Screw machine

Abstract

A screw machine comprises a male rotor (3) and a female rotor (2) enclosed in a housing (4) or body, the male and female rotors rotating in opposite directions within the housing or body. Said body (4) comprising oppositely shaped openings (41) and (42) into which the rotors are inserted and closed on one delivery side by a delivery assembly (5) and on the other suction side by a suction assembly (6), the delivery side and the suction side corresponding to the aforementioned openings, from which gas (or air) passes through a suction duct formed between the two rotors; rotation closes the suction conduit and the compressed gas is urged toward the delivery side. Between the delivery assembly and the housing and between the suction assembly and the housing there are respective flanged suction engagement connections (7) or delivery engagement connections (8), which are suitably shaped to receive the rotor shaft and couple with the housing opening and the suction assembly or delivery assembly. In association with the flanged connectors, in the forming region, the machine includes a filled polymer insert covering the rotor-facing surface of the metal body.

Description

[0001] This invention relates to screw machines, such as compressors or expanders.

[0002] A screw compressor is a positive displacement rotary compressor comprising two parallel rotors, each externally fitted with multiple helical profiles (screws) for interlocking. The two rotors are housed within a stator composed of two longitudinally intersecting cylindrical sections, within which the rotors rotate with a clearance that cannot be reduced beyond a certain limit.

[0003] The rotor shaft is supported by bearings, and typically, one rotor guides the other through an interlocking mechanism of the same helical profile (oil-filled compressor). Sometimes both rotors can be controlled by a pair of external gears to avoid contact and friction that would otherwise occur (dry compressor). During rotation, the screw profile exposes an intake port located at one end of the stator through which air or gas enters to fill the volume between the profiles themselves until their maximum extension.

[0004] On opposite sides, the contours penetrating each other reduce volume and compress the gas enclosed within until the delivery port is exposed. The operation of a screw compressor is based on the counter-rotating action of two helical rotors that compress the gas or air drawn from the suction pipe and transport it toward the delivery pipe. During this path, the space decreases, and therefore the pressure increases.

[0005] Screw compressors have gained widespread use due to the diffusion of the technology used in their construction. Many manufacturers and assemblers offer a variety of models: single-stage and two-stage for high pressure, and oiled or oilless for "oil-free" applications. The rotational speed of the motor can differ from that of the conductor rotor, as they are not only directly connected but also, in the presence of a belt, connected via multiplier / reduction gears or pulley ratios.

[0006] These types of industrial compressors continuously supply compressed gas or air, are highly controllable, extremely efficient, and quiet (in terms of work safety, environmental protection, and noise emissions).

[0007] Similar to a compressor, a screw expander comprises two counter-rotating rotors (a male screw and a female screw) connected to corresponding shafts that transmit motion to a generator. Fluid expands axially by rotating the rotors and traveling in a volume created between the screw protrusions. Gas fills the volume between the screws, is isolated, and is then discharged in a low-pressure delivery region.

[0008] Similar to a compressor, an expander includes a stator housing, within which a rotor is housed, and the expansion of the working fluid occurs within the stator housing. The expander has inlet and outlet ports (or flanges) for connection to the equipment. This component is typically obtained from gray cast iron or ductile iron billets, but can also be made from other materials.

[0009] Seals are also used in these machines (expanders or compressors). Their primary function is to seal the working fluid outwards from the inside of the housing and to confine lubricating oil—if present—within the machine's interior or to a clearly defined area, such as between the support bearings and the compression chamber, thus preventing any type of contamination. The lubrication system supplies oil to bearings and other mechanical components that are expected to come into contact with the lubrication system to reduce internal friction and lower localized temperatures.

[0010] In such machines, the engagement area between the rotor and the stationary body is particularly critical. Indeed, a gap exists in this area, which can lead to internal leaks and subsequent efficiency losses. Therefore, to address this drawback, the gap is reduced by limiting the space. On the other hand, excessive reduction of the gap, or thermal or mechanical transients that may occur in standard machines, can often lead to abnormal contact, wear, and jamming, thereby reducing efficiency and machine lifespan over time.

[0011] The present invention addresses the aforementioned problems by inserting a sacrificial filler insert into a screw-type machine. The sacrificial filler insert is positioned at the junction between the rotor and the stationary body and has a configuration similar to a sealing element, but its primary purpose is to improve the performance and reliability of the machine itself.

[0012] One aspect of the invention relates to a screw machine, such as a screw compressor or screw expander, having the features of the appended claim 1.

[0013] Other features of the invention are included in the dependent claims.

[0014] The features and advantages of the present invention will become more apparent from the following exemplary, rather than limiting, description of embodiments of the invention with reference to the accompanying drawings, in which:

[0015] • Figure 1 A screw compressor according to one of the scenarios provided in this invention is illustrated in perspective and exploded view.

