Composite Sucker Rod Assemblies
Sucker rod assemblies are provided. A sucker rod assembly includes one or more continuous fiber reinforced thermoplastic rods. Each rod has a core comprising a plurality of generally unidirectionally oriented continuous fibers embedded in a thermoplastic resin. A sucker rod assembly further includes a first end fitting and a second end fitting, at least one of which is connected to the plurality of continuous fiber reinforced thermoplastic rods. Each rod has an ultimate tensile strength of between approximately 280,000 pounds per square inch and approximately 370,000 pounds per square inch, and the continuous fibers have a ratio of ultimate tensile strength to mass per unit length of greater than about 1,000 Megapascals per gram per meter. The continuous fibers constitute from about 25 wt. % to about 80 wt. % of each rod, and the thermoplastic resin constitutes from about 20 wt. % to about 75 wt. % of each rod.
The present application claims priority to U.S. Provisional Application Ser. No. 62/102,796, filed on Jan. 13, 2015, which is incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTIONA sucker rod is a rod uses in the oil and gas industry to join together surface and downhole components of a reciprocating piston pump installed in an oil well. In most cases, a number of sucker rods are connected together, end-to-end, to obtain the necessary length between the surface and downhole components. Each sucker rod can including fittings on each end of the rod in order to facilitate the connection to other sucker rods and the surface and downhole components.
Many known sucker rods are formed from metals, such as steel. However, there are significant problems with the use of such sucker rods. For example, metal sucker rods are heavy and have relatively small strength-to-weight ratios. Additionally, the chemical and temperature resistance capabilities of metal sucker rods are relatively low, particularly when subjected to oil well environments. Further, metal sucker rods are very susceptible to mechanical wear during operation. Still further, the requirement that a number of sucker rods of limited lengths be connected together to obtain longer necessary lengths introduces weak spots into the assembly, due to the connection joints between the various sucker rods.
More recently, fiberglass sucker rods have been introduced. While these sucker rods have addressed some of the issues raised above, many concerns remain. Additionally, known fiberglass sucker rods are relatively stiff, and thus cannot be spooled for transportation purposes, etc.
Accordingly, improved sucker rods are desired in the art. In particular, sucker rods which have improved strength-to-weight ratios, chemical and temperature resistance capabilities, mechanical wear resistance, and flexibility, and which can have relatively longer lengths which meet application requirements, would be advantageous.
SUMMARY OF THE INVENTIONIn accordance with one embodiment of the present disclosure, a sucker rod assembly is provided. The sucker rod assembly includes a plurality of continuous fiber reinforced thermoplastic rods arranged in a stranded bundle. Each of the plurality of continuous fiber reinforced thermoplastic rods has a core which includes a plurality of generally unidirectionally oriented continuous fibers embedded in a thermoplastic resin. The sucker rod assembly further includes a first end fitting and a second end fitting, at least one of the first and second end fittings connected to the plurality of continuous fiber reinforced thermoplastic rods. Each of the plurality of rods has an ultimate tensile strength of between approximately 280,000 pounds per square inch and approximately 370,000 pounds per square inch. The continuous fibers constitute from about 25 wt. % to about 80 wt. % of each of the plurality of rods and the thermoplastic resin constitutes from about 20 wt. % to about 75 wt. % of each of the plurality of rods.
In accordance with another embodiment of the present disclosure, a sucker rod assembly is provided. The sucker rod assembly includes a single monolithic continuous fiber reinforced thermoplastic rod. The continuous fiber reinforced thermoplastic rod has a core which includes a plurality of generally unidirectionally oriented continuous fibers embedded in a thermoplastic resin. The sucker rod assembly further includes a first end fitting and a second end fitting, at least one of the first and second end fittings connected to the continuous fiber reinforced thermoplastic rod. The continuous fiber reinforced thermoplastic rod has an ultimate tensile strength of between approximately 280,000 pounds per square inch and approximately 370,000 pounds per square inch. The continuous fibers constitute from about 25 wt. % to about 80 wt. % of the rod and the thermoplastic resin constitutes from about 20 wt. % to about 75 wt. % of the rod.
In some exemplary embodiments, the continuous fibers of a rod of a sucker rod assembly of the present disclosure have a ratio of ultimate tensile strength to mass per unit length of greater than about 1,000 Megapascals per gram per meter. For example, in some exemplary embodiments, the continuous fibers of a rod of a sucker rod assembly of the present disclosure are carbon fibers.
In some exemplary embodiments, the thermoplastic resin of a rod of a sucker rod assembly of the present disclosure includes a polyarylene sulfide, such as polyphenylene sulfide.
In some exemplary embodiments, a rod of a sucker rod assembly of the present disclosure includes a capping layer surrounding the core of the rod. For example, in some exemplary embodiments, the capping layer may include polyetherether ketone and be free from fibers.
Other features and aspects of the present invention are set forth in greater detail below.
A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:
Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.
DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTSIt is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention.
Generally speaking, the present disclosure is directed to sucker rod assemblies. A sucker rod assembly in accordance with the present disclosure is formed from one or more continuous fiber reinforced thermoplastic (“CFRT”) rods. In some embodiments, a plurality of CFRT rods may be utilized, with the rods arranged for example in a stranded bundle. In other embodiments, a single monolithic CFRT rod may be utilized. In exemplary embodiments, the CFRT rods may include a polyarylene sulfide, such as polyphenylene sulfide, in or as the thermoplastic resin. Further, in exemplary embodiments, the CFRT rods may utilize carbon fibers embedded in the thermoplastic resin.
