US1609123A - Power controller - Google Patents

Description

Nov. 30 1926.

1,609,123 F.B.PEEBLES POWER CONTROLLER Filed March 26, 1925 3 Sheets-Sheet 1 y @im @1121@ mili L, a f 0 Nov. 30 1926.

v 1,609,123 F. B. PEEBLES POWER CONTROLLER Filed March 2e, 1925 3 sheets-sheet 2 Npv. 30 1926.

F. B. PEEBLES POWER CONTROLLER Filed March 26, 1925 3 Sheets-Sheet 5 rrnnliifra I f Patented Nov. 30, 1926.

,unirse armas PATENT or FIQE.

rimini: B. riiiiBLiis, or sYnAofUsE, NEW YORK, .assisiren 'ro THE Lai/isoNeoi/IPANY,

or sYiaAcUsii, new Yoan,

POV/ER CONTROLLER.

Applica-tion filed Ivi-arch 2S, i925. Serial No. iS/l.

This invention pertainsto powerl controllers for .pneumatic despatch systems and `relates more particularly to automatically acting controllers oit-the/so-caflled minimum flow type of which the patent to Libby No. 968,- 578, August 30, '1910, furnishes an early example. A

Controllers ofl this type comprise essentially `a valve, hereinafter .referred lto vas :the

main valve located between the transmission tube and an air exhauster or vacuum drum, such valve normally cutting oil" carrier propelling Aair =low through the `tube when the `tube is idle, although there is vat afll times a continuous flow of air .of small volume lthrough the transmission tube, insullicient to 4propel `a carrier and known as the minimum flow, and al pneumatic, tor exam-ple a piston or diaphragm. which respondsV either directly or indirectly to changes in pressure in lthetube due to the momentary Ycl/itting off or checking ot' "the minimum ,flow of -air incident .to the insertion of a carrier in the tube, Vand which by reason oft' such response lopens wide the Ymain valve to Vpermit carrier propelling aliil flow through the transmission tube.

In 4the form of appara-tus .described .in -the Libby patent the period during which lthe val-ve remains open is .determined solely by the operation ol' a timing dev-ice. The present invention is intended to improve the operation ot a device `or" this general type by eliminating` Athe timing device, .and in place thereotl 4providing means which responds directly to the change of pressure in the transmission ltube incident to discharge of vthe last carrier therefrom vfor initiating closure of the main valve.

`Systems of the above type are oftten'rcquired to work under very adverse conditions. For example, the exhauster `for produciing` the vacuum may slow down, or by reason ot age or lack ot'a-ttention may become incapable o-t maintaining the vacuum tor which the system was designed; the ransmission tube and otherpiping, as well as terminal valves and pipe iittings may develop leaks; and the carriers may become so worn as to tit but `loosely in the tubes.

The `present invention is intended so to improve power controllers oit that type which depend solely upon differences `in pressure i'or opening and closing the main valve as to make them reliable vand certain in operation even for extended periods ot use whenzapplied to systems .in which :for one cause Vor another the `vacuum luctuates irregularly, or is below normal.

In designing myV improved controller I have endeavoured to el-iminate complicated systems of electrical wiring, keeping` suoli electrical circuits as are employed as short and simple as possible, and also to make `the device of compact and rugged coiistr ction well able to sustain prolonged wear.

In the accompanying drawings a -prefei'red .embodiment is illustrated by way lof example: 4

Fig. 1 being a diagrammatic elevation, partly in section, showing the improved controller installed between one transmis` sion `tube of a pneumatic system andthe exhaust header thereof;

Fig. 2 `is a plan view to larger scale of the improved power controller, Athe transmission tube being shown in section;

Fig. 3 is a side elevation of the device .as viewed Vfrom the right side of Fig. .2;

Fig. 4 .is a side elevation at lright angles to Fig. 3 andpartly in section on vthe 'line 4--4 of the latter ligure, the .par-ts `ibeilng (iii shown .in their normal position with' the main valve closed; l

Fig. 5 is a view similar to Fig 4- but showing the main valve open;

Fig. 6 is a :fragmentary vertical sectionsubstantially on the line 6 6 oi F Qsliowing the auxiliary controlling devices for determining operation of the main valve.;

Fig. 7 is a diagrammatic view illustrating' the electrical circuit employed;

Fig. 8 is a view similar to Fig. 6 but showing the corresponding parts in lthe Vposition which they assume immediately .after insertion of a carrier in the transmission tube;

Fig. 9 is a similar View showing the corresponding parts as they are vpositioned after the main valve has fully opened;

Figs. `10 and 11 are fragmentary vertical sections, to larger scale, illustrating certain ot 4the elements appearing in Fig. 6 but in different operative positions.;

Fig. l2 is a side elevation of a sleeve valve constituting an elementoi the pressure regulating device; and

Fig. 13 is a fragmentary horizontal section showing details of a bleeder valve torming a part of the main motor mechanism.

