ROTARY GRIPPER

Abstract

A rotary gripper having two gripping jaws and an actuating mechanism displaceable along a displacement path and rotatable about a rotational axis. The gripping jaws are displaced and/or swiveled during displacement of the actuating mechanism and rotation of the actuating mechanism leads to joint rotation of the gripping jaws about the rotational axis. The rotary gripper has a magnet, a magnetic field sensor and a processing device. The magnet is attached to the actuating mechanism so that a magnetizing direction runs at an angle to the rotational axis. The magnetic field sensor is arranged to detect the magnetic field of the magnet and to detect components of the magnetic flux density of the magnetic field for at least two spatial directions. The processing device is set up, depending on the components of the magnetic flux density detected, to detect rotational information relating to a rotational angle of the joint rotation of the gripping jaws and gripping information relating to the gripping position.

Claims

1. A rotary gripper having two gripping jaws and an actuating means which is mounted by a bearing means, particularly formed by a housing, so as to be linearly displaceable along a displacement path and rotatable about a rotational axis running parallel to the displacement path, wherein the actuating means is movement-coupled with the gripping jaws in such a manner that the gripping jaws are displaced and/or swiveled during a displacement of the actuating means along the displacement path in opposite directions to one another, in order to adopt different gripping positions, and that a rotation of the actuating means about the rotational axis leads to a joint rotation of the gripping jaws about the rotational axis, wherein the rotary gripper has a magnet, a magnetic field sensor and a processing device, wherein the magnet is attached to the actuating means in such a manner that a magnetizing direction runs at an angle, in particular perpendicularly, to the rotational axis, wherein the magnetic field sensor is arranged in a stationary manner relative to the bearing means, such that the magnetic field of the magnet can be detected by the magnetic field sensor, wherein the magnetic field sensor is set up to detect components of the magnetic flux density of the magnetic field for at least two spatial directions, wherein the processing device is set up, depending on the components of the magnetic flux density detected, to detect rotational information relating to a rotational angle of the joint rotation of the gripping jaws and gripping information relating to the gripping position.

2. The rotary gripper according to claim 1, wherein the actuating means extends from an end coupled with the gripping jaws in the direction of the displacement path up to an end facing away from the gripping jaws, wherein the magnet is arranged on the end of the actuating means facing away from the gripping jaws, and is particularly arranged on an end face of the actuating means facing away from the gripping jaws.

3. The rotary gripper according to claim 2, wherein the actuating means is formed from a material which has a relative magnetic permeability at its end facing away from the gripping jaws of less than 4 or less than 2 or less than 1.5.

4. The rotary gripper according to claim 1, wherein the magnetic field sensor is arranged on a side of the actuating means facing away from the gripping jaws and spaced apart from the actuating means in the direction of the displacement path.

5. The rotary gripper according to claim 1, wherein at least one portion of the actuating means is received in a receiving space formed by the, or a, housing of the rotary gripper, wherein the magnetic field sensor is arranged on a side of a side wall of the receiving space facing away from the receiving space, wherein the side wall is formed at least sectionally from a material which has a relative magnetic permeability of less than 4 or less than 2 or less than 1.5.

6. The rotary gripper according to claim 5, wherein the, or a, housing of the rotary gripper exhibits a first housing component with which the actuating means engages, and which delimits the receiving space along with the side wall designed as a separate component, wherein on the side of the side wall facing away from the receiving space, a further receiving space which receives the magnetic field sensor is delimited by a second housing component along with the side wall.

7. The rotary gripper according to claim 1, wherein the displacement path runs at an angle of at least 30 or at least 60, in particular perpendicular, to a plane which is formed by the spatial directions or two of the spatial directions, for which components of the magnetic field can be detected by the magnetic field sensor.

8. The rotary gripper according to claim 1, wherein it has a shield or that the housing forms a shield which encloses a sensor region, within which the magnetic field sensor is arranged, in the circumferential direction in relation to the rotational axis and/or which ends the sensor region on a side of the sensor region facing away from the magnet, wherein the shield is formed by a material with a relative magnetic permeability of at least 300.

9. The rotary gripper according to claim 1, wherein at least the, or a, portion of the actuating means is received in the, or a, receiving space formed by the, or a, housing of the rotary gripper, wherein the displacement of the actuating means along the displacement path is limited in such a manner that the magnet is arranged within the receiving space in all displacement positions of the actuating means, wherein the receiving space is limited in the circumferential direction in relation to the rotational axis by the, or a, material which has a relative magnetic permeability of at least 300.

10. The rotary gripper according to claim 1, wherein the processing device is set up, on the one hand, depending on the detected components of the magnetic flux density, to determine a measurement for an amount, either of the magnetic flux density or of the magnetic flux density projected into the plane formed by the spatial directions, and to determine the gripping information depending on this measurement, and/or on the other hand, to determine a ratio of the detected components of the magnetic flux density or two of these components, and to determine the rotational information depending on this ratio.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0043] FIG. 1 an exemplary embodiment of a rotary gripper according to the invention, and

[0044] FIG. 2 data structures relevant to determining the rotational and gripping information.

