Sealing ring assembly configured for pressure locking

Abstract

To provide sealing ring assemblies configured for pressure locking.SOLUTION: A sealing ring (200) includes a first sealing element (220) having a first mating surface and a second sealing element (230) having a second mating surface. A high-pressure boundary (250) extends across at least a portion of the first sealing element and across at least a portion of the second sealing element, and a low-pressure boundary (252) extends across at least a portion of the first sealing element and across at least a portion of the second sealing element. The first mating surface, the second mating surface, or both, includes a recess (221) open to the low-pressure boundary and not open to the high-pressure boundary. The recess may include a groove (223), for example. The first mating surface is sealed against the second mating surface by a first force (290) acting on the first sealing element and a second force (291) acting on the second sealing element. These forces act to pressure-lock the assembly.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] This disclosure is directed to a seal ring assembly, and more particularly, to a seal ring assembly including a pressure locking feature. This application claims the benefit of U.S. Provisional Patent Application No. 62 / 543,302, filed Aug. 9, 2017, and No. 62 / 543,299, filed Aug. 9, 2017, the disclosures of which are incorporated herein by reference in their entireties. [Background technology]

[0002] For economic reasons, it is desirable for the seals of a piston-cylinder assembly to function for as long as possible before requiring replacement. For example, a typical target may be hundreds or thousands of hours of operation. During these operating hours, the seals wear radially and gaps may develop between portions of the seal. The resulting total circumferential arc length of the gap opens by 2×π×ΔR, where ΔR is the amount of radial wear of the seal. For self-lubricating materials with relatively high wear rates, the gap opens to an amount that results in unacceptable leakage flow, thus limiting the useful operating life of the seal. It would therefore be desirable for the seal to maintain performance throughout its life. The surfaces of the seal may be exposed to a wide range of pressures and contact forces. Summary of the Invention [Means for solving the problem]

[0003] In some embodiments, the present disclosure is directed to a seal ring assembly. The seal ring assembly includes a first seal element having a first mating surface. The seal ring assembly also includes a second seal element having a second mating surface. The seal ring assembly also includes a high pressure boundary extending across at least a portion of the first seal element and across at least a portion of the second seal element. The seal ring assembly also includes a low pressure boundary extending across at least a portion of the first seal element and across at least a portion of the second seal element. At least one of the first mating surface and the second mating surface includes a recess that is open to the low pressure boundary and not open to the high pressure boundary such that the first mating surface is sealed against the second mating surface by a first force acting on the first seal element and a second force acting on the second seal element.

[0004] In some embodiments, a first force acting on the first seal element is directed opposite a second force acting on the second seal element.

[0005] In some embodiments, the recess is configured to cause the first and second forces to maintain the relative positions of the first and second seal elements.

[0006] In some embodiments, the first mating surface is sealed to the second mating surface in at least one of the radial, axial, and azimuthal directions. For example, the first and second surfaces may be flat, angled, curved, compound, or combinations thereof, and may seal to one another in one or more directions across all or a portion of the interface.

[0007] In some embodiments, the seal ring assembly includes a rear axial surface configured to seal against a land of the piston, hi some embodiments, the seal ring assembly includes a radially outer surface configured to seal against a bore of the cylinder between a high pressure boundary and a low pressure boundary.

[0008] In some embodiments, the recess comprises a groove.

[0009] In some embodiments, the recess is a first recess in the first mating surface and the second mating surface includes a second recess configured in interfacing contact with the first recess.

[0010] In some embodiments, the first seal element includes a first ring segment and the second seal element includes a second ring segment.

[0011] In some embodiments, the first seal element includes a ring segment and the second seal element includes a gap cover element.

[0012] In some embodiments, at least one of the first and second seal elements includes a radial pressure balancing feature configured to induce a radially inward force, for example, in some embodiments, the radially inward force reduces wear on the seal ring assembly.

[0013] In some embodiments, the first and second mating surfaces seal against one another to prevent the recess from opening to the high pressure boundary.

[0014] In some embodiments, the present disclosure is directed to a piston assembly including a piston and a seal ring assembly. The piston includes a circumferential groove, and the piston is configured to move axially within a bore of a cylinder. The seal ring assembly is disposed within the circumferential groove and configured to seal against the bore. The seal ring assembly includes a first seal element having a first mating surface and a second seal element having a second mating surface. The seal ring assembly also includes a high pressure boundary extending across at least a portion of the first seal element and across at least a portion of the second seal element, and a low pressure boundary extending across at least a portion of the first seal element and across at least a portion of the second seal element. At least one of the first mating surface and the second mating surface includes a recess that is open to the low pressure boundary and not open to the high pressure boundary such that the first mating surface is sealed against the second mating surface by a first force acting on the first sealing element and a second force acting on the second sealing element.

[0015] In some embodiments, the present disclosure is directed to a device including a cylinder, a piston, and a seal ring assembly. The cylinder includes a bore having a high pressure region and a low pressure region. The piston includes a circumferential groove, the piston configured to move axially within the bore. The seal ring assembly is disposed within the circumferential groove and configured to seal against the bore and define a high pressure region and a low pressure region. The seal ring assembly includes a first seal element having a first mating surface and a second seal element having a second mating surface. At least one of the first and second mating surfaces includes a recess that is open to the low pressure region and not open to the high pressure region such that the first mating surface is sealed against the second mating surface by a first force acting on the first seal element and a second force acting on the second seal element.

[0016] In some embodiments, the circumferential groove includes an axially rear land, and the seal ring assembly is configured to seal against the axially rear land.

[0017] In some embodiments, a first force acting on the first seal element is directed opposite a second force acting on the second seal element.

[0018] In some embodiments, the recess is configured to cause the first and second forces to maintain the relative positions of the first and second seal elements.

[0019] In some embodiments, the seal ring assembly includes a radially outer surface configured to seal against the bore.

[0020] In some embodiments, the seal ring assembly includes a first boundary extending across at least a portion of the first seal element and at least a portion of the second seal element and opening to the high pressure region, in some embodiments, the seal ring assembly also includes a second boundary extending across at least a portion of the first seal element and at least a portion of the second seal element and opening to the low pressure region, the recess opening to the first boundary and not opening to the second boundary.

[0021] In some embodiments, the present disclosure is directed to a seal ring assembly including a first ring and a second ring. The first ring includes an axially aft extending extension including a radially outwardly facing surface. The second ring includes an inner radial surface configured to interface with the radially outwardly facing surface. The seal ring assembly also includes a groove extending circumferentially along at least one of the radially outwardly facing surface of the extension and the inner radial surface of the second ring. For example, the groove may be included in either or both of the first ring and the second ring.

[0022] In some embodiments, the groove is configured to open to a low pressure boundary of the seal ring assembly.

[0023] In some embodiments, the second ring includes a circumferentially extending pocket in an outermost radial surface of the second ring, the pocket configured to receive high pressure gas, e.g., the outermost radial surface configured to seal against the bore of the cylinder.

[0024] In some embodiments, the second ring includes an orifice configured to allow gas to flow from the high pressure boundary to the pocket, for example, in some embodiments, the second ring includes an orifice, slot, or other through feature.

[0025] In some embodiments, the seal ring assembly is configured to be disposed in a ring groove of the piston, the seal ring assembly including an anti-rotation feature to prevent substantial azimuthal movement of the seal ring assembly.

[0026] In some embodiments, the first ring includes an outermost radial surface and the outer radial surface of the extension is radially inward of the outer radial surface, e.g., the outermost radial surface is configured to seal against the bore of the cylinder.

[0027] In some embodiments, at least one of the first ring and the second ring comprises a self-lubricating material. For example, the first ring, the second ring, or both may comprise graphite or other ceramic, a polymer, or a combination thereof.

