The invention relates to a force limiter comprising a control member displaceable with respect to a holder and a chamber, whose shape is determined inter alia by the holder and the control member and which is located between a gas supply and a leakage resistance.
The invention also relates to a device for ultrasonically deforming an article made of synthetic material by means of a sonotrode that can be pressed against the article by a displacement device.
The invention further relates to a method of limiting a contact force with which a first article displaceable by a motor drive is pressed against a second article, the motor drive when switched into operation being switched off in response to the contact force with which the two articles come into contact with each other.
In a so-called force-to-pressure converter known from German Patent Application DE-A1-3326138, an air current at a pressure which is kept constant exerts a force on a ball connected to the control member. A counter force exerted on the control member in the form of a rod ensures, when the force exerted by the air current is exceeded, a relative displacement between the rod (control member) and a housing (holder). The leakage control provided between the ball and an edge of an opening in the housing and located between an air inlet, a chamber and an air outlet connected thereto varies comparatively strongly upon a displacement of the rod with the ball. This involves the disadvantage that the force exerted on the ball by the air current can be kept constant only with great difficulty. Such a disadvantage is only recognized if the recognition is obtained that a substantially constant force is necessary if the known a disadvantage is only recognized if it is realized that a substantially constant force is necessary if the known force-to-pressure converter should be used as a force limiter. This use has not been mentioned, however, in German Patent Application DE-A1-3326138.
Further, a device for ultrasonically deforming, for example, polymeric synthetic material by means of a sonotrode that can be pressed by a displacement device against the synthetic material is known from the book "Ultrasonic Engineering" by J. R. Frederick (1965), pp. 191-192. This book does not state the manner in which the contact force between the sonotrode and the synthetic material to be deformed is limited.
Finally, it should be noted that methods are well known in which, when a first article is pressed against a second article, the motor drive is switched off at the instant at which contact is made between the two objects. However, overshooting of the first article due to the mass inertia involves the risk of an inadmissibly great contact force between the articles.