Tool driving or impacting – Means to drive tool about an axis – Electric motor
Patent
1993-10-18
1997-07-29
Smith, Scott A.
Tool driving or impacting
Means to drive tool about an axis
Electric motor
310 50, 173183, B25F 500
Patent
active
056514190
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a powered hand tool.
More particularly, it relates to a powered hand tool which has a housing, a motor arranged in the housing and provided with a gear unit and with a spindle, a tool holder carried by the spindle and an electric lead extending in a duct of a wall of the housing.
A hand-held machine tool of the generic type in which an electric lead is arranged in cable ducts of the housing which extend in planes dividing the two shell parts of the housing is known from EP-PS 129 754. The electric lead is installed in these ducts without any special steps for securing it in position and is accordingly exposed to vibrations occurring during operation of the hand-held machine tool. There is no sure way to rule out the possibility of a break in the lead or damage to the insulation particularly when the invention is used in percussion drills or drill hammers. Further, a creepage barrier of at least 4 mm length is prescribed for electric leads in electric hand-held machine tools. Under certain circumstances, this can lead to construction-related problems in the known invention.
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, in which the electric lead, in particular a multi-wire flat-ribbon cable, is arranged so as to be fixed in the duct in the wall of the housing.
When the hand-held machine tool is designed in accordance with the present invention, it has the advantage over the prior art that the electric lead is arranged so as to be fixed and sealed in such a way as to prevent displacement or tearing of the lead even during heavy vibrations. Further, a creepage barrier with a minimum creepage path of 4 mm is ensured for the electric lead in the hand-held machine tool according to the invention at a normal housing wall thickness well below 4 mm. Above all, sensitive sensor cables can be installed in hand-held machine tools in a particularly reliable manner by means of the invention.
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 lateral partial section of a power hand drill and FIG. 2 shows a section through the housing according to the embodiment example in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The hand-held machine tool shown in section in FIG. 1 is a power hand drill 1 with a housing 3 which is constructed from shell parts and tapers toward a spindle bearing arrangement in the neck 4. The housing 3 has a housing wall 5 and holds a motor 7 and a gear unit 9. The motor 7 is in a working connection with a spindle 11 which carries a drill chuck 13. The spindle 11 also carries a pulse generator constructed as a magnet 15. A sensor 17 is arranged in the housing wall 5 in close proximity to the magnet 15 and is connected via an electric lead 19 with an electronic monitoring and control unit 21 arranged in the motor housing 3 and including an adjusting wheel 22 for regulating the speed or torque. The electric lead 19 is guided in the interior of the housing wall 5, i.e. in a duct 23 constructed as a groove which leads to the neck 4. The duct 23 is recessed into the narrow side of the housing wall 5 of the housing shell part 27 at a dividing plane 30 dividing it from another adjoining housing shell part 29. In addition, a first bead-like rib 25 is formed into the contour of the end face of the housing wall 5 and extends adjacent to the duct 23 s
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Holzer Peter
Schaible Hermann
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