A device for centering tubular fabric

Abstract: A device (15) for centring a tubular fabric (10) comprises a central fixed supporting portion (16) located within the fabric. A pair of oscillating arms (17) each having an end mounted to said central fixed portion (16), are kept divaricated against the tubular fabric. A motor driven roller unit (18) is secured to the free end of each oscillating arm (17) and has an electric motor (19). Motors (19) control rotation, in the same direction of rotation, of respective supporting members (21) each fitted with a plurality of idle rollers (22). The rollers (22) are angularly equally spaced around their respective supporting member (21) and are free to rotate about respective axes of rotation transverse to the direction of advancement of the fabric. Rotation of supporting members (21) in the same direction causes the fabric to rotate, while oscillating arms (17) keep the fabric stretched.

Description: Field of the invention The present invention falls within the field of textile equipment for untwisting, widening and cutting tubular fabric. More particularly, the invention relates to a device for centring a tubular fabric. Background of the invention As known, tubular fabric usually comes out in rope-like form after dyeing operations. Firstly, the fabric needs to be untwisted, and then has to be widened transversally so as to carry out successive lenghtwise cutting, opening and spreading operations. Cutting is attained along the line determined by a missing weft. The position of such a line is continuously sensed by suitable reading means that are associated with a device for centring the fabric. Depending on the direction and displacement of the missing weft line relative to the central position, as sensed by the reading means, the centring device rotates the tubular fabric in either direction so as to get the missing weft line to face the cutting device precisely. Besides accuracy, a basic requirement of the centring device is that it must be able to work at high speed. Rotation and counter-rotation must occur very quickly, not to limit the speed of advancement of the fabric. The fabric must necessarily be stretched to be able to react promptly to the stresses it is subjected to by the centering device. Also, wrinkles and overlapping of the fabric can be prejudicial to the accuracy with which the missing weft line is positioned, thereby compromising correct lengthwise cutting of the fabric. EP-A-0.603.645 (upon which the preamble of claim 1 is based) discloses a centering and an expanding device provided with idly mounted rollers that do not hinder lengthwise advancement of the fabric. By rotating transversally relative to the direction of advancement of the fabric, the rollers cause the fabric to rotate for centering the missing weft line on the cutting tool. However, this centering device does not work on a stretched fabric. As a result, it is not able of attaining required corrections of position quickly enough and therefore represent a slow point of the textile plant. EP-A-0.603.645 and GB-A-2.070.660 further disclose centering devices constituted respectively by an umbrella and a basket that rotate about their own vertical axis, the umbrella being provided of idle rollers mounted on their arms, upon which the fabric slides. However, the arms of the umbrella and of the basket can be widened or contracted only manually to change the stretching of the device on the fabric sliding over it. DE-A-2.015.239 discloses a centering device comprising three parallel arms, which are provided with a relevant vertical roller, and in which two of them are fixed arms and one of them is a movable arm powered by driven means. The fabric slides upon the vertical roller, and the movable arms change the stretching of the device on the fabric, which is particularly stressed either by the high friction because of the high contact surface, or by the fact that the stretching capability can be changed by moving the movable arm to and from the fixed arms with said driven means, that are too much rigid, or else very little sensible to the elastic changing of the fabric. Summary of the invention It is an object of the present invention to provide a centering device capable of overcoming the above prior art drawbacks. Particularly, it is an object of the present invention to provide a device capable of giving the fabric the necessary tension to let it react as quickly as possible to stresses it is subjected to, in order to reset the fabric's position immediately and allow the entire section to work at higher speed. In accordance with one aspect of the invention as claimed, these objects are accomplished by the provision of a device for centering a tubular fabric, of the type disclosed in EP-A-0.603.645 and further characterized according to claim 1. Brief description of the drawings In order that the present invention may be well understood there will now be described a few preferred embodiments thereof, given