US20190076929A1

US20190076929A1 - A seal for barrel shaped cylinder

Info

Publication number: US20190076929A1
Application number: US16/084,559
Authority: US
Inventors: Stanley Moon Kai Ko; Kyong Tae Chang
Original assignee: Neo Mechanics Ltd
Current assignee: Neo Mechanics Ltd
Priority date: 2016-03-15
Filing date: 2017-03-15
Publication date: 2019-03-14
Also published as: WO2017157309A1; CN109312862A; CN109312862B

Abstract

A helical coiled seal for sealing a barrel-shaped cylinder piston-cylinder assembly, comprising: a piston-sealing C-shaped ring; a connecting C-shaped ring comprising an inward wing protruded inwardly from a section near a first end on an inner perimeter of the connecting C-shaped ring, and an outward wing protruded outwardly from a section near a second end on an outer perimeter of the connecting C-shaped ring; and a cylinder-sealing C-ring; wherein the piston-sealing C-ring is connected end-to-end to the first end of the connecting C-ring and cylinder-sealing C-ring is connected end-to-end to the second end of the connecting C-ring forming a three-ring helical structure having a contraction-dilation response time sufficiently short required for the up-down stroke speed of the cylinder piston-cylinder assembly.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority under the Paris Convention to the U.S. Provisional Application No. 62/308,239 filed Mar. 15, 2016; the disclosure of which is incorporated herein by reference in its entirety. This application is related to the Korea Patent Application No. 10-2006-0031762, filed Apr. 7, 2006; the disclosure of which is incorporated herein by reference in its entirety. This application is also related to the PCT International Application No. PCT/CN2012/071634 filed Feb. 24, 2012; the disclosure of which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The presently claimed invention relates generally to piston technology and more specifically relates to the piston-cylinder sealing mechanisms.

BACKGROUND

The piston is a component of reciprocating internal combustion engines, reciprocating pumps, gas compressors, pneumatic cylinders, and other similar mechanical devices. The piston is the moving component that is contained by a cylinder and is made gas or fluid tight by piston rings.
The piston rings are installed around the piston and are traditionally rubber O-rings. FIG. 1 shows the cross-sectional view of an exemplary embodiment of a piston-cylinder assembly with conventional multi-rubber O-rings seal applied on the piston. In order to achieve the effective sealing of the cylinder by rubber O-rings, the rubber O-rings must maintain a certain range of elasticity. The elasticity of rubber O-ring is essential characteristic in performing the sealing function. However, at temperature below −50° C., the rubber molecules are frozen and the elasticity of rubber O-ring is lost. At temperature above +250° C., the rubber molecules carburize and the elasticity is lost as well. Therefore, the rubber O-rings typically are designed to operate under the ambient temperature range of between −50° C. and +250° C.
The use of rubber O-rings also limits the maximum internal pressure of the cylinder. When exposed to an internal pressure at above 450 kg/cm²the rubber is squeezed out of gap between the cylinder wall and the piston. Therefore, the rubber O-ring sealed piston-cylinders typically are designed to operate with an internal pressure of no more than 450 kg/cm².
One existing technique to overcome the temperature and pressure limitation is to use a multiple piston rings design. In such design, while a sealing ring is providing the sealing function, one or more assistant rings are installed around the piston for withstanding high internal pressure of the cylinder. The sealing ring is also being complemented by a wear ring made of i.e. hard polymer such as glass fiber reinforced phenol resin for prolonging its operational lifespan. Hard polymer rings may also be employed for lessening the friction between the rings and the cylinder wall. In total, there can be as many as sixteen piston rings of different functions, resulting in a complex mechanical structure, requiring costly and complicated manufacturing process. The use of multiple piston rings for sealing also creates tremendous friction regardless of material use during high-speed reciprocation of the piston in the cylinder, which causes loss of power, excessive scratching of the cylinder interior wall, and shorter lifespan of cylinder.
Most modern internal combustion reciprocating engines are designed to have slightly barrel shaped cylinders. It is because the piston can severely scratch on the cylinder wall during the up-down strokes, especially when the piston is positioned near the upper end or lower end of the cylinder at the transitions of the up and down strokes. The scratching is relatively less in between the upper and lower end. To compensate the difference in severity of the scratching, and hence the different rate of erosion of the cylinder wall as a consequence, the cylinder is made such that its cross-sectional interior diameters are progressively smaller toward the upper end and lower end from the middle part of the cylinder, resembling the shape of a barrel. In this case, the piston rings installed around the piston must be designed to be open ended so that it can contract when the piston is travelling towards either end of the cylinder and dilate or expand when the piston is travelling through the middle section of cylinder.
Furthermore, a piston ring only seals the cylinder interior wall but never the piston. Leaks take place from around the piston crown area. In an internal combustion engine, this allows fuel and lube oil to mix up with each other inside the crankshaft case, causing undesirable blow-by.

