Eccentric sander and forced drive for an eccentric sander

Abstract

The invention relates to an eccentric sanding machine (10), in particular a battery-powered eccentric sanding machine, with at least one housing (12), with at least one motor (14), in particular a brushless electric motor, with at least one eccentric (16) which can be driven via a motor shaft (18) of the motor (14), in particular by means of a rotationally fixed connection with the motor shaft (18), rotating about an eccentric axis (22) of the eccentric (16) which runs at least substantially parallel to an axis of rotation (20) of the motor shaft (18), and with at least one positive drive (24). It is proposed that the positive drive (24) has at least one dimensionally fixed positive guide element (28), in particular provided with an internal toothing (26), which is arranged rotationally fixed on an inner side of the housing (12).

Description

State of the art From EP 0 559 020 B1, an eccentric grinding machine is already known with at least one housing, with at least one motor, with at least one eccentric which can be driven via a motor shaft of the motor rotating about an eccentric axis of the eccentric which runs at least substantially parallel to a rotational axis of the motor shaft, and with at least one positive drive. Disclosure of the invention The invention relates to an eccentric grinding machine, in particular a battery-operated eccentric grinding machine, with at least one housing, with at least one motor, in particular a brushless electric motor, with at least one eccentric which can be driven via a motor shaft of the motor, in particular as a result of a rotationally fixed connection with the motor shaft, rotating about an eccentric axis of the eccentric which runs at least substantially parallel to an axis of rotation of the motor shaft, and with at least one positive drive. It is proposed that the positive drive has at least one dimensionally stable positive guide element, in particular one with internal teeth, which is arranged in a rotationally fixed manner on an inside of the housing. The design of the eccentric sander according to the invention advantageously allows for a particularly compact construction. Furthermore, a particularly simple and cost-effective design can be advantageously provided. In addition, a particularly precise positive guidance system can be advantageously provided. Vibrations and wear can be advantageously kept to a minimum. Particularly advantageous is the exceptionally long service life of the eccentric sander. The advantageously compact design allows for an eccentric sander with exceptionally high ergonomics and ease of use. The eccentric sander is preferably designed to transmit a combination of rotary and eccentric motion, in particular orbital motion, to a machining tool arranged on a tool holder unit of the eccentric sander for machining a workpiece surface. The eccentric sander is preferably electrically operated. Particularly preferred is a battery-powered eccentric sander. Alternatively, it is conceivable that the eccentric sander is corded. It is also conceivable that the eccentric sander is pneumatically operated. Preferably, the housing of the eccentric sander is made at least partially, and in particular entirely, of plastic.Alternatively or additionally, the housing of the eccentric sander is at least partially, and in particular entirely, made of a metal. Preferably, the housing is at least partially made of aluminum using an aluminum die-casting process. Alternatively, however, it is also conceivable that the housing is made of a combination of materials of any kind. The housing preferably has a grip area designed to allow a user to hold and operate the random orbital sander with at least one hand. Preferably, the grip area of ​​the housing is shaped as a support surface for one hand, particularly ergonomically, to facilitate one-handed operation of the random orbital sander. Preferably, a grip pad, for example made of rubber, plastic, silicone, or another material deemed suitable by a person skilled in the art, is fixedly attached to the housing in the grip area. Preferably, the grip area is located near the center of mass of the random orbital sander. "Nearby area" is understood to mean, in particular, a spherical space around a point, wherein the radius of the spherical space is preferably less than 100 mm, more preferably less than 50 mm, and most preferably less than 20 mm.The housing of the eccentric sander preferably has a dust extraction port for removing particles, particularly sanding dust, generated during surface processing. The dust extraction port is preferably detachably connected to a particle collection device, especially a dust box, via a connection interface, preferably by means of a positive and / or non-positive connection. Alternatively, the dust extraction port could be connected to a hose of a dust extraction device, such as a vacuum cleaner, for particle removal. The dust extraction port is preferably located near the positive drive. Furthermore, the eccentric sander preferably has a switch for turning the sander on and off.Preferably, the switch is located adjacent to the handle area and particularly preferably within the handle area. Preferably, the switch is designed as a momentary switch, a toggle switch, a rocker switch, or the like. However, it is also conceivable that the switch is designed as an adjustable control or has another design for operating the eccentric sander that would appear sensible to a person skilled in the art. Preferably, the eccentric sander has a tool holder for receiving a tool. Particularly preferably, the tool holder of the eccentric sander is designed as a sanding disc intended to receive the tool, such as sandpaper, a polishing bonnet, or the like.The machining tool is particularly preferably attachable to the tool holder, preferably to the grinding wheel, by means of a hook-and-loop fastener, in particular in a detachable manner. "Provided for" is to be understood in particular as being specially configured, specially designed, and / or specially equipped. The fact that an object is intended for a specific function is to be understood in particular as the object fulfilling and / or performing this specific function in at least one application and / or operating condition. The motor is preferably designed as an electric motor. Preferably, the motor is designed as a brushless electric motor. Particularly preferably, the motor is designed as a brushless DC motor, a so-called BLDC motor. It is also conceivable that the motor is designed as a permanent magnet synchronous motor (PMSM motor). Alternatively, it