[0028] In some embodiments, the seal ring assembly is configured for operation without a liquid lubricant, for example, in some embodiments, the seal ring assembly is configured for oil-less operation.

[0029] In some embodiments, the first ring includes at least two first ring segments arranged such that ends of each of the at least two first ring segments form at least one interface between one another.

[0030] In some embodiments, the second ring comprises at least two second ring segments arranged such that ends of each of the at least two second ring segments form at least one interface between each other.

[0031] In some embodiments, the present disclosure is directed to a piston assembly including a piston and a seal ring assembly. The piston includes a ring groove. The seal ring assembly is disposed within the ring groove and includes a first ring and a second ring. The first ring includes an axially aft extending extension including a radially outward facing surface. The second ring includes a radially inner surface configured to interface with the radially outward facing surface of the extension. The seal ring assembly includes a groove extending azimuthally along at least one of the radially outer surface of the extension and the inner radial surface of the second ring.

[0032] In some embodiments, the piston is an open piston.

[0033] In some embodiments, the present disclosure is directed to a device including a cylinder, a piston, and a seal ring assembly. The cylinder includes a bore. The piston includes a ring groove and is configured to travel within the bore along an axis of the bore. The seal ring assembly is disposed within the ring groove and includes a first ring and a second ring. The first ring includes an axially rearwardly extending extension including a radially outwardly facing surface. The second ring includes an inner radial surface configured to interface with the radially outwardly facing surface. The seal ring assembly also includes a groove extending azimuthally along at least one of the radially outer surface of the extension and the inner radial surface of the second ring.

[0034] In some embodiments, the seal ring assembly is configured to seal between the bore and the piston, for example, the seal ring assembly is configured to seal a region of high pressure in the bore from a region of low pressure in the bore. The present invention provides, for example, the following: (Item 1) 1. A seal ring assembly, comprising: a first seal element having a first mating surface; a second seal element having a second mating surface; and a high pressure boundary extending across at least a portion of the first seal element and across at least a portion of the second seal element; a low pressure boundary extending across at least a portion of the first seal element and across at least a portion of the second seal element; Equipped with a seal ring assembly, wherein at least one of the first mating surface and the second mating surface includes a recess that is open to the low pressure boundary and not open to the high pressure boundary, whereby the first mating surface is configured to be sealed against the second mating surface by a first force acting on the first seal element and a second force acting on the second seal element. (Item 2) 2. The seal ring assembly of claim 1, wherein the first force acting on the first seal element is directed opposite the second force acting on the second seal element. (Item 3) 2. The seal ring assembly of claim 1, wherein the recess is configured to cause first and second forces to maintain a relative position of the first seal element and the second seal element. (Item 4) Item 2. The seal ring assembly of item 1, wherein the first mating surface is sealed against the second mating surface in at least one of a radial, axial, and azimuthal direction. (Item 5) a rear axial surface configured to seal against a land of the piston; a radially outer surface configured to seal against a bore of a cylinder between said high pressure boundary and said low pressure boundary; Item 2. The seal ring assembly of item 1, further comprising: (Item 6) Item 2. The seal ring assembly of item 1, wherein the recess comprises a groove. (Item 7) Item 2. The seal ring assembly of item 1, wherein the recess is a first recess in the first mating surface, and the second mating surface comprises a second recess configured in interfacing contact with the first recess. (Item 8) Item 2. The seal ring assembly of item 1, wherein the first seal element comprises a first ring segment and the second seal element comprises a second ring segment. (Item 9) Item 2. The seal ring assembly of item 1, wherein the first seal element comprises a ring segment and the second seal element comprises a gap cover element. (Item 10) Item 2. The seal ring assembly of item 1, wherein at least one of the first and second seal elements includes a radial pressure balancing feature configured to induce a radially inward force. (Item 11) Item 2. The seal ring assembly of item 1, wherein the first and second mating surfaces seal against one another to prevent the recess from opening to the high pressure boundary. (Item 12) A piston assembly comprising: a piston having a circumferential groove; a seal ring assembly disposed within the circumferential groove; Equipped with The seal ring assembly includes: a first seal element having a first mating surface; a second seal element having a second mating surface; and a high pressure boundary extending across at least a portion of the first seal element and across at least a portion of the second seal element; a low pressure boundary extending across at least a portion of the first seal element and across at least a portion of the second seal element; Equipped with At least one of the first mating surface and the second mating surface includes a recess that is open to the low pressure boundary and not open to the high pressure boundary, whereby the first mating surface is sealed against the second mating surface by a first force acting on the first sealing element and a second force acting on the second sealing element. Piston assembly. (Item 13) Item 13. The piston assembly of item 12, wherein the first force acting on the first sealing element is directed opposite the second force acting on the second sealing element. (Item 14) Item 13. The piston assembly of item 12, wherein the recess is configured to cause the first and second forces to maintain a relative position of the first seal element and the second seal element. (Item 15) The piston further comprises a land and is configured to move within the bore of the cylinder, and the seal ring assembly comprises: a rear axial surface configured to seal against said land; a radially outer surface configured to seal against the bore between the high pressure boundary and the low pressure boundary; Item 13. The piston assembly of item 12, further comprising: (Item 16) Item 13. The piston assembly of item 12, wherein the recess comprises a groove. (Item 17) Item 13. The piston assembly of item 12, wherein the recess is a first recess in the first mating surface, and the second mating surface comprises a second recess configured to interface with the first recess. (Item 18) Item 13. The piston assembly of item 12, wherein the first seal element comprises a first ring segment and the second seal element comprises a second ring segment. (Item 19) Item 13. The piston assembly of item 12, wherein the first seal element comprises a ring segment and the second seal element comprises a gap cover element. (Item 20) Item 13. The piston assembly of item 12, wherein at least one of the first and second sealing elements includes a radial pressure balancing feature configured to induce a radially inward force. (Item 21) Item 13. The piston assembly of item 12, wherein the first and second mating surfaces seal against one another to prevent the recess from opening to the high pressure boundary. (Item 22) A device, the device comprising: a cylinder having a bore with a high pressure region and a low pressure region; a piston including a circumferential groove, the piston configured for axial movement within the bore; a seal ring assembly disposed within the circumferential groove; Equipped with The seal ring assembly is configured to seal against the bore and define the high pressure region and the low pressure region, the seal ring assembly comprising: a first seal element having a first mating surface; a second sealing element having a second mating surface; and Equipped with At least one of the first and second mating surfaces includes a recess that is open to the low pressure region and not open to the high pressure region, whereby the first mating surface is sealed against the second mating surface by a first force acting on the first sealing element and a second force acting on the second sealing element. (Item 23) the circumferential groove further comprises an axial rear land; Item 23. The device of item 22, wherein the seal ring assembly is further configured to seal against the axial rear land. (Item 24) 23. The device of claim 22, wherein the first force acting on the first sealing element is directed opposite the second force acting on the second sealing element. (Item 25) Item 23. The device of item 22, wherein the recess is configured to cause the first and second forces to maintain a relative position of the first seal element and the second seal element. (Item 26) Item 23. The device of item 22, wherein the seal ring assembly further includes a radially outer surface configured to seal against the bore. (Item 27) The sealing assembly includes: a first boundary extending across at least a portion of the first seal element and at least a portion of the second seal element and opening to the high pressure region; a second boundary extending across at least a portion of the first seal element and across at least a portion of the second seal element and opening to the low pressure region; Further equipped with Item 23. The device of item 22, wherein the recess is open to the first boundary and not open to the second boundary. (Item 28) 23. The device of claim 22, wherein the first seal element comprises a first ring segment and the second seal element comprises a second ring segment. (Item 29) Item 23. The device of item 22, wherein the first seal element comprises a ring segment and the second seal element comprises a gap cover element. (Item 30) Item 23. The device of item 22, wherein the first and second mating surfaces are configured to seal against one another to prevent the recess from opening to the high pressure region. [Brief description of the drawings]

[0035] The present disclosure according to one or more various embodiments will be described in detail with reference to the following figures. The drawings are provided for illustrative purposes only and merely depict typical or exemplary embodiments. These drawings are provided to facilitate understanding of the concepts disclosed herein and are not to be considered as limiting the scope, scope, or applicability of these concepts. Please note that for clarity and ease of illustration, these drawings are not necessarily made to scale.

