Patent Application
20090078320
The present invention relates to a steam exhaust assembly for use with sterilization equipment which employs steam for sterilizing and superheated steam for drying of medical or dental instruments.
Sterilization processes which are used to sterilize medical and dental instruments and the like typically use steam in the sterilization of such instruments. Some sterilization processes further use superheated steam in the drying of such instruments. Sterilization equipment, such as cassette autoclaves, also are being made more compact in order to fit into smaller environments, such as those found in a dental office or medical clinic setting. Since these devices may emit significant amounts of heat and steam during the sterilization process, there is a need to remove the excess heat and steam in a controlled, effective and efficient manner rather than releasing the heat and steam into the ambient environment. Further, building codes also may regulate the discharge and disposal of exhaust steam thereby requiring a removal of excess heat and steam in a controlled manner.
Currently in autoclaves that do not recycle exhaust water, a condensate bottle or receptacle is used to capture, condense and store exhaust steam and any condensed steam which exits the sterilization unit. However, a single receptacle, which is limited in size since it must be emptied comfortably by a user, may be insufficient to receive and properly dissipate the exhaust steam and heat from the sterilization unit. The heat and steam from the sterilization equipment may build up in the area immediately surrounding the unit and the condensate receptacle, causing damage to the environment's shelving, and cabinetry or causing harm or discomfort to nearby users.
Embodiments of the present invention provide an assembly and method for condensing exhaust heat and steam, including superheated steam, from a sterilization device.
In accordance with an embodiment of the present invention, there is provided an exhaust assembly for a sterilization apparatus. The exhaust assembly comprises a first exhaust vessel having a first inlet port, primary condensing means, a heat exchange media and a first outlet port, and a secondary exhaust vessel having a second inlet port connected to the first outlet port of the first exhaust vessel, secondary condensing means and a condensate exit.
In accordance with a further embodiment of the present invention there is provided an exhaust assembly for condensing steam. The exhaust assembly comprises a first exhaust vessel having a first inlet port, primary condensing means, a heat exchange media and a first outlet port, a second exhaust vessel having a second inlet port connected to the first outlet port, secondary condensing means, a condensate exit, exiting within the second exhaust vessel and a condensate outlet, and drainage means connected to the condensate outlet for draining condensate from the second exhaust vessel.
In accordance with a further embodiment of the present invention, there is provided a method of condensing exhaust steam from a sterilization apparatus using an exhaust assembly. The exhaust assembly comprises a first exhaust vessel having a first inlet port, primary condensing means and a first outlet port. There is a second exhaust vessel having a second inlet port connected to the first outlet port, secondary condensing means, a condensate exit, exiting within the second exhaust vessel, a condensate outlet and a condensate conduit, connected to said condensate outlet and extending within said second exhaust vessel. Drainage means is provided, comprising a drain tube and an air vent. The drainage means is connected to the condensate outlet for draining condensate from the second exhaust vessel. The method comprises the steps of: filling the first exhaust vessel with a heat exchange media; filling the second exhaust vessel with water to a level above the condensate intake end of the condensate conduit in the second exhaust vessel to prevent exhaust steam from exiting said second exhaust vessel via the intake end of said condensate conduit; passing exhaust steam from the sterilization apparatus to the first exhaust vessel; at least partially condensing exhaust steam in the first exhaust vessel, creating a mixture of exhaust steam and condensate; conveying the mixture of exhaust steam and condensate to the second exhaust vessel; condensing the mixture of exhaust steam and condensate, creating condensate, and draining the condensate from the second exhaust vessel. Air is vented from the drainage means preventing water from siphoning out of the second exhaust vessel to a level below the condensate intake end of the condensate conduit in the second exhaust vessel.
These and other advantages of the invention will become apparent upon reading the following detailed description and upon referring to the drawings in which:
While the invention will be described in conjunction with the illustrated embodiments, it will be understood that it is not intended to limit the invention to such embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.
In the following description, similar features in the drawings have been given identical reference numerals where appropriate.
The exhaust assembly 10 of the present invention is suitable for use with the applicant's current STATIM CASSETTE AUTOCLAVE™ sterilizers but also with a sterilizer that uses superheated steam in the drying of the medical and dental instruments after sterilization. Such a sterilizer is described in the applicant's PCT Application No. PCT/CA2007/001197, the contents of which are incorporated herein by reference. It has been found that the volume of exhaust steam from the superheated steam sterilizer far exceeds that from the conventional sterilizer, thus necessitating a better exhaust handling system.
