Parallel straightedge drafting board

A portable, parallel straightedge drafting board is disclosed which utilizes a unique wire arrangement with control locks attached thereto to achieve a movable straightedge that will always be parallel to itself when moved during use of the drafting board.

FIELD OF THE INVENTION

This invention relates to drafting boards and more particularly to a cord mounted straightedge assembly in proper movable position on a drafting board.

BACKGROUND OF THE INVENTION

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.

SUMMARY OF THE INVENTION

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.

DETAILED DESCRIPTION

InFIG. 1is a perspective view of the drafting board assembly10when it is set up for use. Board assembly10comprises a flat board11having a carrying handle12that used to both carry board assembly10, and also to rotate a rod elevation piece20from a position folded up against the bottom of board11, as shown inFIG. 2, to the extended position as shown inFIG. 1. Handle12is firmly fixed to rod elevation piece20. On the bottom corners of rod elevation piece20are feet13aand13b, one toward each side of the board11. In their extended position, as shown inFIG. 1, rod elevation piece20is locked in its extended position by two snap lock mechanisms21(not shown inFIG. 1) on the bottom of board11. Snap lock mechanisms21are shown in and described with reference toFIGS. 2 and 4.

InFIG. 1are shown pulley15ain the upper left of drafting board assembly10and pulley15bin the lower left corner of board11. There is a duplicate pulley15c(not shown inFIG. 1but shown inFIG. 2) in the upper right corner of drafting board assembly10and another pulley15d(also not shown inFIG. 1but shown inFIG. 2) in the lower right corner of board11. The pulleys15a-15dare described in greater detail with reference toFIG. 2. Also shown is straightedge25which can slid up and down board11and remain parallel to all previous positions of straightedge25. When in a particular, desired position straightedge25is locked in that position using edge locks of control elements17aand17bwhich are shown in and described in greater detail with reference toFIG. 3.

Straightedge25is made of extruded and machined aluminum and a novel control element17aattached to the left end and control element17battached to the right end thereof. Control elements17aand17bincludes other elements that are shown in and described with reference toFIG. 3. Control element17ais mounted on the left edge of board11and control element17bis mounted on the right edge of board11. On control element17ais shown a brake knob23aand a top adjustment knob26a, and on control element17bis shown a brake knob23band a top adjustment knob26b. The function of the knobs are described with reference toFIG. 3.

FIG. 2shows a bottom view of the drafting board10showing how a single cord16is routed around the edges of board11and is connected to either end of straightedge25(not seen in this Figure) by control elements17aand17b.

There is also rod elevation piece20that is made of rigid steel rod so it will not easily bend. Rod elevation piece20is formed in a closed loop as shown and handle12firmly attached to the middle of the top of the loop as shown. A piece of the loop of elevation piece20passes through snap lock mechanisms21aand21bas shown, where it is held by a cover. The snap lock mechanisms21aand21bare each fastened to the underside of board11where shown. Attached to the lower corners of closed loop rod20are feet13aand13bwhich provide friction preventing or limiting movement of drafting board10when it is set up on a table or other surface. Snap locks21aand21bare better shown in and described with reference toFIG. 4.

In each of the four corners of board11is fastened a wire guide15a,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 board11. There is also another, different wire guide19fastened to the bottom center of board11. More particularly, each wire guide fits over one of the corner edges of board11before it is fastened to the underside of the board.

There is a piece of wire cable16that is passed around wire guides15a-15din the corners of board11and through wire guide19in an “X” pattern as shown inFIG. 2. This wire cable and its routing is part of the present invention. Initially, before being fastened into a closed loop, wire26is routed around each if the wire guides15a-15dand through wire guide19in the “X” pattern shown inFIG. 2.

The two ends of wire16are shown fastened together and centered above wire guide19but they may off to one side of the wire guide. The two ends of wire16are then fastened to the two ends of a stretched spring18. To do this one end of wire16is attached to a first end of spring18using an eyelet (not shown). The other end of wire16also has an eyelet (not shown) attached thereto. Spring18is stretched approximately 1 inch beyond its un-stretched length and the eyelet attached to the other end of wire16is attached to the other end of spring18. More particularly, inFIG. 2the portion of wire16passing between the lower left corner of board11to the upper right corner of board member11passes through wire guide19. In this manner spring18does not contact the piece of wire16passing through wire guide19.

