Tool Shaft for a Tool of the Percussive and Rotative Type

The invention is related to a device on hand machine tools.

Such a device is already known from DE-PS 25 51 125. Tools constructed according to this patent are also usable in principle in tool receptacles provided according to AT-PS 285 405, wherein the locking elements applied in the latter engage in the recesses which are closed on both sides and arranged in the tool shaft outside the rotary driving grooves. The width and depth of the rotary driving grooves opening out at the end of the tool shaft are selected in such a way that they can not receive the locking elements, and accordingly the tool can not be incorrectly inserted.

However, particularly in severe construction site operation, the rotary driving grooves can become worn out after long use of the tool to such an extent that the tool can unintentionally be inserted into the tool holder in a position in which the locking elements engage in the rotary driving grooves. This brings about the risk that the machine may be unexpectedly disengaged from the tool when withdrawing the machine from the workpiece during operation, since the locking elements of the tool receptacle can slide out of the rotary driving grooves, which are open toward the end of the tool, in an unimpeded manner. This is particularly dangerous because when working with the machine the operator can not determine in certain cases that the tool is incorrectly inserted. In this case, the operator will only notice it--but in an entirely unanticipated manner--when he withdraws the machine from the workpiece and the tool, which is possibly stuck in the workpiece, remains in the latter. Since this separation of machine and tool is entirely unanticipated by the operator, there is the danger that he will lose his balance when working on a ladder or scaffold, which brings about a considerable risk of accident.

Accordingly, it is an object of the present invention to provide a tool of the above-described percussive and rotative type which is safer to operate than that currently available.

In keeping with this object and with others which will become apparent hereinafter, one feature of the present invention is that the rotary drivers of the tool receptacle assigned to the rotary driving grooves in the tool shaft are distributed around the circumference of the receptacle bore hole in such a way that two rotary drivers are never located diametrically opposite each other. The device according to the invention has the advantage that the tool can never be inserted in the tool holder in a position in which the locking elements arranged in the tool receptacle can engage in the rotary driving grooves opening out at the end of the tool shaft; this can be achieved without the necessity of applying additional locking means or the like.

It is particularly advantageous that a plurality of rotary driving grooves be arranged between the recesses which are closed on both sides, since the specific surface loading during the transmission of the driving torque is reduced as the number of rotary driving grooves increases, and the wear is accordingly decreased.

If one of the rotary driving grooves in the tool shaft is constructed so as to be deeper than the other rotary driving grooves and the respective strip-shaped rotary driver of the tool receptacle is constructed so as to be correspondingly higher, another advantageous step consists in providing a conical inserting bevel at the inserting end of the tool shaft, which inserting bevel encloses an angle .alpha. with the tool axis, and in providing the front sides of the strip-shaped rotary drivers at the tool side with inserting bevels which enclose an angle .beta. with the axis of the tool receptacle which is greater than the angle .alpha.. If, in addition to this, the conical inserting bevel is dimensioned in such a way that it cuts into the bases of the shallower rotary driving grooves, while leaving the base of the deeper rotary driving groove untouched, this arrangement provides the advantage that when introducing the tool into the tool receptacle, a contact between the rotary driving strips and rotary driving grooves can only be effected if the tool has first been rotated relative to the tool receptacle until the highest rotary driver lies opposite the deepest rotary driving groove. Until then, however, the smooth, i.e. "untoothed" portion of the inserting bevel of the tool shaft slides along the inserting bevel at the highest strip-shaped rotary driver. Accordingly, the tool fits into the receptacle only in this position and the operator is not irritated by a catch-like engagement of the rotary driver in the shallower rotary driving grooves.

Various embodiment examples of the invention are shown in the drawing and expalined in more detail in the following description.

FIG. 1 is a detailed longitudinal cross-sectional view of a tool holder arranged in a drill hammer with inserted tool;

FIG. 2 is a transverse cross-sectional view taken along section line II--II of FIG. 1;

FIG. 3 is a side view of a second embodiment of a tool shaft according to the present invention;

FIG. 4 is a cross-sectional view taken along section line III--III of FIG. 3;

FIG. 5 is a side view of a third embodiment of a tool shaft according to the present invention;

FIG. 6 is a cross-sectional view taken along section line IV--IV of FIG. 5;

FIG. 7 is a side view of a fourth embodiment of a tool shaft according to the present invention;

FIG. 8 is a transverse cross-sectional view taken along the section line V--V of FIG. 7;

FIG. 9 is a longitudinal cross-sectional view of a fifth embodiment of a tool shaft in connection with a tool holder taken along the section VI--VI of FIG. 10;

FIG. 10 is a cross-sectional view taken along VII--VII of FIG. 9;

FIG. 11 is a plan view of a sixth embodiment of a tool shaft as seen in the direction XI of FIG. 10; and

FIG. 12 is a plan view of a seventh embodiment of a tool shaft as seen in the direction of arrow XII of FIG. 10.

