US2448612A - Aided tracking aiming mechanism - Google Patents

Description

, Sept. 7, 1948. P. J. MCLAREN 2,448,612

AIDED TRACKING AIIIING IBCBANISII Filed 00L 30, 1943 4 Sheets-Sheet 1 I if INVENTOR.

Pefer J M Laren Sept. 7, 1948. P. J. M LAREN 2,448,612

AIDED TRACKING AIMING MECHANISM Filed Oct. 30, 1943 4 Sheets-Sheet s "@ii i24 IN VEN TOR.

77 Pefer'JM l/aren v M v M Sept. 7, 1948; P. .1. M LAR EN AIDED TRACKING AIHING HECHANIS" 4 Sheets-Sheet 4 Filed on. so, 1943 YINVENTOR. Pel et Q1 M I/aver: B

Fate:- 3. MoLaren, New York, N. Y., asslgnor, by

mesne assignments, to The W. L. Manson Corporation, New York, N. Y a corporation of New York Application October 30, 19413, Serial No. 508, l35

(i. Mit -257) 9 Claims. 1

This invention relates to aided tracking in power operated aiming mechanism, and more particularly in power operated gun carrying tur= rets. By aided tracking is meant the automatic temporary introduction of a supplementary speed control factor when a change of speed of the turret is sought, which, for the time being augments the effect on the speed of the turret normally to be expected from the mere change of position of a, speed control member effected by the operator.

Aided tracking is very advantageous in enabling an operator quickly to pick up a moving target in the turret sight and to track the target without excessive over-running and hunting. When an operator brings the turret sight to bear on a moving target he has necessarily done so by causing the speed of the turret in the direction in which it is operated to exceed the angular rate of target traverse in that direction. In order to produce tracking he must bring about an alteration of the speed of the turret to make the speed of the 'turret coincide with the angular speed of traverse of the target, and this with the turret sight bearing on the target This is apt to involve either a cautious and delayed picking up of the target or a picking up of the target at an over-running speed of the turret.

As an over-running gap begins to appear the "speed of the turret must be retarded, not only to prevent increase of the over-running, but to correct the over-running which has already been observed. It the speed of the turret were dependent exclusively upon the position of the control member, the control member would have to be moved in making such a correction to a. setting which produces a turret speed substantially different from that of coincidence with the angular traverse of the target.

If, however, a temporary augmentation factor is introduced by the movement of the control member for effecting such change of speed, the sight may be returned to bear upon the target more quickly andwithout so great a change .of position of the control member as would be necessary if change of speed of the turret depended solely upon change of position of the control member. Thus, the new settling of the control member, when thesight has again been brought to bear onthe target will differ less from the speed of coincidence by reason of the fact that the temporary augmentation of speed change has been introduced and utilized. The same principle applies to subsequent corrective steps, and tracking can be maintained with much less deviation of the control member from the average position thereof corresponding to the speed of coincidence by virtue of the aided tracking feature.

It is a primary object of the present invention to provide, in combination with a normal turret speed control mechanism, which makes the speed of turret operation a pure function of the position of a speed control member, of auxiliary speed control mechanism for automatically introducing a supplemental speed control factor in response to movement of the co'ntrol member, to augment temporarily the. change of speed which would normally be brought about by the mere change of position of the control member resulting from such movement.

Other objects and advantages will hereinafter appear.

The invention is illustratively disclosed herein as an improvement upon the invention disclosed in the pending application of Peter J. Mc-

Laren, John A. Vaughan and Macon Fry, Serial No. 27,807, filed May 18, 1948, a continuation of Serial No. 473,800, filed January 28, 1943, now abandoned, for Continuously adjustable speed electric drive, and the pending application of Donald S. Kellogg, Serial No.- 481,681, filed April 3, 1943, now Patent No. 2,395,000, issued February 19, 1946, for Electric drive, although it is to be understood that such disclosure is intended to be illustrative, and that the invention in its broader aspects is susceptible of other applications.

