Scraper ring

A scraper ring for a linear motion assembly including an annular body having a contact face adapted to contact an inner component, wherein the annular body comprises a material having a coefficient of linear thermal expansion of at least 75×10−6/° C. An assembly for linear motion including an outer component defining a bore and a first annular recess extending radially outward from the bore; an inner component disposed in the bore, wherein the inner component is adapted to translate longitudinally within the bore; and a scraper ring disposed in the first annular recess and contacting the inner component, wherein there is no component disposed between any portion of the spacer ring and the outer component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No. PCT/US2015/042054, entitled “SCRAPER RING”, by Jon M. LENHERT et al., filed Jul. 24, 2015, of which application is assigned to the current assignee hereof and incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to linear motion assemblies, and more particularly to sealed linear motion assemblies.

BACKGROUND ART

Seal assemblies are typically used to prevent leakage from occurring within an annulus between two components. A seal may be positioned between an inner component and an outer component to maintain different fluidic pressures or to separate different fluidic components on opposing sides of the seal. Under certain situations, such as upon exposure to harsh environmental conditions, like extreme cold (e.g., below −100° C.), seals and their associated components typically lose their effectiveness and fail. Industries utilizing seal assemblies continue to demand improved components which can withstand harsh environmental conditions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring toFIG. 1, a linear motion assembly100in accordance with one or more embodiments can generally include an outer component102, an inner component104, and a scraper ring110. The outer component102may define a bore106having an annular recess108extending radially outward from the bore106. The annular recess108may have a cross-sectional profile having polygonal surfaces, arcuate surfaces, or a combination thereof. The scraper ring110may be disposed within the annular recess108. In an embodiment, the scraper ring110may extend into the bore106so as to contact the inner component104. In a particular embodiment, the scraper ring110may extend into the bore106or contact the inner component104only below certain temperatures (e.g., below −50° C.).

In a particular instance, the assembly100can include a linear actuator, such as a piston assembly. In an embodiment, the outer component102can include a housing for a piston. The inner component104may include a rod, such as a piston rod adapted to longitudinally translate within the outer component102. One or more piston rings140may circumscribe the inner component104. Some of the piston rings140amay be unbiased by secondary features in the radial direction, while other piston rings140bmay be biased by secondary features such as energized elements. In certain embodiments, the assembly100may be adapted for use at temperatures of less than −100° C., less than −125° C., less than −150° C., less than −175° C., less than −200° C., or less than −225° C. In a particular embodiment, the assembly100is part of a piston assembly for a use with a liquid hydrogen fuel cell automotive infrastructure. The piston assembly may be used to pump or urge liquid hydrogen, for example, from one storage vessel to another or between a storage vessel and an automotive tank. The piston assembly may also be used, for example, in a liquid oxygen tank vapor recovery compressor. In other embodiments, the assembly100may be part of aircraft or aerospace vehicles. The assembly100may be used to circulate liquid hydrogen, liquid carbon dioxide, liquid nitrogen, liquid oxygen, liquid helium, liquid argon, gaseous oxygen, or any other material having cryogenic, or near cryogenic, temperatures. In a particular embodiment, translation of the inner component104with respect to the outer component102may permit compression of the liquid or gaseous material, permitting storage of the material for readily available use.

In an embodiment, the scraper ring110may contact the inner component104. In a more particular embodiment, the scraper ring110may contact a portion of a circumference of the inner component104. In yet a more particular embodiment, the scraper ring110may contact the inner component104around the entire circumference. In certain embodiments, the scraper ring110may be at least partially, such as fully, spaced apart from the inner component104at a first temperature and contact the inner component104at a second temperature. In a particular instance, the first temperature can be greater than the second temperature. For example, by way of a non-limiting example, the first temperature may be 22° C. and the second temperature may be −150° C.

In an embodiment, the scraper ring110may contact the outer component102. More particularly, the scraper ring110may contact a radially outer surface126of the annular recess108when exposed to at least one temperature condition.

