GB2195180A - Compass - Google Patents

Abstract

A compass 10 comprises a freely suspended magnet 12; a compass card 42 connected to a first member 22 and a second member 26 arranged to be connected to a vessel. The first member 22 can move relative to the second member 26 and the compass card 42 and said first member 22 are able to move relative to the magnet 12. The compass card 42 can be aligned with said magnet 12. Alignment means 58 detects movement of said first member 22 relative to said magnet 12. Upon alteration in the course of said vessel the first member 22 and the compass card 42 move relative to said magnet 12 and the alignment means 58 relays information relating to such movement to an analyser which in turn signals a motor to operate a drive to move the compass card 42 and the first member 22 to realign the compass card 42 with said magnet 12. <IMAGE>

Description

SPECIFICATION Compass The present invention relates to a compass and, in particular, to a mariner's compass or aviation compass.

In accordance with one aspect of the present invention there is provided a compass comprising: a freely suspended magnet; a compass card connected to a first member; a second member arranged to be connected to a vessel, said first member able to move relative to said second member; said compass card and said first member able to move relative to said magnet, said compass card able to be aligned with said magnet; alignment means to detect movement of said first member relative to said magnet; wherein, upon an alteration in the directional course of said vessel said first member and said compass card move relative to said magnet and said detection means relays information relating to such movement to a control means which in turn signals a motor means to operate drive means to move said compass card and said first member to realign said compass card with said magnet.

The invention will now be described, by way of example, with reference to the accompanying drawings, wherein: Figure 1 is a perspective view of the compass of the present invention; Figure 2 is a sectional view of the compass shown in Figure 1; and Figure 3 is a schematic representation of the compass shown in Figure 1 showing it connected in its operational environment.

In Figures 1 and 2, there is shown a compass 10 comprising a magnet 12 surrounded by a first member in the form of a phantom ring 22 and a second member in the form of an outer ring 26.

The phantom ring 22 is connected to a phantom ring upper bearing 24 and a phantom ring lower bearing 46. The phantom ring 22 is rigidly held against the surface of the phantom ring upper bearing 24 by a locknut 21.

The phantom ring upper bearing 24 is rotatably mounted in an aperture in the upper portion of the outer ring 26.

The outer ring 26 is rigidly connected to an outer ring lower bearing 44.

The phantom ring lower bearing 46 is rotatably mounted in the outer ring lower bearing 44.

The phantom ring 22 is thus rotatable relative to the outer ring 26 via the rotatable mountings of the phantom ring upper bearing 24 and the phantom ring lower bearing 46.

The outer ring 26 is mounted to a framework (not shown) that is rigidly connected to the structure, e.g. a vessel, in which the compass 10 is located. This mounting may be a gimbal mounting. Accordingly, each end of the upper portion 34 of the outer ring 26 is provided with a bearing 38 and 40 respectively.

The bearings 38 and 40 are pivotably positioned in recesses (not shown) contained in an annular part of the framework, to permit pivoting around a first horizontal axis. The annular part is connected to the remainder of the framework by a second pair of pivotable connections. The second pair of pivotable connections permits pivoting around a second horizontal axis, transverse to the first horizontal axis.

The gimbal mounting thus allows the outer ring 26 to pivot around two transverse horizontal axes, but is precluded from rotating about a vertical axis. The outer ring 26 is thus able to pivot backwards and forwards, and from side to side, only.

The gimbal mounting, itself, is a known type mounting. A spur gear 41 is rigidly attached to the phantom ring upper bearing 24. A compass card 42, having the usual indicia thereon, is fixedly connected to the spur gear 41 by way of screws 43. The spur gear 41 is mounted on a bearing 90. A flexible worm drive 72 is provided on the upper portion 34 of the outer ring 26 to drive the spur gear 41, in the manner to be later described.

The magnet 12 is mounted on the outside of an inner tube 53 by way of lock nuts 55 and a bushing 92. The inner tube 53 is suspended from a spindle 57 connected to the phantom ring upper bearing 24 by a high tensile strength cord 14 which is minimally affected by torsional changes.

