US 4,651,833 AGranted

Pneumatic impact tool

AssigneeEmil Schenker AG

InventorsKurt Karpf, Franz Bobst

Life of this patent

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Abstract

A pneumatic impact tool wherein a two-stage piston is reciprocable in the two-stage chamber of a cylinder. The tool which is to penetrate into a bone is mounted in the front portion of the cylinder and the piston strikes against such front portion in response to admission of compressed air against its rear end face. A relatively small annular shoulder of the piston faces forwardly and is continuously acted upon by compressed air. When the piston approaches or reaches the end of its forward stroke and rebounds from the front end portion of the cylinder, it seals the source of compressed air from its rear end face so that the action of compressed air upon the shoulder suffices to propel the piston rearwardly against the rear end portion of the cylinder at which time the piston reestablishes a path for the flow of compressed air against its rear end face so that it is propelled forwardly against the front end portion of the cylinder.

Claims17

Dependent claims

A pneumatic impact tool, particularly for removing material from bones preparatory to the insertion of prostheses, comprising a cylinder having a tool-supporting front portion and a rear portion and defining a chamber which is disposed between said portions;

a piston reciprocably installed in said chamber and having a first surface facing the rear portion and a smaller second surface facing the front portion of said cylinder;
a source of compressed gaseous fluid, said cylinder and said piston defining a path for admission of compressed gaseous fluid from said source against said first surface to thus effect a forward propulsion of said piston and the application of an impact to the front portion of said cylinder, and said cylinder having a channel which is connected with said source and admits compressed gaseous fluid against said second surface in each position of said piston with attendant propulsion of said piston toward the rear portion of said cylinder;
and means for propelling said piston against said rear portion so that the piston impacts upon and rebounds from said rear portion, said propelling means including said source and said second surface and the fluid being free to flow along said path when said piston impacts against the rear portion of said cylinder.

Dependencies are inferred from the claim text.

Facts

Application: 06/675,523Filed 28 Nov 1984
Priority: CH 6428/831 Dec 1983
Granted: 24 Mar 1987
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

A61B 17/1659
Instruments for performing osteoclasis; Drills or chisels for bones; Trepans: surgical rasps, files, planes, or scrapers
B25D 9/20
Valve arrangements therefor: involving a tubular-type slide valve
B25D 9/26
Control devices for the reciprocating piston: control devices for adjusting the stroke of the piston or the force or frequency of impact thereof
A61B 2017/00544
Pneumatically or hydraulically operated: pneumatically