DETAILED DESCRIPTION OF THE INVENTION

[0045] FIG. 1 shows a rotary gripper 1 with two gripping jaws 2, 3, which, on the one hand, can be displaced in the transverse direction in FIG. 1 in opposite directions to one another, as depicted by arrows 29, 30, in order to perform a gripping movement or to clamp an object between the gripping jaws 2, 3 and, on the other hand, are jointly rotatable about the rotational axis 7. The two degrees of freedom of movement are implemented by a common actuating means 4, which is mounted so as to be linearly displaceable along a displacement path 6 and rotatable about a rotational axis 7 running parallel to the displacement path 6 by a bearing means 5, which is formed by a housing 31 of the rotary gripper 1 in the example.

[0046] The actuating means 4 in this case is coupled with the gripping jaws 2, 3 in such a manner that a displacement of the actuating means 4 along the displacement path 6 lead to a movement of the gripping jaws 2, 3 opposite one another. This is achieved in that the gripping jaws are fastened to the housing 31 by forced guidance 10, which blocks a displacement of the gripping jaws 2, 3 in the vertical direction in FIG. 1. At the same time, the gripping jaws 2, 3 each have a strut which passes through a respective opening 9 in the actuating means 4. The openings 9 in this case extend at an angle to the rotational axis 7 or the displacement path 6, so that a displacement of the actuating means 4 in the vertical direction in FIG. 1 due to the forced guidance 10 and the forced guidance through the opening 9 leads to a movement of the gripping jaws 2, 3 perpendicularly to the rotational axis 7, as depicted by the arrows 29, 30. This coupling also results in a rotation of the actuating means 4 leading to a rotation of the gripping jaws 2, 3 about the rotational axis 7.

[0047] In order firstly to determine rotational information 25 affecting the rotation of the gripping jaws 2, 3, and secondly to determine gripping information 26 affecting the gripping position of the gripping jaws 2, 3, the rotary gripper 1 has a magnet 19, a magnetic field sensor 20, and a processing device 21. The magnetic field sensor 20 and the processing device 21 are supported by a joint printed circuit board 43 in the example. In order to reduce vibrations, it may be advisable for the magnetic field sensor to be clamped between the printed circuit board 42 and the side wall 46, wherein a thermally conductive film, or the like, may also be arranged to balance the tolerance between the side wall 46 and the magnetic field sensor 20. The determination of the aforementioned variables is explained in greater detail with additional reference to FIG. 2.

[0048] The magnet 19 in the example is attached to the end face of the actuating means 4 facing away from the gripping jaws 2, 3, for example adhered there, and has a magnetizing direction 22 which runs at an angle, in the example perpendicular, to the rotational axis 7. At least two components of the magnetic flux density of the magnetic field of the magnet 19 are detected by the magnetic field sensor 20. As has already been explained in the general part, it may under some circumstances be advantageous for a magnetic field sensor 20 to be used, which detects the components for three spatial directions. It is assumed in the example, however, that only two components of the magnetic flux density are detected for spatial directions which are perpendicular to one another and perpendicular to the rotational axis 7.

[0049] As is schematically depicted in FIG. 2, a measurement 27 for the amount by which the magnetic flux density projects into the plane perpendicularly to the rotational axis 7 can be determined from the two components 23, 24 of the magnetic flux density detected in the region of the magnetic field sensor 20. The measurement may directly be the amount that can be calculated as the root of the component squares or, in order to simplify the calculation, only the total of the component squares may be used as the measurement, for example.

[0050] The amount, and therefore the measurement 27, is a good measurement for the distance between the magnet 19 and the magnetic field sensor 20, and therefore for the position of the magnet 19, and therefore of the actuating means 4, along the displacement path 6, and therefore in turn for the gripping position of the gripping jaws 2, 3. It is namely known in the art for the amount of the magnetic flux density at one location to be strictly monotonically dependent on the distance from the field source, in other words, in the rotary gripper 1, on the distance from the magnet 19.

[0051] If the amount should be determined from components of the magnetic flux density, it would generally be necessary for components of the magnetic flux density to be detected for three spatial directions. With the geometry of the rotary gripper 1 as shown, it can be assumed, however, that the field lines of the magnet 19 in the region of the magnetic field sensor 20 are roughly perpendicular to the rotational axis, or at least that the angle between the field lines and the plane standing perpendicularly to the rotational axis 7, in which the spatial directions for which components of the magnetic flux density are detected, lie, does not change. Based on this assumption, the amount by which the magnetic flux density projects into the aforementioned plane is scaled, as with the overall amount of the magnetic flux density, so that this amount of the projected magnetic flux density, or the measurement 27 for this amount, represents a good measurement for the gripping information 26, which can therefore be determined with the help of a look-up table, for example, or a previously determined analytical relationship, directly from the measurement 27 for the amount.

