US1599892A - Governor - Google Patents

Description

Sept. 14, 1926. 1,599,892

F. HODGKINSON GOVERNOR T Filed Dec. 17, 192.4

ifiodr xkinson NVENTQR 4 I BY ATTORN EY Patented Sept. 14, 1926.

UNITED STATES PATENT OFFICE.

FRANCIS HODGKINSON, OF SWARTHMORE, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC do VANIA.

MANUFACTURING COMPANY. A CORPORATION or PENNSYL- GOVERNOR.

Application filed December 17, 1924. Serial No. 756,433.

2 invention is illustrated in the accompanying drawing in which Fig. 1 is a view show-- ing a steam turbine having my improved governing apparatus applied thereto; and Fig. 2 is a sectional view, partly diagram matic, of the governing apparatus, and Fig. 3 is a view showing a modified detail of my invention.

In the applications of Henry F. Schmidt, Serial No. 580,378, filed August 7, 1922, and of John S. Myers, Serial No. 662,316, filed September 12, 1923, now'Patent 1,533,888, both assigned to the WVestinghouse Electric and Manufacturing Company, there is illustrated and described fluid-pressure operated governing apparatus embodying a centrifugal pump which develops fluid pressure Varying as a function of the speed'of the machine governed and an element actuated by the fluid pressure having a reciprocatory motion for controlling the admission valve or other energy supply means of the machine governed.

Inasmuch as the pressure developed by a centrifugal pump is the pressure due to its speed of rotation plus the pressure existant at the pump inlet, it has been found that more dependable results are obtained with such apparatus by providing the pump with a positive, constant inlet pressure. Means for accomplishing this purpose are disclosed in the application of Henry F. Schmidt, Serial No. 688,292, filed January 24, 1924, and assigned to the Westinghouse Electric and Manufacturing Company.

\Vith apparatus such as has been mentioned, in case there should be a failure of pressure or a marked diminution in pressure at the inlet of the pump, it is evident that there is an immediate drop in fluid pressure delivered by the pump to the governing apparatus. Upon a reduction in governing fluid pressure the motive fluid supplied to the machine governed is increased, which might result in overspeeding.

In accordance with my invention, which is particularly applicable to apparatus such as isdescribed in the beforementioned applications, I provide a relay valve actuated by a piston normally held in a fixed position by the pump inlet pressure and movable upon a predetermined diminution of the inlet pressure, which relieves the fluid pressure from that side of the operating piston of the governing apparatus which is effective for moving the controlling element of the machine governed in a direction for supplying additional motive fluid thereto,

resulting in a shutting down of the machine governed. I

Referring now to the drawing for a more detailed description of my invention, I show in Fig. l at 10, an elastic-fluid turbine, hereinafter referred to as a steam turbine, having an admission valve 11, controlled by fluid-pressure actuated governing apparatus at 12. Fluid under pressure for the governing apparatus is developed by a centrifugal pump 13 supplied from a fluid reservoir 14 and which is delivered to the governing apparatus through a conduit 16 A part of the fluid pressure developed by the pump 13 is delivered through a conduit 17 to an ejector 18. The ejector 18 is located within the fluid reservoir 14 and serves to supply fluid to the inlet of the pump 13 at a positive, constant, pressure through aconduit 19 and also serves other purposes to be more particularly pointed out hereinafter in the specification. The term positive pressure as employed in this specification is meant to define a pressure above atmospheric pressure as distainguished from subatmospheric pressure. By introducing a positive pressure at the inlet of the pump 13, the reliability of the a paratus is greatly improved- The action 0 the ejector 18 is such as to provide the fluid required by the pump 13 at a positive pressure.

The governing apparatus at 12 comprises a housing 21 having a supply chamber 22 and an operating cylinder 23. Within the operating cylinder 23 is disposed a hollow operating piston 24 provided with upper ion and lower stem portions 30 and 35, respectively, which extend through the upper and lower covers of the cylinder 23 forming therewith fluid tight joints. The operating piston 24 controls the admission valve 11 through a stem 26 and a lever 27, which is fulcrumed on a suitable support 28 and is connected to the admission valve 11 through a link 29. The operating iston 24 is actuated by the governing fluid pressure and has a reciprocatory motion within the cylinder 23 for moving the admission valve 11 in an opening and a closing direction. Upward movements of the operating piston 24 result in a closing movement of the admission valve 11 and downward movements of the operating piston result in an opening movement of the admission valve.

The operating piston 24 is hollow, and closed at its upper end, the hollow portion thereof defining a cylinder in which is located a pilot valve 31 for controlling it.

