Angle Grinder

Abstract

The present invention relates to an angle grinder having a front transmission housing for enclosing a transmission arrangement which has a closing surface that faces away from a free end of the tool spindle, and wherein the maximum distance between the closing surface and an end face of the free end of a tool spindle defines a height of the transmission housing, and wherein the height has a predefined ratio to a diameter of a disc-shaped tool, of about 1 to about 5.

Description

The present invention relates to an angle grinder. In the present application, the term angle grinder is also intended to include typical parting-off grinders.

A multiplicity of angle grinders of the type mentioned, above, have become known from the prior art. In those cases, various possibilities for realizing an angle transmission arrangement have been proposed, including the use of belt drives (for example, according to DE 43 42 986 C1). Also known from the prior art are angle transmission arrangements having a pinion gear on the motor shaft and having a bevel gear or crown wheel that is fastened to the tool spindle (e.g. DE 100 65 658 A1 or U.S. Pat. No. 6,386,961 B1). Finally, flexible drive shafts have also been proposed in the prior art (cf., for example, EP 0 579 949 A1).

The applicant's German patent applications DE 10 2008 059 247 A1 and DE 10 2009 053 614 A1 likewise deal with the actual design of an angle grinder, which, in particular, has a compact, flat-structured transmission housing, to make it easier for the angle grinder to access confined working spaces such as, for example, acute-angled corners or the like.

For this purpose, my application DE 10 2008 059 247 A1 discloses a hat-shaped crown-wheel angle transmission arrangement, and wherein the recess of the crown wheel is oriented so as to face towards the tool, or towards the free end of the tool spindle.

DE 10 2008 059 247 A1 proposes that the tool spindle be provided as one piece and have at least one bearing seat portion for a rolling bearing, a portion of the angle transmission arrangement that is realized as a crown wheel, a support portion for the abrasive tool or for a support flange for the abrasive tool, and a threaded portion for a clamping means for fixing the abrasive tool to the tool spindle. The purpose of the one-piece arrangement is to achieve a particularly compact design.

The present invention is therefore based, at least in part, on the object of providing an alternative solution for an angle grinder, of the type described above, and which likewise is of a compact, flat-structured design, at least in the region of the transmission housing of the angle transmission arrangement.

This object is achieved, according to the invention, by an angle grinder having the features of the claims as provided hereinafter.

Accordingly, there is proposed an angle grinder having a motor for driving a tool spindle, and wherein the tool spindle is arranged, by means of an angle transmission arrangement, at an angle in relation to a driving shaft of the motor, and wherein the angle transmission arrangement is accommodated or enclosed in an associated transmission housing, from which there is able to extend a free end of the tool spindle, and to which a disc-shaped tool, which can rotate about the central longitudinal axis of the tool spindle, can be fastened by means of a tool flange. According to the teachings of the present invention, the transmission housing is realized or formed in such a manner that at least the front transmission housing of the angle transmission arrangement has a closing surface that faces away from the free end of the tool spindle, and wherein the maximum distance between this closing surface and an end face of the free end of the tool spindle defines a height of the transmission housing, and wherein the height has a predefined ratio to the diameter of the disc-shaped tool, of maximally 1 to 2, and in particular of 2 to 5.

The free end of the tool spindle is thus defined as the region that projects out of the transmission housing and to which the tool can be attached.

The tool flange in the present application constitutes a support portion for the disc-shaped tool, and which can be brought to bear against the latter, at least partially, in order to assume a defined position relative to the tool spindle. For the purpose of fastening to the tool spindle, a clamping means such as, for example, a clamping nut, may be used to clamp the tool against the tool flange. The tool flange in this case may be realized as a separate element that can be fastened to the tool spindle, or it may be realized or formed so as to constitute a single piece with the tool spindle.

Usually, during use of an angle grinder, such as the angle grinder according to the teachings of the present invention, the region of the disc-shaped tool that is used to perform work is that which extends forwards from the tool spindle, i.e. away from the motor. Accordingly, the transmission housing dimensions in precisely this front region are also particularly relevant to the access capability of the angle grinder in the case of a confined working space. As should be understood, the front region of the transmission housing is the region that, relative to the longitudinal axis of the driving shaft of the motor driven, extends axially from the tool spindle to the front end of the transmission housing, i.e. the end facing away from the motor.

By definition, therefore, the closing surface that faces away from the free end of the tool spindle constitutes the highest portion of the front transmission housing in this region, i.e. the most axially distant from an end face of the free end of the tool spindle, and consequently, together with the end face, delimits the relevant height of the front transmission housing.

