US3112649A - Airborne mechanical pressure sensing and communication system - Google Patents

Description

DAVID s. LITTLE B FREDERICK c. MELCHIOR A7 TORNEYS 3, 1963 E. w. PIKE ETAL AIRBORNE MECHANICAL PRESSURE SENSI AND COMMUNICATION SYSTEM Filed May 16, 1960 MM m N w mo m magma w 22223: I\ w 9% 8 WEEK 3 Qu H 3 H mmmouzm 1 #565 W G IE I; R 8 R Q a.

llnited States Patent 0 AIREEGRNE R EE'CHANECAL PRESSURE ENSENG AND COMMUNICATZON SYSTEM Edward W. Ellie, 7 St. Nicholas Drive, Shepperton, England; David Little, 35 Eogart Ave, Port Washington, N.Y.; and Frederick C. Melchior, 258 Riverside Drive, New York, NX.

Filed May 16, 1?:50, Ser. No. 29,386

3 Claims. (Cl. 73-386) This invention relates to air to ground communications and, more particularly, to an airborne mechanical pressure sensing system and associated communication system to transmit the pressure measurement to a ground system.

In recent years, increased air traffic and the necessity of maintaining safe separation of air trafiic during all weather operations has resulted in development of systems for air trafiic control. In the United States, air traffic control is generally broken down into (a) Air route trafi'ic control: covering en route trahic in designated controlled airspace between airports, ([2) Approach and departure control: handling IFR arrivals into and departures from airports, and (c) Airport traffic control: handling trafic in the immediate vicinity of and on an airport.

Since the objectives of air traidc control is to provide safe and expeditious movement of air traffic, including the necessary control of aircraft separation, the control function must obtain information as to the position, speed, and flight path. In general, the information has been supplied by the aircraft pilot in the form of position reports at specific points. Unfortunately, the present air trafiic density is now such as to overburden the slow, cumbersome method of voice reporting of position and confirming of ATC clearances.

In addition, the trafi'lc density and the increasing variation between speeds of the individual aircraft in the control networks has made it clear that the present position reporting will not provide adequate information for proposed air traffic control. it is clear that more information, rendered at more frequent intervals, is necessary to allow air traffic control systems to extrapolate from the position reports for flight path planning and control. Ground based computors can easily handle the necessary information storage and data processing. However, the data acceptance speed of computers and the increased information necessary for utilization of computer processing capabilities obsoletes cumbersome voice communication.

It is planned to establish ground stations provided with the necessary computers. Upon interrogation, each aircraft will report position information to the ground station. Such systems have been generally termed data link systems.

In the data link systems proposed to date, each aircraft will be assigned an airframe address. The ground station Will reach the aircraft by interrogation, using the assigned address. The position information of each aircraft will be communicated to the ground automatically in response to the interrogation signal. In this manner, the position information may be requested by ground control at time intervals which can be adjusted to the traiiic and the reporting frequency needed for air traflic control. Digital coding of the information transmission and address information allows use of pulse train transmimion.

Of the many factors related to aircraft flight which bear on air trafiic control, the factor of aircraft altitude, of direct concern to air t-rafiic control in the vertical plane, is that to Which this application is directed.

' disclosed in Melchior Patent 2,760,260

3ft field Patented Dec. 3,, 1953 The art has proposed that aircraft altitude be determined by slant-range, height-finding radar. Despite intensive development, such altitude determination has not been satisfactory.

Although aneroid sensors have the operational capabilities and the accuracy necessary to determine aircraft altitude Within the accuracy required, the use of aneroid sensors has not been extensive due to the difliculty of deriving vertical position information therefrom in form compatible with the communication link and without loading the sensor with a mechanical and/ or frictional load which would obviate the inherent accuracy of the sensor.

Although it is necessary to convert the pressure sensor (such as an aneroid capsule) measurement into altitude units for the display in the aircraft to have significance to the pilot, such conversion is not necessary for transmission to a central co-mputor. The computer can easily make this conversion, if necessary, or operate in pressure units if the flight path information (erg. obstacles) is stored in pressure units. Thus a reduction in the complexity, Weight and size of the airborne unit is possible.

It is therefore the one object of this invention to provide an improved method and means for determining the position of a mechanical sensor at selected intervals.

It is a further object of this invention to provide an improved method and means for determining the position of a factor-responsive sensor and translating the position determination into a digitally coded signal.

Other objects and advantages of this invention will be pointed out hereinafter.

