US1533767A - Governor - Google Patents

Description

April 14, 1925.4 1,533,767

H. F. SCHMIDT GOVERNOR Fild Sept. 12. 1924 2 Sheets-Sheet 1 HJZSchn-Iidt Wye; INVENTOR BY I,

ATTO RN EY April 14, 1925. 1,533,767

H. F. SCHMIDT GOVERNOR Filed Sept. 12, 1924 2 Sheets-Sheet 2 H.F. Schmidt WITNESSES: INVENTOR ATTORNEY Patented Apr. 14, 1925.

UNITED STATES PATENT OFFICE.

HENRY F. SCHMIDT, OF LANSDO'WNE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

GOVERNOR.

Application filed September 12'. 1924. Serial No. 737,386..

To all whom it may concern:

Be it known that I, HENRY F. SCHMIDT, a citizen of the United States, and'a resident of Lansdowne, in the county of Delaware and State of Pennsylvania, have invented a new and useful Improvement in Governors, ot' which the following is a specification, this application being a continuation, in part, otmy application, Serial No. 580,378, tiled August 7, 19:22.

My invention relates to governing apparatus for elastic fluid motors and it has for an object the provision of apparatus of the character designated which shall so control the admission valve of the elastic fluid motor that a given change in volume of fluid delivered thereto shall be effected for a given change in speed of the motor.

Another object of my invention is to proride, in a'variable fluid-pressure operated governing apparatus embodying an element actuated by the variable fluid pressure in opposition to the force exerted by a spring, means for securing wide ranges of move meut per unit of deflection of the spring.

..\nother object of my invention is to provide, in a variable fluid-pressure governing apparatus, means for varying the unit of movement of the actuating element thereof per unit of change of governing pressure during movement of the acuating element.

Apparatus embodying features of my invention is illustrated in the accompanying drawings, in which Fig. 1 is a view of a simple form of governing apparatus illustrative of a feature of my invention; Fig. 2 is a sectional view of a variable fluidpressure governing apparatus embodying my invention; and Figs. 3 and 4 are detail views of apart of the invention.

In the design and manufacture of governors for turbines and other power-developing apparatus, the difliculty is frequently encountered that aspring possessing the desired strength and scale characteristics will have physical dimensions that prohibit its use. M invention provides means by which t e scale characteristic desired for a predetermined range of speed and'per cent of speed variation ma be secured in a spring of reasonable dimensions and possessing the necessary strength or stiffness.

In accordance with my invention, I may employ the ordinary form of disc admission valve and I provide a cam member, simple of design and easy of manufacture, associated with the actuating element of the governing apparatus and the admission valve, whereby, up to a certain degree, a constant unit of movement of the admission valve is provided for a given change in speed of the prime mover and thereafter, a varying unit of movement of the admission valve per unit of change in speed of the elastic fluid motor is provided. In any modification of the invention the cam mem-.

her is so designed as to give an approximately constant rate of opening of the admission valve until the pressure on the low pressure side of the valve is equal to .57 of the pressure onthe high pressure side, and thereafter an increasing rate of opening so as to give a constant increment of steam admitted to the elastic fluid motor per unit of increase in speed thereof.

7 Referring now to the drawings for a better understanding of my invention, I show in Fig. 1 an elastic fluid motor, such as a steam turbine, at 10, having an admission valve 11, controlled by a centrifugal speed governor 12, driven by the motor 10. Movements of the speed governor 12 are transmitted to the admission valve 11, through a lever 13 having arms 14 and 15, said lever being fulcrumed at an intermediate point on my improved cam member 16. Upon an increase in speed of the motor the arm 14: of the lever is raised and the arm 15 lowered. Upon a decrease inspeed of the motor the arm 14 is lowered and the arm 15 raised, moving the admission valve 11 in an opening direction.

The fulcrum member 16 is provided with a curved surface 18 and an approximately flat surface 17 (Figs. 3' and 4:), said surfaces meeting at approximately a right an- .gle at an edge 20. The curved surface 18 is hollowed out so as to form a trough 19 there in and thus better to hold the lever 13 in position.

The fulcrum member 16 is so arranged that the lever 13, within a. limited range of movement, and a consequent limited opening of the admission valve 11 is fulcrumed at the edge 20 of the flat surface 17 and the arm -15 has a constant radius of movement. Upon a decrease in speed, with a consequent downward movement of the lever arm 14, the lever 13 comes in contact with the curved surface 18 of the cam member 16 and the arm 15 is lengthened, giving an increasingly wider range of movement thereto as the arm 14 moves downwardly.

