ELECTRONIC CAPACITY CONTROL VALVE FOR PORTABLE SCREW COMPRESSOR

Abstract

A spiral valve and a screw compressor having a compressor housing and the spiral valve are provided. The spiral valve includes an actuator module disposed adjacent an exterior of the compressor housing, the actuator module includes an electric motor, a gearbox mechanically coupled to the electric motor to transmit torque from the electric motor, a shutter coupled to the gearbox to rotate in response to a transmitted torque from the electric motor, wherein the shutter is positioned to open and close one or more of a plurality of bypass ports formed in the compressor housing based on the rotational position of the shutter, wherein the compression length of the screw compressor may be controlled by controlling the opening and closing of the one or more bypass ports.

Description

BACKGROUND

Field

[0001] The present disclosure relates to a spiral valve and in particular a spiral valve configured for electronic control.

Related Art

[0002] Twin screw gas compressors may be known in the related art. In the related art, a screw compressor may include a compressor housing and a motor (for example, a permanent magnet rotor/stator motor) is used to drive one (e.g., a first compression screw) of the two compression screws. The second of the two compression screws may be mechanically coupled to the compression screw that is driven by the motor. The second compression screw may thus be driven by the first compression screw. In the related art, gas may be drawn into the compressor through an inlet, compressed between the two compression screws as they turn, and output through an outlet which is downstream of the gas inlet and the compression screws.

[0003] In some related art, one or more bypass ports or valve openings may be formed in the compressor housing or a rotor cowling to allow gas to exit the housing to control or prevent over pressurization or compression along the length of the compression screws. In the related art, the one or more bypass ports or valve openings may be positioned adjacent to a spiral valve that controls the opening and closing of the bypass ports or valve openings by being rotated to a point that allows one or more of the bypass ports to communicate with spiral valve chamber. In the related art, the spiral valve may be pneumatically actuated. In other words, in the related art, the bypass ports or valve openings were opened and closed based on a discharge pressure differential. For example, in some related art systems, a differential pressure of 10 PSI or greater was required to move or position the spiral valve.

[0004] However, the pneumatically actuated spiral valves require significant pressure differentials to achieve a full spiral valve stroke. Thus, pneumatically actuated spiral valves may only provide coarse control of the pressure resulting in over capacity, under capacity, and inefficient energy use. Also, the cold temperatures often encountered in the use of portable air compressors are problematic for pneumatic control systems. These systems utilize rubber diaphragms or components to seal the air actuator. The durometer of the rubber components increases as temperatures decrease and can cause leakage and will decrease the effort that the actuator provides. Water trapped in the control system can freeze and reduce or eliminate control until the entire system is warm enough to allow the water to return to vapor.

SUMMARY

[0005] Aspects of the present application may include a spiral valve for a screw compressor. The screw compressor may have a compressor housing. The spiral valve may have an actuator module disposed adjacent an exterior of the compressor housing, the actuator module having: an electric motor, a gearbox mechanically coupled to the electric motor to transmit a torque from the electric motor, a shutter coupled to the gearbox to rotate in response to the transmitted torque from the electric motor, wherein the shutter is positioned to open and close one or more of a plurality of bypass ports formed in the compressor housing based on a rotational position of the shutter, wherein a compression length of the screw compressor may be controlled by controlling the opening and closing of the one or more bypass ports.

[0006] Additional aspects of the present application may include a spiral valve, wherein the plurality of bypass ports includes a first bypass port and a second bypass port adjacent to the first bypass port, and within a distance between the first bypass port and the second bypass port is less than 120% of a manufacturing tolerance of the compressor housing, and greater than or equal to 100% of the manufacturing tolerance of the compressor housing.

[0007] Further aspects of the present application may include a spiral valve, wherein the plurality of bypass ports include at least one pair of bypass ports, each bypass port of the pair of bypass ports being positioned at a same position along a length of the compressor housing, and wherein the shutter is positioned and shaped to open and close the pair of bypass ports simultaneously.

[0008] Still further aspects of the present application may include a spiral valve, wherein the plurality of bypass ports include at least one pair of bypass ports, each bypass port of the pair of bypass ports being positioned at a same position along a length of the compressor housing, and wherein the shutter is positioned and shaped to open one bypass port of the pair of bypass ports in sequence with an other bypass port of the pair of bypass ports.

