US3826007A

US3826007A - Drawing apparatus for perspective views

Info

Publication number: US3826007A
Application number: US00392626A
Authority: US
Inventors: H Senshu; M Koenuma; Y Gibu
Original assignee: Fuji Sokuryoki Seizo KK; SENSHU SEKKEI JIM YK
Current assignee: Fuji Sokuryoki Seizo KK; SENSHU SEKKEI JIM YK
Priority date: 1972-09-02
Filing date: 1973-08-29
Publication date: 1974-07-30
Anticipated expiration: 1991-07-30
Also published as: DE2343820A1; AU6192673A; DE2343820C3; DE2343820B2; AU489674B2

Abstract

A drawing apparatus for preparing perspective views is described herein which includes a mechanism for adjusting the position of a straight edge to draw perspective lines having vanishing points throughout the range of from zero to infinity. In addition, a combination of mechanisms is disclosed for moving the straight edge to various positions on a drawing surface to draw perspective lines having a single vanishing point.

Description

United States Patent [191 Senshu et al. I

DRAWING APPARATUS FOR PERSPECTIVE VIEWS Inventors: Haruzo Senshu; Masao Koenuma,

both of Tokyo; Yoshitaka Gibu, Niiza, all of Japan Assignees: Fuji Sokuryoki Seizo Kabushiki Kaisha; Yugen Kaisha Senshu Sekkei Jimusho, both of Tokyo, Japan Filed: Aug. 29, 1973 Appl. No.: 392,626

Foreign Application Priority Data Sept. 2, I972 Japan 47-l02530 U.S. Cl. 33/77 Int. Cl. B431 13/14 Field of Search 33/77 [11] 3,826,007 1 July 30, 1974 [56] References Cited UNITED STATES PATENTS 2,565,724 8/1951 Foster 33/77 2,854,750 l0/l958 Pirogow 33/77 Primary Examiner-Harry N. Haroian Assistant Examiner-John W. Shepperd Attorney, Agent, or FirmGriffin, Branigan and Butler 5 7] ABSTRACT A drawing apparatus for preparing perspective views is described herein which includes a mechanism for adjusting the position of a straight edge to draw perspective lines having vanishing points throughout the range of from zero to infinity. In addition, a combination of mechanisms is disclosed for moving the straight edge to various positions on a drawing surface to draw perspective lines having a single vanishing point.

5 Claims, 10 Drawing Figures PAIENTEBM 3.826.007

' sum 20? 5 mun-10mm 3.826.007

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KNEE- SHEET 5 [)F 5 DRAWING APPARATUS FOR PERSPECTIVE VIEWS The present invention relates to a universal drawing apparatus for drawing perspective views.

A first object of the invention is to provide a universal drawing apparatus for perspective drawing in which a vanishing point may be freely and easily adjusted from a position of infinity to an extremely near position.

A second object of the invention is to provide a universal drawing apparatus for perspective drawing by which perspective lines may be effectively drawn within a certain range without displacement of the vanishing point and of a head.

A third object of the invention is to provide a universal drawing apparatus for perspective drawing by which perspective lines may be effectively drawn within a certain range without displacement of the vanishing point but with displacement of a head.

A fourth object of the invention is to provide a universal drawing apparatus for perspective drawing by which perspective lines may be effectively drawn beyond said certain range without displacement of the vanishing point but with displacement of a head.

A fifth object of the invention is to provide a universal drawing apparatus for perspective drawing, which is provided with a particular scale graduation to facilitate accomplishment of said fourth object.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings in which reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention in a clear manner.

