DREHGREIFER

Description

[0001] The invention relates to a rotary gripper with two gripping jaws and an actuating means which is mounted by a bearing means, which is formed in particular by a housing, so as to be linearly displaceable along a displacement path and rotatable about a rotation axis running parallel to the displacement path, wherein the actuating means is movement-coupled to the gripping jaws in such a way that, when the actuating means is displaced along the displacement path, the gripping jaws are displaced and / or pivoted in mutually opposite directions in order to assume different gripping positions, and that a rotation of the actuating means about the rotation axis leads to a common rotation of the gripping jaws about the rotation axis.

[0002] Such rotary grippers, which are used, for example, to grip and rotate components in production or assembly processes, are well known per se. The applicant, for example, offers rotary grippers with the model designations DG 16 and DG 20. The use of a common actuating means for both degrees of freedom of movement enables a particularly compact design. Models currently commonly available on the market are generally pneumatically actuated. In principle, however, other actuators, such as direct electro-motor actuation or hydraulic actuation, can also be used. DE202018006092U1 also discloses a linear, gripping, clamping, rotating, or pivoting device with a microprocessor, a base housing, and at least two sensors (e.g., magnetic field, acceleration, and / or gyro sensors), wherein the microprocessor is designed to merge output signals from the at least two sensors into one signal.

[0003] When operating such rotary grippers, it is often desirable to monitor the rotation and / or gripping movement. This may be necessary, for example, to achieve desired gripping or rotational positions with greater accuracy using a control loop, to validate the function of the rotary gripper (e.g., to detect a blockage in the rotation or gripping movement), and / or to control downstream or upstream components to synchronize them with the gripping or rotational movements.

[0004] Until now, separate sensors have been used to record the two degrees of freedom, i.e., the gripping and the rotary movement. It is known to use magnetic field sensors for both degrees of freedom. These sensors are inserted as separate components into so-called C-slots on the outside of the housing of the rotary gripper and fixed there. This approach requires improvement for several reasons: Firstly, the correct positioning of the respective sensor in the respective slot is highly relevant for measurement accuracy, so that arranging separate sensors when setting up a system in the field that includes a rotary gripper is relatively complex. In addition, the arrangement on the outside of the housing makes the sensors relatively susceptible to interfering external fields, so that, for example, complex additional shielding must be installed compared to linear drives, which are often used together with rotary grippers.In addition, the sensors used so far are relatively expensive.

[0005] The invention is therefore based on the object of providing an improved approach for detecting the gripping and rotating movement of a rotary gripper, wherein in particular the assembly effort and the susceptibility to failure are to be reduced and additional costs for detecting the aforementioned variables are to be kept to a minimum.

[0006] The object is achieved according to the invention by a rotary gripper of the type mentioned at the outset, 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 way that a magnetization direction runs at an angle, in particular perpendicular, to the axis of rotation, wherein the magnetic field sensor is arranged in a stationary manner with respect to the bearing means in such a way 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 to determine, as a function of the detected components of the magnetic flux density, rotation information relating to a rotation angle of the common rotation of the gripping jaws and gripping information relating to the gripping position.

[0007] Due to the angled or, in particular, perpendicular course of the magnetization direction to the rotation axis and the detection of components of the magnetic flux density for two spatial directions, a distinction can be made between a displacement of the magnet relative to the magnetic field sensor and thus the bearing means or the housing and a rotation around the rotation axis. While a rotation of the magnet and thus the actuating means and the gripping jaws leads to a change in the field direction, which, for example, changes the relationship between the detected components, a displacement of the magnet and thus the actuating means and thus a gripping movement of the gripping jaws leads to a change in the distance between the magnetic field sensor and the magnet, causing the detected components to rise or fall uniformly.

[0008] By measuring the two components, the degrees of freedom of movement can be separated, thus providing both rotational information and gripping information, even though only a single magnet is used. Furthermore, since magnetic sensors capable of detecting multiple field components are relatively inexpensive and compact, the rotary gripper according to the invention can be manufactured at relatively low cost, and the detection of rotational information and gripping information can be implemented with minimal space requirements.