Referring to the drawings and particular ly to F ig. 1, the numeral 1 indicates ap0r tion of a central station desk provided with the despatch terminal 2 forming a part otl the sending transmission 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 power control apparatus to the usual suction drum or header 9 in which a vacuum or low pressure is maintained Yby means of a suitable exhauster, not shown. A continuous air passage or conduit is thus provided extending from the terminal 2 to the exhauster, that portion of the conduit provided by tubes 3 and 4 forming the transmission line.

The improved power control forming the immediate subject matter of the present invention preferably comprises a hollow casing 10 desirably of generally cylindrical form and open at its opposite ends. One end of this casing is closed by a cover 11 secured in position in any desired manner, and

the opposite end is closed by a cover 12 ot concave form, also removably secured by any suitable means, for example, by the bolts 12a.

A. partition or septem 13 substantially midway the length of the casing 10 divides the latter into an inlet chamber 14 and an outlet chamber 15. The partition 13 is furnished with a valve orifice 16 providing communication between the chambers 14 and 15.

The side wall of the casing 10 is furnished with a flange 17 defining an opening for the reception of the end of the transmission tube extension 6 which opens into the chamber 14. The wall of the chamber is also turnished with an opening defined by a flange 18 adapted to receive the upper end of the suction tube 9, so thatthe chamber `15 is always in communication with the exhauster. The chamber 14 communicates at all times with the chamber 15 or the pipe 8 by means of a small passage suc-h as may be furnished by a pipe 2O of small diameter or by a small orifice in the partition 13.

The valve orilice 16 is normally closed by means ot a'valve 21 hereinafter referred to as the main valve provided with a stem 22 sliding in a suitable guide opening in a spider 23 projecting from the partition 13 into the chamber 15. The valve 21 is normally held against its seat by means ot a compression spring 24 bearing at one end against'the cover 11 and at its other against the valve 21.

A flexible diaphragm 26 is clamped at its edges between the end flange 27 of the casing 10 and a marginal flange 28 provided upon the cover 12. This diaphragm thus separates the chamber 15 from a chamber 29 within the cover 12. The diaphragm is connected to the stem 22 by means ot clamping plat-es 30 and a nut 31 engaging the threaded extremity of the siem. Movement of the diaphragm to the lett thus retracts the valve 21 from its seat and permits a free flow of air from the transmission tube 6 through the chambers 14 and 15 to the suction tube 8. The chamber 29 communicates with the chamber l5 by means of a restricted passage 29a preferably controlled by means of a needle valve 29h.

The upper wall of the chamber 29 is turnished with a valve orifice 32 normally closed by a valve 33 hereinafter referred to as the auxiliaryrvalve carried by, or forming a part of, the core of a solenoid 34. This solenoid is secured to the upper surface of the cover 12 by means of bolts 35 and 36, land is furnished with suitable binding posts 35a and 36a for the reception of the terminals ot an electrical circuit hereinafter described.

Upon the upper part of the casing 10 an auxiliary control mechanism is mounted. This auxiliary control mechanism comprises two meter cylinders 38 and 39 and a regulator cylinder 40 respectively, which may form integral parts of the casing 10 or which may be made separately and mounted upon the latter in any suitable manner. The cylinder 38 is of somewhat larger diameter than either of the others, and preferably somewhat shorter than the others. Each of these cylinders communicates with the external atmosphere at its lower end by means of a suitable passage, for example, by means of the channel 41 extending through the upper wall of the casing 10 and which communicates with the respective cylinders by means of ports 42, 43 and 44, Figs. 6, 8 and 9. The upper part of the cylinder 38 communicates with the outer atmosphere by means of a small bleeder passage 38a preferably controlled by an adjustable needle valve 381.