[0009] Additional aspects of the present application may include a screw compressor having a compressor housing, a female compression screw, a male compression screw, a plurality of bypass ports, and a spiral valve. The compressor housing may define a compression chamber. The female compression screw may be disposed within the compression chamber. The male compression screw may also be disposed within the compression chamber and interfacing with the female compression screw. The plurality of bypass ports may be formed in the compressor housing, providing fluid communication through the compressor housing. The spiral valve may include an actuator module disposed adjacent an exterior of the compressor housing, the actuator module comprising an electric motor, a gearbox mechanically coupled to the electric motor to transmit a torque from the electric motor, a shutter coupled to the gearbox to rotate in response to the transmitted torque from the electric motor, wherein the shutter is positioned to open and close one or more of the plurality of bypass ports formed in the compressor housing based on a rotational position of the shutter, wherein a compression length of the screw compressor may be controlled by controlling the opening and closing of the one or more bypass ports of the plurality of bypass ports.

[0010] Further aspects of the present application may include a screw compressor, wherein the plurality of bypass ports includes a first bypass port and a second bypass port adjacent to the first bypass port, within a distance between the first bypass port and the second bypass port, is less than 120% of a manufacturing tolerance of the compressor housing, and greater than or equal to 100% of the manufacturing tolerance of the compressor housing.

[0011] Additional aspects of the present application may include a screw compressor, wherein the plurality of bypass ports include at least one pair of bypass ports, each bypass port of the pair of bypass ports being positioned at a same position along a length of the compressor housing, wherein the shutter is positioned and shaped to open and close the pair of bypass ports simultaneously.

[0012] Still further aspects of the present application may include a screw compressor, wherein the plurality of bypass ports include at least one pair of bypass ports, each bypass port of the pair of bypass ports being positioned at a same position along the a length of the compressor housing, wherein the shutter is positioned and shaped to open one bypass port of the pair of bypass ports in sequence with an other bypass port of the pair of bypass ports.

[0013] Additional aspects of the present application may include a screw compressor, wherein the plurality of bypass ports include at least one pair of bypass ports, each bypass port of the pair of bypass ports being positioned at a same position along a length of the compressor housing, wherein one bypass port of the pair of bypass ports is aligned with a largest diameter region of a lobe of the female compression screw, wherein another bypass port of the pair of bypass ports is aligned with a largest diameter region of a lobe of the male compression screw, and wherein the lobe of the female compression screw and the lobe of the male compression screw are located at regions of equal pressure within the compression chamber.

[0014] Still further aspects of the present application may include a screw compressor, wherein the plurality of bypass ports define a bypass window along an area of the compressor housing between compression chamber inlet and a compression chamber outlet; and wherein a bypass port of the plurality of bypass ports that is positioned closest to the compression chamber inlet is aligned with a largest diameter region of a lobe of the female compression screw closest to the compression chamber inlet.

[0015] Additional aspects of the present application may include a screw compressor, wherein the plurality of bypass ports define a bypass window along an area of the compressor housing between compression chamber inlet and a compression chamber outlet, and wherein a bypass port of the plurality of bypass ports that is positioned closest to the compression chamber inlet is aligned with a largest diameter region of a lobe of the male compression screw closest to the compression chamber inlet.

[0016] Further aspects of the present application may include a screw compressor, wherein the plurality of bypass ports define a bypass window along an area of the compressor housing between compression chamber inlet and a compression chamber outlet, wherein a bypass port of the plurality of bypass ports that is positioned closest to the compression chamber outlet is aligned with a largest diameter region of a lobe of the female compression screw, and wherein compression chamber volume between the lobe of the female compression screw and the compression chamber outlet corresponds to minimum compression volume of the screw compressor.

[0017] Additional aspects of the present application may include a screw compressor, wherein the plurality of bypass ports define a bypass window along an area of the compressor housing between compression chamber inlet and a compression chamber outlet, wherein a bypass port of the plurality of bypass ports that is positioned closest to the compression chamber outlet is aligned with a largest diameter region of a lobe of the male compression screw, and wherein compression chamber volume between the lobe of the male compression screw and the compression chamber outlet corresponds to minimum compression volume of the screw compressor.

