Patent Description:
Reliability testing for an assembly, or moving components of an assembly, may involve repetitively performing intended and/or unintended movements of the components to verify that the components and/or assembly reliably operates for a defined minimum number of cycles of the movements. For example, reliability testing of a flexible substrate may involve repeatedly flexing the substrate in one or more ways, while testing for continued operation of the device and/or monitoring various modes of failure.

Methods and apparatus to perform load measurements on flexible substrates are disclosed, substantially as illustrated by and described in connection with at least one of the figures, as set forth more completely in the claims.

Conventional flexible substrate testing systems do not measure loads or stresses on the flexible substrates during folding or unfolding. Instead, conventional flexible substrate testing systems may involve testing such as defect analysis and other static testing and analysis.

Disclosed example flexible substrate testing systems and methods provide stress testing for flexible substrates, including measurement of dynamic and/or static loads on the flexible substrate during deformation such as folding and/or unfolding. Some disclosed example systems and methods reduce or minimize additional stress induced on the flexible substrate by the flexible substrate testing system itself. For example, some disclosed flexible substrate testing systems include fixturing that provides repetitive folding and unfolding of a flexible substrate, such as a flexible display screen. Disclosed examples configure the fixturing, such as guiding of the moving parts, such that the fixturing does not create additional compression or tension on the flexible substrate as the ends of the substrate are folded together or unfolded.

Disclosed example flexible substrate testing systems include: a first substrate support structure configured to hold stationary a first portion of a flexible substrate under test; a second substrate support structure configured to hold a second portion of the flexible substrate; an actuator configured to move the second substrate support structure to fold the flexible substrate and to unfold the flexible substrate; and a load cell configured to measure a load on the flexible substrate.

Some example flexible substrate testing systems further include a first guide configured to guide a motion of the second substrate support structure to fold the flexible substrate and to unfold the flexible substrate. In some example flexible substrate testing systems, the first guide is configured to guide the motion of the second substrate support structure in accordance with a first predetermined bend radius of the flexible substrate. In some example flexible substrate testing systems, the first guide is interchangeable with a second guide configured to guide the motion of the second substrate support structure in accordance with a second predetermined bend radius of the flexible substrate.

In some example flexible substrate testing systems, the first guide includes a first guide plate having a groove configured to guide a cam follower attached to the second substrate support structure. In some example flexible substrate testing systems, the first guide plate includes an actuator groove configured to guide an actuator pin coupled to the second substrate support structure and positioned within the actuator groove, and the actuator is configured to move the second substrate support structure by moving the actuator pin.

In some example flexible substrate testing systems, the first guide is configured to guide the motion of the second substrate support structure without incurring additional stress on the flexible substrate due to the motion or weight of the second substrate support structure. Some example flexible substrate testing systems further include a second guide coupled to the second substrate support structure and on an opposite side of the second substrate support structure from the first guide, in which the second guide plate is configured to guide the motion of the second substrate support structure to fold the flexible substrate and to unfold the flexible substrate.

Some example flexible substrate testing systems include a load limiter configured to limit displacement of the first substrate support structure toward the load cell. Some example flexible substrate testing systems include control circuitry configured to determine the load on the flexible substrate based on load information from the load cell. In some example flexible substrate testing systems, the control circuitry is configured to determine the load on the flexible substrate based on a dynamic load measured by the load cell during the folding or unfolding of the flexible substrate. In some example flexible substrate testing systems, the control circuitry is configured to determine the load on the flexible substrate based on a static load measured by the load cell at a completion of the folding or unfolding of the flexible substrate.

Some example flexible substrate testing systems include control circuitry configured to control the actuator to move the second substrate support structure in a first direction to fold the flexible substrate or in a second direction to unfold the flexible substrate. Some example flexible substrate testing systems include a translation linkage configured to hold the first substrate support structure and to limit motion of the first substrate support structure to a direction in which the load cell is configured to measure the load.

