Device and method for measuring a friction coefficient
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-06-05
- Publication Date
- 2026-04-15
AI Technical Summary
Existing methods for measuring friction coefficients are inaccurate due to interference from compression forces and configuration issues, particularly when testing materials with varying sizes or shapes, leading to unequal compression forces and affected measurement results.
A device with sample holders, tensioning arms, and a tensioning mechanism that allows for adjustable and uniform compression forces between samples and a test piece, using cylindrical or spherical surfaces for rotation and self-adjustment, ensuring no torque affects the compression force, and incorporating a force gauge for precise measurements.
The device provides more accurate friction coefficient measurements by ensuring identical compression forces across samples and test pieces, regardless of size changes, and allows for temperature control, enhancing the representativeness and precision of the measurements.
Smart Images
Figure HU2024050040_12122024_PF_FP_ABST
Abstract
Description
[0001] Device and method for measuring a friction coefficient
[0002] The invention relates to a device for measuring a friction coefficient measurable between samples and a test piece, the device comprising sample holders adapted for securing the samples, sample mounts adapted for seating the sample holders, tensioning arms connected to the sample mounts, a tensioning mechanism that is connected to the tensioning arms and is adapted for pressing the samples against the test piece, and a pull frame connected to the tensioning arms.
[0003] The prior art includes various technical solutions for determining friction coefficients between two different materials, and for testing the friction behaviour of the materials. These solutions are typically specialised for the automotive industry, and are typically less accurate due to their configuration being aimed at meeting special demands.
[0004] A prior art technical solution is disclosed by the document US2007 / 0169539 Al, which, relying on a similar principle as the solution according to the present invention, tests friction between two test pieces undergoing linear displacement, wherein the forces arising during the displacement are measured. However, a significant disadvantage of the device and method according to the document is that due to the setup of the compression forces and to the configuration of the machine, a number of factors are not eliminated that could interfere with accurate measurements, and thus distort the measurement results.
[0005] The prior art also includes a device named eXpert 7603 - Engineered System for Material Coatings Coefficient of Friction Testing and eXpert 7603 -Compression Actuator marketed by the company ADMET. The disclosed devices are suited for determining the coefficients of static and kinetic friction between wires of various diameters and inserts or material samples made of various materials, for example polyoxymethylene, and for tracking the amortisation of the material pairing under repeated load.
[0006] The prior art device measures the friction coefficient of a wire clamped between two inserts or material samples and clamped in the measuring machine such that the measuring machine pulls the wires clamped between the samples relative to the samples. The sample holders are connected to the device body through sample mounts, with a linearly movable connection. During the preparation of the test, the two samples approach the wire in a direction perpendicular to the longitudinal axis of the wire. The linear movement of the two sample holders in opposite directions is provided by a spindle. A load cell is connected between one of the sample holders and the sample mount. A characteristic feature of the mechanism is that the compression forces between the two samples and the wire are identical only if it can be assumed that the distances between the two samples and the wire are identical after preparing the measurement and the displacements of the two samples are the same, or the wire is able to incline (bend) under a negligibly small force such that the compression forces between the two samples and the wire become equalised.
[0007] A disadvantage of the device and the measurements it can perform is that, as a result of the compression force and the loads to which samples are subjected, the size of the samples may change during the measurement. The compression force between the two samples and the wire can be identical only in case the wire is able to bend under a negligibly small force, and thus the two forces can become equalised.
[0008] In case a friction coefficient measurement is to be performed at a greater compression force, like one that is required between a test piece having the shape of a parallel-sided block (rather than that of a wire) and the samples, care should be taken to equalise the compression force between the samples and the test piece, and it must also be ensured that pull forces on the test piece do not affect the compression force between the samples and the test piece.
[0009] The object of the present invention is to provide a device and method that are able to test and measure friction for specific material pairs more accurately and under conditions more representative of eventual practical applications compared to the prior art technical solutions.
[0010] The objective has been realised based on the recognition that, in case identical compression forces are provided between the test piece and the samples pressed against it even in case the size of the samples or the test piece changes, then the performed measurement can be more accurate, and that in order to perform still more accurate measurements, the pull force acting on the test piece must not affect the compression force arising between the samples and the test piece.
