Патент USA US2407891код для вставки
Sept. 17, 1946. 2,407,890 G. T. MCCLURE PROTEGTION’VALVE DEVICE Filed March 15, 1945 à-.„\É, .o INVENTOR, Glenn ÍMcCZu're BY _ ATTURNEY Patented Sept. 17, 1946 ` 2,407,890 UNITED STATES PATENT OFFICE PROTECTION VALVE DEVICE Glenn T. McClure, McKeesport, Pa., assignor to The Westinghouse Air Brake Company, Wil merding, Pa., a corporation of Pennsylvania ' Application March 15, 1945, Serial N0. 582,934 11 Claims. (Cl. 30S-«84) 1 2 This invention relates to fluid pressure brakes, and more particularlyto an air brake equipment locomotive unit in the event that the compressor of the type employed on a railway locomotive. i A further object is to provide means operative to permit the flow of fluid under pressure from Diesel-powered locomotivesfor certain classes on the leading unit should fail. „ l Y - of railway service in some instances comprise a the main reservoirs on the first locomotive‘unit plurality of individual power'units coupled to gether. For example, a complete Diesel locomo through the main reservoir pipe to the reservoirs on the trailing locomotive units only after _the tive may consist of one “A” (control) unit cou ñuid under pressure in the reservoirs on the first pled to first and second “B” (auxiliary) units, locomotive unit attains a selected degree of prese all three power units carrying engine equipments 10 sure and operative thereafter when the ñuid controlled from the “A” unit. Diesel locomotives pressure in the main reservoir pipe is- reduced of `this class are operative to exert great tractive to a chosen lower degree to prevent the flow of effort. particularly` at low speeds. Although such iiuid under pressure from the reservoirs on the Diesel locomotives are regularly operated to great ñrst unit to the main reservoir pipe, which means advantage and` without undue risk of separation maybe readily installed in an existing` brake of the several units, actual experience has dem equipment for cooperation with standard brake onstrated that suchV an accident is possible,- and controlling devices without impairing the normal that the leading portion’of a Diesel locomotive functioning of the apparatus. l 1 v- ~ might break away from the other units and the Other objects and advantages will be appar rest of the train. The engineer stationed in the 20 ent in the following more detailed description of leading portion may in fact be unaware that a break-in-two has occurred, by reason of the enormous power which that unit delivers, and as the invention. l' ‘ The single figure in the accompanying draw' ing is a diagrammatic view, partly in section,> of a result, the parting of the main reservoir pipe a protection valve device constructed in accord-' between the separated units of the locomotive 25 ance with the invention and associatedwith such may seriously impair his control of the brake portions of the air brake equipment of a` multi equipment, The locomotive brake equipment on ple unit Diesel locomotive as concern the invent a multiple unit Diesel locomotive is, of course, de tion. A signed to operate automatically upon parting of In the drawing, the reference numerals I and the brake pipe to effect an emergency applica 30 2 indicate a pair of main reservoirs which are `tion of the brakes, but if the engineer is un carried on the leading locomotive unit and com aware of a break-in-two and consequently allows prise a part of the usual air brake equipment his brake valve to remain in running, position, (not shown) thereon. The main reservoirs land and if, as is usually the case, the controlled 2 are connected by means of a pipe 3 vto aprœ emergency feature of the equipment has been set 35 tection valve device 4, which device operates to for freight service to permit only a slow rate of control communication between the pipe 3 and brake cylinder pressure development, the loss of a main reservoir pipe 5, as will hereinafter more main reservoir pressure through the broken main fully appear. A check valve device 6 is` provided reservoir pipe will in a short time seriously limit to prevent a back flow of fluid under` pressure the brake cylinder pressure obtainable in the 40 from the main reservoir 2 to the pipe 3, the main leading portion of the locomotive. reservoir 2 being provided for the purpose of It is an object of my invention to provide an storing fluid under pressure to be supplied by improved locomotive brake equipment designed way of pipe 'l to the usual air brake equipment for Diesel units of the above identified class, in (not shown) installed on the leading unit of a cluding means operative to prevent brake fail 45 Diesel locomotive. The main reservoir pipe 5 ures of this nature. _ ' comprises a section 8, carried on the leading 1o Another object of the invention is to provide comotive unit, Aand a section 9 carried on the an improved protection `valve device operative trailing locomotive unit, the sections 8 and 9 to prevent complete loss of main reservoir pres being connected by a coupling means I 0. The sure in the leading locomotive in case of a train 50 section 9 is connected'to another main.