ENGINEERED CRUMB RUBBER COMPOSITION FOR USE IN ASPHALT BINDER AND PAVING MIX APPLICATIONS

Abstract

An engineered crumb rubber asphalt additive may comprise a plurality of a structural particles and a non-elastomeric liquid. At least a portion of the surface of the structural particles is coated with the non-elastomeric liquid. The structural particles may be crumb rubber particles. The engineered crumb rubber asphalt additive may also comprise a reagent. The non-elastomeric liquid may be selected from the group consisting of workability/compaction agents, slipping agents, and anti-stripping agents.

Claims

1. An engineered crumb rubber asphalt additive comprising: a plurality of structural particles; and a non-elastomeric liquid; wherein at least a portion of the surface of the structural particles is coated with the non-elastomeric liquid.

2. The engineered crumb rubber asphalt additive of claim 1, wherein the non-elastomeric liquid is selected from the group consisting of workability/compaction agents, slipping agents, and anti-stripping agents.

3. The engineered crumb rubber asphalt additive of claim 1, wherein the structural particles are crumb rubber particles.

4. The engineered crumb rubber asphalt additive of claim 3, wherein the crumb rubber particles are selected from the group consisting of rubber ground through ambient processing, rubber ground through cryogenic processing, recycled rubber, vulcanized rubber, and un-vulcanized rubber.

5. The engineered crumb rubber asphalt additive of claim 4, wherein the recycled rubber is from auto tires or truck tires or a combination thereof.

6. The engineered crumb rubber asphalt additive of claim 1, wherein the majority of the structural particles have a size between minus 16 mesh and plus 300 mesh.

7. The engineered crumb rubber asphalt additive of claim 6, wherein the majority of the structural particles have a size between minus 30 mesh and plus 300 mesh.

8. The engineered crumb rubber asphalt additive of claim 7, wherein the majority of the structural particles have a size between minus 40 mesh and plus 300 mesh.

9. An asphalt composition comprising the engineered crumb rubber asphalt additive of claim 1 and a heated asphalt mix.

10. An engineered crumb rubber asphalt additive comprising: a plurality of structural particles; one or more non-elastomeric liquids; and a reagent; wherein at least a portion of the surface of the structural particles is coated with both the one or more non-elastomeric liquids and the reagent.

11. The engineered crumb rubber asphalt additive of claim 10, wherein the reagent is a solvent.

12. The engineered crumb rubber asphalt additive of claim 10, wherein the one or more non-elastomeric liquids are self-hardening.

13. The engineered crumb rubber asphalt additive of claim 10, wherein the one or more non-elastomeric liquids are selected from the group consisting of workability/compaction agents, slipping agents, and anti-stripping agents.

14. The engineered crumb rubber asphalt additive of claim 10, wherein the structural particles are crumb rubber particles.

15. The engineered crumb rubber asphalt additive of claim 14, wherein the crumb rubber particles are selected from the group consisting of rubber ground through ambient processing, rubber ground through cryogenic processing, recycled rubber, vulcanized rubber, and un-vulcanized rubber.

16. The engineered crumb rubber asphalt additive of claim 14, wherein the recycled rubber is from auto tires or truck tires.

17. The engineered crumb rubber asphalt additive of claim 10, wherein the majority of the structural particles have a size between minus 16 mesh and plus 300 mesh.

18. The engineered crumb rubber asphalt additive of claim 17, wherein the majority of the structural particles have a size between minus 30 mesh and plus 300 mesh.

19. The engineered crumb rubber asphalt additive of claim 18, wherein the majority of the structural particles have a size between minus 40 mesh and plus 300 mesh.

20. An asphalt composition comprising the engineered crumb rubber asphalt additive of claim 10 and a heated asphalt mix.

21. An engineered crumb rubber asphalt additive comprising: a plurality of structural particles; a liquid non-elastomeric coating disposed on said structural particles; and a reagent disposed on said liquid non-elastomeric coated structural particles to create a hardened chemically-bonded coating on the surface of said structural particles.

22. The engineered crumb rubber asphalt additive of claim 21, wherein the reagent is a solvent.

23. The engineered crumb rubber asphalt additive of claim 21, wherein the non-elastomeric liquid is selected from the group consisting of workability/compaction agents, slipping agents, and anti-stripping agents.

