US3508443A

US3508443A - Emergency governor exerciser

Info

Publication number: US3508443A
Authority: US
Inventors: Norman E Nutter
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1968-06-20
Filing date: 1968-06-20
Publication date: 1970-04-28
Anticipated expiration: 1987-04-28

Description

1970 N. E. NUTTER 3,508,443

EMERGENCY GOVERNOR EXERCISER Filed June 20; 1968 INVENTOR NORMAN E. NUTTER,

BY 40. Q. ms ATTORNEY.

United States Patent US. Cl. 73-509 4 Claims ABSTRACT OF THE DISCLOSURE A device for exercising or testing an emergency governor by injecting pressurized fluid inside the rotating governor cavity from a plunger arranged to move against the end of the governor shaft. Pressure builds up within the governor causing the governor to be exercised.

BACKGROUND OF THE INVENTION Prime movers, such as steam turbines, are generally supplied with an emergency overspeed governor ,to trip an overspeed mechanism and shut down the prime mover in the event of overspeed. Since such occurrences are relatively rare, it is desirable to provide a device to periodically test or exercise the overspeed governor to insure that it is in proper working order. Many systems have been devised for exercising the emergency governor while the prime mover is running without actually tripping out or overspeeding the prime mover, examples of such systems being seen in US. Patents 2,926,680, Eggenberger; 2,998,- 017, Cavalieri; and 3,342,194, Dwight, all assigned to the present assignee.

All of the foregoing patents employed an emergency governor which incorporated a ring or bolt with an offcenter cavity for exercising the governor. Introduction of hydraulic fluid into the cavity created an added off-center mass which tended to move outward due to the centrifugal force of rotation, thereby creating an artificial overspeed condition in so far as the governor was concerned. This type of testing mechanism is well known and exemplified by US. Patent 1,666,490, Dryer, assigned to the present assignee.

One of the shortcomings of the foregoing type of governor exerciser is that the centrifugal force on the'oilfilled cavity is dependent upon the speed of rotation. Therefore, the testing mechanism becomes less effective with reduced speeds. This caused the testing mechanism tobe less useful on variable speed turbines.

It has been suggested in the prior art that the oil dump type 'of emergency governors can also be tested by dumping or evacuating a pressurized governor cavity, as shown in US. Patent 3,026,891, Hoffman, but such testing devices are based upon a system involving normal oil pressure within the governor cavity for normal overspeed op: eration and usually re'quiresome type'of rotating-seal;

Accordingly, one object of the present invention is to provide an improved emergency governor exerciser which enables testing the emergency governor over a wider range of prime mover operating speeds than with previous designs.

Another object of the invention is to provide an improved device for exercising an emergency governor of the olf-center bolt type with a pressurizing fluid.

DESCRIPTION OF THE DRAWING The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of practice, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawing, in which the single figure of the drawing is a sectional detailed view of the emergency governor exerciser.

SUMMARY OF THE INVENTION Briefly stated, the invention is practiced by providing a piston area on a spring-biased off-center bolt and an inlet port through the shaft to the rotating governor cavity. A spring-biased orificed plunger is disposed to move against the inlet port and inject pressurized fluid therethrough to move the off-center bolt to a tripping position. The pressurizing fluid also provides a lubricating function to reduce wear between shaft and plunger.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawing, the end of a rotating shaft member 1 is arranged to incorporate an emergency governor 2 which actuates a trip lever 3 in the event of overspeed. Other devices, not shown, and not material to the present invention, bring the shaft 1 to rest and may include provi s'ion for resetting the trip lever 3.

The emergency governor 2 may take various forms but as shown here comprises an off-center bolt 4, slidably disposed in members 5, 5a. Members 5, 5a are threaded into either end of a hole through the shaft so that they may be adjusted to set the biasing force of a spring 6 and to balance the device.

The threaded members 5, So also close off either end of the hole through shaft 1 to define a chamber 7. An access hole 8 to chamber 7 is preferably located on the shaft centerline and the shaft end 9 is machined to a flat or planar surface. The off-center bolt 4 includes a piston area 10 exposed to chamber 7 and located on the same side of the shaft centerline as the eccentrically disposed center-of-mass 11.

Other devices (not shown and not material to the present' invention) are arranged to deactivate the normal prime mover trip system when the exerciser is actuated. These may be systems as described in the aforementioned Eggenberger, Cavalieri and Dwight patents. It will be understood that actuation of lever 3 by the exerciser to be described will not actually shut down the prime mover, which may be running while exercising takes place.

A pressurized fluid injector, shown generally at 12, is

disposed close to the end of shaft 1. The injector comprises a stationary body 13 with a bore 14 coaxial with theshaft centerline. An injector plunger 15 is held slidably disposed in the bore by means of a land 16 and a collar 17. It is lightly biased to the seated position shown by means of a spring 18. The plunger includes an access hole 19 to its hollow interior and an outlet orifice 20 coaxial with the shaft centerline.

The construction of the plunger 15 will vary somewhat with'design's but suitable resultslhave been obtained with a"1 diameter plunger having a a orifice at 20. The face end 21 of the plunger is flat and disposed about A; of an inch from the shaft end 9.

