Patent Publication Number: US-2006016201-A1

Title: Actuator alarm for critical environments or applications

Description:
The present invention relates to an air damper or valve actuator system with an alarm feature and a distributed system for monitoring a plurality of such actuator systems and methods for detecting and issuing an alarm indicative of potential impending mechanical failure of the air damper or valve systems.  
     BACKGROUND OF THE INVENTION  
      Actuators are utilized to open and close air dampers in heat, air conditioning and ventilation systems (HVAC systems) and are also used to open and close valves in hydraulic systems. These actuators customarily include motors and controllers which respond to control signals applied thereto by external master HVAC or hydraulic control centers. In most situations, air damper actuators (which control air flow through HVAC ventilation systems) and valve actuators (which control hydraulic flow through pipes and tubes) are installed and located in places which are easy to reach by installers and subsequent maintenance personnel. Therefore, potential failures of these actuators are typically not critical and the installation of these actuators and the operation of the actuators are typically not protected or fall within the scope of recommended periodic maintenance contracts and building maintenance procedures.  
      However, some applications which utilize of air damper actuators or valve actuators are critical in that the failure of the actuator (to open or close upon command) can create significant economic or safety repercussions. For example, when an actuator is used in an unmanned cellular telephone transfer station which is remote and moderately inaccessible during winter time (or during other adverse weather conditions), the failure of the actuator may result in a system wide failure of the cellular telephone system. In this example, the actuator is an important part of the overall temperature control and command assembly system in the unmanned station. A failure of the actuator in these unmanned cellular telephone transfer stations may deprive thousand of customers of cellular telephone service for prolonged periods of time. Therefore, the cellular service provider is both economically at risk and its reputation for high quality “always ON” cellular telephone service may be affected. Another example of a critical application of these actuators is the utilization of an air damper actuator or valve actuator in laboratory ventilation hood systems. In these hood systems, the actuator controls the air flow of contaminated air away from the operator of the hood. If the actuator fails to open or close the damper or valve (due to damper/valve failure), dire consequences may result.  
      It may be beneficial to predict actuator/air damper/valve failures before the actuator and mechanically driven system ceases operation. In this manner, in a distributed command and control system, the central control station can note the deteriorated or poor condition of the actuator and associated mechanical system and issue appropriate personnel commands and recommendations for the preventive maintenance of the “at risk” actuator prior to actuator failure. Actuator failure usually results due to a failure of the air damper or valve or a “locking up” of the damper or valve rather than the actuator failing to operate. In other words, the actuated component fails, not the actuator per se.  
      Since the actuator motors are coupled, either directly or via a gear system, to mechanically movable air dampers or valves, the air dampers or valves may become sticky and difficult to move or motivate over time. Although less likely, hydraulic valves are subject to similar deteriorating operating conditions. Time frames of 5-10 years are not unusual. Further, the grease or lubricant utilized in and on air dampers or valves may become sticky or less lubricous and the mechanical damper or valve may generate resisting torque contrary to the movement of the actuator motor. Also, the air damper and valve may oxidate (rust) over time and such oxidation further restricts the movement of the air damper or valve. It is beneficial to develop a system which monitors the operational condition of the air damper actuator or valve actuator and, hence, all mechanical systems effected thereby.  
     OBJECTS OF THE INVENTION  
      It is an object of the present invention to provide an air damper or valve actuator system with an alarm feature for sensing indications of potential impending mechanical failure of the air damper or valve.  
      It is another object of the present invention to provide a distributed monitoring system for a plurality of actuators.  
      It is a further object of the present invention to provide an actuator system with an alarm feature which monitors an electrical power characteristic during the actuator motor&#39;s motive operation thereby triggering an alarm when a sensor exceeds a predetermined value.  
      It is a further object of the present invention to provide an actuator system which disables the alarm when the motor and the coupled air damper or valve reaches an operational end point (the physical limit of the air damper or valve).  
