US1815188A - Power controller - Google Patents

Description

Filed Nov.v

7, 1928 2 Sheets-Sheet l 2 9. ,u w; .o 5,2 a@ o 23 fr@ J .M e y@ y o 1 W 31.1/ n. if,... afm g July 21, 1931. f J. T. cowLEY 1,815,188

PowER CONTROLLER Filed Nov. '7. 1928 2 sheets-shan 2 aff 15 .fir 9 mi 2g "la a 1 .fr If/ 49 12"/ f d'1 a 65 auf 6a" 44 3 64 62 v ze la e 56 2 g VW@ l ,a J

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NTED STATES lii i 'MS T. COWLEY, OF SYRACUSE, NEW YORKQASSIG-NOR TO -E LAI/ISDN COTJIEQ'Y,

OF SYRACUSE, .NEW YCPRK, A CDRPORATION GF MIQSSACEUSETTS POWER CNTROLLER Application led November 7, 1928.

ri`his invention pertains to power controllers for pneumatic despatch systems and relates more particularly to automatically actuated controllers of the so-called minimum iio i type of which my Patent No. 1,536,424 dated May 5, 1925 furnishes an example.

Pneu ,iatic despatch tube apparatus of the minimum flow type are vacuum systems as distinguished from pressure systems and are open or continuous current systems as distinguished from closed systems in which normally no air current is maintained through the line when the line is idle. Controllers for such open or continuous current vacuum cms oit the minimum flow type comprise essentially an air-controlling valve, located in the exhaustpipe between the transit tube andthe air exhauster or vacuum drum, Wh ich normally cuts down the air current -to a minimum when the line is idle, never Wholly cutting it oii' but at all times permitting a continuous flow ot relatively small Volume called minimum How, and `a pneumatic, such piston or diaphragm, which responds o change of pressure in the line due to the momentary cutting otl' or checking of "he minimum tion* of air by the insertion of a carrier into the tube and by its response opens de the controlling valve to permit a Jfull iiow et air tor driving the carrier. As is common in describingdevices of this type l herein employ t ie term pneuma'ic to designate l y any pressure or vacuum actuated Ati.imentality, for example, eiible dif.-

iston, or bellows, by means of Which vure is converted into mechanical motion.

fis aboye stated, the pneumatic is arranged to respond to the slight variation in pressure in the tube to the reduction or cutting olii ot' the minimum flow by the insertion of the carrier, and to insure certainty of operation, the pn matic must respond sensitively to li at pressure changes. ln order that *valve may close at the proper time le some auxiliary-control- A L either after a predei e interval, or in response to the ,l 'ce of a carrier from the tube, for ringing about a change in pressure condi- Serial No. 3??,35?.

prossime condition is such as to that produced by cutting' ott the i den', and the diaphragm or other 'inmediately responds and again valve, although no carrier may at the time. if, to av id this difficulty, the pneumatic be made less sensitire, then tail to respond to the introduction et a carrier in the line and thus, under some conditions, great ditiiculty is eX- perience-l in sc ting' the control apparatus so that it may be depended upon `for a long period ot use.

ln orde;y to avoid the above dilhculties resort has been had in some instances to very complicated structures involving; the use of interacting` pneumatics, and require fricatest care in initial adjustment and sance, Such devices are expensive to build a n install and in many instances the adjustable elements are so disposed that it is extremely clinicult to obtain access to them in thc limited space available Where the controllelr is installed'.

(l Vite commonly the pneumatic moves rather slorrly in its return to normal position, and sometimes decreases in speed as it apjiroaciizes normal position, and as the main to c e Illini .llll

`Valve is usually connected directly to this dia- Areturn movement, and then closes very suddenly so thatthere is no tapering oil or Wire drawing of the air current in the tube. l also provide tor shielding` the pneumatic from Variations in pressure conditions in the tube subsequent to the closure of the main controlling valve until conditions have returned substantially to normal, that is to say, to normal minimum flow conditions. In conjunction with and in addition to the above desirable features I provide others, including an arrangement which insures adequate force for returning the pneumatic to its normal position, a simplified and cheaper' construction of parts,'and the disposal of the adjusting elements so that they are all readily accessible from the front side of the apparatus.

