Perspective drafting instrument

Claim 2

A drafting instrument for drawing perspective lines without physically pre-establishing and marking a vanishing point comprising: a carriage; a drawing blade on said carriage providing an edge for drawing said lines; roller means pivotally mounted to said carriage and supporting said carriage for movement along a drawing surface; and control means for adjustably pivoting said roller means such that each point along said drawing blade scribes an arc about a common point as said carriage moves, said drawing blade defining substantially parallel lines in perspective radiating substantially from said common point as a vanishing point as said carriage moves; wherein said roller means comprises axle means pivotably mounted to said carriage and having wheel means rotatably secured thereto, said axle means and said wheel means having different pivot axes, and wherein said control means comprises means for adjustably setting the degree of pivoting of said axle means to selectively set the radius of said arc and the distance of said vanishing point.

Claim 3

The invention according to claim 1 wherein said control means comprises means for moving said blade and scribing an arc selectively about right and left vanishing points comprising first and second stop means for setting clockwise and counterclockwise pivoting of said axle means, and actuator means for selectively pivoting said axle means clockwise and counterclockwise.

Claim 4

The invention according to claim 1 wherein said drawing blade is pivotally mounted to said carriage and operatively coupled to said control means to pivot in response to actuation of the latter.

Claim 5

The invention according to claim 1 wherein said axle means comprises first and second spaced axles each pivotally mounted to said carriage and operatively coupled to said control means and pivoting in opposite directions in response to actuation of said control means, each axle having wheel means at the distal ends thereof.

Claim 6

The invention according to claim 4 wherein said control means is actuatable to pivot said first axle clockwise and said second axle counterclockwise such that said wheel means at right ends of said axles move towards each other and scribe an inner arc about said vanishing point and said wheel means at left ends of said axles move away from each other and scribe an outer arc about said vanishing point.

Claim 7

The invention according to claim 2 wherein said axle means comprises first and second spaced axles each pivotally mounted to said carriage and operatively coupled to said control means and pivoting in opposite directions in response to actuation of said control means, each axle having wheel means at the distal ends thereof, and wherein said axles are pivotally mounted to said carriage between their said distal ends, and said control means is actuatable to a first condition pivoting said first axle clockwise and said second axle counterclockwise such that said wheel means at right ends of said axles move towards each other and scribe an inner arc about a right vanishing point and said wheel means at left ends of said axles move away from each other and scribe an outer arc about said right vanishing point, and said control means is actuatable to a second condition pivoting said first axle counterclockwise and said second axle clockwise such that said wheel means at said left ends of said axles move towards each other and scribe an inner arc about a left vanishing point and said wheel means at said right ends of said axles move away from each other and scribe an outer arc about said left vanishing point.

Claim 8

A drafting instrument for drawing perspective lines without physically pre-establishing and marking a vanishing point comprising: a carriage; a drawing blade on said carriage providing an edge for drawing said lines; a first axle pivotally mounted on said carriage between the distal ends of said first axle and having wheels rotatably mounted at said distal ends; a second axle pivotally mounted on said carriage between the distal ends of said second axle and having wheels rotatably mounted at said last mentioned distal ends; and actuator means movably mounted to said carriage and having a first condition oppositely pivoting said first and second axles at their right ends towards each other, and having a second condition oppositely pivoting said first and second axles at their left ends towards each other.

Claim 9

A drafting instrument for drawing perspective lines without physically pre-establishing and marking a vanishing point comprising: a carriage; a drawing blade on said carriage providing an edge for drawing said lines; a first axle pivotally mounted on said carriage between the distal ends of said first axle and having wheels rotatably mounted at said distal ends; a second axle pivotally mounted on said carriage between the distal ends of said second axle and having wheels rotatably mounted at said last mentioned distal ends; and actuator means movably mounted to said carriage and having a first condition oppositely pivoting said first and second axles at their right ends towards each other, and having a second condition oppositely pivoting said first and second axles at their left ends towards each other.

Claim 10

The invention according to claim 7 wherein said drawing blade and said actuator means are pivotally mounted to said carriage at the same point.

Claim 11

The invention according to claim 7 wherein said first and second axles are pivotally mounted to said carriage at the same point.

Claim 12

The invention according to claim 7 wherein said first axle is connected by a first link to transition means which is connected by a second link to said second axle effecting movement of said second axle oppositely to said first axle, said transition means also being connected by a third link to said drawing blade for pivoting the latter in response to movement of said actuator means transmitted through said first link.

Claim 13

The invention according to claim 10 wherein said transition means comprises first and second spaced connecting rods each pivotally mounted to said carriage between its distal ends and hinge means operatively coupling said rods, said first rod connected on one side of its pivot to said first link and on the other side of its pivot to said hinge means, said second rod connected on one side of its pivot to said second link and on the other side of its pivot to said hinge means, such that said actuator means in said first condition pivots said first axle clockwise which causes said first link to pivot said first rod clockwise which acts through said hinge means to cause said second rod to pivot counterclockwise which causes said second link to pivot said second axle counterclockwise, said hinge means being connected to said third link to pivot said drawing blade clockwise, and such that said actuator means in said second condition pivots said first axle counterclockwise which causes said first link to pivot said first rod counterclockwise which acts through said hinge means to cause said second rod to pivot clockwise which causes said second link to pivot said second axle clockwise, said hinge means through said connection to said third link causing said drawing blade to pivot counterclockwise.

Claim 14

The invention according to claim 11 comprising right and left adjustably movable stops on said carriage, said right stop stopping said clockwise pivoting of said first axle and said counterclockwise pivoting of said second axle to selectively set the arc radius of rolling movement of said wheels along a drawing surface such that each point along said drawing blade scribes a right-hand arc about a common right point as said carriage moves, said drawing blade defining substantially parallel lines in perspective radiating substantially from said common right point as a right vanishing point, movement of said first stop selectively setting the radius of said right-hand arc and the distance of said right vanishing point, said left stop stopping said counterclockwise pivoting of said first axle and said clockwise pivoting of said second axle to selectively set the arc radius of rolling movement of said wheels along a drawing surface such that each point along said drawing blade scribes a left-hand arc about a common left point as said carriage moves, said drawing blade defining substantially parallel lines in perspective radiating substantially from said common left point as a left vanishing point, movement of said second stop selectively setting the radius of said left-hand arc and the distance of said left vanishing point.