The present disclosure relates to liners and liner systems for machine bodies, and more particularly, to liners and liner systems including those formed from polyurethane.
Machines such as off-highway trucks may be used to carry material excavated from the earth or from other sources such as scrap yards. For example, such machines may have material-carrying bodies configured to receive, carry, and deposit such material. The material may be transferred to the machine by earth moving machines such as excavators and loaders, which use buckets to dump the material into the machine body. The repeated process of receiving the dumped material and depositing the material may result in premature wear of the machine body due to the impact of the material as it is dumped into the machine body and slides against the body as it is deposited from the machine. Therefore, it may be desirable to provide the machine body with a liner to protect the machine body from premature wear.
It may be desirable for a liner to have a combination of properties. For example, it may be desirable for a liner to be cut- and chip-resistant, abrasion resistant, have a low coefficient of friction, and have a superior fatigue life. This may prevent excessive wear as the material is deposited into the machine body and is evacuated from the machine body. In addition, it may be desirable for the liner to be deformable, have a relatively low modulus, and have a relatively high energy absorbing capacity, for example, to protect the machine from shock as the material is being deposited into the machine body.
It may also be desirable to provide a liner retention system that provides a secure coupling between the liner and the machine body to prevent the liner from unintentionally sliding out of the machine body during dumping of the material from the machine body. In addition, it may be desirable for such a system to be relatively lightweight to avoid unnecessarily increasing the weight in the machine body. It may also be desirable to provide a system that is relatively easily and inexpensively installed or replaced.
An example of a protective overlay for a truck box is disclosed in U.S. Pat. No. 4,029,354 to Valeri (“the '354 patent”). In particular, the '354 patent discloses a pair of elongated anchors having a Z-shaped cross-section, each having one flange embedded in an elastomeric block and the other flange welded to the truck box. The sides of each elastomeric block are angled so as to form a converging slot between adjacent blocks. An elongated strip of elastomeric material softer than the blocks is pressed into each slot to create a generally flush relation with the blocks. According to the '354 patent, the elastomeric material may be polyurethane, and the blocks may be used to completely cover the surface of the truck box to be protected.
Although the protective overlay disclosed in the '354 patent may provide some level of protection for the truck box, it may suffer from a number of possible drawbacks. For example, the elastomeric blocks may not provide a desirable combination of characteristics for a machine bed liner. For example, the overlay may not provide a combination of one or more of cut- and chip-resistance, abrasion resistance, a low coefficient of friction, and superior fatigue life. It may also not provide one or more of a desired level deformability, a relatively low modulus, and a relatively high energy absorbing capacity. In addition, by virtue of the anchors being welded to the truck box, the overlay of the '354 patent may be relatively complex or expensive to install or replace.
The liner and liner system disclosed herein may be directed to mitigating or overcoming one or more of the possible drawbacks set forth above.
According to a first aspect, the present disclosure is directed to a liner for a machine body. The liner may include a first layer including a first polyurethane having first material characteristics, and a second layer coupled to the first layer. The second layer may include a second polyurethane having second material characteristics different than the first material characteristics, wherein the first layer and the second layer are chemically bonded to one another. For example, the first layer may be a top layer, and the first layer may have a Shore hardness ranging from about 80A to about 98A. According to a further aspect, the second layer may be a base layer, and the second layer may have a Shore hardness ranging from about 50A to about 80A.
According to still a further aspect, the liner may further include an interlayer between the first layer and the second layer, wherein the interlayer may include a third polyurethane, and wherein the first layer and the second layer may be chemically bonded to one another via the interlayer. For example, the interlayer may have a Shore hardness ranging from about 75A to about 85A.
According to yet another aspect, the liner may further include a third layer coupled to the first layer, wherein the third layer may include a third polyurethane having third material characteristics different than the first material characteristics. For example, the third layer may be a top layer, and the third layer may have a Shore hardness ranging from about 80A to 98A. According to a further aspect, the first layer may be an intermediate layer, the first layer may have a Shore hardness ranging from about 55A to about 75A, and the second layer may be a base layer.
According to still a further aspect, the liner may further include an interlayer between the first layer and the third layer, wherein the interlayer includes a fourth polyurethane, and wherein the first layer and the third layer are chemically bonded to one another via the interlayer. For example, the interlayer may have a Shore hardness ranging from about 75A to about 85A.
According to yet another aspect, the liner may further include a second interlayer between the second layer and the first layer, wherein the second interlayer includes a fifth polyurethane having fifth material characteristics. For example, the second layer may be a base layer, the first layer may be an intermediate later layer, and the third layer may be a top layer. According to still another aspect, the second layer may be harder than the first layer, and the third layer may be harder than the first layer.
