US3897633A

US3897633A - Draftsman{3 s aid for preparing axonometric drawings and projections

Info

Publication number: US3897633A
Application number: US430722A
Authority: US
Inventors: Minton E Whitt
Original assignee: Individual
Current assignee: Individual
Priority date: 1974-01-04
Filing date: 1974-01-04
Publication date: 1975-08-05
Anticipated expiration: 1992-08-05

Abstract

A draftsman''s aid for preparing axonometric drawings and projections having a primary article representing the frontal and profile planes and equipped with a pair of protractors, and adapted to be used with a secondary triangular shaped article representing the horizontal plane, is disclosed.

Description

United States Patent Whitt Aug. 5, 1975 [5 DRAFISMANS AID FOR PREPARING 655,005 7/1900 Penfield 33/75 R AXONOMETRIC DRAWINGS AND :8: PROJECTIONS 3:358:9l6 10/1966 Suto Q: .11. 33/77 [76] Inventor: Minton E. Whitt, P.O. Box 558,

Farmers, Ky. 403 l9 [22] Filed: Jan. 4, 1974 [21] Appl. No.: 430,722

[52] US. Cl. 33/77; 33/75 R [5i] lnt. Cl. B43L 13/14 [58] Field of Search 33/75 R, 75 A. 75 B, 77

[56] References Cited UNITED STATES PATENTS 262,137 8/1882 Silliman 33/77 Primary E.raminerRichard E. Aegerter Assistant Examiner-Michael H. Thaler Attorney, Agent, or Firm-William E. Sherwood [5 7] ABSTRACT A draftsmans aid for preparing axonometric drawings and projections having a primary article representing the frontal and profile planes and equipped with a pair of protractors, and adapted to be used with a secondary triangular shaped article representing the horizontal plane, is disclosed.

5 Claims, 7 Drawing Figures PATENTEDAUB "51975 3,897, 633 SHEET 1 FIG. 3

OIIIII o l l F|G.I

DRAFTSMANS AID FOR PREPARING AXONOMETRIC DRAWINGS AND PROJECTIONS BACKGROUND OF THE INVENTION The construction of axonometric drawings and projections, particularly of the dimetric and trimetric types, are laborious and time-consuming, and many forms of aids for the draftsman have been proposed to assist him in this task. However, such aids usually are unduly complicated and expensive and often do not materially simplify the work of the draftsman. It is a purpose of the present invention to overcome these and other disadvantages of conventional articles used in the making of such drawings and projections.

By definition, drawings or projections of the simpler isometric type have each of the X, Y and Z axes 120 apart and these axes representing the width, height and depth of object to be depicted remain in the same proportional ratios. On the other hand, dimetric drawings or projections are more difficult to construct in that two of the three axes make equal angles of more than 90 with the plane of projection and with the third axis at a different angle, thus permitting only two of the three dimensions to have the same proportional ratio.

Finally, the most difficult drawing or projection to construct is the trimetric type in which all three axes make unequal angles with the plane of projection and wherein each axis must be developed separately since no two of the three axes have the same proportional ratio.

During the construction of an axonometric drawing little or no consideration is given to the degree of foreshortening whereas in constructing an axonometric projection the object being constructed not only is placed in proper relationship to the plane of projection, but also embodies the correct degree of foreshortening along each of its three axes. As will later appear, the present invention provides a means whereby the draftsman may construct any of these three types of drawings and projections in an accurate and relatively simple manner as contrasted with present practices.

SUMMARY The invention comprises a draftsmans aid including a primary article with which axonometric drawings may be made, and a supplementary triangular article which when used in conjunction with the primary article enables the draftsman to make axonometric projections. The primary article includes right and left protractors pivotally mounted on arms extending from a flat frame member which has a straight lower edge adapted to be referenced against a T-square or the like, and the protractors move in the plane of the flat member. At least one of the protractors is provided with an array of holes through which markings representative of the setting of the protractor can be made upon an underlying worksheet. The supplementary article includes scales along edges representative of X-axis and Z-axis readings and with arrays of holes along those scales.

Among the objects of the invention are the provision of an improved, simple, and inexpensive draftsmans aid for making axonometric drawings in a less laborious and more accurate manner; the provision of a draftsmans aid consisting of separate primary and secondary articles which cooperate in the making of axonometric projections; the provision of a draftsman's aid by means of which the teaching of the principles of mechanical drawing for complex showings of objects may be simplified; and the provision of a draftsmans aid which permits the production of axonometric projections in a shorter time than heretofore possible.

These and other objects and advantages of the invention will become more apparent as the description proceeds and when considered in conjunction with the accompanying drawings in which FIG. 1 is a plan view of the primary article to be employed by the draftsman.

