Patent Publication Number: US-7707953-B2

Title: Gripper device for tufting machine

Description:
This Application is a U.S. Utility Patent Application which claims priority from European Application No. 06 003 769.4, filed Feb. 24, 2006, the complete disclosure of which is incorporated herein by reference. 
   The invention relates to a gripper device for tufting machines as are used, in particular, in carpet manufacturing. 
   Frequently, tufting processes are used in the manufacture of carpets. Referring to such tufting methods, a flat support material (so-called “backing”) is provided with a pile. The pile consists of a large number of individual pieces of yarn which are punched by tufting needles—row by row—through the backing. In so doing, the backing is gradually advanced stitch by stitch underneath a row of needles. The thusly formed loops are temporarily held by a gripper in order to be maintained during the reverse stroke of the needles. If the loops remain unharmed, looped pile is formed. If the loops are cut, cut pile is formed. 
   In order to produce structured carpets having a pattern, it is frequently desirable to use one and the same machine, to be able to produce—possibly by enabling appropriate knives and grippers—uncut, as well as cut, loops, i.e., to be able to create looped pile, as well as cut pile. Referring to this, U.S. Pat. No. 4,185,569 discloses a tufting machine comprising a loop gripper having a closing member. This closing member is pivotally supported on the loop gripper, whereby, in a first pivot position, said closing member—together with the gripper—defining an internal gripper space that is closed toward the outside. In a second pivot position, said closing member is pivoted away by a free end of the gripper, in order to thus clear an entrance into the internal space. In its internal space, the gripper has a straight cutting edge, which is disposed to be able to cut picked up loops by means of a knife in order to be able to produce cut pile. On its reverse side, the closing member is provided with a flat cutout that accepts loops which are not to be cut. The closing member can be adjusted by means of an adjustment device in such a manner that the entrance into the internal gripper space is cleared or not, so that the loops either move into this internal space or (if the entrance is not cleared) are temporarily picked up by the closing member. In the first case, the loops are cut on the cutting edge of the gripper. Cut pile is being created. In the second case, the loops are held by the gripper and then thrown off. Looped pile is being created. 
   Referring to this gripper device, the target-specific production of cut pile and of looped pile on the same backing and in alternating sequence is possible. However, pile damage may occur when the pile yarn is pinched between the closing member and the gripper. Furthermore, the gripper interacts with the needle, on the one hand, and with the knife, on the other hand. If the gripper is too hard, it wears out the needle. If it is too soft, it is worn down by the knife. It is difficult to find a compromise. If the yarn tension is centrally pre-specified, the configuration of the gripper and the closing member, as well as the size of the cut pile and the size of the looped pile, are pre-specified. Different pile sizes are formed, which can result in undesirable differences of pile height during the alternation between looped and cut pile in the same carpet. 
   Considering this, it is the object of the invention to eliminate one or more of the aforementioned difficulties. 
   This object is attained with the gripper device in accordance with the invention: 
   In accordance with the invention, the gripper device comprises a gripper that is divided into two sections. A first gripper section is used to produce looped pile. This gripper section picks up the loops in looped pile mode. A second gripper section is used to produce cut pile. It picks up the loops in cut pile mode. Consequently, the loops are held by the gripper during the operating cycle that is decisive in terms of defining loop size, i.e., during the return stroke of the needles, whereby the gripper section for the looped pile and the gripper section for the cut pile can be respectively located in such a position relative to the gripper that the desired pile height is produced. The height offset is measured at a right angle with respect to the gripper edges. The gripper sections may be arranged on, or provided on, the gripper relative to each other, i.e., offset, or not offset, with respect to height. In so doing, differences in pile height, which result in the production of cut pile by cutting the loops, can be compensated for. It is possible to manufacture carpets, in which the pile height of the looped pile and the pile height of the cut pile are the same, and also carpets, in which the cut pile is higher or even lower than the looped pile. 
