FLOW RESTRICTOR AND GAS COMPRESSOR

Abstract

A flow restrictor is adapted for application in a bearing arrangement between a piston and a cylinder of a gas compressor. The compressor includes a protective block that involves the cylinder externally, and also includes at least one inner cavity, which is fluidly fed by a discharge flow resulting from a compression movement exerted by the piston inside the cylinder. The compressor includes a bearing-arrangement clearance that separates the piston and an inner wall of the cylinder. The compressor includes at least one flow restrictor provided with a housing that associates fluidly the inner cavity to the bearing-arrangement clearance. The flow restrictor is associated to the housing by a process of at least partial plastic deformation inside the housing, the flow restrictor being provided with channels for passage of fluid, the plastic deformation being sized for limiting the gas flow through the inner cavity to the bearing-arrangement clearance.

Claims

1. A method of mounting a flow restrictor for an aerostatic bearing application in a gas compressor, said method comprising: providing a bushing made of a metallic material comprising at least one of aluminum, tin, copper, bronze, and brass; wherein the bushing is provided with at least one passage channel for an aerostatic bearing fluid; plastically deforming the bushing such that the plastic deformation of the bushing associates the bushing to a housing whereby the at least one passage channel of the plastically deformed bushing defines a restrictive path provided with a cross-section sized to limit flow of aerostatic bearing fluid through the at least one passage channel; wherein the step of plastically deforming the bushing is made by flattening, reducing the length and increasing a diameter of the bushing with a gradual decrease in the cross-sectional area of the at least one passage channel and constriction of the at least one passage channel.

2. The method of mounting a flow restrictor according to claim 1, wherein the deformation is either partial or total.

3. The method of mounting a flow restrictor according to claim 1, wherein the deformation is made either by: (i) a single tool; or (ii) two or more tools counterposing the movement of each other.

4. The method of mounting a flow restrictor according to claim 1, wherein the bushing is made of a porous material.

5. The method of mounting a flow restrictor according to claim 1, wherein the at least one passage channel in the bushing comprises straight or helical grooves formed in an outer surface of the bushing along a length of the bushing.

6. The method of mounting a flow restrictor according to claim 1, wherein the at least one passage channel in the bushing comprises a serration formed in an outer surface of the bushing along a length of the bushing.

7. The method of mounting a flow restrictor according to claim 1, wherein the at least one passage in the bushing comprises an inner thread throughout a length of the bushing such that said inner thread defines a passage for aerostatic bearing fluid to flow through the bushing.

8. The method of mounting a flow restrictor according to claim 1, wherein the at least one passage in the bushing comprises at least one of a slot, a cavity, or a bore throughout a length of the bushing such that said at least one slot, cavity, or bore defines a passage for aerostatic bearing fluid to flow through the bushing.

9. The method of mounting a flow restrictor according to claim 1, wherein the bushing further comprises at least one cavity of cylindrical or conical shape defined therein, wherein said cavity facilitates deformation of the bushing.

10. A method of mounting a flow restrictor in a cylinder for a gas compressor, said method comprising: providing a cylinder for a gas compressor, said cylinder adapted to receive an associated piston, said cylinder comprising a housing bore provided through a wall of the cylinder; installing a bushing in the housing bore, wherein said bushing is made of a metallic material comprising at least one metal selected from the group of: aluminum, tin, copper, bronze, brass, and wherein said busing comprises a passage channel defined therein for flow of aerostatic bearing fluid through the passage channel; said step of installing said busing in said housing bore comprising deforming said bushing and the passage channel relative to said housing bore such that said bushing is engaged with the wall of the cylinder and fixedly secured in said housing bore and such that the deformed passage channel defines a restricted flow path through said housing bore for aerostaic bearing fluid.

11. The method of mounting a flow restrictor according to claim 10, wherein the deforming of the bushing is either partial or total.

12. The method of mounting a flow restrictor according to claim 10, wherein the deforming comprising using either: (i) a single tool; or (ii) two or more tools counterposing the movement of each other.

13. The method of mounting a flow restrictor according to claim 10, wherein the bushing is made of a porous material.

14. The method of mounting a flow restrictor according to claim 10, wherein the passage channel in the bushing comprises a straight or helical groove formed in an outer surface of the bushing along a length of the bushing.

15. The method of mounting a flow restrictor according to claim 10, wherein the passage channel in the bushing comprises a serration formed in an outer surface of the bushing along a length of the bushing.

16. The method of mounting a flow restrictor according to claim 10, wherein the passage in the bushing comprises an inner thread throughout a length of the bushing.

17. The method of mounting a flow restrictor according to claim 10, wherein the passage in the bushing comprises at least one of a slot, a cavity, or a bore throughout a length of the bushing such that said at least one slot, cavity, or bore defines a passage for aerostatic bearing fluid to flow through the bushing.

