阅读说明：本技术 用于机器人辅助研磨的研磨机 (Grinding machine for robot-assisted grinding ) 是由 R·纳德雷 于 2018-04-19 设计创作，主要内容包括：本发明涉及一种研磨机,所述研磨机适用于机器人辅助的研磨过程。根据一个实施例,所述研磨机具有壳体；布置在所述壳体内部的电机；布置在所述壳体的内部中的电机轴上的风扇叶轮和与所述电机轴耦联的、用于容纳砂轮的支撑垫。所述支撑垫具有用于将研磨粉尘吸入到所述壳体的内部中的开口。所述研磨机此外具有布置在所述壳体的壁中的出口,所述出口用于从所述壳体的内部中抽出研磨粉尘,以及布置在所述壳体的壁中的止回阀。所述止回阀使空气能够从所述壳体的内部中流出,但是阻止空气被吸入到所述壳体的内部。(The present invention relates to a grinding machine which is suitable for a robot-assisted grinding process. According to one embodiment, the grinding mill has a housing; a motor disposed inside the housing; a fan impeller arranged on a motor shaft in the interior of the housing and a support pad coupled to the motor shaft for receiving a grinding wheel. The support pad has an opening for drawing abrasive dust into the interior of the housing. The grinding mill furthermore has an outlet arranged in the wall of the housing for withdrawing grinding dust from the interior of the housing, and a check valve arranged in the wall of the housing. The check valve allows air to flow out of the interior of the housing, but prevents air from being drawn into the interior of the housing.)

1. A grinding mill comprising:

a housing;

a motor disposed inside the housing;

a fan impeller disposed on a motor shaft of the motor inside the housing;

a support pad coupled to the motor shaft for receiving a grinding wheel, wherein the support pad has an opening for drawing grinding dust into the interior of the housing;

an outlet arranged in a wall of the housing for drawing grinding dust from the interior of the housing, wherein the outlet is connected to a suction device capable of generating a negative pressure inside the housing of the grinding mill; and

a check valve disposed in a wall of the housing, the check valve enabling air to flow out of the interior of the housing but preventing air from being drawn into the interior of the housing.

2. The grinding mill according to claim 1,

wherein the motor is arranged in the interior space of the housing in such a way that an air flow, which thereby carries away the grinding dust, flowing from the openings in the support mat to the outlet also cools the motor.

3. The grinding mill of claim 1 or 2, further comprising:

an eccentric bearing connecting the motor shaft with the support pad such that the support pad can perform an orbital motion,

wherein the air flow flowing from the opening in the support pad to the outlet, thereby carrying away the grinding dust, cools the eccentric bearing.

4. The grinding mill according to any one of claims 1 to 3,

wherein-in the absence of suction-air sucked in through the outlet by means of the fan impeller through the opening in the support mat flows out through the non-return valve.

5. The grinding mill according to any one of claims 1 to 4,

wherein, in the event of a back pressure in the interior of the housing caused by the fan impeller, air can flow out of the interior of the housing to the environment through the check valve.

6. The grinding mill of any one of claims 1 to 5, further comprising:

a cable for supplying current to the motor, wherein the cable is routed substantially helically around the housing.

7. A method for cooling a grinding mill having a rotatable support pad for receiving a grinding wheel; the method comprises the following steps:

generating a negative pressure inside the shell of the grinding mill by means of a suction device, which is connected with the inside of the shell via an air outlet in the shell wall,

wherein an air flow through openings in the support pad is generated by the negative pressure, the air flow carrying grinding dust to the interior of the housing, the grinding dust being drawn off through an outlet in the housing wall, and

wherein a motor arranged inside the housing is also cooled by the air flow;

and wherein, without activating the suction device, the method comprises:

a further air flow for cooling the electric motor is generated by means of the fan impeller through an opening in the supporting mat, as a result of which a back pressure is generated inside the housing, so that a check valve arranged in the housing wall opens and the further air flow can flow out.

8. The method of claim 7, wherein the first and second light sources are selected from the group consisting of,

wherein the fan impeller is mounted on a motor shaft of the motor and forms an axial fan.

9. The method according to claim 7 or 8,

wherein the non-return valve is closed in case of an activated suction device.

