Sensor systems and methods for detecting conveyor tension in a mining system

Abstract

Conveyor system (100) comprising: a sprocket (132); a conveying element (120) coupled to the sprocket (132) such that it rotates around the sprocket (132); a sensor (205) positioned adjacent to the sprocket (132), the sensor (205) being configured to generate an analog output signal having a value indicative of a distance between the sensor (205) and the conveying element (120); a clamping system (210);and an electronic processor (215) connected to the sensor (205) and the clamping system (210), wherein the electronic processor (215) is configured to receive the output signal from the sensor (205), to determine whether the value of the analog output signal is within a predetermined range, to determine a voltage correction amount based on the value of the analog output signal if the value of the analog output signal is outside the predetermined range, to control the clamping system (210) based on the voltage correction value, and to change the distance between a first conveyor shaft (110) and a second conveyor shaft (115) of the conveyor system (100) by the correction amount, wherein a timer sets a duration during which the clamping system (210) is activated to change the distance between the first conveyor shaft (110) and the second conveyor shaft (120), and the correction amount corresponds to the duration.

Description

RELATED APPLICATIONSThe present application claims the benefit of U.S. Provisional Patent Application No. 62 / 573,552, filed Oct. 17, 2017, the entire contents of which are hereby incorporated by reference herein.BACKGROUNDThe present invention relates to methods and systems used to detect tension of a conveyor, such as a scraper chain conveyor (also called an armor conveyor) ("AFC") or a Beam Stage Loader ("BSL").DE 10 2007 043 043 A1 describes an extraction installation for mining with two drive stations and a drive chain rotating between their sprockets, wherein magnetic sensor devices for detecting a chain state of the drive chain are provided for detecting suspended chain or chain wear of a conveyor chain in a conveyor installation.US 4 657 131 A describes a voltage regulator for a chain drive, the voltage regulator comprising a sensor positioned and mounted adjacent the chain, a logic switching unit connected to the sensor and signalling when the distance between the sensor and the chain changes, and a voltage controller connected to the logic switching unit. The logic switching unit signals and controls the tension control of the chain drive so that the chain tension is maintained at a preset value.US 5 624 162 A describes a face construction machine with a working chain carrying conveyor wings or mining tools and being slidable in a chute provided with rows of inductive proximity type sensors which react to the chain and tools and generate measurement pulse sequences which are compared with target pulse sequences to signal operating parameters of the chain operation. The slack of the chain is detected by a series of sensors and a chain tensioning unit may be controlled in response to the slack.OVERVIEWIn accordance with the present invention, there are provided a conveyor system having the features of claim 1 and a computer implemented method for maintaining a conveyor system at proper tension having the features of claim 11. Advantageous further developments are evident from the dependent dependent claims.Before any embodiments of the invention are explained in detail, it should be understood that the invention is not limited in its application to the details of the configuration and arrangement of components set forth in the following description or illustrated in the accompanying drawings. The invention is capable of other embodiments and is also capable of being practiced or carried out in various ways. It should also be understood that the terminology and terminology used herein are for the purpose of description and are not to be regarded as limiting. The use of "comprise," "include," "comprise," or "have," and variations thereof, is intended herein to include the items listed thereafter, and equivalents thereof, as well as additional items. Unless otherwise specified or limited, the terms "attached", "mounted", "attached", "connected", "supported", and "coupled", and variations thereof, are used broadly and include both direct and indirect attachments, connections, supports, and couplings.Additionally, it should be understood that embodiments of the invention may include hardware, software, and electronic components or modules, which for purposes of discussion may be illustrated and described as if the plurality of components were implemented solely in hardware. However, one of ordinary skill in the art would recognize, even based on reading the present detailed description, that in at least one embodiment, the electronically-based aspects of the invention may be implemented in software (e.g., stored in a non-transitory computer readable medium) executable by one or more processing units, such as a microprocessor and / or application specific integrated circuits ("ASICs"). Thus, it should be noted that a variety of hardware and software based devices, as well as a variety of different structural components, may be used to implement the invention. For example, "servers" and "computing devices" described in the patent specification may include one or more processing units, one or more computer readable medium modules, one or more input / output interfaces, and various connections (e.g., a system bus) that connect the components.Other aspects of the invention will become apparent from a consideration of the detailed description and the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a schematic diagram of a conveying system. FIG. 2 is a block diagram of a control system for the conveyor system of FIG. 1. FIG. 3 illustrates a sensor arrangement of the control system of FIG. 2 in accordance with an embodiment of