US1399774A - Control mechanism - Google Patents

Description

J. F. JOHNSON.

CONTROL MECHANISM.

APPLICATION FILED MAY 31, um.

1,399,774. Patented Dec. 13, 1921.

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, ATTORNEYS.

UNITED STATES PATENT Oi l 'itJE.

JOSIAH FRANCIS JOHNSON, OFEDGEWOOD, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC dz; MANUFACTURING COMPANY, A. CORPORATIDN 0F PENNSYL- VANIA.

CONTROL IVIEGI-IANISM.

Specification of Letters Patent.

Patented Dec. 13, 1921.

Application filed. May 31, 1917. Serial No. 171,986.

To all whom it may concern:

Be it known thatl, J osrArr FnANois JoI-IN- SON7ZL citizen oi the United States, and a resident of Edgewood, in the county of Allegheny and State of Pennsylvania, have made anew and useful Invention in Corr trol Mechanisms, of which the following is a specification.

This invention relates to control mechanisms and has for an object to produce a new and improved mechanism for controlling the delivery of fluid through at least two diii'erent valves.

A. further: object is to produce a control i mechanism which is responsive only to non synchronous movements of a two. elements which normally move synchronously.

A further object is to produce a control mechanism in which synchronous movements oia controlling device and one valve have no effect upon a second valve, but in which an independent movement of the controlling device and the first valve will occasion an opening or closing of the second valve.

A further object is to produce a new and improved control mechanism which is especially adapted for controlling the delivery otan auxiliary supply of motive fluid to a low pressure engine or turbine.

it further object is toproduce a new and improved control mechanism which will operate independently of the turbinegovernor in causing high pressure motive fluid to be delivered to a low or mixed pressure turbine when the supply of low pressure motive i'luid fails or is insufficient to carry the load.

These and other objects, which will be madeapparent throughout the further description oi my-invention, are attained by means of a mechanism embodying my invention, hereindescribed, and illustrated in the drawing accompanying and forming a part hereof.

i The control mechanism illustratedas an emboi liment or my invention is well adapted to control the delivery of motive fluid to low pressure turbines. It is common to supply auxiliary high'pressure motive fluid to low pressure steam turbines in order to augment or replace the supply of low pressure steam when the available supply oi low pressure steam fails oris insufficient to carry the load on the turbine. Mechanisms for controlling the admission of: high pressure motive fluid,

hereinafter called steam, to a low pressure turbine, generally require an appreciable reduction in speed oi the turbine before the high pressure steam valve is opened. This causes wide variations in the speed of the turbine, -which are objectionable in some lines of work and particularly where the turbme is employed in driving an electric generator. By, means of my invention high pressure steam may be admitted the instant the supply of low pressure steam becomes insuiiicient to carry the load, consequently good regulation of the turbine may be maintained. Furthermore, my invention not only enables a more eflicient control than was obtainable with other control mechanisms now in use and known to me, but it also enables the use of simpler and more compactapparatus than these other mechanisms.

Figure 1 is a diagrammatic sectional view of v a governing apparatus embodying my invention; and Fig. 2 is a diagrammatic view showing the relationship of parts for non-synchronous movements.

As illustrated, the invention is applied to the valve mechanism oi a low pressure turbine, the main elements in the mechanism being a governor actuated controlling device h, a low pressure steam delivery valve 13,

and a high pressure steam delivery valve C. The low pressure valve B is adapted to deliver low pressure steam to the working passages of a low pressure'turbine, (not shown) and the valve C is adapted to deliver high pressure steam to either the same working passages or to a different passage especially adapted to receive high pressure steam.

in this embodiment of my invention, the

valve B is of the constant pressure type,

having a casing 5 and a valve disk 6 oi? relatively large size. Steam is delivered to the valve through an inlet port 7 below the valve disk 6. As shown, the upper part of the valve casing 5 is cylindrical in form, and the valve disk 6 is adapted to slide like a piston in this cylindrical portion of the casing. When in its closed position the valve disk 6 cooperates with a valve seat 8, and when open it allows the steam to pass from the lower part of the valve, after entering the inlet port 7, into an annular chamher 9, which surrounds the central portion oi. the valve immediately above the seat 8, and communicates with a delivery port 10. In the center of the valve disk 6 and on its upper side I have shown a neck 11, which is enlarged to form a plunger 12 on its upper end. This plunger is adapted to slide in a cylinder 13 formed on top of the valve casing 5 and communicating with the atmosphere by means of a small open port 14 in the cylinder wall above the plunger 12. The hole 14 may be so located and be of such a size that the cylinder 13 will also act as the only force which tends to open the valve,

and it must overcome the weight of the valve disk 6, the neck 11 and the plunger 12, and also. the air pressure above the plunger 12 before it can do so. It is evident that the valve will only open when the pressure of the steam entering through the inlet port 7 has reached a definite pressure, and for this reason the valve is'called a constant pressure-valve. If the pressure should decrease below, this the valve would immediately be closed by its own weight and the force of the air pressure above the plunger 12.

