Patent Publication Number: US-2012024208-A1

Title: Gripper with dual-insert body

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the priority of European Patent Application No. 10 171 112.5, filed Jul. 28 2010, the subject matter of which, in its entirety, is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a tufting gripper for a tufting machine, in particular for the manufacture of goods with cut pile. 
     Goods that are provided with cut pile, for example carpets, are typically produced on tufting machines that comprise a gripper arrangement with a plurality of grippers. The grippers are associated with cutting knives. This arrangement has been known, for example, from publication EP 1 826 306 A1. As can be seen, in that publication the grippers interact with needles of a sinker that punch the pile thread through a backing material. The resultant loops are picked up by grippers that are provided with a cutting edge. Each gripper is associated with a cutting knife that is disposed to cut the loops picked up by the respective gripper. 
     Publication EP 1 826 307 A1 also discloses a similar arrangement. Also in this case each of the grippers has a base body that works as a counter knife element for the cutting knives and has an appropriate cutting edge. 
     Furthermore, it has been known to design the cutting edge to be provided on the gripper with an insert of hard metal, said insert being inserted in a pocket of the gripper body. Regarding this, reference is made, for example, to EP 1 953 290. This publication suggests that the body of hard metal be secured in a form-fitting manner in the pocket by plastic deformation of the pocket edge. In doing so, a certain disengagement of the insert of hard metal from the flexible lateral deformations of the gripper body is achieved. 
     When the tufting arrangement is being operated, the grippers that are disposed to pick up the pile thread loops sweep along the tufting needles. This can result in damage to the tufting needles. For example, while the eye of the tufting needle sweeps long the hard-metal insert of the gripper, sharp edges may form on the eye and, as a result of this, individual filaments of the pile thread can be damaged. Also, damage to the tufting grippers at the contact points between the gripper body and the needle cannot be precluded. 
     Considering this, it is the object of the invention to suggest a concept with which the service life of the tufting device can be improved. 
     SUMMARY OF THE INVENTION 
     The above object generally is achieved with the tufting gripper in accordance with the invention that comprises a gripper body that is provided with a cutting insert having a surface of a hard material, as well as with an additional insert that has a surface that is different from the surface of hard material. The cutting insert having the hard-material surface is preferably a straight, curved, convoluted, stepped or cogged cutting edge and is preferably placed on the gripper body in such a manner that it interacts with the associate cutting knife. Preferably, the cutting insert is a rigid body such as, for example, a hard-metal body, a ceramic body, a steel body provided with a hard-material layer, another type of body or the like. In this case, the cutting insert is inserted in an appropriate pocket, i.e., a recess of the gripper body, and secured in said pocket. Alternatively, the cutting insert may also be designed entirely in one piece with the gripper body; however, also in this case, said cutting insert defines the hard-material surface, for example, in the form of a coated region of the gripper body. The hard-material surface may be the surface of a hard-metal insert, for example, a tungsten carbide surface, the surface of a ceramic insert, or another layer applied to the respective base body by PVD or DVD process or coated by means of another method, such layers being, for example, a DLC layer, TiN layer, TiC layer, AL 2 O 3  layer or the like. In view of the material of the cutting knife and the pile thread to be cut, such a layer is designed so as to display the highest possible wear resistance. 
     The additional insert in accordance with the invention has a different surface and is preferably positioned at the point of the gripper body that comes into contact with the tufting needle. Preferably, this insert has a surface that does not damage the tufting needle when the tufting needle and said additional insert come into contact with each other. In particular, the surface may display good sliding properties. For example, the additional insert may consist of a soft metal or non-metal, for example, a ceramic material displaying a low coefficient of friction, or of a metal having a coating that ensures a low coefficient of friction and a low abrasion effect between the surface of the insert and the tufting needle. For example, the surface may be a carbon-nitride coating or a ceramic coating. This coating may also be applied directly to the gripper body so that the additional insert and the gripper body can ultimately be viewed as being a one-piece component. 
