Description:1
A.
TECHNICAL FIELD OF THE INVENTION 5
[0001] The present invention relates to refrigeration screw compressors, specifically to hydraulic piston-cylinder arrangements used for capacity control. The present invention more particularly relates to an improved hydraulic piston guiding mechanism utilizing guide rings to enhance piston movement precision, reduce wear and tear, and improve 10 the reliability and operational efficiency of the refrigeration screw compressor.
B.
BACKGROUND OF THE INVENTION
[0002] Screw compressors are widely used in industrial refrigeration systems due to their 15 high efficiency and ability to handle large cooling loads. These compressors use a hydraulic piston-cylinder system to control and adjust their cooling capacity. However, in conventional designs, the piston moves directly against the cylinder wall, causing friction and wear over time. This friction reduces efficiency, increases energy consumption, and leads to frequent maintenance and potential breakdowns. 20
[0003] Several prior arts attempt to solve these issues, but they each have limitations. For example, US Patent No. 4928516 teaches a hydraulic control system for a screw compressor but does not provide any means to reduce direct metal-to-metal contact in the piston-cylinder arrangement. Similarly, European Patent No. 2134567 teaches a slide valve arrangement but does not focus on minimizing wear in the hydraulic piston system. 25
[0004] Similarly, Japanese Patent No. 2003112345, discloses improved lubrication techniques to reduce friction and wear. While lubrication can provide temporary relief, it does not eliminate direct contact between the moving metal components, the same limitation of prior art US Patent No. 4928516, leading to long-term wear and frequent maintenance. Also similarly, US Patent No. 6789456 teaches the use of specialized 30 coatings on the piston and cylinder surfaces to reduce friction, but such coatings wear out over time, requiring costly refurbishments.
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[0005] Another prior art DE Patent No. 102015003276 teaches an alternative piston 5 configuration aimed at improving efficiency. However, this design still permits metal-to-metal contact, which leads to progressive degradation of the compressor’s internal components.
[0006] These and other limitations of various prior arts creates a need for an improved hydraulic piston-cylinder arrangement that effectively eliminates or reduces metal-to-10 metal contact to negligible, thereby enhancing durability, reducing maintenance costs, and improving overall efficiency.
[0007] The teachings of the complete description below shall be sufficient to disclose and understand the need of incorporating and integrating guide rings in the hydraulic piston-cylinder assembly. These guide rings act as a barrier between the piston and cylinder 15 walls, preventing direct metal-to-metal contact while maintaining precise alignment.
C.
OBJECTS OF THE INVENTION
[0007] The primary object of the present invention is to improve the efficiency and 20 lifespan of screw compressors by reducing friction and wear within the hydraulic piston-cylinder system.
[0008] Another object of the present invention is to integrate the guide rings to prevent direct metal to metal contact between piston and cylindrical wall.
[0009] Yet another object of the present invention is to minimize the friction and wear 25 and tear by preventing direct contact between the piston and the cylindrical wall by placing the guide rings.
[0010] Yet another object of the present invention is to enhance the efficiency and performance of the compressor by improving the smooth movement of the piston within the cylinder, reducing the power losses that occur due to high friction and maintain 30 consistent and precise control ensuring optimal performance of the compressor.
[0011] Yet another object of the present invention is to lower maintenance costs and downtime of the compressor. Ease of movement and reduction in the metal to metal
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contact reduces the need and frequency for the need of maintenance and replacement 5 of worn out and damaged components.
[0012] Yet another object of the present invention is to minimize unexpected breakdowns caused by excessive wear, leading to improved reliability of the refrigeration system and decrease the sustainability of the systems by enhancing operational efficiency and output.
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D.
SUMMARY OF THE INVENTION
[0013] The various embodiments of the present invention provide for an improved piston-cylinder arrangement for screw compressors, incorporating a guide ring assembly that enables and facilitates capacity control while reducing friction and wear. The piston-15 cylinder mechanism comprises a piston housed within a cylinder, wherein the movement of the piston controls the compression process. It also includes one or more guide rings positioned along the piston body, ensuring controlled movement within the cylinder bore. These guide rings are made from low-friction or self-lubricating materials, preventing direct metal-to-metal contact between the piston and the cylinder. 20
[0014] According to one embodiment of the present invention, the piston includes grooves designed on its outer surface, wherein the guide rings are seated. These grooves are dimensioned to securely retain the guide rings while allowing for movement as needed for operational efficiency. The placement and thickness of the guide rings are configured based on the clearance requirements and load distribution of the piston-25 cylinder assembly, ensuring uniform movement.
[0015] According to another embodiment of the present invention, the guide rings are made as per the requirement of the system or the application. The guide rings may be continuous or segmented. A segmented guide ring configuration allows for expansion and contraction due to thermal variations, whereas a continuous guide ring arrangement 30 provides uniform support along the entire piston circumference.
