HANDHELD POWER TOOL WITH AIR-GUIDING ELEMENT

Abstract

A handheld power tool, including a housing wall and a fan device with an air intake and an air outlet in the housing wall. The fan device has an air guide, and an outflow space is delimited between, on the one hand, the housing wall at the air outlet and, on the other hand, an outflow side of the air intake, as well as laterally by a first surface contour and by a second surface contour of the air guide. The first surface contour and the second surface contour each extend from the housing wall to the outflow side of the air-intake means, and the air-guiding element is shaped in such a way that the size of the cross-sectional surface of the outflow space increases continuously crosswise to the outflow direction of the air intake in the outflow direction.

Description

This claims the benefit of German Patent Application DE 10 2010 063 525.1, filed Dec. 20, 2010 and hereby incorporated by reference herein.

The invention relates to a handheld power tool, comprising a housing wall and a fan device with an air-intake means and an air outlet in the housing wall. In particular, the invention relates to a handheld power tool in which an air-guiding element that delimits a diffusor-like outflow space is additionally arranged between the housing wall and the air-intake means.

BACKGROUND

The term “handheld power tool” refers, for example, to an electrically operated handheld power tool such as a diamond-tipped device, a hammer drill, a chisel hammer, a screwdriver or a battery-operated drill or the like.

German patent application DE 103 58 027 A1 discloses that, in order to cool a handheld power tool, cooling air is drawn in by an air-intake means through air inlets into the housing of the handheld power tool, and then guided over elements of the handheld power tool that are to be cooled such as, for instance, the electric motor and/or the gear, after which it is blown out through air outlets that are likewise located in the housing.

Such a prior-art handheld power tool is schematically shown in FIG. 1 and in FIG. 2.

SUMMARY OF THE INVENTION

It is desirable to ensure adequate cooling of the components of the handheld power tool that need to be cooled, even in case of a handheld power tool having a compact design.

It is an object of the present invention to provide a handheld power tool having an air-guiding system with a favorable flow pattern in order to exhaust the air that has been drawn in by the air-intake means and that has been warmed up by the heat given off by the components of the handheld power tool that are to be cooled.

The invention is based on the consideration that the handheld power tools known from the state of the art do not guide the air from the air-intake means to the air outlet, as a result of which the air flows incorrectly on its way to the air outlet, ultimately preventing the volume of drawn-in air from flowing quickly over the elements of the handheld power tool that are to be cooled, and thus detrimentally affecting the cooling process.

Therefore, unlike the handheld power tools known from the state of the art, the fan device here additionally has an air-guiding element that laterally delimits a diffusor-like outflow space.

With the invention, it has been recognized that the above-mentioned hindrance of the air flow and the associated detrimental effect on the cooling can be due to various reasons. For instance, in the prior-art handheld power tools, the driving unit and the driven unit are joined to each other by means of screwed connections. These screwed connections are arranged in the space between the housing wall and the fan, which is located between the driving unit and the driven unit. Especially in the case of compact models, the screwed connections prevent a fast and smooth exit of the air from this space. Moreover, such screwed connections have to be incorporated into a housing that cannot be provided with air outlets everywhere, for example, because a drill stand or a handle is located in the immediate vicinity, or else other ergonomic considerations do not permit the placement of additional air outlets.

The hindrance of the air flow caused by the screwed connections in the prior-art handheld power tools also occurs when the fan is positioned between the handle and the driving unit of a prior-art handheld power tool, since the handle and the driving unit are also joined to each other by screwed connections, and a fan positioned between the handle and the driving unit is hindered by them when the air is being blown out.

The air flow can also be detrimentally affected by a given design that, for example, does not allow a housing with a round or asymmetrical shape. Moreover, the air outlet might be designed in such a way that it is not adapted to the direction of the air flowing out of the air-intake means, and this might cause the air to flow incorrectly.

With the invention, it has also been recognized that, with an eye towards compensating for the above-mentioned hindrance of the air flow, the solution known from the state of the art, namely, the provision of a stronger fan, does not lead to the desired results, since a stronger fan in a compact model only allows a small space between the housing wall with the air outlet and the air-intake means, so that pressure can build up in this small space, something which is detrimental to a fast air flow over the components of the machine that are to be cooled, especially since the small space that remains is also already reduced even more by the above-mentioned screwed connections. Moreover, a stronger fan would also entail greater power consumption, which would have a negative effect on the efficiency of the handheld power tool.

