Centring device for reversible attachment to a setting tool for blind rivet nuts

Abstract

In a centring device (1) for reversible fastening to a setting tool (3) for blind rivet nuts (17), a base element (2) is provided for connection to the setting tool (3), to which a support element (4) is arranged at a distance. An opening (9) is provided in the support element (4), which is designed for the passage of at least one region of a screwing tool (10) of the setting tool (3) and the centre axis of which can is alignable coaxially with a longitudinal axis of the screwing tool (10) that can be passed through. There are centring means (13) arranged around the opening (9), which extend axially to the centre axis of the opening (9) and are radially elastic. The centring means (13), which are fixed with their one end (14) to the support element (4) around the opening (9), extend symmetrically in a conical shape away from the support element (4) towards the centre axis and form an expandable conical head (16) with their second free end (15).

Description

[0001] The invention relates to a centring device for reversible attachment to a setting tool for blind rivet nuts with a base element which can be connected to the setting tool and to which a support element is arranged at a distance, to which centring means are attached.

[0002] Blind rivet nuts are used in thin sheet applications as a means of thread reinforcement. A blind rivet nut typically has an elongate body, that is generally cylindrical or hexagonal in cross section, and hollow for the major part of its length, with one end being either closed (blind) or open. Part of the hollow portion is threaded to receive a setting tool or bolt. A flange is formed at an open end of the blind rivet nut remote from the threaded end and extends laterally therefrom. The flange extends beyond the periphery of the hollow body and has a generally flat face that abuts the surface of an outer layer or sheet of material.

[0003] Installation of the blind rivet nut commences with the blind rivet nut being threaded onto a threaded mandrel of a setting tool and together inserting the blind rivet through preformed apertures of one or more layers of sheets of materials. On initiation of the setting cycle the setting tool mandrel, still in engagement in the blind rivet nut, is pulled rearwards towards the flange of the blind rivet nut thereby causing deformation of the blind rivet nut body walls beyond the side of the workpiece remote from the operator and sandwiching the, or each sheet of material, against the face of the flange. EP 3 980 220 A1 discloses for instance in more detail such setting tools.

[0004] When setting the blind fastener into the aperture of the workpiece, one of the difficulties encountered lies in positioning the blind fastener, after screwing it onto the bolt, in the aperture of the workpiece in which it must be crimped. Indeed, the precision of the location of this aperture by industrial robot driving for instance the setting tool or the setting head remains uncertain. An offset may occur between the axis of the aperture and the tool axis. A poor alignment between the tool axis and the aperture axis makes it impossible to set the blind fastener.

[0005] To overcome this drawback, DE 10 2010 039 460 A1 discloses a setting tool comprising means allowing the bolt and the anvil of a setting tool to move freely relative to the tool housing from a rest position to a temporary working position and for automatically and elastically returning said assembly towards the rest position. The automatic reset of the bolt and anvil into the rest position may lead to unintentional stresses on the threaded rod or the tool, resulting either in wear or in unintended or unwanted movements which may negatively influence the setting of the blind fastener.

[0006] The object of the present invention is to provide a device that can be used to align the blind rivet nut to be set with the setting hole.

[0007] The object is solved by the features of claim 1. Preferred embodiments are described in the dependent claims.

[0008] The object is solved by providing a centring device for reversible attachment to a setting tool for blind rivet nuts, with a base element that can be connected to the setting tool, with a support element arranged at a distance from the base element, with an opening in the support element that is intended for the passage of at least one region of a screwing tool of the setting tool and whose centre axis is alignable coaxially with a longitudinal axis of the screwing tool that can be passed through, and with centring means that are arranged around the opening, extending axially to the centre axis of the opening and of radially elastic design, which are fixed by one end to the support element around the opening and extend symmetrically in a conical shape away from the support element towards the centre axis and form an expandable conical head with their second free end.

