Oct. 1,1946. ' " HARLEE AIR SPEED INDICATOR 6 2,408,661 _ Filed Nov. 20, 1943 ' " mmvrox I 14.5.4 Pay is: 6 BY 2,408,661 Patented Oct. 1, 1946 UNITED STATES ' PATENT OFFICE _ I 7 2,408,661 AIR-SPEED INDICATOR ’ v I [Asa Ben Lee, Cleveland, Ohio, .assignon- to . Designers-z forv Industry, Inc-., Cleveland,‘ Ohio, a corporation of. Ohio Application November 20, 1943-, Serial‘ No. 511,167‘ 5 Claims.‘ (ems-212) 2 response to changes occurring in the velocity of a ?uid. bythe conductors 22 and 23 and by the con , Another object of my invention is to provide a novel form of indicating instrument for visibly indicating the true and indicated air speeds of an aircraft. A further object of my invention is to provide 10 a- novel indicating instrument containing a meter, and an operating or control means therefor em bodying electron tubes which are responsive to changes in the pressure and velocity factors of a ?uid. ' ' The invention may be further brie?y sum marized as consisting in certain novel combina tions and arrangements hereinafter described . heated by the heater 20 a flow of electrons will take place from the cathode to the plate 18'. The plates 18 of the electron tubes I12 and I3‘ are connected in parallel plate or output circuits This invention relates to indicating instru ments- and aim-s to» provide a novel form of in strument by which indications will be given in ductor 24 which connects the cathodes I9 with each other. An appropriate voltage or potential is. supplied to the plate circuits by the conductors 25’ and 2b which are connected with voltage source suitable for this purpose. In the circuit arrange ment here shown the conductor 26 is connectedv with the plate ‘circuits through unequal sections 21 and 28 of an inductive coupling or transformer ' ‘as, so thatthe plate circuits include parallelpor 15 tions extending to the electron tubes l2 and I3‘ as represented by the conductors 22 and 23. Electric current of appropriate characteristics is supplied to the heaters 20' of the electron tubes by- con ductors 30 and 3|. ' and. particularly set out in the appended claims. The meter I0 comprises any suitable form of In the accompanying sheet of drawings, the 20 electrically operated meter or indicator, for ex single View is a diagram representing anuindi ample, a galvanometer of conventional construc cating instrument embodying my invention. ' tion and having a movable pointer or needle. 33. My novel indicating instrument is applicable to Conductors 34’ and 35- connect the meter with a various uses where it is desiredv that indications be given'of changes occurring in the pressure and 25 coil 3510f the inductive coupling 29 and provide an energizing circuit for the meter. The meter is velocity factors of a ?uid. The embodiment: of also provided with a» series of numerals or indi the invention illustrated in the drawing shows cations 31 forming a scale with which the mov the instrument adapted for use as an air speed able pointer 33 cooperates. The distance which indicator for aircraft and for which use the in the pointer moves along the scale 31 is dependent strument is especially suitable. . upon'the extent to which the meter circuit is» As shown in the drawing, my novel indicating instrument comprises a meter It and a control or energizing means I I therefor embodying elec tron tubes I2 and I3 which are responsive re spectively to changes in» the pressure'and velocity energized. As mentioned above in a general way, the elec tron tubes I2 and I3 have a quantity of gas sealed therein and are responsive respectively to at‘ ,mospheric changes occurring in the static and factors of a ?uid. As will be explained in greater Pitot tubes I4 and I5. To render the“ electron detail hereinafter the electron-tubes I2 and I3 tube [2 responsive to such atmospheric changes are connected respectively with the static tube in the static tube I4, I provide this electron tube l4’ and the Pitot tube l5 of an aircraft so that with a ?exible wall portion which, in this in the electron tubes will be responsive to atmosé stance, is in the form of a hollow diaphragm de pherlc changes occurring in the static and Pitot vice or bellows 3'8 having a chamber 39 therein. tubes in response to operation of. the aircraft at The ?exible device 38 has a sealed’ connection different speeds and altitudes. The static and with the envelope I ‘I of the electron tube so that Pitot tubes I4 and I5 are represented as being the chamber 39 is in direct communication with of a conventional form used on. aircraft and. the the interior of theenvelope. The diaphragm de direction of flightis represented by the arrow IS. vice 38 is located in an air-tight housing 4| which The electron tubes 12. and. I3 are substantially is connected with the static tube M‘ by a conduit _ identical. and each comprises an envelope or cas 42. When pressure changes occur in the static tube ing. [1 containing a plate l8, a cathode “land a 50 l4 as the result of operation of the airplane at heater 2!] for the cathode. In constructing these different altitudes, these changes are transmitted electron tubes, the envelope I1 is initially evacu through the conduit 42 to the housing 4| and act ated and a. small amount of a suitable gas, such on the outside of the ?exible diaphragm of the asyneon' gas, is introduced