US3004527A

US3004527A - Condition regulating apparatus

Info

Publication number: US3004527A
Authority: US
Inventors: Drake George Forrest
Original assignee: Woodward Governor Co
Current assignee: Woodward Inc
Priority date: 1959-07-09
Filing date: 1959-07-09
Publication date: 1961-10-17
Anticipated expiration: 1978-10-17

Description

Oct. 17, 1961 G. F. DRAKE 3,004,527

CONDITION REGULATING APPARATUS Filed July 9, 1959 2 Sheets-Sheet 1 Oct. 17, 1961 G, FDRAKE 3,004,527

CONDITION REGULATING APPARATUS Filed July 9, 1959 2 Sheets-Sheet 2 @Tw'o rams v f 3,004,527 CONDITION REGULATING APPARATUS George Forrest Drake, Rockford, Ill., assigner to Woodward Governor Company, Rockford, lll., a corporation of Illinois Filed .uly 9, 1959, Ser. No. 826,010 7 Claims. (Cl. 121-42) This invention relates to condition regulating apparatus of the hydraulic type shown in Patent 2,478,753. The control point of the apparatus is maintained at a constant value by a so-called restoring or compensating effect derived through the action of a spring loaded buffer piston through which pressure changes produced by a control valve are transmitted to a iluid servo.

The primary object of the present invention is to reduce the cost of manufacturing apparatus of the above character through a novel construction of the valve plunger which permits all of the various lands spaced along the plunger to be of the same diameter.

A more detailed object is to arrange the control valve and the associated parts in a novel relation which permits the two pressures for producing the compensating force to be applied to opposite ends of the valve plunger.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawing in which:

FIGURE 1 is a fragmentary sectional view and hydraulic circuit diagram of a speed governor embodying the novel features of the present invention.

FIG. 2 is a similar view of a temperature regulator.

While the improved control apparatus is illustrated in the drawings as applied to the regulation of speed and temperature, it will be apparent that the apparatus is applicable to regulators for various other conditions. Accordingly, I do notintend to limit the invention by the typical application herein disclosed but aim to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Referring first to the speed governor shown in FIG- URE l, a hydraulic servo for adjusting the throttle of a control prime mover is variably energized in response to speed changes detected by a speed senser 11 driven in synchronism with the prime mover through a shaft 12. The operating parts and fluid passages are mounted on and enclosed within a suitable multiple part casing indicated generally at 13. As shown, the servo 16 is of the single acting type comprising a piston 14 reciprocable in a cylinder 15 and urged in the fuel decreasing direction by a spring 16. The rod 17 of the piston may be connected to the engine throttle through a suitable linkage. As in the patented governor, the head end of the servo cylinder communicates through a passage 18 with one end of a cylinder 19 having a piston or wall 20 slidable therein and biased toward a centered position by two

compression springs

21 and 22 which are under some initial tension and adapted to exert equal and opposite forces on the wall 2li when the system is at equilibrium.

The opposite end of the cylinder 19 communicates with a passage 23 to which oil or other fluid under pressure is admitted from a supply passage 24 or from which the oil is released to a drain Vpassage 25 by opening of a valve 26 actuated by the speed senser 11. The valve is of the spool type and comprises an elongated plunger rod 27 having

guide lands

28 and 29 at opposite ends closely tting and slidable in an elongated bore 30 in the casing 13. These lands are spaced axially from an intermediatel or control land 31 of the same axial length as the diametrical width of a port 32 opening into the bore 30 at the ends ofthe passage 23.

3,994,527. Patented Oct. 17, 1961 fic Ports at the ends of the supply and drain passages 24V and 25 communicate at all times with spaces disposed within bore and surrounding the

stems

33 and 34 which connect the guide lands with the control land. With this arrangement, the port 32 is covered when the plunger is inthe centered position shown, thus closing olf the end of the passage 23. `In response to lowering of the land 31 from this position, pressure iiuid from the passage 24 is admitted to the passage 23, thus moving the wall 20 to compress the spring 21 and force fluid through the passage 18 into the servo cylinder 15 thereby adjusting the engine throttle to increase the fuel ilow. On the other hand, when the land 31 is moved above the port 32 in response to a detected speed increase, the valve 26 is opened to the drain passage 25. Under the action of the spring 16, fluid is forced out of the cylinder 15 as permitted by the escape of iiuid from the passage 23 and movement of the piston 20 to compress the spring 22.

