Patent Publication Number: US-7717049-B2

Title: Gripper for a tufting machine

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims the priority of European patent application No. 07 002 185.2 filed Feb. 1, 2007, the subject matter of which, in its entirety, is incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   The invention relates to a gripper for a tufting machine, in particular to a gripper for the production of so-called “cut-loop pile”, also referred to as cut pile. 
   Tufting machines are used, for example, for the production of carpets/carpeting. In most cases, said machines comprise a table, above which a needle bar is arranged. This needle bar bears a plurality of tufting needles that are disposed to punch a pile thread through the textile support material that is intermittently transported across the table, said support material being referred to as the backing. A bar provided with grippers is provided under the table. With each punch of the tufting needles, the grippers insert loops formed of the tufting threads and hold said loops in place underneath the backing. In order to produce cut pile, knives are provided, said knives being held on a knife bar. These knives are moved toward the grippers and cut the loops held on said grippers. 
   Usually, appropriate grippers that are provided for the production of cut pile have a cutting insert that acts as a counterpart to the knife. Such a counterpart has been disclosed, for example, by document DE 23 41 567 A1 or also by document DE 28 23 408. In so doing, the gripper, in each case, consists of a flat gripper body that has a cutout for a cutting insert. The cutting insert consists of hard metal. A solder connection is used to secure said insert to the gripper body. 
   The hard metal insert and the gripper body display different wear resistance properties as well as different stiffness and thermal expansion properties, which can lead to problems. 
   Considering this, it is the object of the invention to produce an improved gripper for tufting machines. 
   SUMMARY OF THE INVENTION 
   The above object generally is achieved according to the invention with a gripper for a tufting machine which gripper comprises a gripper body with a gripper section for picking up thread loops, and a cutting insert set into a recess of the gripper body and being secured in the cutout in a form-closed manner. 
   The gripper in accordance with the invention comprises a gripper body with a cutting insert that is secured in a form-closed or force-closed manner in the appropriate cutout of the gripper body. The cutting insert is held in the cutout by positive-acting fastening means, whereby, however, both elements, i.e., the cutting insert and the gripper body, are allowed to behave consistent with their respective inherent elasticity and thermal expansion properties. The cutting insert and the gripper body are in contact with each other along a separating joint, whereby they are not connected to each other in said separating joint. Thus, micro-movements are possible. Consequently, a given elasticity of the gripper body is not reduced by the relatively stiffer cutting insert. Likewise, different coefficients of thermal expansion cannot lead to a bending of the gripper under conditions of temperature changes. 
   It is also advantageous that the gripper can be manufactured without a soldering process. Consequently, the gripper and/or the cutting insert are not subjected to any thermal stress. In particular, the cutting insert and the gripper body can be machined separately with the method that is suitable for their materials and can be exposed to corresponding treatment processes. In particular, they can be thermally treated individually separate from each other. The cutting insert, which is preferably made as a hard metal insert, is not damaged by the effect of heat as occurs during hard-soldering. The hard metal insert can be connected to the base body of the gripper without additional substances such as adhesives or solder, or any fluxing agent or similar chemicals. In addition, the gripper bodies and/or the hard metal inserts can be provided with coatings that are formed at low temperatures and do not tolerate high tempera rues. Furthermore, it is possible to provide the gripper body and the cutting insert with various coatings. For example, the gripper body may be provided with a coating that displays good sliding properties in order to reduce wear of the tufting needles, for example. Such coatings are Teflon coatings, for example. They also improve the sliding properties of the tufting thread. In contrast, the cutting insert may be provided with a layer to increase wear resistance. Such a coating may be, for example, a metallic hard material layer, a ceramic layer or the like. 
   The cutting insert preferably has cutouts on at least two opposing locations, whereby projections on the gripper body project into said cutouts. The cutouts may be limited by surfaces that are inclined relative to the flat sides. These inclined surfaces are preferably oriented at an angle of 40° to 70° relative to said flat side and define a free space into which the material of the gripper body may be stamped or pressed. 
   Additional details of advantageous embodiments of the invention are the subject matter of the drawings, the description or of the claims. In so doing, the description is restricted to essential aspects of the invention and other situations. The drawing is to be viewed as supplementary and discloses additional details. The drawings show exemplary embodiments of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view of a tufting device with the gripper bar. 
       FIG. 2  is a perspective view of a detail of a gripper with the gripper bar in accordance with  FIG. 1 . 
       FIG. 3  is a view, from the bottom, of the gripper in accordance with  FIG. 2 . 
       FIG. 4  is a side view of the gripper in accordance with  FIG. 2 , without the cutting insert. 