The closing surface that faces away from the free end of the tool spindle is constituted or defined by an outer surface of the transmission housing in the region of the tool spindle. The closing surface of the housing and the end face of the tool spindle may be realized or formed such that they are parallel to each other, or realized such that they are inclined relative to each other. In this arrangement, the maximum distance between them defines, at least, the height of the angle grinder in the region of the tool spindle, and the height having a predefined ratio of at least 2 to 5 relative to the diameter of the disc-shaped tool. This ratio of the height to the diameter of the tool, for example and which is realized as an abrasive disc, makes it possible, in turn, to ensure that the angle grinder is better able to access confined, or acute-angled, corners.

Furthermore, it may be provided in one form of the invention that the closing surface of the tool flange that faces toward the tool spans a notional plane that intersects the motor, at least partially.

The closing surface of the tool flange that faces towards the free end of the tool spindle denotes the side of the tool flange that is closest in the free end of the tool spindle and that projects out of the housing. As described above, this normally coincides with the top side of a disc-shaped tool which is in bearing contact and which further faces towards the transmission housing, and which additionally defines a notional plane that is offset relative to the motor housing, and the motor, such that it intersects the motor, at least partially.

The transmission housing thus has a smaller axial extent (in respect of the tool spindle axis), than the motor housing and the motor located therein, at least in the region of the tool flange.

Furthermore, it may be provided that a tangent that, starting from a circumferential edge of the disc-shaped tool, can be placed against the transmission housing, and which further encloses, together with the notional plane, an angle of maximally 40°, and in particular maximally 35°, and preferably less than 34°. Consequently, a tangent is defined as that, line starting from a circumferential edge of a disc-shaped tool, and which is placed against the transmission housing. The slope of the tangent, as provided, thus depends on two factors, namely, on the one hand, the diameter of the abrasive tool used and, on the other hand, the actual design of the transmission housing, and in particular bevels, which are possibly applied to the housing, and which have a slope that is favourable relative to the tangent. This likewise notional tangent, with the notional plane defined above, encloses an angle of maximally 40°. Clearly, the lesser the angle, the more the access capability of the angle grinder, and therefore its handling characteristics, are also improved.

It is possible, in principle, to project the circumferential edge of the disc-shaped tool into the notional plane, in order to achieve a uniform specification of the angle described, above. In this way, the tangent—irrespective of the actual design of the tool, whether as a dish-shaped disc or as a flat disc—always has the same slope for discs having the same diameter. Alternatively, however, it is also possible to take as a basis the actual circumferential edge, since the latter determines the actual access capability of the angle grinder, in practice. In this case, the actual design of the tool, whether as a dish-shaped disc or as a flat disc, also determines the slope of the resulting notional tangent.

It may additionally be provided, advantageously, that the radius of the disc-shaped tool is smaller than the radial extent of the transmission housing from the central longitudinal axis of the tool spindle. Accordingly, the radial extent of the transmission housing runs parallelwise in relation to the tool plane. According to the teachings of the present invention, the transmission housing has a comparatively small measurement in the axial direction (in respect of the central longitudinal axis of the tool spindle), out from the central longitudinal axis of the tool, but in the radial direction has a greater measurement than the radius of the disc-shaped tool. in combination with the offset, according to the teachings of the present invention, the transmission housing, whose notional plane is able to intersect the motor, at least partially, the transmission housing can be provided in a form that is axially shorter than the motor housing. In this arrangement, the access capability of the angle grinder is greatly improved. Owing to this radially comparatively elongate realization of the transmission housing, the abrasive disk can be attached close to the closing surface of the transmission housing which faces towards the free end of the tool spindle, and irrespective of the dimension of the motor housing. As will be recognized, the part of the tool spindle projecting out of the transmission housing can be kept comparatively short.

Furthermore, in one possible form of the invention, the angle transmission arrangement may have a crown wheel, and wherein the crown wheel is substantially hat-shaped, and further has a full-perimeter flange and a receiving portion that forms the hat shape, wherein a toothing of the crown wheel is provided on the flange, and wherein the receiving portion is suitable for receiving at least one part of a bearing means that supports the tool spindle relative to the transmission housing.

The receiving portion of the crown wheel is thus open in one direction, and wherein the opening of the receiving portion is thus delimited in the other direction by a projection which is formed towards the other side of the crown wheel. This projection may be dome-shaped and have, for example, a cylindrical or conical basic shape, as viewed from the outside.

