US2668556A

US2668556A - Turbine apparatus

Info

Publication number: US2668556A
Application number: US126329A
Authority: US
Inventors: Frank A Meyer
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1949-11-09
Filing date: 1949-11-09
Publication date: 1954-02-09
Anticipated expiration: 1971-02-09

Description

Feb. 9, 1954 F. A. MEYER 2,668,556

TURBINE APPARATUS Filed Nov. 9, 1949 E a A if m t? A w v f INVENTOR F WITNESSES: F k A Meyer V. A) W 2- BY s ATTORNEY Patented Feb. 9, 1954 STATE? TENT 2 Claims.

The invention relates to an admission valve fora prime mover, more particularly to the admission valve of the intermediate-pressure turbine of a turbine installation, andit has for an object to provide for limiting of the motive fluid pressure differential applied to the servo operating piston in the direction to open the ad mission valve when the latter is stopped in wide open position in order to limit the stresses applied to the mechanism Connecting the operating piston and the admission valve.

Where the admission valve of a turbine, particularly the admission valve of an intermediatepressure turbine of an installation, is normally wide "'open if the admission valve is stopped in wide open position, unless provision is made for limiting the diiTerential pressure applied to the operating piston of the servo, the connecting linkage between the operating piston and the admiss'ionvalve must be made quite heavy or large, or an elastic link arrangement used, to avoid large stresses in the linkage due to 'dilferential pressure acting on the operating piston in a direction for opening movement of the admission valve. The present invention is concerned with a pressure limiter to limit the force applied by the operating piston and the eonse'que'nt stresses imposed on the linkage connecting the piston and the admission valve. I v H The foregoing and other objects are eii'ected b'ylny inventiona's will be apparent from the following description an'd claims taken in connection with the accompanying drawings, formthe a part of this application, in which:

The figure is a sectional view of apparatus incorporating the invention. In the drawing, there is shown an intermediat'e-pressure turbine is havingan admission valve ll of the pliig type. The admission valve has a stein I2 pivotally connected to'th'e link 14, which is pivotally co nected, at [5, to one end Of the lever iii, fulcrumed at IT. The other end of the lever is pivotally connected, at l8, to the stem 20 of the servo operating piston 2| arranged in the Cylinder v The admission and exhaust of motive fluid for movement of the operating piston is secured by means of a relay piston valve zf having lands 2 5, 26 and 2l controlling communication of pressure ports 28 and 29 and the exhaust or drain port 30 with passages 3| and 32 connected to the operating cylinder above and below the operating piston 2|.

The relay piston valve 24 is positioned by means of a pressure responsive piston 34, that 2 a M is, if the pressure-responsive piston moves, it followed by the relay piston valve, .as more particularly disclosed and claimed in the patentxto Schwendner 2,224,321 granted December 10; 1940.

The pressure-responsive piston 34 is located in the cylinder 35 and it has "a stem .38.. The upper end of the stem 36 is connected, by the follow-up spring 37, to the follow-up lever '38 having one end "connected to the 'fiX'ed fulcrum 39 and having its other end pivotally connected, at it], to the operating piston stem 21). A passage ll provides for liquid'undercontrolling pres"- sure being supplied to the cylinder 35 above the piston 34.

