Patent Application
20070234800
This invention generally relates to level sensors and, in particular, to a level sensor suitable for sensing a level of a material in a storage container.
Bin monitors are used to monitor the level of materials at various discrete locations in storage bins, hoppers, tanks, silos or other structures. Monitor units can be installed almost anywhere materials are stored and can be used in a wide variety of applications, such as, for example, with: feed, silica sand, rocks, pellets, wood, calcium dust, rubber, metals, regrind materials, coal, peanuts, malt, clays, resin, limestone, grain, foundry materials, sand pre-mix, rawhide, sawdust, and many other applications.
Monitor Technologies, LLC, the assignee of the instant application, manufactures and sells bin monitors such as, for example, the bin monitor disclosed in U.S. Pat. No. 6,696,965 to Stout, et al. These bin monitors are typically installed through a roof or a wall of a storage container. As such, the bin monitors are able to locate a surface of the material and/or determine an amount of material inside the storage container.
While bin monitors such as those sold by Monitor Technologies, LLC, the assignee of the present application, have met with substantial commercial success, there is always a desire to improve the accuracy of the bin monitor. In particular, the use of optics in the bin monitors has been attempted, but such sensors are subject to accumulation of dust on the lenses and related equipment. Dust can be especially problematic in dry bulk powders such as at grain elevators. Sealing the monitor housing is only effective up to a point and has not effectively eliminated the dust sufficiently for optical devices to maintain their accuracy.
Further areas of improvement pertain to providing more than a simple “on/off” type of motor control capability, to giving the bin monitor the ability to check for errors and detect particular conditions, and to improving the accuracy of level measurements provided by the bin monitor.
The invention provides a bin monitor that improves upon accuracy through a sensor that provides feedback to indicate whether another sensor (e.g., optical sensor) is operating properly and providing accurate results and/or data. The bin monitor includes a housing that forms a magnetically penetrable bulkhead. The mechanical components are disposed on one side of the bulkhead in a mechanical compartment while the electrical components are disposed on another side of the bulkhead in an electrical compartment. Moreover, since the mechanical compartment houses a swing arm carrying a magnet and the electrical compartment includes one or more hall effect sensors, the bin monitor is able to sense a position of the swing arm. A portion of the housing also forms an optical compartment within the electrical compartment. The optical sensor is located in the optical compartment such that the optical sensor is redundantly isolated from the mechanical compartment, which is where contaminants are more prevalent. In addition, the optical sensor is able to detect errors, detect known conditions, and determine a direction of rotation.
Other aspects, objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:
While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.
Referring to
As collectively shown in
As best shown in
The housing 22 can be constructed using one or more of a variety of suitable materials. For example, the housing 22 can be formed in part or entirely from metal, plastic, and the like. Also, the housing 22 can be formed from two or more shells or layers of material so as to provide a plurality of contaminant barriers. In addition, seals, gaskets, and other similar parts (not shown) can be disposed between engaged portions of the housing 22 in an effort to protect internal components from contaminants. In a preferred embodiment, the bulkhead 34 is formed from a material that does not substantially interfere with a magnetic field such as, for example, aluminum, plastic, and the like.
As illustrated in
The housing 22 further includes and forms a socket 46 and has a mounting flange 48. As shown in
The motor assembly 24 is generally disposed in the housing 22 and includes a motor 52 and a reel 54 (i.e., storage reel) configured to carry a cable 56. In one embodiment, the cable 56 is a heavy duty, stainless steel cable. Alternatively, the cable 56 can be formed from other suitable cordage materials. As shown in
The swing arm assembly 26 controls and/or is responsive to tension in the cable 56. The swing arm assembly 26 is generally disposed in the housing 22 and includes a swing arm 58 and a sensor circuit 60. As shown in
Between the first and second distal ends 62, 66, the swing arm 58 includes a pulley 70. In one embodiment, as shown in
The sensor circuit 60 shown in
The optical assembly 28 includes a measuring wheel 78, a code wheel 80, and an optical encoder circuit 82. The cable 56 is routed around and engages the measuring wheel 78. Therefore, when the reel 54 winds the cable 56, the measuring wheel 78 is, for example, rotated clockwise and, in contrast, when the reel unwinds the cable, the measuring wheel 78 is rotated counterclockwise. The measuring wheel 78 is operably coupled to the code wheel 80 and, therefore, when the measuring wheel is rotated the code wheel 80 also rotates. As illustrated in
The code wheel 80 and the optical encoder circuit 82 are disposed in the optical compartment 40 found within the electrical compartment 38. Preferably, the optical compartment 40 is sealed off from the electrical compartment 38. Therefore, the code wheel 80 and the encoder circuit 82 are twice insulated from contaminants that originate within the storage vessel 16. Once due to the fact that the optical compartment 40 is sealed off from the electrical compartment 38 and twice because the electrical compartment is sealed off from the mechanical compartment 36 by the bulkhead 34. Any contaminants found outside the storage vessel 16 and proximate the monitor 10 must compromise at least a third layer of protection in the form of the housing 22 itself.
