US20110021120A1

US20110021120A1 - Hand-held machine tool, in particular hand-guided grinding machine

Info

Publication number: US20110021120A1
Application number: US12/933,257
Authority: US
Inventors: Balazs Bogardi; Roland Kaplar
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-03-18
Filing date: 2008-11-18
Publication date: 2011-01-27
Also published as: EP2252431A1; CN101977730A; WO2009115143A1; DE102008000737A1; EP2252431B1

Abstract

A hand-held machine tool is provided with a split housing, the two parts of which are to be connected via a connecting device that is designed as a plug-in connection. The plug-in connection has a connection piece on the first housing part and an opposite connection piece on the second housing part. At least one section of the connection piece and of the opposite connection piece extends at an angle from the longitudinal axis of the connection piece.

Description

The invention relates to a hand-held power tool, in particular hand-guided grinding machine with the defining characteristics of the preamble to claim 1.

PRIOR ART

EP 0 583 280 B1 has disclosed an angle grinder that has a housing containing a drive motor for rotatably driving a tool shaft to which a grinding tool is fastened. Angle grinders of this kind are usually driven by an electric motor; the drive shaft of the electric drive motor is situated perpendicular to the tool shaft and is coupled to it by means of a transmission.
During operation, the housing of the angle grinder is subjected to considerable stresses caused on the one hand by oscillations of the drive motor and on the other hand by the contact between the grinding tool and the work piece to be machined. It is therefore also necessary to ensure a high degree of stability in addition to a simple assembly.
It is also necessary to take into account the fact that lubricants, which are particularly used for supporting the drive shaft and the tool shaft, heat up during operation and liquefy as a result, leading to the risk of an undesired escape of the lubricant.

DISCLOSURE OF THE INVENTION

The object of the invention is on the one hand to simplify the assembly of a hand-held power tool and on the other hand, in particular to embody the housing of the hand-held power tool in a stable fashion.
This object is attained according to the invention by means of the defining characteristics of claim 1. Suitable modifications are disclosed in the dependent claims.
The hand-held power tool according to the invention, which is in particular a hand-held grinding machine such as an angle grinder, is provided with an at least two-part housing, with the two housing parts of the hand-held power tool being connected to each other by means of a connecting device. The connecting device is embodied in the form of a plugged connection that includes a connecting piece on the first housing part and a counterpart connecting piece on the second housing part; in the assembled position, the connecting piece and the counterpart connecting piece engage each other in a form-locked fashion. At least a part of the connecting piece is provided with a shaped bevel that encloses an angle relative to the longitudinal axis of the connecting piece and the counterpart connecting piece is adapted to the shaped bevel.
This embodiment has the advantage that the connection between the housing parts can be easily produced thanks to the shaped bevel, which assumes an angle in relation to the assembly direction. The bringing together of the housing parts during assembly occurs in the direction of the longitudinal axis of the connecting piece and the shaped bevel provides an automatic centering of the housing parts. This significantly simplifies assembly.
At the same time, the centering achieves an improvement in the stability because the two housing parts engage each other in the assembled position and the form-locked engagement, which secures the housing parts against rotation, further increases the stability.
The shaped bevel can either be embodied on the connecting piece itself by assuming a conical shape according to an advantageous embodiment, with the cone extending either over the entire axial length of the connecting piece or, according to another embodiment, extending over only an axial segment and with the non-conical segment being embodied for example in the form of a cylinder. According to yet another embodiment, an axially protruding shaped bevel is formed onto the connecting piece and encloses an angle with the longitudinal axis of the connecting piece. In this case, the shaped bevel that is of one piece with the fitting constitutes the angled segment that is inclined at an angle relative to the longitudinal axis of the connecting piece, which simultaneously constitutes the assembly direction. Guide recesses that are adapted to the shaped bevel are provided on the counterpart connecting piece. The connecting piece provided with the axially protruding shaped bevel can itself be embodied in the form of either a cylinder or a cone; the cone angle advantageously coincides with the angle of the shaped bevel, but can also differ from it if necessary, in particular having a smaller cone angle than the shaped bevel.
A plurality of shaped bevels is advantageously provided on the connecting piece, distributed over the circumference, and corresponding guide recesses are provided on the guiding connecting piece, with the shaped bevels protruding axially beyond the connecting piece. In the assembled position, this produces a form-locked denticulation in the circumference direction between the connecting piece and counterpart connecting piece.
The connecting piece and counterpart connecting piece are advantageously embodied for accommodating the drive shaft of a drive motor of the hand-held power tool. As a result, the plugged connection also performs the additional task of supporting the drive shaft. The drive shaft is guided through the connecting piece and counterpart connecting piece and is coupled to the tool shaft via a transmission. The connecting piece and counterpart connecting piece simultaneously support and stabilize the drive shaft, for which purpose a pivot bearing is also inserted into the connecting piece. It can also be useful to provide an additional sealing ring, which is positioned between the circumference of the pivot bearing and the inner wall of the connecting piece and prevents an overflow of liquefied lubricant, in particular lubricating oil. The sealing ring advantageously has a minimum hardness of 40 ShoreA in order to ensure a sufficient seal in the presence of the stresses occurring during operation.
The two housing parts to be connected are constituted in particular by a motor housing in which the motor is accommodated and a transmission housing in which the tool shaft for driving the tool is supported. The motor housing is advantageously comprised of plastic, whereas the transmission housing can be produced out of light metal such as aluminum. If need be, the motor housing is embodied of multiple parts, for example two half-shells that are connected to each other to complete the motor housing, which is connected to the transmission housing by means of the plugged connection.
Other advantages and suitable embodiments can be inferred from the remaining claims, the description of the figures, and the drawings themselves.

