Patent Publication Number: US-6665578-B2

Title: Linking method and linking apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a linking method and a linking apparatus, and in particular, to a linking method and a linking apparatus enabling quick and accurate linking of knitted fabrics. 
     2. Description of the Prior Art 
     In a knitted fabric, a loose course is conventionally formed. The loose course consists of knitted loops which are larger than the other knitted loops (hereinafter, such large knitted loops are referred to simply as linking loops) such that the knitted fabric is linked to another knitted fabric to produce the defined size and shape of a product when the knitted loops are joined to each other by linking. When a knitted fabric is disposed on a linking apparatus, an operator stretches the knitted fabric with both hands so as to look through the knitted fabric to identify the linking loops which define a loose course. In this manner, the operator inserts a point needle through each of the linking loops defining the loose course. 
     This operation is performed in a similar manner for a tubular knitted fabric having a tubular shape. First, an operator puts his (her) hands into an opening of a tubular knitted fabric to laterally stretch the tubular knitted fabric so as to look through the knitted fabric on a far side when seen from the operator. In this manner, the operator identifies linking loops so as to insert a point needle of a linking apparatus through each of the linking loops. 
     Thereafter, the operator performs a similar operation for the knitted fabric on the operator side, thereby attaching the tubular knitted fabric to the linking apparatus. 
     However, it is extremely difficult to insert point needles through the linking loops because the linking loops are only slightly larger than normally knitted loops. For the tubular knitted fabric, in particular, after piercing point needles through a knitted fabric on the far side, it is difficult to stretch the knitted fabric on the operator side. Therefore, the difficulty of piercing with the point needles is increased. 
     As a result, the linking operation disadvantageously takes a long time to complete. Moreover, an inconvenience occurs in that point needles are withdrawn when linking of the loops is carried. Consequently, the yield of products is reduced. 
     In view of the problems described above, methods described in Japanese Patent Laid-Open Publication Nos. Hei. 11-207061 and 11-207062 have been developed. In the methods disclosed in the above-cited patent publications, it is necessary to insert a point needle through linking loops while one-by-one adjusting the positions of the point needles with respect to the linking loops in a linking operation because the linking loops are rarely placed at constant intervals. Moreover, in these methods, it is necessary to manually insert point needles through the linking loops provided on the edge of a knitted fabric because it is difficult to detect the linking loops provided in the vicinity of the edge of the knitted fabric. As a result, the amount of time required to complete the linking is increased, making it impossible to quickly perform the linking. 
     SUMMARY OF THE INVENTION 
     To overcome the problems described above, preferred embodiments of the present invention provide a linking method and a linking apparatus, which allow point needles to be quickly and accurately inserted through linking loops formed in a knitted fabric so as to enable tight and accurate linking of knitted fabrics. 
     A first preferred embodiment of the present invention provides a method for linking knitted fabrics, each having a loose course for linking, including the steps of opposing the knitted fabrics to be linked to each other, stretching the opposed knitted fabrics in a course direction, stretching the opposed knitted fabrics in a wale direction, picking up a multiple gray-scale image including an image of linking loops defining a loose course of each of the stretched knitted fabrics, performing an image processing on the multiple grayscale image so as to detect positions of the linking loops, inserting a point needle through each of the linking loops, sewing a linking loop in the vicinity of an edge of each of the knitted fabrics, and threading the linking loops other than the sewn linking loop by using the point needle inserted through the linking loop so as to link the knitted fabrics together. 
     In the first preferred embodiment, the linking loops in the vicinity of the edges of the knitted fabrics are quickly and accurate linked. The remaining linking loops are accurately threaded to perform the linking. 
     The step of sewing the linking loop in the vicinity of the edge of each of the knitted fabrics preferably involves threading one linking loop a plurality of times. 
     With this step, the linking loops in the vicinity of the edges of the knitted fabrics are more tightly linked. 
     The step of stretching the opposed knitted fabrics in the course direction includes piercing a plurality of needles through the knitted fabrics while the knitted fabrics are being stretched in the course direction so as to fix the knitted fabrics 
     With this step, the knitted fabrics in a stretched state become stable, thereby enabling more accurate linking. 
     The step of stretching the opposed knitted fabrics in the course direction according to the first preferred embodiment preferably further includes the steps of pinching the opposed knitted fabrics in a stretched state in the course direction, and piercing a plurality of needles through the knitted fabrics which are pinched in a stretched state so as to fix the knitted fabrics. 
     With these addition steps, the knitted fabrics in a stretched state is even more stable, thereby enabling more accurate linking. 