[0036] [Figure 1] FIG. 1 shows a cross-sectional view of an illustrative piston and cylinder assembly according to some embodiments of the present disclosure.

[0037] [Diagram 2] FIG. 2 shows a cross-sectional view of an illustrative piston and cylinder assembly with a seal ring assembly exposed to pressure according to some embodiments of the present disclosure.

[0038] [Diagram 3] FIG. 3 shows a cross-sectional view of an illustrative seal ring assembly being subjected to a force according to some embodiments of the present disclosure.

[0039] [Figure 4] FIG. 4 shows a cross-sectional view of an illustrative seal ring assembly being subjected to a force according to some embodiments of the present disclosure.

[0040] [Diagram 5] FIG. 5 shows a cross-sectional view of a portion of an illustrative seal ring assembly subjected to pressure and contact forces according to some embodiments of the present disclosure.

[0041] [Figure 6] FIG. 6 shows a cross-sectional exploded view of a portion of an illustrative seal ring assembly being subjected to a force according to some embodiments of the present disclosure.

[0042] [Figure 7] FIG. 7 shows a cross-sectional exploded view of a portion of an illustrative seal ring assembly being subjected to a force according to some embodiments of the present disclosure.

[0043] [Figure 8] FIG. 8 shows a cross-sectional view of an illustrative piston and cylinder assembly with a seal ring assembly exposed to pressure according to some embodiments of the present disclosure.

[0044] [Figure 9] FIG. 9 shows a cross-sectional exploded view of an illustrative seal ring assembly being subjected to a force according to some embodiments of the present disclosure.

[0045] [Figure 10] FIG. 10 shows a cross-sectional exploded view of an illustrative seal ring assembly being subjected to a force according to some embodiments of the present disclosure.

[0046] [Figure 11] FIG. 11 shows an exploded perspective view of a portion of an illustrative seal ring assembly according to some embodiments of the present disclosure.

[0047] [Figure 12] FIG. 12 shows a perspective view of the illustrative seal ring assembly of FIG. 11 according to some embodiments of the present disclosure.

[0048] [Figure 13] FIG. 13 shows a cross-sectional view of an illustrative seal ring assembly including features for pressure locking according to some embodiments of the present disclosure.

[0049] [Figure 14]FIG. 14 illustrates a cross-sectional view of the illustrative seal ring assembly of FIG. 13 showing the aft ring gap according to some embodiments of the present disclosure.

[0050] [Figure 15] FIG. 15 shows a perspective view of a portion of an illustrative seal ring assembly including features for balancing radial forces according to some embodiments of the present disclosure.

[0051] [Figure 16] FIG. 16 shows a perspective view of a portion of the illustrative seal ring assembly of FIG. 10A including features for balancing radial forces according to some embodiments of the present disclosure.

[0052] [Figure 17] FIG. 17 shows a rear face view of an illustrative seal ring assembly according to some embodiments of the present disclosure.

[0053] [Figure 18] FIG. 18 shows a cross-sectional view of an illustrative engine including two piston assemblies, each including a seal ring assembly, according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] In some embodiments, the present disclosure is directed to a seal ring assembly configured to separate a relatively higher pressure region from a relatively lower pressure region. The seal ring assembly may include seal elements, such as, for example, one or more rings, one or more segments thereof, one or more gap covers, any other suitable components, or any combination thereof. There may be one or more surfaces of a first seal element that must remain in contact (e.g., at the entire surface or any suitable portion thereof) with one or more corresponding surfaces of a second seal element to adequately maintain seal functionality. As the seal ring assembly experiences wear, moves to accommodate changes in cylinder diameter, or otherwise undergoes geometric changes or force changes, some of the seal elements may move relative to one another. In some embodiments, the present disclosure is directed to a pressure locking feature configured to ensure that at least a portion of the mating surfaces of the seal elements remain in contact to maintain a seal. For example, the mating surfaces may provide a seal between a high pressure region and a low pressure region. In an illustrative example, either or both of the two mating surfaces include a channel or other recess that opens to a region of lower pressure. The geometry of the channel (e.g., area, volume, length, aspect ratio, surface area to volume ratio) is such that the pressure acting on a portion of the mating interface is at a lower pressure than the pressure in the region of higher pressure. The surface in which the channel is included forms a continuous boundary of contact with the mating surface (e.g., around the periphery of the channel on all sides except where the channel opens to the region of lower pressure). For example, the channel does not create a significant short-circuit flow path (e.g., leakage) between the region of higher pressure and the region of lower pressure. The particular percentage of the surface area exposed to the low pressure channel is selected such that the sum of the pressures acting on the two segments (e.g., from the area exposed to the region of higher pressure) has a net resultant force that causes the two segments to contact each other at the surface that includes the pressure locking feature. Thus, the pressures to which the seal ring assembly is exposed and the resulting contact forces act to maintain the configuration of the seal elements of the seal ring assembly.

[0055] The term "seal" as used herein refers to the creation, maintenance, or both of high and low pressure regions. For example, a seal may include a seal ring assembly configured to reduce the leakage rate of gas from a high pressure region to a low pressure region by restricting flow between the high pressure and low pressure boundaries of the seal. Thus, a seal may be defined in terms of its constraints on leak rate. It should be understood that a seal or seal ring assembly as described herein may have any suitable corresponding leak rate. For example, in some circumstances, a relatively poor seal may allow more leakage but may be acceptable based on certain performance criteria. In a further example, a seal ring assembly configured for high efficiency operation of a piston and cylinder device may have a relatively low leak rate (e.g., be a more effective seal).

[0056] As used herein, a "ring segment" refers to a sealing element that extends azimuthally greater than zero degrees, has a radially outer surface, and is configured to seal against the bore along at least a portion of the radially outer surface. If the ring segment is not azimuthally continuous around the entire bore, it may include end faces.

[0057] As used herein, "ring" refers to a sealing element that includes at least one ring segment that may, but need not, be azimuthally continuous along the bore. For example, a ring may include one ring segment, in which case the terms overlap. In a further example, a ring may include four ring segments, in which case the ring refers to a collection of the four ring segments. A ring may, but need not, include one or more interfaces between one or more ring segments. "Ring" also refers to a sealing element that includes at least one ring segment that is configured to seal against a land of a piston.

[0058] As used herein, "gap cover element" refers to a sealing element configured to seal against one or more ring segments at an interface and to seal against at least a portion of a bore during wear of the one or more ring segments. Although the gap cover element may function as a ring segment as the rings wear, for purposes of discussion in this disclosure, the gap cover element will not be considered to be a ring segment for purposes of clarity.

[0059] As used herein, "seal ring assembly" refers to an assembly of one or more rings, and sometimes also one or more gap cover elements, configured to engage a piston and seal between high and low pressure regions of a cylinder. For example, a single ring segment is a ring and can be a seal ring assembly. In a further example, several ring segments and corresponding gap covers can be a seal ring assembly.

[0060] As used herein, a "pressure locking feature" refers to a feature included in at least one component of a seal ring assembly that provides a pressure locking function. As used herein, "pressure locking" refers to the action of inducing a resultant force on one or more components of a seal ring assembly to maintain (or otherwise control) the relative geometric relationship between the components of the seal ring assembly during operation, to apply a force that presses the components of the seal ring assembly together, or both. The action of a pressure differential across a seal element can induce a resultant force that helps to maintain the relative geometric relationship.