10. An apparatus for robot-assisted abrading, the apparatus comprising:

a manipulator;

the grinding mill of any one of claims 1 to 6;

a linear actuator coupling the grinder with the TCP of the manipulator;

a suction device connected to an outlet in the housing of the mill.

11. The apparatus of claim 10, wherein the first and second electrodes are disposed on opposite sides of the substrate,

wherein the direction of action of the linear actuator extends substantially parallel to the axis of rotation of the motor.

12. The apparatus of claim 10 or 11,

wherein the suction device is connected with the outlet via a hose arranged substantially helically around the housing of the grinding mill and the linear actuator.

13. The apparatus of any one of claims 10 to 12,

wherein the cable required for running the grinding mill is arranged along a helical curve around the longitudinal axis of the grinding mill and the housing of the linear actuator, wherein the end of the cable is mechanically connected with the manipulator.

14. The apparatus of claim 14, wherein the first and second electrodes are disposed on opposite sides of the substrate,

wherein the cable is arranged in a cable hose together with other cables.

15. An apparatus for robot-assisted abrading, the apparatus comprising:

a manipulator;

a grinder;

a linear actuator coupling the grinder with the TCP of the manipulator;

a suction device connected to an outlet in the housing of the mill,

wherein the suction device is connected with an outlet on the mill via a hose which is arranged helically around the mill housing and the linear actuator and which is mounted with one end on the manipulator.

Technical Field

The present invention relates to a grinding machine for robot-assisted grinding, in particular a compact and light grinding machine for mounting on a manipulator.

Background

In a robot-assisted grinding device, a grinding tool (e.g., an electric grinder with a rotating grinding wheel) is guided by a manipulator, such as an industrial robot. In this case, the grinding Tool can be coupled to the so-called TCP (Tool Center point) of the manipulator in different ways, so that the manipulator position and orientation of the Tool can be adjusted virtually arbitrarily. Industrial robots are usually position-regulated, which enables the TCP to move precisely along a desired trajectory. In order to obtain good results in robot-assisted grinding, in many applications process forces (grinding forces) need to be adjusted, which are often difficult to achieve with sufficient accuracy by conventional industrial robots. The large and heavy arm segments of an industrial robot have too much inertia that the regulator (closed-loop controller) cannot react fast enough to fluctuations in the process force. In order to solve this problem, a linear actuator, which is smaller than an industrial robot and couples the TCP of the manipulator with the grinding tool, may be arranged between the TCP of the manipulator and the grinding tool. The linear actuator adjusts only the process forces (i.e. the contact pressure between the tool and the workpiece) during grinding, while the manipulator moves the grinding tool together with the linear actuator in a positionally controlled manner along a predeterminable trajectory.

Conventional orbital grinders or eccentric grinders, by far, perform poorly because they are designed for manual work. The robot can work faster and therefore with greater force and thus require greater grinding efficiency. However, small and compact designs cause thermal problems in orbital mills or eccentric mills. Furthermore, the bending forces of small hoses and cables can create disturbing forces that can alter the process forces during grinding, but which cannot be eliminated by the regulator.

The aim of the inventors was to develop a compact grinding machine which is suitable for robot-assisted grinding and which enables a relatively precise adjustment of the process forces during grinding.

Disclosure of Invention

The above-mentioned objects are achieved by a grinding mill according to claim 1, a method according to claim 7 and an apparatus according to claim 10. Various embodiments and further developments are the subject matter of the dependent claims.

A grinder is described which is suitable for use in a robot-assisted grinding process. According to one embodiment, the grinding machine comprises a housing, a motor arranged inside the housing, a fan impeller arranged on a motor shaft of the motor inside the housing, and a support pad coupled to the motor shaft for accommodating a grinding wheel. The support pad has an opening for drawing grinding dust into the interior of the housing. The grinding mill furthermore comprises an outlet arranged in the wall of the housing for withdrawing grinding dust from the interior of the housing, and a check valve arranged in the wall of the housing. The check valve allows air to flow out of the interior of the housing, but prevents air from being drawn into the interior of the housing.

Furthermore, an apparatus for robot-assisted grinding is described. According to one embodiment, the apparatus comprises a manipulator, a grinder, a linear actuator coupling the grinder with a TCP of the manipulator, and a suction device connected with an outlet in a housing of the grinder.

