VOLUMETRIC LOBE COMPRESSOR FOR AN EQUIPMENT AND/OR A SUCTION COMPRESSION PLANT OF MATERIAL IN LIQUID, GASEOUS, SOLID, POWDER, OR SLURRY FORM

Abstract

The present invention concerns a volumetric compressor (1) that can be used. preferably. for producing equipment and/or a plant for the suction of material in liquid. solid. powder or slurry form. The compressor according to the invention comprises a body (2) defining an operative chamber (5). a suction section (51) and a discharge section (52) of an operating fluid. The compressor further comprises at least two lobe rotors (8A. 8B), the lobes (81A. 81B) of which are housed inside said operative chamber (5), cach rotor (8A. 8B) rotating around a corresponding longitudinal rotation axis (101A. 101B). The compressor comprises a first header (6) and a second header (6) which delimit on opposite sides the operative chamber (5): cach header comprises a bank (61, 61) connected to the body (2) and configured to support the rotors (8A, 8B) and a cover (62, 62) connected to the bank (61, 61) so as to define an inner volume (65, 65) comprised between the cover (62, 62) and the bank (61, 61) and designed to house, in use, a lubricating bath. According to the invention the compressor comprises a generator unit for generating a forced flow of cooling gas and, for at least one of the headers (6, 6), the bank (61, 61) defines a cooling chamber (70, 70) physically separated from the operative chamber (5) and from the inner volume of lubricant. Said chamber (70, 70) comprises an inlet (71, 71) and an outlet (72, 72) for a cooling gas, where said inlet communicates with the generator unit of the forced flow of said cooling gas.

Claims

1-13. (cancelled)

14. A volumetric compressor comprising: a body defining an operative chamber, a suction section, and a discharge section of an operating fluid; at least two lobe rotors, wherein lobes of each lobe rotor are housed inside the operative chamber, each rotor configured to rotate around a corresponding longitudinal rotation axis; a first header and a second header that delimit on opposite sides the operative chamber, wherein each of the first and second headers comprises: a bank connected to the body and configured to support the at least two rotors; a cover connected to the bank to define an inner volume comprised between the cover and the bank, and configured to house, in use, a lubricating bath; and a generator unit configured to generate a forced flow of cooling gas; wherein, for at least one of the first and second headers, the respective bank defines a cooling chamber physically separated from the operative chamber and from the inner volume, wherein the cooling chamber comprises an inlet communicating with the generator unit and an outlet for the cooling gas.

15. The volumetric compressor of claim 14, wherein the inlet and the outlet of the cooling chamber are arranged on opposite sides with respect to a reference plane containing the respective rotation axes of the rotors.

16. The volumetric compressor of claim 15, wherein the outlet of the cooling chamber is defined in a position near the suction section of the body, and the inlet is defined in a position near the discharge section of the body.

17. The volumetric compressor of claim 14, wherein the generator unit comprises at least one operating machine driven independently of the rotors of the compressor.

18. The volumetric compressor of claim 14, wherein the bank comprises a first portion and by a second portion connected to each other to define the cooling chamber, wherein the first portion is connected to the body and the second portion is connected to the cover.

19. The volumetric compressor of claim 18, wherein the second portion is made of a material having a thermal conductivity higher than that of a material of the first portion.

20. The volumetric compressor of claim 14, wherein the bank comprises a first portion and by a second portion connected to each other to define the cooling chamber, and wherein on an inner side of one of the first and second portions, ribs are defined that develop towards an inside of the cooling chamber to increase a thermal exchange surface with the cooling gas.

21. The volumetric compressor of claim 14, wherein: for each of the first and second headers the corresponding bank defines a cooling chamber physically separated from the operating chamber and from the corresponding inner volume; each cooling chamber comprises an inlet and an outlet for a cooling gas; and for each cooling chamber, the inlet communicates with the generator unit.

22. The volumetric compressor of claim 21, wherein the generator unit comprises a first operating machine and a second operating machine, each of which is connected, directly or indirectly, to a corresponding bank wherein an air flow delivery of each operating machine communicates with the inlet of a corresponding cooling chamber.

23. The volumetric compressor of claim 22, wherein the first and second operating machines are arranged on the same side with respect to a reference plane containing the rotation axes of the rotors.

24. The volumetric compressor of claim 22, wherein each of the first and second operating machines is connected to a corresponding bank by a connection sleeve which establishes communication between the delivery of the respective operating machine and the corresponding cooling chamber.

25. The volumetric compressor of claim 21, wherein the generator unit comprises an operating machine and a delivery duct communicating with an air flow delivery of the operating machine and defining two outlet sections, each communicating, directly or indirectly, with an inlet of a corresponding cooling chamber.

26. A system comprising fixed or movable equipment for suction/compression of material in liquid, gaseous, solid, powder, or slurry form, the equipment comprising the volumetric compressor of claim 14.

27. The system of claim 26, wherein the inlet and the outlet of the cooling chamber are arranged on opposite sides with respect to a reference plane containing the respective rotation axes of the rotors.

28. The system of claim 27, wherein the outlet of the cooling chamber is defined in a position near the suction section of the body, and the inlet is defined in a position near the discharge section of the body.

29. The system of claim 26, wherein the generator unit comprises at least one operating machine driven independently of the rotors of the compressor.

30. The system of claim 26, wherein the bank comprises a first portion and by a second portion connected to each other to define the cooling chamber, wherein the first portion is connected to the body and the second portion is connected to the cover, and wherein the second portion is made of a material having a thermal conductivity higher than that of a material of the first portion.

31. The system of claim 26, wherein the bank comprises a first portion and by a second portion connected to each other to define the cooling chamber, and wherein on an inner side of one of the first and second portions, ribs are defined that develop towards an inside of the cooling chamber to increase a thermal exchange surface with the cooling gas.

32. The system of claim 26, wherein: for each of the first and second headers the corresponding bank defines a cooling chamber physically separated from the operating chamber and from the corresponding inner volume; each cooling chamber comprises an inlet and an outlet for a cooling gas; and for each cooling chamber, the inlet communicates with the generator unit.

33. The system of claim 32, wherein the generator unit comprises a first operating machine and a second operating machine, each of which is connected, directly or indirectly, to a corresponding bank wherein an air flow delivery of each operating machine communicates with the inlet of a corresponding cooling chamber.

Description

LIST OF FIGURES

[0035] Further characteristics and advantages of the invention will become evident from examination of the following detailed disclosure of some preferred but non-exclusive embodiments of the volumetric compressor, illustrated by way of non-limiting example, with the support of the attached drawings, in which:

[0036] FIGS. 1 and 2 are perspective views of a possible embodiment of a volumetric compressor according to the present invention;

[0037] FIG. 3 is an exploded view of the compressor of FIGS. 1 and 2;

[0038] FIG. 4 is a frontal view of the compressor of FIGS. 1 and 2;

[0039] FIG. 5 is a section view according to the line V-V of FIG. 4;

[0040] FIG. 6 is a lateral view of the compressor of FIGS. 1 and 2;

[0041] FIG. 7 is a section view according to the line VII-VII of FIG. 6;

[0042] FIGS. 8 and 9 are exploded views from different observation points of a header of the compressor of FIGS. 1 and 2;

[0043] FIG. 10 is a perspective view of a second possible embodiment of a volumetric compressor according to the present invention;

[0044] FIGS. 11 to 13 are graphs relative to operation of the compressor of FIGS. 1 and 2.

[0045] The same numbers and the same reference letters in the figures identify the same elements or components.

