Automated laboratory device for dynamically testing durability of self-sealing tire sealant

Abstract

An automated laboratory device for dynamically testing the durability of a coating is provided. The apparatus includes an actuator that drives at least one test cell. Each test cell includes a pressure chamber assembly having a body and a clamping member. The body includes a monitoring window, an opening, and an inner chamber wall defining a pressure chamber within the body. The clamping member includes a central opening. The clamping member and the body are adapted to sandwich a substrate including the coating between the clamping member and the body to close the pressure chamber. A driven member extends through the central opening in the clamping member and is contactable with the substrate. The actuator drives one or both of an oscillatory linear motion and an oscillatory rocking motion of the driven member. A method of testing the durability of a tire coated with a self-sealing sealant for leak-proof performance is also provided.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and all advantages of U.S. Provisional Patent Application No. 63 / 407,327, filed on September 16, 2022, the contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates generally to testing the durability of coating materials on substrates, and more particularly to apparatus and methods for testing the durability of self-sealing tire sealant materials. Background Art

[0004] A "self-sealing tire" (SST) is a tire whose interior surface is coated with a layer of a self-sealing sealant material, which is typically composed of a viscous polymer, synthetic rubber, or natural rubber material. The self-sealing material fills and seals punctures in the tire tread of the tire to a certain size such that the tire does not experience a loss of air pressure. Thus, a vehicle on which the tire and associated wheel are mounted can be driven safely without any noticeable loss of control or handling until the tire is permanently repaired.

[0005] Traditionally, testing the reliability and durability of self-sealing tire materials contained in self-sealing tires has been extremely challenging and time consuming. Current testing methods require that the tire be mounted on a vehicle and the vehicle be driven on a road, test track or other proving ground at various driving speeds and road conditions for a significant period of time in order to obtain sufficient test data related to the performance of the tire when punctured and subjected to road and environmental stresses. As a result, current testing methods are costly and require a significant amount of time to complete. Therefore, there is a need for a method of testing self-sealing tire sealants that can be completed in one or more of a shorter time frame, at a lower cost, and at a lower level of CO2 emissions. Summary of the invention

[0006] An automated laboratory device for dynamically testing the durability of a coating is provided. The device includes: an actuator; and a drive shaft, the drive shaft being coupled to the actuator. The device also includes a test unit, the test unit including a cam assembly, a support flanking the cam assembly, and a pressure chamber assembly. The cam assembly is mounted on the drive shaft and includes a cam lobe, a follower, and a driven member. The cam lobe is eccentrically mounted on the drive shaft. The follower is forced to engage with the cam lobe and includes a circular body surrounding the cam lobe. The drive arm protrudes from the circular body. The pressure chamber assembly is mounted on the support and aligned with the cam assembly. The pressure chamber assembly includes a body and a clamping member. The body includes a monitoring window, an open end including an opening, and an inner chamber wall adjacent to the opening and defining a pressure chamber within the body. The clamping member includes a central opening. The clamping member and the body are adapted to sandwich a substrate including the coating therebetween to close the pressure chamber, the coating facing the interior of the pressure chamber. The driven member extends through the central opening in the clamping member and is capable of contacting the base plate. Rotation of the drive shaft drives one or both of an oscillatory linear motion and an oscillatory rocking motion of the driven member via the cam assembly.

[0007] In certain embodiments, the driven member is one of a piercing object and a blunt object.

[0008] In a specific embodiment, the piercing object is one of a nail, a screw, and a member having a pointed head.

[0009] In certain embodiments, the body of the pressure chamber assembly includes a seal circumscribing the opening. The seal includes a pair of concentric annular ridges forming an annular groove therebetween.

[0010] In certain embodiments, the device further comprises an insert disposed between the support member and the clamping member for adjusting the height of the pressure chamber assembly relative to the cam assembly.

[0011] In certain embodiments, the device further comprises a pressure sensor for monitoring the pressure in the pressure chamber.

[0012] In certain embodiments, the device further comprises a source of compressed air in fluid communication with the pressure chamber via a supply line and at least one valve connected to the supply line for filling and exhausting the pressure chamber.

[0013] In certain embodiments, the device further comprises a controller electrically connected to one or more of the actuator, the pressure sensor, and the at least one valve.

[0014] In certain embodiments, the apparatus further comprises a user interface electrically connected to the controller for setting test parameters and monitoring the pressure in the pressure chamber.

[0015] In certain embodiments, the device comprises a plurality of such test units.

[0016] A method for testing the durability of a tire coated with a self-sealing sealant for leak-proof performance is also provided. The method includes the steps of providing the automated laboratory device and providing the substrate. The substrate is a tire sample cut from a tire. The tire sample includes a tire tread on one surface and an opposite inner surface having a self-sealing sealant layer thereon. The method also includes sandwiching the tire sample between the pressure chamber body and the clamping member, the tire tread of the tire sample facing the clamping member, and the sealant layer on the inner surface of the tire sample facing the pressure chamber. The method also includes inserting the driven member into the tire sample through the central opening in the clamping member, wherein the driven member is a piercing object. The method also includes mounting the pressure chamber assembly to the support and mounting the inserted driven member to the cam assembly. The method also includes filling the pressure chamber with compressed air to a predetermined set pressure. The method also includes actuating the actuator to drive the piercing object and move the piercing object in one or both of an oscillating linear motion and an oscillating rocking motion within the tire sample. The method also includes monitoring the pressure in the pressure chamber while the piercing object is driven. The method also includes removing the piercing object from the cam assembly and removing the pressure chamber assembly to check whether there is a leak at the piercing site in the tire sample. The method also includes removing the piercing object from the tire sample and mounting another follower member to the cam assembly, wherein the follower member is a blunt object. The method also includes mounting the pressure chamber assembly to the support member, whereby the blunt object contacts the tire tread of the tire sample. The method also includes actuating the actuator to drive the blunt object and move the blunt object so that it periodically punches the tire tread of the tire sample near the piercing site. The method also includes monitoring the pressure in the pressure chamber while the blunt object is driven. The method also includes subsequently subjecting the automated laboratory device including the tire sample to a thermal cycle while further monitoring the pressure in the pressure chamber and checking whether there is a leak at the piercing site.

