Gripping device for gripping non-rigid workpieces

Abstract

Gripping device (1) for gripping a non-rigid workpiece (2) comprising a central element (12), a frame (11) and a gripping leg spreading element (10), wherein two gripping arms (13) mounted on the frame (11) can be brought into three distinct, defined positions by changing the relative position of the central element (12), frame (11) and gripping arm spreading element (10) to each other, namely a workpiece holding position, a workpiece placement position and a workpiece receiving position, wherein the gripping device (1) comprises at least two sets of tension springs, wherein a first set of tension springs (14a) is arranged between the central element (12) and the frame (11) and determines an initial position of the central element (12) relative to the frame (11), a second set of tension springs (14b) is arranged between the frame (11) and the gripper leg spreader element (10) and determines an initial position of the gripper leg spreader element (10) relative to the frame (11) and the two sets of tension springs (14a, 14b) are each stretched in their direction of action by a movement supported against a multitude of plungers.

Description

[0001] The invention relates to a gripping device for gripping non-rigid workpieces at high temperatures, in particular carbon fiber rods.

[0002] Fiber-reinforced plastic components have been used for many years in various technical fields, including extensively in automotive engineering. They offer significant lightweight potential and, compared to other materials such as metals or unreinforced plastics, can withstand high tensile forces due to the incorporated fibers. The weight-specific advantages of fiber-reinforced plastics are best utilized when the fibers in the matrix material are designed to follow the load path, which requires a load-optimized material design.

[0003] Reinforcing fiber rods are used in the construction of fiber-reinforced composite components and differ from fiber layers or fabrics in that they are formed by a multitude of fibers running in one direction, i.e., the fibers are shaped into a predetermined rod form. The cross-sectional shape used is usually round, square, or hexagonal with a height-to-width ratio greater than or equal to 1 / 10. Lower height-to-width ratios do not refer to shaped fiber rods, but rather to types of non-woven fabrics.

[0004] To follow the load paths, the fiber rods must be adapted to these load paths. For this purpose, a fiber rod can, for example, be heated and then formed. The hot workpieces must be picked up by the gripping device and placed into a forming fixture.

[0005] Various designs of gripping devices are already known from the prior art, but most of them would deform the workpieces too much or often do not function satisfactorily at high temperatures.

[0006] For example, DD 203842B1 discloses a gripper with non-deformable or dimensionally stable jaws. While the force exerted on the workpiece via the jaws during gripping is adjustable via a spring and its preload, the jaws would irreversibly deform the workpiece due to the necessary clamping force.

[0007] In the grippers disclosed by DD 257995A1 and DE 2916899A1, in addition to irreversible deformation due to the contact force, the actuators for moving the gripping elements or jaws are mounted directly on the gripper and are not designed for continuous use at high temperatures, or this actuator system incurs high costs if it has to be specially designed for high temperature loads.

[0008] Disclosures DE 10 2015 015 727 A1 and EP 2810901 B1 each describe gripping solutions other than pincer grippers. These suction gripper solutions require cuffs in contact with the workpiece to create a vacuum. These cuffs must be flexible and sealing, and are therefore usually made of rubber-like materials and thus generally unsuitable for high temperatures. Furthermore, in practice it is not possible to grip non-rigid workpieces with suction grippers, as these would either deform or it would be impossible to develop a sufficient gripping vacuum.

[0009] DE 10 2014 226 317 A1 shows a parallel jaw gripper that generates its force via spring steel strands. Although the necessary actuators are located far enough away from the gripping area that the temperature at the gripper is not critical for them, the parallel jaws cause irreversible deformation of the workpiece.

[0010] Further gripping devices and aspects of such gripping devices are also known from the documents DE 30 11 837 A1, EP 0 767 125 B1, US 2007 / 0 241 573 A1 and US 6 435 583 B1.

[0011] The invention is therefore based on the objective of overcoming the aforementioned disadvantages and providing a simple and cost-effective solution that does not irreversibly deform the workpiece or a fiber rod and can also be used at high temperatures of, for example, approximately 300°C and higher.

[0012] This problem is solved by the combination of features according to claims 1, 9 and 10.

[0013] According to the invention, a gripping device for grasping a non-rigid workpiece is proposed. The gripping device comprises a central element, a frame, and a gripper leg spreading element. Two gripper legs, mounted on the frame, can be brought into three distinct, defined positions by changing the relative position of the central element, frame, and gripper leg spreading element to one another. These positions are a workpiece holding position, a workpiece placement position, and a workpiece receiving position. The three positions enable the device to handle various situations when handling non-rigid workpieces.

