Tool driving or impacting – Drive adjustable to completely change kind of drive – Adjustable to impacting device
Reexamination Certificate
2002-07-17
2004-07-27
Gerrity, Stephen F. (Department: 3723)
Tool driving or impacting
Drive adjustable to completely change kind of drive
Adjustable to impacting device
C173S004000, C173S162200
Reexamination Certificate
active
06766868
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electric combination hammer.
BACKGROUND INFORMATION
Published German Patent Application 197 20 947 A1 describes a generic electric combination hammer for use either as a drilling hammer or as a chisel hammer. The electric combination hammer has a housing having an electric motor by which a tool mounted in a tool mount may be driven. A bracket-shaped handle is integrally molded in one piece onto the housing on a side facing away from the tool. A pawl for operating an electric on-off switch for the electric motor is situated on a side of the handle facing the housing. The pawl is designed as an operating rocker having two rocker arms attached to the handle so it is pivotable about a pivot axis, a contact pin of the on-off switch being applied to the lower rocker arm under the force of a spring.
In chisel operation, the pawl may be locked in a latched position by a catch device. In drilling operation, however, a latched position is prevented. The catch device has a first catch element situated on the pawl and a second catch element situated on a pivot lever that is mounted on the housing by an articulated joint. The pivot lever is linked to a cam situated on a switch knob for switching manually from drilling to chisel operation and vice versa, and the pivot lever presses on its periphery by a compression spring. In a switch position of the switch knob for setting the tool for drilling operation, the catch element situated on the pivot lever is outside a contact travel of the catch element situated on the pawl. In a switch position of the switch knob which sets the tool for chisel operation, the pivot lever is pushed over the cam with its catch element into the contact travel of the catch element situated on the pawl. The catch element attached to the pawl is formed by a part which forms a catch spring having on its free end a peak which is able to engage in the catch element formed by a catch depression in the pivot lever in chisel operation.
SUMMARY OF THE INVENTION
The present invention is based on an electric combination hammer for use either as a drilling hammer or as a chisel hammer having a housing and a handle arranged on it, in which is arranged an on-off switch having a pawl and having a switch element for manually switching from drilling operation to chisel operation and vice versa and having a catch device by which the pawl may be engaged in chisel operation and which prevents a latched position from being engaged in drilling operation.
The catch device has a catch bracket having two legs which are connected by a joint and may be brought into an operative connection with a blocking element that blocks the joint in at least one pivot direction to establish the catch function and having at least one catch element which may be brought into operative connection with a catch element that is in operative connection with the pawl. The catch device may have a simple design, friction may be avoided in drilling operation and the catch bracket may have a flexible arrangement. In particular, the catch bracket may be mounted in the handle in a simple design in the case of a movably mounted handle, thus preventing any relative movement, caused by a movement of the handle, between the corresponding catch elements and unwanted release of the catch connection.
The blocking element is advantageously mounted on the housing and its movement may be controlled by the switching element. If the handle is connected to the housing by a joint at a first end and by an isolation device at a second end, and if the catch bracket is mounted on the side of the handle facing the joint, then it is possible to minimize any relative movement between the blocking element mounted on the housing and the catch bracket, as well as the resulting friction and wear.
The blocking element may be designed to be purely mechanically controllable by the switch element, e.g., by having the blocking element in operative connection with the switch element by way of a switch lever, or it may be designed to be controlled electrically by the switch element. With an electric control, a mechanical connection between the switch element and the blocking element may be avoided, and parts, space, weight, assembly, complexity and cost may be saved. Furthermore, degrees of freedom in design may also be created. The blocking element may be designed to be operable by an electric motor or by an electromagnetic actuator, which is especially advantageous. A corresponding electromagnetic actuator may be simple in design and inexpensive.
To save on parts, space, weight and assembly complexity, a controller for controlling the blocking element is advantageously designed at least partially, preferably completely, in one piece with a controller for controlling the change from drilling operation to chisel operation and vice versa. Furthermore, parts, space and weight may be saved by designing at least one catch element in one piece with a catch spring and/or at least one leg of the catch bracket in one piece with a catch element.
REFERENCES:
patent: 1356556 (1920-10-01), Payne
patent: 4204580 (1980-05-01), Nalley
patent: 4342931 (1982-08-01), Grossmann et al.
patent: 4348603 (1982-09-01), Huber
patent: 4506743 (1985-03-01), Grossmann
patent: 4998588 (1991-03-01), Manschitz
patent: 5697456 (1997-12-01), Radle et al.
patent: 6123158 (2000-09-01), Steffen
patent: 19720947 (1997-12-01), None
patent: 1075905 (2001-02-01), None
patent: WO 88/01219 (1988-02-01), None
Frauhammer Karl
Schnerring Heinz
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