The point in the movement of the lever 13 at which it engages the curved surface of the cam member 16' is at that opening of the admission valve when the pressure on the .low pressure side of the. valve is equal to .57 of the pressure on the high pressure side. When moving from a closed position of the admission valve. 11 to this point, the flow of steam thereby varies directly with its movement, the area of the valve opening being assumed to increase directly with its opening. Upon arriving at this point, a comparatively wider range of movement is required to furnish a constant increment of steam to the prime mover per unit of change in speed. It will be a parent from the drawings that the increasing length of the lever arm 15 and shortening of the lever arm 14, as the valve 11 is opened, gives this comparatively wider range of movement.

turbine, journalled in a casing 22. Menu e Referring now to Fig. 2, I show at 21 a shaft of an elastic fluid motor, such as on the shaft 21 is a rotary pump 23, constituting a source of fluid under pressure which varies with the speed of the turbine. Fluid for the pump 23 is supplied from any convenient source through a port 25. Attached to the turbine casing 22 in any well-known manner is a governor casing 24 having a cylindrical upper portion defining an operating cylinder 26 in which an operating piston 27 is disposed. The operating piston 27 is hollow and is provided with tubular extensions 28 and 29 at its top and-bottom, respectively, the top extension being closed by a cap 31 and provided with vent holes 32. The piston 27 is also provided with upper and lower admission ports 33 and 34, and an exhaust port 36 by means of which ports the operating pressure fluid may be admitted above or below the piston 27 to move it down or up in the cylinder 26, or to maintain it stationary as is well understood. in the art to which my invention relates. The admission of fluid to the ports 33 and 34 of the piston 27 is; controlled by a tubular pilot valve 37, said pilot valve being disposed within the hollow portion ofthe piston 27, and being provided with suitable upper and lower ports 38 and 39. The pilot valve 37 is also provided'with a restricted portion forming an annular exhaust passage 41, affording communication between either of the piston ports 33 and 34 and the exto the operating piston head 31 by means of a link 48. The admission valve 11 is also connected to the link 48 and to the lever 46 so that it is moved in an opening or a closing direction directly by the operating piston 27. A lever 51 f-ulcrumed'. at 52 in a web 53 attached to the casin 24 is disposed below the pilot valve 37.- The outer end of the lever 51 is actuated through a link 54 by the lever 46. The fulcrum point 52 is so selected that the inner arm of the lever 51 I ployed which would prevent the passage of fluid therethrough. The link 54 is provided at its upper endwiththe cam member 16 as illustrated in Fig. 1, except, that in this figure the cam member is shown in an inverted position from that illustrated in Fig. 1. The lever 46 bears against this cam memben in actuating the link 54. During a limited range of movement and a limited opening of the admission valve 11, the lever 46 bears upon the edge 20 of the surface 17 of the cam member 16, and during wider ranges of movement when the admission valve 11 is opened wider, the lever 46 bears upon the curved'surfzTce within the trough 19 of the cam member 16. It will be a parent that, beyond the point where tl a lever 46 first engages the curved surface of the cam member 16, upon a further downward movement of the operating piston 27,

the relative rate of movement of the link 54 compared with the operating piston 27 will be increased, and that within the limited range of movement aforesaid the relative rate of movement of the link 54 and mean? at normal turbine speed its tension balances the pressure of the fluid on the head 42 to maintain the pilot valve 37 in its neutral or cut-ofl' posit-ion, closing the admission ports 33 and 34 of the piston 37, and thus maintaining said piston, and consequently the admission valve 11, stationary. The exhaust port 36 of the piston 27 is connected to an appropriate passage 59 through which the fluid exhausted from above or below the piston 27 is conducted to the intake of the pump 23. The passage 59- may also communicate with an overflow 61 leading to a drain passage. 62 in case the fluid discharged from the operating cylinder is more than is required for the pump 23.

From the foregoing description it will be seen that as the speed of the turbine increases, the greater fluid pressure resulting from the increased pump speed overcomes the tension of the spring 57 and moves the pilot valve upwardly, uncovering the piston port 34 and admitting fluid beneath the piston 27. Fluid above the piston 27 is exhausted through the port 33 and the passage 41 through the exhaust port 36. The pressure of the fluid beneath the piston 27 moves the latter upwardly until the ports 33 and 34 are again closed and at the same time the admission valve 11 is operated through the linkage shown.

