US2548871A

US2548871A - Bore sight

Info

Publication number: US2548871A
Application number: US729203A
Authority: US
Inventors: Richard S Cranmer
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-02-18
Filing date: 1947-02-18
Publication date: 1951-04-17
Anticipated expiration: 1968-04-17

Description

ipr E?, 395i R. s. CQANMER BORE SIGHT Filed Feb. 18, 194'? Invenclr :Rich 1rd 1. Granma? @www www@ E?, R93 R. s. @HAMMER BORE SGHT Filed Feb. 18, 1947 2 Sheetsc-Sheet 2 FE'. J0 J 20 o 46 l 6 4% lliln lf3 Ill l" --7 VI l 49 35 2 7 :ij-'E' El- 55 g o 8 l /8 l s /9 /0 /2 Inven'lzcl heu-Ef El. Eranmai Patented Apr. 17, 1951 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 3 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental. purposes without payment of any royalty thereon.

This invention relates to bore sights. Such sights are used to determine the angular relation between the line of sight determined by the sights of a gun and the axis of the gun bore. Such sights,uwhen mounted upon the upper gun carriage or cradle are usually adjustable relatively to thegun to vary the angular relation between the line of sight and the bore axis both in a plane through the bore axis and normal to the trunnion axis and in a plane parallel to a nor-- mally horizontal plane through the trunnion axis. Scales are usually provided for determining these angular relations and it is important, for angular settings corresponding to given conditions of. range, windage, etc., that the trajectory of the projectile intersect the line of sight at the selected or predetermined range.

Due to various causes such as jump of the gun when fired, subsidence of the gunemplacement during firing, and others, the aforesaid relations are frequently and easily deranged and plug or frame with all parts removed therefrom.

Referring in detail to the drawings, the numeral I identifies a frame, tampion, or breech plug turned with a slight taper to fit snugly within the breech portion of the bore of the gun G, as shown at Fig. 2. This frame is recessed for a horizontal slide 6.

one of the prerequisites for a high average of accurate gun fire, is frequent and precise bore sighting.

way 1.

y A second upper fiat guideway 'I is provided by a block 8 secured by cap screws 9 and I0 to frame I with the elements of guideway 'I parallel to those of 5. The block is guided into proper posiv I1, Fig. 3, to form a clamping face substantially coplanar with the face of guideway 1. The block It is therefore an object of my invention to l versely of the bore of any degree within the limits of the instrument to accurately compensate for errors in aim that would otherwise be introduced by gun jump, subsidence of the gun emplacement, and other causes.

In the drawing:

Fig. 1 is an elevation of the rear face of the bore sight forming the subject of my invention showing thesighting element, means for adjust ing the same in two mutually normal directions;

together with the scale means for determining the amounts of such adjustments.

Fig. 2 is a side elevation looking from the right, Fig. 1, and showing the device in position within the breech portion of a gun bore.

Fig. 3 is a vertical diametrical cross section on a plane indicated by line 3-3, Fig. 1. L

Fig. 4 is a horizontal diametrical cross section taken upon a plane indicated by line 4-4, Fig. 1.

Fig. 5 is a cross section taken upon the line 55, Fig. l, and showing the construction for detachably mounting one of two opposed guides.

Fig. 6 is a view of the rear face of the breech has a transverse dimension less than that of channel I5, and is so proportioned that, when moved to the right, as seen in Fig. 3, its face I'I binds against the contiguous face of slide 6 and clamps or confines the latter against sliding. As best seen in Figs. 3 and 5, clamping movement of block I6, is effected by a shaft I8 journaled in block 8 and threadedly-engaging the block. The shaft has a reduced outer end forming a shoulder I9 abutting against a corresponding shoulder formed by a counterbore in block 8. A knob 20 is pinned to the reduced end of shaft I8 projecting outwardly from block .8 so that, as the knob is turned .in one direction, clamp I6 is forced to the right as s een in Fig. 3, to bind against the beveled face of slide 6 and thus clamp the slide in adjusted position.

From Figs. l, 3 and 6 it will be noted that frame I, has a second segment-shaped projection 2 I, recessed as at 22, Fig.,1, to accommodate the top end of clamp I 6.

Projections

4 and 2| may have coplanar outer or 'rear faces, as may be seen from Fig. 3.

