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    Re: Beating a Dead Horse (aka Worley's Sextant)
    From: Brad Morris
    Date: 2014 Jan 22, 09:34 -0500

    Hi Bill

    Are you stating prior art for the detachment lever? 

    Images 3 and 4 show a Plath sextant with a similar arrangement to the Heath Hezzanith arrangement, yet the Plath shown is for a decade later.  So that is disqualified on the basis of precedence.  The Heath came first for this example.

    I had a look at the NMM NAV1130, which shows the trigger arrangement of the Plath referenced by Dunn.  So that is disqualified on the basis as not the same arrangement as the Heath.  This is not prior art.

    In order to support a claim of prior art, there must be evidence of it.  The Heath patent is an extremely narrow one.  Its not a patent for a spring loaded tangent screw.  Its a patent for the method of detachment, to wit: the lever.  The Plath devices presented thus far do not provide that evidence.


    On Jan 22, 2014 4:07 AM, "Bill Morris" <engineer@clear.net.nz> wrote:

    Brad, you wrote :

    <<...In Richard Dunn's book (Sextants at Greenwich....) a description of the C. Plath mechanism is given right next to the Heath Hezzanith mechanism.

    As expected, they are different.>>

    Yes, but they also did a version that wasn't different from the Heath mechanism. See Figures 3 and 4 here: http://sextantbook.com/2012/11/

    Bill Morris
    New zealand
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