Hermetic packages with laser scored vent systems
View Patent ↗A hermetically sealed package, for example a freezable, microwavable package containing a food product, having a sealing film that includes a vent system that is scored by a laser into the package. The vent system includes at least one linear or non-linear vent pattern scored into a portion of the outer surface of the sealing film so as to form at least one weakened wall pattern. According to certain embodiments, the vent pattern may be scored by a laser to a depth that does not perforate the sealing film. The inner surface of the sealing film that is adjacent to the weakened wall pattern is directly exposed to pressure that is generated in the inner region of the package during heating. According to some embodiments, the vent pattern may have a vent pattern span that is approximately 1% to 50% of the size of the inner region span.
1. A method of providing a package for storing and cooking food products, the method comprising the steps of
providing a sealing film including, in sequence, an outer protective layer, an adhesive layer, an outer skin layer, a core layer, and an inner heat sealable layer,
scoring at least the outer protective layer of the sealing film to a depth that does not perforate the sealing film to cause a weakened wall pattern to be formed in the sealing film, and
using the sealing film after the scoring step to form a heatable hermetically sealed package having an inner region bounded by the inner heat sealable layer of the sealing film and an exterior skin defined in part by the outer protective layer of the sealing film and configured to block microorganisms and oxygen from entering the inner region through the weakened wall pattern until the heatable hermetically sealed package is exposed to microwave energy during a microwave cooking cycle and a pressure generated in the inner region exceeds a predetermined magnitude to cause tearing of at least a portion of the weakened wall pattern and venting of the inner region.
2. The method of claim 1 , wherein the scoring step comprises the steps of providing a CO 2 laser characterized by a wavelength of about 10.2 μm to 10.6 μm and operating the CO 2 laser at about 20 watts to 200 watts.
3. The method of claim 2 , wherein during the scoring step, the CO 2 laser is moved relative to the sealing film at a rate of about 70 feet per minute (0.36 meters per second).
4. The method of claim 1 , wherein the scoring step is accomplished using a CO 2 laser and the CO 2 laser is moved relative to the sealing film at a rate of about 70 feet per minute (0.36 meters per second).
5. The method of claim 1 , wherein the depth is greater than a thickness of the outer protective layer.
6. The method of claim 5 , wherein the depth is greater than a combined thickness of the outer protective layer and the adhesive layer.
7. The method of claim 6 , wherein the depth is greater than a combined thickness of the outer protective layer, the adhesive layer, and the outer skin layer.
8. The method of claim 7 , wherein the depth is greater than a combined thickness of the outer protective layer, the adhesive layer, the outer skin layer, and the core layer.
9. The method of claim 8 , wherein the depth is greater than a combined thickness of the outer protective layer, the adhesive layer, the outer skin layer, the core layer, and the inner heat sealable layer.
10. The method of claim 1 , wherein the sealing film has a thickness of about 2 mils (50 microns) to about 5 mils (130 microns).
11. The method of claim 1 , further comprising the step of freezing the heatable hermetically sealed package without fracturing the sealing film.
12. The method of claim 11 , further comprising the step of heating the heatable hermetically sealed package to a cooking temperature after the freezing step.
13. The method of claim 12 , further comprising the step of generating heat and steam in the inner region formed in the heatable hermetically sealed package during the heating step until the predetermined magnitude is exceeded to cause a portion the weakened wall pattern to fracture so that steam is communicated from the inner region through the sealing film to atmosphere surrounding the heatable hermetically sealed package so that a maximum pressure and a maximum temperature are not exceeded during the heating step.
14. The method of claim 1 , wherein the weakened wall pattern includes a circle.
15. The method of claim 14 , wherein the circle has a diameter of about 12 mm.
16. The method of claim 14 , wherein the weakened wall pattern further includes a second circle spaced apart from the circle.
17. The method of claim 16 , wherein each circle has a diameter of about 12 mm.
18. The method of claim 14 , wherein the weakened wall pattern further includes a cross.
19. The method of claim 18 , wherein each line forming the cross has a length of about 12 mm.
20. The method of claim 1 , wherein the weakened wall pattern includes a cross.
21. The method of claim 20 , wherein each line forming the cross has a length of about 12 mm.
22. The method of claim 20 , wherein the weakened wall pattern further includes a second cross spaced apart from the cross.
23. The method of claim 22 , wherein each line included in each cross has a length of about 12 mm.
24. A method of providing a package for storing and cooking food products, the method comprising the steps of
providing a sealing film including, in sequence, an outer protective layer, an adhesive layer, an outer skin layer, a core layer, and an inner heat sealable layer,
scoring a portion of the sealing film to cause a weakened wall pattern to be formed in the sealing film at a depth that does not perforate the sealing film,
sealing a first portion of the sealing film together to establish a pouch formed to include an inner region therein and adapted to receive food products therein and a mouth opening into the inner region, and
sealing a second portion of the sealing film together to close the mouth and form a heatable hermetically sealed package that blocks the communication of air between the inner region and atmosphere surrounding the heatable hermetically sealed package until heating of the heatable hermetically sealed package causes pressure generated in the inner region to exceed a predetermined magnitude to cause tearing of at least a portion of the weakened wall pattern.
25. The method of claim 24 , wherein the scoring step includes scoring the outer protective layer.
26. The method of claim 25 , wherein the scoring step further includes scoring the adhesive layer.
27. The method of claim 26 , wherein the scoring step further includes scoring the outer skin layer.
28. The method of claim 27 , wherein the scoring step further includes scoring the core layer.
29. The method of claim 24 , wherein the scoring step is performed using a laser.
30. The method of claim 29 , wherein the laser is a CO 2 laser.
31. The method of claim 30 , wherein the CO 2 laser is characterized by a wavelength in a range of about 10.2 μm to 10.6 μm.
32. The method of claim 31 , wherein the CO 2 laser is operated at a power in a range of about 20 watts to 200 watts.
33. The method of claim 32 , wherein the CO 2 laser moves relative to the sealing film at a rate of about 70 feet per minute (0.36 meters per second).
34. The method of claim 24 , wherein the sealing film has a thickness of about 50 μm to 130 μm prior to the scoring step.
35. The method of claim 34 , wherein the sealing film has a thickness of about 88.9 μm prior to the scoring step.
36. The method of claim 34 , wherein the portion of the sealing film that has been scored has a thickness in a range of about 5 μm to 50 μm.
37. The method of claim 34 , wherein the portion of the sealing film that has been scored has a thickness in a range of about 5 μm to 25 μm.
38. The method of claim 37 , wherein the heatable hermetically sealed package has an inner region span, the weakened wall pattern as a vent pattern span, and the vent pattern span is about 4% to 8% of the inner region span.
39. The method of claim 24 , wherein the heatable hermetically sealed package has an inner region span, the weakened wall pattern as a vent pattern span, and the vent pattern span is about 1% to 100% of the inner region span.
40. The method of claim 39 , wherein the vent pattern span is about 1% to 50% of the inner region span.
41. The method of claim 40 , wherein the vent pattern span is about 2% to 15% of the inner region span.
42. The method of claim 41 , wherein the vent pattern span is about 4% to 8% of the inner region span.
43. The method of claim 24 , wherein the weakened wall pattern includes a circle.
44. The method of claim 43 , wherein the weakened wall pattern further includes a second circle spaced apart from the circle.
45. The method of claim 44 , wherein each circle has a diameter of about 12 mm.
46. The method of claim 43 , wherein the weakened wall pattern further includes a cross.
47. The method of claim 46 , wherein each line forming the cross has a length of about 12 mm.
48. The method of claim 24 , wherein the weakened wall pattern includes a cross.
49. The method of claim 48 , wherein the weakened wall pattern further includes a second cross spaced apart from the cross.
50. The method of claim 49 , wherein each line forming each cross has a length of about 12 mm.
51. The method of claim 24 , further comprising the step of placing food products in the inner region before the step of sealing the second portion of the sealing film.
52. The method of claim 51 , further comprising the step of freezing the heatable hermetically sealed package and the food products located in the inner region to cause the heatable hermetically sealed package and the food products to have a temperature of about −5 degrees Fahrenheit (−21 degrees Celsius).
53. The method of claim 52 , wherein one layer in the sealing film does not fracture when exposed to the temperature.
54. The method of claim 53 , further comprising the step of heating the heatable hermetically sealed package and the food products located in the inner region to cause heat and steam to be generated in the inner region to cause pressure and temperature in the inner region to increase until the predetermined magnitude is exceeded that causes at least a portion of the weakened wall pattern to fracture and form a vent pattern so that steam is communicated from the inner region through the sealing film to atmosphere so that a maximum pressure and a maximum temperature are not exceeded during heating and the food products are heated throughout to a food temperature.
55. The method of claim 54 , wherein the maximum pressure is about 0.98 pounds per square inch (0.07 bar).
56. The method of claim 54 , wherein the maximum temperature is about 229.4 degrees Fahrenheit (110 degrees Celsius).
57. The method of claim 54 , wherein the food temperature is about 193.5 degrees Fahrenheit (90 degrees Celsius).