Patent Publication Number: US-6666623-B1

Title: Buoyancy control device and method for controlling divers ascent

Description:
FIELD OF THE INVENTION 
     This invention relates to a buoyancy control device for scuba divers and more particularly to a buoyancy control device for controlling the vertical motion of a scuba diver under normal and emergency conditions. 
     BACKGROUND FOR THE INVENTION 
     Buoyancy compensators for scuba divers are well known for use in controlling buoyancy while diving. Such compensators typically consists of a flexible air bladder and hand-activated pneumatic fill and release valves. In this manner, the buoyancy force acting on the diver is changed by adjusting the volume of air in the flexible bladder. 
     Such compensators generally require careful attention from a diver to attain and maintain neutral buoyancy, to safely descend, to safely ascend and to establish adequate positive buoyancy at the surface. The diver controls buoyancy by using the hand-activated air valves to add and release air to and from the buoyancy compensator. Such control is based on vertical motion changes, references to stationary objects or the use of a depth gauge. 
     Neutral buoyancy is achieved at a selected depth and must be adjusted as the depth of the dive changes. A deviation from neutral buoyancy also occurs due to changes in the hydrostatic pressure of the water which changes in depth as well as changes in the loss of weight as air from the compressed air tank is used. 
     An improved buoyancy compensator that reduces the scuba divers attention and exertion required for buoyancy control is disclosed in the U.S. Pat. No. 5,496,136 of Egan. As disclosed therein, a buoyancy compensator includes an electronic sensor/valve assembly and a flexible air bladder which automates and controls the vertical motion of a diver. A computer acquires pressure, temperature and air flow data to determine the diver&#39;s vertical motion and the amount of air in the bladder. The computer controls electronic fill and release valves to change the volume of air in the bladder. Algorithms are implemented by the computer to automate controlled vertical propulsion for ascending, descending, neutral buoyancy, maintenance and surface operation. Automated transitions are provided between modes of operation and for a timed safety stop during the ascent from the dive. 
     Another approach for an improved buoyancy compensator device is disclosed in the U.S. Pat. No. 5,560,738 of Noel. As disclosed therein, a depth sensitive diver safety system is utilized with an underwater breathing apparatus. The system includes a first automatic ascent control stage which initiates gradual regulated inflation of a personal flotation device from a pressurized air source when a user drops below a danger/low air level corresponding to a diver&#39;s depth. The system also includes a second automatic ascent control stage which is structured to initiate gradual, regulated inflation of the personal flotation device upon the diver&#39;s depth exceeding a pre-set depth level. The 5,560,738 patent is incorporated herein in its entirety by reference. 
     A more recent approach to buoyancy compensators is disclosed in the U.S. Pat. No. 5,746,543 of Leonard. The Leonard patent discloses a volume control module for controlling the buoyancy of a diver by controlling the volume of air in a buoyancy chamber of a buoyancy compensator. The Leonard device is used in conjunction with underwater equipment which is provided with an adjustable buoyancy chamber. The Leonard patent is also incorporated herein in its entirety by reference. 
     Notwithstanding the advances disclosed in the aforementioned patents, it is presently believed that there is a need and a commercial demand for an improved buoyancy control device. It is believed that there is a need for a device in accordance with the present invention that provides buoyancy control without excessive diver attention through all phases of the dive. In addition, the buoyancy control device in accordance with the present invention provides for automated compensation for changes in buoyancy of a scuba tank as the air is consumed by a diver. 
     A further advantage of the buoyancy control devices in accordance with the present invention is that they provide automatic vertical propulsion and vertical velocity control of a diver during the descent portion of the dive and also during the ascent portion of the dive. A still further advantage of the present device is the inclusion of a safety feature that allows a diver or a second diver to provide for a relatively fast ascent under an emergency with a limited risk of a lung expansion injury or decompression sickness. 
     Further, the improved device in accordance with the present invention allow a second diver to send an injured or unconscious diver to the surface unaccompanied by the second diver at a controlled rate. In addition, it is believed that the devices in accordance with the present invention can be manufactured at a competitive price, and are reliable and durable. 