Lugs

23 and 24 project from the face of projection 4: and are formed with aligned apertures 25 and ,26 (Figure 6') in which is journaled an adjusting screw 21. Axial movement of the screw is prevented by a knob 28 pinned to shaft 2l and abutting the adjacent einem inner face of lug 24. A nut 29 is threaded on screw 21 and has a bore at right angles to the axis of screw 21, in which a pin smoothly ts.

Pin 3|] is fixed in, and projects from, the lower side of slide 6. This slide, as previously implied, has upper and lower dove-tail guide surfaces tting smoothly between, and guided by the beveled faces 5 and |1 of projection 4 and block 8, respectively. The slide has a relatively large, vertically-extending bore 3| spaced from the bottom of the slide, but opening through the top surface thereof, as indicated at 32, Figs. 1 and 4, between an upper projection 33 and a lower projection 34, both formed integrally with the slide. Slide 6 also has a slot shown at Figure 4 below slide and forming a communication between bore 3| and the lower or forward face of the slide. A generally cylindrical vertical slide 35 has a smooth t within bore 3| and is cut away in a plane parallel to its axis, to provide a flat outer face, as indicated at 36, Fig. 4, projecting a little beyond the plane of the.outer face of slide 6. A central sighting hole 31 is drilled diametrically through slide 35 as well as larger locating

holes

38 and 39 on either side of 3l.

Horizontal slide 6 is provided with an upper lug 40 and a lower lug 4l, both extending to the right as seen in Figure l. These lugs are preferably integral with slide 6, and have aligned holes journaling a vertical adjusting screw 42. A nut 43 is threaded on this screw and has a hole, normal to the axis of screw 42 in which a pin 44 has a smooth t, see Fig. 4. This pin projects with a smooth t through an elongated slot in slide 6, and has a press fit in a radial hole in slide 35. A knob 45 is pinned to screw 42 between lugs 4@ and 4| and acts to prevent axial movement of the screw. By turning this knob the slide 35 may be translated vertically within and along bore 3|.

- As shown upon Figs. 1 and 4, slide 6 is formed with'a channel 46, normally horizontal and opening into bore 3|. A clamping element 41 has a loose t within the channel and is formed with a portion of a cylindrical surface adapted to be forced into clamping engagement with the surface of slide S5. Element 41 has a threaded hole engaged by an enlarged threaded portion of a shaft 48. provided by a hole in slide 5, and is prevented from axial movement in one direction by the aforesaid enlarged threaded portion, and in the other direction by a collar 4S pinned to the shaft. The upper end of shaft 48 carries a knob 55 which, on being turned, in one direction, eiects movement of element 41 downwardly into clamping engagement with slide 35 to lock the same in adjusted position. A scale plate 5| is attached to the top surface of slide 6 by screws 52. This plate extends over and across channel 45 and is slotted, as indicated in dotted lines, Fig. l, to clear shaft 4B. As shown in Fig. 4, slide 35 is grooved to accommodate the adjacent edge of plate 5|. The latter has a scale 53 graduated in opposite directions from a central zero indication. Slide 35 carries an index 54 in closely adjacent position for cooperation with scale 53.

As shown in Figure l, a horizontal scale plate 55 is secured by screws 56 to the plane outer surface of block 8 and carries a graduated edge closely adjacent and in cooperative relation with an index 51'l on slide- 6. Scales 5| and 55v are graduated in mils. l; vv- This shaft is journaled in a bearing From Fig. 6 it will be noted that the plug l is formed with a central hole 58 as well as four smaller lightening and observation holes 59. In addition, normally horizontal slots 6U and 6| are provided between each pair of vertically-spaced holes 59. These slots are in substantial alignment with peep hole 31 and assist the operator in initially adjusting the bore sight into a desired relation with respect to the muzzle cross-wires of well-known construction. All parts are preferably. of corrosion-resisting metal such as bronze.

In using the device, a distant target is selected or set up at the optimum range for the gun being bore sighted. A muzzle sight consisting of a frame tting the muzzle portion of the gun bore, is inserted into the muzzle. This sight provides mutually normal cross-wires extending diametrically across the bore. The sight is so positioned that one wire is horizontal. The intersection of such wires locates a point upon the axis of the gun bore.

