VACUUM PUMPING SYSTEM PROVIDED WITH A SOUNDPROOFING ARRANGEMENT

A vacuum pumping system includes a vacuum pump and a soundproofing arrangement. The vacuum pump is accommodated in a pump housing. The soundproofing hood surrounds the pump housing and includes a hood air inlet and a hood air outlet. To improve dampening of the noise generated by the vacuum pumping system, one or more additional soundproofing shielding element(s) is/are provided between the hood air inlet and the pump housing air inlet and/or between the hood air outlet and the pump housing air outlet, respectively. The additional soundproofing shielding element(s) may be designed as a casing surrounding the pump housing and including a casing air inlet and a casing air outlet.

RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. 119 of European Patent Application No. EP 17204792.0, filed Nov. 30, 2017, titled “VACUUM PUMPING SYSTEM PROVIDED WITH A SOUNDPROOFING ARRANGEMENT,” the content of which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to a vacuum pumping system comprising a vacuum pump and provided with a soundproofing arrangement. More particularly, the present invention relates to a vacuum pumping system comprising a rotary vane vacuum pump and provided with a soundproofing arrangement.

BACKGROUND

Vacuum pumps are employed in a wide range of applications for obtaining sub-atmospheric pressure conditions, going from rough vacuum conditions (i.e. about 10−1Pa) to very high vacuum conditions (i.e. about 10−8Pa).

More specifically, rotary vane vacuum pumps are mechanical pumps, namely positive displacement pumps, that are generally used to obtain low vacuum conditions, in a pressure range from atmospheric pressure to about 10−1Pa.

According to prior art, rotary vane vacuum pumps generally include a pump housing having a gas suction port and a gas exhaust port and receiving a stator defining a cylindrical chamber; a cylindrical rotor is eccentrically arranged inside the stator chamber, which rotor is equipped with spring-loaded radial vanes cooperating with the wall of the stator chamber for pumping a gas from the gas suction port to the gas exhaust port. The pump housing is filled with oil so that the stator is immersed in an oil bath, which has the function of cooling down and lubricating the pump and isolating it from the outside environment.

Pumps of such kind are known for instance from U.S. Pat. No. 6,019,585 and GB 2151091A.

Still according to prior art, a drive motor, namely an electric motor, is operatively connected to the pump through a shaft connection in order to drive in rotation the rotation shaft of the pump rotor. The drive motor is typically arranged outside the pump housing and it is connected to the pump housing through an interface flange.

One or more blowers or fans are provided for cooling down the rotary vane vacuum pump and, in particular, for keeping the temperature of the oil of the vacuum pump oil bath in the pump housing below a predetermined temperature threshold.

The above-described vacuum pumping systems generate a considerable amount of noise, which makes working conditions in their vicinity uncomfortable and which is considered a severe drawback in laboratory environments.

Vacuum pumping systems comprising other kinds of vacuum pumps including moving parts (such, as for instance, turbomolecular pumps, which are commonly used for obtaining high vacuum conditions) and/or comprising pump accessories including moving parts also generate noise, which could represent remarkable drawbacks in some applications.

The noise generated by a vacuum pumping system increases upon increase of the pumping speed of the vacuum pump.

Accordingly, a possible solution for reducing the noise generated by the vacuum pumping system is to run the vacuum pump at low speed.

However, such a solution is not attractive, as it would negatively affect the performance of the vacuum pumping system.

In order to dampen the noise generated by the vacuum pumping system while running the vacuum pump at high speed, it has been suggested to provide the vacuum pumping system with a casing enclosing the vacuum pump and its drive motor.

U.S. Pat. No. 5,145,335 discloses a vacuum pumping system comprising a rotary vane vacuum pump comprising a first housing, receiving the pump stator and the pump rotor and filled with oil, a drive motor associated to the vacuum pump, and a second housing surrounding the first housing and the drive motor.

The presence of such second housing allows to partially reduce the noise transmitted to the surrounding environment by the vacuum pump and by its drive motor.