The code wheel 80 includes coded patterns of opaque and transparent sectors and the optical encoder circuit 82 generally includes at least one light source 84 and at least one photo detector 86 (i.e., optical sensor). Light from the light source 84 shines through the transparent sectors and gets blocked by the opaque sectors. As a result, when the code wheel 80 is rotated, light is intermittently received by the photo detector 86. Each time light is detected, the photo detector 86 generates a pulse or signal. In contrast, when the light is blocked a pulse or signal is not generated. The pulses or signals are generally relayed to the electrical control circuit 32. Since the code wheel 80 rotates relative to the measuring wheel 78, the pulses directly correspond to the length of cable 56 that has been released or collected and the electronic control circuit 32 is able to determine the level. 12 of material 14.
The optical encoder circuit 82 is also configured to sense direction of rotation (e.g., clockwise or counterclockwise) of the code wheel 80 in addition to sensing the length of the cable 56 dispensed or retracted. For example, in one embodiment the optical encoder circuit 82 includes a quadrature encoder and the code wheel 80 has two parallel code tracks that are offset from each other such that the opaque and transparent sectors of the parallel code tracks are not aligned. As a result, the quadrature encoder outputs two pulse trains (e.g., A and B) ninety degrees out of phase. If pulse train A leads pulse train B, for example, the electronic control circuit 32 is advised that the code wheel 80 is rotating in a clockwise direction. If pulse train B leads pulse train A, the electronic control circuit 32 is advised that the code wheel 80 is rotating in a counterclockwise direction. In other words, the quadrature outputs permit the direction of rotation of the code wheel 80 to be determined. This prevents an inaccurate count of pulses due to an undesirable “bounce” in the cable 56 that can occur when the material surface detector 30 is raised and lowered. Specifically, the pulses can be added or subtracted based on the direction of rotation of the code wheel 80.
In another embodiment, the optical encoder circuit 82 includes more than one light source 84 and/or more than one photo detector 86. For example, two photo detectors 86, one light source 84, and a code wheel 80 with two code tracks can be employed. Each of the two photo detectors 86 is oriented with respect to one or the other of the code tracks. Since the code tracks are offset, the rotation of the code wheel can be determined. In another case, two photo detectors 86, two light sources 84, and a code wheel 80 with a single code track can be used. The two photo detectors 86 are offset at different angles compared to the equidistant angles between the teeth on the code wheel 80. Once again, the rotation of the code wheel can be determined by this arrangement.
With either configuration of light sources 84 and photo detectors 86, the optical encoder circuit 82 is able to determine whether the code wheel 80 is rotating in either a clockwise or counterclockwise direction (i.e., a forward or reverse direction).
In one embodiment the optical encoder circuit 82 includes an amplifying device 88 such as, for example, an operational amplifier. The amplifying device 88 immediately amplifies or strengthens the pulse or signal generated by the photo detector 86. This amplification inhibits or prevents the degradation of the pulse such that the signal can be beneficially used and analyzed by the electronic control circuit 32.