     Both the cutting insert and the additional cutting insert have to be arranged in a pocket of the gripper body and be secured in said pocket. For securing purposes, the respective cutting insert, as well as any other insert, must be in form-fitting and/or material-bonding connection with the gripper body. Preferably, the cutting insert and/or the other insert are joined to the gripper body by soldering, gluing, welding (e.g., by welding spots or seams provided on the pocket edge) and/or are secured in place by a plastic deformation of the pocket edge of the pocket that accommodates the respective insert. In addition, one or more spring means may be provided on the gripper body, said spring means displacing the cutting insert and/or other insert into their desired positions, preferably toward the gripper tip, and thus secure said cutting inserts in the desired positions. This can be aided by a material-bonding connection between the respective insert and the gripper body, for example, by using a hard solder or any other, e.g., flexible, connecting material. The spring means provided on the gripper body then mainly becomes active when the insert is in correct positional arrangement. 
     The two inserts (cutting insert and additional insert) may be accommodated in separate pockets or also in a shared pocket. The pocket may be configured as a cutout on the gripper body and thus be open toward both flat sides of the gripper body. The two inserts may be arranged so as to lie flat on top of each other in this cutout or pocket and be connected with the gripper body. The two inserts may also be connected with each other, for example, by material-boding. They may be soldered, glued or welded to each other. They consist of different materials or have at least different surfaces. They may consist of the same base material and be only provided with different coatings on the two sides that face away from each other. It is also possible to provide the two coatings on a single carrier body. 
     When the cutting insert and the additional insert are connected or combined with each other in accordance with at least one of the aforementioned methods, a combined unit is being formed, said unit having a hard-material surface as well as a surface different from the hard-material surface. The combined insert can be connected with the gripper body in any of the previously described ways. 
     In order to achieve a material-bonding connection displaying controlled quality, it is desirable to maintain a prespecified joint thickness at the joint, said joint being filled with glue or hard solder (or another joining material). To do so, spacer means may be provided on the respective insert (cutting insert and/or any other insert and/or combined unit). Such spacer means are, for example, projections placed on one or more suitable points of the circumference of the insert, for example, small ribs or knobs that are higher than the edge of the insert. In doing so, the height of the respective projection corresponds to the desired thickness of the joint. 
     Additional details of advantageous embodiments of the invention are the subject matter of the drawings, the description or the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a tufting system comprising a tufting gripper, tufting needle and tufting knife. 
         FIG. 2  is a perspective view of the tufting gripper as in  FIG. 1 . 
         FIG. 3  is another perspective view of the tufting gripper as in  FIGS. 1 and 2 . 
         FIG. 4  is a representation of a detail, in section along line IV-IV, of the tufting gripper as in  FIG. 3 . 
         FIG. 5  is a view corresponding to  FIG. 4 , vertically in section, of a modified embodiment of the tufting gripper modeled after the gripper as in  FIGS. 1 through 3 . 
         FIG. 6  is a sectional view corresponding to  FIG. 4  or  FIG. 5 , of a further modified embodiment of the tufting gripper. 
         FIG. 7  is a side view of an insert for the tufting gripper as in  FIGS. 1 through 4 . 
         FIG. 8  is an alternative embodiment of a tufting gripper in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a tufting device  10  that is used for the manufacture of tufted goods  11 . Such goods are, for example, cut pile carpets. This includes a flat, planar, e.g., textile, backing material  12  as indicated in dashed lines in  FIG. 1 . 
     This backing material is provided with a pile thread  13  that is punched through the backing material  12  in order to first form the loops  14 . As the process continues, these are cut open in order to form open loops and thus form cut pile  15 . This is accomplished with a tufting gripper  16  that is associated with a cutting knife  17 . Numerous tufting grippers  16  are arranged next to each other on a sinker that imparts the tufting grippers  16  with the desired working motion. A corresponding number of cutting knives  17  is also arranged on a sinker that, for the cutting operation, performs a movement directed against the grippers  16 . 