[0018] Further aspects of the present application may include a compressor, wherein the plurality of bypass ports define a bypass window along an area of the compressor housing between compression chamber inlet and a compression chamber outlet, and wherein an area, A.sub.w, of the bypass window is defined by the equation A.sub.w=10%.+-.5%*D.sub.RB/N.sub.L, wherein D.sub.RB equals the diameter of the rotor bore of each bore of the compressor housing surrounding each of the male and female compression screws, and N.sub.L equals the number of lobes of the male and female compression screw associated with each bore.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] A general architecture that implements the various features of the disclosure will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate example implementations of the disclosure and not to limit the scope of the disclosure. Throughout the drawings, reference numbers are reused to indicate correspondence between referenced elements.

[0020] FIG. 1 illustrates a perspective view of a screw compressor having a spiral valve structure in accordance with example implementations of the present application.

[0021] FIG. 2 illustrates a section view from above of the screw compressor in accordance with an example implementation of the present application.

[0022] FIGS. 3A and 3B illustrate section views from each side of the screw compressor in accordance with an example implementation of the present application.

[0023] FIG. 4 illustrates support platform for a portable screw compressor configuration mounted to a transportation structure in accordance with example implementations of the present application.

DETAILED DESCRIPTION

[0024] The following detailed description provides further details of the figures and example implementations of the present application. Reference numerals and descriptions of redundant elements between figures are omitted for clarity. Terms used throughout the description are provided as examples and are not intended to be limiting. For example, the use of the term "automatic" may involve fully automatic or semi-automatic implementations involving user or operator control over certain aspects of the implementation, depending on the desired implementation of one of ordinary skill in the art practicing implementations of the present application. Further, sequential terminology, such as "first", "second", "third", etc., may be used in the description and claims simply for labeling purposes and should not be limited to referring to described actions or items occurring in the described sequence. Actions or items may be ordered into a different sequence or may be performed in parallel or dynamically, without departing from the scope of the present application.

[0025] As described above, related art screw compressors use a pneumatically actuated spiral valve to control opening and closing of bypass ports or valve openings. However, pneumatically actuated spiral valves may provide only coarse control and may lead to inefficiencies and/or leakage. In order to provide more accurate control of the actuation of the spiral valve, and thereby finer control of the bypass port or valve openings, example implementations may include an electronically actuated spiral valve. For example, an electronic actuator motor coupled to the spiral valve may provide very fine control of the bypass valve opened (e.g., +/-1 PSI pressure control band compared to +/-10 PSI for a pneumatically controlled valve). With finer control of the compressor pressure, energy usage may be optimized by minimizing the gas allowed to flow into the rotors and minimizing gas leakage prior to compression. Additional efficiencies may be achieved by optimizing the bypass port geometry. For example, the number of bypass ports may be maximized, the shutter geometry may be matched to the window geometry, and the bypass port window area may be minimized as described in greater detail below.

[0026] By coupling the optimized bypass port geometries with the finer spiral valve control offered by an electric actuator, a number of performance improvements may be achieved. For example, the energy consumed during operation may be reduced while still maintaining consistent pressures and compression volumes due to the finer control of bypass volumes during operation of a screw compressors coupled to electric motors and screw compressors coupled to Internal Combustion (IC) engines.

[0027] Further with respect to electric motor implementations (industrial implementations), by being able to dynamically adjust the bypass valve opening within a 1 PSI pressure control band, the in-rush current experienced during start-up or shut down may be reduced, thereby extend operational life of electrical components including the motor, the switch gear and the power distribution components. Similarly, by dynamically adjusting the bypass valve opening in a tight pressure control band, the compression cycle may be controlled to reduce heat loss thereby reducing heat rejection requirements of a compressor cooling system.

[0028] Further with respect to IC engines implementations (construction implementations), by being able to dynamically adjust the bypass valve opening within a 1 PSI pressure control band, the start-up torque required may be reduced allowing smoother or easier start-up operations in non-ideal conditions (e.g., cold environment starts, hot environment starts, high-altitude starts, etc.). For example, the bypass ports may be fully opened to reduce the initial compression value to minimize torque demand during start-up. By reducing strain on the IC engine during start-up, starter component (e.g., starter motor, battery, etc.) life may be extended.

[0029] Similarly, by being able to dynamically control the compression volume, compression volume may be reduced to prevent or delay engine de-rate or shutdown that may be caused by cold, hot or high-altitude operation conditions.

[0030] Additionally, by controlling bypass valve opening dynamically, smoother transitions between idle and full operational speeds may be achieved, and stress on power train components (couplers and mountings) may be reduced. Further, by dynamically reducing compressor load more finely, the engine may be run at lower revolutions per minute (RPM) while reducing stress on the engine and compressor coupler.

