Fluid handling – Self-proportioning or correlating systems – Supply and exhaust type
Reexamination Certificate
2003-04-11
2004-08-10
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Self-proportioning or correlating systems
Supply and exhaust type
C137S270000, C137S596170
Reexamination Certificate
active
06772784
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates, generally, to pressure regulators and, more specifically, to a proportional pressure regulator having the capability to deliver both negative and positive pressure, as well as providing a system exhaust.
2. Description of the Related Art
Pressure regulators are well known in the art and are employed in numerous environments to regulate a pneumatic supply pressure down to a predetermined system pressure. The system pressure is then supplied to operate various pneumatically actuated devices. In the past, a regulated system pressure was achieved through the use of a purely mechanical arrangement within the regulator, often with the assistance of a pressure feedback line returned to the regulator from the output side.
Some types of pneumatic systems still utilize mechanical regulators where course regulation and/or large volume pneumatic control is involved. However, where accuracy and fine regulatory control of pneumatic system pressure is required, regulators have rapidly evolved. The current state of the art provides pressure regulators that include an electrically controlled actuator, most often a solenoid, to regulate the output pressure. Pressure feedback is also utilized for more responsive control. In this case, a transducer may be employed to sense pressure and convert it to an electrical signal that is used by a feedback control circuit to assist in regulating the output. In this manner, the system pressure is regulated about a predetermined setpoint using feedback measurements from the particular process involved or the downstream output pressure.
Regulators of this type are well known and are sometimes referred to in the related art as proportional pressure regulators. The term “proportional” is used in the sense that if a difference is measured between a desired predetermined output setpoint and the actual downstream pressure, then the regulator changes, and thereby controls, the output pressure in “proportion” to that difference. Refinements in proportional regulators have included the use of digital circuits that have the capability to employ sophisticated control algorithms to more precisely control the regulator. The proportional pressure regulators with digital electronic control circuits use the feedback signal to electronically determine a difference or “error” between the desired output pressure setpoint and the actual output pressure.
More sophisticated digital control circuits use a control algorithm along with other system inputs to generate an overall control or scheme that operatively controls the regulator to adjust, or vary, the output pressure in an attempt to resolve the “error” and return the output to the predetermined setpoint. These known digital control schemes often employ complex calculations for error resolution, as evidenced in U.S. Pat. No. 6,178,997 B1 to Adams et al, which discloses an “Intelligent Pressure Regulator”. The Adams '997 regulator has a PID (proportional-integral-derivative) controller that calculates the mathematical integral and derivative of the proportional error and employs the results of these calculations in its control algorithm. A PID controller uses the current value of the error to calculate both the integral of the error over a recent time interval, and the current derivative of the error signal. The PID controller then sums the error with the results of these calculations to determine not only the required amount of adjustment necessary, but also the duration of the adjustment to avoid overshoot of the setpoint.
Proportional pressure regulating devices have evolved to include regulating systems for advanced applications that require complex pressure sensing and monitoring, and equally complex regulating schemes. These pressure regulating systems have the capability to not only produce an accurate regulation of a constant predetermined setpoint, but to also respond to system sensors and dynamically vary the pressure setpoint and regulate the system pressure to it, even as the setpoint changes during the operation of the process. For example, regulator systems of this type may be employed in connection with devices used to polish the surface of semiconductor wafers. A polishing pad is pneumatically controlled so as to apply a predetermined force to the surface of the semiconductor wafer during the polishing process. In these circumstances, it is desirous to maintain a certain predetermined downward force of the polishing device to the wafer surface, while countering various dynamic physical effects that make the applied downward force a constantly varying value.
In some other particular processes and working environments, it is further desirable to have a pressure regulating system that not only has variable setpoint proportional regulation for control of system pressure in a positive pressure range, as described above, but one that also has variable setpoint proportional regulation to control system pressure in the negative (vacuum) pressure range. For some processes, this can offer greater accuracy of pneumatic control by providing a variable pressure setpoint of the system pressure that can be readily moved between positive and negative supply pressures for any given active device. For example, the highly precise manufacturing process involving the polishing of silicone wafers for use as integrated circuit chips, as well the polishing processes for disk media, such as CDs, DVDs, and the like, often use both negative and positive regulated pressures to operate and control the various precision mechanisms involved. U.S. Pat. No. 5,716,258 to Metcalf and U.S. Pat. Nos. 6,203,414 and 6,319,106 to Numoto disclose devices for use in silicone wafer polishing processes that rely on variable and precisely regulated positive and negative pressures to provide extremely fine control of the polishing procedure.
In applications such as these, the pressure regulating system must control each active pneumatic component in both positive and negative pressures. Systems known the related art require separate proportional regulator valves to effect control in both positive and negative pressures. The separate proportional regulators are each distinct and are selectively employed remote from one another. Thus, for each active pneumatic device, the separate regulators must be incorporated at various positions relative to one another in the system and must be interconnected via conduits or other flow passages. Additionally, the positive and negative regulators each have a separate electronic control circuitry, operatively connected to each other, to coordinate the positive and negative pressure regulating functions. While these separate components have generally worked well in the past, there remains an ongoing need in the art to simplify pneumatic systems and thereby lower costs of manufacture and/or assembly by eliminating separate components, shortening flow paths and thereby reducing related hardware.
The disadvantages apparent with the conventional complexity of these positive and negative pressure regulated systems are further compounded when efforts have been made to increase the accuracy in these systems. Specifically, while variable setpoint proportional regulation of the positive and negative system pressures is an effective control means for some process applications, the response times and accuracy of control can be further enhanced by additionally providing an exhaust, or vent capability to the pneumatic regulating scheme.
U.S. Pat. No. 6,113,480 to Hu et al discloses a wafer polishing apparatus that uses negative and positive pressure with an exhaust vent to control the polishing procedure. The use of an exhaust vent, as in the Hu '480 patent, decreases the response time of the pneumatic regulating circuit by providing a rapid and almost instantaneous reduction or complete removal of the supplied pressure when needed. This allows for very fast control changes from one pressure to the other, as in the case of changing from a regulated p
Jones Thomas R.
Khan Zafar A.
Bliss McGlynn P.C.
MAC Valves, Inc.
Michalsky Gerald A.
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