GB2113147A - Transporting webs of textile material in screen printing machines - Google Patents

Abstract

Carpet (3) is transported along several processing stations (2) in a screen printing machine (1) by a first pinned roller (5) ahead of the foremost processing station, a second pinned roller (6) downstream of the last processing station, and a driven blanket (4) whose upper stretch supports the carpet (3) between the two pinned rollers (5,6) below the processing stations. The second pinned roller (6) is driven at a peripheral speed which exceeds the peripheral speed of the first pinned roller (5) so that the web portion between the two rollers is tensioned in the space above the blanket (4) and below the processing stations. Discrete driving units (50-58 60-65 and 70-75) are provided for the two rollers (5,6) and for the blanket (4). Any changes in the speed of the driving unit (70-75) for the blanket (4) are communicated to the driving units for the pinned rollers so that the ratio of speeds of the two rollers (5, 6) relative to each other, and to the speed of the blanket (4), remains unchanged irrespective of eventual fluctuations in the speed of the blanket (4). The peripheral speed of the first roller (5) equals or approximates the speed of the blanket (4). In the driving arrangement illustrated, the drive motors (51,61, 71) are controlled and synchronised by tachogenerators and revolution counters (55,65,75), digital regulator (57) and selector (58). The arrangement provides for optimum guidance and tensioning as the carpet passes through the printing machine, <IMAGE>

Description

SPECIFICATION Apparatus for transporting webs of textile material or the like in screen printing or analogous machines The present invention relates to apparatus for transporting webs of textile material or the like in screen printing or analogous machines.

German Pat. No. 960,416 discloses a web transporting apparatus which employs carded rollers or drums (the term "carded" is intended to denote that the peripheral surfaces of the rollers are provided with projections in the form of needles, pins, studs or like protuberances adapted to positively engage the web which is trained over such rollers) which are mounted in lateral carriers of the machine wherein the web is treated and positioned in such a way that the web extends tangentially of their peripheral surfaces. The machine in which such transporting apparatus is put to use can serve for the treatment (e.g. for the application of ink to) webs of carpeting or similar textile materials. The protuberances of the carded rollers penetrate into the underside of the web which is guided therealong in tensioned condition.

A pair of such carded rollers is provided between each pair of successive printing or patterning stations in the patented machine. Each of the carded rollers is an idler roller, i.e. it is driven by the web which is pulled lengthwise through the machine. The purpose of carded rollers in the patented machine is to ensure uniform transport of the web, especially to counteract the suction which is applied to the web at each of the stations at a level below the path for the web.

A drawback of the apparatus which transports the web in the machine of the German patent is that the carded rollers cannot influence the tension or pull upon the web, i.e., they merely engage the web and are rotated as a result of lengthwise movement of the web along its path.

Thus, it can be said that the web guides the carded rollers as a result of its movement through the machine.

Controlled transport of the web of carpeting or the like in a machine which applies to the web one or more flowable media in the form of liquids, pastes or foams is of utmost importance. It is necessary to admit the web into the machine at a controlled rate, to effect a predictable movement of the web through or past one or more treating stations, and to remove the web from the machine is an equally predictable manner. The machine which is disclosed in the aforementioned German patent and/or other conventional machines are not equipped with transporting apparatus which can ensure such predictable admission into, transport through and removal from the machine of a continuous or elongated web, strip or band of carpeting, other textile material, metallic or plastic foil, paper or the like.The heretofore known apparatus for guiding and transporting a web of carpeting, especially a tufted carpet, are incapable of controlling the movement of the web with a required degree of precision and reproducibility, namely, with a degree which is required to meet the ever-increasing quality requirements of manufacturers, wholesalers and ultimate purchasers of such products. Furthermore, the nature of the materials which are being treated in screen printing and like machines has undergone substantial changes, and the conventional transporting apparatus are incapable of adequately guiding and advancing numerous new types of carpeting or the like.

