Abstract:
A system and device for monitoring the content of a gas/liquid or gas only containment vessel such as a cylinder is provided. The disclosed apparatus is easily affixed to a standard gas cylinder and configured to monitor the pressure of the cylinder contents and activate a visual and/or audio alarm when the contents of the gas/liquid cylinder are no longer in a liquid or partially liquid state as well as activate another visual and/or audio alarm at a prescribed pressure when the contents of the cylinder are nearing depletion.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an apparatus for monitoring the content of a gas only or a gas/liquid containment vessel, and more particularly to an apparatus that is easily affixed to a standard gas cylinder wherein the apparatus monitors the pressure of the cylinder contents and activates a visual and audio alarm at a prescribed pressure when the contents of the cylinder are no longer in a liquid or partially liquid state. In addition to monitoring the contents of a compressed gas cylinder or gas/liquid containment vessel, the apparatus also functions as a handle or grasp so as to easily lift or maneuver the cylinder. 
       BACKGROUND 
       [0002]    Gas cylinders are widely used in medical and industrial settings for the dispensing of compressed liquefied gas such as nitrous oxide or carbon dioxide, etc. In a compressed liquefied state, certain gases (e.g. nitrous oxide or carbon dioxide, etc.) exist in the cylinder in two phases, namely liquid phase and gas phase. In this two phase state, the gas pressure of the system is generally dependent on the temperature and independent of the liquid volume in the cylinder. During usage of the cylinder, there will come a time when the liquid within the cylinder is consumed. At this point, the remaining gas pressure in the cylinder is dependent on gas volume such that as the volume of gas within the cylinder decreases so does the pressure. Compressed gas cylinders typically include a mechanical or electronic manometer to alert the user as to the pressure of the compressed gas within the cylinder and thus the volume of remaining gas within the cylinder. Such mechanical or electronic manometers are of little use when the contents of the cylinder are a compressed liquefied gas or two phase fluid. 
         [0003]    Users of a compressed liquefied gas need to know the contents of the containment vessel and when the contents are nearing or at a depleted condition. Prior art systems used to monitor compressed liquefied gases or two phase fluids would employ liquid level measurement technologies to accurately determine the compressed liquefied gas contents of such cylinders. Unfortunately, such liquid level measurement technologies are more costly and complex than the standard mechanical or electronic manometers, and often dependent of the orientation of the cylinder or vessel. Thus, there is an ongoing need to provide a simple, inexpensive apparatus that alert users of a compressed liquefied gas to when the contents of the cylinder are nearing or at a depleted condition. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention may be characterized as an a cylinder content indicator device for monitoring contents of a containment vessel configured to hold a fluid in a compressed liquid state, the cylinder content indicator device comprises: (i) a housing body configured to be affixed to a valve that is operatively coupled to the containment vessel; (ii) a pressure gauge dispose in the housing body and capable of detecting the pressure of the contents of the containment vessel when the device is attached to the valve that is operatively coupled to the containment vessel and displaying the pressure of the contents of the containment vessel in analog or digital form; and (iii) an electronics assembly attached to the housing body and operatively connected to the pressure gauge and capable of producing an electronic alarm to signify audibly, visibly, or both audibly and visibly when the pressure of the contents of the containment vessel, as detected by the pressure gauge, falls below one or more predetermined threshold pressure values; wherein at least one of the predetermined threshold pressure values is a pressure at which the fluid in the containment vessel is no longer in a compressed liquid state. 
         [0005]    In a preferred embodiment, the cylinder content indicator device is affixed to the valve with the use of a clamp plate assembly affixed to the housing body in a manner that surrounds the valve. In addition, the cylinder content indicator device preferably uses rechargeable batteries to provide power to the electronics assembly and may include another electronic alarm to signify audibly, visibly, or both audibly and visibly when the power level of the batteries falls below one or more predetermined threshold power levels. 
         [0006]    The present invention may also be characterized as a cylinder content indicator system comprising: (i) a containment vessel having pressurized contents in a compressed liquid state; (ii) a valve operatively coupled to the containment vessel and configured to controllably close or open a passageway for the flow of gas from the containment vessel through the valve; and (iii) a cylinder content indicator device coupled to the valve and in fluid communication with the pressurized contents of the containment vessel, the cylinder content indicator device comprising a pressure gauge dispose in operative association with the valve and capable of detecting the pressure of the contents of the containment vessel and displaying the pressure of the contents of the containment vessel in analog or digital form, and preferably analog form. The cylinder content indicator device further comprises an electronics assembly operatively connected to the pressure gauge and capable of producing an electronic alarm to signify audibly, visibly, or both audibly and visibly when the pressure of the contents of the containment vessel, as detected by the pressure gauge, falls below one or more predetermined threshold pressure values, wherein at least one of the predetermined threshold pressure values is a pressure at which the pressurized contents in the containment vessel is no longer in a compressed liquid state. 
