USRE22409E - Rate and attitude indicating - Google Patents

Description

Dec. 21, 1943. J. LYMAN ET AL RATE AND ATTITUDE INDICATING INSTRUMENT Original Filed April 10, 194]. 5 Sheets-Sheet l FREQUENCY DOUBLER AMPUHER Dec. 21, 1943. J. LYMAN ET AL Re. 22,409

RATE AND ATTITUDE INDICATING INSTRUMENT Original Filed April 10, 1941 5 Sheets-Sheet 2 PIER;

TO ATTITUDE INDICATOR INVENTORS JOSEPH LYMAN ELWOOD NOFXDEN BMQWZMA THETR ATTORNEY,

Dec. 21, 1943. J. LYMAN ET AL Re. 22,409

RATE AND ATTITUDE INDICATING INSTRUMENT Original Filed April 10, 1941 5 SheetsSheet 3 FIE-.5

AMPLIFIER AMPLIFIER INVENTORS JOSEPH LYMAN ELWOOD NO DEN THEIR ATTORNEY Dec. 21, 1943. J. LYMAN ETAL RATE AND ATTITUDE INDICATING INSTRUMENT Original Filed April 10, 1941 5 Sheets-Sheet 4 INVENTORS CZmsSEmE I I I I I. I EOF Owk HQ UQQIQ JOSEPH LYMAN ELWOOD NORDEN JLVL/WQQ .THEIR ATTORNEY i mm Dec. 21, 1943. J. LYMAN ET AL RATE AND ATTITUDE INDICA'IING INSTRUMENT Original Filed April 10, 1941 5 Sheets-Sheet 5 FREQUENCY DOUBLER R l E .R N E m W S C O A E OY H T TLN P E N E D E 0 V O NE. S 0 v Reissued Dec. 21, 1943 RATE AND ATTITUDE INDICATING IN STBUMENT Joseph Lyman, Huntington, and Elwood Norden, Roslyn, N. Y., assignors to Sperry Gyroscope Company, Inc., Brooklyn, N. Y., a corporation of New York Original No. 2,309,853, dated February 2, 1943, Serial No. 387,810, April 10, 1941. Application for reissue July 28; 1943, Serial No. 496,498

31 Claims.

This invention relates, generally, to rate and attitude indicating instruments and the invention has reference, more particularly, to a novel instrument especially adapted to provide navigational information such as the heading of a craft with respect to the meridian or other reference, the rate of turn of a craft, and the attitude of a craft about the fore and aft and transverse axes thereof.

Heretofore, it has been common to employ gyroscopic instruments such as directional gyroscopes, turn gyroscopes and artificial horizon. gyroscopes for providing necessary rate and atti- I 'tude indications for aircraft. In the present invention a vibrating element secured at one or both ends is employed to provide rate and attitude indications of movable craft, suitable electrical pick-off means being utilized in connection with the vibrating element to pick-of! electrical signals for operating suitable indicators giving the desired information.

One object of the present invention is to provide a novel direction indicating instrument suitable for use, among other purposes, as upon a moving craft to indicate the heading of the craft with respect to the meridian or other reference.

Another object of the invention is to provide a novel instrument adapted to serve as a rate of turn indicator for showing the rate of turn about any desired axis.

Still another object of the invention is to provide means for rigidly mounting a vibratory element at one or both ends, with means for vibrating the same, and with electrical pick-of! means therefor producing potentials adapted to control a suitable indicating means. I

A further object of the invention is to provide a direction indicator comprising an element of U-shaped or substantially tuning fork form, the

same being mounted for free movement about acentral axis extending parallel to its arms and carrying a direction indicator, together with means for vibrating the arms of said member,

whereby said arms continue to vibrate in a fixeding its deflecting plates excited by the outputs of pick-off coils associated with a horizontally vibrating rod, said cathode ray tube depicting on the face thereof an artificial horizon bar, the indications of which are similar to those of the standard artificial horizon. 1

Other objects and advantages will become apparent from the specification, taken in connection with the accompanying drawings wherein the invention is illustrated in several forms.

In the drawings,

Fig. 1 is a vertical section through one form of our invention useful as a directional indicator.

