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Drafting instrument

  • US 4,439,928 A
  • Filed: 02/08/1982
  • Issued: 04/03/1984
  • Est. Priority Date: 11/26/1979
  • Status: Expired due to Fees
First Claim
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1. A drafting instrument having a large number of independently viewable scales, comprising:

  • a hollow housing, the housing having a viewing slot;

    a resilient graphics guide, the resilient graphics guide being fixedly attached to the housing;

    a rear rotatable shaft, the rear rotatable shaft being adapted to fit within the housing;

    a forward rotatable shaft, the forward rotatable shaft being adapted to fit within the housing;

    a flexible graphics sheet, the flexible graphics sheet having a plurality of scales thereon, the flexible graphics sheet having a first end attached to the rear rotatable shaft, the flexible graphics sheet having a second end attached to the forward rotatable shaft, the flexible graphics sheet being adapted to be wound around the rear rotatable shaft or the forward rotatable shaft, the flexible graphics sheet being adapted to slide over the resilient graphics guide, the resilient graphics guide being adapted to urge the flexible graphics sheet into engagement with the viewing slot;

    a right end piece and a left end piece adapted to rotatably hold the front rotatable shaft and the rear rotatable shaft; and

    ,a cursor assembly, the cursor assembly being slidably engageable upon the housing, the cursor assembly having a rib adapted to correspond with the viewing slot, the rib having hairline means thereon, the rib being adapted to engage the flexible graphics sheet and bring the hairline means into engagement with the scales to reduce parallax problems when the hairline means is viewed from different viewing angles.

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