An automated laboratory device for dynamically testing the durability of self-sealing tire sealants.

Abstract

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

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to and the full benefit of U.S. Provisional Patent Application No. 63 / 407,327, filed September 16, 2022, the contents of which are incorporated herein by reference.

[0002] FIELD OF THE INVENTION FIELD OF THE DISCLOSURE This disclosure relates generally to testing the durability of coating materials on substrates, and more particularly to an apparatus and method for testing the durability of self-sealing tire sealant materials.

[0003] 2. Description of Related Art A "self-sealing tire" (SST) is a tire having an inner surface coated with a layer of a self-sealing sealant material, typically composed of a tacky polymer, synthetic rubber, or natural rubber material. The self-sealant material fills and seals punctures up to a certain size in the tire tread of the tire so that the tire does not suffer a loss of air pressure. Thus, the vehicle on which the tire and associated wheel are mounted can be safely driven without noticeable loss of control or maneuverability until the tire is permanently repaired.

[0004]

[0003] Conventionally, testing the reliability and durability of self-sealing tire materials contained in self-sealing tires is very difficult and time-consuming. Current testing methods require mounting a tire on a vehicle and running the vehicle on roads, test tracks, or other test sites at various driving speeds and road conditions for a significant period of time to obtain appropriate test data regarding the tire's performance when punctured and subjected to road and environmental stresses. Therefore, current testing methods are expensive 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 achieved in a shorter time frame, at a lower cost, and with lower levels of carbon dioxide emissions. Summary of the Invention

[0005] An automated laboratory apparatus for dynamically testing the durability of coatings is provided. The apparatus includes an actuator and a drive shaft coupled to the actuator. The apparatus further includes a test unit including a cam assembly, a support flanking the cam assembly, and a pressure chamber assembly. The cam assembly is attached to the drive shaft and includes a cam lobe, a follower, and a driven member. The cam lobe is eccentrically attached to the drive shaft. The follower is in biasing engagement with the cam lobe and includes a circular body surrounding the cam lobe. A drive arm protrudes from the circular body. The pressure chamber assembly is attached to the support and aligned with the cam assembly. The pressure chamber assembly includes a body and a clamp member. The body includes a monitoring window, an open end including an opening, and an inner chamber wall adjacent the opening that defines a pressure chamber within the body. The clamp member includes a central opening. The clamp member and body are adapted to sandwich a substrate including a coating therebetween to close the pressure chamber with the coating facing the inside of the pressure chamber. The driven member extends through a central opening in the clamp member and is capable of contacting the substrate. Rotation of the drive shaft drives one or both of an oscillatory linear motion and an oscillatory rocking motion of the driven member via a cam assembly.

[0006] In certain embodiments, the driven member is one of a piercing object and a blunt object.

[0007] In certain embodiments, the piercing object is one of a nail, a screw, and a pointed member.

[0008] In certain embodiments, the body of the pressure chamber assembly includes a seal surrounding the opening, the seal including a pair of concentric annular ridges forming an annular groove therebetween.

[0009] In certain embodiments, the apparatus further includes an insert disposed between the support and the clamp member for adjusting the height of the pressure chamber assembly relative to the cam assembly.

[0010] In certain embodiments, the apparatus further includes a pressure sensor for monitoring the pressure in the pressure chamber.

[0011] In certain embodiments, the apparatus further includes a compressed air source in fluid communication with the pressure chamber via a supply line, and at least one valve connected to the supply line for filling and draining the pressure chamber.

[0012] In certain embodiments, the apparatus further includes a controller electrically connected to one or more of the actuator, the pressure sensor, and the at least one valve.

[0013] In certain embodiments, the apparatus further includes a user interface electrically connected to the controller for setting test parameters and monitoring the pressure in the pressure chamber.

[0014] In certain embodiments, the device includes multiple test units.

[0015] 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 providing an automated laboratory apparatus and providing a 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 layer of self-sealing sealant thereon. The method further includes clamping the tire sample between a pressure chamber body and a clamping member with the tire tread of the tire sample facing the clamping member and the layer of sealant on the inner surface of the tire sample facing the pressure chamber. The method further includes inserting a driven member, which is a puncturing object, into the tire sample through a central opening in the clamping member. The method further includes mounting the pressure chamber assembly on a support and mounting the inserted driven member on a cam assembly. The method further includes filling the pressure chamber with compressed air to a predetermined set pressure. The method further includes the step of actuating the actuator to drive the puncturing object and move the puncturing object within the tire sample in one or both of an oscillatory linear motion and an oscillatory rocking motion. The method further includes the step of monitoring the pressure in the pressure chamber while the puncturing object is being driven. The method further includes the step of detaching the puncturing object from the cam assembly and removing the pressure chamber assembly to check for leaks at the puncture site in the tire sample. The method further includes the step of removing the puncturing object from the tire sample and mounting another driven member, the blunt object, on the cam assembly. The method further includes the step of mounting the pressure chamber assembly on a support whereby the blunt object contacts the tire tread of the tire sample. The method further includes the step of actuating the actuator to drive the blunt object and move the blunt object so that the blunt object periodically punctures the tire tread of the tire sample proximate the puncture site. The method further includes the step of monitoring the pressure in the pressure chamber while the blunt object is being driven.The method then further includes subjecting the automated laboratory device containing the tire sample to a thermal cycle while further monitoring the pressure in the pressure chamber and checking for leaks at the puncture site.