[0061] FIG. 1 illustrates a cross-sectional view of an illustrative piston and cylinder assembly 100 according to some embodiments of the present disclosure. The cylinder 160 may include a bore 162, which is an inner cylindrical surface along which the piston assembly 110 travels. The piston assembly 110 may include a piston 126 that includes a seal ring groove 122 in which the seal ring assembly 120 is configured to ride. As the piston assembly 110 translates along an axial direction indicated by an axis 180 within the cylinder 160 (e.g., during an engine cycle), the gas pressure within the high pressure region 150 may change (the high pressure region 150 may be closed off using a cylinder head or opposing piston). For example, as the piston assembly 110 moves against the direction of the axis 180 (i.e., to the left in FIG. 1), the pressure within the high pressure region 150 may increase. A low pressure region 170 located behind the seal ring assembly 120 may be at a gas pressure below the pressure of the high pressure region 150 over at least a portion, if not most, of the piston stroke or cycle of the piston and cylinder assembly 100. The pressure ranges within the high pressure region 150 and low pressure region 170 may be any suitable range (e.g., from subatmospheric to well above 250 bar) and may depend on the compression ratio, breathing details (e.g., boost pressure, pressure waves, port timing), losses, thermochemical properties of the gases, and their reactions. Thus, the seal ring assemblies described herein may be used to seal any suitable high and low pressure regions having any suitable pressure range. It should be understood that the "front" of the seal ring assembly 120 refers to the surface axially closest to the high pressure region 150 and the "rear" of the seal ring assembly 120 refers to the surface axially closest to the low pressure region 170.

[0062] It should be understood that unless otherwise specified, all pressures referred to herein are in absolute units (eg, not gauge or relative units).

[0063] It should be understood that high and low pressures may refer to transient pressure conditions of the piston and cylinder device. For example, with reference to an engine cycle, the high pressure side of the seal ring assembly may have a pressure greater than the low pressure side of the seal ring assembly throughout most of the engine cycle (e.g., possibly except during the breathing or near-breathing portions of the cycle). Thus, high and low pressures are relative and depend on the condition of the gas being sealed.

[0064] The seal ring assembly may be used to seal high and low pressure regions, each operating within any suitable pressure range. It should also be understood that the seal ring assembly may seal differently at different positions in the cycle. Additionally, it should be understood that the low pressure region may include a pressure that exceeds the pressure of the high pressure region over a portion of the piston stroke or cycle of the piston and cylinder assembly. For example, the seal ring assembly may seal the high pressure region from the low pressure region at all times. In a further example, the seal ring assembly may seal the high pressure region from the low pressure region as long as the pressure in the high pressure region exceeds the pressure in the low pressure region. In a further example, the seal ring assembly may seal the high pressure region from the low pressure region as long as the pressure in the high pressure region exceeds the pressure in the low pressure region, and conversely, may seal the low pressure region from the high pressure region as long as the pressure in the low pressure region exceeds the pressure in the high pressure region.

[0065] In some embodiments, the seal ring assembly 120 may deposit a material (e.g., including a self-lubricating material) on the bore 162 of the cylinder 160. The deposited material may lubricate (e.g., provide a dry lubricant) the bore / seal ring assembly interface between the bore 162 and the seal ring assembly 120. Thus, in some embodiments, the piston and cylinder assembly 100 may operate without a liquid (e.g., oil) for lubrication.

[0066] In some embodiments, piston 126 may be an open piston. For example, piston 126 may include an opening, notch, or other fluid pathway from high pressure region 150 to ring groove 122. Thus, in some embodiments employing an open piston, an inner radial surface of seal ring assembly 120 (e.g., with reference to radial axis 182 in FIG. 1 ) may be exposed to gas pressure in high pressure region 150.

[0067] FIG. 2 illustrates a cross-sectional view of an illustrative piston and cylinder assembly 200 in which a seal ring assembly according to some embodiments of the present disclosure is subjected to pressure. FIG. 2 illustrates an azimuthally oriented view, with axis 282 oriented radially and axis 280 oriented axially. Ring 220 and ring 230 make up a seal ring assembly, each of which may include one or more ring segments. Although not shown in FIG. 2, either or both of rings 220 and 230 may include one or more gap cover elements. The seal ring assembly is disposed within groove 205 of piston 202 and configured to seal against land 203. Although only pressure is illustrated in FIG. 2, it should be understood that the seal ring assembly may also be subjected to contact forces from the bore, piston land, another seal ring assembly, or combinations thereof. The seal ring seals a high pressure region 250 from a low pressure region 252 against cylinder 260 (e.g., against the bore of cylinder 260). Thus, the seal ring assembly includes a high pressure boundary exposed to high pressure region 250 and a low pressure boundary exposed to low pressure region 252. As illustrated in FIG. 2, the seal ring assembly is exposed to force 292 (i.e., directed axially aft from high pressure region 250), force 291 (i.e., directed radially outward from high pressure region 250), force 290 (i.e., directed radially inward from pressure in the clearance gap between the seal ring assembly and cylinder 260), and force 293 (i.e., directed axially forward from pressure in low pressure region 252). It should be understood that forces may be in the azimuthal direction, but are not shown in FIGS. 2-4 for simplicity. Ring 220 includes recess 223 coupled to low pressure region 252 by passage 221. Forces may also be applied at the interface between rings 220 and 230. For example, when rings 220 and 230 are not accelerating relative to piston 202 or each other, the forces on each of rings 220 and 230 are balanced in all directions. Further explanation of the interface forces is provided in connection with Figures 3-4.

[0068] FIG. 3 shows a cross-sectional view of a portion of an illustrative seal ring assembly 300 subjected to forces according to some embodiments of the present disclosure. As illustrated, in FIG. 3, only radial pressure acting on the seal ring assembly 300 is shown, but axial pressure (e.g., from contact with a bore, piston land, other seal elements, or other surfaces) and axial and radial contact forces may also be present during operation. For example, the contact forces may have a magnitude and direction to balance the pressure in each direction (e.g., so that ring segments 320 and 332 do not move relative to each other). FIG. 3 shows an azimuthally oriented view, with axis 382 oriented radially and axis 380 oriented axially. The seal ring assembly 300 includes a first ring and a second ring. The first ring includes ring segment 320 and the second ring includes ring segment 332. The seal ring assembly 300 is configured to seal between a high pressure region 350 and a low pressure region 352 (e.g., in a bore of a cylinder). The radially outwardly directed force 302 is caused by pressure from the high pressure region 350 acting on a portion of the high pressure boundary of the seal ring assembly 300. The radially inwardly directed force 301 is caused by pressure from a clearance gap, asperities, or both between the seal ring assembly 300 and the cylinder bore. The force 303 acting on the ring segment 332 is caused by gas pressure from the high pressure region 350 gas in the gap between the ring segments 320 and 332 (e.g., a similar force may act in the opposite direction on the ring segment 320). The resultant force 305 is the net radial force experienced by the ring segment 332 from the pressure during operation. For example, the larger the resultant force 305, the greater the contact force from the bore that may occur during operation (e.g., wear rate is increased).

