Seam protecting device for textile finishing machines

Abstract: Device (15) to protect the stitches (19) on the fabric (12) being worked in textile machines, particularly raising or grinding machines, with a drum (10), the device (15) cooperating with sensor means (17) located upstream of the drum (10) and suitable to monitor the arrival at the machine of a transverse stitch (19) joining adjacent pieces of fabric (12), the device (15) including bar means (16) equipped on the periphery with attachment means (20), the bar means (16) including a first inactive position wherein the attachment means (20) do not interfere with the fabric (12) and a second working position wherein the attachment means (20) attach themselves to the fabric (12) in the area around the stitch (19) and lift it from the working cylinders (11), the bar means (16) being arranged outside the fabric (12) and substantially parallel to the axis of the drum (10) and rotating on a circumference outside the fabric and with a greater radius than the radius of the drum (10) from a starting position (16a) to a position of arrival (16b) cooperating respectively with the inlet and outlet of the drum (10).

Description: FIELD OF THE INVENTION This invention concerns a device to protect the stitches on the fabric being worked on textile machines as set forth in the main claim. The invention is applied in textile machines, particularly raising and grinding machines with a drum, to protect the stitches used to join together the pieces of fabric so as to make a single continuous strip which is then subjected to processing. To be more exact, the device prevents the join stitches from being subjected to the action of the working elements of the textile machines, and thus prevents possible damage and breakages. BACKGROUND OF THE INVENTION In the textile field, the state of the art covers the joining together of various pieces of fabric, by means of transverse stitches, which will then be subjected to processing to make a single continuous strip of great length; the purpose is to increase the productivity of the machines by making them work in a continuous and prolonged manner. This technique, however, has the disadvantage that the areas where the pieces are joined are structurally weak, since the stitches, if hooked up by the working elements of the machine, can be damaged and possibly torn. If these stitches break, the adjacent pieces are separated, and consequently the machine has to be stopped to restore the continuity of the textile strip. This disadvantage particularly occurs in raising machines or grinding machines, where the working cylinders are lined with metal points or abrasive elements which exert a more or less intense action, of abrasion or removal, on the threads of the fabric. In these machines, therefore, the fabric is subjected to mechanical stresses which can cause the stitches between adjacent pieces to break. The stitches used may be of the "cut and sew" type, which provides to put the two edges which are to be joined side by side without laying one on top of the other. This type of stitch has the advantage that it maintains unchanged the thickness of the fabric but, on the other hand, it is structurally weak since the sewing threads are not protected from the action of the working cylinders, and thus there is a high probability they may break and rip. There are also the stitches known as "chain stitches", which provide to put the pieces of fabric to be joined one on top of the other so that the join stitches are made on the opposite side of the fabric from the side subjected to processing, and therefore they are protected from the action of the working cylinders. If the work has to be done on both sides of the fabric, the stitch is doubled, or tripled, and the edges of the fabric which have to be joined are put on top of each other several times. "Chain stitching", however, causes an increase in thickness of the fabric which, when the fabric is lapped or rolled, forms a line on the layers of fabric adjacent to the stitch. The line is repeated over several laps or rolls, which causes a deterioration in the quality of the fabric and, often, it is necessary to repeat the work or discard several metres of fabric. To solve the problems of the stitching threads breaking, yet still using stitches of a reduced thickness which therefore will not ruin the fabric, there has been a proposal to position, upstream and downstream of the drums, sensors suitable to monitor the presence of these stitches and to command the working cylinders to idle. This solution has the advantage that it is simple but, on the other hand, it entails the discard of many metres of fabric since the cylinders do not work parts of the fabric which in length are substantially almost twice the circumference of the drum of the textile machine, which, in average-size raising and grinding machines, can be quantified as about four metres. To overcome this problem, it has been proposed to use a device which provides to use a protection element consisting of a cusp-shaped bar arranged between the fabric and the working cylinders, raising or grinding, and suitable to rotate around the drum of the textile machine (see EP-A-0613972). This protection element, which