US1791249A

US1791249A - Governing mechanism

Info

Publication number: US1791249A
Application number: US381367A
Authority: US
Inventors: Anthony F Schwendner
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1929-07-26
Filing date: 1929-07-26
Publication date: 1931-02-03
Anticipated expiration: 1948-02-03

Description

Feb. 3, 1931.

WITNESS A. F. SCHWENDNER GOVERNING MECHANISM Filed July 26, 1929 Fla. 2..

INVENTOR A-Scr|wEN0uEm ATTORNEY Patented Feb. 3, I 1931 rr STATES VPATENT'I'OFFICE ANTHONY r. son'wnivnnnn, or ESSINGTON, PENNSYLVANIA, AssIGNon'ro WESTING- nousn ELECTRIC & MANUFACTURING VANIA eovnnmne Application filed July 26,

My invention relates to governing-mechanism, more particularly to a governing mechanism for a prime, mover having an overspeed governor for shutting off the admission of motive fluid upon the attainment of a predetermined overspeed of'the prime mover, and it has for its object the provision of means whereby the governor may admit suiiicient fluid to permit a speed of the prime mover-above the predetermined overspeed while the governor still retains speedcontrol and prevents the attainment of a speed high enough to make operation of unsafe. 1

Elastic fluid turbines are generally provided with an overspeed governor, which trips ata predetermined overspeed, usually about 11% above the normal operating speed, and completely shuts elf the supply of motive fluid. This overspeed governor is provided addition to the regulating or speedgovernor, which regulates the admission of motive fluid to maintain thedesired operating speed, andit is providedfor the purpose of safeguarding against a possible failure of the speedgovernor. Inasmuch as the overspeed governor operates in service only in an emergency, it is very desirable to test the same to guard against sticking or other difiiculty.

A test of the" overspeed governor at the predetermined overspe'ed requires an amount of motive fluid greater than thatwhich the speed governor will admit, the speed changer being fadjustable' to provide a maximum speed .of only about 4% "or 5% above normal operating speed, and

the prime mover COMPANY, A, CORPORATION- 0F PENNSYL- MECHANISM 1929. Serial No. 381,367.

my invention as will be apparent fromthe following description and claims taken in com nection with the accompanying drawings, forming a part of this application, in which: Fig. 1 is a diagrammatic view, with parts in section, of one embodiment of my invention;and, I 1

- Fig. 2 isa similar View of. a slightly modilied portion of the governing mechanism.

Referring now to the drawings more in deta-il, I show anelasticfluid turbine 10, having a rotating shaft 11. Motive fluid for the ltvhen' through a governing valve 14 t0 theturune. 1

In the present embodiment, I show invention applied to a fluid pressure governor, and hence I provide a centrifugal impeller pump 15, preferably disposed within a bear ing housing 53 and includingan impeller-16 mounted directly on the'rotor' shaft 11. The pump is supplied with fluid under a positive pressure from any suitable source, conveyed through a conduit 51 to a chamber 52' in the bearing housing 53, said chamber constituting a suction or inlet chamber for the pump.

turbine is supplied from a conduit 12 and passes first through a throttle valve 13 and The pump provides a pressure varying as 'the square of; the speed of rotation of the shaft, increased by the pressure of the fiuid in the suction chamber'52. The fluid under pressure delivered by the pump is. conveyed througha conduit '17 to the pilot'valve casing 18 of a fluid prcssurerelay mechanism 19 and supplied to the lower end of a pilot valve 21;

, The relay mechanism '19 actuates the governing valve ll an d it includes an operating piston 22, a rod 23 conneotingthe piston to the valve'l l, acylinder 24 for the piston, and 'a spring 25 within thei' cylinder for biasing thepiston 22 downwardly, orin the direction for closing the admisson valve. The re lay mechansmfurther includes. a lever 26 having one end pivoted to a stationary part'at 27, and its otherendpivotedto the rod 23.

Intermediate itsiends, the lever 26 is pivoted to the lower end of a stem '28. which projects through the lower end of the pilot valve cas- .ing 18. A spring 29 is secured at its upper.

end to the pilot valve 21 and at its lower end to the stem 28.