FIG. 2 is a plan view of the secondary article to be employed with the primary article when constructing trimetric projections.

FIG. 3 is a sectional view to an enlarged scale taken on line 3-3 of FIG. I.

FIG. 4 is an isometric drawing of an object as constructed with the primary article.

FIG. 5 is a dimetric drawing of an object as constructed with the primary article.

FIG. 6 is a trimetric drawing of an object as constructed with the primary article of the invention; and

FIG. 7 is a preferred geometrical and graphical construction of a trimetric projection as developed by use of the primary and secondary articles of the invention.

Referring now to FIG. I, the primary article comprises a flat frame member 10 preferably constructed of rigid transparent plastic material and having a straight lower edge II adapted to rest against the usual T-square or other reference means employed in drafting work. Rigid right and left arms 12 and I3 respectively are attached as by bonding to the upper surface of the member and provide

pivotal supports

14, 15 for a pair of protractors l6, 17 respectively. The frame member is cut away beneath these supports and is shaped to provide for movement of the protractors in the plane of the member. Moreover, the central portion of the member is formed with an open notch having symmetrical

straight edges

18 and 19 respectively representing the X-axis and Z-axis directions for certain drawings made by means of the primary article. These edges intersect at point 20 from which a visible line 21 on the surface of the frame member extends normally toward the long edge I] and represents the Y-axis.

Theoretically, axonometric drawings and projections are graphic representations of resulting positions of objects which have been revolved and tilted with respect to the plane of projection. The

top edges

22 and 23 of the right and left arms are on a common line parallel to the lower edge 11 and represent the plane of projection while the right hand edge 24 of arm 12 is perpendicular thereto and represents the profile plane; the flat body 10 of the primary article meanwhile representing the frontal plane. The protractors are movable to provide selected settings, for example between 0 and 1 5 and between 0 and and by means of

suitable thumb screws

25, 26 mounted in the arms may be held in the selected position following the setting of the protractor.

The right hand protractor which serves the dual purpose of determining the angle at which the Z-axis (depth dimension) recedes (slopes) from the plane of projection, and of determining the tilt angle for the profile plane, is provided with a scale 27 on its top straight edge and with an open slot 28 with accompanying scale 29 for measuring along the intended Y-axis. This scale 29 employs a zero mark which lies on the line extending from pivot 14 to the 90 mark on the quadrant scale of protractor 16. Various profile tilt angles depending upon the selected adjustment made on the right frontal protractor 16 may be drawn directly on the worksheet by a pencil moving in this slot. A series of holes in the protractor adjacent this scale provides for the making of reference points on the worksheet by means of a pencil point or the like inserted through these holes and with each such point being uniformly related to the Y-axis angle of the slot. As will later appear, these points are used for drawing lines to help in establishing foreshortening of the object.

The left hand protractor serves three purposes, namely; to determine the angle at which the X-axis (width dimension) recedes from the plane of projection; to measure true heights on the Y-axis; and to provide a support for the secondary article when developing axonometric projections. This protractor has a scale along its straight top edge and also a vertical scale 36 along its leftmost edge which is normal to that top edge.

The scales (normally subdivided into degrees) along the quadrant portion of both protractors are read at points where such scales revolve beneath the inner edges of the respective upright arms 12 and 13 and, if desired. supplementary vernier scales 37, 38 (subdivided into minutes) may be mounted upon the respective arms in order to provide for more precise settings. Moreover the arms 12 and 13 may be recessed as shown at 37A and 38A to make visible scale portions on the protractors representing settings thereof employed in making perspective drawings, as when the straight top edges of the protractors are revolved in a reverse direction. As later to be explained, in the making of certain projections it is important to position the primary article at an exact point beneath the pivotal axis of the protractor and as seen in FIG. 3 a hollow ferrule 40 pinning the protractor to the arm and containing a magnifying glass insert 41 with a pair of cross hairs thereon may be employed.

For use with the above described primary article the secondary article shown in FIG. 2 is employed in the making of projections and comprises a flat transparent triangular member representing the horizontal plane. This member is formed with one straight edge 45 having a scale 46 for X-axis readings and a series of holes 47 for establishing points on the work sheet along that X-axis. In addition one straight edge 48 having a scale 49 for Z-axis readings and with a series of holes 50 for establishing points on the work sheet along that Z-axis is provided; the

edges

45 and 48 intersecting at a right angle and with a visible line 51 representing the Y-axis being present on the surface and bisecting the right angle.

