Abstract:
A dental water sterilization unit having a heat treater which raises the temperature of domestic water supply to the sterilization unit sufficiently to sterilize and deoxygenate the water and then cools the water to a suitable temperature for comfort of the dental patient. The unit may have a water chiller or heat exchanger to lower the temperature. The unit may also have a porous packing in the heat treater to enter mixed steam and water to facilitate the sterilization and deoxygenation process.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of our copending provisional application serial No. 60/074,620 filed Feb. 13, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to water disinfecting systems and particularly those for medical use such as in the field of dentistry. 
     2. Related Art 
     Modern dental units contain water supply systems that provide coolant and rinse water to a number of dental instruments, such as for example, high-speed dental hand-pieces, ultrasonic scalers and air and water syringes. Dental professionals have become aware that the microbiologic quality of water used in dental treatment should be improved. 
     Dental unit waterlines have been shown to harbor a wide variety of microorganisms including bacteria, fungi and protozoa. These microorganisms colonize and replicate on the interior surfaces of the waterline tubing, resulting in microbial accumulations termed “biofilms.” Biofilms serve as a reservoir significantly amplifying the numbers of free-floating microorganisms in the water that exits the waterline into the patient&#39;s mouth. 
     Levels of contamination in dental unit treatment water frequently exceed 100,000 colony forming units per milliliter (cfu/ml). Although there is no solid evidence of a public health problem, the presence in dental waterlines of potential human pathogens including Pseudomonas, Legionella, and non-tuberculous Myco-bacterium species suggest reason for concern. The American Dental Association&#39;s Council on Scientific Affairs recommended in September, 1995, that by the year 2000, water delivered to patients during non-surgical dental procedures consistently contain no more than 200 colony forming units per milliliter (cfu/ml) of aerobic mesophilic heterotrophic bacteria at any point in time in the unfiltered output of the dental unit. 
     It is a common practice to slightly heat dental unit water to increase patient comfort because cool water in the patient&#39;s mouth can be painful depending on the procedure being performed. However, it has been suggested that the heating of the water for patient comfort may further promote the formation of biofilm. 
     The conventional methods for addressing the problem of microbial infestation of dental water supply systems are independent water reservoirs, chemical treatment regimens, point of use filters, or oxidation and ozonation. Some of these conventional methods require daily draining and purging regimens even in the case of independent purified water reservoirs. These prior methods are also very costly and some of the chemical treatment regimens have been suspected as causing potentially toxic or carcinogenic byproducts when the treating chemical reacts with the material of the waterline. Also, the chemicals chosen must be bio-compatible because of the possibility that a chemical residue may remain in the waterline. Many of the chemicals proposed for treatment of dental waterlines have the potential to react with the material of the dental water delivery system. For example, chlorine compounds may react with the biofilm or other dissolved organic compounds to produce an undesirable class of chemicals known as tri-halomethanes. Other agents such as bromine and ozone may also produce undesired chemical by-products. Finally, the point of use filtration systems (filter in the hand-piece) does nothing for build-up of biofilms in the waterline and usually the filter has the annoying need to be replaced daily. With the problem of undesired chemical by-products being produced and the problem of high cost and maintenance, this is a difficult problem to solve particularly if one utilizes the prior conventional methods. 