- reservoir ‘ break-inftwo. ‘ Another object is to provide an improved pro' tection valve device operative to supply fluid un der pressure from the main `reservoirs of the trailing locomotive units to those of the leading l I which comprises a part of the usual air brake equipment (not shown) for the trailing locomo tive unit. It` will’be understood that the main reservoirs l and 2 are adapted to be charged with ñuid under pressure delivered by way of a pipe 2,407,890 3 I2 from a compressor (not shown) >mounted on the leading locomotive unit and the main reser voir II is adapted to be charged with fluid under pressure from a suitable compressor (not shown) mounted on the trailing locomotive unit. The protection valve device 4 may comprise a base structure I3 supporting a casing structure 4 V between a surface 41 of the member 46 and a shoulder 48 provided in the peripheral wall of the chamber 31, as shown Yin the drawing.v The spring seat member 44 slidably engages a stud portion 49 of the follower member 43 for the purpose of retaining the spring 45-in opera tive engagement with the follower 43 and also for I4 and containing a, supply chamber |.5„_Áwhich limiting, in a manner Íto. be explained later, the chamber'i-s in constant4v open communication with upward travel ofV a pistongmember ¿50 ‘mounted the main reservoir I by way of the pipe 3'. Con in the chamber 33. The member 44> i's'substan tially tubular inshape having its upper end 5I turned inwardly forV engagement with a washer tained in the supply chamber I5 is a supply con trol valve I6, which valve cooperates with a valve seat I1, formed on the end of a bushing I8, t0v control communication by way of said bushing between the supply chamber I5 and _a passage I9.,_. which passage connects with thel main reservoir pipe 8. Formed in the casing structure I4 is a strainer and check Valve chamber 20, which chamber is ` `52 secured to' the stud portion 49 to thereby limit the downward movement of the member 44 and , having'its lower end 53 ñared outwardly for sup pQrtìI'lgj andretaihing the spring 45 at its lower end. ` f .The piston member 5I] is substantially cup shaped for accommodating the lower ends of the in constant open communication with the supply 20 spring 45 and seat member 44 and abuts the chamber I5 by way of a passage 2I and with a diaphragm chamber 23 by way of a-passage 22. For the protection of the passage 22 against the passing` of dirt therethrough there is provided in chamber 20 a wire screen strainer 24 which is clamped between two sectionsof the casing struc turev I 4f. Also contained in the chamber 2u is a ball check valve 25 arranged for operative engage ment with a valve seat 26 formed in a suitable bushing 21' mounted in the casing structure I4, . the under side of the‘check valve 25 being in com bottom surface of kthe seat member for propelling ' the same upwardly until the upper end 5I thereof engages the follower 43.. A'sealing ring 54 is pro' Vided in» an annular groove in the periphery of ' the piston‘member 50 for preventing the leak age of iluid'under pressure from the chamber 33 to the atmospheric chamber 31. The piston mem ber 58 is further provided with a downwardlyïex tending steinv 55 which is slidably 'mounted in a through bushing 56 in a` wall in the casing struc- Y ture I 4 and extends transversely through thepas sage I9 andv bushing I8 into the supply passage I5. The stem 55 is also provided with a sealing' sage 28 and a chamber 29. For the protection of ring' 51 for preventing leakage of iiuid under pres Ythe valve device 4 and the other air brake equip sure between the passage I9 andV chamber 33. ment when iiuid under pressure from the main Secured by means of a pin 58 and a retaining reservoir pipe» 5 flows past the check valve 25, as spring or clip 59 to the lower end -of the stem will hereinafter more fully appear, a tubular air cleaner or' strainer 30 of the cartridge type is 55 of the piston member 5U is the valve I5 which, asl will' later appear, may be operated thereby into mounted