I have illustrated a valve stem 16 mounted on the plunger 6 and extending out through the head of the cylinder 13. External pressure on this stem is adapted to move the disk 6 to its seatin opposition 'to the unbalanced differential pressure of the steam on the lower surface of the disk.

The high pressure valve C is shown as of the familiar balanced puppet type, having a double seated valve disk 17 inclosed by a casing 18. lVhen in the closed position the valve disk 17 is adapted to cotiperate with valve seats 19 and 20. Steam is delivered to the valve through an inlet port 21 at the bottom of the casing 18 and then flows to an annular chamber 22 and an outlet port 23 when the valve disk 17 is raised from the valve seats 19 and 20. The valve disk 17 is controlled by means of a stem 24, which extends out'through the cover plate 25 of the valve C The controlling device A, illustrated as forming a detail of this embodiment of my invention, may be an oil relay controlled piston and cylinder such as is commonly employed in the governing mechanisms of steam turbines. As shown it consists of a cylinder 26 in which a piston 27 operates. Actuating fluid is delivered to the cylinder either above or below the piston 27 by apilot valve 27, which is controlled by a speed governor 27 A piston rod 28 is attached to the piston 27 and is shown as carrying a yoke 29 on its upper end. The yoke 29 is connected to a similar yoke -3,0, b.elo w the cylinder 26, by

means of two rods 31 and 32. As shown, the lower yoke 30 is provided with a block 33, which is adapted to engage the outer end of the low pressure valve stem 16 and to thereby control the low pressure valve disk 6. The controlling device A and the low pressure valve B are so located that when the turbine attains the maximum permissible speed the piston 27 and therefore the yoke 30 are in their lowest positions and hold the low pressure valve disk 6 against its seat 8 so as to completely shut off the supply of low pressure steam to the turbine. As the turbine speed decreases the yoke 30 is raised by the piston 27 and if the pressure of the low pres sure steam is suflicient to raise the valve disk 6, the disk immediately follows the yoke 30 by reason of the unbalanced differential steam pressure on it, and admits steam to the turbine. The mechanism is so arranged that the yoke 30 has considerably more travel than the low pressure valve disk 6. so that after the valve disk 6 has reached the upper limit of its travel, the block 33 moves away from the stem 16 as the yoke 30 continues its upward movement.

This independent movement of the yoke 30 is adapted to immediately open the high pressure valve 0 by means of a system of links and levers operatively connecting the yoke 30 and valve stem 16 with the valve The system includes a lever 34, which is pivoted to the block 33 and, at its other end, is slidably mounted on a stationary pin 36, which I have shown as mounted on a stationary standard 37. The system also includes a lever or link 35, which is pivoted at one end to the low pressure valve stem 16, and at the other end is connected to the high pressure valve stem 24 by means of a link 38. These levers are preferably normally parallel and are illustrated as connected by a short link 39 at a point intermediate their ends. This link may be placed at any intermediate position, depending on the ratio of movementv desired between the opposite ends of the rods 34 and 35.

The operation of the apparatus is as follows: If plenty of low pressure steam is available and the turbine is assumed to be running and subjected to an increasing load, the valve 6 is allowed to open because the turbine governor, operating through the device A, moves the yoke 30 upwardly and the steam pressure below the valve disk 6 causes the valve to open in following the yoke. As the load is increased the yoke 30 continues to rise and the valve 6 continues to follow it until the valve reaches the limit of its travel. During this movement the levers 34 and 35 remain parallel, the former pivoting on the stationary pin 36 and the latter on the pivot pin betwen the lever and the link 38.

If the load on the turbine continues to increase a-fter the low pressure valve is fully variation in the speed of the turbine.

open and consequently after the low pressure steam supply is incapable of supplying suli'icient steam. to the turbine to maintain the speed at the increasing load, the governor will cause the piston 27 to continueits upward movement and consequently move the block 33 out of contact with the stem 16. This will immediately cause the high pressure valve C to open, since the lever 35 will be caused to fulcrum about its pivotal connection with the stem 16. a In this way high pressure steam is supplied to the turbine as soon as the low pressure steam supply is inadequate, and in addition to this the governing function is immediately shifted to the high pressure valve, since it alone moves in response to the governor.

a. closing movement of the valve 6, due to a decrease in the low pressure steam supply, and a consequent decrease in the steam pressure below the valve disk will also impart an opening movement to the high pressure valve C, because the downward motion o't the valve 6 will cause the lever 35 to tut erum on the connecting link 39. From "this it will be apparent that a fa-ilure of the low pressure steam supply acts direetlyon the high pressure valve without the necessity of the intervention of the governingmechair ism, and consequently the time element due togovernor'lag is eliminated and the steam supply is maintained substantially constant under varying steam pressure conditions and without occasioning apprecialcgle n fact, the adjustment of the valves may be such that a failure of the low pressure steam supply and a consequent increase in thehigh pressure steam supply will take place without occasioning any variation inthe speed of the turbine. It will also be apparent that a building up of the low pressure steam supply, alter the turbine is in operation and is receivin high pressure steam from the valve C, wlll cause the valve B toopen and will occasion a corresponding closing ofthe valve C without the necessaryintervention of the governing mechanism.

