This utility model appears to be for the, rather unremarkable, design of the pulley wheels on a Sun-Bow derailleur. It is one of three documents regarding features of this derailleur.

I cannot read Japanese, but I am assured that scan 1 also mentions the company name 'Yamashita Iron Works Ltd', and the address 'No 36 Sambocho 4-Cho, Sakai, Osaka'. This is the name and address given on the SY advert on page 254 of the 1956 Japan's Bicycle Guide.

So the SY brand and the Sun-Bow brand appear to originate from the same company.

• Publisher: Japan Patent Office
• Inventor: unknown - any Japanese readers out there to help me out?
• Country: Japan
• Date: Priority date October 1977
• Derailleur brands: Sun-Bow, SY
• Derailleurs: Sun-Bow YA100 (1st style), Sun-Bow YA100 (2nd style), Sun-Bow YA100 (3rd style)