However, some noise is in any case transferred to the surrounding environment, also in view of the need of providing the second housing with an air inlet and an air outlet in order to allow an air stream to flow inside the second housing for cooling down the vacuum pump and the drive motor.

As a result, the noise-dampening effect obtained by a solution as disclosed in U.S. Pat. No. 5,145,335 has proven to be insufficient for certain applications (such as the so-called “quiet laboratories”), in which a noise lower than 55 dB, and preferably lower than 50 dB, is required in the environment surrounding the vacuum pumping system.

It is also to be considered that the presence of a soundproofing arrangement can cause a remarkable deterioration of the cooling of the vacuum pump.

US 2010/0116583 suggests to provide a soundproofing hood that radially encloses the vacuum pumping system and is open at both axial ends, so that the cooling of the vacuum pumping system is not hindered.

However, such a solution would not be sufficiently effective in dampening the noise generated by the vacuum pumping system and, in particular, it would not be capable of satisfying the above-mentioned need of keeping the noise below a threshold of 50-55 dB in certain applications.

As an alternative, the soundproofing arrangement should be provided with its own blowers or fans in order to guarantee that the temperature of the vacuum pump is kept below a desired threshold.

It is evident that the provision of such additional blowers or fans (and of the related electronic circuitry and control arrangements) is highly disadvantageous, since on one hand it involves additional costs and power consumption, and on the other hand it makes the vacuum pumping system less reliable, as it introduces additional potential sources of failures and malfunctioning.

In view of the above, there is a need to obviate the above-identified drawbacks by providing a vacuum pumping system provided with an improved soundproofing arrangement, capable of dampening the noise generated by the vacuum pumping system to below a threshold of 50-55 dB.

There is also a need to provide a vacuum pumping system provided with an improved soundproofing arrangement which allows to maintain the noise below the desired threshold without reducing the speed of the vacuum pump.

There is also a need to provide a vacuum pumping system provided with an improved soundproofing arrangement which does not deteriorate the cooling of the vacuum pumping system and does not involve the need for additional cooling devices.

SUMMARY

To address the foregoing problems, in whole or in part, and/or other problems that may have been observed by persons skilled in the art, the present disclosure provides methods, processes, systems, apparatus, instruments, and/or devices, as described by way of example in implementations set forth below.

In general, the vacuum pumping system of the invention comprises a vacuum pump, accommodated in a pump housing, and a soundproofing hood which surrounds the pump housing and is provided with a hood air inlet, which is in communication with the pump housing air inlet, for allowing fresh air to flow into the inside of the hood and then through the vacuum pump for cooling it down, and with a hood air outlet, which is in communication with the pump housing air outlet, for allowing heated air coming from the vacuum pump to flow out from the hood.

According to the invention, the vacuum pumping system comprises one or more additional soundproofing shielding element(s) arranged between the hood air inlet and/or outlet and the pump housing air inlet and/or outlet, respectively.

Thanks to the presence of said additional soundproofing shielding element(s), a straight air flow from the surrounding environment to the vacuum pump through the hood air inlet and the pump housing inlet and/or a straight air flow from the vacuum pump to the surrounding environment through the pump housing outlet and the hood air outlet can be prevented, which allows to strongly reduce the noise generated by the vacuum pumping system and transmitted to the surrounding environment, down to below a threshold of 50-55 dB.

According to a preferred embodiment of the invention, said additional soundproofing shielding element(s) is/are designed as a casing surrounding the pump housing, said casing being provided with an air inlet and an air outlet for allowing fresh air to flow into the casing and then through the vacuum pump for cooling it down and for allowing heated air coming from the vacuum pump to be discharged from the casing, respectively.

According to this preferred embodiment of the invention, the hood air inlet is preferably provided on the peripheral wall of the soundproofing hood at a location which is as far as possible from the casing air inlet of the underlying casing, so that the noise dampening effect is optimized, the path of the fresh air inside the hood and around the casing surrounding the vacuum pump is maximized and the cooling efficiency is also maximized.

