Патент USA US2407926код для вставки
Sept. 17,1946. H. w. GILFILLA‘N‘ _ ‘ 2,407,925 APPARATUS FOR'COMPAR‘ING PRESSURES original Fiied‘Mavrch’27, 1943 2 Sheets-Sheet 1 31%7,wmiw f .50.2“ IN VENTOR HENRY BY HTTORNEYS. seppdv, 1946.’ H. w. GILFILLA‘N . 23071925 APPmi'US ‘FOR COMPARING PRESSURES Original Filed March 1 27,194: 2 Sheets-Sheet 2 ' INVENTOR zfm Zm. “3%. .5 Z Patented Sept. 17, 1946 or 1 L 4 M We; r‘ rs h? is 2,4d7,925 ‘ r e was > error. ] we 2,407,925 APPARATUS FOR COMPARING PRESSURES Henry W‘. Gil?llan, Detroit, Mich, assignor to Chrysler Corporation, Highland Park, Mich, a corporation of Delaware ()‘riginal application March 27, 1943, Serial No. 480,786. Divided and this application Decem ber 31, 1943, Serial No. 516,423 ‘ 11 Claims. ‘i 2 i This application is a, division of Gil?llan et al., application Serial No. 480,786, ?led March 27, 1943. Copending application Serial No. 518,829, ?led January 19, 1944:, in the name of David M. Borden relates broadly to a type of pumping-limit detector such as shown in the drawings as D in o especially when the plane participates in‘ aerial combat. Accordingly, a coordinated control sys tem, subject in some respects to the pilot’s super vision, but otherwise as automatic in its reac tions as may be, is indicated. It will have been observed that use has been made of the ten , “pumping limit.” When the characteristic curve for a supercharger, operat— the present application. The present application relates to this speci?c form of pumping-limit detector and to certain details thereof that may at some designated speed, is plotted, it is read have use in other than a pumping-limit detector. 10 ily noticeable that a point is reached where fur The pumping-limit detector for a supercharger thcr reductions in the quantity of air passing disclosed herein is based on the discovery that through the machine fail to produce proportion pumping limit is reached when a, certain relation creases in the difference between the de is reached between increase in pressure produced y and inlet pressures. Tins point is some by the supercharger and velocity head of gas en .- es called the surge point, and, With respect tering the supercharger, Velocity head is actu to axial ?ow compressors, its existence may be ally a very small quantity in relation to increase explained by considering the character of flow in pressure, and thus if a balancing of one against through. the supercharger. Too- low a velocity of the other is to be obtained as is the case in the the with respect to the rotational speed of present application, it is necessary to ?nd some 20 iblades and their formation, causes the air to practical way of multiplying‘in effect, the force meet the blades at too- great an angle of attack, developed by the velocity head in relation to the aerodynamic how is interrupted and the machine force developed by the increase in pressure. The stalls. This condition produces noises and vibra means developed in the invention of the present tions and pulsations which may cause physical application for carrying this out is of special ad 25 failure of the parts, with attendant disruption of vantage with the particular type of pumping the entire power plant, Accordingly, operation limit detector disclosed, but may be employed of the supercharger at or beyond the surge point is to be avoided. On the other hand, the supercharger has the just as well in other situations, where it is neces sary to balance a small force against a large force or to make comparisons between large and small forces. As herein employed, the term “power plant” embraces the internal combustion engine proper, the propeller connected to the engine, and the supercharger which compresses the relatively rare air for delivery with the fuel to the engine inlet duty of supplying to the engine that quantity of air, under suitable pressure, which is needed under its Wide range of operating speeds and horse pcwer demands. ’ ince the aircraft operates from sea level to very high altitudes, it is apparent that the density, and therefore the mass, of in ducted air is also a variable. Presupposing a supercharger designed to supply enough low den manifold. rThese units are often interconnected by gearing for simultaneous rotation. For satis sity air, compressed to a suitable pressure, for factory performance, it is necessary to correlate an open throttle condition of the engine, then a number of variables, such as engine or propeller 40 the samesupercharger may not operate effec speed the amount of fuel mxture and the pro tively with denser air at the same speed, nor portions of air and fuel in such mixture delivered with the rare?ed air at a lower speed, since to the engine, the actual speed of the super a change in either of these factors may adversely charger and its ratio to the engine speed, and effect the angle of attack. . When the surge points for the same super the pressure at which the fuel mixture is sup 45 plied. The wide variations in speed and power charger, subjected to changes in these variables, are plotted, it is found that they lie in or along loads on the and the variations in the air supply due to changes in‘ density andf’tem another curve, which establishes the “pumping limit”. for the supercharger throughout the perature with changes in altitude, coupled with range of operating conditions which it may en the incidents of ?ight service, make the integra-' tion and resolution. of these variables an extremely counter. In practice, it means that; a certain difficult task. Independent manual adjustments, relationship must be maintained between the made by the‘ pilot or crew in‘ response to indicat pressure rise through the machine, and the quantity of air which passes through the super ing dial readings, are too dependent on human frailties and preoccupations to be satisfactory, 55 charger. Mathematically, the relationship may 2,407,§25 3 4 be expressed, with su?icient accuracy for present D insures the operation of the supercharger S purposes, by a simple equation in this form: within its pumping limit‘. The unit E, on the righthand side of the control rotor A, is pro vided to govern the speed ratio between the where P2 is the pressure of the discharged air; ' P1 is the inlet or barometric pressure; p is the supercharger S and the engine (not, shown). density of the inducted air; 1) its velocity; and K, K’, are constants. This relation may also be expressed by the equation: . In one aspect, this invention contemplates a control system in which the supercharger is made to operate within the pumping limit. The principles and means hereinafter discussed in 15 detail will disclose how such result is obtained. An object of the present invention is to provide improvement in a pumping-limit detector. Another object is the provision of improve-' ment in a pumping limit detector of the type 20 functioning on a relation of pressure increase With this unit is associated a solenoid control valve H and electrical circuits illustrated dia grammatically at the upper right of the ?gure. The unit M is a mechanism provided to adjust the fuel mixture and it is also responsive 'to the setting of the rotor A. The linkage L, also con nected to the rotor A, is connected at its oppo site end to the propeller governor (not shown) of the engine in'such manner as to govern the speed of the