Profiled pile cutter

The pile cutter 10 according to the invention allows tufted goods to be produced using materials which, for example, have a friction-reducing coating for forming a dirt-repellant surface that is soft to the touch. Such materials are known to be problematic in the production of pile and occasionally irregular pile is produced. Adjacent to the narrow cutting edge 25 of the pile cutter 10 according to the invention is a comparatively broader step 27 and 33, which prevents the loop from slipping, without cutting into the latter.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is the national phase of PCT/EP2015/054327 filed Mar. 2, 2015, which claims the benefit of German Patent Application No. 10 2014 102 801.5 filed Mar. 3, 2014.

TECHNICAL FIELD

The invention relates to a pile cutter for tufting machines, in particular for the production of cut pile.

BACKGROUND

Pile cutters for tufting machines have been known from various prior-art embodiments. For example, document U.S. Pat. No. 2,090,021 discloses a pile cutter with a gripper finger being provided on its underside with a cutting edge having two steps. Furthermore, a cutting knife arranged in the pile cutter is disposed for cutting the open the taken up loops in a targeted manner in order to produce cut pile.

Furthermore, document EP 0 200 810 A1 shows a pile cutter having a hard-metal inlay that defines a cutting edge offset upward relative to the lower edge of the pile cutter. Adjoining the cutting edge, there is a step on which extends a straight edge up to the free end of the pile cutter. A leaf spring is movably arranged on the pile cutter in longitudinal direction of the gripper finger. By sliding the leaf spring forward or retracting it, the cutter can be switched from one operating mode in which the loop pile is produced into another operating mode in which the cut pile is produced.

Knives moving next to the grippers are used in the production of cut pile in most cases. A problem occurring here is the asymmetrical cut. The loops grasped by the pile cutter tend to be cut open not precisely on their vertex but slightly to the side, thus resulting in a not fully uniform pile height. In order to eliminate this problem, document EP 1 953 290 A1 has suggested that a lateral recess be provided on the pile cutter. On the other side of the pile cutter there is provided a flat hard metal inlay that supports the cutting edge. Due to the recess, the pile cutter is particularly narrow at the cutting edge, so that taken up loops are cut at least approaching their vertex.

Still, problems may result when the loops consist of particularly slippery material. If these are shifted in longitudinal direction of the cutting edge before or during the cutting operation, the loop may draw, and the cut may not be clean or, again, be off-center.

In order to prevent a slipping of the loops on a pile cutter, document EP 76783 B1 suggests that a serrated cutting edge be formed on a pile cutter for cut pile. This serration of the cutting edge prevents a slipping of the taken up loops in longitudinal direction of the pile cutter.

In addition, document U.S. Pat. No. 2,842,080 discloses a pile cutter with a stepped cutting edge for the production of various pile heights.

In the production of cut pile using particularly slidable, however cutting-resistant, pile thread the latter tends to evade ahead of the cutting knife. Therefore, during the cutting operation, the thread may be shifted along the cutting edge and be ultimately partially cut or cut all the way through due to the increasing tension on the cutting edge, while the cut is not guided cleanly by the knife. This is true, in particular, for materials that slide easily but, at the same time, are not easy to cut such as, e.g., certain synthetics, for example polyester threads, or coated threads that are used in the production of dirt-repellant carpeting.

SUMMARY

It is the object of the invention to provide a pile cutter that is also suitable for difficult materials.

The pile cutter in accordance with the invention comprises a gripper finger that is provided with a cutting edge on its underside. This cutting edge adjoins an elevation that has a width to be measured transversely to the cutting edge, said width being greater than the width of the cutting edge to be measured in the same direction. As a result of this, the cutting edge may be made particularly narrow, in which case a symmetrical cut can be achieved in the vicinity of the vertex of the loop taken up by the pile cutter. However, the elevation adjoining the cutting edge displays a greater width than the cutting edge, so that threads moving up there—even if they tighten against the elevation during the work process—are not cut open without the action of the cutting knife. Preferably, the elevation does not have a sharp edge that comes into contact with the thread.

