Patent GB-730745-A (GB)
Title: Improvements in or relating to observation posts
IPC: F41G11/00
Filed: 1953-04-27
Abstract: 730,745. Supports for optical apparatus. LEWIS, D. A. April 27, 1953 [July 15, 1952], No. 11547/53. Classes 97 (1) and 97 (2). [Also in Groups XIV and XXXVIII] An observation post comprises a swivel chair, a horizontal shaft journalled in bearings carried by the chair back, an arm pinned to said shaft extending around in front of the chair and adapted to receive and hold binoculars, an annular gear loosely surrounding said shaft, gravity-actuated means for holding said gear against turning on its axis, a pinion meshing with said gear carried eccentrically by said shaft and bodily rotatable therewith, a flexible shaft attached to said pinion, and an angle of elevation registering instrument operatively connected with the other end of said flexible shaft. As shown, a seat 17 is secured to a casting 16 on a shaft 15 rotatably mounted in a housing 11 having a cover 37 which is provided with lugs engaging in the face of an annular spiral gear 40 freely rotatable on the shaft and which supports in a bore 45 a spiral gear 49 in mesh with the gear 40 and connected by a flexible shaft 50 to an azimuth pointer in an indicator 52 secured to the chain back which is vertically adjustable in brackets 21 on a frame member 19 pivoted at 20 on the casting 16 so as to be rearwardly pivotable against the action of an adjustable return spring 25. Also carried by the chair back is a horizontal shaft 60 to the one end of which is secured an arm 61 having a counterweight 62 and curved to extend forwardly to the front of the chair at eye-level. This end of the arm carries in a horizontal split sleeve 64 a bar 65 which bears a vertical split sleeve 67 in which is supported a bar 69 having a releasable clamp for the pivot of a pair of binoculars 70, the split sleeves being provided with spring clamps for locking the bars. Freely rotatable on the shaft 60 are a gear 103 and a bush 99 to which the gear is keyed and to which is attached a weight 102 so that the gear does not rotate with the shaft. An annular gear casing 105 which is keyed to the shaft carries a spindle bearing a pinion 106 meshing with the gear 103 and connected to a flexible shaft 107 which through a worm and pinion 108, 109 rotates an angle of elevation drum visible in a window in the indicator 52. The rearward swing of the chair back is restricted to the limit shown in dotted lines but the head rest 33 is independently rearwardly pivotable to permit observation up to the zenith, while a manually releasable detent 79 (Fig. 2) is provided to hold the arm perpendicular to the back. In use, the operator first selects the approximate azimuth position in which the chair is locked by an expanding shoe brake carried by the shaft 15 and operable by a cable 93 secured to the hub of a lever 95 carried by the arm 61. The operator then tilts the chair back and/or moves the arm 61 by means of a handle 80 to select the elevation, both these movements combining to rotate the shaft 107. By adjustments of both azimuth and elevation the target is brought into the line of sight and when this is done the operator closes a pushbutton switch 83 to light an " on target " lamp in the indicator 52. The azimuth and elevation readings may be transmitted to a gunnery control point, the rotation of the chair shaft 15 and of the shaft 60 being caused to rotate gears to which are connected Selsyn generators 114, 116, respectively, which drive Selsyn motors rotating indicator dials in the control room. The " on target " signal may then alternatively be given by telephone. Four observation posts may be provided on a ship, one each fore-and-aft on the port and starboard sides, and each may be arranged to register azimuth and elevation readings in a control room. A slave compass card driven by a Selsyn motor from a gyrocompass may have concentric with it four nesting shaft sleeves, each driven by a Selsyn motor off the azimuth movements of the chair and bearing a pointer so that the true bearing of the object sighted may be found as well as the bearing relative to the ship indicated by a fixed bearing card, while an angle of elevation board having four drums operated by Selsyn motors controlled by the rotation of the shaft 60 and having "on target " signal lamps may be provided adjacent it. By this means the apparatus may be used also as a navigation aid by observ. ing landmarks, the distance between the observation posts being known.