GB2215111A - Map holder with bearing indicator - Google Patents

Abstract

A navigational aid comprises a light box 1 having an internal light source for illuminating a diffuser plate 2, on which a map (not shown) can be supported. The aid also includes a member which can be pivotted over the map, the pivotal mounting of the member being slidable over the map. A compass rose is also provided. As shown, the member 6 is pivotal about the compass rose 4, both being slidably mounted on a sliding arm 7. In another embodiment (Figure 2), the compass rose is marked round the periphery of the diffuser plate and the pivotal member is a set square. <IMAGE>

Description

Navigational Aid This invention relates to a navigational aid.

When trying to read a map or chart outdoors and particularly at night time it is generally necessary to use a battery operated light source such as a torch. This can be inconvenient especially, for example, on board a yacht, while trying to navigate. Another inconvenience of reading maps in such confined spaces is that the map or chart very often has to be folded to reveal a small part of the map at any one time.

According to the present invention there is provided a navigational aid comprising a light box having an internal light source for illuminating a diffuser plate, which forms the top of the light box, for supporting a map, a compass rose and a pivoted bearing arm slidably mounted on the light box.

The compass rose may be marked out on the perimeter of the light box, or it may be mounted together with the bearing arm on a mounting arm which is slidably attached to the light box.

The mounting arm is preferably slidably attached to the light box by means of a guide at one or both ends of the mounting arm.

Preferably the map is on a transparent sheet of plastics material.

The light box preferably comprises an opaque walled container having a detachable diffuser plate to close the box. The light source is preferably provided inside the box with an external switch to make contact with a battery inside the box, through an electrical circuit.

Means for varying the current to the light source may be included in the electrical circuit to allow the intensity of the light source to be varied.

The opaque walls may be coated inside with a reflective coating.

A diffuser plate may be provided on both sides of the light box.

The detachable diffuser plate is preferably hinged to the container and may be held in a closed position by a spring clip arrangement between the plate and container.

A set of transparent sheets, which in combination may provide a large map, may be used with the navigational aid. The spare sheets in a set are preferably contained within the light box, when the sheets are not in use. The navigational aid may be the size of a standard brief case and may include a carrying handle.

It is highly desirable that the navigational aid be made from water-proof materials. The walls of the light box may be manufactured from plastics material or from wood, and the diffuser plate is preferably made from plastics material. The bearing arm and compass rose are preferably made from transparent plastics material.

Specific embodiments of the apparatus of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a perspective view of a first embodiment of a navigational aid; and Figure 2 is a plan view of a second embodiment of a navigational aid.

Figure 1 shows a light box 1, having a diffuser plate 2, a light switch with a dimmer control (not shown), and a stainless steel spring clip 3. The light box 1 further has a compass rose 4 and a bearing arm 6 mounted on a mounting arm 7 extending across most of the width of the box 1. The mounting arm 7 is attached to a guide 8 which is free to slide in a dovetail groove 9 extending longitudinally along the lower side of the light box 1. The compass rose 4 is slidably mounted on the mounting arm 7 with downwardly extending lugs 11, in fixed orientation thereto, and the bearing arm 6 is mounted so that it is free to rotate about the compass rose 4.

On the reverse side of the light box 1 is a second diffuser plate (not shown), for use with a log and passage plan also on cellulose acetate sheets. A pen with erasable but water -indelible ink is used on the map and log sheets to plot a course directly. This ink can be removed from the sheets afterwards with spirit. The map is reproduced in such a manner that it remains permanently on the cellulose acetate sheet.

In use a map on a cellulose acetate sheet is clipped to the light box 1 using the clip 3 and the compass rose 4 is positioned at any desired point on the map. The bearing arm 6 is used to determine a bearing between two fixed points on a map by reading the angle on the compass rose 4. This enables a course to be plotted. A second guide may be attached at the other end of the mounting arm 7 to slide within a second dovetail groove to give the mounting arm 7 more stability.

Figure 2 show a light box 12 having a handle 13 and a diffuser plate 14, and a recessed on/off switch 15 for an internal light (not shown). A mounting arm 16 is slidably mounted on the light box 12 by guides 16a which run within a groove 17 on either side of the light box 12. A compass rose 18 is marked out on the perimeter of the light box 12. A pivoted bearing arm 19 in the form of a set square is slidably mounted on the mounting arm 16.

A screw 20 is provided on the bearing arm 19 at the pivot point to act as a handle and to lock the bearing arm 19 onto the mounting arm 16.

In use one side of the set square 19 is positioned at the intersection of two points on a map placed over the diffuser plate 14. The bearing arm 19 is then positioned at a centre reference 21 on the diffuser plate 14, so that the angle of the bearing arm can be read on the compass rose 18.

The embodiment of navigational aid of Figure 2 is slightly less convenient to use than the embodimentt of Figure 1 but the embodiment of Figure 2 is more accurate.

The apparatus according to these embodiments have additional advantages over a standard navigation aid, for example, a conventional map used with a standard navigation aid on a small boat is usually folded up in a plastic cover so that the map does not get wet. This embodiment has the advantages that the light box and map are water proof and the map can be changed relatively easily by clipping an overlapping adjacent map onto the light box, instead of having to take the map out of its plastic cover, to refold and replace it in the cover.

Claims (8)

1. A navigational aid comprising a light box having an internal light source for illuminating a diffuser plate, which forms the top of the light box, for supporting a map, a compass rose and a pivoted bearing arm slidably mounted on the light box.

2. A navigational aid according to claim 1, in which the compass rose is marked out on the perimeter of the light box.

3. A navigational aid according to claim 1, in which the compass rose is mounted together with the bearing arm on a mounting arm which is slidably attached to the light box.

4. A navigational aid according to any preceding claim, in which !the map is on a transparent sheet of plastics material.

5. A navigational aid according to any preceding claim, in which the light box comprises an opaque walled container having a detachable diffuser plate to close the box.

6. A navigational aid according to any preceding claim, in which the light source is provided inside the box with an external switch tomake contact with a battery inside the box, through an electrical circuit for dimming the light source.

7. A navigational aid according to any preceding claim made from water-proof materials.

8. A navigational aid substantially as hereinbefore described with respect to any one or more of the accompanying drawings.