Fiber optic-based hazardous environmental flowmeter

Abstract

To provide a flowmeter usable even in a hazardous environment.SOLUTION: A flowmeter system includes a flowmeter having a body defining a flow channel and a recess. A paddle wheel is positioned in the recess and is rotatable in response to gas flow through the channel. An optical source provides a light beam on an input cable that crosses the recess and is received by an output cable. A light detector receives the light beam from the output cable. The light beam is intermittently interrupted by the paddle wheel as the paddle wheel rotates so that the light beam on the output cable is a pulsed light beam. A processing electronic apparatus converts the pulsed light beam to a rotational speed of the paddle wheel that is then converted to a gas flow rate through the flow channel. The flowmeter is positioned in the hazardous environment of a painting robot, and the processing electronic apparatus is positioned outside the hazardous environment.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates generally to a flow meter for measuring the flow rate of gases, and more particularly to a flow meter for measuring the flow rate of hazardous gases through a robot. The flow meter includes a paddle wheel that intercepts a light beam as the paddle wheel rotates to provide a measured air flow rate. [Background technology]

[0002] Robots are known to perform a variety of tasks, including painting objects such as car bodies. For example, a typical robotic paint station for painting the exterior of a car body in both continuous-transport and stationary-station systems includes a spray booth, multiple painting robots, and open / close robots located around the perimeter. These robots may be mounted on the floor, wall, ceiling, or side rails. The painting robots carry either spray guns or rotary applicators to direct sprayed paint toward the car body. Spray booths typically include sophisticated environmental air handling equipment to treat and exhaust vapor-laden air from the spray booth, preventing paint vapors from entering operator aisles where people are present.

[0003] Atomized paint sprayed from a robot creates a flammable environment in the spray booth consisting of paint vapors, referred to herein as hazardous gases. Hazardous gases, which can ignite when the robot's motors are powered, must be prevented from entering the robot during its operation. One known protective strategy for eliminating and preventing hazardous gases from entering the robot is called a purging or pressurizing strategy. Purging is performed during robot downtime to eliminate hazardous gases that may have collected inside the robot and other non-intrinsically safe (IS) devices. During robot downtime, air supply to the chamber and pressure monitoring are discontinued for an optional period of time. For this strategy, clean air is admitted into the robot before the robot starts to remove any hazardous gases that may have accumulated in the robot. Pressurization maintains a positive pressure inside the robot during its operation to prevent hazardous gases from entering the robot. It is necessary to measure the air flow rate during both the purging and pressurizing operations to ensure that the robot receives the proper amount of air during the purging operation and that the proper positive pressure is maintained during the pressurizing operation. Summary of the Invention [Problem to be solved by the invention]

[0004] Existing purge systems often rely on a set of differential pressure sensors to measure the flow rate during purging of hazardous gases from a robot or other powered enclosure operating within a hazardous environment. Another set of differential pressure sensors is required to monitor the relative pressure between the purged, pressurized cavity and the external, combustible environment. The differential pressure sensors continuously monitor the internal, pressurized cavity to ensure it is always at a higher relative pressure than the external, combustible environment, thereby ensuring that any leakage is pure air leaking from inside the pressurized cavity into the hazardous environment and not in the other direction. However, these types of pressure sensors are electronic devices that require power to be supplied to the hazardous environment, which requires agency approval and increases product costs. Furthermore, the electrical contacts employed in these pressure sensors frequently open and close in response to turbulent flow, shortening the sensor's lifespan due to wear. Furthermore, the electrical contacts employed in these pressure sensors are prone to carbon buildup, which reduces the electrical connection. [Means for solving the problem]

[0005] The following description describes a flow meter system that is part of a purge and pressurization system associated with a painting robot that purges hazardous gases from the robot prior to operation and maintains a positive pressure within the robot while the robot is operating. The flow meter system includes a flow meter positioned within the robot, the flow meter including a body having a flow input end and a flow output end, forming a flow path therebetween, and a recess in fluid communication with the flow path. A paddle wheel is positioned in the recess, extends into the flow passage, and is rotatable on the shaft in response to gas flow through the flow passage. A check valve allows gas to flow through the flow path from the input end to the output end and prevents gas from flowing through the flow path from the output end to the input end. A gas flow conditioner is attached to the input end of the body and includes a plurality of holes through which gas enters the flow passage to reduce turbulence in the gas flow. An optical input cable is coupled to the body adjacent the recess, and an optical output cable is coupled to the body adjacent the recess. The processing electronics are located outside the robot in a non-hazardous environment. The processing electronics includes a light source that provides a light beam provided to the optical input cable, traverses the recess, and is received by the optical output cable. The processing electronics includes a photodetector that receives the light beam from the optical output cable. The light beam is intermittently interrupted as the paddle wheel rotates, causing the light beam at the optical output cable to become a pulsed light beam. The processing electronics converts the pulsed light beam into a rotational velocity of the paddlewheel, which in turn converts into a flow rate of gas through the flow passage.