The bearing means as mentioned, above, may comprise, in particular, two rolling bearings that serve to support the tool spindle in a rotatable manner inside the transmission housing. In one embodiment of the invention, the receiving portion is able to receive, not just one but, if necessary, also a plurality of bearings and which constitute the bearing means. In this way, it is possible to save yet more structural space in the axial direction, as compared with the prior art teachings.

The toothing of the crown wheel (as mentioned, above) serves to engage with a pinion gear that is driven by the motor shaft. The torque is thus transmitted from the motor shaft to the tool spindle via the toothing of the crown wheel. In this arrangement, the crown wheel can be connected to the tool spindle in a rotationally fixed manner, and wherein the tool spindle is rotatably mounted inside the transmission housing, for example by means of two rolling bearings which constitute a bearing means.

According to one embodiment of the present invention, the toothing of the crown wheel may be arranged on a side of the crown wheel that faces towards the free end of the tool spindle. In such an arrangement of the toothing of the crown wheel, the opening of the receiving portion of the crown wheel is preferably oriented away from the free end of the tool spindle, in order to provide a particularly space-saving realization of the crown wheel in the axial direction.

Alternatively, the toothing of the crown wheel may also be arranged on a side of the crown wheel that faces away from the free end of the tool spindle. In the case of this design variant, the opening of the receiving portion of the crown wheel may possibly be oriented towards the free end of the tool spindle.

As a further conceivable alternative, however, it is also possible for the angle transmission arrangement to have a crown wheel that is substantially disc-shaped, and wherein a toothing, which is arranged on one side of the crown wheel, is provided at the outer edge of the crown wheel. In this arrangement, at least one part of a bearing means that supports the tool spindle relative to the transmission housing, and preferably all parts of the bearing means, is or are arranged, relative to the crown wheel, on the same side as the toothing.

Further advantages and particular features of the present invention will be understood by the claims and by the following description of the figures, and the drawings which are provided, herewith.

The present invention is described in greater detail in the following paragraphs with reference to the appended drawings, and wherein the latter represent, by way of example, preferred embodiments of the invention in which the individual features of the invention have been combined with each other. Clearly, however, persons skilled in the art will also be able to consider these separately from each other and/or combine them into appropriate combinations.

In the drawings:

FIG. 1 shows an angle grinder according to the teachings of the present invention, and which is represented in a longitudinal sectional view;

FIGS. 2 a to 2c show differing variants of a crown wheel which forms a feature of the angle grinder according to the present invention, and which is represented schematically in a longitudinal sectional view.

FIG. 1 shows a power tool according to the invention, and which is illustrated in the form of an angle grinder 10 according to a first embodiment. The latter differs from the embodiments of FIGS. 2a to 2c solely in the actual design of an angle transmission arrangement 14 of the angle grinder 10. For features that are the same, therefore, the variants shown in FIGS. 2a to 2c have the same references, but with the prefixed numerals “1”, “2” or “3”, respectively, according to the embodiment.

The angle grinder, as seen in FIG. 1 has been illustrated as it would be seen along a central longitudinal axis L₁, and which comprises a motor 12. The motor further comprises a stator 12a, which encompasses a rotor 12b that, with a driving shaft 12c of the motor 12, rotates about the longitudinal axis L₁ thereof. Additionally an angle transmission arrangement 14, is provided for transmitting the torque from the driving shaft 12c of the motor 12 to a tool spindle 18 and which is arranged at an angle relative thereto. The angle transmission arrangement 14 is accommodated in a transmission housing 16 and comprises, in addition to the tool spindle 18, a tool flange 20, which, together with a clamping nut 34, serves to fasten a disc-shaped tool 22 to the tool spindle 18, a bearing means 28, for supporting the tool spindle 18 inside the transmission housing 16, and a crown wheel 24, which is provided to take off the input torque from the driving shaft 12c. The tool spindle 18, together with a tool 22 fastened thereto, is able to rotate about its central longitudinal axis L₂.

As shown clearly by FIG. 1, the tool flange 20 is arranged with an upward offset relative to the (in FIG. 1) lower edge of the motor stator 12a as shown in FIG. 1, such that its closing surface 20a that faces towards the tool spans a notional plane E that intersects the motor 12 in the region of its stator 12a.

