vice connecting said tubes and adapted for regulating the flow of air therethrough, a minimum flow of air being permitted through the tubes when the control device 'is closed, said device including a casing, having a valve seat therein disposed in substantial registration with the opening of the transmission tube, a reciprocatory valve member, a valve stem connected to the valve member, a spring normally tending to move the valve member off its seat, a lever fulcrumed in the casing and havingat one end a one-way connection with the valve stem for moving the valve member toward its seat, a spring normally tending to swing the lever in valve closing direction, and a pneumatic adapted to counteract the effect of said last mentioned spring for causing the lever to disengage the valve stem when there is suction in the tubes, thus permitting the valve member to be opened by the first mentioned spring after the suction in the transmission tube is increased by the introduction of a carrier therein.

19. In a pneumatic dispatch system, a transmission tube, an exhaust tube connected to a source of suction, a normally closed control device connecting said tubes and adapted for regulating the fiOW of air therethrough, a minimum flow of air being permitted through the tubes when the control device is closed, said device including a casing, having a valve seat therein disposed in substantial registration with the opening of the transmission tube, a main valve member associated with the seat and having a sleeve connected thereto, said main valve member being formed with a reduced port opening and auxiliary seat, an auxiliary valve member for the port in the main valve member, a stem connected thereto and extending through the sleeve, a spring acting on the stem tending to hold the auxiliary valve member on its seat, said auxiliary valve member being arranged for opening by the direct action of the increased suction thereon resulting from the insertion of a carrier in the "ransmission tube, and a one-way connection between the stem and sleeve for causing opening of the main valve member after the auxiliaryvalve has been moved off its seat, for opening the transmission line to full carrierimpelling suction.

2o. In the combination defined in claim 19, said auxiliary valve having an area greater than the port of the 'main valve, whereby the increased flow of air caused by the discharge of a carrier will impinge thereagainst and serve to move it toward its seat.

21. In the combination defined in claim 19, said auxiliary valve having an area greater than the port of the main valve, whereby the increased flow of air caused by the discharge of a carrier will impinge thereagainst and serve to move it toward its seat, said movement of the auxiliary valve causing the main valve to move to closing position with the assistance of the spring member.

22. In the combination defined in claim 19, a pneumatic exposed on one side to atmospheric pressure and at the other side to the pressure in the exhaust tube, and having means associated therewith for positively moving both said valve members to their respective seats when there is no suction in the tubes.

23. In a pneumatic dispatch system, a transmission tube, an exhaust tube connected to a source of suction, and a normally closed control device for regulating the flow of air through the tubes, a minimum flow being permitted when the valve is closed, said device including a reciprocating valve member arranged to seat in the direction of air flow, a stem connected to said valve member, a spring constantly tending to hold said valve member seated, a pneumatic mounted for movement independently of the stem, and a second spring reacting between the pneumatic and a stop shoulder on the stem, said pneumatic being arranged for causing the last mentioned spring to exert a force greater than the first mentioned spring and in opposition thereto when there is the said minimum flow of air in the tube.

24. In a pneumatic dispatch system, a transmission tube, an exhaust tube connected to a source of suction, and a normally closed control device for regulating the flow of air through the tubes, 2, minimum flow being permitted when the valve is closed, said device including a reciprocating valve member arranged to seat in the irection of air flow, a stem connected to said valve member, a spring constantly tending to hold said valve member seated, a pneumatic mounted for movement independently of the stem, and a second spring reacting between the pneumatic and a stop shoulder on the stem, said pneumatic being adapted for causing the latter spring to exert a force in valve opening direction in excess of the opposing force of the first mentioned spring, when there is the ininimum fiow or" air through the system, said pneumatic also being arranged render said last mentioned spring substantially ineffective when there is no suction in the system, thereby permitting thefirst mentioned spring to exert its force for positively holding the valve member seated.

25. In a pneumatic dispatch system, .a transmission tube, an exhaust tube connected to a source of suction, and a normally closed control device" for regulating the flow or" air through the tubes, 2. minimum flow being permitted when the valve is closed, said device including a reciprocating valve member arranged to seat in the direction of air flow, a stem connected to said valve member, a spring constantly tending to hold said valve member seated, a pneumatic mounted for movement independently of the stem and constantly exposed on one side to at mosp' eric pressure, and at the other side to the pressure in the exhaust tube, and a second spring reacting between the pneumatic and a stop shoulder on the stem, said pneumatic be-- ing adapted, when there is the said minimum flow of air in the system, to cause the last men tioned spring to exert a force in valve opening direction in excess of th opposing force of the first mentioned spring, the valve being held sea ed by the difierential pressures on said valve member, in opposition to the force exerted by said second spring, and said valve member being arranged to open in response to the decrease in pressure in the transmission tube caused by introduction of a carrier therein.

26.111 a pneumatic dispatch system of the minimiun flow type, a transmi sion tube, an exhaust tube connected to a source of suction, and a normally closed control device for governing the carrier-impelling flow of air through the tubes, a minimum flow of air being permitted through the tubes when the control device is closed, said control device including a reciprocatory disk type valve member disposed substantially centrally of the transmission tube and a seat for said valve member, member having an areasubstantially greater than its port, said valve member being adapted for movement in opening direction by direct action of the increased suction in the transmission tube resulting from the introduction of a carrier in said tube, said valve seat having an exterior tapered formation adapted for deflecting the air currents against the under side of the valve mem ber, after it has been cracked off its seat, for assisting the movement of the same in opening direction.

" SAMUEL OLSON.