According to a further aspect, the liner may further include a composite layer coupled to the second layer, wherein the third layer may include a metallic layer. According to another aspect, the composite layer may further include a third polyurethane. For example, the metallic layer may be a first metallic layer, the composite layer may further include a second metallic layer, and the third polyurethane may be sandwiched between the first metallic layer and the second metallic layer. According to still another aspect, the liner may further include an interlayer between the first layer and the second layer, wherein the interlayer includes a fourth polyurethane, wherein the first layer and the second layer may be chemically bonded to one another via the interlayer.
According to a further aspect, the present disclosure is directed to a liner system for a machine body. The liner system may include a liner including a first layer including a first polyurethane having first material characteristics, and a second layer coupled to the first layer. The second layer may include a second polyurethane having second material characteristics different than the first material characteristics. The first layer and the second layer may be chemically bonded to one another. The liner system may also include a liner retention system configured to couple the liner to the machine body. The liner retention system may include at least one retention strip configured to be coupled to the machine body. The retention strip may have a cross-section including a base portion, an intermediate portion, and a head portion forming a lateral profile. The base portion may have a base width, and the head portion may have head width, wherein the base width and head width are greater than an intermediate width of the intermediate portion. At least one edge of the liner may have a shape configured to substantially correspond to the lateral profile of the retention strip.
According to another aspect, the retention system may further include a coupling system associated with the base portion, and the coupling system may be configured to couple the retention strip to the machine body. For example, the coupling system may include at least one of adhesive, double-sided tape, a hook and loop fastener system, and fasteners.
According to yet another aspect, the present disclosure is directed to a method of making a liner for a machine body. The method may include forming a first layer including a first polyurethane having first material characteristics, and partially curing the first polyurethane. The method may further include forming a second layer including a second polyurethane having second material characteristics different than the first material characteristics. The method may also include heating the first and second layers for a sufficient time to cure the first and second polyurethanes, such that the first and second layers are chemically bonded to one another. For example, heating the first and second layers may result in the first and second layers being covalently bonded to one another.
According to another aspect, the method may further include forming an interlayer between the first layer and the second layer, wherein the interlayer includes a third polyurethane. The method may further include partially curing the interlayer, and heating the first layer, the second layer, and the interlayer for a sufficient time to cure the first, second, and third polyurethanes, such that the first and second layers are chemically bonded to one another via the interlayer. According to another aspect, the interlayer may be formulated to range from 50% to 90% stoichiometric.
According to yet another aspect, the method may further include forming a third layer coupled to the first layer, wherein the third layer includes a third polyurethane having third material characteristics different than the first material characteristics. The method may further include heating the first, second, and third layers for a sufficient time to cure the first, second, and third polyurethanes, such that the first and third layers are chemically bonded to one another.
According to another aspect, the method may further include forming an interlayer between the first layer and the third layer, wherein the interlayer includes a fourth polyurethane. The method may also include partially curing the interlayer, and heating the first layer, second layer, third layer, and interlayer for a sufficient time to cure the first, second, third, and fourth polyurethanes, such that the first and third layers are chemically bonded to one another via the interlayer. According to a further aspect, the method may further include forming a second interlayer between the second layer and the first layer, wherein the second interlayer includes a fifth polyurethane having fifth material characteristics. The method may further include partially curing the second interlayer, and heating the first layer, second layer, third layer, interlayer, and second interlayer for a sufficient time to cure the first, second, third, fourth, and fifth polyurethanes, such that the first and second layers are chemically bonded to one another via the second interlayer.
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As used herein, the terms “first,” “second”, “third,” etc., and forms thereof, are not necessarily indicative of order. Rather, these terms are used primarily to differentiate between different layers and different materials.
According to some embodiments, first layer 44 may be a top layer, and second layer 46 may be a base layer. First layer 44 and second layer 46 may be coupled to one another such that first layer 44 and second layer 46 are chemically bonded to one another (e.g., the first polyurethane of first layer 44 is covalently bonded to the second polyurethane of second layer 46). For example, at least some of the first polyurethane of first layer 44 is covalently bonded to at least some of the second polyurethane of second layer 46. This may result in a superior bond than bonds formed via adhesives, mechanisms, or fasteners. According to some embodiments, first layer 44 and second layer 46 are coupled directly to one another (i.e., they are in direct contact with one another). According to some embodiments, bed 14 may be formed from steel or another similar material, and second layer 46 may be coupled to bed 14 (e.g., floor 34) with adhesive 47. According to some embodiments, second layer 46 may be coupled to bed 14 via coupling systems and/or fasteners, as explained in more detail herein.