SUMMARY

It is an objective of the present invention to provide a piston-cylinder sealing method and apparatus using a dynamic sealing apparatus such that the aforementioned performance and manufacturing deficiencies can be eliminated. It is a further objective of the presently claimed invention to provide the dynamic sealing apparatus using helical coiled seal rings applicable in barrel-shaped cylinders.
In accordance to various embodiments of the present invention, pistons and piston rods of cylinders are fitted with helical coiled seal rings. The resulting piston-cylinder mechanical device has a simpler structure, lesser number of components without the numerous piston rings, improved durability and higher performance with extreme temperature tolerance, enhanced internal pressure capacity, reduced power loss due to reduced piston-cylinder friction, and significantly reduced leakage.
In accordance to one aspect of the present invention, the helical coiled seal rings seal the piston and the cylinder at all time during the entire up-down stroke cycle. For a regular cylindrical shaped cylinder,

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in more detail hereinafter with reference to the drawings, in which:

FIG. 1 shows the cross-sectional view of an exemplary embodiment of a piston-cylinder assembly with conventional multi-rubber O-rings seal applied on the piston;

FIG. 2 shows the cross-sectional view of one embedment of a piston-cylinder assembly with helical coiled seal applied on the piston;

FIG. 3 shows the individual C-shaped rings of a helical coil seal in accordance to one embodiment of the present invention;

FIG. 4 shows the helical coil seal used in a piston-cylinder assembly;

FIG. 5 shows the individual C-shaped rings of an improved helical coil seal in accordance to one embodiment of the present invention;

FIG. 6 illustrates the construction of the improved helical coil seal from the individual C-shaped rings; and

FIG. 7 shows the top, side, and bottom views of the improved helical coil seal during construction.