The use of such rods in sucker rod assemblies in accordance with the present disclosure provides numerous advantages over previously known sucker rods. For example, the use of CFRT materials provides lightweight and strong rods, thus increasing the strength-to-weight ratios of the resulting sucker rod assemblies. Further, as discussed herein, CFRT rods formed in accordance with the present disclosure have excellent flexibility, thus allowing spooling of the resulting sucker rod assemblies. Additionally, CFRT rods formed in accordance with the present disclosure can be provided at relatively long lengths, which can be adjusted to meet application requirements. Thus, resulting sucker rod assemblies may advantageously not require increased connections and resulting weak spots, due to the ability of the CFRT rods to have lengths which are adapted to fit the requirements of particular applications.
Still further, CFRT rods formed in accordance with the present disclosure may have improved chemical and temperature resistance capabilities. For example, each rod may include a core and a capping layer surrounding and bonded to the core. This capping layer may protect the rod generally from harsh environmental conditions, and may further improve the wear resistance of the rod. In exemplary embodiments, for example, a capping layer may include polyetherether ketone, and may be free from fibers.
Referring now to
Any suitable fittings 20, 22 may be utilized in a sucker rod assembly 10 in accordance with the present disclosure. For example,
Referring now to
As illustrated, the rod 750 has a generally circular shape and includes a core 760 formed from one or more consolidated rovings 142. By “generally circular”, it is generally meant that the aspect ratio of the rod (height divided by the width) is typically from about 1.0 to about 1.5, and in some embodiments, about 1.0. Due to selective control over the process used to impregnate fiber rovings and form tapes 152, 156 as discussed herein, as well the process for compressing and shaping the tape(s) into a preform and finally into a core 760, as discussed further herein, the rod 750 and core 760 thereof may possess a relatively even distribution of resin 214 across along its entire length. This also means that the continuous fibers are distributed in a generally uniform manner about a longitudinal central axis “L” of the core 760. As shown in
The cross-sectional thickness (“T”) of the rod 750 may be strategically selected to help achieve a particular strength. For example, the rod 750 may have a thickness (e.g., diameter) of from about 0.1 to about 40 millimeters, in some embodiments from about 0.5 to about 30 millimeters, and in some embodiments, from about 1 to about 10 millimeters. The thickness of the capping layer 800 depends on the intended function of the part, but is typically from about 0.01 to about 10 millimeters, and in some embodiments, from about 0.02 to about 5 millimeters. Regardless, the total cross-sectional thickness or height of the rod typically ranges from about of from about 0.1 to about 50 millimeters, in some embodiments from about 0.5 to about 40 millimeters, and in some embodiments, from about 1 to about 20 millimeters. While the rod 750 may be substantially continuous in length, the length of the rod is often practically limited by the spool onto which it will be wound and stored or the length of the continuous fibers. For example, the length often ranges from about 1000 to about 5000 meters, although even greater lengths are certainly possible.
Referring still to
The thermoplastic material of the core 760 may further include a plurality of fibers embedded therein to reinforce the thermoplastic material. In exemplary embodiments, the CFRT material includes continuous fibers, although it should be understood that long fibers may additionally be included therein. The fibers may be dispersed in the thermoplastic material to form the CFRT material. As used therein, the term “long fibers” generally refers to fibers, filaments, yarns, or rovings that are not continuous, and as opposed to “continuous fibers” which generally refer to fibers, filaments, yarns, or rovings having a length that is generally limited only by the length of a part. The fibers dispersed in the polymer material may be formed from any conventional material known in the art, such as metal fibers, glass fibers (e.g., E-glass, A-glass, C-glass, D-glass, AR-glass, R-glass, S-glass such as S1-glass or S2-glass), carbon fibers (e.g., graphite), boron fibers, ceramic fibers (e.g., alumina or silica), aramid fibers (e.g., Kevlar® marketed by E. I. duPont de Nemours, Wilmington, Del.), synthetic organic fibers (e.g., polyamide, polyethylene, paraphenylene, terephthalamide, polyethylene terephthalate and polyphenylene sulfide), and various other natural or synthetic inorganic or organic fibrous materials known for reinforcing polymer compositions. Glass fibers, carbon fibers, and aramid fibers are particularly desirable. In exemplary embodiments, the continuous fibers may be generally unidirectional.
A rod 750 in accordance with the present disclosure may be formed using any suitable process or apparatus. Exemplary embodiments of suitable processes and apparatus, such as pultrusion processes and apparatus, for forming a tape and rod according to the present disclosure are discussed in detail below.
Referring to
A continuous fiber roving 142 or a plurality of continuous fiber rovings 142 are supplied from a reel or reels 144 to die 150. The rovings 142 are generally positioned side-by-side, with minimal to no distance between neighboring rovings, before impregnation. The feedstock 137 may further be heated inside the die by heaters 146 mounted in or around the die 150. The die is generally operated at temperatures that are sufficient to cause and/or maintain the proper melt temperature for the thermoplastic material, thus allowing for the desired level of impregnation of the rovings by the thermoplastic material. Typically, the operation temperature of the die is higher than the melt temperature of the thermoplastic material, such as at temperatures from about 200° C. to about 450° C. When processed in this manner, the continuous fiber rovings 142 become embedded in the thermoplastic material, which may be a resin 214 processed from the feedstock 137. The mixture may then exit the impregnation die 150 as wetted composite, extrudate, or tape 152.
