Measuring clamp for measuring the conductivity properties of vehicle tires, and corresponding method

Abstract

The invention relates to a measuring clamp (10) for measuring the conductivity properties of vehicle tires, comprising: i) a main part (12), ii) a first clamp element (14) which is connected to the main part (12), said first clamp element (14) comprising an electrically conductive first contacting element (16), iii) a second clamp element (18) which is connected to the main part (12) and is arranged at a distance to the first clamp element (14), said second clamp element (18) comprising an electrically conductive second contacting element (20), and iv) a measuring unit (22) which is connected to the first contacting element (16) and the second contacting element (20) for measuring the connectivity properties, wherein the first contacting element (16) is arranged on the first clamp element (14) face facing in the direction of the second clamp element (18), and the second contacting element (20) is arranged on the second clamp element (18) face facing in the direction of the first clamp element (14). The measuring clamp (10) is designed such that the distance between the first clamp element (14) and the second clamp element (18) can be modified in a reversible and nondestructive manner, and the first contacting element (16) comprises a plurality of electrically conductive first conductor elements which extend from the surface of the first clamp element (14).

Description

[0001] Clamp meter for measuring the conductivity properties of vehicle tires and associated method

[0002] Description

[0003] The invention relates to a measuring clamp for measuring the conductivity properties of vehicle tires and a corresponding method for determining the conductivity properties of vehicle tires using such a measuring clamp.

[0004] A key component of modern pneumatic vehicle tires, which in many cases is largely responsible for the performance characteristics of these products, is the tread. Today, treads usually consist of several different components, particularly various rubber materials, which can be obtained by vulcanization from vulcanizable rubber compounds.

[0005] In cross-sectional view, most treads, especially those used on cars and trucks, comprise one or more rubber materials intended to come into contact with the road surface during later use, and whose properties are optimized for this purpose. This layer, which essentially acts as a top layer, is made from a vulcanizable rubber compound, sometimes referred to as a "cap compound," which often contains large amounts of non-electrically conductive fillers, such as precipitated silica.

[0006] Beneath the rubber material intended for road contact is usually a base layer (often referred to as a "base"). In the majority of cases, this base layer serves primarily to create sufficient adhesion between the top layer intended for road contact and the other parts of the pneumatic vehicle tire, thus ensuring a high bond strength between the tread and the other components of the pneumatic vehicle tire.

[0007] Those skilled in the art are aware that, for the vast majority of applications, a tread must, for technical and / or regulatory reasons, exhibit a certain degree of electrical conductivity throughout, which can prevent unwanted static charging. In many cases, however, the rubber material of the cover layer does not possess sufficient electrical conductivity to ensure this.

[0008] Therefore, the electrical conductivity of the entire tread in the prior art is usually achieved by the base mixture of the underlying base, which has increased electrical conductivity, particularly as a result of a high carbon black content. For this purpose, for example, a material strand is guided from the base to the upper side of the tread, thereby creating an electrically conductive connection between the surface of the tread and the base. The electrically conductive base mixture is usually formed up to the surface of the tread by a pre-template in the extruder. The corresponding structure is also referred to as a "carbon center beam" (CCB). Information on the technological background is disclosed, for example, in DE 4445758 B4, DE 69717958 T2, EP 1792720 A2, NL 2006420 C2 and US 2018170123 A1.

[0009] Due to the high safety and regulatory relevance of sufficient conductivity of vehicle tires, checking for the presence of the desired conductivity is an important part of the quality testing of vehicle tires.

[0010] The conductivity of vehicle tires is usually determined on a special test bench, for example, according to Guideline 110 of the German Rubber Industry Association (WdK). For this purpose, the vehicle tire is mounted on a steel rim, where it must remain for a specified eight hours before the measurement is performed. The vehicle tire is then pressed against a steel plate with a defined force, and conductivity measurements are automatically performed at three different circumferential points (offset by 120°). This test is very time-consuming and requires a lot of equipment for each vehicle tire. Accordingly, only a few tires can be measured in succession on a regular basis, particularly because larger batches would require a correspondingly large number of rims. This means that only individual tires from a batch can be measured at a time, unless a lot of time is needed to test an entire batch.Further information on the technological background is disclosed, for example, in WO 2020109995 A1 , CN 207703756 U, EP 3894847 A1 , US 8211258 B2 and CN 1390698 A.

