Abstract:
A door closure system for a vacuum sterilization chamber includes a mechanism to allow movement of the door with respect to the chamber at the hinge. An elongated slot on the door captures a fixed shaft to allow rotation of the door. A spring in the door operates against the shaft biasing the door toward the chamber. Forces applied by the hinge and by an opposite latch are normalized.

Description:
[0001]     This application is a continuation-in-part of U.S. application Ser. No. 10/609,639 filed Jun. 30, 2003, the entire contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to a sterilization vacuum chamber and a door closure therefor.  
         [0003]     When closing a door to a sterilization chamber which will be put under vacuum, it is desirable to distribute forces evenly to avoid leaks or damaging a seal between the door and chamber. A typical closure comprises hinges at one side of the door and a latch at the other. When the latch pulls the door closed, unless the hinges and latch are precisely placed forces between the door and chamber will be higher on one side of the door than the other. This can lead to leaks and damage seals between the door and chamber and also damage the hinges.  
       SUMMARY OF THE INVENTION  
       [0004]     A vacuum sterilization chamber according to the present invention has a sealable doorway which comprises an opening into the chamber, a door for covering the opening, a latch between the door and the chamber and a hinge connecting the door to the chamber. The hinge comprises a shaft mounted to either the door or the chamber and an elongated slot mounted to the other of the door and chamber. The shaft is positioned within the slot and a biasing member acts against the shaft to bias the door toward the chamber.  
         [0005]     Preferably, the shaft is mounted to the chamber and the slot is located on the door. Preferably, the latch is on an opposite side of the opening from the hinge. Also preferably, a seal is provided about the opening between the door and the chamber.  
         [0006]     The biasing member preferably comprises a spring. It can be located within a cavity adjacent to and opening into the slot with the spring positioned between a wall in the cavity and the shaft. Preferably, a low friction bushing surrounds the shaft. It can be made of PTFE. Preferably, a button is positioned between the spring and the bushing. Preferably, the button has a smooth surface which allows it to ride smoothly over the bushing.  
         [0007]     A source of sterilant, such as for example a source of hydrogen peroxide, is preferably connected to the chamber.  
         [0008]     A method, according to the present invention, of sealing a door to a vacuum sterilization chamber at an opening thereinto comprises the steps of: closing the door about a hinge between the door and the chamber, the hinge comprising a shaft mounted to one of the door and chamber and an elongated slot mounted to the other of the door and chamber, the shaft being positioned within the slot; latching the door to the chamber with a latch; and applying a biasing force against the shaft to bias the door toward the chamber.  
         [0009]     Preferably, sterilant gases are subsequently admitted into the chamber. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a block diagram of a BIER vessel according to the present invention;  
         [0011]      FIG. 2  is a perspective view of the BIER vessel of  FIG. 1 ;  
         [0012]      FIG. 3  is a detailed perspective view of a latch mechanism on the BIER vessel of  FIG. 1 ;  
         [0013]      FIG. 4  is cross-sectional view taken along lines  4 - 4  of  FIG. 2  showing a spring-loaded floating hinge;  
         [0014]      FIG. 5  is an exploded perspective view of an alternative spring-loaded floating hinge mechanism;  
         [0015]      FIG. 6  is an exploded perspective view of a mounting bracket of the hinge mechanism of  FIG. 5 ;  
         [0016]      FIG. 7  is a side elevation view of a hinge attachment mechanism of the hinge mechanism of  FIG. 5 ;  
         [0017]      FIG. 8  is a perspective view of a sample rack for use within the BIER vessel of  FIG. 1 ;  
         [0018]      FIG. 9  is a perspective view of an alternative sample rack for use within the BIER vessel of  FIG. 1 ;  
         [0019]      FIG. 10  is a perspective view of an alternative hinge arrangement for the BIER vessel of  FIG. 1 ; and  
         [0020]      FIG. 11  is a sectional view taken along lines  11 - 11  of  FIG. 10 . 