     In order to produce the loops  14  to be picked up by the gripper  16 , i.e., for punching the pile thread  13  through the backing material  12 , tufting needles  18  are used, each of said needles having its own pile thread  13  moving through its eye. The tufting needles  18  and the cutting knives  17  have a design that has been known per se. The tufting gripper  16  may be inserted like a conventionally designed tufting gripper; however, the gripper has been modified in accordance with the invention in order to improve service life, in particular the service life of the tufting needles  18 : 
     The tufting gripper  16  in accordance with the invention comprises a gripper body  19  as is shown, in particular, by  FIGS. 2 and 3 . The gripper body  19  is configured so as to represent a flat component and has two flat sides  20 ,  21 . These are not necessarily plane, however, they may have plane regions. The flat sides  20 ,  21  of adjacent grippers  16  define between them narrow, slit-like passages for the legs of the loops  14  and the cut pile  15 , as well as for the tufting needles  18  and the cutting knives  17 . In particular when dense pile is concerned, these passages are relatively tight. By definition, the tufting needles  18  thus contact the grippers  16 . Likewise, the cutting knives  17  contact the grippers  16 , at least while the loops  14  are being cut. 
     As shown by  FIG. 1 , the body  19  of the gripper  16  comprises an elongated gripping finger  22  extending toward the tufting needle  18 , as well as a base section  24 . On its free end, the gripping finger  22  may have a catch  23  that is bent away from the backing material  12 , said catch forming a hook. The finger  22  is straight between the catch  23  and the base section  24  of the body  19  of the gripper  16 . As is shown by  FIG. 1 , the finger  22  is disposed to pick up the loops  14 . To do so, said finger has a straight edge  25  on its lower side. This edge acts as the cutting edge  26 , i.e., at least on one side of the gripper body  19 . 
     The cutting edge  26  is provided on one cutting insert  27  and, at least in the present exemplary embodiment, extends—however not necessarily—along the entire length of the finger  22  from the base section  24  to the catch  23 . Arranged adjacent to the cutting insert  27  is an additional insert  28  which, in the present exemplary embodiment, has the same contour as the cutting insert  27  and abuts against said insert at a plane surface  29 . While the cutting insert  27  adjoins the flat side  21  of the tufting gripper  16  ( FIG. 3 ), the other insert  28  adjoins the flat side  20  without steps and offsets ( FIG. 2 ). 
     The cutting insert  27  and the additional insert  28  are connected to each other at the plane surface  29 , for example, by glue or solder, and thus form a unit  30 , as is obvious from  FIG. 4 , in particular. Other joining techniques such as, e.g., using laser spots or laser seams at the edge of the surface  29  can be employed. 
     The unit  30  and thus also the cutting insert  27 , as well as the additional insert  28 , are positioned in a pocket  31  that is formed in the gripper body  19  and extends from the base section  24  to the catch  23 . As is obvious from  FIGS. 2 and 3 , the pocket  31  is open toward both flat sides  20 ,  21  of the gripper body  19 . The unit  30  consisting of the two inserts  27 ,  28  can be secured by material boding. For example, solder may be used for material-bonded securing, said solder being used to solder the unit  30  to the gripper body  19 , i.e., along the edge of the pocket  31 . 
     The cutting insert  27  has a hard-material surface  32 . If the cutting insert  27  consists of a hard material, the surface  32  may be a surface consisting of such a material, for example. Such a material can be hardened steel, hard metal such as, for example, tungsten carbide, a cermet or also a ceramic. It is also possible to make the cutting insert  27  of a first hard material and the hard-material surface  32  of a second hard material. For example, the cutting insert  27  may consist of tungsten carbide and the hard-material surface  32  may consist of titanium nitride, aluminum oxide, another hard material or of a layer assembly consisting of various hard materials. 
     The hard-material surface  32  extends at least up to the cutting edge  26  and, preferably, circumscribes said cutting edge up to a narrow underside  33  of the cutting insert  27  ( FIG. 4 ). 