in the chamber 29-so as to have its inner peripheryA open to the passage 28 and its outer 40 engagement with the valve seat I 1. It is pre periphery exposed to the passage I9. Upon re' ferred that the clearances in the mounting means munication with the passage I9 by way of a pas l moval of a cap nut 3I which closes the outer end of the chamber 29 and hassealing engagement with one end ofthe strainer 30, the strainer may be readilyl removedv for cleaning. Clamped‘ at> its periphery between two sections ofthe' casing structure I4 is a flexible diaphragm 32 having at: its upper side the chamber 23, which chamber is constantly open to the chamber- 28 by way of the passage 22'A and, as shown, maybe connected to'a piston chamber 33 byY way’ of a Valve chamber 34. and` a. passage 35, they passage 35. beingV open to atmosphere also by way of a choke- 3B?. At; the, under side of' thel diaphragm is» a. spring> chamber 31 which i's constantly> open to atmosphere by way.y of-a passage 38. of the valve I Ii beisuflicient to permitthe valve tov be> self-aligning in its operation. » In charging the locomotive with fluid under pressure and' under normal conditions, ñuid un der pressure is supplied from the usual compres sor (not shown) on the leadinglocomotive to the main reservoir Iï by' way of theV pipe I2 and iiows therefrom by wayy ofthe pipe 3, check valve de* vice 6, and a pipe 60 to the main reservoir» 2, from which fluid under pressure is supplied by way of pipe 1 to the usual air brake control equip ment found on the leading unit of' a Diesel loco-Ãmotive. Fluid under pressure also flows from pipe 3 through a passage 6I to the supply chamber I5 of the protection valve device 4. At the same Contained> in the valve chamber 34 is a valve 'time' fluid under pressure is also supplied to the 39A having a fluted': stem 40 which extends through main reservoir- I`I on the trailing unit by the op a suitable.’ bore in the casing so that its- lower eration of auxiliary compressor meang` (not endY may be . operativelyA engaged by the dia 60 shown) mounted' on that'unit. Y ‘ phragmv 32. Interposed between and operatively Fluid under pressure supplied to the chamber engagingy a cap nut 42| at the top of the >chamber 34 and' the; valve 39 is a springY 42 which urges I5 of the protection valve device 4 flows from that chamber by way of the passage 2l to the chamber 28, thence by> way of a choke 62, in' said‘ valve toward its seated position. Contained: in the,` chamber 31I andV interposed betweenl a diaphragmv follower 43 and a spring seat; member 424 isl aL compression spring 45, which, asY will hereinafter more fully» appear, serves to establish they degrees of fluid pressure in the sup ply chamber> I5 at: which the Valve I6- will be , opened or closed'. The` follower 43 is slidably serted in passage 22 for reasons which will appear later, and the passage 22 to the diaphragm cham ber 23, whence it will flow past the fiuted stem 40 and valve 39 to the piston chamber V33 by way of >the passage 35. Fluid under pressure being sup plied to the piston‘chamber 33 will also iiow to atmosphere by way of choke 35 at a, restricted. guided-»in an annular member 46, the _member .46 Aalso serving as amedium for clamping the dia initial charging', fluid under pressure in'cham'ber ’ phragm 32' andl being arranged in the chamber 31 so, as~ to coniine. the travel of the' follower'43 the bushing- I3, chamber I9 and main reservoir rate. The valve I6 being unseated as shown» at ' I5 may-'also lflow to main reservoir II by Way of 2,407,890 6 ‘ pipe 5, if the iluid‘pressure in the main reservoir >the fluid pressure therein to be rapidly depleted. II is‘lower, such `as when the compressor (not It will be apparenttherefore that substantiallyV shown) on the trailing unit is not operating. Since the degree of iluid pressure in the cham the full force of the spring 45 will be effective at once to open the valve I6 promptly. It should be further explained that any tem porary ñuid pressure vdrop in the chamber I5, which' might be caused by the sudden opening of ‘ bers 23 and 33 is substantially the same and, the ï effective area of the piston member 5l) is greater than that of the diaphragm 32, the piston mem ber 5I] will respond to a lower degree of ñuid pres sure than will the diaphragm 32. It will here be the valve I6, especially with a high pressure dif ferential across it, will not, due to the how re understood that the relative flow capacities of 10 stricting choke (i2,v result in a corresponding re chokes ‘B2 and 3B are such that the flow of fluid duction in