US1947128A - Fluid pressure governing mechanism - Google Patents

Description

Feb. 13, 1934.

C. C. FRANCK FLUID PRESSURE GOVERNING MECHANISM Filed Aug. 25, 1950 INVENTOR C. C FQQNCR.

I WENN. IH

ATTORNEY Patented Feb. 13, 1934 UNITED STATES PATENT OFFICE FLUID PRESSURE GOVERNING MECHANISM Application August 25, 1930. serial No. 477,747 11 claims. (o1. 264;-14)

My invention relates to a iiuid pressure governingmechanism for a prime mover, and it has for its object to provide improved mechanism of the character set forth.

A more particular object is to provide a governing mechanism employing a direct-acting pressure-responsive element for actuating the admission valve, and in which provision is made for applying a more positive closing force should the prime mover exceed a determined speed above normal.

Fluid pressure governing mechanisms are known in which fluid pressure varying inversely with the speed of the prime mover is applied in l'valve opening direction to a pressure-responsive element which directly actuates the admission valve or valves. Such mechanisms possess the virtue of simplicity. However, they have the disadvantage that the variations in fluid pressure 'may not provide a great enough force on the pressure-responsive element should the admission valve stick.

In accordance with my invention, I employ a governing mechanism of the character just described and provide suitable means for applying a iiuid pressure to the pressure-responsive element in valve closing direction, said iluid pressure being sufficient to provide an excess valve-closing force which assures positive closing of the admission valve.

The above and other objects are effected byl my invention as will be apparent from the following description and claims taken in connection with the accompanying drawing forming a part of this application, in which:

The single figure is a diagrammatic view, with parts in section, of the governing mechanism applied to a steam turbine.

Referring now to the drawing more inA detail, I show a steam turbine 10, having a primary admission valve 11 and a secondary admission valve 12, the latter opening after the primary admission valve has opened.v Each admission valve is operated by amotor device 13, including a piston 14 directly connected to the admission valve by a rod 15.

The piston 14 operates in a cylinder 16 and is biased in valve-closing direction by a spring 17. The spring 17 is a compression spring and abuts at its upper end against a spring holding member 18, the position of which may be varied by turning a screw-threaded stem 19 extending through the upper end of the cylinder 16. The piston 14 is normally actuated by iiuid pressure 55 4admitted from a conduit 20 to the lower end of the cylinder and acting on the piston in valveopening direction.

The fluid pressure for controlling the motor` devices is provided by a uid pressure device 21, with which the conduit 20 communicates. The device 21 includes a pressure-responsive piston 22, to which uid pressure varying as the squarev of the speed of the prime mover is applied. The latter pressure is preferably provided by a fluid impeller 23 mounted directly on the turbine shaft 24 and is communicated through a conduit 25. It is admitted to a chamber 26 in a casing 27 in which the piston 22 is disposed and biases the piston upwardly against the force of a compression spring 28. The spring engages at its upper end against an abutment 29 carried on the lower end of a stem 30 screw-threaded in the upper end of the casing 27.

A valve member 31 is connected to the piston 22 and is formed with piston portions 32 to 35, inclusive. The casing 27 is formed with an annular row of ports 36 communicating with the conduit 20 and normally covered by the piston portion 34. It is also formed with an annular. row of inlet ports 37 communicating through a conduit 38 with a suitable source of fluid pres` sure.` Said source may be provided by a second uid impeller 39 mounted on the turbine shaft f 24.

The casing 27 is also formed with a row of discharge ports 40 communicating with the space between the piston portions 32 and 33, and with a row of discharge ports 41, communicating with the space between the piston portions 34 and 35. A row of ports 42 is disposed so as to be just above the piston portion 33 when the valve member 31 is in its normal position. The ports 42 communicate througha conduit 43 with the upper end of the cylinder 16 of each motor device.

The fluid pressure in the conduit 20 is communicated through a branch conduit 20 and a row of ports 44, to a chamber 45, in which it biases the piston portion 35 upwardly against y the force of the spring 28.

The normal position of the valve member 31 is that shown on the drawing, in which the piston portion 34 covers the ports 36. The fluid pressure provided by the impeller 23 applied to the piston 22, plus the pressure in the conduit 20 applied to the piston 35, provide a deflection i of the spring 28 which brings the valve member to the above-mentioned normal position. The 'i area of surface of the piston 22 on which the impellerl pressure is applied, that is, the area of surface of the piston 22 less the area of surface of the piston portion, 35 is preferably about ten times the area of surface of the piston portion 35. Upon a given variation in the impeller pressure, therefore, a variation ten times as great in the opposite direction must be effected, in the pressure in the conduit 20 in order to provide the same force against the spring 28.