is made to start by sensors which monitor the arrival of the stitches at the textile machine, lifts the fabric in correspondence with the stitch and safeguards it from the action of the working cylinders. The protection element rotates by 360° around the drum, which entails that it passes in correspondence with the brushes provided below the drum used to clean the working cylinders. In another solution, when it approaches the point where the fabric is detached from the drum, the protection element stops and inverts its direction of travel, returning to its starting position while awaiting the new stitch. This device placed between the fabric and the working cylinders has a plurality of disadvantages. If the fabric is over-tensioned, there is a risk that the cusp-shaped bar can bend in such a way as to come into contact with the coverings of the raising/grinding cylinders, damaging itself and them. If the fabric breaks, which can happen due to tears upstream from the raising operation, it may be that the fabric itself ties the bar to the working cylinders, in this case too causing damage to the coverings or to the bar itself. If the bar rotates through 360° around the drum, it is necessary to distance the brushes, with their relative suction assemblies and command units, from the drum in order to allow the bar to pass, which involves considerable complications both in construction and in operation. If the bar returns back, following the same travel, it necessarily lifts the fabric again, causing a different raising action from where the fabric is not lifted. A further disadvantage is that, given the width of the machine, the tension of the fabric and to avoid excessive bending, the bar must have a large size in the radial direction. Moreover, to avoid possible contacts with the coverings of the raising cylinders, or the abrasive elements of the grinding cylinders, the bar must be located at a certain distance therefrom. This causes a considerable lifting of the fabric and therefore a consistent segment of the fabric, about 60÷70 cm, either side of the stitch is not raised and therefore must be eliminated when the pieces are separated at the end of the process. The present Applicant has devised, tested and embodied this invention to overcome all these shortcomings and to obtain further advantages. SUMMARY OF THE INVENTION The invention is set forth and characterised in the main claim, while the dependent claims describe other characteristics of the invention. The purpose of the invention is to provide a device to protect the stitches from the action of the working elements in a textile machine with a drum, which will have a minimum impact on the working of the fabric itself and which, at the same time, is simple to achieve and to operate, economical and easy to maintain. Another purpose of the invention is to provide a device which can also be used on already existing textile machines without substantially altering the configuration thereof. The device according to the invention provides to use bar means equipped with attachment means suitable to lift the fabric in correspondence with the stitches which join two adjacent pieces, distancing the fabric from the working elements of the textile machine. According to the invention, the bar means are located outside the fabric being worked and rotate around the drum, which allows to avoid the problems of interference with the cleaning means and also of lifting the fabric when it is not necessary. The bar means are positioned substantially parallel to the axis of rotation of the drum and rotate with the same centre of rotation as the drum and with a radius greater than the radius of the drum. The bar means have a first inactive position wherein the attachment means with which they are equipped do not interfere with the fabric and a second working position wherein the attachment means interfere with the fabric, gripping it and lifting it from the working cylinders. When sensor means monitor the arrival of the stitch at the machine, the bar means move to the working position wherein they grip the fabric in the area around the stitch and lift it from the working cylinders. Then, the bar means are made to rotate outside and around the drum to approximately the point where the fabric leaves the drum. At this point, the bar means move to the inactive position wherein the attachment means release the fabric which can thus be discharged from the drum. The bar means, free of the fabric, can then be returned to the starting position to await the new stitch without any interference with the fabric. According to one embodiment, the bar means are driven by drive means with a controlled drive so as to assume moment to moment the same speed as the fabric which they have attached. To be more exact, the drive means cause the bar means to rotate at a speed which, at the moment of attachment, is synchronised with the speed of the inlet drawing cylinder and, at the moment of release, is synchronised with the speed of the outlet drawing cylinder, the speeds being different from each other due to the stretching of the fabric during the raising operation. According to a variant, the drive means start the bar means at a speed synchronised with the inlet drawing