In some example flexible substrate testing systems, the load cell is configured to measure the load on the first portion of the flexible substrate. In some example flexible substrate testing systems, the load cell is configured to measure at least a portion of the load on the second portion of the flexible substrate. Some example flexible substrate testing systems include control circuitry configured to compensate a load measurement from the load cell for a weight of the second substrate support structure and a momentum of the substrate support structure during folding or unfolding, and to determine at least a portion of the load on the flexible substrate based on load information from the load cell and the compensation. Some example flexible substrate testing systems include a second load cell configured to measure a portion of the load on the first portion of the flexible substrate.

Disclosed example methods to measure loads on a flexible substrate involve: holding stationary, via a substrate support structure, a first portion of a flexible substrate under test; moving, via an actuator, a second portion of the flexible substrate to fold the flexible substrate or to unfold the flexible substrate; and measuring a load on the flexible substrate resulting from the moving.

Some other example flexible substrate testing systems include: a first plate comprising a first surface configured to hold stationary a first side of a flexible substrate under test; a translation linkage configured to hold the first plate and to limit motion of the plate in directions parallel to the first surface of the plate; a second plate comprising a second surface configured to hold a second side of the flexible substrate; a first guide plate configured to guide a motion of the second surface to fold the flexible substrate and to unfold the flexible substrate; an actuator configured to move the second plate in accordance with the first guide plate to fold the flexible substrate and to unfold the flexible substrate; and a load cell configured to measure loads on the first plate while the actuator moves the second plate.

<FIG> is a block diagram of an example flexible substrate test system <NUM> to perform mechanical property testing on a flexible substrate <NUM>. The example flexible substrate <NUM> may be a flexible display screen or other device, fabric, material, and/or any other substrate. The system <NUM> of <FIG> is configured to repeatedly fold and unfold the flexible substrate <NUM> to measure stress on the substrate <NUM>.

The example system <NUM> includes a first plate <NUM>, a second plate <NUM>, a guide plate <NUM>, an actuator <NUM>, a load cell <NUM>, and a translation linkage <NUM>. The system <NUM> may include additional features, such as structural support or framing, processing circuitry, communications and/or input/output (I/O) circuitry, and/or any other components.

When folded, the flexible substrate <NUM> is considered to have a first side <NUM> and a second side <NUM> on opposing ends of the bend <NUM> or fold in the substrate <NUM>. The first side <NUM> and the second side <NUM>. <FIG> illustrates the substrate in an unfolded or flat position (solid line) and folded position (dotted line).

The first plate <NUM> is a first substrate support structure, and has a first surface <NUM> to which the first side <NUM> of the substrate <NUM> is attached or affixed. The first side <NUM> of the substrate <NUM> is held stationary with respect to the first surface <NUM>. The second plate <NUM> is a second substrate support structure, and has a second surface <NUM> to which the second side <NUM> of the substrate <NUM> is attached or affixed. The second side of the substrate <NUM> is held stationary with respect to the second surface <NUM>. The plates <NUM>, <NUM> are separated by a gap, which is bridged by a portion of the substrate <NUM> that forms the curve <NUM> when the substrate <NUM> is folded.

While the first and second substrate support structures in <FIG> are first and second plates, in other examples the first and second substrate support structures may be different. For example, other first and second substrate support structures may include clips or clamps to hold portions of the substrate <NUM> to enable folding without attachment of the substrate <NUM> to the plate.

The guide plate <NUM> guides a motion of the second plate <NUM> and, thus, the second surface <NUM>, to fold and unfold the flexible substrate <NUM>. As described in more detail below, the guide plate <NUM> may include multiple grooves, which are engaged by corresponding cam followers attached to the second plate <NUM> to guide translation and rotation of the second plate <NUM>. By including multiple grooves and cam followers instead of a single groove and cam follower, the example system <NUM> may avoid creating additional stress on the substrate <NUM>. For example, multiple grooves that have a consistent spacing prevent introduction of a moment due to the weight of the second plate <NUM>, which may cause additional stress on the substrate <NUM> and influence the test results.

