GB1560641A

GB1560641A - Method and apparatus for the application of patterns onto a continuous web of pile material

Info

Publication number: GB1560641A
Application number: GB30033/76A
Authority: GB
Original assignee: Maschinenfabrik Peter Zimmer AG
Current assignee: Maschinenfabrik Peter Zimmer AG
Priority date: 1975-07-28
Filing date: 1976-07-19
Publication date: 1980-02-06
Also published as: IT1064861B; CH613387A5; FR2319433B1; DK336976A; DE7710895U1; DE7622143U1; NL7608300A; NL7803800A; DE2631553A1; JPS5217539A; NL7803799A; NZ181536A; FR2319433A1; DE2631553B2; LU75450A1

Abstract

For applying patterns to a material (1), preferably to a web material, nozzles (8) are used which can be controlled in their opening and closing and either lie on the material surface or are at a distance of at most 2 mm from the material surface. The position of the material surface is precisely determined as regards the nozzles. A material or web material can thereby be provided with a selectable pattern in a simple manner without a screen printing template having to be used. <IMAGE>

Description

(54) METHOD AND APPARATUS FOR THE APPLICATION OF PATTERNS ONTO A CONTINUOUS WEB OF PILE MATERIAL (71) We, MASCHINENFABRIK PE TER ZIMMER AKTIENGESELL SCHAFT, a Company incorporated under the laws of Austria of A 6330, Muenchner Strasse 17-19, Austria, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed. to be particularly described in and by the following statement: This invention relates to the application of a pattern to a continuous web of pile material particularly by means of spraying into the pile of the material a substance which creates a pattern thereon. Such a substance may be, for example, a printing ink or a dye the deposition of which to discrete areas of the surface of the article colours or otherwise marks or imprints those areas in a predetermined distinguishable manner.

Printing processes hitherto known in the art print patterns on surfaces of continuous webs through stencils. Recently proposals have also been made to produce a printed pattern on such surfaces by tracing them with thin jets of ink without the use of a screen. However, the quality of the printing obtained by such a process has not yet proved satisfactory.

The object of the present invention is to provde methods and apparatus which will eliminate the shortcomings of processes already known.

According to the invention there is provided a method of applying a pattern to a continuous web of pile material by spraying into the pile of the material a substance which creates a pattern thereon, wherein the substance is sprayed onto the material directly in the form of a plurality of jets which issue from a plurality of nozzles adjustably located and substantially touching the pile surface of the material.

and wherein the nozzles are opened and closed by reference to a preselected programme.

The invention also provides apparatus for carrying out the method of applying a pattern to a continuous web of pile material as hereinbefore defined, comprising a plurality of jet nozzles adjustably located for spraying directly into the pile of the material jets of a substance which creates a pattern thereon, means for opening and closing the nozzles, programme control means for controlling said means for opening and closing the nozzles according to a preselected programme, and means for supporting the web of material such that the pile surface thereof is opposed to the nozzles and is substantially in contact with the nozzles.

The jet nozzles may each contain a needle adapted to open and close a nozzle mouthpiece, and electromagnetic means for operating the needle, the mouthpiece communicating with a chamber for containing the substance that is to be sprayed, and a diaphragm which is connected to the needle and constitutes a wall of the chamber. A jet nozzle of this construction is disclosed and claimed per se in our co-pending Application No. 7906132. (Serial No. 1560642).

For controlling the opening and closing of the nozzle the magnet coil may be connected through a first power transistor to a high voltage source and through a second power transistor to ground, the connection between the first power transistor and the coil being further connected through a diode to a low voltage source, and the base of the first power transistor may be connected to the output of means including a multivibrator for generating a pulse of slectably adjustable amplitude and duration on receiving an input, the input being also coupled to the base of the second power transistor.

A circuit for energising an electromagnetically controlled jet nozzle for spraying a substance onto a continuous web of material to create a pattern thereon, comprising means for connecting an operating coil of the jet nozzle through a first power transistor to a high voltage source and through a second power transistor to ground, the connection between the first power transistor and the coil being further connected through a diode to a low voltage source, the base of the first power transistor being connected to the output of means including a monostable multivibrator associated with a timing capacitor and a trimming resistor for generating a pulse of selectably adjustable amplitude and duration on receiving an input and for applying said pulse to the base of the first power transistor to swtich the first power transistor on for the duration of the pulse, said input being also coupled to the base of the second power transistor is disclosed and claimed per se in our copending Appln. No. 7906133. (Serial No.

1560643).