     The step of performing the image processing on the multiple gray-scale image so as to detect the positions of the linking loops according to the first preferred embodiment preferably includes detecting the positions of the linking loops by pattern matching. 
     With this step, large knitted loops formed immediately above or immediately below the loose course are not misrecognized as linking loops, thereby enabling more accurate linking. 
     The linking method according to the first preferred embodiment preferably further includes the step of placing a plate-like material between the opposed knitted fabrics, the plate-like material having a visual effect which allows clear visualization of a boundary between a knitted portion of the knitted fabric and a portion including no knitting yarn. 
     With this step, the positions of the linking loops is easily detected, thereby enabling more accurate linking. 
     The plate-like material preferably emits light, such that the positions of the linking loops are more easily detected, thereby enabling more accurate linking. 
     The knitted fabrics according to the first preferred embodiment preferably defined a tubular knitted fabric, and the step of opposing the knitted fabrics to be linked involves opposing the knitted fabrics to each other into a shape to be formed by linking the tubular knitted fabric, so as to quickly link the linking loops present in the vicinity of an edge of the tubular knitted fabric which is flattened or nearly flattened such that the knitted fabrics to be linked together are opposed to each other. Moreover, the remaining linking loops are accurately threaded to be linked together. 
     Each of the knitted fabrics according to the first preferred embodiment preferably includes a course formed to have a thin thickness, and the step of pinching the opposed knitted fabrics in the stretched state in the course direction involves pinching each of the knitted fabrics at the course formed to have the thin thickness, such that the knitted fabrics is easily and firmly pinched along the loose course so as to allow the loose course to be regularly arranged. As a result, accurate and quick linking is made possible. 
     Each of the knitted fabrics according to the first preferred embodiment preferably include a loose course formed in a vicinity of the course formed to have a thin thickness, and the step of pinching the opposed knitted fabrics in a stretched state in the course direction involves pulling a side of each of the knitted fabrics where the loose course is not formed in a state where the knitted fabrics at the course formed to have the thin thickness are pinched so as to arrange the loose course along an edge of a member pinching the knitted fabrics, such that the loose course is more regularly arranged, thereby enabling more accurate and quick linking. 
     A second preferred embodiment of the present invention provides a linking apparatus for linking knitted fabrics, each having a loose course for linking, including a course stretching device for stretching the knitted fabrics in a course direction in a state where the knitted fabrics are opposed to each other, a wale stretching device for stretching the opposed knitted fabrics in a wale direction, an image-pickup device for picking up a multiple gray-scale image including an image of linking loops constituting a loose course of each of the stretched knitted fabrics, a linking loop detection device for performing an image processing on the multiple gray-scale image so as to detect positions of the linking loops, a point needle insertion device for inserting a point needle through each of the linking loops, and a sewing machine mechanism for sewing a linking loop in a vicinity of an edge of each of the knitted fabrics and for threading the linking loops other than the sewn linking loop by using the point needle inserted through the linking loops to link the linking loops together. 
     With the linking apparatus according to the second preferred embodiment of the present invention, the linking loops present in the vicinity of an edge of the knitted fabric are quickly linked, whereas the remaining linking loops are accurately threaded to be linked together. 
     The sewing machine mechanism according to the second preferred embodiment threads the linking loop in the vicinity of the edge of each of the knitted fabrics for a plurality of times, such that the linking loops in the vicinity of the edges of the knitted fabrics are more tightly linked. 
     The course stretching device according to the second preferred embodiment is preferably defined by a plurality of needles piercing through the knitted fabrics while the knitted fabrics are being stretched in the course direction, such that the knitted fabrics in a stretched state become stable, thereby enabling more accurate linking. 
     The course stretching device according to the second preferred embodiment preferably further includes a pinching device for pinching the opposed knitted fabrics in a stretched state in the course direction, and a fixation device for piercing a plurality of needles through the knitted fabrics which are pinched in a stretched state so as to fix the knitted fabrics, such that the knitted fabrics in a stretched state become stable, thereby enabling more accurate linking. 
     The linking loop detection device according to the second preferred embodiment preferably detects the positions of the linking loops by pattern matching, such that large knitted loops formed immediately above or immediately below the loose course are not misrecognized as linking loops, thereby enabling more accurate linking. 
     The linking apparatus according to the second preferred embodiment of the present invention preferably further includes a plate-like material having a visual effect which allows clear visualization of a boundary between a knitted portion of the knitted fabric and a portion including no knitting yarn when the plate-like material is placed between the opposed knitted fabrics, such that the positions of the linking loops are easily detected, thereby enabling more accurate linking. 
     The plate-like material is preferably a light emitter. such that the positions of the linking loops are more easily detected, thereby enabling more accurate linking. 
