Luminous gun sight

Dec. 14, 1943. g. h. davis 2,336,718

LUMINOUS GUN SIGHT

Filed Oct. 4, 1940

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attorneys

Patented Dec. 14, 1943

2,336,718

UNITED STATES PATENT OFFICE

2,336,718

LUMINOUS GUN SIGHT

George Howlett Davis, Detroit, Mich.

Application October 4, 1940, Serial No. 359,649

Claims. (Cl. 88—24)

This invention relates to sighting devices for firearms and in particular to luminous gun sights for use at night or in dark places, or where the light is dim.

One object of this invention is to provide a 5 luminous gun sight for firearms and having means for optically projecting upon the target a luminous pattern such as cross lines, a circle, or other indicia at the point of impact of the bullet at the end of its trajectory. 10

Another object of the invention is to provide a luminous gun sight as set forth in the preceding object wherein the device is self-contained and compact, and is attachable or detachable at will from the gun. ^J:’

Another object is to provide a luminous gun sight as set forth in the preceding object wherein a spot on the target is brilliantly illuminated by reason of the use of a source of electricity, such as a battery, which supplies voltage con- 20 siderably in excess of the rated voltage of the light bulb filament.

Another object is to provide a luminous gun sight attachable to the gun at a point immediately beneath the barrel, thereby enabling the gun and gunsight to be inserted in a compact holster, as well as locating the gun sight in a position where it is not in the way of the user if he desires to use the regular sights on the top of the gun.

Another object is to provide a luminous gun sight, all parts of which are self-contained, in a compact casing mounted beneath the barrel of the gun in the vicinitv of the muzzle, thereby making the gun “muzzle-heavy,” a condition ' which pistol experts generally favor for accurate shooting, in contrast to a “muzzle-light” condition.

Another object is to provide a luminous gun _Ar)sight having a gravity-responsive switch, such as a mercury switch, for automatically energizing the gun sight as the gun is raised into aiming and firing position, but de-energizing the gun sight when the gun is lowered or is main- /, tained in a lowered position, as in a holster, or when held at the user’s side.

Another object is to provide a luminous gun sight as set forth in the object immediately preceding, wherein a safety switch is provided in so series with the gravity-responsive switch, the safety switch being operated by· the holster to de-energize the electrical system, thereby preventing the gun sight from becoming illuminated when the gun is laid on a shelf or table in a 55 horizontal position in its holster, thereby saving current.

Another object is to provide a luminous gun sight as set forth in the two objects immediately preceding, wherein an additional hand-operated switch is provided to by-pass the gravity-responsive switch so that in an emergency the user can switch on the luminous gun sight when he must shoot downward, as in shooting down a stairway, downhill, or from a roof or window.

In the drawing:

Figure 1 is a central vertical section through a preferred form of the luminous gun sight of this invention.

Fig. 2 is a top plan view of the luminous gun sight shown in Figure 1.

Figure 3 is a front elevation of the luminous gun sight shown in Figure 1.

Figure 4 is a rear elevation, partly broken away, of the luminous gun sight shown in Figure 1.

Figure 5 is a horizontal longitudinal section taken along the line 5—5 in Figure 1.

Figure 6 is a fragmentary vertical cross-section taken along the line 6—S in Figure 1.

Figure 7 is a similar view of a modification of a portion of Figure 6, showing a modified reticule or sighting indicia.

Figure 8 is a diagrammatic view of the electrical circuit of the luminous gun sight of this invention.

Figure 9 is a side elevation partly in section showing the luminous gun sight attached to a pistol of the revolver type.

Figure 10 is a top plan view of the arrangement shown in Figure 9.

General arrangement

In general, the luminous gun sight in the preferred form of this invention consists of a compact casing attachable to the barrel or forward portion of a gun and containing an optical projection system with batteries for supplying current to energize the electric light bulb used as the source of light for the projecting system. The luminous gun sight is attached to a pistol of the revolver type by sliding a tubular portion over the barrel of the pistol and rotating it until the front sight of the pistol locks against an abutment.

The optical projecting system consists of a condensing lens having a reticule, preferably etched thereon, or optionally, upon a separate plate or using separate cross-wires. Optionally, also, a light filament itself may be used as the reticule, or sighting index. The optical system is also provided with one or more objective lenses for projecting the image of the reticule upon the target. The axis of the optical system is arranged at an angle to the axis of the gun bore so that any errors of parallax, “drift” or other deviation may be compensated for.

The optical system also contains an electric light bulb which serves to illuminate the reticule. The filament of the electric light bulb is energized by one or more battery cells, these battery cells supplying a voltage which is considerably in excess of the rated voltage of the filament. By this means the electric light bulb is caused to deliver a much more brilliant illumination than is possible in using a bulb of the same rated voltage as the voltage of the batteries. Thus the life of the light bulb filament is necessarily shortened, but this shortening is not serious when it is remembered that the gun sight is used only intermittently for short periods of time. Under such circumstances, it has been proved experimentally that the light bulb filament has a life far longer than its life for steady burning at the excess voltage at which it is operated.