[0017] In certain embodiments, the method further includes monitoring the inner surface of the tire sample in the pressure chamber via the monitoring window.

[0018] In certain embodiments, the method further comprises using a camera to monitor and / or record activity in the pressure chamber at the puncture site.

[0019] In certain embodiments, the method further comprises providing an environmental chamber in which the automated laboratory device is placed. When the automated laboratory device is in the environmental chamber, one or both of the temperature and humidity in the environmental chamber are adjusted.

[0020] In certain embodiments, the method further comprises performing the steps of: actuating the actuator; and monitoring pressure at one or both of a plurality of ambient temperatures and a plurality of humidity levels. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Various advantages and aspects of the present disclosure may be understood from the following detailed description when considered in conjunction with the accompanying drawings, in which:

[0022] Figure 1 shows a side cross-sectional view of a laboratory testing apparatus according to some embodiments of the present disclosure;

[0023] Figure 2 yes Figure 1 A partially exploded perspective view of a laboratory test apparatus;

[0024] Figure 3 is a perspective view of a laboratory testing device according to other embodiments of the present disclosure;

[0025] Figure 4 Shows Figure 3 A side view of a laboratory test apparatus;

[0026] Figure 5 Shown along Figure 4 The line 5-5 in Figure 3 A cross-sectional view of a laboratory test apparatus;

[0027] Figure 6 Shows Figure 3 Top view of a laboratory test setup;

[0028] Figure 7 Shown along Figure 6 The line 7-7 in Figure 3 A cross-sectional view of a laboratory test apparatus;

[0029] Figure 8 shows a cross-sectional view of a cam assembly of a laboratory testing device according to some embodiments of the present disclosure;

[0030] Fig. 9 shows a cross-sectional view of a cam assembly of a laboratory testing device according to other embodiments of the present disclosure;

[0031] Fig.10 shows a perspective view of a cam assembly of a laboratory testing device according to other embodiments of the present disclosure;

[0032] Fig.11 Shows Fig.10 A side view of a cam assembly;

[0033] Fig.12 Shown along Fig.11 The line 12-12 in Fig.10 A cross-sectional view of a cam assembly;

[0034] Fig.13 shows a driven member of a laboratory testing device according to certain embodiments of the present disclosure;

[0035] Fig.14 shows a perspective cross-sectional view of the body of a pressure chamber assembly of a laboratory testing apparatus according to some embodiments of the present disclosure;

[0036] Fig.15 shows an exploded view of a pressure chamber assembly of a laboratory testing apparatus according to some embodiments of the present disclosure;

[0037] Fig.16 shows a perspective view of a laboratory test setup;

[0038] Fig.17 shows a schematic diagram of a movable cart including an interface display screen according to some embodiments of the present disclosure; and

[0039] Fig.18 A photograph showing the sheath and cap features formed in the tire sealant at the puncture site of the tire. DETAILED DESCRIPTION

[0040] Provided is an automated laboratory test device for testing the durability of a coating on a substrate and a method for testing the durability of a tire coated with a self-sealing tire sealant for leak-proof performance. As will be understood from the description herein, the disclosed test device and method provide a rapid screening test for coating materials including self-sealing tire sealants, and reduce or eliminate the need for on-board, road testing of self-sealing tires to determine performance. The test device and method are also capable of testing the effects of both the in-and-out (insertion-extraction) and swing (lateral) stresses applied to the tire by a puncturing object on the sealant pressure retention performance using only a small portion of the self-sealing tire sample. Therefore, the test device and method of the present invention are dynamic rather than static because it actively simulates the force applied by the puncturing object in the puncture site of the tire, and the road stress applied to the puncture site after the puncturing object has been removed. In addition, the device is capable of testing self-sealing tire samples at multiple different driving speeds (i.e., frequencies) and air temperatures to simulate on-board testing at different vehicle speeds and different road conditions and climate conditions.

[0041] refer to Figures 1 to 17 , wherein like numerals indicate corresponding parts throughout the several views, illustrates an automated laboratory test apparatus (also referred to herein as a test apparatus or simply as an apparatus) and is generally designated 10. Certain features of the test apparatus 10 are functional, but may be implemented in different aesthetic configurations. The test apparatus 10 generally includes an actuator 12 and at least one test unit 14 driven by the actuator.

[0042] The actuator 12 is mounted on a planar base 16. The actuator 12 is illustrated by way of example as an electric motor, such as a stepper motor or the like. In this embodiment, the actuator 12 is coupled to a drive shaft 18, and the drive shaft connects the actuator to the test unit 14. More specifically, a coupler 20 connects the drive shaft 18 to the actuator 12. The drive shaft 18 is rotatably supported by a plurality of bearing assemblies 22 (such as high-speed mounted ball bearings) mounted on the base 16. The drive shaft 18 transmits the power of the actuator 12 to the test unit 14 via a cam mechanism. However, it should be understood that other types of actuators and drive arrangements are also within the scope of the present disclosure, and therefore, the actuator may be a pneumatic or hydraulic cylinder, an electromagnetic device, or a reciprocating device such as a shaker, and the actuator may drive the test unit via a pneumatic line, a hydraulic line, an electromagnetic pulse, or the like.

[0043] The test unit 14 is mounted on the base 16 and is connected to the actuator 12 and driven by the actuator. As shown in the example, the device 10 may include two test units 14 arranged in series on the same drive shaft 18; however, it should be understood that the device only requires one test unit. The two test units 14 allow two different samples to be tested simultaneously, as described in more detail below, thereby increasing the test capacity and output of the device 10. In other embodiments, the device may include more than two test units. For example, the device may include four test units arranged in series on the same drive shaft, and the device may also include two actuators and associated drive shafts arranged in parallel, wherein the four test units are connected in series to each of the drive shafts. Due to the modularity of the test unit 14, the device 10 can be easily expanded to include more or less test units. In addition, even if more than one test unit is included in the device, it is not necessary to use all test units at the same time. For example, only one test unit in the two test units can be used. Additionally, multiple test units on one drive shaft allow multiple parts of the same sample to be tested simultaneously with more than one type or size of test object (nails, screws, punches, etc.), while multiple drive shafts, each with one or more test units, allow simultaneous testing using independent operating conditions (frequency, amplitude, cycles) for each drive shaft.

[0044] Each test unit 14 includes a cam assembly 24, which is mounted on the drive shaft 18 by a bushing 26 (such as a steel quick-clamp screw clamp bushing). The cam assembly 24 includes a cam lobe 28, a follower 30, and a driven member 32. The cam lobe 28 is eccentrically mounted on the drive shaft 18. The cam lobe 28 can be, for example, an offset cam ring, the center of which is offset from the center of the drive shaft 18 by about 2 mm (e.g., 2±0.1 mm), or about 1.5 mm (e.g., 1.5±0.1 mm). The distance of the offset is related to the length of the driven member 32 and the desired degree of movement of the driven member. For example, as will become more apparent below, a 2 mm eccentricity provides the driven member 32 with a linear motion of ±2 mm and a rotational (torsion, back-and-forth rocking) motion of ±1.8° relative to its neutral position. The follower 30 is mounted and retained on the cam lobe 28 in a forced engagement manner via a bearing ring 34 (such as a steel needle bearing, etc.). Specifically, the follower 30 includes a circular body 36 having a circular internal opening 38, in which the cam lobe 28 and the sandwiched bearing ring 34 are disposed. The follower 30 also includes a linear drive arm 40 that protrudes from the circular body 36 and extends outwardly. The drive arm 40 includes a recessed portion 42, and the follower member 32 is retained in engagement with the drive arm in the recessed portion. Figure 8 In one arrangement shown, the driven member 32 is fixedly mounted in the recess 42 by a set screw 44 and a lock nut 46. In this arrangement, the set screw 44 is screwed a certain distance into the recess 42, and the driven member 32 is held in tight engagement against the outwardly facing surface 45 of the set screw 44 by the lock nut 46 screwed into the recess 42. The set screw 44 provides a hard contact with the driven member 32, which represents hard road conditions. On the other hand, in Fig. 9In the alternative arrangement shown, the driven member 32 is flexibly mounted in the recess 42 by a resilient member 48 (such as a spring). In this arrangement, the spring 48 is disposed in the recess 42, and the driven member 32 is fixed in the recess by a locking nut 46. The spring 48 pushes the driven member 32 outward away from the drive arm 40, but also allows the driven member to retract. The flexible contact provided by the spring 48 represents a soft road condition. In addition, the spring 48 is more forgiving during the installation of the test sample (see below) and applies less undesirable stress to the coating of the test sample due to factors such as thickness variations of the test sample. At the same time, the spring force of the spring 48 must be large enough to overcome the force required to move the driven member 32 during the dynamic durability test. For example, during sample testing, a force between about 72N and 163N may be required to move the driven member 32, and accordingly, the spring 48 may have a spring rate between 2.5lb / mm and 4.5lb / mm, more preferably between 2.9lb / mm and 3.9lb / mm, and a maximum load between 27lb and 32lb, more preferably between 28lb and 21lb. In addition, given a recess 42 length of 24.8mm, the spring 48 may have a compressed length between 22mm and 24.5mm, more preferably between 22.4mm and 24mm. Figures 10 to 12 In yet another arrangement shown, modular cam lobes may be utilized so that the eccentricity may be varied (eg, by replacing one cam lobe with another cam lobe having a different eccentricity) to vary the in and out displacement of the driven member and vary the rocking angle amplitude.

[0045] In some embodiments, the cam assembly 24 is capable of floating and self-adjusting along the axis of the drive shaft 18. Specifically, in certain embodiments, the floating of the cam assembly 24 is achieved by setting the cam width to approximately 1.25 inches and setting the bearing assembly 22 width to approximately 1.00 inches. The floating and self-adjustment of the cam assembly 24 provides improved alignment of the driven member 32 and adjusts for different positions of the driven member. This helps to reduce any potential premature coating failures (see below) in the test samples, which may be caused by excessive stresses introduced into the coating by the undesired tilting of the driven member 32, thereby improving test consistency.

[0046] The follower member 32 retained in the drive arm 40 of the cam assembly 24 is interchangeable by tightening and loosening the lock nut 46. The follower member 32 may be selected from the group consisting of a piercing object and a blunt non-sharp object. The piercing object may be a nail, a screw, and / or any other member having a pointed end, such as but not limited to a member including or simulating a glass shard. The follower member 32 may be provided in a plurality of positions. Figures 8 to 12 In the example shown as a nail, or in Fig.13exemplarily shown as a blunt-tipped object. The blunt-tipped object may be a punch 32' in the form of a cylinder with a generally flat end face, or may be any other object that is not sharp at the end and does not normally pierce the substrate. The apparatus 10 may also include a plurality of piercing objects and / or blunt-tipped objects of each type, such as a plurality of nails having a diameter range of 1 mm to 5 mm and a plurality of screws having a diameter range of 1 mm to 5 mm. The range of sizes of the nails and / or screws allows the ability of the substrate to withstand piercing by piercing objects of various sizes to be tested, as described in more detail below.