FIG. I is a schematic plan view illustrating the manner in which a universal drawing apparatus for perspective drawing according to the present invention is used;

FIG. 2 is a plan view illustrating a portion of the universal drawing apparatus of FIG. 1 wherein a head arm and an angle arm have been rotated with respect to an arm holder;

FIG. 3 is a plan view similar to FIG. 2 wherein the head arm and th angle arm are not rotated with respect to the arm holder;

FIG. 4 is a sectional view that is reversed from that taken on line 44 in FIG. 3;

FIG. 5 is a bottom view of a portion of the universal drawing apparatus of FIG. 1 in one phase of operation;

FIG. 6 is a partially schematic view illustrating the principle upon which a drawing apparatus according to the present invention is based.

FIGS. 7 to I0 are schematic views illustrating the manner in which the universal drawing apparatus of the present invention is used. respectively, of which FIG. 7 illustrates the manner in which perspective lines are drawn without displacement of the vanishing point but with linear displacement of a head, FIG. 8 illustrates the general manner in which a range of possibility for drawing perspective lines is effectively enlarged without displacement of the vanishing point, FIG. 9 illustrates the manner in which a scale graduation of the invention is utilized to enlarge a range of possibilityfor drawing perspective lines and FIG. 10 illustrates the principle upon which an apparatus employing principles of the invention is based.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I, a head support 1 comprises a sccured portion Ia (FIG. 3), adapted to be secured at a first end 2 to a movable body B (FIG. I) mounted on a vertical bar A, and an opposite supporting end portion 1b, adapted to support a head shaft 3 (FIG. 4*) in a pivotable manner.

The secured end 2 of the secured portion la has two

screw holes

2a and 2b (FIG. 2) so that said secured end 2 may be engaged with a mounting portion of the movable body B by clamp screws. The vertical bar A is lateraly movable along a transverse bar D (FIG. 1) which is, in turn, fixed along an upper edge of a drawingboard C in a manner such that the vertical bar A may be fixed at any lateral position. The movable body B is vertically movable along the vertical bar A, also in a manner such that the body B may be fixed at any vertical position. With such an arrangement the head support 1 may be positioned to any desired point on the drawing-board C.

The head support 1 is arranged such that the supporting end portion lb thereof may be slightly swung around a pivot 4 with respect to the secured portion 1a, or may be fixed together with the secured portion la through operation of a clamp screw 5a (FIG. 2) and a base line lever 5 so as to finely adjust the position of a base line.

The supporting portion lb has a rotatable sleeve 6 (FIG. 4) with a lower end formed as a flange portion 6a, vertically mounted therein and the head shaft 3 is rotatably held in the sleeve 6. A stop member 7 is fixedly threaded on a threaded portion 6b at the upper end of the sleeve 6, and a depressing piece 9a of an arm handle 9 bears against the upper surface of said stop member 7. A fixing member 8 is also threaded on the threaded portion 6b of the sleeve 6 together with said stop member 7. A head 10 and a head arm 11 (FIGS. 3 and 4) are fixedly mounted on upper and lower ends of the head shaft 3, respectively, and each is rotatable therewith. A plate 10a and nuts 12a and 12b secure the head 10 to the head shaft 3.

A pulley 13 (FIG. 4) is also fixedly mounted on lower end of the head shaft 3 so that the pulley is also rotated in unison with the head shaft 3. The head arm 11 is fixed at the lower end of this pulley 13.

The head shaft 3, between the upper surface of the pulley l3 and the sleeve 6, is provided with a pivotal portion 15a of an arm holder 15. The arm holder 15 has a width and a length substantially corresponding to those of the head support 1. The pivotal portion 15a may be rotated with respect to the head shaft 3 on a bearing 14.

The arm handle 9 is threaded on a clamping member 16, which has an outer thread, and which is fixed to the head shaft 3. As the arm handle 9 is rotated in a direction of clamping, the head shaft 3 is pulled upwarly as seen in FIG. 4 and the pivotal portion 15a of the arm holder 15 is forcibly fixed between the upper surface of the pulley 13 and the flange portion 6a of the sleeve 6.

Thus, the head shaft 3, the head arm 11 and the arm holder are held fixed with respect to one another because the depressing piece 9a of the arm handle 9, the stop member 7 and the sleeve 6 are maintained together relative to the axial movement of said head shaft 3.