   The gripper edges of the two gripper sections are preferably straight and are located on a common (vertical) plane. Furthermore, referring to an advantageous embodiment, said gripper sections are arranged parallel to each other, and are offset with respect to each other in longitudinal direction of the gripper edges, as well as in pile height direction. Furthermore, the gripper edges are preferably arranged parallel to an adjustment device of the gripper opposite the modular block which supports or holds the gripper. In so doing, the gripper sections are arranged relative to each other, preferably at a distance, in particular at a distance measured in longitudinal direction of the gripper edges. They may be separated from each other by a step. In addition, this step may have a projection that is also referred to as the gripper hook. This projection is disposed to prevent the pile yarn from inadvertently sliding from one gripper section onto the other. 
   The gripper edges are preferably rounded transversely to their longitudinal direction and are thus blunt to the extent that a pile yarn sliding along the gripper edge is not harmed. This careful handling of the pile yarn results in the high quality of the looped pile that is to be produced. 
   Preferably, the gripper is adjustably supported on a guide member, whereby said gripper is connected to an adjustment unit. By means of the adjustment unit, the gripper can be moved into a retracted position, in which it is activated—via its first gripper section—to produce the looped pile. In addition, the adjustment unit can be used to position said gripper in an forward position, which is at a distance from said gripper&#39;s free end and is located behind said gripper&#39;s step or behind said gripper&#39;s hook, so that the loops are no longer thrown off, but are moved to a cutting edge. The cutting edge may be provided on the guide member that is associated with a knife. By providing the cutting edge on the guide member it has been advantageously achieved that the gripper only comes into frictional contact with the tufting needle, but not with the knife. In view of its wear characteristics, the gripper can thus be adjusted to the interaction with the tufting needle. In contrast, the guide member can be adjusted—regarding its material and wear characteristics—to the knife. Consequently, the gripper and the guide member can each be made in one piece, and without any seams, of any optimal material, for example, softer steel for the gripper and harder steel for the guide member. 
   Several guide members together may be set in one module. In so doing, it is possible to arrange the guide members interchangeably or to hold them in the module joined in a material-to-material manner. For example, this can be achieved by cementing, casting—in case of metal or non-metal materials, by soldering, etc. It is also possible to mount the guide members directly to the bar of a tufting machine. 
   Additional details of advantageous embodiments or developments of the invention are the subject matter of the drawings, the description or of the claims. 

   
     The drawings show an exemplary embodiment of the invention. They show in 
       FIG. 1  a perspective illustration of a tufting needle and of a modular block of a tufting device; 
       FIG. 1   a  a highly simplified plan view of the arrangement of a gripper device relative to the L-tufting needle; 
       FIG. 2  a perspective view of a guide member for the modular block in accordance with  FIG. 1 ; 
       FIG. 3  a perspective illustration of a gripper for the modular block in accordance with  FIG. 1 ; 
       FIG. 4  a schematic side view of the modular block with the guide member and the gripper in a first operating mode in an operative position when a pile loop is being picked up; 
       FIG. 5  the device in accordance with  FIG. 4  in the first operating mode when the loop is being thrown off while the looped pile is being produced; 
       FIGS. 6 and 7  different schematic views of operative positions of the modular block in accordance with  FIG. 1 , comprising a gripper device that is a mirror image—with respect to a vertical plane—of the configuration in accordance with  FIG. 1 , in a second mode of operation with said gripper pushed forward in order to produce cut pile; 
       FIG. 6   a  a detail of a part of the side view of  FIGS. 6 and 7 ; and, 
       FIG. 7   a  a highly simplified plan view of the arrangement of a gripper device relative to the tufting needle, with an R-tufting needle. 
   

     FIG. 1  shows a modular block  1  associated with a tufting machine, a larger number of such blocks being used in a tufting machine. Such modular blocks are mounted next to each other to a bar that extends in a direction transverse to the direction of movement of the carpet to be manufactured, and preferably extends under said carpet. In addition, the tufting machine comprises a bar with tufting needles, one of these tufting needles  2  being shown in  FIG. 1 . These needles are used to punch pile yarn through the backing. The modular blocks are disposed to hold the thusly produced loops and release them unharmed or, optionally, cut said loops. 
   The modular block  1  comprises a base body  3  having abutment surfaces  4 ,  5 , which are assigned to the bar. A bore  6  is used to mount the modular block  1  to the bar. 
