CLAMPING DEVICE

Description

[0001] The invention relates to a clamping device for holding a workpiece to be machined by a machine tool according to the preamble of claim 1.

[0002] Such a clamping device is already known from DE 10 2012 014 617 B3. Further prior art can be found in EP 3 391 991 A1 and EP 3 653 333 B1.

[0003] Such clamping devices can be used as chucks, vises, or zero-point clamping systems. For all such clamping devices, the centered arrangement of the workpiece relative to a reference plane or axis, for example, the axis of symmetry of the housing, is of crucial technical importance, as the workpiece should be machined by a machine tool with the lowest possible error tolerance. This requires knowing the exact position of the workpiece relative to a reference plane or axis and achieving this clamping position with repeatable accuracy when replacing an identical workpiece.

[0004] A disadvantage is that currently, the workpieces to be processed must be changed manually by the operator. Each workpiece must therefore be clamped in place and, after the machining process, removed from the clamping device in order to insert another workpiece.

[0005] Furthermore, a disadvantage of known clamping devices has been found to be that the workpiece position changes during insertion and / or during the machining process due to the prevailing centrifugal forces, for example, from the chuck or the rotation of a pallet or the workpiece table of a machine tool. When inserting the workpiece, particles in the form of chips or other contaminants can be present between the workpiece and the clamping jaw, or between the workpiece and a contact surface on the housing onto which the workpiece is to be placed flat. This can then cause a change in the workpiece's position. Therefore, before the start of the machining process, the machine tool must first check whether the workpiece is correctly inserted in the clamping device.However, since the workpiece is inserted manually and the known clamping devices often use hydraulic or mechanical drive systems to move the clamping jaws, checking the position of the inserted workpiece is time-consuming and requires appropriate technical knowledge from the operating personnel to perform this check.

[0006] It is therefore an object of the invention to further develop both an automated insertion and a clamping device of the type mentioned above, by which an automated position check of the inserted workpiece can be carried out and that, when the test result is available, either the start of the machining process is automatically initiated or a check of the position of the workpiece in the clamping device is carried out.

[0007] This problem is solved according to the invention by the features of the characterizing part of claim 1.

[0008] Further advantageous embodiments of the invention are set out in the dependent claims.

[0009] By providing an electromechanical and / or inductive interface on the housing, which is inductively and / or electrically connected to the drive unit and / or an evaluation unit, and by making the interface accessible to an external robot arm and communicating with it in such a way that electrical data signals and / or electrical energy can be transmitted alternately and bidirectionally between the interface and the robot arm, an automated query regarding the clamping position of the workpiece in the clamping device is carried out before the machining process by the machine tool begins.

[0010] Advantageously, the robot arm used for automated verification of the workpiece's clamping position in the clamping device can be mounted on a chassis, allowing it to move freely within an assembly hall and thus access multiple machine tools and query their clamping parameters. It is also conceivable to attach the robot arm to a ceiling, crane, or similar structure and move it within a specific area where the corresponding machine tools are located.

[0011] A control unit integrated into the robot arm's chassis can advantageously control both the robot arm's movement and the workpiece's clamping position in the clamping device. Only after the control unit has verified the correct clamping position does it issue a corresponding electrical command signal, enabling the machine tool. Consequently, after the workpiece is inserted into the clamping device, its clamping position can be automatically verified, and the machining process can be initiated if the measurement results are positive.

[0012] To establish electrical data signal transmission between the clamping device and the robot arm, the housing is provided with pins or slots for mechanical and electrical coupling. Optionally, an inductive interface in the form of a contact surface can be provided. Corresponding mechanical or inductive interfaces are provided at the free end of the robot arm, so that the robot arm is either mechanically and electrically connected to the housing's mechanical interface during the inspection period, or contactless data transmission occurs between the robot arm and the housing's inductive interface. The mechanical and inductive interfaces used allow for the bidirectional transmission of both electrical data signals and electrical power between the clamping device and the robot arm.The robot arm communicates with a control center via antennas, Wi-Fi connections, or electrical cables, enabling the immediate transmission of measurement data evaluated or received by the robot arm to the control room. Therefore, a machine hall containing several such machine tools can be centrally monitored and operated from a single control room.