the pressure of fluid in diaphragm under pressure through choke 52 will be sufficient chamber 23, thus insuring against anlundesirable `to maintain the fluid pressure acting on the pis« operation of the diaphragm 32 and the piston ton member 53 at approximately that of the member 53 to again close the valve i6. Thus the main reservoir against the flow of fluid under 15 choke 62 serves to stabilize the diaphragm so that pressure to atmosphere through choke 33. When communication from the main reservoir I to the `the pressure of fluid in the chamber 3.3 ‘has piston chamber 33 is maintained closed :and the > reached a chosen degree (22 pounds for example) communication from main reservoir I to the l as determined by the valve of the spring 45, the main reservoir I I `is maintained open against ac piston member 56 will move the spring seat mem 20 cidental movement. i ber 44 upwardly against `the opposing pressure of the spring 45 until the valve I5 engages the valve ,ls'eat I1. With this movement the piston member “50 acts through the medium of its stem 55 and `the pin 58 to move the valve I6 into sealing en gagement with' the valve seat I'I, closing commu nication between the chambers I5 and I9 and thus between mainreservoir I and main reser If, however, the main reservoir line` 5 is broken or opened to the atmosphere as by the accidental separation of the locomotive units, fluid under pressure in the main reservoir I will flow to at 25 mosphere by way of the pipe 3, protection valve device il, and the undesired rupture in the main reservoir pipe 5. The resulting reductionin the fluid pressure in chamber I5 of the valve device 4 will cause fluid under pressure to flow from the `diaphragm chamber 23 by way of passage 22, However, fluid under pressure will continue to flow from chamber I5 to chambers 23 and 33 by choke 62, chamber 23 and passage 2| to chamber the route previously described. When the pres i5 and thence to atmosphere by way of bushing sure of fluid in the diaphragm chamber 23 has I3, passage I3 and main reservoir pipe 5. When attained a higher chosen degree, such as 100 the pressure of fluid in chamber 23 has been re pounds, th‘e diaphragm 32 will deflect downward 35 duced to some chosen low degree such as eighty pounds, the predominant pressure of the spring ly in response thereto, causing the follower 43 to move downwardly until stopped by the engage 35 will cause the diaphragml32 to deillect up wardly and act through the medium of the stem ment of the lower outer` surface thereof with the dû to move the valve 39 against the opposing shoulder 48 in the chamber 3l. It should be noted that the spring 45 had previously been 40 pressure of the spring 42 to itsunseated position compressed a certain amount due to the upward in which it is shown in the drawing. -movement of the piston member 58,' consequently With the valve 39 unseated, fluid under pres sure in diaphragm chamber 23, and consequently `theforce of the spring acting to oppose the down ward deflection of th'e diaphragm was corre fluid under pressure in chamber I5 connected to spondingly increased. chamber 23 by way of passage ZI, chamber 2l), choke G2 and passage 22, will flow to the piston Upon the deflection of the diaphragm 32 to its chamber 33. In response to the fluid pressure lower position the spring 42 will act to move the acting on the piston member 5I), the piston mem-^ valve 39 from the position in which it is shown4 ber will move upwardly against the opposing .to its lower seated position, closing commmuni pressure of the spring 45. This movement of `cation between chambers 23 and 33. This is the the piston member will cause the valve IIS to again normal position for valve 39 on a leading unit engage the valve seat I'I, thus preventing fur with the brake equipment thereof fully charged. ther loss of fluid under pressure from the mainV . Fluid under pressure in the piston chamber 33 reservoir I by way of pipe 5. , and the passage 35 will continue to now to atmos ph'ere by way of the choke 36, thereby reducing The reduction` in the pressure of fluid inthe the fluid pressure in chamber 33. When the main reservoir I will cause the compressor on the leading locomotive unit to start operating in »pressure of ñuid in the chamber 33 acting on the `lower side of the piston member 50 decreases be the usual manner. This action in combination low the pressure of the spring 45 acting on the with the closing of the valve I5 might, if the choke upper side of the piston member, the springwill 60 52 were not employed, cause a rapid increase in `act to move