[0047] In some embodiments, the drive arm holding the driven member 32 can be held and guided by a fixture to control the depth and directionality of the driven member 32 as it is driven through the test sample (see below). Specifically, the fixture can be cylindrical and can have a through hole corresponding in shape to the drive arm. The drive arm is (partially) inserted into the through hole so that the through hole guides the movement of the drive arm as it moves in a reciprocating back and forth motion.

[0048] exist Figure 1 In the illustrated embodiment, the cam assembly 24 of one of the two test units 14 is offset 180 degrees relative to the cam assembly of the other of the two test units in the circumferential direction of the drive shaft 18. More specifically, the cam lobe 28 of one of the cam assemblies 24 is rotated 180 degrees relative to the cam lobe of the other cam assembly on the drive shaft 18. The 180-degree offset between the two cam lobes reduces the imbalance in the system and the vibrations generated thereby. In addition, the offset causes the follower member 32 of one of the cam assemblies 24 to be at its highest point (farthest from the drive shaft 18), while the follower member of the other cam assembly is at its lowest point.

[0049] Each test unit 14 also includes a support member 50 and a pressure chamber assembly 52. ​​The support member 50 extends vertically from the base 16, is located on the side of the cam assembly 24, and supports the pressure chamber assembly 52. ​​The support member 50 may include a single member, or, as shown in the example, may include a pair of pillars in the form of vertical blocks or wall members 54, 54' disposed on opposite sides of the cam assembly 24. Specifically, each block member 54, 54' includes an opening 55 through which the drive shaft 18 extends, two bearing assemblies of the bearing assembly 22 are disposed between the two block members 54, 54' of the support member 50, and the cam assembly 24 is sandwiched between the two bearing assemblies. The pressure chamber assembly 52 is mounted on each of the two block members 54, 54' and is suspended between the block members and above the cam assembly 24. In addition, as shown in FIG. Figure 1As shown, the pressure chamber assemblies 52 of two adjacent test units 14 may share a common block member 54' therebetween, in which case the common block member is wider in the longitudinal direction of the drive shaft 18 than the block member 54 on the end that is not disposed between the two pressure chamber assemblies. In some embodiments, an elastic member (such as a coil spring) may be inserted between the support 50 and the pressure chamber assembly 52 to control the weight of the pressure chamber assembly (e.g., 40 pounds) when the pressure chamber assembly is assembled to the support, thereby reducing potential premature failure of the test sample that may be caused by the driven member 32 during assembly / installation (see below).

[0050] Go to Figure 1 , Figure 2 , Fig.14 and Fig.15, the pressure chamber assembly 52 includes a body 56 having a monitoring window 58, an open end 60 including an opening 61, and an inner chamber wall 62 adjacent to the opening and defining a pressure chamber 63 within the body. The body 56 can be a generally hollow cylinder having an annular flange 64 at the open end 60. The monitoring window 58 can be a generally circular opening opposite the open end 60, or alternatively can be provided along the side of the body or at the bottom of the body, and can include a sight glass 66 formed of a polycarbonate sheet or the like. In another embodiment, the entire body can constitute the observation window, and the body can include a transparent polycarbonate material or the like, i.e., the entire body is transparent and thus constitutes the observation window. The pressure chamber assembly 52 also includes a clamping member 68. The clamping member 68 can be in the form of a disk having a central opening 70. The clamping member 68 cooperates with the flanged open end 60 of the body 56 to sandwich a test sample substrate 72 between the clamping member and the body so as to close the pressure chamber 63, wherein the surface of the substrate (including the coating thereon) faces the pressure chamber. The central opening 70 circumscribes a test area of ​​the test sample substrate 72 that is sandwiched in the pressure chamber assembly 52, and the coating in the test area of ​​the substrate is inside the pressure chamber. Therefore, the central opening 70 is sized to be large enough to allow leak spray detection (described in more detail below) without causing any interference with the driven member 32, while being sized to be small enough to limit any deformation of the test sample substrate under pressure during testing (e.g., substrate bulging, whereby the pressure in the pressure chamber causes the substrate to bulge outwardly away from the pressure chamber). The body 56 is held together with the clamping member 68 by a plurality of fasteners (such as threaded bolts 74), which are inserted through holes in the flange 64 of the body 56 and screwed into corresponding threaded holes in the clamping member 68. In some embodiments, the body 56 includes a seal 76 that circumscribes the opening 61. Specifically, the seal 76 may include a pair of concentric annular ridges 78, forming an annular groove 80 between the ridges. When the substrate 72 is sandwiched between the clamping member 68 and the body 56 and clamped, the annular ridge 78 bites into the side of the substrate including the coating and facing the body to obtain a gas-tight seal of the pressure chamber 63. When the body 56 and the clamping member 68 of the pressure chamber assembly 52 are assembled together (with the test sample substrate 72 sandwiched therebetween), the pressure chamber assembly can be mounted on the support 50 by other fasteners (such as threaded bolts 82) extending through the flange 64 of the body 56 and other holes in the clamping member 68 and screwed into threaded holes in each block member 54, 54' of the support 50.

