US2588166A - Variable pitch propeller - Google Patents

Description

March 4, 1952 c. R. SACCHINI 2,588,166

VARIABLE PITCH PROPELLER Filed March 1, 1946 7 SheetsSheetvl /N VEA/TOP March 4, 1952 c. R. SACCH'INI VARIABLE PITCH PROPELLER Filed March 1, 1946 7 Sheets-Sheet 2 nvvavroe COLl/M5U5 e j/ICCH/N/ ATTOP/VEY March 4, 19 c. R. SACCHINI VARIABLE PITCH PROPELLER Filed March 1, 1946 7 Sheets-Sheet 3 Q INVENTOP C01. W505 la jACCH/N/ March 4, 1952 c. R. SACCHINI VARIABLE PITCH PROPELLER 7 Sheets-Sheet 5 Filed March 1, 1946 will OMN

lNVE/VTOP COLUMBUJE 5/4CCH/N/ Arrog/vfy March 4, 1952 c. R. SACCHINI 2,588,166

VARIABLE PITCH PROPELLER Filed March 1, 1946 7 Sheets-Sheet 6 INVENTOP COLUMBUS e JAcc/v/N/ HTTOP/VEY March 4, 1952 c. R. SACCHINI VARIABLE PITCH PROPELLER 7 Sheets-Sheet '7 Filed March 1, 1946 7 w m 6 9 7 0 Z m Z 2 7 3 a zze 2 1 FIG. /2

4% ATTORNEY FIG. 11

Patented Mar. 4, 1952 UNITED STATES 2,588,166 VARIABLE PITCH PROPELLER Columbus R. Sacchini, Willoughby, Ohio, assignor to The Marquette Metal Products Company, Cleveland, Ohio, a corporation of Ohio Application March 1, 1946, Serial No. 651,278

5 Claims. (01. 170-16931) This invention relates to a variable pitch propeller mechanism and particularly to a mechanism provided with fluid pumping and servomotor means connected with the blade or blades to be adjusted, which pumping means is operated as 5 a consequence of rotation of the propeller.

The general object is to provide an improved hydraulically operated controllable pitch propeller.

Another object is to provide an improved hy- 1 draulically operated controllable pitch propeller in which the operating fluid is contained in a sealed system rotatable with the propeller, characterized in that no matter how full of fluid thesystem is, no part of the fluid control mech- 1 anism can thereby be restricted against free operation.

Another object is to provide, in a hydraulically actuated controllable pitch propeller, an improved means for preventing the blade or blades from 2 being moved out of adjusted position by forces opposing the pitch adjusting mechanism of the propeller, and specifically to provide an improved hydraulically-acting anti-creep mechanism for the blade or blades. 2

A further object is to provide, in a hydraulically operated controllable pitch propeller, an improved means for controlling, independently of the speed of rotation of the propeller, the rate at which the blades are adjusted.

A further specific object is to provide a simplifled fluid actuated mechanism for initiating the operation of a blade pitch adjusting means.

A further object is to provide an improved hydraulically actuated selectively operable mechanism for causing initiation of operation of a blade pitch changing mechanism of a propeller.

A further object is to provide, in a hydraulically operated propeller, a blade pitch control system which includes a releasable pitch limiting latc H rendered operative in part by fluid in a hydraulically operated actuating system separate from the pitch adjusting mechanism, means to enable the actuating mechanism always to be operated instantly to a full functioning position where it is retained until the pitch limiting latch has been operated in a manner to permit blade adjustment to an abnorma1 pitch setting.

A concomitant object is to provide an improved means for enabling a latch-release-actuating hydraulic mechanism to be moved quickly manually into a self retaining position so as to store energy for subsequent hydraulic operation.

A further object is to provide an improved manually operable hydraulic actuator for an oppositely acting blade pitch adjusting mechanism of a propeller, which actuator is self centering to neutral position upon release of manually applied force.

Other objects and features of the invention will so become apparent from the following description of the illustrative forms shown in the drawings, wherein:

Fig. l is a longitudinal assembly sectional view in a vertical plane of a propeller mechanism of the three-blade type;

Fig. 2 is a view partly in section as indicated by the line 2-2 on Fig. 1 and showing, in elevation, the preferred hydraulic actuator mechanism;

Fig. 3 is a schematic assembly view showing the fluid supply, pumping mechanism and part of the hydraulic actuator system in one form;

Fig. 4 is a central longitudinal sectional view of one of two fluid control units shown schematically on Fig. 3;

Fig. 5 is a fragmentary central sectional view of a fluid control unit similar to that shown by Fig. 4, provided for control of the pitch limiting latch mechanism;

Fig. 6 is a detail sectional view as indicated at 6-5 on Fig. 4, showing a typical shape of valve plungers used in the fluid control units;

Fig. 7 is a schematic partial assembly view similar to Fig. 3, but showing a somewhat modified arrangement of fluid control mechanism;

Fig. 8 is a view similar to Fig. 4, showing more in detail part of the modified construction according to Fig. '7;

Fig. 9 is an elevational view of the unit similar to Fig. 8, shown partly in central section;

Fig. 10 is a vertical sectional view of the main hand pump or actuator portion of the mechanism shown at the right in Fig. 2;

Fig. 11 is a sectional detail view taken as indicated at |I-ll onFig. 2;

Fig. 12 is a detail sectional view taken along the plane indicated at l2-l2 on Fig. 11, and

Fig. 13 is a detail sectional view taken at l3-I3 on Fig. 10.