     In this case, it is possible to quickly link the linking loops present in the vicinity of an edge of the tubular knitted fabric which is flattened or nearly flattened so that the knitted fabrics to be linked together are opposed to each other. Moreover, the remaining linking loops are accurately threaded to be linked together. 
     The knitted fabrics preferably define a tubular knitted fabric, and the course stretching device and the wale stretching device stretch the tubular knitted fabric while the knitted fabrics are being opposed to each other into a shape to be formed by linking the tubular knitted fabric. 
     In this case, the knitted fabrics can be easily and firmly pinched along the loose course so as to allow the loose course to be regularly arranged. As a result, accurate and quick linking is made possible. 
     Each of the knitted fabrics preferably includes a course having a thin thickness, and the pinching device for pinching the opposed knitted fabrics in the stretched state in the course direction pinches each of the knitted fabrics at the course having the thin thickness, such that the loose course is more regularly arranged, thereby enabling more accurate and quick linking. 
     Each of the knitted fabrics preferably includes a loose course formed in a vicinity of the course having the thin thickness, and the pinching device for pinching the opposed knitted fabrics in the stretched state in the course direction includes a pulling device for pulling a side of each of the knitted fabrics where the loose course is not formed in a state where the knitted fabrics at the course formed to have the thin thickness are pinched so as to arrange the loose course along an edge of the pinching device. 
     Other features, elements, advantages and characteristics of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram showing a preferred embodiment of a linking apparatus according to the present invention; 
     FIG. 2 is a diagram showing a tubular knitted fabric to be linked in the preferred embodiment; 
     FIG. 3 is a plan view showing a pinching tool; 
     FIG. 4 is a cross-sectional view, taken along a line IV—IV in FIG. 3; 
     FIG. 5 is a plan view showing a portion of a chain; 
     FIG. 6 is a partially enlarged view showing a needle; 
     FIG. 7 is an enlarged cross-sectional view showing a light guiding plate; 
     FIG. 8 is a plan view showing a point needle unit; 
     FIG. 9 is a plan view showing the point needle unit in another state; 
     FIG. 10 is a plan view showing the point needle unit in a further state; 
     FIG. 11 is a diagram showing another example of a light guiding plate in one state; 
     FIG. 12 is a diagram showing the light guiding plate of FIG. 11 in another state; and 
     FIG. 13 is a diagram showing another pinching member. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a diagram showing a preferred embodiment of a linking apparatus according to the present invention. The linking apparatus  10  according to this preferred embodiment is optimized to link a tubular knitted fabric to be formed into a sock as shown in FIG.  2 . The sock is formed by linking loops defining a loose course formed in the vicinity of a toe of the tubular knitted fabric. A tubular knitted fabric to be linked in this preferred embodiment includes Rosso courses. The Rosso courses correspond to two courses arranged above the loose course, and have a smaller thickness than that of the remaining knitted fabric by reducing the number of knitting yarns or by changing knitting yarns with finer ones for these two courses. 
     The linking apparatus  10  includes a pinching transfer section  12  as shown in FIG.  1 . The pinching transfer section  12  transfers the tubular knitted fabric in a stretched state in a course direction and a wale direction while holding the tubular knitted fabric at the Rosso courses, the tubular knitted fabric being flattened such that linking loops to be linked are approximately opposed to each other. The pinching transfer section  12  includes a pinching tool  14 . 
     The pinching tool  14  holds the flattened tubular knitted fabric at its Rosso courses. The pinching tool  14  is defined by a pair of pinching members  14   a . Each of the pinching members  14   a  has a gradually reducing thickness and width from its approximately middle portion toward its tip, as shown in FIGS. 3 and 4. Each of the opposing faces of the pinching members  14   a  has a linear plane shape as shown in FIG.  3 . 
     A projecting line  14   b  is provided on each of the opposing faces of the pinching members  14   a  so as to extend from one end of the pinching member  14   a  to the other end. The projecting line  14   b  has a fixed height and a fixed width. In this preferred embodiment, the projecting line  14   b  has a height of 1 mm from the opposing faces of the pinching members  14   a , and a width of 1.2 mm. The projecting line  14   b  has a varying height position from the vicinity of the approximately middle portion of the pinching member  14   a  toward its rear end to form a curved line as shown in FIG.  4 . 
