Apparatus for controlling polymer pressure

Claim 2

Apparatus for controlling polymer pressure in an extrusion molding process, comprising: a. a means for shaping molten polymeric material; b. a feed duct for directing said molten polymeric material from an extrusion means to said shaping means; c. a baffle in said feed duct for varying polymer flow from the extrusion means to the molding means, said baffle tending to close the feed duct due to polymer pressure within the duct; d. primary baffle control means responsive to polymer pressure for maintaining the baffle in equilibrium at a preferred polymer pressure, said baffle control partly closing the baffle when the preferred polymer pressure has been exceeded by a first level; and e. secondary baffle control means responsive to polymer pressure for closing the baffle, said secondary baffle control means operating in addition to said primary baffle control means to rapidly close the baffle when the preferred polymer has been exceeded by a second higher pressure level.

Claim 3

Apparatus for controlling polymer pressure in an extrusion molding process comprising: a feed duct for directing molten polymeric material from an extrusion means to a molding means; a baffle in said feed duct for varying polymer flow from the extrusion means to the molding means, said baffle tending to close the feed duct due to polymer pressure within the duct; a double-acting diaphragm operably connected to the baffle; a diaphragm housing comprising an opening chamber and a closing chamber separated by the diaphragm, said opening and closing chamber having inlets for receiving compressed gas; a pressure sensing means in said molding means for emitting a first high pressure signal and a second high pressure signal, the first signal being emitted when a given polymer pressure higher than the preferred polymer pressure exists in the molding means, the second signal being emitted when a given polymer pressure higher than the first signal pressure exists; an opening valve connected to the inlet of the diaphragm housing opening chamber for alternately supplying a first compressed gas and a second compressed gas to the inlet, said first gas pressure displacing the diaphragm to open the baffle in the feed duct whereby a preferred polymer pressure is maintained in the molding means, and said second gas pressure displacing the diaphragm by a lesser amount than said first means thereby restricting polymer flow from the extrusion means to reduce polymer pressure in the molding means; a closing valve connected to the inlet of the diaphragm housing closing chamber for alternately supplying a gas at ambient conditions and a third compressed gas to the closing inlet, said third compressed gas tending to displace the diaphragm to close the baffle; and switching means connected to said opening valve and closing valve, said switching means urging the opening valve to supply the first compressed gas to the opening chamber and urging the closing valve to supply ambient gas when the preferred polymer pressure is maintained in the molding means, said switching means urging the opening valve to supply the second compressed gas to the opening chamber in response to said first emitted signal, and said switching means urging the closing valve to supply the third compressed gas to the closing chamber in response to said second emitted signal, the combination of the third gas, second gas and polymer pressure on the baffle causing a rapid closing of the baffle to prevent high polymer pressure in the molding means.

Claim 4

Apparatus for controlling polymer pressure in an extrusion molding process comprising: a feed duct for directing molten polymeric material from an extrusion means to a molding means; a baffle in said feed duct for varying polymer flow from the extrusion means to the molding means, said baffle tending to close the feed duct due to polymer pressure within the duct; a double-acting diaphragm operably connected to the baffle; a diaphragm housing comprising an opening chamber and a closing chamber separated by the diaphragm, said opening and closing chamber having inlets for receiving compressed gas; a pressure sensing means in said molding means for emitting a first high pressure signal and a second high pressure signal, the first signal being emitted when a given polymer pressure higher than the preferred polymer pressure exists in the molding means, the second signal being emitted when a given polymer pressure higher than the first signal pressure exists; an opening valve connected to the inlet of the diaphragm housing opening chamber for alternately supplying a first compressed gas and a second compressed gas to the inlet, said first gas pressure displacing the diaphragm to open the baffle in the feed duct whereby a preferred polymer pressure is maintained in the molding means, and said second gas pressure displacing the diaphragm by a lesser amount than said first means thereby restricting polymer flow from the extrusion means to reduce polymer pressure in the molding means; a closing valve connected to the inlet of the diaphragm housing closing chamber for alternately supplying a gas at ambient conditions and a third compressed gas to the closing inlet, said third compressed gas tending to displace the diaphragm to close the baffle; and switching means connected to said opening valve and closing valve, said switching means urging the opening valve to supply the first compressed gas to the opening chamber and urging the closing valve to supply ambient gas when the preferred polymer pressure is maintained in the molding means, said switching means urging the opening valve to supply the second compressed gas to the opening chamber in response to said first emitted signal, and said switching means urging the closing valve to supply the third compressed gas to the closing chamber in response to said second emitted signal, the combination of the third gas, second gas and polymer pressure on the baffle causing a rapid closing of the baffle to prevent high polymer pressure in the molding means.

Claim 5

The apparatus of claim 2 wherein the second signal is not emitted until polymer pressure in the molding means has exceeded at least one and one-half times the difference between the preferred polymer pressure and the first signal pressure.