Venturi flow sensor

A venturi flow sensing method, system, and apparatus. A tube or chamber may be tapered from a larger to smaller diameter to create a venturi region within the tube or chamber. The venturi region causes a local increase in flow velocity. The change in velocity creates a local change in pressure which is, in turn, used to drive flow through a parallel bypass tube or chamber. Inside this bypass, a flow sensor can be located, and in some cases, a pressure sensor as well. The flow is then either exhausted back into the original tube or the bypass tube may alternatively dead end. In either case, flow can be measured without causing a significant overall pressure drop in the system.

TECHNICAL FIELD

Embodiments are generally related to flow sensors. Embodiments are also related to the measurement of airflow and pressure. Embodiments additionally relate to the flow sensors utilized in medical applications.

BACKGROUND OF THE INVENTION

Medical devices such as ventilators and CPAP (Continuous Positive Airway Pressure) machines are designed to provide air to a patient to foster correct breathing. A ventilator, for example, is designed to move air in and out of a person's lungs to assist breathing mechanically (e.g., a life support machine). A similar device is a respirator, which is used to assist or control breathing. Other similar machines facilitate breathing in persons with an impaired diaphragm function. These and other mechanical breathing devices often require a significant pressure change in order to accurately measure airflow. Such pressure changes, however, are often uncomfortable for the patient and do not promote optimal fan performance.

Flow rate control is a key to maintaining the comfort of the patient and proper working order of the mechanical breathing device. The ability to control flow to a patient, during the operation of such mechanical devices, is critical not only during surgical procedures but also during routine medical operations and patient bed rest, particularly with patients who suffer from lung and/or heart disease.

Other devices, such as electronic flow controllers, may be utilized to maintain flow rate control. These types of devices, however, are often expensive. Many hospitals and medical facilities cannot afford or do not have access to such expensive machines. Generally, air flow sensing techniques require an adequate pressure drop in order to sense air flow. It is therefore believed that a solution to these problems involves the implementation of inexpensive yet efficient devices and components for the detection of flow. The embodiments disclosed herein address this problem by providing an improved flow sensor system, method and apparatus

BRIEF SUMMARY OF THE INVENTION

It is therefore, one aspect of the present invention to provide an improved flow sensor method and system.

It is another aspect of the present invention to provide an improved method and system for sensing flow without causing a significant global pressure change.

It is yet another aspect of the present invention to provide an improved method and system for sensing flow in mechanical breathing machines without inducing a pressure change which may be uncomfortable to the patient and detrimental to the operation of the machine.

The aforementioned aspects of the invention and other objectives and advantages can now be achieved as described herein. A venturi flow sensor method and system are disclosed herein, which offers the ability to measure the flow rate through a chamber or tube without creating a significant system wide pressure change. The venturi flow sensor is generally configured from a main chamber, including a tapered venturi region, and a parallel bypass flow chamber connected to the main chamber by a tap. The venturi region creates a local increase in flow velocity, which in turn creates a local change in static pressure. This change can be utilized to drive flow through the bypass flow chamber, where a flow sensor is used to measure flow. Although a localized pressure change is created, the overall pressure drop in the system is very low.

DETAILED DESCRIPTION OF THE INVENTION

The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment of the present invention and are not intended to limit the scope of the invention.

FIG. 1illustrates a side view of one embodiment of a venturi flow sensor100, which can be implemented in accordance with a preferred embodiment. Venturi flow sensor100consists of a cylindrically enclosed flow chamber118and a bypass flow chamber114connected to the cylindrically enclosed flow chamber118via taps108and110. Cylindrically enclosed flow chamber118may be composed of three separate segments. Flow chamber118's first segment102has a larger diameter than the last segment104. In between segment102and104is a tapered venturi region106which tapers from the larger diameter of segment102to the smaller diameter of segment106. This segment causes a venturi effect in cylindrically enclosed flow chamber118when a fluid is run through the chamber. In addition, within bypass flow chamber114is flow sensor116. Notice that in this embodiment, tap108exhausts back into cylindrically enclosed flow chamber118downstream from venturi region106.

A venturi is a region within a pipe, tube, or chamber where the diameter of the pipe is decreased from a larger to smaller diameter. The constriction in the pipe causes the local flow velocity to increase and creates a localized pressure change. Thus, the pressure change created by the increase in flow velocity can be used to drive flow through a bypass channel.

