US1875326A

US1875326A - Control mechanism

Info

Publication number: US1875326A
Authority: US
Publication date: 1932-09-06
Anticipated expiration: 1949-09-06

Description

P 1932- I c. B, CAMPBELL 1,875,326

CONTROL MECHANISM Filed July 9. 1950 as 61 ea H95 7' SECOND F/ SECOND FLU/D FLU/D FL U/D FLU/D PEA-$5025 C. 5. Campbell.

ATTORNEY Patented Sept. 6, 1932 can an; 1212s BATE am" .cmnnnon B. oAMrnELn'or. MooREs, PENNSYLVANIA, essmnoa'ro wns'rmcnousn ELECTRIC; &. mnnrncrnnme. COMPANY, Aloolmonmmn 0.1? BENNSXLVAHIA oonrxor; r nonnnrsm Application filed Jul -9,- 193m- Serialf ito; 466,797.

Mjy. invontio1r-relzltes to as; control mechar: nism for a prime mover more particularlyto control; mechanism I fora multi-stage elastic fluid. prime: mover having: openings two or, more;intermediate-pressure:-stages for extracting-partially expanded 1110lJlV8- fluidifromthe. PIiHIGi-HIOVGIT'IOIL fonadmitting. motive fiuid:thereto,-.and it'hasfor itseobJect:

to provide an .iinprcvediconstnuction off such.

mechanism.

A more particular object is to provide an improved: control mechanismofzthe character: set forth .1 which w-ilhup on change in, demand for flow of fluid through oneof; the openings, operate the valve means at, said; one opening'toefi'ect the desired? change in flow and to maintain; the. desired pressure, and which will? at; the sametime; operate the ad;-- mission valve and. the valve: means at tho- 51ozother opening to maintain: the proper.- load on.

Still the prime mover and thepnopen' flow and. pressure at: said other openings.

In accordance with my invention, I pro vide a: control device associated: with: each opening which provides two, fluid: pressures varying'inopposit'e' directions to each other in response to. variations in: pressure at. the opening; A regulating means/for control-- ling-the'fiow at eachiopeningxis responsive to that one of the fluid pressures: ofi each; con.- troL device, whose variationsarezin; the proper direction.

The aboveand other objects are effected. by my invention, asiwill be apparent from jthetollowingdescription and claimstaken in connection with the accompanying, drawing forming apart of. this application in which:

The single: figure is, a. diagrammatic view of the control mechanism applied toja, multiistage fluid turbine.

Referring now to the drawing more in detail, I- show an elastic, fluid turbine 10 having a-casing 11 and a rotor 12. Theturbine is supplied with motive fluid, which may be am suitable elastic fluid such as steam from a conduit 13 and the admission thereofto the turbine is controlled by an admission valve The turbine 10 is designed for operation in connection with demand forel'astie fluid at;which.inotive fluidis admitted to the ture bine. For example, elastic fluidat pressures 015,125.. lbsnpersq inch and1'8 lbs. per sq. inch may: be required,-. while elastic fluid may beadmittedito the turbine, at a pressure of 400. lbs-ipersq. inch; Theexpansion from the latter-pressure to either. of the lower pressures is utilized in the turbine to develop power.

The casing: 11; is formedwith an opening 15,- ,at: an intermediate-pressure stage 155 iirom which; elastic fluid. at the higher extraction pressure may be withdrawn .from. the turbine twat-conduit 1-6.- It is formedw-ith-a: similar opening. 1!7 at a lower, intermediate-pressure stage 17 from which elastic fluid of lower extraction pressuremay be withdrawn to a. conduit-.18., The openings and.17 divide the; turbine; into at highrpressure section. 19, anlintenmediatapressure section 21 and alow, pressune section22,theintermediate-pressure stages .15, and, 1&7. receivingpartially exp and.- ed motive fluid from the discharge or lowpressure'ends ofthe high-pressuresection19 and the-.intermediatepressure section 21, re-s spectively.