The cylinders 38 and 39 communicate by means of a port 45 adjacent to the upper end of the cylinder 38, and cylinders 39 and 40 communicate by means of a port 46 adj accnt to their upper ends. A small pipe 47 or other suitable conduit connects the upper part of the cylinder 40 with the transmission tube or with the chamber 14 of the casing 10, as may be most convenient.

A piston 48 is arranged to slide within thc cylinder 38. This piston is furnished with a stem 49 passing up through the closed top of the cylinder. and this stem is 'furnished with a liv-:ed abutment 50 forming a support for the lower end of a compression spring- 51. A circular washer or annular plate 52 rests upon the upper end ot the spring 51. sliding freely on the stem 49. The upper part of the stem 49 passes through a guide openingl in a bridge piece V58, mountedupon Supports 54. This bridge piece carries a pair of spaced Contact members 55 and 56 respectively, with which ithe washer or 4.plate 52 is adapted to engage when the piston 48 is aised. The contacts 55 and 56 are connected by means of wires 57 and 58 to the terminals of fthe solenoid 34, a battery 59 7) or other suitable source of electrical energy being interposed in one ot' these wires, for example, the wire 57.

A piston (50 is also mounted within the cylinder 39. This piston is longer than the piston 48 and is relatively heavy, so that it tends to return to the lower part of the cylinder when raised. This piston is provided with a stem 61 furnished with a iXed shoulder or abutment 62 upon which a spring 63` rests. An annular. plate or washer-64 is supported upon the upper end of this spring'. The stem or rod 61 of the piston is guided in an `opening in a bridge piece 65 carried by suitable supports 66 and 67 and may, it necessary, be furnished with an auxiliary weight l68 at `its upper end. The bridge piece 65 supports a pair of spaced contacts 69 and 7 O, respectively, with which the plate 64 is adapted to engage when the piston 60 is raised. The contacts 69 and 70 are connected by means oi? Wires 71 and 72 (Fig. 7) to the wires 57 and 58 respectively.

A piston 7 4 is arranged to slide within the pressure regulator Acylinder 40. A spring 75 bearing at its lower end against the piston 74 and at its upper end against the top ot the cylinder tends to -rctain the piston 74 in the lower end of the cylinder. The cylinder 40 is furnished with a cylindrical guide extension 76 projecting' from its upper end, and a sleeve valve 77 (Figs.,10, 11 and 12) is arranged to slide within this guide extensioii. This .sleeve valve is closed at its upper end except tor a central port or orifice 78, and is normally supported by resting upon the upper end `of the stem 7 8 of the piston 74. rlhis sleeve valve is open at its lower end and has a .port 79 in its side wall. This port is of triangular .or vinverted .V- Shape, `and the sleeve lvalve is normally so positioned Athat this port is entirely below the upper end 80 ot" the .guide extension 76 as shown in Fig. 9. lhen the parts are in this position .the 1port 78 at the end of the sleeve vvalve is closed` by the end of .the stem 73.

"lhe operation of the device is .substantially as follows. it being` Aunderstood that when the transmission tube' is idle the main valve 21 is closed, .the diaphragm 26 occupies the position shown in Fig. 4 and the auxiliary valve 83 is closed. At this time a minimum 'How ot air is ventering the transmission terminal 2 .and Vpassing` through .the pipes 8 .and 4 traverses Vthe pipe 2O on its way to the exhauster.

Then a carrier is ,inserted inthe transmission tube it obstructs the .passage of the lminimum flow ot air, thus resulting in building up vacuum in the cylinder 38, and causing the piston 48 to rise, thereby closing the circuit Vthrough the solenoid 34.

The area ot' the piston 48 and its weight are so'chosen that it tends to rise when subject to the very slightest pressure decrease in the transmission tube, so that even though the tube Aleak or the carrier be Worn, the piston will rise with certainty.

