Jan. 7, 1947. _ w, A, FLETCHER ' f I 2,413,757 VALVE Filed Jan. 5, 1944 v2 Sheets-Sheet'l‘ y5. “~99 ‘ .92 9? > . r\ A _ v > 73 P “I /@ v- 97 - , ‘ ~77 . - ~ _ INVENTOR %4% BY , 114 WMH’” ATTORN EYb Patented Jan. 7, 1947 2,413,752 UNITED‘ STATES PATENT OFFICEVALVE William A. Fletcher, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application January 5, 1944, Serial No. 517,080 5 Claims. . .(Cl. 137-'—144) 1 2 . This invention relates to a valve unit for con trolling ?uid pressure in- an hydraulic servo-sys tem which operates, for example, to control the course of an airplane. " > rection of the position of the steering apparatus _ required to maintain the ‘course. Further objects and advantages of the present invention will be apparent from the following ' It'is an object of the present invention to con trol ?uid pressure in accordance with the value ,_ of a controlling force of relatively small mag nitude, for example, the force of attraction upon a movable armature of an electromagnet respon sive to variations in voltages of small magnitude 10 Fig. 1 is‘ ahydraulic diagram including sec tional views of valves embodying the present in such as used in the automatic-pilot system of air- ' vention. description, reference being had to ,the accom panying drawings wherein a preferred embodi-_ ment of the present invention is clearly shown. In the drawings: , Fig. 2 is a top view of the electrically operated plane control. In the disclosed embodiment of valve unit ‘embodying the present invention. the invention, this object is accomplished by the Fig. 3 is a view taken in the direction of ar cooperation of a main valve for controlling the discharge of ?uid from the high pressure line to 15 row 3 of Fig. 2. Fig. 4 is a sectional view on line 4-4 of Fig. 3. Fig. 5 is a view drawn to a- larger scale than the low pressure side of the hydraulic system, an hydraulic relay having a cylinder which receives Figs. 2, 3 and 4 and is in part a side view looking pressure ?uid from the high pressure line, a pis in ‘the direction of arrow 5 of Fig. 4 and‘ is in ton within the cylinder for applying ?uid pres sure to force the main valve toward its seat, and 20 part a sectional view taken on line 5A-5A and on line 5B-5B of Fig. 4. . -_ means for regulating the pressure in the cylin-J Referring to Fig. 5, a base It) is provided with der in accordance with the magnitude of the con cylindrical portions ll each receiving a valve seat trolling force and comprising a duct connecting member l2 having a central bore l3. Body I0 is the cylinder with the low pressure side and pass ing through a pilot valve seat provided by the 25 provided with apertured ears l4‘ each for receiv ing a screw not shown by which the body 10 may main valve, a pilot valve whose movement toward be secured to a plate [5, Fig. 1. the pilot valve seat is opposed by the pressure of Each cylindrical portion ll receives a valve the ?uid escaping through the pilot valve seat, guide l6 which receives a valve l'l. Each valve H and means for applying to the pilot valve, a force for urging it toward its seat. As the controlling 30 has a conically tapered lower end 18 adapted" to _ engage the edge I!) of the valve seat 12. The valve force is applied to urge the pilot valve toward its seat, the pressure in the cylinder increases and . l1 has a portion 20 of reduced diameter providing a shoulder at 2|. A passage 22 extends upwardly the main valve approaches its seat to increase the ' thru the center of the valve l1 and connects with pressure in the high-pressure line. The control ling force continues to move the pilot valve with 35 a passage 23 terminating at the shoulder 2|, thus providing communication between the exterior the main valve until equilibrium status is reached of the valve I1 and a chamber 24 within the valve wherein the fluid pressure upon the pilot valve is guide l6 which provides the cylinder with which , _ balanced by the controlling force and the weight of the pilot valve and the ?uid pressure acting upon the piston to ‘close the main valve balances the ?uid pressure tending to open the main valve. Thus the line pressure maintained by the main the valve l'l cooperates as a piston. Valve 11 has . 