[0014] A further advantage is a design in which the gripping arms are formed from a spring steel sheet, preferably a spring steel strip. Due to the properties of the spring steel sheet or strip, no excessive stress is exerted on the workpiece. The gripping arms yield because of the material from which they are formed. Furthermore, the central element and / or the gripping arm spreading element allow for deformation and shaping of the gripping arms.

[0015] A further advantage is a design in which the gripping arms are curved in their unactuated state, preferably substantially concave and / or convex. The unactuated state can be either the workpiece holding position, which corresponds to the initial position of the central element together with the initial position of the gripping arm spreading element, or a disassembled state. The disassembled state is the state in which the gripping arms are not connected to each other or to the frame. The gripping arms have a predetermined shape. The curvature of this shape can vary from positive to negative values.

[0016] It is further advantageous if, in a further development form, the gripping legs in the workpiece holding position converge at their workpiece-side ends and / or touch at their workpiece-side ends, whereby a held workpiece is kept in its holding position by means of a pretension of the gripping legs and by a frictional force between gripping leg and workpiece.

[0017] Another design variant is advantageous if the central element is moved along the longitudinal extension of the gripping arms to reach the workpiece placement position. In the workpiece placement position, the gripping arms extend completely, or at least substantially completely, along their longitudinal extension between the central element and the frame. Considering the movement along the longitudinal extension of the gripping arms, the gripping arms retract behind the central element. In the workpiece placement position, they are completely, or at least mostly, retracted behind or into the central element.

[0018] According to the invention, the gripping device comprises at least two sets of tension springs. A first set of tension springs is arranged between the central element and the frame. These tension springs define a starting position of the central element relative to the frame. They pull it back into any other position unless a counterforce acts upon it. A second set of tension springs is arranged between the frame and the gripping leg spreader element. These tension springs define a starting position of the gripping leg spreader element relative to the frame. They pull it back into any other position unless a counterforce acts upon it. The two sets of tension springs are each extended in their direction of action by a movement supported against a plurality of plungers.

[0019] To enable operation at high temperatures, a further development variant benefits from transferring the movement of the central element and the gripper leg spreader element to the gripping device, preferably to the central element, via an external actuator. This is achieved, for example, by a robot or similar actuators connected to the gripping device via a linkage on the central element. The gripping device can be moved into different positions by pressing it against a counter plate or a workpiece tray using plungers. The mechanics and electronics required for the actuator are located outside a high-temperature area and therefore do not require special protection against high temperatures.

[0020] A further advantageous design variant involves the plungers being formed on the frame and / or on the gripper leg spreader and / or on an external counter plate and / or on a workpiece support form. For proper function, two sets of plungers are required: one set for moving the central element and one set for moving the gripper leg spreader. Various plunger arrangements are conceivable. For example, a first set of plungers could be formed on the workpiece support form and a second set on the counter plate, or a first set on the workpiece support form and a second set on the gripper leg spreader.

[0021] According to the invention, a gripper arrangement with a plurality of gripping devices is further proposed. The gripper arrangement comprises at least two of the proposed gripping devices, wherein parts of the gripping devices are integrally formed with a gripper arrangement plate. For example, the central elements of all gripping devices of the gripper arrangement can be integrated into the gripper arrangement plate. Other parts are then not arranged on individual central elements, but on the gripper arrangement plate. The gripping devices of the gripper arrangement are arranged relative to one another in such a way as to enable their intended use. For example, four gripping devices can be arranged such that four components are held and arranged in a cross shape.The gripper assembly plate can represent a counterpart or a counterpart to a workpiece tray, so that workpieces are first held in place by the gripping devices and then their position is determined by the shape of the workpiece tray and the gripper assembly plate. For example, for a curing or cooling process, the gripper assembly plate can remain on the workpiece tray, while the actuators connected to the gripper assembly plate are decoupled from it and perform other or identical process steps at other processing stations.

[0022] According to the invention, a gripping process is further proposed, comprising the following steps: a) Moving the central element along the multiple plungers in the direction of the workpiece tray shape to reach the workpiece tray position, b) Moving the frame along the multiple of plungers towards the central element to reach the workpiece holding position and to restore the starting position of the central element by means of a spring force from the first set of tension springs, c) Moving the gripper leg spreading element along the multiple plungers towards the external counter plate to reach the workpiece holding position, d) Moving the frame along the multiple of plungers in the direction of the gripper leg spreader element to reach the workpiece holding position and restore the gripper leg spreader element to its starting position by means of a spring force from the second set of tension springs.

[0023] The features disclosed above can be combined in any way as far as is technically possible and they do not contradict each other.