     Preferably, the additional insert  28  consists of another material than the cutting insert  27 . Preferably, this is a material having a low coefficient of friction. Adjoining the flat side  20 , the insert  28  has a surface  34  that is distinctly different from the hard-material surface  32 . In particular the surface  34  exhibits a low abrasion effect in view of the contact with the tufting needle  18 . For example, the additional insert  28  may consist of a material displaying emergency lubrication properties, for example a carbon-containing metal structure, a tin-containing metal structure or the like. Also, the surface  34  may be a ceramic surface having a low coefficient of friction and the most minimal roughness height. 
     Briefly, the tufting device  10  described so far operates as follows: 
     During operation, the plurality of tufting needles  18  held on a sinker punch the pile thread  13  through the backing material  12  and to form loops. These loops are grasped by the plurality of tufting grippers  16  supported by the sinker due to a relative movement of said gripers, so that the loops  14  can be picked up by the fingers  22 , as is obvious from  FIG. 1 . During the operating cycle, the plurality of knives  17  held on a sinker bar push in the direction of the picked-up loops  14  and separate them on the cutting edges  26  of the plurality of tufting grippers  16 , so that the cut pile  15  is formed. 
     During this process, the cutting knives  17  contact the cutting insert  27  and slide along the hard-material surface  32  of said insert. The wear is minimal. 
     The tufting needles  18  come into contact with the tufting grippers  16 . In particular, in doing so, the tufting needles  18  slide along the additional insert  28 . The minimal abrasion effect of the insert  28  that could result, for example, due to the hardness and/or smoothness and/or softness and/or emergency lubrication property of said insert, the wear of the needles is negligibly small. In particular a partial sharpening of the needle eye edges is prevented which, otherwise could lead to damage to the pile thread  13 . 
     Numerous modifications of the tufting gripper  16  are possible. As is shown by  FIG. 5 , for example, the cutting insert  27  and the additional insert  28  can be configured as separate inserts. In this case, the pocket  31  does not extend through the entire thickness of the tufting gripper  16 . Rather, said pocket has a bottom  35  that divides the pocket  31  into two individual pockets  36 ,  37 . The pockets  36 ,  37  may have the same contour or different contours. They are open toward different sides. While the individual pocket  36  borders the flat side  21 , the individual pocket  37  borders the flat side  20 . Also, considering this exemplary embodiment, the cutting insert  27  and the additional insert  28  can be fastened in the pockets  36 ,  37  by material-bonding, for example, by gluing or soldering. 
     Furthermore, as is shown by  FIG. 6 , the combined unit  30  comprising both inserts  27 ,  28  can be based on a shared base body  38 . Said base body may be provided, on one side, with a thin plate or also with a layer  39  that represents the hard-material surface  32 . The hard-material surface  32 , in turn, adjoins the flat side  21  in a manner without offset and without gaps. The surface  34  located on the other side of the tufting gripper  16  preferably consists of a different material that may be applied in the form of a thin layer or a plate  40  to the base body  38 . This plate or layer  40 —in the form of the lateral surface  34 —then creates a sliding surface for the tufting needle  18 , in particular. Each of the previously mentioned connecting techniques may be used for fastening the unit  30  in accordance with  FIG. 6  in the pocket  31 . The cutting insert  27 , the additional insert  28  and/or the unit  30  in accordance with  FIG. 4  or  6  may have the side view in accordance with  FIG. 7 . The external circumference of the respective insert that is facing the wall of the pocket  31  ( 36  or  37 ) may be provided with spacer means  41 . Such spacer means are, for example, knob-like or rib-like projections  42 ,  43  having a height corresponding to the thickness of the desired joint that is formed between the circumference of the unit  30  and the edge of the pocket  31 . Preferably, this height is a few tenths of a millimeter. It is disposed, for example, to produce a hard solder joint of defined thickness and also to position the respective insert  27  or the respective unit  30  in an extremely precise manner in the pocket  31 . 
