Compass with means for correcting angle of magnetic variation

#This invention relates to new and useful improvements in compass constructions and is more particularly concerned with improvements relating to means for correcting the angle of magnetic variation to make the compass accurate for a certain area.

#Magnetic compasses of the type which operate in a horizontal plane are furnished to the consumer in a condition wherein the compass magnet is directed to the north magnetic pole on the compass card rather than to the true north geographic pole. Since many navigating means are charted in relation to the north geographic pole, corrections in compass readings for different areas must be made to compensate for this angle of variation. In my Patent No. 3,177,591, I provided a convenient means for correcting the angle of variation wherein by using a magnet key separate from the compass, the compass card can be rotated relative to the compass magnet and when the magnet key is removed, after first properly adjusting for the angle of variation, the compass card and the compass magnet will be reconnected and maintained in the corrected form.

#According to the present invention and forming a primary objective therefore, I provide an improvement over the structure of my U.S. Pat. No. 3,177,591 in an arrangement wherein the means for correcting the angle of magnetic variation is extremely simplified and furthermore positive connection of adjustment is provided to insure that the magnet and compass card will not separate under normal usage even if the compass is bounced up and down or turned over.

#FIG. 1 is a cross sectional view of a compass embodying the present invention, the compass being shown in normal functioning position;

#FIG. 2 is a view similar to FIG. 1 but showing the parts in position for adjusting the compass card;

#FIG. 3 is a fragmentary bottom plan view taken on the line 3--3 of FIG. 2; and

#With particular reference to the drawings, the numeral 10 designates a transparent compass housing and the numeral 12 designates an integral base portion therefor. Housing 10 is generally sealed and contains a liquid therein in which operates a compass card 14 supported on a needle point support or pedestal 16 projecting integrally upwardly from base portion 12. Base portion 12 is usually associated with a standup support and/or a bracket for mounting the compass in a desired place.

#The compass card 14 of the present invention comprises an inverted cup-shaped or skirted member with standard compass designations 18 thereon. Compass card 14 has a downwardly projecting central hub 20 provided with an upwardly extending recess 22 terminating at its upper end in a tapered seat 24 for rotational engagement by the pedestal 16. A compass magnet 26 has a central bore or opening 28 therethrough of a diameter to freely receive the hub 20. As will be apparent, the magnet 26 can have rotatable as well as vertical adjustment relative to the hub. Magnet 20 has integral wing projecting portions 26a, although it is to be understood that the shape of the magnet may vary to suit a specific compass application.

#The lower end of the hub 20 has a bottom washer-like flange 30 secured thereto which is about the diameter of the round magnet body portion. Such flange may comprise an integral part of the hub 20 or may have suitable securement thereto as by an upwardly directed tubular extension portion 32 having a pressed or adhesive connection within the recess 22. Importantly, the flange 30 is formed of a magnetically permeable material such as steel or soft iron in order that there will be a magnetic connection between it and the compass magnet 26 in a connected arrangement such that the magnet 26 will rotatably operate the compass card 14 on the pedestal 16.