BACKGROUND TO THE INVENTION Engineers or planners engaged in the estimating or scheduling of materials for construction tasks need to make calculations of the quantities of materials required. For example, when planning a concrete floor or wall the amount of steel reinforcing required must be accurately forecast. An error in calculating the amounts can result in cost over-runs and extensive delays in job completion.

At present, the job of the estimator or scheduler involves a considerable number of calculations. Taking the steel reinforcing case as an example, the estimator will first examine the engineers plans to identify the various lengths of steel reinforcing employed in the job. In general, a set of engineering drawings will show a sketch of the steel reinforcing bars to be used and will include a bisecting line to inform the reader of the area over which such bars are spaced. The length of the bisecting line indicates the length over which the indicated steel reinforcing bars are to be used.

The bisecting line is measured and the measurement is entered into a calculator. The calculator is used to divide the measurement by the nominated spacing of the steel reinforcing bars that has been given on the plan. This division will result in a whole number and may include a remainder. The whole number is the number of bars to be spaced over the length of the bisecting line at the nominated spacing. It is not the full number of steel reinforcing bars to be used since one extra bar must be added at the beginning of the row. Furthermore, if the calculation results in a remainder another extra bar must be added since there must be a bar at each end of

the row.

It will be appreciated that the number of calculations required in a given estimating task is enormous and it is therefore not surprising that errors occur from time to time. There is a clear need to simplify the task of the estimator or scheduler as much as possible.

OBJECT OF THE INVENTION One object of the present invention is to provide an apparatus and method useful as an aid when determining the number of items in a given area. DISCLOSURE OF THE INVENTION

In one form, although it need not be the only or indeed the broadest form, the invention resides in an apparatus for determining the number of items in a given area, the apparatus comprising a scale rule marked with a plurality of indicia, said indicia corresponding directly to the number of items in the said area at a given spacing scale when drawn according to a given drawing scale.

In preference the indicia are numbered with allowance for an extra item at the beginning of a row and the indicia are read to the next highest whole number. In preference the scale rule has a straight edge and the indicia comprise a number of equally spaced lines drawn substantially perpendicular to the straight edge.

The indicia are preferably numbered sequentially from one to a maximum and grouped with every fifth or tenth indicia being labelled as appropriate for the drawing scale and spacing scale.

The apparatus may further comprise an additional indicia drawn beyond the last group, said additional indicia being equally spaced from the indicia as appropriate for the drawing scale and spacing scale.

In preference the spacing scale has a spacing of indicia selected from those commonly used in engineering drawings such as .125, .150, .175, .200, .225, .250, .275, .300, .325, .350, .375, or .400.

In preference the apparatus may have a plurality of scale

surfaces, each surface being marked with indicia at a different scale to that of the other surfaces.

In preference one surface of the apparatus may be marked with a conventional measurement scale for the drawing scale. The drawing scale is preferably a commonly used scale such as 1 : 1 , 1 : 10 or 1 : 100.

The apparatus may find application in any situation in which the number of identical items spaced along a given line is to be determined.

The inventor envisages that the invention will find primary application in the estimation of the number of steel reinforcement bars required in a construction task.

In another form, although again not necessarily the broadest form, the invention resides in an apparatus for determining the number of steel reinforcement bars in a given area on an engineering drawing, the apparatus comprising a scale rule marked with a plurality of indicia, said indicia corresponding directly to the number of steel reinforcement bars in the said area at a given spacing scale when drawn according to a given drawing scale, wherein the indicia are numbered with allowance for an extra bar at the beginning of a row and wherein the indicia are read to the next highest whole number. In a still further form the invention resides in a method of determining the number of items required for a given area using a scale rule marked with a plurality of indicia, said indicia corresponding directly to the number of items in the said area at a given spacing scale when drawn according to a given drawing scale, including the steps of : identifying an area of a drawing indicated as requiring a plurality of items; selecting a required spacing scale on the scale rule; applying the spacing scale to a bisecting line running from one extremity of the area to an opposite extremity such that a first indicia is aligned with a first extremity; sighting across the scale rule to the other extremity; reading the next highest indicia beyond the point where the

other extremity intersects with the scale rule, said indicia being the number of items required in the area.

In a yet further form the invention resides in a method of determining the number of steel reinforcing bars required for a given area using a scale rule marked with a plurality of indicia, said indicia corresponding directly to the number of steel reinforcement bars in the said area at a given spacing scale when drawn according to a given drawing scale, including the steps of: identifying an area of an engineering drawing indicated as requiring a plurality of steel reinforcing bars; selecting a required scale on the scale rule; applying the scale rule to a bisecting line running from one extremity of the area to an opposite extremity such that a first indicia is aligned with a first extremity; sighting across the scale rule to the other extremity; reading the next highest indicia beyond the point where the other extremity intersects with the scale rule, said indicia being the number of steel reinforcing bars required in the area.

BRIEF DESCRIPTION OF THE DRAWINGS To further assist in understanding the invention reference will be made to the following drawings in which: FIG 1 shows one side of a first embodiment of an apparatus for determining the number of items in a given area; FIG 2 shows an opposite side of the apparatus of FIG 1 ; FIG 3 shows a first side of a second embodiment of an apparatus for determining the number of items in a given area; FIG 4 shows an opposite side of the apparatus of FIG 3; FIG 5 shows a cross-sectional end view of the embodiment of FIG 1 ; FIG 6 shows a cross-sectional end view of a third embodiment of an apparatus for determining the number of items in a given area;

FIG 7 shows a simplified section of an engineering drawing indicating the required length and spacing of reinforcing bars;

