US2008481A - Magnetic compass - Google Patents

Description

July 16, 1935. P. F. WEBER ET AL 2,008,481

MAGNETIC COMPASS y Filed June e. 1934 2 sheets-sheet 1 (in i NVENTORS. P//f//l'o IC.' Weber Wa/er E. .Dan/fau TTORNFY July 16, 1935. P. F. wr-:BER AL 2,008,481

MAGNETIC COMPASS Filed June e, 19:54 2 sheets-sheet 2 INVENTORS. l P/y/g, E weber Wa/er f. Dan/fau BY fmw Patented `luly 16, 1935 UNITED 4STATES PATENT OFFICE Walter E. Dankau, Ozone Park, N. Y.,

assignors to Bendix Aviation Corporation, South Bend, Ind., a corporation ol Delaware Application June 6, 1934, Serial No. 729,320

7 Claims. (Cl. 33-223) The present invention relates to compasses and more particularly to means for supporting the compass card thereof.

One of the objects of the present invention is v to provide in a magnetic compass of the liquid type, a novel compass card structure whereby the effective weight of the card is substantially reduced by the buoyant eiect of the liquid thereon so that rotation of the card on its pivot due to vibrations and acceleration forces is substantially eliminated.

Another object is to provide in a magnetic compass of the liquid type having its card pivoted on a jewel bearing, a novel'compass card structure embodying a float disposed at the top of the card and arranged concentrically therewith and balanced with respect to the pivot of the card, whereby the buoyant effect of the liquid on the card substantiallyreduces the eilective weight thereof and hence reduces the pressure of the card pivot on the bearing to a substantially negligible value.

Still another object of the invention 'is to provide in a magnetic compass oi.' the class described, a novel compass card structure embodying a oat disposed at the top of the card and a spring cooperating with the float and pivot of the card whereby the oat substantially reduces the efiective weight of the card and the spring serves as the sole support of 'the iloat and card on the pivot of the latter so that rotation oi the card due to acceleration forces and vibration is substantialy eliminated or prevented.

'I'he above and other objects and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein two embodiments of the invention are illustrated. It is to be expressly understood, however, that the drawings are for purposes of illustration and description only and are not to be construed as dening the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings wherein like reference characters refer to like parts throughout the several views:

Fig. 1 is a vertical sectional view of a compass including one form of novel card supporting means embodying the present invention;

Fig. 2 is an enlarged sectional view of another form of card structure embodying the invention;

Fig. 3 is a perspective view ofthe spring employed for resiliently supporting the card structure;

Fig. 4 is an enlarged sectional view of still another form-of card structure embodying the invention; and

Fig. 5 is a top view of the structure shown in Fig. 4.

Referring tothe drawings and more particularly to Fig. 1, there is disclosed one form oi novel compass card structure embodying the present invention for use in a compass of the liquid type. In the form shown, the compass comprises acontainer orvcompass bowl 4 which is provided with a cover glass 5 secured thereto in any suitable manner as by means of a clamping ring 6 and screws 1. 'I'he compass may be o1' the panel type and mounted on an instrument panel 8 in any suitable manner (not shown) so that the compass card may be viewed through the cover glass 5 which projects through an opening 9 in the panel 8. The compass bowl 4 is iilled with a suitable liquid III such as kerosene or varnolene through a well II having a closure member I2 which is 4arranged to be screwed into place. `The wall II is connected by a passage I3 to the uppermost portion of the compass bowl so that the well serves as a bubble house in addition to its purpose as a lining opening, i. e., any bubbles accumulating in the upper portion of the compass bowl will pass through the passage I3 and into the well II thereby leaving the liquid surrounding the compass card free from bubbles.

Means are provided for compensating the compass for semi-circular deviation, such means being indicated generally by the reference numeral I4. Since the compensating means may be of any known type and does not constitute part of the present invention a detailed description thereof is unnecessary herein.

Means are also provided for compensating for the expansion and contraction of the liquid Il) dueto temperature changes and in the form shown said means comprise a bellows I5 extending into the compass bowl 4 and secured thereto by means of a nut I6. The interior of the bellows is in communication with the atmosphere by means of an opening I'I so that upon expansion of the liquid in the bowl due to increased temperature, the bellows I5 are compressed and the air therewithin passed out through the opening I'I. Upon a contraction of the liquid due to a drop in temperature, air enters the bellows through the opening I1 thereby restoring the liqquid pressure within the compass bowl to normal. A compass card I8 is pivotally mounted within the compass bowl'on a pivot post I9 extending vertically from the bottom of vthe bowl and secured to the latter in any suitable manner as by means of threads 20. The card is in the form of a disc 2| having a downwardly and outwardly extending annular ange 22v on the exterior surface of which are inscribed compass graduations (not shown). 'Ihe card is arranged so that it may be viewed through the cover glass and a lubbers mark in the form of a curved member 23 is provided for obtaining readings on the card, said lubbers means being secured to the pivot supporting member 24.

