US2386110A - Turbine control apparatus - Google Patents

Description

Oct. 2, 1945. J. R. HAGEMANN 2,386,110

TURBINE CONTROL APPARATUS Filed Jan. 22, 1942 Patented Oct. 2, 1945 TURBINE CONTROL APPARATUS John R. Hagemann, Wauwatosa, Wls., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application January 22, 1942, Serial No. 427,698 9 Claims. (01. 137158) a This invention relates genlerally to control mechanism for prime movers and more particularly to an acceleration responsive control thereto large capacity prime movers driving loads which are subject to sudden removal, such for example, as large elastic fluid turbine driven electric generator units. since after a sudden loss of load, a

short but appreciable period of time is required for the speed of the turbine to accelerate sufliciently to render a conventional speed responsive governor operative to close the turbine admission valve. The continued admission of the steam or other working fluid during said period of time produces a degree of overspeed which is usually suflicient to eflect an operation of the overspeed trip mechanism to stop the turbine. Operation of the overspeed trip inechanism is objectionable in such instances as it necessitates a manual operation of the massive throttle valve and a resetting of the overspeed trip mechanism which causes considerable delay before the turbine can be again rendered/operative to carry load.

Attempts have been made to prevent an immediate operation of the overspeed trip mechanism in response to a sudden loss of load by the inclusion of a solenoid controlled pilot valve which is operatively associated with a fluid pressure relay having a motor operative to open and close the turbine admission valve. Energization of the pilot valve solenoid is controlled by an electromagnetic relay connected in circuit with a current transformer operatively associated with the power leads of the turbine driven generator. Theoretically this type of control should func tion satisfactorily but in actual tests it has been found entirely too sluggish to accomplish the desired result, probably due to residual magnetism in the armatures of the pilot valve solenoid and the electromagnetic relay.

Attempts have also been made to prevent operation of the overspeed trip mechanism in response to a sudden loss of load by employing a combination inertia and centrifugal governor for actuating the prime mover throttle or admission valve. However, this form of control has also proved impractical to accomplish the desired result since although the modifying action of the inertia element in response to a sudden loss of load does effect a movement of the throttle toward its fully closed position, its action in this respect is necessarily limited. Consequently, the continued admission of the working fluid, even The invention is particularly applicable to though at an appreciably reduced rate, together with the working fluid in the turbine when the load is dropped. is usually sufficient to produce a degree of overspeed which is efiective to operate the overspeed trip mechanism to stop the turbine.

It is therefore the primary object of this invention to provide an improved control mechanism for prime movers which will sufliciently minimize the increase in speed accompanying a sudden removal or decrease in the load thereof to prevent the operation of the associated overspeed trip mechanism.

In accordance with this invention, the above mentioned results are accomplished by providing in addition to the usual centrifugal governor and the usual overspeed trip device, a mechanism which efiects an immediate closing of the prime mover admission valve whenever the speed of the prime mover is accelerated in excess of a predetermined rate. In other words, the controlling factor is the rate at .which the speed increases and not the extent of the increase and consequently, the centrifugal governor, the overspeed trip device, and the acceleration responsive mechanism normally operate entirely inde-' pendent of each other.

The invention accordingly consists of the various details of construction, combinations of elements and arrangements of parts as is more fully set forth in the accompanying claims and in the detailed description, in which:

Fig. 1 schematically illustrates an elastic fluid turbine control system embodying the invention;

Fig. 2 is a partial sectional view taken on line IIII of Fig. 1;

Fig. 3 is a partial side view of the inertia governor showing the dashpot connection; and

Fig. 4 is an enlarged sectional view of the dashpot piston.

Referring to Fig. 1 of the drawing, it is seen that the control system is applied to an elastic fluid turbine l and comprises a back pressure regulator or governor 2, a speed governor 3, an inertia governor 4, a means or operator 6 which is operatively connected with a turbine admission valve 1 and which is controllably connected with the back pressure regulator 2, the speed governor 3 and the inertia governor 4, and an overspeed trip device 8 which is operatively connected with a turbine cut-off valve 9 and which is also controllably connected with the operator 6. In an actual installation, the arrangement of the valves 1 and 9 in the motive fluid supply line It) would probably be the reverse of that herein shown which was selected solely to effect a simihe operation of the plificatlon of actuating lever arrangements. However, insofar as this invention is concerned, any valve arrangement is sufficient which will effect the mode of control hereinafter described.

