GB1252611A - - Google Patents

Abstract

1,252,611. Calculating apparatus. A.SAXON, and H. J. T. CLEMENTS. 21 Jan., 1970 [21 Jan., 1969], No. 3345/69. Heading G4B. A calculator for the fertile period in a female menstrual cycle comprises a pair of flat rotatable indicating members 6 pivotally secured one to each of the holes 5 in a base 1, and a flat calender disc 14 placed over the indicators 6 and rotatably secured to the base 1 at hole 4. An opaque smaller disc is secured concentrically to the under surface of transparent disc 14 so that the circumferential portion 16 which bears the scale is left transparent. A radial edge surface 11<SP>1</SP> of one indicating member 6 is curved so that when it abuts the straight surface 11 of the second indicating member a small angle sector 12 of the base 1 is exposed, corresponding to five days of scale 16. A woman whose menstrual cycle is of constant length aligns the mark 10 of each indicating member 6 with the number on scales 19 corresponding to the length of her period. Calender disc 14 is then rotated until the date of the start of the current period is aligned with the start mark 17. The five day fertile period is then indicated by the gap between members 6, the portion 18 of the base visible through this gap being coloured red to add emphasis. If the length of the menstrual period is irregular the left hand indicator is set to its minimum duration whilst the right hand indicator is set to its maximum duration. The gap between the indicating members thus widens by an amount equivalent to the difference between the maximum and minimum periods, thus ensuring that the fertile period falls within the days indicated in red at 18. The indicators 6 are frictionally held in their set positions so that the fertile periods of future cycles are shown merely by rotating disk 14. The calculator may be constructed from rigid P.V.C.