Wire16is positioned on and fastened to novel control elements17aand17bon the edges of board11as shown inFIG. 2. Control element17ais mounted on the left edge of board11and control element17bis mounted on the right edge of board11. This is shown in and described in greater detail with reference toFIG. 3.

InFIG. 3is shown a control element17and there is one (17a) mounted on the left side of board11and one (11b) mounted on the right side of board11as shown inFIG. 1. Element17has a wire capture screw28on its bottom, a brake knob23on its side and a top adjustment knob26on its top. All these screws and knobs are mounted on a side bracket27that has a “U” shape and is positioned sideways as shown to fit over an edge of board11as shown inFIGS. 1 and 2. Straightedge25has a slot in either end thereof and one of the two control elements17aand17bis mounted to each end of straightedge25. For both elements17aand17bthe upper side of bracket27fits into the slot and knob26is tightened to firmly hold the top of side bracket27to the top side of straightedge25. There is a control element17aand17battached to either end of straightedge25, as shown inFIG. 1, in this manner.

Brake knob23on the side edge of control element17has a knurled outer end that is turned by hand, and an inner end to which is affixed a brake pad24adjacent to board11. When straightedge25with control elements17aand17battached thereto is mounted on a board11the side bracket27of both control elements are adjusted and tightened to have room for the two brake knobs23to be turned both in and out, and then the two top adjustment knobs26are locked.

To lock the loop of wire16to each control element17wire capture screw28is utilized. As shown inFIG. 3wire16is forced into a slot near the inner end of screw28where the wire is captured and tightly held. Wire16may also be attached to screw28in alternative ways. Straightedge25is carefully positioned on board11before wire16is fastened to wire capture screw28. When board11is in use the flat end of screw28rests against and rides along the bottom edge of board11.

Brake knob23is mounted through the side wall of side bracket27and on its inner end is a brake pad24that rests against the side wall of board11. More particularly, pad24of brake knob23of control element17arests against the left side of board11as seen inFIG. 1, and pad24of brake knob23of control element17brests against the right side of board11.

When straightedge25is located at a desired position on top of board11the left and right side brake knobs23aand23bare turned inward to push their brake pads24against the sides of board11and thereby lock straightedge25at the desired position on board11. When it is desired to move straightedge25up or down board11to a new position the two brake knobs are unscrewed a small amount to back off the brake pads24and thereby unlock the straightedge. Straightedge25is then slid up or down board11to a new position and the two brake knobs23are then turned inward to again push their brake pads24against the sides of board11and thereby lock straightedge25at the new position.

InFIG. 4is shown a snap lock21two of which,21aand21b, are used to maintain the drafting board10in an upward inclined position, as shown inFIG. 1, when board11is in use. Rod20is formed into a rectangular loop as best shown inFIG. 2. Rod loop20is moved between a flat position against the bottom of board11, as shown inFIG. 2, when board11is not is use, and to an upright position, as shown inFIG. 1, when board11is to be used.

Looped rod20passes through the two snap locks21aand21band as rod20is rotated between its flat position against the bottom off board11and its upright position extending away from board11it rotates approximately ninety degrees in snap locks21aand21b. Snap locks21aand21bpinch rod20to lock it in whatever of the two positions selected by a user of drafting board10. The locking and unlocking is accomplished by locking levers22. The locked and unlocked position of locking levers22is shown inFIG. 2.

With the locking levers of22aand22bof the snap locks21aand21bin their unlock position looped rod20can be rotated within the two snap locks21aand21bbetween the position against board11(FIG. 2) and extended away from board11(FIG. 1). After handle12is moved to rotate looped rod20in snap locks21aand21bto extend its bottom end corners and feet13aand13bdownward away from the bottom of board11locking levers22aand22bare moved as indicated inFIG. 2, as seen from the bottom of drafting board10, to clamp looped rod20where it passes through snap locks21aand21band thereby lock looped rod20with its feet13aand13bin the downward position as shown inFIG. 1.

When it is desired to rotate looped rod20up against the bottom of board11to store the board, the locking levers22aand22bare moved as shown inFIG. 2, as seen from the bottom of board11, to unlock or unclamp looped wire rod20where it passes through snap locks21aand21b. After looped rod20is rotated up against the bottom of board11using handle12the levers22aand22bare moved to the their lock position to again lock looped rod20in its up or retracted position against the bottom of board11.

In each of the four corners of board11is fastened a wire guide15a,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 board11. There is also another, different wire guide19fastened to the bottom center of board11. More particularly, each wire guide fits over one of the corner edges of board11before 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.