OPEN- WIDTH FABRIC DRYING APPARATUS
Description
Technical Field
[0001] The present invention relates to the field of fabric processing machines, and more particularly to an open-width drying apparatus to be preferably arranged upstream of a continuous tumbler processing machine.
[0002] Further objects of the invention are a drying method and a method for openwidth fabric processing.
State of the Art
[0003] Fabric treatment machines known as "continuous tumblers" are known, which enhance the fabric by emphasizing its softness and bulk.
[0004] Generally, in a continuous tumbler, the fabric continuously enters a closed treatment space, is subjected to a series of impacts within suitably shaped metal grids, and exits the treatment space. The treatment occurs hot and with the fabric wet. The fabric is drawn by aeraulic systems that are based on the fluid-dynamic principle of the ejector. Thus, in addition to the mechanical treatment of "controlled impact," the fabric also undergoes a drying treatment that takes place in the machine due to the temperature and the high air velocity with which it is continuously comes into contact.
[0005] The treatment is continuous thanks to a “back and forth” system that allows the fabric to move from one chamber of the machine to another through an accumulation system positioned immediately next to the impact grids.
[0006] Fabric accumulation is managed through load cells that continuously detect the weight of the accumulation tanks and, consequently, adjust the speeds at which the fabric is fed into/extracted from the machine.
[0007] The demand for increasingly efficient machinery, characterized by low energy consumption and, at the same time, reduced dimensions, drives a comprehensive review of the use of continuous tumblers. [0008] The task of the present invention is to optimize power consumption in fabric treatment, especially in relation to treatments that involve at least partial drying of the fabrics.
[0009] Within this task, an important object of the present invention is to provide a drying apparatus, and a method, for continuously drying an open-width fabric, that is particularly efficient.
[0010] A further important object of the present invention is to provide a drying apparatus, and a method, for continuously drying an open-width fabric, that is particularly compact.
[0011] Another important object of the present invention is to provide a drying apparatus, and a method, for continuously drying an open-width fabric, that is reliable in operation.
[0012] A further object of the present invention is to provide a fabric treatment method using an efficient drying method.
[0013] According to a first aspect, these and other obj ects, which will be clearer later, are achieved through a system for drying a fabric, preferably an open-width fabric, comprising an internal space,
- within the internal space, a path along which the open-width fabric is adapted to be drawn and which comprises a plurality of drying sections that extend from the bottom upward and vice versa, at least two upper return rollers arranged along the path, at least one lower return roller arranged along the path between two upper return rollers, wherein a drying section is provided between an upper return roller and a lower return roller, a plurality of drying channels, which extend from the bottom upward and within which the drying sections for the fabric are provided, each channel comprising two opposite banks facing a respective drying section, at least one bank being provided with air ejection mouths facing the drying section, i.e. configured to eject air toward the drying section, i.e. toward the fabric passing in the drying section, a hot air management system comprising a hot air source that is operationally connected to the air ejection mouths, so that hot air strikes the fabric as it passes along the channels.
[0014] The at least two upper return rollers and the at least one lower return roller are provided within the internal space, so that the fabric path completely extends in a controlled space.
[0015] The internal space is for example delimited by an outer casing provided with an inlet and an outlet for the fabric. Preferably, the path is between the inlet in, and the outlet from, the outer casing.
[0016] The fabric is preferably arranged in open width within the machine, and can be, for example, either of the open type, i.e., with its extension transverse to the fabric feed direction having a single flap (two free side flaps), or of the tubular type, i.e., with cross-section closed in a loop (no flaps, i.e., two side flaps joined together).
[0017] The term "continuously" refers, for example, to the fact that the fabric is not all fed into the apparatus and not all exits the apparatus after having being dried, but enters continuously and exits continuously while the part of the fabric in the apparatus is being dried. The movement of the fabric can be continuous without interruptions, or with brief interruptions, and with interruptions or slowdowns along the path within the apparatus.
[0018] The term “hot air” refers to air well above room temperature and generally to a temperature above 90°C, for example between 98°C and 180°C. In general, the drying temperature depends on the type of fabric being treated and the type of further treatment the fabric will undergo later.