the invention. FIG. 4 illustrates a bottom perspective view of the analog output sensor of FIG. 3. FIG. 5 is a process for maintaining tension in the conveyor system of FIG. 1 using the sensor assembly of FIG. 3. FIG. 6 illustrates a sensor arrangement of the control system of FIG. 2 in accordance with an embodiment of the invention. FIG. 7 is a diagram illustrating the relationships between different combinations of output signals from a sensor assembly and a corresponding conveyor state. FIG. 8 is a process for maintaining tension in the conveyor system of FIG. 1 using the sensor assembly of FIG. 6. FIG. 9 illustrates a sensor arrangement of the control system of FIG. 2 in accordance with an embodiment of the invention. FIGS. 10A through 10D illustrate chain trajectories for the conveyor system of FIG. 1. FIG. 11 illustrates a sensor arrangement of the control system of FIG. 2 in accordance with an embodiment of the invention. FIG. 12 is a process for maintaining tension in the conveyor system of FIG. 1 using the sensor assembly of FIG. 11. FIG. 13 is a process for analyzing whether the conveyor system of FIG. 1 approaches an unacceptable voltage range.DETAILED DESCRIPTIONConveyor systems are typically used in mining operations for transporting material. In longwall mining, for example, the track conveyor system is used to transport the mined coal from the scraper chain conveyor (also called an armor conveyor) ("AFC") to the main conveyor, which transports the coal to the surface. FIG. 1 illustrates a schematic diagram of a conveying system 100 used for the transport of mineral material. As shown in FIG. 1, the conveying system 100 includes a conveyor 105, a first conveyor shaft 110, a second conveyor shaft 115, a first conveying chain 120, and a second conveying chain 125. In some embodiments, the conveyor 105 may include more or fewer conveyor chains. In some embodiments, the conveyor chains 120, 125 are replaced with another conveyor element such as a belt or the like. The conveying system 100 is at least partially supported by a frame 130 (see FIG. 3 ). In some embodiments, the frame 130 includes a first end portion for supporting the first conveyor shaft 110, a second end portion for supporting the second conveyor shaft 115, and a conveyor chute for supporting the first and second conveyor chains 120, 125 or another conveyor element. The first conveyor chain 120 and the second conveyor chain 125 (e.g., the conveyor elements) are positioned around the first conveyor shaft 110 and the second conveyor shaft 115 to form the conveyor 105. As shown in FIG. 1, the first conveyor chain 120 is positioned around a first end of the first conveyor shaft 110 and around a first end of the second conveyor shaft 115, while the second conveyor chain 125 is positioned around a second end of the first conveyor shaft 110 and around a second end of the second conveyor shaft 115.Each conveyor shaft 110, 115 has a sprocket for each conveyor element. The sprocket engages the conveying member to rotate the conveying member about the sprocket. In the illustrated embodiment, each conveyor shaft 110, 115 includes two sprockets. In the illustrated embodiment, a first sprocket 132 on the first conveyor shaft 110 engages the first conveyor chain 120 and a second sprocket 135 on the first conveyor shaft 110 engages the second conveyor chain 125. Similarly, a third sprocket 140 on the second conveyor shaft 115 engages the first conveyor chain 120 and a fourth sprocket 145 on the second conveyor shaft 115 engages the second conveyor chain 125. The sprockets 132, 135, 140, 145 are driven by one or more drive mechanisms (e.g., electric motors) that cause movement of the chains 120, 125 around the first conveyor shaft 110 and the second conveyor shaft 115 such that the conveyor 105 transports the mining material. In the illustrated embodiment, the conveyor 105 includes scrapers 150 that assist in transporting the mining material through the conveyor 105. As shown in FIG. 1, the scrapers are supported by the first and second conveyor chains 120, 125. In some embodiments, the conveyor 105 also includes chain covers to cover and protect the conveyor chains 120, 125.In the illustrated embodiment, the conveyor system 100 is part of the track conveyor of a longwall mining system. However, in other embodiments, the conveyor system 100 may be part of another mining machine such as a scraper chain conveyor, a break-through conveyor, the main conveyor in a longwall mining system, and the like.FIG. 2 illustrates a block diagram of a control system 200 for the conveyor system 100. The control system 200 is configured to maintain the conveyor system 100 within an appropriate tension range. If the conveyor 105 is improperly tensioned (e.g., if the tension of the conveyor 105 is outside of an appropriate tension range), then the mining material cannot be efficiently transported. Additionally, the conveyor 105 may be more susceptible to wear, interference, or a combination thereof when the conveyor 105 is improperly tensioned. The appropriate tension range may vary based on, for example, the material being transported by the conveyor 105, the type of conveyor element being used, the speed at which the conveyor 105 is operated, or combinations thereof. An appropriate tension for the conveyor 105 corresponds to an amount of tension that is not too high and not too low, for example. A tension that is too high in the conveyor 105 could damage the conveyor 105 as more material is added to the conveyor 105 (which could cause, for example, breakage of the conveyor 105). Tension that is too low in the conveyor 105 may cause a slack chain (e.g., a distance between a sprocket and a conveyor chain). An appropriate tension in the conveyor corresponds to circumstances where the tension is not too high or too low under the given current operating condition of the conveyor 105.As shown in FIG. 2, the control system 200 includes a sensor assembly 205, a clamping system 210, and an electronic