DRAWINGS

FIG. 1 is a sectional view of a hand-held power tool embodied in the form of an angle grinder, with a motor housing for accommodating the drive motor and a transmission housing for accommodating the tool shaft,

FIG. 2 is a perspective view of the transmission housing and the section of the motor housing to be connected to the transmission housing, in a position in which the parts have been brought close to each other during assembly,

FIG. 3 shows a depiction corresponding to the one in FIG. 2, but in the assembled position of the motor housing and transmission housing,

FIG. 4 is a detail depiction of a section of the motor housing from the region of the connection to the transmission housing,

FIG. 5 is an end view of the transmission housing, with an assembled section of the motor housing,

FIG. 6 is a sectional view along the cutting line VI-VI from FIG. 5,

FIG. 7 is a sectional view along the cutting line VII-VII from FIG. 5,

FIG. 8 is a perspective view of the housing parts to be assembled, with a pivot bearing that is to be inserted into the connecting piece on the transmission housing and is for accommodating the motor shaft, and with a sealing ring that is placed around the pivot bearing,

FIG. 9 is a sectional view of the assembled position of the motor housing and transmission housing.

In the figures, components that remain the same have been labeled with the same reference numerals.
The hand-held power tool 1 shown in FIG. 1 is embodied in the form of an angle grinder that has a two-part housing with a motor housing 2 and a transmission housing 3. The motor housing 2 contains an electric drive motor 4; a tool shaft 7 to which the grinding tool 8 is fastened is supported in rotary fashion in the transmission housing 3. In addition, a wheel guard 10 that encompasses the tool 8 is fastened to a support flange 9 on the transmission housing 3.
The drive shaft or armature shaft 5 of the electric drive motor 4 extends at right angles to the tool shaft 7 and is coupled to the tool shaft 7 for co-rotation via a transmission 6 contained in the transmission housing 3. The motor housing 2 and the transmission housing 3 are connected to each other by means of a connecting device 11 embodied in the form of a plugged connection that is described in greater detail in the figures that follow.
As is clear from FIGS. 2 and 3, the connecting device 11 embodied in the form of a plugged connection includes a connecting piece 12 that is embodied of one piece with the transmission housing 3 and an associated counterpart connecting piece 13 that is embodied of one piece with the motor housing 2. In the assembled position (FIG. 3), the connecting piece 12 and counterpart connecting piece 13 are plugged into each other and the assembly direction simultaneously constitutes the axial direction of the connecting piece 12 and counterpart connecting piece 13. This axial direction coincides with the axial direction of the drive shaft or armature shaft of the motor, which is guided through the opening in the connecting piece 12 and counterpart connecting piece 13. The connecting piece 12 and counterpart connecting piece 13 are embodied essentially in the form of a cylinder and hollow cylinder, respectively; but in at least some parts, they have a slight conical angle, such that the conical segments on the connecting piece 12 and counterpart connecting piece 13 taper in the direction toward the transmission housing 3. This achieves a centering and simplified assembly of the motor housing 2 and transmission housing 3 when these two housing components are assembled.
Axially protruding shaped bevels 14 are provided on the connecting piece 12 on the transmission housing 3 and each extend across an angular segment in the circumference direction of the connecting piece 12. A total of four such shaped bevels 14 are provided in the exemplary embodiment. Each of the shaped bevels 14 is associated with a respective guide recess 15, which is provided on the counterpart connecting piece 13 on the motor housing 2 (FIG. 3 and FIG. 4) and is embodied as complementary to the shaped bevel; in the assembled position, the shaped bevels 14 protrude into the guide recesses 15, producing a form-locked engagement in the circumference direction. Essentially, it can be sufficient to merely embody the shaped bevels 14 and the guide recesses 15 with a cone angle in relation to the axis of the connecting piece and counterpart connecting piece and to respectively embody the connecting piece 12 and counterpart connecting piece as cylindrical. According to an alternative embodiment, however, the connecting piece 12 with the shaped bevels 14 and the counterpart connecting piece 13 with the guide recesses 15 are each embodied as having a cone angle over the entirety of their respective axial lengths.
As is also clear from FIGS. 2 through 4, a pivot bearing 16 in which the drive shaft is supported in rotary fashion is inserted into the recess in the counterpart connecting piece 13 on the motor housing 2. The counterpart connecting piece 13 is embodied on a transverse member 17 that is embodied of one piece with the motor housing 2 and extends from a side wall of the motor housing 2 in a transverse direction.
As is clear from FIGS. 5 through 7, the inner wall of the connecting piece 12 and the outer wall of the counterpart connecting piece 13 are embodied as conical, with a cone angle α that is preferably less than 20° and in the exemplary embodiment is approximately 10°. The inner wall of the connecting piece 12 is embodied as conical over the entire axial length including the shaped bevels 14 (FIG. 6); by contrast, the outer wall of the counterpart connecting piece 13 is only conical over the axial length of the guide recesses 15. The inner wall of the counterpart connecting piece 13 into which the pivot bearing 16 is, inserted is embodied as cylindrical.
As is clear from FIGS. 8 and 9, the pivot bearing 16 is encompassed by a sealing ring 18 that is inserted into the connecting device composed of the connecting piece 12 and counterpart connecting piece 13. In the assembled position shown in FIG. 9, the sealing ring 18 is situated on the circumference side of the pivot bearing 16; the connecting piece 12 and counterpart connecting piece 13 can be embodied so that a small circumferential receiving groove is provided for the sealing ring 18. In the assembled position, the sealing ring 18, which has a ShoreA hardness of at least 40, is situated precisely at the abutting edge between the connecting piece 12 and counterpart connecting piece 13.

