EP2105261A1 - Electric tool, in particular hammer drill and/or chipping hammer - Google Patents

Abstract

The tool has a coil (30) and an armature shaft (31) e.g. electric motor, held in motor and gear housings (100, 110), and a tool holder (120) holding a tool (50) at an end of the housings. A crown gear (40), an eccentric (41), axles (42, 44, 46), a connecting rod (43), a piston (45), an air cushion (47), an impact body (48) and a rivet snap (49) are held in the housings for direct/indirect transmission of a drive force to the tool. The housings are enclosed in an area of a capsule completely insulating noise sources (51, 52) from noise, where the capsule is flexibly suspended at the housings.

Description

The present invention relates to power tools and in particular drill and / or chisel hammer. In particular, the present invention relates to power tools in which sound-reducing measures are to be taken to comply with regulations and regulations.

For example, with regard to such power tools, it is necessary to take into account EU Regulation 2000/14 / EC, which regulates the allowable noise emissions of equipment intended for outdoor use.

On the basis of z. As this regulation may be necessary in existing power tools, as mentioned, to take noise reduction measures. However, these should neither lead to a significant increase in the weight of the tool nor to an increase in manufacturing costs and beyond its external appearance (design) does not adversely affect.

Therefore, the object of the present invention is to develop a power tool of the type mentioned in such a way that the noise emission emanating from it is reduced without substantially increasing the weight and the manufacturing costs and impairing the external appearance.

This object is achieved by a power tool having the features of patent claim 1. Advantageous developments of the present invention can be found, inter alia, in the dependent claims.

The present invention is based on the idea of the area of a power tool in which the noise source generating the noise to be reduced is preferably completely surrounded by a sound-insulating or sound-insulating capsule, which is attached to the power tool via an elastic suspension in order to avoid structure-borne sound transmissions.

Accordingly, an inventive power tool, which is in particular a drill and / or chisel hammer defined by a housing, a recorded in the housing drive, for. Example, an electric motor, for generating a driving force, a tool holder for receiving a tool, such as a drill or bit, at one end of the housing and a housed in the housing gear for direct or indirect transmission of the driving force to the tool, wherein at least one Noise source is located in the housing. In a pure chisel hammer, this noise source may be located, for example, at the point of impact between a striker and an anvil or the striker and the tool or between the striker and the tool and thus in the transmission housing. Alternatively, the noise source may also be formed by a fan, for example for cooling the drive. However, other places are conceivable as a source of noise. In addition, the power tools according to the invention are power tools in the weight class under 25 kg, but in particular to power tools in high weight classes of about 10-25 kg. In order to reduce the noise emissions emanating from the noise sources and thereby meet the existing regulations and regulations, a sound-insulating or insulating capsule is provided according to the invention, which completely surrounds the housing at least in the region of at least one noise source. Complete here means that the capsule is located on both sides of the noise source in the longitudinal direction of the tool extends out and surrounds the housing circumferentially completely. Completely enclosing the housing at the axial ends is not mandatory. Due to the sound-insulating design of the capsule, the noise is absorbed by the capsule. In order to prevent structure-borne sound transmission from the housing to the capsule with a noise emission associated therewith from the capsule, the capsule according to the invention is attached to the housing via an elastic suspension or suspended elastically on the housing. This can be done, for example, that the attachment of the capsule on the housing is positively, wherein between the capsule and the housing elastic devices or suspensions, z. B. are provided from rubber. These elastic devices may, for. B. are formed by O-rings. The capsule may be formed in one embodiment of a glass fiber reinforced polyamide, magnesium or aluminum of 5 mm thickness. With this configuration, it becomes possible to reduce the sound pressure and sound power level by a few dB (A) (for example, by 6 dB (A)) so that the required regulations and regulations can be maintained.