     One prior art system is shown in U.S. Pat. No. 5,556,279 issued Sep. 17, 1996 to Wolf, which discloses a system which utilizes a combination activated charcoal resin filter and an iodinated fixed rate exchange resin filter which could be categorized as a point-of-use filter system or a point-of-use chemical treatment system. U.S. Pat. No. 5,158,454 issued Oct. 27, 1992 to Viebahn and assigned to Dr. Hanslet, shows ozone radical converters to ozonize water to make the water virtually microbe free. U.S. Pat. No. 4,978,297 issued Dec. 18, 1990 to Vlock, shows an auxiliary chamber to communicate with the water line. The auxiliary chamber can receive an automatically dissolving tablet for disinfectant. U.S. Pat. No. 4,973,247 issued Nov. 27, 1990 to Varnes, shows the removal of the dental unit from the domestic water supply by utilizing a sterile coolant supply. The above noted Wolf U.S. Pat. No. (5,556,279) shows a two stage filter/chemical treatment cartridge and the first stage filters or neutralizes any chlorine from the source water with a charcoal resin and the second stage releases an iodinated resin which neutralizes and kills bacteria. The Viebahn prior art U.S. Pat. No. (5,158,454) uses a type of oxidation to ozonize the water to kill the bacteria. The Vlock U.S. Pat. No. (4,978,297) shows provisions to place a dissolving tablet in the waterline for purification purposes. The Varnes prior art patent U.S. Pat. No. (4,973,247) has a stand alone separate sterilized coolant supply. These patents show that there is a long felt need for sanitary dental water and that the problem continues to be addressed without satisfactory resolution. 
     As noted in the above discussion of the related art, the methods used in the above cited patents have problems that vary from the possible production of harmful chemical byproducts, to high level cost and maintenance. Better systems are needed, as suggested by the American Dental Association&#39;s Council of Scientific Affairs. 
     SUMMARY OF INVENTION 
     The applicants have recognized the real need to provide sterilized water to the waterline systems of dental units. The applicants have also recognized the inherent problems when utilizing the conventional methods. 
     The invention addresses the water sanitization difficulties of the prior art by economically providing sterilized water by deoxygenating and by raising the water temperature to a temperature within the range of about 190 to about 300 degrees Fahrenheit under 2 to 25 pounds of steam or operating pressure for water traveling through a dental unit waterline system. This is preferably done by sterilizing water used during medical-dental procedures without introducing disinfectants into the waterline, and thus, without trying to overcome the possibly thousands of adverse chemical reactions that could occur or remedy the adverse effects of chemical treatment systems and the high maintenance associated with such systems as well as the high maintenance involved in stand alone reservoir systems. 
     The invention preferably provides sanitary medicinal water on demand by using and maintaining approximately a one to four liter vessel to receive and to sterilize the water in virtually real-time through use of a sterilized heater-coil in the vessel to raise and maintain the temperature of the water in the vessel and to deoxygenate the water in the vessel. 
     The invention preferably delivers sterile water to the dental apparatus at a temperature comfortable to the patient through the use of a cooling jacket of a heat exchanger and/or refrigeration-chiller. 
     These objects are achieved in the invention by providing a water heater unit that heats tap water to sterilize it, deoxygenates it and stores a quantity of the resulting deoxygenated sterilized water in a heated deoxygenated state and then cools a selected amount of such water for comfortable use. The water heater unit includes a connection to a domestic water service received through a shut-off valve; either a heat-exchanger that receives domestic water and passes it through a cooling jacket to raise its temperature prior to traveling to the heater while passing the selected amount of water to be used through a heat exchanger and/or refrigeration cooler to lower its temperature prior to traveling to the dental apparatus; an optional water release line and optional shut off valve which releases water from the heat-exchanger back into the domestic water system; a waterline with shut off valve that channels water from the cooling jacket of the heat-exchanger, if the heat exchanger is being used, to the water heater; a vent valve on the water heater unit for venting; a pressure gauge that monitors the pressure of the water heater unit; a pressure switch that is tripped if pressure is greater than 20 to 30 psig shutting off the heater; a water heater unit with heater coil; a pressure relief that relieves overpressure; a level control to maintain the proper amount of water in the heater; a water pump, if required, to deliver the output water to a dental apparatus; a test point auxiliary water line with shut-off valve that connects to the water in water heater; a heat-exchanger and/or refrigeration-chiller; a test point auxiliary waterline with shut-off valve that communicates with the waterline leading to the dental apparatus; a waterline with shutoff valve from the heat-exchanger and dental apparatus; and a temperature switch which communicates with the waterline from the heat-exchanger to the dental apparatus and connected to the heater coil. 