processor 215. The sensor assembly 205 is configured to generate an output signal based on its detection of the conveyor elements (e.g., the first and second conveyor chains 120, 125). The electronic processor 215 is, for example, a controller including a processing unit and a memory. The memory may be a non-transitory computer readable medium operable to store executable instructions that may be fetched by the processor and executed by the processor. The executable instructions correspond to the various control and regulation techniques and operations described herein. The terms electronic processor and controller are used interchangeably herein.The clamping system 210 changes the distance between the first conveyor shaft 110 and the second conveyor shaft 115. The distance between the first conveyor shaft 110 and the second conveyor shaft 115 determines the tension of the conveyor 105. As the distance between the first and second conveyor shafts 110, 115 increases, the tension of the conveyor 105 also increases. Conversely, when the distance between the first and second conveyor shafts 110, 115 becomes smaller, the tension of the conveyor 105 decreases. In some embodiments, the tensioning system 210 includes a first hydraulic cylinder coupled to the first conveyor shaft 110 and a second hydraulic cylinder coupled to the second conveyor shaft 115. In other embodiments, the clamping system 210 may include more or fewer hydraulic cylinders. The hydraulic cylinders change the position of the respective conveyor shafts 110, 115 to thereby change the distance between the first and second conveyor shafts 110, 15. As discussed above, as the distance between the first and second conveyor shafts 110, 115 changes, the tension of the conveyor 105 will also change. The hydraulic cylinders may be driven by a hydraulic system, for example.As shown in FIG. 2, the electronic processor 215 is coupled to the sensor assembly 204 and the clamping system 210. More specifically, the electronic processor 215 receives the output signal(s) from the sensor assembly 205, determines whether the conveyor 105 is within an appropriate voltage range based on the output signal(s), and activates the tensioning system 210 when the conveyor 105 is outside the appropriate voltage range or when the electronic processor 215 predicts that the conveyor 105 will be outside the appropriate voltage range without any preventive action by the tensioning system 210. In one embodiment, the clamping system 210 includes a hydraulic and / or electronic system for driving the hydraulic cylinders. In such an embodiment, the electronic processor 215 sends an activation signal to the tensioning system 210 when the distance between the first and second conveyor shafts 110, 115 needs to be changed.FIG. 3 illustrates an embodiment 300 of the sensor assembly 205. In the illustrated embodiment 300, the sensor assembly 205 includes an analog output sensor 310 or sensor 310, respectively, having an analog output for each conveyor element (i.e., each conveyor chain 120, 125). For example, a first analog output sensor 310 detects a characteristic of the first conveyor chain 120 and a second analog output sensor 310 detects a characteristic of the second conveyor chain 125. Although FIG. 3 illustrates only a single analog output sensor 310 positioned adjacent to the first sprocket 132 to sense a characteristic of the first conveyor chain 120, a second analog output sensor 310 is similarly positioned adjacent to the second sprocket 135 or the fourth sprocket 145 to sense a characteristic of the second conveyor chain 125. In some embodiments, additional analog output sensors may be positioned adjacent to the third sprocket 140 to obtain a second measurement of the tension of the first conveyor chain 120, and another sensor may be positioned adjacent to the fourth sprocket 145 to obtain a second measurement of the tension of the second conveyor chain 125. As shown in FIG. 3, the analog output sensor 310 is supported by the frame 130 near the unloading point of the first conveyor chain 120 (e.g., the conveyor member).The analog output sensor 310 may be, for example, an ultrasonic sensor, an IR sensor, a magnetometer, and the like. The analog output sensor 310 generates an analog output signal indicative of a distance between the analog output sensor 310 and the first conveyor chain 120. Specifically, the analog output signal has a variable output range such as 0 to 10 V, 200 to 500 MHz, 100 to 300 μF, and the like, for example. The value (e.g., magnitude) of the analog output signal is linearly related to the distance between the analog output sensor 310 and the first conveyor chain 120. In the illustrated embodiment, the value of the analog output signal increases as the distance between the analog output sensor 310 and the first conveyor chain 120 decreases. That is, the analog output sensor 310 outputs a minimum value when the first conveyor chain 120 is positioned at an edge 320 of a detection range 325 of the analog output sensor 310. The analog output sensor 310 thereby indicates at least one indirect measurement of the slack distance of the first conveyor chain 120. The electronic processor 215 may then determine whether to activate the tensioning system 210 (e.g., whether the conveyor 105 needs to change tension). Since the analog output sensor 310 generates a variable output signal, control by the tensioning system 210 may be more accurate than, for example, using a switch-like detector for the slack distance of the conveyor chains 120, 125. In addition, a single analog output sensor 310 produces more accurate information than is produced by the use of switch-like detectors which produce only binary outputs. Accordingly, by using the analog output sensor 310, a reduction in the total number of components can be achieved. In some embodiments, analog output sensor 310 uses a time-of-flight measurement to generate the analog output signal. However, in other embodiments, other measurement