The upper portion of the inner tube 53 is provided with an inner tube bearing 59. The spindle 57 is rotatable in the bearing 59. The other end of the cord 14 is connected to the inner tube 53 near the base thereof by way of the connection 61.

A first outer tube 63 encloses the upper portion of the inner tube 53. The outer tube 63 is held in place around the inner tube 53 by way of locknuts 65 and a thrust washer 67.

The lower portion of the inner tube 53 is provided with an inner tube lower bearing 69.

The phantom ring lower bearing 46 has an elongated member 48 rotatably positioned in the inner tube lower bearing 57. A second outer tube 71 encloses the lower portion of the inner tube 53. The outer tube 71 is held in place around the inner tube 53 by way of lock nuts 73 and a thrust washer 75.

The inner tube 53, and consequently the magnet 12, which is attached to the inner ring 53, are freely suspended by the cord 14 from the spindle 57.

The compass 10 further comprises an alignment device 58 and an optical fibre 54 for conveying light to the alignment device 58.

The alignment device 58 detects movement of the phantom ring 22 relative to the magnet 12.

The optical fibre 54 extends from the phantom ring upper bearing 24, along the outer face of the phantom ring 22, through an aperture in the phantom ring 22 and along the inner face of the phantom ring 22 to the top of an upper plate 56 extending from the inner face of the phantom ring 22.

Light may be conveyed to the alignment device 58 from a remote light source 77 powered by a power supply 89, shown in Figure 3. The light may be conveyed from the source 77 to the optical fibre 54 by an optical fibre 60. A gap 62 exists between the bearing 90 and the phantom ring upper bearing 24, between the ends of the optical fibres 54 and 60. This allows the phantom ring upper bearing 24 to rotate through 360 degrees unimpeded.

Another optical fibre 64 extends from the bottom of a lower plate 66 that extends from the inner face of the phantom ring 22. The optical fibre 64 extends along the inner face of the phantom ring 22 to the phantom ring lower bearing 46. An optical fibre 68 extends from the outer ring lower bearing 44 to control unit 79, shown in Figure 3. A gap 70 exists between the phantom ring lower bearing 46 and the outer ring lower bearing 44, the ends of the optical fibres 64 and 68. This allows the phantom ring lower bearing 46 to rotate through substantially 360 degrees, unimpeded.

The alignment device 58 comprises a plate 52 connected to the magnet 12. A portion of the plate 52 extends into the gap between the upper plate 56 and the lower plate 66 that extend from the inner face of the phantom ring 22.

The plate 52 is provided with a central portion 8t opaque to all light frequencies with adjacent portions 83 and 85, each transparent two a different light frequency or frequency range. Thus, the portions 83 and 85 may be light filters.

Alternatively, the central opaque portion 81 may be opaque only to the frequencies that are transmissible through the portions 83 and 85.

The compass 10 further comprises a flexible worm drive 72 mounted on the outer ring 26.

The flexible worm drive 72 is connected to a stepping motor 87 by way of a pulse drive 74, shown in Figure 3.

The flexible worm drive 72 is arranged to turn the spur gear 41, to thereby turn the compass card 42 and phantom ring 22. The phantom ring 22 may carry a pair of arms 78 provided with stops 80, as shown in Figure 1.

The arms 78 and stops 80 could alternatively be positioned on the opposed portion of the phantom ring 22, to that shown in Figure 1.

As a further alternative, a pair of arms 78 could be positioned on each opposed portion of the phantom ring 22. As an alternative to positioning the arms 78 as shown in Figure 1, they may be positioned such that the stops 80 contact the magnet 12 at its upper portion.

The stops 80 are preferably made of neoprene.

The stops 80 are provided to cushion the magnet 12, if required.

The manner of operation of the compass 10 of the present invention will now be described by way of example, with reference to the compass 10 being located in a seafaring vessel.

In use, the magnet 12 seeks out and aligns itself in the direction of magnetic north.

Light is then conveyed to the alignment device 58, from the light source 77, by the optical fibres 60 and 54.

