The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 07, 1990
Filed:
Jul. 25, 1989
Takanobu Yamanaka, Yao, JP;
Nippon Pneumatic Manufacturing Co., Ltd., Osaka, JP;
Abstract
An impact tool including a cylinder, a piston slidably mounted in the cylinder and a valve for selectively opening and closing oil feed channels to move the piston up and down. A cylindrical member is slidably mounted on the piston around its large-diameter portion or thereunder. Its bottom end defines the top end of a lower chamber formed in the cylinder. The cylindrical member is adapted to descend together with the piston. But when the piston strikes the object and rebounds upwardly, the cylindrical member keeps descending away from the piston owing to the inertia force. Thus the volume of the lower chamber is kept from increasing excessively after the piston has struck the object. This will prevent cavitation in the lower chamber. When thereafter the lower chamber communicates with the oil feed port and pressure oil is fed thereinto, the cylindrical member will be pushed up toward the large-diameter portion under oil pressure in the lower chamber.