Robot-assisted grinding device

Abstract

Extraction device comprising: a housing (40) with a vacuum nozzle (48) and an outlet (45) for connecting a hose (44); a suspension having a coupling square, which connects the housing to a mounting plate (33) and which is pivotally mounted on the mounting plate (33) about an axis (R1); a counterweight (41) connected to the suspension, wherein the weight of the housing (40) about the axis (R1) causes a first torque and the counterweight about the axis (R1) causes a second torque which at least partially compensates for the first torque, and a spring element coupled to the housing (40) or the suspension, which directly or indirectly generates a spring force (F S ) between the mounting plate (33) and the housing (40) so that the housing (40) is pressed against a workpiece surface.

Description

TECHNICAL FIELDThe exemplary embodiments described here relate to a suction device for a machine tool operated by a manipulator (e.g. industrial robot) for suction of material which is removed from the workpiece surface.BACKGROUNDIn the processing of workpieces, robot-assisted surface processing processes such as grinding and polishing processes play an increasingly important role. In automated, robot-assisted production, industrial robots are used, with the aid of which, for example, grinding processes can be tomographyed out.In robot-assisted machining devices, a machine tool with a rotating tool (for example grinding machine with grinding wheel or radial brush) is guided by a manipulator, for example an industrial robot. The so-called TCP (Tool Center Point) of the manipulator moves during the machining process along a defined path (trajectory) which can be programmed in advance, for example by means of teaching. The predefined path of the TCP determines the position and orientation of the TCP and thus of the machine tool for each point in time. The robot controller that controls the movement of the manipulator therefore generally includes position control. Furthermore, a spring or an additional actuator can be provided which presses the tool against the workpiece surface with a specific force.Frequently, suction removal of the material removed from the workpiece surface (e.g. grinding dust) is desired or necessary. For this reason, the machine tool can be equipped with a suction device which ensures a suction of the removed material from the workpiece surface. Known suction devices have a suction hood which partially surrounds the tool. The suction hood is connected to a suction line, via which a negative pressure is generated in the suction hood and loose material is suctioned off. Suction devices with suction surfaces are known per se. For example, the publication US 2008 / 0311824 A1 discloses a belt grinding machine with a suction device which is designed to suck grinding residues from the grinding belt. Reference is also made to the publications US 2002 / 0133173 A1 and AT 399466B.For machining small or narrow workpieces or workpieces with curved surfaces, suction devices are often complicated to handle or are simply too large to be able to machine the workpiece properly. Machining "upside down" (tool below the workpiece surface) is also problematic in some suction devices.The inventor has made an object to provide an improved suction device for robot-assisted surface treatment devices.SUMMARYThe above object is achieved by the device according to claim 1. Various embodiments and further developments of the invention are the subject matter of the dependent claims.A suction device for a robot-assisted surface machining machine tool will be described. According to one exemplary embodiment, the suction device has a housing with a vacuum nozzle and an outlet for connecting a hose. Furthermore, the suction device has a suspension which connects the housing to a mounting plate and which is mounted on the mounting plate such that it can be pivoted about an axis. A counterweight is connected to the suspension such that the counterweight substantially balances the weight of the housing with respect to the axis.According to a further exemplary embodiment, the suction device comprises a housing with a vacuum nozzle and an outlet for connecting a hose, and a suspension which connects the housing to a mounting plate and which is mounted on the mounting plate such that it can be pivoted about at least one axis. A counterweight is connected to the suspension such that the weight of the housing about the axis causes a first torque and the counterweight about the axis causes a second torque that at least partially compensates for the first torque.Furthermore, an apparatus for the robot-supported processing of surfaces of workpieces is described. According to one exemplary embodiment, the device comprises a holder which can be mounted on a manipulator, a machine tool which is mechanically coupled to the holder and has a rotating tool, and a suction device which is pivotably mounted on a mounting plate, wherein the mounting plate is part of the holder.BRIEF DESCRIPTION OF THE DRAWINGSThe invention is explained in more detail below with reference to the examples shown in the figures. The representations are not necessarily true to scale and the invention is not limited only to the aspects shown. Rather, emphasis is placed on illustrating the principles underlying the invention. Regarding the figures: FIG. 1 is an exemplary schematic illustration of a robot-assisted grinding apparatus having a grinding machine coupled to an industrial robot by means of a force-controlled linear actuator. FIG. 2 is a side view of a grinding device mountable on a manipulator with a suction device. FIG. 3 is a front view corresponding to the side view of FIG. 2. FIG. 4 is a detailed view of a part of the suction device from FIGS. 2 and 3. FIG. 5 schematically illustrates an example of a balanced suspension for the