While the example of <FIG> includes a guide plate <NUM> as a guide to define the folding path, in other examples the guide may be different and/or may be omitted to enable the flexible substrate to define the folding and/or unfolding path(s). For example, other guides may include having multiple gears, in which a first gear is free to spin and is aligned with the edge of the first side of the substrate <NUM>, and a second gear is meshed with the first gear and fixed with respect to the second half of the substrate <NUM>. Other example guides may include combination of two linear actuators arranged perpendicular to each other, with one mounted to the other, in which the second plate <NUM> is attached to the actuators, and could move freely in an x-y plane and trace out the folding path. Multiple linear actuators may enable the guide to implement different types of paths, including folds of different radii and/or non-circular folds. Some other example guides may include a series of linkages defining the folding path.

The actuator <NUM> is coupled to the second plate <NUM> to move the second plate <NUM>. As illustrated in <FIG>, the actuator <NUM> moves the second plate <NUM> between a first position in which the substrate <NUM> is unfolded (e.g., shown in solid lines) and a second position in which the substrate <NUM> is folded (e.g., in broken lines). In some examples, the actuator <NUM> may be a motor attached to the second plate <NUM> via linkage and an actuator pin coupled to the second plate <NUM>. The actuator pin may also be guided via the guide plate <NUM> to control the direction in which the actuator <NUM> exerts force on the second plate <NUM>.

The load cell <NUM> measures loads on the first plate <NUM> while the actuator <NUM> moves the second plate <NUM>. In particular, the load cell <NUM> measures stress (e.g., folding force) on the substrate <NUM> as the substrate <NUM> is folded by measuring load exerted by the first side <NUM> of the substrate <NUM> onto the first plate <NUM>. The load cell <NUM> may output load measurements during folding and/or unfolding (e.g., measurements of dynamic load) and/or at the conclusion of a folding and/or unfolding process (e.g., measurements of static load).

The translation linkage <NUM> limits movement of the first plate <NUM> in directions other than the direction in which the load cell <NUM> is loaded by the first plate <NUM>. For example, if the load cell <NUM> is configured to measure loads in a direction perpendicular to the plane of the first surface <NUM>, the translation linkage <NUM> limits movement of the first plate <NUM> in directions parallel to the plane of the first surface <NUM> while permitting load to be transferred from the first plate <NUM> to the load cell <NUM>. An example translation linkage <NUM> may include one or more four-bar linkages coupled to a frame that is fixed with respect to the load cell <NUM>. In some examples, the translation linkage <NUM> is further limited in a direction toward the load cell <NUM> to prevent overloading of the load cell <NUM>. For example, a stopping point may be attached to the frame to prevent movement of the four-bar linkage(s) and the plate <NUM> toward the load cell <NUM> beyond the stopping point.

In operation, the example load cell <NUM> may be biased or offset after securing the substrate <NUM> to the first plate <NUM> and the second plate <NUM> to subtract a preload from the test measurements. For example, the preload on the load cell <NUM> may occur due to the weight of the plate <NUM>, the weight of translation linkage <NUM>, and the weight of the first side <NUM> of the substrate <NUM> on the first plate <NUM>. By determining the preload on the load cell <NUM>, the load cell <NUM> can be calibrated or offset to measure the stress on the substrate <NUM> during folding and unfolding.

<FIG> is a block diagram of another example flexible substrate test system <NUM> to perform mechanical property testing on the flexible substrate <NUM>. The flexible substrate test system <NUM> of <FIG> is similar to the flexible substrate test system <NUM> of <FIG>, but the load cell <NUM> is coupled to the second plate <NUM> (e.g., the moving plate) instead of the first plate <NUM> (e.g., the stationary plate), and measures loads on the portion of the flexible substrate <NUM> coupled to the second plate <NUM>. In still other examples, load cell(s) may be coupled to both plates <NUM>, <NUM> to measure forces on both portions of the flexible substrate <NUM>.

