Patent Description:
It hardly needs be mentioned that sterilizing means performing a physical or chemical process destroying all microorganisms, including bacterial spores.

In the art, there are provided substantially two types of autoclaves:.

The present invention can be used in bench-top autoclaves, or small autoclaves, working with water steam, which are commonly found in medical/dental/veterinary practices making use of re-usable instruments needing sterilization after their use.

Water steam autoclaves are supplied with water, usually demineralized water, which is brought to high temperature and pressure. The water steam so generated is conveyed inside a sterilization chamber, wherein the instruments to be sterilized are placed, often inside sterilization pouches or suitable sterilization cassettes. The contact at a known pressure and for a pre-set time between water steam and instruments allows to sterilize said instruments.

A sterilization cycle comprises many steps:.

In the art, it is known to perform said pre-heating step of the sterilization and of the load to be sterilized by using suitable heating means (e.g. an electrical resistance) applied to said sterilization chamber.

The drying step typically comprises maintaining a suitable temperature in the sterilization chamber and of the sterilized load, maintaining a negative pressure inside the sterilization chamber (i.e. a pressure lower than the atmospheric pressure), and optionally generating an airflow at atmospheric pressure that reaches the sterilization chamber passing through a bacteriologic filter.

Typically, in an autoclave there are provided at least two kinds of sterilization cycles:.

In the art, there are provided class B, class S, class N autoclaves.

The autoclave according to the present invention is preferably an autoclave capable of performing class B sterilization cycles.

In the known art, typically autoclaves comprise the following components:.

Providing autoclaves with a system allowing to extract both air and water steam from the sterilization chamber is known in the art, e.g. in the two documents of the known art in the following.

<CIT> of Dentalwerk Buermoos GmbH describes an autoclave provided with a vacuum pump extracting water steam from the sterilization chamber. To this aim, a vacuum pump, preferably a membrane pump, is used to remove steam from the sterilization chamber, in conjunction with a condenser which is intended to bring the steam to a pressure and temperature wherein steam goes back to liquid state. It is worth mentioning that the vacuum pump is probably one of the most expensive components of an autoclave.

<CIT> of W & H Sterilization describes a refinement of the preceding invention, wherein the sterilization chamber is connected with two three-way valves allowing to inject a pre-set quantity of hot steam directly inside the condenser; said steam is cooled and condensed inside said condenser, and therefore its volume and pressure decrease to levels lower than those of the sterilization chamber. Said condenser is placed in direct communication with the sterilization chamber in order to perform steam removal. <CIT> and <CIT> of Shandong Shinva Med Instr CO describe instead a hydraulic circuit for an autoclave comprising a boiler that can be considered like the combination of a reservoir of water used to generate steam and of an element generating steam, a pump, a sterilization chamber, two steam condensers, a manifold. Although not explicitly named as such, said hydraulic circuit of the autoclave comprise a Venturi tube that works through steam (paragraph <NUM>: In the steam ejector <NUM>, the steam is accelerated and sprayed from the steam inlet to the steam outlet. When the high-speed steam passes through the evacuation port between the steam inlet and the steam outlet, a negative pressure is generated at the outlet of the evacuation port, and this negative pressure can realize the extraction. The air and moisture in the sterilization chamber <NUM> realize the vacuuming of the sterilization chamber <NUM>).

Aim of the present invention is providing an autoclave allowing to remove air/water steam from the sterilization chamber without a vacuum pump, so that a cheaper autoclave is obtained by removing one of its costlier components.

This object is achieved by an apparatus and a method having the features of the independent claims. Advantageous embodiment and refinements are specified in the claims dependent thereon.

Substantially, the solution consists in replacing the vacuum pump with an ejector, which, exploiting the Venturi effect, allows to generate a suction flow capable of removing residual air/water steam from the sterilization chamber.

The ejector is a known commercial component, used for a variety of other applications.

In a first embodiment, the ejector is actuated by a compressed air flow coming from outside the autoclave, e.g. from the compressed air circuit customarily provided in a dental practice.

In a second embodiment, the ejector is actuated by the water steam flow generated by the autoclave itself.

In a third, preferred embodiment, said Venturi ejector works using steam that is produced starting by the condensed water coming back from the sterilization chamber of the autoclave. The steam used to actuate the ejector (Venturi tube) is further condensed and conveyed to the used water tank, so that used water is used many times.

