Gripping device and method for gripping

Abstract

gripping device comprising at least one holding element (1), wherein the at least one holding element (1) comprises the following: a guide element (2), a plurality of elongated plungers (3a-3h), each elongated in a longitudinal direction, wherein the plungers (3a-3h) are arranged side by side in the guide element (2) with their longitudinal directions parallel to each other and are guided by the guide element (2) in the direction of their longitudinal directions, an insertion detection device (5) with which the reaching of an end position of at least one of the plungers (3a-3h) can be detected, wherein the gripping device also has an actuator (8) with which the at least one holding element (1) can be moved in the direction of the longitudinal axes of the plungers (3a-3h) of this holding element, wherein the actuator (8) is controllable such that it moves the at least one holding element (1) until the insertion detection device (5) detects that at least one of the plungers (3a-3h) of one, several or all of the at least one holding element (1) has reached its end position and, upon detection of this reaching position, terminates the movement of the at least one holding element (1), wherein the at least one retaining element (1) has a rear contact surface which is located less than the length of the plungers (3a-3h) away from a surface of the guide element (2) facing away from the rear contact surface, wherein the insertion detection device (5) is a contact detection device which is configured to detect contact of at least one of the plungers (3a-3h) with the rear contact surface, wherein the actuator (8) is controllable such that the at least one holding element (1) can be moved by it until the contact detection device (5) detects contact between at least one of the plungers (3a-3h) of one, several or all of the at least one holding element (1) and the corresponding rear contact surface, wherein the contact detection device (5) is a resistive plate or resistive film which is configured to change its electrical resistance when touched by at least one of the plungers (3a-3h), wherein the guide element (2) and the rear contact surface are opposite inner walls of a housing.

Description

[0001] The invention relates to a gripping device comprising a holding element with a plurality of elongated plungers, wherein the at least one holding element also comprises an insertion detection device with which the attainment of an end position by at least one of the plungers can be detected. The invention further relates to a method for gripping an object using the gripping device according to the invention.

[0002] The reliable handling of complex components requires a handling system that closely matches the contours of the component. For demanding handling tasks, custom negative templates are ideal, as they precisely replicate the component surface and thus enable safe handling. However, such systems are limited in their variability. Variants with differing contours are difficult to reproduce. For this reason, flexible clamping systems similar to impression-taking nail boards have been developed.

[0003] Such systems are used in machining, where high forces are required, as well as in measuring and handling tasks where low forces are used. To securely hold a gripped component and, if necessary, clamp it with increased holding force, the plunger fields can be locked after impression taking. This locking can be done manually, for example with screws, or automatically, for example with pneumatic cylinders.

[0004] A problem with prior art solutions is the force exerted on the object by the plungers. If the plungers strike a rear stop, for example, in an uncontrolled manner, those plungers that reach the stop during the molding process exert a high force on the object. To prevent this, the molding process would have to be stopped prematurely, which would compromise the secure holding of the object.

[0005] DE 198 02 320 A1 relates to a holding device for workpieces, comprising a clamping jaw with a plurality of clamping pins having a circular cross-section, aligned parallel to one another, laterally abutting each other and individually displaceable in their main extension direction, a frame laterally encompassing the clamping pins and a fixing device for fixing the clamping pins relative to the frame by a lateral fixing force, and a clamping device for applying a clamping force directed towards the workpiece to the clamping jaws, wherein a common translational actuating element is provided for the fixing device and the feed device, wherein gear means translate the force exerted by the actuating element into the fixing force and the clamping force.

[0006] DE 10 2019 126 361 A1 describes a device for supporting a workpiece with a frame, a support field consisting of end faces of a plurality of support pins guided parallel to each other in their main extension directions in the frame and each of which can be pressed in against a restoring force relative to the frame, and a detection device for detecting the relative positions of the support pins of the plurality relative to the frame, wherein the detection device has a light barrier, wherein a light source and a light sensor of the light barrier are opposite each other across the main extension directions of the support pins of the plurality.