The magnet elements are in the form of bar magnets 25 carried by' the compass card by means of hooked members 26 secured to the card as indicated at 21 and projecting downwardly therefrom in order to bring the center of gravity of the card structure at or below the card pivot, or at any other suitable point depending upon the card construction employed.

Means are now provided for reducing the effective weight of the compass card I8 and for preventing transmission of vibrations from the compass bowl 4 through the post I9 or through the liquid in the container to the compass card I8 whereby rotation of the card due 'to acceleration forces and/or vibrations is substantially eliminated or prevented.

In the embodiment illustrated said means comprise a. float which is shown in Fig. 1 in the form of a solid member 28 made of some suitable floating material such as cork and in Fig. 2 in the form of an air-tight hollow member 29. The oat, in both instances, may beI secured to the card I8 preferably by the ends of the hooked members 26 and the under side of the float is substantially flat so as to rest evenly on the disc 2| of the compass card I8 and the upper side of the oat is at a maximum height at the center of the card and tapers downwardly toward the periphery Vof the card. The compass card is supported on a jewel bearing 30 by means of a pivot 3| which extends through coincident openings'provided centrally of the disc 2| of the card and of the oat and the upper end of the pivot abuts against a flat spring 32 having its ends bent upon itself and secured to the float 28 or 29 in any suitable mannerso that the spring acts as the sole support for the float and card on the pivot 3|, the latter being capable of relative longitudinal sliding movement with respect to the float and card. Secured to the pivot 3| is an inverted cup-shaped member 33 which cooperates with an inturned flange 34 of a twopart cylindrical member 35 carried by the supporting member 24, said ange 34 providing an opening smaller than the upper portion of the inverted cup-shaped member 33 thereby preventing the compass card I8 and'its pivot 3| from being dislodged from the jewel bearing 30.

It will be apparent from the foregoing construction that by virtue of the shape and form of the float and its disposition at the top of the compass card centrally thereof, the effective weight of the card is substantially reduced to any extent desired depending upon the size of the float, but preferably the oat is of such size as to make the pressure of the pivot 3| on the bearing 30 almost negligible, thus materially :reducing the friction of the pivot and preventing excessive shocks on the bearing 30 by said pivot. Obviously, since the effective weight of the card is lsubstantially reduced it will not be readily acted upon by acceleration forces so that turning of the card on its pivot due to such forces is also substantially reduced. Inasmuch as the entire card structure is supported solely by means of the spring 32 against which-the pivot 3| abuts,

the latter being free to slide in the openings provided in the card and float, any vibrations which .are imparted to the pivot post I9 and support member 24 are taken up by the spring 32 and, hence, prevented from being transmitted to the card I8.

It may be desirable to further reduce the weight of the compass card and to this end the card structure may be constructed as shown in Fig. 4 wherein the central portion of the horizontal part of the car is cut away as shown at 36 to form a relatively narrow horizontal ring 31 having a downwardly and outwardly extending scale portion 38 and a relatively short annular flange 39 extending inwardly from the lower edge of the scale portion 38 for reinforcing said edge. The card'in this instance is preferably made of aluminum or other suitable light-weight material.

'I'he iioat in this embodiment is made up of two parts, namely, a hollow frusto-conical member 40 open at the base and having an annular ange 4I at said base, and a fiat disc member 42 forming the base of the float, said frusto-conical member 40 and said disc member 42 being soldered together at the flange 4| in order to make the interior of the float air-tight. In order to provide for adequate soldering of the iioat the latter is preferably made of phosphor bronze or some other suitable material which may be readily soldered. The float is then disposed on top of the card so as to cover the cut-away portion thereof and is secured thereto by means of the hooked members 26 which carry the magnets 25 as in the embodiment shown in Figs. 1 and 2. A sleeve 43 having as flange 44 at the upper end thereof is provided which extends through the oat and is soldered to the latter in order to completely seal the float at the point where Vthe sleeve 'extends therethrough. In this construction the ends of the spring 32 are preferably secured to the flange 44 of the sleeve and the pivot 3| is then slldably positioned within said sleeve 43 so as to have its upper end abut the body portion of the spring. The inverted cup-shaped member or dome 33 is then press-fitted on the sleeve 43 and is provided with an annular flange 45 at the top thereof which is arranged to abut against the under side of the disc member 42 of the float. The remainder of the structure which cooperates with the inverted cup-shaped member 33 is the same as that shown in Figs. 1 and 2.

There is thus provided a novel compass card structure whereby the effective weight of the card is substantially reduced to almost a negligible value and vibrations thereof prevented so that rotation of the card which would otherwise occur due to such vibrations and due to acceleration forces is practically eliminated.

Although three embodiments of the invention' have been illustrated and described other changes in the form, construction and relative arrangement of the parts, which will now appear to those skilled in the art, may be made without departing from the scope of the invention. Reference is, therefore, to be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In a magnetic compass of the liquid type having a compass card `pivotally mounted on a jewel bearing, the combination with said card, of a oat disposed coaxially therewith, a pivot passing through the center of the card and oat and adapted for relative longitudinal movement with respect to said card and float, and a substantially flat spring having its ends bent upon itself Aand. anchored on opposite sides of the opening from which the pivot projects so that the body of thespring is disposed over and on the upper end of the pivot of the card and constitutes the sole support for the card and float on the pivot and on the bearing on which the pivot rests.