[0016] According to yet another embodiment of the present invention, the cylinder in the present invention is designed with a precision-machined inner bore, ensuring
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compatibility with the guide rings and piston arrangement. The bore diameter and surface 5 finish are optimized to minimize frictional resistance while providing necessary clearance for the guide rings.
[0017] According to yet another embodiment of the present invention, the invention features a multi-guide ring arrangement, wherein multiple guide rings are positioned at different axial locations along the piston. This configuration enhances load balancing and 10 vibration damping, particularly in high-speed compressor applications. The spacing and positioning of these guide rings are determined based on different parameters of the compressor system.
[0018] According to yet another embodiment of the present invention, the guide rings may include integrated sensors or wear indicators, enabling real-time monitoring of 15 piston movement, friction levels, and wear conditions.
[0019] According to yet another embodiment of the present invention, the guide rings disclosed in the present invention can be used and extrapolated to arious types of screw compressors, including oil-free, oil-injected, single-stage, and multi-stage compressors. The guide ring arrangement provides consistent and precise control over the piston-20 cylinder interface, making it suitable for a wide range of pressure and temperature conditions.
E.
BRIEF DESCRIPTION OF THE DRAWINGS
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[0020] Fig. 1 illustrates a cross-sectional view of refrigeration screw compressor
[0021] Fig. 2 illustrates a cross-sectional view of Hydraulic Piston – Cylinder arrangement with Guide rings.
[0022] Fig. 3 illustrates a detailed view of Piston – Cylinder arrangement with Guide rings
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F.
DETAILED DESCRIPTION OF THE INVENTION
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[0023] The present invention relates to an improved piston-cylinder arrangement for 5 screw compressors, incorporating a guide ring assembly that optimizes capacity control, reduces friction, and enhances the operational lifespan of the compressor. The invention is designed to address limitations in conventional piston-cylinder systems by introducing guide rings that provide precise control over piston movement within the system.
[0024] The slide valve in a screw compressor moves linearly to vary the effective 10 compression length of the screw rotors, controlling the compressor’s capacity. A hydraulic piston-cylinder arrangement is used to drive this movement. The efficient operation of the slide valve is critical in ensuring the compressor runs optimally and maintains its intended cooling performance. The ability to precisely control the slide valve directly impacts the energy efficiency, longevity, and operational effectiveness of the compressor. 15
[0025] The piston enables controlled, stable motion of the slide valve. Conventional designs rely on the cylinder wall to guide the piston, necessitating highly precise manufacturing. Due to the reliance on direct metal-to-metal contact, even minor imperfections in the piston or cylinder bore can result in improper movement, increased friction, and wear, leading to inefficiencies in compressor operation. The introduction of 20 guide rings in the present invention addresses these concerns by ensuring precise guidance without the need for excessive machining precision.
[0026] The invention introduces guide rings that are mounted on the piston within specially designed grooves. These guide rings replace direct metal-to-metal contact with a guided interface, reducing friction and wear. Guide rings act as stabilizers that maintain 25 the alignment of the piston within the cylinder while also absorbing radial forces. The material composition of these guide rings ensures that they are softer than the piston and cylinder, thus preventing the harder metal components from experiencing wear while enabling an easy and cost-effective replacement when necessary.
[0027] The guide rings act as a protective barrier, preventing direct piston-cylinder 30 contact, thus minimizing degradation of critical components. In conventional designs, continuous friction between the piston and the cylinder wall leads to gradual deterioration, reducing the lifespan of the compressor. With guide rings in place, this direct contact is eliminated, ensuring longer-lasting components and reduced maintenance requirements. The guide rings, being made from wear-resistant materials, 35
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absorb the stresses that would otherwise be borne by the piston and cylinder, thereby 5 significantly enhancing the durability of the system.
[0028] Relaxed manufacturing tolerances for the piston and cylinder lower production expenses, as the dependency on the specifications is reduced. Traditional manufacturing processes require extreme precision to minimize piston misalignment and friction-related wear. However, with the introduction of guide rings, these stringent tolerances can be 10 relaxed since the guide rings provide the necessary precision in guiding the piston. This not only simplifies the production process but also leads to significant cost savings in material procurement, machining, and quality control.
[0029] Since only the guide rings wear over time, they can be replaced without requiring a new piston or cylinder, resulting in reduced operational costs and downtime. In 15 conventional designs, when the piston or cylinder wears out, it necessitates an expensive replacement process. The proposed guide rings, however, act as sacrificial components that can be easily replaced at minimal cost, thereby extending the life of the main compressor components and significantly reducing long-term operational expenses. This feature also minimizes service interruptions and enhances overall efficiency. 20
[0030] The guide rings ensure smooth, precise piston movement, enhancing compressor performance and reliability by eliminating irregular friction-based obstructions. Without guide rings, any minor imperfections in the piston or cylinder could lead to jerky or uneven motion, causing inefficiencies and even potential damage over time. By maintaining uniform guidance along the piston’s movement path, guide rings ensure stable and 25 predictable motion. This stability is crucial for maintaining optimal compressor function, as any irregularities in piston movement could negatively impact the efficiency and effectiveness of the slide valve operation.
