EP0495926B1 - Flexible looping tool - Google Patents

Abstract

PCT No. PCT/EP90/01689 Sec. 371 Date Apr. 9, 1992 Sec. 102(e) Date Apr. 9, 1992 PCT Filed Oct. 9, 1990 PCT Pub. No. WO91/05896 PCT Pub. Date May 2, 1991.Flexible abrasive means having an underlay, which comprises a knitted fabric, which consists of a base knitted fabric (1) and at least one layer of warp threads (6) and at least one layer, separated from the latter, of weft threads (5) and includes a strengthening size. In each case a plurality of warp threads (6) per needle space (3) are held next to one another by different binding into the pattern in such a way that they run partly under and partly over the cross threads (4) of the base knitted fabric (1). All of the warp threads of a group of warp threads can be separated from one another by cross threads of this base knitted fabric alternating from the upper side to the underside of this warp thread group. A high dimensional stability of the abrasive means in the directions other than the directions of the warp and weft threads is obtained.

Description

The invention relates to an abrasive belt with a base which comprises a knitted fabric which consists of a basic knitted fabric and at least one layer of warp threads and at least one layer of weft threads separate therefrom and which contains a setting finish.

In the case of abrasive belts with a textile backing, the strength and the elongation are naturally greatest in the direction of the weft and warp threads. In many applications, however, high dimensional stability is also desired in directions that deviate from the warp and weft directions. This is particularly evident in so-called segmented brait tapes, in which the direction of the warp and weft threads does not match the direction of travel. If the dimensional stability is insufficient, they show a tendency to wrinkle. The general dimensional stability is also very important for all applications that lead to heavy punctual or walking loads on the grinding belt.

Even with fabrics, the drop in dimensional stability is pronounced when there are deviations from the thread directions. It is even greater in recent times than Abrasive pad used knitted fabrics, the structure of which is much looser than that of fabrics.

The invention has for its object to provide an abrasive belt of the type mentioned, which has high dimensional stability in the directions deviating from the directions of the warp or weft threads.

The solution according to the invention consists in that several warp threads per needle alley are held next to one another by different pattern integration in such a way that they run partly under and partly over the transverse threads of the basic knitted fabric, and that the coverage of the warp threads is at least 60%. The desired effect can be increased in that all the warp threads of a group are separated from one another by cross threads of the basic knitted fabric which change from the top to the bottom of this warp thread group. This does not have to apply to every crossover point. However, it should be ensured by crossover points which follow one another in the longitudinal direction in the repeat.

The following relationships play a role in explaining the advantageous behavior of the material according to the invention. When the material is stretched diagonally, the warp and weft threads twist or bend against each other at each crossover point. The mutual connection of the threads at these points by the finish can reduce these relative movements but cannot rule them out. In the known knitted fabrics (EP-B 45 408) there is only a limited number of crossover points between weft and warp threads, namely only one crossover point per needle row in each stitch row. This also applies if several warp threads are introduced per needle lane, because these are tied together in a strand by the sewing threads to form a bundle of threads with a uniform round thread cross-section. This constriction is avoided by the invention. The multiple warp threads per Nadelgasse spread out flat. Depending on the number of warp threads per needle alley, there is a multiplication of the crossover points compared to known knitted fabrics and thus a multiplication of the connection points between the warp and weft threads and with the knitting threads. This considerably limits their ability to twist against each other to diagonally stretch. Since the distances between adjacent crossover points are also reduced for a given rod spacing, the ability to bend the threads is also reduced. - Furthermore, an antiparallel displacement of adjacent warp or. Weft threads to each other instead. If these threads - as in the case of known knitted fabrics - are at a large distance from one another, the finish is only able to a limited extent to bring about a strong connection between them, or for this purpose a massaged use of finish agent is necessary, so that the properties of the material in would be improperly changed. Thanks to the invention, the warp threads move closer together so that they can be connected to one another by the finish and thereby secured against relative longitudinal displacement.

The invention does not lead to a higher use of warp threads because the individual warp threads can have such a reduced cross-section in comparison with the warp threads used in conventional knitted fabrics that the total cross-sectional area of the warp threads per needle alley remains unchanged.