In the case of the handheld power tool according to the concept of the invention, the air-guiding element can delimit a diffusor-like outflow space between, on the one hand, the housing wall at the air outlet and, on the other hand, an outflow side of the air-intake means, whereby a volume that widens in all three spatial directions and that leads to the air outlet is made available to the air flowing out of the air-intake means. This improves the outflow conditions at the air outlet of the housing, especially in terms of a reduction of flow losses and in terms of pressure recovery. Moreover, the air-guiding element can be configured in such a way that the air flowing out of the housing flows away from users of the handheld power tool and consequently does not bother them during their work.

Thanks to the improved outflow conditions, the fan device can achieve an improved cooling effect while the power consumption of the air-intake means remains the same. Some of the advantages ensuing from this are obvious. For instance, the fan device can be dimensioned smaller and/or can require less energy, which at the same time translates into a better energy balance of the entire handheld power tool.

The air-guiding element can be a passive, single-part or multi-part component that is situated in the space between the housing wall of the handheld power tool and the air-intake means, the latter usually being arranged axially and usually blowing air out radially, so that, together with the housing wall and the outflow side of the air-intake means, the air-guiding element delimits an outflow space with a favorable, in other words, diffusor-like, flow pattern; this outflow space guides the air that flows out of the air-intake means and that usually is swirling, to the air outlet, thereby avoiding flow losses caused by friction and/or incorrect flow patterns.

In other words, thanks to the orientation and shaping of the air-guiding element, the air can be guided particularly effectively and with a favorable flow pattern. The constant increase in the surface area of the free cross section, approximately perpendicular to the outflow direction, offers the possibility of converting kinetic energy of the air flow into useful static pressure. In addition, since the sides of the air-guiding element are shaped in such a way that they either face or face away from the rotational direction of the air-intake means, the air-guiding element—like a distribution blade—deflects the air opposite to the rotational direction of the air-intake means. This, too, builds up static pressure and increases the volume flow.

Altogether, the air-guiding element also can combine the advantages of a diffusor with vanes and the advantages of a diffusor without vanes which—in spite of a barrier installed in the housing for technical or ergonomic measures—allows the air to flow out as it makes a full revolution, in other words, by 360°, along the circumference of the air-intake means, without interrupting the air flow from the air-intake means.

Within the scope of an especially preferred structural refinement, the first surface contour and the second surface contour each extend from the housing wall to the outflow side of the air-intake means, thereby leaving a gap between the air-guiding element and the outflow side of the air-intake means. The air-guiding element thus makes contact with the air-intake means, preferably not on the outflow side, but rather, it approaches it while leaving a gap, and, in terms of the flow, the air-guiding element separates the outflow space from the remaining space between the air-intake means and the housing wall of the handheld power tool. The air-guiding element thus approaches the air-intake means, thereby ensuring that, in terms of the flow, the outflow space is separated from the remaining space. This type of separation in terms of the flow serves to exhaust the drawn-in air with a favorable flow pattern.

For example, as a result of the shape of the air-guiding element, the size of the cross-sectional surface increases continuously crosswise, preferably perpendicular, to the outflow direction of the air-intake means, at least in a partial area of the outflow space.

For instance, the air-guiding element is shaped in such a way that the cross-sectional surface has a first value in a first area that is adjacent to the air-intake means, while it has a second value that is greater than the first one in a second area that is adjacent to the air outlet.

Advantageously, the diffusor-like outflow space with the favorable flow pattern can be delimited in that, relative to the outflow space, the first surface contour follows a path that is laterally curved outwards.

Advantageously, the diffusor-like outflow space with the favorable flow pattern can be further limited in that, relative to the outflow space, the second surface contour has a curved path with a segment that is laterally curved outwards as well as a segment that is laterally curved inwards. Here, it is preferable for the second surface contour with the segment that is laterally curved inwards to extend from the housing wall in the direction of the air-intake means and, towards the air-intake means, to make the transition to the segment that is laterally curved outwards.

Therefore, the first surface contour can follow a path that is concave as seen from the outflow space, while the second surface contour, also as seen from the outflow space, follows a path that is essentially S-shaped, with a convex segment that is adjacent to the housing wall and with a concave segment that is adjacent to the outflow side of the air-intake means.

In an advantageous manner, these paths of the first and second surface contours bring about the above-mentioned enlargement of the cross-sectional surface as the distance from the air-intake means towards the outflowing air increases, in other words, in the outflow direction, and thus they achieve the diffusor effect.

It is also possible to configure the second surface contour with more than two curves in order to promote a friction-free air guidance.