     BRIEF SUMMARY OF THE INVENTION 
     In essence, the present invention contemplates an improved buoyancy control device for scuba divers. The device includes a buoyancy compensator or vest to be worn by or attached to a diver. The device also includes one or more compressed air tanks adapted to be carried by a diver in a conventional manner and means such as a depth or pressure gauge for measuring the depth of a diver. A valve or other means is connected to the buoyancy compensator and the compressed air tank for releasing air from the compressed air tank into the buoyancy compensator and for releasing air out of the buoyancy compensator. The device also includes a microprocessor operatively connected to the means for measuring the depth of the diver and to the valve for controlling the amount of air in the buoyancy compensator in response to the depth of a diver. In addition, the device includes means for inputting a first selected rate of ascent for controlling the vertical movement of a diver under normal conditions and a second selected rate of ascent for controlling the vertical movement of a diver under emergency conditions. An additional element in the device is means accessible by a second diver for overriding the first rate of ascent and activating the second rate of ascent. In this way, a disabled or unconscious diver can be safely sent to the surface without escort by a rescuing diver at a rate which is greater than normal but acceptable under emergency conditions. 
    
    
     The invention will now be described in connection with the accompanying drawings wherein like numbers are used to indicate like parts. 
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a prior art depth sensitive safety system of a type used in connection with scuba diving; 
     FIG. 2 is a block diagram which illustrates the operation of a prior art device; 
     FIG. 3 is block diagram which illustrates the operation of a device in accordance with the present invention; and 
     FIG. 4 is a schematic illustration of a control panel for use in a device in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
     The buoyancy compensator device according to a preferred embodiment of the present invention is designed for use with conventional scuba diving equipment. For example, a depth sensitive diver safety system as disclosed in the aforementioned Noel patent is shown in FIG.  1 . As shown therein, a scuba diving system  10  includes first and second automatic control stages  12  and  14 . The system  10  also includes at least one pressurized air tank and possibly more which can be defined as a pressurized air source  16 . A high-low pressure regulator  18  and a personal flotation device  20  such as a vest which is adapted to be worn or attached to a diver are also provided. 
     The conventional scuba diving system  10  typically includes an air outlet  22  connected to the high-low pressure regulator  18  to provide a source of air for various purposes. For example, the high-low pressure regulator  15  includes at least one high pressure air source  24  and one low pressure source  26 . It is common for regulators  18  to include a high pressure source  24  connected with a plurality of gauges  28  which indicate the quantity of air remaining in the air source  16  and a plurality of low pressure sources  26  which lead to a second stage  30  through which the diver breathes and the personal flotation device  20  is connected to the source  16 . The low pressure air source  26  is constructed and arranged so that air will be supplied at a breathable pressure which co-responds to a diver&#39;s depth. To be more specific, as a diver descends beneath the water surface, the breathable pressure which corresponds to the diver&#39;s depth will increase. Similarly, as the diver ascends to the surface, the breathable pressure will decrease. This same breathable pressure is the pressure at which the low pressure air source  26  which exits the regulator  18  are maintained. 
     As taught by the aforementioned Noel patent, a first ascent control stage  12  is constructed and arranged to initiate inflation of a personal flotation device  20  upon an air pressure within the air tank or pressurized air source  16  dropping to a dangerously low level with respect to a diver&#39;s depth. Further, as a diver descends beneath the water surface, he/she will require greater quantities of air to safely return to the water surface. Additionally, at greater depths, the pressure is greater such that air will be drawn from the pressurized air source  16  at a much more rapid rate which necessitates additional air for the diver to return to the surface. 
     In addition, the device in accordance with the U.S. Pat. No. 5,560,738 includes a second automatic ascent control stage  14 . The second ascent control stage  14  is constructed and arranged to initiate gradual regulated inflation of a personal flotation device  20  when the diver&#39;s depth exceeds a pre-set safe depth level. The second automatic ascent control stage  14  is connected in line with the low pressure air source  16  either integrally or separately from the first automatic control stage  12  and can alternatively be connected at and/or replace the conventional inflator connections of a personal flotation device  20 . 
