GB2154010A

GB2154010A - Device for plotting a course on a chart

Info

Publication number: GB2154010A
Application number: GB08403263A
Authority: GB
Inventors: Raymond Walter Farr
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-02-07
Filing date: 1984-02-07
Publication date: 1985-08-29
Also published as: GB8403263D0; GB2154010B

Abstract

A plate 26 to relate to a course direction line is pivoted beneath protractor 22 that is mounted for sliding movement on rail 16, which bridges a chart midway along strips 14 and 20. In use edge 24 is aligned with the course or bearing to be determined and the value read off using line 30. The chart can be advanced transversely along guide 32 that is attached relative to a suitable base, or can be made removable by the use of hook-and-loop tape to form guide <IMAGE>

Description

SPECIFICATION Apparatus for plotting a course on a chart The invention relates to apparatus for plotting a course on a chart.

While navigating, it is often required to measure the compass bearing of a line connecting two points on a chart. This can be done by placing a protractor at one point and measuring the angle between north and the line passing through the other point. To measure the bearing relative to north, one must first line the protractor with a meridian line and it may be difficult to do so if no meridian line is drawn nearby on the chart. Either the drawing of a line or lining up a protractor correctly using other navigational aids such as parallel rules requires a steady flat surface and this is sometimes not available especially when navigating a small boat.

Some bulky and complicated devices have been proposed in the past generally resembling drawing board mechanisms which use mechanical linkages to permit a protractor to be moved in mutually orthogonal directions relative to a chart while retaining its correct orientation on the chart. Such devices are again not suited to small boats both because of their costs and because of their size and weight.

The invention seeks to provide an apparatus to mitigate the foregoing difficulties which is of simple and robust construction and yet is relatively inexpensive to manufacture.

According to the present invention, there is provided an apparatus for plotting a course on a chart, comprising a guide for guiding an edge or a fold of a chart, a transparent rail fixed relative to the guide and extending transversely thereto, a transparent protractor mounted for sliding movement along the rail without rotating about its centre and a transparent plate movable along the rail with the protractor and rotatable about a point lying at the centre of the protractor, the plate defining two parallel lines of which the first passes through the centre of the protractor and the other is manually aligned during use with the points on the chart from which a bearing is to be taken.

The invention will now be described further, by way of example, with reference to the accompanying drawing which is a plan view of an apparatus of the invention.

In the drawing, there is shown a chart 10 which rests with its lower edge on a guide 1 2. The chart may first have been folded and placed within a plastics sleeve. The guide 1 2 may be any raised edge secured to a flat or cylindrical surface. A retaining strip 14 overlies the guide 1 2 to prevent accidental displacement of the chart. The strip may conveniently be of a transparent plastics material such as PVC sheeting and may be secured in position either permanently, such as by use of fixing screws or adhesive, or may be releasable mounted by means of a strip 32 of Velcro (Registered Trade Mark).

A rail 1 6 is fixed to the strip 14 by means of rivets 1 8 and extends at right angles to the strip 1 4. At its end remote from the strip 14, the rail 1 6 passes through a slot in an optional second strip 20 which may be arranged along the upper edge of the chart.

In use, the strips 14, 20 and the rail 16 extending between them are stationarily mounted and the chart is moved from left to right as viewed, as represented by the arrow 34, relative to the rail 1 6.

A transparent protractor 22 has slots which receive the rail 1 6. This mounting permits the protractor to move along the rail 1 6 without rotating. A plate 26 is rotatable about the centre of the protractor, as represented by the arrow 36, and has an edge 24 which in use is aligned with the points on the chart from which a bearing is to be taken. A line 30 is drawn on the plate 26 which is parallel to the edge 24 but passes through the centre of the protractor 22.

To use the apparatus, the chart is inserted between the strips 14, 20 and moved along the guide 1 2. In any position of the chart, north will be aligned with the north reading on the protractor 22. The chart may be moved manually until the two points of interest lie near the plate 26. The plate is now rotated as necessary and moved along the rail 16, moving with it the protractor, until the two points lie on the edge 24. While applying fingure pressure to the centre of the protractor to prevent any movement, the bearing required may then be read from the intersection of the line 30 with the protractor markings.

The protractor 22 and the plate 26 are all made of a transparent material so that the line 30 as well as the chart 10 itself may be seen through the rail 1 6 and the protractor 22.

1. Apparatus for plotting a course on a chart, comprising a guide and retaining strip for retaining and guiding an edge of a chart and having midway along its length a rail fixed relative to the aforesaid guide strip and extending transversely thereto which thus bridges the chart, a protractor mounted for sliding movement along the rail, a plate rotatable about a point laying at the centre of the protractor, the plate defining two parallel lines of which the first passes through the centre of the protractor and the other being the edge of the plate.