     The invention has achieved an economical, safe and low maintenance approach to solving the water quality problem of dental units. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood by reference to the Drawing, in which: 
     FIG. 1 is an overall system diagram showing a preferred embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention is first described with reference to FIG. 1, which depicts the overall system  10 . The unit  10  basically comprises the heat exchanger, refrigerator-chiller and the water heater unit the detailed function of which will then described with reference to FIG.  1 . All parts and connections listed and used within FIG. 1 are preferably either stainless steel, brass, or copper with solder joints completed with a lead-free solder or other heat resistant, non-contaminating conduits. Pre-manufactured systems, i.e., refrigerator-chiller, heat-exchanger, pressure and temperature switches, valves and their controls, are preferably both UL and FDA approved. 
     Referring to FIG. 1, there is a preferred exemplary dental water sterilization system  10  shown. System  10  comprises a water input section  12 , a water sterilization section  14 , a control section  16 , a cooling section  18 , a primary outlet section  20 , and a secondary outlet section  22 . 
     The input section of  12  contains, among other things, a domestic water inlet line  101  that is in selective fluid communication with a domestic water source  11  through a valve  101   a  and with the inlet of a heat exchanger  102 . This waterline source  101  selectively provides the water supply for the cooling jacket for the heat exchanger  102  and for the supply of water to the heater. The water flowing into the exchanger or  102 , in this manner, flows through the cooling jacket and out of the outlet of the heat exchanger and into water lines  103  and  104 . A valve  103   a  provides a means to cause water from line  103  to be forced into line  104  and thus to heater  107  when valve  130  is open. Alternatively, valve  103   a  can be opened to allow domestic water to flow through the cooling jacket of heat exchanger  102  to cool the water in the cooling section  18 , as below described. Temperature switch (3 way valve)  125  is in operative communication with valve  103   a . Temperature at least equal to a preset value for valve  125  can activate valve  125  to provide recall back to chiller  102   a  in the event the water being delivered to the dental apparatus is too hot, so that the water never can reach the dental apparatus until the temperature switch  117  senses that it is cool enough for comfort. Temperature that is too low is sensed already by sensor  116 , described below. Core waterline passageway  105  containing heated sterilized water is in heat transfer adjacency with cooling jacket of heat exchanger  102 . Water line  104  has an outlet end in fluid communication with inlet  128  of heater unit  107 . 
     Looking next to the treater section  14 , it is seen that water received in inlet  128  will pass through heater  107  where it will be heated by heating element  109  and then flow out of the outlet  122  of the heater  107  and into line  124  of outlet section  20 . During its passage through heater  107 , the water is deoxygenated and heated to a saturated state at the given pressure for sterilization. 
     The heated sterilized water is then provided to the output section  20  and then to the dental patient or dental unit for subsequent use. In order to be more comfortable for the patient, the water is cooled in outlets section  20  prior to being delivered to the patient or dental apparatus. Since the sterilization of water by heating is likely to generate steam or oxygen, a steam or oxygen relief passage  120  is provided. This steam or oxygen relief passage  120  can serve to provide for a supply of steam to another device such as an autoclave (not shown) or a route for oxygen to escape when deoxygenating the water in the heater unit  107 . Water from waterline  104  flows into heater unit  107  and then through packing  108 . This water partially heated by steam rising from water heated by heating element  109  within heater unit  107  as water drops through packing  108 . Packing  108  disperses the water passing therethrough to promote heating by steam. This intimate upward passage of steam through the downward flowing water in heater  107  promotes the deoxygenation of the water during passage through the heater  107 . 