As used herein, the term “roving” generally refers to a bundle of individual fibers 400. The fibers 400 contained within the roving can be twisted or can be straight. The rovings may contain a single fiber type or different types of fibers 400. Different fibers may also be contained in individual rovings or, alternatively, each roving may contain a different fiber type. The continuous fibers employed in the rovings possess a high degree of tensile strength relative to their mass. For example, the ultimate tensile strength of the fibers is typically from about 1,000 to about 15,000 Megapascals (“MPa”), in some embodiments from about 2,000 MPa to about 10,000 MPa, and in some embodiments, from about 3,000 MPa to about 6,000 MPa. Such tensile strengths may be achieved even though the fibers are of a relatively light weight, such as a mass per unit length of from about 0.05 to about 2 grams per meter, in some embodiments from about 0.4 to about 1.5 grams per meter. The ratio of ultimate tensile strength to mass per unit length may thus be greater than about 1,000 Megapascals per gram per meter (“MPa/g/m”), in some embodiments greater than about 4,000 MPa/g/m, and in some embodiments from about 5,000 to about 20,000 MPa/g/m. Carbon fibers are particularly suitable for use as the continuous fibers, which typically have a tensile strength to mass ratio in the range of from about 5,000 to about 7,000 MPa/g/m. The continuous fibers often have a nominal diameter of about 4 to about 35 micrometers, and in some embodiments, from about 9 to about 35 micrometers. The number of fibers contained in each roving can be constant or vary from roving to roving. Typically, a roving contains from about 1,000 fibers to about 50,000 individual fibers, and in some embodiments, from about 5,000 to about 30,000 fibers.
A pressure sensor 147 may sense the pressure near the impregnation die 150 to allow control to be exerted over the rate of extrusion by controlling the rotational speed of the screw shaft 134, or the feed rate of the feeder. That is, the pressure sensor 147 is positioned near the impregnation die 150, such as upstream of the manifold assembly 220, so that the extruder 130 can be operated to deliver a correct amount of resin 214 for interaction with the fiber rovings 142. After leaving the impregnation die 150, impregnated rovings 142 or the extrudate or tape 152, which may comprises the CFRT material, may enter an optional pre-shaping or guiding section (not shown) and/or a preheating device to control the temperature of the extrudate before entering a nip formed between two adjacent rollers 190. Although optional, the rollers 190 can help to consolidate the impregnated rovings 142 into a tape 156 or consolidate the tape 152 into a final tape 156, as well as enhance fiber impregnation and squeeze out any excess voids. In addition to the rollers 190, other shaping devices may also be employed, such as a die system. Regardless, the resulting consolidated tape 156 is pulled by tracks 162 and 164 mounted on rollers. The tracks 162 and 164 also pull the impregnated rovings 142 or tape 152 from the impregnation die 150 and through the rollers 190. If desired, the consolidated tape 156 may be wound up at a section 171. Generally speaking, the resulting tapes are relatively thin and typically have a thickness of from about 0.05 to about 1 millimeter, in some embodiments from about 0.1 to about 0.8 millimeters, and in some embodiments, from about 0.1 to about 0.4 millimeters.
Perspective views of one embodiment of a die 150 according to the present disclosure are further shown in
Within the impregnation die, it is generally desired that the rovings 142 are traversed through an impregnation zone 250 to impregnate the rovings with the polymer resin 214. In the impregnation zone 250, the polymer resin may be forced generally transversely through the rovings by shear and pressure created in the impregnation zone 250, which significantly enhances the degree of impregnation. This is particularly useful when forming a composite from tapes of high fiber content, such as about 35% weight fraction (“Wf”) or more, and in some embodiments, from about 40% Wf or more. Typically, the die 150 will include a plurality of contact surfaces 252, such as for example at least 2, at least 3, from 4 to 7, from 2 to 20, from 2 to 30, from 2 to 40, from 2 to 50, or more contact surfaces 252, to create a sufficient degree of penetration and pressure on the rovings 142. Although their particular form may vary, the contact surfaces 252 typically possess a curvilinear surface, such as a curved lobe, pin, etc. The contact surfaces 252 are also typically made of a metal material.
As shown in
The plurality of channels 222 may, in exemplary embodiments as shown in
If desired, the runners 222 may include a second branched runner group 234 diverging from the first branched runner group 232, as shown. For example, a plurality of runners 222 from the second branched runner group 234 may branch off from one or more of the runners 222 in the first branched runner group 232. The second branched runner group 234 may include 2, 3, 4 or more runners 222 branching off from runners 222 in the first branched runner group 232.
If desired, the runners 222 may include a third branched runner group 236 diverging from the second branched runner group 234, as shown. For example, a plurality of runners 222 from the third branched runner group 236 may branch off from one or more of the runners 222 in the second branched runner group 234. The third branched runner group 236 may include 2, 3, 4 or more runners 222 branching off from runners 222 in the second branched runner group 234.
In some exemplary embodiments, as shown, the plurality of branched runners 222 has a symmetrical orientation along a central axis 224. The branched runners 222 and the symmetrical orientation thereof generally evenly distribute the resin 214, such that the flow of resin 214 exiting the manifold assembly 220 and coating the rovings 142 is substantially uniformly distributed on the rovings 142. This desirably allows for generally uniform impregnation of the rovings 142.
Further, the manifold assembly 220 may in some embodiments define an outlet region 242. The outlet region 242 is that portion of the manifold assembly 220 wherein resin 214 exits the manifold assembly 220. Thus, the outlet region 242 generally encompasses at least a downstream portion of the channels or runners 222 from which the resin 214 exits. In some embodiments, as shown, at least a portion of the channels or runners 222 disposed in the outlet region 242 have an increasing area in a flow direction 244 of the resin 214. The increasing area allows for diffusion and further distribution of the resin 214 as the resin 214 flows through the manifold assembly 220, which further allows for substantially uniform distribution of the resin 214 on the rovings 142. Additionally or alternatively, various channels or runners 222 disposed in the outlet region 242 may have constant areas in the flow direction 244 of the resin 214, or may have decreasing areas in the flow direction 244 of the resin 214.