The electrical appliances according to the invention usually have a cooling device for cooling the drive (electric motor), for which purpose cooling air inlets and cooling air outlets are provided in the housing. Furthermore, a fan is generally provided on the drive to suck in the cooling air and to blow it through the housing or to flow. The inventive encapsulation of a portion of a housing, the problem may arise that the cooling air outlets (outflow) are covered by the capsule. If outlets were formed in the capsule corresponding to the outflow openings in order to allow outflow of the cooling air, this would again reduce the abovementioned and achieved noise emission reduction, as a sound transmission could take place via the outlets. To solve this problem, proposes the present invention in the region of an outlet for the cooling air, which is formed in the capsule to provide a muffler. In other words, a space is formed between the housing and the capsule into which the cooling air can flow out of the outflow openings of the housing. Subsequently, and after passing through a silencer, the cooling air can flow out of the capsule. In addition, the outlet for the cooling air from the capsule is provided with a defined cross-section in order to achieve a sufficiently high air flow rate. This can avoid a significant reduction in engine performance and associated risk of overheating.

In particular for filtering out low frequencies, it is preferable to provide a region in the muffler which functions similarly to a Helmholtz resonator. The combination of muffler and Helmholtz resonator similar range leads to a nearly complete or even complete elimination of the high whistling frequencies of> 500 Hz and a reduction of the low frequencies.

In power tools according to the invention, the housing usually consists of a gear housing, generally made of a metallic material, for. As aluminum or magnesium die-cast, and a drive or motor housing made of a plastic. The at least one noise source may, as mentioned above, lie in the transmission housing. Since the transmission housing can transmit structure-borne noise, it is particularly preferred for the capsule to completely surround the transmission housing in the longitudinal direction or axial direction in order to counteract this structure-borne sound transmission via the transmission housing.

In addition, it should also be noted that a structure-borne sound transmission via the tool holder and the tool itself can be done. To prevent or limit this, the capsule preferably extends beyond the tool holder and leaves only a relatively small sized opening for passage of the tool. However, care must be taken to ensure that the tool holder for insertion and removal of the tool remains easily accessible or can be opened over the tool holder portion extending the capsule in a simple manner and closed or moved to grant access to the tool holder. With regard to the latter, simple and uncomplicated handling must be ensured.

Furthermore, it is particularly preferred that the capsule has a sound-insulating material on its inner side facing the housing. This makes it possible to form the outside of the capsule facing away from the housing, for example, from a hard plastic, magnesium or aluminum, which can be configured with regard to the external appearance. The design may possibly be modeled on the existing contour of the transmission housing.

As already mentioned above, the electric tool for flowing through the housing with cooling air, in particular for cooling the electric motor, can have a fan which is provided in the housing. The fan is advantageously also driven by the drive and may form the mentioned at least one noise source. Both by the flowing cooling air and by the fan itself or in the housing air noise, in particular whistling, be generated, which represent another source of noise. In order to reduce these noises by the sound-absorbing or -dämmende function of the capsule, it is preferred that the capsule surrounds the housing in the region of the fan.

• Fig. 1 eine perspektivische Ansicht eines erfindungsgemäßen Elektrowerkzeugs, bei dem die Kapsel zweischalig ausgebildet ist und nur eine Schalenhälfte dargestellt ist;
• Fig. 2 einen Längsschnitt durch das in Fig. 1 dargestellte Elektrowerkzeug entlang der Teilungsebene der zweischaligen Kapsel.

Further advantages, embodiments and features of the present invention will become apparent from the following description of a preferred embodiment, which is incorporated herein by reference Reference is made to the accompanying drawings. In the drawings show:

• Fig. 1 a perspective view of a power tool according to the invention, in which the capsule is double-shelled and only one shell half is shown;
• Fig. 2 a longitudinal section through the in Fig. 1 shown power tool along the dividing plane of the clam shell capsule.

In the figures, the same elements are also provided with the same reference numerals. In addition, in the illustrated embodiments, a chisel hammer of the 20 kg class is described as a purely exemplary power tool. It is understood, however, that the present invention is not limited to such a power tool, but also to other power tools such. As angle grinder, saws, etc. is transferable.

This in Fig. 1 shown power tool comprises a two-part housing consisting of a motor housing 100 and a gear housing 110. In this case, the gear housing 110 is made of a metallic material, here aluminum die casting, whereas the motor housing 100 is made of plastic. In the region of the end of the gear housing 110, which faces away from the motor housing, a tool holder 120 is provided, in which a chisel is used as a tool 50 in the illustrated embodiment. Furthermore, the motor housing 100 comprises handles in the form of the handles 101, 102. Furthermore, cooling air inlets 103 are provided in the region of the front side of the motor housing 100, which faces away from the gear housing 110, through which cooling air for cooling the electric motor can flow. The gear housing 110 also has slot-like cooling air outlets 112, through which the cooling air can flow out after cooling.

