WO2023009076A2

WO2023009076A2 - A portable crack testing device

Info

Publication number: WO2023009076A2
Application number: PCT/TH2022/000028
Authority: WO
Inventors: Kosin HACHAWEE; Chairat PONGTONGCHAROEN; Warot PROMBOON; Jarun LOMRATSIRI; Siriluk PONGKEATCHAI; Suwarat RAKCHOY; Anon SANGRUNGRUENG
Original assignee: Scg Packaging Public Company Limited
Priority date: 2021-07-30
Filing date: 2022-07-11
Publication date: 2023-02-02
Also published as: WO2023009076A3

Abstract

This invention relates with a portable crack testing device that comprises a sliding rail where a movable base is disposed on a movable mean of the rail such that the movable base is movable on the sliding rail; a force sensor fixedly attached to the movable base; a blade base fixedly attached to the sensing area of the force sensor; a blade, for applying force to a test material, fixedly attached to the blade base such that the blade protrudes from the force sensor and aligns with a test slit of a material holder, allowing the force sensor to measure pressing force when the blade is applied onto a test material; wherein a control unit processes the force value measured by the force sensor, the elongation of the test material that is analyzed from the displacement of the blade when pressing on the material, with material cracking information database to determine the chance of the test material to be cracked.

Description

A PORTABLE CRACK TESTING DEVICE

Technical Field

Engineering related to a portable crack testing device.

Background Art

In corrugated box production processes, a corrugated paper is pressed by a creaser to create a folded line before it is shaped into a box. If the corrugated paper is not strong enough, there may be cracks on the paper inside the box. It is therefore essential to specify the characteristics of the paper and test its strength before sending it out to customers.

There are no suitable tools or devices to perform crack testing of materials, such as a liner or corrugated paper, that are also portable. The test requires a clamper to hold the test liner or corrugated paper and requires a blade to press on the test paper. In general, the clamper is attached to a universal testing machine to measure a maximum load and a maximum elongation of the test paper. The load and elongation are used to determine the behavior of the paper, e.g. fragility or softness, when a force is exerted on it. The universal testing machines are big, not easy to move, and too expensive for regular factories. Most of the corrugated box and paper factories cannot therefore perform the test in their regular production processes.

United States patent US5574227 discloses an apparatus and method for determining crease characteristics of a corrugated paper board. A board sample holding area is provided to hold and fold the sample. One part of the sample is located on a force sensor and the other is located on a foldable area. When the sample is folded, the pressing force that is exerted on the sample is measured by the sensor. The objective of this invention is to measure the folding resistivity of a paper board and to determine how much weight a corrugated box can carry if it is made of the same material. The invention provides its result shown in a graphical format as a force vs angle plot.

United States patent US6684167B2 discloses a method and an apparatus for predicting a score- line cracking propensity of a multi- ply paperboard. They stretch and fold the test paperboard on a spindle. Users observe cracks or tears on the paperboard, especially on the upper side of the paperboard. Users press a keypad on three stages when cracks are visually detected. The three stages are “ crack” , “ gap” , and “ flap” . A control computer takes the information on each stage with its tension force and shows a plot of force and elongation of the paper on a display. Although the apparatuses and the methods mentioned above can measure foldable capability of a paper by measuring forces exerted on the paper while it is folding until the paper cracks or tears, and they may be applied for outside crack testing, they cannot determine inside cracks that occur inside the crease of corrugated paper. They do not possess any component that represents flute pitch on corrugated paper. The flute pitch is directly related to the elongation of a liner on the corrugated paper. When the paper is folded, the flute causes the liner to stretch. If the flute pitch is not properly designed to match the elongation of outer liner, the liner will be cracked when the paper is folded. If the crack is outside of the folding edge, it can be easily detected by visualization when performing quality checks within the production process. If, however, the crack is inside of the crease, it may be easily overlooked. Damaged boxes may be shipped from the production factory to customers and they may lose consumer trusts about the products.

It is therefore essential to provide a device and a method to test inside cracks on a liner or corrugated paper, that can show flute pitches and the cracks that are related to them. The device and method can improve the production quality of corrugated paper boxes and liners. Preferably, the device should be cheap, small, and portable.