[0052] On the other hand, a rotation of the actuating means 4 about the rotational axis 7 means that only the direction of the field lines, in which they pass through the magnetic field sensor 20, changes. Consequently, the relationship 28 of the two detected components 23, 24 corresponds to the tangent of the rotary angle of the actuating means 4 about the rotational axis 7, with which the rotational information 25 can be directly determined from this.

[0053] The integration of the magnet 19 and of the magnetic field sensor 20 in the rotary gripper 1, as described, means that no further separate components are needed, in order to determine the rotational information 25 and the gripping information 26, as a result of which the assembly of machines or systems which include the rotary gripper 1 can be made substantially easier. At the same time, the housing 31 of the rotary gripper 1 can also be used, in order to shield from potentially interfering external magnetic fields, as a result of which a robust detection of the rotational information 25 and the gripping information 26 is possible, even in usage situations in which strong leakage fields occur, for example when used in the region of linear motors. Various formulations for using the rotational information 25 and the gripping information 26 have already been explained in the general section.

[0054] In the example shown, the movement and rotation of the actuating means 4 takes place pneumatically. The end of the actuating means 4 facing away from the gripping jaws 2, 3 is arranged in a receiving space 32 or a pressure chamber, which is jointly delimited by the side wall 46 and the housing components 33, 34. This pressure chamber is divided into two partial chambers by the actuating means 4, which has a piston-like design, and these partial chambers can be exposed to pressure from a compressed air channel 11, 12 in each case. Exposure to pressure from the compressed air channel 11 means that the actuating means 4 can be displaced downwardly in the figure, and exposure to compressed air from the compressed air channel 12 means it can be displaced upwardly in the figure. Sealing means, which are not depicted for reasons of transparency, are typically arranged between the actuating means 4 and the side walls formed by the housing component 33. Further sealing means, which are typically arranged between different components, are also not depicted in FIG. 1 for reasons of transparency, since the design of the seals is not relevant to the essence of the invention.

[0055] The rotation of the actuating means 4 is likewise pneumatically actuated. The housing component 34 forms a further pressure chamber 16 for this purpose, in which a piston is mounted displaceably. Through exposure to pressure from the compressed air channels 13, 14, the piston 15 in the figure can be upwardly or downwardly displaced.

[0056] The piston 15 has a projection 17 which engages with a thread 18 of the actuating means 4, as a result of which a displacement of the piston 15 leads to a rotation of the actuating means 4. The piston 15 is secured to prevent rotation in this case by the guide means which is not shown.

[0057] The end of the actuating means 4 facing away from the gripping jaws 2, 3 is formed from a material 39 which has a low magnetic permeability, for example brass. In this way, it is possible to prevent the field lines of the magnet 19 from being conducted by the actuating means 4 to the housing component 33, which, in the case of the embodiment of the housing components 33, 35 made of ferromagnetic material, as explained later, would result in a large part of the field being guided past the magnetic field sensor 20. In order to be able to form the lower portion of the actuating means 4 in the figure from another material, the actuating means 4 is formed from two partial elements 36, 37 which are connected via a screw connection 38.

[0058] As has already been explained in the general section, it is advantageous, particularly with an embodiment of the receiving space 32 for the upper end of the actuating means 4 in the figure as a pressure chamber for pneumatic actuation, for the magnetic field sensor 20 to be arranged outside this receiving space 32. The magnetic field sensor in the example is therefore separated by the side wall 46 from the receiving space 32. Nevertheless, in order to enable there to be a substantially unimpeded detection of the magnetic field of the magnet 19 by the magnetic field sensor 20, the side wall 46 is formed from a material with a relative magnetic permeability close to one. The side wall 46 in the example is made of aluminum.

[0059] Through the housing component 35, a further receiving space 40 or sensor region 41 is jointly delimited with the side wall 46, which receives the magnetic field sensor 20. The housing component 35 is formed from a ferromagnetic material, for example from steel, and therefore acts as a shield 42 which, on the one hand, encloses the sensor region in the circumferential direction in relation to the rotational axis 7 and, on the other hand, ends at the side facing away from the magnet 19.

[0060] In order to avoid interference of the field lines in the region of the magnetic field sensor it is advantageous in this case for a certain minimum distance 44 to be observed between the portion of the housing 31, or the housing component 35, facing away from the magnet 19 and the magnetic field sensor 20. The minimum distance 44 should not be much smaller than the maximum possible distance between the magnetic field sensor 20 and the magnet 19 within the displacement path 6.

[0061] The housing component 33 is preferably also formed from a ferromagnetic material and therefore acts as a shield 42 in the region in which the magnet 19 is displaceable.

[0062] The housing 31, or the housing components 33, 35, therefore simultaneously act as a shield 42, 45, as a result of which the rotational information 25 and the gripping information 26 can be detected with a high degree of accuracy, even in the presence of interfering extraneous fields in the region of the rotary gripper 1.

[0063] While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.