US2294355A - Magnetic compass - Google Patents

Description

Aug. 25, 1942. LL 12,294,355

. MAGNETIC COMPASS Filed 001;. 2, 1940 Zinventor Patented Aug. 25, 1942 UNITED STATES FATENT OFFICE MAGNETIC COMPASS Walter E. Hull, Warren, Ohio Application October 2, 1940, Serial No. 359,380

2 Claims.

This invention relates to magnetic compasses, and particularly, to pocket or other compasses of an inexpensive but efiicient character.

Heretofore, it has been the standard practice to employ a jeweled bearing in a compass so as to obtain a minimum amount of friction between the magnetic needle and its bearing support; However, constructions of this type are relatively expensive. Attempts have been made to reduce the cost of a compass by employing a metal to metal contact bearing. These all metal bearings have not proven satisfactory in use because of Wear and also because of the relatively high friction between the moving parts which prevents the accurate operation of the compass. As a result, inexpensive compasses have had a very bad reputation due to poor operation and unsatis-- factory results.

It is the general object of my invention to avoid and overcome the foregoing and other difficulties and disadvantages of prior art structures by the provision of a very inexpensive compass which will operate over long periods in a completely satisfactory and fool-proof manner.

Another object of my invention is to provide a compass in which a bearing of hard steel working against hard steel is provided, and in which the friction is at a minimum and approaches the minimum of friction provided by jeweled bearing.

Another object of my invention is to provide an efiicient but inexpensive magnetic compass in which the magnetic needle itself, usually made of high carbon steel, is provided with an integral cone bearing adapted to cooperate with the sharply tapered point of a steel pin.

Another object of my invention is the provision of an inexpensive compass wherein the magnetic needle is accurately balanced on the supporting pin so that the needle rests parallel with the bottom of the compass case regardless of the pull of the earths magnetic pole.

Another object of my invention is to provide an assembly of a magnetic needle, compass card and cap which is inexpensive to construct, pleasing in appearance, readily assembled, and which will function as required for many years.

Another object of my invention is the provision of an inexpensive compass case, bearing pin support, and compass case closure.

The foregoing and other objects of my invention are achieved by the combination in a magnetic compass of a hard metal pin having a long tapered point on its upper end, a magnetic needle made of a suitable magnetic steel, and an integral upwardly-converging cone formed in the needle near its center and adapted to receive the pointed end of the pin in bearing relation. More particularly, I may employ a molded plastic case of substantially cylindrical form and having an integral bottom and an upwardly protruding boss formed integral with and centrally of the case bottom. The boss serves to hold the pin with its pointed end upwardly. The magnetic needle may be made with an integral upwardly-extending hub positioned slightly offset center toward the north end of the needle, the hub carrying the integral upwardly-extending cone. A centrally-apertured circular compass card of bristol board, or the like, fitting over the hub and down against the needle in snug relation, a pressed thin metal cap positioned with a pressed fit over the hub and holding the compass card in position, and a disk of transparent flexible plastic cemented to the top of the case may complete the combination. The disk is positioned suiiiciently close to the cap to prevent the dislocation of the cone and pin even though the compass is inverted.

For a better understanding of my invention, reference should be had to the accompanying drawing wherein Fig. 1 is a plan view of one embodiment of the principles of my invention; Fig. 2 is a vertical transverse sectional View taken on line IIII of Fig. 1; and Fig. 3 is a plan view of the magnetic needle forming a part of the compass assembly.