       FIG. 8  illustrates another embodiment of the invention represented by the form of the tufting gripper  44 . This gripper comprises an elongated finger  22 . For example, the catch  23  may be omitted. It is assumed that the cutting insert  27  and the additional insert  28  are arranged as a combined unit in the pocket  31 . On its tip end, the pocket  31  has a form-fitting structure  45 , said structure securing the unit  30  in the pocket  31  when the unit  30  is pushed against said form-fitting structure  45 . For example, the edge of the pocket  31  has an arcuate form on its tip-side end. The edge of the pocket  31  circumscribes the insert or the unit  30  in a hook-like manner, thus securing said insert in a form-fitting manner in vertical direction. The edge of the pocket  31  may be straight, relative to the transverse direction, from the flat side  20  to the flat side  21 . Alternatively, the form-fitting structure  45  may have a shape that is rounded or angled in a direction transverse to the tufting gripper  45  in order to also secure the lateral position of the unit  30  in a form-fitting manner. 
     A spring means  46  is arranged on the opposite end of the pocket  31 , said spring means biasing the unit  30  with respect to the form-fitting structure  45 . The spring means  46 , for example, is a released spring tab  47  provided on the body of the tufting gripper  44 . As a result of the spring force is applied by the spring means  46  the unit  30  is positioned in a spring-actuated, non-positive, manner. As a result of this, the gap at the transition from the body  19  of the tufting gripper  44  to the insert or the unit  30  is as small as possible. When the unit  30  is connected with the tufting gripper  44  in a material-bonded manner, an exact positioning of the insert or the unit  30  is accomplished. This position is decisive for the quality of the resultant transition between the lateral surfaces of the insert or the unit  30  and the flat sides of the tufting gripper  44 . Due to the precise non-positive fixation of the unit  30  during the soldering operation, laterally impinging forces when the solder solidifies or the glue hardens do not have a negative influence on fastening. 
     In all the aforementioned embodiments, this way of securing the insert by spring force due to a spring means  46  may be separately applied to the unit  30  as well as to the cutting insert  27  and the additional insert  28 , i.e., to embodiments comprising spacer means  41  as well as to embodiments without spacer means  41 . 
     In order to reduce or to prevent wear on the tufting gripper  16  at the contact point with the tufting needle  18 , an additional insert  28  is provided in addition to a wear-resistant cutting insert  27 , said additional insert  28  being directed at interacting with the tufting needle  18 . Said additional insert consists of a material that, paired with the tufting needle  18 , forms an optimal sliding combination. 
     Preferably, the additional insert  28  is a soft needle-saving insert. Preferably, the cutting insert  27  is a hard wear-resistant insert. The two inserts  27 ,  28  may be accommodated separately in different pockets  36 ,  37  or together in one pocket  31 . They may be connected with each other or be made in one piece. 
     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 NUMERALS 
     
         
           10  Tufting device 
           11  Goods 
           12  Backing material 
           13  Pile thread 
           14  Loops 
           15  Cut pile 
           16  Tufting gripper 
           17  Cutting knife 
           18  Tufting needle 
           19  Body of  16   
           20  Flat side 
           21  Flat side 
           22  Gripping finger 
           23  Catch 
           24  Base section of  19   
           25  Lower edge of finger  22   
           26  Cutting edge of the cutting insert  27   
           27  Cutting insert 
           28  Additional insert 
           29  Plane surface between the inserts  27 ,  28   
           30  Unit comprising the cutting insert  27  and the additional insert  28   
           31  Pocket 
           32  Hard-material surface of the cutting insert  27   
           33  Narrow side of the cutting insert  27   
           34  Lateral surface of the additional insert  28   
           35  Bottom of the pockets  36 ,  37   
           36  Individual pocket for the cutting insert  27   
           37  Individual pocket for the additional insert  28   
           38  Common base body for the inserts  27 ,  28   
           39  Plate or layer with hard-material surface  32   
           40  Plate or layer with sliding surface 
           41  spacer means 
           42  Knobs 
           43  Knobs 
           44  Tufting gripper 
           45  Form-fitting structure 
           46  Spring means 
           47  Spring tab