       FIG. 5  is a side view of the gripper in accordance with  FIG. 4 , with the cutting insert. 
       FIG. 6  is a sectional view, along line VI-VI, of the gripper in accordance with  FIG. 5 . 
       FIG. 7  is an enlarged detail of  FIG. 6 . 
       FIG. 8  is a perspective view of a modified embodiment of the gripper, similar to  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a tufting system  1  comprising a gripper bar  2  with a plurality of grippers  3  arranged parallel next to each other, and comprising a needle bar  4  holding a plurality of tufting needles  5  parallel with respect to each other, and further comprising knives  6  that are disposed to produce cut-loop pile. A backing or support material  7  is guided over the gripper bar  2 , whereby the tufting needles  5  are used to punch pile threads  8  into said backing. Among each other, the grippers  3  have the same configuration. Hereinafter, one gripper  3  is described, said gripper representing all the remaining grippers. 
   The gripper  3  shown separately, in detail, in  FIG. 2  comprises a gripper body  9  and a cutting insert  10 . Furthermore, the gripper body  9  and the cutting insert  10  are shown by  FIGS. 3 through 6 . As is obvious, the gripper body  9  represents a flat component with two lateral surfaces  11 ,  12  ( FIG. 3 ) that are essentially flat and located parallel to each other. On its underside, the gripper has a small flat side  40  that connects the lateral surfaces  11  and  12  with each other. The gripper body  9  has a holding section  13  ( FIG. 4 ), a center section  14  and a loop-pickup section  15 . The underside  40  extends over these sections  13 ,  14  and  15 . In so doing, the underside  40  may be slit in the region of the center section  14 . Consequently, the underside  40  consists of several sections that are offset relative to each other. The holding section  13  and the loop-pickup section  15  extend away from each other from different sides of the center section in opposing directions. While the gripper body  9  has a uniform thickness in the region of the center section  14  and of the holding section  13 , said gripper may be somewhat thinner along its loop-pickup section  15 , as is obvious from  FIG. 3 . Thus, said gripper tapers toward its end  16  in the loop-pickup section  15 . A cutout or recess  17  may be provided on the loop-pickup section  15 , for example along the lateral surface  11 , in order to avoid the so-called “J-cut”. A “J-cut” is understood to mean differently long sides of a cut-open loop. In order to produce a pile with equally long sides of a cut-open loop, the knife—in the ideal case—would have to cut the loop exactly in the middle of the underside  40  of the gripper body. This cannot be technically implemented. The cutting site where the knife  6  contacts the cutting insert  10  and cuts open the loop is offset relative to the center of a loop. In order to keep this offset as minimal as possible, the gripper body  9  has the cutout  17 . This cutout may have the shape of a surface that is arranged at an angle with respect to the lateral surfaces  11  and  12 , beginning at the lateral surface  11  and ending at the underside  40 . The center section  14  may be provided with a guide cutout in the form of a narrow deep longitudinal groove  18  in which a slider (not illustrated) can be supported so as to be movable in longitudinal direction. The slider is used in the production of looped goods in level-cut loop applications and, for this purpose, covers—in the front-most moved-out position—the end  16  of the gripper  3 . 
   The loop-pickup section  15  has a straight edge  19  or narrow side, on which the loops  20  may slide, as is obvious from  FIG. 1 . In a short curved region, the edge  19  terminates in an edge  21 , said latter edge forming the front end of the center section  14 . One side of the gripper body  9  has a cutout  22  extending through the lateral surface  12  ( FIG. 4 ), said cutout bordering the edge  19  as well as the edge  21 . The cutout  22  is relatively flat. Its depth is smaller than half the thickness of the gripper body  9 . A thin strip remains between the cutout  17  and the cutout  22 . It consists of the material of the one-piece gripper body  9 . The cutout  17  and the cutout  22  are at a distance from each other and do not communicate. 
   The cutout  22  preferably has an essentially uniform depth. Its contour corresponds to that of a rectangle with rounded corners, with a small rectangular piece taken off said rectangle by the edges  19 ,  21 . Consequently, the recess or cutout  22  has a first longer narrow section  23  and a second shorter wider section  24 . 
