Patent Application
20120324995
The invention relates generally to chemical dispensing systems for laundry, ware-wash, and healthcare, and more particularly to detecting amounts of product in the chemical dispensing system.
The dispensing of liquid chemical products from one or more chemical receptacles is a common requirement of many industries, such as the laundry, textile, ware wash, healthcare instruments, and food processing industries. For example, in an industrial laundry facility, one of several operating washing machines will require, from time to time, aqueous solutions containing quantities of alkaloid, detergent, bleach, starch, softener and/or sour. Increasingly, such industries have turned to automated methods and apparatus systems for dispensing chemical products. Such automated methods and apparatus systems provide increased control of product use and reduce human contact with potentially hazardous chemicals.
Contemporary automatic chemical dispensing systems used in industry rely on pumps to deliver the liquid chemical products from a storage container. Generally, these pumps deliver raw product directly to a machine for use or to a dilution manifold or container where the product is mixed with a diluent, typically water. Such systems are relatively simple in concept, but they can be expensive to build and operate. A number of methods for the control of dispensing these chemical products have been developed and employed and are well known in the art.
In many contemporary chemical dispensing systems, the chemical products are stored in containers and probe assemblies are used to monitor the level of the product in these containers. One common type of probe assembly includes two probes separated by a distance so that the probe assembly has a high input impendence when exposed to air. Because the products are typically conductive, the input impendence of the probe assembly is lower when the probes are in contact with the product. To provide an indication of the level of product in a container, the probe assembly is mounted in the container so that the probes are in contact with the product when the container is sufficiently full. When the level of product drops below the probes, the probes are exposed to air, increasing the input impedance of the probe assembly. To notify the operator of the chemical dispensing system that the container is running low on product, a monitoring device is connected to the probe assembly. In this type of detection system, the monitoring device is configured to detect the increase in the input impedance of the probe assembly, and may thereby notify an operator that the product is about to run out by providing an alarm.
The operator may be responsible for multiple chemical dispensing systems, each of which will typically be located remotely from the operator's workspace. In addition, the machines connected to each of the chemical dispensing systems may require several different chemical products in order to perform properly. The monitoring system will therefore typically include multiple probe assemblies and monitoring devices so that each of several containers containing different chemical products is individually monitored. Thus, a typical monitoring system may require several cable runs from multiple locations in order to provide full coverage of all the containers the operator is responsible for maintaining. Increasing the number of containers and locations that must be monitored will further result in increased cabling requirements. This large number of cable runs will increase the complexity and expense of the monitoring system, and may also reduce the monitoring system's reliability due to the increased number of connections and potential failure points.
Further reliability issues may arise from use of conventional probe assembly designs. Because the aforementioned level monitoring systems rely on the measured input impedance of the probe assembly to detect the level of the product, anything that affects this measurement can have a negative impact on the reliability of the system, Probe assemblies may experience reliability issues over time from the product attacking the probes due to the corrosive nature of many of the chemicals typically found in the product. Even when the probes utilize resilient types of materials such as stainless steel or graphite, the probes are generally being electrically charged by the monitoring device in order to measure the capacitance or input impedance of the probe assembly. This electrical charge may result in electrolysis occurring at the electrodes, which will tend to foul even a chemically resistant material after a sufficient period use. The product may also be sufficiently viscous so that the product clings to the probes or leaves a semi-dried residue, causing the probes to indicate that sufficient product is present in the container after the level of the product has dropped below the probes.
Fouled or otherwise compromised probe assemblies and/or monitoring devices may cause erroneous readings. These erroneous readings may result in false alarms and/or failures to notify the operator that a product is running out. These errors can be addressed by performing continuous maintenance of removing and cleaning the probe assembly, undesirably increasing operational expenses. False alarms may result in unnecessary trips to refill a container that already contains sufficient product, which also increases operating expenses. Frequent false alarms may also cause operators to either ignore or disconnect the monitoring system, increasing the likelihood that a container running low on product will go unnoticed.
Large numbers of cables and compromised probe assemblies may thus collectively reduce the reliability and increase the cost of chemical product level monitoring systems. For the aforementioned reasons, unreliable monitoring systems may result in machines attached to the chemical dispensing system running without the required amounts of the chemical products being dispensed. The performance of the machines fed by the chemical dispensing system may thereby be adversely affected due to too little of the product being dispensed, reducing the quality of machine's output and increasing expenses by requiring goods to be re-processed through the affected machine.
Therefore, there is a need in the art for improved monitoring system components and methods that more accurately and reliably detect the presence of chemical products over time for use with chemical dispensing systems.
