GB2459191A - Hand-held power tool with additional air inflow opening - Google Patents

Abstract

A hand-held power tool comprises a housing 2, which accommodates a motor 8, a fan wheel 9, and a main air inflow opening (4, fig 1). An additional inflow opening 6 is provided in the housing, which is connected to the main inflow opening by an air duct 11. The additional inflow opening may open into the air duct downstream of the motor, and may be arranged closer to a tool 12, such as a grinding disc, than the main inflow opening. The additional inflow opening may lie in an inflow stub 7, which rises above a wall of the housing. The tool may be covered by a protective hood 13, in which there is provided an opening 14 connected by a flow line 15 to the additional inflow opening.

Description

Description Title

Hand-held power tool The invention relates to a hand-held power tool according to the precharacterising clause of Claim 1.

Prior art

Electric motor driven hand-held power tools, such as, for example, angle grinders, which have in a housing an electric motor driving a rotationally mounted tool shaft with tool fastened thereon, are known. In order to prevent overheating of the motor and the brushes, bearings and other components of the hand-held power tool, an air flow is generated with the aid of a fan wheel arranged in the housing by leading ambient air via an inflow opening into the housing, guiding it inside the housing via an air duct to the fan wheel and subsequently leading it away out of the housing again. The air flow may optionally be used also for discharging soil particles which arise in particular as abraded material during the machining of a workpiece.

The air is usually sucked in behind the motor through ventilating slits in the housing of the hand-held power tool, led past the motor and also further functionally important components and expelled in the front region of the power tool again. Care is to be taken here that the air supply through the slits is not obstructed, for example by inadvertent covering of the ventilating slits.

Disclosure of the invention

The object on which the invention is based is to design a hand-held power tool using simple measures in such a manner that effective cooling is guaranteed for a long operating time.

This object is achieved according to the invention by the features of Claim 1. The subclaims specify expedient developments.

The hand-held power tool according to the invention, which is in particular a grinding machine, such as an angle grinder, has in a housing a drive motor for driving the rotatably mounted tool, and a fan wheel which generates an air flow for cooling the drive motor and also optionally further units. Situated in the housing is a main inflow opening, via which ambient air is led into the housing interior, in which an air duct for the air flow is formed.

The air duct is led, starting from the inflow opening, past the drive motor and in the direction of the fan wheel, which generates a negative pressure which is responsible for the inflow of the ambient air via the main inflow opening.

According to the invention, an additional inflow opening, which is flow-connected to the air duct, is provided in the housing, the additional inflow opening lying in the flow path between the main inflow opening and the fan wheel.

This design affords various advantages. The additional inflow opening ensures a sufficient air supply even if the main inflow opening is inadvertently covered or clogged.

Furthermore, it is ensured that less heavily soiled air is sucked in via the main inflow opening, since part of the soiled air is already led into the interior of the housing via the additional inflow opening, so that the air flow guided past the motor contains fewer soil particles and accordingly the risk of soiling of motor parts is also reduced. Overall, the service life of the hand-held power tool can thus be increased.

Via the additional inflow opening it is possible to maintain an emergency air circulation, via which air is guided to the fan wheel even if the flow thereto via the main inflow opening is reduced. This ensures that the fan wheel rotates against a sufficiently high air resistance, with the result that the rotational speed of the fan wheel is kept at a desired rotational speed. Since the fan wheel is driven by the drive motor, undesired fast running of the drive motor is thus also avoided. This corresponds to effective motor braking.

A further advantage resides in the fact that via the additional inflow opening a better diffuse spatial distribution of the heated air led out of the housing is achieved, which results in better cooling of the heated air before it enters the main or additional inflow opening.

Overall, there is a lower temperature level in the hand-held power tool.

Finally, the design according to the invention also results in a reduction of flow noises, since the overall inflow cross-section into the housing of the hand-held power tool is considerably increased via the additional inflow opening, so that a lower flow velocity is sufficient, for the same or an only slightly increased air mass flow.

Optionally, the air mass flow may, however, also be markedly increased, although in this case increased noise generation compared with designs from the prior art is not to be expected, despite the greater air flow rate.

The additional inflow opening enables filter elements for filtration of the inflowing air to be provided without this leading to an inadmissibly high pressure drop of the inflowing air. Such a filter element may be arranged particularly in the region of the main inflow opening, via which the air is guided past the drive motor, in order to avoid soiling of the drive motor or the components belonging to the drive motor. The reduction in the volume flow rate is compensated for by the inflow via the additional inflow opening. Optionally, a filter element may also be provided in the region of the additional inflow opening, either additionally or alternatively to the filter element at the main inflow opening.

According to a further advantageous embodiment, provision is made for the additional inflow opening to open into the air duct in the interior of the housing downstream of the drive motor or at least partially downstream of the drive motor, whereas the main inflow opening is placed upstream of the drive motor. In this way, it is ensured that the air mass flow introduced via the additional inflow opening is led into the housing while bypassing the drive motor. This embodiment is particularly advantageous in combination with an additional inflow opening which is positioned close to the tool shaft or the tool of the hand-held power tool, since in this case the partial mass flow introduced via the additional inflow opening contains a higher proportion of soiling particles which are led into the housing interior while bypassing the drive motor. At the same time, it is thus ensured that a relatively high proportion of the soiled air is guided via the additional inflow opening and the partial mass flow which is guided via the main inflow opening at a greater distance from the tool or the tool shaft contains a correspondingly lower proportion of soiling particles.