     SUMMARY OF THE INVENTION  
      The air damper or valve actuator system with an alarm may be part of a distributed monitoring system (communicatively linked to a central control station). The actuator system includes a motor coupled to the air damper or valve, an electrical power sensor for sensing an electrical power characteristic of the motor during the motor&#39;s motive operation of the air damper or valve and a threshold sensor. The threshold sensor determines and generates an alarm signal when the power characteristic exceeds a predetermined value during the motor&#39;s motive operation. An end point sensor is utilized to detect when the motor and coupled air damper or valve reaches a mechanical operational end point thereby disabling the alarm. The method for detecting and issuing an alarm indicative of potential impending mechanical failure includes sensing the power characteristic and determining and generating an alarm when the power characteristic exceeds a predetermined value before the motor driven actuator reaches a pre-set mechanical end position. The distributed system monitors a plurality of actuator systems and utilizes a central control station. Each actuator system, as part of the distributed system, generates and transmits its respective alarm signal to the central control station when the power characteristic exceeds a predetermined value during the motor&#39;s motive operation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Further objects and advantages of the present invention can be found in the detailed description of the preferred embodiments when taken in conjunction with the accompanying drawings in which:  
       FIG. 1  diagrammatically illustrates an actuator system mechanically coupled to an air damper as part of an HVAC system;  
       FIG. 2  diagrammatically illustrates a valve actuator coupled to a valve in a hydraulic system;  
       FIG. 3  is a system diagram showing a distributed system for monitoring a plurality of actuator systems;  
       FIG. 4  diagrammatically illustrates one embodiment of the actuator system components in a schematic format;  
       FIG. 5  diagrammatically illustrates another embodiment of the actuator system in schematic form;  
       FIG. 6  diagrammatically illustrates a sensor detecting an operational end point position of the actuator coupler (the coupler ultimately connected to an air damper or a valve); and  
       FIG. 7  diagrammatically illustrates an actuator deployed in a critical environment such as a laboratory ventilation hood. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The present invention relates to an air damper or valve actuator system with an alarm feature and a distributed system for monitoring a plurality of such actuator systems and methods for detecting and issuing alarms indicative of potential impending mechanical failure of the air damper or valve actuator systems.  
       FIG. 1  diagrammatically illustrates air damper actuator  12  (which includes a motor, not shown) coupled via coupling  20  to a mechanical linkage system (not shown) permitting vanes  14  to move and open and close the air duct  17 . The vanes dampen air flow through the duct. Air damper  16  is known by persons of ordinary skill in the art. Actuator  12  receives power control signals  18  from a command and control system usually located somewhere in the facility which houses the entire ventilation system, of which duct  17  is a part thereof.  
       FIG. 2  diagrammatically illustrates valve actuator  30  receiving power control signals  32 . Actuator  30  is mechanically coupled via coupling  36  to a valve  34 . Valve  34  controls fluid flow through hydraulic line  35 . Sometimes air damper actuator  12  and valve actuator  30  operate in critical environments or applications such as remotely disposed mechanical facilities or in conjunction with ventilation hoods handling hazardous chemicals and biologic aerosol agents. Other critical utilizations may incorporate air damper and valve actuators.  
      Further details of air damper and air valve actuators are found in U.S. Pat. No. 5,278,454 to Strauss, the content of which is incorporated herein by reference thereto.  