Unsatisfactory guidance and/or transport of a web of carpeting in a screen printing machine entails a number of serious drawbacks. Thus, the web is likely to exhibit transversely extending streaks as a result of unsatisfactory rapport between the patterns which are applied at successive treating stations of the screen printing machine. The web is likely to run askew to the right or to the left so that the entire pattern is mispiaced or that a portion of the web is not imprinted or patterned at all. Furthermore, the web is likely to develop folds which entail unsatisfactory application of ink.All in all, improper guidance and advancement of the web in a screen printing or like machine can lead to the production of a low-quality product, to a product which must be discarded, or to a product which is much too expensive because the speed of the machine must be reduced well below the rated speed in order to be in a position to control the advancement of the web through or past one or more treating stations. Improper guidance and transport can affect the quality of the pattern of colour which is applied to the web and /or the condition of the web itself and/or the condition of the machine in which the web is treated.

In many heretofore known screen printing or analogous machines, the web is adhesively secured to an endless printing blanket so that it cannot shift with reference to the blanket. Such mode of preparing the web for treatment in a screen printing or like machine obviates quite a few of the aforementioned problems but it also creates other problems, especially as concerns the output of the machine. Furthermore, the use of adhesive to secure relatively heavy materials, such as webs of carpeting or the like, to a printing blanket is either extremely difficult or plain impossible so that the just discussed solution is not universally applicable in each and every situation where a web, sheet or panel of textile or other material is to be treated in a screen printing machine.For example, if the nap of the carpet consists of tufts, portions of the loops are likely to adhere to the blanket if the underside of a tufted carpet is adhesively secured to the blanket so that the appearance of the web is utterly unsatisfactory when its removal from the blanket is completed.

Each and every attempt to solve the problems which arises as a result of the utilization of heretofore known apparatus for guidance and transport of webs in screen printing or analogous machines must involve careful consideration of a large number of factors including the nature of the web, the weight of the web, and the required or desired output of the machine which utilizes the transporting apparatus. This will be more readily appreciated upon perusal of the following example.

A tufted workpiece of the type presently used as blank for conversion into a carpet normally comprises a base (which may but need not be woven) and one or more types of yarn which forms the tufts. The bases of presently manufactured tufted carpets are more readily treatable in a screen printing machine than fleeces; however, their form stability is very low so that they can cause defects in the application of many types of patterns, especially geometrical patterns. The treatment of webs whose base is a fleece is more difficult than that of webs having bases in the form of woven layers, but their form stability is more satisfactory so that they are often preferred in lightweight products.If the tufting operation affects (damages, destroys or appreciably changes) the base, the application of water or chemicals in the printing or patterning machine enables or even causes the base to tend to reassume its original state. This releases forces which can lead to undersirable, highly pronouned and hence readily detectable alterations of the entire product. Such changes or alterations can take place during printing and are a frequent cause of pronounced defects. This holds true even if the application of ink or another flowable medium takes place in such a way that the applicator or applications need not touch the tufts at all.

Contact between the nap of a carpet and the ink applying instrumentalities is normally interpreted as involving the application of a slight pressure against the adjacent stratum of the web; this is deemed necessary in order to ensure that the ink will penetrate into the nap, i.e., that the nap will be coloured all the way to the base rather than only at the tips of the individual fibres or loops. The just mentioned pressure must be sufficient to prevent the ink (e.g., a paste) from lifting the applicator (e.g. a rotary cylindrical screen) off the nape so that the applied ink is simply smeared over the exposed surface of the web. As a matter of fact, when one operates with cylindrical stencils whose interstices permit ink to advance into contact with the nap, a slight pressure between the stencil and the nap will be required even under optimal operating conditions.Such slight pressure suffices to increase the normally slight inclination of fibres or loops of the nap, and this change of inclination can present problems in connection with the transport of the web in the printing or patterning machine, especially in the regions where the web is causes to move below the screens. If the application of ink or another flowable medium takes place without any contact between the applicator and the nap of a web of carpeting, velvet or the like (e.g., when the applicator comprises nozzles which spray the ink onto the web or plungers which propel the ink into contact with the web), water or chemicals invariably penetrate into the base which can cause pronounced changes in the characteristics of the base and may require special treatment, such as drying.Moreover, such mode of applying ink or the like is uneconomical because large quantities of ink are wasted as a result of application to the base which, in many instances, should not be coated with the material that is being applied to the nap.