[0009] An example of such a magnetic field sensor is the MLX90395 component from Melexis, which is also available as an SMD component and can even detect components for three mutually perpendicular spatial directions of the magnetic field. When using this sensor, it has proven advantageous to select the field strength of the magnet and the minimum and maximum distances between the magnet and the magnetic field sensor along the displacement path such that a maximum field strength of approximately 45 mT and a minimum field strength of approximately 12 mT occur at the sensor. However, since a variety of different magnetic field sensors with different properties are now available that can detect two or three components of the magnetic flux density, other field strength ranges can also be used as needed.

[0010] It can be advantageous to record and evaluate components of the magnetic field strength for three spatial directions, as this allows a robust distinction to be made between a change in the direction of the field line and a scaling of the field due to a change in distance. Since the described rotary gripper preferably restricts the movement of the actuating means and thus of the magnet to exactly two degrees of freedom, namely the rotational movement around the rotation axis and the displacement along the displacement path, preliminary tests have shown it to be sufficient to evaluate only two components for spatial directions at an angle to one another.

[0011] In particular, two mutually perpendicular spatial directions, both perpendicular to the rotation axis, are considered. When considering components for only two spatial directions, a loss of detection accuracy only results if the angle of the field lines traversing the magnetic field sensor to the plane spanned by the considered spatial directions, which is particularly perpendicular to the rotation axis, changes significantly during the movement of the actuating means. However, in the configuration explained in more detail below, this is only the case if the magnet is brought very close to the magnetic field sensor, which is not the case in typical setups.

[0012] The described procedure makes it possible to integrate the components required for rotation and gripping detection, namely the magnet and the magnetic field sensor, into the rotary gripper during its manufacture, particularly into its housing. This avoids the complex arrangement of additional sensors described above, and separate shielding is typically not required, as the magnetic field sensor is usually already sufficiently shielded by the housing of the rotary gripper itself.

[0013] The gripping information and the rotation information can be used to validate a desired movement, for example, to detect a blockage in rotation or gripping or releasing and to issue a warning signal in this case. The warning signal can be issued directly by the rotary gripper itself, for example, visually or acoustically, or standard communication interfaces can be used to report the corresponding information, for example, to a central control device of a machine that includes the rotary gripper.

[0014] In addition or alternatively, the gripping information or rotation information can also be used for control purposes, for example, to enable more precise rotation and / or gripping movements, and / or to control upstream or downstream devices, as already discussed at the beginning. Based on the gripping information, it can also be determined, for example, whether an object has been gripped correctly, since in this case the gripper jaws are held at a certain distance from each other, whereas when the gripper passes the object, the gripper jaws are moved significantly closer together.

[0015] The gripping information and the rotation information can, for example, be recorded repeatedly during a movement of the rotary gripper in order to monitor the entire movement path. The recorded components or the result, i.e. the gripping or rotation information, can also be averaged over several measurements in order to reduce interference. In this case, it may be expedient to only monitor the reached end positions at which the gripper jaws are located, since averaging during movement would result in the current state not being accurately reflected. Averaging can be particularly advantageous if the measurement of the components of the magnetic flux density provided by the magnet itself is impaired due to relatively poor shielding of the magnetic field sensor against external interference fields or due to strong external interference fields.

[0016] To the extent that alignments are described as parallel or perpendicular, tolerance-related deviations are possible, whereby a permissible deviation can in particular be less than 2°, less than 1° or less than 0.5°.

[0017] The processing device can, for example, be integrated into a sensor module implementing the magnetic field sensor, such as an IC, or it can be arranged as a separate component within or on the housing of the rotary gripper, for example, on a circuit board that also carries the magnetic field sensor. Alternatively, the processing device can also be arranged at a distance from the rotary gripper or its housing. In particular, it can also be used to control or monitor other components of a machine that includes the rotary gripper, such as motors, other rotary grippers, etc.