     The pinching members  14   a  are connected to each other by connection members  16 . Each of the connection members  16  includes fixedly attached portions  16   a  and a connecting portion  16   b . The fixedly attached portions  16   a  are fixedly attached to the rear end and the approximate middle portion of an upper face of each of the pinching members  14   a , respectively. A through hole  16   c  is provided through the fixedly attached portion  16   a  in a direction in which the pinching members  14   a  are opposed to each other. The connecting portion  16   b  is made of a bar-shaped material. After being passed through the through hole  16   c , the connecting portion  16   b  is fixed by a stopper  16   d  via a screw structure so as to connect the pinching members  14   a  to each other. The connection members  16  connects the pinching members  14   a  to each other such that a gap between the projecting lines  14   b  is smaller than a thickness of normally knitted portions of the flattened tubular knitted fabric (a portion other than the Rosso courses). The gap between the projecting lines  14   b  is constant from the tip to the rear end. The connection members  16  can vary the gap between the projecting lines  14   b  by varying the relative fixed position between the fixedly attached portion  16   a  and the connecting portion  16   b.    
     On an upper face of each of the pinching members  14   a , a transfer tool  18  is attached so as to extend from the approximate middle portion to the rear end of the pinching member  14   a . The transfer tool  18  includes driving gear parts  18   a , gears  18   b , and a transfer chain  18   c . Each of the driving gear parts  18   a  includes a rotation axis  20   a  attached rotatably onto an upper surface of the pinching member  14   a  in a vertical direction so as to be arranged inside the fixedly attached portion  16   a  on the rear end. A driving gear  20   b  and a chain gear  20   c  are fixedly attached to the rotation axis  20   a  of the driving gear part  18   a . The driving gear  20   b  mates with a gear (not shown) for transferring the driving power supplied from a driving power source such as a motor so as to be rotated. The driving gears  20   b  mate with each other. The driving gears  20   b  are configured such that, when one of the driving gears  20   b  is rotated by the gear for transferring the driving power from the driving power source, the other driving gear  20   b  is driven by that rotation. Under the driving gear  20   b , the chain gear  20   c  is fixedly attached. The chain gear  20   c  includes teeth to mate with the transfer chain  18   c  so as to move the transfer chain  18   c  in response to the rotation of the driving gear  20   b.    
     The gear  18   b  includes a rotation axis attached rotatably onto an upper surface of the pinching member  14   a  in a vertical direction so as to be situated outside the fixedly attached portion  16   a  at the approximate middle portion of the pinching member  14   a . The gear  18   b  is attached at the same height as the chain gear  20   c  of the driving gear part  18   a.    
     The transfer chain  18   c  includes a circular chain  22   a  provided so as to extend between the gear  18   b  and the chain gear  20   c . The chain  22   a  is provided so as to be parallel to an edge of the pinching member  14   a  when passing through the side where the pinching members  14   a  face each other. Moreover, the chain  22   a  is arranged so as to have a desired distance from the edge of the pinching member  14   a  when passing through the side where the pinching members  14   a  face each other. On an outer periphery of the chain  22   a , gearing teeth  22   b  are provided in an outwardly protruding manner as shown in FIG.  5 . The gearing teeth  22   b  cooperate with the opposing gearing teeth  22   b  so as to stop the tubular knitted fabric with the gearing teeth and transfer the tubular knitted fabric. As a result, the tubular knitted fabric transferred by the transfer chain  18   c  extends from the rear end of the pinching members  14   a  while being stretched in a course direction. 
     On the respective bottom faces of the pinching members  14   a  in the vicinity of their rear ends, knitted fabric guides  23  are attached. The knitted fabric guides  23  hold the tubular knitted fabric which hangs downwardly from the pinching member  14   a  while transferring the tubular knitted fabric. The knitted fabric guides  23  prevent the downwardly hanging tubular knitted fabric from swinging and moving in a lateral direction of the pinching members  14   a . These knitted fabric guides  23  ensure accurate insertion of needles  24   b  described below. 
     In the rear of the end of the pinching transfer section  12  from which the tubular knitted fabric extends, a knitted fabric fixing tool  24  is placed as shown in FIG.  1 . The knitted fabric fixing tool  24  includes a plate material  24   a  having a rectangular plane shape. The plate material  24   a  is attached to a horizontally moving module  26 . The plate material  24   a  is moved by the horizontally moving module  26  from left to right as seen in FIG.  1 . On an upper end of the plate material  24   a , a plurality of needles  24   b  are fixedly attached. As shown in FIG. 6, the needles  24   b  are fixedly attached at an angle slanting in a right direction in FIG. 6 from their fixed bottoms toward the open ends. The knitted fabric fixing tool  24  moves the plate material  24   a  so as to sequentially pierce the needles  24   b  through the tubular knitted fabric immediately before the release of the tubular knitted fabric from the pinching transfer section  12 , thereby fixing the tubular knitted fabric in a stretched state in a course direction. In this preferred embodiment, the needles  24   b  pierce through the course situated three courses below the loose course. The horizontally moving module  26  is configured to be temporarily stopped at the position where all the needles  24   b  pierce through the tubular knitted fabric. 
     Above the knitted fabric fixing tool  24 , a light guiding plate  28  is provided. The light guiding plate  28  includes a metal plate  30 , as shown in FIG.  7 . The metal plate  30  is formed of a thin rectangular plate which is not easily deformed. On a front surface and a rear surface of the metal plate  30 , transparent acrylic plates  34  are provided so as to sandwich the metal plate  30  therebetween, as shown in FIG.  7 . Each of the transparent acrylic plates  34  is formed of a flat plate made of colorless or colored transparent acrylic. The transparent acrylic plate  34  has a gradually reducing thickness toward its side edges and lower edge by tapering. As a result, the side edges and the lower edge of the light guiding plate  28  are formed to have a nearly wedge-like cross-sectional shape. 
     A cold-cathode tube  34  is provided on an upper end of the light guiding plate  28  so as to be opposed to the light guiding plate  28 . The cold-cathode tube  34  radiates a light beam onto an upper end face of the light guiding plate  28 . The light guiding plate  28  irregularly reflects or outputs the light beam which is incident on its upper end face so as to emit light from its lower end face. 
     The light guiding plate  28  is fixedly attached to a lifting module  36  on an upper portion of its side face. The lifting module  36  raises and lowers the light guiding plate  28 . The lowermost position to which the lifting module  36  can be lowered is set such that the lower end of the light guiding plate  28  is in close proximity to the needles  24   b  of the knitted fabric fixing tool  24 . 
     Suction tools (not shown) are provided in the vicinity of the front side and rear side of the knitted fabric fixing tool  24 , respectively. The suction tools serve to broaden an opening of the tubular knitted fabric fixed to the knitted fabric fixing tool  24  by air suction in front and rear directions of the knitted fabric fixing tool  24 . 
     Opening tools  38  are provided in the vicinity of both sides of the knitted fabric fixing tool  24 . Each of the opening tools  38  is provided so as to be driven in an arbitrary direction by a driving module (not shown). The opening tool  38  is configured so as to be stopped at the opening of the tubular knitted fabric by engagement therewith, and further stretches the opening of the tubular knitted fabric which is widely opened by the suction tool, in a direction in which the tubular knitted fabric is flattened. The light guiding plate  28  is lowered by the lifting module  36  so as to be inserted into the opening of the knitted fabric fixed to the knitted fabric fixing tool  24 . By this operation, the light guiding plate  28  illuminates the linking loops whose image is to be picked up by CCD cameras  40  described below. 
     At the front side and the rear side of the light guiding plate  28 , rollers  39  are movably provided. The rollers  39  further stretch the knitted fabric, in which the light guiding plate  28  is inserted, in a wale direction. The rollers  39  rotate while pressing the knitted fabric against the light guiding plate  28  so as to upwardly move the knitted fabric, thereby stretching the knitted fabric in a wale direction. 
     In the vicinity of the front side and rear side of the knitted fabric fixing tool  24 , the CCD cameras  40  are provided. The CCD cameras  40  pick up multiple gray-scale images including images of the linking loops defining the loose course formed in the tubular knitted fabric being fixed to the knitted fabric fixing tool  24 . The multiple gray-scale images picked up by the CCD cameras  40  are input to an image processor  42 . 
     The image processor  42  detects the positions of linking loops of the tubular knitted fabric based on the multiple gray-scale images picked up by the CCD cameras  40 . A pattern matching processing is used to detect the positions of the linking loops. The image of the linking loops, which is obtained by picking up the image of the linking loops of the tubular knitted fabric while the light guiding plate  28  is inserted into the tubular knitted fabric, is stored as a standard pattern in the image processor  42 . The image processor  42  moves while superimposing the standard pattern onto the multiple gray-scale image input from the CCD cameras  40  so as to check whether these two images correlate at the pixel data level or not. The image processor  42  detects a pixel portion that correlates with the standard pattern as a linking loop. The positional information of the linking loops calculated by the image processor  42  is input to a CPU as information for operation control of point needle inserting units  44  which will be described later. 
