Abstract:
Apparatus, methods and systems for controlling a dust collecting system are presented. A system includes a plurality of sensors paired to a corresponding plurality of blast gates, and a controller coupled to receive a signal from each of the plurality of blast gates. The sensor non-invasively detects power flow through a tool&#39;s power cord. The controller is coupled between a collector and the blast gates. The blast gates may be configured in a star and/or daisy-chained configuration allowing for flexible installation. The controller instructs the collector to turn on and off based on a sensor signal received via a corresponding blast gate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of and priority to U.S. Provisional Patent Application 61/536,355, titled “Automated Dust Collection System” to inventor Charles E. Heger and filed on Sep. 19, 2011. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    This disclosure relates generally to apparatus and methods for dust collection. More particularly, the disclosure relates to an automated dust collection system scaled for operation in a small shop, such as a woodshop. 
         [0004]    II. Background 
         [0005]    Many woodworking shops have central dust collection systems to help maintain a clean and healthy environment. With multiple machines connected to a single dust collector, it is essential that only those machines in current use be actively connected to the dust collector. Otherwise a much larger dust collector would be required to handle all the airflow from all the various machines. This is typically accomplished by means of a “blast gate.” A blast gate is a shutter-type valve associated with each tool that can close off the duct connecting a particular tool to a central dust collector or fan via the ductwork. 
         [0006]    In operation, the user must open the required blast gate, turn on the dust collector and then proceed to turn on the tool and do whatever operation is needed such as sawing, jointing, etc. After the task is completed, the reverse actions must take place. That is, the tool is powered down, the dust collector turned off and finally the blast closed. Unfortunately, the user may forget to turn on the blast gate before use or to turn off the blast gate after use. 
         [0007]    U.S. Pat. No. 6,012,199 issued Jan. 11, 2000, discloses a refuse vacuum system including sensors, blast gates and a controller. A central controller communicates with a sensor and a blast gate at a particular machine whereby the sensor signals the controller of the activity of the particular machine and the controller in turn communicates with the blast gate to open the blast gate. This system architecture thus requires dedicated communications links from each sensor and blast gate pair to the controller. This requirement significantly adds to the complexity of the installation wiring. 
         [0008]    U.S. Pat. No. 7,146,677 issued Dec. 12, 2006, discloses an energy saving vacuum system utilizing variable power to a dust collector that is responsive to calculated airflow requirements. While advantageous for large installations with many machines, the cost of such a system is prohibitive for small shops having only a few machines. 
         [0009]    Thus what is needed is a system to automatically turn on and turn off a dust collection system without the need for direct user interaction and having ease of installation. 
       BRIEF SUMMARY 
       [0010]    Disclosed are apparatus, methods and systems for operating a dust collection system. According to some aspects, disclosed is a system for operating a dust collection system the system comprising: a sensor; a blast gate coupled to receive a signal from the sensor; and a controller coupled to receive a signal from the blast gate, wherein the controller is coupled between a dust collector and the blast gate to communicate signals; wherein the blast gate communicates with the controller in a pseudorandom manner. 
         [0011]    According to some aspects, disclosed is a system for operating a dust collection system the system comprising: a sensor; a blast gate paired to the sensor and coupled to receive a signal from the sensor; and a controller coupled to receive a signal from the blast gate; wherein the controller couples between a collector and the blast gate; and wherein the controller is for sending a signal to the collector. 
         [0012]    According to some aspects, disclosed is a method in a blast gate for operation in a dust collection system, the method comprising: receiving, at the blast gate, an indication from a sensor non-invasively sensing power of a tool energizing status; sending, from the blast gate, a signal to a controller in response to the signal from the sensor; and actuating the blast gate in response to the signal from the sensor. 
         [0013]    According to some aspects, disclosed is a blast gate for operation in a dust collection system, the blast gate comprising: means for receiving an indication from a sensor non-invasively sensing power of a tool energizing status; means for sending a signal to a controller in response to the signal from the sensor; and means for actuating the blast gate in response to the signal from the sensor. 
         [0014]    It is understood that other aspects will become readily apparent to those skilled in the art from the following detailed description, wherein it is shown and described various aspects by way of illustration. The drawings and detailed description are to be regarded as illustrative in nature and not as restrictive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  shows a typical wiring for a system installation, in accordance with some embodiments of the present invention. 
           [0016]      FIG. 2  shows a sensor, in accordance with some embodiments of the present invention. 
           [0017]      FIG. 3  shows an electronic design of a sensor, in accordance with some embodiments of the present invention. 