         [0007]    The present embodiments may also be characterized as a cylinder content indicator device for monitoring contents of a containment vessel configured to hold a compressed gas or a fluid in a gas/liquid state, the cylinder content indicator device preferably comprises: (i) a housing body configured to be affixed to a valve that is operatively coupled to the containment vessel, the housing body having an upper surface and a substantially flat lower surface and defining a body width that is greater than the width of the valve and less than the width of the containment vessel; (ii) a pressure gauge dispose in the housing body and capable of detecting the pressure of the contents of the containment vessel when the device is attached to the valve that is operatively coupled to the containment vessel and displaying the pressure of the contents of the containment vessel in analog or digital form; and (iii) an electronics assembly attached to the housing body and operatively connected to the pressure gauge and capable of producing an electronic alarm to signify audibly, visibly, or both audibly and visibly when the pressure of the contents of the containment vessel, as detected by the pressure gauge, falls below one or more predetermined threshold pressure values. The housing body is affixed to the pin indexed valve and extends in a lateral orientation from the valve and forms a grasp configured to lift or maneuver the containment vessel or gas cylinder. 
         [0008]    In various embodiments, the electronics assembly is a front panel electronics assembly forming a visible forward facing surface of the cylinder content indicator device. In such embodiments, the front panel electronics assembly further comprises one or more integrated membrane switches and an integrated printed circuit board with surface mount components. Also, the electronic alarm is preferably a visual indication that the pressure of the contents of the containment vessel, as detected by the pressure gauge, is below the predetermined threshold pressure value corresponding to a pressure at which the fluid in the containment vessel is in a totally gaseous state or is no longer in the liquid or partially liquid state. 
         [0009]    The present invention is particularly suitable for use with compressed liquefied gas cylinders, such as cylinder of carbon dioxide or nitrous oxide. When used with a cylinder of nitrous oxide, the electronic alarm may be a visual indication that the pressure of the nitrous oxide within the cylinder is below the vapor pressure at the present temperature (e.g. about 600 psig for nitrous oxide at about 60 degrees Fahrenheit) thus indicating that the cylinder contents is no longer in the compressed liquid state. Another electronic alarm would be a visual indication and an audible indication that the pressure of the nitrous oxide within the cylinder is in a gaseous state (e.g. below 350 psig or 300 psig for nitrous oxide at about 60 degrees Fahrenheit) and that the cylinder is nearing an empty or depleted condition. In addition, many applications of nitrous oxide also require use of compressed oxygen gas to be delivered concurrently with the nitrous oxide, preferably using a dual cylinder arrangement, a first cylinder for the gas/liquid nitrous oxide and a second cylinder for the compressed oxygen gas. The present cylinder content indicator device is suitable for use on both cylinders of such dual cylinder arrangements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    While the specification concludes with claims specifically pointing out the subject matter that Applicant regards as the invention, it is believed that the invention will be better understood when taken in connection with the accompanying drawings in which: 
           [0011]      FIG. 1  is an exploded perspective view the cylinder content indicator device in accordance with an embodiment of the present invention; 
           [0012]      FIG. 2  is a front plan view of the embodiment of the device shown in  FIG. 1 ; 
           [0013]      FIG. 3  is a cross-sectional view of the embodiment of the device shown in  FIG. 1  taken along line A-A; 
           [0014]      FIG. 4  is a cross-sectional view of the embodiment of the device shown in  FIG. 1  taken along line B-B; 
           [0015]      FIG. 5  is a partially exploded perspective view of an embodiment of the device of the present invention as attached to the regulator valve at the top of a cylinder; 
           [0016]      FIG. 6  is a perspective view of the embodiment of the device of  FIG. 1  as attached to the regulator valve at the top of a cylinder; and 
           [0017]      FIG. 7  is a graph depicting cylinder pressure in psig versus cylinder content in liters for nitrous oxide at 60 degrees Fahrenheit in a standard ‘E’ size cylinder. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Turning to the figures, and specifically  FIGS. 1 through 6 , there is shown a cylinder content indicator device  10 . As seen therein, the device includes a body  20 , a clamp plate assembly  30 , a pressure gauge  40  and a front panel electronics assembly  50 . As shown in  FIG. 5  and  FIG. 6 , the device  10  is preferably coupled to and integrated with a valve  14 , preferably a CGA pin indexed valve that is operatively coupled to and disposed on a cylinder  12  or other pressurized containment vessel. The device  10  and pressure gauge  40  are further configured to align with an orifice  13  on the valve  14  so as to be in fluidic communication with the contents of the cylinder  12  or other pressurized containment vessel. 
