Patent Application
20050141972
The invention relates to an insertion end for a rotary or percussively driven tool such as a chisel boring tool, chisel or a cutting core bit for working rock, concrete or masonry.
Conventionally a rotary or percussively driven tool has an insertion end extending longitudinally along an axis of a rotary or percussive hand tool machine. The interface between the insertion end of the tool and the tool holder of the hand tool machine must be compatible within a specific performance class to provide options for the use of a wide variety of tools. The internationally most widely used standardized insertion ends and associated tool holders, which are disclosed in DE 2 255 125 A1 and DE 3 716 915 A1, have a tool-side cylindrical sleeve-shaped guide surface oriented in the direction of the free leading end axially closed locking groove and towards the free leading end axially open trapezoidal rotary driving groove, wherein at least one radially displaceable locking element of the associated tool holder engages in a locking groove and can restrict the axial mobility of the tool in the tool holder.
The practically standardized insertion end and tool holder according to DE 2 551 125 A1 have a guide diameter of 10 mm, whereby each have precisely two identical, diametrically opposed locking grooves and rotary driving grooves, which are disposed symmetrically on the circumference. A guide surface, which does not contributed to torque transfer, extending up to the tool-side end of the insertion end communicates with the slightly longer rotary driving groove. These insertion ends were originally designed for a bit diameter of up to 17 mm and are consequently grouped in the range of the small, lower-power percussive drills with a power of less than 650 W. The increasingly higher output hand tool machines, in particular the percussion drilling machines [hammer drills], however, make it possible to transmit high torques to the tool in certain operating modes. An extension of the practical range of application of these percussion drilling machines has resulted in a drill diameter of 30 mm. Furthermore, when removing the tool from the work piece, in particular in tools stuck in the bore hole, high torques are brought to bear on the tool by the user by virtue of the hand tool locking up. It has been shown, that the drill diameter of more than 17 mm has an increasing tendency to damage; for example, increasing the tendency of the insertion end to break in the zone of the locking groove and to be destroyed within the tool holder. These breakages are more bothersome when the broken end remains inside the percussion drill and can only be removed by dismantling the front part of the percussion drill from the tool holder. Even when there is no breakage when utilizing drills of greater drill diameters, there is a plastic deformation at the insertion end, which results in a disproportionately high wear on the tool holder.
The standardized insertion ends and tool holders disclosed in DE 3 716 915 A1 have a guide diameter of 18 mm, whereby precisely two identical, diametrically opposed locking grooves are present and exactly one rotary driving groove is arranged in one section half of these grooves and precisely two rotary driving grooves are symmetrically arranged in the other section half of these grooves. These insertion ends are designed for higher performance, larger percussion drills and the transmission of greater torques, whereby the problems mentioned in the above paragraphs occurs at higher power classes or torques. Tools with a guide diameter of 18 mm having a substantially smaller drill diameter of 14 mm, however, have poor impact pulse transmission. Furthermore, such disproportional tools are not economical to manufacture.
The resulting loads have the following composition: On the one hand, there is a loading of the insertion end by virtue of the percussive energy of the percussion drill; and on the other hand, there is, a torsion load emanating from the rotary wedges of the tool holder by virtue of the torque generated at the cutting edge. The torsion load transmits to the rotary driving slots of the insertion end. The torque loading is particularly high when there is a wedging of the cutting edge in a drilling reinforcement.
An additional load occurs when the user attempts to withdraw the percussion drill that is exerted by the locking element on the axial locking end of the locking groove and acts upon an at-risk, posterior cross-section of the locking groove. Many years of experience have shown that the cross-section situated in the zone of the axial locking end is especially at-risk by virtue of these combined, multiple-axis loads. The breakdown-mechanical is due to the locally pronounced, multiple-axis stress condition on the axial locking end, which effects a local stiffening via the transverse contraction. The transverse contraction represents a preferred fissure initiator and limits the fatigue strength of the alternately loaded insertion end.
