US1729931A - Valve mechanism for compressed-air brakes - Google Patents

Description

Oct. 1, 1929. I. DROLSHAMMER 1;729,931

VALVE MECHANISM FOR COMPRESSED AIR BRAKES Filed Dec. 2, 1926 2 Sheets-Sheet l Oct. 1, 1929. I. DROLSHAMMER 1,729,931

VALVE MECHANISM FOR COMPRESSED AIR BRAKES I Fil ed Dec 2, 1926 2 Sheets-Sheet 2 Fly. 4.

Patented Oct. 1, 1929 UNITED STATES PATENT orrice IVAR DROLSHAMMER, or DRAMMEN, NORWAY VALVE MECHANISM FOR COMPRESSED-AIR BRAKES Application filed Dec-ember 2, 132$,Se1ia1 No.

c discharges from the pipe, so that after starting the first stage of braking'the brake'power can be increased by small steps. The introduction of the second transfer chamber depends only on the speed with which the train 15 pipe pressure is reduced. This speed varies very much, according to the length of the train and the number of cars connected to the pipe. If a plurality of cars are connected in series the second transfer chamber in the -20 rear cars isnot introduced. As it is impos sible in practice to avoid that some of the control pistons become more sluggish than others it may occur, that when the first reduction of pressure is made some of the pisv25 tons do not move far enoughto move the valves. l/Vhen a further reduction of train pipe pressure is made, to increase the brake power, a control piston may then suddenly move to its end position and throw in the to first and second transfer chambers, because it is only influenced by the pressure difference between the auxiliary air reservoir and the train pipe. Consequently. sudden application of the brake occurs when it is not desired. In this arrangement both transfer chambers are disconnected again from the train pipe and placed in communication with the atmosphere when the train pipe pressure is increased by about 0.15 atmosphere, and thebrake control valvemoves to the lap position. The mechanism is, therefore, unsuitable for brakes whose power is to be reduced to any required extent. x

In connection with the Drolshammer '45 type there has become known a gradually releasable brake wherein the piston which actuates the brake control valve, itself intro,- duces a transfer chamber whentheapplication of the brake is started, this chamber re- J'naining in communication with. the train 152,274, "and in Germany December 10, 1925;

pipe during the graduated application and release of the brake, and only being disconnected from the pipe and opened to the atmos phere when thebrake is wholly or nearly released.- This has the defect that the brake can only be released by means of a particular train pipe pressure, for example 5 atmospheres, depending on the strength of the spring acting on the controlling piston when thebrake is released.

This invention relates to a brake accelerator with a single transfer chamber or a'plurality of'trans'fer chambers, in which the said a defect is removed so that the brake can be used withany train pipe pressure and also for graduated braking, this result being obtained by quite simple meansfaccording to a stable law. The control piston isunder the influence of (1) train pipe pressure ;'(2) controlling cha'niber pressure; and (3) cylinder pressure, and makes a stable, continuous movement whereby it cuts in or cuts out the transfer chamber or chambers. Normally there occurs in each position of the control piston a definite reduction oftrain pipe pressure, with a definite cylinder pressure, so that no accelerated application of the brake can occur accidentally. There may. be'a transfer chamberwhiohis cut in as soon 'as'the application ofthebrake is started, and there may be a second transfer chamber, which in the course of normal braking is not cut in till approximately the maximum "cylinder pressureis attained. The sudden reduction of train pipe'pressure then occurring is indicated bythe train pipe manometer on the locomotive, and indicated to the driver that the maximum brake power has been applied and that it is useless to discharge more air from the train pipe. In the case of very powerful braking being required in the course of normal working, and for emergency braking, the second transfer chamber is cut in earlier.

It is of advantage to sub-divide the transfer chamber for the first stage of braking, making two chambers, so that the flow of air from the train pipe to a transfer chamber begins before the control piston need overcome the considerable resistanceof the inlet valve. This has the result thatthe brake con.-

trol valve is much more sensitive and acts earlier than if the discharge of air does not begin till the inlet valve is opened. Substantially quicker braking throughout the train is thus obtained, as it takes a substantially shorter time to obtain at the end of a long train a reduction of pressure of, say, 0.12 or 0.16 atmosphere, to make the last brake controlling valve act. Moreover, the discharge of air from the trainpipe through the transfer chamber may be substantially greater without correspondingly increasing the brake power in the first stage. This results in more rapidly propagating the pressure reduction through the train pipe, and substantially increasing the speed with which all brakes are applied.

An apparatus according to the invention is shown in the annexed drawings, in which:

Fig. 1 is a longitudinal section of the valve mechanism with the parts in the positions occupied when the brake is released, Fig. 2 being a longitudinal section of part of the mechanism in the position occupied. when the lightest application of the brake is started, and

Fig. 3 being a section of part of the mechanism in the position occupied when the maximum brake cylinder pressure has been reached or emergency. application of the brake is made.