DETAILED DISCLOSURE

[0046] With reference to the cited figures, the present invention concerns a volumetric compressor generically indicated by the reference 1. The compressor 1 comprises a body 2 defining an operative chamber 5 (or work chamber 5). The latter develops in a longitudinal direction 100. The body 2 also defines a suction section 51 and a discharge section 52 of the operative chamber 5. The two sections 51, 52 are configured respectively for suction and discharge of an operating fluid, for example air or other gas. The compressor 1 comprises at least two lobe rotors 8A, 8B, in which said lobes 81A, 81B are housed inside the work chamber 5. Each rotor 8A, 8B rotates around a corresponding rotation axis 101A, 101B which is substantially parallel to the longitudinal direction 100 of development of the work chamber 5.

[0047] The form of the rotors 8A, 8B is not important for the purposes of the present invention. The rotors 8A, 8B could have straight lobes or alternatively the lobes could develop according to a substantially helical profile, as in the embodiment shown in the figures. Also the number of lobes of the rotors is not important. In fact, the rotors 8A, 8B could have two lobes or three lobes 81A, 81B (as in the solution shown in the figures) or also a greater number of lobes. In any case, the rotors 8A, 8B comprise two end parts 83A-84A, 83B-84B defining the corresponding rotation axis 101A, 101B and a central part between said end parts and defining the lobes 81A, 81B. The parts of the rotors 8A, 8B indicated above are evaluated in the longitudinal direction 100.

[0048] The compressor 1 comprises a first header 6 and a second header 6 connected to the body 2 on opposite sides so as to delimit longitudinally the operative chamber 5. The two headers 6, 6 support the two rotors 8A, 8B in the area of their end parts 83A-84A, 83B-84B.

[0049] More precisely, each header comprises a first part 61, 61 directly connected to the body 2 and indicated below by the term bank. Each header 6, 6 also comprises a second part 62, 62 connected to the corresponding bank 61, 61 and indicated below by the term cover. For each header 6, 6, the corresponding bank 61, 61 is comprised between the body 2 and the corresponding cover 62, 62 and supports the two rotors 8A, 8B in the area of their end parts 83A-84A, 83B-84B. Furthermore, for each header 6, 6, the corresponding cover 62, 62 is configured so as to define, once it has been connected to the corresponding bank 61, 61, an inner volume 65, 65 which can contain, in use, a lubricating oil bath. In practice, said inner volume 65, 65 is defined, and therefore comprised, between the corresponding cover 62, 62 and the corresponding bank 61. 61.

[0050] According to the present invention, for at least one of the two headers 6, 6, preferably for both, the corresponding bank 61, 61 defines a cooling chamber 70, 70 physically separate from the work chamber 5 and from the inner volume 65, 65 defined above. Said cooling chamber 70, 70 comprises an inlet 71, 71 and an outlet 72, 72, communicating with the inlet 71, 71, respectively to allow a cooling gas (preferably, but not exclusively, air) to enter, flow through and out of the cooling chamber 70, 70. According to the invention, the inlet 71, 71 is connected to a forced flow generator unit 21, 22 of the compressor 1, which is configured to generate a forced flow of cooling gas to the inlet 71, 71 of the cooling chamber 70, 70. In other words, the forced flow generator unit 21, 22 has the function of forcing the cooling gas into the cooling chamber 70, 70.

[0051] In particular, according to the invention, the inlet 71, 71 and the outlet 72, 72 are both configured by the bank 61, 61 so that the cooling gas flow passes through the cooling chamber 70, 70 without entering the work chamber 5. As it passes through the cooling chamber 70, 70, the cooling gas laps the walls of the corresponding bank 61, 61, removing heat by convection. As better specified below, it has been seen that this solution limits heating of the oil contained in the inner volume 65, 65 with the advantage of prolonging the life of the oil. In addition to this, the invention leads to a reduction in the heating of the body 2 of the compressor 1, in particular at the discharge section 52. In any case, the cooling chamber 70, 70 defines an empty space between the body 2 and the warmer portion of the header 6, 6 containing the lubricating oil. Said empty space, crossed by the cooling gas, forms a type of barrier that limits transmission of the heat from the lubricating oil to the body 2 and vice versa.