is also conceivable that the motor is designed as an AC motor. Preferably, the motor has a no-load speed of at least 6,000 rpm and at most 12,500 rpm, more preferably at least 8,000 rpm and at most 10,000 rpm. The motor includes the motor shaft, which is designed to transmit a uniform rotational movement of the motor to the eccentric. The eccentric is preferably designed to superimpose an eccentric movement on the uniform rotational movement of the motor and to transmit this to the tool holder unit, preferably to the grinding wheel.The term "essentially parallel" is understood to mean, in particular, an alignment of a direction relative to a reference direction, especially in a plane, wherein the direction has a deviation from the reference direction of, in particular, less than 8°, advantageously less than 5°, and most advantageously less than 2°. The eccentric axis of the eccentric has a maximum offset, in particular a maximum eccentricity, of preferably at most 20 mm, more preferably at most 10 mm, and most preferably at most 5 mm. On a side of the eccentric facing away from the motor, the tool holder unit, in particular the grinding disc, is preferably rotatably mounted about its own central axis, particularly about its own central axis. A ball bearing, needle bearing, or the like of the positive drive is particularly preferably arranged on the side of the eccentric facing away from the motor to provide rotatable support for the tool holder unit, in particular the grinding disc. Preferably, the eccentric is positively and / or frictionally connected to the motor shaft at an axial end facing the motor, for example, by means of a splined connection or the like. Alternatively, it is conceivable that the eccentric is materially bonded to the motor shaft at an axial end facing the motor, for example, by welding or bonding.Preferably, the eccentric is made of a metal, such as aluminum, cast iron, steel, or the like. However, it is also conceivable that the eccentric is made of a plastic or any combination of materials that would be considered sensible by a person skilled in the art. The positive drive is preferably designed to superimpose a rotation about the tool holder unit's own central axis, preferably the grinding disc's own central axis, onto an eccentric movement transmitted by the eccentric to the tool holder unit, preferably the grinding disc. Preferably, the rotation of the grinding disc superimposed by the positive drive is at least 1% and at most 20% of the motor's no-load speed, more preferably at least 2% and at most 15% of the motor's no-load speed, and most preferably at least 3% and at most 4% of the motor's no-load speed.Preferably, the positive guidance element is designed as a component separate from the housing and arranged on the inside of the housing in a rotationally fixed manner. Preferably, the positive guidance element has an annular shape. However, it is also conceivable that the positive guidance element has a shape other than an annular one, for example, an elliptical ring shape or the like. Preferably, the positive guidance element is firmly connected to the housing by means of a positive and / or force-fit connection. Alternatively or additionally, it is conceivable that the positive guidance element is bonded to the housing by means of a material bond, for example, by means of an adhesive layer.Preferably, the rigid positive guide element is designed such that a surface and / or base shape of the rigid positive guide element experiences a maximum elastic deformation of, in particular, less than 5 mm, and preferably less than 1 mm, and most preferably less than 0.1 mm, as a result of the application of drive forces, particularly along a direction extending at least substantially perpendicular to the axis of rotation of the motor shaft. The rigid positive guide element is preferably made of a material which preferably has a maximum tensile strength of at least 200 MPa and most preferably at least 500 MPa, particularly according to DIN 53455. Furthermore, the material from which the rigid positive guide element is made preferably has a modulus of elasticity of at least 10 GPa, more preferably at least 50 GPa, and most preferably at least 70 GPa, particularly according to DIN 53457.Preferably, the rigid positive guide element is made of a plastic, preferably as an injection-molded part, a fiber-reinforced composite material, a metal, or the like. Preferably, the material from which the rigid positive guide element is made is different from rubber, an elastomer, or another material that is spring-elastic due to its material properties. It is also conceivable that the positive guide element is designed as a sintered component, for example, as a component sintered from a metal, a ceramic material, or the like. Alternatively, it is also conceivable that the rigid positive guide element is formed integrally with the housing.The term "one-piece" is to be understood in particular as being joined by at least a material bond, for example by a welding process, an adhesive bonding process, an injection molding process, and / or another process that would appear appropriate to a person skilled in the art, and / or advantageously as being formed in one piece, such as by being manufactured from a single casting and / or by being manufactured using a single- or multi-component injection molding process, and advantageously from a single blank. Preferably, the positive guidance element has a maximum axial extent of at most 20 mm, more preferably at most 15 mm, and particularly preferably at most 10 mm. Preferably, the positive guidance element has internal teeth that extend along the entire inner circumference of the positive guidance element. Preferably, the internal teeth are designed to mesh with external teeth of a positive rotation element of the positive drive.Preferably, the internal toothing is designed as a spur tooth internal toothing. Alternatively, however, it is also conceivable that the internal toothing is designed as a helical tooth internal toothing. It is further proposed that the positive guidance element comprises a first axial section, which has an internal toothing extending, in particular, over the entire inner circumference of the positive guidance element, and a second axial section, which has a rolling and / or sliding surface extending, in particular, over the entire inner circumference of the positive guidance element, for a further rolling and / or sliding surface arranged on a positive circulation element of the positive drive, wherein the first axial section and the second axial section are adjacent to each other. Preferably, the