US20050281687A1

US20050281687A1 - Bearing device and fan apparatus

Info

Publication number: US20050281687A1
Application number: US11/124,842
Authority: US
Inventors: Karl Frauhammer; Heinz Schnerring; Willy Braun; Axel Kuhnle
Original assignee: Individual
Current assignee: Robert Bosch GmbH
Priority date: 2004-05-15
Filing date: 2005-05-09
Publication date: 2005-12-22
Also published as: CN1696526A; GB2414049A; GB2414049B; GB0509614D0; DE102004024287A1

Abstract

In a bearing device equipped with a fastening element for rotatably supporting a drive shaft of a hand tool unit, the fastening element has a heat conducting structure for conveying heat from a bearing region of the fastening element into a ventilation region of said bearing element, and in a fan apparatus provided with a fan impeller for cooling a drive unit of a machine tool the fan impeller is provided to cool a heat conducting structure which conveys heat from a bearing region of the hand machine tool into a ventilation region of the same.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a bearing device and also to a fan apparatus.
A bearing device equipped with a fastening element for rotatably supporting a drive shaft of a hand tool unit is known in the art. The fastening element is frequently provided to hold a ball bearing in which the drive shaft is supported. Also, a fan apparatus equipped with a fan impeller is known in the art. The fan apparatus with the fan impeller is frequently provided for cooling a drive unit of a hand machine tool.
It is believed that the above-mentioned existing devices can be improved.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a bearing device of the above mentioned general type and also a fan apparatus of the above mentioned general type, which are further improvements of the existing constructions.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a bearing device with a fastening element for rotatably supporting a drive shaft of a hand tool unit, wherein the fastening element has heat conducting means for conveying heat from a bearing region of the fastening element into a ventilation region of the fastening element.
This makes it advantageously possible to prevent the fastening element from overheating in the bearing region. It is thus advantageously possible to prevent the occurrence of damage, for example to seals or ball bearings, due to an overheating of the bearing region. Furthermore a favorable thermal contact between the bearing region and the ventilation region is possible, without it being necessary for dust-laden air to penetrate into the bearing region. This advantageously prevents an increased wear due to a dust-induced contamination of the bearing region.
Hereinafter, the term “provided” is understood in this context to also mean “designed” and “equipped”. In principle, the design according to the present invention can be used in all bearings deemed appropriate by those skilled in the art. But it can be used to particular advantage in hand machine tools due to the typically high dust loads to which they are subjected and in particular, in hammer drills or percussion drilling machines, due to the high mechanical loads to which the bearing devices are subjected.
In another embodiment of the present invention, the heat conducting means are designed so that air circulates around them, at least in a ventilation region. This makes it possible to achieve a particularly effective removal of heat from the heat conducting means.
According to another embodiment, the heat conducting means include at least one metallic subregion. The typically high thermal conduction coefficient and high stability of metallic substances permit the achievement of a particularly robust and effective heat removal.
A particularly space-saving integration of the heat conducting means into the hand tool unit can be achieved if a rotation axis of the drive shaft constitutes a symmetry axis of at least one subregion of the heat conducting means.
An inexpensive design of the heat conducting means can be achieved if the heat conducting means has a cylindrical subregion, which, in a particularly advantageous embodiment, can be designed to encompass the drive shaft.
A favorable thermal contact and advantageous dust protection can be achieved if the heat conducting means are designed to constitute a part of a labyrinth fan.
If the bearing device has at least one clamping element designed to clamp the fastening means to a housing, then it is possible to achieve a particularly rapid, inexpensive assembly.
It is possible to eliminate the provision of additional tolerance compensation devices if the clamping element is provided to assure a tolerance compensation.
In accordance with another object of the present invention, a fan apparatus equipped with a fan impeller for cooling a drive unit of a hand machine tool is provided, wherein the fan impeller is provided for cooling heat conducting means in order to convey heat from a bearing region of the hand machine tool into a ventilation region. This makes it possible to advantageously prevent an overheating of the bearing region.
An effective dust protection of the bearing region can be achieved if the fan apparatus includes a labyrinth fan.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a section through a hammer drill with a bearing device and a fastening element for supporting a drive shaft,
FIG. 2 shows a section along the line II-II in FIG. 1,
FIG. 3 shows the fastening element from FIGS. 1 and 2,
FIG. 4 is a top view of the fastening element from FIG. 3,
FIG. 5 shows a drive unit with a fan apparatus, the fastening element, and the drive shaft,
FIG. 6 shows an alternative bearing device of a hammer drill, with a clamping element,
FIG. 7 the fastening element from FIG. 6,
FIG. 8 a part of a housing of a hammer drill, with a clamping element in another embodiment of the present invention,
FIG. 9 is a sectional view of a hammer drill with a bearing device and a fastening element for supporting a drive shaft in another embodiment of the present invention,
FIG. 10 is a top view of the fastening element and a motor housing from FIG. 9,
FIG. 11 is a sectional view of the fastening element from FIGS. 9 and 10,
FIG. 12 shows a flexible tolerance compensation element in another embodiment of the present invention,
FIG. 13 shows a flexible tolerance compensation element in another embodiment of the present invention, and
FIG. 14 shows a wedge-shaped tolerance compensation element in another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a bearing device equipped with a fastening element 10 for rotatably supporting a drive shaft 12, which belongs to a hand tool unit embodied in the form of a hammer drill and is attached to an armature of a drive unit 28 embodied in the form of an electric motor. A first bevel gear 30 is press-fitted onto the drive shaft 12 and engages with a second bevel gear 32 attached to a transmission shaft 34. The bevel gears 30, 32 transmit a rotating motion of the drive shaft 12 to the transmission shaft 34, which in turn drives a hammer mechanism and a rotating drive of the hammer drill to which the bearing apparatus belongs.