     As shown in FIG. 2, a buoyancy compensator device  10  for providing automatic control over the vertical motion of a scuba diver includes a buoyancy compensator bladder  42  and a subassembly  44  which are coupled together to provide fluid communication as indicated by arrows  43  and  45 . 
     The bladder  42  is flexible so that when air is added to the bladder  42  through a coupling as indicated by arrow  43 , the volume of water displaced increases. Also, when air is released from the bladder  42  as indicated by arrow  45 , the volume of water displacement decreases. The bladder  42  compresses and expands with changes in the hydrostatic pressure of the surrounding water. 
     The subassembly  44  is coupled to regulator  18  (see FIG. 1) in a conventional manner to provide fluid communication between the source of pressurized air  16  (FIG. 1) as indicated by arrow  46 . The assembly  44  is also coupled to a vent passage (not shown) as indicated by arrow  48  for fluid communication with the surrounding water. A check valve  50  provides a discharge path for air out of the assembly  44  and into the vent passage. The check valve  50  also blocks the flow of water into the assembly  44 . 
     The scuba tank regulator  18  (FIG. 1) is coupled to the assembly  44  at the input of a fill valve  47 . Fill valve  47  is conventional and includes electronic driver circuitry so that the valve can be opened or closed based on an input digital signal. The fill valve  47  is normally closed when no electrical power is applied to it and is used to gate the flow of air into the buoyancy compensator  42  which is supplied from a conventional air supply  16  (See FIG.  1 ). 
     The output of the fill valve  47  is coupled to the input of a fill gas flowmeter  49  by a coupling  51  which provides fluid communication between the two components. Flowmeter  49  is any suitable meter that provides an analog electrical output signal that is directly related to the sensed gas flow rate. The gas output of flowmeter  49  is connected to flexible air bladder  42  by coupling  43  which provides fluid communication between flowmeter  49  and flexible air bladder  42 . The flowmeter  49  senses the amount of air added to the bladder  42 . 
     The flexible air bladder  42  is also in fluid communication with the input of a release gas flowmeter  53  of subassembly  44  by the coupling  45 . The flowmeter  53  can be any suitable meter that provides an analog electrical output signal that is directly related to the sensed gas flow rate. The flowmeter  53  senses the amount of air released from the bladder  42 . 
     The gas outlet of the flowmeter  53  is connected to an input release valve  54  by a coupling  55  which provides fluid communication between the two components. The release valve  54  may be of any suitable design that includes an electronic driver circuit such that the release valve  54  can be opened or closed based on the state of an input signal. The output of the release valve  54  is connected to the check valve  50  by means of a coupling  57  which provides fluid communication between the release valve  54  and check valve  50 . The release valve  54  is used to gauge the flow of air from the bladder  42  into the surrounding water. 
     A computer  60  is part of the subassembly  44  and may be any suitable computer which has sufficient computing capacity and memory to implement the controls. The microprocessor  60  has digital output ports to provide digital output high/low voltage levels and digital inputs to receive digital input high/low voltage levels. The computer  60  is connected to fill valve  47  and release valve  54  by digital control lines  61  and  62  respectively. The high/low voltage state of the signal from the computer  60  on control line  61  dictates the open/close state of fill valve  47  while the high/low voltage state of a signal from the microprocessor  60  on control line  62  dictates the open/closed state of release valve  54 . 
     A scuba diver can input information into the computer  60  by means of a diver&#39;s control panel  65  which is connected to the computer  60  by a digital bus represented by a double arrow  66 . The panel  65  provides an interface to input pre-dive information as well as manual selection of the dive mode during a dive. The panel  65  may also display dive output status information for the dive from the computer  60  such as time elapsed, dive depth and vertical velocity. 
     Computer  60  is also connected to an analog-to-digital converter  67  via a digital bus represented by arrow  68 . Converter  67  is any suitable 8 bit analog-to-digital converter. The conversion input signal to converter  67  is provided by computer  60  via a control line  69 . 
     An analog input signal to converter  67  is provided by an analog multiplexer  70  via a signal line  71 . Multiplexer  70  may be any conventional analog multiplexer that outputs one of four analog input signals to signal line  71 . The signal to be output on signal  71  is based on the state of two digital input control lines provided by computer  60  and represented by a double line arrow  72 . 
