Title of Invention

# "A BOBBIN ELLIPSOGRAPH FOR DRAWING ELLIPSES"

Abstract A bobbin ellipsograph (1) for drawing ellipses comprising: a pair of divider arms (2) with two parallel pins (5,5') carried by two extension arms (4) hinged to said divider arms; amounting means (9) for mounting a bobbin (6) carrying a non-elastic string (7) on to one of said pins (5); and a writing means (14) for drawing an ellipse with the help of said string by placing said pins on the two focuses of said ellipse wherein the free end of said string (7) from said bobbin (6) is taken out through a hole 13 provided at the bottom of said mounting means (9) and tied to said other pin (5') at a groove 12' provided therein and in that total length of the said string in between the two pins (5,5') is selected as '2r' when the length of the major diamcter of the required ellipse is '2r'.
Full Text The present invention relates to a drawing instrument for drawing ellipses. More specifically, the invention relates to a bobbin ellipsograph for drawing ellipses. Ellipses may be required to be drawn by students of physics for studying elliptical orbits of planets. The isometric view of a circle being an ellipse, students or practising draughtsman, engineers and architects also are required to draw ellipses for their drawings. People engaged in creative art, carpenters, etc may also need to draw ellipses for their work. For any point on an ellipse, the sum of its distances from the two focuses will remain constant. This principle is used for drawing ellipses. Ellipses can be drawn by any of the following methods. by free hand technique with the help of french curves by four-centre and four-arc technique None of the above mentioned methods however, are convenient to use and such crude methods may not give an ellipse of any reasonable accuracy. -2- There is a fourth method available which may be called the string method for drawing an ellipse using a string of fixed length. However, no devices are known which uses this method for drawing ellipses. One objective of the present invention thus is to provide a device for drawing an ellipse conveniently in a much shorter time. Another objective of the present invention is to provide a device for drawing an ellipse with reasonable accuracy. These and other objectives of the invention are achieved by using the string method of drawing an ellipse, with the help of a device. A predetermined length of any non-elastic string can be stored in a bobbin. This bobbin with the stored string can be mounted on divider like drawing instrument having parallel pins.-When the two pins of such a divider are placed on the two focuses of the ellipse to be drawn, and adequate amount of string is released from the bobbin, it should be possible to draw the required ellipse with the help of a writing device. According to this invention there is provided a bobbin ellipsograph (1) for drawing ellipses comprising a pair of divider arms (2) with two parallel pins (5,5') carried by two extension arms (4) hinged to said divider arms; a mounting means (9) for mounting a bobbin (6) carrying a non-elastic string (7) on to one of said pins (5); and a writing means (14) for drawing an ellipse with the help of said string by placing said pins on the two focuses of said ellipse wherein the free end of said string (7) from said bobbin (6) is taken out through a hole 13 provided at the bottom of said mounting means (9) and tied to said other pin (5') at a groove 12' provided therein. Thus the present invention relates to a bobbin ellipsograph for drawing ellipses comprising a pair of divider 3- arms with two parallel pins carried by two extension arms hinged to said divider arms; a mounting means for mounting a bobbin carrying a non-elastic string, on to one of said pins; one end of said string being tied to said bobbin, with the other end on to the other pin; and a writing means for drawing an ellipse with the help of said string by placing said pins on the two focuses of said ellipse. Brief description of the accompanying drawings: Figure 1. Shows the geometry of an ellipse. Figure 2. Shows the bobbin ellipsograph with a parallel pin divider. Figure 3. Shows one arrangement of fining the bobbin to its frame and mounting it on to the ellipsograph . Figure 4. Shows another embodiment of the ellipsograph. Figure 5. Shows a third embodiment of an