Patent GB-283175-A (GB)
Title: Logarithmic apparatus for determining quotients
IPC: G06G3/00
Filed: 1928-01-04
Abstract: 283,175. Govare, H. P., and Salomon, F. M. M. B. Jan. 6, 1927, [Convention date]. Logarithmic calculators.-A quotient is evaluated by obtaining rectilinear movements along parallel paths proportional to the logarithms of the dividend and divisor and thence deriving the difference of the logarithms by a parallel motion mechanism. A form of application of the invention for determining average speeds is described. As shown in Fig. 1 two cam grooves 39, 43 formed in respective plates rotated by a vehicle about a centre 40<1> produce logarithmic displacements of a slider 1 along the line x, x<1>. The plates are geared in a ratio such that one functions to position the slider over the first part of its range and the other then takes up the control to move the slider over the remainder of the range. The cam plates are rotated from the vehicle by means of reducing gear and a clutch 30, and another pair of plates and a slide 1<1> are similarly driven by a clock 44. The two sliders 1, 1<1> are connected by a parallel motion linkage the middle point s of which is thus constrained to follow the line z, z<1>, and a lever 19 pivoted at 19<1> and slidably jointed to the point s moves a pointer 17 over a scale to show the average speed. Fig. 2 shows a device for zeroizing the sliders in cases wherein the cams are driven by clockwork under time or distance control. By depressing a knob 63 a spur wheel 61 is disengaged from the clockwork drive 66 and a pawl 71 is forced into engagement with a ratchet wheel 70 preventing reverse rotation. The spindle 62 is then rotated to restore the cams and slider through the gear wheel 60 and also to re-wind the clockwork spring. In a modified arrangement the wheel 61 only meshes with the ratchet wheel 70 when depressed for zeroizing. An indication may be given of the beginning and end of the working range of the instrument, a signal-bearing lever being directly engaged and displaced by the slider in one or other extreme position. The Specification as open to inspection under Sect. 91 (3) (a) also describes two other methods of obtaining the difference of the logarithmic displacements. As shown in Fig. 5 (Cancelled) a slotted arm 83 at right angles to a spindle 82 is mounted by screw and nut on the spindle which is driven logarithmically according to distance traversed. A spindle 85 driven similarly in accordance with the elapsed time, positions a. slotted rod 86 and the intersection of the rod and arm moves another guided rod 90 to displace a rack and pinion 95, 96 to show the average speed by means of a pointer 97. In another form, Fig. 8 (Cancelled), a solid cam 98 is rotated in accordance with one logarithmic variable and a screwed spindle 106 according to the other. A lever 102 rotatable with a shaft 101 and moved axially by spindle 106 is spring-drawn against the cam the shape of which is such as to vary the slope of the arm and therefore the rotary displacement of the shaft 101 in proportion to the difference of the logarithmic variables, the average speed being shown by pointer 112. This. subject-matter does not appear in the Specification as accepted.