[0016] In certain embodiments, the method further includes monitoring the inner surface of the tire sample within the pressure chamber through a monitoring window.

[0017] In certain embodiments, the method further comprises using a camera to monitor and / or record activity within the pressure chamber at the puncture site.

[0018] In certain embodiments, the method further includes providing an environmental chamber in which the automated laboratory equipment is placed, and while the automated laboratory equipment is within the environmental chamber, one or both of the temperature and humidity within the environmental chamber may be regulated.

[0019] In certain embodiments, the method further includes operating the actuator and monitoring the pressure at one or both of a plurality of ambient temperatures and a plurality of humidity levels. [Brief explanation of the drawings]

[0020] Various advantages and aspects of the present disclosure may be understood by consideration of the following detailed description when considered in conjunction with the accompanying drawings. [Figure 1] 1 is a cross-sectional side view of a laboratory test apparatus according to some embodiments of the present disclosure. [Figure 2] FIG. 2 is a partially exploded perspective view of the laboratory test apparatus of FIG. 1. [Figure 3] FIG. 1 is a perspective view of a laboratory test apparatus according to another embodiment of the present disclosure. [Figure 4] FIG. 4 is a side view of the laboratory test apparatus of FIG. [Figure 5] 5 is a cross-sectional view of the laboratory test apparatus of FIG. 3 taken along line 5-5 of FIG. 4. [Figure 6] FIG. 4 is a top view of the laboratory test apparatus of FIG. 3. [Figure 7] 7 is a cross-sectional view of the laboratory test apparatus of FIG. 3 taken along line 7-7 of FIG. 6. [Figure 8] 1 is a cross-sectional view of a cam assembly of a laboratory test apparatus according to some embodiments of the present disclosure. [Figure 9] FIG. 10 is a cross-sectional view of a cam assembly of a laboratory test apparatus according to another embodiment of the present disclosure. [Figure 10] FIG. 10 is a perspective view of a cam assembly of a laboratory test apparatus according to yet another embodiment of the present disclosure. [Figure 11] FIG. 11 is a side view of the cam assembly of FIG. 10. [Figure 12] 12 is a cross-sectional view of the cam assembly of FIG. 10 taken along line 12-12 of FIG. 11. [Figure 13] 1 illustrates a driven member of a laboratory test apparatus according to an embodiment of the present disclosure. [Figure 14] FIG. 1 is a perspective cross-sectional view of a body of a pressure chamber assembly of a laboratory test apparatus according to some embodiments of the present disclosure. [Figure 15] FIG. 1 is an exploded view of a pressure chamber assembly of a laboratory test apparatus according to some embodiments of the present disclosure. [Figure 16] FIG. 1 is a perspective view of a laboratory test apparatus. [Figure 17] 1 is a schematic diagram of a mobile cart including an interface display screen according to some embodiments of the present disclosure. [Figure 18] 1 is a photograph of a jacket and hat feature formed in a tire sealant at a tire puncture site. DETAILED DESCRIPTION OF THE INVENTION

[0021] An automated laboratory testing apparatus for testing the durability of coatings on substrates and a method for testing the durability of tires coated with self-sealing tire sealants for leak-proof performance are provided. As will be appreciated from the description herein, the disclosed testing apparatus and method provide rapid screening tests for coating materials, including self-sealing tire sealants, reducing or eliminating the need for on-vehicle road testing of self-sealing tires to determine performance. The testing apparatus and method can also utilize only a small portion of a self-sealing tire sample to test the effects of both in-out (insertion / extraction) and rocking (lateral) stresses exerted on the tire by a puncturing object on sealant pressure retention performance. Thus, the testing apparatus and method of the present invention are dynamic rather than static, as they actively simulate the forces exerted by a puncturing object at a tire puncture site and the road stresses exerted on the puncture site after the puncturing object is removed. The apparatus can also test self-sealing tire samples under multiple different driving speeds (i.e., frequencies) and air temperatures to simulate on-vehicle testing at different vehicle speeds and under different road and weather conditions.

[0022] 1-17, wherein like numerals indicate corresponding parts throughout the several views, an automated laboratory test apparatus (also referred to herein as a test apparatus or simply apparatus) is illustrated and generally designated 10. While certain features of test apparatus 10 are functional, they may also be implemented in different aesthetic configurations. Test apparatus 10 generally includes an actuator 12 and at least one test unit 14 driven by the actuator.

