Method of printing pile fabrics
This is a continuation of application Ser. No. 760,549, filed Jan. 19, 1977, now abandoned which is a divisional of Ser. No. 464,464, filed Apr. 26, 1974, now U.S. Pat. No. 4,018,066. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to a method of printing pile fabrics with a pile containing thermoplastic fibres by thermoprinting. More particularly, the invention relates to a method of thermoprinting in conjunction with a synchronously performed relief-forming and/or surface forming patterning of pile fabrics which are preferably intended for imitation animal skins and which have a pile containing or consisting entirely of thermoplastic fibres. 
     According to the invention, the textile pile fabrics, preferably in web form, are printed in accordance with the known principles of thermoprinting, although the invention is concerned with the particular application of thermoprinting to highly sensitive pile fabrics. 
     In the context of the invention, thermoprinting is a printing process in which dyes are transferred from a print consisting, for example, of paper to the article to be dyed by sublimation of the dyes under dry heat. 
     An object of the invention is to allow the printing of pressure-sensitive pile fabrics by the thermoprinting process and at the same time obtain a relief-formed and/or surface-formed pattern on the surface of the pile fabric. 
     THE INVENTION 
     The invention provides a method of printing pile fabrics, the pile containing thermoplastic fibres in which thermoprinting and relief-forming and/or surface-forming patterning are carried out successively in synchronism and combination with one another. The process according to the invention comprises thermoprinting a pattern onto the pile fabric with a thermoprinting web in a heating zone in which the pile fabric is exposed to a contact pressure, adapted to the particular type of fabric, against the thermoprinting web such that about 40 to 60% of the pile is compressed and immediately afterwards relief-forming and/or surface-forming the pile fabric while still hot with a pattern which bears a strict relationship to the printed pattern. 
     To produce imitation animal skins, the pile fabric can be patterned by embossing, ironing, stenciling or any similar treatment. 
     The method of the invention for printing pile fabrics which contain thermoplastic fibres is carried our by a thermoprinting unit with an adjustable contact pressure, followed immediately by a relief-forming and/or surface-forming patterning unit which functions synchronously and in coordination with the thermoprinting unit. 
     DISCUSSION OF THE INVENTION AND ITS PREFERRED EMBODIMENTS 
     The thermoprinting unit generally comprises a printed web which travels over a heating plate, being offwound from one roll and wound onto another roll and preferably travelling synchronously with the web of pile fabric to be printed. This printed web comes into contact with the outer ends of the fibres of the pile in the vicinity of the heating plate, the web of pile fabric being pressed under an adjustable contact pressure against that side of the printed web carrying the dyes, so that it is possible to transfer the dyes onto the pile fibres without producing any undesirable changes in the texture of the pile. The contact pressure is preferably adjusted by the provision, opposite the heating plate, of a guide surface which can be adjusted relative to the heating plate. 
     The guide surface is preferably adjusted relative to the heating plate by means of a screw threaded spindle which is arranged on the guide surface and which provides for precision adjustment. Thus, the thermoprinting unit can be individually adjusted to the particular fabric to be printed. 
     An embossing roller with a counter roller for example is provided as the relief-forming or surface-forming patterning unit. Another possible embodiment of the patterning unit comprises a stencil drum with a turbulence beam built into it. The patterning unit can also comprise pressure stamps cooperating with a fixed supporting surface. These patterning units each working in synchronism with the preceeding thermoprinting unit produce a relief-forming and/or surface-forming pattern in the fabric pile which has already been printed with sublimated dyes. Since the fabric has already been heated during thermoprinting to the temperature range required for the relief-forming and/or surface-forming patterning treatment, it is thus possible to directly couple two finishing operations which can be synchronised and carried out one immediately after the other. 
     In this way, not only is it possible to tranfer extremely fine prints of animal skins to the pile of pile fabrics, but it is also possible to produce a relief-like and/or surface-like pattern belonging to the particular colour with complete coordination between both patterns. 
     In cases where an embossing roller with a counter roller is used as the patterning unit, the embossing roller remains unheated and can be provided internally with a cooling system. The embossing roller can rotate with or without friction relative to the fabric to be embossed. 
     In the case of pile fabrics with a pile containing thermoplastic fibres, intended for the production of imitation animal skins, the application of thermoprinting in its known form would crush the pile fabric under the effect of the excessive contact pressure generated. This would not only spoil the appearance of the fabric, it would also prevent the sublimated dye from penetrating deeply into the pile, because the pile would change into a compact, shingle-like structure under the effect of the high contact pressure. 