ln the accompanying drawings in which T have illustrated one desirable embodiment of the invention, byway of example Fig. l is a fragmentary elevation illustrating part of the central station desk of a pneumatic despatch system having my improved power control apparatus applied thereto;

Fig. 2 is a fragmentary vertical section to larger scale, showing details of the power control apparatus with its parts in normal position; that is to say, with the controlling valve closed;

Fig. 3 is a view similar to Fig. 2, but showing the controlling valve wide open, the auX- iliary valve open, and the pilot valve unseated;

Fig. 4 is a view similar to Fig. 3, showing the controlling and pilot valves open, but with the auxiliary valve closed; and

Fig. 5 is a view similar to Fig. 4, but showing the pneumatic which actuates the main valve restored to its normal position, the auxiliary valve closed, the main valve on the point of closing, and the pilot valve closed.

Referring to Fig. 1, the numeral l indicates a fragmentary portion of the central station desk of a pneumatic despatch system. This .sj-,fstem may comprise, for example, a tube 3 leading to an outlying or sending station from which another run 4 of the tube returns to the central station. The tube 3 is provided with a despatch terminal 2 and the tube 4 with a delivery terminal 5, the tubes 3 and 4 collectively constituting a single transmission line of tl e system. The tube 4 is provided with a continuation 6 connecting it to an individual power controlling device indicated generally at 7. This power controlling device is connected by a suction tube 8 to a vacuum drum or header 9 in which a low pressure is continuously maintained by means of a suitable pump or eXhauster not shown. The above arrangement in general is old and well known and requires no further specific description, the present invention being confined to improvements in the power control apparatus per se.

Referring to Figs. 2 and 3, the improved power control apparatus comprises a casing 10, preferably of more or less cylindrical form, having the upper and lower parts ll and 12 adapted to receive the lower end of the tube V6 and the upper end of the tube 8, respectively; The casing l() is provided with Lerares an elongate aXial passage 13 which is aligned with the tubes 6 and 8, thus forming an intermediate portion of the air conduit.

A shaft 14 extends transversely across the passage 13, being journaled in suitable bearings in the walls of the casing 10. This shaft carries a controlling or main valve 15, preferably of butterfly type, which. in closed position, is preferably inclined to the axis of the conduit as shown in Fie'. 2. Preferably the upper wing of this valve is of slightly greater area than the lower wing so that the air pressure tends to hold the valve closed.

lreferably one eri-Ll the shaft l-i projects ful er sur. of the casing and 3 adapted to engage l) when the valve is in lvlhen in 'the latter of the p ssage lf3 .hat the pressure of the i open.

casing I provide a hou S- e uarts 18 and betwe l lie diaphragm :'20 divin housing intov charbers seing open to the outer i port 2?) in the part as indicated continuer Yflow of air the minimum flow about the valve l` of this po i he ve. fr

l y way bj.' hand ie port 2T, but when once stem member 3l is clamped to the center of main diaphragm Q0 in any suitable and usual way is guided to slide n aligned ape in the Walls of the cas- O ai .e art 19. The upper r ob S Y*tivo chambers 50 an;Y

1ers,

c so that the eltective leverage through which the si when the ing i parts are arranged as snon n in 2.

rl"he lower Wing 15a of the valve 15 is provided With an opening 41 ugh vwinch the st 31 sass-.es looselv. llreferably that portion ol the in Si which passes through the opening is e las a separate element ot smaller dialnet J .han the main portion of the stem 81 and lits Within an ail-- ial socket in the latter, being .secured .therein in any desired manner. lilith this contruction a shoulder is formed at the point 43, such shoulder constituting an actua abutment engageable with the valve 15 to push the latter open as the stem 31 moves to the lett viewed in Fi fit the opposite side oi the Wing 15, the stem member 42 carries a second abutment 44, the abutments 43 and 44 being spaced apart to provide lost motion in the actuation ol" the valve as hercinatter more fully described. Preferably the abutment 44 is adjustable on the part 42.