Brief Summary of the Invention

The present invention relates to a portable crack testing device that comprises a sliding rail where a movable base is disposed on a movable mean of the rail; such that the movable base is movable on the sliding rail; a force sensor fixedly attached to the movable base; a blade base fixedly attached to the sensing area of the force sensor; a blade, for applying force to a test material, attached to the blade base such that the blade protrudes from the sensor and aligns with a test slit of a material holder, allowing the sensor to measure pressing force when the blade is applied onto a test material; a material holder disposed at one end of the sliding rail, as a place clamp the test material and control tension of material, and having a test slit which aligns with the blade; such that when the movable base on the sliding rail moves toward the material holder, the blade then presses on the test material which extends into the slit; and a control unit electrically connected to the movable mean of the sliding rail to control the movement of the movable base and electrically connected to the force sensor to record the force value measured from the blade when it is pressing on a test material and to record the elongation of the test material that is calculated from the displacement of the blade when pressing on the material, wherein the control unit has a user interface - for a user - to input the material information, to operate the device, and to display the device information to the user.

In some embodiments of this invention, the control unit comprises a non-volatile memory to record the material cracking information, which includes material’s type, thickness, moisture content, maximum elongation, maximum load, flute pitch, and blade type, wherein the control unit determines the chance of the test material to be cracked by processing the pressing force measured by the sensor, the elongation of the test material calculated from the displacement of the blade when pressing on the material, and the material cracking information from the non volatile memory together.

In another embodiment of this invention, the portable crack testing device may comprise a stretching device to control tension of material disposed at one end of the sliding rail, wherein the stretching device has a clamper, extended beyond the material holder, which stretches the test material to control tension of material and attached to the material holder.

In some embodiments of this invention, the slit on the material holder has its width, measured from the bottom edge to the upper edge, that can be selected from one of the following: 8.0-9.5, 6.8-8.0, 5.5-6.5, and 3.0-3.5 millimeters. The widths match different types of the flute pitches.

In some embodiments of this invention, the shape of the blade can be selected to match different type of creasers in production process. The blade can be selected in shapes of a rectangle sharp edge, a rectangle rounded edge, a semi-circular sharp edge, and a semi-circular rounded edge.

In an embodiment of this invention, the process of the control unit of the portable crack testing device operates following the steps: a. receiving input data from the user, b. controlling the movement of the sliding rail such that the movable base and the blade move toward the test material with a constant velocity, c. measuring the pressing force from the force sensor which happens from the pressing of the blade on the test material, d. calculating the displacement of the blade when it starts pressing on the material until the material cracks, and converting the displacement to the elongation of the test material, e. analyzing the elongation and the pressing force from the force sensor of the test material and comparing them to the material cracking information database, and f. determining the chance of the test material to be cracked.

The objective of this invention is to provide a crack testing device that can be used to test a paper, a corrugated paper, or other sheet materials. It simulates the placement of a paper on flutes of corrugated papers. The blade that presses on a corrugated paper simulates the elongation of the paper when a creaser is pressed on it. The distance that a test paper extends until it breaks is further calculated to be the elongation of the paper. The elongation information of the paper is used in combination with material crack information to determine the chance of the test paper to be cracked or torn inside the folded edge when the paper is used to make boxes.

Brief Description of the Drawings

Fig. 1 shows a portable crack testing device according to this invention.

Fig. 2 shows a section view of the portable crack testing device.

Fig. 3 shows a schematic diagram of the device operation when the blade is pressing on the test material.

Fig. 4 shows an enlarged view of the test material when it is pressed by the blade.

Fig. 5 shows a plot of relationship between the pressing force on the blade and its displacement.

Fig. 6 shows an example of the material cracking information.

Fig. 7 shows an example of the relational scatter plot between the elongation of materials and their parameters.

Fig. 8 shows a portable crack testing device according to this invention when it further comprises a stretching device.

Fig. 9 shows a vertical-cut view of the device when it further comprises a stretching device.

Fig. 10 shows a blade with rectangle sharp edge.

Fig. 11 shows a blade with rectangle rounded edge.