The energization of the light bulb is controlled by a gravity-responsive switch, such as a mercury switch, so arranged that the circuit is broken when the gun is pointed downward, but closed when the gun is raised. With this arrangement, the user, such as a policeman, watchman or soldier, does not need to disclose his position until the instant he is ready to fire, and the gun sight becomes illuminated automatically when he raises the gun to fire.

In order to avoid the waste of current when the gun is placed in a horizontal position in its holster, an additional safety switch is provided in series with the gravity-responsive switch so that engagement with the holster opens this switch and cle-energizes the electrical system. Optionally, an additional hand-operated switch is provided for by-passing the gravity-responsive switch or mercury switch so that the user can employ the luminous gun sight in shooting downward, as down hill, down a stairway, or from a roof or upper window.

Construction

Referring to the drawing in detail, Figures 1 to 4 show a preferred embodiment of the luminous gun sight of this invention as housed in a casing SO, preferably of metal or molded plastic material. The casing 10 is provided with an upper bore I!, a lower bore 12, and intermediate bores 13 and !S running longitudinally therethrough. The casing 19 is provided with front and rear closure plates IS and 16 held together by a longitudinal screw 17 threaded into the threaded bore 18 in the rear plate. In order to prevent short-circuiting the electrical system, it is preferable that the rear plate 16 shall be of insulating material, or that the screw 17 shall be insulated from one of the plates 15 or 16.

The casing 18 is provided with an upper projection 19 to which is secured a tubular member 20 as by the bolts or rivets 21 (Figure 1). The tubular member 20 is provided with a longitudinal slot 22 offset from the vertical and communicating with a set-back portion 23 having an abutment 24 forming a part thereof. In attaching the device to a pistol of the revolver type, the tubular portion 29 is slid over the barrel of the revolver with the front sight of the gun passing through the slot 20 and coming to rest in the offset portion 23 against the abutment 24 as the 75

3,336,718 device is rotated into its working position. The tubular member 20 is also provided with an access hole 25 to prevent the insertion of a screw driver for tightening or loosening the bolts 21.

The upper bore 1 1 serves to receive the optical projection system. This consists of a convex condensing lens 26 having a reticule 27 associated therewith. The reticule 27 may consist of cross lines 28 (Figure 6) either alone or associ10 ated with a circle 29 (Figure 7). Other indicia may be employed in the reticule 27, as desired by the user or as'adapted to the particular conditions under which the gun sight is to be used. The optical system also contains a convex ob15 jective lens 3Q having its principal focus coinciding with the cross-lines 28 of the reticule 27. The cross-lines 28 may be conveniently etched upon the rear surface of the condensing lens 26 •or placed upon a separate plate, as is most con20 venient. The condensing lens 2S and objective lens 39 are separated from each other and maintained in. accurate positions relatively to each other and to the source of illumination by spacing tubes 31, 32 and 33, the latter being in abut25 ting relationship with the front closure plate 15. The source of illumination consists of an electric light bulb 34 having a filament 35 and a tubular base 36. The latter is permanently secured within a holder 37 of disk-like form by means 30 of a metallic insert 38. The metallic insert 38 is preferably of low melting alloy, such as an alloy of bismuth and antimony or solder.

The purpose of the metallic insert 38 is to enable the filament 35 to be accurately located ex35 actly in the axis of the cylindrical outer surface of the holder 37. Ordinarily, the filaments 35 of light bulbs are often eccentric to their bases 36 so that accurate adjustment relatively to the axis of an optical projecting system varies with the particular bulb. In the present invention, the bulb 34 is seated in the holder 37 by means of a jig in the laboratory of the manufacturer of the gun sight and adjusted until the filament 35 is exactly co-axial relative to the outer surface 45 39 of the holder 37, after which the fuseable metal 36 is allowed to solidify. This arrangement increases the optical accuracy of the projecting system.

The electrical system by which the filament 35 ^δθ is energized consists of a pair of battery cells inserted in the lower bore 12. The central pole 41 of the rearward cell 40 is in engagement with the metallic casing 42 of the forward cell, whereas the central pole 41 of the forward cell js in engagement with the forward plate 15.

Contact is made with the casing 42 of the rearward cell 40 by means of a spring member 43 which is provided with an aperture 44 surrounding the screw 17 and preventing contact there60 with. The upper end of the spring member 43 is secured to the holder 37, which is of conducting material and which is held in position by the set screw 45 passing through a hole in the casing i 0 and having its threads engaging a thread65 ed hole 46 in the holder 37. The fuseable metal establishes a circuit between the holder 37 and the base 36 of the light bulb 34.

