Abstract:
A container for enabling fluid flow therethrough for cleaning or sterilizing of the contents, comprises a tray ( 10 ) and lid ( 20 ) and having respective bases ( 11, 21 ) and side walls ( 17, 27 ). The bases ( 11, 21 ) have perforations ( 12, 22 ) defined by elliptically shaped perforation walls ( 13, 23 ) with their major axes vertical to allow easy flow of the cleaning fluid through the container and minimum contact points with the contents or other containers. The internal corners ( 30 ) of the perforations ( 12, 22 ) in horizontal sections are smoothly curved to minimize debris or deposits collecting and resisting removal. A method of cleaning or sterilizing using the container is also described.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a U.S. national entry under 35 U.S.C. §371 of International Application No. PCT/AU2008/000956, filed 30 Jun. 2008, published in English as PCT International Publication No. WO 2009/003227 A1 on 8 Jan. 2009 which is based upon and claims the priority of Australian Patent Application No. 2007903573 filed 29 Jun. 2007. The entire contents of these applications and their associated specifications are incorporated herein by this cross-reference. 
     TECHNICAL FIELD 
     This invention relates to a container component for enabling fluid flow therethrough for cleaning or sterilising of the contents within the container and further relates to a method of cleaning or sterilising the contents within a container. 
     BACKGROUND 
     In medical and dental establishments, because of environmental problems and the cost and difficulty of burning and dumping of medical waste, there is a growing tendency to return to reusable products. For example medical and dental instruments after use are frequently returned in a container to a washing or sterilising facility where the instruments are decontaminated. The instruments can then be safely handled without risk from infections such as HIV and Hepatitis caused by inadvertent cutting or puncturing of the person handling a contaminated instrument. The instrument can be cleaned and serviced as necessary and sterilisation in an autoclave follows, usually with porous filter medium surrounding the tray or other container holding the instruments. The instruments while remaining protected by the porous wrapping are then stored and subsequently returned to the surgery for reuse by the dentist or doctor. 
     Trays made of stainless steel and synthetic materials are known for holding dental and medical instruments for sterilisation in an autoclave. Such stainless steel trays have a base made of a sheet of flat stainless steel material which has an array of cylindrical holes drilled through the base to allow steam in the autoclave to pass through the base. However such stainless and synthetic steel trays are expensive and/or may not allow steam or washing liquid to reach all parts of the instruments resting on them. 
     Australian Patent Specification No. AU-24539/88 discloses an autoclave container in the form of a tray made of a plastics material, the tray having a base with perforations defined by walls, the walls progressively widening from a top point to a flat bottom surface of the base. The flat bottom surface enables a substantial amount of the heat stored within the plastics material after the tray has been an autoclave to be yielded up through the flat base surface and thereby help evaporate any moisture, such as condensation, particularly within the filter material placed around the tray when in the autoclave. However the tray in this patent specification would not be particularly effective in a washer where water jets are directed upwardly against the base of the tray, since the large flat bottom surface area would deflect much of the water downwardly rather than allowing the water to pass upwardly through the perforations to reach the instruments in the tray. 
     A type of closed autoclave vessel frequently used in hospitals for holding instruments to be sterilised in an autoclave has a square bottom of about 40 cm width and which has a perforated central opening, e.g. having a diameter of about 10 cm. The circular central opening in use is covered by a permeable filter material. The lid of the vessel is similarly constructed, having a 10 cm diameter circular perforated opening in the centre of the lid covered in use by a permeable filter. Inside the closed vessel there can be a tray which is perforated and which supports the instruments to be sterilised. Steam flows through the upper circular opening in the lid to reach the interior of the vessel and passes out through the lower central perforated opening. The flow of steam through such a vessel tends to be greatest in the central region of the space enclosed within the vessel, this effect being the result of the steam flowing through a path of least resistance. Hence it is possible that the outer sides and particularly the corners of the vessel may be inadequately heated to effectively sterilise the instruments at the edges or in the corners of the vessel. 
     Australian Patent Specification No. AU-24396/95 (Patent No. 682770) discloses a container component for enabling cleaning of articles by fluid flow therethrough, the component having a base with perforations defined by intersecting perforation walls. Each of the walls in vertical cross section has a narrow top, widens in a downwards direction to a maximum width, and then narrows again to a narrow bottom. The preferred cross sectional shape of the perforation walls is elliptical with the major axis of the ellipse being upright. This container component, and also the tray disclosed in AU-24539/88, has many locations such as corners or crevices where small quantities of blood, debris, or other deposits or contaminants can be lodged and can be difficult to completely remove during the cleaning process. Such deposits can later contaminate instruments or other articles stored within the container component, or can dislodge in a surgery or other environment where all possible sources of contamination are desirably excluded. Even if the deposits are sterilised during the cleaning operation which the container component and instruments or articles carried thereby undergo, nevertheless the deposits are an undesirable potential source of particulate contamination in surgery, dental procedure, etc. 