by way of example, reference being made to the accompanying drawings, in which: FIG. 1 is a side view of an apparatus for untwisting, widening and cutting tubular fabrics; the apparatus includes a centering device according to the present invention; FIG. 2 is a front view of the apparatus of FIG. 1; FIG. 3 is a plan view of the apparatus of FIG. 1; FIG. 4 is a view, to an enlarged scale, of a detail of the device of this invention shown in FIG. 2; FIG. 5 is a side view of an apparatus for working tubular fabrics different from the apparatus of FIGS. 1 to 3 but still incorporating a centring device of this invention; FIGS. 6 and 7 show a front and a plan view of the apparatus of FIG. 5, respectively; FIG. 8 is a side view of another apparatus for working tubular fabrics still different from the apparatus of FIGS. 1 to 7 but still incorporating a centring device of this invention; and FIGS. 9 and 10 show a front and a plan view of the apparatus of FIG. 8, respectively. Detailed description of preferred embodiments With reference initially to FIGS. 1 and 2, there is shown an apparatus for carrying out continuously a series of operations on a tubular fabric 10 advancing therethrough. Numeral 11 designates a straightening equipment for untwisting the fabric arriving in rope-like form. Direction of advancement is indicated by arrow A (FIG. 1). The straightening equipment 11, being of known kind, is not hereinafter described in detail. Untwisting equipment 11 rotates the fabric in rope-like form, as it is after dyeing, in the two opposite directions with respect to its direction of advancement, in order to provide a substantially untwisted fabric ready for widening, lengthwise cutting and tentering. The fabric 10 coming out of the straightening equipment is widened. In the preferred embodiment shown in the drawings, the fabric is widened by inflating it with an air blow. Air is inflated counter-current within the tubular fabric by means of a conventional widening device 12 composed of a power fan 29 delivering air into the tubular fabric through a conduit 28 open at one end. In this inflated condition, the tubular fabric arrives to a cutting unit. Generally, cutting unit 13 employs a vertical rotating disc 14 to cut the fabric lengthwise along a line determined by a missing weft. Within the tubular fabric, immediately upstream or above cutting unit 13, there is installed a fabric centring device, designated overall by numeral 15. Centring device 15 rotates the inflated fabric in the two opposite directions about an axis parallel to the direction of advancement with an aim to keep the line of the missing weft continuously centred on cutting unit 13. The centring unit 15 is operatively coupled to a reading assembly, preferably of optical kind. The reading assembly senses continuously the position of the missing weft line. Should this line be displaced with respect to the ideal line where it should be, the reading assembly informs the centring device so that this may be immediately activated to centre the tubular fabric. According to the present invention, the centring device 15 comprises a central supporting fixed portion 16 to which a pair of oscillating arms 17 is mounted. At the free end, each oscillating arm 17 is fitted with a motor driven roller unit 18. Each roller unit 18 has an electric motor 19 having an output shaft 20 rotating a substantially annular-shaped supporting member 21 about an axis substantially parallel to the direction of advancement of the fabric. Mounted to supporting member 21 is a plurality of idle wheels or rollers 22 having axes of rotation substantially horizontal or transversal with respect to the direction of advancement of the fabric. In the preferred embodiment illustrated, the idle rollers 22 are preferably angularly equally spaced around the axis of shaft 20. In addition, the supporting member 21 illustrated is of annular shape, but it may also take other shapes, such as a polygonal arrangement, to perform its function of supporting and distancing the rollers. By being rotated in a same direction by motors 19, the two supporting members 21 cause the rollers to exert some friction on the surrounding fabric, thereby rotating it in the desired direction of rotation, transverse with respect to the direction of advancement. Being idle, the rollers 22 exert no friction or almost no friction on the fabric 10 moving vertically. Therefore, the fabric can keep its vertical speed. Each motor driven roller unit 18 is hinged at 30 to an end portion of the respective oscillating arm 17 through a connecting bracket 23. Bracket 23 is also connected to an end of an elastic member 24, the opposite end of which is secured to the central supporting fixed portion 16. The function of elastic members 24 is to resiliently divaricate the two oscillating arms for keeping the fabric stretched so that it can be rotated quickly and be arrive in a centred arrangement to the successive workstations for cutting, tentering, etc. Also, elastic