     In order that heater  107  may perform properly, a control section  16  is provided. This control section  16  comprises a control unit  140  and various gauges and controls in electrical communication with unit  140 . For example, a level control  111  monitors the water level in a water column  110  and supplies a signal to control unit  140  when the water level reach a preset height in column  110  indicative of the desired level being reached in heater  107 . A sight glass  110   a  is needed to visualize the water level if a visual sensor mechanism is used for control  111 . The water column  110  can be a typical vertical, tube-type, level control  111 . Other level controls could be substituted, if desired. Level control  111  is in electrical communication with control unit  140  by a signal line  150  and control unit  140  is in turn connected by a signal line  152  to a solenoid inlet valve  130  of water line  104 . Solenoid inlet valve  130  provides a shutoff capability to waterline  104  so that water line  104  is fully or partially shut off when the water level in water column  110  reaches a pre-set level. A conventional pressure switch  114  monitors the pressure of the heater unit  107  and sends a signal through a line  146  to control unit  140  indicative of the pressure in heater  107 . Pressure switch  114  is in operative communication with control unit  140  through signal line  146  and optionally through a command line  148  capable of sending signals to switch  114  to vary the set point at which switch  114  generates a signal in line  146 , and thus to vary the maximum pressure and temperature in the heater  107 . Control unit  140  is also in electrical communication with heater coil  109 . Pressure relief valve  113  relieves the pressure of heater unit  107  when the pressure in unit  107  reaches the set point of relief valve  113 . Valve  113  serves as a safety valve to prevent overpressurization which might damage the system or cause an explosion. Before excessively high pressure is reached in heater  107 , the relief valve  113  is actuated to relieve the pressure within heater unit  107  and any exhausted fluid output flows safely into drain  115 . Once the pressure in heater  107  returns to a safe level, valve  113  closes. Optionally, valve  113  could be a single use blowout disk type pressure relief valve that is only operable to open and once opened cannot reclose, thus requiring service should a preselected overpressure condition be reached in the system. The single use pressure relief valve would have the advantage of allowing the system to be checked for other problems that might have given rise to the overpressure condition before the system is repressurized. The pressure relief valve has the advantage of not requiring a service call where the operator can readily determine the problem. Thermostat  116  monitors the temperature of the water in the water reservoir of heater unit  107  and sends a signal to control unit  140  through signal line  156  to allow control unit  140  to issue the appropriate commands to keep the temperature up to saturated conditions so that deoxygenation occurs. When control unit  140  determines that the signal from line  156  indicates that a pre-set maximum desired temperature has been reached in the water reservoir, control unit  140  shuts off electrical current to heater coil  109  within the heater  107 . Thus the system  10  has both pressure shutoff as part of the function of control unit  140  via pressure switch  114  and line  146  and temperature shutoff via switch  116  and line  156 , although this redundancy is optional since the pressure and temperature are interrelated functions. Line  129  could also selectively lead to a drain to allow selective draining of the heater  107  for cleaning of the system, repair of the systems, or for shutdown of the system for long periods. Flow through line  129  would normally be closed by valve  126 , and valve  126  would be opened, either manually or through control unit  140  when it was desired to drain the system. Temperature switch  117  monitors the temperature of water output from fluid pump  119  and signals control unit  14  to shut off power to the heater element when the temperature in the cooled sterilized water going to the dental apparatus reaches a predetermined value. The heater element could also be shut on or off in response to predetermined low or high temperatures, respectively being reached within the heater unit  107 . Temperature switch  117  could also be provided with a shut off feature at a given maximum temperature, to provide some assurance that the need dental patient will not receive water at an uncomfortably high temperature. Temperature switch  117  is also in operative communications with control unit  140 . As previously stated, control unit  140  is also in control communication with heater coil  109  of heater unit  107 . Temperature switch  117  shuts off heater coil  109  if the temperature of the water exiting fluid pump  119  is too hot. 
     The cooling section  18  of the sterilization system  10  includes a chiller, a heat exchanger and associated valves and lines and control connections to make either one or both work to cool the heated sterilized deoxygenated water that line  124  brings to the cooling section from the water sterilization section  14 . A waterline  106  leads from the outlet of the chiller  102   a  to a split where water can go either to line  106   a  and then through valve  106   d , bypassing the heat exchanger, or to line  106   b  leading through a valve  106   c  to the inlet of the core  105  of the heat exchanger  102  for further cooling. There is no need to bypass the chiller  102   a , as it would simply be turned off if it was not desired for cooling the water entering it from line  124 . If the operator desired to bypass the heat exchanger, valve  106   d  would be open and valve  106   c  would be closed. 