           [0018]      FIG. 4  shows a blast gate, in accordance with some embodiments of the present invention. 
           [0019]      FIG. 5  shows a detailed block diagram of a blast gate controller, in accordance with some embodiments of the present invention. 
           [0020]      FIG. 6  shows a system controller, in accordance with some embodiments of the present invention. 
           [0021]      FIG. 7  shows a detailed block diagram of a system controller, in accordance with some embodiments of the present invention. 
           [0022]      FIG. 8  shows the structure of the pseudo-random signal generated by firmware in microcontroller  204  of the gate controller in the gate  200 , in accordance with some embodiments of the present invention 
           [0023]      FIG. 9  shows a block diagram of a system using a daisy-chain current modulation architecture, in accordance with some embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    The detailed description set forth below in connection with the appended drawings is intended as a description of various aspects of the present disclosure and is not intended to represent the only aspects in which the present disclosure may be practiced. Each aspect described in this disclosure is provided merely as an example or illustration of the present disclosure, and should not necessarily be construed as preferred or advantageous over other aspects. The detailed description includes specific details for the purpose of providing a thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that the present disclosure may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the present disclosure. Acronyms and other descriptive terminology may be used merely for convenience and clarity and are not intended to limit the scope of the disclosure. 
         [0025]    In some embodiments, the system includes a sensor, a blast gate, a controller and a collector. The collector may be conveniently referred to as a dust collector. The collector, or dust collector, may collect dust, sawdust, metal shavings, vapor, exhaust, steam, shaving, chips or the like. The system automates the actions of opening and closing the blast gate and energizing and de-energizing the collector fan. A sensor at each tool signals when a particular tool has been turned on. In response, the blast gate associated with that tool opens and the collector is energized. After the operation has been completed and the tool turned off, the collector is automatically turned off and the blast gate closed. The tool may be a drill, a band saw, a planar or similar tool that generates dust such as wood dust or metal shavings. 
         [0026]      FIG. 1  shows a typical wiring for a system installation, in accordance with some embodiments of the present invention. Typically, daisy-chained gates reside along a common duct line. Ducting generally follows a main line with ducting drops to various tools. Network connections and cabling may follow and be routed along the ducting layout. The system architecture includes a collector  400  coupled to a system controller  300 , which is in turn coupled to at least one gate  200 . Each gate  200 , also referred to as a blast gate  200 , is coupled to a sensor  100 . 
         [0027]    In this embodiment, the system controller  300  includes at least four network jacks allowing up to four cables to fan out to the various blast gates  200 , and each blast gate  200  has two jacks allowing a daisy-chain of gates  200  further away from the system controller  300 . The embodiment shown includes four gates  200  directly coupled to the system collector  300 . The first gate  200  is coupled to a sequence of four more gates  200  in daisy chain fashion. The second gate  200  is couple to two additional gates  200  and the third gate  200  is coupled to one additional gate. The final gate  200  is not coupled to an additional gate. Each gate  200  is also shown paired to an individual sensor  100 . 
         [0028]      FIG. 2  shows a sensor  100 , in accordance with some embodiments of the present invention. The sensor  100  is coupled between a tool (e.g., a wood saw) and blast gate  200 . The sensor  100  detects current flowing in the power tool&#39;s power cord and signals the associated blast gate. In turn, the blast gate signals the system controller  300 , which then energizes the collector  400  or dust collector. 
         [0029]    The sensor  100  includes a jack  109  for use with a pre-made plug-and-play cable. In some embodiments, all system parts are connected with pre-made plug-and-play cables. For example, a system may use standard telephone connectors (RJ-12) or computer-type connectors (RJ-45) with standard communication cables. The sensor  100  also includes a V-notch  110  (which is positioned to align with a tool&#39;s power cord) and side notches  111  (which position a fastener to hold the tool&#39;s power cord against the sensor  100 . The sensor  100  mechanically attaches to the power cord of the tool. For example, the V-notch  110  on the case of the sensor  100  is placed onto the power cord and a spring, rubber band, VELCRO® brand hook and loop fasteners, or other suitable retainer is hooked over the cord and into the side notches  111  of the case. Unlike other sensors, the sensor  100  passively senses the current in the power cord without breaking the electrical connection, as other sensors actively connect to the machine&#39;s wiring or enter the machine&#39;s wiring enclosures, for example, if a toroid current sensor were used. This passive arrangement significantly eases the installation and minimizes safety concerns. 
