A device for regulating a flow rate in an air-liquid centrifugal separator

Abstract: The device for regalating a flow rate of an air-liquid centrifuge separator comprises a gas outlet pipe (2), an outlet pipe (4) for separated liquids and an inlet pipe (3) through which a fluid to be separated enters the separator (1). The device comprises a by-pass pipe (7), arranged between the liquid outlet pipe (4) and the fluid inlet pipe (3), which removes liquid from the liquid outlet pipe (4) and transfers it to the fluid inlet pipe (3) when a pressure of the liquid in the liquid outlet pipe (4) exceeds a predetermined level. The device is particularly useful in separators for dental aspiration plants.

Description: Specifically, though not exclusively, the invention is usefully applied in the field of dental aspiration plants. As is well known, dental aspiration plants enable fluids to be removed from the mouth of a patient during a dental operation. These fluids comprise a gaseous part, generally air, a liquid part, generally water, blood and other liquids which are used in the dental plant) and a solid part which is made up of particles, generally obturation material and other débris. The flow of the aspirated fluids, which contain various polluting substances, is usually discontinuous and can be quite substantial, such as, for example, when the plant is being washed and flushed out. The separated liquids, before being discharged into the municipal sewers, have to be treated in order to remove the polluting substances. Whatever the nature of this treatment, a counter-pressure is generated in outlet which hinders the exit of the liquids from the plant. Other and many-varied factors (both constant and accidental) can cause a similar counterpressure. In plants equipped with an air-liquid separator centrifuge, i.e. a separator in which the fluid to be separated enters and subsequently exits through different outlets, the air (or other gases) being aspirated by the separator, for example by a suction pump, and the liquid being sent on to subsequent treatments before being discharged into the sewers, it can happen that an excessive incoming fluid flow leads to difficulty in liquid discharge, possibly giving rise to a flooding in the separator, with liquid being sucked into the air outlet. This drawback is to be avoided, as it can lead to serious damage of the air suction pump. As it is not possible to discharge any excess liquid directly into the sewers, various solutions have been offered to obviate this drawback. A first of these solutions consists in halting plant operation (in practice this means shutting down the suction pump) when the liquid level or the pressure of liquid in the pipe goes over a certain level. This is a rather drastic solution which is not popular with users. Another solution consists in providing a buffer tank which, when the level of the liquid or the pressure of the liquid in the pipe goes over a certain level, receives the excess liquid which is then sent on to subsequent treatments before being discharged into the sewers. This solution, though quite functional in other areas, leads to a complication in the construction of the plant as well as to an increase in its size. A further solution is disclosed in US 3,715,863, wherein a pump/air separator apparatus for use in dispensing gasoline includes an air separator of the cyclone type in which air and a low percentage of gasoline are removed from the pressurized gasoline by the air separator, with the air being vented to the atmosphere and the gasoline being returned to the suction side of the pump. Simultaneously pure gasoline is delivered from the air separator through an outlet valve to a meter and the to the nozzle dispenser, and any excess of such pure gasoline is by-passed back to the suction side of the pump. The main aim of the present invention is to obviate the above-mentioned drawbacks in the prior art, by providing a device which simply and economically prevents separator flooding in any operating circumstances without shutting down aspiration plant operation. An advantage of the device is that it can be easily applied on known-type plants. A further advantage is that it provides a device which, in case of necessity, activates and deactivates automatically with no need for manual intervention on the part of the operator, nor any need for an external energy supply, such as electrical or pneumatic energy, or any other type. These aims and advantages and more besides are all achieved by the invention as it is characterised in the claims that follow. Further characteristics and advantages of the present invention will better emerge from the detailed description that follows of a preferred but non-exclusive embodiment of the invention, illustrated purely by way of a nonlimiting example in the accompanying figures of the drawings, in which: figure 1 is a diagram of an air-liquid separator centrifuge; figure 2 is an enlarged-scale drawing of a detail of figure 1 relating to a possible embodiment of the device of the invention. With reference to the figures of the drawings, 1 denotes in its entirety an air-liquid centrifuge separator, of known type, for separating a gaseous part of a fluid from a liquid part thereof. This type of separator centrifuge is commonly used, for example, in dental aspiration plants. The inside of the separator 1 is kept in depression by means for aspirating, for example by a suction pump of known type and not represented in the figures. The suction pump aspirates the gaseous part of the fluid to be separated, and expels the gas through a gas outlet pipe 2, in the flow direction indicated by arrow A. The separator 1 further comprises a liquid outlet pipe 4, through which the separated liquids are sent in flow direction L to a liquid treatment device, for example a solid particle separator of known type and not represented in the figures. The fluid to be separated enters the separator 1 in flow direction F through a fluid inlet pipe 3; the fluid is sucked into the separator by effect of the depression inside the separator itself. The device of the invention comprises a by-pass pipe 7 which is arranged between the liquid outlet pipe 4 and the fluid inlet pipe 3. When the liquid pressure in the liquid outlet pipe 4 exceeds a predetermined level, a part of the liquid is taken away from the liquid outlet pipe 4 and transferred to the fluid inlet pipe 3 through this by-pass pipe 7. The point at which the by-pass pipe 7 meets the fluid inlet pipe 3 is immediately upstream of the separator 1, while the connection with the liquid outlet pipe 4 is immediately downstream of the separator 1. This particular arrangement increases (as will become more evident herein below) the immediacy of the device response to an excess of liquid in the liquid outlet pipe 4. The by-pass pipe 7 is connected to the liquid outlet pipe 4 through a pressure relief valve 5, which, in a preferred embodiment shown in the figures, is two-way and comprises an obturator 9, normally in the form of a membrane, which during normal operation is kept closed by an adjustable spring 8 (for example regulatable by a preload obtained using screws, not illustrated in the figures). The loading, or regulation, of the spring 8 decides on the pressure level at which the valve 5 opens and places the liquid outlet pipe 4 in communication with the by-pass pipe 7. The fluid inlet pipe 3 comprises a sleeve 6 which exhibits a choke 10; the by-pass pipe 7 is connected to the fluid inlet pipe 3 at a point upstream of the choke 10 with respect to the separator 1; thus the ingress of the liquid from the by-pass pipe 7 into the sleeve 6 of the fluid inlet pipe 3 is countercurrent to the motion of the fluid internally of the fluid inlet pipe 3. In the illustrated embodiment, the liquid enters in a perpendicular direction to that of the motion of the fluid internally of the fluid inlet pipe 3; this is solely for reasons of constructional simplicity and does not substantially affect the operation of the device in relation to a possible slightly more functional countercurrent ingress. During normal operation, when there is no excess of liquid in the liquid outlet pipe 4, the valve 5 remains closed and the by-pass pipe 7 is not crossed by liquid or fluid, and the separator 1 functions normally. When there is an excess of liquid, which might occur during a plant washing and flushing operation, when the amount of liquid aspirated with the fluid is greater, generally for quite brief periods, than the amount of fluid being discharged, the liquid level and pressure in the liquid outlet pipe 4 reach a predetermined level, which level is in any case lower than one which would cause separator 1 flooding, the valve 5 opens and the liquid is discharged through the by-pass pipe 7 into the fluid inlet pipe 3. Inletting of liquid into the fluid inlet pipe 3 causes an increase in pressure upstream of the choke 10, with a consequent diminution in the volume of fluid aspirated. This means that there is effectively an automatic reduction in the volume of fluid aspirated, which tends to reduce the excess of liquid and brings the separator 1 back into normal operating condition parameters, without the plant having to be shut down, and even without the operator's noticing the change in operating mode, especially given the brevity of the excess fluid condition. Once the liquid level in the liquid outlet pipe 4, and consequently the pressure therein, have returned to acceptable levels, the valve 5 automatically closes and the separator 1 returns to normal functioning. It is worth noting that the positioning of the by-pass pipe 7 close to the separator 1 means that an increase in pressure is almost immediately detected, as is a reduction in the volume in the fluid inlet pipe 3. The device of the invention realizes a device which perfectly solves the problem of preventing separator flooding, which has no need of maintenance, which can be applied to known-type plants, which enters into operation and deactivates with no need to shut the plant down. The device also has no need for manual intervention nor is any external supply required, but it processes the totality of the liquid sent to it, without the operator even noticing its entry into operation.