In the example of <FIG>, the measurements output by the load cell <NUM> are compensated for the weight of the second plate <NUM> and the inertial load of the second plate <NUM>, to provide a measurement of the force on the flexible substrate <NUM>. For example, the portion of the weight of the second plate <NUM> and the portion of the inertial load of the second plate <NUM> that results in a measurable force by the load cell <NUM> may continuously change during the folding motion. A processing system (e.g., the processor <NUM> disclosed below) may be configured to compensate measurements received from the load cell <NUM> based on the characteristics, the folding direction, the folding speed, and/or the folding path of the second plate <NUM> and/or of the actuator <NUM>, and/or any other dynamic forces occurring during the folding and/or unfolding processes.

<FIG> is a block diagram of an example implementation of the flexible substrate test system <NUM> of <FIG>. As illustrated in <FIG>, the flexible substrate test system <NUM> includes a test fixture <NUM> and a computing device <NUM>.

The example computing device <NUM> may be a general-purpose computer, a laptop computer, a tablet computer, a mobile device, a server, an all-in-one computer, and/or any other type of computing device. The computing device <NUM> of <FIG> includes a processor <NUM>, which may be a general-purpose central processing unit (CPU). In some examples, the processor <NUM> may include one or more specialized processing units, such as FPGA, RISC processors with an ARM core, graphic processing units, digital signal processors, and/or system-on-chips (SoC). The processor <NUM> executes machine-readable instructions <NUM> that may be stored locally at the processor (e.g., in an included cache or SoC), in a random access memory <NUM> (or other volatile memory), in a read-only memory <NUM> (or other non-volatile memory such as FLASH memory), and/or in a mass storage device <NUM>. The example mass storage device <NUM> may be a hard drive, a solid-state storage drive, a hybrid drive, a RAID array, and/or any other mass data storage device. A bus <NUM> enables communications between the processor <NUM>, the RAM <NUM>, the ROM <NUM>, the mass storage device <NUM>, a network interface <NUM>, and/or an input/output interface <NUM>.

An example network interface <NUM> includes hardware, firmware, and/or software to connect the computing device <NUM> to a communications network <NUM> such as the Internet. For example, the network interface <NUM> may include IEEE <NUM>. X-compliant wireless and/or wired communications hardware for transmitting and/or receiving communications.

An example I/O interface <NUM> of <FIG> includes hardware, firmware, and/or software to connect one or more input/output devices <NUM> to the processor <NUM> for providing input to the processor <NUM> and/or providing output from the processor <NUM>. For example, the I/O interface <NUM> may include a graphics-processing unit for interfacing with a display device, a universal serial bus port for interfacing with one or more USB-compliant devices, a FireWire, a field bus, and/or any other type of interface. The example extensometer system <NUM> includes a display device <NUM> (e.g., an LCD screen) coupled to the I/O interface <NUM>. Other example I/O device(s) <NUM> may include a keyboard, a keypad, a mouse, a trackball, a pointing device, a microphone, an audio speaker, a display device, an optical media drive, a multi-touch touch screen, a gesture recognition interface, a magnetic media drive, and/or any other type of input and/or output device.

The computing device <NUM> may access a non-transitory machine-readable medium <NUM> via the I/O interface <NUM> and/or the I/O device(s) <NUM>. Examples of the machine-readable medium <NUM> of <FIG> include optical discs (e.g., compact discs (CDs), digital versatile/video discs (DVDs), Blu-ray discs, etc.), magnetic media (e.g., floppy disks), portable storage media (e.g., portable flash drives, secure digital (SD) cards, etc.), and/or any other type of removable and/or installed machine-readable media.

The test fixture <NUM> is coupled to the computing device <NUM>. In the example of <FIG>, the test fixture <NUM> is coupled to the computing device via the I/O interface <NUM>, such as via a USB port, a Thunderbolt port, a FireWire (IEEE <NUM>) port, and/or any other type serial or parallel data port. In some examples, the test fixture <NUM> is coupled to the network interface <NUM> and/or to the I/O interface <NUM> via a wired or wireless connection (e.g., Ethernet, Wi-Fi, etc.), either directly or via the network <NUM>.

