Sterilizing procedures and equipment

#This invention relates to the sterilising of articles to kill or destroy bacteria or other unwanted or toxic bodies. The invention is of particular utility in the sterilising of equipment used for medical or surgical purposes, but may have other applications, for example in industry.

#It is of course well-known to sterilise metal surgical instruments by steam and it has also been common practice to sterilise various articles in sterilising liquids. High temperature steam sterilising is simple and effective for certain metal objects, but has limitations and disadvantages, for example it is inefficient in sterilising any object within a sealed package, and the high temperatures involved may cause degradation of plastic articles. The use of sterilising liquids also has limitations, for example air bubbles may be trapped within the object thus preventing full effectiveness, and it may be difficult or impossible to remove all trace of the liquid afterwards.

#It has also been common practice to sterilise medical or surgical equipment by means of a toxic gas and many existing sterilisers in hospital use, for example, involve contacting the articles with Ethylene Oxide in a sealed sterilising chamber. Ethylene Oxide is an extremely effective bactericide, and is effective not only for metal objects such as surgical implements, but also relatively delicate instruments and equipment, including synthetic plastics. The gas is effective at medium or low temperatures and thus the effects of high temperatures on degrading materials can be avoided. The gas penetrates or permeates plastic wrappings and can thus be used to sterilise pre-packaged objects.

#The invention may be performed in various ways and one specific embodiment will now be described by way of example with reference to the accompanying drawings, in which:

#FIG. 1 is a diagrammatic side elevation of a gas sterilising apparatus according to the invention,

#FIG. 2 is a diagrammatic plan view of the apparatus,

#Referring first to the essential elements of the apparatus illustrated in FIGS. 1 and 2, the equipment comprises a sterilising chamber 10 having a stainless steel cylindrical side wall designed to withstand internal pressures, for example of up to five atmospheres, or a partial vacuum. The top of the chamber is closed by a circular lid or cap 11, which is hinged to the side wall at 12 and provided with a circumferential O-ring or other fluid seal 13, and a metallic knit-mesh microwave seal 9. The lid can be held closed by a hinged clamp 14 provided with a tightening screw 15. The lid may also have a rupturable pressure relief disc valve 16, to prevent build up of excessive internal pressures.

#On the side of the chamber 10 is an air entry 23 which may be connected to a source of supply for a controlled selected gas, or atmosphere, as required. The side wall of the chamber is also provided with another port 29 intended to act as an air outlet, and this may be connected to a special vent duct with a filter, or to atmosphere, as required. The filter conveniently includes a mass of high molecular weight polymeric material designed to adsorb Ethylene Oxide, from which the gas can later be reclaimed for disposal or recycling. The wall of the chamber is also provided with a microwave spectrometer 24, as illustrated in FIG. 7, and at another part of the side wall is a special sealed injector unit 25 for admitting controlled quantities of Ethylene Oxide when required. This is illustrated in greater detail in FIGS. 5 and 6.

#Within the chamber is a rotary basket 27 for equipment to be sterilised, the basket being supported by bearings 28 mounted on the side wall of a chamber and a special drive system 30 for causing rotation of the basket is illustrated in detail in FIGS. 3 and 4. The bottom wall 31 of the chamber is formed of a material such as Polypropylene which is capable of transmitting electromagnetic radiation and acts as a microwave window, and below the chamber are located three microwave generators 32,33,34 associated with launching "horns" 35,36 and a "mode stirrer" 38 driven by a motor 37. Means are provided to vary the output of the generator 33 and to augment this as required by one or both of the generators 32,34 so as to provide for variation over all three ranges.