[0019] In preferred embodiments, both the two opposite banks of a channel are provided with air ejection mouths facing the drying section and operationally connected to the hot air source, so that hot air strikes both the sides of the fabric as it passes along the respective channel. [0020] In preferred embodiments, the apparatus comprises at least one ejection chamber, or ejection sleeve, arranged between two adjacent channels; the at least one ejection chamber comprises two opposite walls, that define at least a part of respective banks of the adjacent channels, and is operationally connected to the hot air source, and at least one wall of the ejection chamber is provided with air ejection mouths.
[0021] Preferably, both the opposite walls of the at least one ejection chamber comprise air ejection mouths.
[0022] In preferred embodiments, the hot air management system comprises hot air supply conveyors configured to supply air, in two opposite directions, to a plurality of mouths associated with a bank; the opposite directions for supplying air are preferably coincident with each other; the opposite directions are preferably approximately parallel, or orthogonal, to the axes of rotation of the rollers; the opposite directions are preferably associated with respective devices for moving air in these directions.
[0023] For example, the at least one ejection chamber defines a hot air supply conveyor; preferably, the ejection chamber that conveys air to the mouths comprises two opposite inlets for the air entering the chamber; preferably, the at least one ejection chamber has a preferably rectilinear extension.
[0024] According to preferred embodiments, each bank of a drying channel is defined by the walls of a plurality of ejection chambers arranged one after the other, facing toward the center of the channel; preferably, a first common manifold is provided at at least first ends of the chambers of the plurality of chambers, that is adapted to receive air from the hot air source and to deliver the received air to all the chambers of the plurality of chambers in order to supply the respective mouths; preferably, a second common manifold is provided at at least second ends of the chambers of the plurality of chambers, that is adapted to receive air from the hot air source and to deliver the received air to all the chambers of the plurality of chambers in order to supply air to the respective mouths in the reverse direction to that of the air coming from the first manifold.
[0025] According to preferred embodiments, the hot air management system comprises two separate air supply branches for delivering hot air from the hot air source to respective opposite ends of the ejection chambers, so as to supply hot air to the mouths of a respective bank in two opposite directions; at least one air mover being preferably provided for each supply branch.
[0026] In preferred embodiments, the hot air management system comprises
- an inlet, through which new air enters the internal space,
- an outlet, which discharges exhausted air from the internal space,
- an air heating system comprising the hot air source and configured to take air from the internal space,
- at least one air supply pipe adapted to supply air from the hot air source to the ejection mouths,
- at least one air mover adapted to move the hot air along the pipe, from the heating system to the ejection mouths.
[0027] According to preferred embodiments, most of, or more preferably all, the at least two upper return rollers are active rollers for drawing the fabric.
[0028] Preferably, if three upper return rollers are provided, at least two upper return rollers out of the three are preferably driven by an independent actuator, so that the two return rollers can rotate at different speeds from each other; preferably, to a first upper return roller, driven by an independent actuator, there is associated at least a second upper return roller, kinematically connected to the same actuator of the first return roller, so that the second return roller is configured to rotate at the same speed as the first return roller; preferably, two adjacent upper return rollers are operationally connected to each actuator, to rotate at the same speed.
[0029] According to further preferred embodiments, each upper return roller of a plurality of adjacent upper return rollers is driven by an own actuator, so that each roller of the plurality of rollers rotates independently of the others, that is, at different speeds.
[0030] In the preferred embodiments, the at least one lower return roller, arranged along the path between two upper return rollers, is passive and configured to rotate driven by the fabric in contact with it.
[0031] In preferred embodiments, a stretching roller is provided along the path before at least one upper return roller, the fabric being partially wound around the stretching roller, so that the fabric being wound on the respective upper return roller is stretched relative to the fabric moving along the adjacent drying section from which it comes; a diverting roller is preferably provided along the path, between the respective stretching roller and the respective upper return roller, arranged so as to be partially wrapped by the fabric and adapted, at the same time, to divert the path of the fabric, increasing the winding of the fabric on the stretching roller.