Within the scope of another especially preferred refinement, the air-guiding element has a first housing extension and a second housing extension that both taper from the housing wall towards the air-intake means, especially while also forming an axial edge that lies perpendicular to the outflow direction.

Here, a first side of the first housing extension facing the outflow direction preferably forms the first surface contour, while a side of the second housing extension facing away from the outflow direction forms the second surface contour.

According to this refinement, the air-guiding element consists of at least two parts and it preferably forms part of the housing of the handheld power tool. Accordingly, for purposes of delimiting the outflow space, in a partial area that surrounds the air-intake means, the housing of the handheld power tool has, on the one hand, the air outlet and, on the other hand, the first housing extension facing inwards and the second housing extension facing inwards.

If the handheld power tool has a part that is proximal to the user, such as a motor part or a drive part, as well as a part that is distal to the user, such as a gear part—said parts being joined to each other via a fastening means and having the fan device located between them—then, in a refined variant, the air-guiding element of the fan device preferably physically surrounds the fastening means, at least on its side facing the air-intake means. However, the fan device could also be positioned in the handle or somewhere else in the handheld power tool where, together with the air-guiding element, it could physically surround the fastening means.

This prevents air that has been drawn in by the air-intake means from flowing over the fastening means. Consequently, the air flow is not swirled or hindered, but instead, the air flows over the air-guiding element that physically surrounds the fastening means.

The fastening means has, for example, a first connection, such as screwed connections. In this case, the first surface contour preferably passes the first connection tangentially in the fastening area.

In another especially preferred structural refinement, the first housing extension forms the first surface contour on a side facing the outflow direction and the second surface contour on a side facing away from the outflow side, whereby the first surface contour and the second surface contour pass the first connection tangentially in the fastening area. Consequently, the air-guiding element covers the fastening means in such a way that it delimits a first outflow space on one side and a second outflow space on the other side.

In accordance with this notion, in another preferred structural refinement, the air-guiding element has a third housing extension that tapers from the housing wall towards the air-intake means, while forming an axial edge that lies perpendicular to the outflow direction, and that, together with the first housing extension and the second housing extension, forms three lateral outflow spaces. Via a number of openings distributed along the housing circumference, each outflow space leads to the outside of the housing of the handheld power tool.

Thus, as a function of the number of connection points between the proximal part and the distal part of the handheld power tool and as a function of the position and geometry of the openings of the air outlet and as a function of the geometry of the air-intake means, in a partial area that surrounds the air-intake means, the housing preferably forms a multi-component spiral housing having extensions facing inwards that delimit a number of diffusor-like outflow spaces with a favorable flow pattern and that guide the drawn-in air in the outflow direction from the air-intake means to the appertaining opening. Here, the area of the second surface contour curved inwards makes a transition to the area curved outwards, preferably at approximately the widest place of the connection in question, which tangentially passes the second surface contour.

Preferably, the air-guiding element, for example, in the form of the first, second or third housing extension, rises above a barrier. The term “barrier” refers to a part of the housing wall that is usually located in the lower section of the housing and that, for structural reasons, does not have any openings leading to the outside. For purposes of achieving a quick air flow, it is advantageous that the air does not flow over such a barrier, but rather, that the air drawn in by the air-intake means is guided by the air-guiding element past the barrier with a favorable flow pattern, after which it is guided into an outflow space having an air outlet.

The air-intake means can be, for example, a radial fan, and the air-guiding element can be a multi-component spiral housing that surrounds sections of the radial fan wheel along the circumference with a closed wall, and a radial distance of the closed wall is elevated from an axis of the radial fan wheel along a rotational direction of the radial fan wheel.

According to a preferred structural refinement, the outflow space is advantageously delimited axially by an air-guiding wall in one direction and by a position-shielding wall in the other direction.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described on the basis of the drawing. The drawing does not necessarily depict the embodiments true-to-scale, but rather, the drawing is presented in schematic and/or slightly distorted form whenever necessary for the sake of clarity. Regarding additions to the teaching that can be gleaned directly from the drawing, reference is hereby made to the pertinent state of the art. In this context, it should be taken into account that a wide array of modifications and changes pertaining to the shape and the detail of an embodiment can be made, without deviating from the general idea of the invention. The features of the invention disclosed in the description, in the drawing as well as in the claims, either on their own or in any desired combination, can be essential for the refinement of the invention. Moreover, all combinations of at least two of the features disclosed in the description, in the drawing and/or in the claims fall within the scope of the invention. The general idea of the invention is not limited to the exact shape or details of the preferred embodiment shown and described below, nor is it limited to an object that would be restricted in comparison to the subject matter claimed in the claims. Regarding the dimensional ranges given, values that fall within the cited limits can also be disclosed as limit values and can be employed and claimed as desired. For the sake of simplicity, the same reference numerals will be used below for identical or similar parts or for parts having an identical or similar function.