[0023] The actuator 12 is mounted on a planar base 16. The actuator 12 is illustrated as an electric motor, such as a stepper motor. In this embodiment, the actuator 12 is coupled to a drive shaft 18, which connects the actuator to the test unit 14. More specifically, a coupling 20 connects the drive shaft 18 to the actuator 12. The drive shaft 18 is rotatably supported by a plurality of bearing assemblies 22 (e.g., high-speed mount ball bearings) mounted on the base 16. The drive shaft 18 transmits power from the actuator 12 to the test unit 14 via a cam mechanism. However, it should be understood that other types of actuators and drive configurations are within the scope of the present disclosure; thus, the actuator may be a reciprocating device, such as a pneumatic or hydraulic cylinder, an electromagnetic device, or a shaker, and the actuator may drive the test unit via pneumatic lines, hydraulic lines, electromagnetic pulses, etc.

[0024] The test units 14 are mounted on a base 16 and connected to and driven by an actuator 12. As shown by way of example, the apparatus 10 can include two test units 14 arranged in series on the same drive shaft 18. However, it should be understood that the apparatus need only include one test unit. Two test units 14 allow for simultaneous testing of two different samples, as described in more detail below, thereby increasing the testing capacity and output of the apparatus 10. In other embodiments, the apparatus may include three or more test units. For example, the apparatus may include four test units arranged in series on the same drive shaft, or the apparatus may further include two actuators and associated drive shafts arranged in parallel, with four test units connected in series to each of the drive shafts. Due to the modularity of the test units 14, the apparatus 10 can be easily expanded to include more or fewer test units. Also, even if more than two test units are included in the apparatus, it is not necessary for all test units to be used simultaneously. For example, only one of the two test units may be used. Furthermore, multiple test units on one drive shaft allow for simultaneous testing of multiple pieces of the same sample with two or more types or sizes of test objects (nails, screws, punches, etc.), while multiple drive shafts, each with one or more test units, allow for simultaneous testing using independent operating conditions (frequency, amplitude, cycles) for each drive shaft.

[0025] Each test unit 14 includes a cam assembly 24 attached to a drive shaft 18 by a bushing 26, such as a steel quick-grip 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 attached to the drive shaft 18. The cam lobe 28 may be, for example, an offset cam ring having a center offset from the center of the drive shaft 18 by approximately 2 mm (e.g., 2 ± 0.1 mm) or approximately 1.5 mm (e.g., 1.5 ± 0.1 mm) from the center of the drive shaft. The offset distance is related to the length of the driven member 32 and the desired degree of motion of the driven member. For example, as will become more apparent below, a 2 mm eccentricity provides the driven member 32 with linear motion with an amplitude of ± 2 mm and rotational (wiggle back and forth) motion with an amplitude of ± 1.8° from its neutral position. The follower 30 is attached to and held in biasing engagement with the cam lobe 28 via a bearing ring 34, such as a steel needle roller bearing. In particular, the follower 30 includes a circular body 36 having a circular interior opening 38 in which the cam lobe 28 and sandwiched bearing ring 34 are disposed. The follower 30 further includes a linear drive arm 40 extending outwardly from the circular body 36. The drive arm 40 includes a recess 42 within which the driven member 32 is held in engagement with the drive arm. In one configuration, shown in FIG. 8 , the driven member 32 is fixedly attached to the recess 42 by a set screw 44 and a lock nut 46. In this configuration, the set screw 44 is threaded a certain distance into the recess 42, and the driven member 32 is held in firm engagement against an outward facing surface 45 of the set screw 44 by the lock nut 46, which is threaded into the recess 42. The set screw 44 provides a firm contact with the driven member 32, representing hard road conditions. 9, the driven member 32 is flexibly mounted within the recess 42 by a resilient member 48, such as a spring or the like. In this configuration, the spring 48 is disposed within the recess 42, and the driven member 32 is secured within the recess by a lock nut 46. The spring 48 biases the driven member 32 outward, away from the drive arm 40, but also allows the driven member to retract.The soft contact provided by the spring 48 represents soft road conditions. Furthermore, the spring 48 is more forgiving during installation of the test sample (see below), resulting in less undesirable stress on the test sample coating due to factors such as test sample thickness variation. 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 dynamic durability testing. For example, a force of approximately 72 N to 163 N may be required to move the driven member 32 during sample testing. Accordingly, the spring 48 may have a spring stiffness of 2.5 to 4.5 lb / mm, more preferably 2.9 to 3.9 lb / mm, and a maximum load of 27 to 32 lb, more preferably 28 to 21 lb. Furthermore, assuming the length of the recess 42 is 24.8 mm, the spring 48 may have a compressed length of 22 to 24.5 mm, more preferably 22.4 to 24 mm. In yet another configuration, shown in Figures 10-12, modular cam lobes can be utilized to vary the eccentricity (e.g., by replacing one cam lobe with another having a different eccentricity) to vary the in-out displacement of the driven member and change the swing angle amplitude.

[0026] In some embodiments, the cam assembly 24 is capable of floating and self-adjusting along the axis of the drive shaft 18. Specifically, in one embodiment, the floating of the cam assembly 24 is achieved by setting the cam width at approximately 1.25 inches and the width of the bearing assembly 22 at approximately 1.00 inches. The floating and self-adjusting of the cam assembly 24 provides improved alignment of the driven member 32 and accommodates various positions of the driven member. This helps reduce any potential premature coating failure in the test sample (see below) that may be caused by excessive stress in the coating introduced by undesired tilting of the driven member 32, thereby improving test consistency.

