US71595A - Thomas evans - Google Patents

Description

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THOMAS EVANS, 0E NEWARK, NEW JERSEY. Letters .Patent No. 71,595, dated December 3, 1867.

IMPROVEMENT IN DRAUGHTIG-INSTRUMENT.

Be it known that I, THOMAS EVANS, of Newark, Essex county, New Jersey, have invented a new and useful Tool for the use of Tinners and other Artisans; and I do hereby declare that the following is a full and exact description thereof, reference being had t0 the annexed drawings.

Figure 1 is an edge view ci' the tool.

Figure 2 is a. front or, full view.

l I Figure 3 is a plan of bar g.

Figure 4 is a development of a conical frustum.

My invention consists of a square, a, graduated on the edges, combined with a sliding bar, g, arranged to move freely along one arm of the square a and stand-at right angles therewith; A straight-edge, b, is clamped tothe b'ar g by a thumb-nut or screw, f, and hield in contact with the other arm of the square a by the piecetz,

fastened to the straight-edge and pinchingthe arm 7c of the square a. These three pieces a, g, and 6, can be, moved into various positions; and, when'the sliding bar g is set at a distance from the base kof the square a equal to the height of the desired frustum of -a cono, and the straight-edge bis set with its' one end intcry secting the graduations on the arm k at a point indicating the semi-diameter of the larger end of said frustum, and its edge intersecting the bar g at a point indicating thereonthe semi-diameter of the smaller end of said frustum, the gradual-tions on the straight-cdge Z1, from its foot to its intersection with the bar g, will indicate the slant height of the frustum, and the distances from m to a and from n to o will represent the correct radius to be employed in developing the surface of the fr ustum on a plane surface. This property of the tool gives it a great degree of usefulness where any one (as a tinner) is frequently employed in cutting sheet metal onpaper to fit conical or pyramidal surfaces.

I The tool isrepresented in the drawings as properly set to lay-out a 1amp-shade of conical form, ten 'inches diameter across the bottom, four inches across the top, and four and a half in height. `The graduations on the straight-edge'from m to n show that the slant heightis five and three-eighth inches, that the radius from m to o is nine inches, and the radius freni n to o is three and tive-eighth inches. The development of the shade in a plane'surface is shown in iig-4, drawn one-fourth of the full size in inches.

-When the proportions of a igure larger than the tool are required, they can be obtained by setting the tool to one-half` of the dimensions required, or one-third or fourth, as the case may need. Thus, the tool can be'made to serve the place of a large stock of tinners patterns.

The bar g is slotted, as Well as the straight-edge b, to afford facility of adjustment; anda piece is secured at its end by a. thumb-screw,f, in the slot of b. This piece has a scriber, d, fastened at its extreme end, which renders it capable, when used in conjunction with the scriber z' at the foot of b, of serving as Compasses, snpposing the pieces'b and c to be detached from the square a and bar g. Thielinstrument, therefore, combines a square, straight-edge, compasses or scriber, several measuring-scales, andfa tool for describing geometrical figures in a practical manner. `It thus affords a new and useful instrument for smiths, metal-workers, shipwrights, millwrights, carpenters, &c.

What I claim as new, and desire to secure by Letters Patent, is-

1. The combination of the scalc-rules b and g with the square a, made adjustable thereon, substantially as set forth.

2. The arm-c, in combination with the slotted straight-edge b, cach being provided with a point, d z, and.'

made adjustable with relation to each other, substantially as and for the purposeset forth.

THOS. EVANS.

Witnesses:-

T. S. CRANE, F. A. EVANS.

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