18. The method of mounting a flow restrictor according to claim 10, wherein the bushing further comprises at least one cavity of cylindrical or conical shape defined therein, wherein said cavity facilitates said step of deforming the bushing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will now be described in greater detail with reference to the attached drawings, in which:

[0025] FIG. 1 represents a side-section view of a gas compressor according to the present invention, which comprises a first preferred embodiment of a flow restrictor, also object of the present invention, when the suction valve is in the open state;

[0026] FIG. 2 represents a side-section view of the gas compressor illustrated in FIG. 1, when the suction valve is in the closed state;

[0027] FIG. 3 represents a first detail of FIG. 2;

[0028] FIG. 4 represents a second detail of FIG. 2;

[0029] FIG. 5A represents a perspective view of a first preferred embodiment of the flow restrictor of the present invention;

[0030] FIG. 5B represents a perspective view of a second preferred embodiment of the flow restrictor of the present invention;

[0031] FIG. 5C represents a perspective view of a third preferred embodiment of the flow restrictor of the present invention;

[0032] FIG. 5D represents a perspective view of a fourth preferred embodiment of the flow restrictor of the present invention;

[0033] FIG. 6 represents a front-section view of a first preferred embodiment of the deformation made on the flow restrictor of the present invention;

[0034] FIG. 7 represents a front-section view of a second preferred embodiment of the deformation made on the flow restrictor of the present invention;

[0035] FIG. 8A represents a perspective view and a side-section view of a fifth preferred embodiment of the flow restrictor of the present invention; and

[0036] FIG. 8B represents a perspective view and a side-section view of a sixth preferred embodiment of the flow restrictor of the present invention.

DETAILED DESCRIPTION OF THE FIGURES

[0037] FIG. 1 illustrates a gas compressor of the linear type according to a preferred embodiment of the present invention.

[0038] Such a gas compressor comprises at least one piston 1, one cylinder 2 and one head 3 positioned at the top or bottom, forming, in conjunction with the piston 1 and the cylinder 2, a compression chamber 4, the axial and oscillating movement of the piston 1 inside the cylinder 2 providing gas compression in the compression chamber 4.

[0039] As can be seen in FIG. 1, the gas compressor is also provided with at least one suction valve 6 and a discharge valve 5, positioned at the head 3, which regulate the entry and the exit of gas from the compression chamber 4. The gas compressor is also provided with an actuator 7, associated to a linear motor, capable of actuating the piston 1. In other words, the piston 1, actuated by said linear motor, has the function of developing a linear alternating motion, which enables movement of the piston 1 inside the cylinder 2, so as to provide an action of compressing the gas admitted through the suction valve 6, until it can be discharged to the high-pressure side through the discharge valve 5.

[0040] The gas compressor is also provided with a discharge passer 10 and a suction passer 11, positioned at a cover 9, which connect the gas compressor with the other parts, pieces and components of a cooling system.

[0041] Besides, the gas compressor also comprises at least one protective block 8, which involves the cylinder 2 externally.

[0042] Additionally, the gas compressor comprises at least one inner cavity 15, arranged between the protective block 8 and the cylinder 2, fluidly fed by a discharge flow resulting from the compression movement exerted by the piston 1 inside the cylinder 2. The inner cavity 15 is formed by the outer diameter of the cylinder 2 and by the inner diameter of the protective block 8.

[0043] Further, the gas compressor comprises at least one bearing-arrangement clearance 12, which separates an outer wall of the piston 1 and an inner wall of the cylinder 2, as shown in FIG. 1. The gas used for the bearing arrangement consists preferably of the gas itself that is pumped by the gas compressor and used in the cooling system. This compressed gas is diverted from a discharge chamber 13 to the inner cavity 15 through a connection channel 14.

[0044] The gas compressor comprises at least one flow restrictor 16, 17, also object of the present invention, provided with a housing that associates fluidly the inner cavity 15 to the bearing arrangement 12. The housing shape may be substantially cylindrical or substantially conical. As mentioned before, the function of the flow restrictor 16, 17 is to provide the bearing arrangement between the piston 1 and the cylinder 2 of the gas compressor. In other words, the flow restrictor 16, 17, arranged between the inner cavity 15 (high-pressure region) and the bearing arrangement 12, is capable of controlling the pressure in the bearing-arrangement region and restricting the gas flow. From FIGS. 2, 3, and 4 one can understand the functioning of the aerostatic material of the present invention. The inner cavity 15, connected to the discharge chamber 13 by the connection channel 14, presents gas with discharge pressure Pd, which feeds the flow restrictors 16, 17. This gas, upon passing through the flow restrictors 16, 17, loses pressure, forming a gas mattress of intermediate pressure Pi in the bearing-arrangement clearance 12. This is the pressure that supports the piston 1 and prevents it from resting against the inner wall of the cylinder 2. Finally, the gas flows out of the bearing-arrangement clearance 12, reaching a low pressure, which corresponds to the suction pressure Ps of the gas compressor.

[0045] When the piston 1 undergoes some axial effort so as to approach the cylinder 2 wall and, as a result, for instance, the flow restrictor 16, the bearing-arrangement clearance 12 in the region decreases (FIG. 3: detail A). The decrease in the bearing-arrangement clearance 12 entails an increase in the loss of charge of gas flow in the region in which the latter flows between the piston 1 and the cylinder 2. This increase in loss of charge entails a decrease in gas-flow rate through the flow restrictor 16 and through the bearing-arrangement clearance in the region adjacent the flow restrictor 16. The decrease in flow rate implies a decrease in velocity of gas flow, which in turn entails a decrease in loss of charge in the flow restrictor 16. This reduction in loss of charge of gas flow that passes through the flow restrictor 16 enables the gas reaching the bearing-arrangement clearance 12 in the region of the flow restrictor 16 to reach a pressure Pi higher than the intermediate pressure Pi. This increase in pressure acts to prevent the piston 1 from coming closer to the cylinder 2 wall in the region of the flow restrictor 16, preventing contact between the piston 1 and the cylinder 2.

[0046] On the other hand, in the opposite region of the bearing-arrangement clearance 12 (FIG. 4: detail B), the piston 1 moves away from the cylinder 2 wall and from the flow restrictor 17. The increase in the bearing-arrangement clearance 12 leads to the decrease in loss of charge of gas flow in the clearance region, increasing the gas-flow rate that passes through the clearance and through the flow restrictor 17. The increase in velocity of the gas flow increases the loss of charge of the flow in the flow restrictor 17, which causes the gas to reach the bearing-arrangement clearance 12 in the region of the flow restrictor 17 with a pressure Pi lower than the intermediate pressure Pi. This decrease in the intermediate in the region of the flow restrictor 17 acts to reestablish the force balance of the bearing, preventing contact of the piston 1 with the wall in the opposite region of the cylinder 2.

[0047] The flow restrictor 16, 17 called also bushing, is associated to the housing, being provided with at least one channel for passage of the bearing-arrangement fluid, representing a restrictive portion provided with a cross-section sized by deformation of the channel, to limit precisely the gas flow that flows from the inner cavity 15 to the bearing-arrangement clearance 12. In this way, the gas passes through at least one of these channels toward the bearing-arrangement clearance 12, forming a gas mattress that prevents contact between the piston 1 and the cylinder 2.

[0048] Thus, the principle of fixing and restricting gas flow consists in deforming plastically the flow restrictor 16, 17 with a tool that applies force F (represented by an arrow), pressing the flow restrictor 16, 17 against the bottom of the stepped bore. Since the deformation force F is applied so as to decrease the length of the flow restrictor 16, 17, the latter undergoes deformation in radial direction, which, as a result, causes a gradual decrease in the cross-sectional area of its channels or grooves or of the diameter of one or more of its bores. The decrease in cross-sectional area of the channels, of the grooves or of the bores entails greater loss of charge of gas flow that passes there, increasing the drop in pressure of said flow. In order to reach the desired flow rate/pressure, one can make a pre-established deformation or measure the flow rate during the deformation process, interrupting it when the desired flow rate has been reached.

[0049] A few possible preferred embodiments are illustrated in FIGS. 5A, 5B, 5C and 5D, in which one presents the embodiments in which the deformable flow restrictor 16, 17 has a surface finish applied to the outer surface of its structure, made in the form of helical grooves 18 with a cavity 19 for passage of gas (FIG. 5A), straight grooves 20 with a slot 21 (FIG. 5B), of serration 22 (FIG. 5C), or a simple bore 23 throughout the length of the bushing (FIG. 5D).

[0050] It should be noted that the present invention is not limited to the embodiments presented in the figures discussed above. So, the inventive concept lies in the capability of the plastic deformation of the flow restrictor 16, 17 and of its channels resting against the housing walls to guarantee control of the flow-rate of bearing-arrangement fluid. Concomitantly, this control obtained through the plastic deformation guarantees the association between the flow restrictors 16, 17 and the housing. In this way, one achieves great advantage in terms of industrial processing, since one manages to achieve excellent restriction characteristics with one simple process step.

[0051] FIGS. 6 and 7 show embodiment representations in which it is possible to obtain plastic deformation of the pushing by finish carried out in the housing itself of the compressor. In a first representation, illustrated in FIG. 6, a single tool 24 applies force (indicated by the arrow) directly to the bushing face that remains in contact with the cavity 15, deforming it permanently and controlling the gas-flow rate by adjusting the cross-sectional area available for passage of gas. In this case, the tool 24 is aided by a housing where one of the ends is obtained by a stepped bore.

[0052] A variation of this form of deforming the flow restrictor 16, 17 is illustrated ion FIG. 7, in which there is another tool 24 that exerts a force that counteracts the deformation force applied by the first tool 24, activating the stresses undergone by the compressor structure during the step of deforming the flow restrictor 16, 17.

[0053] Variations in the geometry of the bushing may be made in order to facilitate the deformation thereof and, as a result, decrease the force required to achieve the necessary plastic deformation. Thus, FIG. 8 presents the insertion of cavities 26, 27 and 28 in the bushing, so that less material will deform, preventing greater compressive loads. These cavities may have any shape, including cylindrical or conical.

[0054] Preferred examples of embodiments having being described, one should understand that the scope of the present invention embraces other possible variations, being limited only by the contents of the accompanying claims, which include the possible equivalents.