Fig. 12 shows a blade with semi-circular sharp edge.

Fig. 13 shows a blade with semi-circular rounded edge.

Fig. 14 shows the test operational steps of the control unit.

Detailed Description of the Invention

A portable crack testing device 1 for testing a crack of a test material 2 by pressing a blade 40 onto the test material as shown in FIG. 1-2 comprises a sliding rail 10, a force sensor 20, a blade base 30, a blade 40, a material holder 50, and a control unit 60.

The sliding rail 10 is used to move the blade 40 on it so that the blade 40 presses on the test material 2 until the test material 2 cracks or breaks. The sliding rail 10 has a movable base 11 disposed on a movable mean of the rail 10; such that the movable base 11 is movable on the sliding rail 10 when it is controlled to move. The movable mean of the rail 10 may be composed of spherical or cylindrical bearings and a motor 12 that allows the movement of the movable base 11 to be controlled by a high precision control circuit.

The force sensor 20 is fixedly attached - by a fixing mean - to the movable base 11. When the movable base 11 moves on the sliding rail 10, the force sensor 20 will move accordingly. An example of the fixing mean is the use of screws and nuts to attach the force sensor 20 to the movable base 11. Nevertheless, any fixing mean that attaches the force sensor 20 to the movable base 11 in similar way can be used as well; for example, attaching by chemical glue, tightening by wire or sling, etc. Preferably, the force sensor 20 is a load cell to measure pressing force when the blade 40 is applied onto a test material 2. The load cell is a proper sensor to measure pressing force on the sensor’s surface. In practice, many kinds of load cells are possible. Preferably, a compression load cell is used as it measures pressing force more accurate than a shear beam load cell. It is easily understood for a person skilled in the art to choose a proper load cell as needed.

The blade base 30 is fixedly attached - by a fixing mean - to the sensing area of the force sensor 20. The blade base 30 is used to attach the blade 40 onto the force sensor 20 whereas the blade 40 moves according to the movement of the movable base 11.

The blade 40 is a device for applying force to a test material. The blade 40 is fixedly attached to the blade base 30 such that the blade 40 protrudes from the force sensor 20 and aligns with a test slit 51 of the material holder 50, allowing the force sensor 20 to measure pressing force when the blade 40 is applied onto a test material 2.

The material holder 50 is disposed at one end of the sliding rail 10, as a place to clamp the test material and control tension of the material so that the material is resistant to pressing force when the blade 40 is pressing on it. The material holder 50 has a test slit 51 which aligns with the blade 40; such that when the movable base 11 on the sliding rail 10 moves toward the holder 50, the blade 40 then presses on the material 2 which extends into the slit 51.

The control unit 60 is electrically connected to the movable mean of the sliding rail 10 to control the movement of the movable base 11 and electrically connected to the force sensor 20 to record the force value measured from the blade 40 when it is pressing on a test material 2. It allows the control unit 60 to record the relationship between the applied force from the blade 40 and its relative movement. The record shows the elongation 72 of the test material 2 when a perpendicular force is exerted on it. When recorded together, they represent a pair of pressing force at each elongation 72 of the test material 2. The measured force on the blade 40 and the blade relative moving distant represent the elongation 72 of the test material 2 when a specific force is exerted on it. The proper control unit 60 can be a microcontroller or microprocessor having a dedicated firmware to control its peripherals, or it can be a general computer running a specific software for the same purposes. A person skilled in the art can understand the idea and choose the control unit 60 as needed.

The control unit 60 further comprises a user interface 61 - for a user - to input the material information, to operate the device, and to display the device information to the user. The user interface 61 is a device or part of a device that displays information to the user of the portable crack testing device 1. It also allows the user to input necessary information for the device operations. The preferred user interface 61 is a touch screen that is electrically connected to the control unit 60 to display and input information from the user. Nevertheless, in some embodiments of this invention, the user interface 61 may have only start and stop push buttons. Or it may have push buttons for inputting information on it depending on its design and requirement. A person skilled in the art can understand the idea and modify it as needed.