Fig. 1 shows part of the mechanism in section to a larger scale.

The brake is made ready for application by the opening of a valve on the locomotive, whereby the driver charges the train pipe and the auxiliary reservoir B to a pressure of 5 atmospheres, the air flowing to the reservoir by way of a non-return valve (not shown) and the duct 24. Air also flows through the cock 95 and pipe 28 to the chamber above the control piston 1 and leaks past this piston through the very small throttling passage 37- and the pipe 39 to the chamber A, till the pressure therein is equal to that in the train pipe. It the train pipe pressure is reduced, say by 0.1 atmosphere, the said nonreturn valve prevents in known manner the return of air from the auxiliary reservoir to the train pipe, and communication between the chamber A and train pipe is broken at the 1 same time, because the difference of pressure between the chamber A and the train pipe causes the piston 1 to rise slightly, and the cup leather 58 masks the hole 37 and makes a tight joint with the cylinder wall. This breaks communication between the chamber A and the train pipe, and the cup leather 115 on the piston rod closes the exhaust port. A further short movement of the piston causes the cup leather 115 to uncover the inlet port 17, so that compressed air from the chamber above the piston 1 and the train pipe can flow through the grooves 21 in the piston rod 2 to the transfer chamber i1. This suddenly reduces the train pipe pressure to the extent of, say, 0.12 atmosphere, so that the piston 1 rises further and the cup leather 115 closes the outlet port 20. Consequently the piston 12 is lifted further and lifts the inlet valve 5. The cup leather 115 also uncovers the inlet port 18, so that more air is discharged from the train pipe by way of the grooves 21, till the transfer chamber 42 is fully charged. This outlet of air again causes a sudden pressure drop of, say, 0.12 atmosphere in the train pipe, so that the piston 1 ascends farther. By this sudden automatic reduction of train pipe pressure and the ascent of the piston 1 the outer, compressed coiled spring 13 is somewhat further compressed, and the still uncompressed spring 11 pushes the piston 12 against the valve 16, so that communication between the brake cylinder C and the atmosphere is interrupted. Air from the auxiliary reservoir then flows by way of duct 24, cock 95, duct 25 and inlet ports 40 past the lifted inlet valve 5 and through duct 22 to the brake cylinder C. A cylinder pressure of, say, 0.8 atmosphere is thus obtained.

When the driver closes the main valve, so that no more air can escape from the train pipe, the piston 1 at once stops in the position to which it has been moved owing to the reduction of pressure, when the pressure difference acting on it, due to the pressure in the chamber A and the reduced train pipe pressure is balanced by the spring 11, whose pressure, like that of the brake cylinder, is multiplied by the area of the discharge piston 12. WVhen the brake cylinder pressure has pushed the piston 12 sufficiently far back, compressing the spring 11, the inlet valve 5 'is closed by its spring 9 and the pressure from the auxiliary reservoir. Each reduction of pressure in the train pipe corresponds, accordingly, to a definite pressure in the cylinder. The power of the spring 13 has hardly any eiiect on the position of the piston 1, because this spring is in fact only required to take the thrust of the piston rod 2, which is only guided at one end.

When the train pipe pressure has been reduced for approximately maximum application of the brake in normal working the piston 1 is in the position shown in Fig. 3. The cup leather115 on the piston rod 2 then opens communication between the train pipe and the transfer chamber 120 by way of the grooves 21 on the rod, and the port 34, so that there is a sudden reduction of pressure in the train pipe. In the case of very heavy normal braking, or emergency braking, the ascent of the piston 1 at once cuts in the transfer chambers 11 and 12, and almost at the same time the transfer chamber 120, because the drop in the train pipe pressure is much more rapid than the rise of the cylinder pressure (charging period). The piston 1 consequently moves very quickly to its end position, as there is no substantial resistance due to cylinder pressure.

