Ted,
This is is a variety of double-escapement action. There have been a number of different ones designed and patented over the years with varying degrees of success. The downside, in vertical pianos, is the added expense so it's seldom that even high-end verticals will utilize them.
I have a Mathushek from around 1890 that has a similar, though even simpler, design. I've worked with a couple of the Mathushek uprights with double-escapement actions in the past and they actually work pretty well. The only bad part about the current one is that someone with more ability with wire cutters than brains snipped the repetition springs at the top of the back checks so I've got to wind a new set. <heavy sigh>
You might want want to also look at Darrell Fandrich's patent on a design they developed some years back for a double-escapement vertical action -
https://patentimages.storage.googleapis.com/2d/30/2d/9f688dcbd9b4f7/WO2014011640A1.pdf
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Allan Gilreath, RPT
Registered Piano Technician & President
Allan Gilreath & Associates, Inc
Calhoun, GA
706-602-7667
allan@allangilreath.com -
www.allangilreath.com------------------------------
Original Message:
Sent: 03-29-2019 11:54
From: Ted Rohde
Subject: Different backcheck
My son was tuning today and ran across a Zeiler vertical. He took this picture and asked if I had ever seen this style backcheck before. Truthfully, I never have. Would some of you Wizards of Smart have information about what this is, and what it does? Appreciated. We aren't doing repairs to the piano, by the way.
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Ted Rohde
Central Illinois
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