US3258914A - Group thrust compensator - Google Patents

Description

y 5, 1966 l G. s. BlSHOP ET AL 3,258,914

GROUP THRUST COMPENSATOR Filed Dec. 26, 1965 5 Sheets-Sheet 1 GEOFFREY s. isnaP INVENTORS RONALD w. How/4RD BY} A TTOR/VEVS y 5, 1956 a. s. BISHOP ET AL 3,258,914

GROUP THRUST GOMPENSATOR 5 Sheets-Sheet 2 Filed Dec. 26, 1963 @EOFFREY 8 )SM P INVENTORS ATTORNEYS July 5, 1966 s. BISHOP ET AL 3,

GROUP THRUST COMPENSATOR Filed Dec. 26, 1965 5 Sheets-Sheet -3 t 110 100 j 76 I ll! 1| 103 25 551% r K 111 INVENTORS GEOFFREY s. BisHoP RauALo w HOVARD U Q as A TTORNEYs United States Patent 3,258,914 GROUP THRUST COMPENSATOR Geoifrey Stanley Bishop, Luton, and Ronald Walter Howard, Gravesend, England, assignors to Elliott Brothers (London) Limited, London, England, a British company Filed Dec. 26, 1963, Ser. No. 333,473 Claims priority, application Great Britain, Jan. 4, 1963, 533/63 6 Claims. (Cl. 6035.6)

This invention relates to a group thrust compensator for an aircraft engine installation, that is to say, a device which ensures that a group of jet engines is always delivering a predetermined total thrust.

In VTOL aircraft employing a plurality of lift engines, possibly arranged in groups contained in wing pods, and possibly operating in conjunction with a further one or more engines delivering both a lift thrust and a forward thrust, it is of supreme importance that the lift thrust should be maintained at a predetermined level since a sudden variation, be it upwards or downwards, in the lift may have disastrous effects before the human pilot can correct it.

The object of the present invention is to provide a simple control arrangement which functions automatically to maintain a predetermined thrust, even when there is a tendency to large variations, such as will result from the failure of one engine of the group.

The invention consists of a group thrust compensator for a group of jet engines generating a lift thrust comprising a double-acting fluid cylinder and a piston and piston rod contained therein for each engine of the group, a source of fluid pressure for each engine to provide a fluid pressure corresponding to the thrust delivered by the engine when in operation, means to apply the fluid pressure from each source to the end of the respective cylinder containing the piston rod, a connection from the source of fluid pressure on each engine to a common chamber through a non-return valve, a connection from the common chamber to the other end of each cylinder, a calibrated leak device to allow the fluid in the common chamber to escape at a controlled rate, mechanical connections from the piston rods of all the cylinders to a single engine throttle control controlling the throttles of all the engines in the group, and resilient means acting on the pistons against the pressure from the common chamber, whereby all the pistons are acted upon at the one side by the highest pressure derived from the plurality of sources, each piston is acted upon at its other side by a pressure derived from the source on the associated engine, and the movements of all the pistons are transmitted to the throttle control.

There may be a further cylinder or cylinders containing pistons and piston rods, each further cylinder being connected at the end containing the piston rod by pressure from a source associated with an engine delivering a combined lift and forward thrust, the pressure source in this case having no connection to the common chamber, the piston rod of each further cylinder being mechanically connected to the throttle control. The further cylinder or cylinders may be of different diameter from that of the cylinders associated with the engines of the group.

Two embodiments of the invention Will now be described with reference to the drawings accompanying this specification, in which:

FIGURE 1 is a diagrammatic cross section of one form of group thrust compensator according to the invention;

FIGURE 2 diagrammatically shows in ghosted form an arrangement of a group of three lift engines in a wing pod, a fourth combined lift-thrust engine in a separate pod and the interconnections between the group thrust 3,258,914 Patented July 5, 1966 compensator, the group engine throttles and the pilots controls;

FIGURE 3 is a diagrammatic section of another group thrust compensator according to the invention; and

FIGURE 4 is a cross section showing a detail of the group thrust compensator of FIGURE 3.