In some embodiments of this invention, the control unit 60 has a non-volatile memory 601 for recording material cracking information that may come from previous tests or other types of databases, such as a database server or an online database. The control unit 60 uses the material cracking information in its processing to properly predict the chance of the test material 2 to be cracked. The information includes the material’ s type, moisture content, maximum elongation, maximum load, flute pitch, and blade type. The information allows the control unit 60 to calculate the elongation 72 of the test material 2 and to determine the chance of the test material 2 to be cracked which is calculated by using the material cracking information database and the displacement of the blade 40 when pressing on the material 2 together.

A person skilled in the art can understand that the non-volatile memory 601 for recording previous material cracking information may be in form of SSD memory, SD-Card, or external database that the control unit 60 can connect with, for example, an online database, etc.

In some embodiments of this invention, the control unit 60 may comprise an on/ off push button 62, a start push button 63, and an emergency stop push button 64 to enhance the usability and safety of the device 1. The user of the device 1 can operate it conveniently. When the emergency stop push button 64 is pressed, the control unit 60 shuts down all electrical components of the device so that the sliding rail 10 stops moving immediately. Such the operation is a prevention measure to protect the user from injuries that may happen when operating the device. In some cases, the device 1 may be further comprised of a protective shield that covers its moving parts. This is to prevent any moving parts from injuring the user during its operation. A tempered grass, as an example, is disposed over the sliding rail area. And in some cases, the control unit 60 may be designed not to operate the device if the protective shield is not properly in place.

The device 1 determines the chance of the test material 2 to be cracked by the control unit 60 based on the following concept. First, the test material 2 is fixedly attached to the material holder 50. On the material holder 50, there are fixing means 52 for fixing the material 2 on the front side of the holder. The fixing means 52 may be screws, screws with nuts, screws with wing nuts, or clamps for holding the test material 2. Preferably, the fixing mean 52 is strong enough to stretch the test material 2 and attach it to the material holder 50.

Then, the control unit 60 controls the movement of the sliding rail 10, on which the blade 40 installed on the blade base 30 and the force sensor 20 are disposed, to move toward the test material 2. The control unit 60 records the force value measured from the blade 40 when it is pressing on a test material 2 and the displacement of the blade 40 (which is the same as the displacement of the movable base 11 on the sliding rail 10).

When the blade 40 starts moving toward the test material 2, the blade 40 may not be pressing on the test material 2 yet. The measurement of the force sensor 20 is not related to the pressing force on the blade 40. The measured force, however, may be caused by noise or the vibration of the blade 40 which is relatively small and trivial. Even though the control unit 60 records the force values and the displacement of the blade 40 during such the movement, it does not use them in its processing when it calculates the chance of the test material 2 to be cracked.

When the blade 40 starts pressing on the test material 2, the pressing force on the blade 40 is transferred to the force sensor 20. The force values measured by the sensor are relatively high when compared with the values measured when the blade 40 is not pressing on the test material 2. When the force value is higher than a predefined start threshold, the control unit 60 processes the force value with the displacement of the blade 40. It specifies the displacement when the measured force value is higher than the threshold as a starting distance. It records the value and the distance and uses them as parameters for determining the chance of the test material 2 to be cracked. FIG.3 shows the schematic diagram of the device when the blade 40 is pressing onto the test material 2. Then the control unit 60 controls the blade 40 to move forward. During this movement phase, the test material 2 is being stretched by the pressing force of the blade 40. The stretching capability of the test material 2 is different depending on the material type used in the test. The control unit 60 records the force values and the displacement of the blade 40 while the blade 40 is kept moving forward until the test material 2 cracks or breaks.

When the test material 2 cracks or breaks, the pressing force measured by the force sensor 20 reduces dramatically as the resistance of the material disappears. When the control unit 60 finds a sudden reduction of the measured force, it determines that the test material 2 cracks or breaks. The control unit 60 stops its recording and stops the movement of the blade 40 by controlling the movable base 11 on the sliding rail 10 to stop its movement. And the control unit 60 calculates the elongation 72 of the test material 2.