DETAILED DESCRIPTION

In the following description, methods and apparatuses of piston-cylinder sealing using helical coiled seals are set forth as preferred examples. It will be apparent to those skilled in the art that modifications, including additions and/or substitutions may be made without departing from the scope and spirit of the invention. Specific details may be omitted so as not to obscure the invention; however, the disclosure is written to enable one skilled in the art to practice the teachings herein without undue experimentation.
Referring to FIGS. 1 and 2. The piston-cylinder assembly employs only one piston-block-sealing helical coiled seal 08 fitted on or tightly encircling radially the piston block 06 in place of as many as eleven different functioning piston rings in the prior art. On the piston rod seal block 04 installed is a single helical coiled seal 12, instead of as many as five different functioning piston rings in the prior art, for the sealing of the piston rod 05 in the cylinder. As the piston-block-sealing helical coiled seal 08 is mounted on piston block 06, the compression spring 09, that is withheld and protruded from the spring holes on the compression ring 07, provides the pressing force on the piston-block-sealing helical coiled seal 08 to keep the source rings of the helical coiled seal intimately contacting the cylinder wall. The tight contact between the helical coiled seal and the cylinder wall reduces leakage close to zero if not absolute zero.
The sealing between the piston block 06 and the piston rod 05 is provided by the rubber O-rings 20. Bolts 10 hold the piston block 06 and compression ring 07 together and the rod nut 11 secures the piston block 06 and the compression ring 07 at the in-cylinder end of the piston rod 05.
The link end 02 of the cylinder 01 is fastened to the cylinder by tie bolts 17. The tie end 03 of the piston rod 05 is fastened to the piston rod 05 by screw threads 15 on both the tie end 03 and the exposed end of the piston rod 05.
The piston rod seal block 04 is fastened to the interior wall of the cylinder 01 by tie bolts 16. The piston rod 05 is placed within the center opening of the piston rod seal block 04. The piston-rod-sealing helical coiled seal 12 is installed around the inward facing side of the center opening of the piston rod seal block 04. The compression spring 14, that is withheld and protruded from the spring holes on the compression ring 13, provides the pressing force on the piston-rod-sealing helical coiled seal 12 to keep the source rings of the helical coiled seal intimately contacting the cylinder wall. The tight contact between the helical coiled seal and the piston rod surface reduces leakage close to zero if not absolute zero.
Referring to FIGS. 3 and 4. The aforesaid helical coiled seal is made of a number of C-shaped (or partial circular) rings connected end-to-end with each other to form a helical coil structure. In one embodiment, the C-shaped rings are connected end-to-end using dovetail connections with welding.
For sealing a piston-cylinder assembly, three groups of C-shaped rings are used in forming the helical coiled seal. One group of C-shaped rings is for sealing the piston (piston sealing section 401). The inner diameter of the piston sealing section rings is slightly smaller than piston diameter so that they encircle tightly around the piston surface and seal it, whilst their outer diameter is sharing the same outer diameter of the connecting section rings, which is smaller than the cylinder inner diameter such that they never touch the cylinder surface.
The second group of C-shaped rings is for connecting the piston sealing section rings and the cylinder sealing section rings in between (connecting section rings 402). These connecting section rings have inner diameter bigger than the piston so they never touch the piston surface, whilst their outer diameter is smaller than the cylinder inner diameter so they also never touch the cylinder interior wall. Because these connecting section rings are suspended from the piston surface and the cylinder interior wall, they also function as a vibration absorption layer.
The third group of C-shaped rings is for sealing the cylinder interior wall (cylinder sealing section 403). These cylinder sealing section rings have outer diameter is slightly bigger than the cylinder inner diameter so that they push against the cylinder interior wall from all directions to seal it, whilst its inner diameter is sharing the same inner diameter of the connecting section rings, which is bigger than the piston diameter that they never touch the piston surface.
Because each C-shaped ring is only a partial circle. In order to provide effective sealing function (380 degree contact with the sealing surface), a minimum of two C-shaped rings are needed in the piston sealing section and a minimum number of two C-shaped rings are needed in the cylinder sealing section. With at least one C-shaped ring for the connecting section, a complete helical coiled seal for sealing a piston-cylinder assembly has at least five C-shaped rings.
The connecting section of the helical coil seal allows big tolerance of misalignments in the piston-cylinder assembly because the rings in this section are movable in the latitudinal directions, swinging around to absorb vibrations and lateral movements caused by the misalignments between the piston and the cylinder under high speed up-down stroke motion. As such, the presence of the connecting section in the helical coil spring seal also reduces the unwanted torque due to misalignment among the centers of a piston pin, of a crank pin and of a crankshaft.
The diameter differences between the sealing rings and the respective piston surface and cylinder interior wall contacting parts are small. The lateral force exerting on the sealing contact is mild, though continuous, thus generating negligible friction on the sealing contact surface. This in turn reduces scratching and erosion on the cylinder interior wall.
If the helical coil seal is widened laterally, the straps at both ends will be shortened to compensate for the change of diameter of the helical structure. Vice versa, if the helical coil seal is squeezed laterally, the straps at both ends will elongate. This design provides high flexibility and minimizes the lateral force exerting on the sealing contact surface. With the help of lubricant oil, the coil spring seal moves smoothly along the cylinder interior wall surface. Scratching on the cylinder interior wall is reduced to a minimum.
In one embodiment, the helical coil seal is made of copper, phosphor bronze, or other alloys with high heat transfer characteristics. This helps cool down the piston by transferring the immense heat from fuel explosion in the combustion chamber to the engine body.
The multiple coil rings in each sealing layer of the helical coil seal assure perfect sealing performance. For example, on the piston surface, each ring in the piston sealing section seals one full 360 degree around the sealing contact surface. If a leak occurs, the immediate neighboring ring that is sealing the sealing contact surface stops the leak. And if there is still a leak, the second neighboring ring that is sealing the sealing contact surface further stops the leak, and so on. This eliminates the seepage problem inherited in the use of piston ring. A fully sealed piston-cylinder assembly can completely separate the fuel from lubricant oil, thus no lubricant oil will seep into the combustion chamber to contaminate pure fuel. The fully sealed piston-cylinder assembly stops unburned fuel and exhaust from escaping into the crankshaft case, so it is not necessary to treat blow-by and there will not be smoke generated in the exhaust. The result is a cleaner engine with more efficient power output.
Turning to the barrel-shaped cylinder. Piston rings installed around the piston must be designed to be open ended so that it can contract when the piston is travelling towards the narrower top and bottom ends of the cylinder and dilate or expand when the piston is travelling through the wider middle section of cylinder. As such, a helical coiled seal in place of the piston rings applied to a barrel-shaped cylinder piston-cylinder assembly must also contract and dilate during the up-down stroke cycle of the piston in barrel-shaped cylinder.
However, due to the helical coil structure, which comprises many C-shaped ring layers, the substantial time needed for its structural contraction and dilation is problematic in a barrel-shaped cylinder piston-cylinder assembly. It is because the structural contraction and dilation must be distributed evenly among the many layers of the seal, and the high RPM of today's internal combustion engines allows only very small time for helical coiled seal to respond. The radial tension of a many-layered helical coiled seal is causing too slow dilation in the cylinder sealing section rings to allow the full contact with the cylinder interior wall during piston travel in the middle part of the barrel shaped cylinder. As such, serious leaks occur.
To increase the contraction-dilation response time of the helical coil seal, less number of ring layers must be used. One embodiment is to use only one ring in the cylinder sealing section and one ring in the piston sealing section of the helical coil seal. However, because each ring is only partial circular, a helical coil structure made of only three C-shaped rings would have gaps on its sealing contact (less than 380 degree contact with the sealing surface), defeating its sealing function.
In accordance to one embodiment the present invention, an improved helical coil seal is provided. The improved helical coil seal comprises an improved C-shaped ring for its connecting section (improved connecting C-shaped ring). Referring to FIGS. 5 and 6. At one end of the improved connecting C-shaped ring that is to be connected to a piston sealing C-shaped ring, an inward wing 501 extending horizontally from the inner perimeter is made. The amount of extension (or width) of the inward wing 501 from the improved connecting C-shaped ring's inner perimeter is such that when the piston sealing C-shaped ring is connected to the improved connecting C-shaped ring, the inner perimeter of the inward wing 501 is aligned with the inner perimeter of the piston sealing C-shaped ring. The length of the inward wing 501 is made longer than the gap (or opening) distance of the piston sealing C-shaped ring. As such, once the piston sealing C-shaped ring is connected with the improved connecting C-shaped ring, the inward wing 501 becomes part of the piston sealing section. Along with the piston sealing C-shaped ring, the piston sealing section is able to embrace the piston surface for equal or more than 360 degree, completely sealing the piston surface.
At the other end of improved connecting C-shaped ring is an outward wing 502. The amount of extension (or width) of the outward wing 502 from the improved connecting C-shaped ring's outer perimeter is such that when the cylinder sealing C-shaped ring is connected to the improved connecting C-shaped ring, the outer perimeter of the outward wing 502 is aligned with the outer perimeter of the cylinder sealing C-shaped ring. The length of the outward wing 502 is made longer than the gap (or opening) distance of the cylinder sealing C-shaped ring. As such, once the cylinder sealing C-shaped ring is connected with the improved connecting C-shaped ring, the outward wing 502 becomes part of the cylinder sealing section. Along with the cylinder sealing C-shaped ring, the cylinder sealing section is able to push or contact the cylinder interior wall for equal or more than 360 degree, completely sealing the cylinder interior wall.
With only three C-shaped rings making up the improved helical coil seal, suitable vertical compression must be applied to the helical coil structure to make sure that all rings are in close contact with each other. This is necessary to avoid leaks from between the ring layers of the helical coil seal. The vertical compression force can be provided by springs installed in the retaining
The foregoing description of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations will be apparent to the practitioner skilled in the art.
The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications that are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalence.