Referring further to the drawings, Figs. 1 to 5 inclusive, the assembly shown by Fig. 1 shows a propeller mechanism I including a central hub 2, formed as a hollow steel forging with a spheroidal central portion 3 and parallel annular front and rear .end flanges 4 and 5. The forging includes equally spaced radially extending barrel portions 6, one being shown, for supporting blade assemblies such as]. Each barrel portion 6 contains suitable bearings enabling the blade assembly to be rotatably adjusted in opposite directions for forward pitch in a normal pitch range, further adjusted forwardly for feathering and reversely adjusted beyondnormal low pitch as for braking.

The hub 2 is mounted on a central hub carrier 8, suitably secured as by a key 9 to a, tapered portion oi an impeller shaft III. A sleeve-like nut engaging threads on the forward end of the shaft further secures the shaft to the hub carrier. J A pitch adjusting 'servomotor M has a w housing or block l2, partly surrounding the sleeve portion |3 of the nut II, and appropriately secured to the hub as against the forward flange 4 thereof.

Journalled between the forward portion of the hub carrier 8 and the servomotor block l2 (partly supported by both) is a master pitch adjusting gear element l5, having gear teeth "i in mesh with teeth of respective tubular por-' tions ll of the blade assemblies. Each tubular portion I! has a pilot bearing at |8 on the hub carrier.

The mechanical parts of the servomotor M comprise identical but relatively oppositely acting pistons and 20' in cylinders 2| and 2| respectively carried in the motor block I2. Each piston 20 has rack teeth 22 in constant mesh with.

gear teeth 23 on the forward sleeve portion of the gear l5, so that as the pistons are reciprocated the blades are adjusted through the master able flller opening, not shown, and is suitably sealed off from the hollow interior of the hub forwardly from the sump and also sealed around the central portion of the hub carrier and impeller shaft. 'The walls forming the sump chamber thus rotate with the hub whenever the pro peller is turned by the shaft l0.

Behind the closure plate 26 of the sump is a fixed, that is nonrotatable, framework 28 providing a generally closed chamber 29 peripherally sealed as by the telescoping joint assembly 29 (top, Fig. 1) so that the chamber 29 may retain suitable lubricant for a fluid control actuator cam mechanism to be described and contained in the chamber 29. Fluid supplied from the sump chamber is selectively pumped to oppositely operating portions of the servomotor M by one.

or the other of two hydraulic control (pumping and valving) units of substantially identical form indicated at 30 and 3|, Fig, 3. A pump plunger 340i the unit 30, through suitable communicating lines partly indicated at 32,;supplies the pressure chambers P and PI of the servomotor and the pump plunger of the unit 3|, through a communicating line diagrammatically indicated at 33," supplies the pressure chambers P2 and P3 of the servomotor.

The hydraulic control units 30 and 3| alsocontain exhaust valve mechanisms generally indicated at 36 and 31. The exhaust valve mechanisms are operated in timed relation to the operation of the pumps 34 and 35 in such a manner that when, for example, the pump 34' supplies fluid to the servomotor chambers P and PI, the exhaust valve mechanism 31 is operated to vent used fluid from the servomotor spaces P2 and P3 to the sump; and when the pump 3'5 of unit 3| is operated, the exhaust valve' mechanism 38 of unit 30 operates to vent fluid from chambers P and PI.

A pitch limiting mechanism generally indicted at 40, Fig. 3 only, cooperates with an element of the servomotor mechanism normally to limit pitch adjustment of the blades in either direction within a range suitable for forward driving and, abnormally, to limitpitch adjustment beyond that range in opposite directions. As shown, a

4- 0 servomotor or plunger 4| of the pitch limiting mechanism operates in a suitable cylinder 42 and has a latch portion 43 normally seated in a recess 44 in, for example, the piston 20.

In the actual design (not shown) the latch 43 cooperates with stepped depression in the forward face of the gear l5, the plunger 4| being mounted in the pitch adjusting servomotor ho -.sing l2.

The normal pitch limits are established by abutments 45 and 46 defining parts of the depression 44; and beyond those abutments, in respective directions of movement of the piston 20, are spacesdefined in part by limiting abutments 41 and 48. The plunger 4| is withdrawn to the illustrated position, against the force of a return spring {-49, by fluid forced by a pumping unit generally indicated at 50, mounted on the hub carrier and operated essentially the same as are the units 30 and 3|. The pump plunger 53 of the unit is connected with a pressure chamber 5| of the latch plunger 4| by a suitable conduit represented in simplified form at 52, Fig. 3. T..c

fluid forcing unit 50 is controlled at the will of the operator to withdraw the latch plunger menber 43 from thevdepression 44 whenever it is desired to effect reverse pitch as by movement of the piston 20 beyond the latch abutment 48 in the direction toward the abutment 48 and also whenever it is desired to move the piston in the. opposite direction past the abutment 45 for feathering.

Reference may be had to an application of Gordon W. Hardy, 629,539, filed November 19,

1945, now Patent Number 2,515,037, issued July. 11, 19,50, and owned by the assignee hereof, for,

constructional details of a mechanism corresponding essentially to that thus far described and which details are not referred to herein.

The pump plunger 53 of the latch control unit 50 and the pump plungers 34 and 35 each has an operating stem projecting out of the sump rearwardly for operative contact with a respective manually settable cam in the chamber 29.

- The exhaust valves 36 and 31 have operating stems similarly arranged, all the stems terminating rearwardly in the same plane.

