US2867906A

US2867906A - Graphical instrument

Info

Publication number: US2867906A
Application number: US466032A
Authority: US
Inventors: Lee Koung-Shin
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-11-01
Filing date: 1954-11-01
Publication date: 1959-01-13
Anticipated expiration: 1976-01-13

Description

a 1959 KOUNG-SHIN LEE 2,867,906

I GRAPHICAL INSTRUMENT Filed Nov. 1.' 1954 I I 0% H l .9 1 .1 z I 20 17 /5 Figu g 33 -2G /2 INVENTOR Koung Shin Lee BY 24 W 9% A 7'7'ORNEYS F/gur 2 United States Patent GRAPHICAL INSTRUMENT Koung-Shin Lee, Forest Hills, N. Y.

Application November 1, 1954, Serial No. 466,032

1 Claim. (Cl. 33-93) This invention relates to a graphical instrument for use in mechanical drawing and related applications where it is desired to construct lines at various slopes and angles relative to a reference edge.

The principal object of this invention is to provide a drafting instrument which gives simultaneous indications of the slope and the angle of a line relative to a reference edge.

Another object is to provide a drafting instrument which will solve graphically various trigonometric problems.

A further object is to provide a drafting instrument which is a combination triangle and trigonometric calculator.

An additional object is to provide a drafting instrument which can be used to construct a line at any angle or slope in any of the four analytical geometric quadrants.

Other objects and advantages will become apparent in the following description and accompanying drawings wherein:

Fig. 1 is a plan view of the graphical instrument, showing the straight edge in a partially extended position in dotted lines and in its closed position in solid lines; and

Fig. 2 is a plan view of the graphical instrument showing two variations in its manner of use on a drawing board.

Referring to the drawings, Fig. 1 shows the graphical instrument of the present invention, generally designated by the numeral 10. The instrument has a right triangular base plate 11 with one acute-angled corner portion 12 rounded off as shown. Overlying the base plate 11 is a sectoral frame 13 which has a curved portion 14 and two straight sides 15, 16 extending from

opposite ends

17, 18 of the curved portion to meet at an offset vertex 19.

Sectoral frame 13 is rotatably attached at the vertex 19 to the base plate 11 by means of a pivot 20 located near the rounded-off corner portion 12 thereof so that the frame can be rotated to different overlying positions relative to the base plate 11, for example, as shown by the dotted lines in Fig. 1.

Attached along one side 16 of the frame 13 is a straight edge member 21 which extends in length beyond curved portion 14 of the frame 13 to form with its outer edge 22, in conjunction with the base plate 11, the hypotenuse of an isosceles right triangle when the frame is in the fully overlying, or closed position relative to the base plate, as shown by the solid lines in Fig. 1. In such position the inner edge 23 of the straight edge member 21 bears against the hypotenuse edge 24 of the base plate, thereby limiting the counterclockwise movement of the frame relative to the base plate as viewed in Fig. 1. The pivoted end 25 of the straight edge member 21 terminates short of the pivot so that the member may be rotated to a position perpendicular relative to the base side or reference edge 26 of the base plate 11 when the latter is being maintained in contact with a straight edge or the like.

Curved portion 14 has an arcuate slot 27 along its length through which a setor clamping-screw 28 is attachable to base plate 11. The screw 28 when loosely attached to base plate 11 rides in the slot 27, permitting a freedom of rotation for the frame 13 relative to the base plate. The screw may be manually tightened to clamp the frame in a fixed position relative to the plate.

The outer edge 29 of the curved portion 14 of frame 13 has angular indicia or a protractor scale 30 marked off on it in appropriate graduations of degrees. Adjacent the rotational path of the latter edge is an arrow or index mark 31 marked into the base plate which indicates on the protractor scale 30 the angular setting of the outer edge 22 of the straight edge 21 relative to the reference edge 26 of the base plate.

Also located on the base plate 11 is a graph-ruled area 32 which is in the shape of an isosceles right triangle having its hypotenuse 33 parallel to the reference edge 26 of base plate 11 and substantially aligned with the inner or index edge 34 of lower side 15 of the sectoral frame 13 when the latter is in its closed position as viewed in Fig. 1. The right angle vertex 35 of the ruled area is adjacent to hypotenuse edge 24 of the base plate 11 and one acute angled vertex 36' thereof is located at pivot 20.

The two sides 37, 38 of the ruled area are each marked off in evenly spaced decimal graduations of equal valuev by means of indicia or

scales

39, 40. Likewise index edge 34 of sectoral frame 13 is marked off in similar units with indicia or scale 41. The preferred major graduations on sides 37, 38 run from 0 to 10 and on index edge 34 from 0 to approximately 14 in the manner as shown in Fig. 1. Minor graduations 42 may be chosen for convenience.

The basic feature of this instrument is the isosceles right triangular graph-ruled area 32 on the base plate 11 and the index edge 34 on the sectoral frame. Together wtih the 45 protractor scale 30 on curved portion 14 of the sectoral frame 13, a straight line of any slope or angle can be constructed by setting straight edge 21 at the desired position relative to reference edge 26 of base plate 11.