[0027] The driven member 32 held within the drive arm 40 of the cam assembly 24 is replaceable by screwing or loosening a locking nut 46. The driven member 32 may be selected from a set including both puncturing objects and blunt, non-sharp objects. The puncturing objects may be nails, screws, and / or any other object with a tip, including or simulating a shard of glass, for example, but not limited to, a shard of glass. The driven member 32 is illustrated as a nail in FIGS. 8-12 and as a blunt object in FIG. 13. The blunt object may be a punch 32' in the form of a cylinder with a generally flat end surface, or any other object with an end that is not sharp and generally does not pierce a substrate. The device 10 may also include a plurality of each type of puncturing object and / or blunt object, such as a plurality of nails having diameters ranging from 1 mm to 5 mm and a plurality of screws having diameters ranging from 1 mm to 5 mm. A range of nail and / or screw sizes allows for testing the substrate's ability to withstand puncture by puncture objects of various sizes, as explained in more detail below.

[0028] In some embodiments, the drive arm that holds the driven member 32 may be held and guided by a fixture (see below) to control the depth and directionality of the driven member 32 as it is driven through the test sample. In particular, the fixture may be cylindrical and have a through-hole that corresponds to the shape of the drive arm. The drive arm is (partially) inserted into the through-hole, whereby the through-hole guides the movement of the drive arm as it moves in a reciprocating back and forth motion.

[0029] In the embodiment shown in FIG. 1 , the cam assembly 24 of one of the two test units 14 is offset 180 degrees circumferentially about the drive shaft 18 relative to the cam assembly of the other of the two test units. More specifically, the cam lobe 28 of one of the cam assemblies 24 is rotated 180 degrees on the drive shaft 18 relative to the cam lobe of the other cam assembly. The 180-degree offset between the two cam lobes reduces imbalance and resulting vibration in the system. Furthermore, this offset ensures that the driven member 32 of one of the cam assemblies 24 is at its highest point (farthest from the drive shaft 18) when the driven member of the other cam assembly is at its lowest point.

[0030] Each test unit 14 further includes a support 50 and a pressure chamber assembly 52. ​​The support 50 extends vertically from the base 16, flanks the cam assembly 24, and supports the pressure chamber assembly 52. ​​The support 50 may include a single member, or, as shown by way of example, a pair of support posts in the form of vertical block or wall members 54, 54' disposed on either side of the cam assembly 24. In particular, each block member 54, 54' includes an opening 55 through which the drive shaft 18 extends, and two of the bearing assemblies 22 are disposed between the two block members 54, 54' of the support 50, with the cam assembly 24 sandwiched between the two bearing assemblies. A pressure chamber assembly 52 is attached to each of the two block members 54, 54' and suspended above the cam assembly 24 between the block members. 1, the pressure chamber assemblies 52 of two adjacent test units 14 may share a common block member 54' between them, where the common block member is wider in the longitudinal direction of the drive shaft 18 than the block member 54 on the end not disposed between the two pressure chamber assemblies. In some embodiments, a resilient 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 it is assembled on 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).

[0031] 1, 2, 14, and 15, the pressure chamber assembly 52 includes a body 56 having an observation window 58, an open end 60 including an opening 61, and an inner chamber wall 62 adjacent the opening and defining a pressure chamber 63 within the body. The body 56 may be a generally hollow cylinder having an annular flange 64 at the open end 60. The observation window 58 may be a generally circular opening opposite the open end 60, or may be located along a side or at the bottom of the body and may include a viewing window 66 formed from a polycarbonate plate or the like. In another embodiment, the entire body may constitute the observation window, or the body may comprise a transparent polycarbonate material or the like, i.e., the entire body may be transparent and thereby constitute the observation window. The pressure chamber assembly 52 further includes a clamping member 68. The clamping member 68 may 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 the test sample substrate 72 between the clamping member and the body, closing the pressure chamber 63 with the surface of the substrate, including the coating layer, facing the pressure chamber. The central opening 70 surrounds the test area of ​​the test sample substrate 72 sandwiched within the pressure chamber assembly 52, with the coating layer within the test area of ​​the substrate inside the pressure chamber. Thus, the central opening 70 is sized large enough to not cause any interference with the driven member 32, as well as to enable leak spray detection, as described in more detail below, while being small enough to limit any deformation of the test sample substrate under pressure during testing (e.g., doming of the substrate, in which pressure within the pressure chamber causes the substrate to bulge outward, 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 apertures in the flange 64 of the body 56 and threaded into corresponding threaded apertures in the clamping member 68. In some embodiments, the body 56 includes a seal 76 that surrounds the opening 61. In particular, the seal 76 may include a pair of concentric annular ridges 78 that form an annular groove 80 between the ridges.To achieve an airtight seal for the pressure chamber 63, the annular ridge 78 bites into the side of the substrate 72, which includes a coating layer, and faces the body when the substrate is sandwiched and clamped between the clamp member 68 and the body 56. When the body 56 and clamp member 68 of the pressure chamber assembly 52 are assembled with the test sample substrate 72 sandwiched therebetween, the pressure chamber assembly may be attached to the support 50 by other fasteners, such as threaded bolts 82, which extend through other apertures in the flange 64 of the body 56 and the clamp member 68 and thread into threaded apertures in each of the block members 54, 54′ of the support 50.