The stem 540i the plunger 53 makes contact with the intermediate one of three concentric ring cams 55,.56and 51. The cams are hinged for movement toward and away from the propeller hub on respective pivot pins 58 near the bottom of the chamber 29 and supported by the framework 28. With that arrangement, the upx. portion of each of the cam rings can be thrust rwardlyat the will of the operator to cause energization of the pumping systems and operation of theexhaust valves. In Fig. 3 the intermediate cam member 55 has been thrust forwardly to cause release of the pitch limiting latch plunger 4 |-43of pitch adjusting mechanism and the outer ring 5l' has ben thrust forwardly to cause reciprocations of the pumping element 34 of the unit 30 and cooperating opening movements of the exhaust valve 37 of the unit3|. Those operations have resulted in movement of the piston 20 toward reverse pitch and beyond the normal pitch limiting abutment 46 with respect to the latch 43.

If, instead of the ring cam 51, the ring cam 56 is thrust forwardly, assuming the other two cams 55 and 57 are retained in their rearward nonoperating positions (latch 43 seated in depression 44), the operation would be an actuation of the pump plunger-35 of unit 3| and valve mechanism ment of the piston 20, then the piston 20 would be free to make the necessary traverse of the latch 43 to enable feathering and the feathering operation would terminate when the latch element 43 engaged the abutment 41.

The selective operation of the ring cams 55, 56 and will be more fully described later, but for the moment it may be noted in reference to Fig. 2 that, with an actuator handle 60 in the position in which it is shown, hydraulic fluid is forced through a line 56a to a servomotor of a vertically sliding cam 56b, causing operation of the innermost ring cam 56 on the pump 35 of the unit 3| and exhaust valve 36 of the unit 30, thus causing forward pitch adjustment of the blades. With the handle 00 in a reversed position as indicated by broken lines at 60c, Fig. 2, actuator fluid is supplied through a line 57a to the servomotor of a cam 511), thus causing the operation of the pump plunger 34 and the exhaust Valve mechanism 3'! of units 30 and 3i respectively so that the blades are moved toward low pitch or reverse positions. Actuation of the intermediate cam ring 55 is accomplished by a movement of a separate actuator handle BI, Fig. 2, from the position in which shown through 180, causing actuating fluid to be fed throu h I a line 55a to a servomotor of a cam 551), thus to move the latch element 43 from between the abutments 45 and 46.

Referring particularly to Fig. 4, wherein one of the fluid cont ol units 30 and 3| is illustrated in detail, it will be noted that said unit comprises a generally cylindrical bodv adapted to fit and sealingly close an opening in a forward wall of the sump chamber at a peripheral flange I2 of the body. Another flange 73 of the body makes peripheral sealing contact with the rearward wall 21 of the sump chamber so that only the reduced diameter space '14 between the two flanges can communicate with the sump through suitable ports in the body. The pump plunger 35 is mounted in a sleeve having an inlet port II communicating with an ali ned port in the wall of the body 70 leading to the sump. A spring 6 in a bore 17 of the body forces the plunger 35 toward the ring cam 56 to the inoperative position shown on both Fi s. 3 and 4. Reciprocation of the pump by the ring cam 56, Fig. 3,

causes movement of fluid trapped in the pump chamber space l8 throu h a cross passage I9 to a check valve plug 80 disposed centrally of the body I0 and slidable in an axial bore 8! of said body. The preferred cross sectional shape of the check valve plug is as shown by Fig. 6, i. e. non-circular to allow fluid to pass the plug. The valve 80 preferably has a ring seal 82 closing against a flat rearward face defining part of the bore BI, which face is centrally ported axially of the body for communication with the cross passage 79. A fairly light weight return spring 84 operates the valve plug 80 to cause the ring seal to close said central port whenever the pump plunger 35 ceases to move to the left as illustrated on Fig. 4.

The fluid pumped past the check valve 80 passes through the central bore of a fitting 85 to the delivery line 33, formed partly in the fitting, but said fluid is also free to flow through a cross passage 06 to the central bore 81 ofan 6 exhaust valve sleeve 88, sealingly fitting an eccentric bore 89 in the body I0. Exit of fluid from the bore 8'! is normally prevented by a valve plug 90 similar to the plug and guided by the bore 81. The plug has a ring seal 9I closing a port 92 formed in a wall 93 of the sleeve 88 intermediate the ends of said sleeve. The ringseals 82 and 9| are of similar construction, being secured to the respective plug members 80 and 90 by respective screws 95 and 96 having tapered or flared heads. The flared head of the screw 96 has a non-circular stem or extension 9'! integral therewith which projects slidingly through the port 92 but does not seal said port. The port 92 communicates with a chamber I00 in the rearward end of the sleeve 88 and when once the ring seal 9| is moved off the valve seat around the port 92 against the pressure of a return spring IOI in the sleeve, fluid is free to flow from port 92 past a non-circular land I92 of a valve operating plunger I03. The plug element 90, seal 9|, stem 96 and the valve operating plunger I 03 constitute the moving parts of the exhaust valve mechanism 31. The plunger I03 is sealed as at I04 against exit of fluid from the rearwardly open bore of the sleeve 88, but rearwardly from the non-circular land I02 of the plunger I03 the sleeve and body are formed to provide an outlet port at I05 leading to the sump. The noncircular stem 97 of the exhaust valve plug 90- operates in advance of the cooperating pump plunger 34 or 35 of the other unit; while the other exhaust valve operates in trailing relation to its cooperating pump. When the two valve stems 91 are of proper length for abutment by the bottom of the socket I03a of the associated plunger I03, the exhaust valves and pumps are in phase. Hence, it is merely necessary to select the proper length of stems 9'1. Alternatively adjustable abutments (not shown) can be provided between the stems 9i and sockets I 03a, which abutments would be set and locked prior toassembly of the propeller mechanism.

