US3266154A - Homocentrograph - Google Patents

Description

16, 1966 CHlNG-YUAN NEOU 3,266,154

HOMOCENTROGRAPH Filed Feb. 25, 1966 INVENTOR.

BY /Z.,w

United States Patent 3,266,154 HOMUCENTROGRAPH Ching-Yuan Neon, 211 Louisiana Ave., Bridgeport, Conn. Filed Feb. 23, 1966, Ser. No. 529,331 1 Claim. (Cl. 33-77) This invention relates to a mechanical device to facilitate the precision drawing or aligning of lines toward a distant common point lying beyond the drawing area.

The primary object is to facilitate the drawing of perspective lines, perspective spacing and measurement involving distant vanishing points, shadow lines cast by a remote light, etc.

A second object is to facilitate the graphical kinematic analysis when the instantaneous centers lie far away.

The third object is to align moving sources of light beams, cameras, reflectors, etc. to a designated spot.

In the drawings wherein like reference numbers indicate like parts.

FIG. 1 is a pictorial showing of the perspective geom etry of a parallelpiped.

FIG. 2 is a plan view of the homocentrograph.

FIG. 3 is a diagrammatic showing of the underlying principle of the homocentrograph.

FIG. 4 is a fragmentary view of the cross-section of the center slider on the leg of the T-section.

FIG. 5 shows a marking device on the perspective arm for drawing perspective lines.

FIG. 6 is a diagrammatic showing of the geometry for aligning the homocentrograph in a new position above the horizon line to a distant vanishing point.

FIG. 7 shows a clamp for holding the T-section in fixed position in the drawing area.

In perspective drawings, all parallel lines displaced angularly from the picture plane converge to a common point known as the vanishing point as they proceed off into the distance. FIG. 1 shows a parallelpiped abcdefgh whose edged ab, ed, ef, and gh tend to converge to the right vanishing point (VPR) on the horizon line (HL) or eye level; and edges ad, be, jg, and eh to the left vanishing point (VPL) on the same horizon line. When the vanishing points lie beyond the drawing area, drawing of precision perspective lines become very difiicult. The present invention is a mechanical aid to establish the remote vanishing points (FIG. 2).

The homocentrograph consists mainly of a T-section having a bar 2, a perpendicular leg 3, an expandable zigzag linkage 4, a cross-bar 5, and a perspective arm 6. The lower edge ab of the bar 2 may be set to coincide with the horizon line or one of the existing perspective lines. The zigzag linkage has its one end hinged on a pin 7, the intersecting point of the line ab and the centerline cd of the leg 3, and the other end attached to a pin 9 on the center slider 8 (FIG. 4) which rides on the leg and has side projections to slidably fit into the grooves in the sides of the leg 3. The graduated cross-bar 5 straddles across the leg 3 and has two short slots to receive the two side pins 10 of the zigzag linkage. The two guide posts 14- and 16 on the crossbar 5 are movable and can be held stationary at predetermined distances from the center-line cd by turning the pins and 17 which have threaded portions in the guide posts 14 and 16. The perspective arm 6 has a narrow slot to engage the pins 9 and 15. Movement of the center slider 8 along the leg 3 will cause a movement in the zigzag linkage which in turn drags the cross-bar along the leg. Differential motions of the pins 9 and 15 result in translation as well as rotation of the perspective arm which will point at all times to the intersecting point of the extended line of ab and the centerline of the perspective arm. A light perspective line can now be drawn by pushing down a marking device 3,266,154 Patented August 16, 1966 18 against the spring in its holder 19 on the perspective arm (FIG. 5) while moving the perspective arm guided by the pin 9 and 15, or by moving a marking device in the slot of the perspective arm.