The back pressure regulator 2 includes a double acting servomotor I! having a piston l2 and a dashpot l3, a pilot valve structure l4 including a reciprocable valve element |6 controlling piston l2, and a pressure responsive device l1 including a flexible bellows |8 having a motion transmitting part IS, a biasing spring 2| having one end seated on the part l9 and having its other end engaging an adjustable seat 22 carried by a rotatable sleeve member 23, and a rod 24 extending loosely through the sleeve member 23 and having one end engaging the part l9 and having its other end operatively connected with one end of a rigid bar 26 which is in effect fulcrumed on the bracket 21 by means of a fiat spring member 28. The other end of the bar 26 is operatively connected with the upper end of a rod 29 which extends into the bore 3| in the valve element l6 and engages same to effect movements thereof. The valve element I6, the rod 29 and the bar 26 are maintained in operative engagement by the spring 32 disposed beneath the valve element "5. The valve structure includes a space 33 which is connected with a fiuid pump 34 by means of pipes 36, 31 and 38 and the valve element i6 controls the flow of fluid from said space through the conduits 38 and 4|. The arrangement is such that when' valve element I6 is in the position shown, no fluid flows through the pipes 39 and 4|; that when the valve element |6 moves upward from the position shown, fluid under pressure flows through the pipe 4| and the pipe 39 is placed in communication with a drain pipe 42, thereby effecting a downward movement of servomotor piston l2; and that when the valve element is moved downward from the position shown, fluid under pressure flows through pipe 39 and the pipe 4| is placed in communication with a drain pipe 43, thereby effecting an up ward movement of the servomotor piston l2. Pipe 43 is in communication with pipe 42 and the latter is connected with a fluid reservoir 44 with which the pump 34 is operatively connected. The piston I2 is provided with an upwardly extending rod portion 46 which is operatively connected with one end of a lever 41 having an intermediate portion fulcrumed on a bracket 48 carried by the valve structure M. The other end of lever 41 is provided with an apertured spring seat 49 through which the rod 29 extends and a spring which surrounds the rod 29, has one end engaging said seat and has its other end engaging the seat 52 secured to the rod 29. The lever 41 together with its operative connection with the piston rod 46 and the valve rod 29 constitutes a return mechanism for the valve element IS. The bellows H! of the pressure responsive device I1 is subjected to the exhaust pressure of the turbine by means of a pipe connection 53 and the arrangement is such that in response to a decrease in exhaust pressure, spring 2| effects a downward expansion of bellows I8 and as a result the springs 32 and 5| effect an upward movement of valve element l6, a clockwise movement of bar 26, and a downward movement of rod 24, thereby maintaining said rod in engagement with the part l9. An increase in exhaust pressure effects a contraction of bellows l8 and a corresponding upward movement of part l9 and rod 24; the latter effecting a counterclockwise movement of bar 26 and a downward movement of rod 29 and valve element |6. Movement of valve element |6 effects the previously described movements of the servomotor piston l2 and a further description of the operation of the back pressure regulator, which is conventional in all material respects, is believed unnecessary for a complete understanding of this invention.

