Method and apparatus for producing a welded joint in thermoplastic strap with differential pressure
First Claim
1. A welded joint defined between two lengths of thermoplastic strap, comprising:
- said two lengths of thermoplastic strap being disposed in a face-to-face overlapping relationship with respect to each other at a location at which said welded joint is to be defined;
at least part of the thickness of each one of said two strap lengths being resolidified from a fused state during which said two lengths of said strap disposed at said location at which said welded joint is to be defined were subjected to above-ambient pressure;
said resolidified thickness part of one of said two strap lengths being merged with the resolidified thickness part of the other one of said two strap lengths so as to define a continuous resolidified region; and
said resolidified region including a peripheral region, and an adjacent central region having a substantially disc-like configuration, wherein said above-ambient pressure was maintained, during said fused state, for a longer period of time within said central region than within said peripheral region.
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Abstract
A novel method and apparatus are provided for making an improved welded joint between overlapping lengths of thermoplastic strap. The welded joint includes a central region and an adjacent peripheral region. The pressure on the strap joint during formation is released first in the peripheral region and subsequently in the central region. An embodiment of tile apparatus for making such a joint includes an anvil, a central strap-engaging member, a peripheral strap engaging member, and a mechanism for moving the anvil subsequently to three positions. At a first position the overlapping strap lengths are pressed between the anvil and both the central and peripheral strap-engaging members. In the second position of the anvil the peripheral strap-engaging member does not press against the strap lengths while the central strap-engaging member continues to press the strap lengths against the anvil. In the third position of the anvil, the anvil and strap-engaging members are sufficiently spaced apart to release all of the pressure on the strap lengths.
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Citations
20 Claims
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1. A welded joint defined between two lengths of thermoplastic strap, comprising:
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said two lengths of thermoplastic strap being disposed in a face-to-face overlapping relationship with respect to each other at a location at which said welded joint is to be defined; at least part of the thickness of each one of said two strap lengths being resolidified from a fused state during which said two lengths of said strap disposed at said location at which said welded joint is to be defined were subjected to above-ambient pressure; said resolidified thickness part of one of said two strap lengths being merged with the resolidified thickness part of the other one of said two strap lengths so as to define a continuous resolidified region; and said resolidified region including a peripheral region, and an adjacent central region having a substantially disc-like configuration, wherein said above-ambient pressure was maintained, during said fused state, for a longer period of time within said central region than within said peripheral region. - View Dependent Claims (2, 3, 4, 5)
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6. A welded joint defined between two lengths of thermoplastic strap, comprising:
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said two lengths of thermoplastic strap being disposed in a face-to-face overlapping relationship with respect to each other at a location at which said welded joint is to be defined; at least part of the thickness of each one of said two strap lengths being resolidified from a fused state; said resolidified thickness part of one of said two strap lengths being merged with the resolidified thickness part of the other one of said two strap lengths so as to define a continuous resolidified region; and said overlapping lengths of said strap disposed in said fused state and at said location at which said welded joint is to be defined comprising a central weld region, having a substantially circular configuration, and an adjacent peripheral weld region, which substantially annularly surrounds said central weld region, wherein said central and peripheral weld regions are subjected to above-ambient pressure, and wherein further, said above-ambient pressure is firstly released within said peripheral weld region and subsequently released within said central weld region. - View Dependent Claims (7, 8, 9, 10)
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11. A welded joint defined between two lengths of thermoplastic strap, comprising:
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two lengths of thermoplastic strap disposed in a face-to-face, overlapping relationship with respect to each other at a location at which a welded joint is to be defined; at least part of the thickness of each one of said two strap lengths being resolidified from a fused state wherein said two lengths of said strap disposed at said location at which said welded joint is to be defined are subjected to above-ambient pressure; said resolidified thickness part of one of said two strap lengths being merged with said resolidified thickness part of the other one of said two strap lengths so as to define a continuous resolidified weld region which defines said welded joint; and said continuous resolidified weld region which defines said welded joint comprises a central weld region at which said above-ambient pressure was maintained for a first predetermined period of time, and a peripheral weld region which substantially surrounds said central weld region and at which said above-ambient pressure was maintained for a second predetermined period of time which was shorter than said first predetermined period of time during which said above-ambient pressure was still maintained upon said central weld region. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A welded joint defined between two lengths of thermoplastic strap, comprising:
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said two lengths of thermoplastic strap being disposed in a face-to-face overlapping relationship with respect to each other at a location at which said welded joint is to be defined; at least part of the thickness of each one of said two strap lengths being resolidified from a fused state during which said two lengths of said strap disposed at said location at which said welded joint is to be defined were subjected to above-ambient pressure; said resolidified thickness part of one of said two strap lengths being merged with the resolidified thickness part of the other one of said two strap lengths so as to define a continuous resolidified region; and said resolidified region including a peripheral region and an adjacent central region, wherein said peripheral region substantially surrounds said central region, and wherein further, said above-ambient pressure was maintained, during said fused state, for a longer period of time within said central region than within said peripheral region. - View Dependent Claims (18, 19, 20)
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Specification