Patent GB-782638-A (GB)
Title: Improvements in or relating to machine for assembling circuit components
IPC: H05K13/04
Filed: 1956-02-07
Abstract: 782,638. Assembling electrical components. GENERAL MILLS, Inc. Feb. 7, 1956 [Feb. 15, 1955], No. 3779/56. Class 83 (2). [Also in Group XXX] A machine for attaching electrical components to a circuit board comprises a conveyer for moving circuit boards past a plurality of component-attaching heads, means for periodically stopping the conveyer with the individual boards positioned adjacent the heads and means for operating the attaching heads to insert the leads of electrical components into holes in the circuit boards. Conveyer and circuit board feeding arrangements. The circuit boards are carried past the attaching heads by two conveyer chains 60, 62 driven by sprockets 70 (not shown) 72 on a shaft 74 which is coupled to a motor 86 through reduction gearing 88, a clutch 102 and a gear box 84. The clutch 102 drives a shaft 104 passing through the gear box 84 and having cams 184, 188, 286 and 496 at its other end. Within the box the shaft 104 carries a pinion 112 meshing with a pinion 114 mounted on a drive gear 110 of a differential gear 108. Gear 110 is freely mounted on a shaft 115 carrying the differential spider 117 which supports bevelled pinions 118 and 120 meshing with gear 1281 secured to the sprocket 82 coupled by chain drive to the conveyer drive shaft 74. To the shaft 115 is secured an arm 122 with a follower 124 bearing on cam 126, the shape of the cam being such as to cause periodic movements of the spider 117 sufficient to neutralize the effect of the gear 110 and so bring the gear 128 and sprocket 82 to rest to halt the circuit boards in front of the attaching heads. Cam 286 operates a switch 288 so that the heads are operated in synchronism with the movement of the conveyer and cam 496 operates a failure detection switch 494 which disengages the clutch 102 if a component is not attached. The conveyer chains 60, 62 move in channels 144, 146, the former being adjustable to vary the distance apart of the chains. The inner sides of the channels carry slotted guides 136 and 138 for the circuit boards 132. Secured to the chains an moving along the tops of the channels are plates 153, 154 from each of which depends a finger such as 162, Fig. 9, which engages and pushes along a board 132. Each finger has a curved top on which bears the end of a leaf spring 168 to position it. In operation the board is accurately positioned beneath the attaching head by a stop 130 which the board engages just before the conveyer comes to rest, the finger 162 being moved back to the position 176 against the spring 168. The stops 130 are carried by arms 128 adjustably clamped to a rod 178 and extending along the machine and being actuated through a rod 182 and lever 184 from the cam 188 so that the stops move up into position just before the conveyer comes to rest and downwards out of the path of the boards just before it restarts. In the event of excess pressure the finger 162 can snap back to the horizontal position 196 to prevent damage and is later reset by an arm 201, Fig. 10, carried by a toothed sprocket 199 mounted on the frame and driven by the conveyer chain. If, when the conveyer stops, a board has not depressed the arm 200, Fig. 7, of a switch 198 at any particular station, the attaching head at that station will not operate. Circuit boards are fed to the conveyer from stocks 226, Fig. 11, within magazines 224 fixed to the top of a turret table 232 which is mounted on a shaft 242 and indexed by a pawl 252 operating on a ratchet 246 secured to the shaft. The pawl is actuated by pressure fluid supplied to a cylinder 258 under the dual control of the switch 288 operated by cam 287 and a switch 208, the arrangement being such that a complete rotation of cam 286 causes the indexing of the table unless switch 208 has been operated by the feeding of a board to the conveyer. In each magazine a stock of boards is supported on four cams such as 310 on two shafts 308 arranged one at each side of the magazine and coupled by gears so that they are rotated together to release the bottom board on to the conveyer when a pawl 292 is struck by an arm 290 of the shaft 178 when the latter is rotated to release the stops 130 just prior to a forward movement of the conveyer. Attaching heads. These are carried on a plate 340 extending longitudinally of the machine and each head includes an upright portion 388, Fig. 17, mounted on the plate 340 through superposed bases which are adjustable by screw and nut means longitudinally and laterally of the machine frame. To the upper part of the portion 388 is bolted a horizontal annular flange 394 within which is a central lipped web 396 supporting an annular disc 400 on which the inserting mechanism is carried. The disc is rotatable within the web 396 through an angle of 90 degrees, the movement being limited by stops 409, 411 striking the ends of an enlarged portion of the web opening and may be