The operation of the above described mechanism is as follows:

Upon an increase in speed of the prime mover occasioned by a decrease in load, the impeller pressure increases and moves the piston 22 upwardly, The piston portion 34 of the valve member 31 places the ports 36 in communication with the discharge ports 41, so that fluid escapes from the conduit 20 until the pressure therein has decreased by an amount equal to ten times the increase in impeller pressure. The total force of the two iluid pressures opposing the spring 23 is then the same as it was before the speed increase, so that the spring deilection again provides normal position of the valve member 31.

The conduit 20 communicates the decrease in pressure to the lower end of the cylinder 16, andv the piston 14 is moved by the spring 17 in valveclosing direction an amount determined by the scale of the spring 17.

Upon a decrease in speed and impeller pressure, the spring 28 moves the piston 22 and the valve member 31 downwardly. The piston portion 34 places the ports 36 in communication with the iiuid supply ports 37, increasing the pressure in the conduit 20 and the chamber 45 until the increase in pressure equals ten times the decrease in impeller pressure, at which time the total force of the fluid pressures opposing the spring 28 again brings the valve member 3l to normal cut-onc position.

The increased pressure in the conduit 20 moves the piston 14 upwardly, and the latter moves the admission valve in opening direction.

The pistons 14 are moved by a force corresponding to the variation in the iiuid pressure communicated by the conduit 20. This force is relatively small in comparison with a fluid pressure relay in which the full force of the relay is applied until the required movement has been completed. For example, the lluid pressure in the conduit 20 may vary between 5 and 55 lbs.

per square inch, which means that the spring 17 for the primary admission valve 1l exerts a force equal to only 5 lbs. per square inch on the piston 14 when the latter is at the lower end of its travel. Should the valve 11 stick when it is near closed position, the force of the spring 17 may not be enough to move the valve, and if there is no load on the turbine, the steam admitted by the valve may be suicient to cause excessive speed of the turbine.

To guard against such contingency, iluid pressure is applied to the top of each piston 14. This pressure is applied in response to a predetermined over-speed of the turbine, which is preferably lower than the over-speed at which the usual automatic stop governor operates.

In the present embodiment, the mechanism operates to apply fluid pressure for closing the valves in the following manner: The increased impeller pressure nrst decreases the pressure in the conduit 20 to zero, after which further increase in impeller pressure moves the `piston 22 and the valve member 31 upwardly, as the increase in impeller pressure is no longer balanced by decrease in pressure in the chamber 45. At

the predetermined over-speed, the piston portion 33 is raised above the ports 42, placing the latter in communication with the fluid supply ports 37.

The full force of the iluid pressure developed by the impeller 39 is thus communicated through the conduit 43 to the top of each cylinder 16 and applied to the piston 14 in valve-closing direction. Since the pressure developed by the impeller 39 may be of the order of 50 or 60 lbs. per square inch, it is apparent that an ample closing force is applied to the piston 14 to insure positive closing of the admission Valve.

In normal operation, the piston portion 33 does not move upwardly far enough to place the ports 42 in communication with the ports 37, as the increases in impeller pressure are balanced by decreases in pressure in the chamber 45 before any substantial movement of the valve member 31 takes place.

The speed setting of the governing mechanism may be varied by turning the screw-threaded stem 30 to raise the lower the speed-holding member 29. This Varies the deflection of the spring 28 for normal position of the valve member. At the same time, the predetermined over-speed at which the ports 42 and 37 are placed in communication is raised or lowered an equal amount.

From the above description it will be seen that I have provided a governing mechanism in which ample force is provided to insure closing of the admission valves should sticking of said valves cause over-speed of the turbine.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire,

therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specically set forth in the appended claims.

What I claim is:

1. The combination with a prime mover having a valve, a device having a movable element connected to the valve for opening and closing the latter, a spring acting on the element to move the valve in a closing direction, means for applying iluid under secondary pressure to said element to movel the valve in an opening direction against the force of said spring, means for developing primary pressure of iluid in accordance with an operating characteristic of the prime mover, means responsive to a change in primary pressure for producing an opposite change in said secondary pressure, and means responsive to a predetermined maximum value of the primary pressure to apply a force to said element assisting the spring moving the valve in a closing direction.

