US2959182A - Manoeuvring arrangement of steam turbine - Google Patents

Description

Nov. 8, 1960 TSUNEO ANDO ETAL MANOEUVRING ARRANGEMENT OF STEAM TURBINE Filed May 24, 1955 4 Sheets-Sheet i INVENTOR. Tsuned Ando lppei Ir ie Maxwell E.Spurrow ATTORNEY.

Nov. 8, 1960 TSUNEO ANDO ETAL 2,959,182

MANOEUVRING ARRANGEMENT OF STEAM TURBINE 4 Sheets-Sheet 2 Filed May 24, 1955 INVENTOR. Tsuned Ando lppei lrle Maxwell E. Sparrow II 1! 7/22? A ATTORNEY.

NOV. 1960 TSUNEO ANDO ETAL 2,959,182

MANOEUVRING ARRANGEMENT OF STEAM TURBINE Filed May 24, 1955 4 Sheets-Sheet 3 57 o 5 55 40 I P3 52 53 P6 FIG .3

INVENTOR. ed Ando BY 1 Irie Maxwell E. Sparrow ATTORNEY.

Nov. 8, 1960 TSUNEO ANDO ETAL 2,959,132

MANOEUVRING ARRANGEMENT OF STEAM TURBINE Filed May 24, 1955 4 Sheets-Sheet 4 INVENTOR. Tsuned Ando lppei ir'ie Maxwell E.Sporrow ATTORNEY United States Patent MANOEUVRING ARRANGEMENT OF STEAM TURBINE Tsuneo Ando and Ippei Irie, Kobe, Japan, assignors t0 Kawasaki Jukogyo Kabushiki Kaisha (Kawasaki Dockyard Co., Ltd.)

Filed May 24, 1955, Ser. No. 510,728

7 Claims. (Cl. 13718) This invention relates to manoeuvring devices of steam turbines, preferably of ships turbines, in general and to hydraulic devices of this kind of machine in time it is important to maintain the necessary pressure of the main bearing lubricant to keep the prime mover from becoming inoperable during the time when all operations of the vessel depend upon its proper function. In addition to this condition, a manoeuvrable condition of the ship has to be maintained all the time during storm periods when there is the danger of overspeeding of the steam turbine due to propeller racing.

Devices and apparatus have been designed to meet the various conditions outlined above, but either they are independent from one another or they are complicated mechanisms which require special skill to handle.

Objects and advantages of this invention will be set forth in part hereafter and in part will be obvious herefrom or may be learned by practicing the invention, the same being realized and attained by means of the instrumental'ities and combinations pointed out in the appended claims.

The invention consists in the novel parts, construction, arrangements, combinations and improvements herein shown and described.

It is the principal object of this invention to provide for new and improved means of manoeuvring controls for ships turbines.

It is a further object of this invention to provide for a device which by virtue of its servo action can be operated lightly, easily and fast.

Another object of the invention is to provide for a controlling means by which the adjustment of the flow of steam or a like motive fluid can be regulated promptly and easily at all times in equal increments of turning angle of the control hand wheel regardless of the posi: tion of the main steam valves.

A further object of the invention is to provide for a hydraulic means for controlling and manoeuving a steam turbine which utilizes a part of the lubricating oil of the turbine unit as its pressure fluid and which is included in the system of the lubricant lines.

This includes another object of the invention, that is, to provide for a foolproof device in the sense that the operator cannot set the controls in motion after the mechanism has shut down in an act of emergency, un less the whole system of pressure balance in the pipe lines is restored to the normal state.

Another object, connected directly with the foregoing, of this invention is to provide for means to return the complete mechanism of the pipe lines automatically to its original position after the dangerous situation causing the emergency action is over, and to restore automatically the functions ascribed to the mechanism without other extraneous hand operation.

I A further object of the invention is to provide for a controlling device by which the steam flow to the turbine automatically is shut off in case of a pressure failure of the lubricant oil whereas simultaneously an emergency flow of lubricant oil to the main bearings of the turbine unitis maintained through a special safety valve and from a separate supply tank until the turbine shaft eventually ceases to rotate.

