Photoelectric marksmanship device

July 25, 1950

D. E. HOOKER

PHOTOELECTRIC MARKSMANSHIP DEVICE

2,516,319

Filed Feb. 12, 1941 2 Sheets-Sheet 1

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July 25, 1950

D. E. HOOKER

PHOTOELECTRIC MARKSMANSHIP DEVICE

2,516,319

Filed Feb. 12, 1941

Sheets-Sheet 2

<img file="US2516319A_D0002.tif" />

<img file="US2516319A_D0003.tif" />

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Patented July 25, 1950

2,516,319

UNITED STATES PATENT OFFICE

2,516,319 PHOTOELECTRIC MARKSMANSHIP DEVICE

This invention relates broadly to photo-electric aiming devices, and has as its principal object the provision of mechanism for projecting a moving image on a wall or screen, and an aiming device or gun adapted to be aimed at the image and including photo-electric means and associated parts actuated when the aim is correct for indicating this fact to the marksman or an instructor.

A further object is the provision of a simulated gun or other aiming device having associated therewith a photo-electric means adapted to be actuated by light reflected from a target element upon which the gun is properly trained, together with means for projecting a luminous background image on a wall or screen and projecting a luminous target upon said screen, and the background thereon, said target image being movable relative to the background if desired, and the background being intended to provide a suitable environmental setting for the target. For example, the background image may represent a wooded scene, and the target image may represent a moving tank or other object of warfare.

A further and important object is the provision for means for rendering the photo-electric device sensitive to the light reflected from the target image but not that reflected from the background image or images.

A further important object is the provision of means for controlling the movement of the target image by an instructor for purposes of training a student marksman in the manipulation of the gun or other weapon associated with the photoelectric means.

Yet another object is the provision in a marksmanship or aiming device of the class hereinabove described, of a photo-electric means which may be associated with an actual, as distinguished from simulated, weapon for the purposes aforesaid.

Still another object is the provision of photoelectric means to be associated with an actual or simulated marksmanship device or weapon, means for projecting by light an image on a target screen or wall surface adjacent the weapon, and means in the nature of a reflecting device adapted to be moved by an instructor to effect various movements and placements of the target image on the screen or wall surface to instruct the student in the art of training the weapon upon said target image, together with means for rapidly varying the intensity of the light forming the target image for the purpose of actuating the photo-electric means.

Donald E. Hooker, Chicago, Ill., assignor to Raymond T. Moloney, Chicago, Ill.

Application February 12,1941, Serial No. 378,645

Claims. (Cl. 273—101.2)

Further objects reside in the provision of circuit connections and apparatus for indicating scores and for controlling the operation of the device, as well as the provision of both mobile and stationary gun units for use therewith.

Additional objects, advantages and novel aspects of the invention reside in the means for providing a movable target image with modulated light with or without a luminous scenic background, and in certain details of construction as well as in the cooperative relationship of the component parts of the illustrative embodiment described hereinafter in view of the annexed drawings in which:

Fig. 1 is a schematic showing of circuit connections and the mechanical parts of one form of the invention;

Fig. 2 is a vertical section through a stationary type of gun unit with the gun shown in elevation;

Fig. 3 is a schematic showing of circuit connections and mechanical parts of a modified form of the invention;

Fig. 4 is a side elevation partly in section of a mobile gun unit;

Fig. 5 is a schematic detail of the cam drive for the image defining means.

Fig 6 is a longitudinal section through the photo-electric telescope.

Heretofore, in the art pertaining to photoelectric marksmanship devices, it has been customary to employ a target having some form of photosensitive means associated therewith, and a gun provided with light projecting means which was adapted to be aimed upon the photosensitive means of the target with the object of actuating some hit indicating or shot register means actuated by the photosensitive means. In this art also various forms of moving target and photo-electric, means associated therewith have been employed, but such arrangements are subject to limitations of several kinds, both structural and functional. In the first place, whereas a relatively large target may be provided, the photo-electric means is necessarily restricted in size and area of sensitivity in relation to the size of the target element with which it is associated, with the result that the marksman cannot aim at any portion of the target but must concentrate his fire on a relatively small portion thereof in order to actuate the photosensitive means. Multiplying the number of photosensitive devices used with a target does not entirely solve this problem for reasons obvious to those skilled in the art.

An additional objection resides in the fact that the mobility of the target structure as a whole ¢5

2,516,318 is limited to the range of movement of the mechanical means employed to mount and move the target structure. Further, electrical connections and instrumentalities necessary in this type of structure become complicated and troublesome as the flexibility or range of movements of the target structure itself is extended.