[0052] In accordance with a preferred embodiment, the inlet 71, 71 and the outlet 72, 72 of the cooling chamber 70, 70 are defined on opposite sides of the bank 61, 61 with respect to the reference plane 200 defined above. Preferably, the inlet 71, 71 is defined in a position near to the discharge section 52 of the body 2, while the outlet 72, 72 is defined in a position near the suction section 51 of the body 2. It has been seen that this solution allows a more uniform distribution of the temperatures inside the body 2 and therefore lower thermal distortion. In fact, the gas flowing out of the cooling chamber 70, 70 increases the temperature of the area of the body 2 adjacent to the suction section 51, where the operating fluid has a lower temperature than the discharge section 52. At the same time, the cold cooling gas flowing into the cooling chamber 70, 70 reduces, or in any case does not increase, the temperature of the body 2 at the discharge section 52.

[0053] In the context of the present invention, the generator unit generating the forced flow of cooling gas comprises at least one operating machine (for example a blower or a fan) provided with an impeller driven by a motor, for example an electric motor, with the purpose of generating in delivery an air flow to the inlet of the cooling chambers 70, 70. According to a possible preferred embodiment, said operating machine is driven independently of the rotors 8A, 8B of the compressor 1. In this operating condition, the number of revolutions of the operating machine, i.e. the rotation speed of the corresponding impellers, can be adjusted (i.e. increased or decreased) independently of the rotation speed, i.e. of the number of revolutions of the rotors 8A, 8B.

[0054] FIGS. 1 and 2 are perspective views, from different observation points, of a compressor 1 in accordance with a first possible embodiment. FIG. 5 is a section view of the same compressor 1 according to a reference plane 200 containing the axes 101A, 101B of the rotors 8A, 8B. In the compressor 1 a first header 6 can be identified comprising a first bank 61 and a first cover 62 and a second header 6 comprising a second bank 61 and a second cover 62. As indicated above, the two headers 6, 6 are connected to opposite sides of the body 2 via the corresponding banks 61, 61.

[0055] In the first header 6 a first inner volume 65 can be identified configured between the first bank 61 and the first cover 62. In the second header 6 a second inner volume 65 can be identified between the second bank 61 and the second cover 62. Both the inner volumes 65, 65 contain an oil bath for lubricating the supports/bearings 701-701, 702-702 mounted on the corresponding bank 61, 61 and allowing rotation of the rotors 8A, 8B.

[0056] According to a possible embodiment, one of the two inner volumes 65, 65 defined above houses a motion transmission unit 130, configured to mechanically connect the two rotors 8A, 8B. In accordance with a solution known per se, the transmission unit 130 is configured to rotate the rotors 8A, 8B in a synchronous manner but in opposite direction. In the case illustrated in the figures (see in particular FIG. 5), the transmission unit 130 comprises a pair of gear wheels 131A, 131B arranged in the inner volume 65 of the first header 6 and each of which is fitted on an end part 83A, 83B of a corresponding rotor 8A, 8B. The two gear wheels 131A, 131B have the same diameter to guarantee that the two rotors 8A, 8B rotate with the same angular velocity.

[0057] According to another aspect, at least one of the two covers 62, 62 comprises an opening 620 (indicated in FIG. 8) from which a free end 181 of one of the two rotors protrudes, preferably the one nearest a support plane PO to which the compressor 1 is fixed. With reference to FIG. 5, in the case illustrated, the free end 181 of the first rotor 8A protrudes from the first cover 62 of the first header 6, i.e. from the one that defines the inner volume 65 in which the transmission unit 130 is housed. However, in an alternative embodiment, the free end of one of the rotors could protrude from the opposite cover from the one defining the housing for the transmission unit. At the same time, said end could be that of the rotor farthest from the support plane PO of the compressor.