Fig. 2 is a fragmentary wiring diagram of the system of Fig. 1 showing the electrical connections to a Telegon type indicator.

Fig. 3 is a vertical section through one form of our invention useful as a rate of turn instrument.

Fig. 4 isa diagram of three vibration paths, useful in explaining the invention shown in Fig. 3, and Fig. 4A as modified.

Fig. 5 is a horizontal section of another form of our invention employing a stretched wire clamped at both ends, which may be used as an attitude indicator.

Fig. 6 is an end view of the device shown in Fig. 5, together with a fragmentary wiring diagram showing a cathode ray indicator operated therefrom.

Fig. 7 is a vertical section through another form of our invention useful as a directional indicator.

Fig. 8 is a vertical section of a modification of the device shown in Fig. 7.

Fig. 9 is a vertical section through another form of our invention which performs the functions of an artificial horizon.

Fig. 9A shows a wiring diagram of a system using the structure of Fig.9.

Fig. 10 is a detail of Fig. 9 taken at right angles to that figure.

Fig. 11 is a simplified wiring diagram useful in explaining the device shown in Figs. 9 and 10.

Fig. 12 is a, horizontal section of another form of our invention useful as a rate of turn indicator.

Fig. 13 is an end view of the same device, showing a fragmentary wiring diagram of a dynamometer type indicator for use with said device.

Fig.'14 is a diagram of three vibration paths useful in explaining the invention shown in Fig. 13.

Fig. 15 is a schematic illustration of a modified form of our rate of turn instrument illustrated in Fig. 3 and showing the use of capacity pick-oil's.

Similar characters of reference are used in all of the'above figures to indicate corresponding parts Referring first to Figs. 1 and 2, we have shown an outer casing l, within which a round rod 2.

is rigidly secured at its lower end in the mounting support or holder 21. Rod 2 is therefore free to vibrate at its upper end. about its lower end as a center. The rate of vibration may be controlled by a mass 3 adlustably secured to the rod as by a set screw. The vibration of the rod 2 the base 21 thereof is normally maintained in an approximately horizontal plane. If the casing l tilts, the plane of vibration of the upper end of the rod 2 tilts correspondingly, the vibrating plane remaining constant with respect to the case. An evacuated glass envelope I surrounding rod 2 and sealed by a metal to glass seal to base 21 is preferably employed to lessen air resistance and to remove any spurious effects caused by air convection currents in the case I. It is to be noted that the rod 2 may be caused to vibrate at the same frequency as that of the driving voltage if the rod is not magnetically polarized, although this is not a preferred method as it is somewhat inefficient. Rod 2 which has both mass and resillence is the vibratory element of the instrument.

In order to obtain an indication or measure of the path of movement of the rod, we have shown a plurality (preferably four) of electrical pickoff coils 6, I, 8 and 9 positioned symmetrically about rod 2 on the interior wall of casing I. These coils are shown as having iron cores, II), II, III, II, respectively, that extend parallel to a narrow portion of the evacuated glass tube 4.

Assuming that the plane of vibration of the rod is in the plane of the paper, it will be evident that if the cores Ill and II. of coils 6 and I respectively, are positioned in the plane of the.

paper on each side of the rod 2, pronounced alternating voltages will be induced therein. On the other hand a substantially negligible E, M. F.

will be generated in the pick-oi! coils 8 and 9 pomtioned at right angles thereto. Should the plane of vibration of the rod be in the plane extending at right angles to the plane of the paper, considerable E. M. F. will be generated in the coils 8 and 9, and very little or no E. M. F. will appear in the coils B and 'I.- If the plane of v1- bration is at an angle between the two planes indicated, proportional E. M.'F.s will be generated in both pairs of coils dependent on the trigonometric functions of the angles the plane of vibration makes with the planes of the coils. The pair of coils 6, I are preferably connected in series opposition and coils 0, 9 similarly connected in series opposition. The resultant voltages of these pairs of coils are then connected in the manner shown in Fig. 2, through suitable amplifiers, such as l2 and i3 respectively, to operate an indicator such as the A. C. self-synchronous repeater motor 90 of the "Telegon" type having its crossed stator windings It and I connected'respectively to the outputs of amplifiers l2 and l3.

