This invention relates to an apparatus and a method for cutting patterned fabrics, particularly but not exclusively patterned fabrics of the type known as lace.

The term lace is understood in the textile industry to mean a fine openwork fabric with a ground of mesh or net on which patterns may be worked at the same time as the ground is formed or applied later, and which is made of yarn by looping, twisting, or knitting, either by hand with a needle or bobbin, or by machinery. It may also be made by crocheting, tatting, darning, embroidering, weaving, or knitting.

Whether formed by weaving, knitting or otherwise, lace and similar fabrics are commonly formed as a parallel- sided strip of a length usually very much greater than its width. The fabrics are produced with pre-existing patterns, specifically scallop patterns, which are generally, but not exclusively, close to an edge parallel to the longitudinal run of the length of the material. Alternatively the lace may have a series of narrow strips which have scallop patterns to be cut and separated from parallel borders at the join of each longitudinal strip.

Pattern strips and pattern pieces may also be formed on the base fabric by techniques including but not

restricted to selective dyeing, printing, embroidering, pile trimming or other localised modifications of the base fabric and while not necessarily being "lace" as defined above, such other patterned fabrics have in common with lace (for the purposes of the present invention) the feature of pattern strips or pattern areas on the base fabric, each pattern strip or pattern area having a discrete boundary.

The common problem with lace and other such patterned fabrics is the requirement that each such pattern strip or pattern area (however formed) requires to be cut from the base fabric strip in a manner which closely follows the pattern boundary, ideally without cutting into the pattern strip or pattern area and without leaving attached portions of the base fabric outwith the pattern strip or pattern area.

Therefore the problem requires an effective and efficient means of cutting the base fabric strip along the boundary or boundaries of the pattern strips or pattern areas. It is already known to provide automatic cutting of longitudinal scallop edges in lace and other materials by means of directing a laser beam. In the known cutting apparatus there are two main methods used for recognising the pre-existing pattern which is to be cut. The first is by using a camera (ccd/tv), the second is by means of a sensor array combined with a suitable light source.

Present methods, using ced cameras and galvanometric beam driving, result in large computing power being employed to control the cutting operation. Resulting speeds of cutting are generally around 8 metres a minute.

A further problem in the prior art arises in the method used to control the direction of the laser cutting beam or multiple beams. It can be difficult to focus the laser power and to position it accurately, since the lace material can be flexible and variable. Lace is not a homogenous material and it is manufactured from different polymers and different types have different physical properties.

It is an object of the present invention to provide an apparatus and a method for cutting lace and similar patterned fabrics which can achieve cutting speeds of at least 20 metres a minute for a wide range of patterns and lace types and for quite complicated re- entry scallop patterns .

The apparatus according to the invention enables pattern pitch and width plus fibre numbers to be measured and recorded along with defects in the material. It can scallop complex re-entry patterns with returning cuts in excess of 10mm. The tension of the flexible and variable lace material is controlled conjointly with the laser operation. The method recognises the variants in lace construction and design in that some types have a more open weave than others, or are more stretchy than others, and so on.

The apparatus and method according to the invention combine improved pattern recognition and pattern following, including a method of electronic masking, with beam directing by galvanometer in a new cutting assembly. The invention envisages alternative cutting assemblies, including a 2-axis galvanometer, a multi- beam and a Raster. The invention improves not only the speed of cutting of more complex patterns and more difficult lace types but also the quality of cut

achieved. The present techniques can cut up to two paths simultaneously, but the invention can achieve the advantage that more than two, even six, eight, ten or more paths can be cut at once.

The present invention includes opto-electronic pattern recognition by scanning methods and pattern cutting by laser or other means, with the laser beam being steered automatically from the data collected by the pattern recognition system and processed in the controlling computer.

The invention also includes opto-electronic pattern recognition by scanning means with the information thus gathered used for inspection for defects int he knitting process. The scanning system may also be applied to measuring and recording the number of fibres in a specific area of the material.