In an embodiment, the ejector is placed downstream the steam condense. and in discharge, upstream the manifold.

In an alternative embodiment, the ejector is placed immediately downstream a manifold and upstream the condenser.

The advantages according to the present invention as defined in claims <NUM> and <NUM> are manifold.

A first advantage is replacing a costly component (the vacuum pump) with a cheaper component (the ejector). In a preferred embodiment, the cost of the autoclave is further reduced by using a plastic ejector, less expensive than the same component made of metal.

A second advantage lies in the fact that the ejector is a static component, and therefore suffers less from wear with respect to a vacuum pump. Therefore, downtimes risk is reduced.

A third advantage is placing said ejector immediately downstream the solenoid valves group (manifold) but upstream the steam condenser: in this way, the suctioning action performed by the ejector is even stronger.

A fourth advantage is generating steam with used water, that is water obtained from the condensation of the steam used in the sterilization chamber, which came into contact with contaminated instruments. In this way, the demineralized water is used for two distinct operations: a first time to generate the steam intended for sterilization; and once it ended up in the user water tank, many times in order to generate the steam intended for actuating the ejector. In this way the consumption of demineralized water is greatly reduced.

Further advantages and properties of the present invention are disclosed in the following description, in which exemplary embodiments of the present invention are explained in detail based on the drawings:.

It is worth mentioning that the solenoid valves shown in the drawings and mentioned in the Description use the following abbreviations: NC means normally closed, NA means normally open, while 3V means three-way.

<FIG> shows an axonometric view of a typical bench-top autoclave <NUM>. The autoclave <NUM> comprises a sterilization chamber <NUM> that is hermetically closed by a door <NUM>. A display <NUM> placed on its front allows a human operator to input the different sterilization cycles and to receive information about the status of the autoclave <NUM>. Above the sterilization chamber <NUM> there are provided two water tanks: a first tank <NUM> is provided for demineralized water, while a second tank <NUM> is provided for water condensed from steam, i.e. already used water.

<FIG> shows a schematic representation of an autoclave according to a first example which is not part of the invention, wherein said ejector is actuated by compressed air.

The hydraulic circuit according to the first embodiment comprises:.

The demineralized water contained in the clear water tank <NUM> is conveyed through a tubing <NUM> firstly to the pulse pump <NUM>, successively to a solenoid valve EV6-NC, and to the steam generator <NUM> inside which it is transformed into steam. Steam is conveyed through a tubing <NUM> to the sterilization chamber <NUM>.

Connected to the sterilization chamber there are provided the safety valve <NUM> for preventing overpressures, the pressure transducer <NUM> to detect the pressure inside said sterilization chamber <NUM>, the pressure switch <NUM> that does not allow the opening of the door <NUM> when the pressure inside the sterilization chamber is higher than atmospheric pressure.

Through a tubing <NUM>, the manifold <NUM> is connected to said sterilization chamber <NUM>. Said manifold <NUM> comprises five solenoid valves. A first EV5-NC solenoid valve controls the airflow incoming through said bacteriologic filter <NUM> in the pressure-balancing step at the end of sterilization cycles. A second solenoid valve EV1-NA connected to the top portion of the sterilization chamber <NUM> allows to control steam discharge. A third solenoid valve EV2-NC connected to atmospheric air allows to control an air flow helping to empty tubings. A fourth solenoid valve EV3-NC connected to the bottom portion of the sterilization chamber <NUM> allows to control the discharge of the condensed from steam. The two solenoid valves EV1-NA and EV3-NC convey the flow of steam/condense to the condenser <NUM> through a tubing <NUM>. A fifth solenoid valve EV4-3V connected to the condenser <NUM> allows to convey the flow of steam/condense alternatively:.

The water/condense outcoming from the ejector <NUM> is finally conveyed to the used water tank <NUM> through a tubing <NUM>.

<FIG> shows a schematic representation of the hydraulic circuit of an autoclave according to a second example which is not part of the invention, wherein the ejector is actuated by a steam flow generated by the steam generator <NUM> of the autoclave <NUM>.

The hydraulic circuit according to the second embodiment comprises:.