internal toothing is designed to transmit a force to the positive circulation element, causing the positive circulation element to rotate in a plane perpendicular to the eccentric axis. The rolling and / or sliding surface of the positive guidance element is preferably designed to interact with a further rolling and / or sliding surface of the positive circulation element.Preferably, the rolling and / or sliding surface is designed to guide the forced circulation element along a path adjacent to the forced guidance element. Preferably, the forced circulation element is connected to the tool holder unit, particularly to the grinding wheel, and in particular in a rotationally fixed manner. Preferably, the first axial section, which has the internal teeth, is arranged in an end region of the forced guidance element facing away from the motor in the axial direction. The second axial section, which has the rolling and / or sliding surface, is preferably arranged in an end region of the forced guidance element facing towards the motor in the axial direction. Alternatively, however, it is also conceivable that the first axial section, which has the internal teeth, is arranged in an end region of the forced guidance element facing towards the motor in the axial direction.In this alternative embodiment, the second axial section, which comprises the rolling and / or sliding surface, can be arranged in an end region of the positive guidance element facing away from the motor in the axial direction. Preferably, the maximum axial extent of the first axial section is at least 10%, more preferably at least 25%, and particularly preferably at most 80% of the total axial extent of the positive guidance element along a direction that runs at least substantially parallel to the axis of rotation of the motor shaft. Preferably, the rolling and / or sliding surface has a minimum inner diameter that preferably corresponds to at least one pitch circle diameter of the internal gearing. Preferably, the rolling and / or sliding surface has a maximum inner diameter that corresponds to at most one root circle diameter of the internal gearing.Alternatively, it is also conceivable that the maximum inner diameter of the rolling and / or sliding surface is larger than the root diameter of the internal gearing. Furthermore, it is alternatively possible that the minimum inner diameter of the rolling and / or sliding surface is smaller than the tip diameter of the internal gearing. The inventive design of the eccentric grinding machine advantageously allows for a particularly compact construction. Furthermore, a particularly simple and cost-effective design can be advantageously provided. In addition, a particularly precise positive guidance can be advantageously provided. Vibrations and wear can be advantageously kept to a minimum. The advantageously compact design allows for an eccentric grinding machine with particularly high ergonomics and ease of use.Such a design allows for advantageously precise forced guidance. Particularly advantageous with such precise forced guidance are the ability to minimize vibrations and wear. This results in a particularly long service life for the eccentric sander. Furthermore, it enables advantageously high material removal rates. Additionally, the option of using sanding discs with forced rotation elements featuring external teeth and / or a rolling and / or sliding surface allows for advantageously high flexibility. Furthermore, it is proposed that the positive drive comprise at least one positive-locking element, preferably the previously mentioned positive-locking element, which has at least one positive-locking extension, preferably arranged radially, for a rotationally fixed connection with a grinding disc, preferably the previously mentioned one. The positive-locking element is preferably designed to interact with the positive-locking guide element and to transmit a force to the grinding disc that acts essentially parallel to a plane perpendicular to the axis of rotation of the motor shaft. The at least one positive-locking extension preferably extends radially, particularly radially inwards. Alternatively, however, it is also conceivable that the at least one positive-locking extension extends axially along the positive-locking element.The positive locking extension is designed to create a rotationally fixed connection with the grinding disc by means of a complementary positive locking opening in the grinding disc. Preferably, the at least one positive locking extension has a polygonal, and in particular rectangular, cross-sectional shape in the plane lying essentially perpendicular to the axis of rotation of the motor shaft. Particularly preferably, the at least one positive locking extension has a trapezoidal cross-sectional shape. However, other embodiments of the at least one positive locking extension that would appear advantageous to a person skilled in the art are also conceivable. Preferably, the forced circulation element has a plurality of positive locking extensions, preferably at least three, and particularly preferably at least five.Alternatively or additionally, the forced rotation element can be axially secured to the grinding disc, for example, by means of a screw, embossing, snap, and / or adhesive connection, or the like. Preferably, the pitch circle diameter of the external teeth of the forced rotation element is at most 95% of the pitch circle diameter of the internal teeth of the forced guide element, more preferably at most 85%, and particularly preferably at most 75% of the pitch circle diameter of the internal teeth of the forced guide element. The forced rotation element is preferably made of a plastic, more preferably of a sintered plastic. It is also conceivable that the forced rotation element is made of a metal. With such a design, advantageously precise forced guidance of the grinding disc of the eccentric sander can be provided. Furthermore, advantageously smooth running can be achieved.Furthermore, wear and tear can be kept advantageously low and a particularly long service life can be achieved. It is further proposed that the positive drive comprise a positive circulation element, in particular the one already mentioned, which has a first axial region having an external toothing extending over the entire outer circumference, and a second axial region having a further running and / or sliding surface extending over the entire outer circumference of the positive circulation element, which is designed to interact with a rolling and / or sliding surface of the positive guidance element, wherein the first axial region and the second axial