[0058] According to a possible embodiment, the inner volume of the header opposite the header containing the transmission unit 130 houses an oil spreader disc 135 fitted at the end of one of the two rotors, preferably the lower rotor 8A nearest the support plane PO. The function of the oil spreader disc is known per se to a person skilled in the art. With reference to FIG. 5, in the case illustrated the oil spreader disc 135 is fitted at the end of the first rotor 8A and is housed in the inner volume 65 of the second header 6.

[0059] According to a preferred embodiment, shown in the figures, for each of the two headers 6, 6, the corresponding bank 61, 61 defines a corresponding cooling chamber 70, 70. In particular, a first cooling chamber 70, defined by the first bank 61 of the first header 6, can be identified and a second cooling chamber 70, defined by the second bank 61 of the second header 6, can be identified. Each cooling chamber 70, 70 comprises a corresponding inlet 71, 71 and a corresponding outlet 72, 72 communicating with each other. According to the invention, each inlet 71, 71 communicates with the flow generator unit so that the inlets 71, 71 of both the cooling chambers 70, 70 are supplied with a flow of cooling gas.

[0060] With reference to FIG. 1, the inlets 71, 71 of the two cooling chambers 70, 70 are preferably defined on the same side with respect to the reference plane 200 defined above. In particular, they are preferably positioned near the discharge section 52 of the body 2. Analogously, the outlets 72, 72 of the two cooling chambers 70, 70 are defined on the opposite side, again with respect to the reference plane 200 (indicated in FIG. 2). The outlets 72, 72 are defined in a position near the suction section 51 of the body 2. Due to this arrangement, the cooling gas flows F1-F2 flowing out of the cooling chambers 70, 70 are substantially in counter-current with respect to the flow F of the operating fluid that passes through the work chamber 5. As mentioned above, this configuration leads to improved temperature distribution inside the body 2 and therefore a reduction in thermal distortions. In accordance with a preferred embodiment, shown in the figures, the flow generator unit comprises a first operating machine 21 and a second operating machine 22 (indicated below also by the terms first blower 21 and second blower 22) communicating respectively with the inlet 71 of the first cooling chamber 70 and with the inlet 71 of the second cooling chamber 70. Preferably, the two blowers 21, 22 are arranged on the same side with respect to the reference plane 200 containing the rotation axes 101, 101 of the two rotors 8, 8 (see for example FIG. 1).

[0061] In an alternative embodiment, not shown in the figures, with respect to the reference plane 200 the inlet 71 and the outlet 72 of the first cooling chamber 70 could be on opposite sides with respect to the inlet 71 and the outlet 72 of the second cooling chamber 70. In this case, also the two blowers 21, 22 could be installed on opposite sides with respect to said reference plane 200.

[0062] Preferably the two blowers 21, 22 are driven independently of the rotors 8A, 8B of the compressor 1, i.e. so that the rotation speed of the corresponding impellers can be set regardless of the number of revolutions of the rotors 8A, 8B. Via this solution it is therefore possible to increase the number of revolutions of the blowers 21, 22, i.e. the flow rate of the flows through the cooling chambers 70, 70, when the rotation speed of the rotors 8A, 8B is low, i.e. when the compressor 1 is subject to greatest heating. Alternatively, it is possible to reduce the flow rate of the flows through the cooling chambers 70, 70 when the rotation speed of the rotors 8A, 8B is high.

