US1537920A - Power-control apparatus for pneumatic-dispatch systems - Google Patents

Description

May 12, A 1925.

c. s. JENNINGS 'ET' AL POWER CONTROL APPARATUS FOR PNEUMATIC DISPATCH SYSTEMS afd? 7/ g Filed Aug'. 12, 1922 M 7 .Z Qu /3 66 7. 6MM. 0 zu Y fd 7 0000 v y 4 $29 y WM /M KW Patented May 12, 1925.

UNITED STATES PATENT OFFICE.

CHESTER S. JENNINGS, OF WELLESLEY FARMS, AND CLIFFORD R. DUMBLE, OF ARLING- TON, MASSACHUSETTS, ASSIGNORS TO THE LAIVISON COMPANY, 0F BOSTON, MASSA- CHUSETTS, A CORPORATION 0F MASSACHUSETTS.

POWER-CONTROL APPARATUS FOR PNEUltIATIC-DISTATCH SYSTEMS.

Application filed August 12, 1922. Serial No. 581,364.

To all whom t may Concern:

Be it known that we, Ciins'rns S JENNINos and CLIFFORD R. DUMBLE, both citizens of the United States ot America, and residents of lVellesley Farms and Arlington, respectively, in the count-ies ot Norfolk and lviiddlesex, respectively, and State of Massachusetts, respectively, have invented new and useful Improvements in Power-Control Apparatus i'ior l'lneuniatic-Dispatch Systems, of which the following is a specification.

rThis invention pertains to power control apparat-us for pneumatic carrier dispatch systems and has special reference to power control devices whose operation is automatically initiated by the introduction ot a carrier into the transmission tube and an instance ot which is disclosed in the patent to Libby, 968,576, August. 30, 1910. lVhile the device ot this patent appears to be correct in principle, it is ot somewhat complex design and requires considerable space Jfor its proper. installation. @ther arrangements. have from time to time been devised with the same general object in view as that disclosed in said patent, but all of such devices known to us consume an excessive amount of power in their operation. Previous arrangements have usually been so designed that the controlling valve is opened upon every introduction of a carrier into the transmission tube, either by the use of electrical, mechanical or pneumatic devices, and in such arrangements the valve. remains open so long as the carrier is in the tube. An excessive amount of air is thus used, as it is manifest that the blast of air produced in the transmission tube upon the introduction of a single carrier would be capable oi' moving several ca riers as readily as one, and that when the carrier or carriers have acquired full velocity a much less quantity of air is required to carry them to their destination, than is necessary at vthe start. ln tact in many instances the admissicu et air might well cease entirely prior to the discharge of the carrier from the transmission tube, while on the other hand. it the carrier emerge while under the full air pressure it is violently expelled from the tube together with a powerful blast oi air,

causing annoyance and possible injury to the attendant and subjecting the carrier to unnecessary wear.

Principal objects otl the invention are to provide a` power regulator by means ot' which the controlling valve will be widely opened, upon the introduction of a carrier into the tube, but which will permit the valve to close after a predetermined interval regardless of the presence ot a carrier in the transmission tube and which will only open again upon a substantial decrease iu pressurel in the'tube due to the continued presence ot' the same carrier therein or the` side elevation of a` portion of a pneumatic' dispatch tube system showingl the present controlling devlce as applied thereto;

Fig. 2 is a vertical, diametral cross section j of the controlling device forming the immediate subject matter of the present invention, drawn to much larger scale;

Fig. 3 is a` fragmentary detail view of a portion of the mechanism illustrated inl Fig. 2, showing the parts in a different position; and

Fig. et is a view similar to Fig. trating a slight modilication.

Referring to Fig. 1, the numeral 1 indicates a portion ot the central station desk of a carrier dispatch system, while 2 designates one of the several carrier transmission' tubes extending from the various sub-stations, and provided at the central station desk with the discharge terminal 3 normally closed by a valve 4 all iu usual manner. The

3 but illustransmission tube 2 is continued as indicated at beyond the v1.lischarge terminal and ends in a substantiallj` horizontal portion 6 forming part of the casing of the controlling device hereinafter more fully described. The usual vacuum drum is indii cated at 8. One end olf the section tube 9 is connected to this drum, the other end of the tube extending in a` substantially horizontal plane and terminating in the part 10 also forming a portion of the casing of the controlling apparatus. The terminal portion 6 otl the transmission tube and the terminal portion 10 of the suction tube are preferably arranged substantially in alignment as indicated in Fig. 2.