techniques are used to generate the analog output signal. FIG. 4 illustrates another perspective of placement for analog output sensor 310. In particular, FIG. 4 illustrates a bottom perspective view of analog output sensor 310. In the illustrated embodiment, the analog output sensor 310 is an ultrasonic sensor configured to generate a variable output signal indicative of the distance between the analog output sensor 310 and the first conveyor chain 120.FIG. 5 is a flow diagram illustrating a method 350 of maintaining the conveyor system 100 at an appropriate tension using the embodiment 300 of the sensor assembly 205 in either the placement shown in FIG. 3 or the placement shown in FIG. 4. In STEP 355, the analog output sensor 310 generates an analog output signal indicative of a distance between the analog output sensor 310 and the first conveyor chain 120. The electronic processor 215 receives the analog output signal (STEP 360) and determines whether the analog output signal is within an acceptable range (STEP 365). The acceptable range is predetermined and stored. The electronic processor 215 accesses the acceptable range and compares a magnitude of the analog output signal to the acceptable range. For example, in some embodiments, the electronic processor 215 may consult a look-up table that stores various magnitudes of the analog output signal and indicates whether the particular magnitude or range of magnitudes is acceptable. The acceptable range for the analog output signal is preferably about half of the possible outputs of analog output sensor 310. For example, if analog output sensor 310 has an output range of about 0V to 10V, then the acceptable range may be 4V to 6V, for example.If the analog output signal is within the acceptable range, the electronic processor 215 continues to monitor the first conveyor chain 120 and receive the analog output signal from the analog output sensor 310. On the other hand, if the analog output is outside the acceptable range, the electronic processor 215 determines a correction amount (STEP 370). The correction amount indicates an amount by which the tension of the conveyor 105 needs to become larger or smaller. Because the analog output signal provides a variable output signal, the magnitude of the analog output signal may be used to more accurately determine an amount by which the voltage of the conveyor 106 needs to be changed.In one embodiment, the electronic processor 215 determines the amount of correction by calculating a difference between the analog output signal and the acceptable range. For example, if the analog output signal is 2V (e.g., indicating that the first conveyor chain 120 is at too low a voltage), then the electronic processor 215 may determine the amount of correction by calculating the difference between 4V (e.g., the lowest value in the acceptable range) and the analog output signal of 2V. The electronic processor 215 calculates that the difference is about 2V.In some embodiments, the electronic processor 15 converts the difference between the acceptable range and the analog output signal into a corresponding change in distance between the first conveyor shaft 110 and the second conveyor shaft 115. In the above example, the electronic processor 215 may then determine that the difference of 2 V corresponds to a change of about 10 inches (25.4 cm) between the first conveyor shaft 110 and the second conveyor shaft 115. The electronic processor 215 may assign a direction to the correction amount to indicate whether the tensioning system 210 is to increase the tension of the conveyor 105 or decrease the tension of the conveyor 105. For example, if the analog output signal indicates that the conveyor 105 is at too high a voltage, then the electronic processor 215 may set the correction amount to a negative value (e.g., -2V) to indicate that the tensioning system 210 is to reduce the tension of the conveyor 105.After determining the correction amount, the electronic processor 215 sends a control signal to activate the clamping system 210 based on the correction amount (STEP 375). Specifically, the electronic processor 215 sends an activation signal to the clamping system 210 such that the clamping system 210 changes the distance between the first conveyor shaft 110 and the second conveyor shaft 115 by the correction amount. In some embodiments, the tensioning system 210 may include a timer that sets a duration during which the tensioning system 210 is activated to change the distance between the first conveyor shaft 110 and the second conveyor shaft 115. In such embodiments, the correction amount may correspond to a duration of the timer. In the above example in which the difference between the analog output signal and the acceptable range is 2V, the correction amount may be 10 seconds, for example. The duration of the timer (e.g., the amount of correction) may be based on the average speed of the tensioning system 210 in such embodiments. The speed of the clamping system 210 may be a predetermined amount stored by (or accessed by) the electronic processor 215. The electronic processor 215 then returns to STEP 355 and continues monitoring the analog output signal for the acceptable range.FIG. 6 illustrates another embodiment 400 of the sensor assembly 205. In the illustrated embodiment 400, the sensor assembly 205 includes two groups of proximity sensors 405, 410. The first group 405 of proximity sensors is positioned on a block side of the conveyor 105 (e.g., on the outside of the first sprocket 132). The first group 405 of proximity sensors includes a first proximity sensor 415, a second proximity sensor 420, and a third proximity sensor 425. The second group 410 of proximity sensors is positioned on a flight side of the conveyor 105 (e.g., toward the inside of the first sprocket 132). The second set 410 of proximity sensors includes a fourth proximity sensor 430, a fifth proximity sensor 435, and a sixth proximity sensor 440. In the illustrated embodiment, each of