40 another portion 25 of reduced diameter having a sliding ?t within an aperture in the upper wall of the valve guide I6. The portion 25 is provided with a side passage 26 connecting with the .v'ver valve depends upon the magnitude of the con tical passage 21 which terminates at a conical trolling force applied to move the pilot valve to 45 valve seat 28 ‘for receiving the spherical lower ward its seat. end of a valve rod 29. To facilitate further-def The present valve unit is useful particularlyin scription, certain parts such as l2,.; l3, l1, 24-?and an automatic-pilot system which provides a sig 29 which are in the left half of Fig. 5 are given . nal or controlling force whose magnitude depends the a?ix l and those in the right half of Fig.1.’: are on the amount of deviation from a predetermined 50 course. The present valve unit provides for con given the ailix r. trol of operating pressure in accordance with the magnitude of the signal. Therefore the hy draulic servo-apparatus performs in accordance with the magnitude of the signal to make the cor- 65 plate 3| is provided with apertures each for re-' ceiving an annular ?ange I Go provided by the up per wall of the valve guide [6 which ‘?ange sur rounds the portion‘ 25 of the valve I 'l.- Plate 3| is 1 ' "i’i'w . Screws 30 secure a plate 3| to the body I0.‘ 5 The 2,413,757 I . 3 seat, the pressure in the cylinders 96 and 91 will provided with a vertical ?ange 33 which provides a mounting pad 34. be equalized and there will be no movement of the rack IIII and the shaft I93. The valves I1 - Screws 35 and 36 secured to the mounting plate 3| the laminated ‘core 49 of an electromag net device which controls the rods 29. The core remain in balanced position so long as the elec tr'o-magnetic effects of the two coils H are the same, the armature 59 being in symmetrical posi 49 includes a horizontal base 4I, two vertically extending side-branches“ and a central branch 43. The branches 42 provide arcuate pole faces 44 concentric with the axis of. a shaft 45 which, as'shown in Fig. 4, is supported by ball bearings tion, that is, with its arm 58 being vertically lo cated and with its arm 51 horizontally located as shown in Fig. 5. The electrical apparatus for 10 46, retained by plates 41 screw threadedly engag ing a frame 48 secured by screws 49 (Fig. 5) to controlling the amount of current ?owing in the coils ‘II is not shown, but it will be understood by those skilled in the art of automatic controls for aircraft that this apparatus operates, when the core branches 42. Each screw 49 passes through a hole 50 in the frame 48 said hole being the airplane departs from a predetermined course, substantially larger than the threaded portion of tromagnet and decrease the magnetism of the other electro-magnet as will result in movement of the shaft I93 to such an extent that the plane the screw.- Screw 49 passes through a non-mag netizable spacer block 5I and threaded engages a tapped hole 52 in a core branch 42. _ ‘ to cause such increase of magnetism of one elec will be brought back into its course. 4 Normally when the electromagnetic effects of 20 laminated T-shaped armature 55 having side magnets H are equal, the armature 56 will be The shaft 45 is connected by pin 55 ‘with a arms 51 and a downwardly extending arm 58 hav ing an arcuate pole face 59 in close proximity located with its arm 51 horizontal (Fig. 5) and the valves I11 and I1r will be located the same to an arcuate pole face 69 provided by the core distance above their valve seats I21 and I21‘ as arm 43, the pole faces 59 and 69 being concentric shown in Figs. 1 and 5. The rods 29 exert equal with the shaft 45._ The pole faces (H of the side forces upon their seats 28 due to their own arms 51 which are located in close proximity to weights which are equal. The screws 84 are so the pole faces 44 of the core branches 42 are con adjusted as to provide the proper opening of the centric with the axis of shaft 45.“ The gap be valves I11 and I11‘ when the magnet coils H are tween each of the pole faces 44 and the adja in balance. Normally the flow of pressure ?uid cent pole face 6| may be varied by turning a screw 30 through the high pressure inlets I3 to the low 62 threadedly received by a lug 63 provided by pressure outlets H3 is equal, and valves I1 are the frame 48. To make the adjustment the screw located in the same distance above the seats I9 49 is loosened so as to permit motion between the as shown in» Figs. land 5. Some pressure ?uid block SI and the core 42 relative to the frame-48. ?ows through each chain of valve passages 22, The screw 62 is turned inorder to push