Fluid at a substantially constant pressure is supplied to Ithe passage 24 by a suitable pump housed within the casing 13 and comprising gears 36, one of which is fast on the shaft 12 which is journaled in a bearing 37 and at its outer end is equipped with a coupling 38 in connection with a drive in the prime mover shaft. Oil discharged from the pump outlet is delivered to the supply passage 24 or by-passed back to the pump inlet 4i) through a valve 39 spring loaded to provide the desired supply pressure. The drain passage 25 communicates with the pump inlet 4?.

Preferably, the speed senser 1l is of the flyball type and includes a ball head 4l whose hub 41a is journaled in a bearing 42 and is integral with the inner end of the shaft 12. Fulcrumed on the ball head at 43 to swing about tangentially disposed axes are upstanding flyweights 44 having inwardly projecting arms 45 bearing upwardly at their free ends against a disk 46. The latter is pressed onto the lower extended end of the valve plunger 29 and carries the lower race ring of an anti-iriction thrust bearing 47.

The centrifugal force acting on the flyballs is balanced against the force of a compression spring 48 seated on the upper race ring of the bearing 47 and bearing upwardly against an abutment 49 adjustable from the exterior of the governor casing. To this end, an arm on the abutment is rigid with the inner end of a nut 56 slidable endwise by turning a screw 51 threaded into the nut with its head 52 outwardly exposed on one side of the casing. A suitable slip type pressure seal 53 provides a fluid tight connection between the casing and the head of the screw. By turning the latter back and forth, the force of the speeder spring 48 and therefore the speed setting of the governor may be adjusted for maintenance of the desired engine speed.

As fully described in the aforesaid patent, superatrnospheric pressures are maintained at all times in the oil yfilled cylinder 15 and valve control passage 23 and, in response to any speed change and the accompanying admission of fluid to or release thereof from this passage, there is developed between the two spaces a pressure difference of a sense which depends on the direction of the speed deviation away from the governor speed setting. r[he pressure difference is exerted on the valve plunger to produce a drooping cha-racteristic which is dissipated gradually by the leakage of fluid between opposite ends of the cylinder 19. Herein, such leakage is through a restriction 55 of small area extending through the buffer piston 20 and properly sized to produce the de which have the same diameter as the control land 31 so that the bore 30 and all of the plunger lands may be nished to the same diameter. As a result, the desired high precision in the sizing of the related surfaces may be achieved easily and at a greatly reduced cost.

To the foregoing end, the two areas for receiving the compensated pressures are disposed at opposite ends of the valve plunger 27 and are exposed within the casing 13 at the opposite ends of the bore 3) which cooperates with the land 3l to form the control valve. One of these areas indicated at 57 comprises the upper end of the land 2S and is exposed to the pressure in a chamber 58 communicating through a passage 59 with the servo cylinder l5. The other area is formed on the extended lower end of the plunger land 29 which extends into a chamber 61D enclosing the pressure senser il and cornmunicating with the valve control passage 23 through a passage 6i. The escape of pressure fluid from this chambere is prevented by the seal 53 and also by a similar slip type seal including a ring 62 of carbon or the like pressed against a finely inished surface on a flange 63 of the ball head. The sealing pressure is derived from a bellows 645 fastened to a ring 65 which is fastened by a snap ring in the casing recess and sealed to the casing wall by a bellows 66. The chamber G is thus effectually sealed against the escape of pressure uid along the drive shaft ,12.

The effective pressure area on the lower end of the plunger is the difference between the areas of the upwardly and downwardly facing surfaces on the extension of the land 2% and the parts joined thereto. Thus, this effective area is equal to the cross sectional area of the land 29 and therefore is equal in size to the upper area 57.

With the two pressure areas formed by opposite ends of the valve plunger and respectively facing outwardly from these ends, it will be apparent that the pressures are derived from the servo cylinder 15 and the passage -23 Without the necessity of providing a separate cylinder along the bore 3G. Moreover, the latter is finished to the same diameter throughout its length and, since al1 of the lands 2S, 2&9 and 31 are of the same diameter, the finishing of the valve plunger may be accomplished at low cost. It will be apparent that these advantages are achieved by the simple addition of the seals around the drive and Speeder spring adjusting shafts, such seals being more or less standard parts which may be assembled at low cost in the governor casing.