The present invention and the various features thereof will now be more particularly described with reference to the accompanying generally schematic drawings and in which: Figure I is an elevation of one embodiment of apparatus for performing the invention; Figure 2 is a side view of a suction box of the apparatus of Figure 1; Figure 3 is a side view of an alternative suction box; Figure 4 is a diagrammatic elevation of another embodiment of apparatus for performing the invention; Figure 5 is a longitudinal cross-section of one form of jet nozzle; Figure 6 is a plan view of a centring disc for the needle of the jet nozzle; Figure 7 is a transverse cross-section of the nozzle chamber; Figure 8 is a longitudinal cross-section of another form of jet nozzle; Figure 9 is a longitudinal cross-section of still another form of jet nozzle; Figure 10 is a diagrammatic elevation of a third embodiment of apparatus for perform ing the invention; Figure 11 is a plan view of the apparatus of Figure 10; Figure 12 is a plan view of a portion of a still further embodiment of apparatus; Figure 13 shows an arrangement for cleaning the nozzles, and Figure 14 is a circuit diagram of a system for controlling the jet nozzles.

Referring to Figure 1 of the drawings a continuous web of material 1 is carried past a system of spraying nozzles 3 on a conveyor 2 in the form of an endless screen. The conveyor 2 may be an endless woven wire mesh or, alternatively, it may be a vulcanised rubber belt provided with perforations. It will be readily understood that such a belt could also be made of a synthetic plastics material instead of rubber, provided it were not elastically excessively stretchable. The web of material 1 is deposited on the conveyor 2 at a point 4 and the conveyor carries it past the first of two sets or arrays 3 of spray nozzles 8. Located underneath the conveyor 2 are suction boxes 5 in which a extractor fan, not shown, which is connected to the box by a pipe 6, maintains a vacuum pressure between a few 100 and 1000 mm water column. The suction draws the conveyor 2 and the web 1 of material downwards onto backing rollers 7 and thus locates the web in an exactly defined position in relation to the several spraying nozzles 8. It will be seen that these backing rollers 7 are preferably arranged opposite to and to register with the nozzles 8. To enable printing on widths of material that vary in relation to the width of the conveyor 2, the open portions of the conveyor screen on the side of the web material may either be covered with an air-impervious masking strip 9 (c.f. Figure 2) or the suction box 5 may be fitted with a adjustable bulkhead 10 which can be set to the width of the web material (c.f. Figure 3). The bulkhead 10 can be shifted transversely to the direction of travel of the web material by a feed screw ila and the width of the chamber 11 in which the vacuum pressure is to be maintained can thus be precisely adjusted to the width of the web 1 of material.

The conveyor 2 in Figure 1, after having passed underneath the last of the two nozzle systems runs over a rear end return roller 12, then travels across a washing system 13 substantially comprising spraying tubes 14 above the underside of the screen 2 and a tank 15 underneath the two sprayer tubes.

An extractor for drying the conveyor 2 may naturally also be provided, although this is not shown in Figure 1. The fixation of the web of material on the surface of the screen 2 is effected by the suction generated in the region above the suction boxes 5. Owing to the precision with which the web 1 of material is located by being drawn onto the backing rollers 7, it is possible to adjust the distance of the spraying nozzle systems 3 from the surface of the web of material very precisely between zero and a few millimetres.

Another advantage afforded by the described arrangement is that ink applied by the nozzle systems can be drawn down by the vacuum pressure maintained in the suction boxes. However, this is merely a general and well known advantage inherent in the use of vacuum pressure under the web of material on a travelling conveyor and it is not one of the advantages specific to the present invention.

Figure 4 shows a spray-printing machine of a design based on a slightly different concept. Some types of material have a very porous foundation weave and considerable suction is needed to draw a web 1 of such material firmly onto the carrier surface. In such a case it is therefore better to pull the web of material down onto the surface of the conveyor and its backing rollers by conducting the web 1 over each backing roller in a manner which by a change of direction creates an enveloping angle. The web 1 of material in this embodiment is deposited on the travelling conveyor 2 immediately after having been deflected over a roller 16. The web 1 is then pulled tightly down onto the face of the conveyor2 where the latter is deflected over its return roller 17. At the next deflecting roller 18 the web 1 of material as well as the conveyor 2 are again deflected through a small angle 19, thereby causing the web 1 of material to be again pulled tightly down onto the roller 18 and against the face of the conveyor 2 by the resultant increase in tension of the web. The web 1 of material should already be under tension as it travels over the return roller 17.

This tension is generated by a tensioning device 20. As the conveyor and the web of material travel over each consecutive roller 21, 22 and 23 the same result is achieved. To prevent the web of material on the conveyor 2 from running slack a small suction box 5 is provided behind the last deflecting roller 23 and this keeps the web in contact with the conveyor surface. This suction box 5 may be dispensed with if in conventional manner the travelling conveyor 2 is armed with needles and the weight of the web is sufficient to keep it impaled on the needles by gravity so that it cannot shift or become slack even though the actual contact pressure is low.

Figure 5 shows one form of a spraying nozzle 8.