[0032] According to preferred embodiments, the drying apparatus comprises a tension adjustment system for adjusting the tension of the fabric along the path portion between the upper return rollers; the tension adjustment system comprises at least one tension sensing device in the path portion, the tension adjustment system being adapted to change the speed of at least one upper return roller on the basis of the tension value measured by the at least one tension sensing device, in order to bring the tension value of the fabric to a preset tension value different greater than a tension zero value.
[0033] The term “predefined tension value” means a value chosen by the operator and set in the apparatus, based on the type of fabric being dried, and possibly the subsequent treatment that the fabric must undergo.
[0034] The term “predefined tension value” can also mean a numerical range related to the tension, defined by a lower extreme and an upper extreme of the tension range, so if tension must be below a predefined value (however, above a null tension value), that value can be understood to be the lower extreme of that numerical range, while if the tension must be above a predefined value, that value can be understood to be the upper extreme of that numerical range. For example, the predefined value can be the central value of the range, with a tolerance range defined by the lower and upper extremes of the range.
[0035] The tension adjustment system preferably comprises at least one device for verifying the rotation of the at least one lower return roller and a control for setting the tension zero value measurable by the at least one tension sensing device, and wherein the tension adjustment system provides for
- reading the tension of the fabric by means of the at least one sensing device, and
- verifying the rotation of the at least one lower return roller and, if the rotation value is zero and the at least one sensing device detects a non-zero tension, - activating the control for setting the tension zero value.
[0036] The sensing device and the rotation verification device act preferably on the same lower return roller, or respectively on two distinct lower return rollers.
[0037] Preferably, the sensing device is a load cell associated with the at least one lower return roller, preferably adapted to detect the vertical load associated with the at least one lower return roller, preferably with the rotation shaft of the at least one lower return roller.
[0038] According to preferred embodiment, the verification device for verifying the rotation of the at least one lower return roller comprises a sensor adapted to detect the passage of one or more elements that are provided on the lower return roller and are adapted to rotate with the lower return roller, so that, in case of rotation, the sensor is adapted to detect a sequence of signals.
[0039] According to preferred embodiments, a control action by the tension adjustment system for controlling the tension in a path portion between two upper return rollers provides for:
- reading the fabric tension by the at least one fabric tension sensing device,
- comparing it with a predefined tension value, in case the read value is greater or less than the predefined value, the adjustment system respectively commands to increase or to decrease the speed of the return roller arranged before the at least one sensing device along the path portion, or respectively commands to decrease or to increase the speed of the return roller arranged after the at least one sensing device along the path portion.
[0040] According to another aspect, the invention relates to a drying method for drying an open-width fabric, that can be carried out, for example, in a drying apparatus according to one or more of the embodiments described above, which comprises
- feeding the fabric into the internal space of a drying apparatus,
- moving the fabric by drawing it along a path through the internal space, wherein along the path the fabric is adapted to be partially wound on at least two upper return rollers and on at least one lower return roller arranged, in the path, between the two upper return rollers, so that the fabric travels along sections from the bottom upward and vice versa, - drying the moving fabric by means of hot air ejected directly onto the fabric traveling along sections from the top downward and vice versa.
[0041] The hot air is preferably ejected directly onto both sides of the fabric traveling along the sections from the top downward and vice versa.
[0042] In the path portion, the hot air is preferably ejected through a plurality of ejection mouths; the hot air is fed to the mouth according to two opposite directions; preferably, supplying hot air in two opposite directions is done by means of two distinct air moving devices.
[0043] Preferably, the drying method for drying an open-width fabric provides for controlling the tension of the fabric traveling between two upper return rollers; this control comprises the measurement of the tension of the fabric traveling between the two upper return rollers and, if the measured tension value is different than a preset value, the change of the speed of at least one upper return roller; the control preferably comprises the steps of verifying the rotation of the at least one lower return roller and, if the rotation is null, of setting to zero the tension value measured by the at least one tension sensing device, and then of changing the speed of at least one upper return roller to bring the tension value back to the preset value.
