Abstract:
An oxygen leakage regulator tester to test for air leaks in O 2  supply equipment, such as oxygen masks and hoses used by flight personnel. The tester uses electromechanical sensors and a central processing unit, coupled to digital displays for accurate readouts.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a machine for detecting leaks in an oxygen supply system, and specifically to an oxygen leakage regulator tester for testing leakage of oxygen regulators in oxygen supply equipment that uses a digital display. 
     2. Description of Related Art 
     It is well known that the partial pressure of oxygen in the atmosphere decreases with altitude. For this reason it is necessary in high altitude aircraft in order to prevent hypoxia at high altitudes to supply aircraft personnel with oxygen through an oxygen regulator including an oxygen mask and supply tube. Oxygen supply regulators in military jet aircraft provide the pilot and the crew with oxygen via breathing masks connected by a pipeline system to a centralized oxygen system. Oxygen regulator supply leaks can be harmful to the user, reduce available supply, and can create a hazardous environment. Therefore, it is necessary to test the oxygen regulating systems used in aircraft for leakage to ensure reliability and operability. 
     A conventional, portable analog tester for leakage detection comprises an air pump attached to an analog pressure gauge having an outlet tube connected to the device to be tested. The air pump is used to pump air into the device to be tested until pressure of a predetermined level is attained which is measured using the pressure gauge. Leakage in the system is determined by monitoring the analog pressure gauge for a drop in pressure per unit time or an analog flow meter. Typically, these devices cannot be calibrated to compensate for ambient air pressure or temperature. This type device is not always accurate in indicating leakage, given the inaccuracies of analog pressure gauges and the potential for error in reading the gauge. Analog devices are subject to ambient atmospheric pressure variations, resulting in inaccurate readings. Gas leakage in a relatively low-pressure system can often be hard to detect through visual inspection without test equipment. 
     Gas leak detectors are known in the prior are. U.S. Pat. No. 4,670,847 to Furuse teaches highly sophisticated equipment which bases its measurements on input reference values and computer analysis of results obtained from a sensor. Circuitry in this invention is not activated by a pressure sensor. Also, U.S. Pat. No. 4,998,434 to Asbra teaches permanently coupled equipment for testing a housing line without a manipulable pressure reservoir. In addition, U.S. Pat. No. 4,775,855 to Cox teaches a leakage detection system adapted for transportation systems such as hoses for primary and secondary fluids, such as those used in the transportation of petroleum products. U.S. Pat. No. 4,350,038 to Soncrant illustrates a machine that accepts or rejects hollow devices using pressurized air and three separate regulators of the prior art teaches a portable leak detector which is highly accurate for low pressures. 
     None of the prior art teaches a leak detector which has a reservoir volume for use during testing which is hand manipulable. 
     None of the prior art teaches a power efficient leak detector which does not use power from its power supply until it is activated manually, and is simple to operate, inexpensive to manufacture and easy to read. 
     Therefore, what is required is a specialized gas leakage detector for use in testing flight crew oxygen regulating equipment with little potential for error in determining the presence of leakage, which is sensitive in measuring relatively low pressures as well as fluid flow. 
     SUMMARY OF THE INVENTION 
     An oxygen leakage regulator tester for testing pilot and air crew oxygen equipment, including oxygen masks and oxygen supply hoses conventionally used aboard aircraft, allowing the expedient and accurate detection of gas leakage with high accuracy using electronic air flow sensors and a digital display. 
     The portable tester includes a hand-operated air pump, a pressure reservoir, an electronic air flow sensor, a plug and tube connected to the air reservoir for connection to a mask or hose, an air release valve, an electronic air pressure air sensor, a central processing unit, an LCD air pressure display, an LCD air flow display, an air pressure activated switch for turning the unit on and off, a carrying enclosure, and a battery power supply. The tester is engaged to a mask hose to be tested with the plug. The hand pump is used to increase air pressure in the mask up to 17 inches of water. Once the system is pressured, the LCD display is watched for air pressure and air flow rate. If the airflow rate is above 0.25 cm 3 /minute, then a leak is detected. 
     The hand air pump is comprised of a squeezable rubber bulb with two one-way valves installed within. When the bulb is compressed, air is forced out of the first end of the bulb and when released, air is drawn in through the second end, refilling the bulb. The first end of the bulb is connected to an air release valve and one end of the pressure reservoir by suitable tubing. The air reservoir is a bladder that maintains a volume of air at the working air pressure for a working supply of high-pressure air during the test. 