Another object of the invention is to provide for a controlling means comprising a stationary head tank which by virtue of its arrangement within the control system is kept full of oil.

A further object of the invention is to provide for a mechanism which operates by the pressure differential between two oil lines causing automatically the stopping of the turbine unit in case of overspeeding.

Another object in connection with the aforementioned one is to provide for control means which can be adjusted with respect to the overspeed limits and which permits testing the whole system at a safe lower speed of the turbine unit without altering the relationship between the various cooperating elements of the control device.

Furthermore, it is an object of this invention to provide for adjustable automatic control means for conditions of navigating with light draft or in storm conditions keeping the usual economic speed without abandoning the safety of operation.

Various further and more specific objects, purposes, features and advantages will clearly appear from the detailed description given below taken in connection with the accompanying drawings which form a part of this specification and illustrate merely by way of an example oneembodiment of the device of the invention.

The invention consists in such novel features, arrangements and combinations of parts as may be shown and described in connection with the apparatus herein disclosed by way of an example only and as illustrative of a preferred embodiment.

In the following description and in the appended claims, parts will be identified by specific names for convenience, but such names are intended to be as generic in their application to similar parts as the art Will pe mit. Like reference characters denote like parts in the several figures of the drawings, in which: 4

Fig. 1 shows a pipe line diagram and the complete arrangement of the device;

Fig. 2 is a cross section of the main ahead and astern manoeuving steam valve A and of the servo oil cylinder B, as shown in Fig. 1; v

Fig. 3 is a cross section of the servo oil cylinder B and the pilot valve C attached thereto, taken along theline 3-3 of Fig. 4; I

Fig. 4 is a horizontal section of the servo oil cylinder B shown in Fig. 3, taken along the line 4-4, partly broken away; I

Fig. 5 is a vertical section of the servo oil cylinder 13 shown in Fig. 4, taken along the line 55;

Fig. 6 is a cross section of the pressure sensing valve PV with the safety valve SV attached thereto, as shown in Fig. 1;

Fig. 7 is a cross section of the emergency valve EV, shown in Fig. 1. U

Referring now in more detail to the drawings illustrate ing a preferred embodiment by which the invention may be realized, there is a main valve assembly for mae noeuvring a head and .astern, generally designated bythe letter A, connected directly to a servo oil cylinder B to which a pilot valve C is attached. A manoeuvring stand h having the conventional handwheel and connecting shafts and two emergency control wheels h and h are connected to the valve assembly A, B and C. The steam turbine T has two oil pumps of the impeller type ll; .114

ends.

IP, for ahead and astern rotation attached to its main shaft which are pumping oil under pressure through the pipe line P into the pilot valve C. Pressure in this pipe line may be adjusted by an adjusting valve AV. Pressure adjusting valves RV in the two discharge lines of 'the impeller pumps 1P and 1P provide for means to balance the oil pressure for ahead and astern drive. The

two impeller pumps 1P and 1P receive the oil from the main oil supply pump P which draws the oil from the main reservoir DT into which all discharge lines lead. Said main supply pump P also feeds oil under pressure into a high tank HT through pipe line P and through a cooling device CL and a filter F. The oil coming down from the high tank HT flows to the main bearings of the turbine at the entering point 1 and subsequently is drained back to the reservoir DT.

A third branch line P feeds oil under pressure from the main oil pump P into a safety valve SV and into a pressure sensing valve PV through pipe line P Two pipe lines emerge from the pressure sensing valve PV:P continuing into the intake port of the servo oil cylinder B, and P leading to the intake orifice 62 of the pilot valve C. The outlet opening of the safety valve SV is connected by a big pipe line P to the main bearing oil feed line coming from the high tank HT and thus is feeding back oil pressure from this tank to the valve SV. A branch line leads from the pressure line P to an emergency valve EV the discharge of which is drained directly into the reservoir DT.