If the driver desires slightly to reduce the maximum brake power he suitably increases the train pipe pressure. moves downwards, and the cup leather 115 on the piston rod 2 exposes the ports 34 leading to the transfer chamber 120, so that air can escape by way of the ports 34 and grooves 23 in the extension 2 of the rod, into the spring chamber and thence through port 34 to atmosphere. If the train pipe pressure is not further increased the piston 1 stops, when so much air has escaped from the brake cylinder C past the outlet valve 16 and through the ports 14 and 54 to the atmos phere, that the spring 11 forces the piston 12 upwards and closes the discharge valve 16. The brake power can thus be reduced stepwise by increasing the train pipe pressure. During this operation the chambers 42 and 41 remain in communication with the train pipe. If the train pipe pressure is reduced so far that the cylinder pressure is reduced to about 0.3 atmosphere the piston 1 is moved down so far that the cup leather 115 closes the port 18 and opens the port 20. The air admitted to the transfer chamber by the action of the brake control valve can then flow by way of port 20, grooves 23 in the rod extention 2 and port 54 to the atmosphere. The control piston 1 and discharge piston 12 do not reach their lowest position till the train pipe pressure is increased again to the valve which it had before the application of the brake. The air left in the brake cylinder then escapes by way of valve 16 and ports 14 and 54 to the atmosphere. At the same time, or shortly before, the cup leather 115 on the piston rod 2, interrupts communication be tween the transfer chamber 41, and the train pipe, by closing the ports 17. Then the outlet 19 is uncovered, so that the chamber 41 can discharge air by way of the port 19, grooves 23 in the piston rod extension 2? and discharge port 54.

In the case of express trains and passenger trains, where the charging period is very short compared with that of goods trains, it is desirable and allowable to allow a substantial quantity of air from the train pipe to pass into the brake cylinder for emergency braking, in order to increase the brake power and further to accelerate the pressure drop in the train pipe. For this purpose the transfer chamber 120 is connected by way of a pipe 74, spring-loaded non-return valve 75 and pipe 76 to the duct 22 leading to the brake cylinder, so that for emergency braking the high train pipe pressure causes the valve to open, with .a sudden discharge of air from the train pipe into the brake cylinder. When a certain cylinder pressure is attained, say 1.5 atmospheres, the non-return valve is closed by its spring and the cylinder pressure.

The piston 1 then the passage from the auxiliary air chamber to the brake control valve is suitably throttled.

' What I claim is 1. Valve mechanism for compressed air also having a transfer chamber into which air from the train pipe is admitted when the application of the brake is started for accelerating the brake action, the admission to said transfer chamber being controlled by the train pipe pressure, the pressure in the controlling chamber, and the brake pressure so that the piston has a stable progressive movement.

2. Apparatus asclaimed in'c'laim 1, having an additional transfer chamber, the two chambers being arranged to come into operation successively, the first coming into operation before the piston has to overcome the resistance of the inlet member of the brake control valve, and suddenly, reducing the train pipe pressure, and the second chamber then coming into operation and producing a further sudden reduction of the train pipe pressure.

3. Apparatus as claimed in claim 1, having an additional transfer chamber, the-two chambers being arranged to come into operation successively, the first coming into operation before the piston has to overcome the resistance of the inlet member of the brake control valve, and suddenly reducing the train pipe pressure, and the second chamber then coming into operation and producing a further sudden reduction of the train pipe pressure, the two chambers being then filled and ineffective till an increase of train pipe pressure and attainment of a brake cylinder pressure of, say, 0.3 atmosphere,"

causes the second chamber to discharge air, and come into operation again as soon as the train pipe pressure is reduced, the first cham ber not being allowed to discharge air till the train pipe pressure is increased to approxi mately the value which it had before the ap plication of the brake.

4. Apparatus as claimed in claim 1, having an additional transfer chamber, the two chambers being arranged to come into 0p 7' eration successively, the first coming into operation before the piston has to overcome the resistance of the inlet member of the brake control valve, and suddenly reducing the train pipe pressure, and the second chamber then coming into operation and producing a further sudden reduction of the train pipe pressure, the apparatus including also a third transfer chamber, which comes into operation for exceptionally powerful braking, or emergency braking, said third chamber being disconnected from the train pipe and opened to the atmosphere when an increase of train pipe pressure and slight fall below maximum brake cylinder pressure occur.

5. Apparatus as claimed in claim 1, wherein the piston is exposed on one side to the train pipe pressure and brake cylinder pressure and on the other side to substantially constant control chamber pressure or the like, and controls the transfer chamber by means of its rod.

6. Apparatus as claimed in claim 1, hav ing also a supplementary transfer chamber which comes into operation for exceptionally powerful braking, or emergency braking, said third chamber being disconnected from the train pipe and opened to the atmosphere when an increase of train pipe pressure and slight fall below maximum brake cylinder pressure occur, the said supplementary chamber communicating with the brake cylinder by way of a spring loaded nonreturn valve which in the case of exceptionally powerful or emergency braking allows air from the train pipe to flow Very rapidly to the brake cylinder till a definite brake cylinder pressure is attained, whereupon that pressure and the spring close the valve.

7. Apparatus as claimed in claim 1, wherein the piston rod is in two parts, and has a cup leather interposed between the parts, for closing the port leading to the transfer chamber.

In testimony whereof I affix my signature.

IVAR DROLSHAMMER.

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