US2422181A

US2422181A - Periscopic bore sight

Info

Publication number: US2422181A
Application number: US514356A
Authority: US
Inventors: Leo H Brown
Original assignee: Individual
Current assignee: Individual
Priority date: 1943-12-15
Filing date: 1943-12-15
Publication date: 1947-06-17
Anticipated expiration: 1964-06-17

Description

June 17, 1947.

L. H. BROWN 'PERISCOPIC BORE SIGHT Filed Dec. 15, 1945- I LEu-H EruwT'L Patented June 17, 1947 UNITED STATES PATENT OFFICE PERISCOPIC BORE SIGHT Leo H. Brown, Glenville, Conn.

Application December 15, 1943, Serial No. 514,356

13 Claims. (01. 8874) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty therein.

The invention pertains to a novel apparatus for bore sighting a gun. The operation consist generally in truing the external sighting device on the gun with respect to the axis of the gun barrel by directing both towards a distant object such as a star. In this operation it is essential that the object be sighted accurately in the center of the gun muzzle.

This invention has for its object a simple device for satisfying the stated requirement. Another object is to provide a device that does not require the operator to apply the usual cross-wires over the muzzle of the gun from without, and thereby expose himself to enemy fire.

The device of the invention comprises, in general, a disk or frame to be inserted in the chamber of the gun and having a central aperture through which the distant object is sighted directly. For the purpose of determining that the object is centered in the muzzle, the frame carries one or more periscopic systems, preferably radially disposed, to produce a View or views of the object at the point of observation. Each of these views includes a segment of the periphery of the muzzle of the bore; and when the object or a portion thereof is centered on the said segment, it follows that the object is centered in the muzzle. Greater accuracy is obtained by providing a plurality of such periscopic systems, advantageously at least three, and whose objective reflectors are arranged on a circle to approximate that represented by the periphery of the bore of the gun barrel.

An illustrative embodiment of the invention is disclosed in the following description and in the accompanying drawings in which:

Figure 1 is a longitudinal section of a gun barrel with the device of the invention mounted therein;

Figure 2 is an elevation of the device;

Figure 3 is a section on the line 33 of Figure 2, and

Figure 4 is an illustration of the composite image seen by the observer.

Figure 5 is a detail showing a modification.

In Figure 1 is shown a gun barrel 1 having at its forward end the usual muzzle 2 and at its rear end the usual chamber 3. The bore sight constituting this invention includes a frame or disk 4 adapted to be fitted in the chamber 3, across the axis thereof, and having a central aperture 5 centered on the axis. The distant reference object used for sighting is visible directly through the aperture 5 by the observer whose eye 6 is positioned at a suitable distance behind the aperture. By this means alone, the distant object can be centered only approximately on the axis of the gun barrel.

The accuracy of the centering is improved and substantially perfected by an optical system for forming at least one and. preferably a plurality of views of segments of the muzzle end of the bore and of the object or a common part thereof around the aperture 5 in a position to be viewed by the observer at location 6. This optical system, in the embodiment of the invention illustrated, consists of a plurality of periscopes mounted radially in the disk 4 between its periphery and the aperture 5. For each periscope, the disk is formed with a radial slot 1 having

mirrors

8 and 9 disposed respectively at the outer and inner ends thereof. It will be understood, however, that prisms may be employed in lieu of mirrors.

Each outer mirror 8 is so positioned as to pick up rays of light traveling along the inner wall ID of the gun barrel I. Some of these rays will obviously be received from the distant object on which the gun is sighted. The inner mirrors 9 receive light from the mirrors 8 and are positioned to reflect this light to the observation point 6 as indicated by the rays II in Figure 1.

Through the aperture 5 the observer sees the rifled inner wall of the gun barrel as illustrated in Figure 4. He also sees the distant object I2 on which the gun is sighted. Each of the periscopes gives a view of a portion IU of the wall l0 and a view l2 of the object l2. When each view l2 of the object is in the same spatial relation to the corresponding view of wall portion Hi, the line of sight on the object is coincident with the axis of the bore of the gun barrel. This condition signifies accurate sighting of the gun on the distant object. If it is assumed that the distance of the object is infinite, each view 12' of the object I 2 will lie adjacent the are defined by the periphery of the muzzle 2 in each view of a portion ll) of the gun bore.