The present invention overcomes these difficulties ahti greatly increases the ’flexibility of the target portions of such a photo-electric marksmanship device. This is accomplished in part by associating the photo-electric means with the gun or other aiming device, and providing a luminous light-projected target and means for effecting movement of the same-over-a relatively unlimited area.

The invention further makes it possible to provide any desired or appropriate scenic background for the luminous target without affecting the photosensitive means associated with the student’s weapon.

The invention further makes it possible for an instructor to Control the movements of the target image simply and with instantaneous precision.

The limitations and problems peculiar to prior art devices are overcome, and the hereinabove specified objects and advantages are achieved, by the arrangement shown schematically inFig. 1 wherein there is shown a simulated machine gun-10 having arranged in the barrel portion thereof a photo-electric cell 11 disposed in alignment with the muzzle portion 12. The weapon is provided with a trigger 13 arranged to close the switch i 4 when depressed.

The gun 10 is adapted to be trained upon various portions of a suitable reflecting surface of a screen or wall surface 15, the extent of which may be considerably larger than that shown in the drawing in actual practice, as will appear hereinafter.

A suitable image, for example that of an airplane 1-6 is projected upon the surface 15 by an arrangement including a fight source 17, an image defining device 16a, and suitable image forming means such as the lens 19 by means-of Which the image defined by the member 16a is focused upon a dirigible reflecting device or mirror 20 arranged in optical relation to the surface 15 so that the airplane image 16 may be caused- to move on surface 15 by manipulation of the mirror 20.

When the marksman aims the gun 10 properly upon the target image 16, the photo-electric device 11 is actuated, which in turn operates the amplifier 22 connected therewith by conductors 21. Amplifier 22 in turn causes operation of the amplifier relay 23 to close switch 24 thereof thus connecting the driving pawl solenoid 25 of the hit counter unit via conductors 26 and-27 with one terminal of a power source or battery 28. The remaining terminal of battery or power source 28 is connected in common to contacts 29 on an interrupter switch having a rotary contact 30 driven by a motor 31. The rotary contact 30 is connected by conductor 32 with one terminal· of trigger switch 14, the remaining terminal of which is connected to ground.

Thus when trigger 13 is depressed the contacts of switch 14 are closed to complete a circuit through the interrupter switch contacts 29 to energize the hit counter solenoid 25 intermittently at a rate corresponding to the speed of movement Of the interrupter switch Wiper^O ‘over contacts 29. This rate may be’ rather’‘rapid--to correspond to the rapidity of fire of fast machine gun action as will appear hereinafter.

The hit counter solenoid 25 will not be energized intermittently as aforesaid, however, ung less the switch 24 on the amplifier relay is closed, and this switch will not be closed unless the gun 18 is properly aimed at luminous target portion

16.

If the gun is properly aimed as aforesaid and trigger '13 is depressed, a hit will be scored and solenoid 25 will actuate a known type of pawl and ratchet mechanism 33 to move a score indicating dial 34.

Means for controlling the operation of the entire mechanism, includes the provision of a reset switch 35 having one contact 35a connected .to ground and another contact 35b connected via conductor 36 to one terminal of a ratchet release -solenoid 37, the remaining terminal of which is connected to battery for completion of its -operating circuit to ground. Thus closure of reset switchcSS-and.particularly contacts 35a and 35b .thereof .will effect ..the release of the pawl and ratchet-mechanism 33 . and permit the dial 34-to be returned , to the normal or zero position by the- customary spring means 3 4a.

Closure of switch-35 also completes a circuit via contacts-35a and 35e to conductor 38 and thence to one side. of a locking. relay winding .39, the remaining terminal of which is connected in a power circuit to grounded battery. It is intended-that-reset switch 35 will be only momentarily-operated; however, as soon as the locking relay 39’is energized by ..closure of switch contacts 35a and 35c, it -makes its own locking circuit to ground via contacts 39a so that there is a holding ground .connection established to conductor .38 as long-as the relay 39 holds up. The aforesaid locking circuit through contacts 39a may be broken by opening a master switch 40.

- Another result of the closure of reset switch 35 iS-to set-up-a locking circuit for the interrupter motor-relay’41, as is apparent from an inspection of the diagram, resulting in a closure of the switch-42 thereof which connects power to motor 31 and causes wiper 30 to traverse the series of contacts-29 in rapid succession, preferably at a rate to give about 850-interruptions per minute, equivalent to 850 shots per minute.

Ά very important feature of the invention resides in the means for rendering the photoelectric device sensitive only to the light reflected fronrthe target image 16, as ‘distinguished from the light in the surrounding room as- well as that reflected from the background image on the screen or other surface f5.