In accordance with these objects, there is provided, in a preferred embodiment of this invention, a pressure-responsive sensor comprising stacked aneroid capsules. The capsules Will expand and contract in accordance with chan es in ambient barometric pressure.

When the position of the capsule stack is to be determined (as for example, on interrogation of the aircraft by a ground station), the capsule stack is clamped in posi tion to prevent change of position during the positiondetermining cycle. A feeler is advanced into contact with the capsule stack from a reference position, stopping when contact is made. Means responsive to the movement of the feeler are provided to set up in digitally coded form a signal directly related to capsule position. The signal is stored for read-out when the position information is required.

To prevent displace .ent of the aneroid stack by the impinging feeler, means are provided to damp the feeler velocity when in incipient engagement with the capsule. Compensation means are provided to correct for nonlinearity of the capsule stack deflection over the operating range to ensure accurate measurement of the ambient pressure and thus the aircraft altitude.

The invention may be more clearly understood by reference to the following description, taken in combina tion with the accompanying drawing, of which:

FIGURE 1 is a schematic diagram of a preferred embodiment of the present invention, and

FIGURE 2 is a side elevation of the portion of the apparatus shown in FIGURE 1.

Referring to the figures, there is shown a pressure-responsive sensor consisting of stacked aneroid capsules 10 joined at their central hubs. Each of the capsules is preferably of the concentrically corrugated diaphragm type One end of the stack is affixed to a structural member 12. Carried by the other end of the capsule stack is a plunger 14. Movement of the plunger Will be the summation of the deflections of the diaphragms of the capsules due to the series coupling of the capsules and is, thus, greater and more easily detected than the deflection of any one capsule diaphragm. Additionally, stacking of the 3 capsules permits selective matching of the deflection characteristics of each capsule, to improve the linearity of deflection of the capsule stack over the entire operating range.

The sensor stack will move the plunger in accordance with changes in ambient barometric pressure over the entire operating range of the sensors. However, for this application, determination of sensor position is required only in response to an interrogation signal from the ground controller. The interrogation signal is received by conventional receivers which are responsive only to properly addressed messages and used to operate switch 16 for readout of vertical position information.

To avoid error in position reporting by movement of the sensor during the read-out cycle, the sensor must be locked in position. For this purpose there is provided a locking solenoid 22 which is energized from battery 18 when switch 16 is closed by the interrogation signal. When the solenoid is energized, the spring 24 coupled between the solenoid armature 2s and a fixed support 28 will be overcome and the armature 26 will move to clamp the plunger between the armature anvil 30 and the fixed anvil 32.

Thus, upon receipt of an interrogation signal, the sensor is clamped in position to permit accurate reading of the position thereof and to prevent change in the position during the read-out cycle. In order to determine the position of the plunger 14, there is provided a'mechanical feeler comprising rod 34, carrying a gauge face 36 at the end thereof. The feeler gauge is biased into a retracted position by a spring 38 coupled between the eye 40 on the end of the rod and member 42. With the closure of switch 16, however, solenoid 44 is energized and pulls in armature 46. The movement of armature 46 will urge the feeler into contact with the plunger 14 through spring 48 which has a spring contact sufiicient to overcome spring 38. Axial positioning of the feeler is maintained by linear bearings 59, 52.

In order to translate linear movement of the feeler rod into a digitally coded signal, there is provided a worm gear thread 54 extending along the feeler rod surface, which gear engages the matching threads on pinion 56 fixedly mounted on shaft 58. The profile and pitch of the teeth of gears 54 and 56 are selected to provide'nonlocking engagement therebetween. Shaft 58 is rotatably mounted and is biased by an anti-back lash spring 66. Rotation of shaft 34 about its axis due to torque imposed by coaction of the worm gears 54, 56 is prevented by pin 61 held against a stop 63 by spring 65.

Shaft 53 is operatively coupled to encoder 62, which sets up a digitally coded signal linearly related to the shaft angular rotation. The digital encoder may be any of the conventional encoders in which angular rotation sets up a digitally coded signal (as for example, a rotatable disc carrying digitally coded angular position information read by direct contact means, magnetic pickup, or optical scanning). The encoderthen stores the digitally coded signal until it is required for combination with other position information and transmission to the ground station. The read-out and combining circuitry is known to the art.