From the fact that the sleeve 6 is rotatably mounted on the head support 1; the head shaft 3, the head arm 11 and the arm holder 15 are rotatable relative to the support 1.

A standard protractor 17 (FIGS. 2 and 4) is fixed by a set screw 18 on a rear surface of the supporting portion lb and having a standard graduation along a circumference which is defined by the head shaft 3 as a circle. A second protractor 19 is mounted on the upper surface of the pivotal portion 15a of the arm holder 15 and is positioned in face-to-face contact with the lower surface of said standard protractor 17. The periphery of the protractor 19 has a graduated portion 19a adjacent the standard protractor 17 which hasa graduated indicia 20 on its upper surface, in opposition to a standard graduated indicia 17a (FIG. 2). A zero point of said standard graduated indicia 17a is selected so that, when the head support 1 is normal to the vertical bar A, the zero point is on a line extending through the axis of the head shaft 3 from, and normal to, the vertical bar A. The graduated indicia 20 has its zero point on a position which concides with the zero point of said standard graduated indicia 17a when the arm holder 15, together with the head support 1 is normal to the vertical bar A. With respect to the graduated indicia 20, on each side of the zero point there are angular graduation marks covering ranges of 180 around the head shaft 3 so that each range extends in a direction opposite to the other.

The second protractor 19 is provided with a guide groove 21 (FIG. 4) at a position on which the protractor comes in contact with the standard protractor 17. The guide groove 21 has an inversed-T cross-sectional shape, and is formed along a circumference around the head shaft 3. A lock member 22 identical in its crosssection to that of said guide groove 21, is slidably engaged in said guide groove and is held at a particular position of the standard protractor. Thus, the lock member 22 cannot be rotated but can be vertically moved. A portion of said lock member 22 projecting from an upper surface of the standard protractor 17 is provided with a thread which mates with a clamping screw 23. A lock lever 24 is secured to said clamping screw 23 so that fastening said clamping screw 23 by operation of said lock lever 24 enables both the head support 1 and the arm holder 15 to be fixed in unison relationship while unfastening said clamping screw 23 enables said arm holder 15 to be rotated with respect to said head support 1.

A click member 25 is mounted on the standard protractor 17 and has a ball 25a adapted to be urged under action of a spring against the upper surface of the protractor 19. There are provided indentations on the upper surface of the protractor 19 at predetermined intervals in which said ball 25a is engaged so that the relative positions of the head support 1 and the arm holder 15 may be temporarily determined at a predetermined rotating position of said arm holder 15 relative to the head support 1.

An index support 26 is secured at its lower end by a set screw 27 to the head arm 11, and an index plate 29 is secured by a flush head screw 28 to upper surface of this index support 26. The index plate 29 is located above the second protractor graduated portion 19a of said protractor 19 so that an index hairline 29a thereon may be aligned with the graduated indicia 20. Said index hairline 29a thereby reads an indication on said protractor graduated indicia 20 with which said index hairline 29a is aligned and determines a particular angle of rotation of the head arm 11 relative to the arm holder 15.

A click member 30 (FIG. 4) is fixedly mounted in the index support 26 at a position opposite to a side surface of the protractor 19 so that a ball 30a thereof is urged under action of a spring into engagement in a click groove of said inner side surface; thus, the head arm 11 may be temporarily held at a desired rotational position.

An arm pivot pin 31 is provided at the other end of the. arm holder 15 so that an axis of said pivot pin 31 lies on a line extending along the axis of the head shaft 3 normal to the vertical bar A when the arm holder 15 is normal to said vertical bar A. A pulley 32 is rotatably mounted by bearing 33 on the arm pivot pin 31 and an angle arm 34 (FIGS. 2 and 4) is secured to a lower surface of the pulley 32. The angle arm 34 is held flush with the head arm 11. The pulley 32 is mounted on the arm pivot pin 31 by a mounting member 35.