into the envelope and sealed therein so» that when the cathode I8 is 55 device 38 so as to cause corresponding varia 2,408,661 3 tions in the pressure of the gas contained in the envelope I‘! of the electron tube l2. Thus when the aircraft is operating at a low altitude, an in creased atmospheric pressure will act on the dia phragm device 38 tending to collapse the same and thereby forcing additional gas into the en velope I‘! to increase the gas pressure in the lat ter. When the aircraft is operating at a rela tively higher altitude, the pressure acting on the diaphragm device 38 is partially relieved, per 10 bined e?'ects of the current values in the coil sections 21 and 28 will result in energization of the meter I0 in a manner to produce accurate indications of the true air speed of the aircraft. The compensating effect of the electron tube [2 is thus automatically applied to the action of the electron tube l3 so that the measurements given by the latter will be accurate for all altitudes. For calibrating purposes, the portion of the plate circuit of the electron tube [2 represented mitting gas to flow thereinto from the envelope by the conductor 22 may contain a variable re l1 and thus decreasing the gas pressure in the latter. When the gas pressure in the electron sistance or potentiometer 5|. For a similar pur pose a variable resistance or potentiometer 52 is provided in the portion of the plate ‘circuit of tube [2 is increased or decreased in this manner the electron tube vl3 which is represented by the conductor 23. A switch 53 is preferably also provided in the plate circuit of the electron tube I 2 so that by atmospheric changes occurring in the Pitot tube opening this switch the electron tube l2 can be I5, I provide this electron tube with a similar 20 isolated or rendered ineffective, whereupon the hollow ?exible diaphragm device or bellows 44 meter ill will be controlled or actuated only by having a chamber 45 therein. This diaphragm the electron tube [3 and relative or indicated air, device is connected with the sealed envelope ll so speeds can be read from the meter instead of that the chamber 45 will be in direct communi true air speed values. By closing the switch 53 cation with the interior of the envelope through 25 the effectiveness of the electron tube I2,is re the passage 46. The diaphragm device 44 is stored, so that true air speed values will again located in an airtight housing 41 which is con be indicated by the meter I0. nected with the pitot 15 by a conduit 48. Although I have shown in the drawing only When the velocity of the aircraft increases, the one meter I0, it should be understood that a num the ?ow of electrons between the cathode and plate, and likewise the plate current or electrical output for this electron tube, will also be varied. To render the electron tube !3 responsive to air pressure or velocity effect in the Pitot tube ber of such meters can be actuated or controlled will be correspondingly increased and will be by the electron tube apparatus ll. These ad transmitted to the casing 41 through the con ditional meters can be located at desired points ‘duit 48 and acting on the outside of the dia in the aircraft and the conductors 34 and 35 can phragm device 44 will tend to collapse the same be extended thereto to connect the same with thereby displacing gas into the envelope I‘! to 35 the coil 36 of the inductive coupling 29. _ correspondingly increase the pressure in the From the foregoing description and the ac latter. A decrease in the speed of the aircraft companying drawing it will now be readily un will produce the reverse effect, that is to say, derstood that I have provided a novel form of the pressure on the outside of the ?exible device indicating instrument which can be used to give 44 will be reduced and the gas pressure in the 40 indications in response to changes occurring in envelope ll will be correspondingly decreased. the velocity of a ?uid, and which is especially Changes in the gas pressure in the electron tube suitable'for use as an air speed indicator for aircraft. l3 produced in the manner just described will result in variations in the ?ow of electrons from While I have illustrated and described my novel the cathode H? to the plate [8 with corresponding 45 indicating instrument in considerable detail it variation in the plate current or electrical out will be understood, of course, that I do not wish put for the electron tube l3. to be correspondingly limited but regard my in Since the electron tubes l2 and 13 are con vention as including all changes and modi?ca nected in parallel plate circuits or output cir tions coming within the scope of the appended cuits through the coil portions 21 and 28 of the 50 claims. inductive coupling 29;, the energization of the Having thus described my invention, I claim: plate circuit in the manner above described, either by the electron tube l3 alone or jointly by both 1. An indicator of the character described comprising a plurality of electron tubes having electron tubes, will result in energization of the output circuits connected in parallel, each of meter circuit and cause movement of the pointer 55 said electron tubes having gas sealed therein and 33 along the scale 3?. The point 50 at which the electrical output of each electron