Patent GB-1267953-A (GB)
Title: Improvements in or relating to machines suitable for use in carrying out h.f. welding operations on workpieces
IPC: B29C65/78
Filed: 1969-03-19
Abstract: 1,267,953. Seaming non-metallic sheet material. BRITISH UNITED SHOE MACHINERY CO. Ltd. 19 March, 1969 [20 March, 1968], No. 14401/69. Headings B4B and B5K. A machine for welding by dielectric heating and cutting-out workpieces comprises a lower platen 2 which provides a lower electrode and on which a workpiece can be supported for a welding and cutting operation to be performed thereon; an upper platen 11 which provides an upper electrode and which is mounted above the platen 2 for movement between two operating stations of the machine, in each of which stations a welding and cutting operation can be performed on a workpiece supported on the platen 2 at the station; means for effecting relative movement of approach and separation between the platens 11, 2, respectively; and means whereby the platens 2, 11 can be connected to a high-frequency electric source HF, so that, after relative movement of approach has been effected between the platens to cause a welding and cutting tool to be pressed against a workpiece supported on the platen 2, a welding operation can be effected on the workpiece. A carriage 6 is mounted on bearings for movement along a beam 5 of the machine and is driven by an electric motor between a first operating station (solid line position) and a second station (chain-dot line position). The carriage 6 supports an hydraulic cylinder 7 having a piston-rod 8 which carries a plate 9 having the platen 11 secured thereto by bolts (not shown). The plates 9, 11 are separated by insulating sleeves 10. The plate 9 is normally held retracted by springs 12 which lift the platen 11 after each welding and cutting operation. The carriage 6 is provided with cams 13a, 13b to operate switches B5, B4 at the first and second stations, respectively. An adjustable switching rod 14 extends upwardly from the plate 9 and a stop collar 84 thereon is adapted to engage a switch B6 on the carriage 6 to determine the upper end position of the upper platen assembly. The rod 14 is adjustable lengthwise by rotation of a member 83. Rods 15, 16 are screwed into the plate 9 and support switching rods 17, 18 slidably mounted in brackets 7a, 7b on the cylinder 7. At the end of the cutting operation, the rods 15, 16 actuate switches B7, B8 which are effective only at the first and second stations, respectively. The cutting stroke of the plate 11 can be altered to the height of the welding and cutting tools at the two stations by adjusting the screw-in depth of the rods 15, 16. A lead 37 extends from an H.F. generator HF to a lead 38 provided with contact springs 39 at opposite angled end portions thereof, these end portions being secured to pillars 3, 4, respectively, by insulation pots 100. When the carriage 6 is at one of the stations, the springs 39 engage in turn with one of two insulated contact blades 40 on the cylinder 7. Setting up the machine.-The operator positions a welding and cutting tool on the platen 2 and effects setting-up at whichever station the carriage 6 happens to be, e.g. the first station. A switch B13 is actuated to lower the piston-rod 8 and bring the plate 11 into contact with the welding and cutting tool. The position of the rod 15 is adjusted whereby, in a normal cycle of operation, the position in which the switch B7 is actuated and thus the pressure at which the return of the platen 11 is initiated is set. Lowering of the platen 11 also actuates the switch B6. While the carriage 6 is still in position the required welding pressure is set manually by a control knob DL and the required welding time and subsequent dwell time is also set by preselection indicators of relays TR1, TR3, respectively. The length of the rod 14 is adjusted by the sleeve 83 to determine the upper stroke limit of the platen 11. Adjustment of the rod 14 can also be made for the second station. After setting the values required for the first station, the operator presses a button B3 to effect rightward travel (Fig. 1) of the carriage 6, the position of the switch B13 being unchanged. Pressing of the button B3 causes the platen 11 to be raised by the springs 12 until the collar 84 hits against the carriage 6 and the rod 14 actuates the switch B6. The carriage 6 moves rightwardly until the cam 13b actuates the switch B4 to cause the platen 11 to move downwardly on to a second welding and cutting tool. Adjustments similar to those made at the first station are effected but with the aid of the rod 16, preselection indicators of relay timers TR2, TR4 and a control knob DR. The switch B13 is returned to its normal position so that the platen 11 is raised by the springs 12 to a position in which the switch B6 is tripped by the rod 14. Welding power for the first and second stations can be set at different values by pressing one of a set of selector switch buttons on blocks B11, B12, respectively. The generator HF is made ready for operation by closing a switch B14. Cycle of operation of the machine.-The operator positions workpiece components on a left-hand portion (Fig. 1) of the platen 2 and a welding and cutting tool is placed thereon. The operator presses a start button B2 so that the carriage is driven to the left to the first station. When the cam 13a actuates the switch B5, the carriage 6 is stopped and the rod 8 and the platen 11 are moved downwardly. When the force of the pressure fluid in the cylinder 7 reaches a pressure at which a gauge KM is set, the welding timer relay TR1 is energized and switches on the generator HF for a predetermined time. The dwell timer relay TR3 is energized until the welded components are consolidated. Pressure in the cylinder 7 is increased to a maximum and the tool cuts out the welded components. As the components are cut, the switch B7 is closed and the rod 8 and the platen 11 return to their retracted positions and actuate the switch B6. Workpiece components with a welding and cutting tool thereon are placed on a right-hand portion of the platen 2 and the carriage is moved to the right, by depression of the button B3, to perform a welding and cutting operation similar to that performed at the first station. Safety trip of the machine.-Normally the cutting stroke of the upper platen assembly is terminated after a stroke of 12 mm. even if the platen 11 has not made contact with the welding and cutting tool. This is effected by the tripping, after a 12 mm. stroke, of a switch B9. To override stroke termination after 12 mm., the operator presses, in addition to one of the buttons B2, B3, a button B10 and holds both buttons depressed until the platen 11 has been lowered on to the tool and the generator HF switched on. Circuit diagrams of hydraulic and electrical control means are described, Figs. 2, 3a and 3b (all not shown).