In some embodiments, as shown, each of the channels or runners 222 disposed in the outlet region 242 is positioned such that resin 214 flowing therefrom is combined with resin 214 from other channels or runners 222 disposed in the outlet region 242. This combination of the resin 214 from the various channels or runners 222 disposed in the outlet region 242 produces a generally singular and uniformly distributed flow of resin 214 from the manifold assembly 220 to substantially uniformly coat the rovings 142. Alternatively, some of the channels or runners 222 disposed in the outlet region 242 may be positioned such that resin 214 flowing therefrom is discrete from the resin 214 from other channels or runners 222 disposed in the outlet region 242. In these embodiments, a plurality of discrete but generally evenly distributed resin flows 214 may be produced by the manifold assembly 220 for substantially uniformly coating the rovings 142.
As shown in
As further illustrated in
In some embodiments, as shown in
Further, as shown in
Upon exiting the manifold assembly 220 and the gate passage 270 of the die 150 as shown in
As shown in
For example, as discussed above, in exemplary embodiments as shown in
In some embodiments, as shown in
In exemplary embodiments, as shown in
Angle 254 at which the rovings 142 traverse the contact surfaces 252 may be generally high enough to enhance shear and pressure, but not so high to cause excessive forces that will break the fibers. Thus, for example, the angle 254 may be in the range between approximately 1° and approximately 30°, and in some embodiments, between approximately 5° and approximately 25°.
As stated above, contact surfaces 252 typically possess a curvilinear surface, such as a curved lobe, pin, etc. In exemplary embodiments as shown, a plurality of peaks, which may form contact surfaces 252, and valleys are thus defined. Further, in many exemplary embodiments, the impregnation zone 250 has a waveform cross-sectional profile. In one exemplary embodiment as shown in
In other embodiments, the contact surfaces 252 are lobes that form portions of a waveform surface of only one of the first or second plate 256 or 258. In these embodiments, impingement occurs only on the contact surfaces 252 on the surface of the one plate. The other plate may generally be flat or otherwise shaped such that no interaction with the coated rovings occurs.
In other alternative embodiments, the impregnation zone 250 may include a plurality of pins (or rods), each pin having a contact surface 252. The pins may be static, freely rotational (not shown), or rotationally driven. Further, the pins may be mounted directly to the surface of the plates defining the impingement zone, or may be spaced from the surface. It should be noted that the pins may be heated by heaters 143, or may be heated individually or otherwise as desired or required. Further, the pins may be contained within the die 150, or may extend outwardly from the die 150 and not be fully encased therein.
In further alternative embodiments, the contact surfaces 252 and impregnation zone 250 may comprise any suitable shapes and/or structures for impregnating the rovings 142 with the resin 214 as desired or required.
As discussed, a roving 142 traversed through an impregnation zone 250 according to the present disclosure may become impregnated by resin 214, thus resulting in an impregnated roving 142, and optionally a tape 152 comprising at least one roving 142, exiting the impregnation zone 250, such as downstream of the contact surfaces 252 in the run direction 282. The impregnated rovings 142 and optional tape 152 exiting the impregnation zone 250 are thus formed from a fiber impregnated polymer material, as discussed above.
As further shown in
As shown in
It should be understood that a tape 152, 156 according to the present disclosure may have any suitable cross-sectional shape and/or size. For example, such tape 152, 156 may have a generally rectangular shape, or a generally oval or circular or other suitable polygonal or otherwise shape. Further, it should be understood that one or more impregnated rovings 142 having been traversed through the impregnation zone 250 may together form the tape 152, 156, with the resin 214 of the various rovings 142 connected to form such tape 152, 156. The various above amounts, ranges, and/or ratios may thus in exemplary embodiments be determined for a tape 152 having any suitable number of impregnated rovings 142 embedded and generally dispersed within resin 214.
To further facilitate impregnation of the rovings 142, they may also be kept under tension while present within the die 150, and specifically within the impregnation zone 250. The tension may, for example, range from about 5 to about 300 Newtons, in some embodiments from about 50 to about 250 Newtons, and in some embodiments, from about 100 to about 200 Newtons per roving 142 or tow of fibers.
As shown in
Additionally, other components may be optionally employed to assist in the impregnation of the fibers. For example, a “gas jet” assembly may be employed in certain embodiments to help uniformly spread a roving of individual fibers, which may each contain up to as many as 24,000 fibers, across the entire width of the merged tow. This helps achieve uniform distribution of strength properties. Such an assembly may include a supply of compressed air or another gas that impinges in a generally perpendicular fashion on the moving rovings that pass across exit ports. The spread rovings may then be introduced into a die for impregnation, such as described above.
It should be understood that tapes 152, 156 and impregnated rovings 142 thereof according to the present disclosure need not be formed in the dies 150 and other apparatus as discussed above. Such dies 150 and apparatus are merely disclosed as examples of suitable equipment for forming tapes 152, 156. The use of any suitable equipment or process to form tapes 152, 156 is within the scope and spirit of the present disclosure.
A relatively high percentage of fibers may be employed in a tape (and resulting rod), and CFRT material thereof, to provide enhanced strength properties. For instance, fibers typically constitute from about 25 wt. % to about 80 wt. %, in some embodiments from about 30 wt. % to about 75 wt. %, and in some embodiments, from about 35 wt. % to about 70 wt. % of the tape or material thereof. Likewise, polymer(s) typically constitute from about 20 wt. % to about 75 wt. %, in some embodiments from about 25 wt. % to about 70 wt. %, and in some embodiments, from about 30 wt. % to about 65 wt. % of the tape 152, 156. Such percentage of fibers may additionally or alternatively be measured as a volume fraction. For example, in some embodiments, the CFRT material may have a fiber volume fraction between approximately 25% and approximately 80%, in some embodiments between approximately 30% and approximately 70%, in some embodiments between approximately 40% and approximately 60%, and in some embodiments between approximately 45% and approximately 55%.