[0011] In concert with the above, the objective of the invention has been realised by providing a device for measuring a friction coefficient measurable between samples and a test piece, the device comprising sample holders adapted for securing the samples, sample mounts adapted for seating the sample holders, tensioning arms connected to the sample mounts, a tensioning mechanism that is connected to the tensioning arms and is adapted for pressing the samples against the test piece, and a pull frame connected to the tensioning arms, wherein the tensioning arms are coupled to the pull frame via cylindrical surfaces allowing the rotation of the arms, with the axes of rotation of the cylindrical surfaces substantially lying in the planes of the contact surfaces of the samples and the test piece.
[0012] In a preferred embodiment of the device according to the invention, the axes of rotation of cylindrical surfaces can be repositioned with the help of bores disposed on the pull frame for adjusting the distance between the tensioning arms.
[0013] In another preferred embodiment of the device according to the invention, for testing plate-like thin samples, the tensioning arms are connected to the pull frame via a common pivot.
[0014] In further preferred embodiments of the device according to the invention, the sample mounts may be connected to the tensioning arms along cylindrical surfaces capable of self- adjustment, with the centre points of the radii of the cylindrical surfaces being located substantially on the mutually contacting surfaces of the samples and the test piece.
[0015] In another preferred embodiment of the device, the sample mounts are connected to the tensioning arms along spherical surfaces capable of self-adjustment, with the centre points of the radii of the spherical surfaces being located substantially on the mutually contacting surfaces of the samples and the test piece.
[0016] In certain embodiments of the device according to the invention, a force gauge is installed between at least one of the sample holders and of the sample mounts of the device.
[0017] Certain preferred embodiments of the device according to the invention comprise a tensioning mechanism operated by spring force.
[0018] Other preferred embodiments of the device according to the invention comprise a tensioning mechanism operated by gravitational force.
[0019] Certain preferred embodiments of the device according to the invention comprise a pressure-operated tensioning mechanism. In possible preferred embodiments of the device according to the invention the device has a force transducing lever-type tensioning mechanism.
[0020] The device according to the invention can be configured such that at least one clamp of the device can be clamped in a tension machine.
[0021] In a preferred embodiment of the device according to the invention at least the test piece can be heated or cooled.
[0022] The objective of the invention can be realised by providing a method for measuring a friction coefficient measurable between samples and a test piece applying the device according to any of the preceding claims, the method comprising the steps of placing the prepared samples in the sample holders, and connecting the prepared test piece and pull frame to the measuring machine, adjusting, utilising the tensioning mechanism, the compression force pressing together the samples and the test piece, moving, utilising the measuring machine, the test piece at the desired velocity with respect to the pull frame and measuring the force corresponding to the movement, and determining the friction coefficient as a ratio of the motive force and the compression force.
[0023] In a preferred realisation of the method, a tension machine is applied as measuring machine.
[0024] In a further preferred realisation of the method, the friction coefficient is determined at a temperature different from the ambient temperature.
[0025] The device and method according to the invention will now be described referring to the accompanying drawings, where
[0026] Fig. 1 shows a longitudinal sectional view of an embodiment of the device according to the invention, with a spring tensioning mechanism,
[0027] Fig. 2 shows a longitudinal sectional view of an embodiment of the device according to the invention that is suited for testing plate test pieces,
[0028] Fig. 3 shows a longitudinal sectional view of an embodiment of the device according to the invention, with a gravitationally loaded tensioning mechanism, Fig. 4 shows a longitudinal sectional view of an embodiment of the device according to the invention, with a pneumatic or hydraulic tensioning mechanism and a force gauge built in the sample mounts,
[0029] Fig. 5 shows a longitudinal sectional view of an embodiment of the device according to the invention, connected to a tension machine,
[0030] Fig. 6 shows a longitudinal sectional view of an embodiment of the device according to the invention, lever-type hydraulic or pneumatic tension mechanism,
[0031] Figs. 7 and 7b, respectively, show a longitudinal sectional view and a cross-sectional view taken along the plane A-A of an embodiment of the device according to the invention, and
[0032] Figs. 8, 8b and 8c, respectively, show a longitudinal sectional view, a cross-sectional view taken along the plane A-A, and a magnified assembled sectional view of an embodiment of the device according to the invention.
[0033] Fig. 1 illustrates a preferred exemplary embodiment of the measurement device according to the invention. The test piece 12 is connected to a measuring machine (not shown in the figure) through a clamp 110. The samples 1 la, 1 lb are seated in sample holders 13a, 13b of the device, each sample holder 13a, 13b being connected to tensioning arms 15a, 15b with a respective screw 144.