[0018] The magnet can be glued to the actuating element. Alternatively, it could also be attached by overmolding, hot-staking, or screwing. The actuating element can, in particular, be rod- or cylindrical-shaped.

[0019] The actuating means can extend from an end coupled to the gripping jaws in the direction of the displacement path to an end facing away from the gripping jaws, wherein the magnet is arranged at the end of the actuating means facing away from the gripping jaws, and in particular is arranged on an end face of the actuating means facing away from the gripping jaws. This arrangement is particularly advantageous if the magnetic field sensor is arranged on the side of the actuating means facing away from the gripping jaws. Such an arrangement of the magnetic field sensor can be advantageous because in this case, there is no installation space conflict with the actuators used to move the actuating means, for example with pneumatic chambers or coupling means for coupling to an electromechanical actuator. In particular, a disk-shaped magnet can be used whose magnetization direction lies in the plane of its main surfaces.Alternatively, a bar magnet can be used, the poles of which are preferably located in a plane perpendicular to the axis of rotation.

[0020] The actuating means can be formed, at least at its end facing away from the gripping jaws, from a material that has a relative magnetic permeability of less than 4, or less than 2, or less than 1.5. A sufficiently low magnetic permeability in this region can ensure that the field guidance of the magnet is little influenced, even if the material at least partially surrounds the magnet laterally. The use of material with low permeability in this region is particularly expedient when the actuating means is surrounded at its end by a housing or, in general, a shield with higher magnetic permeability, as will be explained later. If, in this case, the end of the actuating means also had a high magnetic permeability, the field lines of the magnet would be guided directly to this housing or shield.However, by using material with low magnetic permeability in the said region, an area within such a housing or shield that accommodates the magnet and the magnetic field sensor can enable essentially undisturbed field conduction between these components.

[0021] In particular, the material can be only weakly paramagnetic or even weakly diamagnetic. For example, the relative magnetic permeability can be between 0.9 and 1.1, or the deviation from a relative magnetic permeability of 1 can even be less than 10 -3 or 10 -4 . Suitable materials include brass, which is typically weakly diamagnetic depending on the specific alloy, or aluminum, which is weakly paramagnetic.

[0022] The magnetic field sensor can be 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. In particular, the magnetic field sensor can be offset from the magnet in the direction of the displacement path. The distance of the offset obviously depends on the displacement position of the actuating means along the displacement path, but this is preferably limited in such a way that contact between the magnet and the magnetic field sensor is avoided.

[0023] If the magnetization direction of the magnet is essentially perpendicular to the displacement path, the field lines in the area of ​​the magnetic field sensor will be essentially perpendicular to the rotation axis, assuming a moderate or at least approximately rotationally symmetrical field influence from the other components of the rotary gripper, and the distance between the magnetic field sensor and the magnet is not too small. In this case, for example, it is sufficient to detect only two components of the magnetic flux density perpendicular to the rotation axis to determine the rotation information and the gripping information with high accuracy.

[0024] At least a section of the actuating means can be accommodated 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 in sections from a material that has a relative magnetic permeability of less than 4 or less than 2 or less than 1.5. As already explained above for the material of the end of the actuating means, the relative magnetic permeability can in particular deviate only slightly from 1, wherein the above-mentioned limits can also be applied here. For example, the side wall can be formed from aluminum or alternatively from brass.

[0025] The use of the side wall to separate the magnetic field sensor from the actuating means or its receiving space is particularly expedient when the displacement of the actuating means is pneumatically actuated. For example, the receiving space can form a pressure chamber which is divided into two sub-chambers by a section of the actuating means in the manner of a piston. By pressurizing these sub-chambers, the actuating means can thus be pneumatically displaced in order to displace or pivot the gripping jaws. On the one hand, the arrangement of the magnetic field sensor outside of such a pressure chamber can avoid mechanical stress on the magnetic field sensor or on the electrical components connected to it, which can occur during sudden pressure changes or the resulting turbulence.On the other hand, the arrangement of the magnetic field sensor outside the pressure chamber makes it easier to seal the pressure chamber, since no or at least fewer electrical connection cables have to be led into the pressure chamber.