After formation of a tape 152, 156, the tape 152, 156 may be formed into a core 760 of a rod 750. Any suitable processes and apparatus may be utilized to form a tape 152, 156 into the core 760 of a rod 750. The specific manner in which rovings and tapes 152, 156, are shaped may be carefully controlled to ensure that rods 750 can be formed with an adequate degree of compression and strength properties. Referring to
The tapes 152, 156 may be heated in an oven 645 before entering a consolidation die. Heating may be conducted using any known type of oven, as in an infrared oven, convection oven, etc. During heating, the fibers in the tapes are unidirectionally oriented to optimize the exposure to the heat and maintain even heat across the entire tape. The temperature to which the tapes 152, 156 are heated is generally high enough to soften the thermoplastic polymer to an extent that the tapes can bond together. However, the temperature is not so high as to destroy the integrity of the material. The temperature may, for example, range from about 100° C. to about 500° C., in some embodiments from about 200° C. to about 400° C., and in some embodiments, from about 250° C. to about 350° C. In one particular embodiment, for example, polyphenylene sulfide (“PPS”) is used as the polymer, and the tapes are heated to or above the melting point of PPS, which is about 285° C.
Upon being heated, the tapes 152, 156 are provided to a consolidation die 650 that compresses them together into a preform 614, as well as aligns and forms the initial shape of the rod. As shown generally in
The desired heating, compression, and shaping of the tapes 152, 156 may be accomplished through the use of a die 650 having one or multiple sections. For instance, although not shown in detail in
If desired, a second die 660 (e.g., calibration die) may also be employed that compresses the preform 614 into the final shape of the rod. When employed, it is sometimes desired that the preform 614 is allowed to cool briefly after exiting the consolidation die 650 and before entering the optional second die 660. This allows the consolidated preform 614 to retain its initial shape before progressing further through the system. Typically, cooling reduces the temperature of the exterior of the rod below the melting point temperature of the thermoplastic matrix to minimize and substantially prevent the occurrence of melt fracture on the exterior surface of the rod. The internal section of the rod, however, may remain molten to ensure compression when the rod enters the calibration die body. Such cooling may be accomplished by simply exposing the preform 614 to the ambient atmosphere (e.g., room temperature) or through the use of active cooling techniques (e.g., water bath or air cooling) as is known in the art. In one embodiment, for example, air is blown onto the preform 614 (e.g., with an air ring). The cooling between these stages, however, generally occurs over a small period of time to ensure that the preform 614 is still soft enough to be further shaped. For example, after exiting the consolidation die 650, the preform 614 may be exposed to the ambient environment for only from about 1 to about 20 seconds, and in some embodiments, from about 2 to about 10 seconds, before entering the second die 660. Within the die 660, the preform is generally kept at a temperature below the melting point of the thermoplastic matrix used in the ribbon so that the shape of the rod can be maintained. Although referred to above as single dies, it should be understood that the dies 650 and 660 may in fact be formed from multiple individual dies (e.g., face plate dies).
Thus, in some embodiments, multiple individual dies 660 may be utilized to gradually shape the material into the desired configuration. The dies 660 are placed in series, and provide for gradual decreases in the dimensions of the material. Such gradual decreases allow for shrinkage during and between the various steps.
For example, as shown in
In further embodiments, the cross-sectional area of an inlet 662 and the cross-sectional area of a corresponding outlet 664 of the first die 660 may have a ratio in a range between approximately 1.5 to 1 and 6 to 1.
The first die 660 thus provides a generally smooth transformation of polymer impregnated fiber material to a shape that is relatively similar to a final shape of the resulting rod, which in exemplary embodiments has a circular or oval shaped cross-section. Subsequent dies, such as a second die 660 and third die 660 as shown in
In further exemplary embodiments, dies 660 having relatively long land lengths 669 may be desired, due to for example desires for proper cooling and solidification, which are critical in achieving a desired rod shape and size. Relatively long land lengths 669 reduce stresses and provide smooth transformations to desired shapes and sizes, and with minimal void fraction and bow characteristics. In some embodiments, for example, a ratio of land length 669 at an outlet 664 to major axis length 666 at the outlet 664 for a die 660 may be in the range between approximately 0 and approximately 20, such as between approximately 2 and approximately 6.
The use of calibration dies 660 according to the present disclosure provides for gradual changes in material cross-section, as discussed. These gradual changes may in exemplary embodiments ensure that the resulting product, such as a rod or other suitable product has a generally uniform fiber distribution with relatively minimal void fraction.
It should be understood that any suitable number of dies 660 may be utilized to gradually form the material into a profile having any suitable cross-sectional shape, as desired or required by various applications.
In addition to the use of one or more dies, other mechanisms may also be employed to help compress the preform 614 into the shape of a core 760 for a rod 750. For example, forming rollers 690, as shown in
The rollers 690 in exemplary embodiments, such as at least the portions contacting the material, may have generally smooth surfaces. For example, relatively hard, polished surfaces are desired in many embodiments. For example, the surface of the rollers may be formed from a relatively smooth chrome or other suitable material. This allows the rollers 690 to manipulate the preform 614 without damaging or undesirably altering the preform 614. For example, such surfaces may prevent the material from sticking to the rollers, and the rollers may impart smooth surfaces onto the materials.