A permanent magnet core 24, in conjunction with a cup-shaped magnetic return 25, maintains a strong magnetic field (e.g. 15 kG) in an annular air gap 26. A coil 27 which is wound on a slotted light metal core 28 or on an unslotted insulating core made for instance of glass-fibre-reinforced polyester resin lies in the air gap. Although a glass-fibre core is an inferior conductor of heat the latter form of construction is to be preferred because the slotting of a light metal core which is needed to suppress eddy and short circuit currents considerably reduces the mechanical strength of a light metal core. A coned configuration of the core 28 towards its end 29 where it is mounted also serves to provide the greatest possible rigidity to guard against unwanted vibration. The annular coil 27 has two connecting wires, not shown, which are taken from the coil to the outside, and which enable shaped signal pulses to be applied to the coil. At its mounting point 29 the core 28 is affixed to a needle 30 having a conical point 44 controlling the nozzle orifice. Centring discs or diaphragms 31 which are interconnected with the interposition of spacing sleeves 32 ensure that the needle 30 moves strictly in the axial direction.

A rubber or plastics diaphragm 33 seals off a chamber 34 containing ink or a dye from the chamber 35 containing the coil.

The dye or ink paste enters this ink chamber 34 through an admission pipe 36. The particular disposition of this pipe for supplying the chamber will be later described in greater detail. The ink chamber 34 is provided with a nozzle mouthpiece 37. The joint between the mouthpiece 37 and the wall 39 of the ink chamber 34 is sealed by an O-ring 38. A face plate 40 secured by screws presses the nozzle mouthpiece 37 against the O-ring 38. The needle 30 moves through a very short distance 41 amounting to only a few tenths of a millimetre. This distance 41 can be determined and adjusted by the setting of a screw 42. The flat contact face 43 between the nozzle mouthpiece 37 and the wall 39 of the ink chamber permits the mouthpiece 37 to be axially precisely aligned with the conical point 44 of the needle 30. Precise control of the annular cross-section between the conically tapered point 44 and the cut-off edge 45 of the bore 46 in the nozzle mouthpiece can thus be achieved. Since the ink in the ink chamber 34 is at a controlled gauge pressure and the forces the annular coil 27 would be required to develop in order to overcome this pressure which also acts on the diaphragm 33 are rather high the coil chamber 35 on the other side of the diaphragm 33 is preferably also pressurised. For this purpose compressed air is introduced at 47 through a pipe 48 into the coil chamber 35, the pressure of this air being roughly the same as that at which the ink is contained in the ink chamber 34.

Minor differences between these two pressures can be utilised either to accelerate the closing or opening of the needle 30.

Moreover, the compressed air in the coil chamber 35 escapes through the annular gap 26 and thus provides additional cooling for the winding 27. Bores 49 in the body of the core 28 permit the pressures on the two sides of the core 28 to equalise, and they also enable the back of the core 28 to be cooled by the escaping air. This air first enters the annular space 50 between the permanent magnet 24 and the cup-shaped magnetic return 25, and then escapes to atmosphere through bores 51 which may preferably be fitted with throttling means (flow control valve, throttling screw) of conventional kinds not shown in the drawing. A throttling screw or flow control valve at this point permits the volume rate of flow of the escaping compressed air to be controlled and kept within appropriate limits.

The extreme front end of the nozzle mouthpiece 37 contains the actual ink ejecting orifice 52. This is provided at the end of a nozzle bore 53 and the ratio of length to diameter of this bore can be used to control the jet issuing from the nozzle.

The jet of ink issues from the nozzle and impinges on the material 54 underneath at a velocity of at least 10 metres/sec. The distance 55 of the nozzle orifice from the surface of the material 54 is preferably between 0.5 and 2 mm. As a result of these features a relatively high viscosity ink will penetrate into the web of material 54 and the delineation of the printing will be extremely well defined.

Figure 6 is a more detailed view of a centring disc 31 which consists of a thin metal sheet and the thickness of which should not exceed 1% of its diameter 56.

Moreover, the disc 31 is formed with radial slot-like incisions 57 which permit deflections of the centre of the diaphragm 58 in relation to its periphery 59 of a few tenths of a millimetre to be produced by small forces.

Figure 7 illustrates the manner in which the ink is admitted into the ink chamber 34.

Since in all such nozzle systems considerable difficulties are experienced in keeping the nozzles clean the ink is admitted through a pipe 36 tangentially into the ink chamber, thereby generating a circulating current which greatly assists cleaning, particularly when the ink chamber 34 is being flushed out. If the entry of pipe 36 into the ink chamber 34 is in the radial direction vortex zones form adjacent the point of entry and stagnant zones form behind the vortices.

This greatly hinders cleaning of the ink chamber 34.

Figure 8 illustrates a different form of construction of an ink spraying nozzle. The design of the ink chamber 34 and of the nozzle mouthpiece 37 is completely identical with that in Figure 5. Moreover, the discs 31 and diaphragm 33 and the spacing sleeves 32 are clamped up on the needle 30 in the same way as in Figure 5 by means of a nut 60 and a peripherally threaded split nut 61 in the body of the nozzle. The space behind the rubber diaphragm 33 in this embodiment is likewise pressurised with air introduced through a pipe 48. The ink enters the ink chamber 34 through an admission pipe 36.

