Telephonic communications – Telephone line or system combined with diverse electrical... – Remote indication over telephone line
Reexamination Certificate
1998-09-30
2003-03-04
Woo, Stella (Department: 2643)
Telephonic communications
Telephone line or system combined with diverse electrical...
Remote indication over telephone line
C379S102010, C340S679000
Reexamination Certificate
active
06529590
ABSTRACT:
BACKGROUND OF THE INVENTION
The present application relates generally to systems and methods for remotely controlling and/or monitoring one or more machines, usually compressors, such that each machine's electronic control system can be assessed by an operator from a remote location using modem communications software, presently preferably, resident on a personal computer (PC) at the remote location. More specifically, it relates to systems and methods for the remote diagnosis of compressor system operating problems. Most specifically, it relates to systems and methods for providing communications through transmissions over a communications link established through a modem from a remote PC to a modem connected to the electronic control system of a compressor to provide instructions to or receive information from the compressor electronic control system.
Rotary screw compressors, such as the compressor disclosed in U.S. Pat. No. 4,435,139, have long been used to provide compressed air in industry. Such rotary screw compressor typically comprises two rotors mounted in a working space limited by two end walls and a barrel wall extending there between. The barrel wall takes the shape of two intersecting cylinders, each housing one of the rotors. Each rotor is provided with helically extending lobes and grooves which are intermeshed to establish chevron shaped compression chambers. In these chambers, a gaseous fluid is displaced and compressed from an inlet channel to an outlet channel by way of the screw compressor. Each compression chamber during a filling phase communicates with the inlet, during a compression phase undergoes a continued reduction in volume, and during a discharge phase communicates with an outlet.
Rotary screw compressors of this kind are often provided with valves for regulating the built-in volume ratio for the capacity of the compressor. When continued regulation is required, slide valves are often used, however, with other regulation needs, it is sufficient to use bypass valves. Such bypass valves are mounted in the barrel wall of the compressor or may be mounted in one of the end walls and in this regard, normally in the high pressure end wall. A bypass valve arrangement of this general type is shown in U.S. Pat. No. 4,453,900 issued Jun. 12, 1984. However, the opening of the bypass valve is directly dependent upon the compression spring as well as the internal pressure of the compressor. The opening and closing of this type of valve is unreliable due to friction, corrosion and other environmental factors which often derogate the positioning this type of bypass valve. Further, while the face of the valve element takes on the approximate shape of the barrel, the valve element is separately formed by casting or other process within predetermined tolerances. In order to economically manufacture such valve elements, the tolerances must be some what relaxed which may result in the leakage of pressurized fluid between compression chambers thereby degrading the efficiency of the compressor.
It is known that these compressors may be controlled by electronic circuits, such as those disclosed in U.S. Pat. Nos. 4,336,001 and 4,227,862 to Andrew et al., which show electronically controlled startup and shutdown routines and control of a bypass slide valve to vary compressor output to maintain pressure at a selected setpoint.
U.S. Pat. Nos. 4,519,748, 4,516,914, and 4,548,549 to Murphy et al. and U.S. Pat. No. 4,609,329 to Pillis et al. show additional electronic control systems for compressors. However, the operating modalities of these systems are primarily designed for refrigerant compression.
U.S. Pat. No. 4,502,842 to Currier et al., assigned to Colt Industries Operating Corp., shows a single electronic control system which can be connected to control a plurality of variably sized compressors. The system gathers data on the operating characteristics of the controlled compressors during a calibration phase and then uses this information to load and unload the compressors during operation, maintaining a preset pressure which can be programmed to vary with time. High and low pressure set points are programmed into the electronic control system and the compressors are selective loaded and unloaded in a predetermined sequence. However, centralized master controllers of this type represent a single point of failure for the entire pressurized air system, and are lacking in versatility since they provide only a limited selection of control modalities.
U.S. Pat. No. 4,335,582 to Shaw et al. shows a system for unloading a helical screw compressor in a refrigeration system. A slide valve is connected so that upon compressor shutdown, the slide valve is automatically driven to a full unload position. This operation is accomplished with air pressure rather than with an electronic control system.
None of the electronic control systems described above provide a complete and versatile solution to the control and maintenance problems experienced when operating one or more compressors in a variety of facility installations with a variety of air storage capacities. In fact, the networking capabilities and choice of operating modes in prior art systems of the type described above, and the ability of the control systems to provide reliable local and remote real-time operating parameter monitoring and remote real-time operating parameter adjustment to respond to actual operating conditions are quite limited.
Compressed air is a fundamental energy source required in most industrial manufacturing facilities. The location and maintenance schedule of the compressors that provide the compressed air is not usually very well thought out. The compressor is usually located in some dark corner of the facility or in a remote building. Maintenance is, in many cases, only performed on the compressors if the air pressure in the facility begins to fall. Thus, one significant problem with almost all air compressor installations is ease of monitoring the compressor to determine when and what maintenance might need to be performed. Another significant problem with almost all air compressor installations is the need for a local operator to monitor the compressor and to input control commands into the compressor electronic control system.
One possible approach to eliminating the monitoring, control and maintenance of compressed air facilities is to have a distributor provide a turnkey facility compressed air system to the facility and to assume all monitoring, control and maintenance responsibilities therefore. By installing a turnkey facility compressed air system, local facility management would turn over complete responsibility for compressed air to the distributor including everyday monitoring, operational control and maintenance of the facility compressed air system.
However, unless there is some way to monitor and control the compressors of the facility compressed air system from a remote location, a distributor would have to hire personnel to be on site with the compressors 24 hours a day, 7 days a week. This constant present would be expensive and may result in the assumption of such responsibility of the facility compressed air system by the distributor being cost prohibitive. Therefore, it would be desirable to develop systems and methods for remotely monitoring and controlling the operation of a facility compressed air system so that the responsible personnel are not required to be on site with the compressors 24 hours a day, 7 days a week.
In situations, such as, for example, missile launch pads, where it is impractical or impossible to have a local operator located with the compressors to monitor the compressor installation and to input control commands into the compressor electronic control system, it is vitally important for launch officials to know if the compressed air source at each launch pad is running or available to run during the launch process, if needed. Typically, a number of backup compressors are positioned at each launch pad that can provide compressed air in the event of
Coltec Industries Inc.
Harrington John M.
Kilpatrick & Stockton LLP
Woo Stella
LandOfFree
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