Patent GB-852738-A (GB)
Title: Improvements in or relating to apparatus adapted for use in soldering printed wiringboards
IPC: B23K3/06
Filed: 1957-05-10
Abstract: 852,738. Making printed wiring-boards; soldering. BRITISH UNITED SHOE MACHINERY CO. Ltd. May 10, 1957 [May 11, 1956], No. 14857/57. Classes 83 (2) and 83 (4). [Also in Group XXX] In apparatus for soldering printed wiring boards a track is arranged to extend through a plurality of stations where the boards are treated prior to, during and subsequent to soldering and a plurality of carriages is provided to ride along the track, each carriage having means to support a board for treatment at the stations. The apparatus comprises loading, fluxing, preheating, dip soldering, cleaning, draining and air cleaning and unloading stations through which extends a track comprising a pair of rails 76, 78, and a single rail 102. Each carriage 42 comprises an open frame 54, Fig. 2, having at one side a vertical roller 58 for rolling on the rail 102 and at the other side being detachably and pivotally connected to a rod 64 pivoted at its forward end to a wheeled dolly having three grooved wheels 70, 72, 74, the wheels 70, 72 engaging the rail 78 and the wheel 74 engaging the rail 76. The dolly is secured to a tow link 52 connected to a lug 50 on an overhead endless roller chain 44 meshing with a driven sprocket 46 and an idle sprocket 48. A carriage at the loading station is provided with a wiring board 40 by pressing the board, circuit side downwards, into fingers 86, Figs. 2 and 9, on resilient arms 84, 88 and the carriage is traversed along the track by the moving roller chain to a fluxing station. In the fluxing station over which an exhaust hood 110 is mounted a spray gun 118, Figs. 9, 10, is connected to air pressure and liquid flux and is arranged to spray flux upwardly through an opening 120 in the floor on to the circuit board. On entering the station a cam 82 on the carriage engages a lever 130 to close one contact in a control circuit and a second contact is closed when a lever 136 is deflected by the wiring board. A solenoid valve, in the control circuit, is energized to allow operation of the spray gun and a time delay device causes the gun to cease operating. The carriage with its fluxed board proceeds to the preheating station where four thermostatically-controlled heating units 150, Fig. 13, to drive off solvent and possibly activate the flux are arranged in an arcuate insulated housing 152 beneath the track. The carriage is slowed during its progress over this station since the chain moves in a path which is not concentric with that of the carriage. Two heating elements are arranged beneath the straight part of the track leading to the dip soldering station. After towing the carriage through the preheating station the chain passes around idler sprockets 108, Fig. 15, to tow the carriage at a reduced speed over a solder tank 158 having thermostatically-controlled heating units and an adjacent, heated, replenishment chamber. Adjacent the tank the track inclines downwardly to allow the leading edge of the board to enter the solder first, then straightens out so that the remainder of the. board gradually enters the solder and then inclines upwardly so that the board leaves the solder. A wiper blade on the carriage removes; dross ahead of the board. A cam 226, Fig. 18, is provided adjacent the rising portion of the track to engage a peg 80 on the rear of the frame 54 to lift the rear end of the carriage about the pivot of the rod 64. The solder tank is automatically replenished by sticks of solder 182 which are moved from a rack 180 into the chamber by a plunger operated by a motor, the actuation of which is controlled by a float which rises and falls with change of solder level. After leaving the soldering station the carriage frame is tilted about the rod 64 by the roller 58 passing over a raised portion of the rail 102 to lift the board over an end wall of an arcuate tank 240, Fig. 30. When the frame resumes its horizontal position the board is immersed in perchlorethylene in the tank to remove flux. Brushes 248 are arranged in the tank to engage the board. When the roller 58 engages a raised portion 252, Fig. 35, of the rail 102 the frame is again tilted about the rod 64 to remove the board from the cleaning fluid tank and guide it into an enclosure where the cleaning fluid drains off into a container 258 and where hot air is blown over the board from tubes 256. The cam 82 operates a switch-operating lever to actuate the valve controlling air supply to the tubes. The carriage returns to the horizontal position and enters the unloading station where the boardsupporting arms 84, 88 on the carriage are urged apart by deflector arms 290, Fig. 38, to release the board which drops into a shoot 296 to finally enter a receptacle 300.