[0006] Additional features of the disclosure will become apparent from the following description and claims, taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is an explanatory diagram of a robot system including a painting robot and a purge / pressurization assembly.

[0008] [Figure 2] FIG. 2 is a perspective view of an optical flow meter positioned within a robot.

[0009] [Figure 3] FIG. 3 is a cutaway perspective view of an optical flow meter.

[0010] [Figure 4] FIG. 4 is a perspective view of a paddle wheel used in an optical flowmeter.

[0011] [Figure 5] FIG. 5 is a side view of the paddle wheel.

[0012] [Figure 6] FIG. 6 is a schematic diagram of a flow meter system including an optical flow meter and signal processing electronics. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following describes an embodiment of the present disclosure relating to a flow meter for measuring air flow through a robot. The flow meter includes a paddle wheel that intercepts a light beam as the paddle wheel rotates to provide a measured air flow rate. Again, the following description is merely exemplary in nature and is not intended to limit the disclosure or its application.

[0014] 1 is an illustration of a robot system 10 including a painting robot 12 mounted to a fixed base 14, which is intended to represent any painting robot suitable for the purposes discussed herein. A turret 16 is rotatably mounted to the fixed base 14. An inner arm 18 is rotatably connected to the base 16 by a joint 20, an outer arm 22 is rotatably connected to the inner arm 18 by a joint 24, and a wrist member 26 is rotatably connected to the outer arm 22 by a joint 28. A paint applicator 30 is secured to the wrist member 26 at an angle optimized for the paint application.

[0015] The robot system 10 includes a purge and pressurization assembly 40 that evacuates hazardous gases from within the robot 12 when the robot 12 is primed for operation and prevents hazardous gases from entering the robot 12 when the robot 12 is in operation. The assembly 40 includes an air inlet port 42, an air outlet port 44, a needle valve 46, and an air solenoid valve 48. An air supply hose 50 connects to the outlet port 44 and to a purge switch (not shown) within the mounting stand 14. Prior to powering up the robot 12, a large volume of air is supplied to the robot 12 via the solenoid valve 48, the hose 50, and the purge switch, and circulated throughout the channels (not shown) within the robot 12. The purge switch measures the flow rate of air supplied to the robot 12, and a timer is used to ensure the proper amount of air is supplied for purging. The air flows through the channels within the robot 12 and exits the robot 12 through an exhaust port. While the robot 12 is operating, a small amount of air is supplied to the robot 12 through needle valve 46, which bypasses solenoid valve 48 and maintains a positive pressure within the robot 12 through hose 50 and purge switch and channel, which again measures the air flow rate to ensure the proper pressure.

[0016] FIG. 2 is a perspective view of the optical flow meter 60, and FIG. 3 is an exploded perspective view of the optical flow meter 60. The optical flow meter 60 is mounted within the fixed base 14 and receives air from the hose 50 in combination with a purge switch. The flow meter 60 includes a housing or body 62, formed, for example, from aluminum. The body 62 defines a cylindrical input channel region 64 at the air input end of the flow meter 60, a cylindrical output channel region 66 at the air output end of the flow meter 60, a cylindrical central flow channel 68, and an upper recess 70. The cylindrical input channel region 64 and the cylindrical output channel region 66 have diameters larger than the diameter of the cylindrical central flow channel 68. A tapered channel portion 72 is formed between the cylindrical input channel region 64 and the cylindrical central flow channel 68, which increases the velocity of air as it flows into the channel 68, allowing for measurement of low air flow rates. The diameter of the channel 68 is important in designing the flow meter 60. A tapered channel portion 74 is provided between the output region 66 and the central channel 68 so that the air flow decreases as it flows from the channel 68 to the output region 66 .

