Application of Chandler

• Decision Date: 20 June 1963
• Docket Number: Patent Appeal No. 6982.
• Parties: Application of Milton E. CHANDLER and Alexander M. Wright.
• Court: U.S. Court of Customs and Patent Appeals (CCPA)

319 F.2d 211 (1963)

Application of Milton E. CHANDLER and Alexander M. Wright.

Patent Appeal No. 6982.

United States Court of Customs and Patent Appeals.

June 20, 1963.

A. M. Prentiss, West Hartford, Conn., for appellants.

Clarence W. Moore, Washington, D. C. (S. Wm. Cochran, Washington, D. C., of counsel), for the Commissioner.

Before WORLEY, Chief Judge, and RICH, MARTIN, SMITH, and ALMOND, Judges.

ALMOND, Judge.

This is an appeal from the decision of the Board of Appeals affirming the action of the examiner rejecting claims 3 to 17, 19 to 24, 26 to 33 and 35 to 43 of appellants' application¹ for a patent on a fuel regulating apparatus for an aircraft turbojet engine. No claims have been allowed.

Appellants' application describes the claimed invention as directed to a fuel flow regulating apparatus to control the engine speed and power by regulating the fuel supply as a function of a manual control and several variables, including engine inlet air temperature and pressure, engine speed, and other engine operating conditions.

The application states, in part, that engines of the type under consideration cannot be operated at maximum speed under all flight conditions; that fuel and speed control should enable the operator to vary speed and power as conditions of flight may require; that engine speed responds to fuel flow, varying as a function of the pressure and temperature of the engine inlet air flow, engine air compressor characteristics and other operating factors; that maximum fuel flow is limited by the maximum permissible compression ratio of the air compressor which results from that fuel flow, under any combination of engine speed, engine inlet air temperature and pressure, and rate of air flow through the engine, that may obtain under varying operating conditions; that for proper regulation of engine operation, and to avoid compressor stall, burner blowout and other causes of engine failure, it is not feasible to rely upon automatic regulation of fuel flow as a function of variables which do not include these factors; that an important requirement of a satisfactory fuel and speed control is responsiveness to engine acceleration at maximum rate without causing compressor stall, and to deceleration of the engine at a maximum rate without causing burner blowout; and that another important requirement is the provision of an emergency fuel supply and control system responsive to operation in the event of failure of the normal fuel supply and control system.

It is stated that in turbojet engine fuel control systems in prior use, engine performance is controlled by regulating the fuel supply by a control apparatus which varies the delivery of a fuel pump by introducing correction factors which modify the delivery, in order to compensate the fuel flow for variations in pressure and temperature of the air entering the engine caused by variations in flight altitude, ambient air temperature, and other operating conditions. Applicants state that they have found that better control of engine operation can be obtained by providing a fuel control system in which inlet air pressure and temperature compensation of the fuel flow to the engine is inherent in the system, and hence, such corrective factors are not required to compensate for changing operating conditions.

More specifically, the application states the salient features of the claimed invention as follows:

"(1) A control apparatus comprising, in a single selfcontained package, a normal fuel supply and control system, and an emergency fuel supply and control system which the pilot may bring into operation in the event of failure of the normal system; each system comprising a series of component coordinated hydraulic devices for regulating fuel delivery to the engine; said devices being collectively responsive to a single manual control, to inlet air pressure and temperature, and to speed of the engine.

"(2) A control apparatus which comprises a combination of devices that measure inlet air absolute temperature and pressure, and engine speed, (rpm) and positions a main fuel metering valve, and thus varies its flow area, in accordance with a selected function of said temperature, pressure and speed; while the pressure differential across said valve is held substantially constant.

"(3) A fully automatic, hydraulic control apparatus in which the fuel flow to the engine is compensated for variations in absolute inlet air pressure and temperature, and engine speed, and said compensation is inherent in the operation of the apparatus, so that additional correction factors for these variables are not required in order to compensate for variations in operating conditions.

"(4) A fully automatic, hydraulic control apparatus which uses as control `parameters,\' for limiting the maximum fuel flow to the engine, the entities: inlet air pressure, and preselected functions of inlet air temperature and engine speed, as defined hereinabove.