The principle of this invention can be explained as follows: a line skeleton of the homocentrograph of FIG. 2 is shown in FIG. 3 in which A and B represent pins 9 and 15 respectively and P is the right vanishing point VPR. Since the two triangles AGB and ACP are similar, we have But G5 is a multiple of E, i.e. FZ=n1GZ (11:6 in

The foregoing equation indicates that for a fixed distance @E, the perspective lines always intersect the extension line of ab at a distance of n53, independent of the posi tion of the center slider A or the perspective arm AB. Thus, by adjusting the distance 65 of the pin 15 on the cross-bar, one can establish a desired vanishing point outside the drawing area for drawing perspective lines within.

It is quite obvious that if the homocentrograph is moved to a new area and so positioned that the line ab and the center line of the perspective arm coincide with any two of the existing perspective lines, the perspective arm will remain aligned to P (FIG. 3). Also, if the perspective arm is held stationary and the T-section is moved, lines drawn along the lower edge ab of the bar 2 become perspective lines converging toward P. This technique may be used to draw perspective lines close to the horizon line.

To draw perspective lines above the horizon line, a new reference line AB' may be drawn (FIG. 6) which is the mirror image of the perspective line AB with respect to the horizon line. The homocentrograph can now be moved and so positioned so that its line ab and the centerline of the perspective arm coincide with line AB' and the horizon line respectively. On fixing the T-section in this new position, the center slider 8 can be moved to draw new perspective lines.

If the cross-bar 5 in FIG. 2 is placed to engage the two pins 11 on the zigzag linkage 4 and the perspective arm pivoted on the pin 12, the perspective arm can be made to point to the same vanishing point, provided the pin 15 is held at a distance of one fourth of I on the cross-bar (FIG. 3).

To draw perspective lines converging to the left vanishing point (VPL), the perspective arm can simply be switched to have its slot engage the pin 17 on the guide post 16 at a predetermined distance from ca. By properly adjusting, positioning and orientating, the homocentrograph can be used to establish vertical vanishing points or any points of convergence.

To hold the T-section in a fixed position within the drawing area, the bar 2 of the homocentrograph may be fixed directly to the drawing board by using thumb nails in the holes provided in the bar 2 or secured to a drafting machine in a locked-in position. A simple fixture as shown in FIG. 7 may also be used. The U-shaped clamp 20 together with the bar 21 in its provided slot can be fixed onto the drawing 'board 25 by a cap screw 23. The bar 22 can be locked up at any angle with respect to the bar 21 by the cap screw 24. The homocentrograph can thus be held in a fixed position by inserting the two pins 14 in the bar 2 into the holes 26 in the bar 22.

The homocentrograph may also be employed to a great advantage to facilitate the perspective spacings and measurement involving remote vanishing points, the drawing of long shadows of objects cast by a distant light source, locating of unreachable instantaneous centers in graphical kinematic analysis, etc.

In addition to the various applications in graphics, the homocentrograph may as well be used to align cameras, reflectors, etc. mounted on the perspective arm so that they will automatically face the same target object as they are moved.

Although several embodiments of the invention have been illustrated and described, it is to be understood that the invention is not limited thereto. As various changes in the construction, arrangement and applications may be made without departing from the spirit of the invention, as will be apparent to those skilled in the art, reference will be had to the appended claim for a definition of the limits of the invention.

The invention is hereby claimed as follows:

A device for establishing distant points of convergence to facilitate the perspective drawing, graphical analysis, the aligning of moving objects to a designated spot, and etc.; comprising a T-section, a zigzag linkage having one end attached to the intersecting point of the lower edge of the bar of the said T-section and the centerline of its leg and the other end attached to a pin on a center slider to be moved along the said centerline of the said leg, a graduated cross-bar riding on the said leg with slots to receive pins on the said zigzag linkage and having adjustable guide posts held at predetermined distances from the centerline of the said leg, perspective arm having slot to engage pins on the said guide posts and the said center slider, means for drawing perspective lines along the said perspective arm.

No references cited.

LEONARD FORMAN, Primary Examiner.

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