Similar and/or different problems arise in connection with the treatment of other types of webs in heretofore known screen printing or analogous machines, and more particularly in machines which employ conventional web guiding and transporting apparatus.

Prior art which might be deemed relevant to the matter of the present invention further includes German Auslegeschrift No. 12 22 941 and the article entitled "Regulierung der Bahnspannung" by Hans Reinsch in the February 1 968 issue of the German-language publication "Neue Verpackung".

There is thus a need for a generally improved apparatus which can be used to guide and transport webs of carpeting or the like in screen printing or analogous machines in such a way that the web is maintained in an optimum position and is placed in an optimum condition for the application of ink, other chemicals, water or other flowable materials of pasty, pronounced liquid or foamy consistency, and which can subject the web to an optimum tensional stress during transport of successive increments of the web past one or more treating stations.

According to the present invention there is provided apparatus for transporting a web of textile material or the like in a screen printing or an analogous machine, comprising means for advancing the web along a predetermined path having an inlet portion and an outlet portion, said advancing means comprising first and second rotary carded members respectively adjacent to said inlet and outlet portions of the path and a mobile printing blanket adjacent to a third portion of said path between said carded members, the web being trained over said carded members and said blanket having a stretch contacting the web between said inlet portion and said outlet portion; and drive means for moving said blanket at a first speed, for rotating said first carded member at a second speed such that the speed of the web on said first carded member at least approximate the speed of the web on said blanket, and for rotating said second carded member at a third speed exceeding said second speed so as to tension the web between said carded members.

The drive means preferably comprises discrete first and second driving units for the respective carded members and most preferably also a discrete third driving unit for the blanket. The construction of the first driving unit may be similar or identical to that of the second and/or third driving unit. The apparatus further comprises means for synchronizing the operation of the third driving unit with that of the first and second driving units so that the ratio of peripheral speeds of the carded members to the speed of the blanket remains at least substantially constant irrespective of eventual changes in the speed of the blanket.In other words, if the speed of the blanket is changed, the synchronizing means changes the peripheral speeds of the carded members that the ratio of such peripheral speeds remain unchanged and the ratio of each peripheral speed to the speed of the blanket also remains unchanged (unless the operator wishes to change such ratio or ratios).

The third driving unit preferably comprises selector means for varying the speed of the blanket within a desired or required range, e.g., as a function of changes in resistance of the web to transport by the carded members and the blanket.

The first driving unit can comprise selector means for varying the speed of the first carded member, and the second driving unit can comprise selector means for varying the speed of the second carded member (e.g., to thereby change the pull upon the web between the two carded members). The speed of the second carded member can be varied as a function of variations in the tension of the web so that such tension remains at least substantially constant.

In accordance with a presently preferred embodiment of the invention, the aforementioned synchronizing means is designed to regulate the operation of two of the three driving units as a function of changes of operation of the remaining unit, preferably as a function of changes of operation of the driving unit for the blanket. Each driving unit preferably comprises a discrete variable-speed motor (e.g., a d-c motor), and the synchronizing means can comprise discrete speed monitoring means for each of the three motors.

Such monitoring means can include tachometer generators which are designed to generate signals or sequences of signals denoting the speed of the - respective motor. Each of the tachometer generators can include or constitute a discrete revolution counter for the respective motor. One or more digital regulator means can be provided for at least one of the driving units; e.g., the first driving unit can comprise at least one digital regulator which receives signals from at least two of the three tachometer generators as well as from a speed selector for the first carded member.

The speed of the first carded member can be varied (e.g., by the just mentioned speed selector) as a function of variations of the thickness of the web.