If the'background image or surface IS, upon which the image &lt;6 -is projected, contrasts in intensity with the -light of the target image arid: ’ or-reflected from said surface, then movement of the image 16 across the optical-range of’the gun TO, while the latter is-held stationary, would'-under ordinary circumstances cause an operation of the photo-electric device 11 and associated -amplifier 22,owing to the fact that the photosensitive- device 11 reacts to relatively Slight variations in light intensity. Therefore, in accordance -with the usual arrangement of such photo-electric devices, it would be impossible to employ · a moving ’ target image under circumstances where -light could be received from the image itself as well as from the surrounding objects or the -background or screen upon..which the image is projected.

Moreover, even if the image- tG were held- sta2,616,319 tionary relative to the background, screen, or other surface 15, mere movement of the gun 10 in adjusting the aim would be quite likely to result in activation of the photocell 11 and cause false operation of the amplifier relay 23, since movement of the gun would cause fluctuations in the intensity of light received from the target and screen in the same manner as when the image is moved relative to the screen or background.

. To achieve a selective, differentiation between the light reflected from the target image and that from any surrounding surface including the background upon which the image may be projected, the amplifier 22 is made to respond effectively only to variations of relatively rapid frequency occuring in the photosensitive device 11; that is to say, the light which strikes, the photosensitive device 11 must vary with relatively great rapidity in order to cause the amplifier 22 to respond with sufficient output to operate. the relay 23. This means that the light from the target image i 6 must vary rapidly at the critical frequency, for which the amplifier 22 may be set or tuned or Altered........

In order to distinguish the light from the target image from other light in the manner aforesaid, the image-projecting light from source 17 is modulated at the frequency to which the amplifier 22 is peaked or tuned to respond effectively; for example if the input frequency is 1080 cycles per second, the light from source 17 must be modulated or varied at a similar frequency. It is understood that, amplifier. 22 may be resonantly or discriminatively peaked to the critical frequency aforesaid or may be provided with a filter circuit to pass only the critical frequency and render energy at other frequencies relatively ineffectual.

Modulation of the projecting light from source 17 is effected by means such as the interrupter disc 5(1, which is rotated by motor means, contained in a housing 51 upon which the light source 17 is also shown mounted for convenience. The motor (not shown) in housing 5i for rotating disc 50 is energized via a conductor 52 through contacts 39b on the holding relay 39 when the latter is locked upon being energized. The disc 50 is provided with a plurality of apertures 53 arranged circumferentially in the path of light projected from source i7 toward lens 19, the apertures 53 being situated in correct optical relation to the focal length of lens 19 with respect to the image forming means 16a. . Obviously, the frequency of interruption of the light projected by the aforesaid system, is a function of the number of holes on disc 59 as well as the speed of rotation of said disc, it being, understood that these variables are determined in each case to give the desired frequency, in the present instance 1080 cycles per second.

From the foregoing, it will be apparent that light varying. at. the relatively low frequencies ordinarily encountered in everyday activity, will not include a frequency component of 1080 cycles of sufficient duration or intensity to cause the amplifier 22 to operate the relay 23. Thus, assuming light from sources other than the imageprojecting means were to be interrupted by ordinary causes such as persons moving in a room, vibration of reflecting surfaces, and so on, the photosensitive apparatus, meaning particularly the; tuned amplifier 22 thereof, would not respond effectively to operate relay 23; even the light variations: resulting from, movements of the image 16 relative to any background including· the screen or surface 15, will not provide a sufficient frequency component at 1080 cycles to cause an operation of the relay 23. Thus it may be said that the photosensitive means is selectively tuned to the image or target frequency, and as a practical matter will respond to no other frequency which might arise from any environmental cause or source.

In Fig. 2 it is contemplated that the gun and projecting means may be conveniently arranged as a stationary unit in a cabinet 55 along with a background image-projecting means such as a known type of moving picture projector 56 adapted to project a relatively large background or environmental scene upon a distant screen with the target image projected for variable movement by movable forming or defining means 16a moved by cam means 57 (see detail Fig. 5).

The arrangement of Fig. 3 is intended primarily for use as an auxiliary training device in connection with actual combat equipment, such for example as the twin machine guns 60 in a gunner’s turret of a combat plane or training turret. In such an arrangement the photoelectric cell I ia cannot be mounted in the gun but is included in an auxiliary telescope device 61 adapted to be mounted conveniently either between the twin machine guns 60 or alongside a single gun unit S8a as shown at 6la in Fig. 4.

As seen in Fig. 6, the telescope 61 has the photocell 11 a mounted at one end thereof behind an aperture plate 62 which is in optical alignment with a- collecting lens 63 at the opposite end of the telescope. A preamplifier unit 64, later to be described, is situated in the bottom of the tube out of the path of light rays directed at the aperture in the aperture plate. The telescope tube is intended to be mounted with its long axis parallel to the axis of fire of the machine guns 60 or 60a. As in the arrangement of Fig. .1, there is employed a means for projecting a target image with modulated or interrupted light, said means including for example a light source and image defining means in a housing 5 ία, and an interrupter disc 50a, similar to the parts.. 17, 16a and 50 of Fig. 1. The image is projected upon a mirror 20a for direction upon the screen or surface 15a.

The modified arrangement of Fig. 3 is especially suitable for use with a mobile training turret, such as indicated at 70 in Fig. 4, and the photo-electric telescope is intended to be connected with the relatively stationary amplifier and score counting mechanism by means of a cable 71 of sufficient length to permit movement of the turret at will in a hanger or training quarters.

Because the signal impulses from the photoelectric cell ί ί a are of very weak character, and must be passed through a shielded conducting means in the cable, and because the impedance of the photo-electric device is quite high, it is found desirable to interpose a matching impedance in the line between the gun turret and the amplifier unit with the object of lowering the impedance of the connections in the relatively long cable 71. For this reason the preamplifier 64 shown in Figs. 3 and 6 is located as close as possible to the photo-electric cell Ila, this amplifier preferably being of the resistance coupled type so that its input impedance will closely approximate the impedance of the photo-electric cell I ία, while its output impedance will be consider&gt; ably below that of the photo-electric cell· when

2,516,319 coupled to the main amplifier 22a as by conductors 7 ία.

The output of the main amplifier 22a Is connected via conductors 73 to the grid circuit 74a of a Thyratron type tube 74, and the plate 75 of this tube is connected to one terminal of a hit counter 76 including an operating coil or solenoid like the solenoid 25 of Fig. 1 (not shown), the remaining terminal of the hit counter unit being connected via conductor 77 to one brush of an interrupter 78 and thence via conductor 79 from the other interrupter brush and through switch 79a to one of the power line conductors 89, the other power conductor 85 being connected by conductor 81 to the cathode 82 of the Thyratron tube.

A shot counter 83, similar to the hit counter indicated at 34 in Fig. 1, and including an operating solenoid (not shown) like the solenoid 25, is connected to the power supply conductors 77 and 81 for the Thyratron tube circuit so as to be operated each time the power circuit is interrupted by the interrupter 78, provided the fire control switch is on, as will be explained hereafter.

The hit counter 76 will be energized through the plate circuit of the Thyratron only if the photo-electric telescope device i 1 a is properly aimed at the luminous target image on screen 15a, while the shot counter 83 will continue to register as long as the fire control switch is on regardless of whether hits are scored or not. This is one of the novel features of the scoring means.

Conductor 81 is connected to the power line 85 via contact 86a of a fire-control relay 86 associated with the gun unit in Fig. 3, and this relay in turn is controlled by a fire-control switch 87 situated on the dash panel 88 in the gun turret. Closing of fire-control switch 87 energizes relay 86 closing the circuit through contacts 86a to connect the lead 81 to the power lead 85 so that one side of the shot counter S3 is connected to power, the return circuit for the shot counter being effected through the interrupter 78 to the power lead 80. Therefore as long as the firecontrol switch 87 remains closed, the shot counter 83 will be rapidly energized at a rate determined by the interrupter 78. This rate is preferably fixed at 850 interruptions per minute to correspond approximately to actual firing practice.

So far as the operation of the modulated light means is concerned, the arrangement of Fig. 3 operates substantially in the same manner as the arrangement of Fig. 1.

Operation

The device of Fig. 1 operates in the following manner:

Assuming the device to be at rest, the reset switch 35 is closed thus momentarily grounding conductors 36 and 38 which causes ratchet release coil 37 to be energized so that the hit counter dial 34 may return to zero; at the same time locking relay 39 and relay 41 pull up and hold owing to the locking circuit established through contacts 39a. Relay 41 and its switch 42 start the motor 31 of the interrupter switch while contacts 39b of the locking relay energize the light projecting means 17—50 thus causing an image of the object-defining device i6a to be projected onto the mirror 20 and thence onto the surface 15, the light by which said images are projected being interrupted by the perforate interrupter disc 58 at a rate which will closely approximate a resultant frequency of 1080 cycles per second.