For example, if it is desired to draw a straight line with a slope of 10/6, the instrument should be adjusted to the position indicated by the dotted lines in Fig. 1, namely, so that index edge 34 of sectoral frame 13 intersects scale 40 of the ruled area 32 at the major graduation 6. Thus a line drawn coincident with straight edge member 21 will have a slope of 10/6 relative to a line drawn coincident with reference edge 26. The angle between the two lines (approximately 59") may be read off in degrees on protractor scale 30 at index mark 31.

It is apparent that at any particular setting of the index edge 34 relative to the ruled area 32, the three sides and included angles of a plurality of similar right triangles are immediately determinable. The protractor scale 30 may be marked in degrees and complementary degrees, so that for the above setting the acute angles could be read to be 31 and 59.

The lengths of the respective sides can be read directly if either one of the two sides or the hypotenuse is known. Thus if the longer side is 5.5 units, such 5.5 units will be read along scale 39. Then read from 5.5 on scale 39 along the line parallel to scale 40 (see dotted arrow A) until such line meets index edge 34, and read from that point along the line parallel to scale 39 (see dotted arrow B) until scale 44) along the side 38 is reached. Thus it is determined that the shorter side is 3.3 units. The point of meeting the index edge marks off on said edge the length of the hypotenuse, in this case about 6.4 units.

Similarly for other lengths of longer sides of a 31"- 5990 triangle read off on scale 39 of ruled area 32, the shorter sides and respective hypotenuses can be read off on scale 40 of the ruled area 32 and the index edge 34 of sectoral frame 13 respectively.

In addition, for the complement of the angle at which the straight edge member 21 is set relative to the reference edge 26, the tangent of such complementary angle can can beread ofi on scale 39. Thusthisinstrument can be used to graphically-solve various-trigonometric prob lems. v

For example, for the setting shown by the dotted lines in-Fig. -1, thertangentof approximately 31 (the'complement-of-the setting'of 59 canbe read off-on scale 40: as .60. Likewisethe sine of -such complementaryyangle of3 1- isindicated from the on index edge 34" to be .52 on scale 40 (see dotted arrow C), and the'cosineis read as .86 on scale 39 (see arrow'D)-.:

As shown'in Fig. 2, the isosceles character ofthebase plate- 11 provides many versatile positions and edgesfor constructing similar triangles for one setting of the'instrument. Such versatility is' helpful for constructing lines in the various geometric quadrants.

For example, when constructing linesat angles greater than 135 in the second quadrant, the straight edge is placed against a perpendicular reference (such as another triangle) and the desired line is drawn coincident with the reference edge 26 of the instrument. Thus to construct-a line at an angle of 150, set the straight edge atan angle of 60 relative to the reference edge, then placing the straight edge perpendicular to a T-square'ori base line, thereferenceedge'of the instrument will form an angle of 30 with said base line, permitting construetion of the line at 150 in the second quadrant.

This instrument-may be constructed of any suitablema changes may be made in its construction andarrange-- ment of parts without departing from the inventive conceptand the scope of the following claim.

What I claim is:

A drafting instrument comprising a 45 right isosceles triangular base plate, a sectoral frame having a curved portion and two straight sides disposed at 45 relative to one another and meeting at a vertex, said frame pivotally attached at said vertex to a corner portion of one of the acute angles of said base plate in overlying relation to r the same to provide an axis of "rotation for said frame relative to said/base,L.a-i straight edgemember attached along one of said sides of said frame, said member movable into limiting' conta'ct alongits'length with the'hypotenuse 'of said baseplate; a-ismallerl similarz4 5? right isosceles triangular graph-ruled area on said base plate having one of its-acute'angledwertices located at said axis and having its hypotenuse disposed parallel to the equal side of said base plate adjacent said axis, and the equal side of the area coincident with said axis disposed parallel to thehypptenuseof said baseplate, ,decimalindicia marked alongtheequal sides of said'area,- corre-' sponding indicia marked along the-other of said sides of, said frame, angular indicia along said curved portion. ofsaid frame marked ofl in actual and complementaryydegrees, and an-index mark on said base plate adjacent therotational path of saidcurved portion of" said :frame to indicate on said angular indicia the angular setting of saidz straight edge relative to saidequal side of said base plate adjacent said axis.

7 References Citedin the file of thlSipatellt UNITED STATES PATENTS- 29,767 Chisholm Aug; 28, 1860 378,257 Leschorn- Feb; 21,1888; 662,977- SchmelZ Decr 4,,1900- 888,173 Justice May 19, 1908;

1,003,857 Adams- Sept; 19, 1911 1,056,206 Norman Mar. 18, 1913;: 2,154,753 Kallio Apr. 18,,1939; 2,412,901: McCoshen Dec..17, 1946 FOREIGN" PATENTS 355,856 Great Britain Sept. 3, 1931 838,653- Germany May 12,.1952;