[0034] During the preparations for the measurement, the samples I la, 11b are pressed against the test piece 12 utilising a tensioning mechanism 16, fixing the position of the sample holders 13a, 13b by tightening the screws 144. It can be assumed that in such a manner the samples I la, 11b are pressed against the test piece 12 along their entire surface with a uniform load.
[0035] The tensioning arms 15a, 15b are coupled to the pull frame 17 via cylindrical surfaces 18a, 18b allowing the rotation of the arms, with the axes of rotation of the cylindrical surfaces substantially lying in the planes Pa, Pb of the contact surfaces of the samples I la, 11b and the test piece 12, so no torque arises on the tensioning arms 15a, 15b as a result of the tensioning of the test piece 12, as a result of which no such force component arises which could affect the compression force between the samples I la, 11b and the test piece 12. The pull frame 17 is coupled to a measuring machine (not shown) through a clamp 19. The tensioning mechanism 16 is connected to the tensioning arms 15a, 15b through articulations 113, 114 with a connection allowing rotation.
[0036] The components of the tensioning mechanism 16 are articulations 113, 114, a spindle 115, an adjustment knob 112 connected to the spindle 115 by thread engagement, a tensioning spring 116 placed between the articulation 114 and the adjustment knob 112 concentrically to the spindle 115, and a counterweight 111 attached to the spindle 115. The spindle 115 engages the articulation 113 by means of a thread, and is attached to the articulation 114 allowing free axial movement. The force generated by the tensioning spring 116 can be adjusted to the desired value by turning the counterweight 111 and the adjustment knob 112 such that the tensioning mechanism 16 is in a balanced state, and that no tilting torque is exerted on the centre points of the cylindrical surfaces 18a, 18b. The tensioning spring 116 pulls the tensioning arm 15a with the same force as it pushes on the tensioning arm 15b, so the samples I la, 11b are subjected identical-magnitude forces determined by the power arm / load arm ratios occurring at the tensioning arms 15a, 15b.
[0037] During friction coefficient measurements, the test piece 12 encompassed and compressed by the samples I la, 11b is pulled between the samples I la, 11b by the measuring machine (not shown here), while measuring the pull force. From the ratio of the pull force and the compression force the friction coefficient can be determined continuously, so the coefficient of static friction and the coefficient of kinetic friction can be measured.
[0038] After releasing the tensioning mechanism 16 and pulling out the test piece 12, the tensioning arms 15a, 15b can be folded out and the samples 1 la, 1 lb can be replaced.
[0039] Fig. 2 illustrates another exemplary embodiment that is suited for testing thin plate test pieces. This exemplary embodiment is similar to the configuration depicted in Fig. 1 with the following differences: The thin plate test piece 22 is clamped in a measuring machine (not shown in the figure) that tensions the test piece 22 between the two samples pressed against it. The tensioning arms 25a, 25b are tightened together by a spring tensioning mechanism 26. Samples 21a, 21b placed in sample holders 23a, 23b are pressed against the test piece 22. The sample holders 23a, 23b are seated in sample mounts 24a, 24b. The sample mounts 24a, 24b are connected to the tensioning arms 25a, 25b along cylindrical surfaces with radii Rcl, Rc2 allowing rotation, thus ensuring that the test piece 22 and the samples 21a, 21b are coupled along their entire surface, with a uniform load. The centre points of cylindrical surfaces of the sample mounts 24a, 24b having respective radii Rcl and Rc2 are essentially located on the mutually contacting surfaces of the samples 21a, 21b and the test piece 22, as a result of which no such torque arises on the samples 21a, 21b due to the pulling of the test piece 22 which would tilt the samples 21a, 21b and would thus cause uneven loading of the contacting surfaces. The tensioning arms 25a, 25b are attached to the pull frame 27 allowing rotation, i.e., by a pivot 28. In this case the geometrical axis of the pivot 28 lies in the symmetry plane P of the plate test piece 22. Because the distance between the plane of symmetry of the plate test piece 22 and the plate’s surface is small, the torque that “wants to rotate” the tensioning arms 25a, 25b about the pivot 22 axis when the plate test piece 22 is being pulled is negligible. This solution has the advantage that the pivot point of the tensioning arms 25a, 25b can be provided in an economical way.