       FIG. 3  diagrammatically illustrates a plurality of satellite stations  21 ,  22 ,  23  and  24  which are communicatively linked to a central control station  26 . The communications system, one of which is communications link  28 , may include cellular telephone networks, land-line telephone networks, wide area networks established by multiple computer-server systems; Internet communications, orbital satellite communications or any other communicative links. In any event, satellite station  21  may include air damper  16  which is opened or closed based upon mechanical actuation by actuator  12 . Station  21  may include also hydraulic line  35  and an actuator valve control  30 . Of course, satellite station  21  may include multiple air dampers  16  and not include valve actuator  30 . Alternatively, multiple valve actuators may be deployed in any one of the satellite stations  21 - 24 . As discussed in detail later, upon detecting an impending potential mechanical failure, air damper actuator or valve actuator  12 ,  30  issues an alarm signal which is transmitted via communications link  28  to central control  26 . Central control  26  includes an alert system  29  which detects the alarm, identifies the particular valve or air damper actuator based upon identification data embedded in the communications data package and also identifies the particular satellite station which generated the alarm signal (also an embedded data signal). Alert system  29  then generates some type of supplemental alert which indicates to the operators at central control  26  that the air damper actuator or valve actuator is subject to potential impending mechanical failure. This results in the operators of central control  26  issuing preventive maintenance orders such that the air damper actuator or air damper or valve actuator or valve be replaced or maintained or cleaned to reduce or eliminate the potential impending mechanical failure.  
       FIG. 4  diagrammatically illustrates one embodiment of the alarmed air damper or valve actuator system. In the illustrated embodiment, controller  40 , which may be a digital control CPU or a programmable controller (a programmable IC), includes a memory sub-system  42 . Controller  40  accepts power control signals  18 ,  32  (not shown in  FIG. 4 ) from an exterior source and ultimately generates control signals which are supplied to signal conditioner SC  44 . Signal conditioner  44  converts the control signal from controller  40  into an appropriate power control signal which is supplied to motor M  46 . The mechanical output of motor  46  is typically applied to a gear system or at least applied to a coupler  48 . The output of coupler  48  is relayed to mechanical output element  50  which is ultimately mechanically connected to vanes  14  of air damper  16  in  FIG. 1  or to valve  34  illustrated in  FIG. 2 . In the illustrated embodiment, mechanical output element  50  is connected to a sensor  52  which generates a signal representative of the movement of mechanical element  50 . This representative movement signal (establishing the motive operation of the actuator motor) is applied to signal conditioner  54  and is ultimately applied to controller  40 .  
      The power or control signal supplied to motor  46  is monitored by feedback monitor line  56 . Signal conditioner  58  changes and modifies the monitor signal, representative of an electrical power characteristic of motor  46 , and the resulting signal is applied to controller  40 . In a preferred embodiment, the current supplied to motor  46 , represented by current symbol i, is monitored by controller  40 .  
      It should be appreciated that although a digital system is discussed herein in connection with controller  40 , persons of ordinary skill in the art could produce an analog system having the same operational characteristics and functional elements as described in conjunction with the controllers illustrated in  FIGS. 4 and 5 .  
      In operation, controller  40  receives control signal from another command and control module (not shown) as is known to persons of ordinary skill in the art. Upon receiving the appropriate power, command and control signal, controller  40  issues an appropriate power control to signal conditioner  44 . Signal conditioner  44  in a digital environment converts the digital power control signal into a generally analog power control signal and that signal is applied to the input of motor  46 . Motor  46  is then turned ON and the motor motivates or moves output shaft  47  and gear or coupler system  48  and mechanical output  50  and ultimately vanes  14  in air damper  16  or valve  34  associated with hydraulic line  35 . Sensor  52 , mechanically attached to mechanical output element  50 , senses the movement of element  50 , and generates a signal ultimately passing through conditioner  54  and to controller  40 . At the same time (or relatively the same time), controller  40  monitors an electrical power characteristic, typically current i, applied to motor  46  based upon feedback monitor line  56 . It is well known that, with respect to DC motors (typically utilized in air damper actuators and valve actuators), when the motors stop rotating due to excessive counter rotational torque applied to output elements  47 , 50 , the power consumption of the motor, particularly current i, increases. This increase is sensed by controller  40  as captured by feedback monitor line  56 . When the motor stops due to excessive counter rotational torque caused by the sticky damper or valve, the motor is placed in a “stall” condition. In a stall condition, the current i consumption of a motor greatly increases. Various electrical characteristics of the motor may be monitored to detect such stall condition.  