As soon as the circuit through the solenoid 34 is completed the core of the solenoid rises. thus lifting valve 33 and opening the port 32 to the atmosphere. Atmospheric pressure thus acts freely upon the `outer side of the diaphragm 26 and as the inner side of the diaphragm is exposed to the pressure .in the suction tube 8 .the diaphragm moves rapidly to the lett, as viewed in Fig. 4. yuntil it assumes the position shown in Fig. 5, thus opening the main valve 21 and permit-ting a carrier .impelling air flow to pass through the transmission tube. When the main valve opens, the vacuum in the transmission tube is increased very considerably, and as this vacuum vpressure is transmitted through the pipe 47 the cylinder 40, andthe port 46 to the cylinder 39. the piston 60 rises, closing the port 45. The piston 60 is of such weight that it does not rise at all `when the carrier is lirst inserted vin the transmission tube and before the main yvalve opens. lfilhen the piston 60 rises and closes the port it also moves the plate 64 into engagement with the contacts 69 and 7 O, the movement of the piston 60 being` such as to compress the spring 63 to a substantial extent.

After the port 45 has closed the piston 48 slowly drops, since air at atmospheric pressure is permitted to -bleed in through the port 38 and thus the circuit through the contacts and 56 is broken, although the circuit through the solenoid is still Ymaintained .by the plate 64 engaging the contacts 69 and 70.

The parts remain in `this vposition during the iiight ot l.the carrier and so long as a single carrier remains in the transmission tube. It but one carrier be inserted the parts remain as described until this carrier emerges from the tube. Then this occurs the pressure in the transmission tube rises slightlvand this permits the weighted piston to drop, thus `remtwing the Aplate 64 from the contacts A6,9 and and breaking the circuit through the solenoid. the valve now closes andthe air vis exhausted from the chamber 29 through the passage 29a. After a very short interval vthe pressures upon the opposite sides ot the rdiaphragm 26 are so nearly balanced that the `spring 24 is able to close the valve 21 thus restoring the parts to initial position.

it, during the iight of the iirst carrier,

one or more additional carriers are inserted in the tube, the contact plate 6e remains in engagement with the contacts 69 and 70 until the last carrier has been delivered from the tube. As each car ier emerges from the tube there may be a momentary slight increase in pressure in the tube, but since the spring` (33 is initially placed under considerable compression such slight fluctuation of the piston as may occur at the delivery ot each carrier, other than the last, is insutlicient to remove the plate 6st trom the contacts 69 and 70, and thus the circuit is maintained until the last carrier is delivered.

As above stated the pistons '-l-t and GO are so designed as to be sensitively responsive to a range ot pressures such as would be :tound in a system in which a very poor vacuum was maintained. Since these pistons are so sensitive to pressure fluctuation, it is evident that it installed in a system in which a high vacuum is maintained they would be inetl'ective for the desired purpose and for this reason the regulator cylinder at) is provided.

Normally the piston 7a occupies the position shown in Fig. 6 and the sleeve valve 7 7 rests upon and is supported by the stem 73. Both ports 78 and 79 of the sleeve valve are thus closed. lt the vacuum in the system to which the apparatus is applied is greater than that for which the pistons 48 and 6() were designed the piston 74 rises in opposition to the spring 75, thus lifting the sleeve valve 77 until the upper end of the port 7 9 is exposed above the top SO of the guide 76. This admits air to the interior ot the cylinder 4:0, thereby decreasing the elective vacuum in the cylinders 88 and 39. although fluctuations in pressure occur in these cylinders corresponding to the fluctuations in pressure in the transmission line, the only difference being that the range ot pressures in the cylinders 38 and 39 is loiver than that in the transmission tube.

lt' a very high vacuum .is maintained in the transmission tube or it a large` number of carriers are simultaneously inserted, which has the eitect ot increasing the vacuum, the sleeve valve 77 may rise to a considerable extent (Fig. 10) and as the port 79 increases in Width trom its top toward its bottom, the admission of air to the cylinder Ll0 increases rapidly, so that the desired pressure in the cylinders 38 and 39 may readily be maintained under all conditions.

It during the operation ot the apparatus, the sleeve valve has been lifted, the delivery o't the last carrier from the transmission tube with its consequent increase in pressure in the latter tends to permit the piston 74 to return rapidly to its normal posit-ion. It the sleeve valve 77 were closed quickly under such circumstances, the net result might be that the pressure in the cylinder 39, instead ot increasing to permit the piston GO to drop, would actually decrease with the result that the circuit through the solenoid would not be broken. To avoid this action the port 78 is provided and when the piston 74 drops suddenly, upon delivery ol the last carrier, the stem 73 o the piston moves away from the port 78 (Fig. ll) and thus permits free entrance ot air into the cylinder 40, so that increase in pressure in the cylinder 39 is certain. yAfter the piston 74; has returned to its normal position the sleeve valve 77 gradually returns to its nornial position by the action ot' lgravity so that the parts are restored to their initial position.