The pilot valve 21 is provided with

piston portions

31, 32, 33 and 34, the

piston portion

32 and 33 controlling ports 35 and 36, in the casing 18, respectively, which communicates with the upper and lower ends of the cylinder 24. The pilot valve casing is also provided with an admission port 37, between the

piston portions

32 and 33, and with exhaust ports 38 and 39, located between

piston portions

31 and 32 and between piston portions 33 and 34, respectively. The port 37 communicates with the conduit 17 by means of a branch conduit 41, and thus fluid under pressure is provided between the

piston portions

32 and 33. The ports 38 and 39 preferably communicate with the conduit 51 through a branch conduit 54, whereby fluid discharged from the relay mechanism is returner directly to the pump.

The operation of the pilot valve in controlling the piston 22 is well known in the art. Upon an increase in the resultant upward force on the pilot valve and consequent elongation of the spring 29, the pilot valve moves upwardly, placing the ports 37 and in communication. Fluid under pressure then flows through these ports to the upper end of the cylinder 24 and moves the piston 22 downwardly to effect decreased opening of the governing valve 14. At the same time, the ports 36 and 39 are placed in communication and the fluid in the lower end of the cylinder 24 is discharged through these ports to the exhaust port 39, and returned to the pump through the conduits 54 and 51.. The lever 26 is moved downwardly by the rod 23, and hence returns the pilot valve to cut oh position by means of the stem 28 and. the spring 29.

Upon a decrease in the resultant upward force on the pilot valve, the mechanism operates in the reverse direction to effect increased pening of the valve 14.

The casing 18 is formed to provide a chamber 42 above the pilot valve 21, and the pilot valve 21 is provided with a restricted orifice 43 through which fluid under pressure flows to said chamber. The casing is further formed to provide an outlet opening for the chamber 42, said opening being controlled by a pressure relief valve 45. disposed within a chamber 46 and biased to closed position by a spring 47. The spring 47, in turn, abuts at its upper end against an abutment or piston member 48. which, in turn, abuts aeainst a lever 49. The deflection or setting or the relief valve spring is thus controlled by the lever 49, which is actuated or adjusted in any desired manner, as by a hand wheel 55.

The chamber 46 is placed in communicaion with the suction chamber 52 by means of a conduit 56 whichcommunicates with the branch conduit 54 through a hand-operated valve 57 which is normally fully open. The fluid discharged by the relief valve is thus returned to the pump, and the pressure of the fluid in the pump suction chamber is imposed on the relief valve in closing direction. The pressure imposed upon the fluid in the chamber 42 is thus increased by this amount, and the variations in pressure acting upwardly on the pilot valve, caused by Variations in pressure in the suction chamber 52 are balanced by equal variations in pressure in the chamber 42. Thus, the effect of pressure variations in the suction chamber on the pilot valve is eliminated.

In order to provide for the increased speed setting of the governor when testing the overspeed governor, I provide a second relief valve 58 communicating with the conduit 56. The setting of the relief valve may be adjusted by turning the screw-threaded spring abutment 59, and I adjust this setting to provide a pressure in the chamber 46 above the pump suction pressure. The fluid discharged by the valve 58 is conveyed by a conduit 61 to any suitable reservoir.

The overspeed governor, which closes the throttle valve 13, is indicated generally at 62. As will be apparent from the drawing, the portion of this apparatus which cooperates With the shaft 11, is duplicated, being shown as seen from the side and also from the end of the turbine. The overspeed governor includes an eccentrically-disposed weight member 63, which. is adapted to fly outwardly therefrom upon a predetermined overspeed of the shaft 11, being usually set to operate at about 11% above the normal operating speed. A trip finger 64, mounted on a shaft 65 is disposed closely to the weight member 63 and in such position that it is struck thereby when the weight member flies outwardly. A trigger 66 is also fired on the shaft 65, and normally engages a lever 67 pivoted at 68. Thelever 67, when engaged by the trigger 66, retains a valve 69 in closed position.

The throttle valve 13 is connected, by means of a stem 7 2, to a piston 71 disposed within a cylinder 74. A passage 7 3 extending through the piston 71 provides communication between the parts of the cylinder above and below the piston. A hand-operated stem 75 is adapted to contact the piston 71. and to close the passage 73. A 76 in the upper end of the cylinder 7 4 biases the piston Tidewnwardly, that is, in the direction for closing the throttle valve 13. Fluidpres' sure is supplied to the lower end of the cylinder 74 from the pump 15, through the conduit 17, a restricted orifice T7, and a conduit '78.