     The point needle inserting units  44  are arranged at the front and rear of the knitted fabric fixing tool  24  at the position where the tubular knitted fabric is pierced by all the needles  24   b  of the knitted fabric fixing tool  24  so as to temporarily stop the knitted fabric fixing tool  24 . Each of the point needle inserting units  44  includes a point needle position control module  46 . The point needle position control module  46  moves the position of a point needle unit  48  to be attached to the point needle position control module  46  in vertical and horizontal directions with respect to the knitted fabric fixing tool  24 . As the point needle position control module  46 , a combination of a plurality of units of moving modules is provided. Each unit of moving modules is defined by attaching a moving module to a movable section of another moving module such as a ball-screw mechanism, a cylinder mechanism or a conveyor. Such a combination of the moving module units is provided so as to allow the vertical and horizontal movement of an attached object. 
     As described above, the point needle unit  48  is attached to the point needle position control module  46 . The point needle unit  48  houses a plurality of point needles  50  to be inserted through the linking loops as shown in FIG.  8 . The point needle unit  48  includes a sleeve portion  52 . A plurality of through holes  52   a  are arranged horizontally in parallel through the sleeve portion  52 . The point needles  50  are housed in the respective through holes  52   a  so as to be freely pushed/pulled in forward/backward directions. Each of the point needles  50  is made of a wire-like material. The point needle  50  includes a spring stopping portion  50   a  formed by upwardly bending a rear end of the point needle  50 , and thus has an L-shaped configuration. On an upper face of the point needle  50 , a groove  50   b  is provided, into which a sewing machine needle of a sewing machine mechanism described later is to be guided. On an upper face of the sleeve portion  52  arranged above the respective through holes  52   a , spring stopping pieces  52   b  are attached. The number of the spring stopping pieces  52   b  corresponds to the number of the point needles  50 . Each of the spring stopping pieces  52   b  is made of a wire-like material, and has an upwardly oriented open end. A spring  54  is provided in a tensioned state between the spring stopping piece  52   b  and the spring stopping portion  50   a  of the point needle  50 . The point needle  50  is spring-loaded in a forward direction by tension of the spring  54 . A needle stopping plate  56 , which is horizontally arranged immediately above the springs  54 , stops the spring stopping portion  50   a  of the point needle  50 . The point needle  50 , which is spring-loaded in a forward direction by the spring  54 , is arranged so as to project from the sleeve portion  52  by a defined length via the needle stopping plate  56 . 
     Above the sleeve portion  52 , a first point needle control plate  60  is provided through the horizontal movement module so as to be horizontally movable. As the first point needle control plate  60 , a metal plate having a rectangular plane shape having a length equal to a width of the sleeve portion  52  is arranged substantially vertically. The first point needle control plate  60  stops the point needles  50  at the spring stopping portions  50   a  so as to control the movement of the point needles  50 . As the control for the point needles  50  performed by the first point needle control plate  60 , two operations of the point needles  50  are controlled, particularly, a pull-back operation and a pushing operation. In a pull-back operation, after placing the spring stopping portions  50   a  of all the point needles  50  so as to be stopped with the first point control plate  60  for pulling back all the point needles  50  projecting in a forward direction, the first point needle control plate  60  is moved backwardly to pull back the point needles  50 . In a pushing operation, the first point needle control plate  60  is horizontally moved as shown in FIG. 9 to release the stopped spring stopping portion  50   a  from the first point needle control plate  60  so as to push the point needles  50  forward. For the operation for pushing the point needles  50 , there are some cases where only one of the point needles is pushed and the other cases where a plurality of point needles  50  are pushed at a time. 
     A second point needle control plate  64  is horizontally movably provided between the first point needle control plate  60  and the needle stopping plate  56  through the horizontally moving module. As the second point needle control plate  64 , similarly to the first point needle control plate  60 , a metal plate having a rectangular plane shape having a length equal to a width of the sleeve portion  52  is arranged substantially vertically. The second point needle control plate  64  controls the movement of the point needles  50  by stopping the point needles  50  released from the first point needle control plate  60  at the spring stopping portions  50   a . The second point needle control plate  64  is arranged at a position where all the point needles  50  are stopped at the spring stopping portions  50   a  until all the point needles  50  are released from the first point needle control plate  60  so as to be pushed toward the far side. For the point needles  50  which are released from the first point needle control plate  60  so as to be stopped again by the second point needle control plate  64 , the second point needle control plate  64  laterally moves as shown in FIG. 10 so as to release the stopped spring stopping portions  50   a  from the second point needle control plate  64 , thereby further pushing the point needles  50 . For an operation of pushing the point needles  50 , as in the case of the first point needle control plate  60 , there are some cases where only one point needle  50  is pushed and the other cases where a plurality of point needles  50  are pushed at a time. 