In a preferred embodiment of the present invention a micro-electromechanical system airflow sensor will be used as flow sensor116. Micro-electromechanical system or “MEMS” devices are ultra-small in scale and used in a wide variety of ways. Most MEMS components range in size from micrometers to several millimeters. MEMS components may be used as gyroscopes, accelerometers, as well as a sensor of various physical phenomena. MEMS components are most often constructed of silicon, polymers, or metals and are generally constructed through deposition of thin film deposits.

In an alternative embodiment, flow sensor116can be implemented as any other sufficiently small airflow sensor. Examples of sensors that may serve such a purpose are vane meter sensors, hot wire sensors, or membrane sensors. These are intended only as examples of air flow sensors capable of serving the intended purpose. Any other sufficiently configured airflow sensor may also be used.

FIG. 2illustrates a venturi flow system200, which can be implemented in accordance with an alternative embodiment. Venturi flow system200includes a cylindrically enclosed flow chamber406connected to bypass chamber114via taps110and202. Cylindrically enclosed flow chamber406is comprised of three separate segments. The first segment102has a constant diameter. In the venturi segment402the initial larger diameter of the first segment102, is tapered down to a minimum diameter and then increased back to the initial diameter of the first segment102. The third segment404is thus returned to the initial larger diameter of the first segment102.

Note that inFIG. 2, tap202can exhaust bypass flow chamber114into cylindrically enclosed flow chamber406at the venturi region402. Note that inFIGS. 2-6herein, identical or similar parts or elements are generally indicated by identical reference numerals.

FIG. 3illustrates a venturi flow system300, which can be implemented in accordance with an alternative embodiment of the invention. Venturi flow system300consists of a cylindrically enclosed flow chamber406and a bypass chamber114connected to the cylindrically enclosed flow chamber406via taps108and110. Bypass chamber114is equipped with flow sensor116. Notice tap108exhausts bypass chamber114down stream from the venturi segment402. In a preferred embodiment, flow sensor116is implemented as a MEMS flow sensor, but any suitable flow sensor may be utilized.

FIG. 4illustrates a side view of a venturi flow sensor400, in accordance with an alternative embodiment. Venturi flow sensor400consists of a cylindrically enclosed flow chamber118and pressure chamber414connected to the cylindrically enclosed flow chamber118via taps110and108.

Note that as depicted inFIG. 4, tap108exhausts pressure chamber414into cylindrically enclosed flow chamber118down stream from the venturi region106. In addition, this embodiment of venturi flow sensor400includes a pressure sensor204included in pressure chamber414. This allows a user to measure airflow of the system by correlating pressure difference to flow rate. Any number of commercially available pressure sensors may be used as pressure sensor204.

FIG. 5illustrates a side view of a venturi flow sensor500, which can be implemented in accordance with an alternative embodiment. Venturi flow sensor500includes a cylindrically enclosed flow chamber118and pressure chambers414and502, which both dead end. Pressure sensors204and206are included in pressure chamber414and502allowing for the measurement of airflow in the system.

FIG. 6illustrates a side view of a venturi flow system600that may be implemented in accordance with an alternative embodiment. Venturi flow sensor600consists of a cylindrically enclosed flow chamber406and pressure chambers414and602which dead end at pressure sensor204. Once again pressure sensor204is included in pressure chamber414and602allowing for the measurement of airflow of the system.

FIG. 7illustrates a side view of a venturi flow system700that may be implemented in accordance with an alternative embodiment.FIG. 7is an adaptation of venturi flow system600wherein pressure chamber602has been replaced by pressure chamber702. Venturi flow system700is designed such that tap108which services pressure chamber702is located downstream from venturi flow region402. As in venturi flow system600, pressure sensor204is included in pressure chambers414and702allowing for measurement of airflow of the system.

The embodiments and examples set forth herein are presented to best explain the present invention and its practical application and to thereby enable those skilled in the art to make and utilize the invention. Those skilled in the art, however, will recognize that the foregoing description and examples have been presented for the purpose of illustration and example only. Other variations and modifications of the present invention will be apparent to those of skill in the art, and it is the intent of the appended claims that such variations and modifications be covered.

The description as set forth is not intended to be exhaustive or to limit the scope of the invention. Many modifications and variations are possible in light of the above teaching without departing from the scope of the following claims. It is contemplated that the use of the present invention can involve components having different characteristics. It is intended that the scope of the present invention be defined by the claims appended hereto, giving full cognizance to equivalents in all respects.