The stationary coil l8 surrounding the Z- shaped rotor or turnable magnetic core ll. of motor 90 is excited from the same A. C. source ll that excites the driving winding I through the frequency doubler 92. The output voltages of amplifiers l2 and I: may also be used to operate a cathode ray tube in the manner shown in Fig. 6, or any other type of instrument which is capable of indicating the angular orientation of the path of the free end of rod 2 or of the plane of vibration of rod 2. Thus, in employing this device as a direction indicator, as on a moving craft to take the place of a directional gyroscope, the pointer is, which may have a friction drive or other adjustable connection with the rotor ll of motor 90. is initially set so that with rod 2 vibrating this pointer will indicate a desired ref- 1 erence direction, such as magnetic north, on the degree scale l8. Then, as the craft is navigated, the reading of pointer I 8' with respect to the original scale setting of this pointer will furnish a continuous indication of the heading of the craft with respect to magnetic north.

Fig. 3 illustrates our invention adapted to serve as a rate of tumdndicator, as for moving craft. A magnetically polarized round rod 2 is symmetrically clamped in a base 26, and is excited by alternating or pulsating current supplied from leads 20 and sent through oppositely disposed coils 20 and 2| adjustably mounted on yoke 23. The natural frequency of the rod 2 may be adiusted by means of the slidably mounted weight 3 to match the frequency of the exciting current. The rod 2 then vibrates in the plane defined by the axes of the exciting coils 20 and 2|, which clearly distinguishes this form of the invention from that shown in Fig. 1, since this plane is fixed to and moves with the craft or vehicle carrying the instrument. At right angles to this plane of vibration are placed two pick-oil coils 24, one not being shown in the drawings.

When the base 26 of the instrument is turned, as when the craft turns, gyroscopie force exerted on the rod caus the end of the rod to tend to precess in a direction at right angles to the axis of the turning couple and at right angles to the axis about which the rod vibrates, causing the free end of the latter to move in an elliptically shaped path. When the rod is traveling in one direction and the base is turning, gyroscopic reaction gives the rod a component of motion up out of the plane of the paper. When the rod reaches its maximum travel and reverses its direction, these same forces operate to force it down out of the plane of the paper. Analysis and experimental evidence show that these reactions result in the rod assuming an elliptical path, the major axis of this ellipse always remaining in the plane defined by the axes of the driving coils 20 and 2|, and the length of its minor axis being functionally related to the rate of turn of the base 26, i. e., of the craft. Fig. 4 illustrates the paths which the end of the rod 2 may take under three different circumstances looking down on the instrument of Fig. 3, the pathA being that for no turn. During a clockwise turn of the base 26 at a given rate, the path rate, the path of the free end of the rod is illustrated by C, this end traveling in the opposite direction to that obtaining in B. A the rate of turn of the craft i increased or decreased, the

magnitude of the minor axis of the elliptical path increases or decreases, respectively.

These components of motion perpendicular to the plane of at-rest vibration induce alternating voltages in the pick-off coils 24. the magnitude of thes voltages depending 'on the rate of turn, and their phase-sense upon the direction of turn. 1. e., the Phase reverses with a reversal in the direction of the turn. The phase reverses because of the fact that the direction that the end of rod 2 moves past the pick-off coils 24 reverses when the craft on which the instrument is mounted changes its direction of turn. The cores 25 are rectangularly shaped and oriented as shown in the drawings to produce a mor nearly sinusoidal output. These reversing phase, variable magnitude pick-off voltages may be fed in series opposition from coils 24 into one windins of a dynamometer type meter such as shown in Fig. 13,. the other winding of this meter beinK connected to leads 20'. Alternatively these pickofl! voltages may be fed into -a thermionic phase detector to operate a direct current meter. A phase meterof the dynamometer type shown in Fig. 13 is more particularly disclosed on page 790 of the textbook published in 1940 entitled "Electrical measurements and measuring instruments" by E. W. Golding. .The device may be used to detect rate of turn about any axis when a suitable mounting is provided.

Fig. 4A shows a somewhat modified structure wherein the vibrating rod 2 is directly observed at a point in its path, preferably at an end of the minor axis of its elliptical path. This is accomplished in Fig. 4A by'use of a neon lamp 24 connected in the pulsating or alternating supply circuit leads 20. In order to adjust the point in the paths at which lamp 24 will illuminate the end of rod 2, a phase adjusting circuit such as 25' is employed. The end of the rod 2 may be colored, as by use of white pigment, so that it may be more readily seen through the slotted window'28', of the instrument 21'. In operation, when the craft makes a turn to the right the end of the rod 2 will appear to move from a. position opposite the central index 28' to the right as one looks through the window 26' as shown in Fig. 4A of the drawings. On the other hand, when the craft makes a turn to the left the end of the rod 2 will appear to mov toward the left,.i. e. will be seen at the other end of the minor axis of the path of motion of the free end of the rod, as shown in dotted lines in Fig.

3 or the sign'al from the pick-ofls may be applied to the deflecting plates 28, 31 of cathode ray tube It to giv lta visible indication of the path of vibration of the wire. The operation is essentially thesame as that of the device illustrated in Figs. 1 and 2. The wire 30 is shown as enclosed within a glass or other non-magnetic tube 22, which is preferably evacuated to reduce air resistance. Adjacent to the pick-oi! coils i, I, I and 8' the tube 32 is of reduced diameter so that the pick-off coils may b placed close to the wire. A magnetically polarized mass Il may be secured near the center of the wire 30 to decrease the period of vibration, thus decreasing the necessary length of the wire 30 and making the instrument more compact. In this instance, the wire ll which has both mass and resilience is the vibratory element of the instrument.

Our invention is adaptable for use in still another form as a directional indicator. According to this form, as shown in Fig. 7, the vibratory rod is shown as a U-shaped member 40, which is preferably magnetically polarized, and may resemble a tuning fork clamped at it bas in support 54, which, in turn, is rotatably mounted about a vertical axis in bearing members 43 and 44. The vibration of the tuning fork may be effected by circumferential three phase coil 4| excited by three phase alternating current from generator 51. To spok pieces extending from the support 54 there may be secured a compass card 45 visible through window 41 providing a reference mark cooperating with the indications of said card, and means may be provided for resetting the same by pushing in setting knob 5i carrying a bevel pinion 49 thereon adapted to engage a bevel gear on the compas card, the knob 5| being pulled outand held by detent 50 after resetting. In this typ of instrument, the tuning fork maintain its plane of oscillation by the momentum of its planar vibration. The instrument is useful in any of the three coordinates.

Another means of driving the tuning fork type of directional indicator is shown in the fragmentary view of Fig. 8. The coil 58 is rigidly at- 4A. When the vibrating rod crosses the viewing slot at its extreme left or right position of movement, viewing the instrument from the front, it is illuminated by lamp 24'. Thus, the operator is enabled by directly observing th instrument to determine whether or not the turn is to the right or to the left and the distance of the spot indicating the end of the rod from the central index 28' is a measure of the rate of turn.

Figs. 5 and 6 show another type or directional indicator employing a wire 30, which may be of magnetic material, stretched between the clamped end 35 and a drum 33 around which the free end of the wire is wound. The tension of the wire may be adjusted by a worm and worm pinion 9|] from a thumb piece 34, thereby adlusting the natural frequency of the wire to half that of the exciting current. Vibration of the wire may be produced by a three phase winding 29, excited by three phase alternating current. Pick-offs 8', I, 8', and 9' may be employed as in Fig. 2 to actuate a suitable "Telegon indicator,

tached to the base or the instrument and the coil 55 to the rotatable shaft 45. The shaft 45 being made of a magnetic material, the two coils and shaft act together as a transformer, thus avoiding the use of slip rings and supplying alternating or pulsating energy to the driving coils 52 and 53 from coil 55, coils 52 and 53 being mounted to rotate with the shaft 45.