[0051] Optionally, an insert 83 may be disposed between the support member 50 and the clamping member 68 to adjust the height of the pressure chamber assembly 52 relative to the cam assembly 24, such as Figure 1 and Figure 2As shown. The insert 83 can be a plate or other planar member formed of a substantially rigid non-elastic material. The device 10 may include more than one size of insert, and the choice of use / not use and which insert to use depends on the thickness of the test sample substrate 72, so as to maintain the same penetration length of the driven member 32 (when the driven member is a piercing object) from the outer surface of the test sample substrate (e.g., the tread surface) to the tip of the driven member 32 piercing the test sample substrate. For example, the penetration length of the driven member 32 can be kept constant at 40 mm. In this case, a test sample substrate with a thickness of 16.5 mm requires an insert with a thickness of 8.0 mm, a test sample substrate with a thickness of 19.5 mm requires an insert with a thickness of 5.0 mm, and a test sample substrate with a thickness of 24.5 mm does not require an insert, i.e., no insert is used.

[0052] refer to Fig.16 , the device 10 may include an air inlet / outlet system that includes a compressed air source 84, such as an air compressor (and an associated air storage tank), which is in fluid communication with the pressure chamber 63 of the pressure chamber assembly 52 via an air supply line 85. One or more valves 86 (such as solenoids) may be connected to the supply line 85 to fill the pressure chamber 63 with compressed air from the air compressor and / or to exhaust the pressurized air in the pressure chamber by releasing the pressurized air to the atmosphere. Additionally, one or more pressure regulators and / or pressure gauges (not shown) may be fluidly connected to the air supply line. The device 10 may also include a pressure sensor 87 for monitoring the air pressure in the pressure chamber 63. By way of example, the pressure sensor 87 may be attached to the air inlet valve 86 of the pressure chamber 63, such as Fig.16 As shown. Alternatively, the pressure sensor may be disposed in the pressure chamber, or may be a non-contact sensor (such as an ultrasonic pressure sensor) mounted outside the pressure chamber and capable of detecting pressure loss in the pressure chamber from the outside. The pressure sensor 87 may be any suitable sensor known in the art capable of measuring pressure level and / or pressure loss.

[0053] A camera 88 may be included to monitor the movement of the driven member 32 and to visually monitor the interaction between the driven member and the test sample substrate 72. The camera lens of the camera 88 may be located at the monitoring window 58 of the pressure chamber assembly 52 and / or may be located near the clamping member 68 to monitor the test sample substrate 72 from outside the pressure chamber.

[0054] Additionally, the device 10 may include a control and data acquisition system including one or more of a controller (CPU) 89 and a user interface (human-machine interface) 90, the user interface including one or more input / output devices electrically connected to the controller, such as a display, keyboard, mouse, printer, etc. The controller 89 is electrically connected to one or more of the actuator 12, the pressure sensor 87, and the at least one valve 86, so as to control the actuator and the test unit and process the data received from the monitoring of the test unit. In some embodiments, the user interface 90 is a touch screen display that visually displays information and allows the user to input by contacting the screen. The control and data acquisition system allows setting and controlling various parameters, including the movement frequency / speed, amplitude and number of cycles of the driven member 32 controlled by the actuator 12, and the pressure drop cut-off set point when the actuator is disabled. Additionally, the system may include an emergency stop control that allows the device 10 to be manually cut off at any time by, for example, triggering a control button. The control and data acquisition system may also receive pressure data from the pressure sensor 87 to monitor, display and store the pressure level in the pressure chamber during testing, and may detect pressure loss during testing. The control and data acquisition system may also receive, display and store visual information provided by the camera (if present). The apparatus 10 (which includes the control and data acquisition system and the test unit) may be disposed on a movable cart 91 (e.g., Fig.17 ), so that the entire device can be easily transported, such as if the device is moved in and out of an environmental chamber. Alternatively, the control and data acquisition system can be stored separately on a movable cart or fixed workstation, and the test unit 14 on the base 16 can be moved to various locations. For example, the base 16 can include a handle 92 so that the actuator 12 and the test unit 14 on the base 16 can be lifted and moved from one location to another.

[0055] like Fig.15As shown in the example of , the test sample substrate 72 can be a tire sample cut from the tread surface (opposite to the sidewall) of the entire tire, the tire sample including a tire tread 73 on one (outer) surface and a coating 75 of a self-sealing tire sealant on the opposite inner surface. The tire sample can be cut into a generally square shape and can have dimensions of approximately 146.1 mm×146.1 mm (5.75"×5.75"). However, the test sample substrate is not limited to these specific dimensions and only needs to be large enough to cover and extend beyond the perimeter of the opening 61 at the open end 60 of the body 56 of the pressure chamber assembly 52. ​​In any case, it is clear that the test sample substrate 72 can be a relatively small portion of the tire and is therefore economical for evaluating the sealant performance of the self-sealing tire sealant, as opposed to on-vehicle testing that requires the use of four complete tires. However, the test sample substrate is not limited to tire samples and can be another substrate with or without a coating thereon. In addition, the coating is not limited to a self-sealing sealant and can be another type of coating material. For example, the test sample substrate can be a tire sample on which a polymer foam is coated (i.e., a sample of a "quiet running tire") for the acoustic effect of noise suppression, and the durability of the adhesion of the noise suppression coating to the inner surface of the tire sample can be tested. Additionally, the test sample substrate can be cut from a tire that already includes a coating on the inner surface (e.g., a manufactured self-sealing tire), or the test sample substrate can be cut from a tire that does not include a self-sealing sealant layer, and the self-sealing sealant can be coated on the non-tread surface of the sample after being cut from the tire. In any case, the amount of material necessary to obtain the tire sample substrate 72 is small.

