Tufting gripper with spring-biased support of an insert

A tufting gripper (16) comprises a pocket (26) with an insert (25) that is associated with a spring means (34) in order to at least temporarily clamp and secure said insert in place in the pocket in a prespecified position. The spring means (34) pushes the insert (25) preferably in the direction of the tip of the gripper and creates a particularly smooth transition at this location between the base body (19) of the tufting gripper (16) and the insert (25), in particular the tip (33) of said insert.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the priority of European Patent Application No. 10 171 111.7, 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 tufting machines for the manufacture of tufted goods, in particular for the manufacture of tufted goods with cut pile.

In tufting machines, tufting grippers are disposed to grip thread loops that have previously been formed by tufting needles, said needles punching a pile thread through a planar backing material. In order to produce cut pile, a large number of tufting grippers held on a sinker interact with cutting knives that are also held on a sinker and that carry out a cutting motion opposing the movement of the tufting grippers. In order to reduce wear on the cutting edge of the tufting gripper, said gripper frequently comprises an insert that is provided with the cutting edge. Such a tufting gripper has been known from EP 1 953 290. The gripper has a cutting insert consisting of a hard metal, said insert being placed in a pocket of the gripper body and being secured in said pocked by projections on the pocket edge. These projections have been produced by plastic deformation of the pocket edge. This arrangement, and this type of fastening of the insert, offers great advantages, in particular in instances in which the tufting gripper must exhibit a certain lateral flexibility and the hard-metal insert exhibits great stiffness. On the other hand, a certain gap must exist between the pocket edge and the hard-metal insert.

Some pile threads used for the manufacture of loop pile, but in particular for the manufacture of cut pile, comprise very fine filaments that slide freely along the lower edge of the tufting gripper and are also not supposed to become caught in gaps or steps between the insert and the gripper body. Even if such gaps are filled by hard solder, remaining steps can result in damage to the thread, which has to be prevented in order to achieve good product quality.

Considering this, it is the object of the invention to disclose a concept that permits the formation of high-quality pile, even in the case of pile threads that are difficult to process.

SUMMARY OF THE INVENTION

The above object generally is achieved by a tufting gripper in accordance with the invention that comprises a gripper body with a pocket into which an insert, for example, a cutting insert, an anti-sliding insert or a combined cutting and anti-sliding insert, can be set. A spring means is arranged on the pocket, said spring means being associated with the insert. When the insert is inserted in the pocket, the spring means clamps the insert in place in a force-fitting manner. Preferably, the spring force is directed toward the tip of the gripper body. Due to the spring force, the insert is positioned in a well-defined position and clamped in place. As a result, the gap size at the transition from the gripper body to the insert—in particular on the tip-side end of the pocket—is minimal or zero. The tufting gripper may be designed in such a manner that the clamping force applied by the spring means is sufficient to hold and fix the insert in place. Alternatively, it is possible to additionally secure the tufting gripper in its desired position with a material-bonding connecting means such as, for example, an adhesive or a solder. In this case, the spring means is disposed to prevent the slipping or misplacement of the insert while an adhesive is being applied and being hardened or while a solder is being applied and being hardened, and to achieve a controlled narrow gap width in the joining gap. The objective is to make the gap width as small as possible, ideally approaching zero. Due to the action of the spring means the exact positioning of the insert and the retention of this position can be ensured in the case of a material-bonding connection of the insert and gripper body, this being instrumental for the quality of the transition between the insert and the gripper body. The more precisely the insert is positioned, the smaller the joining gap becomes. Laterally impacting forces do not affect the fastening negatively while the connecting agent (adhesive, solder or the like) is solidifying. This also applies to welding processes used for connection such as, for example the application of laser weld spots, said spots connecting the pocket edge with the insert.