[0017] A gas flow conditioner 80, made, for example, from a nylon composite, is attached and secured to the input end of body 62. Conditioner 80 includes a series of holes 82 configured to filter out turbulence in the airflow to obtain stable flow measurements. The number and diameter of holes 82 in conditioner 80 depend on the path of the airflow through the channels in robot 12 and the amount of turbulence created thereby.

[0018] A check valve 84, made from, for example, a nylon composite, is secured to the body 62 at the output end of the body 62. The check valve 84 includes a fixed portion 86 secured to the body 62 by tabs 88 and bolts 90, and a movable portion 92 that seals against a valve seat 94 in the tapered portion 74 under the bias of a spring (not shown). When there is no air flow through the channel 68, or when the pressure in the channel 68 is so low that the pressure on the tapered portion 74 is less than the force of the spring bias, the movable portion 92 presses against the valve seat 94, preventing air from entering the robot 12 through the output end of the flow meter 60. When there is air flow through the channel 68 and the pressure in the channel 68 is high enough to exert a force on the tapered portion 74 that is sufficient to overcome the spring bias, the movable portion 92 is pushed away from the valve seat 94, allowing air to flow through the channel 68 from the input end to the output end.

[0019] The cartridge 96, formed, for example, from a nylon composite, is inserted into the recess 70 and secured to the body 62 by bolts 98. The cartridge 96 includes a cavity 100 that receives a paddle wheel 102, also formed from a nylon composite. The paddle wheel 102 is free to rotate on a shaft 104 in the cavity 100. The rotational inertia of the paddle wheel 102 helps smooth out flow fluctuations caused by turbulence, resulting in more consistent flow measurements. Airflow from the input end of the body 62, through the channel 68, and to the output end causes the paddle wheel 102 to rotate clockwise.

[0020] As described in more detail below, a light beam is transmitted to cartridge 96 through input fiber cable 110, which is coupled to cartridge 96 by fitting 112. The light beam enters cartridge 96 through bore 114, traverses cavity 100, and is received by output fiber cable 116 via fitting 118 (see FIG. 6). Paddle wheel 102 is positioned within cavity 100 so that, as paddle wheel 102 rotates, the light beam is intermittently interrupted by paddle wheel 102 and output fiber cable 116 receives pulses of light. The light pulses have a frequency and pulse width determined by the rotational speed of paddle wheel 102, which is dependent on the air flow rate through channel 68. The light pulses are converted to an electrical signal by amplification equipment located outside the hazardous environment of the paint booth and therefore do not require agency approval for flow meter 60.

[0021] The paddle wheel 102 is configured to operate effectively at extremely low flow rates. Figure 4 is a perspective view of the paddle wheel 102 separated from the flow meter 60, and Figure 5 is a side view of the paddle wheel 102. The paddle wheel 102 includes three spaced-apart radial paddle elements 130. The radial paddle elements 130 extend from a flat web member 132 having an aperture 128 through which the shaft 104 extends. Each radial paddle element 130 includes a first curved segment 134, a second curved segment 136, a sensing segment 138 coupled to the first curved segment 134 and the second curved segment 136, and an opening 140 defined by all of the segments 134, 136, and 138. A pair of opposing airfoil members 142, 144 are provided on opposite sides of the first curved segment 134, and a pair of opposing airfoil members 146, 148 are provided on opposite sides of the second curved segment 136. The airfoil members 142-148 are shaped and angled with respect to the channel 68 so that as air flows over them, the lift and drag created by the airfoil members 142-148 causes the paddlewheel 102 to rotate more efficiently and allows the paddlewheel 102 to rotate properly at low flow rates.

[0022] FIG. 6 is a schematic diagram of a flow meter system 150. The flow meter system 150 includes a cross-section of the cartridge 96 in the optical flow meter 60 and signal processing electronics 152. The electronics 152 resides outside the hazardous environment of the paint booth. The electronics 152 includes an optical transceiver and amplifier device 154 having a light source 156, such as a diode. The light source 156 transmits a light beam 158 down the input fiber cable 110 to the fitting 112, causing the sensing segment 138 to be intermittently interrupted as the beam 158 traverses the cavity 100 and the paddle wheel 102 rotates. The interrupted light beam is transmitted to the fitting 118 and transmitted as light pulses down the output fiber cable 116 to a sensor 160, such as a photodiode, in the device 154, where the light pulses are converted to electrical pulses. The electrical pulses are amplified by an amplifier 162 in the device 154, and the amplified pulse train is transmitted to a control unit 164. The control unit 164 performs the calculations to convert the electrical pulses into a rotational speed, or revolutions per minute (RPM), of the paddlewheel 102 that is linearly proportional to the flow rate of air through the channel 68 .