The conduit'73 also communicates with the valve 69, and pressure can be maintained in theconduit 78 and the lower end of the cylinder 74 only when said valve 69 is closed. When the valve 69 is opened, the fluid under Ell "(8 is discharged. The operation of pressure in the cylinder '74 and the conduit paratus is as follows:

During normal operation of the turb ne .10, an increase'in load thereon results in a decrease in speed'thereof. The decrease in speed results in a decrease in pressure dis-,

18 below the pilot valve 21 is the pressure discharged by the pump 15 and varies as the square of the speed increased by the pressure of the fluid admitted to the pump. 'A small flow of fluid from beneath the pilot valve 21 to the chamber'4-2is provided by the restricted orifice 43, and the pressure in the chamber 42 is controlled entirely by the relief valve 45, whichisbiased to closed position 'bythe spring 4? and the pressure of the fluid in the chamber 46, which is the same pressure as that in the suction chamber. "Fluid 1n the chamber 42 attains pressure equal tot-he.v

closing forces on the valve '45; I

The pressure within the chamber 42 may be varied by changing the deflection or setting of the spring 47, which may be accomplished by adjusting the hand wheel 55. For

example, if it is desired to increase the'speed 7 setting of the governor, the hand'swheel55 is turned to move the lever 46 downwardly to increase the compression of the spring 47. The increased compression of. the spring 47 effects an increased pressure in thechamber 4-2, and, in turn, results in a downwardmovement of the pilot valve 21 and an increased opening of the admissionvalve 14 to effect an increased speed. The hand Wheel 55 is perated in the reverse direction to'move the lever 49 upwardly, to effect setting. V

The maximum speed setting that can be providedby the above prescribed mechanism is ordinarily about4% or 5% above the normal operating speed, and net high enough to permit operation of the overspeed governor. I v When it is desired to test the overspeed governor, the load on the turbine is first preferably removed, particularlyif it is driving a load in common with other turbines. The valve 57 is then'slowly closed, cutting on the escape to the suction chamber 52 of the fluid discharged by the'relief valve The pressure in the chamber '46 and the conduit 56, therefore, beglns to increase until it is sufficient to open the relief valve 58. As,

above indicated, the pressure in the chamber 42 is increased by the amount of pressure in the above-described ap a lower speed the chamber 46, and hence a speed setting of the fluid pressure governor is now effected which is greater than can be obtained by the hand wheel 55. The relief valve 58 is'so adjusted as to discharge at a pressure {which will provide a speed setting of the governor above the. speed required to operate the overspeed governor, and which speed is within a the limit of safe operation of the turbine 10. An elastic fluid turbine is ordinarily designed to be safely operated up to aspeed'approximately 20% above its normal operating speed, and the relief valve 58 may therefore,

desirably be set to permit a speed approximategy 15% above the normal operating spee The overspeed governor operates as follows:

Upon attainment of a predetermined overspeed, the weight member 68 strikes the trip finger 64, which, in turn, disengages the trigger 66 from the lever 67 V The closing forceon .the valve 69 is thus released and the fluid pressure within the lower'end of the cylinder 74 'isdischarged. The piston 71 is moved downwardly by the spring 76 to close the throttle valve, and the latter cannot again be opened until the stem 7 5 is brought down to close the'passage 7 3, and the trigger .66 and the lever (Ware reset.

Referring toFig. 2, I show a modified form of governor apparatus. In Ithisform, the change in speed setting-of the speed governor effected by-moving the fulcrum'of the lever 26, which'ispivoted to the upper end of a stem 81. hand wheel 82 is provided for raising or lowering the stem 81.

The chamber 42 ;abovethe pilot valve 21, in this case, communicates with the suction conduit 54 througha conduit 83 and a valve 84-. During normal operation, the'pump suce tion pressure isjmaintained in the chamber I 42 to balance the effect of variations in the pressure delivered by the pump 15.. By

closing the valve 84,.the escape of fluid to the suction'conduit 54 is cut off, and the'preswhich the relief valve :58 is set. The latter sure in the chamber'42 increases'to that at s is set at a pressure which will provide the j desired increased speed setting for testing the over-speed governor.