engine. Supercharger discharye'pressure regulation Air enters the supercharger S through an inlet line H, ?owing through a venturi l2 and thence into the inlet of the supercharger for delivery into a line 13 which is connected to the engine inlet manifold at a point not shown. The line I3 is provided with a lateral or spill pipe Ill in which is and velocity. .A further object is to provide an improved device for balancing or comparing large and rotatably mounted the waste gate or spill valve G. , Additional objects, and the advantages to be 25 An open position of the valve G permits the super charger discharge to bleed to the atmosphere, a derived from the practice of the invention, both closed position of the valve G directs all of the ' in its entirety or by use of its several components, discharge to the engine manifold, and interme will become apparent from a perusal of the fol lowing description of a preferred embodiment, 30 diate‘ positions of the valve permit proportionate withdrawals of the compressed air, either to read in connection with the accompanying draw diminish its quantity or its pressure. ings. The system is such that the pilot may manually For the purposes of clarity and simplicity, position the gate G. For this purpose a link l5, there are omitted from the drawings representa small forces against one another. tions of various standard parts, accessories, and design details, since these, as such, form no part operable from the pilot’s position, is connected. by 35 a clevis to a radial arm l6 extending from the outer surface of the unit A. The unit A comprises of the present invention and are here unneces a pivotally mounted rotatable member having a sary for a full presentation of the subject to plurality of cams formed on its external periphery, those skilled in the art. For like reasons, no attempt has been made to illustrate an airplane 40 and internally divided into two chambers by means of inwardly extending sectors H and 18. engine, nor the details of a supercharger, nor These are cut away at the center to receive a themechanism interconnecting the same. diametrically extending vane l9, rotatable within Fig. 1 is a diagrammatic view partially in sec and with respect to the casing of the rotor A. tion of controls for a supercharger; Fig. 2 shows ‘an airplane propeller and pitch control there 45 There are thus formed pairs of opposed chambers 2| and 22, the chambers in each pair being con for; and Fig. 3 is a sectional view of a pumping limit detector. ‘ In approaching a consideration of the draw ' ings, it may be initially helpful to designate cer tain of the units by reference letters, the de 50 tails of which will be presented hereinafter. The unit A is a rotary member manually operable by the pilot into various positions and, the auto matic control features are, to a large extent, governed by the setting of this control instru V55 mentality. The unit B is a valve including member, man ually operable by reason of its connection to the unit A, and further subject to automatic adjust nected by holes 24 diagonally drilled through the hub of the vane IS. The several chambers 2| and 22 are ?ooded with hydraulic pressure ?uid ad mitted from a suitable source through the oil ?lter F and normally blocked off from free flow by valve mechanism hereinafter described. Ad mission or withdrawal of the pressure ?uid to the chambers is effected by piping 25 and 25 entering the pairs of chambers through ducts formed in the rotor casing wall. The vane I9 is, of course, rotatably pivoted for motion relative to the rotor casing, and the unit as illustrated is also pro vided with a cover plate in order to close the ment. The unit C is a valve device responsive 60 chambers and preclude oil leakage. _ i It will be observed that, with the parts in the to excess changes in the pressure conditions oc position illustrated, a left hand movement of the curring therein. The three units A, B, and C link 15 will effect a counter-clockwise rotation of operate conjunctively with a supply of hydraulic the rotor A. Since it has been assumed that the pressure ?uid entering the units through a ?lter F, and in such manner as to establish the posi 65 chambers 21 and. 22 are blocked against ?ow of oil, then such movement will drag the vane [9 also tion of a waste gate or spill valve G positioned in a counterclockwise direction to rotate an at in the supercharger delivery line. These units, tached shaft 21 upon which is mounted the'gate therefore, modulate the discharge pressure of valve G. counterclockwise rotation of the valve the ‘supercharger, which is designated by the reference letter S. 70 will close the lateral l4, and thereby operate to build up rapidly the pressure in the engine inlet The unit D at the left of the ?gure is a pump line 13. Conversely clockwise rotation of the unit A ing limit detector whose function it is to super would, under the same blocked condition for the vise, and even to overrule, the decisions made by *vane 19, open the valve G to its limiting position. the foregoing units in connection with the set ting of the valve G. In other words, the detector 75 A gear segment 28 is formed on the lower external 2,457,925 portion of the rotor A and its teeth'engage with a rack 29 included in the unit B. This unit comprises a stationary cylindrical housing 3| (note, for example, the ‘securing lugs 32 at the extreme right). The cylinder 3| is suit ably cut away at its mid portion to permit en gagement of the teeth of the gear and rack .28 and 29, while the right hand portion 33 is to the‘ left. The ?ow into and away from the rotor would now be reversed, admission being effected through the ports 42 and 54, and dis charge occurring through the ports 53 and 45. The remainder of the circuits is the same as here tofore noted. ‘Too rapid overtravel of the vane IS in‘ either rotational direction is forestalled, how ever, by the operation of the stabilizing unit C. A‘rapid increase in pressure in either chamber enlarged. Within the bore of the cylinder 3| is a longitudinally movable sleeve 34 having on its 10 58‘ or 59, coupled with a sudden release of hy external surface the rack 29. The sleeve 34 in draulic pressure in the opposite chamber, creates turn receives a valve unit 35 provided with a stem momentarily a substantial pressure di?erential 36 which extends to the right hand section 33 on the opposite ends of the piston 51. This pres where it is coupled with a bellows assembly in~ cluding the bellows 31 and 33. The left hand 1-5 sure differential, therefore, drives the piston into one chamber or the other, to close, by means of section of. the sliding sleeve 34 is provided with abutting valve discs 62, one or the other of the ports and ?uid pressure line connections adapted . connections to the ports 53 or 54. Accordingly, to be opened or closed by relative movement of the the outwardly ?owing oil develops a back pres valve 35. a sure in the discharging chambers 2| or 22, and Pressure ?uid is admitted to the unit B through a pressure line 4! into’ any inlet chamber 42 con 20 in this way prevents the vane l9 from going to its extreme position too rapidly. Obviously, the nected to the clear space between the valve'discs action of the piston 51 is the same, except for its 43 and 44. Similarports 45 and 41 are provided direction‘ of motion, irrespective of the applica for normal connection to the space between discs tion of the hydraulic pressure to either side of 43 and 48 and 44 and 49 respectively. These last mentioned ports are coupled together by tubes 25 the vane member I9. Accordingly, the valve G will initially move to that position determined 5l-which in turn are connected to a drain line by the manual setting of the control unit A and 52. The sleeve 34 is also provided, at a radially will thereafter tend to creep forward to its limit remote region, with two additional ports 53 and ing position. 