The speed governor 3 includes a conventional ilyball mechanism 54 which is operatively mounted on a spur gear shaft 56 for rotation therewith and which is operatively connected with one end of a coaxially slidable rod member 51. Shaft 56 is connected by gearing 55 to a shaft 58 which in turn is geared to the turbine shaft 59, thereby rendering the flyball mechanism 54 responsive to the turbine speed. Rod 51 has its other end operatively connected with one end of a lever 68 having an intermediate portion thereof'adjustably fulcrumed at 6| and having its other end held in operative engagement with the upper end portion of a servomotor pilot valve element 62 by means of a spring 65. The servomotor embodies a double acting piston 64 which surrounds the valve element 62 and which includes a fluid pressure space 66 operatively connected with the pump 34 by means of pipes 61, 31 and 38. The ser omotor arrangement is such that when the valve element 62 is moved downward from the position shown, fluid under pressure flows into the space 68 and through the port 69 into the space H at the top of the piston and the fluid in the space I2 at the bottom of the piston flows through port 13 into space 14 and through port I6 into the drain pipe thereby effecting a downward movement of the piston 64; and that when the valve element 62 is moved upward from the position shown, fluid under pressure flows into the space 14. and through port 13 into the space 12 at the bottom of the piston and the fluid in the space II at the top of the piston flows through port 69 into space 68 and through port 18, the space 19 and into the drain pipe 88, thereby effecting an upward movement of the piston 64. Piston 64 has a rod portion 8| which is in the nature of a sleeve and which is operatively connected with one end of a lever 82 having an intermediate portion 83 fulcrumed on a stationary bracket 84. The other end of lever 82 is held in opera tive engagement with the upper end of a link 86 by means of a spring and a lever 88 which has an intermediate portion fulcrumed on the piston rod 46 of servomotor piston l2 has one end held in operative engagement with the lower end of link 86 by means of a spring 81 and has its other end pivotally connected with an end portion of a link 89. Upward movement of link 89 is limited by an adjustable stop device 9| which carries the bracket 84. The other end of link 89 is operatively connected with a rock shaft 92 which in turn is operatively connected with one end of a link 93 and it should be obvious that the previously described connections render the servomotor pistons l2 and 64 of the back pressure regulator and the speed governor, respectively, jointly and severally operable to effect a rocking movement of the shaft 92 and a corresponding reciprocation of the link 93.

The inertia governor 4 includes a shaft 94 which is also connected to the shaft 58, the gearing 55, a disk member 96 which is secured to the shaft 94 for rotation therewith, a sleeve structure 91 which is rotatably mounted on the shaft 94 and which is connected to the disk member 96 by means of a torsion spring 98 disposed in concentric relation about the shaft 94, and a bearing structure 99 in which the upper end of the shaft 94 is journaled. The upper end portion of the shaft 94 is provided with an axial bore IOI and radially extending bores I02 which place the axial bore IOI in communication with a pipe I03 by means of the annular space I04, bore I06 and annular space I01 provided in the bearing structure 99. Shaft 94 is also provided with another set of radially extending bores I88, which are arranged to place the axial bore IOI in communication with the slots I09 in the sleeve member 91 when the shaft 94 and the sleeve member 91 assume a predetermined angular relation. Slots I09 are provided with drain passages III and the arrangement is such that when the turbine is accelerated in excess of a predetermined rate, the shaft 94 is moved relative to the sleeve member 91 a sufficient distance in the direction indicated by the arrow in Fig. 2 to place the bores I08 in communication with the slots I09, thereby placing the annular space I04, which is connected with the pump 34 by means of a pipe I I2 containing a suitable constriction II3 and the pipe 38,

with the drain passages III. Disk member 96 is provided with a dashpot mechanism H4 and a diametrically disposed balancing weight II6, but

if desired, another dashpot may be employed in place of the weight I I6. The dashpot mechanism includes a piston I I1 (see Fig. 4) which is provided with a plurality of openings II8, an annular valve member -I I9 arranged to close said openings, a weak spring I2I acting to maintain .the valve member in a position closing said openings.

and one or more slots I22 in the periphery of the piston I I1. Piston H1 is provided with a stem I23 which is operatively connected with a slot I24 provided in the adjacent depending portion of the sleeve member 91 (see Fig. 3) by means of a bell crank lever I26 Journaled on a bracket I21 carried by the disk member 96. The arrangement is such that when the acceleration of the turbine is sufficiently rapid to effect an angular movement of the shaft 94 and the disk member 96 secured thereto relative to the sleeve member 91 (note the arrow shown in Fig. 2), piston H1 is moved upward and affords but little resistance to such movement since the resulting pressure and suction acting on the top and bottom surfaces of the valve I I9 respectively causes the vane to immediately uncover the openings H8; and that when the acceleration decreases below said predetermined rate, the spring I2I causes the valve I I9 to again cover the openings II8, thereby rendering the spring 98- ineffective to rapidly return the piston II1 to the position shown. The rapidity with which the piston is returned to said position is obviously determined by the number and the size of the peripheral slots I22.