The fastening element 10 is embodied in the form of a fastening plate and has a subregion 18 that is metallic, cylindrical, and represents a ventilation region 18 of the fastening element 10. The fastening element 10 and in particular the subregion 18 assumes the function of heat conducting means 14 that extend between the bearing region 16 of the fastening means 10 and the ventilation region 18. The bearing region 16 is an annular region encompassing a round opening of the fastening element 10 that is in turn encompassed by the ventilation region 18. The bearing region 16 is provided to hold a ball bearing 36 of the bearing device, which ball bearing can be subjected to intense heat during operation of the hammer drill. The heat absorbed in the bearing region 16 is conducted by means of the metal of the fastening element 10 to the ventilation region 18 during operation, from whence the heat can radiate from an inner surface and an outer surface. The opening is provided to allow the drive shaft 12 to pass through, whose rotation axis constitutes a symmetry axis of the cylindrical subregion 18.
A fan apparatus with a fan impeller 26 for cooling the drive unit 28 of the hand machine tool embodied in the form of a hammer drill is also provided to continuously circulate air around the ventilation region 18 of the fastening element 10 and the heat conducting means 14 during operation in order to assure an improved removal of heat. To that end, on a back side oriented toward the fastening element 10, the fan impeller 26 has a labyrinth fan 20, which is partially formed onto the fan impeller 26 and includes two cylindrical baffles encompassing the symmetry axis of the drive shaft 12 and one sleeve.
The cylindrical sleeve, which is integral to the fan impeller 26, is provided for sliding the fan impeller 26 onto the drive shaft 12, which rests against an inner surface of the sleeve while an outer surface of the sleeve constitutes an inner wall of the labyrinth fan 20. The ventilation region 18 protrudes into an intermediate space between the outer surface of the sleeve of the fan impeller 26 and a first baffle of the labyrinth fan 20. A baffle formed onto the housing 24 of the hammer drill protrudes into the annular intermediate space between the first and second baffle of the labyrinth fan 20. During operation, air must flow along a meandering path in the radial direction between the baffles to the ventilation region 18, which prevents dust particles from penetrating into the vicinity of the ventilation region 18. During operation, the fan impeller 26 rotates and generates an airflow that flows quickly past the surfaces of the ventilation region 18, thus circulating around the ventilation region 18; the fan impeller 26 is provided to cool the heat conducting means 14, which are designed to remove heat from the bearing region 16.
The sectional view depicted in FIG. 2 clearly shows how the fastening element 10 is attached to the housing 24 of the hammer drill. For this purpose, the fastening element 10 has two hook- shaped tabs 38, 38′ on opposite sides, which engage with a clamping element 22 that is equipped with corresponding hook elements and is embodied as a strip spring part. The clamping element 22 embraces a part of the plastic housing 24, which in turn encompasses the transmission shaft 34. When mounted in place, the clamping element 22 clamps the fastening element 10 and with it, the ball bearing 36, the drive shaft 12, and the fan impeller 26 to the housing 24 in the axial direction in relation to the rotation axis of the drive shaft 12. The hook elements of the clamping element 22 are integral to it, are formed out of a strip spring, and have a curvature radius of approximately 3 mm, which permits an elastic deformation of the clamping element 22, thus assuring a tolerance compensation between the housing 24 and the fastening element 10.
During an assembly process, first the fan impeller 26, then the fastening element 10, then the ball bearing 36, and finally the bevel gear 30 are slid onto the drive shaft 12 (FIG. 5). The assembled unit thus produced is then clamped to the housing 24 by means of the clamping element 22.
FIGS. 6-14 show details or components of additional embodiments of the present invention. The description will essentially concentrate on differences in relation to the exemplary embodiment depicted in FIGS. 1-5. With regard to characteristics that remain the same, reference is hereby made to the description regarding FIGS. 1-5. Characteristics and components that essentially function in the same manner have been provided with the same reference numerals.
In the exemplary embodiment depicted in FIGS. 6-8, the tabs 38, 38′ of a fastening element 10 have threaded holes provided to accommodate screws 40, 40′ that attach the fastening element 10 to a housing 24. The housing 24 encompasses a hammering mechanism, is composed of multiple parts, and has an upper shell 42 and a lower shell 44. A clamping element 46 embraces the upper shell 44, to which it is attached by means of a screw 52, and engages in ribs in the lower shell 42 (FIG. 8).
In the exemplary embodiment shown in FIGS. 9-11, tabs 38, 38′ of a fastening part 10 are elongated in comparison to the preceding exemplary embodiments. As a result, the fastening part 10 is suitable for diagonal placement inside a cross-section of a housing 24 in the shape of a rounded square (FIG. 10). In an assembly process, the housing 24 is screwed to a motor housing 48. In this assembly process, the tabs 38, 38′ of the fastening element 10 are clamped between the housing 24 and the motor housing 48 and are subjected to a slight bending stress for tolerance compensation purposes.
FIGS. 11-14 show other U-shaped tolerance compensation elements 50-50″, which are designed to be positioned between a fastening part 10 and a housing 24. The tolerance compensation elements 50, 50′ each have spring elements on the legs of their U-shape, which in the tolerance compensation element 50 (FIG. 12), are embodied in the form of elongated tabs that protrude from the legs at an angle and in the tolerance compensation element 50′ (FIG. 13), are embodied in the form of cambered subregions. The tolerance compensation element 50″ (FIG. 14) has wedge-shaped legs provided for insertion between the fastening element 10 and the housing 24. Tolerances can be compensated for through adaptation of the insertion depth. In addition, it is possible for a bearing device equipped with the tolerance compensation element 50″ to be offset in the axial direction with a prestressing force, thus permitting the elimination of play.
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 bearing device and fan apparatus, 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.

