Capacitive sensor for a flow control valve

A flow sensor for use downstream from a particulate media dispensing device is provided having an inlet to receive particulate media and an outlet to dispense the media. The flow sensor has an inlet portion with a funnel to direct particulate media towards a central axis. An axially mounted flow director is located downstream from the funnel to direct the media outwards towards a sensor portion. A capacitive sensor located in the sensor portion surrounds the flow director to create an annular flow path to measure the amount of media that passes through sensor rings in the sensor.

BACKGROUND OF THE INVENTION

This present disclosure relates to flow control valves that control the flow of particulate, such as is used in media blasting, shot peening, or other systems where the user desires to control the flow of different types of flowable particulate and sense the amount passing through the valve. Existing flowable particulate valves in the art suffer from complexity, manufacturability, and functionality issues. Most valves use a fixed orifice and a movable pintle that retracts to allow media to flow. The pintle is spring-loaded to bias it towards the closed position, creating issues for assembly and maintenance. The spring can wear, break, or become damaged, creating functionality issues. When actuated, the pintle can bounce, creating control problems. Another problem is having closed loop control of the valve by knowing exactly the amount of media that is being dispensed. Other designs use a deflected beam as a means to measure, while others use optical or other sensing technology. An improved valve with media sensing is needed.

Other applications utilize an upstream flow valve that lacks the ability to measure the flow of particulate. This can result in poor flow control in systems that lack a true measurement of the particulate flow. Some flow sensors rely on the displacement of an arm as the media drops down on to it, while others use a non-contacting sensor style. These sensors have difficulty in measuring flow, particularly as the type of media changes or when the flow stream is unpredictable (i.e. when it moves from side to side in the flow path). An improved flow sensor is needed.

SUMMARY OF THE INVENTION

The present disclosure describes a valve designed to regulate the flow of a particulate media. The valve has an inlet portion that funnels the particulate media down through the center of the valve. The inlet portion has repelling magnets and a shield. The shield reduces the magnetic field from the magnet that passes through the center of the valve. The inlet portion has a shuttle sleeve that carries the particulate media on the inside. Surrounding the outside of the shuttle sleeve is a movable shuttle. The shuttle has shuttle magnets and a magnetic shield that reduces the magnetic field from the magnets that passes through the center of the valve. The shuttle has a movable orifice attached to it that contacts a flow director. The flow director is located in the outlet portion and channels the media past a flow sensor to detect the amount of particulate being dispensed. A portion of the valve is made from a metal, such as brass or copper that interacts with the shuttle magnets to generate eddy currents when the shuttle is in motion. The eddy currents act to dampen the movement of the shuttle.

A capacitive flow sensor uses sensing rings in conjunction with a fixed flow director. The flow sensor uses a funnel portion near or at an inlet to direct flow towards the center. Located in the flow path after the funnel portion is the fixed flow director that directs the particulate outwardly towards the inside surface of the tube and therefore the sensing rings. The funnel and fixed flow director create an indirect and uninterrupted flow path that slows the flow of particulate and creates accurate sensing of particulate. The signal from the flow sensor can be used to regulate or control an upstream valve for particulate.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An electrically operated valve10is shown inFIGS. 1-8with an inlet12and an outlet14. The valve10is designed to regulate the flow of particulate media that is not ferro-magnetic. The particulate media is flowable, commonly a blasting media such as glass, plastic, aluminum oxide, or other particulate. In other words, particulate media made from steel or alloys of Iron are not commonly used with the valve10. The particulate media is loaded into the inlet12, commonly from a hopper or other storage vessel (not shown). The valve10is operable between an opened state and a closed state. The opened state allows particulate media to flow from the inlet12to the outlet14, while the closed state blocks the particulate media from flowing. The valve10can operate in positions between the open and closed positions in order to regulate the flow of particulate media.

The valve10has a tube20that is shown as a hollow cylindrical tube with a consistent wall thickness, but other structures are contemplated, such as a square, rectangular, or other elongate hollow component that allows a flow path. The inlet12is located near a top edge22and the outlet14is located near a bottom edge24. The tube20may be threaded at its ends or have a feature to allow it to attach to other containers, tubes, or devices. The valve10has a central axis16that is located at the center of the tube20. The tube20has an inside surface26where other components contact or seal against. The tube20in the embodiment described herein is formed from copper or a copper alloy, such as brass or bronze. The tube20may also be made from aluminum or other material that is electrically conductive or responds to a changing magnetic field.

