Claims
- 1. A method for processing a warp sheet of synthetic multifilament yarns, and comprising the steps of
- advancing the warp sheet along a path of travel while drawing the sheet,
- guiding the advancing warp sheet across a heated surface,
- monitoring the advancing sheet to detect a breakage of a yarn in the sheet,
- detecting the breakage of a yarn,
- terminating the advance of the sheet upon detecting the breakage of a yarn, and then
- advancing the warp sheet in the reverse direction for a predetermined distance wherein any undrawn yarn is returned to a position upstream of the heated surface.
- 2. The method as defined in claim 1 wherein the step of advancing the warp sheet includes contacting the sheet with upstream and downstream pairs of yarn delivery rolls, with the upstream and downstream pairs being operated at different speeds to impart a desired draw ratio.
- 3. The method as defined in claim 1 wherein the step of advancing the warp sheet in the reverse direction includes operating the upstream and downstream pairs of delivery rolls at a one to one speed ratio.
- 4. The method as defined in claim 3 comprising the further subsequent step of re-starting the forward advance of the warp sheet, and including forwardly operating the upstream and downstream delivery rolls at a one to one speed ratio for the same number of revolutions as occurred during the advance in the reverse direction.
- 5. A method for processing a warp sheet of synthetic multifilament yarns and comprising the steps of
- advancing the warp sheet along a path of travel,
- drawing the advancing sheet while applying heat to the sheet by contacting the sheet with at least one heated roll and by positioning a generally flat heated surface closely adjacent the path of travel,
- monitoring the advancing sheet to detect a breakage of a yarn in the sheet,
- detecting the breakage of a yarn,
- terminating the advance of the sheet upon detecting the breakage of a yarn, and
- interrupting the application of the heat during any such termination of the advance thereof, and including separating said heated roll from the warp sheet by moving a cover between the sheet and said roll so as to separate and insulate the sheet from said roll and so that the cover acts to move the sheet to effectively separate the same from said heated surface.
- 6. A method for processing a warp sheet of synthetic multifilament yarns and comprising the steps of
- advancing the warp sheet along a path of travel,
- drawing the advancing sheet while applying heat to the sheet by contacting the sheet with at least one roll having fluid conduit means extending through the interior thereof, and while conveying a heated fluid through the fluid conduit means,
- monitoring the advancing sheet to detect a breakage of a yarn in the sheet,
- detecting the breakage of a yarn,
- terminating the advance of the sheet upon detecting the breakage of a yarn, and
- interrupting the application of the heat during any such termination of the advance thereof, and including terminating the flow of the heated fluid through the fluid conduit means.
- 7. The method as defined in claim 6 wherein the step of interrupting the application of the heat further comprises conveying a relatively cool fluid through the fluid conduit means.
- 8. A method of processing a warp sheet of synthetic multifilament yarns and comprising the steps of
- advancing the warp sheet along a path of travel between a pair of spaced apart guide rolls,
- drawing the warp sheet as it advances between said pair of guide rolls,
- positioning a generally flat heated surface closely adjacent the path of travel so as to apply heat to the warp sheet as it advances between said pair of guide rolls,
- monitoring the advancing sheet to detect a breakage of a yarn in the sheet,
- detecting the breakage of a yarn,
- terminating the advance of the sheet upon detecting the breakage of a yarn, and
- interrupting the application of the heat during any such termination of the advance thereof, and including separating said heated surface from the warp sheet by moving a cover between the sheet and each of said pair of guide rolls so as to move the sheet and thereby separate the same from said surface.
- 9. The method as defined in claim 8 comprising the further step of heating each of said pair of guide rolls so as to apply additional heat to the advancing warp sheet, and wherein the step of moving a cover between the sheet and each of said pair of guide rolls serves to also interrupt the application of heat to said sheet from said pair of guide rolls.
- 10. A method for processing a warp sheet of synthetic multifilament yarns and comprising the steps of
- advancing the warp sheet along a path of travel,
- drawing the advancing sheet while applying heat to the sheet by contacting the sheet with the heated surface of a heated roll which extends transversely across the warp sheet,
- providing a cover of flexible sheet material which is mounted for movement about a pivotal axis which is parallel to the axis of the roll, with said cover having a leading edge which is disposed in a direction parallel to the axis of the heated roll,
- monitoring the advancing sheet to detect a breakage of a yarn in the sheet,
- detecting the breakage of a yarn,
- terminating the advance of the sheet upon detecting the breakage of a yarn, and
- interrupting the application of the heat during any such termination of the advance thereof, and including separating the heated surface from the warp sheet by moving said cover between the sheet and said heated surface so as to separate and insulate the sheet from said surface, with the step of moving the cover between the sheet and the heated surface including pivoting the cover about said pivotal axis between an inoperative position wherein the warp sheet is in contact with the heated surface of the heated roll and an operative position wherein the warp sheet is in contact with the cover and is separated from the heated roll.