the piston member downwardly to the fluid pressure‘in the diaphragm chamber 23 -the position in which it is shown in the drawing. causing the valve 43 to seat and the valve I6 to . open again before the fault causing the loss of The downward movement of the piston member `will cause the valve I5 to assume the position in fluid under pressure had been corrected. There which it is shown, this being the normal position 65 'would then follow another reductionv in fluid 4for `valve I6 on a leading unit with the brake Lpressure and a consequent rapid pumping action. This rapid pumping action is obviated yby the equipment thereof fully charged. Communica effect of the choke 62 in the passage `22 which tion is again established between the main reser >delays the> pressure build-up in the chamber 23 voir I on the leading unit and the main reservoir and thereby lengthens the time interval between 1 I I on the trailing unit by way of pipe 3, passage the closing and opening of the valve IS. 6I, chamber I5, bushing I8, passage I3 and main As previously noted, the effective area of` the ‘reservoir pipe 5. piston member 53 is considerably greater than It will be understood that th'e volume of the that of the diaphragm 32. For this reason and passage 35 and the chamber 33 is relatively small ‘and that consequently the choke 35 will cause 75 also because chamber 33 is at atmospheric pres 2,407,890 8 7 sure 4and the pressure of the spring 4.5 has been reduced by the upward movementI of Athe dia phragm, Ythe piston member will exert a force greatly in excess of that required to propel the valve I6 to its seated position. This excess of force is desired to insure the seating of the valve l‘even though it or the- valve seat I'I might be dirty .and :covered with sludge which usually accumu lates in the communicating pipes of a fluid pres .,sure brake system. closing said valve, a spring urging the'movable abutment in ya direction for opening -said valve, and valve means for controlling communication between one of said two passages and said mov able abutment means, said valve means being re sponsive to a reduction in iluid Apressure in vsaid one passage to a predetermined degree to open the latter communication and responsive to an increase in fluid pressure in said one passage to r10 a predetermined higher degree to close the latter Assuming now that the compressor means on communication. 2. The combination with a fluid conducting `inoperative and that the compressor means on conduit normally charged with ñuid under pres the trailing unit is operating to supply fluid under sure, of a valve device comprising a casing having pressure to the main reservoir I I, the various two communicating passages constituting a por parts of the protection valve device 4 will be in tion of -said conduit, a valve operative to open` ¿the positions in which they are shown in -the and close the communication between said pas drawing. Fluid under pressure in the main res sages, movable abutment means for actuating ervoir II will flow therefrom to the main reser said valve and operative in response to ?luid'pres' voir I by way of the main reservoir pipe 5, passage 20 sure for closing said valve, a spring urging the I9, bushing I8, chamber I5, passage 6I and pipe movable abutment in a direction for opening said V3 until the exemplary 22 pounds are reached, at valve, valve means for controlling communica which ytime the valve I6 will be operated to its tion between one of said two passages and vsaid `seated position in the same manner as herein movable abutment means, said valve means being lbefore described for 22 pounds of main reservoir 25 responsive to a reduction in ñuid pressure in said ' pressure during the initial charging of the loco one passage to a predetermined degree to open motive. ' the latter communication and responsive to an :the leading locomotive unit has been rendered . However, although the flow of iiuid under pres -increase in fluid pressure in said one passage to sure above 22 pounds from the main reservoir II a predetermined higher degree to close the latter to the main reservoir I is interrupted at valve I6, 30 communication, and means for reducing the lpres this flow `will continue from passage I9, and res sure of fluid acting on said movable abutment ervoir II, 'by Way of strainer 3G in chamber 29, passage 28, past ball check valve 25, chamberZIì, passage 2I, chamber I5, passage 6I and pipe 3. means. ’ 3. In a fluid pressure flow control valve device comprising a casing having two connected pas When a ñuid pressure of 100 Ypounds is