The spreading of the warp threads has the further advantage that the degree of coverage of the warp threads is increased and the risk of the penetrating agent penetrating too deeply or even breaking through is avoided. The question arises as to whether one should not fear, when the adjacent warp threads are in close contact with one another, that the finishing agent cannot penetrate sufficiently to bring about the mutual connection of adjacent warp threads. However, such fear is unfounded, because the warp threads are separated from each other by the difference in the patterned integration at each crossover point or at least at short intervals by transverse threads of the basic knitted fabric, as a result of which capillary spaces are generated between them, into which the finishing agents penetrate. This ensures that they are not only firmly connected to each other, but also to the basic fabric through the finish. In this context, it is advantageous if all of the warp threads of a group are separated from one another by cross threads of the basic knitting that change from the top to the bottom of this warp thread group, so that the capillary distances mentioned are created. In this context, it is also advantageous if at each crossing point of a cross thread with a group of warp threads at least one warp thread lies above the cross thread.

It applies to the invention as well as to knitted fabrics that the position of the warp threads during the knitting process is limited to the needle lanes; however, since the warp threads cross alternately with the sewing threads, they are not combined into a single, compact bundle of threads, but spread out over a large area, so that, in addition to increased area coverage, a less ribbed structure but a rather smooth surface is achieved. Depending on the particular embodiment of the invention, the warp threads can be arranged adjacent to one another, immediately adjacent to one another or also overlapping one another after they have spread. This creates a large number of the capillary-like spaces mentioned, into which the finishing agent can penetrate. After curing, this leads to a substantial solidification of the entire underlay.

Different consistency of the finishing agent and different adhesion properties of the hardened finish can make a different penetration depth appear desirable. Likewise, different uses of the grinding tool and different Consistency of the hardened finish gives the desire for different penetration of the base through the finish. The invention can take these desires into account in that the distance and the degree of coverage of the warp threads can be set practically as desired. In this way - in the hardened state - hard finishes or low-viscosity finishes with a small warp thread spacing can be processed without the need to fear penetration too deep and thus undesirable embrittlement of the base, while with finishes that are less flow-resistant due to their higher toughness or foaming and / or which are sufficiently flexible in the hardened state, a larger distance or a lower degree of coverage can be selected. The abrasive according to the invention therefore enables a hitherto unknown variability through the type of knitted fabric forming the base.

In this context, it should be noted that a solidifying finish is to be understood as any means which can be applied to the knitted fabric from a moldable and in particular flowable state and at least partially introduced into it, after which it hardens and, in the hardened state, causes the base to solidify. A finish in the sense of the invention can therefore also be understood to be a hardening impregnation or coating which primarily serves other purposes, for example binding the abrasive grain to the base.

It is known that the knitted fabric used according to the invention can be endowed with high tensile strength and has a high surface smoothness and is therefore advantageous, for example, for toothed belts or printing blankets and generally for applications which require a smooth surface (EP-A 0 069 589; EP- A 0 069 590). However, it is unknown that this material, in conjunction with a finish suitable for flexible abrasives, leads to a high level Dimensional stability leads in the directions that deviate from the weft and warp direction.

In a prospectus (Gustav Ernstmeier GmbH & Co. KG, Herford: "ernstmeier schleiftextil - era" 5/88 / D), which offers as a service the equipment of textile backing materials as a base for abrasives, includes laying pictures as decorative pictures, below which also contains the pattern of a knitted fabric as used in principle according to the invention. There is nothing to suggest that this knitted fabric, once it has been finished and made into an abrasive belt, ensures high dimensional stability in directions that deviate from the directions of the warp or weft threads. Nor can it be seen that the degree of coverage of the warp threads is increased because the representation appears to be extremely open.

The invention results in an improvement in the dimensional stability and the coverage factor even in connection with knitted fabrics. Even better results are achieved with a cloth binding. It can be achieved that the wales are wholly or partially covered by warp threads that are bound by sewing threads that belong to other rods. This is based on the described phenomenon that the warp threads, which are limited to a specific needle path during the knitting process, can subsequently shift laterally beyond this needle path within the region predetermined by the cross threads of the knitted fabric.

