US2622866A - Speed governing mechanism - Google Patents

Description

Dec. 23, 1952 H. sTEEN-JoHNsEN SPEED GovERNING MECHANISM 2 SHEETS- SHEET l Filed June 50, 1950 NVENTOR.

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BY @www ,fb/Mw fw @MM Patented Dec. 23, 1952 SPEED GOVERNING MECHANISM Hall Steen-Johnsen, Greensburg, Pa., assignor to Elliott Company, Jeannette, Pa., a corporation of Pennsylvania Application June 30, 1950, Serial N0. 171,399

2 Claims.

This invention relates to speed governing mechanisms for prime movers operated by iiuid Ipressure, such as steam turbines.

It is among the objects of this invention to provide such a governing mechanism which is very sensitive to speed changes of the prime mover, and in whi-ch fluid pressure operated means control the operation of the fluid admission valves of the prime mover,

In accordance with this invention a uid pressure operated servo-motor controls the admission valve or valves of a prime mover, such Aas a steam turbine. Admission of fluid under pressure to the servo-motor is controlled by a pilot valve that is operated by a second uid pressure operated servo-motor. Admission of fluid under pressure -to the second servo-motor is controlled by a governor pilot valve that is operated by a rotating centrifugal device which is responsive to the speed of the prime mover.

The centrifugal device, or governor, includes a support which is rotated continuously by the prime mover and which carries flyweights that are supported by rubber bushings rigidly connected with the support and flyweights. Swinging of the flyweights, due to centrifugal force, puts the bushings in elastic torsion. There is no friction for the yweights to overcome. A oating rotary member, coaxial with the support, is rotated and moved axially by means of flexible strip means connecting it with the yweight-s.

The governor pilot valve includes a valve member rigidly connected at one end to the rotary member of the governor coaxially thereof. A piston is secured to the valve member, and a housing rotatably and slid-ably receives the valve member and piston. The housing has a fluid passage therethrough that is controlled by the valve member and that is provided with an inlet end for fluid under pressure and a discharge end. The latter end is connected to the second servo-motor by a conduit, so that when the valve passage between the inlet and discharge ends is opened by the governor, fluid under pressure is delivered toanism with its movable parts in an intermediate position; Fig. 2 is an enlarged plan view of the governor itself, partly broken away in section on the line II-II of Fig. l; and Fig. 3 is an enlarged vertical section through the governor pilot valve when the turbine is not running.

Referring to Fig. 1 of the drawings, the governing mechanism is illustrated as used for controlling 4the steam admission valves of a steam turbine, although it will be understood that the mechanism is equally applicable to other forms of prime movers using other forms of iiuid pressure. Only one of the several steam admission valves, with which the tur-bine may be provided, is shown. This valve I is in a steam line that is controlled by a main shut-olf valve (not shown) which is closed to shut down the turbine. When the main shut-off valve is closed, the admission valve opens Wide so that the full pressure of the steam will be delivered to the turbine as soon as the shut-off valve is opened again. The movable valve member 2 of the admission valve is moved up and down by an arm 3 on a rocker shaft 4. The outer end of the arm is pivotally connected to the upper end of a rod 6, the lower end of which is pivotally connected to a block l. Screwed into the block is the upper end of a piston rod 8 that extends down through an open chamber 9 and into the cylinder l0 of a servo-motor II for the steam admission valve. The lower end of the rod carri-es a piston I2. In cases where it is desired to close the steam admission valves when the turbine is shut down and there is no uid pressure for that purpose, a coil spring I3 may be compressed between the top of chamber 9 and a collar I4 mounted on the rod for urging the piston downward.

One side of the servo-motor cylinder block has an integral projection which forms a pilot valve I6 for the motor. For this purpose the cylinder block is provided with a downwardly extending bore in which a sleeve I'l is mounted. This sleeve is provided with axially spaced discharge ports I8 and I9 communicating with passages 20 and 2|. respectively, extending from them through the block to the upper and lower ends of cylinder Ill. Between these ports the sleeve is provided with another port 22 communicating with an inlet passage 23 through the block. Below the lower port I9 the sleeve is provided with an exhaust port 24 that connects with a passage 25 leading out of the block. Another exhaust port 26 is formed in the sleeve above port I8, and communicates with a passage 21 also leading out of the block. The flow of high pressure oil delivered to inlet passage 23 is controlled by means of a valve member 30 slidably mounted in sleeve l1. The major portion of this member is considerably smaller than the inside of the sleeve so as to provide an annular space between them, but the valve member has enlarged portions 3l and 32 which fit snugly in the sleeve so that when the v-alve member is in centered position, both discharge ports I8 and I9 will be closed. It will be seen that if the valve member is raised, the inlet passage 25 will be placed in communication with the upper discharge port I8, and the lower discharge port I9 will be connected with exhaust port 25. The passages that are opened when the valve member is lowered from centered position will be obvious.