cylinder, and then are de-activated, leaving the fabric itself to draw the bar means, in which case the speeds are consequently adapted. The outside position of the means which lift the fabric from the working elements of the textile machine entails a plurality of advantages. In the first place, the absence of elements between the fabric and the drum prevents possible contact and therefore reciprocal damage with the coverings of the working cylinders. In this case the fabric may be lifted by very little, since the bar means, as they attach the fabric from outside, can lift it even only by a few millimetres, at most 10. Consequently, the zone where no raising is carried out is drastically reduced on either side of the stitches, and is no more than 15÷20 cm. The fact that the speed of rotation of the bar means is synchronised with respect to the fabric ensures a perfect control of the non-raised zone, and therefore of the loss of fabric on either side of the stitches. Since the return travel of the bar means is made outside the drum, there are no long segments of fabric raised in a disuniform manner and therefore unacceptable in quality. Moreover, there is no need for special assemblies such as for example those used to distance the brushes from the drum. Another advantage is that it is possible to make the fabric itself draw the bar means, which ensures that the device can be adapted perfectly to every type of fabric and every type of tension, yet an extremely limited non-raised area can still be maintained on either side of the stitches. Furthermore, the fabric can be released at any moment if there are operational problems and blockages during the passage of the stitch, without any consequences; the machine, moreover, can be rapidly restored to working conditions. BRIEF DESCRIPTION OF THE DRAWINGS The attached Figures are given as a non-restrictive example, and show some preferential embodiments of the invention as follows: Fig. 1 shows in diagram form the working principle of the device according to the invention applied to a raising machine; Fig. 2 is a side view of an embodiment of the device according to the invention; Fig. 3 is a front view, in part section, of the device according to the invention; Fig. 4 shows an enlarged detail of Fig. 2. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Fig. 1 is a side view in diagram form of a drum 10 of a raising machine, on the circumference of which there are parallel raising cylinders 11 lined with a covering equipped with metallic points 11a which on the even cylinders are inclined in the direction of feed, and on the odd cylinders in the opposite direction. The metal points 11a pull the fibres of the threads which make up the fabric 12, so that at the outlet of the drum 10 a fabric 12a is obtained which has a downy worked surface. At inlet to and at outlet from the drum 10 there are drawing cylinders, inlet 14a and outlet 14b, and at the lower part there are cleaning means 13, in this case consisting of two counter-rotating brushes 13a. The device 15 according to the invention comprises bar means 16, equipped on the periphery with attachment means 20, governed by means 17 to monitor the arrival of a stitch 19 joining the pieces of fabric 12. The attachment means 20 are suitable to lift the fabric 12 in correspondence with the stitch 19, preventing contact with the raising cylinders 11. The bar means 16 move along a path 18, shown in Fig. 1 with a line of dots and dashes; they move from a starting or start of cycle position 16a, wherein the attachment means 20 attach and lift the fabric 12, to an arrival or end of cycle position 16b, wherein the attachment means 20 release the fabric 12, and vice versa. The path 18 is outside the fabric 12, which allows to prevent problems of interference between the bar means 16 and the cleaning means 13, and also problems of unwanted lifting of the fabric 12 when not necessary. Moreover, the lifting of the fabric 12 is reduced to a minimum since the attachment means 20, acting from outside, lift the fabric 12 even only by a few millimetres, which allows to have non-raised segments "t" of an extremely limited length, not more than about 15÷20 cm, and a maximum lifting "s" of the fabric 12 of about 10 mm. The device 15 according to the invention functions as follows: The sensor means 17, with the bar means 16 in their starting position 16a, monitor the arrival of the stitch 19 at the machine and command the attachment means 20, which attach the fabric 12 in the area around the stitch 19 and lift it from the raising cylinders 11. Then, the bar means 16 are made to rotate externally around the drum 10 until they reach the arrival position 16b where the attachment means 20 release the fabric 12. At this point the bar means 16 are returned to the starting position 16a along the path 18 and without interference with the fabric 12, as they await a new stitch 19. Figs. 2÷4 show a possible form of embodiment of the device 15 according to the invention wherein the bar means 16 are parallel to the axis of rotation 21 of the drum 10 and the attachment means 20 consist of a plurality of hooks 23 aligned longitudinally to the bar means 16 and suitable to be inserted between the meshes of the fabric 12 and