The pocket may have a bottom and thus be open only toward one side of the tufting gripper. It is also possible for the pocket to be open toward both flat sides. In this case, two different inserts may be arranged in the pocket, said inserts facing toward the two flat sides of the tufting gripper and having different surfaces. It is also possible to provide a combined insert that exhibits different surface properties on the sides facing away from each other. Preferably, the pocket edge is designed so as to be straight in transverse direction of the tufting gripper. In this case, the insert is held by friction while, or as long as, there is no solder or any other material-bonding connecting agent introduced. The pocket edge may also be provided with one or more undercuts that secure the insert in the pocket in a form-fitting manner. In this instance, the spring means preferably pushes the insert in the direction toward the gripper tip toward recesses that are appropriately formed in the pocket edge. The recesses or elevations provided on the pocket edge securely hold the insert—even during operation of the tufting gripper—without additional connecting means.

Preferably, the spring means is a spring tab that may be released on the edge of the pocket. Preferably, it consists of the material of the tufting gripper and adjoins said tufting gripper in a seamless and gapless manner. Preferably, the spring tab extends by more than three quarters of the corresponding lateral length of the insert, thus securely clamping in place said insert with sufficient elasticity on the one hand and with sufficient clamping force on the other hand.

In order to ensure the desired joint thickness, the insert or the gripper body may comprise spacing means, these being configured as knobs, for example. In doing so, it is possible to ensure the quality of the adhesive or solder joint.

Additional details of advantageous embodiments of the invention are the subject matter of the claims or the description and the drawings.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows a tufting device10that is disposed for the manufacture of pile goods11such as, for example, carpets and the like. The pile goods11comprise a planar backing material12to which loops14are applied with the use of a plurality of pile threads13, said loops—once they are cut open—forming a cut pile15. This is accomplished by means of a larger number of tufting grippers16held by a sinker, said grippers being associated with cutting knives17. The pile thread13is punched through the backing material12by means of a group of tufting needles18held by a sinker. The resultant loops14are picked up by the tufting gripper16. To do so, said tufting gripper comprises a gripper body19with a finger21extending toward a tip20. The gripper body19, including the finger21, represents a flat component having two flat sides22,23that may be plane or at least have plane sections. Slit-like passages are formed between the adjacent flat sides of adjacent tufting grippers16, whereby the tufting needles18enter said passages so that, subsequently, the tufting grippers16can pick up the loops punched by the tufting needles18through the backing material12.

In order to hold the loops on the finger21and keep them from sliding off, the tip20of the tufting gripper16may be angled downward in the form of a hook. However, as shown, said tip may also be located in the straight extension of the finger21. In this case, the stitches may be prevented from sliding off by a spring24indicated in a dashed line inFIG. 1. This spring24may be a thin spring steel tab laterally abutting against the end of the finger21.

The tufting gripper16is provided with an insert25that consists, for example of hard metal, ceramic or the like. The insert25is seated in a pocket26that is provided in the gripper body19and whose edge27follows the contour of the insert25. The insert25may be configured as a cutting insert, for example. Said insert then extends over a longer section of the finger21and is arranged in the pocket26. A cutting edge28(FIG. 3) may be provided on the wavy, toothed, straight, bent or stepped lower, for example horizontal, edge of the insert25, said cutting edge interacting with the knife17when the loops14are being cut open.

As shown, the insert25may comprise two flat partial inserts29,30that are superimposed in a contour-matched manner and optionally joined together, for example glued together, welded together or soldered together. These partial inserts may abut against each other or be joined together along a boundary surface31that is flat or provided with a profile. For example, the partial insert30is configured as a hard insert and defines the cutting edge28. This partial insert may consist of hard material or be provided with a hard-material surface. In terms of this, hard materials comprise hard metals, metal carbides such as, for example, tungsten carbide, or also hard-material layers such as titanium nitride, titanium carbide, aluminum oxide, ceramic and the like. This ensures the wear resistance of the cutting edge28.

The other insert29may be configured, for example, as an anti-sliding insert. It may consist of another material that reduces or eliminates damage to the needle when the needle sweeps along said anti-sliding insert. For example, this material may be a soft material, optionally a material displaying emergency lubricating properties, or it may be a particularly smooth material having a surface displaying a low coefficient of friction when the material is paired with that of tufting needle18. The use of ceramics, in particular those with a glass-like surface, carbon or tin-filled metal matrices, carbon-nitride-coated surfaces or the like is possible.FIG. 4shows the basic structure in cross-section. As can be seen, the edge27of the pocket26is straight in transverse direction, for example. Thus, the flat sides22,23extend at a right angle with respect to the edge27of the pocket26.

