Patent Application
20230287961
The invention relates to drive belts, in particular V-belts, V-ribbed belts or toothed belts on an elastomer or polyurethane base, with belt backing and at least one tension member, comprising an optically detectable load and wear state display according to the preamble of Claim 1, a structure consisting of a support material with a nonwoven, knitted, woven or crocheted or film base according to Claim 12, and a use of a structure as sensor for optical detection without electronics of elevated temperatures during operation of the drive belt according to Claim 16.
A V-ribbed belt and a method for displaying a wear state of a V-ribbed belt is already known from EP 3 117 122 B1.
According to the definition of the problem stated in that document, it should also be possible to check the wear state of a V-ribbed belt when it has been fitted. In this regard, a material abrasion at the base of the rib is detected as the criterion for the wear state.
A V-ribbed belt of such kind comprises a belt backing and a tension member arranged underneath the belt backing, and a substructure, in which V-ribs with sloping rib flanks are constructed, each extending in the longitudinal direction of the V-ribbed belt and parallel to one another and separated by an intermediate space.
In the event of material abrasion on the substructure, a first material in the rib base is exposed, while the surface of the rib flanks is still formed by a second material. The material abrasion in the rib base is detected as the criterion for the wear state. It is thus easily possible to make such an observation visually, by creating the surface in the rib base from one material, and arranging a visibly distinct material underneath it. The optically detectable exposure of the visibly distinct material serves as the criterion for the wear state.
The drawback associated with a solution of such kind is the need to integrate two different materials with different colour properties in the manufacturing process of V-ribbed belts of such kind.
Furthermore, it is only possible to detect wear states that are attributable directly of indirectly to material abrasion.
From EP 1 481 229 B1, it is known to use a thermochromic material as a component of a rubber product, in particular a tyre, a strap or a belt. The thermochromic material serves as an indicator based on a visible change of colour when a certain temperature range is exceeded. From this it is concluded that the capability of the corresponding product has deteriorated and it needs to be replaced.
From EP 0 597 923 B1, a cord with a heat-sensitive component is known, which component undergoes a visible change in appearance when it has been exposed to a selected, elevated temperature due to deformation or friction in conjunction with a release of heat of the individual strands of the cord.
The elastomer part according to DE 10 2014 214 330 A1 and the method explained therein for monitoring the operating capability of an elastomer part are intended to permit detection as to whether and to what extent a corresponding elastomer part has been exposed to thermal load since it was put into operation. This should enable conclusions to be drawn as to how long the elastomer part will remain usable in operation.
In this respect, the elastomer part presented in that document has at least one region with thermochromic properties that is visible or can be detected optically from the outside.
This region which can be detected optically from the outside may be created by means of a coating applied directly over at least a portion of the surface of the elastomer part.
Alternatively, at least a section of the elastomer part may consist of a material to which thermochromic pigments or fillers have been added.
The materials used to enable to the thermochromic properties are chosen with consideration for the operating temperatures that arise in the respective use case. In particular, the region of the elastomer part that is visible from the outside should change colour at critical temperatures.
Accordingly, it is possible in this way to conclude from a visual check whether the corresponding part has suffered any damage, thereby allowing statements to be made about the remaining service life of the part.
Thus, with the solution according to DE 10 2014 214 330 A1 it is possible to quickly detect signs of wear, particularly those caused by the effects of temperature. However, the addition of thermochromic pigments or fillers to parts made from elastomer material that are exposed to high loads impairs the durability and the mechanical properties of the part in question.
On the other hand, if a coating is applied to the surface of an elastomer, a structure forms which is unfavourable for many operational cases.
For example, if a coating with thermochromic material were applied to the belt backing side of a drive belt, in particular a V-belt, this would lead to problems with regard to “backrolling capability”. Furthermore, such a layer would wear off relatively quickly.
All things considered, integrating a method for applying or incorporating thermochromic materials in a process that accompanies temperature-controlled vulcanisation is counterproductive, since the thermal treatment in the manufacturing process itself brings about a change in the properties of the thermochromic particles or substances.