Referring to the drawing, the numeral l0 indicates a compass case made of any desired, nonmagnetic material but conveniently made from molded plastic of a suitable nature. The compass case I0 is of a substantially cylindrical shape and is formed with an integral bottom 12 and an upwardly extending boss l4 positioned centrally of the bottom [2. The boss 14 is formed with a bore l6 adapted to receive and hold a metal pin 18, preferably of hard steel, and having a long tapered point 20, The point 20 of the pin l8 engages in bearing relation with a cone 22 formed integrally with a magnetic needle 24. Usually, the cone 22 extends upwardly from a hub 26 formed integrally with the magnetic needle 24. The magnetic needle 24 is made of hard magnetic steel and preferably the cone 22 and hub 26 are oiTset a distance marked X (see Fig. 3) from the center of balance of the needle. This is done so that the north pole of the magnetic needle 24 is somewhat lighter than the south pole of the magnetic needle after the needle is supported on the pin l8. However, the magnetic lines of force radiating from the earths magnetic north pole tend to deflect the north pole great deal more.

of the compass magnetic needle downwardly. The distance X is such that the compass magnetic needle will lie substantially parallel to the bottom of the case I at all times.

The long taper on the point of the hard pin I8 and the approximately sixty degree angle at the apex of the hard steel cone 22 combine to provide a substantiall frictionless bearing capable of operation over long periods in a completely satisfactory manner.

A substantially circular, centrally-apertured compass card 28 made of thin bristol board, or the like, and appropriately marked with the points of the compass, is positioned over the hub 26 and rests down against the upper surface of the magnetic needle 24. Usually, the centralaperture in the compass card is such that there is a snug relation between the card and the hub. Completing the assembly, and serving to hold the compass card 28 in position at all times is a cup 32 made of pressed brass or other thin light-weight non-magnetic material. The cap 32 has a press fit on the hub and the card 28 and cap 32 can be readily and quickly assembled on the magnetic needle 24, as will be understood.

The top of the case I0 is closed with a disk 34 of transparent material. Preferably this takes the form of a disk of transparent relativelyflexible plastic which is beveled at its periphery and is received down upon a shoulder 36 formed in the upper end of the casing Ill. The disk 34 is cemented to the case It so that the case is moisture and dust; proof. The clearance between the top of the cap 32 and the bottom of the disk 34 is such that even though the compass be inverted, positioned on its edge, or otherwise supported, the cone 22- will not be dislocated from the pin l8.

From the foregoing, it will be recognized that the objects of my invention have been achieved by the provision of a relatively inexpensive but efiicient and practical compass which is readily assembled. In fact, compasses constructed in accordance with the present invention have proven to substantially duplicate the results obtained with compasses costing and weighing a It will be understood that a compass of my invention can be made in any desired size but one convenient and practical size is between approximately one and two and onehalf inches in diameter and between about threesixteenths and one-half inch in height.

Although in accordance with the patent statutes, I have particularly illustrated and described one embodiment of my invention, it will be understood that I am not to be limited thereto or thereby but that the scope of my invention is defined in the appended claims.

1. In combination in a compass, a molded plastic case of substantially cylindrical form, an integral bottom on the case, an upwardly protruding boss formed centrally of the bottom and integrally therewith, a hard metal pin held in the boss and having a pointed upper end extending vertically of the bottom, a magnetic needle made of hard magnetic steel, and integral upwardly-extending hub positioned slightly offcenter of the needle, an integral upwardlyextending cone formed centrally on the hub and receiving in bearing relation the pointed end of the pin, a centrally-apertured, circular flat compass card fitting over the hub and down against the needle in snug relation, a cap of non-magnetic material positioned with a pressed fit over the hub and holding the compass card in position, and a disk of transparent, flexible plastic cemented to the top of the case and closing the same, said disk being sufiiciently close to the cap to prevent the dislocation of the cone and pin even though the compass is inverted.

2. In combination in a compass, a case of substantiall cylindrical form, a bottom on the case, a pin held in the case bottom and having a pointed upper end extending vertically of the bottom, a magnetic needle made of steel, an integral upwardly-extending hub on the needle, an integral upwardly-extending cone formed on the hub and receiving in bearing relation the pointed end of the pin, a centrally-apertured, circular flat compass card fitting over the hub and down against the needle in snug relation, a cap positioned with a pressed fit over the hub and holding the compass card in position, and a disk of transparent, material secured to the top of the case and closing the same, said disk being sufliciently close to the cap to prevent the dislocation of the cone and the pin even though the compass is inverted.

WALTER E. HULL.

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