[0032] Optionally, as shown in FIGS. 1 and 2 , an insert 83 can be positioned between the support 50 and the clamp member 68 to adjust the height of the pressure chamber assembly 52 relative to the cam assembly 24. The insert 83 may be a plate or other planar member formed of a generally rigid, inelastic material. The apparatus 10 can include two or more sizes of inserts, and the choice of which insert to use depends on the thickness of the test sample substrate 72 to maintain the same penetration length of the driven member 32 (if the driven member is a piercing object) from the outer surface (e.g., tread surface) of the test sample substrate to the tip of the driven member piercing the test sample substrate. For example, the penetration length of the driven member 32 may be kept constant at 40 mm. In this case, a test sample substrate having a thickness of 16.5 mm requires an insert having a thickness of 8.0 mm, a test sample substrate having a thickness of 19.5 mm requires an insert having a thickness of 5.0 mm, and a test sample substrate having a thickness of 24.5 mm does not require an insert, i.e., no insert is used.

[0033] 16 , the apparatus 10 may include an air inlet / outlet system including a compressed air source 84, such as an air compressor (and associated air storage tank), 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 a solenoid, may be connected to the supply line 85 for filling the pressure chamber 63 with compressed air from the air compressor and / or for venting the pressurized air in the pressure chamber by releasing it 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 apparatus 10 may further 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, as shown in FIG. 16 . Alternatively, the pressure sensor may be located within the pressure chamber or may be a non-contact sensor, such as an ultrasonic pressure sensor, located outside the pressure chamber and capable of externally detecting a pressure loss within the pressure chamber. Pressure sensor 87 may be any suitable sensor known in the art capable of measuring pressure level and / or pressure loss.

[0034] A camera 88 can 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 can be positioned in the observation window 58 of the pressure chamber assembly 52 and / or can be positioned adjacent to the clamping member 68 to monitor the test sample substrate 72 from outside the pressure chamber.

[0035] The apparatus 10 may further include a control and data acquisition system including one or more of a controller (CPU) 89 and a user interface (human-machine interface) 90 including one or more input / output devices, such as a display, keyboard, mouse, or printer, electrically connected to the controller. The controller 89 is electrically connected to one or more of the actuator 12, pressure sensor 87, and at least one valve 86 to control the actuator and test unit and process data received from monitoring the test unit. In some embodiments, the user interface 90 is a touchscreen display that visually displays information and allows user input by touching the screen. The control and data acquisition system allows for setting and control of various parameters, including the frequency / speed, amplitude, and number of cycles of movement of the driven member 32 via control of the actuator 12, as well as a pressure drop shutoff setpoint at which the actuator is stopped. Additionally, the system may include an emergency stop control that allows the apparatus 10 to be manually shut off at any time, for example, by toggling a control button. The control and data acquisition system may also receive pressure data from a pressure sensor 87 to monitor, display, and store the pressure level in the pressure chamber during testing and may also detect pressure loss during testing. The control and data acquisition system may also receive, display, and store visual information provided by a camera, if present. The apparatus 10, including the control and data acquisition system and test unit, may be provided on a mobile cart 91, as shown by the embodiment in FIG. 17, so that the entire apparatus can be easily transported, such as when the apparatus is moved into or out of an environmental chamber. Alternatively, the control and data acquisition system may be stored separately on a mobile cart or a fixed workstation, while the test unit 14 on the base 16 may be moved to various locations. For example, the base 16 may include a lifting handle 92 so that the actuator 12 and test unit 14 on the base 16 can be lifted and moved from one location to another.

[0036] As shown by the example of FIG. 15 , the test sample substrate 72 may be a tire sample cut from the tread surface (as opposed to the sidewall) of an entire tire, the tire sample including the tire tread 73 on one (outer) surface and a coating layer 75 of the self-sealing tire sealant on the opposite inner surface. The tire sample may be cut into a generally square shape and may have dimensions of approximately 146.1 mm x 146.1 mm (5.75 inches x 5.75 inches). However, the test sample substrate is not limited to these particular dimensions and need only be large enough to surround and extend beyond the opening 61 in the open end 60 of the body 56 of the pressure chamber assembly 52. ​​In any event, it will be apparent that the test sample substrate 72 may be a relatively small portion of a tire and, therefore, be economical for evaluating the sealant performance of a self-sealing tire sealant, as opposed to on-vehicle testing, which requires the use of four complete tires. However, the test sample substrate is not limited to a tire sample and may be another substrate, with or without a coating layer thereon. Additionally, the coating layer is not limited to a self-sealing sealant and may be other types of coating materials. For example, the test sample substrate may be a tire sample coated with a polymer foam for noise-suppressing acoustic effects (i.e., a "quiet running tire" sample), and the durability of adhesion of the noise-suppressing coating layer to the inner surface of the tire sample may be tested. Additionally, the test sample substrate may be cut from a tire already including a coating layer on its inner surface (e.g., a manufactured self-sealing tire), or the test sample substrate may be cut from a tire that does not include a self-sealing sealant layer, and the self-sealing sealant may be coated on the non-tread surface of the sample after it is cut from the tire. In either case, the amount of material required to obtain the tire sample substrate 72 is small.