[0063] According to an embodiment, the two blowers 21, 22 each comprise a corresponding volute 24, 24 that guides the flow generated through the corresponding impeller 25, 25 and defines the delivery of the same blower. As shown in the figures, for each blower 21, 22, a coupling sleeve 41, 41 is provided to connect the delivery (meaning the volute) 24, 24 of a blower 21, 22 to the inlet 71, 71 of the corresponding cooling chamber 70, 70. For each header 6, 6 of the compressor 1, the coupling sleeve 41, 41 is internally hollow and is fixed, at a first side thereof, on the bank 61, 61 at of the inlet 71, 71 of the cooling chamber 70, 70. For each blower 21, 22, the volute 24, 24 is fixed on a second side of the coupling sleeve 41, 41, opposite the first, so that the flow generated by the blower 21, 22 in delivery is conveyed into the cooling chamber 70, 70 through the sleeve itself. Advantageously, the use of a coupling sleeve 41, 41 allows the use of readily available blowers as it represents a low cost connection interface that is easy to produce.

[0064] However, the present invention also comprises the possibility of connecting the volute 24, 24 of the blower 21, 22 directly to the corresponding bank 61, 61 without using a coupling sleeve.

[0065] According to a possible embodiment shown in FIG. 10, the flow generator unit can comprise a single operating machine 21A, i.e. one single blower/fan or equivalent, to generate both the flows for the cooling chambers 70, 70. In this embodiment, the flow generator unit comprises a supply conduit 150 communicating with the operating machine 21A and defining two discharge sections: a first section communicating with the inlet 71 of the first cooling chamber 70 and a second section communicating with the inlet 71 of the second cooling chamber 70.

[0066] As can be seen in FIG. 10, also in this embodiment, two sleeves 41, 41 are provided for connecting each discharge section of the supply conduit 150 to the bank 61, 61 of the corresponding header 6, 6. Again with reference to FIG. 10, the supply conduit 150 has a partially arc-shaped conformation that enables said conduit to be positioned adjacent to the body 2 of the compressor 1, advantageously below the discharge section 52. In this way, the compressor 1 maintains a relatively compact conformation.

[0067] According to a preferred embodiment shown in the figures, for at least one of the two headers 6, 6, the corresponding bank 61, 61 comprises a first portion 61A, 61A and a second portion 61B, 61B connected to each other, preferably through screw connection means 501-502 (see FIGS. 8 and 9). The first portion 61A, 61A is connected to the body 2 and longitudinally delimits the work chamber 5. The second portion 61A, 61B is connected to the corresponding cover 62, 62 and with it defines the corresponding inner volume 65, 65 of the header 6, 6.

[0068] In the embodiment shown in the figures, the configuration with two portions of the bank 61, 61 is adopted for both the headers 6, 6. In particular, for each bank 61, 61, the corresponding two portions 61A-61B, 61A-61B are configured so as to define, once they have been joined, the cooling chamber 70, 70 in accordance with the purposes of the present invention.

[0069] More precisely, the cooling chamber 70, 70 is delimited by an inner side 63, 63 of the first portion 61A, 61A and by an inner side 64, 64 of the second portion 61B, 61B. An outer side 67, 67 of the first portion 61A, 61A longitudinally delimits the work chamber 5, while an outer side 68, 68 of the second portion 61B, 61B remains in contact with the oil bath delimiting the corresponding inner volume 65, 65 of the header 6, 6. In short, the term inner is used to indicate the sides of the portions 61A, 61B-61A, 61B of the bank 61, 61 that delimit the relative cooling chamber 70, 70, while the term onder is indicated for the sides opposite the inner ones.

[0070] According to a possible embodiment, the two portions 61A, 61B-61A, 61B are made of metallic materials having different thermal conductivity. Preferably, the second portion 61B, 61B is made of a first material, for example cast iron, having a thermal conductivity greater than a second material, for example steel, with which the first portion 61A, 61A is made. This solution is designed to favour dissipation of the heat from the oil bath which is in contact with the outer side of the second portion 61B, 61B. In fact, although on the one hand the gas flow through the cooling chamber 70, 70 subtracts heat also from the body 2, on the other hand this solution favours the heat exchange by convection with the second portion 61B, 61B of the bank 61, 61 with greater thermal conductivity.

