US2523039A - Dual pressure-responsive safety device for prime movers - Google Patents

Description

lhventors Harry A. Mayor; Dana M. B urgess,

Then" Abt ovn ey i JFFE? H. A. MAYOR ET AL DUAL PRESSURE-RESPONSIVE SAFETY DEVICE FOR PRIME MOVERS Filed April 26. 1949 Sept. 19, 1950 Patented S ept. 19 1950 it aszepeea.

PREssURE-mzsfon'swE SAFETY i onv-ren FOR; PRIME MOVERS Harry-A ..,Mayor, Eitchburg, andzDa-narM. Burgess;

, .Leomlnster, Mass. assignors. to. GeneralEleQtticn @pmpany, acor poration of New York Application April 26, 1949; Serial Nb; 89,646

This invention relates j-tosa .pressureeresponsive;

safety device for shutting-down or otherwise modifying theoperation. ot a .prime mover: in accordance with two pressure: conditions appur'-- tenant to the operation anther-machine, oneof which pressures i notltonexce'eda preselected. maximum value, the" other ot- 1Which. isenotl to drop below a preselected minimum.value.,.- More spe-- cifically, the invention is applicable. to .a, dual pressure-responsive safety device I01: the govere I pressure limiting function is also sometimesd'e sired. in order to prevent excessive heatingrof the turbine. which may occur with abnormally high. backpressuresi Likewise; where oil for lubri'oat ing the turbine bearings anii'aotuating a hydrau lic' governor is derived frorn' a'pump driven from the turbine shaft, or from some other suitable source',it may bedesired' to; provide a safety devicewhich will act to shut down the" turbine in the eventthe oil pressure falTsfbelow a"presel'e'cted"- safe'value'. Heretofore thesesafetyfdevi'ces have 4 Claims. (01. co 1) I Fig. illustrates: anstearn.

bine incorporating .a .dual .pressureeresponsive safety. device in accordance. with the. invention; Fig.2. is an ,enlargedvview. of the. safety device partly inrsectionr; Figs-.1 3),, 4. and. E Qillustrate the.

safety mechanismim various conditions. of opera-; tion; and: Fi ids... side view, levation, of the satety me hanism correspondin to he f nt view. s wn. F 2c .A A L l .Re errine art cularly to; r 1, the: s eam. tu in shown, n ener l outli o m n: cludes hydraulic governing mechanism indicated. en r y a Lan a aneed: to a a am at s mot. h wn in. the nlet cas 2 hence the motive. fluid flows into the main turbine oa sing 3 containing the nozzles and turbine rotor (not shown) thence into the exhaust casing indicated generallyat 4 and having the flanged out-.

let 5. The. turbine rotor 6, issupported in suitable able, gears (not shown) from the turbine ro'tori been manufacturedas separateicomponents and" mounted on the turbine in suitable relation the governing mechanism? An object of the present"invention isfto providean improved integral safety" mechanism "moor-'- porati'ng both high exhaust pressure and low oil pressure responsive meansacting-on a singleoutput shaft connected to the turbine 'steam admis-- sion' or trip throttle valves; l

'Another objectof the invention-is to provi'de a nun pressure-responsive safety mechanism of the type described so arranged that during-normal operation either or thatwol'satety-devices may act to shut. down themturbine:regardless oi -the conditionrofrrtheiother devicez Still another object is to provide a very simple" compact. dualln pressureeresponsive; wmechanism which can bemanufactured, testeduandlinstal'led.

as a. complete. integral; unit.-

Other objects andixadvantages will apparent. Iromsthe following. description takenvimiconnecetion with the: accompanying;.drawingpin...which;i

hearings. in thecasings, T,, a 'the. details of which are not. important" to understanding. of the present invention. It needjonly be noted that oilf for lubricatihg tfleef bearings is suppli ed' by branch conduits 9; IOI'fro'm a header l'l' connected to a suitable pump 1'2 located in the oil reservoir 13- and arranged to be driven by a shaft'andsuit shaft." While it may be of any suitable type, the pump I2 is convenientlyofthe simple positive displacement gear type, "Ofil iromj the reservoir l3"is' admitted to the pump l"2 through an inlet conduit M; Since the'pump is directly geared to the turbine rotor shaftitvtill' be apparent that thedischarge' pressure ofthe pumpbears a d'efi nite relationto rotor-shaft"speed. "It will-heap preciated by those-skilled in the art that, in addition to supplyinglubricant for the bearings; oil from pump 12 may be supplied tothe hydraulic governing mechanism l serving" as the motive liquid therein. l