When the compass 10 is correctly aligned, the opaque central portion 81 of the plate 52 will be between the ends of the optical fibres 54 and 64, between the upper plate 56 and the lower plate 66. When the alignment device 58 is aligned in this manner, the compass card 42 is aligned with the magnet 12, in the direction of magnetic north.

If the vessel alters course, the outer ring moves, relative to the magnet 12, in a corresponding manner, since the outer ring 26 is connected to the vessel by way of the framework and gimbal mounting previously described.

This movement of the outer ring 26, in turn causes the phantom ring 22 to move in a manner corresponding to the movement of the outer ring 26. The compass card 42, being connected to the phantom ring upper bearing 24, is thus moved out of alignment with the magnet 12.

When the phantom ring 22 moves in this manner, light will pass through one of the portions 83 or 85 (depending upon the direction of the vessel's change of course) of the plate 52, since the magnet 12 (and therefore the plate 52) will always remain substantially stationary, pointing toward magnetic north.

The light that passes through one of the portions 83 or 85 of the plate 52 passes via optical fibre 64 to the optical fibre 68 and out of the compass 10.

The optical fibre 68 leads to control unit 79.

The control unit 79 may be in the form of a light frequency sensor and a series of photoelectric cells, which analyse the information coming from the optical fibre 64. The light frequecy sensor may be a prism which directs light passing through it to appropriately positioned groups of photoelectric cells. These groups of photoelectric cells generate a current that is dependant upon the frequency of the light conveyed to them by the optical fibres 64 and 68 from the alignment device 58. The photoelectric cells may produce a current only when light of the appropriate frequency falls on the appropriate photoelectric cells. The current thus generated may be used by the stepping motor 87.

The stepping motor 87 is able to cause the flexible worm drive 72 to rotate in a direction dependent upon the output of the control unit 79.

The worm drive 72 causes the spur gear 41 to rotate in the appropriate direction which causes the compass card 42 and the phantom ring 22 to rotate in a corresponding manner to realign the compass card 42 with the magnet 12.

This causes the compass 10 to be correctly aligned again, such that the phantom ring 22 moves via the phantom ring upper bearing 24 and the phantom ring lower bearing 46 until the end of the optical fibre 54 is again positioned over the opaque control portion 81 of the plate 52. In this position, no light is transmitted to the optical fibre 64 and thus the control unit 79 does not emit any output to ease the stepping motor 87 to rotate the flexible worm drive 72.

The compass card 42 is thus realigned with the magnet 12 in the direction of magnetic north.

Whilst the preceding embodiment of the present invention has been described with reference to the use of portions sensitive to different light frequencies in the alignment device 58, other suitable systems could be used.

As an illustration of other alternatives the use of light frequency sensitive portions on the plate 52 could be replaced by neutral density portions. These would control the amount (or intensity) of light4ransmitted by a particular portion, with minimal effect upon its frequency. The control unit 79 would need to be appropriately modified to operate when neutral density portions are used.

A further alternative would be to sub-divide the portions 83 and 85. Each of these subdivided portions would be sensitive to different frequency or range of frequencies. Each respective sub-divided portion 83 and 85 would be graduated in its sensitivity.

Thus, any means which allows for a change in a physical property of the light being transmitted through the alignment device 58, to be detected upon movement of the phantom ring 22, may be used in the present invention. Also, any appropriate type of electromagnetic radiation could be used in place of visible light.

Additionally, the present invention may employ any suitable means as an alignment device provided that it will allow for the detection of movement of the phantom ring 22 relative to the magnet 12 and then allows information relating to such movement to be forwarded to the control unit 79, e.g., ultrasonics might, alternatively, be used.

The signals that are fed to the flexible worm drive 72 are preferably also relayed to any steering controls and repeaters on the vessel.

This may be done by way of a normal universal system of 200 pulses per minute being transmitted to the steering controls and repeaters. In this way, the vessel may be properly maintained on course. A casing (not shown) would enclose the various parts of the compass 10 so that only the outside of this casing and the compass card 42 would be visible from the outside.