24. The engineered crumb rubber asphalt additive of claim 21, wherein the structural particles are crumb rubber particles.

25. The engineered crumb rubber asphalt additive of claim 21, wherein the crumb rubber particles are selected from the group consisting of rubber ground through ambient processing, rubber ground through cryogenic processing, recycled rubber, vulcanized rubber, and un-vulcanized rubber.

26. The engineered crumb rubber asphalt additive of claim 21, wherein the recycled rubber is from auto tires or truck tires.

27. The engineered crumb rubber asphalt additive of claim 21, wherein the majority of the structural particles have a size between minus 16 mesh and plus 300 mesh.

28. The engineered crumb rubber asphalt additive of claim 27, wherein the majority of the structural particles have a size between minus 30 mesh and plus 300 mesh.

29. The engineered crumb rubber asphalt additive of claim 28, wherein the majority of the structural particles have a size between minus 40 mesh and plus 300 mesh.

30. An asphalt composition comprising the engineered crumb rubber asphalt additive of claim 21 and a heated asphalt mix.

31. An asphalt mix comprising the engineered crumb rubber asphalt additive of claim 1, gravel, sand, and binder.

32. The asphalt mix of claim 31, wherein said asphalt mix is dense graded asphalt mix, gap graded asphalt mixes, porous mixes, open graded mix, or stone matrix asphalt mixes.

33. The asphalt mix of claim 31, wherein said asphalt mix is used to produce a chip seal surface.

34.-50. (canceled)

Description

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

[0035] The following is a description of the examples depicted in the accompanying drawing. The figure is not necessarily to scale, and certain features and certain views of the figure may be shown exaggerated in scale or in schematic in the interest of clarity or conciseness.

[0036] FIG. 1 shows a schematic of a coated crumb rubber particle.

[0037] FIG. 2 shows a schematic of a coated crumb rubber particle.

[0038] FIG. 3 shows a schematic of an asphalt plant and engineered crumb rubber (ECR) feeder.

[0039] The preceding summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawing. For the purposes of illustration, certain embodiments are shown in the drawing. It should be understood, however, that the claims are not limited to the arrangements and instrumentality shown in the attached drawing. Furthermore, the appearance shown in the drawing is one of many ornamental appearances that can be employed to achieve the stated functions of the system.

DETAILED DESCRIPTION

[0040] In the following detailed description, specific details may be set forth in order to provide a thorough understanding of embodiments of the present invention. However, it will be clear to one skilled in the art when embodiments of the present invention may be practiced without some or all of these specific details. In other instances, well-known features or processes may not be described in detail so as not to unnecessarily obscure the invention. In addition, like or identical reference numerals may be used to identify common or similar elements.

[0041] When introducing elements of various embodiments of the present disclosure, the articles a, an, the, and said are intended to mean that there are one or more of the elements. The terms comprising, including, and having are intended to be inclusive and mean that there may be additional elements other than the listed elements. As used herein, approximately may generally refer to an approximate value that may, in certain embodiments, represent a difference (e.g., higher or lower) of less than 1% from the actual value. That is, an approximate value may, in certain embodiments, be accurate to within (e.g., plus or minus) 1% of the stated value. In certain other embodiments, as used herein, approximately may generally refer to an approximate value that may represent a difference (e.g., higher or lower) of less than 10% or less than 5% from the actual value.

[0042] The present technology is directed to a dry process for asphalt mix modification. This dry process employs the use of a unique engineered crumb rubber (ECR) asphalt mix modifier introduced like a fine aggregate during the production of asphalt mixes for use in asphalt paving applications. The ECR is precisely metered into the asphalt mix production process like a powder or fine aggregate.

[0043] According to the present disclosure, one may produce asphalt binders and mixes that include crumb rubber. As noted, crumb rubber modified asphalt binders can separate during transport and production, creating potential quality problems in asphalt mix production. In production, rubberized asphalt mixes tend to be difficult to produce because of higher binder viscosity, stickiness and separation. Due to the heated, softened and swollen rubber content, rubberized asphalt mixes are often sticky, harder to handle, transport, unload and compact.

