Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1996-05-08
1999-11-23
Yao, Sam Chuan
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
156290, 156324, 1565802, B32B 3108, B32B 3120
Patent
active
059893702
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for the ultrasonic welding of material webs which move at high speeds in the nip between the ultrasonic horn of a welding unit and an anvil holder in which anvils are disposed in a given pattern.
BACKGROUND OF THE INVENTION
When ultrasonically welding, the materials to be welded together are worked mechanically by moving the end of an ultrasonic horn up and down in the material with a frequency that lies within the ultrasonic range. Heat is generated in the material as a result of the internal friction created by this mechanical working process, causing the material to melt in the worked area so that materials located in between horn and anvil will melt and therewith fuse together. Naturally, the heat generated in the materials will depend on the degree to which the material is worked, and if the material is worked to an excessively low degree the bond between the materials will be weak or non-existent, whereas if the material is worked to an excessive degree the materials will be perforated. The anvils are often comprised of projections which stand-out from the surface of an anvil holder, so as to provide a small "contact surface" between horn and anvil, and the energy delivered by the welding unit is concentrated over a small area. When welding moving webs of material, the anvils often comprise a suitable pattern of projections on a pattern cylinder or drum. One problem encountered when ultrasonic welding moving webs, for instance when bonding together the outer sheets of absorbent articles, such as diapers, sanitary napkins or incontinence guards, is that of providing a weld seam at the high rates of web travel that are desirable in such manufacture.
U.S. Pat. No. 4,414,045 teaches an arrangement for producing nonwoven fabric by ultrasonic welding of the fibers in a mat of loosely-laid weldable fibers, this mat being moved at speeds greater than 50 m/min. This arrangement includes a plurality of anvil rolls which are disposed sequentially in the movement direction of the mat and each of which has an anvil density such that the sum of the anvils per unit area on all cylinders will correspond to the desired number of bonding points per unit area of the nonwoven fabric. An arrangement of this kind is bulky and requires the anvil cylinders to be driven synchronously in order to achieve a desired bonding pattern.
SUMMARY OF THE INVENTION
The object of the present invention is to solve the problem of obtaining weld bonds in a simple and attractive manner when ultrasonically welding webs of material that move at high speeds.
This object is achieved by means of a method of the kind defined in the introduction which is characterized by determining the weld width of each ultrasonic horn in the ultrasonic welding unit in accordance with the intended highest travelling speed of the webs. When the welding width of the ultrasonic horns is reduced for webs that travel at high speeds, the counterpressure exerted by the anvil cylinder and the webs is also reduced, so that the amplitude of horn movement can be maintained and a good weld bond ensured.
According to one preferred embodiment of the method, the welding width of each ultrasonic horn is made so small that welding is effected with an average power intake of the ultrasonic welding unit concerned. In this way, the major part of the energy delivered to the welding unit is used for useful work. When ultrasonic welding webs that are comprised of nonwoven fabric which includes polypropylene with a combined or total thickness of 0.4-1.4 mm, the welding width of each ultrasonic horn in the ultrasonic welding arrangement will be smaller than 70 mm for web speeds in excess of 60 m/min. In the case of maximum web speeds, in excess of 100 and 160 m/min, the welding width of each ultrasonic horn in the ultrasonic welding arrangement will be smaller than 50 and 30 mm respectively.
The invention also relates to an ultrasonic welding arrangement for mutually bonding webs of material which run in the nip between an
REFERENCES:
patent: 3733238 (1973-05-01), Long et al.
patent: 3879256 (1975-04-01), Rust, Jr.
patent: 4311540 (1982-01-01), Hill
patent: 4404052 (1983-09-01), Persson et al.
patent: 4414045 (1983-11-01), Wang et al.
patent: 4713132 (1987-12-01), Abel et al.
patent: 5433816 (1995-07-01), Stewart et al.
SCA Hygiene Products Aktiebolag
Yao Sam Chuan
LandOfFree
Method and arrangement for ultrasonic welding does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and arrangement for ultrasonic welding, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and arrangement for ultrasonic welding will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1216895