     A sewing machine mechanism  66  is provided in the vicinity of the point needle unit  48 . As the sewing machine mechanism  66 , a sewing machine for sewing a knitted fabric, which has variable moving speed of a sewing machine needle and transfer speed of a knitted fabric, is used. The sewing machine mechanism  66  is arranged so as to move in a course direction of a knitted fabric. The sewing machine mechanism  66  functions to link a knitted fabric by using the point needles  50  and to directly sew a knitted fabric without using the point needles  50 . 
     The linking apparatus  10  includes a central control section  68 . The central control section  68  is electrically and electronically connected to all of the image processor  42 , the respective modules included in the linking apparatus  10 , the rollers  39  and the sewing machine mechanism  66 , such that various electric and electronic signals are input to the central control section  68 . The central control section  68  controls the operation of each of the sections based on the input electric and electronic signals. The control by the central control section  68  will be described below in detail in the description of an operation according to this preferred embodiment. 
     Next, an operation of this preferred embodiment will be described. First, a tubular knitted fabric is flattened by an operator such that loops to be linked on the operator side of the tubular knitted fabric approximately coincide with those on the opposite side. The flattened tubular knitted fabric is further stretched in a course direction by the operator such that a portion including the Rosso courses is inserted between the projecting lines  14   b  of the pinching members  14   a . The operator continues inserting the tubular knitted fabric until a rear edge of the inserted tubular knitted fabric is stopped by the gearing teeth  22   b  such that the tubular knitted fabric is transferred. 
     The tubular knitted fabric stopped by the gearing teeth  22   b  is horizontally transferred by the transfer chains  18   c  along the projecting lines  14   b  of the pinching members  14   a . At this point, a portion of the tubular knitted fabric is stretched in a wale direction by the gearing teeth  22   b  and the projecting lines  14   b . A portion of the knitted fabric is stretched in a wale direction in this manner, that is, an upper portion of the tubular knitted fabric is upwardly pulled, such that the linking loops situated immediately below the projecting lines  14   b  are arranged so as to be in contact with the lower edges of the projecting lines  14   b . As a result, along a portion of the projecting lines  14   b  having a linear shape on the rear ends of the pinching members  14   a , the linking loops are regularly arranged in a straight line. 
     The tubular knitted fabric, which continues to be horizontally transferred by the transfer chains  18   c , is sequentially pierced through by the needles  24   b  of the horizontally moving knitted fabric fixing tool  24  for fixation thereof immediately before the tubular knitted fabric is ejected from the pinching members  14   a . When the tubular knitted fabric is fixed over a course direction, the knitted fabric fixing tool  24  is stopped. 
     An opening of the tubular knitted fabric is broadened by the suction tools in forward and backward directions of the knitted fabric fixing tool  24 . 
     The opening tool  38  is inserted through the broadened opening of the tubular knitted fabric and is stopped by engagement therewith, such that the tubular knitted fabric is further stretched in a course direction. 
     The light guiding plate  28  is inserted into the broadened opening of the tubular knitted fabric from above the knitted fabric fixing tool  24 . 
     After insertion of the light guiding plate  28 , the opening tool  38  is released from the opening of the tubular knitted fabric such that the tubular knitted fabric is in close contact with the light guiding plate  28 . 
     The rollers  39  are placed in front and rear of the light guiding plate  28  so as to press the tubular knitted fabric against the light guiding plate  28 . The rollers  39  rotate while pressing the knitted fabric against the light guiding plate  28  so as to upwardly move the knitted fabric, thereby stretching the knitted fabric in a wale direction. At this point, a portion of tubular knitted fabric in the vicinity of the linking loops is illuminated with light emitted from the light guiding plate  28 , from inside of the tubular knitted fabric. 
     Images of the linking loops of the tubular knitted fabric which is stretched in a course direction and a wale direction are picked up by the CCD cameras  40 . The multiple gray-scale images including the images of the linking loops on the front side and the back side, which are picked up by the CCD cameras  40 , are input to the image processor  42  so as to calculate the positions of the linking loops. 
     After the position of the point needle unit  48  is adjusted by the point needle position control module  46 , the first point needle control plate  60  is horizontally moved to insert the point needles  50  through the linking loops on the front side, whose positions are calculated by the image processor  42 . In the case where a plurality of linking loops are positioned such that these loops can be simultaneously pierced through by the point needles  50 , the first point needle control plate  60  is horizontally moved such that a plurality of the point needles  50  are pushed forward. The point needles  50  are not inserted through the linking loops situated in the vicinity of the edges of the tubular knitted fabric in a course direction, but are inserted through all the remaining linking loops. In this preferred embodiment, all the linking loops other than those situated at both extremities of the knitted fabric and adjacent thereto are pierced through the point needles  50 . 
