Patent GB-339662-A (GB)
Title: Improvements in or relating to time-interval indicating devices
IPC: G04F8/00
Filed: 1929-08-07
Abstract: 339,662. Slee, J. A. Aug. 7, 1929. Determining distances acoustically. -Apparatus which may be used for echo sounding comprises a driven member which actuates an indicating needle and is clutched to a. driving member rotating at constant speed on the reception of a first electrical impulse; and a stationary member which, on the reception of a second impulse breaks the driving connection and retains the driven member in the position reached during its time of motion. Visible means for ensuring the rotation of the driving member at the correct speed and relay means for rendering the apparatus independent of the magnitude of the impulses are provided. A disc A driven by a suitable constant speed motor B carries a pin N which, at the same point in each revolution of the disc A carries 'forward a pallet M integral with a rotatable disc J which is normally held in the position shown in Fig. 1 with the pallet M held against a stop L by a spring K. The disc A has a window O with a green glass OG, a red glass OR and a space 03. The oscillating disc J returns to normal position after the pin N has left the pallet M, and, its natural period being, by suitable means, maintained constant under varying conditions, correct speed of disc A will be indicated when the light from a source P gives white flashes through the space 03 and the hole R in the disc J, a red or a green flash indicating respectively that the speed is slow or fast. The disc A carries a pot magnet C having operating and holding windings CWO, CWH, Fig. 3, respectively, provided with slip rings. The stationary member comprises a fixed pot magnet D having operating and holding windings DWO, DWH the driven member comprising an armature E connected by a. spindle to a pointer F movable over a dial G and normally held against a zero stop by a spring H. Operation. The impulses, the time between which is required, are applied across the terminals Q, Fig. 3, of a resistance-inductance bridge LR having a polarized relay b so that its winding a is actuated by current growths only, and at the commencement of each impulse rocks a tongue d from contact f to g to alter the grid-bias on a triode valve e causing the anode current to rise from about zero to say 50 milliamps. This current actuates the operating windings CWO and TO (of a relay T) over the tongue h and contact j. The armature E is thus clutched to the driving member A and contacts y are closed, thereby energizing the holding windings CWH, TH, and winding of the relay S, the tongue h now contacting with w. The second impulse is applied therefore by way of tongue h, contact w, operating coils DWO, UO (of relay U) thus causing armature E to be captured and held stationary by the magnet D, and closing of contacts l. A circuit is now closed over contacts l for holding windings UH and DWH thus holding the pointer F after the second impulse has ceased and until the current is switched off when a momentary demagnetizing current is sent through UH and DWH to further the release of armature E. The relay tongue may be adapted to operate the timing device direct. If the first impulse persists the tongue h will reach contact w before cessation of the first impulse and the magnet D will immediately operate to hold the armature E. To avoid this the impulses may be applied to the primary of a transformer 2, Fig. 4 in series with a condenser 4 both being shunted by a resistance 5 to leak away the first impulse before the second arrives. Alternatively the time lag of relay S could be increased or a delayed relay put in series with winding DWO. Safety contacts I arranged to be actuated by the pointer F ensure that the armature E cannot be rotated more than one revolution. High voltage may be applied to the armature windings and the current brought to the required maximum by non-induction resistances. The pointer may be geared to the armature spindle to allow a suitable scale to be used, or if a long pointer is used it may be free on the armature spindle and constrained against a stop thereon by a spring.