A tool spindle 2 extends out of the end of the housing of a drill hammer 1, which end is on the side of the workpiece and is only shown in part. The tool spindle 2 transmits a torque on the one hand and axial strokes, on the other hand, to a tool receptacle 3 which is securely connected with it. The tool shaft 5 of a drill 6 is inserted into the concentric receptacle bore hole 4 of the tool holder 3. Two recesses 7 which are closed in the axial direction at both sides are arranged at the tool shaft 5 so as to be located opposite one another on a diagonal line; assigned locking bodies 8 of the tool holder 3 are constructed as balls to engage in the recesses 7. As can be seen in FIG. 2, the slot- or groove-like recesses 7 have a circular-cylindrical cross-sectional shape. The locking bodies 8 can move out of the recesses 7 of the tool shaft 5 by means of axial displacement of a sleeve 12, so that the drill 6 can be removed from the tool holder 3. In addition to the recesses 7, rotary driving grooves 9 opening out at the end of the tool shaft 5 are arranged at the tool shaft 5. As can be seen in FIG. 2, the rotary driving grooves 9 are situated so as to be offset at different angles relative to the recesses 7. The rotary driving grooves 9 have two planar flanks 10 which extend at least approximately radially and cooperate with assigned surfaces of strip-shaped rotary drivers 11 which are arranged at the cylindrical inner wall of the receptacle bore hole 4 of the tool receptacle 3.

The rear end of the tool shaft contacts an anvil continuation 2' of the tool spindle 2 of the drill hammer, which anvil continuation 2' transmits the axial strokes. The front portion of the drill 6 located in the front of the tool shaft 5 is constructed in a conventional manner, a view of the latter being omitted in the drawing for this reason. A portion of the drill 6 which contains a conveying spiral for carrying away drillings knocked loose from the drilling head adjoins a drillings head comprising carbide cutting edges.

As can be seen from FIG. 2, one of the rotary driving grooves 9 is angularly offset by approximately 90.degree. relative to the recesses 7, while the other rotary driving groove is angularly offset in an assymmetrical manner relative to the recesses 7. It is advisable for reasons of stability to arrange the rotary groove 9 in such a way that the flank 10' transmitting the torque during operation is farther from the recess 7 adjacent to it than the flank 10" is from the recess adjacent to it.

During rotation of the tool spindle 2, the torque is transmitted to the tool shaft 5 of the drill 6 via the rotary drivers 11 engaging in the rotary driving grooves 9. Very favorable conditions result from the planar flanks 10, which extend at least approximately radially, and the assigned surfaces of the strip-shaped rotary drivers 11, since the forces to be transmitted are approximately normal on the cooperating surfaces. The force transmission always occurs--even in the state of advanced wear--at surfaces and not ultimately at the edges of the recesses. The recess 7 arranged in the tool shaft 5 serve only for the axial locking of the drill shaft in the tool receptacle 3. The stress and accordingly also the wear on the locking bodies 8, which are constructed as balls, is very sharply reduced by means of this.

A second embodiment of the tool shaft designated here by 13 is shown in FIGS. 3 and 4 of the drawing. Recesses 7 which correspond to the recesses 7 of the first embodiment (FIGS. 1 and 2) are again arranged at the tool shaft 13. With reference to the circumference of the tool shaft 13, one rotary driving groove 14 is arranged between the two recesses 7 on one side and two rotary driving grooves 15, 16 are arranged on the other side.

FIGS. 5 and 6 show an embodiment which is distinguished from that according to FIGS. 3 and 4 in that in the first case two rotary driving grooves 18, 19; 20, 21 are arranged between the recesses 7 in the tool shaft 17.

FIGS. 7 and 8 show an embodiment in which two (23, 24) driver grooves are arranged in the tool shaft 22 between the recesses 7 on one side and three (25, 26, 27) driver grooves are arranged between the recesses 7 on the other side in the tool shaft 22.