A hook may be provided on the free end of the gripper finger. This hook is disposed to pick up loops and take over said loops from a tufting needle. The hook may be a downward angled section of the gripper finger.

Typically, the pile cutter has two lateral surfaces as well as, in between, one upper and one lower narrow side. In doing so, the lateral surfaces are those surfaces along which the sides of the taken-up loops are sliding. The lower narrow side is that side which faces away from the carrier material of the tufting goods to be manufactured. As opposed to this, the upper narrow side is that side which faces the carrier material, this side also being referred to as the backing. These descriptions of directions apply independently of the orientation relative to the viewer. The term “upper” generally refers to the side facing the backing, “upward” refers to the direction toward the backing. The term “lower” generally refers to the side facing away from the backing, “downward” refers to the direction away from the backing.

The lateral surfaces may be oriented parallel to each other. It is also possible to taper the gripper finger along its entire length, or over a part thereof, toward its free end, so that the lateral surfaces are oriented at an acute angle with respect to each other. Preferably, the lateral surfaces are flat with the exception of said recess and any potential elevations provided on one or both lateral surfaces. On the hook of the gripper fingers, they may extend toward each other at an acute angle and/or transition into a rounded region.

Preferably, the gripper finger is provided with a recess that is sunk into one lateral surface and extends at least through the lower narrow side. In doing so, only one narrow surface region bordered by a sharp edge remains of the narrow side. This surface region is referred to as the “cutting edge”. Between the cutting edge and the adjoining lateral surface, there is formed a sharp edge on which the loop is severed by the associate knife. The recess is adjacent to the cutting edge. The cutting edge may extend beyond the recess in one or both its ends. Conversely, it is also possible that the recess extends on one or both its ends beyond the cutting edge.

Preferably, the cutting edge is configured so as to be straight. However, if needed, it may also be convoluted or otherwise profiled. In doing so, however, it is preferably located in a plane in which is also located that lateral surface of the gripper finger which delimits the sharp edge of the cutting edge. The cutting edge may be oriented parallel to the upper narrow side of the gripper finger or also at an acute angle relative thereto.

The elevation adjacent the cutting edge may be a step rising from the cutting edge, said step being arranged on the lower narrow side of the gripper finger. In doing so, the elevation may display the width of the gripper finger existing at this location. In doing so, the width is to be measured as the distance between the lateral surfaces. Consequently, in this case the elevation projects only downward beyond the cutting edge and is flush with the lateral surfaces. On its side facing the hook, the elevation may have a sliding ramp surface, so that a loop catching space is formed between the hook and the sliding ramp surface.

Alternatively or additionally, the elevation may also extend across one of the lateral surfaces or both lateral surfaces. Also in this case the elevation is preferably arranged on that end of the cutting edge which faces the free end of the gripper finger. The recess may extend into a lateral elevation. The thusly configured elevation prevents a sliding of the loop off the cutting edge and an unclean cutting or partial cutting of said loop.

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

DETAILED DESCRIPTION

FIG. 1is a schematic representation of a pile cutter10of an otherwise not specifically illustrated tufting machine. The pile cutter10is one of a larger number of pile cutters that are held together on a sinker of a tufting machine in order to be moved in a synchronous manner. Each pile cutter10is disposed to take up loops11,12,13of tufting threads that are punched through a carrier material referred to as “backing” in order to form a pile. The backing and the associate tufting needle are not shown inFIG. 1. The pile cutter10is disposed for the production of cut pile. To accomplish this, the pile cutter10is associated with a knife14that is disposed to cut open the picked-up loops11to13. To do so, the knife14is moved up and down (upward and downward) in order to cut open the loops13,14in the vicinity of their vertex in such a manner that sides having substantially the same lengths are formed.

The pile cutter10is made of flat material and shown inFIG. 2—additionally toFIG. 1—in a view from the bottom. As is obvious from both figures, the pile cutter10comprises a gripper finger15that extends from a holding end16to a free end17. The holding end16is disposed for mounting the pile cutter10to the sinker. The free end17is disposed to take loops off a tufting needle.

