Patent Application
20130185917
The present invention relates to a method for attaching a bolt element to a component consisting of a composite material such as a fiber reinforced plastic part or a fabric reinforced plastic part, with the bolt element having a head part and a shaft part extending away from the head part, with the shaft part being provided with a tip at its end remote from the head part and optionally merging via a cylindrical region into a thread cylinder.
Composite materials are frequently used in most diverse areas and consist mainly of plastic with embedded fiber reinforcement The fiber reinforcement can for example take the form of tapes, fabrics, felts and mats. For example, coachwork parts of polyester resins reinforced with glass fibers and plastics such as epoxy resins reinforced with carbon fibers are frequently used in motor car construction and numerous further components such as consoles and cladding are likewise manufactured from such composite materials. When using carbon fibers as a reinforcement, fabrics of carbon fibers are frequently used because one can then obtain a reinforcement in all directions of the component.
The field of composite materials is however in no way restricted to glass fibers and carbon fibers there are many other reinforcement fibers which can be considered. Furthermore, the most diverse plastics can also be used as a matrix material. All such materials are described here generically as composite materials or fiber reinforced plastics. They can also be described by the generic term “organic sheet metals”. This term is understood in some circles as a specialist term. The present invention primarily uses those composite materials which use a thermplastic material, i.e. a thermoplastic as matrix material which softens or becomes pasty at elevated temperatures below the melting point. It is however not precluded that duroplastics can also be used as a matrix material provided these are adequately soft or become soft or pasty at elevated temperature, i.e. at temperatures which lie beneath the temperatures at which the matrix material is permanently damaged. The invention can also be used for composite materials with matrix materials which are indeed not thermoplastics but have not yet reached their final state but rather are present in a state in which they soften with or without heating but which can be transferred into a harder state in the course of time or by the action of ultraviolet light or humidity or otherwise through progressive polymerization or cross-linking.
It is frequently necessary to use components of composite materials with fastener elements, for example in order to secure the corresponding components to other parts or to attach other parts to the fiber reinforced plastic components.
The attachment of bolt elements to components of composite materials makes it possible, for example, to secure the corresponding components to other parts or to secure other parts to the fiber reinforced plastic parts. A nut element at the further component can be used as a counterpiece to the respective bolt element.
It is usually necessary to provide a hole in the component of composite material through which the shaft part of the bolt element can be passed. Both threaded inserts or eyes can already be integrated into the plastic component during the manufacture of the component, which is however very time consuming and complicated and leads to further costs and sometimes makes a local thickening of the plastic part necessary. The manufacture of holes is mainly achieved by a drilling process, whereby material residues, such as cuttings, arise and the composite material is weakened in the region of the bore. It is conceivable to punch the component in order to generate the holes as required, whereby waste in the form of punching slugs which has to be dispensed of arises as well as a local weakening of the component.
Composite materials consist of any desired reinforcement material or fibers and any desired plastically deformable or meltable matrix material. The term “composite materials” as used here in accordance with the invention includes therefore not only plastics with fiber reinforcement but, for example, also matrix materials of metal, for example aluminum, with a reinforcing material, such as for example carbon fibers or ceramic particles.
The object of the present invention is to enable an at least substantially loss-free attachment of a bolt element to a component of composite material without pronounced weakening of the component.
This object is satisfied by a method having the features of claim 1.
A method in accordance with the invention provides that the bolt element is pressed with the tip to the fore against the component and the tip is pressed through the component until the side of the component adjacent the head part of the bolt element enters to contact with the thread cylinder and the tip thereby generates a hole in the component and in that the bolt element is subsequently turned so that the thread of the thread cylinder forms an internal thread in the wall of the hole and that the contact surface is brought into engagement against the said side of the component.
Since the tip of the bolt element is driven through the component a hole arises for the shaft part of the bolt element. An unfavorable drilling or punching process can thus be avoided. Through the formation of the internal thread the bolt element is firmly seated in the component as a result. The invention makes use in particular of the recognition that many composite materials—optionally after corresponding heating—have an adequately soft or pasty consistency in order to easy pressing of a tip into the material. Insofar as the composite material of the component relates to reinforcing fibers, the elongate fibers are pushed to one side during the pressing of the tip to the component rather than being parted so that, in comparison to a drilling or punching process, only a small weakening of the material arises. A particular advantage of the invention consists also to the fact that both the hole for the passage of the shaft of the bolt and also the internal thread for the holding of the bolt element in the component are to a certain extent automatically produced during introduction of the bolt element, so that additional working steps can be spared.
In principle it is not out of the question that a pre-piercing could be effected. For example, such a pre-piercing could take place during a manufacture of the fiber reinforced components in a press or in a drilling process, for example when a type of pre-positioning or pre-centering of the fiber reinforced component relative to another component or vice versa is to be ensured by the pre-piercing.