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According to some embodiments, second layer 46 may be formed from a second polyurethane that is relatively soft in order to absorb impact of rocks falling into bed 14. For example, second layer 46 may be formulated with polyurethane polyether prepolymers, such as, for example, ADIPRENE® L 42, ADIPRENE® LW 520, or VIBRATHANE® B625, or a similar material. Such prepolymers may be reacted with materials, such as, for example, DURACURE® C3-LF, or a similar material, at about 98% stoichiometry. That is, in a polyurethane urea system there is a theoretical point where each isocyanate group will react with each curative (amine) functional group. Such a point would be considered to correspond to a stoichiometry of 100%. In a case where excess curative (diamine) is added, the stoichiometry would be considered to be greater than 100%. In a case where less curative is added, the stoichiometry would be considered to be less than 100%. For example, if a polyurethane part is formed with a stoichiometry less than 100%, there will be excess isocyanate functionality remaining in the part. Upon high temperature postcuring of such a part (e.g., subjecting the part to a second heating cycle following an initial, incomplete curing), the excess isocyanate groups will react to form urea linkages, biuret linkages, and isocyanurates through cyclo-trimerization, or crosslinks through allophanate formation.
According to some embodiments, the second polyurethane of second layer 46 is supplied to a liner mold and is partially cured by heating second layer 46 for a time and temperature sufficient to partially cure the second polyurethane (e.g., a temperature ranging from about 110° C. to about 140° C. for a duration ranging from about 1 hour to about 4 hours). This partial curing may result in the second polyurethane becoming at least gel-like, but not necessarily completely solidified.
Thereafter, the third polyurethane of interlayer 48 may be cast over the partially cured second layer 46. According to some embodiments, the third polyurethane may include materials, such as, for example, DURACAST® S900, DURACAST® C900, or DURACAST® C930, or a similar material. In addition, the third polyurethane may include, for example, a prepolymer mixed with DURACURE® C3-LF formulated to range from about 50% to about 90% of theoretical stoichiometry (i.e., from about 50% to about 90% “stoichiometric”) (e.g., from about 60% to about 80% stoichiometric (e.g., about 60% stoichiometric)). This exemplary formulation making up the third polyurethane may be cast over second layer 46, and the second and third polyurethanes may be heated for a time and temperature sufficient to partially cure the third polyurethane (e.g., at a temperature ranging from about 110° C. to about 140° C. for a duration ranging from about 0.5 hour to about 2 hours, for example, for interlayer 48 being relatively thinner than second layer 46). This partial curing of interlayer 48 allows for initial chemical reactions of the third polyurethane constituents, so that the third polyurethane is gel-like, while retaining residual reactivity.
Following partial curing of interlayer 48, first layer 44 may be cast over interlayer 48. For example, the first polyurethane of first layer 44 may include the same materials as the third polyurethane of interlayer 48, but formulated at about 98% stoichiometry instead of the about 50% to about 90% stoichiometry of third polyurethane. Following the casting of the first polyurethane over interlayer 48, first layer 44, interlayer 48, and second layer 46 may be postcured by heating at a temperature ranging from about 120° C. to about 160° C. for a duration ranging from about 6 hours to about 24 hours. Thereafter, liner 42 may be removed from the liner mold.
During the final postcuring stage, the third polyurethane of interlayer 48 reacts chemically with the first and second polyurethanes of first layer 44 and second layer 46 to provide chemical bonds, so that first layer 44, interlayer 48, and second layer 46 are joined together to form a single, monolithic liner 42 while substantially maintaining the respective different material characteristics of first layer 44 and second layer 46. Interlayer 48 may serve to bridge the modulus gradient between first layer 44 and second layer 46. For example, if interlayer 48 is formulated with prepolymers that would normally result in a cured polyurethane having a Shore hardness ranging from about 90A to about 95A when formulated at 98% stoichiometry, interlayer 48 may be expected to have a Shore hardness ranging from about 75A to about 85A when cured according to the example above. Intermediate layer 48, having a stoichiometry ranging from about 50% to about 90% (e.g., about 60%), has sufficient curative to gel when first cast and heated, but the residual isocyanate groups will not react further until subjected to higher temperatures for longer durations occurring during postcuring. The residual isocyanate groups will react with urethane linkages in both first layer 44 and second layer 46 to form allophonate crosslinking, and the residual isocyanate groups will react within intermediate layer 48 to form allophonate crosslinking as well as biuret dimerization and isocyanurate cyclo-trimerization.
