GRIPPING OR CLAMPING DEVICE WITH MAGNETIC POSITION DETECTION

Description

[0001] The present invention relates to a gripping or clamping device comprising a housing with a clamping guide and at least one clamping jaw movable in this clamping guide, wherein a position sensor for detecting a position of the at least one clamping jaw is assigned to the housing, wherein a magnetic coding is assigned to the at least one clamping jaw, which has at least the length of a clamping stroke of the at least one clamping jaw and has magnetically coded markings over this length, which can be read out by means of a position sensor in the form of a magnetic sensor assigned to the housing.

[0002] Such a gripping or clamping device is already known from DE 100 26 196 A1. Reference is also made to US 2002 / 190710 A1 and US 11,421,975 B2.

[0003] Furthermore, DE 10 2021 122 975 A1 is previously known. It provides that a measuring chamfer is incorporated into a clamping jaw, which is scanned using a proximity sensor. Depending on the distance of the proximity sensor from a section of the measuring chamfer within its field of view, the position of the clamping jaw can be determined because, as the clamping jaw is moved, the sensor's field of view slides along the measuring chamfer.

[0004] However, this solution has some disadvantages. First, proximity sensors are optical sensors, which are relatively expensive. Furthermore, a certain distance to the reference surface, from which the distance is measured, must be maintained to prevent contamination. A spacer sleeve is used for this purpose, through which the optical measurement of the angle of inclination is taken.

[0005] Less susceptible to contamination but comparatively expensive is the subject of DE 10 2021 121 686 A1, in which an electric field is generated using a coil, which is detuned by the movement of the clamping element and whose detuning is evaluated and the distance is thereby determined.

[0006] An older approach involves measuring the feed rate and, starting from a given position, determining how long the machine traveled in that direction to calculate its position. However, this solution is inaccurate, requiring repeated reference runs to the initial position to achieve the most accurate position determination.

[0007] Based on this prior art, the present invention aims to create a gripping or clamping device that is insensitive to contamination, can be purchased cost-effectively, and enables precise position determination.

[0008] This problem is solved by a gripping or clamping device according to the features of independent claim 1. Useful embodiments of such a device can be found in the subsequent dependent claims.

[0009] The device provided is a gripping or clamping device comprising a housing with a clamping guide and at least one clamping jaw movable in this clamping guide, wherein the housing is associated with a position sensor for detecting the position of the at least one clamping jaw. According to the invention, this device is characterized in that the at least one clamping jaw is assigned a magnetic coding which has at least the length of a clamping stroke of the at least one clamping jaw and has magnetically coded markings over this length, which can be read by means of a position sensor in the form of a magnetic sensor associated with the housing.

[0010] By magnetically detecting the position based on the relative displacement between the magnetic coding on the clamping jaw and the magnetic sensor in the housing, the position sensor can be designed to be very compact. While not necessary, it is possible to maintain a larger distance between the magnetic coding and the magnetic sensor. As the clamping jaw with the magnetic coding moves across the magnetic sensor, the sensor detects the changing markings within the coding, and the position of the clamping jaw can be deduced through signal analysis. The signal from the magnetic sensor can be processed in an evaluation circuit on the magnetic sensor itself, on a sensor board, on the main board of the gripping or clamping device, or in an external control unit connected via a terminal on a terminal board.

[0011] In a specific embodiment, the magnetic coding can be applied to a plastic strip and this strip connected, preferably glued, to the at least one clamping jaw. This makes it possible to use pre-made, magnetically coded plastic strips and to keep the manufacturing costs of the position sensor as low as possible. For defined attachment and prior damage-free storage, the magnetically coded plastic strip can be applied to a steel strip, which is then attached to the at least one clamping jaw.

[0012] To ensure backlash-free guidance of the clamping jaw in the clamping guide, it can be advantageous for at least one clamping jaw to have a recess for receiving the steel band. A correctly cut, magnetically coded plastic band can then be inserted into this recess along with the steel band, preferably glued in place.

[0013] During the initial commissioning of the position sensor, a reference run of at least one clamping jaw will be required after the magnetic coding has been positioned. The end positions are approached, and upon reaching these positions, the signals of the coding detected by the magnetic sensor are read out. In a preferred embodiment, the magnetic coding can be absolute, meaning that each magnetically coded mark in a longitudinal direction of the coding is uniquely identifiable by the magnetic sensor. This allows the magnetic sensor to determine, based on the signal at a specific point in the coding, how far the clamping jaw is open, or its exact position.

[0014] The alternative, but less preferred, solution is incremental coding, in which identical, recurring markers are placed along one longitudinal direction of the magnetic coding. With this method, a reference run may be necessary after decommissioning, as the individual markers can only be counted as the vehicle passes by, but not individually identified. Since counting is only meaningful from a specific end position, such incremental coding is simpler but also suffers from the aforementioned disadvantage.

[0015] It is designed that the magnetic coding is located on the underside of at least one clamping jaw, and the magnetic sensor is positioned below the clamping guide opposite at least one clamping jaw. This places the coding and magnetic sensor in a defined relative position, protecting the coding from external influences. Nevertheless, the clamping jaws can move freely between their end positions. An externally protruding solution, as found in the prior art, is therefore unnecessary. Instead, this design allows for a particularly compact device.

[0016] If the clamping device has not just one but several clamping jaws, these jaws can also have multiple magnetic codes. In the simplest solution, each code is assigned its own magnetic sensor. However, in a more advanced embodiment, several adjacent codes can be read simultaneously by a single magnetic sensor. This allows for redundant evaluation of multiple codes, so that in the event of minor deviations, an average can be determined between the positions calculated from the two codes.