     
    
     DETAILED DESCRIPTION  
       [0021]      FIG. 1 . discloses in block diagram format an improved BIER vessel  10  according to the present invention. The BIER vessel  10  comprises a first chamber  12  typically employed as a vaporization chamber and a second chamber  14  typically employed as a test chamber. In this example the chambers  12  and  14  are of similar size, however their sizes can be varied to accommodate individual needs. A plurality of test chambers  16  attach to the vaporization chamber  12 . These test chambers  16  are much smaller in size then the vaporization chamber  12  whereby upon placing the test chamber  16  into communication with the vaporization chamber  12  the conditions of the vaporization chamber  12  are quickly established within the test chamber  16  to provide an accurate starting point for a test. The most desirable starting point in a test would have the concentration of vaporized sterilant in the test chamber  16  change instantaneously from zero to the desired test concentration. A conduit  18  connects the first chamber  12  and second chamber  14  and incorporates an isolation valve  20  to separate the first chamber  12  from the second chamber  14 . Similarly, each of the test chambers  16  are isolated from the first chamber  12  by an isolation valve  22 .  
         [0022]     Monitoring of conditions within the BIER vessel system  10  helps assure that the process is proceeding as desired. A separate pressure monitor  24 , temperature sensor  26  and sterilant concentration monitor  28  is provided for each of the first chamber  12 , second chamber  14  and test chambers  16 . Sterilant monitors for hydrogen peroxide preferably employ light absorption techniques, such as described in the Prieve et al. U.S. Pat. No. 6,269,680, incorporated herein by reference.  
         [0023]     A vacuum system  30  comprises vacuum pump  32  and vacuum lines  34  from the vacuum pump  32  to the first and second chambers  12  and  14  and vacuum lines  36  serving the smaller test chambers  16 . Vacuum vent valves  38  and  40  on the first chamber and second chamber  12  and  14 , respectively isolate these chambers from the vacuum line  34  and vacuum vent valves  42  isolate the smaller test chambers  16  from the vacuum lines  36 . The volume of the vacuum lines  36  exceeds the volume of their associated test chamber  16  such that upon opening the vent valves  42  contents of the test chamber  16  are quickly evacuated. When this occurs at the end of an exposure period to a sterilant, the concentration of sterilant in the test chamber  16  is quickly diminished so as to provide a controllable end point the exposure period. Similar to the starting point, the most desirable end point would have the sterilant concentration drop from the desired testing concentration to zero instantaneously.  
         [0024]     A plasma generator  44  connects to electrodes  46  in the first and second chambers  12  and  14  provide the capability of driving the gases therein into the plasma state. The electrodes  46  are isolated from their respective chambers  12  and  14  and the plasma generator  44  applies an electrical potential between the electrode  46  and the respective test chamber  12  or  14 . Examples of appropriate plasma generation systems are described in U.S. Pat. Nos. 4,801,421, 5,656,238 and 6,447,719, incorporated herein by reference.  
         [0025]     A control system  48  interconnects to the various sensors  24 ,  26 ,  28 , valves  20 ,  22 ,  38 ,  40 ,  42 , the plasma generator  44  and the vacuum system  30  and other equipment as may be needed or desired to affect control over the process of the BIER vessel  10 . Preferably, the control system includes data storage and networking capabilities for easy handling of the test data.  
         [0026]     Vent valves  50  are provided on each of the chambers,  12 ,  14  and  16  to allow venting of the chamber to atmospheric pressure or a target pressure below atmospheric. These vent valves  50  are also connected to, and are under the control of the control system  48 . Preferably they comprise a dual valve couple, one being larger than the other, to provide quick venting of large volumes and fine tuning of desired pressure. They are cycled open and closed until the target pressure is reached. A separate injector  52  is provided for first chamber  12  and second chamber  14 , through which a pre-measured quantity of liquid sterilant solution can be injected via a syringe through a septum and then vaporized into the chamber  12  or  14 .  