Below the piston, thestem 3 61's provided with a cup valve lZ arranged in covering r'l'ation'with respect to the core drain passage '43 fornfid' the relay piston valve. The upper end of the relay piston valve has piston or p es-sunsets id exposed to the chamber 15 into whichthe cup valve extends, the chamber being su through an orifice 46 with liquid than p from a suitable source, for example, from so the pressure ports. A spring in areas i force on the relay piston valve in h to fluid pressure force exerted on the piste In operation, if the pressure in the '5; pressure passage 4.! decreases, then; one to the upward pull exerted by the fdllowfj p 3?, the piston 34 moves upwardly, ther by e: ducing the pressure in thefchamber 45', n sequence of which the springflniovest piston valve upwardl'y to follow the the piston 34. With the relay piston j tion with the lands 25 and 26 'j'u'stlap pressure ports 28 and za a a the land 21 just lapping the return or exhaust port, just a on as the relay piston valve starts to move I ly from mid-position, pressureissupplied the passage 3! to the cylinder 22 abo piston 2! tomove the latter downwardl 011 below the operating piston being p ed through the passage 32 which is en m-{coziimunication with the ex aust or retui h -piiit iii. The operating piston 2;! moves downwardly to' move the admission valve in an opening direction, the force of the spring 31 being reduced, whereby, with reduced controlling pressure, the relay piston valve may be restored to mid-position through the follow-up action. On the other hand, if the controlling pressure increases, the opposite operation takes place, higher pressure supplied below the operating pis't r ""ng the latter upwardly to move the a'dmissi n valv" iii a closing direction aha increasing the fore?) t pin 3 the spring 3'! until the relay piston valve is restored to neutral position.

Because of the power required for the servomotor to operate the admission valve, with the latter wide open and stopped by the stem seal 48 constituted by engaging conical surfaces formed on the valve stem and on the valve cover, if, with the admission valve stopped in wide-open position by abutment of the stem sealing surfaces, the controlling pressure in the passage 4| changes so as to reduce the pressure supplied above the piston 34, then the difierential liquid pressure acting on the piston 2| in a valve-opening direction may exert very high stresses in the linkage mechanism connecting the operating piston and the admission valve, such stresses necessitating either an elastic link construction or linkage which is quite cumbersome and heavy. The present invention involves the provision of means which operates to limit the differential pressure applied to the operating piston with the result that the stresses applied to the linkage are limited, in consequence of which the linkage may be of relatively light and simple construction.

The pressure limiter comprises a passage 50 communicating with the operating cylinder 22 above the operating piston and a passage 5| communicating with such cylinder below the piston. The passages 5!) and 5| are connected to the cylinder 52 above and below the pressure-limiting piston 53. A spring 54 exerts upward force on the piston 53. The piston has a stem 55 whose lower end is provided with a cup valve 56 arranged in the exhaust chamber 51 with which communicates the pressure port 58 whose discharge end is covered by the cup valve 56. The port 58 is supplied with liquid under pressure through an orifice 59 from any suitable source. A passage 60 connects the pressure port 58 to the controlling pressure passage 4|.

The passage 60 has a check valve 6| opening toward the passage 4| so that, as long as the controlling pressure is higher than the variable pressure in the passage 60, the valve 6| closes preventing any back flow of controlling pressure through the passage 60. Similarly, the controlling pressure passage 4| has a check valve 62 arranged at the upstream side of the junction of the variable pressure passage 60 therewith, the check valve 62 closing in the event of the pressure in the passage 60 being higher than the controlling pressure, whereupon the variable pressure supersedes the controlling pressure and exerts downward force on the piston 34 for movement of the relay piston valve downwardly to connect the space above the operating piston with the exhaust or return, whereby the pressure attainable above the operating piston with the admission valve stopped in wide-open position is limited.

In operation of the pressure limiter, let it be assumed that a reduction in regulated oil pressure in passage 4| has permitted spring 31 to raise piston 34 and cup valve 42, and that spring 41 has moved the relay piston valve 24 upwardly, to efiect supply of fluid under pressure to the portion of cylinder 22 above the piston 2|, and consequently to cylinder 52 above piston 53, while releasing fluid from the space below piston 2| and likewise from the space below piston 53. Let it further be assumed that the piston 2| is thus positioned, as shown in the drawing, with valve I open and the stem seal 48 thereof seated. The same difierential in pressures above and below piston 2| thus exists above and below the piston 53. If this pressure differential exceeds a predetermined value, the piston 53 forces the cup valve 56 downwardly to further limit escape of high pressure oil from the pressure port 58 until sufiicient back pressure is developed therein, and consequently in passages 60 and 4|, to override and supersede the main controlling pressure in the control of downward force on piston 34. With the downward pressure on the latter thus increased, the relay piston valve 24 will be moved downwardly to effect sufiicient reduction in the pressure above piston 2| to lessen the valve opening force applied thereby through the medium of the members 20, I6, l4 and I2 to the valve after which the relay piston valve will again be returned to lap position, as already explained.