[0009] In the context of the invention, the term 'setting hole' is used to refer to the corresponding prepared receptacles for a blind rivet nut, such as preformed apertures in a workpiece or other bores.

[0010] The device according to the invention makes it possible to align a blind rivet nut or the setting tool carrying it with the setting hole, or more precisely to align its axes. Alignment is often subject to errors, particularly in robot-controlled setting processes. The invention closes this gap in a simple and pragmatic way and provides a device that can be easily installed to existing setting tools. The device can be reversibly attached to the setting tool and is reusable.

[0011] In order to achieve simple mounting of the device on a setting tool, it can be advantageous if the base element is annular and forms a receptacle for holding the setting tool. The setting tool can be clamped in the receptacle and can be fastened to the base element using fastening means known to the skilled person.

[0012] The support element with an opening is arranged at a distance from the base element. The support element can advantageously be plate-shaped. It is preferred that the first ends of the centring means, which are in particular rod-shaped, are fixed to the support element at a uniform distance from one another. In particular, the centring means are arranged around the opening. The opening has preferably a round shape. However, a different shape of opening can also be provided, with a holder inserted into the opening to accommodate a cylindrical setting tool. The arrangement of the centring means around the opening is not fixed and can be adapted to the application.

[0013] In one embodiment, a ring element is provided around the opening, which has channels running axially to the centre axis of the opening on its circumference for guiding the centring means. The ring element can be conical so that the channels run radially inwards towards the centre axis of the opening. This design simplifies the attachment of the centring means to the support element.

[0014] In addition, the design of the channels can advantageously influence the conical shape formed by the centring means, as a change in the angle of the channels to the centre axis of the opening also changes the conical shape. By replacing the ring element, the device can therefore be adapted to the usage and in particular to the diameter of the setting tool to be accommodated. The ring element can be attached to the support element using fastening means.

[0015] It is preferable for the centring means to be made of spring steel or an elastic plastic. It can also be advantageous if the free ends of the centring means are spherical or have a friction-reducing coating to prevent damage to the setting tool. In an embodiment, the centring means comprise wire rods or another flexible element, e.g. a type of collet or a spring-loaded lever.

[0016] In a preferred embodiment, the support element is designed to be movable relative to the base element. Notably, there is a relative translational movement between the support element and the base element along a longitudinal axis. The movement changes the distance between the support element and the base element. Since the centring means are attached to the support element, these are also moved in the embodiment. The support element can advantageously be connected to the base element via linear guide elements. These ensure a linear movement of the elements in relation to each other. The linear guide elements can be provided by rail systems, cylinder-piston devices or a linear motor, for example. Advantageously, the linear guide elements can be controlled and moved by a motor, notably an electric motor or actuator. Automatic movement of the support element relative to the base element is preferred, but manual, i.e. non-automatic, movement is also possible.

[0017] In a preferred embodiment, at least one lifting cylinder is provided between the support element and the base element, in which a piston is operatively connected to the support element or the base element and a cylinder is operatively connected to the base element or the support element. The lifting cylinder can, for example, be designed as a pneumatically, hydraulically or electrically actuated lifting cylinder. An electric drive can be used alternatively or additionally.

[0018] In one embodiment, the centring means can be moved from a first position, in which they form the conical head, to a second position, in which they are spread out and rest at least partially against a screwing tool that can be guided through the opening. It is obvious to the skilled person that there are intermediate positions between the first and second positions and that the first and second positions merely define end positions. The movement of the centring means can be achieved by changing the distance between the support element and the base element, especially if a setting tool is held by the base element. In an alternative embodiment, however, a movement of the setting tool relative to the support element can also be provided, which in turn causes the centring means to be moved from their first position to their second position.