In Figure 5 is shown a modification wherein prisms I3 are employed in place of the

mirrors

8 and 9. This type offers several advantages of assembly and maintenance. For instance, it is much easier to grind the end faces of a prism to the proper angles than it is to mount small mirrors at the proper angles, and in the case of mirrors, contact is difficult for cleaning, whereas in the case of a prism only two surfaces need be cleaned and these are easily contacted.

While preferably three or four pairs of reflectors are employed, equally spaced about the bore of the gun, fairly accurate results may be obtained by the use of a single pair of reflectors. This is because, when sighting upon an object such as a star that may, for all practical purposes, be assumed to be at an infinite distance, the object will appear to coincide with the muzzle edge of the bore and to be centered with respect to the image of the arc of said edge, when the gun is properly bore sighted. Therefore, if the image is centered within aperture 5 as closely as possible, and is also positioned with respect to one image of the muzzle edge as shown in Figure 4, the gun is bore sighted with a fair degree of accuracy.

By means of the apparatus herein described, the bore sighting operation may be performed from within the protective enclosure. The operator is not required to expose himself to enemy fire by going to the muzzle of the gun for mounting the cross wires in the conventional manner. This characteristic of the invention is especially valuable in tank warfare.

While a specific embodiment of the invention has been shown and been described, it will be understood that various alterations may be made without departure from the spirit of the invention as indicated by the appended claims.

What I claim is:

1. In combination with a gun barrel, a frame mounted at the breech end of said barrel and having a sighting aperture centered on the axis of the bore of said barrel, a plurality of first reflecting means carried by said frame and positioned to reflect respective images of circumferentially spaced portions of the muzzle end of said bore and respective images of a distant object, and second reflecting means disposed radially inwardly of said first reflecting means and positioned to reflect said images rearwardly adjacent and along said axis to an observation point on said axis at the breech end of said bore whereby the images of a distant object may be observed in relation to the images of said portions, simultaneously with direct observation of said object through said aperture.

2. In a bore sighting device, first means adapted to be positioned across and in predetermined relation with the breech portion of a gun bore, said means defining a plurality of angularlyrelated planes each containing the axis of said bore, and light-reflecting means carried by said first means to project respective images of each portion of the bore at the muzzle intersected by said planes together with images of a remote object, radially inwardly, then rearwardly closely adjacent and along said axis, whereby an observer at the breech may simultaneously observe said images.

3. A bore sighting device comprising a disc having a central aperture and slots extending radially of said aperture to define radial planes containing the axis of a gun bore when said disc is positioned centrally of and across a breech portion of the bore of a gun, and a pair of mirrors mounted in and adjacent opposite ends of each slot, respectively, each pair of mirrors being ositioned to project an image of one of the muzzle portions of said bore intersected by the plane of its slot, together with an image of a remote object, radially inwardly, then rearwardly adjacent and along said axis, whereby an observer at said breech portion may simultaneously observe a distant object through said aperture and a plurality of images thereof with relation to the respective images of said muzzle portions.

4. A bore sighting device comprising a disc having a central viewing aperture, said disc being adapted to be positioned across a breech portion of the bore of a gun with said aperture on the axis of said bore, there being a plurality of slots in said disc extending radially from said aperture to define respective radial planes with said bore axis, and reflector means mounted within each said slot and carried by said disc to deflect light rays passing along the respective intersections of said planes with said bore surface, radially inwardly then rearwardly from said disc along and closely adjacent the axis of said bore to a common point of view, the light rays deflected by each said reflector means including an image of the muzzle portion of said bore intersected by its plane; together with an image of a remote target when said bore axis is aligned with said target.

5. In a bore sighting device, a disc adapted to be secured in predetermined position across the breech portion of the bore of a gun, there being slots in said disc extending radially of the bore axis and defining with said axis, radial planes, and a plurality of light-reflecting means carried by said disc each being positioned within a respective slot to project a discrete image of the muzzle portion of said bore intersected by the respective one of said planes together with an image of a remote object when aligned with said bore axis, radially inwardly of said disc, then rearwardly along the axis of said bore to a point on said axis adjacent the breech of said gun.

6. In combination with a gun barrel, first means defining a plurality of radial planes containing the axis of the bore of said barrel, and light reflecting means carried by said first means and adapted to project images of the muzzle portions of said bore intersected by said planes, and images of a remote target when in alignment with said axis, radially inwardly, then rearwardly adjacent and along said axis to a viewing position rearwardly of said bore.

