Title: Protractor

The present invention relates to a protractor and particularly, but not exclusively, to a bevel protractor for measuring and marking angles in carpentry, cabinet work, metal work and plastics work.

Background to the Invention

It is known to provide a bevel protractor for use in carpentry, woodwork and other crafts for measuring and marking off angles. The protractor may be part of a set, known as a combination square, in which 90° and 45° set squares and a ruler are also provided.

A problem of a combination square is that it comprises several parts, for use independently, depending on the angle to be marked off. These parts have to be carried and/or stored and are cumbersome. Furthermore, the length of the ruler, which generally is removably attached to the protractor, is often too short, for example, when marking off an angle on a board.

It is an object of the invention to provide a protractor which substantially reduces or obviates the problems associated with combination squares.

Statement of Invention

According to the first aspect of the present invention there is provided a protractor comprising a body portion having at least a first straight side, a ruler having at least a first straight side, the ruler being adjustably mounted to the body portion about a pivot, and an angular scale indicating the angle between the respective straight sides of the ruler and body portion, characterised in that the ruler includes a plurality of discrete lengths which are hinged together at their adjacent ends, the ruler folding between a closed position in which the discrete lengths overlie one-another and an extended position in which the discrete lengths abut one-another end to end.

The protractor is advantageous because it can be extended from the closed position for marking larger work-pieces. The ruler neatly folds away when not in use for ease of storage, for example, in a tool box or bag.

The scale may include a fixed marking provided on the body portion, and a rotary dial with a numbered angular scale which rotates with the ruler.

The ruler may slide relative to the body portion. This enables the ruler to be adjusted to a desired length to one or both sides of the body portion, for use in situations when the fully extended ruler is too long or marking of an angle to both sides of the protractor is required.

The body portion may have a second side, parallel with the first side and a spirit level disposed between the first and second sides for indicating when one of the sides is horizontal. This enables the protractor to be used as a carpenter's level.

A second spirit level may be disposed between the first and second sides for indicating when one of the sides is at 45° to the horizontal.

Means may be provided for automatically stopping and retaining the side(s) of the ruler at 90° to the side(s) of the body portion. A 90° angle is most commonly required to be marked and by having an automatic stop and retaining means, there is no requirement for a 90° set square.

Means may also be provided for automatically stopping and retaining the side(s) of the ruler at 45° to the side(s) of the body portion. This removes the requirement for a separate 45° set square.

The extended ruler may be approximately Im in length. Different lengths of ruler may optionally be provided, e.g. 0.5m, 0.75m and 1.25m.

The ruler may be provided in 4 discrete lengths or separate parts. There may be more or less discrete lengths or parts of the ruler, as required.

The ruler may have a second side parallel with the first side, each side having an axial slot therein for receiving keys provided on the body portion.

Locking means may be provided for locking the ruler relative to the body portion. This enables easy marking of angles, in use, because the ruler can be fixed relative to the body portion at any given angle.

Description of the Drawings

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1 shows a schematic perspective view of a protractor of the invention with the ruler in a closed position;

Figure 2 shows a schematic end view of the protractor of Figure 1 ;

Figure 3 shows a schematic front view of the protractor of Figure 1 with the ruler in an extended position;

Figure 4 shows a schematic perspective view, partly in cut-away, of the protractor of Figure 1;

Figure 5 shows a schematic side view of the protractor of Figure 1, in a part-extended condition; and

Figure 6 shows a schematic perspective view of the protractor of Figure 1, in use, positioned for marking an angle on sheet material.

Description of Preferred Embodiments

Referring firstly to Figure 1, a protractor is indicated generally at 10. The protractor 10 includes a body portion 12, a ruler 14 pivotally mounted to the body portion at one

end thereof, and an angular scale 16 mounted on a rotary dial 18. A knurled locking nut 20 is provided at the centre of the rotary dial 18 for locking the body portion 12 at a desired angle relative to the ruler 14. The ruler 14 is provided in four discrete lengths or parts 22, 24, 26 and 28, as shown particularly in Figures 2, 3 and 5. The first part 22 of the ruler 14 is connected to the body portion 12, when in the closed position, as will be described further below. The parts 22, 24, 26, 28 are hinged together at their ends about hinges 30, 32, 34, which enable the parts to be folded flat against one another, as shown in Figures 1 or 2, or extended to form a single length of ruler, as shown in Figure 3. The hinges provided at the respective ends of each member open in different directions. For example, the hinge 30 opens in a different direction to that of the hinge 32, as indicated in Figure 5.