The fluid operator 6 includes a double acting power piston I28, a hollow valve I29 controlling operation of piston I28, a hollow double acting piston I3I which has its bottom wall bolted to the spider I30 provided on the valve I29. and a pilot valve I32 extending coaxially within the piston I3I for controlling same. Valve I29, which is disposed within a stationary sleeve member I33 and forms therewith an annular space I34 communicating with the fluid supply pipe 38 by means of a bore I36, an annular space I31 and the bores I38, controls a plurality of upper and lower ports I39 and MI, respectively, which communicate with the annular spaces I42 and I43 and the passages I44 and I46 respectively. The space I41 within and beneath the valve I29 communicates with a drain pipe I48 which in turn communicates with the reservoir 44. The arrangement is such that when the valve I29 is moved upward from the position shown, fluid under pressure flows from the annular space I94 through the ports I39 into the space I42 and through the passage I44 to the space I49 at the top side of the piston I28 and the fluid in the space I5I beneath the piston I28 flows through passage I46, annular space I43, ports I, and space I41 into the drain pipe I48, thereby effecting a downward movement of the piston I28; and that when the valve I29 is moved downward from the position shown, fluid under pressure flows from the annular space I34 through ports I" into the space I43 and through the passage I46 into the space I5I at the bottom of the piston I28 and the fluid in the space I49 at the top ofthe piston I28 and the fluid in the space I49 at the top of the piston I 28 flows through the passage I44, annular space I42, ports I39, the interior of valve I29, and space I41 into the drain pipe I48, thereby effecting an upward movement of the piston I28. Piston I28 is provided with a rod portion atively connected with the turbine admission valve I by means of a bell crank lever I53 fulcrumed on a bracket I54, link I56, and a lever I51 having an intermediate portion fulcrumed at I68.

The lower interior portion of piston I3I is counter bored and closed by apap member I59 to provide an enlarged circulalrgspace I6I in which is slidably disposed a hollow piston I62.

Upward movement of piston I62 is-limited by an annular shoulder I63 and the piston I62, which has a lower portion of reduced'diam'eter, is normally held against said shoulder by fluid under pressure which is admitted to the .space beneath the piston by means of a passage I64 terminating at its upper end in an annular groove I66, an annular groove I61 in piston I3I which is always in communication with the groove I66, and a passage I68 which places the groove I61 in communication with a branch pipe I69 which is connected with the fluid supply pipe I03. The interior of piston I62 is provided with an annular flange III on which is disposed a spring I12 having its upper end abutting an annular shoulder I13 provided by the counter-boring of the interior of the power piston I3I. Spring I12 acts to urge piston I62 downward from the position shown. Pilot valve I32 has a stem portion I14 which extends into the piston I62 and beyond the annular flange "I provided therein and which is provided with at its lower end a laterally projecting annular part I16 disposed approximately halfway between the bottom surface of the flange HI and the inner surface of the piston head. The arrangement is such that when the space beneath the piston I62 is connected to a drain pipe or the like, the resulting reduction in fluid pressure permits spring I12 to move the piston I62 downward .a suificient distance to engage the bottom surface of the annular flange I'II with the projection I16 on the pilot valve I32 and thereby effect a downward movement of said valve. continuous communication with the space I15 immediately beneath the cap member I59 of piston I3I, the space I41 and the drain pipe I48.

The pilot valve I32 is also provided with axially spaced enlarged portions I18 and I19; the former controlling the flow of fluid from the annular space I 8I beneath the piston I3I through the passage I82, the space I83 surrounding an I52 which has an intermediate part oper- A passage I11 places the space I6I in intermediate stem portion of valve I32, and the port I84 into the annular space I86 at the top of the piston I3l and the latter controlling the flow of fluid from the space I83 through the port I81 into the annular space I88 and through the passage I89 to the space I15, thereby placing the space I86 in communication with the drain pipe I48.