Pin auvilit` y valve 45 oontrfols the port 'this valve is mounted upon a slil g valve which entends transversely across the passage 13 and into the housing of an auX- y pner a-atic. This housig preferably prises parts 48 havingthe 'liary diaphragm 49 clamped between them. This 1diaphragm divides the space Wit-hin the auxiliary housing into 51, respectively, the latter alvfays communicating vfith the outatmosphere by means oiC port t The liragm 49 is clamped to a sleeve which freely on an extension 51'- ilia .i me point 55. luis abutment shoi by to e\ 49 Aoccupies the position shofe'n in 2, sans holding the auxiliary valve 45 Aoila lof its se She. stem porti 54 carries a second abn ment 55al normally spaced from the sleeve I.nd constituting a stop to limit movement the diaphragm 49 to lett as viewed in g. 2. Preferably the abutment 55a is adst-able along the part 54. il. Acoiled spring 6 'vithin the chamber 50 constantly tends move the diaphragm 49 to the lett s vieived in 2.

`ihe ciamber 50 com-uumioates vby means ot' z. lea r pa. f h 'Jh a lchamber 58 con- O in i 17K -J O Aune stem member 42 ot' the main les diaphragm, .and this chamber 58 in turn communicates by means of a passage 59 with the'passage 13 in the casing 10 at a point belovv the valve 15. An adjusting screvv 8O provides for varying the effective diameter of the leak passage 57.

'The outer end of the chamber 58 is defined by an annular valve seat 61 against which a valve 62 is normally pressed by atmospheric pressure.

The stem member 42 preferably terminates in a screw-threaded portion 64 or" reduced diameter, such portion passing loosely through the valve G2. At the junction of the part 84 ivi-th the part 42 an abutment shoulder 63 is termed and when in the movement ot the stem to the left, as viewed in Fig. 2, this abutment engages the valve 62, it unseats the latter, thus equalizing the air pressure upon its opposite side. A spring .65 housed in the chamber 58 tends to unseat the valve 62, and when the valve has been unseated by the action of the abutment shoulder G3, the spring holds this valve unseated until it is positively restored by engagement with an abutment 86 adjustably mounted upon the screw-threaded portion V64 of the stem. The parts 55a and GG are adjusted in the factory and preferably pinned in adjusted position and are not further adjusted during use.

Normally he several parts of the power controller oc-cupy the position shown in Fig. 2, the main controlling valve 15 being closed and in the inclined position shown; the diaphragm 2O being` held in its eXtreme righthand position by the action of the spring 38 and the lever 84; the abutments 48 and 44 being spaced from the valve 15 at opposite sides thereof; the auXiiiary valve 45 being open.; the pilot valve 62 being closed; and the diaphragm 49 being held in its righthand position against the tension of spring 56 by atmospheric pressure acting upon its lett-hand seat. The chamber 50 is in communication with the suction tube 8 throl-igh the passages 57 and 59, and a minimum flow of air is taking pla-ce. such loW passing from the tube 6 through the by-pass 27 and into the suction tube 8.

When a carrier is introduced into .the transmission tu-be the minimum liovv is substantially cut olia so that the pressure drops in the passage 13. As this passage communicates by means ot the port 24 With the chamber 21, the pressure in the latter chamber also drops and atmospheric pressure, acting on the outer side of the diaphragm 2G.v moves the latter lto the left as shou'nnin Fig. Boring the rection', such movement being stopped by engagement of the inger 16 with the pin 17. Thus, in its fully open position, the valve wing 15n may be slightly spaced from the abutment 43 which avoids the necessity of exact adjustment ot the parts. As the valve 15 approaches its fully open position, the abutment 63 engages the pilot valve 62 and unseats the latter, whereupon the spring 65 moves the pilot valve down against the abutment 66 as shown in Fig. 3.

The opening et the pilot valve 62 breaks the vacuum in the chamber and permits the spring 56 to push the diaphragm 49 to the lett as viewed in Fig. 2 until. it occupies the position shown in Fig. 4. Near the end of this movement ot' the auXili ary diaphragm 49 the sleeve 53 strikes the abutment 55 and thus moves the stem 46 and closes the valve 45, cutting ott communication between the chamber 21 and passage 13.