The pulley 13 on said head shaft 3 and the pulley 32 on the pivot pin 31 are of the same diameter and in a flush relationship. A steel belt 36 extends around these pulleys and is fixed by pins 37a, 37b thereon (see FIG. 5). A pulley 38 is for providing tension and is mounted on a displacement pivot pin 38a. The head arm 11 and the angle arm 34 are always maintained in parallel relationship by the steel belt 36. In this regard, the pulleys l3 and 32 and the steel belt 36 constitute a gearing mechanism through which the head arm 11 is operatively associated with the angle arm 34 with a high precision. Alternately, another measure, such as a timing belt or a gear train, could be employed as a linkage mechanism.

The angle arm 34 has a length which is longer than that of the head arm 11 but shorter than the distance between the head shaft 3 and the pivot pin 31. The angle arm 34 has a central slit 39 (FIG. 2) along which a pin 40 may slide without rotating, said pin 40 being adapted to engage both sides of said slit 39. A part of said pin 40 that projects from an upper surface of the arm 34 is provided with a thread around which a fixed knob 41 is threaded. It is possible through operation of this fixed knob 41 to position and to fix the slidable pin 40 at a desired position along slit 39.

A scale base 42 has a horizontal scale 43 for drawing a perspective line and a vertical scale 44 for drawing a line normal to said perspective line. The horizontal and

vertical scales

43 and 44 are removably mounted by fixed

knobs

45 and 46, respectively, on the respective ends of the scale base 42, in the manner of prior art. The scale base 42 is rotatably supported by a pivot pin 48 through a bearing 47 in an end of the head arm 11. The pivot pin is located on an extension of a perspective line which is defined by a line drawn along the horizontal scale 43. The scale base 42 is provided at its rear end with a guide slit 49 so that an extension of said perspective line P longitudinally extends along a central line of the slit 49.

A slide member 40a (FIG. 4), mounted on a lower portion of the slidable pin 40 associated with said angle arm 34, is rotatably and slidably engaged with the guide slit 49 so that the axis of the slidable pin 40 always lies on an extension of the perspective line P. The guide slit 49, as seen from FIG. 5, is defined by slit frames 50a and 50b which are originally adjustably mounted onto the scale base 42. The frames 50a and 50b may be adjusted mainly to accomplish alignment of the slidable pin 40 with the perspective line P during manufacturing process. The slide slit 39 of the angle arm 34 is provided with an angle graduation indicia 51 (FIG. 2) corresponding to an angle 9, established by the perspective line P with respect to a base line h extending from an axis O (FIG. 6) of the head shaft 3 to the axis 0 of the arm pivot 31 when the head arm 11 and the angle arm 34 are normal to said base line h. The slidable pin 40 is provided with an index mark 52 for reading a position along the angle graduation indicia 51.

The principle on which the universal drawing apparatus of this invention operates will be described with reference to FIG. 10, in which there are shown a first circle, defined by a center 0 and a radius R, and a second circle, defined by a center 0 and a radius r, displaced from each other by a distance I. A line P passing through the ends A and B of the radii R and r, respectively, which are parallel to each other, intersects the base line h passing thrggh tl i e two centers 0,, 0 at a point V. In this case, V0 VO r R since yo Bfi homolo oust oAVO A From the fact that V0 V2 ,O l said proportional relationship V0 V0, V0 (V0 +1 r R and therefore The point V corresponds to a vanishing point which is determined by values of r, R and l, and a ccordingle the line P corresponds to a perspective line passing said vanishing point V when r and R and l are maintained constant and the radii r and R are kept parallel to each other. It is assumed in FIG. 10 that said vanishing point V corresponds to a point on which a tangent line P common to the two circles intersects tl i e base line h. When the values of r and R are equal V0 will be infinitely great and the perspective line P will be parallel to the base line h.