This invention proposes several improvements over the prior art. The apparatus and method incorporate novel pattern recognition techniques with galvano etric beam directing. The techniques include electronically masking areas of the pattern adjacent to the path to be cut. The scanning system further enables continuous measurement to be made of the pitch and width of the pattern which allows the control of the pattern mask in defining the complex pattern paths such as the re- entrant and "Y" junction types of pattern. They also encompass a novel cutting head assembly which combines laser safety and fume extraction and the whole is capable of lateral movement to cut at any desired position. Additionally, the use of an angled material conveyor system will enable several cutting passes to be made in a continuous spiral. Re-entrant cutting of complex patterns can be cut utilising the raster

capability of the laser and steering mirror assembly. Finally this invention proposes a novel method whereby more than one pre-existing path can be cut simultaneously.

Particular embodiments of the apparatus and method according to the invention are defined in the claims.

According to the general principle of the invention machine woven lace is transported in a lightly stretched condition across a free span between a roller and a support bar.

At the input side of the span, the material passes a scanning array (preferably digital) similar to the scanner of a facsimile machine. This array is coupled to a computer system which generates an image of the passing lace. As part of the initial set-up, the operator views this image and designates the part of the existing pattern to be scalloped.

Preferably also coupled to the computer system, which acts as a pattern recognition means, is an encoder, which measures the incremental movement of the fabric as it passes under the scanning array. The scanning array may be a linear array which detects light as a single line of received image data, such that one line of received image data corresponds directly to one incremental movement of the fabric (as measured by the encoder or other means) and a corresponding incremental movement of the cutting means, which is moved according to information obtained by the scanning array. Such a scanning system is of course not limited to lace-type fabrics, nor to electromagnetic cutting beams directed by mirrors, but may be used with any patterned materials and cutting means such as hot wire cutters.

The laser beam is first expanded, and collimated, to reduce divergence, then concentrated by a long focus lens onto the surface of the material. This controls the path of the beam. The beam of the focused energy is steered by a small mirror positioned close to the lens and mounted on the shaft of a limited angle torque motor. The angular position of the motor shaft, and thus the mirror, is determined by the computer system.

The laser beam may be replaced by any other energy source capable of vaporising the material contacted to achieve cutting thereof.

The high energy beam from the laser is thus concentrated onto the material and performs the cutting function. In the apparatus shown there are two steering mirrors mounted orthogonally such that the first steers the beam across the material and the second positions the beam lengthwise. This function is used to set the distance longitudinally from the scanning array, and also to dynamically facilitate complex and steep cutting as in re-entry. Re-entrant cutting follows complex paths in which the pattern returns on itself to the "normal" line of flow of the material and pattern.

The steering mirror assembly is mounted on a slideway such that it can be positioned across the width of the material to allow cutting in any position. For convenience, this is powered. This feature is facilitated by the optical configuration in which the focusing lens is mounted on the beam steering carriage.

Electronic pattern masking may form part of the programme to be used for controlling the laser when cutting complex cutting paths, including those such as

re-entrant paths. The following three methods will be greatly enhanced by use of "masking". Indeed it is seen as almost essential, in order to avoid problems of cumulative position errors .

Re-entry cutting can be facilitated by multiple laser beams (Multi-beam) produced from additional optics whose drive motors are programmed to "switch on and off" further laser beams to cut simultaneously at different parts of the scallop each time the re-entrant feature is crossed.

Re-entry cutting can be facilitated by the use of a galvanometric drive. This may comprise .a two-axis galvanometer, with simple optics, and capable of directing a continuous laser beam both across the material and in a lengthwise direction within the cutting area. The material forward speed may vary to accommodate the laser cutting rate, especially in deep scallops, allowing the laser beam to "catch up" with the continuously forward moving material, and the calculation of the galvanometer steps is complex.

A further re-entry cutting method is to use the high switching capability of the pulsed laser and the high speed scan of the aforementioned galvanometer to cut in very short bursts effectively "drilling holes" at several points in a single axis on the re-entrant feature.

Scanning will be carried out on scallop paths which are in excess of 200mm, by motorising the scanning apparatus across the lateral width of the pre-existing pattern on the lace or other material .

As an extension to the powered cross-slide function for

very deep scalloping work, which is outside the range of available 200mm arrays, the cross-slide can be used to maintain the array substantially centrally on the cutting path. The cross-slide would require to be a low friction backlash free type with encoder feedback of carriage position. In this way the large departures are followed, with the accurate high speed departures utilising the galvanometer action.