Additionally, for protecting the hydraulic mechanism against damage by overpressure after the latch 43 has engaged one of the abutments 45-43, the body I0 is provided with a relief valve communicating with the cross passage 19 and preferably located coaxially of the check valve 80 in a rearwardly open bore I08 of the body 10.

diameter central portion of the exhaust valve plunger I03.

In operation, the pulsations of the pump plunger 35 cause movement of fluid through the conduit 32 to operate the servomotor pistons 20- and 20' to the desired positions or until the pistons are stopped by relative abutment of the pitch limiting latch mechanism elements. After such relative abutment any further operation of cras es-r:

theL-pump plunger causes movement of the relief valve plunger I09 to .the right, Fig. 4, dumping excess pressure fluid to the sump chamber 25. To .exhaust fluid from the servomotor M, the plunger I33 of the unit 39 is operated by the appropriate ring cam, said plunger I93 of unit 30 abutting the stem 9'! of the associated valve plug assembly (90, 9?), thus opening the valve and allowing fluid to move through the line 33 to the sumpchamber. Due to the non-circular cross section of the stem 91 of the exhaust valve plug 90; there is no pocketing of fluid within the central bore of the actuating plunger I03 in which the stem slides.

The pump portion 53 of the latch release control unit 53. is the same as'that already described in connection with Fig. 4 and it will be noted in Fig. 3 that a counterpart of the check valve 80 is provided as at H5 ahead of the delivery line 52' leading to the latch release plunger chamber 5If.' Also, the unit 59 has a relief valve II6 to prevent damage to the latch mechanism upon over-delivery of fluid by the pump 53. The relief valve H5 is identical with relief valve I09, III, Fig. 4.

Venting of operating pressure from the latch plunger chamber 5I (Fig. 8) after the release of the latch has been accomplished requires only a bleed-off operation. As shown at the upper right in Fig. 5, a fixed plug I I8 corresponding in position to the exhaust valve plunger I03, is seated in the rearward portion of a sleeve I IS. The plug H8 is formed with a central necked portion terminating rearwardly at an enlarged head I28, sealing the rearward end of the sleeve I I9 behind an exhaust port I2I leading to the sump chamber. Fcrwardly from the port I2I a relatively smaller diameter enlargement I22 of the plug I I8 occupies the central bore of the sleeve H9 and provides a peripheral gap I23 around the enlargement I22 and within the sleeve. The gap may be on the order of a few thousandths of an inch radial width to provide a restricted orifice for passage of fluid from the port I24 wh ch is open to communication with the delivery line 52 as shown by Fig. 3. The forward end of the plug II 8 has a groove I25 across the face of the plug which rests against the partit on I25. Thus, whenever the pump 53 of the latch release control unit 50 is operated, the latch 43 is withdrawn from position necessary to make contact with either latch abutment 45 or 46, and the restriction at I23, Fig. 5, blocks return movement of the latch to init al position temporarily only. When the pump 53 is caused (by the operation of the mechanism through manipulation of the actuator handle iiI, 2) to cease operation,

then the operating fluid for the latch plunger is bled from the supply conduit 52 and the connecting passages to the sump chamber through the restricted orifice I23 and the latch is returned to its initial forwardmost position by the spring 49. Said spring forces the actuating fluid past the restricted orifice.

It will be seen from comparison of Figs.-

leading from the servomotor M are filled withfluid, the operation of opening the exhaust. valve will be blocked because hydraulic fluid is substantially incompressible. Also, after either pump plunger 34 or .35 on its pumping stroke has closed its associated inlet port II and assuming the cooperating exhaust valve has been opened, a complete charge of fluid in the sump chamber 25 and communicating passages leading to the then exhausting cylinder chambers of the servo motor M will block further. movement of such pump plunger. In actual practice, with a similar system it was found that it was impossible to fill the sump chamber entirely with operating fluid because, until such time as some of the charge had been forced or bled out of the system, the cam rings could not be moved to exhaust valve and pump plunger operating positions. To overcome that difficulty, a readily compressible element I30 is placed in the sump chamber 25. In the mechanism shown by Figs. 1 and 2, the compressible element is preferably in the form of a tubular elastic ring formed either as a single length of tube sealed at both ends or as an endless ring. Said element could be of any other desired shape. A suitable material for the ring I30 is synthetic rubber. The ring lies outwardly from all the pump and valve units 30, 3| and 59 as against the inner surface or" the radially outward wall of the sump chamber.

In order, independently of the speed of rotation of the propeller, to govern the rate at which pitch adjustment is effected by operation of the pump plungers 34 and 35, each of the feeding and exhausting conduits 32 and 33 is provided with a suitable needle valve with a restricted orifice (not shown).

Conventional needle valves are represented at I32 and I33 respectively in the lines 32 and 33. Those valves are not adapted or intended to be adjusted during flight. Since the strokes of the plungers 34 and 35 are of a length determined by the set or adjusted positions of the cam rings 5'5 and 57 and that may be varied by the operator and the speed of reciprocation of the pump varies according to propeller speed, the rate of fluid delivery to the servomotor chambers P, PI, etc. would ordinarily vary greatly. By restricting the passage of fluid from the pumps to the servomotor, the rate can be controlled at a value considerably less than the maximum capacity of the pumping mechanisms.v In event the propeller is rotating above the speed required for cruising speed, for example, the pumps will tend to de-. liver fluid at greater than the desired rate and.. in that event, the over-delivery will be returned .plungers are in position to open the fluid inlet ports I6, is prevented by the check valves -82, Fig. 4.,

Referring to the arrangement according to Figs. 7, 8 and 9, these differ from the construction described above principally in that anticreep valve mechanisms are provided and the mechanically. "opera-ting exhaust valve mechanisms. are omitted. The cam ring 56,.Fig.-7, operates only the pump plunger 35a corresponding to the plunger 35 of Fig. 3 and the cam ring 51 operates only the pump plunger 34a which corresponds to the plunger 34 of Fig.4. The cam ring 55 has exactly the same function as described in connection with Fig. 3, namely, to operate the pump plunger 53a of the pitch limit latch release mechanism. The fluid delivery and exhaust lines 32 and 33 are identical with the previously described construction. The servo portion of the latch release mechanism is the same as previously described and the cam rings are or may be adjusted as previously described above, through the servomotor portions of the manual actuating mechanism (right, Figs. 1 and 2).