[0037] As an example, the apparatus 10 may be used to test the durability of a tire test sample 72 that includes a layer of self-sealing sealant thereon. As noted above, the test apparatus 10 can be used to simultaneously test two (or more than two, depending on the number of test units 14) samples using two test units as shown in FIG. 1. For purposes of explanation, the discussion of the test procedures will generally be made with reference 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 testing procedure may generally include the steps of assembling a pressure chamber assembly, inserting a nail into a test sample, mounting the pressure chamber assembly in a test unit, performing durability tests on the nail at room temperature, high temperature, and low temperature and monitoring for leaks, removing the nail and checking for leaks, removing the nail and performing a durability test by perforating the tread surface of the tire sample near the puncture site to simulate removing the nail from the tire and driving the tire, and performing a storage test by subjecting the test sample held in the test unit to thermal cycles including room temperature, high temperature, and low temperature and again checking for leaks.

[0038] 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 members 68, with the tire tread 73 of the tire sample facing the clamping members and the layer of sealant 75 on the inner surface of the tire sample facing the pressure chamber 63, and inserting bolts 74 into appropriate apertures in the body and clamping members. As described above, the tire sample 72 is sized to completely cover the opening 61 in the body 56 and extend beyond the perimeter of the opening, but generally within the outer boundary of the body flange 64 and the perimeter of the clamping members 68. The central opening 70 in the clamping members 68 is also completely covered by the tire sample 72. A 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 in the clamping members 68 and pierces through 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 into the pressure chamber 63. The nail may be driven into the tire sample 72 to a controlled depth using a hammer or mallet, or the nail may be driven into the tire sample using a universal tensile tester, bench amber press, or any other suitable means. Once the nail is inserted through the tire sample 72, the pressure chamber assembly 52 is mounted on the support 50 and secured with two bolts 82, one for each block member 54 of the support. If a coil spring is inserted between the pressure chamber assembly 52 and the support 50, the spring reduces the amount of load exerted on 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 relieving any potential overstress in the test sample introduced by the driven member penetrating into the test sample. Alternatively, the nail or other piercing object may be driven into the tire sample after the pressure chamber assembly 52 is mounted on the support 50. The head of the nail is secured to the drive arm 40 of the cam assembly 24 using a lock nut 46.Next, the pressure chamber 63 is pressurized by filling it with compressed air from the compressed air source 84, for example, to a pressure of 36 psi. The sealed pressure chamber assembly with the tire sample attached can withstand pressures generally ranging from 30 to 50 psi, covering typical inflation pressures of vehicle tires. After pressurization, test parameters may be set through the user interface. Test parameters may include, but are not necessarily limited to, nail movement frequency, amplitude, and number of test cycles based on factors such as tire diameter, simulated driving speed, simulated road conditions, and simulated distance traveled at each driving speed to mimic on-the-road testing. Test parameters may also include a shutoff setpoint pressure, which automatically stops the test run if the pressure in the pressure chamber 63 drops below the setpoint pressure. Once the test parameters are set, the controller 89 activates the actuator 12 to drive the nail, causing it to move within the tire sample in both an oscillating linear back-and-forth motion and an oscillating rocking motion. Specifically, actuator 12 rotates drive shaft 18, which in turn rotates cam lobe 28. Due to the eccentricity of cam lobe 28, the cam lobe moves follower 30 in an up-and-down motion and simultaneously in a slight oscillatory motion. The movement of follower 30 drives a nail attached to drive arm 40 of follower 30 in the same oscillatory linear and oscillatory oscillatory motion. The movement of the nail within the tire sample simulates the moving forces exerted on a punctured nail as the tire rolls over the nail on the road and tests the durability of the self-sealing sealant surrounding the nail at the puncture site. While the nail is being driven, the pressure within pressure chamber 63 is monitored to ensure no pressure loss occurs. The inner surface of the tire sample within pressure chamber 63 can be visually monitored through observation window 58, and a camera can be used to monitor and / or record activity within the pressure chamber at the puncture site or activity outside of the pressure chamber, i.e., on the tire tread side of the puncture site. If no loss of pressure is detected by pressure sensor 87 after the desired number of cycles has been reached, actuator 12 is deactivated.The pressure chamber assembly 52 can then be removed from the support 50, and the sealant's leak-proof performance can be tested using a spray method, optionally by spraying a leak detection liquid (e.g., soapy water, salt water) onto the puncture site (with the nail still inserted) and examining the formation of an air bubble that grows around the puncture site. The nail can then be removed from the tire sample 72, and the puncture site can be checked again for air leakage. With the nail removed, the tire sample can then be tested for sealant pressure-retention performance by simulating a self-sealing tire cyclically interacting with the ground and measuring pressure loss over time. Specifically, another driven member, such as a blunt object 32', such as a punch, is attached to the cam assembly 24, and the pressure chamber assembly 52 is reattached to the support 50 so that the blunt object can contact the tire tread 73 of the tire sample 72 in the area of ​​the tire sample containing the puncture site. Test parameters are again set using the user interface 90, and the actuator 12 is activated to drive the blunt object, moving it to periodically puncture the tire tread of the tire sample adjacent the puncture site. The pressure in the pressure chamber 63 is continuously monitored while the blunt object is driven to check for a pressure drop indicative of an air leak at the puncture site. The inner surface of the tire sample within the pressure chamber 63 can also be visually monitored through the monitoring window 58, and a camera 88 can be used to monitor and / or record activity within the pressure chamber at the puncture site or activity outside of the pressure chamber, i.e., on the tire tread side of the puncture site. Once the desired number of cycles is completed, the actuator is shut off.