      Typically during normal operation, at maximum load, motor  46 , as an example, may utilize 35 ma. Other motors use different amounts of current and are subject to different threshold levels. In a stalled condition, the typical 35 ma motor may utilize or draw 150 ma (a measure of current i). Further, it is typical that these types of motors may include an electronic or electrical control limiter which limits the supply current to a certain maximum value. As an example, 85 ma may be the maximum input current permitted by the electric control limit system. Since it is known that when the motor comes close to a stall condition, current consumption greatly increases, controller  40  includes a threshold sensing circuit or program function monitoring the feedback current i from line  56  such that when the current exceeds, in the example discussed herein, 75 ma, an alarm signal is generated. Upon detection of the alarm signal and if sensor  52  is still detecting rotational movement on mechanical output element  50  (the motor&#39;s motive operation), control  40  issues an alarm signal which is sent to the communication system. Controller  40  may supply an alarm signal to another transmitter and the transmitter may utilize communications link or channel  28  ( FIG. 3 ) to communicate with central control  26 . Alternatively, the alarm signal could be stored in the local command and control system and satellite station  21  and then, upon batch processing of data (that data) indicating the particular actuator subject to the impending mechanical failure alarm plus a data representing the satellite station plus any other additional operating data from the satellite station) may be transmitted in a batch communication session to central control  26 . Central control  26  decodes this batch communication, identifies the particular satellite station subject to the alarm, identifies the particular actuator subject to the alarm and generates the appropriate preventive maintenance report. The preventive maintenance report is delivered to personnel who place the satellite station and the particular actuator on a preventive maintenance list which, in the near future, results in service to the particular air damper or valve that is subject to the potential impending mechanical failure. Such service may include cleaning, repair, replacement or readjustment of the air damper, the valve or the actuator. Alternatively, memory  42  may store the impending failure signal and, when polled by a local unit in the satellite station  21 , may upload this impending failure signal to station  26 .  
      Memory  42  is utilized to store data, such as actuator id data, and particularly the predetermined threshold value which triggers the alarm signal. The threshold value at which an alarm is generated may be pre-set by the factory or may be set by the installer. Typically, factory settings are utilized.  
      The term “impending failure” is used because it is believed that the excessive feedback power signal will be indicative of a soon to fail mechanical system. However, at a minimum, the alarm system senses a failed damper or valve (one that refuses to open or close to the pre-set position).  
      Sensor  52  in a preferred embodiment is a potentiometer or variable resistor that outputs a variable electrical signal based upon rotational movement of mechanical output element  50  coupled thereto. Other types of sensors sensing rotational movement may be utilized. Also, sensor  50  could be connected directly to the output shaft  47  of motor  46 . Further, sensor  52  could be located anywhere along the drive chain from motor  46 , shaft  47 , gear or coupler  48  and mechanical output element  50 . Other types of sensors could be utilized.  
      The reason for utilizing sensor  52  or any other type of operational end point position sensor is as follows. Motor  46  generally drives the output system  47 ,  48 ,  50  and ultimately air damper  16  or valve  34  to a mechanical end point (either full open or full close or some other mechanically set position). Motor  46  continues to drive the system even beyond the mechanical end point reached by air damper  16  and valve  34 , generally as a safety factor (the overdrive is a safety factor). Hence, when the air damper or valve reaches its mechanical end point position, motor  46  is still running. The motor then transitions into a stall condition (or near stall condition) and current on the power control line increases as is common in a stall condition. Control  40  must be able to discern or determine when motor  46  has driven the air damper or valve to its required end point position in contrast to a stall condition when the motor is attempting to move or motivate the air damper at an intermediate position. At intermediate positions, the motor is positively driving or operating the air damper or valve. Since these air dampers or valves are customarily located in remote locations either in large buildings or hidden under ventilation chemical hoods or in satellite stations remote from central control positions, the air dampers and valves or not regularly cleaned and relubricated. Therefore, the air dampers tend to get sticky and may ultimately not open or not close as designed by the engineer. The same is true regarding valves. Therefore, since the actuator motors drive the air dampers and the valves beyond the standard or pre-set mechanical end point, control  40  has to determine when the actuators reach the pre-set mechanical end point as distinct from the stall condition obtained when the actuator is in a potential impending mechanical failure mode. In other words, the stall condition during impending potential mechanical failure occurs prior to the time that sensor  52  senses the end position by the mechanical limits of the air damper or valve.  