     This difficulty is overcome by the precision-adjustable fine setting of the interval between the thermoprinting paper travelling over the heated plate on the one hand and the pile of the pile fabric to be printed on the other hand, for which provision is made in the machine according to the invention. The elastic pile can be compressed without any adverse effects to around 40 to 60% of its normal volume, in other words if the normal depth of the pile is about 12 mm for example, the pile can be reduced to between 5 and 6 mm in depth during printing. When this only moderately compressed pile comes into direct contact with the heated thermoprinting paper in the heating zone at a temperature of for example about 210° to 230° C., the transfer of colours to the fabric obtained by the sublimation of dispersion dyes is surprisingly better than that obtained in cases where the fabric is more heavily compressed, as is normally the case in thermoprinting, with the thermoprinting paper pressed correspondingly more heavily onto the fabric. 
     The fabrics differing widely in regard to density and depth of pile needed for the production of imitation animal skins from pile fabrics each require an individual, precision adjustment of the interval between the heating plate carrying the thermoprinting paper and the support over which the pile fabric travels in the vicinity of the thermoprinting unit. This precision adjustment of the plate interval and, hence, of the contact pressure is essential for the satisfactory thermoprinting of pile fabrics. On the one hand, it prevents excessive compression of the sensitive pile and, on the other hand, provides for satisfactory sublimation and diffusion of the dyes from the thermoprinting paper into the fibres of the pile. 
     Pile fabrics suitable for treatment by the process according to the invention are pile fabrics produced by the known techniques of weaving, knitting, circular knitting, tufting, also the pile fabrics produced by the Malipol and Voltex techniques. The thermoplastic fibres present in the pile are preferably synthetic fibres, such as polyamides, acrylic fibres and their copolymers, polyesters, cellulose-21/2 acetate and triacetate. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     Embodiments of the most important parts of the machine for performing the method according to the invention are diagrammatically illustrated by way of example in the accompanying drawings, in which: 
     FIG. 1 is a side elevation, partly in section, of the thermoprinting unit and patterning unit of a machine according to one embodiment of the invention. 
     FIG.2 is a diagrammatic side elevation of a modified patterning unit. 
     FIG. 3 shows another modified embodiment of a patterning unit. 
    
    
     In the interests of clarity, only the thermoprinting unit and the following patterning unit have been diagrammatically illustrated in the drawings, although it is pointed out that, in all the illustrated embodiments of the invention, both units are accommodated in a common frame (not shown) so that the thermoprinting unit provided in every case and the following patterning unit are arranged at a fixed interval from one another and can be operated in synchronism with one another. A common main drive is preferably also provided for both units. 
     As shown in FIG. 1, a pile fabric 5 in web form is delivered by way of a brake roller 6 to a guide surface 7 which can be vertically adjusted by means of a screw threaded spindle 8 arranged underneath the guide surface 7. A fixed heating plate 2 over whose under surface travels a web 17 of thermoprinting paper, is arranged opposite the guide surface 7. The thermoprinting paper is offwound from a supply roll 3 and guided by means of a guide roller 4 onto the underneath of the heating plate 2. A take-off roller 11 ensures that the used thermoprinting paper is wound onto another roll 1. 
     The thermoprinting unit for printing the pile fabric 5 by sublimation of the dyes applied in layers to the thermoprinting paper consists essentially of the fixed heating plate 2 and of the guide surface 7 adjustable relative to the heating plate 2 by means of the screw threaded spindle 8. By virtue of the fact that the interval between the heating plate 2 and the guide surface 7 can be precision-adjusted, the pile fabric 5 travelling through between the heating plate 2 and the guide surface 7 can be compressed to around 40 to 60% of the particular thickness of its pile. 
     Immediately after the thermoprinting unit, through which the pile fabric 5 travels continuously at a speed of, for example, about 2 meters per minute, the pile of the pile fabric is embossed by means of an embossing roller 10 with a built-in cooling system. The embossing roller, which is arranged opposite a take-off roller 12 for the pile fabric, works on the pile of the pile fabric 5 as long as it remains hot. The embossing roller 10 is provided internally with a cooling system (not shown). 
     The heating plate is heated to and kept at the particular temperature required by means of a temperature control system (not shown). The temperature is adjusted in such a way that the thermoplastic fibres of the pile of the pile fabric are heated to a temperature at which they begin to undergo plastic deformation. 
     Behind the patterning unit consisting of the embossing roller 10 and the take-off roller 12, the printed and embossed pile fabric 5 travels over a guide roller 9 and is then wound into a roll or cut into required lengths (not shown). 
     The difference between the embodiment illustrated in FIG. 2 and the embodiment illustrated in FIG. 1 is that, in FIG. 2, the patterning unit comprises a stencil drum 14 with a built-in turbulence beam 13 which is arranged opposite the take-off roller 12 instead of the embossing roller. 
     The difference between the embodiment illustrated in FIG. 3 and the embodiments illustrated in FIGS. 1 and 2 is that, according to FIG. 3, the patterning unit consists of a fixed supporting surface 16 over which the pile fabric 5 travels, and of pressure stamps 15 adjustable relative to the supporting surface 16. 
     The pile fabric whose pile is to be printed and patterned in the manner described can travel into the thermoprinting unit already coloured, for example by partial or full printing from the back of the fabric. The pile could also be unicoloured or ombre-dyed.