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Constant bevel doctor blade and method and apparatus using same

  • US 4,184,429 A
  • Filed: 01/29/1976
  • Issued: 01/22/1980
  • Est. Priority Date: 02/09/1972
  • Status: Expired due to Term
First Claim
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1. In a printing method of a type wherein excess ink is wiped from the printing surface of a printing form with a doctor blade having conventionally a given constant blade thickness between two mutually parallel blade surfaces and a generally wedge-shaped tip portion including a run-in blade bevel having an optimum tonal quality size and extending from one of said blade surfaces at an angle corresponding to an angle of attack of the doctor blade relative to said printing surface, and an inclined wedge surface extending from said blade bevel to the other of said blade surfaces, whereby the effective area of said blade bevel would increase from said optimum size through progressive wear of said tip portion during use of said blade to sizes eventuating in progressive degradation of print quality, the improvement comprising in combination the steps of:

  • preparing a second doctor blade for use in lieu of said conventional doctor blade by providing a doctor blade blank having said blade thickness between said parallel blade surfaces, shaping a marginal portion of said blank into a second blade tip portion, providing said second blade tip portion with a second blade bevel essentially identical to said run-in blade bevel having said optimum tonal quality size and providing said second blade tip portion throughout a useful depth of said second blade tip portion with a constant second blade tip thickness equal to the height of said second blade bevel measured essentially perpendicularly to said useful depth, with said useful depth being made equal to several times said second blade bevel height, whereby the effective area of said second blade bevel remains constantly at said optimum size through progressive wear of said second blade tip portion in the direction of and throughout its useful depth;

    applying said second doctor blade to said printing surface at an angle essentially equal to said angle of attack, with said second blade bevel being in contact with said printing form;

    applying said ink to said printing surface and printing form;

    effecting relative movement between said printing form and second doctor blade whereby said second blade tip portion is caused to wipe excess ink from the printing surface at said optimum size second blade bevel; and

    continuing said excess ink wiping by continuing said relative movement and advancing said second doctor blade toward said printing form to compensate for wear of said second blade tip portion and to maintain said second doctor blade continuously in contact with said printing form via a second blade bevel maintaining continuously said optimum size throughout said useful depth of said second blade tip portion.

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