Finally, a method for cooling a grinding mill comprising a rotatable support pad for receiving a grinding wheel is described, according to one embodiment, the method comprising: the negative pressure is generated inside the housing of the grinding mill by means of a suction device which is connected to the interior of the housing via an air outlet in the housing wall. In this case, an air flow through the openings in the support mat is generated by the negative pressure, which air flow carries the grinding dust to the interior of the housing. The grinding dust is then drawn off through an outlet in the housing wall. Simultaneously, the electric motor arranged inside the housing is also cooled by the air flow. In the case of a non-activated suction device, the method comprises: a further air flow for cooling the electric motor is generated by means of a fan impeller through an opening in the supporting mat, as a result of which a back pressure is generated inside the housing, so that a check valve arranged in the housing wall opens and the further air flow can flow out.

Drawings

The invention will be explained in more detail below with the aid of examples shown in the drawings. The drawings are not necessarily to scale and the invention is not limited only to the aspects shown. Emphasis instead being placed upon illustrating the principles upon which the invention is based. Shown in the figure:

fig. 1 schematically shows an example of a robot-assisted abrading device.

Fig. 2 shows a schematic example of a rail grinder with combined air cooling and suction.

Figure 3 shows the example of figure 2 with a non-activated suction device.

Fig. 4 shows the rotary support (support pad) with openings in fig. 2 in a view from below.

Fig. 5A and 5B together fig. 5 shows an example of cabling on a robot-assisted abrading device.

Detailed Description

Before explaining in detail the various embodiments of the present invention, an example of a robot-assisted abrading device is first described. The grinding device comprises a manipulator 1, for example an industrial robot, and a grinding machine 10 (for example an orbital grinding machine) with a rotating grinding tool, wherein the rotating grinding tool is coupled to a so-called Tool Center Point (TCP) of the manipulator 1 by means of a linear actuator 20. In the case of an industrial robot with six degrees of freedom, the manipulator may be constructed from four segments 2a, 2b, 2c and 2d, which are connected by joints 3a, 3b and 3c, respectively. The first segment is usually, but not necessarily, rigidly connected to the base 41. Joint 3c connects segments 2c and 2 d. The joint 3c may be 2-axis and allow rotation of the segment 2c about a horizontal rotation axis (elevation) and a vertical rotation axis (azimuth). Joint 3b connects segments 2b and 2c and allows pivotal movement of segment 2b relative to the position of segment 2 c. A joint 3a connects the segments 2a and 2 b. The joint 3a may be 2-axis and thus (similar to the joint 3 c) allows pivotal movement in both directions. The TCP has a fixed relative position with the segment 2a, wherein this segment 2a typically also comprises a rotational joint (not shown) allowing a rotational movement around the longitudinal axis a of the segment 2a (shown in dashed lines in fig. 1, corresponding to the rotational axis of the grinding tool). Each shaft of the joint is associated with an actuator that can cause rotational movement about the respective joint axis. The actuators in the joints are controlled by the robot controller 4 according to a robot program.

The manipulator 1 is typically position-regulated, that is, the robot controller may specify the attitude (position and orientation) of the TCP and move the TCP along a predefined trajectory. In fig. 1, the longitudinal axis of the segment 2a in which the TCP is located is indicated with a. When the actuator 20 abuts on one end stop, then the attitude of the grinding tool is also defined by the attitude of the TCP. As already mentioned at the outset, the actuator 20 serves to set the contact force (process force) between the tool (grinding machine 10) and the workpiece 40 to a desired value during the grinding process. The direct force adjustment by the manipulator 1 is generally too inaccurate for grinding applications, since it is virtually impossible to quickly compensate for force peaks (for example when placing the grinding tool onto the workpiece 40) by means of conventional manipulators due to the high inertia of the segments 2a-c of the manipulator 1. For this reason, the robot controller is designed to adjust the attitude of the TCP of the manipulator, and the force adjustment is performed only by the actuator 20.