   On its side facing the backing ( FIG. 1 , top), the modular block is provided with grooves  7 ,  8 ,  9  that are in parallel alignment with respect to each other and, in which case, respectively one gripper device  10  is seated in said grooves. Each gripper device  10  consists of a gripper  11  and of a guide member  12 . Whenever the guide member  12  is immovably connected to the modular body  3 , the gripper  11  can be moved against the guide member  12  and thus against the modular block  1 . In the preferred exemplary embodiment, the gripper  11  is supported such that it can be shifted in linear direction against the guide member  12 . 
     FIG. 1  and  FIG. 1   a  show a knife  47  that has a cutting edge  48  and interacts with the guide member  12 —as will be explained later—in order to produce cut pile. The guide member  12  and the knife  47  form a cutting device. The tufting needle shown in  FIG. 1   a  is an L-tufting needle, i.e., its chamfer is on left side when the groove of the needle faces downward, i.e., on the right side of  FIG. 1   a.    
     FIGS. 2 and 3  show the gripper  11  and the guide member  12  in a perspective opposite the viewing direction of  FIG. 1 . The guide member  12  extends from a flat body having a substantially uniform thickness, whereby this thickness corresponds approximately to the width of one of the grooves  7  through  9 . An upper section has a flat, wide groove  13  that extends along the entire length of the guide member  12 , said groove preferably having a plane groove bottom  14  and two parallel flanks  15 ,  16  facing each other. The groove  13  represents a guide for the gripper  11 , said gripper having a cross-section that substantially corresponds to the cross-section of the groove  13  in such a manner that said gripper is held in an easily movable manner, and with minimal play, in longitudinal direction of the groove parallel to the groove bottom  14  and to the flanks  15 ,  16 . 
   Underneath the groove  13 , the guide member  12  has a holding section  17  that is provided with two bores  18 ,  19 . The bores  18 ,  19  are in alignment with corresponding bores  20 ,  21 , which are provided in the modular body  3  and which extend through the grooves  7 ,  8 ,  9 . 
   Adjoining the holding section  17 , below the groove  13 , is a section  22 , which can have the shape of a wedge such that said section has an edge  23  aligned parallel to the groove  13 . The edge  23  is preferably inclined at an acute angle with respect to the groove  13 . The free space created by the arrangement of the section  22  at an acute angle is necessary to permit the knife  47  of the adjacent gripper device  10 , which is arranged diagonally with respect to the guide member  12 , to perform its advance movement without collision. The diagonal arrangement of the knife  47  helps to create sufficient force for the cutting operation. The section  22  is essentially limited in a rectangular direction. Said section may have on its front end—away from the holding section  17 —an edge  24  that is aligned at a right angle with respect to the groove  13 . Alternatively, the edge  24  may be aligned diagonally with respect to the groove  13 . 
   Above the edge  24 , the guide member  12  is cut out in such a manner that only an upper portion of the groove bottom  14  and the flank  15  remain. The flank  16  is missing in this region. An upper edge  25 , which forms the flank  15  on the groove side, ends in a wedge  26  on the end side. Due to the wedge-shaped chamfer at the end of the guide member  12 , the groove bottom  14  ends in a more or less sharp edge  27 . The cutting edge  28  is formed by the border or the edge  28  of the groove bottom  14 , said border or said edge extending at a right angle thereto. The cutting edge  28  is formed by the groove bottom  14  and by an edge  50  ( FIG. 6   a ), said cutting edge being arranged at an angle α of 90 degrees with respect to said groove bottom and being oriented parallel to the flank  16 . As is obvious from  FIGS. 6 and 7 , the rear side of the guide member  12  forms the abutment surface for the knife  47  in the region of the cutting edge  28 . The cutting angle α may be varied as a function of the location of the edge  50 . An arrangement of the edge  50  at a 90-degree angle with respect to the cutting edge  28 , results in a cutting angle of 0 degrees. An arrangement of the edge  50  at an angle smaller than 90 degrees results in an acute angle of the cutting edge  28 . 