FIG. 5 is a cross-section showing a detail of an autoselector valve of FIG. 4.

Referring initially to FIGURE 1, a group thrust compensator according to the invention comprises a casing 11 which contains four fluid cylinders, respectively 12, 13, 14 and 15. Each fluid cylinder contains a piston, re-

spectively 16, 17, 18 and 19. The piston 16 is provided with a piston rod or ram 20 which passes through the one end 21 of the cylinder 12, and in a similar manner the piston 17 has a piston rod 22 passing through the end 23 of the cylinder 13, the piston 18 has a piston rod 24 passing through an end 25 of the cylinder 14 and the piston 19 has a piston rod 26 passing through the end 27 of the cylinder 15. The other ends of the cylinders 12, 13, 14 and 15 are open to a chamber 28 formed by one end of the casing 11. Stops 29 are provided to prevent the pistons 16, 17, 18 and 19 moving out of their respective cylinders under the influence of fluid pressure and of a spring 30, supported by an abutment 31, which acts upon all the piston rods through the medium of a common member 32.

At this stage, it is desirable to consider the arrangement of the group thrust compensator in relation to the engines and controls of the aircraft, which is shown in the diagram of FIGURE 2. FIGURE 2 is a ghosted diagram showing an aircraft having a fuselage 33, wing 34, tail plane 35 having control surfaces 36 and a rudder 37 having control surfaces 38. Wing flaps providing control surfaces for braking purposes are indicated at 39. Three lift engines, respectively 40, 41 and 42, are located in a wing pod 43 while a combined lift/thrust engine 44 is located in a wing pod 45. The group thrust compensator 46 is located close to the group of lift engines 40, 41, 42 inside the wing pod 43. Each of the lift engines 40, 41 and 42 is provided with a source which produces a fluid pressure depending upon the pressure in the respective jet pipe and therefore corresponding to the thrust output of the engine. This may consist of a Pitot tube in the jet, or a static tapping, or it might consist of two identical venturis, one having its inlet closed, the difference in pressure in the two venturis being a measure of the thrust pressure in the jet.

The fluid pressure from the source associated with the engine 40 is transmited to the group thrust compensator through a pipe 47, the pressure from the source associated with the engine 41 is transmitted to the group thrust compensator through a pipe 48, and pressure from the source associated with the engine 42 is transmitted to the group thrust compensator through a pipe 49. A simisimilar source of fluid pressure is provided for the engine 44 and the pressure is transmitted by a fourth pipe 50 to the group thrust compensator 46.

Reverting now to FIGURE 1, the three pipes 47, 48 and 49 are shown connected respectively to the closed ends of the cylinders 12, 13 and 14. The pipe 47 is provided with a branch 51 which is connected through a non-return valve 52 to the common chamber 28 and in similar fashion the pipe 48 is provided with a branch 53 connected through a non-return valve 54 to the chamber 28, and the pipe 49 is provided with a branch 55 connected through a non-return valve 56 to the chamber 28, the valves all being arranged in such a sense that fluid under pressure may pass into the chamber 28 but not out of it. The chamber 28 is also provided with a leak device 57 through which fluid under pressure in the chamber 28 may leak at a controlled rate into an exhaust pipe 58.

The three cylinders 12, 13 and 14 are of identical diameter but it will be observed that the cylinder 15 is of smaller diameter and is longer, so that the piston 19 may have a longer stroke. The pipe from the combined lift/thrust engine 44 is connected to this cylinder but there is no branch from the pipe 50 connected to the chamber 28.

The common member 32 shown in FIGURE 1 is mechanically connected to a rod 59 which forms the throttle control run and is mechanically connected to the three engines 40, 41 and 42 by means of linkage which is also connected to the pilots primary throttle control 61 (FIGURE 2-).