[0016] • Figure 2 The illustration shows the placement in Figure 1 A first example of a filling sacrificial insert in the suction region of a compressor;

[0017] • Figure 3 The illustration shows that it is still placed in Figure 1 A second example of a filling sacrificial insert in the suction region of a compressor;

[0018] • Figure 4 The illustration shows the placement in Figure 1 A first example of a filling sacrificial insert in the delivery area of ​​a compressor;

[0019] • Figure 5 The illustration shows the placement in Figure 1 A second example of a filling sacrificial insert in the delivery area of ​​a compressor;

[0020] • Figure 6 and Figure 7 The illustration shows the placement in Figure 1 An example of a sacrificial insert filled in the opening of the compressor body.

[0021] Referring to the accompanying drawings, the screw-type machine of the present invention (in an exemplary case, the screw-type machine is a compressor) includes two helical screws or rotors, namely a male rotor 3 and a female rotor 2, which are enclosed in a housing or body 4 and rotate in opposite directions within the housing or body 4.

[0022] The body includes relatively shaped openings 41 and 42, into which the rotor is inserted.

[0023] The compressor body is closed on one side (the conveying side) by the conveying assembly 5 and on the other side (the suction side) by the suction assembly 6. The conveying side and the suction side correspond to the aforementioned openings 41 and 42, respectively.

[0024] Gas (or air) is drawn from the intake assembly through an intake duct formed between the two rotors; rotation closes this intake duct, and compressed gas is propelled toward the delivery side. In the case of an expander, compressed gas is introduced into the machine and expands within it, causing the two rotors to rotate and follow a natural expansion process (from the smaller volume duct to the larger volume duct).

[0025] Each rotor includes rotating shafts 21 and 31 that rotate within the housing due to specific bearings, and each rotor includes central helical profile regions 22 and 32 that are designed to gradually reduce the space between the rotor and the stator.

[0026] These two rotors are typically designed with different profiles. The male rotor is usually configured with a convex protrusion, while the female rotor is usually configured with a concave cavity. It is because of these features that the male and female rotors interlock with each other.

[0027] A specific motor provides the necessary power to the compressor. The motor is typically used to rotate the male rotor, which in turn drives the female rotor. In the case of an expander, a generator can be associated with one of the two shafts 21 or 31.

[0028] Specific bearings are located at the ends of both rotors to hold them in the correct position. These components are located in a stationary body, typically on the suction side and the delivery side (assemblies 5 and 6).

[0029] The spiral contour regions 22 and 32 can be made of polymer materials.

[0030] Choosing polymer materials to fabricate the helical profile regions results in significant performance advantages. The material's inherent temperature behavior and greater deformability allow for reduced gaps during operation. In fact, unlike metals, polymer materials involve reduced surface friction and non-stick properties, enabling greater contact during the interlocking process, thus facilitating profile mating.

[0031] Furthermore, in order to minimize fatigue and / or shaft deformation problems, and considering more critical application conditions, the central body of the screw, including the external protrusions, particularly shafts 21 and 31, can be made of a more wear-resistant material in terms of mechanical resistance, and is subsequently mechanically connected to the polymer helical component.

[0032] Typically, there are corresponding flanged suction coupling connectors 7 or flanged conveying coupling connectors 8 between the conveying assembly and the housing, and between the suction assembly and the housing. The flanged suction coupling connectors 7 or flanged conveying coupling connectors 8 are provided with seals to ensure the sealing of components inside the machine.

[0033] These flanged engagement connectors are appropriately shaped in the internal region to accommodate the rotor shaft and bearings, and are connected to the housing openings and the suction or conveying assembly.

[0034] According to the invention, in association with this flanged engagement connector, in the forming region, the machine includes filled polymer inserts called polymer anti-friction plates (PAFPs) that cover the rotor-facing surface of the metal body.

[0035] Such inserts essentially cover the rotor-facing surface of the metal body, allowing them to move closer together to reduce gaps that would otherwise lead to internal leakage and thus efficiency loss.

[0036] Excessive reduction in clearance, or potential thermal or mechanical transients in standard machines, can often lead to abnormal contact, wear, and jamming, thereby reducing efficiency and machine lifespan over time. Furthermore, once worn parts are removed, they can be easily repaired during maintenance activities by simply replacing these polymer inserts at the joint between the rotor and the stationary body, without compromising the overall tolerances of the "repaired" parts.

[0037] The insert can be secured to the flanged joint connector using different anchoring systems, depending on the type of polymer selected. Specific sealants / adhesives can be used, or mechanical fastening alone may be employed.

[0038] Mechanical fastening can be achieved by screws that allow components to be secured, or by an interlocking system, which involves creating appropriate grooves in the metal component and, taking advantage of the material's deformability, inserting specific shaped areas created in the polymer insert into these grooves.

[0039] In the case of using sealant, in order to further improve the adhesive's bonding ability on one side and create a system for containing fluids inside the machine, grooves of different thicknesses and depths can be cut into the board as needed.

[0040] The flanged suction engagement connector 7 includes a generally flat peripheral profile 71, with a lowered region 72 inside the peripheral profile 71 surrounding a bore 73 that receives the rotor shaft.