ellipsograph in operation. Figure 6. Shows a fourth embodiment. F igure 7. Shows a fifth embod iment. --4- The bobbin ellipsograph of present invention will now be described with the help of the accompanying drawings. Fig. 1 Shows the parameters of an ellipse. The projection of a circle to a plane which is at an angle to the plane of the circle; is an el1ipse.The major axis of the ellipse will be same as the diameter of the circle 2r Eccentricity e for an isometric view is equal tc Thus while drawing an isometric view, if the cirole diameter 2r is known, all the points Fl , F2, B, P, and A can be determined for drawing an el1ipse. The bobbin ellipsograph 1 (Fig. 2) comprises a pair of divider arms 2 hinged at one end with pins 5,5' carried by two adjustable extension arms 4 which can be adjusted to stand vertically parallel to each other- The distance between the two pins 5,5' can be adjusted by adjusting the divider arms 2 and also the extension hinges 3. A thin bobbin 6 carrying a 1 ength of string 7 is mounted on one of the two pins 5,5 with the help of a mounting means 9. One end of the string is tied to the bobbin 6 and the other end to the other pin. -5- The mounting means 9 comprises a mounting clamp fitted to pin 5 (Fig 3) with the help or a guard key 10 such that the mounting means 9 along with the bobbin 6 can rotate freely along with axis of pin 5. The bobbin can be made of plastic material riveted to the mounted means 9 with rubber washers 8. The thin bobbin 6 carries the string 7, with one end of the string tied firmly to bobbin drum and a good amount of string is wound to the bobbin. The other end of string is brought out through a hole 13 provided at the bottom of mounting means 9. This end of string is then tied to the groove 12' (see figure 2) formed on the other pin 5' of the bobbin ellipsograph 1. The rubber washers 8 provided makes the bobbin 6 somewhat tight so that ft cannot move freely along its axis. When the required amount of string is to be released the bobbin 6 has to be rotated with the fingers with some effort as it does not rotate freely. The bottom portion 12 of the mounting means 9, is about the same height from the end of pin 5 as is the groove 12' provided on the other pin 5'. For the purpose of accuracy or drawing the ellipse, this height should be as low as possible. A height of about 2 mm from the end of the pins 5,5' is found to be satisfactory. "2r" Is the length of major dia of required ellipse and have to take total length of loose or straight string in between the two parallel pins amounted as "2rB units approximately. -6- Placing the two pins 5,5' over the two focuses of the el1ipse to he drawn and releasing adequate amount of string 7 from the bobbin 6 the required ellipse can be drawn with the help of a writing means (14) like a pen or a pencil. The stem of a pen (ball point pen) or the lead of a pencil can have a groove made with the help of an ampule cutter.This groove can be used for passing the string while the pen or pencil is used to draw the ellipse. Alternatively, a small washer can be fitted on to the pen or pencil for holding on to the string while drawing. The bobbin ellipsograph 1 of Fiq.2 can have an arc type holder 11 firmly riveted or welded on to one of the extension arms 4 for holding the instrument with the left hand while drawing the ellipse. The string 7 used can be of any non-elastic thread, even ordinary sewing thread is found good enough for the purpose. The bobbin ellipsograph in its simplest form as described, is shown in Fig. .2. The other embodiments using the same inventive concept of the present invention are shown in Fig. 4, Fig. 5, Fig. 6 and Fig.7 The embodiment of Fig. 4 shows the -7- divider pins 5,5' fitted to the divider arms 2 at right angles and a third pin 5" is fitted near the divider arm joint. The height of all the three pine 5,5 ',5" can be about 2.5 cm for sma 1 1 instrument to abou t 4 cm for a medium sized instrument . Fig. 5, shows an embodiment in use for drawing an ellipse. Here the pin carrying extension arms 4 are connected to the divider arms 2 with the help of knee joints 3'. In this embodiment the method of mount ing the bobbin is different from the ones described earlier. The mountinq means comprises a cylindrical plastic tube 15 on to which the bobbin 6 i s mounted with the help of a specially designed aluminium rivet 