In the drawing forming part of'this specification Fig. 1 is a fragmentary perspective view illustrating a turret and turret operating mechanism embodying the present invention Fig. 2 is a view in right side elevation, partly broken away, of a control box and control mechanism associated therewith;

Fig. 3 is a top plan view of the control box of Fig. 2 together with associated mechanism;

Fig. 4 is a sectional view taken upon the line i i of Fig. 2 looking in the direction of the arrows;

Fig. 5 is a. view in sectional elevation taken along the line 55 of Fig. 2 looking in the direction of the arrows;

Fig. 6 is a schematic diagram of turret control mechanism including the aided tracking device as applied to a resistor type electric drive; and.

Fig. '7 is a schematic diagram of turret control mechanism including the aided tracking device as applied to a motor generator type electric drive.

In Fig. 1 all of the parts illustrated are mounted upon and form parts of a. rotary turret structure,

with the exception of a. stationary internal ring gear I.

The turret is caused to rotate about a vertical axis which coincides with the center ring gear I by means of a turret carried azimuth drive motor 2a whose output shaft 30 has fast upon it a gear to in mesh with the internal teeth of the stationary ring gear I. A horizontal shaft 5 is revolubl mounted in fixed bearings of the turret (not sh wn) and has fast upon it a pair of guns 6 and 1. A gear segment 8, pinned to the shaft 5, meshes with an output gear 4e of an elevation drive motor 2e for raising and lowering the guns. The azimuth drive motor 2a and the elevation drive motor 2e are both controlled in their operations from a common control box II which is equipped with handles l2. The control box II and a supporting box l3 therefor are carried by the turret, but the supporting box I3 is made fast with the turret, while the control box II is mounted for limited manual rotation relative to the turret about a vertical axis. V

The control mechanism which is mounted within and associated with the control box It is designed to operate the azimuth and elevation motors through the control of the respective motor operating circuits. Suitable circuits are illustrated in Figs. 6 and 7, respectively, and will be described presently.

When the handles i2 are operated to swing the control box about its vertical axis in one direction from azimuth neutral, the azimuth motor 2a is driven in one direction and at a speed proportional to the extent of displacement of the control box from its azimuth neutral position, and when the handles are operated to swing the control box about its vertical axis in the opposite direction from azimuth neutral, the azimuth motor 2a is driven in the opposite direction and at a speed proportional to the extent'of displacement of the control box H from its azimuth neutral position. I

When the handles l2 are depressed, the elevation motor 26 is operated in a direction to raise the guns and at a speed proportional to the extent of displacement of the handles from their elevation neutral attitude, and when the handles |2 are raised, the elevation motor 2c is operated in the direction to depress the guns and at a speed proportional to the extent of displacement of the handles from their elevation neutral attitude.

The motor control illustrated in Fig. 6 is like that disclosed in Serial No. 473,800 and will be briefly described and explained.

Line conductors I and Hi are constantly connected through the armature ll of motor 2 and through a resistor I8. Current may flow from conductor i5 through conductor l9 and thence alternatively through opposed field windings 26 and 2| of the motor ll. Winding 29 is connected through conductor 22 to a stationary contact 23, while winding 2| is connected through a conductor 24 with a stationary contact 25.

A contact arm 26 is interposed between the contacts 23 and 25 and is provided with contacts 21 and 28 for cooperating, respectively, with the contacts 23 and 25. The contact arm 26 is conected throgh a conductor 29 with line conductor Hi.

When contacts 23 and 27 are closed, current flows through field winding to drive the motor 2 in one direction, and when contacts and 28 are closed, current flows through field winding 2| to drive the motor 2 in the opposite direction. Output shaft 30 of motor 2 drives a D. C. I

When the arm I2 is swung in either direction from the neutral attitude in'which it is illustrated in Fig. 6 it exerts through the spring 36 a contact closing bias upon the arm 26. This energizes either field 20 or field 2| of motor 2, depending upon the direction the arm 26 is moved from neutral, and sets the motor 2 into operation in the direction characteristic of the energized field winding. The voltage generated by. generator 3| is a function of the speed and direction of rotation of the motor 2, and the torque developed by the galvanometer 34 is a function of the voltage generated by generator 3|, and hence of the speed and direction of rotation of the motor 2.