suction device.DETAILED DESCRIPTIONBefore explaining various embodiments in detail, a general example of a robot-assisted grinding apparatus will be described first. Although the exemplary embodiments described here are explained on the basis of a grinding device, these are not limited to grinding devices, but rather can be applied to any desired devices for machining (abrasive machining) surfaces, such as, for example, machine tools for milling, grinding, polishing, etc.The example shown in FIG. 1 comprises a manipulator 1 (for example an industrial robot) and a grinding machine 10 with a rotating grinding tool (grinding wheel), wherein the grinding machine 10 can be coupled to the tool center point (TCP) of the manipulator 1 via a linear actuator 20 (which, however, does not have to be the case in all exemplary embodiments). In the case of an industrial robot with six degrees of freedom, the manipulator can be constructed from four segments 2a, 2b, 2c and 2d, which are connected via joints 3a, 3b and 3c, respectively. The first segment is usually rigidly connected to a foundation B (which, however, does not necessarily have to be the case). The joint 3c connects the segments 2c and 2d. The joint 3 cmay be 2-axis and allow rotation of the segment 2 cabove a horizontal axis of rotation (elevation angle) and a vertical axis of rotation (azimuth angle). The joint 3 bconnects the segments 2 band 2 cand allows a pivoting movement of the segment 2 brelative to the position of the segment 2 c. The joint 3a connects the segments 2a and 2b. The joint 3a may be 2-axis and therefore (similar to the joint 3c) allow for bi-directional pivotal movement. The TCP has a fixed relative position to the segment 2 a, wherein this usually also comprises a pivot joint (not shown) which enables a rotational movement about a longitudinal axis A of the segment 2 a(drawn in FIG. 1 as a dot-dash line). Each axis of a joint is assigned an actuator which can bring about a rotational movement about the respective joint axis. The actuators in the joints are controlled by a robot controller 4 according to a robot program. The TCP can be positioned (within certain limits) as desired (with any orientation of the axis A).The manipulator 1 is usually position-controlled, i.e. the robot controller can define the pose (position and orientation) of the TCP and move it along a predefined trajectory. When the actuator 20 abuts an end stop, the pose of the grinding tool is also defined with the pose of the TCP. The actuator 20 can be used to set the contact force (process force) between the tool (grinding wheel 11) and the workpiece W to a desired value during the grinding process. A direct control of the process force by the manipulator 1 can in many cases be difficult or undesirable, since reliable control is made more difficult by the high mass inertia of the segments 2 a- 2 cof the manipulator 1. For this reason, the robot controller can be designed to regulate the pose (position and orientation) of the TCP, while the regulation of the contact force (see also FIG. 2, contact force F K) is effected exclusively by the actuator 20 which is coupled between grinding machine 10 and manipulator 1. As mentioned, the actuator 20 is not necessary in all applications and can also be omitted. In some applications, the actuator may be replaced by a simple spring.In the present example, the actuator 20 is a pneumatic actuator, for example a double-acting pneumatic cylinder. However, other pneumatic actuators such as bellows cylinders and air muscles are also applicable. As an alternative, electrical direct drives (gearless) are also possible. In the case of a pneumatic actuator, the force control can be implemented in a manner known per se with the aid of a control valve, a controller (implemented in the controller 4) and a compressed air accumulator. However, the specific implementation is not important to the further explanation and will therefore also not be described in more detail.FIG. 2 shows a side view of an exemplary embodiment of a grinding machine 10 mountable on a manipulator and having a suction device. FIG. 3 is a front view of the corresponding device. As in the example of FIG. 1, the grinding machine 10 is coupled to the manipulator via a linear actuator 20. In the example illustrated in FIG. 2, unlike in FIG. 1, the direction of action of the actuator 20 is not parallel to the longitudinal axis A of the segment 2 aof the manipulator (illustrated on the right in FIG. 2, cf. also FIG. 1 ) but at right angles thereto. For the coupling of the actuator 20 and the grinding machine 10 to the manipulator, an angle 3 (mounting angle) is provided, which has a first mounting plate 31 (flange) and a second mounting plate 32, which are each at right angles to one another. The mounting plate 31 is designed such that it can be mounted on the manipulator. The TCP of the manipulator is located on a surface of the mounting plate 32 on the axis A in this example. a first end of the actuator 20 is connected to the mounting plate 32 (e.g., by means of screws) and the grinding machine 10 is connected to a second end of the actuator 20 (e.g., also by means of screws). In the example shown, the axis of rotation A' of the motor shaft of the motor 12 of the grinding machine 10 is at right angles to the direction of action of the actuator 20 and parallel to the longitudinal axis A of the distal segment 2A of the robot. The deflection of the actuator 20 thus determines the normal distance between the axes A and A'. A rotating tool 11 is connected to the motor shaft of the motor 12 of the grinding machine 10. In the present example, this is a radial brush (bristle brush). Depending on the respective application, another tool can also be provided (e.g. a grinding wheel, a grinding belt, etc.).It should be noted that the axes A and A' need not necessarily be parallel. Furthermore, the