Patent GB-802659-A (GB)
Title: Improvements in or relating to apparatus adapted for use in assembling electrical components upon workpieces
IPC: H05K13/00
Filed: 1955-09-26
Abstract: 802,659. Assembling electrical components on circuit boards. BRITISH UNITED SHOE MACHINERY CO., Ltd. Sept. 26, 1955 [Sept. 27, 1954], No. 27305/55. Class 83 (2). Apparatus for assembling electrical components on workpieces comprises work supports at a number of operating stations, conveyer means to carry each workpiece successively to the supports, positioning means arranged to dissociate the workpieces from the conveyer means and position them automatically in operating positions on the supports, and dislodging means arranged to dislodge the workpieces automatically from the supports so that they are re-associated with the conveyer means for conveyance to the next support. Wiring boards W are mounted on pallets P which are carried by two conveyer belts 730 from a loading station M, Fig. 1, past the operating stations A, B ... Z at each of which is an attaching head as described in Specification 802,658 to an unloading station N, Fig. 2, the whole apparatus being carried on a series of rectangular frames such as 744, 746 and 748 arranged end to end to form a continuous row. The belts 730 are driven from the unloding end by a motor 750, gearing 754, chain 756 and pulleys 762, adjustment of tension being by a pulley 768 at the loading section 746. Each pallet comprises an open rectangular frame of light alloy and supports a wiring board by positioning lugs 776 and spring clips 784, 790 and is itself guided by means of pins 786, 792 and 793. At one side of each pallet is a trigger projection 794. The pallets with boards attached are stacked at the loading station so as to be at a slight angle to the horizontal and to the belts 730 and are retained between guides 802, 804, 806 upstanding from a casting 800 which is also provided with blocks 808, 809, faces 810, 812, Fig. 12, and three tongues with end portions 820 for accurately locating the lowermost pallets of the stack. The discharge of a pallet is effected by a bell-crank lever 824 pivoted on the casting 800 and actuated by a rod 822 extending along the length of the apparatus. Movement of rod to the right, as seen in Fig. 12, causes a supporting arm 828 to be withdrawn from beneath a marginal portion of a pallet which then drops into horizontal position resting on faces 810, 812 and block 808, 809. Return movement of the rod 822 causes the arm 828 to abut the side of the pallet and turn it bodily clockwise until it drops on to .the belts. Thereafter the pallets are positioned by their pin 792, 793 which pass through inverted U-channels on the frame 746. For initially supplying pallets to the working stations, a manually-operated lever 836 is provided on the casting 800. At the first operating station A the guideway 846 for the pins 792 and 793 is widened to form two longitudinally spaced portions with backstops 848 and 850, Fig. 10, the latter having also a laterally projecting stop 852. Also at station A are two stationary cams, a flat-topped front cam 878 and a rear cam 920 in the form of a bevelled rail. These members together form the work support at station A. As the pallet approaches the station, its trigger 794 engages a signal arm 858 and rocks it clockwise to engage a roll 866 of a switch-operating arm 868 on a vertical stem 870 extending into a switch housing 874, Fig. 16. The effect is to close electric contacts 884, 884. The corresponding contacts at all the stations are in series so that the circuit is not completed until a pallet has arrived at each station, whereupon closing of the circuit serves to open a valve to supply compressed air to a motor 896 to move endwise a push-rod 902 to rock a bell-crank lever 904 pivotally connected to the control rod 822, the movement of which actuates positioning and clamping means simultaneously at each station. Movement of rod 822 at station A turns arm 908, pivot 910 and clamping arm 912 so that the rounded end 918 of the arm 912 engages the edge portion 796 of the pallet so as to force it rearwardly when it rides up the cams 878 and 920 away from the belts 730 and is clamped in operative position with pins 792 and 793 abutting stops 850, 852 and stop 848 respectively. Before the attaching head at station A can operate, the signal arm 858 must return to its original position under the influence of a spring 876 and to do this it must be able to clear the pallet trigger projection 794 heightwise. To effect this, arm 858 is mounted on a block 862 which is caused to pivot about a bolt 930 against a spring 936 by a cam 932 on the arm 908 during its clamping movement. The return movement of the arm 858 again operates the switch 874 to open contacts 884, 884 and close contacts 890, 890 to actuate a valve supplying compressed-air for operating the attaching head. After the actuation of the attaching head at station A, the pallet is dislodged from the supports and slides back on to the belts for conveyance to station B. In riding up the cam 920, the pallet displaces a detent 922 against a torsion spring 926 and when the clamping pressure is released, this detent pushes the pallet off the cams and back on to the belts. The return movement of rod 822 which allows the detent to return the pallet to the belts also causes a fresh pallet to be discharged on to the belts at the loading station M as previously described. After a pallet has left the last operating station Z, it actuates the switch 520, the roll 522 of which is disposed at a distance two and a fraction times the length of a pallet from the stop brackets 524 so that if the unloading station is not being cleared, a third completed pallet, having opened switch 520, comes to rest beneath the roll 522 and holds the switch open, thus preventing further actuation of the machine.