     One of the input signals to the multiplexer  70  is a signal provided by a pressure sensor  73  via signal line  74 . Sensor  73  may be any suitable sensor with supporting circuitry, that provides an analog output voltage which is directly related to the hydrostatic pressure of the surrounding water. A second signal provided to multiplexer  70  is a signal provided by a temperature sensor  75  via a signal line  76 . Sensor  75  may be any suitable sensor, with supporting circuitry, that provides an analog output voltage which is directly related to the temperature of the air within the bladder  42 . 
     The remaining two signals provided to the multiplexer  70  are provided by flowmeters  49  and  53  via signal lines  77  and  78  respectively. The input signals on line  57  is an analog voltage from flowmeter  49  which is directly related to the amount of air flowing into the bladder  42 . The input signal on signal line  58  is an analog voltage from flowmeter  53  which is directly related to the amount of air flowing out of the bladder  42  and into the surrounding water. 
     A power source for the above described buoyancy compensator device is a conventional battery pack (not shown). A conventional method for operating the afore-described device is set forth in the aforementioned U.S. Pat. No. 4,549,136 of Egan which is incorporated herein in its entirety by reference. 
     In essence, a preferred embodiment of the present invention includes the same essential elements as shown in FIGS. 1 and 2. However, the device in accordance with the presently preferred embodiment of the invention includes an added safety feature which will be described in connection with FIGS. 3 and 4. 
     As illustrated in FIG. 3, a buoyancy control device  80  will typically include a flexible bladder, a compressed air tank, a depth gauge, a microprocessor for controlling the amount of air in the flexible bladder. It will also include computer input means  81  for inputting a first selected rate of ascent for controlling the vertical movement of a diver under normal conditions. For example, a diver can enter a preselected depth and a preferred rate of ascent including stops as for example a vertical ascent of about 10 ft. per minute with our without stops. A diver may for example program a stop of several minutes at about 14 ft. below the surface as commonly used. 
     The buoyancy control device  80  also includes input means  82  for inputting a second rate of ascent for use under emergency conditions. The second input means  82  may utilize the first input means  81  such as a rate selection switch to program a rate of vertical movement into a computer plus means for bypassing the first selected rate of ascent. 
     After selecting a first and second rate of ascent, a diver swims to a preselected depth as indicated in box  83  and uses the buoyancy compensator for neutral buoyancy at that depth. The diver may also adjust the buoyancy in a conventional manner to maintain a given depth, descend or ascend under manual control. The diver may choose to return to the surface under manual control or choose to return to the surface by initiating a first rate of ascent  84  for automatic control of their vertical movement. In those cases, the diver will be returned to the surface as indicated by the box  85  in a controlled manner. 
     However, when a diver fails to initiate action to return to the surface as for example due to an inability to take such action, it may be necessary for a second diver to come to the aid of the impaired diver. In such cases, it may be desirable to return the impaired diver to the surface at a slightly higher rate as for example, 15 ft. per minute for medical attention, but at the same time avoiding serious problems due to too rapid decompression. 
     The second diver may elect to initiate the second selected rate of ascent as indicated by box  86  and send the impaired diver to the surface automatically and unescorted as indicated by box  87 . 
     The buoyancy during a dive may be maintained in a conventional manner using a conventional control panel. However, a control panel  89  in accordance with the present invention includes means for initiating a first rate of ascent as indicated by a switch  90  in FIG.  4 . The device may also include means such as a recessed and covered button  91  for bypassing the first selected rate of ascent and automatically sending an unaccompanied or impaired diver to the surface without the necessity of escorting the impaired diver. A cover  92  prevents any inadvertent use of the second rate of ascent. The control panel  89  must also include variable means  93  for varying the rate of ascent under emergency conditions and/or to select a programmed step at preselected depths or for preselected times. 
     The buoyancy control device in accordance with the present invention is generally controlled by conventional techniques such as a switchable computer program which is well within the skill of a person of ordinary skill in the art. 
     While the invention has been described in connection with its preferred embodiments, it should be recognized that changes and modifications can be made therein without departing from the scope of the appended claims.