A coil32surrounds the tube20that is also fixed with respect to the tube20. The coil32has windings34that generate a magnetic field when energized. The valve10may include a housing (not shown) that surrounds a portion of the tube20and includes controls, wiring, and circuit boards.

A funnel40is located adjacent the top edge22and is shown as centered about the central axis16. A seal42seals the funnel40to the inside surface26of the tube20. The funnel40has a wide open mouth with an inside surface44that narrows down to a cylindrical surface46. The inside surface44is conical in nature but the device is not limited to that shape. It is contemplated that the inside surface44of the funnel40is straight and any funnel or conical feature is externally located above the valve10. The funnel40may also be considered as an inlet portion. The funnel40is axially located in the tube20by a step surface45and includes set screws41that impinge against the tube20and prevent movement of the funnel40with respect to the tube20. The funnel40includes repelling magnets48that are equally spaced around the cylindrical surface46. The repelling magnets48are pressed into place or otherwise secured with adhesive or fasteners that prevents the magnets48from falling out or becoming loose. The funnel40is made from a non-magnetic material, such as plastic, aluminum, ceramic, or other material that does not short out or conduct the magnetic field from the repelling magnets48. The inside surface44and cylindrical surface46cooperate to direct particulate to the inside of a shuttle sleeve50. The shuttle sleeve50is a cylindrical tubular component, made from a non-magnetic material such as plastic or aluminum, with an inside surface52and outside surface54. The shuttle sleeve50is secured to the funnel40through a press fit, threading, or other attachment method that affixes the two components. The shuttle sleeve50is centered about the central axis16and has a terminal edge56that is opposite the open mouth. To maintain the coaxial position of shuttle sleeve50to the central axis16, a skirt surface58that is closely matched to the inside surface26of the tube20extends down from the open mouth to the top of the shuttle sleeve50. Adjacent the repelling magnets48is a funnel shield60that conducts magnetic field from the repelling magnets48to keep the magnetic field away from the inside flow path of the funnel40. Because ferrous or other particulates with magnetic attraction may pass through the flow path, a strong enough magnetic field in the flow path would create an undesirable buildup of these particles that would impede flow of the particulate media. The funnel shield60shunts the field to the point that ferrous or magnetic particles do not accumulate.

A shuttle70is located around the shuttle sleeve50and also centered about the central axis16. The shuttle70is hollow and slidable along the outside surface54of the shuttle sleeve50between an open position (shown inFIG. 4) and a closed position (shown inFIG. 3). The shuttle70has shuttle magnets72that are contained in a shuttle body74. The shuttle body74is made from a non-ferromagnetic material, such as plastic, aluminum, ceramic, or other material that does not short out or conduct the magnetic field of the shuttle magnets72, and includes a shuttle magnet shield76that is located adjacent the shuttle magnets72and closer to the central axis16. The shuttle magnet shield76shunts the magnetic field generated by the shuttle magnets72that could attract ferrous particles or other particles. The particles may be attracted to a magnetic field and build up on the shuttle sleeve50or the shuttle70, or get stuck between the shuttle body74and shuttle sleeve50. Extending from the lower portion of the shuttle body74and affixed thereto is a movable orifice78. The movable orifice78is a tubular component with a terminal sealing edge80, shown inFIG. 4. In the embodiment described herein, the movable orifice78is made from metal (such as aluminum), but other materials are contemplated. The movable orifice78includes a tapered surface82located on the inside that extends from the inside surface84. The media flows from the shuttle sleeve50and into the inside of the movable orifice78. The tapered surface82may include other features designed to modify the flow properties of the particulate media, such as channels, different angles, or additional surfaces. To remove the shuttle70for maintenance, cleaning, or exchange the movable orifice78, the user removes the funnel40and shuttle sleeve50and lifts the shuttle70out through the top of the tube20.