   Seated in the recess  22  is a cutting insert  10  such as is obvious from  FIG. 2 , as well as from  FIGS. 5 through 7 . This cutting insert  10  preferably consists of a different material than the gripper body  9 . While the gripper body  9  may consist, for example, of a flexible steel or even of another, e.g., non-metallic material, the cutting insert preferably is made of hard metal or of another wear-resistant material such as, for example, ceramic. Said gripper body has two flat sides  25  and  26 , whereby the flat side  25  abuts against the bottom of the cutout  22 . The other flat side  26  is located on the outside and is flush with the lateral surface  12  ( FIG. 5 ). It may also project somewhat beyond the lateral surface  12 . In particular, it is advantageous if the cutting insert  10  has, on its end facing in the direction of the free end of the loop-pickup section  15 , a ramp-like inclined surface  27 . Preferably, in a level-cut looper, this inclined surface  27  is in alignment with an inclined surface  28  of the loop-pickup section  15 . As a result of the stepless transition between the two inclined surfaces  28  and  27 , the pile thread forming the loop is prevented from being speared or damaged by the front edge  41  of the cutting insert  10 , when said loop slides from the front end  16  of the gripper body  9  into the region of the cutting insert  10 . As is shown, in particular, by  FIG. 3 , the inclined surface  28  forms the transition of the loop-pickup section  15  from a smaller thickness to a greater thickness. 
   Referring to another (not illustrated) embodiment of a cut-pile looper, the flat side  11 , which does not contain the cutout  22 , has the inclined surface  28 . 
   As is obvious from  FIGS. 2 and 5 , the cutting insert  10  has a cutting edge  29  having a contour following the contour of the edge  19 . The cutting edge  29  terminates in another edge section  30  having a contour that essentially follows that of the edge  21 . Consequently, the cutting insert  10  has a first, front, section  31  that can be viewed as the cutting section and has a second, rear, section  32  that can be viewed as the holding section. 
   It is also possible for the cutting edge  29  of the cutting insert  10  to project beyond the edge  19  of the gripper body  9 . This is indicated in  FIG. 5 . In so doing, the cutting edge  29  has a ramp  39  in order to form a stepless transition to the edge  19 . 
   The contour of the cutting insert  10  corresponds to the edge of the cutout  22 . Consequently, the cutting insert  10  is seated, essentially without play, in the cutout  22 . In order to fasten the cutting insert, said cutting insert has cutouts  33 ,  34  in its holding section  32 , as is shown by  FIGS. 2 and 5 . The cutouts  33 ,  34 , are configured, for example by inclined surfaces  35 ,  36  arranged diagonally with respect to the flat side  26 . The inclined surfaces  35 ,  36 , together with the flat side  26 , subtend an angle of preferably 40° to 70°. The cutouts  33 ,  34  are arranged on opposite sides of the holding section  32 . 
   In order to mount the cutting insert  10 , the gripper body  9  is wedged over the cutting insert  10 . To achieve this, the edge regions of the cutout  22  are plastically deformed so as to reach over the inclined surfaces  35 ,  36 . The thusly formed deformation regions  37 ,  38  thus hold the cutting insert in a form-closed manner in the cutout  22 . This is particularly obvious from  FIGS. 6 and 7  that show a greatly enlarged view thereof. Considering a depressing depth T of, for example, 0.05 mm and a resultant projection B of the deformation region  37  over the inclined surface  35 , a durable and secure form-closed mounting of the overall cutting insert  10  is achieved. In so doing, it is sufficient if the length of the deformation regions  37 ,  38  accounts for only approximately two thirds of the length of the wider, rear, section  32  of the cutting insert  10 . 
   The so-far described gripper  3  is disposed to operate as follows: 
   During operation, one end  16  of said gripper picks up loops  20  that mover over the edge  19 . To do so, the gripper bar  2  is rhythmically moved, as a rule. The loops  20  move onto the cutting edge  29  of the cutting insert  10 . There, they are cut open by knives  6  that are also rhythmically moved. In so doing, the knife  6  can move, e.g., over the inclined surface  27 ; this prevents said knife from impacting blunt on an edge of the cutting insert  10 . 
   As mentioned, the gripper body  9  and the cutting insert  10  may consist of different materials. In addition, they may have different coatings. For example, the gripper body  9  may be provided with a friction-reducing coating of synthetic material, for example, a Teflon coating. In contrast, the cutting insert  10  may be provided with a wear-minimizing coating, for example, a metallic hard coating such as titanium nitride, titanium carbide or the like. 
   Referring to the above-described exemplary embodiment, the cutting insert  10  is secured in axial direction in the cutout  22  in that the cutting insert  10  is fitted exactly into the cutout  22 . As is shown by  FIG. 2 , it is additionally possible to restrict the inclined surface  36  to a short axial region of the corresponding edge so that the deformation region  38  assumes the function of axially securing the cutting insert  10 . As is shown by  FIG. 8 , this may also be done with regard to the two inclined surfaces  35 ,  36 . Other than that, the above description of  FIG. 8 , using the same reference numbers, applies analogously. 