The pressure-responsive safety mechanismwhich constitutes=-the special?) subject'- matter of the present invention is indicatedin 1*genorally at I-5,- l )ei-ng: s'l 1own -asmounted directly on the sicle of"thehydrau-l ic governing mechanism 1 The precise nature'andi mechanieal details of the turbine governing mechanism "I are not necessary in understandingathe present invention. 1 Typical governing systemsiincluding arotatable trip shaft. analogous tosha-fit lie aredisclosed in U. S. Patent 2,183,181; issued January- 23, 1940,.-on an application or P. Know/item also 2 021848; issued January 14', 19.36, on; an application of D. E. .Warner,, and 229%74533: issued September 1942, on an applicatiomofiSoNlEIedman. It need only be noted here that a trip shaft l6 (Figs. 2 and 6) projects into the governing mechanism I and is provided with suitable latch surfaces l6a formed by machining diametrically opposed fiat surfaces on the rod it. As will be seen hereinafter, this trip shaft has a normal running position and an emergency tripped position, rotation of the shaft from one to the other causing the latch portion Ilia to trip the governor l to the inoperative position, or perform some other function to modify the operation of the governing system.

As will also be seen from Figs. 2 and 6, the trip shaft I6 is journaled in a plate I! which serves as the main frame member supporting the various components of the safety device on the casing of the governing mechanism I. It will of course be understood that the frame plate I! is secured by suitable threaded fastenings 18 to the governor housing. Carried on trip shaft It at the exterior side of frame plate I1. is a first lever member 19 arranged to oscillate through a limited arc, the extreme clockwise position being determined by a stop pin 28 fixed to the frame plate ll. A suitable coil spring 2| is connected to a fixed pin 2 la at one end, the other end being connected to a transverse pin 22 extending entirely through the lever 19. Spring 2| is arranged to bias the lever l9 lightly upward in the counterclockwise direction about trip shaft [6. It is to be noted that this spring is just sufficiently strong to counterbalance the weight of lever I9 and overcome the friction in the respective parts so that lever l9 will return to its counterclockwise position when permitted to do so by the other components of the system.

Secured to the depending lower portion of frame plate I! is a casing 23 containing two pressure- responsive pistons 24, 25. Piston 24 is carried on a rod 26 slidably projecting through a bushing formed by a cylindrical nut 21 threadedly received in an opening in the top of casing 23. Similarly piston 25 is carried on rod 28 slidably projecting through a cylindrical bushing nut 29. The pistons are strongly biased to their lowermost positions by a pair of comparatively heavy coil springs 38, 3| the upper ends of which engage the under surfaces of the respective nuts 21, 29. It will be obvious from consideration of Fig. 2 that the compressive'force exerted by the springs 30, 3| may be readily adjusted by applying a suitable spanner wrench and turning the nuts 21, 29 so as to move'them longitudinally in the threaded recesses in the casing top member 2301.. As will be seen more particularly hereinafter, the uppermost position of the pistons is determined by engagement with the top casing member 23a. The lowermost position of piston 24 is defined by a cylindrical abutment or stop tube 32, which may be conveniently formed integral with a fitting 33 defining a nipple for receiving a threaded pipe coupling at 33a and a nut 33b for securing As will be apparent from Fig. 1, the steam pressure obtaining in the exhaust casin 4 is transmitted by way of pressure transmitting pipe 3'! to the fitting 33 so that the exhaust casing pressure is communicated through the bore of fitting 33 and a plurality of radial holes 32a to the chamber defined within bellows 34 and the bottom surface of piston 24. Likewise, the pressure of the oil discharged from pump I2 is communicated by a pressure line 38 connected to the fitting 35 so that the bellows 35 is responsive to oil pump discharge pressure.

The pressure-responsive pistons are connected to the trip shaft [8 by a special linkage, as follows. Piston rod 26 is connected by a pivot 39 to a link 40 having at its other end an elongated slot 4 I in which slides a pivot pin 42 fixed to the lefthand end of the trip shaft l9. Similarly, piston rod 28 is pivoted at 43 to a link 44 having a slot 45 in which slides the exterior end of the pin 22 fixed in the lever IS.

