This invention relates to drafting boards and more particularly to a cord mounted straightedge assembly in proper movable position on a drafting board.
In the prior art, portable drafting boards have moveable straightedges that maintain a fairly good parallel orientation as the straightedge moved up and down the drafting board. However, the mechanisms for maintaining parallel orientation of the straightedge as is it moved have limited compensation for any error on the left side of the drafting board to the right side of the board to maintain the straightedge parallel to previous positions as it is moved.
A straightedge drafting boards is described that is simple in design but has the ability to maintain a straightedge mounted on the drafting board in continuous parallel orientation as the straightedge is moved up and down the board.
To provide for this compensation a single cord is connected between the left and right side edges of the drafting board and the left and right ends of the straightedge are connected to this cord. Any position of the single cord and the left end of the straightedge connected thereto along the left side of the drafting board is reflected via the single cord to the position of the single cord along the right side of the drafting board. This better maintains the straightedge mounted on the drafting board in continuous parallel orientation as the straightedge is moved up and down the board.
The invention will be better understood upon reading the following Detailed Description in conjunction with the drawing in which:
In
In
Straightedge 25 is made of extruded and machined aluminum and a novel control element 17a attached to the left end and control element 17b attached to the right end thereof. Control elements 17a and 17b includes other elements that are shown in and described with reference to
There is also rod elevation piece 20 that is made of rigid steel rod so it will not easily bend. Rod elevation piece 20 is formed in a closed loop as shown and handle 12 firmly attached to the middle of the top of the loop as shown. A piece of the loop of elevation piece 20 passes through snap lock mechanisms 21a and 21b as shown, where it is held by a cover. The snap lock mechanisms 21a and 21b are each fastened to the underside of board 11 where shown. Attached to the lower corners of closed loop rod 20 are feet 13a and 13b which provide friction preventing or limiting movement of drafting board 10 when it is set up on a table or other surface. Snap locks 21a and 21b are better shown in and described with reference to
In each of the four corners of board 11 is fastened a wire guide 15a, 15b, 15c, 15d, each wire guide consisting of a plate with a small pulley attached thereto. The axis of the shaft on which the pulleys are mounted extends downward from and perpendicular to board 11. There is also another, different wire guide 19 fastened to the bottom center of board 11. More particularly, each wire guide fits over one of the corner edges of board 11 before it is fastened to the underside of the board.
There is a piece of wire cable 16 that is passed around wire guides 15a-15d in the corners of board 11 and through wire guide 19 in an “X” pattern as shown in
The two ends of wire 16 are shown fastened together and centered above wire guide 19 but they may off to one side of the wire guide. The two ends of wire 16 are then fastened to the two ends of a stretched spring 18. To do this one end of wire 16 is attached to a first end of spring 18 using an eyelet (not shown). The other end of wire 16 also has an eyelet (not shown) attached thereto. Spring 18 is stretched approximately 1 inch beyond its un-stretched length and the eyelet attached to the other end of wire 16 is attached to the other end of spring 18. More particularly, in
Wire 16 is positioned on and fastened to novel control elements 17a and 17b on the edges of board 11 as shown in
In
Brake knob 23 on the side edge of control element 17 has a knurled outer end that is turned by hand, and an inner end to which is affixed a brake pad 24 adjacent to board 11. When straightedge 25 with control elements 17a and 17b attached thereto is mounted on a board 11 the side bracket 27 of both control elements are adjusted and tightened to have room for the two brake knobs 23 to be turned both in and out, and then the two top adjustment knobs 26 are locked.
To lock the loop of wire 16 to each control element 17 wire capture screw 28 is utilized. As shown in
Brake knob 23 is mounted through the side wall of side bracket 27 and on its inner end is a brake pad 24 that rests against the side wall of board 11. More particularly, pad 24 of brake knob 23 of control element 17a rests against the left side of board 11 as seen in
When straightedge 25 is located at a desired position on top of board 11 the left and right side brake knobs 23a and 23b are turned inward to push their brake pads 24 against the sides of board 11 and thereby lock straightedge 25 at the desired position on board 11. When it is desired to move straightedge 25 up or down board 11 to a new position the two brake knobs are unscrewed a small amount to back off the brake pads 24 and thereby unlock the straightedge. Straightedge 25 is then slid up or down board 11 to a new position and the two brake knobs 23 are then turned inward to again push their brake pads 24 against the sides of board 11 and thereby lock straightedge 25 at the new position.
In
Looped rod 20 passes through the two snap locks 21a and 21b and as rod 20 is rotated between its flat position against the bottom off board 11 and its upright position extending away from board 11 it rotates approximately ninety degrees in snap locks 21a and 21b. Snap locks 21a and 21b pinch rod 20 to lock it in whatever of the two positions selected by a user of drafting board 10. The locking and unlocking is accomplished by locking levers 22. The locked and unlocked position of locking levers 22 is shown in
With the locking levers of 22a and 22b of the snap locks 21a and 21b in their unlock position looped rod 20 can be rotated within the two snap locks 21a and 21b between the position against board 11 (
When it is desired to rotate looped rod 20 up against the bottom of board 11 to store the board, the locking levers 22a and 22b are moved as shown in
In each of the four corners of board 11 is fastened a wire guide 15a, 15b, 15c, 15d, each wire guide consisting of a plate with a small pulley attached thereto. The axis of the shaft on which the pulleys are mounted extends downward from and perpendicular to board 11. There is also another, different wire guide 19 fastened to the bottom center of board 11. More particularly, each wire guide fits over one of the corner edges of board 11 before it is fastened to the underside of the board.
What has been described herein is a preferred embodiment of the invention but those skilled in the art will recognize that numerous changes may be made without departing from the spirit and scope of the invention.
This utility patent application claims benefit under U.S. Provisional Patent Application No. 61/597,968, entitled “Parallel Straightedge Drafting Board”, filed on Feb. 13, 2012.
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Number | Date | Country | |
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61597968 | Feb 2012 | US |