     After all the linking loops on the front side other than those situated at both extremities of the knitted fabric and adjacent thereto are pierced through by the point needles  50 , the position of the point needle unit  48  is adjusted by the point needle position control module  46 . Thereafter, the second point needle control plate  64  is controlled so as to insert the point needles  50  through the linking loops on the back side. 
     Then, the light guiding plate  28  are upwardly pulled out from the tubular knitted fabric. 
     On the back side of the tubular knitted fabric, the sewing machine mechanism  66  is arranged so as to sew the tubular knitted fabric. The sewing machine mechanism  66  sews the tubular knitted fabric such that each of the linking loops, through which the point needles  50  are not inserted, is threaded several times regardless of the position of the linking loops. Then, the sewing machine mechanism  66  threads the linking loops, through which the point needles are inserted, by utilizing the grooves  50   b  formed on the point needles  50 . 
     In this manner, according to this preferred embodiment, an inserting operation of the point needles through the linking loops formed in the tubular knitted fabric is quickly and accurately performed in an automatic manner, allowing the tight linking of the tubular knitted fabric. 
     Although the linking of the tubular knitted fabric has been described in this preferred embodiment, the present invention is not limited thereto. It is possible to link two flat knitted fabrics, which are set in the pinching transfer section so as to be opposed to each other. 
     Moreover, in this preferred embodiment the knitted fabric is fixed to the knitted fabric fixing tool in its stretched state in the pinching transfer section. Alternatively, the knitted fabric may be manually fixed to the knitted fabric fixing tool. 
     Furthermore, although the light guiding plate is used such that a boundary between a knitted portion of the knitted fabric and a portion where no knitting yarn is present becomes clearly visible in this preferred embodiment, the present invention is not limited thereto. Alternatively, a mere plate material having a distinctly different color tone from that of the knitting yarn may be used. 
     Moreover, instead of the light guiding plate, a member for performing uniform surface light emission such as an EL panel or a plasma display can also be used. 
     Although the tubular knitted fabric is brought into close contact with the surface of the light guiding plate in this preferred embodiment, the present invention is not limited thereto. A plate like material may be simply arranged such that a boundary between a knitted portion of the knitted fabric and a portion where no knitting yarn is present becomes clearly visible. 
     Although a single light guiding plate is used as the light guiding plate in this preferred embodiment, the present invention is not limited thereto. A plurality of light guiding plates which are arranged so as to be movable as shown in FIG. 11 may also be used as the light guiding plate of the present invention. In such a case, as shown in FIG. 12, when the light guiding plates are to be inserted into a knitted fabric, it is preferable that the light guiding plates are arranged so as to define a small width for facilitating the insertion. After insertion, the light guiding plates are adjusted so as to be extended in a course direction of the knitted fabric. 
     Furthermore, although a plate material having a rectangular plane shape is used as the knitted fabric fixing tool in this preferred embodiment, the present invention is not limited thereto. A knitted fabric fixing tool formed by fixedly attaching a plurality of needles on an upper edge of the outer periphery of a cylindrical member may alternatively be used as the knitted fabric fixing tool. In this case, it is preferable to use a cylindrical member having the outer periphery having a relatively low curvature such that the needles do not fall out of a knitted fabric when a planar plate such as the light guiding plate is inserted into the knitted fabric. 
     Although the linking loops on the front side and the back side are arranged to be pierced through by a single point needle unit in this preferred embodiment, the present invention is not limited thereto. Alternatively, point needle units may be arranged on the front side and the back side, respectively. In this case, after the point needles are inserted through the linking loops, the tips of the point needles on the both sides, which are inserted through the loops to be linked, are abutted to each other such that the knitted fabric on one side is transferred to the point needle on the other side. 
     Although the rollers are used for stretching the knitted fabric in a wale direction in this preferred embodiment, the present invention is not limited thereto. The knitted fabric may be stretched in a wale direction by using a pinching member as shown in FIG.  13 . In the case where this pinching member is used, after a needle of the knitted fabric fixing tool pierces through the knitted fabric, the knitted fabric is stretched in a wale direction by the needles and projecting lines. In the case where this pinching member is used, the point needles may be pierced through the knitted fabric on the rear end of the pinching member without releasing the knitted fabric from the pinching member. 
     As described above, according to the present invention, a point needle is quickly and accurately inserted through linking loops formed in a knitted fabric in an automatic manner, thereby tightly linking the knitted fabric. 
     The present invention is in no way restricted to the preferred embodiments described above. Instead, various adaptations and modifications may be made with regard to specific patterns of the main line and sub line, the number of layers for layered structures, and other characteristics and features, without departing from the spirit or scope of the invention.