专利名称：Vacuum molding apparatus for forming a
sheet of plastic material into apredetermined shape
发明人：Henry H. Jenkins申请号：US08/231403申请日：19940422公开号：US05529472A公开日：19960625
摘要：An apparatus for performing a vacuum forming operation utilizing first andsecond vacuum producing devices connected to an air space beneath a heated plastic filmwhich is located over a mold in which the film is to be shaped or molded. The first vacuumproducing device is capable of removing a relatively large volume of air from the airspace and producing a relatively weak vacuum. The second vacuum producing device iscapable of removing a relatively small volume of air and producing a relatively high orstrong vacuum. This enables the initial portion of the vacuum forming method to rapidlyremove a large volume of air with a relatively inexpensive turbine type mechanism andproduce a small or weak vacuum and once this has been accomplished, then the secondvacuum producing device is activated which rapidly removes the small amount of airremaining and produces a relatively high vacuum. A valve member is provided and isbiased to a closed position to prevent fluid flow between the first vacuum device and theair space. Upon initial actuation of the first vacuum device, the valve is caused to move toopen position against its biasing and upon production of the relatively weak vacuum, thevalve member closes. This disconnects the first vacuum device from the air space and
thereafter a second valve device connecting the second vacuum device to the air space isactuated connecting the second vacuum device to the air space which creates a relativelystrong vacuum and assists in holding the valve member closed.
申请人：JENKINS; HENRY H.
代理机构：Woodling, Krost & Rust
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