[0040] Fig. 3 shows another preferred embodiment that is similar to the embodiment depicted in Fig. 1. In this case, the sample mounts 34a, 34b are coupled to the tensioning arms 35a, 35b in a manner allowing self-adjustment, along spherical surfaces having radii Rsl, Rs2. In such a way, the parallel error of the sides under test of the test piece 32 can also be compensated. The tensioning arms 35a, 35b are attached to the pull frame 37 by pivots 38a, 38b, allowing rotation, of which the axes of rotation substantially lie in the planes Pa, Pb of the contact surfaces of the samples and the test piece 32, so no torque about the axis of the pivots 38a, 38b arises on the tensioning arms 35a, 35b due to the pulling of the test piece 32, as a result of which no such force component arises which could affect the compression force between the samples and the test piece 32. A tensioning mechanism 36 is connected to the tensioning arms 35a, 35b.
[0041] The tensioning mechanism 36 includes an adjustment weight 312, a force distributor 318, a threaded spindle 314, and a counterweight 311. By adjusting the lever arm L of the adjustment weight 312, the pivots 316 and 317 are subjected to a pull force and a pressing force, respectively. The pull force is transmitted from the pivot 316 to a tensioning arm 35a through a threaded spindle 314 via an articulation 313. From the pivot 317, the pressing force is transmitted to the tensioning arm 35b via a bar 319 and a pivot 315. The counterweight 311 and a nut attached to the articulation 313 can be applied for adjusting the balance of the device. After completing preparation for a measurement, the device is in a balanced state; the samples are not subjected to any force required for preserving the balance of the device. After the measurement, the tensioning arms 35a, 35b can be folded out by pulling out the pivot 316 and the samples can be removed and replaced, and, if necessary, a new test piece can be inserted into the device.
[0042] Fig. 4 shows a technical solution that is similar to the embodiment depicted in Fig. 3. The sample mounts 44a, 44b are coupled to the tensioning arms 45a, 45b in a manner allowing self-adjustment, along spherical surfaces having radii Rsl, Rs2. In such a way, the parallel error of the sides under test of the test piece 42 can also be compensated. The tensioning arms 45a, 45b are attached to the pull frame 47 by pivots 48a, 48b, allowing rotation, with the axes of rotation of the pivots substantially lying in the planes Pa, Pb of the contact surfaces of the samples and the test piece 42, so no torque arises on the tensioning arms 45a, 45b about the axes of the pivots 48a, 48b as a result of the pulling of the test piece 42, as a result of which no such force component arises which could affect the compression force between the samples and the test piece 42. A tensioning mechanism 46 is connected to the tensioning arms 45a, 45b. In the pull frame 47, the pivots 48a, 48b can be inserted into bores 466 symmetrically to the centre plane of the apparatus, corresponding to the distance between the sides included in the test of the test piece 42. In such a manner, test pieces with different distances between their sides included in the test can be applied. In case the samples 41a, 41b are subject to greater loads, significant friction heat is generated; in such cases it can be advantageous to apply test pieces with a greater distance between their sides such that the generated heat affects measurement temperature to the least possible extent.
[0043] In the embodiment shown in Fig. 4, the samples 41a, 41b are seated in sample holders 43a, 43b, with the sample holders 43a, 43b being slid / inserted into sleeves 416a, 416b firmly attached to the sample mounts 44a, 44b in a manner allowing free axial movement. Force gauges 417a, 417b are connected between the sleeves 416a, 416b and the sample holders 43a, 43b. The device can also be configured such that a force gauge is only included between one pair of the mutually corresponding sleeves 416a, 416b and sample holders 43a, 43b. A hydraulic tensioning mechanism 46 is connected to the tensioning arms 45a, 45b.
[0044] The tensioning mechanism 46 is similar to the solution depicted in Fig. 1, but instead of applying a spring, a piston 415 movable in a hydraulic cylinder 412 is utilised for tensioning the tensioning arms 45a, 45b towards each other.