While l have shoivn pistons ivorlring in cylinders as the auxiliary controlling agents, as ivell as the pressure regulating means, l contemplate that other forms ot pneumatic motor, such Yfor example, as diaphragins disposed in suitable casings may be substituted 'lor the pistons here shown, with such corresponding changes in details as might be necessary in making` such substitutions. I also contemplate that the main diaphragm 26 may be replaced by a piston or other form o1" motor, and that the various parts constituting the controlling apparatus as a Whole may be ditlferently arranged and ditiierently proportioned as circumstances mayv warrant.

It is also to be understood that the pressure regulating means comprising the cylinder Ll() or its equivalent may be employed in other environments and in connection with other power control apparatus but that herein specifically illustrated.

I claim:

l. A pow-er controller for use in a pneumatic despatch system having a transmission tube, means for creating a carrier propelling air current in the tub-e, and a valve for controlling carrier propelling air tloiv through the tube, said controller comprisingr a motor for operating the valve and electro-magnetic means for controlling the motor, fixed control means and a contact movable into engagement with the fixed contact means to complete an electrical circuit through the electro-magnetic means, and means for moving the movable contact comprisingr a pressure responsive element and a coiled compression spring, the spring being substantially collapsed by full mov-ement of the pressure responsive element and thereby maintaining the movable Contact in engagement With the fixed contact means regardless of slight subsequent movements of the pressure responsive el-ement.

2. A power controller for use in a pneumatic despatch system of the vacuum type having a transmission tube. an exhauster connected therewith and a valve for controlling carrier propelling air flow through the tube, said controllercomprising a motor for operating the valve, an electro-magnetic delvice ior determining operation ot' the motor, a pair of pneumaticsV of relatively different effective area, each Apneumatic having a 'stem and normally being exposed to transmission tube pressure, a resilient circuit closer movable by each stem, and contact means engageable by the respective circuit closers to close the circuit through the electro-magnetic device.

3. A ,power controller tor use in a pneumatic despatch system ot the vacuum type having a vtransn'iission tube, an exh'auster connected therewith and a valve for controlling lcarrier propelling air flow through the tube, said controller comprising a motor for ope 'ating the valve, an electro-magnetic device for determining'operation of tthe motor, a pair 'of pneumatics each normally exposed to transmission tube pressure, one of said pneumatics being of greater eective area than the other, each pneumatic having a stem, an annular contact plate encircling each stem, a spring connected .to each stem and resiliently supporting the respective contact plates, and contact means engageable by the respective Iplates `lor closing the circuit through the electro-magnetic device.

Zl. A power controller for use in a pneumatic despatch system having a transmission tube, means for creating carrier propelling air flow therein, and a valve for controlling carrier .propelling air `flow through the tube, said controller comprising a motor for operating said valve, electro-magnetic means controlling the motor valve, a pair of auxiliary pneumatics normally exposed to `pressure fluctuations corresponding to those in the transmission tub-e, one of said auxiliary pneumatics responding to slight change in pressure in the transmission tube due to introduction of a carrier thereby to close the `circuit through the electro-magnetic means,

the other of said auxiliary pneumatics responding to the relatively `greater change in pressure in the transmission tube due to opening of the main valve, said latter auxiliary pneumatic thereby cutting oft' communication between the transmission tube and the first auxiliar pneumatic.

5. A powercontro leil for use in a pneumatic despatch system of the vacuum type having a transmission-tube, an exhauster connected therewith and a valve for controlling carrier propelling air flow through the tube, said controller comprising a motor Vconnected to the main valve for operating the latter, and meansfor determining operation of the motor comprising an electro-magnetic device, a pneumatic responsive to the slight change in pressure in the transmission tube incident to introduction of a carrier to close theeircuit through the electro-magnetic device, a second pneumatic responsive Vto the greater change in pressure in the transmission tube dueto opening of the valve thereby to cut oit communication between the first pneumatic and the tube, said second pneumatic also, by its response 'to such Apressure change, actuating circuit closing means to maintain the circuit through the electro-magnetic device when the first pneumatic becomes inoperative.