When this ECR additive is used in an asphalt mix design, the following benefits accrue: (1) the mix will be is no more difficult to produce, handle, transport and place than standard unmodified hot or warm mix asphalt (2) the mix will readily compact and will not adhere to compaction tooling and equipment, (3) the ECR will permit a reduction in warm mix additives commonly used in asphalt production. Metered feeding of ECR into the asphalt production process will eliminate the risk of rubber/binder separation and associated pavement quality problems. The use of an ECR and a metered feeding process permits the production of crumb rubber modified asphalt in a manner more efficient than previously disclosed methods.

[0044] According to the present disclosure, the ECR asphalt mix modifier may be manufactured by coating at least a portion of the surface of crumb rubber particles with one or more non-elastomeric liquid chemicals. In some instances, the asphalt additive is manufactured by coating at least a portion of the surface of the crumb rubber particles with a non-elastomeric liquid. Some embodiments include methods for producing an asphalt additive comprising adding a non-elastomeric liquid to a plurality of crumb rubber particles wherein the non-elastomeric liquid coats a least a portion of the surface of the crumb rubber particles.

[0045] Non-limiting examples of the non-elastomeric liquids include workability/compaction agents, anti-stripping agents, slipping agents, glycols, organosilanes, and water. Non-limiting examples of workability/compaction agents include Evotherm (DAT, 3G), Sasobit, Vestenamer, Zycotherm, Zycosoil, Rediset (WMX, LQ), Advera, Cecabase RT, Sonnewarmix, Hydrogreen, Aspha-Min, and QPR Qualitherm. Non-limiting examples of anti-stripping agents include hydrated lime, hydrated lime slurry, Anova 1400, Anova 1410, Fastac, Evotherm (J12, M1, M14, U3), Morlife (5,000, T280), Pave Bond Lite, Pavegrip 550, Ad-here (77-00LS, HP PLUS Type 1, HP PLUS with Cecabase-RT 945, LOF 65-00, LOF 65-00 LSI, LOF 65-00 EU), Nova Grip (1016, 975, 1012), Zycotherm, Zycotherm (EZ, SP), Kohere (AS 700, AS 1000, AT 1000), Pavegrip 200, and Surfax AS 500. Non-limiting examples of slipping agents include industrial waxes, trans-polyoctenamer rubber (TOR) and polymethylsiloxane. Those skilled in the art may add other additives (apart from those listed) as, for example, workability/compaction agents, anti-stripping agents, or slipping agents.

[0046] In some instances the modified rubber is produced by coating at least a portion of the surface of the crumb rubber with at least two non-elastomeric liquids. In yet another instance the modified rubber is produced by coating at least a portion of the surface of the crumb rubber with a plurality of non-elastomeric liquids.

[0047] In some embodiments, an ECR asphalt mix modifier is produced by mixing the crumb rubber 200 and non-elastomeric liquid chemical to achieve a coating 210 on at least a portion of the crumb rubber 200, as shown schematically in FIG. 1. The crumb rubber can be vulcanized or un-vulcanized. This mixing can be done, for example, using a paddle mixer, a ribbon blender or mixer, a V blender, a continuous processor, a cone screw blender, a counter-rotating mixer, a double & triple shaft mixer, drum blenders, a intermix mixer, a horizontal mixer, or a vertical mixer. One of skill in the art will appreciate that mixing can be synonymous with other terms such as blending.

[0048] In some embodiments, an ECR asphalt mix modifier is produced by first mixing a non-elastomeric liquid chemical and reagent before mixing with the crumb rubber 300 to form a coating 310 on at least one portion of the crumb rubber 300, as shown schematically in FIG. 2. The crumb rubber may be vulcanized or un-vulcanized. This process will produce a dry coating that is firmly attached to the rubber and will not readily separate. The coating will not change the handling characteristics of the coated crumb rubber.

[0049] In some embodiments, when the ECR is added to a heated asphalt mix, the modified asphalt additive reduces the stickiness modified asphalt mix. In this instance the mix modification does not negatively impact the performance of the modified asphalt mix when used in paving applications.

[0050] In some embodiments, the ECR asphalt mix modifier is produced by combining a wet, non-elastomeric element with vulcanized or un-vulcanized crumb rubber to form a coating on at least one portion of the crumb rubber. In this embodiment, the resultant modified asphalt additive can be used in the manufacture of hot or warm mix asphalt.