The space I8I is in continuous communication with the source of fluid under pressure, the pump 34, by means of a passage I9I which is in communication with the passage I36 and thereby pipe 30. The motion producing portion of the piston surface which is acted upon by the fluid in the space I8I is materially less than that acted upon by the fluid in the space I86 and, as a result, the arrangement is such that when the pilot valve I32 is moved downward from the position shown, fluid under pressure flows from the space I8I through the passage I82, space I83, port I84 and into space I86, thereby effecting a downward movement of the piston I3I which is sufficient to bring the passage I82 in closing relation with the enlarged portion I18 of the pilot valve and that when the pilot. valve I32 is moved upward from the position shown, fluid in the space I86 flows through port I84, space I83, port I81, space I88, passage I89, spaces I and I41, and into the drain pipe I48, thereby effecting an upward movement of the piston I3I which is sufficient to bring the port I81 in closing relation with the enlarged portion I19 of the pilot valve.

As previously pointed out, a movement of valve I29, which is secured to the cap portion I59 of piston I3I, produces an opposite movement of piston I28 and it should therefore be obvious that whenever the pilot valve I32 moves downward, the piston I3I and valve I29 also move downward and-the piston I28 moves upward and that whenever the pilot valve I32 moves upward, the piston I3I and valve I29 also move upward and the piston I28 moves downward. The upper end of piston rod I52 is operatively connected with one end of a lever I92 which has an intermediate' portion held in operative engagement with the upper end portion of the stem of pilot valve I32 by means of a spring I90 and which has its other end held in operative engagement with the end of link 93 by means of a spring 95. An upward movement of piston I28, which is effected by a downward movement of pilot valve I32, piston I3I and valve I29, produces a clockwise movement of lever I92 about its point of connection with link 93 which in turn effects an upward movement of pilot valve I32 and the return of pilot valve I32, piston I 3| and valve I29 to the positions shown. Obviously, a downward movement of piston I 28 will also effect a return of the pilot valve I32, the piston I3I and the valve I2 9 to the positions shown. Bell crank lever I53, link I56 and lever I51 render upward and downward movements of piston I28 operable to effect closing and opening movements of the turbine admission valve 1, respectively.

The overspeed trip mechanism 8 includes a conventional flyball mechanism I93 which is operatively connected with the turbine shaft 59 and with an axially movable rod I94. The arrangement is such that when the turbine speed exceeds a predetermined maximum, the flyball mechanism I93 moves the rod I94 axially toward the left as viewed in Fig. 1 and against the pivoted latch member I96 with sufficient force to disengage same from the reciprocable locking bar I91. Bar I91 is operatively connected with the turbine cut-off valve 9 by means of a rock shaft I98, a link I99 on which is mounted a suitable weight 20I, a bell crank lever 202, link 203, and a pivoted latch member 204 which is arranged to engage and hold the axially movable member 208 of valve 9 in the position shown. Member 206 which is provided with a radially projecting and axially extending rotation preventing rib or key 201, is slidably mounted in the valve casing 9 and upward movement thereof is limited by an annular bottom flange 208. The valve 9 also includes a plug portion 209 and a stem portion 2 which extend through and threadably engage an internally threaded bore 2I2 which extends axially through the member 206. A spring 2I3 urges the valve toward its fully closed position and the arrangement is such that with the parts in the position shown, disengagement of the latch member I96 results in the weight 20I effecting a downward movement of the link I99 which in turn effects (1) a counterclockwise movement of rock shaft I98 and a downward movement of the locking bar I91 and (2) a clockwise movement of bell crank 202 and the disengagement of the latch 204 from the member 206 whereupon the spring 2I3 effects a closure of the valve 9; the member 208 moving downward with the valve stem 2| I. The valve 9 remains closed and the flow of motive fluid terminates, irrespective of the position of the admission valve 1, until the overspeed trip mechanism is again reset to hold the valve 9 open. Resetting of the overspeed trip mechanism 8 is preferably accomplished by first turning the valve stem 2I I, which effects an upward axial movement of member 206, until the flange 288 thereon engages the inner surface of the valve casing as shown; thenraising the weight 20I and link I99 until the locking bar I91 is in a position to be engaged by the latch member I96 (this movement of link I99 also engages the latch member 204 with the valve memher 206), then moving the latch member I96 into locking engagement with the bar I91 which retains the parts, with the exception of the plug ,member 209 which is still in closed position, in

the relative positions shown, and then continuing to turn the valve stem 2II until the plug memher is moved upward sufficiently to effect the desired degree of valve opening. Rock shaft I98 is also operatively connected with a balanced valve structure 2I4 which together with a pipe 2 I 6 provides a connection between the fluid supply pipe H2 and the drain pipe I48. Valve 2I4 includes spaced piston portions 2I1 and 2I8 defining therebetween a space 2I9 which is in continuous communication with the pipe H2. The lower interior portion of the valve casing is enlarged at 22l and a downward movement of the piston portions 2I1 and 2I8, which is effected by a release of the overspeed trip mechanism as previously described, places the space 2I9 and thereby the pipe H2 in communication with the enlarged portion HI and thereby the drain pipe I48.

Under normal conditions, the speed governor 3, which is operatively connected with pilot valve I32 of the operator 6 by means of lever 82, link 86, lever 88, link 89, rock shaft 92, link 93 and lever I92, operates in response to a decrease in turbine speed and effects an upward movement of pilot valve I32 and thereby a downward movement of piston I28 and an opening movement of the admission valve 1. Obviously an increase in turbine speed effects a downward movement of pilot valve I32 and thereby an upward movement of piston I28 and a closing movement of the admission valve 1. Normally, the back pressure regulator 2, which is operatively connected with the pilot valve I32 by means of lever 88, link 89, rock shaft 92, link 93 and lever I92, operates in response to a decrease in turbine exhaust pressure and effects an upward movement of pilot valve I32 and thereby a downward movement of piston I28 and an opening movement of admission valve 1. Obviously, an increase in turbine exhaust pressure effects a downward movement of pilot valve I32 and thereby an upward movement of piston I28 and a closing movement of admission valve 1. As previously described, the interconnection between levers 82 and 88 renders the speed governor 3 and back pressure regulator 2 jointly and severally operable to vary the position of the turbine admission valve 1.

In the event the speed of the turbine is accelerated in excess of a predetermined rate, the inertia governor 4 immediately operates as previously described and places the ports I08 in communica- -,tion with the slots I09, thereby connecting the fluid supply line I03 and the branch pipe I69 with the drain passage III. Pipe I03 receives fluid under pressure through pipe II2 which contains the constriction H3 and because of said constriction, the'connection of the pipe I03 to drain passage III effects an immediate reduction in the pressure of the fluid in the space beneath the piston I52 and as a result, the spring I12 immediately moves the piston I62 and thereby the pilot valve I 32 downward which in turn eiIects an upward movement of piston I28 and the closure of the turbine admission valve 1. Spring I12 is materially stronger than spring 95 and as a result the above described downward movement of pilot valve I32 is accompanied by a pivotal movement of lever I92 about its point of connection with piston rod I52 and a corresponding compression of the spring 95. Consequently, the upward movement of piston I28 effects, instead of the usual movement of lever I92, i. e., a pivotal movement of the lever I92 about its point of connection with link 93 and a return movement of the pilot valve I32 to the position shown, a pivotal movement of lever I92 about its point of connection with the stem of pilot valve I32 and a further compression of the spring 95. Consequently, the piston I28 now operates to completely close the admission valve I rather than to merely move said valve toward its closed position. Therefore, it should now be obvious (1) that the pilot valve I32 remains in the position to which it is moved by the spring I12 until the connection between the pipe I03 and the drain passage III is terminated or if in the meantime the overspeed trip mechanism should operate, until the overspeed trip mechanism is again reset which repositions the valve 2 to terminate communication between the pipe H2 and the drain pipe I48; (2) that the dashpot mechanism H4 is operatively associated with the inertia governor to interpose a predetermined time delay between a reduction in the acceleration below said predetermined maximum and the termination of the connection between the pipe I 03 and the drain passage III; (3) that during the time interval the pipe I 03 is connected with either the drain passages I I I or the drain pipe I48, the springs 85 and 81, which hold the ends of the levers 82 and 88 in operative engagement with the ends of link 88, render the speed governor 3 and the back pressure regulator 2 inoperative to effect an upward movement of the link 93, i. e., a