         [0019]    As seen in  FIGS. 1 and 3-6 , the housing body  20  is preferably a strong, lightweight and impact resistant nickel plated aluminum housing. The physical dimensions of the housing body  20  and device  10  are selected so as to ensure the profile of the device  10  does not exceed the outer diameter (OD) of cylinder  12  and does not interfere with the intended operation of the valve  14 . Preferably, the housing body  20  has an upper surface and a substantially flat lower surface defining a body width and length that are greater than the width of the valve and less than the width or diameter of the containment vessel. The clamp plate assembly  30  is configured to attach to the back of the housing body  20  using a plurality of screws  32  arranged to affix the clamp plate assembly  30  to the housing body  20  in a manner that surrounds the valve  14  as shown in  FIGS. 5 and 6 . Advantageously, when the device  10  is affixed to the valve  14  and cylinder  12 , the housing body  20  and clamp provides a handle, grasp or other convenient means to hold, maneuver or lift the gas cylinder  12 . 
         [0020]    The housing body  20  or housing further includes one or more cavities configured to receive one or more 3.6V AA sized rechargeable lithium batteries  26  and associated battery cap assemblies  24  and electrical contacts  22 . Power to the device  10  is provided by the rechargeable batteries  26 . Although not shown in the figures, the rechargeable batteries  26  may be recharged while disposed within the device  10  by means of an integrated solar cell or through a charging interface or receptacle disposed on the housing body  20  that operatively couples the rechargeable batteries to a battery charging station or source via a wired connection or via direct contact. The battery charging station or source may recharge the batteries directly or inductively. 
         [0021]    The device  10  preferably uses a ‘C’ shaped Bourdon tube, direct drive pressure gauge or a helical Bourdon tube, direct drive pressure gauge  40  or a disposed in direct communication with the contents in the cylinder  12  or other pressurized containment vessel. In particular, the proximal end of the pressure gauge  40  includes a fitting or coupling  44  that extends from the housing body  20  into a recessed space  45  that is dimensioned to accommodate the valve  14 . The proximal end of the pressure gauge  40  is further configured to engage the orifice of the valve  14  and, when engaged, to open a flow path between pressure gauge  40  and the cylinder  12 . As the pressure changes within the cylinder  12 , pressure gauge  40  responds and a needle of the pressure gauge  40  moves relative to a stationary scale  60 . Thus, at a given pressure within the cylinder  12 , the needle of the pressure gauge  40  will be positioned at a particular location on the stationary scale  60  indicative of that cylinder pressure. The stationary scale  60  is preferably printed on a forward facing, non-ferrous distal end surface  46  of the pressure gauge  40 . The pressure gauge  40  also includes an alignment pin  42  disposed at or near a forward facing, distal end surface  46  of pressure gauge  40 . The alignment pin  42  ensures precise alignment between the stationary scale  60  of the pressure gauge  40  and the front panel electronics assembly  50 . 
         [0022]    The front panel electronics assembly  50  comprises a front panel  52  and an underlying electronics board  54 . The front panel  52  is a scratch resistant, clear, durable plastic layer with printed graphics and one or more indicator windows or ports. In particular, the front panel  52  includes a button  58  that when depressed is configured to silence any audible alarms activated by the electronics board  54 . The front panel  52  also includes a first visual indicator port  55  that illuminates when the contents of the cylinder  12  low as determined by the pressure gauge  40  and electronics board  54  as well as a second visual indicator port  56  for a low battery condition as determined by the batteries  26  and the electronics board  54 . An audio or sound aperture  57  is also located on the front panel  52  through which the audio indicators or alarms are emitted. The front panel  52  further includes a window  59  or opening to provide visibility to the stationary scale  60  on the forward facing, non-ferrous distal end surface  46  of pressure gauge  40 . As illustrated, the preferred device  10  displays the pressure gauge reading together with any visual indicators as well as provides any audio indicators. By viewing the front panel  52 , a user is able to read the cylinder content information directly from the gauge. 