In some embodiments, the temperature of the rollers 690 is controlled. This may be accomplished by heating of the rollers 690 themselves, or by placing the rollers 690 in a temperature controlled environment.
Further, in some embodiments, surface features 692 may be provided on the rollers 690. The surface features 692 may guide and/or control the preform 614 in one or more directions as it is passed through the rollers. For example, surface features 692 may be provided to prevent the preform 614 from folding over on itself as it is passed through the rollers 690. Thus, the surface features 692 may guide and control deformation of the preform 614 in the cross-machine direction relative to the machine direction A as well as in the vertical direction relative to the machine direction A. The preform 614 may thus be pushed together in the cross-machine direction, rather than folded over on itself, as it is passed through the rollers 690 in the machine direction A.
In some embodiments, tension regulation devices may be provided in communication with the rollers. These devices may be utilized with the rollers to apply tension to the preform 614 in the machine direction, cross-machine direction, and/or vertical direction to further guide and/or control the preform.
As indicated above, the resulting rod is also applied with a capping layer to protect it from environmental conditions or to improve wear resistance. Referring again to
The capping layer is generally free of continuous fibers. That is, the capping layer contains less than about 10 wt. % of continuous fibers, in some embodiments about 5 wt. % or less of continuous fibers, and in some embodiments, about 1 wt. % or less of continuous fibers (e.g., 0 wt. %). Nevertheless, the capping layer may contain other additives for improving the final properties of the rod. Additive materials employed at this stage may include those that are not suitable for incorporating into the continuous fiber material. For instance, it may be desirable to add pigments to reduce finishing labor, or it may be desirable to add flame retardant agents to enhance the flame retarding features of the rod. Because many additive materials are heat sensitive, an excessive amount of heat may cause them to decompose and produce volatile gases. Therefore, if a heat sensitive additive material is extruded with an impregnation resin under high heating conditions, the result may be a complete degradation of the additive material. Additive materials may include, for instance, mineral reinforcing agents, lubricants, flame retardants, blowing agents, foaming agents, ultraviolet light resistant agents, thermal stabilizers, pigments, and combinations thereof. Suitable mineral reinforcing agents may include, for instance, calcium carbonate, silica, mica, clays, talc, calcium silicate, graphite, calcium silicate, alumina trihydrate, barium ferrite, and combinations thereof.
While not shown in detail herein, the capping die 672 may include various features known in the art to help achieve the desired application of the capping layer. For instance, the capping die 672 may include an entrance guide that aligns the incoming rod. The capping die may also include a heating mechanism (e.g., heated plate) that pre-heats the rod before application of the capping layer to help ensure adequate bonding. Following capping, the shaped part 615, or rod 750, is then finally cooled using a cooling system 680 as is known in the art. The cooling system 680 may, for instance, be a sizing system that includes one or more blocks (e.g., aluminum blocks) that completely encapsulate the rod while a vacuum pulls the hot shape out against its walls as it cools. A cooling medium may be supplied to the sizer, such as air or water, to solidify the rod in the correct shape.
Even if a sizing system is not employed, it is generally desired to cool the rod 750 after it exits the capping die (or the consolidation or calibration die if capping is not applied). Cooling may occur using any technique known in the art, such a water tank, cool air stream or air jet, cooling jacket, an internal cooling channel, cooling fluid circulation channels, etc. Regardless, the temperature at which the material is cooled is usually controlled to achieve optimal mechanical properties, part dimensional tolerances, good processing, and an aesthetically pleasing composite. For instance, if the temperature of the cooling station is too high, the material might swell in the tool and interrupt the process. For semi-crystalline materials, too low of a temperature can likewise cause the material to cool down too rapidly and not allow complete crystallization, thereby jeopardizing the mechanical and chemical resistance properties of the composite. Multiple cooling die sections with independent temperature control can be utilized to impart the optimal balance of processing and performance attributes. In one particular embodiment, for example, a water tank is employed that is kept at a temperature of from about 0° C. to about 30° C., in some embodiments from about 1° C. to about 20° C., and in some embodiments, from about 2° C. to about 15° C.
If desired, one or more sizing blocks (not shown) may also be employed, such as after capping. Such blocks contain openings that are cut to the exact rod shape, graduated from oversized at first to the final rod shape. As the rod passes therethrough, any tendency for it to move or sag is counteracted, and it is pushed back (repeatedly) to its correct shape. Once sized, the rod may be cut to the desired length at a cutting station (not shown), such as with a cut-off saw capable of performing cross-sectional cuts or the rod can be wound on a reel in a continuous process. The length of rod will then be limited to the length of the fiber tow.
As will be appreciated, the temperature of the rod as it advances through any section of the system of the present invention may be controlled to yield optimal manufacturing and desired final composite properties. Any or all of the assembly sections may be temperature controlled utilizing electrical cartridge heaters, circulated fluid cooling, etc., or any other temperature controlling device known to those skilled in the art.
Referring again to
The rods 750 that result from use of dies and methods according to the present disclosure may have a very low void fraction, which helps enhance their strength. For instance, the void fraction may be about 5% or less, in some embodiments about 4% or less, in some embodiments about 3% or less, in some embodiments about 2% or less, in some embodiments about 1.5% or less, in some embodiments about 1% or less, and in some embodiments, about 0.5% or less. The void fraction may be measured using techniques well known to those skilled in the art. For example, the void fraction may be measured using a “resin burn off” test in which samples are placed in an oven (e.g., at 600° C. for 3 hours) to burn out the resin. The mass of the remaining fibers may then be measured to calculate the weight and volume fractions. Such “burn off” testing may be performed in accordance with ASTM D 2584-08 to determine the weights of the fibers and the polymer matrix, which may then be used to calculate the “void fraction” based on the following equations:
Vf=100*(ρt−ρc)/ρt
where,
Vf is the void fraction as a percentage;
ρc is the density of the composite as measured using known techniques, such as with a liquid or gas pycnometer (e.g., helium pycnometer);
ρt is the theoretical density of the composite as is determined by the following equation:
ρt=1/[Wf/ρf+Wm/ρm]
ρm is the density of the polymer matrix (e.g., at the appropriate crystallinity);
ρf is the density of the fibers;
Wf is the weight fraction of the fibers; and
Wm is the weight fraction of the polymer matrix.