         [0030]      FIG. 3  shows an electronic design of a sensor  100 , in accordance with some embodiments of the present invention. For additional details, see U.S. Pat. No. 7,714,567 issued May 11, 2010, titled “Power cable magnetic field sensor” to Charles E. Heger, the entirety of is incorporated herein by reference. In some embodiments, the sensor  100  is powered from the gate  200 . Furthermore, two magnetic coils  101  are physically arranged such that they are orthogonal to each other and to the axis of the machine or tool&#39;s power cable  102  (not part of the sensor  100 ). The orthogonal coils  101  along with amplifiers  103  detect stray magnetic field generated due to current flowing when the machine or tool is energized. The outputs of both amplifiers are detected by peak detectors  104  comprising a diode coupled in series and a capacitor coupled in parallel. In this matter, the orthogonal coils  101 , amplifiers  103  and peak detectors  104  act as a detector of current flowing in the tool&#39;s power cable. The resultant DC level from both detectors  104  is summed by adder  105 . The resultant sum is compared against reference value or reference voltage  106  (V REF ) by comparator  107  and if the sum exceeds reference voltage  106 , the comparator  107  will energize open collector output transistor  108 . The open collector/open drain transistor  108  writes an output signal, which is provided to the gate  200 . Upon detection of power to the tool, the transistor  108  is turned on establishing a low impedance logic level. A corresponding resistive pull-up current source in the gate  200  (see resister  209  in  FIG. 5 ) established a high level. This signal, in turn, will signal the gate  200 . For manual operations such as bench and floor sweeps, the sensor  100  may be replaced or supplemented with an accessory switch to control the gate  200  and collector  300 . For example, when turned on, the switch establishes the logic low level thus activating the gate  200 . 
         [0031]      FIG. 4  shows a blast gate  200 , in accordance with some embodiments of the present invention. A blast gate  200  includes a motor and is coupled between a sensor  100  and a system controller  300 , as described above. 
         [0032]    In the embodiment shown, the motorized blast gate  200  couples to standard four-inch ducting. A blast gate  200  is placed interrupting in the ducting at each tool or machine. A blade, such as a rotating blade pivoting about a post, opens and closes the duct line. There are identical four-inch duct flanges  214  on both sides of the gate  200  with tapers and a stepped section to allow connection to a broad variety of duct work. A plurality of slots  215  in the gates allow a visual check of blast gate operation as well as keeping possible debris buildup minimized Sawdust ports  216  are arranged around the perimeter to allow any captured or accumulated debris to exit. The gate  200  also includes one two-wire connector  201  to couple the gate  200  to the controller  300 . Alternatively, the gate  200  includes two two-wire connectors  201  for daisy chaining a sequence of gates  200 . That is, the connectors  201  allow a gate  200  to couple to upstream gates  200  towards the controller  300  and to additional downstream gates  200 . 
         [0033]    After receiving a signal from the sensor  100 , the blast gate  200  opens to allow a vacuum to suck debris from the tool to the collector  400 . In some embodiments, the gate  200  provides a short delay to allow the blast gate  200  to partially complete opening, and then the blast gate  200  signals the controller  300  to start the collector  400 . This short delay reduces the possibility of a high vacuum condition in the duct work. In other embodiments, the gate  200  waits to signal the controller  300  until the blast gate  200  is entirely open. In this manner, a high vacuum condition is avoided. 
         [0034]      FIG. 5  shows a detailed block diagram of a blast gate controller within the gate  200 , in accordance with some embodiments of the present invention. A two-wire connector  201 , which is coupled to the system controller  300 , is energized with 24 VDC. This voltage is connected to bridge rectifier  202  allowing the voltage from the controller  300  to be of positive or negative polarity. The universal polarity guarantees any cable may be used regardless of the actual connector makeup. In some embodiments, there are two network connectors  201 , both identical, allowing the system wiring to be daisy-chained from gate to gate, as described above. Typically, there is a central trunk duct from which individual tools or machines are teed. Daisy chaining allows a single network line to be started at the master controller  300  and to extend to the farthest gate on the main duct line. The rectified 24VDC from the bridge rectifier  202  is regulated by regulator  203  providing 5 VDC for a microcontroller  204  and LEDs  212 . Additionally, the 24VDC provides power for the motor  206  via motor controller  205 . A resister  209  provides a pull-up current source for open collector transistor  108  in the sensor  100 . 