[0019] The invention also related to an arrangement for setting a blind rivet nut, comprising a setting tool with a screwing tool present at its free end for receiving the blind rivet nut and a centring device as described reversibly attachable to the setting tool. In an embodiment, the centring means can be moved from a first position, in which they form an unspread conical head, in which the free end of the screwing tool is located within the conical shaped centring means, into a second position, in which the centring means, when spread, rest at least partially against the screwing tool guided through the opening and penetrating the conical head. It has been observed that the arrangement makes it easy to align the blind rivet nut or the setting tool with a setting hole. The axes, i.e. the longitudinal axis of the setting hole and that of the blind rivet nut, can be brought into alignment by means of the centring device. The arrangement can also be used for robot-based assembly by attaching the setting tool to the free end of a handling robot. Further advantages and embodiments of the centring device described above can also be applied to the arrangement.

[0020] The invention also concerns a method of setting a blind rivet nut with a described arrangement, comprising the steps of: moving the setting tool to a standby position in which it is spaced from a workpiece having a setting hole, screwing the blind rivet nut onto the screwing tool of the setting tool, moving the centring means over the screwing tool and the blind rivet nut into their first position, so that the free ends of the centring means form a conical head, moving the conical head into the setting hole in the workpiece, which is provided for receiving the blind rivet nut, wherein a longitudinal axis of the setting hole may be unequal to the longitudinal axis of the screwing tool, further insertion of the conical head into the setting hole, so that the longitudinal axis of the screwing tool is radially aligned with the longitudinal axis of the setting hole, moving the centring means back over the screwing tool with the blind rivet nut so that the blind rivet nut is exposed, setting the blind rivet nut in the setting hole.

[0021] The process enables efficient and secure installation of blind rivet nuts, with the centring device serving to align the blind rivet nut with the setting hole.

[0022] It is preferred that the free end of the screwing tool is moved axially to its longitudinal axis after the radial alignment of the longitudinal axis of the screwing tool. This can reduce the cycle time of the setting process. Alternatively, the complete setting tool can be moved back axially to its longitudinal axis after the radial alignment of the longitudinal axis of the screwing tool, before the centring means are then moved to the second position and the blind rivet nut is set.

[0023] The invention is explained in more detail below with reference to an embodiment of the invention, which is shown in the drawings. It shows Figure 1exploded view of a preferred centring device, Figure 2perspective view of a design of a centring device attached to a setting tool and Figure 3-10an example of a setting process for a blind rivet nut using a preferred arrangement.

[0024] Figure 1 shows an exploded view of a preferred centring device and Figure 2 a perspective view of a design of a centring device attached to a setting tool. The centring device 1 comprises a base element 2, which is intended for reversible attachment to a setting tool 3. The base element 2 can be designed differently depending on the application. In the embodiment shown, the base element 2 is shaped like a ring and is positioned on the circumference of the setting tool 3. Due to the preferred design, the base element 2 is easy to mount to setting tools 3 and can be attached in a simple manner. In addition, the setting tool 3 is still accessible for maintenance purposes. The base element 2 can, for example, be attached to the setting tool 3 via flange connections and screws.

[0025] A support element 4 is arranged at a distance from the base element 2, which is basically supported by the base element 2. There are linear guide systems 5 between the base element 2 and the support element 4, which enable linear movement of the support element 4 relative to the base element 2. These can be guided rails or, as shown, piston-cylinder arrangements. These arrangements can be designed as simple guides in which a cylindrical piston is attached to the support element 4 and engages in a cylindrical tube fixed to the base element 2. The tube can be provided without pneumatic or hydraulic fluid and only serves as a linear guide. Additionally or alternatively, however, a lifting cylinder 6 or several lifting cylinders can also be provided. In this embodiment, the piston 7 can be fixed to the support element 4 and the cylinder 8 to the base element 2. Of course, the reverse arrangement is also possible. The lifting cylinder 6 can be designed as a pneumatic, hydraulic or electric lifting cylinder 6. A control unit not shown and, for example, an electric motorised unit can be connected to the lifting cylinder 6 so that the stroke of the cylinder 6 can be changed in a controlled manner. This allows the distance between the support element 4 and the base element 2 to be varied in a controllable manner.