mounting plates 31 and 32 also do not have to be arranged at a right angle. It can be seen in FIG. 2 that the position of the grinding machine 10 merely depends on the position (including its orientation) of the TCP and the deflection of the actuator 20. A controller (controller, e.g., robot controller) may determine position (including for any known angle and distance between the mounting plates 31 and 32. Determine the orientation) of the axis of rotation A' motor shaft of the grinding machine 10 from the position of the TCP and the deflection of the actuator 20. In exemplary embodiments without actuator 20, the position of the motor shaft of the grinding machine can be determined from the position of the TCP by a simple coordinate transformation.The suction device is mounted on a holder, which in the present examples is formed as an angle 3. The mentioned mounting plates can be (e.g. integral) part of the holder. In the example shown, the angle 3 has a further mounting plate 33 on which the suction device is mounted. The suction device comprises a comparatively narrow housing 40, which can be shaped similar to a joint nozzle (vacuum crevice nozzle) of a vacuum cleaner. That is, at the lower end of the housing, a vacuum nozzle 48 is disposed through which dust and other particles can be sucked. A detailed view of the housing 40 is also shown in FIG. 4. In addition to the nozzle at the lower end of the housing 40, a roller 42 may be mounted on the housing 40. The roller 42 can be arranged such that it rolls on the workpiece surface during operation and thus ensures a defined distance d between the housing 40 and the workpiece W. A brush 47 can be arranged on one side of the housing, which brush additionally cleanses the already machined workpiece surface. However, roller 42 and brush 47 are optional and may be omitted depending on the application. The housing 40 has an outlet 45 at the end opposite the vacuum nozzle 48 (on the upper side), through which the suctioned-off material is transported away. For this purpose, a hose 44 is connected to the outlet 45, which hose can also be fixed at the angle (for example at the mounting plate 32). The hose 44 leads from the housing 40 to the suction side of a blower (not shown). Suitable fans are known per se and are therefore not discussed further here.In FIG. 2, the suspension (suspension) of the housing 40 at the angle 3 can be seen. Accordingly, the housing 40 for the suction is mounted on the mounting plate 33 by means of a planar coupling quadrilateral (flat four-bar coupling). The four-bar linkage is formed essentially by the linkage rods 51 and 52, which are rotatably mounted on the mounting plate 33 (axes of rotation R 1 and, respectively, axes of rotation R. R 2). One end each of the coupling rods 51 and 52 is also rotatably supported with the housing 40 (rotation axes R 3 and R 4), wherein in the present example the rotation axes R 1, R 2, R 3 and R 4 are arranged such that the coupling rods 51 and 52 are substantially parallel. One of the coupling rods (in the present example, the coupling rod 52) is connected to a counterweight 41 (center of gravity of the counterweight is denoted by R 5 ). This counterweight 41 is located on the side of the axis of rotation R 1 opposite the housing 40 and is dimensioned such that it balances the weight force of the housing 40. That is, without any external force acting on the connecting quadrilateral, no torque acts on the connecting rods 51 and 52; the connecting quadrilateral is balanced in any position, even if the grinding device is operated upside down (upside-down). In other words, the torque on the connecting quadrilateral (e.g., about the axis of rotation R 1) caused by the weight force of the grinding device (without hose 44) is substantially compensated by the torque on the connecting quadrilateral caused by the weight force of the counterweight.In FIG. 5, the forces acting on the connecting quadrilateral are shown once again, it being assumed without restriction of generality that the masses of the housing 40 and of the counterweight 41 are concentrated in each case on one point (center of gravity) and the masses of the connecting rods are added to the masses of the housing and of the counterweight. The torque about the axis R 1 caused by the weight force F 40 of the housing 40 is F 40 ·(L 0+ L 1) ·cos(α), and the torque about the axis R 1 caused by the weight force F 41 of the counterweight 41 is -F 41 ·L 2 ·cos(α), where L 0 is the distance between axis R3and the center of gravity at which the force F40acts. L 1 is the distance between the axes R 1 and R 3, and L2 is the distance between the axis R 1 and the center of gravity of the counterweight 41. the four bar linkage is balanced when F 40 ·(L 0+ L 1) ·cos(α)-F 41 ·L 2 ·cos(α)=0. It can be seen that the angle α does not matter to the equation, and F 41= F 40 ·(L 0+ L 1) / L 2. is obtained.In order for the housing 40 to be pressed against the workpiece surface, for example with the roller 42, a very low force is sufficient, which acts in the direction of the workpiece surface (other than the weight forces) in each position. This low force can be effected, for example, by a spring element which acts directly or indirectly between the angle 3 (for example the mounting plate 33) and the four-bar linkage. In the example shown in FIG. 2, this spring force F S is generated by the hose 44, which is connected to the outlet 45 of the housing 40) and is fixed to the mounting plate 32 of the angle 3. The spring force exerted by the hose 44 thus acts between the mounting plate 32 and the housing 40 and thus indirectly also between the mounting plate 33 (or the angle 3) and the four-bar linkage. This situation is also shown in Fig. 5. The bearing points symbolized as triangles are all rigidly connected to the angle 3 (i.e. they lie on one of the mounting plates 32 or 33).