Our invention is also adapted to use as an artificial horizon, one such form being shown in Figs. 9, 10 and 11. In this form of the invention, round magnetically polarized rod 2 is clamped at one end in the casing 58 in a horizontal position and is vibrated by an alternating or pulsating current sent through a solenoid 5. The plane of oscillation of the rod 2 .is normally maintained horizontal by electromagnets Bi secured to a bearing member 62, which is rotatably mounted on boss 9! on the interior of casing 58 in which rod 2 is secured. The axes of magnets GI are normally maintained truly horizontal by a pendulum 61 secured to the bearing member 62, so that under normal conditions the rod 2 vibrates in a, horizontal plane and therefore generates no signals in the pick- oil coils 59 and 80. If the support becomes inclined, the position of the pick-off coils will be changed with respect to the plane of vibration of the rod, which plane is by the horizontal vibrational momentum of the rod, andtherei'ore a signal will be generated in pick-off coils '59 and 80 that is. a function of ,2

' total acceleration forces on the pendulum will be slightly increased in accordance with the vector resultant of the acceleration force of gravity and the centrifugal acceleration force. As shown, the pendulum bob 6! is secured to a sleeve slidablymounted on a stem 65, the mass of the pendulum being normally just balanced by the coil spring 60. Therefore, in the presence of acceleration forces, the pendulum bob 61 will move downward slightly and thus break contacts 69,

one of which is secured to the pendulum bob 81 and the other to the fixed stem 65. These contacts 69 are normally in series with the coils ii, and when opened interrupt the restraint exerted on the vibrating rod by the coils ii. The effect of this interruption is to provide a means for averaging out normal turn errors. Two Dickofl coils 03 may be placed at right angles to the coils 59 and 60. as indicated by dotted lines in Fig. 9, for use of the instrument as part of an attitude indicator to register pitch and roll of an aircraft as shown in Fig. 9A.

' In Fig. 9A we produce on the screen of the cathode ray tube 96 a line I08 whose position in the vertical direction depends upon the angle 01' pitch of the craft and whose angle with respect to the horizontal index line II marked on the face of the tube indicates the angle of roll of the craft. This eifect is produced by the following means.

For indicating pitch we have shown schematically an instrument I06 like that of Fig. 9, with no horizontal pick-off coils 93, but with two vertically mounted pick-off coils 50" and 60", the device being mounted so that the end of the rod 2 vibrates for normal level flight in a horizontal plane parallel to the direction of flight of the aircraft, the central position of rod 2 being in the direction of flight. For indicating roll, we employ another instrument I like that of Fig. 9 which has pick-off coils mounted horizontally U3) as well as vertically (59', 60'). This instrument is mounted so that its rod 2 vibrates in a horizontal plane with the central rod position at right angles to the corresponding position of the rod 2 in instrument I06. The rods are driven by means of power supplied from generator I04 through frequency doubler 82 to exciting coils 5' and i".

From the roll axis instrument I05, alternat ng voltages'which appear in-pick-oif coils 50 and 60' are applied in series opposition to the vertical previous discussion of Flg. 9, it is evidentthat the angle this trace makes with index mark'l ll .on'the face of the screen then indicates to th pilot the anEle of roll of the craft.

As is well known in the artificial horizon art. the pitch angle is usually indicated by the distance of the center of trace I00 above or below index H4, the trace appearing above the index when the aircraft dives, and below when the craft climbs. The instrument I08 is mounted to provide this indication. The ignal from coils II" and 60" is, by means of the electronic phase detegtor I00, compared in phase with a signal from generator I04 through transformer I03, by means of diodes 01 and 00. Whenever the attitude of the craft is altered. a voltage app ars across wires I I I, II2, which is proportional to ELE: cos 0 where E1 is the voltage from transformer I00, E: is the signal voltage and 0 is the phase angle between the two voltages. This unidirectional voltage is inserted in series with the voltage derived from coils 59', and is amplified by amplifler 95, which is designed to amplify direct current as well as alternating current signals, and thence is applied to the vertical plates of cathode ray tube 06 to move the trace I00 up or down. Knobs III and H0 are provided on amplifiers 04 and 05. respectively, to furnish means for adjusting their outputs.

Another form of turn indicator type of instrument is shown in Figs. 12 and 13. In these figures the rod 2 is shown as a flat magnetically polarized rod or strip I2 clamped near one end in a bearing member I3 so that the flat surface of the rod is horizontal. Member I3 is rotatably mounted in a bracket within casing II. By fiattching the strip and by using acentralizing spring I5 extending between the short end of the strip I2 and bracket II, a vertical plane of vibration is predetermined. A-coil 80 supplied with alternating or pulsating current is shown for the purpose of vibrating the strip. Upon turn of the craft, the center of the end of the rod will depart from a vertical plane and will trace a figure 8 as shown at B in Fig. 14. The amplitude and phase of the vibration again are functionally related to the rate of turn and to the sense of turn, respectively. Due to the dissymmetry in stiffness of the fiat rod,'the clamped end of the rod will twist with the same frequency of vibration with which the other end of the rod vibrates back and forth. The behavior of the rod under these circumstances may he arrived at from obvious analysis somewhat similar to that used in discussing the rod 2 of Fig. 3.