Claims: A device for regulating a flow rate in an air-liquid centrifuge separator, for application to a separator (1), comprising: a fluid inlet pipe (3), through which a fluid to be separated enters the separator (1); a gas outlet pipe (2) through which, aided by use of means for aspirating, gas is removed from the fluid to be separated; a liquid outlet pipe (4), through which liquids separated from the gas are sent on to a further device, for treatment of liquids; a by-pass pipe (7), arranged between the liquid outlet pipe (4) and the fluid inlet pipe (3), which by-pass pipe (7) removes liquid from the liquid outlet pipe (4) and transfers the liquid to the fluid inlet pipe (3) when a pressure of liquid in the liquid outlet pipe (4) exceeds a predetermined level; characterised in that the by-pass pipe (7) is arranged between the fluid inlet pipe (3) and the liquid outlet pipe (4), immediately upstream of the separator (1) on the fluid inlet pipe (3) and immediately downstream of the separator (1) on the liquid outlet pipe (4). The device of claim 1, characterised in that the by-pass pipe (7) is connected to the liquid outlet pipe (4) via a pressure relief valve (5). The device of claim 2, characterised in that the pressure relief valve (5) is two-way and comprises an obturator (9) which is normally kept in a closed position by an adjustable spring (8). The device of claim 1, characterised in that : the fluid inlet pipe (3) exhibits a sleeve (6) having a choke (10); the by-pass pipe (7) being connected to the fluid inlet pipe (3) at a point which is upstream of the choke (10) with respect to the separator (1). The device of claim 4, characterised in that ingress of the liquid from the by-pass pipe (7) into the sleeve (6) is in a direction which is countercurrent to a motion direction of the fluid internally of the fluid inlet pipe (3).

Inventors: CATTANI ENNIO, CATTANI, ENNIO
Applicants: CATTANI SPA, CATTANI S.P.A.
Application year: 2000
Main classification: A61C17
IPC codes: A61C17, B04B11, B01D19