[0069] FIG. 4 shows a cross-sectional view of a portion of an illustrative seal ring assembly 400 subjected to forces according to some embodiments of the present disclosure. As illustrated, in FIG. 4, only radial pressure acting on the seal ring assembly 400 is shown, but axial pressure (e.g., from a bore, piston land, other seal elements, or other surfaces) and axial and radial contact forces may also be present during operation. For example, the contact forces may have a magnitude and direction to balance the pressure in each direction (e.g., so that ring segments 420 and 432 do not move relative to one another). FIG. 4 shows an azimuthally oriented view, with axis 482 oriented radially and axis 480 oriented axially. The seal ring assembly 400 includes a first ring and a second ring. The first ring includes ring segment 420, and the second ring includes ring segment 432. The ring segment 432 includes a recess 440 disposed at the interface between ring segment 432 and ring segment 420. The seal ring assembly is configured to seal between a high pressure region 450 (e.g., in a bore of a cylinder) and a low pressure region 452. The radially outwardly directed force 402 is caused by pressure from the high pressure region 450 acting on a portion of the high pressure boundary of the seal ring assembly 400. The radially inwardly directed force 401 is caused by pressure from a clearance gap, an asperity, or both between the seal ring assembly 400 and the cylinder bore. The force 403 acting on the ring segment 432 is caused by gas pressure from gas in the interface between the ring segments 420 and 432 (e.g., a similar force may act in the opposite direction on the ring segment 420). Because the recess 440 opens to the low pressure region 452 by the passage 441, any high pressure gas that enters the interface between the ring segments 420 and 432 will have its pressure reduced as illustrated by force 403 (e.g., with a reduced magnitude from the reduced pressure at the recess 440). For example, high pressure gas entering the gap will flow through recess 440 into passage 441 and into low pressure region 452 .Resultant force 405 is a net radial force experienced by ring segment 432 from pressure during operation that is less than resultant force 305 for similar operating conditions. For example, similar operating conditions may include similar pressures in high pressure regions 350 and 450 and similar pressures in low pressure regions 352 and 452. For example, the smaller resultant force 405 is, the smaller the contact force from the bore that may occur during operation (e.g., wear rate is reduced). Thus, the inclusion of recess 440 allows seal ring assembly 400 to experience a reduced resultant force from pressures (e.g., resultant force 405) on the seal element (e.g., ring segment 432) compared to the resultant force (e.g., resultant force 305) acting on ring segment 332 of seal ring assembly 300.

[0070] A recess that is open to a low pressure region may cause the pressure at the interface between the seal elements of the seal ring assembly to be relatively lower (e.g., than if the recess were not included). For example, the pressure at the recess may be equal to the pressure in the low pressure region, but need not be. A pressure relatively lower than that of the high pressure region may be sufficient to provide a pressure lock. Thus, the recess need only partially reduce the pressure from the high pressure region. For example, a greater pressure reduction at the recess may provide a stronger pressure lock (e.g., by reducing the resulting pressure at the seal elements).

[0071] FIG. 5 illustrates a cross-sectional view of a portion of an illustrative seal ring assembly 500 exposed to pressure and contact forces according to some embodiments of the present disclosure. FIG. 5 illustrates an axially oriented view, with axis 582 oriented radially and arrow 581 illustrating the azimuthal direction. Ring segment 520 and gap cover element 530 form part of seal ring assembly 500, which may include any suitable number of ring segments, gap cover elements, or other suitable components (e.g., additional rings, etc.) not illustrated in FIG. 5. Seal ring assembly 500 is configured to be disposed in a groove of a piston and to seal against a land. Seal ring assembly 500 is configured to seal a high pressure region of a cylinder (e.g., its bore) from a low pressure region. As illustrated in FIG. 5, the seal ring assembly is subjected to force 590 (i.e., directed radially inward from the pressure in the clearance gap), force 591 (i.e., directed radially outward from the high pressure region), force 592 (i.e., directed azimuthally from the pressure), and force 593 (i.e., directed azimuthally opposite force 592 from the pressure). It should be understood that the forces may be axial, but are not shown in FIGS. 5-7 for simplicity. Ring segment 520 includes recess 523 coupled to a low pressure region (not shown) by passage 521. Forces can also be applied at the interface between ring segment 520 and gap cover element 530. For example, when ring 520 and gap cover element 530 are not accelerating relative to the piston or each other, the forces on each of ring segment 520 and gap cover element 530 are balanced in all directions. Further explanation of interface forces is provided in conjunction with FIGS. 6-7.

[0072] FIG. 6 shows a cross-sectional exploded view of a portion of an illustrative seal ring assembly 600 exposed to forces according to some embodiments of the present disclosure. As illustrated, in FIG. 6, only pressure forces acting on the seal ring assembly 600 are shown, but contact forces (e.g., from a bore, a piston land, other seal elements, or other surfaces) may also be present during operation. For example, the contact forces may have a magnitude and direction to balance the pressure in each direction (e.g., so that the ring segment 620 and the gap cover element 630 do not move relative to each other, the piston, or both). FIG. 6 shows an axially oriented view, with axis 682 oriented radially and arrow 681 illustrating the azimuthal direction. The ring segment 620 and the gap cover element 630 constitute part of the seal ring assembly 600, which may include any suitable number of ring segments, gap cover elements, or any other suitable components. The seal ring assembly 600 is configured to be disposed in a groove of a piston and configured to seal against a land. The seal ring assembly 600 is configured to seal a high pressure region from a low pressure region of a cylinder (e.g., its bore). The seal ring assembly 600 is exposed to a radially inwardly directed force 601 from pressure in the clearance gap. The seal ring assembly 600 is also exposed to a radially outwardly directed force 602 (e.g., caused by gas from the high pressure region). The seal ring assembly 600 is also exposed to an azimuthally directed force 603 from pressure between a gap cover element (e.g., similar to gap cover element 530 of FIG. 5) and a ring segment 620. The resultant force 505 is the azimuthally directed net force experienced by the ring segment 620 from the pressure during operation. For example, a larger resultant force 605 may reduce the effectiveness of the seal between the ring segment 620 and the gap cover element 630, may increase wear of the seal ring assembly 600, or both.

[0073] FIG. 7 shows a cross-sectional exploded view of a portion of an illustrative seal ring assembly 700 exposed to forces according to some embodiments of the present disclosure. Seal ring assembly 700 is similar to seal ring assembly 500 of FIG. 5. As illustrated, in FIG. 7, only pressure forces acting on seal ring assembly 700 are shown, but contact forces (e.g., from a bore, a piston land, other sealing elements, or other surfaces) may also be present during operation. For example, the contact forces may have a magnitude and direction to balance the pressure forces in each direction (e.g., so that ring segments 720 and gap cover elements 730 do not move relative to one another). FIG. 7 shows an axially oriented view, with axis 782 oriented radially and arrow 781 illustrating the azimuthal direction. Ring segments 720 and gap cover elements 730 constitute part of seal ring assembly 700, which may include any suitable number of ring segments, gap cover elements, or any other suitable components. Seal ring assembly 700 is configured to be disposed in a groove of a piston and configured to seal against a land. The seal ring assembly 700 is configured to seal a high pressure region from a low pressure region of a cylinder (e.g., its bore). The seal ring assembly 700 is exposed to a radially inwardly directed force 701 from the pressure in the clearance gap. The seal ring assembly 700 is also exposed to a radially outwardly directed force 702 (e.g., caused by gas from the high pressure region). The seal ring assembly 700 is also exposed to an azimuthally directed force 703 from the pressure between the gap cover element 730 and the ring segment 720. A recess 740 in the ring segment 720 is open to the low pressure region (not shown), thus causing the force 703 to be less than the force 603 of FIG. 6 for similar operating conditions. The resultant force 705 is the net azimuthally directed force experienced by the ring segment 720 from the pressure during operation. For example, a smaller resultant force 705 relative to resultant force 605 may aid in sealing between the ring segment 720 and the gap cover element 730 by increasing the contact force between their mating surfaces, may reduce wear on the seal ring assembly 700, or both.