In operation, and assuming that all the engines are running normally, a fluid pressure corresponding to the thrust output of each of the engines 40, 41 and 42 is applied respectively to the cylinders 12, 13 and 14, while a pressure corresponding to the output of the engine 44 is applied to the cylinder 15. By virtue of the non-return valves 52, 54 and 56 the pressure in the chamber 28 is equal to the highest of the three pressures in the pipes 47, 48 and 49. l

A study of one of the cylinders will show that the pressure in the chamber 28 acts upon the outer face of the piston and this pressure is, as previously explained, the highest pressure existing in any of the jets. The other face of the piston is acted upon only by the jet pressure in the associated engine and, because of the presence of the piston rod or ram this face has a smaller effective area, so that in normal conditions the piston would move to the right in FIGURE 1. However, such movement is resisted by the spring 30 which applies such force as to make up for the difference in the forces acting on the two sides of the three pistons 16, 17 and 18. If the three jet pipe pressures of the three engines are equal then the pressures in the three cylinders 12, 13 and 14 and in the chamber 28 are all equal and the spring 30 applies equal mechanical pressure to the piston rods 20, 22 and 24, to balance the differences in the forces acting on the two faces of the respective pistons. If, now, one of the engines 40, 41 or 42 should develop a reduced output, or fail, then the fluid pressure acting on the inner face of the respective piston will fail, whereas the pressure in the chamber 28 will be unaffected because of the presence of the non-return valves 52, 54 and 56. In consequence the force acting on the inner face of the piston associated with the faulty engine either drops in magnitude or disappears altogether. As a result the forces on the pistons become unbalanced and they all move together to the right in FIGURE 1, thereby compressing the spring 30 until a new balanced position is reached. This movement of the common member 32 causes an equal movement of the rod 59 and it is arranged that the direction of movement of the rod 59 is such as to open the throttles of all the engines so as to restore the total thrust of the engines to its original level.

It will be observed that while the engine 44 communicates a pressure to its cylinder 15 corresponding to its jet pipe pressure it can have no effect on the pressure in the chamber 28, but the pressure in the cylinder 15 does add to the total force acting to assist the spring 30, so that a loss of thrust in the engine 44 will also cause the throttles of all the engines to be opened. Due to the fact that the cylinder 15 has a smaller cross-sectional area, a given loss in jet pressure will have less effect than the same loss of pressure in the three lift engines. However, this is what is required, since a part of the output of the engine 44 is used for providing a forward thrust and only a part is used for lifting.

The spring 30 may be a biasing spring, as shown, acting through the common member 32. However, separate springs can be provided, and a known type of adding mechanism may be used in place of the common member 32, as shown diagrammatically in FIGURE 3, in which it will be seen that the piston rods 20, 22, 24 and 26 are provided with abutment plates and separate springs, respectively 62, 63, 64. and 65 each hearing at its other end on a fixed abutment plate. The four piston rods are coupled together through an adding mechanism, the piston rods 20 and 22 being pivoted to the ends of a bar 66 the centre of which is pivoted to a rod 67, and the piston rods 24 and 26 being pivoted to the ends of a bar 68 the centre of which is pivoted to a rod 69, While the rods 67 and 69 are pivoted to the ends of a bar 70 the centre of which is coupled by a rod 71 to one end of a bar 72 which receives the mechanical output representing the algebraic sum of the movements of the four piston rods. The other end of the bar 72 is coupled to a rod 73, equivalent to the rod 59, while the centre of the bar 72 is coupled through a rod 74 to the pilots primary control.

The lift/thrust engine 44 is provided with a separate throttle control which is not shown in the figures.