[0044] According to a further aspect, the invention also relates to treatment method for treating a fabric comprising a preliminary step of drying the fabric and a subsequent step of inserting the dried fabric into a treatment machine that provides for the following steps accumulating a fabric on at least one containing structure; feeding the fabric toward a shrinking and softening area, where the fabric is pneumatically drawn and subjected to a repetitive impact action against opposite impact walls with an alternating motion; removing the fabric from the shrinking and softening area, and collecting the treated fabric.
[0045] The drying step can advantageously be that of the embodiments of the drying method described above. of the
[0046] The invention will be better understood by following the description below and the attached drawing, showing some non-limiting embodiments of the invention.
More particularly, in the drawing:
- Fig. 1 is a schematic axonometric view from the outside of a drying apparatus according to the invention;
- Fig. 2 is a schematic enlargement of the inside of a corner portion of the apparatus of Fig. 1, showing the inside of a manifold, from which the ends of hot air ejection chambers extend;
- Fig. 3 is a schematic cross-sectional side view of the apparatus of the previous figures;
- Fig. 4 is a schematic axonometric view of the apparatus of Fig. 1, cut-away according to the two planes indicated by the line IV-IV in Fig. 3;
- Fig. 4A shows an enlargement of Fig. 4, of the manifold of the ejection chambers;
- Fig. 5 is a schematic front view of the apparatus of Fig. 1, cut-away according to the plane indicated by the vertical portion of the section line IV-IV in Fig. 3;
- Fig. 6 is an axonometric view of the upper and lower rollers, separate from the outer casing structure of the apparatus according to the invention;
- Fig. 7 shows a detail of the connection of a lower return roller to a support structure of the apparatus according to the invention;
- Fig. 8 shows a side diagram of the central part of the apparatus according to the invention, where the fabric path, the return rollers, the drying channels, the ejection chambers, etc. are schematized;
- Fig. 9 shows a front diagram of the apparatus according to the invention, highlighting the components of the hot air management system; - Fig. 10 shows a side diagram, a variant of that of Fig. 8, of a portion of the central part of the apparatus according to the invention, where the fabric path, the return rollers, the drying channels, the ejection chambers, etc. are schematized;
Detailed description of embodiments
[0047] With reference to the previously cited figures, a drying apparatus according to the invention for drying an open-width fabric is indicated as a whole with number 10.
[0048] The apparatus 10 comprises a casing 11, consisting of walls and a ceiling, that defines an internal space 12. The casing has an inlet section 13, into which the fabric T enters continuously, taken for example from a reel B or a folded pile, or coming from a fabric supply line. The casing also has an outlet section 14, from which the fabric exits continuously, to be for example accumulated in a storage space or directly fed to the treatment station.
[0049] The inlet section 13 and the outlet section 14 are provided in the upper part of the apparatus, close to the ceiling.
[0050] A plurality of drying channels 20 are provided within the casing 11, which are parallel to one another, directed from the top downward, and preferably vertical, within which the fabric T passes continuously.
[0051] Basically, a path is defined in the casing 11, along which the fabric is adapted to be drawn and dried. In Figs. 3 and 8, the path and the fabric T coincide with each other and are indicated by a dash-dot line.
[0052] The path portions within the drying channels 20 are drying sections Pl for the fabric and extend from the bottom upward, if the fabric passes within them in upward direction, or vice versa, if the fabric passes within them in downward direction, as well shown in Fig. 3 and in the diagram of Fig. 8.
[0053] Upper return rollers 22I-22VI are provided above, and outside, the drying channels 20, which allow the fabric T, coming upward from a channel 20, to be sent to the following channel 20, i.e., returned downward. Here below, if it is not necessary to refer to a specific upper return roller, the upper return rollers are generically indicated by the reference number 22 with no superscript.
[0054] In this example, there are a first upper return roller 221 that moves the fabric to a portion outside the internal space 12, a second upper return roller 221 that moves the fabric downward into the first drying channel immediately next to the inlet section 13, a plurality of subsequent upper return rollers, each of which is arranged astride a respective pair of adjacent channels 20, respectively a third, a fourth, and a fifth upper return roller 22ni-22v, and a sixth upper return roller 22VI that moves the fabric coming from the bottom out of the last drying channel, toward the outlet section 14.