rlhe casing of the controlling apparatus is provided with a` chamber 11 which communicates with the end 6 ot' the transmission tube and with a chamber12 communicat ing with the suction tube, these chambers being separated by means of a transverse partition 13 extending across. the casing. This partition is provided with an opening 14 of substantial area to provide communication between the chambers 11 and 12, this opening being defined by an annular valve seat 15. A main disc valve 16 co-operates with the valve seat, being carried by a stem 17 which slides in a bore in a sleevel member 18 supported centrally ot the opening 14 by mea-ns ot' arms such as 19. The upper or rear wall of the chamber 12 is defined by a flexible diaphragm 20. The edges of this diaphragm are clamped between a flange 21 carried by the main part of the casing and a liange` 22 forming the edge of a secondary portion 23 ot the casing. The space to the rear of the diaphragm constitutes a chamber 24 which is normally closed against the entrance of atmospheric air.

The central part of the diaphragm is `clamped between rear and front plates or washers 25, 26 respectively, which are secured to the end of the valve stem 17 by means of a nut 27. A spiral spring 28 is interposed between the washer 26 and the rarms 19 which support the sleeve 18 and vaxial passage 29 which opens at one end into chamber 24 behind the diaphragm 20 and whose other end opens as indicated at 31 through the side wall of the stem 17. The opening at 31, when the parts are arranged as shown in Fig. 2 lies slightly to the rear of the end wall 321 of the sleeve 18 thus providing a passage of small capacity for the flow of air from the chamber 24 to the chamber 12, but when the valve 16 is fully open, the orifice at 31 is covered by the sleeve 18 thus closing the passage 29. A restricted by-pass opening comprising the ports 33, 34 is also provided for permitting air to pass from the chamber 24 to the chamnssaeeo ber 12, being regulated by means of a needle valve 35 controlled by a handle 36. The partition 13 between the chambers 11, 12 is also furnished with a constantly open passage 37.

The secondary part 23 of the casing is furnished with the outwardly flaring walls 38 having openings 39 therein and terminating in a llange 40. The edges of a dia phragm 41 are clamped between the flange and the flange 42 or' the cover member 43 of the casing, this diaphragm 41 forming the bottom wall of a chamber 44 within the cover member. The cover member 43 is `furnished with a lateral extension 45 providing a passage 46 which communicates with one end ot' a pipe or tube 47 whose other end extends through the side wall of the tube 6 and is bent as indicated at 48 at substantially right angles to the main part thereof so that its opening is directed oppositely to the flow of air in the tube 6, the direction of which is .indicated by the arrow 49. The cover member 43 is provided with a boss 50 having a screw-threaded bore 51 axially aligned with the valve stem 17, and with which a screw 52 engages. This screw is provided with a knurled head 53 for turning it, and has an aXial bore within which a` stem 54 slides freely.y The central part of the diaphragm 41 is clamped between a pair of plates or washers 55, 56` respectively which are secured to the end ol the stem 54 by means of a nut 57, and a spring 53 surrounds the stem 54, bearing at one end against the plate and at its other against the inner end of the screw 52. This spring normally tends to hold the diaphragm 41 in the position shown in Fig. 2, the tension of the spring being variable by means of the screw 52.

The secondary member 23 of the casing is provided with an opening 59 for admitting air into the chamber 24. This opening is normally closed by means of an auxiliary governing or regulating valve 60 having an arm 61 pivoted at 62 between a pair of lugs or ears such as 63 projecting upwardly from the top member `64 of the part 23. A latch member 66 is pivoted upon a pin 67 secured to t-he lever arm 61 and a spring` 68 surrounding such pin tends normally to swing the latch 66 in a clockwise direction as viewed in Fig. 3. The latch is provided with a toe 69 engageable with a stop pin 70 for limiting the turning of the latch.

The stem 54 extends through the diaphragm 41 and is provided with an enlarged head comprising one or more flanges of truncated conical iorm, three of such flanges 71., 72, 73 respectively being shown in Figs. 2 and 3. Each liange is provided with the conically inclined peripheral surface 74 and with an abrupt radialshoulder 75. The latch 66 is provided with a shoulder 7G engageable with either of the radial abutment shoulders'75 and with a cam fame 77 engageable with either of the inclined faces 74. In the normal position of the parts the latch is spaced from the upper shoulder as shown in Fig. 2, thus permitting slight movement of the diaphragm 41 to take place without affecting the position of the valve 60.