[0023] The foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. Those skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications, and variations can be made without departing from the spirit and scope of the disclosure, as defined in the following claims. Furthermore, the following notes are added regarding the above-described embodiment and modifications. (Appendix 1) The flow meter system is A flow meter is provided. The flow meter comprises: a body having a flow input end and a flow output end, defining a flow passage therebetween, and having a recess in fluid communication with the flow passage; a paddle wheel positioned in the recess, extending into the flow passage, and rotatable on a shaft in response to gas flow through the flow passage; a check valve that allows gas to flow through the flow path from the input end to the output end and prevents gas from flowing through the flow path from the output end to the input end; The flow meter system further comprises: an optical input cable coupled to the body adjacent the recess; an optical output cable coupled to the body adjacent the recess; processing electronics; the processing electronics including a light source provided on the optical input cable, providing a light beam that traverses the recess and is received by the optical output cable; a photodetector that receives the light beam from the optical output cable; the light beam is intermittently interrupted as the paddle wheel rotates, thereby causing the light beam to become a pulsed light beam at the optical output cable; The processing electronics converts the pulsed light beam into a rotational speed of the paddle wheel and then into a flow rate of gas through the flow path. (Appendix 2) 2. The flow meter system of claim 1, wherein the paddle wheel comprises a web portion and a plurality of spaced apart radial members extending from the web portion, each radial member including a detector that blocks the light beam when the paddle wheel rotates. (Appendix 3) 3. The flow meter system of claim 2, wherein each of the radial members includes a first curved segment connected to one end of the sensing portion and a second curved segment connected to the other end of the sensing portion, whereby the first curved segment, the second curved segment, and the sensing portion form a central opening. (Appendix 4) each of the radial members further including opposing airfoil members on either side of the first curved segment and opposing airfoil members on either side of the second curved segment; 4. The flow meter system of claim 3, wherein the airfoil is configured such that when the gas flows over the airfoil, lift and drag forces on the airfoil increase rotation of the paddle wheel. (Appendix 5) 2. The flow meter system of claim 1, further comprising a gas flow conditioner attached to the input end of the body, the gas flow conditioner including a plurality of holes through which gas enters the flow path to reduce turbulence in the gas flow. (Appendix 6) the flow path includes a cylindrical input portion located at the input end of the body, a cylindrical output portion located at the output end of the body, a cylindrical central portion between the cylindrical input portion and the cylindrical output portion, a first tapered portion between the cylindrical input portion and the cylindrical central portion, and a second tapered portion between the cylindrical output portion and the cylindrical central portion; 2. The flow meter system of claim 1, wherein the cylindrical input section and the cylindrical output section have diameters greater than the diameter of the cylindrical central section. (Appendix 7) the flow meter further includes a cartridge inserted into the recess and secured to the body; 2. The flow meter system of claim 1, wherein the cartridge includes a cavity, and the paddle wheel is rotatably mounted on the shaft in the cavity. (Appendix 8) the flow meter system is part of a purge and pressurization system associated with the robot that purges hazardous gases from the robot before the robot operates and maintains a positive pressure within the robot during operation of the robot; 2. The flow meter system of claim 1, wherein the flow meter is located within the robot and the processing electronics are located outside the robot in a non-hazardous environment. (Appendix 9) 9. The flow meter system of claim 8, wherein the robot is a painting robot. (Appendix 10) 1. A flow meter system that is part of a purge and pressurization system associated with a painting robot that purges hazardous gases from the robot prior to operation of the robot and maintains a positive pressure within the robot during operation of the robot, comprising: The flow meter system comprises: A flow meter is provided. The flow meter comprises: a body having a flow input end and a flow output end, defining a flow passage therebetween, and having a recess in fluid communication with the flow passage; a paddle wheel positioned in the recess, extending into the flow passage, and rotatable on a shaft in response to gas flow through the flow passage; a check valve that allows gas flow through the flow path from the input end to the output end and prevents gas flow through the flow path from the output end to the input end; a gas flow conditioner attached to the input end of the body, the gas flow conditioner including a plurality of holes through which gas enters the flow passage to reduce turbulence in the gas flow; the flow