the block 23, 25, 21 and out through‘ a valve seat 28 under 5I and consequently the core branch 42 toward neath the lower end of a rod '29. ‘When oil the shaft 45 to reduce the gap between pole faces is being pumped there is pressure upon the lower 44 and GI and the screw 62 maybe turned in the ends of the rods su?icient to 'raise them up opposite direction to permit the core 42 to move against the screws 84,. and the valves I11 and HT away from the shaft 45 due to the resiliency of 40 are elevated above their seats a distance sufficient the core. After the adjustment of the gaphas to give a certain low balanced pressure. The un been made, the screw 62 is secured by lock nut interrupted circulation of oil through passages 64 cooperating with a lock-washer 65, and the 22, 23, 2G, 21 provides for scavenging any‘ par screw 49 is tightened. ' I .' ticles of dirt which might be present in the oil ‘Each core branch 42 is surrounded by a non conducting spool 19 upon which an electro-mag net coil 1 I is ‘wound. The spool 10 is urged against the core base M by leaf spring 13 carrying a stud 14 received by a recess in lug 63 of a frame 48. Pin 80 secures to shaft 45 the hub 8I, (Fig. 4) of a walking beam lever 82, each end of which is provided with a tubular portion 83 for receiving theupper end of a valve rod 29 and for threadedly in the cylinder 24, and prevents the accumula tion of dirt particles in the cylinder. The total pressure force acting upwardly on the valves I1 is balanced by the total pressure forcewithin the cylinders 24 acting downwardly upon the valves I1. The device (not shown) which is responsive to deviation of the airplane from a predetermined course will cause .current in one magnet H to increase and the current in the other magnet H to decrease depending on the direction of deviation. Assuming that the left hand magnet 1I1 receives more current than the right hand receiving a screw 84 for engaging the valve rod - 29.‘ By turning the screw 84 the relation between ‘ the valve rod 29, the valve I1 and the lever 82 is-adjusted. The screw 84 is secured in the de sired positions of adjustment by lock nut 85. ' Referring to Fig. 1, a valve unit is submerged . below the level 9I of pressure ?uid contained in a magnet 1Ir, armature 56 will rotate slightly counterclockwise to cause rod 291 to move down Ill to increase the restriction between the lower end Y. ‘tank v99. Submerged motor driven gear pumps "':~~92:>and 93. force pressure fluid from the tank of rod 291 and the adjacent valve seat 28. The pressure in cylinder 241 increases and valve I11 moves down to increasev the restriction between the lower end of valve I11 and the adjacent seat 65 I9, and thereby to increase the pressure in pas sage I31. As valv'e I11 moves downarmature 56 zI??eproviding a rack IIlI meshing with a moves counterclockwise to move the rod 291 through passages 94 and 95 vconnected respective ly='-with cylinders 96 and 91 of hydraulic servo motor which include pistons 99 and 99 connected ' 2 .fdndriving a shaft I03 for operating the deviceet‘obe controlled which may be, for ex <.>.-: ample;f”the steering apparatus of an airplane. The passages 94 and 95 are connected by passages I94 and I05 respectively with ports I31 and I31 ~ provided by the left end valve seat I21 and the . right hand valve seat I21". When the valves I1 1 are in balanced portion as shown in Fig. 1, each valve being elevated the same distance from its 75 againstthe pressure of fluid escaping at the ad jacent seat 28. Equilibrium is established when the total pressure, acting upwardly on the rod 291 equals the weight of the rod 291 plus the force acting downwardly on the rod 291, which force is due to the differential of the vmagnetic effects of the magnet coils H. The greater this differen tial, the. greater will be the total“ ?uid pressure ane-n7 ‘ 6 in the cylinder 24! to force the valve I'll down against an equal total ?uid pressure acting up wardly through the passage I31. Thus for each .value of force applied magnetically to the rod 291, to vary is counteracted by a movement of valve Ill into a position of equilibrium such that the pressure in passage I31 will remain constant so ‘ long as themagnetic di?erential’ioi the coils ‘Ill there is' a corresponding value of total ?uid pres sure in the passage I31. As valve I'll moves toward closed position, valve l'lr moves upwardly to e?ect a reduction in pres sure