6. A 'power controller for use in Vva pneumatic despatch system having a transmission tube, means 1tor creating carrier 'impelling air `flow therein, and a valve :tor `controlling carrier propelling air tloiv'through the tube, said controller comprising ay motor for 'operating the valve, and an eleCtro-magnetic device `-for determining operation Vof fthe mo! tor, a ,pair of independently actuable circuit closers for closing the 'circuit through the electro-magnetic device, and a pneumatic for operating `each circuit closer. lsaid pneumatics normally being exposed Ato ltransmissi'ou tube pressure, one of said pneumatics being more sensitive to pressure change than the second, the latter when responding 'to pressure change cutting oifithe tirstI pneuinatic from the transmission tube.

7. A power controller :for use in a pneumatic `despatch systemhaving a transmission tube, means for creating carrier impelling air flow in said tube, andavalve V for controlling carrier propelling air flew through the tube, said controller vcomprising.; a motor for operating the valve, `and an electro-magnetic device for. determining operation of the m'otor, `a pair 4"of independently actuable circuit closersrfor closing the circuit 'through the electro-magnetic device, a pair of cylinders' oi dilierent diameters, anpisto'n in each cylinder, the cylinder of smaller diameter constantly cornmunicatir'i'g lv with the transmission tube, the'larger cylinder normally communicating with the smaller cylin'der by means of a port in its side wall and means for transmitting .movement from the pistons to the respective circuitfclosers, the larger piston responding to slight pressure change to .actuate one circuit closer to Yclose the circuit throughthe electr'o-i'nagn'eti'c device, and thesmall'er piston responding toa relatively 'greater Vpressure chanwefto close the port leading to the larger cy inder and to actuate the other circuit closer to .keep the circuit closed through the electro-magnetic device. v p

l 8. Pneumatic despatch" apparatushavi'ng a transmission tube, an exhauster connected therewith and a main valve forcontrolling carrier propelling flow of airthrough Vthe tube, a motorfor o'peratingthe main valve, an electro-magnetic device for determining operation of the motor, a pair of` cylinders closed at ,one end and open to the atniosphei'e at the other, a piston normally positioned near the opcn end of each cylinder, one cylinder constantly communicating with the transmission tube and having a port in its wall lea ding to the other cylinder; each piston being operative to close a circuit through the electro-magnetic device, the piston in the cylinder which constantly communicates with the transmission tube being slower to respond to pressure change than the other and when it does so respond closing the port leading` to the other cylinder.

9. A power controller tor use in a pneumatic despatch having a transmission line and a valve for controlling carrier propelling air low in the line, said controller comprising a pneumatic connected to the valve for operating the latter, pressure responsive means for controlling movement of the pneumatic to open and close the valve, and automatic regulating means tor determining the range of pressure to which the pressure responsive means is subjected.

10. A power controller tor use in a pneumatic despatch system of the vacuum type having a transmission line and an exhauster connected therewith and a valve for controlling carrier propelling air flow through the line, said controller comprising means responsive to relatively slight differences in pressure in the line to determine opening or closing of the controlling valve, respectively, said means being equally operative without manual adjustment whether a high or low vacuum normally be maintainedin the line. Y

11. A power controller for use in a pneumatic despatch system ot the vacuum type having a transmission tube. an exhauster connected therewith, and a valve for controlling carrier propelling air flow through the tube, said controller comprising means for actuating the valve, pressure sensitive means for determining the operation of the valve actuating means` said pressure sensitive means being operative at predetermined pressure range slightly below atmospheric pressure, and means for transmitting pressure from the transmission tube to said pressure sensitive means and means for changing said transmission tube pressure, it of a higher order ot vacuum, to bring it within said predetermined pressure range.

l2. A power controller for use in a pneumatic despatch system of the vacuum type having a transmission tube in which a relatively7 high range of vacuum pressure normally obtains, an eXhauster connected to the tube, and a valve tor controlling carrier propelling airs-flow through the tube, said controller comprising means for actuating the valve, pressure lsensitive means for determining operation of the valve actuating means, said pressure sensitive means being operativeat a lower range of vacuum pressures than obtains in the transmission tube,

and means for transmitting transmission tube pressure to said pressure sensitive means and for changing such transmitted pressures to bring them within the range of operation of said pressure sensitive means.

