US 4,290,492 AGranted

Idling and air replenishing system for a reciprocating hammer mechanism

AssigneeBlack & Decker Inc.

InventorsDaniel H. Sides, Hanspeter E. Beisch

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Abstract

An improved air replenishing and idling system for a reciprocating hammer type tool having an outer housing and reciprocal drive mechanism, comprising an elongated barrel mounted within that housing. The barrel includes an axially disposed, air passageway. Slideably positioned within the barrel is a piston member which includes a closed end portion and a hollow, tubular forward portion having first and second air passageways. The piston is reciprocally moved within the barrel by the drive mechanism. Slideably positioned within the hollow tubular portion of the piston is an impact ram. In the operational mode, the ram, tubular portion of the piston member, and barrel cooperate to seal or expose the first and second air passageways and provide a communicative path to the "outside" air through the barrel air passageway whereby the ram is urged axially towards and away from the tool bit through the pressure differentials created. Further, in the idling mode, the first and second air passageways and the barrel passageway insure that the ram is inactive when the tool bit is removed or when the tool is lifted from the work surface.

A hammer tool having a housing which carries a detachable bit toengage a work piece,

(a) drive means mounted in the housing to power the tool,
(b) a barrel fixedly connected to the housing, and in communication with the atmosphere,
(c) the barrel has an open forward end and an open rearward end,
(d) an air passageway formed intermediate the ends of the barrel,
(e) a piston member slidingly disposed in the barrel, the piston member has a closed end adjacent the rearward end of the barrel, and the piston member has an open end adjacent the forward end of the barrel,
(f) the piston member connected to be reciprocated by the drive means,
(g) a ram slidingly disposed in the open end of the piston freely to move substantially forward of the open end of the piston member in an idling mode defined by the absence of the bit, and the ram to reciprocate responsive the driven piston member to deliver impact blows to the bit in a hammering mode defined by the presence of the bit,
(h) the ram having a sealing surface disposed opposite the closed end of the piston member,
(i) a chamber means of variable volume formed in the open end of the piston member between the closed end of the piston member and the sealing surface of the ram,
(j) a front port and a rear port formed in the open end of the piston member in predetermined spaced relationship to each other,
(k) the rear port to communicate the chamber means with the barrel air passageway upon the piston member reaching the limit of its forward travel to permit replenishing air in the chamber means, and thereafter said communication between the chamber means and the barrel air passageway being selectively closed by the independent motions of the ram or the piston member during the hammering mode, the rear port continuously communicating with the chamber means during the idle mode, and
(l) the front port during the hammering mode is closed by the ram, the barrel, or by both the ram and the barrel, the front port to intermittently communicate the barrel air passageway with the chamber means during the idling mode upon the rear port being closed by the barrel and the sealing surface of the ram being disposed forwardly of the front port.

9 more elements

Abstract

Claims5