         [0023]    The electronics board  54  is preferably a laminated construction and includes one or more integrated membrane switches and an integrated printed circuit board with surface mount components. The electronics board  54  may further include an adhesive gasket which forms a seal with the housing body  20  of the device  10  to prevent water ingress into the device  10 . The electronics board  54  also includes an on-board microcontroller. The microcontroller takes input from the pressure gauge  40  or other contacts actuated by a user to access functionality of the device  10 , such as, power control, alarm control, built in test actuation, status actuation, device configuration, etc. In the preferred embodiment, the pressure gauge  40  interfaces with the microcontroller via one or more electrical contacts, at least one of which is actuated by movement of the needle across the stationary scale  60 . When actuated, the electrical contacts will cause the microcontroller on the electronics board  54  to produce audio and/or visual indications or alarms. One such audio or visual indication (i.e. alarm) occurs when the cylinder contents are low as determined when the pressure within the cylinder  12 , as measured by the pressure gauge  40 , falls below a predetermined threshold. Another such audio or visual indication (i.e. alarm) occurs when the battery power is low. 
         [0024]    The preferred audio indications or alarms may be produced by a speaker, piezo device or similar component disposed on the electronics board  54 . The preferred visual indications or alarms will be provided by a colored light source, such as a light emitting diode (LED) or combination of LEDs also disposed on the electronics board  54 . Bi-color or multi-color LEDs can be used for the visual indication associated with the battery such that when the battery power level is acceptable, the LED displays a green or flashing green color and when the battery power level is low and preferably below a predetermined threshold, the LED displays a red color or flashing red color. Similarly, multi-color LEDs can also be used for the visual indications associated with the cylinder contents such that when the cylinder pressure is above a first prescribed threshold (e.g. 600 psig), the LED displays a green color and when the cylinder pressure is below the first prescribed threshold (e.g. 600 psig) but above a second prescribed threshold (e.g. 300 psig), the LED displays a yellow color and when the cylinder pressure is below the second prescribed threshold (e.g. 300 psig), the LED displays a red color. 
         [0025]    Although not shown, the preferred device may also include ‘Bluetooth’ capability or other wireless communication technologies to allow the device  10  to connect with nearby or remote devices to convey and/or display the cylinder content status and any alarm conditions on such nearby or remote devices. In medical cylinder applications, such communications would preferably be compliant or example with ISO/IEEE 11073-30300, “Health informatics—Point-of-care medical device communication—Part 30300, et seq. Such wireless communications incorporated within the device would preferably be configured with power saving features, so as to minimize power usage and preserve the battery life. 
         [0026]    Turning now to  FIG. 7 , there is shown is a graph depicting cylinder pressure in psig versus cylinder content in liters for nitrous oxide at 60 degrees Fahrenheit containing in a standard ‘E’ size cylinder. When filled, the cylinder contains nitric oxide in a two phase state. As such, the cylinder pressure will remain somewhat constant at a given temperature until the liquid phase within the cylinder has completely evaporated. Only when the contents of the cylinder are in a completely gaseous state, the pressure within the cylinder is dependent on the volume of gas within the cylinder. During usage of the cylinder, the disclosed cylinder contents indicator or device  10  will indicate the contents of the cylinder as acceptably full in region  92  where the cylinder pressure is at or above a first prescribed pressure (e.g. 600 psig), which is at or near the point when the cylinder contents is in a two phase state. In region  92 , the two phase state of the cylinder contents is transitioning to a gas-only state. In region  94  the pressure within the cylinder is now dependent on the volume of gas within the cylinder. In region  94 , the cylinder contents indicator or device  10  will produce a visual indication that the contents of the cylinder is running low as the cylinder pressure is below the first prescribed threshold (e.g. 600 psig) but above a second prescribed threshold (e.g. 300 psig to 350 psig). In region  97 , the cylinder pressure is within the second prescribed threshold limits (e.g. 300 psig to 350 psig) and the cylinder contents indicator or device  10  will produce a visual indication and audio warning that the cylinder contents are dangerously low and that the cylinder should be replaced. In region  96 , the cylinder pressure is below the second prescribed threshold (e.g. 300 psig) and the cylinder contents indicator or device  10  will produce a visual indication and audio warning that the cylinder needs to be replaced. 
         [0027]    While the present invention has been described with reference to a preferred embodiment and features, it is understood that numerous additions, changes and omissions to the disclosed device may be made without departing from the spirit and scope of the present invention as set forth in the appended claims.