[0026] The support element 4 can be plate-shaped. There is an opening 9 in the support element 4, which can have a round shape, for example. The diameter of the opening 9 is dimensioned in such a way that at least one free end of a setting tool 3, in particular its screwing tool 10 with a blind rivet nut, can be passed through it. A ring element 11, which is conical in shape, at least its outer surface, is fastened in the edge area of the opening 9. The ring element 11 can be attached to the support element 4 via screw connections or flange connections. Axially extending grooves or channels 12 are inserted on its circumference, which incline radially towards the centre axis of the opening 9 due to the conical design.

[0027] In the edge area of the opening 9 or in the ring element 11, there may be receptacles for centring means 13. The centring means 13 are preferably rod-shaped. A first end 14 of a centring means 13 can be fastened in a corresponding receptacle, for example by clamping or screwing it in place. A snap-on or latching connection between the first end 14 of a centring means 13 and the receptacle is also possible. For this purpose, the end area of the first end 14 of the centring means 13 can have corresponding configurations. The centring means 13 are fixed to the support element 4 around the opening 9 at a uniform distance from one another.

[0028] The centring means 13 fit into the channel-like grooves 12 of the ring element 11, i.e. the diameter of the grooves 12 is adapted to that of the centring means 13. Of course, it is also possible for the centring means 13 not to be guided via the groove-like channels 12 in the ring element 11. Anchoring the centring means 13 in the edge area of the support element 4 around the opening 9, in particular in an angled receptacle, is also possible.

[0029] The centring means 13 extend symmetrically in a conical shape away from the support element 4 towards the centre axis, with the free second ends 15 of the centring means 13 forming a pointed conical head 16. The centring means 13 are radially elastic so that the conical head 16 can be expanded. When no pressure is applied, the centring means 13 are in a first unspread position, which is shown in Figure 2. The second ends 15 of the centring means 13 can touch each other in the conical head 16. However, it is also possible for the second ends 15 not to touch each other, but to be spaced apart. The centring means 13 can be made of spring steel, for example. In order to form a uniform conical head 16, it is advantageous for all centring means 13 to have the same length. The centring means 13 may comprise, as depicted in Figure 1 or Figure 2, a plurality of wire rods, regularly distributed around the opening 9. More generally, the centring means could comprise or be formed by a flexible element, e.g. a type of collet or a spring-loaded lever.

[0030] In the embodiment depicted in Figure 2, a centring device 1 is already attached to a setting tool 3. The free end of the screwing tool 10 of the setting tool 3 lies within the conical form of the centring means 13 and the conical head 16 is not spread. Due to the movability of the supporting element 4 and thus also of the centring means 13 attached to it, the centring means 13 can be present in different positions. In the arrangement shown, consisting of setting tool 3 and centring device 1, the centring means 13 can be moved from a first position, in which they form an unspread conical head 16, in which the free end of the screwing tool 10 is located inside the conical centring means 13, into a second position, in which the centring means 13 are spread out and rest at least partially against the screwing tool 10, which is guided through the opening 9 and penetrates the conical head 16. In order to prevent damage to the setting tool 3, in particular the screwing tool 10, due to the movement of the centring means 13, the free second ends 15 of the centring means 13 can, for example, be spherical in shape. Alternatively, a protective layer could be applied that has a friction-reducing effect.

[0031] Figures 3-10 illustrate an example of a setting process for a blind rivet nut. An arrangement comprising a setting tool 2 and a centring device 1 attached thereto as explained above is shown. In the ready position of the setting tool 3 shown in Figure 2, the free end of the setting tool 3, in particular that of the screwing tool 10, opens into the cone formed by the centring means 13. To enable the screwing tool 10 to pick up a blind rivet nut 17, the centring means 13 are moved from this first position into their second position, in which the centring means 13 are spread apart and rest at least partially against the screwing tool 10, which is guided through the opening 9 and penetrates the conical head 16. The screwing tool 10 is now accessible. In one embodiment, the movement of the centring means 13 is achieved by moving the support element 4 by changing the stroke of the lifting cylinder 6 and reducing the distance between the support element 4 and the base element 2.

