[Leica] Re: More on Leitz Patents

[Gaifana@aol.com]

Bob: 

Was it that Leica submarined (a la Lemelson) the patent on the bayonet mount 
for a while and then finalized the patent when Canon would have been on the 
verge of producing an M-clone? I suspect they could have gotten away with 
submarining because there was probably not a huge market for clone lenses, 
even in 1953. Back then everyone was making screwmounts, whether Leica, Canon 
or others (including the Russians, who I guess cared little about the 
patents). So what they could have done is waited to perfect the patent until 
the last minute, threatening all comers with royalties for a "patent pending" 
abroad, while simultaneously exhibiting a DBP mark on the top plate. 
Interesting problem. Or were there extensions of patents in before the 1980s 
(I thought you got one, but I may be thinking of copyrights).

I'm not in the IP department in my firm, but I find it a little surprising 
nonetheless that such small improvements can be patented... Note that most 
modern SLRs have three-claw bayonets.

Cheers
Dante



In a message dated 2/18/00 4:56:03 PM, rjr@usip.com writes:

<< In response to Gaifana and Austin:

>>I'm kind of curious to know how the M mount (or any bayonet mount) could be 
patented after Contax had presumably done it or introduced it to the public). 

Improvements can be patented over prior art, and that is what they did.  The 
two critical patents I have found so far are Wehrenfennig '581 and Brohl 
'201.  Wehrenfennig teaches the use of 4 lugs on a bayonet arranged so that 
light coming from long focal length lenses, or of high intensity, is not 
cut-off in 35mm cameras, and Brohl teaches the use of protuberances or 
notches to align the lens and camera body.

(BTW, how do I represent an umlaut in e-mail?)

Further in the 1950s more patents were secured on the coupling between the 
rangefinder and the lens.  So, in order to make a lens to fit the M3, several 
patents would have had to be considered.

>>>I know I'm looking with U.S. patent law retrospect, but that would have 
never flown today. 

Well, the basic patent law on this hasn't changed that much in the interim.

>>>Perhaps the only reason it was "patented" in the U.S. was reciprocity with 
Germany, which perhaps had weaker patent standards. 

No, I don't think that is the answer.  The patents demonstrate  novel, 
non-obvious improvements over the prior art.  There is no concept of such 
reciprocity as you suggest in patent law, beyond allowing the filing date to 
be extended back to the date of filing the foreign patent in some cases.

>>>By 1952, the bayonet mount was present in Contaxes and Rollei filters, 
both of which predate the M3.

Yes, that is correct, the existence of bayonet mounts is disclosed in the 
patents (as of January 1951).

>>>Of course, today, any patent today only lasts 20 years - if today's regime 
had been in place in the 1950s, the Leica clones would have shown up in the 
1970s. 

The US patents granted in 1953 lasted 17 years from issuance.  Patents 
granted today last 20 years from filing (with some exceptions).  Since a 
patent can take 3 years to prosecute, the difference is not usually too much.

Nevertheless, your point is well taken.  The 1950 patents were gone by the 
1970s.  Why did we not get clones sooner?  I am researching this.  

>>>>[Austin] My 1949 Hasselblad has a red dot on the body, and a red dot on 
the lense, to aid in mounting alignment.  Perhaps there is more to the patent 
than the red dots?

Actually, the red dots would be equivalents to the notches and protuberances 
taught by Brohl.  A notch on the lug is also taught.  It is hard to be sure 
without the file history, but it seems that Brohl was filed 2/7/1951, and 
claimed priority to 2/13/1950 based on a German patent filing date.  That 
makes the one-year critical date 2/13/1949.  Without boring everyone, a 
public use or sale in 1949 of the invention therefore might or might not make 
it prior art.  It depends :-)  Don't know, but that is another interesting 
avenue for further research.

Hope everyone is still awake,
Bob Rose

</XMP>

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From: "Robert Rose" <rjr@usip.com>
To: <leica-users@mejac.palo-alto.ca.us>, <leica@topica.com>
Cc: <Gaifana@aol.com>, <austin@darkroom.com>
Subject: More on Leitz Patents
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