Assuming that the low pressure valve B is wide open, thatthe high pressure valve C is partly open, and that theload on the tun bine is either gradually or suddenly re moved, the governor of the turbine will cause a downward movement of the yoke 30 of the controlling device A. This will first shut oil the supply of high pressure steam by moving the levers at and 35 into parallelisni and thereby closing the valve C, then the block will engage the stem 16 and force the low "pressure valve disk downwardly in opposition to. the unbalanced steam pressure acting onit and will therefore shut off the supply of low pressure steam so as to maintain the speed of the tur bine normal. The variations in s eed necessary to actuate the governor are slight and, as there is no lost motion in the controlling mechanism illustrated, no material reduction or increase in speed is necessary in order to bridge the gap between the limit of the operation of one valve and the beginning of the operation of the other valve. In tact, in the apparatus illustrated, there is no gap between the operation of the valves B and U and as soon as one valve has reached the limit of its controlling function the other valve immediately assumes that :tunetion. In the illustrated embodiment of my invention the high pressure valve is immediately opened either by failure of the low pressure steam supply or by an increase in. load be yond the capacity ofthe low pressure steam supply. i

its long as the block 33 and the stem 16 move in synchronism, the high pressure valve U is unaffected by variations in the position of the governing mechanisms. It the load be light it is understood that the control mechanism A will hold the low pressure valve disk 6 nearly closed and, of course, will allow it to open as the load is increased. Any movements of the controlling device A or the stem 16 which are not in synchronism will immediately actuate the high pressure valve C.

The apparatus which I have illustrated as an embodiment of my invention is unusually simple, reliable and flexible. It efiectually prevents the turbine from racing, and provides for good regulation when operating either on low pressure steam, high pressure steam, or a mixture of both. In action it is smooth and continuous, so that no appreciable drop in speed occurs when the change is made from low pressure to high pressure operation or when the load is increased be yond the capacity of the low pressure steam supply.

While I have described and illustrated but one embodiment of my invention, it will be apparent to those skilled in the art that various changes, modifications, additions and omissions may be made in the apparatus illustrated without departing from the spirit and scope of my invention, as set forth by the appended claims.

What I claim is:

1. In a control mechanism, substantially parallel members connected together at an intermediate point by a pivotally mounted connecting member, one end of one member being restrained by a fixed pin so that synchronous movements of the other ends or": the members will not aitect the substantially parallel relation of the two members, and independent movements of said other ends willcause the members to assume a nonparallel position.

2. In a control mechanism, a system of levers comprising substantially parallelmembers connected at an intermediate point by a connecting member, the system being restrained by a stationary pivot at one corner so that a-point in the system adjacent to the fixed point is unresponsive to synchronous movements of adjacent points at the other end of the system but is immediately responsive to non-synchronous move ments of said points.

3. In a fluid control mechanism, a speed responsive device, a low-pressure fluid con trolling valve, responsive to variations in pressure of the fluid controlled and adapted to be contacted by the speed responsive device to impart a closing movement vthereto, a high-pressure fluid controlling valve, and means connecting said high-pressure valve to the low-pressure valve and to the speed responsive device so as to allow said highpressure valve to remain closed as long as the low-pressure valve and the speed responsive device cooperate, and to open said high-pressure valve when the low-pressure valve and the speed responsive device are separated.

4. In combination in a governing apparatus, a governing mechanism, a valve adapted to be moved in only one direction by movement of thegoverning mechanism, and adapted to be moved in the opposite direction by an independent controlling force, a second valve, a system of links and levers connecting said first and second valves and said governing mechanism so arranged that non-synchronous movement of said first valve and said governing mechanism actuates the second valve.

-5. A governing apparatus comprising in combination, a valve chamber having inlet and discharge ports, a valve in the chamber to control communication between the ports and responsive to the pressure of motive fluid at the inlet side to move to open position, a governing mechanism for the valve adapted to have operative and inoperative controlling relation therewith, a second valve, means for connecting the valves with the governing mechanism whereby the second valve is controlled by the governing mechanism and the first valve when the first valve is out of operative controlling relation with the governor.

