US1615510A - grotendorst - Google Patents

Description

Jan. 25, 1927. 1,615,510

W. F. GROTENDORST TABULAR CALCULATING APPARATUS PARTICULARLY FOR USE IN THE LAYING OF ORDNANCE Original Filed March 29 1926 I5 Sheets-Sheet 1 fluenrr: 2M1, G rozznolorsif,

Jan. 25 927. 1,615,510

w. F.,GROTENDORST TABULAR CALCULATING APPARATUS PARTICULARLY FOR USE IN THE LA ING C" ORDNANCE Original 11 d larch 29, 1926 3 Sheets-Sheet 2 lNVEN TOR MFGroQndo -Ft, J

ATTO R N EYS 1,615,510 w F. GROTENDORST TABULAR CALCULATING APPARATUS PARTICULARLY FOR USE IN THE LAYING OF ORDNANCE Original Filed March 29, 1926 3 Sheets-Sheet 5 WE Grafendora, 7

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Patented Jan. 25, 1927.

UNITED STATES 1,615,510 PATENT OFFICE.

WILLEM FREDERIK GROTENIDORST, OF HELDER, NETHERLANDS.

lABULAR-CALC ULATING APPARATUS PARTICULARLY FOR USE IN THE LAYING OF ORDNANCE.

Original application filed March 29, 1926, Serial No. 88,324, and in the Netherlands November 19, 1923. Divided and this application filed August 7, 1926. Serial No. 127,962.

This application is a division of my copending application Serial No. 98,324, filed March 29, 1926. r

This invention relates to tabular calculating apparatus particularly for use in the laying of ordnance. The invention is particularly intended for use in conjunction with the device described in the specification of my co-pending patent application.

The main purpose of this invention is to provide a tabular device which shall permit of calculating the distance of an ob ect or target from data obtained by simultaneous observations taken from each end of a known base line.

The present invention consists in an improved tabular calculating apparatus comprising a logarithmic scale constituted by a series of rows of equal lengths arranged one 29 below the other, a ruler adapted to be used with said logarithmic scale three times the length of each of such rows and carrying an adjustable indicating mark and being uniformly graduated to indicate lengths in terms of the length of a row as a unit,-and an anti-logarithm table for converting lengths read from the ruler into the data required, said table giving a plurality of answers for each fraction of a unit, so that when the answer is approximately known the ruler need only be read to the nearest two places of decimals in order to obtain an approximation corresponding to the use of three figure logarithms. I

One form of the present invention is illustrated for the sake of example in the accompanying drawings in which Fig. 1 indicates the positions of two observation posts and an object, and corresponds with part of the Fig. 1 ofmy above mentioned co-pending patent application.

Figs. 2 to 5 show the various elements of the apparatus, which are intended to be used in combination.

Fig. 2 shows a logarithmic chart indicating angles.

Figs. 3 and 3 show an anti-logarithm 1 table for converting logarithms into distances.

Fig. 4 shows a logarithmic rule with cursor. v

Fig. 5 shows an indicating plate.

In Fig. 1, Z, and Z represent two observation posts provided with angle measuring instruments, and D represents the position of an object or target. The distance Z Z =b. a is the bearing angle at which the object or target is seen from Z and ,8 is the supplement of the bearing angle at which the object or target is seen from Z t is the so-called vertical angle.

The angles a and ,8 are measured simultaneously'at the posts Z and Z From'this we find sint whence log. Z D=log. b+log sin a-lOg sin t. (1)

From this formula the distance Z D can be calculated, which distance is necessary for determining certain data required -for the indirect laying of ordnance, as described in the specification of my co-pending patent application.

The calculation of Z 1) according to the formula (1) would of course in practice require too much time and to facilitate rapid calculation of this distance Z,D the apparatus which embodies the present invention is provided, the various details of which are illustrated in the Figures 2, 3, 4 and 5. By this calculating device a simple displacement of some parts, which may be done by unskilled hands, permits of immediately reading Z 1). The usual table of logarithms works with numbers which must be added or subtracted. The principle of the calculating device consists of a table (one of which is shown in Figures-3 and 3*); four rulers with transparent slide (in Figure 4 one of them is shown) and a small transparent plate of special shape (Figureii).