[0056] By way of example, the apparatus 10 may be used to test the durability of a test sample 72 of a tire including a self-sealing sealant layer thereon. As mentioned above, the test apparatus 10 may be used to test the durability of a test sample 72 of a tire including a self-sealing sealant layer thereon. Figure 1 The two test units shown test two (or more than two, depending on the number of test units 14) samples simultaneously. For purposes of explanation, discussion of the test procedures will generally refer to one test sample substrate 72 and one test unit 14, and it should be understood that the test procedures apply equally to all test units. An exemplary test procedure may generally include: assembling a pressure chamber assembly; inserting a nail into a test sample; attaching the pressure chamber assembly to the test unit; durability testing the nail at room temperature, high temperature, and low temperature and monitoring for leaks; pulling out the nail and checking for leaks; durability testing with the nail removed by punching the tread surface of the tire sample near the puncture site to simulate driving on the tire with the nail removed from the tire; and storage testing by subjecting the test sample held in the test unit to a thermal cycle including room temperature, high temperature, and low temperature and again checking for leaks.

[0057] More specifically, once the desired tire sample 72 is obtained, the pressure chamber assembly 52 is assembled by sandwiching the tire sample 72 between the body 56 and the clamping member 68 (with the tire tread 73 of the tire sample facing the clamping member and the sealant layer 75 on the inner surface of the tire sample facing the pressure chamber 63) and inserting the bolts 74 through the appropriate holes in the body and the clamping member. As discussed above, the tire sample 72 is sized so that it completely covers the opening 61 in the body 56 and extends beyond the perimeter of the opening, but generally within the outer boundary of the flange 64 of the body and the perimeter of the clamping member 68. The central opening 70 in the clamping member 68 is also completely covered by the tire sample 72. The driven member 32 (in this case, a piercing object such as a nail or screw (a nail is shown by way of example in the drawings)) is inserted through the central opening 70 of the clamping member 68 and pierces the tire tread 73 of the tire sample 72, so that the nail contacts the tire sample and the tip of the nail extends beyond the tire sample and into the pressure chamber 63. The nail can be driven into the tire sample 72 to a controlled depth using a hammer or mallet, or a universal tensile tester, a table amber press or any other suitable means can be used to drive the nail into the tire sample. Once the nail is inserted through the tire sample 72, the pressure chamber assembly 52 is mounted on the support 50 and fixed with two bolts 82, one bolt for each block member 54 of the support. In the case where the coil spring is inserted between the pressure chamber assembly 52 and the support 50, the spring reduces the load applied to the driven member 32 due to the weight of the pressure chamber assembly, thereby reducing the possibility of premature failure of the test sample by alleviating any potential excessive stress introduced in the test sample by the driven member piercing the test sample. Alternatively, after the pressure chamber assembly 52 is installed on the support 50, the nail or other piercing object can be driven into the tire sample. In addition, the head of the nail is fixed to the drive arm 40 of the cam assembly 24 using a locking nut 46. Next, the pressure chamber 63 is pressurized by filling the pressure chamber with compressed air from the compressed air source 84 to pressurize the pressure chamber to a pressure of, for example, 36 psi. The sealed pressure chamber assembly in which the tire sample is installed can withstand pressures generally in the range of 30 psi to 50 psi, which covers the typical inflation pressure of the vehicle tire. After pressurization, the test parameters can be set via the user interface. The test parameters may include, but are not necessarily limited to, the nail movement frequency, amplitude, and test cycle number based on factors such as the diameter of the tire, the driving speed to be simulated, the road conditions to be simulated, and the driving distance to be simulated at each driving speed in order to simulate the road test. The test parameters may also include a cut-off set point pressure, at which the pressure in the pressure chamber 63 drops below the set point pressure, and the test run will automatically stop. Once the test parameters are set, the controller 89 actuates the actuator 12 to drive the nail and move the nail in the tire sample in two ways, an oscillating linear forward and backward motion and an oscillating rocking motion.Specifically, the actuator 12 rotates the drive shaft 18, which in turn rotates the cam lobe 28. Due to the eccentricity of the cam lobe 28, the cam lobe moves the follower 30 in an up-and-down motion and in a slight rocking motion. The movement of the follower 30 drives the nail mounted in the drive arm 40 of the follower 30 to perform the same oscillating linear motion and oscillating rocking motion. The movement of the nail in the tire sample simulates the moving force applied to the nail piercing the tire when the tire rotates over the nail on the road, and tests the durability of the self-sealing sealant around the nail at the puncture site. The pressure in the pressure chamber 63 is monitored while the nail is driven to check whether no pressure loss occurs. In addition, the inner surface of the tire sample in the pressure chamber 63 can be visually monitored through the monitoring window 58, and a camera can be used to monitor and / or record the activity in the pressure chamber at the puncture site, or the activity at the puncture site on the outside of the pressure chamber (i.e., the tire tread side of the puncture site). After reaching the desired number of cycles, if the pressure sensor 87 does not detect a pressure loss, the actuator 12 is stopped. The pressurized chamber assembly 52 is then removed from the support 50, and optionally, a spray method can be used to test the leak-free performance of the sealant by spraying a leak detection liquid (e.g., soapy water, salt water) onto the puncture site (with the nail still inserted) and checking whether larger and larger bubbles are generated around the puncture site. Next, the nail is removed from the tire sample 72, and the puncture site can be checked again for any air leaks. With the nail removed, the sealant pressure retention performance of the tire sample can then be tested by simulating a self-sealing tire periodically interacting with the ground and measuring any pressure loss over time. Specifically, another driven member (i.e., a blunt object 32' such as a punch) is mounted on the cam assembly 24, and the pressure chamber assembly 52 is again mounted on the support 50 so that the blunt object can contact the tire tread 73 of the tire sample 72 in the area including the puncture site. The test parameters are again set using the user interface 90, and the actuator 12 is actuated to drive the blunt object and move the blunt object so that it periodically presses the tire tread of the tire sample near the puncture site. While the blunt object is driven, the pressure in the pressure chamber 63 is continuously monitored to check for any pressure drop indicating air leakage at the puncture site. In addition, the inner surface of the tire sample in the pressure chamber 63 can be visually monitored through the monitoring window 58, and the camera 88 can be used to monitor and / or record the activity in the pressure chamber at the puncture site, or the activity at the puncture site on the outside of the pressure chamber (i.e., the tire tread side of the puncture site). Once the desired number of cycles has been completed, the actuator is turned off.