- 6. Governing apparatus comprising in combination, a valve, a governor controlled element adapted to engage and control the movements of the valve between open and closed positions, a lever pivoted at one end to the governor controlled element and to a fixed point remote therefrom, a second valve, a link pivoted to the first valve and to the second valve so that synchronous movement of the said element and the first valve does not alter the angular relation of the lever and the link or actuate the second valve, and

a pivotal connection between the lever and the link whereby independent movement of the valve or the said element actuates the second valve.

7. Governing apparatus comprising in combination, a valve, a governor controlled element adapted to enga e and control the movements of the valve etween open and closed positions, a lever pivoted at one end to the governor controlled element and to a fixed point remote therefrom, a second valve, a link pivoted to the first valve and to the second valve so that synchronous movement of the said element and the first valve does not alter the angular relation of the lever and the link or actuate the second valve, and a pivotal connection between the lever and the link whereby alteration of the angular relation of the lever and the link causes actuation of the second valve.

8. Governing apparatus comprising in combination a governing mechanism, a mlve adapted to be controlled thereby and moved synchronously therewith within certain limits of movement of the governing mechanism, a lever pivoted to the governing mechanism at one end and to a fixed point at the other, a second valve, a link pivoted to the first and second valves so that synchronous movement of the first valve and the governing mechanism does not alter the angular relation of the lever and the link, and a pivotal connection between the link and the lever whereby independent movement of the link or lever will actuate the second valve.

9. Governing apparatus comprising in combination, a governing mechanism, a. pressure actuated controlling valve for low pressure fluid adapted to be opened in response to the fluid pressure within the valve and controlled by the governing mechanism, the said overnlng mechanism and the control valve being adapted to operate synchronouslybetween the open and closed positions of the valve and non-synchronously after the valve has opened, a lever pivoted to the governing mechanism and to a fixed point, a high pressure valve, a link pivoted to the high pressure valve and the low pressure valve, so that synchronous movement of the governing mechanism and the low pressure valve does not alter the angular relation of the lever and the link or actuate the high pressure valve, and a pivotal connection between the link and the lever whereby independent movement of the link or the lever will actuate the second valve.

10. In combination in a governing apparatus, a valve responsive to variations in fluid pressure, a governing mechanism for the valve capable only of closing said valve, a second valve, and means for connecting the valves with the governing mechanism whereby the second valve is controlled by the governing mechanism and the first valve neaavva when the first valve is out of operative controlling relation with the governor.

11. In combination in a governing apparatus, a valve responsive to variations in fluid pressure, a governing mechanism for the valve capable only of closing said valve, a second valve, and means ifgr connecting the valves with the governing mechanism whereby the second valve may be actuated by either or both the governing mechanism and the first valve.

12. Governing apparatus comprising in combination, a first valve normally biased to closed position and responsive to fluid pres sure to open, a governor mechanism, a second valve, and linkage mechanism between the governor mechanism and the valves including a fulcrumed lever between the valves, whereby, when the pressure or fluid for the first valve drops the second valve is opened independently of the governor mechanism.

13. Governing apparatus comprising in combination, a first valve normally biased to closed position and responsive to fluid pressure to open, a governor mechanism, abutment means carried by said valve and the governor mechanism whereby, upon movement in one direction of the governor mechanism, the valve is given a closing movement, a second valve, and linkage mechanism between the governor mechanism and the valves including a fulcrumed lever connected to the valves, whereby, when the pressure of fluid for the first valve drops, the second valve is opened independently of the governor mechanism. a

14. In governing apparatus, the combination of a differential low-pressure valve responsive to fluid pressure to open and to a decline in pressure to close, a governor mechanism, a high-pressure valve, linkage mechanism between the governor mechanism and the valves including a fulcrumed lever pivotally connected to the valves, whereby, when the governor mechanism moves in one direction, the low-pressure valve i'ully opens and further movement of the governor mechanism operates through the lever fulcruming on the low-pressure a.

valve to open the high-pressure valve.

15. Governing apparatus comprising in combination, a low-pressure motive fluid valve responsive to pressure of motive fluid to move to open position, a governor mechanism, a iever connected at one end to the governor mechanism, a stationary fulcrum for the other end oi lever, a high-pressure motive fluid valve, a lever pivotally connected to the valves, and fulcrum means carried by the first lever for supporting the second lever between the valve connections.

16. Governing apparatus comprising in combination, a low-pressure motive fluid valve responsive to pressure of motive fluid to move to open position, a governor mechanism, a lever connected at one end to the governor mechanism, a stationary iulcrum for the other end of lever, a high-pressure motive fluid valve, a lever pivotally connected to the valves, fulcrum means carried by the first lever for supporting the second lever between the valve connections, and abutment means between the first valve and the governor mechanism for moving the JOSIAH FRANCIS JOHNSON. Witness:

C. W. MoGrmn.

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