[0007] DE 43 39 102 A1 discloses a handling device for the mechanical gripping, holding, moving or similar handling of objects, in particular for handling equipment, wherein a retaining pin guide plate, which is provided with a plurality of closely spaced bores, is connected to a mounting plate and is movable towards the objects to be gripped, in which round or polygonal retaining pins are guided longitudinally and projecting freely downwards, the lower ends of which, tangent to the object, come into frictional engagement and, if necessary, positive engagement with the contour areas of the object by elastic deformation of the retaining pins when approaching, and above the retaining pin guide plate an ejector plate which can be lowered onto it by means of an ejector device.

[0008] US Patent 5,608,206 A describes a device that grasps three-dimensional objects and transmits digital data across the grasped surface, using pneumatically actuated mechanical probes for grasping and optomechanical encoding for data transmission. This optomechanical encoding uses coding tubes with columns of patterned slots and holes to selectively transmit light through synthetic plastic fibers.

[0009] DE 25 01 205 A1 relates to a device for obtaining a scan and for making the scan visible.

[0010] The object of the present invention is therefore to provide a gripping device that enables a secure hold of an object and keeps the forces exerted on the object controllable.

[0011] The problem is solved by the gripping device according to claim 1 and the method for gripping an object according to claim 7. The respective dependent claims specify advantageous embodiments of the gripping device and the method according to the invention.

[0012] The present invention relates to a gripping device with which, for example, an object can be grasped. The gripping device has at least one holding element. Advantageously, the gripping device can have two or more holding elements; however, one holding element is generally sufficient if the object only needs to be shaped in one direction or if a counter element is provided opposite the holding element against which the object can be placed. If two holding elements are provided, they can grip the object from two sides, which are advantageously opposite each other.

[0013] According to the invention, the at least one retaining element comprises a guide element and a plurality of elongated plungers. The direction in which the plungers are elongated shall be referred to here as the longitudinal direction. The plungers can each be, for example, cylindrical, preferably at least partially circular cylindrical. The longitudinal direction can then be coaxial with the cylinder axis.

[0014] According to the invention, the plungers in the guide element are arranged parallel to each other and side by side with their longitudinal directions. The fact that the plungers are arranged side by side means that the projection of one plunger perpendicular to the longitudinal axis onto another plunger lies on the other plunger. Preferably, all plungers are of the same length in their longitudinal direction. In a basic state, in which no object is being formed by the plungers, the ends of the plungers can lie in a common plane on one or both sides. If the plungers are all of the same length, then both ends of the plungers lie in a common plane.

[0015] The guide element directs the plungers along their longitudinal axes. This means that the guide element allows the plungers to move along their longitudinal axes but prevents movement perpendicular to them. Furthermore, the guide element preferably also prevents the plungers from tilting. To achieve this, the plungers pass through the guide element in a plane that is preferably perpendicular to their longitudinal axes. The guide element can, for example, be a perforated plate with one hole per plunger, or a large opening that is filled by the plungers in such a way that they cannot move perpendicular to their longitudinal axes.

[0016] According to the invention, the at least one retaining element also includes an insertion detection device with which the reaching of an end position of at least one of the plungers can be detected. Preferably, the end position for all plungers is a position in which an end of the plunger facing away from the object reaches or intersects a plane that is parallel to the plane in which the plungers penetrate the guide element. Thus, the insertion detection device makes it possible to detect when this plane is reached by one or more of these impacts.

[0017] The gripping device according to the invention also includes an actuator with which the at least one holding element can be moved. The holding element is also movable at least in the direction of the longitudinal axis of the plunger of the corresponding holding element. This allows the actuator to move the holding element towards an object and cause the plunger to create a mold of the object.

[0018] According to the invention, the actuator is controllable such that it moves the at least one holding element until the insertion detection device detects that at least one of the plungers of one, several, or all of the at least one holding element has reached its end position. Upon detection of this, the movement of the at least one holding element can then be stopped. The following cases can be distinguished here. If only one holding element is provided, it should preferably be stopped as soon as a plunger of this holding element reaches its end position.

[0019] For example, if two holding elements are provided that approach the object from opposite sides, it can be advantageous to stop the movement of both holding elements as soon as at least one plunger of at least one of the holding elements reaches its end position. The other holding element will then often be moved far enough towards the object to ensure a secure hold. This design is useful, for instance, if the object cannot be moved by the holding elements. Further movement of the holding element, in which one plunger has reached its end position, would then exert an undesirable force on the object.