The main manoeurvring valve A comprises a valve body 11 having a main steam intake opening 12. The steam or the motion fluid or the like can flow either through the ahead valve 13 or through the astern valve 13' and from there through the corresponding outlets 14 and 14' to the corresponding ahead or astern turbines. Valve stems 15 and 15 of'the valves 13 and 13' project to the outside of the valve body 11 having respectively spring supports 16 and 16' attached to their lower Coil springs 17 and 17' placed between the valve body 11 and the spring supports 16 and 16 are pressing the valves 13 and 13' constantly downward and thus provide for the tendency to have said valves shut. Connecting links 18 and 18 join said valve stems 15 and 15 with the two ends of a lever 19 which is pivotally supported in its center by a short stud 20 held by a bracket 21 which bracket is attached to the upper part of the servo oil cylinder generally designated in the figures by the letter B. On the side of the ahead valve stem 15, an extension 23 of the oil piston 24 is connected with the pivotal point 22 of the lever 19.

Said oil piston 24 of the servo oil cylinder B has a vertical bore 25 in its center and has a peripheral groove 26 in the equatorial place of its body, forming a space between cylinder wall and piston which space is connected by a horizontal bore 27 to a circular space 42 around the vertical bore 25 and which is connected to the pipe line P Above and below said circular space 42 there are two grooves 28 and 28 arranged concentrically to said vertical bore 25. These concentric grooves 28 and 28' are connected by two corresponding channels 29 and 29' to the upper and lower side respectively of the piston 24. A hollow pilot sleeve 30 is fitted in the vertical bore 25 of the piston 24. This pilot sleeve 30 projects downward through the bottom of the servo oil cylinder B and has a forked end 31. Pins, not shown in the drawing, are arranged in the two protruding ends of said fork 31 and engage right and left in corresponding grooves of a cam 33 (grooves not visible in the drawing), which cam is firmly attached to the shaft h of the manoeuvring handwheel.

The pilot sleeve carries ring-shaped cylindrical faces 34 and 35 arranged in such way that they may just close the circular grooves 28 and 28 in their middle position. Bores 37 and 38 in the well of the pilot sleeve connect the inner bore 36 of said pilot sleeve to the surrounding area between said pilot sleeve and the inner wall of the vertical bore 25. A further series of bores 39 connects the inner bore 36 of the pilot sleeve to a circular discharge chamber 40 having an outlet 41 and a pipe line P leading to the oil reservoir DT (Fig. 1).

Attached to the servo oil cylinder B is a pilot valve, generally designated by the letter C, which has two parallel vertical passageways 51 and 52 in its body 50 which passageways are connected, respectively, by channels 54 and 55 to the upper and to the lower side of the oil piston 24. A piston valve 57 operating in the vertical bore 52 has a pressure plate 58 on top of which is arranged a compression spring 60 the force of which can be adjusted by a screw 59. Oil pressure lines P and P are connected to the intake openings 61 and 62 of the pilot valve C.

As mentioned above, the oil pressure lines P and P which lead to the intake openings of the servo oil cylinder B and to the opening 62 of the pilot valve C are coming from the pressure sensing valve PV to which the safety valve SV is attached. As shown in Figure 6, the pressure sensing valve is a double valve comprising the two valve bodies 70 and 70 containing an upper valve 71 for the pipe line P and a lower valve 72 for the pipe line P therein. The two valves are connected by a common valve stem 73 and have on top of it a compression spring 74 the force of which is adjustable by a screw 75.

The safety valve SV is a regular safety valve comprising a valve and a spring 81 in a housing 82. The connection of it to the pressure sensing valve PV is made in such a way that oil under pressure in the pipe line P may open the safety valve against the combined spring force of the spring 81 and the static head pressure of the high tank HT in order to discharge directly through the big pipe line P into the main bearings of the steam turbine.

