Cutting by use of rotating axially moving tool – With randomly-actuated stopping means – Responsive to condition of tool or tool-drive
Patent
1993-10-08
1995-03-28
Bishop, Steven C.
Cutting by use of rotating axially moving tool
With randomly-actuated stopping means
Responsive to condition of tool or tool-drive
7386229, 173176, 408 9, B23B 4724
Patent
active
054011248
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a hand-held machine tool.
More particularly, it relates to a hand-held machine tool, in particular a drill hammer, which has a housing and a tool driven in rotation by a motor with a gear unit. A hand-held machine tool having a separate bearing block and electrical force measuring device arranged at the latter for detecting sudden jamming or blockage of the tool is already known from EP 199 883 A2. This construction requires a specially designed bearing block which is also supported in the machine housing so as to be rotatable at a swivel axis. Since the bearing forces or reaction forces occurring as a result of the transmission of torque are measured, there is also a risk of faulty triggering when moment-transmitting shocks or impacts occur in normal operation.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a hand-held machine tool, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a hand-held machine tool which has a sensor arranged at a bearing of a rotating part of the gear unit so that it lies in the effective region of the bearing forces produced by the moment of the occurring gyroscopic effect when the housing of the hand-held machine tool rotates around the rotational axis of the tool.
When the hand-held machine tool is designed in accordance with the present invention, it has the advantage over the prior art that the blocking of a tool can be detected in a reliable and simple manner without additional expenditure on construction. To do this the invention makes use of the effect whereby a forced change in position of a rotating body which is suspended at least at one point produces an additional angular momentum directed at a right angle to the deflection. This gyroscopic effect produces reaction or bearing forces in the bearings of the rotating part which do not occur in normal operation.
It is particularly advantageous to arrange the sensor or sensors on a line extending parallel to the rotational axis of the tool and through the center axis of the rotating part, particularly of the motor. The sensor can be constructed as a force measuring device or as a pressure sensor. It is also particularly advantageous if the rotating part is formed by the armature of the motor. As a result of the large mass moment of inertia of the armature, this leads to a correspondingly large additional angular momentum. The additional angular momentum can be detected particularly well if the bearing forces occurring in normal operation act in a different direction, especially so as to be offset by 90.degree. relative to the gyroscopic forces. This can be achieved in that the gear members cooperating with the rotating part are arranged in such a way that the transmission forces do not act in the direction of the rotational axis of the tool, but rather at a right angle thereto. The measurement signal of the sensor is fed to a control device which causes an interruption in the rotational driving of the tool, particularly by switching off the motor or by opening a safety coupling.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a section through a hand-held machine tool formed as a drill hammer.
DESCRIPTION OF PREFERRED EMBODIMENT
A drill hammer 1 with a housing 2 and a tool carrier 3 which projects out of the housing and in which a drilling tool 4 is inserted is shown schematically in FIG. 1. A hammer mechanism which is accommodated in the housing 2 is not shown in
REFERENCES:
patent: 4063600 (1977-12-01), Krzes
patent: 4448261 (1984-05-01), Kousek et al.
patent: 4487270 (1984-12-01), Huber
patent: 4534420 (1985-08-01), Golelius
patent: 4638870 (1987-01-01), Kousek
Bishop Steven C.
Robert & Bosch GmbH
Striker Michael J.
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