2. Apparatus for plotting a course on a chart as claimed in claim 1 wherein an optional second guide and retaining strip which may be arranged parallel to the first guide strip to retain the opposite edge of the chart and having two parallel slots at its mid point

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Apparatus for plotting a course on a chart The invention relates to apparatus for plotting a course on a chart. While navigating, it is often required to measure the compass bearing of a line connecting two points on a chart. This can be done by placing a protractor at one point and measuring the angle between north and the line passing through the other point. To measure the bearing relative to north, one must first line the protractor with a meridian line and it may be difficult to do so if no meridian line is drawn nearby on the chart. Either the drawing of a line or lining up a protractor correctly using other navigational aids such as parallel rules requires a steady flat surface and this is sometimes not available especially when navigating a small boat. Some bulky and complicated devices have been proposed in the past generally resembling drawing board mechanisms which use mechanical linkages to permit a protractor to be moved in mutually orthogonal directions relative to a chart while retaining its correct orientation on the chart. Such devices are again not suited to small boats both because of their costs and because of their size and weight. The invention seeks to provide an apparatus to mitigate the foregoing difficulties which is of simple and robust construction and yet is relatively inexpensive to manufacture. According to the present invention, there is provided an apparatus for plotting a course on a chart, comprising a guide for guiding an edge or a fold of a chart, a transparent rail fixed relative to the guide and extending transversely thereto, a transparent protractor mounted for sliding movement along the rail without rotating about its centre and a transparent plate movable along the rail with the protractor and rotatable about a point lying at the centre of the protractor, the plate defining two parallel lines of which the first passes through the centre of the protractor and the other is manually aligned during use with the points on the chart from which a bearing is to be taken. The invention will now be described further, by way of example, with reference to the accompanying drawing which is a plan view of an apparatus of the invention. In the drawing, there is shown a chart 10 which rests with its lower edge on a guide 1 2. The chart may first have been folded and placed within a plastics sleeve. The guide 1 2 may be any raised edge secured to a flat or cylindrical surface. A retaining strip 14 overlies the guide 1 2 to prevent accidental displacement of the chart. The strip may conveniently be of a transparent plastics material such as PVC sheeting and may be secured in position either permanently, such as by use of fixing screws or adhesive, or may be releasable mounted by means of a strip 32 of Velcro (Registered Trade Mark). A rail 1 6 is fixed to the strip 14 by means of rivets 1 8 and extends at right angles to the strip 1 4. At its end remote from the strip 14, the rail 1 6 passes through a slot in an optional second strip 20 which may be arranged along the upper edge of the chart. In use, the strips 14, 20 and the rail 16 extending between them are stationarily mounted and the chart is moved from left to right as viewed, as represented by the arrow 34, relative to the rail 1 6. A transparent protractor 22 has slots which receive the rail 1 6. This mounting permits the protractor to move along the rail 1 6 without rotating. A plate 26 is rotatable about the centre of the protractor, as represented by the arrow 36, and has an edge 24 which in use is aligned with the points on the chart from which a bearing is to be taken. A line 30 is drawn on the plate 26 which is parallel to the edge 24 but passes through the centre of the protractor 22. To use the apparatus, the chart is inserted between the strips 14, 20 and moved along the guide 1 2. In any position of the chart, north will be aligned with the north reading on the protractor 22. The chart may be moved manually until the two points of interest lie near the plate 26. The plate is now rotated as necessary and moved along the rail 16, moving with it the protractor, until the two points lie on the edge 24. While applying fingure pressure to the centre of the protractor to prevent any movement, the bearing required may then be read from the intersection of the line 30 with the protractor markings. The protractor 22 and the plate 26 are all made of a transparent material so that the line 30 as well as the chart 10 itself may be seen through the rail 1 6 and the protractor 22. CLAIMS

2. Apparatus for plotting a course on a chart as claimed in claim 1 wherein an optional second guide and retaining strip which may be arranged parallel to the first guide strip to retain the opposite edge of the chart and having two parallel slots at its mid point through which passes the unattached end of the protractor bearing rail.

3. Apparatus for plotting a course on a chart as claimed in claim 1 and 2 wherein the guide strips are attached to a suitable base by means of hook and loop fastener tape whereby the inner edges are used to form the guide.

4. Apparatus for plotting a course on a chart as claimed in claim 1 and 2 wherein the guide strips may be attached to a suitable base by any convenient means.

5. Apparatus for plotting a course on a chart as claimed in claim 1 wherein a protractor having a slot at each opposing end through which passes a flat transparent rail, the bending forces thus applied on both components provides a degree of resistance to the sliding action thus resisting inadvertent movement of the protractor.

5. Apparatus for plotting a course on a chart as claimed in claim 1 wherein a protractor having a slot at each opposing end through which passes a rail, the bending forces thus applied on both components provides a degree of resistance to the sliding action thus resisting inadvertent movement of the protractor.

6. Apparatus for plotting a course on a chart as claimed in claim 1 and claim 2 wherein the construction is of a transparent resilient material.

7. Apparatus for plotting a course on a chart substantially as described with reference to the accompanying drawing.

CLAIMS Amendments to the claims have been filed, and have the following effect: Claims 1 and 5 above have been deleted or textually amended.

New or textually amended claims have been filed as follows:

1. Apparatus for plotting a course on a chart, comprising a guide and retaining strip for retaining and guiding an edge of a chart and having midway along its length a flat transparent rail fixed relative to the aforesaid guide strip extending transversely thereto which thus bridges the chart and carries a protractor mounted for sliding movement along the rail.