In an embodiment, the scraper ring110can have a thickness, as measured in a radial direction, less than a depth of the annular recess108, as measured from a surface of the bore106. In a particular embodiment, an outer diameter of the scraper ring110can be less than a diameter of the radially outer surface126of the annular recess108when exposed to at least one temperature condition. That is, an outer surface of the scraper ring110can be spaced apart from the radially outer surface126when exposed to at least one temperature.

In an embodiment, there may be no component disposed between the scraper ring110and the radially outer surface126of the annular recess108. Traditional seal assemblies utilize secondary features such as O-rings, compression straps, spring energizers, and other similar components disposed outside of sealing elements to radially bias sealing elements toward the inner component and generate a sufficient scraping and sealing characteristics. To the contrary, in an embodiment herein the scraper ring110may be self-energized. That is, the scraper ring110can maintain effective sealing and scraping without the use of secondary features. In a particular instance, this can reduce overall manufacturing expense, prevent accidental disconnect of the secondary feature, promote easier assembly, and extend operational system lifespan.

The scraper ring110may include an annular body112. In an embodiment, the annular body112may include a contact face114adapted to contact the inner component104. In a particular instance, the contact face114may be generally cylindrical. As used herein, “generally cylindrical” refers to an instance where the contact face114occupies at least 90% of a best fit cylinder, at least 95% of a best fit cylinder, or at least 99% of a best fit cylinder. In a more particular instance, the contact face114may be cylindrical. In an embodiment, a groove116can extend into the annular body112from the contact face114. The groove116may extend around at least a portion, or the entire, circumference of the scraper ring110. In certain embodiments, the groove116may extend around the annular body112transverse to a central axis of the annular body112. In other embodiments, the groove may have one or more arcuate or angled portions. In an embodiment, the groove may include a helical spiral. In an embodiment, the groove116may have a depth of at least 0.1 mm, at least 0.5 mm, or at least 1 mm. In another embodiment, the groove116may have a depth of no greater than 100 mm, no greater than 50 mm, or no greater than 10 mm.

As illustrated, the groove116may have a symmetrical cross section (i.e., viewed in cross section, the groove may be symmetrical about a line extending radially from the inner component104). Use of a symmetrical groove may permit installation of the scraper ring110within the annular recess108in either rotational orientation. That is, use of a symmetrical groove can permit installation of the scraper ring110in either the forward or backward orientation. In certain embodiments, the groove116can have an arcuate cross-sectional profile. For example, as illustrated, the groove116can be a hemi-circle. In other embodiments, the groove116can have a polygonal cross-sectional profile. Exemplary polygonal cross-sectional profiles include portions of triangles, quadrilaterals, pentagons, hexagons, heptagons, octagons, nonagons, decagons, hendecagons, or dodecagons. The polygonal cross-sectional profile may also include other shapes such as stars, Greek letters, or a combination of different linear sidewall segments. In yet further embodiments, the groove116can have a partially arcuate, partially polygonal cross-sectional profile.

In an embodiment, the scraper ring110may include a plurality of grooves116. For example, in a particular instance, the scraper ring110may include at least 2 grooves, at least 3 grooves, at least 4 grooves, or at least 5 grooves. In another instance, the scraper ring110may include no greater than 20 grooves or no greater than 10 grooves. In an embodiment, the grooves116may be equally spaced apart from one another. In another embodiment, the grooves116may have an uneven spacing configuration. In a particular instance, the grooves116may have similar cross-sectional profiles as one another. In another instance, at least two of the grooves116may have different cross-sectional profiles.

In a particular instance, the annular body112may have a generally rectangular cross-sectional profile. As used herein, a “generally rectangular cross-sectional profile” refers to a cross-sectional profile occupying at least 90% of a best fit rectangle, at least 95% of a best fit rectangle, or at least 99% of a best fit rectangle. In another particular instance, the annular body112may have a rectangular cross-sectional profile. In an embodiment, the annular body112may include a radially outer face118and first and second axial faces120and122, respectively, extending from the radially outer face118to the contact face114. In a particular embodiment, at least one of the first and second axial faces120or122can lie along a line that intersects the contact face114at a perpendicular angle. In a more particular embodiment, both the first and second axial faces120and122can lie along lines that intersect the contact face114at a perpendicular angle. In an embodiment, at least one of the first and second axial faces120and122can form a 90 degree angle with respect to the contact face114at the junction formed with the contact face114. That is, the junction between at least one of the first and second axial faces120and122and the contact face114may be essentially free of a chamfer. In another embodiment, at least one of the first and second axial faces120and122can meet the contact face114so as to form an acute or obtuse internal angle. Use of a perpendicular or acute junction between at least one of the first and second axial faces120and122and the contact face114may enhance scraping performance.