     The hand pump, air release valve, pressure reservoir, electronic air pressure and air flow sensors and air pressure switch are connected in fluid communication in-line, using suitable sealed tubing. The LCD air pressure and flow displays, electronic pressure and flow sensors, air pressure switch, and central processing unit are mounted within a portable housing or case which is formed by an elongated box having a lid and a handle. The housing also encloses the battery power supply. 
     The air pressure switch, battery power supply and central processing unit are electrically connected so that when the air pressure reaches a preset level in the test tube, the electrical switch is closed, and the central processing unit is supplied with operating power. The air pressure and flow displays are mounted visibly within the housing so that when the lid is open the gauges are viewable by the user. When the lid is closed, the gauges are protected from damage due to handling. The housing is portable and contained in a brief case sized box with an openable lid and a carrying handle. 
     The housing is sized for storing the hand pump, pressure reservoir and test operational air supply tubing when not in use. The aircraft oxygen supply system including mask and O 2  supply hose to be tested is connected in-line to the plug end of the test tube. The hand pump is used to create increased air pressure (17 inches) within the mask hose or hose being tested from the high-pressure air in the reservoir. The air pressure switch closes the circuit between the central processing unit and the battery power supply, giving the central processing unit and LCD displays operating power. Fluid pressure and airflow can then be observed by reading the LCD pressure and flow displays. Leakage can be determined if the air flow display quantified air flow LCD reading exceeds an acceptable predetermined limit, such as 0.25 cm 3 /minute. 
     It is an object of this invention to provide an accurate, easy-to-read air leakage detector used for testing oxygen supply equipment which measures test air pressure and air fluid flow utilizing LCD displays while testing the actual equipment. 
     It is a further object of this invention to provide a leakage detector which is accurate for low leakage flow rates. 
    
    
     In accordance with these and other objects which will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings. 
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 shows a schematic diagram of the invention. 
     FIG. 2 shows an exploded view in perspective of the invention. 
     FIG. 3 is a perspective view of the invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, the general functional elements of the invention are shown. Oxygen leakage regulator tester  10  includes flexible, squeezable, hand air pump  6  for creating air pressure during testing, an expandable pressure reservoir bladder  8 , air release valve  4  for adjusting the pressure being tested or releasing the pressure when testing is complete, electronic air pressure and flow sensor  12 , central processing unit (CPU)  14 , digital LCD air pressure display  14   a , digital LCD flow display  14   b , a battery power supply  18  and a portable housing  22  (shown in FIG.  2 ). Suitable tubing with a rubber stopper  17  having an aperture is used to connect the tester  10  to the flight personnel oxygen supply equipment such as a mask or hose to be tested. 
     Hand air pump  6  is formed by a flexible rubber bulb having an air inlet and an air outlet from two one-way air flow valves  6   a  and  6   aa  installed within so that when the bulb is manually compressed, air is forced out of the first end valve  6   aa  (outlet) of the bulb and when released the bulb draws air in through the second end valve  6   a  (inlet), refilling the bulb. Hand pump  6  is connected in fluid connection to air release valve  4  which may be opened and closed by the user so that the pressure being created by hand pump  6  may be adjusted or dumped. Pressure reservoir  8  is constructed of a flexible material such as rubber which expands as pressure increases thereby increasing the volume of air within the testing system. Reservoir  8  may be hand manipulated (squeezed) during testing to maintain adequate air pressure in the equipment being tested should air pressure quantities drop due to leakage. 
     Electronic transducer air pressure and air flow sensor  12  is of the conventional type, such as that produced by Alicat, Inc., that electromechanically measures air pressure in inches of water and air flow in liters per minute. Sensor  12  sends digital signals through connector  52  to Central Processing Unit  14 . Central Processing Unit  14  is of the conventional type that interprets the signals from air pressure and air flow sensor  12  and displays the quantitative amounts or readings of the air pressure and air flow sensor  12  separately through LCD pressure display  14   a  and LCD flow display  14   b . Test air pressure is predetermined and in one example is  17  inches of water. In this example a leak would be considered at 0.25 liters of air flow per minute. 
