Patent GB-652534-A (GB)
Title: Improvements relating to recording instruments and equipment
Inventor: CLARKE WILLIAM HERBERT VICTOR
Filed: 1948-02-16
Abstract: 652,534. Electric indicating-systems. AIRSPEED, Ltd. Feb. 16, 1948, No. 4511. [Class 40 (i)] [Also in Groups XIX and XXIV] In a multiple recording apparatus a stylus .traverses in succession a number of zones extending in a row along a recording surface and each corresponding to a physical quantity to be recorded, and during each traverse, which is generally transverse to the row of zones, the stylus makes a mark which indicates by its position the quantity to be recorded. As applied to recording the condition of a large number of resistance type strain gauges, an electrolytic recording surface attached to a display board manually movable along a frame - work is divided into a number of zones each subdivided into a number of sections, one for each strain gauge and a mark is made by passing an electric current through one of three styli on a band driven round a carriage which is driven from left to right of the display board so that a vertical path of each zone is traversed by a stylus successively and a mark is made in each section. At the end of its travel the carriage is returned to its starting point, the display board is shifted manually and the test conditions are varied, the cycle being repeated to record the new values. Each strain gauge is connected in a Wheatstone bridge network with a corresponding reference strain gauge and with two resistance arms which are connected to each pair of strain gauges in sequence by an automatic switching arrangement when the pair is selected as a stylus traverses its corresponding section of a zone, at some stage of which the bridge is automatically balanced and an electronic circuit provides a current pulse through the operative stylus. The carriage 4 carries an electric motor which drives it from end to end of the framework through sprocket wheels 237, 237<SP>1</SP>, co-operating with roller chains 220, 230 secured to the framework at each end, Figs. 11, 17, 20 and the lower 220 passing over a double ramp in the carriage and beneath the sprocket wheel 237 and a flanged jockey pulley 238 with a plate for preventing slipping off on one side, similar provision being made at the top for the chain 230. A stylus chain 266 is driven from the electric motor 241, Fig. 20, through friction discs, sprockets and chain, spindles and gears and drives sprockets 271, 269 which assist in the reverse drive to the carriage and sprocket 267 and thence gear 274 which together with gear 262 assists in the forward drive to the carriage. The carriage driving sprocket 237, receives its drive from the gear 262 for forward travel or from the faster moving sprocket 271 for reverse travel according to the position of a rocker arm controlled from other rocker arms 316, 319 pivoted each side of the carriage 4, Fig. 17, linked together and bearing rollers 317, 320 which ride up ramps at the ends of the framework to give the necessary control movement to effect the reversal. The position of the ramps is adjustable. To avoid mechanical shock to the system upon each reversal, a spring coupling is used (see Group XXIV). The driving gear train, reversing mechanism and spring coupling are duplicated at the top of the carriage. Upon reversal after each return journey the rocker arm 316 actuates a switch to stop the motor, while the display board is advanced and the conditions of the test varied. A push-button switch is provided for restarting. At three equal intervals. round the chain 266, the links are held by hollow rivets into which insulated bushes are pressed. A stylus 340 makes an easy sliding fit in each bush and when pushed forward into working position by a nose 351, Fig. 31, on a rocking bar 352 its point makes contact with the record paper 103 until at the bottom a magnet 358 withdraws this stylus and the next is pushed forward into position. The bottom of the path of the chain 266 is set back from the top by the width of a recording zone and the relative speed of the carriage and stylus chain are such that the path of each stylus relative to the display board is a vertical line, each offset from the next by the width of a zone. The rocking bar 352 is swung out of the path of the styli when the spindle 275 reverses for the return journey of the carriage 4 so that the styli remain out of contact with the paper and only returns into operative position when a feeler controlling a flexible cable moves forward with the carriage free from a ramp on the front side of the upper rail, thus preventing a stylus from fouling the leading edge of the display board at the beginning of another record cycle. As a stylus traverses each of the five sections of each zone of the record sheet a bridge network is balanced to trigger an electronic circuit which provides a current impulse and, passing from the rocking arm 352 through a stylus 340 and the electrolytic paper 103 to the conducting surface of the display board, causes a record to be made. The triggering of the electronic circuit is related to the downward movement of the stylus by gearing a contact arm 391, Fig. 20, of a rotary potentiometer 390 to the stylus chain and carriage drive mechanism so that, at some point in each revolution of the arm 391, a balance is reached in the bridge network to which the potentiometer is connected. After each revolution of the arm 391 a maltese cross mechanism 393 steps on the moving arm of a distributer switch 395 so that its five segments are connected in turn through relay controlled switches to the five wipers respectively of five banks of a multi-bank distributer switch of automatic telephone type, Fig. 36, not shown, corresponding contacts of the five banks being connected to the five bridges of the strain gauges whose conditions are to be recorded in the vertical traverse of a stylus 340 over one zone. Cams 280, 281 control muting switches 283, 284 to prevent recording while the contact arm 391 passes between the ends of the balance wire of the potentiometer 390 and while the stylus passes between the sections of a zone. During the traverse of the fifth section of each zone a switch is closed to energize a solenoid, which, when released at the end of the traverse, advances the wipers to enable the conditions of another five gauges to be recorded in the next zone. A series of contacts corresponding in number and width with the zones is swept by a contact carried by the carriage and, if at any time the wipers are out of unison with the carriage, the solenoid for advancing the wipers is repeatedly energized until they are in unison whereupon its circuit is opened and control passes to the switch which is closed at the end of each traverse of a zone. When the traverse of the last zone is completed carriage actuated switches are closed, relay and holding circuits are closed and both means for advancing the wipers are put out of action while the carriage returns to its initial position whereupon a contact is closed to cut-off the driving motor while the conditions under test are varied and the display board is shifted. If it is desired to repeat the recording for a particular gauge, a number of switches ganged together are moved from their position for automatic setting to that for manual setting which is effected through a second distributer switch for selecting the bank of contacts and therefore the section of a zone corresponding to the said gauge and a further wiper for selecting the contact corresponding to the zone for the gauge. Having selected the gauge another set of switches ganged together are changed over from their position for normal recording to one for a repeat recording and a solenoid is energized to break the line from the bridge network to the circuit controlling recording to prevent recording, the solenoid being deenergized to allow recording only when the contact on the carriage sweeps the contact corresponding to the zone and when the arm of the distributer switch 395 contacts the segment corresponding to the section of the zone of the required gauge. An alarm is given when the wipers are out of step with the carriage and the recording circuit is open to prevent recording. Specification 629,478 is referred to.