Two intersecting halfmoon slots 23 are cut in the face 21 of the plunger. These extend outward beyond the diameter of access hole 8 in the shaft so that oil will be supplied to the interface between surfaces 9, 21. Auxiliary flow may be provided, if desired, by means of additional small holes, such as 24.

Means to provide a pressurized fluid for testing purposes include a pressurized source, not shown, controlled by a valve 25 and an actuator 26. It will be understood that the actuator 26 may be, for example, a solenoid which is interconnected with a more complicated exerciser system in order to check the complete system and to prevent tripping the turbine inadvertently. The pressurized fluid of 200 p.s.i.

OPERATION The operation of the invention is as follows: Conventional overspeed tripping of the emergency governor 2 takes place when the speed of the shaft is suflicient for the force on the center-of-mass 11 of bolt 4 to overcome the bias of spring 6 whereupon the bolt moves outward to strike trip lever 3.

To actuate the trip mechanism 3 without shaft I reaching an overspeed condition, in accordance with the present invention, pressurized oil is admitted to chamber 14 by opening valve 25. Oil flowing into the interior of plunger 15 causes it to move to the right and to maintain it against the face 9 of the shaft end while oil continues to flow through orifice 20. The pressure drop across the orifice maintains a differential force which holds the plunger 15 in place. This is true even after the cavity 7 in the governor has been filled, due to slight leakage flow.

The oil pressure in cavity 7 acts against piston portion 10 of off-center bolt 4 to assist the off-center force which is also acting on the bolt center of mass 11. This causes the bolt to move outward and actuate trip mechanism 3.

An oil film is maintained between surfaces 9, 21 by viscous pumping flow due to rotation of the shaft end. Additional flow for this purpose may be provided by the small holes 24 in the plunger. This oil film acts to lubricate the surfaces to prevent wear.

For resetting, valve 25 is closed. As the pressure in cavity 14 is reduced, spring 18 will retract injector plunger 15. As oil drains from cavity 7 of the shaft, bolt 4 assumes its previous seated position.

Since the exercising of the governor is accomplished by pressure of the injected fluid, rather than by eccentric mass of the fluid as in previous devices, exercise of the governor is not wholly dependent upon speed of rotation. Therefore, exercise can take place at low speeds as well as high, which is desirable in variable speed applications.

While the embodiment shown has been designed for liquid or hydraulic fluid, it is also within the scope of the present invention to substitute air or pneumatic fluids to test the trip mechanism. Also a modification of the invention could include introduction of pressurized fluid from the shaft periphery rather than from the shaft axis.

The present arrangement, however, is very successful because of the lubricating and sealing functions performed by the hydraulic fluid at the shaft end.

What I claim is:

1. An emergency governor exerciser comprising:

a governor including a rotatable shaft portion defining a chamber with an inlet port and having an off-center member disposed therein with means biasing said member toward a seated position, said member being radially movable to a tripping position and having a piston portion thereon disposed to assist said movement when the chamber is pressurized,

injector means for selectively pressurizing the chamber to exercise said governor, said injector means comprising a plunger member coaxial with the shaft and axially movable in response to receipt of pressurized fluid and having an orificed outlet arranged to cover said shaft portion inlet port and inject pressurized fluid into said chamber when the plunger moves.

2. The combination according to claim 1, wherein said shaft portion inlet port comprises a shaft centerline hole and wherein said plunger member defines a flat face movable'to cover both the inlet hole and a portion of the shaft end, said face defining a slot extending beyond the. inlet hole and supplied with pressurized fluid from the orifice to lubricate the interface between plunger'and shaft.

3. The combination according to claim 1, including second biasing means retracting said plunger when pressurized fluid is cut off, said retracting movement of the plunger acting to uncover the shaft portion inlet port, whereby the chamber pressure is reduced and oil drained to allow the off-center member to return to a seated position. 1 t

4. An emergency governor exerciser comprising:

a source of hydraulic fluid under pressure,

a stationary body defining a second chamber arranged to selectively receive hydraulic fluid from said source and having a plunger member disposed therein coaxial with the shaft portion,

second means biasing said plunger member to a retracted seating position axial spaced from the shaft portion, said plunger defining an orifice coaxial with the shaft centerline,

said plunger face defining a slot supplied by the orifice and extending beyond the shaft inlet port, whereby introduction of pressurized hydraulic fluid will cause the plunger to move axially to supply fluid through said inlet port to exercise the emergency governor, said fluid also flowing radially outward between the plunger face and the shaft end to lubricate the interface between members.

References Cited UNITED STATES PATENTS 1,441,353 1/1923 Johnson 137-24 1,621,084 3/1927 Rigsby 137-24 1,622,100 3/ 1927 Flanders 137-24 X 1,623,822 4/1927 Wilkinson 137-24 X 1,666,490 4/ 1928 Dryer 137-24 1,756,850 4/1930 Caughey 137-24 1,970,420 8/1934 Floret 137-24 X CLARENCE R. GORDON, Primary Examiner' I US. 01. X.R. 73 54s; 137-798; 2s1 14 s; 415-16