In another embodiment, at least one of the first and second axial faces120or122can lie along a line that intersects the radially outer face118at a perpendicular angle. In an embodiment, at least one of the first and second axial faces120or122can form a 90 degree angle with respect to the radially outer face118. That is, the junction between at least one of the first and second axial faces120and122and the contact face114may be essentially free, such as devoid, of a chamfer.

In an instance, the radially outer face118of the seal ring110can be planar as viewed in cross section. That is, the radially outer face118can be essentially free of grooves, recesses, dimples, or other features typically used in traditional seal assemblies to prevent disconnect of a secondary feature such as O-rings, compression straps, spring energizers, and other similar components used to bias sealing elements toward the inner component and generate a sufficient scraping and sealing characteristic.

In an embodiment, the annular body112can further include a bumper124disposed on at least one of the first and second axial faces120or122. The bumper124may extend from the first or second axial face120or122a distance of at least 0.1 mm, at least 0.5 mm, at least 1 mm, at least 5 mm, or at least 10 mm. In an embodiment, the bumper124may extend from the first or second axial face120or122by no greater than 100 mm or no greater than 20 mm. The bumper124may reduce frictional resistance between the annular recess108and the scraper ring110by reducing contact area therebetween. Specifically, the bumper124may have a thickness, as measured in a radial direction, less than a thickness of the scraper ring110, as measured in a radial direction. In an embodiment, the bumper124may extend around an entire circumference of the scraper ring110. In another embodiment, the bumper124may extend around only a portion of the circumference of the scraper ring110. In yet another embodiment, the bumper124may include a plurality of segments spaced apart around the circumference of the scraper ring110. In a particular embodiment, the scraper segments may be equally spaced around the circumference of the scraper ring110. In another particular embodiment, the scraper segments may be located at uneven intervals around the circumference of the scraper ring110. Radially inner and outer walls of the bumper124may form an internal bumper angle of at least 90 degrees, at least 100 degrees, at least 110 degrees, at least 120 degrees, or at least 130 degrees.

The scraper ring110can have a thickness, as measured in a radial direction under ambient conditions, of at least 1 mm, at least 2 mm, at least 3 mm, at last 4 mm, at least 5 mm, or at least 10 mm. In an embodiment, the scraper ring110can have a thickness of no greater than 1000 mm, no greater than 100 mm, no greater than 75 mm, no greater than 50 mm, or no greater than 25 mm. In certain embodiments, the scraper ring can have a width, as measured in an axial direction under ambient conditions, of at least 1 mm, at least 5 mm, at least 10 mm, at least 25 mm, at least 50 mm, at least 75 mm, or at least 100 mm. In other embodiments, the scraper ring110can have a width of no greater than 1000 mm, no greater than 500 mm, no greater than 250 mm, or no greater than 150 mm. In a particular instance, the annular recess108can have a width, as measured in the axial direction, greater than the width of the scraper ring110.

In traditional seal assemblies, as the temperature within the assembly is reduced (e.g., to a point of cryogenic, or near cryogenic, operation), the sealing assembly can lack sufficient radial compressive strength to maintain sufficient contact with the inner component. In this regard, the sealing assembly can have reduced sealing performance when handling cryogenic, or near cryogenic substances, such as liquid nitrogen and liquid hydrogen. In an embodiment, the scraper ring110may include, comprise, consist of, or consist essentially of a material having a high coefficient of linear thermal expansion (CTE). For instance, the scraper ring110can include a material having a CTE of at least 75×10−6/° C., at least 100×10−6/° C., at least 110×10−6/° C., at least 120×10−6/° C., at least 130×10−6/° C., at least 140×10−6/° C., at least 150×10−6/° C., at least 160×10−6/° C., at least 170×10−6/° C., at least 180×10−6/° C., at least 190×10−6/° C., or at least 200×10−6/° C. In a further embodiment, the scraper ring may include a material having a CTE of no greater than 500×10−6/° C., no greater than 400×10−6/° C., or no greater than 250×10−/° C. In this regard, the scraper ring110can be highly responsive to thermal environmental adjustments. Thus, as the temperature of the assembly100decreases, the scraper ring110can exhibit thermal shrinkage, causing the scraper ring110to generate a force against the inner component104.