As a pick-oil for this type of instrument, we have shown a downwardly extending permanent magnetic member I1 secured to the short end of rod 12. On each side of the lower end of the magnet are shown pick-oil coils I0 and I9. when the aircraft is at rest or moving uniformly in a straight line, the magnetic pole ll of the magnet II will remainstationary, but upon turn of the craft it will be oscillated between the pick-oi! coils at a frequency equal to the frequency of the vibration of the "rod I2 with an amplitude proportiona1 to the rate of turn and a phase depending on sense of turn. Any suitable form of indi cator may be actuated therefrom, such as a leftright turn indicator 84, which is a zero center dynamometer type meter. As is well known in the art, coil 83 of this meter is fixed and may be supplied with current of the same frequency as the driving coil 80; and coil 82, to which the 15, the rod 2 is driven by power supplied to exciter coils 20 and 2i through frequency doubler I20 from generator I2I-, The theory of operation of the rod 2 is exactly that described in discussing Fig. 3. When the craft on which the instrument is mounted is at rest or is maintaining straight line flight, the rod 2 vibrates in a straight line path in the plane defined by the axis of the rod and the coils and 2I so that the ratio of the capacity between plates I22 and I22 to that. between the plates I22 and I 24 is a constant. If the craft makes a turn, the path of the end of rod 2 opens into an ellipse, and plate I22 then has an alternating component of motion such that this capacity ratio varies with a frequency equal to that of the rod 2.

An alternating current bridge is employed and is made up of these two capacities and the condensers I21 and I28. The condenser I28 is made variable so that the ratio of the capacities of condensers I28 to I21 may be made the same at the ratio of the capacities between plates I22 and I23 to that between plates I22and I24 for straight line vibration of the rod 2 corresponding to straight flight. To one diagonal of this bridge is applied an alternating current of frequency f (on the order of 10,000 cycles) generated by oscillator I25 and fed through transformer I26. As long as the rod vibrates in a straight line parallel to the plates, the bridge remains balanced; but

when the pick-off capacity ratio varies due to a turn of the craft, a voltage of the frequency 1 modulated by the frequency of the rod 2 appears at the other diagonal of the bridge and is impressed across series resistors l29 and I30. -By means of triodes I32 and I33, this signal is amplitied and fed to the detector circuit I35, which removes the frequency 1 signal, leaving a low frequency voltage. The magnitude of this low frequency voltage depends upon the rate of turn of the craft, and its phase-sense upon the direction of the turn.

The phase detector I38 operates in a similar manner to that shown as circuit I09 in Fig. 9A.

In phase detector I38, the reversing phase low frequency signal voltage is compared to, the phase of the standard signal provided by generator I2I. The indicator I21 may be any of the devices suggested for operation with the instrument shown in Fig. 3. The device is useful in any of the three coordinates, if suitable mounting is provided.

Also, while we have not heretofore referred, to .our invention as a gyroscope, since the motion ings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a rate of turn instrument, a support, a rod carried by said support, means for vibrating said rod in a plane, and electrical pick-off means positioned adjacent said vibrating rod for p oducing potentials responsive to movements of said rod departing from vibration in said plane.

2. In an instrument of the character described, a support, a vibratory element carried by said support, electrical means for vibrating said element, electrical pick-off means positioned adiacent said element producing potentials responsive to movement thereof departing from vibration in a plane, and indicating means controlled by the output of said pick-off means.