The scanning system may also continuously measure and record the pitch and width of the material pattern. Compensation is made for the difference between the material in its lightly tensioned condition on the machine and its finished relaxed sated. Such pitch measurement further allows the control of the electronic pattern masks to define complex cutting paths, which would otherwise suffer cumulative error as the material may stretch as it passes through the machine. Using such a mask allows materials with a "Y" junction pattern (where the scanned cutting path divides into two or more branches) and re-entrant features to be processed.

The scanning system may also be applied to continuous inspection for defects in the material (lace) knitting process.

The scanning system may also be applied to measuring and recording the number of fibres in a specified area of the material.

The scanning system preferably comprises a segmented optical sensor array which detects light transmitted through the pattern of said fabric. Linear sensor arrays are available in limited lengths, and a number of arrays may be combined in an offset arrangement to

provide a scanning area of greater total width than the length of one individual scanner. However, the sensors cannot simply be arranged in a collinear manner, as this would leave gaps between adjacent sensors in which the fabric would not be scanned, due to the fact that the each sensor is mounted in a housing and the scanning elements themselves do not extend over the full length of the housing. To overcome this, the sensors are offset from each other both in a transverse direction parallel to the length of the sensor and in a longitudinal direction perpendicular to the length of the sensor. The software of the pattern recognition means takes account of the fact that adjacent sensors are not collinear and do not scan the fabric on the same transverse line at the same time.

This machine is capable of performing following and cutting or other operations on materials other than lace where there is a pre-existing pattern or similar outline on the material. For example leather sometimes has irregular patterns on its surface which may be followed and cut as part of a quality control system. Such materials will use the reflective method of material scanning in place of scanning through the material as used for lace. In reflective scanning the scanning sensor and the light source are on the same side of the material for cutting. In through material scanning they are on opposite sides.

Because of the long focus lens adopted it is possible to move the beam angularly to achieve cutting position over a substantial distance (eg ± 110mm in our case) without excessively reducing cutting power. This means that the cutting plane can be substantially flat. Near flatness is achieved by lightly stretching the material between cylindrical supports. This is unlike other

machines where the material is pulled across a cutting platen. The advantage of free span is that the beam passes through the material and can be baffled or dissipated in the defocused condition on a plate some distance below the material. Also, cutting debris which could stain the material is not present.

To enable re-entry cutting (where the pre-determined pattern follows an acute angle or even doubles-back on itself) the beam forming the cutting means may be reflected from two galvanometric mirrors, arranged substantially orthogonally to each other. Where more than one cutting means is present, each will have a dedicated pair of orthogonal galvanometric mirrors.

Thuε, where an acute curve in the pattern is encountered, the beam can follow the pattern line side- ways whilst keeping pace in the lengthwise direction with the constantly moving material . The beam can be returned to its original location by cutting through less-acute portions of the pattern at a rate exceeding the movement rate of the material. Extremely fast cutting rates are possible since the only moving part involved in the cutting means is the galvanometric mirror which tilts through very small angles to produce a relatively large beam deflection.

In a preferred embodiment the material (which may be lace - whether lingerie, Jacquard or Focard lace - leather, paper (such as wallpaper or wallpaper border strips), or any other material where a shaped edge is desirable) may be suspended over two sets of rollers, the cutting area formed in between the rollers being otherwise unsupported.

Embodiments of the invention will now be described by

way of example, with reference to the accompanying drawings wherein:-

Figs 1 and 2 are respectively a side elevation and an end elevation of a lace cutting apparatus according to a first embodiment of the invention;

Figs 3 and 4 are respectively a side elevation and a plan view of a lace cutting apparatus according to a second embodiment of the invention;

Fig 5 is a partial view of a multi-beam cutting head of a lace cutting apparatus according to a third embodiment of the invention;

Figs 6, 7 and 8 are plan views of a portion of a lace strip showing a re-entrant cut path;

Figs 9 and 10 are schematic views of pre-defined masks used to assist in cutting path calculations; and

Figs 11, 12 and 13 are plan views of a portion of a lace strip showing the cut path imposed against the pattern boundary.