In the process of determining the chance of the test material 2 to be cracked, the control unit 60 uses maximum force value that cracks or breaks the test material 2 and the elongation 72 of the material 2. The elongation can be calculated from the pressing distance 71 that the blade is pressing onto the material and the width of the test slit 51 according to the equation z = yx² + y² where z is the elongation 72, x is the pressing distance 71 of the blade, and y is half the width of the test slit 51, as shown in FIG.4 respectively.

Once the elongation 72 and the maximum force value are known, they are recorded together as a paired value of cracking relation point 73. By comparing the resulting cracking relation point 73 with cracking relation points of different material stored in the database or non-volatile memory 601, the control unit 60 calculates the chance of the test material 2 to be cracked.

The control unit 60 processes the pressing force value on the blade 40 that cracks or breaks the test material 2 in the unit of Newton (N) and the distance that the blade 40 moves until the material 2 cracks in the unit of millimeter (mm) . The example of the relationship between the pressing force on the blade 40 and its displacement is shown in FIG.5.

The material cracking information stored in the non-volatile memory 601 or any kind of database should be the cracking relation point 73, which reflects the elongation of the material, and the parameters of the material 2, such as thickness, brittleness, moisture content, carbon content, etc. The parameters of the material 2 may be different depending on the use of the materials. Example material cracking information is shown in FIG.6. The preferred processing of the control unit 60 for determining the chance of the test material 2 to be cracked comprises the steps of: a) selecting several cracking relation point 73 of the same material as the test material 2, b) generating a relational scatter plot 90 showing the relationship between the elongation 72 and the crack probability of the material, c) dividing the area of the relational scatter plot 90 into three risk of cracking zones, which are (1) a high risk zone 91, (2) a moderate risk zone 92, and (3) a no risk zone 93, d) plotting the cracking relation point 73 obtained from the test on the relational scatter plot 90, whereas the cracking relation point 73 is plotted in one of the three zones. The control unit 60 displays the relational scatter plot 90 along with the obtained cracking relation point 73 of the test material 2 to the user via the user interface 61. This allows the user to see the zone that the cracking relation point 73 of the test material 2 belongs. FIG.7 shows an example of the relational scatter plot 90 of this invention showing the risk that a corrugated paper will be cracked or torn when it is folded into a box shape. It shows the samples of cracking relation points 73 that are recorded in the non volatile memory 601 or database and the cracking relation point 73 obtained from the test (indicated as ‘x’) that tends to be cracked as it is plotted in the moderate risk zone 92.

In some embodiments of this invention, the control unit 60 may automatically process the zoning of the cracking relation points 73 of the test material 2 on the relational scatter plot 90. And it may display the resulting risk - whether the test material 2 has high, moderate, or no risk - to the user through the user interface 61 without showing the relational scatter plot 90.

It is seen that the device 1 of this invention measures load profile, maximum load, and the elongation of the test material 2. The load profile shows the applied force on the test material 2 or the time- varying relationship between the applied force and the elongation 72 of the test material 2. This information shows the behavior of the test material 2, such as fragility or softness, when it is exerted by a force. The maximum load characterizes the usage of a material by telling how much load it can handle when the load is applied on it or when the load is applied by different blade shapes. The elongation of the material can characterize the usage of a material as well. The quality of a material can be enhanced by using this information as a benchmark to compare the test material with others. For example, using the information can tell how a paper behaves when adding or changing its composite. Or how much strength is added to the paper to resisting a pressing force. It can be used to show the effect of the blade 40 when its shape is different. In some embodiments of this invention, the portable crack testing device 1 may be further comprised a limiter 101 disposed on the sliding rail 10 in front of the material holder 50 to prevent the movable base 11 from hitting the material holder 50. Sometime the limiter 101 may have a touch sensor attached to it. When the movable base 11 hits the limiter 101, the sensor sends a signal to the control unit 60 so that it stops the sliding rail 10. Thus, it prevents the damage to the material holder 50 if it is hit by the movable base 11. Especially, when the test material 2 is strong and can resist a strong pressing force from the blade 40.