However, the needle 30 in this form of construction is controlled by a disc armature 62 consisting of a stack of thin dynamo sheet metal laminations. The stack consists of two or three circular thin laminations tightly clamped together. The armature 62 is movable in the direction indicated by arrows 64 between two shell cores 63 for opening and closing the nozzle. The shell cores 63 which are as such of a type known as 'throttle cores' are made of ferrites which substantially prevent the generation of eddy currents in the cores and thus minimise loss.

Copper windings 65 are inserted into the cores 63. For opening the nozzle the upper copper winding 65 is switched off. For exactly adjusting the distance of deflection an adjusting screw 66 is provided which works in a cover plate 67. The shell cores 63 can be adjusted by set screws 68 and clamping screws 69 finally locate the cores 63 in their holders 70. The compressed air entering through pipe 48 for equalising the pressures acting on the diaphragms 31 and 33 can here likewise escape to atmosphere through bores 73. The advantage of the embodiment according to Figure 8 over that illustrated in Figure 5 is that sufficiently powerful magnetic forces can be generated in armatures having relatively small mass, and that the entire electrical coil system is outside the moving armature components.

This offers additional advantages in connection with energising the electrical coils which may be rigidly located, and which suffer no damage due to sudden high accelerations. On the other hand the mass of the coils can be readily made large enough to eliminate problems due to the generation of heat.

The advantage of the embodiment illustrated in Figure 5 compared with that in Figure 8 is that the ratio of thrust to needle mass can be increased as may be desired by driving sufficiently high currents through the annular coil 27. However, it will then be necessary to ensure that the dissipation of heat is good enough to abstract the heat loss due to the high currents. The applicational range of the two nozzles differs accordingly.

However, first it must be mentioned that both forms of nozzle - or rather the windings of both types of nozzle - are controlled by square wave current pulses. First a high intensity current is sent through the coil for a few tenths or hundredths of a millisecond followed by a longer current which is lower by a factor of about 10. This method of energisation enables the embodiment in Figure 5 to function with very high accelerations, and the nozzle is particularly suitable for the production of very fine tracing, always bearing in mind that sufficiently long periods within which the continuous current flows through the annular coil 27 must intervene between consecutive control functions. Since the conditions for the dissipation of heat are much better in the embodiment according to Figure 8, and the magnetic forces can be increased beyond the point of saturation of the armature, this embodi ment cannot provide high accelerations, although the nozzle can be opened and closed at a much higher frequency. In principle the construction of the nozzle in Figure 8 is designed for continuous control functions at a repetition frequency of about 2000 to 3000 c/s. In other words, the nozzle needle would be opened and closed about 2000 to 3000 times per second. This type of operation of the nozzle is intended more particularly to permit the printing of half tones. It is known from stencil printing that half tone sequences cannot well be produced so that they are true. In stencil printing half tone sequences are usually obtained by using a stencil having different sized openings. However, openings of different sizes in stencils are likely to change the tone values as a consequence of the production process of the stencil itself so that unexceptionable reproduction of half tone values is impossible to achieve by using silk screen stencils. On the other hand a rapidly operable spraying nozzle enables different quantities of ink to be sprayed per unit of area of the material that is to be printed upon by opening and closing the nozzle opening for longer and shorter periods of time at a constant repetition frequency or by varying the repetition frequency of opening and closing whilst leaving the opening time constant and proportional to the required grey value.

Figure 9 shows yet another embodiment of a nozzle. It will be seen that in this embodiment the coils 65 are enclosed by specially shaped outer cores 74 and 75. The inner portion 75 of these cores consists of a base plate and an inner iron core which is embraced by the winding 65. Inner portion 75 is adhesively attached to the external ring portion 74, the joint being shown at 76. An insulation such as paper is inserted into this joint to suppress the generation of eddy currents. The external ring portion 74 is conically off-angled at 77 inwards towards the armature 78.

The periphery of the armature 78 is bevelled and forms a sharp edge 79, and the cross-section of the armature becomes thicker towards the centre. Whereas the height of a notional cylinder about axis 80 increases with decreasing radius from the edge at 79 to the discontinuity at 81, the height remains constant between the two surface discontinuities 81 and 82. Nevertheless the thickness of the armature continues to increase slightly though at a reduced rate as the radius decreases between the discontinuities 81 and 82. From 82 towards axis 80 the heights again become less. At 83 a small disc of constant thickness adjoins the armature of the described configuration. This disc serves to keep the armature attached to the needle 30.

Because of the described configuration very considerable thrusts can be obtained even when the armature is of minimum weight. Each annular section of the armature 78 just contains an area suitable for the armature to be magnetically saturated to a constant degree. The described annular cross-section (i.e. the cross-sections obtained by interpenetration of the armature 78 with cylinders which are concentric about axis 80) are only about half as large as the magnetically effective cross-sections available to the magnetic flux in the core portions 75 and 74. The air gaps 84 between the armature 78 and parts 75 and 77 of the core are just of sufficient size for the armature to move axially a few tenths of a millimetre. The winding 65 is so calculated that the armature 78 may just be saturated without the winding 65 being inadmissible heated. Yet another advantage of the described disposition of the armature 78 is that the mass of the armature 78 is shifted towards radii that are further inwards so that the natural frequency of the armature is shifted to higher values. All the remaining details substantially agree with those already described with reference to Figure 8.