region are adjacent to each other. The further rolling and / or sliding surface of the positive circulation element is preferably designed to interact with the rolling and / or sliding surface of the positive guidance element.Preferably, the first axial region of the forced circulation element, which has the internal teeth, is arranged in an end region of the forced circulation element facing axially towards the grinding disc. Preferably, the second axial region of the forced circulation element, which has the further rolling and / or sliding surface, is arranged in an end region of the forced circulation element facing away from the grinding disc in the axial direction. Alternatively, however, it is also conceivable that the first axial region of the forced circulation element, which has the internal teeth, is arranged in an end region of the forced circulation element facing away from the grinding disc in the axial direction. In this alternative embodiment, the second axial region of the forced circulation element, which has the further rolling and / or sliding surface, is preferably arranged in an end region of the forced circulation element facing axially towards the grinding disc.Preferably, the further rolling and / or sliding surface has a maximum outer diameter that preferably corresponds to at most one pitch circle diameter of the external gearing. Preferably, a minimum outer diameter of the further rolling and / or sliding surface corresponds to at least one root circle diameter of the external gearing. Alternatively, however, it is also conceivable that the minimum outer diameter of the further rolling and / or sliding surface is smaller than the root circle diameter of the external gearing. Furthermore, it is also conceivable as an alternative that the maximum outer diameter of the further rolling and / or sliding surface is larger than the pitch circle diameter of the external gearing. Preferably, the pitch circle diameter of the external gearing of the positively driven element is at most 95%, more preferably at most 85%, and particularly preferably at most 75% of a value of the pitch circle diameter of the internal gearing of the positively driven guide element.This design allows for advantageously precise guidance of the grinding wheel. Furthermore, it enables particularly efficient power transmission and a significantly high material removal rate. It also allows for exceptionally smooth running and ease of use. Additionally, it minimizes wear and results in a significantly longer service life. Furthermore, it is proposed that the eccentric sander have at least one battery interface arranged on the housing, to which a battery pack can be attached. The battery interface is located in close proximity to the positive drive, particularly the positive guide element, preferably at a maximum distance of less than 100 mm, more preferably less than 50 mm, and most preferably less than 20 mm. Preferably, the battery interface is arranged such that the center of mass of a battery pack located at the battery interface lies in close proximity to the motor shaft. This design allows the center of mass to be advantageously positioned close to the axis of rotation of the motor shaft. This advantageously minimizes the risk of the eccentric sander tipping over. Furthermore, it allows for advantageously simple operation and a particularly high level of user comfort.Furthermore, an eccentric sanding machine can be provided with a significantly high level of safety for the user. Furthermore, it is proposed that the eccentric grinding machine has at least one fluid conveying unit, driven by the motor shaft and / or the eccentric, for generating a fluid flow to remove particles. This fluid conveying unit is arranged radially within the positive guidance element. The fluid conveying unit is preferably designed to remove particles from the surface during machining with the machining tool mounted on the tool holder unit, for example, by conveying them through the extraction port into a particle collection device. For example, a dust box for collecting the particles can be connected to the extraction port, particularly by a positive and / or non-positive connection. The fluid conveying unit is preferably designed to generate an airflow by which the removed particles can be conveyed, in particular into the dust box.Preferably, the fluid delivery unit is designed as an axial or radial fan or the like. Preferably, the fluid delivery unit is designed separately from the motor cooling system. However, it is also conceivable that the fluid delivery unit, in addition to generating a fluid flow for particle removal, is provided as an alternative or supplement to motor cooling. Preferably, the positive guidance element covers at least 5%, preferably at least 20%, particularly preferably at least 50%, and most preferably at least 75% of the maximum axial extent of the fluid delivery element along a direction extending at least substantially parallel to the axis of rotation of the motor shaft, in a direction extending at least substantially parallel to the axis of rotation of the motor shaft.It is also conceivable that the positive guidance element preferably completely covers the fluid conveying element along a direction that is at least substantially perpendicular to the axis of rotation of the motor shaft. Such a design allows for an advantageously compact construction. Furthermore, by conveying particles into a particle collection device with such a fluid conveying unit, a particularly high level of user safety can be advantageously achieved. Additionally, particularly high efficiency for surface treatment can be attained. Furthermore, it is proposed that the eccentric grinding machine includes at least one counterweight designed to counteract an imbalance of the eccentric in at least one operating state, wherein the fluid delivery unit includes a fan wheel on which the counterweight is arranged. The fan wheel is preferably designed as a radial fan. Alternatively, an axial fan design is also conceivable. Preferably, the fan wheel is made at least partially, and in particular entirely, of a plastic. Alternatively, it is conceivable that the fan wheel is made at least partially, and in particular entirely, of a metal. The at least one counterweight is preferably made of the same material as the fan wheel.However, it is also possible that at least one counterweight is made of a different material, for example, a metal with a particularly high density, such as steel, or another material that would be suitable to a person skilled in the art. Preferably, the counterweight is bonded to the fan wheel, for