FIGURE 4 shows a modification of the arrangement depicted in FIGURE 1. In this case the casing 11 containing the integral cylinders 12, 13, 14 and 15 and the chamber 28 are replaced by four separate cylinders, respectively 75, 76, 77 and 78, and a separate container 79. The cylinder 75 is fed through a pair of pipes, respectively 80 and 81, the cylinder 76 is fed by a pair of pipes 82 and 83, the cylinder 77 is fed by a pair of pipes 84 and 85, and the cylinder 78 is fed by a pair of pipes 86 and 87. In each case the two pipes of the pair are connected to the one source at the engine and at the other end to an autoselector valve, respectively 88, 89, 90 and 91. The autoselector valve is shown in section in FIGURE 5 and comprises a casing 92 having a bore 93 which contains a valve member 94. The cylinder 93 has inlets at opposite ends which are connected to the two pipes of a pair, for example, pipes 80 and S1, and the cylinder 93 has outlet ports, respectively and 96 spaced some distance from its ends. Both the pipes 30 and 81 carry a fluid pressure from the respective pressure source provided on the associated engine and in normal operation the valve member 94 occupies the centre position, as shown. If, however, one of the pipes 80 or 81 should fracture, the pressure acting on one end of the valve member 94 will fall and the valve will move to one end or the other of the cylinder 93 and thereby close the port 95 or 96 associated with the inlet connected to the fractured pipe. This is one example of the way in which redundancy may be employed in connection with the invention.

Reverting to FIGURE 4, since the cylinders 75, 76, 77 and 78 are now fed through pairs of pipes the taking of a branch connection from one pipe of a pair to feed the container '79 is not advisable, unless it is desired to provide redundant branch pipes, in which case it would be necessary to employ further autoselector valves and use two branch pipes. However, FIGURE 4 shows a pipe 97 leading from the one end of cylinder 75 to a nonreturn valve 98, which is exactly the same as the nonreturn valves 52, 54 and 56 in FIGURE 1. In the same way, a pipe 99 leads from the one end of the cylinder 76 through a non-return valve 100 to the container 79 and the cylinder 77 is similarly connected through a pipe 101 and a non-return valve 102. The other ends of the respective cylinders 75, 76, 77 and 78 are connected by means of pipes, respectively 113, 114, 115 and 116, to the container 79. A controlled leak device 103 and an exhaust pipe 105 are connected to the container 79 and fulfill exactly the same functions as the member 57 and pipe 58 in FIGURE 1. The four piston rods 106, 107, 108 and 109 bear upon a common member 110, equivalent to the member 32 and this is engaged with a spring 111 and with a rod 112, equivalent to the members 30 and 59 respectively in FIGURE 1.

The arrangement of FIGURE 4 functions in precisely the same way as that of FIGURE 1. The container 79 is maintained at a fluid pressure corresponding to that of the highest pressure in any of the three pairs of pipes and the said other end of each of the four cylinders is subjected to this pressure, While the said one end of each cylinder is fed only with the pressure derived from the respective jet pipe, while the spring 111 provides an extra force to balance the total forces acting on the two faces of each of the four pistons. If any one of the four engines should suffer a reduction in thrust output, thereby reducing the pressure in the associated jet pipe, then the force acting on the one or rearward face of the respective piston is reduced, so that the pressure in the container 79 is enabled to move all four pistons in a direction to the right in FIGURE 4 and thereby move the rod 112 connected to the throttle control to open all the engine throttles.

Various modifications may be made in the described embodiments within the scope of the invention. For example, a mechanism equivalent to a zero rate spring, sometimes called a bang-bang mechanism, may be substituted for the springs 30, 6266 and 111. Alternatively a pneumatic system may be used. In either case the important feature of the invention, that the information on Which the control operates is all obtained directly from the engines and no external source is required.

It will be understood that embodiments other than those described and illustrated, or modifications thereof, may be devised within the scope of the invention as defined in the appended claims.