Despite high clamping pressures obtainable by solenoid clamping of the plunger, the impact of rod 34 thereon may jolt the plunger from its frictionally held position. in order to damp the rod movement without adversely can affecting the traversal speed, there is provided a damping disc 64 coupled to shaft 58. An eddy current brake 65, is provided, the coils of which are energized by source 18 when the circuit is completed by contact of the face plate 36 mounted on and insulated from rod 34- by insulator block 37 with the defiectable spring contact 68 on the plunger. The circuit to ground is completed through the capsules in? and plunger 14. The action of the eddy current brake softens the impact without unnecessary loss of time in operation.

Although the capsules in the capsule stack may be matched for linearity of response, it is rarely possible to obtain absolute linearity over the entire operating range. To compensate for nonlinearity, the stop 63 is provided with a cam surface 70 (FIGURE 2), which is custom calibrated for the specific capsule stack used. The cam surface will, through coaction with pin 61, rotate the shaft 34- and output shaft 58 to compensate for nonlinearity of capsule deflection.

The information as to vertical position may be extracted from the storage element 62 by timer and transmission device 72. As soon as the signal is transmitted to the ground station, the timer 72 resets switch 16. On resetting of switch 16, the solenoids 22 and 44 are deenergized, allowing the apparatus to be reset by return of the feeler to the reference position via spring 38 and freeing of the sensor by return of the clamp 26 via spring 24.

This invention may be variously modified and embodied within the scope of the subjoined claims.

What is claimed is:

1. An airborne mechanical pressure measuring system comprising aneroid capsules arranged in a stack, one end of said stack being fixedly secured, a plunger aifixed to the other end of said stack and moved thereby in accordance with changes in the pressure measured by said aneroid capsules, a first solenoid means responsive to an electric signal for clamping said plunger, a feeler rod,a second solenoid means responsive to said electric signal to drive said feeler rod from a reference position into engagement with said plunger, said feeler rod being provided with threads along the length thereof, a rotatably mounted shaft having a pinion thereon, said pinion being provided with external threads which engage the threads on said feeler rod, the threads on said pinion and said rod engaging in non-locking engagement to rotate said shaft as said feeler rod is advanced into contact with said plunger, and means to encode rotation of said shaft in digital form as a measure of said feeler movement from said reference position to provide a measure of said pressure.

2. A system in accordance with claim 1 which includes means for slowing the movement of said feeler when said feeler is in incipient contact with said plunger.

3. A system in accordance with claim 2, which includes an eddy current brake energized when said feeler is in incipient engagement with said plunger.

References Cited in the file of this patent UNITED STATES PATENTS 1,332,182 Leeds Feb. 24, 1920 2,109,776 Johnson Mar. 1, 1938 2,364,450 Keeler Dec. 5, 1944 2,729,780 Miller et aL Jan. 3, 1 956

Claims (1)

1. AN AIRBORNE MECHANICAL PRESSURE MEASURING SYSTEM COMPRISING ANEROID CAPSULES ARRANGED IN A STACK, ONE END OF SAID STACK BEING FIXEDLY SECURED, A PLUNGER AFFIXED TO THE OTHER END OF SAID STACK AND MOVED THEREBY IN ACCORDANCE WITH CHANGES IN THE PRESSURE MEASURED BY SAID ANEROID CAPSULES, A FIRST SOLENOID MEANS RESPONSIVE TO AN ELECTRIC SIGNAL FOR CLAMPING SAID PLUNGER, A FEELER ROD, A SECOND SOLENOID MEANS RESPONSIVE TO SAID ELECTRIC SIGNAL TO DRIVE SAID FEELER ROD FROM A REFERENCE POSITION INTO ENGAGEMENT WITH SAID PLUNGER, SAID FEELER ROD BEING PROVIDED WITH THREADS ALONG THE LENGTH THEREOF, A ROTATABLY MOUNTED SHAFT HAVING A PINION THEREON, SAID PINION BEING PROVIDED WITH EXTERNAL THREADS WHICH ENGAGE THE THREADS ON SAID FEELER ROD, THE THREADS ON SAID PINION AND SAID ROD ENGAGING IN NON-LOCKING ENGAGEMENT TO ROTATE SAID SHAFT AS SAID FEELER ROD IS ADVANCED INTO CONTACT WITH SAID PLUNGER, AND MEANS TO ENCODE ROTATION OF SAID SHAFT IN DIGITAL FORM AS A MEASURE OF SAID FEELER MOVEMENT FROM SAID REFERENCE POSITION TO PROVIDE A MEASURE OF SAID PRESSURE.

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