13. A power controller for use in a pneumatic despatch system having a transmission tube, means for creating carrier impelling air flow in the tube, and a valve for controlling carrier propelling air iiow through thel tube, said controller comprising a pressure actuated element sensitively responsive to pressure luctuations within a normal range varying little from atmospheric pressure, means for transmitting transmission tube pressure to said pressure actuated element, and means tor changing such transmitted pressure, if different from the normal range for which the pressure actuated element is designed, to bring it within such range.

lll. A power controller Ytor use in a pneumatic despatch system ot the vacuum typo having a transmission tube, an exhauster connected therewith and a valve tor controlling carrier propelling air flow through the tube, .said controller comp rising a. casing having a chamber therein, said chamber communicating with the transmission tube, a pressure actuated element forming one wall ot said chamber, said element being sensitively responsive to a lower range ot vacuum pressures than that ot the transmission tube, and means for admitting atmospheric air to said chamber whereby to reduce the vacuum therein and bring it within the range ot pressures to which said element is responsive.

l5. A power controller tor use in a pneumatic despatch system having a transmission tube, means tor creating carrier impelling air tiow in the tube, and a valve for controlling carrier propelling air low through the tube, said controller comprising a pneumatic Connected to the valve 'for operating the latter, a casing having a chamber therein communicating with the transmission tube, a pressure actuated element t'orming one wall ot' said chamber, means actuable b 'ff said element-for determining operation o? the pneumatic, said element being responsive to a range ot pressures nearer to atmospheric pressure than obtains in the transmission tube, and a pressure actuated device for opening said chamber to the atmosphere whereby automatically to maintain the pressure therein within the range at which said pressure sensitive element is operative.

16. A power controller tor use in a pneumatic despatch system ot the vacuum type having a transmission tube, an efzhauster connected therewith, and a valve tor controlling carrier propelling air flow through the tube, said controller comprising a pneumatic connected to the valve for operating the latter, an auxiliary valve for determining actua-tion of the pneumatic, a casingY having LII achamber therein comn'iunicating with the transmission tube, `an element responsive to pressure fluctuation in saidchamber to operate the auxiliary valve, and means` responsive to vacuum in excess of apredeter-` mined amount in Vthe transmission' tube to admit atmospheric air to said chamber.

17.` A power controller for use in a pneumatic despatch system of the vacuum Itype having a transmission tube, an exhauster connected therewith, andl a valve for controllingcarrier propellingl air `iiow through the tube, said controller comprising a pneumatic connected to the valve for operating the'latter, said pneumatic being exposed o n one side toexhauster pressure and normally closed from the atmosphere at its other side, a normally closed auxiliary valve tor admi tting atmospheric pressure to act upon the latter side ot the pneumatic, means Jfor operatingthe auxiliary valve comprising an auxiliary pneumatic forming a movable wall Ator a` chamber communicating with the transmission tube, and a pressure actuated valve operable to admit atmospheric pressure to said chamber in direct ratio to the increase in vacuum in the transmission tube above a predetermined point. i i

18. A power controller for use in a pneu-v matic despatch system having a transmission tube, means for creating carrier impelling air flow in said tube, and a valve for controlling carrier propelling air flow through the tube, said controller comprising a pneumatic connected to the valve for operating the latter, said pneumatic being exposed on one side t0 transmission tube pressure and normally closed from the atmosphere at its other side, a normally closed auxiliary valve for admitting atmospheric pressure to act upon the latter side of the pneumatic, means for operating the auxiliary valve comprising an auxiliary pneumatic forming a movable wall for a chamber communicating with the transmission tube, a normally closed valve for admitting atmospheric air to said chamber, and a pneumatic exposed to transmission tube pressure Yfor openingV said valve.

19. A power controller for use in a pneumatic despatch system of the vacuum type having` a transmission tube, an exhaust'er connected therewith and a valve for controlling carrier propelling air flow through the tube, said controller comprising a pneumatic connected to the valve for operating -the latter, said pneumatic being exposed on one side to exhauster pressure and normally cloced from the atmosphere at its other side, a normally closed auxiliary valve 'for admitting atmospheric pressure to act upon the latter side of the pneumatic, means for operating the auxiliary valve comprising an auxiliary pneumatic forming a movable wall for a chamber communicating with the transmission tube, Aa reciprocable sleeve valve having a V-shaped port i'ior admitting air to said chamber, said valve i'iormally being closed, and a. pneun'iatic for opening said sleeve valve. 1 l