In an embodiment, the scraper ring110can include a material having a modulus of elasticity (MOE) of no less than 1,000 MPa, no less than 2,000 MPa, no less than 3,000 MPa, no less than 4,000 MPa, or no less than 5,000 MPa. In another embodiment, the scraper ring110can include a material having a MOE of no greater than 10,000.

In an embodiment, the scraper ring110can include a material having a specific gravity, as measured at 22.8° C. according to ASTM D792, of less than 1, less than 0.99, less than 0.98, less than 0.97, less than 0.95, or less than 0.94. In another embodiment, the scraper ring110can include a material having a sand wheel wear, as measured according to the Abrasion Test, of less than 500, less than 400, less than 300, less than 200, or less than 150. In yet a further embodiment, the scraper ring110can include a material having a Shore D durometer, as measured according to D2240, of at least 50, at least 60, at least 70, or at least 80.

In a particular instance, the scraper ring110can include a polymeric material, such as for example, a thermoplastic polymer. Exemplary thermoplastic polymers include Nylon, polyethylene (PE), ultra high molecular weight polyethylene (UHMWPE), high-density polyethylene (HDPE), medium-density polyethylene (MDPE), polypropylene (PP), polyvinyl chloride (PVC), polyaryletherketone (PEAK), fluoropolymers, or any combination thereof. Exemplary fluoropolymers include fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroalkoxy (PFA), a terpolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride (THV), polychlorotrifluoroethylene (PCTFE), ethylene tetrafluoroethylene copolymer (ETFE), ethylene chlorotrifluoroethylene copolymer (ECTFE), or any combination thereof. The scraper ring110can have a homogenous composition in accordance with a particular embodiment.

In certain embodiments, the scraper ring110can include a low temperature hard coating, such as, for example, a diamond-like coating (DLC). In particular embodiments, the DLC can have a lattice structure similar to a diamond, wherein each carbon atom comprises four carbon atoms equally spaced. Alternatively, the scraper ring110can include a material impregnated therein by use of a high velocity oxygen fuel (HVOF) coating. HVOF coatings can extend valve life by significantly increasing the scraper ring's resistance to wear and corrosion. Moreover, HVOF coatings can affect a smoother surface finish with bond strengths in excess of 68 MPa.

In certain embodiments, the scraper ring110can include a material or coating such that it is inert to liquid natural gas, liquid nitrogen, liquid hydrogen, liquid helium, petrochemical residuals such as hydrogen sulfide (H2S), carbon monoxide (CO), carbon dioxide (CO2), sulfur dioxide (SO2), and trade halides. In a particular embodiment the scraper ring110can comprise a polyethylene such as UHMWPE. UHMWPE offers several advantages such as its resistance to degradation, superior tensile strength at, or near, cryogenic temperatures, and a minimal elongation at break. Further, the annular nature of the scraper ring110allows the inner diameter of the scraper ring110to contract upon exposure to cryogenic, or near cryogenic temperatures, thereby increasing the scraping force against the inner component104at low temperatures.

In an embodiment, the scraper ring110can have an initial inner diameter, IDI, as measured at ambient conditions prior to exposure to cryogenic temperatures and prior to installation, and an effective inner diameter, IDE, as measured prior to installation at −183° C., where IDEis less than IDI. For example, in a particular instance, IDEmay be less than 0.99 IDI, less than 0.98 IDI, less than 0.97 IDI, less than 0.96 IDI, less than 0.95 IDI, less than 0.9 IDI, less than 0.85 IDI, or less than 0.8 IDI. In another instance, IDEmay be no less than 0.1 IDI.

