Patent GB-191015480-A (GB)
Title: An Instrument for use in connection with Fire Control for the Prediction of Ranges, Bearings, Allowance for Deflection, and the like.
Inventor: BARR ARCHIBALD
Filed: 1910-06-28
Granted: 1911-05-25
Abstract: 15,480. Barr, A., and Stroud, W. June 28. Range-finders.-Apparatus for indicating the average rate of change of a variable (such as the range or bearing of a target), or for predicting the probable value of the variable at a subsequent time, comprises a drum revolving at a definite rate (or equivalent moving surface) to represent the element of time and a mechanism to produce relative translational motion parallel to the axis of the drum between the drum and a piece carrying a pencil, trailer, or other indicator, such motion being in accordance with the changing value of the variable. In the form where a pencil traces a mark upon the drum, means for measuring the deviation of the trail, which is a measure of the rate of change of the variable, may comprise an arm pivoted upon a centre so that it can be set with half of the undulating trace on the drum on one side and half on the other, or the general direction may be ascertained by a mirror capable of being rotated until the reflection appears to have the same direction as the trace itself. The adjustable rod or mirror is geared to a suitable pointer or indicator. In another form, shown in Fig. 7, the nut N is traversed along the screw S, set parallel to the axis of the rotating drum A, in accordance with the range, and has pivoted to it an arm carrying a roller or trailer pressed upon the drum A. The deviation of the arm corresponding to the rate of change of range &c. may be indicated by actuating a follower M so as to keep an index mark opposite the end of the arm, the follower M being mounted on screws S<1>, S<2>, which can be actuated either by hand or automatically, and have geared to them an indicator R. In the form shown, the follower M is moved automatically by means of two electro-magnets energized by completion of the appropriate circuit according as the trailer arm end carrying contacts K<1>, K<2> moves in advance of or to the rear of the follower M, the electromagnet actuated serving to stop the intermediate member of one of the two differential gears shown on the right-hand side of the Figure, and so allow the screws S', S<2> to be driven by the motor. Stopping the intermediate member of the other differential causes rotation of the screws S<1>, S<2> to move the follower in the opposite direction. The axle of the indicator R is fast with the intermediate member 8 of the differential gear 7, 8, 9, the outer members of which are geared with the large screw S and the screws S', S<2> respectively. In predicting apparatus, the contacts are not fixedly mounted on the follower M but on a slider W, Fig. 13, moved transversely of the direction of motion of the follower by a guide V shaped to suit the rate of diminution of velocity with range for a particular gun. The follower M is thus in advance of or behind the range nut M by an amount depending on the rate of change and on the range and the indication of a range transmitter .actuated from the screws S<1>, S<2> differs from the range corresponding to the position set by the nut N on its screw by a corresponding amount. In order to reduce the movement of the slider W, the screws S', S<2> may be set at an angle with the screw S as shown.