US2388282A

US2388282A - Centrifugal type speed governing mechanism

Info

Publication number: US2388282A
Application number: US431604A
Authority: US
Inventors: Harold M Otto
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1942-02-19
Filing date: 1942-02-19
Publication date: 1945-11-06
Anticipated expiration: 1962-11-06

Description

" No v. 6, 1945. H. M. OTTO l 2,388,282

CENTRIFUGAL TYPE SPEED GOVERNING MECHANISM WM i' /3 f4 f6.

hve'tor:

2;/ f\ Harold M. CD1-,+505y --H-b y HIS Attorney.

`perienced in case of Patented Nov. 6, 1945 CENTRIFUGAL TYPE srEEDG ,vERNINGm l MEoHANrsM g Harold M. Otto, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application February 19, 1942, seri-a1 No. 481,604f 7 claims. (el. 264-17) The present invention relates to centrifugal type speed governing mechanisms for controlling or actuating a machine element in response to speed changes or upon the occurrence of certain speed conditions. The invention is of particular significance in connection with centrifugal type emergency governing mechanisms although it is not necessarily limited thereto. Such mechanisms are used, for example, for shutting down prime movers such as elastic fluid turbines as their speed rises `a certain percentage above the norma1 operating speed. In elastic fluid turbine arrangements it is in general customary to provide an emergency speed governor for closing the turbine stop and control valves when the speed rises about 10% above normal speed. Emergency governors in such arrangements constitute the final safety device of the turbine and for this reason should be in perfect operating condition. As it rarely occurs that an emergency governor has to operate to effect shutdownlof a turbine, it is customary to test the governor at frequent intervals, particularly during starting and shutdown'of the turbine, to assure that it is in safe operating condition. It is not desirable to carry out the testing or checking of the governor at the actual emergency speed for which the governor is designed and for this reason arrangements have been devised whereby the governor may be tested at a speed below the emer- Y gency speed. One such arrangement is disclosed in the patent to W. P. Dryer, No. 1,666,490, issued April 17, 1928, and assigned to the same assignee as the present application. According to these arrangements the mass of the flyweight is increased by the supply of liquid such as oil to a chamber formed by the ilyweight. Thus a governing mechanism designed normally to act on an element at a speed of 2000 R. P. M. may be caused to actuate such element at a lower speed,`

say 1000 R. P. M., by the supply of oil to a chamber formed in its flyweight. Diliiculties are exgoverning mechanisms designed to operate at'higher speeds of the order of 5000 R. P. M. and more when it is desired to test such mechanisms at much lower speeds of the order of 1000 R. P. M. The methods and arrangements heretofore used would necessitate the provision of ilyweights forming very large chambers to permit the supply of an amount of liquid suicient to cause actuation of themechanism at much lower speed. I f

One object of my invention is to provide an improved construction and arrangement of governing mechanisms; which may be used as emer- .port or cylinder I3 gency governors and readily tested at a compara` tively small fraction of their normal operating` speedby a relatively small change of the mass of one of their flyweights.

'Another object of my invention is to provide a governi-ng mechanism with an improved and readily variable governor characteristic.

These and other objects are accomplished' in accordance with my invention by the provision of a governing mechanism which includes at least two yweights arranged to produce centrifugal forces opposing each other and producing together a differential or resultant actuating force for controlling or actuating a machine element. Each of the yweights is biased by a separate spring against its centrifugal force. By properly choosing the spring characteristics, the masses of the flyweights and their normal radii of rotation, a governing mechanism may be produced in which the ratio of the centrifugal forces of the two fiyweights varies in a desired manner with variations in speed.

For a better understanding of what I believe to be novel and my invention, attention is directed to the following description and the claims appended thereto in connection with the accompanying drawing.

In the drawing Fig. 1 illustrates a governing mechanism embodying my invention; and Fig. 2 is a section along line 2-2 of Fig. 1.