Additional advantages, features and details of the invention ensue from the description below of preferred embodiments as well as from the drawing. This shows the following:

FIG. 1: a longitudinal section of a handheld power tool known from the state of the art;

FIG. 2: a cross section of a handheld power tool known from the state of the art;

FIG. 3: a cross section of the preferred embodiment of a handheld power tool; and

FIG. 4: a longitudinal section of the preferred embodiment of a handheld power tool.

DETAILED DESCRIPTION

FIG. 1 shows a longitudinal section and FIG. 2 shows a cross section of a handheld power tool 10 known from the state of the art. The prior-art handheld power tool 10 has a driving unit 13 and a driven unit 11. The driving unit 13 and the driven unit 11 are joined to each other by screwed connections 19. A radial fan 15 that is also referred to as a centrifugal fan, is arranged between the driving unit 13, that is to say, the electric motor, and the driven unit 11, that is to say, the gear, of the handheld power tool 10. Between the fan 15 and the housing wall, there is usually a space 17. The air drawn in by the fan 15 reaches openings in the housing via this space 17 and then leaves the interior of the handheld power tool 10 via these openings. Due to a barrier 14 created for technical manufacturing reasons, there is no opening there in the lower section of the housing.

FIG. 3 shows cross section of a handheld power tool 100 according to the concept of the invention, while FIG. 4 shows the same handheld power tool 100 in a lengthwise section A-A′. Reference will be made below to both figures.

The handheld power tool 100 has a part 104 that is proximal to a user or holder of the tool 100 and a part 102 that is distal to the user, both of which are joined to each other by screwed connections 151, 152, 153 and 154. The proximal part 104 is normally the driving part with an electric motor while the distal part 102 is the driven part with the gear. In FIG. 4, these two parts meet at the place marked by a broken line. The fan device 118 could also be arranged in the handle or elsewhere in the handheld power tool.

The handheld power tool 100 has a fan device 118—some components of which can be seen in FIG. 4 and some in FIG. 3—for purposes of cooling the driving and/or driven part. The fan device 118 has an air-intake or air-intake means 114 in the form of a radial fan wheel 120 that is arranged axially and that blows approximately in the radial direction. In the housing wall 110 of the handheld power tool 100, there is an air outlet 116 of the fan device 118 in the form of three openings 121, 122 and 123 by means of which the air that is drawn in and blown out by the fan wheel 120 leaves the interior of the handheld power tool 100.

The fan device 118 also has an air guide or air-guiding element 130 in the form of three housing extensions 131, 132 and 133 that together laterally delimit three outflow spaces 141, 142, and 143, by means of which the air that is drawn in and blown out by the fan wheel 120 is guided with a favorable flow pattern to the appertaining openings 121, 122 and 123 of the air outlet 116. The fan device as defined herein thus includes both rotating and stationary components. The outflow spaces 141, 142, and 143 are also delimited axially by an air-guiding wall 126 and by a position-shielding wall 128 shown in FIG. 4.

The three housing extensions 131, 132 and 133 each form a first surface contour 161 and a second surface contour 162 that extend from the housing wall 110 to an outflow side 124 of the fan wheel 120. Here, the three housing extensions 131, 132 and 133 each form an edge, as can be clearly seen. A gap normally remains between the edges of the housing extensions 131, 132, 133 and the outflow side 124, and this gap is normally dimensioned in such a way that the three outflow spaces 141, 142, and 143 are largely separated from each other in terms of the flow. The three edges each form a flow-exposed edge that is approximately parallel to the longitudinal axis of the handheld power tool 110 (axial edge).

The outflow direction 127 of the fan wheel 120 or of the air exiting the fan wheel 120 is indicated by the plurality of short arrows on the fan wheel 120. The direction of rotation of the fan wheel 120 is indicated by the curved arrow.

The first surface contour 161 is shaped in such a way that a tangent of the first surface contour 161 on the flow-exposed edge of the first housing extension 131 forms an angle α of between 0° and 45° with a straight line that runs through a first screwed connection mid-point 151.1 of the first screwed connection 151 and that runs through the flow-exposed edge.