      If sensor  52  is still moving (in a motive operation), as shown by the changing electrical condition (voltage, current or resistance) on the feedback line fed through signal conditioner  54 , and the current i monitored by feedback monitor line  56  exceeds the alarm trigger threshold, and control  40  issues an alarm signal. If the position sensor  52  indicates no movement and, thereafter, current i from feedback line  56  approaches and exceeds alarm trigger threshold, the alarm is disabled (or the controller ignores the alarm (end position sensor overrides alarm)) because controller  40  has detected that mechanical output element  50  is at the mechanical limit for the air damper or valve actuator.  
      It is possible, although not recommended, that a timer may be utilized by control  40  rather than a position sensor  52 . The timer will time the amount of time necessary to close the air damper or valve. Excessive feedback signals within the time cause an alarm whereas signals outside the time frame are ignored. Further, sensor  52  can be mechanically coupled to mechanical output element  50  or can optically sense the rotational movement of element  50  or utilize other type of electronic sensor system such as tachometers, accelerometers or items that have electromagnetic sensors. Further, an electromagnetic sensor may be attached or mounted to motor  46  to detect when the rotor of motor  46  stops movement. Memory  42  includes data specifically identifying the actuator and such data is attached or bundled with the alarm signal and sent to systems and communications link  28 . Controller  40  has programming elements or routines which carry out the functional tests outlined herein.  
      If the actuator control system in  FIG. 4  is configured as an analog system, signal conditioners  44 ,  54  and  58  may simply change the control signal into an appropriate value (for example, voltage into current) utilized by the analog controller  40  and the motor. Although memory  42  may be included in an analog version of controller  40 , the memory setting for the threshold value would simply be established by a resistance or a limit current or voltage sensor on an analog basis.  
       FIG. 5  diagrammatically illustrates another embodiment of the actuator controller. Controller  40  outputs a digital signal in  FIG. 5  and signal conditioner  44  includes a digital component unit  60  which is coupled, typically through optoelectrical transistors, to an analog power component unit  62 . Motor  46  is connected to analog power unit  62  in signal conditioner  44 . Monitor feedback line  56  is coupled to the analog power component unit  62 . One important feature of the present invention is that an electrical power characteristic of motor  46  is monitored and such monitoring occurs on or with respect to a power input ultimately supplied to motor  46 .  
       FIG. 6  diagrammatically illustrates actuator  12  and coupler  20  with a position sensor switch SW  64 . Position sensor switch SW  64  is a sensor detecting a physical operational end point position of coupler  20 . The output of switch  64  is applied to controller  40  as discussed earlier in connection with  FIGS. 4 and 5 . When coupling  20  reaches a certain arcuate position, switch SW changes state OFF/ON.  
       FIG. 7  diagrammatically illustrates a critical application of actuator  80 . In the illustrated embodiment, actuator  80  opens and closes air damper  82  (or position it to a pre-set location) which damper is intermediate duct  84  and miscellaneous vent elements area  86 . Hood system  90  is utilized by its operators such that noxious or hazardous fumes are controlled within hood area  92 . Various other vent elements, such as sprayers, fans, vanes and vents may be positioned in elements area  86 . Actuator  80 , upon issuance of the alarm as explained above in connection with  FIGS. 4, 5 , sends the alarm to a central control unit in the event of impending mechanical failure. This alerts the operators and the monitoring personnel at central control of an impeding mechanical failure or the possibility thereof at actuator  80 . Further, the alarm may be issued to the operator utilizing hood  90 . This local alarm may require the operator to stop using the hood. Of course, hood  90  may use an alarmed valve actuator.  
      The claims appended hereto are meant to cover modifications and changes within the scope and spirit of the present invention.