[0058] The above test procedures can be performed at room temperature. Optionally, by testing with the device 10 located in an environmental chamber, the test procedures can be performed at room temperature, low temperature (e.g., below 20°C and as low as -50°C, such as -50°C, more preferably -30°C, even more preferably -20°C) and high temperature (such as above 20°C and up to 150°C, such as 150°C, more preferably 100°C, even more preferably 70°C) and at different humidity levels. The environmental chamber allows the temperature and humidity to be adjusted to simulate various climates and seasonal weather conditions. Additionally, after performing the above test procedures, the device 10 (which includes the mounted tire sample or simply includes a pressure chamber assembly with the mounted tire sample) can be subjected to thermal cycling in an environmentally controlled room, while further monitoring the pressure in the pressure chamber and checking for leaks at the puncture site. The thermal cycle can be in the range of -50°C to 150°C, more preferably -30°C to 100°C, even more preferably -20°C to 70°C. In addition to temperature changes, various actual road conditions such as rain, snow (salt-treated roads), mud, etc. can also be simulated by spraying various substances (such as, for example, a liquid spray of soap or salt water, a liquid spray mixed with ground calcium carbonate, or a liquid spray mixed with dust) on the tread surface of the tire sample.

[0059] The following two tables provide exemplary test procedure steps and test conditions.

[0060] Table 1: Exemplary test procedure for simulated cold circuit testing

[0061]

[0062] Table 2: Example test procedure to simulate a more severe cold circuit test

[0063]

[0064] The testing frequency of a tire sample can be estimated based on the outer circumference of the tire from which the sample was cut and the expected simulated road test speed using the following formula:

[0065]

[0066] Where f is the test frequency in Hz, v is the expected road test speed in km / h, and p is the outer circumference of the tire in meters. The following table is an illustrative example of the correlation between the test frequency and the equivalent driving speed for a tire with a circumference of 2.1 meters calculated according to the above formula.

[0067] Table 3: Test frequency associated with driving speed when p = 2.1 m

[0068]

[0069] The swing amplitude of a piercing object (e.g., a nail) can be estimated based on the road conditions, vehicle mass, and road test speed. Generally, a larger amplitude should be associated with a lower frequency (e.g., ±3° at 6 Hz) to simulate a vehicle driving in rough road conditions (such as on a gravel road). On the other hand, a smaller amplitude should be used in conjunction with a higher frequency (e.g., ±1° at 12 Hz) to simulate a vehicle driving in smooth road conditions (such as on a highway).

[0070] The equivalent travel distance of a tire sample can be calculated based on the outer perimeter of the tire from which the sample was cut using the following formula:

[0071] d = n*p / 1000

[0072] Where d is the equivalent driving distance (in km), n is the number of test cycles, and p is the outer circumference of the tire (in meters).

[0073] Table 4: Test cycle number associated with driving distance when p = 2.1 m

[0074]

[0075] The pressure level set in the pressure chamber should be based on the application of the tire and should be approximately 2.5 bar for passenger car tires.

[0076] The test parameters can also be varied to test for small, very slow leaks over a period of days.

[0077] Go to Fig.18 , depicting two different sealant failure modes. Specifically, the tests performed by the test apparatus may result in two types of sealant failures. For example, as shown on the left hand side, the oscillating motion of a driven member (such as a nail) may form a "sheath" feature 93 in the tire sealant, i.e., when the nail is lifted from the inner surface of the tire sample, the sealant forms a sheath or sleeve around the shaft of the nail. Alternatively, as shown in the middle and right hand side, the driven member (such as a nail) may form a "cap" feature 94 in the tire sealant, i.e., the sealant forms a cap that covers the tip at the end of the nail.

[0078] Although the pressure chamber assembly is shown as being mounted above the cam assembly, with the driven member interacting with the test sample substrate from below (to simulate the interaction between the road and the driven member in the tire), the pressure chamber assembly and the cam assembly may have other orientations such that the driven member of the cam assembly interacts with the pressure chamber assembly from above, from the side (horizontally), or at an angle between horizontal and vertical. Various orientations can be used to simulate different road conditions or provide alternative means of monitoring leakage. For example, if soap / soapy water is sprayed onto the substrate to monitor air leakage around the puncture site, the driven member should interact with the tire substrate from above so that the soap is set on the upper surface of the substrate (rather than the lower surface). In addition, if small particles are used to simulate the effect of dirt on the puncture site, an orientation from above should also be used so that the dirt stays on the upper surface of the substrate. In addition, when the tire rotates on the road under different conditions (rain, snow and / or mud containing coating-degrading chemicals), wear particles combined with coating-degrading chemicals are likely to penetrate the puncture site and reach the coating-tire interface on the inner surface of the tire. When the tire sample is arranged above the driven member, since the tire tread faces downward, little or no spray placed on the tire tread surface during the liquid spray test reaches the coating tire interface. This configuration gives the least conservative performance results for testing the durability of the coating under these road conditions simulated by the liquid spray. On the other hand, when the tire sample is arranged below the driving member, the tire tread faces upward, and the spray placed on the tire tread surface has the maximum ability to reach the coating tire interface. This configuration provides the most conservative performance results for testing the durability of the coating to various chemicals contained in the liquid spray. In addition, when the liquid spray may partially reach the coating tire interface, the configuration in which the tire sample is horizontally or tilted at a certain angle to the side of the driven member gives a result between the top configuration and the bottom configuration. Additionally, it has been found that abrasive particles and chemicals that may be contained in the liquid spray can damage the organic coating used on the inner surface of the tire, while the silicone coating is not sensitive to these materials. Therefore, for the silicone coating, the orientation of the tire sample relative to the driven member may not be as significant as that of the organic coating.