The emergency valve EV, as illustrated in Fig. 7, comprises in a valve body 96 a valve 91 operating against a valve seat forming part of a valve stem 92 which extends upwardly and which is forced down by a spring 93 thus having the tendency to stay open. Said valve stem has on its upper end a collar 95 having a protruding flange 94. The collar 95 is connected to a handwheel 97 by means of a spline 95 which handwheel can be turned freely on top of the housing 96 but cannot be moved up and down by virtue of a ring 97'. Thus the collar 95 can be turned by the handwheel 97 and can slide up and down in it. Hooks 98 pivotally mounted on the valve housing 96 having handles 99 are supporting the collar 95 by means of the protruding flange 94 and thu are keeping the valve 91 in a certain preset position against the spring pressure.

In order to control the turbine manoeuvers by hand in a case of emergency due to failure of the automatic system, there are arranged on top of the main valve body (Fig. 2) levers 100 and 101 which have on one end a small piston rod 102 and 102 and pistons 103 (corresponding part 103' not shown) and connecting shafts and gears and handwheels h and h by which the valves 13 and 13' may be operated if the oil pressure is not strong enough to move the valve stems 15 and 15.

Operation The description of the operation may start with the assumption that a normal state of running of the steam turbine has been reached. As it is shown in Fig. l, the flow of the lubricant oil of the main bearings of the turbine shaft follows a closed circuit into which the various control elements are built. Oil under pressure is supplied by the main lubricant oil pump P, the high tank HT is filled through pipe line P and oil flows into the bearings, and circulates back into reservoir DT. Through the connecting line P oil pressure is brought on top of the safety valve SV where the valve 30 is kept closed by said oil pressure and the additional spring pressure of the spring 81. At the same time, oil is fed through the branch lines P and P into the pressure sensing valve PV and under the valve 80 of the safety valve SV, and since a balanced state against the spring 74 is reached, oil flows into the servo cylinder B and into the line 62 of the pilot valve C. A part of the oil may bleed through the emergency valve back into the reservoir DT for reasons which will be described later, thus lowering the pressure in the line P Since the turbine is running, the impeller pump IP (or 1P for the opposite direction'of rotation) which is directly driven by the turbine shaft, supplies oil which it receives from the main pump P, under a pressure corresponding to its speed, through pipe line P into which regulating valves and an adjusting valve AVare inserted, into the upper part of the pilot valve C through the orifice 61. Thus, a state of balance between oil pressure from the impeller pump IP; with the spring pressure of the spring 60 on one side and the oil pressure from oil line P on the other side has been established, the piston .24 is in a lifted position according to the position of the pilot sleeve 30, which in turn is determined by the position of the control wheel h and the cam 33, and the ahead steam valve 13 is open accordingly, admitting the right amount of steam to the turbine. Any change in the position of the controlling wheel h changes by virtue of the profile of the cam 33 the position of said pilot sleeve 30, whereby the grooves 28 and 28 are opened, oil under pressure supplied by pipe line P can enter the area below or above the piston 24 through the passages 29 or 29' and raises or lowers said piston and the main steam valve 13 (or 13) exactly as much as the position of said pilot valve 30 indicates; that is, until the grooves 28 and 28' are closed again by the rising piston. When the lever 19 is in a horizontal position, both main steam valves 13 and 13' are closed, the control wheel shows the neutral position and the piston 24 of the servo oil cylinder B is in its center position, as shown in Fig. 3. Any turn of the control wheel h in one or the other direc tion will raise or lower immediately by the oil pressure and piston and will open or close by the valve stems 18 or 18' the ahead or astern steam valves whereby the connection of the valve stems 18 and 18 with the lever 19 is made in such way that the springs 17 and 17' can .keep one valve shut while the other is lifted. It is obvious to those skilled in the art that by a proper profile of the cam 33 the increase and the decrease of the steam flow can be controlled in a linear proportion to the turning angle of the control wheel h and that the operation is attained with great ease and precision due to the servo action of the piston 24.