In operation, the head support 1 (FIG. 1) is fixed on the movable body B (FIG. 3) of the vertical bar A and the arm holder (FIGS. 1 and 4) is fixed on said head support 1 through operation of the lock lever 24 in the manner that the zero point of the graduated indicia (FIG. 2) on the protractor l9 coincides with the zero on the standard graduated indicia 17a on the standard protractor 17. The arm handle 9 (FIG. 4) is unfastened so as to rotate the head 10 and the attached head shaft 3. The pulley 13, being fixed on the head shaft 3, and the pulley 32, being fixed on the arm pivot pin 31 are rotated in a synchronous manner by the steel belt 36 and consequently the angle arm 34, which is fixed on the pulley 32 is rotated and maintained parallel to the head arm 11.

The pivot pin 48 (FIG. 6) of the head arm 11 and the slidable pin 40 are rotated at predetermined distances from the head shaft 3 and the pivot pin 31, respectively. The horizontal scale 43, lying on'a line which passes the axes of the pivot pin 48 and the slidable pin 40, therefore, draws the perspective line P. Thus, the horizontal scale 43 is moved along any one of straight lines which intersect the base line h at the vanishing point (i.e., the perspective lines P). The vanishing point V may be displaced as the case demands by displacement of the slidable pin 40 along the slide slit 39 of the angle arm 34 so as to vary the rotating radium thereof.

A position of the vanishing point V may be easily obtained from the theoretical formula as aforementioned, since the rotating radium R of the head arm 11, the rotating radius r of the slidable pin 40 of the angle arm 34 and the distance 1 between the two arms are known.

To displace the head 10 with respect to the drawingboard C along the direction of the base line h without displacement of the vanishing point V, the head 10 may be displaced by a desired distance, then the slidable pin 40 of the angle arm 34 may be displaced by operation of the fixed knob 41 (FIG. 2) with respect to any optional one of the perspective lines P which have already been drawn prior to this displacement and the two

arms

11, 34 are so rotated by the head 10 that the horizontal scale 43 draws said particular perspective line P, as shown in FIG. 7.

The range within which the perspective lines P may be drawn without displacement of the vanishing point V with the head 10 being at a predetermined position is limited, as shown by FIG. 8, to the range as defined by the head arm 11 which has been rotated around said head 10 by with respect to the base line h. This effective range is indicated by an angle t, around the vanishing point V.

To draw a perspective line on an upper or lower area of the drawing-board C, the base line h of the head itself is displaced around the vanishing point V just onto another base line, for example, as indicated by h With such a method wherein the head itself is rotated for displacement, the head arm 11 is rotated upward from the original position of the base line h by a predetermined angle, for example, by 90, and then a perspective line is drawn, on which line a desired position of the graduation on the horizontal scale 43 is plotted. Then, said head arm 11 is rotated downward by said predetermined angle (i.e., 90) from said base line h and thereafter said head arm 11 is fixed by fastening the arm handle 9 with respect to the arm holder 15. Now, the lock lever 24 is unfastened so that said arm holder 15 is rendered rotatable around the head shaft 3 relative to the head support 1 and then the vertical bar A is displaced relative to the transverse bar D so that the horizontal scale 43 angularly coincides with said perspective line which has been previously drawn. Then, the head support 1 and the arm holder 15 are fixed by operation of the lock lever 24 with the graduation being set to the plotted point. On this time point, the base line of the head itself has been displaced to the position of h as shown by FIG. 8. Accordingly, the head 10 is rotated by unfastening the arm handle 11 and thereby the horizontal scale 43 may draw perspective lines around the vanishing point V within the range as indicated by the angle The head itself may be further rotated for displacement upward or downward in the same manner as above mentioned.

The arm holder is fixed by operation of the lock lever 24 at a desired regular position with respect to the head support 1, as aforementioned, and thereby a perspective line may be drawn on the drawing-board C in association with a base line in a desired direction.