attained 35 sages through which ñuid under pressure may in the main reservoir I and a camber 23 of the flow from one section of a fluid conduit to :an protection valve 4, the same operation for unseat other spaced section of the conduit, a valve ing the valve I6 will take place as previously mounted in said casing and operative to one po described in connection with the initial charging sition to close communication between said `pas Of `the locomotive. It will thus be seen that the greatest possible protection for the braking means on the leading unit of the locomotive against loss of fluid under pressure is provided by the protection valve device ' 4 embodying the invention. It prevents the pass sages and operative to another position to open communication between said passages, means responsive to the pressure of fluid in one of said passages for actuating said valve to its closed po sition and responsive to a reduction in the pres sure of fluid acting thereon for actuating said ing of fluid under pressure from the first main reservoir to the main reservoir pipe until oper ating pressures with a marginal degree of safety are available; When, due to some failure behind valve to its open position, a second Valve having a position for establishing communication through which the -fluid under pressure in said one passage may be supplied to said means and the leading locomotive unit, the margin of safety 50 having a position for closing said communication, is lost the main reservoir I will again be segre a movable member responsive to an increase in gated from the main reservoir pipe leading to the fluid pressure in said one passage toa chosen trailing locomotive units. If, for any reason, the degree for eiïecting .the operation of said second `fluid pressure supply to the ñrst main reservoir valve to its communication closing position and `should fail and fluid Vunder pressure is available 55 responsive to a reduction in the 'ñuid pressure in in any of the trailing units, the protection valve said one passage for effecting the operationrof -device will then operate -to supply Iluid under said second valve to its communication establish pressure from the main reservoir pipe to the ñrst ing position, and means for reducing the pressure main reservoir. Upon attaining safe operating of fluid acting on said means. Y pressures in the ñrst main reservoir, the protect 60 4. In a fluid pressure flow control valve device ing valve device will again function to retain those having two connected passages adapted to estab ypressures if the ñuid under pressure in the main lish communication between two ñuid conducting reservoir pipe is being depleted beyond a safe conduits, a valve operative to one position lto close degree. « the connection between said passages and opera Having now described my invention, what I 65 tive to another position for opening the com claim as new and desire to secure by Letters Pat munication between said passages, means oper ent, is: ative by ñuid under pressure from one of vsaid passages for actuating said valve to close the con nection between said passages and operative upon a reduction in the pressure ,of ñuid supplied thereto for-actuating said valve to open the con nection between said passages, valve means re sponsive to variations in the pressure of Afluid in -said one passage for controlling the pressure -of iluid acting on the ñrst mentioned means„a pas 1. The combination with a fluid conducting conduit normally charged with fluid under pres sure, of a valve device comprising a casing having two communicating passages constituting a por tion of said conduit, a valve operative to open and close the communication between said passages, movable abutment means for actuating said valve and> operative in response to fluid pressure for 2,407,890 sage by-passing sald valve and leading from the other of said passages to said one passage through which fluid under pressure may flow from said other passage to said one passage when said valve of fluid pressure acting thereon to interrupt said supply, thereby causing the first mentioned means to` operate said valve to open said connection, is Iclosed, and means interposed in the by-pass passage 4for preventing the ñow of fluid there said'valve means being conditioned as an inci dent to the opening of said valve to respond to a degree of fluid pressure acting thereon lower through from said one passage to said other pas than said certain degree for again supplying fluid sage. « _ ~ A I _ Y under pressure from said one passage to the ñrst „5. In a Vfiuid pressure