[0011] Given the high time and cost involved, the established standard procedure makes it impossible in practice, from an efficiency point of view, to carry out the desirable complete inspection of an entire batch of tires.

[0012] For this reason, tire production often relies on an unofficial test to more quickly estimate the conductivity properties of pneumatic vehicle tires. For this purpose, an insulation measuring device is used which is equipped with a crocodile clip and an electrode tip. In use, the crocodile clip is usually clamped into the tire bead and the tip is used to make contact with the conductive area of ​​the tread, i.e. the CCB. This test delivers conductivity values ​​much more quickly, which are at least qualitatively comparable to the values ​​of the official test. The challenge when using such a handheld device is usually that correct and reproducible contact with the vehicle tires is a challenge. In particular, it is challenging to reliably hit the CCB with the pointed electrode, which is usually thin and difficult to identify due to its color in the tread surface.Together with the effort required to position the crocodile clip, the workers tasked with measuring conductivity still require a relatively long time due to the impractical handling per vehicle tire, and comprehensive training of the workers is also required.

[0013] The primary object of the present invention was to eliminate or at least reduce the disadvantages of the prior art.

[0014] In particular, it was the object of the present invention to provide a device for measuring the conductivity properties of vehicle tires, with which these conductivity properties of the vehicle tires can be determined in a fast and reliable manner.

[0015] Furthermore, it was an object of the present invention to improve the time and cost efficiency of the determination compared to the devices and methods known from the prior art, while in particular enabling a more reliable and accurate measurement than with known handheld devices. In this respect, it was desirable that the device and the corresponding method to be specified should enable the time- and cost-efficient determination of conductivity in entire tire batches, thereby eliminating, in particular, the need to first mount the vehicle tires on rims and store them for several hours.It was a further object of the present invention that the conductivity properties of vehicle tires determined with the device to be specified and the corresponding method should correspond as closely as possible to those which would be obtained in the standardized, but operationally relatively complex test procedure according to the WdK guideline.

[0016] It was a further object of the present invention that the devices to be specified and the corresponding method should be as easy to automate as possible, wherein it was also desirable that the devices to be specified should be as easy to manufacture as possible and at the same time be of robust design.

[0017] It was a further object of the present invention that the devices to be specified and the corresponding method should reduce the requirement for training and instruction of the workers entrusted with conductivity measurement by making the use particularly easy and intuitive.

[0018] Another task was that the devices to be specified should be particularly mobile so that they can also be used outside of normal production lines to check vehicle tires.

[0019] The inventors of the present invention have now found that the objects described above can be achieved if a measuring clamp is used whose clamp elements each comprise an electrically conductive contacting element and are designed to be reversibly and non-destructively movable relative to one another in order to be able to contact the tire bead and the tread surface, if at least the contacting element provided for contacting the tread is equipped with a plurality of electrically conductive guide elements, for example with conductive bristles, in order to enable reliable contacting of the conductive regions of the tread surface, as defined in the claims.

[0020] The complementary contact element, which can preferably also be designed as a brush, is applied to the tire bead, whereupon the measuring clamp is tensioned and the other end with the conductive elements of the contact element is placed on the tread. The two contact elements are connected via measuring cables, for example to an insulation tester. In this state, without the user coming into contact with any contacts, the vehicle tire is in contact at the tire bead and the tread, allowing the measurement to be initiated with the insulation tester. The desired measurement information regarding the conductivity properties can be easily read off the insulation tester. The measurement can then be repeated with little effort at additional circumferential points of the vehicle tire before the process is repeated on another vehicle tire.

[0021] The corresponding measurements can be advantageously carried out with both stationary and lying tires - at least as long as they are not lying on a conductive surface - and do not require that the vehicle tire be mounted on a rim beforehand.

[0022] This advantageously reduces the need for equipment, and the clamp-on probe ensures repeatable and reliable contact, which allows for reliable conductivity information to be obtained. In the inventors' experiments, numerous vehicle tires could thus be measured in a short time and with minimal effort. The automation of the measurement was also advantageously possible, for example, for vehicle tires transported on a conveyor belt.

[0023] The above-mentioned objects are thus achieved by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention emerge from the subclaims and the following statements.