The horizontal scale 43 of the universal scale head according to the present invention is, on the other hand, provided with a special graduation 53 (FIG. 3) for displacement; and serves to facilitate the operation of displacement of a position on which the base line of the head itself lies. This operation is intended for enlargement of the range within which perspective lines may be effectively drawn without displacement of the vanishing point V. As shown by FIG. 6, the index mark 52 on the slidable pin 40 is aligned with an angle 0 of the angle arm 34 on the angle graduation 51 when the head arm 11 and the angle arm 34 are normal to the base line h and the perspective line P intersects the base line h at the angle 0 on the vanishing point V. Under the situation that the head arm 11 has been clockwise rotated by 90 so that the perspective line of point A. When a point M QIG. 6) is selected on the scale 43 so that a distance VM from the vzgishing point V to this point M is equal to a distance VA fro rn s aid wishing point V to said point A, a relation BM VA(l cos 0) is established. Assume here that a line passing through the point A normal to the perspective line P intersects the base line on a point C (FIG. 6), a

relation VA AB AC/BC is established and VA is obtained from this relation even in the case that the vanishing point V is out of the drawing-board aid BM is determined by the relationship between VA and 0. Considering the fact that, the angle Q91 the angle arm 34 is varied, the particular distance BM is correspondingly determined, there may be provided on the horizontal scale 43 as a graduation 53 which bears thereon a series of the points M based on the standard point B. Assume that a perspective line P (FIG. 6) is obtained at the angle 0' when the vanishing point V lies on right hand side as seen in FIG. 6, points A, C' correspond to said pgints C and a point M as defined by the relation V 'A' V'M occupies a position which is symmetrical to the point M with respect to the standard point B. Here again a relation similar to that as previously mentioned, namely,

B'M V'A' (l -cos0') VIK! A! B! AICI/BIG'I is established. Thus, the graduation 53 is provided which bears a series of the points M corresponding to the particular angles 0' of the angle arm based on the standard point B. The graduation 53 for displacement on the horizontal scale 43 is accomplished by an arrangement such that the standard point B corresponds to the zero point of the graduation 51 and the points M, M correspond to 0, 0' on said graduation 51.

The aforegoing description has been made in reference to the case wherein angles 0, 0' of the angle arm 34 given on the

graduations

51 and 53, respectively,

are established by a perspective line P with respect to a base line h when the head arm 11 and the angle arm 34 are normal to the base line h. However, the relation as above mentioned is valid even in the event that 6, 0 are based on any position at which said

arms

11, 34 are not normal to the base line h. However, it should be noted here that the extent to which a possibility to draw perspective lines may be enlarged is reduced in comparison to the event when said

arms

11 and 34 are normal to the base line h.

The vertical scale 44 is mounted on a position at which said scale 44 can draw lines passing the standard point B of the horizontal scale 43.

When the horizontal scale. 43 is provided with the graduation 53 for displacement of such an arrangement as aforementioned, the range within which the perspective lines P can be drawn through rotation of the head 10 by around the base line it of the arm holder 15 when said base line lies on the position h (FIG. 9) is defined by an angle [.1 as shown by FIG. 9. To enlarge said range to by displacement of the horizontal scale 43 to the position of the base line k the head 10 is rotated upward by 90 around the base line h, and thereafter a perspective line is drawn, then said head 10 is clockwise rotated by 90 so that the horizontal scale 43 coincides with said base line h,. The point A is established by a line normal to the standard point B of the graduation 53 for displacement (said line to be drawn by the vertical scale 44) which intersects said perspective line h 2 and is plotted on the drawing-board. Subsequently, the

arms

11 and 34 and the arm holder 15 are fixed by fastening the arm handle 9. The arm holder 15 is then rendered rotatable relative to the head support 1 by unfastening the lock lever 24, and the vertical bar A as well as the movable body are displaced so that the point M on the graduation 53 for displacement, which corresponds to the angle 0 of the angle arm 34, (which is, in turn, determined by the position of the slidable pin 40 relative to the graduation indicia 51) coincides with said plotted point A. Meanwhile, the horizontal scale 43 coincides with the perspective line resulting in the arm holder 15 coming onto the new base line h. The arm holder 15 is fixed by fastening the lock lever 24 whereby the vertical bar A and the movable body B are fixed and thereafter the head 10 is rotated so that the horizontal scale 43 can draw perspective lines within the range as defined by the angle 0 with respect to the vanishing point V. Th i may be easily supported by the fact that the relation VM =VA is established in connection with the point M selected on the graduation 53 for displacement.

