Patent Application
20210031327
This nonprovisional application claims priority under 35 U.S.C. § 119(a) to German Patent Application No. 20 2019 104 156.0, which was filed in Germany on Jul. 29, 2019, and which is herein incorporated by reference.
The present invention relates to a gear head for a hand-held power tool for machining workpieces, in particular for an angle grinder, comprising a housing, closable by a gear plate, in which a power take-off is accommodated, which is connectable to a drive of a hand-held power tool, the power take-off including a tool shaft protruding from the gear plate, which is at least partially surrounded by a safety guard accommodated on a gear flange of the housing, also comprising a securing lever for locking the safety guard on the gear flange, which is supported on the gear plate, adjustable around a pivot axis from a first position, in which the safety guard is rotatably fixedly connected to the gear flange, and a second position, in which the safety guard is rotatably with respect to the gear flange, against the force of a restoring element acting in the direction of the first position. The invention also relates to a hand-held power tool comprising a gear head according to the invention.
Gear heads have long been known from the prior art, in particular in angle grinders. To protect the user, it is required to use them only with a safety guard, which surrounds a part of the tool connected to the tool shaft and makes the grinding wheel accessible only within a certain angle range. This is intended to protect the user, in particular against particles which may arise during the machining of workpieces. To allow a preferably versatile use of the hand-held power tool equipped with the gear head, the safety guards are rotatably fastened to the gear flange, the safety guard being lockable by the securing level, i.e. its rotational position being fixable.
The securing lever must ensure that the safety guard and the securing lever also withstand the stresses which occur when a tool connected to the tool shaft breaks, for example a grinding wheel. The breaking tools pose an enormous risk of injury, due to the high rotational speeds, which must be mitigated by the safety guard. If the safety guard rotates an impermissible distance during the breaking of the tool, parts of the breaking tool may strike the user, which would be associated with serious injuries. The safety guard should therefore not, or only slightly, rotate during the breaking of the tool. The forces acting upon the safety guard and the securing lever during the breaking of the tool are so high that the securing lever is partially deformed, and there is the risk that the locking of the safety guard by the securing lever is released.
In the present case, the tool shaft is the part of the power take-off to which the tool is fastened. In angle grinders, this tool shaft is usually perpendicular to the motor longitudinal axis.
It is therefore an object of the present invention to reduce the aforementioned disadvantages and to provide an improved gear head. The object of the invention is also to provide an improved hand-held power tool.
The object relating to the gear head is achieved according to the invention in a gear head of the type mentioned at the outset in that a securing device limiting the adjustment of the securing lever beyond the first position is provided, which has a contact surface.
The forces occurring, in particular upon the breaking of a tool, are conducted by the contact surface of the securing device from the safety guard via the securing lever and the securing device into the gear plate and the gear head, which reduces the risk of a mechanical overload of the securing lever, which would result in a structural failure of the securing lever locking the safety guard.
It has also proven to be favorable if a gap, whose width is between 0.5 mm and 1.0 mm, is formed between the securing lever and the contact surface in the first position. The forces occurring upon the breaking of the tool are conducted hereby directly into the gear plate and thus into the gear head without a deformation of the securing lever first occurring. A replacement of the securing lever may thus be dispensed with after the tool breaks.
In addition, the adjustment of the securing lever from the first position into the second position is not disadvantageously influenced hereby. Within the scope of the invention, however, it is also provided that the securing lever abuts the contact surface in the first position.
It has also proven to be advantageous if the ratio between the length of the contact surface and the length of the securing lever is between 1:8 and 1:4. The occurring forces are thus particularly effectively conducted into the gear plate, and it is simultaneously ensured that the additional weight of the securing device does not negatively affect the handling of the hand-held power tool.
It has also proven to be successful if the contact surface is formed in the area of the pivot axis of the securing lever. This area has proven to be particularly vulnerable if, when a tool breaks, the breaking parts thereof strike and accelerate the safety guard. In this case, there is namely the risk that the securing lever is literally pulled into the intermediate space between the gear flange and the pivot axis. Therefore, if the contact surface is provided in this area, this risk is significantly reduced.
It has also proven to be favorable if the securing device having the contact surface has an essentially wedge-shaped cross section. An improved force absorption is also achieved hereby, which has a positive effect.
It has also proven to be particularly favorable if the securing device is formed as a single piece with the gear plate. A particularly high mechanical rigidity and load tolerance may be achieved hereby.
Within the scope of the invention, however, it is also provided that the securing device is detachably connected to the gear plate. This makes it possible to easily replace a damaged securing device. In this connection, it has also proven to be successful if the securing device is screwed to the gear plate. For this purpose, the securing device may have a screw eyelet, and a recess is advantageously provided in the gear plate, into which the securing device may be rotatably fixedly inserted.
It has furthermore proven to be advantageous if the securing device has an S-shaped design, with a first leg, which forms the contact surface, and with a second leg, which is accommodated in the gear plate. For example, a slot or a recess, with which the second leg may engage or on which it may be supported, may be formed in the gear plate to accommodate the second leg. For example, the screw eyelet may be disposed in the area formed perpendicularly to the legs.
Alternatively or additionally, it has also proven to be particularly favorable if the securing device has a securing engagement formed on the gear plate and a securing hook formed on the securing lever. One again, occurring forces may be easily absorbed hereby and prevent the securing lever from being deformed. The securing hook may also be positioned with respect to the securing engagement in such a way that these components come into engagement with each other only upon a slight deformation of the securing lever. In particular, a deflection of the securing lever in the direction of the pivot axis is prevented hereby. The securing engagement ultimately forms the contact surface of the securing device or at least a part thereof.
In this connection, it has also proven to be favorable if the securing hook is disposed in the area of the end of the securing lever facing away from the pivot axis. In addition to an improved force transmission, this has, in particular, a positive effect on the assembly complexity.
It has further proven to be successful if the pivot axis is oriented in parallel to the tool shaft. This allows the securing lever to be particularly easily gripped by the user, which has a positive effect on the user-friendliness of a hand-held power tool equipped with the gear head according to the invention. Within the scope of the invention, the pivot axis may, however, also be oriented perpendicularly to the tool shaft.
The object relating to the hand-held power tool is also achieved according to the invention by a hand-held power tool comprising a gear head according to the invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes, combinations, and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:
As is apparent, in particular in the view illustrated in
In the third exemplary embodiment of gear head 1 illustrated in
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 2019 104 156.0 | Jul 2019 | DE | national |