As the scraper rings110shrinks, it can provide a radially oriented loading force against the inner component104. In an embodiment, the loading force, as measured at −183° C., can be no less than 1 N/cm2, no less than 2 N/cm2, no less than 3 N/cm2, no less than 4 N/cm2, no less than 5 N/cm2, no less than 6 N/cm2, no less than 7 N/cm2, no less than 8 N/cm2, no less than 9 N/cm2, no less than 10 N/cm2, no less than 15 N/cm2, no less than 20 N/cm2, no less than 30 N/cm2, no less than 40 N/cm2, no less than 50 N/cm2, no less than 60 N/cm2, no less than 70 N/cm2, no less than 80 N/cm2, no less than 90 N/cm2, or no less than 100 N/cm2. Moreover, the loading force, as measured at −183° C., can be no greater than 500 N/cm2, such as no greater than 400 N/cm2, no greater than 300 N/cm2, no greater than 200 N/cm2, no greater than 175 N/cm2, no greater than 150 N/cm2, no greater than 125 N/cm2, or even no greater than 100 N/cm2. In certain embodiments, the loading force can be uniform as measured along the contact face114. In other embodiments, the loading force can change along the contact face114. For example, the loading force may be highest near at least one of the axial faces120and122.

In an embodiment, the scraper ring110can provide a loading force, as measured at room temperature (e.g., 22° C.), of no greater than 100 N/cm2, no greater than 50 N/cm2, no greater than 25 N/cm2, no greater than 10 N/cm2, no greater than 5 N/cm2, no greater than 1 N/cm2, no greater than 0.1 N/cm2, or no greater than 0.01 N/cm2. In a particular embodiment, the loading force at room temperature can be at least 0 N/cm2.

In an embodiment, the assembly100can further include an annular seal128disposed in an annular recess138. The seal128may include a heel130having fingers132and134extending from the heel130in parallel with respect to one another. An energizing element136can be disposed between and radially bias the fingers132and134apart from one another so as to provide an effective sealing characteristic. The fingers132and134are illustrated inFIG. 1exaggerated into the inner and outer components102and104as they would appear prior to assembly. Skilled artisans will recognize after reading the entire disclosure that the fingers132and134compress in a radial direction upon assembly.

In an embodiment, the annular seal128may include a material that is different than the material of the scraper ring110. In a particular embodiment, the annular seal128may include a polymer. The polymer can include, for example, a polyketone, a polyaramid, a polyimide, a polytherimide, a polyphenylene sulfide, a polyetherslfone, a polysulfone, a polypheylene sulfone, a polyamideimide, ultra high molecular weight polyethylene, a fluoropolymer, a polyamide, a polybenzimidazole, or any combination thereof. Exemplary fluoropolymers include fluorinated ethylene propylene (FEP), PTFE, polyvinylidene fluoride (PVDF), perfluoroalkoxy (PFA), a terpolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride (THV), polychlorotrifluoroethylene (PCTFE), ethylene tetrafluoroethylene copolymer (ETFE), ethylene chlorotrifluoroethylene copolymer (ECTFE), or any combination thereof. Fluoropolymers are used according to particular embodiments.

In a particular embodiment, the annular seal128can include lubrication to enhance sliding characteristics against the inner or outer components102or104. Exemplary lubricants can include molybdenum disulfide, tungsten disulfide, graphite, grapheme, expanded graphite, boron nitrade, talc, calcium fluoride, or any combination thereof. Additionally, the lubricant can comprise alumina, silica, titanium dioxide, calcium fluoride, boron nitride, mica, Wollastonite, silicon carbide, silicon nitride, zirconia, carbon black, pigments, or any combination thereof.

In certain embodiments, the scraper ring110may be spaced apart from the annular seal128in an axial direction. For example, in an embodiment, the scraper ring110and annular seal128may be spaced apart by at least 0.1 cm, at least 1 cm, at least 2 cm, at least 3 cm, at least 4 cm, at least 5 cm, at least 10 cm, or at least 25 cm. In other embodiments, the scraper ring110and annular seal128may be spaced apart by no greater than 1000 cm, no greater than 500 cm, or no greater than 100 cm. Such spacing may be desirable in applications where the assembly may be exposed to a large temperature gradient. For instance, in a particular application the temperature of the assembly100near the annular recess108may be significantly colder than the temperature near the annular recess138. While a material such as PTFE may be suitable for the annular seal128, it may be desirable for the scraper ring110to include a different material such as UHMWPE in view of the low temperature operating conditions at the annular recess108. Upon exposure to these low temperature operating conditions, the scraper ring110may effectively scrape contaminant from the inner component104, preventing the contaminant from reaching the urged liquid.

