Tension-relieving device for stretchable sheet material

Claim 2

With apparatus for advancing a knitted fabric or other stretchable web material, comprising a roller drivingly engageable with the material for imparting advancing travel to the material, material guide means spaced from said roller in the travel direction and arranged to cause formation of a shallow sagging portion of the travelling material, the combination of means for relieving tension in said travelling material comprising controllable drive means connected to said roller, speed control means connected to said drive means and having a proximity sensor arranged for out-of-contact response to said sagging portion of material and responsive to at least one of given lower and upper limits of said respectively, said drive means being speed controlled by said sensor response to regulate the speed of said roller for substantially tension-free advance of the material, said drive means comprising a speed change transmission drivingly connected with said roller and having two selective speeds above and below respectively the desired travel speed of the material, said speed change transmission being set by said speed control means to the leading speed when said sensor responds to said upper limit of sag and being set to the lagging speed when said lower limit of sag is reached, said speed control means comprising a presettable timer which is connected to said speed change transmission for setting it to said lagging speed.

Claim 3

In apparatus according to claim 1, said speed change transmission having two speed-setting means which are both in connection with said sensor so that said setting to lagging speed is also controlled by response of said sensor.

Claim 4

In apparatus according to claim 1, said proximity sensor being responsive to given respective maximum and minimum distances from the surface of the web material in said sagging portion, whereby said speed control means operate substantially as a distance regulator.

Claim 5

With apparatus for measuring the length of knitted fabric or other stretchable web material having measuring means, a feed roller drivingly engageable with the material for passing the material to said measuring means, and material guide means arranged to cause formation of a shallow sagging portion of the travelling material, the combination of means for relieving tension in said travelling material comprising controllable drive means connected to said feed roller, speed control means connected to said drive means and having a proximity sensor arranged for out-of-contact response to said sagging portion of material and being responsive to at least one of given lower and upper limits of sag respectively, said drive control means being intermittently controllable by said sensor response to vary the speed of said roller between leading and lagging speed magnitudes for substantially tension-free advance of the material to said measuring means, said measuring means comprising a measuring roller engageable with the web material downstream of said feed roller and having a main drive, said drive means for said feed roller being connected with said main drive, and said drive control means being connected to said feed roller drive So as to vary the feed roller peripheral speed between respective values above and below the peripheral speed of said measuring roller, and further including a withdrawal roller engageable with the web material and arranged downstream of said measuring roller, further drive means connecting said main drive with said withdrawal roller, and further speed control means for varying the peripheral speed of said withdrawal roller between respective values above and below the peripheral speed of said measuring roller, means for forming a second shallow sagging portion of the web material between said measuring roller and said withdrawal roller, said further speed control means having a proximity sensor responsive to the sag of said web portion.

Claim 6

With apparatus for measuring the length of knitted fabric or other stretchable web material having measuring means, a feed roller drivingly engageable with the material for passing the material to said measuring means, and material guide means arranged to cause formation of a shallow sagging portion of the travelling material, the combination of means for relieving tension in said travelling material comprising controllable drive means connected to said feed roller, speed control means connected to said drive means and having a proximity sensor arranged for out-of-contact response to said sagging portion of material and being responsive to at least one of given lower and upper limits of sag respectively, said drive control means being intermittently controllable by said sensor response to vary the speed of said roller between leading and lagging speed magnitudes for substantially tension-free advance of the material to said measuring means, said measuring means comprising a measuring roller engageable with the web material downstream of said feed roller and having a main drive, said drive means for said feed roller being connected with said main drive, and said drive control means being connected to said feed roller drive So as to vary the feed roller peripheral speed between respective values above and below the peripheral speed of said measuring roller, and further including a withdrawal roller engageable with the web material and arranged downstream of said measuring roller, further drive means connecting said main drive with said withdrawal roller, and further speed control means for varying the peripheral speed of said withdrawal roller between respective values above and below the peripheral speed of said measuring roller, means for forming a second shallow sagging portion of the web material between said measuring roller and said withdrawal roller, said further speed control means having a proximity sensor responsive to the sag of said web portion.

Claim 7

In apparatus according to claim 4, said speed control means comprising time delay means for delaying the switching of said feed roller to the lagging speed and the switching of said withdrawal roller to the leading speed during forward travel of the web material.

Claim 8

In apparatus according to claim 4, said main drive comprising selective reversing means for causing the web material to travel in the forward and reverse direction respectively, and switching means connected to said speed control means for shifting the points of response of said sensors at which said rollers switch between leading and lagging speeds, said switching means being coupled with said reversing means so as to be effective when said main drive is switched to reverse travel of the web material.

Claim 9

Apparatus according to claim 4, comprising two blow devices mounted at respective localities beneath said two sagging portions of the web material for partially compensating the weight of said web portions.

Claim 10

With apparatus for advancing a knitted fabric or other stretchable web material, comprising a roller drivingly engageable with the material for imparting advancing travel to the material, material guide means spaced from said roller in the travel direction and arranged to cause formation of a shallow sagging portion of the travelling material, the combination of means for relieving tension in said travelling material comprising controllable drive means connected to said roller, speed control means connected to said drive means and having a proximity sensor arranged for out-of-contact response to said sagging portion of material and responsive to at least one of given lower and upper limits of sag respectively, said drive means being speed controlled by said sensor response to regulate the speed of said roller for substantially tension-free advance of the material, and a blow device mounted beneath the sagging portion of the web material for partially compensating the weight of said web portion.

Claim 11

With apparatus for advancing a knitted fabric or other stretchable web material, comprising a roller drivingly engageable with the material for imparting advancing travel to the material, material guide means spaced from said roller in the travel direction and arranged to cause formation of a shallow sagging portion of the travelling material, the combination of means for relieving tension in said travelling material comprising controllable drive means connected to said roller, speed control means connected to said drive means and having a proximity sensor arranged for out-of-contact response to said sagging portion of material and responsive to at least one of given lower and upper limits of sag respectively, said drive means being speed controlled by said sensor response to regulate the speed of said roller for substantially tension-free advance of the material, and a blow device mounted beneath the sagging portion of the web material for partially compensating the weight of said web portion.