     Referring next to the output section  20  of the sterilization system  10 , which begins just before the juncture of line  106   a  with line  105  as it comes out of heat exchanger  102 , it is seen that there are provided two test lines  142 ,  158  having normally closed test valves  142 ,  160 , respectively, to allow for collecting samples of the water exiting the heat exchanger and chiller, respectively, for testing purposes to determine if the water entering the output section is sterilized and deoxygenated and A at an appropriate temperature or as a drain for the cooling section. There is also provided in output section  20  a pump  119 . This pump  119  has inlet end in fluid communication with to the downstream end of cooling section  20  and has an outlet leading through a downstream portion  132  of the outlet passageway  124 ,  106 ,  106   a / 106   b ,  132  to the dental apparatus  118 . Water exiting heating zone outlet  122  flows through lines  124 ,  106 ,  106   a  or  106   b / 105  and pump  119  to the downstream portion or system outlet  132  to the dental apparatus or other medical device. Water line  105  serves as the core of heat exchanger  102  and/or refrigeration-chiller  102 a. Fluid pump  119  has outlet end in fluid communication with the outlet  132 , which leads to a dental apparatus  118 . Fluid pump  119  thus draws water from the water-reservoir of heater unit  107  to the core water line passageway  105  and/or refrigeration-chiller  102   a . It will be appreciated that the water sterilization  14  can generate substantial pressure due to the creation of steam and that this pressure may be sufficient to drive fluid through the cooling section  18  and output section  20  without operating pump  119 . This may be desirable to reduce noise. In this way, the sterilization unit  10  is capable of delivering sterilized water to dental apparatus  118  at a temperature comfortable for the patient because the previously heated water is subsequently cooled by the cooling jacket of heat-exchanger  102 , and/or refrigeration-chiller  102   a . The downstream portion  132  is provided with a temperature responsive valve  125  that opens if the temperature is at or above a certain preset temperature, to try to achieve the desired amount of cooling by recycling a portion of the contents of line  132  back to the inlet of cooling section  18  to be further cooled. Output section  20   a  also preferably has a thermostat  117  that senses the temperature in line  132  either upstream via line or downstream of the temperature responsive valve  125 , or both, depending on the desire off the operator and sends a signal to control unit  140  to shut of heater element  109  if the temperature sensed reaches some preset maximum level, such as  120  degrees, indicating that the cooling is not working properly. Thermostat  117  serves as a safeguard in case even recycling is insufficient to achieve the desired cooling, as that would indicate cooling section  18  is not working properly. The test line  144  controlled by normally closed valve  142  allows for confirmation of the effectiveness of the system through sampling of the water in the output section  20 . 
     The unit is preferably provided with a number of optional advanced features that assist in more efficient and versatile operation. The cooling system can be equipped with a chiller or a heat exchanger or both, as described above to achieve maximum flexibility of application. Either can be used or both can be used, by the proper manipulation of the valves  106   c  and  106   d . This heater can be adjusted as desired in order to cool the sterilized water from the sterilization and saturation temperature, such as 270 degrees Fahrenheit, to which it is heated, down to the patient use temperature, such as 95 degrees Fahrenheit. The heat treater is used to heat the water to the temperature selected for sterilization and deoxygenation of the water. At the sterilization temperature, the water is too hot to be comfortable to the dental patient. Since this is so, the water must be cooled to a lower temperature by some device, such as chiller  102   a  or the heat exchanger  102  in FIG. 1, in order so that it can be made comfortable for the dental patient. 
     In view of the foregoing, it is seen that the stated objects of the invention are achieved. The above description explains the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are best suited to the particular use contemplated. As various modifications could be made in the constructions and methods herein described and illustrated without departing from the scope of the invention, it is intended that all matter contained in the foregoing description shall be interpreted as illustrative, rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above described exemplary embodiments, but should be defined in accordance with the following claims appended hereto and their equivalents.