example, with an adhesive layer. Particularly preferably, the at least one counterweight is integrated into the fan wheel, for example, cast in, pressed in, or formed integrally with the fan wheel. This can advantageously achieve particularly smooth running. Ease of use can be advantageously improved. Vibrations and wear can be advantageously kept to a minimum. Furthermore, it is proposed that the positive drive comprises at least one locking element arranged on the positive guide element to secure its position relative to the housing, and in particular, that the locking element is formed integrally with the positive guide element, with the locking element extending in the axial and / or radial direction of the positive guide element. The at least one locking element is designed to counteract rotation and axial movement of the positive guide element relative to the housing. The at least one locking element preferably engages in a corresponding recess arranged in the housing. For example, the at least one locking element can be configured as a tongue-and-groove element between the housing and the positive guide element. It is also conceivable that the at least one locking element is formed by a screw connection between the positive guide element and the housing.The positive drive can preferably include further locking elements arranged on the positive guide element in a radial and / or axial direction. The positive drive particularly preferably has at least three locking elements in the axial direction. Furthermore, the positive drive particularly preferably has at least three locking elements in the radial direction. This provides advantageously reliable position locking of the positive guide element. It is further proposed that the positive drive comprise at least one vibration damping element arranged between an outer surface of the positive guide element and the housing. The vibration damping element is preferably designed to counteract the transmission of vibrations from the positive guide element to the housing. The vibration damping element is preferably made of an elastic material, such as rubber, a thermoplastic elastomer, damping foam, or the like. Preferably, the vibration damping element extends over the entire outer surface of the positive guide element.It is also conceivable that the vibration damping element extends only over a portion of the outer surface of the positive guidance element, for example, in the form of one or more rings, such as O-rings, arranged between the outer surface and the housing. Preferably, the vibration damping element has a maximum radial extension of at most 10 mm, more preferably at most 5 mm, and most preferably at most 2.5 mm. Preferably, the vibration damping element is bonded to the positive guidance element, for example, by means of an adhesive layer. Such a design allows for advantageously simple assembly, as the precision requirements can be kept to a minimum.Furthermore, the transmission of vibrations, which can occur due to the rolling of the forced circulation element against the forced guide element, can be advantageously minimized. Furthermore, the invention relates to a positive drive, in particular the one already mentioned, for an eccentric sander, especially for the eccentric sander according to the invention. Preferably, the positive drive comprises at least the dimensionally stable positive guide element, in particular having internal teeth, which can be arranged in a rotationally fixed manner on the inside of the housing of the eccentric sander, in particular the eccentric sander according to the invention. This enables advantageously efficient surface processing. Furthermore, an advantageously compact design can be achieved. In addition, particularly high ergonomics and user comfort can be attained. The eccentric grinding machine and / or the positive drive according to the invention are not intended to be limited to the application and embodiment described above. In particular, the eccentric grinding machine and / or the positive drive according to the invention may, in order to fulfill a function described herein, have a different number of individual elements, components, and units than the number specified herein. Furthermore, values ​​within the specified limits of the value ranges stated in this disclosure are also considered disclosed and freely usable. drawing Further advantages become apparent from the following description of the drawings. The drawings illustrate two exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into meaningful further combinations. Figure 1 shows a schematic representation of an eccentric grinding machine according to the invention, Figure 2 shows a schematic sectional view of the eccentric grinding machine according to the invention in a section plane parallel to an axis of rotation of a motor shaft of the eccentric grinding machine according to the invention, Figure 3 shows a schematic sectional view of the forced drive according to the invention and an eccentric, a counterweight and a fluid conveying unit of the eccentric grinding machine according to the invention in a section plane perpendicular to the axis of rotation of the motor shaft of the eccentric grinding machine according to the invention, Figure 4 shows a grinding disc of the eccentric grinding machine according to the invention with the forced rotation element of the eccentric grinding machine according to the invention arranged thereon in a schematic representation, and Figure 5 shows a sectional view of the eccentric grinding machine according to the invention.5 a forced guidance element and a forced circulation element of an alternative embodiment of a forced drive according to the invention in a schematic sectional view in a section plane parallel to a rotation axis of a motor shaft. Description of the exemplary implementations Fig. 1 shows an eccentric sander 10a with a housing 12a. The eccentric sander 10a is designed as a battery-powered eccentric sander 10a. A battery pack 54a is arranged at a battery interface 52a of the eccentric sander 10a. Alternatively, the eccentric sander 10a could be designed as a corded, electrically operated, or pneumatically operated eccentric sander 10a. The housing 12a has a grip area 72a, which is designed as a support surface, particularly ergonomically shaped, for the hand of a user of the eccentric sander 10a, enabling it to be held and operated with one hand. A rubber grip pad is firmly attached to the housing 12a in the grip area 72a. Alternatively, the grip pad could be made of a different material, for example, silicone, plastic, or the like.The eccentric sander 10a has a