     It is an object of the present invention in a first aspect to provide a container component for enabling fluid flow therethrough for effective cleaning of contents of the container with reduced risk of contaminants or deposits lodging or remaining in the container component. 
     It is a preferred object of the present invention to provide a container component suitable for placement within a washer in which washing liquid is directed upwardly and/or downwardly so as to pass through the container component thereby washing articles in the container and removing any contaminants or deposits in or on the container component. 
     It is a further preferred object of the present invention to provide a container component suitable for use in an autoclave and enabling steam to flow through the container component for effective sterilisation of articles in the container and removing any contaminants or deposits in or on the container component. 
     It is an object of the present invention in a second aspect to provide a method for cleaning or sterilising articles located within a container having a container component enabling a fluid flow therethrough with reduced risk of contaminants or deposits lodging or remaining in or on the container component. 
     SUMMARY OF INVENTION 
     According to the first aspect of the invention there is provided a container component for enabling cleaning of articles located within the container component by fluid flow through the component, comprising a base, the base having perforations provided over substantially the entire area where the articles are in use located and through which the cleaning fluid can flow, the perforations in the base being defined by perforation walls, each of the walls in vertical cross section having a narrow top, widening in a downwards direction to a maximum width and then narrowing again to a narrow bottom, the maximum width being less than the distance from the top to the bottom, wherein the perforation walls include longitudinal perforation walls extending in a first direction and transverse perforation walls extending in a different second direction so that the longitudinal and transverse perforation walls meet at intersections defining corners of the perforations, and wherein the internal corners are smoothly rounded so that there is no sharp internal angle formed where the longitudinal and transverse perforation walls meet. 
     Terms used in the specification, including claims, which may normally mean or at least imply some particular orientation are used for convenience and do not limit the invention to the particular implied orientation. For example, the term “base”, although normally implying a bottom or lower position, nevertheless could comprise a top or covering component, e.g. in the case of the container component comprising a lid of an autoclavable instrument tray in which the “base” would comprise the top wall of the container. In another example, the term “horizontal” in reference to the cross-sections through the intersections is not to be interpreted to necessarily mean that the base is a horizontal planar base since the base may, for example, comprise an upright side wall of the container component. Likewise other orientation terms such as “vertical”, “top” “downwards”, “bottom” are not to be interpreted literally and narrowly but are to be interpreted as relative orientational terms. 
     The radius of curvature of each internal corner may progressively increase in successive horizontal cross-sections through the respective intersections starting from cross sections near the tops of the walls and progressing towards cross sections approaching and at the maximum width of the walls. 
     Preferably the curvature of the internal corners of the perforations in the horizontal plane where the walls reach their maximum width is greater than the curvature of the internal corners of the perforations at any other horizontal cross-section. 
     In one possible embodiment of the container component, each intersection in any one of multiple horizontal cross-sections therethrough is of generally cruciform shape. The term “cruciform shape” is not to be interpreted narrowly to necessarily refer only to a shape in which the longitudinal and transverse perforation walls intersect at substantially 90° to each other. The expression is intended merely to indicate that the longitudinal and transverse perforation walls intersect and cross each other and, for example, the crossings could be at angles other than 90° e.g. at a 60° internal angle so as to also define internal corners with an internal angle of about 120°. 
     In one embodiment suitable for medical or dental instrument containers each of the internal corners of the perforations in the horizontal plane where the walls reach their maximum width may have a radius of curvature of about 1 mm or greater. 
     In one preferred embodiment, the component comprises a tray, the base of the component defining a bottom of the tray, a plurality of side portions being located around the perimeter of the base, the perforations in the base being provided over substantially the entire surface area out to the perimeter where the side portions are located, so that the articles to be cleaned are located by the side portions entirely within the perimeter of the base where the perforations are provided, the tray having an open top through which the cleaning fluid can flow, wherein the perforation walls have terminal ends which meet and join with the side portions, and wherein a horizontal cross-section through each meeting of the terminal end of a perforation wall with the side portion is generally of T-shape and the internal corners of the T-shape are smoothly rounded so that there is no sharp internal angle formed where the perforation wall meets with the side portion. 