[0071] In an alternative embodiment, falling within the present invention, the two portions 61A, 61B-61A, 61B of the bank 61, 61 could be made of the same material, i.e. have the same thermal conductivity. In another possible embodiment, the material forming the first portion 61A, 61A could have a thermal conductivity higher than the one used for the second portion 61B, 61B.

[0072] FIGS. 8 and 9 are exploded views of the first header 6 from different observation points and show in detail a possible embodiment of the first bank 61 and in particular of the two component portions 61A, 61B. In the case illustrated, the outer side 67 of the first portion 61A is defined by a flat surface orthogonal to the rotation axes 101A, 101B of the rotors 8A, 8B to delimit in a corresponding manner the work chamber 5. The inner side 63 of the first portion 61A is mainly flat-shaped comprising two support portions 615 that develop towards the second portion 61B to support the end parts 83A, 83B of the rotors 8A, 8B. The support portions 615 are crossed by a cavity 615A housing at least one first support 701 (indicated in FIG. 5) that allows the rotation of a corresponding rotor 8A, 8B.

[0073] In the case illustrated, the second portion 61B is defined by a body that comprises a core part 610B (indicated in FIG. 5) defining the inner side 64 and the outer side 68 of the second portion 61B. The latter also comprises a perimeter part 612B (indicated in FIGS. 8 and 9) that surrounds the core part 610B. Preferably, the two parts 610B and 612B are made in one single body. The perimeter part 612B delimits a first housing space SI (see FIG. 9) that develops from the inner side 64 towards the first portion 61A of the bank 61, and a second housing space S2 (see FIG. 8) that develops from the outer side 68 towards the cover 62. Following the connection with the first portion 61, the first space SI defines part of the first cooling chamber 70, while the second space S2 defines part of the inner volume 65 for the lubricating bath. On the outer side 68 of the second portion 61B, support portions 625 are defined, wherein they are crossed by a through cavity 612C in which a second support 702 (indicated in FIG. 5) is positioned for the rotation of a corresponding rotor 8A, 8B. Following their connection, the two portions 61A, 61B define the form of the bank 61 in which two sides 91A-91B, substantially opposite with respect to the reference plane 200 defined above, a lower part 91C and an upper part 91D can be identified (see FIG. 4). As can be seen for example from FIGS. 1 and 2, following connection of the two portions 61A, 61B, the inlet 71 and the outlet 72 of the first cooling chamber 70 are defined in the area of the sides 91A, 91B of the first bank 61.

[0074] As shown in the figures, according to a possible embodiment, in the lower part 91C of the bank 61, fixing feet 711 can be installed for fixing the compressor 1 (see FIG. 7). For example, two fixing feet 711 can be provided on opposite sides with respect to the reference plane 200.

[0075] In an embodiment, also shown in the figures, in the upper part 91D an eyebolt 715 can be provided to lift the compressor 1 (see FIG. 4).

[0076] The technical solutions described above with reference to the first bank 61 of the first header 6 are preferably adopted also for the second bank 61 of the second header 6, as can be seen also from the section view of FIG. 5. Therefore, the above description should be referred to for the structure of the second bank 61.

[0077] According to a possible embodiment, the inner side of one of the two portions 61A, 61B-61A, 61B of the bank 61, 61 defines ribs 77 which develop towards the inside of the corresponding cooling chamber 70, 70 in order to increase the thermal exchange surface with the cooling gas.

[0078] In the embodiment shown in the figures, said ribs 77 are defined on the inner side 64, 64 of the second portion 61B, 61B of the bank 61, 61. Also this arrangement is designed to favour dissipation of the heat from the lubricating bath contained in the inner volume 65, 65. However, in alternative embodiments, the ribs could be provided on the inner side 63, 63 of the first portion 61A, 61A or on the inner side 63, 64 of both the portions 61A, 61B-61A, 61B of the bank 61, 61.

