Retainer for a pneumatic tool and assembly therefor is disclosed. The retainer includes a tool body having an internal surface defining a bore and an external surface having a threaded portion. A retainer cap is used with the tool body and includes an internal surface having a threaded portion adapted to engage the threaded portion of the tool body.

An insert having an outer surface is rotatably mounted in the retainer cap. The insert includes an inner surface with a first inner surface portion adapted for conforming with a non-circular lug surface of a tool shank and a second inner surface portion radially offset from the first portion adapted for conforming with the non-circular lug surface.

Heretofore, various types of retainers have been used in conjunction with pneumatic and other power tools. U.S. Pat. No. 4,174,113 to Eckman discloses a bit retainer for pneumatic tools arranged to releasably receive a bit. The retainer includes a body having a nose portion of generally elliptical configuration, a center portion of circular configuration and a rear portion of generally elliptical configuration that has its major axis disposed at about 90° relative to the major axis of the front portion of the bore. Radially moveable locking members are provided that operate in cooperation with a moveable sleeve. The sleeve is movable between unlatched and latched positions to permit and prevent radial movement of the locking members to positively retain the bit unless the sleeve is intentionally moved to the unlatched position.

German Auslegeschrift 1,073,410 shows a retainer for a pneumatic tool which has elongated slots and a tool with flanges which fit therein.

U.S. Pat. No. 1,968,380 to Curtis discloses a lug chuck for rock drills. The shank of the drill is rotatably mounted within the front end of the front housing bore. A chuck is formed with a plurality of a opposed clutch jaws capable of cooperation with the sleeve clutch jaws to lock the two parts against relative rotation. The unbroken portion of the chuck is formed with a slot opening into the base of the jaws. This slot is properly machined to permit the passage of the shank and lug of the drill steel.

U.S. Pat. No. 5,170,560 to Allemann et al. discloses a hand nibbling machine which has a manipulatable housing with a drive head in which there is a downwardly opening passage. The upper portion of the tool assembly is releasably engaged in the passage of the drive head by interengaging surfaces. See FIGS. 7-17 for various types of interengaging surface.

U.S. Pat. No. 802,303 to Murphy discloses a pneumatic hammer. The pneumatic hammer of Murphy discloses an inner section of engaging left threads of the cylinder and interior right threads engaging right threads of the cylinder. This reference discloses the use of a threaded retainer for pneumatic tool.

U.S. Pat. No. 4,545,440 to Treadway also discloses a threaded retainer for a pneumatic tool. The attachment is in the form of a housing which receives a punch and a punch holder and can be screwed on the muzzle end of a pneumatic hammer.

The above related art summaries are merely representative of portions of the inventions disclosed in each reference. In no instance should these summaries substitute for a thorough reading of each individual reference. All the references mentioned herein are hereby incorporated by reference.

One of the difficulties not adequately addressed by the prior art is providing a threaded retainer cap for retaining a tool in a pneumatic tool body. After a tool is inserted into a tool body it is generally maintained in a rotationally fixed position relative to the tool body. Rotationally fixing the tool with respect to the tool body permits the operator to control the chisel cutting edge during operation.

During assembly of the pneumatic tool into the tool body, a threaded retainer cap is rotated with respect to the tool body to secure the tool into the tool body. During this assembly, the tool must remain fixed with respect to the tool body. Thus, in accordance with the present invention a need arose to have a threaded retainer cap which allows the tool to remain rotationally fixed in the tool body and yet permits the retainer cap to be tightened on the tool body.