EXAMPLES OF USAGE OF THE AID Considering now the preparation ofa trimetric drawing as seen in FIG. 6 with angles as indicated; the draftsman first sets the left frontal protractor 17 to 0 and then draws the Y-axis line of the intended object to the selected scale by means of the scaled left edge 36 of the primary article. Then he adjusts the protractor 17 to a 25 setting and draws X-axis line 61 from the upper end of line 60 using the scale edge 35 for direction and scaling purposes and leaving the protractor 17 at its 25 setting. Then he adjusts the right frontal protractor 16 to a 35 setting and using the scale edge 27 draws a Z-axis line 62 from the upper end of line 60, leaving protractor 16 at its 35 setting.

Thereafter he shifts the primary aid with its protractors locked at the above settings to draw the lower X- axis line 63 followed by shifting of the primary aid to draw the lower Zaxis line 64. Further shifting of the primary aid allows the drawing of the distant X-axis line 65 and the distant Z-axis line 66. After this, the left frontal protractor is restored to its 0 setting and its left vertical scale edge 36 is used to complete the drawing by means of the left Y-axis line 67 and the right Y-axis line 68. As will be seen, this trimetric drawing of a cube has been made merely by using the straight lower edge 11 resting against a reference surface such as an adjustable T-square; (b) the left scale edge 36; (c) the upper scale edge 35 of one protractor; (d) the upper scale edge 27 of the other protractor and (e) the quadrant scales of both protractors.

By contrast, the preparation of a trimetric projection of the cube of FIG. 6 (with foreshortening, tilting, and revolving) involves use of both the primary and secondary articles of the draftsmans aid. Referring now to the construction shown in FIG. 7 the draftsman sets both protractors at 0 and draws the straight horizontal line 70 representing the plane of projection (P.O.P.) line and after shifting the primary aid then draws the vertical line 71 (the Y-axis line of the drawing) by means of the scale edge 36 of the left protractor. The thumb screw 25 is then loosened and the right protractor is revolved 45 out of the way. The thumb screw 26 is then loosened and the left protractor 17 (which now acts as the horizontal protractor) is revolved to the desired angle of revolution of the top view of the intended object after which thumb screw 26 is tightened. The primary article is then shifted with its line 21 coinciding with line 71 on the drawing sheet and using the scale edge 35 an inclined line 72 is drawn. This line intersects the POP. line at X and the Y-axis at 0.

Now using the secondary article with its X-axis edge coinciding with line 72 and its apex at 0, a line 73 is drawn to intersect with the P.O.P. line at Z.

The left protractor of the primary article being reset to 0 is then used to draw a laterally displaced vertical construction line 74 downwardly from point A on the POP. line. Also a line 75 parallel to the POP. line from point 0 to the point B of intersection with line 74 and extending therefrom a suitable distance is drawn using the lower edge 11 of the aid.

The right protractor I6 is then set to and the primary article is laid upon the work sheet with the cross hair of the insert 41 at the pivot support 14 coinciding with point A and with its lower edge 11 being parallel with line 75. A reading is then taken on the right protractor corresponding to where line 75 extended intersects quadrant scale of the protractor, and this reading is jotted down by the draftsman.

Keeping the primary article in the same position as when the reading is taken, rotate the right protractor to the desired tilt angle of the object to be depicted, for example 35, lock the thumb screw 25 and with a pencil make a dot C on the work sheet corresponding to a reading of the scale on the quadrant of the protractor which is the same as the reading earlier jotted down. Then draw the line 76 from dot C to point A using the scale edge 27 of the protractor and thereafter shift the primary article while still locked at its 35 setting and with its lower edge 11 still parallel to line 75 to bring the scale side 29 of the slot 28 into alignment with dot C.

A line 77 is then drawn from dot C by means of a pencil moving in the slot and this line is extended to intersect with line 74 at point D. A scaled series of dots 99 are then made on the work sheet by inserting a pencil point through the holes 30 adjacent the slot in the protractor. A line 78 is then drawn from dot C horizontally parallel to line 75 to intersect with line 71 at point Y which establishes the initial point in the front view showing of the object to be depicted. Following this a series of parallel lines 100 which are parallel to line 78 are drawn to their intersection with the Y-axis line 71 whereupon the true shape and size of the height of the foreshortened front vertical Y-axis edge of the cube (as it would appear to an observer looking into the frontal plane in a perpendicular manner) is established along line 71. Thereafter using any

straight edge lines

79 and 80 are drawn respectively from point Y to points X and Z whereupon the space bounded by

lines

70, 80 and 79 represents the front view of the object after it has been tilted and projected from the profile view, or in other words these three lines are the lines which the cube makes with the frontal plane of projection.

From point D using a straight edge a construction line 81 is drawn parallel to line 75 to intersection with the Y-axis line 71 at point E and

lines

82 and 83 are drawn respectively to points X and 2 from point E.