[0031] FIG. 1 illustrates a perspective view of a screw compressor 100 having a spiral valve structure in accordance with example implementations of the present application. As illustrated, the screw compressor 100 includes a compressor housing 10 that surrounds the compressor inner structure and forms a compression chamber 3 (not shown in FIG. 1, illustrated in FIGS. 2 and 3). The housing 10 may include one or more mounting brackets or feet 2 that support the screw compressor 100 and allow the screw compressor 100 to be secured to a floor or other support platform. For example, the feet 2 may allow the screw compressor 100 to be mounted on a portable support platform or trailer (shown in FIG. 4). The housing 10 also defines a main gas flow intake 26, a main gas flow discharge 28, and one or more bypass gas outlets 215/220. Arrows are provided to illustrate gas flow through the screw compressor 100. Additionally, the compressor housing 10 may allow a drive shaft 15 to pass from the compressor inner structure (illustrated in FIGS. 2 and 3) to the area surrounding the compressor 100.

[0032] The drive shaft 15 may be used to mechanically couple the screw compressor 100 to a motor or engine to drive the screw compressor 100. The screw compressor 100 may be driven by an IC Engine, such as a gasoline engine, a diesel engine, or any other type of engine that might be apparent to a person of ordinary skill in the art. The screw compressor 100 may also be driven by an electric motor, or any type of machine that supplies rotary motive power that might be apparent to a person of ordinary skill in the art.

[0033] Further, an actuator module 5 may be attached to the compressor housing 10 and control a spiral valve structure (shown in FIGS. 2 and 3A, 3B) located within the compressor housing 10. As described below, the actuator module 5 may include an electric motor coupled to a gearbox that is coupled to the spiral valve. Additionally, the actuator module 5 may also include an integrated processor component that may include onboard control logic that controls the actuator module 5 automatically, semi-automatically based partially on a user input or manually based entirely on a user input.

[0034] FIG. 2 illustrates a section view from above of the screw compressor 100 in accordance with an example implementation of the present application. The compressor housing 10 forms a compression chamber 3 defining two adjoining bores 6 and 8, each of which includes a screw 7, 9 of the twin screw gas compressor 100, when the unit is assembled and functioning. As illustrated, one of the screws 9 (also known as the drive screw) is mounted on the driven gear 210 and mechanically coupled to shaft 15 by drive gear 205. The motor or engine that drives the screw gas compressor is coupled to shaft 15. The other screw 7 (also known as the driven screw) is driven by drive screw 9. Both screws 7, 9 may each be supported by a bearing group 225, such as roller bearings or any other type of bearing or bushing that might be apparent to a person of ordinary skill in the art.

[0035] Further, in some example implementations, one of the screws may have a female lobe configuration, and the other of the screws may have a male lobe configuration. In other words, one of the screws may be a female compressor screw and the other screw may be a male compressor screw that interfaces with the female compressor screw. For example, the drive screw 9 may be a male compression screw and the driven screw 7 may be a female compression screw. As may be apparent to a person of ordinary skill in the art, example implementations of the present application are not limited to this configuration and some example implementations may have an alternative configuration (e.g., the drive screw 9 may be a female compression screw and the driven screw 7 may be a male compression screw).

[0036] The end of the compressor housing 10 shown in FIG. 2 is the outlet end 28, and the inlet 26 (in FIG. 1) is not shown in FIG. 2, as it is cutoff in the section view. Gas flow channels 215, 220 may connect each bore 6, 8 with the inlet 26 to allow gas to flow into each bore 6, 8. Each bore 6 and 8 also comprises one or more bypass ports collectively represented by oval 12. The bypass ports 12a-12e are formed in bore 6 associated with the driven screw 7. Further, the bypass ports 12f-12j are formed in bore 8 associated with the drive screw 9. As shown in FIGS. 3A, 3B discussed below, each bypass port 12a-12j shown in FIG. 2 fluidly communicates with a bypass chamber 22 that contains a spiral valve 20 that is rotatable along an axis 24. The length of each bore 6, 8 associated with the bypass ports 12a-12j may be referred to as the bypass window 245.

[0037] As described above, the compressor housing 10 has a gas inlet 26 and a gas outlet 28. Within the compressor housing, the gas flow channels 215, 220 provide fluid communication between the inlet 26 and the compression chamber 3. As the screws 7 and 9 turn within the respective bores 6, 8 of the compression chamber 3, gas is compressed inside the compression chamber 3. The compression chamber 3 has a length that runs between compression chamber inlets 230, 235 and a compression chamber outlet end 240. The compressed gas is then output through the gas outlet 28. Arrows illustrate gas flow through the compression chamber 3.