Z. In a magnetic compass of the liquid type having a compass card pivotally mounted on a jewel bearing, the combination with said card of a oat disposedbn said card centrally thereof, a sleeve passing through the center of the float and rigidly secured thereto, a pivot slidably positioned in said sleeve, and a substantially ilat spring having its ends bent upon itself and secured to the upper end of the sleeve so thatthe body of the spring is disposed directly over the upper end of the pivot and constitutes the sole support for the card and float on the pivot and on the bearing on which the pivot rests, said float being in the form of an air-tight hollow member.

3. In a magnetic compass of the liquid type, the combination of a compass card pivotally mounted on a jewel bearing, said card having the central portion thereof cut away to form a relatively nar- -row horizontal ring and having a downwardly and outwardly extending annular scale portion and a relatively short annular flange extending inwardly from the lower edge of the scale portion for reinforcing said edge, a hollow air-tight float disposed on top of the card so as to cover the cut away portion of said card whereby the effective weight of the card is reduced to a substantially negligible value by the buoyant eiect of the liquid on the float, a .sleeve extending through the center of the float and rigidly secured thereto, a pivot slidably positioned in said sleeve, and a substantially at spring having its ends bent upon itself and secured to said sleeve so that the body of the spring is disposed over and on the upper end of the pivot whereby said spring constitutes thrsole support of the card and float on the sliding pivot for preventing vibrations from being transmitted `to the card and float by the pivot.

4. In a magnetic compass of the` liquid typethe combination of a compass card-pivotally mounted on a jewel bearingsaid card having the central portion thereof cut away and having a downwardly and outwardlyextending annular scale portion and a relatively short annular flange extending inwardly ,df/rom the lower edge of the scale portion for reinforcing said edge, a hollow air-tight float disposdfcoaxially with the cut away portion of the card and secured to said card at a plurality of points arranged circumferentially on the card about the cut away portion whereby the effective weight of the card is reduced to a substantially negligible value bythe buoyant eiect of the liquid on the oat, a sleeve extending through the body of the float at the center thereof and., secured thereto, a pivot slidably positioned in said sleeve, and a substantially flat spring having its ends bent upon itself and secured to the upper end of the sleeve so that the body of the spring is disposed over and on the upper 'end of the pivot whereby said spring constitutes the sole support of the card and float on the sliding pivot for preventing vibrations from being transmitted to the card and float by the pivot.

5. In 4a magnetic compass of the liquid type, the

.combination of a compass card pivotally mounted on a jewel bearing, said card having the central portion thereof cut away and having a downwardly extending scale portion, a hollow airtight float disposed coaxially` with the cut away portion and formed of two parts one of which constitutes a plate secured to the card concentrically therewith in substantially the plane of the cut away 'portion of the card, and the other of which constitutes a. cup-shaped member having a horizontally extending flange at the periphery and secured to said plate thereby providing a closed air-tight and liquid-tight chamber whereby the effective weight of the card is reduced to a substantially negligible value by the buoyant effect of the liquid on the float, a sleeve extending through the body' of the float at the center thereof and secured thereto, a pivot slidably, positioned in said sleeve, and a substantially fiat spring having its ends bent upon itself and 6.-In a magnetic compass of the liquid type,

the combination of a compass card pivotally mounted on a jewel bearing, said card .having the central portion thereof out away and having a downwardly extending scale portion and a relatively short annular flange extending inwardly from the lower edge of thel scale portion for reinforcing said edge, a hollow air-tight float disposed coaxially with the cut away portion' and formed of two parts one of which constitutes a at plate secured to the card concentrically therewith in substantially the plane of the cut away portion of the card, and the other of which constitutes a cup-shaped member having a horizontally extending annular flange at the periphery thereof secured to said flat plate substantially at its periphery thereby providing a closed airtight and liquid-tight chamber, whereby the effective weight of the card is reduced to a substantially negligible value by the buoyant effect of the liquid on the float, a sleeve extending through the body of the float at the center thereof and rigidly secured thereto, a pivot slidably positioned in said sleeve, and a substantially iiat spring having its ends bent upon itself and secured to the upper end of the sleeve so that the body of the spring is disposed over and on the upper end of the pivot' whereby said spring constitutes the sole support of the card and float on the sliding pivot for preventing vibrations from being transmitted to the card and oat by the pivot.

7. In a magnetic compass of the liquid type having a compass card pivotally mounted on a jewel bearing, the combination with said card, of a float disposed coaxially therewith, a sleeve passing through the center of the float and rigidly secured thereto, a pivot slidably positioned in said sleeve, and a substantially at spring having its ends bent upon itself and secured to the upper end of the sleeve so that the body of the spring is disposed directly over the upper end of the pivot and constitutes the sole support for the card and oat on the pivot and. on the bearing on which the pivot rests.

PHILIP F. WEBER. WALTER E. DANKAU.

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