[0026] The side wall can, for example, have a recess on its side facing away from the receiving space, into which the magnetic field sensor engages or is inserted. For example, the magnetic field sensor can be arranged on a side of a circuit board facing the side wall and protrude from this in the direction of the side wall. The magnetic field sensor can be supported on the side wall in order to prevent or minimize vibrations of the magnetic field sensor with respect to the side wall or the housing or the bearing means. For example, the thermal conductivity sensor can be clamped between the side wall and a circuit board, wherein a thermal conductivity film or the like can also be clamped between the side wall and the magnetic field sensor in order to compensate for tolerances.

[0027] The or a housing of the rotary gripper can have a first housing component into which the actuating means engages and which, together with the side wall formed as a separate component, delimits the receiving space. On the side of the side wall facing away from the receiving space, a second housing component, together with the side wall, delimits a further receiving space that accommodates the magnetic field sensor. Due to the described design, the pressure gripper can be assembled with relatively little effort. In addition, by appropriately selecting the material for the housing components, in particular by using ferromagnetic materials, robust shielding of the magnetic field sensor against external fields can be achieved.

[0028] The displacement path can extend at an angle of at least 30° or at least 60°, in particular perpendicular, to a plane spanned by the spatial directions or second spatial directions for which components of the magnetic field can be detected by the magnetic field sensor. By extending the displacement path as perpendicular as possible to said plane, the sensitivity of the detection can be maximized. This applies in particular when the magnetization direction of the magnet lies substantially in said plane, i.e., is approximately perpendicular to the rotation axis or forms an angle of at least 30° or at least 60° with it.

[0029] The rotary gripper can have a shield, or the housing can form a shield that encompasses a sensor region within which the magnetic field sensor is arranged in the circumferential direction relative to the rotation axis and / or that closes off the sensor region on a side of the sensor region facing away from the magnet. The shield is formed by a material with a relative magnetic permeability of at least 300. The sensor region can, in particular, correspond to the additional receiving space explained above, which is closed off by the second housing component. This can, in particular, form the explained shield.

[0030] The specified permeability limit means that the shield is ferromagnetic. Preferably, the shielding material used is a material with a higher magnetic permeability, for example, with a relative magnetic permeability of at least 700 or more than 1,000 or more than 10,000. The shielding essentially shields external fields in all directions from which no field detection is intended to detect the field lines of the rotary gripper's magnet. This can significantly reduce the influence of interference sources external to the rotary gripper, such as magnets from linear motors, on the detection of gripping and rotation information.

[0031] To minimize the impact on the path of the magnet's magnetic field lines through the shielding, or to minimize the number of field lines passing the sensor due to the shielding, it is advantageous to maintain a certain minimum distance between the magnetic field sensor and the part of the shielding that encloses the sensor area on the side facing away from the magnet. This minimum distance can be selected so that it is comparable to the maximum possible distance between the magnet and the magnetic field sensor when utilizing the displacement path, for example, at least 20% of this distance, at least 50% of this distance, or at least equal to this distance.

[0032] At least the or a portion of the actuating means can be accommodated 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 such 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 with respect to the axis of rotation by the or a material which has a relative magnetic permeability of at least 300.

[0033] The boundary of the receiving space can be formed, in particular, by the first housing component explained above, which can act as a shield due to the choice of material. The material, like the material of the shield explained above, is a ferromagnetic material, and, as also explained above, a material with an even higher magnetic permeability is preferably used. For example, the shield explained above and the boundary of the receiving space can be formed from the same material. By defining the receiving space with a ferromagnetic material, the entry of external interference fields from the area to the side of the magnet or the displacement path is essentially completely suppressed. The shielding of the magnetic field sensor against interference fields can thus be further improved.