So far the pressure differential between the oil in the line P coming from the impeller pumps 1P or IP in.- creased by the adjustable spring pressure of the spring 60 on one side and pressure in the line P coming from the pressure feeler valve on the other side, has been considered as being in balance. Therefore, the cylinder valve 57 kept the opening 55 closed. If by any one of the reasons given below the pressure differential is no longer maintained, that is, if either the pressure on top of the valve 57 increases or if the counter pressure in the line P decreases, said valve 57 opens the connecting lines between the upper and the lower area of the piston 24, thus equalizing the pressure in the two areas and causing the springs 17 or 17 to close automatically the main steam valve. When the cause of the unbalance again is removed, the valve 57 automatically returns to its original position. Consequently the piston 24 returns by the oil pressure coming from pipe line P automatically to the position indicated by the pilot sleeve 30, thus opening the steam valve 13 or 13' whereupon the turbine resumes its normal running.

The reasons for an unbalance of the oil pressure differential in the pilot valve C and thus for a change of the position of the valve 57 can be the following:

(I) The oil pressure in the pipe line P can increase by d an increase of the pressure from the impeller pump 1P (or 1P due to over-speeding of the turbine that happens for example when in a storm the ships propeller gets out of the water and starts racing. (2) The pressure below the valve plate 58 and the valve 57 can decrease, if:

(a) The oil pressure of the main lubricant oil pump P drops; (b) The safety valve SV opens; (c) The oil pressure in the pipe line P drops due to opening of the emergency valve EV.

The oil pressure of the main lubricant oil pump can drop for the following reason.

As shown in Fig. 1, the pressure sensing valve PV, described in Fig. 6, is built into the pipe lines P and P at the point where these lines part, in such a way that both pipe lines may be shut by the valve. As it is shown the adjustable spring 74 tends to keep the valve closed. Oil is supplied constantly by the main lubricant oil pump P through the parallel line P through the filter F and the cooling device CL into the high tank HT, thus supplying the necessary oil to the turbine shaft bearings. If the pressure of the pump is high enough to keep the level of oil in the high tank HT, the oil pressure is suflicient to open the double valve 71 and 72 against the spring pressure. Thus, oil is supplied under pressure to both the pilot valve C and to the servo oil cylinder B; In case the main lubricant oil pump would stop or in case its pressure would not be more sufiicient to feed oil'into the high tank HT, the force of the spring 74 would be greater than the oil pressure and the valve 71 and 72 would close. This in turn lowers the pressure under the pilot valve C, and, as described before, would shut off the steam supply to the turbine. In other words, it is the differential between the dynamic pressure from the pump P and the static pressurefrom the high tank HT which controls the position of the pressure sensing valve PV against the force of the adjustable spring 74 by the action of this pressure differential on the safety valve SV, as explained above.

Directly connected with the pressure feeler valve PV is the safety valve SV, as shown in Fig. 1 and Fig. 6. This valve is kept closed by the oil pressure in the big connecting line P which is the same static pressure of the high tank HT as mentioned before, increased by the force of the spring 81 on top of the valve'80. Through the connecting pipe line P the dynamic pressure ofthe main lubricant oil pump P is acting against the static oil pressure and the spring pressure. Under normal operating conditions, if the high tank HT is full, the additional force of the spring 81 is set in such a way that the combined static and spring force is greater than the dynamic force of the pumps and keeps the valve closed. But when the oil level in the high tank drops, the combined static and spring force can not keep the valve closed any longer against the dynamic force of the pump P. Consequently, the valve opens and oil is supplied directly to the turbine shaft bearings through the big pipe line P At the same time, the dynamic pressure from the pump P drops in the pipe lines P and P the pressure of the spring 74 closes the double valve 71 and 72 and again the pilot valve C and the servo oil cylinder B closes automatically the steam fiow to the turbine.

This arrangement also prevents the turbine to be set in motion until the high tank HT is filled with oil and until the oil pressure supplied by the main lubricant oil pump has reached a sufficient level.

It also provides for suflicient emergency lubrication during the time when the turbine unit runs by the inertia of the rotor after the steam supply is shut off, because the shaft bearings receive the lubricant oil directly through the pipe line P and the danger of damage is avoided.