A fixed flow director90is affixed to the tube20near the bottom edge24and is also centered about the central axis16. The flow director90has a removable cone portion92with a replaceable seal93having a sealing surface94. The terminal edge56of the shuttle sleeve50is spaced above the sealing surface94and the two are a fixed distance apart. In the embodiment described herein, the replaceable seal93is made from steel, but other materials are contemplated. The sealing surface94is groove-shaped to receive and locate the terminal sealing edge80on the shuttle70. It is held between the cone portion92and the flow directing portion100, which may be press fit or threaded. The cone portion92, as shown, is tapered with a top and conical surface96,98. The cone portion92may be parabolic, curved, or straight, depending on the properties of the particulate media that may be used. The flow directing portion100has an outer diameter surface102. A mounting base104locates the fixed flow director90to be aligned with the central axis16and allows flow through it via arcuate apertures106. The cone portion92and sealing surface94is designed to mate with the movable orifice78and the terminal sealing edge80to open or close a flow path between the funnel40and flow directing portion100. The fixed flow director90is separable from the base104to allow different cone portion92and flow directing portions100to be exchanged for different desired flow properties of the particulate media. The flow director90may have a different shape than the flow director90shown inFIG. 3. The purpose of the flow director90is to direct media outwardly from a central region of the tube20and toward the inside surface26of the tube20. For instance, it is not necessary that the flow director90have a cone portion92. The flow directing portion100of the flow director90will prevent media from being located in the central region of tube20, which corresponds to areas of the tube26that adjacent to the central axis16of the tube26.

The absence of an applied magnetic field from the coil32, gravity, and the repelling magnets48result in the shuttle70resting in the closed position where it contacts the fixed flow director90. Additionally, if it is desired that shuttle70be closed quickly, the polarity on the coil32may be reversed so that the coil32drives the shuttle70downward. In the closed position, shown inFIG. 5A, the movable orifice78contacts and seals against the sealing surface94and particulate media does not flow. As an electrical current is applied to the coil32, the shuttle70begins to move away from the fixed flow director90, such as shown inFIG. 5B. Due to the shape of the cone portion92and tapered surface82, the distance the shuttle70moves away from the cone portion92creates a variable gap for the particulate media to pass through. Increasing the amount of energy applied to the coil32increases the amount that the shuttle70moves away from the closed position.

A flow sensor110surrounds the fixed flow director90that detects the amount of particulate media that is passing between the outer diameter surface102and flow sensor110. The flow sensor110is shown as located and attached to a flow sensor body112. The flow sensor body112is located between the mounting base104and a step107in the tube20. The flow sensor body112is sealed to the tube20with seals108,109and has a lead-in surface111. The lead-in surface111is angled and directs any media into the flow path. The sensor110is capacitive and includes sensor rings114,116that sense movement of the particulate media adjacent the sensor rings114,116. The sensor rings114,116are near the inside surface26of the tube20. Wires connect the sensor rings114,116to an external circuit through a channel118in the sensor body112and out through the wire egress120. The external circuit is commonly located inside the housing (not shown) and can be used by the valve10for closed loop control of the shuttle70. The flow sensor110and sensor body112are secured to the tube20using fasteners, adhesive, or other method. The mounting base104is secured through fasteners122. Removing the fasteners122allows the mounting base104, flow directing portion100, cone portion92, and replaceable seal93to be removed for maintenance, cleaning, or component exchange for a different media. The flow sensor110is shown as using sensor rings114,116that are adjacent the flow path for the particulate media, but it is contemplated that other sensor designs are used. To obtain a reliable signal for detecting media, within the flow sensor110, it is desirable to have the media near the sensor rings114,116. For this reason, the flow director90directs media relatively near the sensor rings and away from the central axis16of the tube20, where the media would be relatively far from the sensor rings. If sensor configurations not using capacitive elements such as rings114,116are employed, it is desirable for the media to be located near the capacitive elements and the flow diverter90serves that purpose. As an alternative embodiment for a sensor could be the use of one sensor ring is located in the flow sensor body112, and the other ring is located in the flow directing portion100. In such a case, it is still desirable that media be predictably directed by the flow director90to consistently locate the flow path of media between and near capacitive elements. It is further contemplated that the flow directing portion100may be made from a material that conducts and connects to the external circuit118to form part of the sensor110.