54. These ports are normally covered by the valve Opposition to overtravel, and restoration of discs 43 and 44. ‘Thus, in the position shown, pres 30 the valve G1 to ‘a ‘suitable position, is effected sure ?uid may enter the region between the discs through the bellows assembly contained'in the 43 and 44 via the port 42, but it cannot go any right hand section 33 of the unit B. The bellows where because the exit ports 53 and 54 are blocked 38 is secured at one end to the wall 65, and, at by these discs. l‘ ‘ to in its opposite end, it is joined to‘ the bellows 31, The ports 53 and 54 are connected by suitable tubing to opposed chambers formed within the casing of the unit C. This casing has a central shoulder portion 56 receiving a piston 51 which is being sealed therefrom by the disc 66. Before sealing, the bellows 38 is evacuated to a very low or negative gauge pressure. The bellows 31, normally maintained in its centralized position 40 which is free to ?oat in the casing 33, is connected at its opposite end to the valve stem 35, and it by the hydraulic pressure exerted on its ends, is also provided with a vent 61 of small diameter. which are in communication with the opposed The space between the bellows and the inner chambers 58 and 59. Each chamber also re wall of the casing 33 is connected to the super ceives a spring 6|. The chamber 58 is connected charger. discharge line I3 by a conduit 58. An to the chambers 2| of the unit A by the ‘above end wall 59, positioned between the casing 33 and mentioned piping 25, while the chambers 22 are the sleeve 34, and formed with a‘ suitable gland connected to the chamber 59 by the piping 26. to receive the stem 35, prevents manifold pressure Since, as previously noted, ports 53 and ,54 of the from being exerted on ‘the valve disc 49. unit B are normally blocked by the valve discs 43 ' Increase in the manifold pressure, caused by and 44, it will now be apparent ,why there can closing the gate G, therefore causes an increased be no displacement of the pressure ?uid in the pressure to be exerted on the sealed bellows 38, chambers 2| and 22, and why thevane l9 must, to contract its length. This movement draws the under these conditions, turn with the unit A. valve stem 36 to the right, and therefore replaces However, while initial rotation of the manually operable rotor A causes the valve G to shift, due 55 the discs 43 and 44 over the ports 53 and 54. Flow of the hydraulic ?uid is accordingly ar to the drag on the vane l9, rotation of the unit A rested, and the valveG is ?xed in position. Con (in a counterclockwise direction, for example) versely, had the rotor A been turned to open the also draws the longitudinally movable sleeve 34 to gate G, then the sleeve 34 would have been shifted the right, due to the intermeshing ofdthe segment to the left, and the diminution of manifold pres 28 with the rack 29. This motionconnects the 60 sure would have permitted the bellows 38 to ex port'53 with the port 42, and the port 54‘with pand. The valve discs 43 and 44 would again the port 41. Accordingly, pressure ?uid may now have followed after the ports 53 and 54 to restore ?ow through the line 4|, ports 42 and 53, chamber and maintain the balanced condition. 59, and line 25, to the pair of chambers 22. The It is apparent that any condition causing a chambers 2| are concurrently connected to the 65 drain line 52 through the piping 25, chamber 58, ports 54' and 41, and lateral 5|. Hydraulic pres sure is now applied through the chambers. 22 to cause the vane l9 to move in a counterclockwise direction to its limiting position, or, the move ment of the rotor A brings into play mechanism causing the rotor l 9 to overtravel. ‘ . Conversely, if the rotor A were rotated in a clockwise direction, as by pulling the link l5 to the right, then the sleeve 34 would be shifted change in the manifold pressure is re?ected by the extension or contraction of the bellows 38, with compatible readjustments of the valve mech anism in the unit B, and the positioning of the gate G. Regulation of the manifold discharge pressure, and its maintenance at a substantially constant value, is thereby effected. Such regulation is not, however, necessarily instantaneous, because of the action of the bellows 31. Since both interior and exterior of this bel lows“ are’normally subjected to equal pressures, 251407326 byreason cfthe vent 61, relatively slow or small changes in manifold pressure have no signi?cant effect on thebellows 31. When rapid pressure changes tend to occur, as for example, during a power dive or steep climb, the rapid change in the pressure on the exterior of the bellows 31 creates a pressure differential, due to therestrict ing effect of the ori?ce 61. The bellows 31~will 8 once in the areas of the diaphrag-msiill-a and 18. Since the diaphragm-13 is only slightly larger in area than the diaphragm 11a, the ‘difference be tween these areas is small and the force exerted to the left, on the valve stem 84 is only a small multiplication of the difference in pressures. . In contrast therewith, the area of the dia phragm 1-5 ‘is larger than that of diaphragm 18 and ‘many ‘times larger than the difference in the then tend to expand or collapse, as the case may areas of ‘the diaphragms 11a and 13. Conse 10 be, and thereby add to or subtract from the force quently, the velocity head in the inlet l i measured acting on the valve stem 36. r I by the difference in pressures in the pipes 16 and It will be noted that thebellows 31, which is 11 is multiplied considerably by the large area of sensitive to the ‘rate of change of manifold pres the diaphragm 1-5 to an appreciable total force sure, eifects a rapid adjustment of the valve unit to the ‘right on the valve stem 81%. 