The bolt element can have an axial ring groove radially within the ring-like contact surface which is arranged concentric to the shaft part, and which is optionally equipped with features providing security against rotation. Furthermore the component can have a ring-like raised portion at its side remote from the head part. In accordance with an embodiment of the invention the bolt element is rotated until the raised portion enters into engagement with the axial ring groove and optionally with the features providing security against rotation provided there. The axial ring groove extends preferably from a radially inner end of the contact surface or from a radial outer edge of the head part up to the shaft part. Raised portions which arise through the pressing of the tip through the component or raised portions which are intentionally provided at the component can be received in ring groove. In order to facilitate the reception process the ring groove can have a rounded cross-sectional shape. Radially extending ribs or grooves can in particular be considered as features providing security against rotation and are preferably uniformly arranged around the periphery of the shaft part. The features providing security against rotation bring about a fixed clawing of the head part of the bolt element into the components so that an undesired release of the screw connection formed by the engagement of the thread cylinder and the internal thread is prevented. Furthermore, the radially inner side of the ring groove can have a diameter which is smaller than the outer diameter of the thread cylinder, with the material of the components around the hole, in particular in the region of the raised portion being so deformed that it at least substantially fills out the ring groove or enters into an undercut formed between the thread cylinder and the head part. As a result of such an engagement of the head side end region of the shaft part by the material of the component the resistance against press-out can be notably increased.
The movement of the tip through the component in order to form the hole can in particular be a translatory movement. For example the tip can be set into a movement which extends exclusively in the direction of the longitudinal axis of the bolt element.
The movement of the tip through the component in order to form the hole can have however also be a rotary movement. The heat of friction which is hereby generated can be exploited for the local heating of the component in the region of the attachment, so that no additional heating power or only little additional heating power is required in order to bring the component locally to a temperature at which the matrix material has a soft or pasty consistency.
Basically it is also possible for the bolt element to be rotated and also pressed from the very start, with the tip thus having a rotational and a translational component of movement and being pressed through the component. This movement can be retained until the contact surface contacts the component.
Furthermore it is basically possible to displace the bolt element only in the direction of its longitudinal axis and to dispense with a rotary movement of the bolt element. Since the soft matrix material is expanded through the movement of the bolt element through the composite material and is pressed inwardly by the outwardly disposed material and/or through the pressing action of a die button that is eventually used, the material and preferably also a part of the reinforcing material that is used can be pressed into the thread of the bolt element. This material is then solid after the cooling down of the material to the environmental temperature and forms a female thread which accommodates the male thread of the bolt element, precisely in the same way as a female thread arises in the embodiment of the rotary movement of the bolt element. This embodiment with only an axial movement of the bolt element is particularly simple to realize. The movement of the tip or of the bolt element can take place in a press, by tongs, by a robot, by means of a C-frame with a power cylinder or a tool such as an arbor press or a pillar drill (drill press) or otherwise.
In accordance with an embodiment of the invention, after the formation of the internal thread in the hole of the component, a force is exerted onto the side of the component remote from the head part and a force is exerted onto the head part in order to press material of the composite material around the hole into any ring groove that is present and into contact with the surfaces of the features providing security against rotation and also optionally to ensure or generate a planar screw-on surface at the side of the component remote from the head part. In this way, an undesired material removal or an undesired material deformation with a rotating contact between any features providing security against rotation and the component surface can be avoided.
Furthermore, the component can be heated in the region of the piercing to a matrix material dependent temperature at which the matrix material of the composite material does not melt but softens or becomes pasty, for example at a temperature of 260° C. when the material is PA6. In this manner the pressing of the tip through the component but also the formation of an internal thread in the wall of the hole on rotation of the thread cylinder is facilitated.
The component can be held during the hole formation by means of the tip either free standing or supported on a support having an opening for receiving the tip. As an alternative or in addition, the bolt element can also be pre-loaded in the direction towards the component during the formation of the internal thread.
As a support a supporting component can be used having a cut-out defining the opening. At the support auxiliary means for the hole formation can also be provided, in particular an iris diaphragm having a small starting opening which can be pressed open to a larger opening. The component of composite material provided for the attachment of the bolt elements is then preferably brought with one side into contact with the iris diaphragm and the tip of the bolt element is pressed through the component coming from the opposite side of the component, with the smaller initial opening of the iris diaphragm accommodating a narrower region of the tip and transforming into a larger opening with increasing penetration of the component by the tip, whereby the component is at least as fully as possible supported over the full area during the hole formation by the support. Thus, the component of a composite material is provided with a hole by means of the tip which is pressed through the component while the component is supported at the underside, and indeed in the area of the piercing always immediately adjacent to the tip, so that as little composite material as possible can escape between the side wall of the tip and the periphery of the hole, because the opening of the iris diaphragm always adapts to the respective diameter or the respective cross-sectional shape of the tip in the region of the widening hole. An iris diaphragm of this kind is described in the German patent application of the present applicants with the attorney's file reference P10447PDE, the content of which is hereby made part of the present application.
The bolt element can also have a cylindrical rivet section which surrounds the shaft part adjacent to the head part, with the ring groove having at the radially inner side not a diameter which is smaller than the outer diameter of the thread cylinder but rather having a boundary at this radially inner side which is aligned with a cylinder section having the same diameter as the outer diameter of the rivet section and which lies between the head part and the rivet section, with the component being supported during the hole formation by means of the tip on a support having an opening for receiving the tip, which preferably has a raised portion surrounding the opening which, on abutment at the rivet section presses a part of the rivet section radially outwardly. In this way, a rivet bead can be formed which engages behind the material of the component and thus increases the resistance against press-out. The raised portion can for this purpose have a conical cross-sectional shape.
The invention relates also to a bolt element, in particular for use in a method as described above and in particular for the attachment to a component of the composite material such as a fiber reinforced plastic part or a fabric reinforced plastic part, with the bolt element having a head part having a contact surface and a shaft part pointing away from the head part, with the shaft part being provided at its end remote from the head part with a tip which merges into a thread cylinder, optionally via a cylindrical region. The cylindrical region can have an axial length which corresponds approximately to the thickness of the component or is longer or shorter than the thickness of the component. The purpose of this cylindrical axially parallel region is to so calibrate the hole of the component that the bolt element is well guided and forms a clean thread in the margin of the hole of the component.
In accordance with the invention the bolt element has an axial ring groove radially within the ring-like contact surface, with the ring groove being arranged concentrically to the shaft part and optionally being equipped with features providing security against rotation, with the radially inner side of the ring groove having a diameter which is smaller than the outer diameter of the thread cylinder, and the thread cylinder has a thread run-out which preferably runs out adjacent to the head part at the level of the contact surface.
The features providing security against rotation can be formed as ribs or grooves which are formed in the radial direction at the base of the ring groove and which are optionally extended further in the radial direction over the ring-like contact surface.
In accordance with an embodiment of the invention the annular contact surface, which is optionally divided into arcuate segments by the feature providing security against rotation, either lies in a plane perpendicular to the central longitudinal axis of the bolt element or at least substantially on a conical surface, the conceptual tip of which lies on the side of the head part remote from the shaft part.
A bolt element can also have a cylindrical rivet section which surrounds the shaft part adjacent to the head part and not have a diameter at the radially inner side which is smaller than the outer diameter of the thread cylinder but rather have a boundary at this radially inner side which is aligned with the outer diameter of the rivet section or with a cylinder section having the same diameter as the outer diameter of the rivet section and which is present between the head part and the rivet section, with the thread cylinder having a thread run-out which preferably runs out adjacent to the rivet section at the level of the free end of the rivet section.
Further developments of the invention are set forth in the dependent claims, the description and also in the accompanying drawing.
The invention will now be explained in more detail by way of example with reference to the drawing.
The bolt element 100 shown in
An axial ring groove 116 is located radially inside the contact surface 102 with respect to a central longitudinal axis L of the bolt element 100. This ring groove 116 is arranged concentrically to the shaft part 106 and has features 118 providing security against rotation in the form of ribs which are formed in the radial direction at the base of the ring groove 116. The radially inner side of the ring groove 116 has a diameter which is smaller than the outer diameter of the thread cylinder 114. Furthermore, the thread cylinder 114 has thread run-out 120 which runs out adjacent to the head part 104 at the level of the contact surface 102.
The ring-like contact surface 102 lies at least substantially on a conical surface 120 the conceptual apex of which lies at the side of the head part 104 remote from the shaft part 106.
A bolt element 100′ in accordance with an alternative embodiment of the invention is shown in
In the bolt element 100′ in accordance with
A method for the attachment of the bolt element 100 of a first embodiment shown in
In accordance with
Through the hole formation and the material displacement which is associated therewith raised portions 132, 133 arise in accordance with
After formation of the internal thread in the hole of the component 130 a force can with advantage be exerted at the side of the component 130 remote from the head part 104 of the bolt element and the force can be exerted on the head part 104 in order to press the material of the composite material around the hole into the ring groove 116 and into contact with the surface of the features 118 (
The planar support surface 138 also serves to generate a planar screw-on surface 142 (
In order to aid the formation of the hole and the internal thread the component 130 can be heated in the region of the piercing to a matrix material dependent temperature at which the matrix material of the composite material is not melted but rather softens or becomes pasty. When the material is PA6 (polyamide 6) heating to 260° C. can be considered by way of example.
The bolt element 100′ in accordance with the second embodiment (
The component 130 is again supported on a support 136′ with the opening 140 during the hole formation by means of the tip 110. However, the support 136′ here has a raised portion 144 surrounding the opening 140. When the rivet section 122 abuts against the upper raised portion 132 of the component 130 a part of the rivet section 122 is pressed radially outwardly so that a rivet bead 150 forms which can be seen in
The present invention can be used both with bolt elements which are realized as press-in elements and also bolts which are riveting bolt elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2012 001 086.9 | Jan 2012 | DE | national |
The present application claims priority under 35 U.S.C. §119 to German Patent Application No. 10 2012 001 086.9, filed on Jan. 20, 2012, the disclosure of which is expressly incorporated by reference herein in its entirety.