The means for treating the web can be disposed between the two carded members. Such treating means can include one or more rotary screens or stencils which are disposed above (whereas the blanket is disposed below) the aforementioned third portion of the path.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying single figure drawing which is a schematic elevational view of one embodiment of a web guiding and transporting apparatus according to the invention and transporting apparatus according to the invention installed in a screen printing machine.

The drawing shows a screen printing machine 1 with a series of six successive treating or processing stations 2 each of which accommodates a cylindrical screen or stencil serving to apply ink or another flowable medium to a running strip or web 3 of textile or other material, e.g., to a running web of carpeting. The manner in which the screens at the stations 2 are mounted and operated is disclosed, for example, in commonly owned U.S. Pats. Nos. 3,965,816; 3,995,551; 4,041,860; 4,055,119 and 4,089,193.

The disclosures of these patents are incorporated herein by reference.

The web 3 is trained over a first carded roller or drum 5 which is located at the inlet 10 of an elongated horizontal path extending below the treating stations 2, and over a second carded roller or drum 6 which is located at the outlet of the path. The means for advancing the web 3 along such path further comprises an endless printing blanket 4 whose upper reach or stretch 4a is adjacent to the underside of the web 3 in the path portion between the inlet 10 and outlet 11. The blanket 4 is trained over a driven pulley 41, over an idler pulley 40 and an adjustable tensioning pulley or roll 42. The mechanism which can move the roll 42 in order to change the tension of the blanket 4 is not specifically shown in the drawing.

The blanket 4 may constitute an endless band of woven textile material, a screen-like endless strip, or a rubber band which is reinforced by strips of textile material of the like. The utilization of blankets as a part of or as the means for advancing webs of textile material or the like in a screen printing machine is known per se. If the tensioning roll 42 is omitted, the pulley 40 and/or 41 (preferably the idler pulley 40) is movable relative to its frame to change the tension of the blanket 4.

The carding of the rollers 5 and 6 may consist of conical pins or studs having a length of, for example, 2-3 mm and being spaced apart from one another by distances in the range of 5 cm.

This is merely an example of the nature and distribution of carding on the rollers 5 and 6.

The drive means for the component parts 4, 5 and 6 of the advancing means for the web 3 comprises three discrete driving units 7 (for the blanket 4), 7A (for the first carded roller 5), and 7B (for the second carded roller 6). The arrangement is preferably such that the peripheral speed of the first carded roller 5 equals or closely approximates the speed of the upper reach 4a of the blanket 4 (the rollers 5, 6 are assumed to rotate in a clockwise direction, as viewed in the drawing, and the upper reach 4a is assumed to advance in a direction from the left to the right), and that the peripheral speed of the roller 6 exceeds that of the roller 5 so that the web portion between the rollers 5 and 6 is invariably subjected to a certain tensional stress which is preferably constant irrespective of eventual fluctuations in the speed of the blanket 4.At least the driving unit 7B is adjustable independently of the other two driving units 7 and 7A so as to select the tensional stress upon the web 3 as a function of one or more parameters including the distance between the rollers 5 and 6, the thickness of the web, the force with which the screens at the treating stations 2 bear against the upper side of the web and/or others. The carding of the roller 5 can readily ensure that the web 3 cannot slip with reference to this roller, i.e., that successive increments of the web are advanced toward the foremost station 2 at a predictable speed. The carded roller 5 further ensures that eventual fluctuations of tensional stresses upon the web 3 upstream of the inlet 10 of the path are not communicated to the web portion which is disposed between the rollers 5 and 6.Still another (guiding) function of the roller 5 is to ensure that the web 3 cannot move sideways but remains in the prescribed path during travel toward and with the upper stretch or reach 4a of the blanket 4. An additional function of the roller 5 is to ensure that the rate of delivery of the web 3 into the path portion between the inlet 10 and the outlet 11 is not influenced by unequal or non-anticipated stressing of the web during travel past the screens at the treating stations 2.