[0034] The processing device of the rotary gripper can be configured to, on the one hand, determine a measure for an amount of either the magnetic flux density or the magnetic flux density projected into the plane spanned by the spatial directions as a function of the detected components of the magnetic flux density and to determine the gripping information as a function of this measure, and / or, on the other hand, to determine a ratio of the detected components of the magnetic flux densities or of two of these components and to determine the rotation information as a function of this ratio.

[0035] As already explained, the gripping movement of the gripper jaws correlates with the position of the actuating element along the displacement path and thus with the distance between the magnet and the magnetic field sensor. Since the magnitude of the magnetic flux density decreases monotonically with the distance between the magnet and the magnetic field sensor, this magnitude is a good measure of the distance.

[0036] If this distance were to be determined for any relative orientation of the magnet and the magnetic field sensor, components of the magnetic flux density would have to be recorded for three spatial directions that do not lie in a single plane. However, in the rotary gripper described above, due to the limited degrees of freedom of movement, it can be assumed, at least approximately, that the angle between the direction of the magnet's field lines and a plane perpendicular to the rotation axis in the area of ​​the magnetic field sensor remains unchanged, at least approximately. Therefore, it may be sufficient to consider components for two spatial directions, which may lie in this plane in particular.

[0037] To calculate the magnitude of the magnetic flux density or the projected magnetic flux density, the square root of the sum of the squares of the components must be calculated. To reduce the computational effort and thus, for example, the processing costs or their energy consumption, the sum of the squares of the components can be used directly as a measure of the magnitude of the magnetic flux density instead of a rather complex square root calculation. This measure or the magnitude can then be converted into the distance or gripping position, for example, using a look-up table or by calculating an analytical relationship.

[0038] Regarding the determination of the rotation information, we initially assume, for example, that the spatial directions for which the components of the magnetic flux density are recorded are perpendicular to each other and lie in a plane perpendicular to the rotation axis. In this case, the tangent of the angle of rotation corresponds to the ratio of the components. The angle of rotation can thus be easily calculated from this ratio or, for example, determined using a look-up table.

[0039] This calculation can be applied accordingly to the detection of components in an oblique coordinate system or for spatial directions that are oblique to the specified plane. However, in general, a rotation angle can also be determined directly from the ratio in these cases, for example, using a suitable look-up table.

[0040] Further advantages and details of the invention will become apparent from the following exemplary embodiments and the accompanying drawings. These schematically show: Fig. 1 shows an embodiment of a rotary gripper according to the invention, and Fig. 2 shows data structures relevant for determining the rotation and gripping information.

[0041] Fig. 1 shows a rotary gripper 1 with two gripping jaws 2, 3, which on the one hand are arranged in the transverse direction Fig. 1 are displaceable in mutually opposite directions, as shown by the arrows 29, 30, in order to carry out a gripping movement or to clamp an object between the gripping jaws 2, 3, and on the other hand are rotatable together about the axis of rotation 7. Both degrees of freedom of movement are implemented by a common actuating means 4, which is mounted by a bearing means 5, which in the example is formed by a housing 31 of the rotary gripper 1, so that it can be linearly displaced along a displacement path 6 and rotatable about a rotation axis 7 running parallel to the displacement path 6.

[0042] The actuating means 4 is coupled to the gripping jaws 2, 3 in such a way that a displacement of the actuating means 4 along the displacement path 6 leads to a mutually opposite movement of the gripping jaws 2, 3. This is achieved in that the gripping jaws are fastened to the housing 31 via a positive guide 10, which enables a displacement of the gripping jaws 2, 3 in the vertical direction in Fig. 1 blocked. At the same time, the gripping jaws 2, 3 each have a strut which passes through a respective opening 9 of the actuating means 4. The openings 9 extend at an angle to the rotation 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 positive guide 10 and the positive guide through the opening 9, this leads to a movement of the gripping jaws 2, 3 perpendicular to the rotation axis 7, as shown 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 rotation axis 7.