Referring especially to Fig. 8, attention is called to the two-part plunger arrangement I35 which replaces the single piece pump plungers 34 and 35 of Figs. 3 and 4. The plunger member I35 slidably seals the cylinder sleeve I36 at the rear-- ward end of the sleeve and the forward end of said sleeve is open at I 31 for communication with the interior of a central bore I38 of the body 3Ia, corresponding to the body 3| of Fig. 4. The body 31a is generally the same as the bodies 36, 3I and '56 already described. An inlet port 1Ia leads from the annular space 14 of the body 3I a to the interior of the sleeve I36 and is initially open at both sides of a sealing land or relatively enlarged portion I40 of the plunger member I35- Behind the land, the plunger member has cross passages at I4I communicating with a central forwardly open socket I42 of the plunger. Rear- Wardly from the cross passages I4I the plunger member I35 is slidably sealed against the inner wall of the sleeve I36 as by a ring seal I43. In the fully retracted or rearmost position of the plunger I35, fluid is free to pass from the sump chamber 25, through the cross passages 1Ia to an annular space I44 around the forward end of the plunger member I35 and within the sleeve I36, thus to charge the pump. As the plunger member is thrust forwardly by the cam ring 56, the land I46 seals off the passage 1Ia so that the fluid occupying the pump sleeve is forced through the passage I31. The return stroke of the plunger member I35 may be accomplished by a fairly light spring 16a as compared to the high rate return spring 16 of Fig. 4 because return movement of the plunger member I35 is; in the Fig. 8 arrangement, unrestricted by vacuum after the check valve (to be described) at the delivery end of the unit 3m closes.

The vacuum breaker arrangement includes a check valve plug I46 which acts to admit low pressure fluid freely to the annular space I44 through the rearward inlet passages MI and I42 of the member 535 on the return stroke of the pump plunger. The plug I46 is held in sealing position by a light spring I41 bearing at one end against an end wall portion of the plug I46 and at the opposite end against a perforated disc I48 within the pump plunger 135. The disc is held in position against a shoulder I49 of the pump plunger by the force of the spring 16a which is materially greater than the force of the return spring I41 oi the vacuum breaker valve.

It will be seen that during return movement of the pump plunger member I35, the vacuum breaker valve I46 is free to move forwardly to open position (to the left) within the plunger member; Wherefore, until the forward edge of the land I46 has moved rearwardly to open the inlet passage Ha to the pressure chamber ahead of thepump plunger assembly, fluid isfreeto passage 1Ia, cross passages MI and socket.l42

to the pressure chamber of the pump.

The fluid delivered. by the pump to the passage I31 travels by way of the central bore I38 in -a space provided by a reduced diameter portion I56 of a valve sleeve I5I. The sleeve I5I is held in fixed position by the fitting 85a to which the delivery duct 33 is connected. Said sleeve has land portions at I52 and I53 tightly fitting the bore I38. The sleeve I 5| has a central smooth bore I 54 from end to end and a rearward portion of the sleeve ahead of the land portion I53 is opened by way of cross passages I55 to said smooth bore I54. Within the bore I 54 is slidably mounted a piston assembly I55 which forms the main portion of the anti-creep valve mechanism. The same valve mechanism functions for exhaust of fluid from the pitch adjusting servomotor.

The anti-creep and exhaust valve piston assembly I55 includes a spool shaped body member I56 having lands I51 and I58 at its rearward and forward portions respectively, slidably fitting the central bore I54 of the sleeveI5I. It is only necessary that the land I51 be especially provided for sealing said bore I54 and ring seals I59 are provided for that purpose. Between the. two

lands of the piston body member I56, the latter has a reduced diameter portion I66 with cross passages at both ends of said portion. The annular space thus provided around the piston body member communicates with the interior axial main bore I6I of said member. The bore I6I terminates rearwardly in a reduced diameter bore portion I62 so as to form a check valve seat for a valve plug I64 which is closed against the seat by a light spring I65. The fluid'forced by the pump to the interior of the sleeve I 5| through the cross passages I55 forces the check valve plug 564 off its seat and then passes through the main bore IM to the outlet fitting 85a. The

check valve plug I64 normally retains the fluid forced by the pump.

The piston body I58 is held in the illustrate position against the fitting a by a relatively strong spring I 66 seated in the bottom of the bore 538 aganist a plug element I61. The plug has a stem with a reduced diameter end portion I66 extending into the bore I62 of the plunger #56 in position to move the relatively small diameter check valve plug I64 off its seat whenever return pressure in the delivery line leading to the servomotor exerts sufiicient pressure on the piston to overcome the spring I66 and move the piston assembly rearwardly or to the right as illustrated in Fig. 8. Then the stem portion I58 engages the rearward end of the check valve plug I64 and unseats said plug. Thereupon, return pressure in the delivery line 33 bypasses the check valve I64 and escapes from the valve body 3m by way of the pump plunger cylinder sleeve I36 and the then retracted pump plunger member I 35. The pressure maintained by the spring I66 is predetermined in accordance with whatever force it takes to hold the blades from being moved out of adjusted position by counter pressure on the blades.