Claims

An exhaust device comprising: a housing (40) having a vacuum nozzle (48) and an outlet (45) for connection of a hose (44); a suspension having a coupling quadrilateral connecting the housing to a mounting plate (33) and being mounted on the mounting plate (33) pivotably about an axis (R 1) ; a counterweight (41) connected to the suspension, wherein the weight of the housing (40) about the axis (R 1) causes a first torque and the counterweight about the axis (R 1) causes a second torque which at least partially compensates the first torque, and a spring element coupled to the housing (40) or the suspension which directly or indirectly causes a spring force (F S) between mounting plate (33) and housing (40), such that the housing (40) is pressed against a workpiece surface.The suction device according to claim 1, wherein the suspension has a first coupling rod (51), which is mounted on the mounting plate (33) such that it can pivot about the axis (R 1).The suction device according to claim 2, wherein the suspension has a second coupling rod (52), which is mounted on the mounting plate (33) such that it can be pivoted about a further axis (R 2) and wherein the first coupling rod (51) and the second coupling rod (52) are both mounted on the housing (40) such that they form a coupling quadrilateral.The suction device according to claim 2 or 3, wherein the counterweight (41) is fixed to the first coupling rod (51).The suction device according to any one of claims 1 to 4, wherein the counterweight (41) is connected to the suspension such that weight of the housing (40) and the counterweight are substantially balanced with respect to the axis (R 1).The suction device according to any one of claims 1 to 5, wherein the spring element is a hose (44) connected to the outlet (45).The suction device according to claim 6, wherein the hose (44) is directly or indirectly fixed to the mounting plate (33).The suction device according to any one of claims 5 to 7, wherein the housing (40) comprises a roller (42) configured to contact the workpiece surface during operation, wherein the spring element presses the roller (42) against the workpiece surface.The suction device according to any one of claims 1 to 8, further comprising: a brush (47) arranged on the housing (40) and configured to contact the workpiece surface during operation.A device for machining surfaces of workpieces, the device comprising: a holder having a mounting plate (33) which is mountable on a manipulator (1); a machine tool (10) having a rotating tool (11); a linear actuator (20) which connects the machine tool (10) to the holder such that it can be displaced relative thereto; a suction device according to one of claims 1 to 9 connected to the mounting plate (33).

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