Claims

What is claimed is:

1. A helical coiled seal for sealing a piston-cylinder assembly, comprising:

a piston-sealing C-shaped ring having a first gap;

a connecting C-shaped ring comprising:

an inward wing protruded inwardly from a section on an inner perimeter of the connecting C-shaped ring near a first end of the connecting C-shaped ring; and

an outward wing protruded outwardly from a section on an outer perimeter of the connecting C-shaped ring near a second end of the connecting C-shaped ring; and

a cylinder-sealing C-shaped ring having a second gap;

wherein the piston-sealing C-shaped ring is connected end-to-end to the first end of the connecting C-shaped ring and cylinder-sealing C-shaped ring is connected end-to-end to the second end of the connecting C-shaped ring forming a helical coil;

wherein the inward wing width allows the inward wing inner perimeter to align with the piston-sealing C-shaped ring inner perimeter;

wherein the outward wing width allows the outward wing outer perimeter to align with the cylinder-sealing C-shaped ring outer perimeter.

wherein the inward wing length is equal or longer than the first gap such that the piston-sealing C-shaped ring with the inward wing form an at least 360 degree piston surface sealing contact; and

wherein the outward wing length is equal or longer than the second gap such that the piston-sealing C-shaped ring with the outward wing form an at least 360 degree cylinder interior wall sealing contact.

2. The helical coiled seal of claim 1, wherein the helical coiled seal is made of copper, phosphor bronze, or other alloys with high heat transfer characteristics.

3. A piston-cylinder assembly, comprising:

a cylinder having an interior wall; and

a piston that is disposed inside the cylinder;

wherein the piston being tightly encircled radially by one or more rings of the helical coiled seal of claim 1; and

wherein the cylinder being intimately contacted by one or more rings of the helical coiled seal of claim 1 providing sealing function to the piston-cylinder assembly.