The arrangement illustrated in the drawing comprises a shaft I0 which may form part of an elastic fluid turbine and an emergency governing mechanism or unit Ilfsecured to the end of the shaft I0. The mechanism is arranged in cooperative relation with an element, in the present instance a trip finger I2, to cause shutting of turbine valves, not shown, as the turbine speed rises a certain percentage above tlie normal operating speed. The governor unit includes a supwhich has one end rigidly fastened to the shaft VIll and another end to which a .cover I4 With'a central opening' I5 is secured. The cylindrical support I3 broadly constitutes a hollow extension of the shaft I0. Diametrically opposite portions of the cylindrical support I3 haveopenings I6, I1 forming seats for plugs or bushings I8 and I9 respectively. A governor spindle 20 vprojects through the plugs I8, I9 and has end portions located outside the support and connected to an emergency ring or main flyweight 2 I. The spindle 20 has sliding t in the bushing I8 and is rigidly secured to the bushing I9, which latter has sliding fit in the support I3. The main flyweight 2l comprises axially spaced rings 22 and 23. The lower halves of the rings are united by an outer wall 24 which has end portions 25 turned inward and suitably secured to the adjacent surfaces of the rings 22, 23. The central portion of the outer wall 24 forms a boss 26 which has screw-thread connection with the lower threaded, end of the spindle 2.0:. The outer wall.

24 and thev side; walls. form two .cups or chambers.

21, 28 with

discharge openings

29 and 30 respectively. During rotation liquid may be conducted' into the

chambers

21, 28 by avalved liquidsupply conduit 3l through axial' openings` 32 with radial discharge ports 33 in the cylindrical support I3.

Upper portions of the amallyspaceds rings 23 are united by a spacer or plug 34 with a central bore 35. The upper end: ofthe spindle projects into the bore 35 and has a slot36 looselyV Cil .whereas the auxiliary or second yweight 44 tending. to move upward is biased downward by il the.V spring 46; Thus, the forces of the two yweights are in opposition and the resultant of .theitwmforces is;.the;.di1erential thereof. This dilerential is a..function of the masses of the ilyweights; the radius at which they rotate, the

`characteristicsorthe. springs opposing them and the speed. At lw speed the centrifugal force on The threaded portion 4L of the spindle has a diametrical slot 43 for accommodating the pin 42. indifferent positions of the ring. 40. Upon removal of the pin 42, the ring 4U. maybe turned one half. or vam-ultiple of one half turn and, thereafter. the pin. 4.2 can be reinserted into the slot. 43.'. The mechanism. so far described. is typical f or arrangements heretofore used. During operation the spindle 2i); withthe flyweight'2l is normally heldin the position. shown` in the drawing by action. of the. spring 3&- counteracting. the Vcentrifugal force on the flyweight. If vthe speed rises beyondvnormal. operating speed the yweight 2| is gradually forced outward, that is, downward whenviewed in the drawing, against'the biasing force; of the-governor spring 38; At emergency speed, which. may be*` 10% above-:normal operating; sp, eed, the.r main; flyweight engages-the trip finger l2 which in turn causes.- through. known mecha-nisms, notv showny the turbine valves Ato close.. The mechanismrmay-he tested at. lower speeds by supplying liquid; froms the conduitJ 3.1 to the chambers-215,28 ofZ the. main flyweight.. VDuring testing-the increase in. mass ofr the mainflyweight caused bvthesupply of liquid to the. chambers f, 2.8 effects tripping or operation of the. mechanisrrr atg alowerspeed The-liquid isdischarged from the; c l'lambersT 2.7,. 2 8. through the aforementionedropenines: 29..` which asindicatedk in the drawing; are; substantially smaller than the supply- Openings or.A portsl 33.

lf: such mechanism were designed. for a normal operating. speed of- 5000 R. E. M. or higher thechambers 21?,A 2.8` would have to be made, of considerable size to permit testing` of the mechamism-ata: low speede of; ,say 1`000.R. P. M.