On the basis of this specific design of the angle transmission arrangement 14, a particularly flat and space-saving design of the angle grinder 10 is provided in the region of its disc-shaped tool 22, thus enabling the angle grinder to be used even in regions in which the available working space is comparatively small (e.g. in the case of acute-angled corners). As can also be seen from FIG. 1, and in the region of the tool spindle 18, the transmission housing 16 comprises a closing surface 16a that faces away from the free end of the tool spindle 18, as well as a housing cover 16b, which is arranged parallelwise in relation to said surface.

Usually, during the use of an angle grinder, such as the angle grinder 10 and as seen in FIG. 1, the region of the disc-shaped tool 22 which is used is that portion which extends forwards away from the tool spindle 18, i.e. away from the motor 12. Accordingly, the transmission housing dimensions in precisely this front region are also particularly relevant to the access capability of the angle grinder in the case of a confined working space. In the following specification, the front region of the transmission housing is understood to be that region that, in respect of the longitudinal axis L₁, extends axially from the tool spindle to the front end of the transmission housing (that faces away from the motor 12).

By definition, therefore, the closing surface 16a that faces away from the free end of the tool spindle constitutes the highest or most elevated portion of the front transmission housing 16 in this region, i.e. the most axially distant from an end face 18a of the free end of the tool spindle 18, and consequently, together with the end face 18a, delimits or defines a height dimension H for the front transmission housing 16.

A further quantity that, apart from this height H, is relevant to the access capability of the angle grinder 10 in, for example, room corners or the like, is the slope of a tangent T, which is denoted by the angle a (FIG. 1). In this case, the tangent T runs or extends from a circumferential edge of the tool 22, along the transmission housing 16, and, together with the notional plane E, encloses or defines the angle α. The smaller the height or elevation dimension H, and the flatter the slope of the tangent T, the better is the access capability of the angle grinder 10 in restricted working spaces.

As shown in FIG. 1, it is possible, in principle, to project the circumferential edge of the disc-shaped tool 22 into the notional plane E (projection point P), in order to achieve a uniform specification of the angle a described above. In this way, the tangent T—irrespective of the actual design of the tool 22, whether as a dish-shaped disc, as in FIG. 1, or as a flat disc—always has the same slope for discs having the same diameter.

Alternatively, however, it is also possible to take as a basis or reference the actual circumferential edge of the disc 22, since the latter determines the actual access capability of the angle grinder 10 in practice. In this case, and in addition to the diameter D and the height H, the actual design of the tool 22, whether as a dish-shaped disc or as a fiat disc, also determines how well the angle grinder 10 reaches into working spaces that are difficult to access.

The other dimensions of the transmission housing 16, from the region of the tool spindle 18 towards the motor 12, are therefore only of relevance to the access capability insofar as these may not have any projections that project beyond the tangent T, or insofar as it must be possible for the disc-shaped tool 22 to bear against the tool flange 20 in an unimpeded manner.

Accordingly, as can be seen from FIG. 1, the radial extent of the transmission housing 16, from the tool spindle 18, or from its central longitudinal axis L₂, in the direction towards the motor 12, along the longitudinal axis L₁ of the driving shaft 12c of the motor 12, is also dimensioned so as to be greater than the radius D/2 of the disc-shaped tool 22. In this way, the tool 22 can easily bear against the tool flange 20 in an unimpeded manner, and a particularly flat structure of the transmission housing 16 is provided, irrespective of the design of the motor housing (not represented).

A further special feature of the present invention is to be seen in the design of the angle transmission arrangement 14, and in particular the crown wheel 24. According to the teachings of the present invention, differing structural forms are proposed for the crown wheel, and which enable the angle transmission arrangement to have a structure that is as space-saving as possible.

In the case of the embodiment shown in FIG. 1, the crown wheel 24 is provided in the form of a disc. This is also the case of the variant shown in FIG. 2a, and wherein, provided at the outer edge 26, 126 of the crown wheel 24, 124, there is a toothing 126a (cf. FIG. 2a), which is arranged on the same side of the crown wheel as the bearings which form a bearing means 28, 128. The toothing serves, in a known manner, to transmit the driving torque of the driving shaft 12c of the motor 12 from a drive pinion 30 to the crown wheel 24, and thereby to the tool spindle 18. In this case, and as shown, the crown wheel 24 may be realized as a separate element that is connected to the tool spindle 18 in a rotationally fixed manner, or alternatively it may be provided as to constitute a single piece with the tool spindle.