The test fixture <NUM> includes a frame <NUM>, a load cell <NUM>, material fixtures <NUM>, and a control processor <NUM>. The frame <NUM> provides rigid structural support for the other components of the test fixture <NUM> that perform the test. The load cell <NUM> may implement the load cell <NUM> of <FIG>, and measures force applied to a material under test (e.g., the substrate <NUM>) by an actuator <NUM> via grips <NUM> (e.g., the plates <NUM>, <NUM>).

The actuator <NUM> applies force to the material under test and/or forces displacement of the material under test, while the grips <NUM> grasp or otherwise couple the material under test to the actuator <NUM>.

Example actuators that may be used to provide force and/or motion of a component of the test fixture <NUM> include electric motors, pneumatic actuators, hydraulic actuators, piezoelectric actuators, relays, and/or switches. While the example test fixture <NUM> uses a motor, such as a servo or direct-drive linear motor, other systems may use different types of actuators. For example, hydraulic actuators, pneumatic actuators, and/or any other type of actuator may be used based on the requirements of the system.

The example grips <NUM> include platens, clamps, and/or other types of fixtures, depending on the mechanical property being tested and/or the material under test. The grips <NUM> may be manually configured, controlled via manual input, and/or automatically controlled by the control processor <NUM>.

The test system <NUM> may further include one or more control panels <NUM>, including one or more input devices <NUM>. The input devices <NUM> may include buttons, switches, and/or other input devices located on an operator control panel. For example, the input devices <NUM> may include buttons that control the actuator <NUM> to jog (e.g., position) the grips <NUM> to a desired position, switches (e.g., foot switches) that control the grips <NUM> to close or open (e.g., via another actuator), and/or any other input devices to control operation of the testing test fixture <NUM>.

The example control processor <NUM> communicates with the computing device <NUM> to, for example, receive test parameters from the computing device <NUM> and/or report measurements and/or other results to the computing device <NUM>. For example, the control processor <NUM> may include one or more communication or I/O interfaces to enable communication with the computing device <NUM>. The control processor <NUM> may control the actuator <NUM> to move in a given direction and/or to control the speed of the actuator <NUM>, control the fixture(s) <NUM> to grasp or release a material under test, and/or receive measurements from the displacement transducer <NUM>, the load cell <NUM> and/or other transducers.

The example control processor <NUM> is configured to implement a repetitive motion testing process in which a test specimen (e.g., the substrate <NUM>) is subjected to testing in the test fixture <NUM>. For example, to measure stress on the substrate <NUM> during or after a series of folding and unfolding motions, the control processor <NUM> controls the actuator <NUM> to move the grips <NUM> (e.g., the first and second plates <NUM>, <NUM>) while monitoring the load cell <NUM> to measure stress on the substrate <NUM>. In some examples, the control processor <NUM> monitors a motor encoder of the actuator <NUM> to determine a folding angle and/or establish a folding degree-per-pulse ratio.

The example processor <NUM> may determine a static load on the flexible substrate <NUM> based on a load measured by the load cell <NUM> at a completion of the folding or unfolding of the flexible substrate <NUM>. The static load measurement may occur after a relaxation time has been permitted to expire to enable the substrate <NUM> to relax following a folding or unfolding process. Additionally or alternatively, the example processor <NUM> may determine a dynamic load on the flexible substrate <NUM> based on loads measured by the load cell <NUM> during the folding or unfolding of the flexible substrate <NUM>. The example processor <NUM> may perform compensation of measurements from the load cell(s) <NUM>, such as removing the effects of weight of the first plate <NUM>, and/or weight and inertial load of the second plate <NUM>, from the load measurements.

<FIG> is a perspective view of an example implementation of the flexible substrate test system <NUM> of <FIG>. The example view of <FIG> illustrates a rotational arm <NUM> configured to move the second plate <NUM>, the load cell <NUM>, and an example implementation of the translation linkage <NUM>. The first plate <NUM> is not shown in <FIG>. The second plate <NUM> may be attached to the rotational arm <NUM>.

