US2378770A - Sextant - Google Patents

Description

lime 1945- Jqv. HORR 2,378,770

- SEXTANT Filed June 22, 1943 2 Sheets-Sheet 1 INVENTOR John 01"? J. V. HORR June 19, 1945;

SEXTANT Filed June 22, 1943 2 Sheets-Sheet 2 INVENTOR .fohn Vfiorr ATTORNEY Patented June 19, 1945 UNITED STATES. PATENT OFFICE h SEXTANT John. V. Horr, North Tarrytown, N. Y., assi'gnor to Einson-Freeman 00., Inc., Long Island City,

N. Y.,a corporation of Delaware Application June 22, 1943, Serial No. 491,779

2 Claims. 7 (CI. 33-70) 7 My present inventionrelatesgenerally; to measuring instruments and has particular reference to sextants. v 7; l i

A general object of the invention is to provide certain structural improvements and innovations which simplify the process of manufacture and which make lit possible to produce sextants more expeditiously and economically.

The structuralimprovements whichI have de vised lend themselves readilytovthe processes of quantity manufacture, and are primarily intendedto make it possible to manufacture sextents in large numbers and at lowvcost.

It is a more particular object of the invention to provide a construction which permits the extensive use of ordinarysheet material whereby relatively simple procedural steps, such as stamping, cutting, printing, and the like may be resorted to. While the invention is by nomeans restricted to the userof any particular material, the present improvements are of such a character that ordinary fiatsheets of cardboard stock, or equivalent relatively inexpensive sheet material, may be satisfactorily,employed. Notwithstanding the fact that a sextant is a relatively delicate instrument requiring accuracy in the arrangement of parts and in the movements provided for, an instrument constructed in accordance with the present invention is adequately precise and, reliable for most normal purposes and is unusually staunch and rigid. l l

Among the numerous respects in which'a sextant structure has been improved by means of .the present invention are the mode of pivoting the swinging arm or alidadeto the basic frame, the manner in which the index portion of the alidade is assembledthe simplified manner in ,which a handle is formed and braced, the mode of pivoting a screen or screens to an edge portion of the frame, the, manner in which a level-glass unitmay be optionally employed, and the general way in which the structure as a whole is simplified and is nevertheless adequately reinforced.

I achieve the foregoing objects and advantages, and such other objects and advantages as may hereinafter appear or be pointed out, in the manner illustratively exemplified in the accompanying drawings in which:

Figure 1 is a front view of a sextant constructed in accordance with the present invention;

Figure 2 is a rear view of Figure 1;

Figure 3 is an enlarged cross-sectional view taken substantially along the line 3-3 of Figure a ,,Figure 4 is an enlarged cross-sectional view taken substantialy along the line 4-4 of Figure 1; Figure 5 is an enlarged cross-sectional view taken substantiallyfalong the line 5-5 of Figure 1; Figure 6 isan enlarged cross-sectional view taken substantially along the line 6-6 of Figure 1; Figure 7 is an enlarged fragmentary view of the edge portion of the frame with which one or more screens maybe associated;

Figure 8 is an end view taken from then'ght of, Figure 7; and a Figure 9 is a cross-sectional View taken substantially along the line 9-9 of Figure 7.,

, The main or body element of the sextant illustrated on the accompanying drawingsis a frame which consists of a flat sheet of substantially triangular contour having an arcuate index edge 2| with degree markingsor graduations 212 thereon. The sheet 20 may be composed, if desired,

of inexpensive cardboard stock. In its midportion, it is provided with two substantially triangular openings 23 and 24. Aportion of' the cut-out material isin each caseretained in only partially-severed andhence hinged relationship to the frame 20, thereby defining two rearwardlydeflected wings Ziand 26 respectively. The openings 23 and 24 are preferably so formed and spaced that the wings 25 and 26 will lie inparallel planes perpendicular tothe frame 20; This rear surface of the frame 20, while the bracing from the plane of the frame 20.

portion 21 extends obliquely rearwardly away The brace 21 may be conveniently provided with spaced slots which engage frictionally with shoulders 30 formed on the wings 25 and 26.

Pivotally associated with the frame 20 in concentric relationship to the graduated edge 2| is a swinging arm or alidade having a pivot portion at one end and an index portion at the opposite end. i l

The index portion is composed of three interconnected superposed plies of fiat sheet material, such as cardboard or the like,the two outer plies 3i and 32 (see Figures 1, 2 and 3)' sandwiching the frame 20 between them, the intermediate ply 33 having an inner edge which conforms in curvahesive means or otherwise, and conjointly define a staunch and rigid index portion which may be shifted along the graduated edge 2! as the sextant is used, the interengagement being firm and accurate. Readings may be taken through the opening 34 with unusual precision, because of,

the abutting relationship between the graduated edge 2| and the vernier graduations on the intermediate ply 33.

The pivot portion of the alidade is similarly composed of three plies of sheet material such as cardboard or-the like, the outer plies 35 and 36 -'(see upper portions of Figures 1, 2 and'3) lying on opposite sides respectively of the frame 20, the intermediate ply 31 being snugly accommodated within a pivot opening of circular shape provided for the purpose in the frame 20. The intermediate ply 31 thus constitutes a journal portion and is preferably a disc of circular contour.

The three plies 35, 36 and 31 may be held towith respect to the grain of the other, and this results in effecting staunchness and rigidity of unusual character.

