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Main valve

  • US 5,560,586 A
  • Filed: 05/16/1995
  • Issued: 10/01/1996
  • Est. Priority Date: 05/25/1994
  • Status: Expired due to Fees
First Claim
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1. A main valve located at an opening for connecting a vacuum chamber and a main vacuum pump, said main valve comprising:

  • a valve seat for opening and closing said opening, said valve seat being larger than said opening;

    at least one cylinder connectable to said valve seat for raising and lowering said valve seat; and

    a driving source for driving said cylinder,said cylinder comprising a cylindrical housing, a rod having one end extending through s aid cylindrical housing and being connectable to said valve seat and at another end a piston housed in said cylindrical housing, a nut coupled to said piston, a ball screw having a threaded portion coupled within said nut and a lower portion connectable to said driving source for rotating said ball screw which drives said nut, said piston, said rod, and said valve seat forward and backward to open and close said opening,wherein said rod has a cavity therein and a part of said threaded portion of said ball screw projects through said nut and said piston and is housed in said cavity in said rod.

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