tube being the conductor 26 is connected with the coupling variable in accordance with changes in the gas 29 or, in other words, the lengths or inductive pressure therein, a Pitot tube located to be acted values of the coil sections 28 and 21 may be upon by a ?uid stream, ?uid impulse conducting varied depending upon various factors such as 60 means connecting said Pitot tube with one of the characteristics of the electron tubes !2 and said electron tubes so that velocity changes in I3 and of the static and Pitot tubes l4 and I5 said stream will vproduce corresponding varia as well as the operating characteristics of the tions in the gas pressure in said one electron aircraft at different altitudes and possibly var tube, a static tube, ?uid impulse conducting ious other factors The above described ar 65 means connecting said static tube with another rangement for the electron tube [2 enables the of said electron tubes for varying the gas pres same to function as an altitude compensator by sure therein in accordance with changes in the supplying varying amounts of plate current static pressure of said ?uid, and a meter elec through the coil section 27 in response to changes trically connected with said output circuits. in the operating altitude of the aircraft. The 2. An instrument for an aircraft having a 70 above described arrangement for the electron static tube and a Pitot tube, comprising a pair of tube l3 enables the latter to measure the rela electron tubes having plate circuits connected in tive or indicated air speed of the aircraft and parallel, vsaid electron tubes having gas therein to produce corresponding current variations in and their electrical ouput being variable in. ac-v the coil section 28 of the couplingi'il. The com 75 cordance with variations in the pressure of the. 2,408,661 other of said electron tubes so that changes in the velocity of vsaid ?uid will act through the ?exible portion of said other electron tube to tron tubes so that the gas pressure in the latter varies with the pressure variations in said static cause corresponding variations in the pressure of tube, ?uid impulse transmitting means connect ing said Pitot tube with the other electron tube the gas therein, and an indicator electrically con- ' nected with said output circuits so as to be re so that the gas pressure in the latter is varied in response to variations in pressure in said Pitot tube, and a meter electrically connected with said sponsive to the combined ouput effect of said electron tubes. 10 parallel plate circuits. 3. An instrument for an aircraft having a static tube and a Pitot tube, comprising a pair of scaled electron tubes containing gas and having plate circuits connected in parallel, a diaphragm 6 ?uid, means connecting said Pitot tube with the gas therein, ?uid impulse transmitting means connecting said static tube with one of said elec ' 5. An instrument of the character described comprising, a pair of electron tubes having out put circuits connected in parallel and each elec tron tube having a sealed envelope containing gas and its electrical output being variable in device connecting said static tube with one of 15 response to changes in the pressure of the gas therein, said envelope including a ?exible hollow said electron tubes so that the‘ pressure of the gas in the latter varies with pressure variations in said static tube, a diaphragm device connect member, a housing for the ?exible hollow mem- . ber of each electron tube, a static tube located to be acted upon by the pressure of a moving ?uid, ing said Pitot tube with the other electron tube so that the pressure of the gas ‘in the latter varies 20 ?uid impulse conducting means connecting said static tube withv the housing of one of said elec with pressure variations in said Pitot tube, and a tron tubes so that changes in the pressure of said meter electrically connected with said plate ?uid will act through the ?exible hollow mem ber of said one electron tube to produce corre 4. An instrument of the character described sponding variations in the pressure of the gas comprising, a pair of electron tubes having out therein, a Pitot tube located to be acted upon by put circuits connected in parallel and each elec the velocity of said ?uid, ?uid impulse conduct tron tube having a sealed envelope containing ing means connecting said Pitot tube with the gas and its electrical output being variable in housing of the‘other of said electron tubes so that response to changes in the pressure of the gas changes in the velocity of said ?uid will act therein, said envelope including a ?exible por through the ?exible hollow member of said other tion, a static tube located to be acted upon by electron tube to produce corresponding varia the pressure of'a moving ?uid, means connect tions in the pressure of the gap therein, and an ing said static tube with one of said electron indicator electrically connected with said output ' ' tubes so that changes in the pressure of said ?uid circuits so as to be responsive to the combined will act through the ?exible portion of said one circuits. r ' . electron tube to produce corresponding variations in the pressure of the gas therein, a Pitot tube located to be acted upon by the velocity of said 'joutput e?ect of said electron tubes. ASA RE'N LEE.