[0032] In a further embodiment, the centring means 13 can be moved by moving a spindle 18 that drives the screwing tool 10. The spindle 18 and with it the screwing tool 10 can also be moved back in such a way that the centring means 13 are moved from their second position to their first position and vice versa. In this embodiment, linear guide systems 5 between the support element 4 and the base element 2 can be omitted. The centring means 13 can be moved from their first position to their second position by a forward movement of the spindle 18.

[0033] There may be an end position on the setting tool 3 that limits the maximum movement of the support element 4 relative to the base element 2. Alternatively, the movement of the lifting cylinder 6 can be controlled and defined positions triggered. For this purpose, the centring device 1 can be connected to a control unit of the setting tool 3 and controlled via this, which has the advantage that their movements can be synchronised.

[0034] In the next step, the blind rivet nut 17, which has an internal thread, is screwed onto the external thread of the screwing tool 10. The blind rivet nut 17 can be held in a holding device 19 to simplify the screwing process. The holding device 19 can be part of an automatic feeder to automatically present blind rivet nuts 17 in front of the setting tool 3.

[0035] After receiving the blind rivet nut 17, the centring means 13 can be moved from their second position to their first position, in which their free ends 15 form an expandable conical head 16 by increasing the distance between the supporting element 4 and the base element 2. Alternatively, as mentioned, the setting tool 3, in particular the spindle 18, can also be moved.

[0036] The screwing tool 10 and the received blind rivet nut 17 lie in the cone shape formed by the centring means 13, so that the conical head 16 forms the free end of the setting tool 3. The setting tool 3 is then moved towards a workpiece 20 with a setting hole 21 and the conical head 16 is moved into the setting hole 21. The longitudinal axis of the setting hole 21 does not have to match the longitudinal axis of the blind rivet nut 17, as the conical head 16 can be used to achieve radial equalisation even if the axes do not align. The inconsistency of the axes can be seen in the enlarged view of Figure 6. The conical head 16 is moved into the setting hole 21 up to a stop so that the axes are aligned, as schematically depicted in the enlarged view of Figure 7. A radial compensation takes place. Once coaxiality has been established, the setting tool 3 can be moved back to its standby position in which it is at a distance from the workpiece 20. The centring means 13 are moved from their first position to their second position, in which they are spread out on the circumference of the screwing tool 10. As can be seen in the enlarged view of Figure 9, a gap can be provided for an angular deviation. The setting tool 3 moves again into the setting hole 21, with the blind rivet nut 17 forming the free end of the setting tool 3. The blind rivet nut 17 is set into the setting hole 21.

[0037] Alternatively, in a further embodiment, it may be provided that the setting tool 3 is not moved out of the setting hole 21, but the centring means 13 are moved from their first position to their second position. For this purpose, it can be advantageous if the spindle 18 is moved back slightly so that no pressure from the screwing tool 10 or the blind rivet nut 17 acts on the centring means 13. Once the centring means 13 are in the second position, the blind rivet nut 17 can be placed in the setting hole 21 by moving the setting tool 3 forward.

[0038] The invention enables the blind rivet nut 17 to be aligned with the setting hole 21 in a simple manner. A significant advantage is that existing setting tools 3 can also be equipped with the centring device 1. It is also not necessary to modify the setting tool 3.