According to the above preferred embodiment of the invention, the hood air outlet is preferably provided in the peripheral wall of the soundproofing hood at a location which is as far as possible from the location of the hood air inlet on said peripheral wall of the soundproofing hood, so that heat exchange between the fresh air entering through said hood air inlet and the heated air exiting through said hood air outlet can be prevented.

According to a particularly preferred embodiment of the invention, said additional soundproofing shielding element(s) is/are designed as a casing surrounding the pump housing and raised above the floor and the casing air outlet is provided at the bottom wall of the casing.

According to such embodiment, the vacuum pumping system of the invention further comprises a soundproofing tray provided at the bottom wall of the casing, between the casing air outlet and the floor.

According to a preferred embodiment of the invention, the soundproofing hood is provided with a partition extending from the inner wall of the soundproofing hood to the outer wall of the underlying casing and separating a space in which the hood air inlet and the casing air inlet are arranged from a space in which the hood air outlet and the casing air outlet are arranged.

Preferably, such partition completely separates the space in which the hood air inlet and the casing air inlet are arranged from the space in which the hood air outlet and the casing air outlet are arranged.

Thanks to the presence of the above-mentioned partition, in the vacuum pumping system according to the invention the heated air coming out of the vacuum pump through the casing air outlet is prevented from coming into contact with the fresh air entering the vacuum pump through the casing air inlet. As a consequence, the temperature of the fresh air entering the vacuum pump is not raised by possible mixing with the heated air coming out of the vacuum pump itself.

Thanks to this measure, the cooling of the vacuum pump is effective and there is no need of providing the soundproofing hood with additional cooling means.

Advantageously, the provision of the soundproofing arrangement of the invention does not involve any relevant increase in manufacturing costs and power consumption, and the overall design of the vacuum pumping system according to the invention is simple and reliable.

According to a preferred embodiment of the invention, the soundproofing hood and/or the additional soundproofing shielding element(s) and/or the soundproofing tray (if provided) has/have a multi-layered structure comprising several layers of soundproofing material, including at least a first, inner layer made of sound-absorbing material and a second, outer layer made of sound-insulating material.

DETAILED DESCRIPTION

In the detailed description of a preferred embodiment of the invention which follows, reference will be made by way of example to a vacuum pumping system comprising a rotary vane vacuum pump.

Such an exemplary embodiment has not to be considered as limiting the scope of the present invention, which could be applied to vacuum pumping systems comprising any kind of vacuum pump that generates noise.

Referring to the attached Figures, a vacuum pumping system100according to the invention is shown.

With particular reference toFIG. 3, in a per se known manner, the vacuum pumping system100comprises a rotary vane vacuum pump10and a drive motor20.

The rotary vane vacuum pump10comprises a pump housing12in which a gas suction port and a gas exhaust port are defined. A stator14defining a cylindrical stator chamber is received inside the pump housing12. A rotor16is also received in the pump housing12, said rotor having an axis parallel to the axis of the stator chamber, but being eccentrically arranged relative to the stator chamber axis.

Depending on different applications and pumping requirements, the rotor16can be a single-stage rotor or a dual-stage rotor. Each stage of the rotor16is equipped with one or more radially movable radial vanes that are mounted on the rotor16and kept against the wall of the stator chamber.

The pump housing12is filled with such an amount of oil that the stator14is immersed in an oil bath acting as cooling and lubricating fluid.

The drive motor20typically is an electric motor.

The drive motor20is arranged externally to the pump housing12and cantilevered thereon, said drive motor20driving in rotation the pump rotor16. More in detail, the shaft of the rotor of the drive motor20is connected to the shaft of the pump rotor16for driving the latter in rotation about its axis.

A cooling fan30for cooling the vacuum pump10, and more particularly the oil of the oil bath of the vacuum pump10, is also mounted on the shaft of the drive motor20.

In order to reduce the noise generated by the vacuum pumping system and transmitted to the surrounding environment, a soundproofing hood50is provided, which soundproofing hood50surrounds the pump housing12as well as the drive motor20.