In; accordance withmy invention as indicated above-, I provide; means permitting, suchvv governor whenused as an emergency governor to be tested at a. small fraction of. its normal operating speed. Thisgmeans in. the; embodiment shown in the drawinggineludesan auxiliary orV second lyweight comprising; a ring- -44=v surrounding thespindle 20 inside thev cylindrical suppDr-t I3 and -biasedtowards.` ai. shoulder; 45 formed` by;l theaforementionednut 4 bymeans ofa spring: 45; having a lower end engaging the ring 44 and an upper thelfrst flyweight is comparatively large and that on the second yweight is.. comparatively small. Thiais. direnot. o nl'yQto.v the fact that. the second iyweight` 44 hasa much smaller mass' than the first ilyweight, ZI'. b ut primarily `due to the fact that, the, second. flyweight 4'4" has. a. center of gravity. 4.1.-.' which at. low speed. isV located close to the center, of. rotation. moi4 the system while the-.first flyweight. 2J. has. a. comparatively great mass.' with a. center. of. gravityv 4,9v at a greater distance ory radius from. the, center of.. rotation.

The whole system. at. low speed has av center ofgravity 5,5 which` iny Fig.. 2 is located. below the center of` rotation. andnaturally above the. center of. gravityv 49. of theirstflyweightin the position shown. in the drawing.. As-.the second flyweight at. low, speed. produces ai comparatively smallforce. in.. opposition to. the greatericen.-

trif-ugalfforce, of therst flyweight it is possible tocauseactuation or tripping of: the mechanism atflowspeedlby the. supply of a comparatively small-amount-of.1iquid,tovthe chambers` 21, 28. Inother words, it is-. possible at-V low speed to overcome;l the opposing, forceoi'- the secondv fly- 33,; Withincreasing. speed; the second` flyweight is, moved. outward,. thatv is; upward. in. the drawing, until .f at a. certain-speed it reaches the position. indicatedaindash-dotted lines l in. Fig. 2. Its-center or grav-ity` 41; thenVv has-moved'. upwardl a considerable distance Yinto the position.4 5I.. Let us assume.- that-during.. this` movement of the Vsec.- ond.Y yweight. 44- the first Vflyweight 2|.- has-A remained; in;its` original; position tdue to the biasing effect of thefcomparatively-strong spring 38. rI'he center of, gravity-Emol theentire system. then mustv havemoved upward-into anew position. 52. With a furtherfincrease in speedy thefrcentrifugal force exertedeon` the, iirst flyweight 2|-, overcomes the; force of the spring;A 3.8.' togetherI witlr the -opposing; force.Y eff; the second-iiyweight. The main flyweighttogether with. the spindle is m'ovedfout.- ward, that is. downwardin.- thedrawing, to' engage. theelement I2.. Under.- this condition: the centenof. gravity lia-of.. the rst-iiyweightisfmoved outward.into.theposition.53.. Ifft-he normal operatingl speed of, the turbine. to f which the governor isattached is.500`0-R..l?. M.,l outwardmovement of the. main.. governor.. weight. and. trippingI of. the finger IZnay take. placeata speedof; say 5500 R. P. M.

If the turbine hasbeen .operating at normal the val'ved conduit 31' is opened andY oil or like liquid-is lsupplied to the chambersll, 28 to cause tripping. of themechanism;

Thus,; this mechanism may be tripped at a speed near itsl normal' operating speed by the supply of oil-to the

chambers

21, 28 and itmaY also` be tripped atal considerably lower speed of ample, at one fifth of the normal operating speed the centrifugal force exerted on the second flyweight may be equal to one fifth only of the centrifugal force exerted on the rst yweight, whereas at a speed equal'to three fths of the normal operating speed the centrifugal force created by the second flyweight is greater than three fifths of the centrifugal force created by the first flyweight.