     The container component may be made of a plastics material, particularly in the case of use in sterilising operations being a material capable of withstanding autoclave temperatures. A preferred material is polypropylene. 
     According to the second aspect of the invention there is provided a method of cleaning or sterilising articles comprising the steps of: 
     providing a container component for receiving the articles during the cleaning or sterilising process, the container component comprising a base, the base having perforations; 
     locating the articles to be cleaned or sterilised within the container component so that they are located within an area where the base has the perforations provided therein; and 
     causing a cleaning or sterilising fluid to flow past the articles within the container component including passing through the perforations of the base throughout substantially the entire area where the articles are located, 
     wherein the perforations in the base are defined by perforation walls, each of the walls in vertical cross section having a narrow top, widening in a downwards direction to a maximum width and then narrowing again to a narrow bottom, the maximum width being less than the distance from the top to the bottom, wherein the perforation walls include longitudinal perforation walls extending in a first direction and transverse perforation walls extending in a different second direction so that the longitudinal and transverse perforation walls meet at intersections defining corners of the perforations, and wherein the internal corners are smoothly rounded so that there is no sharp internal angle formed where the longitudinal and transverse perforation walls meet. 
     Further preferred features of the container component used in the method according to the second aspect of the invention can be substantially as described above in connection with the first aspect of the invention. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Possible and preferred features of the present invention will now be described with particular reference to the accompanying drawings. In the drawings: 
         FIG. 1  shows a cross-section through a fragment of a container having a tray and a lid both embodying the present invention, 
         FIG. 2  shows a fragmentary perspective sectional view of a portion of a previously known container component, 
         FIG. 3  shows a fragmentary perspective sectional view of a portion of a container component according to the invention, 
         FIG. 4  shows a cross section through an intersection of walls at the widest part of the vertical cross sectional shape, 
         FIG. 5  shows a plan view of an intersection of walls with contour lines indicated so as to show the curvature at the internal corners of the perforations, 
         FIG. 6  is a detailed fragmentary perspective sectional view of the intersection of two perforation walls, 
         FIG. 7  is a cross section through one possible configuration of a support for instruments or articles to be carried in the container component for cleaning, and 
         FIG. 8  is a cross section through another possible configuration of a support for instruments or articles to be carried in the container component for cleaning. 
     
    
    
     DETAILED DESCRIPTION 
     The two part container shown in  FIG. 1  comprises a tray  10  and a cover or lid  20  each of which embodies the present invention. However the invention also relates to simple open topped trays such as the tray  10 , e.g. for holding dental instruments to be placed in a washing apparatus where washing water containing disinfectant is directed in multiple directions within the washer so as to pass through the tray and wash the articles in the tray. 
     The tray  10  includes a base  11 . Similarly the lid  20  has a base  21 . The base  11  has perforations  12  and similarly the lid  20  has perforations  22  to allow cleaning fluid, such as water in a washer or steam in an autoclave, to pass through the base  11  or  21  to contact articles received within the tray  10 . 
     The tray  10  and lid  20  can be moulded from plastics material such as polypropylene capable of withstanding autoclave temperatures. 
     The tray  10  has a side wall  17  extending upwardly from the perimeter or edge of the perforated base  11 , and the lid  20  has side wall  27  having a complementary shape at its edge to the top of the side wall  17  to enable the lid  20  to fit to the tray  10 . 
     As shown in  FIG. 2  which shows a known construction of tray, and as shown in  FIG. 3  which shows a tray embodying the present invention, the perforations  12  are defined by perforation walls  13 . Each wall  13  in vertical cross-section is elliptical with the major axis vertical so as to commence at a top point  14 , widens in a downwards direction to a maximum width  15  corresponding to the minor axis of the ellipse, and then narrows to a bottom point  16 . The maximum width  15  is less than the distance from the top point  14  to the bottom point  16 , i.e. the major axis. In  FIGS. 1 and 3 , the width  15  is less than half the distance from point  14  to point  16 . 
     With this shape of the walls  13 , the cumulative area of the perforations  12  in plan view can be maximised for flow of water or steam through the perforations. The narrowing of the wall shape from the width  15  downwardly to the bottom point  16  enables much of the water directed upwardly in a washer against the tray  10  to be deflected into the perforations  12  so that most of the water being directed upwardly can continue to flow upwardly through the perforations  12  to reach articles within the tray  10  even if the water first impinges on the walls  13 . 