[0045] In Fig. 5, the measurement device 50 according to the invention is attached to a tension machine 51. Fig. 6 shows an arrangement that is similar to the embodiment depicted in Fig. 3, with the difference that the pull frame 67 and the test piece 62 are attached to the measuring machine (not shown) through bores 69a, 69b and a clamp 610, respectively. Further, a force transducing tensioning mechanism 66 is connected to the tensioning arms 65a, 65b that are attached to the pull frame 67 by pivots 68a, 68b. The load arms 626a, 626b of the tensioning mechanism 66 - which are coupled to the pull frame 67 via the pivots 622a, 622b - are connected to the tensioning arms 65a, 65b through auxiliary arms 621a, 621b. A hydraulic or pneumatic cylinder 632 is coupled to the load arms 626a, 626b through pivots 623a, 623b and rods 631, 633. Effected by the cylinder 632, the load arms 626a, 626b are rotated about the pivots 622a, 622b, tensioning towards each other the tensioning arms 65a, 65b through the auxiliary arms 621a, 621b. The spring tensioning mechanism described in relation to Fig. 1 can also be applied instead of the hydraulic or pneumatic cylinder 632. This configuration produces a higher force transmission ratio, so the samples can be pressed against the test piece with greater force.
[0046] Figs. 7 and 7b, respectively, depict a longitudinal section of a preferred embodiment of the invention and a sectional view thereof taken along the plane A-A of the axes of the pivots 78a, 78b. The device according to the invention is coupled to a measuring machine (not shown) through clamps 79 and 710. Samples 71a, 71b are pressed against a test piece 72. The samples 71a, 71b are seated in sample holders 73a, 73b that are connected to sample mounts 74a, 74b. The sample mounts 74a, 74b are configured to have spherical surfaces with radii Rsl, Rs2, of which the centres substantially lie on the common surfaces of the samples 71a, 71b and the test piece 72. The sample mounts 74a, 74b are pressed in the direction of the test piece 72, i.e., towards each other, by the tensioning arms 75a, 75b. A spring tensioning mechanism 76 is connected to the tensioning arms 75a, 75b. The tensioning mechanism 76 includes a threaded spindle 715, an adjustment knob 712, and a counterweight 711 that can be applied for setting the desired load and the balance state of the tensioning mechanism 76 and thus of the device. The tensioning arms 75a, 75b are attached to a pull frame 77 via pivots 78a, 78b, allowing rotation. The device according to the invention is symmetrical to the section plane of the longitudinal section shown in Fig. 7, which can be clearly seen in the section taken along the plane A-A of the axes of the pivots 78a, 78b shown in Fig. 7b. Further pivots 78c, 78d are placed along the axial line of the pivots 78a, 78b, so the tensioning arm 75a rotates about pivots 78a and 78c, while the tensioning arm 75b rotates about pivots 78b and 78c relative to the pull frame 77. In such a way, it can be ensured that the axes of the pivots 75a, 75b, 75c, 75d are substantially located in the planes defined by the contact surfaces of the test piece 72 and the samples 71a, 71b while the mechanism is loaded symmetrically. The test piece 72 compressed between the samples 71a, 71b is located between the pivots 75a, 75b, 75c, 75d, and is pulled during the measurement by the clamp 710 as it gets further from the pull frame 77. The configuration of the device according to the invention shown in Figs. 7 and 7b allows that the samples can be pressed against the test piece with an increased surface load conforming to the ratio of the lever arms in the configuration. In addition to that, the mechanism’s compact size allows that a smaller-sized tension machine can be applied as a measuring machine.
[0047] After completing the measurement, by tilting the spindle 715 about the axis of T-nut 713, a slot 726 allows that the tensioning arm 75b can be folded up, and, after pulling out the test piece 72 the samples 71a and 71b can be replaced.
[0048] Fig. 8 shows the longitudinal sectional view of a heatable and coolable embodiment of the device according to the invention, with Figs. 8b and 8c, respectively, depicting a cross section of the test piece along plane A-A, and a magnified assembled view of the section of the test piece.
[0049] A test piece 82 is coupled to a measuring machine (not shown) through the clamp 810 of the device. Samples 81a, 81b are pressed against a test piece 82 by means of tensioning arms 85a, 85b. A channel 877 adapted for receiving a heater wire 892 shown in Fig. 8c is formed in the centre of the test piece 82. For providing an outlet and an inlet for the heater wire 892, bores 866 are formed to open into the channel 877. Seats 855 for receiving temperature sensors 893 shown in Fig. 8c are machined into the test piece 82. The heater wire 892 and the sensors 893 move together with the test piece 82 during the measurement, and are connected to the measuring machine with hanging cables. The cables connecting the heater wire 892 are mounted (preferably by adhesive) in a groove 881 shown in Fig. 8b, with the cables 891 of the sensors 893 being mounted (preferably by adhesive) in a groove 882.
