Patent GB-799668-A (GB)
Abstract: 799,668. Recording apparatus. CLEVITE CORPORATION. Nov. 16, 1954 [Jan. 5, 1954], No. 33159/54. Class 106 (4). [Also in Group XXXVIII] In a seismic prospecting system a shot 1, Fig. 1, is fired by a relay K4 energized by a switch S 1 actuated by a pin 79 on a rotating drum 41 and the signals received by a plurality of spaced geophones a, b, c, d are recorded simultaneously during one rotation of the drum 41 on magnetic tape 40 carried by the drum by corresponding magnetic heads 7a ... 7d. During the next rotation of the drum the signals recorded on the first magnetic track are picked up by the head 7a and applied through a switch 10 to a stylus motor 145 to produce a corresponding visual record on a record 146 also carried by the drum. The stylus motor 145 is then moved axially along the drum and during the next rotation a displaced visual record of the signals recorded on the second magnetic track is produced the process being repeated until a visual record of all the magnetic tracks is obtained, the apparatus being then automatically reset for another cycle of operation. The visual recorder is of the electro-chemical type and the stylus motor may be as described in Specification 626,215. As described the output from each geophone, e.g. geophone a, is applied through a pre-amplifier 2a and amplifier 3a to frequency modulate a multivibrator 5a whose output is applied through an amplifier 6a to the corresponding magnetic head 7a, the amplitude of the signal being sufficient to erase any previous record, and the switch 10 is connected to the stylus motor 145 through an amplifier-limiter 11, demodulator 12, filter 13 and amplifier 14, a relay K5 controlled by the drum switch S-1 being provided in the 300 v. power supply 4 such that amplifiers 6a ... 6d are energized only during the magnetic recording and components 11, 12 and 14 are energized only during the visual recording. Means are also described for (1) resetting the apparatus to its initial condition at any time during the. recording periods; (2) repeating the visual recording of any one magnetic track or of all the tracks: and (3) testing the equipment by applying a 4 c/s. square wave from generator 256 to the magnetic heads. The effective frequency response of the visual recorder may be increased by reducing the drum speed during the visual recording. Constructional details, Figs. 4 and 6 and Fig. 5 (not shown). As shown in Fig. 4 the drum 41 is rotated by an electric motor 47 through a reduction friction drive 44-46. The magnetic tape 40 with a resilient rubber backing fits into a wide shallow grave near one end of the drum and the visual record strip 146 passes round the drum in another shallow grave near the other end of the drum and through an axial slit to storage and take-up reels inside the drum. The magnetic heads are assembled in a housing 48 and the stylus motor 145 is mounted on a carriage 181 carrying the switch contact 10 and having a locating member 182 which normally engages a slot 183, Fig. 6, in a pivoted locking member 184 which is forced against locating member 182 by a spring 188; the number and spacing of the slots 183 in locking member 184 determine the number and spacing of the visual record channels on paper 146. An internally threaded hub 193, Fig. 6, mounted on a threaded shaft 194 fits loosely into an aperture 190 in the carriage 181 with the right-hand flanged end 197 of the hub 193 projecting from the aperture 190 and when the locking member 184 is withdrawn by energization of a solenoid K-10 the carriage 181 is urged to the right into contact with the flange 197 by a compressed spiral spring 192. During such movement of the carriage 181 a solenoid K-11 mounted on the carriage is deenergized to lift the stylus 149 from the paper 146 and close a switch S-9 to short-circuit the deflection coil of the stylus motor 145 and a switch S-8 in the energization circuit of the stylus 149 is opened. When the carriage 181 moves towards a new recording position a switch S-4 mounted on the carriage is actuated to energize an indexing motor B-2 which rotates the shaft 194 and thereby moves the hub 193 further out of the aperture 190 and further compresses the spring 192 until the flange 194 engages the contacts 197a of the switch S-4 to de-energize the indexing motor B-2. Operation of apparatus. Initially the locating member 182 engages the left-hand notch in the locking member 184 and the hub flange 197 is in engagement with contact 197a of switch S-4. To initiate an operation cycle the drum motor 47 is energized by a starting switch and when a lever 42 projecting from the drum engages a switch S-2 relays are operated which connect switch S-1 in the energization circuits of relays K4, K5 and a solenoid K-6 such that these components are energized when the drum pin 79 actuates switch S-1 thereby firing the shot and lighting an indicator lamp, energizing amplifiers 6a ... 6d, Fig. 1, and positioning a switch S-6 in the path of the drum lever 42. During the first rotation of the drum the signals received by the geophones a ... d are recorded by the magnetic heads 7a ... 7d but when the drum lever actuates the switch S-6, relays K4, K5 and solenoid K-6 are de-energized, lever 42 and switch S-6 are retracted and switch S-1 is connected into the energization circuit of the locking release solenoid K10. During the second rotation of the drum the signals recorded on the first magnetic track are re-recorded by the stylus 149 and on completion of this rotation the drum pin 79 actuates switch S-1 to momentarily energize solenoid K10, de-energize solenoid K11 and close switch S-9 thereby displacing the stylus carriage to the next visual record channel as described above and connecting the output from the second magnetic head 7b to the stylus 149 via switch contacts 10 and 9b; at the same time the drum pin 161 momentarily opens switch S-8 to disconnect the power supply from the stylus 149. This process is repeated until all the signals have been recorded visually at which stage the switch contact 10 actuates a limit switch S-3 which (1) energizes solenoid K10 to withdraw the locking member 184 (2) disconnects switch S-1 from the energization circuit of solenoid K10 and energizes the indexing motor B-2 reversely thus traversing the stylus carriage 181 to the left until it encounters and actuates a limit switch S-5 thereby (1) deenergizing solenoid K10 to lock the carriage 181 in its first position, and (2) reversing motor B-2 which thus advances the hub 193 until it actuates switch S-4 to stop the motor B-2. When the drum lever 42 is reset manually the equipment is ready for another operation cycle. The electrical control circuit is illustrated in Fig. 7, not shown.