A second latch lever 46 is supported on the frame plate I! by means of a fixed fulcrum pin 41. At its lefthand end, latch lever 46 is connected by a pin and slot arrangement to the link 48, and at its righthand end it carries a springbiased latch or detent 48. As may be seen in Fig. 6, detent 48 pivots in a slot in the end of latch lever 46 on a stud 49 fixed to the latch lever 46. A'coil sprin 490. disposed around stud 49 has a remote end engaging a flange on the end of stud 49, the other end engaging the latch 48 so as to bias it in the clockwise direction as viewed in Fig. 2. The extreme clockwise position of detent 48 relative to latch lever 45 is determined by a small laterally projecting ear 48a adapted to engage adjacent portions of the lever 48. The extreme tip of detent 48 is shaped to engage a cooperating notch 50 formed in the lower edge of the trip lever I9.

The method of operation of this improved safety device may be seen by reference to Figs. 2-5.

' Fig. 2 represents the shut-down or inoperative condition of the powerplant, with both pressure- responsive pistons 24, 25 in their lowermost positions. It will be seen that the piston 24 is engaging the stop tube 32, while the lowermost position of piston 25 is determined by the engagement of the slotted link 44 with the pin 22, the

position of Iwhich is determined by the stop pin 28 engaging the lever I9. In this connection it may be noted that the comparatively stiff coil spring 3| overcomes the comparatively lighter resistance of coil spring 2|, so that piston 25 is strongly biased to its lowermost position as determined by stop pin 20 whenever the oil pressure supplied to bellows 35 falls below the preselected value. It will be seen from Fig. 2 that, in the inactive condition, the pivot pins 4-2 and 22 are both at the extreme upper portions of the respective slots 4|, 45, and that the detent 48 is in the disengaged position relative to lever l9 and in its extreme clockwise position relative to lever 46. When shut down, there is of course no fluid pressure in either of the bellows 34, 35, atmospheric pressure prevailing throughout the system.

Suppose now it is desired to start the turbine. It is first necessary to put the turbine governor l in condition to permit operation by manually lifting the trip lever l9 to the counter-clockwise position shown in Fig. 3. It will be observed that ,the'extreme counterclockwise position of lever A ['9 is determined by the engagementof pivot pin fl with the lower end of" slot H.- R will be seen in Fig. 3 that pin 4% is almost but'notquite-atthe-bottom" of slot. Itwill also; be observed that this counterclockwise movement of trip lever l-9 causes the oil pressure piston 25120 be pulledalm'ost, but not quite, to the extreme uppermost limit. of its range of movement. Nowwith-thetrip lever I 9" manually held in its uppermos-t position, the detent 48 is manually rotated counterclockwise against the bias of its coil. spring 49a so that the tip of the detent engages the no'tch 50 in lever l9. It will be observed that the sl i-ght-clockwise rotation of trip lever [9 as the end of detent 48 drops into. the notch 50 accounts'fortheslight clearance between pivot pin 4! andthebottom end of slotM- in link 4!]. This slightclearanee isi significant for a reason noted hereinafter. With detent" 48 engaging the trip lever I9, the latter is held in: the position corresponding to the normal running condition of thegovernor l3, against the strong downward bias of 'coil spring 3h associated with theoil pressure piston '25. The-governing mechanism lis now-in such condition that steam can be supplied to the turbinerotor. As therotor-speed increases, inaccordance with the operation of the steam inlet valves' controlled by the hydraulic governor I, the rotational speed of the. oilpump I2 also increases, warn the result that oil pressure builds upin thebellows 35 Eventually, theoiLpressurebecomes:

sufiici'ent to move piston. 25. upwardly until it engages the underside of easing 130p member 23a; as shown in Fig. 4. i This small additional increment-of upwardmovement, beyond the position ofpiston 25"illustrated in Fig. 3, permits the light biasing spring 2 torotate lever l9 slightly councounterclockwise"position, the back-pressure pis:

ton- 2'4 in its lowermost position and the oil pressurepiston 25 floating in its uppermost position; being supported by the oil pressure in-bel Assumenow that for some reason the steam pressure'in the exhaust casing 4 should increase to--a= dangerously high level, for instance, a pressure on the order of lbs; per squareinch gage. This pressure, communicated to bellows 34' throughv the pressure sensing" conduit causes the back pressure iston to rise against the biasof sprin'g 3lll Since in the normal running condition' represented by- Fig. 4- the pivot pin 42 was at; the; bottom of slot 41, this upward movement of" piston zd immediately eifects clockwise rotation of 'the trip lever l9. As noted above, rotation of lever [9 to theextreme clockwiseposition against stop pin causes the latch particns' Hid of the trip-shaft l6 to effect shuttingdownrz f the turbine'. 0f course, the turbine trip mechanism maybe so arranged that rotation of the lever I9 allthe' way to'the stop pin 20 may noubeneededi Thedegree of movement of trip H lever HI --requiredto shut downtheturbinefwill" of-coursea depend upon the" nature and-"arrange--:

It on the other. hand during. operation the pressure shouldiaillfor some reason, as. for ma. stance throughifailiire of the pump Her-breakage of. one of the; hydraulic. lines the. decrease. in.

oil pressure. below the preselected critical value. will permit; the) oil pressurepiston. 25 to, descend from the position. shown. in Fig. 4-. This, will of course cause. clockwise rotation of the triplever m sc that the governor l is. again disabled and. theturbineshutdown.

. I-twill beobserved: from. the above. that regard.- less at whether theturbine: shut down by high.

back pressure or low oiL pressure, the resulting. decrease in oil-pressure acting. onthe piston 25 when the: machine is-shutdownxwill. insure that.

. the linkage will be restored to the inactive conditionrepresented in-Fig. 2e ltwill alsolbe noted that the arrangementofithe slots in the linksitfl 44 is such that, when the running condition.

either of the -pressure-responsi ve pistons is completely freeatomove the trip-lever 1-9 in the clockwise direction: tc shutdowmthe turbine? regardless of the position: of the other piston.- Thusv each ofthe safety: devicesincorporated in the: present invention isfree duringnormah operation" to performits function completely independent.

of the other safety d'evicez Attila-same time thex. present arrangement. provides a very neat. com

pact combination. occupying. a .niininium: of: space,

and having: a; minimumnumber of partsireo uirect to correlate theoperation: of: the: two: safety de;-=

vices with each: other and the. governor tripshattl.

It will also be seen thatthe. critical pressures for which the devices arezset may. be, readily: ad-

justed by means: of the. nuts 21., 29 by varying;

causes the detent 48. to disengage: the notch. 50.

in lever 1'9, so that-detent 481 snaps to'its clockwiseposition showniin Fig. l leaving: the backpressure piston Zifree-to move trip-lever l 9 clockwise to shutdown'thesturbine =as1described above It will. thus beseenthatthisimproved safety device combines in one: simple mechanism two pressure-responsive:devices-one for insuring that.

a first pressure condition in the powerplant does not rise above-a preselected value, while the-other insures that asecond pressure. conditionwill not fall below another preselected critical value; bothpistons being connected by a'---specially arranged common linkage system to the trip lever of the .It willbe obvious from the above description that many modifications might be made in the nature of the pressure-responsive devices used and the mechanical details of the linkage interconnecting them with the turbine trip lever, and it is desired to cover by the appended claims all such changes and modifications as fall within the true spirit and scope of the invention.

- What we claim as new and desire to secure by Letters Patent of the United States is:

1. In a dual pressure-responsive control device for a machine in which a first fluid pressure condition is not to exceed a first preselected maximum value and a second fluid pressure condition is not to drop below a second preselected minimum value, the combination of a trip lever member pivotally supported at an intermediate point for oscillation through a limited are from a nor.- mal running. position to an emergency tripped position, spring means lightly biasing the trip lever to one extreme position representing the normal running condition of the machine, first rluid pressure motor means including a first actuating member with, means biasing it to one extreme position and walls defining an expansible chamber adapted to move said actuating member against its biasing means in accordance with values of the first pressure condition exceeding said preselected maximum value, second fluid pressure motor means including a second actuating member with means strongly biasing it to an extreme position corresponding to an emergency tripped position of the lever, and walls defining an expansible chamber adapted to hold said second actuating member in normal running position against its biasing means in accordance with the second fluid pressure condition, a first lost motion connection between the first actuating member and the trip lever adapted to effect rotation of the trip lever to the emergency position upon increase of the first pressure condition above said preselected value, a second lost motion connection between the second actuating member and I the trip lever adapted to effect rotation of the trip lever to the emergency position upon decrease of the second pressure condition below said second preselected value, a latch lever ful crumed at an intermediate point and pivotally connected at one end to said first actuating member, a detent pivoted to the other end of the latch lever and having a portion adapted to hold the trip lever and second actuating member in normal running position when the trip lever is manually moved to said position and the detent manu ally caused to engage the lever, means biasing the detent out of engagement with the trip lever when the second fluid pressure condition rises above said second preselected value, each of said lost motion connections being adapted to permit free movement of the trip lever relative to the 8, for apparatus in which a first fluid pressure con-' dition is not to exceed a first preselected maximum value and a second fluid pressure condition is not to drop below a second preselected minimum value during normal operation, the combination of first and second fluid pressure-re sponsive means each, having a member adapted to reciprocate in transversely spaced substantially parallel paths in accordance with changes in said respective pressure conditions, stop means positively limiting the movement of both members in the increase pressure direction, stop means positively limiting the movement of the first pressure responsive member in the decrease pressure direction, a trip lever member pivotally supported on a fixed fulcrum located between said paths and adapted to oscillate through a limited are from a normal operating position to an emergency tripped position, first and second lost motion means connecting the pressure responsive members tothe trip lever at opposite sides of said fulcrum, means lightly biasing the trip lever to the normal running position, means strongly biasing the respective pressure-responassociated actuating member in the event the sive members to their minimum pressure positions, and a latch lever member pivotally supported on a fixed fulcrum located between the pressure responsive members, one end of the latch lever being connected to the first pressure responsive member and the other end carrying a pivoted detent adapted to engage the trip lever to hold it latched in the normal operating position with the second pressure responsive memher in substantially the maximum pressure position when the second pressure condition is below said preselected minimum value, and means biasing said detent to disengaged position relative to the trip lever, whereby either movement of the first pressure responsive member in the increase pressure direction or slight movement of the second pressure responsive member from the latched position in the increase pressure direction effects disengagement of said detent from the trip lever thereby rendering it free to move to the emergency tripped position in accordance with movement of the first pressure responsive member in the increase pressure direction or of the second pressure responsive member in the decrease pressure direction.

3. In a dual pressure-responsive safety device exhaust casing pressure, second fiuid pressure responsive means having a member adapted to reciprocate in a path parallel to and transversely spaced from the path of movement of said first pressure-responsive member in accordance with changes in oil supply pressure, stop means positively limiting the movement of both pressure responsive members in the increase pressure direction, stop means positively limiting the movement of the back pressure-responsive member in the decrease pressure direction, a trip lever adapted to modify the action of the turbine governor and pivotally supported on a fixed fulcrum located between the paths of movement of said pressure responsivemembers and adapted to oscillate through a limited are from a normal operating position to an emergency tripped po-' sition, first lost motion means connecting the back pressure responsive member to one end of the trip lever, second lost motion means connecting the oil pressure responsive member to the trip lever at the opposite side of said fixed fulcrum, means lightly biasing the trip lever to the normal running position, means strongly biasing the pressure-responsive members to their respective minimum pressure positions, and a latch lever member pivotally supported on a fixed fulcrum located between the pressure-responsive members, means pivotally connecting one end of said latch lever to said first pressure-responsive member, a detent pivotally carried on the other end of the latch lever and adapted to engage the trip lever to hold it latched in the normal operating position during the starting cycle when oil pressure is below the preselected minimum value, and means biasing said detent to disengaged position relative to the trip lever, whereby either movement of the backpressure responsive member from its iminimum pressure stop or movement of the oil pressure responsive member to its'maximum pressure position effects disengagement of the detent from the trip lever thereby rendering the latter free to move to the emergency position in' accordance with either an increase in turbine back pressure above the preselected maximum value or a decrease in turbine tioned in a linear path substantially parallel to ,thatof the first member in accordance with turbine oil pressure, stop means positively limiting the movement of both pressure responsive members in the maximum pressure direction, stop means positively limiting the movement of the back pressure responsive member in the minimum pressure direction, a pivoted trip lever adapted to oscillate through a limited are from a normal running position to an emergency tripped posiposition, first means lightly biasing the trip lever rying at the other end a pivoted detent adapted to hold the trip lever latched in the normal operating position with the oil pressure-responsive member in substantially the maximum pressure position when oil pressure is below the preselected minimum value, means biasing said detent to disengaged position relative to the trip lever, the

second pressure-responsive connecting means between the back pressure-responsive member and the trip lever being adapted to permit slight relative movement therebetween when the oil pressure-responsive member moves from the latched position in the increase pressure direction, whereby said first biasing means effects relative movement between said trip lever and latch lever to disengage the detent and render the trip lever free to move to the emergency tripped position in accordance with either movement of the back pressure-responsive member in the increase pressure direction or movement of the oil pressure-responsive member in the decrease pressure direction;

' HARRY A. fMEAYOR DANA M. BURGESS,

No references cited.

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