[0074] FIG. 8 illustrates a cross-sectional view of an illustrative piston and cylinder assembly 800 in which a seal ring assembly (e.g., including rings 820 and 830) is exposed to pressure according to some embodiments of the present disclosure. FIG. 8 illustrates an azimuthally oriented view, with axis 882 oriented radially and axis 880 oriented axially. In FIG. 8, only pressure is illustrated, but it should be understood that the seal ring assembly may also be subjected to contact forces from the bore, the piston land, another seal ring assembly, or combinations thereof. Rings 820 and 830 comprise a seal ring assembly, each of which may include one or more ring segments. Although not shown in FIG. 8, either or both of rings 820 and 830 may include one or more gap cover elements. The seal ring assembly is disposed within groove 805 of piston 802 and configured to seal against land 803. The seal ring seals a high pressure region 850 from a low pressure region 852 against cylinder 860 (e.g., against the bore of cylinder 260). As illustrated in FIG. 8, the seal ring assembly is subjected to force 892 (i.e., directed axially aft from high pressure region 850), force 891 (i.e., directed radially outward from high pressure region 850), force 890 (i.e., directed radially inward from pressure in the clearance gap between the seal ring assembly and cylinder 860), and force 893 (i.e., directed axially forward from pressure in low pressure region 852). It should be understood that the forces may be in azimuthal directions, but are not shown in FIGS. 8-10 for simplicity. Ring 820 includes recess 823 coupled to low pressure region 852 by passage 821. Forces can also be applied at the interface between rings 820 and 830. For example, if rings 820 and 830 are not accelerating relative to piston 802 or each other, the forces on each of rings 820 and 830 are balanced in all directions. Further explanation of interfacial forces is provided in connection with Figures 9-10.

[0075] FIG. 9 shows a cross-sectional exploded view of an illustrative seal ring assembly 900 subjected to forces according to some embodiments of the present disclosure. As illustrated, in FIG. 9, only axial pressure acting on the seal ring assembly 900 is shown, but pressure and contact forces in other directions (e.g., from the bore, piston lands, other sealing elements, or other surfaces) may also be present during operation. For example, the contact forces may have a magnitude and direction that balances the pressure in each direction (e.g., so that rings 920 and 930 do not move relative to each other, relative to the piston, or both). FIG. 9 shows an axially oriented view, with axis 982 oriented radially and arrow 980 illustrating the axial direction. Rings 920 and 930 constitute at least a portion of seal ring assembly 900, which may include any suitable number of ring segments, gap cover elements, or any other suitable components. Seal ring assembly 900 is configured to be disposed in a groove of a piston and configured to seal against a land. The seal ring assembly 900 is configured to seal a high pressure region from a low pressure region of a cylinder (e.g., its bore). The ring 920 is oriented axially rearward and is exposed to a force 903 caused by gas in the high pressure region. A force 906 from the gas pressure between rings 920 and 930 acts on the mating surface of ring 920. A resultant force 925 is the net axial force experienced by ring 920 from the pressure during operation. For example, a smaller resultant force 925 may reduce the effectiveness of the seal between rings 920 and 930. Respective forces 907 and 908 caused by the pressure between rings 920 and 930 and the gas from the low pressure region act on ring 930.

[0076] FIG. 10 shows a cross-sectional exploded view of an illustrative seal ring assembly 1000 subjected to forces according to some embodiments of the present disclosure. As illustrated, in FIG. 10, only axial pressure acting on the seal ring assembly 1000 is shown, but pressure and contact forces in other directions (e.g., from the bore, piston land, other seal elements, or other surfaces) may also be present during operation. For example, the contact forces may have a magnitude and direction that balances the pressure in each direction (e.g., so that the rings 1020 and 1030 do not move relative to each other). FIG. 10 shows an azimuthally oriented view, with axis 1082 oriented radially and axis 1080 oriented axially. The seal ring assembly 1000 includes a first ring (i.e., ring 1020) and a second ring (i.e., ring 1030). The ring 1030 includes a recess 1040 disposed at the interface between the rings 1020 and 1030. The seal ring assembly is configured to seal between a high pressure region and a low pressure region (e.g., in a bore of a cylinder). The recess 1040 opens to the low pressure region by a passage 1041. The ring 1020 is oriented axially rearward and is exposed to a force 1003 caused by gas in the high pressure region. A force 1006 from the gas pressure between the rings 1020 and 1030 acts on the mating surface of the ring 1020. The resultant force 1025 is the net axial force experienced by the ring 1020 from the pressure during operation. For example, a larger resultant force 1025 may improve the effectiveness of the seal between the rings 1025 and 1030. Respective forces 1007 and 1008 caused by the pressure between the rings 1020 and 1030 and the gas from the low pressure region act on the ring 1030. Because recess 1040 opens to the low pressure region by way of passage 1041, any high pressure gas entering the gap will have its pressure reduced as illustrated by resultant force 1025 (e.g., with a reduced magnitude from the reduced pressure at recess 1040). For example, high pressure gas entering the interface between rings 1020 and 1030 will flow through recess 1040 into passage 1041 and into the low pressure region.Resultant force 1025 is the net axial force experienced by ring 1020 from pressure during operation and is less than resultant force 925 of FIG. 9 for similar operating conditions. For example, similar operating conditions may include similar pressures in the high pressure region and similar pressures in the low pressure region. For example, a larger resultant force 1025 may improve the effectiveness of the seal between ring 1020 and ring 1030, may improve wear of the seal ring assembly, or both. Respective forces 1007 and 1008 caused by the pressure between rings 1020 and 1030 and gas from the low pressure region act on ring 1030.

[0077] It should be understood that Figures 2-10 are illustrative only and that the seal ring assemblies may be configured for axial, radial, or azimuthal pressure locking, or any suitable combination thereof. For example, the seal ring assemblies may include one or more recesses disposed at corresponding interfaces and configured to provide axial, radial, and azimuthal pressure locking. Additionally, the interfaces between the seal elements may include any suitable (e.g., flat, segmented, contoured) shapes and be disposed in any suitable (e.g., perpendicular, parallel, or at an angle to an axis in any direction) orientation or combination of orientations. Any of the illustrative seal ring assemblies of Figures 2-10 may be combined or modified in accordance with the present disclosure.

[0078] 11 shows an exploded perspective view of a portion of an illustrative seal ring assembly according to some embodiments of the present disclosure. The seal ring assembly 1100 includes a first ring 1120 and a second ring 1130. Although the first ring 1120 and the second ring 1130 are illustratively shown as having two segments and two gaps, the rings may include any suitable number (e.g., one or more) of segments and gaps in accordance with the present disclosure.

[0079] The first ring 1120 includes a first ring segment 1122 and a second ring segment 1124. Additionally, the first ring 1120 may be referred to as a ring with two splits or a ring split into two ring segments. The first ring being "split" may refer to the manufacturing process (e.g., the first ring is manufactured as a single piece and separated into two ring segments) or the general geometry of the first ring segments 1122 and 1124 that are disposed end-to-end and extend azimuthally around the ring groove of the piston in whole or in part. The split itself refers to the interface between the first ring segments 1122 and 1124, which may include a gap, an interface, or a combination thereof between the first ring segments.

[0080] The second ring 1130 includes a second ring segment 1132 and a second ring segment 1134. Additionally, the second ring 1130 may be referred to as a two-cleft ring or a ring split into two ring segments. Any suitable number of anti-rotation features may be included and configured to engage with any suitable number of corresponding features of the first or second rings or segments thereof. In some embodiments, the second ring 1130 includes anti-rotation features 1137 and 1138 that engage with the first ring 1120 or its interface to prevent substantial azimuthal movement of the second ring segments 1132 and 1134.

[0081] Each of the first ring segments 1122 and 1124 may include a groove 1126 that extends circumferentially along an outer radial surface of the extension 1128, which may also be split (e.g., as shown in FIG. 11). The groove 1126 may be open to a low pressure boundary of the seal ring assembly 1100, for example, during operation. Thus, the groove 1126 may enable pressure locking of the seal ring assembly 1100 during preferred operation. For example, the groove 1126 may be configured to use a pressure differential to lock (e.g., via pressure locking) the different ring segments to one another (e.g., the first ring segments 1122 and 1124 to the ring segments 1132 and 1134). As shown, the groove 1126 does not extend azimuthally along the extension 1128 to the interface between the first ring segments 1122 and 1124, and thus would not be open to a high pressure region during operation. FIG. 12 shows a perspective view of the illustrative seal ring assembly 1100 of FIG. 11 as an assembly according to some embodiments of the present disclosure.