The operation of the anti-creep valve mechanism for servomotor exhausting purposes is the same as described above. The pump pressure of unit 36a overcomes the pressure of the spring I68 of unit 3| a and vice versa for exhaust.

In the event operation of either pump 34a or 35a, Fig. '1, is continued until the latch plunger slides.

masseuse l3-iengages one ofthe pitchlimiting stops described in connection with Fig. .3, the over-delivery of the pump is'ventedfrom the unit 30a 01' 31a to the sump through a respective relief valve' assembly I'IO, Fig. 8, the construction and operation of which is essentially the same as that of the relief valve I09-III of Fig. 4. To

' communicate the annular space around the sleeve fI5I with the relief valve, a portion of the cross 'passage I3'I designated I3'Ia leads to an outlet bore I'II in a valve sleeve I12. The relief valve bore I14 of the sleeve I12 in which the plug The'main body of the unit 3Ia has an outlet passage at I16 for communicating the interior of the sleeve I-I2 with the sump. The return spring for the relief valve plug has usually nearly twice the rate of the anti-creep valve spring I66.

' The. anti-creep valve mechanism of Fig. 8 is not needed for the control unit 50a of Figs. '7

and 9 which controls the pitch limiting latch operating servomotor. A restricted orifice for exhausting fluid from the latch release control system (line '52 etc, Fig. 7) is needed and that can easily be provided by removing the sealing rings 159 from the rear land of the piston member I56a as shown by Fig. 9. The annular gap I" (Fig. 9) between the piston land I5! and the inner bore of the sleeve I5I serves as the bleed-oil aperture for the latch operating servo 'system.

The valve construction according to Fig. 8 may bemodified so as to employ the compressible ring seal closures and flat valve seats such as provided'for the valve plugs 80, 90 and I09 of Fig. 4. "Inother words, in Fig. 8 the anti-creep valve 'plug 184 and the relief valve plug I10 may be "made-with appropriate recesses for ring type seals, held in place as by flared head screws and closing against flat valve seats. Such construction greatly reduces the time required to machinethe valve seats, since the ports closed by "the compressible ring seals do not have to be aligned accurately with the guide bores for the plugs. Moreover, centrifu al force acting on the fiat seat-engaging valve plugs of Fig. 4 never affects the sealing operation, even though the valve plugs have considerable lateral clearance 'inthe guide bores. In'the type of valve plug em- A further advanta e of the :less apt to cause faulty valving operation.

Attention 'is'called to the fact that it is un-'- necessary in the fluid control units according to .Figs. 4; 5, .8 and 9 to seal the rear end faces of -the'main"unit bodies against the back closure plate 26, Fig. 1. That feature is of special importance inxconnection with the relief val es I09, Fig. 4, and corresponding reliefvalve I10 of'Fig. 8. The rearwardly open bores in the unit bodies which receive the valve'plug assemblies are plugged by positively acting compressed linear seals so that when the valve assemblies aresubjected' .to sufiiciently high pressure to open therelief valve plugs there is never any likelihoodof loss of'fluid from the sealed hydraulic system as along the operating stems of the 'ring cam actuated parts.

' cylinder sleeve of the cylinder sleeve.

Referring further to the ringucam actuating mechanisms shown by Figs. 1 and 10 to 13inelusive, the. sliding cams b, 56b and 5112 are mounted on the framework 28 in suitable guides and each hasa bevelled lower end portion I80 (one shown in Fig. l) which, through contact with an adjacent bevelled rear surface of the associated ring cam; thrusts the selected ring cam forwardly into pump or valve actuating position with respect to the control units 30, 3!, 50, etc. as already described. Each of the sliding cams has an arm portion at its upper end as at I8I, Fig. l, whichv is normally forced downwardly by a spring I82 to hold the sliding cam in inoperative position. Adjustable limit stops for the sliding cams may be provided on the framework 28in position to engage the upper ends of the sliding cams. To operate the sliding cams, each arm I 8I overhangs a respective servomotor plunger orpiston I83 in a suitable cylinder bore of the framework 28. The actuator feed lines 55a, 56a and 51a communicate with the cylinders of respective pistons I83 in sealed relation thereto.

Referring to the actuator pump mechanism of Figs. 10 to 13 inclusive, the lines 55a and 51a are'supplied by oppositely disposed pump pressure chambers I85 and I8! in a common housing I88 having fittings I90 and I9I connected to the respective feed lines 56a and 51a, Fig. 2, and also acting as sealing plugs for the outer ends of the chambers I86 and I81. A common I92, Fig. 10, is fitted tightly into a horizontal bore I 93 of the housing I88. The end fittings I90 and IOI have ring seals I94 and I95 pressed against the re pective ends The pressure chambers I86 and I81 are each open to communicate with a common supply chamber I96 for reserve fluid preferably formed in the housing I88 above the cylinder sleeve I92. Vertical ports I 98 and I9! formed in the cylinder sleeve and housing I88 communicate the respective pressure chambers head portions 202 and 203 suitably sealed against a the wall of the cylinder sleeve.

The land portions, in the illustrated neutral or inactive position of the piston, are so disposed that both supply passages I98 and I99 are open. The piston is held in the centered neutral position by fairly strong springs 204 and 205 of equal length and scale. The springs surround reduced diameter extensions 206 and 20'! of the piston and bear oppositely upon shoulders adjacent the piston heads and may be seated at their opposite ends'in respective socket portions of the plugs I and I9I.