7 " 5 :in anticipating the adjustments to be secured 15 What is accomplished is the use of a small area :by'the .bellcws 38. Thus, in a power dive, the for one unitiforce and of a large area-tor another because of the rapid _ manifold pressure increases, smaller unit force to establish a relation between transferto a region of denser air. The pressure the two unit forces depending upon a multiplica- increase operatesto foreshorten the bellows 31, thus admitting pressure ?uid through port 54 to chambers 2i, to open the spill valve G, as pre viously described. As the pressures within and tion of the smaller unit force. This. might have been accomplished by the use of a very small dia phragm, but this would increase the possibility’ of errors very considerably. Instead, I have accom plished the same result by the use of two rela tively large diaphragms 11a, and 1,8, which "are of In fact, due to the falling external pressure, 25 slightly different areas and are opposed to one caused by the opening of gate G, the bellows may another, so that they have the effect of one small 7 actually be extended beyond its free length. By diaphragm. _ > this time, however, the bellows 38v has taken a This arrangement‘ is ‘of special advantage with new position to govern the setting of the gate, pumping-limit detector disclosed‘hcrein, for and the combined ‘assembly therefore works to 30 the this detector functions by vbalancing velocity meet a rapid pressure change with a rapid read head, a Very small ‘quantity, against pressure justment, followed by rapid dampening to pre difference, :a more appreciable quantity. How outside of the bellows‘?! become equalized, by flow through the orifice 61, the bellows expands. ' vent hunting of the valve 35. Pumping limit detector The pumping limit detector D best shown in Fig. 3 is provided to supervise the performance of the units A, B and C, as just described, and ever, it should be’ understoodthat this arrange ment is not limited to pumping-limit detectors of this type vorpumping-limit detectors of any type, for it may be applied ‘as well to other devices. ' It should ‘bev noted that a bellows 91 ‘is secured element of the combinations constituting a part 40 to the right end of the chamber 113 and to the outer side of the diaphragm 1.8,. reducing the of this invention. effective or pressure-responsive area of the outer The unit D comprises a cylinder 1| provided side of diaphragm. Without the bellows-91 the with left and right hand chambers 12 and 13 of pumping-limit detector ‘D would operate accord different diameters, and a central bore 14. The ' chamber 12 is divided into two parts by a dia 45 ing to the equation: it will be herein treated insofar as it forms an phragm 1-5, the left hand part being connected to P2-—P1=K1/2pV2 inlet pressure by a pipe 16 leading to the super charger inlet .l i. The right hand part is con With the bellowsthe equation ‘is either nected by a pipe 11 to the venturi l2. The dia phragm 15 is, therefore, subject to an unbalanced 50 pressure proportionate to the pressure drop be tween the upstream and throat regions of the ventur-i, which pressure tends .to force the dia The diaphragms 11a and 18 have members or portions secured to their inner sides, which ‘The right hand chamber 13 is divided into three 55 abut one another and transmit the forces exerted sections by two spaced diaphragms 11a and 18. upon one diaphragm to the votherdiaphragm and The middle chamber, between the two dia vice-versa. I phragms, is subjected to inlet pressure by a con Interposed between the two chambers 12 and 1.3, duit 19 leading to the pipe 16. The right hand and in the bore 14, is a valve unit whose stem section of the chamber 13 is connected to the 60 84 abuts both the vd-iaphragms 15 and 11a.v A supercharger discharge line 13 by a pipe 8|, and centrally located valve disc -85 normally uncovers to the left hand section by a duct 82. Thus, the a port ‘86., which ‘is connected to high pressure same high pressure is applied in opposing direc hydraulic ?uid by a branch $1. The liquid is thus tions on the diaphragms 11a and 18 against the admitted to the clear space between the disc 85 relatively low resistance of inlet pressure in the 65 and another disc 88, which space is connected to phragm 15 to the right. . space between the diaphragms. the pressure line 4| by a port .89. > ‘The previously The area of diaphragm 18 is slightly larger than described drain line '52 is coupled to a port Bi that of diaphragm 11a. Since the inlet pressure leading torthe clear space between the "disc »85 in pipe ‘i9 is applied in opposed directions on the and a third disc 92, for connection to a port 93 in, diaphragms Tia and 18 in the chamber between 70 communication with the master drain line 94. these diaphragms, and the outlet pressure in pipe Another drain line‘95 leads through an additional 8i'is. applied in opposed directions on the outer port Q6 tothe :clear space between the discs 85 sides .of diaphragms 11a and’ 18, the net thrust and 588,110 become effective when the valve assem to the left due‘to these pressures is a product of blyzpushed over to the left. At that time, the ‘the difference in these pressures and the differ 2,407,925 9 - inlet line 87 is coupled to the li' e while the master drain is connected to the line ill Any sh"ting of the valve stem which makes: the line a drain, and the line 52 a pressure supply line, of course completely reverses the ' direction of application of force on the vane it of unit A, as heretofore described. I“ o’her word‘ the val Ye settings of u it D, in existing pressure cond- ‘> ‘ I B iiiil, pulling it along to close the damper I06, and thereby additionally throttle the engine. pressure line, v hereby the units A, a; late the setting of the gate G as forme When the settings are reversed, then 1. - vane .10 nected to a linkage 5'95, which is connected in turn to a damper 5G5 pivoted in the manifold line is. Normal :back and forth motion of the rod lei? simply causes the pin iiiil to ride in the slot m3. Under these conditions the damper I05 hangs wide open, and is not aifected at all. However, if the link it is pulled to its extreme position, the end of the slot engages the pin Restoration of the link iii to a normal operating , range permits the‘ damper’ to open, restoring the control ofthe air supply to the units heretofore tion, for example, will move it an open posit on. considered. The detector D may therefore on .pletely l'illillfy .15 the natural inclination of the or its A, B and C Supcrchargerdrive control instead of moving the gate G to charger in actuating discharge the valve pressure. G, closed pom.. the The supercharger ‘S is driven from the engine through a drive unit H2, which, as herein indi The detector operates to overrule the waste cated includesnuid coupling members and gearing gate regulator, and reverse its action, when the amount of delivered is so small, with respect to the pressure rise, that the pumping limit of the supercharger is reached. Such a situation may arise under variation in the controlling fac tors heretofore discussed. Referring again to the left hand chamber 72 permitting the supercharger to run at one or the other of two speed ratios. Normally, the gearing will be set to drive in the low speed ratio. ‘How , ever, when high altitudes are encountered, it may be necessary to shift to the higher speed ratio, .25 so that the supercharger may deliver an adequate quantity of air and still operate safely ‘within the pumping limit. The particular drive just re ferred to is not the subject matter of this inven cf the unit D, it will be seen that the force ex~ erted in the right hand direction, which tends to keep the main pressure line in communica ticn with the line ill, is proportional to the work in‘T of the diaphragm "l5 and to the pressure .30 drop from atmosphere to the‘ Venturi throat l2. vThe ‘pressure drop is in turn proportional to the density of the air, and its velocity. Hence, tion, and therefore, is not shown in detail. Here, the description is concerned with the control of the drive, and, since a fluid coupling is involved, the control means is made to» govern the supply oi'hydraulic ?uid to thegcoupling. There are two hydraulic pressure fluid lines, 2' 53, l Hi, which lead from the unit H to the cou pl'ng ! l2, and a main feeder i it extends‘ from the expression: [p02]. The left hand thrust is simi F to the unit H. When the feeder H5 is larly proportioned to the ‘pressure rise (Pg-$1), connected to the line M3, the unit H2 is in low since the middle section of chamber l3 is con when the unit H is actuated to couple nected to atmosphere, while the other faces of 40 speed, the lines 5 l5 and i it, the supercharger S is driven the differential diaphragms l'lc ‘iii are sub? through the high speed ratio. Selection of the jected to the supercharger discharge pressure.