Tool driving or impacting – Impacting devices – With means for rotating tool
Patent
1991-01-29
1992-05-12
Yost, Frank T.
Tool driving or impacting
Impacting devices
With means for rotating tool
173 14, 173201, B25D 904
Patent
active
051118904
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a hammer drill, in particular a percussion hammer comprising a tool holder, an air cushion striking mechanism including a piston displaceable in a guide tube and a striker, and a device which holds the striker in its front position facing the tool holder by venting the air cushion, when the hammer is idle. In a hammer known from DE-PS 26 41 070, a fixed guide tube in which the piston and striker are guided so as to be tight and sliding, is enclosed by a control body which is axially displaceable for idling control. The control body embraces the guide tube at the front in such a way that a collar of the intermediate anvil contacts the base of the control body and the latter can accordingly be pushed axially inward during hammer operation. Such a construction has the disadvantage that it is only suitable for pure chisel hammers, but not for drill hammers with rotary drive. A rotary drive of the guide tube is not possible, and the rotating movement can also not be transmitted to the tool holder, since the control body prevents the connection of the guide tube with the tool holder. Moreover, the additional control body brings about an increased cost in manufacturing and is a hindrance when the hammer is to be supplemented with further functions.
SUMMARY OF THE INVENTION
The object of the invention is a percussion hammer in which an additional control sleeve can be entirely dispensed with. The object of the invention is achieved by providing a displaceable guide tube having a plurality of guide elements and a control opening in an area of one of the guide elements, which opening can be closed or opened by tube displacement. The invention makes possible a rotary drive of the hammer and guide tube which can be displaceable to the tool holder, and a striking mechanism which is simple and has fewer parts. In addition, the idling behavior is improved by a greater distance between the striker and idling bore hole. In the arrangement of the idle control openings outside the travel path of the piston and accordingly outside of the compression area of the air cushion, the guide element need not be sealed particularly relative to the guide tube. The gap seal between the two structural component parts is sufficient.
The striker is constantly forced against the anvil during idling by providing the idle control opening with a valve. Idling is accordingly ensured in a substantially more reliable manner--even when the machine is held vertically facing upward.
The advantageous inventive idea may be applied to a hammer with the proven L-shaped arrangement of the striking mechanism and motor. Because of the gear ratio, the bevel gear for the rotary drive is still located at the place, as shown in FIGS. 4 and 5, relative to the striking mechanism.
The hammer shown in FIG. 4 has the advantage that the switching mechanism for switching on and off or blocking the rotational movement is constructed in a very simple manner and is very economical and simple to manufacture. The switching ring shown in FIG. 4 and comprising only one toothing can also be used for switching a hammer striking mechanism on and off.
The present invention both as to its construction so to its mode of operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of the preferred embodiments when read with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A to 1B show cross-sectional views of longitudinal hammer drill, according to a first embodiment of the invention in two different positions of the guide tube;
FIG. 2 shows a longitudinal cross-sectional view of a second embodiment of a hammer drill according to the invention;
FIGS. 3A and 3B show cross-sectional views of a third embodiment of a hammer drill according to the invention in the hammering position and in the idling position of the striking mechanism;
FIGS. 4 and 5 show cross-sectional views of fourth and fifth embodiments, respectively, of
REFERENCES:
patent: 3774699 (1973-11-01), Schmuck
patent: 3921729 (1975-11-01), Schmuck
patent: 4582144 (1986-04-01), Mizutani
patent: 4823886 (1989-04-01), Dyatov
patent: 4825961 (1989-05-01), Neumaier et al.
Hellbach Manfred
Kaltenecker Johann
Meixner Gerhard
Ranger Ulrich
Wanner Karl
Robert & Bosch GmbH
Smith Scott A.
Striker Michael J.
Yost Frank T.
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