   The gripper  11  is designed as a slider, which has, on its end  29 , a first gripper section  30  for picking up loops and, at a distance therefrom, a second gripper section  31 . The gripper sections  30 ,  31  are preferably arranged at a distance with respect to one direction of movement, said direction being indicated by an arrow  32  in  FIG. 1  and being pre-specified by the longitudinal groove direction of the groove  13 . Furthermore, a step  33  is preferably provided between the gripper sections  30 ,  31 . In addition, this step may end in an extension  34  that is also referred to as a hook. The step  33  and the extension  34  prevent an undesired transfer of a loop from one gripper section  30 ,  31  to the other. 
   Each of the gripper sections  30 ,  31  has—on the same side of the gripper  11  (in  FIG. 1  on the lower side)—a gripper edge  35 ,  36  that is designed to hold the pile yarn loops. The gripper edges  35 ,  36  are straight in the direction of movement (arrow  32 ) and parallel thereto. However, these gripper edges are curved or rounded in lateral direction in order to not harm the pile yarn of the picked up loop. In addition, the gripper edges  35 ,  36  are rounded on the end  29 , on the hook  34 , on the step  33 , as well as on the edge end  37  of the gripper edge  36 . Moreover, the gripper  11 , which is to be set like a slider in the groove  13 , is limited by the straight narrow sides  38 ,  39 , between which said gripper has essentially plane flat sides. On its end  29  away from the end  40 , the gripper  11  is provided with a cutout  41  that is used for the attachment of an adjustment unit  42 , as schematically indicated in  FIG. 4 . This adjustment unit may be seated on a schematically indicated bar  43  that also supports the modular block  1 . 
   The gripper device  10  described so far operates as follows: 
   In a first mode of operation as illustrated by  FIGS. 4 and 5 , the modular block  1  and the gripper device  10  are used to produce a carpet with looped pile. To achieve this, each tufting needle  2  of the needle bar punches one pile yarn  44  through the backing  45 , in which case the tufting needles  2  are congruently arranged behind each other, as in  FIG. 4 . Applications using so-called staggered modules are also known. These comprise two rows of tufting needles  2 , which are spaced apart, and in which case the tufting needles of each row, again, are congruently arranged behind each other. The adjustment unit  42  is used for the selection of the gripper  11  in order to produce looped pile and/or cut pile. This means that, within a module  1 , each gripper  11  can be controlled individually by the adjustment unit  42 . Within the range of a module  1 , it is possible to produce loop goods, as well as velour goods. In order to produce looped pile, the adjustment unit  42  adjusts the gripper  11  in its retracted position in accordance with  FIG. 4 . The gripper  11  remains in this position with respect to the modular block  1  during the entire tufting operation for the production of looped pile.  FIG. 4  shows an example of a tufting machine, in which the gripper  11  is set against the direction of movement of the backing  45 , as indicated by an arrow  46 . Once the tufting needle  2  has punched the pile yarn  44  through the backing  45 , the bar  43  is moved, so that the gripper section  30  of the gripper  11  punches between the tufting needle  2  and the pile yarn  44 . As long as the tufting needle  2  is retracted, the bar  43  remains in the position as illustrated in  FIG. 4 , so that the forming loop is held in place. 
   During the next step the bar  43  in  FIG. 4  is moved to the right, so that the gripper section  30  throws off the just now still retained loop  49 , as illustrated in  FIG. 5 . In so doing, the bar  43  can be moved in linear direction or, as illustrated, perform a pivoting movement. The backing  45  is advanced by one stitch width in the direction of the arrow  46 , and the tufting needle  2  again begins—as illustrated—to punch the pile yarn  44  through the backing  45 . 
   As a whole, this process repeats itself continuously, in which case—as long as looped pile is to be produced—the adjustment unit  42  holds the gripper  11  in its retracted position. 