The pile cutter10has two lateral surfaces18,19that, for example, may be configured as flat sides and, in particular, as planar surfaces. The lateral surfaces18,19are those surfaces along which the sides of the loops11to13are sliding. During use, they are positioned essentially at a right angle with respect to the backing, as well as essentially parallel to the flat knife14. Substantially smaller from the viewpoint of surface size are an upper narrow side20facing the backing and a lower narrow side21facing away from the backing. At the transition from the gripper finger15to the holding end16, the lower narrow side21has a step22which has a size such that no loop may move beyond this step22to the holding end16. The step22extends essentially at a right angle with respect to the longitudinal direction L of the gripper finger15.

On its free end17, the gripper finger15transitions into a wedge form in order to be able to take up loops such as the loop11by a secure process. Other than that, the lateral surfaces are, as mentioned, preferably parallel to each other—on the gripper finger15, as well as on the holding end16. However, it is also possible to orient the lateral surfaces together—or, for example, starting at step22—at an acute angle relative to each other, so that the gripper finger15becomes slimmer from its holding end toward its fee end17. Additional modifications are possible. For example, the lateral surfaces18,19may be slightly crowned or domed.

Considering the pile cutter10according to the invention, the lower narrow side21is configured in a special manner. A recess23extending through the lateral surface19is open toward the underside of the gripper finger15and thus also extends through the lower narrow side21. On the opposite side, a sharp edge24is formed on the lower edge of the lateral surface18. The section of the lateral surface18adjoining the sharp edge24is preferably flat and forms a knife sliding surface for the knife14. The knife sliding surface and the sharp edge24may be provided on the body of the one-piece gripper finger15, said body consisting of steel, for example. However, in order to form a sharp edge24and the sliding surface, the gripper finger may also comprise an inlay, e.g., a hard metal inlay. This inlay is seated in a flat pocket formed in the lateral surface18and is secured therein in an interlocking or material-bonded manner by suitable means. It may be soldered, welded, cemented and/or clamped or additionally or supplementally fastened to the gripper finger15. Such an inlay is not shown in the figures. In any event, the thickness of the inlay is smaller than the thickness of the gripper finger15in order to allow the formation of the recess23.

Of the narrow side21there only remains a reduced surface shown cross-hatched inFIG. 2, said surface being hereinafter referred to as the cutting edge25. The cutting edge25is delimited on the sides of the lateral surface19by the recess23and on the sides of the lateral surface18by the sharp edge24. Toward the holding end16, the cutting edge25is delimited by the step22. Toward the free end17, the cutting edge25is delimited preferably by a short-nosed elevation26that extends from the lower narrow side21in downward direction. In conjunction with this, the term “downward” is indicated as a direction R that is oriented substantially at a right angle with respect to the longitudinal direction L and thus at a right angle with respect to the backing. The direction R is parallel to the lateral surfaces18,19.

One step27of the elevation26borders the cutting edge25. Preferably, the step27is thus substantially oriented at a right angle with respect to the cutting edge25. The step27preferably transitions in a rounded region into a sliding ramp surface28that preferably is longer than the surface of the step27. The sliding ramp surface28is preferably oriented at an acute angle with respect to the longitudinal direction L. Furthermore, it is preferably oriented at an acute angle with respect to the longitudinal direction L. The cutting edge25is preferably oriented parallel to the longitudinal direction L. The sliding ramp surface26can delimit a loop catching space30with a hook29extending downward as an extension, said hook being formed to the free end of the gripper finger15. This loop catching space is disposed for collecting the loops12,13that are later to be transferred into the cutting space31. The cutting space31is delimited below the cutting edge by the steps22,27.

As can be inferred fromFIG. 2in particular, the elevation26extends from one lateral surface18to the other lateral surface19. Accordingly, it has a width B that is greater than the width S of the cutting edge. In doing so, the width S of the cutting edge is the smallest distance of the recess23from the lateral surface18and thus is understood to be the smallest width that is displayed by the cutting edge25that is configured as a narrow strip. The relationships can be inferred fromFIGS. 2 and 3. Preferably, the width S of the cutting edge25is smaller than half the width B of the elevation26.

