Metal working – Method of mechanical manufacture – With testing or indicating
Reexamination Certificate
2002-01-30
2004-03-30
Hong, John C. (Department: 3726)
Metal working
Method of mechanical manufacture
With testing or indicating
C029S407010, C029S516000
Reexamination Certificate
active
06711799
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for seal-tightly attaching a flexible tubing of elastomeric material, especially of flexible members for air springs, to a connecting part by means of a clamping ring, which is radially pressed by a clamping tool. The invention further relates to a clamping tool for carrying out the method.
BACKGROUND OF THE INVENTION
It is known to use a radially pressed-together metal clamping ring for pressing the end of a flexible member to the roll-off piston or to the cover of an air spring. The radial pressing of the clamping ring takes place with a clamping tool which comprises individual clamping jaws arranged to have a circular form. When clamping the clamping ring, the individual clamping jaws are moved so far toward each other until the required clamping between the wall of the flexible member and the connecting part (roll-off piston or cover of the air spring) is achieved.
What is decisive for the quality of the attachment of the flexible member is the precise achievement of the necessary clamping between the wall of the flexible member and the clamping region. The clamping cannot be too little because, in this case, the friction force, which results from the clamping, between the wall of the flexible member and the connecting part and therefore the required holding force of the wall of the flexible member on the connecting part is reduced. Likewise, the clamping force may not be too great because then the wall of the flexible member as well as the connecting part can be damaged. Furthermore, a clamping force which is too high and a deformation of the connecting part resulting therefrom can likewise lead to a reduction of the holding force.
Basically, two methods are known for attaching a flexible member to a connecting part of an air spring. In the one method, the clamping jaws of the clamping tool are moved toward each other with the force controlled, that is, the clamping operation is stopped when the force, which is generated by the clamping tool, corresponds to a pregiven force. The disadvantage of this method is that force tolerances can result in the total system and the force, which is generated by the clamping tool, therefore is not in a clear relationship to the force which arises between the flexible member and the connecting part.
Thus, it is, for example, possible that increased friction within the clamping tool occurs because of the deterioration thereof. In this case, an increased part of the force, which is applied by the clamping tool, has to be used to overcome this friction. For the same pregiven total force which the clamping tool generates, the force becomes less which adjusts between the flexible member and the connecting part as a consequence of the pressing of the clamping ring.
It is likewise possible that, when carrying out the method, clamping rings of different hardness are used. Only a small force is required to deform a soft clamping ring, whereas a large force is required for deforming a hard clamping ring. If a pregiven total force is generated in both cases by the clamping tool, then this leads, in the first case, to the situation that the force between the flexible member and the connecting part is increased and, in contrast, this force is reduced in the second case. Finally, the connecting part itself can have different stiffnesses, which, for a pregiven total force of the clamping tool, likewise leads to the situation that different forces adjust between the flexible member and the connecting part.
In the other known method, the clamping jaws of the clamping tool are moved together in a displacement-controlled manner, that is, a clamping operation is ended as soon as the clamping jaws have passed through a pregiven path. This method has the disadvantage that dimension tolerances in the components lead to different forces between the flexible member and the connecting part. If, for example, a clamping ring is used whose cross section lies below the pregiven cross section because of manufacturing tolerances, then this leads to a reduction of the force between the flexible member and the connecting part. On the other hand, the use of a clamping ring whose cross section lies above the pregiven cross section, leads to an increased force between the flexible member and the connecting part.
In summary, it can be said that, with neither of the two above-mentioned methods, flexible members can be connected to the connecting parts of air springs in such a manner that a pregiven defined force adjusts between the flexible members and the connecting parts of the air spring, which is the same for all manufactured air springs.
SUMMARY OF THE INVENTION
The invention has as its task to provide a method with which the clamping ring, which is used for attaching a flexible member to a connecting part, can be radially clamped in such a manner that a defined pregiven force adjusts between the flexible member and the connecting part. The invention likewise has the task of providing a clamping tool for carrying out the method.
According to the invention, the task is solved starting from a method of the above-explained type with the following method steps:
a force-displacement characteristic line of the clamping tool is determined, which is recorded during the radial clamping of the clamping ring with the recording being started before the connecting part, the flexible member and the clamping ring lying one against the other without force and without play;
the loss force, which is necessary for overcoming the friction in the clamping tool, is determined from the force/displacement characteristic line;
the force, which exceeds the loss force, is so adjusted that it corresponds to a pregiven force between the flexible member and the connecting part.
The advantages, which are achieved with the invention, are especially seen in that a defined pregiven force between the flexible member and the connecting part can be adjusted independently of “force tolerances” in the system (for example, different friction within the clamping tool or different hardness of the individual used clamping rings) and independent of dimension tolerances of the individual used components (that is, of the flexible member, of the connecting part and of the clamping ring). For this reason, neither a force which is too high nor a force which is too low can develop between the flexible member and the connecting part so that the initially-explained disadvantages and the disadvantages associated therewith cannot occur. A further advantage of the method is that it is simple to carry out and therefore the costs of a component manufactured in accordance with the method are not increased.
According to a first embodiment of the invention, the loss force is determined in the region of the force/displacement characteristic line in that the clamping tool is moved together so far that the connecting part, the flexible member and the clamping ring lie in contact with each other free of force and free of play.
It has been shown that the force/displacement characteristic line, which arises during the clamping action of the clamping tool, is essentially a straight line before and behind the region wherein the connecting part, the flexible member and the clamping ring lie one atop the other free of force and free of play. The straight lines have different slopes. According to a further embodiment of
FIG. 3
of the embodiment of
FIG. 2
, the loss force is determined at that point at which the lines intersect (see the description with respect to the FIGS. as to how this occurs in detail). The advantage of this further embodiment is that the loss force can be determined in a simple manner at one point.
According to a further embodiment of the invention, the loss force is determined as follows:
the straight line ahead of the region (in which the clamping tool is moved together so far that the connecting part, the flexible member and the clamping ring lie one atop the other free of force and free of play) is extended beyond this region as a straight line;
from the e
ContiTech Luftfedersysteme GmbH
Hong John C.
Ottesen Walter
LandOfFree
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