In order to improve the effect of the extraction of the soiling particles from the tool region still further, it may be expedient to arrange the additional inflow opening on the lower side of the housing adjacent to the tool or the tool shaft. The inflow is improved still further in that, according to a further advantageous embodiment, the additional inflow opening is provided in an inflow stub which rises above the outside of the housing. This inflow stub is inclined in particular in the direction of the tool or the tool shaft and is situated at the lower side of the housing, whereas the main inflow opening lies expediently in the rear lateral region or at the upper side of the housing. The inclination of the inflow stub improves the directed inflow from the tool region.

According to a still further expedient embodiment, the additional inflow opening, in particular when designed as an inflow stub, is connected to the tool region of the hand-held power tool via a flow line. Optionally, it is sufficient merely to provide an outlet opening, in a protective hood which covers the tool, on the side facing the additional inflow opening, so that the material abraded during the machining of the workpiece can be led directly from the tool region in the direction of the additional inflow opening via the outlet opening.

Further advantages and expedient embodiments can be found in the further claims, the description of the figures and the drawings, in which: Fig. 1 shows a hand-held power tool in a perspective view from below, having an additional inflow opening on the lower side of the housing at the transition between motor housing and gearbox housing, Fig. 2 shows an enlarged illustration of the housing region having the additional inflow opening, Fig. 3 shows a side view of the front part of the hand-held power tool, Fig. 4 shows a section longitudinally through the hand-held power tool.

In the figures, identical components are provided with the same reference symbols.

The hand-held power tool 1 illustrated in the figures is, in particular, a grinding machine, for example an angle grinder. As can be seen in Fig. 1, the hand-held power tool 1 has a multi-part housing 2, consisting of a motor housing 2a for accommodating an electric drive motor and a gearbox housing 2b for the accommodation and rotatable mounting of a tool shaft 3, which is driven by the electric drive motor. A tool is to be fastened on the tool shaft 3. In addition, a protective hood may be fastened on a receiving flange on the tool shaft 3.

Situated in the rear lateral region of the housing are ventilating slits 4, which form a main inflow opening for ambient air to be led into the housing 2 in order to cool the drive motor and other components in the housing. The ambient air flowing into the housing via the ventilating slits 4 is guided along inside the housing in an air duct and leaves the housing again via an outlet opening 5, the outlet opening 5 being situated at the upper side of the housing and directed in the direction of the front side of the hand-held power tool. The air duct runs substantially in the longitudinal direction through the housing.

Situated on the lower side of the housing at the transition between motor housing 2a and gearbox housing 2b is an additional inflow opening 6, which can also be seen in an enlarged illustration in Figures 2 and 3. The additional inflow opening 6 is situated at an inflow stub 7 (Fig. 3), which is formed integrally with the wall of the motor housing 2a and rises in relation to the surrounding wall sections. The inflow stub 7 is inclined in the direction of the tool region, that is of the tool shaft 3, so that a direct and rectilinear flow path from the tool region to the inflow stub 7 having the additional inflow opening 6 is obtained.

As can be seen in the sectional illustration according to Fig. 4, the electric drive motor 8 is accommodated in the motor housing 2a. Situated coaxially with the drive motor 8 in the direction of the gearbox housing 2b is a fan wheel 9, which is driven by the drive shaft of the drive motor 8.

The fan wheel 9 lies directly adjacent to the transition between the motor housing 2a and 2b. An air flow is to be generated via the fan wheel 9, the air flow being indicated by the arrows lOa, lOb, lOc and lOd and being guided through the housing interior in order to cool the drive motor 8 and optionally further components. A first partial mass flow l0a leads through an air duct 11 in the motor housing 2a, which duct runs in the longitudinal direction through the housing, the first partial mass flow lOa constituting the main flow, which is led in via the ventilating slits 4 (Fig. 1) in the rear lateral region of the motor housing. The air duct 11 leads in particular past the outside of the electric drive motor 8 and extends parallel to the axial direction of the drive motor.

The air flow lOa merges with a second air flow lob, which is led into the housing interior via the inflow stub 7 and the additional inflow opening 6, to be precise at the level of the front section of the electric drive motor 8 in the region facing the front part of the hand-held power tool.

The merged whole mass flow lOc is subsequently guided through the fan wheel 9 and led away, downstream of the fan wheel 9, out of the housing 2 of the hand-held power tool again as an outlet mass flow lOd via the outlet opening 5.

It may be expedient to provide a filter element inside the housing in the region of the ventilating slits 4 in order to subject the main mass flow of the introduced air to filtration. A filter element is usually not present in the region of the additional inflow opening 6; nevertheless, it may be expedient additionally or alternatively to provide a filter element at this location as well.

Reference symbol 12 schematically indicates a tool which is connected in a rotationally fixed manner to the tool shaft 3 and is covered by a protective hood 13. An outlet opening 14 may be provided in the protective hood 13, via which opening abraded particles which arise beneath the protective hood during the machining of a workpiece are fed to the inflow stub 7 and the additional inflow opening 6.

Optionally, the outlet opening in the protective hood 13 is connected to the inflow stub 7 or the additional inflow opening 6 via a flow line 15.