As already mentioned, during the grinding process, by means of the (linear) actuator 20 and the force regulator (which can be realized, for example, in the controller 4), the contact force FK (also referred to as process force) between the tool (grinding machine 10) and the workpiece 40 can be adjusted in such a way that the contact force (in the direction of the longitudinal axis a) between the grinding tool and the workpiece 40 corresponds to a predeterminable target value. In this case, the contact force is a reaction force to an actuator force with which the linear actuator 20 is pressed against the workpiece surface. In the absence of contact between the workpiece 40 and the tool, the actuator 20 moves towards one end stop (not shown, as integrated in the actuator 20) due to the absence of contact forces on the workpiece 40. The position regulator of the manipulator 1 (which may also be implemented in the controller 4) may work completely independently of the force regulator of the actuator 20. The actuator 20 is not responsible for the positioning of the grinding machine 10, but only for adjusting and maintaining the desired contact force during the grinding process and identifying the contact between the tool and the workpiece.

The actuator may be a pneumatic actuator, such as a double acting pneumatic cylinder. However, other pneumatic actuators may be used, such as bellows-type hydraulic cylinders and air muscles. Alternatively, an electric direct drive (without a gear mechanism) can also be considered. It should be noted that the direction of action of the actuator 20 does not necessarily have to coincide with the longitudinal axis a of the segment 2a of the manipulator. In the case of a pneumatic actuator, the force regulation can be effected in a manner known per se by means of regulating valves, regulators (which are implemented in the control 4) and compressed air reservoirs. However, the specific implementation is not important for further explanation and is therefore not described in more detail. The grinding mills generally have a suction device to suck the grinding dust out. In that

Fig. 1 shows a connection head 15 for a hose of a suction device. The suction device will be discussed in more detail later.

As mentioned at the outset, the inertia of the grinding machine can contribute to a precise adjustment of the contact force (process force). However, the small and compact design of the grinding mill leads to a greater power density, which in turn leads to a large heat discharge (and correspondingly high temperatures) in a relatively small space. In the case of orbital grinding machines, lost heat (e.g. ohmic losses, iron losses, friction losses in the bearings) is generated in the motor of the grinding machine on the one hand and in the eccentric bearings which effect the orbital motion on the other hand. In the example shown here, among other things, a compact design is achieved by combining cooling and suction. That is, in "normal" operation, the air flow caused by the suction of the grinding dust is simultaneously used for cooling.

Fig. 2 shows a schematic example of a grinding mill 10 with combined cooling and suction. The grinding machine 10 can be mounted on the manipulator 1 as shown in fig. 1, with the following robot-assisted grinding process. Fig. 2 is a schematic longitudinal section along the longitudinal axis a of the grinding mill 10 (which may coincide with the axis of the segment 2a, see fig. 1). The grinding mill 10 comprises a housing 11, which housing 11 may, but need not, have a substantially cylindrical basic shape. In the housing 11, a motor 12 is arranged. The axis of rotation of the motor shaft of the motor 12 also corresponds to the longitudinal axis a of the grinding mill 10. In the present example, the motor shaft is coupled via an eccentric bearing 16 to a rotating support 19 (support pad, pad) on which the grinding wheel is mounted during operation. The grinding wheel can be mounted on the rotary support, for example, by means of Velcro (Velcro, hook and loop fastener). The eccentric bearing 16 allows the rotation of the rotary support about an eccentric axis of rotation a' which rotates about the longitudinal axis a. The axial offset between the motor shaft (rotation axis a) and the eccentric shaft (rotation axis a') is denoted by e in fig. 2. The basic structure of the drive of the rotary support 19 is known per se and is therefore not explained in more detail.

As mentioned, the grinding mill, in particular the rail grinding mill, can be coupled with a suction device for sucking grinding dust. The suction device, similar to a vacuum cleaner, generates a negative pressure and is coupled to the interior of the housing 11 by means of a hose. In this example, the hose of the suction device may be connected to the air outlet 15. During the grinding operation, air is sucked in through the opening 17 in the rotary support 19, wherein the dust particles are conveyed by the air flow through the opening 17 into the interior of the housing 11 and finally drawn out through the air outlet 15. The air flow through the housing 11 is shown in fig. 2 by dashed arrows. Due to the negative pressure generated by the suction device in the interior of the housing (the pressure pi in the interior is less than the ambient pressure pa), the non-return valve 14 shown in fig. 2, which connects the interior of the housing 11 with the environment, is closed. In the illustrated situation with the suction device activated and the non-return valve 14 closed, the axial fan 13 mounted on the motor shaft is in fact redundant and enhances the air flow caused by the suction device.