flow control valve device mentionedmeans, means for controlling the rate having `two connected passages adapted to estab 10 at which fluid is supplied to said valve means to lish communication between two fluid conducting prevent the pressure in said valve means from conduits, a valve operative to one position to close being varied prematurely. the connection between saidfpassages and opera-_l A3. The combination with a fluid conducting tive to another position for opening` the connec conduit, ofga fluid pressure iiow control valve tion between said passages, means operative by 15 device comprising a casing having two connect fluid under pressure from one of said passages for ed `passages constituting Va portion of said con actuating said valve to close the connection be duit, a valve operable to open and close the con tween said passages and operative upon a reduc nection between said passages, a movable mem tion in the pressure of fluid supplied thereto for ber responsive to iiuid pressure for operating said actuating said valve to openthe connection be 20 valve to close said connection and responsive to tween said passages, valve means responsive to a reduction in the fiuid pressure for operating variations in the pressure of fluid in said one pas said valve to open said connection, means for , sage for controlling the pressure of ;ñuid acting reducing the iluid pressure acting on the mov able member at a relatively slow rate, and valve means responsive to variations in the pressure of . on the ñrst mentioned means, a passage by-pass ing said valve and leading from the other ofsaid passages to said one passage through which fluid under pressure may ñow from said other passage to said one passage j when said valve is closed, means interposed in the by-pass passage for pre venting the ñow of fluid therethrough from said fluid in said one-passage to control the supply of fluid under pressure from said` one passage to said movable member and thereby the ñuidpres sure acting on said movable member, said valve 30 means being _operative in >response to a `cer-,v one passage to said other passage, and fluid tain degree of fluid pressure to supply fluid un cleaning means interposed in the by-pass passage der pressure to said movable member to eiîect at a point located between said other passage the operation of said valve to close said connec and the last mentioned means. tion and being conditioned as an incident to the 6. The combination with a iluid conducting connection closing operation of said valve to be conduit of a iluid pressure flow control valve de operative at a degree of fluid pressure higher vice comprising a casing having two fluid flow -than said certain degree to interrupt the supply connecting passages constituting a portion of of fluid under pressure from said one passage to said movable member. ‘ said conduit, a valve operable to open and close the iiuid flow connection between said passages, 40 9. The combination with a fluid conducting means responsive to fluid pressure for- operating conduit, of a fluid pressure flow control valve said valve to close said connection and respon device comprising a casing having two connected sive to a reduction in fluid pressure for operating passages constituting a portion of said conduit, said valve to open said connection, means for a valve operable to open and close the connection reducing the fluid pressure acting on the first 45 betweenV said passages, a movable member re mentioned means at a relativ'ely slow rate, and sponsive to fluid pressure for operating said valve valve means operative to supply fluid under pres to close said connection and responsive to a re sure from said one passage to the ñrst mentioned duction in the fluid pressure for operating said 4 means to effect the operation to close said valve valve to open said connection, means for reduc and operative in response to a certain degree ing the fluid pressure acting on the movable of fluid pressure acting thereon to interrupt said member at a relatively slow rate, valve means re supply, thereby causing the ñrst mentioned means sponsive to variations in the pressure of iluid in to operate said valve to open said connection, said one passage to control the supply of fluid said valve means being conditioned as an inci under pressure from said ‘one passage to said dent to the opening of said valve to respond to a degree of fluid pressure acting thereon lower movable member and thereby the ñuid pressure acting on said movable member, said valve means than said certain degree for again supplying fluid