[0017] However, it is particularly preferred that, when several clamping jaws are provided, they are synchronized with each other by means of a mechanical toothing. In such a case, it is only necessary that a magnetic coding is provided on only one clamping jaw. If one clamping jaw is driven by a motor, the toothing allows at least one other clamping jaw to be moved in the opposite direction, or generally in the same manner, towards or away from a workpiece without any deviation in its path.

[0018] The invention described above will be explained in more detail below using an exemplary embodiment.

[0019] They show Figure 1 shows a gripping or clamping device with two opposing clamping jaws in perspective view; Figure 2 shows the gripping or clamping device according to Figure 1 in a lateral cross-sectional view, as well as Figure 3, the gripping or clamping device according to Figure 2in a longitudinal section view as in Figure 2 displayed.

[0020] Figure 1Figure 1 shows a gripping or clamping device 1, which can be used, for example, on a robot gripper of a machine tool. The device 1 is enclosed by a housing 2 in which a clamping guide 8 is provided. Two clamping jaws 9 and 10 are provided in this clamping guide 8 and are movable along it. The clamping guide 8 is formed in the form of a T-shaped undercut groove, which is integrated into the housing 2 from a top surface. Each clamping jaw 9 and 10 is assigned a half-T for guidance, with these guides running past each other in such a way that the clamping fingers attached to them can move towards each other over a flat surface. The adjustment of the clamping jaws 9 and 10 towards and away from each other is carried out by an electric motor, whereby electrical energy can be supplied, control commands can be sent, and measured values ​​can be transmitted to a control unit via a connection 5.

[0021] As in Figure 2As becomes clear, connection 5 is connected via a terminal board 4 to a main board 3, where the control commands from the control unit (not shown here) are generated into control commands for a drive 13. The drive 13 actuates the two clamping jaws 9 and 10 via a gear 11, which are thus necessarily operated synchronously with each other. Therefore, it is sufficient that only the first clamping jaw 9 is assigned a magnetic code 12 in the form of a plastic strip, which is affixed to the underside of the first clamping jaw 9, facing a magnetic sensor 7 on a sensor board 6.As the clamping jaw 9 is moved towards the clamping guide 8 via the magnetic sensor 7, the magnetic sensor 7 reads the magnetic code 12 and, in the case of an absolute code, can read the position of the first clamping jaw 9 relative to the housing 2 at each individual mark. From this, the position of the second clamping jaw 10 can be determined analogously due to the toothing 11. The magnetic sensor 7 is mounted on the sensor board 6 inside the housing 2 of the device in [location missing]. Figure 3 shown again. The sensor board 6 is located off-center in the housing 2, so that the magnetic sensor 7 can optimally read the magnetic coding 12 which is attached to only one clamping jaw 9.

[0022] The above description thus describes a gripping or clamping device which is insensitive to contamination, can be purchased cost-effectively and enables precise position determination. REFERENCE MARK LIST

[0023] 1 Gripping or clamping device 2 Housing 3 Main board 4 Connection board 5 Connection 6 Sensor board 7 Magnetic sensor 8 Clamping guide 9 First clamping jaw 10 Second clamping jaw 11 Gearing 12 Magnetic coding 13 Drive

Claims

1. Clamping or gripping device comprising a housing (2) with a clamping guide (8) and at least one clamping jaw (9, 10) movable in this clamping guide (8), wherein a position sensor for detecting a position of the at least one clamping jaw (9, 10) is associated with the housing (2), wherein the at least one clamping jaw (9, 10) has a magnetic coding (12) associated with it, which has at least the length of a clamping stroke of the at least one clamping jaw (9, 10) and has magnetically coded markings over this length, which can be read out by means of a position sensor in the form of a magnetic sensor (7) assigned to the housing (2), characterised in that the magnetic coding (12) is arranged on the underside of the at least one clamping jaw (9, 10), and the magnetic sensor (7) is arranged below the clamping guide (8) opposite the at least one clamping jaw (9, 10).

2. Gripping or clamping device according to claim 1, characterised in that the magnetic coding (12) is applied to a plastic strip and this is connected, preferably glued, to the at least one clamping jaw (9, 10).

3. Gripping or clamping device according to claim 2, characterised in that the magnetically coded plastic strip is applied to a steel strip which is attached to the at least one clamping jaw (9, 10).

4. Gripping or clamping device according to claim 3, characterised in that the at least one clamping jaw (9, 10) has a recess for receiving the steel strip.

5. Gripping or clamping device according to one of the preceding claims, characterised in that the magnetic coding (12) is an absolute coding in which each magnetically coded marking can be uniquely identified by the magnetic sensor (7) in a longitudinal direction of the coding (12).

6. Gripping or clamping device according to one of claims 1 to 4, characterised in that the magnetic coding (12) comprises an incremental coding in which recurring, identical markings are set in a longitudinal direction of the magnetic coding (12).

7. Gripping or clamping device according to one of the preceding claims, characterised in that several clamping jaws (9, 10) are provided and have several magnetic codings (12).

8. Gripping or clamping device according to claim 7, characterised in that a plurality of magnetic codes (12) can be read simultaneously by a common magnetic sensor (7).

9. Gripping or clamping device according to one of claims 1 to 6, characterised in that several clamping jaws (9, 10) are provided, which are synchronised with each other by means of a mechanical interlocking mechanism (11), and a magnetic code (12) is provided on only one clamping jaw (9, 10).