     As seen in  FIG. 1 , the bottom points  16  of the tray  10  define a bottom plane  18  and the bottom edge  19  of the side wall  17  meets but does not extend below this plane  18 . Also, the perforation walls  13  and perforations  12  are provided across the entire area of the base  11  so that the bottom edge  19  of the side wall  17  presents only the same area in bottom plan view as a perforation wall  13 . This enables articles in the tray  10 , even if they are located at one side against a side wall  17 , to be reached and contacted by cleaning fluid passing upwardly or downwardly through the container. 
     The same functional features are provided by the lid  20  so that the top points  24  of the perforation walls  23  define a plane  28  and the side wall  27  at its top edge  29  does not project above this plane  28 . This construction enables containers comprising tray  10  and lid  20  as shown in  FIG. 1  to be stacked one on top of each other with contact points being restricted to the bottom points  16  of tray  10  meeting and resting on top points  24  of a lid  20 . This minimises the contact surface areas between stacked containers to minimise obstruction to flow of cleaning fluid through the stacked containers and also to minimise areas where moisture could collect at the areas of contact. 
     In the tray shown in  FIG. 2  which is known, the perforation walls  13  intersect each other forming internal corners  30  which in horizontal cross section will form right angles. Such corners  30  can provide locations for debris, blood, or other deposits to lodge and such deposits will be more difficult to remove during the cleaning process. Likewise the corners  31  formed where the walls  13  meet with the side wall  17  form sharp internal angles more likely to be the sites of deposits. 
     As shown in  FIGS. 3 to 6 , the container component according to the present invention has perforation walls  13  including longitudinal perforation walls  13   a  extending in a first direction and transverse perforation walls  13   b  extending in a different second direction. 
     The term “longitudinal” is arbitrary and does not necessarily signify that the tray is longer in the direction of the walls  13   a . The longitudinal and transverse perforation walls  13   a ,  13   b  meet at intersections which define corners  30  of the perforations  12 . The intersections as best shown in  FIGS. 4 and 5  in plan view or in horizontal cross section are of generally cruciform shape, which in the illustrated embodiments have the walls  13   a ,  13   b  meeting at right angles, but other angles of intersection are possible. The internal corners  30  are smoothly rounded so that there is no sharp internal angle formed where the longitudinal and transverse perforation walls  13   a ,  13   b  meet. 
     The radius of curvature of each internal corner  30  as shown in  FIGS. 5 and 6  progressively increases in successive horizontal cross sections through the respective intersections starting from the cross sections near the tops  14  of the walls and progressing towards cross sections approaching and at the maximum width  15  of the walls. The curvature of the internal corners  30  in the horizontal plane where the walls reach their maximum width at  15  is at a maximum and therefore is greater than the curvature of the internal corners  30  of the perforations at any other horizontal cross section. This can be seen with the contour lines indicated in  FIGS. 5 and 6  on the surfaces of the walls  13   a ,  13   b  including particularly contour line  35  at the maximum width  15 , and contour line  36  at a horizontal section closer to the top  14  which has a smaller radius of curvature. At the internal corner  30 , contour line  37 , closer yet to the top  14  and having a yet smaller radius of curvature at the corner  30 . The radius of curvature at the contour line  35  within the corner  30  may be for example about 1 mm or greater. The smooth rounding of the internal corners  30  of the intersections substantially reduces the likelihood that debris, blood, or other deposits will form at the internal corners  30  compared to the prior art and, if there are such deposits, the cleaning and/or sterilising operation has a substantially greater effectiveness in dislodging and removing and/or sterilising any such deposits that may be found in the corners  30 . 
     The preferred container component according to the embodiment of the invention shown in  FIGS. 1 and 3  has a plurality of side portions  17  around the perimeter of the base  11 . The perforations  12  in the base are provided over substantial the entire surface area out to the perimeter of the base where the side portions  17  are located so that the instruments or other articles to be cleaned are located by the side portions  17  entirely in the perimeter of the base  11  where the perforations are provided. The tray  10  can have an open top  20  through which cleaning fluid can flow. The perforation walls  13   a ,  13   b  have terminal ends  13   t  which meet and join with the side portions  17 . A horizontal cross section through each meeting of the terminal end  13   t  of a perforation wall  13  with the side portion  17  is generally of T-shape and the internal corners  31  of the T-shape are smoothly rounded in the same way as internal corners  30  so that there is no sharp internal angle formed where the perforation wall  13  meets the side portion  17 . 