in the passage I31‘. As pressure in cylin and 1 Ir remains constant, regardless'of the quan tity of ?uid moving from the, pump 92. Obviously. the foregoing applies to the con trol of pressure in passage l3r. Because the con trol valves are not affected by rate of oil circula ' der 96 (Fig. 1) increases, pressure in- cylinder 10 tion, automatic control of the steering of the 91 decreases. Pistons 98 and‘ 99 move right to plane is very sensitive to deviation from a pre move the steering apparatus in such direction as determined course. ' to cause the airplane to return to the predeter While the embodiment'of the present invention ‘ mined course. As the deviation frompredeter-l as herein disclosed, constitutes a preferred form, mined course diminishes, the current in the coil 15 it is ‘to be understood that other forms might be ,‘lll diminishes while the current in coil ‘Hr in adopted, all coming within the scope of the claims creases. Valve ill moves up toward the position . which follow. _ - shown in Fig. 5 while valve "1' moves down to What is claimed is as follows: ward the position shown in Fig. 5. Pressure in 1. A valve unit for‘controlling ?uid pressure cylinder 91 increases while pressure in cylinder 20 comprising, in combination, a pressure ?uid re 96 decreases. When these pressures are equal, ceiving duct providing a valve seat, a main pres- ' movement of the pistons 98 and 99 ceases. When sure relief valve cooperating with the seat for the course of the plane has been restored to the ' controlling the discharge of ?uid from the duct, predetermined course, the magnetic e?’ects of the an hydraulic relay controlling the main valve and coils ‘Ill and Hr are equal and the armature 5B is 25 including relatively movable cylinder and pis , in normal position as shown in Figs. 3 and 5. ton members, one of which is ?xed and the other of which is connected with the main valve, a The pistons remain in the position to the right of the symmetrical positions shown in Fig; 1 so long as the steering apparatus is adjusted to .maintain the course. If the condition which re quired movement of thepistons to the right of symmetrical position diminishes in e?ect, the adjustment of the steering apparatus would be duct connecting the ?rst duct with the cylinder, a duct for the discharge of ?uid from the cylin 30 der, means for controlling the discharge of ?uid from the cylinder. through the second duct and including a pilot valve 'seat movable with the ‘ main valve and a pilot valve cooperating with 'the pilot valve seat and receiving upon its face 35 the pressure of ?uid escaping from the cylinder for urging the pilot valve away from its seat and means for applying a controlling force to the pilot valve to urge it toward its seat, where greater than required to eifect the deviation from course and there will be a deviation in the op posite direction. When this occurs, coil ‘Hr will receive more current than coil ‘Ill; and valve Ilr will close while yalve I'll opens. Then the pres sure in cylinder 91 exceeds‘ the pressure in cyl by in equilibrium status, the pilot valve is in inder 96 and the pistons move left until the steer 40 balance between the force urgingethe pilot valve ing apparatus is so adjusted as to maintain the i toward'its seat and the pressure ?uid force urg predetermined course. ing the pilot valve away from its seat and where ‘While the pistons 98 and 99 are moving in either - by, the main valve is in balance between cylin-_ direction, there will be a tendency for a change der pressure and fluid pressure acting against the in operating pressure in cylinders 95 and 91, while Cl face of the main valve. _ I the magnetic di?erential remains constant. To 2. A valve unit for controlling a ?uid pressure offset this the valves I ll and HT are automatical in accordance with a controlling force and com ly moved into positions for maintaining the pres- _ prising, in combination, a pressure ?uid receiv sure called for by the magnetic effects of the mag ing duct, 2. control element, apparatus for main~ nets ‘HZ and 1|r. Assuming that the pressure 50 taining the control element in a normal posi in passage I31 tends to increase above a certain tion to obtain a corresponding normal ?uid pres value corresponding to a certain magnetic dif sure, in the duct and sensitive to the operation of ferential, the pressure in cylinder 241 begins to in a controlling force demanding