Lines

79 and 80 are then extended a suitable distance as lines 79A and 80A respectively and using the secondary triangular article with its apex lying upon line 79A and its X-axis and Z axis edges touching points E and Z respectively, lines 84 and 85 are drawn from the apex to points E and Z respectively. Then with the triangular article held with its line of holes 50 over line 85 a series of scaled dots 86 are made through those holes. Using a straight edge a series of parallel lines 87 which are parallel to line 79A are drawn to their intersections with line 80 thus depicting the upper Z-axis edge of the cube in the desired foreshortened size.

In like manner, the secondary triangular article is placed with its apex on line 80A and its X-axis and Z- axis edges touching points X and E respectively and

lines

88 and 89 are drawn from the apex to points X and E respectively. Then with the article held with its line of holes 47 over line 88 a series of scaled dots 90 are made through these holes. Using a straight edge a series of parallel lines 91 which are parallel to line 80A are drawn to their intersections with line 79 thus depicting the upper X-axis edge of the cube in the desired foreshortened size.

Having thus established the desired reference edges of the object in three planes, a straight edge is employed to draw in the remaining X-axis edges; edges and 102; the remaining Y-

axis edges

103 and 104; and the remaining Z-

axis edges

105 and 106.

As will be understood. if desired and without departing from the invention, the left protractor 17 may also be equipped with a slot, scale and row of holes so that a similar construction of a trimetric projection involving the tilting and revolving of an object in a reverse direction may be carried out. Also the right protractor may be equipped with a vertical scale along its right hand edge.

Having described the use of the draftsmans aid in the construction of the difficult trimetric projection it will be apparent that it also is suitable for use with the much less difficult construction of the simpler isometric and dimetric projections, such as would be involved in the drawings of FIGS. 4 and 5 having angles as shown.

Obviously many modifications and variations of the present invention are possible in the light of the above disclosure. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. A draftsmans aid comprising; a rigid, flat member having a straight edge along its lower portion and formed along its upper portion with a central notch having symmetrically disposed upwardly inclined relatively short straight edges with right and left arcuate edges extending downwardly from the respective ends of said short edges, upwardly extending right and left support arms affixed to said flat member along its side portions and disposed in a plane above the plane of said flat member, right and left protractors pivotally mounted upon the upper ends of said arms and adapted to revolve in the plane of said flat member and along the arcuate edges thereof, said protractors being mounted in confronting spaced relation in proximity to each other and having scaled straight upper edges along which lines may be drawn representative of the settings of said protractors, and at least one of said protractors having a Yaxis slot therethrough located normally to the straight upper edge of the same protractor whereby markings may be made through said slot upon a worksheet underlying said flat member and which are representative of the selected setting of the slotequipped protractor.

2. A draftsmans aid as defined in claim 1 wherein at least one of said protractors includes a scaled straight exposed side edge normal to the upper edge of the same protractor.

3. A draftsman's aid as defined in claim 1 wherein said member is formed of transparent material and includes a visible reference line extending downwardly from the apex of said notch and normal to the lower straight edge of said member.

4. A draftsmans aid as defined in claim 1 including a scale along said slot and an array of holes through the protractor adjacent said slot.

5. A draftsmans aid as defined in claim 1 wherein at least one of said protractors is pivotally mounted upon the arm by means of a cylindrical ferrule containing a magnifying glass through which the worksheet may be observed.

Claims

1. A draftsman''s aid comprising; a rigid, flat member having a straight edge along its lower portion and formed along its upper portion with a central notch having symmetrically disposed upwardly inclined relatively short straight edges with right and left arcuate edges extending downwardly from the respective ends of said short edges, upwardly extending right and left support arms affixed to said flat member along its side portions and disposed in a plane above the plane of said flat member, right and left protractors pivotally mounted upon the upper ends of said arms and adapted to revolve in the plane of said flat member and along the arcuate edges thereof, said protractors being mounted in confronting spaced relation in proximity to each other and having scaled straight upper edges along which lines may be drawn representative of the settings of said protractors, and at least one of said protractors having a Y-axis slot therethrough located normally to the straight upper edge of the same protractor whereby markings may be made through said slot upon a worksheet underlying said flat member and which aRe representative of the selected setting of the slot-equipped protractor.

2. A draftsman''s aid as defined in claim 1 wherein at least one of said protractors includes a scaled straight exposed side edge normal to the upper edge of the same protractor.

3. A draftsman''s aid as defined in claim 1 wherein said member is formed of transparent material and includes a visible reference line extending downwardly from the apex of said notch and normal to the lower straight edge of said member.

4. A draftsman''s aid as defined in claim 1 including a scale along said slot and an array of holes through the protractor adjacent said slot.

5. A draftsman''s aid as defined in claim 1 wherein at least one of said protractors is pivotally mounted upon the arm by means of a cylindrical ferrule containing a magnifying glass through which the worksheet may be observed.