In the table of angles log. sin a and log. sin tare indicated, in the ruler log. I), and

in the table of distances log. Z D. This is effected in the following way The table of angles (Fig. 2) is constituted by a number of rows arranged under each other and provided with graduations show ing degrees and 'minutes. .The degrees and minutes are indicated by numbers under and" above the marks, namely the degrees in large type and the minutes in small type. The numbers indicatingangles greater than 90 are arranged under the corresponding rows, and those which indicate angles less than 90 are arranged above the rows. The marl-z indicating 90 is arranged at the top right hand corner, so that proceeding from th1s point the rows run from the right to the left and then downward to the next row, etc.,

above. the rows the angles decrease from- .and therefore 146 will he found in the second row fromthe top,'the first decimal of the log. sin being 8 and this number 8 being found opposite said second row.

The position of the angles in the row de pends on the second and third decimal. of the log. sines.- It is suflicient to take the log.

sines to three places of decimals. Again taking as-example a=46 30', log sin a being 9.861 1o.

- The second and third decimal form the numher 61. The angle 46 30' should therefore be 61/100ths of the length ofa row from the left edge of the row.

Similarly log. sin 10 20'=9.25410.

- The angle 10 20" is therefore found in the row opposite which 2 is placed, and 54/100ths of the length of a row from the left edge of the row.

By locating the indications of the angles in this way 1t.follows that, in order to obtain log. sin log. sin t, the first decimal is obtained by subtracting the number at the .end of that row in which angle t is found from the number at the end of. that row in which angle 0 15 found, and the sec nd and meters (or yards,

their centers,

third decimals are found by reading, by means of one of the rulers shownin Fig. 4, by what percentage of the length of a row tllile angle indications are 'separated latera y. I

A ruler by which these lateral distances are determined is'shown in Fig. 4, and comprises three portions each having a length equal to the length of a row in the tableof angles, shown in Fig. 2, and each uniformly 7 5 graduated from right to left into one hundred divisions with suitable indications for each five divisions. Above and below the graduations of the middle portion, other. graduations are provided together with suit able indications of distance. The last-mentioned graduations are made such that the distances given correspond with the logarithmic divisions in the middle portion of the ruler, i. e. each graduation of distances is placed opposite that mark of the logarithmic scale which denotes the second and third decimal of the logarithm of the distance concerned. The distances indicated in the ruler shown m Fig. 4 are those from 1260. (the logarithm of which is 3.100) to 1585 (the logarithm of which is 3.200). It will he understood that a suitable number of "rules is provided to cover any length of base line which it is desired to use. For instance, if another base llne is established having. a length of 3758 or other unit in which'it is desired to measure range) another rule would be provided on which 3162 (the.loga rithm of which is 3500) would be indicated at the right edge or zero of the center por-. tion of the ruler, and 3981 (the logarithm of which is 3.600). would be indicatedat the 4 left edge or mark of such center portion. In order to adjustthe ruler to a certain distance a transparent slide M, made for instance of mica and provided with two indieating points is provided. In order to ad'- just this slide to a given distance it is so set thatthe vertical line connecting the two in- (heating points coincides with the graduation showing the base line used. Adjacent each portion of each ruler such as shown inFig. 4 bears-an identifying indication, the left portion bearing the indication V+2, the central portion V+1 and the right portion V. The letter V is used, in using the apparatus, to indicate the difference between the first decimals of log sin .1

and log sin't, which is found in the table of angles Fig. 2) by subtracting the numbers found at the ends of the rows inwhich the angles a and t occur. ThlS difference usually constitutes the first decimal of the logarithm pf the range Z,D but this first decimal w1ll be one more i the left hand portion of the ruler must be iised or one less if the nght .hand portionmustbe used.