[0082] 13 shows a cross-sectional view of an illustrative seal ring assembly 1300 including features for pressure locking according to some embodiments of the present disclosure. Coordinate axes 1370 (i.e., radial) and 1372 (i.e., axial) are provided in FIG. 13 for purposes of clarity. Seal ring assembly 1300 is configured to be disposed within a ring groove of piston 1310.

[0083] A feature for pressure locking, referred to herein as a pressure lock (i.e., groove 1380 as illustratively shown in FIG. 13), may help maintain seal ring assembly 1300 in an intended configuration during operation. During operation (e.g., in a device including a piston and cylinder assembly), groove 1380 may be configured to contain gas at a pressure close to the pressure of a low pressure boundary of seal ring assembly 1300. For example, during operation, groove 1380 may achieve or nearly achieve the pressure of a low pressure region (e.g., low pressure region 1311) at the rear of seal ring assembly 1300. Although groove 1380 is shown as being integrated into front ring 1320, groove 1380 may also be included in rear ring 1330, or both front ring 1320 and rear ring 1330. Additionally, groove 1380 may be replaced by any suitable recess configured to apply pressure to a suitable surface of the seal ring assembly. For example, recesses may include any suitable shape having any suitable geometric characteristics in accordance with the present disclosure.

[0084] To illustrate, without the groove 1380, when a "twin ring" (e.g., seal ring assembly 1300) wears, the rear ring 1330 may tend to wear at a more rapid rate than the front ring 1320. This is due to the axial pressure drop along the axial length of the seal ring assembly 1300 (e.g., decreasing from left to right as illustrated by the downward top arrow 1390). Thus, the pressure at the outside of the rear ring is lower than the peak pressure (e.g., in the high pressure region 1313). If high pressure gas were to enter between the front ring 1320 and the rear ring 1330 (e.g., thus exposing the rear segment of the ring 1330 to the pressure of the high pressure region 1313), the rear ring 1330 would tend to be forced radially outward more strongly than the front ring 1320. As the rear ring 1330 wears at a higher rate, the gap between the rear ring segments would open up. Gas from the high pressure region can then more easily find its way between the segments, increasing the outward force, and a runaway condition may result. Additionally, the flow of gas from the high pressure region 1313 into the gap may be characterized as a leak past the seal.

[0085] In some embodiments, a groove (e.g., groove 1380) is formed (e.g., cut) in one of the rings at the radial interface between the front ring 1320 and the rear ring 1330. The groove may be included in the interface on the outer surface of the front ring 1320, the inner surface of the rear ring 1330, or both. In some embodiments, the groove is centered over and opens into a cleft in the rear ring 1330. The end of the groove 1380 is closed before reaching the cleft in the front ring 1320 (e.g., as illustrated by groove 1126 in FIG. 11). When the seal ring assembly 1300 is operating (e.g., in a piston-cylinder device), the cleft in the rear ring 1330 is at low pressure because it opens to the rear of the seal ring assembly 1300 and is blocked from the front of the seal ring assembly 1300. Thus, the groove 1380 between the two rings is also at low pressure, ensuring low pressure between the front and rear segments, which helps keep them radially locked together.

[0086] Illustrative radial pressure fields 1390 (i.e., acting radially inward) and 1392 (i.e., acting radially outward) may act on seal ring assembly 1300 during operation. Radial pressure field 1392 is directed radially outward and is created by gas from a high pressure region acting on a radially inner surface of seal ring assembly 1300. Radial pressure field 1390 is directed radially inward and is created by gas in the gap between seal ring assembly 1300 and the corresponding bore of a cylinder.

[0087] Figure 14 shows a cross-sectional view of the illustrative seal ring assembly 1300 of Figure 13 showing the aft ring gap 1430 according to some embodiments of the present disclosure. Figure 14 is shown from cross-section 1399 of Figure 13 (i.e., looking in a radially inward direction, opposite to the direction of axis 1370). The groove 1380 opens to the low pressure region 1311 and is sealed from the high pressure region 1313 by the front ring 1320.

[0088] FIG. 15 shows a perspective view of a portion of an illustrative seal ring assembly 1500 including features for balancing radial forces according to some embodiments of the present disclosure. FIG. 16 shows a perspective view of a portion 1570 of the illustrative seal ring assembly 1500 of FIG. 15 according to some embodiments of the present disclosure. The seal ring assembly 1500 includes a first ring 1520 (e.g., a front ring) and a second ring 1530 (e.g., an aft ring). The second ring 1530 includes a pocket 1560 extending circumferentially within an outer radial surface of the second ring. In some embodiments, the pocket 1560 is configured to receive high pressure gas (e.g., from a high pressure region of a piston-cylinder device). In some embodiments, the second ring 1530 may include an orifice 1562 that may allow gas to flow from a high pressure boundary of the seal ring assembly 1500 (e.g., exposed to a high pressure region) to the pocket 1560. For example, the orifice 1562 may open into the pocket 1560 to allow gas to flow. The first ring 1520 may include a recess 1564 or other feature to allow the orifice 1562 to receive high pressure gas during operation. The orifice 1562 may include a hole, passageway, or other opening that may allow suitable gas flow.

[0089] A portion of the seal ring assembly 1500 indicated by section 1570 of FIG. 15, viewed in direction 1572, is illustrated in FIG. 16. The recess 1564 in the first ring 1520 allows a relatively open flow path for high pressure gas to enter the orifice 1562. Thus, in some circumstances, the seal ring assembly 1500 may be configured to seal between high and low pressure regions and exhibit relatively lower wear (e.g., compared to the seal ring assembly 1100 of FIG. 11) due to pockets for radial pressure balance. Under some circumstances, the first ring 1520 and the second ring 1530 may move azimuthally relative to one another as the seal ring assembly 1500 wears. Thus, the recess 1564 may include a slot (e.g., as shown in FIG. 16) rather than a circular hole so that the pressurized path remains open as the rings wear.

[0090] 17 shows a rear face view of an illustrative seal ring assembly 1700 according to some embodiments of the present disclosure. Seal ring assembly 1700 includes ring segments 1732, 1734, 1736, and 1738 and gap cover elements 1742, 1744, 1746, and 1748. Seal ring assembly 1700 illustratively corresponds to seal ring assembly 200 after having undergone relatively less wear than seal ring assembly 230 (e.g., ring segment 266 corresponds to ring segment 206 after having undergone an intermediate amount of wear).

[0091] The surface 1737 (e.g., axially forward and axially aft facing of gap cover element 1746) of the interface between ring segments 1732 and 1738 is nominally a flat plane perpendicular to the axis of the ring. As shown in FIG. 17, the side surface 1735 of the interface between ring segments 1736 and 1738 is symmetrical about a plane passing through the center of the radial cleft of the ring. The sides of gap cover elements 1742, 1744, 1746, and 1748 need not be symmetrical, but are shown symmetrical for clarity. The sides together form an narrow angle that is widest at the radially inner surface of the ring and narrowest at the radially outer surface (e.g., narrow angle 1739 in FIG. 17 is formed by gap cover element 1736). The mating surfaces between the gap cover element 1746 and the ring segments 1736 and 1738 may include at least one recess configured to be open to the low pressure region and not open to (e.g., sealed from) the high pressure region. For example, the recess may be included within the side surface 1735, the front face, the corresponding mating surface of the gap cover element 1746, or any combination thereof. Similarly, the recess may be included within any suitable sealing surface between any of the illustrative ring segments 1732, 1734, 1736, and 1738 and suitable gap cover elements 1742, 1744, 1746, and 1748.

[0092] 18 shows a cross-sectional view of an illustrative device 1800 including two free piston assemblies 1810 and 1820 including respective seal ring assemblies 1812 and 1822 according to some embodiments of the present disclosure. In some embodiments, the device 1800 may include linear electromagnetic machines 1850 and 1855 for converting between kinetic energy of the respective free piston assemblies 1810 and 1820 and electrical energy. In some embodiments, the device 1800 may include gas regions 1860 and 1862 that may be at a relatively lower pressure than the gas region 1870 (e.g., high pressure region) for at least a portion, if not most, of a cycle (e.g., engine cycle or air compression cycle). For example, the gas regions 1860 and 1862 (e.g., low pressure region) may be open to respective breathing ducts (e.g., intake manifold, intake system, exhaust manifold, exhaust system). To illustrate, the breather ports 1834 and 1835 are configured to provide reactants to the bore 1832 of the cylinder 1830 and remove exhaust therefrom. In a further example, the gas regions 1860 and 1862 can be vented to atmosphere (e.g., at about 1.01 bar absolute pressure). In some embodiments, the device 1800 can include gas springs 1880 and 1885 that can be used to store and release energy during a cycle in the form of compressed gas (e.g., the drive section). For example, each of the free piston assemblies 1810 and 1820 can include a respective piston 1882 and 1887 with grooves for respective seal ring assemblies 1881 and 1886 to seal the respective gas regions 1883 and 1888 (e.g., high pressure regions) from the respective gas regions 1884 and 1889 (e.g., low pressure regions).

[0093] The cylinder 1830 may include a bore 1832 centered on an axis 1872. In some embodiments, the free piston assemblies 1810 and 1820 may translate along the axis 1872 within the bore 1832, allowing the gas region 1870 to compress and expand. For example, the gas region 1870 may be at a relatively high pressure compared to the gas region 1860 over at least a portion of the stroke of the free piston assemblies 1810 and 1820 (which may translate along the axis 1872, e.g., in the synchronization of opposed pistons). The seal ring assemblies 1812 and 1822 may seal the gas region 1870 from the respective gas regions 1860 and 1862 within the bore 1832. In some embodiments, the free piston assemblies 1810 and 1820 may include respective pistons 1814 and 1824 and respective seal ring assemblies 1812 and 1822 that may be disposed in corresponding grooves of the pistons 1814 and 1824. It should be understood that the gas regions 1860 and 1862 and the gas region 1870 may change volume as the free piston assemblies 1810 and 1820 move along an axis 1872 or are differently positioned in different locations. A portion of the respective seal ring assemblies 1812 and 1822 closest to the gas region 1870 may each be referred to as a front, and a portion of the seal ring assemblies 1812 and 1822 closest to the respective gas regions 1860 and 1862 may each be referred to as a rear. Each of the seal ring assemblies 1812 and 1822 may include a high pressure boundary, each of which may depend on the pressure in the gas region 1870. For example, a high pressure boundary of seal ring assembly 1812 may open to gas region 1870 (e.g., bounded by one or more orifices or other openings) and have a corresponding pressure that is the same (e.g., if gas from gas region 1870 is not throttled at the seal ring assembly) or less (e.g., if gas from gas region 1870 is throttled at the seal ring assembly) than the pressure in gas region 1870. Each of seal ring assemblies 1812 and 1822 may include a low pressure boundary, which may depend on the gas pressure in gas regions 1860 and 1862, respectively.For example, the low pressure boundary of seal ring assembly 1812 may open to gas region 1860 and have a corresponding pressure approximately equal to the pressure in gas region 1860. In some embodiments, as seal ring assemblies 1812 and 1822 pass axially over respective ports 1835 and 1834 (e.g., corresponding port bridges, not shown), they may experience a non-uniform or reduced inward force from bore 1832.

[0094] In some embodiments, each of the pistons 1814 and 1824 may include one or more grooves in which one or more respective seal ring assemblies may be disposed. For example, as shown in FIG. 18, each of the pistons 1814 and 1824 may include one groove in which the seal ring assembly 1812 and the seal ring assembly 1822, respectively, may be mounted. In a further example, not shown in FIG. 18, the piston 1814 may include two grooves in which two respective seal ring assemblies may be mounted. In a further example, the piston 1814 may include two grooves, a first seal ring assembly 1812 and a second one (not shown) disposed at the rear of the seal ring assembly 1812 but with its front closer to the gas region 1860, thereby sealing the pressure in the gas region 1860 against the pressure between the two seal ring assemblies (e.g., which may be less than the pressure in the gas region 1870). Thus, the seal ring assemblies may be used to seal any suitable high and low pressure regions from each other.

[0095] In some embodiments, the free piston assemblies 1810 and 1820 may include respective magnet segments 1851 and 1856 that interact with respective stators 1852 and 1857 to form respective linear electromagnetic machines 1850 and 1855. For example, as the free piston assembly 1810 translates along an axis 1872 (e.g., during a stroke of an engine cycle), the magnet segments 1851 may induce currents in the windings of the stator 1852. Further, the currents may be supplied to respective phase windings of the stator 1852 to generate electromagnetic forces on the free piston assembly 1810 (e.g., resulting in motion of the free piston assembly 1810).

[0096] In some embodiments, pistons 1814 and 1824, seal ring assemblies 1812 and 1822, and cylinder 1830 may be considered a piston and cylinder assembly. In some embodiments, device 1800 may be an engine, an air compressor, any other suitable device having a piston and cylinder assembly, or any combination thereof. In some embodiments, device 1800 need not include two free piston assemblies. For example, cylinder 1830 may be closed (e.g., with a cylinder head) and only free piston assembly 1810 may translate along axis 1872.

[0097] It should be understood that the present disclosure is not limited to the embodiments described herein, but may be implemented in the context of any suitable system. In some preferred embodiments, the present disclosure is applicable to reciprocating engines and compressors. In some embodiments, the present disclosure is applicable to free piston engines and compressors. In some embodiments, the present disclosure is applicable to combustion and reaction devices such as reciprocating engines and free piston engines. In some embodiments, the present disclosure is applicable to non-combustion and non-reaction devices such as reciprocating compressors, free piston heat engines, and free piston compressors. In some embodiments, the present disclosure is applicable to gas springs. In some embodiments, the present disclosure is applicable to oil-free reciprocating and free piston engines and compressors. In some embodiments, the present disclosure is applicable to oil-free free piston engines with internal or external combustion or reaction. In some embodiments, the present disclosure is applicable to oil-free free piston engines that operate using compression ignition, chemical ignition (e.g., exposure to catalytic surface, spontaneous ignition), plasma ignition (e.g., spark ignition), thermal ignition, any other suitable energy source for ignition, or any combination thereof. In some embodiments, the present disclosure is applicable to oil-free free piston engines that operate using gas fuel, liquid fuel, or both. In some embodiments, the present disclosure is applicable to linear free piston engines. In some embodiments, the present disclosure is applicable to engines that can be combustion engines with internal combustion / reaction, or any type of heat engine with external heat addition (e.g., from a heat source such as waste heat or an external reaction such as combustion).

[0098] The foregoing merely illustrates the principles of the present disclosure, and various modifications may be made by those skilled in the art without departing from the scope of the present disclosure. The embodiments described above are presented for purposes of illustration and not limitation. The present disclosure may take many forms other than those expressly described herein. It is emphasized, therefore, that the present disclosure is not limited to the methods, systems, and apparatus expressly disclosed, but is intended to include modifications and variations therein that are within the spirit of the following claims.

Claims

[Claim 1] The invention described in this specification.

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