‘ position of the unit l-I may be effected either man Accordingly, under normal conditions of op the mean effective thrust on the left hand end of the valve stem 3% may be proportioned to the eration, or over that range of pressure quantity ratios within the pumping limit, thedetector D 45 p rinits admission of ‘the hydraulic pressure ?uid L to the line Ill. The units A, B and ‘C then ‘func tion as ?rst described, the manifold pressure‘ is regulated, and any excess air delivered at that pressure, which is not needed by the engine, passes to waste through the partially open spil1 valve ‘ G. When this relationship changes in such man~ nor as to cause the supercharger S to approach its pumping limit, the gate rather than ‘being ually, or automatically through the unit E. The at comprises a fixed cylindrical casing l2! ' <3: a movable follower :22 projecting from end thereof, and held in engagement with a cam on the rotor unit ‘A by means of a spring‘ 3 disposed in the casing l2! between end wall and the inner end of the follower. . hollows is ?xed to the free end of he follower i223, and it abuts a push pin I26 of .is electric switch 523. The follower ‘122 is open ‘he atmosphere, and the bellows E25 isevacu Hence, atmospheric pressure tends to col turned to closed po tion in the manner ?rst .55 lapse the bellows withdraw its inner end from outlined, will new ‘so ti‘: rust toward an open posi tion, The resulting reduction of discharge pres sure head, 1by the relief of the compressed air, is re?ected in the line and on the diaphragms engagement with the push pin 52%‘. At higher altitudes the bellows will expand, due to the lower air density, and may do so even to a point where it can press the pin i255 sufficiently hard to shift Tia and id, as well as the bellows ‘3i and 38. fit) the switch till, everything else disregarded. Nor mally, the parts so proportioned that, at sea restoring to line Iii its function as a pressure ?uid Valve stem tbl may then move toward the right, supply line, and thereby making the unit 13 once more the control instrumentality. It may ‘be assumed that operation of the air craft causing the detector D to cut in and out of service will be accompanied by other conditions observed by the pilot. He may then elect to» shift the link 55 to the extreme right, thereby .to open the gate G, manually, and he may moreover de level, the maximum lift of the cam £23, brought into by rot on of unit A, is insu?cient to offset the contraction of the bellows 125. As higher altitudes are reached, extension of the ‘bel lows E25 permits the actuation of the pin I26 diirerent settings of the cam I23, until ?nally a point is reached where actuation of the rotor A becomes _ unnecessary, as just pointed out. Thus, theswitch l2? will shift at some predeter sire to throttle the engine to an even greater mined altitude,"established by the setting of the extent. For this purpose, the arm it, connected rotor A and the barometric pressure. Or,~stated_ to the link i is vpcovided with a pin illl, to otherwise, each setting of the rotor A, by ‘the which is attached a, rod it? formed with a termi ‘ nal slot ‘I93. The slot receives a pin lllll con manual lever i5, determines the altitude at which 75 the supercharger may go into high speed. 2,407,925 12 high speed line H4, and blocking line II3 except The switch I21, as shown in the diagrammatic repetition in the drawings, is of a single pole, dou for the reduced lubricating flow alluded to. On the next energization, the motion is reversed and the stem I5I is pushed up to restore it to‘the ble throw type, wherein inward movement of the pin I26 forces the resiliently supported lever I28 into engagement with a high speed contact 7 I29, while withdrawal of the pin I26 permits the position illustrated. ' The stem I5I carries spaced conductive discs I64 and I65, which respectively bridge either’ lever I28 to move forward against a low speed contacts I66 and I61 or contacts I69 and I69, depending upon the position of the valve. Con contact I3I.l Manual control over the electrical circuit is obtained through a switch having a tacts I66 and I69 are connected by a common pivoted arm I33 which maybe selectively set 10 wire IN to the solenoid I63, the other side of on an automatic control contact I34, a low speed contact I35, or a high speed contact I36. When which is grounded.’ Let it be assumed that the machine has been running in the lower speed ratio, the parts of the arm is in the position shown, the gearing I I2 may be in either high or low ratio; when point the solenoid valve unit H being as shown, and I35 is used only a low ratio is available, and 15 that the pin I26 has just been moved to force when point I36 is connected, the high speed ratio is selected, subject to certain limitations here after stated. the switch arm I28 into engagement with the high speed contact I29, the switch arm I33 then contacting the automatic control point I34. A ; The circuits established by the vsettings of circuit for energizing the solenoid I63, thereby switches I33 and I21 (which will be traced di 20 to shift the valve member 539, is now established rectly) determine whether ?uid will flow from as follows: ‘ line II5, through unit H, to line H3 or line II4. , From the power source through arm I33, con This unit comprises a housing I31 formed with a tact I34, wire I12‘ to arm I28 and high speed bore I38 in which is slidably mounted a valve contact I29, thence via wire I13 and junction, I14 25 member I39. The feeder line II5 connects to a to wire I15 into the armature I16 of a relay R, port I4I, communicating with the bore I38, while then engaging contact I11 connected to wire I18 leading to contact I61.at'stem I5I; thence through disc I64 to contact I66 and wire I1I to the winding of the solenoid I63, to ground and .the lines H3 and H4 are respectively connected to axially spaced ports I42 and I43. The valve member carries a series of spaced discs which serve to direct pressure ?uid to the 30' return. Plunger I62 is thereupon lifted to pull line H3 or II4, depending upon their relation down the Valve I39 as previously described, the disc I64 being separated from contacts I66 and ‘to the port MI. The structure is so similar to I61 to break the circuit just traced when the the valves heretofore described that it is believed links I6I approach dead center. The disc I65 unnecessary to elaborate thereon. It may, how 35 will accordingly engage contacts I68 and I69 ever,'be noted that the unit is formed with addi tional, similar ports I45 which seem to re-open the feeder II5 to the line from which it other when the parts have come to rest. , When the pin I26 is withdrawn, switch arm I28 engages low speed contact I3I, and a re wise would be, blocked. This, however, is desir able, since the short-circuiting connection is 40 versal of the ?uid connections, to restore the low taken