members 24 adjust the angle of arms 17 to tubular fabrics of any size without generating lateral stresses therein. After cutting and tentering, the fabric 10 normally passes through a driving unit 25 (FIGS. 1 and 2) to be subjected to further operations or simply stored. FIGS. 5 and 6 show the case where the centring device 15 according to the present invention is installed in a processing plant comprising a widening and centring unit 26 fitted with spiral surface rollers located immediately upstream of the final driving unit 25. In FIGS. 8 and 9, a widening equipment using a suspended roller device 27 is interposed between the widening and centring device 26 and the final driving unit 25. As will be apparent, the centring device 15 of the present invention is completely inserted within the tubular fabric. The fabric is not only spread out by the air being blown in, but it is also stretched by the centring device itself. As a result, it is possible to transmit quicker centring rotary motion to the fabric. The great advantage is that the fabric is allowed o travel much more rapidly in comparison to conventional centring devices. As the fabric is properly widened and stretched, stresses caused by friction that normally occur as the fabric advances within the equipment are considerably reduced. Moreover, the oscillating arms divaricate and adjust immediately and automatically to the tubular fabric's diameter, whereby the centring device 15 is adapted to work with tubular fabrics having different diameter. Another advantage concerning the fact that the tubular fabric is widened and stretched is an improvement in the response of the twist sensing device incorporated in the straightening assembly. As set forth, the tubular fabric is kept very wide by the device of this invention (and the air blow coming from below); consequently, the length of fabric still twisted in ripe-like form leaving the straightening unit is minor as in comparison with prior art. Therefore, the effect of the straightening unit will be more efficient, having to eliminate twist on a shorter length of fabric. Finally, it will be appreciated that this centring device can also be employed with tubular fabrics not having a missing weft line, where centring can only be carried out consequent to twists being detected as the tubular fabric advances. While a specific embodiment of the invention has been disclosed, it is to be understood that such disclosure has been merely for the purpose of illustration and that the invention is not to be limited in any manner thereby. Various modifications will be apparent to those skilled in the art in view of the foregoing example. The scope of the invention is to be limited only by the appended claims.

Claims: A device (15) for centering a tubular fabric (10), the device (15) comprising: two groups of rollers (22) idly mounted to supporting members (21), and having axes of rotation transverse with respect to a given direction of advancement of the fabric; the supporting members (21) being controlled by photoelectric cell means, positioned along the path of the tubular fabric upstream of cutting means for cutting the fabric lengthwise, and by motor units (19) for moving the rollers (22) sideways relative to their planes of rotation and rotating the fabric about an axis substantially parallel to said given direction; and stretching means (17, 24) adapted for stretching the tubular fabric transverse to said given direction, said stretching means being operatively associated with said supporting members (21) for supporting said rollers (22); characterized in that said stretching means (17, 24) comprise: a central fixed supporting portion (16) located in use within the tubular fabric (10), and a pair of oscillating arms (17), each of them having a relevant end portion mounted to said central fixed portion (16); said supporting members (21) and said motor units (19) being two, each of them being secured to a relevant free end of a respective oscillating arm (17), and said arms being kept divaricated against the tubular fabric by resiliently yieldable biasing means (24). A device according to claim 1, characterized in that said motor units (19) are adapted for controlling rotation, in the same direction of rotation about respective axes substantially parallel with respect to said given direction, of a respective supporting member (21); each of said supporting members (21) being fitted with a plurality of idle rollers (22) or wheels having respective axes of rotation substantially transverse to said given direction. A device according to claim 2, characterized in that the idle rollers (22) are angularly equally spaced around their respective supporting member (21). A device according to claim 3, characterized in that said supporting members (21) are of substantially annular shape.

Inventors: BIANCO MARIO, BIANCO, MARIO
Applicants: BIANCO SPA, BIANCO S.P.A.
Application year: 1995
Main classification: D06H7
IPC codes: D06H7