With the universal drawing apparatus for perspective drawing, according to the present invention, as obviously understood from the aforegoing description, the head arm 11 and the angle arm 34 may be rotated by operation of the head 10 after the arm holder 15 has been fixed at an appropriate position with respect to the head support 1, to draw perspective lines converging on the same vanishing point. The position of the slidable pin 40 may be adjusted along the slide slit 39 of the angle arm 34 to shift the position of the vanishing point from infinity to an extremely near position. Furthermore, from the fact that the arm holder 15 may be rotated relative to the head support 1, it is possible to enlarge the range within which perspective lines passing the same vanishing point can be drawn as well as to draw perspective lines havingv base lines in desired di rections relative to the drawing-board.

Still furthermore, there is provided the graduation for displacementon the scale which is used to draw perspective lines, so that it is possible to enlarge the range within which the perspective lines passing the same vanishing point can be drawn.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A drawing apparatus for perspective drawing comprising:

a straight edge support assembly means for supporting a straight edge and for allowing said straight edge to be moved in first and second orthogonal directions;

a head shaft rotatably mounted in said straight edge support assembly means;

a head arm mounted on the lower end of said head shaft;

an elongated arm holder mounted on said head shaft;

an elongated angle arm rotatably mounted on said elongated arm holder at a pivot pin spaced from said head shaft along said elongated arm holder;

a linking mechanism for interconnecting said head arm and said angle arm so as to rotate these members together and maintain them in a parallel relationship;

a straight edge base pivotally mounted on said head arm and said angle arm, said base also being longitudinally movable to various positions along said angle arm;

a horizontal straight edge fixedly mounted on said.

straight edge base along which straight perspective lines may be drawn.

2. A drawing apparatus as claimed in claim 1 wherein said straight edge support assembly means includes first and second orthogonally situated bar means, said straight edge being movable along said first bar in a first orthogonal direction and said first bar being movable along said second bar in a second orthogonal direction.

3. A drawing apparatus for perspective drawings as claimed in claim 1 wherein:

a head grip is attached at the upper end of said head shaft for allowing said shaft to be manually rotated;

said elongated arm holder is rotatably mounted on said head shaft;

is further included an arm-holder locking means for selectively locking and unlocking said arm holder against and for rotation relative to said head support;

is further included a head-arm locking means for selectively locking and unlocking said head arm and said arm holder against and for relative rotation.

4. A drawing apparatus as claimed in claim I wherein:

said horizontal straight edge is provided with longitudinally oriented graduation indicia for displacement which has thereon a series of marks M and a single standard mark B;

said angle arm is provided with longitudinally spaced graduation indicia which has thereon a series of angle marks 0, said angle marks 0 displaying the position of said base along said angle arm, and each of said marks M on said horizontal straight edge corresponds to an angle mark 6 on said angle arm;

a vertical straight edge mounted on said base perpendicular to said horizontal straight edge, and defining a vertical line which intersects said horizontal straight edge at said standard mark B;

wherein, when said drawing apparatus is set to draw a first range of perspective lines about a first base line, which is a straight line passing through the axes of said head shaft and said pivot pin, perspective lines, defined by said horizontal straight edge, intersect said base line at a vanishing point V, a particular angle mark 0 is indicated along said angle arm, corresponding to a particular mark M along said horizontal straight edge, and a point A is the intersection of said vertical line and said perspective line when said head arm and said angle arm are in a position at which the base line coincides with the horizontal straight edge, it is desired to move the elongated arm holder to a second base line position at which a second range of perspective lines can be drawn having the same vanishing point V as said first range of perspective lines, said elongated arm holder is rotated so that said new base line corresponds to said particular perspective line and said point M on said horizontal straight edge corresponds to said point A on said perspective line.

