This invention relates to a rule particularly a multi-directional
type parallel rule.
The two types of parallel rules presently in common use are the stepping
type and the one way roller type.
In particular for navigational plotting stepping type parallel rules
are not always satisfactory as they require both hands to operate. The movement
of a boat can be such that it is often desirable to hold oneself steady with one
hand while plotting a course or drawing a position.
Present types of roller parallel rules move in one direction only,
namely forward and backwards, therefore the area covered is limited to the length
of the rule unless it is lifted off the paper and reset for another area.
Neither stepping type or one way roller type parallel rules can perform
all the functions normally required in line drawing or chart plotting without the
use of other instruments such as set squares, protractors and dividers and in
the case of chart plotting, mathematical calculations to allow for compass variation
and magnetic deviation.
As such existing parallel rules are disadvantageous.
It is therefore an object of the present invention to provide a rule
which will obviate or minimize the foregoing disadvantages in a simple yet effective
manner or which will at least provide the public with a useful choice.
Accordingly the invention consists in a rule comprising a straight
edge or edge shaped to a selected shape, a first pair of spaced apart wheels, mounted
to enable said edge to be moved in a first direction and a second pair of wheels
mounted to enable said edge to be moved in a second direction substantially at
right angles to said first direction.
This invention may also broadly be said to consist in the parts,
elements and features referred to or indicated in the specification of the application,
individually or collectively, and any or all combinations of any two or more of
said parts, elements or features, and where specific integers are mentioned herein
which have known equivalents in the art to which this invention relates, such
known equivalents are deemed to be incorporated herein as if individually set forth.
The invention consists in the foregoing and also envisages constructions
of which the following gives examples only.
One preferred form of the invention will now be described with reference
to the accompanying drawings in which:
- Figure 1 is a plan view of a rule according to one preferred form of the invention;
- Figure 2 is an end view of the rule of Figure 1.
Referring to the drawings a rule 1 is provided which in the preferred
form has a plate 2 which provides a desirably shaped edge and in particular straight
edge 3. Two pairs of spaced apart wheels are mounted in the plate and in the preferred
construction a housing 4 is provided with a pair of dividing walls 5 spaced inwardly
from the end walls 7 of the housing. Between the dividing walls 5 are provided
a pair of spaced apart first wheels or rollers 8 which may be mounted on an axle
8 the ends 9 of which may be engaged with apertures in the walls 5. A keyhole type
aperture extending from the bottom edge of the wall 5 may be provided into which
the axle ends 8 may be snapped. In the preferred construction the wheels or rollers
6 have some width for example about 1cm and are provided with a knurled finish
preferably being formed of metal such as copper or brass.
A pair of second wheels 10 are provided and these again may be about
1cm in width with a knurled finish being formed in metal and these are provided
so that there axis of rotation is substantially at right angles to the axis of
rotation of the wheel 6. The wheels 10 may be provided on axles 11 which may snap
into keyhole apertures in the front wall 12 and rear wall 13 of the housing 4.
The wheels 6 are set so that the bottom parts 15 of the wheels extend
below the plate 2 thus the plate 2 can rock a little on the axle of the wheel 6.
The wheels 10 are positioned so that with the straight edge 3 resting on the surface
16 the lower part 15 of the wheel 6 will be in contact with the surface 16 but
the wheel 10 will be free of that surface. However the position of the axle 11
in the rear wall 13 is desirably higher in use than the position of the axle 11
in the front wall 12.
Thus the lower surface 16 of the wheel 10 is at an angle to the plate
2 as can be clearly seen in Figure 2. Thus in use if the wheel is rocked about
the wheel 6 until the wheel 10 comes into contact with the surface 16 a further
continuation of that motion will cause the lower part 17 of the wheels 10 to come
into contact with the surface allowing the lower part 15 of the wheel 6 to be
lifted from the surface as can be seen in Figure 2.
The included angle between the plane of the plate 2 and the plane
of the lower surface of the wheels 10 is desirably quite small and about 5 degrees
has been found suitable.
In that position the ruler can be moved in the direction of arrow
18 shown in Figure 1. When rocked onto the wheel 6 movement of the rule in a direction
at right angles to the arrow 18 is possible.
The plate 2 can be marked with any suitable markings for example
for navigational purposes, draughting purposes or otherwise.
In the preferred form of the invention a pivoting arm 20 is provided
and this can be attached to a flexible dome 21 for example moulded into a plate
2 desirably formed of a plastics material. Thus the arm 20 has an aperture 22 at
one end thereof that may be snapped onto the dome as the diameter at the base
of the dome is smaller than the diameter at the top as can be seen from Figure
2. The walls of the aperture 22 may be similarly sloped. The dome 21 is made in
several segments so that each segment can flex and cause the top of the segment
to bend inwards therefore reducing the diameter of the segmented circle when the
arm 20 is pulled off the dome 21 to be placed on a further dome 22 at the other
end of the construction. The fit between the domes 21 and 23 are sufficiently tight
so that friction will keep the arm 22 at whatever angle it is set to during use.
For measuring distances between two position for navigation purposes
the arm 20 and the ruler edge 3 are marked with small arrow heads 24 and 25 and
the arm 20 can be adjusted so that the arrow heads 24 and 25 will span over the
distance to be measured. The distance is then matched against the latitudes scale
on the chart to obtain naughtical miles thereby eliminating the need for separate
dividers. the pivoting arm 20 can be placed on either dome 21 or 23 to suit west
or east variation and the degree set at the sum of compass variation and magnetic
deviation to obtain true course, along the ruler edge 3 and compass course along
the pivoting arm edge 26 which eliminates or reduces the need for further mathematical
The use of the invention is as follows.
In use the ruler can be moved in a direction substantiate at right
angles to the direction of the edge 3 by pivoting the construction so that the
bottom part 15 of the wheel 6 engage the surface 16.
Movement in the direction parallel to the edge 3 can be achieved
by rocking the construction back to the position shown in Figure 2 so that bottom
16 of the wheel 10 engages the surface 16.
Thus it can be seen that at least in the preferred form of the invention
a rule is provided which has the advantage that movement in two directions can
be achieved with a single hand and without the need to lift the rule from the
page. This is desirable both for draughting and navigational plotting purposes
and is particularly useful for navigational plotting purposes where the free hand
can be used to hold a person steady whilst plotting a course or drawing a position.