We claim:

1. A group thrust compensator for a group of jet engines generating a lift thrust comprising a double-acting fluid cylinder and a piston and piston rod contained therein for each engine of the group, a source of fluid pressure for each engine to provide a fluid pressure corresponding to the thrust delivered by the engine when in operation, means to apply the fluid pressure from each source to the end of the respective cylinder containing the piston rod, a connection from the source of fluid pressure on each engine to a common chamber through a non-return valve, a connection from said common chamber to the other end of each cylinder, a calibrated leak device to allow fluid in the common chamber to escape at a controlled rate, mechanical connections from the piston rods of all the cylinders to a single engine throttle control controlling the throttles of all the engines in the group, and resilient means acting on the pistons against the pressure from said common chamber, whereby all the pistons are acted upon at the one side by the highest pressure derived from the plurality of sources, each piston is acted upon at its other side by a pressure derived from the source on the associated engine, and the movements of all the pistons are transmitted to the throttle control.

2. A compensator as claimed in claim 1 comprising a further cylinder or cylinders containing pistons and piston rods, each further cylinder being connected at the end containing the piston rod to pressure from a source associated with an engine delivering a combined lift and forward thrust, the pressure source in this case having no connection to the common chamber, the piston rod of each further cylinder being mechanically connected to the said throttle control, each combined lift and thrust engine having a throttle control which is separate from the said throttle control.

3. A compensator as claimed in claim 2 in which each further cylinder is of diiferent diameter to that of the cylinders associated with the engines of said group.

4. A compensator as claimed in claim 1 in which all said piston rods are rigidly connected to a member coupled to said engine throttle control, said resilient means comprising a single spring which, during normal operation, compensates for the difference in the forces acting on the two sides of each piston due to the difference in eifective area resulting from the presence of said piston rod.

5. A compensator as claimed in claim 1 in which all said piston rods move independently, each being provided with a spring, comprising an adding mechanism coupled to all said piston rods and to said throttle control 'by which the algebraic sum of the individual piston positions is transmitted to said throttle control.

6. A compensator as claimed in claim 1 comprising a pair of pipes from each source of fluid pressure, an autoselector valve for each pair of pipes to cut off the connection with either pipe if the pressure therein should fail, each autoselector valve being connected to that end of one cylinder containing the piston rod, and a connection from the said end of each cylinder to the common chamber through the said non-return valve.

References Cited by the Examiner UNITED STATES PATENTS 2,737,015 3/1956 Wright 35.6 3,159,000 12/1964 McCombs 60-3915 3,176,936 4/1965 Howard et al. 6039.15 X

MARK NEWMAN, Primary Examiner.

D. H RT, Assistant Examiner.

Claims (1)

1. A GROUP THRUST COMPENSATOR FOR A GROUP OF JET ENGINES GENERATING A LIFT THRUST COMPRISING A DOUBLE-ACTING FLUID CYLINDER AND A PISTON AND PISTON ROD CONTAINED THEREIN FOR EACH ENGINE OF THE GROUP, A SOURCE OF FLUID PRESSURE FOR EACH ENGINE TO PROVIDE A FLUID PRESSURE CORRESPONDING TO THE THRUST DELIVERED BY THE ENGINE WHEN IN OPERATION, MEANS TO SUPPLY THE FLUID PRESSURE FROM EACH SOURCE TO THE END OF THE RESPECTIVE CYLINDER CONTAINING THE PISTON ROD, A CONNECTION FROM THE SOURCE OF FLUID PRESSURE ON EACH ENGINE TO A COMMON CHAMBER THROUGH A NON-RETURN VALVE, A CONNECTION FROM SAID COMMON CHAMBER TO THE OTHER END OF SAID CYLINDER, A CALIBRATED LEAK DEVICE TO ALLOW FLUID IN THE COMMON CHAMBER TO ESCAPE AT A CONTROLLED RATE, MECHANICAL CONNECTIONS FROM THE PISTON RODS OF ALL OF THE CYLINDERS TO A SINGLE ENGINE THROTTLE CONTROL CONTROLLING THE THROTTLES OF ALL THE ENGINES IN THE

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