[0051] In some embodiments, the ECR asphalt mix modifier is produced by combining a wet, non-elastomeric element with vulcanized or un-vulcanized crumb rubber to form a coating on at least one portion of the crumb rubber. In some embodiment the non-elastomeric coating element is self-hardening. This allows for low-variability flow of the coated rubber grains into granular material metered feeder systemsmeaning that the addition rate can't make the rubber sticky so that it has a highly variable flow rate in a metered feeding system. This embodiment also allows for low-variability flow of the coated rubber grains into, for example, a pneumatic feeder system, an auger-driven feeder system or a belt feeder system.

[0052] In some embodiments, the ECR asphalt mix modifier comprises a plurality of structural particles; a liquid non-elastomeric coating disposed on said structural particles; and a reagent disposed on said liquid non-elastomeric coated structural particles to create a hardened chemically-bonded coating on the surface of said structural particles. In further embodiments the structural particles are crumb rubber particles. The crumb rubber can be from a variety of rubber sources such as rubber ground through ambient processing and rubber ground through cryogenic processing. In one embodiment the rubber is a recycled rubber such as one that is made from auto tires and/or truck tires. In another embodiment the crumb rubber is made from vulcanized rubber. In another embodiment the crumb rubber is made from un-vulcanized rubber.

[0053] In some embodiments, the size of the structural particles may range between smaller than 16 mesh (which may be referred to as minus 16 mesh, meaning that the structural particles pass through a mesh having square openings that are 1/16.sup.th of an inch wide, and thus that the diameters of the structural particles are smaller than 1/16.sup.th of an inch) and larger than 300 mesh (which may be referred to as plus 300 mesh, meaning that the structural particles do not pass through a mesh having square openings that are 1/300.sup.th of an inch wide, and thus that the diameters of the structural particles are larger than 1/300.sup.th of an inch). In some embodiments, the size of the structural particles may range between minus 20 mesh and plus 300 mesh. In some embodiments, the size of the structural particles may range between minus 30 mesh and plus 150 mesh. In some embodiments, the size of the structural particles may range between minus 40 mesh and plus 60 mesh. In other embodiments, different combinations of mesh openings between minus 16 mesh and plus 300 mesh may be used. The recycling of crumb rubber can be inherently variable because cutting tools may vary in sharpness over time (e.g., the tools may become duller over time), producing some size variation in the product. As used in the present disclosure, the size of the structural particles refers to the size of the majority (at least approximately 90%) of the structural particles; as such, there may thus be a minority of structural particles (up to approximately 10%) that fall outside of the stated size range (either larger or smaller). Thus, majority as used in the present disclosure with respect to the size of structural particles means that at least approximately 90% of the structural particles have the stated size. The minority of structural particles are thus the up to approximately 10% of structural particles that are either oversize or undersize (as compared to the stated size range or value. Also, the size of the structural particles refers to the size of uncoated structural particles, which may be made from either vulcanized or un-vulcanized rubber.

[0054] In some embodiments, the ECR asphalt mix modifier is added to an asphalt mix. In further embodiments this asphalt mix comprises gravel, sand and binder. The asphalt mix may be, for example, dense graded asphalt mix, gap graded asphalt mixes, porous mixes, open graded mix, or stone matrix asphalt mixes. The asphalt mix may be, for example, used to produce a chip seal surface.

[0055] In some embodiments, the structural particles and non-elastomeric liquid chemical are mixed into the binder and heated before mixing with aggregate. In other embodiments, the structural particles and non-elastomeric liquid chemical are mixed with the aggregate before the addition of asphalt binder.

[0056] FIG. 3 shows a schematic of an example asphalt production plant with ECR modification. Coarse aggregate 300 and fine aggregate 302 are moved by front end loader 310 to feeders 320 that meter various aggregate mix designs through a scalping screen 330, then convey the screened aggregate to a rotating heated drum 340 where the aggregate is heated and mixed. In many mix designs, Recycled Asphalt Pavement (RAP) is fed into the drum via a feeder system 322 through a collar on the drum 350. In mix designs using the Engineered Crumb Rubber (ECR) referenced in this application, the ECR is metered into the drum using a metered feeder 324 or 320 (located at either location as indicated). A heating system 370 keeps the asphalt binder stored in a tank 360 in a liquid state so that the binder can be pumped into the rotating drum 340 where it is mixed with aggregate, RAP, and rubber to make a warm or hot mix asphalt. The heated mix is transported by belt or auger to a holding silo 380, after which it is loaded onto trucks 390 for transport to a paving project.

