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Gentlemen

Lines 11 thru 15 describe one realization of a tangent screw that engages/disengages.  I do not profess to know if it is indeed Platt's.  I'll take Bill's word for it.

Lines 20 thru 25 describe a manner of adjustment "simpler and more expeditious than heretofore" known.  While the patent may be a narrow patent, being strictly based on the engagement/disengagement mechanism,  it apparently was different enough to be granted as novel. 

Patent language will often identify competitor's devices and explain how this is different / novel, so that the patentee can avoid the charge that it is basic knowledge known within the art.  That would void a patent application.  For example, we all know how a wheel works, so you cannot patent a wheel.  No surprise, to me anyway, that Heath would reference the Platt mechanism.

For Bill's argument to be supported, the two devices must be show to be identical or that the Heath device is really the Platt device plus.  You cannot add a feature to another's device and patent the whole thing, only the additional feature may be patented. For the Heath device to be granted a patent, it must represent a "simpler and heretofore" unknown arrangement. 

Knowing how careful and measured Bill is, I think we can anticipate a white paper on just this topic. 

Brad