pressure increase crease, and the pressure acting on the lower end for moving the element to obtain a pressure in - of rod 291 begins to exceedthe total of the force 55 the duct corresponding to the magnitude of the of gravity on the rod and the magnetically derived controlling force, a main valve seat provided by force acting thereon._ The rod 281 begins mov the duct through which pressure ?uid can be dis ing upwardly and the armature 56 begins to move clockwise. Rod 2,91 begins moving up to decrease ' charged from the duct a member providing at the restriction :at the adjacent seat 28, thereby 60 valve seat and providing, at the other end remote reducing the pressure in cylinder 24!. Valve ill moves up to reduce the pressure in passage _l3_l. one end a main valve cooperating'with the main from the main valve seat, a pilot valve seat, and providing, intermediate its ends, a piston, a cyl If the pressure in passage I31 tends to fall below inder receiving the piston and guiding the move the value which corresponds to a certain mag ments of the valve, a‘ duct connecting the ?rst netic differential, the pressure in cylinder 24! be ' duct with the cylinder whereby ?uid'pressure is gins to decrease, and the pressure acting on the applied to the piston to urge the main valve to lower end of rod 291 begins to'fall below the total ward its seat in opposition to ?uid pressure in of the force of gravity and the magnetically de the ?rst duct acting upon the main valve, a duct rived force ‘acting thereon. The rod 291 begins ' providing for discharge of pressure ?uid from moving-down and the armature 58 follows-it by a 70 the cylinder and terminating at the pilot valve counterclockwise movement. The restriction at seat, and a pilot valve positioned between the seat 28 increases to cause pressure in cylinder 241 pilot valve seat and the control element and to increase and to cause downward movement of , actuated away from its seat by the pressure of valve I'll to increase pressure in passage I31. ?uid escaping through the seat from the cylin Thus the tendency of the pressure in passage I31 75 der, the control element limiting said ?uid pres " 8,418,767 , sure actuated movement or the pilot valve away from its seat thereby controlling the ?uid pres sure acting upon‘jthe piston to urge the main valve toward its seat whereby a certain pressure is normally maintained in the ?rst duct when the control element is in its normal position, and whereby ‘a higher‘ pressure is maintained in the ' 8 - sure in the ?rst duct to a certain normal value, means for applying‘ a force to move the control element to- decrease the gap between the pilot ' valve and its seat in order to cause the pres sure‘ in the cylinder to increase whereby the main valve moves toward its seat to increase the pressure in the ?rst duct, movement of the con trol element along with the pilot valve and main valve continuing until equilibrium is established controlling force urging the pilot valve toward 10 between the control force acting upon the control its seat.’ element to‘ urge the pilot valve toward its seat, 3. A valve unit for controlling ?uid pressure and the force of the pressure or the ?uid escap in‘ accordance with control by opposing forces ing from the cylinder through thepilot valve seat and comprising, in combination, a pressure ?uid and acting upon the pilot valve and between the ?rst duct depending on the magnitude of the receiving duct a control element, apparatus sensi pressure of the ?uid in the cylinder acting upon tive to the action of two opposing forces for 15 the main valve to urge it toward its seat and the maintaining the control element in a normal posi pressure of the ?uid at the main valve seat act . tion when the forces are equal and for moving the ing upon the main valve, whereby a pressure element from normal position when the forces in the ?rst duct is established depending upon the are unequal, a main valve seat provided by the magnitude of the controlling force. duct through which pressure ?uid can be dis 20 5. A valve unit for controlling ?uid pres charged from the duct, a member providing at sure in accordance with a controlling tome and one end a main valve cooperating with the main comprising, in combination, a pressure ?uid re valve seat and providing, at the other end remote ceiving duct a main valve seat provided by the from the main valve seat, a pilot valve seat, and duct