The body portion 12 is formed preferably from a plastics moulding and has two parallel sides 36, 38. Cut-outs 40, 42 are provided between the sides 36, 38 of the body portion 12 which mount respective spirit levels 44, 46. The first spirit level 44 is disposed parallel with the parallel sides 36, 38 of the body portion, whereas the second spirit level 46 is disposed at an angle of 45° relative to the parallel sides of the body portion. The width of the body portion 12 is wider than that of the portions of the ruler 14, and therefore when in a closed position, the body portion can be used to indicate when a surface is horizontal and also when a surface is at 45° relative to the horizontal by virtue of the spirit levels 44, 46.

Referring also to Figures 7 and 8, the rotary dial 18 is connected to a rotary mount 48, which engages in a circular recess 50 in the rear of the body portion 12. The rotary mount is provided with two opposing part circular side members 52, 54 having tongues 56, 58 which face one another. Slots 60, 62 are provided in respective edges of the ruler 14, which engage with the tongues 56, 58. The slots 60,62 slide on the tongues enabling sliding of the ruler 14 relative to the body portion 12, as indicated by the arrow A in Figure 8. When the adjoining parts of the ruler are aligned, the ruler can slide along the tongues 56,58 over its full length.

The angular scale 16 on the rotary dial 18 can be used to set the angular position of the ruler relative to the body portion 12. The angular scale 16 can be read against a reference marking 64 provided at the end of the body portion 12. In the position

shown in Figure 7, the sides of the ruler 14 are presented at right angles (90°) to the sides of the body portion 12.

A screw thread 66 passes through the rotary dial and body portion 12, and is locked by means of the knurled nut 20. This locks the position of the ruler 14 relative to the body portion 12. Detents 68, one of which is shown in Figure 4, are provided on the periphery of the rotary mount 48 at positions corresponding to angular positions of the ruler 14 relative to the body portion 12 of 45° and 90°. A corresponding recess is provided on the inside of the circular recess 50 in the body portion 12, and when one of the detents 68 meets the recess as the rotary dial and ruler are rotated, then the detent snaps into the recess and retains the ruler and rotary dial at the set angle. Increased force can be applied to the ruler and body portion in order to release the detent 68 from the recess.

In use, the protractor 10 is typically stored and carried in the closed position as shown in Figures 1 and 2. In this position, the body portion 12 overlies the individual parts 22, 24, 26, 28 of the ruler 14, which overlie one another in a tightly formed stack. The pars of the ruler 14 are also aligned with the body portion 12 and may be locked in position by means of the knurled locking nut 20. When it is desired to use the protractor 10 to measure an angle, then the locking nut 20 can be released, and the ruler 14 rotated to a desired angle as indicated on the scale 16. Optionally, the ruler 14 may be extended by simply folding the parts of the ruler outwards as indicated in Figure 5 by use of the hinges 30, 32, 34. If the same angle is to be measured on both sides of the body portion 12, then the ruler can be slid relative to the body portion on the tongues 56, 58, for example to a position as shown in Figure 6. In this position, the ruler extends to both sides of the body portion 12 and the ruler 14 can be locked in position by virtue of the knurled locking nut 20. The ruler 14 is provided with a graduated scale, as most clearly shown in Figure 4. The scale may be metric or imperial, as desired. In the arrangement shown, a metric scale is shown on one edge of the ruler 14 and an imperial scale is shown on the other edge of the ruler 14.

When the protractor 10 is no longer required, the knurled locking nut 20 can be undone and the ruler rotated to be in alignment with the body portion 12, i.e. at 0° on the scale. The ruler 14 may be folded to the closed position and the tongues 56, 58 of

the rotary mount may be positioned at the end of the first ruler part 22, such that the body portion 12 overlies the closed ruler 14 as shown in Figures 1 and 2.

It will be appreciated, that the protractor is highly adaptable, since it can be used as a spirit level, a 45° set square and a 90° set square. It can also be used directly as a ruler and optionally the ruler can be completely removed from the rotary mount 48 thereby enabling the ruler to be used independently. The protractor substantially obviates the need for a traditional combination square and is considered to be a highly adaptable multipurpose tool.