According to DE 4 338 818, an insertion end of larger diameter is received in a tool holder. The tool holder can also receive an insertion end of smaller diameter. The tool holder has extra rotary driving grooves and locking grooves. The cross-section, which is reduced extremely in the axial region, has a poor impact pulse transmission and a low breaking strength, as already mentioned above.
The object of the invention is to provide an insertion end designed for damage-free transmission of high torque and optimum impact pulse transmission.
This object is achieved by the invention where an insertion end of a tool driven is provided at least partially rotational or percussively along an axis. The insertion end extends along the axis within a maximum guide diameter and has at least one axially closed locking groove at an axial locking end toward the free leading end and rotary driving grooves having a groove width having at least one tangential force contact surface, at least two rotary driving grooves, which have a length comprising at least three times the guide diameter, is arranged on the tool side in front of the axial locking end, and at least one contact length comprising at least 1.5 times the guide diameter, wider than a fifth, advantageously wider than a fourth, of the guide diameter.
The essential portion of the torque is, at least on the tool side, applied to the axial locking end by the rotary driving groove, which is arranged at least over an essential contact length on the tool side in front of the axial locking end. The breaking mechanically critical axial zone of the multiple-axis stress conditions at the axial locking end is thus exposed to lower stresses, whereby with given fatigue strength limits, a higher torque can be applied. In particular, higher torques can be applied at lower guide diameters with low-damage, whereby the impact pulse behavior is improved at lower drill diameters.
Advantageously, an axial guide length between a tool-side guide end with the guide diameter to a tool-side groove end of at least two rotary driving grooves is less than 1.5-times the guide diameter, whereby a torque can be applied in close proximity to the tool-side end of the insertion end.
Advantageously, the groove end of a tool-side locking end is offset axially on the tool-side by at least 1.5-times the guide diameter, whereby in this axial zone the cross-section is not attenuated by locking grooves, whereby the torsional strength is increased and higher torques can be applied with low wear.
Advantageously, the tangential contact surfaces run both parallel and perpendicular to the axis, at least over the contact length, whereby the surface normal is oriented tangential to the tangential contact surface and no shear forces favoring wear are induced upon application of the torque.
Advantageously, the radial groove depth of each rotary driving groove, at least over the contact length, is between 0.5 to 1.0 times the groove width, whereby high torques can be applied without substantial attenuation of the cross-section with adequate flexural strength of the rotary driving webs of the tool holder engaging in the rotary driving groove.
Advantageously, at least three rotary driving grooves are present, which are arranged symmetrically, whereby a higher torque can be applied.
Advantageously, two diametrically opposed locking grooves are present, whereby the insertion end can be introduced ergonomically advantageously in two orientations oriented at 180° into the tool holder.
Advantageously, the locking grooves transition on the tool-side into the rotary driving grooves, whereby the cross-section is less attenuated.
Alternatively, the rotary drive grooves on the tool-side are axially separated from the locking grooves, whereby the functional zones are separated from each other and accordingly can be easily manufactured.
Advantageously, the rotary driving grooves are circumferentially and symmetrically offset from the locking grooves, whereby there is more free space for the rotary driving means and the locking means in the associated tool holder.
Advantageously, the rotary driving grooves are open on the machine side, whereby the rotary driving means can be introduced from the frontal side of the insertion end into the rotary driving grooves.
The preferred embodiment of the invention will be explained in more detail with reference to the drawings, wherein:
a represents an insertion end according to the invention;
b represents an enlarged cross-section of the insertion end of
a represents another variant of the insertion end of
b represents an enlarged cross-section of the insertion end of
According to
According to
According to
The guide length F is equal to, the contact length K 4-times and the length L 3.5-times the guide diameter D, whereby the groove end 13 of the tool-side locking end 14 is offset axially on the tool side by double the guide diameter D.
| Number | Date | Country | Kind |
|---|---|---|---|
| 103 57 380.1 | Dec 2003 | DE | national |