meter is located within the robot; The flow meter system further comprises: an optical input cable coupled to the body adjacent the recess; an optical output cable coupled to the body adjacent the recess; processing electronics; the processing electronics including a light source provided on the optical input cable, providing a light beam that traverses the recess and is received by the optical output cable; a photodetector that receives the light beam from the optical output cable; the light beam is intermittently interrupted as the paddle wheel rotates, thereby causing the light beam at the optical output cable to become a pulsed light beam; the processing electronics converting the pulsed light beam into a rotational velocity of the paddle wheel and then into a flow rate of gas through the flow path; The flow meter system wherein the processing electronics are located external to the robot in a non-hazardous environment. (Appendix 11) 11. The flow meter system of claim 10, wherein the paddle wheel includes a web portion and a plurality of spaced apart radial members extending from the web portion, each radial member including a detector that blocks the light beam when the paddle wheel rotates. (Appendix 12) 12. The flow meter system of claim 11, wherein each of the radial members includes a first curved segment connected to one end of the sensing portion and a second curved segment connected to the other end of the sensing portion, whereby the first curved segment, the second curved segment, and the sensing portion form a central opening. (Appendix 13) each of the radial members further including opposing airfoil members on either side of the first curved segment and opposing airfoil members on either side of the second curved segment; 13. The flow meter system of claim 12, wherein the airfoil is configured such that when the gas flows over the airfoil, lift and drag forces on the airfoil increase rotation of the paddle wheel. (Appendix 14) the flow path includes a cylindrical input portion located at the input end of the body, a cylindrical output portion located at the output end of the body, a cylindrical central portion between the cylindrical input portion and the cylindrical output portion, a first tapered portion between the cylindrical input portion and the cylindrical central portion, and a second tapered portion between the cylindrical output portion and the cylindrical central portion; 11. The flow meter system of claim 10, wherein the cylindrical input section and the cylindrical output section have diameters greater than a diameter of the cylindrical central section. (Appendix 15) the flow meter further includes a cartridge inserted into the recess and secured to the body; 11. The flow meter system of claim 10, wherein the cartridge includes a cavity, and the paddle wheel is rotatably mounted on the shaft in the cavity. (Appendix 16) In a flow meter, The flow meter comprises: a body having a flow input end and a flow output end, defining a flow passage therebetween, and having a recess in fluid communication with the flow passage; a paddle wheel positioned in the recess, extending into the flow passage, and rotatable on the shaft in response to gas flow through the flow passage; the paddle wheel having a web portion and a plurality of spaced radial members extending from the web portion, each radial member including a detector portion that blocks the light beam when the paddle wheel rotates; Each of the radial members includes a first curved segment connected to one end of the sensing portion and a second curved segment connected to the other end of the sensing portion, whereby the first curved segment, the second curved segment, and the sensing portion form a central opening. (Appendix 17) each of the radial members further including opposing airfoil members on either side of the first curved segment and opposing airfoil members on either side of the second curved segment; 17. The flow meter of claim 16, wherein the airfoil is configured such that when the gas flows over the airfoil, lift and drag forces on the airfoil increase rotation of the paddle wheel. (Appendix 18) the flow path includes a cylindrical input portion located at the input end of the body, a cylindrical output portion located at the output end of the body, a cylindrical central portion between the cylindrical input portion and the cylindrical output portion, a first tapered portion between the cylindrical input portion and the cylindrical central portion, and a second tapered portion between the cylindrical output portion and the cylindrical central portion; 17. The flowmeter of claim 16, wherein the cylindrical input section and the cylindrical output section have diameters greater than a diameter of the cylindrical central section. (Appendix 19) the flow meter further includes a cartridge inserted into the recess and secured to the body; 17. The flow meter of claim 16, wherein the cartridge includes a cavity, and the paddle wheel is rotatably mounted on the shaft in the cavity. (Appendix 20) the flow meter system is part of a purge and pressurization system associated with the painting robot that purges hazardous gases from the robot before the robot operates and maintains a positive pressure within the robot during operation; 17. The flow meter of claim 16, wherein the flow meter is located within the robot and the processing electronics are located external to the robot in a non-hazardous environment. [Explanation of symbols]

