US644184A - Combined centrolinead and parallel-rule. - Google Patents

Description

No. 644,|84. Patented Feb. 27, I900. G. McMULLEN.

COMBINED CENTROLINEAD AND PARALLEL RULE.

(Application filed June 16, 1899.)

(No Model.)

I W- z NITED STATES PATENT rrrc.

COMBINED CENTROLINEAD AND PARALLEL-RULE.

SPECIFICATION forming part of Letters Fatent No. 644,184, datedFebruary 27, 1900. Application filed June 16, 1899. Serial No. 720,792. (No model.)

To all whom it may concern:

Be it known that I, GEORGE MOMULLEN, a subject of the Queen of Great Britain and Ireland, residing at Perth,inthe' Colony of Western Australia, have invented an Improved Instrument for Use in Preparing Perspective or other Drawings, (in respect whereof I have applied for a patent in Great Britain to bear date February 4,1899, No. 2,578, and in Germany on February 11, 1899, No. M. 16,395,) of which the following is a specification.

This invention relates to improved means for use in preparing perspective and geomet rical drawings, its object being to provide an instrument whereby centrolineads may be produced with sufficient accuracy for the purpose of perspective drawing and which may be readily adapted for use in drawing parallel lines. Centrolineads are open to objection, as they are not easily or conveniently adapted for the purpose intended and are not capable of being readily adjusted for preparing drawings in perspective on a large or small scale. These objections are obviated in the improved apparatus hereinafter described. Theinstrument may be constructed of metal or other suitable material.

In the accompanying drawings, Figure 1 is a plan of the instrument complete. Fig. 2 is an elevation. Figs. 3 and 4 are transverse sections taken, respectively, on the lines 00 m and y y, Fig. 1. Fig. 5 is a transverse section taken on the line a 2, Fig. 1.

The blade A has its outer or working edge beveled or chamfered and is connected to the blade B by means of slotted links 0 and D, whereof the extremities work on pivots c d c d. The pivots c and at are carried by tongued slides ct b, which Work in slots adapted for their reception formed in the blades A and B. The respective pivots c and d are fixtures in the blades A and B. The links 0 and D, besides being arranged to pivot at their extremities, are also furnished with an adjustable pivot E, carried by the tongued slide F, the latter working in the grooved slot in the link D. The pivot E passes through another tongued slide F, which is capable of being moved along the grooved slot in the link 0 by means of the screw G, the latter being furnished with a milled turning-nut G.

The tongued slide F passes freely along the screw H and may be secured in position thereon by the nuts H H. For determining the radius of any circle desired and the angle of any perspective required the link 0 is marked with the respective distances of the center of the circle from a point in the center of the blade A, and when the pivot E is brought opposite this figured distance and the blade B held stationary converging or approximately converging lines may be produced along the blade A. Thus perspective or convergent lines may be drawn with approximate accuracy, such lines apparently converging to a long and inaccessible vanishing point. As an illustration, if the link is set at nine feet and the pivot is fixed there the lines which are drawn along the blade A will converge approximately to the center of a circle having a radius of nine feet, and so with any other measurements to which the pivot may be fixed. When the pivot E is fixed in the center of the link C, as shown, the lines drawn along the blade A willbe parallel. The improved centrolinead can thus be readily adjusted to serve as a parallel-rule, such rule being capable of doing the work straightforwardly instead of in the manner achieved by parallel-rules of the usual construction. This will be found a great advantage. The instrument may also be used for doing the work of an ordinary T-square.

I is a fixing-piece whereby the instrument may be secured to a drawing-board or other surface, the bladeB being hinged to the said fixing-piece at K. I I are screws for adjusting the angle of inclination of the blade B. All the pivots are provided with nuts.

What I claim as my invention, and desire to secure by Letters Patent, is-

1. An instrument for use in preparing perspective and other drawings comprising a pair of blades connected by crossed links each attached at one end by a fixed pivot and at the other end by a sliding pivot to the respective blades and slotted for the greater portion of its length for the reception of a slide and adjustable pivot whereby the instrument is rendered available for drawing either radial or parallel lines; one of the blades being provided with a working edge and the other with means for attaching the instrument to a drawing-board, substantially as herein described. v

2. In an instrument for use in preparing 5 perspective and other drawings the combination with a pair of blades connected by diagonally-pivoted slotted plates, whereof one is provided with the graduated scale C, of the tongued slides F F and screws G and H, sub- 10 stantially as and for the purpose specified.

In an instrument for use in preparing perspective drawing and for drawing parallel lines, the combination, with the blades A, B, of the slotted links 0, D, the pivots c, c, d, d, 15 the tongued slides a, b, the adjustable pivot

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