A, diaphragm 23. isprovided between, the pressure;- stage 15 and the section. 21,.and a I diaphragm 24:. is; provided between. the pres- '.sune sta-gel'? and. the section,22.. A passage 25-prouides a by-pass around the diaphragm, 23, and contains a valve 2,6.for controlling. the flow. o'f motivefluid. to. theintermediate pressuresectiort 2,1. Likewise,sa passage 27 providesaby pass around. the diaphragm 24;,and: a valve 28iis interposed in the passage tofcon:

trot theflow oi motive fluidto. the low pres sune section 22:. s I

It is-the-fiunction ofthevalves26v and 28 to maintain the desired pressures atthe-pressure stages. 15,- and 147:; and the corresponding openings L5 andl'h by holding backfromthe lower stages: the amount; oi motive fluid. res quinedi for'extractien'. In; order to-maintain. the'pressur'es; at the; extraction; stages and the speed 025 theturbine substantially constant, the action of these- VaILVQS and the admission t alv'el l, upon changes-.in load and demands for "extracted fluid, should be as follows Assume first, constant demands and flow-S:

14 and decreased openings of the valves 26 and 28. The increased amount of motive fluid held back by the valve 26 and the increased admission by the valve 14 provide the increased amount of extracted fluid. The valve 28 decreases the admission to the low-pressure section 22 by an amount equal to the decrease in flow through the intermediate-pressure section 21, so that the amount of fluid for extraction through the opening 17 remains the same. A portion of the power development is transferred from the intermediate-pressure section 21 and the low-pressure section 22 to the high-pressure section 19. 7

Assume now constant load and constant demand at the opening 15, and an ncrease in demand for fluid at the lower extraction pressure. The openings of the

valves

14 and 26 should be increased and the opening of the valve 28 should be decreased. The increased flow through the high-presslure section 19 and the intermediate-pressuresection 21 and the increased amount held back by the valve 28 provide the increased amount of fluid for 8X4 traction, and a portion of the power development of the low-pressure section 22 is transferred to the highepressure section 19 and the intermediate-pressure section 21.

In other words, as the demand for extracted fluid increases at any one opening, the valves on the high-pressure side thereof should be moved in opening direction, while the valves on the low-pressure side thereof should be moved in closing direction.

Such operation of the valves is effected by my novel control mechanism which will now be described. The

valves

14, 26 and 28 are connected to

fluid pressure governors

29, 31, and 32, respectively. Each governor includes a cylinder 33, and a piston 34 operat-' ing therein and connected to the associated valve through a lever 35 pivoted to a stationary fulcrum at 36. A spring 37 biases the piston 34 in the direction for opening the associated valve.

Fluid pressure varying as the square of the speed of the turbine is developed by an impeller 38 mounted on the rotor shaft 39. It is conveyed through a conduit 41 to the cylinder 33' of each governor and imposed on the piston 34 in opposition to the spring 37 and in the direction for closing the associated valve.

form of governor may be employed, and that it may embody a fluid pressure relay mechanism. Two forms of suitable constructionare shown in the patent of O. N. Bryant, Patent No. 1,778,004, granted October 7, 1930.

I11 order to modify the action of the several governors in accordance with the variations in demand for extracted fluid, I apply an op dicated at 43, 44, and 45, respectively. The

compensators include

pressure relief valves

46, 47, and 48, respectively, communicating with the governors through

conduits

49, 51, and 52.

Each compensator further. includes a plurality of pressure-responsive elements 53, there being one such element for each opening. The elements 53 bias the pressure relief valves in closing direction, and each element is connected thereto by a lever 54 hearing on a knife edge fulcrum 55. The fulcrum 55 is mounted on a stationary supporting plate 56 and is secured thereto by a screw 57 passing through a longitudinal slot 58 in the supporting plate. The fulcrum may be moved longitudinally of the lever to vary the lever arm ratio.