The operation of this embodiment is otherwise the same as that described above. 7 7 i From the abovedescription, it will be seen that I have )rovide d a novel mechanism for effecting a speed setting of the speed 'goven nor which will permit testing of the overspeed governor, while, at thesame time, con- D n a vent a speed which is unsafe.

trollin thev admission of motive fluid r01 preceptible of various other changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only suchlimitations 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 prime mover having an overspeed governor for shutting 05 the admission of motive fluid to the prime mover upon a predetermined overspeed thereof, of a governor responsive to the speed of the prime mover for regulating the admission of motive fluid thereto, a speed changer for varying the speed setting of the regulating governor, and means operative Without changing the adjustment of said speed changer for establishing a speed setting of the regulating governor above said predetermined overspeed and Within the limit of safe speed for adi'nitting, under speed-responsive governor control, suflicient motive fluid to test the overspeed governor.

2. The combination With a prime mover having an overspeed governor for shutting off the admission of motive fluid to the prime mover upon a predetermined overspeed thereof, of a governor for regulating the admission of motive fluid to the prime mover in response to the speed thereof, and means for effecting speed setting of the regulating governor above the predetermined overspeed and Within the limit of safe speed for admitting, under speed-responsive governor control, suflicient motive fluid to test the overspeed governor.

8. The combination with a prime mover having an overspeed governor for shutting off the admission of motive fluid thereto upon a predetermined overspeed thereof, of means for regulating the admission of motive fluid thereto, comprising means providing a fluid pressure varying as a function of the speed, an element responsive to said pressure, means controlled by said element for regulating the admission of motive fluid to the prime mover, means for imposing a sec ond fluid pressure on the pressure responsive element, and means for varying the second fluid pressure to effect a governing range of the pressure-responsive element extending above the predetermined overspeed and within the limit of safe speed, whereby suficient motive fluid may be admitted to the prime mover under speed-responsive control to test the overspeed governor.

4:. The combination with a prime mover having an overspeed governor for shutting off the admission of motive fluid thereto upon a predetermined overspeed thereof, of means for regulating the admission of motive fluid thereto comprising means prov1ding a fluid pressure varying as a function of v the speed, an element responsive to said pressure, means controlled by said element for regulating the admission of motive fluid to the prime mover, means for imposing a vsec- 0nd fluid pressure on the pressure-responsive element in opposition to the first-mentioned fluid pressure, and means for increasing the second fluid pressure to effect a governing range extending above the predetermined overspeed.

5. The combination With a prime mover having an overspeed governor for shutting off the admission of motive fluid to the prime mover upon a predetermined overspeed thereof, of a governor responsive to the speed of the prime mover for regulating the admission of motive fluid thereto, means providing an enclosed space, said last-mentioned governor being responsive to the pressure in said space, means providing a flow of fluid under pressure into said space, means permitting the escape of fluid from said space in the normal operation of the governor, and means for cutting off said means of escape' and for imposing a pressure on the fluid in said space effecting a governing speed of said governor above the predetermined overspeed and Within the limit of safe operation of the prime mover.

6. The combination With a prime mover having an overspeed governor for shutting off the admission of motive fluid to the prime mover upon a predetermined overspeed. thereof, of a governor responsive to the speed of the prime mover for regulating the admission of motive fluid thereto, a speed changer for varying the speed setting of the regulating governor, and auxiliary means for establishing a speed setting of the regulating governor above said predetermined overspeed and Within the limit of safe speed for admitting, under speed-responsive governor control, sufficient motive fluid to test 7 the overspeed governor.

7. The combination With a prime mover havm an overs eed overnor for shuttin b b on the admissmn of motlve fluidto the prmie mover upon a predetermined overspeed thereof, of a governor responsive to the speed of the prlme mover for regulating the admission of motive fluid thereto, a

speed changer forv varying the speed setting of the regulating governor, the maxi mum speed setting provided by said speed changer being less than the predetermined overspeed, and auxiliary means for establishing a speed setting of the regulating governor above the predetermined overspeed and Within the limit of safe speed for admitting, under speed-responsive governor control, suflicient motive fluid to test the overspeed governor.

In testimony whereof, I have hereuntosubscribed my name this 24th day of July, 1929.

ANTHONY F. SCHW ENDNER.