2. The combination with a prime mover having an admissionv valve, a spring for moving the valve in a closing direction, abutment means connected to the valve, means f or developing fluid under primary pressure which depends upon an operating characteristic of the prime mover, means for transforming said primary pressure into a secondary pressure so the changes in primary pressure in one direction secure proportionate and larger changes in secondary pressure in the other direction, means for applying secondary pressure to said abutment means to open the Valve against the force of the spring, and means responsive to a predetermined maximum primary pressure for applying uid under pressure to said abutment Ver* means to assist the spring in closing the admission valve.

' 3. The combination With a prime mover having an admission valve, a spring for moving the'valve in a closing direction, abutment means connected to the valve, means for developing liuid under primary pressure which is dependent upon prime mover speed, a source of fluid under pressure, means responsive to primary'pressure for transforming vfluid derived from said sourceV into a secondary pressure such that changes in primary pressure in one direction cause proportionate and greater changes in secondary pressure in the other direction, means for applying secondary pressure to said abutment means to open the valve against the force of the spring, and means responsive to predetermined maximum primary pressure for applying said source pressure to the abutment means to assist the spring in closing the valve.

4. The combination with a prime mover having f an admission valve, of a device having a movable element connected to the valve for opening and closing the latter; a spring acting on the element ,ftomove the valve in a closing direction; means providing for the application of uid under secondary pressure to said element to move the valve from closed to Wide open positions against the force of said spring, said means including a ,source or uid under pressure, an exhaust port,

" munication of said supply passage with the exhaust port with increase in primary pressure and to move the control valve to establish communication of said supplyv passage with said source with decrease in primary pressure; means for applying the secondary pressure to said pressure-responsive device so that changes in sec` ondary pressure in consequence of movement of the control valve are eiective to restore the latter toneutral cut-off position; and means operated by said pressure-responsive device upon the attainment of a predetermined maximum primary pressure to apply fluid under pressure to the movable element of said device to assist the spring in moving the admission valve in a closing direction.

5. The combination with a prime mover having an admission valve, of a device having a movable element connected to the valve for opening and closing the latter; a spring acting on the element to move the valve in a closing direction; means providing a secondary pressure for application to said element to move the Valve from closed to Wide open positions against the force of said spring, said means including a source of fluid under pressure, an exhaust port, a secondary pressure supply passage, a control valve for placing the passage in communication With the source or with the exhaust port; means operated by the prime mover for developing iluid under primary pressure whose magnitude is a function of prime mover speed; operating mechanism for said control valve including a spring for moving the control valve to establish communication of the supply passage With the pressure source, means connected to the control valve for providing a first piston face subject to primary pressure to move the control valve in opposition to the spring to establish communication between the supply passage and the exhaust port, and means providing a second piston face connected to the control valve and subject to secondary pressure and eifective to restore the control valve to neutral position with the forces acting thereon in equilibrium; and means responsive to extreme movement of the first piston under influence of a high primary pressure, due to overspeeding of the turbine in consequence of the admission valve not moving in the closing direction to the extent required by the relative forces of the spring and of the secondary pressure, to apply a force to said movable element to assist the spring in moving the admission valve in a closing direction.

6. The combination With a prime mover having an admission valve, of a spring for closing the valve; an abutment connected tc the valve; means providing a secondary pressure and for applying such pressure to said abutment to open the valve against the force of the spring including a secondary fluid pressure supply passage, a pressure port connected to a iluid pressure source, an exhaust port, and a control valve for establishing communication of the passage with the pressure and exhaust ports; means operated by the prime mover for devoloping fluid under primary pressure which is dependent upon prime mover'speed; means responsive to primary pressure for operating said control valve; and means responsive to predetermined maximum primary pressure to apply force assisting said spring to move the admission valve in a closing direction.

7. The combination with a prime mover having an admission valve, of a spring for closing the valve; an abutment connected to the valve; means providing a secondary pressure and for applying such pressure to said abutment to open the valve against the force of the spring including a secondary iluid pressure supply passage, a pressure port connected to a iluid pressure source, an exhaust port, and a control valve for establishing communication of the passage with the pressure and exhaust ports; means operated by the prime mover for developing uid under primary pressure which is dependent upon prime mover speed; means responsive to primary pressure for operating said control valve so that increases in primary pressure cause decreases in secondary pressure and vice versa; and means responsive to predetermined maximum primary pressure-to apply fluid under pressure to said abutment assisting said spring to move the admission valve in a closing direction.