Fig 1 shows a side elevation of the machine. Lace 23 is drawn into the machine by input drive roller 1 driven by motor 4 and trapped between input roller 1 and support roller 3 by weighted trap roller 2. The material passes up and round tension roller 5 which is supported on strain gauged beams and incorporates an encoder to meaεure the material travel. The lace then spanε unεupported between roller 5 and εupport bar 6 in which region cutting will take place. It then paεεeε through output drive roller 7, trap roller 9 and εupport roller 8 performing the same function as the

input roller set. The material tension is controlled by setting up the required speed relationship between the input motor 4 and output motor 10 as directed by the tension roller system. The speed of movement of the material may be altered by means of the motorised rollers, but is conveniently maintained at a constant rate.

Laser energy is generated in laser unit 21, collimated by lens 22 and turned through a right angle by fold mirror 11. The energy thus travelling acroεε the machine if focuεed by lenε 12 and εteered in 2 axes by εteering mirror pair 13 mounted on the shafts of galvanometer motors 14. The required position of the laser beam 17 is determined in the first instance by scanning array 15 with illumination being provided by the light source array 16 placed below the lace, although it can be above the lace.

The lens and steering mirror assembly is mounted on the carriage of a motorised εlideway 19 and hence can be poεitioned anywhere acroεε the width of the material. Fumes from the cutting action are contained by a hood 18 and are drawn off from below via a fume tray which is mounted on a second slideway 20 mechanically synchronised with the first slideway 19. The illumination array 16, being mounted on the fume extractor 25, stays in position below scanning array 15.

The mechanical and electrical components are all mounted on machine frame 24.

Figs 3 and 4 illustrate an embodiment of the invention, in which an angled handling method is provided. The cutting head 31 comprising the scanner assembly, laser,

optics and steering mirror may be mounted in a fixed position at one side of the machine frame 24, allowing cutting of one or more paths 32 with each pasε of the material 33. The uncut material 34 iε returned to the infeed of the machine uεing a conveyor 36 poεitioned at an angle, and the leading edge iε εewn to the trailing edge 37 with the pattern aligned but offεet, εo that the material may pass through the machine several times in a continuous spiral.

As the material width reduces with each pasε, the handling εyεtem may traverse by means of the scrolled roller 38 across the width of the machine frame 24 to maintain the material position with respect to the centre line of the cutting head 35. Further the scanner asεembly may be used to control the material tracking, so that the positions of the cutting paths are maintained.

Such a cutting head may alεo cut leεε than the maximum number of pathε with each pass of the material, by deflecting the unused laser beams using the steering mirrors.

Fig 5 is an isometric view of an eight path cutting head, in which eight laεer beamε 42 are each deflected by a mirror 40 and focuεed by a focusing lens 41 to cut the fabric along a cut path 45. The intended cut paths 46 have not yet been scanned and cut. Each mirror 40 can deflect the laser beam from a source (not shown) along a range of paths within the subtended angle 44, such that the path can vary from the beam path 42 (shown by solid lines) when the mirror is in the poεition 40 (indicated by solid lines) to the beam path 42' (shown by dotted lines) when the mirror is in the position 40' (indicated by dotted lines).

Figs 6 to 8 show three methods of re-entrant cutting made possible by the present invention.

The first method, shown in Fig. 6, useε a two-axiε galvanometer. The fabric is propelled in a first direction M, while the galvanometer deflects the cutting beam in two axes G, and G ₂ which are parallel and perpendicular to the direction of material flow M respectively. The cutting beam moves along the intended cut path P from point Si to point S ₂ and so on by deflection along the perpendicular galvanometer axiε G ₂ until it reaches point S ₉ . At this point the cutting beam has to move in the direction parallel to the direction of material flow M in order to "chase" the material. This is achieved by deflecting the cutting beam along both axes Gj and G ₂ until the cutting beam reaches point S ₁₂ , at which point deflection is again only necesεary along perpendicular axiε G ₂ .

The εecond method, εhown in Fig. 7, uses a multi-beam arrangement, in which a second beam and a third beam are switched on when required to cut re-entrant features. The fabric is propelled in a first direction M, while a galvanometer deflects a single cutting beam along an axis G which is perpendicular to the direction of material flow M. The cutting beam moves along the intended cut path P from point S ₀ to point S _x , at which point two additional cutting beams are switched on, so that three beams are in operation. A first beam cuts along the path S _x to S _y , a second beam cuts along the path S _z to S _y , and a third beam cutε along the path S _z to S _n . When the firεt and second cutting beams reach and meet at point S _y they are switched off, so that the third beam continues on its own to point S _n . Thuε the multi-beam zone T extends along the length of the re- entrant feature in the direction M of fabric movement.