switch 74a for turning the machine on and off. The switch 74a is located on the housing 12a within the grip area 72a. The switch 74a is designed as a rocker switch. Alternatively, the switch 74a could be designed as a momentary switch. The housing 12a has a dust extraction port 76a for removing particles generated during surface processing. The dust extraction port 76a is located near a positive drive 24a. A particle collection device 70a is detachably connected to the dust extraction port 76a via a connection interface. The particle collection device 70a is designed as a dust box.Alternatively, a vacuum cleaner hose or other particle extraction device can be connected to the extraction port 76a to extract the particles. Furthermore, the eccentric sander 10a has a tool mounting unit designed as a sanding disc 36a. The sanding disc 36a is designed to hold a processing tool 68a, such as sandpaper, a polishing bonnet, or the like. The processing tool 68a is detachably connected to the sanding disc 36a by means of a hook-and-loop fastener. Alternatively, the processing tool 68a can be attached to the tool mounting unit, in particular to the sanding disc 36a, by means of a snap-fit, screw-in connection, or the like. It is also possible for the processing tool 68a to be permanently connected to the sanding disc 36a.The machining tool 68a is designed to remove particles from a surface to be machined. The eccentric sander 10a further comprises a motor 14a (see Fig. 2). The motor 14a is designed as an electric motor, in particular as a brushless DC motor. Alternatively, it is conceivable that the motor 14a is designed as an AC motor. The motor 14a has a no-load speed of at least 8,000 rpm and at most 10,000 rpm. It is also conceivable that the motor 14a has a no-load speed of at least 6,000 rpm and at most 12,500 rpm. The motor 14a has a motor shaft 18a with a rotation axis 20a. The eccentric sander 10a further comprises a battery interface 52a, in particular the aforementioned battery interface 52a. A battery pack 54a can be arranged at the battery interface 52a to supply power to the eccentric sander 10a. The battery interface 52a is located in close proximity to the forced drive 24a with a minimum distance of less than 50 mm. The eccentric sander 10a further comprises an eccentric 16a with an eccentric axis 22a. The eccentric 16a is designed to superimpose an eccentric movement onto the uniform rotational movement of the motor 14a and to transmit this movement to the sanding disc 36a. The eccentric 16a has an eccentricity of at most 5 mm. It is also conceivable that the eccentric 16a has an eccentricity of at most 10 mm. The eccentric 16a is made of metal. It is also conceivable that the eccentric 16a is made of plastic or of any combination of materials. The eccentric axis 22a runs parallel to the axis of rotation 20a of the motor shaft 18a. To ensure a rotationally fixed connection of the eccentric 16a with the motor shaft 18a, the eccentric 16a is positively connected to the motor shaft 18a of the motor 14a by means of a splined shaft connection.It is also conceivable, however, that the eccentric 16a is connected to the motor shaft 18a of the motor 14a by means of a screw connection or a weld. The eccentric 16a is driven by the motor 14a in a rotational fashion about the eccentric axis 22a. On a side of the eccentric 16a facing away from the motor 14a, the grinding disc 36a is rotatably mounted about its own central axis. For rotatable mounting of the grinding disc 36a on the eccentric 16a, a bearing element 38a designed as a radial bearing is arranged on the side of the eccentric 16a facing away from the motor 14a. It is also conceivable that for rotatable mounting of the grinding disc 36a, a bearing element 38a designed as a needle bearing, roller bearing, or the like is arranged on the side of the eccentric 16a facing away from the motor 14a. Furthermore, the eccentric sander 10a has a positive drive 24a. The positive drive 24a is designed to superimpose a rotation about the central axis of the sanding disc 36a onto an eccentric movement transmitted to the sanding disc 36a by the eccentric 16a. The rotation of the sanding disc 36a superimposed by the positive drive 24a is at least 3% and at most 4% of the no-load speed of the motor 14a. However, it is also conceivable that the rotation of the sanding disc 36a superimposed by the positive drive 24a is at least 2% and at most 15% of the no-load speed of the motor 14a. The positive drive 24a has a rigid positive guide element 28a. The positive guide element 28a is designed as a component separate from the housing 12a. The positive guide element 28a is arranged in a rotationally fixed manner on an inner surface of the housing 12a.It is also conceivable that the positive guidance element 28a is formed integrally with the housing 12a. The positive guidance element 28a has an annular shape. The positive guidance element 28a has a maximum axial extent of at most 10 mm. However, it is also conceivable that the positive guidance element 28a has a maximum axial extent of at most 15 mm. The positive guidance element 28a is designed as a component sintered from a hard metal. Alternatively, it is possible that the positive guidance element 28a is made of a plastic, a ceramic material, or the like. The dimensionally stable positive guidance element 28a is designed such that a surface and / or basic shape of the dimensionally stable positive guidance element 28a experiences a maximum elastic deformation of less than 1 mm along a direction extending at least substantially perpendicular to the axis of rotation 20a of the motor shaft 18a as a result of the application of drive forces.The positive guidance element 28a has internal teeth 26a. The internal teeth 26a extend along the entire inner circumference of the positive guidance element 28a. The internal teeth 26a are designed as spur teeth. However, it is also conceivable that the internal teeth 26a are designed as helical teeth. The positive drive 24a includes at least one locking element 62a. However, it is also conceivable that the positive drive 24a has more than one locking element 62a. The locking element 62a is arranged on the positive guidance element 28a. The locking element 62a is designed to secure the position of the positive guidance element 28a relative to the housing 12a. The locking element 62a is formed integrally with the positive guidance element 28a. In the present embodiment, the locking element 62a extends in the axial direction of the positive guidance element 28a.It is also conceivable that the locking element 62a extends radially or radially and axially to the positive