[0039] The above-described test procedures can be performed at room temperature. Optionally, the test procedures can be performed at one or more of room temperature, low temperatures (e.g., below 20°C and around −50°C, e.g., −50°C, more preferably −30°C, even more preferably −20°C), and high temperatures (e.g., above 20°C and around 150°C, e.g., 150°C, more preferably 100°C, even more preferably 70°C), as well as at different humidity levels, by conducting the tests with the apparatus 10 located in an environmental chamber that allows for temperature and humidity adjustments to simulate various climatic and seasonal weather conditions. Furthermore, after the above-described test procedures are performed, the apparatus 10 including the mounted tire sample, or the pressure chamber assembly simply having the mounted tire sample, can be subjected to a thermal cycle in the environmentally controllable chamber while further monitoring the pressure in the pressure chamber and checking for leaks at the puncture site. The thermal cycle can range from −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 real-world road conditions such as rain, snow (salted roads), mud, etc. can be simulated by spraying various substances onto the tread surface of the tire sample, 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.

[0040] The following two tables provide exemplary test procedure steps and test conditions.

[0041] [Table 1]

[0042] [Table 2]

[0043] The test frequency of a tire sample can be estimated based on the circumference of the tire from which the sample was cut and the desired simulated road test speed using the following formula:

[0044]

number

[0045] [Table 3]

[0046] The oscillation amplitude of the puncture object (e.g., nail) can be estimated based on the road conditions, the vehicle mass, and the road test speed. Typically, a larger amplitude should be associated with a lower frequency (e.g., ±3° at 6 Hz) to simulate a vehicle traveling under rough road conditions, such as a gravel road. On the other hand, a smaller amplitude should be used in combination with a higher frequency (e.g., ±1° at 12 Hz) to simulate a vehicle traveling under smooth road conditions, such as a highway.

[0047] The equivalent mileage of a tire sample can be estimated based on the circumference of the tire from which the sample was cut and can be calculated using the following formula: d=n * p / 1000 where d is the equivalent distance traveled (km), n is the number of test cycles, and p is the circumference of the tire in metres (metres).

[0048] [Table 4]

[0049] The pressure level set in the pressure chamber should be based on the tire's application and should be approximately 2.5 bar for passenger tires.

[0050] The test parameters may also be varied to test for small, very slow leaks over a period of several days.

[0051] Referring to FIG. 18, two different sealant failure modes are depicted. In particular, there are two types of sealant failure that can result from tests performed by the testing apparatus. For example, as shown on the left, the oscillatory motion of a driven member, such as a nail, can form a "jacket" feature 93 in the tire sealant, i.e., the sealant forms a jacket or sleeve around the shaft of the nail as it is lifted from the inner surface of the tire sample. Alternatively, as shown in the center and right, the driven member, such as a nail, can form a "hat" feature 94 in the tire sealant, i.e., the sealant forms a hat that covers the tip of the end of the nail.

[0052] Although the pressure chamber assembly is shown mounted atop 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 within a tire), the pressure chamber assembly and cam assembly may have other orientations, such as the driven member of the cam assembly interacting 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 to provide alternative means of monitoring leaks. For example, if soap / soapy water is sprayed onto the substrate to monitor air leaks around a puncture, the driven member should interact with the tire substrate from above so that the soap is located on the upper surface (rather than the underside) of the substrate. Also, if small particles are used to simulate the impact of dirt on a puncture, a top-down orientation should also be used so that the dirt remains on the upper surface of the substrate. Furthermore, as the tire rotates on the road under different conditions (rain, snow, and / or mud containing coating-degrading chemicals), abrasive particles combined with the coating-degrading chemicals may penetrate the puncture and reach the coating-tire interface on the inner surface of the tire. When the tire sample is placed on top of a driven member, the tire tread faces downward, so little or no spray applied to the tire tread surface during the liquid spray test reaches the coating-tire interface. This configuration provides the most conservative performance results when testing the durability of the coating under these simulated road conditions using a liquid spray. On the other hand, when the tire sample is placed under a driving member, the tire tread faces upward, and the spray applied to the tire tread surface has the greatest ability to reach the coating-tire interface. This configuration provides the most conservative performance results when testing the durability of the coating against various chemicals contained in the liquid spray. Furthermore, configurations in which the tire sample is horizontal or tilted at an angle to the side of the driven member result in a result that falls between the top and bottom configurations, as the liquid spray may partially reach the coating-tire interface.Additionally, abrasive particles and chemicals that may be present in the liquid spray have been shown to degrade organic coatings used on the inner tire surface, while silicone coatings have been shown to be insensitive to these materials. Therefore, the orientation of the tire sample relative to the driven member may not be as important with silicone coatings as it is with organic coatings.