The third method, shown in Fig. 8, useε a raster cutting method, in which a single cutting beam is switched on and off rapidly and "flies" between a number of cutting points along a raster line. The fabric is propelled in a first direction M, while a galvanometer deflects a single cutting beam along an axis G which is perpendicular to the direction of material flow M. The cutting beam moves along the intended cut path P from point S ₀ to point S _x , at which point the raster cutting method is brought into operation. The scanning means determines all the points on the intended cut path P which are intercepted by a raster line (R,, R ₂ , etc) which is parallel to the galvanometer axis G, and the cutting beam is then deflected to cut the fabric at each interception point on the raster line in turn. When the re-entrant feature has been pasεed, so that the raster line R _y only intercepts the intended cut path at one point S _y , the raster cutting method ceases and the cutting method reverts to normal. Thus the raster zone R extends along the length of the re-entrant feature in the direction M of fabric movement.

Although the multi-beam and raεter methodε of re- entrant cutting illuεtrated in Figs 7 and 8 are described above as using a galvanometer to deflect the cutting beams, other methods of controlling the position of the cutting beam can be utilised.

A masking method using an electronic/software maεk algorithm involves the use of a pre-defined mask to assiεt in cutting path calculations. The mask can be defined in one of two ways:

1. Vector list (see Fig 9) - a list of x, y co- ordinate pairs of a succession of vectors V,, V ₂ ,

V ₃ etc. along a path P. As material moves through, allowance is made for the material velocity vector when cutting a re-entrant pattern. The movement of the cutting beam is restricted to a rectangular operating window, hence the laser slows down when going against the flow of the material, and speedε up when chaεing the material. The vectors are defined relative to a known feature on the material .

2. Raster bit mask (see Fig 10) - a list of raster lines, each line made up of lε (εhown by X in Fig 10) and Oε (εhown by 0 in Fig 10) where the 0ε indicate the cutting path profile. Again, the "εet" iε relative to a known material feature. The bitmap maεk iε overlaid on incoming data from the scanner to derive the cutting path.

Both methods involve the pre-definition of the data for a given lace pattern. This is done once and retained as a database. The creation of the retained data, which allows a given material pattern to be cut, can be considered as collecting a complete scanned picture of the material and then allowing an operator to select the required cutting line through the pattern. The selected cutting line information then becomes the data which is stored in a memory ready for use when cutting.

A +/- tolerance band is applied to each of the cutting path points in the cutting line information. This tolerance band is selected to ensure that extraneous paths falling outside the tolerance are ignored by the syεtem, particularly at "Y" and "T" junctions.

When in use the cutting line data is used as a mask over the data collected by the scanner forming a moving

"window" whose width is twice the +/- tolerance on the cutting path points. The selectivity imposed by the mask on the data collected by the scanner therefore limits the amount of data to be procesεed at any given point along the cutting line and allowε high speed cutting.

The cutting procesε muεt complete the re-entry pattern before the material leaves the "window" defined by the mask. This "window" may be limited by physical limits of the cutting apparatuε, for example the fact that the mirror guiding the cutting beam can only εwing 25 degreeε or εo from a centre-line. In this case the mirror is the y-coordinate mirror which operates the cutting beam in the line of flow of the material, either against it or chasing it.

The raster or bitmap mask is a "true" electronic mask; the vector list mask is obtained by producing approximate X,Y pairs in the first run of a new pattern and inputting this information into the machine memory. It εhould be noted that this masking method may be used to cut any fabrics, not only lace, with any cutting apparatus other than electromagnetic beams, for example hot wire cutting, and with any means for controllably varying the relative poεition of fabric and cutting apparatuε, not only tiltable mirrors.

The cutting algorithm may employ various edge following mechanismε illuεtrated in Figs 11, 12 and 13 and described below. The mask may act as a guide where backward/forward paths are found or at "Y" junction events.