In some embodiments of this invention, the portable crack testing device 1 as previously mentioned may be further comprised a stretching device 80 disposed at one end of the sliding rail 10 as shown in FIG.8- 9. The stretching device 80 has a clamper 82, extended beyond the material holder 50, which clamps the test material 2 and keeps it attached to the material holder 50. To get accurate test results, the test material 2 should be pulled with a constant force before it is attached to the material holder 50. Different test material 2 or the same material that is made by different process may have different flexibility. To stretch the test material 2 with the same force is equivalent to adjusting the test material 2 to the same condition as much as possible for the test. The applied force on the blade 40 that breaks the material is then considered more accurate.

The stretching device 80 of this invention can be in different form. The stretching device 80 may be a sliding rail having two clampers 82 attached to it on the top and bottom for holding the test material 2. One of the clampers 82 is disposed to the rail that is movable by a motor drive. The two clampers 82 can move away from each other so that they stretch the test material 2. One the pulling force reaches a pre- defined value; the rail stops while both clampers 82 are still holding the test material 2. The user attaches the test material 2 to the material holder 50 by using the fixing means 52. Once the test material 2 has already attached to the material holder 50, the user moves the stretching device 80 away from the sliding rail 10 so that the pressing test can be started.

A person skilled in the art can understand and uses different stretching devices 80 to pull the test material 2. They can be controller electronically or mechanically. Any kind of stretching device 80 that can be used to stretch the test material 2 before it is attached to the material holder 50 is considered within scope of this invention. To this invention, the stretching device 80 should be able to pull or stretch the test material 2 with the tension force range of 0.05-0. 5 Newton. Preferably, the stretching device 80 stretches the test material 2 with tension force of 0.25 Newton.

In practice, when the test material 2 is pulled by the stretching device 80, the test material 2 is attached to the material holder 50 by the fixing means 52 that are disposed around the test slit 51 to prevent the test material 2 from moving once the clamper 82 releases the test material 2 or when the blade 40 is pressing on it. In some cases, the stretching device 80 may compose a movement locking mean to keep it stretching the test material 2 while performing the test. This is to ensure that the test material 2 will not experience further force from its desire while it is pressing by the blade 40. When the portable crack testing device 1 of this invention is used to simulate pressing of a creaser, the blade 40 may be selected to have the same shape as the blade of the creaser in corrugated paper box production processes. The blade 40 can be selected in shapes of a rectangle sharp edge 42, a rectangle rounded edge 43, a semi-circular sharp edge 44, and a semi circular rounded edge 45 as shown in FIG. 10- 13. The semi-circular blade is best choice to simulate pressing of a creaser as it has the same shape as the one used in corrugated paper production processes.

Moreover, if the flute of the corrugated paper is to be simulated in the test, the slit 51 may be selected to have its width 511 that can be selected from one of the following: 8. 0-9. 5, 6. 8- 8.0, 5.5 -6.5, and 3.0-3.5 millimeters to match the actual flute pitch of corrugated paper as shown in TABLE-1

TABLE- 1 FLUTE PITCH OF CORRUGATED PAPERS

By selecting the width 511 of the slit 51 according to the actual flute pitch of corrugated papers, the portable crack testing device 1 of this invention can be used to determine the quality of the paper even before it is made, which is the objective of this invention. In some embodiments of this invention, the control unit 60 may further comprise a joystick electrically connected to the control unit 60 for controlling the movement of the movable base 11 on the sliding rail 10. This allows the user to better control the movement of the blade 40.

In an embodiment of this invention, the control unit 60 may further comprise a numeric keypad for inputting the materiaT s moisture content information. This information is an important parameter that affects the strength of the test material 2. Even though the test materials 2 are made of the same material type, if they have different moisture content, they may have different elongation 72. Thus, the pressing force to break or crack the materials will be different as well. The control unit 60 should, therefore, use the materiaT s moisture content information in its processing to increase the accuracy of its determination for the chance of the test material 2 to be cracked. The user can input this information to the device by typing in the numeric keypad of the control unit 60.

In some embodiments of this invention, the control unit 60 may further comprise a USB connector 66 electrically connected to the control unit 60 for transmitting data to external devices. An example of the external device is a hard drive.

In some embodiments of this invention, to transmit test data through the internet, the control unit 60 may further comprise a LAN connector or a wireless adaptor for transmitting data to the internet.

