opinion: EDGERTON, Associate Justice.
  This is a suit i to obtain a patent. The Patent Office and the District Court held that the claims lack invention.
  The claimed device is a blowout preven-ter, with rams and pistons, for sealing the head of an oil well by closing the space between the drill pipe and the well casing. For this purpose appellant uses three independent sources of power; well pressure, independent fluid pressure, and a manually operated screw. Abercrombie patent 1,834,922 uses, in a blowout preventer, fluid pressure and a manually operated screw; similarly, Rasmussen patent 1,709,949 uses well pressure and independent fluid pressure. Appellant’s use of all three of these previously-used sources of power is not inventive. Claims which call for the admission of both fluid pressures behind the rams as well as behind the pistons have been allowed and are not involved in this appeal.
  Appellant claims a packing with oppositely-flared resilient lips, which is practically identical with King patent 2,081,040. Though the King claims do not mention blowout preventers, the King specification states that the packing “will withstand enormous pressures” and points out that one of the accompanying drawings shows the packing “in position on a pump piston which piston may be of the type used in the blowout preventer or slush pumps in the drilling of wells.” The King specification also states that “the combination of the present type packing with a blowout pre-venter is claimed in my simultaneously filed copending application Serial No. 617,837 for a Blowout preventer.” No. 617,837 has been assigned by King to appellant, and is the application now on appeal. Use of the King packing in appellant’s blowout pre-venter is not inventive. The granting of the appealed claims would involve double patenting, with consequent prolongation of the patent monopoly.
  Affirmed.
  Under R.S. Sec. 4915, U.S.C.A. Tit. 35, Sec. 63.
instruction: What follows is an opinion from a United States Court of Appeals.
  Intervenors who participated as parties at the courts of appeals should be counted as either appellants or respondents when it can be determined whose position they supported. For example, if there were two plaintiffs who lost in district court, appealed, and were joined by four intervenors who also asked the court of appeals to reverse the district court, the number of appellants should be coded as six.
  When coding the detailed nature of participants, use your personal knowledge about the participants, if you are completely confident of the accuracy of your knowledge, even if the specific information is not in the opinion. For example, if "IBM" is listed as the appellant it could be classified as "clearly national or international in scope" even if the opinion did not indicate the scope of the business. 
  
  Your task concerns the first listed appellant. The nature of this litigant falls into the category "private business (including criminal enterprises)", specifically "manufacturing". Your task is to determine what subcategory of business best describes this litigant.
choices: auto chemical drug food processing oil refining textile electronic alcohol or tobacco other unclear