Claims

1. A bearing device, comprising a fastening element for rotatably supporting a drive shaft of a hand tool unit, said fastening element having a bearing region and a ventilation region, said fastening element having heat conducting means for conveying heat from said bearing region of said fastening element into said ventilation region of said fastening element.

2. A bearing device as defined in claim 1, wherein said heat conducting means are configured to permit air to circulate around said heat conducting means at least in said ventilation region.

3. A bearing device as defined in claim 1, wherein said heat conducting means have at least one metallic subregion.

4. A bearing device as defined in claim 1, wherein said at least one subregion of said heat conducting means has a symmetry axis which corresponds to a rotation axis of the drive shaft.

5. A bearing device as defined in claim 1, wherein said heat conducting means have a cylindrical subregion.

6. A bearing device as defined in claim 1, wherein said heat conducting means are configured to form a part of a labyrinth fan.

7. A bearing device as defined in claim 1; and further comprising a housing, and at least one clamping element for clamping said fastening element to said housing.

8. A bearing device as defined in claim 7, wherein said clamping element is configured to provide a tolerance compensation.

9. A fan apparatus, comprising a fan impeller for cooling a drive unit of a hand machine tool having a bearing region and a ventilation region, said fan impeller being arranged to cool heat conducting means provided to convey heat from said bearing region into said ventilation region.

10. A fan apparatus as defined in claim 9, wherein said fan impeller is provided with a labyrinth fan.