Is a
Patent attributes
Patent Jurisdiction
Patent Number
Patent Inventor Names
Masao Ishida0
Date of Patent
June 21, 2011
Patent Application Number
12172506
Date Filed
July 14, 2008
Patent Citations Received
Patent Primary Examiner
Patent abstract
A piston 1 contains multiple ring grooves 2, 3 on the outer circumference of the piston 1, and piston rings 4, 10 are mounted in the ring grooves 2, 3. The piston 1 contains oil path grooves 7, 9 extending respectively to the outer circumference of the piston 1 on the upper and lower surfaces of the lowermost ring groove 2, and an oil path groove 12 extending to the outer circumference of the piston 1 on the lower surface of the ring groove 3 just above the lowermost ring groove 2. The weight of the lowermost piston ring 4 is equal to or smaller than the weight of the piston ring 10 just above the lowermost piston ring 4; and expanders 5, 11 are installed on the rear side of the piston rings 4, 10 respectively.
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