movement of the link 93 in a direction tending to effect an opening movement of the turbine admission valve 1; (4) that unless the overspeed trip has operated, the termination of the connection between the pipe I03 and the drain passages III immediately restores the system, to normal operating conditions, i. e., the admission valve 1 is placed under the control of the speed governor 3 and back pressure regulator 2 which are jointly and severally operative to effect regulating movements thereof; and (5) that the operation of the overspeed trip mechanism effects an immediate closure of the turbine cut-ofi valve 9 and a substantially simultaneous closing of the turbine admission valve 1, closure of the latter being effected by actuating the valve 2I4 to place the pipe H2 and thereby the pipe I03 in communication with the drain pipe I48 which, as previously described, renders the spring actuated piston I62 operative to close the admission valve 1 and the speed governor 3 and the back pressure regulator 2 inoperative to eifect an upward movement of the link 93.

It should also be obvious that the inertia governor 4 and the overspeed trip mechanism 8 are responsive to entirely different conditions of speed; the former being responsive to the rate.

of speed increase and the latter being responsive to the extent of speed increase irrespective of the rate of increase. Consequently, if the rate of speed increase is sufficiently rapid, the inertia governor 4 effects an immediate closure of the admission valve 1, which in most instances prevents an insuiflcient increase in speed for the operation of the overspeed trip mechanism, and after a relatively short time interval again places the admission valve 1 under the control of the speed governor 3 and/or the back pressure regu- 49 lator 2 without an interruption of power development. However, if the speed gradually increases to an excessive degree, the inertia governor remains inoperative, and the overspeed trip mechanism operates to effect a complete shut-down as previously described.

The invention is applicable to prime movers generally and although it has been illustrated and described in connection with the control of an elastic fluid turbine, it should be understood that it is not desired to limit the invention to either the exact mode of operation or the exact details of construction herein shown and described as various modifications within the scope of the apperided claims may occur to persons skilled in the ar It is claimed and desired to secure by Letters Patent:

1. In combination in a prime mover embodying means for conducting motive fluid to the prime mover and control means including a governing device for automatically regulating the flow of motive fluid to said prime mover in accordance with variations in an operating condition thereof, an inertia device movable independently of said governing device in response to the rate of change of prime mover speed, said control means including at least one part which is moved to a position for eifecting a termination of said flow in response to a speed-increasing pro-.

duced movement of said inertia device, and additional means operative to retain said part in said position for a time interval suificient to terminate said flow each time said part is so positioned by a speed-increasing produced movement of said inertia device.

2. In combination, a prime mover, means for. conducting motive fluid to said prime mover, a first means operative to vary and to terminate the flow of motive fluid to said prime mover, a governing device movable in response to changes in an operating condition of said prime mover, an acceleration device movable independently of said governing device in response to the rate of change of prime mover speed, control means responsive to and rendering said movements of the governing device operative to actuate said first means for varying said flow, and additional control means responsive to and rendering a speed-increasing produced movement of said acceleration device operative to initiate and complete a flow terminating actuation of said first means, said additional control means including time delay apparatus operative to retain said first means in its flow terminating position for a predetermined time interval each time a flow terminating actuation of said first means is initiated by a speed-increasing produced movement of the acceleration device.

3. In combination. a prime mover, means for conducting motive fluid to said prime mover, a first means operative to vary and to terminate the flow of motive fluid to said prime mover, a governing device movable in response to changes in an operating condition of said prime mover, control means including an element responsive to and rendering the movements of said governing device operative to actuate said first means for varying said flow, an acceleration device movable independently of said governing device in response to the rate of change of prime mover speed, and additional control means responsive to said acceleration device and including a movable member controllably associated with said element, said additional means being operative in response to a speed-increasing produced movement of said acceleration device to place said element in a position eifective to initiate a flow terminating actuation of said first means and to retain said element in said position for a time interval sufficient for said first means to terminate said fiow.