The example translation linkage <NUM> includes a first four-bar linkage <NUM>, a second four-bar linkage <NUM>, and a frame <NUM>. The frame <NUM> and the load cell <NUM> are stationary with respect to each other by attachment to a fixture frame (e.g., the frame <NUM> of <FIG>). The first and second four-bar linkages <NUM>, <NUM> are each configured to attach the first plate <NUM> via the innermost links. The first and second four-bar linkages <NUM>, <NUM> limit movement of the first plate <NUM> in directions parallel to the surface of the first plate <NUM> on which the substrate <NUM> is mounted (illustrated as directions X and Y in <FIG>), while permitting loads from the first plate <NUM> to be transferred to the load cell <NUM> (e.g., via an extension post <NUM> coupled to the load cell <NUM>) in a direction perpendicular to the surface of the first plate <NUM> (illustrated as direction Z in <FIG>).

To avoid overloading of the load cell <NUM>, the frame <NUM> includes a stopping point configured to prevent the first and second four-bar linkages <NUM>, <NUM> and/or the first plate <NUM> from traveling toward the load cell <NUM> beyond the stopping point. The stopping point may be implemented using, for example, a pin or other rigid fastener configured to contact an underside of the first and/or second four-bar linkages <NUM>, <NUM>, a top surface of the frame <NUM>, a bumper or rigid offset coupled to a top surface of the frame <NUM> to provide the stopping point via contact with first plate <NUM>, and/or any other technique.

The rotational arm <NUM> is configured to rotate and translate the second plate <NUM> with respect to the first plate <NUM> to fold and unfold the substrate <NUM>. The rotational arm <NUM> is coupled to the guide plates <NUM> via rotational assemblies <NUM>, which include cam followers configured to travel through cam grooves in the guide plates <NUM> as discussed below with reference to <FIG>.

<FIG> is an elevation view of the example flexible substrate test system <NUM> of <FIG>, including a guide plate <NUM> (e.g., the guide plate <NUM> of <FIG>). The example guide plate <NUM> includes two cam grooves <NUM>, <NUM>, within which two cam followers <NUM>, <NUM> are moved to rotate and move the second plate <NUM>. The grooves <NUM>, <NUM> are separated by the same distance over the arc lengths of the grooves <NUM>, <NUM>, such that the cam followers <NUM>, <NUM> support the weight of the second plate <NUM> via the rotational arm <NUM> and the rotational assemblies <NUM>, and substantially no stress is induced on the substrate <NUM> due to the weight of the second plate <NUM>.

The guide plate <NUM> includes an actuator groove <NUM> configured to receive an actuation pin <NUM> coupled to the second plate <NUM>. The actuator groove <NUM> is separated by the same distance from the cam groove <NUM> over the arc lengths of the grooves <NUM>, <NUM> and is separated by the same distance from the cam groove <NUM> over the arc lengths of the grooves <NUM>, <NUM>.

The example grooves <NUM>, <NUM>, <NUM> may be configured to cause a specified bend radius in the substrate <NUM> when the second plate <NUM> is rotated toward the first plate <NUM>. To this end, the guide plate <NUM> may be interchangeable with other guide plates that cause different bend radii in the substrate <NUM>. The arrangements and geometries of the grooves <NUM>, <NUM>, <NUM> may be determined by calculating a set of angles and positions at which the cam followers <NUM>, <NUM> and the actuation pin <NUM> are located with reference to an effective bend axis of the substrate <NUM>, over the course of travel of the substrate <NUM>, such that the length of the substrate <NUM> does not change and, therefore, compression and tension forces are not introduced to the substrate <NUM>.

In the example of <FIG>, the guide plate <NUM> includes a bend viewing window <NUM>, through which a camera or other monitoring device may observe the bend radius of the substrate <NUM>.