[0013] The drawing shows an embodiment of a clamping device according to the invention in different structural configurations, which are explained in more detail below. Specifically, it shows: Figure 1a shows a clamping device mounted on a worktable, through which a workpiece is inserted between three clamping jaws and clamped by them during the machining process of a machine tool, and a robot arm mounted on a chassis which automatically places the workpiece on the clamping device, in perspective view. Figure 1b shows the machine tool, the clamping device and the robot arm according to the diagram. Figure 1a , wherein the robot arm and the clamping device communicate with each other via electromechanical and inductive interfaces, Figure 2 the clamping devices according to Figure 1a , wherein the robot arm is rotated by 90° to align the interfaces with each other, Figure 2b the clamping device according to Figure 2a from another side in an enlarged view, Figure 3 the clamping device according to Figure 1aIn an enlarged view and with a breakdown to illustrate the construction and function of a zero-point clamping system, Figure 4 shows the clamping device according to Figure 1a , in the form of a vise with two adjustable clamping jaws and the externally accessible electromechanical and inductive interfaces, as well as the robot arm, which is arranged adjacent to the interface of the housing, and Figure 5 a pallet or a tool table of the machine tool on which the clamping device according to Figure 1a It can be mounted in the form of a chuck.

[0014] Out of Figure 1aThe loading process involves a robot arm 14 removing a workpiece 3, to be machined by a machine tool 2, from a clamping device 1. The robot arm 14 holds the workpiece 3 and places it onto the open clamping device 1. The clamping device 1 is designed as a so-called zero-point clamping system. This means that each identical workpiece 3 from a production series must be positioned with repeatable accuracy at the precisely defined position of the clamping device 1 to ensure that the machining steps performed by the machine tool 2 can be carried out within a tool series without reprogramming.

[0015] In this illustrated embodiment, the clamping device 1 consists of a housing 4 containing three clamping jaws 7, 8, 9. In zero-point clamping systems, such clamping jaws are often also referred to as clamping slides. The function and design of a zero-point clamping system are such that the workpiece 3 or a clamping bolt connected to the workpiece 3 is inserted into a receiving opening machined into the housing 4. An electrically operated drive unit 11 is provided in the housing 4, by which the clamping jaws 7, 8, 9 are moved synchronously. The clamping jaws 7, 8, 9 are axially movably inserted into guide grooves (not shown); the respective guide grooves extend radially to a reference axis 4', which corresponds to the axis of symmetry of the receiving opening of the housing 4.

[0016] The robot arm 14 has a free end 15, at which a gripping device for holding the workpiece 3 is arranged, and an electromechanical and inductive interface 12' and 13' are arranged. An electromechanical interface 12 and an inductive interface 13 are provided on the outside of the housing 4, which communicate with the respective interface 12' and 13' of the robot arm 14 for the transmission of electrical data signals and electrical energy.

[0017] The robot arm 14 is mounted on a chassis 17, to which a control unit 18 is assigned. The control unit 18 is intended to enable the chassis 17 to be moved automatically on a surface and, at the same time, to allow the control unit 18 to execute the movements required for the robot arm 14 depending on the position of the chassis 17 or the robot arm 14.

[0018] In Figure 1bIt is shown that the robot arm 14 has placed the workpiece 3 onto a support surface 6' formed by the housing 4. Thus, the workpiece 3 rests on the support surface 6' defined by the housing 4. Inside the housing 4, the electric drive unit 11 has positioned the three clamping jaws 7, 8, and 9. Through design features, a clamping force is generated during the positioning of the clamping jaws 7, 8, and 9, which initially presses the workpiece 3 onto the support surface 6' and simultaneously generates a radial holding force that clamps the workpiece 3 in a positionally oriented manner to the housing 4.