The student trains the gun 10 upon the image 16, which may be caused to move in various manners by manipulation of the mirror 20 in the hands of an instructor, and when satisfied with his aim the student depresses trigger 13 closing switch (4 which completes the circuit through the interrupter switch means 29—30 thus rapidly energizing the noise-maker solenoid NS and setting up a rapid operating circuit to the score counter or hit counter solenoid 25.

If the weapon is accurately aimed, the modulated light from image 16 will rapidly actuate the photocell 11 and the amplifier will be impulsed at its timed or peaked frequency and hence will cause the amplifier relay 23 to pull up closing switch 24 so that the hit counter solenoid 25 will be energized intermittently at a rate depending upon the rate of the interrupter switch 30. This rate is preferably 850 interruptions per minute, corresponding to the firing rate of one type of machine gun.

Thus as long as the student’s aim is held accurately on the image 16, the hit counter will be rapidly stepped forward. Should the weapon continue to be correctly aimed but the trigger switch 14 opened or released, the photo-electric mechanism would respond but the hit counter would not register owing to the ineffectiveness of the interrupter switch 30. Likewise, should the trigger switch continue to be depressed but the aim lost, the interrupter switch would continue to operate but no score would be stepped up on the counter 34 because relay 23 would not be pulled up by operation of the photo-electric means.

If it is desired to reset the score counter, reset switch 35 is closed causing the ratchet release solenoid 37 to withdraw the ratchet dog so that the score dial 34 may return to zero. To stop the entire mechanism, master switch 40 may be opened, thus breaking the ground circuit through contacts 39a and 39b, causing locking relays 39 and 41 to drop out.

Operation of the arrangement of Fig. 3 is as follows:

Assuming the main power switch 87X to be closed, a modulated image 16b will be projected on the screen 15a from mirror 20a by operation of the projector lamp and image defining means (identical to means 17 and 16a of Fig. 1) associated with housing 5la, the image being interrupted at a frequency of 1080 C. P. S. by a disc 50a identical with disc 50 of Fig. 1. The student in the gun turret trains the guns 60 upon the image 16b, and if his aim is correct, light reflected from the image on screen or surface 15a will be focused upon the photocell ila in the photo-electric telescope 61 through lens 63 and aperture 62.

When the photo-electric cell I la is struck by light and activated as aforesaid, the small preamplifier 64 in the telescope is actuated and the electrical impulse therefrom carried through the shielded cable 71 to the input of the main amplifier 22a. The output of the amplifier is passed to the grid circuit 74a of the Thyratron tube 74 thus completing an energizing circuit for hit counter 76 (constructed similarly to the means 25--33 of Fig. 1). The latter circuit is interrupted at 850 breaks per minute by the interrupter 78 (assuming target switch 79a to be closed) and the hit counter will be rapidly advanced if the aim is correct, providing the firecontrol switch 87 on the dash board of the training turret is closed to complete the circuit

2,516,319 for cathode 82 of the Thyratron. So long as the fire-control switch 87 remains closed the shot counter 83 (similar in construction to the parts 25—33—34 of Fig. 1) will be advanced. The score is calculated by comparing the readings of the j hit and shot counters which may be reset by means similar to that shown in Fig. 1 and included in the block diagram of the counters in Fig. 3.

It will appear that by locating the photocell in i'i the gun or in association with the gun or other weapon, and by projecting a luminous target image on a suitable surface, it is possible to increase the flexibility of the target structure to the point where there is no limit to the move- 15 ment or movements which can be imparted to the target member, thus at once obviating all of the principal objections to the previous forms of photo-electric targe''·· structure wherein the photosensitive means ha d in some manner to be 20 associated more or less directly with the target element or elements.

By tuning the responsiveness of the photosensitive means with a keyed or modulated projecting light, interference from extraneous 25 sources is wholly eliminated.

In addition to the foregoing advantages, the present invention makes it possible to simulate more closely than with any previously known means, actual firing conditions inherent in the eo present day use of high speed machine guns, it having been impossible heretofore to approach anything like 850 shots a minute with a projected light to cause operation of a photo-electric target capable of registering any substantial portion of 33 the successful hits. By employing a luminous image for a target as distiguished from some form of physical target structure, and by using a trigger controlled interrupter circuit breaker operating at the approximate firing speed, the 40 efficiency of the marksman’s aim can be determined by consulting the score actually registered or indicated as a function of the number of shots registered or indicated. In this way a very close approach to real conditions is 45 achieved without any sacrifice of accuracy, and the equipment may be used in conjunction with actual combat weapons or simulated weapons adapted to house the photo-electric means.

The various advantages and objects of the in- 50 vention may be realized by modifications of the particular devices and embodiments specifically described herein, and it is the intention that the appended claims shall include all equivalent arrangements and constructions fairly coming 55 within their call.