The direction of travel of the vessel can be determined by reference to a heading direction indicator 91. The heading direction indicator 91 would be carried by the vessel, e.g., by a casing of the compass 10. The heading direction indicator 91 would be carried by the ves sel, e.g., by a casing of the compass 10. The heading direction indicator 91 is aligned in the direction of travel of the vessel. Since the heading direction indicator 91 is aligned in this manner, its position relative to the markings on the compass card 42 will indicate the direction of travel of the vessel. The heading direction indicator 91 is, accordingly, placed in a suitable position in relation to the compass card 42.

The heading direction indicator may be a lubber line. The various parts of the compass 10, e.g., the outer ring 26, phantom ring 22 and casing are made of non-magnetic materials. A suitable material would be plastics.

This would also be light weight.

The compass of the present invention would be particularly suitable as a mariner's compass. It may be used on ocean-going vessels and smaller pleasure craft.

Modifications and variations such as would be apparent to a skileed addressee are deemed within the scope of the present invention.

Claims (12)

1. A compass comprising: a freely suspended magnet; a compass card connected to a first member; a second member arranged to be connected to a vessel, said first member able to move relative to said second member; said compass card and said first member able to move relative to said magnet, said compass card able to be aligned with said magnet; alignment means to detect movement of said first member relative to said magnet; wherein, upon an alteration in the course of said vessel said first member and said compass card move relative to said magnet and said alignment means relays information relating to such movement to an analyser means which in turn signals a motor means to operate drive means to move said compass card and said first member to realign said compass card with said magnet.

2. A compass according to claim 1, wherein said first member is rotatable about said magnet.

3. A compass according to claim 2, wherein said first member is non-rotatably connected to an upper bearing and a lower bearing said upper bearing and said lower bearing being rotatably mounted in said second member.

4. A compass according to claim 3, wherein said magnet is freely suspended via cord means having a first end and a second end, said first end being connected to a spindle means connected to said upper bearing and said second end being connected to tube means surrounded by said magnet, said tube means enclosing said cord means.

5. A compass according to any one of the preceding claims wherein, said alignment means comprises plate means having a first portion arranged to allow the passage therethrough of electro-magnetic radiation of a first frequency or intensity range, a second portion arranged to allow the passage therethrough of electro-magnetic radiation of a second frequency or intensity range and a third portion substantially opaque to at least said first frequency or intensity range and said second frequency or intensity range.

6. A compass according to claim 5, wherein a source of electro-magnetic radiation conveys electro-magnetic radiation of a frequency or intensity range that comprises said first frequency or intensity range and said second frequency or intensity range to said alignment means and said third portion being substantially opaque to substantially the entire frequency range conveyed by said source of electro-magnetic radiation to said alignment means.

7. A compass according to any one of claims 5 or 6, wherein electro-magnetic radiation passing through said first portion or said second portion of said plate means is conveyed from said alignment means to control means which determines the frequency or intensity range of the electro-magnetic radiation passing through said plate means.

8. A compass according to any one of claims 5 to 7, wherein when said vessel alters its directional course said first member rotates in a first direction thereby allowing electro magnetic radiation to pass through said alignment means which is then analysed by control means which causes a motor means to activate a drive means to rotate said first member in a second direction opposed to said first direction and dependent upon the fre quency or intensity range of the electro-mag netic radiation that passes through said alignment means such that said first member rotates to cause said third opaque portion to be positioned to prevent passage of said electro-magnetic radiation through said alignment means.

9. A compass according to claim 8, wherein a compass card is attached to said first member said compass card comprising indicia which are correctly aligned with the said magnet when said opaque portion is positioned to prevent passage of said electro-magnetic radiation through said alignment means.

10. A compass according to any one of claims 5 to 9, wherein said electro-magnetic radiation is conveyed to and from said alignment means by optical fibre means.

11. A compass according to any one of claims 1 to 10, wherein said first member comprises a phantom ring and said second member comprises an outer ring encircling said phantom ring.

12. A compass substantially as hereinbefore described with reference to the accompanying drawings.