         [0035]    The microcontroller  204  monitors the signal from a sensor  100  connected to connector  213  and upon receipt of a low logic level from the sensor  100 , the microcontroller  204  energizes blast gate motor  206  via motor driver  205  with a polarity such that the blast gate blade rotates to open and thus establishing a passage through the blast gate  200 . Motor driver  205  is comprised of four electronic switches. The polarity of the voltage energizing the motor is dependent upon which switches are activated. Turning on switches  205 A and  205 D, for example, will drive the motor in one direction. Activating switches  205 B and  205 C will cause the reverse rotation to occur. Motor braking can be caused by activating switched  205 C and  205 D effectively shorting the motor resulting in rapidly stopping its rotation without excess coasting. This braking ensures the position of the blade will be constant and repeatable when the blade is in the open position and the closed position following detection by a blade-rotation-limit switches  208 . In some embodiments, the blade-rotation-limit switches  208  are switched using magnetic sensing, such as with reed switches or Hall-affect sensors. Magnets may be used within the blade rotor such that the magnets set the appropriate open or close rotation position of the blade. 
         [0036]    Motor current is monitored with resistor  207  and subsequently monitored by microcontroller  204  via A/D converter  204 A. Should the motor current exceed a preset level as defined by firmware indicating a possible blast gate jam, microcontroller  204  will de-energize motor  206 . A short delay is incorporated in the firmware to ignore the initial high start current of motor  206  upon motor activation. The microcontroller  204  may allow a short delay, which allows the blast gate to partially open, or may allow a longer delay, which allows the blast gate to fully open. The microcontroller  204 , via a current modulator  210 , generates a pseudo random current modulated signal impressed on the network wiring. 
         [0037]    In some embodiments, blast gate signals sent from the blast gate  200  to the controller  300  are communicated with current modulation placed on the power line supplying voltage to the gates  200 . Current modulation is a low impedance signaling method that is robust and highly immune to extraneous electrical noise sources such as those generated by motors, light ballasts and the like. In some embodiments, the blast gate signal is identical in structure to signals coming from each blast gate  200 . To help guarantee there will be no signal cancellation due to additive out-of-phase addition should more than one blast gate  200  be simultaneously signaling controller  200 , the blast gate signal structure may be a pulsed burst, for example between 1 kHz to 20 kHz AC with the bursts having 10 to 200 cycles and being pseudo randomly timed. The statistical chance of any two signals from two gates aligning exactly to produce phase cancellation is very remote. The blast gate signal is further described below with reference to  FIG. 8 . 
         [0038]    In some embodiments, the blast gate  200  has a user-selectable turn-off delay time that may be selected with switch  211 . A short turn-off delay is used where a machine, such as a table saw or jointer, is typically turned on for a minute or more with longer intervals between uses. Alternatively, a longer delay of several minutes may be selected allowing the collector to run without constantly cycling off and back on during repetitive, short cycle time operations such as chop sawing. This reduces excess cycling to the dust collector fan motor. 
         [0039]      FIG. 6  shows a system controller  300 , in accordance with some embodiments of the present invention. The system controller  300  is coupled between one or more blast gates  200  and a collector  400 . In the embodiment shown, the system controller  300  includes a manual on/off switch, a power to accept power, a port to enable and disable the collector  300 , and four connectors to couple one or more daisy-changed gates  200 . 
         [0040]      FIG. 7  shows a detailed block diagram of a system controller  300 , in accordance with some embodiments of the present invention. As explained above, the blast gates  200  are wired to the system controller via connectors  301 . In some embodiments, there are four network connectors  301 , all identical and wired in parallel, allowing up to four network lines to fan out to various blast gates. A power supply  313  provides 24 VDC power to the blast gates  200  and voltage regulator  314 . The voltage regulator  314  provides a regulated 5 VDC. Current being used by the blast gates  200  flows through a current sampling resistor  302 , which is coupled to one of the two-wire input lines of each connector  301 . The total current being supplied by the gates  200  includes current from any static gates in the controller in the gate  200 , blast gate motor  206 , and any sensor or pseudo-random signaling current modulation. 