If the thickness of the web 3 varies, i.e., if the apparatus is used to transport a succession of webs whose thickness is not uniform, the neutral layers of the webs are disposed at different levels nd, accordingly the carded roller 5 transports different lengths of the web per unit of time. This necessitates an adjustability of the driving unit 7A for the front carded roller 5, i.e., an adjustability of the quantity of material which is transported per unit of time, in order to ensure that the speed at which the web advances between the inlet 10 and the outlet 11 always matches the speed of the upper reach 4a of the blanket 4, irrespective of the thickness of the web which happens to be in the process of being treated during travel past the stations 2 at a level above the blanket 4.

It is further necessary to employ for the second carded roller 6 a driving unit 7B which is adjustable as a function of variations in the tension of the web 3 as well as for the purpose of ensuring that the operator or an automatic control unit can select the exact tension to which the web is subjected during travel past the treating stations 2. The magnitude of the pull or tensional stress upon the web 3 should be selected in such a way that the pull is more pronounced than the force which is released in the web itself, e.g., as a result of moistening of the substrate of the web during travel past the stations 2. This was described hereinabove in connection with the discussion of the treatment of tufted goods.

The driving unit 7A comprises a variable-speed d-c motor 51 which drives the shaft for the carded roller 5 through the medium of a suitable transmission 50. The speed of the motor 51 is monitored by a combined tachometer generator and revolution counter 55 which transmits corresponding signals idenoting the actual RPM of the motor 51) to a current regulator 53 for the motor 51 and to a digital regulator 57. The reference character 58 denotes a speed selector for the web 3 (e.g., a potentiometer), the output of this speed selector is connected to the corresponding input of the digital regulator 57.

The driving unit 7 is the primary driving unit of the drive means and its operation is synchronized with those of the driving units 7A and 7B which can be said to constitute slave driving units. The mode of synchronizing is such that any acceleration or deceleration of the variable-speed d-c motor 71 of the primary driving unit 7 entails appropriate changes in the speed of the aforementioned d-c motor 51 in the driving unit 7A as well as of the variable-speed d-c motor 61 of the driving unit 7B. The motor 71 can further serve to transmit motion to the mobile components at the treating stations 2 as well as and/or to other mobile components of the machine 1.The motor 71 drives the shaft of the pulley 41 for the blanket 4 through the medium of a suitable transmission 70 (e.g., a gear transmission), and the motor 61 drives the shaft of the carded roller 6 through the medium of an additional transmission 60 (e.g., a gear transmission which can be similar to or identical with the transmission 70 and/or 50). The control circuit for the d-c motor 61 includes a current regulator 63 which can comprise a potentiometer for regulation of armature current in such a way that the pull upon the web 3 is constant within a predetermined range of speeds of the blanket 4.

The tension in the web 3 can be selected within a wide range; however, once a given tension is selected, the system which synchronizes the operation of the driving unit 7 with the operation of the driving unit 7A and the operation of the driving unit 7A with that of the driving unit 7B ensures that the selected or given tension remains unchanged, even if the speed of the blanket 4 changes. As a rule, when a given web 3 is transported along the path which is defined by the rollers 5, 6 and blanket 4, the tensional stress upon each increment of such web is the same and the web is thus compelled to remain in its prescribed path which leads past the various components of the machine 1 at the stations 2.

If the machine 1 is arrested for a relatively short interval of time, the apparatus of the present invention preferably continues to maintain the driving unit 7B in operation. The arrangement is preferably such that the speed of the d-c motor 61 is then reduced, the same as the speed of the motors 51 and 71, so that the tensional stress upon the web 3 remains unchanged in spite of the fact that the speed of each of the motors 51, 61 and 71 is or can be reduced. The motor 1 is supplied with a predetermined minimum amount of armature current to ensure that the carded roller 6 rotates at a certain minimal speed which exceeds the speed of the roller 5, i.e., the roller 6 ensures that the web 3 is tensioned in the region between the inlet 10 and the outlet 11 of its path.