The material surface detector 30 is a device generally configured to engage the material 14 within the storage vessel 16 and provide an indication of the level 12 of the material. In the illustrated embodiment of
The material surface detector 30 is able to move into and between several positions relative to the storage vessel 16 and/or the monitor 10. For example, when the reel 54 has fully retracted the cable 56, the material surface detector 30 engages with the socket 46 and assumes a “socketed” position 94. When the material surface detector 30 takes the socketed position 94, the downward force of the cable 56 upon the swing arm 58 increases and pulls the swing arm into a corresponding socketed position 96 proximate the measuring wheel 78. In contrast, when the reel 54 has expended the cable 56 until the material surface detector 30 has contacted the level 12 of the material 14, the material surface detector is in a “material contact” position 98. When the material surface detector 30 takes the material contact position 98, the downward force of the cable 56 upon the swing arm 58 decreases and/or is eliminated and permits the swing arm 58 to move upwardly into a corresponding material contact position 100 away from the storage vessel 16. Finally, when the material surface detector 30 is moving between the socketed position 94 and the material contact position 98, the material surface detector is said to be in a “traveling” position 102 (moving either upwardly or downwardly) between the socketed and material contact positions. Likewise, the swing arm 58 settles into a corresponding traveling position 104.
The electronic control circuit 32 (i.e., main control station) is a computing device such as a programmable logic device, a programmable logic controller, a computer, and the like disposed in the electrical compartment 38. The electric control circuit 32 is operably coupled to the motor 52, the sensor circuit 60, and the optical encoder circuit 82. The electronic control circuit 32 is able to activate and deactivate the motor 52. In particular, the electronic control circuit 32 can instruct the motor 52 to move the material surface detector 30 between the socketed position 94 and the material contact position 98 based upon input from the sensor circuit 60.
The electronic control circuit 32 also receives input from the photo detector 86 in the optical encoder circuit 82 based on the amount and direction of rotation of the code wheel 80. The input typically comes in the form of a series of pulses or signals generated by the photo detector 86. When these pulses are counted, surface or level 12 of the material 14 in the storage vessel 16 can be quickly determined. If any undesirable bounce in the cable 56 was noticed, the electronic control circuit 32 is able to adjust the level reading by adding to or subtracting from the pulse count depending on the direction of rotation of the code wheel 80. This is in contrast to simply adding a count for every pulse created and provides for more accurate results when ascertaining the level 12. With the level 12 of the material 14 known, the electronic control circuit 32, peripheral hardware and/or software are able to calculate and determine one or more parameters (e.g., amount, volume, temperature, pressure, etc.) of the material 14 within the storage vessel 16.
In operation, when a measurement cycle is initiated the material surface detector 30 and the swing arm 58 are in their socketed positions 94, 96 and the electronic control circuit 32 activates the motor 52. The activated motor 52 begins to turn the reel 54 such that the cable 56 begins to dispense. Preferably, the speed of the motor 52 is optimized to aid in the elimination of slack in the cable 56 and to improve the life of the motor 52. As the cable 56 is released from the reel 54, the material surface detector 30 begins to descend into the storage vessel 16 and the swing arm 58 is biased upwardly into their traveling positions 102, 104.
As the material surface detector 30 is being lowered, the hall effect sensors 74 monitor the position of the magnet 68, and thus the swing arm 58, and the same is reported to and monitored by the electronic control circuit 32. In addition, as the material surface detector 30 is being lowered the measuring wheel 78 is rotated by the cable 56. The rotating measuring wheel 78 causes the code wheel 80 to turn. The photo detector 86 in the optical encoder circuit 82 generates a pulse each time light passes through the code wheel 80. These pulses are transmitted to the electronic control circuit 32 where they are counted or otherwise analyzed. By counting the pulses, the dispensed length of the cable 56 can be calculated.
When the material surface detector 30 reaches the level 12 of the material 14, the downward force of gravity on the material surface detector is increasingly counteracted by the material 14. Therefore, the cable 56 begins to slacken. The slack in the cable 56 is generally absorbed by the swing arm 58 as the swing arm is biased upwardly by the biasing member. The hall effect sensors 74 can anticipate, based on the upward movement of the swing arm 58, when the swing arm will reach the material contact position 100. As such, the electronic control circuit 32, using the information relayed from the hall effect sensors 74, can deactivate the motor 52 at the most beneficial time. The undesirable bounce can therefore be mitigated and more accurate measurement results achieved.
