In the art a number of methods or processes for connecting two objects have been described. In case of objects partially consisting of plastic materials it has been found difficult to find a method for connecting these objects through this plastic portions as there is a problem with respect to the compatibility of the materials. On the one hand, traditional connecting techniques such as screws, bolts or rivets are not always possible because of the shape of the objects of the application in which the connected objects will be used.

On the other hand it is not always possible to use different processes based upon gluing or welding, as the plastic material are not suitable for such techniques or in that it is not possible, because of the shape of the objects to use the required equipment for the application thereof.

It is an object of the invention to provide a process for connecting such objects which is generally applicable and in which the above mentioned problems are avoided.

This object is obtained by means of a process as described above, which process further comprises the step of making contact between a plastic part of the first object with a plastic part of the second object and subsequently subjecting the so contacted surfaces to vibration welding.

In this way it becomes possible to connect two objects of all kind of shapes and irrespective of the place where the different connections between the two objects has to be made.

Vibration welding can make use of different frequencies, dependent upon the desired result. So it is possible to use low frequency vibration i.e. below 3000 Hz, whereby a high strength of the joint can be obtained. As a rule however the joint is much stronger than the bracket itself, so that ultrasonic vibrations may be used, preferably

above 20.000 HZ. The use of such high frequency offers better production possibilities, as there is no sound generated and the amplitude of the vibration might be small.

Preferably the two plastic materials of the two objects to be connected are substantially identical. It has been found that better bounds can be obtained if the chemical base structure of both plastic material is identical, i.e. the same polymer and polymer structure. Otherwise there may be small differences between the two plastic materials with respect to secondary characteristics such as filling agents, plastifiers etc., which may be selected in view of the construction and application of the two objects to be connected.

Preferably the plastic material is polyamide.

The invention also relates to a process for connecting a metal tube to a bracket or the like, which metal tube has been coated with a plastic material, preferably polyamide and the bracket being made of the same or another plastic material.

In a number of applications metal tubes are used. In the automotive industry especially metal tubing is applied e.g. as gasoline supply tube, tube connection for power steering, tubing for air conditioning purposes and liquid connection for the brakes.

It was standard to use metal tubes, especially steel tubes for this purpose. These tubes were mostly so-called welded tubes, which after being cut to the desired length, were bent in the shape necessary for the application and provided with brackets to fix the tube in its final position. Preferably the fixing between the bracket and the tube was done by welding or bracing the bracket to the outer wall of the tube.

The use of loose brackets which are fixed by means of clamping forces to the tube shows a number of disadvantages especially in automotive applications, in which the tubes are generally exposed to environmental conditions and erosion or abrasive circumstances due to gravel or stones hitting the tubes. The slits between the bracket and the tube are especially sensitive to corrosion and wear under such conditions, as they will act as a catch for these objects. Fixed brackets are preferred as it becomes

impossible to change the position or orientation of the bracket afterwards. This improves substantially the mounting time of the tube in the end product such as a car.

Metal welding or bracing for fixing brackets to a metal tube has a number of disadvantages. After the application of the bracket, the tube must be submitted to a so-called burst pression operation in order to see whether the tube has not been damaged in view of possible leakage.

Before the application of the welding or bracing techique the tube must be chemically cleaned, with possible negative environmental influence, or the need for special precautions as aggressive chemical compositions have to be used. After the welding or bracing the interior of the tube must be cleaned once more in order to remove the dirt introduced by joining the bracket to the tube in this way. Recycling of metal tubes with welded or braced brackets is also a difficult task as generally a number of different metals and alloys are present in the combination, which are difficult to separate, as this generally requires a complete remelting and separation of the mixture.

After connecting the metal bracket to a metal tube by welding or bracing there still is a need for additional protection against corrosion or abrasion, which requires either a chemical treatment or a coating. This is generally complicated as the tube has already its ultimate shape which might be very complex to handle.

Recently metal tubes have been used provided with a coating of plastic material.

Preferably these tubes were made out of aluminium. In a preferred form these were extruded tubes, but welded tubes might be used as well. After the manufacturing of these tubes, either by extrusion or welding these tubes are coated with plastic material preferably polyamide. Polyamide has the advantage of being well processable and at the same time offer a good protection against corrosion and abrasion.

Furthermore polyamide coatings have the special advantage of being well resistant to impact by gravel, stones or the like, because they have the right combination of strength and elasticity. After coating the tube this can be cut to the desired length and bent or otherwise deformed in order to bring it in the right shape for its application.

In order to fix the tube in its application it is provided with brackets. Preferably these brackets are also made of plastic material such as polyamide and most preferably the two materials, coating and bracket, are identical as this will result in the best bond between the two parts. The bracket might be in the shape of U-shaped member having an open end with a width corresponding substantially to the diameter of the

tube to which it must be applied. One leg of this U-shaped member may be extended and provided with a bore through which a screw may be passed in order to fix the bracket to its appliance.

In order to fix the bracket to the tube use is made of vibration welding. Vibration welding is a technique whereby the two parts are moved relatively to each other at a defined frequency whereby sufficient heat is generated to partly melt the two parts and after solidifying connect the two parts.

The use of Al-tubes coated with polyamide combined with brackets made from polyamide has a special advantage in the recycling of these tubes. After loosening the tube from its appliance by e.g. unscrewing the polyamide can be removed easily for the aluminium, by either melting, solving or even burning. Burning does not have any negative environmental effect as only water, carbondioxide and nitrogen are generated. After that the pure aluminium alloy used for making the tube remains, which can easily be remelted and reused; without need for a cumbersome separation step.

The invention also relates to a process for connecting a metal tube to a flexible hose, which metal tube has been coated with a plastic material, preferably polyamide and the hose being made of the same or another plastic material.

The tube is of the type as described above and a number of problems encountered in the use of such tubes when being connected to a flexible hose applies as well to this application of the invention.

In practice the flexible hose can be connected in different ways to an aluminium tube.

The most common system, mostly used in car manufacturing is the insertion of the tube into the hose and applying a clamping ring around both the tube and the hose at the overlap area. This type of connection is labour intensive and especially in case of thin walled tubes special precautions are required in order to not deform the tubes.

In German patent application 1960 0010 there is described a method using injection moulding in order to connect the tube to the hose. Although this will result in a reliable connection , the system is cumbersome in that it requires an injection moulding

machine and a special die design. This makes the equipment not very flexible, especially not if different sizes of tubes and hoses must be processed.

By the use of vibration welding a very reliable and flexible process has been obtained allowing a quick change to different dimensions. In order to have a sufficient transmission of the energy during vibration welding it is recommended to provide the plastic material of the hose with a filling agent. This filling agent must have the physical characteristics of transferring the energy to the interface between the hose and the tube. Especially suitable are glass fibres with a length of less than 10 mm, preferably less then 3 mm.

It is obvious that the invention is not restricted to the above described examples, but that modifications within the scope to the claims are possible.