[0050] With the help of the heater wire 892, the sensors 893, and an electronic control unit (not shown here) the test piece 82 can be heated or cooled to the desired temperature, and can be kept at the given temperature in a controlled manner. This means that the friction coefficients can be measured not only at ambient temperature but at other temperatures, which has special significance in the case of polymeric materials.
[0051] The device can be equipped with thermal insulation housing 833, and thus a thermally insulated space 844 can be provided. The space 844 helps bring about a more uniform temperature distribution in the vicinity of the test piece 82 and the samples 8 la, 8 lb. The thermally insulated space 844 may also be heated, by means of which the temperature of the entire device can be increased, and thereby the uniformity of the temperature distribution in the vicinity of the test piece 82 and the samples 81a, 81b can be improved.
[0052] The thermally insulated space 844 can also be cooled down, and, after temperature equalisation, measurements can be performed, i.e., friction coefficients can be determined, also at ambient temperature.
Claims
AMENDED CLAIMS received by the International Bureau onAmended Claims 18 November 2024 (18.11.2024)1. Device for measuring a friction coefficient measurable between samples (I la, 11b; 21a, 21b; 41a, 41b; 71a, 71b; 81a, 81b) and a test piece (12; 22; 42; 62; 72; 82), comprising sample holders (13a, 13b; 23a, 23b; 43a, 43b; 73a, 73b) adapted for securing the samples (I la, 11b; 21a, 21b; 41a, 41b; 71a, 71b; 81a, 81b), sample mounts (14a, 14b; 24a, 24b; 44a, 44b; 74a, 74b) adapted for mounting the sample holders (13a, 13b; 23a, 23b; 43a, 43b; 73a, 73b), tensioning arms (15a, 15b; 25a, 25b; 35a, 35b; 45a, 45b; 65a, 65b; 71a, 71b; 81a, 81b) connected to the sample mounts (14a, 14b; 24a, 24b; 44a, 44b; 74a, 74b), a tensioning mechanism (16; 26; 36; 46; 76) that is connected to the tensioning arms (15a, 15b; 25a, 25b; 35a, 35b; 45a, 45b; 65a, 65b; 71a, 71b; 81a, 81b) and is adapted for pressing the samples (I la, 11b; 21a, 21b; 41a, 41b; 71a, 71b; 81a, 81b) against the test piece (12; 22; 42; 62; 72; 82), and a pull frame (17; 27; 37; 47; 67; 77; 87) connected to the tensioning arms (15a, 15b; 25a, 25b; 35a, 35b; 45a, 45b; 65a, 65b; 71a, 71b; 81a, 81b), characterised in that the tensioning arms (15a, 15b; 25a, 25b; 35a, 35b; 45a, 45b; 65a, 65b; 71a, 71b; 81a, 81b) are connected to the pull frame (17; 27; 37; 47; 67; 77; 87) along cylindrical surfaces (18a, 18b; 28; 38a, 38b; 48a, 48b; 68a, 68b) allowing their rotation, with the axes of rotation of the cylindrical surfaces (18a, 18b) being located substantially in the planes of the contacting surface of the samples (I la, 11b; 21a, 21b; 41a, 41b; 71a, 71b; 81a, 81b) and the test piece (12; 22; 42; 62; 72; 82), and the sample mounts (14a, 14b) are connected to the tensioning arms (15a, 15b) along cylindrical surfaces (Rcl, Rc2) capable of self-adjustment, with the centre points of the radii (Rcl, Rc2) of the cylindrical surfaces being located substantially on the mutually contacting surfaces of the samples (I la, 11b) and the test piece (12).
2. The device according to claim 1, characterised in that, for adjusting the distance between the tensioning arms (45a, 45b), the axes of rotation of cylindrical surfaces (48a, 48b) can be repositioned with the help of bores (466) disposed on the pull frame.
3. The device according to claim 1 , characterised in that for testing plate-like thin samples, the tensioning arms (25a, 25b) are connected to the pull frame (27) via a common pivot (28).
4. The device according to any of the preceding claims, characterised in that a force gauge (417a, 417b) is installed between at least one of the sample holders (43a, 43b) and of the sample mounts.