[0038] FIGS. 3A and 3B illustrate section views from each side of the screw compressor 100 in accordance with an example implementation of the present application. FIGS. 3A and 3B more clearly shows how the spiral valve 20 functions to regulate compression volume in the compressor. As depicted in FIGS. 1-3B, the compressor housing 10 defines the compression chamber 3, which fluidly communicates with a gas inlet 26 and a gas outlet 28. As the screws 7, 9 turns, gas is compressed inside the compression chamber 3 defined by the radially intersecting bores 6 and 8. The compression chamber 3 has a length that runs between compression chamber inlets 230, 235 and a compression chamber outlet end 240. The compressed gas is then output through the gas outlet 28.

[0039] FIG. 3A shows several bypass ports 12a-12e formed in the compressor housing 10 adjacent to the bore 6 housing the driven screw 7. A similar structure is illustrated in FIG. 3B showing the opposite side for bypass ports 12f-12j formed in the compressor housing 10 adjacent to the bore 8 housing the male compression screw 9. As depicted in FIGS. 3A and 3B the spiral valve 20 includes a shutter 335 that selectively either blocks (close) or opens the bypass ports 12a-12j, depending on a rotational position of the spiral valve 20. As the spiral valve 20 is turned to a point that allows one or more of the bypass ports 12a-12j to fluidly communicate with the spiral valve chamber 22, the effective compression volume of the compression chamber 3 may be reduced due to the smaller compression chamber length. In FIG. 3A, bypass ports 12c-12e indicate flow and bypass ports 12a and 12b do not indicate flow. With at least one bypass port 12c-12e open, the effective compression length of the compression chamber 3 is defined by the distance between the open bypass port closest to compression chamber outlet end 240 and the compression chamber outlet end 240 itself. Similarly, in FIG. 3B, bypass ports 12h-12j indicate flow and bypass ports 12g and 12h do not indicate flow. With at least one bypass port 12h-12j open, the effective compression length of the compression chamber 3 is defined by the distance between the open bypass port closest to the compression chamber outlet end 240 and the compression chamber outlet end 240 itself.

[0040] When the effective compression volume is reduced in this manner, torque is reduced, which saves power, increases efficiency, and extends the life of the components of the gas compressor.

[0041] The spiral valve 20 is coupled to an actuator module 5 that controls the rotation and position of the shutter 335 of the spiral valve 20. As illustrated, the actuator module 5 includes a motor 325 mechanically coupled to a gearbox 330. The gear box 330 mechanically couples the motor 325 to the spiral valve 20. Thus, a torque from the motor may be transmitted to the shutter 335 of the spiral valve 20 by the gearbox 330 causing the shutter 335 to rotate. The motor 325 may be an electric actuator motor that provides precise control of rotational speed and rotational position of the spiral valve.

[0042] The actuator module 5 may be attached to the compressor housing 10 to control a spiral valve structure (shown in FIGS. 2, 3A and 3B) located within the compressor housing 10. Additionally, the actuator module 5 may also include an integrated processor component that may include onboard control logic that controls the motor 325 module automatically, semi-automatically based partially on a user input or manually based entirely on a user input.

[0043] The spiral valve 20 may be rotated (or actuated) along its axis 24 from a fully open position (where all of the bypass ports are open) to a fully closed position (where all of the bypass ports are closed), and all points in between. In FIGS. 3A and 3B, flow is indicated as if the spiral valve 20 was rotated to a point that allowed for a partial bypass of gas from the compression chamber 3 to the bypass chambers 215, 220. Specifically, bypass ports 12c-12e and bypass ports 12h-12j allow gas to flow from the compression chamber 3 to the bypass chambers 215,220. Gas flow is represented by arrows.

[0044] In order to maximize efficiency of the screw compressor 100, the bypass ports 12a-12j of FIGS. 2, 3A and 3B may have specific geometric arrangements according to some example implementations. For example, in order to maximize the number of bypass ports 12a-12j within the bypass window 245, several geometric arrangements described below may be implemented either alone or in combination.