The pilot valve 31 is provided with a series of ports 32 leading from the interior to the exterior thereof. The operating piston 24 is provided with a series oi ports 33 leading from the upper side to the interior thereof. When the ports 32 are in registry with the ports 33 fluid under pressure is admitted to the upper side of the piston 24. Below the ports 32 is an annular shoulder 34 on the pilot valve 31, which, in registry with the ports 33, prevents a flow of fluid to or from the upper face of the operating piston 24. Beneath the annular shoulder 34 the pilot valve 31 is provided with a reduced portion 36 which is, at all times, in. communication with an exhaust port 37 leading to the underside of the operating piston 24.

In operation, fluid pressure developed by the pump 13, which varies as a function of the speed of the turbine 10, is delivered through the conduit 16 to the supply chamher 22 and is always present acting against the lower stem portion 35 of the operating piston 24 and within the hollow portion of the pilot valve 31. It will be seen that the fluid pressure acting against the lower stem portion 35 of the piston 24 tends at all times to mpve the piston 24 upwardly and the admisslon valve 11 in a closing direction.

Movements of the operating piston 24 are governed by the pilot valve 31. Upon downward movement of the pilot valve 31 from the position shown in the drawing, fluid is admitted through the ports 32 and 33 to the upper face of the operating piston 24, which. being larger in area than the area of the stem portion 35, forces the piston downwardly. Upon upward movements of the pilotvalve 31. fluid above the operatmgpiston 24 passes through ports 33 around the reduced portion 36 of the pilot "alve 31 through the exhaust port 37. a

branch conduit 40 and a conduit 41 into the conduit 19 leading to the inlet of the pump 13. It will be seen, therefore, that the pressure prevailing at the inlet of the pump 13 is at all times present beneath the operating piston 24.

The pilot valve 31, as before pointed out, is at all times subjected to the fluid pressure developed by the pump 13 which tends to force it upwardly. The fluid pressure acting against the pilot valve 31 is resisted by a spring 42 which is secured in any appropriate manner to the pilot valve at .43, at its upper end, and which has its lower end secured to an abutment 44. The spring 42 is of such strength as to withstand the normal fluid-governing pressure so that upon increases thereof, above the normal, the pilot valve is moved upwardly, permitting fluid to pass from above the piston 24 to the exhaust in a manner already described. Fluid pressure acting against the stem portion 35 then forces the piston 24 upwardly. pon decreases in fluid pressure, the spring 42 pulls the pilot valve downwardly, admitting fluid governing pressure to the upper face of the piston 24, forcing it downwardly.

In order to secure wide ranges of movement of the piston 24 with a small deflection of the spring 42, a follow-up mechanism is provided which permits, upon movement of the piston 24, a similar, somewhat lesser, movement of the lower abutment 44 of the spring 42. This follow-up "mechanism comprises a lever 46 secured at one end to the stem 26. The lever 46 is fulcrum-med at 47 and secured at its opposite end to a link 48. The link 48 is connected at its lower end to a lever 49 which extends into the supply chamber 22 and which is provided with a ball and socket joint 51 with the housing 21, said ball and socket joint providing a fulcrum for the lever 49. The inner end of the lever 49 is secured at 52 to the abutment 44 of the spring 42. The inner arm of the lever 49 is somewhat shorter than the inner arm of the lever 46 so that upon a movement of the piston 24 and the stem 26 a movement in the same direction is transmitted to the inner end of the lever 49 through the lever 46 and link 48, said movement being less than the movement of the piston 24 as determined by the relative lengths of the lever arms. By means-of the follow-up mechanism just described, the movement of the pilot valve 31 in response -to a given variation in governing fluid pressure is equal to the deflection of the spring 42 plus the movement transmitted to the pilot valve through the followup mechanism: Inasmuch as movements of the'operating piston. 24 are equal to and in the same direction as iriovements of the pilot valve 31, it can be seen that a comparatively wide movement of the operating piston 24 results from a small deflection of the spring 42 and thus permits the use of a short spring of requisite strength to withstand the governing fluid pressure.

In order that movements of the pilot valve 31, responsive to variations in governing fluid pressure will not be affected by small variations in the inlet fluid pressure, I provide a branch conduit, 56, connecting the. conduit 41 to an annular passage 57 provided in the upper part of the housing 21. From thence the fluid at the inlet pressure passes through a port 58 in the upper stem portion 30 of the piston 24, thence through an. upper restricted portion 59 of the pilot valve 31 and thence through suitable slots or passages 61 to the space above the pilot valve 31 within the closed hollow end of the piston 24. Inasmuch as the pressure within the supply chamber 22 and acting against the under side of the pilot valve 31 is the pressure existing at the inlet of the pump 13 plus the pressure due to its speed of rotation and the ressure above the pilot valve 31 is that existing at the inlet of the pump 13, it will be seen that slight variations of the inlet pressure do not affect the pilot valve and cause movements thereof. If, however, there should be a failure of pressure at the inlet of the pump 13, due to stoppage in the conduit 19, or to any other cause, there would result a sudden 'drop in the pressure developed by the pump 13 and delivered to the governing apparatus through the conduit 16 to the pressure chamber 22. rThis would result in a downward movement of the pilot valve 31 followed by downward movement of the operating piston 24 and an opening movement of the'admission valve 11 which might result in the turbine overspeeding. I accordingly provide means operable upon a failure of the inlet pressure, or upon a marked diminution thereof, for causing an upward movement of the operating piston 24 and a closing movement of the admission valve 11.