The upward movement of the swing arm 58 and the lack of downward movement of the material surface detector 30 also causes the measuring wheel 78 to stop rotating. When the measuring wheel 78 stops, the code wheel 80 is correspondingly halted and the photo detectors 86 and/or the optical encoder circuit 82 report the discontinued rotation to the electronic control circuit 32. Once the swing arm 58 has ascended to the material contact position, the electronic control circuit 32 instructs the motor 52 to stop. Because the electronic control circuit 32 has been monitoring the input from the photo detectors 86, the electronic control circuit can adjust the pulse count for any bounce or other unexpected conditions that might have occurred during the descent.
After a predetermined amount of time, the electronic control circuit 32 instructs the motor 52 to begin operating in an opposite direction such that the cable 56 is now retracted. When the cable 56 is retracted, the photo detector 86 in the optical encoder circuit 82 once again begins generating and transmitting pulses. This time, the pulses represent the retracted length of the cable 56. As the material surface detector 30 is extracted or lifted from the level 12 of the material 14, the swing arm 58 and the material surface detector 30 each transition to their traveling positions 102, 104. Once again, the hall effect sensors 74 in the sensor circuit 60 monitor the position of the swing arm 58.
When the material surface detector 30 reaches and engages the socket 46, the material surface detector enters its socketed position 94. With the material surface detector 30 held firmly against the socket 46, the cable 56 can no longer be retracted and the tension on the cable 56 increases. This increased tension pulls the swing arm 58 downwardly towards its socketed position 96. The downward movement of the swing arm 58 also causes the measuring wheel 78 and code wheel 80 to stop turning. Therefore, the optical encoder circuit 82 discontinues sending pulses to the electronic control circuit 32. The socketed position 96 of the swing arm 58 is reported by the sensor circuit 60 to the electronic control circuit 32. In response, the electronic control circuit 32 halts the motor 52.
Similar to before, the hall effect sensors 74 can anticipate, based on the downward movement of the swing arm 58, when the swing arm will reach the socketed position 94. As such, the electronic control circuit 32, using the information relayed from the hall effect sensors 74, can once again deactivate the motor 52 at the most beneficial time. The undesirable bounce can therefore be mitigated and more accurate measurement results achieved.
In one embodiment, with the material surface detector 30 having been lowered and raised (i.e., undergone a measurement cycle), the electronic control circuit 32 compares the length of the cable 56 measured during the descent of the material surface detector 30 with the length of cable measured during the ascent of the material surface detector. If there is a substantial or excessive discrepancy between the two lengths, the electronic control circuit 32 reports an error. If no large difference is found, the electronic control circuit 32 employs an algorithm to determine the length of the cable 56, accounts for any bounce observed by the optical encoder circuit 82, and determines the level 12 of the material 14 in the storage vessel 16. Knowing the size and dimensions of the storage vessel 16, electronic control circuit 32 can determine the amount of material 14 as well.
The length of the cable 56, the level of the material 14, and/or the amount of material in the storage vessel 16 can be displayed, relayed, and/or utilized by using peripheral hardware components and/or software such as those described in Monitoring Bulletins 343A through 343D, which are available from Monitor Technologies, LLC, of Elbum, Ill.
From the foregoing, it can be seen that the above-noted monitor 10 provides substantial benefits. As those skilled in the art will recognize, knowing the position of the swing arm 58 at any given time is valuable information relating to the position or location of the material surface detector 30. This information can be combined with the information gathered by the optical encoder circuit 82 such that the electronic control circuit 32 is able to make better decisions and react more favorably in certain circumstances.
Also, due to the unique configuration of the monitor 10, the monitor is able to ascertain and alert a user of numerous conditions. For example, the user will be alerted to a broken cable 56 if the optical encoder circuit 82 is reporting no pulses or counts and the swing arm 58 is sensed in the material contact position. Also, the user will be notified when the material surface detector 30 has contacted the level 12 of the material 14 and is progressing toward an angle of repose if the optical encoder circuit 82 is reporting counts while the swing arm 58 is progressing toward the material contact position 100. As such, a mechanical brake commonly required by other known monitors is not needed. Also, the progression of the swing arm 58 in such a scenario might warrant the electronic control circuit 32 ignoring or discounting some of the pulses in arriving at a final pulse count. Further, the user will be advised when the material surface detector 30 is pulling out of the material 14 if the optical encoder circuit 82 is reporting counts and the swing arm 58 is rapidly moving toward the socketed position 96.
All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non- claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