According to a further feature of the invention, the warp threads can be selected in such a way and density that they are present in the finished knitted fabric in a flattened form, the ratio of their width to their height being at least about 1.8 and in practice slightly in the order of 2 , 3 lies. The flattening does not require that originally flattened threads are used in the manufacture. Rather, the flattening can also be achieved in the case of threads originally round in cross section, in particular if they consist of smooth, not or only slightly twisted filament yarn and sufficient expansion space is made available to them. This depends on the ratio of the diameter of the originally round threads to the width available to them in the product, i.e. the diameter of the warp threads multiplied by the number of warp threads per needle lane in relation to the center distance of the wales. This ratio is suitably not more than 80%, suitably not more than 70%, further suitably not more than 60%, further suitably not more than 50%. For example, a value of at least 80% is approximately achieved with a fineness of the knitted fabric of 20 needles per inch (7.8 per cm) and an insertion of four warp threads (fineness 550 dtex, Multifilament yarn, polyester) per cone. The diameter of the originally round warp threads can be determined by converting the cross-section found in the finished product into the circular cross-section. Instead, it can also be determined according to the principles specified in EP-B 0 073 313, page 6 above. The width of the warp threads is to be understood as their dimension transverse to their longitudinal extension in the plane of the base. Its height is its cross-sectional dimension. If you arrange the warp threads accordingly tightly, the finished product has a large mutual overlap due to the flattening of the threads. If this is not desired, it is possible to use a smaller number, for example instead of four warp threads (fineness 550 dtex) only two warp threads (fineness 1100 dtex) per needle alley. The fineness of the knitted fabric can also be reduced. In principle, the appropriate selection of the yarns, the fineness of the knitted fabric, the number of warp threads, the weave and other parameters familiar to the person skilled in the art can provide a base which corresponds to the specific requirements of the respective grinding process. It has proven to be particularly advantageous to vary the degree of surface coverage and thus also the spacing of the individual warp threads from one another by using the design features according to the invention in such a way that the amount of the finishing agent taken up as a result leads to the desired flexibility or rigidity of the grinding tool . An essential advantage of the invention over conventional sewing fabrics is that multiplying the number of warp threads without increasing the amount of warp thread material leads to an increase in the degree of coverage. For example, if the number of warp threads is quadrupled, the degree of coverage is doubled.

The degree of coverage of the warp threads is over 60%, preferably over 70%, more preferably over 80%. As already stated, it can reach 100% if the Warp threads lie directly against one another or even overlap one another.

In known abrasives, the backing of which contains sewing fabric, the warp thread side is unsuitable for taking up the abrasive grain layer. However, the warp thread arrangement achieved in the abrasive according to the invention permits such a good anchoring of the finish or the binder that the abrasive grain can now be arranged on the warp side if desired. In addition to a quality of the grinding pattern not previously achieved with knitted fabrics and the possibility of using a knitted base also for fine abrasive grain, the arrangement of the abrasive grain on the warp side also has the advantage that the grinding forces are transferred from the grain directly to that layer of the base, which transmits the longitudinal forces without a weft layer being arranged between them.

Fig. 1

einen Querschnitt durch ein herkömmliches Nähgewirk,

Fig. 2 bis 4

Draufsichten auf erfindungsgemäße Gewirke mit Trikotbindung (Kettfadenseite),

Fig. 5 und 6

Querschnitte unterschiedlichen Maßstabs durch eine erfindungsgemäßes Gewirk in Trikotbindung,

Fig. 7

die Draufsicht auf ein erfindungsgemäßes Gewirke in Tuchbindung (Kettfadenseite) und

Fig. 8 und 9

Querschnitte unterschiedlichen Maßstabs durch ein solches Gewirk.

The invention is explained in more detail below with reference to the drawing. In it show:

Fig. 1

a cross section through a conventional sewing fabric,

2 to 4

Top views of knitted fabrics according to the invention with tricot weave (warp thread side),

5 and 6

Cross sections of different scales through a knitted fabric according to the invention,

Fig. 7

the top view of a knitted fabric according to the invention in cloth weave (warp thread side) and

8 and 9

Cross sections of different scales through such a knitted fabric.

An abrasive belt of the type affected by the invention (see FIG. 5) is composed of a base U and a grain layer K, which are connected to one another by a binder B. The underlay contains a textile surface material that absorbs the forces and is solidified by a finish A, which is used to avoid a Embrittlement should usually only penetrate to a limited depth in the textile material. A finish can be provided on both sides of the textile material or only on one. In addition to solidification, it can have other purposes, for example to prevent the binder from penetrating through the base and / or to promote adhesion to the binder and / or to generate a high coefficient of friction on the back of an abrasive belt compared to the drive rollers. For the sake of simplicity, only the textile material is shown in the remaining figures.