5. The device according to any of claims 1-4, characterised by comprising a tensioning mechanism (16, 26, 76) operated by spring force.AMENDED SHEET (ARTICLE 19)6. The device according to any of claims 1-4, characterised by comprising a tensioning mechanism (36) operated by gravitational force.
7. The device according to any of claims 1 -4, characterised by comprising a pressure-operated tensioning mechanism (46, 66).
8. The device according to any of claims 1-4, characterised by comprising a force transducing levertype tensioning mechanism (66).
9. The device according to any of the preceding claims, characterised in that at least one clamp (19, 110, 610, 79, 710) of the device is configured such that it can be clamped in a tension machine.
10. The device according to any of the preceding claims, characterised in that at least the test piece (82) can be heated or can be cooled.
11. Method for measuring a friction coefficient measurable between samples (I la, 11b; 21a, 21b; 41a, 41b; 71a, 71b; 81a, 81b) and a test piece (12; 22; 42; 62; 72; 82) applying the device according to any of the preceding claims, comprising the steps of placing the prepared samples (I la, 1 lb; 21a, 21b; 41a, 41b; 71a, 71b; 81a, 81b) in the sample holders (13a, 13b; 23a, 23b; 43a, 43b; 73a, 73b) and connecting the prepared test piece (12; 22; 42; 62; 72; 82) and pull frame (17; 27; 37; 47; 67; 77; 87) to the measuring machine, adjusting, utilising the tensioning mechanism (16; 26; 36; 46; 76), the compression force pressing together the samples and the test piece, moving, utilising the measuring machine, the test piece at the desired velocity with respect to the pull frame and measuring the force corresponding to the movement, and determining the friction coefficient as a ratio of the motive force and the compression force.
12. The method according to claim 11, characterised in that a tension machine is applied as measuring machine.
13. The method according to claim 11, characterised in that the friction coefficient is determined at a temperature different from the ambient temperature.AMENDED SHEET (ARTICLE 19)StatementThe following declaration is submitted in relation to the PCT patent search:In our Opinion, neither the document DI (figure 1) nor the document D2 (figure 9) describe a solution where the axes of rotation of the tensioner arms are in line with the surface of the test specimen. The said circumstance has an important role in the operation of the invention.The relevant part of the description can be found on page 5 of the specification, lines 23-28 as follows:“The tensioning arms 15a, 15b are coupled to the pull frame 17 via cylindrical surfaces 18a, 18b allowing the rotation of the arms, with the axes of rotation of the cylindrical surfaces substantially lying in the planes Pa, Pb of the contact surfaces of the samples Ila, 11b and the test piece 12, so no torque arises on the tensioning arms 15a, 15b as a result of the tensioning of the test piece 12, as a result of which no such force component arises which could affect the compression force between the samples Ila, 11b and the test piece 12. ”The related feature can be found also in claim 1, which is the main claim:“ ... characterized in that the tensioning arms (15a, 15b; 25a, 25b; 35a, 35b; 45a, 45b; 65a, 65b; 71a, 71b; 81a, 81b) are connected to the pull frame (17; 27; 37; 47; 67; 77; 87) along cylindrical surfaces (18a, 18b; 28; 38a, 38b; 48a, 48b; 68a, 68b) allowing their rotation, with the axes of rotation of the cylindrical surfaces (18a, 18b) being located substantially in the planes of the contacting surface of the samples (Ila, 11b; 21a, 21b; 41a, 41b; 71a, 71b; 81a, 81b) and the test piece (12; 22; 42; 62; 72; 82). ”Based on the application parts cited, we take the view that our application meets the requirement of novelty. Furthermore, this feature of the invention provides high measurement benefits that were not obvious on their own, and the beneficial effect of this was not considered in previous solutions, thus establishing the existence of inventive step.If the requirement of novelty and inventive step is not fulfilled by the present scope of protection, the feature of claim 4 may be included in the main claim to achieve the best effect on the accuracy of the measurement."... characterized in that the sample mounts (14a, 14b) are connected to the tensioning arms (15a, 15b) along cylindrical surfaces (Rd, Rc2) capable of self-adjustment, with the centre points of the radii (Rd, Rc2) of the cylindrical surfaces being located substantially on the mutually contacting surfaces of the samples (Ila, 11b) and the test piece (12). ”The specific use of a cylindrical surface instead of ball surface or other different geometrical form further enhances the technical advantage of the present solution.STATEMENT UNDER ARTICLE 19 (1)