Patent GB-568674-A (GB)
Title: An improved electrical machine for the classification and segregation of dielectric sheets
IPC: G01R31/01
Filed: 1943-03-11
Abstract: 568,674. Detecting faults; capacitance and power-factor measurements. CROAD, A. K. (Aerovox Corporation). March 11, 1943, No. 3945. [Class 37] An automatic machine for testing dielectric sheets comprises mechanism for conveying the sheets in sequence from a supply magazine to a testing block and means responding to a tested characteristic of the successive sheets, such as the leakage current therethrough, to control the transmission of the sheets to appropriate collector magazines. Fig. 3 shows a machine for testing mica sheets for condensers by applying a high voltage to each individual sheet in turn and stacking those sheets that meet a certain specification of dielectric strength in one collector magazine and those sheets failing to meet such specification in a second magazine. Mica sheets to be tested are stacked in a supply magazine 20 from which the top sheet is picked up by suction applied to a pick-up head 56 and transferred to a testing block 21, the suction being released to deposit the sheet. The pickup head 56 is carried by a tube 59 to the upper end of which is connected a flexible suction hose 60. The tube 59 is fixed to a cross-bar 73 provided with rollers 74 that ride in a track 75 comprising a pair of bars fixed to a back plate. The tube 59 slides vertically in a carriage 65 which is fixed to a pair of horizontal tubes 63, 64 which slide in bearings 61, 62. A selector head 44, which picks up by suction the tested sheet from the testing block 21, is carried by a tube 90 fixed to a cross-bar 91 with rollers 92 which ride in the track 75. The tube 90 slides vertically in a carriage 80 which is slidable along the rails 63, 64. A link 81 is pivoted at 82 to the carriage 80 and at 83 to a disc 85 keyed on an axle 87 which is journalled in a tractor frame 88 fixed to the slide tubes 63, 64. Up and down movement of the suction heads 56, 44 is effected in unison by lifting the track 75 and with it the cross-bars 73, 91 and the tubes 59, 90 affixed thereto. This lifting is effected by arms 109, 110 operated by a cam. When the heads 56, 44 have been raised clear of the magazine 20 and testing block 21 the slide rails 63, 64, and with them the carriages 65, 80, are moved laterally by means of a cam-operated arm 119. If the tested sheet is satisfactory the disc 85 remains in the position shown and the carriage 80 moves with the frame 88 and the bars 63, 64. The stroke of the lateral movement is such as to bring the pick-up head 56 into alignment with the testing block 21 and the head 44 in alignment with the collector magazine 22. The track 75 is then lowered and the heads 56, 44 are lowered into engagement with the testing block 21 and collector magazine 22. The suction is then released by a cam-controlled valve so that the head 56 delivers afresh sheet to the testing block 21 and the head 44 delivers the previously tested sheet to the collector magazine 22. Should a sheet be faulty a solenoid 155 is energized and causes the disc 85 to be clutched to a gear-wheel which is rotated through half a revolution by engagement with a stationary rack 174 during the lateral movement of the slide bars 63, 64, thereby causing the carriage 80 to slide along the bars until it comes into alignment with the collector magazine 23 for below-standard sheets. Rotation of the disc 85 winds up a spring in a tension reel 176, which returns the disc to its normal position on the reverse stroke of the bars. To prevent sheets from springing out of the magazine 20 owing to the resiliency of the mica, rubber shoes 192, Fig. 7, are normally pressed by a spring 189 against the edges of the sheets and are released by the engagement of a screw 198 with a lever 197 when the head 56 has entered the upper end of the magazine. The sheets are pressed upwards by a follower 26 carried. by a rod 200 which has a cross-bar 201 at its lower end and is thrust upwards by a pair of tension springs 203 anchored to pins 204 on the socket of the magazine. The rod 200 passes through an aperture in a brake arm 205 which is pivoted at one end and pulled up at the other by a spring 207. Upward motion of the rod 200 and follower 26 is thus prevented except when the brake arm 205 is released by a cam lever 210 at the time when the pressure of the shoes 192 is released. The magazines 20, 22, 23 are removable from the bed of the machine for replacement. Each has a hub 216 with flanges 218 engaging the faces of the bed, the socket being laterally introduced through a slot in the bed and held in place by a latch 219, Fig. 3. The magazine has lateral studs 222 which pass through lateral slots in the socket 25 and are provided with securing nuts 24. The testing block 21 comprises a conducting rod 30, Fig. 8, passing through an insulating bushing 31 and encased by an insulating cylinder 33 fixed in a socket 34. Slidably fitted at the upper end of the testing block is a metal platform 36 carried by a leaf spring 38 on the upper end of the rod 30. A nozzle 179 is arranged to deliver a blast of air before the selector head 44 enters the testing block, in order to blow out any sheet that may have become jammed against the platform 36 in the previous cycle. The plate 36 and selector head 44 are connected, in series with a relay coil 151 and timing switch 150, across the secondary winding 40 of a high tension transformer. If the sheet being tested is faulty, the relay 151 closes its contact 154 and thereby energizes the solenoid 155 and also a relay 157 which maintains the circuit closed. When the supply magazine is empty the follower 26 engages a spring 225 and energizes a relay coil 229 in series with a low-voltage secondary 227. The contact 230 is thereby opened and opens a relay 231 which de-energizes a solenoid 232 and opens the main switch, which cannot be closed until the relay 231 is manually reset. If either of the collector magazines is filled the follower 27 engages a spring 235 and causes the same sequence of operations. When the slide rails 63, 64 reach the end of their movement, towards the right they engage a spring 180 and open a switch 182 which interrupts the circuit of the relays 155, 157. The clutch connecting the disc 85 to its gear-wheel is then opened and the disc is rotated back through half a turn to its normal position. The apparatus may be used to sort sheets according to their dielectric capacity or power factor instead of leakage current.