In the same. manner, when the turbine speed is reduced, the pump speed and consequently the fluid pressure decreases, the tension of the spring 57 overcomes the pressure of the fluid and moves the pilot valve 37 downwardly. Downward movement of the pilot valve 37 admits fluid through the port 33 above the piston 27 which then follows the pilot valve 37 in its downward movement until cut off occurs and the parts reach a new state of equilibrium.

In order to secure wide ranges of movement of the operating piston 27 with relatively small deflections of the spring 57 a follow-up:mechanism is provided. This follow-up mechanism consists of the link 54, the lever 51, and. its associated spring abutment 56. It-will be apparent from the foregoing description that an upward movement of the pilot valve 37, with the resultingdeflection of the spring 57, is followed by a proportional upward movement of the piston 27. This movement is transmitted to the lever 46 and thence throughthe follow-up mechanism to. the spring abutment 56, so that the lower end of the spring 57 is given'an upward movement of compensation for its previous deflection. As the inner arm of the lever 51 is shorter than the inner arm of the lever 46, the upward movement of t he pis-. ton 27 will be greater than the upwardmovement of the spring abutment 56. The effect of this action is to permit the pilot valve 37 and operating piston 27 to travel a relatively wide distance for each unit of spring deflection before the ports 33 and 34 are covered. By suitable location of the rel ative position of the fulcrum points 47 and 52, this ratio of movement may be varied from zero to any desired within practical limits.

During a limited range of movement of described. is that wherein the pressure at the exit side of the admission valve is .57 or less of thepressure at the inlet side. The cam member 16 is so arranged that upon increases in load and decreases in speed, requiring greater increments of steam to the prime mover, the lever 46 engages-with the curved surface 18 of the cam member 16 and the motion transmitted thereby through the link 54 to theleve'r 51 is at an increasing rate, as the admission valve 11 is moved in an opening direction, in order to secure a direct increment of steam admitted to the prime mover per unit of change in speed, governing pressure, and deflection of the spring 57.

In order to vary the turbine speed, I provide means for adjusting the efi'ective scale and tension of the spring 57. The flanged roller 47, which constitutes the fulc-run'i of the lever 46, is rotatably mounted on one end of a bell crank lever 64, fulc-rumed at 66, to a lug 67 which is rigidly mounted on the governor casing 24. A radius link 68 is also connected to the lug 67 and to the cam member 16 .which radius link serves to limit the lateral movement.- of the link 54 in relation-to the fulcrum 47'. The other end-of the bell crank lever 64'is connected by means of a link 69 to any suitable speedchanging means, such as the screw and nut gearing 71. The gearing 71 is adapted for manual operation by a hand wheel 7 2, though any suitable means known to the art may be employed in adjusting the speedchanging mechanism. A movement of the link 69 in a downward direction causes the roller 47- to move upwardly. This raises the lever 46,'increasing the distance between the two spring anchors 43 and 56. The link 54 and the outer end of the lever 51' are raised by this movement and the inner end of the lever 51 lowered, pulling the .pilot valve 37 downwardly, followed by the op.- erating piston 27, thus opening the admission valve 11 wider. \Vith the wider opening of the admission valve llfthe speed of the turbine is increased and the fluid pressure developed by the pump increased. The increased fluid pressure forces the pilot valve 37 upwardly stretching the spring 57 and moving the pilot valve to lap position. The initial tension load on the spring 57 is now greater than before the movement ofthe fulcrum roller 47, above referred to, and the normal speed of the turbine is thereby increased. In a similar manner an adjustment of the speed-changing mechanism causing a lowerin of the roller 47 effects a decreased norma speed of the turbine.

A movement of the lever or also causes a slight lateral movement of the roller 47 along the lever 46. A downward movement of the link 69 causes a slight movement of the rollc 47 tothe right, shortening the inner arm of the lever 46 and lengthening the outer arm, while an upward movement of the link 69 effects a shortening of the outer arm and a lengthening of the inner arm.

