Patent Publication Number: US-9890486-B2

Title: Loop cutting apparatus for circular knitting machines

Description:
FIELD OF THE INVENTION 
     The present invention relates to a loop cutting apparatus for circular knitting machines and particularly to a loop cutting apparatus for circular knitting machines that cuts a pile loop immediately after it is formed. 
     BACKGROUND OF THE INVENTION 
     Fabrics with fine pile provide the look and touch feel of furs or pelts, hence are appealing to consumers. Conventional circular knitting machines that can knit fine plush fabrics, like U.S. Pat. Nos. 7,146,829 and 7,127,920, include a cylinder with a plurality of latch-less needles located thereon, a needle dial contained a plurality of latch needles and a plurality of sinkers. The sinkers are located on a sinker holder circulating the cylinder. Each sinker has a cutter at the front end. The sinker is driven by a cam on the sinker holder to slide toward the cylinder, and the cutter on the sinker severs a pile loop formed by a yarn to form a pile. References of other types of circular knitting machines that can knit fine pile fabrics also can be found in PRC patents Nos. CN201136946 and CN201546011, Germany patent No. DE19518490, U.S. Pat. Nos. 4,592,212 and 6,094,944. However, the conventional circular knitting machines that can produce fine pile fabrics require to add a sinker holder around the cylinder, hence significantly increase the total size of the circular knitting machines and the number of components required. As a result, the circular knitting machines are complex in structure, and fabrication and assembly also are more difficult. 
     Aside from severing the pile loops via the sinkers, the circular knitting machine can also be equipped with blade-contained needles to cut the pile loops. For instance, R.O.C. patents Nos. 205255 and 208294 disclose a pile cutting apparatus. It has multiple sets of vertical cutter needles, horizontal knitting needles and horizontal sinkers located on a cylinder of a knitting machine. These three sets of elements can be moved in collaborated displacements so that the knitting needles can pick up yarns to form loops in cutter needle slots, then the sinkers move forwards to press the surface of the loops and the cutter needles are moved upwards to the apex, and the blades at the lower end of the slots sever the pile loops. However, in order to push the cutter needle to the apex its travel path has to increase, that means that the time to cut each pile loop is longer, that adversely affects the knitting efficiency of the fine pile fabrics. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to solve the problems of the conventional knitting machines for knitting fine pile fabrics of requiring an additional and complex pile loop cutting apparatus and lower efficiency in knitting the fine pile fabrics. 
     To achieve the foregoing object the present invention provides a loop cutting apparatus for circular knitting machines adopted for use on a circular knitting machine. The circular knitting machine has a circular cylinder and a yarn conveying system to provide a plurality of yarns to the circular cylinder. The circular cylinder has a plurality of first needle slots parallel with the axis of the circular cylinder and a plurality of knitting needles located in the first needle slots and movable independently. The loop cutting apparatus includes an upper needle dial and a plurality of yarn cutting needle sets. The upper needle dial has a plurality of second needle slots radially centered about the axis of the circular cylinder and corresponding to the first needle slots. Each yarn cutting needle set includes a first cutter needle and a second cutter needle in parallel with the first cutter needle and movable against the first cutter needle in a first yarn cutting displacement thereof. The first cutter needle is located between two neighboring knitting needles. The first cutter needle has a yarn holding section leaned by the yarn and collaborated with the abutting knitting needles at two sides to pick up and draw the yarn to form a pile loop and a first cutter section connected to the yarn holding section. The second cutter needle has a second cutter section staggered against the first cutter section in the first yarn cutting displacement to cut the pile loop. 
     In one embodiment the first cutter section of the first cutter needle inclines away from the knitting needles, and the second cutter section of the second cutter needle is bent towards the first cutter needle. 
     In another embodiment the first yarn cutting displacement includes a first middle displacement with a closed yarn cutting space among the first cutter section, second cutter section and yarn holding section to hold the yarn. 
     In yet another embodiment the first cutter section inclines towards the knitting needles, and the second cutter section is bent towards the first cutter needle. 
     In yet another embodiment the first yarn cutting displacement includes a second middle displacement with an open yarn cutting space between the first cutter section and second cutter section that has an upper opening to hold the yarn. 
     In yet another embodiment the first cutter needle includes a first distal end towards the knitting needles that contains the first cutter section. 
     In yet another embodiment the first cutter needle has a first yarn laying displacement moved towards the knitting needles to lean on the yarn. 