At 63, I show a relay valve mechanism comprising a valve chamber 64 having a port 66 leading through a branch 67 to the conduit 41 and having a port 68 leading,

through a' conduit 69 to the operating cylinder 23 above the operating 'iston 24. Within' the housing 64 is located a valve member 71 having piston portions 72, 73, 74 and 76 with reduced portions 77, 78 and 79 therebetween. The valve member 71 is normally held in the position shown in the drawing by means 0 lower side to pressure existing at .the inlet of the pump 13 through a branch conduit 82'leading from the conduit 41. The u per side of the piston 81 is subjected to the orce exerted by-a spring 83 which is of just sufa piston 81 subjected on its.

ficient strength to force the piston downwardly upon a failure of, or a marked diminution in, the inlet pressure of the pump. The piston 81 is. located within a cylinder 84 which has an upper cylindrical portion 86, smaller in diameter than the lower portion. The piston 81 is provided on its upper side with an annular flange 87 which, when in its upper position as shown in the drawing, makes a fluid-tight joint with the smaller cylindrical portion 86 and prevents the passage of fluid thereby. Fluid which may leak past said flange 87 passes out through a conduit 88 to a drain 89 and thence back to the fluid reservoir 14. When in the position shown, the piston portion 74 of the valve 71 covers the port 68 leading'to the upper end of the operating cylinder 23 and prevents the escape of fluid therefrom.

' The reduced portion 8 of the valve 71 is at all times in communication with the port 66 leading to the conduit 41 through the branch 67 and is therefore at all times in communication with the inlet of the pump 13.

Fluid leaking past the piston portion 73 above the reduced portion 78 passes into the drain 89 through a branch conduit 91.

Upon a downward movement of the piston and acting against the stem portion 35 of the piston 24 to force said piston upwardly and close the admission valve 11. In order to insure a closing of the admission valve 11 should there be a total failure of governing pressure, I provide a spring 92 positioned between a fixed abutment 93 and an abutment 94 secured to the stem of the valve 11 which biases-the admission valve 11 at all times in a closing direction.

Operation of apparatus made in accordance with *my invention will be apparent. Fluid under pressure varying as a function of the speed of the turbine 10 is developed by the pump 13 and delivered through the conduit 16 to the supply chamber 22 of the I conduit 19v through conduit 41 and brancli conduit 40 to the underside of the piston 24, through branch conduit 56 .to the upper side of the pilot valve 31, and throu h the branch conduit 82 to the lower end 0 the cylinder 84 beneath the piston 81. The pressure developed by the ejector 18 and acting against the underside of the piston 81 serves to hold said piston in the position shown, with the port 68, communicating with the upper side of the piston 24, covered. So long as there is no marked diminution in pressure within the conduits 19 and 41, the relay mechanism 63 is inactive and does not in any way interfere with the functioning of the governing apparatus.

Upon increases in speed of the turbine 10 and consequent increases in fluid pressure developed by the pump 13, the pilot valve31 moves upwardly responsive thereto, followed by upward movement of the piston 24 in a manner already described and moving the admission valve 11 in a closing direction. Upon decreases in speed of the turbine 10 and conse uent decreases in pressure developed by t e pump 13 the pilot valve 31 is forced downwardly by the spring 42 followed by downward movement of the piston 24 and an opening movement of the admission valve 11. If for any reason there should be a failure of, or a sudden diminution in, pressure within the conduits 19 and 41 and, consequently, at the inlet of the pump 13, the piston 81 is forced downwardly by the spring 83, carrying the valve 71 downwardly. Port 68 isthen laced in cominunication with the upper en of the cylinder 23 and with the port 66 connected to the conduit 41 and leading to the inlet of the pump 13, by way of the reduced portion 78 of the valve 71. The action just described results in relieving pressure from above the piston 24, whereuponv the governing fluid pressure within the supply chamber 22 is effective for moving the piston 24 upwardly and closing the admission valve 11."