In one aspect of the invention, a multi-probe monitoring unit capable of monitoring multiple probe assemblies is provided for use in a chemical dispenser monitoring system. The multi-probe monitoring unit provides multiple electrical input ports to which probe assemblies may be connected, facilitating system scalability and remote monitoring of multiple containers. The multi-probe monitoring unit is configured to monitor multiple probe assemblies at the location of the chemical dispensing machine and provides an interface for connecting a remote alarm unit over a single cable. The multi-probe monitoring unit thereby provides a mechanism whereby a single remote alarm may be used notify the operator that any one of many container(s) serving a particular chemical dispensing machine is running low on product. To this end, the multi-probe monitoring unit includes a detection circuit, a switch matrix having a plurality of electrical input ports, and a processor operatively coupled to the detection circuit and the switch matrix. Each monitored probe assembly is connected to an electrical input port on the switch matrix and provides a low impedance at the electrical input port when the probe assembly is in contact with the product in the container and a high impedance when the probe assembly is not in contact with the product—i.e., when the product falls out of contact with the probe assembly. Using the switch matrix, the processor selectively couples the electrical input port associated with each probe assembly to the detector in a sequential manner. The detector thereby provides an indication to the processor of the product level status in each monitored container. If a low product condition is detected in any of the containers, the multi-probe monitoring unit will supply a signal to the remote alarm unit, notifying the operator that one of the containers is low on product.
In a second aspect of the invention, the probe assembly for detecting a level of a product in a container is configured to resist corrosion, fouling, and false readings caused by viscous and/or corrosive products. The probes are formed from a material resistant to chemical attacks from the monitored product, such as polypropylene. To provide the needed electrical connection between the product and the detection circuitry, the probe is preferably rendered conductive such as with a conductive substance like carbon preferably infused into the probe material to render it conductive. The probe assembly is further constructed to have a unique product shedding configuration that further reduces false readings that may be caused by viscous products clinging to the probes.
In a third aspect of the invention, a method of detecting a minimum level of product in a container is provided that involves coupling a probe assembly to a detection circuit that includes an oscillator. The oscillator is designed so that it will oscillate when the electrical impedance provided to the input of the detection circuit is sufficiently high, such as when the input of the detection circuit is connected to a probe assembly that is not in contact with the product. The detection circuit thereby provides a signal to the processor indicating that the product level has dropped below a minimum acceptable level. In contrast, when the input of the detection circuit is connected to a probe assembly that is in contact with the product, the additional electrical load provided by the probe assembly to the input causes the oscillator to change in frequency (depending on the conductivity of the fluid) or to stop running. Because of the nature of the loading of the resistive probes in the oscillator circuitry, the voltages placed on the probes by the detection circuit are minimized while the probes are in contact with the product, thereby reducing electrolysis and probe fouling.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.
It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the sequence of operations as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes of various illustrated components, will be determined in part by the particular intended application and use environment. Certain features of the illustrated embodiments have been enlarged or distorted relative to others to facilitate visualization and a clear understanding. In particular, thin features may be thickened, for example, for clarity or illustration,
Embodiments of the invention provide a system for monitoring a level of product in containers supplying a chemical dispensing system that assists in overcoming the difficulties with contemporary probes and product level monitoring systems. The probes utilize industry proven materials, such as polypropylene, to substantially reduce the issues related to chemical attacks on the probes, but that are modified so that the probes are electrically conductive. The probe assemblies also have a unique mechanical configuration that reduces false readings caused by viscous solutions clinging to the probes, increasing the reliability of chemical level indications over contemporary probes. The probe assemblies consistent with embodiments of the invention are used with detection circuitry that provides an indication that the level of a chemical in a container of the chemical dispensing system has dropped below a minimum level, indicating that the container is out or about to run out of the chemical.
The detection circuitry minimizes probe fouling caused by electrolysis, which coupled with the improved probe materials and shape, further increases the reliability of product minimum level indications by the probe assemblies. A multi-probe monitoring unit allows a single detection circuit to monitor multiple probe assemblies, reducing the cost and complexity of the system. The multi-probe monitoring unit may thereby provide system operators with indications of whether a sufficient level product remains in multiple containers of the chemical dispensing system or an indication that one or more containers is out of a chemical. The multi-probe monitoring unit is configured to interface with a remote alarm so that the operator may be notified that any one of a plurality of container(s) is running low on product without visiting the physical location of chemical dispensing unit. The remote alarming capability may thereby improve worker productivity by reducing the need for site visits. By consolidating the monitoring of multiple probe assemblies into a single multi-probe monitoring unit, system set up and monitoring may also be simplified, with a resulting improvement in the cost of the system and the reliability of the low product alarming.