         [0027]      FIG. 2  shows in perspective view the BIER vessel  10  depicted in block diagram form in  FIG. 1 . Each of chambers  12  and  14  has a large door  60  having a floating hinge mechanism  62  and interlocking latch  64 . The latch  64  is connected to the control system  48  and plasma generator  44  to extinguish the plasma if the door  60  is opened during the cycle when there is plasma present or when the concentration of sterilant is too high. As also seen in  FIG. 3 , a pneumatic piston  65 , under control of the control system  48 , extends over the latch  64  to prevent opening of the latch during unsafe conditions.  
         [0028]      FIG. 4  shows the hinge mechanism  62  which comprises a hinge  66  attached to the door  60  and slideably attached to the outer wall of the chamber  12  or  14 . The hinge  66  is trapped between an outer plate  68  and an inner plate  70  while retaining freedom to slide therebetween. Preferably, the plates  68  and  70  are formed out of or coated with a low friction substance such as polytetrafluoroethylene (PTFE). A spring  72  biases the hinge toward the chamber  12  or  14 . When the door  60  is closed, the spring normalizes the forces applied at the top and bottom of the chamber  12  or  14 .  
         [0029]     FIGS.  5  to  7  show an alternative version hinge mechanism  74 . A hinge mounting bracket  76  affixes to a chamber  78 . Two mounting plates  80  connect to the bracket  76  via screws  82  passing through elongated slots  84  in the mounting plate  80  so as to provide a limited degree of lateral movement of the plate  80  relative to the bracket  76 . The screws  82  comprise an unthreaded shoulder  85  between machine threads  86  and a head  88  to allow easy movement of the shoulder  85  within the slots  84 . A spring  90  biases the mounting plate  80  away from a door  92 .  
         [0030]     Two hinges  94  attach to the door  92  and have connectors  96  extending therefrom toward the mounting plates  80 . A clip plate  98  attaches to each mounting plate  80  and has rear notches  100  and front notches  102  into which snap respectively a proximal pin  104  and distal catch  106  on the connectors  96  thus allowing easy attachment and detachment of the door  92 . A latch  108  is provided on a side of the door  92  opposite the hinges  94 . A seal  109  about an opening  111  into the chamber  78  and between the door  92  and the chamber  78  helps preserve a vacuum in the chamber  78 .  
         [0031]     Although the hinges  94  are shown slidably attached to the chamber  78 , one of skill in the art would see that their design could be modified to slidably attach the hinges  94  to the door  92 . Further, rather than allow movement at the hinges to normalize forces on the door seal  109 , movement could instead be provided at the latch  108  or at both the latch  108  and the hinges  94 .  
         [0032]     Test racks for holding biological indicators are helpful in getting even distribution of the indicators within the test chambers  14  and  16 .  FIG. 8  shows a rack  110  suitable for holding twenty flat test packs (not shown), each containing a biological indicator, for use within the large test chamber  14 .  FIG. 9  shows a rack  112  suitable for holding four biological indicators within the cylindrical test chamber  16 . An open circular ring  114  having evenly spaced holder  116  about its circumference fits snugly within the test chamber  16 . Each holder  116  has a pair of end flanges  118  between which can be placed a biological indicator.  
         [0033]     A typical cycle in the BIER vessel  10  comprises the following.  
         [0034]     Heat all portions of the BIER Vessel  10  to 50° C. OPTIONALLY: Heat the vaporizer chamber  12  to 65° C., the large test chamber  14  to 50° C., and the small test chambers or ports  16  to 45° C. The temperature differentials cause small pressure gradients in the gas which can be manipulated to help control gas flow.  