- 11. The method as defined in claim 10 wherein in said inoperative position said leading edge is disposed adjacent the nip formed between the surface of said roll and the warp sheet, and wherein the step of pivoting said cover about said pivotal axis includes advancing said leading edge of said cover into said nip upon commencement of the termination of the advance of the warp sheet and so that the leading edge is clamped between the surface of the heated roll and the warp sheet, and continuing to advance the cover to said operative position.
Priority Claims (2)
| Number |
Date |
Country |
Kind |
| 3343499 |
Dec 1983 |
DEX |
|
| 3406937 |
Feb 1984 |
DEX |
|
Parent Case Info
This application is a divisional of application Ser. No. 676,722, filed Nov. 30, 1984, now U.S. Pat. No. 4,630,340, issued Dec. 23, 1986.
The present invention relates to an apparatus and method for processing a warp sheet of synthetic multifilament yarns, and wherein the yarns may be withdrawn from supply packages, heated and drawn while in warp sheet form to orient the filaments, and then wound for example on a warp beam. Up to 1000 or more yarns may be simultaneously processed in this manner.
In the case of a yarn break during processing of a warp sheet in the manner generally described above, it is necessary to immediately terminate the winding operation, so as to prevent further yarn breaks and to avoid having a broken end travel through the apparatus to a point where it can no longer be readily pieced up. A sudden shut down of the apparatus however involves the risk that the remaining unbroken yarns will remain in contact with the heaters of the draw system, and be melted or otherwise damaged, such that they may break upon re-starting of the winding operation.
Heretofore, non-movable heating means such as snubbing pins have been used to stabilize the drawing area by the application of heat and drag to the yarns, which is particularly useful in drawing yarns of polyethyleneterephthalate. Though having the advantage of avoiding overheating of the yarns in case of a shut-down of the apparatus, such non-movable heating means has been unsatisfactory in the drawing of warp sheets of yarns, since uneven drawing, yarn breakage, and uneven dyeing often occur.
It is accordingly an object of the present invention to provide an apparatus and method of the described type which uses heated rolls rather than non-movable heaters for stabilizing the drawing area in the undrawn yarn, and which effectively avoids the problem of having any of the yarns damaged by overheating during termination of the advance of the warp sheet upon a yarn break, or when the apparatus is otherwise shut down.
These and other objects and advantages of the present invention are achieved in the embodiments illustrated herein by the provision of an apparatus and method which includes means for advancing the warp sheet along a path of travel while drawing the sheet, heating means positioned along the path of travel for applying heat to the advancing warp sheet, and control means for terminating the advance of the warp sheet upon a yarn break or the like, for interrupting the application of heat to the warp sheet by the heating means upon the termination of the advance, and for re-establishing the application of heat upon the re-starting of the advance.
In one preferred embodiment, the heating means comprises at least one heated roll, and the control means comprises means for selectively moving the roll into and out of contact with the warp sheet. More particularly, in this embodiment the heating means preferably comprises a pair of rolls mounted at the ends of a pivotal lever arm and such that one of the rolls is positioned above the warp sheet and the other of the rolls is positioned below the warp sheet. The lever arm may be pivoted so that the rolls are adapted to deflect the path of travel of the advancing warp sheet into an S or Z configuration. Also, the lever arm may be pivoted to a non-operative position wherein the rolls are substantially out of contact with the warp sheet.
To maintain the tension of the warp sheet when not contacted by the heated rolls, compensating unheated rolls may also be positioned within the drawing zone. The unheated pair of rolls are similar in construction to the heated rolls, and both pairs of rolls cooperate in such a manner that the heated pair of rolls contacts the sheet while advancing, and the unheated pair contacts the sheet while it is stopped. The movements are coordinated such that the pair of rolls moving into contact with the warp sheet compensates for a release in tension resulting from the other pair moving out of contact with the sheet. By coordinating the movement of the two pairs of rolls to the momentary speed of the sheet, and such that the heated rolls move fully into contact only when the maximum advancing speed has been reached and that they otherwise take corresponding intermediate positions, it is possible to insure that an appropriate supply of heat is provided which is adapted to any operational stage. The unheated rolls, may if desired be actively cooled.