Increasing the length of the outer arnr of the lever 46 increases the rate of motion transmitted to the lever 51 and to the spring abutment 56, while decreasing the length of the outer arm decreases the rateof motion transmitted to the lever 51 and spring 56. This affects to a certain degree the range of movement of the operating piston per unit of change in governing pressure and per unit of deflection of the spring 57. lVhen the roller 47 is in its uppermost position, the outer arm of the lever 46 is at its longest and the motion transmitted to the follow-up mechanism is greatest. In this position, therefore, as the pilot valve moves responsive to changes in governing pressure followed by movement of the operating piston and the spring abutment 56 in the same direction, the movement continues until the governing pressure overcomes the forceofthe spring 57 and laps the pilot valve 37. Due to the increased rate of travel of the follow-up mechanism the movement just described is greatest. On the other hand, if the roller 45? is in its lowermost position, with the outer arm of the lever 46 at its shortest effective length, the motion transmitted through the follow-' up mechanism is at its least, and the movement of the pilot valve followed by the. operating piston, per unit. of change in governing pressure and spring deflection, is less than before described, with the roller l7 in its uppermost position. v

It will be apparent from the above that the speed-changing mechanism-effects two things, namely, varies the tension vof the spring 57 in opposition to the governing fluid pressure and changes the rate of motion of the follow-up mechanism; \Vhen set for high speeds of the turbine, the range of movement of the pilot valve and the op-- .of the fulcrum 47. This eflects a very close regulation of the turbine for all speeds.

\Vhile I have shown my invention in but two forms, it will be obvious to those skilled in the art. that it is not so limited, but is susceptible of various changes and modifications witho-ut 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

1. A governor mechanism comprising means adapted to be actuated by fluid pressure, a spring associated with said means opposing the fluid. pressure thereon, and means associated with the first mentioned means for maintaining the deflection of said spring small with relation to the movement of said first mentioned means.

2. A governor mechanism comprising means adapted to be actuated by fluid pressure, a spring associated with said means to oppose the fluid pressure, and means actuated by the first mentioned means to provide translator movements of the spring, whereby the eflection of said spring is maintained small relatively to movements of said first mentioned means.

3. A governor mechanism comprising a piston operated by fluid under variable pressure, a pilot valve controlling the operation of said piston and actuated by the pressure of the fluid, a spring attached at one end to the pilot valve and adapted to oppose the fluid pressure thereon, and means actuated by movements of the piston to move the other end of said spring, whereby its deflection is maintained small relatively to movements of said piston.

4. A governor mechanism comprising a piston operated by fluid under variable pressure, a pilot valve controllin the operation of said piston and actuated y the pressure of the fluid, a spring attached at one end to the pilot valve and adapted to op'posethe fluid pressurethereon, and means actuated by movements of the piston to position the other end of said spring'to maintain the deflection thereof small relatively to the pis ton movement. p I 5. A governor mechanism comprising a piston operated by fluid under variable pressure, a pilot valve controlling the operation of said piston and actuated by the pressure of the fluid, a spring attached at one end to the pilot valve and adapted to oppose the Illlll Dltllll't [in in ill in In mechanism actuated by movements of the piston to position the other end of said spring to maintain the deflection thereof small relatively to movements of the piston.

6. A governor. mechanism comprising a piston operated b fluid under variable pressure, a pilot Va ve controlling the operation of said piston and actuated by the pressure of the fluid, a spring attached at one end to the pilot valve and adapted to oppose the fluid pressure thereon, and follow-up mechanism including a pair of spaced levers actuated by movements of the piston to' position the other end of said springs to maintain the deflection thereof small relatively to movements of said piston.

7. Incombination with a governor mechanism comprising a piston operated by fluid under variable pressure and controlled by a pilot valve actuated by said fluid, a spring attached at one end to the pilot valve and adapted to oppose the fluid pressure thereon, a lever attached at one end to the piston, a second lever attached at one end to the other end of the spring, and a link connecting the other ends of the levers, whereby the lever end of the spring is positioned to reduce'its deflection.

8. In combination with a governor mechanism comprising a piston operated by fluid under variable pressure and controlled by a pilot valve actuated by said fluid, a spring attached at one end to the pilot 'valve and adapted to oppose the fluid pressure thereon, a follow-up Inechanism for the spring including a link and lever train actuated bv the piston to .give to the other end of said spring'a movement in compensation for its deflection, whereby the said deflection is maintained small relatively to the piston travel.

, 9. In combination with a governor mechanism'including a piston operable by a fluid under variablapressure, a pilot valve controlling the admission of fluid to the piston and actuated by the pressure of the fluid, a spring connected at one end to the pilot valve and adapted'to oppose the. pressure of the fluid thereon, a follow-up mechanism comprising a lever having an adjustable fulcrum. and connected at one of its ends to said piston, a second lever having a fixed-fulcrum and connected at one of its ends to the other end of the spring, and a link connecting the other ends of the two levers, where the effective scale and tension of the sprin may be adjusted.