Example 1

[0057] In this example, an ECR asphalt mix modifier was used in demonstration projects on a heavily-travelled interstate highway in the Northern Plains. This is an area with significant truck traffic, high summer heat, sub-zero winter air temperatures, and a high frequency of freeze-thaw events. The ECR-based mix designs incorporated in the project were built around two stone mastic asphalt (SMA) mix designs with polymer-modified asphalt. Instead of using a 70-28 performance-graded polymer modified (stiff) asphalt binder, the ECR mix used a 58 28 performance graded (softer) binder with a mix modification including 10% ECR by weight of virgin binder. Both mix designs had 12.1% recycled asphalt pavement (RAP) and 5% recycled asphalt shingles (RAS) content with a design binder content of 6%. Testing of the polymer modified mix produced Hamburg Test rutting of 2.06 mm of rut after 20,000 passes and a DCT (Disc-shaped Compact Tension) Test scoring of 566. Mixes produced with ECR mixing generated testing results of 2.51 mm of rut on the Hamburg Test after 20,000 passes and 602 on the DCT. Both mix designs are roughly compatible in performance testing. Multiple year field trial results show comparable field performance between the ECR asphalt mix designs and polymer modified asphalt mix designs.

[0058] Trial Results Summary

TABLE-US-00001 HAMBURG TEST DCT MIX DESIGN RESULTS RESULTS POLYMER MODIFIED SMA 2.06 mm 566 ECR MODIFIED SMA 2.51 mm 602

Example 2

[0059] In this example, ECR was used as an asphalt modifier in demonstration projects on a heavily-travelled interstate highway in the Northern Plains. As noted above, this is an area with significant truck traffic, high summer heat, sub-zero winter air temperatures, and a high frequency of freeze-thaw events. ECR mix designs were compared with terminal blend crumb rubber modified asphalt mix designs, both in the lab and field.

[0060] The ECR-based mix designs incorporated in the project were built around one SMA mix originally designed with 70, 28 polymer-modified asphalt. 58, 28 and 46, 34 performance graded binders were used as the base binder in a series of mix designs that included moderate levels of asphalt binder replacement with recycled asphalt shingles (RAS) and recycled asphalt pavement (RAP). These mix designs were designed with the same base binders and modified with either terminal blend rubber or ECR. The terminal blend crumb rubber modified binders used 12% by weight rubber content. The ECR design mixes used 10% by weight of virgin binder rubber content.

[0061] Mix testing demonstrated the following:

For the 58, 28 base binder (soft binder) mix designs, terminal blend rubber mix designs exhibited a 3.85 mm rut under Hamburg Wheel Testing, while the ECR mix designs exhibited a rut of 3.12 mm. Crack testing using the I-FIT semicircular bend cracking test showed results of 3.51 for the terminal blend rubber mix designs and 4.14 for the ECR mix designs. In both sets of mix testing results, ECR mixes outperformed terminal blend rubber mixes while using 17% less rubber content.

[0062] For the 46, 34 base binder (very soft binder) mix designs, terminal blend rubber mix designs exhibited a 5.29 mm rut under Hamburg Wheel Testing, while the ECR mix designs exhibited a rut of 3.2 mm. Crack testing using the I-FIT semicircular bend test showed results of 4.55 for the terminal blend rubber mix designs and 6.42 for the ECR crumb rubber mix designs. In both sets of mix testing results, the ECR mixes outperformed terminal blend rubber mixes while using 17% less rubber content.

[0063] Multiple year field trial results show comparable field performance between ECR and terminal blend rubber modified designs.

[0064] Additional evaluation of these SMA mix designs included an evaluation of the workability and compactability of the mix following the addition of ECR. The standard SMA mix designs on the project included the addition of a commonly used warm mix additive designed to allow easier compaction of the mix following placement at lower compaction temperatures. Laboratory testing of the mix compaction requirements revealed that with the use of approximately 8 lbs. of ECR in the mix design, the use of warm mix additives could be reduced by more than 50%.