The valve member 3D is raised and lowered in sleeve I1 by means of a stem 35 pivotally connected to its upper end and to a lever 3G. One end of the lever straddles block 1, to which it is connected by a pivot pin 31, while the other end of the lever is pivotally connected to the lower end of a link 38 whose upper end is pivotally connected to one end of an arm 39. The central portion of this arm is pivotally mounted in a bracket 4| supported by a case 42. The other end of the arm is pivotally connected to the upper end of a piston rod 43 that extends down into a cylinder 44 formed in the case. The lower end of the rod carries a piston 45 which is urged upward in the cylinder by means of a coil spring d1. The piston and cylinder and spring form a governor servo-motor 48.

It will be seen that whenever piston 56 is moved downward, it will rock arm 39 clockwise and raise the right-hand end of lever 35. The lever, being ulcrumed on the pin 31, will raise the valve member 35 of pilot valve IS so that oil entering the valve through inlet 23 will be delivered to the upper end of servo-motor cylinder Ill. This will move piston I2 down in the cylinder and thereby pull the left-hand end of the lever down. The lever, then fulcruming on the lower end of link 38, will lower the valve member in the pilot valve to again close both discharge ports I8 and I9 of the valve. This will trap the oil in both ends of the servo-motor cylinder Ill and hold the piston therein stationary until the pilot valve is opened again. When the servo-motor piston is moved downward, the steam admission valve member 2 is moved toward closed position. Of course, upward movement of piston l in the governor servo-motor 45 will just reverse all the movement just described, and the steam admission valve will be opened.

In order to supply fluid pressure to the upper end of the governor servo-motor cylinder de, a pipe 5I connects it with a governor pilot valve 52. This valve includes an open-ended housing 53, the inside of which is formed from a sleeve 54. The internal diameter of the sleeve is enlarged at its upper end to form a cylinder 56. A short distance below the enlarged portion the sleeve is provided with a radial inlet port 51 ccmmunicating with an inlet 58 through the housing adapted to be connected to a high pressure oil supply. At a little lower level the sleeve is provided with radial discharge ports 59 communicating with a housing discharge port 5I connected to pipe 5I. At a still lower level the sleeve has an exhaust port 62. The sleeve also has a vertical passage or duct 63 connecting its discharge port 6I with the bottom of cylinder 55.

Rotatably and slidably mounted in sleeve 5f?. is a valve member 65 which has secured to its upper end a piston 66 disposed in the cylinder. The valve member extends out of the lower end of the sleeve and is rigidly connected to a vertically movable rotary member 61 forming part of a centrifugal device, the rotation of which is controlled by the speed of the turbine as will be described presently. The valve member 65 has axially spaced cylindrical portions 68, 69 and 15 that t snugly within sleeve 55, the upper and lower portions sealing the upper and lower ends of the smaller part of the sleeve. Between these cylindrical portions the diameter of the valve member is much smaller in order to form ud passages. When the valve member is in exactly centered position, its middle portion 69 extends across the inner end of the sleeves discharge ports 59 to close them. However, if the valve member is moved up or down only a few thousandths of an inch, the discharge ports will be placed in communication with either the inlet port 51 or the exhaust port 62, depending upon which direction the valve member is moved. Thus, when the valve member is moved down, high pressure oil passes through the pilot valve and pipe 5I to the upper end of the governor servo-motor 48. When the valve member is raised above centered position, spring i1 forces oil out of the upper end of the servo-motor cylinder de and back through the pilot valve discharge ports 6I and 59 and out of its exhaust port 62. When the valve member is in centered or closed position, any oil in the upper end of cylinder 44 is trapped therein to hold piston d6 stationary.

It also is a feature of this invention that while oil pressure is being delivered through pilot valve 52 to the governor servo-motor, the oil also will exert pressure against the lower surface of the valve piston 65 until the pressure is great enough to raise the piston far enough to close the valve by moving the valve member 55 up to centered position. Therefore, the high pressure oil passage through the pilot valve never opens more than a few thousandths of an inch before it is closed again by means of piston 55.

