A pneumatic controller for controlling a device.
Original Assignee: Veris Industries, LLC
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional App. No. 60/641,983, filed Jan. 7, 2005.
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic controller.
Pressure transducers typically include at least first and second pressure ports. The first pressure inlet port is normally attached to a high pressure inlet line and the second pressure port is normally attached to a lower pressure outlet line. The pressure transducer receives an input signal indicative of the desired output pressure. The pressure transducer is intended to provide the desired output pressure with little flow between the input and output pressure lines. The transducer may include a single diaphragm or other sensor element affected by the input pressure and input signal to provide the desired output pressure, or it may include two separate pressure transducers.
Such pressure transducers are most commonly provided as a stand-alone device. Installation in the field may require two or more individuals, namely, an electrician to run the electrical lines and a plumber or pipe-fitter to run the fluid lines. Additionally, the plumber or pipe-fitter may install an isolation valve on the high pressure input line. The isolation valve can be closed to close off or “isolate” the high pressure line from the pressure elements.
Pressure transducers assemblies may incorporate both the transducer(s) and the isolation valve assembly as a single product, and thus require less field installation time. In particular, the connections made between the isolation valve and the pressure transducer(s) may be made as a manufacturing step for the assembly rather than in the field.
In many cases, input control signals are provided from a remote controller using a voltage signal, current signal, or digital input signal. In this manner, the output pressure may be remotely controlled. In order to control the pressure transducer and thus the output pressure, the controller is programmed with suitable instructions to provide the desired input signals at the desired times.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 illustrates a pneumatic controller.
FIG. 2 illustrates a pneumatic controller with a cover.
FIG. 3 illustrates a pneumatic cover.
FIG. 4 illustrates a pneumatic transducer.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
A traditional pneumatic transducer provides an industry standard 0-20 PSI or 3-15 PSI output pressure range. The pressure may be with reference to an absolute value, such as a vacuum or known pressure, or otherwise relative to another variable pressure (e.g., differential pressure). Selecting between 0-20 PSI or 3-15 PSI is normally selectable by the installer with a set of jumpers. In some environments, such as when the pneumatic controller needs to position a damper, the damper may have essentially no movement from 0 to 8 PSI because of internal friction. Then from 8 to 15 PSI the damper has movement across its full range of motion, and from 15 to 20 PSI the damper has exceeded its movement range and thus no movement of the damper occurs. Accordingly, in order to accommodate the actual movement of the damper the pneumatic controller or a control system associated with a pneumatic transducer is programmed to use a range of 8 to 15 PSI for the damper. Unfortunately, using a reduced range reduces the resolution with which the pneumatic transducer may be controlled and requires extra time and expense to properly program the system, which is prone to error.
Referring to FIG. 1, to reduce one or more of these concerns, the preferred pneumatic controller 10 includes an adjustable lower set point adjustment 12 and an adjustable higher set point adjustment 14 for the range of output values to be provided. The pressure set points are illustrated on a display 16 integral to the pneumatic controller 10 so that the installer may view the values as they are adjusted. Accordingly, the installer may adjust the lower set point while viewing the lower pressure setting value on the display 16, and the installer may adjust the higher set point while viewing the higher pressure setting value on the display 16. In this manner, the installer may readily set the pressure range while viewing the values on the display in an intuitive manner. Also, the resolution of the range defined by the higher and lower settings is preferably greater than the resolution that would be available if the settings remained at the maximum range. In other words, there may be a finer gradation in the available output levels within the smaller defined range that would be available in the same range if the settings remained at the maximum range. The operation of the pneumatic controller 10 is controlled by a processor 20.
In operation, the pneumatic controller 10 receives a standard input signal, such as 0 to 10 volts, or 4 to 20 ma, from a controller 21. The processor 20 converts the input signal to control an associated transducer 23 for a desired output pressure 22 using the defined mapping. In this manner, the controller 21 may be programmed in a normal manner with a full signal range used to define the full range of the device being controlled using the internal mapping. Moreover, the mapping is performed by the pneumatic controller 10 which permits multiple different controllers 21 to operate the same device, without customizing the programming at each controller 21.
A pair of alarm contacts 28 may be included which provide a normally open condition when no power is applied to the controller 10 or when in an alarm state occurs. The alarm contacts are closed in normal operation. In addition, the alarm function may include an automatic mode and a manual mode, where the alarm contacts 28 are open when the alarm function is in the manual mode. The manual mode of operation permits the installer to control the transducer 23 locally for configuring the device and for over-riding the centralized controller 21. However, in the event that the installer forgets to turn the device off from manual mode, then an alarm condition will be activated, so that the installer is reminded that the device is in manual mode. The alarm contacts 28 will close in the automatic mode (normal operation). Also, a pressure loss alarm 26 may be included in the same device to provide an output when the branch pressure 22 is reduced below a predetermined level, such as 20% below the desired pressure for a period of 2 minutes. The pressure alarm 26 is indicated by opening the contacts, which are normally closed. The controller 10 includes both capabilities, which are either both simultaneously enabled or jumper selected in the alternative.
The controller 10 may include a set of colored light emitting diodes 30, such as green and red, to provide an indication of the operational status of the device. The colored light emitting diodes 30 may blink to provide an indication of the status.
Slow green with one fast red
Manual mode alarm active (contacts
Slow green with two fast reds
Pressure loss alarm active (contacts
Device not in operate (run) mode
Two fast reds
Device not in operate (run) mode and
alarm (contacts open)
Three fast reds
Over voltage or over current fault
Four fast reds
Over pressure on branch side
Referring to FIG. 2, the controller 10 may include a plastic cover 40. The plastic cover 40 may include a dual elevational profile having a raised portion 42 and a lower portion 44. The installer observes the display 16 through the lower portion of the cover 40. The cover 40 protects the device from the environment, but obscures clearly difficult observing the light emitting diodes 30 and the display 16 through the cover 40. Referring to FIG. 3, the lower portion of the cover 40 may include a window 50 that is more transparent the adjoining material. In this manner the display 16 may be readily observed while tending to protect the remainder of the controller 10 from undesirable light. In addition, a light pipe 60 of plastic material may be included from the lower surface of the cover 40 to a location proximate the diodes 30 so that the diodes are more readily observable by the light being directed by the light pipe 60 to the exterior surface of the cover 40.
Typically a pneumatic controller 10 receives control signals and in response thereto provides an appropriate output pressure 22. In the event of a problem an alarm condition is not indicated to the controller 21 from the pneumatic controller 10 the controller 21 presumes that the pneumatic controller 10 is functioning properly. In order to have additional confidence that the pneumatic controller 10 is functioning properly, a redundant analog output signal 35 in the form of a 4-20 ma signal or 0 to 10 volt signal may be provided representative of the output pressure 22. In this manner the controller 21 may have an additional indication of whether the pneumatic controller 10 is functioning properly.
Referring to FIG. 4, the pressure transducer 23 needs to ‘bleed’ off excessive air into the atmosphere during its normal operation. While this is a simple matter, this tends to result in excessive noise which is troubling to some installers and use in quiet environments. To reduce the noise levels, the pressure transducer 23 may include a small chamber 70 which acts to muffle the air. A small opening 72 in the small chamber 70 then bleeds the air into the atmosphere or otherwise the region under the cover 40.
The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.