screw system

Abstract

A screwing system (10) for automatically carrying out screwing operations, comprising a screwing tool (24), a feed device (42) for automatically feeding screws, a hold-down device (28) for supporting the screwing system (10) on two components (36, 38) to be screwed together, a positioning head (26) for positioning a fed screw (40) relative to the components (36, 38) to be screwed together, and a feed device (16) for advancing the screwing tool (24) in a feed direction, characterized in that the positioning head (26) is mounted on the hold-down device (28) so as to be displaceable in the feed direction relative to the hold-down device (28), and in that the positioning head (26) comprises a holding mechanism (44) for holding the fed screw (40).

Description

[0001] The invention relates to a screwing system with a screwing tool, a feeding device for automatically feeding screws, a hold-down device for supporting the screwing system on two components to be screwed together, a positioning head for positioning the screw relative to the components to be screwed together, and a feed device for advancing the screwing tool in a feed direction.

[0002] Such screw systems are generally well-known and are used to automatically perform screwing processes, allowing for rapid execution, for example, in vehicle construction. Conventional screw systems have the disadvantage that they must be precisely adjusted to the dimensions of the components to be screwed together. For example, when switching from non-pre-drilled to pre-drilled components, a conventional screw system must be reconfigured, which requires the production flow to be stopped.

[0003] Document DE 1 577 079 A1 discloses a screw system which, however, does not have a retainer. Document DD 88 442 A1 discloses a screw system according to the preamble of claim 10.

[0004] The invention is based on the object of creating a screw system that can be used in a variety of ways.

[0005] The problem is solved by a screw system with the features of the independent claims.

[0006] The screw system according to the invention is particularly well suited for flow hole forming screwing and has the advantage that it can screw together differently configured and / or dimensioned components without the screw system having to be specially adjusted for each individual case.

[0007] In this context, configuration means, for example, that one of the components, particularly the component facing the screw system, is pre-drilled. The dimension of the components here refers to the thickness of the components, particularly the thickness of the component facing the screw system.

[0008] To produce an optimal screw connection, it is advantageous, among other things, if the screw driven by the screwing tool is held laterally and / or can be supported on one of the components to be screwed together, since otherwise it could tilt relative to the components. The inventive displaceability of the positioning head relative to the hold-down device, i.e. the quasi-floating mounting of the positioning head, ensures that the screw is supported not only on a component that has not been pre-drilled, in this case on the component facing the screw system, but also if the component facing the screw system is pre-drilled, namely on the component facing away from the screw system, since the screw positioned by the positioning head can penetrate into the pre-hole and be supported on the component facing away from it.

[0009] Due to the floating bearing of the positioning head, the screw tip can, depending on the configuration and dimensions of the components, in particular the component facing the screw system, assume the position in the axial direction relative to the hold-down device that is required for axial support for correct positioning of the screw, almost automatically and in particular without modifying the screw system.

[0010] Advantageous embodiments of the invention can be found in the dependent claims, the description and the drawing.

[0011] According to a particularly simple design, the positioning head can be moved toward the hold-down device against the restoring force of a spring element. The positioning head is therefore normally held at a distance from the hold-down device by the spring element. If necessary, e.g., if the component facing the screw system is pre-drilled, this distance can be reduced by overcoming the restoring force of the spring element, e.g., by the feed device, and the screw to be positioned can be inserted into the pre-drilled hole so that it can rest on the component facing away from it.

[0012] Advantageously, a releasable locking mechanism is provided for locking the positioning head to the hold-down device. When the locking mechanism is locked, the positioning head cannot move relative to the hold-down device, i.e., the positioning head and hold-down device can only be moved together. Furthermore, particularly with a vertical alignment of the screw system, sagging of the positioning head—i.e., movement of the positioning head relative to the hold-down device due to gravity or inertia—is effectively prevented.

[0013] The locking mechanism can be implemented, for example, by at least one catch hook which is rotatably arranged on the hold-down device and can engage the positioning head.

[0014] Preferably, the locking mechanism is unlocked by tying it to the advance movement of the screwing tool. This eliminates the need for an additional drive for the locking mechanism. For example, the locking mechanism can be unlocked by means of a sliding plate mounted on a screw unit supporting the screwing tool. This slide plate, when the screwing tool is advanced, moves onto the catch hook, rotating it to release the positioning head from the hold-down device.

[0015] In order to ensure a defined alignment of the screw relative to the components to be screwed and a clean engagement between the screw and the screwing tool during each screwing process, the positioning head of the screwing system defined in claim 1 comprises a holding mechanism for holding the fed screw.