Turning now to the drawings,
Probe assemblies 26 (such as in
Referring now to
The processor 38 executes or otherwise relies upon computer program code, instructions, or logic to execute the functions of the multi-probe monitoring unit 30. To this end, a probe monitor program 53 may reside in memory 39 and may be executed by the processor 38. The probe monitor program 53 controls and manages the other components of the multi-probe monitoring unit 30 so as to provide a monitoring function for the probe assemblies 26. To provide control over the probe assemblies 26, the processor 38 is in electrical communication with the switch matrix 42, which includes one or more suitable switches such as analog complementary metal-oxide-semiconductor (CMOS) switches. The switches connect each electrical input port 31 of multi-probe monitoring unit 30 to an input 41 of the detection circuit 40. The probe monitor program 53 thereby selectively electrically couples an individual electrical input port 31 of the multi-probe monitoring unit 30 to the detection circuit 40 by outputting a signal that closes the appropriate switch in the switch matrix 42.
The channel LEDs 44 may comprise a plurality of LEDs electrically coupled to the processor 38. The probe monitor program 53 associates each switch in the switch matrix 42 with a channel LED 44, which allows the processor 38 to periodically illuminate the appropriate channel LED 44 when that port 31 is coupled to the detection circuit 40. The probe monitor program 53 thereby provides a visual indication of which probe assembly 26 is currently being monitored or polled by the multi-probe monitoring unit 30. The probe monitor program 53 also illuminates the appropriate channel LED 44 to indicate a product out or other condition associated with a particular container 18, 20, 22.
The processor 38 is also electrically coupled to the local alarm LEDs 48 and the local alarm buzzer 50 so that the probe monitor program 53 may provide visual and audible indications of a product low level condition within the chemical dispensing system 10. The probe monitor program 53 also provides a product low level indication by activating the remote alarm 36 (when connected), which will typically be located in the operator's office or other desired remote location.
A mute button 52 allows the operator to silence the audible alarm. In some embodiments, the remote alarm 36 may be provided by a stand-alone unit 32 having an input port electrically coupled to the processor 38. To this end, the multi-probe monitoring unit 30 is configured to provide a signal to an electrical input port of the stand-alone unit 32 when the probe monitor program 53 determines that the product level in one of the monitored containers is below the minimum level set point. As will be described in more detail below, this signal will cause the stand-alone unit 32 to sound an alarm. The probe monitor program 53 is configured to provide different mute responses depending on how long or how many times the mute button 52 is pressed. By way of example, in some embodiments of the invention, the first time the mute button 52 is pressed, the alarm might be silenced for a short period, such as an hour. If the mute button 52 is held down for a length of time, such as 3-4 seconds, the alarm might be silenced for a longer period, such as a weekend. To provide an indication that the local alarm buzzer 50 has been muted, the local alarm LED's 48 will flash at a slower rate than normal. The rate of flashing is further adjusted so that the local alarm LED's 48 flash at a slower rate when a long duration alarm silencing period has been activated (such as a weekend) than when a short duration silencing period has been activated (such as an hour).
Referring now to
A pair of conductive probes 56, 58 comprising the probe assembly 26 are connected to the detection circuit 40. The probe assembly 26 is connected across the input 41 of the detection circuit 40 so that one probe 56 is connected to one side of load element 47 and the other probe 58 is connected to the other side of load element 47, which may also be coupled to a reference ground 49. When the probe assembly 26 is suspended in air, such as when the chemicals in the monitored container 18, 20, 22 have dropped below the probe assembly 26, the impedance of the probe assembly 26 as seen by the detection circuit 40 has a low loading effect on the oscillator 45. The quality factor of the oscillator 45 is thus relatively unaffected by the presence of the probe assembly 26 so that the detection circuit 40 outputs a time varying voltage signal at the nominal frequency as illustrated in the schematic diagram of
In some embodiments of the invention, the output 43 of the detection circuit 40 is fed into additional drive logic 46 (
Referring now to
Extension tubes 60, 62 may be formed from polypropylene or other suitable material resistant to chemical attack, and are sufficiently rigid so as to maintain the positions of probes 56, 58 within their associated container. Electrical leads 64, 66 are formed from insulated wire or other suitable conductor, and are located within the extension tubes 60, 62 to prevent contact with the product. Electrical leads 64, 66 are electrically coupled to their corresponding conductive probes 56, 58 by clip leads 72, 74 to provide an electrical connection between the probes 56, 58 and the multi-probe monitoring unit 30 or standalone unit 32, as the case may be.