The air flow caused by the suction simultaneously cools the interior of the housing and carries away the heat of the motor 12 and the eccentric bearing 16. Due to the compact design, such cooling is necessary in order to prevent overheating of the mill. Temperatures in excess of 150 ° may damage the motor or mechanical components if not cooled. There is now the risk that the suction device cannot be operated as intended for some reason, for example because the worker forgets to switch on the suction device, or because the air hose has been detached, etc. In conventional grinding mills, this is generally not problematic, since on the one hand the waste heat is less because the construction is less compact, and on the other hand the suction and cooling are two subsystems which are independent of one another. However, the compact design of the mill with combined cooling and suction described here depends on the suction device functioning properly, unless other measures are taken which prevent the mill from overheating when the suction device is not functioning properly. When the suction device fails, the axial fan 13 is not always able to generate sufficient convection, in particular when the flow resistance through the air outlet 15 is too high. This may occur, for example, in situations where the suction device is connected to the air outlet 15 by a hose, but the suction device is shut off or otherwise fails.

Fig. 3 shows the example from fig. 2 in a situation with an unactuated suction device. However, in order to prevent overheating of the grinding mill 10, an axial fan (fan impeller, propeller) is mounted on the motor shaft of the motor 12 (which is practically superfluous for normal operation with suction equipment), which can generate an air flow through the interior of the housing for cooling purposes. As shown in fig. 3, the axial fan also draws in air through the opening 17 and generates an air flow for cooling the interior of the housing 11. As mentioned, there may occur a situation in which it is not ensured that the air flow generated by the axial flow fan 12 can be blown out to the outside through the outlet 15. If, for example, a hose is also fitted to the outlet 15, the air resistance of the hose may be so great that the axial fan 12 cannot generate a sufficient volume flow to cool the interior of the housing sufficiently. For this reason, the grinding mill shown in fig. 2 and 3 has a non-return valve 14 which enables air to flow out of the interior of the housing 11 into the environment. In the case of an unactivated suction device, the axial fan generates an internal pressure pi (back pressure) in the housing, which is greater than the ambient pressure pa. The check valve is thus open and air can escape from the housing through the check valve 14 at a relatively low air resistance and at the same time reject heat. Thus, in machines without a separate (separate from the suction device) cooling device, the axial fan 13-in combination with the check valve 14-is a safety feature that prevents overheating of the motor when the suction device does not generate sufficient air flow to cool the motor. The axial fan may be (but need not be) the only fan in the housing 11. It should be emphasized again here that in "normal" operation, in the case of an activated suction device, the air flow which cools the motor is generated by the suction device.

Fig. 4 shows the rotary support 19 (support pad) with the opening 17 in a view from below. As mentioned, the surface of the support 19 may be adhesive (for example by means of velcro) in order to mount the grinding wheel thereon. In fig. 4, the axis of rotation a of the motor shaft and the eccentric axis of rotation a' of the support 19 are also shown. It should be noted that the embodiments described herein are not limited to orbital grinders. The combined cooling and suction described with reference to fig. 2 and 3 can also be applied to other grinding machines having a rotating grinding tool (grinding wheel), even if the grinding tool performs a purely rotational movement instead of an orbital movement.

As mentioned at the outset, the compact and lightweight design of the grinding machine can contribute to a reduction in the inertial forces and an improved adjustment of the contact forces. Another aspect that may play a role in the adjustment of the contact force is interference forces, which are caused by bending of the cable and hose. These disturbing forces act parallel to the actuator 20 (between the grinding machine 10 and the TCP of the manipulator 1) and can therefore not be easily compensated by the actuator. Fig. 5A and 5B show an example of cabling on a robot-assisted finishing apparatus with a finishing machine 10 and an actuator 20, wherein the cables (wires) required for running the finishing machine are routed around the longitudinal axis a substantially along a helical curve. Fig. 5A is a schematic view from the front, and fig. 5B is a schematic view from below.