10. In com ination with a governor mechanism including a piston operable by a fluid under variable pressure, a pilot valve controlling the admission of fluid to the piston and actuated by the pressure of the fluid, a spring connected at one end to the pilot valve and adapted to oppose the presmechanism to maintain the deflection of the spring small relatively to trav el of the piston during operation of the governor mechanism, comprising a lever havinoan adjustable fulcrum and connected at one of its ends to said piston, a second lever having a fixed fulcrum and connected at one of its ends to the other end of the spring, and a link connecting the other ends of the two levers in such mannor that the effective scale and tension of the spring may be adjusted.

11. In combination with a governor mechanism including a piston operable by a fluid under variable pressure, a pilot valve controlling the admission of fluid to the piston and actuated by the pressure of the fluid, a spring connected at one end to the pilot valve and adapted to oppose the pressure of the fluid thereon, a follow-up mechanism to secure a small deflection of the spring during operation of the governor mechanism by compensating for relative movement between the ends of the spring caused by movements of the pilot valve, comprising a lever having a fulcrum simultaneously' adjustable in two directions and connected at one of its ends to said piston, a second lever having a fixed fulcrum and connected at one of its ends to the other end of the spring, and a link connecting the other ends of the two levers, in such manner that the effective scale, and tension of the spring may be adjusted.

12. In combination with a governor mechanism including a piston operable by a fluid under variable pressure, a pilot valve controlling the admission of fluid to the piston and actuated by the pressure of the fluid, a spring connected at one end to the pilot valve and adapted to oppose the pressure of the fluid thereon, a follow-up mechanism compensating for relative movement. between the ends of the spring caused by movements of the pilot valve to maintain the deflection thereof small relatively to the piston travel, comprising a lever having an adjustable fulcrum and connected at one of its ends to said piston, a second 'lever having a fixed fulcrum and connected at one of its ends to the other end of the spring, and a link connecting the other. ends of the two levers,- whereby the spring end of the secondlever is moved successively to variations in spring deflection, and in the same direction.

-13. 'In 'combination with a governor mechanism including a piston operable by a fluid under variable pressure, a pilot valve controlling the admission of fluid to the piston and actuated by the pressure of the fluid, a spring connected at one end ,to the pilot valve and adapted to oppose the pressure of the fluid thereon, a follow-up mechanism to maintain the deflection of the spring-small relatively to travel'of the piston during operation of the governor mechanism comprising a lever having. a fulcrum simultaneousl adjustable in two directions and connects at one of its ends to said piston, means including a bell-crank for mane ually adjusting the fulcrum of the lever, a second lever having a fixed fulcrum and connected at one'of its ends to the other end of the sprin and a link connecting the other ends 0 the'two levers, in such manner that the effective scale and tension of the spring may be adjusted.

14. In combination with a speed-responsive governor mechanism having a spring and a follow-up device adapted to main-. tain a small spring deflection during 0 ration of the governor mechanism, inc uding a lever, means adapted to move the fulcrum of said lever in a direction oblique to the longitudinal axis of said spring whereby the component of motion parallel to said. axis is efi ective to change the spring tension and the component of motion normal to said axis is effective td change the ratio of'lever arms determined by said fulcrum on said lever.

15. In combination with a speed-responsive governor mechanism havin a spring and a follow-up device adapte to maintain a small spring deflection during operation of the governor mechanism, including a lever, means comprising a bellcrank adapted to move the fulcrum of said lever in a direction oblique to the longitudinal axis of said spring whereby the component of motionparallelto said axis is effective to change the spring tension and the component of motion normal to' said axis is efi'ective to change the ratio of lever arms determined by said fulcrum on said lever.

16. A overnor mechanism comprising a hollow piston operated by fluid under va- Y -riable pressure, a pivot valve within the piston to control operation thereof and actuated b the pressure of the fluid, a spring within t e ilot valve and attached to one end thereo to oppose the fluid pressure thereon, and means actuated by movements of the piston to move the other end of said spring, whereby the deflection is maintained small relatively to movements of said piston.

17. A governor mechanism comprising a hollow piston operated by fluid under variable pressure, a pilot valve within the piston to control operation thereof and exposed to the pressure of the fluid, spring means acting on said pilot valve to oppose the fluid pressure thereon, and means actuated by the iston' to bodily move said sprin means w ereby its deflection; is maintain small.