[0055] Analogously, a plurality of lower return rollers 24I-24I v are provided below, and outside, the drying channels 20, each lower return roller arranged astride a respective pair of adjacent channels 20, which move the fabric, coming from the top of a channel, upward into the adjacent channel. Here below, if it is not necessary to refer to a specific lower return roller, the lower return rollers are generically indicated by the reference number 24 with no superscript.
[0056] The drying channels 20 are delimited by banks 25 that extend, for example discontinuously, in an approximately vertical direction.
[0057] The banks 25 are formed by the walls 31 of ejection chambers 30 provided between the drying channels 20. Ejection mouths 32 are provided on the banks 25, i.e., on the walls 31, from which hot drying air from a hot air source 41 of a hot air management system 40 exits, as described below.
[0058] The ejection chambers 30 mainly extend in a direction transverse, preferably orthogonal, to the feed direction of the fabric T in the drying channels 20. These chambers extend, for example, approximately horizontally.
[0059] Basically, in this example, each bank of a drying channel is defined by corresponding walls 31 of a plurality of ejection chambers 30 arranged one after the other in vertical direction, facing toward the center of the respective drying channel 20. [0060] The ejection chambers 30 are arranged basically as columns of a matrix, and the drying channels 20 are defined between the columns. In this example, three ejection chambers for each column are provided.
[0061] The ejection chambers 30 are basically end sleeves made of sheet metal, into which hot drying air arrives from the hot air source 41. For example, the ejection chambers 30 have quadrangular cross-section, with two opposite walls 31 forming portions of banks of adjacent channels.
[0062] In this example, both the opposite walls 31 of the ejection chambers 30 (excluding the chambers related to the initial and final columns of the matrix arrangement) are provided with air ejection mouths 32. In this way, ejection air enters an ejection chamber 30 and is ejected to two adjacent channels through the ejection mouths 32 provided on the two opposite walls 31.
[0063] Hot air AC strikes both the sides of the fabric T as it passes along the respective channel 30.
[0064] In the first column of ejection chambers 30, i.e., on the vertical set of ejection chambers closest to the inlet section, approximately below the second upper return roller 22n, the ejection mouths 32 are provided only on the walls of the chambers facing the side of the apparatus where the outlet section is provided.
[0065] Similarly, in the last column of ejection chambers 30, i.e., on the vertical set of ejection chambers closest to the outlet section, approximately below the sixth upper return roller 22VI, the ejection mouths 32 are provided only on the walls of the chambers facing the side of the apparatus where the inlet section is provided.
[0066] In other embodiments, not shown in the figures, the path between the drying channels is realized by pairs of chambers arranged side by side in the overall feed direction X of the fabric within the apparatus, and the walls defining the banks of the respective channels are provided with ejection mouths, while the walls of the chambers facing one another are devoid of ejection mouths, so that each chamber supplies air into only one drying channel.
[0067] As mentioned, in the examples described above, at least one plurality of ejection chambers (arranged one above the other vertically) is provided for each drying channel, the ejection chambers ejecting, from corresponding walls, hot air into a drying channel. In other embodiments, not shown, the plurality of ejection chambers arranged one above the other vertically is replaced by a single large ejection chamber with a wall provided with ejection mouths for ejecting air into a respective drying channel.
[0068] With reference to the main direction of extension of the chambers (transverse, i.e., orthogonal to the fabric feed direction), each chamber 30 has a first end 33 for the air entering the chamber from the hot air source 41, and an opposite second end 34, again for the air entering the chamber from the hot air source 41.
[0069] All the first ends 33 of a plurality of chambers 30 relating to the same bank of a drying channel are connected to a common first manifold 35. All the opposite second ends 34 of the same plurality of chambers 30 are connected to a common second manifold 36.
[0070] For example, hot air enters the ejection chambers according to two opposite directions H and K.
[0071] The first and second manifolds 35 and 36 are operationally connected to the hot air source 41 through a first and second supply pipe 42, 43.
[0072] In practice, each ejection chamber 30 defines a hot air supply conveyor configured to supply air, in two opposite directions H and K, to the plurality of ejection mouths 32 provided in the wall(s) of the chamber, i.e., a portion of bank. In this example, the opposite directions H and K for supplying air toward the mouths 32 are coincident with each other, approximately parallel to the axes of rotation of the upper and lower return rollers.