If in turn some trouble should occur in the pump P itself, the double valve 71 and 72 closes before the dy 7 namic pressure from the pump P becomes weaker than the static pressure of the oil in the completely filled high 'tank HT. Therefore, sufficient oil is available from the high tank HT at the time when the rotor of the turbine "starts to run by its'inertia only until it eventually stops.

If the pump P still continues operating, although at a lower rate, after the pressure sensing valve PV has closed, the safety valve SV which closed when the dynamic pressure from the pump P dropped, opens again, when the static pressure of the high tank HT, sinking as the oil in it is more and more used up, reaches a level lower than the rate. at which the pump is operating, and as much lubricant oil as possible is supplied to the bearings of the turbine rotor.

The oil pressure in the pipe line P can be lowered by the operation of the emergency valve EV, as shown in Fig. l and described in more detail in Fig. 7. This operation serves three purposes.

First, under normal conditions and circumstances, a part of the oil under pressure in the pipe line P is permitted to drain back into the reservoir DT by setting the position of the valve by means of the handwheel 97. Thus, the pressure in the pipe line P can easily be controlled and adjusted.

Second, in a case of emergency, if the turbine unit has to be stopped at once, moving the handle 99 downward releases the hooks 98, the spring 93 opens the valve immediately and completely whereupon all the oil in the pipe line P flows into the reservoir DT. The pilot valve C opens immediately and the servo oil cylinder B shuts the main steam valves of the turbine.

Third, if the pressure sensing valve PV reacts on trouble in the circulation system of the lubricant oil and cuts the flow of oil to the pipe lines P and P off, the pressure in the pipe line P drops due to the continuous drain of oil through the emergency valve. This again causes the pilot valve C to open and consequently to shut olf the main steam valves.

There is an additional advantage provided for by the emergency valve EV. The operator is enabled to adjust the amount of oil which is drained directly back to the reservoir DT and by this adjustment he can change at his will the limit of overspeed of the turbine at which limit the steam valves are automatically closed.

The oil pressure in the pipe line P depends directly upon the adjustment of the emergency valve. The pressure of the oil in the pipe line P which is acting on the valve plate 58 for opening the valve 57, depends upon the speed of the impeller pump 1P (or 1P said speed being proportional to the speed of the turbine. By said adjustment it is possible to arrange that the oil pressure in the pipe line P builds up rapidly at a lower speed to the pressure level in the pipe line P Thus, the pilot valve C operates at a speed of the turbine which is lower than the normal speed.

The usefulness of this device may be explained. It cannot be avoided that a ship having a common steam turbine slows down her speed in a storm during her navigation with light draft. This means to keep the speed of the turbine unit far below its regular horsepower as it frequently falls into a state of danger when the speed of the turbine unit reaches the overspeed limit due to propeller racing. With a device as described herein a ship can continue her navigation as a fixed economical speed with the overspeed limit of the turbine only set closer to the normal speed by merely adjusting the amount of oil drain through the emergency valve. The turbine unit stops at all time with the automatic action of the pilot valve when the preset overspeed limit due to propeller racing is reached, but resumes it original function, when it falls below the regulated speed because the pilot valve C returns to its closed position, the servo oil cylinder piston returns to its position coinciding with that of the pilot sleeve 30 which is set by the handle 21 and so the navigation keeps on going automatically.

Furthermore, at the routine performance test of the manoeuvring valves it is possible to test all functions at a lower overspeed limit than its regular speed, and it is not necessary to run the turbine up to its top speed.

While the invention has been described and illustrated with respect to a certain particular preferred example which gives satisfactory results, it will be understood by those skilled in the art after understanding the principle of the invention, that various other changes and modifications may be made without departing from the spirit and scope of the invention and it is intended therefore in the appended claims to cover all such changes and modifications.