[0045] In some example implementations, the spacing or distance between adjacent bypass ports 12a-12j (e.g., the spacing between a first bypass port and a second bypass port adjacent to the first bypass port) may be within 20% of the minimum spacing permitted based on the manufacturing tolerances associated with the compressor housing 10 manufacturing (e.g., less than 120% of the manufacturing tolerance and greater than or equal to 100% of the manufacturing tolerance). For example, if the compressor housing 10 is formed by a casting process, the casting tolerances may require that the minimum bypass port spacing be at least 5 mm in order to permit proper molten metal flow in the casting mold. If the casting tolerances are 5 mm, then the spacing between adjacent bypass ports may be less than 6 mm (the 5 mm casting tolerance+20%) and greater than or equal to 5 mm (the casting tolerance). Different bypass port spacing parameters may be dictated by different manufacturing tolerances.

[0046] In some example implementations, the leading edge of the first bypass port 12e of the bypass window 245 associated with the female compression screw 7 of the screw compressor 100 may be positioned at or in front (on inlet side) of an apex (greatest diameter) of the first lobe 305 of the female compression screw 7.

[0047] Similarly, in some example implementations, the leading edge of the first bypass port 12j of the bypass window 245 associated with the male compression screw 9 of the screw compressor 100 may be positioned at, but not in front (on inlet side) of an apex (greatest diameter) of the first lobe 340 of the male compression screw 9.

[0048] Further, some example implementations may include bypass ports 12a-12j positioned to improve matching of the at least one shutter 335 and the bypass window 245. For example, in some example implementations, the bypass ports 12a-12e associated with the bore 6 of the female compression screw 7 may be symmetrically positioned with the bypass ports 12f-12j associated with the bore 8 of the male compression screw 9. Further, the bypass ports of each chamber (e.g., the bypass ports 12a-12e of the bore 6 and the bypass ports 12f-12j of the bore 8) may be positioned at the apex (maximum diameter) of lobes of the respective screws 7, 9 that are at equal pressures in the compression cycle.

[0049] In some example implementations, the valve shutter 335 may be shaped and positioned to open and close each pair of female and male bypass ports (e.g., 12a-12f, 12b-12g, 12c-12h, 12d-12i, 12e-12j) simultaneously. In other words, bypass ports 12a and 12f open simultaneously, bypass ports 12b and 12g open simultaneous, etc.

[0050] Alternatively, in some example implementations, the valve shutter 335 may be shaped and positioned to open each pair of female and male bypass ports (e.g., 12a-12f, 12b-12g, 12c-12h, 12d-12i, 12e-12j) simultaneously. In other words, one of bypass ports 12e and 12j may open, followed in sequence by the other of bypass port 12d and 12i. Similarly, one of bypass ports 12e and 12j may open, followed in sequence by the other of bypass port 12d and 12i. Similarly, the other bypass port pairs 12c-12h, 12b-12g, 12a-12f may each open sequentially.

[0051] Additionally, some example implementations may include bypass ports 12a-12j positioned to minimize the size of the bypass window 245. For example, in some example implementations, the bypass ports 12a-12j may be positioned in a bypass window area of the compressor housing 3 that is less than or equal to an area (A.sub.W) defined by equation 1 below:

A.sub.w=10%.+-.5%*D.sub.RB/N.sub.L (Equation 1)

[0052] where D.sub.RB equals the diameter of the rotor bore of each bore, and N.sub.L equals the number of lobes of the screw associated with each bore. In other words, the bypass window 245 area is no less than 10% and no more than 15% of the rotor bore diameter of each bore (e.g., bores 6 and 8) divided by the number of lobes of the screw associated with each bore (e.g., screws 7 and 9).

[0053] Further, in some example implementations, the trailing edge of the last bypass port 12a of the bypass window 245 may be located at a position of the apex (greatest diameter) of the lobe 310 of the female compression screw 7 that is located in a position where a lowest desired compression volume would be produced. In other words, the volume between the lobe 310 and the chamber outlet end 240 may be associated with lowest desired compression volume of the bore 6 of the screw compressor 100. Thus, the last bypass port 12a may be positioned adjacent to the apex of the lobe 310 in some example implementations.

[0054] Additionally, in some example implementations, the trailing edge of the last bypass port 12j of the bypass window 245 may be located at a position of the apex (greatest diameter) of the lobe 345 of the male compression screw 9 that is located in a position where a lowest desired compression volume would be produced. In other words, the volume between the lobe 345 and the chamber outlet end 240 may be associated with lowest desired compression volume of the bore 8 of the screw compressor 100. Thus, the last bypass port 12f may be positioned adjacent to the apex of the lobe 310 in some example implementations.