[0073] The hot air management system 40 comprises two separate hot air supply branches, respectively comprising the first supply pipe 42 and the second supply pipe 43, for delivering hot air from the hot air source 41 to respective opposite ends of the ejection chambers 30, so as to supply hot air to the ejection mouths 32 according to the two opposite directions H and K.
[0074] In more detail, the hot air management system 40 comprises a pair of inlets 44, for new air AN entering the internal space 12 delimited by the casing 11, and an outlet 45 for exhausted air exiting the internal space 12, provided for example on the ceiling of the casing 11, and using for example an air extractor 45 A.
[0075] The hot air management system 40 also comprises an air heating system comprising the hot air source 41, conformed to take air AZ from the internal space 12 through a mouth 41 A.
[0076] The hot air source 41 comprises a burner 46, for example a gas burner, associated with a compartment 47 defined on a side and toward the bottom of the casing 11. The burner 46 heats the air coming from a supply inlet 48 to the compartment 47, preferably provided with a filter and open toward the internal space 12. The two separate hot air supply branches for supplying to the respective first and second manifolds 35 and 36 through the pipes 42, 43 extend from opposite sides of the compartment 47.
[0077] Two air movers 49, for example two fans, one for each branch, are provided to move air from the hot air source 41 to the ejection mouths 32.
[0078] Adequately, the arrangement of the air supply branches/pipes 42, 43 with the air movers 49, as well as of the chambers 30 and of the first and second manifolds, is approximately symmetrical, or nearly symmetrical, relative to a centerline plane W of the internal space, i.e., of the apparatus 10, so that the hot air load is equivalently distributed and the air flow rate in the two directions H and K for supplying air to the ejection mouths 32 is approximately corresponding.
[0079] In the embodiments described above, the ejection chambers 30 extend orthogonally to the direction X, approximately horizontally, and the first and second manifolds are therefore arranged at the side of the centerline plane W, at the same level. In other embodiments, not shown in the figures, where the drying channels extend again vertically, the ejection chambers mainly extend in vertical direction, parallel to the centerline plane W, and the first and second manifolds are therefore arranged at different levels. In practice, the chambers with the manifolds are rotated by 90° around a horizontal axis (in this case the opposite directions for supplying hot air in the chambers to the mouths are orthogonal to the axes of the upper and lower return rollers). [0080] A stretching roller 50, of known type, is provided along the fabric path, before some upper return rollers, and preferably before each upper return roller 22ni-22VI, against which the fed fabric is partially wound, so that the fabric being wound on the respective upper return roller is stretched relative to the fabric fed along the adjacent drying section from which it comes.
[0081] A diverting roller 52 is provided, arranged along the fabric path between the respective upper return roller 22 and the stretching roller 50. The diverting roller 52 is arranged so as to be partially wrapped by the fabric and adapted, at the same time, to divert the path of the fabric, increasing the winding of the fabric on the stretching roller 50.
[0082] The stretching roller 50 can be associated with all or only some of the upper return rollers, or it can be omitted.
[0083] Appropriately, one or more upper return rollers 22 are active rollers for drawing the fabric T, for example, as they are motorized.
[0084] At least two pairs of adj acent upper return rollers 22 are for example provided. For example, a first pair 22I-22n, a second pair 22ni-22IV, and a third pair 22V-22VI of rollers are provided.
[0085] The upper return rollers 22 of each pair of rollers are kinematically connected to each other and to a respective independent actuation motor 22A through a pulleybelt drive system 23, so that the rollers of a pair can rotate at the same speed, and, at the same time, can rotate at different speed than the rollers of the following and/or the preceding pair (which is associated with another independent actuation motor).
[0086] In other embodiments, such as the one shown in Fig. 10, an independent motorization 22A is associated with each upper return roller 22, so that each upper return roller 22 can rotate at different speed from the adjacent return roller 22.
[0087] In other embodiments, the upper return rollers kinematically connected to each other and to an independent motorization can be more than two.