The peripheral speed of the first carded roller 5 matches or closely approximates the speed of lengthwise movement of the upper stretch 4a of the blanket 4 irrespective of whether the roller 6 is driven at a minimal speed, at a maximal speed, or at a speed between the minimal and maximal speeds. The influence of the screens and/or other components at the treating stations 2 upon the tension of the running web 3 is minimal or nil. Any deviations of the mode of operation (e.g., speed of such components from the normal mode of operation must be accounted for or eliminated by the controls at the respective stations 2. As mentioned above, the mobile components at the various treating stations 2 and/or in other parts of the machine 1 can receive motion from one of the motors 51, 61 and 71, preferably from the motor 71 of the primary driving unit 7 which moves the blanket 4.As also mentioned above, the stations 2 preferably accommodate rotary cylindrical or otherwise configurated stencils or screens which can receive motion from the motor 71. However, the treating stations can also employ other types of ink applying devices, e.g., nozzles, plungers or other conventional means which can apply ink or another flowable medium in a predictable and reproducible manner to thus provide the web 3 with a multicolored pattern, with a unicolored pattern exhibiting several shades of one and the same color, or with a uniform coat of dyeliquor in a particular color.

The primary driving unit 7 is preferably adjustable; however, once this unit is adjusted, the speed of the upper stretch 4a of the blanket 4 preferably remains constant. This is desirable for several reasons, e.g., to reduce the wear upon the driving units and especially to avoid vibrations of component parts of the driving units because each and every change of speed of the motor 71 in the primary driving unit 7 is followed by a change in the speed of the motors 51 and 61 in the respective slave driving units 7A and 7B. It has been found that the selected speed of the motor 71 can be maintained with a high degree of accuracy if the control unit or regulating means for this motor includes a thyristorized inverse shunt connection for a so-called four-quadrant operation. Such control circuits are highly accurate and they can also furnish a desirable braking action.A tachometer generator 75 of the synchronizing means can be designed to transmit a given number of signals or pulses (e.g., 500) per revolution of the motor 71, and such signals are transmitted to the current regulator 73 for the motor 71 (to indicate whether or not the speed of the motor 71 matches the selected speed) as well as to the digital regulator 57 which also receives pulses from the output of the tachometer generator 55 and causes the current regulator 53 to control the motor 51 accordingly, i.e., so that the ratio of the speed of the blanket 4 to the peripheral speed of the roller 5 matches a selected or optimum value. The transmission of approximately 500 pulses per revolution of the motor 71 corresponds to a resolution of approximately 50 pulses per millimeter of the web 3.In actual practice, the deviation of optimum resolution from actual resolution is +4 pulses which amounts to an effective deviation of 0.040/co.

The operation of the drive means including the driving units 7, 7A and 7B is as follows: The operation of the master d-c motor 71 forming part of the primary driving unit 7 is preferably a four-quadrant operation which ensures that the selected speed of the blanket 4 fluctuates very little or not at all. The operator is free to select the speed of the motor 61 and hence the speed of the blanket 4 by actuating the keys of a data selector 72 which is connected with an input of the four-quadrant current regulator 73 for the motor 71. The selected speed of the master motor 71 further influences the speeds of the d-c motors 51 and 61 in the respective slave driving units7A,7B as well as the speeds of the moving parts or components at the treating stations 2 and /or at other stations of the machine 1.

The four-quadrant current regulator 53 controls the operation of the motor 51 which drives the first carded roller 5 through the medium of the respective transmission 50. As mentioned above, the operation of the driving unit 7 is synchronized with that of the driving unit 7A, and the synchronizing means includes the tachometer generator 75, the conductor means connecting the tachometer generator 75 with the digital regulator 57, the digital regulator 57 and the conductor means connecting the regulator 57 with the current regulator 53. The tachometer generator 55 transmits pulses at a rate which is proportional to the RPM of the motor 51, and such signals are transmitted to the digital regulator 57 for comparison with signals which are transmitted by the tachometer generator 75.The speed of the motor 51 can be furher influenced by the selector 58 to influence the speed of the web 3 at the inlet 10 of the path along which the web is advanced past the treating stations 2 and toward the outlet 11. The digital regulator 57 can be said to constitute a superior substitute for a rigid mechanical connection (e.g., a shaft) between the driving units 7 and 7A. The synchronizing system of the drive means can comprise more than one digital regulator 57. The illustrated digital regulator 57 evaluates the pulses which are transmitted by the tachometer generators 55, 75 and converts such pulses into signals which are transmitted to the current regulator 53 for the d-c motor 51. Such digital regulators allow for a change in synchronization of the operation of the primary driving unit 7 with the slave driving unit 7A and/or 7B.