Secured to the central pole 47 of the light bulb 34 is a conductor 48 which passes downward (Fig70 ure 4) through an aperture 49 and through the intermediate bore 13 to the rear pole 51 of a gravity-responsive mercury switch 52. The rear pole 51 is insulated as at 53 from the switch casing 54, which contains a quantity of mercury 55. The switch casing 54 is slidably mounted

3,336,718 in a bore enlargement 56 and is urged toward the forward end thereof into engagement with the front closure plate i 5 by a coil spring 57. The switch casing 54 is provided with a forward projection 58 which projects through an aperture 59 in the front closure plate 15. Consequently, the closure plate 15 completes the circuit, as shown in Figure 8, between the battery cells 42 and the light bulb filament 35, except when the device is in a vertical position or when the projection 58 and the mercury switch 52 are pushed backward as by engagement with the holster. When either of these situations occurs, the circuit is broken and the filament 35 remains deenergized.

Optionally, an additional switch is provided for by-passing the mercury switch 52 and establishing a contact between the front closure plate 15 and the conductor 48. The purpose of this manually operated switch is to enable the filament 35 to be illuminated when the police officer or other user finds it necessary to shoot downward from an elevation. Without this manual switch, the filament 35 cannot be energized when the gun is pointed downward and is only energized when the gun is raised toward a horizontal or upward vertical position.

This manual switch 63 is pivotally mounted on the rear end of the screw i 7, and is engageable with a spring contact 64, the inner end of which engages the central pole 47 of the light bulb 34. This enables the bulb 34 to be energized, regardless of the position of the mercury switch 52.

Operation

In the operation of the luminous gun sight of this invention, it is assumed that the batteries 42 have been loaded into the lower bore 12 and the end closure plates 15 and >6 secured in the positions shown in Figure 1. The circuit is now complete except for its possible Interruption by the mercury switch 52.

The device is attached to the gun by sliding it over the barrel with the front sight passing through the slot 22 into the cutaway position 23 as described above. Obviously, suitable means of attaching the device to an automatic pistol or to a rifle, shotgun or sub-machine gun will be evident by slight modifications of this arrangement.

The holster for the gun is preferably made in substantially rectangular shape so that it will accommodate the device in its position upon the gun. When the gun and luminous gun sight are thus assembled, as in Figure 9, and secured in the holster, the contact with the bottom wall of the holster pushes the projection 58 and switch 52 inward out of contact with the end closure plate 15. This breaks the electrical circuit and prevents the lighting of the filament 35 of the bulb 34 even though the gun and its holster are laid in a horizontal position. As soon as the operator removes the gun from the holster, however, the coil spring 57 pushes the mercury switch 52 to the left, bringing its front edge into engagement with the end closure plate 15 and conditioning the circuit for closure as soon as the gun is raised.

As long as the user keeps the gun lowered, the mercury in the mercury switch 52 is out of contact with the switch pole 5 i and no current can flow to the light bulb filament 35. Thus, a police officer, watchman, detective or soldier does not need to disclose his position to a possible criminal or enemy while he is waiting for a favorable opportunity to act. If, however, he finds (55 io it necessary to use the gun, he merely raises it to a horizontal position in the natural act of sighting the gun. As he does this, the mercury 55 flows into contact with the switch pole 5i and closes the circuit shown in Figure 8, causing the light bulb filament to become illuminated. This causes an image of the reticule 27 with its cross lines 28 to be projected upon the distant target, with the cross lines intersecting at the point where the bullet will strike. The user may thus raise his gun and fire, lowering it quickly before his opponent has an opportunity to sight accurately and fire. Moreover, the user can hold the pistol around one side of an obstacle such as a barrel or tree while he peers around the opposite side, thereby deceiving the opponent into thinking that he is behind the gun instead of to one side of it.

Moreover, the use of batteries 42 which supply voltage considerably in excess of the voltage rating of the light bulb filament 35 causes a brilliant illumination to occur and the cross lines 28 to be sharply seen on the target against a brilliant circular patch of light. This feature gives the device great superiority over previously used devices where the dimness of image and the lack of contrast greatly interfered with the accuracy of shooting.

Figure 9 shows the relationship of the axis 60 of the gun bore as compared with the axis 6! of the optical system of the gun sight. The axis 61 is seen to be angled upward slightly so as to compensate for parallax, “drift” and other errors of trajectory. The angle of inclination between the axes 60 and 6 ί in Figure 9 is somewhat exaggerated to indicate the principle more clearly. Obviously, the trajectory of the bullet will also have much influence upon the adjustment of the luminous gun sight, especially if it is adjusted for shooting at distances greater than the ordinary distances, or is used with cartridges having low ballistic characteristics.

While I have shown and described my invention in detail, it is to be understood that the same is to be limited only by the appended claims for many changes may be made without departing from the spirit and scope of my invention.