'7. In a bore sighting device, means adapted to be secured across a breech portion of the bore of a gun and carrying means to define a plurality of angularly-related planes each containing the longitudinal axis of said bore, said last-named means including a first reflector adjacent and at 45 to each respective line of interesection of a said plane with the surface of said bore, and a second reflector parallel to and radially inward of each corresponding first reflector, whereby discrete images of the muzzle portions of said bore intersected by said plane respectively together with images of a remote object in alignment with said axis, are projected rearwardly along said bore axis to an observation point.

8. In a bore sighting instrument, a disc having a sighting aperture centrally thereof and angularly-spaced slots extending radially of said aperture, said disc being adapted to fit within and across the breech portion of a gun bore so that the aperture lies on the axis of said bore and the radial slots in said disc define with said axis, angularly related planes intersecting said bore along elements thereof, a mirror in the radially outward end of each slot and positioned adjacent and at 45 to its respective element, a

Search second mirror in the radially inward end of each slot parallel to its respective first mirror, whereby each pair of mirrors projects an image of a distant object in alignment with said axis and an image of a muzzle portion of said bore intersected by the corresponding plane, for observation simultaneously with direct observation of said object through said aperture.

9. In a bore sighting device, a disc having a central sighting aperture and angularly-related slots extending radially of said aperture, said disc being adapted to fit within and across the breech portion of the bore of a gun so that the aperture therein lies on the axis of said bore, and an optical reflectin element positioned within each said slot each element acting to project an image of a portion of the bore adjacent the muzzle, together with an image of a distant object when said axis is aligned therewith, radially inwardly along its slot, then rearwardly along and adjacent said axis, whereby a plurality of images of said distant object and images of said portions, may be viewed simultaneously with observation of the object itself through said aperture.

10. In a bore sighting device, a frame having a central sighting aperture and adapted to be secured across the breech portion of the bore of a gun, means carried by said frame for engaging the gun bore at circumferentially-spaced points to thereby positively locate said aperture on the longitudinal axis of said bore, and optical means carried by said frame to project an image of a sector of the muzzle portion of said bore and an image of a distant target when aligned with said axis, first radially inwardly, then rearwardly along and closely adjacent said line of sight whereby said target and an image thereof in relation to said muzzle portion, may be simultaneously observed the direct view of said target and its image being discrete.

11. In combination with a gun barrel, four substantially equally spaced light reflecting means positioned at the breech of the barrel, said means being disposed adjacent the surface of the bore of the barrel and inclined so as to reflect radially inwardly four discrete images of respective circumferentially-spaced segments of the muzzle of the gun and four images of a distant object, and other light reflecting means light reflecting means and positioned so that the four separate images of said respective segments and the four images of the object reflected by said first named reflecting means, are reflected thereby into theeye of an observer positioned at the rear of the gun barrel.

12. In combination with a gun barrel, a plurality of plane light reflecting surfaces, spaced circumferentially of the gun bore adjacent the wall thereof and inclined to the axis of said bore so that each said surface projects radially inwardly of said bore and image of a segment of the muzzle of said gun including the image of a remote object when aligned with said axis, said segments being circumferentially spaced, and a number of light reflecting means equal to said light reflecting surfaces, each said means being positioned radially inwardly of a corresponding surface and inclined to the bore of said gun, to project rearwardly along the axis of said bore to the eye of an observer discrete images of a respective segment and said object.

13. In a bore-sightin device, a disc having a central sighting aperture therein and adapted to be secured within the breech end of a gun bore with said aperture positioned upon the longitudinal axis of said bore, means carried by said disc and defining, with said axis, a plane extending radially of said axis and intersecting the surface of said bore along an element thereof, and optical means on said disc to receive and project an image of a limited muzzle portion of said bore encompassing said element, together with an image of a distant object when aligned with said axis, first radially inwardly of said disc, then rearwardly along and closely adjacent the direct line of sight to said object through said aperture.

LEO H. BROWN.

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

UNITED STATES PATENTS Number Name Date 1,454,950 Boyle May 15, 1923 669,705 Reeh Mar. 12, 1901 2,045,093 Newcomer June 23, 1936 2,058,484 Mihalyi Oct. 27, 1936