The peripheral speed of the second carded roller 6 should be selected with a view to ensure proper tensioning of the web 3 between the inlet 10 and the outlet 11 of the path at a level below the treating stations 2 and above the upper stretch 4a of the blanket 4. The tension is preferably adjustable and, to this end, the driving unit 7B comprises a selector circuit 62 (e.g., a potentiometer) which is actuable to transmit appropriate signals to the corresponding input of the four-quadrant current regulator 63 for the d-c motor 61 which drives the roller 6 via transmission 60. For example, the adjustment can be such that the peripheral speed of the roller 6 exceeds that of the roller 6 by approximately ten percent. At the same time, the regulator 63 limits the armature current for the motor 61 to thereby regulate the driving torque of the unit 78.The control voltage is applied at all times to ensure that, when the machine 1 is arrested for a relatively short interval of time, the roller 6 continues to tension the web 3 with an unchanged force, i.e., that the pull upon the web in the path between the rollers 5 and 6 remains unchanged while the machine 1 is arrested. The drive means of the improved apparatus can be arrested only by actuating a master switch in the circuit of one or more current regulators. The tachometer generator 65 of the driving unit 7B transmits pulses to the current regulator 63 which further receives pulses from the tachometer generator 55 so that the operation of the slave driving unit 7B is synchronized with that of the primary driving unit 7.

The improved apparatus is susceptible of many additional modifications without departing from the spirit of the invention. For example, the master motor 71 of the primary driving unit 7 need not necessarily drive the movable parts at the treating stations 2. Thus, each of the stations 2 can be equipped with a slave driving unit whose operation is synchronised with that of the primary driving unit 7 or with that of one of the slave driving units 7A, 7B. The apparatus can further comprise a front feed device which controls the movements of the web 3 between the carded rollers 5 and the foremost station 2. A front feed control device is shown schematically at 8. The main purpose of the device 8 is or can be to ensure that the web 3 is urged against the upper stretch 4a of the blanket 4 with an optimum force.Two or more front feed devices 8 or analogous front feed devices can be provided, if necessary. As mentioned above, the tensioning roll 42 is optional because the pulley 40 and/or 41 can be mounted for movement with reference to its frame to thereby change the tension of the blanket 4.

A computer (not shown) can be used to automatically select and/or change the speed of the roller 5 or 6 or blanket 4 via speed selector means 58, 62, 72, respectively.

As utilized in the appended claims, the term "web" is intended to embrace all kinds of textile or other webs which can be transported by resort to carded rollers. The web may constitute a carpet, another textile material which is woven, knitted or otherwise formed to constitute a coherent strip or band, materials which resemble or are velvets, fleeces, strands and/or others. The web can also constitute or contain a sheet or strip of paper or synthetic plastic material. In addition, the web can consist of or include wire mesh which need not be printed but might require an entirely different treatment.

As concerns the machine in which the improved apparatus is put to use, such machine can constitute a screen printing machine with one or more rotary stencils or screens which can be used for coating, patterning, colouring, wetting, cleaning or a combination of such (and/or other) treatments. The medium which is to be applied to the web can constitute a dye liquor, ink or any other chemical which can positively influence the appearance and/or the characteristics of the web.

Moreover, the machine which employs the improved apparatus can constitute any one of a variety of presently known printing machines other than screen printing machines, for example, a relief printing or an intaglio printing machine.