FIGURE 2 illustrates one way of utilizing the present invention in the measurement of temperature or pressure, in this instance temperature, and positioning the piston 14 of the servo 10 in accordance with the changing temperature values. For example, a force proportional to the temperature in a space whose temperature is to be measured may be derived from a rigid walled bulb 69 filled in the usual way with an expansible liquid and communicating with a capillary tube 68 extending to the casing i3 of the servo control mechanism. The parts of the latter in common with the apparatus first described are indicated by corresponding but primed reference numbers.

As before, the servo cylinder 1 5 communicates with one end of the cylinder i9' having a piston 2h' slidable therein and communicating at its other end with the space 23' to which fluid from the supply line 24 is admitted by the valve 26 or released to the drain line 25. Springs 2.1' and 22 urge the piston toward an equilibrium position, movement of the piston being permitted by iiuid leakage through the restriction 55' which, in this instance, is in a passage 72 connected to opposite ends of the cylinder 19.

To reduce static friction, the cylinder 30' of the slidable valve plunger Z7' is the bore of a sleeve 70 carried by a. continuously rotating shaft 71 and journaled inthe casing 13. The sleeve is ported and formed with external grooves communicating with ports at the ends of the Various iiuid passages.

The end of the land Z9 at one end of the valve plunger 27' is enclosed by the chamber 60 which communicates through the fluid filled passage 61 with the valve space 23' and the adjacent end of the cylinder 19'. -T he other end of the latter communicates through the passage 72 with the fluid lled chamber 58 Which'surrounds the end 57 of the land 28 and is closed so as to be maintained at the same pressure as the servo cylinder.

As in the apparatus iirst described, the invention contemplates the provision of means within one of the sealed chambers, in this instance the chamber 58', for exerting on the exposed end of the valve plunger a force which varies with the temperature to which the bulb 69 is subjected. Herein, this means includes a fluid iilled Ybellows 74 closed at its free end and sealed at its other end to the wall of the chamber 5S around the terminal end of the capillary tube 63. Within the chamber 58' the closed end of the bellows is pivotally joined to one end of a lever 75 fulcrumed at 76 intermediate its ends ou a lever 77 which crosses the lever 75. The other end of the lever 7S is connected to the closed free end of a second bellows 78 also disposed within the chamber 58' and sealed around the end of a. capillary tube 79 similar in length and exposed to the same ambient medium Ias the tube 68. The tube 7 9 is closed at its outer end 80.

With this arrangement and for a given temperature of the bulb 69, opposite endsof the lever 75 will move in opposite directions and through equal distances in response to the same temperature changes of the tubes 68 and 79. As a result, changes in the temperature of the signal transmitting tube 63 arevcompensated for automatically so that the fulcrum 76 moves back and forth parallel to the valve plunger and is always disposed in a position corresponding to the prevailing temperature of the bulb 69.

To convert the motion of the fulcrum 76 into a force proportional to the bulb temperature, one end of the lever 77 is connected to the end of the plunger land 2S through `a relatively stiff compression spring S1. The other end of this lever is pivotally connected within the chamber 58 with one end of a rod S2 extending outwardly through a seal S3 in the wall of the chamber 5S. A spring 84- urges the rod outwardly and holds the same against an abutment which is adjustable axially as by mounting on a plug 36 screw threaded into the casing 13 with its knurled head exposed on the exterior of the casing.