As the speed of the motor 2 increases the torque of the galvanometer 34 increases until it is sufficient to overcome the bias exerted by the spring 36 upon the effective pair of contacts and to cause disengagement thereof. The motor thereupon loses speed and the torque applied by the galvanometer 34 is correspondingly diminished, so that if the position of the arm |2 is unchanged, the force exerted by the spring 36 will cause the previously engaged contacts to become reengaged. This alternate make and break action will continue, maintaining the speed of the motor 2 at a definite value corresponding to the extent of displacement of the arm I2 from the neutral position. The same explanation holds good regardless of the direction of displacement of the handle l2 from neutral position, the only difference being that the rotation of the motor 2 will be in one direction for one direction of displacement of the handle l2, and in the. opposite direction for the opposite direction of displacement of the handle l2. The description thus far given has nothing to do with aided tracking, but is in accordance with the normal law of operation of the illustrative mechanism if no aided tracking provision were made.

In the alternative form of control circuit illustrated in Fig. '7, line conductors 4| and 42 are ,constantly connected through conductors 43 and 44 with the armature 45 and the field winding 46 of a self-shunt motor 41. The output shaft 48 of the motor 4! drives a generator 49. The generator 49 is provided with opposed field windings 50 and 6|, the former being connected to conductor 4| through conductor 52 and to a fixed contact 53 through a conductor 54, and the latter being connected to the conductor 4| through a'condutcor 55 and to a fixed contact 56 through a conductor 51. The purpose of the generator 49 is to provide armature current for the armature 51 of a power motor 58. The current is delivered to the armature 51 from the motor 49 through conductors 59 and 60. The direction of current flow through the armature 5! depends upon which one of the fields 50 and 5| of the generator 49 is effective, and the voltage generated by the generator 49 depends upon the position of control handle l2 through which the circuits of field windings 50 and 6| are controlled.

Output shaft 6| of motor 58 drives a D. C. I

generator 62 which is connected through conductors 63 and 64 with a galvanometer or torque motor 65. The output shaft 66 of galvanometer 66 is connected through a contact arm 61 having contacts 68 and 69 for cooperating, respectively, with the contacts 55 and 53. As in thecase of Figure 6, the arm I2 is connected to contact arm 61 through a coil spring 10. The contact closing bias of the spring 10 is determined by the extent age which is a function of the speed and direction of rotation of the motor 58, and this voltage oping a torque which is a function of the voltage and hence of the speed and direction of rotation of the motor 58.

When the motor 58 has attained the speed characteristic of the position in which the handle I2 is held, the galvanometer torque overcomes the torque of spring 10 an opens the engaged pair of contacts. The energized one of. field windings 50 and is thereupon deenergized, the armature current supplied to the motor 58 is diminished, and the motor loses speed. Again an alternate make and break action is set up as the motor 58 alternately rises above and falls below the speed characteristic of the position in which the handle I2 is held. This description has nothing to do with aided tracking; but is in accordance with the normal law of operation of the illustrative mechanism if no aided tracking provision were made.

InFig. 2 the control box II is shown as revolubly mounted upon a stationary base member II which is afiixed to the stationary supporting box I3. Raising or lowering of the handles I2 does not involve rotation of the control box II, but serves only to effect control of the elevation drive. The control handles I2 are interconnected through a horizontal shaft I2 which, through bevel gears I3 and I4, drives a vertical shaft 15.

The shaft I5 has pinned to it a segment 16 which meshes with a gear -I| loose on a vertical shaft I8. The shaft 18 has pinned to it a disc I9.

Motion of the gear I1 is yieldingly transmitted to the disc I9 and the shaft I8 through a coil spring 89 which surrounds the shaft. The opposite ends SI and 82 of the spring 80 extend outcausing a pin IIIIJ aflixed to the shaft 18 to extend outward into a notch IIII formed in the lower end of the hub of the bevel gear 99.

ward and receive between them adownwardly of enabling limit mechanism to override the effect of the manual control normally asserted .by the handles I2, as will presently be explained. Normally the disc 19 turns in unison with the gear 11.

A clamping collar 85 which is clamped upon the shaft 18 has affixed to it one end of spring 88e. The opposite end of the spring 36c is aflixed to contact arm 26c which is fast upon output shaft 35c of galvanometer Me. The arm 26c carries the contacts 21c and 28a for cooperating with fixed contacts 23c and 25a, respectively.