5. A drawing apparatus as claimed in claim 4 wherein the marks M are set with respect to the standard mark B t the horizo ntal sgaight edge so that a relation VA VM and BM VA" (1 c050) may be established where VA is a distangiaetween the vanishing point V and the point A, and VM is a distance b tween the vanishing point V and the point M, and BM is a distance between the point B and the point M, and 6 in the angle of the straight edge with respect to the first base line when the head arm and the angle arm are at to the elongated arm holder.

Claims

1. A drawing apparatus for perspective drawing comprising: a straight edge support assembly means for supporting a straight edge and for allowing said straight edge to be moved in first and second orthogonal directions; a head shaft rotatably mounted in said straight edge support assembly means; a head arm mounted on the lower end of said head shaft; an elongated arm holder mounted on said head shaft; an elongated angle arm rotatably mounted on said elongated arm holder at a pivot pin spaced from said head shaft along said elongated arm holder; a linking mechanism for interconnecting said head arm and said angle arm so as to rotate these members together and maintain them in a parallel relationship; a straight edge base pivotally mounted on said head arm and said angle arm, said base also being longitudinally movable to various positions along said angle arm; a horizontal straight edge fixedly mounted on said straight edge base along which straight perspective lines may be drawn.

3. A drawing apparatus for perspective drawings as claimed in claim 1 wherein: a head grip is attached at the upper end of said head shaft for allowing said shaft to be manually rotated; said elongated arm holder is rotatably mounted on said head shaft; is further included an arm-holder locking means for selectively locking and unlocking said arm holder against and for rotation relative to said head support; is further included a head-arm locking means for selectively locking and unlocking said head arm and said arm holder against and for relative rotation.

4. A drawing apparatus as claimed in claim 1 wherein: said horizontal straight edge is provided with longitudinally oriented graduation indicia for displacement which has thereon a series of marks M and a single standard mark B; said angle arm is provided with longitudinally spaced graduation indicia which has thereon a series of angle marks theta , said angle marks theta displaying the position of said base along said angle arm, and each of said marks M on said horizontal straight edge corresponds to an angle mark theta on said angle arm; a vertical straight edge mounted on said base perpendicular to said horizontal straight edge, and defining a vertical line which intersects said horizontal straight edge at said standard mark B; wherein, when said drawing apparatus is set to draw a first range of perspective lines about a first base line, which is a straight line passing through the axes of said head shaft and said pivot pin, perspective lines, defined by said horizontal straight edge, intersect said base line at a vanishing point V, a particular angle mark theta is indicated along said angle arm, corresponding to a particular mark M along said horizontal straight edge, and a point A is the intersection of said vertical line and said perspective line when said head arm and said angle arm are in a position at which the base line coincides with the horizontal straight edge, it is desired to move the elongated arm holder to a second base line position at which a second range of perspective lines can be drawn having the same vanishing point V as said first range of perspective lines, said elongated arm holder is rotated so that said new base line corresponds to said particular perspective line and said point M on said horizontal straight edge corresponds to said point A on said perspective line.

5. A drawing apparatus as claimed in claim 4 wherein the marks M are set with respect to the standard mark B on the horizontal straight edge so that a relation ''''VA VM'''' and ''''BM VA'''' (1 -cos theta ) may be established where VA is a distance between the vanishing point V and the point A, and VM is a distance between the vanishing point V and the point M, and BM is a distance between the point B and the point M, and theta in the angle of the straight edge with respect to the first base line when the head arm and the angle arm are at 90* to the elongated arm holder.