In order to print on webs of material with the aid of controlled spraying nozzles a nozzle bar may be located rigidly above the material that is to be printed upon and the material traversed underneath the nozzles.

In order to achieve a correspondingly fine resolution of the printed pattern into individual lines a very large number of nozzles is needed so that the arrays become fairly bulky. The cost and the expenditure in means are therefore increasingly difficult to accept. Particularly when conventional nozzles are replaced by relatively high speed nozzles, as above described, it is desirable to impart motion to the nozzles themselves instead of feeding the printed material past the nozzles. Such an arrangement enables the number of nozzles to be substantially reduced and is capable of providing a material with patterns of the highest resolution with a lower number of transmission devices, i.e. reading elements, input amplifiers and power amplifiers. Figures 10 to 12 illustrate two forms of construction of such apparatus.

Referring to Figures 10 and 11 a web of material 1 is carried on an endless conveyor or printing cloth 2 past arrays of nozzles 3 which provide the web with a printed pattern. The printing cloth 2 is taken over two return rollers 94 mounted in a machine frame 95. After having received the printing the web 1 of material is lifted off the printing cloth 2 and passed through a drying tunnel 96.

The printing cloth may be a wire cloth as before and the web of material may be pulled firmly onto the surface of the printing cloth by the suction generated by suction boxes underneath.

Rails 99 are fixed transversely across the direction of travel 101 of the web 1 of material. The rails carry rollers 97 which in turn carry nozzle arrays 3. The rollers 97 permit the nozzle arrays to be moved in the direction of arrow 98, i.e. across the direction of travel 101. The rails 99 also span regions 100 forming ink collecting troughs on each side of the web 1 of material. These troughs are containers adapted to carry out ink when a colour change is required, or the washing water when the system is being flushed.

In order to provide the surface of a material with a printed pattern the nozzle arrays 3 are conveyed from their starting position shown in Figure 11 in the direction of arrow 98 across the web 1 of material.

During this traversing motion they spray ink on the surface of the web according to a programme determined by the required pattern. When the nozzle arrays have crossed over the web 1 of material to the other side the web is advanced one step in the direction 101 by an intermittent feed. The length of this step can be arbitrarily controlled and depends, on the one hand. upon the structural disposition of the nozzles and, on the other hand, upon the desired fineness of the pattern. The nozzle arrays 3 then return into their starting positions and spray a fresh transverse line of patterning on the material, the nozzles being controlled for this purpose by data transmitting or control lines not shown in this drawing. The advantage of the arrangement is that for applying a pattern to goods of substantial width only a small number of nozzles are needed, The printing speeds which can be achieved in this system are within the range of printing speeds of conventional carpet printing machines, i.e. between 3 and 10 metres per minute, notwithstanding that the investment cost in the present instance is fairly low.

In Figure 12 the web 1 of material is spanned by a nozzle bar 103, 106 which can be intermittently moved in a direction across the material indicated by an arrow 102. Naturally each bar may carry several rows of nozzles. However, for the sake of greater clarity the drawing assumes the presence of only one row of nozzles. A feature of this arrangement is that two bars 103, 106 are interconnected by cranks 104 in the manner of a four-bar linkage so that when bar 103 moves in one direction bar 106 will move in the opposite direction. This arrangement enables the reactive forces transmitted to the machine bed to be minimised because the centre of gravity of the four-bar linkage remains stationary. Each nozzle on bar 103 and 106 moves only across a fraction of the total printing width 105.

This distance of reciprocation may amount to for instance 2.5 cms. Hence the hinges 107. 108 at the ends of the two bars 103, 106 will also move only 2.5 cms in the crosswise direction of the web 1 of material. The spatial requirements of the mechanism are therefore very small. The deflection of the cranks 104 in the illustrated arrangement is effected by a common connecting rod 176 and a hydraulic actuator 111. When the bars 103, 106 have completed a half reciprocation the printing cloth 2 carrying the web 1 of material is advanced one step by an intermittent feed in the direction indicated by arrow 109.