Since, according to the teachings of the present invention, the toothing is arranged on the same side of the crown wheel as the bearings of the bearing means, the structural space required for the bearing means in the axial direction (with regard to the central longitudinal axis L₂ of the tool spindle 18) is also used at the same time for the arrangement of the toothing 126a of the crown wheel, and for the engagement of the toothing in the drive pinion 30.

In the case of an alternative configuration of the crown wheel according to FIGS. 2b and 2c, the crown wheel is not disc-shaped, but hat-shaped and, in addition to having an outer flange 226, 326, on which the toothing 226a or 326a, respectively, is realized, has a receiving portion 232, 332 that forms the hat shape.

The receiving portion 232, 332 of the hat-shaped crown wheel 224, 324 is delimited by a projection 232a, 332a, which is dome-shaped and has, for example, a cylindrical or conical basic shape, as viewed from the outside, although this is not absolutely necessary. The receiving portion serves to receive at least one part of the bearing means 228, 328, i.e., for example, as shown in FIG. 2b, one of the rolling bearings 228a of the bearing means 228, or even, as shown in FIG. 2c, both rolling bearings of the bearing means 328. The toothing 226a or 326a, respectively, is in each case realized on a side of the crown wheel 224, 324 that faces away from the opening of the receiving portion 232, 332. Since the toothing 226a, 326a is provided on the side of the crown wheel on which the projection 232a, 332a extends, the axial structural space required for this in any case (in respect of the longitudinal axis L₂ of the tool spindle 18) is again used at the same time for the pinion shaft 230, 330, thus reducing the axial structural height.

Regardless of the design of the crown wheel, which is selected, the rolling bearings of the bearing means 28 can be secured in their position inside the housing 16, in the usual manner, by projections or shoulders on the transmission housing 16 and by the provision of a circlip or the like.

Claims

1. An angle grinder comprising: a motor for driving a tool spindle, and wherein the tool spindle is arranged, by means of an angle transmission arrangement, at an angle in relation to a driving shaft of the motor, and wherein the angle transmission arrangement is enclosed, at least in part, in an associated transmission housing, and from which extends a free end of the tool spindle, to which a disc-shaped tool, which can rotate about a central longitudinal axis of the tool spindle, can be fastened by means of a tool flange, and wherein at least a front of the transmission housing of the angle transmission arrangement has a closing surface that faces away from the free end of the tool spindle, and wherein the maximum distance between the closing surface and an end face of the free end of the tool spindle defines a height of the transmission housing, and wherein the height has a predefined ratio to the diameter of the disc-shaped tool, of maximally 1 to 2, and preferably of 2 to 5.

2. An angle grinder as claimed in claim 1, and wherein the closing surface of the tool flange that faces in a direction towards the tool spans a notional plane that intersects the motor, at least partially.

3. An angle grinder according to claim 2, and wherein a tangent that is defined as a line extending from a circumferential edge of the disc-shaped tool and which is further oriented against the transmission housing, and encloses, together with the notional plane, an angle of a maximally angular value of less than about 40°, and preferably less than 34°.

4. An angle grinder as claimed in claim 3, and wherein a radius of the disc-shaped tool is smaller than the a radial dimension of the transmission housing when measured from the central longitudinal axis of the tool spindle.

5. Angle An angle grinder as claimed in claim 4, and wherein the angle transmission arrangement has a crown wheel, and wherein the crown wheel is substantially hat-shaped, and further has a full-perimeter flange and a receiving portion that forms the hat shape, and wherein a toothing of the crown wheel is provided on the flange, and wherein the receiving portion is suitable for receiving at least one part of a bearing means that rotatably supports the tool spindle relative to the transmission housing.

6. An angle grinder as claimed in claim 5, and wherein the toothing of the crown wheel is arranged on a side of the crown wheel that faces towards the free end of the tool spindle.

7. An angle grinder as claimed in claim 6, and wherein the opening of the receiving portion of the crown wheel is oriented away from the free end of the tool spindle.

8. An angle grinder as claimed in claim 5, and wherein the toothing of the crown wheel is arranged on a side of the crown wheel that faces away from the free end of the tool spindle.

9. An angle grinder as claimed in claim 4, and wherein the angle transmission arrangement has a crown wheel which is substantially disc-shaped, and wherein a toothing, which is arranged on one side of the crown wheel, is provided at the outer edge of the crown wheel, and wherein at least one part of a bearing means that rotatably supports the tool spindle relative to the transmission housing, and wherein all parts of the bearing means are arranged on the same side of the crown wheel.