[0079] The section view of FIG. 7 shows a possible arrangement of the ribs 77 referring to the first cooling chamber 70 defined in the bank 61 of the first header 6. In detail, said ribs 77 are arranged around the rotors 8A, 8B if evaluated on an observation plane orthogonal to the axis thereof and passing through the cooling chamber 70.

[0080] In particular, the ribs 77 develop according to an arrangement reflecting that of the flow lines followed by the cooling gas as it crosses the cooling chamber 70 from the inlet 71 to the outlet 72 thereof. In particular, said ribs 77 are preferably symmetrical with respect to the first reference plane 200 defined above, and likewise with respect to a second reference plane 250 orthogonal to the first reference plane.

[0081] The arrangement shown in FIG. 7 and described above should be considered a possible, and therefore non-exclusive, arrangement and/or form of the ribs. The present invention therefore includes the possibility of configuring said ribs differently, and the possibility of defining the same on the inner side of the first portion defining the bank and/or on the inner side of both the portions defining the bank.

[0082] According to a possible embodiment, not shown in the figures, the bank 61, 61 of one or both the headers 6, 6 could be made in one single piece. In this case, the cooling chambers 70, 70 of the two banks 61, 61 could be defined directly through a fusion process.

[0083] The technical solutions described above fully achieve the predefined tasks and objects. In particular, the main effect of the passage of forced air through the cooling chambers 70, 70 is to limit the thermal level of the lubricating bath contained in the inner volume 65, 65 of the header 6, 6 consequently prolonging the life of the lubricating oil.

[0084] In this regard, with reference to the compressor 1 shown in the figures, the graph of FIG. 11 shows the trend of the temperature T of the lubricating oil in the inner volume 65 of the first header 6 as a function of the rotation speed. In particular, the continuous line curve shows the trend of the temperature T in the absence of flow (fan/blower deactivated) through the cooling chamber 70, while the broken line curve shows the trend of the temperature T in the presence of a cooling flow (fan/blower activated) through the same chamber. Said temperature is measured by a temperature sensor (thermocouple) inserted in the inner volume 65 in contact with the lubricating oil.

[0085] From comparison of the two curves in FIG. 11 it can be seen that the forced flow of cooling gas into the cooling chamber 70 leads to a reduction in the temperature of the lubricating oil by over 20% substantially independently of the number of rotations.

[0086] The graph of FIG. 12 refers to heating of the lubricating oil contained in the inner volume 65 of the second header 6. Also in this case, the two curves shown indicate the temperature trend with variation in the number of rotations, respectively in the absence (continuous line) and in the presence (broken line) of active cooling, i.e. flow of cooling gas, into the cooling chamber 70 defined in the second bank 61 of the second header 6.

[0087] Also from the graph of FIG. 12 a significant reduction in heating of the lubricating oil in the presence of a gas flow through the cooling chamber 70 can be seen. Also in this case, the temperatures drop by over 20% with respect to operation in the absence of forced cooling (i.e. with the flow generator unit deactivated).

[0088] The graph of FIG. 13 refers to heating of the body 2 of the compressor 1 at of the discharge section 52. In particular, the two curves show the temperature trend (again as a function of the rotation speed of the rotors 8A, 8B) in the area of the discharge section 52, respectively in the absence (continuous line) and in the presence (broken line) of a forced flow through the cooling chambers 70, 70. The graph of FIG. 13 shows lesser heating when the flow generator unit is activated. This is proof that the forced flow of cooling gas through the banks 61, 61 is advantageous also with reference to the lesser heating of the body 2. Advantageously, the lesser heating of the body 2 allows greater efficiency of the compressor 1 and results in increased performance of the compressor. In particular, with respect to the known solutions, in the presence of more limited heating of the compressor 1, in the in pressure operating mode it is possible to obtain greater pressures at the discharge section, whereas in the vacuum operating mode it is possible to advantageously increase the degree of vacuum.