attach it. In other embodiments which are not shown here, the attachment means 20 consist of grippers, needles, crooks or other similar elements. It is also possible to use attachment means 20 made of velcro or other material suitable to attach and lift the fabric 12. One advantageous solution provides that the attachment means 20 are shaped in such a manner that, at outlet from the drum 10, they become detached from the fabric 12 simply because the bar means 16 stop rotating. The bar means 16 are supported at the ends by a pair of levers or arms 22, provided at the sides of the drums 10 and rotating on the same axis of rotation 21 as the drum 10. The arms 22 are driven by drive means 24 on the shaft 25 of which drive wheels 26 are keyed, the drive wheels 26 being associated by flexible transmission means 27, for example belts or chains, to respective driven wheels 28 solid with the arms 22. According to one embodiment, the drive means 24 are driven in a controlled manner so that the bar means 16 move along the path 18 at the same speed as the fabric 12. According to a variant, the drive means 24 are driven only at the start, so that they are synchronised with the speed of the fabric 12, after which they are de-activated, so that the fabric 12 itself is left to draw the bar means 16. The attachment means 20 have an inactive position wherein they do not interfere with the fabric 12 and a working position wherein they grip the fabric 12 and lift it by a desired value "s". In this case to pass from the inactive position to the working position and vice versa, the bar means 16 rotate through 90°, the rotation being achieved by a pair of actuators 29, each of which is constrained on the outer face of a respective arm 22. According to a variant which is not shown here, the actuators 29 are constrained on the inner face of the respective arm 22. The pistons of the actuators 29 are constrained oscillating to a first end of a lever 30 radially associated with the bar means 16 so that every time the pistons of the actuator 29 are activated, the lever 30 is taken to respective positions which are orthogonal to each other.

Claims: Device to protect the stitches on the fabric being worked in textile machines, particularly raising or grinding machines with a drum (10), the device cooperating with sensor means (17) located upstream of the drum (10) and suitable to monitor the arrival at the machine of a transverse stitch (19) joining adjacent pieces of fabric (12), the device being characterised in that it includes bar means (16) equipped on the periphery with attachment means (20), the bar means (16) including a first inactive position wherein the attachment means (20) do not interfere with the fabric (12) and a second working position wherein the attachment means (20) attach the fabric (12) in the area around the stitch (19) and lift it from the working cylinders (11), the bar means (16) being arranged outside the fabric (12) and substantially parallel to the axis of the drum (10) and rotating on a circumference outside the fabric and with a greater radius than the radius of the drum (10) from a starting position (16a) to a position of arrival (16b) cooperating respectively with the inlet and outlet of the drum (10). Device as in Claim 1, characterised in that the starting position (16a) and the arrival position (16b) of the bar means (16) coincide respectively with the point of first contact and the point of detachment of the fabric (12) from the drum (10) of the machine. Device as in Claim 1 or 2, characterised in that the attachment means (20) are arranged longitudinally on the bar means (16) and consist of crooks, grippers, hooks, velcro or other similar means. Device as in any claim hereinbefore, characterised in that the bar means (16) are associated with actuators (29) suitable to define the respective positions thereof, working and inactive, by rotating on their own axis. Device as in any claim hereinbefore, characterised in that the bar means (16) are mounted rotatable at the end of arms or levers (22) provided at the sides of the drum (10) and governed by drive means (24), the arms or levers (22) including a center of rotation lying on the axis of rotation (21) of the drum (10). Device as in Claim 5, characterised in that there is a pair of drive wheels (26) keyed onto the shaft (25) of the drive means (24), each drive wheel (26) being kinematically associated by means of flexible transmission means (27) with driven wheels (28) concentric to the axis of rotation (21) of the drum (10) and solid with the respective arm or lever (22). Device as in Claim 5 or 6, characterised in that the drive means (24) are driven in a controlled manner correlated to the speed of the drawing cylinders (14a, 14b) provided at inlet and outlet of the drum (10) in such a manner that the bar means (16) assume, moment by moment, the same speed as the fabric (12). Device as in Claim 5 or 6, characterised in that the drive means (24) start the bar means (16) at the speed of the fabric (12) and are then de-activated leaving the fabric (12) itself to draw the bar means (16).

Inventors: SCORTEGAGNA BRUNO, SCORTEGAGNA, BRUNO
Applicants: LAFER SPA
Application year: 1999
Main classification: D06C11
IPC codes: D06C11