Inorder to use a single piston for supplying fluid selectively to the feed lines 56a and 51a, it is necessary to provide a fluid bypass from one pressure chamber to the other in order that return of the piston to centered position will not be blocked 'by vacuum in the last active pressure chamber. The bypass is formed as a central axial bore 208 in the piston 200, said bore terminating in respective counterbores 2H) and 2H within the reduced diameter extensions 286" and 201. The counterbores provide check valve guides for valve plugs, each in the form of a metal ball as indicated at 2I2 and 2I3, slidably fitting the guides. The piston extensions 206 and 201, Figs. 10 and 13, have slots as at 228' and 229 leading from the outer ends of the extensions past theballs'sothat fluid :from the I 203 cuts 01f the supply passage I99.

the bore 208 out of contact therewith for its entire length. Opposite reduced ends 2I8 and 2I9 of the rod provide shoulders 2I6 and 2I'i which abut the valve balls in such a position that both balls are held out of contact with their seats in the position of the rod 2I5 illustrated in Fig. 10. The reduced diameter ends of the rod 2I5 extend through diametral openings in the balls, partly to provide supports for respective ends of rod and ball centering springs 220 and 22I. The centering springs are very light in comparison to the centering springs for the piston, but the light springs are also of substantially equal length and scale in order to center the ball and rod assembly.

To operate the piston 200, the lower side of both the cylinder sleeve I92 and the housing I88 are open as at 222 and adjacent the opening a reduced diameter central portion of the piston between the lands is provided with rack teeth 223. The rack teeth continuously mesh with a pinion 224 supported on a horizontal shaft 225, suitably journalled in the housing I88 as shown in Fig. 11. The shaft is suitably keyed as by flutes or serrations to the pinion 224 and the outwardly proiecting end of the shaft carries the actuator handle 60. The handle 60 is vertical in the neutral position of the actuator piston 200. 1

In operation, the handle 60 is normally held in its vertical position by the relatively heavy centering springs 204 and 205. Movement of the handle in either direction away from sa d central position as to the full line or broken line positions shown on Fig. 2 effects movement of the piston 200 in the selected direction for operation of the ring cams 56 and 51 of the propeller control mechanism. Movement of the piston 200 to the left, Fig. 2 (right, Fig. 10), as by turning of the arm toward the broken line illustrated position, Fig. 2, traps fluid in the pressure chamber I81 when the piston land The operation also causes closing movement of the check valve 2I3 due to the fact that the springs 22'! and 22I continue to center the ball and rod assembly 2I2, 2l3 and 2I5. Thereupon, the trapped charge of fluid in the chamber I 8! moves through the supply line 51a to the associated servomotor I83 to move the ring cam 56 to operating position. An opposite movement of the piston 200 (right, Fig. 10) obviously operates the ring cam 57 as will be readily apparent.

In order to release the operating ring cam and allow it to he returned to initial position as by contact with the actuating stems of the operating pump and/or valve assemblies of units and 3i, the operator merely releases the handle 60 and the compressed high rate centering spring returns the piston and the arm to the centered position illustrated in Fig. 10. Since the centering springs 220 and 22! of the ball check valves 2E2 and 2I3 are relatively weak, the .ball ZIZ or 253 which sealed its center port leading through the piston will be opened by inertia so. that fluid is free to pass from one pressure chamber to the other as soon as the operator releases the handle 60.

The separate means for operating the pitch limit latch releasing ring cam is a vertical 14 piston 230 slidable in a sleeve 23I in a vertical bore 232 of the housing I88. The piston'230 has its upper end normally held in position to unseal lateral inlet ports 234 of the sleeve 23I leading to the supply chamber 2I5 as through a cross passage 235 in the housing. The piston 230 is held in the illustrated position by a spring 236 acting directly against the top end of the piston 230 at its lower end and seated against a socket in an outlet fitting 231 of the housing to which the fluid line 55a is connected. Normally balancing the spring 236 to hold the piston 230 normally in its illustrated position, the lower end of the piston 230 has an axial closed socket 238 which receives the upper end of a coil spring 239. The lower end of the coil spring 230 bears against a cross head 240 slidable in the lower end portion of the cylinder sleeve 23I and resting against a rotatably mounted operating cam 242. The cross head 240 has an axially vented socket 263 which receives and supports the lower end of the coil spring 239. The cam 242 preferably comprises a metal disc of generally circular form but provided with opposite flat surfaces at 244 and 24.5, apart about an eccentric supporting shaft 246 keyed to the cam as by serrations at 25!. The shaft is suitably journalled as at 248 and 249 in spaced portions of the housing I88.

When the operating handle 6| of the pitch limit latch release actuator mechanism is in the position illustrated in Fig. 2, the flat surface 244 (Fig. 12) is in contact with the lower end of the cross head 240, thus retaining the cam and handle 6! in the positions illustrated in Figs. 11 and 12. When the handle 6! is movedthro-ugh 18 in either direction, the cross head 240 is raised until finally the flat surface 245 is moved in contact with the lower end of the cross head. That operation results in compressing the coil spring 239, overccming the counter-pressure of the spring 236 and raising of the piston 230 to out ofi the inlet ports 234 and move the trapped fluid in the upper end of the cylinder 23I to the servomotor of the intermediate ring cam 55. That causes initiation of operation of the pitch limit release latch 43 of Figs. 3 and 7.