[0024] 12. Robot 14 Mounting stand 16 base 18 Inner Arm 22 outer arm 24 Joint 26 List member 30 Paint applicator 40 Pressurizing assembly 42 Air inlet port 46 Needle valve 50 Horse 60 Optical flowmeter 62 Main Unit 64 Cylindrical input channel area 68 Cylindrical central flow channel 70 recess 72, 74 Tapered channel section 80 Conditioner 86 Fixed part 88 tabs 94 Valve seat 102 Paddle Wheel 110 Input Fiber Cable 112 Fitting 116 Output Fiber Cable 128 holes 130 Radial Paddle Elements 134 First curved segment 136 Second curved segment 138 detection segments 140 Aperture 142, 144, 146, 148 Airfoil members 150 Flow Meter System 156 Light source 160 sensors 164 Control Unit

Claims

1. The flow meter system is A flow meter is provided. The flow meter comprises: a body having a flow input end and a flow output end, defining a flow passage therebetween, and having a recess in fluid communication with the flow passage; a paddle wheel positioned in the recess, extending into the flow passage, and rotatable on a shaft in response to gas flow through the flow passage; a check valve that allows gas to flow through the flow path from the input end to the output end and prevents gas from flowing through the flow path from the output end to the input end; The flow meter system further comprises: an optical input cable coupled to the body adjacent the recess; an optical output cable coupled to the body adjacent the recess; processing electronics; the processing electronics including a light source provided on the optical input cable, providing a light beam that traverses the recess and is received by the optical output cable; a photodetector that receives the light beam from the optical output cable; the light beam is intermittently interrupted as the paddle wheel rotates, thereby causing the light beam to become a pulsed light beam at the optical output cable; The processing electronics converts the pulsed light beam into a rotational speed of the paddle wheel and then into a flow rate of gas through the flow path.

2. 2. The flow meter system of claim 1, wherein the paddle wheel comprises a web portion and a plurality of spaced apart radial members extending from the web portion, each radial member including a detector portion that occludes the light beam when the paddle wheel rotates.

3. 3. The flow meter system of claim 2, wherein each of the radial members includes a first curved segment connected to one end of the sensing portion and a second curved segment connected to the other end of the sensing portion, whereby the first curved segment, the second curved segment, and the sensing portion form a central opening.

4. each of the radial members further including opposing airfoil members on either side of the first curved segment and opposing airfoil members on either side of the second curved segment; The flow meter system of claim 3 , wherein the airfoil is configured such that lift and drag forces on the airfoil increase rotation of the paddle wheel when the gas flows over the airfoil.

5. 10. The flow meter system of claim 1, wherein the flow meter further includes a gas flow conditioner attached to the input end of the body, the gas flow conditioner including a plurality of holes through which gas enters the flow path to reduce turbulence in the gas flow.

6. the flow path includes a cylindrical input portion located at the input end of the body, a cylindrical output portion located at the output end of the body, a cylindrical central portion between the cylindrical input portion and the cylindrical output portion, a first tapered portion between the cylindrical input portion and the cylindrical central portion, and a second tapered portion between the cylindrical output portion and the cylindrical central portion; 2. The flow meter system of claim 1, wherein the cylindrical input section and the cylindrical output section have diameters greater than a diameter of the cylindrical central section.

7. the flow meter further includes a cartridge inserted into the recess and secured to the body; The flow meter system of claim 1 , wherein the cartridge includes a cavity, and the paddle wheel is rotatably mounted on the shaft in the cavity.

8. the flow meter system is part of a purge and pressurization system associated with the robot that purges hazardous gases from the robot before the robot operates and maintains a positive pressure within the robot during operation of the robot; 10. The flow meter system of claim 1, wherein the flow meter is located within the robot and the processing electronics is located external to the robot in a non-hazardous environment.

9. 9. The flow meter system of claim 8, wherein the robot is a painting robot.