The tip-side end of the pocket26is preferably configured as a section32(FIGS. 2 and 3) that is short and arcuate, said section circumscribing the tip33of the insert25and thus extending under said tip. Viewed from below, the arcuate section32forms an undercut on the tip-side end of the pocket26. This undercut secures the insert25on the finger21in vertical direction in a form-fitting manner. For example, the section32follows a cylindrical wall. Consequently, the insert25can be laterally inserted in the pocket26and then held in said pocket.

The end of the pocket26located on the opposite side in the section32preferably is represented as a spring means34that is disposed to push the insert25in the direction of the tip20, i.e., into the end of the pocket26, said end being adjacent to the tip20. In principle, the spring means34may be arranged at another point of the pocket26; however, the described arrangement on the rear pocket edge as shown inFIGS. 1 through 3is preferred.

Preferably, the spring means34is a flexible spring35that comes into intimate contact with the contour36of the insert25, i.e., follows said contour, said contour being opposite the tip33. In the present example, the contour36is rounded in an arcuate manner. Likewise, the flexible spring35on the side facing the insert25is rounded in an arcuate manner. Consequently, the flexible spring35forms a part of the edge27of the pocket26.

Preferably, the flexible spring35consists of the material of the gripper body19, whereby a notch37is formed therein, said notch extending from the edge27and away from the edge27and then following said edge at a distance. As a result of this, the flexible spring35is released. As shown, said flexible spring may have a uniform thickness along its length from its tip to its end38, i.e., its root, where it terminates in the gripper body19. However, as indicated inFIG. 3, the flexible spring35may also display increasing thickness toward its root. In addition, said flexible spring may have a shallow indentation39in the vicinity of its root38on the side facing the pocket26in order to prevent the insert25from pushing against non-resilient or poorly resilient components of the flexible spring35.

Such a gripper16is assembled in that the insert25is pressed into the pocket26and positioned there as desired. In the desired position, the two flat sides40,41of the insert25adjoin the flat sides22,23of the gripper body19in a stepless manner and without offset (FIG. 6). Due to the clamping action of the flexible spring35or any other spring means34, the tip33of the insert25is pushed into the arcuate end at the section32of the pocket26. As a result of this, the insert35is clamped in place with respect to the transverse direction and is held in a form-fitting manner in vertical direction. Each gap or each step at the transition of the insert25to the gripper body19is minimal. If necessary, at least optionally, the insert25may be connected with the gripper body19in a material-bonding manner, for example, by gluing or soldering or welding. In the case of gluing, the spring means34ensures the secure seat of the insert in its desired position until the adhesive has fully hardened. In the case of soldering, this applies analogously until the solder has cooled and solidified. If welding is used for the connection, the resilient clamping action also fixes the insert in place. Consequently, in the case of a material-bonding connection of the insert25with the gripper body19, the spring means34ensures the exact positioning of the insert25, thus retaining said insert in its position. This is instrumental for the quality of the transition between the insert25and the gripper body19. The more precise the insert25is positioned, the smaller does the gap or a step become. Lateral forces occurring while the material-bonding joint is solidifying do not have any negative influence on fastening.

During operation, the grippers16held on a sinker perform an oscillating movement, in the course of which they continuously pick up pile thread loops that are formed by the tufting needles18when puncturing the backing material12. As is shown byFIG. 1, the loops14gather on the finger21. Due to the advance of the backing material12, the loops14picked up by the tufting griper16always slide away from the tip20of the tufting gripper16. Inasmuch as the tip33is located in the pocket26and is covered by the arcuate section32, it is ensured that none of the loops14can enter any gap between the edge27and the insert25.

Many modifications are possible on the invention that has been illustrated so far. For example, the spring means34may consist of an independent component that is fastened to the edge27of the pocket26or is arranged in an appropriate recess. Furthermore, the material-bonding connection may be restricted to components or sections of the insert25or also take up the entire edge27. In the first-mentioned case, the result is an increased elasticity in comparison with the tufting tools comprising inserts whose entire surfaces are connected by material-bonding. Consequently, the tufting tools in accordance with the invention are able to better respond to any impacting transverse forces that result from the cutting knife17of the tufting needle18or from the loops14.

