Patent EP-0010743-A1 (EP)
Inventor: SCHMITZ DIETER
IPC: B29C48/06
Filed: 1979-10-26
Abstract: 1. A device for feeding measured quantities of liquid components, in particular interlacing agents, into a plastic base material provided in an extruder for the extrusion of plastic-insulated cables, comprising the following structural components interconnected by the conduits necessary to conduct the liquid components : a feed pump (1) and a storage tank (12) with a maximum contact (14a) communicating therewith, a dosing pump (33) connected to the outlet end of the said storage tank (12), as well as solenoid valves (9, 18) a flow meter (28) and a pulsation damper (30), characterized in that (a) the said first solenoid valve (9) is provided at the inlet end of the said storage tank (12) and another storage tank (13) with a solenoid valve (11) provided at its inlet end is connected in parallel to the said storage tank (12), each of the storage tanks (12, 13) comprising one probe (14, 15) with maximum (14a, 15a) and minimum contacts (14b, 15b) ; that (b) a further solenoid valve (18) taking the form of a reversing valve is connected to the outlets of the storage tanks (12, 13), the reversing valve (18), the two solenoid valves (9, 11), the maximum contacts (14a, 15a) and the minimum contacts (14b, 15b) of the storage tanks (12, 13) being interconnected by an appropriate circuitry ensuring that one storage tank (for instance 13) is cut off by the said reversing valve (18) from the outgoing line connecting it with the downstream portion of the system until complete drainage of the other storage tank (for instance 12) and until this fact has been signalled by the minimum contact (for instance 14b), whereupon the reversing valve (18) will connect the one storage tank (for instance 13) to the outgoing line and the solenoid valve (for instance 10) will be opened to permit filling of the other storage tank (for instance 12) ; that (c) a three-way cock (22) is provided downstream of the said reversing valve (18) and followed by two cleaning filters (23, 24) connected in parallel ; that (d) the flow meter (28) is connected to the interconnected outlets of filters (23, 24) ; that (e) the pulsation damper (30) is connected to the flow meter (28) ; that (f) there is connected between the feed line (6) to the solenoid valves (9, 11) and the pulsation damper (30) the series circuit of an expansion tank (7) and a solenoid valve (17) so that when the reversing valve (18) is switches over the solenoid valve (17) will be opened until the tank of the pulsation damper (30) is filled up ; that (g) the dosing pump (33) is connected to the pulsation damper (30) and has another dosing pump (34) connected to it in parallel, each of the said pumps being coupled to a speed-controlled drive motor whose speed may be controlled for instance in response to a reference value which can be preset at a potentiometer (43) ; that (h) there are provided means for supplying the actual value picked up in the flow meter (28) to an indicating instrument (44) having adjustable tolerance marks (44a and 44b), and that when one of the said tolerance marks is exceeded, the dosing pump (33 or 34) then in operation is switched off and the other dosing pump (34 or 33) is switched on ; and that (i) the outlets of the dosing pumps (33, 34) communicate via conduits with the extruder (40).