As already mentioned, an electric motor is accommodated in the motor housing 100. This is how it looks Fig. 2 can be seen from a coil 30 and an armature shaft 31 together. The armature shaft 31 is rotatably mounted in the motor housing 100 and has at its end facing the transmission, a fan 32 and a pinion 33.

In the transmission housing 110, the transmission is added. This comprises on the one hand a ring gear 40, which is rotatably mounted in the gear housing 110 via an axle 42. The ring gear 40 is engaged with the pinion 33 of the armature shaft 31 and is rotated by the rotation of the armature shaft. Rotationally connected to the ring gear 40 is an eccentric 41, on the eccentric axis 44 is mounted. This axis 44 is connected to a connecting rod 43, which in turn is connected via an axis 46 with a piston 45. The piston 45 is guided in a cylinder 53, in which further a striker 48 is guided. Between the facing end faces of the piston 45 and the impactor 48, an air cushion 47 is formed. The impactor 48 acts in operation on an anvil 49, which in turn acts on the bit 50.

During operation of the chisel hammer, ie upon actuation of the electric motor, the armature shaft 31 is rotated. About the engagement of the pinion 33 with the ring gear 40, the eccentric 41 rotates, whereby the piston 45 is translated over the connecting rod 43 in the cylinder 53 translationally back and forth. During the advancing movement of the piston 45, the air cushion 47 is compressed, so that the striker 48 strikes against the striker 49, which in turn strikes against the chisel 50 to produce the advancing movement of the chisel 50. During the return stroke of the piston 45, the return of the impactor 48 and the striker 49 takes place.

From the above description it will be seen that, in particular, impact sounds occur between the striker 48 and the striker 49 as well as the striker 49 and the chisel 50 during operation Fig. 2 are designated as first noise source 51 and second noise source 52. Another source of noise, in the illustrated embodiment, is the fan 32.

In order to reduce the noise emissions of the illustrated power tool, a capsule 10 is provided according to the invention. The capsule 10 is formed in the illustrated embodiment by a plastic housing 11 which is lined with an insulating material 12. The insulating material is preferably a foam, for example with a foam thickness of 28 mm, preferably between 20 and 35 mm. As sound-insulating foam, it is possible to use all sound-absorbing foams which withstand temperatures of at least 90 ° C. Examples of such foams are PUR esters or polyethylene. As already mentioned, the capsule 10 is designed with two shells and is screwed, for example. Due to the configuration with a plastic housing 11 and an insulating material 12 on the inside, it is possible to provide the outside of the plastic housing with a desired external appearance, which is modeled, for example, the conventional outer contour of the gear housing 110. Alternatively, however, it is of course also conceivable to construct the capsule 10 in one piece from a sound-absorbing foam, wherein, for example, the density of the foam on the outside is greatly increased. The latter can be achieved for example by a targeted heating of the foam in the outdoor area. Also conceivable is a capsule made of lightweight, z. As magnesium, aluminum, which is formed with foam or insulating material.

In the illustrated embodiment, the capsule 10 completely surrounds the gear housing 110 in the axial direction and, moreover, extends completely beyond the tool holder 120. At the tool-side end of the capsule 10, an opening 22 is provided for the passage of the bit 50, which is to be kept as small as possible in their dimensions. The connection of the capsule 10 with the housing via O-rings 14, 15, 16, so that the capsule 10 is elastically or resiliently suspended on the housing parts 100 and the tool holder 120. A fixation of the capsule 10 in the longitudinal direction (axial direction) of the power tool also takes place in a form-fitting manner. For this purpose, a fixing device 13 is provided between the and the tool holder 120, the O-rings 15, 16 are interposed. The capsule is clamped for fixing with the interposition of the O-ring 16 between the fixing device and a shoulder 121 of the tool holder 120. At the other end, the fixing device is supported via the O-ring 15 on a shoulder 111 of the transmission housing 110. A displacement of the capsule 10 in the longitudinal direction is therefore not possible. The O-rings 15, 16, 17 are made of rubber, z. B. NBR formed. The capsule consists of a glass fiber reinforced polyamide of 5 mm thickness, which corresponds approximately to the basis weight of a 1 mm thick steel sheet.

