Welding thermoplastic material with a laser

• US 5,279,693 A
• Filed: 07/30/1992
• Issued: 01/18/1994
• Est. Priority Date: 05/09/1990
• Status: Expired due to Fees

• Current Assignee: LPS Industries, Inc.
• Original Assignee: LPS Industries, Inc.
• Inventors: Robinson, John P., Zuvich, John A., Trigger, Daniel, Clawges, Thomas L., Stadick, William R.
• Primary Examiner(s): Simmons, David A.
• Assistant Examiner(s): Barry, Chester T.
• Application Number:
  US07/921,383
• Time in Patent Office: 537 Days
• Field of Search: 219/121.75, 219/121.63, 219/121.64, 156/272.8, 156/275.1, 156/308.2, 156/308.4, 156/324, 156/379.6, 156/379.8, 156/379.9, 156/380.9, 383/63, 383/65
• US Class Current: 156/272.8
• CPC Class Codes: B23K 26/073 Shaping the laser spot
• CPC Class Codes: B29C 65/1619 Mid infrared radiation [MIR], e.g. by CO or CO2 lasers
• CPC Class Codes: B29C 65/1635 at least passing through one of the parts to be joined, i.e. laser transmission welding
• CPC Class Codes: B29C 65/1658 scanning once, e.g. contour laser welding
• CPC Class Codes: B29C 65/1664 making use of several radiators
• CPC Class Codes: B29C 65/7894 of continuously moving sheets or webs
• CPC Class Codes: B29C 66/001 Joining in special atmospheres
• CPC Class Codes: B29C 66/00141 Protective gases
• CPC Class Codes: B29C 66/0242 Heating, or preheating, e.g. drying B29C66/3464 takes precedence
• CPC Class Codes: B29C 66/0342 Cooling, e.g. transporting through welding and cooling zone
• CPC Class Codes: B29C 66/1122 Single lap to lap joints, i.e. overlap joints B29C66/45, B29C66/472, B29C66/52272 take precedence
• CPC Class Codes: B29C 66/43 Joining a relatively small portion of the surface of said articles B29C66/45 takes precedence
• CPC Class Codes: B29C 66/431 Joining the articles to themselves B29C66/4322 and B29C66/4332 take precedence
• CPC Class Codes: B29C 66/4722 Fixing strips to surfaces other than edge faces fixing strips to edge faces B29C63/0026
• CPC Class Codes: B29C 66/474 said single elements being substantially non-flat
• CPC Class Codes: B29C 66/71 characterised by the composition of the plastics material of the parts to be joined welding bar compositions B29C65/125
• CPC Class Codes: B29C 66/712 the composition of one of the parts to be joined being different from the composition of the other part
• CPC Class Codes: B29C 66/73115 Melting point
• CPC Class Codes: B29C 66/73116 of different melting point, i.e. the melting point of one of the parts to be joined being different from the melting point of the other part
• CPC Class Codes: B29C 66/73921 characterised by the materials of both parts being thermoplastics
• CPC Class Codes: B29C 66/8161 : said pressing elements being supported or backed-up by springs or by resilient material
• CPC Class Codes: B29C 66/83411 : Roller, cylinder or drum types B29C66/83431 takes precedence; rollers, cylinders or drums moving relative to and tangentially to the parts to be joined B29C66/8362
• CPC Class Codes: B29C 66/83413 : cooperating rollers, cylinders or drums
• CPC Class Codes: B29C 66/8432 : Machines for making separate joints at the same time mounted in parallel or in series
• CPC Class Codes: B29C 66/8511 : Bag making machines
• CPC Class Codes: B29C 66/91411 : of the parts to be joined, e.g. the joining process taking the temperature of the parts to be joined into account
• CPC Class Codes: B29C 66/91645 : by steps
• CPC Class Codes: B29C 66/919 : characterised by specific temperature, heat or thermal flux values or ranges specific electrical resistance values B29C66/81262
• CPC Class Codes: B29C 66/91921 : in explicit relation to another temperature, e.g. to the softening temperature or softening point, to the thermal degradation temperature or to the ambient temperature
• CPC Class Codes: B29C 66/9241 : by controlling or regulating the pressure, the force or the mechanical power
• CPC Class Codes: B29K 2023/06 : PE, i.e. polyethylene
• CPC Class Codes: B29K 2023/0633 : LDPE, i.e. low density polyethylene
• CPC Class Codes: B29K 2023/083 : EVA, i.e. ethylene vinyl acetate copolymer
• CPC Class Codes: B29K 2101/12 : Thermoplastic materials
• CPC Class Codes: B29L 2005/00 : Elements of slide fasteners
• CPC Class Codes: B29L 2031/7128 : Bags, sacks, sachets tea bags B29L2031/7122; medical bags B29L2031/7148

Abstract

An apparatus for forming a weld between first and second thermoplastic materials in which the softening temperature of the second thermoplastic material is lower than that of the first thermoplastic material. The apparatus includes a supplier for supplying the first thermoplastic material and the second thermoplastic material to the same weld position with the second thermoplastic material at a first side of the first thermoplastic material, and a projector for projecting a laser beam to the weld position from a second side of the first thermoplastic material.

Claims

1. A welding method comprising the steps of:

continuously feeding a first sheet of a first polyethylene material past a weld station;

continuously feeding a second polyethylene material comprising EVA past a weld station to contact a first side of said polyethylene sheet at the weld station; and

projecting a laser beam to the weld station from a second side of said polyethylene sheet opposite said first side thereof to weld said materials together, wherein said projecting step comprises focusing the laser beam through a lens system into a generally elliptical shape, as seen in a focal plane substantially coincident with a contact point between said first and second materials,

said elliptical shape elongated in the feed direction of said first and second materials.

2. The welding method of claim 1, wherein said contacting step comprises relatively guiding said first and second materials past a groove in a grooved member.

3. The welding method of claim 1, wherein said contacting step comprises leading said first and second materials past a support plate and a guide wheel that are offset from one another in a direction longitudinally along a feed direction of said first and second materials in such a manner as to bring the materials into close contact with one another.

4. The welding method of claim 1, further comprising the step the step of laterally adjusting the position of said first material relative to the position of said second material.

5. The welding method of claim 1, wherein the second EVA polyethylene material is provided with between 0% and 20%, by weight, of EVA.

6. The welding method of claim 1, wherein the second EVA polyethylene material is provided with approximately 10%, by weight, of EVA.

7. The welding method of claim 1, wherein said first material is U-shaped, and said second material is an interlocking zipper strip, wherein said method further comprises the step of inserting said zipper strip between the legs of said U-shaped first material.

8. The welding method of claim 7, further comprising the step of projecting a plurality of laser beams through both legs of said U-shaped sheet of said first material.

9. The welding method of claim 7, wherein the weld station is offset toward the open end of said U-shaped first material.