Figure 13 illustrates an arrangement for cleaning the nozzles. Again the nozzle array 3 is mounted on rollers 97 adapted to run on rails 99 which are fixed in an anchorage 113 on each side of the printing machine. The web 1 of material is either carried on a travelling endless conveyor, as already described, or, as shown in the Figure, it may lie on a printing table 118. On one or both sides of the printing table 118 there is a recess or shaft in which a cleaning roller 115 is rotatably mounted. The surface of this roller 115 may be provided with a layer of foamed material. When the nozzle array 3 is traversed, the ends of the nozzles move across the cleaning roller 115 and dirt or droplets of ink are wiped off by the surface of the cleaning roller 115. In order to remove the dirt and residual ink from the cleaning roller 115, water jets 116 and squeeze rollers 117 are provided. The squeeze rollers 117 can be pressed against the cleaning roller 115 by means of a linkage 119. The water jets 116 and the squeeze rollers may be operated automatically in functional dependence upon the traversing movements of the nozzle array 3. The nozzle array receives a voltage of about +8 volts through a diode 205. This voltage suffices to drive the holding current through the magnet coil 201 for as long as the power transistor 203 is turned on. As soon as the power transistor 203 is turned off the passage of current through the coil 201 should cease as quickly as possible. For this purpose the end of the coil 201 connected to the power transistor 203 is also connected to a voltage of about 70 volts through a resistor 206 and a diode 207. Consequently the energy stored in the coil will at one feed back into the supply system or, in other words, the stored energy will not be converted to heat subjecting the controlling cicuitry to a considerable thermal load, but it will be returned into the supply network.

The two power transistors 202 and 203 are turned on and off as follows: A square wave signal pulse which is intended to control the time the coil 201 is energised is introduced into the circuit through a contact 208. Through a resistor 209 this pulse energises the diode 210 of an opto-coupler 211. The transistor 212 of the opto-coupler 211 applies a predetermined low level voltage to the input 213 of a Schmitt comparator 214 for the duration of the square wave input signal. During this period a signal appears in the output 215 of the Schmitt comparator 214, which is roughly equal to ground potential. This signal is sent along two different lines. One line applies the signal to the base of a driving transistor 217. The driving transistor 217 blocks and its collector becomes positive, thus turning on the controlled power transistor 203. However, the signal appearing in the output 215 of the Schmitt comparator 214 is also transmitted to a second Schmitt comparator 214 is also transmitted to a second Schmitt comparator circuit 218 which provides an output signal that is inverted at 220 and applied to the input 219 of a monostable multivibrator. A short needle pulse appears in the output 221 of the monostable multivibrator. The duration of this needle pulse can be determined by a timing capacitor 222 and a trimming resistor 223. For the duration of the needle pulse a second driving transistor 224 is rendered conductive and turns on the power transistor 202 to connect the coil 201 to the voltage of for instance 70 volts. At the end of the needle pulse the power transistor 202 is turned off again, returning the coil 201 via diode 205 to the +8 volts supply.

In order to avoid any possible multiple triggering of the monostable multivibrator 220 and a consequential destruction of the circuitry, provision is made for measuring and limiting the current. If the monostable multivibrator 220 were repeatedly triggered the power transistor 202 might well be connected to the 70 volt supply for inadmissibly long periods. This would mean that the current flowing through the magnet coil 201 and naturally through the transistors 202 and 203 would incrementally rise. In order to prevent this from happening the voltage drop which the current generates across the very low ohmic resistor 204 (14.2 m) is used to turn off the power transistor 202 through an operational amplifier 225 connected to function as a Schmitt trigger whenever it is supplied with a voltage of 70 volts for too long a time. If the voltage drop becomes greater than is admissible the voltage in the output 226 of the operational amplifier 225 becomes zero and this output is applied via diode 227 to the base of the driving transistor 224. The driving transistor 224 therefore blocks and consequently operates to turn off the power transistor 202.

The invention is not limited in scope to the illustrated examples. The printing nozzles enable printing on any continuous web of pile material. The advantage is that no printing stencils need be rolled over surfaces of given geometry. The spray nozzles need not touch such a surface at all. Another possibility is that of producing patterns with the printing nozzles on the surface of materials that are sensitive to any kind of contact. Moreover, it is also envisaged to use such nozzles to apply gaseous fluids or finely pulverulent media in gaseous carriers to the surface of a web of material, or also solid media in finely pulverised form.

WHAT WE CLAIM IS: 1. A method of applying a pattern to a continuous web of pile material by spraying into the pile of the material a substance which creates a pattern thereon, wherein the substance is sprayed onto the material directly in the form of a pluraity of jets which issue from a plurality of nozzles adjustably located and substantially touching the pile surface of the material, and wherein the nozzles are opened and closed by reference to a preselected programme.

2. A method according to Claim 1, wherein the programme is derived by scanning a master pattern thereby to obtain information which is converted to commands for operating the nozzles.

3. A method according to claim 1 or 2, wherein within spraying range of the nozzles the article is located in a precisely defined position relative to the nozzles.

4. A method according to any one of the preceding claims, wherein the substance sprayed on to the material exits from the or each nozzle at a velocity of at least 10 metres/sec.