10. 1. A flow meter system that is part of a purge and pressurization system associated with a painting robot that purges hazardous gases from the robot prior to operation of the robot and maintains a positive pressure within the robot during operation of the robot, comprising: The flow meter system comprises: A flow meter is provided. The flow meter comprises: a body having a flow input end and a flow output end, defining a flow passage therebetween, and having a recess in fluid communication with the flow passage; a paddle wheel positioned in the recess, extending into the flow passage, and rotatable on a shaft in response to gas flow through the flow passage; a check valve that allows gas flow through the flow path from the input end to the output end and prevents gas flow through the flow path from the output end to the input end; a gas flow conditioner attached to the input end of the body, the gas flow conditioner including a plurality of holes through which gas enters the flow passage to reduce turbulence in the gas flow; the flow meter is located within the robot; The flow meter system further comprises: an optical input cable coupled to the body adjacent the recess; an optical output cable coupled to the body adjacent the recess; processing electronics; the processing electronics including a light source provided on the optical input cable, providing a light beam that traverses the recess and is received by the optical output cable; a photodetector that receives the light beam from the optical output cable; the light beam is intermittently interrupted as the paddle wheel rotates, thereby causing the light beam at the optical output cable to become a pulsed light beam; the processing electronics converting the pulsed light beam into a rotational velocity of the paddle wheel and then into a flow rate of gas through the flow path; The flow meter system wherein the processing electronics are located external to the robot in a non-hazardous environment.

11. 11. The flow meter system of claim 10, wherein the paddle wheel comprises a web portion and a plurality of spaced apart radial members extending from the web portion, each radial member including a detector portion that occludes the light beam when the paddle wheel rotates.

12. 12. The flow meter system of claim 11, wherein each of the radial members includes a first curved segment connected to one end of the sensing portion and a second curved segment connected to the other end of the sensing portion, whereby the first curved segment, the second curved segment, and the sensing portion form a central opening.

13. each of the radial members further including opposing airfoil members on either side of the first curved segment and opposing airfoil members on either side of the second curved segment; The flow meter system of claim 12 , wherein the airfoil is configured such that lift and drag forces on the airfoil increase rotation of the paddle wheel when the gas flows over the airfoil.

14. the flow path includes a cylindrical input portion located at the input end of the body, a cylindrical output portion located at the output end of the body, a cylindrical central portion between the cylindrical input portion and the cylindrical output portion, a first tapered portion between the cylindrical input portion and the cylindrical central portion, and a second tapered portion between the cylindrical output portion and the cylindrical central portion; 11. The flow meter system of claim 10, wherein the cylindrical input section and the cylindrical output section have diameters greater than a diameter of the cylindrical central section.

15. the flow meter further includes a cartridge inserted into the recess and secured to the body; The flow meter system of claim 10 , wherein the cartridge includes a cavity, and the paddle wheel is rotatably mounted on the shaft in the cavity.

16. In a flow meter, The flow meter comprises: a body having a flow input end and a flow output end, defining a flow passage therebetween, and having a recess in fluid communication with the flow passage; a paddle wheel positioned in the recess, extending into the flow passage, and rotatable on the shaft in response to gas flow through the flow passage; the paddle wheel having a web portion and a plurality of spaced radial members extending from the web portion, each radial member including a detector portion that blocks the light beam when the paddle wheel rotates; Each of the radial members includes a first curved segment connected to one end of the sensing portion and a second curved segment connected to the other end of the sensing portion, whereby the first curved segment, the second curved segment, and the sensing portion form a central opening.

17. each of the radial members further including opposing airfoil members on either side of the first curved segment and opposing airfoil members on either side of the second curved segment; 17. The flow meter of claim 16, wherein the airfoil is configured such that lift and drag forces on the airfoil increase rotation of the paddle wheel when the gas flows over the airfoil.

18. the flow path includes a cylindrical input portion located at the input end of the body, a cylindrical output portion located at the output end of the body, a cylindrical central portion between the cylindrical input portion and the cylindrical output portion, a first tapered portion between the cylindrical input portion and the cylindrical central portion, and a second tapered portion between the cylindrical output portion and the cylindrical central portion; 17. The flow meter of claim 16, wherein the cylindrical input section and the cylindrical output section have diameters greater than a diameter of the cylindrical central section.

19. the flow meter further includes a cartridge inserted into the recess and secured to the body; 17. The flow meter of claim 16, wherein the cartridge includes a cavity, and the paddle wheel is rotatably mounted on the shaft in the cavity.

20. the flow meter system is part of a purge and pressurization system associated with the painting robot that purges hazardous gases from the robot before the robot operates and maintains a positive pressure within the robot during operation; 17. The flow meter of claim 16, wherein the flow meter is located within the robot and the processing electronics are located external to the robot in a non-hazardous environment.

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