the proximity sensors 415- 440 is actuated when the first conveyor chain 120 (or a scraper 150) is detected. In the illustrated example, the proximity sensors 415- 440 are inductive proximity sensor sensors having an approximate sensing range of 40 mm. Accordingly, each of the proximity sensors 415- 440 generates a binary output signal that is sent to the electronic processor 215. In some embodiments, the proximity sensors 415- 440 may be longer range IR sensors, lasers, and the like. As will be explained in more detail below, the electronic processor 215 determines whether the clamping system 210 needs to be activated based on the combination of binary output signals received from the first and second groups 405, 410 of proximity sensors. In other embodiments, the first and second groups 405, 410 of proximity sensors may include more or fewer proximity sensors. In the illustrated embodiment, the accuracy of embodiment 400 of sensor assembly 205 is improved by increasing the number of proximity sensors 415- 440 and decreasing a distance between each of proximity sensors 415- 440.As shown in FIG. 6, the first, second, and third proximity sensors 415, 420, 425 are linearly arranged, with the first proximity sensor 415 positioned closest to the first sprocket 132 and the third proximity sensor 425 positioned furthest away from the first sprocket 132. Similarly, the fourth, fifth, and sixth proximity sensors 430, 435, 440 are linearly arranged, with the fourth proximity sensor 430 positioned closest to the first sprocket 132 and the sixth proximity sensor 440 positioned furthest away from the first sprocket 132. The first and fourth proximity sensors 415, 430 are positioned at a first height (e.g., a distance from the first sprocket 132 or the support frame). Similarly, the second and fifth proximity sensors 420, 435 are positioned at a second height different from the first height and the third and sixth proximity sensors 425, 440 are positioned at a third height different from the first and second heights. In the illustrated embodiment, the first height corresponds to a slack distance of 0 mm, the second height corresponds to a slack distance of 75 mm, and the third height corresponds to a slack distance of 150 mm. That is, when the first conveyor chain 120 is at the first height, the first conveyor chain 120 has a slack distance of 0 mm; when the first conveyor chain 120 is at the second height, the first conveyor chain 120 has a slack distance of 75 mm; and when the first conveyor chain 120 is at the third height, the first conveyor chain 120 has a slack distance of 150 mm. Because the first group 405 of proximity sensors and the second group 410 of proximity sensors are positioned on opposite sides of the first sprocket 132, a combination of the outputs of each proximity sensor provides more accurate information about the slack distance of the first conveyor chain 120 and, accordingly, relative to the tension of the conveyor 105.FIG. 7 illustrates an example diagram or table indicating the different combinations of sensor outputs and indicating each combination with respect to a state of tension of the conveyor 105. The exemplary diagram illustrates an "X" at the location where the signal from that particular sensor is irrelevant to determining the condition of the conveyor 105. Because the proximity sensors in each group 405, 410 are linearly arranged, the signal from the proximity sensor that is furthest away from the sprocket 132 indicates the slack distance of the first conveyor chain 120, and therefore the signal from the proximity sensors that are closer to the sprocket 132 is not taken into account to determine the tension state of the conveyor 105. For example, if the second sensor 420 outputs a positive signal (e.g., indicating that the first conveyor chain 120 is within the sensing range of the second sensor), the output of the first sensor 415 is irrelevant to the determination of the tension state of the conveyor 105 and is therefore set to "X".Based on the illustrated diagram, a high tension state of the conveyor 105 is indicated when a positive signal is received from the first sensor 415 and the fourth sensor 430 (e.g., the first conveyor chain 120 is within the detection range of the first sensor 415 and the fourth sensor 430) and a negative signal is received from the second, third, fifth, and sixth sensors 420, 425, 435, 440 (e.g., the first conveyor chain 120 is outside the detection range of the second, third, fifth, and sixth sensors). Also, as illustrated in the exemplary diagram, a too low voltage state of the conveyor 105 is indicated by six different output combinations from the proximity sensors 415 to 440. Moreover, by using the sensor arrangement of FIG. 6, abnormal conditions of the conveyor 105 can also be detected. In the illustrated embodiment, abnormal conditions of the conveyor 105 may be indicated, for example, when the first sensor 415 outputs a positive signal but the second group 410 of sensors outputs negative signals, and separately, when the fourth sensor 430 outputs a positive signal but the first group 405 of sensors outputs negative signals. Such exits may indicate, for example, that the conveyor is bent or meets an abnormal load condition. A lack of positive signal from the first group 405 or the second group 410 of proximity sensors may also indicate that one of the proximity sensors is malfunctioning.FIG. 8 illustrates a method 450 for maintaining the conveyor system 100 at an appropriate tension using embodiment 400 of the sensor assembly 205. In STEP 455, the electronic processor 215 receives output signals from each of the proximity sensors 415- 440. The electronic processor 215 then identifies an applicable combination of outputs from the proximity sensors 415-440 (STEP 460). For example, the electronic processor 215 may determine which combination of outputs from the example diagram of FIG. 7 matches the proximity output signals received by the electronic processor 215. In some