In addition to the textile material, the underlay can contain further layers, but further layers are preferably dispensed with.

The sewing fabric of conventional type illustrated in FIG. 1 comprises sewing threads 1, which form wales 2, which are connected in the needle streets 3 by transverse threads 4. The sewing threads 1 connect weft threads 5 and warp threads 6. There is only one warp thread per needle alley. The warp threads are bundled by the sewing threads and kept at a distance. This does not change even if thicker warp threads or several warp threads are used per needle alley. The drawing, which is an enlarged representation of a photograph of a knitted fabric used in practice, clearly shows the actual conditions and in particular shows that the degree of coverage is low and the distance between the warp threads is large.

FIGS. 2 to 4 show layout images of knitted fabrics in jersey weave, as are used according to the invention. The knitting threads 1 form wales 2, which are connected in the needle lanes 3 by transverse threads 4. In all exemplary embodiments, a weft thread 5 is inserted in each course. A plurality of weft threads can also be inserted or a layer of thread can additionally be applied by sewing or in some other way. Warp threads 6, the number of which are in the figures. They form part of the knitted fabric in that they are integrated in a pattern. This means that they run partly under and partly over the transverse threads 4. The arrangement is chosen so that at least one warp thread runs above and below each transverse thread at each crossover point.

FIGS. 5 and 6 illustrate the cross-sectional shape that results in practice when using the layout image according to FIG. 2 and when using the data from example 1. A Since the knitting threads 1 stretch over a greater width than the width proportion of a warp thread, the warp threads are not tightly bundled and their space in the transverse direction is not as rigidly defined as in conventional sewing fabrics. They can therefore spread in cross-section and move together, so that a high degree of coverage of the warp threads is achieved. As shown in FIG. 6, there can even be a mutual overlap of adjacent warp threads. This is made possible by the fact that the transverse threads, which alternately bind one and the other weft thread, do not appear at the same crossing point, but at a longitudinal distance from one another. At the point at which the cuts according to FIGS. 5 and 6 are made, the knitting thread binding the warp thread appearing on the left in each needle alley lies. This favors an overlap of the right warp thread over the left one. On the other hand, where the knitting thread binding the right warp thread is located, the left warp thread will tend to overlap the right one.

The illustration also illustrates that a good degree of coverage is achieved, whereby the transverse threads ensure that the adjacent warp threads do not unite to form a single bundle, but rather that a certain distance remains between them, at least in the vicinity of the transverse threads 4, depending on the situation Thickness of the warp threads is larger or smaller, but at least one of the thickness of the cross threads has corresponding capillary width so that finishing agents of suitable consistency can penetrate and connect the adjacent warp threads and the transverse threads with one another.

With the same warp thread use (sum of the warp thread cross-sections per needle alley), a significantly higher degree of coverage is achieved in this way than with conventional sewing fabrics (FIG. 1). Moreover, even with the same degree of coverage of the warp threads, the binding conditions would be considerably more favorable because the number of crossover points doubled and the distance between adjacent warp threads was halved.

It is therefore the case that the knitted fabric according to the invention opposes all those deformations which are associated with a stress in a direction deviating from the thread direction, much greater resistance than a conventional sewing fabric.

Furthermore, a comparison of FIGS. 5 and 1 catches the eye that, according to the invention, a substantially greater surface smoothness is achieved on the warp thread side than in conventional knitted fabrics. This is also due to the fact that at each crossing point at least one warp thread runs above and below each transverse thread. Next to each cross thread is a warp thread that is at least as high. In contrast to conventional sewing fabrics, the cross threads do not appear as the highest points and are therefore less exposed to external mechanical stress.

Despite their dense arrangement, the warp threads are always clearly separated and kept parallel to one another by the transverse threads. This ensures, on the one hand, their maximum spread in the knitted fabric level and, on the other hand, the guarantee of sufficient anchoring options between them. Even with other layings, especially with a larger number of warp threads per needle alley, it should always be ensured that the transverse threads partly above and partly below the Warp threads lying next to each other run so that the closed structure is achieved, which prevents the basic binder from breaking through, and enables the finishing compound to be adequately anchored.

The knitted fabric loses the longitudinally oriented rib structure typical of sewing knitted fabrics and has a rather smooth, uniform surface; in a knitted fabric of this construction, the sewing thread is practically no longer exposed to any significant wear. In addition, a knitted fabric with such a smooth surface quality can also be used for fine abrasive grain and also offers significant application advantages, particularly an improved grinding pattern and less wear on support elements, in the fields of use on which knitted fabrics have previously been used.