The compensators are controlled by

control devices

59 and 61, associated with the

openings

15 and 17, respectively. Each control device provides two fluid pressures which vary in opposite directions to each other upon variation in pressure at the associated opening; that is, one of the fluid pressures increases and the other decreases upon increase in pressure at the opening, while the first decreases and the other increases upon decrease in pressure at the opening.

The control device 59 includes a lever 62 pivoted to a fulcrum 63, the latter being vertically adjustable to vary the setting of the control device. A diaphragm 64 is connected to the lever 62, and is subjected to the pressure of the fluid in the conduit 16, which is communicated to the diaphragm through a conduit 65. A spring 60 biases the lever 62 in opposition to the force of the pressure on the diaphragm 64.

The control device 59 further includes

relief valves

66 and 67 which are biased to It is to be understood that any suitable closed position by

springs

68 and 69, the latter being compression springs interposed between the relief valves and spring-holding mam- 74, respectively, each of which is supplied with a restricted flow offluid under pressure from a branch: oi? the: conduit ALL-through The control device 61! is of the same con- -s struction as: the control dGVICB' 59,, and the corresponding parts thereof bear" the same" reference numerals with the prime'mark added. The di-apln'agm. 64 is; subjected to the pressure in the: conduitlS, communicated thereto: through a conduit 65/. V

The

pressure relief valves

66 and 67 con trolthe escape of fl-ui d' from conduits-76 and. 77 which are alsosupplied through orifices Lwith a restricted flow oi? ii'ui'd under'presi sure from the branch oi theiconduit 412.

The flluid pressure provided by each of the reliet valves 66' 66 varies in the saline direction as the fluid: pressure imposed on the associated diaphragmg. while the pressure provided by" the corresponding valve 6 7? or 6'2 varies at the same. time in the opposite direction. may be termed the firsufluid pressure and the other the second fluid: pressure-,- and for the purpose oft-he present description, the form-- or is designated the first fluid pressure and the latter the second: fluid pressure; I

Each or. the compensators is: subjected to the first fluid pressure of the control device or devices associated with opening or openings on the high-pressu-re' sidfe 02E the valvecontrolled' by the" compensator, and to the second fluid pressureiof any control de-' vice or devices associated with an opening or openings on: the low-pressure side oi the valve controlledby'the compensator;

Accordingly. the second. fluid! pressuresof botlr control: devices are: communicated through; the conduits 74* and '27 v to the" pressure-responsive elements of the compensator l the openings 15 and 1'5 being on: the lowpressure'side of theadmissionval ve' 14; One of the pressure responsive elements of the compensatortet is subjected to the first fluid pressure of the control device 59" communi cated through thecondilit 7 3; since: the opening' 15* associated with the control device" 59- is onthe highrpressure orup-st'ream side of the valve 26, and the other pressure respone sive element is subjected to thesecondfluid pressure of the control device 61 communicated through the conduit 7 7; since tlieopen? ing 1? associated with the control? device 61 is on thelow-pressure or down-stream side of the valve 26s The compensator 45 is: con

trolled by the first fluidpressurescom-municatedl throughthe conduits- 7 and? 76; as both pressures side of the: valve 28:.

Either of these. fluid pressures ,ThE -OPGI'BJtiOH of-the above-described mcchail-ism! is as follows;

Assume, first, a change in load on the turbine withthe extraction pressures remaining constant. providing constant opposing fluid pressures thegovernors; If the load is decreased, thespeed' increases, and the increased impeller pressure acts on the piston 34 of each governor tomove the associated valve in closing direction The flow to each o-ii the sections 19,21, and 22 is decreased by alike a mount,the-difference in flow between the"high-prcss-ure section and the intermechate pressuresectlon 21-,wh1ch is suppliedto the opening l5,,rema1n-1-ng constant and the d-iiferen'ce betweenthe flow through the-interi mediate-pressuresection Ql-and the low-pressure SGClZl QITQQJVhiClIlS sir olied to thee I en- I The resultingdecreased in'ipellcr pressure permits the spring 37' of each governor to move the piston: 34: in vwl-We-opening-direction. An increase in flow throughout all the sections of the-turbine is provided to carry the increased load, the: flow through each openinga'gain remaining thesame.