embodiments, the electronic processor 215 may access a look-up table from memory that is similar to the example diagram of FIG. 7. However, in other embodiments, the electronic processor 215 may apply rules and thresholds in software to determine the combination of outputs that matches the output signals received by the electronic processor 215. The electronic processor 215 then determines a tension state of the conveyor 105 based on the combination of proximity output signals received by the electronic processor 215 (STEP 465).If the electronic processor 215 determines that the conveyor 105 is at too high a tension, then the electronic processor 215 activates the tensioning system 210 to reduce the tension of the conveyor 105 (STEP 470). On the other hand, if the electronic processor 215 determines that the conveyor 105 is under tension, the electronic processor 215 activates the tensioning system 210 to increase the tension of the conveyor 105 (STEP 475). In some embodiments, the electronic processor 215 may also detect abnormal conditions of the conveyor 105 based on the proximity output signals received by the electronic processor 215. When the electronic processor 215 detects an abnormal condition, an alarm is generated (STEP 480). In some embodiments, the alarm may be communicated to an operator via, for example, a human machine interface, a speaker, or an external device (e.g., smartphone, mobile phone, tablet, laptop computer, desktop computer, and the like). As shown in FIG. 8, the electronic processor 215 continues to monitor the proximity output signals in STEP 455 to further monitor the tension of the conveyor 105.FIG. 9 illustrates another embodiment 500 of the sensor assembly 205. In the illustrated embodiment 500, the sensor assembly 205 includes a first proximity sensor 505 and a second proximity sensor 510. As shown in FIG. 9, the first proximity sensor 505 has a first sensing direction illustrated by the arrow A, while the second proximity sensor 510 has a second sensing direction illustrated by the arrow B. In the illustrated embodiment, the first sensing direction is approximately perpendicular to the second sensing direction. Similar to the proximity sensors 415 to 440 of the second embodiment 400, the first and second proximity sensors 505, 510 are also controlled when the first conveyor chain 120 (or a scraper 150) is detected. Accordingly, the first and second proximity sensors 505, 510 generate a binary output signal that indicates whether the first conveyor chain 120 (or the scraper) is within a detection range of the sensors 505, 510.In the illustrated embodiment, the first proximity sensor 505 detects a vertical distance between the first proximity sensor 505 and the first conveyor chain 120. The second proximity sensor 510 detects a horizontal distance between the second proximity sensor 510 and the first conveyor chain 120. FIG. 9 illustrates an example of when the conveyor 105 is at too low a tension and the first conveyor chain 120 is outside a first sensing region 515 of the first proximity sensor 505 and outside a second sensing region 520 of the second proximity sensor 510.When the embodiment 500 of the sensor assembly 205 is used, the electronic processor 215 performs a method similar to the method 450 shown in FIG. 8. For example, the electronic processor 215 receives the output signals from the first and second proximity sensors 505, 510, and determines whether the first conveyor chain 120 is of too low voltage, of too high voltage, or is within an acceptable voltage range based on the combination of the output signals. For example, as illustrated in FIG. 9, if the first and second proximity sensors 505, 510 generate a negative (or null) signal, then the electronic processor 215 determines that the conveyor 105 is at too low a voltage. On the other hand, if only one of the proximity sensors 505, 510 generates a positive signal, then the electronic processor 215 determines that the conveyor 105 has an appropriate voltage. Finally, if both the first and second proximity sensors 505, 510 generate a positive signal, the electronic processor 215 determines that the conveyor is at too high a voltage. The electronic processor 215 may then activate the tensioning system when the conveyor 105 is outside the appropriate tensioning range.In some embodiments, the electronic processor 215 receives the proximity output signals using the sensor embodiment 400 or the sensor embodiment 500 of the sensor assembly 205 and generates an estimated chain trajectory based on the output signals from the various proximity sensors 415- 440, 505, 510. For example, FIGS. 10A to 10D illustrate various generated chain trajectories based on the output signals from the proximity sensors. In particular, the chain trajectory may also be generated based on the output from the analog output sensor 310, or in some embodiments, from a plurality of analog output sensors 310 used together. FIG. 10A illustrates a generated chain trajectory in which the first conveyor chain 120 has too high a tension and has a sag distance of about 0 mm. FIGS. 10B and 10C illustrate generated chain trajectories in which the first conveyor chain 120 is properly tensioned and each has a slack distance of 50 mm (FIG. 10B ) and 100 mm (FIG. 10C ). FIG. 10D illustrates a generated chain trajectory in which the first conveyor chain 120 has too low a tension and has a sag distance of about 150 mm. In embodiments where the chain trajectory is generated, the electronic processor 215 may use the output signals from the proximity sensors 415- 440, 505, 510 or from the analog output sensor 310 to generate the estimated chain trajectory, and then may determine the slack distance from the generated chain trajectory instead of directly from the output sensor signals.FIG. 11 illustrates another embodiment 600 of the sensor assembly 205. In the illustrated embodiment 600, the sensor assembly 205 includes a first optical sensor 605. The optical sensor 605 may be, for