The routing of the one or more cables 18 around the grinder 10 and the actuator 20 along a generally helical curve (at least partially) allows the bending of the cable 18 to be changed as little as possible when changing the deflection a of the actuator 20. Furthermore, due to the bending of the cable 18, a helical cable routing is generally able to achieve very low disturbing forces along the longitudinal axis a (that is to say along the direction of action of the actuator). In contrast thereto, in the case of conventional cabling, in which the cable 18 (or these cables) is bent in a loop on one side of the actuator 20, the disturbance forces can be considerably larger and more strongly varied.

A hose (not shown) connected to the outlet 15 (see fig. 3) through which the sanding dust is drawn may be guided along a helical curve in a similar manner to the cable(s) 18. A plurality of cables 18 can be guided together in a cable hose. As shown in fig. 5, one end of the cable 18 is connected with the grinding machine 10 (and is guided through the wall of the housing 11), whereas the other end of the cable 18 is mechanically connected with the outermost segment 2a of the manipulator 1.

Some important aspects of the embodiments described herein are summarized below. However, the following should not be construed as a complete enumeration but rather as exemplary. One embodiment relates to a grinder 10 suitable for use in a robot-assisted grinding process (see fig. 2). The grinding machine has a housing 11, a motor 12 arranged inside the housing, a fan wheel 13 arranged on the motor shaft of the motor 12 inside the housing, and a rotatable receiving body (support pad) coupled to the motor shaft for receiving a grinding wheel. The support pad has an opening 17 for drawing grinding dust into the interior of the housing 11. The grinding mill 10 furthermore has an outlet 15 arranged in the wall of the housing for withdrawing grinding dust from the interior of the housing 11, and a check valve 14 arranged in the wall of the housing 11. The check valve 14 allows air to flow out of the interior of the housing, but prevents air from being drawn into the interior of the housing (see fig. 2 and 3).

In another embodiment, the electric motor 12 is arranged in the interior of the housing 11 in such a way that the air flow which carries away the grinding dust and which flows from the openings 17 in the support mat 19 to the outlet 15 also cools the electric motor 12. Therefore, the air flow generated for the suction is also used for cooling the engine. In the case of an orbital grinder, the grinder has an eccentric bearing 16 that connects the motor shaft with a support pad 19 so that the support pad 19 can undergo orbital motion. The mentioned air flow, which thereby carries away the grinding dust, flowing from the openings 17 in the support cushion 19 to the outlet 15 also cools the eccentric bearing 16 in this case.

In the absence of suction through the outlet 15, the air sucked in by means of the fan impeller 13 through the openings 17 in the support mat 19 flows out through the non-return valve 14 (see fig. 3). In other words, the fan wheel 13 is embodied to generate a back pressure in the interior of the housing 11, so that air can flow out of the interior of the housing 11 through the non-return valve 14 into the environment.

In order to reduce disturbing forces due to cables and hoses connected to the grinding machine, the cable 18 for supplying current to the motor 12 may be routed substantially helically around the housing 11.

Another aspect relates to an apparatus for robot-assisted grinding having a manipulator 1 (e.g., an industrial robot), a grinding machine 10 according to the examples described herein, a linear actuator 20 coupling the grinding machine 10 with a TCP of the manipulator, and a suction device connected with an outlet in a housing of the grinding machine (see fig. 1 and 2). Another aspect relates to a method for cooling a grinding mill 10 having a rotatable support pad 19 for receiving a grinding wheel. The method comprises generating a negative pressure in the interior of the housing 11 of the grinding mill 10 by means of a suction device which is connected to the interior of the housing via an air outlet 15 in the housing wall (see fig. 2 and 3). In this case, an air flow through the openings 17 in the support mat 19 is generated by the negative pressure, which carries the grinding dust into the interior of the housing 11. The ground dust is then drawn off through an outlet 15 in the housing wall. At the same time, the motor arranged in the interior of the housing is also cooled by the air flow. In the case of an unactuated suction device, the method comprises: a further air flow for cooling the electric motor 12 is generated by means of the fan impeller 13 through the opening 17 in the supporting mat 19, as a result of which a back pressure is generated in the interior of the housing 11, so that the non-return valve 14 arranged in the housing wall and the further air flow can flow out.