through a restricted ori?ce, as shown. speed ratio, is effected through the following Admission of a limited amount of ?uid to the blocked line H3 or II4 assures lubrication and cooling of the coupling then’ out of service, but circuit: the total flow is too small, for power transmission purposes. The valve member I39 has an extended stem I5I terminating in a olevis I52, the pin of which is positioned in a slot I53 of a lever I54, pivoted on a fulcrum I55. The opposite arm of the lever is formed with a fork I56, in which may ride a From the power source to contact I3I, wire I19, junction IBI, wires I82 and I83, thence through disc I65 and contacts I58 and I6g9'to the solenoid I63. ' ' Let it be assumed that the pilot selects the low speed contact I35 for the switch arm I33. Cur rent then ?ows through contact I35 and wire I83 to contact I69, thereby to establish a circuit for low speed position of the unit E. If it be as 50 sumed that the high speed contact I36 is selected, the solenoid valve unit will (subject to a subse pin I51 extending from a rocker segment. The segment, which is centrally pivoted on a stud quently stated limitation) remain in the desired position, being actuated through the following I59, carries a pair of links I6I at one corner, which extend to a plunger I62 of a solenoid I63. 55 circuit: Contact I36, wire I15, .armature I16 When the solenoid is energized, the plunger is and contact I11 of relay R, thence via- wire I18 pulled up, thereby to rotate the segment I58 and ‘to contact I61, etc. to bring the links I6I into a substantially verti The relay R is introduced into the ‘high speed cal position. As will presently appear, such move circuit to enforce a low speed gearing when the ment simultaneously breaks the energizing cir compressed air in the delivery line I3 exceeds a predetermined temperature.~ The relay in cuit, permitting the plunger I62 to drop away. Due to the inertia of the moving parts, however, the segment does not fall back to its starting position, but continues its travel to the opposite upper quadrant from which it started. Thus, 65 through a thermostatic" switch I88 positioned in the pipe I3. Thus, the coil I85 will be ener each energization of the solenoid shifts the pin‘ gized whenever switch I88 closes at a predeter I51 up or down. mined temperature. ' r This motion is transmitted through the lever ‘ cludes a coil I85, connected directly to the power , source by a wire I86 and a wire I61 leading I54 to shift the valve stem I5I either down or For example, the draw up, as the case may be. ings show the links I6I in the second quadrant and the valve discs I44 so located as to supply pressure ?uid to the low speed-line II3. Upon, energizing the solenoid I63, links I6I swing to the ?rst quadrant, and stem I5I is pulled down to connect ports MI and I43, thereby supplying Armature I16 is then'pulled down against the .urge of its holding spring I89 to‘ engage contact 70 I9l, which leads via wire I92 to junction I8I, and so into the low speed selecting circuit. The armature I16 is latched into this posi tion by an armature I93 of a second coil I94, which must be energized to permit the armature ' 75 I16 to return into engagement with contact I11,‘ 2,407,925 “ 13 after the switch l88 has opened. A circuit for this coil is established by contacts I95 andvl??, connected to the coil, and adapted to be bridged by a manually depressiblo switch arm £91. It will thus be seen that the control of the supercharger speed ratio .is quite ‘?exible, the pilot may insist ‘on a low ratio, or a high ratio subject to the thermostatic supervision; or he may let the ratio be ‘determined automatically but still subject to his positioning of the rotor A. Engine regulation ' 14 crease the speed. This can :be done by changing the propeller pitch. 7 . V The ,unit L is therefore provided to adjust the propeller and engine speeds in response to the manifold pressure. The periphery .of they rotor of unit A is formed with a milled cam slot M5, to which ‘is connected a bellcrank lever ‘M6, the upper arm of which is pivoted to a linkf I]. This link extends to a control mechanism 218 fora propeller governor speed control, the propeller being indicated by 21 9. Hence, an extreme move ment of the rotor A, representing a high or low The engine of the power plant is supplied with air ?owing past the damper Hi6, and fuel which V is later mixed with such air. It is common in the art to include, with the engine, a propor ‘manifold pressure, will affect the propeller pitch, while in intermediate positions the inner end of “the vlever lid is free to ride in the slot 215. The slot EI‘S is advantageously ‘so cut as to insure a tioning device through which the relative per de?nite relationship between engine speed and centages of fuel and air are determined and manifold pressure, the curve being laid out from knowledge of the engine characteristics. In such maintained. However, it is desirable to super vise the performance cf such device in response to the manifold pressure, as determined by the instrumentalities heretofore considered. Thus, if the manifold pressure becomes either high or low, a rich mixture is indicated, while at inter mediate pressures, the mixture may be lean. Means for assuring the rich mixture are pro vided by the unit M, operating in conjunction with the manifold control unit A. The unit M comprises a valve casing 29! enclosing a spring , loaded piston 282, whose stem 253 extends be yond the casing for connection to the carbu retor controls, not shown; ‘ The casing 2!!! also contains a bore 2% re case, intermediatesettings of the rotor A cause the lever M6 to be'positoned so as to follow the speed and pressure relationship. It will thus be seen that the present invention provides an integrated control, automatic in oper ation, for the various components of the power plant, and accordingly relieves the pilot of the , necessity-of making a large number of independ ent adjustments. He is, however, free to'super vise many such adjustments by his overriding ‘manual controls, and he may therefore exercise his judgment with considerable latitude. The system is obviously directed to one wherein the supercharger is regulated by control of ‘the dis ceiving a plunger 205, formed with a stem ace . charge pressure, rather than by throttling the which normally engages the dwell portion be supercharger inlet, and any excess of air deliv ered at the predetermined pressure is according ly sent to waste. Such plan of control admits of tween two similar cams 201 on the rotor A. The bore 2% is formed with ports on either side of the head on the plunger 285, one of which is connected by a pipe 285 to the main hydraulic feeder line H5. The other port is connected to a drain line, and it also communicates with the l upper side of the piston 2E2 through a duct 289. Hydraulic pressure therefore urges the plunger 295 to the right, bringing the stem 2535 into en 45 gagement with the periphery of the unit A. The plunger?d? normally partially uncovers a port 2“ below the piston 2&2‘, thereby en abling pressure ?uid from the line 238 'to urge the piston and its stem ‘2.93 ‘upward. This posi tion, by connection to any suitable linkage, sets the carburetor for operation in the usual ‘manner. If, however, the rotor A is moved to either ex treme position, the stem .236 rides