[0041] The first polymer insert 91 is inserted into the lowering region 72 in the compression initiation region on the suction plane in contact with the rotor. This polymer insert can be connected to a second peripheral insert 92, which overlaps with the peripheral profile 71 of the flanged engagement connector 7.

[0042] Such a first insert and a second insert can be made into a single body.

[0043] The flanged conveying coupling 8 further includes a substantially flat peripheral profile 81, within which there is a lowered region 82 surrounding a bore 83 that receives the rotor shaft.

[0044] The third polymer insert 93 is inserted into the lowered region 82 in which the rotor operates, and substantially completely covers the region.

[0045] This third polymer insert can be connected to a fourth peripheral insert 94, which overlaps with the peripheral profile 81 of the flanged engagement connector 8.

[0046] These third and fourth inserts can be manufactured as a single body.

[0047] An additional annular polymer insert can be positioned within the bore 84 that receives the rotor. This annular insert can be accommodated in a suitable recess formed in the inner edge 85 of the bore of the flanged engagement connector. This annular insert is intended to form a radial sealing element for the body, thereby further sealing any potential internal leakage points.

[0048] The connection between a flanged delivery coupling or a flanged suction coupling and a thick polymer insert can be achieved through machining, injection molding, or 3D molding. This 3D molding can be performed using FDM technology.

[0049] The purpose of this polymer insert is to form a thin, “sacrificial” barrier between the rotor and the machine housing to limit gaps and subsequent leaks without the risk of the rotor getting stuck. In fact, despite contact with the machine’s moving parts, the polymer insert does not generate significant friction with those parts.

[0050] Furthermore, inserts can be shaped to meet specific requirements, particularly regarding suction and conveying, which define the machine's internal compression ratio. Custom machining of the port profiles on these inserts allows for direct mounting onto higher-value standard metal components, where the specific port geometry in mass production will influence supply inventory in response to particular demands. By employing these specially shaped inserts, the optimal internal compression ratio can be modified at installation time based on the specific application.

Claims

1. A screw-type machine comprising a male rotor (3) and a female rotor (2) enclosed in a housing (4) or body, the male rotor (3) and the female rotor (2) rotating in opposite directions within the housing (4) or body. The body (4) includes opposing openings (41) and (42), into which the rotor is inserted. The body (4) is closed on one conveying side by a conveying assembly (5) and on the other suction side by a suction assembly (6), the conveying side and the suction side corresponding to the aforementioned openings, respectively. Gas, or air, enters from the intake unit through an intake duct formed between the two rotors; rotation closes this intake duct and the compressed gas is propelled toward the delivery side. Between the conveying assembly and the housing, and between the suction assembly and the housing, there are corresponding flanged suction engagement connectors (7) or flanged conveying engagement connectors (8), the flanged suction engagement connectors (7) or the flanged conveying engagement connectors (8) being suitably shaped to accommodate the rotor shaft and to connect with the housing opening and the suction assembly or the conveying assembly. Its features are, Associated with these flanged engagement connectors, in the forming region, the machine includes a filler polymer insert that covers the rotor-facing surface of the metal body.

2. The screw-type machine according to claim 1, wherein, The flanged suction engagement connector (7) includes a substantially flat peripheral profile (71) with a lowered region (72) inside the peripheral profile (71) surrounding a hole (73) that accommodates the rotor shaft. A first filler polymer insert (91) is inserted into the lowered region (72) in a compression initiation region on the suction plane in contact with the rotor.

3. The screw-type machine according to claim 2, wherein, The first polymer is connected to a second peripheral filler insert (92), which overlaps with the peripheral profile (71) of the flanged engagement connector (7).

4. The screw-type machine according to claim 1, wherein, The flanged delivery engagement connector (8) includes a substantially flat peripheral profile (81) with a lowered region (82) inside the peripheral profile (81) surrounding a hole (83) that accommodates the rotor shaft. A third filler polymer insert (93) is inserted into the lowered region (82) for the rotor to operate and substantially completely covers the region.

5. The screw-type machine according to claim 4, wherein, The third polymer filler insert is connected to the fourth peripheral filler insert (94), which overlaps with the peripheral profile (81) of the flanged engagement connector (8).

6. The screw-type machine according to claim 1, wherein, An annular polymer insert is positioned within the hole (84) that accommodates the rotor.

7. The screw-type machine according to claim 6, wherein, The annular insert is accommodated in a suitable excavation portion formed in the inner edge (85) of the hole in the flanged engagement connector.

8. The screw-type machine according to claim 1, wherein, The insert is mechanically fastened to the plate.

9. The screw-type machine according to claim 1, wherein, The insert is fixed to the flanged joint connector using a specific sealant / adhesive.

10. The screw-type machine according to claim 9, wherein, When using a sealant, grooves of different thicknesses and depths are excavated on the flanged joint as needed.

11. The screw-type machine according to claim 3, wherein, The first insert and the second insert can be manufactured into a single body.

12. The screw-type machine according to claim 5, wherein, The second insert and the third insert can be manufactured as a single body.

13. A screw-type machine, characterized in that, The screw-type machine includes a compressor or an expander.

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