The demineralized water contained in the clear water tank <NUM> is conveyed through a tubing <NUM> firstly to the pulse pump <NUM>, successively to a solenoid valve EV6-NC, and to the steam generator <NUM> inside which it is transformed into steam. Steam is conveyed through a tubing <NUM> to the valve EV8-3V, which according to its state conveys it alternatively to the sterilization chamber <NUM> through a tubing <NUM> or to the ejector <NUM> through a tubing <NUM>.

Through a tubing <NUM>, the manifold <NUM> is connected to said sterilization chamber. Said manifold <NUM> comprises five solenoid valves. A first EV5-NC solenoid valve controls the airflow incoming through said bacteriologic filter <NUM> in the pressure-balancing step at the end of sterilization cycles. A second solenoid valve EV1-NA connected to the top portion of the sterilization chamber <NUM> allows to control steam discharge. A third solenoid valve EV2-NC connected to atmospheric air allows to control an air flow helping to empty tubings. A fourth solenoid valve EV3-NC connected to the bottom portion of the sterilization chamber <NUM> allows to control the discharge of the condense from steam. The two solenoid valves EV1-NA and EV3-NC convey the flow of steam/condense to the condenser <NUM> through a tubing <NUM>. A fifth solenoid valve EV4-3V connected to the condenser <NUM> allows to convey the flow of steam/condense alternatively:.

In the first example, the operating principle of the ejector <NUM> provides that an airflow coming from outside the autoclave, controlled by the solenoid valve EV8-NC <NUM>, is conveyed to the ingress of the ejector, accelerated through its nozzle, so as to generate suction through a Venturi effect. This allows the removal of steam/condense from the sterilization chamber <NUM>, up to pressure values lower than atmospheric pressure (conventionally indicated as <NUM>).

In the second example, the operating principle of the ejector <NUM> provides that a steam flow generated by the steam generator <NUM> and controlled by the solenoid valve EV8-3V is conveyed to the ingress of the ejector, accelerated through its nozzle, so as to generate suction through a Venturi effect. This allows the removal of steam/condense from the sterilization chamber <NUM>, up to pressure values lower than atmospheric pressure (conventionally indicated as <NUM>).

In the examples shown in <FIG> and <FIG>, the ejector <NUM> is placed downstream the steam condenser <NUM>.

In alternative, not shown embodiments, the ejector <NUM> is placed immediately downstream the manifold <NUM> and upstream the condenser <NUM>.

In all the embodiments, the discharge of the condensed steam outcoming from said ejector <NUM> is conveyed to the used water tank <NUM> through a tubing <NUM>.

<FIG> shows a schematic representation of an autoclave as defined in claim <NUM>, wherein an ejector <NUM> is actuated by a steam flow produced by the steam generator <NUM> of the autoclave <NUM> by using used water contained in the discharge tank <NUM>.

The water contained in the tanks <NUM> and <NUM> is conveyed trough tubing <NUM> and <NUM> first to the solenoid valve EV2-<NUM>/<NUM>-NC and successively to an impulse pump <NUM>, through a tubing <NUM>. Consecutively, the water is channelled to a solenoid valve EV6-NC and to a steam generator <NUM> inside which is converted into steam. The steam is channelled through a tubing <NUM> to the valve EV4-<NUM>/<NUM>-NC that, according to its actuation state, sends it alternatively to the sterilization chamber <NUM> through a tubing <NUM> or to the ejector <NUM> through a tubing <NUM>.

To the sterilization chamber <NUM> there are connected the safety valve <NUM> for preventing overpressures, the pressure transducer <NUM> for detecting the pressure inside the sterilization chamber, the pressure switch <NUM> that does not allow the opening of the door <NUM> when the pressure inside the chamber <NUM> is higher than the atmospheric pressure.

Through tubing <NUM> and <NUM>, a manifold <NUM>, comprising three solenoid valves, is connected to the sterilization chamber <NUM>. A first valve EV5-NC controls the input air flow through a bacteriologic filter <NUM> in the step of pressure levelling at the end of the sterilization cycle. A second solenoid valve EV1-NA connected to the upper portion of the chamber <NUM> allows to control steam discharge, through the tubing <NUM>. A third solenoid valve EV3-NC connected to the lower portion of the chamber <NUM> allows to control the discharge of condensed water and steam through the tubing <NUM>. The two solenoid valves EV1-NA e EV3-NC send, through a tubing <NUM>, the flow of steam/condense coming from the chamber <NUM> to the ejector <NUM>.

The steam generator <NUM> supplies, through a tubing <NUM>, the ejector <NUM> allowing the passage, through tubing <NUM> and <NUM>, of the water/condense coming out from the condenser <NUM>. The water/condense coming out from said condenser <NUM> is finally sent to the discharge tank <NUM>, through a tubing <NUM>.

The operating principle of the ejector <NUM> provides that a steam flow generated by the steam generator <NUM> employing used water withdrawn from the tank <NUM> through the tubing <NUM> is controlled by the solenoid valve EV4-<NUM>/<NUM>-NC. Such steam flow is conveyed to the ingress of the ejector <NUM>, accelerated through its nozzle, so as to generate suction through a Venturi effect. This allows the removal of steam/condense from the sterilization chamber <NUM>, up to pressure values lower than atmospheric pressure (conventionally indicated as <NUM>).

In the embodiment shown in <FIG>, the ejector <NUM> is placed in suction downstream the manifold <NUM> and in discharge, upstream the steam condenser <NUM>.

In an alternative (not shown) embodiment, the ejector <NUM> is placed in suction, downstream the condenser <NUM>, and in discharge, upstream the manifold <NUM>.

<FIG> shows the operating principle of a vacuum ejector, i.e. the ejector <NUM>.

Said ejector comprises an ingress A and a nozzle B for the motive fluid, an ingress C for the mixture steam/condense suctioned from the sterilization chamber <NUM>. Downstream said ingresses, perpendicular to each other, there is provided an egress D, in axis with the ingress A and the nozzle B.

In <FIG>, the bold arrows show the ingresses and the egress of the fluids, while the thin arrows show the pathway of said fluids inside the ejector.

The operating principle of the ejector <NUM>, based on the Venturi effect, provides that a pressurized motive fluid (compressed air or steam) is conveyed to the ingress A and accelerated through the nozzle B. At the egress of said nozzle B, the motive fluid flows at an increased speed due to the compression exerted by the nozzle. At the same time the motive fluid generates a suction dragging the steam/condense coming from the sterilization chamber and entering into the ejector <NUM> through the ingress C. Downstream the ingress C, the motive fluid mixed with the suctioned steam/condense reach the egress D and from there the used water tank <NUM> through the tubing <NUM>.

In the first example, the motive fluid used is compressed air coming from a compressed air net independent from the autoclave <NUM>.

In the second example, the motive fluid used is steam, generated by the steam generator <NUM> and conveyed to the ejector <NUM> through tubing <NUM>.

In the embodiment according to the invention, downstream the ingress C, the motive fluid mixed with the suctioned steam/condense reach the egress D and from there the used water tank <NUM> through the tubing <NUM> and <NUM>.

Claim 1:
Hydraulic circuit for a water steam autoclave (<NUM>) for sterilizing instruments, comprising in the order
- a first tank (<NUM>) for the demineralized water intended for generating steam for a sterilizing chamber and a second tank (<NUM>) for collecting used water,
- a pump (<NUM>) for conveying water, in sequence, toward the following units
- a steam generator (<NUM>),
- a sterilizing chamber (<NUM>) wherein steam and instruments to be sterilized come into contact,
- a steam condenser (<NUM>),
- a manifold (<NUM>),
which units are connected to each other through suitable tubing (<NUM>-<NUM> or <NUM>-<NUM>) and solenoid valves,
wherein the hydraulic circuit further comprises an ejector (<NUM>) to suction the content of said sterilization chamber (<NUM>) and
wherein said ejector (<NUM>) is actuated by steam generated from water withdrawn from said second tank (<NUM>) for collecting used water,
characterized in that the hydraulic circuit comprises a first tubing (<NUM>) and a second tubing (<NUM>) connecting respectively the said first tank (<NUM>) and the said second tank (<NUM>) to the said steam generator (<NUM>) through a solenoid valve (EV2-<NUM>/<NUM>-NC) allowing to select the demineralized water tank <NUM> or the used water tank <NUM> from which water to be conveyed to the circuit can be withdrawn and a third tubing (<NUM>) for channelling the steam to a further valve (EV4-<NUM>/<NUM>-NC) that according to its actuation state sends it alternatively to the sterilization chamber (<NUM>) through a fourth tubing (<NUM>) or to the ejector (<NUM>) through a fifth tubing (<NUM>).