     The tester turns on and off automatically. Air pressure switch  16  is electrically connected to battery power source  18  and Central Processing Unit  14  so that when the air pressure in the system is pumped up to a threshold value, air pressure switch  16  is closed and Central Processing Unit  14  is supplied with operating power. When the oxygen supply equipment to be tested is connected to tester  10  via rubber stopper  17 , hand air pump  6  is used to create pressure within the oxygen supply system equipment being tested, such as a mask hose. Air release valve  4  can be used to reduce or release the pressure within the system as required. Air pressure switch  16  is calibrated to close the circuit between central processing unit  14  and battery power supply  18  upon encountering a pressure of 5 inches barometric water pressure thus supplying central processing unit  14  with operating power. Air pressure switch  16  may be calibrated to close the circuit at any suitable pressure. Pressure reservoir  8  serves to, allow manual squeezing to increase or sustain the air pressure within the system by increasing the volume of air contained in the system being tested. The air pressure held by the tester and equipment tested and the airflow (leakage if present) can be easily observed by reading the measurements displayed by LCD pressure display  14   a  and LCD flow display  14   b . Leakage within the equipment being tested can be determined if the air flow exceeds a predetermined limit, for example 0.25 liters per minute. 
     Referring to FIG. 2, electronic air pressure and air flow sensor  12 , air pressure switch  16 , central processing unit  14 , LCD pressure display  14   a  and LCD flow display  14   b  are mounted within a portable, box-shaped housing  22  having a closeable hinged lid  24 , a base  26 , a handle  28 , a mounting plate  30  and a closure latch  32 . The base  26  and lid  24  are preferably attached by a hinge allowing lid  24  to pivot open and close. Closure latch  32  is attached to base  26  and lid  24  so that lid  24  may be secured in the closed position by locking latch  32 , or other known equivalent securing devices. Handle  28  is attached to the top of lid  24  for ease of transporting apparatus  10  and may be flush mounted. The housing  22  and the closing devices may be constructed of metal, plastic, resin or any other suitable rigid material. 
     Electronic air pressure and air flow sensor  12 , air pressure switch  16  and central processing unit  14  (not seen in FIGS. 2 &amp; 3) are preferably attached to the underside of mounting plate  30  which is enclosed within base  26  of enclosure housing  22 . LCD pressure display  14   a  and LCD flow display  14   b  are mounted to mounting plate  30 . When lid  24  is open LCD pressure display  14   a  and LCD flow display  14   b  are viewable by the user, while electronic air pressure and air flow sensor  12 , air pressure switch  16  and central processing unit  14  are concealed from view as seen in FIG.  3 . 
     A power supply such as battery  18  (not shown) is detachably affixed within base  26  using straps, hook and loop fasteners or any other suitable detachable fasteners. When lid  24  is closed, LCD pressure display  14   a  and LCD flow display  14   b  are protected from possible damage due to handling and transport. The lid  24  may be secured in the closed position by latch  32 . Hand air pump  6 , air release valve  4 , pressure reservoir  8 , rubber stopper  17  and the attached tubing can be stored within enclosure housing  22  when not in use. 
     To operate the present invention, as an example, an oxygen mask that includes a regulator and flexible hose is tested. Referring to FIG. 1, the hose end of the oxygen mask is connected in a sealable manner to plug  17 . The operator then squeezes hand pump  6  with the pressure release valve  4  being open, causing air pressure to increase in reservoir  8 . Once the pressure reaches a threshold value through tube  42  of approximately 5 inches of water, the pressure-activated switch  16  turns on power to the CPU  14 , activating LCD pressure display  14   a  and flow display  14   b . Air pressure also increases in tube  44  and in pressure and flow sensor  12 . Flow sensor  12  is connected electrically to CPU  14  and provides digital information to the CPU, which is then used and processed to provide a readable, digital display in the LCD pressure display  14   a  and the LCD flow display  14   b , which is critical to the test. LCD  14   b  is connected to the CPU by wiring  56 , and LCD  14   a  is connected to the CPU by wiring  54 . A threshold air pressure is utilized for system operation, such as 17 inches of water which is created using hand air pump  6  and read on the LCD pressure display  14   a . Once the threshold operating value is achieved, a time element is selected and LCD airflow display  14   b  is observed. If, after a few minutes, the indication is that there is zero or less than 0.25 liters per minute of flow, it is believed that the mask being tested is operating satisfactorily. 
     The oxygen mask hose is then detached from plug  17 . Air pressure in the system may be further released by the air pressure release valve  4  connected to hand pump  6 . Once the air pressure in the pressure switch  16  drops below 5 inches, the system will electrically turn off through wiring  50  to CPU  14 . 
     The use of a digital display for airflow leak detection in air pressure, in conjunction with electronic transducers that provide digital information with a CPU, greatly enhances the accuracy of the portable system. 
     The instant invention has been shown and described herein in what is considered to be the most practical and preferred embodiment. It is recognized, however, that departures may be made therefrom within the scope of the invention and that obvious modifications will occur to a person skilled in the art.