[0043] In order to determine, on the one hand, rotation information 25 relating to the rotation of the gripping jaws 2, 3 and, on the other hand, gripping information 26 relating to the gripping position of the gripping jaws 2, 3, the rotary gripper 1 comprises a magnet 19, a magnetic field sensor 20 and a processing device 21. The magnetic field sensor 20 and the processing device 21 are carried in the example by a common circuit board 43. To reduce vibrations, it may be expedient to clamp the magnetic field sensor 20 between the circuit board 42 and the side wall 46, wherein, for example, a heat-conducting foil or the like can be arranged between the side wall 46 and the magnetic field sensor 20 to compensate for tolerances. The determination of the above-mentioned variables is carried out with additional reference to Fig. 2 explained in more detail.

[0044] In the example, the magnet 19 is attached to the end face of the actuating means 4 facing away from the gripping jaws 2, 3, for example, glued there, and has a magnetization direction 22 that runs at an angle, in the example perpendicular, to the rotation 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 already explained in the general section, it may be advantageous under certain circumstances to use a magnetic field sensor 20 that detects components for three spatial directions. In the example, however, it is assumed that only two components of the magnetic flux density are detected for spatial directions that are perpendicular to one another and perpendicular to the rotation axis 7.

[0045] As in Fig. 2 As shown schematically, a measure 27 for the magnitude of the projection of the magnetic flux density into the plane perpendicular to the rotation axis 7 can be determined from the two detected components 23, 24 of the magnetic flux density in the region of the magnetic field sensor 20. The measure can be directly the magnitude that can be calculated as the root of the component squares, or, to simplify the calculation, only the sum of the component squares can be used as the measure.

[0046] The amount and thus the dimension 27 is a good measure of the distance between magnet 19 and magnetic field sensor 20 and thus of the position of the magnet 19 and thus of the actuating means 4 along the displacement path 6 and thus in turn of the gripping position of the gripping jaws 2, 3. It is known that the amount of the magnetic flux density at a location depends strictly monotonically on the distance to the field source, i.e. in the rotary gripper 1 on the distance to the magnet 19.

[0047] If the magnitude is to be determined from components of the magnetic flux density, it would generally be necessary to record components of the magnetic flux density for three spatial directions. However, given the geometry of the rotary gripper 1 shown, it can be assumed that the field lines of the magnet 19 in the area of ​​the magnetic field sensor 20 are approximately perpendicular to the rotation axis, or at least that the angle between the field lines and the plane perpendicular to the rotation axis 7, in which the spatial directions for which the components of the magnetic flux density are recorded, do not change.Under this assumption, the amount of the magnetic flux density projected into the plane mentioned scales in the same way as the total amount of the magnetic flux density, so that this amount of the projected magnetic flux density or the measure 27 for this amount also represents a good measure for the gripping information 26, which can thus be determined directly from the measure 27 for the amount, for example with the aid of a look-up table or a previously determined analytical relationship.

[0048] A rotation of the actuating means 4 about the rotation axis 7, on the other hand, results in a change only in the direction of the field lines passing through the magnetic field sensor 20. Thus, the ratio 28 of the two detected components 23, 24 corresponds to the tangent of the angle of rotation of the actuating means 4 about the rotation axis 7, from which the rotation information 25 can be directly determined.

[0049] Due to the described integration of the magnet 19 and the magnetic field sensor 20 in the rotary gripper 1, separate components are no longer required to determine the rotation information 25 and the gripping information 26, which can significantly simplify the construction of machines or systems that include the rotary gripper 1. At the same time, the housing 31 of the rotary gripper 1 can also be used to shield potentially disruptive external magnetic fields, thus enabling robust detection of the rotation information 25 and the gripping information 26 even in usage situations where strong stray fields occur, for example, when used in the area of ​​linear motors. Various approaches for utilizing the rotation information 25 and the gripping information 26 have already been explained in the general section.

