Joints and connections – Molded joint – Fusion bond – e.g. – weld – etc.
Reexamination Certificate
1998-08-24
2001-04-24
Browne, Lynne H. (Department: 3629)
Joints and connections
Molded joint
Fusion bond, e.g., weld, etc.
C403S265000, C403S267000, C403S335000, C403S336000, C156S156000, C156S073100, C156S580100
Reexamination Certificate
active
06220777
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to improvements in injection molding of plastics. More particularly, the invention relates to advantageous aspects of methods and apparatus for producing ultrasonic weld joints for injection molded plastic parts.
BACKGROUND OF THE INVENTION
The step joint is a particular type of ultrasonic joint which is useful in joining plastic parts. This type of joint is frequently selected as the exuded melt does not result in a visual defect. Moreover, the exuded melt assists in locating the part and improves the shear resistance of the interface. However, as the nominal wall thickness of the plastic parts to be joined becomes thinner, the wall section required by the typical geometry of the step joint becomes thicker relative to the nominal wall thickness. This localized thick section will create a cosmetic blemish, known as a sink mark, on the surface of the part. This sink mark or depression is created as the hot resin cools after molding.
One prior art solution is to create a style line on the outside of the part to eliminate the extra thickness of plastic which creates the sink mark. In many cases, however, such a style line will not be acceptable because it affects the appearance of the part.
A need therefore exists in the art for a part design which permits a step joint interface which will create a structurally robust joint without creating a sink mark and without creating a style line
SUMMARY OF THE INVENTION
A joint interface according to the present invention replaces a continuous surface with an interrupted surface created by a series of ribs. At a cross section through a rib, the geometry produces a localized thick plastic region. At a cross section in between the ribs, the geometry produces a desired uniform wall thickness.
A more complete understanding of the present invention, as well as further features and advantages of the invention, will be apparent from the following Detailed Description and the accompanying drawings.
REFERENCES:
patent: 4564932 (1986-01-01), Lange
patent: 4781423 (1988-11-01), Muenzer et al.
patent: 5114807 (1992-05-01), Rowlette
patent: 5335771 (1994-08-01), Murphy
patent: 5454506 (1995-10-01), Jordhamo et al.
patent: 6019628 (2000-02-01), Shinchi
Branson Sonic Power Company, Technical Brochure, “Joint Design for Ultrasonic Welding”, 1980.*
“Ultrasonis Assembly”, Machine Design, Mar. 16, 1967, The Penton Publishing Co. Cleveland, Ohio.
Clarke John E.
Masterson Vince Joseph
Zhu Ningsheng
Browne Lynne H.
Garcia Ernesto
Lucent Technologies - Inc.
Priest & Goldstein PLLC
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