         [0035]     Evacuate all portions of the BIER Vessel to 0.2 Torr and light a plasma. The vacuum and plasma both aid in eliminating any possible residuals, such as water or sterilant from a prior cycle, in the vessel. As plasma energy creates heat, the pressure may rise. The 0.2 Torr pressure can be maintained with the throttling valves  50  that opens and closes to raise or lower pressure.  
         [0036]     Vent all chambers  12 ,  14  and  16  to atmospheric pressure and load samples. Samples are preferably positioned within all portions of the chamber  14  so that when sterilant is introduced into the portions, it exposes all samples equally.  
         [0037]     Evacuate all portions of the BIER Vessel  10  to 0.2 Torr. The vacuum enhances sterilant vaporization and diffusion. OPTIONALLY: Plasma may be introduced to condition/heat the samples/load. Stop the plasma at the end of the conditioning time.  
         [0038]     Close respective valves to isolate all portions of the BIER vessel  10  at the 0.2 Torr pressure.  
         [0039]     Introduce sterilant, such as 59% hydrogen peroxide solution, into the vaporizer chamber  12  until the desired concentration is reached, as detected by the sterilant monitor  28  therein. If too much is accidentally introduced, a small portion can be evacuated out. The addition and removal of sterilant can be manipulated until the desired sterilant concentration and pressure is achieved.  
         [0040]     The sterilant in the vaporizer chamber  12  will cause the pressure to rise higher than the other portions of the vessel that are currently at 0.2 Torr. Once the valves  20  or  22  isolating the other portions of the vessel are opened, the pressure (and temperature) differentials will immediately force the sterilant into the other portions of the vessel. OPTIONALLY: The valves  22  do not have to be opened or closed simultaneously, allowing for different exposure times for different samples.  
         [0041]     At the end of the desired exposure time, evacuate the vessel portions to 0.2 Torr to remove the remaining sterilant before opening the doors to remove the samples. The evacuation time will be less than 30 seconds for the chambers and less than 5 seconds for the Ports. Optionally, plasma may be introduced to enhance the removal of sterilant residual.  
         [0042]     Quickly vent the portions of the vessel to allow the filtered air rushing in to “scrub” the surfaces, freeing sterilant that was being held by other materials, and remove the samples/load. Test the biological indicators.  
         [0043]      FIGS. 10 and 11  show an alternative hinge  200  which provides a function similar to the hinge mechanism  62  with reduced complexity. A hinge bracket  202  mounts to a side wall  203  of a chamber  204 . A shaft  206  fixedly mounts to the hinge bracket  202  in a vertical orientation. It operates within an elongated slot  208  on a door  210 . The slot  208  is elongated in the direction toward the chamber  204  when the door is closed. A spring  212  disposed within a cavity  214  biases the door  210  toward the chamber  204 .  
         [0044]     The cavity  214  extends horizontally perpendicular to the shaft  206  and intersects the slot  208 . The spring  212  operates between a wall  216  in the cavity  214  and the shaft  206  to push the door  210  toward the chamber  204 . A bushing  218  of low friction material surrounds the shaft  206  to ease rotation of the door  210  around the shaft  206 . This low friction material can comprise nylon, PTFE (polytetrafluoroethylene) and the like. A button  220  disposed at one end of the spring  212  contacts the bushing  218  to prevent binding of the spring  212  as the door  210  rotates. Preferably it is formed of Aluminum, although other materials, including low friction materials, can be employed as will be recognized by those of skill in the art.  
         [0045]     This design improves over the design of hinge  62  in that fewer parts achieve a comparable result. Preferably at least two hinges  200  are located on one side of the door  210  with one or more latches (preferably one) on the side opposite the hinges  200 . The forces on the door  210  are thus balanced as it is latched closed aiding in achieving a better seal against the chamber  204 .  
         [0046]     Although described above in connection with particular embodiments of the present invention, it should be understood the descriptions of the embodiments are illustrative of the invention and are not intended to be limiting. Various modifications and applications may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined in the appended claims.