     The invention further provides a loop cutting apparatus for circular knitting machines adopted for use on a circular knitting machine. The circular knitting machine has a circular cylinder and a yarn conveying system to provide a plurality of yarns to the circular cylinder. The circular cylinder has a plurality of first needle slots parallel with the axis of the circular cylinder. The loop cutting apparatus includes an upper needle dial on the circular cylinder and a plurality of yarn cutting needle sets. The upper needle dial has a plurality of second needle slots radially centered about the axis of the circular cylinder corresponding to the first needle slots and a plurality of knitting needles located in the second needle slots and movable independently. The yarn cutting needle sets are located in the first needle slots. Each yarn cutting needle set includes a first cutter needle and a second cutter needle in parallel with the first cutter needle and movable against the first cutter needle in a second yarn cutting displacement. The first cutter needle is located between two neighboring knitting needles. The first cutter needle has a yarn holding section leaned by the yarn and collaborated with the abutting knitting needles at two sides to pick up and draw the yarn to form a pile loop and a first cutter section connected to the yarn holding section. The second cutter needle has a second cutter section staggered against the first cutter section in the second yarn cutting displacement to cut the pile loop. 
     The yarn cutting apparatus of the invention can have the yarn cutting needle sets selectively mounted onto the circular cylinder or the upper needle dial. Through the movable first cutter needle and second cutter needle in each yarn cutting needle set, the yarn of the pile loop is in contact at the same time with the first cutter section of the first cutter needle and second cutter section of the second cutter needle, and is shorn at two sides to sever the pile loop. Compared with the conventional circular knitting machines for knitting fine pile fabrics, the invention does not need an extra sinker holder to guide the sinkers and also does not need to extend the travel path of the cutter needle, thus space utilization of the circular knitting machine is more efficient and the efficiency of knitting the fine pile fabrics also improves. 
     The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a holistic view of an embodiment of the invention adopted on a circular knitting machine. 
         FIG. 2  is a perspective view of an embodiment of the loop cutting apparatus of the invention. 
         FIG. 3  is a fragmentary perspective view of an embodiment of the loop cutting apparatus of the invention. 
         FIG. 4  is a perspective view of an embodiment of the yarn cutting needle set of the invention. 
         FIGS. 5A through 5D  are schematic views of an embodiment of the yarn cutting needle set of the invention in loop cutting processes. 
         FIGS. 6A through 6D  are schematic views of another embodiment of the yarn cutting needle set of the invention in loop cutting processes. 
         FIGS. 7A through 7D  are schematic views of yet another embodiment of the loop cutting apparatus of the invention in loop cutting processes 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Please refer to  FIGS. 1 through 4  for an embodiment of a loop cutting apparatus of the invention adopted on a circular knitting machine. The loop cutting apparatus  20  of the invention is used on a circular knitting machine  10  to knit fine pile fabrics which have a pile surface and a ground fabric to hold the pile surface. The circular knitting machine  10  has a circular cylinder  11  with an axis A and a yarn conveying system  14  to provide a plurality of yarns to the circular cylinder  11 . The yarns include at least one first yarn  51  (generally called pile yarn) to form the annular yarn surface and at least one second yarn  52  (generally called ground yarn) to form the ground fabric. The circular cylinder  11  has a plurality of first needle slots  111  parallel with the axis A of the circular cylinder  11  and a plurality of knitting needles  112  located in the first needle slots  111  and movable independently. In this invention the knitting needles  112  can be moved and controlled through a lower cam set  15  at the periphery of the circular cylinder  11  like the conventional techniques do. The lower cam set  15  has a corresponding control track (not shown in the drawings) corresponding to a protrusion  113  of each knitting needle  112  (also referring to  FIG. 5A ). The lower cam set  15  can move against the circular cylinder  11 , and the protrusion  113  is driven by the control track so that the knitting needle  112  also is moved in one first needle slot  111 . The loop cutting apparatus  20  includes an upper needle dial  21  located on the circular cylinder  11  and a plurality of yarn cutting needle sets located on the upper needle dial  21 . The upper needle dial  21  has a plurality of second needle slots  211  radially centered about the axis A of the circular cylinder  11  corresponding to the first needle slots  111 . Each yarn cutting needle set is held in one second needle slot  211 . 
     Each yarn cutting needle set includes a first cutter needle  22  and a second cutter needle  23  parallel with the first cutter needle  22  and movable against the first cutter needle  22  in a first yarn cutting displacement P thereof. The first cutter needle  22  has a first distal end  221  towards the knitting needles  112  and a yarn holding section  222  leaned by the first yarn  51 , a first cutter section  223  located at the first distal end  221  and connected to the yarn holding section  222  and a first control bump  224 . The second cutter needle  23  has a second cutter section  231  staggered against the first cutter section  223  in the first yarn cutting displacement P and a second control bump  232 . In this invention the first cutter needle  22  and second cutter needle  23  can be moved and controlled by an upper cam set  24  on the upper needle dial  21  like in the conventional techniques do. The upper cam set  24  has a plurality of control tracks (not shown in the drawings) corresponding to the first control bump  224  and second control bump  232 . When the upper cam set  24  is moved against the upper needle dial  21  the first control bump  224  and second control bump  232  are driven by the control tracks to move the first cutter needle  22  and second cutter needle  23 . 
     In this embodiment, referring to  FIGS. 3, 4 and 5A , the first cutter section  223  of the first cutter needle  22  inclines away from the knitting needles  112 , and the first cutter section  223  and yarn holding section  222  form a first included angle α smaller than 90 degrees between them. The second cutter section  231  of the second cutter needle  23  is bent towards the first cutter needle  22 , even can be bent in contact with the first cutter needle  22 . 
     Please refer  FIGS. 5A through 5D  for an embodiment of the loop cutting apparatus of the invention in loop cutting processes. First, the yarn conveying system  14  guides the first yarn  51  and second yarn  52  to the circular cylinder  11 ; the first cutter needle  22  is controlled by the upper cam set  24  to move towards the knitting needles  112  to proceed a first yarn laying displacement S 1 ; the first yarn  51  leans on the yarn holding section  222  of the first cutter needle  22  as shown in  FIG. 5A ; the second yarn  52  passes through below the yarn holding section  222 . Since each first cutter needle  22  is located between two abutting knitting needles  112 , when the knitting needles  112  are driven by the lower cam set  15  to move downwards as shown in  FIG. 5B , the first yarn  51  leaned on the yarn holding section  222  and the second yarn  52  located below the yarn holding section  222  are picked up together by the knitting needles  112  at the two sides; because of the distance between the yarn holding section  222  and the first yarn  51  picked up by the knitting needles  112  a pile loop  53  is formed, and the second yarn  52  winds around and holds the bottom of the pile loop  53 ; next, the second cutter needle  23  is controlled by the upper cam set  24  to proceed the first yarn cutting displacement P. During the second cutter needle  23  is in the first yarn cutting displacement P, namely, the first cutter section  223  and second cutter section  231  start in a staggered manner, as shown in  FIG. 5C , the first cutter section  223 , second cutter section  231  and yarn holding section  222  form a first middle displacement P 1  with a closed yarn cutting space  30  among them to hold the first yarn  51 . When the second cutter needle  23  continuously proceeds the first yarn cutting displacement P, the first cutter section  223  and second cutter section  231  are in contact respectively to two sides of the first yarn  51  to form two-side cutting like scissors. After the second cutter needle  23  has finished the first yarn cutting displacement P to sever the pile loop  53  a pile  54  is formed as shown in  FIG. 5D . In this embodiment first yarn  51  is held in the closed yarn cutting space  30  formed among the first cutter section  223 , second cutter section  231  and yarn holding section  222 , hence can be securely shorn to form the pile  54 . 
     Please refer to  FIG. 6A  for another embodiment of the invention. The first cutter section  223   a  of the first cutter needle  22  inclines towards the knitting needles  112 , and the first cutter section  223   a  and yarn holding section  222  form a second included angle β greater than 90 degrees between them. The second cutter section  231   a  of the second cutter needle  23  is bent towards the first cutter needle  22 , or even bent in contact with the first cutter needle  22 . 
     Please refer  FIGS. 6A through 6D  for the another embodiment of the loop cutting apparatus of the invention in loop cutting processes. First, the yarn conveying system  14  guides the first yarn  51  and second yarn  52  to the circular cylinder  11 ; the first cutter needle  22  is controlled by the upper cam set  24  to move towards the knitting needle  112  to proceed a first yarn laying displacement S 1 ; the first yarn  51  leans on the yarn holding section  222  of the first cutter needle  22  as shown in  FIG. 6A ; the second yarn  52  passes through below the yarn holding section  222 . Since each first cutter needle  22  is located between two abutting knitting needles  112 , when the knitting needles  112  are driven by the lower cam set  15  to move downwards as shown in  FIG. 6B , the first yarn  51  leaned on the yarn holding section  222  and the second yarn  52  located below the yarn holding section  222  are picked up together by the knitting needles  112  at the two sides; because of the distance between the yarn holding section  222  and the first yarn  51  picked up by the knitting needles  112  a pile loop  53  is formed, and the second yarn  52  winds around and holds the bottom of the pile loop  53 ; next, the second cutter needle  23  is controlled by the upper cam set  24  to proceed the first yarn cutting displacement P. During the second cutter needle  23  is in the first yarn cutting displacement P, namely, the first cutter section  223  and second cutter section  231  start in a staggered manner, as shown in  FIG. 6C , the first cutter section  223 , and second cutter section  231  form a second middle displacement P 2  with an open yarn cutting space  40  between them with an upper opening to hold the first yarn  51 . When the second cutter needle  23  continuously proceeds the first yarn cutting displacement P, the first cutter section  223  and second cutter section  231  are in contact respectively to two sides of the first yarn  51  to form two-side cutting like scissors. After the second cutter needle  23  has finished the first yarn cutting displacement P to sever the pile loop  53  a pile  54  is formed as shown in  FIG. 6D . 
