Tool driving or impacting – Drive adjustable to completely change kind of drive – Adjustable to impacting device
Reexamination Certificate
2002-07-29
2004-03-02
Smith, Scott A. (Department: 3721)
Tool driving or impacting
Drive adjustable to completely change kind of drive
Adjustable to impacting device
C173S104000, C173S110000, C173S109000
Reexamination Certificate
active
06698530
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is based on hand power tool.
DE 197 26 383 A1 has disclosed a hand power tool that defines the species, specifically an electrically driven hammer drill. The hammer drill has a rotary driven working spindle that is supported in a housing and in turn drives a tool holding fixture of a tool. The hammer drill also has a mechanical hammer unit with a hammer, which can move axially inside the working spindle embodied as a hollow shaft and can be accelerated in the axial direction, and which acts directly or indirectly on a shaft of the tool during operation. The hammer is acted on by a driver unit, which converts a rotary motion of the working spindle into an axial acceleration of the hammer.
The driver unit has a feeler unit that can move axially and rotates synchronously with the working spindle and that is guided with axial play between two annular curved paths, which do not rotate in relation to the working spindle and have raised areas and recessed areas oriented toward each other in the axial direction of the working spindle. The feeler unit is constituted by an annular component, which can be moved on the hammer in the axial direction, counter to a compression spring and which has a feeler element extending radially outward, which reaches through a slot in the working spindle between the curved paths and can thus bring the feeler unit into an operative connection with the curved paths.
For a switching on and off of the hammer unit, the curved path oriented toward the tool is supported so that it can move axially in tandem with the working spindle. If the tool is pressed against a working surface, the working spindle at the curved path oriented toward the tool is slid axially toward the curved path oriented away from the tool, counter to an idling spring embodied as a compression spring so that the feeler element comes into contact with the two curved paths during a rotating motion. The hammer unit is switched on.
If the tool is lifted up from the working surface, the curved path oriented toward tool and the working spindle are restored to their initial position by the idling spring. The distance between the two curved paths is thereby enlarged to such an extent that the feeler element in rotate freely between the two curved paths, without coming into contact with them. The hammer unit is switched off.
SUMMARY OF THE INVENTION
The invention is based on a hand power tool, in particular a hammer drill, with a drivable drive mechanism accommodated in a housing and a mechanical hammer unit, which is for percussion-driving a tool in a tool holding fixture and has a hammer that can be driven in its hammering motion by means of a driver unit, which has at least one curved path with raised areas and recessed areas oriented axially toward the tool and has a feeler unit, which is operationally connected to the hammer and which, by means of at least one feeler element, can be brought into operational connection with the raised areas and recessed areas of the curved path.
The invention proposes that the feeler unit has at least two and preferably three or more feeler elements that can be brought into operational connection with the curved path. A tilting moment on the feeler unit and the hammer can be prevented and a centering of the feeler unit on the curved path can be achieved. The efficiency can be increased and the wear can the reduced.
If the feeler elements have at least one sloped surface at least partly oriented in the rotation direction and/or counter to the rotation direction, the feeler elements can be advantageously guided with a minimum of wear from a recessed area of a curved path onto a raised area of the curved bath and from a raised area of the curved path into a recessed area of the curved path. A tilting contact between the feeler elements and the curved paths can be prevented. The sloped surfaces can, for example, be constituted by a concavely curving sloped surface or by a phase.
In order to assure a reliable engagement and disengagement of the hammer unit and to assure a reliable neutral position, when in this neutral position, a respective stop limits the movement of the feeler elements of the feeler unit in the axial direction toward at least one curved path, or when there are two curved paths, advantageously limits this movement of the feeler elements in the axial direction toward both functional curved paths. If the drive mechanism is supported in an axially mobile fashion, and if a stop is constituted by a device affixed to the drive mechanism, for example a securing ring, a shoulder formed onto the drive mechanism, or the like, then a disengaging movement of the drive mechanism can be advantageously used to correspondingly position a stop in order to limit the movement of the feeler elements of the feeler unit.
Another embodiment of the invention proposes that a stop is constituted by a component, which, when the hammer unit is in a hammering position, forms a part of curved path, which permits an embodiment that is particularly compact and lightweight to be produced. This can be achieved in a structurally simple manner particularly in that the component is comprised of a ring with openings, which extend in the circumference direction and are separated by struts, and in the hammering position, partial regions of the curved paths protrude through the openings, the struts plunge into recesses between the partial regions, and form a part of the curved path.
Instead of two curved paths between which the feeler unit is disposed, the driver unit can also be embodied with only one curved path, one whose raised areas and recessed areas are oriented axially toward the tool. The device must be balanced in such a way that the feeler unit is moved back toward the curved path by a spring and/or by the hammer rebounding off a stop surface. This permits additional components, space, and weight to be saved in comparison to a driver unit with two curved paths.
REFERENCES:
patent: 1755565 (1930-04-01), Shook
patent: 2850739 (1958-09-01), Turner
patent: 2970483 (1961-02-01), Schrum, Sr.
patent: 5427188 (1995-06-01), Fisher
patent: 5449044 (1995-09-01), Phillips
patent: 5513709 (1996-05-01), Fisher
patent: 6199640 (2001-03-01), Hecht
patent: 810 140 (1951-08-01), None
patent: 197 26 383 (1998-12-01), None
Nathaniel Chukwurah
Robert & Bosch GmbH
Smith Scott A.
Striker Michael J.
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