Exhaust, which may include condensate, steam, superheated steam and air, is vented from the sterilization apparatus 12 through one or more exhaust ports 14 to prevent moisture from remaining on the sterilized equipment contained within the apparatus. One or more exhaust ports 14 may be connected to the exhaust assembly 10. As shown in
The exhaust steam entering the first exhaust vessel 26 is condensed to a mixture of exhaust steam and condensate via a primary condensing means. As shown in
As the exhaust steam travels through the primary condenser coil 28, it is cooled and condensed to a mixture of condensed water and residual exhaust steam. The mixture of condensate and exhaust steam exits the first exhaust vessel 26 through a first outlet port 30 and is carried via an interconnect tube 32 to the second exhaust vessel 38. The interconnect tube 32 may be constructed of PTFE or any other suitable material for carrying high temperature exhaust and condensate.
As seen in the Figures, there is no mixing of the exhaust steam with the heat exchange media 24 in the first exhaust vessel 26.
The mixture of condensate and exhaust steam enters the second exhaust vessel 38 through a second inlet port 34. The residual exhaust steam in the mixture of condensate and exhaust steam is further condensed as it travels through a secondary condensing means in the second exhaust vessel 38. As seen in
As shown in
Typically, the size of the second exhaust vessel 38 corresponds to the size of the water reservoir in the sterilization apparatus 12 so that the second exhaust vessel 38 may hold at least as much condensate or waste water as the initial water reservoir supply. Thus, when the water reservoir of the sterilization apparatus is empty and needs to be refilled, the corresponding second exhaust vessel 38 is relatively full and can be emptied by a user at the same time. Although not shown in
The first and second exhaust vessels 26, 38, may be any suitable container for storing the heat exchange media 24 and condensate or water, such as a polypropylene bottle. The vessels 26, 38 are of varying sizes but it has been found that a six-litre vessel functions well in that it provides a sufficient volume of heat exchange media in the first exhaust vessel 26 to effectively condense the majority of the exhaust steam for several hours of uninterrupted sterilizer use, yet it is an appropriate size to be handled by any user when the vessels 26, 38 need to be emptied and/or refilled. In operation, the vessels may be connected via an appropriate interconnect tube 32, such as PTFE tubing.
Since some building codes may prohibit the disposal of steam directly into a drainage system, it may be necessary to ensure that residual exhaust steam is prevented from entering the sink or drainpipe through the condensate outlet 50 and drain tube 54. In this case, in a further embodiment of the present invention, a condensate conduit 56 is provided which is connected to the condensate outlet 50 and which extends within the second exhaust vessel 38 below the condensate outlet 50. As shown in
In operation, the second exhaust vessel 38 is initially filled with a liquid condensate, such as tap water, to a minimum condensate level 58 above the condenser coils 36 and the condensate conduit intake 60. As shown in
As the sterilization apparatus 12 progresses through the drying operation, a slight buildup in pressure may occur in the second exhaust vessel 38. An exhaust vent 44 may be provided in the cap 42 of the second exhaust vessel 38. Exhaust vent 44 may be used to control the air pressure in the second exhaust vessel 38 and to prevent an increase in air pressure from forcing the condensate level below the level of the condensate conduit intake 60.
The exhaust assembly of the present invention provides a significant improvement in condensing exhaust steam from a sterilization apparatus over a conventional single-vessel system for condensing and storing exhaust steam. A conventional system was tested using two single-vessel condensers inside a closed cabinet, each single-vessel condenser connected to one of two exhaust ports of a sterilization apparatus. After running back-to-back sterilization cycles for wrapped packages of equipment within the sterilizing apparatus, namely the cassette autoclave, for a duration of 120 minutes, the average relative humidity inside the cabinet housing the exhaust bottles was 65%, and the temperature reached a maximum of 52 degrees Celsius. Visual inspection revealed that the walls inside the cabinet contained a large build-up of moisture due to the high humidity, indicating that a significant amount of steam was not being condensed to water.
Using an exhaust assembly of the present invention, such as the embodiment illustrated in
Thus, it is apparent that there has been provided in accordance with the invention an apparatus for condensing and disposing of exhaust steam, such as from a sterilization apparatus, that fully satisfies the objects, aims and advantages set forth above. While the invention has been described in conjunction with illustrated embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and broad scope of the invention.