The speed responsive centrifugal device or governor which controls governor pilot valve 52 is described in detail in my copending patent application Serial Number 74,394, led February 3, 1949, now Patent No. 2,546,911. It includes a at head 15 which is rigidly mounted on the upper end of a shaft 15 that is rotated by a worm gear 11 driven by a worm 18 from the turbine shaft. Mounted on this head is a pair of laterally spaced parallel supporting members, which may be in the form of metal blocks 1S. Between these blocks is a pair of flyweights 8| of any desirable form, the ones shown being more or less in the form of an inverted letter L.. The upper portion of each weight is provided with a horizontal opening through which a pivot pin 32 extends. The parallel pins also extend through axially aligned openings in the upper portions of the supporting blocks, and have threaded ends that project from those blocks. The diameter of the block openings is materially greater than that of the pins, and an outer metal ring 83 is mounted rigidly in each opening. Bonded to the inner surface of this ring is a considerably thicker ring of rubber S5, or similar material having the elastic characteristics of rubber. All such material will be referred to herein as rubber-like material. Bonded to the inner surface of this intermediate ring or bushing is an inner metal ring 8G `that ts snugly around the adjoining end of the pin. Extending from the inner rings to the weight between them are a pair of sleeves 81 which encircle the pin. In order to fasten all of these members rigidly to the pin so that the swinging,

vweight will turn the pin and the pin will turn the inner rings, collars 88 are mounted on opposite ends of the pin and are pressed tightly against the outer ends of the adjoining inner rings by means of nuts 89 screwed on the projecting ends of the pin. The result is that when rotation of the head 'I5 causes the lyweights to swing outward, they turn the pins which thereupon rotate the inner rings in the blocks and stretch the rubber bushings circumferentially.

An important feature of this governor is that the inner rings 86 on the pivot pins do not rub against any supporting elements. Instead, their rotation is absorbed by torsional elastic deformation of the rubber-like bushings that connect them to the outer rings 83. There is no friction or wear between relatively rotating parts, no bearing surfaces that require lubrication, and no starting friction to be overcome. Consequently, the device is exceptionally sensitive to speed changes of the prime mover. Some of the centrifugal force on the weights as head 'I5 rotates is absorbed by a coil spring 9| connecting the two weights. The distance that the weights can move outward is limited by the outer ends of brackets 92, and the distance they can move inward is adjustably limited by set screws 93 mounted in the inner ends of the brackets. These brackets are secured to the head between blocks 19. The upper ends of the weights which project toward each other are clamped by set screws 94 to the lower ends of resilient metal strips 96, the upper ends of which are clamped by set screws 91 to the rotary member 61 mounted on the lower end of the movable valve member 65 of the governor pilot valve. It will be seen that the rotary member and valve member are rotated and moved up and down by the strips 96 connected to the flyweights.

In order to vary the speed at which the governor must be rotated so as to swing the flyweights out any given distance. the upper end of the pilot valve member 65 above piston 66 is rotatably mounted in a bearing pivotally supported by a bell crank |0I. The crank is pivotally supported in a bracket |02 connected to the pilot valve housing 53, and the free end of the crank bears against a disc |03 which is pressed against it by a coil spring |64 carried by the inner end of a non-rotatable threaded rod |05. The outer end of the rod is threaded in a hand wheel |01 rotatably mounted in a projection I 08 of case 42. By turning this wheel, the amount of pressure that the spring exerts against the bell crank can be varied. For example, when thejpressure is increased, the increased resistance of the pilot valve member to being pulled down requires the governor to rotate at a higher speed in order to swing the flyweights out as far as before. This means that the turbine can reach a higher speed before steam valve I will start to close. Consequently, the hand wheel serves as a manually adjustable speed changer for the turbine. It also will be seen that piston 6B operates against the downward pull of the outwardly swinging ilyweights on the pilot valve member 65.

When the main shut-off valve is closed and the turbine is idle, the governor flyweights are pulled in against the set screws 93 by means of coil spring 9|. This causes the flexible metal strips 96 to raise pilot valve member 65 to its upper position shown in Fig. 3, in which discharge ports 59 are connected with the exhaust port 62. Consequently, spring 4l in governor servo-motor 48 is able to move piston 46 up as far as it will go in the cylinder, thereby rocking arm 39 in a counterclockwise direction. This tilting of the arm will push the right-hand end of lever 36 down and thereby connect inlet 23 of pilot valve I6 with lower passage 2| leading to the bottom of servo-motor cylinder I0. Oil pressure in cylinder l0 will move piston |2 upward and thereby open steam valve wide. Upward movement of this piston will simultaneously lift the left-hand end of lever 36 and thereby restore pilot valve member 30 to centered position.