4. In combination, a prime mover, means for conducting motive fiuid to said prime mover, a first means operative to vary and to terminate the fiow of motive fluid to said prime mover, a governing device movable in response to changes in an operating condition of said prime mover, control means including an element responsive to and rendering the movements of said governing device operative to actuate said first means for varying said flow, a movable member controllably associated with said element and operable, when moved a predetermined distance from one position thereof, to position said element for immediately effecting a flow terminating actuation of said first means, an acceleration device responsive to the rate of change of prime mover speed, and a second means controlled by said acceleration device for efi'ecting said movement of the member and for positioning and retaining same in its said one position, said second means being operative to move said member said predetermined distance from said one position thereof in response to the speed of the prime mover increasing in excess of a predetermined rate.

5. In combination, a prime mover, means for conducting motive fluid to said prime mover, a first means operative to vary and to terminate the flow of motive fluid to said prime mover, a

governing device responsive to changes in an operating condition of said prime mover, control means including an element responsive to and rendering the movements of said governing device operative to actuate said first means for varying said flow, a movable member controllably associated with said element and operable, when moved a predetermined distance from one position thereof, to position said element so that said first means is actuated to quickly terminate said flow, a second means acting to move said member said predetermined distance, an acceleration de vice responsive to the rate of change of prime mover speed, and additional control means responsive to said acceleration device for positioning and controllably retaining said member in its said one position, said additional means being operative in response to a speed-increasing produced movement of the acceleration device to release said member for a time interval sufficient for said second means to move said member said predetermined distance.

6. In combination, a prime mover, means for conducting motive fluid to said prime mover, a first means operative to vary and to terminate the flow of motive fluid to said prime mover, a governing device responsive to changes in an operating condition of said prime mover, control means including an element responsive to and rendering the movements of said governing device operative to actuate said first means for varying saidflow, a movable member controllably associated with said element and operable, when moved a predetermined distance from one position thereof, to position said element so that said first means is actuated to quickly terminate said flow. a second means continuously acting to move said member said predetermined distance, a source of fluid under pressure connected with and operable to position and retain said member in its said one position, an acceleration device responsive to the rate of change of prime mover speed, and additional control means responsive to said acceleration device for quickly reducing the pressure of the fluid acting on said member sufllciently to render said second means effective to move said member said predetermined distance.

7. In combination, a prime mover, means for conducting motive fluid to said prime mover, a first means operative to vary and to terminate the flow of motive fluid to said prime mover, a governing device responsive to changes in an operating condition of said prime mover, control means including an element responsive to and rendering the movements of said governing device operative to actuate said first means for varying said fiow, a movable member controllably associated with said element and operable, when moved a predetermined distance from one position thereof, to position said element so that said first means is actuated to quickly terminate said flow, a second means operative to move said member said predetermined distance, an acceleration device movable in response to the speed of the prime mover increasing in excess of a predetermined rate, an overspeed device movable in response to the prime mover attaining a predetermined high speed, a third means operative to position and retain said member in its said one position, and additional control means responsive to and rendering said movements of the acceleration and overspeed devices severally operative to render said third means inoperative for a time interval sumcient for said second means to move said member said predetermined distance.

8. In combination, a prime mover, means for conducting motive fluid to said prime mover, a first means operative to vary and to terminate the flow of motive fluid to said prime mover, a governing device responsive to changes in an operating condition of sa. id prime mover, control means including an element responsive to and rendering the movements of said governing device operative to actuate said first means for varying said flow, a movable member controllably associated with said element and operable, when moved a predetermined distance from one position thereof, to position said element so that said first means is actuated to quickly terminate said flow, a second means operativ to move said second member said predetermined distance, a third means operative to position and retain said memher in its said one position, an acceleration device 20 ing produced movement of the acceleration device to render said third means inoperative for a time interval sufficient for said second means to move said member said predetermined distance.

9. In combination, a prime mover, a first means operative to vary and to terminate the flow of motive fluid to said prime mover, a governing device movable in response to changes in an operating condition of said prime mover, an acceleration device movable independently of said governing device in response to the rate of change of prime mover speed, and control means including a part responsive to and rendering movements of said governing device operative to actuate said first means for varying said flow, said control means including at least one additional part responsive to and rendering a speed-increasing produced movement of said acceleration device operative, independently of said governing device, to initiate and continue a flow-terminating actuation of said first means until said flow is terminated.

JOHN R. HAGEMANN.

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