"(5) A control apparatus which produces a substantially constant engine speed, corresponding to any selected position of a single manual control lever, under all engine operating conditions.

"(6) A control apparatus which functions so that the engine can be accelerated at a maximum rate, corresponding respectively to the pressure and temperature of the air entering the engine compressor, without causing compressor stall or excessive turbine temperature; and decelerated at a maximum rate without causing burner blowout.

"(7) A control apparatus wherein the fuel flow to the engine under normal operation is regulated by:

"(A) a substantially constant metering head across a variable area metering orifice; and

"(B) a metering orifice whose area is varied:

"(a) during engine acceleration, in accordance with the temperature and pressure of the air entering the engine compressor; and in accordance with engine speed, at each instant.

"(b) during steady state engine operation, by centrifugal speed governor geared to the engine, whose action is responsive to the position of a manual control lever; and

"(c) during engine deceleration, by said governor and limited by an adjustable cam and stop.

"(8) A control apparatus wherein the fuel regulating mechanism operates in its own fluid, acts directly on the fuel supplied by a constant delivery pump, and regulates its flow to the engine by means of a plurality of suitably controlled by-pass valves.

"(9) A fuel and speed control apparatus having control devices which vary the fuel flow in accordance with variations in temperature and pressure of the ambient atmosphere, to prevent engine failure at high altitudes and low atmospheric temperatures.

"(10) A control apparatus having an override speed control device which prevents the engine from operating at excessive speeds." (Emphasis applicants\'.)

Claims 3 and 40 are sufficiently illustrative and read as follows:

"3. Fuel regulating apparatus for an aircraft turbojet engine having an incorporated air compressor, comprising: a fuel feeding system having a linearly positionable fuel feed valve therein, an engine speed-responsive governor for linearly varying the position and hence varying the flow area of said valve; and means, independent of said governor and responsive to variations in the pressure of the air entering said compressor, for modifying the linear positioning by said governor of said valve in accordance with said pressure, under all operating conditions of said engine, without changing the simultaneous position of said governor.

"40. An aircraft turbojet engine fuel control apparatus comprising: a conduit supplying fuel to said engine, a metering restriction in said conduit, first linearly movable means for varying the flow area through said restriction, second manually-operable means, and third engine speed-responsive means, for varying the linear position of said first means; fourth cam means reversibly positionable in two different directions and having a warped surface, for limiting the action of said second means on said first means, without changing the position of said third means; fifth means, responsive to engine induction air temperature, for varying the adjustment of said fourth means in one direction, as a preselected function of said temperature; sixth means, responsive to said third means, for varying the adjustment of said fourth means, in the other direction, as a preselected function of engine speed; and seventh means for varying the position of said first means, independently of the action of said third, fourth, fifth and sixth means, in accordance with a preselected function of engine induction air pressure; whereby the fuel flow to said engine is conjointly controlled in accordance with the position of said second means, engine speed, and said functions of said temperature and pressure.

The references relied upon are:

                  Davies et al.    2,674,847      April 13, 1954
                  Kunz             2,720,751    October 18, 1955
                  Fox              2,836,957        June 3, 1958
                

The Board of Appeals affirmed the rejection by the examiner of claims 3 to 8, 10, 11, 13 to 17, 19 to 23, 26 to 33, 35, 36, and 39 to 43 as unpatentable over Kunz in view of Davies et al.; of claim 9 as unpatentable over Kunz; of claims 3, 5 to 8, 10, 12, 14 to 17, 19, 20, 26 to 29, 31 to 33, 35, 36 and 39 to 43 as unpatentable over Fox in view of Davies et al.; and of all of the claims on the ground of undue multiplicity.

In aid of analysis and correlation of the cited references to the relevant features of appellants' claimed invention, we reproduce the following figures from the drawings:

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Davies et al. discloses an engine fuel supply control apparatus in which fuel flows from tank 16 through filter 14 by means of line 13 through engine driven variable delivery pump 10, through line 17 to flow restricting valve 34, through control valve 42 to burner 21. Movement of diaphragms 29 and 37...