5. A method according to any one of the preceding claims, wherein the article is carried past the nozzles on a conveyor.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. receives a voltage of about +8 volts through a diode 205. This voltage suffices to drive the holding current through the magnet coil 201 for as long as the power transistor 203 is turned on. As soon as the power transistor 203 is turned off the passage of current through the coil 201 should cease as quickly as possible. For this purpose the end of the coil 201 connected to the power transistor 203 is also connected to a voltage of about 70 volts through a resistor 206 and a diode 207. Consequently the energy stored in the coil will at one feed back into the supply system or, in other words, the stored energy will not be converted to heat subjecting the controlling cicuitry to a considerable thermal load, but it will be returned into the supply network. The two power transistors 202 and 203 are turned on and off as follows: A square wave signal pulse which is intended to control the time the coil 201 is energised is introduced into the circuit through a contact 208. Through a resistor 209 this pulse energises the diode 210 of an opto-coupler 211. The transistor 212 of the opto-coupler 211 applies a predetermined low level voltage to the input 213 of a Schmitt comparator 214 for the duration of the square wave input signal. During this period a signal appears in the output 215 of the Schmitt comparator 214, which is roughly equal to ground potential. This signal is sent along two different lines. One line applies the signal to the base of a driving transistor 217. The driving transistor 217 blocks and its collector becomes positive, thus turning on the controlled power transistor 203. However, the signal appearing in the output 215 of the Schmitt comparator 214 is also transmitted to a second Schmitt comparator 214 is also transmitted to a second Schmitt comparator circuit 218 which provides an output signal that is inverted at 220 and applied to the input 219 of a monostable multivibrator. A short needle pulse appears in the output 221 of the monostable multivibrator. The duration of this needle pulse can be determined by a timing capacitor 222 and a trimming resistor 223. For the duration of the needle pulse a second driving transistor 224 is rendered conductive and turns on the power transistor 202 to connect the coil 201 to the voltage of for instance 70 volts. At the end of the needle pulse the power transistor 202 is turned off again, returning the coil 201 via diode 205 to the +8 volts supply. In order to avoid any possible multiple triggering of the monostable multivibrator 220 and a consequential destruction of the circuitry, provision is made for measuring and limiting the current. If the monostable multivibrator 220 were repeatedly triggered the power transistor 202 might well be connected to the 70 volt supply for inadmissibly long periods. This would mean that the current flowing through the magnet coil 201 and naturally through the transistors 202 and 203 would incrementally rise. In order to prevent this from happening the voltage drop which the current generates across the very low ohmic resistor 204 (14.2 m) is used to turn off the power transistor 202 through an operational amplifier 225 connected to function as a Schmitt trigger whenever it is supplied with a voltage of 70 volts for too long a time. If the voltage drop becomes greater than is admissible the voltage in the output 226 of the operational amplifier 225 becomes zero and this output is applied via diode 227 to the base of the driving transistor 224. The driving transistor 224 therefore blocks and consequently operates to turn off the power transistor 202. The invention is not limited in scope to the illustrated examples. The printing nozzles enable printing on any continuous web of pile material. The advantage is that no printing stencils need be rolled over surfaces of given geometry. The spray nozzles need not touch such a surface at all. Another possibility is that of producing patterns with the printing nozzles on the surface of materials that are sensitive to any kind of contact. Moreover, it is also envisaged to use such nozzles to apply gaseous fluids or finely pulverulent media in gaseous carriers to the surface of a web of material, or also solid media in finely pulverised form. WHAT WE CLAIM IS:

1. A method of applying a pattern to a continuous web of pile material by spraying into the pile of the material a substance which creates a pattern thereon, wherein the substance is sprayed onto the material directly in the form of a pluraity of jets which issue from a plurality of nozzles adjustably located and substantially touching the pile surface of the material, and wherein the nozzles are opened and closed by reference to a preselected programme.

6. A method according to Claim 5,

wherein within spraying range of the nozzles one side of the conveyor or of the web of material is subjected to a vacuum pressure.

7. A method according to Claim 5 or Claim 6, wherein the conveyor or the web of material is led in tension around part of the surface of consecutively disposed backing rollers.

8. A method according to Claim 7, wherein the web of material is tensioned before reaching the first backing roller.

9. A method according to any one of the preceding claims, wherein the or each nozzle is traversed relative to the article in a direction normal to the direction of travel of the article.

10. A method according to any one of the preceding claims, wherein a plurality of the said nozzles are combined in an array which array is moved as a unit across the direction of travel of the article, and through a distance exceeding the width of the article, the article is intermittently advanced after each traverse and the array returned to its starting position.

11. A method according to Claim 10 wherein the array of nozzles is mounted on rollers running on rails extending across the direction of travel of the article.

12. Apparatus for carrying out the method of applying a pattern to a continuous web of pile material as claimed in Claim 1, comprising a plurality of jet nozzles adjustably located for spraying directly into the pile of the material jets of a substance which creates a pattern thereon, means for opening and closing the nozzles, programme control means for controlling said means for opening and closing tlre nozzles according to a preselected progralnme, and means for supporting the web of material such that the pile surface thereof is opposed to the nozzles and is substantially in contact with the nozzles.

13. Apparatus according to Claim 12, wherein the supporting means comprises backing rollers for supporting an article in the form of a web material under tension.

14. Apparatus according to Claim 13, wherein the nozzles are opposed to the backing rollers.

15. Apparatus according to Claim 13 or 14, wherein the supporting means includes a conveyor which runs over the backing rollers.

