Tool driving or impacting – Impacting devices – Hammer head driven by pulsating fluid pressure
Reexamination Certificate
2002-12-13
2004-11-02
Gerrity, Stephen F. (Department: 3721)
Tool driving or impacting
Impacting devices
Hammer head driven by pulsating fluid pressure
C173S104000, C173S200000, C173S210000, C173S211000
Reexamination Certificate
active
06810969
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is based on a hand power tool, in particular a drilling-and/or chipping hammer.
A hand power tool of this type is known in practice and is developed as a drilling hammer, for example, that comprises a hammer tube situated in a machine housing, in which said hammer tube a drive piston developed as a pot-type piston is guided. The pot-type piston is coupled via an air cushion with a “striker” which, in turn, is actively connected with a punch dolly for driving a tool situated in a tool guiding element, which said tool is developed as a drill bit, for example. “Drive teeth” with which the tool meshes are formed on the tool guiding element.
The drilling hammer has an idle position and an operating/striking position. In the idle position, the tool, the punch dolly, and the striker are situated in a “forward” position. The striker is held by a safety catch. In the operating position, in which the tool is placed on a surface to be worked, for example, the tool is subjected to axial pressure, so that the entirety composed of the tool, the punch dolly, and the striker are moved into a “rear” position, and “idle openings” in the pot-type piston are closed by the striker. As a result, a compressed air cushion forms between the pot-type piston and the striker, by means of which movement of the pot-type piston is transferred to the striker and, therefore, to the punch dolly and the tool.
In the case of the known drilling hammer, the tool guiding element and the safety catch are each fixed in stationary fashion in the housing in the axial direction, so that, during transition from the idle position to the operating position, or from the operating position to the idle position, relative motion takes place between the tool guiding element and the tool.
SUMMARY OF THE INVENTION
The invention is based on a hand power tool, in particular a drilling- and/or chipping hammer, having a machine housing, a tool guiding element, a hammer tube, and a safety catch—fixed in stationary fashion in the housing in the axial direction—for a striker that can be driven by means of a drive piston and that is actively joined with a tool situated in the tool guiding element.
It is proposed that the tool guiding element is designed so that it is axially displaceable in relation to the machine housing. During transition from the idle position to the operating position, or from the operating position to the idle position, axial displacement of the tool and axial displacement of the tool guiding element can take place. The relative motion between the tool and the tool guiding element can be kept to a minimum. Operation-induced wear in the joint region between these two components is therefore minimal which, in turn, results in a long service life of the components. In particular when the tool guiding element is turnably supported and comprises drive teeth for the tool, a large tooth contact surface area can be realized between the tool and the tool guiding element in the direction of rotation. This results in a slight surface pressure, which, in turn, has a favorable effect on wear.
A compression spring is a cost-effective means for setting the idle position of the tool guiding element, by means of which the tool guiding element is preloaded in the direction of the tool.
According to a preferred embodiment of the hand power tool according to the invention, the tool guiding element is designed integral with the hammer tube. This results in a reduced number of components and, therefore, to reduced installation expense. The assembly comprising the tool guiding element and the hammer tube is then designed to be axially displaceable, so that, during transition from the idle position to the operating position, or from the operating position into the idle position, the hammer tube also undergoes axial displacement. In this exemplary embodiment, the compression spring can act directly on the hammer tube or on the tool guiding element.
In order for the safety catch to follow a rotation of the tool guiding element or the hammer tube, the safety catch is advantageously supported in a guide ring fixed in the housing in stationary fashion. Particularly when the tool guiding element and the hammer tube are designed as a single component, the safety catch is supported axially in the housing in stationary fashion, without negatively affecting the rotation of the hammer tube.
A pin associated with the safety catch and that meshes with the guide ring is a structurally simple means of attaining the object for guiding the safety catch in the guide ring. In order to drive the pin when the hammer tube rotates, said pin advantageously passes through a slot in the hammer tube that extends in the axial direction.
In the case of an alternative exemplary embodiment, in which the tool guiding element and the hammer tube are designed as at least two components, the safety catch can be fastened to the hammer tube that is joined with the machine housing. In this exemplary embodiment, the hammer tube and the safety catch are fixed in the housing in stationary fashion in the axial direction. The tool guiding element can be replaced individually if it becomes worn.
In order to obtain a good start-up behavior of the hand power tool according to the invention, the drive piston is advantageously designed as a pot-type piston. This is of particular advantage in the case of heavy drilling- and/or chipping hammers. It is also feasible, however, to design the drive piston as a cylindrical piston.
So that the striker is always guided securely in the pot-type piston, the safety catch can extend into the pot-type piston. In this case, the safety catch serves as a stop for the striker when it is displaced in the pot-type piston.
Further advantages result from the following description of the drawing. Exemplary embodiments of the invention are presented in the drawings. The drawings, the description, and the claims contain numerous features in combination. One skilled in the art will advantageously consider them individually as well and combine them into reasonable further combinations.
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patent: 5050687 (1991-09-01), Prokhorov
patent: 5201373 (1993-04-01), Bloechle
patent: 6116352 (2000-09-01), Frauhammer et al.
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patent: 0 884 138 (1998-12-01), None
patent: 2 412 391 (1979-07-01), None
Chukwurah Nathaniel
Gerrity Stephen F.
Striker Michael J.
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