18. Ina variable fluid pressure governing apparatus, the combination of an element actuated by the variable fluidpressure, a spring associated with the element for opposing the variable fluid pressure, means efl'ecting a comparatively wide range of movement of the element per unit of deflectionof the spring, and means for varying the rate of movement of the element per unit of deflection of the spring during movement of the element.

19. In a variable fluid pressure governing apparatus, the combination of an ele-- ment' actuated by the variable fluid pressure, a spring associated with the element for opposing the variable fluid pressure, means effecting a comparatively wide range of movement of. the element per' unit of deflection of the spring, and means effecting a constant ratioof movement of the element per unit of deflection of the spring during a limited range of movement of the element and thereafter elfectinga varying ratio of -movement of the element per unit I of deflection of the spring. 4

20. A governor mechanism comprising a hollow piston operated by fluid under variable pressure, a pilot valvewithin the piston to control operatibn thereof and actuated by the pressure of the fluid, sprin means located within the pilot valve an adapted to oppose the fluid pressure there on, and a follow-up mechanism including a pair of spaced levers actuated by the piston to 'bodil move said spring means, whereby its deflection relatively to piston movement is maintained small.

21'. In a device for controlling the admission valve to an elastic fluid motor embody ing means responsive to .the speed of the motor, an element actuated by said means, and a member transmitting the movements of the element to the admission valve, a second member associated with the element and with the first-mentioned member for varying the rate of movement of the first-mentioned member relative to changes in speed of the elastic fluid motor.

.22. In a device forcontr'olling the admission valve to an elastic fluid motor embodyapparatus, the combination of an element actuated by the, variable fluid pressure, biasing means for the element opposing the variab e flu d pressure, and means for accelerating the variation in force exerted by the biasing means during movement of the element.

24. In a variable fluid pressure governing apparatus, the combination of an element actuated by the variable fluid pressure, biasing means for the element opposing the variable fluid pressure, and means associated with the biasingmeans and operable during movement of the element for eflecting a varying unit of actuation of the element controlled by'tlie pilot valve and following its movements, means associated with the operating piston for actuating the movable abutment in the same direction and at a lesser rate of movement than the pilot valve, and means coacting with the last-mentioned means for varying the rate of movement of the movable abutment.

26. In a variable fluid pressure governing apparatus for a prime mover having an admission valve, the combination oi a pilot valve actuated by the variable fluid pressure, an operating piston controlled by the pilot valve and following its movements, said piston being actuated by the variable fluid pressure and controlling the opening and closing of the admission valve, a spring attached at one end to the pilot valve and at the opposite end to a movable abutment, means for actuating the movable abutment in the same direction, but at a lesser rate of movement than the operating piston, and means for increasing the rate of movement of the movable abutment relative to that of the operating piston during the opening ton being actuated by the variable fluid pressure and controlling the opening and closing of the admission valve, a spring connected at one end to the pilot valve and at the opposite end to a movable abutment, means for actuating themovable abutment in the same direction, but at a lesser rate of movement than the operating piston, and means for main taining a constant relative rate of movement of the operating piston and the movable abutment during a desired range of movement and thereafter increasing the rate of movement. of the movable abutment relative to that of the o erating piston during the opening of the a mission valve.

28. In a variable fluid pressure'governing apparatus-for a prime mover having an admission valve, the combination of a pilot valve actuated by the variable fluid pressure,

an operating piston controlled by the pilotvalve and following its movements, said piston being actuated by the variable fluid pressure and controlling the opening and closing of the admission valve, a spring attached at one end to the pilot valve and at the opposite end to a movable abutment, means-for actuating the movable abutment in the same direction, butat a lesser rate of movement than the operating piston comprisingtwo substantially parallel levers each fulcrumed at an intermediate point and having lever arms of unequal length, means connecting one of said levers at one end to the operating piston, means connecting the other of said levers at one end to the movable abutment, a link for transmitting the movements of the first-mentioned lever to the second-mentioned lever, and a cam member carried by said link through which the motion of the first-mentioned lever is transmitted to the other, said cam member permitting a constant radius of movement of the lever arm through a limited distance when the admission valve is being opened and thereafter increasing the radius of movement of said lever arm whereby motion transmitted to the movable abutment relative to the movement of the operating piston is increased.

In testimony whereof I have hereunto subscribed my name this second day of September, 1924.

HENRY F. scHMID'r;

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