The portable crack testing device 1 has the control unit 60 that operates following the steps shown in FIG.14, comprising: a. Receiving input data from the user, b. Controlling the movement of the sliding rail 10 such that the movable base 11 and the blade 40 move toward the test material 2 with a constant velocity, c. Measuring the pressing force from the force sensor 20 which happens from the pressing of the blade 40 on the test material 2, d. Calculating the displacement of the blade 40 when it starts pressing on the material 2 until the material 2 cracks, and converting the displacement to the elongation 72 of the test material 2.

In some embodiments of this invention, the control unit 60 may be further operating in the following steps: e. Analyzing the elongation 72 and the pressing force from the force sensor 20 of the test material 2 and comparing them to the material cracking information database, and f. Determining the chance of the test material 2 to be cracked.

Preferably, the operational steps of the control unit 60 further comprises sub- steps that adds convenience and increases choices to the user. When the user chooses the blade 40 type and the width of the slit 51 for the material holder 50, the user switches on the device by pressing ON/ OFF push button 62. The control unit 60 starts its processing unit to calibrate the force sensor 20 that is used in the test. The calibration is performed to the sensor to ensure that the pressing force read by the sensor is accurate every time. The calibration may be scheduled to perform as a time- based schedule such as to calibrate once every day. Or it can be unit to calibrate every time the device is turned on as an example. Once the device is ready, the control unit 60 displays information on a display unit.

The user, then, attaches the test material 2 to the material holder 50 and adjusts the force sensor 20 and blade 40, attached on the movable base 11, to move toward or away from the test material 2 by using the joystick or control buttons, which are designed to control the movement of the movable base 11 on the sliding rail 10. Once the force sensor 20 and the blade 40 are in proper positions, the user start pressing the start push button.

Once the test starts, the force sensor 20 moves toward the test material 2 with a constant velocity. At the same time, the processor of the control unit 60 receives the pressing force value from the force sensor 20 and records it with a timestamp. It compares the force value at time t and t+ 1 to measure the change of the pressing force on the blade 40. If the pressing force increases higher than its initial value 100%, it means that the blade 40 has touched the test material 2 and starts pressing on it. The force value is rising until the test material 2 breaks or cracks. Then, the pressing force reduces dramatically (or reduced less than 50%) . When the processor detects the abrupt change, it records the pressing force value before the reduction as the “maximum load” of the test material and shows the value on the display unit. At the same time, the processor controls the movement of the force sensor 20 to move away from the test material 2 and back to its initial position.

The processor of the control unit 60 determines the time duration that the blade 40 starts touching the test material 2 until it receives the “maximum load” and calculates the elongation 72 of the test material 2. It then compares the result with the material cracking information and predicts the chance of the test material 2 to be cracked in the real uses. It shows the prediction result along with the message showing the end of the test on the display unit.

Preferably, if the force sensor 20 is moved too far forward until it reaches the limiter 101, the control unit 60 sends a control signal to control the sensor to move back to its initial position to prevent any damage on the sliding rail 10. Similarly, if the test material 2 is too soft and it extends too far until the force sensor reaches the limiter 101 that protects the blade 40 or the force sensor 20 from hitting the material holder 50, the control unit 60 sends a control signal to control the sensor to move back to its initial position.

The test material 2 may be selected from a duplex, liner, corrugated paper, both- sides coated paper (BCT), or matte coated paper (MCT). Preferably, the test material 2 is a liner or corrugated paper.

Claims

1. A portable crack testing device, comprising: a sliding rail ( 10) where a movable base ( 11) is disposed on a movable mean of the rail (10) such that the movable base (11) is movable on the sliding rail (10); a force sensor (20) fixedly attached - by a fixing mean - to the movable base (11); a blade base (30) fixedly attached - by a fixing mean - to the sensing area of the force sensor (20); a blade (40), for applying force to a test material, fixedly attached to the blade base (30) such that the blade (40) protrudes from the force sensor (20) and aligns with a test slit (51) of a material holder (50), allowing the force sensor (20) to measure pressing force when the blade (40) is applied onto a test material (2); a material holder (50) disposed at one end of the sliding rail (10), as a place to clamp the test material and control tension of the material and having a test slit (51) which aligns with the blade (40); such that when the movable base (11) on the sliding rail (10) moves toward the material holder (50), the blade (40) then presses on the material (2) which extends into the slit