[0050] In the example shown, the movement and rotation of the actuating means 4 is pneumatic. 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 by the piston-like actuating means 4 into two sub-chambers, which can be pressurized by a respective compressed air channel 11, 12. By pressurizing the compressed air channel 11, the actuating means 4 can thus be displaced downwards in the figure, and by pressurizing the compressed air channel 12, it can be displaced upwards in the figure. Sealing means, which are not shown for reasons of clarity, are typically arranged between the actuating means 4 and the side walls formed by the housing component 33.Other sealants that are typically arranged between different components are also included. Fig. 1 not shown for reasons of clarity, since the design of the seals is not relevant to the core of the invention.

[0051] The rotation of the actuating means 4 is also pneumatically actuated. For this purpose, the housing component 34 forms a further pressure chamber 16 in which a piston 15 is displaceably mounted. By applying pressure to the compressed air channels 13, 14, the piston 15 can be displaced upwards or downwards in the figure. The piston 15 has a projection 17 that engages a thread 18 of the actuating means 4, whereby a displacement of the piston 15 leads to a rotation of the actuating means 4. The piston 15 is secured against rotation by guide means (not shown).

[0052] The end of the actuating means 4 facing away from the gripping jaws 2, 3 is formed from a material 39 with low magnetic permeability, for example, brass. This prevents the field lines of the magnet 19 from being guided through the actuating means 4 to the housing component 33, which, in the case of the housing components 33, 35 made of a ferromagnetic material, which will be explained later, would result in a large portion of the field being guided past the magnetic field sensor 20. In order to be able to form the lower section of the actuating means 4 from a different material in the figure, the actuating means 4 is formed from two sub-elements 36, 37, which are connected via a screw connection 38.

[0053] As already explained in the general section, it is particularly advantageous when the receiving space 32 for the upper end of the actuating means 4 (in the figure) is configured as a pressure chamber for pneumatic actuation to arrange the magnetic field sensor 20 outside this receiving space 32. Therefore, in the example, the magnetic field sensor 20 is separated from the receiving space 32 by the side wall 46. To nevertheless enable essentially unimpaired 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. In the example, the side wall 46 is made of aluminum.

[0054] The housing component 35, together with the side wall 46, defines a further receiving space 40 or sensor area 41, which accommodates the magnetic field sensor 20. The housing component 35 is formed from a ferromagnetic material, for example steel, and thus acts as a shield 42, which, on the one hand, encompasses the sensor area in the circumferential direction with respect to the rotation axis 7 and, on the other hand, closes it off on the side facing away from the magnet 19.

[0055] To avoid interference with the field lines in the area of ​​the magnetic field sensor 20, it is advantageous to maintain a certain minimum distance 44 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.

[0056] Preferably, the housing component 33 is also formed from a ferromagnetic material and thus acts as a shield 42 in the area in which the magnet 19 is displaceable. The housing 31 or the housing components 33, 35 thus simultaneously act as a shield 42, 45, whereby the rotation information 25 and the gripping information 26 can be captured with high accuracy even in the presence of interfering external fields in the area of ​​the rotary gripper 1.

Claims

1. Rotary gripper with two gripping jaws (2, 3) and an actuating means (4) which is mounted by a bearing means (5), in particular formed by a housing (31), such that it can be displaced linearly along the displacement path (6) and can be rotated about a rotational axis (7) which runs parallel to the displacement path (6), wherein the actuation means (4) is movement-coupled to the gripping jaws (2, 3) in such a way that the gripping jaws (2, 3) are displaced and / or pivoted in opposite directions in the case of a displacement of the actuating means (4) along the displacement path (6), in order to assume different gripping positions, and that a rotation of the actuating means (4) about the rotational axis (7) leads to a common rotation of the gripping jaws (2, 3) about the rotational axis (7), characterized in that the rotary gripper (1) has a magnet (19), a magnetic field sensor (20) and a processing device (21), wherein the magnet (19) is attached to the actuating means (4) in such a way that its magnetization direction (22) runs in an angled manner, in particular perpendicularly, with respect to the rotational axis (7), wherein the magnetic field sensor (20) is arranged in a stationary manner with regard to the bearing means (5) in such a way that the magnetic field of the magnet (19) can be detected by the magnetic field sensor (20), wherein the magnetic field sensor (20) is configured to detect components (23, 24) of the magnetic flux density of the magnetic field for at least two spatial directions, wherein the processing device (21) is configured to determine a rotational information item (25), relating to a rotary angle of the common rotation of the gripping jaws (2, 3), and a gripping information item (26), relating to the gripping position, in a manner which is dependent on the detected components (23, 24) of the magnetic flux density.