up on one or the other of the cams Zill, and moves to the left to block the line 208, and connect the port 2-H to drainage. This permits the piston .262 to drop. If the rotor A is rapidly shifted from one extreme the simultaneous governing of the other related Variables, as hereinabove explained. While the invention has been described with reference to one embodiment only, it will be ap parent that numerous changes and modi?cations may be made without departure from its prin ciples, or the scope of ‘the following claims. I claim: ' 1. A device for comparing a small pressure quantity with a much larger pressure quantity by causing the small quantity to act against a “much ‘larger area than that acted against by the much ‘larger quantity, said device comprising ?rst and second diaphragms positioned opposite one another, the pressure-responsive area of the , ?rst diaphragm being larger than that of the sec ond diaphragm, means for causing the much larger pressurequantity to apply force in one di rection against the outer side of the ?rst dia phragm, means for causing the much larger pres sure quantity to apply force in the opposite ‘di- , position to the other, the piston 2532 will not, however, be signi?cantlly affected. This is due 00 rection against the second diaphragm, members secured to the inner sides of the first and sec to the fact that the admission of pressure ?uid ond .diaphragms and abutting one another for through the port Eli is slow, in comparison to causing ‘the forces ,to act in opposition to one the drainage rate. Accordingly, the valve unit another and to be resolved to a small force act protects against sudden mixture changes which one direction and being propor might be conducive to creating backfires. When G 5 ing in vthe tional ‘to the product of the much larger pressure the piston 2'52 drops, the corresponding move quantity and the difference in the pressure-re ment of the stem 2% sets the carburetor unitin sponsive areas of the ?rst and second diaphragms, such position that only a rich fuel mixture can ‘ a ‘third diaphragm, means ,for applying the small be supplied. Since the extreme movement of pressure quantity against the third diaphragm in unit A corresponds to a high or low manifold pressure, the apparatus therefore achieves the purpose intended. . > the said opposite direction, and means connecting the third diaphragm with the ?rst and second diaphragms. , Under take-oil conditions, a relatively high .2. A device for comparing a large difference in propeller, and engine, speed are desirable, while pressures between two regions at high and low under flight conditions it may be better .to .de 75 pressures with a small difference in pressure be 2,407,925 15 tween two regions at high and low pressures; said device comprising ?rst and second diaphragms having inner and outer pressure-responsive areas and being positioned with inner pressure-respon sive ‘areas opposite one another, the ?rst dia f phragm having larger pressure-responsive areas than the second; means for applying in opposite directions against the inner pressure-responsive 16 the high pressure of the other of the two regions having the low difference in unit pressures, the last mentioned high and low pressures producing a resultant force directed toward the ?rst and second diaphragmsand beingproportional to thev product of the area of the third diaphragm. and the small difference in pressures; and means connecting the third diaphragm with the ?rst and second diaphragms for balancing the result areas of the ?rst and second diaphragms the low pressure of the one of the two regions having a 10 ant force produced at the third diaphragm against the resultant force produced at the ?rst large difference in pressures; means for applying and second diaphragms. in opposite directions. against the outer pressure 4. A device for comparing a large difference in responsive areas of the ?rst and second dia pressures between two regions at high and low phragms the high pressure of the other of the two regions having a large difference in pressures; 15 pressures with a small di?erence in pressures be tween two regions at high and low pressures, said 'means connecting the diaphragms for causing device comprising a ?rst means providing inner ‘ the said large difference in pressures to produce and outer pressure-responsive areas, a second aresultant force acting‘ in a direction from the means providing inner and outer pressure-respon ?rst diaphragm toward the second diaphragm and proportional to the product of the said large 20 sive areas somewhat larger than the pressure responsive areas of the ?rst means, the two inner difference in pressures times the difference be pressure-responsive areas being opposite one an tween the pressure-responsive areas of the ?rst other, means for applying in opposite directions and second 'diaphragms; a third diaphragm dis against the inner pressure-responsive areas of posed on the outer side of the second diaphragm in spaced relation thereto; means for applying 25 the ?rst and second means the low pressure of the one of the regions having a large difference in against the side of the third diaphragm facing pressures, means for applying in opposite direc the second diaphragm the low pressure of one tions against the outer pressure-responsive areas of the two regions having the low difference in of the ?rst and second means the high pressure pressures; means for applying against the other side of the third diaphragm the high pressure 30 of the other of the two regions having a large dif ference in unit pressures, means connecting the of the other of the two regions having the low ?rst and second means for causing the said high di?erence in pressures, the last mentioned high and low pressures to produce a resultant force act and low pressures producing a resultant force ing in a direction from the second means toward directed toward the ?rst and second diaphragms and being proportional to the product of the area 35 the ?rst means and proportional to the product of the said large difference in pressures times the of the third diaphragm and the small difference di?erence between the areas of the ?rst and sec~ in pressures; and [means connecting the third 0nd means, a third means having opposed pres diaphragm with the ?rst and second diaphragms sure-responsive areas, means for'applying against for balancing the resultant force produced at the ‘third diaphragm against the resultant force pro 40 one area of the third means the low pressure of the one of the two regions having the low differ duced. at the ?rst and second diaphragms. 3. A device for comparing a large di?erence in ‘ ence in pressures, means for applying against the other area of thethird means the high pressure pressure between two regions at high and low ‘ . pressures with a small difference in pressures be tween two regions at high and low pressures; said ' device. comprising ?rst and second diaphragms having inner and outer pressure-responsive areas I and being positioned with inner pressure-respon sive areas opposite one another, the ?rst dia phragm having larger pressure-responsive areas then the second; means for applying in opposite directions against the inner pressure-responsive of the other of the two regions having the low difference in pressures, the last mentioned high and low pressures producing a resultant force op posed to the resultant force produced at the ?rst and second means and being proportional to the area of [the third means times the small differ ence in pressures, and means connecting the third means with the ?rst and second means for bal ancing the aforesaid resultant forces. 