The limit stop control mechanism, previously referred to, comprises a bellcrank 9| mounted on the shaft 5 (see Fig. 1) with provision for relative rotation of the bellcrank and the shaft. A stop pin 92, fast on the bellcrank at the lower- As the guns approach an upper orlower limit because of the maintenance of the control handles I2 in a displaced position, a limit stop impulse will be transmitted through bellcrank 9i, cable 95 and crank 96, causing displacement of shaft 91 and, through gears 98 and 99 and the removal of the remaining lost motion between gear 99 and shaft 18, restoration of disc 19 to its neutral position against the torsion of spring 80. Restoration of disc I6 to neutral removes the torque from spring 36c, causing the arm 26c to assume its neutral attitude.

Subsequent movement of the control handles to neutral permits the primary control elements to return to neutral and results in the normal realignment of pins 83-and 84.

When the control handles I2 are operated to turn the control box II about its vertical axis, controlled operation of the azimuth motor 2a is brought about.

A gear III is afllxed to a vertical shaft II2 supported by hearings in inwardly reaching arms H3 and H4 of the control box II. The gear III meshes with a stationary segment II5 which is carried by the stationary base II and travels planetwise about said segment. Thus, rotation of the control box produces rotation of the gear III and the shaft II2 about the common axis of the gear III and the shaft H2. The shaft II2 has aflixed to it a clamp 85a to whichone end of coil spring 88a is amxed. The opposite end of spring 36a is aflixed -to contact arm 2611 which is fast on output shaft 950. of galvanometer 34a. The arm 26a carries contacts 21a and 28a for cooperating respectively with stationary contacts 23a and 25a.

The control is the same as that already described for the elevation motor. The transmission from gear III to shaft H2 is not yieldingly effected as in the case of transmission from gear 11 to shaft I8, for the reason that no azimuth limit stops are provided, the upper and lower limits being assumed to be planes.

In accordance with the description of the elevation and-azimuth mechanisms as thus far given, the direction and speed of the elevation motor would be a pure function of the elevation atti tude of the handles I2, and the direction of the speed of the azimuth motor would be a-pure function of the azimuth attitude of the handles I2.

The present invention, however, is designed to introduce a temporary supplemental speed control which is a function of movement of the handles I2, as distinguished from the mere position thereof. This is done by operating eddy current drag cups from the handles I2 to apply a temporary supplemental torque to the galvanometer shaft 35c, 35c in augmentation of the change of contact closing torque which is mechanically effected through the springs 38a, 36a by the change of position of the handles I2. This supplemental torque comes into being and persists only so long as the handles are in motion.

In the case of the elevation mechanism, the

shaft I2 has fast upon it a gear segment I2I which drives a small pinion I22 fast on a horizontal shaft I23. The shaft I23 through bevel gears I24 and I25 drives a vertical shaft I28. A large gear I20, pinned to the shaft I26, drives a gear I28 which is revolubly mounted upon a vertical shaft I21.

The gear I28 frictionally transmits rotation to shaft I21 so that a slip drive is provided. The

. I 7 purpose of the slip drive, as will be more fully explained, is to enable the shaft I21 to be held stationary notwithstanding rotation of gear I28 when a limit of movement of the guns in elevation or depression is reached. A collar I28 pinned to the shaft I21 presses a spring washer I38 against the gear I23, and causes the gear I28 to press a friction disc I 3| against a toothed wheel I32 fast on shaft I21. Normally shaft I21 turns in unison with gear I28, the turning being very extensive and very rapid as compared with the turning of shaft 12, because the entire train from shaft 12 to shaft I21 is designed to produce a large multiplication of motion.

The shaft I21 extends into an extension housing 8 (see Fig. 4) of galvanometer 34c, being revoiubly supported in a partition plate I33 and end plate I34 of the extension housing II8.' The shaft I21 has fast upon it a permanent magnet I38 whose opposite poles extend into proximity with an eddy current cup I38 of highly conductive metal such as copper.

The eddy current cup is-carried by a supportin yoke or spider I31. The yoke or spider I3! is pinned to the output shaft lie of galvanometer 34c, so that the cup is constrained to move in unison with the shaft. The arms of spider I31 extend through openings in the partition plate I33, and since the mechanical range of movement of the shaft 38c from neutral position may be approximately plus or minus'lO", the openings in partition plate I33 may readily be made wide enough to accommodate movement of the spider I31 and the eddy current cu I38 with the shaft 35c. v

The eddy current cup I" is surrounded by a ring I38 of highly permeable metal such as iron, so as to promote the passage of the lines of force from one pole or the magnet I38 through the eddy current cup and thence through the ring I38 back through the eddy current cup to the opposite pole of the magnet III.