being operative in response to a certain degree under pressure from said one passage to the ñrst of fluid pressure to supply fluid under pressure mentioned means. ` to said movable member to effect the operation 7.' The combination with a fluid conducting 60 of said valve to close said connection and being conduit of a fluid pressure iiow control valve de conditioned as an incident to the connection vice comprising a casing having-two fiuid ilow connecting passages constituting a portion of said a degree of fluid pressure higher than said cer closing operation of said valve to~be operative at conduit, a valve operable to open and clos-e the tain degree to interrupt the supply of ñuíd under fiuid flow connection between said passages, pressure from said one passage to said movable means responsive to liuid pressure for operating member, and means for restricting -the rate at said valve to close said connection and respon which fluid under pressure is supplied to the valve sive to a reduction in fluid pressure for operat means to prevent the pressure of fluid in said ing said valve to open said connection, means valve means from increasing at such a fast rate for reducing the fluid pressure acting on the first 70 as to cause the valve means to operate prema mentioned means at a relatively slow rate, valve turely to interrupt said supply. means operative to supply ñuid under pressure 10. In a ñuid pressure brake system compris from said one passage to the íirst mentioned ing a plurality of ñuid pressure reservoirs inter means to effect the operation to close said valve connected by means of a common conduit in and operative in responsive to a certain degree 75 which system it is `desired to maintain fluid in ¿comme 11 lI2 one reservoir at pressures above a »chosen degree, passage psf-*passing ‘said ‘valve throughfwhieh aprotection valve device interposed vbetween said iluid under pressure may ñow vfrom ¿said other one reservoir and 4said conduit -comprising ya cas passage to said one passage. ' ' ' ing having two connected passages one of which is connected to said one reservoir and the other to said conduit, a valve operative to one position to close the connection between said passages and operative to another position to open the connection between said passages, va movable 11. In a fluid vpressure brake system ¿compris ing »a plurality of 'fluid pressure main reservoirs interconnected by means of la Vcommon conduit in which system it 'is desired `to maintain Yiiuid in‘one reservoir at pressures Within a chosen range, a vprotection valve dev-ice interposed ¿be tween said reservoir Íand said »conduit 'comprising a casing having one ‘passage 'open to said conduit and «another passage open to »said one reservoir, a valve controlling communication between »fs‘aid passages, piston means lconnected vto said ‘valve and 'operative .to `one-position to close "said fva'lv-e in response toa constant supply of fluid at a pressure above a certain chosen degree and op erative to another'position upon the ‘interrup-` tion of said »supply to 'open »said Valve, and valve member responsive to fluid' pressure Vfor operating said valve to -close said connection and respon sive to »a reduction in theiîuid pressure for oper ati-ng said valve to open said connection, means for reducing the vfluid pressure acting on the movable member at -a »relatively slow rate, valve means responsive to varia-tions in the pressure of fluid lin said one «passage to control the supply of fluid under pressure from V'said one passage to sa'id movable member and 4thereby the fluid pres sure 'acting on said movable'member, «said valve means open ïfor supplying fluid'under pressure from said one reservoir to said piston means, said means being operative in »response to 'a -certain `degree »of lfluid pressure to supply >ñuid under pressure «to-said movable lmember to »effect the operation of Vsaid valve yto close said connection and lbeing conditioned -as an incident to »the con nection clos-ing operation »of'said >valve to be op valve means being -conditîonable by said piston means when in vsaid yone position to respond to an increase in ñuid pressure 'to a, predetermined 25 degree above said chosen degree to ‘close said erative at -a ïdegree?of ñuid pressure higher than said V`certain degree to interrupt the supply 'of ñuid under pressure from said 4one -passage vto said movable member, `-and >a unidirectional -ñow 30 communication and to respond ‘to a decrease -in " fluid pressure to a certain predetermined >lower degree tovopen said communicat-ion. ¿GLENN T.