FIG 8 depicts a step in determining the number of reinforcing bars required for the section of engineering drawing of FIG 7; and FIG 9 depicts a further step in determining the number of reinforcing bars required for the section of engineering drawing of FIG 7. 5 DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to the drawings in detail there is shown in FIG 1 and FIG 2 the opposing surfaces of a first embodiment, generally indicated as 1 , of an apparatus for determining the number of items required in a given area of a drawing. FIG 3 and FIG 4 show the opposing surfaces of a second o embodiment, generally indicated as 2, of an apparatus for determining the number of items required in a given area of a drawing. The apparatuses, 1 and 2, are designed for use with engineering plans having a drawing scale of 1:100. It will be appreciated that an apparatus can be constructed for any given drawing scale without departing from the inventive concept. 5 The apparatus 1 differs from the apparatus 2 in the combination of spacing scales showing on the surfaces. FIG 1 shows a first surface 3 having indicia, generally indicated as 4, labelled for three different spacing scales. In the particular example the scales are .200, .300 and .400. The surface 3 also incorporates a conventional ruler scale 6 at the drawing 0 scale of 1:100.

FIG 2 shows the reverse surface 5 of the apparatus of FIG 1. The reverse surface has indicia labelled for spacing scales of .150, .250, .350 and .450. The surfaces 3, 5 of FIG 1 and FIG 2 are applied to a flat ruler having a cross-section as depicted in FIG 5. 5 FIG 3 and FIG 4 show opposite surfaces 7 and 8 of the apparatus 2 with spacing scales of .125, .225, .325, .425 on surface 7 and .175, .275, .375 and .475 on surface 8. The inventor has found that the pair of apparatus shown in FIG's 1, 2, 3 and 4 can conveniently be labelled for fifteen different common spacing scales used in engineering drawings. 0 The indicia 4 are marked upon the apparatus in a manner to enhance the visual effect. Looking for example at FIG 2 it can be seen that every fifth indicia, such as 10, are longer than the intervening indicia and

connected such that the indicia are contained within a box. Every fifth indicia is labelled with a number which directly indicates the required number of steel reinforcing bars.

It will be appreciated that every fifth indicia is numbered for convenience. On smaller scales it may be convenient to number only every tenth indicia so as to avoid a distracting clutter of labels. Furthermore, the embodiments shown indicate metric scales but the invention is not limited to any particular system of measurement. An equivalent measuring apparatus can be constructed for imperial scales or indeed any desired spacing scale. Each set of indicia are labelled with prominent numerals, such as 11 to indicated the item spacing for which the indicia applies. An additional index, such as 12, is provided at the end of each set of indicia. The purpose of the extra index is to facilitate the marking of the next measurement start point if the apparatus is not long enough to make the measurement in a single action. This process is described in more detail below.

It will be appreciated that the invention is not limited to the flat apparatus profile shown in FIG 5 and described above. An apparatus having a triangular shape in cross-section as depicted in FIG 6 may also be constructed. The advantage of this embodiment is that there are three surfaces on which to print indicia (six edges on which to print spacing scales). The inventor envisages that for many applications a single apparatus will support sufficient spacing scales for the application. An example of such an application is the determination of the number of posts and panels required for constructing a fence.

For ease of explanation the use of the apparatus 13 will be described in determining the quantity of steel reinforcing required in a specific portion 14 of an engineering drawing 15 shown in FIG 7. The full detail of the engineering drawing is shown in FIG 8. The engineering drawing 15 indicates the spacing of steel reinforcing bars in the portion to be 300 mm. The 300 scale is selected and applied to the bisecting line 16 as shown in FIG 8. The zero indicia 17 is aligned with one extremity 18 of

the bisecting line 16. The number of steel reinforcing bars required is read directly from the apparatus 13 as 31 bars.

To complete the estimating task the conventional scale 19 is used to measure the length of the steel reinforcing bar 20 as shown in FIG 9. In the example the length of steel reinforcing is 3.8 metres. Thus the amount of steel reinforcing required in this portion is 117.8 metres (31 bars times 3.8 metres).

It will be appreciated that this calculation can be done progressively or the quantities can be simply noted and totalled later. For example, the estimator could compile a list of quantities in the form of "Y12 bars - 31 off x 3.8 m long" where Y12 indicates the gauge of the steel reinforcing bar required. If the calculation is made progressively it would be noted as Y12 bars x 117.8 metres and the grand totals of each gauge made at the end of the estimating task. The specific example shows the region over which reinforcing bars are required being indicated by a bisecting line marked with clear extremities. In some cases the extremities may be marked by a change in reinforcing bar size or shape, or a length of the bisecting line may be indicated numerically. In these cases a preliminary operation may be required to delineate mark the extremities of the bisecting line.

The above method is slightly varied if the length of the bisecting line is greater than length of the relevant set of indicia. If using the 300 spacing scale a note is made of the number 50. A mark is made on the bisecting line at the 51st position. The apparatus is then repositioned with the starting index aligned with the mark and the process is continued as above. The number of reinforcing bars required will be 50 plus the number read.

The inventor has made a comparison of the time required to complete an estimating task when using the invention compared to prior art methods using a conventional scale rule. Two tests were conducted, the first involved 32 estimations and the second involved 58 estimations. Using the prior art method with a conventional scale ruler the time per estimation was

6.64 seconds compared to 3.62 seconds per estimation when using the invention.

The preferred embodiment described herein is intended to illustrate the principles of the invention, but not to limit its scope. Other 5 embodiments and variations to the preferred embodiment may be evident to those skilled in the art and may be made without departing from the spirit and scope of the invention. The inventor perceives that the apparatus and method will find primary application in estimation of the number of reinforcing bars required in concrete slabs, concrete walls and block walls. Another o application would be for determining the number of posts and panels required to construct a fence. The apparatus and method will also be useful for other similar applications.