In the illustrated preferred embodiment, the soundproofing hood50comprises a roof50aand a peripheral wall50bcompletely surrounding the pump housing12. In the illustrated embodiment, the roof50ahas a rectangular shape and the peripheral wall50bcomprises four side walls, equal and parallel two by two, which downwardly extend from respective sides of the roof50a.

The roof50aand the side walls forming the peripheral wall50bare preferably made as separate parts, which can be assembled together, for instance by screws or rivets.

As can be seen from the Figures, in the illustrated embodiment the soundproofing hood50does not comprise any bottom wall. This allows the soundproofing hood50to be easily lowered onto the pump housing12after the latter has been moved to the desired location and this also allows said soundproofing hood50to be easily lifted from the pump housing12when necessary, for instance for inspection or maintenance of the vacuum pumping system.

It is evident that, in an alternative embodiment, the soundproofing hood50could be provided with a bottom wall, if desired. In a further alternative embodiment, the soundproofing hood50could be provided with a peripheral frame extending from the lower edge of the peripheral wall50band having a suitable width so as not to interfere with the casing when the soundproofing hood50is lowered or lifted.

As can be seen inFIGS. 2 and 3, the soundproofing hood50preferably has a multi-layered structure comprising two or more layers made of soundproofing material.

In the illustrated preferred embodiment, the soundproofing hood50comprises a first, inner layer50′ made of a sound-absorbing material and a second, outer layer50″ made of a sound-insulating material. The first, inner layer50′ can be made, for instance, of an open-cell foam such as polyurethane foam and it can be provided with pyramid or wedge shapes on its inner side. The second, outer layer50″ can be made, for instance, of a heavy plastic material having long molecules.

In general, the number, thickness and materials of the soundproofing hood50can be chosen in each case according to the needs of the specific application, taking into account the vacuum pump size and speed, the spectrum of the generated noise and the required threshold for the noise in the environment surrounding the vacuum pumping system100.

The soundproofing hood50is provided with a hood air inlet52, which is in communication with the pump housing air inlet, for allowing a stream of fresh air to enter the soundproofing hood50for cooling down the vacuum pump10, and it is also provided with a hood air outlet54, which is in communication with the pump housing air outlet, for discharging the heated air, which has passed through the vacuum pump10and has cooled it down, from the soundproofing hood50.

Although the hood50dampens the noise generated by the vacuum pumping system100, it has proven to be unable to reduce the noise in the environment surrounding the vacuum pumping system100below the threshold required in certain demanding applications such as the so-called “quiet laboratories”, i.e. to below the threshold of 50-55 dB.

According to the invention, in order to improve the noise dampening effect and to further reduce the noise generated by the vacuum pumping system100and transmitted to the outside environment, one or more additional soundproofing shielding element(s) is/are arranged between the hood air inlet52and/or outlet54and the pump housing air inlet and/or outlet, respectively.

In a very simple embodiment of the invention, the vacuum pumping system100according to the invention may comprise a suitably shaped wall arranged between the hood air inlet52and the pump housing air inlet and/or a suitably shaped wall arranged between the pump housing air outlet and the hood air outlet54.

However, in the preferred embodiment shown in the drawings, such additional soundproofing shielding element(s) is/are designed as a casing40, which can be contained under the soundproofing hood50and surrounds the pump housing12, so as to form an effective shield between the hood air inlet52and the pump housing air inlet and between the hood air outlet54and the pump housing air outlet, respectively.

Preferably, the casing40has a top wall40a, a peripheral wall40bcompletely surrounding the pump housing12and the drive motor20and a bottom wall40c. In the illustrated embodiment, the top wall40aand the bottom wall40cof the casing40have a substantially rectangular outline, and the peripheral wall40bof the casing correspondingly comprises four side walls, substantially equal and parallel two by two. The casing40is preferably mounted on wheels42, allowing to move the vacuum pumping system100in the surrounding environment for carrying it to the desired location. Thanks to the presence of the wheels42, the bottom wall40cof the casing40is raised above the floor.