Assume; now, a' condition of constant demand-forextracted fluid at the lower extraction pressure, and an increase in demand for. extracted fluid at, the higher extraction pressure at the'openinglh', theload remaining constant. The increase demand for the higher-- pressure extracted fluid is accompaniedbya decrease in pressure thereof, which decrease: pressure is communicated through the conduit 65- to the diaphragm 64. The lever is rocked in clockwise direction by the spring 60* an amount determined by the scaleoii the spring, and the scaleeflect of the

springs

68 and 69. The compression of the spring 68 is decreased, while the compressioni ofthe spring 69 is increased, resulting in decreased first fluid pressure in the corn duit 7 3 and. increased second: fluidpressure inzthe conduit 74:: 1

The. decrease in first fluid pressure of the control device- 59 reduces the closing force on: the valves 4:7 and 418 of the

compensators

44 and 45 so that said valves effect decrease inthe: opposing fluid" pressures in. the governors 31 and The impeller pressure in the governors 3 1 and 32 now preponderates, and the. pistons 34: thereot movethe by-pass valves 26 in closing direction.

In response to the increased second fluid pressure provided by the control device 59, thecompensator, 43 provides increased opposing pressure in the governor 29, and the latterthereupon moves the admission valve 14' in opening direction;

The additional motive fluid held back by the valve 28 andthe additional motive fluid admitted by the admission valve 14 supplies the additional: high-pressure extracted fluid to the opening 15.- The decrease in power development in the intermediate pressure 21* p and the low-pressure section 22, is balanced "2 19 is decreased, and the flow through the intcrmediate-pressure section 21 and the'lowpressure section 22 is increased.

Assume, now, an increase in demand for low-pressure extracted fluid, with the demand for high-pressure extracted fluid and the load on the turbine remaining constant. The pressure of the fluid flowing through the opening 17 and the conduit 18 decreases,

which decrease is communicated through the conduit 65 to the diaphragm 64. The lever (32' is rocked in clockwise direction by the spring a corresponding amount providing decreased first fluid pressure in the conduit 76 and increased second fluid pressure in 'the conduit 7 7 The

compensators

43 and 44 act in response to the increase in second flu1d pressure to provide increased opposed fluid pressures in the

governors

29 and 31, and the latter eifect increased opening of the admission valve 14 'rection.

and the by-pass valve 26. The compensator 45 responds to the decreased firstfluldpressure by providing'decreased opposing fluld pressure in the governor 32, and the latter eflects closing movement of the bypass valve 28. V

The increased openings of the

valves

14 and 26 are such as to provide equal increases in flow through the high-pressure section 19 and the intermediate-pressure section 21.

This increased flow, together with the additional steam held back by the valve 28, supplies the increased demand for low pressure extracted fluid. Said increase in flow is so related to the steam held back by the valve 28 that the decrease in power development by the low-pressure section 22 is balanced by the increase in power development by the highpressure section 19 and the intermediatepressure section 21. V v

Upon decrease in demand for low-pressure extracted fluid, the pressure thereof increases and the parts each move in the'opposite di- The flow through the high-pressure section 19 and the intermediate-pressure section 21 is decreased, and the flow through the low-pressure section 22 is increased. The decrease in power development by the first two sections is balanced byjthe' increase in ,

diaphragm

64 or 64.

power development by the low-pressure section 22.

The proper proportion of valve movement of the various valves in response to a change in pressure at one of the openings is obtained by adjusting the position of each knife edge fulcrum 55 to provide the proper lever arm ratios of the lever 54 which contacts therewith. It is to be understood that suitable well known forms of adjustment may be used throughout the control mechanism.

It will be apparent that the pressure within the region enclosed by an extraction pressure stage and the opening and extraction conduit communicatingtherewith is substantially the same, or at least varies similarly with changes in demand, andthat the pressure for controlling the associated pressureresponsive diaphragm may be taken at any point within that region.