In the above embodiment, each of the two pairs of rolls are preferably mounted on respective lever arms, and the lever arms are adapted to pivot about an axis which extends across the warp sheet and generally parallel to the axes of the heated rolls. Also, the lever arms are adapted to pivot at an angle of between about 30 degrees to not more than 180 degrees. Such pivotal movements of the two pairs of rolls are coupled to each other, and with the lever arms arranged parallel to each other, the rotational directions of the arms would be oppositely directed. Where the lever arms are arranged in mirror symmetry, they would rotate in the same direction. Such rotation may be actuated by the control for braking and re-starting the advance of the warp sheet.
The nature of the pivoting movement of the two pairs of rolls is preferably controlled so that a change in tension is substantially avoided during a change of the engagement between the pairs of rolls with respect to the warp sheet.
In the case of large drawing systems, in which for example 1000 multifilament yarns or more are being processed, a further embodiment of the invention may be employed wherein the heated rolls themselves are not moved, which often involve substantial mass. In this further embodiment, the sheet of yarns itself performs the necessary relative movement for being removed from the heated roll or other heated member. For this purpose, a lifting cover is associated with each heated roll, with each roll being mounted for rotation about a stationary axis. The cover is adapted to move between the periphery of the roll and the sheet of yarns when the machine is stopped, to thereby separate and shield the sheet from the heat of the roll.
The cover for each of the rolls preferably has an arcuate curvature in cross section, i.e. in the circumferential direction, which is similar to the curvature of the outer periphery of the associated roll, and each cover also has an angular extent which is greater than the looping angle of the warp sheet about the roll. For example, the angular extent of the cover is preferably about 4 to 20 percent greater than the looping angle about the roll.
The lifting cover may be mounted for rotation about the axis of the heated roll itself, or it may be mounted eccentrically thereto. When the lifting cover is in its neutral or inoperative position, the sheet of yarns is adapted to partially loop the heated roll. When the draw system is stopped, the lifting cover is then pivoted, preferably in the running direction of the sheet, so that it comes between the sheet and the roll and lifts the sheet from the roll and holds it spaced therefrom while the sheet is immobile. Upon the advancing of the sheet being re-started, the lifting cover is further pivoted until it is separated from contact with the sheet and again reaches its neutral or inoperative position.
The pivoting motion of the lifting cover is initiated by its own drive, which is actuated when the sheet of yarns is slowed down. The point in time at which the drive starts to operate may be related to the braking retardation of the advancing system, so that the sheet of yarns itself moves the lifting cover to its operative position, where it stops. As soon as the advancing system re-starts, the sheet of yarn automatically moves the lifting cover from its operative position back to its neutral or inoperative position. By this arrangement, the self contained drive of the lifting cover may be limited so that it is only necessary to bring the cover into contact with the sheet while it is still advancing, but has slowed down to a predetermined extent. The lifting cover also has the advantage that the sheet of yarns may be held during a shut down under a nearly unchanged tension, to thereby avoid the risk of the yarns entangling.
The pivoting axis of the lifting cover may be eccentric to the axis of the associated roll, and located in a plane which is defined by the axis of the roll and the bisector of the looping angle. Thus while the sheet of yarns is advancing, the lifting cover is removed a relatively substantial distance from the heated surface of the roll, so that it may remain cool. When pivoted to its lifting or operative position, the cover reaches a position in which it is only slightly spaced from the surface of the roll, to minimize the deflection of the yarn sheet and thereby cause a minimal increase of the tension in the yarns.
The minimum distance between the roll surface and the inner surface of the lifting cover in the lifting position, should, depending on the overall dimensions of the roll, typically amount to about 0.5 to 2 mm. In the nonoperative position, such distance may be about 10 to 15 mm. The latter separation helps insure that the lifting cover does not unduly heat in its inoperative position, and this objective may be assisted by constructing the lifting cover from a heat insulating material. For example, the cover may comprise a reflective inner layer, an insulating intermediate layer, and a wear resistant outer layer which contacts the warp sheet. The edges of the cover which extend transversely to the warp sheet may be suitably formed of a wear resistant material, since the edges must withstand the relatively high relative movement of the yarns at their first contact with the sheet. In another embodiment, such lifting covers may be used for separating the warp sheet of yarns from a heated plate disposed between two guide rolls.