The repelling magnets48in the funnel40have a north-south orientation that puts the magnetic field as it exits the magnet parallel to the central axis16. Some of the field is conducted through the funnel shield60. The shuttle magnets72are aligned in a similar fashion such that the magnetic field as it exits the magnet is parallel to the central axis16, with some of the field conducted through the shuttle magnet shield76. The shuttle magnets72and repelling magnets48have identical facing poles and generate an increasing repelling force as they are brought closer to each other. For example, if the shuttle magnets72have a north pole that faces the repelling magnets48, the repelling magnets would be oriented to have a north pole that faces the shuttle magnets72. The repelling force generated by the magnets48,72acts like a spring that biases the shuttle70away from the funnel40. Because of the biased force from the magnets48,72, no spring is required. Ordinarily, a valve would require a spring to ensure the shuttle returns to the closed position when the electric current is removed.

When an electric current is passed through the windings34in the coil32, a magnetic field is generated that draws the shuttle70towards the funnel40, which separates the terminal sealing edge80from the sealing surface94. The greater the electrical current that is passed through the coil32, the greater the magnetic force is that is applied to the shuttle70, which causes it to move closer to the funnel40. As the shuttle70gets closer to the funnel40, the repelling magnets48begin to counteract the magnetic force from the coil32. When a magnetic field is generated by the coil32, the response from the shuttle70is non-linear due to the exponential increase of magnetic field over decreased distance. This means that when the shuttle70moves closer to the desired position, the amount of magnetic field needed to position the shuttle70would be less than what was generated to move it from its closed and resting position, resulting in the shuttle70moving past the desired position. By adding in the repelling magnets48, magnetic force repelling the shuttle70counteracts the natural increase of force as the shuttle moves closer to the coil32. With this, the shuttle position is more proportional to the amount of electrical current provided to the coil32.

As previously mentioned, the tube20may be made from copper, aluminum, or a copper alloy, and the shuttle70has an array of shuttle magnets72. Because the shuttle magnets72are in close proximity to the tube20, any movement of the shuttle70creates eddy currents in the tube20. Eddy currents are created when a magnet is moved with respect to a conductive metal, such as brass, copper, or aluminum. The tube20in the embodiment herein is described as brass but other materials are contemplated. The valve10takes advantage of the eddy currents and uses them to act as a dampening force on the shuttle70. Without eddy currents, when the coil is first energized, the shuttle70would react in an underdamped fashion73, where it would first overshoot its desired position71and then oscillate until it settles down to its desired position71. In other words, the shuttle70would bounce back and forth before arriving at its desired position71, represented inFIG. 9. Because the position of the shuttle70directly determines the amount of particulate media dispensed, overshoot and oscillation of the shuttle70would cause the particulate media to be dispensed unevenly, particularly when the valve10is first actuated or when the shuttle70is otherwise moved by the coil32. Because of the eddy currents generated by the movement of the shuttle70, overshoot and oscillation of the shuttle70are reduced or eliminated and the shuttle70responds in a damped fashion75.

The valve10is separated into several general chambers where the particulate can be present or flow through, shown inFIGS. 5A and 5B. The valve10is designed to be attached in a vertical orientation, with axis16being aligned with the force of gravity and have a supply of media present in the inlet chamber130. The inlet chamber130starts at the top edge22of the tube20and is generally comprised of the internal volume inside of the funnel40and shuttle sleeve50. The outlet and sensor chamber132is defined by the internal volume starting at the sealing surface94, extending between the outer diameter surface102and inner diameter surface113of the sensor body112, and terminating at the arcuate apertures106. The outlet and sensor chamber132will only contain particulate while it is flowing through the valve10, while the inlet chamber130will contain media regardless of flow. Located between the inlet chamber130and outlet and sensor chamber132is a center chamber134that is defined by the internal volume between the terminal edge56and terminal sealing edge80. The internal volumes herein described are the areas inside the valve10that can hold and dispense media. The internal volumes make up the flow path through the valve10. The media contacts the inside surfaces82,84of the shuttle sleeve78. The center chamber134, like the inlet chamber130, may have media regardless of flow. Media that is released when the shuttle70moves and separates the terminal sealing edge80from the sealing surface94passes through the outlet and sensor chamber132substantially unimpeded. The media located in the inlet chamber is tightly packed together, shown inFIG. 5A, while the dispensed media as it exits the center chamber134is entrained in a fluid (commonly air). As the media passes through the portion of the outlet and sensor chamber132that is surrounded by the flow sensor110, the media is detected by the flow sensor110. Because the outlet and sensor chamber132is encircled by the sensor rings114,116at an equal distance, the media is reliably detected. Detection is further enhanced by having the flow diverter90predictably locate the media in a flow path very near the sensor rings114,116. The velocity of the dispensed media, as it passes the flow sensor110is predictable because the distance from the replaceable seal93to the sensor rings114,116is fixed.

