EP0495926A1

EP0495926A1 - Flexible looping tool.

Info

Publication number: EP0495926A1
Application number: EP91900239A
Authority: EP
Inventors: Ernst Prahl
Original assignee: Hermes Schleifmittel GmbH and Co KG
Current assignee: Hermes Schleifmittel GmbH and Co KG
Priority date: 1989-10-10
Filing date: 1990-10-09
Publication date: 1992-07-29
Anticipated expiration: 2010-10-09
Also published as: DK0495926T3; NZ235629A; FI114161B; ES2086524T3; DE59010284D1; CA2066218C; US5317886A; AU6732990A; CA2066218A1; ATE136595T1; EP0495926B1; DE9017910U1; FI921509A0; NO921252D0; WO1991005896A1; NO921252L; AU637851B2; FI921509A; DE8912060U1; JP2860159B2

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

Flexible grinding tool

The invention relates to a flexible grinding tool 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 consolidating finish.

In the case of flexible grinding tools with a textile base, 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 the case of so-called segmented broadbands, in which the direction of the warp and weft threads does not match the running direction. If the dimensional stability is insufficient, they tend to wrinkle. The general dimensional stability is also very important for all applications that lead to heavy punctual or flexing stress on the grinding tool.

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 a grinding tool 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 a plurality of warp threads per needle alley are held next to one another by different patterned integration such that they run partly under and partly over the transverse threads of the basic knitted fabric.

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 in the diagonal direction, the warp and weft threads twist or bend relative to 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 alley, because these are tied together in a strand shape by the sewing threads to form a thread bundle 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 as well as with the knitting threads. As a result, their ability to twist against each other to form diagonal expansion is considerably restricted. Since the distances between adjacent crossover points are also reduced for a given rod spacing, the ability to bend the threads is also reduced. - In addition, in the case of diagonal stretching, there is an antiparallel displacement of adjacent warp or weft threads relative to one another. If these threads - as in the case of known knitted fabrics - have a large distance from one another, the finish is only able to a limited extent to bring about a reliable connection between them, or for this purpose a use of finish agent so massed is necessary that the properties of the Material would be changed in an impermissible manner. 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 path 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, in the case of close mutual contact of adjacent warp threads, 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 one another at each crossing point or at least at short intervals by cross threads of the basic knitted fabric due to the difference in the pattern integration, whereby capillary distances 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 knitted fabric by the finish. In this context, it is advantageous if all the warp threads of a group are separated from one another by transverse threads of the basic knitted fabric which 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 is true for the invention as well as for the knitted fabrics that the position of the warp threads during the knitting process is limited to the needle gases; 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 an 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 due to the type of knitted fabric forming the base.

In this context, it should be noted that a solidifying finish is to be understood to mean any agent which can be applied to the knitted fabric from a moldable and, in particular, flowable state and at least partially incorporated therein, after which it hardens and, in the hardened state, solidifies the base causes. 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 timing 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.

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 phenomenon described 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 range 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 magnitude of 2.3. The flattening does not presuppose that originally flattened threads are used in the production. 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 in the product, i.e. the diameter of the warp threads multiplied by the number of warp threads per needle alley in relation to the center distance of the wales. This ratio is expediently not more than 80%, expediently not more than 70%, further expediently not more than 60%, further expediently 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 and an entry 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 particular 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 construction features according to the invention in such a way that the amount of the finishing agent absorbed as a function of this corresponds to the desired flexibility or rigidity of the Grinding tool leads. An essential advantage of the invention compared to 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 preferably over 60%, more 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 allows the finish or the binder to be anchored so well that the abrasive grain can now be arranged on the warp side if desired. In addition to the quality of the scuff pattern not previously achieved in the case of knitted fabrics and the possibility of using a knitted fabric base also for fine abrasive grain, the arrangement of the abrasive grain on the warp side also has the advantage that the grinding forces from the grain directly onto that layer be transferred to the base, which transmits the longitudinal forces, without a weft thread layer being arranged in between.

The invention will now be described in more detail with reference to the

Drawing explained. In it show:

Fig. 1 shows a cross section through a conventional

2 to 4 top views of knitted fabrics according to the invention

Jersey binding (warp thread side), FIGS. 5 and 6 cross sections of different scales through a knitted fabric according to the invention, FIG. 7 the top view of an inventive one

Knitted fabrics in cloth weave (warp thread side) and FIGS. 8 and 9 cross sections of different scales through such a knitted fabric.

A flexible grinding tool 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 the solidification, it can have other purposes, for example preventing the binding agent from penetrating through the base and / or effecting adhesion to the binding agent and / or producing 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.

Figures 2 to 4 show laying pictures of knitted fabrics according to the invention in tricot weave. 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. Since the knitting threads 1 stretch over a greater width than corresponds to the proportion of width of a warp thread, the warp threads are not bundled tightly and their place in the transverse direction is also 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 lies, the left warp thread will tend to overlap the right one.

The illustration further illustrates that a good degree of coverage is achieved, the transverse threads ensuring that the adjacent warp threads do not unite to form a uniform bundle, but rather that there is a certain distance between them, at least in the vicinity of the transverse threads 4 depending on the thickness of the warp threads is larger or smaller, but at least one of the thickness of the cross threads has a corresponding capillary width so that finishing agents of suitable consistency can penetrate and connect the adjacent warp threads and the transverse threads to 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 load in a direction deviating from the thread direction, much greater resistance than a conventional sewing knitted 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 with conventional sewing fabrics. This is also due to the fact that at each crossover 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 knitted fabrics, the transverse threads therefore 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 one another run so that the closed structure is achieved, which prevents the basic binder from penetrating, 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 subjected to 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-related advantages in the fields of use in which knitted fabrics have hitherto been used, in particular an improved grinding pattern and less wear on support elements.

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.

Fig. 7 illustrates the laying pattern of a knitted fabric according to the invention with a cloth binding. 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 out 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 which are held by transverse threads which belong to the wales which are adjacent to the covered wales. In practice, the layout image according to FIG. 7 leads to a cross-sectional image, as is illustrated in FIGS. 9 and 10. 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.

Yarns: warp thread: multifilament yarn, dtex 1100 f 210

Polyester high tenacity sewing thread: multifilament thread, dtex 150 f 48

Polyester weft: multifilament yarn, dtex 1100 f 210

Polyester high strength The yarns are commercially available and can be obtained, for example, from Hoechst AG, Frankfurt.

Laying and moving in:

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

Example 2

Machine: According to example 1

Yarns: According to example 1

L 3 L 4

Second warp thread Third warp thread

0 2 0 2

2 2 2 2

0 0 0 0

0 2 0 2

full full ls dtex 1100 f 210 polyester high strength

The knitted fabric obtained corresponds to FIG. 3.

The knitted fabric according to the invention is further processed into a coated abrasive using conventional technology. Example 3

Machine: According to example 1

Yarns: According to example 1

L 3

0 0

4 4

2 2

4 4

full ls dtex 1100 f 210 polyester high strength

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

The knitted fabric according to the invention is further processed into a coated abrasive using conventional technology.

Claims

1. Flexible grinding tool 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 contains a consolidating finish, characterized in that in each case several warp threads (6) per needle alley (3) are held next to each other by different patterned inclusion such that they run partly under and partly over the transverse threads (4) of the basic knitted fabric.

2. Grinding tool according to claim 1, characterized in that all the warp threads of a group are separated from one another by cross threads of the basic knitting alternating from the top to the bottom of this warp thread group.

3. Grinding tool according to claim 1, characterized in that at each crossover point of a cross thread with a group of warp threads at least one warp thread (6) over the cross thread (4).

4. Grinding tool according to one of claims 1 to 3, characterized in that the basic knitted fabric has a tricot binding.

5. Grinding tool according to one of claims 1 to 3, characterized in that the basic knitted fabric has a cloth binding.

6. Grinding tool according to claim 5, characterized in that the wales are completely or partially covered by warp threads.

7. grinding tool according to one of claims 1 to 6, characterized in that the warp threads are flattened with a ratio of their width to their height of at least about 1,

8. Grinding tool according to one of claims 1 to 7, characterized in that the original diameter of the warp threads multiplied by the number of warp threads per needle alley is not more than 80% of the center distance of the wales.

9. Grinding tool according to one of claims 1 to 8, characterized in that the degree of coverage of the warp threads is at least about 60%.

10. Grinding tool according to one of claims 1 to 9, characterized in that the abrasive grain layer is arranged on the chain side of the base.

11. Grinding tool according to one of claims 1 to 10, characterized in that it is a segmented grinding belt in which the direction of the warp and weft threads deviates from the longitudinal direction of the belt.