The parts now remain substantiallyT in this position until through leakage at the port 25, suii'lcient pressure is built up in the chamber 21 to permit the spring 3S to move the diaphragm 2O with the stem 31 to the right. Buring the early part of this movement of the stem 31 the valve 15 remains fully open but when the abutment 44 engages the valve it swings the latter to the lett or in a counterclecl-:wise direction until the valve is slightly inclined to the lett of the vertical whereupon it is seized by the air current and suddenly closed, the spacing ot the abutments 43 and 44 permitting this relative motion between the parts. This sudden closure of the controlling valve cuts off the current quickly, although leaving` a full iiow up to the moment ot cut-oil.

As the diaphragm 2O approaches its normal right-hand position the abutment 66 returns the pilot valve 6:2'to its seat. The suction in the pipe 8 now acts, through the passages 59, 58 and 57, to reduce the pressure in the chamber 50, but by setting the adjusting screw 60 so as to restrict the passage 57 to the proper amount, a considerable time interval may elapse before the suction in the chamber 50 is suiiicient to overcome the spring 56 and thus open the valve 45. The spacing ot the abutm- ents 55 and 55"L also results in delay in opening the valve 45. Thus the valve 45 remains closed for an appreciable time after the closure et the valve 15 and, although the closing ot the valve 15 may result in setting up a series ot powerful compression waves in the transmission line, these waves are not transmitted to the chamber 21 so as to atleet the diaphragm 20, and it is only after the subsidence of this series of pressure waves that the valve 45 opens. lt is thus possibleto adjust the diaphragm 20 so as to respond very sensitively to pressure changes in the tranmission line without danger that it will respond improperly upor'i closure of the main valve.

It may be noted that the diaphragm housing comprising the parts 18 and 19 is so disposed that the stem 31 of the diaphragm 30 is oblique to the axis of the passage 13. The purpose of this arrangement is two-told; iirst, it permits such an inclination of the stem 31 that the latter makes substantially equal angles with the valve 15 when the latter is closed and when it is open, respectively, thus securing equal movement ot the valve by the diaphragm stem in both directions of movement of the latter. Second, the arrangement ot t-he diaphragm housing as disclosed provides ample space tor the adjusting screws 26, 29 and 39 so that they are accessible from the front side ot 4the power control device. Thus, when the device is installed in the cramped quarters usually provided Jfor such apparatus, it is possible to get at all of these adjustable parts without ditticulty.

It has already been pointed out that the spring 38 and the lever 34 are preferably so arranged that the torce for returning the diaphragm Q0 to its normal position is slightly greater as it approaches the end ot its movement toward normal position than at the beginning of such movement. The spring is thus able to overcome the slightly increasing resistance which the diaphragm and connected parts oppose as the diaphragm nears the end of its movement and also preferably provides a slightly accelerated movement of the diaphragm which insures rapid return of the parts to normal position ready for a repetition of the operation.

Vihile I have herein disclosed one desirable embodiment ot the invention by way of example, T wish it to be understood that various changes in size, proportion and relative arrangement of parts as well as the substitution of equivalents may be made without departing trom the spirit of the invention.

I claim:

l. Power control apparatus for a pneumatic despatch system of the vacuum minimum tlow type having a transmission tube and an exhaust-er connected to the tube, said apparatus comprising a valve for controlling the flow of carrier impelling air current in the tube, the valve turning about an axis transverse to the tube, actuating means 'for initiating the opening of the valve when a carrier is inserted in the tube, and stop means for limiting opening movement ot the valve, the valve completing its opening movement independently ot said actuating device.

2. Power control apparatus for a pneumatic despatch system of the vacuum minimum flow type having a transmission tube and an exhauster connected to the tube, said apparatus comprising a valve for controlling the flow. ot carrier impelling air current in the tube, a pneumatic, and means actuable by the pneumatic for initiating both opening and closing ot the valve, said actua-ting means being so constructed and arranged as to permit the valve to complete its opening and closing movements independently et the pneumatic.

3. Power control apparatus for a pneumatic despatch system of the vacuum minimum flow type having a transmission tube and an exhauster connected to the tube, said apparatus comprising a valve for controllingV the flow of carrier impelling air current in the tube, a pneumatic for actuating the valve, and a stem secured to the pneumatic, said stem having valve actuating abutments disposed at opposite sides of the valve and spaced apart to provide lost motion between them and the valve.

fi. A power control apparatus for a pneumatic despatch s vstem of the vacuum minimum How type having a transm... ion tube and an erhauster connected to the tube, said apparatus comprising a valve for controlling the. flow ot carrier impelling air current in the tube, the valve having an aperture therethrough, a pneumatic for actuating the valve, and stem secured to the pneumatic and extending through the aperture in the valve, said stem having an abutment element disposed at one side of the valve and being` movable relative to the latter.

5. Power control apparatus for a pneumatic despatch system ot' the vacuum minimum flow type having a transmission tube and an exhauster connected to the tube, said apparatus comprising a` valve for controlling the. iiov.lv of carrier impelling air current in the tube, the valve having an aperture therethrough,y a pneumatic for actuating the valve, and a stem secured to the pneumatic and extending through the aperture in the valve, the valve being mounted to turn about an s transve-se to the tube, and the aperture in the valve being at one side of its axis.

6. Power control apparatus :tor a pneumatic despatch s vstem of the vacuum minimum flow type having transmission tube and an e-Xhauster connected to the tube, said apparatus comorising a valve for controlling the tiow'o't carrier impelling air irrent in the tube, the vaive being mounted to turn about an anis extending transversel57 of the tube, means, including a pneumatic, for swinging the valve to open position through r angle greater than the angle between the ot' the tube and the plane of the closed valve, and means for limiting the swing ot' the valve.

7. Power control apparatus for a pneumatic despatch s tem oi the vacuum minimum tiow type. having a transmission tube and an eXhauster connected to the tube, said apparatus comprising a valve for controlling the how of carrier impelling air current in the tube, the valve being et butterfly type and turning about an artis transverse to the anis of the tube, a. pneumatic for opening and closing the valve, the vaive when open being retained in such pisition the air pressure, and lost rf between the pneumatic iermit mg return of the pneumatic subs" position, after opel vaive begins to close.

S. Pow-er control apparatus for a pneumatic despatch stem 0In the vacuum minimum tio-iv pe having aK transmission tube and an exhauster connected to the tube. said apparatus comprising a valve past which the carrier impeliing current travels and by which the liow et such current in the tube is controlled, the valve being of butterfly type, and means :tor opening the valve in reA sponse to in duction of a carrier into the tube therebj,7 permitting such tlow and for closing the valv suddeniv after a predetermined intervai or time thereby cutting oit such flow.

9. Power control apparatus for a pneumatic. despatch system of the vacuum minimum iiow type having a transmission tube and an enhauster connected to the tube, said apparatus comprising a` valve for controlling the flow of carrier impelling air current in the tube, a pneumatic for actuating the valve, and spring means tending to more the pneumatic in one direction, said spring means being arranged to exert an increasing torce as the pneumatic approaches the end ot its path of movement in such direction.

10. Power control apparatus tor pneumatic despatch system of the vacuum minimum How type having a transmission tube and an exhauster connected to the tube, said apparatus comprising a valve for controlling the flow of carrier impelling air current in the tube, a pnemnatic for actuating the valve, a spring for moving the pneumatic in one direction, and lever means interposed between the spring and pneumatic and so arranged that the spring exerts an increasing torce as the pneumatic approaches the end of the path of movement in such direction.

11. Power control apparatus for a pneumatic despatch system of the vacuum minimum iiow type having a transmission tube and an exhauster connected to the tube, said apparatus comprising a valve for controlling the flow of carrier iinpelling air current in the tube, the valve being of buttery type and turning about an axis transverse to the tube, the valve normailj,7 being closed and, means for swinging the valve toward open position, and means for stopping the valve when it has opened to such a point that the air current in the tube tends to hold it open.

12. Power control apparatus for a pneumatic despatch system of the vacuum miniairv to its normal g the vaii'e, before the mum flow type having a transmission tube and an Xhauster connected to the tube, said apparatus comprising a valve for controlling the flow of carrier impelling air current in the tube, the valve being of butteriiy type and turning about an axis transverse to the tube, the valve normally being held in closed position by air pressure, means for moving the valve to an open position such that if unrestrained the valve would continue to move in the same direction under the action of air pressure, and means for preventing such continued movement.

13. Povver control apparatus of the minimum flow type comprising a casing having a passage adapted to connect the transmission and suction tubes of a pneumatic despatch system, a valve in said passage, a housing at one side of the casing and a pneumatic in the housing, the pneumatic comprising a part Which moves in a path making an acute angle With the axis of the passage in the casing, and reciprocatory means for transmitting movement of the part to the valve for opening and closing the same, Which means moves in the path or" said part and makes substantially equal angles with the valve Whether open or closed whereby equal movements of the valve are secured in both directions of travel or the means.

14. Power control apparatus of the minimum ow type comprising a casing having a passage adapted to connect the transmission and suction tubes of a pneumatic despatch system, a valve in said passage, a diaphragm housing at one side of the casing, a diaphragm in the housing. the housing being so arranged with respect to the casing th at the plane of the diaphragm is at an acute angle to the axis of the passage in the casing, and reciprocatory means for transmitting movement from the diaphragm to the valve for opening and closing the same, which means moves in the path of said part and makes substantially equal angles with the valve Whether open or closed whereby equal movements of the valve are secured in both directions or" travel ot the means.

l5. Power control apparatus of the minimum Flow type comprising a casing having a passage adapted to connect the transmission and suction tubes of a pneumatic despatch system, said valve being normally closed and inclined .vith respect to the axis of the passage, a diaphragm housing at one side ot' the casing., a diaphragm Within the housing., and a stem carried by the diaphragm and extending through an opening in the valve, the diz phragm housing being so disaosed that the plane ot the diaphragm makes an acute angle with the airis of the passage.

16. Power control apparatus of the minimum flow type comprising a casing having a passage adapted to connect the transmission and suction tubes of a pneumatic despatch system, a pivoted valve in the casing, a pneumatic, a stem projecting from the pneumatic, and means on the stem for opening or closing the valve, the stem making substantially equal angles With the valve When the latter is closed and open respectively and thereby securing equal movement of the valve in both directions of travel of the stem.

17. Power control apparatus of the minimum ioiv type comprising a casing having a passage adapted to connect the transmission and suction tubes of a pneumatic despatch system, a controlling valve in the casing, a pneumatic comprising a diaphragm Within a housing, a spring for moving the diaphragm in one direction, means Jfor adjusting the spring, means transmitting movements from the diaphragm to the valve, the diaphragm housing having a leak passage, means for adjusting said passage, the casing having a minimum flow passage, and means for adjusting the latter passage, all of said adjusting means being accessible from one side of the control apparatus.

lS. Power control apparatus for a pneumatic despatch system of the vacuum minimum iiov.'v type having a transmission tube and an eiliauster connected to the tube, said apparatus c-on'iprising a valve for controlling the flow of carrier impelling air current through the tube, a minimum flow of air through the tube being permitted When the controlling valve is closed, a pneumatic normally exposed on one side to the pressure in the transmission tube, means for transmitting movement from the pneumatic to the controlling valve, and means operative a predetermined time after opening of the controlling valve completely to shut off the pneumatic from the pressure in the tube and to keep it shut olf from the tul e oressure for a predetermined time after the controlling valve closes.

19. Power control apparatus for a pneumatic despatch system of the vacuum minimum flow type having a transmission tube. and an exhauster connected to the tube, said apparatus comprising a 4valve for controlling the flow of carrier impelling air current through the tube, a minimum flow of air through the tube being permitted when the controlling valve is closed, a pneumatic normally exposed on one side to the pressure in the transmission tube, means for transmitting movement from the pneumatic to the controlling` valve, the pneumatic responding to pressure change in the tube resulting 'from introduction of a carrier and by such response opening the controlling valve, an auxiliary valve which closes a predetermined time a `ter the controlling valve opens and Which opens a predetermined time after the. controlling valve closes, said auxiliary valve when closed cutting ofi the pneumatic from pressure variations in the tube, and means for adjustably throng through determining the lag between the movements of the contr and au iary valves.

7 i. Power control apparatus tor a pneumatic despatch system ot the vacuum minimum tionv type having a transmission tube, and an e auster connected to the tube, said appar-1 comprising a valve for controiling the carrier impelting air current through the tube, minimum lovv of' air tbtube being permitted when the g valve is ciosed, a pneumatic normally expo ed on one side to the pressure in the transni lon tube, means actuable by the pneumatic for initiating opening and closing control /ot the controlling valve, tle pneumatic resno. ling to iressure change in the tube rei ,j l j c 9 suit from iiit-oducrron or a carrier into the Vabe and by such response initiating` the opening of the c rolling valve, the completion ot the opening ot the valve resulting from differential air pressure on its opposite rides., an auf liary valve Jfor cutting cti comnunication bet veen the tube and the pneunatic, motor means including auxiliary meumatic for closing and opening said auxi-la:y valvev and an adjustable timing controrler for said motor means whereby the latter is adapted to close the au ilary valve after 'he conti-ching valve opens and to open auxiliz-iry vaive a predetermined time ay ter the controlling valve closes.

21. ovver control apparatus for a pneumatic despatch system of the vacuum minimum now type having a transmission tube, and an exhauster connected to the tube, said apparatus comprising a valve for controlling the tioiv ot carrier impelling air current thror^h the tube, a minimum iovv of air i the tube being permitted when the controlling valve is closed, a pneumatic normally exposed on one side to the pressure in the transmission tube, means for transmitting movement Jfrom the pneumatic to the controlling valve, the pneumatic responding to pressure change in the tube resulting from introduction of a carrier into the tube and by such response opening the controlling valve, an auxiliary valve for cutting ofi' communication between the tube and the pneumatic, an auxiliary pneumatic, a stem secured to the auxiliary valve, said stem having spaced abutment elements alternately engageable by the pneumatic to open and to close the auxiliary valve, respectively, and spring means tending to hold the pneumatic in contact with one of said abutment-s.

22. Power controi apparatus for a pneumatic despatch system of the vacuum minimum flou* type having a transmission tube, and an exhauster connected to the tube, said apparatus comprising a valve 4for controlling the flow of carrier impolling air current through the tube, a minimum flow of air through the tube being permitted When th controlling` valve is closed, a pneumatic normally exposed on one side of the pressure in the transmission tube, means for transmitting movement from the pneumatic to the controlling valve, the pneumatic responding to pressure change in the tube resulting from introduction of a carrier into the tube and by such response opening the controlling valve, an auxiliary valve for cutting off communication between the tube and the pneumatic, and motor means, including an auxiliary pneumatic, for closing and opening the auxiliary valve, said motor means comprising lost motion connections between the auxiliary valve and the pneumatic permitting limited movement of the pneumatic in one direction at least Without corresponding movement of the valve.

23. Power control apparatus for a pneumatic despatch system of the vacuum minimum fioW type having a transmission tube, and an exhauster connected to the tube, said apparatus comprising a valve for controlling the ovv of carrier impelling air current through the tube, a minimum flow of air through the tube being permitted When the controlling valve is closed, a pneumatic noimalty exposed on one side to the pressure in the transmission tube, means for transmitting movement from the pneumatic to the controlling valve, the pneumatic responding to pressure change in the tube resulting from introduction of a carrier into the tube and by such response opening the controlling valve, an auxiliary valve for cutting oit communication between the tube and the pneumatic, an auxiliary pneumatic, a stem secured to the auxiliary valve and extending through an opening in the pneumatic, said stem having an abutment element engageable by the pneumatic for moving the stem in one direction, and means for moving the pneumatic in the opposite direction away from said abutment.

24. Power control apparatus for a pneumatic despatch system of the vacuum minimum flow type having a transmission tube, and an exhauster connected to the tube, said apparatus comprising a valve for controlling the fion' of carrier impelling air current through the tube, a minimum flow of air through the tube being permitted when the controlling valve is closed, a pneumatic normally exposed on one side to the pressure in the transmission tube, means for transmitting movement from the pneumatic to the controlling valve, an auxiliary valve for shutting oli the main pneumatic from the pressure in the tube, an auxiliary pneumatic for actuating the auxiliary valve, a pilot valve for the auxiliary pneumatic, said pilot valve normally being exposed on one side to atmospheric pressure and on its other to sub-atmospheric pressure, means actuable by the main pneumatic for unseating the pilot valve against atmospheric pressure, and means for moving the unseated valve away from its seat.