5. A device for comparing a small pressure dif areas of the ?rst and second diaphragms the low ference representing velocity head of gas entering pressure of the one of the two regions having a large difference in pressures; means for applying 55 a supercharger with a large pressure difference equal to the pressure of gas discharged from the in opposite directions against the outer pressure supercharger minus the pressure of gas entering responsive areas of the ?rst and second dia the supercharger, said device comprising a ?rst phragms the high pressure of the other of the two means providing inner and outer pressure-respon regions having a large difference in pressures; members secured to the inner sides of the ?rst 60 sive areas, a second means providing inner and outer pressure-responsive areas somewhat larger and second diaphragms and abutting one an than the pressure-responsive areas of the ?rst other for causing the said large difference in means, the two inner pressure-responsive areas pressures to produce a resultant force acting in a being opposite one another, means for applying direction from the ?rst diaphragm toward the 65 the pressure of entering gas in opposite directions second diaphragm and proportional to the prod against the inner pressure-responsive areas of the uct of the said large difference in pressures ?rst and second means, means for applying the times the difference between the pressure-respon pressure of discharged gas in opposite directions sive areas of the ?rst and second diaphragms; a third diaphragm disposed on the outer side of ' against the outer pressure-responsive areas of the and second means, means, connecting the the second diaphragm in spaced relation thereto; 70 ?rst ?rst and second means for causing a resultant means for applying against the side of , the third force proportional to the diiference in pressures diaphragm facing the second diaphragm the low times the di?erence between the pressure-respon pressure of one of the two regions having the low sive areas of the ?rst and second means and act vdifference in pressures; meanszfor applying against the other side of the third diaphragm 75 ing in a direction from the second means toward 17 2,407,925 the ?rst means, a third means having pressure responsive areas, means for applying against the pressure-responsive areas of the third means the small pressure difference representing veloc 18 discharged from the supercharger and pressure of entering air, to reverse control apparatus for the supercharger by switching certain lines of the control apparatus from a source of fluid pressure to exhaust and vice versa, said detector the resultant force produced at the ?rst and sec comprising a ?rst means having inner and outer ond means, and means connecting the third means pressure-responsive areas, a second means having with the ?rst and second means for balancing the inner and outer pressure-responsive areas larger‘ aforesaid resultant forces against one another. than those of the ?rst means, means for applying 6. A device for comparing velocity head of gas 10 the pressure of entering air against the inner entering a supercharger represented by a small areas of the ?rst and second means, means for ity head .to produce a resultant force opposed to pressure di?erence between a, pressure at one applying the pressure of discharged air against region of entering air and a pressure at another the outer areas of the ?rst and second means, region of entering air, with a large pressure dif means connecting the ?rst and second means to ference between the pressure of air discharged 15 produce a resultant force proportional. to the ' from the supercharger and the pressure of enter large pressure difference times the di?erence ing air, said device comprising ?rst and second between the pressure-responsive areas of the > diaphragms having inner and outer pressure» ?rst and scond means, a third means having responsive areas and being positioned with inner opposed pressure-responsive areas, means for pressure-responsive areas opposite one another, 20 applying the pressures having the small di?er~ the ?rst diaphragm having larger pressure-re ence in pressure against the areas of the third sponsive areas than the second, means for apply means to produce a resultant force opposed in ing the pressure of entering air in opposite direc direction to the resultant force produced at the tions against the inner pressure-responsive areas ?rst and second means, and means connecting of the ?rst and second diaphragms, means for ap the third means with the ?rst and second means plying the pressure of discharged air in opposite for balancing the resultant forces against one directions against the outer pressure-responsive another and including valve means for switch areas of the ?rst and second diaphragms, means ing the said certain lines of the control appa connecting the diaphragms for producing a re ratus from pressure to exhaust and vice versa, sultant force proportional to the difference in pres 30 depending upon the relative sizes of the result sure-responsive areas of the ?rst and second dia ant forces produced at the ?rst and second means phragms times the large difference in pressure and at the third means. , 7 between discharged air and entering air to pro 8. A device as speci?ed in claim 3, the outer duce a resultant force acting in a direction from pressure-responsive area of the ?rst diaphragm the ?rst diaphragm toward the second diaphragm, 35 being smaller than the inner pressure-responsive a third diaphragm, means for applying against area of the ?rst diaphragm. the opposite sides of the third diaphragm the 9. A device as speci?ed in claim 3 and further pressures having the small di?erence in pressures including a bellows means ?xed to the outer side representing the velocity head of entering air to’ of the ?rst diaphragm for making the said outer produce a resultant force proportional to the area 40 pressure~responsive area smaller than the inner of the third diaphragm times the small difference pressure-responsive area of the ?rst diaphragm.v in pressures and opposed to the resultant force 10. A device as speci?ed in claim 5, the outer produced at the ?rst and second diaphragms, and pressure-responsive area of the second means means connecting the third diaphragm with the being smaller than the inner pressure-responsive ?rst and second diaphragms for balancing the 45 area of the second means. aforesaid forces against one another. 11. A device as speci?ed in claim 5 and fur '7. A pumping-limit detector for a supercharger ther including a bellows means ?xed to the outer operating by comparison of 'a small di?erence side of the second means for making the outer between pressures at one region of entering air pressure-responsive area of the second means and another region of entering air representing 50 smaller than the inner pressure-responsive area velocity head of gas entering the supercharger of the second means. with a large di?erence between pressure of air HENRY W. GILFILLAN.