   In a possible modification of the gripper  3  in accordance with the invention, the front edge  41  of said gripper&#39;s cutting insert  10  is lowered relative to the lateral surface  42  of the loop-pickup section  15  of the gripper body  9 . In addition, the lower narrow side of the cutting insert  10  is bent at a site  43  so that the cutting edge  29  forms an oblique angle  44  at that point. A section  45  of the lower narrow side of the cutting insert  10  terminates in the cutout  22  of the gripper body  9 . Other than that, the above description applies analogously. The thus-described embodiment may be further modified in that the oblique angle  44  has a size on the order of 150° to 185°, preferably 165°. In the vicinity of the section  45 , the otherwise straight edge  19  or its narrow side  19  of the gripper body  9  is provided with an indentation  46  that has approximately the shape of a bell. The cutting edge  29  of the cutting insert  10  projects downward beyond the edge  19 . The edge  19 , which is thus located above the cutting edge  29  and thus—initially starting from the edge  21 —extends parallel to the cutting edge  29 , terminates to the left in the indentation  46 . In its continued course, the leg of the edge  19  extending from the cutting insert  10  intersects the section  45 . An oblique angle is formed at the point of intersection between the indentation  46  of the edge  19  and the section  45 . A thread  47  moving along the edge  19  thus does not impact the tip of the cutting insert  10  but its lower section  45 . 
   In the vicinity of the edge  41 , the edge of the cutout  17  is provided with an inclined surface  48 . The inclined surface  48  forms a stepless transition from the edge  41  to the essentially flat lateral surface  42  of the loop-pickup section  15  of the gripper body  9 . Thus one edge of the inclined surface  48  adjoins the edge  41  or the inclined surface  27  in a smooth and stepless manner. Its other edge adjoins the lateral surface  42 . The transitions may be configured as embossed edges or may be rounded. The inclined surface  48  may be straight or arcuate, i.e., it may have a constant slope or alternating slopes. 
   Referring to the latter embodiment, the tip of the cutting insert  10  is located within the gripper body  9 . As marked by the thread  47 , the transition point for the transfer of the thread from the edge  19  to the cutting insert  10  is located at a distance from the tip or the end of the cutting insert  10 . It is offset from the tip toward the edge  21 . During the outward displacement of the gripper, the throat or indentation  46  improves the transfer of the thread or yarn onto the cutting insert  10 . During the gripper&#39;s reverse stroke, said throat or indentation improves the transfer of the thread from the cutting insert  10  onto the gripper body  9 . 
   The inclined surface  48  prevents the thread  47  from becoming caught on the edge  41  or on the rim of the cutout  17 . In addition, the cutout  17  has a rounded wall section  49  that terminates in the edge  19 . Furthermore, this chamfer or rounding  49  also prevents the thread from becoming caught or damaged. 
   A gripper  3  for a tufting machine comprises a gripper body  9  having a cutout  22  for a cutting insert  10 , said cutting insert preferably consisting of a hard metal. Connecting means acting in a form-closed manner are provided for the connection of the cutting insert  10  with the gripper body  9 . In their simplest embodiment, said connecting means are formed by the deformation regions  37 ,  38  that are provided on the gripper body  9  and that reach around matching cutouts  33 ,  34  of the cutting insert  10 . 
   It will be appreciated that the above description of the present invention is susceptible to various modifications, changes and modifications, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims. 
   LIST OF REFERENCE NUMBERS 
   
       
         1  Tufting system 
         2  Gripper bar 
         3  Gripper 
         4  Needle bar 
         5  Tufting needle 
         6  Knife 
         7  Support material 
         8  Pile threads 
         9  Gripper body 
         10  Cutting insert 
         11  Lateral surface 
         12  Lateral surface 
         13  Holding section 
         14  Center section 
         15  Loop-pickup section/gripper section 
         16  End 
         17  Cutout 
         18  Guide cutout 
         19  Edge/narrow side 
         20  Loop 
         21  Edge 
         22  Cutout/recess 
         23  Section 
         24  Section 
         25  Flat side 
         26  Flat side 
         27  Inclined surface 
         28  Inclined surface 
         29  Cutting edge 
         30  Edge section 
         31  Section 
         32  Section 
         33  Cutout 
         34  Cutout 
         35  Inclined surface 
         36  Inclined surface 
         37  Deformation region/projections 
         38  Deformation region/projections 
         39  Ramp 
         40  Underside 
         41  Edge 
         42  Lateral surface 
         43  Site 
         44  Oblique angle 
         45  Section 
         46  Indentation 
         47  Thread 
         48  Inclined surface 
         49  Wall section