guidance element 28a. The locking element 62a is designed to engage in a corresponding recess in the housing 12a. Alternatively, it is conceivable that the locking element 62a is designed as a tongue-and-groove element. The positive drive 24a also includes a vibration damping element 64a. The vibration damping element 64a is designed to counteract the transmission of vibrations from the positive guide element 28a to the housing 12a. The vibration damping element 64a is arranged between an outer surface 66a of the positive guide element 28a and the housing 12a. The vibration damping element 64a extends over the entire outer surface 66a of the positive guide element 28a. The vibration damping element 64a is made of a thermoplastic elastomer. It is also possible for the vibration damping element 64a to be made of another material, for example, rubber or plastic. In the present embodiment, the vibration damping element 64a has a maximum radial extension of no more than 5 mm.The vibration damping element 64a is bonded to the outer surface 66a of the positive guidance element 28a and the inside of the housing 12a, in particular by means of an adhesive layer. Alternatively, the vibration damping element 64a could be designed as one or more O-rings arranged on the outer surface 66a of the positive guidance element 28a. The positive drive 24a comprises a fluid conveying unit 56a, driven by the motor shaft 18a and / or the eccentric 16a, for generating a fluid flow to remove particles (see Fig. 2 and Fig. 3). The fluid conveying unit 56a is arranged radially within the positive guide element 28a. The fluid conveying unit 56a is designed to generate an airflow. In the present embodiment, the airflow is directed through the suction nozzle 76a into the particle collection device 70a to remove particles. Alternatively, it is also conceivable that the fluid conveying unit 56a could generate an airflow to cool the motor 14a, either alternatively or additionally. It is also conceivable that the positive drive 24a comprises a further fluid conveying unit 56a, particularly for cooling the motor 14a, which is driven by the motor shaft 18a and / or the eccentric 16a. The eccentric sanding machine 10a includes a counterweight 60a.The counterweight 60a is designed to counteract an imbalance of the eccentric 16a in at least one operating condition. The fluid conveying unit 56a further comprises a fan wheel 58a on which the counterweight 60a is arranged. In the present embodiment, the fan wheel 58a is designed as a radial fan. However, it is also conceivable that the fan wheel 58a is designed as an axial fan. The fan wheel 58a of the fluid conveying unit 56a is surrounded in the axial direction by the positive guidance element 28a for at least 50% of its axial extent. Alternatively, it is also possible that the fan wheel 58a is completely surrounded in the axial direction by the positive guidance element 28a. The fan wheel 58a is made of a plastic. However, alternative embodiments made of a different material, such as a metal or a combination of materials, are also conceivable.The counterweight 60a is arranged on the fan wheel 58a such that, in one installation position in the eccentric grinding machine 10a according to the invention, it is radially opposite the eccentric 16a. It is also possible for the counterweight 60a to be integrated into the fan wheel 58a. The counterweight 60a is made of a plastic. Alternatively, it is also conceivable that the counterweight 60a is made of a metal. Fig. 3 also illustrates how, in the positive drive 24a, the external toothing 40a of a positively driven element 42a rolls on the internal toothing 26a of the positively driven guide element 28a due to an eccentric movement caused by the eccentric 16a. The meshing of the internal toothing 26a and the external toothing 40a transmits a force to the grinding disc 36a, which causes it to rotate about its own central axis. Fig. 4 shows the grinding disc 36a, on which the machining tool 68a, in particular a grinding paper, is arranged, and the forced circulation element 42a of the forced drive 24a. The forced circulation element 42a has the external toothing 40a. The forced circulation element 42a comprises at least one positive-locking extension 44a, in the present embodiment six positive-locking extensions 44a. The positive-locking extensions 44a are arranged radially inwards on the forced circulation element 42a. The positive-locking extensions 44a are designed to provide a rotationally fixed connection between the forced circulation element 42a and the grinding disc 36a by means of complementary positive-locking openings in the grinding disc 36a. It is also possible for the forced circulation element 42a to have one of six different numbers of positive-locking extensions 44a.Alternatively and / or additionally, it is conceivable that the forced circulation element 42a is axially secured to the grinding disc 36a by means of a screw, embossed, snap-fit, and / or adhesive connection or the like. The at least one positive-locking extension 44a has a polygonal, in particular a rectangular, cross-sectional shape in a plane perpendicular to the motor shaft 18a. The forced circulation element 42a is made of a plastic. However, a design of the forced circulation element 42a from another material is also conceivable. Alternatively, it is also possible that the forced circulation element 42a is formed integrally with the grinding disc 36a. Figure 5 shows a further embodiment of the invention, in particular an alternative configuration of the positive guidance element and the positive rotation element of the positive drive. The following description and the drawing are essentially limited to the differences between the embodiments, whereby with regard to identically designated components, in particular with regard to components with the same reference numerals, reference may also be made to the drawings and / or the description of the other embodiments, in particular Figures 1, 2, 3 to 4. To distinguish the embodiments, the letter "a" is appended to the reference numerals of the embodiment in Figures 1, 2, 3 to 4. In the embodiment of Figure 5, the letter "a" is replaced by the letter "b". Fig. 5 shows a sectional view through a portion of a positive drive 24b for an eccentric grinding machine, comprising a positive guide element 28b and a positive recirculation element 42b. The positive drive 24b is an alternative embodiment of the positive drive 24a and can be arranged / integrated on / in an eccentric grinding machine 10a as described in Figs. 1, 2, 3 to 4. The positive guide element 28b comprises a first axial section 30b. The