example, a laser emitter / scanner, a light detection and ranging (LIDAR) sensor, a camera, and the like. Unlike the proximity sensors 415 to 440, 505, 510 and the analog output sensor 310 described above, the optical sensor 605 acquires image data. As shown in the illustrated embodiment, the optical sensor 605 is positioned proximate the first sprocket 132 and is directed toward the first conveyor chain 120.FIG. 12 is a flow diagram illustrating a method 650 of maintaining the conveyor system 100 at an appropriate tension using the fourth embodiment 600 of the sensor assembly 205. In STEP 655, the electronic processor 215 receives the image data from the optical sensor 605. The electronic processor 215 then identifies the first conveyor chain 120 in the image data acquired by the optical sensor 605 (STEP 660). The electronic processor 215 uses a plurality of image processing techniques to identify the conveyor chain 120 from the image data captured by the optical sensor 605, such as shape detection, straight edge detection, outlier detection, and the like. Based on the image data and the identified conveyor chain 120, the electronic processor 215 then generates an estimated chain trajectory (STEP 665). The estimated chain trajectory may be similar to those shown in FIGS. 10A to 10D, for example. In the illustrated embodiment, the electronic processor 215 continues to measure a sag distance from the estimated chain trajectory (STEP 670). In other words, the slack distance is measured from the virtual estimated chain trajectory and not from the first conveyor chain 120 itself. The electronic processor 210 then determines whether the measured slack distance is within an acceptable range (STEP 675). The acceptable range may be, for example, between 25 and 120 mm. Therefore, when the slack distance is less than 25 mm or greater than 120 mm, the electronic processor 215 determines that the slack distance is outside the acceptable range. If the slack distance is within the acceptable range, the electronic processor 215 continues to receive the image data from the optical sensor 605 (STEP 655). Otherwise, if the slack distance is outside the acceptable range, the electronic processor 215 activates the tensioning system (STEP 680) and then continues to receive the image data from the optical sensor 605 (STEP 655).In some embodiments, the electronic processor 215 stores each measurement related to the tension of the conveyor 105 in a memory. Based on the stored measurements, the electronic processor 215 may also be able to perform trend analysis to identify when the conveyor 105 is likely to be outside the acceptable voltage range. FIG. 13 is a flow diagram illustrating an example method 700 for analyzing previously acquired conveyor voltage data to determine whether the conveyor 105 tends to have too low a voltage or too high a voltage. As shown in FIG. 13, the electronic processor 215 receives sensor signals from one of the embodiments of the sensor assembly 205 described above (STEP 705). The electronic processor 215 then stores the received sensor signals (STEP 710). When it implements trend analysis, the electronic processor 215 accesses previously stored sensor signals (STEP 715). The electronic processor 215 then determines a difference between the current sensor signal and the previously stored sensor signal (STEP 720). The electronic processor 215 then proceeds and determines whether the difference is greater than a predetermined amount (e.g., indicating that the slack distance has increased by, for example, greater than 30 mm) in STEP 725. If the electronic processor determines that the difference is not greater than the predetermined amount, the electronic processor continues to receive the sensor signals as described in STEP 705. On the other hand, if the electronic processor 215 determines that the difference is greater than the predetermined amount, then the electronic processor activates the tensioning system 210 to prevent the conveyor 105 from getting a too low tension or a too high tension (STEP 730).In one embodiment, the electronic processor 215 accesses sensor signals associated with the previous activations of the clamping system 210. For example, the electronic processor 215 accesses the sensor signals of the previous five times that the clamping system 210 was activated. The electronic processor 215 then identifies a pattern associated with the previous signals before activating the tensioning system 210. The electronic processor 215 then compares the most recently received sensor signals to the identified pattern. If the most recently received sensor signals match the identified pattern, the electronic processor activates the tensioning system 210 to prevent the conveyor 215 from assuming too low a tension or too high a tension. In some embodiments, the electronic processor 215 accesses previously stored sensor signals and calculates a rate of change in sag distance. If the rate of change of the slack distance exceeds a predetermined threshold, then the electronic processor 215 determines that the conveyor 105 tends to be under tension or under tension and activates the tensioning system 210 to prevent the conveyor 105 from being under tension or under tension.In some embodiments, the electronic processor 215 may activate the tensioning system 210 before the conveyor 105 begins operation such that the conveyor 105 starts with a predetermined (e.g., calibrated) tension. The electronic processor 215 may then evaluate the tension condition of the conveyor 105 as described above.Accordingly, the present application describes various sensor arrangements used to determine a tension of a conveyor element (e.g., a conveyor chain). The output signals and data from the sensor assemblies are used by the electronic processor to determine when to actuate the tensioning system to maintain the conveyor within an appropriate range of tensions. Various features and advantages of the invention are set forth in the following claims.