[0016] In the screw system of independent claim 10, a separate actuator is provided for opening the holding mechanism, by means of which the holding mechanism can in principle be opened at any desired time, preferably to release the held screw. In particular, the holding mechanism does not need to be opened by the held screw itself, thereby significantly reducing or even completely preventing wear on components of the holding mechanism. A separate actuator for opening the holding mechanism can in principle also be provided in the screw system of claim 1. As already described, this allows the holding mechanism to be opened at any desired time, and the held screw to be released.

[0017] According to a particularly robust and simple design, the actuator can be operated pneumatically or hydraulically.

[0018] Advantageously, the holding mechanism comprises two jaws for holding the fed screw. For example, the jaws can be designed as half-shells and, when compressed, at least almost completely enclose the fed screw, thereby securely holding the screw.

[0019] According to a particularly simple structural embodiment, the jaws are arranged on the front ends of jaw arms facing the hold-down device, which are rotatably mounted on the positioning head, with the axes of rotation running particularly perpendicular to the feed direction. The rotatable mounting of the two jaw arms enables the function of a pliers, allowing a fed screw to be easily and reliably held and released.

[0020] The actuator can, for example, comprise two push rods that, controlled by the actuator, move onto the jaw arms, thereby rotating them to open the jaws. To prevent accidental opening of the jaws and thus a tilted position or even loss of the fed screw, the jaw arms are preferably deflectable against the restoring force of a spring element to open the jaws.

[0021] Since a targeted control of the opening of the jaws can in principle also be realized without the positioning head being mounted so as to be displaceable relative to the hold-down device, a further subject of the invention is also a screw system with the features of claim 11. By means of this, the advantages described above can be achieved accordingly.

[0022] The invention is described below purely by way of example using a possible embodiment with reference to the accompanying drawings. They show: Fig. 1 a side view of a screw system according to the invention with a hold-down device and a positioning head; Fig. 2 an exploded view of the screw system of Fig. 1; Fig. 3 (A) a partial sectional view and (B) a perspective view of the screw system of Fig. 1 before a screwing operation with a distance to the components to be screwed; Fig. 4 (A) a partial sectional view and (B) a perspective view of the screw system of Fig. 1, whereby the hold-down device rests against the components to be screwed together; Fig. 5 (A) a partial sectional view and (B) a perspective view of the screw system of Fig. 1, wherein a supplied screw is positioned in a pilot hole of one component on the other component; Fig. 6 (A) a partial sectional view and (B) a perspective view of the screw system of Fig. 1 after completion of a screwing operation; and Fig. 7 a plan view of a positioning head of the screw system of Fig. 1 arranged holding mechanism.

[0023] Fig. 1 and Fig. 2 show a screwing system 10 for automatically carrying out screwing operations, in particular flow hole forming screwing operations.

[0024] The screw system 10 comprises a base unit 12, which can be mounted on a handling device not shown, for example on a robot arm.

[0025] The base unit 12 carries a screw unit 14, which can be moved in a feed direction relative to the base unit 12 by means of a feed cylinder 16 of the base unit 12. For this purpose, the base unit 12 comprises two guide rails 18 on which the screw unit 14 is slidably mounted.

[0026] The screwing unit 14 comprises a drive motor 20 which, via a drive shaft 22 extending in the feed direction, rotatably drives a screwing tool 24 which is mounted in a positioning head 26 so as to be displaceable in the feed direction.

[0027] The screw unit 14 further carries a hold-down device 28, which extends in front of the positioning head 26 as seen in the feed direction and which is mounted on the screw unit 14 by means of a hold-down device slide 30 so as to be displaceable in the feed direction. The hold-down device slide 30 is provided with a laterally arranged catch hook 32, which interacts with a locking projection 34, which is correspondingly provided laterally on the positioning head 26, in order to releasably secure the hold-down device 28 and the positioning head 26 against relative movement.

[0028] To carry out a screwing process, the screwing system 10 is first positioned by the handling device at a short distance, e.g. at a distance of approximately 20 mm, in front of two components 36, 38 to be screwed together ( Fig. 3).

[0029] A screw 40 intended for screwing is fed to the positioning head 26 by means of a feed device 42 known per se. To align and hold the screw 40 in a defined screw position, the positioning head 26 has a holding mechanism 44, which will be described in more detail below.

[0030] Subsequently, the screw unit 14 is advanced in the direction of the components 36, 38 by actuating the feed cylinder 16 until the hold-down device 28 is supported on the component 36 facing the screw system ( Fig. 4). To compensate for positioning tolerances of the components 36, 38, the hold-down slide 30 can deflect slightly relative to the screw unit 14, counter to the restoring force of a spring, e.g., an air spring 46. Due to the locking of the positioning head 26 and the hold-down slide 30 by means of the catch hook 32, the positioning head 26 moves together with the hold-down slide 30.

[0031] The screwing tool 24 is located in the Fig. 4, it is still in a retracted position in which it is not engaged with the screw 40.

[0032] Next, the screw unit 14 is advanced further by the feed cylinder 16 to engage the screw tool 24 with the screw 40. During this process, the screw tool 24 rotates at a low speed at most.

[0033] As soon as the screwing tool 24 is engaged with the screw 40, a release plate 48 of the screwing unit 14 runs onto the catch hook 32 of the hold-down slide 30 as the screwing unit 14 is advanced further, in order to rotate the catch hook 32 and thereby decouple the positioning head 26 from the hold-down slide 30.

[0034] By unlocking the positioning head 26 from the hold-down slide 30, the positioning head 26 can now move relative to the hold-down device 28, so that when the screw unit 14 is further advanced, it is pushed towards the hold-down device 28 via the screwing tool 24 and the screw 40 supported on the holding mechanism 44, to a maximum extent until a front stop surface 50 of the positioning head 26 abuts a rear stop surface 52 of the hold-down device 28.

[0035] During the relative movement of the positioning head 26 toward the hold-down device 28, a helical compression spring 54 mounted on the positioning head 26 is compressed by a pressure piece 56, which is supported on the rear stop surface 52 of the hold-down device 28. The restoring force of the compressed helical compression spring 54 ensures that the positioning head 26 moves back to its initial position spaced from the hold-down device 28 when the screw unit 14 retracts and can be locked again in this position.

[0036] By advancing the screwing unit 14, the screw 40 is moved by means of the screwing tool 24 towards the components 36, 38 to be screwed together until the screw tip hits the surface of one of the components ( Fig. 5). In the illustrated embodiment, the component 36 facing the screw system 10 is provided with a pilot hole 58. The screw 40 must therefore be moved into the pilot hole 58 in order to be able to support itself on the remote component 38, i.e., it must be advanced further than would be necessary if the facing component 36 did not have a pilot hole 58. These different feed rates until the screw 40 is supported on the components 36, 38 are compensated by the floating bearing of the positioning head 26 on the hold-down slide 30, i.e., by the possible relative movement between the positioning head 26 and the hold-down device 28.

[0037] The time at which the screw 40 strikes the component 38 can be known in advance and / or detected, for example, by a force measurement on the feed cylinder 16, depending on the configuration and dimension of the facing component 36, ie whether a pilot hole 58 is present and, if so, how deep it is.

[0038] As soon as the screw 40 abuts one of the components 36, 38, in the embodiment shown here the opposite component 38, the screw 40 is fixed between the component 38 and the screwing tool 24 and thus secured against tilting.

[0039] Now the actual process of screwing the components 36, 38 can begin, in the present embodiment in the form of a flow hole forming screwing process.

[0040] To avoid wear caused by friction between the screw 40 and components of the holding mechanism 44, the holding mechanism 44 is first released from the screw 40 and then the speed of the screwing tool 24 is increased to the speed required for the screwing process. By appropriately advancing the screwing unit 14, the screw 40 is then driven into the components 36, 38 (in the illustrated embodiment, only into the opposite component 38) in order to connect them together ( Fig. 6).

[0041] The Fig. The holding mechanism 44, shown in more detail in Figure 7, comprises two jaw arms 60, which are mounted on opposite sides of the positioning head 26, each rotatably mounted on the positioning head 26 about a rotation axis 62 oriented at right angles to the feed direction. In the region of their front ends facing the hold-down device 28, half-shell-shaped jaws 64 are attached to the jaw arms 60, which at least approximately completely enclose the screw 40 to be held in the circumferential direction and thereby hold it in the screwed position.

[0042] The rear end of each jaw arm 60 facing away from the hold-down device 28 is located on the side of the rotation axis 62 opposite the respective front end. The rear sections 66 of the jaw arms 60 located between the rotation axes 62 and the rear ends are pressed apart by means of a closing spring 68, e.g. a helical compression spring, which in turn presses the jaws 64 together to hold the screw 40.

[0043] In the region of their rear ends, the jaw arms 60 are each provided with an actuating roller 70 mounted rotatably parallel to the rotation axis 62. The actuating rollers 70 are arranged in the region of exits of guide channels 72 extending in the feed direction, which are provided on opposite sides of the positioning head 26.