The station or stations along which the improved apparatus guides and advances the web can include means for spraying a pasty, foamed or liquid medium onto successive increments or onto selected portions of the web, one or more squeegees for spreading the flowable medium onto the web, needles for the application of ink or the like to each portion or to selected portions of the web, and/or other implements which can be used for the application of flowable media and/or for other types of treatment of certain stratum or strata of the running web.

Claims (21)

1. Apparatus for transporting a web of textile material or the like in a screen printing or an analogous machine, comprising means for advancing the web along a predetermined path having an inlet portion and an outlet portion, said advancing means comprising first and second rotary carded members respectively adjacent to said inlet and outlet portions of the path and a mobile printing blanket adjacent to a third portion of said path between said carded members, the web being trained over said carded members and said blanket having a stretch contacting the web between said inlet portion and said outlet portion; and drive means for moving said blanket outlet portion; and drive means for moving said blanket at a first speed, for rotating said first carded member at a second speed such that the speed of the web on said first carded member at least approximates the speed of the web of said blanket, and for rotating said second carded member at a third speed exceeding said second speed so as to tension the web between said carded members.

2. The apparatus of claim 1, wherein said drive means comprises discrete first and second driving units for the respective carded members.

3. The apparatus of claim 2, wherein said drive means further comprises a discrete third driving unit for said blanket.

4. The apparatus of claim 3, wherein the construction of said third driving unit at least approximates that of said first and second driving units.

5. The apparatus of claim 3, further comprising means for synchronizing the operation of said third driving unit with that of said first and second driving units so that the ratio of peripheral speeds of said carded members to the speed of said blanket remains at least substantially constant irrespective of eventuai changes in the speed of said blanket.

6. The apparatus of claim 5, wherein said third driving unit includes selector means for varying the speed of said blanket within a predetermined range.

7. The apparatus of claim 5, wherein said third driving unit comprises selector means for varying the speed of said blanket within a predetermined range as a function of changes in the resistance of the web to the transport by said carded members and said blanket.

8. The apparatus of claim 3, wherein said first driving unit comprises selector means for varying the speed of said first carded member.

9. The apparatus of claim 1, wherein said drive means comprises selector means for varying the speed of said second carded member as a function of variations of tension of the web so that such tension is maintained at a substantially constant value.

10. The apparatus of claim 1, wherein said drive means includes discrete first, second and third driving units for said first and second carded members and said blanket, respectively, and further comprising synchronizing means for regulating the operation of two of said driving units as a function of the operation of the remaining unit.

11. The apparatus of claim 10, wherein said remaining unit is said third unit.

12. The apparatus of claim 1, wherein said drive means comprises discrete first, second and third variable speed motors for said first and second carded members and said blanket, respectively, and discrete speed monitoring means for each of said motors.

13. The apparatus of claim 12, wherein each of said monitoring means comprises a tachometer generator arranged to generate signals denoting the speed of the respective motor.

14. The apparatus of claim 1, wherein said drive means comprises discrete first and second motors for said first carded member and said blanket, and discrete first and second revolution counters for the respective motors.

1 5. The apparatus of claim 1 wherein said drive means includes discrete first, second and third driving units for said first and second carded members and said blanket, respectively, and digital regulator means for at least one of said driving units.

16. The apparatus of claim 15, wherein said one driving unit is said first driving unit.

1 7. The apparatus of claim 1 for transporting webs of varying thicknesses, wherein said drive means comprises selector means for varying the speed of one of said carded members as a function of variations of the thickness of the web.

18. The apparatus of claim 17, wherein said one carded member is said first carded member.

1 9. The apparatus of claim 1, wherein said drive means comprises a variable-speed motor for second carded member and means for operating said motor at a constant load regardless of speed.

20. The apparatus of claim 1 , further comprising means for treating the web intermediate said carded members.

21. Apparatus for transporting a web of textile material or the like in a screen printing or an analogous machine, substantially as hereinbefore described with reference to the accompanying drawing.