The cooperating flat surface 245 of the cam 2 32 and the lower flat face of the cross head 246 hold the cross head 240 in its raised position and maintain pressure on the piston operating spring 230. Because of the yielding connection between the cross head and the piston 230, the piston cannot block the cam 242 in its movement toward piston actuating position, even though the pressure chamber spaces and connecting delivery line 55a are of insufiicient capacity to receive the volume of fluid attempted to be forced thereto. Because of the possibility of leakage in the pressure chambers of the pitch limit latch release actuator system, the mechanism is so designed as to provide some over-delivery of fluid to the servomotor of the sliding cam 55b, but no matter how much provision for over-delivery is made'in order to insure immediate response of the pitch limit latch release servomotor, the cross head 240 can always be moved to its acting position where it is retained by the cooperating flat surfaces 245 of the cam and the fiat bottom end of the cross head 249.

A further feature of the construction shown by I :rshown, the shaft 225 has a peripheral groove at 255 rand vertically aligned therewith the shaft 246 has a peripheral groove 256. Formed adjacent and intersecting the two grooves the housing I88'has a vertical bore 251 which receives a secur- "ing key tangent to the peripheral grooves of the two shafts and occupying said grooves. The key may be formed simply as a short section of 'wire (not shown) held in position by a cap screw 258 in the lower end of the bore 251.

I claim:

1. In a controllable pitch propeller, a pitch adjustable blade, two simultaneously and oppositely acting blades adjusting power mechanisms and means turned by said mechanisms to change the pitch of the blade, all rotatable with I the propeller, a fluid'operated actuating mechanism including servomotors respectively operable to cause operation of the blade" adjusting means, said actuating mechanism including a double ended piston and cooperating cylinder "means forming pressure chambers connected with respective servomotors, said piston being movable manually in opposite directions from a neutral position, spring means arranged to re-' turn the piston to neutral position after movement in either direction, and a by-pass valve "system capable of communicating said pressure chambers, said system including spring means maintaining the by-pass open in the neutral position of the piston but closing the by-pass whenever the piston is moved in either direction from that position.

2.1m a controllable pitch propeller, a pitch adjustable blade, simultaneously and oppositely acting blade adjusting power mechanisms and means turned by said mechanisms to change the pitch of the blade, all rotatable with the propellr, a fluid operated actuating mechanism including servomotors respectively operable to- "cause operation of the blade adjusting means,

said actuating mechanism including a double ended piston and cooperating cylinder means 'forming pressure chambers connected with respective servomotors, said piston being movable manually in opposite directions from a neutral position, spring means arranged to return the piston to neutral position after movement in either direction, and a by-pass valve system in a through passage of the piston capable of communicating said pressure chambers through the piston, said system including spring means maintaining the through passage open in the neutral position of the piston but closing the passage whenever the piston ismoved in either direction from that position.

3. In a rotary assembly, a reversible hydraulic motor, two alternately acting pumps each supplying a respective pressure chamber of the motor,

non-rotating means operable selectively to actuate the pumps during rotation of the assembly, a. non-return valve between each pump and the motor pressure chamber supplied thereby, plungers supporting respective non-return valves, each plunger being movable by a predetermined back pressure from its connected motor chamber to cause the associated non-return valve to be opened, and cooperating fluid passage means so :arranged that the non-return valve connected to onemotor chamber can be forced open by exhaust fluid from the motor while the other motor chamber is being supplied by its pump.

- plug then to be moved to openposition; and oooperating fluid passage means so arranged that the non-return valve mechanism connected to one motor pressure chamber can operate as an exhaust valve for that chamber while the other motor chamber is being supplied by its pump.

5. In a' rotary assembly, means rotatable with the assembly and forming a hydraulic fluid supply chamber, a pump including a pressure chamber and a reciprocatable piston therein operable to open the pump pressure chamber to the supply chamber on each return stroke of the piston, means to reciprocate the piston during and as a result of rotation of the assembly, a motor having a fiuid connection with the pump pressure chamber, said connection including a non-return"'valve, and a vacuum breaker valve in the piston between the pump pressure chamber and the supply chamber and operating oppositely of the non-return valveon the return stroke of the piston.

COLUMBUS R. SACCHINI.

REFERENCES CITED The following references are of record in'the file of this patent:

UNITED STATES PATENTS Number Name Date 65,435 Richter June4, 1867 1,705,293 Horthy et 'al Mar. 12, 1929 1,803,858 MacClatchie May 5, 1931 1,972,462 Schafer Sept. 4, 1934 1,980,617 Engel Nov. 13, 1934 1,987,651 Wiegand Jan. 15,1935 2,023,785 Hoover Dec. 10, 1935 2,057,934 Brown Oct. 20, 1936 2,146,030 Schiohn Feb. 7, 1939 2,178,061 Bachman et al Oct. 31, 1939 2,190,228 Bowen Feb. 13, 1940 2,207,635 Nardone July 9, 1940 2,214,257 Pfauser Sept. 10, 1940 2,282,297 Keller May 5, 1942 2,296,288 Martin Sept. 22, 1942 2,333,316 Klossner Nov. 2, 1943 2.343,416 Keller Mar. 7, 1944 2,357,386 Dick Sept. 5, 1944 2,403,532 Hoover July 9, 1946 2,422,966 Hoover June 24, 1947 2,433,990 Hardy Jan. 6, 1948 2,491,375 Hardy Dec. 13, 1949 2,515,037 Hardy July 11, 1950 FOREIGN PATENTS Number Country Date 18,445 Great 'Britain 1897 369,761 Great Britain Mar. 31, 1932 464,203 Great-Britain Apr. 12, 1937

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