[0024] Such embodiments, which are designated as preferred below, are combined in particularly preferred embodiments with features of other embodiments designated as preferred. Combinations of two or more of the embodiments designated as particularly preferred below are thus particularly preferred. Likewise preferred are embodiments in which a feature of one embodiment designated as preferred to any extent is combined with one or more further features of other embodiments designated as preferred to any extent. Features of preferred methods result from the features of preferred clamp meters.

[0025] The invention particularly relates to a measuring clamp for measuring the conductivity properties of vehicle tires, comprising: i) a base body, ii) a first clamp element connected to the base body, wherein the first clamp element comprises an electrically conductive first contacting element, iii) a second clamp element connected to the base body and spaced from the first clamp element, wherein the second clamp element comprises an electrically conductive second contacting element, iv) a measuring unit connected to the first contacting element and the second contacting element for measuring the conductivity properties, wherein the first contacting element is arranged on the side of the first clamp element facing in the direction of the second clamp element, wherein the measuring clamp is configured tothat the distance between the first clamp element and the second clamp element can be changed reversibly and non-destructively, wherein the first contacting element comprises a plurality of electrically conductive first conducting elements which extend from the surface of the first clamp element.

[0026] The measuring clamp according to the invention is a device in which a first and a second contacting element are provided for contacting a vehicle tire at the tire bead and at the surface of the tread, in which the pneumatic vehicle tire is, so to speak, clamped into the measuring clamp. For this purpose, the first and second contacting elements are each provided on a clamp element so that they point toward the interior of the clamp. The clamp elements attached to a base body are designed such that the distance between the clamp elements can be changed reversibly and non-destructively in order to reliably enable contact with the vehicle tire between the contacting elements.In other words, it is a measuring clamp according to the invention, wherein the measuring clamp is designed so that a vehicle tire can be arranged between the first clamp element and the second clamp element in such a way that the tread of the vehicle tire can be contacted with the first guide elements of the first contacting element and a tire bead of the vehicle tire can be contacted with the second contacting element.

[0027] The clamp meter according to the invention is used to measure the conductivity properties of the vehicle tire. These conductivity properties are determined with expert understanding between the surface of the tread and the tire bead, as these conductivity properties are of the greatest relevance for subsequent operation. In the vast majority of cases, the measured conductivity property determined with the clamp meter according to the invention will directly relate to the electrical conductivity of the tire. However, the person skilled in the art will understand that it is also possible, in principle, to determine other quantities as conductivity properties that correlate with or are derived from electrical conductivity.For example, it is also possible to determine the electrical resistance between the tire bead and the tread instead of the electrical conductivity, or to design the measuring clamp according to the invention so that, instead of the electrical conductivity itself, a value derived from it is output, for example, as a relative value after standardization by a desired conductivity. A measuring clamp according to the invention is preferred, wherein the conductivity properties are selected from the group consisting of the electrical conductivity of the vehicle tire between the tire bead and the tread and the electrical resistance of the vehicle tire between the tire bead and the tread.In this respect, the person skilled in the art readily understands that the contacting elements should be sufficiently insulated, in particular from the base body, in order to allow a reliable measurement of the electrical conductivity properties between the contacting elements, for example by making the clamp elements from a non-conductive material.

[0028] An essential component of the measuring clamp according to the invention is the base body, which has the particular function of allowing the other components of the measuring clamp to be arranged on it. An example of a measuring clamp according to the invention is one in which the base body is made of metal or plastic, preferably metal.

[0029] The base body serves, in particular, to create the structural prerequisites for the first clamp element and the second clamp element to be reversibly and non-destructively adjustable in terms of their distance from one another. For example, a measuring clamp according to the invention is conceivable, wherein the base body comprises a guide rail for guiding the first clamp element and / or the second clamp element.

[0030] It can be seen as an advantage of the measuring clamp according to the invention that it can be particularly easily designed as a handheld device, which can be manually operated by the workers entrusted with measuring the conductivity properties. Handling can be improved by providing a handle on the base body. Accordingly, a measuring clamp according to the invention is preferred, wherein the base body comprises a handle, and / or wherein the measuring clamp is a handheld device.