8'. This cylindrical tube is provided with a small ring at its bottorn through which passes th e other end of the string. Operation of the other embodiments are self expanatory from the figures 6 and 7. Because many possible embodimen is may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth are shown in the accompanying drawinqs and shouId be interpreted as illustrative and not in a limiting sense. -8- I CLAIM: 1. A bobbin ellipsograph (1) for drawing ellipses comprising: a pair of divider arms (2) with two parallel pins (5,5') carried by two extension arms (4) hinged to said divider arms; a mounting means (9) for mounting a bobbin (6) carrying a non-elastic string (7) on to one of said pins (5); and a writing means (14) for drawing an ellipse with the help of said string by placing said pins on the two focuses of said ellipse characterized In that the free end of said string (7) from said bobbin (6) is taken out through a hole 13 provided at the bottom of said mounting means (9) and tied to said other pin (S') at a groove 12' provided therein, and in that the total length of said string in between the two pins (5,5') is selected as '2r' when the length of the major diameter of the required ellipse Is '2r'. 2. The bobbin ellipsograph as claimed in claim 1, wherein said mounting means (9) comprises a clamp fitted to said pin (5) with the help of a guard key (10) such that said mounting device can rotate freely along the axis of said pin. 3. The bobbin ellipsograph as claimed in the preceding claims, wherein said bobbin (6) made of plastic material is riveted to said mounting means with rubber washers (8) so that said bobbin cannot rotate freely. 4. The bobbin ellipsograph as claimed in the preceding claims, wherein the height of the bottom portion of said mounting means (9) and that of said groove (120 on said pin (5') are same and not more than 2 mm from the end of said pins (5.5'). 5. The bobbin ellipsograph as claimed in the preceding claims, wherein one of the said extension arms (4) is provided with an arc type holder (11) firmly riveted to said arm for holding the instrument while drawing an ellipse. - 9 - 6. The bobbin ellipsograph as claimed in the preceding claims, wherein said writing means (14) is a pen or pencil and the stem of said pen or lead of said pencil has a groove made therein for passing the string through while drawing. 7 The bobbin ellipsograph as claimed in the preceding claims, wnerein said pins (5,5') are fitted at right angles to said divider arms 2 and a third pin 5" is fitted near the joint of said divider arm 2; and the height of all said pins (5,5'5") is about 2.5 cm, for a small instrument to about 4 cm for a medium sized instrument. - 10- 8. The bobbin ellipsograph as claimed in the preceding claims, wherein said extension arms (4) carrying said pins (5, 5') are connected to the divider arms (2) with the help of knee joints 3'; and a third pin (5") is fitted near the joint of said divider arms 2. 9. A bobbin ellipsograph for drawing ellipses, substantially as herein described and illustrated. A bobbin ellipsograph (1) for drawing ellipses comprising: a pair of divider arms (2) with two parallel pins (5,5') carried by two extension arms (4) hinged to said divider arms; amounting means (9) for mounting a bobbin (6) carrying a non-elastic string (7) on to one of said pins (5); and a writing means (14) for drawing an ellipse with the help of said string by placing said pins on the two focuses of said ellipse wherein the free end of said string (7) from said bobbin (6) is taken out through a hole 13 provided at the bottom of said mounting means (9) and tied to said other pin (5') at a groove 12' provided therein and in that total length of the said string in between the two pins (5,5') is selected as '2r' when the length of the major diamcter of the required ellipse is '2r'.

### Documents:

00308-cal-1999-abstract.pdf

00308-cal-1999-claims.pdf

00308-cal-1999-correspondence.pdf

00308-cal-1999-description(complete).pdf

00308-cal-1999-drawings.pdf

00308-cal-1999-form-1.pdf

00308-cal-1999-form-2.pdf

00308-cal-1999-form-3.pdf

00308-cal-1999-letters patent.pdf

00308-cal-1999-p.a.pdf

Patent Number 201198
Indian Patent Application Number 308/CAL/1999
PG Journal Number 06/2007
Publication Date 09-Feb-2007
Grant Date 09-Feb-2007
Date of Filing 05-Apr-1999
Name of Patentee PADMA CHARAN KAR