It is sometimes desirable to provide the sextant with one or more screens which may be swung into and out of the optical axis of the device to intercept and filter the rays of light which pass from the index mirror 49 to the horizon mirror 43. I have illustratively shown two such screens 49 and 50 (see Figures 7, 8.and 9) and an improved manner in which these screens may be pivotally associated with an edgeportion of the frame 20. As shown most clearly in Figure 8, the edge portion to which the screens are to be pivoted is composedof three plies of sheet material.

, The outer ply is constituted of a portion of the,

gether in any convenient manner, by adhesive means or otherwise, and the interconnection may be enhanced by nails or similar elements 38 which extend through all three plies and thence into a block 39 (of wood or the like) which carries the usual index mirror 49. l

The body portion 4| of the alidade-may be conveniently formed of one piece of sheet material, such as cardboard or the like, with the outer ply 3| of the index portion and the outer ply I of the pivot portion.

The other essential elements of the sextant structure are the telescope 42 and the so-called horizon mirror 43. These elements are permanently secured. in proper relationship to the front face 29! Preferably, the telescope 42 consists of atube of cardboard or the like firmly anchored in a block 44 which may be composed of woodand which is held in position by adhesive means,

preferably with the aid of nails 45 or similar fasteners. At the eye-piece end of the telescope I prefer to insert an apertured plug or disc 46 which reduces the size of the peep opening, and at the opposite end of the telescope,

I provide a nail or pin 4'! which extends diametrically across the tube 42 and serves to-facilitate the sighting procedure.

Similarly, the horizon mirror 43 may be conveniently mounted on a block 48, composed of wood or the like, this block. being permanently secured to the frame 20 by adhesive means or the like, with or without the aid of nails or similar additional fasteners.

In order to rigidify the frame 20 and to retain the telescope and the horizon mirror in proper predetermined relationship at all times, the upper portion 29 of the brace is of such a size and shape that it extends behind at least a portion of the block 44 which supports the telescope, behind at least a portion of the block 48 which carries the horizon mirror, and across the entire area between them, as indicated most clearly 'the like, the grain of one is arranged transversely sired region of the frame 20.

ally mounted within a suitable slot formed in this three-ply edge portion. Because the screens are of relatively thin material, such as celluloid or the like, a firm engagement within the slot is assured by the unique arrangement of the elements (as shown most clearly in Figures 7 and 8) whereby one side of the slot is defined by the aligned shoulders 55 formed on the plies 20 and 5|, while the opposite side of the slot is defined by an opposed shoulder 55 formed on the intermediate ply 29. Each of the shoulders 55 is preferably provided for by cutting a slot of substantial dimensions in the corresponding ply, and the shoulder 56 may similarly be formed by means of a slot in the intermediate ply 29, but these cut-out portions need not be of critical dimensions because the staggered relationship of the plies, as shown in Figure 8, provides a resultant slot of adequately minute width toiaccommodate the'screen or screens 49 and 50 in the proper manner.

The actual pivoting of these screens may be conveniently established by means of a pivot pin 52 which extends across the slot and has its opposite end portions accommodated within aligned recesses 53 formed in the'intermediate ply 29, the pin 52 being permanently held in proper position by the sandwiohing action of the outer plies 29 and 5|.

A screen or screens of similar character may be provided for in similar fashion in any other de- It is an additional feature of the present construction .to provide a means for removably securing an optional level-glass unit to the frame 20. This unit may consist, for example, of a block 51, of wood or the like, within which the level-glass itself 58 is permanently secured, a mirror 59 being carried by the block 51' at a suitable'angl'e to make the level-glass visible to the user of the device when looking through the telescope 42. To provide for the removable attachment of this unit, the frame 29 is provided with a slit 60, and the level-glass unit carries adjustable fasteners which may be associated with this slit. I prefer to employ as fasteners one or more screw-threaded elements 6| having enlarged heads, such as the looped head shown in Figure 5 at 62. The screwthreaded engagement permits these fasteners to be rotated through When adjusted to bring 'the'heads 62 into alignment with each other and preventing withdrawal of the fasteners thus locking the level-glass unit to the frame.

In general, it will be, understood that the pose of describing the general nature of the present structural improvements may be modified by those skilled in the art without departing from the spirit and scope of the invention as expressed in detailsherein described and illustrated for the purgraduated edge whose curvature is concentric with I said opening, and an alidade having a, pivot por tion engaging with said pivot opening and having an index portion slidably engagin said graduated edge, said index portion being formed of three interconnected superposed plies, the outer plies sandwiching said graduated edge between them and the intermediate ply having a curved inner edge abutting said graduated edge, the pivot portion of the alidade being also formed of three interconnected superposed plies, the outer plies overlying said pivot opening and sandwiching said frame between them and the intermediate ply constituting a journal snugly accommodated within said pivot opening, the body of the alidade being of one piece with one of the outer plies of the index portion and'with the corresponding outer ply of the pivot portion.

2. In a sextant, a frame having an edge portion formed of three interconnected superposed plies, a slot in said edge portion, and atscreen pivotally mounted in said slot for swinging movements into and out of the optical axis of the sextant, one wall of said slotbeing defined by aligned shoulders formed on two of said plies, the opposite wall of said slot being defined by an opposed shoulder formed on the third ply, said third ply being the intermediate one of the three plies.

I IJOHN v. KORE.

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