[0065] Trial Results Summary

TABLE-US-00002 HAMBURG TEST IFIT MIX DESIGN RESULTS RESULTS 58-28 BINDER TERMINAL BLEND RUBBER 3.85 3.51 ENGINEERED CRUMB RUBBER 3.12 4.14 46-34 BINDER TERMINAL BLEND RUBBER 5.29 4.55 ENGINEERED CRUMB RUBBER 3.20 6.42

Example 3

[0066] In this example, ECR was used to modify an SMA mix design and the modified product was used on a test pavement section located on a heavily-traveled interstate highway near a major urban metropolitan area in the southern Central Plains of the United States. The area climate is characterized by cold winters with a moderately high freeze-thaw frequency, very hot summers and relatively high amounts of precipitation.

[0067] The base SMA mix design included no Rap or RAS, and a 6% binder content using a polymer-modified 70, 28 performance-graded binder.

[0068] During production of the crumb rubber modified mix designs, ECR was fed into the production process with the use of a loss-in-weight pneumatic feeder system (See FIG. 1). The flow of ECR into the mixing plant was measured every 45 seconds throughout the production run. Based on the operating tempo of the production plant, the target feed rate for ECR was 52 lbs. a minute. The field mean output of the unit averaged 52.13 lbs. per minute with a three-minute standard deviation of 1.3 lbs., indicating that the flow of ECR into the asphalt mix production process is both consistent and accurate. This also indicated that the distribution of rubber in the mix output was consistent as well.

[0069] Testing of lab-generated mix performance revealed the following characteristics for the polymer modified mix design: Hamburg testing with a 12.5 mm rut and DCT testing scoring 662. The higher levels of rut were due to the characteristics of the aggregate used for paving in the region, and the cracking resistance of the mix was considered good.

[0070] A similar mix design was produced with the same aggregate but with a 58, 28 binder and 10% by weight ECR substituted for the 70, 28 polymer modified binder. Testing of this lab-generated mix performance revealed the following characteristics: Hamburg testing with a 6.7 mm rut and DCT testing scoring 690. Although the higher levels of rut are due to the characteristics of the aggregate used for paving in the region, the rutting resistance of the rubber modified mix design was higher than the polymer modified mix design. The cracking resistance of the mix was considered excellent.

[0071] Both mix designs were produced at an operating production facility and used in a demonstration project on an interstate highway. Field mixes were tested after production and compaction. Because this was a thin lift application, rutting test data on cores were unavailable, but DCT testing indicated that the polymer modified mix scored a 715 while the rubber modified mix scored an 884. This suggests that the rubber modified asphalt is materially more resistant to cracking when compared to polymer modified asphalts in a similar mix design.

[0072] Additional evaluation of this SMA mix design included an evaluation of the workability and compactability of the mix following the addition of ECR. The standard SMA mix design on the project included the addition of a commonly used warm mix additive designed to allow easier compaction of the mix following placement at lower compaction temperatures. Laboratory testing of the mix compaction requirements revealed that with the use of approximately 12 lbs. of ECR in the mix design, no warm mix additives were required to provide easier compaction at the same compaction temperatures found with the use of a warm mix additive.

[0073] Trial Results Summary

TABLE-US-00003 HAMBURG TEST DCT MIX DESIGN RESULTS RESULTS LAB GENERATED SAMPLES POLYMER MODIFIED SMA 12.5 mm 662 ECR MODIFIED SMA 6.7 mm 690 ASPHALT FIELD SAMPLES POLYMER MODIFIED SMA 715 ECR MODIFIED SMA 884

[0074] Some of the elements described herein are identified explicitly as being optional, while other elements are not identified in this way. Even if not identified as such, it will be noted that, in some embodiments, some of these other elements are not intended to be interpreted as being necessary, and would be understood by one skilled in the art as being optional.

[0075] While the present disclosure has been described with reference to certain implementations, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present method and/or system. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from its scope. For example, systems, blocks, and/or other components of disclosed examples may be combined, divided, re-arranged, and/or otherwise modified. Therefore, the present disclosure is not limited to the particular implementations disclosed. Instead, the present disclosure will include all implementations falling within the scope of the appended claims, both literally and under the doctrine of equivalents.