[0019] As soon as the workpiece 3 is positioned on the support surface 6' and the clamping jaws 7, 8, 9 are engaged, the machining process on the machine tool 2 can theoretically begin. However, since the insertion of the workpiece 3 is performed fully automatically by the robot arm 14, the position of the workpiece 3 relative to the reference surface 6' must be checked. For this purpose, an electrical evaluation unit 11' is provided in the housing 4, which is inductively and / or via electrical cables coupled to the electrical drive unit. It is readily possible to measure the rotational speeds and the associated movements of the electrical drive unit 11 and thereby calculate the stroke of the respective clamping jaw 7, 8, 9.

[0020] Furthermore, several bores 31 can be machined into the support surface 6', each containing a proximity sensor 32. The proximity sensors 32 are inductively operated and measure the distance between themselves and the underside of the workpiece 3 as soon as the workpiece is positioned. Should any of the measurement results, i.e., the stroke of the respective clamping jaws 7, 8, 9 and / or the measurement result of the proximity sensor 32, deviate from a predefined tolerance range, this is determined by the electrical evaluation unit 11'.

[0021] Therefore, as soon as the robot arm 14 has placed the workpiece 3 on the support surface 6', the robot arm 14 rotates the free end 15 such that the electromechanical and inductive interfaces 12', 13' provided on the free end 15 of the robot arm 14 are aligned with the electromechanical and inductive interfaces 12 and 13 of the housing 4. According to the Figures 2a and 2bIn the figures where this position is shown, the electromechanical interfaces 12 and 12' either have pins 19 and slots 21 or, conversely, slots 20 and pins 22, which are mechanically and electrically coupled. Consequently, an electromechanical or inductive data signal or energy transfer occurs between the robot arm 14 and the electrical components located inside the housing 4. Thus, electrical energy can be transferred from the robot arm 14 to the electric drive unit 11 or to an accumulator connected to it, and the electrical evaluation unit 11' can transmit corresponding measurement signals from the proximity sensors 31 to the robot arm 14 and the control unit 18 integrated therein. The control unit 18 evaluates these generated measurement signals and compares them with stored data in a pre-programmed query cycle.If the measurement results are within a predefined tolerance range, the control unit 18 activates the machine tool 2 via interfaces 12, 12' or 13, 13' or generates an error signal to check the position of the workpiece 3 manually or automatically. Once the control unit 18 has transmitted the activation signal for the machine tool 2, the robot arm 14 moves away from the housing 4, thus initiating the machining process by the machine tool 2.

[0022] In Figure 3The constructive and functional design of the zero-point clamping system, configured as a clamping device 1, can be seen from the figure. It is also shown that one or more coils, functioning as transceivers 24, are provided for the inductive interface 13. The interface 13 forms a button 25 onto which a button 25', located at the free end 15 of the robot arm 14, can be aligned without contact. Thus, the inductive signal and energy transmission is contactless; whereas the paired pins 19 and slots 21, and slots 20 and pins 22, require mechanical and electrical coupling.

[0023] In Figure 4A vise, comprising two adjustable jaws 7 and 8, is to be removed as a clamping device 1. The workpiece 3 is clamped between these jaws. Electromechanical and inductive interfaces 12 and 13, respectively, are arranged on one of the free outer surfaces of the housing 4. These interfaces are aligned with the electromechanical and inductive interfaces 12' and 13' on the robot arm 14 for communication purposes. Consequently, any robot arm 14 can be moved to any clamping device 1 to communicate with it. It is only necessary that the arrangement of interfaces 12 and 13 corresponds spatially to the arrangement of interfaces 12' and 13' and is thus converted into either a mechanical and electrical or an inductive coupling state.