for the discharge of pressure ?uid, a main _ providing, intermediate its ends, a piston, a cyl 25 valve cooperating with the seat to limit the ?ow inder receiving the piston and guiding the move of ?uid therethrough, means for urging the main ment of the valve, a duct connecting the ?rst valve toward its seat and comprising a piston duct with the cylinder whereby ?uid pressure is provided by the. main valve and a cylinder receiv applied to the piston to urge the main valve ing the piston, a duct connecting the ?rst duct 30 toward its seat in opposition to ?uid‘ pressure with the cylinder, a duct through the valve com acting upon the main valve, a duct providing ~ municating with the cylinder and terminating in for the discharge of pressure ?uid from the cyl ‘ a pilot valve seat at the end of said member re inder and terminating at the pilot valve seat, and mote from the ‘main valve portion, a pilot valve a pilot valve positioned between the pilot valve. facing said seat, a control element for'the pilot 35 seat and the control element and actuated away valve normally, located so as to permit limited from its seat by the pressure of ?uid escaping ' movement of the pilot'valve away from its seat through the seat of the cylinder, the control ele due to the pressure of the ?uid escaping from the ment limiting said ?uid pressure actuated move vcylinder through the pilot valve seat, thereby ment of the pilot valve away from its seat there by controlling the ?uid pressure acting upon the 40 limiting the escape of ?uid from the cylinder so that a pressure is maintained therein such as to piston to urge the main. valve toward its seat , cause the main valve to‘ be located in a position whereby a certain pressure is normally main permitting such discharge through the main tained in the ?rst duct when the control element valve seat as to limit the pressure in the ?rst is in its normal position, and whereby a‘higher duct to a certain normal value, means for posi pressure is maintained in the ?rst duct depend 45 tioning the control element and sensitive to two ing on the magnitude of the force differentia urging the pilot valve toward its seat. > 4. A valve unit for controlling ?uid pressure ' “ opposing forces which, when equal, cause the ‘in accordance with a controlling force and com prising, in combination, a pressure ?uid receiv ing duct, a main valve seat provided by .the duct for the discharge of pressure ‘?uid, a main valve cooperating with the seat to limit the ?ow of. ?uid therethrough, means for urging the main valve toward its seat and comprising a piston provided by the main valve and a cylinder receiv ing the piston, a duct connecting the ?rst duct with the cylinder, a duct through the valve com municating with the cylinder and terminating in a pilot valve seat at the end of said ,member remote from the main valve portion, a pilot valve facing said pilot valve seat, a control element for the pilot valve normally located so as to permit limited movement of the pilot valve awayfrorn its seat due to the pressure of the ?uid escap , ing from the cylinder throughthe pilot valve seat, thereby limiting the escape of ?uid from the cylinder so that a pressure is maintained therein such as to cause the" main valve to be located in‘ a position permitting such discharge 70 through the main valve seat as to limit the pres control element to be-maintained in its normal position, said means being operable in response to a force differential demanding pressure in crease in the ?rst duct to move the control ele ment to decrease the gap between the pilot valve and its seat in order to cause the pressure in the cylinder to increase whereby the‘ main valve moves toward its seat to increase the‘pressure in the ?rst duct, movement of the control ele ment‘along with the pilot valve and main valve - continuinguntil equilibrium is established be tween the .force differential acting upon the con trol element to urge the pilot valve toward its seat and the force of the pressure of the ?uid escaping from the cylinder through the pilot valve seat and acting upon the pilot valve and between the pressure of the ?uid in the cylinder acting upon the main valve to urge it toward its seat and the pressure of the ?uid at the main valve seat acting upon the main valve, whereby a pressure in the ?rst duct is established depend ing upon the magnitude of the force differential. WILLIAM A. rmz'rcrma.