The pressure limiter just described is operated to limit the difierentialpressure of motive fluid acting on the operating piston 2| with the admission valve stopped in wide-open position, therefore, serves to limit the stresses to which the connecting linkage between the operating piston and the admission valve is subjected, in consequence of which the construction of such linkage may be relatively light and simple.

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.

What I claim is:

1. The combination, with a prime mover mo-. tive fluid admission valve having a stop limiting its wide open position and a servo-motor having its operating piston connected through lever and link mechanism to the admission valve, said servo-motor including a relay movable in response to controlling pressure supplied by a passage such that a decrease in controlling pressure results in movement of the relay for movement of the operating piston to open the admission valve, of apparatus efiective, with the admission valve stopped in wide open position, to limit the motive fluid pressure differential applied to the operating piston, in the admission valve opening direction, to limit the stresses applied by the latter to the lever and link mechanism; said apparatus comprising variable pressure developing means including an element disposed in flow restricting relation with a fluid escape port to establish a variable pressure, a passage including a check valve for supplying liquid under such variable pressure from the variable pressure developing means to the controlling pressure passage when such variable pressure is higher than the controlling pressure, said variable pressure developing means further including a pressure-limiting piston operatively connected to said element and a spring, said pressure-limiting piston being operable to exert force on said element in a direction to efiect an increase in such variable pressure, and said spring exerting force on the pressure-limiting piston in the opposite direction to reduce the variable pressure, and passages for applying the pressures present at opposite sides of the operating piston, respectively, to opposite sides of the pressure-limiting piston, one of the last-named passages being arranged to transmit the pressure urging said operating piston in the valve open ing direction to said pressure limiting piston in opposition to the force of said spring, whereby, when the pressure difierential applied to the operating piston to open the admission valve.

exceeds a predetermined value, with the admission valve stopped in wide open position, the pressure-limiting piston is moved thereby against the force of the spring to increase the pressure developed by the variable pressure developing means to exceed the controlling pressure and act on the relay to move the latter in a direction to reduce the pressure difierential applied to the operating piston.

2. In a prime mover control equipment including a motive fluid admission valve, a stop engageable thereby upon movement to a wide open position, a servo-motor comprising a cylinder, an operating piston mounted therein and connected through a lever and link mechanism to said valve, said operating piston being operative by pressure of fluid supplied to said cylinder for opening said valve, a relay mechanism subject to pressure of fluid in a control chamber for controlling the supply and release of fluid under pressure to and from said cylinder, said relay being responsive to a reduction in the pressure of fluid in said control chamber for effecting an increase in pressure of fluid in said cylinder resulting in closing movement of said valve, and a main controlling pressure passage communicating with said control chamber for normally supplying fluid under a controlling pressure thereto, the combination therewith of pressure limiter means for limiting the force applied to said valve in the opening direction, comprising casing structure forming a second cylinder, a conduit connecting said second cylinder with the first-named cylinder, a pressure fluid escape passage formed in said casing structure, a source of high pressure fluid communicating with said escape passage, a pressure developing element mounted in said casing structure in flow restricting relation between said source of high pressure fluid and said fluid escape passage for establishing a variable back pressure, a movable abutment mounted in said second cylinder and connected to said element for operation thereof to effect an increase in such back pressure upon an increase in pressure of fluid in said second cylinder incident to operation of said operating piston to open said admission valve, a spring engaging said movable abutment for biasing said pressure developing element in the back pressure reducing direction, and a communication connected to said source of high pressure fluid and including a check valve for supplying fluid under such back pressure to said main controlling pressure passage and consequently to said control chamber when such back pressure exceeds the pressure of fluid normally supplied to the control chamber from said main controlling pressure passage.

FRANK A. MEYER.

No references cited.