Claims

A conveyor system (100) comprising: a sprocket (132); a conveyor (120) coupled to the sprocket (132) to rotate about the sprocket (132); a sensor (205) positioned adjacent the sprocket (132), the sensor (205) configured to generate an analog output signal having a value indicative of a distance between the sensor (205) and the conveyor (120); a tensioning system (210); and an electronic processor (215) coupled to the sensor (205) and the tensioning system (210), the electronic processor (215) configured to receive the output signal from the sensor (205), determine whether the value for the analog output signal is within a predetermined range, determining a voltage correction amount based on the analog output signal value when the analog output signal value is outside the predetermined range, controlling the tensioning system (210) based on the voltage correction value, and changing the distance between a first conveyor shaft (110) and a second conveyor shaft (115) of the conveyor system (100) by the correction amount, wherein a timer sets a duration during which the tensioning system (210) is activated to change the distance between the first conveyor shaft (110) and the second conveyor shaft (120), and the correction amount corresponds to the duration.The conveyor system (100) of claim 1, wherein the electronic processor (215) is further configured to calculate a difference between the value for the analog output signal and the predetermined range to determine the amount of voltage correction.The conveyor system (100) of claim 1, wherein the magnitude of the analog output signal is linearly related to the distance between the sensor (205) and the conveyor element (120).The conveying system (100) of claim 1, wherein the analog sensor is one selected from the group consisting of an ultrasonic sensor, an infrared (IR) sensor, and a magnetometer.The conveyor system (100) of claim 1, wherein the electronic processor (215) is further configured to assign a direction to the correction amount to indicate whether the tensioning system (210) is to increase tension or decrease tension.The conveyor system (100) of claim 1, wherein to control the tensioning system (210) based on the tension correction value, the electronic processor (215) is configured to reduce the tension in the conveyor element (120) when the analog output signal indicates that the conveyor element (120) is at too high a tension.The conveyor system (100) of claim 1, further comprising: a second sprocket (135); a second conveyor (125) connected to the second sprocket (135) to move about the second sprocket (135); and a second sensor (205) positioned adjacent the second sprocket (135), the second sensor (205) configured to generate a second analog output signal having a second value indicative of a second distance between the second sensor (205) and the second conveyor (125).The conveyor system (100) of claim 7, further comprising: a plurality of followers (150), each follower (150) being interposed between the conveyor element (120) and the second conveyor element (125).The conveyor system (100) of claim 1, further comprising: a frame (130), wherein the analog output sensor (310) is supported by the frame (130) proximate an unloading point of the conveyor element (120).The conveyor system (100) of claim 1, further comprising: wherein the analog output sensor (310) measures the distance between the sensor (205) and the conveyor element (120) in a sensing area below the analog output sensor (310).A computer-implemented method for maintaining a conveyor system at appropriate tension, the conveyor system (100) comprising a conveyor element (120), a sprocket (132), an analog output sensor (310), an electronic processor (215), and a tensioning system (210), the method comprising: receiving, by the electronic processor (215), an analog output signal from the analog output sensor (310), the analog output signal having a value indicative of a distance between the analog output sensor (310) and the conveyor element (120); determining, by the electronic processor (215), whether the analog output value is within a predetermined range, determining, by the electronic processor (215), a voltage correction amount based on the analog output value when the analog output value is outside the predetermined range, controlling, by the electronic processor (215), the clamping system (210) based on the voltage correction amount, and changing the distance between a first conveyor shaft (110) and a second conveyor shaft (115) of the conveying system (100) by the correction amount, wherein a timer sets a duration during which the clamping system (210) is activated to change the distance between the first conveyor shaft (110) and the second conveyor shaft (120), and the correction amount corresponds to the duration.The method of claim 11, further comprising: calculating a difference between the value for the analog output signal and the predetermined range to determine the voltage correction amount.The method of claim 11, wherein the magnitude of the analog output signal is linearly related to the distance between the sensor (205) and the conveyor (120).The method of claim 11, wherein controlling the tensioning system (210) based on the amount of tension correction comprises: decreasing the tension in the conveyor (120) when the analog output signal indicates that the conveyor (120) has too high a tension.The method of claim 11, further comprising: receiving, by the electronic processor (215), a second analog output signal from a second sensor (205) positioned adjacent to a second sprocket (135), the second analog output having a second value indicative of a second distance between the second sensor (205) and a second conveyor (125) moving around the second sprocket (135).The method of claim 11, wherein the analog output sensor (310) is supported by a frame (130) proximate a discharge point of the conveyor (120).The method of claim 11, wherein the analog output sensor (310) measures the distance between the sensor (205) and the conveying element (120) in a sensing area below the analog output sensor (310).

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