(51); and a control unit (60) electrically connected to the movable mean of the sliding rail ( 10) to control the movement of the movable base (11) and electrically connected to the force sensor (20) to record the force value measured from the blade (40) when it is pressing on a test material (2) and to record the elongation (72) of the test material (2) that is calculated from the displacement of the blade (40) when pressing on the material (2), wherein the control unit (60) has a user interface (61) - for a user - to input the material information, to operate the device, and to display the device information to the user.

2. The portable crack testing device as in claim 1, wherein the control unit (60) further comprising a non-volatile memory (601) to record the material cracking information, which includes materiaT s type, thickness, moisture content, maximum elongation, maximum load, flute pitch, and blade type, wherein the control unit (60) determines the chance of the test material (2) to be cracked by processing the pressing force measured by the sensor (20), the elongation (72) of the test material (2) calculated from the displacement of the blade (40) when pressing on the material (2) , and the material cracking information from the non-volatile memory (601) together.

3. The portable crack testing device as in claim 1, further comprising a limiter ( 101) disposed on the sliding rail (10) in front of the material holder (50) to prevent the movable base (11) from hitting the material holder (50).

4. The portable crack testing device as in claim 1, further comprising a stretching device (80) to control tension of material disposed at one end of the sliding rail ( 10), wherein the stretching device ( 80) to control tension of material has a clamper ( 82) , extended beyond the material holder (50), which clamps the test material (2) and control tension of material and attached to the material holder (50).

5. The portable crack testing device as in claim 4, wherein the stretching device (80) to control tension of material stretches the test material (2) with the tension force range of 0. 05- 0.5 Newton.

6. The portable crack testing device as in claim 5, wherein the stretching device (80) to control tension of material stretches the test material (2) with tension force of 0.25 Newton.

7. The portable crack testing device as in claim 1, wherein the blade (40) can be selected in shapes of a rectangle sharp edge (42), a rectangle rounded edge (43), a semi-circular sharp edge (44), and a semi-circular rounded edge (45).

8. The portable crack testing device as in claim 1, wherein the slit (51) has its width (511) that can be selected from one of the following: 8.0-9.5, 6.8-8.0, 5.5-6.5, and 3.0-3.5 millimeters.

9. The portable crack testing device as in claim 1, wherein the user interface (61) is a monitor electrically connected to the control unit (60) for displaying information to the user.

10. The portable crack testing device as in claim 1, wherein the control unit (60) further comprising a joystick electrically connected to the control unit ( 60) for controlling the movement of the movable base (11).

11. The portable crack testing device as in claim 1, wherein the control unit (60) further comprising a numeric keypad.

12. The portable crack testing device as in claim 1, wherein the control unit (60) further comprising an on/ off push button (62), a start push button (63), and an emergency stop push button (64).

13. The portable crack testing device as in claim 1, wherein the control unit (60) further comprising a USB connector (66) electrically connected to the control unit (60) for transmitting data to external devices.

14. The portable crack testing device as in claim 1, wherein the control unit (60) further comprising a LAN connector or a wireless adaptor for transmitting data to the internet.

15. The portable crack testing device as in claim 1, wherein the control unit (60) operates in the following steps: a. Receiving input data from the user, b. Controlling the movement of the sliding rail (10) such that the movable base (11) and the blade (40) move toward the test material (2) with a constant velocity, c. Measuring the pressing force from the force sensor (20) which happens from the pressing of the blade (40) on the test material (2), d. Calculating the displacement of the blade (40) when it starts pressing on the material (2) until the material (2) cracks, and converting the displacement to the elongation (72) of the test material (2).

16. The portable crack testing device as in claim 15, wherein the control unit (60) further operates in the following steps: e. Analyzing the elongation (72) and the pressing force from the force sensor (20) of the test material (2) and comparing them to the material cracking information database, f. Determining the chance of the test material (2) to be cracked.