By adjusting the abutment 85, it will be apparent that the stressing of the spring S1 for a given temperature of the bulb 69 and position of the fulcrum 76 will he changed correspondingly. Thus, the control point of the temperature senser may be varied as desired.

l claim as my invention:

1. In a condition regulator, the combination of, a casing providing first `and second closed uid lled chambers connected by a cylindrical bore, a valve plunger having three lands of equal diameters axially spaced along its length and slidable axially in said bore, said plunger having axially facing pressure areas of equal size and no larger than said lands disposed at opposite ends and exposed to the duid in the respective chambers, means sealed in a wall of one of said chambers and transmitting therethrough a signal which varies with changes in a condition to be regulated, a condition senser enclosed in said one chamber and exerting on said plunger a force which varies with deviations in said signal, a port in Vthe Wall of said bore communicating with said first chamber and cooperating with the intermediate one of the lands to form a valve for admitting pressure iiuid to or releasing the same from said first chamber, a uid servo including a cylinder `communicating with said second chamber, a wall between said chambers yieldably urged in opposite directions and movable back andforth to transmit the pressure changes produced by opening of said valve, and a restricted passage permitting the slow leakage of uid therebetween to equalize the pressures therein.

2. Condition regulating apparatus, having in combination, a fluid lilled space, a lluid filled passage adapted for connection with a servo actuator, a movable wall separating said passage and said space and yieldably urged in opposite directions toward a centered position, means defning an elongated bore, means delining closed uid filled chambers enclosing opposite ends of said bore and respectively communicating with said space and said passage, a plunger slidable in said bore and having two end Ilands and one intermediate land of equal diameters axially spaced apart, the outer ends of said end lands providing outwardly facing pressure areas of equal size and no larger than said lands exposed to the fluid in said irst and second chambers respectively, means disposed in one of said chambers and operable to move said plunger in opposite directions away from said centered position in response to deviations in a condition to be regulated away from a predetermined value, a valve formed by said intermediate land and closed when said plunger is in said centered position but open to admit said pressure uid to or release said fluid from such space in response to opposite movements of said plunger away from such position, and means providing continuous restricted communication between said chambers.

3. In condition regulating apparatus, the combination of, a casing providing iirst and second uid filled closed chambers connected by a cylindrical bore, a valve plunger having three lands of equal diameters slidable in said bore, said plunger having pressure areas of equal size at opposite ends and exposed to the fluid in the respective chambers, said areas being no larger in size than said lands, means within one of said chambers exerting on said plunger a force which varies with the value of a condition to be regulated, a port in the Wall of said bore communicating with said lirst chamber, the intermediate one of said three lands cooperating with said port to form a valve for admitting pressure Huid to or releasing the same from said chamber, a fluid servo including a cylinder communicating with said second chamber, a wall between said chambers yieldably urged in opposite directions and movable back and forth to transmit the pressure changes produced by opening of said valve, and a restricted passage permitting the slow leakage of uid between said chambers.

4. In condition regulating apparatus, the combination of, a casing providing first and second closed tluid lilled chambers connected by a cylindrical bore, a valve plunger slidable in said bore and having pressure areas of equal size disposed at opposite ends and exposed to the uid in the respective chambers, means enclosed in one of said chambers and exerting on said plunger a force 'which varies With changes in the value of a condition to be regulated, a port in the wall of said bore communicating with said 'first chamber, a land intermediate the ends of said plunger cooperating with said port to form a valve for admitting pressure uid to or releasing the same from said first chamber, said pressure areas being no larger in size than said land, a lluid filled cylinder having opposite ends in closed communication with said rst and second chambers respectively, a piston slidable in said cylinder and yieldably urged toward a center position, and means providing for the slow leakage of uid between opposite ends of said cylinder.

5. Apparatus as defined in claim 3 in which said force exerting means comprises a rotary speed senser driven by a shaft projecting through a wall of said one chamber combined with a lluid tight seal around the shaft bearing.

6. Apparatus as defined in claim 3 in which said force exerting means comprises a bellows expansible and contractible in response to pressure changes therein and having one end sealed against the wall of said one chamber.

7. Apparatus as defined in claim 3 in which said force exerting means comprises a bellows expansible and contractible in response to pressure changes therein and having one end sealed against the wall of said one chamber, a tube providing a fluid lled passage extending through said wall and communicating with the interior of said bellows, and means disposed externally of said chamber and responsive to changes in said condition to vary the fluid pressure in the tube and said bellows.

References Cited in the le of this patent UNITED STATES PATENTS 2,400,126 Matthews May 14, 1946 2,478,752 Drake Aug. 9, 1949 2,478,753 Parker Aug. 9, 1949 2,654,348 Beck Oct. 6, 1953 2,782,769 Best Feb. 26, 1957