[0088] At the same time, some, preferably all, lower return rollers 24 are passive and configured to rotate driven by the fabric in contact with them. [0089] The drying apparatus 10 also comprises a tension adjustment system 60 for adjusting the tension of the fabric T along the path portion Pl between two upper return rollers 22, thus a portion that also comprises passage for a lower return roller 24. In this example, two tension adjustment systems 60 for adjusting the tension of the fabric T are provided, one arranged between the second upper return roller 22n and the third upper return roller 22in, and one arranged between the fourth upper return roller 22IV and the fifth upper return roller 22v.
[0090] The tension adjustment system 60 comprises at least one tension sensing device 61 in the path portion between two upper return rollers 22, that in this example belong to two pairs of upper return rollers associated with different motors. The tension adjustment system 60 is configured to change the speed of the primary return rollers 22 of a pair of rollers (kinematically connected to a common motor) on the basis of the tension value measured by the sensing device 61, in order to bring the tension value of the fabric to a predefined value greater than a tension zero value.
[0091] As already mentioned, the term “predefined tension value” means a value chosen by the operator and set in the apparatus, based on the type of fabric being dried, and possibly the subsequent treatment that the fabric must undergo.
[0092] For example, a control action by the tension adjustment system 60 for controlling the tension in a path portion between two primary return rollers 22 of two adjacent pairs provides for: reading the tension of the fabric by the fabric tension sensing device 61, comparing it with the predefined tension value Vp, and, in case the read value Vg is greater than the predefined value Vp, the adjustment system 60 commands to increase the speed of the primary return rollers 22 of the pair of rollers having a common motorization 22 A arranged before the sensing device 61 along the path portion. In case the read value Vg is less than the predefined value Vp, the adjustment system 60 commands to decrease the speed of the upper return rollers 22 of the pair of rollers having a common motorization arranged before the sensing device 61 along the path portion.
[0093] Alternatively, in case the read tension value Vg is greater than the predefined value Vp, the adjustment system 60 command to decrease the speed of the primary return roller 22 arranged after the sensing device 61 along the path portion Pl, or, in case the read tension value Vg is less than the predefined value Vp, the adjustment system 60 commands to increase the speed of the primary return roller 22 of the pair of rollers having common motorization and arranged after the sensing device 61 along the path portion Pl. Essentially, the command has been reversed between the pair of return roller arranged after/before. Clearly, the same procedure can be applied even in the case that a single motorized roller is provided instead of a pair of rollers (Fig. 10), and the adjustment in this case concerns the single motorized roller.
[0094] The tension sensing device 61 is, for example, a load cell associated with the lower return roller 24, associated with the rotation shaft of the lower return roller; two load cells can be for example provided, arranged at the axial ends of the lower return roller 24. The lower return roller 24 is hinged, for example, to a substantially fixed support structure, so the load on the roller is measured by verifying the load measured by the load cell at an end thereof (or by the load cells at the ends thereof).
[0095] In order to limit the effect of high temperature on the tension sensing device 61 (i.e., the load cell), the tension sensing device is provided, for example, outside the casing 11, and the deformation at the shaft of the lower return roller 24 due to the fabric load is transmitted to the sensing device/load cell 61 through a tie rod system 63 connected to a hinge of the roller shaft. Another example, not shown in the figures, for constraining the lower return roller provides for the use of a lower return roller hinged at the ends on two arms that are in turn hinged to a support structure. The lower return roller can therefore pivot around the axis of hinging the arms to the fixed structure. This mode of supporting the roller is also known as "swivel” mode. In this case, the tension is adjusted by adjusting the inclination of the arms, i.e., by adjusting the angular position of the assembly arms-lower return roller (e.g., a pneumatic actuator can be adjusted to determine the angular position of the assembly arms-lower return roller); for example, the belt tension can be increased by tilting that assembly downward, that is, by lowering the lower return roller. By adjusting the rotation speed of the upper return rollers it is possible, for example, to adjust the tension in order to keep the position of the lower return roller in the center of the pivoting range.