As the magnet I38 revolves. it tends to drag the eddy current cup around with it. The eddy current cup is not free to follow, but the drag upon it is applied as a torque to shaft 38c of gelvanometer 34c.

If the handles I2 are displaced from neutral in a direction tending to apply clockwise torque to the shaft 33c through the spring 388, the galvanometer torque applied to the shaft will be counterclockwise and the eddy current torque will be clockwise, opposing the galvanometer torque and aiding the torque applied through spring. 38c. While this condition prevails the motor speed will be higher than that which is characteristic of the position of the handles I2. The eddy current torque will disappear as soon as the handles are brought to rest and the contact breaking speed will then be dependent exclusively upon the position of the handles I2.

11, now, the shaft 18 is rotated in a direction to increase the clockwise torque exerted by the spring lie, the supplemental torque applied by the eddy current cup will be in the same direction as the torque applied by the spring 38c and in the same direction as the change of torque applied by the spring 332, will augment opposition to the counterclockwise galvanometer generated torque, and hence will maintain the eii'ective control contacts engaged until a higher speed of the motor 2c is attained than that which would result from the unaided change of torque introduced by the spring 38c as a result of the chang of position of the shaft 13.

If, on the other hand, the shaft 13 is set to apply clockwise torque through the spring 38c, and

the handles- "are moved in a direction back toward neutral, not only will the torque of spring 33c be reduced by virtue of the change of position of shaft 13, but the torque exerted by the eddy current cup will be in counterclockwise direction to assist the counterclockwise torque generated by the galvanometer 34c. Now the effective contacts will be opened at a lower motor speed than that at which such opening would be brought about by the effect of spring 38c alone. Hence, an enhanced retarding effect will be introduced in this instance by the eddy current cup, which, however, will be maintained only so long as the control handles I2 are actually in motion.

The principle of operation is precisely the same,

whether the motor 26 is operated in one direction or the other.

' If,- when the guns have been moved in elevation to a limit of movement, so that the cable 88 has superseded the handles I2 for preventing further operation of the guns toward that limit, the handles I2 should be moved in a direction normally designed to carry the guns toward or through that limit, the eddy current torque thus generated would cause reengagement of the contacts, and, therefore, an attempted resumption or continuation of movement of the guns toward the interference. To obviate this objection, there is provided means whereby the aided tracking device will be prevented from rotating in a direction to engage the contacts for carrying the guns toward the interference.

To' this end, as previously mentioned, the gear I28 is connected frlctionally to drive a toothed wheel I32 which is fast with the shaft I21 of permanent magnet I38. Means are further provided responsive to the cable for blocking r0- tation of the wheel I32 and the connected magnet shaft I21.

When the limit stop impulse is transmitted through cable 88 and shaft 81 is rotated, a gear I, fast on the shaft, is displaced. The gear I4I has driving engagement with a segment level;

I42 which is pivotally mounted upon a stud I43. 7

The upper end of the segment lever I42 has driving engagement with a segment lever I44'which is pivotally mounted on a stud I48. The se ment lever I45, carries a hair pin spring I48, the free ends of which embrace the tail portion of a two toothed pawl I41. The pawl I41 is mounted on a pivot screw I48 on top of the control box II in position to cooperate with the spaced teeth of wheel I32.

Displacement of Hair pin spring I48 from the neutral position in which it is illustrated in Fig. 5, rock pawl I41 interposing one of the teeth I48, ISO in the path of the teeth of wheel I32. Further displacement of the control handles, therefore, will cause gear I28 to rotate against the friction disc I3I without driving the wheel I32, and hence without driving the permanent magnet I38.

Movement of the control handles in the opposite direction, however, that is, 'in a direction tending to carry the guns away from the interference, is nevertheless effective to drive the magnet I35 through the gear I28 and wheel I32. The contour of the fingers I48, I50 is such that the teeth of wheel I32 may click past the engaged finger of pawl I41,

The supplemental speed control means for the azimuth motor 2a is essentially the same as that for the elevation motor 2e, the principal differshaft I53 which is mounted in upper and lowerbearing arms I54 and I55 of the control box II.