Alternatively, the void fraction may be determined by chemically dissolving the resin in accordance with ASTM D 3171-09. The “burn off” and “dissolution” methods are particularly suitable for glass fibers, which are generally resistant to melting and chemical dissolution. In other cases, however, the void fraction may be indirectly calculated based on the densities of the polymer, fibers, tape and/or rod in accordance with ASTM D 2734-09 (Method A), where the densities may be determined ASTM D792-08 Method A. Of course, the void fraction can also be estimated using conventional microscopy equipment.
As discussed above, after exiting an impregnation die 150, 412, the CFRT material may in some embodiments form a tape 152, 156. The number of rovings employed in each tape 152, 156 may vary. Typically, however, a tape 152, 156 will contain from 2 to 80 rovings, and in some embodiments from 10 to 60 rovings, and in some embodiments, from 20 to 50 rovings. In some embodiments, it may be desired that the rovings are spaced apart approximately the same distance from each other within the tape 152, 156. In other embodiments, however, it may be desired that the rovings are combined, such that the fibers of the rovings are generally evenly distributed throughout the tape 152, 156, such as throughout one or more resin rich portions and a fiber rich portion as discussed above. In these embodiments, the rovings may be generally indistinguishable from each other. Referring to
Through use of apparatus and methods according to the present disclosure and control over the various parameters mentioned above, tapes and rods having a very high strength may be formed. For example, the rods may exhibit a high maximum load. Maximum load may be determined according to ASTM D3039. The maximum load may be, for example, greater than about 290 pounds per square inch (psi), or for example greater than about 130 kilograms per square inch (130 ksi).
The rods may exhibit a relatively high flexural modulus. The term “flexural modulus” generally refers to the ratio of stress to strain in flexural deformation (units of force per area), or the tendency for a material to bend. It is determined from the slope of a stress-strain curve produced by a “three point flexural” test (such as ASTM D790-10, Procedure A), typically at room temperature. For example, the rod of the present invention may exhibit a minimum flexural modulus of about 10 Gigapascals (“GPa”), in some embodiments a flexural modulus from about 12 to about 400 GPa, in some embodiments a flexural modulus from about 15 to about 200 GPa, and in some embodiments a flexural modulus from about 20 to about 150 GPa. Furthermore, the ultimate tensile strength of a rod may be between approximately 280,000 pounds per square inch and approximately 370,000 pounds per square inch, such as between approximately 320,000 pounds per square inch and approximately 370,000 pounds per square inch. The term “ultimate tensile strength” generally refers to the maximum stress that a material can withstand while being stretched or pulled before necking and is the maximum stress reached on a stress-strain curve produced by a tensile test (such as ASTM D3916-08) at room temperature. The minimum tensile modulus of elasticity may also be about 50 GPa, or in some embodiments the tensile modulus of elasticity may be from about 70 GPa to about 500 GPa, or in some embodiments the tensile modulus of elasticity may be from about 100 GPa to about 300 GPa. The term “tensile modulus of elasticity” generally refers to the ratio of tensile stress over tensile strain and is the slope of a stress-strain curve produced by a tensile test (such as ASTM 3916-08) at room temperature. Notably, the strength properties of the composite rod referenced above may also be maintained over a relatively wide temperature range, such as from about −40° C. to about 300° C., and particularly from about 180° C. to 200° C.
Rods made according to the present disclosure may further have relatively high flexural fatigue life, and may exhibit relatively high residual strength. Flexural fatigue life and residual flexural strength may be determined based on a “three point flexural fatigue” test (such as ASTM D790, typically at room temperature. For example, the rods of the present invention may exhibit residual flexural strength after one million cycles at 160 Newtons (“N”) or 180 N loads of from about 60 kilograms per square inch (“ksi”) to about 115 ksi, in some embodiments about 70 ksi to about 115 ksi, and in some embodiments about 95 ksi to about 115 ksi. Further, the rods may exhibit relatively minimal reductions in flexural strength. For example, rods having void fractions of about 4% or less, in some embodiments about 3% or less, may exhibit reductions in flexural strength after three point flexural fatigue testing of about 1% (for example, from a maximum pristine flexural strength of about 106 ksi to a maximum residual flexural strength of about 105 ksi). Flexural strength may be tested before and after fatigue testing using, for example, a three point flexural test as discussed above.
The linear thermal expansion coefficient of the composite rod may be, on a ppm basis per ° C., less than about 5, less than about 4, less than about 3, or less than about 2. For instance, the coefficient (ppm/° C.) may be in a range from about −0.25 to about 5; alternatively, from about −0.17 to about 4; alternatively, from about −0.17 to about 3; alternatively, from about −0.17 to about 2; or alternatively, from about 0.29 to about 1.18. The temperature range contemplated for this linear thermal expansion coefficient may be generally in the −50° C. to 200° C. range, the 0° C. to 200° C. range, the 0° C. to 175° C. range, or the 25° C. to 150° C. range. The linear thermal expansion coefficient is measured in the longitudinal direction, i.e., along the length of the fibers.