Given the situation as described in the preceding, it is therefore the object of the invention to describe an advanced rive belt that is equipped with an optically detectable load and wear state display, which itself has no adverse effects on the actual drive belt manufacturing process and may be prefabricated in such manner that it is possible to take into account the extremely varied temperature profiles in corresponding drive belt products.
The object of the invention is solved with a drive belt according to the combination of features described in Claim 1, supported by a structure with the combination of features described in Claim 12 and with the use of the structure as a sensor for optical detection of elevated temperatures by non-electronic means during use of drive belts as described in Claim 16.
According to the invention, a recess is formed on a drive belt, for example on the back of the belt, at least over a section of the belt.
This recess may preferably be created in the manufacturing process, that is to say in the process of vulcanising the belt.
Therefore, it is not necessary to create recesses in the belt, particularly in the belt backing, by material removal afterwards, which weakens the belt and creates predetermined breakage points.
Thus, the recess serves to accommodate a film-like or textile structure, adapted to the dimension of the recess, wherein the film-like or textile structure is furnished, in particular coated, e.g. printed or impregnated, with irreversible thermochromic pigments, in such manner that a colour change or discolouration takes place at a predefinable temperature load threshold.
When such a thermal limit load is reached, it is then possible to determine with a simple visual inspection that a certain wear or load condition has been reached. A decision can be made afterwards as to whether the drive belt in question is to be replaced as a preventative measure or whether replacement will not be necessary until the following servicing operation, depending on the servicing schedule.
As was explained previously, the recess is created in the form of a cavity in a step in the belt manufacturing process.
The textile structure consists of a nonwoven material, a woven, a crocheted or knitted fabric. A thermoplastic material may be used in the form of a film.
The textile structure furnished with the irreversibly thermochromic pigments or the film is affixed adhesively in the recess.
In this case, it is possible on the one hand to use an adhesive that is compatible with the materials used, particularly with regard to the properties of the drive belt.
On the other hand, bonding connections such as ultrasonic welds or vibration weld connections are also possible, if and to the extent that incompatibilities exist with adhesives that would otherwise be necessary.
In a further development of the invention, the recess is formed over the entire course of the belt backing. In this case, the textile structure or film has the form of a strip or strand and is inserted and fixed within the recess.
The textile structure or film may have multiple layers or sections with thermochromic pigments, each of which exhibit discolouration at different temperatures, so that different load states may be represented, in the manner of a traffic light function.
In addition or alternatively thereto, a textile structure or a film with irreversibly thermochromic pigments is provided in or an at least one belt flank, one rib flank, on the rib base and/or on the tooth in the case of a toothed belt.
The irreversibly thermochromic pigments may be contained in a colour coating, or a in a colour application for the textile structure.
In one variant of the invention, the free, visible surface side of the textile structure or film has a layer that is preferably transparent functions as a protective layer against abrasion.
The textile structure or film with its irreversibly thermochromic pigments may be supplied as a plaster-like, prefabricated product.
Depending on the thermal behaviour of drive belts taking with consideration for their material characteristics, thermochromic materials and pigments are chosen that cause an irreversible colour change in the relevant, critical temperature range.
The adhesive bonding of the textile structure or film with the drive belt is carried out at normal temperature, in particular at room temperature. The manufacturing and conditioning process of the textile structure or film is also performed in such manner that temperatures which might cause a premature colour change of the pigments are not reached. This applies at least to the step of applying or impregnating with the thermochromic pigments or substances.
According to a further aspect of the invention, a structure is provided which consists a support material based on a nonwoven, knitted, woven or crocheted fabric, or a film, wherein the support material is furnished with at least one containing that contains irreversibly thermochromic pigments or consists of such pigments.
The structure also has an underside, which is suitable for adhesive bonding with an elastomer material, in particular a drive belt. In addition, an optically trans- parent protective layer is provided on the upper side.
The structure is preferably designed as a strip or band.
The underside may be provided with an adhesive coating.
A separating layer may be provided between the adhesive coating and the support material to prevent an undesirable reaction from taking place between the constituents of the adhesive layer and the thermochromic pigments or the material used therefor.
A temperature-dependent actuation behaviour and therewith also the time at which the pigments change colour may be adjusted with the selection of the support material thickness.
When selecting the support material, and choosing the thermochromic pigments and there arrangement relative to the drive belt, it must be ensured that heat is transferred from the drive belt material to the textile structure as evenly as possible, so that the colour change under corresponding temperature load takes place as clearly and unmistakeably as possible, and is correspondingly visually detectable.
A further aspect according to the invention is the use of the previously described structure as sensor for optical detection without electronics of elevated temperatures during the operation of drive belts, wherein the sensor is permanently attached to the respective drive belt.
Surprisingly, it has been found that detection of a temperature change in the region of the belt backing during operation of a drive belt is sufficient to recognise certain load cases and load limits, although in the case of V-belts the temperature rise is greater on the belt flanks compared with the temperature on the belt backing. The formation of the recess or cavity on the belt backing instead of an arrangement on the belt flanks does not result in any reduction of the load-bearing capacity of the belts, nor any restrictions in their range of use.
In the following text, the invention will be explained in greater detail with reference an embodiment thereof.
With regard to the production of a recess for a drive belt, in particular a V-belt, in the case of flank-open V-belts a shaped element, for example in the form of a metallic strip, is attached directly to a fixed drum. In this case, this is a standard assembly drum, on which the belt material is assembled in steps.
The shaped element may be treated and/or surrounded with a corresponding separating agent.
The shaped element used then lies transversely over the drum and is wound round the drum. When vulcanisation is complete, the shaped element is removed from the winding.
The production of the exemplary textile structure as a temperature sensor without electronics relies on textile fabrics and nonwoven materials.
The advantage of using nonwoven materials consists in that readily absorb and are effectively penetrated by corresponding thermochromic pigments and dyes.
The colour change may be delayed by means of the choice of substrate materials used relative to the thermochromic pigments, as a longer period is needed to bring the substrates to the temperature of the drive belt.
Irreversibly thermochromic pigments or dyes are commercially available. In this case, pigments with a colour change temperature from 100° C. and 120° C., with a with colour change from colourless/whitish to magenta were used. A corresponding dye exists as a water-based ink.
When choosing the thermochromic materials, it must be ensured that a colour change is irreversible under all circumstances, and the change cannot be reversed as a result of environmental influences, such a atmospheric humidity.
The underside of the textile starting material may be furnished with a coating, in particular a polyurethane coating, in order to form a barrier layer, as it were, against an adhesive material underneath it, and thereby preventing unfavourable influencing the properties of the thermochromic component or dye.
A protective layer in the form of an exemplary acrylic resin layer may be applied to the upper side of the textile structure. This protective layer prevents undesirable abrasion of the thermochromic dye.
For exemplary purposes, 3M Scotch-Weld cyanoacrylate adhesive in liquid or gel form is used as the adhesive to provide an adhesive bond, that is to say a particular kind of adhesive bonding technology.
It was found that gel-like adhesives are preferable. The adhesive material is selected with consideration for the base material of the drive belts, for example an EPDM rubber.
In order to improve the adhesion properties with respect to the cavity in the drive belt, bonding agents may be used, or a physical surface treatment may be carried out.
The thermochromic pigments or a corresponding dye may be applied directly to the textile substrate using a doctor blade in a screen printing process. Air drying serves to avoid an undesirable colour change caused be elevated temperature.
Of course, techniques such as digital printing to apply the colour to the textile substrates are also conceivable.
The protective layer on the upper side forming a cover layer described previously is applied for example in a spray process. Here too, it is important to avoid the generation of any heat or the application of any heat to dry or cure the protective layer.
The textile substrate functionalised and equipped in this way is cut to size, in particular punched out in terms of the dimensions of the recesses and cavities in the drive belt. In the case of an bonded connection using adhesive, this is applied directly to the region of the cavity or to the underside of the flexible support, preferably after a surface cleaning process. Application of a thin layer reduces the likelihood of undesirable colour change reactions due to the chemical properties of the adhesive.
PES textile fabrics and PES nonwovens demonstrated particularly advantageous properties when used as the starter material for the functionalised structure.
Thermochromic dyes used for exemplary purposes demonstrated a clear, irreversible colour change from white to magenta in response to temperatures starting from as low as about 90° C.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102022105552.3 | Mar 2022 | DE | national |