The pile cutter10described so far operates as follows:

During operation, the pile cutter10performs an oscillating back-and-forth movement in longitudinal direction L. This movement may be superimposed by an additional pivoting movement, in which case the pile cutter10obvious fromFIG. 1pivots to the left in order to take up a loop punched through the backing by a tufting needle and hold it like the loop11upon retraction of the needle. The backing that is intermittently moved to the right during the tufting process takes along the corresponding loops until they—like the loops12,13—have passed the sliding ramp surface28and come to rest on the cutting edge25. The knife14that is rhythmically moved up and down cuts them open with its cutting edge32at this location.

The loops11,12preferably consist of a highly slidable, for example anti-adhesion-coated material, that offers high resistance to cutting as is the case, for example, with polyester. However, the inventive pile cutter is also suitable for non-problematic yarns such as wool, cotton or other natural fibers or synthetic fibers.

When the cutting edge32acts on the loops12,13, they cannot leave the cutting space31. The step27effectively prevents the loops12,13from slipping and being elongated or drawn in any other way. At the same time, the step27—due to its great width B—offers a planar contact surface for the lower U-shaped sections of the loops12,13, so that they—even if they are firmly pressed against the step27—are not partially cut or partially torn. This will not occur, even if the step27transitions into the lateral surfaces18,19at an extremely minimal radius of curvature. However, if necessary, the transition from the step27to the lateral surfaces18,19may also be rounded.

The elevation26need not necessarily be arranged on the lower narrow side21. Alternatively or additionally, it may be arranged on one of the two lateral surfaces18,19or on both lateral surfaces.FIGS. 4 and 5illustrate, as an example, an embodiment wherein the elevation26is both arranged on the narrow side21and additionally takes up a portion of the lateral side19. The description given hereinabove regardingFIGS. 1 to 3applies accordingly. In addition, it is pointed out that the elevation26—to the extent that it is provided on the lateral surface19—can have a step surface33facing the recess23, said step surface potentially having the recess23. The latter measure may be used to keep the cutting edge25up to the step27relatively narrow in order to produce sides of loops having as much as possible the same length when the loops12,13are being cut. The step surface33preferably transitions in a round portion into a sliding surface34that is at an acute angle with respect to the other lateral surface19. The length of the sliding surface34may correspond to the length of the sliding ramp surface28or, as illustrated inFIG. 5, be defined in a different manner. The step surface33may be oriented at a right angle with respect to the lateral surface19or, according toFIG. 4, also be oriented at another angle, for example an oblique angle, with respect thereto.

If the elevation26is provided on a lateral surface18and/or19, it is not necessary to provide such an elevation at the same time on the narrow side21. In this case, the width B is measured from the lateral surface18up a the point of the lateral elevation26, said point being laterally the farthest projecting. In any event, this width is greater than the width S, preferably at least twice the width S and, even more preferably at least three times the width S. This also applies to embodiments wherein the elevation26takes up the narrow side21as well as a portion of the lateral surface19.

However, an embodiment according to one of the figures is preferred. It is pointed out that it is possible to provide—on the narrow side21, as well as on the lateral surface18and/or the lateral surface19—also two or several such elevations instead of one single elevation28, which elevations may be arranged, for example, in a stepped manner in longitudinal direction so as to respectively prevent a sliding back of taken up loops during the movement of the tufting gripper and the backing. However, it is essential to prevent the evading or slipping away of the loops12,13when cutting is performed by the blunt, non-cutting step27or step surface33.

The pile cutter10according to the invention allows the production of tufted goods using materials which, for example, have a friction-reducing coating for forming a dirt-repellant surface that is soft to the touch. Such materials are known to be problematic in the production of cut pile and occasionally irregular pile heights are produced. Adjacent its narrow cutting edge25, the pile cutter10according to the invention is provided with a comparatively broader step27or33, which prevents the loop from slipping, without cutting into said loop.