In certain instances, the annular seal128may have a maximum thickness, as measured in a radial direction prior to installation in the assembly, greater than the thickness of the scraper ring110. This may allow the annular seal128to protect against ingress of loose contaminant while the scraper removes contaminant frozen or adhered to the inner component102.

In certain embodiments, the assembly100may further include an annular spacer142disposed at an axial end120or122of the scraper ring110. The annular spacer142may be disposed in the annular recess108. In an embodiment, the annular spacer142may abut the axial end120or122of the scraper ring110. In another embodiment, the annular spacer can have a thickness, as measured in a radial direction prior to installation, that is no less than the thickness of the scraper ring110. In a further embodiment, the annular spacer142may include a material different than the material of the scraper ring110. For example, the annular spacer142may include a polyketone, a polyaramid, a polyimide, a polytherimide, a polyphenylene sulfide, a polyetherslfone, a polysulfone, a polypheylene sulfone, a polyamideimide, ultra high molecular weight polyethylene, a fluoropolymer, a polyamide, a polybenzimidazole, or any combination thereof. Exemplary fluoropolymers include fluorinated ethylene propylene (FEP), PTFE, polyvinylidene fluoride (PVDF), perfluoroalkoxy (PFA), a terpolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride (THV), polychlorotrifluoroethylene (PCTFE), ethylene tetrafluoroethylene copolymer (ETFE), ethylene chlorotrifluoroethylene copolymer (ECTFE), or any combination thereof. Fluoropolymers are used according to particular embodiments.

Installation of the scraper ring110in the assembly100may be performed prior to installation of the inner component102within the bore106. The scraper ring110may be deformed, e.g., by compressive force, and urged into the bore106at an angle until it achieves contact with the annular recess108. The scraper ring110may then be pivoted into position within the annular recess108. In certain embodiments, undersizing the scraper ring110relative to the annular recess108may permit easier installation by allowing a user to over-install, pivot, and arrange the entire scraper ring110into the annular recess108. After installation, the inner component102may be translated into position within the bore106. Traditional assemblies utilizing overlapping (or partially overlapping) components may be relatively more difficult to install as the components may deform at different rates, the components may occupy a greater volume making it more difficult to pivot to final orientation, and the components may slip relative to one another, requiring removal of the assembly for correction. Moreover, it is often impossible to see whether the components are aligned once in the annular recess as the innermost component typically blocks a user's view of the outer components.

Referring toFIG. 2, in other embodiments, an assembly200may include a secondary scraper ring244disposed in an annular recess208. The secondary scraper ring244may have any number of similar attributes or characteristics as described above with respect to the scraper ring110. In a particular instance, an annular spacer242may be disposed between the scraper ring210and the secondary scraper ring244. The scraper ring210, annular spacer242, and secondary scraper ring244may float with respect to one another within the annular recess208. That is, the scraper ring210, annular spacer242, and secondary scraper ring244may be disconnected from one another and move relative to one another. The annular spacer242may enhance relative sliding of the scraper ring210or secondary scraper ring244with respect to one another, thus permitting relative rotational movement therebetween.

In a particular embodiment, the second scraper ring244, annular spacer242, and scraper ring210may be installed individually, permitting maximum installation space and making it easier to reach final assembly. In other embodiments, the second scraper ring244, annular spacer242, and scraper ring210may be installed as a single unit, i.e., they may be installed together at a single time.

Referring toFIG. 3, in an embodiment, an assembly300can include a scraper ring310having grooves316with asymmetrical cross-sectional profiles. The scraper ring310may have any number of similar attributes or characteristics as described above with respect to the scraper ring110or210. In an embodiment, asymmetrical grooves316may enhance fluid pumping, expelling potential contaminants before passing along the bore306. A secondary scraper ring344may have grooves316oriented in reverse to permit enhanced bi-directional scraping and pumping action.