[0024] Other advantageous embodiments of the invention are characterized in the dependent claims or are described in more detail below together with the description of the preferred embodiment of the invention with reference to the figures. The figures show: Fig. 1 Three-dimensional representation of a gripping device Fig. 2 a front view of a gripping device Fig. 3. A side view of a gripping device Fig. 4. A top view of a gripping device Fig. 5 A partially cut-away front view of a gripping device in workpiece holding position Fig. 6 A partially cut-away front view of a gripping device in a transition position Fig. 7 A partially cut-away front view of a gripping device in workpiece storage position Fig. 8 A cutaway front view of a gripping device in workpiece holding position

[0025] The figures are schematic examples. Identical reference symbols in the figures indicate identical functional and / or structural features.

[0026] In Fig. Figure 1 shows a gripping device 1 in a three-dimensional representation. The gripping device 1 is shown in its home position, which corresponds to the workpiece holding position and the starting position of the gripper leg spreader 10 in combination with the starting position of the central element 12. The main components of the gripping device 1 are visible: the gripper leg spreader 10, the frame 11, the central element 12, and the gripper legs 13, which are guided by the gripper leg guide 12a of the central element 12. Also visible are two tension springs 14a of the first set of tension springs and, due to the view, one tension spring 14b of the second set of tension springs. The first and second sets of tension springs are in their starting position. They are only slightly pre-tensioned but not deflected.The central element 12 therefore rests against the stops 11b and is restrained by the guides 11a in directions orthogonal to the longitudinal axis X of the gripping leg spreader element. The guides 11a simultaneously form a first set of plungers of the plurality of plungers and serve to support the frame on a surface, for example, a workpiece tray, in order to enable the movement of the central element 12 in the direction of the workpiece tray. The upwardly directed extensions of the gripping leg spreader element 10 form a second set of plungers of the plurality of plungers. The actuating element 10a can be seen at the lower end of the gripping leg spreader element 10.

[0027] The Fig. 2, Fig. 3, Fig. 4 and Fig. Figure 5 shows a gripping device 1 in the same position as in Fig. 1, but from different perspectives.

[0028] The Fig. Figure 2 shows a gripping device 1 from the front view. All elements of the gripping device 1 are visible, as are also shown in Fig. 1 were visible, except for the gripper leg guide 12a which lies behind a side surface of the central element 12.

[0029] The Fig. Figure 3 shows a gripping device 1 from the side. Also visible are the gripping leg spreader element 10, with the arms at whose lower ends the tension springs of the second set are suspended from tension springs 14b, the central element 11, with stop 11b and guide 11a, and the central element 12, which can move along the longitudinal axis X. A gripping leg 13 is also visible.

[0030] The Fig. Figure 4 shows a gripping device 1 from a top view, revealing all the tension springs of the first and second sets of tension springs 14a and 14b. The main components, namely the gripping leg spreader element 10, frame 11, and central element 12, are also visible. Furthermore, both stops 11b are also shown.

[0031] The Fig. 5, Fig. 6 and Fig. Figure 7 shows the same components of a gripping device 1 as Fig. 2 except for the tension springs 14b of the second set of tension springs, which are not visible due to the view and section. However, the section through the central element reveals the first and second control surfaces 12b and 12c, which lie in the gripper arm guide 12a. Furthermore, a workpiece support form against which the gripping device rests is visible. The concave / convex shape of the gripper arms is also clearly recognizable in the aforementioned figures. A gripper arm changes along its longitudinal axis from one curvature to the opposite curvature, resulting in a concave shape that transitions into a convex one, or vice versa.

[0032] The Fig. Figure 5 shows a gripping device 1 in workpiece holding position with the workpiece 2.

[0033] The Fig. Figure 6 shows a gripping device 1 in an intermediate position that occurs during the transition from workpiece holding to workpiece placement, or vice versa. In contrast to Fig. 5 the tension springs 14a of the first set of tension springs are stretched, but are not yet at their maximum intended extension.

[0034] The Fig. Figure 7 shows a gripping device 1 in the workpiece placement position. The tension springs 14a of the first set of tension springs are in their maximum intended extension, and the central element 12 rests against the workpiece support form, which directly forms a mold for the workpiece 2. The central element 12 has pressed the workpiece 2, which is guided laterally by the gripping arms 13, into the placement position. It can be clearly seen that the gripping arms 13 retract relative to the central element 12. As a result, no forces are exerted on the workpiece 2, enabling non-destructive placement of the workpiece 2 in the workpiece support form.