     To support instruments or other articles, particularly delicate and/or expensive articles such as surgical instruments, endoscopic apparatus and the like, there may be provided article supports  40  projecting up above the base  11 . As shown in  FIGS. 7 and 8 , each article support  40  can be in the form of an upright projection  41  mounted to the base by a resilient formation  45  which fits with and is retained within one or more perforations  12 . The upright projection  41  may be in the form of an elongated web having a top edge  43  which is narrow in cross section so that articles resting on the top edge  43  meet with essentially a point contact. If desired, there may be concavities such as notches formed at spaced locations along the top edge  43  to more positively locate and retain articles such as delicate or expensive medical instruments. The formations  45  are shown as complementary in shape to perforations  12  and the supports  40 , and more particularly the formations  45  may be made of a resilient material such as silicone rubber so that the support can be fitted to and securely retained in position in use. The use of silicon rubber or similar soft material can enable users of the tray to create customised locating concavities or notches in the top edges  43  of the supports  40  by cutting the notches using a razor or the like and thus create a support for different shapes and sizes of instruments. Multiple formations  45  would be provided along an elongated article support  40  with the spacing between successive formations  45  exactly corresponding to the spacing between perforations  12 . 
     In the preferred embodiment or construction of the base of a tray for supporting instruments or other articles to be cleaned or sterilised, the spacing between adjacent parallel longitudinal perforation walls is preferably equal to the spacing between adjacent parallel transverse perforation walls. In this preferred embodiment, the perforations are substantially square in plan view (except for the smoothly rounded corners of the perforations). This preferred arrangement with the dimensions of the mesh formed by the longitudinal and transverse perforation walls being the same in the direction of a longitudinal X axis and a transverse Y axis enables article supports  40  to be fitted to the base  11  either extending transverse relative to the tray or longitudinally along the tray. This enables the arrangement and configuration of article supports  40  anywhere on the tray to suit the instruments or other articles that the tray may need to accommodate for a cleaning or sterilising operation. The article supports can be removed and relocated in different positions to support different instruments or other articles as required. It can also be appreciated that the article supports  40 , particularly supports which are elongated, can form dividers separating the space within the tray into compartments for better organisation of articles to be cleaned or sterilised. 
     It will be seen that the container component, whether it be a tray or lid or cassette comprising a tray and lid, according to the present invention enables articles to be effectively reached by cleaning fluid, such as washing liquid in a washer or steam in an autoclave with reduced risk of debris, blood or other deposits collecting in corners of perforations or, if there are such deposits, the invention improves the effectiveness in removal during cleaning and sterilising. The cleaning fluid can also be peroxide gas or any other gas sterilant or oxidising gas. Also the cleaning fluid may be liquid, gaseous or plasma state. Apart from using high temperature or pressure sterilising operations such as an autoclave, the container component may be used in microwave sterilisation processes. 
     The method of cleaning or sterilising articles according to the second aspect of the invention can be readily understood from the preceding detailed description of the preferred embodiment of the container component. In particular, it can readily be understood how, according to the method of the second aspect of the invention, articles to be cleaned or sterilised are located within the container or container component so that the washing fluid or sterilising fluid effectively reaches the articles and there is reduced risk of debris, blood or other deposits collecting in corners of perforations with resulting higher risk of transfer to or contamination of the articles being cleaned or sterilised because, if there are such deposits, the particular construction of the perforations of the container component improve the effectiveness in removal of deposits during the cleaning or sterilising method of the invention. 
     The manufacture of the container component according to the first aspect of present invention, or used in the method according to the second aspect of the invention, is preferably performed by a moulding process, particularly an injection moulding process. The moulding of the container component without sharp corners for holding or retaining contaminants produces a substantially improved product compared a prior known fabrication process in which stainless steel wires are welded within a frame to form a mesh to receive instruments or other articles to be washed or sterilised. Such a fabrication process cannot achieve the objectives of preferred embodiments of the present invention in substantially eliminating corners within the container component. The manufacture of the dies used to form the mould for manufacture of the container component can be carried out by a suitably programmed CNC machine. The die cutting tools used to form the die cavities for the perforation walls can be hemi-spheroidal in shape, and more particularly hemi-ellipsoidal in shape, so as to thereby form the elliptical cross section of the perforation walls. To form the rounded corners at each intersection of the perforation walls, the cutting tool will be traversed around the corners from a transverse wall forming cavity to the intersecting longitudinal wall forming cavity, such traversal being controlled by the CNC machine. Different cutting tools may need to be used to form the different radii of curvature around the internal corners as herein described. 
     It is to be understood that various alterations, modifications and/or additions may be made to the features of the possible and preferred embodiment(s) of the invention as herein described and claimed without departing from the spirit and scope of the invention.