The advantage of the arrangement according to FIGS. 3 to 8 consists in that the specific surface loading during the transmission of the driving moment is smaller the more driving grooves are present. The wear is also smaller to this extent.

When using a plurality of grooves in the tool shaft, it may happen that, when the tool shaft is inserted into the tool holder and the correct drill position is sought by means of rotating to both sides, the front side of the tool shaft and the front sides of the opposite rotary drivers slide along one another in the manner of a catch until the correct inserting position is found. This not only impedes handling when inserting a tool into the tool receptacle, but is also irritating for the operator. A remedy is provided for this by means of an embodiment form shown in FIGS. 9 and 10.

As can be seen from FIG. 9, the tool shaft 28 comprises rotary driving grooves of different depths. In the shown embodiment, a rotary driving groove 29 having a greater depth is located opposite two rotary driving grooves 30, 31 of shallower depth. Strip-shaped rotary drivers 34, 35, 36 are arranged at the cylindrical inner wall of the receiving bore hole 33 of the tool receptacle 32. The rotary driver 34 projecting farther forward is intended for cooperation with the rotary driving groove 29, the rotary drivers 35, 36 which project forward less far engage in the rotary driving grooves 30, 31. The tool shaft 28 has a conical inserting bevel 37 at its front side. The latter encloses an angle .alpha. with the tool axis 38. The bevel 37 is dimensioned in such a way that it cuts into the bases 39 of the rotary driving grooves 30, 31, while leaving the base 40 of the rotary driving groove 29 untouched. The rotary drivers 34, 35 and 36 are provided with inserting bevels 41 at their front sides on the tool side, which inserting bevels 41 enclose an angle .beta. with the axis of the tool receptacle 32 coinciding with the axis 38. After the insertion of a tool shaft 28 in the receiving bore hole 33 of the tool receptacle 32, the rotary driving grooves 29, 30, 31 will generally not meet exactly on the respective rotary drivers 34, 35, 36. Rather, it is necessary to rotate the tool shaft 28 in the receiving bore hole around the axis 38 until the rotary driving grooves and the rotary drivers are located opposite one another so as to fit in with one another and the tool can be completely inserted into the tool receptacle. Until this point, the tool shaft 28 is supported against the inserting bevel 41 of the rotary driver 34 with the edge 42 formed by its front side in connection with the spherical outer surface area of the inserting bevel 37. During the rotation of the tool, the edge 42 moves smoothly along the inserting bevel 41 in a sliding manner until the rotary driving groove 29 is located opposite the rotary driver 34 and the rotary driving grooves 30, 31 are located opposite the rotary drivers 35, 36 and the tool shaft can be completely inserted into the tool receptacle.

Two additional embodiments of a tool shaft constructed according to the invention are shown in FIGS. 11 and 12. A coding which contains the tool-dependent data is arranged at the base of the rotary driving grooves 49, 50 opening out at the end of the tool shaft 48, 58 (compare XI, XII in FIG. 10). This data can refer to the type of tool--drill or chisel--, the tool dimensions--drill diameter--or the material of the tool--drill comprising heavy-duty tool steel or drill with carbide plating.

In the embodiment according to FIG. 11, the coding consists of a bar code which is painted on. In the embodiment shown in FIG. 12, the coding is formed by means of areas which are formed in the shape of stripes and comprise different surface roughness at the base of the rotary driving groove 59. This surface roughness can be produced on the one hand by means of chemical abrasion processes or can also be produced mechanically, e.g. in the manner of file cutting.

In addition to these two examples, it is also possible to achieve the coding by means of other geometric differences, e.g. different widths of the rotary driving grooves.

The coding is read by mechanical or electrical sensors, known per se, and converted into a mechanical or electrical signal which switches corresponding mechanical or electrical couplings, or is fed, as an electrical signal, to the electronic control unit of the hand machine tool. The selection of determined rates of rotation, striking speeds, individual striking energy, response time of the safety clutch, turning off the drill drive or the striking mechanism, slow starting or changes of other machine parameters can be achieved by means of this.

The arrangement of the coding constitutes an advisable feature of the tools, according to the invention, since the rotary driving groove carrying the coding or the recess carrying the coding, which recess is closed on both sides, can always be inserted into the assigned tool receptacle in the same angular position only when using shafts of tools which are constructed according to the invention. This is necessary in order to be effective if the mechanical or electrical sensor for reading the coding in the tool receptacle is to be used.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a tool shaft for a tool of the percussive and rotative type, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.