16. Apparatus according to any one of Claims 13 to 15, wherein the backing rollers are located in suction boxes which face the nozzles.

17. Apparatus according to any one of Claims 13 to 16, wherein suction boxes are provided underneath the web of material or the conveyor.

18. Apparatus according to any one of Claims 15 to 17, wherein the conveyor is permeable to gas, and a gas-impervious masking strip is provided for covering any parts of the conveyor not covered by the web of material.

19. Apparatus according to any one of Claims 16 to 18 wherein the suction boxes each contain a shiftable bulkhead wall which can be adjusted to conform to the width of the web of material.

20. Apparatus according to any one of Claims 13 to 19, wherein the centres of the backing rollers are disposed on a curve so that the web of material or the conveyor respectively will envelop part of the surface of each roller.

21. Apparatus according to any one of Claims 13 to 20, including means for tensioning the web of material before it travels over the first backing roller.

22. Apparatus according to any one of Claims 12 to 21, wherein the plurality of nozzles are combined in an array which is mounted on rollers running on rails to traverse the web of material across its direction of travel.

23. Apparatus according to Claim 22, wherein the nozzles are mounted on two bars and the bars are linked to form a four-bar parallel linkage.

24. Apparatus according to preceding claim 22 or 23, wherein cleaning devices for the nozzles are provided at one or both ends of the rails.

25. Apparatus according to Claim 24, wherein the or each cleaning device consists of rollers having a soft surface projecting into the path of traverse of the nozzle orifices.

26. Apparatus according to Claim 12, wherein the jet nozzles each contain a needle adapted to open and close a nozzle mouthpiece and electromagnetic means for operating the needle, the mouthpiece communicates with a chamber for containing the substance that is to be sprayed, and a wall of the chamber is constituted by a diaphragm which is connected to the needle.

27. Apparatus according to Claim 26, wherein the needle carries centring discs clamped together with the interposition of spacing sleeves.

28. Apparatus according to Claim 27, wherein the thickness of each centring disc is less than 1% of its diameter.

29. Apparatus according to Claim 27 or 28, wherein the centring disc is radially slotted.

30. Apparatus according to any one of Claims 26 to 29, including a chamber above the diaphragm or above the centring discs or between the discs which communicates through a pipe with a source of pressurised gas.

31. Apparatus according to any one of Claims 26 to 30, comprising means for limiting axial movement of the needle to a few tenths of a millimetre.

32. Apparatus according to any one of Claims 25 to 31, further comprising a flat abutment face between the nozzle mouthpiece and the wall of the chamber for containing the substance to be sprayed.

33. Apparatus according to Claim 30, wherein the chamber communicating with the pressure gas pipe also communicates with a chamber containing the magnet coil of the magnet system.

34. Apparatus according to any one of Claims 26 to 33, wherein the chamber for containing the substance to be sprayed has a tangentially disposed entry opening through which the substance to be sprayed is admitted.

35. Apparatus according to any one of Claims 26 to 34, including a disc armature for operating the nozzle needle.

36. Apparatus according to Claim 35, wherein the armature has a cross-section which with decreasing radius first increases in thickness, then has a constant thickness and finally again diminishes in thickness with a further decrease of radius.

37. Apparatus according to Claim 36, including coil cores, which comprise an inner portion and an outer ring portion which conically tapers inwards towards the armature, the annular cross-section of the armature being equal to half the magnetic cross-section of the cores.

38. Apparatus according to any one of Claims 26 to 37, wherein the windings of the magnet system are adapted to be energized by square wave current pulses consisting of a high intensity very short period initial pulse followed by a much longer and lower intensity pulse.

39. Apparatus according to Claim 26.

wherein for controlling the opening and closing of the nozzle the magnet coil is connected through a first power transistor to a high voltage source and through a second power transistor to ground, the connection between the first power transistor and the coil being further connected through a diode to a low voltage source, the base of the first power transistor is connected to the output of means including a multivibrator for generating a pulse of selectably adjustable amplitude and duration on receiving an input, and the input is also coupled to the base of the second power transistor.

40. Apparatus according to Claim 39, wherein the second power transistor is connected to ground through a very low ohmic resistor.

41. Apparatus according to Claim 40, wherein means are provided for determining the potential drop across the resistor between the second power transistor and the ground, said means being connected to the driving connection of the first power transistor which it is adapted to turn off.

42. Apparatus according to Claim 39, wherein the end of the coil connected to the second power transistor is also connected via a diode and a resistor to the high voltage source.

43. Apparatus according to Claim 39, wherein a switching transistor precedes each of the power transistors.

44. Apparatus according to Claim 39, wherein the pulse generating means is a monostable multivibrator associated with a timing capacitor and a trimming resistor.

45. A method according to any one of Claims 1 to 11, wherein the substance sprayed is a printing ink or dye.

46. A method of applying a pattern to the surface of a material substantially as hereinbefore described with reference to the accompanying drawings.

47. Apparatus for applying a pattern to the surface of a material substantially as hereinbefore described with reference to the accompanying drawings.