GB1508979A - Machines suitable for use in carrying out hf operations - Google Patents

Abstract

1508979 Embossing BRITISH UNITED SHOE MACHINERY CO 22 May 1975 [22 June 1974 18 Dec 1974] 27829/74 and 54778/74 Heading B6J [Also in Division B5] An HF welding machine, defined as an HF machine for (a) welding or welding and cutting a workpiece made of thermoplastic layers or non-activatable layers with a heat-activatable adhesive layer therebetween or (b) embossing a workpiece using either an indenting tool or a flow-moulding die, comprises two platens to apply pressure to a workpiece located therebetween and which act as electrodes, and temperature regulating means to regulate the surface temperature of at least one of the platens provided with passages through which fluid can circulate, the temperature regulating means comprising means for heating circulating fluid, means for cooling circulating fluid, fluidtemperature sensing means adjacent the outlet of the passages of the platen(s), and valve means for controlling the flow of fluid selectively through the heating and cooling means according to the fluid temperature sensed. Preferably, the temperature regulating means regulates the surface temperature of both platens the passages of which may be arranged in series with one another. Thermostats for sensing the fluid temperature are located adjacent the outlet ports of the passages of the platens and are each adjusted to a setting, which may be the same or different, the arrangement being such that, while the fluid temperature sensed by either thermostat is higher than the set level, the cooling means is operative and only when both thermostats sense a temperature below the setting is the heating means operative. The valve means comprises a solenoid valve switchable to direct fluid selectively through the heating and cooling means. A restrictor may be positioned downstream of the heating means so that when the valve is in the cooling condition the major proportion of the fluid passes through the cooler but a minor proportion passes through the heater to avoid overheating of fluid remaining therein. The thermostats are set to give a platen surface temperature of 30-60‹ C., e.g. 60‹ C. In a modification, each platen is provided with temperature regulating means independent with that of the other. The invention is applicable to a single station machine, a twin-tray machine or a multi-station machine as described in Application 14911/74. The latter machine comprises upper and lower platens and a turntable having a plurality of, e.g. three, workpiece supporting portions which can be brought successively into opposed relation with the upper platen and overlying the lower platen. Radiant heating means can be swung over the supporting portions not in opposed relation in order to preheat such portions before the start of a working day or shift.