The breech sight is then inserted into the breech of the gun and is rotatably adjusted until the aforesaid horizontal wire of the muzzle sight lies along the center of slot-s 6|! and 5| after which the plug is pressed firmly into position. In case the jump value of the gun is known in terms of horizontal and vertical angular values, the

knobs

23 and 55 are loosened to free the respective slides, and thumbpiece 28 is turned to thereby horizontally move slide 6 and all parts carried thereby until index 51 indicates the known horizontal jump on scale 55. Knob 25 is then tightened to lock slide 5 in adjusted position. Thumbpiece 45 is nextturned to move slide 35 vertically until index 54 indicates the known vertical jump on scale 5|. In each case the adjustment should be in a direction opposite to the direction of jump. For example, if the gun is known to have an elevational increase of 3 mils on firing, then the slide 35 should be moved downwardly until a line through peep sight 31 and the intersection of the muzzle wires, makes an angle of 3 mils with the bore axis.

Having set the sight as aforesaid, the gun is moved until a line of sight through aperture 31 and the intersection of the cross-wires at the muzzle, intersects the target. The sights of the gun are now adjusted relatively to the gun until they too, are directed upon the target. This completes the adjustment.

In cases where the jump Values of the gun are not known, a target is set up at an optimum ring range. The gun is aimed on the target using ring table data. If the gun is cold, at least two warm-up shots should be fired. Thereafter, at least three more shots are fired and the center of impact of the shots upon the target is determined and measured. The horizontal and vertical jump are then calculated, using the known range of the target.l Thereafter, the sight is adjusted for the horizontal and vertical jump values, in the manner previously described, and after training the bore sight upon the target, the gun sights are also adjusted relatively to the gun so that their lines of sight intersect the target. If check firing shows that a closer setting is required, the foregoing operation can be repeated until the desired accuracy is obtained.

It will thus be noted that I have provided a bore sight that is built for rugged service while being relatively simple in construction and highly accurate in use. Because of the ease with which it may be applied to a gun and used to correct for jump,the bore'sight forming the subsans aia ject of my invention encourages the frequent checking necessary for sustained accuracy of fire and thus is a decided aid in increasing the average accuracy of fire of any gun with which it is used.

While I have shown a preferred form of the invention, various substitutions and alterations will occur to those skilled in the art after a study of the foregoing disclosure. Hence the disclosure should be taken in an illustrative rather than a limiting sense; and it is my wish to reserve all such changes, modifications and variations as fall .within the scope of the sub-joined claims.

Having now fully disclosed the invention what I claim and desire to secure by Letters Patent is:

1. A bore sight comprising a frame adapted to engage the walls of and be supported by the breech portion of the bore of a gun, said frame having a first pair of opposed guideways determining a first path transversely across said bore, a rst slide mounted between said guideways for translation along said path, a screw journaled on said frame for rotation upon an axis parallel to said first path, a nut threaded upon said screw, a pin on said slide fitting a hole in said nut, said rst slide having a second guideway determining a second path normal to said bore and rst path, a second slide mounted on said first slide for translation along said second path, a second screw journaled on said first slide for rotation about an axis parallel to said second path, a second nut on said second screw, and a pin xed in said second slide and tting a hole in said second nut.

2. A bore sight comprising a tapered plug adapted to t snugly within the breech portion of thc bore of a gun, said plug having opposed segmental projections from one face thereof, undercut to form parallel guideways defining a first path normal to said bore, a slide having opposed projections tting said guideways, respectively, for translation along said path, a screw journaled on one said projection for rotation on an axis parallel to said path, a nut threaded on said screw,

a pin xed in said slide and iitting a hole in said nut, there being a bore in said slide defining a second path normal to said gun bore and rst path.

3. In a bore sight, a frame having a frustoconical peripheral contour and rst and second opposed segmental projections upstanding from one face thereof, said rst projection being undercut to provide a first guideway, a block secured to said frame adjacent said second projection and being undercut to provide a seco-nd guideway confronting and parallel to said rst guideway, a slide engaging said guideways and guided thereby for translation in a first path transversely of the bore of said gun, a screw journaled in lugs carried by said first projection for rotation upon an axis parallel to said path, a nut on said screw, a pin secured to said slide and smoothly fitting a bore in said nut, a thumbpiece ixed to said screw, and a second slide translatable in and along a bore in said rst slide, said second slide having a sighting aperture lying on the axis of the bore of said gun when said slides are in central position.

RICHARD S. CRANMER.

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

UNITED STATES PATENTS Number Name Date 37,512 Learock Jan. 27, 1863 763,348 Andrews June 28, 1904 793,131 Henkes June 27, 1905 803,435 Saegmuller Oct. 31, 1905 1,636,509 Hatcher July 19, 1927 2,294,913 Kaufman et al Sept. 8, 1942 FOREIGN PATENTS Number Country Date 307,257 Germany Aug. 6, 1918