3. A direction indicating instrument comprising a substantially vertical rod fixed at one end and free to vibrate at its other end, electromagnetic means for vibrating the free end of said rod at substantially the natural frequency thereof,

pick-off coils disposed about said rod for generat 5. A direction indicating instrument comprising a substantially vertical rod supported at one end and free to' vibrate at its other end, a varying source of current supply, a magnet coil disposed adjacent the free end of said rod in substantial alignment with the vertical axis thereof and excited from said source for vibrating said rod, two pairs of pick-off coils surrounding said rod and disposed substantially at right angles to one another, an indicator having crossed stator windings connected respectively to be energized with a version of the output of a respective pair of said pick-oil coils, said indicator having a rotor provided with a winding excited from said source, and direction indicating means actuated by said rotor.

6. A rate of turn indicating instrument comprising a substantially vertical rod supported at one end and free to vibrate at its other end, a varying source of current supply, electromagnetic coils disposed on opposite sides of said rod and excited from said source for vibrating said rod in a desired vertical plane, pick-off coils disposed on opposite sides of said rod at right angles to said vibrating coils for producing potentials responsive to motion of the rod at right angles to its plane of vibration between said vibrating coils, and an indicator having a winding excited by a version of the output of said pick-off coils and another winding excited from said source, said windings being relatively movable.

'7. In an instrument of the character described, a vibratory element, means for supporting said element, electromagnetic means fed from an alternating current source for, vibrating said element, and means for loading said element so that its natural frequency is made a function of thefrequency of the alternating current source.

8. In a direction )indicator, a wire secured at both ends, electromagnetic means for vibrating said wire, an electrical pick-off disposed adjacent from said pick-oil.

9. In a direction indicator, a wire secured at both ends, a' driving coil surrounding said wire,.

said coil being arranged to be energized with alternating current for vibrating said wire, means for varying the tension or said wire so that its natural frequency will substantially conform to that oi said alternating current, two pairs of pickoi! coils disposed at right angles to one another about said wire, and an indicator controlled from said pick-oi! coils.

10. In a direction indicator for movable craft, a wire secured at both ends, a driving coil surrounding said wire, said coil being arranged to be energized with alternating current for vibrating said wire, means for varying the tension of. said wire so that its natural frequency will substan tially conform to that of said alternating current, two pairs of pick-oil coils disposed at right angles to one another about said wire, a cathode ray tube having deflecting plates, means for supplying a version of the output of one pair of said pick-oil coils to one pair oi said plates, and means for supplying a version oi the output of the other pair of said coils to the other pair of deflecting plates of said tube, whereby the cathode ray beam of said tube is caused 'to draw a line the direction 01' which varies with change in course.

11. In a direction indicator, a U-shaped rod member having two vertical legs and a transverse connecting portion, a turnable support for said rod member connected to said transverse portion substantially midway between said legs, means for vibrating the legs oi said member in a common plane, and a compass card carried by.

said turnable support.

12. In a direction indicator, a U-shaped rod member having two vertical legs and a transverse connecting portion, a turnable support for said rod member connected to said transverse portion substantially midway between said legs, electrical means for vibrating the legs of said member in a common plane, a compass card carried by said turnable support, and means for turning said compass card and said support for setting up a desired course.

13. Means for indicating roll or pitch of a craft comprising a substantially horizontally disposed rod supported at one end and free to vibrate at its other end, means for vibrating said rod and for normally maintaining the plane of such vibration horizontal, pick-off coils disposed adjacent said rod, and indicating means controlled from a version of the outputs oi. said coils.

14. Means for indicating roll or pitch of a craft comprising a substantially horizontally disposed rod supported at one end and free to vibrate at its other end, means for vibrating said rod, pendulously controlled means for normally maintaining the plane of vibration of said'rod horizontal, means for nulliiying the operation of said pendulously controlled means during tuming movements for averaging out turn errors, pick-off coils disposed on opposite sides oi said rod, and an attitude indicator controlled from the outputs of said pick-oil coils.

15. An instrument for indicating pitching of a craft comprising a rod supported at one end for extending substantially transversely of the craft, a driving coil excited by varying current disposed adjacent the free end of said rod for vibrating said rod, pendulously controlled electromagnetic means for confining the vibration of said rod in a direction substantially parallel to the direction oi hsdoi the craft, pick-up coils disposed above a controlled from theoutputs of said coils.

man instrument for indicating rolling of a craft co rising a rod supported at one end for extending\ substantially tors and -aft oi the craft, ,a driving coil excited by varying current disposed adjacent the free end of said rod ior vibrating said rod, pendulously controlled electromagnetic means for confining the vibration of said rod in a direction substantially at right angles to the direction of flight oi the craft, two pairs of pick-oil! coils disposed at right angles to one another around said rod, and indicating means controlled from the outputs of said coils.