2. Rotary gripper according to Claim 1, characterized in that the actuating means (4) extends from an end, coupled to the gripping jaws (2, 3), in the direction of the displacement path (6) as far as an end which faces away from the gripping jaws (2, 3), wherein the magnet (19) is arranged at that end of the actuating means (4) which faces away from the gripping jaws (2, 3), and is arranged, in particular, on an end face, facing away from the gripping jaws (2, 3), of the actuating means (4).

3. Rotary gripper according to Claim 2, characterized in that, at least at its end which faces away from the gripping jaws, the actuating means (4) is formed from a material (39) which has a relative magnetic permeability of less than 4 or less than 2 or less than 1b.5.

4. Rotary gripper according to one of the preceding claims, characterized in that the magnetic field sensor (20) is arranged spaced apart from the actuating means (4) on a side, facing away from the gripping jaws (2, 3), of the actuating means (4) and in the direction of the displacement path (6).

5. Rotary gripper according to one of the preceding claims, characterized in that at least one portion of the actuating means (4) is received in a receiving space (32) which is formed by the or a housing (31) of the rotary gripper (1), wherein the magnetic field sensor (20) is arranged on a side, facing away from the receiving space (32), of a side wall (46) of the receiving space (32), wherein at least portions of the side wall (46) are formed from a material which has a relative magnetic permeability of less than 4 or less than 2 or less than 1.5.

6. Rotary gripper according to Claim 5, characterized in that the or a housing (31) of the rotary gripper (1) has a first housing component (33), into which the actuating means (4) reaches and which, together with the side wall (46) which is configured as a separate component, delimits the receiving space (32), wherein a further receiving space (40) which receives the magnetic field sensor (20) is delimited on that side of the side wall (46) which faces away from the receiving space (32) by a second housing component (35) together with the side wall (46).

7. Rotary gripper according to one of the preceding claims, characterized in that the displacement path (6) runs at an angle of at least 30° at least 60°, in particular perpendicularly, with respect to a plane which is defined by the spatial directions or two of the spatial directions, for which components (23, 24) of the magnetic field can be detected by the magnetic field sensor (20).

8. Rotary gripper according to one of the preceding claims, characterized in that it has a shield (42), or in that the housing (31) configures a shield (42) which reaches in the circumferential direction with regard to the rotational axis (7) around a sensor region (41), within which the magnetic field sensor (20) is arranged, and / or which closes off the sensor region (41) on a side, facing away from the magnet (19), of the sensor region (41), wherein the shield (42) is formed by a material with a relative magnetic permeability of at least 300.

9. Rotary gripper according to one of the preceding claims, characterized in that at least the or a portion of the actuating means (4) is received in the or a receiving space (32) which is formed by the or a housing (31) of the rotary gripper (1), wherein the displacement of the actuating means (4) along the displacement path (6) is limited in such a way that the magnet (19) is arranged within the receiving space (32) in all displacement positions of the actuating means (4), wherein the receiving space (32) is delimited in the circumferential direction with regard to the rotational axis by the or a material which has a relative magnetic permeability of at least 300.

10. Rotary gripper according to one of the preceding claims, characterized in that the processing device (21) is configured firstly to determine a measure (27) for a magnitude either of the magnetic flux density or of the magnetic flux density projected into the plane defined by the spatial directions, in a manner which is dependent on the detected components (23, 24) of the magnetic flux density, and to determine the gripping information item (26) in a manner which is dependent on this measure (27), and / or secondly to determine a ratio (28) of the detected components (23, 24) of the magnetic flux density or of two of these components (23, 24), and to determine the rotational information item (25) in a manner which is dependent on this ratio (28).