[0031] The hydraulic piston-cylinder arrangement consists of the following key components: 30
i. Hydraulic Cylinder (Unloader) houses the hydraulic piston and facilitates controlled movement through pressurized fluid actuation.
ii. Hydraulic Piston comprises of an unloader piston and unloader piston cover plate, featuring grooves for guide rings and hydraulic seals.
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iii. Guide Rings are mounted on the piston, in direct contact with the cylinder, 5 ensuring precise guidance and eliminating frictional wear. These rings are fabricated from self-lubricating materials to minimize frictional losses.
[0032] The hydraulic piston-cylinder arrangement controls compressor capacity by adjusting the slide valve. Guide rings facilitate smooth piston movement, prevent metal-to-metal contact, and reduce operational costs. The hydraulic cylinder receives pressure input, causing 10 the piston to move in a linear motion, which in turn adjusts the position of the slide valve. With the introduction of guide rings, this motion remains precisely controlled, reducing erratic movements and ensuring that the compressor’s performance remains within its intended parameters. The guide rings stabilize the piston movement and ensure that the hydraulic force applied translates into a smooth and efficient adjustment of the slide valve. 15 This controlled motion prevents sudden jolts or inconsistencies, thereby maintaining the integrity of the compression process and preventing unnecessary energy losses or mechanical stress on the system.
[0033] The integration of guide rings into the hydraulic piston-cylinder arrangement of a refrigeration screw compressor represents a significant advancement in compressor design. 20 Traditionally, refrigeration screw compressors rely on a hydraulic piston to adjust the slide valve, which controls the compressor’s capacity. In conventional systems, the piston moves within the cylinder with direct metal-to-metal contact, leading to wear, friction, and efficiency losses over time. The present invention overcomes these challenges by incorporating guide rings, which are mounted within grooves on the piston. These guide rings act as an 25 intermediary layer between the piston and the cylinder, ensuring smoother movement and reducing the adverse effects of direct contact.
[0034] The use of guide rings provides multiple benefits. First, they help in maintaining proper alignment of the piston as it moves within the cylinder, preventing undesired tilting or uneven movement that can result from minor imperfections in machining. By ensuring a stable and 30 controlled motion, the guide rings significantly enhance the precision of the slide valve operation, which directly impacts the compressor's efficiency and performance. Furthermore, these guide rings are made from low-friction, wear-resistant materials such as polytetrafluoroethylene (PTFE) or polymer composites, which allow for minimal resistance and improved energy efficiency during compressor operation. 35
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[0035] In addition, the integration of guide rings into the refrigeration screw compressor’s 5 hydraulic piston-cylinder arrangement contributes to reduced maintenance requirements. Since the guide rings serve as sacrificial components, they absorb wear over time instead of the piston or the cylinder. This means that rather than replacing expensive and difficult-to-manufacture components, only the guide rings need periodic replacement, significantly reducing downtime and maintenance costs. 10
[0036] In conventional refrigeration screw compressors, the hydraulic piston moves within the cylinder, adjusting the position of the slide valve to regulate the compression process. In traditional designs, this piston movement involves direct contact between the metal surfaces of the piston and the cylinder. Over time, continuous friction between these components leads to material wear, surface degradation, and an increase in clearance gaps, ultimately 15 affecting the compressor's performance. This wear not only necessitates frequent maintenance but also results in operational inefficiencies, increased downtime, and higher replacement costs.
[0037] The present invention eliminates direct piston-cylinder contact by introducing guide rings that serve as an intermediary interface between the moving piston and the stationary 20 cylinder wall. These guide rings, typically made from self-lubricating, wear-resistant materials such as PTFE (polytetrafluoroethylene) or specially formulated polymer composites, drastically reduce friction and mechanical wear. Since the guide rings bear the brunt of the operational stress instead of the piston or cylinder, the primary metal components remain intact, extending their lifespan and significantly reducing maintenance frequency. 25
[0038] By removing the metal-to-metal interaction, the invention minimizes the generation of metallic debris caused by wear, which is a common issue in traditional compressors. Such debris can contaminate the hydraulic fluid, causing further damage to internal components and reducing overall system efficiency. The use of guide rings ensures that wear is limited to a replaceable, cost-effective component, rather than critical parts of the compressor. 30
[0039] Another major advantage of eliminating direct contact between the piston and the cylinder is the reduction in maintenance complexity. In conventional compressors, once the piston or cylinder shows significant signs of wear, extensive repairs or complete component replacements are required. These repairs are costly, time-consuming, and often require a full shutdown of the compressor system. However, with the incorporation of guide rings, 35
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maintenance becomes a much simpler process. Instead of replacing an entire piston or 5 cylinder, only the guide rings need to be replaced periodically. This straightforward replacement procedure reduces downtime, lowers operational costs, and ensures that the compressor remains in optimal working condition with minimal interruptions.