Fig 11 shows the edge following mechanism. In this routine, a reasonably well defined single pattern edge

51 is required in the fabric 52. The reference edge 51 is identified by the operator and this edge is followed by the software, keeping the laser or cutting beam a fixed distance D away from it to form the cut path 53. Localised smoothing is used to eliminate deviations in the edge profile.

Fig 12 showε the track (or two edge) following mechanism. This routine is required where the fabric 52 has a reasonable track running between two pattern edges 54, 55 which need not be as well defined as the single edge 51 routine above. In this case the edge routine would fail due to the close proximity of the other edge. The edges 54, 55 essentially form "tram lines" between which the laser or cutting beam is guided along the cut path 53. If one edge becomes "weak" then the other edge will keep the software on track since "smoothing" is employed to eliminate local deviations .

Fig 13 showε the hole following mechaniεm. This method is used where no edges are available in the fabric 52. In thiε case the pattern is such that a series of holes 56 is used to guide the cutting beam along the cut path 53. The software "looks ahead" to locate a hole 56, then moves in a straight line towards that hole, then progresses centrally through the hole.

In the mechanismε of Figε 11 to 13 suitable contraεt adjustment and operator judgement is required for optimum choice of routine.

The advantages of the invention are described below.

The method of masking of εectionε of the pattern by electronic/software means, to leave only the desired

butting path to be followed, is a considerable advance in the procesεing of data used in controlling the laser beam's(s') direction. It resultε in the increased ability to concentrate only on the relevant calculations. This method itself is further enhanced by the continuous pitch measurement method, also a part of this invention.

The previous methods of directing a laser beam to cut paths on pre-existing patterns on lace fabric suffered speed reεtrictions owing to the limits imposed by the stepper motor arrangement used to linearly drive the fixed mirrors which guided the laser to the required cutting point.

This invention by incorporating galvanometric drive for the mirrors allows for greater speed and flexibility in the complexity of pattern which can be cut. Cutting εpeeds will be increased from around 10 meters a minute to 30 metres a minute. The actual cutting speed will vary according to the complexity of the pattern, but this is a considerable advantage over previous capability.

This invention adds to the existing arrangement of pattern recognition, which has single edged path following, in that two edge following, and pattern hole-to-hole tracking is now possible. The control system can perform the computing necessary to cope with these and will be capable of adaption for other styles of lace materials and patterns.

The simplicity of this invention over the prior art is in the method by which the lace can pass freely across the cutting zone without the need for a platen. The function of the platen has been replaced by the cutting

tension control system. This removes any restriction on cutting area imposed by the support and the aperture embodied therein. It also avoids staining, and energy is easily dissipated in the defocused state.

This invention has the advantage of having a unified complete assembly incorporating: the cutting arrangement; the fume extraction hood; the laser beam protection requirements; and the path recognition and following scanner. The whole is able to be motor driven along guide rails to any point acrosε the full width of the lace with the laεer beam maintaining the required focuε for cutting.

The previouε known arrangementε are restricted in cutting only up to two different tracks simultaneously using opto-electronics . This invention enables more than two tracks to be cut simultaneouεly, again uεing beam εplitting and opto-electronics.

This invention haε the advantage over previous methods of having continuous pitch and width measurement and recording, inspection for defectε in the knitting proceεs and measuring and recording the number of fibres in a given distance along or across the material, all allowing greater procesε control and producing important quality control statistics.

This invention can accommodate complex patterns including those with "Y" junction and re-entrant features with return pattern paths in excess of 10mm, allowing the automatic cutting of a far wider range of material styles and offering much greater design flexibility.

A multi-head cutting system clearly offers higher

production rates, but, together with this invention's angled handling method and operation techniqueε described above, higher rates can be achieved with the minimum of operator intervention. Such a system alεo allows the flexibility of procesεing a wide variety of material widths and styleε using the same scanner and cutting head assembly.

In summary this invention produces the advantage of: far greater cutting speeds than previous methods, (30 metres per minute); multiple cutε; and conεiεtent higher quality of cut finish; plus, the advantage of lesε fall off in cutting speed when scalloping more complex and multi-strip fabric. The former is a particular benefit to furnishings lace production while the latter is of benefit to garment and lingerie production.

While certain variations and modifications have been described above, the invention is not restricted thereto, and other modifications and variations can be adopted without departing from the scope of the invention as defined in the appended claimε.