From a consideration of the above described operation, it will be seen that should the inlet pressure of the pump 13 fail and then be restored before a final shut-down of the turbine 10 occurs, the piston 81 will be forced upwardly by the pressure beneath it and thus close off communication between the upper side of the piston 24 and the conduit 41. The governing apparatus then resumes its normal operation. It might, under certain conditions, be desirable to effect a complete shut-down of the turbine upon a failure of, or a marked diminution in, the inlet fluid pressure at the pump 13 in prder that the trouble may be located and correction made. I therefore show in Fig. 3 a modified form of the relay 63 which accomplishes the aforementioned purpose.

The valve member71 shown in Fig. 3 is the same inall particulars as that shown in Fig. 2. The difference between the apparatll sho n th s m di cat q n ha shown in Fig. 2 applies to the arrangement of the piston 81. In accordance with this modification the piston 81 is made a loose fit within the cylinder 86 so that fluid can flow freely around it. When the piston is in the position shown in the drawing the annular flange 87 prevents the passage of fluid from beneath the iston to the upper side thereof. Upon a ailure of the inlet pressure of the pump 13 the piston 81 is moved downwardly by the spring 83. Should the inlet pressure of the pump be again restored before a complete shut-down of the turbine occurs, fluid can now flow freely around the piston 81 and outwardly through the drain 88 and 89 and the piston 81 remains in its downward position. The spring 92 accordingly closes the admission Valve 11 and effects a complete shut-down of the turbine 10. When it is again desired to start the turbine 10 the piston 81 is lifted to its uppermost position by means of a handle 97 until the inlet pressure at the pump is again restored, whereupon it is held in its uppermost position until a failure of inlet pressure again occurs.

From the foregoing it will be apparent that I'have invented an improved fluid-pressure governing apparatus, wherein upon a failure of pressure at the inlet of the pump employed for developing the governing fluid-pressure the governing mechanism operates to close off the energy supplied to the machine governed.

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 other changes and modifications, without departing from the spirit therof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically setforth in the appended claims. 4

What I claim is:

1. In a fluid-pressure operated governing apparatus embodying an element having a reciprocatory motion and actuated by the fluid pressure andv a pump for developin the fluid pressure, said pump being supplied at its inlet with fluid under a positive pressure, means operable upon failure of the pump inlet pressure for relieving fluid pressure from one side of the element.

2. In a fluid-pressure operated governing apparatus embodying an element having a reciprocatory motion and actuated by the fluid pressure and a pump for developing the fluid pressure, said pump being supplied at its inlet with fluid under a positive pressure, a piston normally held in a fixed position by .the pump inlet fluid pressure, a spring for actuating the piston upon a predetermined diminution in inlet pressure, and a valve operated by the piston for relieving pressure from one side of the elefor moving the admission valve in an openment. ing direction, and a piston operable upon 3. In a fluid-pressure operated governing failure of the inlet pressure for operating apparatus embodying an element having a the valve.

reciprocatory motion and actuated by the 5. In a fluid-pressure operated governing fluid. pressure and a pump for developing apparatus for a prime mover having an adthe fluid pressure, said pump being supplied mission valve embodying a pump for de a at its inlet with fluid under a positive presveloping fluid pressure, means for supplysure, a piston normally held in a fixed posiing the pump with fluid at its inlet under tion by the pump inlet fluid pressure, a a positive pressure and an operating piston spring for actuating the piston upon a prehaving a reciprocatory motion and actudetermined diminution in pump inlet presated by the fluid pressure for moving the sure, a housing having aport leading to admission valve in an opening and a closone side of the element and a port leading to ing dirction, said operating piston having a region of lower pressure and, a valve withan area subjected at all times to'fluid presin the housing normally closing off comsure developed by the pump and tending to munication between the ports and operated move the admission valve in a closing direoby the piston to connect the orts upon a tion, a relay valve for relieving fluid prespredetermined diminution in uid pressure sure from that side of the operating piston at the inlet of the pump. efiective for moving the admission valve in 4. In a fluid-pressure operated governing an opening direction, and a piston for actua-pparatus fpr a prime mover having an adating the relay valve, said piston being submission valve embodying an operating pisjeoted on one side-to the pressure existent ton havin a reciprocatory motlon and actuat the pump inlet and on the opposite side to ated by the fluid under pressure for movthe force exerted by a spring, whereby upon ing the admission valve in an opening and apredetermined diminution of pump inlet a closing direction, the combination of a pressure the spring moves the piston and pump for developing the fluid 'pressure, actuates. the relay valve. means for supplying the pump at its inletv In testimony whereof, I have hereunto with fluid under a positive pressure, a subscribed my name this ninth day of Devalve ocperable for relieving pressurefrom cember 1924.

that si e of the operating piston effective FRANCIS HODGKINSON.

Images