Claims

1. Centring device (1) for reversible attachment to a setting tool (3) for blind rivet nuts (17), with a base element (2) that can be connected to the setting tool (3), with a support element (4) arranged at a distance from the base element (2), with an opening (9) in the support element (4) that is intended for the passage of at least one region of a screwing tool (10) of the setting tool (3) and whose centre axis is alignable coaxially with a longitudinal axis of the screwing tool (10) that can be passed through, and with centring means (13) that are arranged around the opening (9), extending axially to the centre axis of the opening (9) and of radially elastic design, which are fixed by one end (14) to the support element (4) around the opening (9) and extend symmetrically in a conical shape away from the support element (4) towards the centre axis and form an expandable conical head (16) with their second free end (15).

2. Centring device (1) according to claim 1, characterised in that the base element (2) is annular and forms a receptacle for receiving the setting tool (3).

3. Centring device (1) according to claim 1 or 2, characterised in that the first ends (14) of the centring means (13) are fixed to the support element (4) at a uniform distance from one another.

4. Centring device (1) according to one of the preceding claims, characterised in that a ring element (11) is present around the opening (9), which ring element has channels (12) on its circumference running axially to the centre axis of the opening for guiding the centring means (13).

5. Centring device (1) according to one of the preceding claims, characterised in that the centring means (13) are made of spring steel, spring-loaded metal elements or an elastic plastic.

6. Centring device (1) according to one of the preceding claims, characterised in that the support element (4) is movable relative to the base element (2).

7. Centring device (1) according to claim 6, characterised in that at least one lifting cylinder (6) is provided between the support element (4) and the base element (2), in which a piston (7) is operatively connected to the support element (4) or the base element (2) and a cylinder (8) is operatively connected to the base element (2) or the support element (4).

8. Centring device (1) according to claim 6 or 7, characterised in that the support element (4) is connected to the base element (2) via linear guide elements (5).

9. Centring device (1) according to one of the preceding claims 6 to 8, characterised in that the centring means (13) are movable from a first position, in which they form the conical head (16), into a second position, in which they are spread out and rest at least partially against a screwing tool (10) that can be guided through the opening (9).

10. Arrangement for setting a blind rivet nut (17), comprising a setting tool (3) with a screwing tool (10) present at its free end for receiving the blind rivet nut (17) and a centring device (13) reversibly attachable to the setting tool (3) according to one of the preceding claims.

11. Arrangement according to claim 10, wherein the centring means (13) can be moved from a first position, in which they form an unspread conical head (16), in which the free end of the screwing tool (10) is located within the conical shaped centring means (13), into a second position, in which the centring means (13), when spread, rest at least partially against the screwing tool (10) guided through the opening (9) and penetrating the conical head (16).

12. Arrangement according to claim 10 or 11, characterised in that the setting tool (3) is attached to a free end of a handling robot.

13. A method of setting a blind rivet nut (17) with an arrangement according to any of claims 10 to 12, comprising the steps of: moving the setting tool (3) to a standby position in which it is spaced from a workpiece (20) having a setting hole (21), screwing the blind rivet nut (17) onto the screwing tool (10) of the setting tool (3), moving the centring means (13) over the screwing tool (10) and the blind rivet nut (17) into a first position, so that the free ends (15) of the centring means (13) form a conical head (16), moving the conical head (16) into the setting hole (21) in the workpiece (20), which is provided for receiving the blind rivet nut (17), wherein a longitudinal axis of the setting hole (21) may be unequal to the longitudinal axis of the screwing tool (10), further insertion of the conical head (16) into the setting hole (21), so that the longitudinal axis of the screwing tool (10) is radially aligned with the longitudinal axis of the setting hole (21), moving the centring means (13) back over the screwing tool (10) with the blind rivet nut (17) so that the blind rivet nut (17) is exposed, setting the blind rivet nut (17) in the setting hole (21).

14. Method according to claim 13, characterised in that the free end of the screwing tool (10) is moved axially to its longitudinal axis after the radial alignment of the longitudinal axis of the screwing tool (10) or the setting tool (3) is moved back axially to its longitudinal axis after the radial alignment of the longitudinal axis of the screwing tool (10).

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