[0020] Another possibility is to detect when at least one plunger in each of the holding elements—or, in the more generalized case, in several or all of them—has reached its end position. In this case, the holding elements continue to move as long as a plunger in only one of them has reached its end position. This can then, for example, cause that holding element to move the object. The movement would continue until at least one plunger in another holding element has also reached its corresponding end position. Further movement of the holding elements should then be stopped, as the object can no longer be moved and a force would therefore be exerted on it. On the other hand, in this state, the object is held in the best possible way.

[0021] According to the invention, the at least one retaining element has a rear contact surface located less than the length of the plunger from a surface of the guide element facing away from the rear contact surface. The contact surface is referred to as the contact area because it can be mechanically contacted by the plunger(s). The distance is chosen such that the plungers abut the rear contact surface when they are fully inserted into the guide element or when they are still protruding from the guide element in the direction of the object. The rear contact surface is preferably a flat surface extending perpendicular to the longitudinal direction of the plunger. In this embodiment, the insertion detection device is configured as a contact detection device designed to detect contact between at least one of the plungers and the rear contact surface.The contact detection device can therefore generate a signal as soon as at least one of the plungers touches the rear contact surface. Advantageously, the rear contact surface itself can be a surface of the contact detection device.

[0022] The actuator can then be controlled in such a way that at least one holding element can be moved by it until the contact detection device of one, several or all of the at least one holding element detects contact of at least one plunger with the corresponding rear contact surface.

[0023] It has proven particularly advantageous that the contact detection device is or comprises a resistive plate or resistive film configured to change its resistance upon contact with at least one of the plungers. Thus, if a voltage is applied across the resistive plate or resistive film and, for example, the current through the resistive plate or resistive film is measured, the current changes upon contact of at least one plunger with the resistive plate or resistive film.

[0024] It is advantageous if the contact detection device is flexibly mounted, for example by providing a soft layer, such as a foam layer, between the contact detection device and a wall in front of which it is arranged.

[0025] Advantageously, the length of the plungers is dimensioned such that their length is greater than or equal to the distance between the contact surface and the surface of the guide element facing away from the contact surface, and less than the distance between a wall on which the contact surface is located—for example, a wall on which the contact detection device is mounted, possibly via one or more intermediate layers—and the surface of the guide element facing away from the contact surface. In this way, the plungers reach the contact surface before a grasped object touches the guide element, but the object touches the guide element before the plungers collide with the wall. This prevents damage to the contact detection device.

[0026] The retaining element is designed with a housing, one wall of which serves as a guide element, and the rear contact surface is located on the opposite wall. In this way, the insertion detection device can be protected from external influences.

[0027] The plungers can advantageously be spring-mounted. This allows them to return to a starting position when contact with the object being gripped is lost. Springs can, for example, be arranged between each plunger and a counter-hole plate through which the plungers pass and which lies parallel to the guide element between the guide element and the contact surface.

[0028] In an advantageous embodiment of the invention, the at least one holding element can have a locking device with which the plungers of this holding element can be locked against displacement in their longitudinal direction. This locking device is, for example, controllable so that it releases the plungers while the molding process is in progress and locks the plungers after the movement of the at least one holding element has ceased. This ensures that the object is securely held by the plungers and prevents the plungers from losing contact with the object or being pressed in deeper when the object is moved by the gripping device.

[0029] The locking device can be designed in various ways. In one advantageous embodiment, it can have a pneumatic lifting cylinder that exerts a force on the plungers in a direction perpendicular to their longitudinal directions, thereby creating a mechanical frictional engagement that fixes the plunger assembly in its relative position. In another embodiment, the locking device can, for example, be designed as an eccentric whose axis of rotation is perpendicular to the longitudinal directions of the plungers and which can be rotated about this axis against the plungers, thereby fixing them by means of a mechanical frictional engagement.