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According to some embodiments, first layer 44 and third layer 50 may be chemically bonded (e.g., covalently bonded) to one another, and first layer 44 and second layer 46 may be chemically bonded to one another, such that liner 42 is a single, monolithic structure. According to the exemplary embodiment shown in
According to some embodiments, exemplary liner 42 shown in
Thereafter, the polyurethane of interlayer 52 may be cast over the partially cured second layer 46. According to some embodiments, the polyurethane of interlayer 52 may include a material content similar to first polyurethane of first layer 44, except with a stoichiometry ranging from about 50% to about 90% (e.g., 60%). The second polyurethane of second layer 46 and the polyurethane of interlayer 52 may be heated for a time and temperature sufficient to partially cure the polyurethane of interlayer 52 (e.g., at a temperature ranging from about 110° C. to about 140° C. for a duration ranging from about 0.5 hour to about 2 hours).
Following partial curing of interlayer 52, first layer 44 may be cast over interlayer 52. For example, the first polyurethane of first layer 44 may include the same materials as interlayer 52, but formulated at about 98% stoichiometry instead of about 50% to about 90% stoichiometry. Following the casting of the first polyurethane over interlayer 52, first layer 44, interlayer 52, and second layer 46 may be partially cured by heating for a time and temperature sufficient to partially cure the first polyurethane (e.g., a temperature ranging from about 110° C. to about 140° C. for a duration ranging from about 1 hour to about 4 hours). This partial curing may result in the first polyurethane of first layer 44 becoming at least gel-like, but not necessarily completely cured.
Thereafter, the polyurethane of second interlayer 54 may be cast over the partially cured first layer 46. According to some embodiments, the polyurethane of second interlayer 54 may include a material content similar to the third polyurethane of third layer 50, except with a stoichiometry ranging from about 50% to about 90% (e.g., 60%). The polyurethane of second interlayer 54 may be heated for a time and temperature sufficient to partially cure the polyurethane of second interlayer 54 (e.g., at a temperature ranging from about 110° C. to about 140° C. for a duration ranging from about 0.5 hour to about 2 hours).
Following the partial curing of second interlayer 54, third layer 50 may be cast over second interlayer 54. For example, the third polyurethane of third layer 50 may include the same materials as second interlayer 54, but formulated at about 98% stoichiometry instead of about 50% to about 90% stoichiometry.
Following the casting of the third polyurethane over second interlayer 54, third layer 50, second interlayer 54, first layer 44, interlayer 52, and second layer 46 may be postcured by heating at a temperature ranging from about 120° C. to about 160° C. for a duration ranging from about 6 hours to about 24 hours. Thereafter, liner 42 may be removed from the liner mold.
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The liner and liner system disclosed herein may be used to protect a machine body of a machine having a bed configured to receive, transport, and deposit a load of material, for example, associated with mining, earthmoving, and construction purposes. Such machines include, for example, off-highway trucks and any type of ground-borne vehicles having a bed for receiving, transporting, and depositing a load of material.
According to at least some embodiments, the liner and liner system may provide a combination of desirable properties. For example, the liner and liner system may be cut- and chip-resistant, abrasion resistant, have a low coefficient of friction, and/or have a superior fatigue life. This may prevent excessive wear as the material is being evacuated from the machine body during dumping. By virtue of the liner having layers of polyurethane with different characteristics, such as, for example, hardness, modulus, and deformability, and energy absorbing capacity, it may be possible to provide a liner and liner system tailored to the desired use of the machine. For example, for a machine intended to be used to receive, carry, and deposit large rocks, it may be desirable to provide a liner and liner system having an upper layer with improved cut- and chip-resistance, combined with a lower layer providing improved energy absorbing capacity and protection of the machine bed. In contrast, for a machine intended to be used to receive, carry, and deposit coal or sand, it may be desirable to provide a liner and liner system having an upper layer with relatively lower cut- and chip-resistance, and a lower layer providing relatively lower energy absorbing capacity and protection for the machine bed. This may result in cost savings for such a liner and liner system.
In addition, at least some embodiments of the liner and liner system may have improved durability and a lengthened service life as a result of chemical bonding between polyurethane layers of the liner. Relative to the use of adhesive bonding, chemical bonding (e.g., covalent bonding) may improve the strength of the bond between polyurethane layers and/or interlayers of the liner. This may prevent or reduce the likelihood that the layers and interlayers separate from one another during repeated receipt and deposit of material from the machine bed.
In addition, according to at least some embodiments, the liner retention system may provide a secure coupling between the liner and the machine bed to prevent the liner from unintentionally sliding out of the machine bed during dumping of material. In addition, the liner retention system may be relatively lightweight when compared to other mechanisms used to hold liners in machine beds. This may avoid unnecessarily adding to the weight in the machine bed. The retention system according to at least some embodiments may also be relatively easily and inexpensively installed or replaced as compared to other systems, such as those that rely on welding to attach the liner to the machine bed.
It will be apparent to those skilled in the art that various modifications and variations can be made to the exemplary disclosed liner, liner system, and related methods. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the exemplary disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.