[0024] The same applies to those in Figure 5The clamping device 1 shown here is designed as a chuck with three clamping jaws 7, 8 and 9, between which the respective workpiece 3 is inserted and clamped. Often, such clamping devices 1 used as chucks rotate during the machining process, so that electromechanical or inductive coupling between the interfaces 12, 13 or 12' and 13' of the robot arm 14 can only take place when the clamping device 1 is at rest.

[0025] The transmission of electrical data signals and electrical energy between the drive unit 11, the evaluation unit 11' and the proximity sensor 32 can take place both inductively and by means of electrical lines 16.

Claims

1. Clamping device (1) for holding a workpiece (3) to be machined by a machine tool (2), comprising: - a housing (4), - a support surface (6') which is formed by the housing (4), - at least one clamping jaw (7) axially movably mounted in the housing (4) and a counter-stop (10) formed by the housing (4), between which the workpiece (3) is clamped, or at least two clamping jaws (7, 8, 9) axially movably mounted in the housing (4), between which the workpiece (3) is clamped, and - a drive device (11) by means of which the movable clamping jaws (7, 8, 9) are controllably movable, and by means of which a holding force transmitted from the clamping jaws (7, 8, 9) to the workpiece (3) or to a clamping bolt (3') coupled with the workpiece (3) is generated during the clamping process, and - an electromechanical and / or inductive interface (12, 13) provided on the housing (4), which is connected to the drive device (11) and / or an evaluation device (11') inductively and / or by means of electrical lines (16), and - a robot arm (14) which communicates with the interface (12, 13) in such a way that electrical data signals and / or electrical energy can be transmitted alternately and bidirectionally between the interface (12, 13) of the housing (4) and an electromechanical and / or inductive interface (12', 13') of the robot arm (14), characterised in that, the drive device (11) is electrically operated and a free end of the robot arm (14), as soon as the robot arm (14) has placed the workpiece (3) on the support surface (6'), is rotatable in such a way that the electromechanical and inductive interfaces (12', 13') provided on the free end (15) of the robot arm (14) are aligned flush with the electromechanical and inductive interfaces (12, 13) of the housing (4).

2. Clamping device (1) according to claim 1, characterised in that, the evaluation device (11') is electrically or inductively connected to at least one proximity sensor (32), in that the position of the workpiece (3) is measured by the respective proximity sensor (32) with respect to a reference axis (4') of the housing (4) and / or with respect to a support surface (6) assigned to the housing (4), and in that the measurement result determined by the respective proximity sensor (32) is forwarded to the evaluation device (11') in the form of electrical data signals.

3. Clamping device (1) according to claim 1 or 2, characterised in that, the robot arm (14) is mounted on a chassis (17), in that a control device (18) is assigned to the chassis (17), by means of which the chassis (17) and / or the movements of the robot arm (14) are automatically moved, and in that a program for checking the clamping situation of the workpiece (3) on the clamping device (1) is run by the control device (18).

4. Clamping device (1) according to claim 3, characterised in that, the rotational speed of the drive device (11) and / or the stroke path of the clamping jaws (7, 8, 9) is generated by the control device (18), in that measurement results are generated by this query, which are used by the control device (18) to enable the machine tool (2).

5. Clamping device (1) according to any one of the preceding claims, characterised in that, the electromechanical interface (12) comprises one or more pins (19, 19'...) or sockets (20, 20'...), and in that corresponding sockets (21, 21'...) or pins (22, 22'...) are provided on the free ends (15) of the robot arm (14), which are mechanically and electrically coupled in pairs.

6. Clamping device (1) according to any one of the preceding claims, characterised in that, the inductive interface (13) comprises an interface surface (23), in that an inductively operated transmitting and / or receiving device (24) is assigned to the interface surface (23), and in that the robot arm (14) comprises an interface surface (25), to which a transmitting and / or receiving device (26) is assigned for communication with the transmitting and / or receiving device (26) of the interface (25) of the clamping device (1).