In order to effectively dampen the noise generated by the vacuum pumping system100, the casing40is provided with a soundproofing lining44, at least partially covering the inner surface of the casing40. Such a soundproofing lining44comprises at least one layer made of a soundproofing material, namely a sound-absorbing material such as polyurethane foam.

The casing40is provided with a casing air inlet46for allowing a stream of fresh air to enter the casing for cooling down the vacuum pump10. The casing air inlet46is preferably provided in the peripheral wall40bof the casing40, at a location which is as far as possible from the cooling air inlet of the pump housing12(i.e. in the side wall40b′ of the peripheral wall40bopposite to the pump housing inlet), so that the path of the fresh air around the pump housing12is maximized and the cooling of the vacuum pump10is accordingly optimized.

The casing40is also provided with a casing air outlet48for discharging the heated air, which has passed through the vacuum pump10and has cooled it down, from the casing40. The casing air outlet48is preferably provided in the bottom wall40cof the casing40.

Thanks to the provision of the additional soundproofing shielding element(s), namely of the casing40, the noise generated by the vacuum pumping system100in the surrounding environment can be further dampened, below the threshold required in certain demanding applications such as the so-called “quiet laboratories.”

According to the preferred embodiment of the invention shown in the drawings, the soundproofing hood50is provided with a partition56extending from the inner wall of the soundproofing hood50to the outer wall of the underlying casing40and separating a space in which the hood air inlet52and the casing air inlet46are arranged from a space in which the hood air outlet54and the casing air outlet48are arranged. Preferably, said partition56is suitably shaped so as to completely separate the space in which the hood air inlet52and the casing air inlet46are arranged from the space in which the hood air outlet54and the casing air outlet48are arranged.

Thanks to the partition56, any contact and heat exchange between the fresh air entering through the hood air inlet52and flowing to the casing air inlet46(and then to the pump housing air inlet) and the heated air coming out of the pump housing12and flowing from the casing air outlet48to the hood air outlet54is prevented.

As a consequence, the temperature of the fresh air entering the vacuum pump10is not raised before entering the casing40, the cooling of the vacuum pump10is effective and there is no need to provide the soundproofing hood50with additional cooling means.

This involves several advantages: first of all, there is no need to provide the soundproofing hood50with electrical connections and/or control arrangements, which makes such soundproofing hood50simple and inexpensive; secondly, the provision of the soundproofing hood50does not cause any increase in the overall power consumption of the vacuum pumping system100of the invention; thirdly, the provision of the soundproofing hood50does not involve the introduction of additional components which could be potential sources of failures and malfunctioning.

In the preferred embodiment of the invention shown in the Figures, the hood air inlet52is provided in a first side wall50b′ of the hood peripheral wall50b, at a certain height above the lower edge of said peripheral wall50b, and the hood air outlet54is provided in a second, opposite side wall50b″ of the hood peripheral wall50b, close to the lower edge of said peripheral wall (see for instanceFIGS. 1aand 1b). Due to the fact that the hood air inlet52and the hood air outlet54are arranged on opposite side walls of the hood peripheral wall50b, they are as far as possible from each other, so that any heat exchange between the fresh air entering the hood air inlet52and the heated air coming out of the hood air outlet54is effectively prevented.

In this embodiment, the partition56is formed as a peripheral frame extending all along the inner side of the peripheral wall50bof the soundproofing hood50, at a height below the hood air inlet52and above the hood air outlet54, and extending to the outer wall of the casing40, so as to completely and effectively separate a space in which the hood air inlet52and the casing air inlet46are located from a space in which the hood air outlet54and the casing air outlet48are located.

Such partition56can be made of any suitable material, e.g. paperboard.

As can be seen fromFIG. 2, the soundproofing hood50is preferably arranged with respect to the underlying casing40in such a way that the hood air inlet52is as far as possible from the casing air inlet46. In other words, the side wall50b′ of the hood peripheral wall50bin which the hood air inlet52is provided is on the opposite side with respect to the side wall40b′ of the casing peripheral wall40bin which the casing air inlet46is provided.