A mechanically simple and reliably operating embodiment comprises a cover of a flexible sheet of material, the width of which corresponds to the length of the working area of the roller, and the length of which corresponds to at least the braking distance. Braking distance is here defined as the distance through which one point of yarn runs between the setting into operation of the brakes and reaching the standstill of the apparatus. The flexible sheet of material preferably has sufficient insulating properties. In case of yarn breakage and application of the brakes, the sheet of material is moved with its broad leading edge into the nip between the surface of the roller and the warp running onto that surface. The cover is then clamped between the warp and the surface and transported until the roll stops. Upon restarting the apparatus, the sheet of material is transported out of the clamping zone and falls down without further impeding the warp. One can see that the length of the insulating sheet of material should essentially be limited to the braking distance, so that the heating of the warp may restart at the first possible moment. The particular advantage of this embodiment is that the flexible sheet of material does not cause any appreciable increase of yarn tension, and it can withstand the forces exerted by the yarn tension by itself. The drive of this kind of cover is very simple and the moved masses are very small.
A further advantageous embodiment of the present invention provides for a heating means which comprises a heated roll, guide plate, or the like which has a hollow interior, and which is connected to a fluid circulation system whereby a heated fluid may be circulated through the interior of the heated member. In this embodiment, the heating fluid is heated by a suitable external heater, and the circulation system may include a parallel circuit which contains a cooling system, or a source of a relatively cool fluid. For example, a cooled container may be provided which contains sufficient quantity of fluid so as to at least effect a partial filling of the circulation system to thereby lower the temperature of the fluid so that the risk of damage to the yarns is avoided. The circulation system preferably also contains valve means which are connected to a yarn monitoring system, either directly or via the machine drive, with the valve means being adapted to switch the fluid circulation from the heating branch, which includes the heating means, to the cooling branch, when a yarn break occurs or the machine is stopped. The advantage of this embodiment of the invention resides in the fact that no mechanical parts are moved when the heating effect is terminated. Such motion of mechanical parts is undesirable in that it may also give rise to substantial vibrations in the machine, and may also lead to changes of the tension being imparted on the sheet of yarns, which in turn may cause the yarns to entangle.
Depending on the operation temperature of the heating means on the one hand, and the temperature of the cooled fluid in the cooling system on the other hand, it is usually sufficient to fill the circulation system with the cool fluid one time. However, to provide further cooling, a circulation of actively cooled heating fluid may be provided. If for example, the heating means serves to set the draw point in polyester yarns, its temperature will be about 100 degrees C. In such instance, a decrease of 20 to 30 degrees will suffice to preclude damage to the yarn, even after a long period of contact. The valve means for the above described fluid conduit system preferably comprises three-way valves which preceed and follow the heater and cool fluid source, respectively.
It is known that in drawing a synthetic filament yarn, and in particular a polyester or polyethyleneterephthalate yarn, a lengthening occurs in a narrowly limited range in the longitudinal direction. The length of this range depends of the spun orientation of the yarn. In yarns with little spun orientation, a flow length of only a few millimeters will develop. In yarns having a greater spun orientation, flow zones of a greater length will form. In each case, the change in length only occurs after the yarn has traveled over the heating means, be it a roll, heated pin, or a hot plate. In accordance with the object of the present invention, namely to avoid contact between the undrawn portions of the yarn and the heating means during termination of the yarn advance, a further embodiment involves a method wherein the feed and draw systems are brought to a standstill upon a yarn break, and then the sheet is advanced in the reverse direction for a predetermined distance wherein any undrawn yarn is returned to a position upstream of the heated surface. As a result, only a drawn yarn length will contact the heating means when the warp sheet is at a standstill, which is behind the flow zone in the traveling direction of the yarn. Thus, following the termination of the yarn advance, an unduly long period of contact between the undrawn yarns and the heater is avoided, since a drawn portion of the yarn is returned to the contact area of the heater. Drawn yarn lengths are adapted to withstand the temperatures normally required for drawing, without damage for a longer period of time, and in particular, for a time normally adequate to eliminate the cause of the breakdown. For example, it has been found that drawn yarn lengths which have contacted the heater for a relatively long period of time, showed no significant differences in dye ability.
The above embodiment of the invention has the particular advantage that the heating means, such as a heated roll, can remain stationary, and that changes of the yarn tension are avoided. It should also be noted that the above embodiment may also be used in association with the other above described embodiments of the invention, should it be found that the sheet of yarns is still unduly exposed to high temperatures which the yarn in its undrawn state cannot withstand without risk of damage.
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Mar 1982 |
EPX |
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Divisions (1)
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Number |
Date |
Country |
| Parent |
676722 |
Nov 1984 |
|
Patent Grant
4814122