We claim:

1. A reversible prime mover having bearings and ha ing spring-loaded ahead and astern admission valves having a manoeuvring device, and comprising a doublearm lever, said valves having stems and having springs mounted on said stems means at the ends of the arms of said double-arm lever for supporting the stems of said admission valves, a hydraulically operated servomotor having orifices for connections to pipe lines having a piston therein connected by a linkage with said doublearm lever acting against the springs of the ahead and astern admission valves and having passages therein connecting its hollow center portion with the upper and the lower side of said piston, a hollow pilot sleeve in the hollow center of said piston having a stem extending through said piston and having a cam-shaped operating member at the end of said stem, a pilot valve attached to said servo-motor having passages connected to the upper and the lower side of said piston of said servo-motor, manually operable means to actuate said hollow pilot sleeve by said cam-shaped member, a main pumping means for lubricant oil for the bearings of said reversible prime mover, impeller pumps for said lubricant oil driven by the ahead and astern parts of said prime mover, respectively, and pipe-lines connecting said main lubricant oil pumping means and said prime mover driven impeller pumps with corresponding orifices of said servo-motor and said pilot valve, respectively, said pilot valve having pistons; said piston of said servo-motor being actuated by the pressure of the lubricant oil coming from said main oil pumping means which action is controlled by the manually operated cam and the said hollow pilot sleeve, and being actuated also by the differential between the oil pressure of said main oil pump and the oil pressure of said prime mover-driven impeller pumps acting upon the lower and the upper face of the said pistons of said pilot valve attached to said servo-motor, respectively when such pressure differential exceeds a predetermined amount.

2. A reversible prime mover having bearings and having spring-loaded ahead and astern admission valves having a manoeuvring device, according to claim 1, and wherein said cam-shaped operating member has a profile for controlling the increase or decrease of the flow of the driving fluid for the prime mover in' a proportion linear to the positioning of the manually operated control means.

3. A reversible prime mover having bearings and ahead and astern admission valves connected with a double armed lever, said valves having stems and having springs mounted on said stems, means at the ends of the'arms of said double armed lever for supporting the stems of said admission valves, a hydraulically operated servomotor having a piston therein connected by a linkage with said double armed lever acting against the spring of the ahead and astern admission valves, a pilot valve attached to the servo-motor, said pilot valve having an intake port connected to a source of constant pressure and an intake port connected to a source of variable pressure, said pilot valve having means therein operable by a drop of said variable pressure to connect said pressures to opposite sides of said piston to thereby close said admission valves, a main pumping means for lubricant oil for the bearings of said reversible prime mover, said main pumping means also providing the source of said Variable pressure, a high storage tank for said lubricant oil connected by pipe lines with said main oil pumping means, a spring biased closed pressure sensing valve connected by a main pipe line between said main oil pumping means and said pilot valve, and by an auxiliary pipe line between said main oil pumping means and said servomotor piston, said pressure sensing valve being held open by pressure in the main pipe line, a safety valve connected between said main pumping means and said pressure sensing valve, said safety valve opening upon a drop in the level of the oil in said high storage tank for allowing oil to pass from said main pipe line to said bearings.

4. The structure as set forth in claim 3, said high storage tank connected to said safety valve and providing fluid pressure on one side of the safety valve tending to hold it closed, said safety valve having a spring biasing the safety valve closed, the fluid pressure in the main pipe line tending to open the safety valve.

5. The structure as set forth in claim 3, an emergency valve connected between the pressure sensing valve and 10 the pilot valve allowing a slight flow of fluid out of the main pipe line, said emergency valve having a manually operative trip to open the valve completely.

6. The structure as set forth in claim 3, including manually operated means for controlling the flow of fluid from the main oil pumping means through the auxiliary pipe line to the servo-motor piston for operating said spring loaded admission valves.

7. The structure as set forth in claim 3, said source of constant pressure comprising impeller pumps for connection to said prime mover, said impeller pumps being connected in a pipe line between said main oil pumping means and said pilot valve.

7 References Cited in the file of this patent UNITED STATES PATENTS 1,859,437 Flanders May 24, 1932 1,902,311 Reavis Mar. 21, 1933 2,197,743 Crafts et al Apr. 16, 1940 2,440,844 Bryant May 4, 1948 FOREIGN PATENTS 762,155 Great Britain Nov. 21, 1956

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