[0031] As an alternative to the handheld device design, the measuring clamp according to the invention can also be designed as an end effector, which advantageously allows its use to be particularly well automated. For this purpose, a measuring clamp according to the invention is preferred, wherein the base body comprises a fastening device for fastening the measuring clamp to an automated movement unit, preferably to a robot. In the measuring clamp according to the invention, the distance between the first clamp element and the second clamp element can be changed reversibly and non-destructively, as is known from pliers. This changeability of the distance can in principle be achieved by only one of the clamp elements being movably arranged on the base body. Alternatively, however, an embodiment can also be implemented in which both clamp elements are movably arranged on the base body.According to the inventors' assessment, a particularly robust and structurally comparatively simple preferred embodiment results, which can also be used particularly efficiently in the method according to the invention if the clamp element designed for contact with the tire bead, together with the contacting element, is designed to be movable, while the parts intended for contact with the tread are designed to be fixed in position. Thus, a measuring clamp according to the invention is conceivable, wherein the second clamp element is connected to the base body in a fixed position, wherein the first clamp element is arranged on the base body for reversible and non-destructive movement, or wherein the first clamp element and the second clamp element are arranged on the base body for reversible and non-destructive movement.However, a measuring clamp according to the invention is preferred, wherein the first clamp element is connected to the base body in a fixed position, wherein the second clamp element is arranged on the base body in a reversible and non-destructively movable manner.

[0032] To ensure the most reliable and reproducible measurement possible, the inventors believe it is preferable to control the change in distance between the clamp elements using suitable mechanisms. At least theoretically, it is possible to control the movement of the clamp elements using a hydraulic mechanism, such as an oil pressure cylinder, or a screw drive. However, the inventors believe it has proven particularly advantageous to provide a preload mechanism between the clamp elements. This mechanism ensures that the tire is inserted into the measuring clamp against the tension exerted by the preload mechanism, as this ensures a good contact force.For example, the second clamp element can be applied to the tire bead along with the corresponding contacting element, whereupon the workers involved in the process expand the measuring clamp against the tension of the pre-tensioning mechanism in order to position the first clamp element over the tread.

[0033] Subsequently, the return movement of the preload mechanism ensures that a predefined force acts between the clamp elements, which fixes the tire between the clamp elements in the desired manner and ensures a particularly reproducible measurement. Accordingly, a measuring clamp according to the invention is preferred, wherein the measuring clamp additionally comprises: vi) a movement mechanism for reversibly and non-destructively changing the distance between the first clamp element and the second clamp element, wherein the movement mechanism is preferably a hydraulic mechanism or comprises a helical gear.

[0034] Additionally or alternatively, a measuring clamp according to the invention is preferred, wherein the measuring clamp additionally comprises: v) a pretensioning mechanism arranged between the first clamp element and the second clamp element, wherein the pretensioning mechanism is preferably designed such that the increase in the distance between the first clamp element and the second clamp element occurs against a tension exerted by the pretensioning mechanism, wherein the pretensioning mechanism preferably comprises a tension spring.

[0035] Within the scope of the present invention, the first contacting element, i.e., the contacting element which, in later use, is intended in particular for contacting the tread, is of particular importance. According to the invention, this element comprises a plurality of electrically conductive first conducting elements extending from the surface of the first clamp element. In other words, this is not a typical, for example, plate-shaped electrode, but rather an arrangement of a plurality of individual conducting elements intended to enable good contact with the tread surface and, in particular, to ensure contact with the CCB.An example is a measuring clamp according to the invention, wherein the first conducting elements consist at least partially, preferably predominantly, particularly preferably substantially completely of an electrically conductive material which is selected from the group consisting of metals and carbon fiber reinforced plastic, preferably selected from the group consisting of stainless steel, copper, silver, gold and carbon fiber reinforced plastic, particularly preferably selected from the group consisting of stainless steel, copper and carbon fiber reinforced plastic, very particularly preferably carbon fiber reinforced plastic.

[0036] In practice, the person skilled in the art readily distinguishes between an electrically conductive material and an electrically insulating material based on his or her expert and clear technical understanding of these terms. In this respect, a material is considered to be electrically conductive within the scope of the present invention in particular if its specific electrical resistance at 20 °C is 1000 Ω mm 2 / m or less, preferably at 100 Q mm 2 / m or less, particularly preferably 10 Q mm 2 / m or less. Conversely, a material is considered to be an electrically insulating material within the scope of the present invention if its specific electrical resistance at 20 °C is 10 8 Q mm 2 / m or more, preferably at 10 10 Q mm2 / m or more, particularly preferably 10 12 Q mm 2 / m or more. Accordingly, metals and alloys, as well as many conductive plastics, are electrically conductive materials, whereas typical, unmodified plastics such as PET or PE are electrically insulating materials, as are most glasses and ceramics.

[0037] In practice, the number of conducting elements will be matched by the person skilled in the art to the size of the vehicle tire and the size of the CCB. The inventors propose that sufficient conducting elements should be provided to allow contact with the tread surface with such a resolution that the CCB is reliably contacted even if there are small deviations in the actual alignment of the measuring clamp to the tire during use, in particular as a handheld device. In this respect, a measuring clamp according to the invention is preferred, wherein the first contacting element comprises 10 or more, preferably 30 or more, particularly preferably 50 or more, very particularly preferably 100 or more, especially preferably 2000 or more, electrically conductive first conducting elements.

[0038] In the inventors' opinion, in addition to a density of guide elements tailored to the vehicle tires to be measured, it is particularly advantageous to design the individual guide elements in such a way that they allow optimal adaptation to the tread surface, which can often be inherently curved and / or structured by a tread profile. In the inventors' opinion, it is conceivable, for example, to design the individual guide elements as spring elements, which can be compressed to varying degrees upon contact with the tread in order to ensure the best possible contact at every position. Following a similar concept, it is also possible to provide conductive pins, which can, for example, be at least partially countersunk into the clamp element in order to map the heights and depths of the tread.In these cases, a measuring clamp according to the invention is preferred, wherein the first conducting elements are electrically conductive springs, with contact plates preferably being arranged at the end of the springs facing away from the first clamp element. Alternatively, a measuring clamp according to the invention is preferred, wherein the first conducting elements are electrically conductive pins, with the electrically conductive pins being arranged in a reversible and non-destructively retractable manner in the first clamp element.

[0039] However, according to the inventors' assessment, particularly powerful measuring clamps are obtained when the first contacting element is designed in the manner of a brush, in which a large number of conductive bristle elements enables reliable, structure-adapted contacting with a generally very high surface resolution, so that this is particularly preferred for essentially all embodiments of the measuring clamp according to the invention. A measuring clamp according to the invention is particularly preferred in which the first contacting element is a brush, and the first conductive elements are electrically conductive bristles, preferably carbon bristles.

[0040] The second contacting element serves to establish a good electrical connection to the tire bead. In practice, contacting the tire bead is often less demanding than hitting the CCB on the structured and possibly curved tread. Thus, according to the inventors, it is also conceivable for the second contacting element to be designed as a conventional flat electrode. A clamp meter according to the invention is thus conceivable, with the second contacting element being a plate-shaped or rod-shaped electrode.

[0041] However, in the inventors' estimation, it is preferable for essentially all embodiments to also provide the second contacting element with a plurality of conductive elements, analogous to the first contacting element, thereby enabling particularly reliable and structurally adapted contacting of the tire bead. The design as a brush with conductive bristles is also particularly preferred here. Accordingly, a measuring clamp according to the invention is preferred, wherein the second contacting element comprises a plurality of electrically conductive second conductive elements extending from the surface of the second clamp element.Additionally or alternatively, a measuring clamp according to the invention is preferred, wherein the second contacting element comprises 10 or more, preferably 30 or more, particularly preferably 50 or more, very particularly preferably 100 or more, particularly preferably 2000 or more, electrically conductive second conducting elements.Additionally or alternatively, a measuring clamp according to the invention is also preferred, wherein the second conducting elements consist at least partially, preferably predominantly, particularly preferably substantially completely of an electrically conductive material which is selected from the group consisting of metals and carbon fiber reinforced plastic, preferably selected from the group consisting of stainless steel, copper, silver, gold and carbon fiber reinforced plastic, particularly preferably selected from the group consisting of stainless steel, copper and carbon fiber reinforced plastic, very particularly preferably carbon fiber reinforced plastic.

[0042] Particularly preferred is a measuring clamp according to the invention, wherein the second conducting elements are electrically conductive springs, wherein contact plates are preferably arranged at the end of the springs facing away from the second clamp element. Alternatively, particularly preferred is a measuring clamp according to the invention, wherein the second conducting elements are electrically conductive pins, wherein the electrically conductive pins are arranged in the second clamp element in a reversible and non-destructively retractable manner. Very particularly preferred is a measuring clamp according to the invention, wherein the second contacting element is a brush, wherein the second conducting elements are electrically conductive bristles, preferably carbon bristles.

[0043] Particularly from a manufacturing perspective, the inventors believe it is particularly advantageous to design the first conducting elements and the second conducting elements essentially identically, with the use of two brushes with conductive bristles resulting in particularly powerful measuring clamps according to the invention. A measuring clamp according to the invention is preferred, wherein the first conducting elements and the second conducting elements are preferably of the same type.

[0044] In terms of dimensioning, the contacting elements, and thus in many cases indirectly also the clamp elements, are matched to the tire elements to be contacted. This means that the components intended for contacting the tire bead can be made significantly shorter, as this is sufficient for reliable contact with the usually narrow tire bead, with a correspondingly shorter design improving handling properties in practice. In contrast, the components intended for contacting the tread surfaces should be designed at least long enough that, when a vehicle tire is arranged in the measuring clamp, they extend sufficiently far beyond the tread to cover the CCB, which is usually located in the center of the tread.An example is a measuring clamp according to the invention, wherein the first contacting element is designed to contact the tread of a vehicle tire in the axial direction over 50% or more, preferably over 70% or more, particularly preferably over 90% or more, of the tread width, and / or wherein the first contacting element has a length in the range of 10 to 50 cm, preferably in the range of 15 to 40 cm, particularly preferably in the range of 20 to 30 cm. An example is additionally or alternatively a measuring clamp according to the invention, wherein the second contacting element is designed to contact the tire bead of a vehicle tire, and / or wherein the second contacting element has a length in the range of 5 to 25 cm, preferably in the range of 7 to 20 cm, particularly preferably in the range of 9 to 15 cm.

[0045] The first contacting element and the second contacting element are connected to a measuring unit via cables, which can be routed, for example, inside the base body. In preferred embodiments, this is an insulation resistance measuring device, which is particularly due to the fact that the expected conductivity values ​​of vehicle tires are comparatively low overall, since even rubber materials made conductive, such as those processed in the CCB, have a relatively high resistance compared to conventional conductive materials, such as metal. A clamp meter according to the invention is preferred, wherein the measuring unit is a resistance measuring device, preferably an insulation resistance measuring device.

[0046] The invention also relates to a method for determining the conductivity properties of vehicle tires using a measuring clamp according to the invention, comprising the method steps: a) producing or providing a vehicle tire comprising two tire beads and a tread located on the outside in the radial direction, b) contacting one of the tire beads with the second contacting element, c) contacting the tread with the first conducting elements of the first contacting element, d) measuring the conductivity properties of the vehicle tire between the first contacting element and the second contacting element with the measuring unit.

[0047] A method according to the invention is preferred, wherein the method is carried out with the vehicle tires in a stationary or lying position.

[0048] Additionally or alternatively, a method according to the invention is preferred, wherein the method is carried out for each vehicle tire at two or more, preferably three or more, particularly preferably four or more, measuring points distributed over the circumference.

[0049] Additionally or alternatively, a method according to the invention is also preferred, wherein the measuring clamp is arranged on an automated movement unit, wherein the method is operated as an automated method, wherein the method is carried out successively for a plurality of vehicle tires, wherein the plurality of vehicle tires are preferably conveyed on a conveyor unit, preferably a conveyor belt, in particular a conveyor belt with a non-conductive surface.

[0050] The invention and preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying figure. It shows:

[0051] Fig. 1 shows a schematic side view of a measuring clamp according to the invention in a preferred embodiment. Fig. 1 shows a measuring clamp 10 according to the invention in a preferred embodiment. A first clamp element 14 and a second clamp element 18 are attached to the base body 12, which is provided with a handle 24. Their distance from one another can be changed reversibly and non-destructively. The second clamp element 18 is movably arranged on the base body 12 via a guide rail (not shown) and is connected to the first clamp element 14 via a pretensioning mechanism 26, which is designed as a spring.

[0052] On the side of the first clamp element 14 facing the interior of the clamp, a first contacting element 16 is arranged. This contacting element is designed as a brush with a plurality of electrically conductive bristle elements made of carbon fibers and is intended to contact a vehicle tire at the tread surface. The second clamp element 18 is shorter than the first clamp element 14, but, as the second contacting element 20, is also equipped with a conductive brush with a plurality of carbon fiber bristles.

[0053] Both the first contacting element 16 and the second contacting element 20 are connected to a measuring unit 22 via cables guided inside the measuring clamp 10, some of which are shown as dashed lines. In the example shown in Fig. 1, this measuring unit is designed as an insulation measuring device.

[0054] The measuring clamp 10 shown in Fig. 1 is used in such a way that, in a vehicle tire to be measured, one of the tire beads is contacted with the shorter, second contacting element 20 and the measuring clamp 10 is clamped against the force acting by the pretensioning mechanism 26 in order to guide the first clamp element 14 and thus the first contacting element 16 over the tread and then to fix the vehicle tire between the first contacting element 16 and the second contacting element 20 so that the conductivity properties of the pneumatic vehicle tire between the first contacting element 16 and the second contacting element 20 can be determined with the measuring unit 22.

[0055] List of reference symbols

[0056] 10 measuring clamp

[0057] 12 basic bodies

[0058] 14 first clamp element 16 first contacting element

[0059] 18 second pliers element

[0060] 20 second contacting element

[0061] 22 measuring unit

[0062] 24 Handle 26 Pre-tensioning mechanism

Claims

Claims 1. Measuring clamp (10) for measuring the conductivity properties of vehicle tires, comprising: i) a base body (12), ii) a first clamp element (14) connected to the base body (12), wherein the first clamp element (14) comprises an electrically conductive first contacting element (16), iii) a second clamp element (18) connected to the base body (12) and spaced from the first clamp element (14), wherein the second clamp element (18) comprises an electrically conductive second contacting element (20), iv) a measuring unit (22) connected to the first contacting element (16) and the second contacting element (20) for measuring the conductivity properties, wherein the first contacting element (16) is arranged on the side of the first clamp element (14) facing in the direction of the second clamp element (18),wherein the second contacting element (20) is arranged on the side of the second clamp element (18) facing in the direction of the first clamp element (14), wherein the measuring clamp (10) is designed so that the distance between the first clamp element (14) and the second clamp element (18) can be changed reversibly and non-destructively, wherein the first contacting element (16) comprises a plurality of electrically conductive first conducting elements extending from the surface of the first clamp element (14).

2. Measuring clamp (10) according to claim 1, wherein the base body (12) comprises a handle (24).

3. Measuring clamp (10) according to one of claims 1 or 2, wherein the first clamp element (14) is connected in a fixed position to the base body (12), wherein the second clamp element (18) is arranged on the base body (12) in a reversible and non-destructively movable manner.

4. Measuring clamp (10) according to one of claims 1 to 3, wherein the first contacting element (16) comprises 10 or more electrically conductive first conducting elements.

5. Measuring clamp (10) according to one of claims 1 to 4, wherein the first conducting elements consist at least partially of an electrically conductive material which is selected from the group consisting of metals and carbon fiber reinforced plastic.

6. Measuring clamp (10) according to one of claims 1 to 5, wherein the first contacting element (16) is a brush, wherein the first conducting elements are electrically conductive bristles.

7. Measuring clamp (10) according to one of claims 1 to 6, wherein the second contacting element (20) is a brush, wherein the second conducting elements are electrically conductive bristles.

8. Measuring clamp (10) according to one of claims 1 to 7, wherein the measuring clamp (10) additionally comprises: v) a pretensioning mechanism (26) arranged between the first clamp element (14) and the second clamp element (18).

9. Clamp meter (10) according to one of claims 1 to 8, wherein the measuring unit (22) is a resistance meter.

10. Method for determining the conductivity properties of vehicle tires with a measuring clamp (10) according to one of claims 1 to 9, comprising the method steps: a) producing or providing a vehicle tire comprising two tire beads and a tread located on the outside in the radial direction, b) contacting one of the tire beads with the second contacting element (20), c) contacting the tread with the first conducting elements of the first contacting element (16), d) measuring the conductivity properties of the vehicle tire between the first contacting element (16) and the second contacting element (20) with the measuring unit (22).

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