[0055] Example implementations are not limited to industrial or fixed location configurations and portable configurations may be achieved. FIG. 4 illustrates a support platform 400 for a portable screw compressor configuration mounted to a transportation structure 405 in accordance with example implementations of the present application. As illustrated, the support platform 400 includes a transportation structure 405 and a compressor enclosure 410. The compressor enclosure 410 that surrounds the compressor (not shown in FIG. 4) and may include one or more removable panels 415 that allows access to the compressor.

[0056] The transportation structure 405 includes a support frame 430 and a pair of wheels 435 to allow the support platform 400 to be moved. The transportation structure 405 may also include one or more transportation couplers 420 to couple the transportation structure 405 to a vehicle to allow movement on the support platform 400. The transportation structure 405 may also include a leveling member 425 to orient the support platform 400 in a level position during operation.

[0057] Through using the spiral valve as illustrated in FIGS. 2, 3A, and 3B, the geometry of the valve is such that it can be controlled accurately by the actuator motor and an electronic controller, thereby reducing overshoot possibilities. In related art implementations, a small movement in the valve (e.g., 2.degree. rotation) might cause a larger than a 5% capacity change. The subsequent 2.degree. may cause no capacity change and then the next 2.degree. may result in a 10% capacity change, which is neither linear nor proportional. The spiral valve design in FIG. 2 and FIG. 3 allows for a linear and proportionate capacity change, in that each 2.degree. produces roughly 1% capacity change. With the fine adjustments made by the actuator motor and electronic controller, the capacity can thereby be regulated more accurately than in the related art.

[0058] Further, example implementations of the portable screw compressor involving the electronic controller can result in requiring less pressure to obtain full actuation. Pneumatic systems in the related art normally require 10 psi to obtain full actuation; however, through the use of the electronic controller and actuator motor, roughly only 1 psi may be required to obtain full actuation of the portable controller. Thus, for a portable compressor system that runs on 100 psi, a pneumatic system would require 110 psi to obtain full actuation, which is a 10% waste of energy, versus the example implementations only requiring 101 psi which is only a 1% waste.

[0059] Example implementations can thereby control the air flow of the portable compressor to within 1 psi instead of 10 psi of the pneumatic system of the related art, through the use of the electronic controller accurately coordinating the engine speed with the spiral valve opening.

[0060] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed.

[0061] The foregoing detailed description has set forth various example implementations of the devices and/or processes via the use of diagrams, schematics, and examples. Insofar as such diagrams, schematics, and examples contain one or more functions and/or operations, each function and/or operation within such diagrams, or examples can be implemented, individually and/or collectively, by a wide range of structures. While certain example implementations have been described, these implementations have been presented by way of example only and are not intended to limit the scope of the protection. Indeed, the novel methods and apparatuses described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the devices and systems described herein may be made without departing from the spirit of the protection. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the protection.

Claims

1. A spiral valve for a screw compressor having a compressor housing, the spiral valve comprising: an actuator module disposed adjacent an exterior of the compressor housing, the actuator module comprising: an electric motor; a gearbox mechanically coupled to the electric motor to transmit a torque from the electric motor; a shutter coupled to the gearbox to rotate in response to the transmitted torque from the electric motor, wherein the shutter is positioned to open and close one or more of a plurality of bypass ports formed in the compressor housing based on a rotational position of the shutter, wherein a compression length of the screw compressor may be controlled by controlling the opening and closing of the one or more bypass ports.

2. The spiral valve of claim 1, wherein the plurality of bypass ports includes a first bypass port and a second bypass port adjacent to the first bypass port; within a distance between the first bypass port and the second bypass port is less than 120% of a manufacturing tolerance of the compressor housing, and greater than or equal to 100% of the manufacturing tolerance of the compressor housing.

3. The spiral valve of claim 1, wherein the plurality of bypass ports include at least one pair of bypass ports, each bypass port of the pair of bypass ports being positioned at a same position along a length of the compressor housing; wherein the shutter is positioned and shaped to open and close the pair of bypass ports simultaneously.

4. The spiral valve of claim 1, wherein the plurality of bypass ports include at least one pair of bypass ports, each bypass port of the pair of bypass ports being positioned at a same position along a length of the compressor housing; wherein the shutter is positioned and shaped to open one bypass port of the pair of bypass ports in sequence with an other bypass port of the pair of bypass ports.