17. An artificial horizon indicating instrument for aircraft comprising a pair of rods fixed at one oi their ends and free to vibrate at their other ends, means for vibrating said rods horizontally,

pick-oi! coils disposed about said vibrating rods,

a cathode ray tube having deflecting plates, and means for applying versions oi the outputs of said pick-oil coils to the deflecting plates of the cathode ray tube to produce an artificial horizon line movable in response to rolling and pitching of the craft.

. l8. A'turn indicator for aircraft comprising a flat rod extending substantially horizontally and rotatably supported at one pointalong its length for turning about a horizontal axis, a centrallizing spring connected to said rod and to a relatively fixed support, means for vibrating said rod in a vertical plane, pick-on means associated with said rod and an indicator operated from said pick-ofi' means.

19. In a rate of turn instrument, a substantially vertical rod fixed at one end, a source of alternating current, means fed from said source for vibrating the other end of said rod in a plane, a bridge circuit including capacity pick-of! means extending adjacent said rod, a phase detector connected for comparing the phase of said source with the output of said bridge circuit, and an indicator controlled from said phase detector.

20. In a rate of turn instrument, a support, a rod carried by said support, means for vibrating said rod in a plane and stroboscopic means for directly indicating departures of said rod from its plane of vibration.

21. A vibratory, gyroscope-like, instrument having an element with mass and resilience, means for causing continuous vibration of said element in some pattern, and means for indicating departure of the path 01' movement 01 said element from said pattern.

22. A vibratory, gyroscope-like, instrument having an element with mass and resilience, means for causing continuous vibration of said element in a plane, and means for indicating the plane.

23. A vibratory, gyroscope-like instrument of the rate of turn class, comprising a support, a rod clamped at one end to said support, means for vibrating the free end of said rod in a fixed plane relative to the support, means for detecting a change in the plane 01' vibration of said rod responsive to turning movement of the support, and a turn indicator controlled by said detecting means.

24. A vibratory, gyroscope-like instrument of the directional gyroscope type, comprising a rod, a clamp to which one end of the rod is fastened, means for mounting the clamp for free movebelow said rod, and indicating means.

ment about a vertical axis, and means for continuously vibrating the free end or said rod without coercing the same in any plane.

25. A gyroscope-like instrument of the characer claimed in claim 24, which includes a plurality of pick-ofl coils adjacent the vibrating position of said rod, and a self-synchronous repeater compass actuated by the output of said pick-of! coils.

26. A gyroscope-like instrument or the character claimed in claim 24, in which said rod is a tuning fork, the base oi which is fastened to the clamp.

2'1. An attitude indicator for aircraft comprising a fixed support, a vibratory rod clamped thereon at one point, magnetic means for coercing said rod to cause it to vibrate in a definite plane, a pendulous member for stabilizing said means whereby a force is exerted on said rod to change its plane of vibration upon relative tilt of said pendulous means and support, pick-oil means responsive to changes in the plane oi vibration of said rod. and an attitude indicator actuated by the output or said pick-oi! means.

28. An attitude, gyroscope-like, instrument of the vibratory type comprising an element having mass and resilience, means for vibrating said element, means for maintaining the normal vibration oi the element in a horizontal plane, and means for indicating a, change in the path of movement of said element.

29. In a vibratory instrument, a casing, an element having mass and resilience carried by said casing, ,means for vibrating said element operable to move the same in a path, and means for measuring deviations of the vibratory movement of said element from said path.

30. A vibratory instrument including an element having mass and resilience, means for vibrating said element operable to move the same in a plane, and means for measuring the direction and magnitude oi! departure of the vibratory movement or said element from said plane.

31. A vibratory instrument comprising a support, an element having mass and resilience carried by said support, means for vibrating said element operable to move the same in a plane, and measuring means responsive to turning movement of the support for detecting a change in the plane of vibration or said element.

JOSEPH LYMAN. ELWOOD NORDEN.

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