Claims

1-13. (canceled)

14. A hand-held power tool, in particular a hand-held grinding machine, comprising a housing of the hand-held power tool which has two housing parts that are connected to each other by a connecting device, the connecting device having a plugged connection equipped with a connecting piece on a first housing part of the two housing parts and a counterpart connecting piece on a second housing part of the two housing parts, with the connecting piece and the counterpart connecting piece engaging each other in an assembled position, wherein at least a part of the connecting piece and counterpart connecting piece is embodied as inclined relative to a longitudinal axis of the connecting piece.

15. The hand-held power tool as recited in claim 14, wherein at least one axially protruding shaped bevel that encloses an angle relative to the longitudinal axis of the connecting piece is formed onto the connecting piece and wherein the counterpart connecting piece has at least one guide recess adapted to the shaped bevel.

16. The hand-held power tool as recited in claim 15, wherein a plurality of shaped bevels is provided distributed over a circumference of the connecting piece and corresponding guide recesses are provided on the counterpart connecting piece.

17. The hand-held power tool as recited in claim 14, wherein the connecting piece and counterpart connecting piece are embodied as conical at least in parts.

18. The hand-held power tool as recited in claim 15, wherein the connecting piece and counterpart connecting piece are embodied as conical at least in parts.

19. The hand-held power tool as recited in claim 16, wherein the connecting piece and counterpart connecting piece are embodied as conical at least in parts.

20. The hand-held power tool as recited in claim 14, wherein the angle is at most 20°.

21. The hand-held power tool as recited in claim 19, wherein the angle is at most 20°.

22. The hand-held power tool as recited in claim 15, wherein like the connecting piece, the shaped bevel is embodied as at least partially conical.

23. The hand-held power tool as recited in claim 17, wherein, like the connecting piece, the shaped bevel is embodied as at least partially conical.

24. The hand-held power tool as recited in claim 20, wherein like the connecting piece, the shaped bevel is embodied as at least partially conical.

25. The hand-held power tool as recited in claim 14, wherein the connecting piece and counterpart connecting piece are embodied to accommodate a drive shaft of a drive motor.

26. The hand-held power tool as recited in claim 25, wherein a pivot bearing for the drive shaft is inserted into the connecting piece.

27. The hand-held power tool as recited in claim 25, wherein a sealing ring is inserted into the connecting piece.

28. The hand-held power tool as recited in claim 26, wherein a sealing ring is inserted into the connecting piece.

29. The hand-held power tool as recited in claim 27, wherein the sealing ring has a ShoreA hardness of at least 40.

30. The hand-held power tool as recited in claim 28, wherein the sealing ring has a ShoreA hardness of at least 40.

31. The hand-held power tool as recited in claim 14, wherein the two housing parts constitute a motor housing for accommodating a drive motor and a transmission housing for accommodating a tool shaft.

32. The hand-held power tool as recited in claim 31, wherein the motor housing is produced out of plastic.

33. The hand-held power tool as recited in claim 31, wherein the transmission housing is produced out of light metal, in particular aluminum.