Furthermore, it is possible to provide the insert25with a spacing means42that creates a space defined between the insert25and the edge27along the edge27of the pocket26or at selected points of said edge. Such a spacing means42may be, for example, knobs43,44that are provided on the outside circumference of the insert25. Such knobs or ribs or other projections preferably have the same elevation as the potential thickness of the adhesive gap or solder gap. This is, for example, a few tenths of a millimeter.

FIG. 6shows another possible modification. The insert25provided in this case comprises a body of a uniform material, said body being provided with a coating45,46on its two flat sides40,41that face a way from each other. Preferably, these coatings are of a different nature. For example, the coating45may be a hard-material layer that also circumscribes the cutting edge28, whereas, for example, the coating46may be a soft friction-reducing coating. In this case the coating45interacts with the cutting edge17, whereas the coating46interacts with the needle and, if possible, does not cause damage due abrasion to the needle.

Alternatively, the base body of the insert25may consist of a hard material that is provided with only the coating46. In this case, the coating45may be omitted. Also alternatively, the insert25may consist of a soft, minimally abrasive material that is provided with the coating45. In this case, the coating46may be omitted.

FIG. 7shows another modification. It is based on the fact that the pocket26has a bottom47. An additional pocket48may be provided on the opposite side of the tufting gripper16. This pocket may be configured to have the same contour as the pocket26or it may have a different contour. This pocket has its own insert49. Each of the inserts25,49may be provided with a suitable spring means as has been previously explained, said spring means clamping the inserts25,49in place in a desired joining position. It is also possible for the two separate inserts25,49to be held in their joining position by a single spring means34. To accomplish this, the gripper body19has an appropriate recess in which the spring means34is held and can exert a spring force on both inserts25,49.

Considering the above description, it was assumed that the edge27is straight along its entire length relative to the transverse direction. As is shown byFIGS. 8 through 11, it is however also possible—at least locally—to deviate from this configuration of the edge. Each of these figures shows a horizontal sectional view in the region of the tip33of the insert25.FIG. 8shows that a small projection50may be provided on the edge27, said projection also laterally securing the tip37in a form-fitting manner. In this case, the insert25need not be secured by material-bonding. This also applies when the edge27, as shown byFIG. 9, is arranged or configured so as to be inclined counter the transverse direction Q.

In contrast,FIG. 10shows the configuration of the edge27without undercut, i.e., the orientation of said edge in transverse direction Q, in which case an adhesive51or solder provided between the bottom47of the pocket26and the insert25takes over the lasting lateral fixation of the insert25.

Also, as is shown byFIGS. 11 and 12regarding the insert25, said insert being continuous along the entire gripper thickness, there are options to secure said insert in a form-fitting manner relative to the transverse direction Q. As is shown byFIG. 12, for example, the edge27may deviate from the straight form in transverse direction, or have projections50,52, in the section32or also in other suitable sections.

A tufting gripper16comprises a pocket26with an insert25that is associated with a spring means34in order to at least temporarily clamp and secure said insert in place in the pocket in a prespecified position. The spring means34pushes the insert25preferably in the direction of the tip of the gripper and creates a particularly smooth transition at this location between the base body19of the tufting gripper16and the insert25, in particular the tip33of said insert.

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

10Tufting device11Pile goods12Backing material13Pile filaments14Loops15Cut pile16Tufting gripper17Cutting knife18Tufting needles19Gripper body20Tip21Finger22First flat side of the tufting gripper1623Second flat side of the tufting gripper1624Spring for holding the loops14on the finger2125Insert26Pocket27Edge of the pocket2628Cutting edge29Partial insert30Partial insert31Boundary surface32Arcuate section of the edge27of the pocket2633Tip of the insert2534Spring means35Flexible spring36Contour37Notch38Root39Indentation40First flat side of the insert2541Second flat side of the insert2542Spacing means43Knobs44Knobs45Coating of hard material46Coating exhibiting sliding properties47Bottom48Pocket49Insert50Projection for laterally securing the insert2551Adhesive52Projection for laterally securing the insert25