Item 1. A scraper ring for a linear motion assembly comprising:an annular body having a contact face adapted to contact an inner component,wherein the annular body comprises a material having a coefficient of linear thermal expansion of at least 75×10−6/° C.

Item 2. An assembly for linear motion comprising:an outer component defining a bore and a first annular recess extending radially outward from the bore;an inner component disposed in the bore, wherein the inner component is adapted to translate longitudinally within the bore; anda scraper ring disposed in the first annular recess and contacting the inner component, wherein the scraper ring comprises ultra high molecular weight polyethylene.

Item 3. An assembly for linear motion comprising:an outer component defining a bore and a first annular recess extending radially outward from the bore;an inner component disposed in the bore, wherein the inner component is adapted to translate longitudinally within the bore; anda scraper ring disposed in the first annular recess and contacting the inner component, wherein there is no component disposed between any portion of the spacer ring and a radially outermost surface of the outer component.

Item 4. The scraper ring or assembly of any one of items 1 and 3, wherein the scraper ring comprises an ultra high molecular weight polyethylene.

Item 5. The assembly of any one of items 2-4, wherein the scraper ring is adapted to provide a loading force against the inner component, as measured at −183° C., of no less than 1 N/cm2, no less than 2 N/cm2, no less than 3 N/cm2, no less than 4 N/cm2, no less than 5 N/cm2, no less than 6 N/cm2, no less than 7 N/cm2, no less than 8 N/cm2, no less than 9 N/cm2, no less than 10 N/cm2, no less than 15 N/cm2, no less than 20 N/cm2, no less than 30 N/cm2, no less than 40 N/cm2, no less than 50 N/cm2, no less than 60 N/cm2, no less than 70 N/cm2, no less than 80 N/cm2, no less than 90 N/cm2, or no less than 100 N/cm2, wherein the scraper ring is adapted to provide a loading force against the inner component, as measured at −183° C., of no greater than 500 N/cm2, such as no greater than 400 N/cm2, no greater than 300 N/cm2, no greater than 200 N/cm2, no greater than 175 N/cm2, no greater than 150 N/cm2, no greater than 125 N/cm2, or even no greater than 100 N/cm2

Item 6. The assembly of any one of items 2-5, wherein the first annular recess comprises a radially outer surface, and wherein the scraper ring is adapted to contact the radially outer surface of the first annular recess and a surface of the inner component when exposed to at least one temperature, wherein the scraper ring has a thickness that is less than a depth of the first annular recess.

Item 7. The assembly of any one of items 2-6, wherein the assembly further comprises:an annular seal comprising:a heel and a first and a second fingers extending from the heel; andan energizing element disposed between the first and second fingers.

Item 8. The assembly of item 7, wherein the scraper ring is spaced apart from the annular seal in an axial direction, wherein the scraper ring is spaced apart from the annular seal by at least 0.1 cm, at least 1 cm, at least 2 cm, at least 3 cm, at least 4 cm, at least 5 cm, at least 10 cm, or at least 25 cm, wherein the scraper ring is spaced apart from the annular seal by no greater than 1000 cm, no greater than 500 cm, or no greater than 100 cm.

Item 9. The assembly of any one of items 7 and 8, wherein the annular seal comprises a different material than the scraper ring, wherein the annular seal comprises a fluoropolymer, wherein the annular seal comprises a PTFE, wherein the annular seal comprises a filler.

Item 10. The assembly of any one of items 7-9, wherein the annular seal is disposed within a second annular recess extending radially outward from the bore.

Item 11. The assembly of any one of items 7-10, wherein the annular seal has a maximum thickness, as measured in a radial direction prior to installation in the assembly, wherein the scraper ring has a thickness, as measured in a radial direction prior to installation in the assembly, and wherein the maximum thickness of the annular seal is greater than the thickness of the scraper ring.

Item 12. The assembly of any one of items 2-11, further comprising:an annular spacer disposed at an axial end of the scraper ring.

