US2261855A - Exhaust steam injector - Google Patents

Description

Nov. 4, 1941.

' 5 D. METCALFE ETAL 2, 1

EXHAUST STEAM INJECTOR Filed July 25, 1940 2 She'ets-Sheet 1 1941 R. D. METCALFE ET L 2,261,855

EXHAUST STEAM INJECTOR Filed July 23, 1940 2 Sheets-Sheet 2 O I. O

v O m n i 0 g 1 x5 4 I lb u y Z P. lczz/flz 9 7 efdiv f Patented Nov. 4, 1941 Richard David Metcalfe and James Crxon Metcalfe, Romiley, England, assignors to Davies & Metcalfe Limited, Romiley, England, a British company Application July 23, 1940', Serial No. 347,072

In Great Britain August 11, 1939 iolaims. (01.103-265) This invention relates to exhaust steam injectors and is concerned with what isknown as the shuttle valve which controls the supply of throttled down or auxiliary live steam to the injector and the opening of the main exhaust steam inlet valve of the injectorin accordance with the pressure conditions in the steam chest of the engine from which the exhaust steam is obtained. The said shuttle valve usually comprises what is known as an auxiliary check valve at its upper end, the said valve being under the pressure in the engine steam chest and therefore held on its seat when that pressure is above a predetermined amount. The shuttle valve proper (which comes beneath the auxiliary check valve) when it rises, opens the latter (due to the absence of pressure in the engine steam chest) and then permits throttled down live steam to pass to the auxiliary live steam space of the injector to work the injector with such live steam, exhaust steam not being available. When the shuttle valve is forced downwards, due to the pressure of the steam in the engine valve chest, it closes the live steam connection to the auxiliary steam space and opens the connection to the piston which opens the exhaust steam valve of the injector.

In practice it is found that when a locomotive is drifting, that is travelling due to its own momentum, the fluctuating vacuum in the engine valve chest causes chattering of the shuttle valve which results in excessive wear of the valve guide and seating. To overcome this difficulty an anti-vacuum valve is provided above the auxiliary check valve, but due to the extreme range and rapidity of the fluctuations, the chattering cannot be eliminated thereby under all conditions.

In accordance with our present invention, we

obviate the difficulties before referred to and the chattering of the shuttle valve, also the necessity for an anti-vacuum valve, by inverting the shuttle valve so that the supply connection for the throttled down or auxiliary live steam (which is controlled by the shuttle valve) is above the valve and the auxiliary check valve is below. There is a drip port with a valve control below the auxiliary check valve. The stem of the latter is guided in an axial hole in the shuttle valve which has a vent connection to the passage to the piston controlling the exhaust steam inlet valve of the injector. I

Referring to the accompanying explanatory drawings:

of the parts indicated in the figures.

exhaust steam injector having our improved shuttle valve fitted thereto.

Figure 2 is a cross sectional view on the line 2-2 of Figure 1. i

The injector'has its exhaust steam inlet at a, itssupplernentary live stem inlet at b, and its ininlet for live steam throttleddown to low pressure (termed auxiliaryiive steam) to work the injector when exhaust steam is not available at c. The double beatvalve d controls the flow of exhaust steam into the injector. Water enters the injector ate under the control of the valve 1 and of the sliding water cone 9. The spindle h con-'- trols the valve f and cone g; The injector combining nozzle is indicated at i and the delivery nozzle at 7'.

Boiler steam enters the injector by the branch 70, Figure 2 and can pass therefrom by the passage m directly to the supplementary steam nozzle b. Such steam can also pass byway of the automatic choke device n (which reduces its pressure to any desired value) and the passage 0 to the space 0 from which it issues into the injector around the nozzle 12. This steam supply is termed the auxiliary live steam supply.

The branch 10 is in communication with the steam chest of the engine supplying exhaust steam to the injector and it will be understood that if the engine has its steam supply cut off, then there will be no pressure in the branch p. The passage q leads to the underside of the piston T which when raised opens the'double beat valve d to pass exhaust steam to the injector.

The injector works with exhaust steam or live steam according as the engine regulator is open or shut. There are four difierent phases in the function of the injector determining the positions of the valves.

(1) Regulator shut while the injector is working. This phase is represented by the position There is no steam pressure in the branch 11 and consequently the valves s, termed the shuttle valve, which controls the flow of throttled down or auxiliary live steam to the injector, is on its lower seat at t, in which position the throttled down or auxiliary live steam can pass to the space 0 of the injector, and the passage q is cut off from any steam supply; the piston r is, therefore, in its lower position and the valves d closed.

(2) Regulator shut, locomotive drifting, and the injector not working. The positions of the parts are the same as in phase I. When the locomotive is drifting, the fluctuating vacuum Figure 1 is a longitudinal section through an which occurs in the engine valve chest has no effect on the shuttle valve s and on the auxiliary check valve w, because the force due to the weight of these two valves acts in the same direction as the vacuum, in other words, both the weight of these valves and the efiect of the vacuum in the pipe 12 tend to keep the valves in the lower position, so that chattering is eliminated.

(3) Regulator open and the injector not working. Steam enters by passage p into the chamber surrounding the auxiliary check valve w. Steam escaping through the vent hole u reduces the pressure on the upper side of the valve w so that this is forced up on to the seating 112. When the auxiliary check valve w is thus on its seating no steam can enter the injector casing from the steam chest. The shuttle valve is raised from its lower seating but the live steam supply to 70 has been cut off. The ball valve 3 closes the vent hole 4 of the chamber 1) due to the flow of steam from this chamber through the vent 4.

(4) Regulator open and injector Working. Steam entering from the branch is, past choke n and passage forces the shuttle valve against its upper seating at y. Steam is thus prevented from passing to the space 0, but can now pass beneath thevalve s, down the annular space 2 to the passage q, and so to the underside of the piston 1' which is raised ,and opens the valves d, so admitting exhaust steam to the injector.

With the aforesaid CODStIUlCtiOIlyi-t is found that the fluctuating vacuum which occurs in the engine steam chest during the drifting of the locomotive, has no effect on the shuttle valve s, which owing to its weight is during the drifting period, on that seating to which the vacuum tends to draw it, so that chattering of the shuttle valve is eliminated.

' The shuttle valve slides in two guide sleeves :1: and 5 which screw into the valve casing above and below the passage q leading to the control piston r of the exhaust steam inlet valve d of the injector. The said sleeves and the shuttle valve are preferably made of stainless steel.

What we claim is:

1. In an exhaust steam injector having a shuttle valve and an auxiliary check valve for controlling the supply of throttled down or auxiliary live steam to the injector and also controlling the supply of steam to operate the exhaust steam supply valve, the arrangement wherein the shuttle valve when raised cuts off the supply of auxiliary live steam to the injector and passes such steam to the piston which opens the exhaust steam supply valve, and when in its lower position admits auxiliary live steam to the injector and cuts off'such steam from the piston controlling the exhaust steam supply valve, there being a valve controlled drain beneath the auxiliary check valve.

2. In an exhaust steam injector as claimed in claim 1, the provision in the shuttle valve of an axial hole to guide the stem of the auxiliary check valve, and a venthole leading from the upper end of such axial hole to the outside of the shuttle valve.

RICHARD DAVID METCALFE. JAMES CROXON METCALFE.

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