The governor may be readily adjusted by changing the position of the nut lll!V on the spindle 20. If the nut 40 is turned downward on the spindle the initial compression of the spring 38 is increased and that of the spring 46 is simultaneously decreased, resulting in a higher tripping speed. The action of the governor may be further varied during'operation by changing the ratio of mass of the two flyweights. This is accomplished in the present instance by supplying liquid from the valved supply conduit 3l to the chambers or

cups

21, 28 of the main flyweight 2 I. This liquid supply means accordingly broadly constitutes a means for varying the mass of one of the yweights during operation. At certain high speeds the flyweights are stopped from further outward movement and thereby rendered inoperative by the cylindrical support I3. As the rst flyweight is forced outward its upper portion in the drawing, that is, the spacer 34, engages the adjacent wall of the cylindrical support which latter constitutes a stop limiting outward movement of the main iiyweight. Similarly, at a certain high speed the second yweight 44 engages a cylindrical projection or stop 55 forming an extension of the bushing I9 preventing further outward movement of the latter. In place of the rigid projection 55 flexible or yieldable means, such as an additional spring, may be provided which above a certain speed aids the spring i6 in biasing the second flyweight 44 against centrifugal force.

Having described the method of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

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

l. Centrifugal type speed governing mechanism comprising a support, a rst flyweight, means including a spring biasing the first flyweight towards the support, a second llyweight and a biasing spring engaging the second flyweight and arranged to counteract movement of the rst iiyweight during operation, the flyweights having centers of gravity located on opposite sides and at different radii from the center of rotation of the support, and means connected to the iiyweights and movable in response to changes of the differential centrifugal force of the iiyweights.

2. Centrifugal .type speed governing mechav nism comprising a? cylindrical support, a spindle slidably projecting `through diametrically oIJPOr. site openings in the support, a mainflyweight se. cured to an end of thespindle outside of thesupport, a biasing spring `surroundingthe spindle inside `'the support to oppose movement ofthe spindle by action of centrifugal force exerted on the main fiyweight, an. auxiliary iiyweight surrounding the spindle inside the support, and a spring engaging the spindle and the auxiliary flyweight opposing centrifugal force exerted on the auxiliary nyweight, the centers of gravity of the flyweights being located on opposite sides of the axis of rotation and the auxiliary `flyweight being arranged to oppose movement of the spindle by action of the main iiyweight in order to produce movement of the spindle in response to changes of the differential centrifugal force of the flyweights.

3. Centrifugal type speed governing mechanism comprising a cylindrical support having diametrically opposite openings, a spindle within the support having end portions projecting through the openings, a main flyweight connected to the spindle outside the support, a

spring surrounding the spindle inside the support to bias the main fiyweight against centrifugal force, an auxiliary flyweight engaging the spindle inside the support to oppose movement of the main flyweight, and a spring surrounding the spindle and engaging the auxiliary nyweight to bias the latter against centrifugal force.

4. Centrifugal type emergency speed governing mechanism comprising a cylindrical support having diametrically opposite openings, a spindle projecting through the openings and forming shoulders inside the support, a main iiyweight 40 forming a chamber being secured to an end portion of the spindle outside the support, spring means biasing the main flyweight towards the support and an auxiliary flyweight engaging the shoulder on the spindle inside the support and a spring surrounding the spindle and biasing the auxiliary flyweight against centrifugal force, the

center of gravity of the auxiliary yweight and the center of gravity of the main flyweight being located on opposite sides from the center of rotation and the centrifugal forces of the two flyweights opposing each other and the center of gravity of the auxiliary iiyweight being located at low speed considerably closer to the center of rotation than the center of gravity of the main yweight to permit testing of the governor by the supply of a comparatively small amount of liquid into said chambers at a speed considerably below the normal operating speed.

5. Centrifugal type speed governing mechanism comprising a rotatable support, means including first and second flyweights arranged on opposite sides of the center of the support and movable independently of and in opposition to each other, separate biasing spring means for the flyweights, stop means to limit movement of one of the yweights at a predetermined speed,

one of the flyweights forming a chamber, andk nism comprising means including a flyweight andY a spring opposing movement of the lyweight,

other means including a yweight independently movable of the rst flyweight and opposing move-