<FIG> is a partially exploded view of the translation linkage <NUM> of <FIG>. In particular, the example translation linkage <NUM> is shown with inner linkages <NUM>, <NUM> of the four-bar linkages <NUM>, <NUM> separated from intermediate linkages <NUM>, <NUM>, <NUM>, <NUM>, respectively. The intermediate linkages <NUM>-<NUM> couple the inner linkages <NUM>, <NUM> to the frame <NUM>, which serves as a portion of the four-bar linkages <NUM>, <NUM>.

<FIG> is a perspective view of the example flexible substrate test system <NUM> of <FIG> in which the second plate <NUM> has been moved to position to fold the substrate under test <NUM>.

<FIG> is a perspective view of another example flexible substrate test system <NUM> that may be used to implement the flexible substrate test system <NUM> of <FIG>. <FIG> is an elevation view of the example flexible substrate test system <NUM> of <FIG>. <FIG> is a plan view of the example flexible substrate test system of <FIG>. <FIG> is an elevation view of the example flexible substrate test system of <FIG>.

The example flexible substrate test system <NUM> includes a first plate <NUM>, a second plate <NUM>, guide plates 708a, 708b, and drive arms 710a, 710b that are driven via a drive shaft <NUM>. The first plate <NUM> remains stationary while the drive arms 710a, 710b moves the second plate <NUM> according to a path defined by the guide plates 708a, 708b to fold a substrate attached to the first and second plates <NUM>, <NUM>.

In the example of <FIG>, the example translation linkage <NUM> includes flexures 714a, 714b, which are coupled to a same base plate <NUM> as the guide plates 708a, 708b. The flexures 714a, 714b support the first plate <NUM> and permit transfer of load from the flexible substrate to a load cell <NUM>. The flexures 714a, 714b limit movement of the first plate <NUM> in directions other than the direction in which the load cell <NUM> measures force.

The example guide plates 708a, 708b are similar to the guide plates <NUM> illustrated in <FIG>. In the example of <FIG>, the guide plates 708a, 708b each include an actuator groove 720a, 720b and one cam groove 722a, 722b. The drive arms 710a, 710b are coupled to the respective actuator grooves 720a, 720b (e.g., via preloaded actuation pins 724a, 724b) to move (e.g., fold, unfold) the second plate <NUM>.

Both the actuator grooves 720a, 720b (e.g., via the preloaded cam followers 724a, 724b) and the cam grooves 722a, 722b (e.g., via cam followers or bearings 726a, 726b) are coupled to the second plate <NUM> to control a path of movement and folding of the second plate <NUM> and, as a result, the path of folding of the substrate. The example guide plates 708a, 708b may include more actuator grooves 720a, 720b and/or cam grooves 722a, 722b.

As illustrated in <FIG>, the drive arms 710a, 710b includes respective slots 802a, 802b extending radially from a pivot axis <NUM> of the drive arms 710a, 710b. In the example of <FIG>, the actuator <NUM> actuates (e.g., rotates) the drive arms 710a, 710b via the drive shaft <NUM> defining the pivot axis <NUM>. The slots 802a, 802b guide the respective bearings 726a, 726b as the drive arms 710a, 710b are rotated, while permitting the bearings 726a, 726b to move freely along the lengths of the slots 802a, 802b as the drive arms 710a, 710b are rotated.

<FIG> is a more detailed view of the example first plate <NUM>, the flexures 714a, 714b, and the load cell <NUM> of <FIG>. The example flexures 714a, 714b are supported by brackets 1102a, 1102b, which are coupled to the base plate <NUM>.

The flexures 714a, 714b include strips of metal attached to the brackets 1102a, 1102b and the first plate <NUM> to support the weight of the first plate <NUM>. The first plate <NUM> is also coupled to the load cell <NUM> to transfer loads to the load cell <NUM> for measurement.