[0040] Furthermore, the elimination of direct piston-cylinder contact also contributes to enhanced energy efficiency. In traditional designs, friction between the piston and cylinder 10 results in resistance to movement, which in turn requires additional energy to overcome. By significantly reducing friction through the use of guide rings, the hydraulic system operates more smoothly, allowing for efficient force transmission and precise motion control. This results in improved compressor efficiency, reduced power consumption, and overall better performance. 15
[0041] The incorporation of guide rings in the hydraulic piston-cylinder arrangement significantly enhances the reliability and precision of slide valve control in refrigeration screw compressors. In conventional designs, the movement of the piston within the cylinder is subject to inconsistencies due to minor surface imperfections, variations in tolerance, and gradual wear. These factors can lead to misalignment, erratic motion, and an overall 20 reduction in efficiency. The guide rings, however, ensure that the piston remains perfectly aligned throughout its stroke, eliminating these inconsistencies and allowing for smooth, controlled motion.
[0042] By maintaining precise guidance of the piston, the guide rings contribute to accurate and repeatable positioning of the slide valve. The slide valve is responsible for regulating the 25 compressor's capacity by varying the effective compression volume within the screw rotors. Any deviation or unintended variation in the piston’s motion can result in an incorrect positioning of the slide valve, leading to fluctuations in capacity control, inefficient energy usage, and potential mechanical stress on the compressor components. The guide rings eliminate such deviations, ensuring that the slide valve moves precisely as intended, thereby 30 optimizing compressor performance.
[0043] Reliability is another key aspect enhanced by the introduction of guide rings. Traditional piston-cylinder systems experience accelerated wear due to direct metal-to-metal contact, leading to frequent maintenance and possible failures over time. The guide rings act as a buffer, reducing friction between the moving piston and the stationary cylinder, thereby 35
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decreasing wear and extending the lifespan of the system. Since the guide rings are made 5 from self-lubricating materials, and, they further minimize resistance during piston movement, ensuring consistent and smooth operation over extended periods.
[0044] Furthermore, precision in slide valve movement translates into better energy efficiency. Inconsistent or imprecise movement of the slide valve can cause unnecessary energy consumption, as the compressor must work harder to compensate for deviations in 10 capacity control. With the guide rings ensuring a stable piston movement, the compressor operates more efficiently, consuming only the necessary amount of power to achieve the desired cooling effect. This results in lower operational costs, reduced strain on the system, and improved overall performance.
[0045] Applications of the guide are as follows: 15
1. They can be used in refrigeration screw compressors to improve piston guiding, reduce maintenance costs, and enhance efficiency.
2. They are applicable in any hydraulic piston-cylinder mechanism that requires improved wear resistance and precise movement control. , Claims:We Claim: 5
1.
A guide ring assisted hydraulic piston-cylinder arrangement, wherein
the hydraulic piston moves within the cylinder to control the compressor's capacity by adjusting the slide valve;
characterized in that
the hydraulic piston is integrated with guide rings mounted within grooves on the 10 piston.
2.
The guide ring assisted hydraulic piston-cylinder arrangement as claimed in claim 1, wherein the guide rings are positioned within grooves on the hydraulic piston, ensuring controlled linear motion.
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3.
The guide ring assisted hydraulic piston-cylinder arrangement as claimed in claim 1, wherein the guide rings prevent direct metal-to-metal contact between the piston and the cylinder.
4.
The guide ring assisted hydraulic piston-cylinder arrangement as claimed in claim 1, 20 wherein the hydraulic piston comprises an unloader piston and an unloader piston cover plate, both configured with grooves for securing the guide rings.
5.
The guide ring assisted hydraulic piston-cylinder arrangement as claimed in claim 1, wherein the guide rings provide uniform radial support to the piston, reducing 25 mechanical misalignment and ensuring smooth operation.
6.
The guide ring assisted hydraulic piston-cylinder arrangement as claimed in claim 1, wherein the guide rings allow for relaxed geometric dimensioning and tolerance (GD&T) requirements in manufacturing the piston and cylinder. 30
7.
The guide ring assisted hydraulic piston-cylinder arrangement as claimed in claim 1, wherein the guide rings enable stable and controlled slide valve movement, optimizing compressor capacity regulation.
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8.
The guide ring assisted hydraulic piston-cylinder arrangement as claimed in claim 1, wherein the guide rings are replaceable, allowing for easy maintenance without the need for piston or cylinder replacement.