5. A screw compressor comprising: a compressor housing defining a compression chamber; a female compression screw disposed within the compression chamber; a male compression screw disposed within the compression chamber and interfacing with the female compression screw; a plurality of bypass ports formed in the compressor housing and providing fluid communication through the compressor housing; a spiral valve comprising: an actuator module disposed adjacent an exterior of the compressor housing, the actuator module comprising: an electric motor; a gearbox mechanically coupled to the electric motor to transmit a torque from the electric motor; a shutter coupled to the gearbox to rotate in response to the transmitted torque from the electric motor, wherein the shutter is positioned to open and close one or more of the plurality of bypass ports formed in the compressor housing based on a rotational position of the shutter, wherein a compression length of the screw compressor may be controlled by controlling the opening and closing of the one or more bypass ports of the plurality of bypass ports.

6. The screw compressor of claim 5, wherein the plurality of bypass ports includes a first bypass port and a second bypass port adjacent to the first bypass port; within a distance between the first bypass port and the second bypass port, is less than 120% of a manufacturing tolerance of the compressor housing, and greater than or equal to 100% of the manufacturing tolerance of the compressor housing.

7. The screw compressor of claim 5, wherein the plurality of bypass ports include at least one pair of bypass ports, each bypass port of the pair of bypass ports being positioned at a same position along a length of the compressor housing; wherein the shutter is positioned and shaped to open and close the pair of bypass ports simultaneously.

8. The screw compressor of claim 5, wherein the plurality of bypass ports include at least one pair of bypass ports, each bypass port of the pair of bypass ports being positioned at a same position along the a length of the compressor housing; wherein the shutter is positioned and shaped to open one bypass port of the pair of bypass ports in sequence with an other bypass port of the pair of bypass ports.

9. The screw compressor of claim 5, wherein the plurality of bypass ports include at least one pair of bypass ports, each bypass port of the pair of bypass ports being positioned at a same position along a length of the compressor housing; wherein one bypass port of the pair of bypass ports is aligned with a largest diameter region of a lobe of the female compression screw; wherein another bypass port of the pair of bypass ports is aligned with a largest diameter region of a lobe of the male compression screw; and wherein the lobe of the female compression screw and the lobe of the male compression screw are located at regions of equal pressure within the compression chamber.

10. The screw compressor of claim 5, wherein the plurality of bypass ports define a bypass window along an area of the compressor housing between compression chamber inlet and a compression chamber outlet; and wherein a bypass port of the plurality of bypass ports that is positioned closest to the compression chamber inlet is aligned with a largest diameter region of a lobe of the female compression screw closest to the compression chamber inlet.

11. The screw compressor of claim 5, wherein the plurality of bypass ports define a bypass window along an area of the compressor housing between compression chamber inlet and a compression chamber outlet; and wherein a bypass port of the plurality of bypass ports that is positioned closest to the compression chamber inlet is aligned with a largest diameter region of a lobe of the male compression screw closest to the compression chamber inlet.

12. The screw compressor of claim 5, wherein the plurality of bypass ports define a bypass window along an area of the compressor housing between compression chamber inlet and a compression chamber outlet; wherein a bypass port of the plurality of bypass ports that is positioned closest to the compression chamber outlet is aligned with a largest diameter region of a lobe of the female compression screw; and wherein compression chamber volume between the lobe of the female compression screw and the compression chamber outlet corresponds to minimum compression volume of the screw compressor.

13. The screw compressor of claim 5, wherein the plurality of bypass ports define a bypass window along an area of the compressor housing between compression chamber inlet and a compression chamber outlet; wherein a bypass port of the plurality of bypass ports that is positioned closest to the compression chamber outlet is aligned with a largest diameter region of a lobe of the male compression screw; and wherein compression chamber volume between the lobe of the male compression screw and the compression chamber outlet corresponds to minimum compression volume of the screw compressor.

14. The screw compressor of claim 5, wherein the plurality of bypass ports define a bypass window along an area of the compressor housing between compression chamber inlet and a compression chamber outlet; and wherein an area, A.sub.w, of the bypass window is defined by the equation: A.sub.w=10%.+-.5%*D.sub.RB/N.sub.L wherein D.sub.RB equals the diameter of the rotor bore of each bore of the compressor housing surrounding each of the male and female compression screws, and N.sub.L equals the number of lobes of the male and female compression screw associated with each bore.