         [0041]    A bandpass amplifier  303  is also coupled to one of the two-wire input lines of each connector  301 . The bandpass amplifier  303  is AC coupled to sense an AC signal from the network current. The bandpass frequency of the bandpass amplifier  303  may be selected to be the same as a frequency of a square wave current modulation signal (described below with reference to  FIG. 8 ) generated by the gate controllers in the gates  200 . The output of the bandpass amplifier  303  provides a filtered signal of any burst of AC passed to the bandpass amplifier. The output of the bandpass amplifier  303  is fed to a peak detector  304 . The resultant pulses of DC corresponding to the modulated AC burst envelopes are integrated by integrate-and-dump (I/D) circuit  305 . The I/D circuit  305  may be allowed to integrate 1 to 5 times the length of the pseudorandom signal code. At the end of this integration time, the microcontroller  306  measures the accumulated integrated voltage from the I/D circuit  305  via an A/D converter  306 A and compares the resultant value against a firmware established threshold. The I/D circuit  305  then is reset by discharging the integration capacitor  305 A by closing electronic switch  305 B which can be a bipolar or MOS transistor. The controller  300  also includes a power relay  308 , which has incoming AC power  315  available. If the resultant voltage from the I/D circuit  305  exceeds a firmware threshold, the power relay  308  may be activated via relay driver  307  resulting in AC power  316  being applied to the collector fan  400 . If all tool sensors  200  detect no machine activity, the output signal of the I/D circuit  305  will not exceed a firmware threshold. The microcontroller  306 , after a possible short delay to allow the duct line to clear of debris, turns off the power relay  308  thus turning off the collector fan  400 . 
         [0042]    The current flowing in all the network connections  301  is monitored by the current-sampling resistor  302  in the controller  300 . The current-sampling resistor  302  senses the pseudo-random signal and also senses the DC level current level. Should this level exceed a threshold established by V REF    310 , a comparator  309  may change output logic levels. The microcontroller  306  may then respond by enabling an LED  311  associated with an error condition to alert the operator. In some embodiments, this over current condition can be used to disconnect the gate network from the 24 VDC voltage source via an electronic switch (not shown) such as a power bipolar or MOS transistor. The detected error would then cease whereon the microcontroller may re-establish power to the gates. This condition may continue to cycle at a rate determined by the microcontroller firmware until such time as the overload condition was resolved. 
         [0043]    A manual switch  312  is included on the master controller to allow turning on of the dust collector without any machine being on. In some embodiments, the LEDs  311  may indicate: (1) POWER; (2) SENSING (when a tool is on or off); and (3) ERROR (when the network cabling power is overloaded or shorted). 
         [0044]      FIG. 8  shows the structure of the pseudo-random signal generated by firmware in microcontroller  204  of the gate controller in the gate  200 , in accordance with some embodiments of the present invention. A maximal length linear sequence code is used as described in “Spread Spectrum Systems”, 2 nd  Edition, Robert C. Dixon, pp. 58-91. In some embodiments, a 4-bit code is used having a run length of 2 4 −1 or 15 unique states. Although a longer code length could be used, little statistical improvement in phase cancellation would be realized with longer codes. 
         [0045]    In some embodiments, a unique pseudo-random code can be used for each sensor/blast gate pair in the system. The user would select a unique setting at the blast gate  200  much like choosing the code on a garage opener. This would allow activities such as data logging and airflow adjustment, etc. The system controller  300  would then have firmware to synchronize and uniquely identify various codes present much like a GPS receiver decodes various satellite signals. 
         [0046]    The microcontroller-generated pseudo-random sequence is used to turn phase modulator  210  of the controller in the gate  200  on and off. The phase modulator forms a constant current source with the current level established by the voltage on the base of the transistor and the resistor value in the emitter. Using a current source rather a simple transistor switch with a resistor in the collector ensures a consistent current modulation level regardless of variations in the incoming 24 VDC from the system controller. 
         [0047]      FIG. 9  shows a block diagram of a system using a daisy-chain current modulation architecture, in accordance with some embodiments of the present invention. A DC voltage source  501  is part of a system controller  300  that supplies power to a series of daisy-chained blast gates  200 . Any number of gates  200  may be connected dependent on the voltage source current capability. 
         [0048]    Each blast gate  200  contains a modulation generator  510 A. This generator produced a time varying signal which in turn controls the switch  510 B. If switch  510 B is open, no additional current will flow in current loop  511 . If switch  510 B is closed, current flows in loop  511  with the current established by resistor  510 C and the value of voltage source  501 . A time varying differential is used to distinguish a signal from a static DC current required to power the gates. Detection circuit  503 A responds only to the time varying signal and ignores the DC component of the current. The varying current is sensed across resistor  502  in system controller  300 , producing a voltage which is detected by circuit  503 . If multiple gates are simultaneously producing modulation, the voltage across sense resistor  502  will increase accordingly. 
         [0049]    The previous description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects without departing from the spirit or scope of the disclosure.