[0030] If two retaining elements are provided, it is advantageous if they can be moved towards each other by the actuator in the direction of the longitudinal axes of the plungers. Preferably, the longitudinal axes of the plungers of the two retaining elements run parallel to each other. Advantageously, all longitudinal axes of all plungers of both retaining elements can be parallel to each other. The actuator can advantageously be a pneumatic or hydraulic actuator. As such, it can be controlled by means of at least one valve, which may have a valve control. The valve can then be controlled based on a signal supplied by the insertion detection device. In particular, the valve can be closed when the insertion detection device detects that at least one plunger of one, several, or all retaining elements has reached its end position.

[0031] The invention also provides a method for gripping an object. First, a gripping device, as described above, is positioned such that the object is located in an area where the plungers of the at least one holding element can be moved by the actuator. For example, the gripping device can be moved into this position by a robot arm. The at least one holding element is then moved towards the object by the actuator until the insertion detection device detects that at least one of the plungers of one, several, or all of the holding elements has reached its end position. The actuator then stops the movement of the holding element. After detecting that the end position has been reached and stopping the actuator, the plungers of the holding element can then be locked in place.

[0032] In an advantageous embodiment of the method, after the plungers of the at least one holding element have been locked, the actuator can exert a force that presses the at least one holding element against the object. Unlike in the prior art, however, this force is very well controlled and also acts via all plungers that are in contact with the object.

[0033] The device and method according to the invention enable the object to be gripped in a state where the plungers are depressed as far as possible. This minimizes the bending moments acting on the plungers, since the effective lever arm is as short as possible and the maximum number of plungers are in contact with the object. This allows the object to be gripped particularly securely.

[0034] The invention thus enables process reliability and automation in gripping and handling technology. The plunger's retraction movement can be used for information generation. Component variants with different dimensions can be distinguished, and manual presetting is unnecessary. Different sized components can be gripped with consistent gripping kinematics. The system's span can be controlled, for example, via a microcontroller and does not need to be limited by mechanical stops. The plunger's full retraction also reduces its extension length. By shortening this distance, the entire system is mechanically more stable than a comparable plunger array with a long overhang. The described locking mechanism of the plunger array allows for further clamping force application, as the plungers can no longer retract further. This combines the characteristics of positive and force-fit connections.The clamped component fixation allows for high accelerations during handling without the risk of the component coming loose due to inertia.

[0035] The invention will be explained below using a few figures as examples.

[0036] It shows: Fig. 1 a section through a holding element of a gripping device according to the invention, Fig. 2 a cut as in Fig. 1 shown with plungers displaced by molding, Fig. 3 a circuit of a gripping device according to the invention and Fig. 4 schematically a gripping device according to the invention.

[0037] Fig. Figure 1 shows an example of a holding element 1 of a gripping device according to the invention. The holding element 1 has at least one guide element 2 and a plurality of elongated plungers 3a to 3h, which are elongated. Fig. Figure 1 shows a plane of plungers 3a to 3h. However, in the example shown, further planes of plungers arranged parallel to these plungers can be provided, lying parallel to the plane of the figure above and below it. In this way, a plunger array is created that can span a surface perpendicular to the plane of the figure, for example, a rectangular area. In the example shown, the guide element 2 guides the plungers 3a to 3h in an opening 4 through which the plungers emerge from the retaining element 1. The guide element 2 thus guides the plungers 3a to 3h in the direction of their longitudinal axes.

[0038] In the example shown, the plungers 3a to 3h are cylindrical in shape, with different radii along their longitudinal direction. Here, the plungers 3a to 3h have in Fig. 1. On the left, the plungers have a first radius, followed by a second radius in the middle section to the right, which is larger than the first radius, and finally, in a right-hand section further to the right, a radius that is smaller than the second radius and, in the example shown, equal to the first radius. At their left ends, which come into contact with an object, the plungers taper to a point in the example shown. In the aforementioned middle section, the plungers can also have a rectangular or square cross-section, which can improve the force transmission from the locking device. The plungers can be spring-mounted with springs (not shown).The springs can, for example, rest on the enlarged radius sections of the plungers on one side and on a counter element, for example another perforated plate (not shown), which is parallel to the guide element 2 and through whose holes the plungers pass.