The first surface contour 161 follows a concave path as seen from the outflow space, and the second surface contour 162, also as seen from the appertaining outflow space, has a segment that is convex close to the housing wall and a path segment that is concave on the outflow side. The concave segments of the surface contours 161, 162 of the first housing extension 131 and of the second housing extension 132 respectively pass the first screwed connection 151 and the second screwed connection 152 tangentially. Therefore, the first screwed connection 151 and the second screwed connection 152 are surrounded by the first housing extension 131 and by the second housing extension 132 respectively, thus causing no disturbances when the drawn-in air is being exhausted.

The third screwed connection 153 and the fourth screwed connection 154 are surrounded by the third housing extension 133, so that these connections likewise do not hinder the air guidance. The third housing extension 133 also rises above a barrier 112 which, for structural reasons, does not have any openings as a rule.

It can be seen in the cross-sectional view according to FIG. 3 and in the longitudinal view according to FIG. 4 that—starting from the outflow side 124 of the radial fan wheel 120 having a height 125 and towards the housing wall 110—the three outflow spaces 141, 142 and 143 each widen in all three spatial directions, as a result of which the outflow spaces 141, 142 and 143 each form a diffusor that guides the outflowing air to the appertaining openings 121, 122 and 123 with a favorable flow path.

Claims

1. A handheld power tool comprising:

a housing wall; and

a fan device having an air intake having an outflow side and outflow direction and having an air outlet in the housing wall, the fan device having an air guide, the air guide having a first surface contour and a second surface contour;

the housing wall at the air outlet, and the outflow side of the air intake, delimiting therebetween an outflow space, the outflow space delimited laterally by the first surface contour and the second surface contour of the air guide, the first surface contour and the second surface contour each extending from the housing wall to the outflow side of the air intake, the air guide shaped in such a way that a size of the cross-sectional surface of the outflow space increases continuously crosswise to the outflow direction as a distance from the outflow side in the outflow direction increases.

2. The handheld power tool as recited in claim 1 wherein the first surface contour and the second surface contour each extend from the housing wall to the outflow side of the air-intake to leave a gap between the air guide and the outflow side.

3. The handheld power tool as recited in claim 1 wherein the air guide is shaped in such a way the size of the cross-sectional surface increases continuously in a partial area of the outflow space.

4. The handheld power tool as recited in claim 1 wherein the air guide is shaped in such a way that the cross-sectional surface has a first value in a first area adjacent to the air intake and has a second value greater than the first one in a second area adjacent to the air outlet.

5. The handheld power tool as recited in claim 1 wherein, relative to the outflow space, the first surface contour follows a path laterally curved outwards.

6. The handheld power tool as recited in claim 1 wherein, relative to the outflow space, the second surface contour has a curved path with a segment laterally curved outwards and a further segment laterally curved inwards.

7. The handheld power tool as recited in claim 6 wherein the further segment extends from the housing wall in the direction of the air intake and, towards the air intake, to make the transition to the segment laterally curved outwards.

8. The handheld power tool as recited in claim 1 wherein the air guide has a first housing extension and a second housing extension that both taper from the housing wall towards the air intake.

9. The handheld power tool as recited in claim 8 wherein the first housing extension forms an axial edge perpendicular to the outflow direction.

10. The handheld power tool as recited in claim 8 wherein a first side of the first housing extension facing the outflow direction forms the first surface contour, while a side of the second housing extension facing away from the outflow direction forms the second surface contour.

11. The handheld power tool as recited in claim 1 further comprising a part proximal to a user and a further part distal to the user, the part and further part being joined to each other via a fastener, the fan device located between the part and the further part, the air-guide physically surrounding the fastener, at least on a side facing the air intake.

12. The handheld power tool as recited in claim 10 wherein the fastener has a first connection, the first surface contour passes the first connection tangentially in a fastening area.

13. The handheld power tool as recited in claim 12 wherein the first connection is a screw connection.

14. The handheld power tool as recited in claim 12 wherein the air outlet is configured in the form of a number of openings distributed along the housing circumference, the air guide having a third housing extension tapering from the housing wall towards the air intake, while forming an axial edge that lies perpendicular to the outflow direction, the third housing extension, together with the first housing extension and the second housing extension, forming three lateral outflow spaces.

15. The handheld power tool as recited in claim 12 wherein the third housing extension of the air guide rises above a barrier.

16. The handheld power tool as recited in claim 1 wherein the air intake is a radial fan and the air guide defines a multicomponent spiral housing.

17. The handheld power tool as recited in claim 1 wherein the outflow space is delimited, on the one hand, axially by an air-guiding wall and, on the other hand, by a position-shielding wall.