first axial section 30b has an internal toothing 26b extending over the entire inner circumference of the positive guide element 28b. The positive guide element 28b further comprises a second axial section 32b. The second axial section 32b has a rolling and / or sliding surface 34b extending over the entire inner circumference of the positive guidance element 28b for a further running and / or sliding surface 50b arranged on the grinding disc 36b.The first axial section 30b and the second axial section 32b are adjacent to each other. The axial extent of the first axial section 30b is 50% of the maximum axial extent of the positive guidance element 28b. The axial extent of the second axial section 32b is 50% of the maximum axial extent of the positive guidance element 28b. The positive circulation element 42b comprises a first axial section 46b. The first axial section 46b has an external toothing 40b extending over the entire outer circumference of the positive circulation element 42b. The positive circulation element 42b comprises a second axial section 48b. The second axial section 48b has a further running and / or sliding surface 50b extending over the entire outer circumference of the positive circulation element 42b. The first axial region 46b and the second axial region 48b are adjacent to each other.The further running and / or sliding surface 50b is designed to interact with the rolling and / or sliding surface 34b of the positive guidance element 28b. The internal toothing 26b of the positive guidance element 28b is designed to mesh with the external toothing 40b of the positive circulation element 42b and to exert a force on the grinding disc 36b, causing it to rotate about its own central axis. The further running and / or sliding surface 50b of the positive circulation element 42b is designed to roll / glide on the rolling and / or sliding surface 34b of the positive guidance element 28b, thereby guiding the positive circulation element 42b along a defined path. QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature EP 0 559 020 B1

[0001]

Claims

Eccentric sanding machine (10), in particular a battery-operated eccentric sanding machine, with at least one housing (12), with at least one motor (14), in particular a brushless electric motor, with at least one eccentric (16) which can be driven via a motor shaft (18) of the motor (14), in particular as a result of a rotationally fixed connection with the motor shaft (18), rotating about an eccentric axis (22) of the eccentric (16) which runs at least substantially parallel to an axis of rotation (20) of the motor shaft (18), and with at least one positive drive (24), characterized in that the positive drive (24) has at least one dimensionally fixed, in particular provided with an internal toothing (26), positive guide element (28) which is arranged rotationally fixed on an inner side of the housing (12). Eccentric grinding machine (10) according to claim 1, characterized in that the positive guidance element (28) comprises a first axial section (30) which has an internal toothing (26) extending, in particular over an entire inner circumference of the positive guidance element (28), and a second axial section (32) which comprises a rolling and / or sliding surface (34) extending, in particular over the entire inner circumference of the positive guidance element (28) for a further running and / or sliding surface (50) arranged on a positive circulation element (42), wherein the first axial section (30) and the second axial section (32) are adjacent to each other. Eccentric grinding machine (10) according to claim 1 or 2, characterized in that the forced drive (24) comprises at least one, in particular having an external toothing (40), forced circulation element (42) which has at least one, in particular radially arranged, positive locking extension (44) for a rotationally fixed connection with a grinding disc (36). Eccentric grinding machine (10) according to one of the preceding claims, characterized in that the positive drive (24) comprises a positive circulation element (42) which has a first axial region (46) which has an external toothing (40) extending, in particular over an entire outer circumference, and which has a second axial region (48) which has a further running and / or sliding surface (50) extending, in particular over an entire outer circumference of the positive circulation element (42), which is provided to cooperate with a rolling and / or sliding surface (34) of the positive guidance element (28), wherein the first axial region (46) and the second axial region (48) adjoin each other. Eccentric sanding machine (10) according to one of the preceding claims, characterized by at least one battery interface (52) arranged on the housing (12), on which a battery pack (54) can be arranged, wherein the battery interface (52) is arranged in a close proximity to the forced drive (24), in particular to the forced guide element (28), in particular with a minimum distance of preferably less than 100 mm, preferably less than 50 mm and particularly preferably less than 20 mm. Eccentric grinding machine (10) according to one of the preceding claims, characterized by at least one fluid conveying unit (56) driven by the motor shaft (18) and / or the eccentric (16) for generating a fluid flow for removing particles, which is arranged radially within the positive guidance element (28). Eccentric grinding machine (10) according to claim 6, characterized by at least one counterweight (60) which is provided to counteract an imbalance of the eccentric (16) in at least one operating state, wherein the fluid conveying unit (56) comprises a fan wheel (58) on which the counterweight (60) is arranged. Eccentric grinding machine (10) according to one of the preceding claims, characterized in that the positive drive (24) comprises at least one locking element (62) which is arranged on the positive guide element (28) for securing the position of the positive guide element (28) relative to the housing (12), in particular being formed integrally with the positive guide element (28), wherein the locking element (62) extends in the axial and / or radial direction of the positive guide element (28). Eccentric grinding machine (10) according to one of the preceding claims, characterized in that the forced drive (24) comprises at least one vibration damping element (64) which is arranged between an outer cylindrical surface (66) of the forced guidance element (28) and the housing (12). Forced drive (24) for an eccentric grinding machine (10) according to one of the preceding claims.

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