[0039] The retaining element 1 also has an insertion detection device 5, which in the example shown is a contact detection device 5. The contact detection device 5 is configured to detect when at least one of the plungers 3a to 3h reaches an end position. This state is in Fig. Figure 2 shows that the plungers 3a to 3h were displaced by an object (not shown) towards the interior of the holding element 1, so that plunger 3e now touches the contact detection device 5, whose surface forms a rear contact area. Since plunger 3e cannot be displaced further inwards, the object should not exert any further force on the plungers, nor should the plungers exert any further force on the object. This is achieved by controlling the actuator 8 so that it stops the movement of the holding element as soon as the reaching of the end position by at least one of the plungers, in this case plunger 3e, is detected.

[0040] The contact detection device 5 can, for example, be a resistive film which changes its resistance when touched by at least one of the plungers 3a to 3h.

[0041] In the Fig. In the example shown, the guide element 2 and a wall on which the contact detection device is arranged are opposite walls of a common housing in which the plungers 3a to 3h are also arranged.

[0042] The in Fig. The holding element 1 shown also has a locking device 6 with which the plungers 3a to 3h can be locked against displacement in their longitudinal direction. In the example shown, the locking device 6 is a plunger which can exert a force on the plungers 3a to 3h by means of a plunger actuator 7 when it is pressed against the plungers by the plunger actuator 7 in a direction perpendicular to the longitudinal axis of the plungers 3a to 3h. The plunger 6 acts on the plungers 3a to 3h in a region where the radius of the plungers is increased. This causes the plungers 3a to 3h to bear against each other in this region of increased radius, whereby the force exerted by the locking device 6 is transmitted to all plungers 3a to 3h, so that all plungers come into mechanical frictional engagement.

[0043] In the Fig. In the example shown, the interior of the retaining element 1 has two areas: a lower area in which the plungers 3a to 3h are slidable, and an upper area in which the punch actuator 7 and the locking device 6 are arranged. The two areas are connected by an opening through which the locking device 6, i.e., the punch 6, extends.

[0044] Fig. Figure 3 shows an exemplary electrical wiring diagram with a detection unit 31, a microcontroller 32, and a locking device 33. Contact of one or more plungers 3a to 3h with the insertion detection unit 5 or 31 triggers a signal, which in this case is a changed voltage in a permanent 5V circuit. This signal is interpreted by the microcontroller 32 as a switching signal for the locking device 33, which in this case is a pneumatic switching valve, to trigger its release. The system demonstrates the design of a gripper with a double gripper jaw configuration.

[0045] Fig. Figure 4 shows an example of a gripping device according to the invention, which here has two holding elements 1a and 1b. The two holding elements 1a and 1b each have a plunger field 3A and 3B respectively, which are opposite each other. The holding elements 1a and 1b can be arranged as shown in Fig. 1. be designed.

[0046] The gripping device according to Fig. Assembly 4 has an actuator 8 with which the retaining elements 1a, 1b can be moved in the direction of the longitudinal axes of the plungers 3A, 3B of the respective retaining element. The actuator 8 is controllable such that it moves the retaining elements 1a and 1b until the insertion detection device 5 detects that the end position has been reached by at least one of the plungers 3a to 3h of one or both of the retaining elements 1a, 1b. Upon detection of this, the movement by the actuator 8 is then terminated.

[0047] The invention makes it possible to monitor the impression-taking process of an object using the plunger fields 3A and 3B in such a way that the gripping device's range of motion does not need to be mechanically or otherwise preset. The invention enables the integration of monitoring of plunger engagement and impression taking with simultaneous control of plunger field fixation. This eliminates the need for external, mechanical, or electrical travel limits of the gripper, thus making presetting unnecessary. The system can autonomously detect that the impression has been completely taken by determining when at least one plunger reaches its full engagement depth. This information can, for example, be transmitted to a control circuit with a microcontroller, which triggers a reactive closure of the field and performs the mechanical fixation.