To avoid overloading of the load cell <NUM>, the first plate <NUM> includes a stopping point configured to prevent the first plate <NUM> from traveling toward the load cell <NUM> beyond the stopping point. In the illustrated example, the stopping point is implemented using stopping blocks 1104a, 1104b. Support brackets 1106a, 1106b couple the flexures 714a, 714b to the first plate <NUM>. The blocks 1104a, 1104b are configured to stop support brackets 1106a, 1106b that couple the flexures 714a, 714b to the first plate <NUM> after a predetermined amount of travel of the support brackets 1106a, 1106b (e.g., a predetermined amount of load on the first plate <NUM>).

<FIG> is a flowchart representative of an example method <NUM> to measure loads on a flexible substrate, which may be performed by the example flexible substrate test systems of <FIG>. The example method <NUM> is disclosed below with reference to <FIG> and <FIG>.

At block <NUM>, the processor <NUM> and/or the control processor <NUM> calibrate the load cell(s) <NUM>, <NUM> to compensate for the weight(s) of the first and/or second substrate support structure(s) (e.g., the first plate <NUM>, the second plate <NUM>), the translation linkage <NUM>, and/or any other forces that affect the measurement by the load cell(s) <NUM>, <NUM>.

At block <NUM>, the first substrate support structure (e.g., the first plate <NUM>) holds a first portion of the flexible substrate <NUM> stationary. At block <NUM>, the second substrate support structure (e.g., the second plate <NUM>) holds a second portion of the flexible substrate <NUM>.

At block <NUM>, the processor <NUM> and/or the control processor <NUM> determine whether to fold the flexible substrate <NUM>. For example, the processor <NUM> may determine whether a folding cycle (e.g., folding and unfolding) is to be performed. If the folding is not to be performed (block <NUM>), control iterates to block <NUM> to await folding.

When folding is to be performed (block <NUM>), at block <NUM> the processor <NUM> and/or the control processor <NUM> control the actuator <NUM> to move the second substrate support structure in a folding direction to fold the flexible substrate <NUM>. In some examples, one or more guides, such as the guide plates <NUM>, may be used to control the bend radius and/or folding path of the flexible substrate <NUM> during the folding. At block <NUM>, the load cell(s) <NUM>, <NUM> measure a dynamic load on the flexible substrate <NUM> during the folding and/or measure a static load on the flexible substrate <NUM> after folding.

At block <NUM>, the processor <NUM> and/or the control processor <NUM> determine whether to unfold the flexible substrate <NUM>. If the unfolding is not to be performed (block <NUM>), control iterates to block <NUM> to await unfolding.

When unfolding is to be performed (block <NUM>), at block <NUM> the processor <NUM> and/or the control processor <NUM> control the actuator <NUM> to move the second substrate support structure in an unfolding direction to unfold the flexible substrate <NUM>. In some examples, one or more guides, such as the guide plates <NUM>, may be used to control the bend radius and/or folding path of the flexible substrate <NUM> during the unfolding. At block <NUM>, the load cell(s) <NUM>, <NUM> measure a dynamic load on the flexible substrate <NUM> during the unfolding and/or measure a static load on the flexible substrate <NUM> after unfolding.

At block <NUM>, the processor <NUM> and/or the control processor <NUM> determine whether to repeat the folding cycle. For example, the flexible substrate <NUM> may be subject to a testing process involving multiple folding cycles. If the folding cycle is to be repeated (block <NUM>), control returns to block <NUM>. If the folding cycle is not to be repeated (block <NUM>), the example method <NUM> ends.

Claim 1:
A flexible substrate testing system (<NUM>), comprising:
a first substrate support structure (<NUM>) configured to hold stationary a first portion of a flexible substrate (<NUM>) under test;
a second substrate support structure (<NUM>) configured to hold a second portion of the flexible substrate (<NUM>);
an actuator (<NUM>) configured to move the second substrate support structure (<NUM>) to fold the flexible substrate (<NUM>) and to unfold the flexible substrate (<NUM>); and
a load cell (<NUM>) configured to measure a load on the flexible substrate,
characterised by
a translation linkage (<NUM>) configured to hold the first substrate support structure (<NUM>) and to limit motion of the first substrate support structure (<NUM>) to a direction in which the load cell (<NUM>) is configured to measure the load.