[0053] The invention has been described in an illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the invention are possible in light of the above teachings. The invention may be practiced other than as specifically described.

Claims

1. An automated laboratory apparatus for dynamically testing the durability of a coating, Actuator and A drive shaft coupled to the actuator, A test unit comprising a cam assembly, a support located on the side of the cam assembly, and a pressure chamber assembly, The cam assembly is attached to the drive shaft, A cam lobe is eccentrically mounted on the aforementioned drive shaft, A follower that is bias-engaged with the cam lobe, the follower including a circular body surrounding the cam lobe and a drive arm protruding from the circular body, The cam assembly includes a driven member that is engaged with and held by the drive arm of the follower, The pressure chamber assembly is mounted on a support and aligned with the cam assembly, and the pressure chamber assembly is A body including a monitoring window, an open end including an opening, and an inner chamber wall adjacent to the opening that defines a pressure chamber within the body, A clamping member including a central opening, wherein the clamping member and the body are fitted to close the pressure chamber with a substrate including the coating sandwiched between them, so that the coating faces the inside of the pressure chamber. The driven member extends through the central opening of the clamp member and is capable of contacting the base material. An automated laboratory apparatus in which the rotation of the drive shaft drives one or both of the vibrational linear motion and vibrational oscillating motion of the driven member via the cam assembly.

2. The automated laboratory apparatus according to claim 1, wherein the driven member is one of a puncturing object or a blunt object.

3. The automated laboratory apparatus according to claim 1, wherein the body of the pressure chamber assembly includes a seal surrounding the opening, and the seal includes a pair of concentric annular ridges forming an annular groove between them.

4. The automated laboratory apparatus according to claim 1, further comprising an insert positioned between the support and the clamp member for adjusting the height of the pressure chamber assembly relative to the cam assembly.

5. The automated laboratory apparatus according to claim 1, further comprising a pressure sensor for monitoring the pressure in the pressure chamber.

6. The automated laboratory apparatus according to claim 1, further comprising a compressed air source in fluid communication with the pressure chamber via a supply line, and at least one valve connected to the supply line for filling and discharging the pressure chamber.

7. The system further includes a controller electrically connected to one or more of the actuator, the pressure sensor, or the at least one of the valves, The automated laboratory apparatus according to claim 1, further comprising, optionally, a user interface electrically connected to the controller for setting test parameters and monitoring the pressure in the pressure chamber.

8. A method for testing the durability of a tire coated with a self-sealing sealant in terms of its leak-proof performance, The steps of providing the automated laboratory apparatus according to any one of claims 1 to 7, The steps of providing a base material which is a tire sample cut from a tire, wherein the tire sample includes a tire tread on one surface and further includes an opposite inner surface having a layer of self-sealing sealant thereon, The step of sandwiching the tire sample between the pressure chamber body and the clamp member, with the tire tread of the tire sample facing the clamp member and the layer of sealant on the inner surface of the tire sample facing the pressure chamber, The step of inserting the driven member, which is the puncture object, into the tire sample through the central opening of the clamp member, The steps include: mounting the pressure chamber assembly onto the support and mounting the inserted driven member onto the cam assembly; The steps include filling the pressure chamber with compressed air to a predetermined set pressure, The steps include: driving the puncture object and operating the actuator to move the puncture object within the tire sample in either or both of the following motions: The steps include monitoring the pressure in the pressure chamber while the puncture object is being driven, To check for leaks at the puncture site within the tire sample, the puncture object is removed from the cam assembly and the pressure chamber assembly is removed. The steps include removing the punctured object from the tire sample and attaching another driven member, which is a blunt object, to the cam assembly, A step of mounting the pressure chamber assembly onto the support, wherein the blunt object comes into contact with the tire tread of the tire sample; The steps include: driving the blunt object and operating the actuator to move the blunt object so that the blunt object periodically perforates the tire tread of the tire sample that is close to the puncture location; The steps include monitoring the pressure in the pressure chamber while the blunt object is being driven, A method comprising the steps of: further monitoring the pressure in the pressure chamber and subjecting the automated laboratory apparatus, including the tire sample, to a thermal cycle while checking for leaks at the puncture site.

9. The method according to claim 8, further comprising the step of monitoring the inner surface of the tire sample in the pressure chamber through the monitoring window.

10. The method according to claim 8, further comprising the step of using a camera to monitor and / or record the activity inside the pressure chamber at the puncture site.

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