[0048] Advantageously, complete engagement can be achieved, for example, via a thin and easily integrated resistive film (FSR). The impact of at least one plunger in at least one of the holding elements leads to a voltage change at the respective component of the sensor film. This voltage change can be detected by the microcontroller and, for example, trigger a switching signal to a component of a valve control system. The valve control system can, for example, actuate a multi-way valve, which can, for instance, actuate a pneumatic lifting cylinder, thereby mechanically locking the plunger assembly(s). The mechanical design of the form clamping jaws, i.e., the holding elements 1, can advantageously be configured such that a hollow chamber is incorporated in the rear area, in which the measuring technology for detecting the complete engagement of the plungers can be housed.Contact with at least one plunger then sends a signal to the microcontroller, which can then trigger the valve control to close the lifting cylinder. Extending the lifting cylinder 6 compresses the keyway, creating a mechanical frictional connection and fixing the plunger in its assumed relative position. This is an alternative to, for example, a pneumatic lifting cylinder as in the... Fig. 1 and Fig. As shown in Figure 2, the locking mechanism can also be achieved by means of an eccentrically mounted pivot bolt, which clamps the plunger field when rotated.

Claims

[1] Gripping device comprising at least one holding element (1), wherein the at least one holding element (1) comprises the following: a guide element (2), a plurality of elongated plungers (3a-3h), each elongated in a longitudinal direction, wherein the plungers (3a-3h) are arranged side by side in the guide element (2) with their longitudinal directions parallel to each other and are guided by the guide element (2) in the direction of their longitudinal directions, an insertion detection device (5) with which the reaching of an end position of at least one of the plungers (3a-3h) can be detected, wherein the gripping device also has an actuator (8) with which the at least one holding element (1) can be moved in the direction of the longitudinal axes of the plungers (3a-3h) of this holding element, wherein the actuator (8) is controllable such that it moves the at least one holding element (1) until the insertion detection device (5) detects that at least one of the plungers (3a-3h) of one, several or all of the at least one holding element (1) has reached its end position and, upon detection of this reaching position, terminates the movement of the at least one holding element (1), wherein the at least one retaining element (1) has a rear contact surface which is located less than the length of the plungers (3a-3h) away from a surface of the guide element (2) facing away from the rear contact surface, wherein the insertion detection device (5) is a contact detection device which is configured to detect contact of at least one of the plungers (3a-3h) with the rear contact surface, wherein the actuator (8) is controllable such that the at least one holding element (1) can be moved by it until the contact detection device (5) detects contact between at least one of the plungers (3a-3h) of one, several or all of the at least one holding element (1) and the corresponding rear contact surface, wherein the contact detection device (5) is a resistive plate or resistive film which is configured to change its electrical resistance when touched by at least one of the plungers (3a-3h), wherein the guide element (2) and the rear contact surface are opposite inner walls of a housing. [2] Gripping device according to one of the preceding claims, wherein the at least one holding element (1) also has a locking device (6) with which the plungers (3a-3h) of this holding element (1) can be locked against displacement in the direction of their longitudinal direction. [3] Gripping device according to one of the preceding claims, comprising two of the holding elements (1) which can be moved towards each other by the actuator (8) in the direction of the longitudinal axes of the plungers (3a-3h). [4] Gripping device according to one of the preceding claims, wherein the gripping device has two of the holding elements (1), wherein the longitudinal axes of the plungers (3a-3h) of the two holding elements (1) are parallel to each other. [5] Gripping device according to one of the preceding claims, wherein the actuator (8) is a pneumatic or hydraulic actuator (8) and is controllable by means of at least one valve, wherein the at least one valve is controllable on the basis of a signal supplied by the insertion detection device (5). [6] Gripping device according to one of the preceding claims 1-4, wherein the actuator (8) is an electromechanical actuator (8) and is controllable on the basis of a signal supplied by the insertion detection device (5). [7] Methods for grasping an object, wherein a gripping device according to one of the preceding claims is positioned such that the object is located in an area into which the plungers (3a-3h) of the at least one holding element (1) can be moved by the actuator (8), then the actuator (8) moves at least one holding element (1) towards the object until the insertion detection device (5) detects that at least one of the plungers (3a-3h) of one, several or all of the holding devices (1) has reached the end position, and the actuator (8) then stops the movement of the holding element (1). [8] Method according to the preceding claim, wherein after detecting that the end position has been reached and the actuator (8) has been stopped, the plungers (3a-3h) of the holding element (1) are locked. [9] Method according to the preceding claim, wherein after locking the plungers (3a-3h) the actuator (8) exerts a force which presses the at least one retaining element (1) against the object.

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