US 1978476 A
Description (OCR text may contain errors)
Oct. 30, 1934. i H. REINEKE 1,978,476
V MOVABLE CONSTANT ORIENTATION MAPBOARD 'Filegi May 18, 1954 Patented Oct. 30, 1934 PATENT OFFiE MOVABLE, CONSTANT-ORIENTATION MAPBOARD Lester H. Reineke, New Haven, Conn., dedicated to the free use of the Public of the United States of America Application May 18, 1934, Serial No. 726,341
(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described is patented, may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.
I hereby dedicate the invention herein described to the free use of the public in the territory of the United States of America, to take effect upon the granting of a patent to me.
This invention relates to means whereby permanently mounted maps, such as are used in forest fire lookout stations, may be held in constant orientation while the map is shifted a limited distance to permit making alidade sights without obstruction by corner posts, window sashings, or other structural members of the lookout cabin.
I attain these objects by the device illustrated in the accompanying drawing in which- Fig. 1 is a top plan view of the device; Fig. 2 is a side elevation thereof; Fig. 3 is a plan view illustrating the operation of the device and Fig. 4 shows the device in a modifying form.
Similar numerals refer to similar parts throughout the several views. The invention consists in a fixed base 1 (pedestal, table, etc.) to which are attached three or more, preferably four, cranks or links 2 of equal length, free to revolve in a horizontal plane as shown at 4. The other ends of the cranks or links are affixed at points 5, in a manner permitting free horizontal revolution, to the under side of the board 3 on which the map is mounted. The spacing of the points of attachment to the mapboard is identical with the spacing of the points of attachment to the fixed base. The length of the cranks or links may be any length less than the shortest distance between points of attachment.
In Fig. 4, a plan view, aA, DB, 00 are the links or cranks for a three-link mounting. A, B, C represent the points of attachment to the fixed base 1; a, b, 0 represent the points of attachment to the mapboard. By construction, aA=bB=cC, and ab=AB, bc=BC, and ac=AC. Since aA=bB, and ab=AB, aABb is a parallelogram and ab is therefore parallel with AB. As links aA and. b3 revolve, theside ab approaches and recedes from AB but remains parallel with it. Therefore, since ab is a part of the mapboard, the mapboard itself will maintain its original orientation as the links aA and DB revolve.
Similarly, bBCc, and aACc are parallelograms,
Each parallelogram acts to maintain the orientation of the mapboard. There are three parallelograms acting concurrently with a three-link mounting; with a four-link mounting (Fig. 3), there are six parallelograms acting concurrently. co
Mechanical inaccuracies resulting in looseness at the points of attachment, will permit variation in length of links 2 (Fig. l). When this variation is unequal in amount or direction the parallelism of ab with AB, ob with GB, or ac with AC will be destroyed. The deviation from true parallelism will be least when the parallelogram approaches a rectangle, greatest when it approaches a line. However, as aABb approaches a line, bBCc approaches a rectangle, the position of least deviation, and in this position it prevents complete take-up of loose play in aABb. Therefore, the maximum mechanical error in orientation of the complete assembly is the maximum error in the parallelogram with least error.
Having fully disclosed my invention, I claim:
1. A device of the class described comprising a base, a horizontal platform above the base and pivoted crank means to hold the horizontal platform above the base and provide for the universal lateral movement of the platform in a horizontal plane.
2. A moveable constant-orientation mapboard comprising a base, a horizontal platform above said base and a plurality of uniformly sized and spaced crank means positioned between the base and the horizontal platform, the lower end of the crank means being pivotally mounted on the base and the horizontal platform being pivotally mounted on the upper end of the crank means.
3. A device of the class described comprising a base, a platform, a crank means supporting said platform above said base, said crank means being pivoted for rotation about axes perpendicular to said platform in such a manner as to provide for planar movement of said platform relative to said base.
LESTER H. REINEKE.
changing concurrently with changes in aABb,
since A, B, and C are attached to surface 1 and a, b, and c are attached to a second surface 3.