     FIGS. 6 and 7  illustrate the operation of the above-described device for the production of cut pile. The adjustment unit  42  has shifted the gripper  11  into its forward position. Therefore, the gripper projects from the guide member  12  considerably farther than before. Referring to the axial direction of movement of the gripper  11 , the gripper section  31  is now approximately at the point—with respect to the bar  43  or the modular block  1 —at which the gripper section  30  was positioned beforehand, in accordance with  FIGS. 4 and 5 . Consequently, as is obvious from  FIG. 6 , when the loop is caught when the gripper  11  is inserted between the tufting needle  2  and the pile yarn  44 , the gripper section  31  moves into the immediate vicinity of the tufting needle  2 . Thus the forming stitch is held behind the step  33 . If the needle  2  is retracted, this stitch cannot slide back onto the first gripper section  30 . This also applies when the bar  43 , as shown by  FIG. 7 , performs its return stroke. The step  33  and the projection  34  secure the loops on the gripper section  31 . 
   During the subsequent operating sequences, the loops, as is again obvious from  FIG. 6 , gradually arrive on the guide member  12 , whereby they move from the gripper edge  36  onto the cutting edge  28  of the guide member  12 . This cutting edge  28  forms a cutting gap with the knife  47  and its cutting edge  48 . The knife  47  may move onto the loops or stitches, so that the cutting gap is closed and the loop is cut. Thus, cut pile made of cut stitch loops is produced. So-called velour goods are being produced. 
   It is possible to switch between the operating modes of “production of looped pile” and “production of cut pile” by adjusting the gripper  11  in longitudinal direction with the use of the adjustment unit  42 . This can be done individually for each gripper  11  of the bar  43 . The bar  43  carries out uniform movements during the production of looped pile and during the production of cut pile. The extension  34  prevents the retracted gripper  11  from allowing loops of the gripper section  30  to move to the gripper section  31  or to the guide member  12 . Such loops are thus protected from the knife  47 . These loops move above the modular block  1  past said knife. In contrast, the pushed forward gripper  11  prevents the picked up loops from being thrown off, said loops being seated on the second gripper section  31  and being transported to the guide device  12  and its cutting edge  23 . The cutting device consists of the guide member  12  and the knife  47 . 
   As a result of the appropriate design of the height offset between the gripper edges  35 ,  36  as is shown by  FIG. 3 , the desired pile height (or pile length) can be individually adjusted separately for looped pile and for cut pile. Correspondingly, desired changes of the pile height and the pile height differences can be achieved by interchanging the gripper  11 . In addition, the gripper  11  and the guide member  12 —being wearing parts—can be replaced separately. 
   The inventive gripper device for a tufting machine comprises a gripper device  10 . The gripper device  10  contains a gripper  11  and a guide member  12  that is provided with a cutting edge  23 . The gripper  11  has two gripper sections  30 ,  31  that are at a distance from each other in the direction of movement and are preferably separated from each other by a step  33  and/or by an extension  34 , said gripper sections being configured as gripper edges  35 ,  36  that are parallel to each other, but spaced apart and offset with respect to each other in view of the pile height direction. The reversal between cut pile operating mode and looped pile operating mode takes place by means of the longitudinal adjustment of the gripper  11 . 
   LIST OF REFERENCE NUMBERS 
   
       
         1  Modular block (base body) 
         2  Tufting needle (L-tufting needle with left-side chamfer; R-tufting needle with right-side chamfer) 
         3  Modular body, base body 
         4 ,  5  Abutment surfaces 
         6  Bore 
         7 ,  8 ,  9  Grooves 
         10  Gripper device 
         11  Gripper 
         12  Guide member 
         13  Groove 
         14  Groove bottom 
         15 ,  16  Flanks 
         17  Holding section 
         18 ,  19 ,  20 ,  21  Bores 
         22  Section 
         23  Cutting edge 
         24  Edge 
         25  Border 
         26  Wedge 
         27  Edge 
         28  Edge/boundary 
         29  End 
         30 ,  31  Gripper section 
         32  Arrow 
         33  Step 
         34  Extension (hook) 
         35 ,  36  Gripper edges 
         37  Edge end 
         38 ,  39  Narrow sides 
         40  End 
         41  Cutout 
         42  Adjustment unit 
         43  Bar 
         44  Pile yarn 
         45  Backing 
         46  Arrow 
         47  Knife 
         48  Cutting edge 
         49  Loop