[0096] Furthermore, the tension adjustment system 60 comprises a verification device 70, for verifying the rotation of the secondary return roller 24, and a control, for setting the tension zero value measurable by the tension sensing device 61, and the tension adjustment system 60 provides for reading the tension of the fabric by means of the sensing device 61, verifying the rotation of the secondary return roller 24 and, if the rotation value is zero and the sensing device 61 detects a non-zero tension, activating the control for setting the tension zero value, i.e. the tension value is initialized to zero in the tension measurement scale. Basically, it is like “taring” the sensing device 61 (the load cell), which will start measuring from zero.
[0097] In fact, if the rotation of the lower return roller 24 is null, the fabric does not slide on it and therefore the load on the roller is null. If the sensing device 61 detects a non-zero tension value on the roller, this means that the measurement chain is altered, for example, due to the drying temperature that could expand the components interconnecting the sensing device and the lower return roller. By initializing the tension sensing device 61 to zero, i.e., by initializing the load cells to zero, the measurement chain alterations due to expansions are canceled.
[0098] Once the tension sensing device 61 has been initialized to zero, the following tension measurements will be correct and the fabric tension adjustment will occur correctly as described above.
[0099] The sensing device (or sensing devices) 61 and the rotation verification device 70 act on the same lower return roller 24. In other examples, not shown in the figures, the sensing device and the verification device act on two separate lower return rollers respectively.
[0100] The verification device 70 for verifying the rotation of the lower return roller 24 comprises a sensor 71 adapted to detect the passage of one or more elements 72 that are provided on the lower return roller 24 (for example fastened on the shaft 24A of the roller 24) and are adapted to rotate with the lower return roller, so that, in case of rotation, the sensor 71 is adapted to detect a sequence of signals. A rotation verification device can be, for example, an encoder.
[0101] The drying of the open-width fabric comprises, for example, feeding the fabric into the internal space 12 through the inlet section 13, drawing the fabric along the looped path provided between the upper 22 and lower 24 return rollers, within the drying channels, from to top downward and from the bottom upward, and continuously extracting the fabric from the outlet section 14. [0102] While traveling in the drying channels, the fabric is invested, preferably on both its faces, by hot air coming from ejection mouths provided on the banks of the channels.
[0103] The hot air is produced by the burner and conveyed to the drying channels through two supply branches. The supply of hot air into the supply branches occurs by means of two distinct air moving devices. The hot air is supplied toward the mouths 32 according to two opposite directions H and K.
[0104] While the fabric travels within the apparatus, the fabric tension is controlled. The fabric tension is controlled in the sections between two preferably adjacent upper return rollers. These sections provide the passage of the fabric in respective lower return rollers 24.
[0105] The control of the tension of the fabric comprises the measurement of the tension of the fabric traveling between the two pairs of upper return rollers having common motorization, measuring the tension at the lower return roller 24 provided between the last upper return roller of a pair and the first upper return roller of the second pair; the measurement is carried out, for example, through a tension sensing device, and the subsequent change in the speed of the upper return rollers of a pair (in some cases, the speed of the upper return rollers of both pairs of rollers can could be changed) if the measured tension value is different from a preset value.
[0106] The control comprises the steps of verifying the rotation of the lower return roller and, if the rotation is null, of setting, i.e. initializing, to zero the tension value measured by the tension sensing device, and then of changing the speed of the upper return rollers to bring the tension value back to the preset value.
[0107] Once the fabric has been dried, it can be treated in a treatment machine, for example a continuous tumbler treatment machine.
[0108] The dried fabric is inserted into a fabric treatment machine, such as the machines described in patent documents EP 1781854, EP2286013 EP2535451, IT 1378395, whose content is included as a reference in the present description. In such a machine, the fabric is accumulated in at least one containing structure, fed to a treating area, for example a shrinking and softening area where the fabric is pneumatically drawn and subjected to a repetitive impact action against opposite impact walls with an alternating motion, and then extracted from the machine and collected.
[0109] It is understood that what is illustrated purely represents possible non-limiting embodiments of the invention, which may vary in forms and arrangements without departing from the scope of the concept on which the invention is based. Any reference numerals in the appended claims are provided for the sole purpose of facilitating the reading thereof in the light of the description above and the accompanying drawings and do not in any way limit the scope of protection.