k2O; A power .controller for use in a pneumatic despatch system oi the vacunmrtype havingza transmissionvtubc, an exhauster connectedi therewith and a valve for controlling carrier propelling air flow through the tube, said controller comprising a main pneumatic connected to the valve for operating the vlatter, means for determining operation of themain pneumatic comprising an auxiliary pneumatic forming a movable wall i'or a chamberv communicating with the transmission tube, andxmeans for admitting atmospheric air to said chamber comprising a cylindrical guide,` a sleeve valve sliding in the guide, said valve having a, port of inverted V-shape in its wall, said port noi'- mally being disposedlvwithin and below the end of the guide, and means for moving the sleeve to expose the port' beyond the end of' the guide. y

2l. A rpower controller lfor use in a pneu-I matic despatch system of the vacuum type having a transmission tube, an exhauster connected therewith and a valve for controlling` carriern propelling. air How through thetube', said latter controller comprising.a,r

main-pneumatic connected to the valve for operating the latter, a casinghaving communicating chambers, one at least of said chambers communicating with Vthe transmission tube, means responsive to pressure Huctuation in one of said chambers for determining operation of the main pneumatic, an auxiliary pneumatic in another chamber, said auxiliary pneumatic havinga stem, and a valve actuable by said stem for admitting atmospheric air to said latter chamber.

22. A power controller for use in a pneui matic despatch system having'a transmission tube, means for creating carrier impelling air How therein, and a valve for controlling carrier propelling air flow through the tube, said controller comprising a main pneumatic connected to the valve for operating the latter, a casing having communicating' chambers, @ne at least of. said chambers commuilicatingk with the transmission tube, means responsive` to pressure fiuctuation in one oi said chambers for determining operation of the main pneumatic, an auxiliary pneumatic in another chamber, said auxiliary pneumatic having a stem, and a valve actuable by said stem for admitting atmospheric air to said latter chamber.

23. A power controller for use in a pneumatic despatch system of the vacuum type having a transmission tube, an exhauster connected therewith and a valve for controlling carrier propelling air flow through the tube, said controller comprising a `main pneumatic connected to the valve for operating the latter, a casing having communicatingchambers, one at least of said chambers communicating vvith the transmission tube, means responsive to pressure iiuctuation in one ot' said chambers for determining operation ot' the main pneumatic, an auxiliary pneumatic in another chamber, said auxiliary pneumatic having a stem, a cylindrical guide extending upwardly from the latter chamber, and a sleeve valve sliding in said guide, said valve having a port in its upper end, the end ot' the stem of the auxiliary pneumatic normally closing said port.

24. A power controller vfor use in a pneumatic despatch system of the vacuum type having a transmission tube, an exhauster connected therewith and a valve for controlling carrier propelling air flow through the tube, said controller comprising a main pneumatic connected to the valve for operating the latter, a casing having communicating chambers, one at least of said chambers communicating with the transmission tube, means responsive to pressure fluctuation in one of said chambers for controlling operation of the main pneumatic, an auxiliary pneumatic in another chamber, said auxiliary pneumatic having a stem, a cylindrical sleeve valve normally supported by said stem, said valve having a port in its end normally closed by the end ot the stem, and a spring for restoring the auxiliaryV pneumatic to normal position after being lifted by differential pressures at its opposite sides.

25. A power controller [or use in a pneumatic despatch system of the vacuum type having a transmission tube, an eXhauster connected therewith and a valve for controlling carrier propelling air flow through the tube, said Controller comprising a main pneumatic connected to the valve tor operating the latter, a casing having communicating chambers, one at least ot said chambers communicating with the transmission tube, means responsive to pressure iuctuation in one ot said vchambers for determining operation ot the main pneumatic, an auxiliary pneumatic in another chamber, said auxiliary pneumatic having a stein, a cylindrical guide projecting from the latter chamber, a sleeve valve sliding in said guide, said valve having a port in its side Wall normally disposed below the end or' the guide and having a second port in its end, the latter port normally being closed by the end of the stem, and a spring for restoring the auxiliary pneumatic to normal position after being moved by differential pressures upon its opposite sides, the sleeve valve being restored to normal position by the action oi' gravity.

Signed by me at Syracuse, N. Y., this twenty-third day of March, 1925.

FRANK B. PEEBLES.

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