When the control box II is turned about its vertical axis, the pinion I52 travels planetwise in mesh with the segment Il, and hence produces rotation of the shaft I53 about the shaft axis. The shaft I53 has fast uponit a gear I56 which drives the smaller member'I5'I of a compound gear I58 which is rotatably mounted upon a stud I59. The larger member I50 of the compound gear I58 drives a gear I6I which is fast upon the upper end of a shaft I2Ia. The shaft I2'Ia corresponds to the shaft I21 of the supplemental speed controlmechanism for the elevation motor.

Since this supplemental speed control mechanism is the same for the azimuth motor as for the elevation motor, it has not been separately illustrated, nor will it be described, but the showing of the mechanism in Fig. 4, and the description of it which has been given, may be taken as fully applicable to the corresponding part of the supplemental speed control mechanism for the azimuth motor,

I have described what I believe to be the best embodiments of my invention. I do not wish, however, to be confined to the embodiments shown, but what I desire to cover-by Letters Patent is set forth in the appended claims.

What I claim is:

1. In an aiming mechanism including an aimed member, in combination, a control member movable in either of two opposite directions from a neutral or at rest position, a reversible electric driving motor for the aimed member, electrical means including pairs of opposed contacts alternatively engageable for operating the motor in either of two opposite directions dependent upon the direction of displacement of the control member from neutral, means for yieldingly applying a closing bias to the engaged contacts whose value depends upon the extent of displacement of the control member from neutral, motor operated speed responsive means for applying a contact opening bias to the engaged contacts whose value depends upon the speed of the motor, whereby the direction of operation of the motor is determined and controlled by the direction of displacement of the control memher from neutral and the speed of the motor is normally determined and controlled by the extent of displacement of the control member from neutral, and supplementary speed responsive control means energized by movement of the control member away from neutral to apply an additional component of contact closing bias to bring about an abnormally high speed of motor operation and by movement of the control member toward neutral to apply an additional component of contact opening bias to bring about an abnormally low speed of motor operation.

2. In an aiming mechanism including an aimed member, in combination, a control member movable in either of'two opposite directions from a neutral or at rest position, a reversible electric driving motor for the aimed member, electrical means including pairs of opposed contacts alterber from neutral, means for yieldingly applying a closing bias to the engaged contacts whose value depends upon the extent of displacement of the control member from neutral, 9, speed responsive generator driven by the motor, a torque motor energized by the generator and having its output shaft connected to operate one of the contacts of each pair to apply a contact opening bias to the engaged ,oneof said contacts when the motor is in operation, whereby the direction of operation of the motor is determined and controlled by the direction of displacement of the control member from neutral, and the speed of operation .of the motor is normally determined and controlled by the extent of displacement of the control member from neutral, and supplementary speed responsive control means energized by movement of the control member away from neutral to apply an additional component of contact controlling bias to the output shaft of the torque motor depending in direction upon the dlrection of movement of the control member and in value upon the speed of movement of the control member, the construction and arrangement being such that the supplementary bias generated by movement of the control member away from neutral opposes the contact opening bias of the torque motor and the supplementary torque generated by movement of the control member toward neutral aids the contact opening bias of the torque motor.

3. In an aiming mechanism including .an aimed member, in combination, a control member movable in either of two opposite directions from a neutral or at rest position, a. reversible electric driving motor for the aimed member, electrical means including pairs of opposed contacts alternatively engageable for operating the motor in either-of'two opposite directions dependent upon the direction of displacement of they control member from neutral, means for yieldingly applying a closing bias to the engaged contacts whose value depends upon the extent of displacement of the control member from neutral, a speed responsive generator driven by the motor, a torque motor energized by the generator and having its output shaft connected to operate one of the contacts of each pair to apply a contact opening bias to the engaged one of said contacts when the motor is in operation, whereby the direction of operation of themotor is determined and controlled by the direction of displacement of the control member from neutral, and the speed of operation of the motor is normally determined and controlled by the extent of displacement of the control member from neutral, and supplementary speed responsive control means energized by movement of the control member, said supplementary means comprising a pair of inductively coupled rotors, the first being mounted for limited rotation in unison with the output shaft of the torque rotor, and the second being mounted for rotation coaxially with the first, and transmission mechanism for driving said second rotor froin the control member.