- By ud lmg he slide upon the ruler tol tne distance Z Z and then placing the ruler .ther observing by the aid of the transparent plate shown. in Figure 5 which number of the ruler is found in the same perpendicular with the angle 2? in the table of angles, there is only determined, strictly speaking, the second and third decimal of log Z., .D which is equal to log b-l-(ldg sin a-log sin is The first decimal of log Z D is indicated in the table of distances namely at the left opposite the rows of distances, while the num-' Three tables of distances are used, one for distances between 1 and 5 kilometres, one between 4 and 10 kilometres and one between 10 and 32 kilometres. By way of example the table 4-10 kilometres is shown in Figures 3 and 3. Each table of distances is provided with two rows of numbers preferably in red (from 0-49 inclusive and from 50-99 inclusive) which as stated above form the second and third decimals of log Z D. Under every red number we find under each other four members preferably in black, which indicate the distances corresponding to these logarithms. In the drawing the usual artillery notation is followed, in which the two numbers before the hyphen indicate hundred of metres, and the number after the hyphen so many times 25 metres, so that for instance the notation 66--3 represents a distance of 6675 metres. g

In this way two groups each having four horizontal rows of distances are formed. Opposite each of these rows a number is placed which as stated above corresponds with V and therefore forms the first decimal of log Z D.

If the calculations are to be effected on the assumption that the base Z Z is 1403 metres for example: then that ruler is taken on which said distance is found, and the indicator of the mica slide is adjusted as exactly as possible to M03 metres (see Figure 4). The ruler is then ready for use. The table of angles (Fig. 2) is then placed ready for use and the table of distances (Figure 3) is attached on it for instance by means'of clips. The choice of which table of distances to use depends on the distance at which-a target may be expected. In the example assumed "here this distance is between 4 kilometres and 10 kilometres. The table of distances referring thereto is indicated in Figures 3 for use is laid in any place on the table of angles, parallel to the rows occurring on that table. Furthermore, a transparent indicating plate (Figure 5) is taken in the right hand, and the operator then waits until the angles a and t are determined.

For the sake of clearness a concrete example will be further worked out, and it will be assumed that The operator looks up A a in the table of angles and finds it on t e second row from the top, at one mark to the right from the 30 mark lying between 41 and 42. The ruler is then displaced horizontally by the left hand over the table of angles until its indicating point is set vertically above or below the, A a i. e. 41 36. He then aseertains by displacing by the right hand the transparent plate, which red number of the ruler is now vertically above the vertical angle i. e. above 8. This appears to be about 26. Below the red number 26 on the table of distances the distance Z D is now found. However, four distances are found there namely 42-4, 53-1, 67--0 and 84-1. As a. rule there is no doubt which of these four distances is the correct one, because from the previous measurement the dista'nce is already known approximately. It may therefore only occur at the first calculation that it is not known which of the four distances is to be chosen. If the distance is measured by a range-finder there is no doubt possible, because although the measurement at large distances is very inaccurate, yet at any rate its accuracy is sufiicient to indicate which of the given four distances is correct. If no rangefinder is at hand, it is still possible by the construction of the calculating device to make the right choice at the .first measurement. This may be done as follows :0 posite the rows on which in the table of ang es the anglesv or. and t occur numbers are indicated. In the given examples these are the numbers 8 and 1. The difference V of these is taken, i. e. 7. Above the group of numbers to which the number read from the ruler (26) belongs is indicated V+1. Now fromthe four distances, that one. must be chosen which belongs to the horizontal row opposite which is the number V+1, in the given case 7+1=8. The correct distance is therefore 67-0, i. c. 6700 m; In practice the use of the calculating device is very simple. It only consists in displacing with one hand the ruler and with the other hand the mica plate.

I claim:

A tabular calculating apparatus comprising a logarithmic scale having a series of rows of equal length and arranged one below the other, each row being indicated by a numeral, and having anti-logarithm indications each located in that row indicated portion thereof of the same length as a row of said-scale graduated into .one'hundred equal divisions adapted when an antilo arithm' thereof representing a factor is adby the first decimal of its logarithm and.

jacent the antilogarithm of another factor on a row of the tabular scale to determine on the rule certain logarithmic characteristics of the final factor by the intersection of a line projected from an antilogarithmic factor on another row of the tabular scale.

In testimony whereof I have. signed my name to this specification.

' WILD-1H FREDERlK GRO'I'ENDORST.

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