The composite rod may also exhibit a relatively small “bend radius”, which is the minimum radius that the rod can be bent without breaking and is measured to the inside curvature of the rod. A smaller bend radius means that the rod is more flexible and can be spooled onto a smaller diameter bobbin. This property also makes the rod easier to implement in processes that currently use metal rods. Due to the improved process and resulting rod of the present invention, bend radiuses may be achieved that are less than about 40 times the outer diameter of the rod, in some embodiments from about 1 to about 30 times the outer diameter of the rod, and in some embodiments, from about 2 to about 25 times the outer diameter of the rod, determined at a temperature of about 25° C. For instance, the bend radius may be less than about 15 centimeters, in some embodiments from about 0.5 to about 10 centimeters, and in some embodiments, from about 1 to about 6 centimeters, determined at a temperature of about 25° C.
These and other modifications and variations of the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in such appended claims.
Claims
1. A sucker rod assembly, the sucker rod assembly comprising:
- a plurality of continuous fiber reinforced thermoplastic rods arranged in a stranded bundle, each of the plurality of continuous fiber reinforced thermoplastic rods having a core comprising a plurality of generally unidirectionally oriented continuous fibers embedded in a thermoplastic resin; and
- a first end fitting and a second end fitting, at least one of the first and second end fittings connected to the plurality of continuous fiber reinforced thermoplastic rods,
- wherein each of the plurality of rods has an ultimate tensile strength of between approximately 280,000 pounds per square inch and approximately 370,000 pounds per square inch, wherein the continuous fibers have a ratio of ultimate tensile strength to mass per unit length of greater than about 1,000 Megapascals per gram per meter, and wherein the continuous fibers constitute from about 25 wt. % to about 80 wt. % of each of the plurality of rods and the thermoplastic resin constitutes from about 20 wt. % to about 75 wt. % of each of the plurality of rods.
2. The sucker rod assembly of claim 1, wherein each of the plurality of rods has an ultimate tensile strength of between approximately 320,000 pounds per square inch and approximately 370,000 pounds per square inch.
3. The sucker rod assembly of claim 1, wherein the continuous fibers have a ratio of ultimate tensile strength to mass per unit length of from about 5,000 to about 20,000 Megapascals per gram per meter.
4. The sucker rod assembly of claim 1, wherein the continuous fibers are carbon fibers.
5. The sucker rod assembly of claim 1, wherein the thermoplastic resin includes a polyarylene sulfide.
6. The sucker rod assembly of claim 5, wherein the polyarylene sulfide is polyphenylene sulfide.
7. The sucker rod assembly of claim 1, wherein the continuous fibers constitute from about 30 wt. % to about 75 wt. % of each of the plurality of rods.
8. The sucker rod assembly of claim 1, wherein the core of each of the plurality of rods has a void fraction of about 3% or less.
9. The sucker rod assembly of claim 1, wherein each of the plurality of rods has a minimum flexural modulus of about 10 Gigapascals.
10. The sucker rod assembly of claim 1, wherein each of the plurality of rods has a minimum tensile modulus of elasticity of about 50 Gigapascals.
11. The sucker rod assembly of claim 1, wherein each of the plurality of rods has a bend radius of from about 0.5 to about 10 centimeters.
12. The sucker rod assembly of claim 1, further comprising a capping layer surrounding the core of each of the plurality of rods.
13. The sucker rod assembly of claim 12, wherein the capping layer includes polyetherether ketone.
14. The sucker rod assembly of claim 12, wherein the capping layer is free from fibers.
15. A sucker rod assembly, the sucker rod assembly comprising:
- a single monolithic continuous fiber reinforced thermoplastic rod, the continuous fiber reinforced thermoplastic rod having a core and a capping layer surrounding the core, the core comprising a plurality of generally unidirectionally oriented continuous fibers embedded in a thermoplastic resin, wherein the fibers are carbon fibers and the thermoplastic resin includes a polyarylene sulfide, the capping layer including polyetherether ketone and free from fibers; and
- a first end fitting and a second end fitting, at least one of the first and second end fittings connected to the continuous fiber reinforced thermoplastic rod,
- wherein the continuous fiber reinforced thermoplastic rod has an ultimate tensile strength of between approximately 280,000 pounds per square inch and approximately 370,000 pounds per square inch, and wherein the continuous fibers constitute from about 25 wt. % to about 80 wt. % of the rod and the thermoplastic resin constitutes from about 20 wt. % to about 75 wt. % of the rod.
16. The sucker rod assembly of claim 15, wherein the continuous fiber reinforced thermoplastic rod has an ultimate tensile strength of between approximately 320,000 pounds per square inch and approximately 370,000 pounds per square inch.
17. The sucker rod assembly of claim 15, wherein the polyarylene sulfide is polyphenylene sulfide.
18. The sucker rod assembly of claim 15, wherein the continuous fibers constitute from about 30 wt. % to about 75 wt. % of the rod.
19. The sucker rod assembly of claim 15, wherein the core of the rod has a void fraction of about 3% or less.
20. The sucker rod assembly of claim 15, wherein the rod has a minimum flexural modulus of about 10 Gigapascals.
21. The sucker rod assembly of claim 15, wherein the rod has a minimum tensile modulus of elasticity of about 50 Gigapascals.
22. The sucker rod assembly of claim 15, wherein the rod has a bend radius of from about 0.5 to about 10 centimeters.
Type: Application
Filed: Dec 15, 2015
Publication Date: Jul 14, 2016
Inventors: Ashish Sen (Winona, MN), Michael L. Wesley (Dover, MN), David W. Eastep (Winona, MN)
Application Number: 14/969,034