In Fig. 4 a slight modification is illustrated in which the stem 54a is furnished with but a single head or flange 71a having the inclined surface 74EL and the radial shoulder 75a. The valve lever 61a is also shown as. supplied with a latch lever 66"L in the same manner as previously described.

In the operation of the pneumatic dispatch system herein disclosed the parts of the controlling device normally occupy the position shown in Fig. 2. As a partial vacuum is maintained in the drum 8 the pressure in chamber 12 is somewhat below atmospheric pressure and thus a small quantity of air is caused to flow from the chamber 11 through the passage 37, this air being drawn through the transmission tube 2. When a carrier is introduced into the transmission tube'at a substation, it iminediately serves to obstruct the free passage of air through the tube 2. This causes a slight drop in pressure in the chamber 11 as well as in the transmission tube and in tube 47, thus decreasing the pressure in the chamber 44 behind the auxiliary motor diaphragm 41. The diaphragm 41 im mediately moves upwardly as viewed in Fig. 2 thereby bringing the uppermost of the shoulders 75 into engagement with the member 76 of the latch 66, raising the valve lever 61 and lifting the regulating valve 60 from its seat. This immediately permits atmospheric pressure to build up in the chamber 24 and as the opposite side of the main motor diaphragm 2O is exposed to the pressure of the vacuum tank, this diaphragm is immediately depressed against the spring 28, thus fully opening the main valve 16 and permitting a large volume of air to rush through the transmission tube 2, thereby moving the carrier along the tube.

As the auxiliary diaphragm 4l moves upwardly, the latch member 66 is caused to assume the position shown in Fig. 3 wherein the surface 76 is shown as on the point of becoming disengaged from the surface 7 5. As soon as the latch is disengaged, the valve 60 closes, thus cutting off communication between the chamber 24 and the outside atmosphere. The air within the chamber 24 now bleeds slowly past the needle valve 35 until the pressure in the chamber 24 is reduced sufiiciently to permit the spring 28V to restore the diaphragm 2O to its original position. This movement of the diaphragm takes place slowly at first in accordance with the reduction in pressure in the chamber 24 but as the opening 31 in the valve stem 17 is uncovered during the upward movement of the stem, a passage is afforded between the chamber 24 and the chamber 12 which permits the air of the chamber 24 to be exhausted at a much more rapid rate than is possible through the needle valve. This causes the main valve 16 to approach its seat much more rapidly during the final movement of the valve than during the first part of its closing movement so that the valve is caused to act with much greater certainty than is usually the case. It will be noted that the closing of the valve 16 depends upon the setting of the needle valve 35 and is entirely independent of the pressure which may prevail in the transmission tube 2, after the controlling operation has once been initiated. In other words the closing of the valve 16 is not dependent upon the reverse movement of the diaphragm 41 but may be caused to occur at a predetermined and definite interval of time after' its opening. If the carrier has emerged from the transmission tube 2 prior to the closing of the valve 16 the parts will occupy the position of Fig. 2, as the spring 58 restores the diaphragm 41 to its normal position as soon as the pressure in thetube 6 rises to or above normal. During the downward movement of the diaphragm 41 the flanges 71, 72, 73 pass freely by the latch member 66 which turns in opposition to its spring for permitting this movement, the latch immediately snapping successively behind the several flanges as the parts appreach normal position. If, however, the carrier has not emerged from the tube 2 when the valve 16 closes, the pressure in the chamber 11 may not rise fully to normal, in which case the shoulder 76 of the latch may only snap over the lowermo-st or the intermediate shoulder 7 5 and if the carrier slows down the resultant decrease in pressure in the tube immediately again lifts diaphragm 41, opening valve 60 part way and thus allowing valve 14 to open partially.- A new impulse is thus imparted to the carrier, but this new impulse need not be as energetic as the original one since the carrier is already moving. Thus by a series of timed impulses the carrier may be moved to'its destination with the expenditure of a minimum amount of air. If while the first carrier is in the tube, a second carrier should be introduced, the main valve 16 is not necessarily opened, as the opening of the valve is only occasioned by a drop in pressure in the transmission tube occurring when the latch 66 is engaged with the stem 54. The tube 47 which connects the tube 6 with the chamber 44 is provided with the bent end 48 so that this tube constitutes an impact tube which servesto transmit very slightest increase in pressure in the air cur-. rent flowing in the -tube 611s immediately felt in the chamber 44 so that the diaphragm 41 isnhighly responsive to increase in pres-y surey and ispquickly restored` to position` whereinvit is operatively engaged with the regulating valve 60. 4*By providing a series ofthe flanges 71 etc.;upon the stem `54thel diaphragm-4l may pick up the valve 60 for further operation even though the diaphragm may not'previously -havebeen restored fullytoits normal position, as above described.

f y,The device shown in Fig. 4 providesbut a single -lange 71a -or engagement with the latchfand under some circumstances this.

may be` found suflicient, it beingpreferred however to employ aplurality of the flanges orthe reasons previously pointed out. The controlling apparatus thus devised is of very compact form and requires relatively few4 parts in .its construction. The parts are nearly all contained within the casing or housing so that they are not exposedto ac cidentalinjury andthe apparatus is readily capable .of installation in the restricted spaces commonly, availableior such purposes. Y

lVhat we claim andfdesire to secure by Letters Patent of the UnitedStates is:

l. Incombination in a pneumatic dispatch system, a carrier transmission tube, means for causing a current-of air of normal predetermined amount constantly to enter lthe mouth of the tube, and controlling means, comprising a pressure actuated element constantly exposed upon one side to the pressure in the transmission tube and freely open upon the other side tothe atmospheric pressure, for admitting an' abnormal-quantity of air to flow through the-tubefor a predetermined interval of time.

Y 2. In combination in a pneumatic dispatch system, a carrier transmission tube through. which a current ofair of normal substantially predetermined amounty flows constantly, and means operative by variation in pressure in the tube due to the introduction of a carrier therein for permitting, an abnormal quantity of air to low through the tube Jfor a. predetermined interval independent of the presence of a carrier in the tube, said means including a diaphragm constantly exposed on one side to full atmospheric pressure.

3. Apparatus of the class described comprising a transmission tube for carriers, and means operative upon decreasein pressure in said tube due to the presence of a. carrier therein foradmitting a. large volume oair to` flow through the tube for a predeterminedlength of time, and thereafter to admit air in relativelyy smaller volumeupon subsequent decrease vin VVpressureinthe tube due tothecontinued presence of the carrier there-in;

4. Apparatusof the class described comprising a normally open transmission tube for carriers, and automatic means for. subjecting alcarrier within the tube to a plurality of impulses of predetermined duration comprising a pressure actuated diaphragm constantlyv exposed upon one side to the pressure of the transmission tube and freely` exposed upon the other side to .atmospheric pressure.

y5. Apparatus of the class described comprising. a normally open transmission tube, a suction tube, valve means normally substantially closing communication `between said tubes, and means actuated by pressure variation in the transmission tube due to introduction of a carrier therein for initiatingl opening of the valve means to determine closing 'thereof after a predetermined interval independentof the continued presence of the ycarrier in the tube, said means comprising adiaphragm constantly exposed ono-ne side to atmospheric pressure.

6. Apparatus of the class described comprising a transmission tube, a suction tube, a spring pressedvalve normally closing a passage between said tubes, la pneumatic motor for opening said valve, an auxiliary motor actuable by introduction of a carrier within the transmission tube, means normally connecting said motors `i'o-r initiating operationof said irst motor upon actuation of the auxiliary motor, and means automat ically disconnecting said motors after said first motor begins to operate.

7 Apparatus of the classkdescribed comprising a transmission tube and a suction tube, al valve for controlling a passage between said tubes, a. pneumatic motor comprising a diaphragm for moving said valve, a device movable in response to luctuat-ion in air pressure in the transmission tube due to introduction of a carrier therein,` and connections actuable by said movable device for determining admission of pressure .fluid to one side of said diaphragm, said'connections` comprising automatically disengageable parts.

8. Apparatus of the c-lass described comprising a transmission] tube -and a suction tube, a valve for controlling a passage between said tubes, a spring normally opera tive to move said valve in one direction, a pneumatic motor for moving the valve in the opposite direction, a regulating valve for determining operation of the motor, a movable element responsive to fluctuation in air pressurey in the transmission tube, and connections between said element and said last named valve, said connections comprising Vdisengageable parts `constructed and aranged automatically to .separate after a Cil lUO

predetermined operative movement of said movable element. Y

9. Apparatus of the class' described comprising a transmission tubeI and a suction tube, a main valve for controlling a passage between said tubes, a spring normally operative to move said valve in one direc tion, a main pneumatic motor comprising a diaphragm for moving the valve in oppo sition to its spring, an auxiliary motor having a diaphragm sensitively responsive to fluctuation in air pressure in the transmission tube, a regulating valve for determining the admission of pressure fluid to one side of the diaphragm of said first motor, and connections between said regulating valve and the diaphragm of the auxiliary motor, said connection comprising a latch pivoted to one of said parts and normally engaging an element moving with the other of said parts.

10. Apparatus of the class described comprising a transmission tube and a suction tube, a valve for controlling a passage between said tubes, a spring normally operative to move said valve in one direction, a motor for moving the valve in opposition to its spring, a movable member for determining initiation of operation of said motor, a pressure actuated part sensitively responsive to variation in pressure in the transmission -tube by introduction of' a carrier therein, a latch lever pivotally motmted upon the movable member, and a latch engaging abutment moving with said pressure actuated part whereby movement of' the latter serves to actuate said movable member.

11. Apparatus of the class described comprising a transmission tube and a suction tube, a main valve for controlling a passage between said tubes, a spring normally operative to move said valve in one direction, a fluid motor for moving the valve in opposition to its spring, a pivotally supported regulating valve for the motor, a part sensitively responsive to decrease in air pressure in the transmission tube, a latch carried by said regulating valve, and a part having a latch engaging abutment shoulder associated and moving with said sensitively responsive part, said latch and shoulder being constructed and arranged automatically to become disengaged after a predetermined movement of said. sensitively responsive part.

12. Apparatus of the class described comprising a transmission tube and a suction tube, a main valve for controlling a passage between said tubes, a spring normally operative to move said valve in one direction, a pneumatic motor for moving the valve in opposition to its spring, a pivotally supported regulating valve for determining actuation of the motor, an auxiliary motor comprising a diaphragm responsive to fluctuation in pressure in the transmission tube by reason of introduction of a carrier therein, a stem secured to said diaphragm having a radial shoulder projecting therefrom, and a latch carried by the regulating valve and engageable with said shoulder for transmitting movement from the diaphragm to the regulating valve, said latch being constructed and arranged to disengage said shoulder upon a predetermined movement of the diaphragm.

13. Apparatus of the class described comprising a transmission tube and a suction tube, a valve for controlling a passage between said tubes, means normally tending to close said valve, a fluid motor for opening the valve, a regulating valve for the fluid motor, a diaphragm responsive to fluctuation in pressure in the transmission tube, a stem carried thereby, said stem having a head of truncated pyramidal form providing a radial shoulder at its base, and a latch carried'by said regulating valve and automatically engageable with said shoulder upon movement of the diaphragm in one direction, and automatically disengageable from said shoulder after a predetermined extent of movement of the diaphragm in the opposite direction.

14. Apparatus of the class described comprising a transmission tube and a suction tube, a main valve for controlling a passage between said tubes, means normally tending to close said valve, a fluid motor for opening the valve, a regulating valve for the fluid motor, a diaphragm responsiveto fluctuation in pressure in the transmission tube, a stem carried thereby, said stem having a plurality of axially spaced shoulders outstanding therefrom, and a latch pivotally secured to said regulating valve and engageable` with either of said shoulders whereby to transmit movement from the diaphragm to the regulating valve.

15. Apparatus of the class described comprising a transmission tube and a suction tube, a main valve for controlling a passage between said tubes, means normally tending to close said valve, a fluid motor for opening the valve, a regulating valve for the fluid motor, a diaphragm responsive to fluctuation in pressure in the transmission tube, a stem carried thereby, said stem having an enlarged head of truncatedV pyramidal form providing an inclined peripheral surface and a radial shoulder, a latch pivotally supported upon the regulating valve, and means for limiting swinging of the latch about its pivot, said latch being constructed and arranged to engage said radial shoulder upon movement of the stem in one direction, and to be disengaged therefrom by a movement of the regulating valve of a predetermined extent.

16. Apparatus of the class described comprising a transmission tube anda suction tube, a main valve for controlling a passage between said tubes, means normally tending to close said valve, a fluid motor for opening the valve, a regulating valve for the fluid motor, a diaphragm responsive to fluctuation in pressure in the transmission tube, a stem' carried thereby, said stem having a series of truncated, pyramidal'flanges providing spaced radial shoulders, and a latch member carried by the regulating valve and engageable with either of said shoulders for transmitting movement from the diaphragm to they regulating valve.

17. Apparatus of the class described comprising a transmission tube, a suction tube, and a valve for controlling a passage between said tubes, fluid motor means for opening said valve', a diaphragm responsive to'fluctuations in pressure in the transmission tube, a regulatingvalve for determining the operation of said motor, means movable with the diaphragm in one direction for opening said regulating valve, and means operative independently of the diaphragm for closingsaid latter' valve. y

18. Apparatus of the class described com` prisinga transmission tube, a suction tube, and a valvefor controlling a passage be` tween'V said tubes, fluid motor means for opening said valve, a diaphragm responsive to fluctuations in pressure in the transmis sion tube,l a valve for regulating the operation of said motor means, automatically disengageable connections' for transmitting movement to'thev regulating valve from the diaphragm during movement of the latter in one directionfonly, and `independent means for moving the regulating valve inthe opposite direction. p f

19,*1Apparatus of the class described comprising a transmission tube, a suction tube, and a. Yvalve for controlling a passage be tween said tubes, a fluid mot-or for opening said valve, a diaphragm responsive to fluctuations in pressure inv the transmission tube, a regulating'valvefor determining the operation of sai-dmotor, means formoving the-regulating valve with the diaphragm Aasfthe'latter movesin one direction, said means automatically becoming inoperative. after a predetermined extent of movement, and spring means for restoring the regulating valve tov initial position.

20. Apparatus of the class described coinprising al transmission tube, a suction tube, a valve for controlling a passage between said tubes, and automaticlmeans for opening and closing said valve, saidI means vbeing constructed and arrangedk to increase the speed of said movement of tbe valve as it nears the end of itsc-losing movement.

21. Apparatus of the class described comprising a transmission tube, a suction tube, and an opening providing"'communication therebetween, said opening being deiined by and a valve. for controlling a passage there? between, a. diaphragm exposed upon its front side tol the pressure in the suction tube, means connecting the diaphragm and valve, a springf normally tendingtoclose the" valve, and means operatives-uddenly to relieve pressure upon theA rear side of the diaphragm duringthe4 closing of the valve tope-rmit the valve to complete its `closing movement rapidly.

23. Apparatus of the class described comprising a transmission tube, a suction tube and a valve for controlling communication therebetween, a diaphragm exposed upon its fronty side to the pressure in the suction tube,a stem connecting the diaphragm'and valve, a springY surro-undingsaid stem and normally tending' to close-the valve, means for admitting pressurefiuid t0 the rear side of the diaphragm for opening the valve, means for exhausting such pressure fluid at a predetermined rate-to permit the valve to close, and means permitting such pressure fluid to'l'exhaust at a greater rate as the valve approaches its closed position.

24. lApparatus of the class described comprising a transmissiontube, a suction tube anda valve for controlling a passage there# between, a diaphragm exposed upon its front 'side to the pressurel in the suction tube, means eonnecting'the diaphragm and valve, a spring normally tending to;close the valve, means admitting pressure fluid to the rear side of the: diaphragm for openingthe valve and for exhausting such ypressure fluid at va predetermined rate'toipermit the valve toclose, anda passage for permitting such pressure fluid to exhaust at a greater rate during the final portion of theE closing move ment of the; valve.

25.` Apparatus' of the class described com prising a transmission tube, a suction tube anda valve for controllinga passage therebetween, a diaphragm exposed upon its front side'to the pressure yin the suction tube, a stem'connecting'the diaphragm and valve, said stem having an axially extending passage opening at one end at the rear side of the"diaphragm and. at the' other at a point in the side of they stem at the front of the diaphragm, a spring'surround# ing the ste-m and normallytending to close the valve; vand means for admitting pressure fluid to therear side of the diaphragm and for permitting it to exhaust therefrom at a predetermined rate, said axially extending passage in the stem being constructed and arranged suddenly to increase the rate of exhaust ot such pressure fluid as the valve nears its closed position.

26. Apparatus of the class described comprising a transmission tube, a suctio-n tube, and a valve for controlling a passage therebetween, a diaphragm exposed upon its front side to the pressure in the suction tube, a stem connecting the diaphragm and valve, a fixed sleeve forming a. guide for said stem, said stem having an axially extending passage opening at one end at the rear side of the diaphragm and at the other end at al point in the side of the stem, a spring' normally tending to close the valve, and means for admitting pressure fluid to the rear of the diaphragm for opening the valve and for permitting such fluid to exhaust at a predetermined rate to allow the valve to close, said sleeve closing the opening of said passage at the side ot the stem when the valve is fully open but exposing such opening as the valve approaches its closed position. n

27. Apparatus of the class described comprising a transmission tube, a suction tube and a valve :tor controlling a passage therebetween, and a fluid motor for determining operative movement of said valve, said motor comprising a diaphragm responsive to slight variations in air pressure, and a tube projecting into the transmission tube. and having its end directed oppositely to the flow of air therein, the other end ot the tube con'lmunicating with the space to one side of the diaphragm.

28. Apparatus of the class described comprising a transmission tube, a suction tube and a valve for controlling a passage therebetween, and a fluid motor for determining operative movement of said valve, said motor comprising a movable element responsive to fluctuations in pressure, and an open ended impact tube having one end thereof disposed within the transmission tube and directed oppositely to the flow et air therein, said tube being constructed and arranged to transmit variations in pressure from the transmission tube to said movable element.

29. Apparatus of the class described comprising a transmission tube, a suction tube and a valve for controlling communication therebetween, and a fluid motor for determining operative movement of said valve, said motor comprising a casing, a diaphragm within the casing movable in response to variations in air pressure upon its opposite sides, and a tube opening at one end into the space to one side of the diaphragm and at the other into the transmission tube, the latter end of the tube being disposed at substantially right angles .to the main part thereof and being directed oppositely to the flow of air in the transmission tube.

30. Apparatus of the class described comprising a transmission tube and a suction tube, said tubes having horizontally disposed, aligned portions, a casing into which said portions open, said casing having a transverse partition provided with an opening defined by a horizontal annular valve seat, a valve movable upwardly into engagement with said seat, a spring normally tending to close the valve, a diaphragm in the upper part of said casing exposed upon its lower side to the pressure of the suction pipe and connected to the valve, an auxiliary diaphragm arranged within a chamber in said casing, means for transmitting fluctuations in pressure in the transmission tube to said auxiliary diaphragm, and means actuable bv said latter diaphragm for admitting atmospheric pressure to the upper side of said first diaphragm.

31. Apparatus of the class described comprising a unitary casing having a chamber communicating with a transmission tube, a second chamber communicating with a suetion tube, a valve controlled passage between said chambers, a diaphragm forming one wall of said second chamber and delining a normally closed space at its opposite side, a regulating valve for admitting atmospheric pressure to said space, a third chamber in said casing, a diaphragm forming one wall of said third chamber and coustantly exposed upon its outer side to atmospheric pressure, means connecting said latter diaphragm with said regulating valve for actuating the latter, and means for connecting said third chamber with the transmission tube.

32. Apparatus of the class described comprising a transmission tube and a suction tube, and a casing having a pair of fluid motors therein, a regulating valve for determining actuation of one of said motors, connections between said other motor and said valve, and a valve for contro-lling a passage between said tubes, said valve being operatively connected with the first motor.

33. Apparatus of the class described coin-- prising a casing having an apertured partition across the same, a valve controlling the aperture in the partition, a diaphragm extending across the chamber to one side of the partition` a valve governed aperture in the Wall of the casing behind said diaphragm, a second diaphragm parallel to and co-axial with the first diaphragm, means actuable by the second diaphragm for opening said valve governed aperture, and means connecting said first diaphragm with the valve in the partition.

34. Apparatus of the class described comprising a easing having (zo-axial diaphragms therein,-v a 'main valve connected with one diaphragm, a regulating valve for the latter diaphragm aotuable by the second diaphragm, and means for transmitting a variablefiuid pressure to said second diapliragm.

35. Power transmission apparatus of the class described comprising a casing having eo-aXial diaphragm chambers, a diaphragm in each chamber, a valve connected to one diaphragm,r a regulating valve for determining admission of pressure Huid to one side of said latter diaphragm, automatically disengageable connections lbetween the said regulating valve and the second diaphragm for transmitting movement to said regulating valve Iduring va predetermined extent only of the movement of said second diaphragm, and means admitting variable fluid pressure to said secondy diaphragm.

Signed `by us vat Boston7V Massachusetts this yfourth dayof August 1922.

CHESTER kS. JENNINGS. CLIFFORD R. DUMBLE.

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