With regard to the thread material used, filament yarn is preferably used. However, staple yarn or other synthetic or natural yarn material can also be used.

7 illustrates the laying pattern of a knitted fabric with a cloth binding used according to the invention. This is characterized in that the transverse threads 4 run between not immediately adjacent wales 2. As a result, the bundling influence of the transverse threads on the warp threads 6 is further reduced, so that the warp threads can practically freely spread laterally after the knitted fabric has been produced. With low warp yarn use, a high degree of coverage is achieved. Even the wales themselves are covered, namely by warp threads that are held by transverse threads that belong to the wales that are adjacent to the covered wales. 7 leads in practice to a cross-sectional image, as illustrated in FIGS. 8 and 9. As can be clearly seen, the degree of coverage based on the data from Example 3 is almost 100%, although a clear separation of the adjacent warp threads from each other while maintaining gaps for anchoring finish is guaranteed.

example 1

Machine:

Raschel knitting machine from Mayer, Obertshausen, Mod. RS4 MSU-N equipped with at least 3-6 laying rails and the associated devices for knitting warp thread patterns as well as a weft insertion device.

Yarn:

Warp thread: multifilament yarn, dtex 1100 f 210 polyester high tenacity Sewing thread: multifilament yarn, dtex 150 f 48 polyester weft thread: multifilament yarn, dtex 1100 f 210 polyester high tenacity
The yarns are commercially available and can be obtained, for example, from Hoechst AG, Frankfurt.

Das derart erhaltene Gewirke entspricht den Fig. 2, 5 und 6 und weist sowohl in Kett- als auch in Schußrichtung eine Reißfestigkeit von ca. 3900 N/5 cm auf.Laying and moving in:

The knitted fabric obtained in this way corresponds to FIGS. 2, 5 and 6 and has a tensile strength of approx. 3900 N / 5 cm both in the warp and in the weft direction.

Example 2

Machine:

According to example 1

Yarn:

According to example 1

Laying and moving in:

The knitted fabric obtained corresponds to FIG. 3.

The knitted fabric is further processed into an abrasive belt using conventional technology.

Example 3

Machine:

According to example 1

Yarn:

According to example 1

Laying and moving in:

The knitted fabric obtained corresponds to FIGS. 7, 8 and 9.

The knitted fabric is further processed into an abrasive belt using conventional technology.

Claims (10)

1. An abrasive belt with a support which comprises a knitted fabric which consists of a basic knitted fabric and at least one layer of warp threads and at least one layer of weft threads separated therefrom, and includes a bonding finish, characterised in that in each case a plurality of warp threads per needle track are retained side by side by different binding according to pattern in such a way that they extend partly under and partly over the cross threads of the basic knitted fabric, and in that the degree of covering of the warp threads is at least approximately 60%.
2. An abrasive belt according to Claim 1, characterised in that all the warp threads of one group are separated from one another by cross threads of the basic knitted fabric alternating from the upper side to the underside of this warp thread group.
3. An abrasive belt according to Claim 1, characterised in that at least one warp thread (6) is situated above a cross thread (4) at each cross-over point of the cross thread with one group of warp threads.
4. An abrasive belt according to any one of Claims 1 to 3, characterised in that the basic knitted fabric has a tricot weave.
5. An abrasive belt according to any one of Claims 1 to 3, characterised in that the basic knitted fabric has a plain weave.
6. An abrasive belt according to Claim 5, characterised in that the mesh stitches are wholly or partly covered by warp threads.
7. An abrasive belt according to any one of Claims 1 to 6, characterised in that the warp threads are flattened with a ratio of their width to their height of at least 1.3.
8. An abrasive belt according to any one of Claims 1 to 7, characterised in that the original diameter of the warp threads multiplied by the number of warp threads per needle track amounts to not more than 80% of the centre distance of the mesh stitches.
9. An abrasive belt according to any one of Claims 1 to 8, characterised in that the layer of abrasive grains is disposed on the warp side of the support.
10. An abrasive belt according to any one of Claims 1 to 9, characterised in that it is a segmental abrasive belt, in which the direction of the warp and weft threads deviate from the longitudinal direction of the belt.

Images