Such arrangement provides two different advantages: on one hand, the hood air inlet52is far from the casing air inlet46so that the noise transmission through the casing air inlet46and the hood air inlet52is strongly reduced; on the other hand, the path of the fresh air inside the soundproofing hood50and around the casing40enclosing the vacuum pump10is maximized, so that the cooling effect on the vacuum pump10is correspondingly maximized.

In the Figures it can be seen that the peripheral wall50bof the soundproofing hood50is further provided with an additional opening58for the passage of electrical cables and connections (not shown) of the vacuum pumping system100. Such opening58is preferably arranged near the hood air inlet52, i.e. as far as possible from the casing air inlet46, in order to minimize noise transmission therethrough.

In the illustrated embodiment, the casing air outlet48is provided in the bottom wall40cof the casing40, so that the flow of heated air coming out of the casing40is directed toward the underlying floor.

In order to dampen the noise possibly generated by said heated air outflow, the vacuum pumping system100according to the invention may further comprise a soundproofing tray60to be arranged at the casing air outlet48, between such casing air outlet48and the floor.

The presence of such soundproofing tray60further enhances the noise dampening effect.

Analogously to the soundproofing hood50, also the soundproofing tray60preferably has a multi-layered structure comprising two or more layers made of soundproofing material, most preferably including a first, upper layer made of sound-absorbing material, and a second, lower layer made of sound insulating material.

According to a preferred embodiment of the invention, the soundproofing tray60preferably has an “L” shape, with a first arm60asubstantially parallel to the bottom wall40cof the casing40and a second arm60bsubstantially perpendicular to said casing bottom wall40cand interposed between the casing air outlet48and the hood air outlet54.

Due to such specific shape, namely due to the presence of the second arm60bof the soundproofing tray60, the soundproofing tray60allows to obtain a further advantage: the heated air discharged from the casing air outlet46cannot directly flow to the hood air outlet54, but it is forced to further flow around the casing40before leaving the soundproofing hood50, thus further increasing the length of the flow path inside said soundproofing hood50and further increasing the cooling of the vacuum pump10.

The overall path of the cooling air inside the vacuum pumping system100of the invention is indicated by thick arrows in the attached Figures. The fresh air sucked by the fan30enters the soundproofing hood50through the hood air inlet52(A) and it is forced to flow along the facing side wall40b″ of the peripheral wall40bof the casing40and along the whole area of the top wall40aof said casing40before reaching the casing air inlet46(B). After passing through said casing air inlet46, the air is forced to flow around the pump housing12before reaching the opposite side of said pump housing12(C) and penetrating into it. Then the air passes through the vacuum pump10and is discharged through the casing air outlet48. At this stage, the air is further forced to flow along the bottom wall40cof the casing40(D) before leaving the soundproofing hood50through the hood air outlet54(E). All along such path the heat exchange between the vacuum pump10and the cooling air takes place, so that by maximizing the length of the air flow path, the cooling efficiency is also maximized.

It is to be noted that the heated air coming out of the casing air outlet48is warmer than the fresh air entering through the hood air inlet52, so that it would have the tendency to move upwards and mix with the colder fresh air. However, in the illustrated embodiment this is effectively avoided by the provision of the partition56.

It is evident from the above description that the vacuum pumping system100according to the invention allows to achieve the objects set forth above.

Experimental tests carried out by the Applicant proved that, thanks to the presence of the soundproofing hood50, the noise in the environment surrounding the vacuum pumping system100of the invention is effectively reduced to below the required threshold of 50-55 dB.

It is also evident that the above exemplary embodiment has been given for a better understanding of the invention and not for limiting the scope of protection of the invention itself and that, starting from the above disclosure, many variants that fall within the scope of protection of the invention will be evident to those skilled in the art.

More particularly, although reference has been made to a rotary vane vacuum pump in such exemplary embodiment, it will be evident to the person skilled in the art that the invention could also be applied to any other vacuum pumping system comprising a vacuum pump and/or vacuum pump accessories which generate(s) an undesired noise.