[0044] Push rods 74 are provided on the screw unit 14, which are pushed through the guide channels 72 and can run onto the actuating rollers 70 in order to press the rear sections 66 of the jaw arms 60 together against the restoring force of the closing spring 68 and thus to press the jaws 64 apart to release the screw 40.

[0045] In the illustrated embodiment, a separate drive is provided for advancing the push rods 74, e.g., a pneumatic or hydraulic drive, which makes it possible to open the holding mechanism 44 and release the held screw 40, essentially independently of the advance position of the screw unit 14. For example, the drive of the push rods 74 can be specifically controlled so that it is activated as soon as abutment of the screw 40 against one of the components 36, 38 to be screwed is detected.

[0046] Alternatively, it is also conceivable to couple the opening of the holding mechanism 44 to the advance of the screw unit 14, e.g. by fixing the position of the push rods 74.

[0047] According to a further embodiment not shown, the holding mechanism 44 can be actuated by an actuator instead of the driven push rods 74, which, alternatively or in addition to the closing spring 68, is located between the rear sections 66 of the jaw arms 60. Such an actuator could, for example, comprise a pneumatic or hydraulic piston, in particular a counter-piston, which is arranged between the rear sections 66 of the jaw arms 60 and contracts them to release the held screw 40. List of reference symbols 10 screw system 12 basic units 14 Screw unit 16 feed cylinders 18 Guide rail 20 drive motor 22 Drive shaft 24 screwing tools 26 Positioning head 28 hold-down clamps 30 hold-down slides 32 catch hooks 34 locking projections 36 components 38 component 40 screw 42 Feeding device 44 Holding mechanism 46 air spring 48 Release plate 50 stop surface 52 Stop surface 54 helical compression spring 56 Pressure piece 58 pilot hole 60 jaw arms 62 axis of rotation 64 cheeks 66 rear section 68 closing spring 70 Actuating roller 72 guide channel 74 push rod

Claims

[1] Screwing system (10) for automatically carrying out screwing operations with a screwing tool (24), a feeding device (42) for automatically feeding screws, a hold-down device (28) for supporting the screwing system (10) on two components (36, 38) to be screwed together, a positioning head (26) for positioning a fed screw (40) relative to the components (36, 38) to be screwed together, and a feed device (16) for advancing the screwing tool (24) in a feed direction, characterized by that the positioning head (26) is mounted on the hold-down device (28) so as to be displaceable in the feed direction relative to the hold-down device (28), and that the positioning head (26) comprises a holding mechanism (44) for holding the fed screw (40). [2] Screw system (10) according to claim 1, characterized by that the positioning head (26) can be moved towards the hold-down device (28) against the restoring force of a spring element (54). [3] Screw system (10) according to claim 1 or 2, characterized by that a releasable locking mechanism (32) is provided for locking the positioning head (26) to the hold-down device (28). [4] Screw system (10) according to claim 3, characterized by that unlocking of the locking mechanism (32) is coupled to the feed movement of the screwing tool (24). [5] Screw system (10) according to one of the preceding claims, characterized by that a separate actuator (74) is provided for opening the holding mechanism (44). [6] Screw system (10) according to claim 5, characterized by that the actuator (74) can be actuated pneumatically or hydraulically. [7] Screw system (10) according to one of the preceding claims, characterized by that the holding mechanism (44) comprises two jaws (64) for holding the supplied screw (40), which jaws in particular at least approximately completely encompass the supplied screw (40). [8] Screw system (10) according to claim 7, characterized by that the jaws (64) are arranged on the front ends of jaw arms (60) facing the hold-down device (28), which are rotatably mounted on the positioning head (26), wherein the axes of rotation (62) extend in particular at right angles to the feed direction. [9] Screw system (10) according to claim 8, characterized by that the jaw arms (60) can be deflected against the restoring force of a spring element (68) to open the jaws (64). [10] Screwing system (10) for automatically carrying out screwing operations with a screwing tool (24), a feeding device (42) for automatically feeding screws, a hold-down device (28) for supporting the screwing system (10) on two components (36, 38) to be screwed together, a positioning head (26) for positioning a fed screw (40) relative to the components (36, 38) to be screwed together, and a feed device (16) for advancing the screwing tool (24) in a feed direction, wherein the positioning head (26) comprises a holding mechanism (44) for holding the fed screw (40) in a screwing position, characterized by that a separate actuator (74) is provided for opening the holding mechanism (44), by means of which the holding mechanism (44) can in principle be opened at any desired time. [11] Screw system (10) according to claim 10, characterized byone of the characterizing features of claims 6 to 9.

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