     Please refer to  FIG. 7A  for yet another embodiment of the invention. The upper needle dial  21  includes a plurality of knitting needles  212  in the second needle slots  211  that are movable independently. The circular cylinder  11  has a plurality of yarn cutting needle sets located in the first needle slots  111 . Each yarn cutting needle set includes a first cutter needle  12  and a second cutter needle  13  parallel with the first cutter needle  12  and movable upward against the first cutter needle  12  in a second yarn cutting displacement Q. The first cutter needle  12  has a first distal end  121  towards the knitting needles  112  and a yarn holding section  122  leaned by the first yarn  51 , a first cutter section  123  located at the first distal end  121  and connected to the yarn holding section  122  and a first control bump  124 . The second cutter needle  13  has a second cutter section  131  staggered against the first cutter section  123  in the second yarn cutting displacement Q and a second control bump  132 . In this embodiment the first cutter needle  12  and second cutter needle  13  can be moved and controlled by a lower cam set  15  at the periphery of the circular cylinder  11  like in the conventional techniques. The lower cam set  15  has control tracks (not shown in the drawings) corresponding to the first control bump  124  and second control bump  132 . Movements of the knitting needles  212  can be controlled by the upper cam set  24  on the upper needle dial  21 . The upper cam set  24  has a plurality of control tracks (not shown in the drawings) corresponding to the bump  213  of the knitting needles  212 . 
     Please refer  FIGS. 7A through 7D  for the yet another embodiment of the loop cutting apparatus of the invention in loop cutting processes. First, the yarn conveying system  14  guides the first yarn  51  and second yarn  52  to the circular cylinder  11 ; the first cutter needle  12  is controlled by the lower cam set  15  to move towards the knitting needle  112  and upward to proceed a second yarn laying displacement S 2 ; the first yarn  51  leans on the yarn holding section  122  of the first cutter needle  12  as shown in  FIG. 7A ; the second yarn  52  passes through below the yarn holding section  122 . Since each first cutter needle  12  is located between two abutting knitting needles  212 , when the knitting needles  212  are driven by the upper cam set  24  to move leftward as shown in  FIG. 7B , the first yarn  51  leaned on the yarn holding section  122  and the second yarn  52  located below the yarn holding section  122  are picked up together by the knitting needles  212  at two sides; because of the distance between the yarn holding section  122  and the first yarn  51  picked up by the knitting needles  212  a pile loop  53  is formed, and the second yarn  52  winds around and holds the bottom of the pile loop  53 ; next, the second cutter needle  13  is controlled by the lower cam set  15  to proceed the second yarn cutting displacement Q. During the second cutter needle  13  is in the second yarn cutting displacement Q, namely, the first cutter section  123  and second cutter section  131  start in a staggered manner, as shown in  FIG. 7C , the first cutter section  123 , second cutter section  131  and yarn holding section  122  form a first middle displacement Q 1  with a closed yarn cutting space  30  among them to hold the first yarn  51 . When the second cutter needle  13  continuously proceeds the second yarn cutting displacement Q, the first cutter section  123  and second cutter section  131  are in contact respectively to two sides of the first yarn  51  to form two-side cutting like scissors. After the second cutter needle  13  has finished the second yarn cutting displacement Q to sever the pile loop  53  a pile  54  is formed as shown in  FIG. 7D . 
     The loop cutting apparatus of the invention can have the yarn cutting needle sets selectively located on the circular cylinder or the upper needle dial. Through the first cutter needle and second cutter needle of each yarn cutting needle set that are movable against each other the first yarn of the pile loop can be in contact at the same time with the first cutter section of the first cutter needle and second cutter section of the second cutter needle, and the pile loop can be securely severed from two sides to form the fine pile without the problem of forming some non-severed pile loops. Compared with the conventional circular knitting machines for knitting fine pile fabrics the invention does not need an extra sinker holder to guide the sinkers, and also does not need to extend the travel path of the bladed knitting needles, thus space utilization the circular knitting machines is more efficient and knitting efficiency of the fine pile fabrics also improves.