Either or both of the

openings

15 or 17 may be utilized to admit motive fluid of suitable pressure to the corresponding stages instead of extracting fluid therefrom. The operation of the parts is exactly the same, although possibly the pressure setting. might be slightly changed by varying the vertical position of the fulcrum 53 or 53.

Assuming admission of motive fluid of suitable pressure to either of the openings, an increase .in supply is accomplished by anincrease in pressure imposed on the corresponding The operation is the same as above described, the valves on the low-pressure side ofthe opening being moved in opening direction in order to utilize the additional supply of relatively low-pressure :motive fluid, and the valves on the high-pressure side of the opening being moved in 010s ing direction to compensate for the increased power development on the low-pressure side of the opening. A decrease in supply is accomplished by an increase of pressure, and

' the valves on the low-presure side .move in closing direction while the valves on the high-pressure side move in opening direction.

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 specifically set forth in the appended claims.

What I claim is 1. The combination with a multi-stage prime mover having openings communicating with a plurality of pressure stages there in, and admission valve for controlling the admission of motive fluid to the prime mover and a valve controlling the flow at each opening, of a control mechanism comprising a device associated with each opening and providing a fluid pressure varying in one direction and another fluid pressure varying in the opposite direction in response to change in pressure at the associated opening, and a means for controlling each valve in response to one of the fluid pressures of each of said devices.

2. The combination with a multi-stage prime mover having openings communicating with a plurality of pressure stages therein, an admission valve for controlling the admission of motive fluid to the prime mover and a valve controlling the flow at each open ing, of a control mechanism comprising a device associated with each opening and providing a fluid pressure varying in one direction and a second fluid pressure varying in the opposite direction in response to change in pressure at the associated opening, means providing a third fluid pressure varying as a function of the speed of the prime mover, and means for controlling each valve in response to the third fluid pressure and one of the fluid pressures of each of said devices.

3. The combination with a multi-stage elastic fluid prime mover having openings communicating with a plurality of pressure intermediate stages therein, an admission valve and a valve controlling the flow at each opening, of a control mechanism comprising a device associated with each opening and providing a fluid pressure varying in one direction and a second fluid pressure varying in the opposite direction in response to change in pressure at the opening, means providing a third fluid pressure varying in response to change in speed of the prime mover, and means for controlling each valve comprising means providing a fourth fluid pressure varying in response to one of the fluid pressures of each of said devices and a governor responsive to the fourth fluid pressure and to the third fluid pressure for controlling the valve.

4. The combination with a multi-stage elastic fluid prime mover having openings communicating with a plurality of pressure stages therein, an admission valve for controlling the admission of motive fluid to the prime mover and a valve controlling the flow at each opening, of a control mechanism comprising a device associated with each. opening and providing a first fluid pressure varying in a given direction and a second fluid pressure varying in the opposite direction in response to change in a given direction in pressure at the opening, and means for controlling each valve in response to the first fluid pressure of each device at an opening on the high pressure side of the valve and to the second fluid pressure of each device at an opening on the low pressure side of the valve.

5. The combination with a multi-stage elastic fluid prime mover having openings communicating with a plurality of pressure stages therein, an admission valve and a valve controlling the flow at each opening, of

a control mechanism comprising a device associated with each opening and providing a first fluid pressure varying in a given direction and a second fluid pressure varying in the opposite direction in response to change in a given direction in the pressure at the opening, means providing a third fluid pressure varying in response to change in speed of the prime mover, and means for controlling each valve comprising means providing a fourth fluid pressure varying in response to the first fluid pressure of each device at an opening on the high pressure side of the valve and to the second fluid pressure of each device at an opening on the low pressure side of the valve and a governor responsive to the fourth fluid pressure and to the third fluid pressure for controlling the valve.

In testimony whereof, I have hereunto subscribed my name this 3rd day of July, 1930.

CLARENCE B. CAMPBELL.