A capacitive flow sensor150, as shown inFIGS. 10-14, may be used as a separate component to measure the flow of particulate that is located downstream of a flow valve. The flow sensor150shares many components as the valve10, with some differences. The flow sensor150has an inlet152and an outlet154. It includes a funnel180that directs the flow from the inlet152towards a central axis156. The funnel180has an inside surface184that is angled, along with a cylindrical surface186. The funnel180fits and is secured within the tube160. It is sealed with an o-ring182and is seated on a step surface185. As opposed to the funnel40, the funnel180is shown without any magnets or magnetic shields. The funnel180forms an inlet chamber270of the flow sensor150that is between the inlet152and a terminal edge196of the cylindrical surface186.

Located on the central axis156is a fixed flow director230that is affixed to the tube160near the outlet154. The fixed flow director230has an outer surface242and is shown as cylindrical. The fixed flow director230has a cone portion232and may have a conical surface238. It is contemplated that the cone portion232is removable for replacement or can be exchanged with a differently contoured outer surface to change the flow properties. It is further contemplated that a flow disrupting ring233is held on the fixed flow director230by the cone portion232. The disrupting ring233may include a surface contour to further refine the flow of the media. The outer surface242has a larger diameter than the cylindrical surface186.

Surrounding the fixed flow director230is the flow sensor110as previously described. The flow sensor110is secured in the tube160where it is sealed with o-rings108,109and abuts a step247in the tube160. The tube160has a wire egress260where the sensor wires (not shown) can pass through to be connected to signal conditioning circuitry, other electronics, or a valve located upstream. The fixed flow director230and flow sensor are located in the outlet portion272as shown inFIG. 14. The fixed flow director230directs particulate media from the center or central region of the tube and towards the inner diameter surface113of the sensor body112.

The flow sensor measures the quantity of particulate present at the sensor rings114,116. With the media falling at a consistent velocity and free-flowing through the outlet154, the higher the density, the more particulate being dispensed. However, as a standalone sensor, the velocity of the media as it enters the inlet can vary for several reasons. First, the vertical distance between the sensor150and the upstream dispensing valve (not shown) causes the media to accelerate. For different types of media, the velocity of the media at the inlet152can vary based on the physical properties, such as the size, shape, and type of material that makes up the media. To normalize the velocity of the media, the funnel180and fixed flow director230cooperate to create a tortuous, winding, zigzag, or otherwise indirect flow path between the inlet152and outlet154. The flow sensor150is designed to be installed in a vertical orientation with the central axis156aligned with the earth's gravity. Some misalignment is tolerated, but the flow of particulate through the sensor150is from gravity and uneven flow may occur as the central axis156is out of alignment. As particulate media enters the inlet chamber270, any media that is farther away from the central axis156than the cylindrical surface186will contact the inside surface184. The media that contacts the inside surface184will change direction. The angle of the inside surface184directs any media that contacts it towards the central axis156. The media then continues to fall through the funnel180and is surrounded by the cylindrical surface186. The height of the cylindrical surface186creates conditions that encourage laminar flow of the particulate. It is contemplated that the cylindrical surface186is shorter to allow more turbulent flow of the particulate. As the particulate passes the funnel180, it contacts the fixed flow director230, particularly the cone portion232. Because the fixed flow director230is larger than the cylindrical surface186, all or nearly all of the particulate will contact the fixed flow director230. This causes the particulate to change direction and slow. The speed of the particulate as it enters the sensor150may vary or have particles that are moving faster than other particles. For accurate sensing, the particles need to be traveling at a consistent speed. The funnel180and fixed flow director230prevent any particulate from passing through the sensor150without contacting at least one surface.

It is understood that while certain aspects of the disclosed subject matter have been shown and described, the disclosed subject matter is not limited thereto and encompasses various other embodiments and aspects. No specific limitation with respect to the specific embodiments disclosed herein is intended or should be inferred. Modifications may be made to the disclosed subject matter as set forth in the following claims.