Navigational aid device

A navigational aid device of the type comprising a disc supporting a map, especially a chart, a protractor being movable over said map, a first carrier movable in the longitudinal direction of said disc, and a second carrier which is movable on said first carrier and in the transversal direction of said disc and upon which said protractor is rotatably journalled. Said first carrier consists of at least one ruler extending across said disc and situated upon said map and sliding means situated between said map and said disc and connected to said at least one ruler, said sliding means being provided with at least one guide member movable along track means provided on and extending longitudinally of said disc.

The present invention is related to a navigational aid device of the type 
comprising a disc supporting a map, especially a chart, a protractor being 
movable over said map, a first carrier movable in the longitudinal 
direction of the disc, and a second carrier which is movable on the first 
carrier and in the transversal direction of the disc and upon which the 
protractor is rotatably journalled. 
Such a navigational aid device is shown and described in the Swedish Pat. 
No. 409,620. When using the previously known device it is troublesome to 
change charts and it is also difficult to fix the chart in a position to 
be held firmly in position at quick movements, e.g. when the device is 
placed down on a floor or ground with force against its edge. 
An object with the invention is to provide a navigational aid device of the 
type named above, which device will set the drawbacks with previously 
known devices aside and which device is easy to handle, holds the map 
firmly and secure in its position, and is umcomplicated according to its 
constructions and function. The device can with advantage be used except 
for charts even for maps used in track-finding, flying navigation and 
similar occasions when courses are to be determined on a map. 
This object is achieved according to the invention by a navigational aid 
device in which the first carrier consists of at least one ruler extending 
across the disc and situated upon the map and sliding means situated 
between the map and the disc and connected to the at least one ruler, the 
sliding means being provided with at least one guide member movable along 
track means provided on and extending longitudinally of said disc.

In FIGS. 1 and 2 a navigational aid device according to the invention is 
shown, FIG. 1 showing the device without and FIG. 2 with a chart in 
position. The navigational aid device comprises a disc 1 which is plane 
and substantially rectangular, a first carrier consisting of, on one hand, 
an upper ruler 2 which is provided on and movable along the disc, and, on 
the other hand, a sliding part 3 which at its ends is connected to the 
ends of the ruler 2 and which has guide means movable in a track 5 in the 
disc 1, a second carrier 6 provided on said upper ruler 2 and movable in 
the cross-direction of the disc, and a protractor 7 rotatably journalled 
on the second carrier 6. Within the scope of the present invention the 
first carrier 2, 3 can be movable in the longitudinal direction of the 
disc and the second carrier 6 in the transversal direction of the disc. 
Further, the chart is placed in an envelope of flexible, transparent 
plastics fastened at the upper edge of the disc. The lower edge of the 
envelope is overlapping the lower edge of the disc and is detachably 
fastened on the backside of the disc. Of course, the envelope can be held 
firmly in other ways within the scope of the invention. It is of great 
importance that the chart is held firmly against rotational movements in 
relation to said disc 1. The chart need not to be placed in an envelope, 
but can be placed directly on the disc, e.g. using charts which have been 
covered in advance with plastics. In this case, fastening means for this 
purpose can be provided on the upper or lower edge sides of the disc. 
In FIG. 2 a chart is placed on the disc between the sliding part 3 and the 
ruler 2 of said first carrier. 
The second carrier 6 is provided with four northern-markings in the form of 
an "N". These markings "N" are provided at 11, 12, 13 and 14 in FIG. 1. 
The purpose thereof is that the positioning of the chart on the 
navigational aid device can be varied so that the northern marking "N" is 
used which corresponds to the northern position of the chart. It is to be 
noted that the scale of the protractor 7 is made so that the scale numbers 
increase clockwise thereon. 
Also, before the chart is placed upon the device, depending upon the 
weather, it can be introduced in a separate envelope of plastics. 
A stop means 15 is provided on said second carrier. This stop means firmly 
locks the first carrier 2, 3 and the second carrier 6 in relation to each 
other by means of a simple manipulation. Moreover, a locking member 16 is 
provided to firmly lock the first carrier 2 on the disc. 
A recess 17 is provided on the protractor 7 by means of which one can 
easily grip the same and turn it to the desired position. 
In FIGS. 3 and 4 a second embodiment of the navigational aid device 
according to the invention is shown, comprising a disc 20, a first carrier 
21 movable in the longitudinal direction of and upon the disc, a second 
carrier 22 movably connected to the first carrier 21 to be moved in the 
transversal direction of the disc 20, and first and second protractor 
parts 23 and 24, respectively, being rotatably journalled on the second 
carrier 22. The first carrier 21 comprises two rulers 25 and 26, 
respectively, between which sliding members 27 and 28, respectively, are 
provided. In the centre of the disc and in the longitudinal direction 
thereof a plate 29 is fastened, in such a way that tracks are provided at 
the longitudinal edges thereof at 30 and 31, respectively. The sliding 
members 27 and 28 each being provided with guide edges 32 and 33, 
respectively, at the inner ends thereof, the guide edges being introduced 
in the tracks 30 and 31 so that the first carrier can be in the 
longitudinal direction of the disc. 
The second carrier 22 which consists of a plate with a circular hole in the 
middle thereof is intended to receive the rings 23 and 24 defining the 
protractor. Those rings 23 and 24 are held in place by holders 34, 35 and 
36. Further, the second carrier has two parallel edges 37 and 38 which are 
bent so as to define parallel channels on the under side of the carrier 
receiving the outer edges of the rulers 25, 26 of the first carrier 21 to 
provide for the transversal reciprocating movement thereof. 
In FIG. 3 some sectional views 39, 40, 41 and 42 are shown to make the 
sectional areas of the rings 23, 24, the second carrier 22 and the first 
carrier 21 clear. 
In FIG. 4 it is shown how the guide edges 32, 33 of the sliding members 27 
and 28, respectively, are received in the tracks 30, 31 between the plate 
29 and the disc 20. 
In this embodiment two rings 23, 24 are provided instead of the ring 7 in 
the first embodiment due to the fact that the second embodiment is formed 
to take deviation from the true North into consideration. For this purpose 
the second carrier 22 is provided with scales 43 and 44. 
The position of the map or the envelope which shall receive the map is 
schematically shown by means of the curved lines 45, 46 in FIG. 3. 
A stop means 47 is provided to firmly lock the first carrier in relation to 
the disc, and another stop means 48 is provided to firmly lock the 
position of the second carrier 2 in relation to the first carrier. 
The navigational aid device according to the invention is of course not 
limited to the shape of the parts shown on the drawings, but the first 
carrier, the second carrier and other details can be formed in other ways 
within the scope of the present invention. For example, the first carrier 
can be detachable in two or more parts which by means of an easy motion 
can be disassembled or assembled. What is claimed is: