Patent Application
20170015048
The present application relates to a vibration welding system, a vibration welding method and a method of upgrading an existing vibration welding system.
By vibration welding, two parts, in particular two plastic parts, can be welded together by employing frictional heat at the joint surfaces of the two parts. The heat is generated by moving one part against the other under pressure. In contrast to ultrasonic welding, the frequencies employed during vibration welding are typically in the range from 50 Hz to 300 Hz and the amplitudes are typically in the range from 0.5 mm to 5 mm. Vibration welding is particularly useful tor welding large parts such as automotive parts, for example for welding an airbag shroud to an as instrument panel.
Vibration welding can be performed as linear vibration welding or as orbital vibration welding. In linear vibration welding, one of the parts is vibrated in only one linear direction. In orbital vibration welding, the vibration occurs not only in one linear direction, but in several directions within one plane. In general, orbital vibration welding is constructively much more involved.
Currently, large plastic parts such as instrument panels are welded by linear vibration welding, wherein the vibration occurs in a horizontal direction. For this purpose, usually a single vibration head is used to impose a linear vibration on one of the parts, wherein this vibration head is installed in a fixed position and orientation. However, certain parts to be welded (as for example automotive parts such as instrument panels) have complex geometries, for example geometries containing undercuts, which allow a vibration welding only in one specific vibration direction. This can be achieved, in principle, by employing a vibration welding system having two or even more vibration heads which each generate respective linear vibrations, wherein these linear vibrations occur in different horizontal vibration directions. However, such a system comprising two or more vibrations heads is constructively complex and is therefore quite expensive. Moreover, the number of possible vibration directions is limited to the number of vibration heads. In addition, a system containing several vibration heads requires a lot of floor space.
In view of these difficulties and disadvantages, it is an object of the present invention to provide a vibration welding system and a vibration welding method which are more flexible in terms of possible vibration directions (in a reference frame of the parts to be welded), however without being constructively too complex, and which require as little less floor space as possible. In some embodiments, loading the parts to be welded and unloading the welded parts shall be facilitated.
These and further objects can be achieved by a vibration welding system for vibration welding two parts together, in particular two plastic parts. The system comprises a machine frame, a lower tooling to which a lower part is nestable and an upper tooling. The upper tooling is arranged to be brought into contact with an upper surface of an upper part. Moreover, the upper tooling is arranged to vibrate with respect to the machine frame in a vibration direction in order to at least partially weld a lower surface of the upper part to an upper surface of the lower part.
According to the invention, the lower tooling is pivotably arranged with respect to the machine frame about a pivot axis. This pivotable arrangement allows first nesting the lower part to the lower tooling when this lower tooling is in a loading orientation, then pivoting the lower tooling to a welding orientation which is suitable for the specific parts to be welded, and then bringing the upper surface of the upper part into contact with the upper tooling for imposing the vibration and thus obtaining the welding. This system is therefore much more flexible in terms of possible vibration directions (in the reference frame of the parts to welder together), but it is constructively less complex and requires less floor space than systems having two or more vibration heads. The vibration welding method, which is also a part of the present invention, will be explained in further detail below.
In order to achieve the pivotability of the lower tooling, the system may comprise a platform and a turntable which is pivotable with respect to a platform about the pivot axis, wherein the lower tooling is fixed or fixable to the turntable.
With preference, the vibration direction is arranged substantially horizontally. This allows welding the two parts together in a stacked relationship in which the upper part is arranged on top of the lower part.
Advantageously, the pivot axis is arranged substantially perpendicularly to the vibration direction. This has the effect that ail vibration directions (in the reference frame of the parts to be welded) lie in a common plane (wherein this plane is then perpendicular to the pivot axis).
In particular when the vibration direction is arranged substantially horizontally, it is further advantageous when the pivot axis of the lower tooling is arranged substantially vertically.
The lower tooling may be pivotable by means of an electrical, hydraulic, pneumatic or mechanical drive, wherein a hydraulic drive is currently preferred.
With preference, the Lower tooling is slidably arranged with respect to the machine frame in a joining direction in order to bring the upper surface of the upper part into contact with the upper tooling. Of course it is also conceivable that the upper tooling or even both the lower tooling and the upper tooling are slidably arranged in the joining direction with respect to the machine frame.
With preference, the joining direction is arranged substantially parallel to the pivot axis. In particular, the joining direction may be arranged substantially vertically.
The lower tooling is also preferably slidably arranged with respect to the machine frame in a plane which is substantially perpendicular with respect to the pivot axis. In particular, said plane may be substantially horizontal. A slidable arrangement of the lower tooling in a horizontal plane make it possible to freely relatively move the two parts to be welded together and thereby to contact different portions of the upper surface of the upper part with the upper tooling. When the system comprises a platform and a turntable as described above, the platform may be slidably arranged with respect to the machine frame in said plane, in particular in said substantially horizontal plane. Such slidable platforms in a vibration welding system as such (but without a turntable) may be constructed as known in the art.
The system may further comprise a vibration generator for generating the vibration of the upper tooling, wherein this vibration generator may be configured to generate vibrations having a frequency in the range from 50 Hz to 300 Hz and/or an amplitude in the range from 0.5 mm to 5 mm. As explained above, such frequencies and amplitudes are particularly useful in vibration welding—in contrast to the much higher frequencies and much lower amplitudes which are employed in ultrasonic welding.
The present invention also relates to a vibration welding method for vibration welding two parts together, in particular two plastic parts. This method may be performed by using a system as disclosed above. The method comprises the steps of
In step b), the lower part may be nested to the lower tooling by clamping. In a first possible variant, only the lower part is nested to the lower tooling and only later contacted with the upper part. In a second possible variant, both the lower part and the upper part are nested to the Lower tooling.
Before and/or during and/or after pivoting in step c), the lower tooling may be slid in the horizontal plane. This provides an even more flexible positioning of the lower tooling and thus the lower part.
Step d) contains two sub-steps, namely a first sub-step of contacting the upper surface of the lower part with the lower surface of an upper part and a second sub-step of contacting the upper surface of the upper part with the upper tooling. These sub-steps may be performed in either order.
Thus, in a first possible order, the upper surface of the lower part may first be contacted with the lower surface of the upper part. For example, the upper part may simply be stacked on top of the upper part. Afterwards, the upper surface of the upper part cart be contacted with the upper tooling. This can be achieved, for example, by relatively moving the lower tooling together with the lower part and the upper part with respect to the upper tooling until the upper surface of the upper part is in contact with the upper tooling. This relative movement may be performed by moving the lower tooling upward, by moving the upper tooling downward or a combination of both movements.
In a second possible order of the two sub-steps of step d), the upper surface of the upper part is first contacted with the upper tooling. This can be accomplished, for example, by attaching the upper part to the upper tooling by suction, which is known as such in the art. Subsequently, the upper surface of the lower part is contacted with the lower surface of the upper part. This may also be achieved by relatively moving the lower tooling together with the lower part with respect to the upper tooling, i.e. by moving the lower tooling downward, by moving the upper tooling upward or a combination of both movements.
Preferably, the frequency of the vibrations lies in the range from 50 Hz to 300 Hz and/or the amplitude of the vibration lies in the range from 0.5 mm to 5 mm, as such frequencies and amplitudes have proved to be suitable for vibration welding.
The parts that are welded together may be automotive parts, such as large injection molded parts. In particular, the parts may be instrument panels, airbag shrouds, instrument panel air ducts, instrument panel reinforcements, automotive interior parts like center consoles, door panels, head liners, automotive exterior parts like bumpers, plastic side panels, non-automatic plastic pallets or plastic fencing.
A further aspect of the present invention relates to a method of upgrading an existing vibration welding system to a vibration welding system as described above. The existing vibration welding system comprises a machine frame, a lower tooling to which a lower part is nestable and an upper tooling. The upper tooling is arranged to be brought into contact with an upper surface of an upper part. Moreover, the upper tooling is arranged to vibrate with respect to the machine frame in a vibration direction in order to at least partially weld a lower surface of the upper part to an upper surface of the lower part.
The method of upgrading comprises the step of providing a lower tooling which is pivotably arranged with respect to the machine frame about a pivot axis. Thus, with this method of upgrading, an existing vibration welding system can be upgraded to a vibration welding system according to the present invention, thereby obtaining an improved vibration welding system having the advantages described above.
The upgrading may be performed by providing a turntable which is pivotable with respect to a platform about the pivot axis and by fixing the lower tooling to the turntable. Said platform may be part of the existing system. For example, this platform may already be arranged sizably with respect to the machine frame of the existing system. Alternatively, the platform may also be provided during upgrading.
An exemplary embodiment of the present invention as shown In the accompanying drawings will now be explained in detail. In the drawings,
a: shows the system with the lower tooling in a welding orientation in a front view;
The figures show a vibration welding system 10 according to the invention, which can be applied for vibration welding two parts 50, 60 together. In this particular example, the lower part 50 is an automotive instrument panel and the upper part 60 is an airbag shroud. However, the invention is certainly not limited to these particular parts.
The system 10 comprises a machine frame (which is not shown in the drawings), a lower tooling 12 and an upper tooling 13. The lower tooling 12 is pivotably arranged with respect to the machine frame about a vertical pivot axis P. For this purpose, the system 10 comprises a platform 14 and a turntable 15 which is pivotable with respect to a platform about the pivot axis P. The turntable 15 and thus the lower tooling 12 are pivotable with respect to the platform 14 by means of a hydraulic drive.
The upper tooling 13 is arranged to be brought into contact with an upper surface 65 of the airbag shroud 60. It can vibrate with respect to the machine frame in a horizontal vibration direction X in order to at least partially weld a lower surface 61 of the airbag shroud 60 to an upper surface 51 of the instrument panel 50, as will also be explained in further detail below.
The lower tooling 12 is also slidably arranged with respect to the machine frame in a vertical joining direction Y. In this way, the upper surface 65 of the airbag shroud 60 can be brought into contact with the upper tooling 13. Moreover, the lower tooling 12 is slidably arranged with respect to the machine frame in a horizontal plane, i. e. in a plane which is perpendicular with respect to the pivot axis P. This slidability is achieved through the platform 14, which is slidable in these directions. As slidable platforms 14 in vibration welding system as such (however without a turntable 15) are known in the art, a detailed description of the construction in this respect can be dispensed with.
The system 10 further comprises a vibration generator for generating the vibration of the upper cooling 13 at a frequency in the range from 50 Hz to 300 Hz and at an amplitude in the range from 0.5 mm to 5 mm. These parameters are suitable for vibration welding. The vibration generator as such may be constructed as known in the art and may comprise a vibrating platen, springs, electromagnets and a bridge. The springs may be mounted to one side of the vibrating platen which also includes the magnets of the electromagnetic system. The upper tooling 13 may be mounted on a lower side of the vibration platen.
In a first step a) of the vibration welding method according to the invention, the lower tooling 12 is provided in a loading orientation L. In a subsequent step b), the instrument panel 50 is nested to the lower tooling 12, for example by clamping. The upper surface 65 of the airbag shroud 60 is attached to the upper tooling 13, for example by suction. Thus, the situation shown in
When the instrument panel 50 has been nested to the lower tooling 12, the lower tooling 12 is pivoted by 90° about the pivot axis P in a step c). The welding orientation W thus obtained is shown in
Subsequently, in a step d), the lower tooling 12 is lifted together with the instrument panel 50 attached thereto towards the upper tooling 13 and the airbag shroud 60 attached thereto, so that the upper surface 55 of the instrument panel 50 is brought into contact with the lower surface 61 of the airbag shroud 60.
In this position, which is shown in
Afterwards, in a step f), the lower tooling 12 together with the instrument panel 50 and the airbag shroud 60 are lowered again so that the upper surface 65 of the airbag shroud is brought out of contact with the upper tooling 13.
Subsequently, in a step g), the lower tooling 12 is pivoted again about the pivot axis P from the welding orientation to the loading orientation L. The parts 50, 60 welded together may then be removed from the system 10.
As can be seen from this exemplary embodiment, the present invention allows loading the parts to be welded in a loading orientation and then welding them in a welding orientation which is different from the loading orientation. This significantly enhances the flexibility of the system in terms of possible vibration directions (in the reference frame of the parts to be welded), reduces that required machine space and also greatly facilitates the loading and unloading process.