Item 13. The assembly of item 12, wherein the annular spacer is disposed within the annular recess, wherein the annular spacer abuts the axial end of the scraper ring, wherein the annular spacer has a thickness, as measured in a radial direction prior to installation in the assembly, that is no less than a thickness of the scraper ring, as measured in a radial direction prior to installation in the assembly, wherein the annular spacer comprises a different material than the scraper ring, wherein the annular spacer comprises a fluoropolymer, wherein the annular spacer comprises a PTFE.

Item 14. The assembly of any one of items 12-13, further comprising a secondary scraper ring, wherein the annular spacer is disposed between the scraper ring and the secondary scraper ring.

Item 15. The scraper ring or assembly of any one of the preceding items, wherein the linear motion assembly comprises a piston assembly.

Item 16. The scraper ring or assembly of any one of the preceding items, wherein the linear motion assembly is adapted to operate at temperatures of less than −100° C., less than −125° C., less than −150° C., less than −175° C., less than −200° C., or less than −225° C.

Item 17. The scraper ring or assembly of any one of the preceding items, wherein the scraper ring has a thickness, as measured in a radial direction at ambient conditions, of at least 1 mm, at least 2 mm, at least 3 mm, at least 4 mm, at least 5 mm, or at least 10 mm, wherein the scraper ring has a thickness of no greater than 100 mm, no greater than 75 mm, no greater than 50 mm, or no greater than 25 mm.

Item 18.The scraper ring or assembly of any one of the preceding items, wherein the scraper ring has a width, as measured in an axial direction at ambient conditions, of at least 1 mm, at least 5 mm, at least 10 mm, at least 25 mm, at least 50 mm, at least 75 mm, or at least 100 mm, wherein the scraper ring has a width of no greater than 1000 mm, no greater than 500 mm, no greater than 250 mm, or no greater than 150 mm.

Item 19. The scraper ring or assembly of any one of the preceding items, wherein the scraper ring has an initial inner diameter, IDI, as measured uninstalled at ambient conditions, and an effective inner diameter, IDE, as measured uninstalled at −183° C. , and wherein IDEis less than IDI, wherein IDEis less than 0.99 IDI, less than 0.98 IDI, less than 0.97 IDI, less than 0.96 IDI, less than 0.95 IDI, less than 0.9 IDI, less than 0.85 IDI, or less than 0.8 IDI.

Item 20. The scraper ring or assembly of any one of the preceding items, wherein the scraper ring comprises an annular body having a generally rectangular cross-sectional profile, wherein the scraper ring comprises an annular body having a rectangular cross-sectional profile.

Item 21. The scraper ring or assembly of any one of the preceding items, wherein the scraper ring comprises an annular body having a contact face adapted to contact the inner component, a radially outer face opposite the contact face, and a first and second axial faces.

Item 22. The scraper ring or assembly of item 21, wherein the annular body of the scraper ring further comprises a bumper disposed on at least one of the first and second axial faces, wherein the bumper extends along the at least one of the first and second faces a distance less than a thickness of the scraper ring.

Item 23. The scraper ring or assembly of any one of items 21 and 22, wherein the scraper ring further defines a groove extending radially outward from the contact face.

Item 24. The scraper ring or assembly of any one of items 1 and 23, wherein the groove comprises at least 2 grooves, at least 3 grooves, at least 4 grooves, or at least 5 grooves, wherein the groove comprises no greater than 20 grooves, or no greater than 10 grooves.

Item 25. The scraper ring or assembly of any one of items 1, 23, and 24, wherein the groove is symmetrical as viewed in cross section.

Item 26. The scraper ring or assembly of any one of items 1 and 23-25, wherein the groove is asymmetrical as viewed in cross section, wherein the groove is adapted to prevent ingress of a contaminant into the assembly, wherein the groove is adapted to pump a contaminant out of the assembly when the seal ring is translated in an axial direction.

Item 27. The scraper ring or assembly of any one of items 1, 2, and 4-26, wherein the scraper ring is disposed such that there is no component between any portion of the scraper ring and an outer component.

Note that not all of the features described above are required, that a portion of a specific feature may not be required, and that one or more features may be provided in addition to those described. Still further, the order in which features are described is not necessarily the order in which the features are installed.

Certain features are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombinations.