Stretchable fabric items
Items such as wrist straps may include a knit fabric tube or other fabric outer layer having first and second knit fabric portions that form an outer surface of the strap. The knit fabric outer layer may surround an interior cavity having one or more channels. Strands of elastomeric material may be located in the channels. The strands of elastomeric material may each stay within a single channel or may weave back and forth between multiple channels while crossing over adjacent strands of elastomeric material to create points of friction. Some strands of elastomeric material may pass back and forth between the interior cavity of the knit fabric tube and the exterior surface of the strap via an array of openings in the knit fabric tube. Constraint points and points of friction may be used to control stretchability of the strap while reducing elongation over time.
1 . A fabric wrist strap, comprising:
a knit fabric tube having first and second knit fabric portions that extend along a length;
a channel within the knit fabric tube extending at least partially along the length of the knit fabric tube, wherein the channel is one of multiple channels within the knit fabric tube and wherein the multiple channels are separated from one another by portions of the knit fabric tube in which the first knit fabric portion is attached to the second knit fabric portion; and
an elastomeric material located in the channel that is configured to stretch along the length of the knit fabric tube.
2 . The fabric wrist strap defined in claim 1 wherein the elastomeric material comprises strands of elastomeric material that are respectively located in the multiple channels.
3 . The fabric wrist strap defined in claim 2 wherein the multiple channels include first and second channels that merge at a given location along the length of the knit fabric tube.
4 . The fabric wrist strap defined in claim 3 wherein the strands of elastomeric material include first and second strands of elastomeric material respectively located in the first and second channels and wherein the first and second strands of elastomeric material cross over each other at the given location where the first and second channels merge.
5 . The fabric wrist strap defined in claim 4 wherein the multiple channels include a third channel located along an edge of the fabric wrist strap and the strands of elastomeric material include a third strand of elastomeric material located in the third channel.
6 . The fabric wrist strap defined in claim 5 wherein the third strand of elastomeric material has a different diameter than the first and second strands of elastomeric material.
7 . The fabric wrist strap defined in claim 1 wherein the elastomeric material is attached to the knit fabric tube at given location along the length to constrain movement of the elastomeric material relative to the knit fabric tube.
8 . The fabric wrist strap defined in claim 1 wherein the elastomeric material comprises a flat strip of elastomeric material having a rectangular cross-section.
9 . A fabric strap, comprising:
a first knit fabric portion;
a second knit fabric portion;
tube-shaped channels extending between the first and second knit fabric portions; and
strands of elastomeric material located in the tube-shaped channels, wherein the first knit fabric portion is attached to the second knit fabric portion in locations between the tube-shaped channels.
10 . The fabric strap defined in claim 9 wherein the tube-shaped channels merge at a given location along a length of the fabric strap.
11 . The fabric strap defined in claim 10 wherein the strands of elastomeric material include first and second strands of elastomeric material that overlap each other at the given location wherein the tube-shaped channels merge.
12 . The fabric strap defined in claim 11 wherein the first and second knit fabric portions are attached to one another to form walls of the tube-shaped channels and are detached from one another to form gaps between the first and second knit fabric portions where the tube-shaped channels merge.
13 . The fabric strap defined in claim 9 wherein the tube-shaped channels include at least first and second tube-shaped channels, wherein the strands of elastomeric material comprise first and second strands of elastomeric material, wherein the first strand of elastomeric material meanders back and forth between the first and second tube-shaped channels and the second strand of elastomeric material meanders back and forth between the second and first tube-shaped channels in an alternating pattern with the first strand of elastomeric material.
14 . A fabric band, comprising:
a knit fabric tube having first and second knit fabric portions that surround an interior cavity and that form an exterior surface of the fabric band, wherein the knit fabric tube has an array of openings and wherein the interior cavity has tube-shaped channels that are separated from one another by portions of the knit fabric tube in which the first knit fabric portion is attached to the second knit fabric portion; and
strands of elastomeric material in the tube-shaped channels that pass back and forth between the interior cavity and the exterior surface of the fabric band through the openings, wherein the strands of elastomeric material are configured to stretch along a length of the knit fabric tube.
15 . The fabric band defined in claim 14 wherein the strands of elastomeric material each comprise a sheath surrounding a core of elastomeric material.
16 . The fabric band defined in claim 15 wherein the core comprises multiple core strands within the sheath.
17 . The fabric band defined in claim 14 wherein the openings comprise first and second openings and wherein a given one of the strands of elastomeric material passes from the interior cavity to the exterior surface through the first opening and passes from the exterior surface to the interior cavity through the second opening.