Air actuated ultrasonic tool

Details Air actuated ultrasonic tool Air actuated ultrasonic tool

2000-05-10

2001-10-30

Sells, James (Department: 1734)

Adhesive bonding and miscellaneous chemical manufacture

Methods

Surface bonding and/or assembly therefor

C156S073100, C156S251000, C156S358000, C156S515000, C156S530000, C156S580200

Reexamination Certificate

active

06309490

ABSTRACT:

TECHNICAL FIELD
The present invention relates to ultrasonic acoustic tooling. More particularly, the invention relates to an ultrasonic acoustic tool having an internal air actuated nodal-mounted spring return air cylinder.
BACKGROUND ART
Ultrasonic tools are used in many industries for welding, swaging, and staking, as well as various other activities. In performing these activities it is sometimes necessary to apply a secondary predetermined amount of force to the parts being assembled. Thus, there are occasional non-ultrasonic functions as well as ultrasonic functions to be performed by the same tool. For example, it is often necessary to pre-compress, die cut, perforate, or score a part before, during or after the ultrasonic process.
Conventional nodal mounted ultrasonic welding tools generally utilize a spring-only plunger assembly. The ultrasonic generator sets the horn assembly into resonance along its longitudinal axis, through the introduction of an acoustic converter, in order to transmit mechanical vibrations to the part at a predetermined frequency. The horn assembly typically is a half- or full-wave design for performing ultrasonic operations, and can have a nodal mounted spring actuated plunger mechanism for performing the non-ultrasonic operations. The plunger mechanism is essentially spring biased to stick out of the end of the horn and is typically the first component to contact the part. The horn then continues to move into contact with the part and subsequently welds, stakes, swages (etc.) the part to another part by applying the mechanism vibrations.
There are a number of opportunities for improvement of the above conventional approach. For example, the spring actuated plunger mechanism has a limited range of forces that can be applied to the part. This is a function of the size and tension of the spring. It is therefore desirable to provide an acoustic horn assembly and method that has a wider range of force operation. Another difficulty is associated with the fact that the plunger mechanism is the first component to contact the part and generally cannot be retracted during the welding process. In fact, retraction of the plunger mechanism can only be enabled by retraction of the entire horn assembly. It is commonly known that problems such as part damage and part marking can occur as a result of this phenomenon. It is therefore desirable to provide an acoustic horn assembly having a plunger mechanism that is retractable before, during, or after the ultrasonic welding process.
SUMMARY OF THE INVENTION
The above and other objectives are provided as a method and system for ultrasonically bonding plastic parts. A nodally mounted air cylinder uses an electronic and pneumatic controller, an air pressure regulator and air supply source to operate. The air regulator generates a predetermined air pressure within the tool. The horn assembly is coupled to the air regulator for applying a desired actuation force to a part based on its predetermined air pressure. The predetermined air pressure therefore corresponds to the desired actuation force. The horn assembly transmits mechanical vibrations to the part at a predetermined frequency. The ultrasonic generator transfers high frequency electrical energy at the required frequency to the converter/horn assembly. The converter/horn assembly operates at a predetermined frequency and applies pressure to the part being assembled. By utilizing the electronic and pneumatic controller, along with the air regulator to supply the air pressure to the nodal mounted air cylinder a significantly wider range of forces can be applied. The aforementioned problems with part damage are therefore eliminated.
Further in accordance with the present invention, an air actuated acoustic horn assembly is disclosed. The horn assembly includes an acoustic horn having a longitudinal bore, where the acoustic horn transmits mechanical vibrations to a part at a predetermined frequency. A plunger mechanism is nodally disposed within the longitudinal bore of the acoustic horn, where the plunger mechanism has a stationary portion and a movable portion. The stationary portion is coupled to the horn. The horn assembly further includes an air channel configuration providing an air pathway between the electronic and pneumatic controller and the movable portion of the plunger mechanism, such that air pressure generated by the electronic and pneumatic controller causes the movable portion to extend from the horn and apply a force to the part. In a highly preferred embodiment, the movable portion of the plunger includes a return spring for retracting the movable portion back into the horn when the air pressure is discontinued.
In another aspect of the invention, a method for forming a plastic part is provided. The method includes the step of transmitting mechanical vibrations to the part at a predetermined frequency. The method further provides for generating a predetermined air pressure, and applying a force to the part based on the predetermined air pressure. The force shapes the part into a desired form.
Further objectives, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings.


REFERENCES:
patent: 4411720 (1983-10-01), Sager
patent: 4701229 (1987-10-01), Arakawa et al.
patent: 5275767 (1994-01-01), Micciche
patent: 5421923 (1995-06-01), Clarke et al.
patent: 6063220 (2000-05-01), Andersson

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