[0035] The Fig. Figure 8 shows a gripping device in workpiece holding position. All components are as shown in Figure 8. Fig. Figure 2 shows that the gripper leg spreading element 10 is pressed against a counter plate, causing the actuating element 10a of the gripper leg spreading element 10 to move to the central element 12. The gripper legs 13 are pressed in between the actuating element 10a and the second control surfaces 12c in such a way that the actuating element 10a and the control surfaces 12c define a shape for them. This shape spreads the workpiece-side ends of the gripper legs 13 open sufficiently to allow a workpiece to be gripped or inserted without damage. The Fig.Eight downward-pointing extensions of the gripping leg spreader element 10 form a second set of plungers in the plurality of plungers. These enable the gripping device to be supported against the counter plate, whereby a force and thus a transfer of motion is exerted on the stops 11b when the central element 12 moves, causing the frame 11 to move towards the counter plate and press the gripping leg spreader element 10 into the frame 11.

[0036] The invention is not limited in its implementation to the preferred embodiments described above. Rather, a number of variants are conceivable that utilize the illustrated solution even in fundamentally different designs. For example, the springs could be replaced by detent elements actuated by an external kinematic mechanism to move into different positions.

Claims

[1] Gripping device (1) for gripping a non-rigid workpiece (2) comprising a central element (12), a frame (11) and a gripping leg spreading element (10), wherein two gripping arms (13) mounted on the frame (11) can be brought into three distinct, defined positions by changing the relative position of the central element (12), frame (11) and gripping arm spreading element (10) to each other, namely a workpiece holding position, a workpiece placement position and a workpiece receiving position, wherein the gripping device (1) comprises at least two sets of tension springs, wherein a first set of tension springs (14a) is arranged between the central element (12) and the frame (11) and determines an initial position of the central element (12) relative to the frame (11), a second set of tension springs (14b) is arranged between the frame (11) and the gripper leg spreader element (10) and determines an initial position of the gripper leg spreader element (10) relative to the frame (11) and the two sets of tension springs (14a, 14b) are each stretched in their direction of action by a movement supported against a multitude of plungers. [2] Gripping device (1) according to claim 1, characterized by , that the gripping legs (13) are formed from a spring steel sheet, preferably from a spring steel strip. [3] Gripping device (1) according to claim 1 or 2, characterized by that the gripping arms (13) are curved in their unactuated state, preferably substantially concave and / or convex. [4] Gripping device (1) according to one of the preceding claims, characterized by, that the gripping legs (13) converge at their workpiece-side ends and / or touch each other at their workpiece-side ends in the workpiece holding position, wherein a held workpiece (2) is held in its holding position by means of a pretension of the gripping legs (13) and by a frictional force between gripping leg (13) and workpiece (2). [5] Gripping device (1) according to one of the preceding claims, characterized by , that the central element (12) is moved along a longitudinal extension of the gripping legs (13) to reach the workpiece placement position, wherein the gripping legs (13) in the workpiece placement position extend completely or at least substantially completely in their longitudinal extension between the central element (12) and the frame (11) or are retracted relative to the central element (12). [6] Gripping device (1) according to one of the preceding claims, characterized by, that the aforementioned movement is transferred to the gripping device (1), preferably to the central element (12), by means of an external actuator. [7] Gripping device (1) according to one of the preceding claims, characterized by , that the plungers are formed on the frame (11) and / or on the gripper leg spreader element (10) and / or on an external counter plate and / or on a workpiece support form. [8] Gripper arrangement with a plurality of gripping devices (1) according to one of the preceding claims, wherein the central elements of the plurality of gripping devices (1) are integrally formed with a gripper arrangement plate on which the frame (11) is arranged and wherein the plurality of gripping devices (1) are in an intended arrangement relative to each other and the gripper arrangement plate represents a counterpart to a workpiece tray form. [9] Gripping process with a gripping device (1) according to claim 7, comprising the following steps: a. Moving the central element (12) along first plungers of the plurality of plungers in the direction of the workpiece support shape, to reach the workpiece support position, b. Moving the frame (11) along the first plunger of the plurality of plungers in the direction of the central element (12) to reach the workpiece holding position and establish the starting position of the central element (12) by means of a spring force of the first set of tension springs (14a), c. Moving the gripper leg spreading element (10) along second plungers of the plurality of plungers towards the external counter plate to reach the workpiece holding position, d. Moving the frame (11) along the second plunger of the plurality of plungers in the direction of the gripper leg spreader element (10) to reach the workpiece holding position and restore the starting position of the gripper leg spreader element (10) by means of a spring force of the second set of tension springs (14b).

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