25. Power contro-l apparatus for a pneumatic despatch system of the vacuum minimum flow type having a transmission tube, and an exhauster connected to the tube, said apparat-us comprising a valve for controlling the flow of carrier impelling air current through the tube, a minimum flow of air through the tube being permitted when the controlling valve is closed, a pneumatic normally exposed on one side to the pressure in the transmission tube, means for transmitting movement from the `pneumatic to the controlling valve, an auxiliary valve for shutting oii the main pneumatic from the pressure in the tube, an auxiliary pneumatic for actuating the auxiliary valve, a pilot valve for the auxiliary pneumatic, said pilot valve normally being exposed on one side to atmospheric pressure and on its other to subatmospheric pressure, a rod carried by the main pneumatic, said rod extending through an opening in the pilot valve, spaced abutments disposed respectively at opposite sides of the pilot valve, one of said abutments acting to unseat the pilot valve, and a spring urging the pilot valve toward the other abutment.

Q6. Power control apparatus for a pneumatic despatch system oit' the vacuum minimum flow type having a transmission tube, and an exhauster connected to the tube, said apparatus comprising a swinging valve ot butterfly type for controlling the How of carrier impelling air current through the tube, a minimum flow of air through the tube being permitted when the controlling valve is closed, a pneumatic normally exposed on one side to the pressure in the transmission tube, lost. motion connections for transmitting movement 'from the pneumatic to the controlling valve, an auxiliary valve for shutting ori" the main pneumatic lfrom the pressure in the tube, an auxiliary pneumatic for actuating` the auxiliary valve, a pilot valve for the auxiliary pneumatic, said pilot valve normally beingexposed on one side to atmospheric pressure and on its other to sub-atmospheric pressure. a stem carried by the main pneumatic, said stem extending loosely through an opening in the pilot valve, an abutment on said stem, said abutment being normally spaced from the pilot valve but engeahle with said valve to unseat it, and a second abutment on said stem, spaced from the first. and enga gcable with said pilot valve to restore it to its seat.

27. Power control apparatus tor a pneumatic despatch system or the vacuum minimum flow type having a transmission tube and an exhauster connected to the tube, said apparatus comprisingl valve for controlling the flow ot carrier impelling air current through the tube, a minimum flow of air through the tube being permitted when the controlling valve is closed, a pneumatic normally exposed on one side to the pressure in the transmission tube, means for transmitting movement from the pneumatic to the controlling valve, an auxiliary valve ior sluitting off the main pneumatic from the pressure in the tube, an auxiliary pneumatic tor actuating the auxiliary valve, a pilot valve Jfor the auxiliary pneumatic, said pilot valve normally being exposed on one side to atmospheric pressure and ou its other to subatmospheric pressure, the main pneumatic being a stem which passes loosely through holes in the controlling valve and pilot valve respectively, and abutments on said stem 'for actuating the controlling and pilot valve respectively.

28. Power control apparatus for a pneumatic despatch system of the vacuum minimum iiow type having a transmission tube, and an exhauster connected to the tube, said apparatus comprising a valve for controlling the flow of carrier impelling air current through the tube, a minimum flow of air through the tube being permitted when the controlling valve is closed, a pneumatic normally exposed on one side to the pressure in the transmission tube, means Jfor transmitmovement from the pneumatic to the controlling valve, an auxiliary valve for shutting oli the main pneumatic from the pressure in the tube, an auxiliary pneumatic for actuatino' the auxiliary valve, a pilot valve for the auxiliary pneumatic. said pilot valve normally being exposed on one side to atmospheric pressure and on its other to subatmospheric pressure, the main pneumatic having a stem which extends through openings in the controlling and pilot valves respectively, and an abutment on the stem at each side of the controlling and pilot valves respectively. the abutments of each pair being arranged to initiate the opening and closing of the respective valves.

Q9. Power control apparatus for a pneumatic despatch system of the vacuum minimum flow type having a transmission tube, and an exhauster connected to the tube, said apparatus comprising a pivoted valve for controlling the flow of carrier impelling` air current through the tube, minimum Yflow of air through the tube being permitted when the controlling valve is closed, a pneumatic' normally exposed on one side to the pressure in the transmission tube. means for transmitting movement from the pneumatic to the controlling valve, an auxiliary valve for shutting off the main pneumatic from the pressure in the tube, an auxiliary pneumatic for actuating the auxiliary valve, a pilot valve for the auxiliary aneumatic, said pilot valve normally being exposed on one side to atmospheric pressure and on its other to sub-

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