With the parts of this governing mechanism in the positions described in the preceding paragraph, the main shut-off valve in the steam line is opened so that steam will be delivered through valve to the turbine. As the turbine gathers speed, the flyweights of the governor rotated by it will swing outward and pull valve member 65 downward until the governor pilot valve discharge ports 59 are connected with inlet ports 51 and 5B. Oil under pressure then will ow through the valve and pipe 5| to the upper end of servo-motor cylinder 44. The pressure above piston 46 will move the piston downward until the oil pressure in cylinder 56 of the governor pilot valve becomes great enough to move its piston B6 upward against the resistance of the centrifugal force of the flyweights. Closing of discharge ports 59 will trap oil in the upper part of cylinder 4t. Fig. l of the drawings shows the different parts of the governing mechanism while the turbine is operating at a predetermined speed, depending on the setting of the hand wheel |01. When piston 46 was moved downward in cylinder 44 as shown, it rocked arm 39 in a clockwise direction and thereby raised the right-hand end of lever 36 which, in turn, lifted pilot valve member 30 to admit oil pressure 4to the upper end of servo-motor cylinder |0. This pressure moved piston |2 down in the cylinder to the position shown and simultaneously pulled down the left-hand end of lever 36 so that valve member 30 was returned to centered position. Downward movement of piston I2 also pulled valve member 2 in the steam admission valve down to the position shown to reduce the delivery of steam to the turbine so that the turbine would operate at the desired speed. Any attempt of the turbine to speed up or slow down will, through the governor, move valve member 65 in the govern-or pilot valve up or down so as to either admit more oil to governor servo-motor cylinder 44 or release some of the oil therefrom, whereby the steam admission valve will be moved toward open or closed position, depending upon whether the turbine is attempting to go faster or slower. Due to the sensitivity of this speed governing mechanism, variations in speed of the turbine for any given speed setting will be very small.

According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

l. In a governing mechanism for a prime mover, a fluid pressure operated servo-motor, a centrifugal device responsive to the speed of the prime mover and including a constantly rotating member that also is movable axially in accordance with said speed, a valve member rigidly 7 connected at one end to said rotating member coaxially thereof, a piston secured to the v'opposite end of the valve member, a housing rotatably and slidably receiving the Valve member and piston, the housing having a fluid passage therethrough controlled by said valve member and provided with an inlet end for fluid under pressure and a discharge end, a conduit connecting said discharge end with the servo-motor, a spring operatively connected with said piston for opposing the pull of said rotating Amember on the valve member, and manually operated means for adjusting the force exerted by the spring on the valve member, the housing also having a duct leading from the discharge end `of said passage to the adjacent side of the piston to deliver uid pressure to the piston when the passage is open, whereby to pull the valve member axially to passage-closing position against the pull of said rotating member in the opposite direction.

2. In a governing mechanism for a prime mover, a fluid pressure operated serve-motor, a centrifugal device responsive to the speed of the prime mover and including a constantly rotating member that also is movable axially in accordance with said speed, a valve member rigidly connected at one end to said rotating' member Coaxially thereof, a piston secured to the opposite end of the valve member, a housing rotatably and slidably receiving the valve member and piston, the housing having a uid passage therethrough controlled by said valve member and provided with an inlet end for fluid under pressure and a discharge end, a conduit connecting said discharge end with the servo-motor, pivoted means connected with said piston, a spring engaging said means to oppose the pull of said rotating member on the valve member, and marrually adjustable means for varying the compression of the spring, the housing also having a duct leading from the discharge end of said passage to the adjacent side of the piston to deliver fluid pressure to the piston when the passage is open, whereby to pull the `valve member axially to passage-closing position against the Apull of said rotating member in the opposite direction.

HALL STEEN-JOHNSEN.

REFERENCES CITED The following references are of record inthe file of this patent:

UNITED STATES PATENTS Number Name Date 1,529,008 Buckle Dec. 23, 1924 1,713,673 Wettstein June 25, .1929 1,377,102 Whitsell Sept. 13, 1932 2,151,569 Sheppard Mar. 21, 1939 2,153,331 Mass Apr. 4, 1939 2,375,909 Fawick May 15, 1-945 2,375,844 Ziebolz May 22, 1945 2,379,394 Kalin June 26, 1945 2,393,713 Martin Apr. 16, 1946 2,463,495 Rodeck et al. Mar. l, 1949 2,578,350 Greene Dec. 11, 19511

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