8. The combination With ya prime mover having an admission valve, of a spring for closing the valve; an abutment connected to the valve; means providing a secondary pressure' and for applying such pressure to said abutment to open the valve against the force of the spring including a secondary fluid pressure supply passage, a pressure port connected to a fluid pressure source, an exhaust port, and a control valve for establishing communication of the passage with the pressure and exhaust ports; means operated by the prime mover for developing fluid under primary pressure which is dependent upon prime mover speed; a pressure responsive device for actuating said control valve including a rst piston face subject to primary pressure, a second piston face subject to secondary pressure, and a spring opposing the effect of the fluid pressure forces applied to said piston faces; and means responsive to movement of the pressure responsive device incident to a high primary pressure, due to overspeeding of the prime mover in consequence of failure of the admission valve to close to the extent required by the relative forces of the spring and of the secondary pressure, for applying uid under pressure to said abutment assisting the spring in moving said admission valve in a closing direction.

9. The combination with a prime mover having an admission valve, of a spring for closing the valve; an abutment connected to the valve; means providing a secondary pressure and for applying such pressure to said abutment to open the valve against the force of the spring including a secondary iluid pressure supply passage, a pressure port connected to a fluid pressure source, an exhaust port, and a control valve for establishing communication of the passage with the pressure and exhaust ports; means operated by the prime mover for developing uid under primary pres-` sure which is dependent upon prime mover speed; a pressure-responsive device for actuating said control valve including a rst piston face subject to primary pressure, a second and smaller piston face subject to secondary pressure, a spring opposing the effect of the fluid pressure forces applied to the piston faces, and means for adjusting the compression of the spring; and means responsive to movement of the pressure-responsive device incident to a high maximum primary pressure, due to overspeeding of the prime mover in consequence of failure of the admission valve to move in a closing direction to the extent required by the spring and secondary fluid pressure forces, for applying uid under pressure to said abutment assisting the spring in moving said admission valve in a closing direction.

l0. The combination with a prime mover having an admission valve, of a spring for moving the valve in a closing direction; a first passage for supplying fluid under pressure for application to the valve to open the latter against the force of the spring; a second passage for supplying uid under pressure for application to the valve to assist the spring to close the valve; high pressure fluid pressure and exhaust connections; a valve movable in a rst direction to establish communication of said first passage with the high pressure connection to increase the pressure of iiuid in said rst passage, normally movable in a second direction to an extent suicient to establish communication of said rst passage with an exhaust connection to decrease the pressure in said passage, and abnormally movable in the second direction to an extent suicient to establish communication of the high pressure connection with the second passage; means providing a governing force dependent upon prime mover speed; and means for applying the governing force to said valve so that, with normal increase in prime mover speed due to reduction in load, said valve moves in said second direction, with decrease in speed due to increase in load said valve moves in said rst direction, and, with overspeeding of the prime mover said valve moves in said second direction to an extent suicient to place said second supply passage in communication with the high pressure connection, whereby uid under pressure is supplied to assist the spring in closing the admission valve.

11. The combination with a prime mover having an admission valve, of a spring for moving the valve in a closing direction; a rst passage for supplying fluid under pressure for application to the valve to open the latter against the force of the spring; a second passage for supplying fluid under pressure for application to the valve to assist the spring in closing the latter; a valve cylinder having a high pressure port, first and second exhaust ports spaced from the high pressure port at either side of the latter, a rst supply port arranged between the high pressure port and the rst exhaust port and connected to said i'irst supply passage, and a second supply port arranged between the high pressure port and said second exhaust port and connected to said second supply passage; a piston valve in said cylinder and having a first piston portion normally occupying a position so as to lap or approximately lap the first supply port and having a second piston portion which is spaced closer to the rst piston portion than the second supply port to the iirst supply port; said piston valve being normally movable in a rst direction to establish communiation of the high pressure and the rst supply ports, normally movable in a seond direction to establish communication between the first supply and the first exhaust ports, and abnormally movable in a second direction to establish communication between the first supply and the iirst exhaust ports, and abnormally movable in a second direction to establish communication of the high pressure and second supply ports; and means providing a governing force dependent upon prime mover speed and for applying said force to the piston valve so that, with an increase in governing force, the valve moves in said second direction and with decrease in governing force the valve moves in said rst direction.

CLARENCE C. FRANCK.

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