In addition, a cooling air space 18 is formed between the capsule 10 and the gear housing 110 at least in the region of the Kühlluftausströmöffnung 112, which is dimensioned such that a sufficiently high air flow rate is possible. This allows the cooling air to flow out of the cooling air outflow ports 112 of the transmission case 110 into the space 18. Thereafter, the cooling air flows as indicated by the arrows KL in Fig. 2 is shown, further through a cooling air passage 19 and exits the capsule 10 via a muffler 17 through a cooling air outlet 21. The cross section of the cooling air outlet 21 is also such defines that it is not too small and allows sufficient air flow so that engine power can be maintained without significant reduction, thus avoiding overheating. The muffler 17 is also at least partially lined with the insulating material 12, which may be the same insulating material as described above.

In addition, in the region of the muffler 17, a region 20 is formed, which functions similar to a Helmholtz resonator. A Helmholtz resonator is an acoustic resonator consisting of a gas volume with a narrow opening 22 to the outside. The elasticity of the volume of air in the interior in combination with the inertial mass of the air in the opening creates a mechanical mass-spring system with a pronounced self-resonance. This makes it possible to reduce the sound pressure from low frequencies. In contrast, the muffler 17 makes it possible to eliminate high whistling frequencies of> 500 Hz. So that the cooling air can actually flow over the muffler 17 and the region 20, the transitions between the motor housing 100, gear housing 110 and capsule 10 and between the capsule shells are airtight. The O-rings 14-16 thus have a dual function in the sealing of the interface between the capsule 10 and the housing 100, 110 and the elastic suspension of the capsule 10th

By the described capsule 10, the sound pressure and sound power level was reduced by 10 dB (A) in the illustrated chisel hammer and compared with a same chisel hammer without capsule 10 and eliminates all whistling noises.

In addition, could be achieved by the design of the capsule 10 of a plastic housing 11 with an insulation lining a desired predetermined appearance. The production is relatively cheap and the Weight gain by the capsule 10 is in a range below 8% of the original weight.

It is understood that the present invention is not limited to the above described embodiment, but various modifications are conceivable. For example, the elastic suspension may be other than by the illustrated O-rings 14-16 are solved, such as springs or other elastic or resilient elements. Also, an integral embodiment of the capsule 10 of a sound-insulating material instead of the two-part configuration is conceivable.

Claims (7)

Electric tool, in particular drill and / or chisel hammer, comprising: a housing, a drive (30, 31) received in the housing (100, 110) for generating a driving force, a tool holder (120) for receiving a tool (50) at an end of the housing; and a transmission (40-49) received in the housing for direct or indirect transmission of the driving force to the tool (50), wherein in the housing at least one noise source (32, 51, 52) is present, characterized in that
the housing (100, 110) is completely surrounded, at least in the region of the at least one noise source (32, 51, 52), by a sound-insulating capsule (10) which is elastically suspended on the housing (100, 110). Power tool according to claim 1, wherein the housing (100, 110) in the area surrounded by the capsule (10) Ausströmöffnungen (112) for through the housing (100, 110) flowing cooling air (KL), the capsule (10) has an outlet (21) for the cooling air and in the region of the outlet (21) a muffler (17) is provided. Power tool according to Claim 2, in which the sound damper (17) comprises a Helmholtz resonator-like region (20). A power tool according to any one of the preceding claims, wherein the housing comprises a transmission housing (110) and a drive housing (100), wherein the at least one noise source (51, 52) lies in the transmission housing (110) and the transmission housing (110) is completely remote from the transmission housing (110) Capsule is surrounded. Power tool according to one of the preceding claims, in which the capsule (10) extends beyond the tool holder (120) and has a passage opening (22) for the tool. Power tool according to one of the preceding claims, in which the capsule (10) has on its inside facing the housing (100, 110) a sound-insulating material (12). Electric tool according to one of the preceding claims, further comprising a fan (32) surrounded by the housing (100, 110), wherein the fan forms the at least one noise source and the capsule (10) the housing (100, 110) in the region of the fan ( 32) surrounds.

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