US2524642A - Drafting instrument - Google Patents

Description

Oct. 3, 1950 p, VANET DRAFTING INSTRUMENT Filed Feb. 20. 1948 INVEN TOR.

Patented Oct. 3, 1950 DPJAFTING INSTRUMENT Paul Vanet, Le Vesinet, France, assignor to La Cellophane, Paris, France, a Fr'enclr company Application February 20, 1948, Serial N 0. 9,650 In France May 17, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires May 17, 1963 1 Claim. 1

The present invention relates to an improvement in drafting instruments as commonly employed in drafting rooms, which comprises a system of jointed ,parallelograms permitting a head carrying two rules at right angles which remain constantly parallel to themselves, to be displaced over the entire surface of a drawing board.

The invention will be better understood from the following desciption and explanation, referring to the accompanying drawing wherein:

Fig. 1 is a schematic top plan view of the general arrangement of a drafting instrument embodying the invention;

Fig. 2 is an elevation showing the essential features of the instrument; and

Fig. 3 is a top plan view thereof.

As will be seen from Fig. 1, drafting instruments of the type in question consist essentially of an arrangement of rigid rods. On a bracket A, secured by screws a to the drawing board (shown dotted), two parallel rods BB are pivoted at b and D The rods are similarly pivoted at their opposite ends to a plate C at c and c Two further rods DD are pivoted at d and d to the plate C, and in turn support a bracket E pivoted at e and e This bracket E serves to support a head such as that described in French Patent No. 872,341 of January 15, 1941.

The system of pivots b-b and cc and the system of pivots d-d and ee each form a parallelogram, permitting the bracket E and the rules'attached thereto (schematically shown dotallelograms, which in consequence cease to afford a strictly parallel displacement of the rules'attached to the bracket E. This deformation is particularly marked when the drawing board is disposed horizontally, or nearly so.

The object of the invention is to counteract this deformation and to assure accurate operation of the drafting instrument regardless of the position of the plate C, whether outside of the drawing board or in contact with the same. This result is obtained by means of a device, one form of which is shown in Figs. 2 and 3.

On the bracket A secured to the drawing board, there is mounted a shaft F, preferably located at the midpoint of the distance b -b This shaft carries a concentric sleeve G to which is attached a ring H movable about an imaginary axis Which is determined by two adjustable setscrews J-J,

which however, do not prevent sleeve G from turning freely on the shaft F. Ball bearings may be provided if necessary. The ring H is provided with a lug K carrying a screw L with the end of its shank bearing upon the sleeve G. In the opposite direction from the lug K, the ring H carries a rod M of suitable length and cross section, preferably flexible, whose tip engages a pin N attached to the plate C at the point of intersection of the line c-c and d-d It will be obvious that when the screw L is tightened, the rod M will pivot about the set screws J, thus raising its end 0 and lifting the plate 0, this motion naturally counteracting the deformation due to the weight of the assembly of rods forming the two joined parallelograms. If the plate C is in contact with the drawing board, its pressure on the board is reduced and may even be entirely eliminated by suitable adjustment of the screw L, thus diminishing or eliminating the friction of that part upon the board.

It is understood that the embodiment of the invention described above is given only by way of example, and that various modifications in design or in detail may be made without departing from the scope of the invention.

Thus in particular, the positions of the pivots F and N may be modified to the extent of simply locating these at two points forming a parallelogram with 11-0. The rod M may also be provided with an extensible portion or a crotch of suitable length permitting the fork O to follow the pivot N throughout all its displacements in which event the pivot points may be displaced from the pivots of the parallelogram.

Likewise, the motion resulting from manipulating the screw L may, be produced by any other mechanical arrangement provided always that the motion obtained permits the application to the plate C or a neighboring portion of the drafting instrument of a force tending to reduce or entirely eliminate the eifect of its weight, this being the essential characteristic of the invention.

What is claimed is:

In a drafting instrument for a drawing board, a bracket to be attached to the board, a plate, a pair of parallel links pivoted to said bracket and said plate to form a parallelogram, a head articulated to said plate for parallel movement over the drawing board, a vertical pin fixed to said bracket at a point centered between the pivot points of said links, a sleeve journalled to rotate thereon, a ring, means pivoting said ring to said sleeve to rotate therewith about the axis of said pin and to pivot on' said sleev about a horizontal axis, and a rod attached to said ring in cantilever relationship and connected at its free end to said plate at a point centered between the pivot points of said links to rigidify the assembly and support said plate, a vertical arm extending upwardly on said ring along said sleeve on the side opposite said plate, and an adjusting screw carried by said arm and bearing against said sleeve for pivotally adjusting said ring and rod to thereby adjust the elevation of said head on said board.

PAUL VANET.

REFERENCES CITED The following references are of record in th file of this patent:

UNITED STATES PATENTS Number Name Date 1,421,921 Doerr July 4, 1922 1,633,629 Fortin June 28, 1927 2,019,473 Anton Nov. 5, 1935 10 2,136,140 Langaner Nov. 8, 1938

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