[0079] The present invention has been described by way of example, and it should be understood that the terms used are intended to be descriptive rather than restrictive. Obviously, many modifications and variations of the present invention are possible according to the above teachings. The present invention may be implemented in other ways beyond the specific description.

Claims

1. An automated laboratory device for dynamically testing the durability of a coating, the device comprising: Actuator; a drive shaft coupled to the actuator; as well as a test unit, the test unit comprising a cam assembly, a support member flanking the cam assembly, and a pressure chamber assembly; The cam assembly is mounted on the drive shaft and comprises: a cam lobe eccentrically mounted on the drive shaft; a follower in forced engagement with the cam lobe, the follower comprising a circular body surrounding the cam lobe and a drive arm protruding from the circular body; and a follower member maintained in engagement with the drive arm of the follower of the cam assembly; The pressure chamber assembly is mounted on the support member and aligned with the cam assembly, and the pressure chamber assembly includes: a body including a monitoring window, an open end including an opening, and an inner chamber wall adjacent to the opening and defining a pressure chamber within the body; and a clamping member including a central opening, wherein the clamping member and the body are adapted to sandwich a substrate including the coating therebetween to close the pressure chamber, the coating facing an interior of the pressure chamber; wherein the driven member extends through the central opening in the clamping member and is capable of contacting the substrate; wherein rotation of the drive shaft drives one or both of oscillatory linear motion and oscillatory rocking motion of the driven member via the cam assembly.

2. The automated laboratory device of claim 1, wherein the driven member is one of a piercing object and a blunt object. 3 . The automated laboratory device according to claim 1 , wherein the piercing object is one of a nail, a screw, and a member having a pointed head.

4. An automated laboratory device according to any one of claims 1 to 3, wherein the body of the pressure chamber assembly comprises a seal circumscribing the opening, the seal comprising a pair of concentric annular ridges forming an annular groove therebetween.

5. The automated laboratory device according to any one of claims 1 to 4, further comprising an insert disposed between the support and the clamping member for adjusting the height of the pressure chamber assembly relative to the cam assembly.

6. The automated laboratory device according to any one of claims 1 to 5, further comprising a pressure sensor for monitoring the pressure in the pressure chamber.

7. The automated laboratory device according to any one of claims 1 to 6, further comprising a compressed air source and at least one valve, wherein the compressed air source is fluidically connected to the pressure chamber via a supply line, and the at least one valve is connected to the supply line for filling and exhausting the pressure chamber.

8. The automated laboratory device according to any one of claims 1 to 7, further comprising a controller electrically connected to one or more of the actuator, the pressure sensor and the at least one valve.

9. The automated laboratory device according to any one of claims 8, further comprising a user interface electrically connected to the controller for setting test parameters and monitoring the pressure in the pressure chamber.

10. The automated laboratory device according to any one of claims 1 to 9, further comprising a plurality of said test units.

11. A method for testing the durability of a tire coated with a self-sealing sealant for leak-proof performance, the method comprising the steps of: Providing an automated laboratory device according to any one of the preceding claims; providing the substrate, wherein the substrate is a tire sample cut from a tire, the tire sample comprising a tire tread on one surface, the tire sample further comprising an opposing inner surface having a self-sealing sealant layer thereon; sandwiching the tire sample between a pressure chamber body and the clamping member, with the tire tread of the tire sample facing the clamping member and the sealant layer on the inner surface of the tire sample facing the pressure chamber; inserting the driven member through the central opening in the clamping member and into the tire sample, the driven member being a piercing object; installing the pressure chamber assembly onto the support member and installing the inserted follower member onto the cam assembly; Filling the pressure chamber with compressed air to a predetermined set pressure; actuating the actuator to drive the piercing object and move the piercing object within the tire sample in one or both of an oscillatory linear motion and an oscillatory rocking motion; monitoring the pressure in the pressure chamber while the piercing object is being driven; removing the puncture object from the cam assembly and removing the pressure chamber assembly to inspect the tire sample for leaks at the puncture site; removing the piercing object from the tire sample and installing another follower member onto the cam assembly, the follower member being a blunt-tipped object; mounting the pressure chamber assembly to the support member whereby the blunt object contacts the tire tread of the tire sample; actuating the actuator to drive the blunt object and move the blunt object so that it periodically presses against the tire tread of the tire sample near the puncture site; monitoring the pressure in the pressure chamber while the blunt object is being driven; as well as The automated laboratory device including the tire sample is then subjected to thermal cycling while further monitoring the pressure in the pressure chamber and checking for leaks at the puncture site.

12. The method of claim 11, further comprising the step of monitoring the inner surface of the tire sample in the pressure chamber via the monitoring window.

13. A method according to any one of claims 11 or 12, further comprising the step of using a camera to monitor and / or record activity in the pressure chamber at the puncture site.

14. The method according to any one of claims 11 to 13, further comprising the step of providing an environmental chamber in which the automated laboratory device is placed, wherein when the automated laboratory device is in the environmental chamber, one or both of the temperature and humidity in the environmental chamber are adjusted.

15. The method of any one of claims 11 to 14, further comprising the steps of: actuating the actuator; and monitoring pressure at one or both of a plurality of ambient temperatures and a plurality of humidity levels.

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