4. In an aiming mechanism including an aimed,

member, in combination, a reversible electric I driving motor for the aimed member, electrical control means for the driving motor comprising two pairs of alternatively engageable contacts, a

movable support carrying one contact of each pair, a control member movable in either oi two opposite directions from neutral position for selectively closing said pairs of contacts, a spring speed dependent upon the speed of operation of the control member.

5. In an aiming mechanism including an aimed member, in combination, a reversible electric driving motor for the aimed member, electrical control means for the driving motor comprising two pairs of alternatively engageable contacts, a movable support carrying one contact of each pair, a control member movable in either of two opposite directions from neutral position for selectively closing said pairs of contacts, a spring 12 ance with the speed thereof, means controlled Jointly by said three biasing mechanisms for determining the speed of operation of the drivin motor, limit mechanism for rendering th control for applying to said movable member a contact closing bias whose magnitude is determined by the extent of displacement of the control member from the neutral position, a speed responsive generator driven by thepower motor, a torque motor energized by the generator and having an output shaft connected to actuate said movable contact support, and electrical drag means comprising a pair of relatively rotatable-inductively coupled members for acting upon the output shaft of the torque motor, and transmission mechanism for driving one of said relatively rotatable members from the control member at a speed dependent upon the speed of operation of the control member.

6. In an aiming mechanism including an aimed member, in combination, a reversible electrio driving motor for the aimed member, electrical control means for the driving motor comprising two pairs of alternatively engageable contacts, a movable support carrying one contact of' each pair, a control member movable in either of two opposite directions from neutral position for selectively closing said pairs of contacts, a sprin for applying to said movable member a contact closing bias whose magnitude is determined by the extent of displacement of the control member from the neutral position, a speed responsive generator driven by the power motor, a torque motor energized by thegenerator and having an output shaft connected to actuate said movable contact support, and electrical drag means acting upon the output shaft of the torque motor comprising a highly conductive eddy current cup, means connecting the eddy current cup for operation 'in synchronism with the output shaft of the torque motor, a permeable ring surrounding the eddy current cup, an inductive rotor within the eddy current cup, and transmission mechanism for driving said rotor from the control member at a speed dependent upon the speed of operation of the control member.

7. In an aiming mechanism including an aimed member, in combination, a driving motor for the aimed member, a control member, biasing mechanism responsive to the position of the control member, speed responsive biasing mechanism energized by the driving motor in accordance with the speed thereof, speed responsive biasing mechanism energized by the control member in accordmember inoperative to influence the motor to drive the aimed member beyond a prescribed limit of movement, and mechanism operated by said limit mechanism to render the speed responsive biasing mechanism which is energized by the control member inoperative to influence the motor to drive the aimed member beyond said limit.

8. In an aiming mechanism including an aimed cluding means for rendering the control member ineffective to influence the driving mechanism to drive the aimed member beyond a prescribed limit of movement, and means concomitantly to render the control member ineffective to operate the aided tracking mechanism in a direction to influence the driving mechanism to drive the aimed member beyond said limit.

- 9. In an aiming mechanism including an aimedmember, in combination, a reversible electric driving motor for the aimed member, operating circuit means for the driving motor comprising alternatively engageable pairs of contacts for operating the motor in opposite directions, a speed responsive generator operated by the motor, a torque motor energized by the generator and having an output shaft, a contact support carried by said output shaft upon which one contact of each pair is carried, an input shaft, a torque transmitting spring interposed between and connected to said shafts. a control member, operating transmission mechanism connecting the control member yieldingly to the input shaft, an electrical slip drag device acting upon the output shaft, slip drive transmission means connecting the control member to the slip drag device, andlimit mechanism for preventing operation of the input shaft by the control member and operation of the slip drag device by the control member in a direction to cause the motor to drive the aimed member beyond a prescribed limit of movement.

PETER J. McLAREN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Anschutz-Kaempfe May 25, 1926 Cooper June 21, 1938 Japolsky Aug. 1, 1939 Geiselman Sept. 8, 1942 Spencer' Oct. 26, 1943 Hanna et a1 Sept. 18, 1945 FOREIGN PATENTS Country Date France June 5, 1930 Great Britain July 22, 1938 Number Number

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