locked in adjusted position by bolts 408, 410 and eccentric washers 413. The above adjustments allow the attaching mechanism to be accurately aligned with the holes in the circuit boards and allow components to be secured longitudinally or laterally of the board or in an intermediate position. The upper part of the head comprises a fixed inner cylindrical member 476 about which is a rotatable cylinder 474 carrying discs 478 and 480 having a series of brackets to support component-carrying magazines 412, only one of which is shown in position in Fig. 17. Each magazine is constructed of sheet metal as shown in Fig. 23 and is normally obstructed at its lower end by a member 450 adapted to be moved away by a member fixed to the disc 400 when the magazine is positioned to supply components to the feeding and straightening device 414. When a magazine has been emptied, a finger 464 of a follower block 462 actuates a switch to rotate the cylinder 474 through a ratchet 482 and a pawl operated by a fluid pressure cylinder 492. As a component leaves the magazine 412 it enters the straightener and feeder 414 comprising curved spaced guides 694 and 696 formed with zig-zag outwardly divergent slots, Fig. 26. At the end of the feeder the component 516 is held by fingers 506, 507, Fig. 35, until such time as the anvil carriage 534 pivots about the shaft 778, when the component rolls down inclined ramps 522 and 524 into notches 526 and 528 of anvil fingers 530, 532 and is centred by inclined guides 538 and 540. In the case of very small components, the centring guides may be between the anvil fingers and engage the ends of the component itself instead of its lead wires. A bumper 542 prevents the component from bouncing out of the anvil fingers. The leads are bent and inserted through the holes in the circuit board by an inserter head 510 which is moved vertically by a fluid cylinder and which comprises a yoke portion 566 connected to the plunger of the cylinder and guided by rods 568, 570, a first inserter member 572 secured to the yoke and a second inserter member 574 sliding on the first. The first inserter member comprises a plate on one side of which a second plate 575 can slide within limits determined by a bolt 618 working in a slot 620 and on the other side is bolted a camplate 616. The inserter plate 575 has rear wardly extending straps carrying a plate 625 which, on the descent of the head, comes into contact with the anvil and so causes the plate 575 to remain at rest and so move upwardly relatively to the plate 572. This movement causes the upper ends of pivoted bending fingers 512, 514 to ride on the cam plate 616 and have their lower ends moved inwardly against a spring 606 to bend the ends of the lead wires, as shown in Figs. 41, 42, around the ridged anvil fingers 530, 532. The ends of the bending fingers have a concave grooved portion which matches the ridges of the anvil fingers and which hold the bent leads firmly after the withdrawal of the anvil. After the bending of the leads, a cam 638 depending from the head disengages a locking arm 640 and then moves a roller 650 to cause the anvil to rotate about a shaft 778 so that the anvil fingers swing away and allow the inserter head to descend farther and the fingers 506, 607 are also moved away to release the foremost component, which cannot however fall out of the feeder slot since it is blocked by the plate 625. The bending fingers, the cam plate 616 and the anvil fingers may readily be replaced by others in order to accommodate components of different sizes or different type. In Fig. 45, for example, is shown a bending finger adapted for a component with two leads at each end. After the anvil has been rotated out of the path of the inserter, the latter descends farther to push the bent leads through the holes in the circuit board, the head being stopped and a signal light illuminated if they are not properly inserted. The switch mechanism for effecting this is supported on a plunger and is raised to a position under the board 132 as the inserter descends and, as shown in Fig. 46, comprises two switch plungers 782, 784, both of which must be fully depressed by the leads 660, 662 if the machine is to continue in operation. Fig. 47 shows a modification of the switch for use with twin lead components wherein the contact 792 is depressed by the plunger 790 only when the leads 772 and 774 bear uniformly on each end of a pivoted switch plate 788. After the insertion of the leads, the inserter head is raised, the bending fingers separated and the anvil swung back to its initial position whereupon the component previously released by the fingers 506, 507 rolls down on to the anvil fingers. A modified form of inserter head, intended more particularly for small components with thin leads is shown in Fig. 37. When this head descends, pressure blocks 736 and 738 engage the leads 740, 742 and press them on to platforms 744, 746 joined by a cross bar 747 carrying a bumper shield 558. Continued downward movement of the head cau