The chemical cap assembly 65 is designed to accommodate several common size container openings and thread sizes. The chemical cap assembly 65 includes a cap 68 and a lid 69. The cap 68 is configured so that it will couple to standard chemical container openings and is held in place by the lid 69. The lid 69 is in the form of a threaded ring that can rotate while the cap 68 remains stationary to facilitate securing the cap 68 to standard threaded container openings without twisting the tubes and/or wires passing through the cap 68. As best illustrated in
As best illustrated in
When the probes 56, 58 are in contact with air, the impedance between the probes 56, 58—and ultimately the leads 64, 66—is very high because the only electrical connection between the probes is through air. When the product contacts the probes 56, 58, a less resistive electrical path is created between the probes 56, 58, which reduces the impedance between the probes 56, 58 and ultimately the leads 64, 66. This change in impedance between the leads 64, 66 alters the operation of the detector circuit 40 as previously described with respect to
In block 94, an electrical input port 31 of the multi-probe monitoring unit 30 for which monitoring is enabled may be selected. The selected electrical input port 31 is electrically coupled to the input 41 of detection circuit 40 by the switch matrix 42, thereby electrically coupling the corresponding probe assembly 26 to the detection circuit 40. To provide a visual indication of which electrical input port 31 is currently being monitored, the probe monitor program 53 will cause the channel LED 44 associated with the electrical input port 31 in question to periodically light. The electrical input ports 31 are selected sequentially starting with a first electrical input port to which an attached probe assembly 26 was detected during system initialization. When the probe monitor program 53 comes to an electrical input port 31 that is flagged as not being associated with a probe assembly 26, the probe monitor program 53 may continue on to the next electrical input port 31 without coupling the electrical input port 31 to the detection circuit 40, or alternatively may simply ignore the output 43 of the detector circuit 40 while the detector circuit is coupled to the electrical input port 31.
In block 96, the probe monitor program 53 monitors the output 43 of the detection circuit 40 for a period of time, such as about 0.5 seconds, to determine if the detected impedance across the probe assembly 26 indicates a low product condition. If a low product condition is indicated, an alarm flag may be set for that electrical input port 31. Alternatively, the probe monitor program 53 may also require that a low product condition be indicated for the same probe assembly 26 for several consecutive polling periods, such as three periods, before setting the alarm flag to reduce the occurrence of false alarms. If an alarm conditions exists (i.e., the alarm flag is set) for the monitored electrical input port 31 (“Yes” branch of decision block 98), then the probe monitor program 53 proceeds to block 10 where an appropriate alarm indicator is set. If an alarm flag is set for a particular electrical input port 31, the channel LED 44 associated with that electrical input port 31 will change state from a periodic illumination to a continuous illumination to provide an indication to the operator as to which container 18, 20, 22 is running out of product.
In response to detecting a low product condition, the probe monitor program 53 will illuminate the local alarm LED's 48 as well as cause the local alarm buzzer 50 and/or remote alarm 36 to indicate a low product condition has been detected. To activate the remote alarm 36, the multi-probe monitoring unit 30 provides a suitable signal, such as a 12 volt DC signal capable of powering the remote alarm unit 36. In some embodiments, the remote alarm unit 36 may be a stand-alone unit 32 configured to alarm when supplied with power. If the alarm flag is not set for the monitored electrical input port, indicating that there is no alarm condition (“No” branch of decision block 100), then the process continues at block 94 where the next electrical input port 31 of the switch matrix 42 is selected. The multi-probe monitoring unit 30 thereby sequentially monitors the electrical input ports 31 connected to probe assemblies 26 to detect a low product condition.
The probe assembly 26 is also capable of being used as a stand-alone probe that does not communicate with a multi-probe monitoring unit 30, such as when there is only one container of product being monitored. In this configuration, the probe assembly 26 may be connected directly to the stand-alone unit 32. The stand-alone unit 32 includes the detection circuit 40 and drive logic 46 configured to light a channel LED 44 when the probe assembly 26 is in contact with product in a container 18, 20, 22. The stand-alone unit 32 is further configured to light the local alarm LED's 48 and/or local alarm buzzer 50 when the probe assembly 26 is not contacting the product. The stand-alone unit 32 may thereby be used without the multi-probe monitoring unit 30 to monitor a single container 18, 20, 22. Multiple probe assemblies 26 may also be operatively deposed within a single container 20 (
The probe assembly 89 may be mounted through the containers 18, 20, 22 or may be mounted on an inside wall of the containers 18, 20, 22 as appropriate. To assist with the mounting and to assist on protecting the electrical connections to the conductive probes 86, 88, a collar 102 may be placed on the assembly around a first portion of the housing 103. A second portion 104 of the housing that is integral with the first portion 103 has a planar face 105 through which ends 107, 108 of the conductive probes 86, 88 extend, which can be best seen in
Similar to the embodiments discussed above, when the probes 86, 88 are in contact with air, the impedance between the probes 86, 88 and ultimately the leads 64, 66 is very high, as the only electrical connection between the probes is through the air between the gap produced by the spacer 116 coupled to the housings 112, 114. When a conductive chemical solution or product contacts the probes 86, 88, a less resistive electrical path may be created between the probes that reduces the impedance between the leads 64, 66. This change in impedance based on contact with air or the product may be used by the detection circuit 40 and/or the processor 38 to appropriately activate alarms or illuminate indicators as discussed above.
While the present invention has been illustrated by a description of one or more embodiments thereof and while these embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope of the general inventive concept.
